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Sample records for fracture strength

  1. Tooth structure and fracture strength of cavities

    DEFF Research Database (Denmark)

    Mondelli, José; Sene, Fábio; Ramos, Renata Pereira

    2007-01-01

    This study evaluated, in vitro, the loss of tooth substance after cavity preparation for direct and indirect restorations and its relationship with fracture strength of the prepared teeth. Sixty sound human maxillary first premolars were assigned to 6 groups (n=10). MOD direct composite cavities......) or 1/2 (Groups III and VI) of the intercuspal distance. Teeth were weighed (digital balance accurate to 0.001 g) before and after preparation to record tooth substance mass lost during cavity preparation. The prepared teeth were submitted to occlusal loading to determine their fracture strength using...... mass loss (13.91%) than composite resin preparations with the same width (10.02%). 1/2-inlay cavities had 21.34% of mass loss versus 16.19% for the 1/2-composite resin cavities. Fracture strength means (in kgf) were: GI = 187.65; GII = 143.62; GIII = 74.10; GIV = 164.22; GV = 101.92; GVI = 50...

  2. Feasibility of progressive strength training shortly after hip fracture surgery

    DEFF Research Database (Denmark)

    Overgaard, Jan; Kristensen, Morten T

    2013-01-01

    To investigate the feasibility of a 6-wk progressive strength-training programme commenced shortly after hip fracture surgery in community-dwelling patients.......To investigate the feasibility of a 6-wk progressive strength-training programme commenced shortly after hip fracture surgery in community-dwelling patients....

  3. Fracture strengths of chair‑side‑generated veneers cemented with ...

    African Journals Online (AJOL)

    Introduction: CAD/CAM (computer‑aided design and computer‑aided manufacturing) systems have refreshed the idea of chair‑side production of restorations, but the fracture of ceramic veneers remains a problem. Cementation with glass fibers may improve the fracture strengths and affect the failure modes of ...

  4. Crack formation and fracture energy of normal and high strength ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. The crack path through composite materials such as concrete depends on the mechanical interaction of inclusions with the cement-based matrix. Fracture energy depends on the deviations of a real crack from an idealized crack plane. Fracture energy and strain softening of normal, high strength, and self- ...

  5. Fracture Resistance, Surface Defects and Structural Strength of Glass

    OpenAIRE

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass strength assessment. The effect of loading conditions, constructional and technological factors on the engineering strength of glass can be evaluated in certain cases using fracture mechanics with inform...

  6. Fracture Energy of High-Strength Concrete in Compression

    DEFF Research Database (Denmark)

    Dahl, Henrik; Brincker, Rune

    is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental...... method has been used to investigate the influence of boundary conditions, loading rate, size effects and the influence of the strength on the fracture energy of high-strength concrete over the range 70 MPa to 150 MPa, expressed in nominal values....

  7. Hot pressing, strength, and fracture of calcium hexaboride

    International Nuclear Information System (INIS)

    Dutta, S.K.

    1975-01-01

    Fracture behavior and strength of hot-pressed CaB 6 were studied. The modulus of elasticity determined by attaching strain gages to the tensile surface of the bend bars to measure strain, was 55 +- 3 x 10 6 psi. The results are compared with values for other low density ceramic materials (B 4 C, SiB 6 , Be 4 B, AlB 12 ) in a table. The fracture mode was observed for both modulus of rupture and impact test specimens. Predominantly transgranular fracture, associated with distinct step cleavages is evident. Fracture origins were examined in an effort to understand the strength limiting features in hot-pressed CaB 6 specimens. Surface defects, large grain agglomerations, and isolated pore pockets were observed and varied from bar to bar; these were similar to those found in B 4 C. (U.S.)

  8. Effect of plastic strain on fracture strength of cracked components

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2009-01-01

    Nuclear power plant components are occasionally subjected to large load by earthquake and may suffer plastic strain. Although the plastic strain induced in materials increases the strength, it may reduce the fracture toughness due to a crack in the components. In this study, the effect of the plastic strain on strength of cracked components was investigated. Firstly, the change in the tensile properties and fracture toughness due to plastic strain were examined for Type 316 stainless steel and carbon steel (SM490). The degree of nominal plastic strain was 5%, 10%, 20% and 40% (only for stainless steel). Secondly, the J-integral values of surface crack on a pipe were evaluated by finite element analyses. Finally, the critical load for fracture of the cracked pipe was evaluated for various pipe and crack geometries using the J-integral values and the fracture toughness obtained. It was concluded that the plastic strain enhances the fracture strength of the cracked components when the induced plastic strain is less than 10%, although the extremely large plastic strain could reduce the strength. (author)

  9. Effect of plastic strain on fracture strength of cracked components

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2010-01-01

    Nuclear power plant components are occasionally subjected to excessive load by earthquake and may suffer plastic strain. Although the plastic strain introduced in materials increases the strength, it may reduce the fracture toughness. In this study, the effect of the plastic strain on strength of cracked components was investigated. Firstly, the change in the tensile properties and fracture toughness due to plastic strain were examined for Type 316 stainless steel and carbon steel (SM 490). The degree of nominal plastic strain was 5%, 10%, 20% and 40% (only for stainless steel). Secondly, the J-integral values of surface crack on a pipe were evaluated by finite element analyses. Finally, the critical load for fracture of the cracked pipe was evaluated for various pipe and crack geometries using the J-integral values and the fracture toughness obtained. It was concluded that the plastic strain enhances the fracture strength of the cracked components when the induced plastic strain is less than 10%, although the extremely large plastic strain could reduce the strength. (author)

  10. Anisotropy of strength and deformability of fractured rocks

    Directory of Open Access Journals (Sweden)

    Majid Noorian Bidgoli

    2014-04-01

    Full Text Available Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non-regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes containing many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a numerical modeling method. A series of realistic two-dimensional (2D discrete fracture network (DFN models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method (DEM, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and suggestions for future study are also presented.

  11. Temperature dependence of the fracture toughness and the cleavage fracture strength of a pressure vessel steel

    International Nuclear Information System (INIS)

    Kotilainen, H.

    1980-01-01

    A new model for the temperature dependence of the fracture toughness has been sought. It is based on the yielding processes at the crack tip, which are thought to be competitive with fracture. Using this method a good correlation between measured and calculated values of fracture toughness has been found for a Cr-Mo-V pressure vessel steel as well as for A533B. It has been thought that the application of this method can reduce the number of surveillance specimens in nuclear reactors. A method for the determination of the cleavage fracture strength has been proposed. 28 refs

  12. Fracture strength of biomimetic composites: scaling views on nacre

    Energy Technology Data Exchange (ETDEWEB)

    Okumura, Ko [Department of Physics, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610 (Japan)

    2005-08-10

    Nacre, layered structure on the nanoscale, found inside certain seashells, shows remarkable strength due to the tiny amount of soft glues between hard sheets. In this paper, we develop an anisotropic elastic theory and fracture mechanics for the laminar structure at the level of scaling laws to reproduce the essence of the previous results in a much simpler way.

  13. Biomechanical Strength of Retrograde Fixation in Proximal Third Scaphoid Fractures.

    Science.gov (United States)

    Daly, Charles A; Boden, Allison L; Hutton, William C; Gottschalk, Michael B

    2018-04-01

    Current techniques for fixation of proximal pole scaphoid fractures utilize antegrade fixation via a dorsal approach endangering the delicate vascular supply of the dorsal scaphoid. Volar and dorsal approaches demonstrate equivalent clinical outcomes in scaphoid wrist fractures, but no study has evaluated the biomechanical strength for fractures of the proximal pole. This study compares biomechanical strength of antegrade and retrograde fixation for fractures of the proximal pole of the scaphoid. A simulated proximal pole scaphoid fracture was produced in 22 matched cadaveric scaphoids, which were then assigned randomly to either antegrade or retrograde fixation with a cannulated headless compression screw. Cyclic loading and load to failure testing were performed and screw length, number of cycles, and maximum load sustained were recorded. There were no significant differences in average screw length (25.5 mm vs 25.6 mm, P = .934), average number of cyclic loading cycles (3738 vs 3847, P = .552), average load to failure (348 N vs 371 N, P = .357), and number of catastrophic failures observed between the antegrade and retrograde fixation groups (3 in each). Practical equivalence between the 2 groups was calculated and the 2 groups were demonstrated to be practically equivalent (upper threshold P = .010). For this model of proximal pole scaphoid wrist fractures, antegrade and retrograde screw configuration have been proven to be equivalent in terms of biomechanical strength. With further clinical study, we hope surgeons will be able to make their decision for fixation technique based on approaches to bone grafting, concern for tenuous blood supply, and surgeon preference without fear of poor biomechanical properties.

  14. Fracture strength of aluminium alloys under rapid loading conditions

    International Nuclear Information System (INIS)

    Joshi, K.D.; Rav, Amit S.; Sur, Amit; Kaushik, T.C.; Gupta, Satish C.

    2016-04-01

    Spall fracture strength and dynamic yield strength of aluminium alloys have been measured at high strain rates generated in plate impact experiments carried out at different impact velocities ranging from 174 m/s to 560 m/s using single stage gas gun facility. In each experiment, the free surface velocity history of the sample plate of aluminium alloy has been derived from time resolved Doppler shift measured employing indigenously developed velocity interferometer system for any reflector (VISAR). The free surface velocity history so determined has been used to evaluate the spall fracture strength and dynamic yield strength of the target material. The two kinds of alloys of aluminium namely Al2014-T4 and Al2024-T4 have been investigated in these experiments. In Al2014-T4 target plates, the spall strength determined from free surface velocity history recorded for impact velocities of 179 m/s, 307 m/s, 398 m/s and 495m/s is 0.90 GPa, 0.96 GPa, 1.0 GPa and 1.1 GPa, respectively. The average strain rates just ahead of spall pulse have been found to vary from ∼ 1.1×10 4 /s to 2.4×10 4 /s. The dynamic yield strength derived from the measured Hugoniot elastic limit ranges from 0.36 GPa to 0.40 GPa. The spall strength for Al2024-T4 samples has been determined to be 1.11 GPa, 1.18 GPa and 1.42 GPa, at impact velocities of 174 m/s, 377 m/s and 560 m/s, respectively. The corresponding average strain rates range from 1.9×104/s to 2.5×104/s. The dynamic yield strength of Al2024-T4 at these impact velocities has been found to vary from 0.37 GPa to 0.43 GPa. The measured spall strengths in all these experiments are higher than the quasi-static value of 0.511 GPa for Al2014-T4 and 0.470 GPa for Al2024. Similarly, the dynamic yield strengths are also larger than the quasi-static value of 0.355 GPa for Al2014-T4 and 0.360 GPa for Al2024-T4. These experimental studies suggest that at high strain rates, both the alloys of aluminium offer higher resistance against the tensile

  15. Statistical fracture mechanics approach to the strength of brittle rock

    International Nuclear Information System (INIS)

    Ratigan, J.L.

    1981-06-01

    Statistical fracture mechanics concepts used in the past for rock are critically reviewed and modifications are proposed which are warranted by (1) increased understanding of fracture provided by modern fracture mechanics and (2) laboratory test data both from the literature and from this research. Over 600 direct and indirect tension tests have been performed on three different rock types; Stripa Granite, Sierra White Granite and Carrara Marble. In several instances assumptions which are common in the literature were found to be invalid. A three parameter statistical fracture mechanics model with Mode I critical strain energy release rate as the variant is presented. Methodologies for evaluating the parameters in this model as well as the more commonly employed two parameter models are discussed. The experimental results and analysis of this research indicate that surfacially distributed flaws, rather than volumetrically distributed flaws are responsible for rupture in many testing situations. For several of the rock types tested, anisotropy (both in apparent tensile strength and size effect) precludes the use of contemporary statistical fracture mechanics models

  16. Effects of cyclic shear loads on strength, stiffness and dilation of rock fractures

    Directory of Open Access Journals (Sweden)

    Thanakorn Kamonphet

    2015-12-01

    Full Text Available Direct shear tests have been performed to determine the peak and residual shear strengths of fractures in sandstone, granite and limestone under cyclic shear loading. The fractures are artificially made in the laboratory by tension inducing and saw-cut methods. Results indicate that the cyclic shear load can significantly reduce the fracture shear strengths and stiffness. The peak shear strengths rapidly decrease after the first cycle and tend to remain unchanged close to the residual strengths through the tenth cycle. Degradation of the first order asperities largely occurs after the first cycle. The fracture dilation rates gradually decrease from the first through the tenth cycles suggesting that the second order asperities continuously degrade after the first load cycle. The residual shear strengths are lower than the peak shear strengths and higher than those of the smooth fractures. The strength of smooth fracture tends to be independent of cyclic shear loading.

  17. Evaluation of tensile strength and fracture toughness of yttria-stabilized zirconia polycrystals with fracture surface analysis

    International Nuclear Information System (INIS)

    Oishi, Manabu; Matsuda, Yukihisa; Noguchi, Kenichi; Masaki, Takaki

    1995-01-01

    The tensile strength of yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) was measured and the fracture surfaces were analyzed with the scanning electron microscope and X-ray microanalyzer. The fracture origins of the pressureless-sintered samples were voids or inclusions such as Al 2 O 3 , Al 2 O 3 with SiO 2 , and cubic-ZrO 2 , while the fracture origins of the hot isostatically pressed samples were inclusions; no voids were detected at fracture origins. The higher strengths of the hot isostatically pressed samples versus those of the pressureless-sintered samples were consistent with the change in fracture origins. The fracture toughness of the samples calculate from the tensile strength and analysis of the fracture origins was 3.4 to 3.7 MPa ·√m. These values are lower than those measured with the SEPB method. These discrepancies might be caused by the difference in the state of the fracture origin and its neighborhood, such as the size of the fracture origin and interaction between two surfaces in the precrack

  18. Risk of vertebral insufficiency fractures in relation to compressive strength predicted by quantitative computed tomography

    International Nuclear Information System (INIS)

    Biggemann, M.; Hilweg, D.; Seidel, S.; Horst, M.; Brinckmann, P.

    1991-01-01

    Vertebral insufficiency fractures may result from excessive loading of normal and routine loading of osteoporotic spines. Fractures occur when the mechanical load exceeds the vertebral compressive strength, i.e., the maximum load a vertebra can tolerate. Vertebral compressive strength is determined by trabecular bone density and the size of end-plate area. Both parameters can be measured non-invasively by quanti-tative computed tomography (QCT). In 75 patients compressive strength (i.e., trabecular bone density and endplate area) of the vertebra L3 was determined using QCT. In addition, conventional radiographs of the spines were analysed for the prevalence of insufficiency fractures in each case. By relating fracture prevalence to strength, 3 fracture risk groups were found: a high-risk group with strength values of L3 5 kN and a fracture risk near 0 percent. Biomechanical measurements and model calculations indicate that spinal loads of 3 to 4 kN at L3/4 will be common in everyday activities. These data and the results described above suggest that spines with strength values of L3<3 kN are at an extremely high risk of insufficiency fractures in daily life. Advantages of fracture risk assessment by strength determination over risk estimation based on clinically used trabecular bone density measurements are discussed. (author). 18 refs.; 4 figs

  19. Strength and fracture behavior of aluminide matrix composites with ceramic fibers

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, M.; Suganuma, K.; Niihara, K.

    1999-07-01

    This paper investigates the fracture behavior of FeAl and Ni{sub 3}Al matrix composites with ceramic continuous fibers 8.5--10 {micro}m in diameter. When stress is applied to these composites, multiple-fracture of fibers predominantly occurs before matrix cracking, because the load carried by the fibers reaches their fracture strength. Fragments which remain longer than the critical length can provide significant strengthening through load bearing even though fiber breaking has occurred. The ultimate fracture strength of the composites also depends on stress relaxation by plastic deformation of the matrix at a crack tip in the multiple-fractured fibers. Ductilizing of the matrix by B doping improves the ultimate strength at ambient temperatures in both composites. However, their mechanical properties at elevated temperatures are quite different. In the case of Ni{sub 3}Al matrix composites, embrittlement of the matrix is undesirable for high strength and reliability at 873--973 K.

  20. Feasibility of progressive strength training implemented in the acute ward after hip fracture surgery.

    Directory of Open Access Journals (Sweden)

    Lise Kronborg

    Full Text Available Patients with a hip fracture lose more than 50% knee-extension strength in the fractured limb within one week of surgery. Hence, immediate progressive strength training following hip fracture surgery may be rational, but the feasibility unknown.To examine the feasibility of in-hospital progressive strength training implemented in the acute ward following hip fracture surgery, based on pre-specified criteria for feasibility.A prospective cohort study conducted in an acute orthopedic hip fracture unit at a university hospital. A consecutive sample of 36 patients, 18 with a cervical and 18 with a trochanteric hip fracture (27 women and 9 men, mean (SD age of 79.4 (8.3 years were included between June and December 2012.A daily (on weekdays program of progressive knee-extension strength training for the fractured limb, using ankle weight cuffs in 3 sets of 10 repetition maximum loadings.The primary outcome was the change in training load (kg during the knee-extension strength training. The secondary outcomes were changes in hip fracture-related pain and maximal isometric knee-extension strength.The strength training was commenced at a mean of 2.4 (0.7 days after surgery. The training loads (kilograms lifted increased from 1.6 (0.8 to 4.3 (1.7 kg over 4.3 (2.2 training sessions (P<.001. The maximal isometric knee-extension strength of the fractured limb increased from 0.37 (0.2 to 0.61 (0.3 Nm/kg (P<.001, while the average strength deficit in the fractured limb decreased from 50% to 32% (% non-fractured, P<.001. Only 3 of 212 sessions were not performed because of severe hip fracture-related pain.Progressive knee-extension strength training of the fractured limb commenced in the acute ward seems feasible, and may reduce strength asymmetry between limbs without hip pain interfering. The clinical efficacy needs confirmation in a randomized controlled design.ClinicalTrials.gov ID: NCT01616030.

  1. Fracture Energy of High-Strength Concrete in Compression

    DEFF Research Database (Denmark)

    Dahl, H.; Brincker, Rune

    1989-01-01

    is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental...

  2. Fracture strength of fiber-reinforced surface-retained anterior cantilever restorations

    NARCIS (Netherlands)

    Oezcan, Mutlu; Kumbuloglu, Ovul; User, Atilla

    2008-01-01

    Purpose: This study compared the fracture strength of direct anterior cantilever fiber-reinforced composite (FRC) fixed partial dentures (FPD) reinforced with 3 types of E-glass fibers preimpregnated with either urethane tetramethacrylate, bisphenol glycidylmethacrylate/polymethyl methacrylate, or

  3. Wearing an active spinal orthosis improves back extensor strength in women with osteoporotic vertebral fractures

    DEFF Research Database (Denmark)

    Valentin, Gitte Hoff; Pedersen, Louise Nymann; Maribo, Thomas

    2014-01-01

    .Study design:Experimental follow-up.Methods:The women used the active spinal orthosis for 3 months. Outcomes were changes in isometric back extensor strength, changes in back pain and changes in physical functioning.Results:A total of 13 women were included in the trial. Wearing the orthosis during a 3-month......Background:Vertebral fractures are the most common clinical manifestations of osteoporosis. Vertebral fractures and reduced back extensor strength can result in hyperkyphosis. Hyperkyphosis is associated with diminished daily functioning and an increased risk of falling. Improvements in back...... extensor strength can result in decreased kyphosis and thus a decreased risk of falls and fractures.Objectives:The aim was to examine the effects of an active spinal orthosis - Spinomed III - on back extensor strength, back pain and physical functioning in women with osteoporotic vertebral fractures...

  4. Feasibility of Progressive Strength Training Implemented in the Acute Ward after Hip Fracture Surgery

    DEFF Research Database (Denmark)

    Kronborg, Lise; Bandholm, Thomas; Palm, Henrik

    2014-01-01

    . RESULTS: The strength training was commenced at a mean of 2.4 (0.7) days after surgery. The training loads (kilograms lifted) increased from 1.6 (0.8) to 4.3 (1.7) kg over 4.3 (2.2) training sessions (P....2) to 0.61 (0.3) Nm/kg (Psessions were not performed because of severe hip fracture-related pain. CONCLUSION AND RELEVANCE: Progressive knee-extension strength training......IMPORTANCE: Patients with a hip fracture lose more than 50% knee-extension strength in the fractured limb within one week of surgery. Hence, immediate progressive strength training following hip fracture surgery may be rational, but the feasibility unknown. OBJECTIVE: To examine the feasibility...

  5. “Evaluation of fracture strength of teeth restored with different types ...

    African Journals Online (AJOL)

    Evaluation of fracture strength of teeth restored with different types of posts luted with different luting ... Nigerian Journal of Clinical Practice ... metal posts and glass‑fiber posts luted with resin‑based luting cement and glass ionomer cement.

  6. Endogenous hormones, muscle strength, and risk of fall-related fractures in older women.

    Science.gov (United States)

    Sipilä, Sarianna; Heikkinen, Eino; Cheng, Sulin; Suominen, Harri; Saari, Päivi; Kovanen, Vuokko; Alén, Markku; Rantanen, Taina

    2006-01-01

    Among older people, fracture-causing fall often leads to health deterioration. The role of endogenous hormone status and muscle strength on fall-related fracture risk is unclear. This study investigates if, after adjustment for bone density, endogenous hormones and muscle strength would predict fall-related limb fracture incidence in older community-dwelling women followed-up over 10 years. As a part of a prospective population-based study, 187 75-year-old women were investigated. Serum estradiol, testosterone, sex hormone binding globulin, and dehydroepiandrosterone sulfate concentrations were analyzed, and isometric muscle strength and bone mineral density were assessed. Fall-related limb fractures were gathered from patient records. Serum estradiol concentration was a significant predictor of fall-related limb fractures. Women with serum estradiol concentrations less than 0.022 nmol/L had a 3-fold risk (relative risk 3.05; 95% confidence interval, 1.26-7.36), and women with estradiol concentrations between 0.022 and 0.066 nmol/L doubled the risk (relative risk 2.24; 95% confidence interval, 0.97-5.19) of fall-related limb fracture compared to the women with estradiol concentrations ()above 0.066 nmol/L. Adjustment for muscle strength and bone mineral density did not materially change the risk estimates. High muscle strength was associated with a low incidence of fall-related limb fractures. This study showed that in 75-year-old women higher serum estradiol concentration and greater muscle strength were independently associated with a low incidence of fall-related limb fractures even after adjustment for bone density. Our results suggest that hormonal status and muscle strength have their own separate mechanisms protecting from fall-related fractures. This finding is of importance in developing preventive strategies, but calls for further study.

  7. Effect of roughness and material strength on the mechanical properties of fracture replicas

    International Nuclear Information System (INIS)

    Wibowo, J.; Amadei, B.; Sture, S.

    1995-08-01

    This report presents the results of 11 rotary shear tests conducted on replicas of three hollow cylinders of natural fractures with JRC values of 7.7, 9.4 and 12.0. The JRC values were determined from the results of laser profilometer measurements. The replicas were created from gypsum cement. By varying the water-to-gypsum cement ratio from 30 to 45%, fracture replicas with different values of compressive strength (JCS) were created. The rotary shear experiments were performed under constant normal (nominal) stresses ranging between 0.2 and 1.6 MPa. In this report, the shear test results are compared with predictions using Barton's empirical peak shear strength equation. observations during the experiments indicate that only certain parts of the fracture profiles influence fracture shear strength and dilatancy. Under relatively low applied normal stresses, the JCS does not seem to have a significant effect on shear behavior. As an alternative, a new procedure for predicting the shear behavior of fractures was developed. The approach is based on basic fracture properties such as fracture surface profile data and the compressive strength, modulus of elasticity, and Poisson's ratio of the fracture walls. Comparison between predictions and actual shear test results shows that the alternative procedure is a reliable method

  8. Heat damage-free laser-microjet cutting achieves highest die fracture strength

    Science.gov (United States)

    Perrottet, Delphine; Housh, Roy; Richerzhagen, Bernold; Manley, John

    2005-04-01

    Unlike conventional laser-based technologies, the water jet guided laser does not generate heat damage and contamination is also very low. The negligible heat-affected zone is one reason why die fracture strength is higher than with sawing. This paper first presents the water jet guided laser technology and then explains how it differs from conventional dry laser cutting. Finally, it presents the results obtained by three recent studies conducted to determine die fracture strength after Laser-Microjet cutting.

  9. Influence of fall related factors and bone strength on fracture risk in the frail elderly.

    Science.gov (United States)

    Sambrook, P N; Cameron, I D; Chen, J S; Cumming, R G; Lord, S R; March, L M; Schwarz, J; Seibel, M J; Simpson, J M

    2007-05-01

    When subjects are selected on the basis of fall risk alone, therapies for osteoporosis have not been effective. In a prospective study of elderly subjects at high risk of falls, we investigated the influence of bone strength and fall risk on fracture. At baseline we assessed calcaneal bone ultrasound attenuation (BUA) as well as quantitative measures of fall risk in 2005 subjects in residential care. Incident falls and fractures were recorded (median follow-up 705 days). A total of 6646 fall events and 375 low trauma fracture events occurred. The fall rate was 214 per 100 person years and the fracture rate 12.1 per 100 person years. 82% of the fractures could be attributed to falls. Although fracture rates increased with decreasing BUA (incidence rate ratio 1.94 for lowest vs. highest BUA tertile, pfalls also affected fracture incidence. Subjects who fell frequently (>3.15 falls/per person year) were 3.35 times more likely to suffer a fracture than those who did not fall. Some fall risk factors such as balance were associated with the lowest fracture risk lowest in the worst performing group. Multivariate analysis revealed higher fall rate, history of previous fracture, lower BUA, lower body weight, cognitive impairment and better balance as significant independent risk factors for fracture. In the frail elderly, both skeletal fragility and fall risk including the frequency of exposure to falls are important determinants of fracture risk.

  10. Knee-extension strength, postural control and function are related to fracture type and thigh edema in patients with hip fracture

    DEFF Research Database (Denmark)

    Kristensen, Morten T; Bandholm, Thomas; Bencke, Jesper

    2008-01-01

    BACKGROUND: Post-surgery thigh edema, loss of knee-extension strength, and reduced physical performance are common following a hip fracture. It is not known if knee-extension strength and physical performance are related to the edema and fracture type. The aim of this study was to examine...... the influence of fracture type and post-surgery edema on physical performances in patients with hip fracture. METHODS: Fifteen women and five men admitted from their own home to an acute orthopedic hip fracture unit were examined. Ten had cervical and ten had intertrochanteric fractures. Correlations between...... fracture type and thigh edema in the fractured limb (% non-fractured) to physical performances of basic mobility, postural control (sway), and isometric knee-extension strength were examined. All measures, except those of basic mobility, were conducted at the time of discharge, 8.5 days post...

  11. Strength and fracture of two-phase alloys: a comparison of two alloy systems

    International Nuclear Information System (INIS)

    Gurland, J.

    1978-01-01

    The functional roles of the hard and soft constituents in the deformation and fracture of two-phase alloys are discussed on the basis of two commercially important alloy systems, namely spheroidized carbon steels and cemented carbides, WC-Co. A modified rule of mixtures provides a structural approach to the yield and flow strength. Consideration of the fracture toughness is attempted by means of a phenomenological modelling of the fracture process on the microscale. While there are large differences in properties between the two alloys, the deformation and fracture processes show broad smilarities which are associated with the features of the interaction between constituents common to both alloys

  12. Evaluation of essential work of fracture in a dual phase high strength steel sheet

    International Nuclear Information System (INIS)

    Gutierrez, D.; Perez, L. I.; Lara, A.; Casellas, D.; Prado, J. M.

    2013-01-01

    Fracture toughness of advanced high strength steels (AHSS), can be used to optimize crash behavior of structural components. However it cannot be readily measured in metal sheet because of the sheet thickness. In this work, the Essential Work of Fracture (EWF) methodology is proposed to evaluate the fracture toughness of metal sheets. It has been successfully applied in polymers films and some metal sheets. However, their information about the applicability of this methodology to AHSS is relatively scarce. In the present work the fracture toughness of a Dual Phase (strength of 800 MPa) and drawing steel sheets has been measured by means of the EWF. The results show that the test requirements are met and also show the clear influence of notch radii on the measured values, specially for the AHSS grade. Thus, the EWF is postulated as a methodology to evaluate the fracture toughness in AHSS sheets. (Author) 18 refs.

  13. Bone geometry, strength, and muscle size in runners with a history of stress fracture.

    Science.gov (United States)

    Popp, Kristin L; Hughes, Julie M; Smock, Amanda J; Novotny, Susan A; Stovitz, Steven D; Koehler, Scott M; Petit, Moira A

    2009-12-01

    Our primary aim was to explore differences in estimates of tibial bone strength, in female runners with and without a history of stress fractures. Our secondary aim was to explore differences in bone geometry, volumetric density, and muscle size that may explain bone strength outcomes. A total of 39 competitive distance runners aged 18-35 yr, with (SFX, n = 19) or without (NSFX, n = 20) a history of stress fracture were recruited for this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Orthometrix, White Plains, NY) was used to assess volumetric bone mineral density (vBMD, mg x mm(-3)), bone area (ToA, mm(2)), and estimated compressive bone strength (bone strength index (BSI) = ToA x total volumetric density (ToD(2))) at the distal tibia (4%). Total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area, cortical vBMD, and estimated bending strength (strength-strain index (SSIp), mm(3)) were measured at the 15%, 25%, 33%, 45%, 50%, and 66% sites. Muscle cross-sectional area (MCSA) was measured at the 50% and 66% sites. Participants in the SFX group had significantly smaller (7%-8%) CoA at the 45%, 50%, and 66% sites (P stress fracture. However, the lower strength was appropriate for the smaller muscle size, suggesting that interventions to reduce stress fracture risk might be aimed at improving muscle size and strength.

  14. Fracture Strength of Fused Silica From Photonic Signatures Around Collision Sites

    Science.gov (United States)

    Yost, William T.; Cramer, K Elliott

    2015-01-01

    Impact sites in glass affect its fracture strength. An analytical model that predicts fracture strength from grey-field polariscope (GFP) readings (photoelastic retardations) has been developed and reported in the literature. The model is suggestive that stress fields, resulting from impact damage, destablizes sites within the glass, which lead to pathways that cause strength degradation. Using data collected from fused silica specimens fabricated from outer window panes that were designed for the space shuttle, the model was tested against four categories of inflicted damage. The damage sites were cored from the window carcasses, examined with the GFP and broken using the ASTM Standard C1499-09 to measure the fracture strength. A correlation is made between the fracture strength and the photoelastic retardation measured at the damage site in each specimen. A least-squares fit is calculated. The results are compared with the predictions from the model. A plausible single-sided NDE damage site inspection method (a version of which is planned for glass inspection in the Orion Project) that relates photoelastic retardation in glass components to its fracture strength is presented.

  15. Fracture strength testing of crowns made of CAD/CAM composite resins.

    Science.gov (United States)

    Okada, Ryota; Asakura, Masaki; Ando, Akihiro; Kumano, Hirokazu; Ban, Seiji; Kawai, Tatsushi; Takebe, Jun

    2018-03-28

    The purpose of this study was to ascertain whether computer aided design/computer aided manufacturing (CAD/CAM) composite resin crowns have sufficient strength to withstand the bite force of the molar teeth. The null hypothesis was that the fracture strength of CAD/CAM composite resin crowns is lower than the average maximum bite force of the molar tooth. The crowns, which shape is the right maxillary first molar, were fabricated using four CAD/CAM blanks made of composite resins (Block HC: HC, KZR-CAD HR: HR, KZR-CAD HR2: HR2, Avencia Block: AVE) and one CAD/CAM blank made of lithium disilicate glass-ceramic (IPS e.max CAD: IPS), which was used as a control. Fracture strength of fabricated crowns bonded to metal abutment and biaxial flexural strength of the materials were evaluated. The results of fracture strength test and biaxial flexural strength test showed different tendencies. The fracture strength of CAD/CAM composite resin crowns except HC ranged from 3.3kN to 3.9kN, and was similar to that of IPS (3.3kN). In contrast, biaxial flexural strength of CAD/CAM composite resins ranged from 175MPa to 247MPa, and was significantly lower than that of IPS (360MPa). All CAD/CAM composite resin crowns studied presented about 3-4 times higher fracture strength than the average maximum bite force of the molar tooth (700-900N), which result leads to the conclusion that CAD/CAM composite resin crowns would have sufficient strength to withstand the bite force of the molar teeth. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  16. Fracture strengths of chair‑side‑generated veneers cemented with ...

    African Journals Online (AJOL)

    2014-06-09

    Jun 9, 2014 ... Group 1), CAD/CAM‑fabricated veneers cemented with a glass fiber ... specimens were tested with a universal testing machine after thermal cycling treatment. ... The purpose of the current in vitro study is to determine the ..... fracture resistance of fiber reinforced cups‑replacing composite restorations.

  17. Fracture Resistance, Surface Defects and Structural Strength of Glass

    NARCIS (Netherlands)

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass

  18. Evaluating the fracture toughness and flexural strength of pressable dental ceramics: an in vitro study.

    Science.gov (United States)

    Gurram, Ravi; Krishna, C H Vamsi; Reddy, K Mahendranadh; Reddy, G V K Mohan; Shastry, Y Mahadev

    2014-12-01

    The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each. Biaxial flexural strength (30 discs,) Biaxial flexural strength for samples treated with 9 % HF acid (30 discs) and fracture toughness (30 discs) were evaluated. Core material Performance Plus had the lowest biaxial strength of 124.89 MPa, Cergo had strength of 152.22 MPa and the highest value of 163.95 was reported for Esthetic Empress. For samples treated 9 % HF, Performance Plus had the lowest biaxial strength of 98.37 MPa, Cergo had strength of 117.42 MPa and the highest value of 143.74 was reported for Esthetic Empress. Core material Performance Plus had the lowest fracture toughness of 1.063 MPa, Cergo had strength of 1.112 MPa and the highest value of 1.225 was reported for Esthetic Empress. The results shows that Esthetic Empress had better mechanical properties compared to Cergo had Performance Plus in relation to the parameters tested.

  19. Influence of heat treatment on the strength and fracture toughness of 7N01 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bo [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Wang, Xiaomin, E-mail: xmwang991011@163.com [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Chen, Hui; Hu, Jie [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Huang, Cui [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Gou, Guoqing [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China)

    2016-09-05

    7N01 aluminum (Al) alloys are treated by five heat treatment methods as peak aging (T6), over aging (T74), high temperature and subsequently low temperature aging (HLA), retrogression and reaging (RRA) and double retrogression and reaging (DRRA). The strength and fracture toughness of the five samples are tested, and the microstructures are investigated by optical microscopy (OM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that 7N01 Al-alloy treated at T6 condition has high strength but low fracture toughness. Compared with T6 treatment, T74 and HLA treatments increase the fracture toughness by 67% and 90% respectively, while the strength decrease by 9% and 17%. RRA process is a proper treatment method for 7N01 which improves the fracture toughness without sacrificing strength. The fracture toughness of DRRA treated alloy is much lower than that of RRA. Quantitative analysis through TEM images shows that the heat treatment affects the mechanical properties of 7N01 Al-alloy highly through changing the precipitates in grains and on grain boundaries, which can be explained by the coherency strengthening mechanism and Orowan mechanism. - Highlights: • Five heat treatments which can change the properties of 7N01 Al alloy were designed. • Quantitative analysis of precipitates was employed to study the mechanism. • RRA treatment can make proper strength/toughness property balances for 7N01 Al alloy.

  20. Influence of heat treatment on the strength and fracture toughness of 7N01 aluminum alloy

    International Nuclear Information System (INIS)

    Li, Bo; Wang, Xiaomin; Chen, Hui; Hu, Jie; Huang, Cui; Gou, Guoqing

    2016-01-01

    7N01 aluminum (Al) alloys are treated by five heat treatment methods as peak aging (T6), over aging (T74), high temperature and subsequently low temperature aging (HLA), retrogression and reaging (RRA) and double retrogression and reaging (DRRA). The strength and fracture toughness of the five samples are tested, and the microstructures are investigated by optical microscopy (OM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that 7N01 Al-alloy treated at T6 condition has high strength but low fracture toughness. Compared with T6 treatment, T74 and HLA treatments increase the fracture toughness by 67% and 90% respectively, while the strength decrease by 9% and 17%. RRA process is a proper treatment method for 7N01 which improves the fracture toughness without sacrificing strength. The fracture toughness of DRRA treated alloy is much lower than that of RRA. Quantitative analysis through TEM images shows that the heat treatment affects the mechanical properties of 7N01 Al-alloy highly through changing the precipitates in grains and on grain boundaries, which can be explained by the coherency strengthening mechanism and Orowan mechanism. - Highlights: • Five heat treatments which can change the properties of 7N01 Al alloy were designed. • Quantitative analysis of precipitates was employed to study the mechanism. • RRA treatment can make proper strength/toughness property balances for 7N01 Al alloy.

  1. Bone strength estimates relative to vertical ground reaction force discriminates women runners with stress fracture history.

    Science.gov (United States)

    Popp, Kristin L; McDermott, William; Hughes, Julie M; Baxter, Stephanie A; Stovitz, Steven D; Petit, Moira A

    2017-01-01

    To determine differences in bone geometry, estimates of bone strength, muscle size and bone strength relative to load, in women runners with and without a history of stress fracture. We recruited 32 competitive distance runners aged 18-35, with (SFX, n=16) or without (NSFX, n=16) a history of stress fracture for this case-control study. Peripheral quantitative computed tomography (pQCT) was used to assess volumetric bone mineral density (vBMD, mg/mm 3 ), total (ToA) and cortical (CtA) bone areas (mm 2 ), and estimated compressive bone strength (bone strength index; BSI, mg/mm 4 ) at the distal tibia. ToA, CtA, cortical vBMD, and estimated strength (section modulus; Zp, mm 3 and strength strain index; SSIp, mm 3 ) were measured at six cortical sites along the tibia. Mean active peak vertical (pkZ) ground reaction forces (GRFs), assessed from a fatigue run on an instrumented treadmill, were used in conjunction with pQCT measurements to estimate bone strength relative to load (mm 2 /N∗kg -1 ) at all cortical sites. SSIp and Zp were 9-11% lower in the SFX group at mid-shaft of the tibia, while ToA and vBMD did not differ between groups at any measurement site. The SFX group had 11-17% lower bone strength relative to mean pkZ GRFs (phistory of stress fracture. Bone strength relative to load is also lower in this same region suggesting that strength deficits in the middle 1/3 of the tibia and altered gait biomechanics may predispose an individual to stress fracture. Copyright © 2016. Published by Elsevier Inc.

  2. Influence of the supporting die structures on the fracture strength of all-ceramic materials.

    Science.gov (United States)

    Yucel, Munir Tolga; Yondem, Isa; Aykent, Filiz; Eraslan, Oğuz

    2012-08-01

    This study investigated the influence of the elastic modulus of supporting dies on the fracture strengths of all-ceramic materials used in dental crowns. Four different types of supporting die materials (dentin, epoxy resin, brass, and stainless steel) (24 per group) were prepared using a milling machine to simulate a mandibular molar all-ceramic core preparation. A total number of 96 zirconia cores were fabricated using a CAD/CAM system. The specimens were divided into two groups. In the first group, cores were cemented to substructures using a dual-cure resin cement. In the second group, cores were not cemented to the supporting dies. The specimens were loaded using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. Data were statistically analyzed using two-way analysis of variance and Tukey HSD tests (α = 0.05). The geometric models of cores and supporting die materials were developed using finite element method to obtain the stress distribution of the forces. Cemented groups showed statistically higher fracture strength values than non-cemented groups. While ceramic cores on stainless steel dies showed the highest fracture strength values, ceramic cores on dentin dies showed the lowest fracture strength values among the groups. The elastic modulus of the supporting die structure is a significant factor in determining the fracture resistance of all-ceramic crowns. Using supporting die structures that have a low elastic modulus may be suitable for fracture strength tests, in order to accurately reflect clinical conditions.

  3. Fracture toughness and strength change of neutron-irradiated ceramic materials

    International Nuclear Information System (INIS)

    Dienst, W.; Zimmermann, H.

    1994-01-01

    In order to analyse the results of bending strength measurements on neutron-irradiated samples of Al 2 O 3 , AlN and SiC, fracture toughness measurements were additionally conducted. The neutron fluences concerned were mostly in the range of 0.6 to 3.2x10 26 n/m 2 at irradiation temperatures of 400 to 550 C. A fracture toughness decrease was generally observed for polycrystalline materials which, however, was considerably smaller than the reduction of the fracture strength. Exceptional increase of the fracture toughness seems typical for the effect of rather coarse irradiation defects. The irradiation-induced change of the fracture toughness of single crystal Al 2 O 3 appeared dependent on the crystallographic orientation; both reduced and increased fracture toughness after irradiation was observed. Recent results of neutron irradiation to about 2x10 25 n/m 2 at 100 C showed, that the strength decrease of various Al 2 O 3 grades sets in at (3-5)x10 24 n/m 2 and seems to be little dependent on the irradiation temperature. ((orig.))

  4. The fracture strength by a torsion test at the implant-abutment interface.

    Science.gov (United States)

    Watanabe, Fumihiko; Hiroyasu, Kazuhiko; Ueda, Kazuhiko

    2015-12-01

    Fractured connections between implants and implant abutments or abutment screws are frequently encountered in a clinical setting. The purpose of this study was to investigate fracture strength using a torsion test at the interface between the implant and the abutment. Thirty screw-type implant with diameters of 3.3, 3.8, 4.3, 5.0, and 6.0 mm were submitted to a torsion test. Implants of each size were connected to abutments with abutment screws tightened to 20 N · cm. Mechanical stress was applied with a rotational speed of 3.6 °/min until fracture occurred, and maximum torque (fracture torque) and torsional yield strength were measured. The mean values were calculated and then compared using Tukey's test. The abutments were then removed, and the implant-abutment interfaces were examined using a scanning electron microscope (SEM). No significant differences in mean fracture torque were found among 3.3, 3.8, and 4.3 mm-diameter implants, but significant differences were found between these sizes and 5.0 and 6.0 mm-diameter implants (p abutment corresponding to the internal notches of the implant body had been destroyed. Smaller diameter implants demonstrated lower fracture torque and torsional yield strength than implants with larger diameters. In internal tube-in-tube connections, three abutment projections corresponding to rotation-prevention notches were destroyed in each implant.

  5. Mechanical strength and analysis of fracture of titanium joining submitted to laser and tig welding

    Directory of Open Access Journals (Sweden)

    Ana Cláudia Gabrielli Piveta

    2012-12-01

    Full Text Available This study compared the tensile strength and fracture mechanism of tungsten inert gas (TIG welds in cylindrical rods of commercially pure titanium (cp Ti with those of laser welds and intact samples. Thirty dumbbell-shaped samples were developed by using brass rods as patterns. The samples were invested in casings, subjected to thermal cycles, and positioned in a plasma arc welding machine under argon atmosphere and vacuum, and titanium was injected under vacuum/pressure. The samples were X-rayed to detect possible welding flaws and randomly assigned to three groups to test the tensile strength and the fracture mechanism: intact, laser welding, and TIG welding. The tensile test results were investigated using ANOVA, which indicated that the samples were statistically similar. The fracture analysis showed that the cpTi samples subjected to laser welding exhibited brittle fracture and those subjected to TIG welding exhibited mixed brittle/ductile fracture with a predominance of ductile fracture with the presence of microcavities and cleavage areas. Intact samples presented the characteristic straightening in the fracture areas, indicating the ductility of the material.

  6. Wet versus dry cement pastes and concretes: a mathematical approach to their strength and fracture properties

    International Nuclear Information System (INIS)

    Suarez Antola, R.

    2006-12-01

    The fracture process of a continuous matrix in a porous medium under the combined effect of filtration and external mechanical loads is considered. Taking into account the differences between the failure mechanisms of cement paste under tension and its failure mechanisms under compression, an analytical approach to the relation between water flow and fracture in saturated porous Portland cement pastes is developed. The well known differences in behaviour between the flexural and compressive strengths of wet and dry Portland cement pastes is explained. The extension of the obtained results to the flexural and compressive strength of normal concrete is briefly discussed, including suggestions for further experimental and digital simulation work

  7. Chemotherapy decreases epiphyseal strength and increases bone fracture risk

    NARCIS (Netherlands)

    Van Leeuwen, BL; Verkerke, GJ; Hartel, RM; Sluiter, WJ; Kamps, WA; Jansen, HWB; Hoekstra, HJ

    To establish the effect of three frequently used chemotherapeutic agents in childhood cancer on the skeleton, growing male Wistar rats were studied. Treatment with doxorubicin, methotrexate, and cisplatin reduces the proximal tibial growth plate shear strength because of a decreased surface area and

  8. Macro-mesoscopic Fracture and Strength Character of Pre-cracked Granite Under Stress Relaxation Condition

    Science.gov (United States)

    Liu, Junfeng; Yang, Haiqing; Xiao, Yang; Zhou, Xiaoping

    2018-05-01

    The fracture characters are important index to study the strength and deformation behavior of rock mass in rock engineering. In order to investigate the influencing mechanism of loading conditions on the strength and macro-mesoscopic fracture character of rock material, pre-cracked granite specimens are prepared to conduct a series of uniaxial compression experiments. For parts of the experiments, stress relaxation tests of different durations are also conducted during the uniaxial loading process. Furthermore, the stereomicroscope is adopted to observe the microstructure of the crack surfaces of the specimens. The experimental results indicate that the crack surfaces show several typical fracture characters in accordance with loading conditions. In detail, some cleavage fracture can be observed under conventional uniaxial compression and the fractured surface is relatively rough, whereas as stress relaxation tests are attached, relative slip trace appears between the crack faces and some shear fracture starts to come into being. Besides, the crack faces tend to become smoother and typical terrace structures can be observed in local areas. Combining the macroscopic failure pattern of the specimens, it can be deduced that the duration time for the stress relaxation test contributes to the improvement of the elastic-plastic strain range as well as the axial peak strength for the studied material. Moreover, the derived conclusion is also consistent with the experimental and analytical solution for the pre-peak stage of the rock material. The present work may provide some primary understanding about the strength character and fracture mechanism of hard rock under different engineering environments.

  9. Fracture strength and fatigue resistance of dental resin-based composites

    NARCIS (Netherlands)

    Keulemans, F.; Palav, P.; Aboushelib, M.M.N.; van Dalen, A.; Kleverlaan, C.J.; Feilzer, A.J.

    2009-01-01

    Objectives: The aim of this study was to evaluate in vitro the influence of fiber-reinforcement on the fracture strength and fatigue resistance of resin-based composites. Methods: One hundred rectangular bar-shaped specimens (2 mm × 2 mm × 25 mm) made of resin-based composite were prepared in a

  10. Strategies for fracture toughness, strength and reliability optimisation of ceramic-ceramic laminates

    Czech Academy of Sciences Publication Activity Database

    Šestáková, L.; Bermejo, R.; Chlup, Zdeněk; Danzer, R.

    2011-01-01

    Roč. 102, č. 6 (2011), s. 613-626 ISSN 1862-5282 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ceramic laminates * Layered ceramics * Residual stress * Fracture toughness * Threshold strength Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.830, year: 2011

  11. Effect of Ultrasonic Versus Manual Cementation on the Fracture Strength of Resin Composite Laminates

    NARCIS (Netherlands)

    Ozcan, M.; Mese, A.

    2009-01-01

    This study evaluated the effect of conventional versus ultrasonic cementation techniques on the fracture strength of resin composite laminates. In addition, the failure modes were assessed. Window-type preparations I mm above the cemento-enamel junction were made on intact human maxillary central

  12. Defect enhanced diffusion process and hydrogen delayed fracture in high strength steels

    International Nuclear Information System (INIS)

    Lung, C.W.; Mu Zaiqin.

    1985-10-01

    A defect enhanced diffusion model for hydrogen delayed fracture in high strength steels is suggested. It is shown that the rate of crack growth is dependent on the square or higher power of the stress intensity factor which is consistent with recent experiments. (author)

  13. Challenges of Estimating Fracture Risk with DXA: Changing Concepts About Bone Strength and Bone Density.

    Science.gov (United States)

    Licata, Angelo A

    2015-07-01

    Bone loss due to weightlessness is a significant concern for astronauts' mission safety and health upon return to Earth. This problem is monitored with bone densitometry (DXA), the clinical tool used to assess skeletal strength. DXA has served clinicians well in assessing fracture risk and has been particularly useful in diagnosing osteoporosis in the elderly postmenopausal population for which it was originally developed. Over the past 1-2 decades, however, paradoxical and contradictory findings have emerged when this technology was widely employed in caring for diverse populations unlike those for which it was developed. Although DXA was originally considered the surrogate marker for bone strength, it is now considered one part of a constellation of factors-described collectively as bone quality-that makes bone strong and resists fracturing, independent of bone density. These characteristics are beyond the capability of routine DXA to identify, and as a result, DXA can be a poor prognosticator of bone health in many clinical scenarios. New clinical tools are emerging to make measurement of bone strength more accurate. This article reviews the historical timeline of bone density measurement (dual X-ray absorptiometry), expands upon the clinical observations that modified the relationship of DXA and bone strength, discusses some of the new clinical tools to predict fracture risk, and highlights the challenges DXA poses in the assessment of fracture risk in astronauts.

  14. Lower-limb pain, disease, and injury burden as determinants of muscle strength deficit after hip fracture

    NARCIS (Netherlands)

    Portegijs, Erja; Rantanen, Taina; Kallinen, Mauri; Heinonen, Ari; Alen, Markku; Kiviranta, Ilkka; Sipilä, Sarianna

    2009-01-01

    BACKGROUND: Hip fracture may result in an asymmetrical lower-limb strength deficit. The deficit may be related to the trauma, surgical treatment, pain, or disuse of the fractured limb. However, disease and injury burden or musculoskeletal pain in the other limb may reduce muscle strength on that

  15. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    Directory of Open Access Journals (Sweden)

    Deborah Pacheco Lameira

    2015-01-01

    Full Text Available The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP crowns in monolithic (1.5 mm thickness and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n=10: Polished monolithic zirconia crowns (PM; Glazed monolithic zirconia crowns (GM; Bi-layer crowns (BL. Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37°C, and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey’s test (P=.05 indicated that monolithic zirconia crowns presented similar fracture strength (PM=3476.2 N ± 791.7; GM=3561.5 N ± 991.6, which was higher than bilayer crowns (2060.4 N ± 810.6. There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength.

  16. Dynamic plantar pressure distribution, strength capacity and postural control after Lisfranc fracture-dislocation

    DEFF Research Database (Denmark)

    Mehlhorn, Alexander T; Walther, Markus; Yilmaz, Tayfun

    2017-01-01

    of life. 17 consecutive patients suffering from a Lisfranc fracture dislocation were registered, underwent open reduction and internal fixation and were followed-up for 50.5±25.7months (Mean±SDM). Biomechanical analysis of muscle strength capacities, postural control and plantar pressure distribution......Substantial progress has been made in the operative treatment of Lisfranc fractures, however, the prognosis remains poor. We hypothesized that Lisfranc injuries change the postural control and muscle strength of the lower limb. Both are suggested to correlate with the clinical outcome and quality...... correlated well with clinical outcome. Altered postural control was evident by a significant reduction in unilateral stance time, from which we calculated a strong correlation between stance time and the isokinetic strength measurement. Plantar pressure measurements revealed a significant reduction in peak...

  17. Improved magnetic properties and fracture strength of NdFeB by dehydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, M. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)]. E-mail: mse_yanmi@dial.zju.edu.cn; Yu, L.Q. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Wu, J.M. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Cui, X.G. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)

    2006-11-15

    Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process.

  18. Improved magnetic properties and fracture strength of NdFeB by dehydrogenation

    International Nuclear Information System (INIS)

    Yan, M.; Yu, L.Q.; Wu, J.M.; Cui, X.G.

    2006-01-01

    Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process

  19. Influence of Fracture Width on Sealability in High-Strength and Ultra-Low-Permeability Concrete in Seawater

    OpenAIRE

    Fukuda, Daisuke; Nara, Yoshitaka; Hayashi, Daisuke; Ogawa, Hideo; Kaneko, Katsuhiko

    2013-01-01

    For cementitious composites and materials, the sealing of fractures can occur in water by the precipitation of calcium compounds. In this study, the sealing behavior in a macro-fractured high-strength and ultra-low-permeability concrete (HSULPC) specimen was investigated in simulated seawater using micro-focus X-ray computed tomography (CT). In particular, the influence of fracture width (0.10 and 0.25 mm) on fracture sealing was investigated. Precipitation occurred mainly at the outermost pa...

  20. Fracture Surface Morphology and Impact Strength of Cellulose/PLA Composites.

    Science.gov (United States)

    Gao, Honghong; Qiang, Tao

    2017-06-07

    Polylactide (PLA)-based composite materials reinforced with ball-milled celluloses were manufactured by extrusion blending followed by injection molding. Their surface morphology from impact fracture were imaged with scanning electron microscopy (SEM) and investigated by calculating their fractal dimensions. Then, linear regression was used to explore the relationship between fractal dimension and impact strength of the resultant cellulose/PLA composite materials. The results show that filling the ball-milled celluloses into PLA can improve the impact toughness of PLA by a minimum of 38%. It was demonstrated that the fracture pattern of the cellulose/PLA composite materials is different from that of pristine PLA. For the resultant composite materials, the fractal dimension of the impact fractured surfaces increased with increasing filling content and decreasing particle size of the ball-milled cellulose particles. There were highly positive correlations between fractal dimension of the fractured surfaces and impact strength of the cellulose/PLA composites. However, the linearity between fractal dimension and impact strength were different for the different methods, due to their different R-squared values. The approach presented in this work will help to understand the structure-property relationships of composite materials from a new perspective.

  1. Fracture strengths of chair-side-generated veneers cemented with glass fibers.

    Science.gov (United States)

    Turkaslan, S; Bagis, B; Akan, E; Mutluay, M M; Vallittu, P K

    2015-01-01

    CAD/CAM (computer-aided design and computer-aided manufacturing) systems have refreshed the idea of chair-side production of restorations, but the fracture of ceramic veneers remains a problem. Cementation with glass fibers may improve the fracture strengths and affect the failure modes of CAD/CAM-generated ceramic veneers. Therefore, this study compared the fracture strengths of ceramic veneers produced at chair side and cemented with or without glass fibers with those of composite veneers. Thirty intact mandibular incisors were randomly divided into three groups ( n = 10) and treated with CAD/CAM-fabricated veneers cemented with dual-cure composite resin luting cement (CRLC; Group 1), CAD/CAM-fabricated veneers cemented with a glass fiber network (GFN) and dual-cure CRLC (Group 2), and a direct particulate filler composite veneer constructed utilizing fiber and a restorative composite resin (Group 3). The specimens were tested with a universal testing machine after thermal cycling treatment. The loads at the start of fracture were the lowest for traditionally fabricated composite veneers and higher for CAD/CAM-generated. Veneers cemented either without or with the GFN. The failure initiation loads (N) for the veneers were 798.92 for Group 1, 836.27 for Group 2, and 585.93 for Group 3. The predominant failure mode is adhesive failure between the laminates and teeth for Group 1, cohesive failure in the luting layer for Group 2, and cohesive laminate failure for Group 3, which showed chipping and small fractures. Ceramic material is a reliable alternative for veneer construction at chair side. Fibers at the cementation interface may improve the clinical longevity and provide higher fracture strength values.

  2. Effectiveness of acute in-hospital physiotherapy with knee-extension strength training in reducing strength deficits in patients with a hip fracture

    DEFF Research Database (Denmark)

    Kronborg, Lise; Bandholm, Thomas; Palm, Henrik

    2017-01-01

    QUESTION: Is acute in-hospital physiotherapy with additional progressive knee-extension strength training (ST) of the fractured limb more effective in reducing knee-extension strength deficit at follow-up compared to physiotherapy without strength training in patients with a hip fracture? DESIGN......: Assessor blinded, randomised controlled trial with intention-to-treat analysis. PARTICIPANTS: 90 patients with a hip fracture admitted to an acute orthopaedic Hip Fracture Unit at a university hospital between October 2013 and May 2015. INTERVENTION: Daily physiotherapy with or without progressive knee...... strength training from baseline to follow-up. In the per-protocol analysis of non-missing data, significant between-group improvements by 10.5% (95% CI 0.3; 20.7) were found in favour of additional ST. No significant between-group differences were found in any secondary outcome. CONCLUSION: Physiotherapy...

  3. Lower-limb pain, disease and injury burden as determinants of muscle strength deficit after hip fracture

    OpenAIRE

    Portegijs, Erja; Rantanen, Taina; Kallinen, Mauri; Heinonen, Ari; Alén, Markku; Kiviranta, Ilkka; Sipilä, Sarianna

    2009-01-01

    Background: Hip fracture may result in an asymmetrical lower-limb strength deficit. The deficit may be related to the trauma, surgical treatment, pain, or disuse of the fractured limb. However, disease and injury burden or musculoskeletal pain in the other limb may reduce muscle strength on that side, reducing the asymmetrical deficit. Our study aim was to explore the asymmetrical strength deficit and to determine potential underlying factors in persons 6 months to 7 years afte...

  4. Bone strength and muscle properties in postmenopausal women with and without a recent distal radius fracture.

    Science.gov (United States)

    Crockett, K; Arnold, C M; Farthing, J P; Chilibeck, P D; Johnston, J D; Bath, B; Baxter-Jones, A D G; Kontulainen, S A

    2015-10-01

    Distal radius (wrist) fracture (DRF) in women over age 50 years is an early sign of bone fragility. Women with a recent DRF compared to women without DRF demonstrated lower bone strength, muscle density, and strength, but no difference in dual-energy x-ray absorptiometry (DXA) measures, suggesting DXA alone may not be a sufficient predictor for DRF risk. The objective of this study was to investigate differences in bone and muscle properties between women with and without a recent DRF. One hundred sixty-six postmenopausal women (50-78 years) were recruited. Participants were excluded if they had taken bone-altering medications in the past 6 months or had medical conditions that severely affected daily living or the upper extremity. Seventy-seven age-matched women with a fracture in the past 6-24 months (Fx, n = 32) and without fracture (NFx, n = 45) were measured for bone and muscle properties using the nondominant (NFx) or non-fractured limb (Fx). Peripheral quantitative computed tomography (pQCT) was used to estimate bone strength in compression (BSIc) at the distal radius and tibia, bone strength in torsion (SSIp) at the shaft sites, muscle density, and area at the forearm and lower leg. Areal bone mineral density at the ultradistal forearm, spine, and femoral neck was measured by DXA. Grip strength and the 30-s chair stand test were used as estimates of upper and lower extremity muscle strength. Limb-specific between-group differences were compared using multivariate analysis of variance (MANOVA). There was a significant group difference (p lower leg, with the Fx group demonstrating 16 and 19% lower BSIc, 3 and 6% lower muscle density, and 20 and 21% lower muscle strength at the upper and lower extremities, respectively. There were no differences between groups for DXA measures. Women with recent DRF had lower pQCT-derived estimated bone strength at the distal radius and tibia and lower muscle density and strength at both extremities.

  5. Cross-education for improving strength and mobility after distal radius fractures: a randomized controlled trial.

    Science.gov (United States)

    Magnus, Charlene R A; Arnold, Cathy M; Johnston, Geoffrey; Dal-Bello Haas, Vanina; Basran, Jenny; Krentz, Joel R; Farthing, Jonathan P

    2013-07-01

    To evaluate the effects of cross-education (contralateral effect of unilateral strength training) during recovery from unilateral distal radius fractures on muscle strength, range of motion (ROM), and function. Randomized controlled trial (26-wk follow-up). Hospital, orthopedic fracture clinic. Women older than 50 years with a unilateral distal radius fracture. Fifty-one participants were randomized and 39 participants were included in the final data analysis. Participants were randomized to standard rehabilitation (Control) or standard rehabilitation plus strength training (Train). Standard rehabilitation included forearm casting for 40.4±6.2 days and hand exercises for the fractured extremity. Nonfractured hand strength training for the training group began immediately postfracture and was conducted at home 3 times/week for 26 weeks. The primary outcome measure was peak force (handgrip dynamometer). Secondary outcomes were ROM (flexion/extension; supination/pronation) via goniometer and the Patient Rated Wrist Evaluation questionnaire score for the fractured arm. For the fractured hand, the training group (17.3±7.4kg) was significantly stronger than the control group (11.8±5.8kg) at 12 weeks postfracture (P<.017). There were no significant strength differences between the training and control groups at 9 (12.5±8.2kg; 11.3±6.9kg) or 26 weeks (23.0±7.6kg; 19.6±5.5kg) postfracture, respectively. Fractured hand ROM showed that the training group had significantly improved wrist flexion/extension (100.5°±19.2°) than the control group (80.2°±18.7°) at 12 weeks postfracture (P<.017). There were no significant differences between the training and control groups for flexion/extension ROM at 9 (78.0°±20.7°; 81.7°±25.7°) or 26 weeks (104.4°±15.5°; 106.0°±26.5°) or supination/pronation ROM at 9 (153.9°±23.9°; 151.8°±33.0°), 12 (170.9°±9.3°; 156.7°±20.8°) or 26 weeks (169.4°±11.9°; 162.8°±18.1°), respectively. There were no

  6. The Evolution of Plate and Extruded Products with High Strength and Fracture Toughness

    Science.gov (United States)

    Denzer, D. K.; Rioja, R. J.; Bray, G. H.; Venema, G. B.; Colvin, E. L.

    From the first use of 2017-T74 on the Junkers F13, improvements have been made to plate and extruded products for applications requiring the highest attainable strength and adequate fracture toughness. One such application is the upper wing of large aircraft. The progression of these product improvements achieved through the development of alloys that include 7075-(T6 & T76), 7150-(T6 & T77) and 7055-(T77 & T79) and most recently 7255-(T77 & T79) is reviewed. The most current advancements include aluminum-copper-lithium, alloy 2055 plate and extruded products that can attain strength equivalent to that of 7055-T77 with higher modulus, similar fracture toughness and improved fatigue, fatigue crack growth and corrosion performance. The achievement of these properties is explained in terms of the several alloy design principles. The highly desired and balanced characteristics make these products ideal for upper wing applications.

  7. Fracture properties of high-strength concrete obtained by direct modification of structure

    Directory of Open Access Journals (Sweden)

    Solodkyy Serhiy

    2017-01-01

    Full Text Available High-strength concrete is effectively used worldwide in the last three decades, but it is more brittle in comparison with normal strength concretes. Partial substitution of cement in concrete by active mineral additives and usage of chemical admixture of plasticizing and air-entraining action can considerably change their fracture properties. The obtained results show that the increase of the fracture properties is observed in concretes modified with chemical admixtures incorporating mineral additives such as zeolite and limestone due to consolidation of the concrete microstructure. Densification takes place as a result of limiting the amount of calcium hydroxide (CH due to its reaction with active silica included in the zeolite and the formation of larger amounts of hydrated calcium silicates of tobermorite type as well as calcium hydroaluminate and hydrocarboaluminate with the simultaneous adsorption modification of hydrated products by chemical admixtures.

  8. Dynamic strength, particle deformation, and fracture within fluids with impact-activated microstructures

    Science.gov (United States)

    Petel, Oren E.; Ouellet, Simon

    2017-07-01

    The evolution of material strength within several dense particle suspensions impacted by a projectile is investigated and shown to be strongly dependent on the particle material in suspension. For stronger particles, such as silicon carbide, the shear strength of the fluid is shown to increase with the ballistic impact strength. For weaker particles, such as silica, the shear strength of the suspension is found to be independent of impact strength in this dynamic range of tests. A soft-capture technique is employed to collect ejecta samples of a silica-based shear thickening fluid, following a ballistic impact and penetration event. Ejecta samples that were collected from impacts at three different velocities are observed and compared to the benchmark particles using a Scanning Electron Microscope. The images show evidence of fractured and deformed silica particles recovered among the nominally 1 μm diameter monodisperse spheres. There is also evidence of particle fragments that appear to be the result of interparticle grinding. The trends observed in the shear strength estimates are interpreted with regards to the particle damage seen in the ejecta recovery experiments to develop a concept of the impact response of these fluids. The results suggest that particle slip through deformation is likely the dominant factor in limiting the transient impact strength of these fluids. Particularly, particle strength is important in the formation and collapse of dynamically jammed particle contact networks in the penetration process.

  9. Fatigue Fracture Strength of Implant-Supported Full Contour Zirconia and Metal Ceramic Fixed Partial Dentures

    Directory of Open Access Journals (Sweden)

    Fariborz Vafaee

    2017-10-01

    Full Text Available Objectives: Zirconia restorations have been suggested as a more durable and more appealing alternative to metal restorations. However, their mechanical properties may be negatively affected by fatigue due to superficial stresses or low temperature degradation. This study aimed to assess the fatigue fracture strength of three-unit implant-supported full contour zirconia and pre-sintered cobalt-chromium (Co-Cr alloy posterior fixed partial dentures (FPDs.Materials and Methods: In this in-vitro experimental study, 28 posterior three-unit implant-supported FPDs were fabricated of full contour zirconia and pre-sintered Co-Cr alloy, and were cemented on implant abutments. To simulate the oral environment, FPDs were subjected to 10,000 thermal cycles between 5-55°C for 30 seconds, and were then transferred to a chewing simulator (100,000 cycles, 50 N, 0.5 Hz. Afterwards, fatigue fracture strength was measured using a universal testing machine. Data were analyzed by Mann-Whitney U test.Results: The mean and standard deviation of fracture strength were 2108.6±440.1 N in full contour zirconia, and 3499.9±1106.5 N in pre-sintered Co-Cr alloy. According to Mann- Whitney U test, the difference in this respect was statistically significant between the two groups (P=0.007.Conclusions: Since the fracture strength values obtained in the two groups were significantly higher than the maximum mean masticatory load in the oral environment, both materials can be used for fabrication of posterior three-unit FPDs, depending on the esthetic demands of patients.

  10. Healing of shear strength and its time dependency in a single rock fracture

    International Nuclear Information System (INIS)

    Kawaguchi, Yuta; Nakashima, Shinichiro; Yasuhara, Hideaki; Kishida, Kiyoshi

    2011-01-01

    Evolution of the long-term mechanical, hydraulic, and transport characteristics of rock fractures should be, in advance, predicted in considering an issue on entombment of energy byproducts of high level radioactive wastes. Under stressed and temperature conditions, those behaviors of the rock fractures of interest may be evolved in time and space likely due to the change in topographical aperture distributions. This irreversible process may be induced by pure mechanical and/or chemo-mechanical creeps such as water-rock reactions like stress corrosion and pressure solution, and chemical effects including mineral dissolution and reprecipitation in the free-walls of fractures. Specifically, the chemo-mechanical processes active at the contacting asperities within rock fractures may exert a significant influence on the mechanical, hydraulic, and transport behaviors throughout a long period, and thus, should be vigorously examined theoretically and experimentally. This paper presents the slide-hold-slide shear test results for fully saturated, single-jointed mortar specimens so as to investigate the effects of load holding on mechanical properties of rock joints. From the test results, it was confirmed that shear strength increased for mortar specimens in both short and long time holding cases. However, the evolution of shear strength recovery in two cases is different. This is because a dominant factor of shear strength recovery during the short time holding may be attributed to a pure mechanical process like creep deformation at contacting asperities, while the one during long time holding is affected by both mechanical and chemical processes like pressure solution. Moreover, to reproduce the shear strength recovery during short time holding we develop a direct shear model by including temporal variation of dilation during holding. The model predictions are in relatively good agreement with the test measurements. (author)

  11. Fracture toughness of welded joints of a high strength low alloy steel

    International Nuclear Information System (INIS)

    Veiga, S.M.B. da; Bastian, F.L.; Pope, A.M.

    1985-10-01

    The fracture toughness of the different regions of welded joints of a high strength low alloy steel, Niocor 2, was evaluated at different temperatures and compared with the toughness of the base metal. The studied regions were: the weld metal, fusion boundary and heat affected zone. The welding process used was the manual metal arc. It is shown that the weld metal region has the highest toughness values. (Author) [pt

  12. "Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

    Science.gov (United States)

    Choi, Sung R.; Gyekenyesi, John P.

    1999-01-01

    The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated

  13. Examination of Relationship Between Photonic Signatures and Fracture Strength of Fused Silica Used in Orbiter Windows

    Science.gov (United States)

    Yost, William T.; Cramer, K. Elliott; Estes, Linda R.; Salem, Jonathan A.; Lankford, James, Jr.; Lesniak, Jon

    2011-01-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outermost pane of the orbiter windows. Four categories of damage: hyper-velocity impacts that occur during space-flight (HVI); hypervelocity impacts artificially made at the Hypervelocity Impact Technology Facility (HIT-F); impacts made by larger objects falling onto the pane surface to simulate dropped items on the window during service/storage of vehicle (Bruises); and light scratches from dull objects designed to mimic those that might occur by dragging a dull object across the glass surface (Chatter Checks) are examined. The damage sites are cored from fused silica window carcasses, examined with the GFP and other methodologies, and broken using the ASTM Standard C1499-09 to measure the fracture strength. A correlation is made between the fracture strength and damage-site measurements including geometrical measurements and GFP measurements of photoelastic retardation (stress patterns) surrounding the damage sites. An analytical damage model to predict fracture strength from photoelastic retardation measurements is presented and compared with experimental results.

  14. Stiffness and strength properties of natural fractures from north ramp drill holes

    International Nuclear Information System (INIS)

    Olsson, W.A.; Price, R.H.; Brown, S.R.

    1994-01-01

    Cores containing natural fractures were obtained from drillholes UE 25 NRG-4 and USW NRG-6 at Yucca Mountain, Nevada. Seven selected fractures were sheared at constant normal stress, either 5 or 10 MPa, in the air-dry condition. Detailed profilometer data were collected from each fracture surface before testing. The tests yielded the normal closure as a function of normal stress, and the shear stress and dilation as a function of shear offset. The constitutive properties resulting from the measurements were: normal stiffness, shear stiffness, shear strength and coefficient of friction, and dilation. Peak friction ranged from 0.89 to 1.11; residual friction ranged from 0.76 to 1.00. The lowest initial dilation angle was found to be 5.29 degrees and the highest was 11.28 degrees. The roughness characteristics of the fracture surfaces agree qualitatively with the simple mathematical model of Brown (1994) derived from fracture data in many other rock types

  15. Effect of hot extrusion, other constituents, and temperature on the strength and fracture of polycrystalline MgO

    Energy Technology Data Exchange (ETDEWEB)

    Rice, R.W. (W.R. Grace and Co.-Conn, Columbia, MD (United States))

    1993-12-01

    Improved agreement was confirmed between the Petch intercept and single-crystal yield stresses at 22 C. Hot-extruded MgO crystal specimens stressed parallel with the resultant axial texture (1) gave the highest and least-scattered strength-grain size results at 22 C, (2) showed direct fractographic evidence of microplastic initiated fracture at 22 C and showed macroscopic yield at 1,315 and especially 1,540 C, and (3) fractured entirely via transgranular cleavage, except for intergranular failure initiation from one or a few grain boundary surfaces exposed on the subsequent fracture surface, mainly at 1,540 C. Hot-extruded, hot-pressed MgO billets gave comparable strength when fracture initiated transgranularly, but lower strength when fracture initiated from one or especially a few grain boundary surfaces exposed on the fracture. The extent and frequency of such boundary fracture increased with test temperature. While oxide additions of [<=] 5% or impurities in hot-pressed or hot-extruded MgO can make limited strength increases at larger grain sizes, those having limited solubility can limit strength at finer grain sizes, as can coarser surface finish. Overall, MgO strength is seen as a balance between flaw and microplastic controlled failure, with several parameters shifting the balance.

  16. Influence of Fracture Width on Sealability in High-Strength and Ultra-Low-Permeability Concrete in Seawater

    Directory of Open Access Journals (Sweden)

    Katsuhiko Kaneko

    2013-06-01

    Full Text Available For cementitious composites and materials, the sealing of fractures can occur in water by the precipitation of calcium compounds. In this study, the sealing behavior in a macro-fractured high-strength and ultra-low-permeability concrete (HSULPC specimen was investigated in simulated seawater using micro-focus X-ray computed tomography (CT. In particular, the influence of fracture width (0.10 and 0.25 mm on fracture sealing was investigated. Precipitation occurred mainly at the outermost parts of the fractured surface of the specimen for both fracture widths. While significant sealing was observed for the fracture width of 0.10 mm, sealing was not attained for the fracture width of 0.25 mm within the observation period (49 days. Examination of the sealed regions on the macro-fracture was performed using a three-dimensional image registration technique and applying image subtraction between the CT images of the HSULPC specimen before and after maintaining the specimen in simulated seawater. The temporal change of the sealing deposits for the fracture width of 0.10 mm was much larger than that for the fracture width of 0.25 mm. Therefore, it is concluded that the sealability of the fracture in the HSULPC is affected by the fracture width.

  17. Influence of Fracture Width on Sealability in High-Strength and Ultra-Low-Permeability Concrete in Seawater.

    Science.gov (United States)

    Fukuda, Daisuke; Nara, Yoshitaka; Hayashi, Daisuke; Ogawa, Hideo; Kaneko, Katsuhiko

    2013-06-25

    For cementitious composites and materials, the sealing of fractures can occur in water by the precipitation of calcium compounds. In this study, the sealing behavior in a macro-fractured high-strength and ultra-low-permeability concrete (HSULPC) specimen was investigated in simulated seawater using micro-focus X-ray computed tomography (CT). In particular, the influence of fracture width (0.10 and 0.25 mm) on fracture sealing was investigated. Precipitation occurred mainly at the outermost parts of the fractured surface of the specimen for both fracture widths. While significant sealing was observed for the fracture width of 0.10 mm, sealing was not attained for the fracture width of 0.25 mm within the observation period (49 days). Examination of the sealed regions on the macro-fracture was performed using a three-dimensional image registration technique and applying image subtraction between the CT images of the HSULPC specimen before and after maintaining the specimen in simulated seawater. The temporal change of the sealing deposits for the fracture width of 0.10 mm was much larger than that for the fracture width of 0.25 mm. Therefore, it is concluded that the sealability of the fracture in the HSULPC is affected by the fracture width.

  18. Effectiveness of acute in-hospital physiotherapy with knee-extension strength training in reducing strength deficits in patients with a hip fracture: A randomised controlled trial.

    Directory of Open Access Journals (Sweden)

    Lise Kronborg

    Full Text Available Is acute in-hospital physiotherapy with additional progressive knee-extension strength training (ST of the fractured limb more effective in reducing knee-extension strength deficit at follow-up compared to physiotherapy without strength training in patients with a hip fracture?Assessor blinded, randomised controlled trial with intention-to-treat analysis.90 patients with a hip fracture admitted to an acute orthopaedic Hip Fracture Unit at a university hospital between October 2013 and May 2015.Daily physiotherapy with or without progressive knee-extension strength training (10RM, 3 x 10 repetitions, of the fractured limb using ankle weight cuffs conducted by ward physical therapists during hospital stay.Primary outcome was the change in maximal isometric knee-extension strength in the fractured limb in percentage of the non-fractured limb from inclusion to postoperative day 10 or discharge (follow-up. Secondary outcome was Timed Up and Go test measured early after surgery and at follow-up.In the intention-to-treat analysis of between-group differences, the primary outcome improved 8.1% (95% CI -2.3; 18.4 by additional strength training from baseline to follow-up. In the per-protocol analysis of non-missing data, significant between-group improvements by 10.5% (95% CI 0.3; 20.7 were found in favour of additional ST. No significant between-group differences were found in any secondary outcome.Physiotherapy with addition of 5 sessions of ST yielded no additional improvements compared to physiotherapy without strength training in reducing the knee-extension strength deficit at follow-up in patients with a hip fracture. It is debatable whether larger improvements than the observed 8-10% can be expected given that only five exercise sessions, on average, were completed. In fragile patients with a hip fracture in the acute phase, where the ability to participate in functional exercise is compromised, we still consider early strength training a

  19. Strength of titanium intramedullary implant versus miniplate fixation of mandibular condyle fractures.

    Science.gov (United States)

    Frake, Paul C; Howell, Rebecca J; Joshi, Arjun S

    2012-07-01

    To test the strength of internal fixation of mandibular condyle fractures repaired with titanium miniplates versus titanium intramedullary implants. Prospective laboratory experimentation in urethane mandible models and human cadaveric mandibles. Materials testing laboratory at an academic medical center. Osteotomies of the mandibular condyle were created in 40 urethane hemimandible models and 24 human cadaveric specimens. Half of the samples in each group were repaired with traditional miniplates, and the other half were repaired with intramedullary titanium implants. Anteroposterior and mediolateral loads were applied to the samples, and the displacement was measured with reference to the applied force. Titanium intramedullary implants demonstrated statistically significant improved strength and stiffness versus miniplates in the urethane model experimental groups. Despite frequent plastic deformation and mechanical failures of the miniplates, a 1.6-mm-diameter titanium intramedullary pin did not mechanically fail in any of the cases. Intramedullary implantation failures were due to secondary fracture of the adjacent cortical bone or experimental design limitations including rotation of the smooth pin implant. Mechanical implant failures that were encountered with miniplate fixation were not seen with titanium intramedullary implants. These intramedullary implants provide stronger and more rigid fixation of mandibular condyle fractures than miniplates in this in vitro model.

  20. Influence of Cyclic Straining on Fatigue, Deformation, and Fracture Behavior of High-Strength Alloy Steel

    Science.gov (United States)

    Manigandan, K.; Srivatsan, T. S.; Vasudevan, V. K.; Tammana, D.; Poorganji, B.

    2016-01-01

    In this paper, the results of a study on microstructural influences on mechanical behavior of the high-strength alloy steel Tenax™ 310 are presented and discussed. Under the influence of fully reversed strain cycling, the stress response of this alloy steel revealed softening from the onset of deformation. Cyclic strain resistance exhibited a linear trend for the variation of both elastic strain amplitude with reversals-to-failure, and plastic strain amplitude with reversals-to-failure. Fracture morphology was essentially the same at the macroscopic level over the entire range of cyclic strain amplitudes examined. However, at the fine microscopic level, this high-strength alloy steel revealed fracture to be mixed-mode with features reminiscent of "locally" ductile and brittle mechanisms. The macroscopic mechanisms governing stress response at the fine microscopic level, resultant fatigue life, and final fracture behavior are presented and discussed in light of the mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents during fully reversed strain cycling, cyclic strain amplitude, and resultant response stress.

  1. Effects of consolidation temperature, strength and microstructure on fracture toughness of nanostructured ferritic alloys

    International Nuclear Information System (INIS)

    Miao, P.; Odette, G.R.; Yamamoto, T.; Alinger, M.; Hoelzer, D.; Gragg, D.

    2007-01-01

    Fully consolidated nanostructured ferritic alloys (NFAs) were prepared by attritor milling pre-alloyed Fe-14Cr-3W-0.4Ti and 0.3 wt% Y 2 O 3 powders, followed by hot isostatic pressing (HIPing) at 1000 o C or 1150 o C at 200 MPa for 4 h. Transmission electron microscopy (TEM) revealed similar bimodal distributions of fine and coarse ferrite grains in both cases. However, as expected, the alloy microhardness decreased with increasing in HIPing temperature. Three point bend tests on single edge notched specimens, with a nominal root radius ρ = 0.15 mm, were used to measure the notch fracture toughness, K ρ , as a function of test temperature. The K ρ curves were found to be similar for both processing conditions. It appears that the coarser ferrite grains control cleavage fracture, in a way that is independent of alloy strength and HIPing temperature

  2. Evaluation of susceptibility of high strength steels to delayed fracture by using cyclic corrosion test and slow strain rate test

    International Nuclear Information System (INIS)

    Li Songjie; Zhang Zuogui; Akiyama, Eiji; Tsuzaki, Kaneaki; Zhang Boping

    2010-01-01

    To evaluate susceptibilities of high strength steels to delayed fracture, slow strain rate tests (SSRT) of notched bar specimens of AISI 4135 with tensile strengths of 1300 and 1500 MPa and boron-bearing steel with 1300 MPa have been performed after cyclic corrosion test (CCT). During SSRT the humidity around the specimen was kept high to keep absorbed diffusible hydrogen. The fracture stresses of AISI 4135 steels decreased with increment of diffusible hydrogen content which increased with CCT cycles. Their delayed fracture susceptibilities could be successfully evaluated in consideration of both influence of hydrogen content on mechanical property and hydrogen entry.

  3. Evaluation of susceptibility of high strength steels to delayed fracture by using cyclic corrosion test and slow strain rate test

    Energy Technology Data Exchange (ETDEWEB)

    Li Songjie [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Hidian Zone, Beijing 100083 (China); Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Zhang Zuogui [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Akiyama, Eiji [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)], E-mail: AKIYAMA.Eiji@nims.go.jp; Tsuzaki, Kaneaki [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Zhang Boping [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Hidian Zone, Beijing 100083 (China)

    2010-05-15

    To evaluate susceptibilities of high strength steels to delayed fracture, slow strain rate tests (SSRT) of notched bar specimens of AISI 4135 with tensile strengths of 1300 and 1500 MPa and boron-bearing steel with 1300 MPa have been performed after cyclic corrosion test (CCT). During SSRT the humidity around the specimen was kept high to keep absorbed diffusible hydrogen. The fracture stresses of AISI 4135 steels decreased with increment of diffusible hydrogen content which increased with CCT cycles. Their delayed fracture susceptibilities could be successfully evaluated in consideration of both influence of hydrogen content on mechanical property and hydrogen entry.

  4. Fracture strength of flared bovine roots restored with different intraradicular posts

    Directory of Open Access Journals (Sweden)

    Victor Grover Rene Clavijo

    2009-12-01

    Full Text Available OBJECTIVE: The aim of this study was to evaluate the fracture strength and failure mode of flared bovine roots restored with different intraradicular posts. MATERIAL AND METHODS: Fifty bovine incisors with similar dimensions were selected and their roots were flared until 1.0 mm of dentin wall remained. Next, the roots were allocated into five groups (n=10: GI- cast metal post-and-core; GII- fiber posts plus accessory fiber posts; GIII- direct anatomic post; GIV- indirect anatomic post and GV- control (specimens without intraradicular post. A polyether impression material was used to simulate the periodontal ligament. After periodontal ligament simulation, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min in a servo-hydraulic testing machine (MTS 810 applied at 135º to the long axis of the tooth until failure. The data (N were subjected to ANOVA and Tukey's post-hoc test (α=0.05. RESULTS: GI and GIV presented higher fracture strength (p0.05 from GI, GII and GIV. Control specimens (GV produced the lowest fracture strength mean values (p<0.05. Despite obtaining the highest mean value, GI presented 100% of unfavorable failures. GII presented 20% of unfavorable failures. GIII, GIV and GV presented only favorable failures. CONCLUSIONS: Although further in vitro and in vivo studies are necessary, the results of this study showed that the use of direct and indirect anatomic posts in flared roots could be an alternative to cast metal post-and-core.

  5. Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

    Directory of Open Access Journals (Sweden)

    Kai Lu

    2016-05-01

    Full Text Available In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of fibers in specimens of the fiber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

  6. Effect of microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels

    International Nuclear Information System (INIS)

    Im, Young-Roc; Lee, Byeong-Joo; Oh, Yong Jun; Hong, Jun Hwa; Lee, Hu-Chul

    2004-01-01

    The effects of the microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels were examined. A four-point bend test and double-notched bend specimens were used to measure the cleavage fracture strength of the alloys and identify the cleavage initiating micro-cracks, respectively. The cleavage fracture strength and DBTT of Mn-Ni-Mo bainitic steels were strongly affected by the alloy carbon content. The decrease in the alloy carbon content resulted in a decrease in the inter-lath cementite-crowded layers and higher cleavage fracture strength. Micro-cracks that formed across the inter-lath cementite-crowded layers were observed to initiate cleavage fracture. The width of these inter-lath cementite-crowded layers was accepted as a cleavage initiating micro-crack size in the micro-mechanical modeling of the cleavage fracture, and the measured cleavage strength values of the bainitic Mn-Ni-Mo steels were well represented by the modified Griffith relationship

  7. Fracture toughness versus micro-tensile bond strength testing of adhesive-dentin interfaces.

    Science.gov (United States)

    De Munck, Jan; Luehrs, Anne-Katrin; Poitevin, André; Van Ende, Annelies; Van Meerbeek, Bart

    2013-06-01

    To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test. Chevron-notched beam fracture toughness (CNB) was measured following a modified ISO 24370 standard. Composite bars with dimensions of 3.0×4.0×25 mm were prepared, with the adhesive-dentin interface in the middle. At the adhesive-dentin interface, a chevron notch was prepared using a 0.15 mm thin diamond blade mounted in a water-cooled diamond saw. Each specimen was loaded until failure in a 4-point bend test setup and the fracture toughness was calculated according to the ISO specifications. Similarly, adhesive-dentin micro-specimens (1.0×1.0×8-10 mm) were stressed in tensile until failure to determine the μTBS. A positive correlation (r(2)=0.64) was observed between CNB and μTBS, which however was only nearly statistically significant, mainly due to the dissimilar outcome of Scotchbond Universal (3M ESPE). While few μTBS specimens failed at the adhesive-dentin interface, almost all CNB specimens failed interfacially at the notch tip. Weibull moduli for interfacial fracture toughness were much higher than for μTBS (3.8-11.5 versus 2.7-4.8, respectively), especially relevant with regard to early failures. Although the ranking of the adhesives on their bonding effectiveness tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Fracture toughness measurement is however more laborious and requires specific equipment. The μTBS nevertheless appeared to remain a valid method to assess bonding effectiveness in a versatile way. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Fractures in high-strength bolts due to hydrogen induced stress corrosion. Causes and corrective actions

    International Nuclear Information System (INIS)

    Hoche, Holger; Oechsner, Matthias

    2017-01-01

    Delayed brittle fractures of high-strength bolts of the strength class 10.9 are presented, taking the example of three damage cases. The respective damage mechanisms could be attributed to hydrogen induced stress corrosion which was caused, in turn, by hydrogen absorption during operation. The examples were chosen with a particular focus on the material condition's susceptibility which explains the cause for the occurrence of the damage mechanism. However, in only one of the three cases the susceptibility was evident and could be explained by violations of normative specifications and an unfavorable material choice. Whereas in the two other examples, only slight or no deviations from the standards and/or regulations could be found. The influencing parameters that caused the damage, those that further promoted the damage, as well as possible corrective actions are discussed taking into account the three exemplary damage cases.

  9. Flat punch adhesion: transition from fracture-based to strength-limited pull-off

    International Nuclear Information System (INIS)

    Jiang, Yijie; Turner, Kevin T; Grierson, David S

    2014-01-01

    The adhesion of a cylindrical flat punch to a surface due to interatomic forces is a well-known problem that is important in many applications, including indentation experiments and the adhesion of fibrillar structures. Traditionally, the pull-off force has been related to the work of adhesion and punch geometry via the Kendall solution that uses a Griffith energy balance to assess crack propagation and pull-off. More recently, it has been shown that under certain conditions, notably at small punch diameters, the contact can behave in a ‘strength-limited’ fashion in which the interface separates uniformly rather than via crack propagation. Here, a Maugis-Dugdale-type analysis of power-law-shaped bodies in contact is used to examine the change in behaviour from the fracture-based Kendall solution to strength-limited pull-off for cylindrical flat punches. The transition from fracture-based to strength-limited behaviour is described in terms of a non-dimensional parameter that is similar to previous quantities used to describe the transition and is a function of the punch size, the elasticity of the contact, and the adhesion properties. The results of this relatively simple analysis compare favourably with results from more complex computational simulations. In addition, the results are used to develop a function that quantifies the transition between the Kendall solution and the strength-limited solution in order to facilitate interpretation of adhesion measurements in the transition regime between the two limits. Finally, the power-law analysis is used to assess the sensitivity of the transition to the exact shape of the punch. (paper)

  10. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    International Nuclear Information System (INIS)

    Diniz, Alexandre C.; Nascimento, Rubens M.; Souza, Julio C.M.; Henriques, Bruno B.; Carreiro, Adriana F.P.

    2014-01-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  11. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Diniz, Alexandre C. [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil); Nascimento, Rubens M. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Souza, Julio C.M. [Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Henriques, Bruno B. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Carreiro, Adriana F.P., E-mail: adrianadafonte@hotmail.com [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil)

    2014-05-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  12. The plane strain shear fracture of the advanced high strength steels

    International Nuclear Information System (INIS)

    Sun, Li

    2013-01-01

    The “shear fracture” which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of “shear fracture” phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a “shear fracture” in the component

  13. Strength and fracture mechanism of iron reinforced tricalcium phosphate cermet fabricated by spark plasma sintering.

    Science.gov (United States)

    Tkachenko, Serhii; Horynová, Miroslava; Casas-Luna, Mariano; Diaz-de-la-Torre, Sebastian; Dvořák, Karel; Celko, Ladislav; Kaiser, Jozef; Montufar, Edgar B

    2018-05-01

    The present work studies the microstructure and mechanical performance of tricalcium phosphate (TCP) based cermet toughened by iron particles. A novelty arises by the employment of spark plasma sintering for fabrication of the cermet. Results showed partial transformation of initial alpha TCP matrix to beta phase and the absence of oxidation of iron particles, as well as a lack of chemical reaction between TCP and iron components during sintering. The values of compressive and tensile strength of TCP/Fe cermet were 3.2 and 2.5 times, respectively, greater than those of monolithic TCP. Fracture analysis revealed the simultaneous action of crack-bridging and crack-deflection microstructural toughening mechanisms under compression. In contrast, under tension the reinforcing mechanism was only crack-bridging, being the reason for smaller increment of strength. Elastic properties of the cermet better matched values reported for human cortical bone. Thereby the new TCP/Fe cermet has potential for eventual use as a material for bone fractures fixation under load-bearing conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Shear bond strength and fracture analysis of human vs. bovine teeth.

    Directory of Open Access Journals (Sweden)

    Stefan Rüttermann

    Full Text Available PURPOSE: To evaluate if bovine enamel and dentin are appropriate substitutes for the respective human hard tooth tissues to test shear bond strength (SBS and fracture analysis. MATERIALS AND METHODS: 80 sound and caries-free human erupted third molars and 80 freshly extracted bovine permanent central incisors (10 specimens for each group were used to investigate enamel and dentine adhesion of one 2-step self-etch (SE and one 3-step etch and rinse (E&R product. To test SBS the buccal or labial areas were ground plane to obtain appropriate enamel or dentine areas. SE and E&R were applied and SBS was measured prior to and after 500 thermocycles between +5 and +55°C. Fracture analysis was performed for all debonded areas. RESULTS: ANOVA revealed significant differences of enamel and dentin SBS prior to and after thermocycling for both of the adhesives. SBS- of E&R-bonded human enamel increased after thermocycling but SE-bonded did not. Bovine enamel SE-bonded showed higher SBS after TC but E&R-bonded had lower SBS. No differences were found for human dentin SE- or E&R-bonded prior to or after thermocycling but bovine dentin SE-bonded increased whereas bovine dentine E&R-bonded decreased. Considering the totalized and adhesive failures, fracture analysis did not show significances between the adhesives or the respective tooth tissues prior to or after thermocycling. CONCLUSION: Although SBS was different on human and bovine teeth, no differences were found for fracture analysis. This indicates that solely conducted SBS on bovine substrate are not sufficient to judge the perfomance of adhesives, thus bovine teeth are questionnable as a substrate for shear bond testing.

  15. Extended Hall-Petch Relationships for Yield, Cleavage and Intergranular Fracture Strengths of bcc Steel and Its Deformation and Fracture Behaviors

    Science.gov (United States)

    Heo, N. H.; Heo, Y.-U.; Kwon, S. K.; Kim, N. J.; Kim, S.-J.; Lee, H.-C.

    2018-03-01

    Extended Hall-Petch relationships for yield ( σy ), cleavage ( σ_{cl} ) and intergranular fracture ( σ_{ig} ) strengths of pure iron have been established through the direct calculation of the proportional constant (k) and the estimation of the friction stress (σ0 ) . The magnitude orders of k and σ0 are generally ky causes the high work hardening rate.

  16. Effect of Lithium Disilicate Reinforced Liner Treatment on Bond and Fracture Strengths of Bilayered Zirconia All-Ceramic Crown

    Directory of Open Access Journals (Sweden)

    Yong-Seok Jang

    2018-01-01

    Full Text Available This study was performed to evaluate the effect of a lithium-disilicate spray-liner application on both the bond strength between zirconia cores and heat-pressed lithium-disilicate glass-ceramic veneers, and the fracture strength of all-ceramic zirconia crowns. A lithium-disilicate reinforced liner was applied on the surface of a zirconia core and lithium-disilicate glass-ceramic was veneered on zirconia through heat press forming. Microtensile and crown fracture tests were conducted in order to evaluate, respectively, the bonding strength between the zirconia cores and heat pressed lithium-disilicate glass-ceramic veneers, and the fracture strength of bilayered zirconia all-ceramic crowns. The role of lithium-disilicate spray-liner at the interface between zirconia and lithium-disilicate glass-ceramic veneers was investigated through surface and cross-sectional analyses. We confirmed that both the mean bonding strength between the zirconia ceramics and lithium-disilicate glass-ceramic veneers and the fracture strength of the liner-treated groups were significantly higher than those of the untreated groups, which resulted, on the one hand, from the chemical bonding at the interface of the zirconia and lithium-disilicate liner, and, on the other, from the existence of a microgap in the group not treated with liner.

  17. Metallic Reinforcement of Direct Squeeze Die Casting Aluminum Alloys for Improved Strength and Fracture Resistance

    Energy Technology Data Exchange (ETDEWEB)

    D. Schwam: J.F. Wallace: Y. Zhu: J.W. Ki

    2004-10-01

    obtained with unreinforced 356 aluminum casting. Good strength can be obtained with a sound die casting without any defects produced by squeeze casting. The use of higher pressure to produce the squeeze casting has been shown to increase the strength of a hemispherical dome casting. This dome shape casting has been produced both with and without reinforcement and tested to determine its pressure resistance under internal pressure of water. Only a slight improvement in strength could be determined because of water leaks at the seal between hemispherical dome and its flat supporting side. However, when the ability of the casting was tested under the compressive force of a plunger, the strengthening effect of wire mesh or sheet was evident. Higher loads to failure were obtained because of the reinforcement of the stainless steel wire and punched sheet. Rather than a sudden failure occurring, the reinforcement of the stainless steel wire or the punched hard stainless steel sheet held the material together and prevented any loss of the fractured casting to the surroundings. Unalloyed steel did not have the required strength or mechanical properties to increase the properties of the casting.

  18. Influence of periodontal ligament simulation on bond strength and fracture resistance of roots restored with fiber posts

    Directory of Open Access Journals (Sweden)

    Ana Maria Estivalete MARCHIONATTI

    2014-10-01

    Full Text Available Objective: Considering that periodontal ligament simulation may influence the stress distribution over teeth restored with intraradicular retainers, this study aimed to assess the combined effect of mechanical cycling and periodontal ligament simulation on both the bond strength between fiber posts and root dentin and the fracture resistance of teeth restored using glass fiber posts. Material and Methods: Ninety roots were randomly distributed into 3 groups (n=10 (C-MC: control; P-MC: polyether; AS-MC: addition silicone to test bond strength and 6 groups (n=10 (C: control; P: polyether; AS: addition silicone, without mechanical cycling, and C-MC, P-MC and AS-MC with mechanical cycling to test fracture strength, according to the material used to simulate the periodontal ligament. For the bond strength test, fiber posts were cemented, cores were built, mechanical cycling was applied (2×106 cycles, 88 N, 2.2 Hz, and 45º incline, and the teeth cut into 3 slices (2 mm, which were then subjected to the push-out test at 1 mm/min. For the fracture strength test, fiber posts were cemented, cores were built, and half of the groups received mechanical cycling, followed by the compressive strength (45° to the long axis and 1 mm/min performed on all groups. Results: Periodontal ligament simulation did not affect the bond strength (p=0.244 between post and dentin. Simulation of periodontal ligament (p=0.153 and application of mechanical cycling (p=0.97 did not affect fracture resistance. Conclusions: The materials used to simulate the periodontal ligament did not affect fracture or bond strength, therefore periodontal ligament simulation using the tested materials could be considered optional in the conditions of the study.

  19. Model of fracture of metal melts and the strength of melts under dynamic conditions

    International Nuclear Information System (INIS)

    Mayer, P. N.; Mayer, A. E.

    2015-01-01

    The development of a continuum model of deformation and fracture of melts is needed for the description of the behavior of metals in extreme states, in particular, under high-current electron and ultrashort laser irradiation. The model proposed includes the equations of mechanics of a two-phase continuum and the equations of the kinetics of phase transitions. The change (exchange) of the volumes of dispersed and carrier phases and of the number of dispersed particles is described, and the energy and mass exchange between the phases due to phase transitions is taken into account. Molecular dynamic (MD) calculations are carried out with the use of the LAMMPS program. The continuum model is verified by MD, computational, and experimental data. The strength of aluminum, copper, and nickel is determined at various temperatures and strain rates. It is shown that an increase in the strain rate leads to an increase in the strength of a liquid metal, while an increase in temperature leads to a decrease in its strength

  20. Model of fracture of metal melts and the strength of melts under dynamic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, P. N., E-mail: polina.nik@mail.ru; Mayer, A. E., E-mail: mayer@csu.ru [Chelyabinsk State University (Russian Federation)

    2015-07-15

    The development of a continuum model of deformation and fracture of melts is needed for the description of the behavior of metals in extreme states, in particular, under high-current electron and ultrashort laser irradiation. The model proposed includes the equations of mechanics of a two-phase continuum and the equations of the kinetics of phase transitions. The change (exchange) of the volumes of dispersed and carrier phases and of the number of dispersed particles is described, and the energy and mass exchange between the phases due to phase transitions is taken into account. Molecular dynamic (MD) calculations are carried out with the use of the LAMMPS program. The continuum model is verified by MD, computational, and experimental data. The strength of aluminum, copper, and nickel is determined at various temperatures and strain rates. It is shown that an increase in the strain rate leads to an increase in the strength of a liquid metal, while an increase in temperature leads to a decrease in its strength.

  1. Effects of strength mis-matching on the fracture behavior of nuclear pressure steel A508-III welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Zhengqiang [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)]. E-mail: zhuzhq01@sjtu.edu.cn; Jing Hongyang [School of Material Science and Technology, Tianjin University, Tianjin 300072 (China); Ge Jingguo [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China); Chen Ligong [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)

    2005-01-15

    In this paper, according to the nuclear pressure steel A508-III, the effect of strength mis-matching on the fracture behavior was analyzed by fracture mechanics test and the crack tip stress field of three-point bend specimen was analyzed by using finite element analysis method (FEM). The fracture of heat-affected zone (HAZ) was emphasized especially. The results of FEM show that if the under-matching weld was used, the opening stress and stress triaxiality in the vicinity of crack tip would increase for weld-crack specimen, and would reduce for HAZ-crack specimen. This tendency was confirmed by the test results.

  2. Fracture toughness and flexural strength of Sm(Co,Fe,Cu,Zr){sub 7-8} magnetic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Libo. E-mail: ren@me.udel.edu; Hadjipanayis, George C.; Parvizi-Majidi, Azar

    2003-02-01

    This paper presents the results of a parametric investigation of the strength and fracture toughness of Sm{sub 2}Co{sub 17} type permanent magnets in the Sm(Co,Fe,Cu,Zr){sub 7-8} family of alloys. The strength and fracture toughness of the as-received materials were characterized as a function of temperature, loading direction, and magnetization. Since these magnets are candidates for applications with service temperatures up to 450 deg. C, the effect of thermal exposure on the mechanical properties was determined by characterizing the properties after a thermal treatment of 40 h at 450 deg. C00.

  3. Fracture toughness and flexural strength of Sm(Co,Fe,Cu,Zr)7-8 magnetic alloys

    International Nuclear Information System (INIS)

    Ren, Libo.; Hadjipanayis, George C.; Parvizi-Majidi, Azar

    2003-01-01

    This paper presents the results of a parametric investigation of the strength and fracture toughness of Sm 2 Co 17 type permanent magnets in the Sm(Co,Fe,Cu,Zr) 7-8 family of alloys. The strength and fracture toughness of the as-received materials were characterized as a function of temperature, loading direction, and magnetization. Since these magnets are candidates for applications with service temperatures up to 450 deg. C, the effect of thermal exposure on the mechanical properties was determined by characterizing the properties after a thermal treatment of 40 h at 450 deg. C

  4. The Effect of Isometric Massage on Global Grip Strength after Conservative Treatment of Distal Radial Fractures. Pilot Study.

    Science.gov (United States)

    Ratajczak, Karina; Płomiński, Janusz

    2015-01-01

    The most common fracture of the distal end of the radius is Colles' fracture. Treatment modalities available for use in hand rehabilitation after injury include massage. The aim of this study was to evaluate the effect of isometric massage on the recovery of hand function in patients with Colles fractures. For this purpose, the strength of the finger flexors was assessed as an objective criterion for the evaluation of hand function. The study involved 40 patients, randomly divided into Group A of 20 patients and Group B of 20 patients. All patients received physical therapy and exercised individually with a physiotherapist. Isometric massage was additionally used in Group A. Global grip strength was assessed using a pneumatic force meter on the first and last day of therapy. Statistical analysis was performed using STATISTICA. Statistical significance was defined as a P value of less than 0.05. In both groups, global grip strength increased significantly after the therapy. There was no statistically significant difference between the groups. The men and women in both groups equally improved grip strength. A statistically significant difference was demonstrated between younger and older patients, with younger patients achieving greater gains in global grip strength in both groups. The incorporation of isometric massage in the rehabilitation plan of patients after a distal radial fracture did not significantly contribute to faster recovery of hand function or improve their quality of life.

  5. Fracture Toughness and Strength in a New Class of Bainitic Chromium-Tungsten Steels

    Energy Technology Data Exchange (ETDEWEB)

    Mao, S. X.; Sikka, V. K.

    2006-06-01

    This project dealt with developing an understanding of the toughening and stengthening mechanisms for a new class of Fe-3Cr-W(V) steels developed at Oak Ridge National Laboratory (ORNL) in collaboration with Nooter Corporation and other industrial partners. The new steele had 50% higher tensile strength up to 650 degrees Celsius than currently used steels and the potential for not requiring any postweld heat treatment (PWHT) and for reducing equipment weight by 25%. This project was closely related to the Nooter project described in the report Development of a New Class of Fe-3Cr-W(V) Ferritic steels for Industrial Process Applications (ORNL/TM-2005/82). The project was carried out jointly by the University of Pittsburgh and ORNL. The University of Pittsburgh carried out fracture toughness measurements and microstructural analysis on base metal and welded plates prepared at ORNL. The project focused on three areas. The first dealt with detailed microstructural analysis of base compositions of 3Cr-3WV and 3Cr-3WBV(Ta) in both normalized (N) and normalized and tempered (NT) conditions. The second aspect of the prject dealt with determining tensile properties and fracture toughness values of K{subIC} at room temperature for both 3Cr-3Wv and 3Cr-3WV(Ta) compositions. The third focus of the project was to measure the fracture toughness values of the base metal and the heat-affectged zone (HAZ) of a plate of Fe-3Cr-W(Mo)V steel plate welded by the gas tungsten are (GTA) process. The HAZ toughness was measured in both the as-welded and the PWHT condition.

  6. A Study on the Small Punch Test for Fracture Strength Evaluation of CANDU Pressure Tube Embrittled by Hydrogen

    International Nuclear Information System (INIS)

    Nho, Seung Hwan; Ong, Jang Woo; Yu, Hyo Sun; Chung, Se Hi

    1996-01-01

    The purpose of this study is to investigate the usefulness of small punch(SP) test using miniaturized specimens as a method for fracture strength evaluation of CANDU pressure tube embrittled by hydrogen. According to the test results, the fracture strength evaluation as a function of hydrogen concentration at -196 .deg. C was much better than that at room temperature, as the difference of SP fracture energy(Esp) with hydrogen concentration was more significant at -196 .deg. C than at room temperature for the hydrogen concentration up to 300ppm-H. It was also observed that the peak of average AE energy, the cumulative average AE energy and the cumulative average AE energy per equivalent fracture, strain increased with the increase of hydrogen concentration. From the results of load-displacement behaviors, Esp behaviors, macro- and micro-SEM fractographs and AE test it has been concluded that the SP test method using miniaturized specimen(10mmx10mmx0.5mm) will be a useful test method to evaluate the fracture strength for CANDU pressure tube embrittled by hydrogen

  7. Prediction of fracture strength in Al2O3/SiCp ceramic matrix nanocomposites

    Directory of Open Access Journals (Sweden)

    Z. Zhang and D.L. Chen

    2007-01-01

    Full Text Available Based primarily on a recent publication [S.M. Choi, H. Awaji, Sci. Tech. Adv. Mater. 6 (2005 2–10.], where the dislocations around the nano-sized particles in the intra-granular type of ceramic matrix nanocomposites (CMNCs were modeled, dislocation activities in Al2O3/SiCp CMNCs were discussed in relation to the processing conditions. The dislocations around the nano-sized particles, caused by the thermal mismatch between the ceramic matrix and nano-sized particles, were assumed to hold out the effect of Orowan-like strengthening, although the conventional Owowan loops induced by the movement of dislocations were unlikely in the ceramic matrix at room temperature. A model involving the yield strength of metal matrix nanocomposites (MMNCs, where the Owowan strengthening effect was taken into consideration, was thus modified and extended to predict the fracture strength of the intra-granular type of CMNCs without and with annealing. On the basis of the characteristics of dislocations in the CMNCs, the load-bearing effect and Orowan-like strengthening were considered before annealing, while the load-bearing effect and enhanced dislocation density strengthening were taken into account after annealing. The model prediction was found to be in agreement with the experimental data of Al2O3/SiCp nanocomposites reported in the literature.

  8. Fracture strength and bending of all-ceramic and fiber-reinforced composites in inlay-retained fixed partial dentures

    Directory of Open Access Journals (Sweden)

    Serkan Saridag

    2012-06-01

    Conclusions: Zirconia-based ceramic inlay-retained fixed partial dentures demonstrated the highest fracture strength. The fiber-reinforced composite inlay-retained fixed partial dentures demonstrated higher bending values than did the all-ceramic inlay-retained fixed partial dentures.

  9. Fracture Strength of Indirect Resin Composite Laminates to Teeth with Existing Restorations : An Evaluation of Conditioning Protocols

    NARCIS (Netherlands)

    Mese, Ayse; Ozcan, Mutlu

    2009-01-01

    Purpose: This study evaluated the fracture strength and failure types of indirect resin-based composite laminates bonded to teeth with aged Class III composite restorations that were conditioned according to various protocols. Materials and Methods: Maxillary central incisors (N = 60) with

  10. Effects of framework design and layering material on fracture strength of implant-supported zirconia-based molar crowns.

    Science.gov (United States)

    Kamio, Shingo; Komine, Futoshi; Taguchi, Kohei; Iwasaki, Taro; Blatz, Markus B; Matsumura, Hideo

    2015-12-01

    To evaluate the effects of framework design and layering material on the fracture strength of implant-supported zirconia-based molar crowns. Sixty-six titanium abutments (GingiHue Post) were tightened onto dental implants (Implant Lab Analog). These abutment-implant complexes were randomly divided into three groups (n = 22) according to the design of the zirconia framework (Katana), namely, uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. The specimens in each design group were further divided into two subgroups (n = 11): zirconia-based all-ceramic restorations (ZAC group) and zirconia-based restorations with an indirect composite material (Estenia C&B) layered onto the zirconia framework (ZIC group). All crowns were cemented on implant abutments, after which the specimens were tested for fracture resistance. The data were analyzed with the Kruskal-Wallis test and the Mann-Whitney U-test with the Bonferroni correction (α = 0.05). The following mean fracture strength values (kN) were obtained in UNI design, ANA design, and SUP design, respectively: Group ZAC, 3.78, 6.01, 6.50 and Group ZIC, 3.15, 5.65, 5.83. In both the ZAC and ZIC groups, fracture strength was significantly lower for the UNI design than the other two framework designs (P = 0.001). Fracture strength did not significantly differ (P > 0.420) between identical framework designs in the ZAC and ZIC groups. A framework design with standardized layer thickness and adequate support of veneer by zirconia frameworks, as in the ANA and SUP designs, increases fracture resistance in implant-supported zirconia-based restorations under conditions of chewing attrition. Indirect composite material and porcelain perform similarly as layering materials on zirconia frameworks. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. Loading rate effects on strength and fracture toughness of pipe steels used in Task 1 of the IPIRG program

    International Nuclear Information System (INIS)

    Marschall, C.W.; Landow, M.P.; Wilkowski, G.M.

    1993-10-01

    Material characterization tests were conducted on laboratory specimens machined from pipes to determine the effect of dynamic loading (i.e., rates comparable to those for high amplitude seismic events) on tensile properties and fracture resistance at 288 C (550 F). Specimens were fabricated from seven different pipes, including carbon steels and stainless steels (both base metal and weld metal), which were to be subjected to full-scale pipe tests in IPIRG Task 1.0. For the stainless steels tested at 288 C (550 F), tensile strength was unchanged, while yield strength and fracture resistance were increased. The increase in fracture resistance was modest for the wrought base metals and substantial for the weld metal and the cast base metal. The carbon steels tested were sensitive to dynamic strain aging, and hence the strength and toughness was affected by both temperature and strain rate effects. The carbon steel base metal and welds exhibited ultimate tensile strength values at 288 C (550 F) that were greater than at room temperature. Furthermore, the ultimate tensile strength at 288 C (550 F) was lowered significantly by increased strain rate and, in the carbon steel base metals, increased strain rate also lowered the fracture resistance, substantially in the base metal of one pipe. In comparing these results to the IPIRG pipe test results to date, it was found that the trends of these tests agree well with the Subtask 1.2 quasi-static and dynamic pipe fracture experiments. Loads measured in the Subtask 1.1 pipe experiments were, however, somewhat higher than would have been expected by the trends observed in the laboratory tests

  12. Effects of exercise improves muscle strength and fat mass in patients with high fracture risk: A randomized control trial

    Directory of Open Access Journals (Sweden)

    Ding-Cheng Chan

    2018-07-01

    Full Text Available Background: The deterioration of the musculoskeletal system imposes significant impact on physical activity. Exercise is an important strategy which minimizes these changes. It is not clear which type of exercise provides better improvement on low physical performance, low muscle mass and low strength of sarcopenia. We aim to develop an integrated care (IC model and compare its relative efficacy in limb fat free mass, muscle strength, and physical performance with low extremities exercise (LEE in community dwelling older adults with high risk of fractures (Fracture Risk Assessment Tool (FRAX® ≧3% for hip fracture, ≧20% for major osteoporotic fracture or 1-min osteoporosis risk test (≧1 point or fall (≧2 falls in previous year. Methods: Patients were assigned randomized to participate in either IC or LEE group (n = 55 each for 3 months. All participants received education including home-based exercise. The IC group consisted of different modalities of exercise while the LEE group performed machine-based low extremities exercise. Fat free mass, muscle strength, and physical performance were measured at their baseline and 3-months follow-up. Results: Mean age was 73.8 ± 7 years with 69.1% women. Entire cohort demonstrated significant increment in fat free mass, muscle strength (4 indicators and physical performance (3 indicators. However, between group differences were not significant. Conclusion: With regular supervise exercise; both groups are equally effective in decreasing fat mass and increasing physical performance, muscle mass and strength. However, the IC group required fewer resources and thus more financially feasible in a community setting. Keywords: Bone mineral density, Gender differences, Integrated care, Low extremities exercise, Muscle strength

  13. Comparison of Marginal Fit and Fracture Strength of a CAD/CAM Zirconia Crown with Two Preparation Designs

    Directory of Open Access Journals (Sweden)

    Hamid Jalali

    2016-08-01

    Full Text Available Objectives: The purpose of this in vitro study was to compare the marginal adaptation and fracture resistance of a zirconia-based all-ceramic restoration with two preparation designs.Materials and Methods: Twenty-four mandibular premolars were randomly divided into two groups (n=12; the conventional group received a peripheral shoulder preparation and the modified group received a buccal shoulder and proximal/lingual chamfer preparation. The marginal fit of the zirconia crowns (Cercon was evaluated using a stereomicroscope. After cementation, load was applied to the crowns. The mean fracture load and the mean marginal gap for each group were analyzed using t-test (P=0.05.Results: The mean marginal gap was 71±16µm in the conventional group and 80±10µm in the modified group, with no significant difference (P=0.161. The mean fracture strength was 830±153N for the conventional group and 775±125N for the modified group, with no significant difference (P=0.396. All but one fracture occurred in the veneering ceramic.Conclusion: Less aggressive preparation of proximal and lingual finish lines for the preservation of tooth structure in all-ceramic restorations does not adversely affect the marginal adaptation or fracture strength of the final restoration.

  14. Process for producing silicon nitride based articles of high fracture toughness and strength

    Science.gov (United States)

    Huckabee, M.; Buljan, S.T.; Neil, J.T.

    1991-09-10

    A process for producing a silicon nitride-based article of improved fracture toughness and strength is disclosed. The process involves densifying to at least 98% of theoretical density a mixture including (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 [mu]m and a surface area of about 8-12 m[sup 2]/g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 [mu]m and a surface area of about 2-4 m[sup 2]/g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. Optionally, the mixture may be blended with a binder and injection molded to form a green body, which then may be densified by, for example, hot isostatic pressing.

  15. Spall strength, dynamic elastic limit and fracture of ittrya dopped tetragonal zirconia

    Science.gov (United States)

    Milyavskiy, Vladimir; Savinykh, Andrey; Schlothauer, Thomas; Lukin, Evgeny; Akopov, Felix

    2013-06-01

    Specimens of the ceramics based on zirconia partially stabilized by yttrium oxide of the composition of 97 mol % ZrO2 + 3 mol % Y2O3 were prepared. The densities of the specimens were 5.79 and 6.01 g/cc. The ceramics mainly have the tetragonal structure (93-98 wt. % of t-ZrO2) . The mechanical action on the ceramic activates the transformation of the tetragonal phase into the monoclinic one: at the abrasive cutting or at the fracture by hammer shock, the content of the monoclinic phase is increasing. The same trend was observed in the specimens, recovered after stepwise shock compression up to 36, 52 and 99 GPa. It was found that shock compression do not initiates tetragonal-monoclinic phase transition directly, and this transition is caused by the destruction. Recovered specimens do not reveal any traces of the phase change which was observed by Mashimo et al. under the pressures 30-35 GPa (J. Appl. Phys. 1995. V. 77. P. 5069). Recording of the profiles of the free surface velocity of the specimens during single-stage shock compression allowed us to determine the dynamic elastic limit, as well as spall strength of the material versus maximal shock stress. In addition, the ceramics were subjected to the action of low temperatures. There were no significant changes in the specimens recovered after storage in liquid nitrogen and helium. The work was supported by The State Atomic Energy Corporation ROSATOM.

  16. COMPARISON OF THE TRADITIONAL STRENGTH OF MATERIALS APPROACH TO DESIGN WITH THE FRACTURE MECHANICS APPROACH

    International Nuclear Information System (INIS)

    Z. Ceylan

    2002-01-01

    The objective of this activity is to show that the use of the traditional strength of materials approach to the drip shield and the waste package (WP) designs is bounding and appropriate when compared to the fracture mechanics approach. The scope of this activity is limited to determining the failure assessment diagrams for the two materials at issue: Ti-7 and Alloy 22. This calculation is intended for use in support of the license application design of the drip shield and the WP. This activity is associated with the drip shield and the WP designs. The activity evaluation for work package number P32 12234F2, included in ''Technical Work Plan for: Waste Package Design Description for LA'' (Ref. 1, p. A-6), has determined that the development of this document is subject to ''Quality Assurance Requirements and Description'' requirements. The control of the electronic management of data is accomplished in accordance with the methods specified in Reference 1, Section 10. AP-3.124, ''Design Calculations and Analysis'' (Ref. 2), is used to develop and document the calculation

  17. Effects of exercise improves muscle strength and fat mass in patients with high fracture risk: A randomized control trial.

    Science.gov (United States)

    Chan, Ding-Cheng; Chang, Chirn-Bin; Han, Der-Sheng; Hong, Cian-Hui; Hwang, Jawl-Shan; Tsai, Keh-Sung; Yang, Rong-Sen

    2017-10-26

    The deterioration of the musculoskeletal system imposes significant impact on physical activity. Exercise is an important strategy which minimizes these changes. It is not clear which type of exercise provides better improvement on low physical performance, low muscle mass and low strength of sarcopenia. We aim to develop an integrated care (IC) model and compare its relative efficacy in limb fat free mass, muscle strength, and physical performance with low extremities exercise (LEE) in community dwelling older adults with high risk of fractures (Fracture Risk Assessment Tool (FRAX ® )) ≧3% for hip fracture, ≧20% for major osteoporotic fracture or 1-min osteoporosis risk test (≧1 point) or fall (≧2 falls in previous year). Patients were assigned randomized to participate in either IC or LEE group (n = 55 each) for 3 months. All participants received education including home-based exercise. The IC group consisted of different modalities of exercise while the LEE group performed machine-based low extremities exercise. Fat free mass, muscle strength, and physical performance were measured at their baseline and 3-months follow-up. Mean age was 73.8 ± 7 years with 69.1% women. Entire cohort demonstrated significant increment in fat free mass, muscle strength (4 indicators) and physical performance (3 indicators). However, between group differences were not significant. With regular supervise exercise; both groups are equally effective in decreasing fat mass and increasing physical performance, muscle mass and strength. However, the IC group required fewer resources and thus more financially feasible in a community setting. Copyright © 2017. Published by Elsevier B.V.

  18. Strontium Is Incorporated into the Fracture Callus but Does Not Influence the Mechanical Strength of Healing Rat Fractures

    DEFF Research Database (Denmark)

    Brüel, Annemarie; Olsen, Jakob; Birkedal, Henrik

    2011-01-01

    in callus bone mineral content (P\\0.05). However, after 8 weeks of healing, no difference was found in either callus volume or bone mineral content. SrR did not influence maximum load or stiffness of the fractures after either 3 or 8 weeks of healing. EDX showed that Sr was incorporated into the callus...

  19. Evolution of the fracture process zone in high-strength concrete under different loading rates

    Directory of Open Access Journals (Sweden)

    Cámara M.

    2010-06-01

    Full Text Available For cementitious materials, the inelastic zone around a crack tip is termed as fracture process zone (FPZ and dominated by complicated mechanism, such as microcracking, crack deflection, bridging, crack face friction, crack tip blunting by voids, crack branching, and so on. Due to the length of the FPZ is related with the characteristic length of the cementitious materials, the size, extent and location of the FPZ has been the object of countless research efforts for several decades. For instance, Cedolin et al. [1] have used an optical method based on the moiré interferometry to determine FPZ in concrete. Castro-Montero et al. [2] have applied the method of holographic interferometry to mortar to study the extension of the FPZ. The advantage of the interferometry method is that the complete FPZ can be directly observed on the surface of the sample. Swartz et al. [3] has adopted the dye penetration technique to illustrate the changing patterns observed as the crack progress from the tensile side to the compression side of the beam. Moreover, acoustic emission (AE is also an experimental technique well suited for monitoring fracture process. Haidar et al. [4] and Maji et al. [5] have studied the relation between acoustic emission characteristics and the properties of the FPZ. Compared with the extensive research on properties of the FPZ under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC. This paper presents the very recent results of an experimental program aimed at disclosing the loading rate effect on the size and velocity of the (FPZ in HSC. Eighteen three-point bending specimens were conducted under a wide range of loading rates from from 10-4 mm/s to 103 mm/s using either a servo-hydraulic machine or a self-designed drop-weight impact device. The beam dimensions were 100 mm 100 mm in cross section, and 420 mm in length. The initial notch

  20. Decreased QOL and muscle strength are persistent 1 year after intramedullary nailing of a tibial shaft fracture

    DEFF Research Database (Denmark)

    Larsen, Peter; Elsoe, Rasmus; Laessoe, Uffe

    2016-01-01

    was measured with the questionnaire Eq5D-5L and compared to norm data from a reference population. Recordings of pain and contralateral muscle strength (isometric maximal voluntary contraction (MVC) for knee flexion and extension were collected at 6 weeks, 3, 6, and 12 months postoperatively. Ipsilateral MVCs......INTRODUCTION:To evaluate the development in patient-reported quality of life (QOL) and muscle strength in the period from surgery to 12 months postoperatively after intramedullary nailing of a tibial shaft fracture. MATERIALS AND METHODS:The design was a prospective, follow-up cohort study. QOL...... compared to the reference population. Six and 12 months after surgery patients demonstrated decreased muscle strength in the injured leg compared to the non-injured leg for knee extension and flexion (P strength during knee...

  1. A study on the fracture strength of steel fiber reinforced concrete structures with initial cracks

    International Nuclear Information System (INIS)

    Chang, Dong Il; Chai, Won Kyu; Lee, Myeong Gu

    1991-01-01

    Fracture tests were carried out in order to investigate the fracture behavior of SFRC(Steel Fiber Reinforced Concrete) structures with initial cracks. Sixty three SFRC beams were used in the tests. And the fracture mode, and relations between loading and mid-span deflection of the beams were observed. On the base of test results, fracture behavior of SFRC beams resulted from steel fiber content and initial crack length to beam depth ratio were found out, and the stress intensity factors, the modulus of rupture and the fracture energy of SFRC beams may then be calculated. According to the results of regression analysis, prediction formulas for the modulus of rupture and the fracture energy of SFRC beams are also suggested. (Author)

  2. Dynamic fracture of high-strength metallic alloys: experiments and modelling

    OpenAIRE

    Pérez Martín, María Jesús

    2017-01-01

    Fracture toughness is a property which describes the ability of a material containing a crack to resist fracture. Such a characteristic is one of the most important properties for describing the failure criteria of materials and may be a function of loading rate and temperature. Therefore, in the case of materials that may be subjected to dynamic loads or extreme conditions, it is crucial to be aware of the evolution of their fracture behaviour with such variables. The main objective of t...

  3. Shear bond strength and enamel fracture behavior of ceramic brackets Fascination® and Fascination®2.

    Science.gov (United States)

    Gittner, Robert; Müller-Hartwich, Ralf; Engel, Sylvia; Jost-Brinkmann, Paul-Georg

    2012-01-01

    The purpose of this study was to compare the shear bond strength and incidence of enamel fractures of the ceramic brackets Fascination® and Fascination®2. A total of 360 teeth (180 first upper bicuspids and 180 lower incisors) were stored in 96% ethanol, while 360 other teeth (180 first upper bicuspids and 180 lower incisors) were stored in 0.1% thymol. All 720 teeth were bonded one-half each with Fascination® and Fascination®2 brackets using three different adhesives and three different light curing units. The teeth were debonded with a debonding-device according to DIN EN ISO 10477 using a universal testing machine with a crosshead speed of 1 mm per minute. The enamel surface was then examined stereomicroscopically (10x and 40x magnification). The non-parametric Mann-Whitney U test was used, since the data were not normally distributed. The Fascination®2 brackets provided significantly lower shear bond strength than Fascination® brackets (p = 0.003). Fascination® brackets demonstrated significantly fewer, smaller enamel fractures than Fascination®2 brackets (p = 0.012). The lower shear bond strength of the Fascination®2 brackets is clinically acceptable, but our study's experimental design did not enable us to prove whether this is clinically associated with a lower risk of enamel fracture.

  4. Cyclic Strain Resistance, Stress Response, Fatigue Life, and Fracture Behavior of High Strength Low Alloy Steel 300 M

    Science.gov (United States)

    Manigandan, K.; Srivatsan, T. S.; Tammana, Deepthi; Poorgangi, Behrang; Vasudevan, Vijay K.

    2014-05-01

    The focus of this technical manuscript is a record of the specific role of microstructure and test specimen orientation on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of alloy steel 300 M. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure for both longitudinal and transverse orientations. Test specimens of the longitudinal orientation showed only a marginal improvement over the transverse orientation at equivalent values of plastic strain amplitude. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by gradual softening for a large portion of fatigue life before culminating in rapid softening prior to catastrophic failure by fracture. Fracture characteristics of test specimens of this alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be a combination of both brittle and ductile mechanisms. The underlying mechanisms governing stress response, deformation characteristics, fatigue life, and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of test specimen orientation, intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude, and response stress.

  5. Fracture Testing with Surface Crack Specimens. [especially the residual tensile strength test

    Science.gov (United States)

    Orange, T. W.

    1974-01-01

    Recommendations are given for the design, preparation, and static fracture testing of surface crack specimens. The recommendations are preceded by background information including discussions of stress intensity factors, crack opening displacements, and fracture toughness values associated with surface crack specimens. Cyclic load and sustained load tests are discussed briefly.

  6. Variations in the Holocene North Atlantic Bottom Current Strength in the Charlie Gibbs Fracture Zone

    Science.gov (United States)

    Kissel, C.; Van Toer, A.; Cortijo, E.; Turon, J.

    2011-12-01

    The changes in the strength of the North Atlantic bottom current during the Holocene period is presented via the study of cores located at the western termination of the northern deep channel of the Charlie-Gibbs fracture zone. This natural roughly E-W corridor is bathed by the Iceland-Scotland overflow water (ISOW) when it passes westward out of the Iceland Basin into the western North Atlantic basin. At present, it is also described as the place where southern sourced silicate-rich Lower Deep Water (LDW) derived from the Antarctic Bottom Waters (AABW) are passing westward, mixing with the ISOW. We conducted a deep-water multiproxy analysis on two nearby cores, coupling magnetic properties, anisotropy, sortable silt and benthic foraminifera isotopes. The first core had been taken by the R. V. Charcot in 1977 and the second one is a CASQ core taken during the IMAGES-AMOCINT MD168- cruise in the framework of the 06-EuroMARC-FP-008 Project on board the R.V. Marion Dufresne (French Polar Institute, IPEV) in 2008. The radiocarbon ages indicate an average sedimentation rate of about 50 cm/kyr through middle and late Holocene allowing a data resolution ranging from 40 to 100 years depending on the proxy. In each core, we observe long-term and short-term changes in the strength of the bottom currents. On the long term, a decrease in the amount of magnetic particles (normalized by the carbonate content) is first from 10 kyr to 8.6 kyr and then between 6 and 2 kyrs before reaching a steady state. Following Kissel et al. (2009), this indicates a decrease in the ISOW strength. The mean sortable silt shows exactly the same pattern indicating that not only the intensity of the ISOW but the whole deep water mass bathing the sites has decreased. On the short term, a first very prominent event centered at about 8.4 kyr (cal. ages) is marked by a pronounced minima in magnetic content and the smaller mean sortable silt sizes. This is typical for an abrupt reduction in deep flow

  7. The influence of poly(acrylic) acid number average molecular weight and concentration in solution on the compressive fracture strength and modulus of a glass-ionomer restorative.

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2011-06-01

    The aim was to investigate the influence of number average molecular weight and concentration of the poly(acrylic) acid (PAA) liquid constituent of a GI restorative on the compressive fracture strength (σ) and modulus (E).

  8. Multifactorial analysis of variables influencing the fracture strength of repair joints for provisional restorative materials using the statistically based Taguchi method

    Directory of Open Access Journals (Sweden)

    Chun-Jen Cheng

    2010-06-01

    Conclusion: Within the limitations of this study, these four design factors had different contributions to the fracture strength of repaired provisional restorations. Clinicians must be aware of the sequence of importance in determining better problem-solving methods.

  9. Grain fracture model and its application to strength evaluation in engineering ceramics

    Science.gov (United States)

    Hoshide, Toshihiko

    1993-02-01

    A new model of cracking process in ceramics is developed assuming the fracture of the grain just ahead of a flaw, such as a crack or a notch, during the loading process, prior to the final unstable fracture. Based on the grain fracture model, a simulation was carried out to explain the anomalous behavior of small flaws and the notch width effect, which were reported by Evans and Langdon (1976) and Hoshide et al. (1984) and by Bertolotti (1973) and Pabst et al. (1982), respectively. It is shown that the analytical relations of the new model can explain the experimental results for both situations.

  10. High strength, biodegradable and cytocompatible alpha tricalcium phosphate-iron composites for temporal reduction of bone fractures.

    Science.gov (United States)

    Montufar, E B; Casas-Luna, M; Horynová, M; Tkachenko, S; Fohlerová, Z; Diaz-de-la-Torre, S; Dvořák, K; Čelko, L; Kaiser, J

    2018-04-01

    In this work alpha tricalcium phosphate (α-TCP)/iron (Fe) composites were developed as a new family of biodegradable, load-bearing and cytocompatible materials. The composites with composition from pure ceramic to pure metallic samples were consolidated by pulsed electric current assisted sintering to minimise processing time and temperature while improving their mechanical performance. The mechanical strength of the composites was increased and controlled with the Fe content, passing from brittle to ductile failure. In particular, the addition of 25 vol% of Fe produced a ceramic matrix composite with elastic modulus much closer to cortical bone than that of titanium or biodegradable magnesium alloys and specific compressive strength above that of stainless steel, chromium-cobalt alloys and pure titanium, currently used in clinic for internal fracture fixation. All the composites studied exhibited higher degradation rate than their individual components, presenting values around 200 μm/year, but also their compressive strength did not show a significant reduction in the period required for bone fracture consolidation. Composites showed preferential degradation of α-TCP areas rather than β-TCP areas, suggesting that α-TCP can produce composites with higher degradation rate. The composites were cytocompatible both in indirect and direct contact with bone cells. Osteoblast-like cells attached and spread on the surface of the composites, presenting proliferation rate similar to cells on tissue culture-grade polystyrene and they showed alkaline phosphatase activity. Therefore, this new family of composites is a potential alternative to produce implants for temporal reduction of bone fractures. Biodegradable alpha-tricalcium phosphate/iron (α-TCP/Fe) composites are promising candidates for the fabrication of temporal osteosynthesis devices. Similar to biodegradable metals, these composites can avoid implant removal after bone fracture healing, particularly in

  11. Enhancement of Impact Toughness by Delamination Fracture in a Low-Alloy High-Strength Steel with Al Alloying

    Science.gov (United States)

    Sun, Junjie; Jiang, Tao; Liu, Hongji; Guo, Shengwu; Liu, Yongning

    2016-12-01

    The effect of delamination toughening of martensitic steel was investigated both at room and low temperatures [253 K and 233 K (-20 °C and -40 °C)]. Two low-alloy martensitic steels with and without Al alloying were both prepared. Layered structure with white band and black matrix was observed in Al alloyed steel, while a homogeneous microstructure was displayed in the steel without Al. Both steels achieved high strength (tensile strength over 1600 MPa) and good ductility (elongation over 11 pct), but they displayed stark contrasts on impact fracture mode and Charpy impact energy. Delamination fracture occurred in Al alloyed steel and the impact energies were significantly increased both at room temperature (from 75 to 138 J, i.e., nearly improved up to 2 times) and low temperatures [from 47.9 to 71.3 J at 233 K (-40 °C)] compared with the one without Al. Alloying with Al promotes the segregation of Cr, Mn, Si and C elements to form a network structure, which is martensite with higher carbon content and higher hardness than that of the matrix. And this network structure evolved into a band structure during the hot rolling process. The difference of yield stress between the band structure and the matrix gives rise to a delamination fracture during the impact test, which increases the toughness greatly.

  12. The effects of ion irradiation on the micromechanical fracture strength and hardness of a self-passivating tungsten alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lessmann, Moritz T., E-mail: mor.lessmann@gmail.com [School of Mechanical Aerospace and Civil Engineering, The University of Manchester, Manchester (United Kingdom); CCFE, Culham Science Centre, Abingdon (United Kingdom); Sudić, Ivan; Fazinić, Stjepko; Tadić, Tonči [Rudjer Bošković Institute, Bijenička cesta 54, 10000 Zagreb (Croatia); Calvo, Aida [Ceit-IK4 and Tecnun (University of Navarra), San Sebastian (Spain); Hardie, Christopher D.; Porton, Michael [CCFE, Culham Science Centre, Abingdon (United Kingdom); García-Rosales, Carmen [Ceit-IK4 and Tecnun (University of Navarra), San Sebastian (Spain); Mummery, Paul M. [School of Mechanical Aerospace and Civil Engineering, The University of Manchester, Manchester (United Kingdom)

    2017-04-01

    An ultra-fine grained self-passivating tungsten alloy (W88-Cr10-Ti2 in wt.%) has been implanted with iodine ions to average doses of 0.7 and 7 dpa, as well as with helium ions to an average concentration of 650 appm. Pile-up corrected Berkovich nanoindentation reveals significant irradiation hardening, with a maximum hardening of 1.9 GPa (17.5%) observed. The brittle fracture strength of the material in all implantation conditions was measured through un-notched cantilever bending at the microscopic scale. All cantilever beams failed catastrophically in an intergranular fashion. A statistically confirmed small decrease in strength is observed after low dose implantation (−6%), whilst the high dose implantation results in a significant increase in fracture strength (+9%), further increased by additional helium implantation (+16%). The use of iodine ions as the implantation ion type is justified through a comparison of the hardening behaviour of pure tungsten under tungsten and iodine implantation.

  13. Strength and fracture energy of foamed concrete incorporating rice husk ash and polypropylene mega-mesh 55

    Science.gov (United States)

    Jaini, Z. M.; Rum, R. H. M.; Boon, K. H.

    2017-10-01

    This paper presents the utilization of rice husk ash (RHA) as sand replacement and polypropylene mega-mesh 55 (PMM) as fiber reinforcement in foamed concrete. High pozzolanic reaction and the ability to become filler make RHA as a strategic material to enhance the strength and durability of foamed concrete. Furthermore, the presence of PMM optimizes the toughness of foamed concrete in resisting shrinkage and cracking. In this experimental study, cube and cylinder specimens were prepared for the compression and splitting-tensile tests. Meanwhile, notched beam specimens were cast for the three-point bending test. It was found that 40% RHA and 9kg/m3 PMM contribute to the highest strength and fracture energy. The compressive, tensile and flexural strengths are 32MPa, 2.88MPa and 6.68MPa respectively, while the fracture energy achieves 42.19N/m. The results indicate high potential of RHA and PMM in enhancing the mechanical properties of foamed concrete.

  14. Fracture Strength of Three-Unit Implant Supported Fixed Partial Dentures with Excessive Crown Height Fabricated from Different Materials

    Directory of Open Access Journals (Sweden)

    Vahideh Nazari

    2017-01-01

    Full Text Available Objectives: Fracture strength is an important factor influencing the clinical long-term success of implant-supported prostheses especially in high stress situations like excessive crown height space (CHS. The purpose of this study was to compare the fracture strength of implant-supported fixed partial dentures (FPDs with excessive crown height, fabricated from three different materials.Materials and Methods: Two implants with corresponding abutments were mounted in a metal model that simulated mandibular second premolar and second molar. Thirty 3-unit frameworks with supportive anatomical design were fabricated using zirconia, nickel-chromium alloy (Ni-Cr, and polyetheretherketone (PEEK (n=10. After veneering, the CHS was equal to 15mm. Then; samples were axially loaded on the center of pontics until fracture in a universal testing machine at a crosshead speed of 0.5 mm/minute. The failure load data were analyzed by one-way ANOVA and Games-Howell tests at significance level of 0.05.Results: The mean failure loads for zirconia, Ni-Cr and PEEK restorations were 2086±362N, 5591±1200N and 1430±262N, respectively. There were significant differences in the mean failure loads of the three groups (P<0.001. The fracture modes in zirconia, metal ceramic and PEEK restorations were cohesive, mixed and adhesive type, respectively.Conclusions: According to the findings of this study, all implant supported three-unit FPDs fabricated of zirconia, metal ceramic and PEEK materials are capable to withstand bite force (even para-functions in the molar region with excessive CHS.Keywords: Dental Implants; Polyetheretherketone; Zirconium oxide; Dental Restoration Failure; Dental Porcelain

  15. Influence of various bonding techniques on the fracture strength of thin CAD/CAM-fabricated occlusal glass-ceramic veneers.

    Science.gov (United States)

    Yazigi, Christine; Kern, Matthias; Chaar, Mohamed Sad

    2017-11-01

    To evaluate the efficiency of immediate dentin sealing and the effects of different bonding protocols on the fracture strength of CAD/CAM occlusal veneers bonded to exposed dentin. Ninety-six extracted maxillary premolars were initially divided into three main groups with 32 specimens each: without immediate dentin sealing, immediate dentin sealing/total etching and immediate dentin sealing/selective etching. Teeth were identically prepared in the dentin to receive occlusal veneers of 0.8mm thickness, milled from lithium disilicate ceramic blocks (IPS e.max CAD). Each main group was later subdivided, according to the pre-cementation surface etching protocol (total/selective), into two subgroups with 16 specimens each. All restorations were adhesively bonded using a resin cement (Variolink Esthetic). Half of the specimens of each subgroup were subjected to thermo-dynamic loading in a chewing simulator with 1,200,000 cycles at 10kg load. The other half and the surviving specimens were subjected to quasi-static loading until failure. Statistical analysis was performed using three-way ANOVA and Tukey's post-hoc tests. All specimens except one survived the artificial aging. A significantly higher fracture strength of restorations (p ≤ 0.001) was obtained when immediate dentin sealing was followed regardless of the etching method with values ranging from a minimum of 1122 ± 336N to a maximum of 1853 ± 333N. Neither the pre-cementation treatment nor the artificial aging had a statistical significant effect on the fracture strength. Immediate dentin sealing protocol is recommended whenever dentin is exposed during the preparation for thin glass-ceramic occlusal veneers. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Effect of strain rate and notch geometry on tensile properties and fracture mechanism of creep strength enhanced ferritic P91 steel

    Science.gov (United States)

    Pandey, Chandan; Mahapatra, M. M.; Kumar, Pradeep; Saini, N.

    2018-01-01

    Creep strength enhanced ferritic (CSEF) P91 steel were subjected to room temperature tensile test for quasi-static (less than 10-1/s) strain rate by using the Instron Vertical Tensile Testing Machine. Effect of different type of notch geometry, notch depth and angle on mechanical properties were also considered for different strain rate. In quasi-static rates, the P91 steel showed a positive strain rate sensitivity. On the basis of tensile data, fracture toughness of P91 steel was also calculated numerically. For 1 mm notch depth (constant strain rate), notch strength and fracture toughness were found to be increased with increase in notch angle from 45° to 60° while the maximum value attained in U-type notch. Notch angle and notch depth has found a minute effect on P91 steel strength and fracture toughness. The fracture surface morphology was studied by field emission scanning electron microscopy (FESEM).

  17. Effect of Nb on hydrogen-induced delayed fracture in high strength hot stamping steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shiqi [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); College of Mechanical Engineering, Yangtze University, Jingzhou 434023 (China); Huang, Yunhua, E-mail: huangyh@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Bintang, E-mail: bingtangsun@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liao, Qingliang [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Hongzhou [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); The School of Resources and Environmental Engineering, East China University of Science and Technology, Meilong road 130, Xujiahui District, Shanghai 200237 (China); Jian, Bian [Niobium Tech Asia, 068898 Singapore (Singapore); Mohrbacher, Hardy [NiobelCon bvba, 2970 Schilde (Belgium); Zhang, Wei; Guo, Aimin [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); Zhang, Yue [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); The State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-02-25

    The effect of Nb addition (0.022, 0.053, 0.078 wt%) on the hydrogen-induced delayed fracture resistance of 22MnB5 was studied by constant load test and electrochemical hydrogen permeation method. It is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of tested steel, especially when the steel contains high concentration of hydrogen, and the maximum delayed fracture resistance is obtained at a Nb content of 0.053%.The result of hydrogen permeation test shows that the diffusion coefficient of hydrogen in the steel containing niobium is lower than that in steel without niobium, which indicates that it is harder for hydrogen in the steels containing niobium to diffuse and aggregate. In addition, the reason for Nb improving the delayed fracture resistance of steels is discussed from two aspects: hydrogen trap effect and grain refinement effect. The analysis shows that the main reason leading to the improvement of the delayed fracture resistance is the hydrogen trapping effect of NbC while the grain refinement effect of Nb(C,N) secondary.

  18. Effect of Nb on hydrogen-induced delayed fracture in high strength hot stamping steels

    International Nuclear Information System (INIS)

    Zhang, Shiqi; Huang, Yunhua; Sun, Bintang; Liao, Qingliang; Lu, Hongzhou; Jian, Bian; Mohrbacher, Hardy; Zhang, Wei; Guo, Aimin; Zhang, Yue

    2015-01-01

    The effect of Nb addition (0.022, 0.053, 0.078 wt%) on the hydrogen-induced delayed fracture resistance of 22MnB5 was studied by constant load test and electrochemical hydrogen permeation method. It is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of tested steel, especially when the steel contains high concentration of hydrogen, and the maximum delayed fracture resistance is obtained at a Nb content of 0.053%.The result of hydrogen permeation test shows that the diffusion coefficient of hydrogen in the steel containing niobium is lower than that in steel without niobium, which indicates that it is harder for hydrogen in the steels containing niobium to diffuse and aggregate. In addition, the reason for Nb improving the delayed fracture resistance of steels is discussed from two aspects: hydrogen trap effect and grain refinement effect. The analysis shows that the main reason leading to the improvement of the delayed fracture resistance is the hydrogen trapping effect of NbC while the grain refinement effect of Nb(C,N) secondary

  19. A Small Area In-Situ MEMS Test Structure to Accurately Measure Fracture Strength by Electrostatic Probing

    Energy Technology Data Exchange (ETDEWEB)

    Bitsie, Fernando; Jensen, Brian D.; de Boer, Maarten

    1999-07-15

    We have designed, fabricated, tested and modeled a first generation small area test structure for MEMS fracture studies by electrostatic rather than mechanical probing. Because of its small area, this device has potential applications as a lot monitor of strength or fatigue of the MEMS structural material. By matching deflection versus applied voltage data to a 3-D model of the test structure, we develop high confidence that the local stresses achieved in the gage section are greater than 1 GPa. Brittle failure of the polycrystalline silicon was observed.

  20. Influence of structure on static cracking resistance and fracture of welded joints of pipe steels of strength class K60

    Science.gov (United States)

    Tereshchenko, N. A.; Tabatchikova, T. I.; Yakovleva, I. L.; Makovetskii, A. N.; Shander, S. V.

    2017-07-01

    The static cracking resistance of a number of welded joints made from pipe steels of K60 strength class has been determined. It has been established that the deformation parameter CTOD varies significantly at identical parameters of weldability of steels. The character of fracture has been investigated and the zone of local brittleness of welded joints has been studied. It has been shown that the ability of a metal to resist cracking is determined by the austenite grain size and by the bainite morphology in the region of overheating in the heat-affected zone of a welded joint.

  1. Effect of bulk-fill base material on fracture strength of root-filled teeth restored with laminate resin composite restorations.

    Science.gov (United States)

    Taha, N A; Maghaireh, G A; Ghannam, A S; Palamara, J E

    2017-08-01

    To evaluate the effect of using a bulk-fill flowable base material on fracture strength and fracture patterns of root-filled maxillary premolars with MOD preparations restored with laminate restorations. Fifty extracted maxillary premolars were selected for the study. Standardized MOD cavities with endodontic treatment were prepared for all teeth, except for intact control. The teeth were divided randomly into five groups (n=10); (Group 1) sound teeth, (Group 2) unrestored teeth; (Group 3) MOD cavities with Vitrebond base and resin-based composite (Ceram. X One Universal); (Group 4) MOD cavities with 2mm GIC base (Fuji IX GP) and resin-based composite (Ceram. X One Universal) open laminate, (Group 5) MOD cavities were restored with 4mm of bulk-fill flowable base material (SDR) and resin-based composite (Ceram. X One Universal). All teeth were thermocycled and subjected to a 45° ramped oblique load in a universal testing machine. Fracture load and fracture patterns were recorded. Data were analyzed using one-way ANOVA and Dunnett's T3 test. Restoration in general increased the fracture strength compared to unrestored teeth. The fracture strength of group 5 (bulk-fill) was significantly higher than the fracture strength of the GIC laminate groups and not significantly different from the intact teeth (355±112N, P=0.118). The type of failure was unfavorable for most of the groups, with the majority being mixed failures. The use of a bulk-fill flowable base material significantly increased the fracture strength of extracted root-filled teeth with MOD cavities; however it did not improve fracture patterns to more favorable ones. Investigating restorative techniques that may improve the longevity of root-filled premolar teeth restored with direct resin restorations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Brittle-fracture statistics for the determination of the strength of fuel particle coatings

    International Nuclear Information System (INIS)

    Bongartz, K.; Schuster, H.

    1976-04-01

    Two influences on characteristic strength values of brittle materials were investigated: the specimen number which is limited in the laboratory by practical reasons, and the procedure for fitting the Weibull formalism to experimental results. The study was performed with respect to the evaluation of the strength of coatings of HTR-fuel particles. Strength values following Weibull statistics were produced artificially to simulate experimental results. The applicability of four different methods was studied to get best fits of the Weibull parameters to these values. The relation of the scatter of strength values and Weibull parameter to the specimen number is determined. (orig./GSCH) [de

  3. Assessing the fracture strength of geological and related materials via an atomistically based J-integral

    Science.gov (United States)

    Jones, R. E.; Criscenti, L. J.; Rimsza, J.

    2016-12-01

    Predicting fracture initiation and propagation in low-permeability geomaterials is a critical yet un- solved problem crucial to assessing shale caprocks at carbon dioxide sequestration sites, and controlling fracturing for gas and oil extraction. Experiments indicate that chemical reactions at fluid-geomaterial interfaces play a major role in subcritical crack growth by weakening the material and altering crack nu- cleation and growth rates. Engineering the subsurface fracture environment, however, has been hindered by a lack of understanding of the mechanisms relating chemical environment to mechanical outcome, and a lack of capability directly linking atomistic insight to macroscale observables. We have developed a fundamental atomic-level understanding of the chemical-mechanical mecha- nisms that control subcritical cracks through coarse-graining data from reactive molecular simulations. Previous studies of fracture at the atomic level have typically been limited to producing stress-strain curves, quantifying either the system-level stress or energy at which fracture propagation occurs. As such, these curves are neither characteristic of nor insightful regarding fracture features local to the crack tip. In contrast, configurational forces, such as the J-integral, are specific to the crack in that they measure the energy available to move the crack and truly quantify fracture resistance. By development and use of field estimators consistent with the continuum conservation properties we are able to connect the data produced by atomistic simulation to the continuum-level theory of fracture mechanics and thus inform engineering decisions. In order to trust this connection we have performed theoretical consistency tests and validation with experimental data. Although we have targeted geomaterials, this capability can have direct impact on other unsolved technological problems such as predicting the corrosion and embrittlement of metals and ceramics. Sandia National

  4. Effect of mix design on the size-independent fracture energy of normal- and high-strength self-compacting concrete

    International Nuclear Information System (INIS)

    Cifuentes, H.; Ríos, J.D.; Gómez, E.J.

    2018-01-01

    Self-compacting concrete has a characteristic microstructure inherent to its specific composition. The higher content of fine particles in self-compacting concrete relative to the equivalent vibrated concrete produces a different fracture behavior that affects the main fracture parameters. In this work, a comprehensive experimental investigation of the fracture behavior of self-compacting concrete has been carried out. Twelve different self-compacting concrete mixes with compressive strength ranging from 39 to 124 MPa (wider range than in other studies) have been subjected to three-point bending tests in order to determine the specific fracture energy. The influence of the mix design and its composition (coarse aggregate fraction, the water to binder ratio and the paste to solids ratio) on its fracture behavior has been analyzed. Moreover, further evidence of the objectivity of the size-independent fracture energy results, obtained by the two most commonly used methods, has been p [es

  5. Effect of reinforcement with resin composite on fracture strength of structurally compromised roots.

    Science.gov (United States)

    Fukui, Yuji; Komada, Wataru; Yoshida, Keiichi; Otake, Shiho; Okada, Daizo; Miura, Hiroyuki

    2009-09-01

    This study was aimed at evaluating the fracture resistance of structurally compromised roots restored with four different post and core systems. Thirty-two bovine roots were uniformly shaped to simulate human mandibular premolar roots. The roots were divided into four groups based on the type of restoration: cemented cast post and core (Group MC), resin composite build-up (Group CR), resin composite and prefabricated glass fiber post build-up (Group FRC), and thick-layer dual-cured resin composite-reinforced small-diameter tapered cast post and core (Group CRM). After a static loading test, the failure mode and fracture resistance were recorded. Group CRM (719.38+/-196.73 N) exhibited a significantly high fracture resistance compared with the other groups (Group MC: 429.56+/-82.43 N; Group CR: 349.56+/-66.21 N; Group FRC: 398.94+/-112.71 N; pCRM exhibited better mechanical properties for structurally compromised roots with no ferrules, although all types of restorations showed non-restorable fracture modes.

  6. Effect of boundary conditions on the strength and deformability of replicas of natural fractures in welded tuff: Data analysis

    International Nuclear Information System (INIS)

    Wibowo, J.; Amadei, B.; Sture, S.

    1994-04-01

    Assessing the shear behavior of intact rock ampersand rock fractures is an important issue in the design of a potential nuclear waste repository at Yucca Mountain Nevada. Cyclic direct shear experiments were conducted on replicas of three natural fractures and a laboratory-developed tensile fracture of welded tuff. The tests were carried out under constant normal loads or constant normal stiffnesses with different initial normal load levels. Each test consisted of five cycles of forward and reverse shear motion. Based on the results of the shear tests conducted under constant normal load, the shear behavior of the joint replicas tested under constant normal stiffness was predicted by using the graphical analysis method of Saeb (1989), and Amadei and Saeb (1990). Comparison between the predictions and the actual constant stiffness direct shear experiment results can be found in a report by Wibowo et al. (1993b). Results of the constant normal load shear experiments are analyzed using several constitutive models proposed in the rock mechanics literature for joint shear strength, dilatancy, and joint surface damage. It is shown that some of the existing models have limitations. New constitutive models are proposed and are included in a mathematical analysis tool that can be used to predict joint behavior under various boundary conditions

  7. Bone strength and management of postmenopausal fracture risk with antiresorptive therapies: considerations for women’s health practice

    Directory of Open Access Journals (Sweden)

    Cheung AM

    2016-09-01

    Full Text Available Angela M Cheung,1–3 Heather Frame,4 Michael Ho,5 Erin S Mackinnon,6 Jacques P Brown7 1Department of Medicine, University of Toronto, 2Centre of Excellence in Skeletal Health Assessment, Joint Department of Medical Imaging, University Health Network (UHN, 3Mount Sinai Hospital, University of Toronto, Toronto, ON, 4Assiniboine Clinic, Winnipeg, MB, 5University Health Network, Toronto, 6Amgen Canada, Inc, Mississauga, ON, 7Rheumatology Division, CHU de Québec Research Centre, Laval University, Quebec City, QC, Canada Abstract: Bone strength – and, hence, fracture risk – reflects the structural and material properties of the skeleton, which changes with bone turnover during aging and following effective pharmacotherapy. A variety of powerful new techniques (quantitative computed tomography, as well as peripheral quantitative computed tomography and high-resolution peripheral quantitative computed tomography provide precise images of bone structure and can be used to model the response of specific bones to different types of mechanical load. This review explores the various components of bone strength and the clinical significance of measures, such as bone mineral density, bone turnover markers, and modern imaging data, with regard to fracture risk in women with postmenopausal osteoporosis, before and after initiating antiresorptive therapy. These imaging and related techniques offer an ever-clearer picture of the changes in bone structure and bone mineral metabolism during normal aging and in osteoporosis, as well as in response to treatment. However, because the newer techniques are not yet available in routine practice, validated tools for absolute fracture risk assessment remain essential for clinical decision making. These tools, which are tailored to patient risk data in individual countries, are based on bone mineral density and other readily available clinical data. In addition, bone turnover marker measurements can be useful in

  8. Fracture and fatigue of high strength filaments. Final report, September 25, 1974--August 30, 1975

    International Nuclear Information System (INIS)

    Holt, N.L.; Finnie, I.

    1975-01-01

    The history of high strength filamentary materials is traced and it is seen that their use has been widespread. It is shown that today's demands upon these materials require a better understanding of their behavior than is presently available. Current theories for both the static and fatigue strength of filamentary materials are reviewed. An analysis of static strength tests on short filaments is presented that explains seemingly anomalous test behavior which has been reported in the literature. The proposed approach is supported by experiments and computer analysis. A new machine for the fatigue testing of filaments or wires was designed and is described in detail. Results are presented for fatigue tests on tungsten wire, graphite filaments and glass filaments. Graphite filaments showed an unexpected deterioration in strength after very many cycles (10 8 ). An explanation of this effect is offered and supported by scanning electron microscope observations. The work concludes with some suggestions for further research

  9. Influence of different catilever extensions and glass or polyamaramid reinforcement fibers on fracture strength of implant-supported temporary

    Directory of Open Access Journals (Sweden)

    Paola Colán Guzmán

    2008-04-01

    Full Text Available In long-term oral rehabilitation treatments, resistance of provisional crowns is a very important factor, especially in cases of an extensive edentulous distal space. The aim of this laboratorial study was to evaluate an acrylic resin cantilever-type prosthesis regarding the flexural strength of its in-balance portion as a function of its extension variation and reinforcement by two types of fibers (glass and polyaramid, considering that literature is not conclusive on this subject. Each specimen was composed by 3 total crowns at its mesial portion, each one attached to an implant component (abutment, while the distal portion (cantilever had two crowns. Each specimen was constructed by injecting acrylic resin into a two-part silicone matrix placed on a metallic base. In each specimen, the crowns were fabricated with either acrylic resin (control group or acrylic resin reinforced by glass (Fibrante, Angelus or polyaramide (Kevlar 49, Du Pont fibers. Compression load was applied on the cantilever, in a point located 7, 14 or 21 mm from the distal surface of the nearest crown with abutment, to simulate different extensions. The specimen was fixed on the metallic base and the force was applied until fracture in a universal test machine. Each one of the 9 sub-groups was composed by 10 specimens. Flexural strength means (in kgf for the distances of 7, 14 and 21 mm were, respectively, 28.07, 8.27 and 6.39 for control group, 31.89, 9.18 and 5.16 for Kevlar 49 and 30.90, 9.31 and 6.86 for Fibrante. Data analysis ANOVA showed statistically significant difference (p<0.05 only regarding cantilever extension. Tukey's test detected significantly higher flexural strength for the 7 mm-distance, followed by 14 and 21 mm. Fracture was complete only on specimens of non-reinforced groups.

  10. Experimental Investigation of the Fracture Behaviour of Reinforced Ultra High Strength Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, J. P.; Henriksen, M. S.; Aarup, B.

    the structural behaviour of a very high strength cement based material with and without steel fibres is investigated. A simple structural geometry has been tested, namely a beam subjected to three point bending. The results shows that the increase of ductility of the material also gives a more ductile behaviour......In the last fifteen years new types of cement based materials have been developed in Denmark at the Aalborg Portland Cement Factory. These types of new materials are characterized by very high strength even when mixed at room temperature and using conventional mixing techniques. In this paper...

  11. A study of microstructure, quasi-static response, fatigue, deformation and fracture behavior of high strength alloy steels

    Science.gov (United States)

    Kannan, Manigandan

    The history of steel dates back to the 17th century and has been instrumental in the betterment of every aspect of our lives ever since, from the pin that holds the paper together to the Automobile that takes us to our destination steel touches everyone every day. Path breaking improvements in manufacturing techniques, access to advanced machinery and understanding of factors like heat treatment, corrosion resistance have aided in the advancement in the properties of steel in the last few years. In this dissertation document, the results of a study aimed at the influence of alloy chemistry, processing and influence of the quasi static and fatigue behavior of seven alloy steels is discussed. The microstructure of the as-received steel was examined and characterized for the nature and morphology of the grains and the presence of other intrinsic features in the microstructure. The tensile, cyclic fatigue and bending fatigue tests were done on a fully automated closed-loop servo-hydraulic test machine at room temperature. The failed samples of high strength steels were examined in a scanning electron microscope for understanding the fracture behavior, especially the nature of loading be it quasi static, cyclic fatigue or bending fatigue . The quasi static and cyclic fatigue fracture behavior of the steels examined coupled with various factors contributing to failure are briefly discussed in light of the conjoint and mutually interactive influences of intrinsic microstructural effects, nature of loading, and stress (load)-deformation-microstructural interactions.

  12. Study of local-zone microstructure, strength and fracture toughness of hybrid laser-metal-inert-gas-welded A7N01 aluminum alloy joint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaomin, E-mail: xmwang991011@163.com [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Li, Bo [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Li, Mingxing; Huang, Cui [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Chen, Hui [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China)

    2017-03-14

    Mechanical properties of hybrid laser-metal-inert-gas-welded A7N01-T5 aluminum alloy joints were studied by using local samples that were extracted from the base metal (BM), heat-affected zone (HAZ), and fusion zone (FZ) of the joint to investigate the triangular relationship of microstructure, strength and fracture toughness of the local zones. The BM had the highest yield strength, ultimate tensile strength (UTS) and lowest elongation, which contrasts with the FZ. The yield strength of the HAZ is lower than that of the BM, whereas its UTS is very close to that of the BM, and its elongation is higher than that of the BM. The fracture toughness of the three local zones decreased as HAZ>BM>FZ. To analyze differences in local mechanical behavior, the detailed microstructure of the three local zones was studied by optical microscopy and electron backscattered diffraction, whereas the fracture surface and precipitation were studied by scanning and transmission electron microscopy. The variation of grain size, especially the morphology and distribution of strengthening phase in HAZ in welding process is the key factor that leads to its different mechanical properties from that of BM, which can be elucidated by different dislocation mechanism, sheared mechanism or Orowan mechanism. The as-cast microstructure and second-phase particles that segregate between dendritic branches provide the FZ with the lowest yield strength and UTS. The factors including area fraction of the precipitates, the difference of strength between the matrix and the grain boundaries, the precipitate-free zone along grain boundaries, as well as the grain boundaries angle are taken into account to explain the difference of fracture toughness among BM, HAZ and FZ, and their fracture modes.

  13. A Fracture-Based Criterion for Debonding Strength of Adhesive-Bonded Double-Strap Steel Joints

    Directory of Open Access Journals (Sweden)

    Prawit Santisukpotha

    2012-01-01

    Full Text Available This paper addresses the debonding strength of adhesive-bonded double-strap steel joints. A fracture-based criterion was formulated in terms of a stress singularity parameter, i.e., the stress intensity factor, which governs the magnitude of a singular stress field near the joint ends. No existing crack was assumed. A total of 24 steel joint specimens were tested under constant amplitude fatigue loadings at stress ratio of 0.2 and frequency of 2 Hz. The joint stiffness ratio was slightly less than one to control the maximum adhesive stresses at the joint ends. To detect the debonding, a simple and practical technique was developed. The test results showed that the interfacial failure near the steel/adhesive corner was a dominant failure mode. The failure was brittle and the debonding life was governed by the crack initiation stage. The finite element analysis was employed to calculate the stress intensity factors and investigate the effects of the adhesive layer thickness, lap length and joint stiffness ratio on the debonding strength.

  14. Recommended practice for fracture toughness testing of weldments with strength mismatch

    International Nuclear Information System (INIS)

    Hornet, P.; Eripret, C.; Wang, Y.Y.; Kirk, M.T.; Gordon, J.R.

    1997-01-01

    Fracture toughness testing requires relationships between experimentally measured quantities, such as load and displacement, and J and crack tip opening displacement (CTOD).The relationships provided in the presently codified procedures (ASTM E813, E1152, E1290 et BSI 7848:Part 1) were derived under the assumption that the specimens have homogeneous mechanical properties. However, these codified procedures are frequently used for testing of weldments despite their strong mechanical properties variations. As a result, the accuracy of the toughness values (J or CCTOD) is sometimes in question. Systematic finite element studies of mismatched single-edge-notched-bend specimens (SENB) having a crack on the centerline have been conducted to resolve this question. The effect of various parameters on these relationships, such as weld size, degree of mismatch, and crack depth, is investigated. The accuracy of the codified J and CTOD testing procedures when applied to the mismatched SE(B) specimens is examined. This systematic examination is extended to several newly proposed procedures, such as those from Joch et al. and Hornet and Eripret. New J and CTOD estimations procedures are proposed. The expected error in applying the codified and the new procedures are shown are proposed. The expected error in applying the codified and the new procedures are shown in terms of mismatch level and level width. Recommendations are made on the use of those procedures for a variety of weld mismatch and crack depth conditions. (authors)

  15. Experimental and finite element study of the effect of temperature and moisture on the tangential tensile strength and fracture behavior in timber logs

    DEFF Research Database (Denmark)

    Larsen, Finn; Ormarsson, Sigurdur

    2014-01-01

    Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and nume......Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments...... and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized...... to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling...

  16. Extension of the principles of the kinetic conception of strength to the process of spalling fracture

    International Nuclear Information System (INIS)

    Molodets, A.M.; Dremin, A.N.

    1983-01-01

    The universality and graphical physical meaning of the characteristic relationship for thermal activation processes and time stimulate attempts for its utilization to describe the time dependence of the spall strength. The involvement of this relationship to describe spall requires a definite model of the spall process first. It is also necessary to to consider the question of the relationship between the applied and local stresses and the selection of a definite connection between these variables. The phenomenological model of spall in which the analogue of the cumulative rudimentary discontinuity is isolated has already been proposed. In this paper, a model is proposed within the framework of this previously described model, taking into account the thermal activation processes and the mean level of the stresses. Comparisons of this model with experimental data on the spall in copper show good agreement. In the spall domain the overstress factor is approximately one third its limit value. This means that higher values of the applied stresses than those found under quasistatic conditions correspond to the identical local stress level. It is possible that the thermal activation stage proceeds during spall in metals exactly as under quasistatic conditions, namely; rudimentary discontinuities are submicrocracks of dimensions less than 10 -7 microns

  17. MICROTOUGH - calculation of characteristic upper shelf fracture toughness values from microstructural parameters for high strength structural steels with normalized or quenched and tempered microstructure

    International Nuclear Information System (INIS)

    Muenstermann, S.; Dahl, W.; Langenberg, P.; Deimel, P.; Sattler, E.

    2004-01-01

    In modern applications, high strength steels are often utilised to increase the load bearing capacity of components. For safe design it is also necessary that these steels have an adequate fracture toughness. The mechanical properties of high strength structural steels are a result of the production process. In consequence, they are strongly related to the microstructure. Therefore, the aim of the research work in the Microtough project is to develop and apply a new method of quantitative correlation between microstructural parameters and characteristic fracture toughness values. This correlation will on the one hand help for the design of new structural steels with high toughness. On the other hand, it shall allow to characterise the fracture toughness of steel without performing expensive fracture mechanics tests. The research work is carried out in the full temperature range from lower to upper shelf. As both RWTH Aachen University and MPA Uni Stuttgart concentrate on ductile fracture behaviour in their research work, the focus of the presentation lies in the upper shelf. (orig.)

  18. Endochondral fracture healing with external fixation in the Sost knockout mouse results in earlier fibrocartilage callus removal and increased bone volume fraction and strength.

    Science.gov (United States)

    Morse, A; Yu, N Y C; Peacock, L; Mikulec, K; Kramer, I; Kneissel, M; McDonald, M M; Little, D G

    2015-02-01

    Sclerostin deficiency, via genetic knockout or anti-Sclerostin antibody treatment, has been shown to cause increased bone volume, density and strength of calluses following endochondral bone healing. However, there is limited data on the effect of Sclerostin deficiency on the formative early stage of fibrocartilage (non-bony tissue) formation and removal. In this study we extensively investigate the early fibrocartilage callus. Closed tibial fractures were performed on Sost(-/-) mice and age-matched wild type (C57Bl/6J) controls and assessed at multiple early time points (7, 10 and 14days), as well as at 28days post-fracture after bony union. External fixation was utilized, avoiding internal pinning and minimizing differences in stability stiffness, a variable that has confounded previous research in this area. Normal endochondral ossification progressed in wild type and Sost(-/-) mice with equivalent volumes of fibrocartilage formed at early day 7 and day 10 time points, and bony union in both genotypes by day 28. There were no significant differences in rate of bony union; however there were significant increases in fibrocartilage removal from the Sost(-/-) fracture calluses at day 14 suggesting earlier progression of endochondral healing. Earlier bone formation was seen in Sost(-/-) calluses over wild type with greater bone volume at day 10 (221%, p<0.01). The resultant Sost(-/-) united bony calluses at day 28 had increased bone volume fraction compared to wild type calluses (24%, p<0.05), and the strength of the fractured Sost(-/-) tibiae was greater than that that of wild type fractured tibiae. In summary, bony union was not altered by Sclerostin deficiency in externally-fixed closed tibial fractures, but fibrocartilage removal was enhanced and the resultant united bony calluses had increased bone fraction and increased strength. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

  19. Comparative Evaluation of Marginal Adaptation and Fracture Strength of Different Ceramic Inlays Produced by CEREC Omnicam and Heat-Pressed Technique

    Directory of Open Access Journals (Sweden)

    F. D. Oz

    2018-01-01

    Full Text Available Objective. The aim of this in vitro study was to evaluate marginal adaptation and fracture strength of inlays produced by CEREC Omnicam using different types of blocs and heat-pressed technique. Methods: Seventy-five extracted human mandibular molars were divided randomly into 5 groups (n=15. 60 molars in four groups received MOD inlay preparations. Experimental groups were CO: Intact teeth, EC: IPS e.max CAD and CEREC, LU: Lava Ultimate and CEREC, EL: IPS Empress CAD and CEREC, EP: IPS Empress Esthetic ingots and heat-pressed technique. Marginal gap measurements were taken with a stereomicroscope. Restorations were cemented with Variolink N and stored in distilled water at 37°C for 24 hours. All samples were subjected to thermocycling. The fracture strength of specimens was determined at a 0.5 mm/min crosshead speed until fracture. Fracture modes were determined. Statistical analyses were performed using one-way analysis of variance for fracture strength data and Kruskal–Wallis for marginal gap data (p=0.05. Results. The mean marginal gap size of EC, LU, EL, and EP were 33.54 µm, 33.77 µm, 34.23 µm, and 85.34 µm, respectively. EP had statistically higher values than other groups. The fracture strength values were significantly higher in the intact teeth group (3959,00 ± 1279,79 N than those of restored groups EC (2408,00 ± 607,97 N, LU (2206,73 ± 675,16, EL (2573.27 ± 644,73 ve EP (2879,53 ± 897,30. Conclusion. Inlays fabricated using CEREC Omnicam demonstrated better marginal adaptation than inlays produced with heat-pressed technique, whereas fracture strength values of inlays fabricated with different type of blocks using CEREC Omnicam exhibited similarity to those fabricated with heat-pressed technique.

  20. Comparative Evaluation of Marginal Adaptation and Fracture Strength of Different Ceramic Inlays Produced by CEREC Omnicam and Heat-Pressed Technique.

    Science.gov (United States)

    Oz, F D; Bolay, S

    2018-01-01

    The aim of this in vitro study was to evaluate marginal adaptation and fracture strength of inlays produced by CEREC Omnicam using different types of blocs and heat-pressed technique. Methods: Seventy-five extracted human mandibular molars were divided randomly into 5 groups ( n =15). 60 molars in four groups received MOD inlay preparations. Experimental groups were CO: Intact teeth, EC: IPS e.max CAD and CEREC, LU: Lava Ultimate and CEREC, EL: IPS Empress CAD and CEREC, EP: IPS Empress Esthetic ingots and heat-pressed technique. Marginal gap measurements were taken with a stereomicroscope. Restorations were cemented with Variolink N and stored in distilled water at 37°C for 24 hours. All samples were subjected to thermocycling. The fracture strength of specimens was determined at a 0.5 mm/min crosshead speed until fracture. Fracture modes were determined. Statistical analyses were performed using one-way analysis of variance for fracture strength data and Kruskal-Wallis for marginal gap data ( p =0.05). The mean marginal gap size of EC, LU, EL, and EP were 33.54  µ m, 33.77  µ m, 34.23  µ m, and 85.34  µ m, respectively. EP had statistically higher values than other groups. The fracture strength values were significantly higher in the intact teeth group (3959,00 ± 1279,79 N) than those of restored groups EC (2408,00 ± 607,97 N), LU (2206,73 ± 675,16), EL (2573.27 ± 644,73) ve EP (2879,53 ± 897,30). Inlays fabricated using CEREC Omnicam demonstrated better marginal adaptation than inlays produced with heat-pressed technique, whereas fracture strength values of inlays fabricated with different type of blocks using CEREC Omnicam exhibited similarity to those fabricated with heat-pressed technique.

  1. Power mixture and green body for producing silicon nitride base articles of high fracture toughness and strength

    Science.gov (United States)

    Huckabee, M.L.; Buljan, S.T.; Neil, J.T.

    1991-09-17

    A powder mixture and a green body for producing a silicon nitride-based article of improved fracture toughness and strength are disclosed. The powder mixture includes (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 [mu]m and a surface area of about 8-12m[sup 2]g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 [mu]m and a surface area of about 2-4 m[sup 2]/g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. The green body is formed from the powder mixture, an effective amount of a suitable oxide densification aid, and an effective amount of a suitable organic binder. No Drawings

  2. Fracture Toughness and Shear Strength of the Bonded Interface Between an Aluminium Alloy Skin and a FRP Patch

    Science.gov (United States)

    Kumar, Prashant; Shinde, Prakash Sonyabapu; Bhoyar, Gaurav

    2018-05-01

    The existing techniques to determine the fracture properties such as critical energy release rate in mode I (GIc) and mode II (GIIc) of an interface between two sheets of same material were modified to determine these properties between the sheets of dissimilar materials and thickness. In addition, the interface shear strength (ISS) was also determined. Experiments were carried out on the specimens made of a pre-cracked thin aluminium alloy skin and a Fiber reinforced polymer (FRP) patch. Two kinds of surface preparation of the aluminium skin were employed; (i) emery-paper roughened surface (ERS) and (ii) Sodium Hydroxide (NaOH) treated surface (NTS). GIc of ERS specimen was found to be 36.1 J/m2, while it was found to be much higher for NTS specimens, that is, 87.3 J/m2. GIIc was found to be 282.4 J/m2 for ERS specimens and much higher as 734.5 J/m2 for NTS specimens. ISS was determined as 32.6 MPa for ERS specimen and significantly higher for NTS specimen, that is, 44.5 MPa. The micrographs obtained from a field emission-scanning electron microscope (FE-SEM) and the surface roughness test showed that the NTS was significantly rougher than the ERS, explaining the higher values of all the three kinds of NTS specimens.

  3. Age-related mechanical strength evolution of trabecular bone under fatigue damage for both genders: Fracture risk evaluation.

    Science.gov (United States)

    Ben Kahla, Rabeb; Barkaoui, Abdelwahed; Merzouki, Tarek

    2018-05-04

    Bone tissue is a living composite material, providing mechanical and homeostatic functions, and able to constantly adapt its microstructure to changes in long term loading. This adaptation is conducted by a physiological process, known as "bone remodeling". This latter is manifested by interactions between osteoclasts and osteoblasts, and can be influenced by many local factors, via effects on bone cell differentiation and proliferation. In the current work, age and gender effects on damage rate evolution, throughout life, have been investigated using a mechanobiological finite element modeling. To achieve the aim, a mathematical model has been developed, coupling both cell activities and mechanical behavior of trabecular bone, under cyclic loadings. A series of computational simulations (ABAQUS/UMAT) has been performed on a 3D human proximal femur, allowing to investigate the effects of mechanical and biological parameters on mechanical strength of trabecular bone, in order to evaluate the fracture risk resulting from fatigue damage. The obtained results revealed that mechanical stimulus amplitude affects bone resorption and formation rates, and indicated that age and gender are major factors in bone response to the applied loadings. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Effect of mix design on the size-independent fracture energy of normal- and high-strength self-compacting concrete

    Directory of Open Access Journals (Sweden)

    H. Cifuentes

    2018-02-01

    Full Text Available Self-compacting concrete has a characteristic microstructure inherent to its specific composition. The higher content of fine particles in self-compacting concrete relative to the equivalent vibrated concrete produces a different fracture behavior that affects the main fracture parameters. In this work, a comprehensive experimental investigation of the fracture behavior of self-compacting concrete has been carried out. Twelve different self-compacting concrete mixes with compressive strength ranging from 39 to 124 MPa (wider range than in other studies have been subjected to three-point bending tests in order to determine the specific fracture energy. The influence of the mix design and its composition (coarse aggregate fraction, the water to binder ratio and the paste to solids ratio on its fracture behavior has been analyzed. Moreover, further evidence of the objectivity of the size-independent fracture energy results, obtained by the two most commonly used methods, has been provided on the self-compacting concrete mixes.

  5. Uniaxial Compressive Strength and Fracture Mode of Lake Ice at Moderate Strain Rates Based on a Digital Speckle Correlation Method for Deformation Measurement

    Directory of Open Access Journals (Sweden)

    Jijian Lian

    2017-05-01

    Full Text Available Better understanding of the complex mechanical properties of ice is the foundation to predict the ice fail process and avoid potential ice threats. In the present study, uniaxial compressive strength and fracture mode of natural lake ice are investigated over moderate strain-rate range of 0.4–10 s−1 at −5 °C and −10 °C. The digital speckle correlation method (DSCM is used for deformation measurement through constructing artificial speckle on ice sample surface in advance, and two dynamic load cells are employed to measure the dynamic load for monitoring the equilibrium of two ends’ forces under high-speed loading. The relationships between uniaxial compressive strength and strain-rate, temperature, loading direction, and air porosity are investigated, and the fracture mode of ice at moderate rates is also discussed. The experimental results show that there exists a significant difference between true strain-rate and nominal strain-rate derived from actuator displacement under dynamic loading conditions. Over the employed strain-rate range, the dynamic uniaxial compressive strength of lake ice shows positive strain-rate sensitivity and decreases with increasing temperature. Ice obtains greater strength values when it is with lower air porosity and loaded vertically. The fracture mode of ice seems to be a combination of splitting failure and crushing failure.

  6. In-vivo assessment of femoral bone strength using Finite Element Analysis (FEA based on routine MDCT imaging: a preliminary study on patients with vertebral fractures.

    Directory of Open Access Journals (Sweden)

    Hans Liebl

    derived FEA models may assess bone strength more accurately than BMD measurements alone, providing a valuable in-vivo fracture risk assessment tool.

  7. Localization of plastic yield and fracture mechanism in high-strength niobium alloy with ultra-fine particles of non-metallic phase

    International Nuclear Information System (INIS)

    Tyumentsev, A.N.; Gonchikov, V.Ch.; Korotaev, A.D.; Pinzhin, Yu.P.; Tyumentseva, S.F.

    1989-01-01

    The regularities of localization of plastic flow in high-strength dispersion-strengthened niobium alloy are studied. On the basis of investigations of the microstructure of strain localization zones the mechanism of stability losses of plastic flow including, the processes of diffusion of nonequilibrium vacancies in fields of nonuniform stresses, is proposed. The role of diffuse strain mechanisms during reorientation of the crystalline lattice is discussed. The regularities of fracture of high-strength alloy under conditions of rotational-shift instability of plastic flow are investigated

  8. Fracture strength and failure mode of maxillary implant-supported provisional single crowns: a comparison of composite resin crowns fabricated directly over PEEK abutments and solid titanium abutments.

    Science.gov (United States)

    Santing, Hendrik Jacob; Meijer, Henny J A; Raghoebar, Gerry M; Özcan, Mutlu

    2012-12-01

    Polyetheretherketone (PEEK) temporary abutments have been recently introduced for making implant-supported provisional single crowns. Little information is available in the dental literature on the durability of provisional implant-supported restorations. The objectives of this study were to evaluate the fracture strength of implant-supported composite resin crowns on PEEK and solid titanium temporary abutments, and to analyze the failure types. Three types of provisional abutments, RN synOcta Temporary Meso Abutment (PEEK; Straumann), RN synOcta Titanium Post for Temporary Restorations (Straumann), and Temporary Abutment Engaging NobRplRP (Nobel Biocare) were used, and provisional screw-retained crowns using composite resin (Solidex) were fabricated for four different locations in the maxilla. The specimens were tested in a universal testing machine at a crosshead speed of 1 mm/minute until fracture occurred. The failure types were analyzed and further categorized as irreparable (Type 1) or reparable (Type 2). No significant difference was found between different abutment types. Only for the position of the maxillary central incisor, composite resin crowns on PEEK temporary abutments showed significantly lower (p Provisional crowns on PEEK abutments showed similar fracture strength as titanium temporary abutments except for central incisors. Maxillary right central incisor composite resin crowns on PEEK temporary abutments fractured below the mean anterior masticatory loading forces reported to be approximately 206 N. © 2010 Wiley Periodicals, Inc.

  9. Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

    Directory of Open Access Journals (Sweden)

    Pooya Hamdi

    2015-12-01

    Full Text Available Heterogeneity is an inherent component of rock and may be present in different forms including mineral heterogeneity, geometrical heterogeneity, weak grain boundaries and micro-defects. Microcracks are usually observed in crystalline rocks in two forms: natural and stress-induced; the amount of stress-induced microcracking increases with depth and in-situ stress. Laboratory results indicate that the physical properties of rocks such as strength, deformability, P-wave velocity and permeability are influenced by increase in microcrack intensity. In this study, the finite-discrete element method (FDEM is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks using the proposed micro discrete fracture network (μDFN approach. The characteristics of the microcracks required to create μDFN models are obtained through image analyses of thin sections of Lac du Bonnet granite adopted from published literature. A suite of two-dimensional laboratory tests including uniaxial, triaxial compression and Brazilian tests is simulated and the results are compared with laboratory data. The FDEM-μDFN models indicate that micro-heterogeneity has a profound influence on both the mechanical behavior and resultant fracture pattern. An increase in the microcrack intensity leads to a reduction in the strength of the sample and changes the character of the rock strength envelope. Spalling and axial splitting dominate the failure mode at low confinement while shear failure is the dominant failure mode at high confinement. Numerical results from simulated compression tests show that microcracking reduces the cohesive component of strength alone, and the frictional strength component remains unaffected. Results from simulated Brazilian tests show that the tensile strength is influenced by the presence of microcracks, with a reduction in tensile strength as microcrack intensity increases. The importance of microcrack heterogeneity in

  10. Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

    Science.gov (United States)

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

    The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

  11. The Effect of High Concentration and Small Size of Nanodiamonds on the Strength of Interface and Fracture Properties in Epoxy Nanocomposite

    Directory of Open Access Journals (Sweden)

    Yasir A. Haleem

    2016-06-01

    Full Text Available The concentration and small size of nanodiamonds (NDs plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites. It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy. Rationally, functionalized-NDs (F-NDs showed a much better performance for the nanocomposite than pristine NDs (P-NDs because of additional functional groups on its surface. The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy, indicating the presence of a strong interface. We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web, which can efficiently hinder further crack propagation. In addition, the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles, whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface. Because of the strong interface in F-ND/epoxy nanocomposites, at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks, parallel to the parent crack, via crack splitting which results in a fiber-like structure on the fracture surface. The plastic void growth, crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites.

  12. Mid-thigh cortical bone structural parameters, muscle mass and strength, and association with lower limb fractures in older men and women (AGES-Reykjavik Study).

    Science.gov (United States)

    Johannesdottir, Fjola; Aspelund, Thor; Siggeirsdottir, Kristin; Jonsson, Brynjolfur Y; Mogensen, Brynjolfur; Sigurdsson, Sigurdur; Harris, Tamara B; Gudnason, Vilmundur G; Lang, Thomas F; Sigurdsson, Gunnar

    2012-05-01

    In a cross-sectional study we investigated the relationship between muscle and bone parameters in the mid-thigh in older people using data from a single axial computed tomographic section through the mid-thigh. Additionally, we studied the association of these variables with incident low-trauma lower limb fractures. A total of 3,762 older individuals (1,838 men and 1,924 women), aged 66-96 years, participants in the AGES-Reykjavik study, were studied. The total cross-sectional muscular area and knee extensor strength declined with age similarly in both sexes. Muscle parameters correlated most strongly with cortical area and total shaft area (adjusted for age, height, and weight) but explained lower limb fractures. Small muscular area, low knee extensor strength, large MA, low cortical thickness, and high BR were significantly associated with fractures in both sexes. Our results show that bone and muscle loss proceed at different rates and with different gender patterns.

  13. Use of TOUGHREACT to Simulate Effects of Fluid Chemistry onInjectivity in Fractured Geothermal Reservoirs with High Ionic StrengthFluids

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Zhang, Guoxiang; Pruess, Karsten

    2005-02-09

    Recent studies suggest that mineral dissolution/precipitation and clay swelling effects could have a major impact on the performance of hot dry rock (HDR) and hot fractured rock (HFR) reservoirs. A major concern is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths. A Pitzer ionic interaction model has been introduced into the publicly available TOUGHREACT code for solving non-isothermal multi-phase reactive geochemical transport problems under conditions of high ionic strength, expected in typical HDR and HFR systems. To explore chemically-induced effects of fluid circulation in these systems, we examine ways in which the chemical composition of reinjected waters can be modified to improve reservoir performance. We performed a number of coupled thermo-hydrologic-chemical simulations in which the fractured medium was represented by a one-dimensional MINC model (multiple interacting continua). Results obtained with the Pitzer activity coefficient model were compared with those using an extended Debye-Hueckel equation. Our simulations show that non-ideal activity effects can be significant even at modest ionic strength, and can have major impacts on permeability evolution in injection-production systems. Alteration of injection water chemistry, for example by dilution with fresh water, can greatly alter precipitation and dissolution effects, and can offer a powerful tool for operating hot dry rock and hot fractured rock reservoirs in a sustainable manner.

  14. Effect of in vitro aging on the flexural strength and probability to fracture of Y-TZP zirconia ceramics for all-ceramic restorations.

    Science.gov (United States)

    Siarampi, Eleni; Kontonasaki, Eleana; Andrikopoulos, Konstantinos S; Kantiranis, Nikolaos; Voyiatzis, George A; Zorba, Triantafillia; Paraskevopoulos, Konstantinos M; Koidis, Petros

    2014-12-01

    Dental zirconia restorations should present long-term clinical survival and be in service within the oral environment for many years. However, low temperature degradation could affect their mechanical properties and survival. The aim of this study was to investigate the effect of in vitro aging on the flexural strength of yttrium-stabilized (Y-TZP) zirconia ceramics for ceramic restorations. One hundred twenty bar-shaped specimens were prepared from two ceramics (ZENO Zr (WI) and IPS e.max(®) ZirCAD (IV)), and loaded until fracture according to ISO 6872. The specimens from each ceramic (nx=60) were divided in three groups (control, aged for 5h, aged for 10h). One-way ANOVA was used to assess statistically significant differences among flexural strength values (Pceramics, however statistically significant was for the WI group (Pceramics presented a t→m phase transformation, with the m-phase increasing from 4 to 5% at 5h to around 15% after 10h. The significant reduction of the flexural strength after 10h of in vitro aging, suggests high fracture probability for one of the zirconia ceramics tested. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. A comparative study to check fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate resin reinforced with different materials: An in vitro study.

    Science.gov (United States)

    Gupt, Parikshit; Nagpal, Archana; Samra, Rupandeep Kaur; Verma, Ramit; Kaur, Jasjeet; Abrol, Surbhi

    2017-01-01

    The purpose of the study was to evaluate the fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate (PMMA) resin using different types of reinforcement materials to determine the best among them. Fifty samples were made (10 samples for each group) with autopolymerizing PMMA resin using reinforcement materials (stainless steel wire: looped and unlooped and glass fiber: loose and unidirectional) as 3-unit posterior bridge. The test specimens were divided into five groups depending on the reinforcing material as Group I, II, III, IV, and V; Group I: PMMA unreinforced (control group), Group II: PMMA reinforced with stainless steel wire (straight ends), Group III: PMMA reinforced with stainless steel wire (looped ends), Group IV: PMMA reinforced with unidirectional glass fibers, and Group V: PMMA reinforced with randomly distributed glass fibers. Universal testing machine was used to evaluate and compare the fracture strength of samples. Comparison of mean ultimate force and ultimate stress was done employing one-way analysis of variance and Tukey's post hoc tests. The highest and lowest mean ultimate force and mean ultimate stress were of Group IV and I, respectively. Tukey's post hoc honestly significant difference multiple comparison for mean ultimate force and stress shows the increase in strength to be statistically significant ( P 0.05). Unidirectional glass fibers showed the maximum strength, which was comparable to mean values of both stainless steel wire groups. Low cost and easy technique of using stainless steel wire make it the material of choice over the unidirectional glass fiber for reinforcement in nonesthetic areas where high strength is required.

  16. Variations of fracture toughness and stress-strain curve of cold worked stainless steel and their influence on failure strength of cracked pipe

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2016-01-01

    In order to assess failure probability of cracked components, it is important to know the variations of the material properties and their influence on the failure load assessment. In this study, variations of the fracture toughness and stress-strain curve were investigated for cold worked stainless steel. The variations of the 0.2% proof and ultimate strengths obtained using 8 specimens of 20% cold worked stainless steel (CW20) were 77 MPa and 81 MPa, respectively. The respective variations were decreased to 13 and 21 MPa for 40% cold worked material (CW40). Namely, the variation in the tensile strength was decreased by hardening. The COVs (coefficients of variation) of fracture toughness were 7.3% and 16.7% for CW20 and CW40, respectively. Namely, the variation in the fracture toughness was increased by hardening. Then, in order to investigate the influence of the variations in the material properties on failure load of a cracked pipe, flaw assessments were performed for a cracked pipe subjected to a global bending load. Using the obtained material properties led to variation in the failure load. The variation in the failure load of the cracked pipe caused by the variation in the stress-strain curve was less than 1.5% for the COV. The variation in the failure load caused by fracture toughness variation was relatively large for CW40, although it was less than 2.0% for the maximum case. It was concluded that the hardening induced by cold working does not cause significant variation in the failure load of cracked stainless steel pipe. (author)

  17. Comparative Evaluation of Marginal Adaptation and Fracture Strength of Different Ceramic Inlays Produced by CEREC Omnicam and Heat-Pressed Technique

    OpenAIRE

    Oz, F. D.; Bolay, S.

    2018-01-01

    Objective. The aim of this in vitro study was to evaluate marginal adaptation and fracture strength of inlays produced by CEREC Omnicam using different types of blocs and heat-pressed technique. Methods: Seventy-five extracted human mandibular molars were divided randomly into 5 groups (n=15). 60 molars in four groups received MOD inlay preparations. Experimental groups were CO: Intact teeth, EC: IPS e.max CAD and CEREC, LU: Lava Ultimate and CEREC, EL: IPS Empress CAD and CEREC, EP: IPS Empr...

  18. An investigation of the influence of strength mis-matching and HAZ width on the fracture behaviour of welds with cracks in the WM/HAZ interface

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, D.M.; Menezes, L.F.; Loureiro, A. [Dept of Mechanical Eng., FCTUC, Coimbra (Portugal)

    2004-07-01

    In this paper a numerical study concerning the influence of the mis-match in mechanical properties and of the heat affected zone width on the crack driving force of welds with cracks in the weld metal / heat affected zone interface is described. This work was performed through the numerical simulation of three-point bending tests, using finite element meshes of weld samples with various HAZ widths and two different crack length sizes. The numerical calculation of the J integral and of the stress fields ahead the notch tip was used to evaluate the fracture strength variation in the welds. (orig.)

  19. In Situ Strength Model for Continuous Fibers and Multi-Scale Modeling the Fracture of C/SiC Composites

    Science.gov (United States)

    Zhang, Sheng; Gao, Xiguang; Song, Yingdong

    2018-04-01

    A new in situ strength model of carbon fibers was developed based on the distribution of defects to predict the stress-strain response and the strength of C/SiC composites. Different levels of defects in the fibers were considered in this model. The defects in the fibers were classified by their effects on the strength of the fiber. The strength of each defect and the probability that the defect appears were obtained from the tensile test of single fibers. The strength model of carbon fibers was combined with the shear-lag model to predict the stress-strain responses and the strengths of fiber bundles and C/SiC minicomposites. To verify the strength model, tensile tests were performed on fiber bundles and C/SiC minicomposites. The predicted and experimental results were in good agreement. Effects of the fiber length, the fiber number and the heat treatment on the final strengths of fiber bundles and C/SiC minicomposites were also discussed.

  20. On the method for fracture strength assessment. Part 2; Kozobutsu no hakai kyodo hyoka no jissai. 2

    Energy Technology Data Exchange (ETDEWEB)

    Onozuka, M. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    1995-09-05

    In order to reduce the economic cost of the generating set etc. the damages to the materials and structures of the structure to last the original design life were observed and it was considered that if damages were fewer the life would be longer. One of the important items in assessing, amending and renewing the rationality of the established structure is the assessment of the defects and flaws existing in the welded joints. In Japan, WES 2805 which is named as the Method for Assessing the Defects for the Brittle Fracture Occurring Properties of Welded Joint was formulated in 1980 as the standard of the Japan Welding Society. Although it has been applied as the criterion in wide range, the part on brittle fracture is now under revision to reflect the research results on fracture mechanics thereafter and to perfect the fracture relationship because many years have passed since its first formulation. In this paper, the contents in the final stage of the revision of WES 2805 standard, including concrete examples, were introduced. 2 refs., 6 figs., 2 tabs.

  1. Effect of boundary conditions on the strength and deformability of replicas of natural fractures in welded tuff

    International Nuclear Information System (INIS)

    Wibowo, J.; Amadei, B.; Sture, S.; Robertson, A.B.

    1993-09-01

    Four series of cyclic direct-shear experiments were conducted on several replicas of three natural fractures and a tensile fracture of welded tuff from Yucca Mountain. The objective of these tests was to examine the effect of cyclic loading on joint shear behavior under different boundary conditions. The shear tests were performed under either different levels of constant normal load ranging between 0.6 and 25.6 kips (2.7 and 113.9 kN) or constant normal stiffness ranging between 14.8 and 187.5 kips/in (25.9 and 328.1 kn/cm) . Bach test in the two categories consisted of five cycles of forward and reverse shear. Normal compression tests were also performed both before and after each shear experiment to measure changes in joint normal deformability. In order to quantify fracture surface damage during shear, fracture-surface fractal dimensions were obtained from measurements before and after shear

  2. On the Specific Role of Microstructure in Governing Cyclic Fatigue, Deformation, and Fracture Behavior of a High-Strength Alloy Steel

    Science.gov (United States)

    Manigandan, K.; Srivatsan, T. S.

    2015-06-01

    In this paper, the results of an experimental study that focused on evaluating the conjoint influence of microstructure and test specimen orientation on fully reversed strain-controlled fatigue behavior of the high alloy steel X2M are presented and discussed. The cyclic stress response of this high-strength alloy steel revealed initial hardening during the first few cycles followed by gradual softening for most of fatigue life. Cyclic strain resistance exhibited a linear trend for the variation of elastic strain amplitude with reversals to failure, and plastic strain amplitude with reversals to failure. Fracture morphology was the same at the macroscopic level over the entire range of cyclic strain amplitudes examined. However, at the fine microscopic level, the alloy steel revealed fracture to be essentially ductile with features reminiscent of predominantly "locally" ductile and isolated brittle mechanisms. The mechanisms governing stress response at the fine microscopic level, fatigue life, and final fracture behavior are presented and discussed in light of the mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents during fully reversed strain cycling, cyclic strain amplitude, and resultant response stress.

  3. The Shear Strength and Fracture Behavior of Sn-Ag- xSb Solder Joints with Au/Ni-P/Cu UBM

    Science.gov (United States)

    Lee, Hwa-Teng; Hu, Shuen-Yuan; Hong, Ting-Fu; Chen, Yin-Fa

    2008-06-01

    This study investigates the effects of Sb addition on the shear strength and fracture behavior of Sn-Ag-based solders with Au/Ni-P/Cu underbump metallization (UBM) substrates. Sn-3Ag- xSb ternary alloy solder joints were prepared by adding 0 wt.% to 10 wt.% Sb to a Sn-3.5Ag alloy and joining them with Au/Ni-P/Cu UBM substrates. The solder joints were isothermally stored at 150°C for up to 625 h to study their microstructure and interfacial reaction with the UBM. Single-lap shear tests were conducted to evaluate the mechanical properties, thermal resistance, and failure behavior. The results show that UBM effectively suppressed intermetallic compound (IMC) formation and growth during isothermal storage. The Sb addition helped to refine the Ag3Sn compounds, further improving the shear strength and thermal resistance of the solders. The fracture behavior evolved from solder mode toward the mixed mode and finally to the IMC mode with increasing added Sb and isothermal storage time. However, SnSb compounds were found in the solder with 10 wt.% Sb; they may cause mechanical degradation of the solder after long-term isothermal storage.

  4. Automated Method for Fractographic Analysis of Shape and Size of Dimples on Fracture Surface of High-Strength Titanium Alloys

    Directory of Open Access Journals (Sweden)

    Ihor Konovalenko

    2018-03-01

    Full Text Available An automated method for analyzing the shape and size of dimples of ductile tearing formed during static and impact fracture of titanium alloys VT23 and VT23M is proposed. The method is based on the analysis of the image topology. The method contains the operations of smoothing the initial fractographic image; its convolution with a filter to identify the topological ridges; thresholding with subsequent skeletonization to identify boundaries between dimples; clustering to isolate the connected areas that represent the sought objects—dimples. For each dimple, the following quantitative characteristics were calculated: area, coefficient of roundness and visual depth in units of image intensity. The surface of ductile tearing was studied by analyzing the peculiarities of parameter distribution of the found dimples. The proposed method is applied to fractograms of fracture surfaces of titanium alloys VT23 and VT23M.

  5. Effectiveness of various isometric exercises at improving bone strength in cortical regions prone to distal tibial stress fractures.

    Science.gov (United States)

    Florio, C S

    2018-06-01

    A computational model was used to compare the local bone strengthening effectiveness of various isometric exercises that may reduce the likelihood of distal tibial stress fractures. The developed model predicts local endosteal and periosteal cortical accretion and resorption based on relative local and global measures of the tibial stress state and its surface variation. Using a multisegment 3-dimensional leg model, tibia shape adaptations due to 33 combinations of hip, knee, and ankle joint angles and the direction of a single or sequential series of generated isometric resultant forces were predicted. The maximum stress at a common fracture-prone region in each optimized geometry was compared under likely stress fracture-inducing midstance jogging conditions. No direct correlations were found between stress reductions over an initially uniform circular hollow cylindrical geometry under these critical design conditions and the exercise-based sets of active muscles, joint angles, or individual muscle force and local stress magnitudes. Additionally, typically favorable increases in cross-sectional geometric measures did not guarantee stress decreases at these locations. Instead, tibial stress distributions under the exercise conditions best predicted strengthening ability. Exercises producing larger anterior distal stresses created optimized tibia shapes that better resisted the high midstance jogging bending stresses. Bent leg configurations generating anteriorly directed or inferiorly directed resultant forces created favorable adaptations. None of the studied loads produced by a straight leg was significantly advantageous. These predictions and the insight gained can provide preliminary guidance in the screening and development of targeted bone strengthening techniques for those susceptible to distal tibial stress fractures. Copyright © 2018 John Wiley & Sons, Ltd.

  6. Application of ductile fracture assessment methods for the assessment of pressure vessels from high strength steels (HSS)

    International Nuclear Information System (INIS)

    Eisele, U.; Schiedermaier, J.

    2003-01-01

    The economical and safe design of pressure vessels requires, besides others, also a detailed knowledge of the vessel failure behaviour in the case of existing imperfections or cracks. The behaviour of a cracked component under a given loading situation depends on material toughness. For ferritic steels, the material toughness is varying with temperature. At low temperature dominantly brittle fracture behaviour is observed, at high temperature the failure mode is dominantly ductile fracture. The transition between these two extremes is floating. In the case of existing or postulated cracks, the safety analysis has to be performed using fracture mechanics methods. In the lower shelf of toughness, K iC as of ASTM E 399 is the characterising value for crack initiation and immediate unstable crack extension (cleavage). In the upper shelf level the characterising value is the ''actual crack initiation toughness'' J i acc. to ISO 12135, characterising the onset of slow stable crack extension. For the transition regime in ASTM E 1921 the instability values K JC are defined, characterising cleavage failure after more or less extended ductile crack growth. The safety analysis of a component operated in the upper shelf of the material toughness, has to consider initiation as well as stable crack extension following initiation. The inclusion of any crack extension into this consideration needs to consider the influence of the constraint in front of a crack tip, leading to multiaxial stress conditions and decreasing the material crack resistance significantly. Thus, the exclusion of crack initiation needs to be proven in a first step of each safety analysis. Assessing the component in a uniform way over the relevant temperature range is possible by using initiation characteristics, which also have the advantage of transferability. A change of criterion considering initiation at the lower shelf, instability in the transition range and again initiation in the upper shelf can be

  7. Improving the standard of the standard for glass ionomers: an alternative to the compressive fracture strength test for consideration?

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2012-03-01

    Three strength tests (compressive, three point flexure and biaxial) were performed on three glass ionomer (GI) restoratives to assess the most appropriate methodology in terms of validity and reliability. The influence of mixing induced variability on the data sets generated were eliminated by using encapsulated GIs.

  8. The effect of aging treatment on the high temperature fatigue strength and fatigue fracture behaviour of friction welded domestic heat resisting steels (SUH3-SUS303)

    International Nuclear Information System (INIS)

    Lee, K.Y.; Oh, S.K.; Kim, H.J.

    1981-01-01

    In this study the experiment was carried out as the high temperature rotary bending fatigue testing under the condition of 700 0 C high temperature to the friction welded domestic heat resisting steels, SUH3-SUS303, which were 10 hr., 100 hr. aging heat treated at 700 0 C after solution treatment 1 hr. at 1060 0 C for the purpose of observing the effects of the high temperature fatigue strength and fatigue fracture behaviours as well as with various mechanical properties of welded joints. The results obtained are summarized as follows: 1) Through mechanical tests and microstructural examinations, the determined optimum welding conditions, rotating speed 2420 rpm, heating pressure 8 kg/mm 2 , upsetting pressure 22 kg/mm 2 , the amount of total upset 7 mm (heating time 3 sec and upsetting time 2 sec) were satisfied. 2) The solution treated material SUH3, SUS303 and SUH3-SUS303, have the highest inclination gradiant on S-N curve due to the high temperature fatigue testing for long time at 700 0 C. 3) The optimum aging time of friction welded SUH3-SUS303, has been recognized near the 10 hr. at 700 0 C after the solution treatment of 1 hr. at 1060 0 C. 4) The high temperature fatigue limits of aging treated materials were compared with those of raw material according to the extender of aging time, on 10 hr. aging, fatigue limits were increased by SUH3 75.4%, SUS303 28.5%, friction welded joints SUH3-SUS303 44.2% and 100 hr. aging the rate were 64.9%, 30.4% and 36.6% respectively. 5) The fatigue fractures occurred at the side of the base metal SUS303 of the friction welded joints SUH3-SUS303 and it is difficult to find out fractures at the friction welding interfaces. 6) The cracking mode of SUS303, SUH3-SUS303 is intergranular in any case, but SUH3 is fractured by transgranular cracking. (author)

  9. Effects of combination of whey protein intake and rehabilitation on muscle strength and daily movements in patients with hip fracture in the early postoperative period.

    Science.gov (United States)

    Niitsu, Masaya; Ichinose, Daisuke; Hirooka, Taku; Mitsutomi, Kazuhiko; Morimoto, Yoshitaka; Sarukawa, Junichiro; Nishikino, Shoichi; Yamauchi, Katsuya; Yamazaki, Kaoru

    2016-08-01

    Elderly patients can be at risk of protein catabolism and malnutrition in the early postoperative period. Whey protein includes most essential amino acids and stimulates the synthesis of muscle protein. The purpose of this study was to investigate the effect of resistance training in combination with whey protein intake in the early postoperative period. We randomized patients to a whey protein group or a control group. The former group received 32.2 g of whey protein pre- and post-rehabilitation in the early postoperative period for two weeks. Outcomes were knee extension strength on either side by Biodex 4.0, and the ability of transfer, walking, toilet use and stair use by the Barthel Index (BI). We performed initial and final assessments in the second and tenth rehabilitation sessions. A total of 38 patients were recruited: 20 in the whey protein group and 18 in the control group. Participants in the whey protein group showed significantly greater improvement in knee extension strength in the operated limb compared with the control group (F = 6.11, P = 0.02). The non-operated limb also showed a similar tendency (F = 3.51, P = 0.07). The abilities of transfer, walking and toilet use showed greater improvements in the whey protein group than in the control group by BI (P patients with hip fracture. Copyright © 2015 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

  10. Fracture strength of zirconia implant abutments on narrow diameter implants with internal and external implant abutment connections: A study on the titanium resin base concept.

    Science.gov (United States)

    Sailer, Irena; Asgeirsson, Asgeir G; Thoma, Daniel S; Fehmer, Vincent; Aspelund, Thor; Özcan, Mutlu; Pjetursson, Bjarni E

    2018-04-01

    There is limited knowledge regarding the strength of zirconia abutments with internal and external implant abutment connections and zirconia abutments supported by a titanium resin base (Variobase, Straumann) for narrow diameter implants. To compare the fracture strength of narrow diameter abutments with different types of implant abutment connections after chewing simulation. Hundred and twenty identical customized abutments with different materials and implant abutment connections were fabricated for five groups: 1-piece zirconia abutment with internal connection (T1, Cares-abutment-Straumann BL-NC implant, Straumann Switzerland), 1-piece zirconia abutment with external hex connection (T2, Procera abutment-Branemark NP implant, Nobel Biocare, Sweden), 2-piece zirconia abutments with metallic insert for internal connection (T3, Procera abutment-Replace NP implant, Nobel Biocare), 2-piece zirconia abutment on titanium resin base (T4, LavaPlus abutment-VarioBase-Straumann BL-NC implant, 3M ESPE, Germany) and 1-piece titanium abutment with internal connection (C, Cares-abutment-Straumann BL-NC implant, Straumann, Switzerland). All implants had a narrow diameter ranging from 3.3 to 3.5 mm. Sixty un-restored abutments and 60 abutments restored with glass-ceramic crowns were tested. Mean bending moments were compared using ANOVA with p-values adjusted for multiple comparisons using Tukey's procedure. The mean bending moments were 521 ± 33 Ncm (T4), 404 ± 36 Ncm (C), 311 ± 106 Ncm (T1) 265 ± 22 Ncm (T3) and 225 ± 29 (T2) for un-restored abutments and 278 ± 84 Ncm (T4), 302 ± 170 Ncm (C), 190 ± 55 Ncm (T1) 80 ± 102 Ncm (T3) and 125 ± 57 (T2) for restored abutments. For un-restored abutments, C and T4 had similar mean bending moments, significantly higher than those of the three other groups (p internal connection had higher bending moments than zirconia abutments with external connection (T2) (p internal connected zirconia

  11. Effect of low appendicular lean mass, grip strength, and gait speed on the functional outcome after surgery for distal radius fractures.

    Science.gov (United States)

    Roh, Young Hak; Noh, Jung Ho; Gong, Hyun Sik; Baek, Goo Hyun

    2017-12-01

    Patients with low appendicular lean mass plus slow gait speed or weak grip strength are at risk for poor functional recovery after surgery for distal radius fracture, even when they have similar radiologic outcomes. Loss of skeletal muscle mass and consequent loss in muscle function associate with aging, and this condition negatively impacts the activities of daily living and increases elderly individuals' frailty to falls. Thus, patients with low appendicular lean mass would show different functional recovery compared to those without this condition after surgery for distal radius fracture (DRF). This study compares the functional outcomes after surgery for DRF in patients with or without low appendicular lean mass plus slowness or weakness. A total of 157 patients older than 50 years of age with a DRF treated via volar plate fixation were enrolled in this prospective study. A definition of low appendicular lean mass with slowness or weakness was based on the consensus of the Asian Working Group for Sarcopenia. The researchers compared functional assessments (wrist range of motion and Michigan Hand Questionnaire [MHQ]) and radiographic assessments (radial inclination, volar tilt, ulnar variance, and articular congruity) 12 months after surgery between patients with and without low appendicular lean mass plus slowness or weakness. Multivariable regression analyses were performed to determine whether appendicular lean mass, grip strength, gait speed, patient demographic, or injury characteristics accounted for the functional outcomes. Patients with low appendicular lean mass plus slowness or weakness showed a significantly lower recovery of MHQ score than those in the control group throughout 12 months. There was no significant difference in the range of motion between the groups. The radiologic outcomes showed no significant difference between groups in terms of volar tilt, radial inclination, or ulnar variance. According to multivariable regression analysis

  12. The effect of different irrigating solutions on the push out bond strength of endodontic sealer to dentin and assessing the fracture modes: An In-vitro study

    Directory of Open Access Journals (Sweden)

    Vasundhara Shivanna

    2014-01-01

    Full Text Available Aim: To evaluate the effect of smear clear, 7% maleic acid, 10% citric acid, and 17% EDTA on the push-out bond strength of epoxy resin-based endodontic sealer to dentin. Materials and Methodos: Fifty extracted mandibular premolars were collected. After decoronation using a diamond disc and water spray to obtain approximately 14 mm long root segments, canal patency and working length were established by inserting K file #15 (Mani. The root canals were enlarged using Protaper nickel-titanium rotary instruments to size #F3 at the working length irrigating with 3 mL of 2.6% sodium hypochlorite between each file size. The roots were then randomly divided into four groups (n = 10 according to the final irrigation regimen Group1: Saline (control. Group 2: 17% EDTA, Group 3: 7% maleic acid, Group 4: 10% citric acid, Group 5: Smear clear. Obturation was done using gutta-percha with AH Plus sealer. Each root section was then subjected to a compressive load via a universal testing machine, to measure the push out bond strength followed by assessment of fracture pattern under stereomicroscope. Results: The data was collected and submitted to statistical analysis by one-way analysis of variance (ANOVA test. Group 3: NaOCl/maleic acid/distilled water showed greater bond strength (2.2+/-0.278 MPa as compared to other groups. Mixed type of bond failure was predominant. Conclusion: Removal of smear layer with maleic acid as a final rinse enhanced the adhesive ability of AH plus sealer, followed by EDTA and smear clear.

  13. Effects of micro arc oxidation on fatigue limits and fracture morphologies of 7475 high strength aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dejun, Kong, E-mail: kong-dejun@163.com [College of Mechanical Engineering, Changzhou University, Changzhou, 213164 (China); Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou, 213164 (China); Hao, Liu; Jinchun, Wang [College of Mechanical Engineering, Changzhou University, Changzhou, 213164 (China)

    2015-11-25

    The oxide coatings with thicknesses of 8 μm, 10 μm, and 15 μm were prepared on 7475 aluminum alloy with micro arc oxidation (MAO) by controlling MAO time, the fatigue limits of original and MAO samples were contrastively measured by the Roccati method. The surface-interface morphologies, fracture morphologies, surface phases, and residual stresses of MAO coating were analyzed with a scanning electron microscopy (SEM), X-ray diffractometer (XRD) and XRD stress tester, respectively. The results show that fatigue limits of the MAO samples decreases as the coating thickness increasing. The fatigue limit of MAO sample with thickness of 8 μm, 10 μm, and 15 μm decreases by 6.48%, 8.33%, and 11.11%, respectively, compared with the original sample. The residual stress and defects introduced by MAO were the main factors of decreasing fatigue limits. - Graphical abstract: The fatigue limit of original sample was 216 MPa (a), while that of MAO samples with thickness of 8 μm, 10 μm and 15 μm was 202 MPa, 198 MPa and 192 MPa (b). The fatigue limit of MAO samples with thickness of 8 μm, 10 μm and 15 μm decreased by 6.48%, 8.33% and 11.11% compared with that of the original sample, as a result, the fatigue limit decreased with the MAO film thickness increasing. - Highlights: • The fatigue limits of MAO samples decrease with the oxide thickness increasing. • The overgrowth regions cause the crack source expanding. • The overgrowth of MAO film and tensile residual stress decrease fatigue limit.

  14. Effects of core-to-dentin thickness ratio on the biaxial flexural strength, reliability, and fracture mode of bilayered materials of zirconia core (Y-TZP) and veneer indirect composite resins.

    Science.gov (United States)

    Su, Naichuan; Liao, Yunmao; Zhang, Hai; Yue, Li; Lu, Xiaowen; Shen, Jiefei; Wang, Hang

    2017-01-01

    Indirect composite resins (ICR) are promising alternatives as veneering materials for zirconia frameworks. The effects of core-to-dentin thickness ratio (C/Dtr) on the mechanical property of bilayered veneer ICR/yttria-tetragonal zirconia polycrystalline (Y-TZP) core disks have not been previously studied. The purpose of this in vitro study was to assess the effects of C/Dtr on the biaxial flexural strength, reliability, and fracture mode of bilayered veneer ICR/ Y-TZP core disks. A total of 180 bilayered 0.6-mm-thick composite resin disks in core material and C/Dtr of 2:1, 1:1, and 1:2 were tested with either core material placed up or placed down for piston-on-3-ball biaxial flexural strength. The mean biaxial flexural strength, Weibull modulus, and fracture mode were measured to evaluate the variation trend of the biaxial flexural strength, reliability, and fracture mode of the bilayered disks with various C/Dtr. One-way analysis of variance (ANOVA) and chi-square tests were used to evaluate the variation tendency of fracture mode with the C/Dtr or material placed down during testing (α=.05). Light microscopy was used to identify the fracture mode. The mean biaxial flexural strength and reliability improved with the increase in C/Dtr when specimens were tested with the core material either up and down, and depended on the materials that were placed down during testing. The rates of delamination, Hertzian cone cracks, subcritical radial cracks, and number of fracture fragments partially depended on the C/Dtr and the materials that were placed down during testing. The biaxial flexural strength, reliability, and fracture mode in bilayered structures of Y-TZP core and veneer ICR depend on both the C/Dtr and the material that was placed down during testing. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  15. Fracture analysis

    International Nuclear Information System (INIS)

    Ueng, Tzoushin; Towse, D.

    1991-01-01

    Fractures are not only the weak planes of a rock mass, but also the easy passages for the fluid flow. Their spacing, orientation, and aperture will affect the deformability, strength, heat transmittal, and fluid transporting properties of the rock mass. To understand the thermomechanical and hydrological behaviors of the rock surrounding the heater emplacement borehole, the location, orientation, and aperture of the fractures of the rock mass should be known. Borehole television and borescope surveys were performed to map the location, orientation, and aperture of the fractures intersecting the boreholes drilled in the Prototype Engineered Barrier System Field Tests (PEBSFT) at G-Tunnel. Core logging was also performed during drilling. However, because the core was not oriented and the depth of the fracture cannot be accurately determined, the results of the core logging were only used as reference and will not be discussed here

  16. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

    Science.gov (United States)

    Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

    1998-01-01

    The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

  17. Fatigue properties for the fracture strength of columnar accessory minerals embedded within metamorphic tectonites: implications for stress magnitude in continental crust at the depth of the brittle-plastic transition zone

    Science.gov (United States)

    Kimura, N.; Iwashita, N.; Masuda, T.

    2009-04-01

    1. Introduction Previous studies have compiled yield-strength profiles of continental lithosphere based on the results of laboratory measurements and numerical calculations; however, yield-strength values remain poorly constrained, especially at depths below the brittle-plastic transition zone. Recent studies by the authors have refined the microboudin technique for estimating palaeostress magnitude in the deep crust (> 10 km depth). This technique has the potential to provide important information on stress levels in the deep continental crust, an environment to which available in situ stress measurements and palaeopiezometric methods cannot be applied. In applying the microboudinage technique, obtaining an estimate of the palaeostress magnitude requires knowledge of the fracture strength of columnar accessory minerals (e.g., tourmaline, amphibole, and epidote) that are subjected to brittle fracturing during plastic deformation of the surrounding matrix minerals. The absolute magnitude of fracture strength is known to show a marked reduction in the case of fatigue fracture. Fatigue fracture falls into two categories: static fatigue and cyclic fatigue. In the field of experimental rock deformation, stress corrosion by water molecules (static fatigue) is commonly invoked as the mechanism of fatigue fracture; however, evidence of both static and cyclic fatigue has been reported from studies of natural geological samples. The present study focused on the fatigue properties of columnar accessory minerals at high temperatures, with the aim of improving the accuracy of estimates of natural palaeostress magnitude at depth in the crust. 2. Constant stress-rate test A constant stress-rate test was performed to determine the influence of static fatigue on the strength of columnar accessory minerals. The test was conducted under three-point bending with a span distance of 10 mm. Temperature conditions and the crosshead speed were set in the ranges of ambient to 600°C, and 0

  18. Fracture Mechanics

    International Nuclear Information System (INIS)

    Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

    1992-08-01

    This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

  19. Comparison of fracture toughness values of normal and high strength concrete determined by three point bend and modified disk-shaped compact tension specimens

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Ríjos, J. D.; Cifuentes, H.

    2017-01-01

    Roč. 11, č. 42 (2017), s. 56-65 ISSN 1971-8993 R&D Projects: GA ČR(CZ) GA16-18702S; GA MŠk LM2015069 Institutional support: RVO:68081723 Keywords : Concrete * Stress intensity factors * T-stress * Compact tension test * Fracture behavior * Fracture toughness Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  20. Experimental study on the usefulness of magnetotherapy in bone fractures (tibial osteotomy in the rat). Accumulation of 99 mTc MDP - tests of tensile strength - determination of alkaline phosphatase

    International Nuclear Information System (INIS)

    Sailer, R.

    1985-01-01

    Non-directional magnetic field therapy using a flux density of 60 G and a frequency of 25 Hz was carried out over 12 hours daily in rats in order to ascertain its influence on the healing process following osteotomy of the tibia with internal splint fixation of the fractured bone being carried out as an additional measure. The results thus achieved were compared to those seen in control animals, were no magnetotherapy was carried out, on the basis of scintiscan studies using 99 mTc MDP (degree of density in the callus formed around the fracture zone), the plasma levels of alkaline phosphatase and tests of tensile strength. The follow-up observations of the healing process were additionally based on radiological and histological evaluations of the animals. Beneficial effects of magnetotherapy on the healing process could not be confirmed with any statistical significance. (TRV) [de

  1. Effects of incorporation of 2.5 and 5 wt% TiO2 nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA).

    Science.gov (United States)

    Abdulrazzaq Naji, Sahar; Behroozibakhsh, Marjan; Jafarzadeh Kashi, Tahereh Sadat; Eslami, Hossein; Masaeli, Reza; Mahgoli, Hosseinali; Tahriri, Mohammadreza; Ghavvami Lahiji, Mehrsima; Rakhshan, Vahid

    2018-04-01

    The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO 2 ) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. TiO 2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO 2 :PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO 2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. SEM images of n-TiO 2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO 2 represented the anatase crystal phase of TiO 2 . Moderate to very strong significant positive correlations were observed between the concentration of n-TiO 2 and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO 2 were significantly higher than those of control ( P ≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO 2 (but not those of 2.5% n-TiO 2 ) was higher than control ( P =.002). Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

  2. [An in vitro study of the fracture strength of tooth preparations for Empress 2 veneers and crowns and mandibular incisors restored with Empress 2 veneers and crowns].

    Science.gov (United States)

    Wei, Xue; Li, Yan

    2009-12-01

    To compare the fracture resistance of mandibular incisors' preparations for veneers and crowns, mandibular incisors restored with Empress 2 veneers and crowns. 50 human mandibular incisors were randomly divided into five groups. Each group consisted of ten teeth and the treatment obtained as follows: A, tooth preparations for veneers; B, tooth preparations for crowns; C, teeth restored with veneers; D, teeth restored with crowns; E, untreated group. The teeth received standardized preparation and the restorations were manufactured with Empress 2 system and cemented with resin luting agent. The fracture resistances of teeth were measured by Instron universal testing machine and statistically analyzed with one-way ANOVA. The fracture resistances of A, B, C, D, E were (576.11 +/- 91.53), (204.13 +/- 85.88), (451.50 +/- 116.81), (386.16 +/- 117.75) and (566.05 +/- 121.37) N, respectively. The statistical analysis demonstrated significant differences between five groups. There were no significant differences between group A and E, group C and D. Tooth preparations for veneers did not significantly reduce the fracture resistance of mandibular incisor. The fracture resistance of teeth restored with Empress 2 veneers and crowns did not significantly differ from each other.

  3. Statistics and thermodynamics of fracture

    Science.gov (United States)

    Chudnovsky, A.

    1984-01-01

    A probabilistic model of the fracture processes unifying the phenomenological study of long term strength of materials, fracture mechanics and statistical approaches to fracture is briefly outlined. The general framework of irreversible thermodynamics is employed to model the deterministic side of the failure phenomenon. The stochastic calculus is used to account for thg failure mechanisms controlled by chance; particularly, the random roughness of fracture surfaces.

  4. A comparative study to check fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate resin reinforced with different materials: An in vitro study

    Directory of Open Access Journals (Sweden)

    Parikshit Gupt

    2017-01-01

    Conclusion: Unidirectional glass fibers showed the maximum strength, which was comparable to mean values of both stainless steel wire groups. Low cost and easy technique of using stainless steel wire make it the material of choice over the unidirectional glass fiber for reinforcement in nonesthetic areas where high strength is required.

  5. Effect of diameter of the drill hole on torque of screw insertion and pushout strength for headless tapered compression screws in simulated fractures of the lateral condyle of the equine third metacarpal bone.

    Science.gov (United States)

    Carpenter, Ryan S; Galuppo, Larry D; Stover, Susan M

    2006-05-01

    To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model. 6 pairs of third metacarpal bones from horse cadavers. Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests. Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes. Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.

  6. Model of T-Type Fracture in Coal Fracturing and Analysis of Influence Factors of Fracture Morphology

    Directory of Open Access Journals (Sweden)

    Yuwei Li

    2018-05-01

    Full Text Available Special T-type fractures can be formed when coal is hydraulically fractured and there is currently no relevant theoretical model to calculate and describe them. This paper first establishes the height calculation model of vertical fractures in multi-layered formations and deduces the stress intensity factor (SIF at the upper and lower sides of the fracture in the process of vertical fracture extension. Combined with the fracture tip stress analysis method of fracture mechanics theory, the horizontal bedding is taken into account for tensile and shear failure, and the critical mechanical conditions for the formation of horizontal fracture in coal are obtained. Finally, the model of T-type fracture in coal fracturing is established, and it is verified by fracturing simulation experiments. The model calculation result shows that the increase of vertical fracture height facilitates the increase of horizontal fracture length. The fracture toughness of coal has a significant influence on the length of horizontal fracture and there is a threshold. When the fracture toughness is less than the threshold, the length of horizontal fracture remains unchanged, otherwise, the length of horizontal fracture increases rapidly with the increase of fracture toughness. When the shear strength of the interface between the coalbed and the interlayer increases, the length of the horizontal fracture of the T-type fracture rapidly decreases.

  7. Effect of boundary conditions on the strength and deformability of replicas of natural fractures in welded tuff: Comparison between predicted and observed shear behavior using a graphical method

    International Nuclear Information System (INIS)

    Wibowo, J.; Amadei, B.; Sture, S.; Robertson, A.B.

    1993-09-01

    Four series of cyclic direct-shear experiments were conducted on several replicas of three natural fractures and a laboratory-developed tensile fracture of welded tuff from Yucca Mountain to test the graphical load-displacement analysis method proposed by Saeb (1989) and Amadei and Saeb (1990). Based on the results of shear tests conducted on several joint replicas under different levels of constant normal load ranging between 0.6 and 25.6 kips (2.7 and 113.9 kN), the shear behavior of joint replicas under constant normal stiffness ranging between 14.8 and 187.5 kips/in. (25.9 and 328.1 kN/cm) was predicted by using the graphical method. The predictions were compared to the results of actual shear tests conducted for the same range of constant normal stiffness. In general, a good agreement was found between the predicted and the observed shear behavior

  8. Plane strain fracture toughness tests on 2.4 and 3.9-inch-thick maraging steel specimens at various yield strength levels.

    Science.gov (United States)

    Fisher, D. M.; Repko, A. J.

    1972-01-01

    Tests of bend and compact specimens were conducted according to ASTM Tentative Method E 399-70T on a 200 grade maraging steel over a range of yield strengths from 123 to 234 ksi. The toughness of any given yield strength level was greater for the overaged condition than for the underaged. Some results which met the specimen size requirements of the method were distinctly lower than corresponding results from larger specimens. Inconsistencies in both validation and invalidation of results by the requirement for linearity of the test record were also noted.

  9. Characterization of fracture and deformation mechanism in a high strength beta titanium alloy Ti-10-2-3 using EBSD technique

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Jalaj, E-mail: jalaj@dmrl.drdo.in; Singh, Vajinder; Ghosal, Partha; Kumar, Vikas

    2015-01-19

    In the present study, fracture toughness tested specimens in longitudinal (LT) and transverse loading (TL) directions of beta titanium alloy have been investigated using Electron Back Scattered Diffraction (EBSD) technique. The orientation images captured at three different locations i.e. machine notch, fatigue pre-crack and final fracture have been compared. The LT sample exhibits with more facets than TL sample. The faceted aspect of the crack is generally associated with quasi-cleavage mechanism. The EBSD analysis clearly points out that in the LT specimen, the hexagonal orientation has moved towards near basal during the test. This may be the reason for the observance of facets in the LT specimen. The cracking in TL specimen might have been taken over by the bcc phase as it is oriented with harder planes of cubic {001} planes. Further, the Schmid factor has also been computed based on the defined loading conditions. Significant variation has been observed in the slip plane orientations and distributions at these three locations. The Schmid analysis has highlighted the significant contribution of different slip systems towards deformation and cracking in LT and TL specimens.

  10. Why ductile fracture mechanics

    International Nuclear Information System (INIS)

    Ritchie, R.O.

    1983-01-01

    Until recently, the engineering application of fracture mechanics has been specific to a description of macroscopic fracture behavior in components and structural parts which remain nominally elastic under loading. While this approach, termed linear elastic fracture mechanics, has been found to be invaluable for the continuum analysis of crack growth in brittle and high strength materials, it is clearly inappropriate for characterizing failure in lower strength ductile alloys where extensive inelastic deformation precedes and accompanies crack initiation and subsequent propagation. Accordingly, much effort has been devoted in recent years toward the development of nonlinear or ductile fracture mechanics methodology to characterize fracture behavior under elastic/plastic conditions; an effort which has been principally motivated by problems in nuclear industry. In this paper, the concepts of ductile (elastic/plastic) fracture mechanics are introduced and applied to the problem of both stationary and nonstationary cracks. Specifically, the limitations inherent in this approach are defined, together with a description of the microstructural considerations and applications relevant to the failure of ductile materials by fracture, fatigue, and creep

  11. Later Age at Onset of Independent Walking Is Associated With Lower Bone Strength at Fracture-Prone Sites in Older Men.

    Science.gov (United States)

    Ireland, Alex; Muthuri, Stella; Rittweger, Joern; Adams, Judith E; Ward, Kate A; Kuh, Diana; Cooper, Rachel

    2017-06-01

    Later age at onset of independent walking is associated with lower leg bone strength in childhood and adolescence. However, it is unknown whether these associations persist into older age or whether they are evident at axial (central) or upper limb sites. Therefore, we examined walking age obtained at age 2 years and bone outcomes obtained by dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) scans at ages 60 to 64 years in a nationally representative cohort study of British people, the MRC National Survey of Health and Development. It was hypothesized that later walking age would be associated with lower bone strength at all sites. Later independent walking age was associated with lower height-adjusted hip (standardized regression coefficients with 95% confidence interval [CI] -0.179 [-0.251 to -0.107]), spine (-0.157 [-0.232 to -0.082]), and distal radius (-0.159 [-0.245 to -0.073]) bone mineral content (BMC, indicating bone compressive strength) in men (all p lower lean mass and adolescent sporting ability in later walkers. These associations were also evident for a number of hip geometric parameters (including cross-sectional moment of inertia [CSMI], indicating bone bending/torsional strength) assessed by hip structural analysis (HSA) from DXA scans. Similar height-adjusted associations were also observed in women for several hip, spine, and upper limb outcomes, although adjustment for fat or lean mass led to complete attenuation for most outcomes, with the exception of femoral shaft CSMI and spine bone area (BA). In conclusion, later independent walking age appears to have a lifelong association with bone strength across multiple skeletal sites in men. These effects may result from direct effects of early life loading on bone growth and mediation by adult body composition. Results suggest that late walking age may represent a novel risk factor for subsequent low bone strength. Existing interventions effective in

  12. Fracture strength and probability of survival of narrow and extra-narrow dental implants after fatigue testing: In vitro and in silico analysis.

    Science.gov (United States)

    Bordin, Dimorvan; Bergamo, Edmara T P; Fardin, Vinicius P; Coelho, Paulo G; Bonfante, Estevam A

    2017-07-01

    To assess the probability of survival (reliability) and failure modes of narrow implants with different diameters. For fatigue testing, 42 implants with the same macrogeometry and internal conical connection were divided, according to diameter, as follows: narrow (Ø3.3×10mm) and extra-narrow (Ø2.9×10mm) (21 per group). Identical abutments were torqued to the implants and standardized maxillary incisor crowns were cemented and subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves, and reliability for a mission of 50,000 and 100,000 cycles at 50N, 100, 150 and 180N were calculated. For the finite element analysis (FEA), two virtual models, simulating the samples tested in fatigue, were constructed. Loading at 50N and 100N were applied 30° off-axis at the crown. The von-Mises stress was calculated for implant and abutment. The beta (β) values were: 0.67 for narrow and 1.32 for extra-narrow implants, indicating that failure rates did not increase with fatigue in the former, but more likely were associated with damage accumulation and wear-out failures in the latter. Both groups showed high reliability (up to 97.5%) at 50 and 100N. A decreased reliability was observed for both groups at 150 and 180N (ranging from 0 to 82.3%), but no significant difference was observed between groups. Failure predominantly involved abutment fracture for both groups. FEA at 50N-load, Ø3.3mm showed higher von-Mises stress for abutment (7.75%) and implant (2%) when compared to the Ø2.9mm. There was no significant difference between narrow and extra-narrow implants regarding probability of survival. The failure mode was similar for both groups, restricted to abutment fracture. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high-strength......Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high......-strength concrete. Chapter 2 A description of the factors which influence the strength and cracking of concrete and high strength concrete is made. Then basic linear fracture mechanics is outlined followed by a description and evaluation of the models used to describe concrete fracture in tension. The chapter ends...... and the goveming equations are explicit and simple. These properties of the model make it a very powerful tool, which is applicable for the designing engineer. The method is also extended to reinforced concrete, where the results look very promising. The large experimental investigation on high-strength concrete...

  14. Rock fracture processes in chemically reactive environments

    Science.gov (United States)

    Eichhubl, P.

    2015-12-01

    Rock fracture is traditionally viewed as a brittle process involving damage nucleation and growth in a zone ahead of a larger fracture, resulting in fracture propagation once a threshold loading stress is exceeded. It is now increasingly recognized that coupled chemical-mechanical processes influence fracture growth in wide range of subsurface conditions that include igneous, metamorphic, and geothermal systems, and diagenetically reactive sedimentary systems with possible applications to hydrocarbon extraction and CO2 sequestration. Fracture processes aided or driven by chemical change can affect the onset of fracture, fracture shape and branching characteristics, and fracture network geometry, thus influencing mechanical strength and flow properties of rock systems. We are investigating two fundamental modes of chemical-mechanical interactions associated with fracture growth: 1. Fracture propagation may be aided by chemical dissolution or hydration reactions at the fracture tip allowing fracture propagation under subcritical stress loading conditions. We are evaluating effects of environmental conditions on critical (fracture toughness KIc) and subcritical (subcritical index) fracture properties using double torsion fracture mechanics tests on shale and sandstone. Depending on rock composition, the presence of reactive aqueous fluids can increase or decrease KIc and/or subcritical index. 2. Fracture may be concurrent with distributed dissolution-precipitation reactions in the hostrock beyond the immediate vicinity of the fracture tip. Reconstructing the fracture opening history recorded in crack-seal fracture cement of deeply buried sandstone we find that fracture length growth and fracture opening can be decoupled, with a phase of initial length growth followed by a phase of dominant fracture opening. This suggests that mechanical crack-tip failure processes, possibly aided by chemical crack-tip weakening, and distributed solution-precipitation creep in the

  15. Hip Fracture

    Science.gov (United States)

    ... hip fractures in people of all ages. In older adults, a hip fracture is most often a result of a fall from a standing height. In people with very weak bones, a hip fracture can occur simply by standing on the leg and twisting. Risk factors The rate of hip fractures increases substantially with ...

  16. Fracture mechanics and parapsychology

    Science.gov (United States)

    Cherepanov, G. P.

    2010-08-01

    The problem of postcritical deformation of materials beyond the ultimate strength is considered a division of fracture mechanics. A simple example is used to show the relationship between this problem and parapsychology, which studies phenomena and processes where the causality principle fails. It is shown that the concept of postcritical deformation leads to problems with no solution

  17. Avaliação da força de preensão e funcionalidade após fratura distal de rádio/Evaluation of strength and functionality after distal radius fracture

    Directory of Open Access Journals (Sweden)

    Bruno Goto Kimura

    2017-09-01

    Full Text Available Esse estudo teve objetivo avaliar se existe diferença em relação a força de preensão e funcionalidade de pacientes com fratura distal de rádio em relação ao gênero e ao tipo de tratamento (conservador e cirúrgico. Os pacientes recrutados para este estudo foram divididos em dois grupos, grupo de homens (G1 e grupo de mulheres (G2. Todos os voluntários realizaram uma única avaliação da força de preensão palmar e a avaliação funcional pelos questionários Disability of the Arm, Shoulder and Hand (DASH e Patient Rated Wrist Evaluation (PRWE.Os valores de força de preensão foram significativamente (p<0,000 menores no grupo de mulheres 5,42 (±3,42 e no tratamento conservador 5,20 (±4,91 quando comparados aos homens 16,01 (±6,86 e ao tratamento cirúrgico 12,28 (±7,56. Enquanto que os valores de incapacidade, avaliados pelos questionários DASH e PRWE, foram maiores no grupo de mulheres e pacientes que realizaram tratamento conservador, porém não foram encontradas diferenças significativas. As fraturas distais de rádio se não reabilitadas precocemente podem comprometer a amplitude de movimento, a força muscular, a precisão, a destreza e controle dos movimentos. Neste caso, os questionários de funcionalidade são um parâmetro importante que refletem o desempenho do indivíduo durante a realização de atividades de vida diária, sendo que quanto pior os escores, pior o desempenho e autonomia desses pacientes. Nesse estudo, podemos concluir que o gênero e o tipo de tratamento influenciaram na diminuição da força de preensão e na maior incapacidade funcional na avaliação inicial após 45 dias da fratura. AbstractThis study had the objective of evaluating whether there is a difference in the grip strength and functionality of patients with distal radius fracture in relation to gender and type of treatment (conservative and surgical. The patients recruited for this study were divided into two groups, group of men (G1

  18. Early age fracture properties of microstructurally-designed mortars

    DEFF Research Database (Denmark)

    Di Bella, Carmelo; Michel, Alexander; Stang, Henrik

    2017-01-01

    This paper compares the fracture properties as well as crack initiation and propagation of real and equivalent mortars. The development of the elastic modulus, tensile strength, and fracture energy at different hydration stages were determined by inverse analysis of load-displacement curves...... the two mortars. At early age, the moisture content has a considerable influence on the tensile strength and the fracture energy....

  19. Strength evaluation code STEP for brittle materials

    International Nuclear Information System (INIS)

    Ishihara, Masahiro; Futakawa, Masatoshi.

    1997-12-01

    In a structural design using brittle materials such as graphite and/or ceramics it is necessary to evaluate the strength of component under complex stress condition. The strength of ceramic materials is said to be influenced by the stress distribution. However, in the structural design criteria simplified stress limits had been adopted without taking account of the strength change with the stress distribution. It is, therefore, important to evaluate the strength of component on the basis of the fracture model for brittle material. Consequently, the strength evaluation program, STEP, on a brittle fracture of ceramic materials based on the competing risk theory had been developed. Two different brittle fracture modes, a surface layer fracture mode dominated by surface flaws and an internal fracture mode by internal flaws, are treated in the STEP code in order to evaluate the strength of brittle fracture. The STEP code uses stress calculation results including complex shape of structures analyzed by the generalized FEM stress analysis code, ABAQUS, so as to be possible to evaluate the strength of brittle fracture for the structures having complicate shapes. This code is, therefore, useful to evaluate the structural integrity of arbitrary shapes of components such as core graphite components in the HTTR, heat exchanger components made of ceramics materials etc. This paper describes the basic equations applying to the STEP code, code system with a combination of the STEP and the ABAQUS codes and the result of the verification analysis. (author)

  20. Rib Fractures

    Science.gov (United States)

    ... Video) Achilles Tendon Tear Additional Content Medical News Rib Fractures By Thomas G. Weiser, MD, MPH, Associate Professor, ... Tamponade Hemothorax Injury to the Aorta Pulmonary Contusion Rib Fractures Tension Pneumothorax Traumatic Pneumothorax (See also Introduction to ...

  1. Root fractures

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

    2012-01-01

    The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

  2. Stress Fractures

    Science.gov (United States)

    Stress fractures Overview Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of ...

  3. Mechanical properties of fracture zones

    International Nuclear Information System (INIS)

    Leijon, B.

    1993-05-01

    Available data on mechanical characteristics of fracture zones are compiled and discussed. The aim is to improve the basis for adequate representation of fracture zones in geomechanical models. The sources of data researched are primarily borehole investigations and case studies in rock engineering, involving observations of fracture zones subjected to artificial load change. Boreholes only yield local information about the components of fracture zones, i.e. intact rock, fractures and various low-strength materials. Difficulties are therefore encountered in evaluating morphological and mechanical properties of fracture zones from borehole data. Although often thought of as macroscopically planar features, available field data consistently show that fracture zones are characterized by geometrical irregularities such as thickness variations, surface undulation and jogs. These irregularities prevail on all scales. As a result, fracture zones are on all scales characterized by large, in-plane variation of strength- and deformational properties. This has important mechanical consequences in terms of non-uniform stress transfer and complex mechanisms of shear deformation. Field evidence for these findings, in particular results from the underground research laboratory in Canada and from studies of induced fault slip in deep mines, is summarized and discussed. 79 refs

  4. [Hip Fracture--Epidemiology, Management and Liaison Service. Risk factor for hip fracture].

    Science.gov (United States)

    Fujiwara, Saeko

    2015-04-01

    Many risk factors have been identified for hip fracture, including female, advanced age, osteoporosis, previous fractures, low body weight or low body mass index, alcohol drinking, smoking, family history of fractures, use of glucocorticoid, factors related to falls, and bone strength. The factors related to falls are number of fall, frail, post stroke, paralysis, muscle weakness, anti-anxiety drugs, anti-depression drugs, and sedatives. Dementia and respiratory disease and others have been reported to be risk factors for secondary hip fracture.

  5. DEM Particle Fracture Model

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Boning [Univ. of Colorado, Boulder, CO (United States); Herbold, Eric B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Homel, Michael A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Regueiro, Richard A. [Univ. of Colorado, Boulder, CO (United States)

    2015-12-01

    An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density and packings o the samples are also studied in numerical examples.

  6. Hydraulic fracture propagation modeling and data-based fracture identification

    Science.gov (United States)

    Zhou, Jing

    Successful shale gas and tight oil production is enabled by the engineering innovation of horizontal drilling and hydraulic fracturing. Hydraulically induced fractures will most likely deviate from the bi-wing planar pattern and generate complex fracture networks due to mechanical interactions and reservoir heterogeneity, both of which render the conventional fracture simulators insufficient to characterize the fractured reservoir. Moreover, in reservoirs with ultra-low permeability, the natural fractures are widely distributed, which will result in hydraulic fractures branching and merging at the interface and consequently lead to the creation of more complex fracture networks. Thus, developing a reliable hydraulic fracturing simulator, including both mechanical interaction and fluid flow, is critical in maximizing hydrocarbon recovery and optimizing fracture/well design and completion strategy in multistage horizontal wells. A novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple nonplanar fractures' propagation in both homogeneous and heterogeneous reservoirs with or without pre-existing natural fractures. Initiation, growth, and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. This physics-based modeling approach leads to realistic fracture patterns without using the empirical rock failure and fracture propagation criteria required in conventional continuum methods. Based on this model, a sensitivity study is performed to investigate the effects of perforation spacing, in-situ stress anisotropy, rock properties (Young's modulus, Poisson's ratio, and compressive strength), fluid properties, and natural fracture properties on hydraulic fracture propagation. In addition, since reservoirs are buried thousands of feet below the surface, the

  7. Acetabular Fracture

    Directory of Open Access Journals (Sweden)

    Chad Correa

    2017-09-01

    Full Text Available History of present illness: A 77-year-old female presented to her primary care physician (PCP with right hip pain after a mechanical fall. She did not lose consciousness or have any other traumatic injuries. She was unable to ambulate post-fall, so X-rays were ordered by her PCP. Her X-rays were concerning for a right acetabular fracture (see purple arrows, so the patient was referred to the emergency department where a computed tomography (CT scan was ordered. Significant findings: The non-contrast CT images show a minimally displaced comminuted fracture of the right acetabulum involving the acetabular roof, medial and anterior walls (red arrows, with associated obturator muscle hematoma (blue oval. Discussion: Acetabular fractures are quite rare. There are 37 pelvic fractures per 100,000 people in the United States annually, and only 10% of these involve the acetabulum. They occur more frequently in the elderly totaling an estimated 4,000 per year. High-energy trauma is the primary cause of acetabular fractures in younger individuals and these fractures are commonly associated with other fractures and pelvic ring disruptions. Fractures secondary to moderate or minimal trauma are increasingly of concern in patients of advanced age.1 Classification of acetabular fractures can be challenging. However, the approach can be simplified by remembering the three basic types of acetabular fractures (column, transverse, and wall and their corresponding radiologic views. First, column fractures should be evaluated with coronally oriented CT images. This type of fracture demonstrates a coronal fracture line running caudad to craniad, essentially breaking the acetabulum into two halves: a front half and a back half. Secondly, transverse fractures should be evaluated by sagittally oriented CT images. By definition, a transverse fracture separates the acetabulum into superior and inferior halves with the fracture line extending from anterior to posterior

  8. Pathogenesis of osteoporotic hip fractures.

    Science.gov (United States)

    McClung, Michael R

    2003-01-01

    Osteoporosis is characterized late in the course of the disease by an increased risk of fracture, particularly in the elderly. It occurs in both sexes, affecting approximately 8 million women and 2 million men aged > or = 50 years (1). While low bone density is a predictor of fractures, it is not the only determinant of fracture risk. Other factors include advanced age, altered bone quality, a personal or family history of falls, frailty, poor eyesight, debilitating diseases, and high bone turnover. A diet with sufficient calcium and vitamin D is important to minimize bone loss and, along with regular exercise, to maintain muscle strength. Bisphosphonates have been shown to reduce the risk of hip fracture. For elderly patients, the use of hip protectors may be used as a treatment of last resort. Regardless of the age of the patient, individual patient risk factors must be considered to target appropriate treatment and prevent fracture.

  9. Mandible Fractures.

    Science.gov (United States)

    Pickrell, Brent B; Serebrakian, Arman T; Maricevich, Renata S

    2017-05-01

    Mandible fractures account for a significant portion of maxillofacial injuries and the evaluation, diagnosis, and management of these fractures remain challenging despite improved imaging technology and fixation techniques. Understanding appropriate surgical management can prevent complications such as malocclusion, pain, and revision procedures. Depending on the type and location of the fractures, various open and closed surgical reduction techniques can be utilized. In this article, the authors review the diagnostic evaluation, treatment options, and common complications of mandible fractures. Special considerations are described for pediatric and atrophic mandibles.

  10. Facial Fractures.

    Science.gov (United States)

    Ghosh, Rajarshi; Gopalkrishnan, Kulandaswamy

    2018-06-01

    The aim of this study is to retrospectively analyze the incidence of facial fractures along with age, gender predilection, etiology, commonest site, associated dental injuries, and any complications of patients operated in Craniofacial Unit of SDM College of Dental Sciences and Hospital. This retrospective study was conducted at the Department of OMFS, SDM College of Dental Sciences, Dharwad from January 2003 to December 2013. Data were recorded for the cause of injury, age and gender distribution, frequency and type of injury, localization and frequency of soft tissue injuries, dentoalveolar trauma, facial bone fractures, complications, concomitant injuries, and different treatment protocols.All the data were analyzed using statistical analysis that is chi-squared test. A total of 1146 patients reported at our unit with facial fractures during these 10 years. Males accounted for a higher frequency of facial fractures (88.8%). Mandible was the commonest bone to be fractured among all the facial bones (71.2%). Maxillary central incisors were the most common teeth to be injured (33.8%) and avulsion was the most common type of injury (44.6%). Commonest postoperative complication was plate infection (11%) leading to plate removal. Other injuries associated with facial fractures were rib fractures, head injuries, upper and lower limb fractures, etc., among these rib fractures were seen most frequently (21.6%). This study was performed to compare the different etiologic factors leading to diverse facial fracture patterns. By statistical analysis of this record the authors come to know about the relationship of facial fractures with gender, age, associated comorbidities, etc.

  11. Fracture sacrum.

    Directory of Open Access Journals (Sweden)

    Dogra A

    1995-04-01

    Full Text Available An extremely rare case of combined transverse and vertical fracture of sacrum with neurological deficit is reported here with a six month follow-up. The patient also had an L1 compression fracture. The patient has recovered significantly with conservative management.

  12. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  13. Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

    Directory of Open Access Journals (Sweden)

    Marte Gutierrez

    2015-12-01

    Full Text Available Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix. Understanding the effects of fracture geometrical distribution, such as length, spacing, persistence and orientation, is important for quantifying the mechanical behavior of fractured rock masses. The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale. In this paper, a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, three different simulation techniques involving Oda's elastic compliance tensor, Monte Carlo simulation (MCS, and suitable probability density functions (PDFs were employed to represent the elastic compliance of fractured rock masses. To yield geologically realistic results, parameters for defining fracture distributions were obtained from different geological fields. The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed. A detailed study was also carried out to investigate the validity of the use of a representative element volume (REV in the equivalent continuum representation of fractured rock masses. A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.

  14. Strength and life under creeping

    International Nuclear Information System (INIS)

    Pospishil, B.

    1982-01-01

    Certain examples of the application of the Lepin modified creep model, which are of interest from technical viewpoint, are presented. Mathematical solution of the dependence of strength limit at elevated temperatures on creep characteristics is obtained. Tensile test at elevated temperatures is a particular case of creep or relaxation and both strength limit and conventional yield strength at elevated temperatures are completely determined by parameters of state equations during creep. The equation of fracture summing during creep is confirmed not only by the experiment data when stresses change sporadically, but also by good reflection of durability curve using the system of equations. The system presented on the basis of parameters of the equations obtained on any part of durability curve, permits to forecast the following parameters of creep: strain, strain rate, life time, strain in the process of fracture. Tensile test at elevated temperature is advisable as an addition when determining creep curves (time-strain curves) [ru

  15. Fracture mechanics and microstructures

    International Nuclear Information System (INIS)

    Gee, M.G.; Morrell, R.

    1986-01-01

    The influence of microstructure on defects in ceramics, and the consequences of their presence for the application of fracture mechanics theories are reviewed. The complexities of microstructures, especially the multiphase nature, the crystallographic anisotropy and the resultant anisotropic physical properties, and the variation of microstructure and surface finish from point to point in real components, all lead to considerable uncertainties in the actual performance of any particular component. It is concluded that although the concepts of fracture mechanics have been and will continue to be most useful for the qualitative explanation of fracture phenomena, the usefulness as a predictive tool with respect to most existing types of material is limited by the interrelation between material microstructure and mechanical properties. At present, the only method of eliminating components with unsatisfactory mechanical properties is to proof-test them, despite the fact that proof-testing itself is limited in ability to cope with changes to the component in service. The aim of the manufacturer must be to improve quality and consistency within individual components, from component to component, and from batch to batch. The aim of the fracture specialist must be to study longer-term properties to improve the accuracy of behaviour predictions with a stronger data base. Materials development needs to concentrate on obtaining defect-free materials that can be translated into more-reliable products, using our present understanding of the influence of microstructure on strength and toughness

  16. Fracture mechanics

    CERN Document Server

    Perez, Nestor

    2017-01-01

    The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

  17. Facial Fractures.

    Science.gov (United States)

    Ricketts, Sophie; Gill, Hameet S; Fialkov, Jeffery A; Matic, Damir B; Antonyshyn, Oleh M

    2016-02-01

    After reading this article, the participant should be able to: 1. Demonstrate an understanding of some of the changes in aspects of facial fracture management. 2. Assess a patient presenting with facial fractures. 3. Understand indications and timing of surgery. 4. Recognize exposures of the craniomaxillofacial skeleton. 5. Identify methods for repair of typical facial fracture patterns. 6. Discuss the common complications seen with facial fractures. Restoration of the facial skeleton and associated soft tissues after trauma involves accurate clinical and radiologic assessment to effectively plan a management approach for these injuries. When surgical intervention is necessary, timing, exposure, sequencing, and execution of repair are all integral to achieving the best long-term outcomes for these patients.

  18. Pisiform fractures

    International Nuclear Information System (INIS)

    Fleege, M.A.; Jebson, P.J.; Renfrew, D.L.; El-Khoury, G.Y.; Steyers, C.M. Jr.

    1991-01-01

    Fractures of the pisiform are often missed due to improper radiographic evaluation and a tendency to focus on other, more obvious injuries. Delayed diagnosis may result in disabling sequelae. A high index of clinical suspicion and appropriate radiographic examination will establish the correct diagnosis. Ten patients with pisiform fracture are presented. The anatomy, mechanism of injury, clinical presentation, radiographic features, and evaluation of this injury are discussed. (orig.)

  19. Stress fractures

    International Nuclear Information System (INIS)

    Berquist, T.H.; Cooper, K.L.; Pritchard, D.J.

    1985-01-01

    The diagnosis of a stress fracture should be considered in patients presented with pain after a change in activity, especially if the activity is strenuous and the pain is in the lower extremities. Since evidence of the stress fracture may not be apparent for weeks on routine radiographs, proper use of other imaging techniques will allow an earlier diagnosis. Prompt diagnosis is especially important in the femur, where displacement may occur

  20. Crack propagation and fracture in silicon carbide

    International Nuclear Information System (INIS)

    Evans, A.G.; Lange, F.F.

    1975-01-01

    Fracture mechanics and strength studies performed on two silicon carbides - a hot-pressed material (with alumina) and a sintered material (with boron) - have shown that both materials exhibit slow crack growth at room temperature in water, but only the hot-pressed material exhibits significant high temperature slow crack growth (1000 to 1400 0 C). A good correlation of the observed fracture behaviour with the crack growth predicted from the fracture mechanics parameters shows that effective failure predictions for this material can be achieved using macro-fracture mechanics data. (author)

  1. Strength and failure modes of ceramic multilayers

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Toftegaard, Helmuth Langmaack; Linderoth, Søren

    2012-01-01

    A model was developed for the prediction of the tensile strength of thin, symmetric 3-layer sandwich specimens. The model predictions rationalize the effect of heat-treatment temperature on the strength of sandwich specimens consisting of an YSZ (Yttria-Stabilized Zirconia) substrate coated with ...... and propagating into the substrate. These predictions are consistent with microstructural observations of the fracture surfaces. A good agreement was found between the measured strength values and model predictions. © 2012 Elsevier Ltd. All rights reserved....

  2. Scaphoid Fracture

    Directory of Open Access Journals (Sweden)

    Esther Kim, BS

    2018-04-01

    Full Text Available History of present illness: A 25-year-old, right-handed male presented to the emergency department with left wrist pain after falling from a skateboard onto an outstretched hand two-weeks prior. He otherwise had no additional concerns, including no complaints of weakness or loss of sensation. On physical exam, there was tenderness to palpation within the anatomical snuff box. The neurovascular exam was intact. Plain films of the left wrist and hand were obtained. Significant findings: The anteroposterior (AP plain film of this patient demonstrates a full thickness fracture through the middle third of the scaphoid (red arrow, with some apparent displacement (yellow lines and subtle angulation of the fracture fragments (blue line. Discussion: The scaphoid bone is the most commonly fractured carpal bone accounting for 70%-80% of carpal fractures.1 Classically, it is sustained following a fall onto an outstretched hand (FOOSH. Patients should be evaluated for tenderness with palpation over the anatomical snuffbox, which has a sensitivity of 100% and specificity of 40%.2 Plain films are the initial diagnostic modality of choice and have a sensitivity of 70%, but are commonly falsely negative in the first two to six weeks of injury (false negative of 20%.3 The Mayo classification organizes scaphoid fractures as involving the proximal, mid, and distal portions of the scaphoid bone with mid-fractures being the most common.3 The proximal scaphoid is highly susceptible to vascular compromise because it depends on retrograde blood flow from the radial artery. Therefore, disruption can lead to serious sequelae including osteonecrosis, arthrosis, and functional impairment. Thus, a low threshold should be maintained for neurovascular evaluation and surgical referral. Patients with non-displaced scaphoid fractures should be placed in a thumb spica splint.3 Patients with even suspected scaphoid fractures should be placed in a thumb spica splint and re

  3. Tensile and fracture behavior of polymer foams

    International Nuclear Information System (INIS)

    Kabir, Md. E.; Saha, M.C.; Jeelani, S.

    2006-01-01

    Tensile and mode-I fracture behavior of cross-linked polyvinyl chloride (PVC) and rigid polyurethane (PUR) foams are examined. Tension tests are performed using prismatic bar specimens and mode-I fracture tests are performed using single edge notched bend (SENB) specimens under three-point bending. Test specimens are prepared from PVC foams with three densities and two different levels of cross-linking, and PUR foam with one density. Tension and quasi-static fracture tests are performed using a Zwick/Rowell test machine. Dynamic fracture tests are performed using a DYNATUP model 8210 instrumented drop-tower test set up at three different impact energy levels. Various parameters such as specimen size, loading rate, foam density, cross-linking, crack length, cell orientation (flow and rise-direction) and solid polymer material are studied. It is found that foam density and solid polymer material have a significant effect on tensile strength, modulus, and fracture toughness of polymer foams. Level of polymer cross-linking is also found to have a significant effect on fracture toughness. The presence of cracks in the rise- and flow direction as well as loading rate has minimal effect. Dynamic fracture behavior is found to be different as compared to quasi-static fracture behavior. Dynamic fracture toughness (K d ) increases with impact energy. Examination of fracture surfaces reveals that the fracture occurs in fairly brittle manner for all foam materials

  4. RESEARCH PROGRAM ON FRACTURED PETROLEUM RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Abbas Firoozabadi

    2002-04-12

    Numerical simulation of water injection in discrete fractured media with capillary pressure is a challenge. Dual-porosity models in view of their strength and simplicity can be mainly used for sugar-cube representation of fractured media. In such a representation, the transfer function between the fracture and the matrix block can be readily calculated for water-wet media. For a mixed-wet system, the evaluation of the transfer function becomes complicated due to the effect of gravity. In this work, they use a discrete-fracture model in which the fractures are discretized as one dimensional entities to account for fracture thickness by an integral form of the flow equations. This simple step greatly improves the numerical solution. Then the discrete-fracture model is implemented using a Galerkin finite element method. The robustness and the accuracy of the approach are shown through several examples. First they consider a single fracture in a rock matrix and compare the results of the discrete-fracture model with a single-porosity model. Then, they use the discrete-fracture model in more complex configurations. Numerical simulations are carried out in water-wet media as well as in mixed-wet media to study the effect of matrix and fracture capillary pressures.

  5. Fluid driven fracture mechanics in highly anisotropic shale: a laboratory study with application to hydraulic fracturing

    Science.gov (United States)

    Gehne, Stephan; Benson, Philip; Koor, Nick; Enfield, Mark

    2017-04-01

    The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the

  6. Sealing of rock fractures

    International Nuclear Information System (INIS)

    Pusch, R.; Erlstroem, M.; Boergesson, L.

    1985-12-01

    The major water-bearing fractures in granite usually from fairly regular sets but the extension and degree of connectivity is varying. This means that only a few fractures that are interconnected with the deposition holes and larger water-bearing structures in a HLW repository are expected and if they can be identified and cut off through sealing it would be possible to improve the isolation of waste packages very effectively. Nature's own fracture sealing mechanisms may be simulated and a survey of the involved processes actually suggests a number of possible filling methods and substances. Most of them require high temperature and pressure and correspondingly sophisticated techniques, but some are of potential interest for immediate application with rather moderate effort. Such a technique is to fill the fractures with clayey substances which stay flexible and low-permeable provided that they remain physically and chemically intact. It is demonstrated in the report that effective grouting requires a very low viscosity and shear strength of the substance and this can be achieved by mechanical agitation as demonstrated in this report. Thus, by superimposing static pressure and shear waves induced by percussion hammering at a suitable frequency, clays and fine-grained silts as well as cement can be driven into fractures with an average aperture as small as 0.1 mm. Experiments were made in the laboratory using concrete and steel plates, and a field pilot test was also conducted under realistic conditions on site in Stripa. They all demonstrated the practicality of the 'dynamic injection technique' and that the fluid condition of the grouts yielded complete filling of the injected space to a considerable distance from the injection point. The field test indicated a good sealing ability as well as a surprisingly high resistance to erosion and piping. (author)

  7. Structural strength of core graphite bars

    International Nuclear Information System (INIS)

    Kikuchi, K.; Futakawa, M.

    1987-01-01

    A HTR core consists of fuel, hot plenum, reflector and thermal barrier blocks. Each graphite block is supported by three thin cylindrical graphite bars called support post. Static and dynamic core loads are transmitted by the support posts to the thermal barrier blocks and a support plate. These posts are in contact with the blocks through hemispherical post seats to absorb the relative displacement caused by seismic force and the difference of thermal expansion of materials at the time of the start-up and shutdown of a reactor. The mixed fracture criterion of principal stress and modified Mohr-Coulomb's theory as well as the fracture criterion of principal stress based on elastic stress analysis was discussed in connection with the application to HTR graphite components. The buckling fracture of a support post was taken in consideration as one of the fracture modes. The effect that the length/diameter ratio of a post, small rotation and the curvature of post ends and seats exerted on the fracture strength was studied by using IG-110 graphite. Contacting stress analysis was carried out by using the structural analysis code 'COSMOS-7'. The experimental method, the analysis of buckling strength and the results are reported. The fracture of a support post is caused by the mixed mode of bending deformation, split fracture and shearing fracture. (Kako, I.)

  8. Trochanteric fractures

    International Nuclear Information System (INIS)

    Herrlin, K.; Stroemberg, T.; Lidgren, L.; Walloee, A.; Pettersson, H.; Lund Univ.

    1988-01-01

    Four hundred and thirty trochanteric factures operated upon with McLaughlin, Ender or Richard's osteosynthesis were divided into 6 different types based on their radiographic appearance before and immediately after reposition with special reference to the medial cortical support. A significant correlation was found between the fracture type and subsequent mechanical complications where types 1 and 2 gave less, and types 4 and 5 more complications. A comparison of the various osteosyntheses showed that Richard's had significantly fewer complications than either the Ender or McLaughlin types. For Richard's osteosynthesis alone no correlation to fracture type could be made because of the small number of complications in this group. (orig.)

  9. Fracture Blisters

    Directory of Open Access Journals (Sweden)

    Uebbing, Claire M

    2011-02-01

    Full Text Available Fracture blisters are a relatively uncommon complication of fractures in locations of the body, such as the ankle, wrist elbow and foot, where skin adheres tightly to bone with little subcutaneous fat cushioning. The blister that results resembles that of a second degree burn.These blisters significantly alter treatment, making it difficult to splint or cast and often overlying ideal surgical incision sites. Review of the literature reveals no consensus on management; however, most authors agree on early treatment prior to blister formation or delay until blister resolution before attempting surgical correction or stabilization. [West J Emerg Med. 2011;12(1;131-133.

  10. Rotating bending fatigue strength evaluation of ceramic materials

    International Nuclear Information System (INIS)

    Govila, R.K.; Swank, L.R.

    1995-01-01

    Cyclic fatigue under rotary bending tests were conducted on partially stabilized zirconia (PSZ) from NGK and Nilsen, and silicon nitride from NGK and Norton. Fractography was performed on the failed specimens to determine the fracture structure and morphology. The results showed that the cyclic fatigue fracture was the same as the fracture structure previously observed in bending tests. The cyclic fatigue data indicated that structural ceramic could function in fatigue stress levels at a higher percentage of their average fast fracture strength than the fifty percent of ultimate strength used for wrought steels

  11. Effect of mix design on the size-independent fracture energy of normal- and high-strength self-compacting concrete; Influencia de la composición de la mezcla sobre la energía de fractura de hormigones autocompactantes de resistencias media y alta.

    Energy Technology Data Exchange (ETDEWEB)

    Cifuentes, H.; Ríos, J.D.; Gómez, E.J.

    2018-04-01

    Self-compacting concrete has a characteristic microstructure inherent to its specific composition. The higher content of fine particles in self-compacting concrete relative to the equivalent vibrated concrete produces a different fracture behavior that affects the main fracture parameters. In this work, a comprehensive experimental investigation of the fracture behavior of self-compacting concrete has been carried out. Twelve different self-compacting concrete mixes with compressive strength ranging from 39 to 124 MPa (wider range than in other studies) have been subjected to three-point bending tests in order to determine the specific fracture energy. The influence of the mix design and its composition (coarse aggregate fraction, the water to binder ratio and the paste to solids ratio) on its fracture behavior has been analyzed. Moreover, further evidence of the objectivity of the size-independent fracture energy results, obtained by the two most commonly used methods, has been p [Spanish] Los hormigones autocompactantes tienen una microestructura interna inherente a su composición específica. Su mayor contenido de partículas finas, en comparación con hormigones vibrados equivalentes, provoca un comportamiento diferente en fractura que afecta a los principales parámetros de fractura. En este trabajo, se ha realizado una amplia investigación experimental del comportamiento en fractura de hormigones autocompactantes. Así, se han realizado ensayos de flexión en tres puntos para determinar sus propiedades de fractura sobre 12 hormigones autocompactantes de diferente composición, con resistencias a compresión que van desde 39 hasta 124 MPa (mayor que en otros estudios). De esta forma, se ha analizado la influencia de la dosificación del hormigón y su composición (contenido en árido grueso, relación agua-cemento y pasta-sólidos) sobre su comportamiento en fractura. Además, se ha validado, para hormigones autocompactantes, la objetividad de los

  12. Evidence Report: Risk of Bone Fracture due to Spaceflight-Induced Changes to Bone

    Science.gov (United States)

    Sibonga, Jean D.; Evans, Harlan J.; Smith, Scott A.; Spector, Elisabeth R.; Yardley, Greg; Myer, Jerry

    2017-01-01

    Given that spaceflight may induce adverse changes in bone ultimate strength with respect to mechanical loads during and post-mission, there is a possibility a fracture may occur for activities otherwise unlikely to induce fracture prior to initiating spaceflight.

  13. Elbow Fractures

    Science.gov (United States)

    ... is also an important factor when treating elbow fractures. Casts are used more frequently in children, as their risk of developing elbow stiffness is small; however, in an adult, elbow stiffness is much more likely. Rehabilitation directed by your doctor is often used to ...

  14. Wrist Fractures

    Science.gov (United States)

    ... All Topics A-Z Videos Infographics Symptom Picker Anatomy Bones Joints Muscles Nerves Vessels Tendons About Hand Surgery What is a Hand Surgeon? What is a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Wrist Fractures Email to a friend * required fields ...

  15. Shoulder Fractures

    Science.gov (United States)

    ... All Topics A-Z Videos Infographics Symptom Picker Anatomy Bones Joints Muscles Nerves Vessels Tendons About Hand Surgery What is a Hand Surgeon? What is a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Shoulder Fractures Email to a friend * required fields ...

  16. Rib fractures predict incident limb fractures: results from the European prospective osteoporosis study.

    Science.gov (United States)

    Ismail, A A; Silman, A J; Reeve, J; Kaptoge, S; O'Neill, T W

    2006-01-01

    Population studies suggest that rib fractures are associated with a reduction in bone mass. While much is known about the predictive risk of hip, spine and distal forearm fracture on the risk of future fracture, little is known about the impact of rib fracture. The aim of this study was to determine whether a recalled history of rib fracture was associated with an increased risk of future limb fracture. Men and women aged 50 years and over were recruited from population registers in 31 European centres for participation in a screening survey of osteoporosis (European Prospective Osteoporosis Study). Subjects were invited to complete an interviewer-administered questionnaire that included questions about previous fractures including rib fracture, the age of their first fracture and also the level of trauma. Lateral spine radiographs were performed and the presence of vertebral deformity was determined morphometrically. Following the baseline survey, subjects were followed prospectively by annual postal questionnaire to determine the occurrence of clinical fractures. The subjects included 6,344 men, with a mean age of 64.2 years, and 6,788 women, with a mean age of 63.6 years, who were followed for a median of 3 years (range 0.4-5.9 years), of whom 135 men (2.3%) and 101 women (1.6%) reported a previous low trauma rib fracture. In total, 138 men and 391 women sustained a limb fracture during follow-up. In women, after age adjustment, those with a recalled history of low trauma rib fracture had an increased risk of sustaining 'any' limb fracture [relative hazard (RH)=2.3; 95% CI 1.3, 4.0]. When stratified by fracture type the predictive risk was more marked for hip (RH=7.7; 95% CI 2.3, 25.9) and humerus fracture (RH=4.5; 95% CI 1.4, 14.6) than other sites (RH=1.6; 95% CI 0.6, 4.3). Additional adjustment for prevalent vertebral deformity and previous (non-rib) low trauma fractures at other sites slightly reduced the strength of the association between rib fracture and

  17. Bimalleolar ankle fracture with proximal fibular fracture

    NARCIS (Netherlands)

    Colenbrander, R. J.; Struijs, P. A. A.; Ultee, J. M.

    2005-01-01

    A 56-year-old female patient suffered a bimalleolar ankle fracture with an additional proximal fibular fracture. This is an unusual fracture type, seldom reported in literature. It was operatively treated by open reduction and internal fixation of the lateral malleolar fracture. The proximal fibular

  18. Residual impairment after lower extremity fracture

    DEFF Research Database (Denmark)

    Faergemann, C; Frandsen, P A; Röck, N D

    1998-01-01

    In a prospective follow-up study of 158 consecutive patients 18 to 64 years old with unilateral lower extremity fracture, our aim was to disclose the impairment and disability 6 months after the injury. The patients were interviewed within 1 week after the trauma, and all patients returned...... the functional status before the injury. Additionally, three major aspects of impairments were measured 6 months after the fractures: range of motion, muscle strength, and pain. Most patients had a significantly higher SIP score 6 months after the fracture(s) than pretraumatically. The mean overall SIP score...... was 2.7 pretraumatically and 8.7 6 months posttraumatically. Major deficits in range of motion was observed, especially in the ankle joint. Additionally, loss of muscle strength was observed in the thigh and calf muscles in one fourth of the patients. Only low levels of residual pain were reported after...

  19. Fracture properties and heat resistance of ceramics consisting of microspheres of stabilized zirconium dioxide

    International Nuclear Information System (INIS)

    Krasulin, Yu.L.; Barinov, S.M.; Ivanov, A.B.; Timofeev, V.N.; Grevtsev, S.N.; Ivanov, D.A.

    1980-01-01

    Determined were effective specific fracture work, critical coefficient of stress intensity in the upper point of the fracture, strength and heat resistance during heat changes (20-1300 deg C) of the material produced by sintering stabilized zirconium dioxide microspheres. Dependence of these characteristics on granulometric composition of microspheres was determined. It was ascertained that the additional introduction of large microspheres into the bulk of small microspheres increased the metal fracture work. Specific work of material fracture progress exceeded specific work of fracture motion initiation. High value of fracture work together with high strength permits to use the material formed of microspheres as structural ceramics

  20. Fracture mechanics

    International Nuclear Information System (INIS)

    Miannay, D.P.

    1995-01-01

    This book entitle ''Fracture Mechanics'', the first one of the monograph ''Materiologie'' is geared to design engineers, material engineers, non destructive inspectors and safety experts. This book covers fracture mechanics in isotropic homogeneous continuum. Only the monotonic static loading is considered. This book intended to be a reference with the current state of the art gives the fundamental of the issues under concern and avoids the developments too complicated or not yet mastered for not making reading cumbersome. The subject matter is organized as going from an easy to a more complicated level and thus follows the chronological evolution in the field. Similarly the microscopic scale is considered before the macroscopic scale, the physical understanding of phenomena linked to the experimental observation of the material preceded the understanding of the macroscopic behaviour of structures. In this latter field the relatively recent contribution of finite element computations with some analogy with the experimental observation is determining. However more sensitive analysis is not skipped

  1. Long-Term Strength of a Thick-Walled Pipe Filled with an Aggressive Medium, with Account for Damageability of the Pipe Material and Residual Strength

    Science.gov (United States)

    Piriev, S. A.

    2018-01-01

    This paper describes the study of scattered fracture of a thick-walled pipe filled with an aggressive medium, which creates uniform pressure on the inner surface of the pipe. It is assumed that the aggressive medium affects only the value of instantaneous strength. Damageability is described by an integral operator of the hereditary type. The problem is solved with allowance for residual strength of the pipe material behind the fracture front. Numerical calculation is carried out, and relationships between the fracture front coordinate and time for various concentrations of the aggressive medium and residual strength behind the fracture front are constructed.

  2. Accelerated Strength Testing of Thermoplastic Composites

    Science.gov (United States)

    Reeder, J. R.; Allen, D. H.; Bradley, W. L.

    1998-01-01

    Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90 deg. direction were conducted at constant temperatures ranging from 149 C to 232 C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 sec. to 24 hrs. (0.5 to 100,000 MPa/sec). Below 204 C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results. To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with temperature reduced stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.

  3. Fracture diagnostics with tube wave reflection logs

    International Nuclear Information System (INIS)

    Medlin, W.L.

    1991-01-01

    This paper reports on the Tube Wave Reflection Log (TWRL) which is acoustic logging method which provides information about the height, location and conductivity of hydraulically induced fractures behind perforated casing. The TWRL tool consists of a transmitter and closely spaced receiver. The transmitter is driven with a short, low frequency tone burst to generate long wavelength tube waves which are little attenuated in unperforated casing. They are partially reflected when they pass perforated intervals communicating with a hydraulically induced fracture. The tool listens for such reflections for 0.1 seconds following each excitation burst. As the tool is moved uphole at logging speed, the transmitter is excited at each foot of depth. VDL displays of the TWRL records provide reflection traces whose projections define the uppermost and lower-most perforations communicating with the fracture. The strength of the reflections depends on the ease of fluid flow into the fracture and thus, is an indicator of fracture conductivity

  4. Analysis of compressive fracture in rock using statistical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Blair, S.C.

    1994-12-01

    Fracture of rock in compression is analyzed using a field-theory model, and the processes of crack coalescence and fracture formation and the effect of grain-scale heterogeneities on macroscopic behavior of rock are studied. The model is based on observations of fracture in laboratory compression tests, and incorporates assumptions developed using fracture mechanics analysis of rock fracture. The model represents grains as discrete sites, and uses superposition of continuum and crack-interaction stresses to create cracks at these sites. The sites are also used to introduce local heterogeneity. Clusters of cracked sites can be analyzed using percolation theory. Stress-strain curves for simulated uniaxial tests were analyzed by studying the location of cracked sites, and partitioning of strain energy for selected intervals. Results show that the model implicitly predicts both development of shear-type fracture surfaces and a strength-vs-size relation that are similar to those observed for real rocks. Results of a parameter-sensitivity analysis indicate that heterogeneity in the local stresses, attributed to the shape and loading of individual grains, has a first-order effect on strength, and that increasing local stress heterogeneity lowers compressive strength following an inverse power law. Peak strength decreased with increasing lattice size and decreasing mean site strength, and was independent of site-strength distribution. A model for rock fracture based on a nearest-neighbor algorithm for stress redistribution is also presented and used to simulate laboratory compression tests, with promising results.

  5. Inclusion-initiated fracture model for ceramics

    International Nuclear Information System (INIS)

    Sung, J.; Nicholson, P.S.

    1990-01-01

    The fracture of ceramics initiating from a typical inclusion is analyzed. The inclusion is considered to have a thermal expansion coefficient and fracture toughness lower than those of the matrix and a Young's modulus higher than that of the matrix. Inclusion-initiated fracture is modeled for a spherical inclusion using a weight function method to compute the residual stress intensity factor for a part-through elliptical crack. The results are applied to an α-Al 2 O 3 inclusion embedded in a tetragonal ZrO 2 ceramic. The strength predictions agree well with experimental data

  6. Risk factors for stress fractures.

    Science.gov (United States)

    Bennell, K; Matheson, G; Meeuwisse, W; Brukner, P

    1999-08-01

    Preventing stress fractures requires knowledge of the risk factors that predispose to this injury. The aetiology of stress fractures is multifactorial, but methodological limitations and expediency often lead to research study designs that evaluate individual risk factors. Intrinsic risk factors include mechanical factors such as bone density, skeletal alignment and body size and composition, physiological factors such as bone turnover rate, flexibility, and muscular strength and endurance, as well as hormonal and nutritional factors. Extrinsic risk factors include mechanical factors such as surface, footwear and external loading as well as physical training parameters. Psychological traits may also play a role in increasing stress fracture risk. Equally important to these types of analyses of individual risk factors is the integration of information to produce a composite picture of risk. The purpose of this paper is to critically appraise the existing literature by evaluating study design and quality, in order to provide a current synopsis of the known scientific information related to stress fracture risk factors. The literature is not fully complete with well conducted studies on this topic, but a great deal of information has accumulated over the past 20 years. Although stress fractures result from repeated loading, the exact contribution of training factors (volume, intensity, surface) has not been clearly established. From what we do know, menstrual disturbances, caloric restriction, lower bone density, muscle weakness and leg length differences are risk factors for stress fracture. Other time-honoured risk factors such as lower extremity alignment have not been shown to be causative even though anecdotal evidence indicates they are likely to play an important role in stress fracture pathogenesis.

  7. Bond strength of resin composite to differently conditioned amalgam

    NARCIS (Netherlands)

    Ozcan, M; Vallittu, PK; Huysmans, MC; Kalk, W; Vahlberg, T

    Bulk fracture of teeth, where a part of the amalgam restoration and/or the cusp is fractured, is a common clinical problem. The aim of this study was to evaluate the effect of different surface conditioning methods on the shear bond strength of a hybrid resin composite to fresh amalgam. Amalgams (N

  8. Shear Bond Strength of a Novel Porcelain Repair System for ...

    African Journals Online (AJOL)

    2018-04-04

    Apr 4, 2018 ... Each fracture type was examined under a stereomicroscope .... fracture types. Statistical analysis. The normal distribution of data was examined using the Kolmogorov–Smirnov test. Shear bond strength data of repaired CAD/CAM .... adhesives to enamel, dentine, and porcelain surfaces can be compared.

  9. Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

    Directory of Open Access Journals (Sweden)

    Ferdinand Stoeckhert

    2015-06-01

    Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

  10. Fracturing process and effect of fracturing degree on wave velocity of a crystalline rock

    Directory of Open Access Journals (Sweden)

    Charalampos Saroglou

    2017-10-01

    Full Text Available The present paper investigates the effect of fracturing degree on P- and S-wave velocities in rock. The deformation of intact brittle rocks under loading conditions is characterized by a microcracking procedure, which occurs due to flaws in their microscopic structure and propagates through the intact rock, leading to shear fracture. This fracturing process is of fundamental significance as it affects the mechanical properties of the rock and hence the wave velocities. In order to determine the fracture mechanism and the effect of fracturing degree, samples were loaded at certain percentages of peak strength and ultrasonic wave velocity was recorded after every test. The fracturing degree was recorded on the outer surface of the sample and quantified by the use of the indices P10 (traces of joints/m, P20 (traces of joints/m2 and P21 (length of fractures/m2. It was concluded that the wave velocity decreases exponentially with increasing fracturing degree. Additionally, the fracturing degree is described adequately with the proposed indices. Finally, other parameters concerning the fracture characteristics, rock type and scale influence were found to contribute to the velocity decay and need to be investigated further.

  11. Fracture criteria of reactor graphite under multiaxial stresses

    International Nuclear Information System (INIS)

    Sato, S.; Kawamata, K.; Kurumada, A.; Oku, T.

    1987-01-01

    New fracture criteria for graphite under multiaxial stresses are presented for designing core and support materials of a high temperature gas cooled reactor. Different kinds of fracture strength tests are carried out for a near isotropic graphite IG-11. Results show that, under the stress state in which tensile stresses are predominant, the maximum principal stress theory is seen as applicable for brittle fracture. Under the stress state in which compressive stresses are predominant there may be two fracture modes for brittle fracture, namely, slipping fracture and mode II fracture. For the former fracture mode the maximum shear stress criterion is suitable, but for the latter fracture mode a new mode II fracture criterion including a restraint effect for cracks is verified to be applicable. Also a statistical correction for brittle fracture criteria under multiaxial stresses is discussed. By considering the allowable stress values for safe design, the specified minimum ultimate strengths corresponding to a survival probability of 99% at the 95% confidence level are presented. (orig./HP)

  12. Hip fracture - discharge

    Science.gov (United States)

    ... neck fracture repair - discharge; Trochanteric fracture repair - discharge; Hip pinning surgery - discharge ... in the hospital for surgery to repair a hip fracture, a break in the upper part of ...

  13. Attitude Strength.

    Science.gov (United States)

    Howe, Lauren C; Krosnick, Jon A

    2017-01-03

    Attitude strength has been the focus of a huge volume of research in psychology and related sciences for decades. The insights offered by this literature have tremendous value for understanding attitude functioning and structure and for the effective application of the attitude concept in applied settings. This is the first Annual Review of Psychology article on the topic, and it offers a review of theory and evidence regarding one of the most researched strength-related attitude features: attitude importance. Personal importance is attached to an attitude when the attitude is perceived to be relevant to self-interest, social identification with reference groups or reference individuals, and values. Attaching personal importance to an attitude causes crystallizing of attitudes (via enhanced resistance to change), effortful gathering and processing of relevant information, accumulation of a large store of well-organized relevant information in long-term memory, enhanced attitude extremity and accessibility, enhanced attitude impact on the regulation of interpersonal attraction, energizing of emotional reactions, and enhanced impact of attitudes on behavioral intentions and action. Thus, important attitudes are real and consequential psychological forces, and their study offers opportunities for addressing behavioral change.

  14. Laboratory investigation of shale rock to identify fracture propagation in vertical direction to bedding

    Science.gov (United States)

    Peng, Tan; Yan, Jin; Bing, Hou; Yingcao, Zhou; Ruxin, Zhang; Zhi, Chang; Meng, Fan

    2018-06-01

    Affected by beddings and natural fractures, fracture geometry in the vertical plane is complex in shale formation, which differs from a simple fracture in homogeneous sandstone reservoirs. However, the propagation mechanism of a hydraulic fracture in the vertical plane has not been well understood. In this paper, a true tri-axial pressure machine was deployed for shale horizontal well fracturing simulation experiments of shale outcrops. The effects of multiple factors on hydraulic fracture vertical propagation were studied. The results revealed that hydraulic fracture initiation and propagation displayed four basic patterns in the vertical plane of laminated shale formation. A hydraulic fracture would cross the beddings under the high vertical stress difference between a vertical stress and horizontal minimum stress of 12 MPa, while a hydraulic fracture propagates along the beddings under a low vertical stress difference of 3 MPa. Four kinds of fracture geometry, including a single main fracture, a nonplanar fracture, a complex fracture, and a complex fracture network, were observed due to the combined effects of flow rate and viscosity. Due to the influence of binding strength (or cementing strength) on the fracture communication effects between a hydraulic fracture and the beddings, the opening region of the beddings takes the shape of an ellipse.

  15. fracture criterion

    Indian Academy of Sciences (India)

    “we never test the strength of glass: all we test is the weakness of its surface” J. T. ... 300. 400. 500. 600. Temperature, T ( C). Supercooled Liquid. Regime ... H eat F low. (m. W. ) Pd40Ni10Cu30P20. PDF Create! 5 Trial www.nuance.com ...

  16. Influence of interface properties on fracture behaviour of concrete

    Indian Academy of Sciences (India)

    Interface; concrete; bond strength; fracture toughness; stiffness; ductility. 1. Introduction .... behaviour of concrete using sandwich, and direct rock-mortar compact specimens under mode I and mode II ... pulse velocity technique. 4.2 Geometry of ...

  17. Tensile Strength of the Eggshell Membranes

    Czech Academy of Sciences Publication Activity Database

    Strnková, J.; Nedomová, Š.; Kumbár, V.; Trnka, Jan

    2016-01-01

    Roč. 64, č. 1 (2016), s. 159-164 ISSN 1211-8516 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : eggshell membrane * tesile test * loading rate * tensile strength * fracture strain Subject RIV: GM - Food Processing

  18. Residual strength evaluation of concrete structural components ...

    Indian Academy of Sciences (India)

    This paper presents methodologies for residual strength evaluation of concrete structural components using linear elastic and nonlinear fracture mechanics principles. The effect of cohesive forces due to aggregate bridging has been represented mathematically by employing tension softening models. Various tension ...

  19. Strength variability of single flax fibres

    DEFF Research Database (Denmark)

    Aslan, Mustafa; Chinga-Carrasco, G.; Sørensen, Bent F.

    2011-01-01

    (linear and nonlinear) of the fibres are found to be correlated with the amount of defects. The linear stress–strain curves tend to show a higher tensile strength, a higher Young’s modulus, and a lower strain to failure than the nonlinear curves. Finally, the fibres are found to fracture by a complex...

  20. Pediatric mandibular fractures.

    Science.gov (United States)

    Schweinfurth, J M; Koltai, P J

    1998-01-01

    Over the last 20 years, a revolution in the management of facial fractures has taken place. Refinements in biocompatible materials of great delicacy and strength along with advances in our understanding of biomechanics of the face, have rendered complex injuries consistently amenable to accurate 3-dimensional reconstruction. Furthermore, with the availability of education in the techniques of internal rigid fixation, these advanced techniques have become routine practice in adults. However, the suitability of rigid internal fixation for children remains controversial. There are many concerns about the effect of implanted hardware in the mandible of a growing child. In addition, some evidence suggests that the elevation of functional matrix off of bone may result in alterations in development. The goal is to restore the underlying bony architecture to its pre-injury position in a stable fashion, with a minimal of aesthetic and functional impairment. However, in children the treatment of bony injuries is most easily accomplished by techniques that may adversely effect craniofacial development. While it is not entirely possible to resolve this dilemma, there exists an extensive body of experimental and clinical information on the appropriate management of pediatric mandibular fractures which can be used to formulate a rational treatment plan for most cases. This paper presents an overview of the contemporary understanding and application of these treatment principles.

  1. Proximal femoral fractures.

    Science.gov (United States)

    Webb, Lawrence X

    2002-01-01

    Fractures of the proximal femur include fractures of the head, neck, intertrochanteric, and subtrochanteric regions. Head fractures commonly accompany dislocations. Neck fractures and intertrochanteric fractures occur with greatest frequency in elderly patients with a low bone mineral density and are produced by low-energy mechanisms. Subtrochanteric fractures occur in a predominantly strong cortical osseous region which is exposed to large compressive stresses. Implants used to address these fractures must be able to accommodate significant loads while the fractures consolidate. Complications secondary to these injuries produce significant morbidity and include infection, nonunion, malunion, decubitus ulcers, fat emboli, deep venous thrombosis, pulmonary embolus, pneumonia, myocardial infarction, stroke, and death.

  2. Reduction of femoral fractures in long-term care facilities: the Bavarian fracture prevention study.

    Directory of Open Access Journals (Sweden)

    Clemens Becker

    Full Text Available BACKGROUND: Hip fractures are a major public health burden. In industrialized countries about 20% of all femoral fractures occur in care dependent persons living in nursing care and assisted living facilities. Preventive strategies for these groups are needed as the access to medical services differs from independent home dwelling older persons at risk of osteoporotic fractures. It was the objective of the study to evaluate the effect of a fall and fracture prevention program on the incidence of femoral fracture in nursing homes in Bavaria, Germany. METHODS: In a translational intervention study a fall prevention program was introduced in 256 nursing homes with 13,653 residents. The control group consisted of 893 nursing homes with 31,668 residents. The intervention consisted of staff education on fall and fracture prevention strategies, progressive strength and balance training, and on institutional advice on environmental adaptations. Incident femoral fractures served as outcome measure. RESULTS: In the years before the intervention risk of a femoral fracture did not differ between the intervention group (IG and control group (CG. During the one-year intervention period femoral fracture rates were 33.6 (IG and 41.0/1000 person years (CG, respectively. The adjusted relative risk of a femoral fracture was 0.82 (95% CI 0.72-0.93 in residents exposed to the fall and fracture prevention program compared to residents from CG. CONCLUSIONS: The state-wide dissemination of a multi-factorial fall and fracture prevention program was able to reduce femoral fractures in residents of nursing homes.

  3. Clinical effects of internal fixation for ulnar styloid fractures associated with distal radius fractures: A matched case-control study.

    Science.gov (United States)

    Sawada, Hideyoshi; Shinohara, Takaaki; Natsume, Tadahiro; Hirata, Hitoshi

    2016-11-01

    Ulnar styloid fractures are often associated with distal radius fractures. However, controversy exists regarding whether to treat ulnar styloid fractures. This study aimed to evaluate clinical effects of internal fixation for ulnar styloid fractures after distal radius fractures were treated with the volar locking plate system. We used prospectively collected data of distal radius fractures. 111 patients were enrolled in this study. A matched case-control study design was used. We selected patients who underwent fixation for ulnar styloid fractures (case group). Three control patients for each patient of the case group were matched on the basis of age, sex, and fracture type of distal radius fractures from among patients who did not undergo fixation for ulnar styloid fractures (control group). The case group included 16 patients (7 men, 9 women; mean age: 52.6 years; classification of ulnar styloid fractures: center, 3; base, 11; and proximal, 2). The control group included 48 patients (15 men, 33 women; mean age: 61.1 years; classification of ulnar styloid fractures: center, 10; base, 31; and proximal, 7). For radiographic examination, the volar tilt angle, radial inclination angle, and ulnar variance length were measured, and the union of ulnar styloid fractures was judged. For clinical examination, the range of motions, grip strength, Hand20 score, and Numeric Rating Scale score were evaluated. There was little correction loss for each radiological parameter of fracture reduction, and these parameters were not significantly different between the groups. The bone-healing rate of ulnar styloid fractures was significantly higher in the case group than in the control group, but the clinical results were not significantly different. We revealed that there was no need to fix ulnar styloid fractures when distal radius fractures were treated via open reduction and internal fixation with a volar locking plate system. Copyright © 2016 The Japanese Orthopaedic Association

  4. Strength of metallic glasses at 4.2-300 K

    International Nuclear Information System (INIS)

    Tabachnikova, E.D.

    1987-01-01

    Investigation into temperature dependence of metallic glass strength (Ni 78 Si 8 B 14 ; Fe 40 Ni 38 Mo 4 B 18 ; Fe 25 Ni 55 Si 10 B 1 0 ; Fe 61 Co 20 Si 4 B 15 ) is conducted within 300-4.2 K temperature interval. By the character of σ (T) x dependence and fracture mode the alloys investigated are subdivided into two groups. In 1 group alloys the fracture up to 4.2 K has the character typical of ductile fracture. In the second group alloys fracture acquires brittle character with the temperature decrease

  5. FROMS3D: New Software for 3-D Visualization of Fracture Network System in Fractured Rock Masses

    Science.gov (United States)

    Noh, Y. H.; Um, J. G.; Choi, Y.

    2014-12-01

    A new software (FROMS3D) is presented to visualize fracture network system in 3-D. The software consists of several modules that play roles in management of borehole and field fracture data, fracture network modelling, visualization of fracture geometry in 3-D and calculation and visualization of intersections and equivalent pipes between fractures. Intel Parallel Studio XE 2013, Visual Studio.NET 2010 and the open source VTK library were utilized as development tools to efficiently implement the modules and the graphical user interface of the software. The results have suggested that the developed software is effective in visualizing 3-D fracture network system, and can provide useful information to tackle the engineering geological problems related to strength, deformability and hydraulic behaviors of the fractured rock masses.

  6. Fracture behaviour of heat cured fly ash based geopolymer concrete

    International Nuclear Information System (INIS)

    Sarker, Prabir K.; Haque, Rashedul; Ramgolam, Karamchand V.

    2013-01-01

    Highlights: ► Fly ash geopolymer (GPC) can help reduce carbon footprint of concrete. ► Fracture behaviour of GPC as compared to OPC concrete was studied. ► Fracture energy of GPC was similar to that of OPC concrete. ► GPC showed higher fracture toughness than OPC concrete. ► Higher bond strength resulted in higher crack resistance of GPC. -- Abstract: Use of fly ash based geopolymer as an alternative binder can help reduce CO 2 emission of concrete. The binder of geopolymer concrete (GPC) is different from that of ordinary Portland cement (OPC) concrete. Thus, it is necessary to study the effects of the geopolymer binder on the behaviour of concrete. In this study, the effect of the geopolymer binder on fracture characteristics of concrete has been investigated by three point bending test of RILEM TC 50 – FMC type notched beam specimens. The peak load was generally higher in the GPC specimens than the OPC concrete specimens of similar compressive strength. The failure modes of the GPC specimens were found to be more brittle with relatively smooth fracture planes as compared to the OPC concrete specimens. The post-peak parts of the load–deflection curves of GPC specimens were steeper than that of OPC concrete specimens. Fracture energy calculated by the work of fracture method was found to be similar in both types of concrete. Available equations for fracture energy of OPC concrete yielded conservative estimations of fracture energy of GPC. The critical stress intensity factor of GPC was found to be higher than that of OPC concrete. The different fracture behaviour of GPC is mainly because of its higher tensile strength and bond strength than OPC concrete of the same compressive strength.

  7. Strength-toughness requirements for thick walled high pressure vessels

    International Nuclear Information System (INIS)

    Kapp, J.A.

    1990-01-01

    The strength and toughness requirements of materials for use in high pressure vessels has been the subject of some discussion in the meetings of the Materials Task Group of the Special Working Group High Pressure Vessels. A fracture mechanics analysis has been performed to theoretically establish the required toughness for a high pressure vessel. This paper reports that the analysis performed is based on the validity requirement for plane strain fracture of fracture toughness test specimens. This is that at the fracture event, the crack length, uncracked ligament, and vessel length must each be greater than fifty times the crack tip plastic zone size for brittle fracture to occur. For high pressure piping applications, the limiting physical dimension is the uncracked ligament, as it can be assumed that the other dimensions are always greater than fifty times the crack tip plastic zone. To perform the fracture mechanics analysis several parameters must be known: these include vessel dimensions, material strength, degree of autofrettage, and design pressure. Results of the analysis show, remarkably, that the effects of radius ratio, pressure and degree of autofrettage can be ignored when establishing strength and toughness requirements for code purposes. The only parameters that enter into the calculation are yield strength, toughness and vessel thickness. The final results can easily be represented as a graph of yield strength against toughness on which several curves, one for each vessel thickness, are plotted

  8. A study on the fracture energy of Steel Fiber Reinforced Concrete structures with initial cracks

    International Nuclear Information System (INIS)

    Chang, Dong-Il; Sim Jongsung; Chai, Won-Kyu; Lee, Myeong-Gu

    1991-01-01

    Fracture test is performed in order to investigate the fracture behavior of SFRC (Steel Fiber Reinforced Concrete) structures. Thirty six SFRC beams are used in this test. The relationships between loading, strain, and mid-span deflection of the beams are observed under the three point loading system. From the test results, the effects of the fiber content, the fiber aspect ratio and the initial crack ratio on the concrete fracture behavior were studied, and the flexural strength and the fracture energy of SFRC beams were also calculated. According to the regression technique, some empirical formulae for predicting the flexural strength and the fracture energy of SFRC beams are also suggested. (author)

  9. Traumatic thoracolumbar spine fractures

    NARCIS (Netherlands)

    J. Siebenga (Jan)

    2013-01-01

    textabstractTraumatic spinal fractures have the lowest functional outcomes and the lowest rates of return to work after injury of all major organ systems.1 This thesis will cover traumatic thoracolumbar spine fractures and not osteoporotic spine fractures because of the difference in fracture

  10. Fractures in multiple sclerosis

    DEFF Research Database (Denmark)

    Stenager, E; Jensen, K

    1991-01-01

    In a cross-sectional study of 299 MS patients 22 have had fractures and of these 17 after onset of MS. The fractures most frequently involved the femoral neck and trochanter (41%). Three patients had had more than one fracture. Only 1 patient had osteoporosis. The percentage of fractures increase...

  11. Falls: epidemiology, pathophysiology, and relationship to fracture.

    Science.gov (United States)

    Berry, Sarah D; Miller, Ram R

    2008-12-01

    Falls are common in the elderly, and frequently result in injury and disability. Most falls result from an interaction between individual characteristics that increase an individual's propensity to fall and acute mediating risk factors that provide the opportunity to fall. Predisposing risk factors include age-associated changes in strength and balance, comorbidities such as osteoarthritis, visual impairment and dementia, psychotropic medications, and certain types of footwear. Fewer studies have focused on acute precipitating factors, but environmental and situational factors are clearly important to fall risk. Approximately 30% of falls result in an injury that requires medical attention, with fractures occurring in approximately 10%. In addition to the risk factors for falls, the fall descent, fall impact, and bone strength are all important determinants of whether a fall will result in a fracture. In recent years, numerous studies have been directed toward the development of effective fall and fall-related fracture prevention interventions.

  12. Engineering Solution for the Uniform Strength of Partially Cracked Concrete

    DEFF Research Database (Denmark)

    Hansen, Elin A.; Hansen, Will; Brincker, Rune

    2005-01-01

    Significant computational resources are required to predict the remaining strength from numerical fracture analysis of a jointed plain concrete pavement that contains a partial depth crack. It is, therefore, advantageous when the failure strength can be adequately predicted with an engineering...

  13. The limit of strength and toughness of steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhen [Univ. of California, Berkeley, CA (United States)

    2001-12-01

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the governing principles of strength and toughness, along with the approaches that can be used to improve these properties and the inherent limits to how strong and tough a steel can be.

  14. Statistical considerations of graphite strength for assessing design allowable stresses

    International Nuclear Information System (INIS)

    Ishihara, M.; Mogi, H.; Ioka, I.; Arai, T.; Oku, T.

    1987-01-01

    Several aspects of statistics need to be considered to determine design allowable stresses for graphite structures. These include: 1) Statistical variation of graphite material strength. 2) Uncertainty of calculated stress. 3) Reliability (survival probability) required from operational and safety performance of graphite structures. This paper deals with some statistical considerations of structural graphite for assessing design allowable stress. Firstly, probability distribution functions of tensile and compressive strengths are investigated on experimental Very High Temperature candidated graphites. Normal, logarithmic normal and Weibull distribution functions are compared in terms of coefficient of correlation to measured strength data. This leads to the adaptation of normal distribution function. Then, the relation between factor of safety and fracture probability is discussed on the following items: 1) As the graphite strength is more variable than metalic material's strength, the effect of strength variation to the fracture probability is evaluated. 2) Fracture probability depending on survival probability of 99 ∼ 99.9 (%) with confidence level of 90 ∼ 95 (%) is discussed. 3) As the material properties used in the design analysis are usually the mean values of their variation, the additional effect of these variations on the fracture probability is discussed. Finally, the way to assure the minimum ultimate strength with required survival probability with confidence level is discussed in view of statistical treatment of the strength data from varying sample numbers in a material acceptance test. (author)

  15. Assessment of fracture risk

    International Nuclear Information System (INIS)

    Kanis, John A.; Johansson, Helena; Oden, Anders; McCloskey, Eugene V.

    2009-01-01

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  16. The healing of fractured bones

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, G E [Central Electricity Generating Board, Cheltenham (United Kingdom)

    1997-04-01

    A method utilising neutron beams of width 1 mm, used on D1B (2.4 A) and D20 (1.3 A) to study the healing of fractured bones is presented. It is found that the callus bone uniting the fractured tibia of a sheep, whose healing had been encouraged by daily mechanical vibration over a period of three months, showed no trace of the large preferential vertical orientation of the apatite crystals which is characteristic of the normal bone. Nevertheless the bone had regained about 60% of its mechanical strength and the callus bone, although not oriented, was well crystallized. It is considered that the new monochromator for D20, expected to give increased intensity at 2.5 A, will be of considerable advantage. (author). 2 refs.

  17. Bond strength of masonry

    NARCIS (Netherlands)

    Pluijm, van der R.; Vermeltfoort, A.Th.

    1992-01-01

    Bond strength is not a well defined property of masonry. Normally three types of bond strength can be distinguished: - tensile bond strength, - shear (and torsional) bond strength, - flexural bond strength. In this contribution the behaviour and strength of masonry in deformation controlled uniaxial

  18. Analysis of nature of brazed joints fracture under operating conditions

    International Nuclear Information System (INIS)

    Orlov, A.V.; Gura, P.M.

    1985-01-01

    Technique establishing causes leading to brazed joint fracture in pressure boundary components, operating under heavy conditions of high temperature and corrosive medium is described. Some cases of tube brazed joint fractures in a superheater of 12Kh1MF and 08Kh18N10T steels are considered. The attention is paid on using metallography for determination of mechanical or corrosion fracture properties. The diagram is developed permitting to take into account the interrelation between the fracture area in the given zone and its strength

  19. Evaluation of fracture toughness for metal/ceramics composite materials by means of miniaturized specimen technique

    International Nuclear Information System (INIS)

    Saito, Masahiro; Takahashi, Hideaki; Jeong, Hee-Don; Kawasaki, Akira; Watanabe, Ryuzo

    1991-01-01

    In order to evaluate fracture strength for Y 2 O 3 -ZrO 2 , 3 mol% Y 2 O 3 -ZrO 2 (PSZ)/SUS 304 composite materials, Macor as a machinable ceramics and comercially available ceramics (SiC, Si 3 N 4 , PSZ, Al 2 O 3 ), fracture toughness tests were carried out by use of RCT or bending specimens. On the other hand, the fracture strength of these materials was evaluated and inspected the correlation between fracture toughness and fracture stress of small punch (SP) or modified small punch (MSP) test data to predict the fracture toughness value by using miniaturized specimens. Characteristic of the MSP testing method is the ability to evaluate elastic modulus (Young's modulus), fracture strength, yield strength, fracture strain, and fracture energy, etc., with high accuracy and good reproducibility for brittle materials. For a series of metal/ ceramics composites which from ductile to brittle, this paper clarified clear the applicable range for SP and MSP testing methods, which suggested that the simultaneous use of SP and MSP test methods can evaluate the fracture strength of metal/ ceramics composites. (author)

  20. Paratrooper's ankle fracture: posterior malleolar fracture.

    Science.gov (United States)

    Young, Ki Won; Kim, Jin-su; Cho, Jae Ho; Kim, Hyung Seuk; Cho, Hun Ki; Lee, Kyung Tai

    2015-03-01

    We assessed the frequency and types of ankle fractures that frequently occur during parachute landings of special operation unit personnel and analyzed the causes. Fifty-six members of the special force brigade of the military who had sustained ankle fractures during parachute landings between January 2005 and April 2010 were retrospectively analyzed. The injury sites and fracture sites were identified and the fracture types were categorized by the Lauge-Hansen and Weber classifications. Follow-up surveys were performed with respect to the American Orthopedic Foot and Ankle Society ankle-hindfoot score, patient satisfaction, and return to preinjury activity. The patients were all males with a mean age of 23.6 years. There were 28 right and 28 left ankle fractures. Twenty-two patients had simple fractures and 34 patients had comminuted fractures. The average number of injury and fractures sites per person was 2.07 (116 injuries including a syndesmosis injury and a deltoid injury) and 1.75 (98 fracture sites), respectively. Twenty-three cases (41.07%) were accompanied by posterior malleolar fractures. Fifty-five patients underwent surgery; of these, 30 had plate internal fixations. Weber type A, B, and C fractures were found in 4, 38, and 14 cases, respectively. Based on the Lauge-Hansen classification, supination-external rotation injuries were found in 20 cases, supination-adduction injuries in 22 cases, pronation-external rotation injuries in 11 cases, tibiofibular fractures in 2 cases, and simple medial malleolar fractures in 2 cases. The mean follow-up period was 23.8 months, and the average follow-up American Orthopedic Foot and Ankle Society ankle-hindfoot score was 85.42. Forty-five patients (80.36%) reported excellent or good satisfaction with the outcome. Posterior malleolar fractures occurred in 41.07% of ankle fractures sustained in parachute landings. Because most of the ankle fractures in parachute injuries were compound fractures, most cases had to

  1. Fracture resistance of welded panel specimen with perpendicular crack in tensile

    International Nuclear Information System (INIS)

    Gochev, Todor; Adziev, Todor

    1998-01-01

    Defects caused by natural crack in welded joints of high-strength low-alloy (HSLA) steels are very often. Perpendicular crack in welded joints and its heat treatment after the welding has also an influence on the fracture resistance. The fracture resistance of welded joints by crack in tense panel specimens was investigated by crack mouse opening displesment (CMOD), the parameter of fracture mechanic. Crack propagation was analysed by using a metallographic analysis of fractured specimens after the test. (Author)

  2. Rheological Characteristics of Cement Grout and its Effect on Mechanical Properties of a Rock Fracture

    Science.gov (United States)

    Liu, Quansheng; Lei, Guangfeng; Peng, Xingxin; Lu, Chaobo; Wei, Lai

    2018-02-01

    Grouting reinforcement, which has an obvious strengthening effect on fractured rock mass, has been widely used in various fields in geotechnical engineering. The rheological properties of grout will greatly affect its diffusion radius in rock fractures, and the water-cement ratio is an important factor in determining the grouting flow patterns. The relationship between shear stress and shear rate which could reflect the grout rheological properties, the effects of water-cement ratio, and temperature on the rheological properties of grouting was studied in the laboratory. Besides, a new method for producing fractured rock specimens was proposed and solved the problem of producing natural fractured rock specimens. To investigate the influences of grouting on mechanical properties of a rock fracture, the fractured rock specimens made using the new method were reinforced by grouting on the independent designed grouting platform, and then normal and tangential mechanical tests were carried out on fractured rock specimens. The results showed that the mechanical properties of fractured rock mass are significantly improved by grouting, the peak shear strength and residual strength of rock fractures are greatly improved, and the resistance to deformation is enhanced after grouting. Normal forces affect the tangential behavior of the rock fracture, and the tangential stress strength increases with normal forces. The strength and stability of fractured rock mass are increased by grouting reinforcement.

  3. Hydromechanical modeling of clay rock including fracture damage

    Science.gov (United States)

    Asahina, D.; Houseworth, J. E.; Birkholzer, J. T.

    2012-12-01

    Argillaceous rock typically acts as a flow barrier, but under certain conditions significant and potentially conductive fractures may be present. Fracture formation is well-known to occur in the vicinity of underground excavations in a region known as the excavation disturbed zone. Such problems are of particular importance for low-permeability, mechanically weak rock such as clays and shales because fractures can be relatively transient as a result of fracture self-sealing processes. Perhaps not as well appreciated is the fact that natural fractures can form in argillaceous rock as a result of hydraulic overpressure caused by phenomena such as disequlibrium compaction, changes in tectonic stress, and mineral dehydration. Overpressure conditions can cause hydraulic fracturing if the fluid pressure leads to tensile effective stresses that exceed the tensile strength of the material. Quantitative modeling of this type of process requires coupling between hydrogeologic processes and geomechanical processes including fracture initiation and propagation. Here we present a computational method for three-dimensional, hydromechanical coupled processes including fracture damage. Fractures are represented as discrete features in a fracture network that interact with a porous rock matrix. Fracture configurations are mapped onto an unstructured, three-dimensonal, Voronoi grid, which is based on a random set of spatial points. Discrete fracture networks (DFN) are represented by the connections of the edges of a Voronoi cells. This methodology has the advantage that fractures can be more easily introduced in response to coupled hydro-mechanical processes and generally eliminates several potential issues associated with the geometry of DFN and numerical gridding. A geomechanical and fracture-damage model is developed here using the Rigid-Body-Spring-Network (RBSN) numerical method. The hydrogelogic and geomechanical models share the same geometrical information from a 3D Voronoi

  4. Fracture toughness of dentin/resin-composite adhesive interfaces.

    Science.gov (United States)

    Tam, L E; Pilliar, R M

    1993-05-01

    The reliability and validity of tensile and shear bond strength determinations of dentin-bonded interfaces have been questioned. The fracture toughness value (KIC) reflects the ability of a material to resist crack initiation and unstable propagation. When applied to an adhesive interface, it should account for both interfacial bond strength and inherent defects at or near the interface, and should therefore be more appropriate for characterization of interface fracture resistance. This study introduced a fracture toughness test for the assessment of dentin/resin-composite bonded interfaces. The miniature short-rod specimen geometry was used for fracture toughness testing. Each specimen contained a tooth slice, sectioned from a bovine incisor, to form the bonded interface. The fracture toughness of an enamel-bonded interface was assessed in addition to the dentin-bonded interfaces. Tensile bond strength specimens were also prepared from the dentin surfaces of the cut bovine incisors. A minimum of ten specimens was fabricated for each group of materials tested. After the specimens were aged for 24 h in distilled water at 37 degrees C, the specimens were loaded to failure in an Instron universal testing machine. There were significant differences (p adhesives tested. Generally, both the fracture toughness and tensile bond strength measurements were highest for AllBond 2, intermediate for 3M MultiPurpose, and lowest for Scotchbond 2. Scanning electron microscopy of the fractured specimen halves confirmed that crack propagation occurred along the bond interface during the fracture toughness test. It was therefore concluded that the mini-short-rod fracture toughness test provided a valid method for characterization of the fracture resistance of the dentin-resin composite interface.

  5. Upper extremity injuries associated with strength training.

    Science.gov (United States)

    Haupt, H A

    2001-07-01

    Most injuries sustained during strength training are mild strains that resolve with appropriate rest. More severe injuries include traumatic shoulder dislocations, tendon ruptures of the pectoralis major, biceps, and triceps; stress fractures of the distal clavicle, humerus, radius, and ulna; traumatic fractures of the distal radius and ulna in adolescent weightlifters; and compressive and stretch neuropathies. These more severe injuries are usually the result of improperly performing a strength training exercise. Educating athletes regarding proper strength-training techniques serves to reverse established injury patterns and to prevent these injuries in the first place. Recognizing the association of anabolic steroid use to several of the injury patterns further reinforces the need for medical specialists to counsel athletes against their use. With the increasing use of supplements such as creatine, the incidence and nature of strength-training injuries may change further. Greater emphasis on the competitive performance of younger athletes undoubtedly will generate enthusiasm for strength training at earlier ages in both sexes. The importance of proper supervision of these young athletes by knowledgeable persons will increase. As the popularity of strength training grows, there will be ample opportunity to continue to catalog the injury patterns associated with this activity.

  6. Cyclic fatigue of a high-strength corrosion-resistant sheet TRIP steel

    Science.gov (United States)

    Terent'ev, V. F.; Alekseeva, L. E.; Korableva, S. A.; Prosvirnin, D. V.; Pankova, M. N.; Filippov, G. A.

    2014-04-01

    The mechanical properties of 0.3- and 0.8-mm-thick high-strength corrosion-resistant TRIP steel having various levels of strength properties are studied during static and cyclic loading in the high-cycle fatigue range. The fatigue fracture surface is analyzed by fractography, and the obtained results demonstrate ductile and quasi-brittle fracture mechanisms of this steel depending on the strength properties of the steel and the content of deformation martensite in it.

  7. The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

    Directory of Open Access Journals (Sweden)

    Lianchong Li

    2016-03-01

    Full Text Available To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, a series of simulations on the hydraulic fracturing are performed. In the simulations, three points, i.e., (1 confining stresses, representing the effect of in situ stresses, (2 strength of the interfaces, and (3 material properties of the layers on either side of the interface, are crucial in fracturing across interfaces between two adjacent rock layers. Numerical results show that the hydrofracture propagation within a layered sequence of sedimentary rocks is controlled by changing in situ stresses, interface properties, and lithologies. The path of the hydraulic fracture is characterized by numerous deflections, branchings, and terminations. Four types of potential interaction, i.e., penetration, arrest, T-shaped branching, and offset, between a hydrofracture and an interface within the layered rocks are formed. Discontinuous composite fracture segments resulting from out-of-plane growth of fractures provide a less permeable path for fluids, gas, and oil than a continuous planar composite fracture, which are one of the sources of the high treating pressures and reduced fracture volume.

  8. Simulating Hydraulic Fracturing: Failure in soft versus hard rocks

    Science.gov (United States)

    Aleksans, J.; Koehn, D.; Toussaint, R.

    2017-12-01

    In this contribution we discuss the dynamic development of hydraulic fractures, their evolution and the resulting seismicity during fluid injection in a coupled numerical model. The model describes coupling between a solid that can fracture dynamically and a compressible fluid that can push back at the rock and open fractures. With a series of numerical simulations we show how the fracture pattern and seismicity change depending on changes in depth, injection rate, Young's Modulus and breaking strength. Our simulations indicate that the Young's Modulus has the largest influence on the fracture dynamics and also the related seismicity. Simulations of rocks with a Young's modulus smaller than 10 GPa show dominant mode I failure and a growth of fracture aperture with a decrease in Young's modulus. Simulations of rocks with a higher Young's modulus than 10 GPa show fractures with a constant aperture and fracture growth that is mainly governed by a growth in crack length and an increasing amount of mode II failure. We propose that two distinct failure regimes are observed in the simulations, above 10 GPa rocks break with a constant critical stress intensity factor whereas below 10 GPa they break reaching a critical cohesion, i.e. a critical tensile strength. These results are very important for the prediction of fracture dynamics and seismicity during fluid injection, especially since we see a transition from one failure regime to another at around 10 GPa, a Young's modulus that lies in the middle of possible values for natural shale rocks.

  9. A review of the strength properties of dental ceramics.

    Science.gov (United States)

    Hondrum, S O

    1992-06-01

    New ceramic materials for restorative dentistry have been developed and introduced in recent years. This article reviews advantages and disadvantages of dental ceramics, concentrating on strength properties. Included are factors affecting the strength of dental ceramic materials and the most common mechanisms for increasing the strength of dental ceramics. The properties of presently available materials such as dispersion-strengthened ceramics, cast ceramics, and foil-reinforced materials are discussed. Current research efforts to improve the fracture resistance of ceramic restorative materials are reviewed. A description of methods to evaluate the strength of ceramics is included, as a caution concerning the interpretation of strength data reported in the literature.

  10. Preparation, mechanical strengths, and thermal

    Science.gov (United States)

    Inoue, A.; Furukawa, S.; Hagiwara, M.; Masumoto, T.

    1987-05-01

    Ni-based amorphous wires with good bending ductility have been prepared for Ni75Si8B17 and Ni78P12B10 alloys containing 1 to 2 at. pct Al or Zr by melt spinning in rotating water. The enhancement of the wire-formation tendency by the addition of Al has been clarified to be due to the increase in the stability of the melt jet through the formation of a thin A12O3 film on the outer surface. The maximum wire diameter is about 190 to 200 μm for the Ni-Si (or P)-B-Al alloys and increases to about 250 μm for the Ni-Si-B-Al-Cr alloys containing 4 to 6 at. pct Cr. The tensile fracture strength and fracture elongation are 2730 MPa and 2.9 pct for (Ni0.75Si0.08B0.17 99Al1) wire and 2170 MPa and 2.4 pct for (Ni0.78P0.12B0.1)99Al1 wire. These wires exhibit a fatigue limit under dynamic bending strain in air with a relative humidity of 65 pct; this limit is 0.50 pct for a Ni-Si-B-Al wire, which is higher by 0.15 pct than that of a Fe75Si10B15 amorphous wire. Furthermore, the Ni-base wires do not fracture during a 180-deg bending even for a sample annealed at temperatures just below the crystallization temperature, in sharp contrast to high embrittlement tendency for Fe-base amorphous alloys. Thus, the Ni-based amorphous wires have been shown to be an attractive material similar to Fe- and Co-based amorphous wires because of its high static and dynamic strength, high ductility, high stability to thermal embrittlement, and good corrosion resistance.

  11. Fracture mechanical materials characterisation

    International Nuclear Information System (INIS)

    Wallin, K.; Planman, T.; Nevalainen, M.

    1998-01-01

    The experimental fracture mechanics development has been focused on the determination of reliable lower-bound fracture toughness estimates from small and miniature specimens, in particular considering the statistical aspects and loading rate effects of fracture mechanical material properties. Additionally, materials aspects in fracture assessment of surface cracks, with emphasis on the transferability of fracture toughness data to structures with surface flaws have been investigated. Further a modified crack-arrest fracture toughness test method, to increase the effectiveness of testing, has been developed. (orig.)

  12. Fracture toughness of manet II steel

    International Nuclear Information System (INIS)

    Gboneim, M.M.; Munz, D.

    1997-01-01

    High fracture toughness was evaluated according to the astm and chromium (9-12) martensitic steels combine high strength and toughness with good corrosion and oxidation resistance in a range of environments, and also show relatively high creep strength at intermediate temperatures. They therefore find applications in, for example, the offshore oil and gas production and chemical industries i pipe work and reaction vessels, and in high temperature steam plant in power generation systems. Recently, the use of these materials in the nuclear field was considered. They are candidates as tubing materials for breeder reactor steam generators and as structural materials for the first wall and blanket in fusion reactors. The effect of ageing on the tensile properties and fracture toughness of a 12 Cr-1 Mo-Nb-v steel, MANET II, was investigated in the present work. Tensile specimens and compact tension (CT) specimens were aged at 550 degree C for 1000 h. The japanese standards. Both microstructure and fracture surface were examined using optical and scanning electron microscopy (SEM). The results showed that ageing did not affect the tensile properties. However, the fracture toughness K Ic and the tearing modules T were reduced due to the ageing treatment. The results were discussed in the light of the chemical composition and the fracture surface morphology. 9 figs., 3 tabs

  13. Fractures (Broken Bones): First Aid

    Science.gov (United States)

    First aid Fractures (broken bones) Fractures (broken bones): First aid By Mayo Clinic Staff A fracture is a ... 10, 2018 Original article: http://www.mayoclinic.org/first-aid/first-aid-fractures/basics/ART-20056641 . Mayo Clinic ...

  14. Fracture toughness correlations

    International Nuclear Information System (INIS)

    Wallin, Kim

    1986-09-01

    In this study existing fracture parameter correlations are reviewed. Their applicability and reliability are discussed in detail. A new K IC -CVN-correlation, based on a theoretical brittle fracture model, is presented

  15. Rib fracture - aftercare

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000539.htm Rib fracture - aftercare To use the sharing features on this page, please enable JavaScript. A rib fracture is a crack or break in one or ...

  16. Sprains, Strains and Fractures

    Science.gov (United States)

    ... fractures. Many fractures and sprains occur during sports. Football players are particularly vulnerable to foot and ankle ... feet and ankles and take a complete medical history. He or she will also order tests, including ...

  17. Infant skull fracture (image)

    Science.gov (United States)

    Skull fractures may occur with head injuries. Although the skull is both tough and resilient and provides excellent ... or blow can result in fracture of the skull and may be accompanied by injury to the ...

  18. Ankle fracture - aftercare

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000548.htm Ankle fracture - aftercare To use the sharing features on this page, please enable JavaScript. An ankle fracture is a break in 1 or more ankle ...

  19. Atraumatic First Rib Fracture

    OpenAIRE

    Koray Aydogdu

    2014-01-01

    Rib fractures are usually seen after a trauma, while atraumatic spontaneous rib fractures are quite rare. A first rib fracture identified in our 17 years old female patient who had not a history of trauma except lifting a heavy weight was examined in details in terms of the potential complications and followed-up for a long time. We presented our experience on this case with atraumatic first rib fracture that has different views for the etiology in light of the literature.

  20. Mechanical properties and fracture of titanium hydrides

    International Nuclear Information System (INIS)

    Koketsu, Hideyuki; Taniyama, Yoshihiro; Yonezu, Akio; Cho, Hideo; Ogawa, Takeshi; Takemoto, Mikio; Nakayama, Gen

    2006-01-01

    Titanium hydrides tend to suffer fracture when their thicknesses reach a critical thickness. Morphology and mechanical property of the hydrides are, however, not well known. The study aims to reveal the hydride morphology and fracture types of the hydrides. Chevron shaped plate hydrides were found to be produced on the surface of pure titanium (Grade 1) and Grade 7 titanium absorbing hydrogen. There were tree types of fracture of the hydrides, i.e., crack in hydride layer, exfoliation of the layer and shear-type fracture of the hydride plates, during the growth of the hydrides and deformation. We next estimated the true stress-strain curves of the hydrides on Grade 1 and 7 titanium using the dual Vickers indentation method, and the critical strain causing the Mode-I fine crack by indentation. Fracture strength and strain of the hydrides in Grade 1 titanium were estimated as 566 MPa and 4.5%, respectively. Those of the hydride in Grade 7 titanium were 498 MPa and 16%. Though the fracture strains estimated from the plastic instability of true stress-strain curves were approximately the half of those estimated by finite element method, the titanium hydrides were estimated to possess some extent of toughness or plastic deformation capability. (author)

  1. on GAGD EOR in Naturally Fractured Reservoirs

    Directory of Open Access Journals (Sweden)

    Misagh Delalat

    2013-01-01

    Full Text Available The gas-assisted gravity drainage (GAGD process is designed and practiced based on gravity drainage idea and uses the advantage of density difference between injected CO2 and reservoir oil. In this work, one of Iran western oilfields was selected as a case study and a sector model was simulated based on its rock and fluid properties. The pressure of CO2 gas injection was close to the MMP of the oil, which was measured 1740 psia. Both homogeneous and heterogeneous types of fractures were simulated by creating maps of permeability and porosity. The results showed that homogeneous fractures had the highest value of efficiency, namely 40%; however, in heterogeneous fractures, the efficiency depended on the value of fracture density and the maximum efficiency was around 37%. Also, the effect of injection rate on two different intensities of fracture was studied and the results demonstrated that the model having higher fracture intensity had less limitation in increasing the CO2 injection rate; furthermore, its BHP did not increase intensively at higher injection rates either. In addition, three different types of water influxes were inspected on GAGD performance to simulate active, partial, and weak aquifer. The results showed that strong aquifer had a reverse effect on the influence of GAGD and almost completely disabled the gravity drainage mechanism. Finally, we inventively used a method to weaken the aquifer strength, and thus the gravity drainage revived and efficiency started to increase as if there was no aquifer.

  2. Metatarsal stress fractures - aftercare

    Science.gov (United States)

    ... Metatarsal stress fracture. In: Safran MR, Zachazewski J, Stone DA, eds. Instructions for Sports Medicine Patients . 2nd ed. Elsevier Saunders; 2012:648-652. Smith MS. Metatarsal fractures. In: Eiff PM, Hatch R, eds. Fracture Management for Primary Care . 3rd ed. ...

  3. Relationships between fractures

    Science.gov (United States)

    Peacock, D. C. P.; Sanderson, D. J.; Rotevatn, A.

    2018-01-01

    Fracture systems comprise many fractures that may be grouped into sets based on their orientation, type and relative age. The fractures are often arranged in a network that involves fracture branches that interact with one another. Interacting fractures are termed geometrically coupled when they share an intersection line and/or kinematically coupled when the displacements, stresses and strains of one fracture influences those of the other. Fracture interactions are characterised in terms of the following. 1) Fracture type: for example, whether they have opening (e.g., joints, veins, dykes), closing (stylolites, compaction bands), shearing (e.g., faults, deformation bands) or mixed-mode displacements. 2) Geometry (e.g., relative orientations) and topology (the arrangement of the fractures, including their connectivity). 3) Chronology: the relative ages of the fractures. 4) Kinematics: the displacement distributions of the interacting fractures. It is also suggested that interaction can be characterised in terms of mechanics, e.g., the effects of the interaction on the stress field. It is insufficient to describe only the components of a fracture network, with fuller understanding coming from determining the interactions between the different components of the network.

  4. Obesity and fracture risk

    OpenAIRE

    Gonnelli, Stefano; Caffarelli, Carla; Nuti, Ranuccio

    2014-01-01

    Obesity and osteoporosis are two common diseases with an increasing prevalence and a high impact on morbidity and mortality. Obese women have always been considered protected against osteoporosis and osteoporotic fractures. However, several recent studies have challenged the widespread belief that obesity is protective against fracture and have suggested that obesity is a risk factor for certain fractures.

  5. Imaging of insufficiency fractures

    Energy Technology Data Exchange (ETDEWEB)

    Krestan, Christian [Department of Radiology, Medical University of Vienna, Vienna General Hospital, Waehringerstr. 18-20, 1090 Vienna (Austria)], E-mail: christian.krestan@meduniwien.ac.at; Hojreh, Azadeh [Department of Radiology, Medical University of Vienna, Vienna General Hospital, Waehringerstr. 18-20, 1090 Vienna (Austria)

    2009-09-15

    This review focuses on the occurrence, imaging and differential diagnosis of insufficiency fractures. Prevalence, the most common sites of insufficiency fractures and their clinical implications are discussed. Insufficiency fractures occur with normal stress exerted on weakened bone. Postmenopausal osteoporosis is the most common cause of insufficiency fractures. Other conditions which affect bone turnover include osteomalacia, hyperparathyroidism, chronic renal failure and high-dose glucocorticoid therapy. It is a challenge for the radiologist to detect and diagnose insufficiency fractures, and to differentiate them from other bone lesions. Radiographs are still the most widely used imaging method for identification of insufficiency fractures, but sensitivity is limited, depending on the location of the fractures. Magnetic resonance imaging (MRI) is a very sensitive tool to visualize bone marrow abnormalities associated with insufficiency fractures. Thin section, multi-detector computed tomography (MDCT) depicts subtle fracture lines allowing direct visualization of cortical and trabecular bone. Bone scintigraphy still plays a role in detecting fractures, with good sensitivity but limited specificity. The most important differential diagnosis is underlying malignant disease leading to pathologic fractures. Bone densitometry and clinical history may also be helpful in confirming the diagnosis of insufficiency fractures.

  6. Relative scale and the strength and deformability of rock masses

    Science.gov (United States)

    Schultz, Richard A.

    1996-09-01

    The strength and deformation of rocks depend strongly on the degree of fracturing, which can be assessed in the field and related systematically to these properties. Appropriate Mohr envelopes obtained from the Rock Mass Rating (RMR) classification system and the Hoek-Brown criterion for outcrops and other large-scale exposures of fractured rocks show that rock-mass cohesive strength, tensile strength, and unconfined compressive strength can be reduced by as much as a factor often relative to values for the unfractured material. The rock-mass deformation modulus is also reduced relative to Young's modulus. A "cook-book" example illustrates the use of RMR in field applications. The smaller values of rock-mass strength and deformability imply that there is a particular scale of observation whose identification is critical to applying laboratory measurements and associated failure criteria to geologic structures.

  7. Tensile rock mass strength estimated using InSAR

    KAUST Repository

    Jonsson, Sigurjon

    2012-11-01

    The large-scale strength of rock is known to be lower than the strength determined from small-scale samples in the laboratory. However, it is not well known how strength scales with sample size. I estimate kilometer-scale tensional rock mass strength by measuring offsets across new tensional fractures (joints), formed above a shallow magmatic dike intrusion in western Arabia in 2009. I use satellite radar observations to derive 3D ground displacements and by quantifying the extension accommodated by the joints and the maximum extension that did not result in a fracture, I put bounds on the joint initiation threshold of the surface rocks. The results indicate that the kilometer-scale tensile strength of the granitic rock mass is 1–3 MPa, almost an order of magnitude lower than typical laboratory values.

  8. Tensile rock mass strength estimated using InSAR

    KAUST Repository

    Jonsson, Sigurjon

    2012-01-01

    The large-scale strength of rock is known to be lower than the strength determined from small-scale samples in the laboratory. However, it is not well known how strength scales with sample size. I estimate kilometer-scale tensional rock mass strength by measuring offsets across new tensional fractures (joints), formed above a shallow magmatic dike intrusion in western Arabia in 2009. I use satellite radar observations to derive 3D ground displacements and by quantifying the extension accommodated by the joints and the maximum extension that did not result in a fracture, I put bounds on the joint initiation threshold of the surface rocks. The results indicate that the kilometer-scale tensile strength of the granitic rock mass is 1–3 MPa, almost an order of magnitude lower than typical laboratory values.

  9. A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation

    Directory of Open Access Journals (Sweden)

    Zhiheng Zhao

    2016-07-01

    Full Text Available To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale formation, were prepared to conduct the hydraulic fracturing experiments. The results reveal that the breakdown pressure increases with the rise of thickness and strength of interbeds under the same in-situ field stress and injection rate. In addition, for the model blocks with thick and high strength interbeds, the hydraulic fracture has difficulty crossing the interbeds and is prone to divert along the bedding faces, and the fracturing effectiveness is not good. However, for the model blocks with thin and low strength interbeds, more long branches are generated along the main fracture, which is beneficial to the formation of the fracture network. What is more, combining the macroscopic descriptions with microscopic observations, the blocks with thinner and lower strength interbeds tend to generate more micro-fractures, and the width of the fractures is relatively larger on the main fracture planes. Based on the experiments, it is indicated that the propagation of hydraulic fractures is strongly influenced by the characteristics of interbeds, and the results are instructive to the understanding and evaluation of the fracability in the continental shale formation.

  10. Effect of cyclic loading on fracture strength of endodontically treated teeth restored with conventional and esthetic posts Efeito da carga cíclica na resistência de dentes tratados endodonticamente restaurados com pinos dentários convencionais e estéticos

    Directory of Open Access Journals (Sweden)

    Anuar Antônio Xible

    2006-08-01

    Full Text Available INTRODUCTION: Esthetic post and core systems were recently introduced. There are few reports regarding their behavior under cyclic loading. OBJECTIVES: This study compared the effect of cyclic loading on survival rate, residual strength and mode of fracture of endodontically treated teeth restored with esthetic and direct metallic post systems subjected to mechanical cyclic loading. MATERIALS AND METHODS: Thirty canines were endodontically treated, decoronated and prepared for metal free ceramic crowns, leaving 1.5 mm of dentin for ferrule effect. They were distributed in 3 groups and restored as follows: group 1 with zirconia posts (Cosmopost and glass-ceramic cores (IPS Empress Cosmopost; group 2 with fiber reinforced composite posts (FibreKor and group 3 with titanium posts (AZthec Anchor. Direct resin composite (Build It FR Resin Composite was used as core in groups 2 and 3. All specimens were restored with all ceramic crowns (IPS Empress 2. A resin cement/adhesive system (Cement It/Bond It Primer A+B was used to lute the posts to root canals and metal free porcelain crowns to the teeth preparation. Specimens were subjected to mechanical load of 250 N for 500,000x at a frequency of 1.7 Hz and then to static load until failure in a universal testing machine. Data were analyzed using One-way ANOVA and Fischer Exact tests alpha=0.05. RESULTS: All groups had 100% survival rate after cyclic loading; fracture strength values (SD in N were: group 1 = 886.5(170.6, group 2 = 762.2(113.6 and group 3 = 768.9(72.9; there was no difference among groups (p=0.08; the percentage of mode of favorable fracture found was: group 1 = 60%, group 2 = 90% and group 3 = 50%; there was no correlation between the mode of failure and post and core system used (P=0.142. CONCLUSIONS: Esthetic post and core systems showed statistically equivalent fracture strength values, mode of failure and survival rate compared to conventional direct metallic post and resin composite

  11. Distribution of crushing strength of tablets

    DEFF Research Database (Denmark)

    Sonnergaard, Jørn

    2002-01-01

    The distribution of a given set of data is important since most parametric statistical tests are based on the assumption that the studied data are normal distributed. In analysis of fracture mechanics the Weibull distribution is widely used and the derived Weibull modulus is interpreted as a mate...... data from nine model tablet formulations and four commercial tablets are shown to follow the normal distribution. The importance of proper cleaning of the crushing strength apparatus is demonstrated....

  12. Fracture mechanics of ceramics. Vol. 8. Microstructure, methods, design, and fatigue

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.H.; Lange, F.F.

    1986-01-01

    This paper presents information on the following topics: fracture mechanics and microstructures; non-lubricated sliding wear of Al 2 O 3 , PSZ and SiC; mixed-mode fracture of ceramics; some fracture properties of alumina-containing electrical porcelains; transformation toughening in the Al 2 O 3 -Cr 2 O 3 /ZrO 2 -HfO 2 system; strength toughness relationships for transformation toughened ceramics; tensile strength and notch sensitivity of Mg-PSZ; fracture mechanisms in lead zirconate titanate ceramics; loading-unloading techniques for determining fracture parameters of brittle materials utilizing four-point bend, chevron-notched specimens; application of the potential drop technique to the fracture mechanics of ceramics; ceramics-to-metal bonding from a fracture mechanics perspective; observed changes in fracture strength following laser irradiation and ion beam mixing of Ni overlayers on sintered alpha-SiC; crack growth in single-crystal silicon; a fracture mechanics and non-destructive evaluation investigation of the subcritical-fracture process in rock; slow crack growth in sintered silicon nitride; uniaxial tensile fatigue testing of sintered silicon carbide under cyclic temperature change; and effect of surface corrosion on glass fracture

  13. Effect of Random Natural Fractures on Hydraulic Fracture Propagation Geometry in Fractured Carbonate Rocks

    Science.gov (United States)

    Liu, Zhiyuan; Wang, Shijie; Zhao, Haiyang; Wang, Lei; Li, Wei; Geng, Yudi; Tao, Shan; Zhang, Guangqing; Chen, Mian

    2018-02-01

    Natural fractures have a significant influence on the propagation geometry of hydraulic fractures in fractured reservoirs. True triaxial volumetric fracturing experiments, in which random natural fractures are created by placing cement blocks of different dimensions in a cuboid mold and filling the mold with additional cement to create the final test specimen, were used to study the factors that influence the hydraulic fracture propagation geometry. These factors include the presence of natural fractures around the wellbore, the dimension and volumetric density of random natural fractures and the horizontal differential stress. The results show that volumetric fractures preferentially formed when natural fractures occurred around the wellbore, the natural fractures are medium to long and have a volumetric density of 6-9%, and the stress difference is less than 11 MPa. The volumetric fracture geometries are mainly major multi-branch fractures with fracture networks or major multi-branch fractures (2-4 fractures). The angles between the major fractures and the maximum horizontal in situ stress are 30°-45°, and fracture networks are located at the intersections of major multi-branch fractures. Short natural fractures rarely led to the formation of fracture networks. Thus, the interaction between hydraulic fractures and short natural fractures has little engineering significance. The conclusions are important for field applications and for gaining a deeper understanding of the formation process of volumetric fractures.

  14. Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

    International Nuclear Information System (INIS)

    Nachtrab, O.; Cassar-Pullicino, V.N.; Lalam, R.; Tins, B.; Tyrrell, P.N.M.; Singh, J.

    2012-01-01

    MR imaging plays a vital role in the diagnosis and management of hip fractures in all age groups, in a large spectrum of patient groups spanning the elderly and sporting population. It allows a confident exclusion of fracture, differentiation of bony from soft tissue injury and an early confident detection of fractures. There is a spectrum of MR findings which in part is dictated by the type and cause of the fracture which the radiologist needs to be familiar with. Judicious but prompt utilisation of MR in patients with suspected hip fractures has a positive therapeutic impact with healthcare cost benefits as well as social care benefits.

  15. The Strength Compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    In the Ph.D-project ͚Strengths-based Learning - Children͛s character strengths as a means to their learning potential͛ 750 Danish children have assessed ͚The Strength Compass͛ in order to identify their strengths and to create awareness of strengths. This was followed by a strengths......-based intervention program in order to explore the strengths. Finally different methods to apply the strength in everyday life at school were applied. The paper presentation will show the results for strengths display for children aged 6-16 in different categories: Different age groups: Are the same strengths...... present in both small children and youths? Gender: Do the results show differences between the two genders? Danish as a mother- tongue language: Do the results show any differences in the strengths display when considering different language and cultural backgrounds? Children with Special Needs: Do...

  16. Orbital fractures: a review

    Directory of Open Access Journals (Sweden)

    Jeffrey M Joseph

    2011-01-01

    Full Text Available Jeffrey M Joseph, Ioannis P GlavasDivision of Ophthalmic Plastic and Reconstructive Surgery, Department of Ophthalmology, School of Medicine, New York University, New York, NY, USA; Manhattan Eye, Ear, and Throat Hospital, New York, NY, USAAbstract: This review of orbital fractures has three goals: 1 to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2 to explain how to assess and examine a patient after periorbital trauma, and 3 to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.Keywords: orbit, trauma, fracture, orbital floor, medial wall, zygomatic, zygomatic complex, zmc fracture, zygomaticomaxillary complex fractures 

  17. Mechanics of Hydraulic Fractures

    Science.gov (United States)

    Detournay, Emmanuel

    2016-01-01

    Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

  18. Fracture in Soft Materials

    DEFF Research Database (Denmark)

    Hassager, Ole

    Fracture is a phenomenon that is generally associated with solids. A key element in fracture theory is the so-called weakest link idea that fracture initiates from the largest pre-existing material imperfection. However, recent work has demonstrated that fracture can also happen in liquids, where...... surface tension will act to suppress such imperfections. Therefore, the weakest link idea does not seem immediately applicable to fracture in liquids. This presentation will review fracture in liquids and argue that fracture in soft liquids is a material property independent of pre-existing imperfections....... The following questions then emerge: What is the material description needed to predict crack initiation, crack speed and crack shape in soft materials and liquids....

  19. Flexural fracture and fatigue behavior of steel-fiber-reinforced concrete structures

    International Nuclear Information System (INIS)

    Chang, D.I.

    1995-01-01

    Fracture and fatigue tests were performed in order to investigate the fracture and fatigue behavior of steel-fibre-reinforced concrete (SFRC) structures. 33 SFRC beams were used in the fracture and fatigue tests. The relationship between loading, strain and midspan deflection of the beams was observed under the three-point loading system.From the test results, the effects of the fiber content, fiber aspect ratio and notch-to-depth ratio on the concrete fracture and fatigue behavior were studied, and the fatigue strengths of SFRC beams were calculated. According to the regression technique, some empirical formulae for predicting the fatigue strength of SFRC beams were also suggested. (orig.)

  20. Specimen-specific modeling of hip fracture pattern and repair.

    Science.gov (United States)

    Ali, Azhar A; Cristofolini, Luca; Schileo, Enrico; Hu, Haixiang; Taddei, Fulvia; Kim, Raymond H; Rullkoetter, Paul J; Laz, Peter J

    2014-01-22

    Hip fracture remains a major health problem for the elderly. Clinical studies have assessed fracture risk based on bone quality in the aging population and cadaveric testing has quantified bone strength and fracture loads. Prior modeling has primarily focused on quantifying the strain distribution in bone as an indicator of fracture risk. Recent advances in the extended finite element method (XFEM) enable prediction of the initiation and propagation of cracks without requiring a priori knowledge of the crack path. Accordingly, the objectives of this study were to predict femoral fracture in specimen-specific models using the XFEM approach, to perform one-to-one comparisons of predicted and in vitro fracture patterns, and to develop a framework to assess the mechanics and load transfer in the fractured femur when it is repaired with an osteosynthesis implant. Five specimen-specific femur models were developed from in vitro experiments under a simulated stance loading condition. Predicted fracture patterns closely matched the in vitro patterns; however, predictions of fracture load differed by approximately 50% due to sensitivity to local material properties. Specimen-specific intertrochanteric fractures were induced by subjecting the femur models to a sideways fall and repaired with a contemporary implant. Under a post-surgical stance loading, model-predicted load sharing between the implant and bone across the fracture surface varied from 59%:41% to 89%:11%, underscoring the importance of considering anatomic and fracture variability in the evaluation of implants. XFEM modeling shows potential as a macro-level analysis enabling fracture investigations of clinical cohorts, including at-risk groups, and the design of robust implants. © 2013 Published by Elsevier Ltd.

  1. Linking Scales in Plastic Deformation and Fracture

    DEFF Research Database (Denmark)

    Martinez-Paneda, Emilio; Niordson, Christian Frithiof; S. Deshpande, Vikram

    2017-01-01

    We investigate crack growth initiation and subsequent resistance in metallic materials by means of an implicit multi-scale approach. Strain gradient plasticity is employed to model the mechanical response of the solid so as to incorporate the role of geometrically necessary dislocations (GNDs......) and accurately capture plasticity at the small scales involved in crack tip deformation. The response ahead of the crack is described by means of a traction-separation law, which is characterized by the cohesive strength and the fracture energy. Results reveal that large gradients of plastic strain accumulatein...... the vicinity of the crack, elevating the dislocation density and the local stress. This stress elevation enhances crack propagation and significantly lowers the steady state fracture toughness with respect to conventional plasticity. Important insight is gained into fracture phenomena that cannot be explained...

  2. Weak layer fracture: facets and depth hoar

    Directory of Open Access Journals (Sweden)

    I. Reiweger

    2013-09-01

    Full Text Available Understanding failure initiation within weak snow layers is essential for modeling and predicting dry-snow slab avalanches. We therefore performed laboratory experiments with snow samples containing a weak layer consisting of either faceted crystals or depth hoar. During these experiments the samples were loaded with different loading rates and at various tilt angles until fracture. The strength of the samples decreased with increasing loading rate and increasing tilt angle. Additionally, we took pictures of the side of four samples with a high-speed video camera and calculated the displacement using a particle image velocimetry (PIV algorithm. The fracture process within the weak layer could thus be observed in detail. Catastrophic failure started due to a shear fracture just above the interface between the depth hoar layer and the underlying crust.

  3. Connection between tectonic stresses and well fracturing data

    Energy Technology Data Exchange (ETDEWEB)

    Scheidegger, A E [Imperial Oil Res. Lab., Calgary, CA

    1961-01-01

    Theoretical considerations of hydraulic well fracturing normally utilize a model in which the borehole is assumed to be a cylinder of infinite length. This leads to treatment of the induced stress state in two dimensions. The two-dimensional model is obviously an oversimplification. Therefore, a three-dimensional model is proposed in which the well pressure is assumed to be equivalent to a spherical pressure center. The bottom hole pressure during fracturing is determined by 4 variables; i.e., the 3 principal geological stresses and the rock strength. The response to fracturing is determined primarily by the prevailing stress state and to a lesser degree by the rock strength. The fracture condition is formulated and the model is used in the calculation of geological stresses from well data.

  4. High-strength beryllium block

    International Nuclear Information System (INIS)

    Pinto, N.P.; Keith, G.H.

    1977-01-01

    Beryllium billets hot isopressed using fine powder of high purity have exceptionally attractive properties; average tensile ultimate, 0.2% offset yield strength and elongation are 590 MPa, 430 MPa and 4.0% respectively. Properties are attributed to the fine grain size (about 4.0 μm average diameter) and the relatively low levels of BeO present as fine, well-dispersed particles. Dynamic properties, e.g., fracture toughness, are similar to those of standard grade, high-purity beryllium. The modulus of beryllium is retained to very high stress levels, and the microyield stress or precision elastic limit is higher than for other grades, including instrument grades. Limited data for billets made from normal-purity fine powders show similar room temperature properties. (author)

  5. Ballistic fractures: indirect fracture to bone.

    Science.gov (United States)

    Dougherty, Paul J; Sherman, Don; Dau, Nathan; Bir, Cynthia

    2011-11-01

    Two mechanisms of injury, the temporary cavity and the sonic wave, have been proposed to produce indirect fractures as a projectile passes nearby in tissue. The purpose of this study is to evaluate the temporal relationship of pressure waves using strain gauge technology and high-speed video to elucidate whether the sonic wave, the temporary cavity, or both are responsible for the formation of indirect fractures. Twenty-eight fresh frozen cadaveric diaphyseal tibia (2) and femurs (26) were implanted into ordnance gelatin blocks. Shots were fired using 9- and 5.56-mm bullets traversing through the gelatin only, passing close to the edge of the bone, but not touching, to produce an indirect fracture. High-speed video of the impact event was collected at 20,000 frames/s. Acquisition of the strain data were synchronized with the video at 20,000 Hz. The exact time of fracture was determined by analyzing and comparing the strain gauge output and video. Twenty-eight shots were fired, 2 with 9-mm bullets and 26 with 5.56-mm bullets. Eight indirect fractures that occurred were of a simple (oblique or wedge) pattern. Comparison of the average distance of the projectile from the bone was 9.68 mm (range, 3-20 mm) for fractured specimens and 15.15 mm (range, 7-28 mm) for nonfractured specimens (Student's t test, p = 0.036). In this study, indirect fractures were produced after passage of the projectile. Thus, the temporary cavity, not the sonic wave, was responsible for the indirect fractures.

  6. Fracture mechanisms in lead zirconate titanate ceramics

    International Nuclear Information System (INIS)

    Freiman, S.W.; Chuck, L.; Mecholsky, J.J.; Shelleman, D.L.

    1986-01-01

    Lead Zirconate Titanate (PZT) ceramics can be formed over a wide range of PbTiO 3 /PbZrO 3 ratios and exist in a number of crystal structures. This study involved the use of various fracture mechanics techniques to determine critical fracture toughness, K /SUB IC/ , as a function of composition, microstructure, temperature, and electrical and thermal history. The results of these experiments indicate that variations in K /SUB IC/ are related to phase transformations in the material as well as to other toughening mechanisms such as twinning and microcracking. In addition, the strength and fracture toughness of selected PZT ceramics were determined using specimens in which a crack was introduced by a Vicker's hardness indentor. The variation of K /SUB IC/ with composition and microstructure was related to the extent of twin-crack interaction. Comparison of the plot of strength as a function of indentation load with that predicted from indentation fracture models indicates the presence of internal stresses which contribute to failure. The magnitude of these internal stresses has been correlated with electrical properties of the ceramic. Fractographic analysis was used to determine the magnitude of internal stresses in specimens failing from ''natural flaws.''

  7. Statistical Analysis Of Failure Strength Of Material Using Weibull Distribution

    International Nuclear Information System (INIS)

    Entin Hartini; Mike Susmikanti; Antonius Sitompul

    2008-01-01

    In evaluation of ceramic and glass materials strength a statistical approach is necessary Strength of ceramic and glass depend on its measure and size distribution of flaws in these material. The distribution of strength for ductile material is narrow and close to a Gaussian distribution while strength of brittle materials as ceramic and glass following Weibull distribution. The Weibull distribution is an indicator of the failure of material strength resulting from a distribution of flaw size. In this paper, cumulative probability of material strength to failure probability, cumulative probability of failure versus fracture stress and cumulative probability of reliability of material were calculated. Statistical criteria calculation supporting strength analysis of Silicon Nitride material were done utilizing MATLAB. (author)

  8. Risk of vertebral compression fractures in multiple myeloma patients

    OpenAIRE

    Anitha, D.; Thomas, Baum; Jan, Kirschke S.; Subburaj, Karupppasamy

    2017-01-01

    Abstract The purpose of this study was to develop and validate a finite element (FE) model to predict vertebral bone strength in vitro using multidetector computed tomography (MDCT) images in multiple myeloma (MM) patients, to serve as a complementing tool to assess fracture risk. In addition, it also aims to differentiate MM patients with and without vertebral compression fractures (VCFs) by performing FE analysis on vertebra segments (T1?L5) obtained from in vivo routine MDCT imaging scans....

  9. Post-surgical rehabilitative approach to fragility fractures.

    Science.gov (United States)

    Gimigliano, F; Iolascon, G; Riccio, I; Frizzi, L; Gimigliano, R

    2013-10-01

    Osteoporosis is a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. The most frequent sites of fragility fractures are the hip, the distal radius, the spine, the proximal humerus, and the ankle. In most cases, a surgical approach with subsequent rehabilitative treatment is required. The general aims of rehabilitation are to increase functioning and improve patients' activities, participation level, and quality of life.

  10. Numerical modeling of shear stimulation in naturally fractured geothermal reservoirs

    OpenAIRE

    Ucar, Eren

    2018-01-01

    Shear-dilation-based hydraulic stimulations are conducted to create enhanced geothermal systems (EGS) from low permeable geothermal reservoirs, which are initially not amenable to energy production. Reservoir stimulations are done by injecting low-pressurized fluid into the naturally fractured formations. The injection aims to activate critically stressed fractures by decreasing frictional strength and ultimately cause a shear failure. The shear failure leads to a permanent ...

  11. Current status of the quantification of roughness and the peak shear strength criteria for rock joints

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoung Yoon; Kang, Chul Hyung

    1999-04-01

    In order to understand the effects of spent nuclear fuel on the hydraulic behaviour of the rock mass it is necessary to have knowledge about the relationship between the stresses and hydraulic properties of the fractures. The roughness of a fracture surface govern the dilation of the fracture and the displacement of the fracture surface under shear stress. The peak shear strength and hydraulic flow properties of fractures depend very much on the surface roughness. This report describes different methods and techniques used in the characterization of rock joint surfaces and their applications in rock mechanics. Joint roughness is an important factor in the shear resistance of a joint. The joint shear strength shows anisotropic properties due to roughness variation with the shearing direction in direct shear tests. Various shear strength criteria are described in this report. (author)

  12. Heavy-section steel technology program: Fracture issues

    International Nuclear Information System (INIS)

    Pennell, W.E.

    1992-01-01

    Large-scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL

  13. Heavy-Section Steel Technology program fracture issues

    International Nuclear Information System (INIS)

    Pennell, W.E.

    1989-10-01

    Large scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL. 24 refs., 18 figs

  14. High temperature tensile properties and fracture characteristics of bimodal 12Cr-ODS steel

    International Nuclear Information System (INIS)

    Chauhan, Ankur; Litvinov, Dimitri; Aktaa, Jarir

    2016-01-01

    This article describes the tensile properties and fracture characteristics of a 12Cr oxide dispersion strengthened (ODS) ferritic steel with unique elongated bimodal grain size distribution. The tensile tests were carried out at four different temperatures, ranging from room temperature to 700 °C, at a nominal strain rate of 10"−"3 s"−"1. At room temperature the material exhibits a high tensile strength of 1294 MPa and high yield strength of 1200 MPa. At 700 °C, the material still exhibits relatively high tensile strength of 300 MPa. The total elongation-to-failure exceeds 18% over the whole temperature range and has a maximum value of 29% at 600 °C. This superior ductility is attributed to the material's bimodal grain size distribution. In comparison to other commercial, as well as experimental, ODS steels, the material shows an excellent compromise between strength and ductility. The fracture surface studies reveal a change in fracture behavior from a mixed mode fracture at room temperature to fully ductile fracture at 600 °C. At 700 °C, the fracture path changes from intragranular to intergranular fracture, which is associated with a reduced ductility. - Highlights: • The steel has a unique elongated bimodal grain size distribution. • The steel shows an excellent compromise between strength and ductility. • Superior ductility in comparison to other commercial and experimental ODS steels. • Fracture behavior changes from mixed mode fracture at room temperature to fully ductile fracture at 600 °C. • Fracture path changes from intragranular to intergranular fracture at 700 °C.

  15. Diabetes mellitus and bone health: epidemiology, etiology and implications for fracture risk stratification.

    Science.gov (United States)

    Valderrábano, Rodrigo J; Linares, Maria I

    2018-01-01

    Skeletal fractures can result when there are co-morbid conditions that negatively impact bone strength. Fractures represent an important source of morbidity and mortality, especially in older populations. Diabetes mellitus is a metabolic disorder that has reached worldwide epidemic proportions and is increasingly being recognized as a risk factor for fracture. Type 1 and Type 2 diabetes have different effects on bone mineral density but share common pathways, which lead to bone fragility. In this review, we discuss the available data on diabetes and fractures, bone density and the clinical implications for fracture risk stratification in current practice.

  16. Dynamic plate osteosynthesis for fracture stabilization: how to do it

    Directory of Open Access Journals (Sweden)

    Juerg Sonderegger

    2010-01-01

    Full Text Available Plate osteosynthesis is one treatment option for the stabilization of long bones. It is widely accepted to achieve bone healing with a dynamic and biological fixation where the perfusion of the bone is left intact and micromotion at the fracture gap is allowed. The indications for a dynamic plate osteosynthesis include distal tibial and femoral fractures, some midshaft fractures, and adolescent tibial and femoral fractures with not fully closed growth plates. Although many lower limb shaft fractures are managed successfully with intramedullary nails, there are some important advantages of open-reduction-and-plate fixation: the risk of malalignment, anterior knee pain, or nonunion seems to be lower. The surgeon performing a plate osteosynthesis has the possibility to influence fixation strength and micromotion at the fracture gap. Long plates and oblique screws at the plate ends increase fixation strength. However, the number of screws does influence stiffness and stability. Lag screws and screws close to the fracture site reduce micromotion dramatically. Dynamic plate osteosynthesis can be achieved by applying some simple rules: long plates with only a few screws should be used. Oblique screws at the plate ends increase the pullout strength. Two or three holes at the fracture site should be omitted. Lag screws, especially through the plate, must be avoided whenever possible. Compression is not required. Locking plates are recommended only in fractures close to the joint. When respecting these basic concepts, dynamic plate osteosynthesis is a safe procedure with a high healing and a low complication rate. 

  17. Evaluation of tensile strength and fracture behavior of friction welded ...

    Indian Academy of Sciences (India)

    In the present study an attempt was made to join austenitic stainless steel ... Experimental details ... This test was carried out on the friction welded samples of .... phenomenon was observed to be true if the rotational speed was increased up to ...

  18. Vertebral strength and fracture risk following long duration spaceflight

    Data.gov (United States)

    National Aeronautics and Space Administration — Mechanical loading is required for maintenance of the musculoskeletal system. Thus, exposure to microgravity induces marked bone loss in both humans and animals, and...

  19. Modeling of flow through fractured tuff at Fran Ridge

    International Nuclear Information System (INIS)

    Eaton, R.R.; Ho, C.K.; Glass, R.J.; Nicholl, M.J.; Arnold, B.W.

    1996-01-01

    Numerical studies have modeled an infiltration experiment at Fran Ridge, using the TOUGH2 code, to aid in the selection of computational models for waste repository performance assessment. This study investigates the capabilities of TOUGH2 to simulate transient flows through highly fractured tuff, and provides a possible means of calibrating hydrologic parameters such as effective fracture aperture and fracture-matrix connectivity. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The field experiments involved the infiltration of dyed ponded water in highly fractured tuff. The infiltration observed in the experiment was subsequently modeled using Fran Ridge fracture frequencies, obtained during post-experiment site excavation. Comparison of the TOUGH2 results obtained using the two conceptual models gives insight into their relative strengths and weaknesses

  20. Factors affecting functional prognosis of patients with hip fracture

    DEFF Research Database (Denmark)

    Kristensen, M T

    2011-01-01

    to just one or two single factors. The current article reviews important factors affecting the functional prognosis, and clinicians are encouraged to include all factors potentially influencing the outcome of patients with hip fracture in their individualised treatment and rehabilitation plan. Especially......Having a hip fracture is considered one of the most fatal fractures for elderly people, resulting in impaired function, and increased morbidity and mortality. This challenges clinicians in identifying patients at risk of worse outcome, in order to optimise and intensify treatment in these patients....... A variety of factors such as age, prefracture function and health status, fracture type, pain, anaemia, muscle strength, and the early mobility level have been shown to influence patient outcome. Thus, the outcome of patients with hip fracture is considered multi-factorial, and can therefore not be related...

  1. Hydraulic fracturing in well ONM 15, Hassi-Messaoud field

    Energy Technology Data Exchange (ETDEWEB)

    Kerbouc, P

    1968-01-01

    In the Hassi-Messaoud field, hydraulic fracturing has been an extremely difficult problem because of the difficult conditions, and numerous tests run with conventional techniques which have had good results elswhere in the Sahara and worldwide, have given poor results. In Dec. 1967, the CFP(A) succeeded in an experimental fracturing operation on the ONM 15 well, increasing the production from 1 to 11 mU3D/hr. The principal results were: (1) in the sandstone reservoir of Hassi-Messaoud, the fracture was successfully propped with high-strength glass beads; (2) the orientation of the fracture was vertical; and (3) in certain favorable cases, such as wells that were mudded off or had a permeability barrier close to the well, the productivity can be increased by a factor of 10. However, it can still not be stated that hydraulic fracturing will be an economic stimulation method for the Hassi-Messaoud reservoir.

  2. The strength compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    of agreement/disagreement. Also the child/teacher is asked whether the actual strength is important and if he or she has the possibilities to apply the strength in the school. In a PhDproject ‘Strengths-based Learning - Children’s Character Strengths as Means to their Learning Potential’ 750 Danish children......Individual paper presentation: The ‘Strength Compass’. The results of a PhDresearch project among schoolchildren (age 6-16) identifying VIAstrengths concerning age, gender, mother-tongue-langue and possible child psychiatric diagnosis. Strengths-based interventions in schools have a theoretical...... Psychological Publishing Company. ‘The Strength Compass’ is a computer/Ipad based qualitative tool to identify the strengths of a child by a self-survey or a teacher’s survey. It is designed as a visual analogue scale with a statement of the strength in which the child/teacher may declare the degree...

  3. Determination of Strength for Reliability Analysis of Multilayer Ceramic Capacitors

    International Nuclear Information System (INIS)

    Breder, K.; Bridge, R.J.; Kirkland, T.P.; Riester, L.; Wereszczak, A.A.

    1999-01-01

    A Nanoindenter TM equipped with a Vickers indenter was used to measure fracture toughness of Multilayer Capacitors (MLCs) and BaTiO 3 blanks. Strength of blanks of 6.3 x 4.7 x 1.1 mm 3 was measured by performing three-point flexure using a 4 mm support span. The size of the strength limiting pores in the flexure tests was compared to pore sizes measured on polished MLC cross sections, and it was found that much larger pores were present in the 3-point flexure specimens. Strength distributions for the MLCs were generated using the measured fracture toughness values, assuming the measured pores or second phase inclusions were strength limiting

  4. Analysis of PITFL injuries in rotationally unstable ankle fractures.

    Science.gov (United States)

    Warner, Stephen J; Garner, Matthew R; Schottel, Patrick C; Hinds, Richard M; Loftus, Michael L; Lorich, Dean G

    2015-04-01

    Reduction and stabilization of the syndesmosis in unstable ankle fractures is important for ankle mortise congruity and restoration of normal tibiotalar contact forces. Of the syndesmotic ligaments, the posterior inferior tibiofibular ligament (PITFL) provides the most strength for maintaining syndesmotic stability, and previous work has demonstrated the significance of restoring PITFL function when it remains attached to a posterior malleolus fracture fragment. However, little is known regarding the nature of a PITFL injury in the absence of a posterior malleolus fracture. The goal of this study was to describe the PITFL injury pattern based on magnetic resonance imaging (MRI) and intraoperative observation. A prospective database of all operatively treated ankle fractures by a single surgeon was used to identify all supination-external rotation (SER) types III and IV ankle fracture patients with complete preoperative orthogonal ankle radiographs and MRI. All patients with a posterior malleolus fracture were excluded. Using a combination of preoperative imaging and intraoperative findings, we analyzed the nature of injuries to the PITFL. In total, 185 SER III and IV operatively treated ankle fractures with complete imaging were initially identified. Analysis of the preoperative imaging and operative reports revealed 34% (63/185) had a posterior malleolus fracture and were excluded. From the remaining 122 ankle fractures, the PITFL was delaminated from the posterior malleolus in 97% (119/122) of cases. A smaller proportion (3%; 3/122) had an intrasubstance PITFL rupture. Accurate and stable syndesmotic reduction is a significant component of restoring the ankle mortise after unstable ankle fractures. In our large cohort of rotationally unstable ankle fractures without posterior malleolus fractures, we found that most PITFL injuries occur as a delamination off the posterior malleolus. This predictable PITFL injury pattern may be used to guide new methods for

  5. Atraumatic First Rib Fracture

    Directory of Open Access Journals (Sweden)

    Koray Aydogdu

    2014-12-01

    Full Text Available Rib fractures are usually seen after a trauma, while atraumatic spontaneous rib fractures are quite rare. A first rib fracture identified in our 17 years old female patient who had not a history of trauma except lifting a heavy weight was examined in details in terms of the potential complications and followed-up for a long time. We presented our experience on this case with atraumatic first rib fracture that has different views for the etiology in light of the literature.

  6. Fracture mechanics safety approaches

    International Nuclear Information System (INIS)

    Roos, E.; Schuler, X.; Eisele, U.

    2004-01-01

    Component integrity assessments require the knowledge of reliable fracture toughness parameters characterising the initiation of the failure process in the whole relevant temperature range. From a large number of fracture mechanics tests a statistically based procedure was derived allowing to quantify the initiation of fracture toughness as a function of temperature as a closed function as well as the temperature dependence of the cleavage instability parameters. Alternatively to the direct experimental determination one also can use a correlation between fracture toughness and notch impact energy. (orig.)

  7. Scaphoid fractures in children

    Directory of Open Access Journals (Sweden)

    Gajdobranski Đorđe

    2014-01-01

    Full Text Available Introduction. Scaphoid fractures are rare in childhood. Diagnosis is very difficult to establish because carpal bones are not fully ossified. In suspected cases comparative or delayed radiography is used, as well as computerized tomography, magnetic resonance imaging, ultrasound and bone scintigraphy. Majority of scaphoid fractures are treated conservatively with good results. In case of delayed fracture healing various types of treatment are available. Objective. To determine the mechanism of injury, clinical healing process, types and outcome of treatment of scaphoid fractures in children. Methods. We retrospectively analyzed patients with traumatic closed fracture of the scaphoid bone over a ten-year period (2002-2011. The outcome of the treatment of “acute” scaphoid fracture was evaluated using the Mayo Wrist Score. Results. There were in total 34 patients, of mean age 13.8 years, with traumatic closed fracture of the scaphoid bone, whose bone growth was not finished yet. Most common injury mechanism was fall on outstretched arm - 76% of patients. During the examined period 31 children with “acute” fracture underwent conservative treatment, with average immobilization period of 51 days. Six patients were lost to follow-up. In the remaining 25 patients, after completed rehabilitation, functional results determined by the Mayo Wrist Score were excellent. Conclusion. Conservative therapy of “acute” scaphoid fractures is an acceptable treatment option for pediatric patients with excellent functional results.

  8. Pathological fractures in children

    Science.gov (United States)

    De Mattos, C. B. R.; Binitie, O.; Dormans, J. P.

    2012-01-01

    Pathological fractures in children can occur as a result of a variety of conditions, ranging from metabolic diseases and infection to tumours. Fractures through benign and malignant bone tumours should be recognised and managed appropriately by the treating orthopaedic surgeon. The most common benign bone tumours that cause pathological fractures in children are unicameral bone cysts, aneurysmal bone cysts, non-ossifying fibromas and fibrous dysplasia. Although pathological fractures through a primary bone malignancy are rare, these should be recognised quickly in order to achieve better outcomes. A thorough history, physical examination and review of plain radiographs are crucial to determine the cause and guide treatment. In most benign cases the fracture will heal and the lesion can be addressed at the time of the fracture, or after the fracture is healed. A step-wise and multidisciplinary approach is necessary in caring for paediatric patients with malignancies. Pathological fractures do not have to be treated by amputation; these fractures can heal and limb salvage can be performed when indicated. PMID:23610658

  9. Strength curves for shales and sandstones under hydrostatic confining pressures

    International Nuclear Information System (INIS)

    Gupta, S.C.; Sikka, S.K.

    1978-01-01

    The experimental data for the effect of confining pressures on the fracture stress have been analysed for shales and sandstones. The normalized compressive strengths are found to lie in a narrow region so that Ohnaka's equation for crystalline rocks, can be fitted to the data. The fitted parameters are physically reasonable and indicate that the functional dependence of strength on porosity, strain rate and temperature is independent of the confining pressures. (author)

  10. Method of making dielectric capacitors with increased dielectric breakdown strength

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

    2017-05-09

    The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

  11. Fracture of the styloid process associated with the mandible fracture

    Directory of Open Access Journals (Sweden)

    K N Dubey

    2013-01-01

    Full Text Available Fracture of the styloid process (SP of temporal bone is an uncommon injuries. Fracture of the SP can be associated with the facial injuries including mandible fracture. However, injury to the SP may be concealed and missed diagnosis may lead to the improper or various unnecessary treatments. A rare case of SP fracture associated with the ipsilateral mandibular fracture and also the diagnostic and management considerations of the SP fracture are discussed.

  12. Investigation of Mechanical Properties and Fracture Simulation of Solution-Treated AA 5754

    Science.gov (United States)

    Kumar, Pankaj; Singh, Akhilendra

    2017-10-01

    In this work, mechanical properties and fracture toughness of as-received and solution-treated aluminum alloy 5754 (AA 5754) are experimentally evaluated. Solution heat treatment of the alloy is performed at 530 °C for 2 h, and then, quenching is done in water. Yield strength, ultimate tensile strength, impact toughness, hardness, fatigue life, brittle fracture toughness (K_{Ic} ) and ductile fracture toughness (J_{Ic} ) are evaluated for as-received and solution-treated alloy. Extended finite element method has been used for the simulation of tensile and fracture behavior of material. Heaviside function and asymptotic crack tip enrichment functions are used for modelling of the crack in the geometry. Ramberg-Osgood material model coupled with fracture energy is used to simulate the crack propagation. Fracture surfaces obtained from various mechanical tests are characterized by scanning electron microscopy.

  13. The Process of Hydraulic Fracturing

    Science.gov (United States)

    Hydraulic fracturing, know as fracking or hydrofracking, produces fractures in a rock formation by pumping fluids (water, proppant, and chemical additives) at high pressure down a wellbore. These fractures stimulate the flow of natural gas or oil.

  14. [Trochanteric femoral fractures].

    Science.gov (United States)

    Douša, P; Čech, O; Weissinger, M; Džupa, V

    2013-01-01

    At the present time proximal femoral fractures account for 30% of all fractures referred to hospitals for treatment. Our population is ageing, the proportion of patients with post-menopausal or senile osteoporosis is increasing and therefore the number of proximal femoral fractures requiring urgent treatment is growing too. In the age category of 50 years and older, the incidence of these fractures has increased exponentially. Our department serves as a trauma centre for half of Prague and part of the Central Bohemia Region with a population of 1 150 000. Prague in particular has a high number of elderly citizens. Our experience is based on extensive clinical data obtained from the Register of Proximal Femoral Fractures established in 1997. During 14 years, 4280 patients, 3112 women and 1168 men, were admitted to our department for treatment of proximal femoral fractures. All patients were followed up until healing or development of complications. In the group under study, 82% were patients older than 70 years; 72% of those requiring surgery were in their seventies and eighties. Men were significantly younger than women (pfractures were 2.3-times more frequent in women than in men. In the category under 60 years, men significantly outnumbered women (pfractures were, on the average, eight years older than the patients with intertrochanteric fractures, which is a significant difference (pTrochanteric fractures accounted for 54.7% and femoral neck fractures for 45.3% of all fractures. The inter-annual increase was 5.9%, with more trochanteric than femoral neck fractures. There was a non-significant decrease in intertrochanteric (AO 31-A3) fractures. On the other hand, the number of pertrochanteric (AO 31-A1+2) fractures increased significantly (pfractures were treated with a proximal femoral nail; a short nail was used in 1260 and a long nail in 134 of them. A dynamic hip screw (DHS) was employed to treat 947 fractures. Distinguishing between pertrochanteric (21-A1

  15. Fracture propagation in cementitious materials

    DEFF Research Database (Denmark)

    Skocek, Jan

    , it is experimentally observed and numerically veried that the cracking plays an important role in mode-I as well as compressive experiments. The approximative particle model extended for materials with heterogeneous matrices predicts strengths matching favorably experimental records in a qualitative way.......Mechanical behavior of structures made from cementitious materials has been successfully modeled using non-linear fracture mechanics in recent decades. On the structural scale, an assumption of homogeneity of the material is valid and well established theories can be applied. However, if focus...... is put on phenomena of a similar scale as is the characteristic size of inhomogeneities of the material, a model which re ects the heterogeneous nature of the material needs to be applied. This is, indeed, the case for prediction of mechanical properties of a material based on the knowledge of properties...

  16. Myostatin (GDF-8) Deficiency Increases Fracture Callus Size, Sox-5 Expression, and Callus Bone Volume

    OpenAIRE

    Kellum, Ethan; Starr, Harlan; Arounleut, Phonepasong; Immel, David; Fulzele, Sadanand; Wenger, Karl; Hamrick, Mark W.

    2008-01-01

    Myostatin (GDF-8) is a negative regulator of skeletal muscle growth and mice lacking myostatin show increased muscle mass. We have previously shown that myostatin deficiency increases bone strength and biomineralization throughout the skeleton, and others have demonstrated that myostatin is expressed during the earliest phase of fracture repair. In order to determine the role of myostatin in fracture callus morphogenesis, we studied fracture healing in mice lacking myostatin. Adult wild-type ...

  17. Hand fracture - aftercare

    Science.gov (United States)

    ... an orthopedic surgeon if: Your metacarpal bones are broken and shifted out of place Your fingers do not line up correctly Your fracture nearly went through the skin Your fracture went through the skin Your pain is severe or becoming worse Self-care at Home You may have pain and swelling for 1 ...

  18. TIBIAL SHAFT FRACTURES.

    Science.gov (United States)

    Kojima, Kodi Edson; Ferreira, Ramon Venzon

    2011-01-01

    The long-bone fractures occur most frequently in the tibial shaft. Adequate treatment of such fractures avoids consolidation failure, skewed consolidation and reoperation. To classify these fractures, the AO/OTA classification method is still used, but it is worthwhile getting to know the Ellis classification method, which also includes assessment of soft-tissue injuries. There is often an association with compartmental syndrome, and early diagnosis can be achieved through evaluating clinical parameters and constant clinical monitoring. Once the diagnosis has been made, fasciotomy should be performed. It is always difficult to assess consolidation, but the RUST method may help in this. Radiography is assessed in two projections, and points are scored for the presence of the fracture line and a visible bone callus. Today, the dogma of six hours for cleaning the exposed fracture is under discussion. It is considered that an early start to intravenous antibiotic therapy and the lesion severity are very important. The question of early or late closure of the lesion in an exposed fracture has gone through several phases: sometimes early closure has been indicated and sometimes late closure. Currently, whenever possible, early closure of the lesion is recommended, since this diminishes the risk of infection. Milling of the canal when the intramedullary nail is introduced is still a controversial subject. Despite strong personal positions in favor of milling, studies have shown that there may be some advantage in relation to closed fractures, but not in exposed fractures.

  19. Physeal Fractures in Foals.

    Science.gov (United States)

    Levine, David G; Aitken, Maia R

    2017-08-01

    Physeal fractures are common musculoskeletal injuries in foals and should be included as a differential diagnosis for the lame or nonweightbearing foal. Careful evaluation of the patient, including precise radiographic assessment, is paramount in determining the options for treatment. Prognosis mostly depends on the patient's age, weight, and fracture location and configuration. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Accuracy of specimen-specific nonlinear finite element analysis for evaluation of distal radius strength in cadaver material.

    Science.gov (United States)

    Matsuura, Yusuke; Kuniyoshi, Kazuki; Suzuki, Takane; Ogawa, Yasufumi; Sukegawa, Koji; Rokkaku, Tomoyuki; Takahashi, Kazuhisa

    2014-11-01

    Distal radius fracture, which often occurs in the setting of osteoporosis, can lead to permanent deformity and disability. Great effort has been directed toward developing noninvasive methods for evaluating the distal radius strength, with the goal of assessing fracture risk. The aim of this study was to evaluate distal radius strength using a finite element model and to gauge the accuracy of finite element model measurement using cadaver material. Ten wrists were obtained from cadavers with a mean age of 89.5 years at death. CT images of each wrist in an extended position were obtained. CT-based finite element models were prepared with Mechanical Finder software. Fracture on the models was simulated by applying a mechanical load to the palm in a direction parallel to the forearm axis, after which the fracture load and the site at which the fracture began were identified. For comparison, the wrists were fractured using a universal testing machine and the fracture load and the site of fracture were identified. The fracture load was 970.9 N in the finite element model group and 990.0 N in the actual measurement group. The site of the initial fracture was extra-articular to the distal radius in both groups. The finite element model was predictive for distal radius fracture when compared to the actual measurement. In this study, a finite element model for evaluation of distal radius strength was validated and can be used to predict fracture risk. We conclude that a finite element model is useful for the evaluation of distal radius strength. Knowing distal radius strength might avoid distal radius fracture because appropriate antiosteoporotic treatment can be initiated.

  1. Fracture toughness of fibrous composite materials

    Science.gov (United States)

    Poe, C. C., Jr.

    1984-01-01

    Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

  2. Development of LTCC Materials with High Mechanical Strength

    International Nuclear Information System (INIS)

    Kawai, Shinya; Nishiura, Sousuke; Terashi, Yoshitake; Furuse, Tatsuji

    2011-01-01

    We have developed LTCC materials suitable for substrates of RF modules used in mobile phone. LTCC can provide excellent solutions to requirements of RF modules, such as down-sizing, embedded elements and high performance. It is also important that LTCC material has high mechanical strength to reduce risk of fracture by mechanical impact. We have established a method of material design for high mechanical strength. There are two successive steps in the concept to achieve high mechanical strength. The first step is to improve mechanical strength by increasing the Young's modulus, and the second step is either further improvement through the Young's modulus or enhancement of the fracture energy. The developed material, so called high-strength LTCC, thus possesses mechanical strength of 400MPa, which is twice as strong as conventional material whose mechanical strength is approximately 200MPa in typical. As a result, high-strength LTCC shows an excellent mechanical reliability, against the drop impact test for example. The paper presents material design and properties of LTCC materials.

  3. Treatment of midfacial fractures

    International Nuclear Information System (INIS)

    Schubert, J.

    2007-01-01

    Fractures of the midface constitute half of all traumas involving facial bones. Computed tomography is very useful in primary diagnosis. Isolated fractures of the nasal bone and lateral midfacial structures may be diagnosed sufficiently by conventional X-rays. An exact description of the fracture lines along the midfacial buttresses is essential for treatment planning. For good aesthetics and function these have to be reconstructed accurately, which can be checked with X-rays. The treatment of midfacial fractures has been revolutionized over the last two decades. A stable three-dimensional reconstruction of the facial shape is now possible and the duration of treatment has shortened remarkably. The frequently occurring isolated fractures in the lateral part of the midface may be treated easily and effectively by semisurgical methods such as the Gillies procedure or hook-repositioning. (orig.)

  4. Dating fractures in infants

    Energy Technology Data Exchange (ETDEWEB)

    Halliday, K.E., E-mail: kath.halliday@nuh.nhs.uk [Department of Radiology, Nottingham University Hospitals, Queen' s Medical Centre, Nottingham (United Kingdom); Broderick, N J; Somers, J M [Department of Radiology, Nottingham University Hospitals, Queen' s Medical Centre, Nottingham (United Kingdom); Hawkes, R [Department of Radiology, Paul O' Gorman Building, Bristol (United Kingdom)

    2011-11-15

    Aim: To document the timing of the appearance of the radiological features of fracture healing in a group of infants in which the date of injury was known and to assess the degree of interobserver agreement. Materials and methods: Three paediatric radiologists independently assessed 161 images of 37 long bone fractures in 31 patients aged 0-44 months. The following features were assessed: soft-tissue swelling, subperiosteal new bone formation (SPNBF), definition of fracture line, presence or absence of callus, whether callus was well or ill defined, and the presence of endosteal callus. Results: Agreement between observers was only moderate for all discriminators except SPNBF. SPNBF was invariably seen after 11 days but was uncommon before this time even in the very young. In one case SPNBF was seen at 4 days. Conclusion: With the exception of SPNBF, the criteria relied on to date fractures are either not reproducible or are poor discriminators of fracture age.

  5. Dating fractures in infants

    International Nuclear Information System (INIS)

    Halliday, K.E.; Broderick, N.J.; Somers, J.M.; Hawkes, R.

    2011-01-01

    Aim: To document the timing of the appearance of the radiological features of fracture healing in a group of infants in which the date of injury was known and to assess the degree of interobserver agreement. Materials and methods: Three paediatric radiologists independently assessed 161 images of 37 long bone fractures in 31 patients aged 0-44 months. The following features were assessed: soft-tissue swelling, subperiosteal new bone formation (SPNBF), definition of fracture line, presence or absence of callus, whether callus was well or ill defined, and the presence of endosteal callus. Results: Agreement between observers was only moderate for all discriminators except SPNBF. SPNBF was invariably seen after 11 days but was uncommon before this time even in the very young. In one case SPNBF was seen at 4 days. Conclusion: With the exception of SPNBF, the criteria relied on to date fractures are either not reproducible or are poor discriminators of fracture age.

  6. Tibial Plateau Fractures

    DEFF Research Database (Denmark)

    Elsøe, Rasmus

    This PhD thesis reported an incidence of tibial plateau fractures of 10.3/100,000/year in a complete Danish regional population. The results reported that patients treated for a lateral tibial plateau fracture with bone tamp reduction and percutaneous screw fixation achieved a satisfactory level...... with only the subgroup Sport significantly below the age matched reference population. The thesis reports a level of health related quality of life (Eq5d) and disability (KOOS) significantly below established reference populations for patients with bicondylar tibial plateau fracture treated with a ring...... fixator, both during treatment and at 19 months following injury. In general, the thesis demonstrates that the treatment of tibial plateau fractures are challenging and that some disabilities following these fractures must be expected. Moreover, the need for further research in the area, both with regard...

  7. Fracturing formations in wells

    Energy Technology Data Exchange (ETDEWEB)

    Daroza, R A

    1964-05-15

    This well stimulation method comprises introducing through the well bore a low-penetrating, dilatant fluid, and subjecting the fluid to sufficient pressure to produce fractures in the formation. The fluid is permitted to remain in contact with the formation so as to become diluted by the formation fluids, and thereby lose its properties of dilatancy. Also, a penetrating fluid, containing a propping agent suspended therein, in introduced into contact with the fractures at a pressure substantially reduced with respect to that pressure which would have been required, prior to the fracturing operation performed using the low-penetrating dilatant fluid. The propping agent is deposited within the fractures, and thereafter, fluid production is resumed from the fractured formation. (2 claims)

  8. Fracture load of different crown systems on zirconia implant abutments.

    Science.gov (United States)

    Albrecht, T; Kirsten, A; Kappert, H F; Fischer, H

    2011-03-01

    The purpose of this study was to evaluate the fracture load of single zirconia abutment restorations using different veneering techniques and materials. The abutment restorations were divided into 6 groups with 20 samples each: test abutments (control group A), lithium disilicate ceramic crowns bonded on incisor abutments (group B), leucite ceramic crowns bonded on incisor abutments (group C), premolar abutments directly veneered with a fluor apatite ceramic (group D (layered) and group E (pressed)) and premolar abutments bonded with lithium disilicate ceramic crowns (group F). The fracture load of the restorations was evaluated using a universal testing machine. Half of each group was artificially aged (chewing simulation and thermocycling) before evaluating the fracture load with the exception of the test abutments. The fracture load of the test abutments was 705 ± 43N. Incisor abutments bonded with lithium disilicate or leucite ceramic crowns (groups B and C) showed fracture loads of about 580N. Premolar restorations directly veneered with fluor apatite ceramic (groups D and E) showed fracture loads of about 850N. Premolar restorations bonded with lithium disilicate ceramic crowns (group F) showed fracture loads of about 1850N. The artificial ageing showed no significant influence on the strength of the examined restorations. All ceramic crowns made of lithium disilicate glass-ceramic, adhesively bonded to premolar abutments showed the highest fracture loads in this study. However, all tested groups can withstand physiological bite forces. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Multiple intramedullary nailing of proximal phalangeal fractures of hand

    Directory of Open Access Journals (Sweden)

    Patankar Hemant

    2008-01-01

    Full Text Available Background: Proximal phalangeal fractures are commonly encountered fractures in the hand. Majority of them are stable and can be treated by non-operative means. However, unstable fractures i.e. those with shortening, displacement, angulation, rotational deformity or segmental fractures need surgical intervention. This prospective study was undertaken to evaluate the functional outcome after surgical stabilization of these fractures with joint-sparing multiple intramedullary nailing technique. Materials and Methods: Thirty-five patients with 35 isolated unstable proximal phalangeal shaft fractures of hand were managed by surgical stabilization with multiple intramedullary nailing technique. Fractures of the thumb were excluded. All the patients were followed up for a minimum of six months. They were assessed radiologically and clinically. The clinical evaluation was based on two criteria. 1. total active range of motion for digital functional assessment as suggested by the American Society for Surgery of Hand and 2. grip strength. Results: All the patients showed radiological union at six weeks. The overall results were excellent in all the patients. Adventitious bursitis was observed at the point of insertion of nails in one patient. Conclusion: Joint-sparing multiple intramedullary nailing of unstable proximal phalangeal fractures of hand provides satisfactory results with good functional outcome and fewer complications.

  10. Fracture healing using degradable magnesium fixation plates and screws.

    Science.gov (United States)

    Chaya, Amy; Yoshizawa, Sayuri; Verdelis, Kostas; Noorani, Sabrina; Costello, Bernard J; Sfeir, Charles

    2015-02-01

    Internal bone fixation devices made with permanent metals are associated with numerous long-term complications and may require removal. We hypothesized that fixation devices made with degradable magnesium alloys could provide an ideal combination of strength and degradation, facilitating fracture fixation and healing while eliminating the need for implant removal surgery. Fixation plates and screws were machined from 99.9% pure magnesium and compared with titanium devices in a rabbit ulnar fracture model. Magnesium device degradation and the effect on fracture healing and bone formation were assessed after 4 weeks. Fracture healing with magnesium device fixation was compared with that of titanium devices using qualitative histologic analysis and quantitative histomorphometry. Micro-computed tomography showed device degradation after 4 weeks in vivo. In addition, 2-dimensional micro-computed tomography slices and histologic staining showed that magnesium degradation did not inhibit fracture healing or bone formation. Histomorphology showed no difference in bone-bridging fractures fixed with magnesium and titanium devices. Interestingly, abundant new bone was formed around magnesium devices, suggesting a connection between magnesium degradation and bone formation. Our results show potential for magnesium fixation devices in a loaded fracture environment. Furthermore, these results suggest that magnesium fixation devices may enhance fracture healing by encouraging localized new bone formation. Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  11. Processing, structure and flexural strength of CNT and carbon fibre ...

    Indian Academy of Sciences (India)

    Administrator

    1Department of Mechanical Engineering, Vignan Institute of Technology and Science, Deshmukhi, ... perties include primarily the tensile stress, flexural stress and fracture parameters. However ... The present work is an attempt to bring out the flexural strength ..... lating Materials Annual Book of ASTM Standards American.

  12. Mechanical and fracture properties of a self-compacting version of ...

    Indian Academy of Sciences (India)

    B S Al-Azzawi

    between the strength and toughness is explained by the non- linear theory of ..... given by dividing the total work-of-fracture by the projected fracture area (i.e. area of ... effect method was proposed in [36], requiring only testing of notched beam ...

  13. The epidemiology of wrist fractures in older men: the Osteoporotic Fractures in Men (MrOS) study.

    Science.gov (United States)

    Wright, N C; Hooker, E R; Nielson, C M; Ensrud, K E; Harrison, S L; Orwoll, E S; Barrett-Connor, E

    2018-04-01

    There is limited wrist fracture information on men. Our goal was to calculate frequency and identify risk factors for wrist fracture in the Osteoporotic Fractures in Men (MrOS) study. We confirmed that fracture history and certain medications are predictors, and identified novel predictors including markers of kidney function and physical performance. To calculate the incidence of wrist fractures and their risk factors in older community-dwelling men from the US Osteoporotic Fractures in Men (MrOS) study. Using triannual postcards, we identified incident wrist fractures (centrally confirmed by radiology) in men aged ≥ 65. Potential risk factors included the following: demographics, lifestyle, bone mineral density (BMD), selected medications, biomarkers, and physical function and performance measures. Both baseline and time-varying models were adjusted for age, race/ethnicity, MrOS geographic location, and competing mortality risks. We observed 97 incident wrist fractures among 5875 men followed for an average of 10.8 years. The incidence of wrist fracture was 1.6 per 1000 person-years overall and ranged from 1.0 among men aged 65-69 to 2.4 among men age ≥ 80. Significant predictors included the following: fracture history after age 50 [hazard ratio (95% CI): 2.48 (1.65, 3.73)], high serum phosphate [1.25 (1.02, 1.53)], use of selective serotonin receptor inhibitor (SSRI) [3.60 (1.96, 6.63), decreased right arm BMD [0.49 (0.37, 0.65) per SD increase], and inability to perform the grip strength test [3.38 (1.24, 9.25)]. We did not find associations with factors commonly associated with wrist and other osteoporosis fractures like falls, diabetes, calcium and vitamin D intake, and alcohol intake. Among these older, community-dwelling men, we confirmed that fracture history is a strong predictor of wrist fractures in men. Medications such as SSRIs and corticosteroids also play a role in wrist fracture risk. We identified novel risk factors including kidney

  14. Preliminary experience with biodegradable implants for fracture fixation

    Directory of Open Access Journals (Sweden)

    Dhillon Mandeep

    2008-01-01

    Full Text Available Background: Biodegradable implants were designed to overcome the disadvantages of metal-based internal fixation devices. Although they have been in use for four decades internationally, many surgeons in India continue to be skeptical about the mechanical strength of biodegradable implants, hence this study. Materials and Methods: A prospective study was done to assess the feasibility and surgeon confidence level with biodegradable implants over a 12-month period in an Indian hospital. Fifteen fractures (intra-articular, metaphyseal or small bone fractures were fixed with biodegradable implants. The surgeries were randomly scheduled so that different surgeons with different levels of experience could use the implants for fixation. Results: Three fractures (one humeral condyle, two capitulum, were supplemented by additional K-wires fixation. Trans-articular fixator was applied in two distal radius and two pilon fractures where bio-pins alone were used. All fractures united, but in two cases the fracture displaced partially during the healing phase; one fibula due to early walking, and one radius was deemed unstable even after bio-pin and external fixator. Conclusions: Biodegradable -implants are excellent for carefully selected cases of intra-articular fractures and some small bone fractures. However, limitations for use in long bone fractures persist and no great advantage is gained if a "hybrid" composite is employed. The mechanical properties of biopins and screws in isolation are perceived to be inferior to those of conventional metal implants, leading to low confidence levels regarding the stability of reduced fractures; these implants should be used predominantly in fracture patterns in which internal fixation is subjected to minimal stress.

  15. Fracture toughness of welded joints of ASTM A543 steel plate

    International Nuclear Information System (INIS)

    Susukida, H.; Uebayashi, T.; Yoshida, K.; Ando, Y.

    1977-01-01

    Fracture toughness and weldability tests have been performed on a high strength steel which is a modification of ASTM A543 Grade B Class 1 steel, with a view to using it for nuclear reactor containment vessels. The results showed that fracture toughness of welded joints of ASTM A543 modified high strength steel is superior and the steel is suitable for manufacturing the containment vessels

  16. Strengths-based Learning

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    -being. The Ph.D.-project in Strength-based learning took place in a Danish school with 750 pupils age 6-16 and a similar school was functioning as a control group. The presentation will focus on both the aware-explore-apply processes and the practical implications for the schools involved, and on measurable......Strength-based learning - Children͛s Character Strengths as Means to their Learning Potential͛ is a Ph.D.-project aiming to create a strength-based mindset in school settings and at the same time introducing strength-based interventions as specific tools to improve both learning and well...

  17. Sensitivity Analysis of the Bone Fracture Risk Model

    Science.gov (United States)

    Lewandowski, Beth; Myers, Jerry; Sibonga, Jean Diane

    2017-01-01

    Introduction: The probability of bone fracture during and after spaceflight is quantified to aid in mission planning, to determine required astronaut fitness standards and training requirements and to inform countermeasure research and design. Probability is quantified with a probabilistic modeling approach where distributions of model parameter values, instead of single deterministic values, capture the parameter variability within the astronaut population and fracture predictions are probability distributions with a mean value and an associated uncertainty. Because of this uncertainty, the model in its current state cannot discern an effect of countermeasures on fracture probability, for example between use and non-use of bisphosphonates or between spaceflight exercise performed with the Advanced Resistive Exercise Device (ARED) or on devices prior to installation of ARED on the International Space Station. This is thought to be due to the inability to measure key contributors to bone strength, for example, geometry and volumetric distributions of bone mass, with areal bone mineral density (BMD) measurement techniques. To further the applicability of model, we performed a parameter sensitivity study aimed at identifying those parameter uncertainties that most effect the model forecasts in order to determine what areas of the model needed enhancements for reducing uncertainty. Methods: The bone fracture risk model (BFxRM), originally published in (Nelson et al) is a probabilistic model that can assess the risk of astronaut bone fracture. This is accomplished by utilizing biomechanical models to assess the applied loads; utilizing models of spaceflight BMD loss in at-risk skeletal locations; quantifying bone strength through a relationship between areal BMD and bone failure load; and relating fracture risk index (FRI), the ratio of applied load to bone strength, to fracture probability. There are many factors associated with these calculations including

  18. FracPaQ: a MATLAB™ toolbox for the quantification of fracture patterns

    Science.gov (United States)

    Healy, David; Rizzo, Roberto; Farrell, Natalie; Watkins, Hannah; Cornwell, David; Gomez-Rivas, Enrique; Timms, Nick

    2017-04-01

    The patterns of fractures in deformed rocks are rarely uniform or random. Fracture orientations, sizes, shapes and spatial distributions often exhibit some kind of order. In detail, there may be relationships among the different fracture attributes e.g. small fractures dominated by one orientation, larger fractures by another. These relationships are important because the mechanical (e.g. strength, anisotropy) and transport (e.g. fluids, heat) properties of rock depend on these fracture patterns and fracture attributes. This presentation describes an open source toolbox to quantify fracture patterns, including distributions in fracture attributes and their spatial variation. Software has been developed to quantify fracture patterns from 2-D digital images, such as thin section micrographs, geological maps, outcrop or aerial photographs or satellite images. The toolbox comprises a suite of MATLAB™ scripts based on published quantitative methods for the analysis of fracture attributes: orientations, lengths, intensity, density and connectivity. An estimate of permeability in 2-D is made using a parallel plate model. The software provides an objective and consistent methodology for quantifying fracture patterns and their variations in 2-D across a wide range of length scales. Our current focus for the application of the software is on quantifying crack and fracture patterns in and around fault zones. There is a large body of published work on the quantification of relatively simple joint patterns, but fault zones present a bigger, and arguably more important, challenge. The methods presented are inherently scale independent, and a key task will be to analyse and integrate quantitative fracture pattern data from micro- to macro-scales. New features in this release include multi-scale analyses based on a wavelet method to look for scale transitions, support for multi-colour traces in the input file processed as separate fracture sets, and combining fracture traces

  19. Computed tomograms of blowout fracture

    International Nuclear Information System (INIS)

    Ito, Haruhide; Hayashi, Minoru; Shoin, Katsuo; Hwang, Wen-Zern; Yamamoto, Shinjiro; Yonemura, Taizo.

    1985-01-01

    We studied 18 cases of orbital fractures, excluding optic canal fracture. There were 11 cases of pure blowout fracture and 3 of the impure type. The other 4 cases were orbital fractures without blowout fracture. The cardinal syndromes were diplopia, enophthalmos, and sensory disturbances of the trigeminal nerve in the pure type of blowout fracture. Many cases of the impure type of blowout fracture or of orbital fracture showed black eyes or a swelling of the eyelids which masked enophthalmos. Axial and coronal CT scans demonstrated: 1) the orbital fracture, 2) the degree of enophthalmos, 3) intraorbital soft tissue, such as incarcerated or prolapsed ocular muscles, 4) intraorbital hemorrhage, 5) the anatomical relation of the orbital fracture to the lacrimal canal, the trochlea, and the trigeminal nerve, and 6) the lesions of the paranasal sinus and the intracranial cavity. CT scans play an important role in determining what surgical procedures might best be employed. Pure blowout fractures were classified by CT scans into these four types: 1) incarcerating linear fracture, 2) trapdoor fracture, 3) punched-out fracture, and 4) broad fracture. Cases with severe head injury should be examined to see whether or not blowout fracture is present. If the patients are to hope to return to society, a blowout fracture should be treated as soon as possible. (author)

  20. Computed tomograms of blowout fracture

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Haruhide; Hayashi, Minoru; Shoin, Katsuo; Hwang, Wen-Zern; Yamamoto, Shinjiro; Yonemura, Taizo

    1985-02-01

    We studied 18 cases of orbital fractures, excluding optic canal fracture. There were 11 cases of pure blowout fracture and 3 of the impure type. The other 4 cases were orbital fractures without blowout fracture. The cardinal syndromes were diplopia, enophthalmos, and sensory disturbances of the trigeminal nerve in the pure type of blowout fracture. Many cases of the impure type of blowout fracture or of orbital fracture showed black eyes or a swelling of the eyelids which masked enophthalmos. Axial and coronal CT scans demonstrated: 1) the orbital fracture, 2) the degree of enophthalmos, 3) intraorbital soft tissue, such as incarcerated or prolapsed ocular muscles, 4) intraorbital hemorrhage, 5) the anatomical relation of the orbital fracture to the lacrimal canal, the trochlea, and the trigeminal nerve, and 6) the lesions of the paranasal sinus and the intracranial cavity. CT scans play an important role in determining what surgical procedures might best be employed. Pure blowout fractures were classified by CT scans into these four types: 1) incarcerating linear fracture, 2) trapdoor fracture, 3) punched-out fracture, and 4) broad fracture. Cases with severe head injury should be examined to see whether or not blowout fracture is present. If the patients are to hope to return to society, a blowout fracture should be treated as soon as possible. (author).

  1. On the impact bending test technique for high-strength pipe steels

    Science.gov (United States)

    Arsenkin, A. M.; Odesskii, P. D.; Shabalov, I. P.; Likhachev, M. V.

    2015-10-01

    It is shown that the impact toughness (KCV-40 = 250 J/cm2) accepted for pipe steels of strength class K65 (σy ≥ 550 MPa) intended for large-diameter gas line pipes is ineffective to classify steels in fracture strength. The results obtained upon testing of specimens with a fatigue crack and additional sharp lateral grooves seem to be more effective. In energy consumption, a macrorelief with splits is found to be intermediate between ductile fracture and crystalline brittle fracture. A split formation mechanism is considered and a scheme is proposed for split formation.

  2. Hip fractures. Epidemiology, risk factors, falls, energy absorption, hip protectors, and prevention

    DEFF Research Database (Denmark)

    Lauritzen, J B

    1997-01-01

    have a high risk of hip fracture (annual rate of 5-6%), and the incidence of falls is about 1,500 falls/1,000 persons/year. Most hip fractures are a result of a direct trauma against the hip. The incidence of falls on the hip among nursing home residents is about 290 falls/1,000 persons/year and about......%, corresponding to 9 out of 247 residents saved from sustaining a hip fracture. The review points to the essentials of the development of hip fracture, which constitutes; risk of fall, type of fall, type of impact, energy absorption, and lastly bone strength, which is the ultimate and last permissive factor......The present review summarizes the pathogenic mechanisms leading to hip fracture based on epidemiological, experimental, and controlled studies. The estimated lifetime risk of hip fracture is about 14% in postmenopausal women and 6% in men. The incidence of hip fractures increases exponentially...

  3. Open channels in fractures maintained by deposition and erosion of colloids

    International Nuclear Information System (INIS)

    Kessler, J.H.; Hunt, J.R.

    1993-01-01

    Material in the colloidal size range is present in many natural groundwater systems at existing or proposed radioactive waste storage locations. Colloids initially suspended in the water in fractures can deposit onto the fracture surfaces, and will partially or fully clog the fracture. The amount of clogging will depend on whether the deposited colloidal material can erode from the fracture surfaces. If the fracture remains only partially clogged the unclogged regions take the form of open channels. The purpose of this paper is to assess under what conditions these open channels form. An analytical model of a steady state, average open channel width is presented which is a function of the fluid flow rate and viscosity, fracture aperture, and the permeability and shear strength of the deposited colloidal material. The implications of the presence of open channels for colloidal transport is also discussed. However, for most repository conditions the fractures are expected to fully clog with colloids

  4. Fracture behavior of nuclear graphites under tensile impact loading

    International Nuclear Information System (INIS)

    Ugachi, Hirokazu; Ishiyama, Shintaro; Eto, Motokuni

    1994-01-01

    Impact tensile strength test was performed with two kinds of HTTR graphites, fine grained isotropic graphite, IG-11 and coarse grained near isotropic graphite, PGX and deformation and fracture behavior under the strain rate of over 100s -1 was measured and the following results were derived: (1) Tensile strength for IG-11 graphite does not depend on the strain rate less than 1 s -1 , but over 1 s -1 , tensile strength for IG-11 graphite increase larger than that measured under 1 s -1 . At the strain rate more than 100 s -1 , remarkable decrease of tensile strength for IG-11 graphite was found. Tensile strength of PGX graphite does not depend on the strain rate less than 1 s -1 , but beyond this value, the sharp tensile strength decrease occurs. (2) Under 100 s -1 , fracture strain for both graphites increase with increase of strain rate and over 100 s -1 , drastic increase of fracture strain for IG-11 graphite was found. (3) At the part of gage length, volume of specimen increase with increase of tensile loading level and strain rate. (4) Poisson's ratio for both graphites decrease with increase of tensile loading level and strain rate. (5) Remarkable change of stress-strain curve for both graphites under 100 s -1 was not found, but over 100 s -1 , the slope of these curve for IG-11 graphite decrease drastically. (author)

  5. Large-scale GWAS identifies multiple loci for hand grip strength providing biological insights into muscular fitness

    DEFF Research Database (Denmark)

    Willems, Sara M; Wright, Daniel J.; Day, Felix R

    2017-01-01

    with involvement of psychomotor impairment (PEX14, LRPPRC and KANSL1). Mendelian randomization analyses are consistent with a causal effect of higher genetically predicted grip strength on lower fracture risk. In conclusion, our findings provide new biological insight into the mechanistic underpinnings of grip...... strength and the causal role of muscular strength in age-related morbidities and mortality....

  6. Radiological diagnosis of fractures

    International Nuclear Information System (INIS)

    Finlay, D.B.L.; Allen, M.J.

    1984-01-01

    This book is about radiology of fractures. While it contains sections of clinical features it is not intended that readers should rely entirely upon these for the diagnosis and management of the injured patient. As in the diagnosis and treatment of all medical problems, fracture management must be carried out in a logical step-by-step fashion - namely, history, examination, investigation, differential diagnosis, diagnosis and then treatment. Each section deals with a specific anatomical area and begins with line drawings of the normal radiographs demonstrating the anatomy. Accessory views that may be requested, and the indications for these, are included. Any radiological pitfalls for the area in general are then described. The fractures in adults are then examined in turn, their radiological features described, and any pitfalls in their diagnosis discussed. A brief note of important clinical findings is included. A brief mention is made of pediatric fractures which are of significance and their differences to the adult pattern indicated. Although fractures can be classified into types with different characteristics, in life every fracture is individual. Fractures by and large follow common patterns, but many have variations

  7. Spontaneous rib fractures.

    Science.gov (United States)

    Katrancioglu, Ozgur; Akkas, Yucel; Arslan, Sulhattin; Sahin, Ekber

    2015-07-01

    Other than trauma, rib fracture can occur spontaneously due to a severe cough or sneeze. In this study, patients with spontaneous rib fractures were analyzed according to age, sex, underlying pathology, treatment, and complications. Twelve patients who presented between February 2009 and February 2011 with spontaneous rib fracture were reviewed retrospectively. The patients' data were evaluated according to anamnesis, physical examination, and chest radiographs. The ages of the patients ranged from 34 to 77 years (mean 55.91 ± 12.20 years), and 7 (58.4%) were male. All patients had severe cough and chest pain. The fractures were most frequently between 4th and 9th ribs; multiple rib fractures were detected in 5 (41.7%) patients. Eight (66.7%) patients had chronic obstructive pulmonary disease, 2 (16.7%) had bronchial asthma, and 2 (16.7%) had osteoporosis. Bone densitometry revealed a high risk of bone fracture in all patients. Patients with chronic obstructive pulmonary disease or bronchial asthma had been treated with high-dose steroids for over a year. Spontaneous rib fracture due to severe cough may occur in patients with osteoporosis, chronic obstructive pulmonary disease, or bronchial asthma, receiving long-term steroid therapy. If these patients have severe chest pain, chest radiography should be performed to check for bone lesions. © The Author(s) 2015.

  8. Orbital wall fractures

    International Nuclear Information System (INIS)

    Iinuma, Toshitaka; Ishio, Ken-ichirou; Yoshinami, Hiroyoshi; Kuriyama, Jun-ichi; Hirota, Yoshiharu.

    1993-01-01

    A total of 59 cases of mild facial fractures (simple orbital wall fractures, 34 cases, other facial fractures, 25 cases) with the clinical suspects of orbital wall fractures were evaluated both by conventional views (Waters' and Caldwell views) and coronal CT scans. Conventional views were obtained, as an average, after 4 days and CT after 7 days of injuries. Both the medial wall and the floor were evaluated at two sites, i.e., anterior and posterior. The ethmoid-maxillary plate was also included in the study. The degree of fractures was classified as, no fractures, fractures of discontinuity, dislocation and fragmentation. The coronal CT images in bone window condition was used as reference and the findings were compared between conventional views and CT. The correct diagnosis was obtained as follows: orbital floor (anterior, 78%, posterior, 73%), medial orbital wall (anterior, 72%, posterior, 72%) and ethmoid-maxillary plate (64%). The false positive diagnosis was as follows: orbital floor (anterior only, 13%), medial orbital wall (anterior only, 7%) and ethmoid-maxillary plate (11%). The false negative diagnosis was as follows: orbital floor (anterior, 9%, posterior, 10%), medial orbital wall (anterior, 21%, posterior, 28%) and ethmoid-maxillary plate (21%). The results were compared with those of others in the past. (author)

  9. Chance Fracture Secondary to a Healed Kyphotic Compression Osteoporotic Fracture

    Directory of Open Access Journals (Sweden)

    Teh KK

    2009-11-01

    Full Text Available Chance fracture is an unstable vertebral fracture, which usually results from a high velocity injury. An elderly lady with a previously healed osteoporotic fracture of the T12 and L1 vertebra which resulted in a severe kyphotic deformity subsequently sustained a Chance fracture of the adjacent L2 vertebrae after a minor fall. The previously fracture left her with a deformity which resulted in significant sagittal imbalance therefore predisposing her to this fracture. This case highlights the importance of aggressive treatment of osteoporotic fractures in order to prevent significant sagittal imbalance from resultant (i.e. kyphotic deformity.

  10. Fracture network topology and characterization of structural permeability

    Science.gov (United States)

    Hansberry, Rowan; King, Rosalind; Holford, Simon

    2017-04-01

    There are two fundamental requirements for successful geothermal development: elevated temperatures at accessible depths, and a reservoir from which fluids can be extracted. The Australian geothermal sector has successfully targeted shallow heat, however, due in part to the inherent complexity of targeting permeability, obtaining adequate flow rates for commercial production has been problematic. Deep sedimentary aquifers are unlikely to be viable geothermal resources due to the effects of diagenetic mineral growth on rock permeability. Therefore, it is likely structural permeability targets, exploiting natural or induced fracture networks will provide the primary means for fluid flow in geothermal, as well as unconventional gas, reservoirs. Recent research has focused on the pattern and generation of crustal stresses across Australia, while less is known about the resultant networks of faults, joints, and veins that can constitute interconnected sub-surface permeability pathways. The ability of a fracture to transmit fluid is controlled by the orientation and magnitude of the in-situ stress field that acts on the fracture walls, rock strength, and pore pressure, as well as fracture properties such as aperture, orientation, and roughness. Understanding the distribution, orientation and character of fractures is key to predicting structural permeability. This project focuses on extensive mapping of fractures over various scales in four key Australian basins (Cooper, Otway, Surat and Perth) with the potential to host geothermal resources. Seismic attribute analysis is used in concert with image logs from petroleum wells, and field mapping to identify fracture networks that are usually not resolved in traditional seismic interpretation. We use fracture network topology to provide scale-invariant characterisation of fracture networks from multiple data sources to assess similarity between data sources, and fracture network connectivity. These results are compared with

  11. A Rare Nasal Bone Fracture: Anterior Nasal Spine Fracture

    Directory of Open Access Journals (Sweden)

    Egemen Kucuk

    2014-04-01

    Full Text Available Anterior nasal spine fractures are a quite rare type of nasal bone fractures. Associated cervical spine injuries are more dangerous than the nasal bone fracture. A case of the anterior nasal spine fracture, in a 18-year-old male was presented. Fracture of the anterior nasal spine, should be considered in the differential diagnosis of the midface injuries and also accompanying cervical spine injury should not be ignored.

  12. Virtual stress testing of fracture stability in soldiers with severely comminuted tibial fractures.

    Science.gov (United States)

    Petfield, Joseph L; Hayeck, Garry T; Kopperdahl, David L; Nesti, Leon J; Keaveny, Tony M; Hsu, Joseph R

    2017-04-01

    Virtual stress testing (VST) provides a non-invasive estimate of the strength of a healing bone through a biomechanical analysis of a patient's computed tomography (CT) scan. We asked whether VST could improve management of patients who had a tibia fracture treated with external fixation. In a retrospective case-control study of 65 soldier-patients who had tibia fractures treated with an external fixator, we performed VST utilizing CT scans acquired prior to fixator removal. The strength of the healing bone and the amount of tissue damage after application of an overload were computed for various virtual loading cases. Logistic regression identified computed outcomes with the strongest association to clinical events related to nonunion within 2 months after fixator removal. Clinical events (n = 9) were associated with a low tibial strength for compression loading (p fracture patients who can safely resume weight bearing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:805-811, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  13. Fracture characteristics in Japanese rock

    International Nuclear Information System (INIS)

    Ijiri, Yuji; Sawada, Atsushi; Akahori, Kuniaki

    1999-11-01

    It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the characteristics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified. (author)

  14. Aspects of modern fracture statistics

    International Nuclear Information System (INIS)

    Tradinik, W.; Pabst, R.F.; Kromp, K.

    1981-01-01

    This contribution begins with introductory general remarks about fracture statistics. Then the fundamentals of the distribution of fracture probability are described. In the following part the application of the Weibull Statistics is justified. In the fourth chapter the microstructure of the material is considered in connection with calculations made in order to determine the fracture probability or risk of fracture. (RW) [de

  15. Fracture Phenomena in Amorphous Selenium

    DEFF Research Database (Denmark)

    Lindegaard-Andersen, Asger; Dahle, Birgit

    1966-01-01

    Fracture surfaces of amorphous selenium broken in flexure at room temperature have been studied. The fracture velocity was found to vary in different regions of the fracture surface. Peculiar features were observed in a transition zone between fast and slower fracture. In this zone cleavage steps...

  16. Locking plate fixation for proximal humerus fractures.

    LENUS (Irish Health Repository)

    Burke, Neil G

    2012-02-01

    Locking plates are increasingly used to surgically treat proximal humerus fractures. Knowledge of the bone quality of the proximal humerus is important. Studies have shown the medial and dorsal aspects of the proximal humeral head to have the highest bone strength, and this should be exploited by fixation techniques, particularly in elderly patients with osteoporosis. The goals of surgery for proximal humeral fractures should involve minimal soft tissue dissection and achieve anatomic reduction of the head complex with sufficient stability to allow for early shoulder mobilization. This article reviews various treatment options, in particular locking plate fixation. Locking plate fixation is associated with a high complication rate, such as avascular necrosis (7.9%), screw cutout (11.6%), and revision surgery (13.7%). These complications are frequently due to the varus deformation of the humeral head. Strategic screw placement in the humeral head would minimize the possibility of loss of fracture reduction and potential hardware complications. Locking plate fixation is a good surgical option for the management of proximal humerus fractures. Complications can be avoided by using better bone stock and by careful screw placement in the humeral head.

  17. Influence of interface properties on fracture behaviour of concrete

    Indian Academy of Sciences (India)

    Hardened concrete is a three-phase composite consisting of cement paste, aggregate and interface between cement paste and aggregate. The interface in concrete plays a key role on the overall performance of concrete. The interface properties such as deformation, strength, fracture energy, stress intensity and its ...

  18. Osteoporosis in clinical practice – bone densitometry and fracture risk

    African Journals Online (AJOL)

    Osteoporosis is a condition of decreased bone mass and bone density associated with an increase in fracture risk. Bone mineral density (BMD) of the lumbar spine and femur can be reliably measured by double-beam X-ray absorptiometry (DEXA), which provides a measure of bone strength. Reduction in BMD is a ...

  19. Functional Outcome of Internal Fixation of Radial and Ulna Fracture

    Directory of Open Access Journals (Sweden)

    mehrdad Mansouri

    2006-02-01

    Conclusion: Anatomic reduction and internal fixation is the standard method for treatment of fractures by displacing radios and ulna in adults. According to results, it seems more intension to motions specially pronation and muscle strengthening foream after surgery will have affect on improving patients’ function specially pronation and Grip strength.

  20. Fracture of Polymers and Interfaces: A Universal Molecular Approach

    Science.gov (United States)

    Wool, Richard

    2003-03-01

    Fracture of polymers, linear or crosslinked, can be viewed as a breaking of molecular connectivity via disentanglement or bond rupture. When treated as a vector percolation phenomenon, we find that it captures the essential physics of fracture and makes broad accurate predictions for strength S, and fracture energy G, of polymers and their interfaces. In the bulk, we find that G ˜ [p-pc], and S ˜ [p-pc]^1/2, where p is the local normalized entanglement density and pc is the percolation threshold. For interfaces, p = nL/w, where n is the areal density of chains of length L ˜M (mol wt) in an interface of width w. For incompatible interfaces of width w, G ˜ [w-wc]; when reinforced with n compatibilizers, G ˜ (n - nc]. For welding, p ˜ L, the welding time tw ˜ L. For adhesion with sticker group X on the polymer and receptor groups Y on the solid, the strength first increases with X, Y and X-Y strength and then decreases after a predictable maximum. For thermosets, the modulus E ˜ [p-pc]^3 and the strength S ˜ [p-pc]^2. Numerous experimental examples are given to support the above universal relations for fracture.

  1. Give Me Strength.

    Institute of Scientific and Technical Information of China (English)

    维拉

    1996-01-01

    Mort had an absolutely terrible day at the office.Everythingthat could go wrong did go wrong.As he walked home he could beheard muttering strange words to himself:“Oh,give me strength,give me strength.”Mort isn’t asking for the kind of strength thatbuilds strong muscles:he’s asking for the courage or ability to

  2. Prevention of distal extension cantilever fracture in mandibular overdentures.

    Science.gov (United States)

    Quirynen, Thomas; Quirynen, Marc; Duyck, Joke

    2015-09-01

    Fractures of distal bar extensions, supporting a mandibular overdenture, do occur with significant functional and economic consequences for the patient. This study therefore aims to evaluate the effect of different bar cross-sectional shapes and surfaces, bar extension lengths and the placement of a support rib under the distal bar extension on fracture resistance. The 2nd moment area and static strength were calculated for 11 frequently used bar designs using finite element analysis (FEA). For two specific designs (Ackermann round Ø 1.8mm and Dolder-Y macro, the former with and without a support rib) additional physical static and fatigue strength tests were included. The FEA static strength data corresponded well to the 2nd moment area (a similar ranking when maximum allowed force was considered). The application of a rib support (Ackermann Ø 1.8mm) and limitations of the bar extension length (6mm for the Ackermann Ø 1.8mm, 8mm for the Dolder-Y macro) allowed the bars to exceed 5 × 10(6) cycles of 120 and 250N, respectively, before fracture. The region of highest stresses in FEA corresponded well with the locations of the fractures observed in static- and fatigue-testing. With some simple guidelines/modifications, the number of bar extension fractures can be reduced significantly. This study focusses on distal bar extensions which improve the positioning of an implant supported overdenture. By combining laboratory testing and finite element simulations we aim to: (1) explain why fractures occur (dependent on physical characteristics of the bar), and (2) give clinical guidelines on how to prevent such fractures. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Vertebral Compression Fractures

    Science.gov (United States)

    ... and monitored to avoid putting pressure on the ribs that can cause new fractures. Surgical Procedures • When there is severe incapacitating pain • When healing is delayed or when bone fragments ...

  4. Paediatric talus fracture.

    LENUS (Irish Health Repository)

    Byrne, Ann-Maria

    2012-01-01

    Paediatric talus fractures are rare injuries resulting from axial loading of the talus against the anterior tibia with the foot in dorsiflexion. Skeletally immature bone is less brittle, with higher elastic resistance than adult bone, thus the paediatric talus can sustain higher forces before fractures occur. However, displaced paediatric talus fractures and those associated with high-energy trauma have been associated with complications including avascular necrosis, arthrosis, delayed union, neurapraxia and the need for revision surgery. The authors present the rare case of a talar neck fracture in a skeletally immature young girl, initially missed on radiological review. However, clinical suspicion on the part of the emergency physician, repeat examination and further radiographic imaging revealed this rare paediatric injury.

  5. Elevated temperature fracture mechanics

    International Nuclear Information System (INIS)

    Tomkins, B.

    1979-01-01

    The application of fracture mechanics concepts to cracks at elevated temperatures is examined. Particular consideration is given to the characterisation of crack tip stress-strain fields and parameters controlling crack extension under static and cyclic loads. (author)

  6. Stress fractures in athletes

    International Nuclear Information System (INIS)

    Kirschberger, R.; Henning, A.; Graff, K.H.

    1984-01-01

    The early exclusion of the presence of a stress fracture may be decisive for the success of an athlete. Scintigraphy with a bone-seeking radiopharmaceutical is suitable for the early detection of stress lesions. Of 30 athletes, fractures were demonstrated in 17 whereas in 6 they were excluded. We found most fractures in the tarsal bones such as os naviculare pedis, ossa cuneiformia and talus. The type of sport engaged in appears to be an important factor in determining the location of the fracture. Scintiphotos were taken in several views using region of interest techniques and two phase-scintigraphy. This method is considered to be useful for localization and follow-up of skeletal stress lesions as well as for differential diagnosis. (orig.) [de

  7. Stress fractures in athletes

    Energy Technology Data Exchange (ETDEWEB)

    Kirschberger, R; Henning, A; Graff, K H

    1984-12-01

    The early exclusion of the presence of a stress fracture may be decisive for the success of an athlete. Scintigraphy with a bone-seeking radiopharmaceutical is suitable for the early detection of stress lesions. Of 30 athletes, fractures were demonstrated in 17 whereas in 6 they were excluded. We found most fractures in the tarsal bones such as os naviculare pedis, ossa cuneiformia and talus. The type of sport engaged in appears to be an important factor in determining the location of the fracture. Scintiphotos were taken in several views using region of interest techniques and two phase-scintigraphy. This method is considered to be useful for localization and follow-up of skeletal stress lesions as well as for differential diagnosis.

  8. Fatigue and insufficiency fractures

    International Nuclear Information System (INIS)

    Lodwick, G.S.; Rosenthal, D.I.; Kattapuram, S.V.; Hudson, T.M.

    1987-01-01

    The incidence of stress fracture is increasing. In our younger society this is due largely to a preocupation with physical conditioning, but in our elderly population it is due to improved recognition and better methods of detection and diagnosis. Stress fracture of the elderly is an insufficiency fracture which occurs in the spine, the pelvis, the sacrum and other bones afflicted with disorders which cause osteopenia. Stress fracture is frequently misdiagnosed as a malignant lesion of bone resulting in biopsy. Scintiscanning provides the greatest frequency of detection, while computed tomography often provides the definitive diagnosis. With increased interest and experience a better insight into the disease has been achieved, and what was once thought of as a simple manifestation of mechanical stress is now known to be an orderly, complex pattern of physiological changes in bone which conform to a model by Frost. The diffuse nature of these changes can be recognized by scintigraphy, radiography and magnetic resonance imaging. 27 refs.; 8 figs

  9. Ontology of fractures

    Science.gov (United States)

    Zhong, Jian; Aydina, Atilla; McGuinness, Deborah L.

    2009-03-01

    Fractures are fundamental structures in the Earth's crust and they can impact many societal and industrial activities including oil and gas exploration and production, aquifer management, CO 2 sequestration, waste isolation, the stabilization of engineering structures, and assessing natural hazards (earthquakes, volcanoes, and landslides). Therefore, an ontology which organizes the concepts of fractures could help facilitate a sound education within, and communication among, the highly diverse professional and academic community interested in the problems cited above. We developed a process-based ontology that makes explicit specifications about fractures, their properties, and the deformation mechanisms which lead to their formation and evolution. Our ontology emphasizes the relationships among concepts such as the factors that influence the mechanism(s) responsible for the formation and evolution of specific fracture types. Our ontology is a valuable resource with a potential to applications in a number of fields utilizing recent advances in Information Technology, specifically for digital data and information in computers, grids, and Web services.

  10. Strength and ductility of Ni3Al alloyed with boron and substitutional elements

    International Nuclear Information System (INIS)

    Ishikawa, K.; Aoki, K.; Masumoto, T.

    1995-01-01

    The effect of simultaneous alloying of boron (B) and the substitutional elements M on mechanical properties of Ni 3 Al was investigated by the tensile test at room temperature. The yield strength of Ni 3 Al+B increases by alloying with M except for Fe and Ga. In particular, it increases by alloying with Hf, Nb, W, Ta, Pd and Si. The fracture strength of Ni 3 Al+B increases by alloying with Pd, Ga, Si and Hf, but decreases with the other elements. Elongation of Ni 3 Al+B increases by alloying with Ga, Fe and Pd, but decreases with other elements. Hf and Pd is the effective element for the increase of the yield strength and the fracture strength of Ni 3 Al+B, respectively. Alloying with Hf leads to the increases of the yield strength and the fracture strength of Ni 3 Al+B, but to the lowering of elongation. On the other hand, alloying with Pd improves all mechanical properties, i.e. the yield strength, the fracture strength and elongation. On the contrary, alloying with Ti, V and Co leads to the lowering of mechanical properties of Ni 3 Al+B. The reason why ductility of Ni 3 Al+B is reduced by alloying with some elements M is discussed

  11. Treatment of displaced mandibular condylar fracture with botulinum toxin A.

    Science.gov (United States)

    Akbay, Ercan; Cevik, Cengiz; Damlar, Ibrahim; Altan, Ahmet

    2014-04-01

    The aim of this case report is to discuss the effect on condylar reduction of botulinum toxin A treatment used in a child with displaced fracture at condylar neck of mandible. A 3-years old boy was admitted to our clinic for incomplete fracture of mandibular symphysis and displaced condylar fracture at the left side. An asymmetrical occlusal splint with intermaxillary fixation was used instead of open reduction and internal fixation because of incomplete fracture of symphysis and possible complications of condyle surgery. However, it was observed that condylar angulation persisted despite this procedure. Thus, botulinum toxin A was administered to masseter, temporalis and pterygoideus medialis muscles. At the end of first month, it was seen that mandibular condyle was almost completely recovered and that fusion was achieved. In conclusion, Botulinum A toxin injection aiming the suppression of masticatory muscle strength facilitates the reduction in the conservative management of displaced condyle in pediatric patients. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  12. Challenges of Fracture Management for Adults With Osteogenesis Imperfecta.

    Science.gov (United States)

    Gil, Joseph A; DeFroda, Steven F; Sindhu, Kunal; Cruz, Aristides I; Daniels, Alan H

    2017-01-01

    Osteogenesis imperfecta is caused by qualitative or quantitative defects in type I collagen. Although often considered a disease with primarily pediatric manifestations, more than 25% of lifetime fractures are reported to occur in adulthood. General care of adults with osteogenesis imperfecta involves measures to preserve bone density, regular monitoring of hearing and dentition, and maintenance of muscle strength through physical therapy. Surgical stabilization of fractures in these patients can be challenging because of low bone mineral density, preexisting skeletal deformities, or obstruction by instrumentation from previous surgeries. Additionally, unique perioperative considerations exist when operatively managing fractures in patients with osteogenesis imperfecta. To date, there is little high-quality literature to help guide the optimal treatment of fractures in adult patients with osteogenesis imperfecta. [Orthopedics. 2017; 40(1):e17-e22.]. Copyright 2016, SLACK Incorporated.

  13. Preliminary assessment of the healing of fractures in salt

    International Nuclear Information System (INIS)

    1983-07-01

    Natural fractures in salt are not common but have been observed. An assessment is made of whether and under what conditions such fractures regain cohesion (heal). Evidence comes from observations in mines, commercial processing, and laboratory testing of both fractured and granular salt. Healing can take the form of chemical precipitation, ductile injection, and creep closure. Of these, creep closure is of principal interest. Healing is measured in terms of recovered strength and reduced permeability. It is found to increase with increased confining pressure and is greatly enhanced when the salt is in contact with brine. Research at Sandia National Laboratories has demonstrated salt fracture healing in relatively short time periods under conditions consistent with the environment of a geologic repository. 45 references

  14. [Proximal femoral fractures in the elderly: pathogenesis, sequelae, interventions].

    Science.gov (United States)

    Runge, M; Schacht, E

    1999-08-01

    Hip fractures are a health problem of paramount importance for the individual and society. They are associated with a sharp increase of the incidence of immobility, dependency, nursing home placement, and death. In Germany, more than 100,000 elderly suffer a hip fracture every year. 90% of fractures of the proximal femur result from a fall with an impact near the hip. The kinetic energy of a fall from standing height without successful protective reactions is far above the fracture threshold of a femur in a man aged 70 and older, regardless of osteoporosis and sex. Therefore, propensity to fall and mechanisms of falling are more important in the pathogenesis of hip fracture than bone mineral density alone. The combination of age-associated gait and balance disorders, which increase the probability of falls, and age-related decreasing strength of the femur is responsible for the high incidence of hip fractures. Besides the interventions to reduce the fall frequency it is possible to decrease the number of hip fractures by a passive protection of the trochanter. An energy-shunting protector (crash helmet-like, hip padding) has been developed by Lauritzen and Lund (safehip). The protector consists of two stiff shells, sewn into special undergarment. The shells disperse the impact away from the trochanter to soft tissue, and increase the area of contact. A controlled study among nursing home residents has demonstrated a relative risk of hip fracture of 0.44 (95% CC 0.21 to 0.94) in the intervention group, i.e., the protector has reduced the number of hip fractures by more than a half. No hip fracture has happened during use of the protector. Using the protector can improve self-confidence and diminish self-restraint of physical activity, which is not rarely caused by fear of falling. Further investigations of compliance are necessary.

  15. Osteoporotic fractures in older adults

    OpenAIRE

    Colón-Emeric, Cathleen S.; Saag, Kenneth G.

    2006-01-01

    Osteoporotic fractures are emerging as a major public health problem in the aging population. Fractures result in increased morbidity, mortality and health expenditures. This article reviews current evidence for the management of common issues following osteoporotic fractures in older adults including: (1) thromboembolism prevention; (2) delirium prevention; (3) pain management; (4) rehabilitation; (5) assessing the cause of fracture; and (6) prevention of subsequent fractures. Areas for prac...

  16. Classical fracture mechanics methods

    International Nuclear Information System (INIS)

    Schwalbe, K.H.; Heerens, J.; Landes, J.D.

    2007-01-01

    Comprehensive Structural Integrity is a reference work which covers all activities involved in the assurance of structural integrity. It provides engineers and scientists with an unparalleled depth of knowledge in the disciplines involved. The new online Volume 11 is dedicated to the mechanical characteristics of materials. This paper contains the chapter 11.02 of this volume and is structured as follows: Test techniques; Analysis; Fracture behavior; Fracture toughness tests for nonmetals

  17. Fatigue and fracture of fibre metal laminates

    CERN Document Server

    Alderliesten, René

    2017-01-01

    This book contributes to the field of hybrid technology, describing the current state of knowledge concerning the hybrid material concept of laminated metallic and composite sheets for primary aeronautical structural applications. It is the only book to date on fatigue and fracture of fibre metal laminates (FMLs). The first section of the book provides a general background of the FML technology, highlighting the major FML types developed and studied over the past decades in conjunction with an overview of industrial developments based on filed patents. In turn, the second section discusses the mechanical response to quasi-static loading, together with the fracture phenomena during quasi-static and cyclic loading. To consider the durability aspects related to strength justification and certification of primary aircraft structures, the third section discusses thermal aspects related to FMLs and their mechanical response to various environmental and acoustic conditions.

  18. Viscoplasticity and the dynamics of brittle fracture

    International Nuclear Information System (INIS)

    Langer, J. S.

    2000-01-01

    I propose a model of fracture in which the curvature of the crack tip is a relevant dynamical variable and crack advance is governed solely by plastic deformation of the material near the tip. This model is based on a rate-and-state theory of plasticity introduced in earlier papers by Falk, Lobkovsky, and myself. In the approximate analysis developed here, fracture is brittle whenever the plastic yield stress is nonzero. The tip curvature finds a stable steady-state value at all loading strengths, and the tip stress remains at or near the plastic yield stress. The crack speed grows linearly with the square of the effective stress intensity factor above a threshold that depends on the surface tension. This result provides a possible answer to the fundamental question of how breaking stresses are transmitted through plastic zones near crack tips. (c) 2000 The American Physical Society

  19. [Periprosthetic knee fractures].

    Science.gov (United States)

    Mittlmeier, T; Beck, M; Bosch, U; Wichelhaus, A

    2016-01-01

    The cumulative incidence of periprosthetic fractures around the knee is increasing further because of an extended indication for knee replacement, previous revision arthroplasty, rising life expectancy and comorbidities. The relevance of local parameters such as malalignment, osseous defects, neighbouring implants, aseptic loosening and low-grade infections may sometimes be hidden behind the manifestation of a traumatic fracture. A differentiated diagnostic approach before the treatment of a periprosthetic fracture is of paramount importance, while the physician in-charge should also have particular expertise in fracture treatment and in advanced techniques of revision endoprosthetics. The following work gives an overview of this topic. Valid classifications are available for categorising periprosthetic fractures of the femur, the tibia and the patella respectively, which are helpful for the selection of treatment. With the wide-ranging modern treatment portfolio bearing in mind the substantial rate of complications and the heterogeneous functional outcome, the adequate analysis of fracture aetiology and the corresponding transformation into an individualised treatment concept offer the chance of an acceptable functional restoration of the patient at early full weight-bearing and prolonged implant survival. The management of complications is crucial to the final outcome.

  20. A Fracture Decoupling Experiment

    Science.gov (United States)

    Stroujkova, A. F.; Bonner, J. L.; Leidig, M.; Ferris, A. N.; Kim, W.; Carnevale, M.; Rath, T.; Lewkowicz, J.

    2012-12-01

    Multiple observations made at the Semipalatinsk Test Site suggest that conducting nuclear tests in the fracture zones left by previous explosions results in decreased seismic amplitudes for the second nuclear tests (or "repeat shots"). Decreased seismic amplitudes reduce both the probability of detection and the seismically estimated yield of a "repeat shot". In order to define the physical mechanism responsible for the amplitude reduction and to quantify the degree of the amplitude reduction in fractured rocks, Weston Geophysical Corp., in collaboration with Columbia University's Lamont Doherty Earth Observatory, conducted a multi-phase Fracture Decoupling Experiment (FDE) in central New Hampshire. The FDE involved conducting explosions of various yields in the damage/fracture zones of previously detonated explosions. In order to quantify rock damage after the blasts we performed well logging and seismic cross-hole tomography studies of the source region. Significant seismic velocity reduction was observed around the source regions after the initial explosions. Seismic waves produced by the explosions were recorded at near-source and local seismic networks, as well as several regional stations throughout northern New England. Our analysis confirms frequency dependent seismic amplitude reduction for the repeat shots compared to the explosions in un-fractured rocks. The amplitude reduction is caused by pore closing and/or by frictional losses within the fractured media.

  1. FRACTURING FLUID CHARACTERIZATION FACILITY

    Energy Technology Data Exchange (ETDEWEB)

    Subhash Shah

    2000-08-01

    Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids and slurries through hydraulically created fractures. During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled ''The High Pressure Simulator'' (HPS). The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of ''The Well Construction Technology Center'' (WCTC). This report documents the summary of the activities performed during 1992-2000 at the FFCF.

  2. Advances in Imaging Approaches to Fracture Risk Evaluation

    Science.gov (United States)

    Manhard, Mary Kate; Nyman, Jeffry S.; Does, Mark D.

    2016-01-01

    Fragility fractures are a growing problem worldwide, and current methods for diagnosing osteoporosis do not always identify individuals who require treatment to prevent a fracture and may misidentify those not a risk. Traditionally, fracture risk is assessed using dual-energy X-ray absorptiometry, which provides measurements of areal bone mineral density (BMD) at sites prone to fracture. Recent advances in imaging show promise in adding new information that could improve the prediction of fracture risk in the clinic. As reviewed herein, advances in quantitative computed tomography (QCT) predict hip and vertebral body strength; high resolution HR-peripheral QCT (HR-pQCT) and micro-magnetic resonance imaging (μMRI) assess the micro-architecture of trabecular bone; quantitative ultrasound (QUS) measures the modulus or tissue stiffness of cortical bone; and quantitative ultra-short echo time MRI methods quantify the concentrations of bound water and pore water in cortical bone, which reflect a variety of mechanical properties of bone. Each of these technologies provides unique characteristics of bone and may improve fracture risk diagnoses and reduce prevalence of fractures by helping to guide treatment decisions. PMID:27816505

  3. Fracture Risk Assessment in Chronic Kidney Disease, Prospective Testing Under Real World Environments (FRACTURE: a prospective study

    Directory of Open Access Journals (Sweden)

    West Sarah L

    2010-08-01

    Full Text Available Abstract Background Chronic kidney disease (CKD is associated with an increased risk of fracture. Decreased bone mass and disruption of microarchitecture occur early in the course of CKD and worsens with the progressive decline in renal function so that at the time of initiation of dialysis at least 50% of patients have had a fracture. Despite the excess fracture risk, and the associated increases in morbidity and mortality, little is known about the factors that are associated with an increase in fracture risk. Our study aims to identify prognostic factors for bone loss and fractures in patients with stages 3 to 5 CKD. Methods This prospective study aims to enroll two hundred and sixty men and women with stages 3 to 5 CKD. Subjects will be followed for 24 months and we will examine the ability of: 1 bone mineral density by dual x-ray absorptiometry at the spine, hip, and radius; 2 volumetric bone density by high resolution peripheral quantitated computed tomography at the radius and tibia; 3 serum markers of bone turnover; 4 bone formation rate by bone biopsy; and 5 muscle strength and balance to predict spine and non-spine fractures, identified by self-report and/or vertebral morphometry. All measurements will be obtained at baseline, at 12 and at 24 months with the exception of bone biopsy, which will be measured once at 12 months. Subjects will be contacted every 4 months to determine if there have been incident fractures or falls. Discussion This study is one of the first that aims to identify risk factors for fracture in early stage CKD patients. Ultimately, by identifying risk factors for fracture and targeting treatments in this group-before the initiation of renal replacement therapy - we will reduce the burden of disease due to fractures among patients with CKD.

  4. Correlation of physical properties of ceramic materials with resistance to fracture by thermal shock

    Science.gov (United States)

    Lidman, W G; Bobrowsky, A R

    1949-01-01

    An analysis is made to determine which properties of materials affect their resistance to fracture by thermal stresses.From this analysis, a parameter is evaluated that is correlated with the resistance of ceramic materials to fracture by thermal shock as experimentally determined. This parameter may be used to predict qualitatively the resistance of a material to fracture by thermal shock. Resistance to fracture by thermal shock is shown to be dependent upon the following material properties: thermal conductivity, tensile strength, thermal expansion, and ductility modulus. For qualitative prediction of resistance of materials to fracture by thermal shock, the parameter may be expressed as the product of thermal conductivity and tensile strength divided by the product of linear coefficient of thermal expansion and ductility modulus of the specimen.

  5. Anisotropic Concrete Compressive Strength

    DEFF Research Database (Denmark)

    Gustenhoff Hansen, Søren; Jørgensen, Henrik Brøner; Hoang, Linh Cao

    2017-01-01

    When the load carrying capacity of existing concrete structures is (re-)assessed it is often based on compressive strength of cores drilled out from the structure. Existing studies show that the core compressive strength is anisotropic; i.e. it depends on whether the cores are drilled parallel...

  6. High strength ferritic alloy

    International Nuclear Information System (INIS)

    1977-01-01

    A high strength ferritic steel is specified in which the major alloying elements are chromium and molybdenum, with smaller quantities of niobium, vanadium, silicon, manganese and carbon. The maximum swelling is specified for various irradiation conditions. Rupture strength is also specified. (U.K.)

  7. Photon strength functions

    International Nuclear Information System (INIS)

    Bergqvist, I.

    1976-01-01

    Methods for extracting photon strength functions are briefly discussed. We follow the Brink-Axel approach to relate the strength functions to the giant resonances observed in photonuclear work and summarize the available data on the E1, E2 and M1 resonances. Some experimental and theoretical problems are outlined. (author)

  8. Interviewing to Understand Strengths

    Science.gov (United States)

    Hass, Michael R.

    2018-01-01

    Interviewing clients about their strengths is an important part of developing a complete understanding of their lives and has several advantages over simply focusing on problems and pathology. Prerequisites for skillfully interviewing for strengths include the communication skills that emerge from a stance of not knowing, developing a vocabulary…

  9. Failure mode and fracture behavior evaluation of pipes with local wall thinning subjected to bending load

    International Nuclear Information System (INIS)

    Ahn, Seok Hwan; Nam, Ki Woo; Kim, Seon Jin; Kim, Jin Hwan; Kim, Hyun Soo; Do, Jae Yoon

    2003-01-01

    Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe Erosion-Corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization, crack initiation/growth after ovalization, local buckling and crack initiating/growth after local buckling. Also, the strength and the allowable limit of piping system with local wall thinning were evaluated

  10. Fracture resistance and fatigue crack growth characteristics of two Al-Cu-Mg-Zr alloys

    Science.gov (United States)

    Sarkar, Bhaskar; Lisagor, W. B.

    1992-01-01

    The dependence of strength, fracture resistance, and fatigue crack growth rate on the aging conditions of two alloy compositions based on Al-3.7Cu-1.85Mg-0.2Mn is investigated. Mechanical properties were evaluated in two heat treatment conditions and in two orientations (longitudinal and transverse). Compact tension specimens were used to determine fatigue crack growth characteristics and fracture resistance. The aging response was monitored on coupons using hardness measurements determined with a standard Rockwell hardness tester. Fracture resistance is found to increase with increasing yield strength during artificial aging of age-hardenable 2124-Zr alloys processed by powder metallurgy techniques. Fatigue crack growth rate increases with increasing strength. It is argued that these changes are related to deformation modes of the alloys; a homogeneous deformation mode tends to increase fracture resistance and to decrease the resistance to the fatigue crack propagation rate.

  11. Effects of cathodic protection on cracking of high-strength pipeline steels

    Energy Technology Data Exchange (ETDEWEB)

    Elboujdaini, M.; Revie, R. W.; Attard, M. [CANMET Materials Technology Laboratory, Ottawa, ON(Canada)], email: melboujd@nrcan.gc.ca

    2010-07-01

    Four strength levels of pipeline steels, ranging from X-70 to X-120, were compared to determine whether higher strength materials are more susceptible to hydrogen embrittlement under cathodic protection. Ductility was measured in a solution at four protection levels, going from no cathodic protection to 500 mV of overprotection. All four steels showed loss of ductility under cathodic protection. Under cathodic polarization, the loss of ductility increased with the strength of the steel and the activity of the potential. After slow-strain-rate experiments conducted in air and examination of fracture surfaces, it is concluded that application of cathodic potentials, cathodic overprotection, higher strength of steel, and exposure to aqueous solution are factors that decrease the ductility of steel. Hydrogen reduction seems to be an important factor in ductility reduction and fractures. Observations suggest that high-strength pipelines need better control of cathodic protection than lower-strength pipelines.

  12. Effect of silicon solar cell processing parameters and crystallinity on mechanical strength

    Energy Technology Data Exchange (ETDEWEB)

    Popovich, V.A.; Yunus, A.; Janssen, M.; Richardson, I.M. [Delft University of Technology, Department of Materials Science and Engineering, Delft (Netherlands); Bennett, I.J. [Energy Research Centre of the Netherlands, Solar Energy, PV Module Technology, Petten (Netherlands)

    2011-01-15

    Silicon wafer thickness reduction without increasing the wafer strength leads to a high breakage rate during subsequent handling and processing steps. Cracking of solar cells has become one of the major sources of solar module failure and rejection. Hence, it is important to evaluate the mechanical strength of solar cells and influencing factors. The purpose of this work is to understand the fracture behavior of silicon solar cells and to provide information regarding the bending strength of the cells. Triple junctions, grain size and grain boundaries are considered to investigate the effect of crystallinity features on silicon wafer strength. Significant changes in fracture strength are found as a result of metallization morphology and crystallinity of silicon solar cells. It is observed that aluminum paste type influences the strength of the solar cells. (author)

  13. Comparison of Weibull strength parameters from flexure and spin tests of brittle materials

    Science.gov (United States)

    Holland, Frederic A., Jr.; Zaretsky, Erwin V.

    1991-01-01

    Fracture data from five series of four point bend tests of beam and spin tests of flat annular disks were reanalyzed. Silicon nitride and graphite were the test materials. The experimental fracture strengths of the disks were compared with the predicted strengths based on both volume flaw and surface flaw analyses of four point bend data. Volume flaw analysis resulted in a better correlation between disks and beams in three of the five test series than did surface flaw analysis. The Weibull (moduli) and characteristic gage strengths for the disks and beams were also compared. Differences in the experimental Weibull slopes were not statistically significant. It was shown that results from the beam tests can predict the fracture strength of rotating disks.

  14. Fractures of the Jaw and Midface

    Science.gov (United States)

    ... switch to the Professional version Home Injuries and Poisoning Facial Injuries Fractures of the Jaw and Midface Symptoms Diagnosis Treatment Treatment of mandible fractures Treatment of maxillary fractures ...

  15. Effect of sized and specimen geometry on the initiation and propagation of the ductile fracture

    International Nuclear Information System (INIS)

    Frund, J.M.; Marini, B.; Bethmont, M.

    1994-02-01

    Strength to the fracture of the pipe in PWR has to be justified with mechanical analyses. These tests are based on the strength to ductile fracture of steels which are tested in lab. The values of resistance to fracture are obtained through tensile tests on CT specimens (determination of J-R curves). The purpose of this study is to justify the sizes of the specimens which have to be used to characterize the strength to ductile fracture of steel in secondary pipes. Tests were conducted on 0,5T-CT, 1T-CT and 2T-CT specimens. Two materials with different suffer contents were studied. The test results show that the JO,2 values gotten from the different specimens are similar. But the strength to ductile fracture in 2T-CT specimens in lower than the one measured in 0,5t-CT and 1T-CT specimens. The surface of fracture of the different specimens displays splits perpendicular to the notch and parallel to the sheet surface. These splits are produced by the separation of the manganese sulfur inclusions. The effect notes on the J-R curves seems to be relevant to these splits. The reason why these splits might be responsible for a decrease of the tearing modulus are not clearly defined up to this point. The results which have been published show the importance of the geometry effects (presence or not of lateral notches...) and the loading mode on the strength to ductile fracture. We note that the curves determined from tests on CT specimens are conservative. A few preliminary studies showed that the geometry effects on resistance to fracture can be studied and explained by using local approach methods. The Rousselier modeling is useful to explain the behaviour of ferritic steels in ductile fracture. (authors). 20 refs., 7 figs., 5 tabs

  16. Dependence of strength on particle size in graphite

    International Nuclear Information System (INIS)

    Kennedy, E.P.; Kennedy, C.R.

    The strength to particle size relationship for specially fabricated graphites has been demonstrated and rationalized using fracture mechanics. In the past, similar studies have yielded empirical data using only commercially available material. Thus, experimental verification of these relationships has been difficult. However, the graphites of this study were fabricated by controlling the particle size ranges for a series of isotropic graphites. All graphites that were evaluated had a constant 1.85 g/cm 3 density. Thus, particle size was the only variable. This study also considered the particle size effect on other physical properties; coefficient of thermal expansion (CTE), electrical resistivity, fracture strain, and Young's modulus

  17. Early-Age Concrete Strength Estimation Technique using Embedded Piezoelectric self-sensing impedance

    OpenAIRE

    Kim , Junkyeong; Kim , Ju-Won; Park , Seunghee

    2014-01-01

    International audience; Recently, demands for the construction of Nuclear Power Plants (NPP) using high strength concrete (HSC) has been increased. However, HSC might be susceptible to brittle fracture if the curing process is inadequate. To prevent unexpected collapse during and after the construction of HSC structures, it is essential to confirm the strength development of HSC during the curing process. However, several traditional strength-measuring methods are not effective and practical....

  18. Radiological classification of mandibular fractures

    International Nuclear Information System (INIS)

    Mihailova, H.

    2009-01-01

    Mandibular fractures present the biggest part (up to 97%) of the facial bone fractures. Method of choice for diagnosing of mandibular fractures is conventional radiography. The aim of the issue is to present an unified radiological classification of mandibular fractures for the clinical practice. This classification includes only those clinical symptoms of mandibular fracture which could be radiologically objectified: exact anatomical localization (F1-F6), teeth in fracture line (Ta,Tb), grade of dislocation (D I, D II), occlusal disturbances (O(+), O(-)). Radiological symptoms expressed by letter and number symbols are systematized in a formula - FTDO of mandibular fractures similar to TNM formula for tumours. FTDO formula expresses radiological diagnose of each mandibular fracture but it doesn't include neither the site (left or right) of the fracture, nor the kind and number of fractures. In order to express topography and number of fractures the radiological formula is transformed into a decimal fraction. The symbols (FTD) of right mandible fracture are written in the numerator and those of the left site - in the denominator. For double and multiple fractures between the symbols for each fracture we put '+'. Symbols for occlusal disturbances are put down opposite, the fractional line. So topographo-anatomical formula (FTD/FTD)xO is formed. In this way the whole radiological information for unilateral, bilateral, single or multiple fractures of the mandible is expressed. The information in the radiological topography anatomic formula, resp. from the unified topography-anatomic classification ensures a quick and exact X-ray diagnose of mandibular fracture. In this way contributes to get better, make easier and faster X-ray diagnostic process concerning mandibular fractures. And all these is a precondition for prevention of retardation of the diagnosis mandibular fracture. (author)

  19. Preferred orientation of ettringite in concrete fractures

    KAUST Repository

    Wenk, Hans-Rudolf

    2009-05-15

    Sulfate attack and the accompanying crystallization of fibrous ettringite [Ca6Al2(OH)12(SO4) 3·26H2O] cause cracking and loss of strength in concrete structures. Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that the c axes of the trigonal crystallites are preferentially oriented perpendicular to the fracture surfaces. By averaging single-crystal elastic properties over the orientation distribution, it is possible to estimate the elastic anisotropy of ettringite aggregates. © 2009 International Union of Crystallography.

  20. Computer model for ductile fracture

    International Nuclear Information System (INIS)

    Moran, B.; Reaugh, J. E.

    1979-01-01

    A computer model is described for predicting ductile fracture initiation and propagation. The computer fracture model is calibrated by simple and notched round-bar tension tests and a precracked compact tension test. The model is used to predict fracture initiation and propagation in a Charpy specimen and compare the results with experiments. The calibrated model provides a correlation between Charpy V-notch (CVN) fracture energy and any measure of fracture toughness, such as J/sub Ic/. A second simpler empirical correlation was obtained using the energy to initiate fracture in the Charpy specimen rather than total energy CVN, and compared the results with the empirical correlation of Rolfe and Novak

  1. Polymer liquids fracture like solids

    DEFF Research Database (Denmark)

    Huang, Qian; Hassager, Ole

    2017-01-01

    While fracture in brittle solids has been studied for centuries until today, there are few studies on fracture in polymer liquids. Recent developments in experimental techniques, especially the combination of controlled filament stretching rheometry and high speed imaging, have opened new windows...... into the detailed study of fracture processes for polymer liquids. High speed imaging shows that polymer liquids fracture like solids with initiation and propagation of an edge fracture. However, remarkable features such as highly reproducible critical stress, independent appearance of multiple fractures...

  2. Femoral neck fractures after removal of hardware in healed trochanteric fractures.

    Science.gov (United States)

    Barquet, Antonio; Giannoudis, Peter V; Gelink, Andrés

    2017-12-01

    Hardware removal in healed trochanteric fractures (TF) in the absence of infection or significant mechanical complications is rarely indicated. However, in patients with persistent pain, prominent material and discomfort in the activities of daily living, the implant is eventually removed. Publications of ipsilateral femoral neck fracture after removal of implants from healed trochanteric fractures (FNFARIHTF) just because of pain or discomfort are rare. The purpose of this systematic review of the literature is to report on the eventual risk factors, the mechanisms, the clinical presentation, and frequency, and to pay special emphasis in their prevention. A comprehensive review of the literature was undertaken using the PRISMA guidelines with no language restriction. Case reports of FNFARIHTF and series of TF with cases of FNFARIHTF due to pain or discomfort published between inception of journals to December 2016 were eligible for inclusion. Relevant information was divided in two parts. Part I included the analysis of cases of FNFARIHTF, with the objective of establishing the eventual risk factors, mechanisms and pathoanatomy, clinical presentation and diagnosis, treatment and prevention. Part II analyzed series of TF which included cases of FNFARIHTF for assessing the incidence of femoral neck fractures in this condition. Overall 24 publications with 45 cases of FNFARIHTF met the inclusion criteria. We found that the only prevalent factors for FNFARIHTF were: 1) preexisisting systemic osteoporosis, as most patients were older and elder females, with lower bone mineral density and bone mass; 2) local osteoporosis as a result of preloading by the fixation device in the femoral neck, leading to stress protection, reducing the strain at the neck, and increasing bone loss and weakness; and 3) the removal of hardware from the femoral neck, with reduction of the failure strength of the neck. The femoral neck fractures were spontaneous, i.e. not related to trauma or

  3. Management of penile fractures

    International Nuclear Information System (INIS)

    Ghilan, Abdulelah M. M.; Al-Asbahi, Waleed A.; Alwan, Mohammed A.; Al-Khanbashi, Omar M.; Ghafour, Mohammed A.

    2008-01-01

    Objective was to present our experience with surgical and conservative management of penile fracture. This prospective study was carried out in the Urology and Nephrology Center, at Al-Thawra General and Teaching Hospital, Sana'a, Yemen from June 2003 to September 2007 and included 30 patients presenting with penile fracture. Diagnosis was made clinically in all our patients. Six patients with simple fracture were treated conservatively while 24 patients with more severe injuries were operated upon. Patient's age ranged from 24-52 years (mean 31.3 years) 46.7% of patients were under the age of 30 years and 56.7% were unmarried. Hard manipulation of the erect penis for example during masturbation was the most frequent mechanism of fracture in 53.3% of patients. Solitary tear was found in 22 patients and bilateral corporal tears associated with urethral injury were found in 2 patients. Corporal tears were saturated with synthetic absorbable sutures and urethral injury was repaired primarily. All operated patients described full erection with straight penis except 3 of the 8 patients who were managed by direct longitudinal incision, in whom mild curvature during erection was observed. The conservatively treated patients described satisfactory penile straightness and erection. The optimal functional and cosmetic results are achieved following immediate surgical repair of penis fracture. Good results can also be obtained in some selected patients with conservative management. (author)

  4. Stress fractures in athletes

    International Nuclear Information System (INIS)

    Steingruber, I.E.; Wolf, C.; Gruber, H.; Czermak, B.V.; Mallouhi, A.; Jaschke, W.; Gabriel, M.

    2002-01-01

    Stress fractures may pose a diagnostic dilemma for radiologists since they are sometimes difficult to demonstrate on plain films and may simulate a tumour. They were first described in military personnel and professional athletes. Recently, there is an increasing incidence in the general population due to increasing sportive activities. Stress fractures occur most often in the lower extremities, especially in the tibia, the tarsal bone, the metatarsal bone, the femur and the fibula. In the upper extremities, they are commonly found in the humerus, the radius and the ulna. Some fractures of the lower extremities appear to be specific for particular sports, for example, fractures of the tibia affect mostly distance runners. Whereas stress fractures of the upper extremities are generally associated with upper limb-dominated sports. A correct diagnosis requires a careful clinical evaluation. The initial plain radiography may be normal. Further radiological evaluation could be performed by means of computerised tomography, magnetic resonance imaging and bone scanning. The latter two techniques are especially helpful for establishing a correct initial diagnosis. (orig.) [de

  5. Making High-Tensile-Strength Amalgam Components

    Science.gov (United States)

    Grugel, Richard

    2008-01-01

    Structural components made of amalgams can be made to have tensile strengths much greater than previously known to be possible. Amalgams, perhaps best known for their use in dental fillings, have several useful attributes, including room-temperature fabrication, corrosion resistance, dimensional stability, and high compressive strength. However, the range of applications of amalgams has been limited by their very small tensile strengths. Now, it has been discovered that the tensile strength of an amalgam depends critically on the sizes and shapes of the particles from which it is made and, consequently, the tensile strength can be greatly increased through suitable choice of the particles. Heretofore, the powder particles used to make amalgams have been, variously, in the form of micron-sized spheroids or flakes. The tensile reinforcement contributed by the spheroids and flakes is minimal because fracture paths simply go around these particles. However, if spheroids or flakes are replaced by strands having greater lengths, then tensile reinforcement can be increased significantly. The feasibility of this concept was shown in an experiment in which electrical copper wires, serving as demonstration substitutes for copper powder particles, were triturated with gallium by use of a mortar and pestle and the resulting amalgam was compressed into a mold. The tensile strength of the amalgam specimen was then measured and found to be greater than 10(exp 4) psi (greater than about 69 MPa). Much remains to be done to optimize the properties of amalgams for various applications through suitable choice of starting constituents and modification of the trituration and molding processes. The choice of wire size and composition are expected to be especially important. Perusal of phase diagrams of metal mixtures could give insight that would enable choices of solid and liquid metal constituents. Finally, whereas heretofore, only binary alloys have been considered for amalgams

  6. Heat treatments and low temperature fracture toughness of a Ti-6A1-4V alloy

    International Nuclear Information System (INIS)

    Nagai, K.; Hiraga, K.; Ishikawa, K.; Ogata, T.

    1984-01-01

    Titanium alloy is one of the reliable structural materials for cryogenic use owing to its high strength, high specific strength and low thermal conductivity. Heat treatment is one method of controlling the normally poor fracture toughness of this alloy at ambient temperature. However, there have been few attempts to improve the low temperature fracture toughness by heat treatment. This study was conducted to elucidate the effects of heat treatments on the low temperature fracture toughness in a Ti-6A1-4V alloy. The effects of the heat treatments were as follows: the beta treatment was a very feasible method to improve the low temperature fracture properties; the alpha+beta treatment was favorable for the increment in the low temperature ductility but did not largely improve the fracture toughness; the double treatment yielded good ductility but was not useful for improving the fracture toughness

  7. Japanese round robin analysis for probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    Yagawa, G.; Yoshimura, S.; Handa, N.

    1991-01-01

    Recently attention is focused on the probabilistic fracture mechanics, a branch of fracture mechanics with probability theory for a rational mean to assess the strength of components and structures. In particular, the probabilistic fracture mechanics is recognized as the powerful means for quantitative investigation of significance of factors and rational evaluation of life on problems involving a number of uncertainties, such as degradation of material strength, accuracy and frequency of inspection. Comparison with reference experiments are generally employed to assure the analytical accuracy. However, accuracy and reliability of analytical methods in the probabilistic fracture mechanics are hardly verified by experiments. Therefore, it is strongly needed to verify the probabilistic fracture mechanics through the round robin analysis. This paper describes results from the round robin analysis of flat plate with semi-elliptic cracks on the surface, conducted by the PFM Working Group of LE Subcommittee of the Japan Welding Society under the contract of the Japan Atomic Energy Research Institute and participated by Tokyo University, Yokohama National University, the Power Reactor and Nuclear Fuel Corporation, Tokyo Electric Power Co. Central Research Institute of Electric Power Industry, Toshiba Corporation, Kawasaki Heavy Industry Co. and Mitsubishi Heavy Industry Co. (author)

  8. Crack tip fields and mixed mode fracture behaviour of progressively drawn pearlitic steel

    Directory of Open Access Journals (Sweden)

    J. Toribio

    2015-07-01

    Full Text Available This paper deals with the influence of the cold drawing process on the fracture behaviour of pearlitic steels. To this end, fracture tests under axial loading were performed on steel wires with different drawing degree (from a hot rolled bar to a commercial prestressing steel wire, transversely pre-cracked by fatigue, analyzing in detail the changes in fracture micromechanisms. The deflection angles of the fracture path were measured by longitudinal metallographic sections and the characteristic parameters of the loaddisplacement plot were related to different fracture events. Results allowed a calculation of critical stress intensity factors for different fracture angles and drawing degrees, thus evaluating the strength anisotropy and obtaining a sort of directional toughness.

  9. Inaccuracy in self-report of fractures may underestimate association with health outcomes when compared with medical record based fracture registry

    International Nuclear Information System (INIS)

    Siggeirsdottir, Kristin; Aspelund, Thor; Sigurdsson, Gunnar; Mogensen, Brynjolfur; Chang, Milan; Jonsdottir, Birna; Eiriksdottir, Gudny; Launer, Lenore J.; Harris, Tamara B.; Jonsson, Brynjolfur Y.; Gudnason, Vilmundur

    2007-01-01

    Introduction and objective Misreporting fractures in questionnaires is known. However, the effect of misreporting on the association of fractures with subsequent health outcomes has not been examined. Methods Data from a fracture registry (FR) developed from an extensive review of radiographic and medical records were related to self-report of fracture for 2,255 participants from the AGES Reykjavik Study. This data was used to determine false negative and false positive rates of self-reported fractures, correlates of misreporting, and the potential effect of the misreporting on estimates of health outcomes following fractures. Results In women, the false positive rate decreased with age as the false negative rate increased with no clear trend with age in men. Kappa values for agreement between FR and self-report were generally higher in women than men with the best agreement for forearm fracture (men 0.64 and women 0.82) and the least for rib (men 0.28 and women 0.25). Impaired cognition was a major factor associated with discordant answers between FR and self-report, OR 1.7 (95% CI: 1.3-2.1) (P < 0.0001). We estimated the effect of misreporting on health after fracture by comparison of the association of the self-report of fracture and fracture from the FR, adjusting for those factors associated with discordance. The weighted attenuation factor measured by mobility and muscle strength was 11% (95% CI: 0-24%) when adjusted for age and sex but reduced to 6% (95% CI: -10-22%) when adjusted for cognitive impairment. Conclusion Studies of hip fractures should include an independent ascertainment of fracture but for other fractures this study supports the use of self-report

  10. Numerical simulation on ferrofluid flow in fractured porous media based on discrete-fracture model

    Science.gov (United States)

    Huang, Tao; Yao, Jun; Huang, Zhaoqin; Yin, Xiaolong; Xie, Haojun; Zhang, Jianguang

    2017-06-01

    Water flooding is an efficient approach to maintain reservoir pressure and has been widely used to enhance oil recovery. However, preferential water pathways such as fractures can significantly decrease the sweep efficiency. Therefore, the utilization ratio of injected water is seriously affected. How to develop new flooding technology to further improve the oil recovery in this situation is a pressing problem. For the past few years, controllable ferrofluid has caused the extensive concern in oil industry as a new functional material. In the presence of a gradient in the magnetic field strength, a magnetic body force is produced on the ferrofluid so that the attractive magnetic forces allow the ferrofluid to be manipulated to flow in any desired direction through the control of the external magnetic field. In view of these properties, the potential application of using the ferrofluid as a new kind of displacing fluid for flooding in fractured porous media is been studied in this paper for the first time. Considering the physical process of the mobilization of ferrofluid through porous media by arrangement of strong external magnetic fields, the magnetic body force was introduced into the Darcy equation and deals with fractures based on the discrete-fracture model. The fully implicit finite volume method is used to solve mathematical model and the validity and accuracy of numerical simulation, which is demonstrated through an experiment with ferrofluid flowing in a single fractured oil-saturated sand in a 2-D horizontal cell. At last, the water flooding and ferrofluid flooding in a complex fractured porous media have been studied. The results showed that the ferrofluid can be manipulated to flow in desired direction through control of the external magnetic field, so that using ferrofluid for flooding can raise the scope of the whole displacement. As a consequence, the oil recovery has been greatly improved in comparison to water flooding. Thus, the ferrofluid

  11. Fracture, aging and disease in bone

    Energy Technology Data Exchange (ETDEWEB)

    Ager, J.W.; Balooch, G.; Ritchie, R.O.

    2006-02-01

    fracture resistance, whereas regulating the level of the cytokine TGF-beta can offer significant improvements in the stiffness, strength and toughness of bone, and as such may be considered as a therapeutic target to treat increased bone fragility induced by aging, drugs, and disease.

  12. Evaluation of fracture behavior of SA-516 steel welds using acoustic emission analysis

    International Nuclear Information System (INIS)

    Na, Eui Gyun; Ono, Kanji; Lee, Dong Whan

    2006-01-01

    The purpose of this study is to evaluate the AE characteristics for the basemetal, PWHT (Post-Weld Heat Treatment) and weldment specimens of SA-516 steel during fracture testing. Four-point bending and AE tests were conducted simultaneously. AE signals were emitted in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were emitted from the weldment samples because of the oxides, and discontinuous mechanical properties. AE signal strength and amplitude for the basemetal or PWHT specimen decreased remarkably compared to the weldment because of lower strength. Pre-cracked specimens emitted even lower event counts than the corresponding blunt notched specimens. Dimple fracture from void coalescence mechanism is associated with low-level AE signal strength for the basemetal or PWHT. Tearing mode and dimple formation were shown on the fracture surfaces of the weldment, but only a small fraction produced detectable AE

  13. Transstyloid, transscaphoid, transcapitate fracture: a variant of scaphocapitate fractures.

    LENUS (Irish Health Repository)

    Burke, Neil G

    2014-01-01

    Transstyloid, transscaphoid, transcapitate fractures are uncommon. We report the case of a 28-year-old man who sustained this fracture following direct trauma. The patient was successfully treated by open reduction internal fixation of the scaphoid and proximal capitate fragment, with a good clinical outcome at 1-year follow-up. This pattern is a new variant of scaphocapitate fracture as involves a fracture of the radial styloid as well.

  14. Osmosis, filtration and fracture of porous media

    International Nuclear Information System (INIS)

    Suarez Antola, R.

    2001-01-01

    Filtration was produced in a small scale physical model of a granular porous medium of cylindrical shape.The same volume flow was obtained either applying a difference in hydrostatic pressure or in osmotic pressure.In the first case a process of sustained erosion ending in an hydraulic short circuit was observed,while in the second case the material remained stable.This paradoxical strength behaviour is explained using some results from differential geometry,classical field theory and thermo-kinetic theory.The fracture process of a continuous matrix in a porous medium under the combined effect of filtration and external mechanical loads in then considered.The obtained results can be applied to the textural and compressive strength of wet concrete

  15. [Distal clavicle fracture].

    Science.gov (United States)

    Seppel, G; Lenich, A; Imhoff, A B

    2014-06-01

    Reposition and fixation of unstable distal clavicle fractures with a low profile locking plate (Acumed, Hempshire, UK) in conjunction with a button/suture augmentation cerclage (DogBone/FibreTape, Arthrex, Naples, FL, USA). Unstable fractures of the distal clavicle (Jäger and Breitner IIA) in adults. Unstable fractures of the distal clavicle (Jäger and Breitner IV) in children. Distal clavicle fractures (Jäger and Breitner I, IIB or III) with marked dislocation, injury of nerves and vessels, or high functional demand. Patients in poor general condition. Fractures of the distal clavicle (Jäger and Breitner I, IIB or III) without marked dislocation or vertical instability. Local soft-tissue infection. Combination procedure: Initially the lateral part of the clavicle is exposed by a 4 cm skin incision. After reduction of the fracture, stabilization is performed with a low profile locking distal clavicle plate. Using a special guiding device, a transclavicular-transcoracoidal hole is drilled under arthroscopic view. Additional vertical stabilization is arthroscopically achieved by shuttling the DogBone/FibreTape cerclage from the lateral portal cranially through the clavicular plate. The two ends of the FibreTape cerclage are brought cranially via adjacent holes of the locking plate while the DogBone button is placed under the coracoid process. Thus, plate bridging is achieved. Finally reduction is performed and the cerclage is secured by surgical knotting. Use of an arm sling for 6 weeks. Due to the fact that the described technique is a relatively new procedure, long-term results are lacking. In the short term, patients postoperatively report high subjective satisfaction without persistent pain.

  16. Foal Fractures: Osteochondral Fragmentation, Proximal Sesamoid Bone Fractures/Sesamoiditis, and Distal Phalanx Fractures.

    Science.gov (United States)

    Reesink, Heidi L

    2017-08-01

    Foals are susceptible to many of the same types of fractures as adult horses, often secondary to external sources of trauma. In addition, some types of fractures are specific to foals and occur routinely in horses under 1 year of age. These foal-specific fractures may be due to the unique musculoskeletal properties of the developing animal and may present with distinct clinical signs. Treatment plans and prognoses are tailored specifically to young animals. Common fractures not affecting the long bones in foals are discussed in this article, including osteochondral fragmentation, proximal sesamoid bone fractures/sesamoiditis, and distal phalanx fractures. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Endogenous PTH deficiency impairs fracture healing and impedes the fracture-healing efficacy of exogenous PTH(1-34.

    Directory of Open Access Journals (Sweden)

    Yongxin Ren

    Full Text Available Although the capacity of exogenous PTH1-34 to enhance the rate of bone repair is well established in animal models, our understanding of the mechanism(s whereby PTH induces an anabolic response during skeletal repair remains limited. Furthermore it is unknown whether endogenous PTH is required for fracture healing and how the absence of endogenous PTH would influence the fracture-healing capacity of exogenous PTH.Closed mid-diaphyseal femur fractures were created and stabilized with an intramedullary pin in 8-week-old wild-type and Pth null (Pth(-/- mice. Mice received daily injections of vehicle or of PTH1-34 (80 µg/kg for 1-4 weeks post-fracture, and callus tissue properties were analyzed at 1, 2 and 4 weeks post-fracture. Cartilaginous callus areas were reduced at 1 week post-fracture, but were increased at 2 weeks post-fracture in vehicle-treated and PTH-treated Pth(-/- mice compared to vehicle-treated and PTH-treated wild-type mice respectively. The mineralized callus areas, bony callus areas, osteoblast number and activity, osteoclast number and surface in callus tissues were all reduced in vehicle-treated and PTH-treated Pth(-/- mice compared to vehicle-treated and PTH-treated wild-type mice, but were increased in PTH-treated wild-type and Pth(-/- mice compared to vehicle-treated wild-type and Pth(-/- mice.Absence of endogenous PTH1-84 impedes bone fracture healing. Exogenous PTH1-34 can act in the absence of endogenous PTH but callus formation, including accelerated endochondral bone formation and callus remodeling as well as mechanical strength of the bone are greater when endogenous PTH is present. Results of this study suggest a complementary role for endogenous PTH1-84 and exogenous PTH1-34 in accelerating fracture healing.

  18. Endogenous PTH deficiency impairs fracture healing and impedes the fracture-healing efficacy of exogenous PTH(1-34).

    Science.gov (United States)

    Ren, Yongxin; Liu, Bo; Feng, Yuxu; Shu, Lei; Cao, Xiaojian; Karaplis, Andrew; Goltzman, David; Miao, Dengshun

    2011-01-01

    Although the capacity of exogenous PTH1-34 to enhance the rate of bone repair is well established in animal models, our understanding of the mechanism(s) whereby PTH induces an anabolic response during skeletal repair remains limited. Furthermore it is unknown whether endogenous PTH is required for fracture healing and how the absence of endogenous PTH would influence the fracture-healing capacity of exogenous PTH. Closed mid-diaphyseal femur fractures were created and stabilized with an intramedullary pin in 8-week-old wild-type and Pth null (Pth(-/-)) mice. Mice received daily injections of vehicle or of PTH1-34 (80 µg/kg) for 1-4 weeks post-fracture, and callus tissue properties were analyzed at 1, 2 and 4 weeks post-fracture. Cartilaginous callus areas were reduced at 1 week post-fracture, but were increased at 2 weeks post-fracture in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice respectively. The mineralized callus areas, bony callus areas, osteoblast number and activity, osteoclast number and surface in callus tissues were all reduced in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice, but were increased in PTH-treated wild-type and Pth(-/-) mice compared to vehicle-treated wild-type and Pth(-/-) mice. Absence of endogenous PTH1-84 impedes bone fracture healing. Exogenous PTH1-34 can act in the absence of endogenous PTH but callus formation, including accelerated endochondral bone formation and callus remodeling as well as mechanical strength of the bone are greater when endogenous PTH is present. Results of this study suggest a complementary role for endogenous PTH1-84 and exogenous PTH1-34 in accelerating fracture healing.

  19. Optimization the initial weights of artificial neural networks via genetic algorithm applied to hip bone fracture prediction

    OpenAIRE

    Chang, Y-T; Lin, J; Shieh, J-S; Abbod, MF

    2012-01-01

    This paper aims to find the optimal set of initial weights to enhance the accuracy of artificial neural networks (ANNs) by using genetic algorithms (GA). The sample in this study included 228 patients with first low-trauma hip fracture and 215 patients without hip fracture, both of them were interviewed with 78 questions. We used logistic regression to select 5 important factors (i.e., bone mineral density, experience of fracture, average hand grip strength, intake of coffee, and peak expirat...

  20. Fractured Petroleum Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Firoozabadi, Dr. Abbas

    2000-01-18

    In this report the results of experiments of water injection in fractured porous media comprising a number of water-wet matrix blocks are reported for the first time. The blocks experience an advancing fracture-water level (FWL). Immersion-type experiments are performed for comparison; the dominant recovery mechanism changed from co-current to counter-current imbibition when the boundary conditions changed from advancing FWL to immersion-type. Single block experiments of co-current and counter-current imbibition was performed and co-current imbibition leads to more efficient recovery was found.

  1. Elastic plastic fracture mechanics

    International Nuclear Information System (INIS)

    Simpson, L.A.

    1978-07-01

    The application of linear elastic fracture mechanics (LEFM) to crack stability in brittle structures is now well understood and widely applied. However, in many structural materials, crack propagation is accompanied by considerable crack-tip plasticity which invalidates the use of LEFM. Thus, present day research in fracture mechanics is aimed at developing parameters for predicting crack propagation under elastic-plastic conditions. These include critical crack-opening-displacement methods, the J integral and R-curve techniques. This report provides an introduction to these concepts and gives some examples of their applications. (author)

  2. Dynamic fracture characterization of material

    International Nuclear Information System (INIS)

    Kobayashi, A.S.; Emery, A.F.; Liaw, B.M.

    1981-01-01

    The influences of a wide range of material properties, i.e. of A533B steel, a silicon nitride ceramic and a Homalite-100 photoelastic polymer, as well as the influences of the specimen sizes on the dynamic fracture response of fracture specimens are presented in this paper. The results of a numerical study show that the dynamic fracture responses of these fracture specimens of proportional dimensions were indistinguishable provided the normalized dynamic fracture toughness versus normalized crack velocity relations of the three materials coincide. The limited results suggest that should the normalized dynamic fracture toughness versus normalized crack velocity relations between prototype and model materials coincide, then dynamic fracture experiments on scaled models can be used to infer the dynamic fracture response of the prototype. (orig./HP)

  3. Fracture surfaces of granular pastes.

    Science.gov (United States)

    Mohamed Abdelhaye, Y O; Chaouche, M; Van Damme, H

    2013-11-01

    Granular pastes are dense dispersions of non-colloidal grains in a simple or a complex fluid. Typical examples are the coating, gluing or sealing mortars used in building applications. We study the cohesive rupture of thick mortar layers in a simple pulling test where the paste is initially confined between two flat surfaces. After hardening, the morphology of the fracture surfaces was investigated, using either the box counting method to analyze fracture profiles perpendicular to the mean fracture plane, or the slit-island method to analyze the islands obtained by cutting the fracture surfaces at different heights, parallel to the mean fracture plane. The fracture surfaces were shown to exhibit scaling properties over several decades. However, contrary to what has been observed in the brittle or ductile fracture of solid materials, the islands were shown to be mass fractals. This was related to the extensive plastic flow involved in the fracture process.

  4. Flexible fixation and fracture healing

    DEFF Research Database (Denmark)

    Schmal, Hagen; Strohm, Peter C; Jaeger, Martin

    2011-01-01

    , noncomminuted fractures. External fixation uses external bars for stabilization, whereas internal fixation is realized by subcutaneous placement of locking plates. Both of these "biologic" osteosynthesis methods allow a minimally invasive approach and do not compromise fracture hematoma and periosteal blood...

  5. Gene Therapy for Fracture Repair

    National Research Council Canada - National Science Library

    Lau, William

    2005-01-01

    .... We have identified a murine leukemia virus (MLV) vector that provides robust transgene expression in fracture tissues, and applied it to the rat femur fracture model to express therapeutic transgenes...

  6. Clinical assessment tools identify functional deficits in fragility fracture patients

    Directory of Open Access Journals (Sweden)

    Ames TD

    2016-05-01

    Full Text Available Tyler D Ames,1 Corinne E Wee,1 Khoi M Le,1 Tiffany L Wang,1 Julie Y Bishop,2 Laura S Phieffer,2 Carmen E Quatman2 1The Ohio State University College of Medicine, 2Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, OH, USA Purpose: To identify inexpensive, noninvasive, portable, clinical assessment tools that can be used to assess functional performance measures that may put older patients at risk for falls such as balance, handgrip strength, and lumbopelvic control.Patients and methods: Twenty fragility fracture patients and 21 healthy control subjects were evaluated using clinical assessment tools (Nintendo Wii Balance Board [WBB], a handheld dynamometer, and an application for the Apple iPod Touch, the Level Belt that measure functional performance during activity of daily living tasks. The main outcome measurements were balance (WBB, handgrip strength (handheld dynamometer, and lumbopelvic control (iPod Touch Level Belt, which were compared between fragility fracture patients and healthy controls.Results: Fragility fracture patients had lower scores on the vertical component of the WBB Torso Twist task (P=0.042 and greater medial–lateral lumbopelvic sway during a 40 m walk (P=0.026 when compared to healthy controls. Unexpectedly, the fracture patients had significantly higher scores on the left leg (P=0.020 and total components (P=0.010 of the WBB Single Leg Stand task as well as less faults during the left Single Leg Stand task (P=0.003.Conclusion: The clinical assessment tools utilized in this study are relatively inexpensive and portable tools of performance measures capable of detecting differences in postural sway between fragility fracture patients and controls. Keywords: fall risk, geriatric fracture, Nintendo Wii Balance Board, Level Belt, fragility fracture

  7. The use of titanium and stainless steel in fracture fixation.

    Science.gov (United States)

    Hayes, J S; Richards, R G

    2010-11-01

    The use of metal in fracture fixation has demonstrated unrivalled success for many years owing to its high stiffness, strength, biological toleration and overall reliable function. The most prominent materials used are electropolished stainless steel and commercially pure titanium, along with the more recent emergence of titanium alloys. Despite the many differences between electropolished stainless steel and titanium, both materials provide a relatively predictable clinical outcome, and offer similar success for fulfilling the main biomechanical and biological requirements of fracture fixation despite distinctive differences in implant properties and biological responses. This article explores these differences by highlighting the limitations and advantages of both materials, and addresses how this translates to clinical success.

  8. Correlation of Hip Fracture with Other Fracture Types: Toward a Rational Composite Hip Fracture Endpoint

    Science.gov (United States)

    Colón-Emeric, Cathleen; Pieper, Carl F.; Grubber, Janet; Van Scoyoc, Lynn; Schnell, Merritt L; Van Houtven, Courtney Harold; Pearson, Megan; Lafleur, Joanne; Lyles, Kenneth W.; Adler, Robert A.

    2016-01-01

    Purpose With ethical requirements to the enrollment of lower risk subjects, osteoporosis trials are underpowered to detect reduction in hip fractures. Different skeletal sites have different levels of fracture risk and response to treatment. We sought to identify fracture sites which cluster with hip fracture at higher than expected frequency; if these sites respond to treatment similarly, then a composite fracture endpoint could provide a better estimate of hip fracture reduction. Methods Cohort study using Veterans Affairs and Medicare administrative data. Male Veterans (n=5,036,536) aged 50-99 years receiving VA primary care between1999-2009 were included. Fractures were ascertained using ICD9 and CPT codes and classified by skeletal site. Pearson correlation coefficients, logistic regression and kappa statistics, were used to describe the correlation between each fracture type and hip fracture within individuals, without regards to the timing of the events. Results 595,579 (11.8%) men suffered 1 or more fractures and 179,597 (3.6%) suffered 2 or more fractures during the time under study. Of those with one or more fractures, rib was the most common site (29%), followed by spine (22%), hip (21%) and femur (20%). The fracture types most highly correlated with hip fracture were pelvic/acetabular (Pearson correlation coefficient 0.25, p<0.0001), femur (0.15, p<0.0001), and shoulder (0.11, p<0.0001). Conclusions Pelvic, acetabular, femur, and shoulder fractures cluster with hip fractures within individuals at greater than expected frequency. If we observe similar treatment risk reductions within that cluster, subsequent trials could consider use of a composite endpoint to better estimate hip fracture risk. PMID:26151123

  9. Hydraulic fracturing in shales: the spark that created an oil and gas boom

    Science.gov (United States)

    Olson, J. E.

    2017-12-01

    In the oil and gas business, one of the valued properties of a shale was its lack of flow capacity (its sealing integrity) and its propensity to provide mechanical barriers to hydraulic fracture height growth when exploiting oil and gas bearing sandstones. The other important property was the high organic content that made shale a potential source rock for oil and gas, commodities which migrated elsewhere to be produced. Technological advancements in horizontal drilling and hydraulic fracturing have turned this perspective on its head, making shale (or other ultra-low permeability rocks that are described with this catch-all term) the most prized reservoir rock in US onshore operations. Field and laboratory results have changed our view of how hydraulic fracturing works, suggesting heterogeneities like bedding planes and natural fractures can cause significant complexity in hydraulic fracture growth, resulting in induced networks of fractures whose details are controlled by factors including in situ stress contrasts, ductility contrasts in the stratigraphy, the orientation and strength of pre-existing natural fractures, injection fluid viscosity, perforation cluster spacing and effective mechanical layer thickness. The stress shadowing and stress relief concepts that structural geologists have long used to explain joint spacing and orthogonal fracture pattern development in stratified sequences are key to understanding optimal injection point spacing and promotion of more uniform length development in induced hydraulic fractures. Also, fracture interaction criterion to interpret abutting vs crossing natural fracture relationships in natural fracture systems are key to modeling hydraulic fracture propagation within natural fractured reservoirs such as shale. Scaled physical experiments provide constraints on models where the physics is uncertain. Numerous interesting technical questions remain to be answered, and the field is particularly appealing in that better

  10. Impact of a community-based osteoporosis and fall prevention program on fracture incidence.

    Science.gov (United States)

    Grahn Kronhed, Ann-Charlotte; Blomberg, Carina; Karlsson, Nadine; Löfman, Owe; Timpka, Toomas; Möller, Margareta

    2005-06-01

    Associations between a 10-year community-based osteoporosis and fall prevention program and fracture incidence amongst middle-aged and elderly residents in an intervention community are studied, and comparisons are made with a control community. A health-education program was provided to all residents in the intervention community, which addressed dietary intake, physical activity, smoking habits and environmental risk factors for osteoporosis and falls. Both communities are small, semi-rural and situated in Ostergotland County in southern Sweden. The analysis is based on incidences of forearm fractures in the population 40 years of age or older, and hip fractures in the population 50 years of age or older. Data for three 5-year periods (pre-, early and late intervention) are accumulated and compared. In the intervention community, forearm fracture incidence decreased in women. There are also tendencies towards decreasing forearm fracture incidence in men, and towards decreasing trochanteric hip fracture incidences in women and in men in the late intervention period. No such changes in fracture incidences are found in the control community. Cervical hip fracture incidence did not change in the intervention and the control communities. Although the reported numbers of fractures are small (a total of 451 forearm and 357 hip fractures), the numbers are based on total community populations and thus represent a true difference. The decrease in forearm fracture incidence among women, and the tendency towards decreasing trochanteric hip fractures, in contrast to the absence of change in cervical hip fractures, might be mainly due to a more rapid effect of fall preventive measures than an increase in bone strength in the population. For the younger age groups an expected time lag between intervention and effect might invalidate the short follow-up period for outcome measurements. Thus, the effect of the 10-year intervention program on fracture incidence should be followed

  11. Complications in ankle fracture surgery

    OpenAIRE

    Ovaska, Mikko

    2015-01-01

    Mikko Ovaska. Complications in Ankle Fracture Surgery. Helsinki Bone and Joint Research Group, Department of Orthopaedic Surgery and Traumatology, Faculty of Medicine, University of Helsinki, Finland. Helsinki 2014. Ankle fractures are among the most frequently encountered surgically treated fractures. The operative treatment of this fracture may be associated with several complications. The most frequently encountered complications are related wound healing, and deep infection may have d...

  12. Management of osteoporotic vertebral fractures

    OpenAIRE

    Dionyssiotis, Yannis

    2010-01-01

    Yannis DionyssiotisRhodes General Hospital, Rhodes, GreeceAbstract: Osteoporotic vertebral fractures are associated with considerable reduction of quality of life, morbidity, and mortality. The management of patients with vertebral fractures should include treatment for osteoporosis and measures to reduce pain and improve mobility. This article provides information for management and rehabilitation of vertebral fractures based on clinical experience and literature.Keywords: vertebral fracture...

  13. Osteoporotic Hip and Spine Fractures

    OpenAIRE

    Cannada, Lisa K.; Hill, Brian W.

    2014-01-01

    Hip and spine fractures represent just a portion of the burden of osteoporosis; however, these fractures require treatment and often represent a major change in lifestyle for the patient and their family. The orthopedic surgeon plays a crucial role, not only in the treatment of these injuries but also providing guidance in prevention of future osteoporotic fractures. This review provides a brief epidemiology of the fractures, details the surgical techniques, and outlines the current treatment...

  14. Some probabilistic aspects of fracture

    International Nuclear Information System (INIS)

    Thomas, J.M.

    1982-01-01

    Some probabilistic aspects of fracture in structural and mechanical components are examined. The principles of fracture mechanics, material quality and inspection uncertainty are formulated into a conceptual and analytical framework for prediction of failure probability. The role of probabilistic fracture mechanics in a more global context of risk and optimization of decisions is illustrated. An example, where Monte Carlo simulation was used to implement a probabilistic fracture mechanics analysis, is discussed. (orig.)

  15. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

    This study is centred on assessment of the fatigue strength of titanium fusion welds for deep-water riser's applications. Deep-water risers are subjected to significant fatigue loading. Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments. The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechanics modelling of fatigue crack growth. Two series of welded grade of titanium consisting of 14 specimens in each series were fatigue tested under constant amplitude loading. Prior to fatigue testing, strain gauge measurements of some specimens was conducted to enable the definition of stress range in the fatigue assessment procedure. The results were compared with finite solid element analysis and related to fatigue stresses in a riser pipe wall. Distribution and geometry of internal and surface defects both in the as-welded and in the post-weld machined conditions were assessed using fractography. This served as a tool to determine the fatigue initiation point in the welds. Fracture mechanics was applied to model fatigue strength of titanium welds with initiation from weld defects. Two different stress intensity factor formulations for embedded eccentrically placed cracks were used for analysis of elliptical cracks with the major axis parallel and close to one of the free surfaces. The methods were combined to give a satisfactory model for crack growth analysis. The model analyses crack growth of elliptical and semi-elliptical cracks in two directions, with updating of the crack geometry. Fatigue strength assessment was conducted using two crack growth models, the Paris-Erdogan relation with no threshold and the Donahue et al. relation with an implied threshold. The model was validated against experimental data, with a discussion on the choice of crack growth model. (author)

  16. Time dependent fracture growth in intact crystalline rock: new laboratory procedures

    International Nuclear Information System (INIS)

    Backers, T.; Stephansson, O.

    2008-01-01

    Short term laboratory tests to determine the strength of rock material are commonly used to assess stability of rock excavations. However, loading the rock below its short term strength may lead to delayed failure due to slow stable fracture growth. This time-dependent phenomenon is called subcritical fracture growth. A fracture mechanics based approach is applied in this study to determine the parameters describing subcritical fracture growth under Mode Ⅰ (tensile) and Mode Ⅱ (in-plane shear) loading in terms of the stress intensity factors of saturated granodiorite from the) Aespoe HRL. A statistical method is applied to data from three-point bending (tension) and Punch-Through Shear with Confining Pressure, PTS/CP, (shear) experiments. One population of each set-up was subjected to rapid loading tests yielding a strength probability distribution. A second population was loaded up to a certain fraction of the statistical percentage for failure and the time-to-failure was determined. From these two populations the subcritical fracture growth parameters were determined successfully. Earlier studies demonstrated subcritical fracture growth under Mode I loading conditions, but this study shows that under a Mode Ⅱ load time-dependent fracture growth exists as well. (authors)

  17. On the temperature independence of statistical model parameters for cleavage fracture in ferritic steels

    Science.gov (United States)

    Qian, Guian; Lei, Wei-Sheng; Niffenegger, M.; González-Albuixech, V. F.

    2018-04-01

    The work relates to the effect of temperature on the model parameters in local approaches (LAs) to cleavage fracture. According to a recently developed LA model, the physical consensus of plastic deformation being a prerequisite to cleavage fracture enforces any LA model of cleavage fracture to observe initial yielding of a volume element as its threshold stress state to incur cleavage fracture in addition to the conventional practice of confining the fracture process zone within the plastic deformation zone. The physical consistency of the new LA model to the basic LA methodology and the differences between the new LA model and other existing models are interpreted. Then this new LA model is adopted to investigate the temperature dependence of LA model parameters using circumferentially notched round tensile specimens. With the published strength data as input, finite element (FE) calculation is conducted for elastic-perfectly plastic deformation and the realistic elastic-plastic hardening, respectively, to provide stress distributions for model calibration. The calibration results in temperature independent model parameters. This leads to the establishment of a 'master curve' characteristic to synchronise the correlation between the nominal strength and the corresponding cleavage fracture probability at different temperatures. This 'master curve' behaviour is verified by strength data from three different steels, providing a new path to calculate cleavage fracture probability with significantly reduced FE efforts.

  18. Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

    Science.gov (United States)

    Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

    2017-12-01

    The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

  19. Patellar Sleeve Fracture With Ossification of the Patellar Tendon.

    Science.gov (United States)

    Damrow, Derek S; Van Valin, Scott E

    2017-03-01

    Patellar sleeve fractures make up greater than 50% of all patellar fractures. They are essentially only seen in the pediatric population because of the thick periosteum and the distal patellar pole apophysis in this group. These fractures can lead to complications if not treated appropriately and in a timely fashion. Complications of missed or untreated patellar sleeve fractures include patella alta, anterior knee pain, and quadriceps atrophy. These can all result in severe limitations in activity. The authors describe a case of a 16-year-old boy who sustained a patellar sleeve fracture 3 years prior to presentation. On presentation, he had patella alta, diminished strength, 5° of extensor lag, and radiographs that revealed bone formation along the patellar tendon. Despite this, he was able to maintain a high level of activity. This case report explores how the patient could have maintained a high level of activity despite having a patellar sleeve fracture. Also, because of the delayed presentation, the patella was ossified and the quadriceps was retracted, which led to a novel approach to reconstructing his distal extensor mechanism. This approach included a V-Y advancement of the quadriceps tendon and patellar tendon reconstruction using the patient's hamstring tendon (semitendinosus). This technique, combined with physical therapy postoperatively, resulted in his return to varsity high school soccer. To the best of the authors' knowledge, this technique has not been reported for this rare condition. [Orthopedics. 2017; 40(2):e357-e359.]. Copyright 2016, SLACK Incorporated.

  20. Frictional stability-permeability relationships for fractures in shales

    Science.gov (United States)

    Fang, Yi; Elsworth, Derek; Wang, Chaoyi; Ishibashi, Takuya; Fitts, Jeffrey P.

    2017-03-01

    There is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO2 sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction-stability-permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate-rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate-rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction-stability-permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.