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Sample records for rotating bending fatigue

  1. 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

  2. Determination and demarcation of fatigue crack initiation phase in rotating bending condition

    International Nuclear Information System (INIS)

    Pasha, R.A.; Rehman, K.; Shah, M.

    2012-01-01

    In engineering applications, components often experience cyclic loading and therefore, have crack initiation propagation phase. In this research work experimental demarcation of fatigue crack initiation has been investigated. Initiation phase of fatigue life of Aluminium was determined by using single and two step fatigue loading test on four point rotating bending fatigue testing machine. Experimental data is used to determine the distinction between the initiation and propagation phase. Initiation phase is determined at different stress levels. The obtained results demonstrate the effect of stress level on initiation phase and propagation phase. (author)

  3. Effect of shot peening using ultra-fine particles on fatigue properties of 5056 aluminum alloy under rotating bending

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Shoichi, E-mail: kikuchi@mech.kobe-u.ac.jp [Department of Mechanical Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe-shi, Hyogo 657-8501 (Japan); Nakamura, Yuki [Department of Mechanical Engineering, National Institute of Technology, Toyota College, 2-1 Eisei-cho, Toyota-shi, Aichi 471-8525 (Japan); Nambu, Koichiro [Department of Mechanical Engineering, National Institute of Technology, Suzuka College, Shiroko-cho, Suzuka-shi, Mie 510-0294 (Japan); Ando, Masafumi [Innovation Team, IKK SHOT Co. Ltd., 412-4, Nunowari, Minami-Shibata-machi, Tokai-shi, Aichi 476-0001 (Japan)

    2016-01-15

    Shot peening using particles 10 μm in diameter (ultra-fine particle peening: Ultra-FPP) was introduced to improve the fatigue properties of 5056 aluminum alloy. The surface microstructures of the Ultra-FPP treated specimens were characterized using a micro-Vickers hardness tester, scanning electron microscopy (SEM), X-ray diffraction (XRD), non-contact scanning white light interferometry, and electron backscatter diffraction (EBSD). The Ultra-FPP treated specimen had higher hardness than the conventional FPP treated specimen with a short nozzle distance due to the high velocity of the ultra-fine particles. Furthermore, the surface hardness of the Ultra-FPP treated specimen tended to increase as the peening time decreased. Fatigue tests were performed in air at room temperature using a cantilever-type rotating bending fatigue testing machine. It was found that the fatigue life of the Ultra-FPP treated specimen tended to increase with decreasing peening time. Mainly, the Ultra-FPP improved the fatigue properties of 5056 aluminum alloy in the very high cycle regime of more than 10{sup 7} cycles compared with the un-peened specimens. This is because the release of the compressive residual stress is small during fatigue tests at low stress amplitudes.

  4. Parallel monostrand stay cable bending fatigue

    DEFF Research Database (Denmark)

    Winkler, Jan Pawel

    This dissertation investigates the bending fatigue response of high-strength steel monostrands and multistrand stay cables to cyclic transverse deformations. Increasing bridge stock numbers and a push for longer cable-supported span lengths have led to an increased number of reported incidents...... of damage and replacement of bridge stay cables due to wind and traffic-induced fatigue. The understanding of fatigue mechanisms in most steel structures is well established. However, in the case of cables composed of steel strands, many important aspects related with bending fatigue remain to be clarified...... associated with variable loading, and different testing procedures. As most of the contemporary stay cables are comprised of a number of individual highstrength steel monostrands, the research study started with an extensive experimental work on the fatigue response of a single monostrand to cyclic flexural...

  5. A preliminary bending fatigue spectrum for steel monostrand cables

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2011-01-01

    This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension...... and flexure and show that localized cable bending has a pronounced influence on the fatigue resistance of cables under dynamic excitations....

  6. Localized bending fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2012-01-01

    In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement of the st......In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...... displacement (opening/closing and sliding) of the helically wound wires. Moreover, the results are a step towards understanding the bending fatigue damage mechanisms of monostrand cables....

  7. Fracture probability properties of pure and cantilever bending fatigue of STS304 steel

    International Nuclear Information System (INIS)

    Roh, Sung Kuk; Park, Dae Hyun; Jeong, Soon Uk

    2001-01-01

    Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frequently. Therefore many people are suffering harm of property. The destruction cause of marcaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed

  8. Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending

    Directory of Open Access Journals (Sweden)

    Kulesa Anna

    2016-03-01

    Full Text Available The paper presents a comparison of the fatigue life curves based on test of 15Mo3 steel under cyclic, pendulum bending and tension-compression. These studies were analyzed in terms of a large and small number of cycles where strain amplitude is dependent on the fatigue life. It has been shown that commonly used Manson-Coffin-Basquin model cannot be used for tests under cyclic bending due to the impossibility of separating elastic and plastic strains. For this purpose, some well-known models of Langer and Kandil and one new model of authors, where strain amplitude is dependent on the number of cycles, were proposed. Comparing the results of bending with tension-compression it was shown that for smaller strain amplitudes the fatigue life for both test methods were similar, for higher strain amplitudes fatigue life for bending tests was greater than for tension-compression.

  9. Fatigue criterion for the design of rotating shafts under combined stress

    Science.gov (United States)

    Loewenthal, S. H.

    1977-01-01

    A revised approach to the design of transmission shafting which considers the flexure fatigue characteristics of the shaft material under combined cyclic bending and static torsion stress is presented. A fatigue failure relation, corroborated by published combined stress test data, is presented which shows an elliptical variation of reversed bending endurance strength with static torsional stress. From this elliptical failure relations, a design formula for computing the diameter of rotating solid shafts under the most common condition of loading is developed.

  10. PROJECT, MANUFACTURING AND QUALIFICATION OF MACHINE TO ROTARY BENDING OF NITI SUPERELASTIC WIRES IN FATIGUE TESTS

    Directory of Open Access Journals (Sweden)

    William Marcos Muniz Menezes

    2014-03-01

    Full Text Available In this work it was developed a rotating bending apparatus for fatigue tests of superelastic NiTi wires, and other materials with high elasticity. It was evaluated the performance, robustness, operability, and reliability through testing of 1 mm thick stainless steel wires. This device is mounted on a steel frame and features semiautomatic rotation speed control, time and testing bath temperature for sample immersion. The equipment qualification tests were performed controlling the following parameters: deformation of the wire, power level and ambient temperature. The results indicated lower discrepancies for the following parameters evaluated: number of cycles in fatigue life, rotation speed, the bath temperature and arc angle of rupture. Besides the reliability, the robustness and operability of the equipment also meet the purpose of the research as evidenced by the small number of failures in the qualification tests and calibration.

  11. Tensile and bending fatigue of the adhesive interface to dentin.

    Science.gov (United States)

    Belli, Renan; Baratieri, Luiz Narciso; Braem, Marc; Petschelt, Anselm; Lohbauer, Ulrich

    2010-12-01

    The aim of this study was to evaluate the fatigue limits of the dentin-composite interfaces established either with an etch-and-rinse or an one-step self-etch adhesive systems under tensile and bending configurations. Flat specimens (1.2 mm×5 mm×35 mm) were prepared using a plexiglass mold where dentin sections from human third molars were bonded to a resin composite, exhibiting the interface centrally located. Syntac Classic and G-Bond were used as adhesives and applied according to the manufacturer's instructions. The fluorochrome Rhodamine B was added to the adhesives to allow for fractographic evaluation. Tensile strength was measured in an universal testing machine and the bending strength (n=15) in a Flex machine (Flex, University of Antwerp, Belgium), respectively. Tensile (TFL) and bending fatigue limits (BFL) (n=25) were determined under wet conditions for 10(4) cycles following a staircase approach. Interface morphology and fracture mechanisms were observed using light, confocal laser scanning and scanning electron microscopy. Statistical analysis was performed using three-way ANOVA (mod LSD test, pTensile and bending characteristic strengths at 63.2% failure probability for Syntac were 23.8 MPa and 71.5 MPa, and 24.7 MPa and 72.3 MPa for G-Bond, respectively. Regarding the applied methods, no significant differences were detected between adhesives. However, fatigue limits for G-Bond (TFL=5.9 MPa; BFL=36.2 MPa) were significantly reduced when compared to Syntac (TFL=12.6 MPa; BFL=49.7 MPa). Fracture modes of Syntac were generally of adhesive nature, between the adhesive resin and dentin, while G-Bond showed fracture planes involving the adhesive-dentin interface and the adhesive resin. Cyclic loading under tensile and bending configurations led to a significant strength degradation, with a more pronounced fatigue limit decrease for G-Bond. The greater decrease in fracture strength was observed in the tensile configuration. Copyright © 2010 Academy of

  12. Fatigue Assessment of High Strength Steel Welded Joints Under Bending Loading

    International Nuclear Information System (INIS)

    Lee, Myeong-Woo; Kim, Yun-Jae; Park, Jun-Hyub

    2014-01-01

    In this study, a fatigue assessment method for vehicle suspension systems having welded geometries was established under a bending loading condition. For the fatigue life estimation of the actual product s welded joints made of different steels, bending fatigue tests were performed on welded specimens with a simplified shape for obtaining the moment-fatigue-life plot. Further, geometry modeling of the simplified welded specimens was conducted. Results of finite element analysis were used to obtain the stress-fatigue-life plot. The analysis results were also used to calculate the stress concentration factors for notch-factor-based fatigue life estimation. The test results were compared with results of the general notch-factor-based fatigue life estimation for improving fatigue assessment. As a result, it was concluded that both the welded fatigue tests and the notch-factor-based fatigue life estimation are necessary for accurate fatigue assessment

  13. High-temperature reverse-bend fatigue strength of Inconel Alloy 625

    International Nuclear Information System (INIS)

    Purohit, A.; Greenfield, I.G.; Park, K.B.

    1983-06-01

    Inconel 625 has been selected as the clad material for Upgraded Transient Reactor Test Facility (TREAT Upgrade or TU) fuel assemblies. The range of temperatures investigated is 900 to 1100 0 C. A reverse-bend fatigue test program was selected as the most-effective method of determining the fatigue characteristics of Inconel alloy 625 sheet metal. The paper describes the reverse bend fatigue experiments, the results obtained, and the analysis of data

  14. Investigation of bending fatigue-life of aluminum sheets based on rolling direction

    Directory of Open Access Journals (Sweden)

    Raif Sakin

    2018-03-01

    Full Text Available High-cycle fatigue (HCF and low-cycle fatigue (LCF fatigue lives of rolled AA1100 and AA1050 aluminum sheets along different directions were evaluated at room temperature. Four types of samples denoted as longitudinal (L and transverse (T to the rolling direction were compared because the samples along the two typical directions show an obvious anisotropy. A cantilever plane-bending and multi-type fatigue testing machine was specially designed for this purpose. Deflection-controlled fatigue tests were conducted under fully reversed loading. The longest fatigue lives in the LCF region were obtained for AA1050 (L while AA1100 (L samples had the longest fatigue lives in the HCF region. Keywords: AA1100, AA1050, Aluminum sheet, Bending fatigue life, Rolling direction

  15. Modeling size effects on fatigue life of a zirconium-based bulk metallic glass under bending

    International Nuclear Information System (INIS)

    Yuan Tao; Wang Gongyao; Feng Qingming; Liaw, Peter K.; Yokoyama, Yoshihiko; Inoue, Akihisa

    2013-01-01

    A size effect on the fatigue-life cycles of a Zr 50 Cu 30 Al 10 Ni 10 (at.%) bulk metallic glass has been observed in the four-point-bending fatigue experiment. Under the same bending-stress condition, large-sized samples tend to exhibit longer fatigue lives than small-sized samples. This size effect on the fatigue life cannot be satisfactorily explained by the flaw-based Weibull theories. Based on the experimental results, this study explores possible approaches to modeling the size effects on the bending-fatigue life of bulk metallic glasses, and proposes two fatigue-life models based on the Weibull distribution. The first model assumes, empirically, log-linear effects of the sample thickness on the Weibull parameters. The second model incorporates the mechanistic knowledge of the fatigue behavior of metallic glasses, and assumes that the shear-band density, instead of the flaw density, has significant influence on the bending fatigue-life cycles. Promising predictive results provide evidence of the potential validity of the models and their assumptions.

  16. Rotating Square-Ended U-Bend Using Low-Reynolds-Number Models

    Directory of Open Access Journals (Sweden)

    Konstantinos-Stephen P. Nikas

    2005-01-01

    bend is better reproduced by the low-Re models. Turbulence levels within the rotating U-bend are underpredicted, but DSM models produce a more realistic distribution. Along the leading side, all models overpredict heat transfer levels just after the bend. Along the trailing side, the heat transfer predictions of the low-Re DSM with the NYap, are close to the measurements.

  17. Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

    Energy Technology Data Exchange (ETDEWEB)

    Haidyrah, Ahmed S., E-mail: ashdz2@mst.edu [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States); Nuclear Science Research Institute, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442 (Saudi Arabia); Newkirk, Joseph W. [Materials Science & Engineering, Missouri University of Science & Technology, 1440 N. Bishop Ave, Rolla, MO 65409 (United States); Castaño, Carlos H. [Nuclear Engineering, Missouri University of Science & Technology, 301 W. 14th, Rolla, MO 65409 (United States)

    2016-03-15

    A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

  18. Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

    International Nuclear Information System (INIS)

    Haidyrah, Ahmed S.; Newkirk, Joseph W.; Castaño, Carlos H.

    2016-01-01

    A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S–N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

  19. Fatigue Performance of SFPSC under Hot-Wet Environments and Cyclic Bending Loads

    Directory of Open Access Journals (Sweden)

    Shanshan Luo

    2018-01-01

    Full Text Available A new structural material named “steel fiber polymer structural concrete (SFPSC” with features of both high strength and high toughness was developed by this research group and applied to the bridge superstructures in the hot-wet environments. In order to investigate the fatigue performance and durability of SFPSC under hot-wet environments, the environment and fatigue load uncoupling method and the coupling action of environment and fatigue load were used or developed. Three-point bending fatigue experiments with uncoupling action of environments and cyclic loads were carried out for SFPSC specimens which were pretreated under hot-wet environments, and the experiments with the coupling action of environments and cyclic loads for SFPSC specimens were carried out under hot-wet environments. Then, the effects of hot-wet environments and the experimental methods on the fatigue mechanism of SFPSC material were discussed, and the environmental fatigue equations of SFPSC material under coupling and uncoupling action of hot-wet environments and cyclic bending loads were established. The research results show that the fatigue limits of SFPSC under the coupling action of the environments and cyclic loads were lower about 15%. The proposed fatigue equations could be used to estimate the fatigue lives and fatigue limits of SFPSC material.

  20. Experimental Study on Fatigue Behaviour of BFRP-Concrete Bond Interfaces under Bending Load

    Directory of Open Access Journals (Sweden)

    Jianhe Xie

    2018-01-01

    Full Text Available Basalt fiber reinforced polymer (BFRP composites are increasingly being used to retrofit concrete structures by external bonding. For such strengthened members, the BFRP-concrete interface plays the crucial role of transferring stresses. This study aims to investigate the fatigue behaviour of the interface under bending load. A series of tests were conducted on BFRP-concrete bonded joint, including static, fatigue, and postfatigue loading. The fatigue failure modes, the development of deflection, the evolution of BFRP strains, and the propagation of interfacial cracks were analysed. In addition, the debonding-induced fatigue life of BFRP-concrete bonded joints was studied. Finally, a new model of fatigue life was proposed by defining the effective fatigue bond stress. The results showed that the fatigue experience has a significant effect on the BFRP strength especially near the root of concrete transverse crack and on the bond performance of the adhesive near the interface crack tip. There are two main fatigue failure modes: BFRP rupture and BFRP debonding. The fatigue damage development of the bond interface has three stages: rapid, stable, and unstable growth. The proposed model for the debonding-induced fatigue life is more conservative for the BFRP-concrete bonded joints under pure shear load than for those under bending load.

  1. Rotary bending fatigue properties of Inconel 718 alloys by ultrasonic nanocrystal surface modification technique

    Directory of Open Access Journals (Sweden)

    Jun-Hyong Kim

    2015-08-01

    Full Text Available This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM technique on fatigue properties of SAE AMS 5662 (solution treatment of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue tester. Results revealed that the UNSM-treated specimens showed longer fatigue life in comparison with those of the untreated specimens. The improvement in fatigue life of the UNSM-treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analysed using a scanning electron microscopy (SEM in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.

  2. Three-point bending fatigue behavior of WC–Co cemented carbides

    International Nuclear Information System (INIS)

    Li, Anhai; Zhao, Jun; Wang, Dong; Gao, Xinliang; Tang, Hongwei

    2013-01-01

    Highlights: ► Mechanical fatigue tests were conducted on a specific designed jig. ► Three-point bending fatigue behavior of WC–Co cemented carbides was studied. ► Fatigue mechanisms of WC–Co cemented carbides with different WC grain sizes and Co binder contents were revealed. -- Abstract: WC–Co cemented carbides with different WC grain sizes and Co binder contents were sintered and fabricated. The three-point bending specimens with a single edge notch were prepared for tests. In the experiments, the mechanical properties of materials were investigated under static and cyclic loads (20 Hz) in air at room temperature. The fatigue behaviors of the materials under the same applied loading conditions are presented and discussed. Optical microscope and scanning electron microscopy were used to investigate the micro-mechanisms of damage during fatigue, and the results were used to correlate with the mechanical fatigue behavior of WC–Co cemented carbides. Experimental results indicated that the fatigue fracture surfaces exhibited more fracture origins and diversification of crack propagation paths than the static strength fracture surfaces. The fatigue fracture typically originates from inhomogeneities or defects such as micropores or aggregates of WC grains near the notch tip. Moreover, due to the diversity and complexity of the fatigue mechanisms, together with the evolution of the crack tip and the ductile deformation zone, the fatigue properties of WC–Co cemented carbides were largely relevant with the combination of transverse rupture strength and fracture toughness, rather than only one of them. Transverse rupture strength dominated the fatigue behavior of carbides with low Co content, whilst the fatigue behavior of carbides with high Co content was determined by fracture toughness.

  3. Fretting fatigue behavior of high-strength steel monostrands under bending load

    DEFF Research Database (Denmark)

    Winkler, Jan; Georgakis, Christos T.; Fischer, Gregor

    2015-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. To measure the local deformations on the strands, a novel method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires...... along the length of the monostrand. Information about the monostrand bending stiffness and the extent of relative displacement between core and outer wires of a monostrand undergoing flexural deformations is provided. From the series of dynamic fatigue tests, a fretting fatigue spectrum is derived...

  4. Improvement of the bending fatigue resistance of the hyper-eutectoid steel wires used for tire cords by a post-processing annealing

    International Nuclear Information System (INIS)

    Yang, Y.S.; Bae, J.G.; Park, C.G.

    2008-01-01

    In this study, the effects of annealing at a low temperature on the bending fatigue resistance have been investigated in the hyper-eutectoid steel wires drawn to an extreme strain of 4.12. The annealing temperature was varied from 100 to 500 deg. C. The bending fatigue resistance of the steel wires was measured by a Hunter rotating beam tester specially designed for thin-sized steel wires. The results showed that fatigue resistance as well as tensile strength improved as the annealing temperature increased up to 200 deg. C (Region I) and gradually decreased after annealing above 200 deg. C (Region II). In order to elucidate this behavior, residual stress was measured by dual beam FIB, surface defects observed by an optical 3D profiler and the microstructure in terms of lamellar spacing (λ p ) and cementite thickness (t c ) was observed by TEM

  5. Rotating Beam Fatigue Testing and Hybrid Ceramic Bearings.

    Science.gov (United States)

    1994-07-01

    Runout and Fast Fracture ......... 20 FIG.7 Stress-life Plots of Rotating Beam Fatigue Testing ............. 23 FIG.8 Fractograph of Rotating Beam...Chand-Kare Engineering Ceramics, Worcester, MA. Diamond wheels of 600 grits were used with longitudinal grinding applied for the final finishing of...stress in the range of 600-850 MPa. Three test completion modes were encountered, i.e. fast fracture at setup, fatigue fracture and runout (no failure

  6. Testing machine for fatigue crack kinetic investigation in specimens under bending

    International Nuclear Information System (INIS)

    Panasyuk, V.V.; Ratych, L.V.; Dmytrakh, I.N.

    1978-01-01

    A kinematic diagram of testing mashine for the investigation of fatigue crack kinetics in prismatic specimens, subjected to pure bending is described. Suggested is a technique of choosing an optimum ratio of the parameters of ''the testing machine-specimen'' system, which provide the stabilization of the stress intensity coefficient for a certain region of crack development under hard loading. On the example of the 40KhS and 15Kh2MFA steel specimens the pliability of the machine constructed according to the described diagram and designed for the 30ONxm maximum bending moment. The results obtained can be used in designing of the testing machines for studying pure bending under hard loading and in choosing the sizes of specimens with rectangular cross sections for investigations into the kinetics of the fatigue crack

  7. Fatigue testing of TBC on structural steel by cyclic bending

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Kovářík, O.; Medřický, Jan; Curry, N.; Bjorklund, S.; Nylen, P.

    2015-01-01

    Roč. 24, 1-2 (2015), s. 168-174 ISSN 1059-9630 R&D Projects: GA ČR(CZ) GPP108/12/P552 Institutional support: RVO:61389021 Keywords : atmospheric plasma spray * failure mechanism * fatigue * NiCoCrAlY * thermal barrier coatings * yttria-stabilized zirconia Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.568, year: 2015 http://link.springer.com/article/10.1007%2Fs11666-014-0180-4

  8. A comparison of two reciprocating instruments using bending stress and cyclic fatigue tests

    Directory of Open Access Journals (Sweden)

    Pantaleo SCELZA

    2015-01-01

    Full Text Available The aim of this study was to comparatively evaluate the bending resistance at 45º, the static and dynamic cyclic fatigue life, and the fracture type of the WaveOne (Dentsply Maillefer, Ballaigues, Switzerland 25-08 and Reciproc (VDW, Munich, Germany 25-08 instruments. A total of 60 nickel-titanium (NiTi instruments (30 Reciproc and 30 WaveOne from three different lots, each of which was 25 mm in length, were tested. The bending resistance was evaluated through the results of a cantilever-bending test conducted using a universal testing machine. Static and dynamic cyclic fatigue testing was conducted using a custom-made device. For the static and dynamic tests, a cast Ni-Cr-Mo-Ti alloy metal block with an artificial canal measuring 1.77 mm in diameter and 20.00 mm in total length was used. A scanning electron microscope was used to determine the type of fracture. Statistical analyses were performed on the results. The WaveOne instrument was less flexible than the Reciproc (p < 0.05. The Reciproc instrument showed better resistance in the static and dynamic cyclic fatigue tests (p < 0.05. The transverse cross-section and geometry of the instruments were important factors in their resistance to bending and cyclic fracture. Both of the instruments showed ductile-type fracture characteristics. It can be concluded that the Reciproc 25-08 instrument was more resistant to static and dynamic cyclic fatigue than the WaveOne 25-08 instrument, while the WaveOne 25-08 instrument was less flexible. Bending and resistance to cyclic fracture were influenced by the instruments’ geometries and transverse cross-sections. Both of the instruments showed ductile-type fracture characteristics.

  9. A dissipated energy comparison to evaluate fatigue resistance using 2-point bending

    Directory of Open Access Journals (Sweden)

    Cinzia Maggiore

    2014-02-01

    Full Text Available Fatigue is the main failure mode in pavement engineering. Typically, micro-cracks originate at the bottom of asphalt concrete layer due to horizontal tensile strains. Micro-cracks start to propagate towards the upper layers under repeated loading which can lead to pavement failure. Different methods are usually used to describe fatigue behavior in asphalt materials such as: phenomenological approach, fracture mechanics approach and dissipated energy approach. This paper presents a comparison of fatigue resistances calculated for different dissipated energy models using 2-point bending (2PB at IFSTTAR in Nantes. 2PB tests have been undertaken under different loading and environmental conditions in order to evaluate the properties of the mixtures (stiffness, dissipated energy, fatigue life and healing effect.

  10. Face/core debond fatigue crack growth characterization using the sandwich mixed mode bending specimen

    DEFF Research Database (Denmark)

    Manca, Marcello; Quispitupa, Amilcar; Berggreen, Christian

    2012-01-01

    Face/core fatigue crack growth in foam-cored sandwich composites is examined using the mixed mode bending (MMB) test method. The mixed mode loading at the debond crack tip is controlled by changing the load application point in the MMB test fixture. Sandwich specimens were manufactured using H45...... and H100 PVC foam cores and E-glass/polyester face sheets. All specimens were pre-cracked in order to define a sharp crack front. The static debond fracture toughness for each material configuration was measured at different mode-mixity phase angles. Fatigue tests were performed at 80% of the static...

  11. A comparison of two reciprocating instruments using bending stress and cyclic fatigue tests.

    Science.gov (United States)

    Scelza, Pantaleo; Harry, Davidowicz; Silva, Licinio Esmeraldo da; Barbosa, Igor Bastos; Scelza, Miriam Zaccaro

    2015-01-01

    The aim of this study was to comparatively evaluate the bending resistance at 45º, the static and dynamic cyclic fatigue life, and the fracture type of the WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) 25-08 and Reciproc (VDW, Munich, Germany) 25-08 instruments. A total of 60 nickel-titanium (NiTi) instruments (30 Reciproc and 30 WaveOne) from three different lots, each of which was 25 mm in length, were tested. The bending resistance was evaluated through the results of a cantilever-bending test conducted using a universal testing machine. Static and dynamic cyclic fatigue testing was conducted using a custom-made device. For the static and dynamic tests, a cast Ni-Cr-Mo-Ti alloy metal block with an artificial canal measuring 1.77 mm in diameter and 20.00 mm in total length was used. A scanning electron microscope was used to determine the type of fracture. Statistical analyses were performed on the results. The WaveOne instrument was less flexible than the Reciproc (p fatigue tests (p ductile-type fracture characteristics. It can be concluded that the Reciproc 25-08 instrument was more resistant to static and dynamic cyclic fatigue than the WaveOne 25-08 instrument, while the WaveOne 25-08 instrument was less flexible. Bending and resistance to cyclic fracture were influenced by the instruments' geometries and transverse cross-sections. Both of the instruments showed ductile-type fracture characteristics.

  12. Study of Bending Fatigue Properties of Al-Si Cast Alloy

    Directory of Open Access Journals (Sweden)

    Tillová E.

    2017-09-01

    Full Text Available Fatigue properties of casting Al-alloys are very sensitive to the microstructural features of the alloy (e.g. size and morphology of the eutectic Si, secondary dendrite arm spacing - SDAS, intermetallics, grain size and casting defects (porosity and oxides. Experimental study of bending fatigue properties of secondary cast alloys have shown that: fatigue tests up to 106-107cycles show mean fatigue limits of approx. 30-49 MPa (AlSi9Cu3 alloy - as cast state, approx. 65-76 MPa (AlSi9Cu3 alloy after solution treatment and 60-70 MPa (self-hardened AlZn10Si8Mg alloy in the tested casting condition; whenever large pore is present at or near the specimen’s surface, it will be the dominant cause of fatigue crack initiation; in the absence of large casting defects, the influence of microstructural features (Si morphology; Fe-rich phases on the fatigue performance becomes more pronounced.

  13. Fatigue Debond Growth in Sandwich Structures Loaded in Mixed Mode Bending (MMB)

    DEFF Research Database (Denmark)

    Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.

    2008-01-01

    Static and cyclic debond growth in sandwich specimens loaded in mixed mode bending (MMB) is examined. The MMB sandwich specimens were manufactured using H100 PVC foam core and E-glass/polyester non-crimp quadro-axial [0/45/90/-45]s DBLT-850 face sheets. Static test were performed to determine...... the fracture toughness of the debonded sandwich specimens at different mixed mode loadings. The mixed mode ratio (mode I to mode II) was controlled by changing the lever arm distance of the MMB test rig. Compliance technique and visual inspection was employed to measure the crack length during fatigue. Fatigue...... tests were performed at 90% of the static fracture toughness at a loading ratio of R=0.1. Fatigue results revealed higher debond crack growth rates when the lever arm distance was increased. For some specimens, the crack propagated just below the face/core interface in the foam core and for others...

  14. The Effects of Hot Bending on the Low Cycle Fatigue Behaviors of 347 SS in PWR Primary Environment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ho-Sub; Hong, Jong-Dae; Lee, Junho; Jang, Changheui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-10-15

    Fatigue damage could be significant for some locations, especially the welds and bends where stress concentration is typically high. As a possible solution, a large radius hot-bending method has been suggested to eliminate some weld joints and all tight bends. However, for the hot-bending process which involves a high temperature thermal cycle, there is a concern about changes in mechanical properties including low cycle fatigue behaviors. In APR1400, Type 347 SS have been used as surge line pipes. Therefore, to verify the applicability of hot-bending on 347 SS surge line pipes, an environmental fatigue test program was initiated. In this paper, the preliminary results of the on-going test program are introduced. Also, the low cycle fatigue behaviors of 347 SS are compared with those of other grade of stainless steels. The effects of hot bending on the low cycle fatigue behavior of 347 SS were quantitatively evaluated. The fatigue life was compared with the estimated values per NUREG 6909 rev. 1. There are no distinct differences between NUREG 6909 and LCF tests. According to fractography and cross section analysis in progress, basically, the reduction of LCF life of 347 SS in PWR water was caused by operation of HIC mechanism. The cyclic stress responses shows that there is no secondary hardening in 330 .deg.C air and PWR water.

  15. Fatigue crack behaviour: comparing three-point bend test and wedge splitting test data on vibrated concrete using Paris' law

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Thienpont, T.; De Corte, W.

    2017-01-01

    Roč. 11, č. 39 (2017), s. 110-117 ISSN 1971-8993 R&D Projects: GA MŠk LM2015069 Institutional support: RVO:68081723 Keywords : Fatigue crack behaviour * Tree-point bending test * Wedge splitting test * Self-compacting concrete Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  16. Evolution of microstructure and mechanical properties of Al 6061 alloy tube in cyclic rotating bending process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zicheng, E-mail: zhangzicheng2004@126.com [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo (Japan); Shao, Shuai [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Manabe, Ken-ichi [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo (Japan); Kong, Xiangwei [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Li, Yanmei [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, Liaoning (China)

    2016-10-31

    To refine the microstructure and improve the mechanical properties of metal tubes, a new concept of severe plastic deformation process of cyclic rotating bending (CRB) was newly introduced. The current study focused on the investigation of evolution of microstructure and mechanical properties of Al 6061 tube in the CRB process with different deformation conditions. For this purpose, the CRB processes were performed with different deformation temperatures, bending angles and deformation times. The tensile test and Vickers hardness test were employed to evaluate the tensile properties and micro-hardness of the tube, respectively. While the Optical Microscope and Scanning Electronic Microscope equipped with Electron Back-Scattered Diffraction were utilized for the microstructure characterizations. The results shows that the deformation temperature, bending angle and deformation time have the strong influences on the mechanical properties and microstructure of the tubes processed by the CRB process. As a result, the tube with an average grain size of about 55 µm, as well as ultimate tensile strength of 244 MPa and total elongation of 10.05% was successfully obtained with the optimized deformation condition of the CRB process with a temperature of 100 °C, bending angle of 174°, the rotation speed of 20 r/min, and deformation time of 5 min, respectively.

  17. Corrosion fatigue studies on a bulk glassy Zr-based alloy under three-point bending

    Science.gov (United States)

    Grell, Daniel; Wilkin, Yannic; Gostin, Petre F.; Gebert, Annett; Kerscher, Eberhard

    2016-12-01

    Corrosion fatigue (CF) tests were carried out on bulk glassy Zr52.5Cu17.9Al10Ni14.6Ti5 (Vitreloy 105) samples under load-controlled three-point bending conditions with a load ratio of R = 0.1 in 0.01 M Na2SO4 + 0.01 M NaCl electrolyte. During cyclic testing, the bar-shaped specimens were polarized in situ at constant potentials and the current was monitored. Three different anodic potentials within the interval between the pitting potential EP and the repassivation potential ER, and three different load amplitudes were applied. In some cases, in situ microscopic observations revealed the formation of black corrosion products in the vicinity of the crack tip during anodic polarization. Fractographic analysis revealed a clear distinction between two modes of crack growth characterized by smooth dissolution induced regions on the one hand and slim fast fracture areas on the other hand. Both alternating features contributed to a broad striated corrosion fatigue fracture surface. Moreover, further fatigue tests were carried out under free corrosion conditions yielding additional information on crack initiation and crack propagation period by means of the open circuit potential (OCP) changes. Thereby, a slight increase in OCP was detected after rupture of the passive layer due to bare metal exposed to the electrolyte. The electrochemical response increased continuously according to stable crack propagation until fracture occurred. Finally, the fracture surfaces of the corrosion fatigue samples were investigated by energy dispersive X-ray with the objective of analyzing the elemental distribution after anodic dissolution. Interestingly, anodic polarization at a near repassivation potential of -50 mV vs. SCE (Saturated Calomel Electrode, E = 0.241 V vs. SHE, Standard Hydrogen Electrode) led to favorable effects on the fatigue lifetime. In conclusion, all results are conflated to a corrosion fatigue model for bulk glassy Vitreloy 105 under anodic polarization in chloride

  18. A New High-Speed, High-Cycle, Gear-Tooth Bending Fatigue Test Capability

    Science.gov (United States)

    Stringer, David B.; Dykas, Brian D.; LaBerge, Kelsen E.; Zakrajsek, Andrew J.; Handschuh, Robert F.

    2011-01-01

    A new high-speed test capability for determining the high cycle bending-fatigue characteristics of gear teeth has been developed. Experiments were performed in the test facility using a standard spur gear test specimens designed for use in NASA Glenn s drive system test facilities. These tests varied in load condition and cycle-rate. The cycle-rate varied from 50 to 1000 Hz. The loads varied from high-stress, low-cycle loads to near infinite life conditions. Over 100 tests were conducted using AISI 9310 steel spur gear specimen. These results were then compared to previous data in the literature for correlation. Additionally, a cycle-rate sensitivity analysis was conducted by grouping the results according to cycle-rate and comparing the data sets. Methods used to study and verify load-path and facility dynamics are also discussed.

  19. A numerical study on the flow development around a rotating square-sectioned U-Bend( II )

    International Nuclear Information System (INIS)

    Lee, Gong Hee; Baek, Je Hyun

    2002-01-01

    The present study investigates in detail the combined effects of the Coriolis force and centrifugal force on the development of turbulent flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a curved region of U-bend, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal force due to the curvature of U-bend. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct. On the other hand, under negative rotation, where these two forces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces. Under the condition that the value of Rossby number and curvature ratio is large, the flow field in a rotating U-bend can be represented by two dimensionless parameters : K LC = Re 1/4 / √ λ and a body force ratio F= λ/Ro. Here, K TC has the same dynamical meaning as K LC = Re/√ λ for laminar flow

  20. On measuring the UNK SC-dipole bending strength with rotating pick-up coil

    International Nuclear Information System (INIS)

    Smirnov, N.L.; Tikhov, A.V.

    1993-01-01

    The experience in measuring the SC-dipole bending strength with the spotting method shown this measurement to be the most complicated and expensive. A convenient and simple method of rotating pick-up coil, which can not provide the required accuracy, may be used for this measurement combined with NMR measurements in the dipole central part. The physical ground and description of the method are given in the paper. The analysis of the errors and measurement results of the SPDMI SC-dipoles are presented. 9 refs..; 7 figs

  1. Rotary bending fatigue behavior of A356 –T6 aluminum alloys by vacuum pressurizing casting

    Directory of Open Access Journals (Sweden)

    Yong-qin Liu

    2015-09-01

    Full Text Available Vacuum pressurizing casting technique, providing better mould filling and inter-dendritic feeding, can reduce the porosity greatly in cast aluminum alloys, and improve the fatigue properties. The rotary bending fatigue properties of A356-T6 alloys prepared by vacuum pressurizing casting were investigated. The S-N curve and limit strength 90 MPa under fatigue life of 107 cycles were obtained. The analyses on the fatigue fractography and microstructure of specimens showed that the fatigue fracture mainly occurs at the positions with casting defects in the subsurface, especially at porosities regions, which attributed to the crack propagation during the fatigue fracture process. Using the empirical crack propagation law of Pairs-Erdogon, the quantitative relationship among the initial crack size, fatigue life and applied stress was established. The fatigue life decreases with an increase in initial crack size. Two constants in the Pairs-Erdogon equation of aluminum alloy A356-T6 were calculated using the experimental data.

  2. Proton irradiation effects on tensile and bend-fatigue properties of welded F82H specimens

    Energy Technology Data Exchange (ETDEWEB)

    Saito, S., E-mail: saito.shigeru@jaea.go.j [JAEA Tokai, J-PARC Center, 2-4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Kikuchi, K.; Hamaguchi, D. [JAEA Tokai, J-PARC Center, 2-4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Usami, K.; Ishikawa, A.; Nishino, Y.; Endo, S. [JAEA Tokai, Department of Hot Laboratories, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Kawai, M. [KEK, Tsukuba-shi, Ibaraki-ken 305-0801 (Japan); Dai, Y. [PSI, Spallation Source Division, 5232 Villigen PSI (Switzerland)

    2010-03-15

    In several institutes, research and development for an accelerator-driven transmutation system (ADS) have been progressed. Ferritic/martensitic (FM) steels are the candidate materials for the beam window of ADS. To evaluate of the mechanical properties of the irradiated materials, the post irradiation examination (PIE) work of the SINQ (Swiss spallation neutron source) target irradiation program (STIP) specimens was carried out at JAEA. In present study, the results of PIE on FM steel F82H and its welded joint have been reported. The present irradiation conditions of the specimens were as follows: proton energy was 580 MeV. Irradiation temperatures were ranged from 130 to 380 deg. C, and displacement damage level was ranged from 5.7 to 11.8 dpa. The results of tensile tests performed at 22 deg. C indicated that the irradiation hardening occurred with increasing the displacement damage up to 10.1 dpa at 320 deg. C irradiation. At higher dose (11.8 dpa) and higher temperature (380 deg. C), irradiation hardening was observed, but degradation of ductility was relaxed in F82H welded joint. In present study, all specimens kept its ductility after irradiation and fractured in ductile manner. The results on bend-fatigue tests showed that the fatigue life (N{sub f}) of F82H base metal irradiated up to 6.3 dpa was almost the same with that of unirradiated specimens. The N{sub f} of the specimens irradiated up to 9.1 dpa was smaller than that of unirradiated specimens. Though the number of specimen was limited, the N{sub f} of F82H EB (15 mm) and EB (3.3 mm) welded joints seemed to increase after irradiation and the fracture surfaces of the specimens showed transgranular morphology. While F82H TIG welded specimens were not fractured by 10{sup 7} cycles.

  3. The Effect of Fatigued External Rotator Muscles of the Shoulder on the Shoulder Position Sense

    Directory of Open Access Journals (Sweden)

    Naoya Iida

    2011-10-01

    Full Text Available This study aimed to investigate the effect of fatigue in shoulder external rotator muscles on position sense of shoulder abduction, internal rotation, and external rotation. The study included 10 healthy subjects. Shoulder position sense was measured before and after a fatigue task involving shoulder external rotator muscles. The fatigue task was performed using an isokinetic machine. To confirm the muscle fatigue, electromyography (EMG was recorded, and an integrated EMG and median power frequency (MDF during 3 sec performed target torque were calculated. After the fatigue task, the MDF of the infraspinatus muscle significantly decreased. This indicates that the infraspinatus muscle was involved in the fatigue task. In addition, the shoulder position sense of internal and external rotation significantly decreased after the fatigue task. These results suggest that the fatigue reduced the accuracy of sensory input from muscle spindles. However, no significant difference was observed in shoulder position sense of abduction before and after the fatigue task. This may be due to the fact that infraspinatus muscle did not act as prime movers in shoulder abduction. These results suggest that muscle fatigue decreased position sense during movements in which the affected muscles acted as prime movers.

  4. Effect of membrane and through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity

    International Nuclear Information System (INIS)

    Yoo, Yeon-Sik

    2003-11-01

    This study clarified the effect of a membrane and a through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity due to irregularity of crack surface. Each stress component relates to fatigue crack growth behavior directly in general and thus the wild-used K I solutions are anticipated to give good evaluation results on it. Meanwhile, it is necessary to notify that surface irregularity for coolant leakage assessment is made by stress history in nature. Surface irregularity is known to be largely classified into the following two aspects: surface roughness due to continuous crack opening and closure behavior and surface turnover due to cyclic bending stress dominance. Therefore, the deterministic parameters on resistance of coolant leakage by surface irregularity are considered to be not only stress history but crack opening behavior. (author)

  5. Modelling of pavement materials on steel decks using the five-point bending test: Thermo mechanical evolution and fatigue damage

    International Nuclear Information System (INIS)

    Arnaud, L; Houel, A

    2010-01-01

    This paper deals with the modelling of wearing courses on steel orthotropic decks such as the Millau viaduct in France. This is of great importance when dealing with durability: due to the softness of such a support, the pavement is subjected to considerable strains that may generate top-down cracks in the layer at right angles of the orthotropic plate stiffeners and shear cracks at the interface between pavement and steel. Therefore, a five-point bending fatigue test was developed and improved since 2003 at the ENTPE laboratory, to test different asphalt concrete mixes. This study aims at modelling the mechanical behavior of the wearing course throughout the fatigue test by a finite element method (Comsol Multiphysics software). Each material - steel, sealing sheet, asphalt concrete layer - is considered and modelled. The modelling of asphalt concrete is complex since it is a heterogeneous material, a viscoelastic medium and it thermosensitive. The actual characteristics of the asphalt concrete (thermo physical parameter and viscoelastic complex modulus) are determined experimentally on cylindrical cores. Moreover, a damage law based on Miner's damage is included in the model. The modelling of the fatigue test leads to encouraging results. Finally, results from the model are compared to the experimental data obtained from the five-point bending fatigue test device. The experimental data are very consistent with the numerical simulation.

  6. Technical report on the fatigue crack Growth Benchmark based on CEA pipe bending tests

    International Nuclear Information System (INIS)

    2001-07-01

    In order to improve the estimation methods of surface crack propagation through the thickness of components, CEA has proposed a benchmark to members of the IAGE WG, sub-group on Integrity of metal components and structures. The subject is a simple configuration of a pipe containing an axisymmetric notch and submitted to a cyclic bending load. An experimental data-set form CEA was used to validate three issues in the topic of Leak Before Break. - Crack initiation, - Crack propagation through the thickness, - Crack penetration. All material and geometrical data which are necessary for the simulation were given in the proposal, including experimental results. Due to the peculiar complexity of the problem, it was decided to focus the work on methodologies comparison so as to allow participants to tune up parameters and adjust their models and tools. This report presents all estimations performed by the participants and collected by CEA. They are compared to the experimental results. An analysis of the used procedures is also proposed. This, associated with the study of the accuracy of different methodologies, leads to comments and recommendations on the analysis of fatigue crack growth. The participation in the first step was important: nine participants have proposed analyses, sometimes parametric analysis to estimate crack growth. Results sorted out three estimation methods groups that give results in accordance with experimental ones (these three groups are based on a strain range evaluation and the fatigue curve of the material): - The use of an elastic stress at the notch tip and a fatigue notch concentration factor to determine the strain range. - The use of a KI (or elastic F.E. calculation) and a Neuber rule for the estimation of the strain range at a characteristic distance from the crack tip. - The direct calculation of the strain range at the characteristic distance by an elastic plastic F.E. calculation. Only 4 participants have proposed an estimate of the

  7. MEMS device for bending test: measurements of fatigue and creep of electroplated nickel

    DEFF Research Database (Denmark)

    Larsen, Kristian Pontoppidan; Rasmussen, Anette Alsted; Ravnkilde, Jan Tue

    2003-01-01

    In situ bending test devices with integrated electrostatic actuator were fabricated in electroplated nanocrystalline nickel. The device features approximately pure in-plane bending of the test beam. The excitation of the test beam has fixed displacement amplitude as the actuation electrodes...

  8. A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

    Science.gov (United States)

    Keivani, M.; Abadian, N.; Koochi, A.; Mokhtari, J.; Abadyan, M.

    2016-10-01

    It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners.

  9. Microstructural changes of AISI 316L due to structural sensitization and its influence on the fatigue properties

    Czech Academy of Sciences Publication Activity Database

    Dundeková, S.; Nový, F.; Fintová, Stanislava

    2014-01-01

    Roč. 21, č. 4 (2014), s. 172-177 ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : AISI 316L * Structural sensitization * Rotating bending fatigue test Subject RIV: JL - Materials Fatigue, Friction Mechanics

  10. Bending fatigue tests on SiC-Al tapes under alternating stress at room temperature

    Science.gov (United States)

    Herzog, J. A.

    1981-01-01

    The development of a testing method for fatigue tests on SiC-Al tapes containing a small amount of SiC filaments under alternating stress is reported. The fatigue strength curves resulting for this composite are discussed. They permit an estimate of its behavior under continuous stress and in combination with various other matrices, especially metal matrices.

  11. Is rotating between static and dynamic work beneficial for our fatigue state?

    NARCIS (Netherlands)

    Luger, T.; Bosch, T.; Hoozemans, M.J.M.; Veeger,D.H.E.J.; Looze, M.P. de

    2016-01-01

    Shoulder disorders comprise a large part of work-related musculoskeletal disorders. Risk factors, such as repetitiveness and monotony, may cause muscle fatigue and be attenuated by task rotation. We investigated rotation between a dynamic box-lifting task and a relatively static pick-and-place task

  12. Stress analysis and fatigue life prediction for a U-bend steam generator tube

    International Nuclear Information System (INIS)

    Cheng Weili; Finnie, I.

    1996-01-01

    An analysis is carried out to determine the stresses in a steam generator tube that failed by fatigue. Using data available for the failed tube and for failures in two similar steam generators, the magnitudes of the alternating and mean stresses produced during operation are estimated. The cause for the early fatigue failure is shown to be the high mean stress caused by denting of the tube in the location where it passed through the tube sheet. (orig.)

  13. Rotary Bending Fatigue Characteristics According to Optimal Friction Welding of SF45 to SM45C Steel Bars

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Yu Sik; Park, Young Whan [Pukyong Nat’l Univ., Busan (Korea, Republic of)

    2017-03-15

    A study on dissimilar friction-welded joints was performed for cam shaft applications using solid bar samples, 20mm in diameter, of forging steel(SF45) and carbon steel(SM45C). The main parameters of friction welding such as tensile tests, Vickers hardness surveys of the bond of area, the heat affected zone (HAZ), and the observation of microstructure were investigated to ensure a good quality of friction welding through visual observations. The specimens were tested as-welded and post weld heat treatment(PWHT). This paper deals with optimizing the welding conditions and analyzing various rotary bending fatigue test(RBFT) properties about heat-treated base metal(BM), as-welded and PWHT. Consequently, two materials for friction welding are strongly mixed with a well-combined structure of micro-particles without any molten material, particle growth, or any defect. Moreover, the fatigue limit of BM(SF45) and PWHT for the RBFT were observed as 180MPa and 250MPa, respectively. It was confirmed that the PWHT causes approximately 40% improvement in the fatigue limit when compared to the BM(SF45).

  14. Evolution of dislocation structure and fatigue crack behavior in Fe-Si alloys during cyclic bending test

    International Nuclear Information System (INIS)

    Ushioda, Kohsaku; Takebayashi, Shigeto; Goto, Shoji; Komatsu, Yoshinari; Hoshino, Akinori

    2010-01-01

    The evolution of dislocation structures was investigated by means of TEM in Fe-Si alloys with 0, 0.5 and 1.0 mass% Si during a cyclic bending test in conjunction with fatigue crack behavior. The addition of Si increased the fatigue strength. In steel without Si the cell structure develops, whereas in steel with 1%Si the vein structure evolves, which is considered to lead to the increased fatigue strength. The cell structure in 0%Si steel is postulated to be caused by the easy cross slip of dislocations, whereas the vein structure in the steels with Si is inferred to be caused by the difficulty in cross slip presumably due to the decrease in stacking fault energy. Furthermore, the steel containing Si shows a dislocation free zone (DFZ) along grain boundaries. A transgranular fracture takes place in 0%Si steel, while in 1%Si steel many intergranular cracks were observed just beneath the top surface, which was thought to be caused by the fact that a) strains are dispersed within grains owing to the vein structure and b) micro cracks are initiated and propagated along a DFZ.

  15. Rotary Bending Fatigue Characteristics According to Optimal Friction Welding of SF45 to SM45C Steel Bars

    International Nuclear Information System (INIS)

    Kong, Yu Sik; Park, Young Whan

    2017-01-01

    A study on dissimilar friction-welded joints was performed for cam shaft applications using solid bar samples, 20mm in diameter, of forging steel(SF45) and carbon steel(SM45C). The main parameters of friction welding such as tensile tests, Vickers hardness surveys of the bond of area, the heat affected zone (HAZ), and the observation of microstructure were investigated to ensure a good quality of friction welding through visual observations. The specimens were tested as-welded and post weld heat treatment(PWHT). This paper deals with optimizing the welding conditions and analyzing various rotary bending fatigue test(RBFT) properties about heat-treated base metal(BM), as-welded and PWHT. Consequently, two materials for friction welding are strongly mixed with a well-combined structure of micro-particles without any molten material, particle growth, or any defect. Moreover, the fatigue limit of BM(SF45) and PWHT for the RBFT were observed as 180MPa and 250MPa, respectively. It was confirmed that the PWHT causes approximately 40% improvement in the fatigue limit when compared to the BM(SF45).

  16. Study on Blade Fatigue Life of Rotating Power Machinery

    Directory of Open Access Journals (Sweden)

    Fu Xi

    2016-01-01

    Full Text Available The linear damage model (LDM is widely applied in engineering calculation, but it does not consider the relationship between damage variable and load parameters. Therefore, the life prediction based on LDM is not satisfied for the aero-engine blades. Besides, it easily brings about error in predicting fatigue life by common nonlinear damage model which neglect the influence of torsional stress. Hence, a modified nonlinear continuum damage model (CDM is put forward based on Chaboche nonlinear damage model in this research. And to determine the damage and fatigue life of TC4 material used in aero-engine blades, axial tension and compression fatigue test is conducted. Compared with LDM results, the fatigue life prediction results of the modified CDM in this work show a good agreement with the tests data. So the correctness of the modified model is verified. Finally, the fatigue life of a certain aero-engine high pressure compressor blade is predicted by the modified nonlinear continuum damage model.

  17. Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings

    Czech Academy of Sciences Publication Activity Database

    Kovářík, O.; Haušild, P.; Čapek, J.; Medřický, Jan; Siegl, J.; Mušálek, Radek; Pala, Zdeněk; Curry, N.; Bjorklund, S.

    2016-01-01

    Roč. 82, January (2016), s. 300-309 ISSN 0142-1123. [International Conference on Fatigue Damage of Structural Materials Conference/10./. Massachusetts, 21.09.2014-26.09.2014] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Crack detection * Damping * Fatigue * Hastelloy-X * Nondestructive test ing Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 2.899, year: 2016 http://www.sciencedirect.com/science/article/pii/S0142112315002443

  18. Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings

    Czech Academy of Sciences Publication Activity Database

    Kovářík, O.; Haušild, P.; Čapek, J.; Medřický, Jan; Siegl, J.; Mušálek, Radek; Pala, Zdeněk; Curry, N.; Bjorklund, S.

    2016-01-01

    Roč. 82, January (2016), s. 300-309 ISSN 0142-1123. [International Conference on Fatigue Damage of Structural Materials Conference/10./. Massachusetts, 21.09.2014-26.09.2014] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Crack detection * Damping * Fatigue * Hastelloy-X * Nondestructive testing Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 2.899, year: 2016 http://www.sciencedirect.com/science/article/pii/S0142112315002443

  19. The Prediction of Fatigue Life Based on Four Point Bending Test

    NARCIS (Netherlands)

    Pramesti, F.P.; Molenaar, A.A.A.; Van de Ven, M.F.C.

    2013-01-01

    To be able to devise optimum strategies for maintenance and rehabilitation, it is essential to formulate an accurate prediction of pavement life and its maintenance needs. One of the pavement life prediction methods is based on the pavement's capability to sustain fatigue. If it were possible to

  20. An advanced revised universal slope method for low cycle fatigue evaluation of elbow piping subjected to in-plane cyclic bending displacement

    International Nuclear Information System (INIS)

    Urabe, Yoshio

    2015-01-01

    In order to rationalize the low cycle fatigue evaluation of elbow piping subjected to in-plane cyclic bending displacement, an advanced revised universal slope method is proposed. In the proposed method, the coefficient of the first term of the fatigue life equation which resembles Manson's equation is expressed by parameters of the multi-axial degree, the tensile strength and the fracture strength. Also, the coefficient of the second term is expressed by the multi-axial degree, the fracture ductility and the minimum fracture ductility under the maximum multi-axial degree. Here equivalent strain range is used for the fatigue life estimation. The previously carried out pipe elbow test data were reanalyzed using the proposed method. As the result, the experimentally obtained fatigue lives had considerably good coincidences with the predicted fatigue lives by the proposed method. Application of the proposed method is also discussed. (author)

  1. Study on deformation behavior and life evaluation method for SUS304 notched plate under bending creep fatigue loading

    International Nuclear Information System (INIS)

    Fukuda, Yoshio; Satoh, Yoshimi; Nakamura, Kazuhiro; Takahashi, Yukio; Kuwabara, Kazuo.

    1990-01-01

    Creep-fatigue tests were carried out on notched plates under cyclic bending loads out of plane at 550degC, and the local strain at the notch-root and micro crack propagation behavior were measured. Then, inelastic analysis was performed for the experiment by using three kinds of constitutive models, such as kinematic hardening, ORNL and Ohno models. From the comparison of the experiment with the results of analysis, the following conclusions were obtained. (1) Creep strain caused at the notch-root during load holding was negligibly small compared with plastic strain, so that the neighborhood of the notch-root is subjected to constrained strain type damage. (2) The strain range at the notch-root can be calculated from the results of elastic-plastic analysis for monotonic loading independent of the constitutive models used, where the cyclic stress-strain relationship was used as the material monotonic deformation property. (3) The mean strain calculated was consistent with the experimental value in case of kinematic hardening or ORNL model, while not in case of Ohno model. (4) A method for predicting the crack initiation life of a notched plate has been proposed on the basis of micro-crack propagation behavior obtained by a fundamental creep-fatigue test. (author)

  2. Fatigue performance of TBCs on Hastelloy X substrate during cyclic bending

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Kovářík, O.; Tomek, L.; Medřický, Jan; Pala, Zdeněk; Haušild, P.; Čapek, J.; Kolařík, K.; Curry, N.; Bjorklund, S.

    2016-01-01

    Roč. 25, 1-2 (2016), s. 231-243 ISSN 1059-9630. [ITSC 2015: International Thermal Spray Conference and Exposition. Long Beach, California, 11.05.2015-14.05.2015] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : atmospheric plasma spray * failure mechanism * fatigue * HVAF * NiCoCrAlY * thermal barrier coatings * yttria-stabilized zirconia Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.488, year: 2016 http://link.springer.com/article/10.1007%2Fs11666-015-0321-4

  3. Low cycle fatigue of pressurized pipes with circumferential flaws under cyclic bending moment

    International Nuclear Information System (INIS)

    Stoppler, W.; Sturm, D.

    1993-01-01

    Pipes of 706 mm inner diameter, 47 mm wall thickness and about 5,000 mm in length were provided with circumferential surface cracks and loaded by internal pressure of 15 MPa whilst being simultaneously subjected to an alternating external bending moment. Usually a load ratio R of -1 (M min /M max ), in one case R = 0.1, was applied. The pipes were fabricated of two types of ferritic steel: one, grade 20 MnMoNi 5 5, with a high upper shelf impact energy of about 200 J and one, MnMoNiV-special melt, with a low upper shelf impact energy of about 60 J. Deformation and crack growth in the wall thickness and circumferential direction were determined and compared with calculated values. 9 refs., 13 figs

  4. Competitive swimmers with hypermobility have strength and fatigue deficits in shoulder medial rotation

    DEFF Research Database (Denmark)

    Liaghat, Behnam; Juul-Kristensen, Birgit; Frydendal, Thomas

    2018-01-01

    rotation (60°/s). Swimmers with GJHS showed significantly larger isokinetic fatigue at 180°/s (0.321 J/repetition; p = .010), and tendencies to lower levels of muscle activity in infraspinatus (20%, p = .066) and pectoralis major (34%, p = .092) at 60°/s during medial rotation. Young competitive swimmers...... rotations. Totally, 38 competitive swimmers (aged 13-17 years) participated, 19 were competitive swimmers with GJHS and 19 were age, sex and club matched swimmers without GJHS. Concentric isokinetic force in medial and lateral rotations were measured at 60°/s (5 repetitions) and 180°/s (10 repetitions...

  5. Influence of rotational speed on the cyclic fatigue of rotary nickel-titanium endodontic instruments.

    Science.gov (United States)

    Lopes, Hélio P; Ferreira, Alessandra A P; Elias, Carlos N; Moreira, Edson J L; de Oliveira, Júlio C Machado; Siqueira, José F

    2009-07-01

    During the preparation of curved canals, rotary nickel-titanium (NiTi) instruments are subjected to cyclic fatigue, which can lead to instrument fracture. Although several factors may influence the cyclic fatigue resistance of instruments, the role of the rotational speed remains uncertain. This study was intended to evaluate the effects of rotational speed on the number of cycles to fracture of rotary NiTi instruments. ProTaper Universal instruments F3 and F4 (Maillefer SA, Ballaigues, Switzerland) were used in an artificial curved canal under rotational speeds of 300 rpm or 600 rpm. The artificial canal was made of stainless steel, with an inner diameter of 1.5 mm, total length of 20 mm, and arc at the end with a curvature radius of 6 mm. The arc length was 9.4 mm and 10.6 mm on the straight part. The number of cycles required to fracture was recorded. Fractured surfaces and the helical shafts of the fractured instruments were analyzed by scanning electron microscopy. The results showed approximately a 30% reduction in the observed number of cycles to fracture as rotational speed was increased from 300 to 600 RPM (p ductile type, and no plastic deformation was observed on the helical shaft of fractured instruments. The present findings for both F3 and F4 ProTaper instruments revealed that the increase in rotational speed significantly reduced the number of cycles to fracture.

  6. Cyclic fatigue resistance of newly manufactured rotary nickel titanium instruments used in different rotational directions.

    Science.gov (United States)

    Gambarini, Gianlucca; Gergi, Richard; Grande, Nicola Maria; Osta, Nada; Plotino, Gianluca; Testarelli, Luca

    2013-12-01

    The aim of this study was to investigate whether cyclic fatigue resistance is increased for nickel titanium instruments manufactured with improved heating processes in clockwise or counterclockwise continuous rotation. The instruments compared were produced either using the R-phase heat treatment (K3XF; SybronEndo, Orange, CA, USA) or the M-wire alloy (ProFile Vortex; DENTSPLY Tulsa Dental Specialties, Tulsa, OK, USA). Tests were performed with a specific cyclic fatigue device that evaluated cycles to failure of rotary instruments in curved artificial canals. Results indicated no significant difference in resistance to cyclic fatigue when rotary nickel titanium instruments are used in clockwise or counterclockwise continuous rotation. In both directions of rotation, size 04-25 K3XF showed a significant increase (P < 0.05) in the mean number of cycles to failure when compared with size 04-25 ProFile Vortex. © 2012 The Authors. Australian Endodontic Journal © 2012 Australian Society of Endodontology.

  7. Effect of bimodal grain size distribution on fatigue properties of Ti-6Al-4V alloy with harmonic structure under four-point bending

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Shoichi, E-mail: kikuchi@mech.kobe-u.ac.jp [Department of Mechanical Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501 (Japan); Hayami, Yosuke; Ishiguri, Takayuki [Graduate School of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577 (Japan); Guennec, Benjamin; Ueno, Akira; Ota, Mie; Ameyama, Kei [Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)

    2017-02-27

    Titanium alloy (Ti-6Al-4V) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network structure of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. The microstructure of the sintered compacts was characterized using electron backscattered diffraction (EBSD). The areal fraction of the fine-grained structure in the harmonic structure tended to increase with the milling time. Tensile tests and four-point bending fatigue tests at a stress ratio of 0.1 were performed in air at room temperature. The tensile strength, 0.2% proof stress and fatigue limit of Ti-6Al-4V alloy with harmonic structure tended to increase as the areal fraction of the fine-grained structure increased. In contrast, elongation decreased due to the formation of a high areal fraction of the fine-grained structure (79.0%), which resulted in a reduction of the fatigue life with a low cycle regime. Thus, titanium alloy with high strength, ductility and fatigue resistance can be formed by optimization of the milling conditions. Furthermore, the mechanism for fatigue fracture of the Ti-6Al-4V alloy with a harmonic structure is discussed with respect to fractography and crystallography. A fatigue crack was initiated from the α-facet of the coarse-grained structure in the harmonic structure.

  8. Correlation between the bending strength and the thickness interlayer of alumina-mild steel friction welded at lower rotational speed

    International Nuclear Information System (INIS)

    Mohamad Zaky Noh; Luay Bakir Hussain; Zainal Arifin Ahmad

    2007-01-01

    The joining of ceramic-metal could be done through a few techniques: brazing, diffusion bonding, friction welding etc. However, the mechanism of ceramic-metal joining was still not properly understood. In this study, alumina rod was bonded to mild steel rod via friction welding technique by using Al 1100 sheet as interlayer. The diameter of the rods was 10 mm. Friction pressure of 20 MPa and forging pressure of 40 MPa were used. Rotational speeds were maintained at 900 rpm and friction times of 2 to 20 seconds were applied. The joining strength was determined through four point bending test. The maximum bending strength, 240 MPa was obtained at the friction times of 20 seconds. Under optical microscope and SEM observation, the deformation of the aluminum interface was clearly obtained. Mechanical interlocking and close contact between the alumina aluminum and aluminum-mild steel were observed at magnifications of 3000X. The strength of alumina-steel bonding is much dependent on the wettability of the alumina surface by the molten aluminum and the existing of mechanical interlocking between interlayer and sample materials. (Author)

  9. Shoulder External Rotation Fatigue and Scapular Muscle Activation and Kinematics in Overhead Athletes

    Science.gov (United States)

    Joshi, Mithun; Thigpen, Charles A.; Bunn, Kevin; Karas, Spero G.; Padua, Darin A.

    2011-01-01

    Context: Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern. Objective: To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes. Setting: Human performance research laboratory. Design: Descriptive laboratory study. Patients or Other Participants: Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side. Interventions: We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction. Main Outcome Measure(s): Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences. Results: We found a decrease in ascending-phase and descending-phase lower trapezius activity (F1,25 = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F1,25 = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F1,24 = 3.7, P = .04) postfatigue. Conclusions: The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular

  10. Static-transmission-error vibratory-excitation contributions from plastically deformed gear teeth caused by tooth bending-fatigue damage

    Science.gov (United States)

    Mark, W. D.; Reagor, C. P.

    2007-02-01

    To assess gear health and detect gear-tooth damage, the vibratory response from meshing gear-pair excitations is commonly monitored by accelerometers. In an earlier paper, strong evidence was presented suggesting that, in the case of tooth bending-fatigue damage, the principal source of detectable damage is whole-tooth plastic deformation; i.e. yielding, rather than changes in tooth stiffness caused by tooth-root cracks. Such plastic deformations are geometric deviation contributions to the "static-transmission-error" (STE) vibratory excitation caused by meshing gear pairs. The STE contributions caused by two likely occurring forms of such plastic deformations on a single tooth are derived, and displayed in the time domain as a function of involute "roll distance." Example calculations are provided for transverse contact ratios of Qt=1.4 and 1.8, for spur gears and for helical-gear axial contact ratios ranging from Qa=1.2 to Qa=3.6. Low-pass- and band-pass-filtered versions of these same STE contributions also are computed and displayed in the time domain. Several calculations, consisting of superposition of the computed STE tooth-meshing fundamental harmonic contribution and the band-pass STE contribution caused by a plastically deformed tooth, exhibit the amplitude and frequency or phase modulation character commonly observed in accelerometer-response waveforms caused by damaged teeth. General formulas are provided that enable computation of these STE vibratory-excitation contributions for any form of plastic deformation on any number of teeth for spur and helical gears with any contact ratios.

  11. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Masanori, E-mail: ando.masanori@jaea.go.jp; Takaya, Shigeru, E-mail: takaya.shigeru@jaea.go.jp

    2016-12-15

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  12. Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel Part II: Plate bending test and proposal of a simplified evaluation method

    International Nuclear Information System (INIS)

    Ando, Masanori; Takaya, Shigeru

    2016-01-01

    Highlights: • Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel is proposed. • A simplified evaluation method is also proposed for the codification. • Both proposed evaluation method was validated by the plate bending test. • For codification, the local stress and strain behavior was analyzed. - Abstract: In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for evaluating the creep-fatigue life of Mod.9Cr-1Mo steel weld joints was proposed based on finite element analysis (FEA) and a series of cyclic plate bending tests of longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and the failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. Inelastic FEA models consisting of the base metal, heat-affected zone and weld metal were employed to estimate the elastic follow-up behavior caused by the metallurgical discontinuities. The elastic follow-up factors determined by comparing the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints. The creep-fatigue life obtained using the plate bending test was compared to those estimated from the results of inelastic FEA and by a simplified evaluation method.

  13. Fatigue

    Science.gov (United States)

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  14. Tension and fatigue behavior of 316LVM 1x7 multi-strand cables used as implantable electrodes.

    Science.gov (United States)

    Lewandowski, John J; Varadarajan, Ravikumar; Smith, Brian; Tuma, Chris; Shazly, Mostafa; Vatamanu, Luciano O

    2008-07-15

    The mechanical behavior of 316LVM 1x7 cables were evaluated in uniaxial tension, and in cyclic strain-controlled fatigue with the use of a Flex tester operated to provide fully reversed bending fatigue. The magnitude of cyclic strains imparted to each cable tested was controlled via the use of different diameter mandrels. Smaller diameter mandrels produced higher values of cyclic strain and lower fatigue life. Multiple samples were tested and analyzed via scanning electron microscopy. The fatigue results were analyzed via a Coffin-Manson-Basquin approach and compared to fatigue data obtained from the literature where testing was conducted on similar materials, but under rotating bending fatigue conditions.

  15. Fatigue degradation and failure of rotating composite structures - Materials characterisation and underlying mechanisms

    DEFF Research Database (Denmark)

    Gamstedt, Kristofer; Andersen, Svend Ib Smidt

    2001-01-01

    The present review concerns rotating composite structures, in which fatigue degradation is of key concern for in-service failure. Such applications are for instance rotor blades in wind turbines, helicopter rotor blades, flywheels for energy storage,marine and aeronautical propellers, and rolls...... for paper machines. The purpose is to identify areas where impending efforts should be made to make better use of composite materials in these applications. In order to obtain better design methodologies,which would allow more reliable and slender structures, improved test methods are necessary. Furthermore...

  16. Inconel 718 and UNSM Treated Alloy Study on the Rotary Bending High Temperature Fatigue Characteristics under a Light Concentrating System

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of); Nahm, Seung Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Woo, Young Han; Hur, Kwang Ho; Hong, Sang Hwui [Gyeongbuk Hybrid Technology Institute, Daegu (Korea, Republic of); Kim, Jun Hyong; Pyun, Young Sik [Sun Moon Univ., Asan (Korea, Republic of)

    2016-11-15

    This study investigated the influence of high temperature and UNSM on the fatigue behavior of Inconel 718 alloy at RT, 300, 500, and 600℃. Fatigue properties of Inconel 718 were reduced at high temperatures compared to those at room temperature. However, the endurance limit was similar to that of the room temperature sample at the design stress level. High-temperature fatigue characteristics of the UNSM-treated specimen were significantly improved at the design stress level as compared to the untreated specimens. Specifically, the influence of temperature on the S-N curves at the design stress level of the UNSM-treated specimen showed the tendency of longer fatigue lives than those of untreated ones. Researchers can obtain rotary fatigue test results simply by heating specimens with a halogen lamp to precise temperatures during specific operations.

  17. Post analysis of AE data of seal plug leakage of NAPS-2 and fatigue crack initiation of three point bend sample using cluster and artificial neural network

    International Nuclear Information System (INIS)

    Singh, A.K.; Mehta, H.R.; Bhattacharya, S.

    2003-01-01

    Acoustic Emission data is very weak and passive in nature that leads to a challenging task to separate AE data from noise. This paper illuminates the work done of post analysis of acoustic emission data of seal plug leakage of operating PHWR, NAPS-2, Narora and Fatigue Crack initiation of three-point bend sample using cluster analysis and artificial neural network (ANN). First the known AE data generated in lab by PCB debonding and pencil leak break were analyzed using ANN to get the confidence. After that the AE data acquired by scanning all 306-coolant channels at NAPS-2 was sorted out in five separate clusters for different leakage rate and background noise. Fatigue crack initiation, AE data generated in MSD lab on three-point bend sample was clustered in ten separate clusters in which one cluster was having 98% AE data of crack initiation period noted with the help of travelling microscope but remaining clusters indicating AE data of different sources and noise. The above data was further analysed with self organizing map of Artificial Neural Network. (author)

  18. The influence of applied heat-treatment on in 718 fatigue life at three point flexural bending

    Directory of Open Access Journals (Sweden)

    J. Belan

    2017-01-01

    Full Text Available The Inconel alloy 718 is an iron-nickel based superalloy with a working temperature up to 650 °C. Presented phases such as γ'' (Ni3Nb, γ' (Ni3Al, and δ (delta – Ni3Nb are responsible for the alloy's unique properties. The δ – delta phase is profitable when situated at grain boundaries in small quantities due to increasing fatigue life. However, at temperatures close to 650 °C the γ'' transforms to δ – delta and causes a decrease in fatigue life. Heat-treatment (800°C/ for 72 hours and its influence on fatigue life are discussed in this paper. Fatigue tests were carried out at room temperature. After the tests we plotted the S-N curves for both stages. SEM (Scanning Electron Microscopy fractography was carried out as well.

  19. Fatigue degradation and failure of rotating composite structures - Materials characterisation and underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Gamstedt, E K; Andersen, S I

    2001-03-01

    The present review concerns rotating composite structures, in which fatigue degradation is of key concern for in-service failure. Such applications are for instance rotor blades in wind turbines, helicopter rotor blades, flywheels for energy storage, marine and aeronautical propellers, and rolls for paper machines. The purpose is to identify areas where impending efforts should be made to make better use of composite materials in these applications. In order to obtain better design methodologies, which would allow more reliable and slender structures, improved test methods are necessary. Furthermore, the relation between structural, component and specimen test results should be better understood than what is presently the case. Improved predictive methods rely on a better understanding of the underlying damage mechanisms. With mechanism-based models, the component substructure or even the material microstructure could be optimised for best possible fatigue resistance. These issues are addressed in the present report, with special emphasis on test methods, and scaling from damage mechanisms to relevant material properties. (au)

  20. Increased supraspinatus tendon thickness following fatigue loading in rotator cuff tendinopathy: potential implications for exercise therapy.

    Science.gov (United States)

    McCreesh, Karen M; Purtill, Helen; Donnelly, Alan E; Lewis, Jeremy S

    2017-01-01

    Exercise imparts a load on tendon tissue that leads to changes in tendon properties. Studies suggest that loading immediately reduces tendon thickness, with a loss of this response in symptomatic tendinopathy. No studies investigating the response of tendon dimensions to load for the rotator cuff tendons exist. This study aimed to examine the short-term effect of loading on the thickness of the supraspinatus tendon and acromiohumeral distance those with and without rotator cuff tendinopathy. Participants were 20 painfree controls, and 23 people with painful rotator cuff tendinopathy. Supraspinatus tendon thickness and acromiohumeral distance were measured using ultrasound scans before, and at three time points after loading (1, 6 and 24 hours). Loading involved isokinetic eccentric and concentric external rotation and abduction. There was a significant increase in supraspinatus tendon thickness in the pain group at 1 (7%, ∆=0.38, 95% CI 0.19 to 0.57) and 6 hours (11%, ∆=0.53, 95% CI 0.34 to 0.71), although only the 6 hours difference exceeded minimal detectable difference. In contrast, there was a small non-significant reduction in thickness in controls. The acromiohumeral distance reduced significantly in both groups at 1 hour (controls: ∆=0.64, 95% CI 0.38 to 0.90; pain: ∆=1.1, 95% CI 0.85 to 1.33), with a larger change from baseline in the pain group. Those diagnosed with painful supraspinatus tendinopathy demonstrated increased thickening with delayed return to baseline following loading. Rehabilitation professionals may need to take into account the impact of loading to fatigue when planning rehabilitation programmes.

  1. The effect of shift rotation on employee cortisol profile, sleep quality, fatigue, and attention level: a systematic review.

    Science.gov (United States)

    Niu, Shu-Fen; Chung, Min-Huey; Chen, Chiung-Hua; Hegney, Desley; O'Brien, Anthony; Chou, Kuei-Ru

    2011-03-01

    Disrupted circadian rhythm, especially working night duty together with irregular sleep patterns, sleep deprivation, and fatigue, creates an occupational health risk associated with diminished vigilance and work performance. This study reviewed the effect of shift rotations on employee cortisol profile, sleep quality, fatigue, and attention level. Researchers conducted a systematic review of relevant articles published between 1996 and 2008 that were listed on the following databases: SCOPUS, OVID, Blackwell Science, EBSCO Host, PsycINFO, Cochrane Controlled Trials Register, and CEPS. A total of 28 articles were included in the review. Previous research into the effects of shift work on cortisol profiles, sleep quality, fatigue, and attention used data assessed at evidence Levels II to IV. Our systematic review confirmed a conflict between sleep-wake cycle and light-dark cycle in night work. Consequences of circadian rhythm disturbance include disruption of sleep, decreased vigilance, general feeling of malaise, and decreased mental efficiency. Shift workers who sleep during the day (day sleepers) experience cortisol secretion increases, which diminish the healing power of sleep and enjoy 1 to 4 hours less sleep on average than night sleepers. Sleep debt accumulation results in chronic fatigue. Prolonged fatigue and inadequate recovery result in decreased work performance and more incidents. Rotation from day shift to night shift and its effect on shift workers was a special focus of the articles retained for review. Disturbed circadian rhythm in humans has been associated with a variety of mental and physical disorders and may negatively impact on work safety, performance, and productivity.

  2. Coupled Bending-Bending-Torsion Vibration of a Rotating Pre-Twisted Beam with Aerofoil Cross-Section and Flexible Root by Finite Element Method

    Directory of Open Access Journals (Sweden)

    Bulent Yardimoglu

    2004-01-01

    Full Text Available The purpose of this paper is to extend a previously published beam model of a turbine blade including the centrifugal force field and root flexibility effects on a finite element model and to demonstrate the performance, accuracy and efficiency of the extended model for computing the natural frequencies. Therefore, only the modifications due to rotation and elastic root are presented in great detail. Considering the shear center effect on the transverse displacements, the geometric stiffness matrix due to the centrifugal force is developed from the geometric strain energy expression based on the large deflections and the increase of torsional stiffness because of the axial stress. In this work, the root flexibility of the blade is idealized by a continuum model unlike the discrete model approach of a combination of translational and rotational elastic springs, as used by other researchers. The cross-section properties of the fir-tree root of the blade considered as an example are expressed by assigning proper order polynomial functions similar to cross-sectional properties of a tapered blade. The correctness of the present extended finite element model is confirmed by the experimental and calculated results available in the literature. Comparisons of the present model results with those in the literature indicate excellent agreement.

  3. The Effect of Fatigue Cracks on Fastener Flexibility, Load Distribution and Fatigue Crack Growth

    Science.gov (United States)

    2012-05-01

    Application of Damage Tolerance Concepts to Critical Engine Components”, “Damage Tolerance Concepts for Critical Engine Components, AGARD - CP 393”, NATO...railroad bridge [71]. The vast majority of fatigue tests during this period were of the rotating bending type [72, 73 ]. In these tests a specimen is...Experiment Station, University of Illinois, October 1921 73 . Mann, J. Y., Fatigue of Materials; An Introductory Text, Melbourne University Press, 1967

  4. Study of fatigue resistance for different steel specimens under conditions of combined action of cyclic bending and torsion

    International Nuclear Information System (INIS)

    Belkin, L.M.; Filimonov, G.N.; Belkin, M.Ya.; Vishnevskij, A.P.; Volkov, I.B.

    1986-01-01

    VP6 alloy is studied for its relaxation stability and fatigue strength. Results of the study are presented. Tests are carried out on the specimens with smooth working part to study relaxation properties of the material, with thread working part to determine stress relaxation in a loose thread, on the thread joints to study relaxation in the working thread. All the studied members of the thread joint under cyclic loading are shown to obey a common regularity. Characteristics of the relaxation material stability under different values on an average stress cycle are presented. Stress concentration associated with inhomogeneity in distribution of axial tensile stresses in a loose thread and nonuniformity in the working thread. All the studied members of the thread joint under cyclic loading are shown to obey a common regularity. Characteristics of the relaxation material stability under different values on an average stress cycle are presented. Stress concentration associated with inhomogeneity in distribution of axial tensile stresses in a loose thread and nonuniformity in the load on the working thread turns along the nut length are studied for their effect on the stress relaxation in the thread joint. Ultimate longevity of the materials under conditions of cyclic stress relaxation is evaluated allowing for relaxation and fatigue characteristics of the material

  5. Fatigue

    Science.gov (United States)

    ... sleep. Fatigue is a lack of energy and motivation. Drowsiness and apathy (a feeling of not caring ... Call your provider right away if you have any of the following: Confusion or dizziness Blurred vision Little or no urine, or recent ...

  6. Cyclic fatigue resistance of RaCe and Mtwo rotary files in continuous rotation and reciprocating motion.

    Science.gov (United States)

    Vadhana, Sekar; SaravanaKarthikeyan, Balasubramanian; Nandini, Suresh; Velmurugan, Natanasabapathy

    2014-07-01

    The purpose of this study was to evaluate and compare the cyclic fatigue resistance of RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) and Mtwo (VDW, Munich, Germany) rotary files in continuous rotation and reciprocating motion. A total of 60 new rotary Mtwo and RaCe files (ISO size = 25, taper = 0.06, length = 25 mm) were selected and randomly divided into 4 groups (n = 15 each): Mtc (Mtwo NiTi files in continuous rotation), Rc (RaCe NiTi files in continuous rotation), Mtr (Mtwo NiTi files in reciprocating motion), and Rr (RaCe NiTi files in reciprocating motion). A cyclic fatigue testing device was fabricated with a 60° angle of curvature and a 5-mm radius. All instruments were rotated or reciprocated until fracture occurred. The time taken for each instrument to fracture and the length of the broken fragments were recorded. All the fractured files were analyzed under a scanning electron microscope to detect the mode of fracture. The Kolmogorov-Smirnov test was used to assess the normality of samples distribution, and statistical analysis was performed using the independent sample t test. The time taken for the instruments of the Mtr and Rr groups to fail under cyclic loading was significantly longer compared with the Mtc and Rc groups (P ductile mode of fracture. The length of the fractured segments was between 5 and 6 mm, which was not statistically significant among the experimental groups. Mtwo and RaCe rotary instruments showed a significantly higher cyclic fatigue resistance in reciprocating motion compared with continuous rotation motion. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  7. Experimental and Simulated Investigations of Thin Polymer Substrates with an Indium Tin Oxide Coating under Fatigue Bending Loadings

    Directory of Open Access Journals (Sweden)

    Jiong-Shiun Hsu

    2016-08-01

    Full Text Available Stress-induced failure is a critical concern that influences the mechanical reliability of an indium tin oxide (ITO film deposited on a transparently flexible polyethylene terephthalate (PET substrate. In this study, a cycling bending mechanism was proposed and used to experimentally investigate the influences of compressive and tensile stresses on the mechanical stability of an ITO film deposited on PET substrates. The sheet resistance of the ITO film, optical transmittance of the ITO-coated PET substrates, and failure scheme within the ITO film were measured to evaluate the mechanical stability of the concerned thin films. The results indicated that compressive and tensile stresses generated distinct failure schemes within an ITO film and both led to increased sheet resistance and optical transmittance. In addition, tensile stress increased the sheet resistance of an ITO film more easily than compressive stress did. However, the influences of both compressive and tensile stress on increased optical transmittance were demonstrated to be highly similar. Increasing the thickness of a PET substrate resulted in increased sheet resistance and optical transmittance regardless of the presence of compressive or tensile stress. Moreover, J-Integral, a method based on strain energy, was used to estimate the interfacial adhesion strength of the ITO-PET film through the simulation approach enabled by a finite element analysis.

  8. Torsion-rotation structure and quasi-symmetric-rotor behaviour for the CH3SH asymmetric CH3-bending and C-H stretching bands of E parentage

    Science.gov (United States)

    Lees, R. M.; Xu, Li-Hong; Guislain, B. G.; Reid, E. M.; Twagirayezu, S.; Perry, D. S.; Dawadi, M. B.; Thapaliya, B. P.; Billinghurst, B. E.

    2018-01-01

    High-resolution Fourier transform spectra of the asymmetric methyl-bending and methyl-stretching bands of CH3SH have been recorded employing synchrotron radiation at the FIR beamline of the Canadian Light Source. Analysis of the torsion-rotation structure and relative intensities has revealed the novel feature that for both bend and stretch the in-plane and out-of-plane modes behave much like a Coriolis-coupled l-doublet pair originating from degenerate E modes of a symmetric top. As the axial angular momentum K increases, the energies of the coupled "l = ±1" modes diverge linearly, with effective Coriolis ζ constants typical for symmetric tops. For the methyl-stretching states, separated at K = 0 by only about 1 cm-1, the assigned sub-bands follow a symmetric top Δ(K - l) = 0 selection rule, with only ΔK = -1 transitions observed to the upper l = -1 in-plane A‧ component and only ΔK = +1 transitions to the lower l = +1 out-of-plane A″ component. The K = 0 separation of the CH3-bending states is larger at 9.1 cm-1 with the l-ordering reversed. Here, both ΔK = +1 and ΔK = -1 transitions are seen for each l-component but with a large difference in relative intensity. Term values for the excited state levels have been fitted to J(J + 1) power-series expansions to obtain substate origins. These have then been fitted to a Fourier model to characterize the torsion-K-rotation energy patterns. For both pairs of vibrational states, the torsional energies display the customary oscillatory behaviour as a function of K and have inverted torsional splittings relative to the ground state. The spectra show numerous perturbations, indicating local resonances with the underlying bath of high torsional levels and vibrational combination and overtone states. The overall structure of the two pairs of bands represents a new regime in which the vibrational energy separations, torsional splittings and shifts due to molecular asymmetry are all of the same order, creating a

  9. An ion-optical design study of a carbon-ion rotating gantry with a superconducting final bending magnet

    International Nuclear Information System (INIS)

    Bokor, J.; Pavlovič, M.

    2016-01-01

    Ion-optical designs of an isocentric ion gantry with a compact curved superconducting final bending magnet are presented. The gantry is designed for transporting carbon-therapy beams with nominal kinetic energy of 400 MeV/u, which corresponds to the penetration range of C"6"+ beam in water of about 28 cm. In contrast to other existing designs, we present a “hybrid” beam transport system containing a single superconducting element – the last bending magnet. All other elements are based on conventional warm technology. Ion-optical properties of such a hybrid system are investigated in case of transporting non-symmetric (i.e. different emittance patterns in the horizontal and vertical plane) beams. Different conditions for transporting the non-symmetric beams are analyzed aiming at finding the optimal, i.e. the most compact, gantry version. The final gantry layout is presented including a 2D parallel scanning. The ion-optical and scanning properties of the final gantry design are described, discussed and illustrated by computer simulations performed by WinAGILE.

  10. Fatigue tests and life estimation of Incoloy alloy 908

    International Nuclear Information System (INIS)

    Feng, J.; Toma, L.S.; Jang, C.H.; Steeves, M.M.

    1997-01-01

    Incoloy reg-sign alloy 908* is a candidate conduit material for Nb 3 Sn cable-in-conduit superconductors. The conduit is expected to experience cyclic loads at 4 K. Fatigue fracture of the conduit is one possible failure mode. So far, fatigue life has been estimated from fatigue crack growth data, which provide conservative results. The more traditional practice of life estimation using S-N curves has not been done for alloy 908 due to a lack of data at room and cryogenic temperatures. This paper presents a series of fatigue test results in response to this need. Tests were performed in reversed bending, rotating bending, and uniaxial fatigue machines. The test matrix included different heat treatments, two load ratios (R=-1 and 0.1), two temperatures (298 and 77 K), and two orientations (longitudinal and transverse). As expected, there is a semi-log linear relation between the applied stress and fatigue life above an applied stress (e.g., 310 MPa for tests at 298 K and R=-1). Below this stress the curves show an endurance limit. The aged and cold-worked materials have longer fatigue lives and higher endurance limits than the others. Different orientations have no apparent effect on life. Cryogenic temperature results in a much high fatigue life than room temperature. A higher tensile mean stress gives shorter fatigue life. It was also found that the fatigue lives of the reversed bending specimens were of the same order as those of the uniaxial test specimens, but were only half the lives of the rotating bending specimens for given stresses. A sample application of the S-N data is discussed

  11. A morphometric investigation on breed-specific features affecting sagittal rotational and lateral bending mobility in the canine cervical spine (c3-c7).

    Science.gov (United States)

    Breit, S; Künzel, W

    2004-08-01

    Vertebral and inter-vertebral parameters obtained in large breeds (n = 74), small breeds (n = 35), and Dachshunds (n = 30) were compared to reveal potential differences in the range of motion of the cervical spine between these three groups of breeds. Body size normalized dimensions of vertebral and inter-vertebral parameters and correlations between these indicate large canine breeds to have a tendency towards higher range of motion in sagittal rotation and lateral bending compared with Dachshunds and small breeds. Higher mobility in large breeds is based on significantly (P inter-vertebral discs, wider but shorter cranial and caudal articular surfaces, larger differences in width between caudal and cranial joining facets (compared with Dachshunds from C3/4 to C6/7, compared with small breeds from C4/5 to C5/6), and larger differences in length between caudal and cranial joining facets. Large differences in width between caudal and cranial joining facets were associated with small distances between the most medial (C3/4 to C6/7) and lateral (C3/4 to C5/6) aspects of the articular surfaces as well as with small differences in length between caudal and cranial joining facets (C3/4 to C5/6). This suggests that from C3/4 to C5/6 a higher range of motion in lateral bending is coupled to a lower range of motion in sagittal rotation. The present findings contribute also to explain the higher incidence of degenerative lesions of the cervical spine in large dogs.

  12. Proposed design procedure for transmission shafting under fatigue loading

    Science.gov (United States)

    Loewenthal, S. H.

    1978-01-01

    The B106 American National Standards Committee is currently preparing a new standard for the design of transmission shafting. A design procedure, proposed for use in the new standard, for computing the diameter of rotating solid steel shafts under combined cyclic bending and steady torsion is presented. The formula is based on an elliptical variation of endurance strength with torque exhibited by combined stress fatigue data. Fatigue factors are cited to correct specimen bending endurance strength data for use in the shaft formula. A design example illustrates how the method is to be applied.

  13. Increased supraspinatus tendon thickness following fatigue loading in rotator cuff tendinopathy: potential implications for exercise therapy

    OpenAIRE

    McCreesh, Karen M; Purtill, Helen; Donnelly, Alan E; Lewis, Jeremy S

    2017-01-01

    Background/aim Exercise imparts a load on tendon tissue that leads to changes in tendon properties. Studies suggest that loading immediately reduces tendon thickness, with a loss of this response in symptomatic tendinopathy. No studies investigating the response of tendon dimensions to load for the rotator cuff tendons exist. This study aimed to examine the short-term effect of loading on the thickness of the supraspinatus tendon and acromiohumeral distance those with and without rotator cuff...

  14. The effect of residual stresses induced by prestraining on fatigue life of notched specimens

    Science.gov (United States)

    Sadeler, R.; Ozel, A.; Kaymaz, I.; Totik, Y.

    2005-06-01

    The effect of tensile prestraining-induced residual stress on the fatigue life of notched steel parts was investigated. The study was performed on AISI 4140 steel. Rotating bending fatigue tests were carried out on semicircular notched specimens with different notch radii in the as-quenched and tempered conditions. Metallography of the specimens was performed by means of light optical microscopy. The finite-element method was used to evaluate the residual stress distribution near the notch region. Fatigue tests revealed fatigue life improvement for notched specimens, which changes depending on the notch radii and applied stress. Scanning electron microscopy was used to examine the fracture surfaces of the specimens.

  15. Effects of casting defects, matrix structures and loading conditions on the fatigue strength of ductile irons

    Directory of Open Access Journals (Sweden)

    Endo Masahiro

    2014-06-01

    Full Text Available A novel method is presented to estimate the lower bound of the scatter in fatigue limit of ductile iron based upon the information of microstructural in homogeneities and loading conditions. The predictive capability of the method was verified by comparing to the experimental data obtained by the rotating-bending, torsion and combined tension-torsion fatigue tests for ductile irons with ferritic, pearlitic and bulls-eye (ferritic/pearlitic microstructures.

  16. Thermal fatigue analysis of vertical annulus with inner rotating cylinder induced by two temperature fluid mixing

    International Nuclear Information System (INIS)

    Miyano, Hiroshi; Narabayashi, Tadashi

    2011-01-01

    Mechanical seal for nuclear reactor coolant recirculation pump must purge the cold water supply from the outside. The cold purge water is flowing into the hot water zone in the pump through a narrow gap between pump shaft and casing over. On the mixing region of the cold purge water and hot water in the narrow gap, the random level temperature fluctuation occurs on the structural metal surface of casing cover and pump shaft. Then it could lead to cyclic thermal stress and fatigue damage. The experiments and analysis have done, made clear the mechanism of generation of temperature fluctuations. Also, it was studied how to measure the structure of the mixing zone temperature control and how to prevent the occurrence of a large temperature fluctuation. In addition, it is proposed the method of evaluating a random temperature fluctuation by using the envelope curve and its fatigue by OOR counting to applying to the evaluation of the similar random fluid temperature fluctuation problems. (author)

  17. Fatigue Analysis of Rotating Parts. A Case Study for a Belt Driven Pulley

    Science.gov (United States)

    Sandu, Ionela; Tabacu, Stefan; Ducu, Catalin

    2017-10-01

    The present study is focused on the life estimation of a rotating part as a component of an engine assembly namely the pulley of the coolant pump. The goal of the paper is to develop a model, supported by numerical analysis, capable to predict the lifetime of the part. Starting from functional drawing, CAD Model and technical specifications of the part a numerical model was developed. MATLAB code was used to develop a tool to apply the load over the selected area. The numerical analysis was performed in two steps. The first simulation concerned the inertia relief due to rotational motion about the shaft (of the pump). Results from this simulation were saved and the stress - strain state used as initial conditions for the analysis with the load applied. The lifetime of a good part was estimated. A defect was created in order to investigate the influence over the working requirements. It was found that there is little influence with respect to the prescribed lifetime.

  18. X-ray residual stress measurement and its variation during plane bending fatigue and sliding wear processes in TiC, TiN, TiB2 and Al2O3 coated carbon steels

    International Nuclear Information System (INIS)

    Endoh, Takashi; Idemitsu, Kohji; Kawakami, Mamoru

    1993-01-01

    The development of ceramic coating to metals was stimulated by the need for high temperature, wear and corrosion resistant materials. Recently TiC, TiN, TiB 2 and Al 2 O 3 are used as ceramic coating materials. In the present study, the X-ray method was successfully applied to measure the residual stress distribution in their ceramics coated steels. The X-ray elastic constants were determined and compared with the mechanically measured values. And plane bending and sliding wear tests were carried out. The X-ray method was successfully applied to measure the residual stress changes during fatigue and wear processes. The relationship between the change of residual stress and damage accumulation was investigated. (author)

  19. Current state of low-cycle fatigue research based on multiaxial stress intensity and its challenges. Part 1. Focusing on low-cycle fatigue strength evaluation method of elbow piping subjected to in-plane cyclic bending displacement load

    International Nuclear Information System (INIS)

    Urabe, Yoshio

    2017-01-01

    The R and D of fatigue strength at multiaxial stress intensity is recognized to become extremely important in the future in terms of the elaboration of low-cycle fatigue evaluation of various structures including piping systems and reflection on those standards. This paper focuses on the evaluation method developed by the author, namely cumulative damage rule in consideration of multiaxial stress intensity, and explains the concept and the results of verification and evaluation. It also discusses the engineering problems of the current low cycle fatigue assessment technology that were clarified in the process of developing low-cycle fatigue assessment method based on multiaxial stress intensity. The conservative lifespan and somewhat more conservative actual lifetime of elbow piping can be estimated by the conventional 'revised universal slope method' and 'advanced revised universal slope method.' However, these are empirical rules, and the theoretical basis is not clear. From 'cumulative damage rule in consideration of multiaxial stress intensity,' the author calculated furthermore 'low cycle fatigue evaluation formula based on cumulative damage rule in consideration of multi-axial stress intensity,' and examined it. As a result, an evaluation formula that can reasonably assume the equivalent thermoplastic strain range could be obtained at half of the repeat count as targeted. Furthermore, at the stage where future high precision FEM analysis can be used, direct low-cycle fatigue life curve can be established. (A.O.)

  20. Improvement of the fatigue strength of AISI 4140 steel by an ion nitriding process

    Energy Technology Data Exchange (ETDEWEB)

    Celik, A. [Atatuerk Univ., Erzurum (Turkey). Dept. of Mech. Eng.; Karadeniz, S. [Dokuz Eyluel Univ., Izmir (Turkey). Dept. of Mech. Eng.

    1995-06-01

    The influence of plasma nitriding on the fatigue behaviour of AISI 4140 low-alloy steel was investigated under varying process conditions of temperature (500-600 C), time (1-12 h), heat treatment before ion nitriding (quenched and tempered, normalized) and gas mixture (50% H{sub 2}-50% N{sub 2}). A rotating bending fatigue machine was used to determine the fatigue strength. It was found that the plasma nitriding improves the fatigue strength and increases the fatigue limit depending on the surface hardness of the case depth. The microstructure of surface and diffusion layers was examined by optical microscopy. The fracture surface of specimens and the origin of fatigue cracks were observed by scanning electron microscopy.

  1. fatigue strength of reinforced concrete flexural members

    African Journals Online (AJOL)

    Dr Obe

    1980-03-01

    Mar 1, 1980 ... cyclic loads behave differently compared with static bending and can collapse due to the fatigue of concrete, reinforcement or both when maximum fatigue stresses of ... under low and medium load levels, than under high load ...

  2. MIT miniaturized disk bend test

    International Nuclear Information System (INIS)

    Harling, O.K.; Lee, M.; Sohn, D.S.; Kohse, G.; Lau, C.W.

    1983-01-01

    A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Other mechanical properties can also be obtained using the MDBT approach. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly. 11 figures

  3. Effect of shot peening process on fatigue behavior of an alloyed austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Amir Sadighzadeh Benam

    2011-08-01

    Full Text Available Shot peening is one of the most common surface treatments to improve the fatigue behavior of metallic parts. In this study the effect of shot peening process on the fatigue behavior of an alloyed austempered ductile iron (ADI has been studied. Austempering heat treatment consisted of austenitizing at 875℃ for 90 min followed by austempering at three different temperatures of 320, 365 and 400℃. Rotating-bending fatigue test was carried out on samples after shot peening by 0.4 – 0.6 mm shots. XRD and SEM analysis, micro hardness and roughness tests were carried out to study the fatigue behavior of the samples. Results indicate that the fatigue strengths of samples austempered at 320, 365 and 400℃ are increased by 27.3%, 33.3% and 48.4%, respectively, after shot peening process.

  4. Fatigue Analysis of Load-Carrying Fillet Welds

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tychsen, Jesper; Andersen, Jens Ulfkjær

    2006-01-01

    that the degree of bending (DOB) has an influence on the fatigue lifetime. The fatigue lifetime decreases significantly when increasing the bending stress. In order to take into account the effect of the bending, a new fatigue stress definition applicable for fillet welds failing through the weld is presented....... Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve....

  5. Metallurgical characterization of M-Wire nickel-titanium shape memory alloy used for endodontic rotary instruments during low-cycle fatigue.

    Science.gov (United States)

    Ye, Jia; Gao, Yong

    2012-01-01

    Rotary instruments made of a new nickel-titanium (NiTi) alloy (M-Wire) have shown improved cyclic fatigue resistance and mechanical properties compared with those made of conventional superelastic NiTi wires. The objective of this study was to characterize microstructural changes of M-Wire throughout the cyclic fatigue process under controlled strain amplitude. The average fatigue life was calculated from 30 M-Wire samples that were subjected to a strain-controlled (≈ 4%) rotating bend fatigue test at room temperature and rotational speed of 300 rpm. Microstructural evolution of M-Wire has been investigated by different metallurgical characterization techniques, including differential scanning calorimetry, Vickers microhardness, and transmission electron microscopy at 4 different stages (as-received state, 30%, 60%, and 90% of average fatigue life). During rotating bend fatigue test, no statistically significant difference (P > .05) was found on austenite finish temperatures between as-received M-Wire and fatigued samples. However, significant differences (P Wire are expected to have higher strength and wear resistance than similar instruments made of conventional superelastic NiTi wires because of its unique nano-crystalline martensitic microstructure. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  6. Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy-Current Phase Rotation

    Science.gov (United States)

    2016-08-01

    Science and Technology Organisation) EDM Electrodischarge machining FSH Full Screen Height on an eddy - current instrument IVD Ion Vapour...electromagnetic skin depth δ is 0.15 mm in the fastener holes3. 4.1 Bolt Hole Eddy Current Inspection Procedure 4.1.1 Calibration on Machined ...UNCLASSIFIED UNCLASSIFIED Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy - Current Phase

  7. Cumulative damage fatigue tests on nuclear reactor Zircaloy-2 fuel tubes at room temperature and 3000C

    International Nuclear Information System (INIS)

    Pandarinathan, P.R.; Vasudevan, P.

    1980-01-01

    Cumulative damage fatigue tests were conducted on the Zircaloy-2 fuel tubes at room temperature and 300 0 C on the modified Moore type, four-point-loaded, deflection-controlled, rotating bending fatigue testing machine. The cumulative cycle ratio at fracture for the Zircaloy-2 fuel tubes was found to depend on the sequence of loading, stress history, number of cycles of application of the pre-stress and the test temperature. A Hi-Lo type fatigue loading was found to be very much damaging at room temperature and this feature was not observed in the tests at 300 0 C. Results indicate significant differences in damage interaction and damage propagation under cumulative damage tests at room temperature and at 300 0 C. Block-loading fatigue tests are suggested as the best method to determine the life-time of Zircaloy-2 fuel tubes under random fatigue loading during their service in the reactor. (orig.)

  8. Statistical Distribution of Fatigue Life for Cast TiAl Alloy

    Directory of Open Access Journals (Sweden)

    WAN Wenjuan

    2016-08-01

    Full Text Available Statistic distribution of fatigue life data and its controls of cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr (atom fraction/% alloy were investigated. Fatigue tests were operated by means of load-controlled rotating bending fatigue tests (R=-1 performed at a frequency of 100 Hz at 750 ℃ in air. The fracture mechanism was analyzed by observing the fracture surface morphologies through scanning electron microscope,and the achieved fatigue life data were analyzed by Weibull statistics. The results show that the fatigue life data present a remarkable scatter ranging from 103 to 106 cycles, and distribute mainly in short and long life regime. The reason for this phenomenon is that the fatigue crack initiators are different with different specimens. The crack initiators for short-life specimens are caused by shrinkage porosity, and for long-life ones are caused by bridged porosity interface and soft-oriented lamellar interface. Based on the observation results of fracture surface, two-parameter Weibull distribution model for fatigue life data can be used for the prediction of fatigue life at a certain failure probability. It has also shown that the shrinkage porosity causes the most detrimental effect to fatigue life.

  9. High cycle fatigue test and regression methods of S-N curve

    International Nuclear Information System (INIS)

    Kim, D. W.; Park, J. Y.; Kim, W. G.; Yoon, J. H.

    2011-11-01

    The fatigue design curve in the ASME Boiler and Pressure Vessel Code Section III are based on the assumption that fatigue life is infinite after 106 cycles. This is because standard fatigue testing equipment prior to the past decades was limited in speed to less than 200 cycles per second. Traditional servo-hydraulic machines work at frequency of 50 Hz. Servo-hydraulic machines working at 1000 Hz have been developed after 1997. This machines allow high frequency and displacement of up to ±0.1 mm and dynamic load of ±20 kN are guaranteed. The frequency of resonant fatigue test machine is 50-250 Hz. Various forced vibration-based system works at 500 Hz or 1.8 kHz. Rotating bending machines allow testing frequency at 0.1-200 Hz. The main advantage of ultrasonic fatigue testing at 20 kHz is performing Although S-N curve is determined by experiment, the fatigue strength corresponding to a given fatigue life should be determined by statistical method considering the scatter of fatigue properties. In this report, the statistical methods for evaluation of fatigue test data is investigated

  10. Fatigue and Fracture Resistance of Heavy-Section Ferritic Ductile Cast Iron

    Directory of Open Access Journals (Sweden)

    Matteo Benedetti

    2017-03-01

    Full Text Available In this paper, we explore the effect of a long solidification time (12 h on the mechanical properties of an EN-GJS-400-type ferritic ductile cast iron (DCI. For this purpose, static tensile, rotating bending fatigue, fatigue crack growth and fracture toughness tests are carried out on specimens extracted from the same casting. The obtained results are compared with those of similar materials published in the technical literature. Moreover, the discussion is complemented with metallurgical and fractographic analyses. It has been found that the long solidification time, representative of conditions arising in heavy-section castings, leads to an overgrowth of the graphite nodules and a partial degeneration into chunky graphite. With respect to minimum values prescribed for thick-walled (t > 60 mm EN-GJS-400-15, the reduction in tensile strength and total elongation is equal to 20% and 75%, respectively. The rotating bending fatigue limit is reduced by 30% with respect to the standard EN-1563, reporting the results of fatigue tests employing laboratory samples extracted from thin-walled castings. Conversely, the resistance to fatigue crack growth is even superior and the fracture toughness comparable to that of conventional DCI.

  11. Tooth bending fatigue failures in gears

    CSIR Research Space (South Africa)

    Fernandes, PJL

    1996-09-01

    Full Text Available . It results in progressive damage to gear teeth and ultimately leads to complete failure of the gear. The characteristics of this failure mode are discussed in detail and a number of actual case studies are presented which show the occurrence of this failure...

  12. Impurity levels and fatigue lives of pseudoelastic NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Rahim, M.; Frenzel, J.; Frotscher, M.; Pfetzing-Micklich, J.; Steegmüller, R.; Wohlschlögel, M.; Mughrabi, H.; Eggeler, G.

    2013-01-01

    In the present work we show how different oxygen (O) and carbon (C) levels affect fatigue lives of pseudoelastic NiTi shape memory alloys. We compare three alloys, one with an ultrahigh purity and two which contain the maximum accepted levels of C and O. We use bending rotation fatigue (up to cycle numbers >10 8 ) and scanning electron microscopy (for investigating microstructural details of crack initiation and growth) to study fatigue behavior. High cycle fatigue (HCF) life is governed by the number of cycles required for crack initiation. In the low cycle fatigue (LCF) regime, the high-purity alloy outperforms the materials with higher number densities of carbides and oxides. In the HCF regime, on the other hand, the high-purity and C-containing alloys show higher fatigue lives than the alloy with oxide particles. There is high experimental scatter in the HCF regime where fatigue cracks preferentially nucleate at particle/void assemblies (PVAs) which form during processing. Cyclic crack growth follows the Paris law and does not depend on impurity levels. The results presented in the present work contribute to a better understanding of structural fatigue of pseudoelastic NiTi shape memory alloys

  13. Effects of Oxygen Content on Tensile and Fatigue Performance of Ti-6Al-4 V Manufactured by Selective Laser Melting

    Science.gov (United States)

    Quintana, Oscar A.; Tong, Weidong

    2017-12-01

    We investigated the selective laser melting (SLM) process for development of Ti-6Al-4 V solid material with oxygen content corresponding to the extra low interstitial (ELI) and non-ELI conditions. The microstructure, chemistry, and tensile properties of samples in as-built and hot isostatically pressed (HIPed) condition were evaluated for both material types, while fatigue performance was evaluated by rotating bending fatigue tests on both smooth and notched SLM ELI and non-ELI Ti-6Al-4 V samples in HIPed condition.

  14. Proposal of a methodology for computing damages from flexo-rotative fatigue considering the theory of the acting average stresses

    International Nuclear Information System (INIS)

    Tanius Rodrigues Mansur; Alvaro Alvarenga Junior; Joao Mario Andrade Pinto; Wellington Antonio Soares; Ernani Sales Palma

    2005-01-01

    The useful life of metallic structures is many times governed by fatigue processes caused by vibrations or by application of dynamic loads, periodic or not. Many times the amplitude of the alternated stress applied to a structural component can vary during its useful life. In this situation the direct use of S-N-P curves cannot be done because they are generated on the basis of alternated stress with constant amplitude. Several theories have been developed during the last times, where some are deterministic and other probabilistic, in order to give a component designer a more efficient and correct tool for approaching the problem. They are called Theories on Damage Accumulation. The phenomenon of creating damages represents the generation of superficial discontinuities caused by micro-cracks or by volumetric cavities [Lemaitre and Chaboche, 1985]. In the continuous mechanics, the superficial density of micro-defects (micro-cracks or cavities) inside the shear plan of the representative element volume of the sample is the variable used to quantify the damage. A methodology for evaluating damage accumulation using average of stresses is proposed in this paper. Results obtained for a 50% failure probability are presented and are compared to those values obtained using the theories of Palmgren-Miner, Henry, Corten-Dolan, Marine, Manson, and Knee-point. (authors)

  15. Surface integrity and fatigue behaviour of electric discharged machined and milled austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, Mattias, E-mail: mattias.lundberg@liu.se; Saarimäki, Jonas; Moverare, Johan J.; Calmunger, Mattias

    2017-02-15

    Machining of austenitic stainless steels can result in different surface integrities and different machining process parameters will have a great impact on the component fatigue life. Understanding how machining processes affect the cyclic behaviour and microstructure are of outmost importance in order to improve existing and new life estimation models. Milling and electrical discharge machining (EDM) have been used to manufacture rectangular four-point bend fatigue test samples; subjected to high cycle fatigue. Before fatigue testing, surface integrity characterisation of the two surface conditions was conducted using scanning electron microscopy, surface roughness, residual stress profiles, and hardness profiles. Differences in cyclic behaviour were observed between the two surface conditions by the fatigue testing. The milled samples exhibited a fatigue limit. EDM samples did not show the same behaviour due to ratcheting. Recrystallized nano sized grains were identified at the severely plastically deformed surface of the milled samples. Large amounts of bent mechanical twins were observed ~ 5 μm below the surface. Grain shearing and subsequent grain rotation from milling bent the mechanical twins. EDM samples showed much less plastic deformation at the surface. Surface tensile residual stresses of ~ 500 MPa and ~ 200 MPa for the milled and EDM samples respectively were measured. - Highlights: •Milled samples exhibit fatigue behaviour, but not EDM samples. •Four-point bending is not suitable for materials exhibiting pronounced ratcheting. •LAGB density can be used to quantitatively measure plastic deformation. •Grain shearing and rotation result in bent mechanical twins. •Nano sized grains evolve due to the heat of the operation.

  16. The MIT miniaturized disk bend test

    International Nuclear Information System (INIS)

    Harling, O.K.; Lee, M.; Sohn, D.S.; Kohse, G.; Lau, C.W.

    1983-01-01

    A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Possibilities exist for applying the MDBT approach to the determination of other mechanical properties. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly

  17. Fatigue limit prediction of ferritic-pearlitic ductile cast iron considering stress ratio and notch size

    Science.gov (United States)

    Deguchi, T.; Kim, H. J.; Ikeda, T.

    2017-05-01

    The mechanical behavior of ductile cast iron is governed by graphite particles and casting defects in the microstructures, which can significantly decrease the fatigue strength. In our previous study, the fatigue limit of ferritic-pearlitic ductile cast iron specimens with small defects ((\\sqrt{{area}}=80˜ 1500{{μ }}{{m}})) could successfully be predicted based on the \\sqrt{{area}} parameter model by using \\sqrt{{area}} as a geometrical parameter of defect as well as the tensile strength as a material parameter. In addition, the fatigue limit for larger defects could be predicted based on the conventional fracture mechanics approach. In this study, rotating bending and tension-compression fatigue tests with ferritic-pearlitic ductile cast iron containing circumferential sharp notches as well as smooth specimens were performed to investigate quantitatively the effects of defect. The notch depths ranged 10 ˜ 2500 μm and the notch root radii were 5 and 50 μm. The stress ratios were R = -1 and 0.1. The microscopic observation of crack propagation near fatigue limit revealed that the fatigue limit was determined by the threshold condition for propagation of a small crack emanating from graphite particles. The fatigue limit could be successfully predicted as a function of R using a method proposed in this study.

  18. Fatigue analysis of aluminum drill pipes

    Directory of Open Access Journals (Sweden)

    João Carlos Ribeiro Plácido

    2005-12-01

    Full Text Available An experimental program was performed to investigate the fundamental fatigue mechanisms of aluminum drill pipes. Initially, the fatigue properties were determined through small-scale tests performed in an optic-mechanical fatigue apparatus. Additionally, full-scale fatigue tests were carried out with three aluminum drill pipe specimens under combined loading of cyclic bending and constant axial tension. Finally, a finite element model was developed to simulate the stress field along the aluminum drill pipe during the fatigue tests and to estimate the stress concentration factors inside the tool joints. By this way, it was possible to estimate the stress values in regions not monitored during the fatigue tests.

  19. Strength measurement of optical fibers by bending

    Science.gov (United States)

    Srubshchik, Leonid S.

    1999-01-01

    A two-point bending technique has been used not only to measure the breaking stress of optical fiber but also to predict its static and dynamic fatigue. The present theory of this test is based on elastica theory of rod. However, within the limits of elastica theory the tensile and shear stresses cannot be determined. In this paper we study dynamic and static problems for optical fiber in the two- point bending test on the base of geometrically exact theory in which rod can suffer flexure, extension, and shear. We obtain the governing partial differential equations taking into account the fact that the lateral motion of the fiber is restrained by the presence of flat parallel plates. We develop the computational methods for solving the initial and equilibrium free-boundary nonlinear planar problems. We derive the formulas for predicting of the tensile strength from strength in the bending and calculate one example.

  20. Performance of engine-driven rotary endodontic instruments with a superimposed bending deflection: V. Gates Glidden and Peeso drills.

    Science.gov (United States)

    Brantley, W A; Luebke, N H; Luebke, F L; Mitchell, J C

    1994-05-01

    A laboratory study was performed on Gates Glidden and Peeso drills to determine the incidence of shaft fracture when a bending deflection was superimposed on the rotating drills. Samples of sizes #1 to #6 stainless steel Gates Glidden drills, sizes #1 to #6 stainless steel and carbon steel-type P Peeso drills, and sizes #009 to #023 carbon steel-type B-1 Peeso drills from each of two manufacturers were evaluated with a unique apparatus that applied a 2-mm bending deflection while rotating the instruments. The apparatus did not restrict movement of the bur head during rotation. The test drills were rotated at 2500, 4000, and 7000 revolutions per minute, and the number of revolutions at failure was recorded. Scanning electron microscopic observations established that the stainless steel Gates Glidden and Peeso drills failed by ductile fracture, whereas the carbon steel Peeso drills failed by brittle fracture. Instrument fracture was always near the handpiece shank with this test, and the length of the fractured drills was measured from the working tip. It is recommended that this additional test be adopted to determine fatigue properties of engine-driven rotary endodontic instruments in establishing international performance standards.

  1. Corrosion fatigue in nitrocarburized quenched and tempered steels

    Science.gov (United States)

    Khani, M. Karim; Dengel, D.

    1996-05-01

    In order to investigate the fatigue strength and fracture mechanism of salt bath nitrocarburized steels, specimens of the steels SAE 4135 and SAE 4140, in a quenched and tempered state, and additionally in a salt bath nitrocarburized and oxidizing cooled state as well as in a polished (after the oxidizing cooling) and renewed oxidized state, were subjected to comparative rotating bending fatigue tests in inert oil and 5 pct NaCl solution. In addition, some of the quenched and tempered specimens of SAE 4135 material were provided with an approximately 50-μm-thick electroless Ni-P layer, in order to compare corrosion fatigue behavior between the Ni-P layer and the nitride layers. Long-life corrosion fatigue tests of SAE 4135 material were carried out under small stresses in the long-life range up to 108 cycles with a test frequency of 100 Hz. Fatigue tests of SAE 4140 material were carried out in the range of finite life (low-cycle range) with a test frequency of 13 Hz. The results show that the 5 pct NaCl environment drastically reduced fatigue life, but nitrocarburizing plus oxidation treatment was found to improve the corrosion fatigue life over that of untreated and Ni-P coated specimens. The beneficial effect of nitrocarburizing followed by oxidation treatment on cor-rosion fatigue life results from the protection rendered by the compound layer by means of a well-sealed oxide layer, whereby the pores present in the compound layer fill up with oxides. The role of inclusions in initiating fatigue cracks was investigated. It was found that under corrosion fatigue conditions, the fatigue cracks started at cavities along the interfaces of MnS inclusions and matrix in the case of quenched and tempered specimens. The nitrocarburized specimens, however, showed a superposition of pitting corrosion and corrosion fatigue in which pores and nonmetallic inclusions in the compound layer play a predominant role concerning the formation of pits in the substrate.

  2. Bend me, shape me

    CERN Multimedia

    2002-01-01

    A Japanese team has found a way to bend and shape silicon substrates by growing a thin layer of diamond on top. The technique has been proposed as an alternative to mechanical bending, which is currently used to make reflective lenses for X-ray systems and particle physics systems (2 paragraphs).

  3. Occipital bending in schizophrenia.

    Science.gov (United States)

    Maller, Jerome J; Anderson, Rodney J; Thomson, Richard H; Daskalakis, Zafiris J; Rosenfeld, Jeffrey V; Fitzgerald, Paul B

    2017-01-01

    To investigate the prevalence of occipital bending (an occipital lobe crossing or twisting across the midline) in subjects with schizophrenia and matched healthy controls. Occipital bending prevalence was investigated in 37 patients with schizophrenia and 44 healthy controls. Ratings showed that prevalence was nearly three times higher among schizophrenia patients (13/37 [35.1%]) than in control subjects (6/44 [13.6%]). Furthermore, those with schizophrenia had greater normalized gray matter volume but less white matter volume and had larger brain-to-cranial ratio. The results suggest that occipital bending is more prevalent among schizophrenia patients than healthy subjects and that schizophrenia patients have different gray matter-white matter proportions. Although the cause and clinical ramifications of occipital bending are unclear, the results infer that occipital bending may be a marker of psychiatric illness.

  4. Influence of Surface Roughness on the Fatigue Life of Nickel-Titanium Rotary Endodontic Instruments.

    Science.gov (United States)

    Lopes, Hélio P; Elias, Carlos N; Vieira, Márcia V B; Vieira, Victor T L; de Souza, Letícia Chaves; Dos Santos, Alexander Lopes

    2016-06-01

    The goal of the present study was to evaluate the influence of surface grooves (peaks and valleys) resulting from machining during the manufacturing process of polished and unpolished nickel-titanium BR4C endodontic files on the fatigue life of the instruments. Ten electropolished and 10 unpolished endodontic files were provided by the manufacturer. Specimens were from the same batch, but the unpolished instruments were removed from the production line before surface treatment. The instruments were evaluated with a profilometer to quantify the surface roughness on the working part of the instruments. Then the files were subjected to rotating bending fatigue tests. Analysis with the profilometer showed that surface grooves were deeper on the unpolished instruments compared with their electropolished counterparts. In the rotating bending fatigue test, the mean and standard deviation for the number of cycles until fracture (NCF) were greater for instruments with less pronounced grooves. Student t test revealed significant differences in all tests (P instruments tested; the smaller the groove depth, the greater the NCF. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  5. Effect of strain-induced martensitic transformation on high cycle fatigue behavior in cyclically-prestrained type 304

    International Nuclear Information System (INIS)

    Uematsu, Yoshihiko; Kakiuchi, Toshifumi; Akita, Masayuki; Nakajima, Masaki; Nakamura, Yuki; Yajima, Takumi

    2013-01-01

    The effects of the cyclic prestrain on the fatigue behavior in type 304 austenitic stainless steel were investigated. Rotating bending fatigue tests have been performed in laboratory air using the specimens subjected to ±5% cyclic prestrain at room temperature (R.T.) and -5°C. Martensitic phase volume fraction of the prestrained specimen at -5°C was 48% and larger than 3.8% at R.T. The prestrained specimens exhibited higher fatigue strengths than the as-received ones, and larger volume fraction of martensitic phase resulted in the higher fatigue limit. EBSD analysis revealed that the martensitic phases were more uniformly distributed in the austenitic matrix in the cyclically-prestrained specimens than in the monotonically-prestrained ones. Fatigue crack initiation from inclusion was observed only in the cyclically-prestrained specimens at -5°C. High volume fraction and uniform distribution of martensitic phase induced the transition of crack initiation mechanism and led to the higher fatigue limit. In type 304 stainless steel with high volume fraction of strain-induced martensitic phase, the prediction of fatigue limit based on Vickers hardness could give unconservative results. (author)

  6. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    Science.gov (United States)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-10-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  7. Influence of mean stress on fatigue strength of ferritic-pearlite ductile cast iron with small defects

    Science.gov (United States)

    Deguchi, T.; Kim, H. J.; Ikeda, T.; Yanase, K.

    2017-05-01

    Because of their excellent mechanical properties, low cost and good workability, the application of ductile cast iron has been increased in various industries such as the automotive, construction and rail industries. For safety designing of the ductile cast iron component, it is necessary to understand the effect of stress ratio, R, on fatigue limit of ductile cast iron in the presence of small defects. Correspondingly in this study, rotating bending fatigue tests at R = -1 and tension-compression fatigue tests at R = -1 and 0.1 were performed by using a ferritic-pearlitic ductile cast iron. To study the effects of small defects, we introduced a small drilled hole at surface of a specimen. The diameter and depth of a drilled hole were 50, 200 and 500 μm, respectively. The non-propagating cracks emanating from graphite particles and holes edge were observed at fatigue limit, irrespective of the value of stress ratio. From the microscopic observation of crack propagation behavior, it can be concluded that the fatigue limit is determined by the threshold condition for propagation of a small crack. It was found that the effect of stress ratio on the fatigue limit of ductile cast iron with small defects can be successfully predicted based on \\sqrt {area} parameter model. Furthermore, a use of the tensile strength, σ B, instead of the Vickers hardness, HV, is effective for fatigue limit prediction.

  8. Influence of stress change on the fatigue behavior and fatigue life of aluminum oxide-dispersion-strengthening copper alloy at room temperature and 350degC

    International Nuclear Information System (INIS)

    Kawagoishi, Norio; Kondo, Eiji; Nisitani, Hironobu; Shimamoto, Atsunori; Tashiro, Rieko

    2004-01-01

    In order to investigate the influence of stress change on the fatigue behavior and fatigue life of an aluminum oxide-dispersion-strengthening copper alloy at elevated temperature, rotating bending fatigue tests were carried out under two-step loading at room temperature and 350degC. Both of static strength and fatigue strength decreased at 350degC. However, at the same relative stress σ a /σ B , fatigue life was longer at 350degC than at room temperature. Although the cumulative ratios Σ(N/N f ) were nearly unity for both the low to high and the high to low block loadings at room temperature, Miner's rule did not hold at 350degC. These results were related to the stress dependence on the log l-N/N f relation. That is, the crack length initiated at the same N/N f was larger in higher stress level at 350degC, whereas there was no stress dependence in the relation at room temperature. The stress dependence on the relation at 350degC was caused by the suppression of crack initiation due to the surface oxidation. (author)

  9. Fatigue Level Estimation of Bill Based on Acoustic Signal Feature by Supervised SOM

    Science.gov (United States)

    Teranishi, Masaru; Omatu, Sigeru; Kosaka, Toshihisa

    Fatigued bills have harmful influence on daily operation of Automated Teller Machine(ATM). To make the fatigued bills classification more efficient, development of an automatic fatigued bill classification method is desired. We propose a new method to estimate bending rigidity of bill from acoustic signal feature of banking machines. The estimated bending rigidities are used as continuous fatigue level for classification of fatigued bill. By using the supervised Self-Organizing Map(supervised SOM), we estimate the bending rigidity from only the acoustic energy pattern effectively. The experimental result with real bill samples shows the effectiveness of the proposed method.

  10. Adjustable Tooling for Bending Brake

    Science.gov (United States)

    Ellis, J. M.

    1986-01-01

    Deep metal boxes and other parts easily fabricated. Adjustable tooling jig for bending brake accommodates spacing blocks and either standard male press-brake die or bar die. Holds spacer blocks, press-brake die, bar window die, or combination of three. Typical bending operations include bending of cut metal sheet into box and bending of metal strip into bracket with multiple inward 90 degree bends. By increasing free space available for bending sheet-metal parts jig makes it easier to fabricate such items as deep metal boxes or brackets with right-angle bends.

  11. Study on high-cycle fatigue behavior of candidate Fe-Cr-Ni alloys for SCWR

    International Nuclear Information System (INIS)

    Zhao Yuxiang; Liu Guiliang; Tang Rui; Xiong Ru; Qiao Yingjie

    2014-01-01

    In the design for supercritical water reactor (SCWR), the operating temperature, pressure, burn up and irradiation damage are very high, so it seems vital to make correct choice of structural materials in core and obtain their key application behavior which would beneficial the research and development of SCWR. In this paper, the high cycle fatigue (HCF) tests of commerce austenite alloys including 6XN and 825 were conducted under bending and rotating loads at room temperature (RT) as well as at 550 ℃ in air. The experimental data were analyzed and the S-N curves were processed, the fracture morphology was also observed by SEM. The results indicate that the fatigue limited stresses at RT for the 2 Fe-Cr-Ni alloy were in such order of 825 < 6XN, which consistent with the order of their tensile strength. Elevated temperature would accelerate the oxidation of the specimen and therefore the fatigue life would decrease, among them 6XN was more sensitive to high temperature with the larger decreasing tendency which make the fatigue limited stress of the two alloys more closer at 550 ℃. While 825 is more sensitive to the stress cycles. All the two alloys have good resistance to high cycle fatigue when comparing their experimental data with the calculated value from the empirical formula. The fracture morphology presents areas of crack initiation, crack growth and fracture, the fracture area has much dimples. This work can be applied to the conceptional design for SCWR. (authors)

  12. Study on high-cycle fatigue behavior of candidate stainless steels for SCWR

    International Nuclear Information System (INIS)

    Xiong Ru; Zhao Yuxiang; Zhang Qiang; Wang Hao; Tang Rui; Qiao Yingjie

    2013-01-01

    The fatigue experiments of commerce stainless steels including 347, 316Ti and 310 were conducted under bending and rotating loadings. The environments were at room temperature (RT) as well as at 550℃ in air. The fracture morphology was observed by SEM, and the S-N curves were processed according to the experimental data. The results indicate the fatigue limited stresses for the 3 stainless steels were in the order of 347 < 316Ti < 310, which consistent with the order of their tensile strength. Elevated temperature would accelerate the oxidation and therefore the fatigue life would decrease, among them 347 was more sensitive to temperature with the maximum decreasing tendency. All the 3 stainless steels have good resistance to high cycle fatigue when comparing their experimental data with the calculated value from the empirical formula. The fracture morphology presents areas of crack initiation, crack growth and fracture, the width of fatigue ripples is about 1 μm, the fracture area has much dimples, and 347 presents much cavities of different sizes in dimples. (authors)

  13. Microstructural influence on fatigue properties of a high-strength spring steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.S.; Lee, K.A.; Li, D.M. [Pohang Univ. of Sci. and Technol. (Korea, Republic of). Center for Adv. Aerospace Mater.; Yoo, S.J.; Nam, W.J. [Technical Research Laboratory, Pohang Iron and Steel Co. Ltd, Pohang 790-785 (Korea, Republic of)

    1998-01-30

    A study has been made to investigate the fatigue properties of a high-strength spring steel in relation to the microstructural variation via different heat treatments. Rotating-bending fatigue and fatigue crack growth (FCG) tests were conducted to evaluate the fatigue properties, and a transmission electron microscope (TEM) equipped with an energy dispersive X-ray (EDX) unit was used to characterize the tempered microstructure. The results indicate that the fatigue endurance {sigma}{sub f} increases with increasing tempering temperature, reaching a maximum at 450 C, then decreases. The increase of {sigma}{sub f} is mainly attributed to the refined distribution of precipitation, together with the structural uniformity of tempered martensite. The softening of tempered martensite due to excessive precipitation accounts for the decrease of {sigma}{sub f}. By contrast, the FCG results show an insensitivity of the stage-II growth behavior to the microstructural changes for the whole range of tempering temperature tested. The insensitivity is interpreted in terms of the counterbalancing microstructure-dependent contributions to the FCG behavior. (orig.) 30 refs.

  14. Dynamic Characteristics of a New Machine for Fatigue Testing of Railway Axles – Part 2

    Directory of Open Access Journals (Sweden)

    Karel FRYDRÝŠEK

    2012-06-01

    Full Text Available There were done some proposal calculations for a new testing machine. This new testing machine is determined for a dynamic fatigue testing of railway axles. The railway axles are subjected to bending and rotation (centrifugal effects. For the right proposition of a new machine is very important to know the basic dynamic characteristics of whole system. These dynamic characteristics are solved via FEM (MSC.Marc/Mentat software in combination with SBRA (Simulation-Based Reliability Assessment Method (probabilistic Monte Carlo approach, Anthill and Python software. The proposed dimensions and springs of a new machine for fatigue testing of railway axles were used for manufacturing. Application of the SBRA method connected with FEM in these areas is a new and innovative trend in mechanics. This paper is continuation of former work (i.e. easier deterministic approach already presented in this journal in 2007.

  15. Effects of laser peening treatment on high cycle fatigue and crack propagation behaviors in austenitic stainless steel

    International Nuclear Information System (INIS)

    Masaki, Kiyotaka; Ochi, Yasuo; Matsumura, Takashi; Ikarashi, Takaaki; Sano, Yuji

    2010-01-01

    Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using an impact wave of high pressure plasma induced by laser pulse irradiation. High compressive residual stress was induced by the LPwC treatment on the surface of low-carbon type austenitic stainless steel SUS316L. The affected depth reached about 1mm from the surface. High cycle fatigue tests with four-points rotating bending loading were carried out to confirm the effects of the LPwC treatment on fatigue strength and surface fatigue crack propagation behaviors. The fatigue strength was remarkably improved by the LPwC treatment over the whole regime of fatigue life up to 10 8 cycles. Specimens with a pre-crack from a small artificial hole due to fatigue loading were used for the quantitative study on the effect of the LPwC treatment. The fracture mechanics investigation on the pre-cracked specimens showed that the LPwC treatment restrained the further propagation of the pre-crack if the stress intensity factor range ΔK on the crack tip was less than 7.6 MPa√m. Surface cracks preferentially propagated into the depth direction as predicted through ΔK analysis on the crack by taking account of the compressive residual stresses due to the LPwC treatment. (author)

  16. Influence of aging condition and reversion austenite on fatigue property of the 300 grade 18Ni maraging steel

    International Nuclear Information System (INIS)

    Moriyama, Michihiko; Takaki, Setsuo; Kawagoishi, Norio

    2000-01-01

    The influence of aging condition on fatigue strength of the 300 grade 18Ni maraging steel has been investigated in relation to the behavior of age hardening and the formation of reversion austenite. In this study, rotating bending fatigue tests were performed for three series of specimens with different aging condition; as solution-treated without aging, aged for various time at 753 K which is the temperature applied for the industrial aging treatment, and over-aged to form a small amount of reversion austenite. Effect of reversion austenite on fatigue strength was examined using specimens with the same static strength which had been controlled by varying aging temperature and time, namely under-aging or over-aging. The main results obtained are as follows. (1) In the case of 753 K aging, the fatigue limits of specimens aged for 11 ks to 48 ks were nearly the same value, although an under-aged (2.8 ks) specimen has as much lower value as a solution-treated specimen without aging treatment. (2) A small amount of reversion austenite is effective for increasing fatigue resistance. For instance, 2 vol% of austenite was enough for improving fatigue limit of the maraging steel used, from 580 MPa to 640 MPa at the same hardness level of Hv 610. (author)

  17. Occipital bending in depression.

    Science.gov (United States)

    Maller, Jerome J; Thomson, Richard H S; Rosenfeld, Jeffrey V; Anderson, Rodney; Daskalakis, Zafiris J; Fitzgerald, Paul B

    2014-06-01

    There are reports of differences in occipital lobe asymmetry within psychiatric populations when compared with healthy control subjects. Anecdotal evidence and enlarged lateral ventricles suggests that there may also be a different pattern of curvature whereby one occipital lobe wraps around the other, termed 'occipital bending'. We investigated the prevalence of occipital bending in 51 patients with major depressive disorder (males mean age = 41.96 ± 14.00 years, females mean age = 40.71 ± 12.41 years) and 48 age- and sex-matched healthy control subjects (males mean age = 40.29 ± 10.23 years, females mean age = 42.47 ± 14.25 years) and found the prevalence to be three times higher among patients with major depressive disorder (18/51, 35.3%) when compared with control subjects (6/48, 12.5%). The results suggest that occipital bending is more common among patients with major depressive disorder than healthy subjects, and that occipital asymmetry and occipital bending are separate phenomena. Incomplete neural pruning may lead to the cranial space available for brain growth being restricted, or ventricular enlargement may exacerbate the natural occipital curvature patterns, subsequently causing the brain to become squashed and forced to 'wrap' around the other occipital lobe. Although the clinical implications of these results are unclear, they provide an impetus for further research into the relevance of occipital bending in major depression disorder. © The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. The effect of microstructure on fatigue performance of Ti-6Al-4V alloy after EDM surface treatment for application in orthopaedics.

    Science.gov (United States)

    Stráský, Josef; Janeček, Miloš; Harcuba, Petr; Bukovina, Michal; Wagner, Lothar

    2011-11-01

    Three different microstructures--equiaxed, bi-modal and coarse lamellar--are prepared from Ti-6Al-4V alloy. Electric discharge machining (EDM) with a high peak current (29 A) is performed in order to impose surface roughness and modify the chemical composition of the surface. Detailed scanning electron microscopy (SEM) investigation revealed a martensitic surface layer and subsurface heat affected zone (HAZ). EDX measurements showed carbon enriched remnants of the EDM process on the material surface. Rotating bending fatigue tests are undertaken for EDM processed samples for all three microstructures and also for electropolished-benchmark-samples. The fatigue performance is found to be rather poor and not particularly dependent on microstructure. The bi-modal microstructure shows a slightly superior high cycle fatigue performance. This performance can be further improved by a suitable heat treatment to an endurance limit of 200 MPa. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Electrochemical investigation of crack initiation during corrosion fatigue of stainless steels in the passive state. Elektrochemische Untersuchung der Rissbildung bei Schwingungsrisskorrosion im stabil-passiven Werkstoffzustand

    Energy Technology Data Exchange (ETDEWEB)

    Spaehn, R. (Technische Hochschule Darmstadt (Germany, F.R.))

    1991-03-01

    The corrosion fatigue behaviour of three stainless steels - ferritic (12% Cr), austenitic (type 316 Ti) and austenitic-ferritic (type 31803; Duplex stainless steel) - was studied under rotating bending moments in aqueous sulphuric acid of 30deg C. An instrumental set-up for recording the transient currents of specimens during potentiostatically controlled corrosion fatigue is described. Based on this transient current signal technique, three stages on the corrosion fatigue process can be discerned. In the incubation period, small stochastic current transients are caused by the response of the passive layer to alternating stresses and environmental conditions. The appearance of sinusoidal current signals indicates crack initiation whereas the phase angle between a fixed marker - i.e. a light barrier signal -, and the anodic amplitude represents the site of initiating cracks. Finally, the crack growth period is characterized by an increasing cell current and steadily growing sinusoidal current signals caused by the interplay of microplastic and repassivation processes at the crack tip. (orig.).

  20. The Effect of Nitriding Treatment Variables on the Fatigue Limit of Alloy Steel (34crnimo6) Under High Cycle Fatigue

    International Nuclear Information System (INIS)

    Mohamed, J.; Al-Alkawi, H.; Salameh, M.

    2009-01-01

    The aim of this research is to improve the fatigue limit for alloy steel (34CrNiMo6) by salt bath nitriding process. This property is more effective to increase the fatigue life for parts which are used in continuous cyclic loading. All the fatigue tests were implemented before and after nitriding process under rotating bending. Constant and variable capacity stresses were applied before and after nitriding processes. The nitriding process were implemented in salt bath component at three different times (1, 2, 3) hr when temperature was constant at (555 degree centigrade). The depth of the nitride layer reached (0.24, 0.37, 0.5) mm. The nitriding process repeated of another specimens at the same times but the temperature was (600 degree centigrade), the layer depth reached (0.28, 0.41, 0.55) mm. The formation of a high nitrogen iron phases were detected with a layer of the hard chrome nitrides on the surface. The nitriding process is forming the barriers on the surface that resist the initiation and propagation of cracks, as well as generating the compressive residual stresses which delay the progress of fatigue crack. This research deduced that the nitriding processes increased the fatigue limit and this limit is proportional to the time of the nitriding process. When the time increased, the depth of nitride layer is increased, but decreased when the temperature increased to (600 degree centigrade) because of the formation of brittle phase,in spite of the increase in layer depth. (author)

  1. AA, bending magnet, BLG

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    The very particular lattice of the AA required 2 types of dipole (bending magnets; BLG, long and narrow; BST, short and wide). The BLG had a steel length of 4.70 m, a good field width of 0.24 m, and a weight of about 70 t. Jean-Claude Brunet inspects the lower half of a BLG. For the BST magnets see 7811105 and 8006036.

  2. High speed rails. Fatigue behaviour

    International Nuclear Information System (INIS)

    Duart, J. M.; Pero-Sanz, J. A.; Verdeja, J. I.

    2005-01-01

    In recent years, passenger train speed and freight train load have increased to enhance efficiency of rail road transportation. These trends have increased the severity of rail service conditions, calling for rails with greater wear resistance, strength and fatigue behaviour. In the United Stated and Europe, track site weld rails are made entirely by aluminothermic process. This work describes the results of experimental study conducted on bending fatigue strength of plain rails and aluminothermic welded rails with preheating procedures (oxipropane and air-induced propane) approved by railways authorities. Compliance with the required fatigue strength shall be ascertained by 4 point pulsating bending test in accordance with European standards by aluminothermic welding in rails. The locati method, based in the empirical Miner's law about the cumulative damage on a fatigue tested material, allows, once known the Wohler curve of the welding process in use to settle the fatigue tensile limit at 50% with only one test. The values obtained at 2.10''6 cycles for plain rails (S f =353 MPa), oxipropane preheated aluminothermic weld rails (S f =225 MPa), and propane-air induced aluminothermic weld rails (S f =210 MPa) are very similar to those resulting from test method stated in the European Standard. From our point of view and due to its ease, speediness and savings, this is the most suitable test to check the quality and compare the aluminothermic processes in use. (Author) 15 refs

  3. Adrenal Fatigue

    Science.gov (United States)

    ... Search Featured Resource New Mobile App DOWNLOAD Adrenal Fatigue October 2017 Download PDFs English Editors Irina Bancos, MD Additional Resources Mayo Clinic What is adrenal fatigue? The term “adrenal fatigue” has been used to ...

  4. Fatigue behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP)

    Science.gov (United States)

    Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

    2015-01-01

    The static and fatigue bending behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP) has been investigated by four-point bending tests. Fatigue panels and weakened panels (wESCP) with an initial interface defect were manufactured for the fatigue tests. Stress σ vs. number of cycles curves (S-N) were recorded under the different stress...

  5. Biomechanical evaluation of an integrated fixation cage during fatigue loading: a human cadaver study.

    Science.gov (United States)

    Palepu, Vivek; Peck, Jonathan H; Simon, David D; Helgeson, Melvin D; Nagaraja, Srinidhi

    2017-04-01

    OBJECTIVE Lumbar cages with integrated fixation screws offer a low-profile alternative to a standard cage with anterior supplemental fixation. However, the mechanical stability of integrated fixation cages (IFCs) compared with a cage with anterior plate fixation under fatigue loading has not been investigated. The purpose of this study was to compare the biomechanical stability of a screw-based IFC with a standard cage coupled with that of an anterior plate under fatigue loading. METHODS Eighteen functional spinal units were implanted with either a 4-screw IFC or an anterior plate and cage (AP+C) without integrated fixation. Flexibility testing was conducted in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) on intact spines, immediately after device implantation, and post-fatigue up to 20,000 cycles of FE loading. Stability parameters such as range of motion (ROM) and lax zone (LZ) for each loading mode were compared between the 2 constructs at multiple stages of testing. In addition, construct loosening was quantified by subtracting post-instrumentation ROM from post-fatigue ROM. RESULTS IFC and AP+C configurations exhibited similar stability (ROM and LZ) at every stage of testing in FE (p ≥ 0.33) and LB (p ≥ 0.23) motions. In AR, however, IFCs had decreased ROM compared with AP+C constructs at pre-fatigue (p = 0.07) and at all post-fatigue time points (p ≤ 0.05). LZ followed a trend similar to that of ROM in AR. ROM increased toward intact motion during fatigue cycling for AP+C and IFC implants. IFC specimens remained significantly (p < 0.01) more rigid than specimens in the intact condition during fatigue for each loading mode, whereas AP+C construct motion did not differ significantly (p ≥ 0.37) in FE and LB and was significantly greater (p < 0.01) in AR motion compared with intact specimens after fatigue. Weak to moderate correlations (R 2 ≤ 56%) were observed between T-scores and construct loosening, with lower T

  6. The influence of microstructure on the cyclic deformation and damage of copper and an oxide dispersion strengthened steel studied via in-situ micro-beam bending

    Energy Technology Data Exchange (ETDEWEB)

    Howard, C., E-mail: cam7745@berkeley.edu [University of California, 2111A Etcheverry Hall, Berkeley, CA 94720-1730 (United States); Fritz, R.; Alfreider, M.; Kiener, D. [Department of Materials Physics, Montanuniversität Leoben, A-8700, Leoben (Austria); Hosemann, P. [University of California, 2111A Etcheverry Hall, Berkeley, CA 94720-1730 (United States)

    2017-02-27

    Service materials are often designed for strength, ductility, or toughness, but neglect the effects of cyclic time-variable loads ultimately leading to macroscopic mechanical failure. Fatigue originates as local plasticity that can first only be observed on the micro scale at defects serving as stress concentrators such as inclusions or grain boundaries. Thus, a recently developed technique to perform in-situ observation of micro scale bending fatigue experiments was applied. Micro-beams fabricated from copper, single grained and ultrafine grained (ufg), and an oxide dispersion strengthened (ODS) steel were subject to cyclic deformation and subsequent damage. The elastic stiffness, yield strength, dissipated energy, and maximum stress were measured as a function of cycle number and plastic strain amplitude. From these properties, cyclic stress-strain curves were developed. Initial pronounced monotonic hardening and an increasing Bauschinger effect were observed in all samples with increasing strain amplitude. Cyclic stability was maintained until plastic strain amplitudes reached a critical value. At this point, dramatic cyclic softening and microcracking occurred. The critical strain amplitude was found to be approximately 5.4×10{sup −3} for the copper with a refined grain structure and 1.2×10{sup −2} for the steel specimen. Grain rotation and noticeable changes in sub-grain structure were evident in the ufg copper after a critical strain amplitude of ε{sub a}=8.3×10{sup −3}. In-situ micro fatigue bending couples the cyclic evolution of bulk mechanical properties measurements with real-time electron microscopy analysis techniques of damage and failure mechanisms, which renders it a powerful method for developing novel fatigue resistant materials.

  7. AGS superconducting bending magnets

    International Nuclear Information System (INIS)

    Robins, K.E.; Sampson, W.B.; McInturff, A.D.; Dahl, P.F.; Abbatiello, F.; Aggus, J.; Bamberger, J.; Brown, D.; Damm, R.; Kassner, D.; Lasky, C.; Schlafke, A.

    1976-01-01

    Four large aperture superconducting bending magnets are being built for use in the experimental beams at the AGS. Each of these magnets is 2.5 m long and has a room temperature aperture of 20 cm. The magnets are similar in design to the dipoles being developed for ISABELLE and employ a low temperature iron core. Results are presented on the ''training'' behavior of the magnets and a comparison will be made with the smaller aperture versions of this design. The magnet field measurements include end fields and leakage fields as well as the harmonic components of the straight section of the magnet

  8. Piezoelectric micromotor based on the structure of serial bending arms.

    Science.gov (United States)

    Tong, Jianhua; Cui, Tianhong; Shao, Peige; Wang, Liding

    2003-09-01

    This paper presents a new piezoelectric micromotor based on the structure of serial bending arms. Serial bending arms are composed of two piezoelectric bimorphs with one end fixed and the other end free, driven by two signals of a biased square wave with a phase difference of pi/2. The free end of a cantilever arm will move along an elliptic orbit so that the cantilever is used to drive a cylinder rotor. The rotor's end surface contacts the free end of the cantilever, resulting in the rotor's rotation. There are six serial bending arms anchored on the base. The driving mechanism of the micromotor is proposed and analyzed. A new micromotor prototype, 5 mm in diameter, has been fabricated and characterized. The maximum rotational speed reaches 325 rpm, and the output torque is about 36.5 microNm.

  9. Loading Analysis of Composite Wind Turbine Blade for Fatigue Life Prediction of Adhesively Bonded Root Joint

    Science.gov (United States)

    Salimi-Majd, Davood; Azimzadeh, Vahid; Mohammadi, Bijan

    2015-06-01

    Nowadays wind energy is widely used as a non-polluting cost-effective renewable energy resource. During the lifetime of a composite wind turbine which is about 20 years, the rotor blades are subjected to different cyclic loads such as aerodynamics, centrifugal and gravitational forces. These loading conditions, cause to fatigue failure of the blade at the adhesively bonded root joint, where the highest bending moments will occur and consequently, is the most critical zone of the blade. So it is important to estimate the fatigue life of the root joint. The cohesive zone model is one of the best methods for prediction of initiation and propagation of debonding at the root joint. The advantage of this method is the possibility of modeling the debonding without any requirement to the remeshing. However in order to use this approach, it is necessary to analyze the cyclic loading condition at the root joint. For this purpose after implementing a cohesive interface element in the Ansys finite element software, one blade of a horizontal axis wind turbine with 46 m rotor diameter was modelled in full scale. Then after applying loads on the blade under different condition of the blade in a full rotation, the critical condition of the blade is obtained based on the delamination index and also the load ratio on the root joint in fatigue cycles is calculated. These data are the inputs for fatigue damage growth analysis of the root joint by using CZM approach that will be investigated in future work.

  10. Fatigue Strength of Reinforced Concrete Flexural Members | Kuryllo ...

    African Journals Online (AJOL)

    It is well known that reinforced concrete flexural members subjected to cyclic loads behave differently compared with static bending and can collapse due to the fatigue of concrete, reinforcement or both when maximum fatigue stresses of concrete and steel are well below the corresponding static strengths. But up till now ...

  11. Secondary flow in sharp open-channel bends

    NARCIS (Netherlands)

    Blanckaert, K.; De Vriend, H.J.

    2004-01-01

    Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in

  12. Simplified elastoplastic fatigue analysis

    International Nuclear Information System (INIS)

    Autrusson, B.; Acker, D.; Hoffmann, A.

    1987-01-01

    Oligocyclic fatigue behaviour is a function of the local strain range. The design codes ASME section III, RCC-M, Code Case N47, RCC-MR, and the Guide issued by PNC propose simplified methods to evaluate the local strain range. After having briefly described these simplified methods, we tested them by comparing the results of experimental strains with those predicted by these rules. The experiments conducted for this study involved perforated plates under tensile stress, notched or reinforced beams under four-point bending stress, grooved specimens under tensile-compressive stress, and embedded grooved beams under bending stress. They display a relative conservatism depending on each case. The evaluation of the strains of rather inaccurate and sometimes lacks conservatism. So far, the proposal is to use the finite element codes with a simple model. The isotropic model with the cyclic consolidation curve offers a good representation of the real equivalent strain. There is obviously no question of representing the cycles and the entire loading history, but merely of calculating the maximum variation in elastoplastic equivalent deformations with a constant-rate loading. The results presented testify to the good prediction of the strains with this model. The maximum equivalent strain will be employed to evaluate fatigue damage

  13. Investigation of fatigue strength of tool steels in sheet-bulk metal forming

    Science.gov (United States)

    Pilz, F.; Gröbel, D.; Merklein, M.

    2018-05-01

    To encounter trends regarding an efficient production of complex functional components in forming technology, the process class of sheet-bulk metal forming (SBMF) can be applied. SBMF is characterized by the application of bulk forming operations on sheet metal, often in combination with sheet forming operations [1]. The combination of these conventional process classes leads to locally varying load conditions. The resulting load conditions cause high tool loads, which lead to a reduced tool life, and an uncontrolled material flow. Several studies have shown that locally modified tool surfaces, so-called tailored surfaces, have the potential to control the material flow and thus to increase the die filling of functional elements [2]. A combination of these modified tool surfaces and high tool loads in SBMF is furthermore critical for the tool life and leads to fatigue. Tool fatigue is hardly predictable and due to a lack of data [3], a challenge in tool design. Thus, it is necessary to provide such data for tool steels used in SBMF. The aim of this study is the investigation of the influence of tailored surfaces on the fatigue strength of the powder metallurgical tool steel ASP2023 (1.3344, AISI M3:2), which is typically used in cold forging applications, with a hardness 60 HRC ± 1 HRC. To conduct this investigation, the rotating bending test is chosen. As tailored surfaces, a DLC-coating and a surface manufactured by a high-feed-milling process are chosen. As reference a polished surface which is typical for cold forging tools is used. Before the rotating bending test, the surface integrity is characterized by measuring topography and residual stresses. After testing, the determined values of the surface integrity are correlated with the reached fracture load cycle to derive functional relations. Based on the gained results the investigated tailored surfaces are evaluated regarding their feasibility to modify tool surfaces within SBMF.

  14. Bend testing for miniature disks

    International Nuclear Information System (INIS)

    Huang, F.H.; Hamilton, M.L.; Wire, G.L.

    1982-01-01

    A bend test was developed to obtain ductility measurements on a large number of alloy variants being irradiated in the form of miniature disks. Experimental results were shown to be in agreement with a theoretical analysis of the bend configuration. Disk specimens fabricated from the unstrained grip ends of previously tested tensile specimens were used for calibration purposes; bend ductilities and tensile ductilities were in good agreement. The criterion for estimating ductility was judged acceptable for screening purposes

  15. Multi-purpose fatigue sensor. Part 1. Uniaxial and multiaxial fatigue

    Directory of Open Access Journals (Sweden)

    M.V. Karuskevich

    2016-10-01

    Full Text Available The paper describes the key principles and results of preliminary experiments aimed at the development of new technique for the fatigue life prediction under conditions of biaxial cyclic tension. The foundations of the method were developed early by the numerous tests with monitoring the process of surface deformation relief formation, which is proved to be an indicator of accumulated fatigue damage under uniaxial fatigue. The employed phenomenon was early applied for the development of a family of uniaxial loading fatigue sensors. The formation of strain induced relief has been recently taken into consideration as a part of damage accumulation criteria under biaxial fatigue as well. The home-made testing machine has been designed to implement combined bending and torsion loading that simulates loads experienced by an aircraft wing skin. The experimental evidences on formation and evolution of the deformation relief revealed under conditions of combined loading, supports the proposed concept of biaxial fatigue sensor

  16. High cycle fatigue properties of inconel 690

    International Nuclear Information System (INIS)

    Lee, Young Ho; Lee, Byong Whi; Kim, In Sup; Park, Chi Yong

    1997-01-01

    Inconel 690 is presently used as sleeve material and a replacement alloy in degraded steam generators, as well as the material for new steam generators. But Inconel 690 has low thermal conductivity which are 3-8% less than that of Inconel 600 at operating temperature. For the same power output, conduction area must be increased. As a result, more fluid induced vibration can cause a fatigue damage of Inconel 690. High cycle fatigue ruptures occurred in the U-bend regions of North Anna Unit 1 and Mihama Unit 2 steam generators. At this study, the effect of temperature on fatigue crack growth rate in Inconel 690 steam generator tube was investigated at various temperature in air environment. With increasing temperature, fatigue crack growth rate increased and grain size effect decreased. Chromium carbides which have large size and semi-continuous distribution in the grain boundaries decreased fatigue crack growth rate

  17. Test Equal Bending by Gravity for Space and Time

    Science.gov (United States)

    Sweetser, Douglas

    2009-05-01

    For the simplest problem of gravity - a static, non-rotating, spherically symmetric source - the solution for spacetime bending around the Sun should be evenly split between time and space. That is true to first order in M/R, and confirmed by experiment. At second order, general relativity predicts different amounts of contribution from time and space without a physical justification. I show an exponential metric is consistent with light bending to first order, measurably different at second order. All terms to all orders show equal contributions from space and time. Beautiful minimalism is Nature's way.

  18. Seafarer fatigue

    DEFF Research Database (Denmark)

    Jepsen, Jørgen Riis; Zhao, Zhiwei; van Leeuwen, Wessel M. A.

    2015-01-01

    Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating...... to seafarer fatigue. Materials and methods: A literature study was conducted aiming to collect publications that address risk factors for fatigue, short-term and long-term consequences for health and safety, and options for fatigue mitigation at sea. Due to the limited number of publications that deals...... with seafarers, experiences from other populations sharing the same exposures (e.g. shift work) were also included when appropriate. Results: Work at sea involves multiple risk factors for fatigue, which in addition to acute effects (e.g., impaired cognition, accidents) contributes through autonomic, immunologic...

  19. Fatigue improvement in low temperature plasma nitrided Ti–6Al–4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Farokhzadeh, K.; Edrisy, A., E-mail: edrisy@uwindsor.ca

    2015-01-03

    In this study a low temperature (600 °C) treatment was utilized to improve the fatigue performance of plasma nitrided Ti–6Al–4V alloy by optimization of microstructure. In order to study the fatigue properties, rotation bending tests were conducted, the S–N curves were constructed, and the results were compared with those obtained by an elevated temperature treatment (900 °C) as well as conventional gas/plasma nitriding treatments reported in literature. The plasma nitrided alloy at 600 °C showed an endurance limit of 552 MPa which was higher than those achieved by conventional nitriding treatments performed at 750–1100 °C. In contrast, plasma nitriding at 900 °C resulted in the reduction of fatigue life by at least two orders of magnitude compared to the 600 °C treatment, accompanied by a 13% reduction of tensile strength and a 78% reduction of ductility. The deterioration of mechanical properties after the elevated temperature treatment was attributed to the formation of a thick compound layer (∼6 µm) on the surface followed by an α-Case (∼20 µm) and phase transformation in the bulk microstructure from fully equiaxed to bimodal with coarse grains (∼5 times higher average grain size value). The microstructure developed at 600 °C consisted of a thin compound layer (<2 µm) and a deep nitrogen diffusion zone (∼45 µm) while the bulk microstructure was maintained with only 40% grain growth. The micromechanisms of fatigue failures were identified by examination of the fracture surfaces under a scanning electron microscope (SEM). It was found that fatigue failure in the plasma nitrided alloy initiated from the surface in the low cycle region (N≤10{sup 5} cycles) and propagated in a ductile manner leading to the final rupture. No failures were observed in the high cycle region (N>10{sup 5} cycles) and the nitrided alloy endured cyclic loading until the tests were stopped at 10{sup 7} cycles. The thin morphology of the compound layer in this

  20. Fatigue improvement in low temperature plasma nitrided Ti–6Al–4V alloy

    International Nuclear Information System (INIS)

    Farokhzadeh, K.; Edrisy, A.

    2015-01-01

    In this study a low temperature (600 °C) treatment was utilized to improve the fatigue performance of plasma nitrided Ti–6Al–4V alloy by optimization of microstructure. In order to study the fatigue properties, rotation bending tests were conducted, the S–N curves were constructed, and the results were compared with those obtained by an elevated temperature treatment (900 °C) as well as conventional gas/plasma nitriding treatments reported in literature. The plasma nitrided alloy at 600 °C showed an endurance limit of 552 MPa which was higher than those achieved by conventional nitriding treatments performed at 750–1100 °C. In contrast, plasma nitriding at 900 °C resulted in the reduction of fatigue life by at least two orders of magnitude compared to the 600 °C treatment, accompanied by a 13% reduction of tensile strength and a 78% reduction of ductility. The deterioration of mechanical properties after the elevated temperature treatment was attributed to the formation of a thick compound layer (∼6 µm) on the surface followed by an α-Case (∼20 µm) and phase transformation in the bulk microstructure from fully equiaxed to bimodal with coarse grains (∼5 times higher average grain size value). The microstructure developed at 600 °C consisted of a thin compound layer (<2 µm) and a deep nitrogen diffusion zone (∼45 µm) while the bulk microstructure was maintained with only 40% grain growth. The micromechanisms of fatigue failures were identified by examination of the fracture surfaces under a scanning electron microscope (SEM). It was found that fatigue failure in the plasma nitrided alloy initiated from the surface in the low cycle region (N≤10 5 cycles) and propagated in a ductile manner leading to the final rupture. No failures were observed in the high cycle region (N>10 5 cycles) and the nitrided alloy endured cyclic loading until the tests were stopped at 10 7 cycles. The thin morphology of the compound layer in this study restricted

  1. Improved Fatigue Performance of Threaded Drillstring Connections by Cold Rolling

    Energy Technology Data Exchange (ETDEWEB)

    Kristoffersen, Steinar

    2002-01-01

    The research work presented in this thesis is concerned with analytical, numerical and experimental studies of the effect of cold rolling on the fatigue behaviour of threaded drillstring connections. A comprehensive literature study is made of the various effects on the fatigue behaviour of residual stresses introduced by mechanical deformation of notched components. Some of the effects studied are cyclic hardening behaviour after prestraining, cyclic creep, fatigue initiation in prestrained materials, short cracks and crack growth models including crack closure. Residual stresses were introduced in the surface of a smooth pipe by a rolling device to simulate a cold rolling process and verify the calculated residual stresses by measurements. Strain hardening and contact algorithm of the two bodies were incorporated in the FE analyses. Two significant errors were found in the commercial software package for residual stress evaluation, Restran v. 3.3.2a also called SINT, when using the Schajer method. The Schajer algorithm is the only hole-drilling algorithm without theoretical shortcomings, and is recommended when measuring large residual stress gradients in the depth direction. Using the Schajer method solved by in-house Matlab-routines good agreement between measured residual stress gradients and residual stress gradients from FE analyses was found. Full scale fatigue tests were performed on pipes cut from used drillstrings with notches of similar geometry as threads used in drillstring connections. The simulated threads consisted of four full depth helix notches with runouts at the surface. The pipe threads were cold rolled and fatigue tested in a full-scale four-point rotating bending fatigue testing rig. The test results showed that cold rolling had an effect on the crack initiation period. A major part of the fatigue life was with cracks observed at the notch root, but due to the increased fatigue crack propagation resistance the final fracture initiated at

  2. Influence of Sludge Particles on the Fatigue Behavior of Al-Si-Cu Secondary Aluminium Casting Alloys

    Directory of Open Access Journals (Sweden)

    Lorella Ceschini

    2018-04-01

    Full Text Available Al-Si-Cu alloys are the most widely used materials for high-pressure die casting processes. In such alloys, Fe content is generally high to avoid die soldering issues, but it is considered an impurity since it generates acicular intermetallics (β-Fe which are detrimental to the mechanical behavior of the alloys. Mn and Cr may act as modifiers, leading to the formation of other Fe-bearing particles which are characterized by less harmful morphologies, and which tend to settle on the bottom of furnaces and crucibles (usually referred to as sludge. This work is aimed at evaluating the influence of sludge intermetallics on the fatigue behavior of A380 Al-Si-Cu alloy. Four alloys were produced by adding different Fe, Mn and Cr contents to A380 alloy; samples were remelted by directional solidification equipment to obtain a fixed secondary dendrite arm spacing (SDAS value (~10 μm, then subjected to hot isostatic pressing (HIP. Rotating bending fatigue tests showed that, at room temperature, sludge particles play a detrimental role on fatigue behavior of T6 alloys, diminishing fatigue strength. At elevated temperatures (200 °C and after overaging, the influence of sludge is less relevant, probably due to a softening of the α-Al matrix and a reduction of stress concentration related to Fe-bearing intermetallics.

  3. Corrosion fatigue behaviour of ion nitrided AISI 4140 steel

    Energy Technology Data Exchange (ETDEWEB)

    Genel, K. [Sakarya Univ., Adapazari (Turkey). Mech. Eng. Dept.; Demirkol, M.; Guelmez, T. [Faculty of Mechanical Engineering, Istanbul Technical University, Guemuessuyu, 80191, Istanbul (Turkey)

    2000-08-31

    Machine components suffer from corrosion degradation of fatigue characteristics and improvement can be attained by the application of a nitriding treatment, particularly to low alloy steels. In the present study, the effect of ion nitriding on corrosion fatigue performance of AISI 4140 steel has been investigated by conducting a series of rotary bending corrosion fatigue tests at 95 Hz, in 3% NaCl aqueous solution. Hourglass shaped, 4 mm diameter fatigue specimens were ion nitrided at 748 K for 1, 3, 8 and 16 h prior to the tests. It was observed that distinct fatigue limit behaviour of ion nitrided steel in air completely disappeared in corrosive environment besides severe degradation in fatigue characteristics. An improvement reaching to 60% in corrosion fatigue strength can be attained by successive ion nitriding practice based on a fatigue life of 10{sup 7} cycles. An attempt was made to establish an empirical relationship between corrosion fatigue strength and relative case depth, which considers the size of the ion nitrided specimen. It was also determined that a power relationship holds between corrosion fatigue strength and fatigue life of ion nitrided steel. The presence of white layer has resulted in additional improvement in corrosion fatigue resistance, and it was observed that corrosion fatigue cracks were initiated dominantly under the white layer by pit formation mechanism. (orig.)

  4. Corrosion fatigue behaviour of ion nitrided AISI 4140 steel

    International Nuclear Information System (INIS)

    Genel, K.

    2000-01-01

    Machine components suffer from corrosion degradation of fatigue characteristics and improvement can be attained by the application of a nitriding treatment, particularly to low alloy steels. In the present study, the effect of ion nitriding on corrosion fatigue performance of AISI 4140 steel has been investigated by conducting a series of rotary bending corrosion fatigue tests at 95 Hz, in 3% NaCl aqueous solution. Hourglass shaped, 4 mm diameter fatigue specimens were ion nitrided at 748 K for 1, 3, 8 and 16 h prior to the tests. It was observed that distinct fatigue limit behaviour of ion nitrided steel in air completely disappeared in corrosive environment besides severe degradation in fatigue characteristics. An improvement reaching to 60% in corrosion fatigue strength can be attained by successive ion nitriding practice based on a fatigue life of 10 7 cycles. An attempt was made to establish an empirical relationship between corrosion fatigue strength and relative case depth, which considers the size of the ion nitrided specimen. It was also determined that a power relationship holds between corrosion fatigue strength and fatigue life of ion nitrided steel. The presence of white layer has resulted in additional improvement in corrosion fatigue resistance, and it was observed that corrosion fatigue cracks were initiated dominantly under the white layer by pit formation mechanism. (orig.)

  5. Yield stress determination from miniaturized disk bend test data

    International Nuclear Information System (INIS)

    Sohn, D.S.; Kohse, G.; Harling, O.K.

    1985-04-01

    Methodology for testing 3.0 mm diameter by 0.25 mm thick disks by bending in a punch and die has been described previously. This paper describes the analysis of load/deflection data from such miniaturized disk bend tests (MDBT) using a finite element simulation. Good simulation has been achieved up to a point just beyond the predominantly elastic response, linear initial region. The load at which deviation from linearity begins has been found to correlate with yield stress, and yield stress has been successfully extracted from disk bend tests of a number of known materials. Although finite element codes capable of dealing with large strains and large rotations have been used, simulation of the entire load/deflection curve up to fracture of the specimen has not yet been achieved

  6. Fatigue (PDQ)

    Science.gov (United States)

    ... Data Conducting Clinical Trials Statistical Tools and Data Terminology Resources NCI Data Catalog Cryo-EM NCI's Role ... Problems getting enough sleep. Being less active. Other medical conditions. Fatigue is common in people with advanced ...

  7. Analytical model of asymmetrical Mixed-Mode Bending test of adhesively bonded GFRP joint

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Martin; Hutař, Pavel; Vassilopoulos, Anastasios P.; Shahverdi, M.

    2015-01-01

    Roč. 9, č. 34 (2015), s. 237-246 ISSN 1971-8993 R&D Projects: GA MŠk(CZ) EE2.3.30.0063; GA ČR GA15-09347S Institutional support: RVO:68081723 Keywords : GFRP materials * Mixed-Mode bending * Fiber bridging * Analytical model Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. Bend strain tolerances of a Nb3Sn conductor proposed for use in the magnetic fusion energy program

    International Nuclear Information System (INIS)

    Luhman, T.; Welch, D.O.; Suenaga, M.

    1980-01-01

    Bend strain tolerances were studied on a 2869 filament bronze-processed Nb 3 Sn wire conductor in magnetic fields to 8 T. Relative values of the wire's current transfer length to twist pitch were shown to influence the bend-strain tolerance. Low matrix resistivities, associated with Sn-depleted bronzes following heat-treatments of 48 h at 725 0 C, produce current transfer lengths less than the twist pitch, 10 mm. The resulting bend-strain tolerances, at 10 -12 ohm.cm, are improved over those found for shorter heat-treatment times. Results from bend-fatigue experiments were divided into two domains separated by the strain value required to produce compound cracking, epsilon/sub f//sup B/. Applied bending strains less than epsilon/sub f//sup B/ were found to increase zero strain critical current values and this increase was independent of the number of fatigue cycles. When applying strains large enough to produce cracking in the compounds critical currents decreased from their asreacted values tending to reach a minimum after several fatigue cycles. Evidence exists for a neutral axis shift during bending and slight differences between tensile and bend strain tolerances are accounted for in terms of such a shift

  9. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    La Cruz, P. de.

    1990-01-01

    In the present work the effect of ion nitriding, laser hardening and hot dip galvanizing upon the fatigue limit and notch sensitivity of a B-Mn Swedish steel SS 2131 have been investigated. The fatigue tests were performed in plane reverse bending fatigue (R=1). The quenched and tempered condition was taken as the reference condition. The microstructure, microhardness, fracture surface and coating appearance of the fatigue surface treated specimens were studied. Residual stress and retained austenite measurements were also carried out. It was found that ion nitriding improves the fatigue limit by 53 % for smooth specimens and by 115 % for notched specimens. Laser hardening improves the fatigue limit by 18 % and 56 % for smooth and notched specimen respectively. Hot dip galvanizing gives a slight deterioration of the fatigue limit (9 % and 10 % for smooth and notched specimen respectively). Ion nitriding and laser hardening decrease the value of the notch sensitivity factor q by 78 % and 65 % respectively. Hot dip galvanizing does not modify it. A simple schematic model based on a residual stress distribution, has been used to explain the different effects. It seems that the presence of the higher compressive residual stresses and the higher uniformity of the microstructure may be the causes of the better fatigue performance of ion nitrided specimens. (119 refs.) (author)

  10. Fatigue strength of socket welded pipe joint

    International Nuclear Information System (INIS)

    Iida, K.; Matsuda, F.; Sato, M.; Higuchi, M.; Nakagawa, A.

    1994-01-01

    Fully reversed four point bending fatigue tests were carried out of small diameter socket welded joints made of carbon steels. Experimental parameters are pipe diameter, thickness of pipe and socket wall, throat depth and shape of fillet welds, slip-on and diametral gaps in the socket welding, lack of penetration at the root of fillet welds, and peening of fillet welds. In most cases a fatigue crack started from the root of the fillet, but in the case of higher stress amplitude, it tended to start from the toe of fillet. The standard socket welded joint of 50 mm diameter showed relatively low fatigue strength, 46 MPa in stress amplitude at the 10 7 cycles failure life. This value corresponds to about 1/5 of that of the smoothed base metal specimens in axial fatigue. The fatigue strength showed decrease with increasing pipe diameter, and increase with increasing the thickness of pipe and socket wall. The effects of throat depth and shape of fillet welds on fatigue strength were not significant. Contrary to the expectation, the fatigue strength of the socket welded joint without slip-on gap is higher than that of the joint with the normal gap. A lack of penetration at the root deleteriously reduced fatigue strength, showing 14 MPa in stress amplitude at the 10 7 cycles failure life for the 50 mm diameter socket joint. (orig.)

  11. Effects of combined plasma chromizing and shot peening on the fatigue properties of a Ti6Al4V alloy

    Science.gov (United States)

    Yu, Shouming; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing

    2015-10-01

    A plasma chromizing treatment was conducted on Ti6Al4V samples by employing the recently developed double glow plasma surface alloying technology. The Cr-alloyed layer consisted of four sub-layers, namely the Cr deposition, Cr2Ti, CrTi4, and Cr-Ti solid-solution layers. The local hardness and moduli were determined via nanoindentation. In addition, the fatigue properties of the samples were evaluated by using a rotating-bending fatigue machine under a given load. The results showed that the hardness or elastic moduli of the adjacent sub-layers differed significantly and the fatigue properties of the Ti6Al4V alloy deteriorated with the plasma chromizing treatment. This deterioration stemmed mainly from cracks initiated at the interfaces between the sub-layers and the microstructural changes of the substrate; these changes were induced by the high temperature used in the plasma chromizing process. However, the fatigue life of the plasma-chromized samples was increased by a shot peening post-treatment. The fatigue life of the samples resulting from this combination of treatments was slightly higher than that of the single-shot-peened Ti6Al4V substrate. In fact, the sample retaining only the Cr-Ti solid-solution layer (that is, the first three sub-layers were removed), when shot-peened, exhibited the highest fatigue life among all the tested samples; this was attributed to that sample having the highest residual compressive stress, the significant work hardening, and the good hardness to toughness balance.

  12. Mean load effects on the fatigue life of offshore wind turbine monopile foundations

    DEFF Research Database (Denmark)

    Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

    2013-01-01

    This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current....... The fatigue damage is analysed in terms of the lifetime fatigue damage equivalent bending moment. Three different mean value correction techniques are considered, namely, Goodman, Walker, and mean sensitivity factor. An increase in the lifetime fatigue damage equivalent bending moment between 6% (mean...... of the fatigue life of offshore wind turbine monopile foundations. Moreover, it is shown that a nonlinear hydrodynamic model is required in order to correctly account for the effect of the current....

  13. Oroclinal Bending and Mountain Uplift in the Central Andes

    Science.gov (United States)

    Mpodozis, C.; Arriagada, C.; Roperch, P.

    2007-05-01

    The large paleomagnetic database now available for the Central Andes permits a good understanding of the overall spatial and temporal variations of rotations. Mesozoic to Early Paleogene rocks along the forearc of northern Chile (23°-28°S) record significant clockwise rotations (>25°) [Arriagada et al., 2006, Tectonics, doi:10.1029/2005TC001923]. Along the forearc of southern Peru, counterclockwise rotations recorded within flat lying red-beds (Moquegua Formation) increase from about -30° at 17.5°S to - 45° at15.5°S and decrease through time from the late Eocene to the late Oligocene-early Miocene [Roperch et al., 2006, Tectonics, doi:10.1029/2005TC001882]. Recently published thermo-chronological studies show evidence for strong exhumation within Bolivian Eastern Cordillera and the Puna plateau starting in the Eocene while structural studies indicate that the majority of crustal shortening in the Eastern Cordillera occurred during the Eocene-Oligocene, although the final stages of deformation may have continued through the Early Miocene. Rotations in the Peruvian and north Chilean forearc thus occurred at the same time than deformation and exhumation/uplift within the Eastern Cordillera. In contrast Neogene forearc rocks in southern Peru and northern Chile do not show evidences of rotation but low magnitude (10°) counterclockwise rotations are usually found in mid to late Miocene rocks from the northern Altiplano. These Neogene rotations are concomitant with shortening in the Sub-Andean zone and sinistral strike-slip faulting along the eastern edge of the northern Altiplano. We interpret the rotation pattern along the southern Peru and north Chile forearc as a result of strong late Eocene- late Oligocene oroclinal bending of the Central Andes associated with shortening gradients along the Eastern Cordillera associated both with the Abancay deflection and the Arica bend. The amount and spatial distribution of pre-Neogene shortening needed to account for

  14. A New Kind of Bend Sensor

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new kind of bend sensor is introduced.It can be used to detect the bend angle of an object or inclination between two objects.It has characteristics of small size, lightweight, high reliability, fine flexibility and plasticity.When this bend sensor is used with a proper converting circuit, it can implement dynamic measuring the bend angle of an object conveniently.The application of the bend sensor in dataglove is also described.

  15. Analysis of Bending a Square Ceramic Plate under Strong Rotation

    National Research Council Canada - National Science Library

    Cooper, Gene

    2000-01-01

    .... Although short in duration, these loads can break even the most robust design. Unfortunately, when failure occurs, it is not obvious that a loading mechanism caused the problem, hence, making it difficult to make design...

  16. 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)

  17. Bending characteristics of resin concretes

    Directory of Open Access Journals (Sweden)

    Ribeiro Maria Cristina Santos

    2003-01-01

    Full Text Available In this research work the influence of composition and curing conditions in bending strength of polyester and epoxy concrete is analyzed. Various mixtures of resin and aggregates were considered in view of an optimal combination. The Taguchi methodology was applied in order to reduce the number of tests, and in order to evaluate the influence of various parameters in concrete properties. This methodology is very useful for the planning of experiments. Test results, analyzed by this methodology, shown that the most significant factors affecting bending strength properties of resin concretes are the type of resin, resin content and charge content. An optimal formulation leading to a maximum bending strength was achieved in terms of material parameters.

  18. Reliability Issues and Solutions in Flexible Electronics Under Mechanical Fatigue

    Science.gov (United States)

    Yi, Seol-Min; Choi, In-Suk; Kim, Byoung-Joon; Joo, Young-Chang

    2018-03-01

    Flexible devices are of significant interest due to their potential expansion of the application of smart devices into various fields, such as energy harvesting, biological applications and consumer electronics. Due to the mechanically dynamic operations of flexible electronics, their mechanical reliability must be thoroughly investigated to understand their failure mechanisms and lifetimes. Reliability issue caused by bending fatigue, one of the typical operational limitations of flexible electronics, has been studied using various test methodologies; however, electromechanical evaluations which are essential to assess the reliability of electronic devices for flexible applications had not been investigated because the testing method was not established. By employing the in situ bending fatigue test, we has studied the failure mechanism for various conditions and parameters, such as bending strain, fatigue area, film thickness, and lateral dimensions. Moreover, various methods for improving the bending reliability have been developed based on the failure mechanism. Nanostructures such as holes, pores, wires and composites of nanoparticles and nanotubes have been suggested for better reliability. Flexible devices were also investigated to find the potential failures initiated by complex structures under bending fatigue strain. In this review, the recent advances in test methodology, mechanism studies, and practical applications are introduced. Additionally, perspectives including the future advance to stretchable electronics are discussed based on the current achievements in research.

  19. Probabilistic Model for Fatigue Crack Growth in Welded Bridge Details

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard; Yalamas, Thierry

    2013-01-01

    In the present paper a probabilistic model for fatigue crack growth in welded steel details in road bridges is presented. The probabilistic model takes the influence of bending stresses in the joints into account. The bending stresses can either be introduced by e.g. misalignment or redistribution...... of stresses in the structure. The fatigue stress ranges are estimated from traffic measurements and a generic bridge model. Based on the probabilistic models for the resistance and load the reliability is estimated for a typical welded steel detail. The results show that large misalignments in the joints can...

  20. The creep bending of short radius pipe bends

    International Nuclear Information System (INIS)

    Spence, John

    1975-01-01

    In existing and proposed liquid metal fast breeder reactor design the pipework has considerable importance. Parts of the LMFBR include thin walled short radius bends which are expected to operate in the creep regime. In linear elasticity it is known that the assumption of long radius bends is not too severe as far as the flexibility characteristics are concerned although some modifications are necessary for accurate determination of the stresses. No data exists for nonlinear creep. Current work is aimed at elucidating the effect of the various assumptions common to linear elastic theory in so far as they affect the creep characteristics of bends on systems. Herein an energy based analysis using a simple n power constitutive law for stationary creep is employed to derive basic design data for flexibilities and stresses which will be necessary before complete systems can be assessed for creep. The analysis shows on comparison with the long radius work that the assumption of R>r is not much more restrictive in creep than for linear elasticity. Flexibilities for short radius bends appear to be well approximated by the long radius values. Thus the attractive reference stress information already derived may be used directly to find deformations without a complete knowledge of the constitutive relationship. However, stresses are somewhat different. Fortunately the maximum deviation occurs at relatively low levels of stress, the peak stresses being in fair agreement. When n=1 the present results reduce essentially to those obtained from existing linear elastic theory

  1. Thermal fatigue evaluation of partially cooled pipes

    International Nuclear Information System (INIS)

    Kawasaki, N.; Kasahara, N.; Takasho, H.

    2004-01-01

    Concerning thermal striping phenomenon with a cold/hot spot, effect of the thermal spot on fatigue strength was investigated. The thermal spot causes membrane stress and enhances bending stress in the structure. Increased stress shortens the fatigue life and accelerates the crack propagation rate. The mechanism to increase stress was found to be the structural constraint of thermal strain by the thermal spot. To consider this mechanism, constraint efficiency factors were introduced to the thermal stress evaluation method based on frequency transfer functions developed by authors. Proposed method with these factors was validated through comparisons with cyclic FEA considering thermal spots. (orig.)

  2. Development of U-frame bending system for studying the vibration integrity of spent nuclear fuel

    Science.gov (United States)

    Wang, Hong; Wang, Jy-An John; Tan, Ting; Jiang, Hao; Cox, Thomas S.; Howard, Rob L.; Bevard, Bruce B.; Flanagan, Michelle

    2013-09-01

    A bending fatigue system developed to evaluate the response of spent nuclear fuel rods to vibration loads is presented. A U-frame testing setup is used for imposing bending loads on the fuel rod specimen. The U-frame setup consists of two rigid arms, side connecting plates to the rigid arms, and linkages to a universal testing machine. The test specimen's curvature is obtained through a three-point deflection measurement method. The tests using surrogate specimens with stainless steel cladding revealed increased flexural rigidity under unidirectional cyclic bending, significant effect of cladding-pellets bonding on the response of surrogate rods, and substantial cyclic softening in reverse bending mode. These phenomena may cast light on the expected response of a spent nuclear fuel rod. The developed U-frame system is thus verified and demonstrated to be ready for further pursuit in hot-cell tests.

  3. Development of U-frame bending system for studying the vibration integrity of spent nuclear fuel

    International Nuclear Information System (INIS)

    Wang, Hong; Wang, Jy-An John; Tan, Ting; Jiang, Hao; Cox, Thomas S.; Howard, Rob L.; Bevard, Bruce B.; Flanagan, Michelle

    2013-01-01

    A bending fatigue system developed to evaluate the response of spent nuclear fuel rods to vibration loads is presented. A U-frame testing setup is used for imposing bending loads on the fuel rod specimen. The U-frame setup consists of two rigid arms, side connecting plates to the rigid arms, and linkages to a universal testing machine. The test specimen’s curvature is obtained through a three-point deflection measurement method. The tests using surrogate specimens with stainless steel cladding revealed increased flexural rigidity under unidirectional cyclic bending, significant effect of cladding-pellets bonding on the response of surrogate rods, and substantial cyclic softening in reverse bending mode. These phenomena may cast light on the expected response of a spent nuclear fuel rod. The developed U-frame system is thus verified and demonstrated to be ready for further pursuit in hot-cell tests

  4. Significance of residual stress on fatigue properties of welded pipes

    International Nuclear Information System (INIS)

    Ohta, A.; Maeda, Y.; Kanao, M.

    1984-01-01

    The mean stress effect on the fatigue properties of two kinds of welded pipes was investigated in cantilever bending. The fatigue strength changed with the mean stress on fillet welded pipes, but did not change on butt welded pipes. The fatigue crack initiated from the toe of weld on the outer surface of fillet welded pipes and from the undercut on the inner surface of butt welded pipes. The measurement of the fatigue crack propagation rate and the residual stress distribution through the thickness of pipe revealed that the difference in the fatigue properties between fillet and butt welded pipes arose from the weld-induced residual stress, tension on the inner surface and compression on the outer surface. It is suggested that the production of compressive residual stress along the inner surface would be an effective means for improving the fatigue strength of butt welded pipes. (author)

  5. Flexural fatigue life prediction of closed hat-section using materially nonlinear axial fatigue characteristics

    Science.gov (United States)

    Razzaq, Zia

    1989-01-01

    Straight or curved hat-section members are often used as structural stiffeners in aircraft. For instance, they are employed as stiffeners for the dorsal skin as well as in the aerial refueling adjacent area structure in F-106 aircraft. The flanges of the hat-section are connected to the aircraft skin. Thus, the portion of the skin closing the hat-section interacts with the section itself when resisting the stresses due to service loads. The flexural fatigue life of such a closed section is estimated using materially nonlinear axial fatigue characteristics. It should be recognized that when a structural shape is subjected to bending, the fatigue life at the neutral axis is infinity since the normal stresses are zero at that location. Conversely, the fatigue life at the extreme fibers where the normal bending stresses are maximum can be expected to be finite. Thus, different fatigue life estimates can be visualized at various distances from the neural axis. The problem becomes compounded further when significant portions away from the neutral axis are stressed into plastic range. A theoretical analysis of the closed hat-section subjected to flexural cyclic loading is first conducted. The axial fatigue characteristics together with the related axial fatigue life formula and its inverted form given by Manson and Muralidharan are adopted for an aluminum alloy used in aircraft construction. A closed-form expression for predicting the flexural fatigue life is then derived for the closed hat-section including materially nonlinear action. A computer program is written to conduct a study of the variables such as the thicknesses of the hat-section and the skin, and the type of alloy used. The study has provided a fundamental understanding of the flexural fatigue life characteristics of a practical structural component used in aircraft when materially nonlinear action is present.

  6. Angular momentum projection of tilted axis rotating states

    Energy Technology Data Exchange (ETDEWEB)

    Oi, M; Onishi, N; Tajima, N [Tokyo Univ. (Japan); Horibata, T

    1998-03-01

    We applied an exact angular momentum projection to three dimensional cranked HFB (3d-CHFB) states. Tilted axis rotating states (TAR) and principal axis rotating states (PAR) are compared. It is shown that TAR is more adequate than PAR for description of the back bending phenomena driven by tilted rotation or wobbling motion. (author)

  7. Fatigue Characteristics of Selected Light Metal Alloys

    Directory of Open Access Journals (Sweden)

    Cieśla M.

    2016-03-01

    Full Text Available The paper addresses results of fatigue testing of light metal alloys used in the automotive as well as aerospace and aviation industries, among others. The material subject to testing comprised hot-worked rods made of the AZ31 alloy, the Ti-6Al-4V two-phase titanium alloy and the 2017A (T451 aluminium alloy. Both low- and high-cycle fatigue tests were conducted at room temperature on the cycle asymmetry ratio of R=-1. The low-cycle fatigue tests were performed using the MTS-810 machine on two levels of total strain, i.e.Δεc= 1.0% and 1.2%. The high-cycle fatigue tests, on the other hand, were performed using a machine from VEB Werkstoffprufmaschinen-Leipzig under conditions of rotary bending. Based on the results thus obtained, one could develop fatigue life characteristics of the materials examined (expressed as the number of cycles until failure of sample Nf as well as characteristics of cyclic material strain σa=f(N under the conditions of low-cycle fatigue testing. The Ti-6Al-4V titanium alloy was found to be characterised by the highest value of fatigue life Nf, both in lowand high-cycle tests. The lowest fatigue life, on the other hand, was established for the aluminium alloys examined. Under the high-cycle fatigue tests, the life of the 2017A aluminium and the AZ31 magnesium alloy studied was determined by the value of stress amplitude σa. With the stress exceeding 150 MPa, it was the aluminium alloy which displayed higher fatigue life, whereas the magnesium alloy proved better on lower stress.

  8. Surface modification and fatigue behavior of nitinol for load bearing implants

    Science.gov (United States)

    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  9. High Frequency Vibration Based Fatigue Testing of Developmental Alloys

    Science.gov (United States)

    Holycross, Casey M.; Srinivasan, Raghavan; George, Tommy J.; Tamirisakandala, Seshacharyulu; Russ, Stephan M.

    Many fatigue test methods have been previously developed to rapidly evaluate fatigue behavior. This increased test speed can come at some expense, since these methods may require non-standard specimen geometry or increased facility and equipment capability. One such method, developed by George et al, involves a base-excited plate specimen driven into a high frequency bending resonant mode. This resonant mode is of sufficient frequency (typically 1200 to 1700 Hertz) to accumulate 107 cycles in a few hours. One of the main limitations of this test method is that fatigue cracking is almost certainly guaranteed to be surface initiated at regions of high stress. This brings into question the validity of the fatigue test results, as compared to more traditional uniaxial, smooth-bar testing, since high stresses are subjecting only a small volume to fatigue damage. This limitation also brings into question the suitability of this method to screen developmental alloys, should their initiation life be governed by subsurface flaws. However, if applicable, the rapid generation of fatigue data using this method would facilitate faster design iterations, identifying more quickly, material and manufacturing process deficiencies. The developmental alloy used in this study was a powder metallurgy boron-modified Ti-6Al-4V, a new alloy currently being considered for gas turbine engine fan blades. Plate specimens were subjected to fully reversed bending fatigue. Results are compared with existing data from commercially available Ti-6Al-4V using both vibration based and more traditional fatigue test methods.

  10. Bending Characteristics of Foldable Touch Display Panel with a Protection Structure Design

    Directory of Open Access Journals (Sweden)

    Hsien-Chie Cheng

    2015-01-01

    Full Text Available The study proposes and demonstrates an enhancement of a touch display panel (TDP through a polymer-based protection structure to achieve higher bendability and reliability. The bending performance of the TDP without or with the protection structure designs is addressed using three-dimensional geometry-nonlinear finite element analysis and mechanical testing. The elastic properties of the components in the TDP structure are derived from nanoindentation and uniaxial tensile/compressive testing. The calculated results are compared with each other and also against the experimental bending fatigue test data. At last, a design guideline and optimal factor setting for enhanced bending performance are sought through parametric FE analysis and Taguchi experimental design, respectively. The optimal design is compared with the original in terms of bending stress. The simulation results show that bending would create significant tensile and compressive bending stresses on the indium tin oxide/dielectric layers, which are the main cause of several commonly observed failures, such as thin film cracking and delamination, in a thin rigid film coating on a thick compliant substrate. It also turns out that a substrate with a lower stiffness has a better mechanical stability against bending stress.

  11. Fatigue strength ofcomposite wind turbine blade structures

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro

    Wind turbines are normally designed to withstand 20-30 years of life. During this period, the blades, which are the main rotating structures of a wind turbine, are subjected to high fluctuating load conditions as a result of a combination of gravity, inertia, and aeroelastic forces. For this reason......, fatigue is one of the foremost concerns during the design of these structures. However, current standard fatigue methods used for designing wind turbine blades seem not to be completely appropriate for these structures because they are still based on methods developed for metals and not for composite...... materials from which the blades are made. In this sense, the aim of this work is to develop more accurate and reliable fatigue-life prediction models for composite wind turbine blades. In this project, two types of fatigue models are implemented: fatigue-life models and damage mechanics models. In the first...

  12. On the Fatigue Analysis of Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Herbert J.

    1999-06-01

    Modern wind turbines are fatigue critical machines that are typically used to produce electrical power from the wind. Operational experiences with these large rotating machines indicated that their components (primarily blades and blade joints) were failing at unexpectedly high rates, which led the wind turbine community to develop fatigue analysis capabilities for wind turbines. Our ability to analyze the fatigue behavior of wind turbine components has matured to the point that the prediction of service lifetime is becoming an essential part of the design process. In this review paper, I summarize the technology and describe the ''best practices'' for the fatigue analysis of a wind turbine component. The paper focuses on U.S. technology, but cites European references that provide important insights into the fatigue analysis of wind turbines.

  13. Analysis of the effect of curtailment on power and fatigue loads of two aligned wind turbines using an actuator disc approach

    International Nuclear Information System (INIS)

    Martinen, Silke; Nilsson, Karl; Breton, Simon-Philippe; Ivanell, Stefan; Carlén, Ingemar

    2014-01-01

    To study the effects of curtailment on both power production and fatigue loading, actuator disc (ACD) simulations of two turbines aligned in the wind direction are performed with the EllipSys3D code developed at DTU/Risø. A simple non-aeroelastic fatigue load evaluation method for ACD simulations is developed. Blade loads, extracted along a line that rotates in the rotor plane with the rotational velocity of the respective turbine, are used to calculate flapwise bending moments. After applying a rainflow counting algorithm an equivalent moment is calculated. Power curtailment is introduced by increasing the blade pitch angle of the first turbine. Evaluation is made with regards to fatigue load reduction at the second turbine and the change in the total production. Further parameters investigated are the spacing between the two turbines and the level of imposed pre-generated turbulence. The aeroelastic code Vidyn, Ganander [1], is used for validation of the ACD load evaluation method. For this purpose, the EllipSys3D simulations are rerun without the second turbine. Time series of cross sectional velocity fields are extracted at positions corresponding to the former placement of the downstream turbine and used as input for aeroelastic turbine load calculations in Vidyn. The results from Vidyn and the results based on the ACD loads show similar trends. Fatigue loads at the downwind turbine are clearly decreasing as the blade pitch angle of the upstream turbine is increasing. The achievable amount of fatigue load reduction depends on the level of the imposed pre-generated turbulence as well as the spacing between the turbines. The presented method is intended for further development of wind park optimization strategies

  14. New specimen design for studying the growth of small fatigue cracks with surface acoustic waves

    Science.gov (United States)

    London, Blair

    1985-08-01

    The study of small surface fatigue cracks in AISI 4140 quenched and tempered steel by a nondestructive surface acoustic wave technique is summarized. A novel cantilevered bending, plate-type fatigue specimen is described that is compatible with the acoustic method. Small cracks are initiated from a 25-μm deep surface pit produced by an electrospark machine. The importance of studying these cracks which closely approximate naturally occurring fatigue cracks is briefly discussed.

  15. An overview of fatigue

    International Nuclear Information System (INIS)

    Mc Evily, A.J.

    1987-01-01

    Four topics are briefly discussed in this paper: fatigue crack initiation and growth in a nickel-base superalloy single crystal, the environment effect on near-threshold fatigue crack growth behaviour, the role of crack closure in load-interaction effects in fatigue crack growth, and the nature of creep-fatigue interactions, if any, during fatigue crack growth. (Author)

  16. A review of literature for the structural assessment of mitred bends

    International Nuclear Information System (INIS)

    Wood, J.

    2008-01-01

    This paper presents a state-of-the-art review of literature available for the structural assessment of all types of mitred pipe bends. Compared with smooth bends, the volume of literature available for mitres is less extensive and its scope is not as wide. Historically, this reflects a reduced application level, as well as a less demanding range of applications, such as non-high temperature use. There is also the issue that an analysis of a mitred bend is complicated by discontinuity stresses, as well as those due to cross-section ovalisation. This fact delayed the development of non-linear analysis of mitred bends. Nevertheless, there is now a substantial body of work on mitred bends. This review tabulates and characterises all publications to date in chronological order. The details of experimental specimens are highlighted, with a view to these perhaps providing useful verification data for any future finite element analysis for example. Issues of particular interest to pipework designers are discussed, including the effects of combinations of loading, out-of-circularity, tangent pipe length and flanges. Failure characteristics and loads are discussed where relevant. Topics for further research are also noted. For example, comprehensive design curves do not exist for the elastic and plastic behaviour of all mitre types, over a practical range of geometry and loading parameters. Similarly, there is still scope for further work on the effect of combined loading, end effects and out-of-circularity. Limit, collapse and burst loads are not yet available across the entire spectrum of bends and loading parameters either. Creep and optimisation represent virgin territory as far as mitred bends are concerned and given that unforeseen vibration is a common source of high-cycle fatigue failure in pipework, there must also be scope for vibration-induced fatigue studies

  17. Influences of semiconductor morphology on the mechanical fatigue behavior of flexible organic electronics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young-Joo; Yeon, Han-Wool; Shin, Hae-A-Seul; Joo, Young-Chang, E-mail: ycjoo@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, 151-744 Seoul (Korea, Republic of); Uk Lee, Yong; Evans, Louise A. [Center for Process Innovation Limited, Thomas Wright Way, NETPark, Sedgefield, TS21 3FG County Durham (United Kingdom)

    2013-12-09

    The influence of crystalline morphology on the mechanical fatigue of organic semiconductors (OSCs) was investigated using 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as a crystalline OSC and poly(triarylamine) (PTAA) as an amorphous OSC. During cyclic bending, resistances of the OSCs were monitored using the transmission-line method on a metal-semiconductor-metal structure. The resistance of the TIPS-pentacene increased under fatigue damage in tensile-stress mode, but no such degradation was observed in the PTAA. Both OSCs were stable under compressive bending fatigue. The formation of intergranular cracks at the domain boundaries of the TIPS-pentacene was responsible for the degradation of its electrical properties under tensile bending fatigue.

  18. Rotating flow

    CERN Document Server

    Childs, Peter R N

    2010-01-01

    Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics titles offer the essential background but generally include very sparse coverage of rotating flows-which is where this book comes in. Beginning with an accessible introduction to rotating flow, recognized expert Peter Childs takes you through fundamental equations, vorticity and vortices, rotating disc flow, flow around rotating cylinders and flow in rotating cavities, with an introduction to atmospheric and oceanic circul...

  19. Rotational seismology

    Science.gov (United States)

    Lee, William H K.

    2016-01-01

    Rotational seismology is an emerging study of all aspects of rotational motions induced by earthquakes, explosions, and ambient vibrations. It is of interest to several disciplines, including seismology, earthquake engineering, geodesy, and earth-based detection of Einstein’s gravitation waves.Rotational effects of seismic waves, together with rotations caused by soil–structure interaction, have been observed for centuries (e.g., rotated chimneys, monuments, and tombstones). Figure 1a shows the rotated monument to George Inglis observed after the 1897 Great Shillong earthquake. This monument had the form of an obelisk rising over 19 metres high from a 4 metre base. During the earthquake, the top part broke off and the remnant of some 6 metres rotated about 15° relative to the base. The study of rotational seismology began only recently when sensitive rotational sensors became available due to advances in aeronautical and astronomical instrumentations.

  20. Side Effects: Fatigue

    Science.gov (United States)

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  1. Behavior of Steel Branch Connections during Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Sládek A.

    2017-09-01

    Full Text Available Fatigue behavior of the branch connection made of low-alloyed steel with yield stress of 355 MPa during low-cycle bending test is investigated in the article. Numerical prediction of the stress and strain distribution are described and experimentally verified by fatigue test of the branch connection sample. Experimental verification is based on low-cycle bending testing of the steel pipes welded by manual metal arc process and loaded by external force in the appropriate distance. Stresses and displacement of the samples induced by bending moment were measured by unidirectional strain gauges and displacement transducers. Samples were loaded in different testing levels according to required stress for 2.106 cycles. Increase of the stress value was applied until the crack formation and growth was observed. Results showed a high agreement of numerical and experimental results of stress and displacement.

  2. Impact of specific fracture energy investigated in front of the crack tip of three-point bending specimen

    Czech Academy of Sciences Publication Activity Database

    Klon, J.; Sobek, J.; Malíková, L.; Seitl, Stanislav

    2017-01-01

    Roč. 11, č. 41 (2017), s. 183-190 ISSN 1971-8993 Institutional support: RVO:68081723 Keywords : Finite element method * Loading curve * Specific fracture energy * Three-point bending test * Work of fracture Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  3. Monitoring of Failure Mechanisms in a Composite Bending Actuator during Cyclic Loading by Acoustic Emission

    Science.gov (United States)

    Woo, Sung-Choong; Goo, Nam Seo

    The objective of this work is to investigate the influence of electromechanical cyclic loading on the performance of a bending piezoelectric composite actuator. We have analyzed the fatigue damage mechanisms in terms of the behavior of the AE event rate. It was found that whether the actuators are subjected to purely electric loading or electromechanical loading, the initial fatigue damage of the bending piezoelectric composite actuator was caused by the transgranular fracture in the PZT ceramic layer; the final failure was caused only in the case of PCAWB under electromechanical loading by a local discharge, which critically affected the performance reduction of the actuators. As the number of cycles increased, a large reduction in displacement performance coincided with a high AE event rate, which was identified via microscopic observations.

  4. Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

    DEFF Research Database (Denmark)

    Stäblein, Alexander; Tibaldi, Carlo; Hansen, Morten Hartvig

    2016-01-01

    Bend-twist coupling of wind turbine blades is known as a means to reduce the structural loads of the turbine. While the load reduction is desirable, bend-twist coupling also leads to a decrease in the annual energy production of the turbine. The reduction is mainly related to a no longer optimal......, and fatigue load for the DTU 10 MW Reference Wind Turbine. The analysis was carried out by calculating the nonlinear steady state rotor deflection in an uniform inflow over the operational range of the turbine. The steady state power curve together with a Rayleigh wind speed distribution has been used...... to estimate the annual energy production. The turbine model was then linearised around the steady state and the power spectral density of the blade response, which was computed from transfer functions and the wind speed variations in the frequency domain, was used to estimate the fatigue loads by a spectral...

  5. A thermodynamic approach to fatigue damage accumulation under variable loading

    International Nuclear Information System (INIS)

    Naderi, M.; Khonsari, M.M.

    2010-01-01

    We put forward a general procedure for assessment of damage evolution based on the concept of entropy production. The procedure is applicable to both constant- and variable amplitude loading. The results of a series of bending fatigue tests under both two-stage and three-stage loadings are reported to investigate the validity of the proposed methodology. Also presented are the results of experiments involving bending, torsion, and tension-compression fatigue tests with Al 6061-T6 and SS 304 specimens. It is shown that, within the range of parameters tested, the evolution of fatigue damage for these materials in terms of entropy production is independent of load, frequency, size, loading sequence and loading history. Furthermore, entropy production fractions of individual amplitudes sums to unity.

  6. Bending and stretching of plates

    CERN Document Server

    Mansfield, E H; Hemp, W S

    1964-01-01

    The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

  7. The travail of River Bend

    International Nuclear Information System (INIS)

    Studness, C.M.

    1990-01-01

    This article looks at the attempts by Gulf States Utilities to get the River Bend Nuclear Plant into its rate base. The review begins with the initial filing of rate cases in Texas and Louisiana in 1986 and continues through many court cases and appeals all the way to the Texas Supreme Court. The preferred and preference shareholders now nominally control the company through election of 10 of 15 members of the company's board of directors. This case is used as an argument for deregulation in favor of competition

  8. END FIELD EFFECTS IN BEND ONLY COOLING LATTICES

    International Nuclear Information System (INIS)

    BEERG, J.S.; KIRK, H.; GARREN, A.

    2003-01-01

    Cooling lattices consisting only of bends (using either rotated pole faces or gradient dipoles to achieve focusing) often require large apertures and short magnets. One expects the effect of end fields to be significant in this case. In this paper we explore the effect of adding end fields to a working lattice design that originally lacked them. The paper describes the process of correcting the lattice design for the added end fields so as to maintain desirable lattice characteristics. It then compares the properties of the lattice with end fields relative to the lattice without them

  9. The effect of shot peening on notched low cycle fatigue

    International Nuclear Information System (INIS)

    Soady, K.A.; Mellor, B.G.; Shackleton, J.; Morris, A.; Reed, P.A.S.

    2011-01-01

    Highlights: → Shot peening improves notched component three point bend low cycle fatigue life. → Notch shape does not affect the efficacy of the peening process. → Strain hardening and residual stress effects need separate consideration. → Loading direction residual stresses do not relax under bend load. - Abstract: The improvement in low cycle fatigue life created by shot peening ferritic heat resistant steel was investigated in components of varying geometries based on those found in conventional power station steam turbine blades. It was found that the shape of the component did not affect the efficacy of the shot peening process, which was found to be beneficial even under the high stress amplitude three point bend loads applied. Furthermore, by varying the shot peening process parameters and considering fatigue life it has been shown that the three surface effects of shot peening; roughening, strain hardening and the generation of a compressive residual stress field must be included in remnant life models as physically separate entities. The compressive residual stress field during plane bending low cycle fatigue has been experimentally determined using X-ray diffraction at varying life fractions and found to be retained in a direction parallel to that of loading and to only relax to 80% of its original magnitude in a direction orthogonal to loading. This result, which contributes to the retention of fatigue life improvement in low cycle fatigue conditions, has been discussed in light of the specific stress distribution applied to the components. The ultimate aim of the research is to apply these results in a life assessment methodology which can be used to justify a reduction in the length of scheduled plant overhauls. This will result in significant cost savings for the generating utility.

  10. Scanning and/or treating surface device for weak bending radius cylindrical airlock

    International Nuclear Information System (INIS)

    Gemma, A.

    1988-01-01

    The device for scanning or treating the surface of a weak bending cylindrical airlock has a support mounted on the airlock outside flange, a central mast perpendicular to the support mounted to rotate about its axis, a geared motor turning the mast, an exploration or treatment tool fixed to the mast and a controller for the motor and the tool [fr

  11. Fatigue life prediction method for contact wire using maximum local stress

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

    2015-01-15

    Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.

  12. Fatigue life prediction method for contact wire using maximum local stress

    International Nuclear Information System (INIS)

    Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean; Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon

    2015-01-01

    Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.

  13. Damage formation, fatigue behavior and strength properties of ZrO{sub 2}-based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kozulin, A. A., E-mail: kozulyn@ftf.tsu.ru; Kulkov, S. S. [Tomsk State University, Tomsk, 634050 (Russian Federation); Narikovich, A. S.; Leitsin, V. N. [Immanuel Kant Baltic Federal University, Kaliningrad, 236041 (Russian Federation); Kulkov, S. N., E-mail: kulkov@ispms.ru [Tomsk State University, Tomsk, 634050 (Russian Federation); Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2016-08-02

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO{sub 2}-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91–0.98, 0.8–0.83, and 0.73–0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{sup 5} stress cycles is in the range 33–34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  14. Damage formation, fatigue behavior and strength properties of ZrO_2-based ceramics

    International Nuclear Information System (INIS)

    Kozulin, A. A.; Kulkov, S. S.; Narikovich, A. S.; Leitsin, V. N.; Kulkov, S. N.

    2016-01-01

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO_2-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91–0.98, 0.8–0.83, and 0.73–0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10"5 stress cycles is in the range 33–34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  15. Global rotation

    International Nuclear Information System (INIS)

    Rosquist, K.

    1980-01-01

    Global rotation in cosmological models is defined on an observational basis. A theorem is proved saying that, for rigid motion, the global rotation is equal to the ordinary local vorticity. The global rotation is calculated in the space-time homogeneous class III models, with Godel's model as a special case. It is shown that, with the exception of Godel's model, the rotation in these models becomes infinite for finite affine parameter values. In some directions the rotation changes sign and becomes infinite in a direction opposite to the local vorticity. The points of infinite rotation are identified as conjugate points along the null geodesics. The physical interpretation of the infinite rotation is discussed, and a comparison with the behaviour of the area distance at conjugate points is given. (author)

  16. Fatigue Performance and Multiscale Mechanisms of Concrete Toughened by Polymers and Waste Rubber

    Directory of Open Access Journals (Sweden)

    Bo Chen

    2014-01-01

    Full Text Available For improving bending toughness and fatigue performance of brittle cement-based composites, two types of water-soluble polymers (such as dispersible latex powder and polyvinyl alcohol powder and waste tire-rubber powders are added to concrete as admixtures. Multiscale toughening mechanisms of these additions in concretes were comprehensively investigated. Four-point bending fatigue performance of four series concretes is conducted under a stress level of 0.70. The results show that the effects of dispersible latex powder on bending toughness and fatigue life of concrete are better than those of polyvinyl alcohol powder. Furthermore, the bending fatigue lives of concrete simultaneously containing polymers and waste rubber powders are larger than those of concrete with only one type of admixtures. The multiscale physics-chemical mechanisms show that high bonding effect and high elastic modulus of polymer films as well as good elastic property and crack-resistance of waste tire-rubber powders are beneficial for improving bending toughness and fatigue life of cementitious composites.

  17. Application of non-destructive impedance-based monitoring technique for cyclic fatigue evaluation of endodontic nickel-titanium rotary instruments.

    Science.gov (United States)

    Chang, Yau-Zen; Liu, Mou-Chuan; Pai, Che-An; Lin, Chun-Li; Yen, Kuang-I

    2011-06-01

    This study investigates the application of non-destructive testing based on the impedance theory in the cyclic fatigue evaluation of endodontic Ni-Ti rotary instruments. Fifty Ni-Ti ProTaper instruments were divided into five groups (n=10 in Groups A to E). Groups A to D were subjected to cyclic fatigue within an artificial canal (Group E was the control group). The mean value of the total life limit (TLL), defined as the instrument being rotated until fracture occurred was found to be 104 s in Group A. Each rotary instrument in Groups B, C and D were rotated until the tested instruments reached 80% (84 s), 60% (62 s) and 40% (42 s) of the TLL. After fatigue testing, each rotary instrument was mounted onto a custom-developed non-destructive testing device to give the tip of the instrument a progressive sideways bend in four mutually perpendicular directions to measure the corresponding impedance value (including the resistance and the reactance). The results indicated that the impedance value showed the same trend as the resistance, implying that the impedance was primarily affected by the resistance. The impedance value for the instruments in the 80% and 60% TLL groups increased by about 6 mΩ (about 7.5%) more than that of the instruments in the intact and 40% TLL groups. The SEM analysis result showed that crack striations were only found at the tip of the thread on the cracked surface of the instrument, consistent with the impedance measurements that found the impedance value of the cracked surface to be significantly different from those in other surfaces. These findings indicate that the impedance value may represent an effective parameter for evaluating the micro-structural status of Ni-Ti rotary instruments subjected to fatigue loading. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

  18. Two micro fatigue test methods for irradiated materials

    International Nuclear Information System (INIS)

    Nunomura, Shigetomo; Noguchi, Shinji; Okamura, Yuichi; Kumai, Shinji

    1993-01-01

    This paper demonstrates two miniature fatigue test methods in response to the requirements of the fusion reactor wall materials development program. It is known that the fatigue strength evaluated by the axial loading test is independent of the specimen size, while that evaluated by the bend test or torsion test is dependent upon the size of specimen. The new type of gripping system for the axial, tension-tension, fatigue testing of TEM disk-size specimens that has been developed is described in this paper. An alignment tool assists in gripping the miniature specimen. The miniature tension-tension fatigue test method seems to provide reliable S-N curves for SUS304 and SUS316L stainless steels. An indentation method has also been developed to determine fatigue properties. A hard steel ball or ceramic ball was used for cyclically loading the specimen, and an S-N curve was subsequently obtained. The merit of this method is primarily simple handling. S-N curves obtained from four materials by this indentation method compared well with those obtained from the rotary bend fatigue test employing a standard-size specimen

  19. Effect of environment on fatigue failure of controlled memory wire nickel-titanium rotary instruments.

    Science.gov (United States)

    Shen, Ya; Qian, Wei; Abtin, Houman; Gao, Yuan; Haapasalo, Markus

    2012-03-01

    This study examined the fatigue behavior of 2 types of nickel-titanium (NiTi) instruments made from a novel controlled memory NiTi wire (CM wire) under various environment conditions. Three conventional superelastic NiTi instruments of ProFile (Dentsply Maillefer, Ballaigues, Switzerland), Typhoon (Clinician's Choice Dental Products, New Milford, CT), and DS-SS0250425NEYY (Clinician's Choice Dental Products) and 2 new CM wire instruments of Typhoon CM and DS-SS0250425NEYY CM were subjected to rotational bending at the curvature of 35° in air, deionized water, 17% EDTA, or deionized water after immersion in 6% sodium hypochlorite for 25 minutes, and the number of revolutions of fracture (N(f)) was recorded. The fracture surface of all fragments was examined by a scanning electron microscope. The crack-initiation sites and the percentage of dimple area to the whole fracture cross-section were noted. Two new CM Wire instruments yielded an improvement of >4 to 9 times in N(f) than conventional NiTi files with the same design under various environments (P Wire instruments was significantly longer in liquid media than in air (P wire had one crack origin. The values of the area fraction occupied by the dimple region were significantly smaller on CM NiTi instruments than in conventional NiTi instruments under various environments (P < .05). Within the limitations of this study, the type of NiTi metal alloy (CM files vs conventional superelastic NiTi files) influences the cyclic fatigue resistance under various environments. The fatigue life of CM instruments is longer in liquid media than in air. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  20. Fatigue Behavior of Modified Asphalt Concrete Pavement

    Directory of Open Access Journals (Sweden)

    saad I. Sarsam

    2016-02-01

    Full Text Available Fatigue cracking is the most common distress in road pavement. It is mainly due to the increase in the number of load repetition of vehicles, particularly those with high axle loads, and to the environmental conditions. In this study, four-point bending beam fatigue testing has been used for control and modified mixture under various micro strain levels of (250 μƐ, 400 μƐ, and 750 μƐ and 5HZ. The main objective of the study is to provide a comparative evaluation of pavement resistance to the phenomenon of fatigue cracking between modified asphalt concrete and conventional asphalt concrete mixes (under the influence of three percentage of Silica fumes 1%, 2%, 3% by the weight of asphalt content, and (changing in the percentage of asphalt content by (0.5% ± from the optimum. The results show that when Silica fumes content was 1%, the fatigue life increases by 17%, and it increases by 46% when Silica fumes content increases to 2%, and that fatigue life increases to 34 % when Silica fumes content increases to 3% as compared with control mixture at (250 μƐ, 20°C and optimum asphalt content. From the results above, we can conclude the optimum Silica fumes content was 2%. When the asphalt content was 4.4%, the fatigue life has increased with the use of silica fumes by (50%, when asphalt content was 5.4%, the additives had led to increasing the fatigue life by (69%, as compared with the conventional asphalt concrete pavement.

  1. Joint excitation synchronization characteristics of fatigue test for offshore wind turbine blade

    Science.gov (United States)

    Zhang, Lei-an; Yu, Xiang-yong; Wei, Xiu-ting; Liu, Wei-sheng

    2018-02-01

    In the case of the stiffness of offshore wind turbine blade is relatively large, the joint excitation device solves the problem of low accuracy of bending moment distribution, insufficient driving ability and long fatigue test period in single-point loading. In order to study the synchronous characteristics of joint excitation system, avoid blade vibration disturbance. First, on the base of a Lagrange equation, a mathematical model of combined excitation is formulated, and a numerical analysis of vibration synchronization is performed. Then, the model is constructed via MATLAB/Simulink, and the effect of the phase difference on the vibration synchronization characteristics is obtained visually. Finally, a set of joint excitation platform for the fatigue test of offshore wind turbine blades are built. The parameter measurement scheme is given and the correctness of the joint excitation synchronization in the simulation model is verified. The results show that when the rotational speed difference is 2 r/min, 30 r/min, the phase difference is 0, π/20, π/8 and π/4, as the rotational speed difference and the phase difference increase, the time required for the blade to reach a steady state is longer. When the phase difference is too large, the electromechanical coupling can no longer make the joint excitation device appear self-synchronizing phenomenon, so that the value of the phase difference develops toward a fixed value (not equal to 0), and the blade vibration disorder is serious, at this time, the effect of electromechanical coupling must be eliminated. The research results provide theoretical basis for the subsequent decoupling control algorithm and synchronization control strategy, and have good application value.

  2. Joint excitation synchronization characteristics of fatigue test for offshore wind turbine blade

    Directory of Open Access Journals (Sweden)

    Lei-an Zhang

    2018-02-01

    Full Text Available In the case of the stiffness of offshore wind turbine blade is relatively large, the joint excitation device solves the problem of low accuracy of bending moment distribution, insufficient driving ability and long fatigue test period in single-point loading. In order to study the synchronous characteristics of joint excitation system, avoid blade vibration disturbance. First, on the base of a Lagrange equation, a mathematical model of combined excitation is formulated, and a numerical analysis of vibration synchronization is performed. Then, the model is constructed via MATLAB/Simulink, and the effect of the phase difference on the vibration synchronization characteristics is obtained visually. Finally, a set of joint excitation platform for the fatigue test of offshore wind turbine blades are built. The parameter measurement scheme is given and the correctness of the joint excitation synchronization in the simulation model is verified. The results show that when the rotational speed difference is 2 r/min, 30 r/min, the phase difference is 0, π/20, π/8 and π/4, as the rotational speed difference and the phase difference increase, the time required for the blade to reach a steady state is longer. When the phase difference is too large, the electromechanical coupling can no longer make the joint excitation device appear self-synchronizing phenomenon, so that the value of the phase difference develops toward a fixed value (not equal to 0, and the blade vibration disorder is serious, at this time, the effect of electromechanical coupling must be eliminated. The research results provide theoretical basis for the subsequent decoupling control algorithm and synchronization control strategy, and have good application value.

  3. A combined wear-fatigue design methodology for fretting in the pressure armour layer of flexible marine risers

    OpenAIRE

    O'Halloran, S.M.; Shipway, P.H.; Connaire, A.D.; Leen, Sean B.; Harte, A.M.

    2017-01-01

    This paper presents a combined experimental and computational methodology for fretting wear-fatigue prediction of pressure armour wire in flexible marine risers. Fretting wear, friction and fatigue parameters of pressure armour material have been characterised experimentally. A combined fretting wear-fatigue finite element model has been developed using an adaptive meshing technique and the effect of bending-induced tangential slip has been characterised. It has been shown that a surface dama...

  4. A Numerical Study of the Spring-Back Phenomenon in Bending with a Rebar Bending Machine

    Directory of Open Access Journals (Sweden)

    Chang Hwan Choi

    2014-10-01

    Full Text Available Recently, the rebar bending methodology started to change from field processing to utilizing rebar bending machines at plant sites prior to transport to the construction locations. Computerized control of rebar plant bending machines provides more accurate and faster bending of rebars than the low quality inefficient field processing alternative. The bending process involves plastic deformation of rebars, where bending stress beyond the yield point of the material is applied. When the bending stress is removed, spring back is caused by the elastic restoring stress. Therefore, an accurate numerical analysis of the spring-back process is required to reduce the bending process errors. The most sensitive factors affecting the spring-back process are the bending radius, the bending angle, the diameter of the rebar, the friction coefficient, and the yielding strength of material. In this paper, we suggest a numerical modeling method using these factors. The finite element modeling of the dynamic mechanical behavior of the material during bending is performed using a commercial dynamic analysis program “DAFUL.” We use the least squares approach to derive the spring-back deflection as a function of the rebar bending parameters.

  5. Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

    Directory of Open Access Journals (Sweden)

    Hitoshi Soyama

    2015-08-01

    Full Text Available It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening.

  6. Measurement of fatigue in knee flexor and extensor muscles.

    Science.gov (United States)

    Kawabata, Y; Senda, M; Oka, T; Yagata, Y; Takahara, Y; Nagashima, H; Inoue, H

    2000-04-01

    In order to examine fatigue of the knee flexor and extensor muscles and to investigate the characteristics of muscular fatigue in different sports, a Cybex machine was used to measure muscle fatigue and recovery during isokinetic knee flexion and extension. Eighteen baseball players, 12 soccer players and 13 marathon runners were studied. Each subject was tested in the sitting position and made to perform 50 consecutive right knee bends and stretches at maximum strength. This was done 3 times with an interval of 10 min between each series. The peak torque to body weight ratio and the fatigue rate were determined in each case. In all subjects, the peak torque to body weight ratio was higher for extensors than flexors. Over the 3 trials, the fatigue rate of extensors showed little change, while that of flexors had a tendency to increase. In each subject, knee extensors showed a high fatigue rate but a quick recovery, while knee flexors showed a low fatigue rate but a slow recovery. As the marathon runners had the smallest fatigue rates for both flexors and extensors, we concluded that marathon runners had more stamina than baseball players and soccer players.

  7. Measurement of developing turbulent flow in a U-bend of circular cross-section

    International Nuclear Information System (INIS)

    Lee, Gun Hyee; Choi, Young Don; Han, Seong Ho

    2007-01-01

    Hot-wire measurements of the full mapping of the velocity and Reynolds stress components are reported for developing turbulent flow in a strongly curved 180 deg pipe and its tangents. A slanted wire is rotated into 6 orientations and the voltage outputs from wires are combined to obtain the mean velocity and Reynolds stress components. The strength of secondary flow reaches up to the 28% of bulk mean velocity. The strong counter-rotating vortex pair induced by the transverse pressure gradient and centrifugal force imbalance grows up to θ = 67.5 .deg. into the bend. But the vortex pair breaks down into two cell pattern after θ=90 .deg. Core vortex formation and reversal of secondary flow direction along the bend symmetry plane is cleanly found in the secondary vector plot. At θ=67.5 .deg. and θ = 90 .deg. into bend a large 'trough' develops in the longitudinal velocity toward the inside of the bend due to the breakdown of secondary flow. In the bend, the mean longitudinal velocity component changes little after θ=90 .deg., but secondary flow never achieves fully-developed state. Similar behaviors are observed in the radial and circumferential stresses

  8. Bends and splitters in graphene nanoribbon waveguides

    DEFF Research Database (Denmark)

    Zhu, Xiaolong; Yan, Wei; Mortensen, N. Asger

    2013-01-01

    We investigate the performance of bends and splitters in graphene nanoribbon waveguides. Although the graphene waveguides are lossy themselves, we show that bends and splitters do not induce any additional loss provided that the nanoribbon width is sub-wavelength. We use transmission line theory...

  9. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

    Højerslev, Christian; Carstensen, Jesper V.; Brøndsted, Povl

    2002-01-01

    The influence of microstructure on fatigue crack initiation and crack growth of a hardened and tempered high speed steel was investigated. The evolution of fatigue cracks was followed in four point bending at room temperature. It was found that a carbide damage zone exists above a threshold load...... value of maximally 80% of the yield strength of the steel. The size of this carbide damage zone increases with increasing load amplitude, and the zone is apparently associated with crack nucleation. On fatigue crack propagation plastic deformation of the matrix occurs in a radius of approximately 4...... microns in front of the fatigue crack tip, which is comparable with the relevant mean free carbide spacing....

  10. Devices for fatigue testing of electroplated nickel (MEMS)

    DEFF Research Database (Denmark)

    Larsen, Kristian Pontoppidan; Ravnkilde, J. T.; Ginnerup, Morten

    2002-01-01

    μm and an effective length from 4μm to 27μm. Maximum stresses of the test beam were calculated to be 500MPa to 2100MPa by use of FEM tools. The test results indicate very promising fatigue properties of nano-nickel, as none of the test devices have shown fatigue failure or even initiation of cracks......In-situ fatigue test devices with integrated electrostatic actuator were fabricated in electroplated nanocrystalline nickel (nano-nickel). The devices feature in-plane approximately pure bending with fixed displacement of the test specimen of the dimensions: widths from 2μm to 3.7μm, a height of 7...... after 108 cycles. The combination of high strength and toughness, which is known for nanocrystalline materials, together with very small test specimens and low surface roughness could be the explanation for the good fatigue properties....

  11. Corrosion fatigue behavior of high strength brass in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S.; Kassem, M.A.; Ramadan, R.M.; El-Zeky, M.A. [Suez Canal Univ., Dept. of Metallurgy and Materials Engineering (Egypt)

    2000-07-01

    Corrosion fatigue behavior of British Standard high strength brass, CZ 127 has been studied in various environments, 3.5%NaC1 solution and 3.5%NaC1 containing 1000ppm ammonia by applying the reverse bending technique, strain-controlled cyclic, at 67 cycles/min. Characteristics of the produced alloy were studied using differential thermal analysis with applying its results in heat treating of the alloy; metallographic examinations; hardness measurements; X-ray; and electrochemical behavior of the unstressed alloy. CZ 127 was fatigued at three different conditions, solution treated, peak aged, and over aged at a fixed strain amplitude, 0.03 5. Solution treated alloy gave the best fatigue properties in all environments tested among the other materials. Results of the alloy studied were compared with that obtained of 70/30 {alpha}-brass. Fracture surface of the fatigued alloy was examined using optical microscope and scanning electron microscope equipped with EDX. (author)

  12. Corrosion fatigue behavior of high strength brass in aqueous solutions

    International Nuclear Information System (INIS)

    Hamada, A.S.; Kassem, M.A.; Ramadan, R.M.; El-Zeky, M.A.

    2000-01-01

    Corrosion fatigue behavior of British Standard high strength brass, CZ 127 has been studied in various environments, 3.5%NaC1 solution and 3.5%NaC1 containing 1000ppm ammonia by applying the reverse bending technique, strain-controlled cyclic, at 67 cycles/min. Characteristics of the produced alloy were studied using differential thermal analysis with applying its results in heat treating of the alloy; metallographic examinations; hardness measurements; X-ray; and electrochemical behavior of the unstressed alloy. CZ 127 was fatigued at three different conditions, solution treated, peak aged, and over aged at a fixed strain amplitude, 0.03 5. Solution treated alloy gave the best fatigue properties in all environments tested among the other materials. Results of the alloy studied were compared with that obtained of 70/30 α-brass. Fracture surface of the fatigued alloy was examined using optical microscope and scanning electron microscope equipped with EDX. (author)

  13. Deformation Parameters and Fatigue of the Recycled Asphalt Mixtures

    Directory of Open Access Journals (Sweden)

    Šrámek Juraj

    2015-12-01

    Full Text Available The deformational properties of asphalt mixtures measured by dynamic methods and fatigue allow a design the road to suit the expected traffic load. Quality of mixtures is also expressed by the resistance to permanent deformation. Complex modulus of stiffness and fatigue can reliably characterize the proposed mixture of asphalt pavement. The complex modulus (E* measurement of asphalt mixtures are carried out in laboratory of Department of Construction Management at University of Žilina by two-point bending test method on trapezoid-shaped samples. Today, the fatigue is verified on trapezoid-shaped samples and is assessed by proportional strain at 1 million cycles (ε6. The test equipment and software is used to evaluate fatigue and deformation characteristics.

  14. Plastic loads of pipe bends under combined pressure and out-of-plane bending

    International Nuclear Information System (INIS)

    Lee, Kuk Hee; Kim, Yun Jae; Park, Chi Yong; Lee, Sung Ho; Kim, Tae Ryong

    2007-01-01

    Based on three-Dimensional (3-D) FE limit analyses, this paper provides plastic limit and TES(Twice- Elastic-Slope) loads for pipe bends under combined pressure and out-of-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic.perfectly-plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide TES plastic loads. A wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and TES plastic load solutions for pipe bends under out-of-plane bending are proposed

  15. Rotating Wavepackets

    Science.gov (United States)

    Lekner, John

    2008-01-01

    Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…

  16. Rotating dryer

    International Nuclear Information System (INIS)

    Noe, C.

    1984-01-01

    Products to dry are introduced inside a rotating tube placed in an oven, the cross section of the tube is an arc of spiral. During clockwise rotation of the tube products are maintained inside and mixed, during anticlockwise products are removed. Application is made to drying of radioactive wastes [fr

  17. Analysis of pipe mitred bends using beam models - by finite element method

    International Nuclear Information System (INIS)

    Salles, A.C.S.L. de.

    1984-01-01

    The formulation of a recently proposed displacement based straight pipe element for the analysis of pipe mitred bends is summarized in this work. The element kinematics includes axial, bending, torsional and ovalisation displacements, all varying cubically along the axis of the element. Interaction effects between angle adjoined straight pipe section are modeled including the appropriate additional strain terms in the stiffness matrix formulation and by using a penalty procedure to enforce continuity of pipe skin flexural rotations at the common helical edge. The element model capabilities are ilustrated in some sample analysis and the results are compared with other available experimental, analytical or more complex numerical models. (Author) [pt

  18. In-plane and out-of-plane bending tests on carbon steel pipe bends

    International Nuclear Information System (INIS)

    Brouard, D.; Tremblais, A.; Vrillon, B.

    1979-01-01

    The objectives of these tests were to obtain experimental results on bends behaviour in elastic and plastic regime by in plane and out of plane bending. Results were used to improve the computer model, for large distorsion of bends, to be used in a simplified beam type computer code for piping calculations. Tests were made on type ANSI B 169 DN 5 bends in ASTM A 106 Grade B carbon steel. These tests made it possible to measure, for identical bends, in elastic regime, the flexibility factors and, in plastic regime, the total evolution in opening, in closing and out of plane. Flexibility factors of 180 0 bend without flanges are approximately the same in opening and in closing. The end effect due to flanges is not very significant, but it is important for 90 0 bends. In plastic regime, collapse loads or collapse moments of bends depends also of both the end effects and the angle bend. The end effects and the angle bend are more sensitive in opening than in closing. The interest of these tests is to procure some precise evolution curves of identical bends well characterized in geometry and metal strength, deflected in large distorsions. (orig./HP)

  19. Fatigue with HIV/AIDS

    Science.gov (United States)

    ... 21, 2014 Select a Language: Fact Sheet 551 Fatigue WHAT IS FATIGUE? IS FATIGUE IMPORTANT? HOW DO ... It can be physical or psychological. With physical fatigue , your muscles cannot do things as easily as ...

  20. Experimental stress analysis and fatigue tests of five 24-in. NPS ANSI Standard B16.9 tees

    International Nuclear Information System (INIS)

    Moore, S.E.; Hayes, J.K.; Weed, R.A.

    1985-03-01

    Experimental stress analyses and low-cycle fatigue tests of five 24-in. nominal pipe size American National Standards Institute (ANSI) Standard B16.9 forged tees are documented in this report. The tees, designated as Oak Ridge National Laboratory tees T10, T11, T12, T13, and T16, were tested under subcontract at Combustion Engineering, Inc. in Chattanooga, Tennessee. Experimental stress analyses were conducted for 12 individual loadings on each tee. Each test model was instrumented with approx. 225, 1/8-in. three-gage, 45 0 strain rosettes on the inside and outside surfaces; and 6 linear variable differential transformers mounted on special nonflexible holding frames for measuring deflections and rotations of the pipe extensions. Following completion of the strain-gate tests, each tee was fatigue tested to failure with either a fully reversed displacement controlled in-plane bending moment on the branch or a cyclic internal pressure that ranged from a value slightly above zero to about 90% of the nominal yield pressure of the pipe extensions

  1. Experimental stress analysis and fatigue tests of five 24-in. NPS ANSI Standard B16. 9 tees. [PWR; BWR

    Energy Technology Data Exchange (ETDEWEB)

    Moore, S.E.; Hayes, J.K.; Weed, R.A.

    1985-03-01

    Experimental stress analyses and low-cycle fatigue tests of five 24-in. nominal pipe size American National Standards Institute (ANSI) Standard B16.9 forged tees are documented in this report. The tees, designated as Oak Ridge National Laboratory tees T10, T11, T12, T13, and T16, were tested under subcontract at Combustion Engineering, Inc. in Chattanooga, Tennessee. Experimental stress analyses were conducted for 12 individual loadings on each tee. Each test model was instrumented with approx. 225, 1/8-in. three-gage, 45/sup 0/ strain rosettes on the inside and outside surfaces; and 6 linear variable differential transformers mounted on special nonflexible holding frames for measuring deflections and rotations of the pipe extensions. Following completion of the strain-gate tests, each tee was fatigue tested to failure with either a fully reversed displacement controlled in-plane bending moment on the branch or a cyclic internal pressure that ranged from a value slightly above zero to about 90% of the nominal yield pressure of the pipe extensions.

  2. Electrostatic bending response of a charged helix

    Science.gov (United States)

    Zampetaki, A. V.; Stockhofe, J.; Schmelcher, P.

    2018-04-01

    We explore the electrostatic bending response of a chain of charged particles confined on a finite helical filament. We analyze how the energy difference Δ E between the bent and the unbent helical chain scales with the length of the helical segment and the radius of curvature and identify features that are not captured by the standard notion of the bending rigidity, normally used as a measure of bending tendency in the linear response regime. Using Δ E to characterize the bending response of the helical chain we identify two regimes with qualitatively different bending behaviors for the ground state configuration: the regime of small and the regime of large radius-to-pitch ratio, respectively. Within the former regime, Δ E changes smoothly with the variation of the system parameters. Of particular interest are its oscillations with the number of charged particles encountered for commensurate fillings which yield length-dependent oscillations in the preferred bending direction of the helical chain. We show that the origin of these oscillations is the nonuniformity of the charge distribution caused by the long-range character of the Coulomb interactions and the finite length of the helix. In the second regime of large values of the radius-to-pitch ratio, sudden changes in the ground state structure of the charges occur as the system parameters vary, leading to complex and discontinuous variations in the ground state bending response Δ E .

  3. Thermal Acoustic Fatigue Apparatus

    Data.gov (United States)

    Federal Laboratory Consortium — The Thermal Acoustic Fatigue Apparatus (TAFA) is a progressive wave tube test facility that is used to test structures for dynamic response and sonic fatigue due to...

  4. Bending stresses in Facetted Glass Shells

    DEFF Research Database (Denmark)

    Bagger, Anne; Jönsson, Jeppe; Almegaard, Henrik

    2008-01-01

    A shell structure of glass combines a highly effective structural principle with a material of optimal permeability to light. A facetted shell structure has a piecewise plane geometry, and together the facets form an approximation to a curved surface. A distributed load on a plane-based facetted...... structure will locally cause bending moments in the loaded facets. The bending stresses are dependent on the stiffness of the joints. Approximate solutions are developed to estimate the magnitude of the bending stresses. A FE-model of a facetted glass shell structure is used to validate the expressions...

  5. Analytic description of the frictionally engaged in-plane bending process incremental swivel bending (ISB)

    Science.gov (United States)

    Frohn, Peter; Engel, Bernd; Groth, Sebastian

    2018-05-01

    Kinematic forming processes shape geometries by the process parameters to achieve a more universal process utilizations regarding geometric configurations. The kinematic forming process Incremental Swivel Bending (ISB) bends sheet metal strips or profiles in plane. The sequence for bending an arc increment is composed of the steps clamping, bending, force release and feed. The bending moment is frictionally engaged by two clamping units in a laterally adjustable bending pivot. A minimum clamping force hindering the material from slipping through the clamping units is a crucial criterion to achieve a well-defined incremental arc. Therefore, an analytic description of a singular bent increment is developed in this paper. The bending moment is calculated by the uniaxial stress distribution over the profiles' width depending on the bending pivot's position. By a Coulomb' based friction model, necessary clamping force is described in dependence of friction, offset, dimensions of the clamping tools and strip thickness as well as material parameters. Boundaries for the uniaxial stress calculation are given in dependence of friction, tools' dimensions and strip thickness. The results indicate that changing the bending pivot to an eccentric position significantly affects the process' bending moment and, hence, clamping force, which is given in dependence of yield stress and hardening exponent. FE simulations validate the model with satisfactory accordance.

  6. Determinants of seafarers’ fatigue

    DEFF Research Database (Denmark)

    Bøggild Dohrmann, Solveig; Leppin, Anja

    2017-01-01

    in the review. The main reason for exclusion was fatigue not being the outcome variable. Results: Most evidence was available for work time-related factors suggesting that working nights was most fatiguing, that fatigue levels were higher toward the end of watch or shift, and that the 6-h on–6-h off watch...

  7. Experimental Investigation on Fatigue Behavior of Epoxy Resin under Load and Displacement Controls

    Directory of Open Access Journals (Sweden)

    Mahmood Mehrdad Shokrieh

    2014-12-01

    Full Text Available The mechanical properties of epoxy resin including tensile and flexural modulus, tensile and flexural strength for static conditions are currently studied. The frequency effect as significant parameter at room temperature is investigated and fatigue behavior of the epoxy resin in tension-tension loading conditions for different frequencies of 2, 3 and 5 Hz are obtained. The epoxy resin has been taken under flexural bending fatigue loading and fatigue life is investigated. The results of the experiments show the values of 2.5 and 3 GPa of tensile and flexural modules and 59.98 and 110.02 MPa of tensile and flexural strengths for the resin, respectively. To achieve a linear load-deflection relationship in a three-point bending experiment, a maximum allowable deflection of 5 mm is acquired. The relationship between the frequency and fatigue life shows higher frequency results in lower fatigue life. Loading with frequency of 2 Hz has provided 5.8 times more fatigue life compared with 5 Hz loading. For a tension-tension fatigue loading condition, the variation of tensile module of epoxy resin shows no noticeable change during the fatigue loading condition. This module decreases significantly only in the primary and failure cycles close to the fracture point. In further experiments, fatigue behavior of epoxy resin was tested under flexural bending fatigue loadings with controlled deflection at room temperature. Maximum applied normalized stresses versus the number of cycles to failure curve are illustrated and it can be performed in order to predict the number of cycles to failure for the resin in arbitrary applied normal stresses as well.

  8. Influence of laser hardening with weld penetration onto mechanical and fatigue properties of 40H steel

    International Nuclear Information System (INIS)

    Napadlek, W.; Przetakiewicz, W.

    2003-01-01

    In the article were described investigations results of mechanical properties (hardness, R 0.2 , R m , A 5 , Z) and fatigue properties (rotary bending) of the 40H steel samples, being quenched and tempered, induction and laser hardened. In the laser hardened samples with weld penetration of top layer cracking process in fatigue strength is started mainly in weld penetration area as structural notch. (author)

  9. On residual stresses and fatigue of laser hardened steels

    International Nuclear Information System (INIS)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

  10. On residual stresses and fatigue of laser hardened steels

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

  11. Big Bend National Park: Acoustical Monitoring 2010

    Science.gov (United States)

    2013-06-01

    During the summer of 2010 (September October 2010), the Volpe Center collected baseline acoustical data at Big Bend National Park (BIBE) at four sites deployed for approximately 30 days each. The baseline data collected during this period will he...

  12. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1996-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Fatigue failure is found to depend both on the total time under load and on the number of cycles.Recent accelerated fatigue research on wood is reviewed, and a discrepancy between...... to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation between stiffness reduction...

  13. Slice of a LEP bending magnet

    CERN Multimedia

    This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich. The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.

  14. Potential fatigue strength improvement of AA 5083-H111 notched parts by wire brush hammering: Experimental analysis and numerical simulation

    International Nuclear Information System (INIS)

    Sidhom, Naziha; Moussa, Naoufel Ben; Janeb, Sameh; Braham, Chedly; Sidhom, Habib

    2014-01-01

    Highlights: • Wire brush hammering increases by 20% the AA 5083-H111 notched parts fatigue limit. • Improvement of fatigue strength is related to the fatigue cracks nucleation. • Fatigue strength prediction accounts for wire brush hammering effects. - Abstract: The effects of milling as machining process and a post-machining treatment by wire-brush hammering, on the near surface layer characteristics of AA 5083-H111 were investigated. Surface texture, work-hardening and residual stress profiles were determined by roughness measurement, scanning electron microscope (SEM) examinations, microhardness and X-ray diffraction (XRD) measurements. The effects of surface preparation on the fatigue strength were assessed by bending fatigue tests performed on notched samples for two loading stress ratios R 0.1 and R 0.5 . It is found that the bending fatigue limit at R 0.1 and 10 7 cycles is 20% increased, with respect to the machined surface, by wire-brush hammering. This improvement was discussed on the basis of the role of surface topography, stabilized residual stress and work-hardening on the fatigue-crack network nucleation and growth. The effects biaxial residual stress field and surface work-hardening were taken into account in the finite element model. A multi-axial fatigue criterion was proposed to predict the fatigue strength of aluminum alloy notched parts for both machined and treated states

  15. A transparent bending-insensitive pressure sensor

    Science.gov (United States)

    Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao

    2016-05-01

    Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.

  16. Bending sound in graphene: Origin and manifestation

    Energy Technology Data Exchange (ETDEWEB)

    Adamyan, V.M., E-mail: vadamyan@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Bondarev, V.N., E-mail: bondvic@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Zavalniuk, V.V., E-mail: vzavalnyuk@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Department of Fundamental Sciences, Odessa Military Academy, 10 Fontanska Road, Odessa 65009 (Ukraine)

    2016-11-11

    Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.

  17. Bending sound in graphene: Origin and manifestation

    International Nuclear Information System (INIS)

    Adamyan, V.M.; Bondarev, V.N.; Zavalniuk, V.V.

    2016-01-01

    Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.

  18. Large Eddy Simulation of Supercritical CO2 Through Bend Pipes

    Science.gov (United States)

    He, Xiaoliang; Apte, Sourabh; Dogan, Omer

    2017-11-01

    Supercritical Carbon Dioxide (sCO2) is investigated as working fluid for power generation in thermal solar, fossil energy and nuclear power plants at high pressures. Severe erosion has been observed in the sCO2 test loops, particularly in nozzles, turbine blades and pipe bends. It is hypothesized that complex flow features such as flow separation and property variations may lead to large oscillations in the wall shear stresses and result in material erosion. In this work, large eddy simulations are conducted at different Reynolds numbers (5000, 27,000 and 50,000) to investigate the effect of heat transfer in a 90 degree bend pipe with unit radius of curvature in order to identify the potential causes of the erosion. The simulation is first performed without heat transfer to validate the flow solver against available experimental and computational studies. Mean flow statistics, turbulent kinetic energy, shear stresses and wall force spectra are computed and compared with available experimental data. Formation of counter-rotating vortices, named Dean vortices, are observed. Secondary flow pattern and swirling-switching flow motions are identified and visualized. Effects of heat transfer on these flow phenomena are then investigated by applying a constant heat flux at the wall. DOE Fossil Energy Crosscutting Technology Research Program.

  19. Mechanical Fatigue Testing of High Burnup Fuel for Transportation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wang, Hong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-05-01

    This report describes testing designed to determine the ability of high burnup (HBU) (>45 GWd/MTU) spent fuel to maintain its integrity under normal conditions of transportation. An innovative system, Cyclic Integrated Reversible-bending Fatigue Tester (CIRFT), has been developed at Oak Ridge National Laboratory (ORNL) to test and evaluate the mechanical behavior of spent nuclear fuel (SNF) under conditions relevant to storage and transportation. The CIRFT system is composed of a U-frame equipped with load cells for imposing the pure bending loads on the SNF rod test specimen and measuring the in-situ curvature of the fuel rod during bending using a set up with three linear variable differential transformers (LVDTs).

  20. Corrosion fatigue of 2219-T87 aluminum alloy

    Science.gov (United States)

    Mcmillan, V. C.

    1986-01-01

    Corrosion fatigue studies were conducted on bare, chemical conversion coated, and anodized 2219-T87 aluminum alloy. These tests were performed using a rotating beam machine running at a velocity of 2500 rpm. The corrosive environments tested were distilled water, 100 ppm NaCl, and 3.5 percent NaCl. Results were compared to the endurance limit in air. An evaluation of the effect of protective coatings on corrosion fatigue was made by comparing the fatigue properties of specimens with coatings to those without.

  1. Cognitive and Physical Fatigue Tasks Enhance Pain, Cognitive Fatigue and Physical Fatigue in People with Fibromyalgia

    Science.gov (United States)

    Dailey, Dana L; Keffala, Valerie J; Sluka, Kathleen A

    2014-01-01

    Objective Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task and a dual fatigue task. Methods Twenty four people with fibromyalgia and 33 healthy controls completed pain, fatigue and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue and perceived physical fatigue were assessed during each task using visual analogue scales. Function was assessed with shoulder range of motion and grip. Results People with fibromyalgia had significantly higher increases in pain, cognitive fatigue and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (pfatigue tasks, respectively. Conclusions These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. PMID:25074583

  2. Estimates of plastic loads for pipe bends under combined in-plane and out-of-plane bending moment

    International Nuclear Information System (INIS)

    Kim, Nak Hyun; Oh, Chang Sik; Kim, Yun Jae

    2008-01-01

    This paper provides a method to estimate plastic loads (defined by twice-elastic-slope) for pipe bends under combined in-plane and out-of-plane bending moment, based on detailed 3-D FE limit analyses using elastic-perfectly plastic materials. Because closing bending moment is always lower than opening bending moment, the combination of in-plane closing bending and out-of-plane bending moment becomes the most significant case. Due to conservatism of each bending moments, the resultant moment provided by ASME B and PV code is unduly conservative. However, the concept of the resultant moment is still valid. In this paper, FE results show that the accurate solutions of bending moments provide better estimates of plastic loads of pipe bend under combined in-plane bending and out-of-plane bending moment

  3. Elasto-plastic behavior of pipe subjected to steady axial load and cyclic bending

    International Nuclear Information System (INIS)

    Yao Yanping; Lu Mingwan; Zhang Xiong

    2004-01-01

    The elasto-plastic behavior of a pipe subjected to a steady axial force and a cyclic bending moment is studied. By using two parameters c and d, which describe the elasto-plastic interfaces of beam cross-section, the boundary curve equations between various types of elasto-plastic behavior, such as shakedown, plastic fatigue, ratcheting, and plastic collapse, are derived. The results are applicable for beams of any cross-section with two orthogonal axes of symmetry. As a result, the load regime diagram for a pipe is obtained, which gives an intuitive picture of the elasto-plastic behavior of the pipe under a given combination of constant axial load and cyclic bending moment

  4. Rotating preventers

    International Nuclear Information System (INIS)

    Tangedahl, M.J.; Stone, C.R.

    1992-01-01

    This paper reports that recent changes in the oil and gas industry and ongoing developments in horizontal and underbalanced drilling necessitated development of a better rotating head. A new device called the rotating blowout preventer (RBOP) was developed by Seal-Tech. It is designed to replace the conventional rotating control head on top of BOP stacks and allows drilling operations to continue even on live (underbalanced) wells. Its low wear characteristics and high working pressure (1,500 psi) allow drilling rig crews to drill safely in slightly underbalanced conditions or handle severe well control problems during the time required to actuate other BOPs in the stack. Drilling with a RBOP allows wellbores to be completely closed in tat the drill floor rather than open as with conventional BOPs

  5. Earth Rotation

    Science.gov (United States)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

  6. Reliability of non-heated tube bends of boilers

    International Nuclear Information System (INIS)

    Bugaj, N.V.; Akhremenko, V.L.; Zamotaev, V.S.

    1984-01-01

    Bend failures are described for non-heated boiler tubes of 12Kh1MF and 20 steels. Methods of reliability evaluations are presented which permit revealing and replacing the bends with inadequate resources. Influences of operation conditions on bend durability is shown as well as the factors which are dominating at bend failures

  7. Clinical neurophysiology of fatigue.

    Science.gov (United States)

    Zwarts, M J; Bleijenberg, G; van Engelen, B G M

    2008-01-01

    Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic disease has been established. If certain criteria are met, chronic fatigue syndrome can be diagnosed. The 4-item Abbreviated Fatigue Questionnaire allows the extent of the experienced fatigue to be assessed with a high degree of reliability and validity. Physiological fatigue has been well defined and originates in both the peripheral and central nervous system. The condition can be assessed by combining force and surface-EMG measurements (including frequency analyses and muscle-fibre conduction estimations), twitch interpolation, magnetic stimulation of the motor cortex and analysis of changes in the readiness potential. Fatigue is a well-known phenomenon in both central and peripheral neurological disorders. Examples of the former conditions are multiple sclerosis, Parkinson's disease and stroke. Although it seems to be a universal symptom of many brain disorders, the unique characteristics of the concomitant fatigue also point to a specific relationship with several of these syndromes. As regards neuromuscular disorders, fatigue has been reported in patients with post-polio syndrome, myasthenia gravis, Guillain-Barré syndrome, facioscapulohumeral dystrophy, myotonic dystrophy and hereditary motor and sensory neuropathy type-I. More than 60% of all neuromuscular patients suffer from severe fatigue, a prevalence resembling that of patients with MS. Except for several rare myopathies with specific metabolic derangements leading to exercise-induced muscle fatigue, most studies have not identified a prominent peripheral cause for the fatigue in this population. In contrast, the central activation of the diseased neuromuscular system is generally found to be suboptimal. The

  8. Effects of various austempering temperatures on fatigue properties in ductile iron

    International Nuclear Information System (INIS)

    Salman, S.; Findik, F.; Topuz, P.

    2007-01-01

    Austempering is an isothermal heat treatment which when applied to ferrous materials, produces a structure that is stronger and tougher than comparable structures produced with conventional heat treatments. In this paper, ductile iron specimens were applied to various austempering temperatures and interpreted fatigue properties. In this test, Denison 7615 fatigue machine was used for doing double sided bending stresses. The iron was austenitized at 900 deg. C and then austempered at 235, 300 and 370 deg. C for 2 h within a salt bath to obtain various austempered microstructures. Also, the fatigue properties of the bainitic structures which occurred by austempering are examined by scanning electron microscope

  9. Bending and tensile deformation of metallic nanowires

    International Nuclear Information System (INIS)

    McDowell, Matthew T; Leach, Austin M; Gall, Ken

    2008-01-01

    Using molecular statics simulations and the embedded atom method, a technique for bending silver nanowires and calculating Young's modulus via continuum mechanics has been developed. The measured Young's modulus values extracted from bending simulations were compared with modulus values calculated from uniaxial tension simulations for a range of nanowire sizes, orientations and geometries. Depending on axial orientation, the nanowires exhibit stiffening or softening under tension and bending as size decreases. Bending simulations typically result in a greater variation of Young's modulus values with nanowire size compared with tensile deformation, which indicates a loading-method-dependent size effect on elastic properties at sub-5 nm wire diameters. Since the axial stress is maximized at the lateral surfaces in bending, the loading-method-dependent size effect is postulated to be primarily a result of differences in nanowire surface and core elastic modulus. The divergence of Young's modulus from the bulk modulus in these simulations occurs at sizes below the range in which experiments have demonstrated a size scale effect on elastic properties of metallic nanowires. This difference indicates that other factors beyond native metallic surface properties play a role in experimentally observed nanowire elastic modulus size effects

  10. Dependence of offshore wind turbine fatigue loads on atmospheric stratification

    International Nuclear Information System (INIS)

    Hansen, K S; Larsen, G C; Ott, S

    2014-01-01

    The stratification of the atmospheric boundary layer (ABL) is classified in terms of the M-O length and subsequently used to determine the relationship between ABL stability and the fatigue loads of a wind turbine located inside an offshore wind farm. Recorded equivalent fatigue loads, representing blade-bending and tower bottom bending, are combined with the operational statistics from the instrumented wind turbine as well as with meteorological statistics defining the inflow conditions. Only a part of all possible inflow conditions are covered through the approximately 8200 hours of combined measurements. The fatigue polar has been determined for an (almost) complete 360° inflow sector for both load sensors, representing mean wind speeds below and above rated wind speed, respectively, with the inflow conditions classified into three different stratification regimes: unstable, neutral and stable conditions. In general, impact of ABL stratification is clearly seen on wake affected inflow cases for both blade and tower fatigue loads. However, the character of this dependence varies significantly with the type of inflow conditions – e.g. single wake inflow or multiple wake inflow

  11. The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

    National Research Council Canada - National Science Library

    Harrison, Richard; Chaiken, Scott; Harville, Donald; Fischer, Joseph; Fisher, Dion; Whitmore, Jeff

    2008-01-01

    The present study was designed to target two specific areas regarding fatigue. The primary purpose was to begin investigations into possible genetic markers linked to fatigue resistance and fatigue susceptibility...

  12. Bending the law: tidal bending and its effects on ice viscosity and flow

    Science.gov (United States)

    Rosier, S.; Gudmundsson, G. H.

    2017-12-01

    Many ice shelves are subject to strong ocean tides and, in order to accommodate this vertical motion, the ice must bend within the grounding zone. This tidal bending generates large stresses within the ice, changing its effective viscosity. For a confined ice shelf, this is particularly relevant because the tidal bending stresses occur along the sidewalls, which play an important role in the overall flow regime of the ice shelf. Hence, tidal bending stresses will affect both the mean and time-varying components of ice shelf flow. GPS measurements reveal strong variations in horizontal ice shelf velocities at a variety of tidal frequencies. We show, using full-Stokes viscoelastic modelling, that inclusion of tidal bending within the model accounts for much of the observed tidal modulation of horizontal ice shelf flow. Furthermore, our model shows that in the absence of a vertical tidal forcing, the mean flow of the ice shelf is reduced considerably.

  13. The influence of cell morphology on the compressive fatigue behavior of Ti-6Al-4V meshes fabricated by electron beam melting.

    Science.gov (United States)

    Zhao, S; Li, S J; Hou, W T; Hao, Y L; Yang, R; Misra, R D K

    2016-06-01

    Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Ultrathin flexible piezoelectric sensors for monitoring eye fatigue

    Science.gov (United States)

    Lü, Chaofeng; Wu, Shuang; Lu, Bingwei; Zhang, Yangyang; Du, Yangkun; Feng, Xue

    2018-02-01

    Eye fatigue is a symptom induced by long-term work of both eyes and brains. Without proper treatment, eye fatigue may incur serious problems. Current studies on detecting eye fatigue mainly focus on computer vision detect technology which can be very unreliable due to occasional bad visual conditions. As a solution, we proposed a wearable conformal in vivo eye fatigue monitoring sensor that contains an array of piezoelectric nanoribbons integrated on an ultrathin flexible substrate. By detecting strains on the skin of eyelid, the sensors may collect information about eye blinking, and, therefore, reveal human’s fatigue state. We first report the design and fabrication of the piezoelectric sensor and experimental characterization of voltage responses of the piezoelectric sensors. Under bending stress, the output voltage curves yield key information about the motion of human eyelid. We also develop a theoretical model to reveal the underlying mechanism of detecting eyelid motion. Both mechanical load test and in vivo test are conducted to convince the working performance of the sensors. With satisfied durability and high sensitivity, this sensor may efficiently detect abnormal eyelid motions, such as overlong closure, high blinking frequency, low closing speed and weak gazing strength, and may hopefully provide feedback for assessing eye fatigue in time so that unexpected situations can be prevented.

  15. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    alloys (2). [--I Fig. 6. Fatigue fracture in Nitrile- butadien rubber ( NBR ). Fig. 7. The characteristic features of fatigue fracture in press moulded...in plastics and even in rubber . It follows therefore, that fatigue fractures must also occur in the mineral layers of our earth or in the rock on...effective until the weakest point yields and forms a crack. To get a feeling for this process, you can imagine that the stressed article is made of rubber

  16. Fatigue 󈨛. Volume 2,

    Science.gov (United States)

    1987-06-01

    ROLAND STICKLER Absolute Fatigue Thresholds in Metallic 801 Materials - J.A. LEWIS Thermometrical Investigations on the Near 809 Threshold Fatigue...impurities reported by Semi- Alloys Inc. totaled less than 0.1%. Specimens were cast in a flat open aluminum mold. Each specimen was 6 mm thick and 12...and 2024-T351 Aluminum Alloy", in "Fatigue Crack Growth Threshold Concepts", D.L. Davidson, S. Suresh, editors, TMS-AIME. 1984, pp. 63-82. (2) Bailon

  17. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, Michael Havbro; Sørensen, John Dalsgaard; Kroon, I. B.

    1993-01-01

    life experiments for the same purpose. The methodology is basedon modern probabilistic concepts amd classical decision theory. The special case where the fatigue life experiments are given in terms of SN curves is considered in Particular. The proposed techniques are illustrated by an example.......This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue...

  18. Fatigue-Arrestor Bolts

    Science.gov (United States)

    Onstott, Joseph W.; Gilster, Mark; Rodriguez, Sergio; Larson, John E.; Wickham, Mark D.; Schoonover, Kevin E.

    1995-01-01

    Bolts that arrest (or, more precisely, retard) onset of fatigue cracking caused by inelastic strains developed. Specifically developed to be installed in flange holes of unrestrained rocket engine nozzle. Fanges sometimes used to bolt nozzle to test stand; however, when rocket engine operated without this restraint, region around bolt holes experience severe inelastic strains causing fatigue cracking. Interference fits introduce compressive preloads that retard fatigue by reducing ranges of strains. Principle of these fatigue-arrestor bolts also applicable to holes in plates made of other materials and/or used for different purposes.

  19. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...

  20. Low cycle fatigue strength of some austenitic stainless steels at room temperature and elevated temperatures

    International Nuclear Information System (INIS)

    Type 304, 316, and 316L stainless steels were tested from room temperature to 650 0 C using two kinds of bending test specimens. Particularly, Type 304 was tested at several cyclic rates and 550 0 and 650 0 C, and the effect of cyclic rate on its fatigue strength was investigated. Test results are summarized as follows: (1) The bending fatigue strength at room temperature test shows good agreement with the axial fatigue one, (2) Manson--Coffin's fatigue equation can be applied to the results, (3) the ratio of crack initiation to failure life becomes larger at higher stress level, and (4) the relation between crack propagation life and total strain range or elastic strain range are linear in log-log scale. This relation also agrees with the equations which were derived from some crack propagation laws. It was also observed at the elevated temperature test: (1) The reduction of fatigue strength is not noticeable below 500 0 C, but it is noted at higher temperature. (2) The cycle rate does not affect on fatigue strength in faster cyclic rate than 20 cpm and below 100,000 cycles life range. (3) Type 316 stainless steel shows better fatigue property than type 304 and 316L stainless steels. 30 figures

  1. A Pilot Study to Examine the Relationship Between Napping and Fatigue in Nurses Practicing on the Night Shift.

    Science.gov (United States)

    Neville, Kathleen; Velmer, Gillian; Brown, Shari; Robol, Nancy

    2017-11-01

    The aim of this study is to explore the relationship of night-shift napping on fatigue. Nurses' fatigue, especially at night, interferes with quality of life and job performance and impacts safety and health. Night-shift nurses completed the Brief Fatigue Inventory and a demographic information sheet to determine differences in fatigue between nurses who napped during their night shift as compared with nurses who did not nap. No statistically significant differences in global fatigue were found; differences in rotating shift, age, and, gender were identified. Rotating shifts, a 2nd job, and caring for family predicted fatigue. Based on this pilot study, further investigations of fatigue among night-shift nurses are needed as well as evidence-based support to promote sleep.

  2. Magnetic field of longitudinal gradient bend

    Science.gov (United States)

    Aiba, Masamitsu; Böge, Michael; Ehrlichman, Michael; Streun, Andreas

    2018-06-01

    The longitudinal gradient bend is an effective method for reducing the natural emittance in light sources. It is, however, not a common element. We have analyzed its magnetic field and derived a set of formulae. Based on the derivation, we discuss how to model the longitudinal gradient bend in accelerator codes that are used for designing electron storage rings. Strengths of multipole components can also be evaluated from the formulae, and we investigate the impact of higher order multipole components in a very low emittance lattice.

  3. Slice through an LHC bending magnet

    CERN Multimedia

    Slice through an LHC superconducting dipole (bending) magnet. The slice includes a cut through the magnet wiring (niobium titanium), the beampipe and the steel magnet yokes. Particle beams in the Large Hadron Collider (LHC) have the same energy as a high-speed train, squeezed ready for collision into a space narrower than a human hair. Huge forces are needed to control them. Dipole magnets (2 poles) are used to bend the paths of the protons around the 27 km ring. Quadrupole magnets (4 poles) focus the proton beams and squeeze them so that more particles collide when the beams’ paths cross. There are 1232 15m long dipole magnets in the LHC.

  4. Bending energy of buckled edge dislocations

    Science.gov (United States)

    Kupferman, Raz

    2017-12-01

    The study of elastic membranes carrying topological defects has a longstanding history, going back at least to the 1950s. When allowed to buckle in three-dimensional space, membranes with defects can totally relieve their in-plane strain, remaining with a bending energy, whose rigidity modulus is small compared to the stretching modulus. In this paper we study membranes with a single edge dislocation. We prove that the minimum bending energy associated with strain-free configurations diverges logarithmically with the size of the system.

  5. IMPROVEMENT OF FATIGUE STRENGTH OF TIN BABBITT BY REINFORCING WITH NANO ILMENITE

    Directory of Open Access Journals (Sweden)

    M. V. S. BABU

    2017-08-01

    Full Text Available Tin Babbitt is an idle journal bearing material, its fatigue strength limits and its usage. To enhance its fatigue strength, in this paper a Tin Babbitt metal matrix is reinforced with nano Ilmenite. The metal matrix nanocomposite was fabricated by using ultrasonic assisted stir casting technique. ASTM standards in statistical planning for fatigue testing were employed in planning the fatigue tests. Fatigue tests were conducted at three stress levels, i.e., 0.9 UTS, 0.7 UTS and 0.5 UTS. Tests were conducted on a rotating-beam type fatigue testing machine. It was observed that the nano Ilmenite reinforcement enhanced the fatigue strength of Tin Babbitt.

  6. A study on multi-axial fatigue model based on structural stress

    International Nuclear Information System (INIS)

    Kim, Cheol; Kim, Jong Sung; Jin, Tae Eun; Dong, P.

    2004-01-01

    In nuclear components, cyclic loadings that cause complex states of stress are common. Through a reference review, four sources of the multi-axial fatigue data were collected from LBF, University of Illinois, EPRI, and TWI. All these tests were conducted using tube to flange specimens with a circumferential fillet welds. The loading conditions were mostly bending/ torsion combinations, except that TWI used tension/ torsion combinations. None of fatigue correlation parameters have been demonstrated to be satisfactory in correlating the multi-axial fatigue data outside of their own. In this paper, we proposed the characterizing multi-axial fatigue behavior in terms of the structural stress methods by using some of the well-known multi-axial fatigue data available in the references

  7. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

    series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a wind turbine rotor...

  8. Clinical neurophysiology of fatigue.

    NARCIS (Netherlands)

    Zwarts, M.J.; Bleijenberg, G.; Engelen, B.G.M. van

    2008-01-01

    Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic

  9. Comparison of different nail bending apparatus

    NARCIS (Netherlands)

    Vianen, H.P.C.A.; Schot, F.; Vermeltfoort, A.Th.

    1992-01-01

    A research to develope a registrated testmethod to define the allowable bending moment of a nail was started in spring of this year. A request for a registrated testmethod is caused by the final project of ir. H.P.C.A. Vianen ‘s study. The consequence of developing new codes in The Netherlands and

  10. Amplification caused by gravitational bending of light

    International Nuclear Information System (INIS)

    Schneider, P.

    1985-01-01

    Gravitational bending of light may not only lead to multiple imaging (gravitational lens effect), but also affects the apparent luminosity of a source. It is shown here that a mass distribution near the line-of-sight to any source always increases the observable flux relative to the case in which the deflector is absent

  11. Interdisciplinary Invitations: Exploring Gee's Bend Quilts

    Science.gov (United States)

    Mitchell, Rebecca; Whitin, Phyllis; Whitin, David

    2012-01-01

    Engaging with the quilts of Gee's Bend offers a rich opportunity for students in grades four through eight to develop appreciation for pattern, rhythm, and innovation while learning about history, entrepreneurship, and political activism. By easily accessing print, film, and Internet resources teachers can include these vibrant quilts and…

  12. Demonstration model of LEP bending magnet

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    To save iron and raise the flux density, the LEP bending magnet laminations were separated by spacers and the space between the laminations was filled with concrete. This is a demonstration model, part of it with the spaced laminations only, the other part filled with concrete.

  13. Tubular lining material for pipelines having bends

    Energy Technology Data Exchange (ETDEWEB)

    Moringa, A.; Sakaguchi, Y.; Hyodo, M.; Yagi, I.

    1987-03-24

    A tubular lining material for pipelines having bends or curved portions comprises a tubular textile jacket made of warps and wefts woven in a tubular form overlaid with a coating of a flexible synthetic resin. It is applicable onto the inner surface of a pipeline having bends or curved portions in such manner that the tubular lining material with a binder onto the inner surface thereof is inserted into the pipeline and allowed to advance within the pipeline, with or without the aid of a leading rope-like elongated element, while turning the tubular lining material inside out under fluid pressure. In this manner the tubular lining material is applied onto the inner surface of the pipeline with the binder being interposed between the pipeline and the tubular lining material. The lining material is characterized in that a part of all of the warps are comprised of an elastic yarn around which, over the full length thereof, a synthetic fiber yarn or yarns have been left-and/or right-handedly coiled. This tubular lining material is particularly suitable for lining a pipeline having an inner diameter of 25-200 mm and a plurality of bends, such as gas service pipelines or house pipelines, without occurrence of wrinkles in the lining material in a bend.

  14. Systematisk løbende refleksion

    DEFF Research Database (Denmark)

    Kristiansson, Michael

    2010-01-01

    Artiklen omhandler en model kaldet systematisk løbende refleksion, der repræsenterer en procedure til overvejelse og genovervejelse af de vurderingskriterier, man lægger til grund for evaluering af et udviklingsprojekt. Pointen er at justere udviklingsprojektet ind i en ønsket retning. Formålet m...

  15. Fuzzy model for Laser Assisted Bending Process

    Directory of Open Access Journals (Sweden)

    Giannini Oliviero

    2016-01-01

    Full Text Available In the present study, a fuzzy model was developed to predict the residual bending in a conventional metal bending process assisted by a high power diode laser. The study was focused on AA6082T6 aluminium thin sheets. In most dynamic sheet metal forming operations, the highly nonlinear deformation processes cause large amounts of elastic strain energy stored in the formed material. The novel hybrid forming process was thus aimed at inducing the local heating of the mechanically bent workpiece in order to decrease or eliminate the related springback phenomena. In particular, the influence on the extent of springback phenomena of laser process parameters such as source power, scan speed and starting elastic deformation of mechanically bent sheets, was experimentally assessed. Consistent trends in experimental response according to operational parameters were found. Accordingly, 3D process maps of the extent of the springback phenomena according to operational parameters were constructed. The effect of the inherent uncertainties on the predicted residual bending caused by the approximation in the model parameters was evaluated. In particular, a fuzzy-logic based approach was used to describe the model uncertainties and the transformation method was applied to propagate their effect on the residual bending.

  16. Aerosol deposition in bends with turbulent flow

    Energy Technology Data Exchange (ETDEWEB)

    McFarland, A.R.; Gong, H.; Wente, W.B. [Texas A& M Univ., College Station, TX (United States)] [and others

    1997-08-01

    The losses of aerosol particles in bends were determined numerically for a broad range of design and operational conditions. Experimental data were used to check the validity of the numerical model, where the latter employs a commercially available computational fluid dynamics code for characterizing the fluid flow field and Lagrangian particle tracking technique for characterizing aerosol losses. Physical experiments have been conducted to examine the effect of curvature ratio and distortion of the cross section of bends. If it curvature ratio ({delta} = R/a) is greater than about 4, it has little effect on deposition, which is in contrast with the recommendation given in ANSI N13.1-1969 for a minimum curvature ratio of 10. Also, experimental results show that if the tube cross section is flattened by 25% or less, the flattening also has little effect on deposition. Results of numerical tests have been used to develop a correlation of aerosol penetration through a bend as a function of Stokes number (Stk), curvature ratio ({delta}) and the bend angle ({theta}). 17 refs., 10 figs., 2 tabs.

  17. The Health Effects of Rotating Shiftwork in the Oil Sector

    OpenAIRE

    McNamara, Katherine Alice

    2018-01-01

    Despite the improvements in safety since the advent of Process Safety Management regulations in 1992, human factors still play a large role in catastrophic accidents. Worker fatigue is a significant risk in the petroleum industry, where rotating shiftwork is relied upon to staff round the clock production. Using reports of work organization factors that contributed to fatigue from the listening sessions hosted by the California Interagency Taskforce on Refinery Safety in 2013, we developed ...

  18. Large eddy simulation of a T-Junction with upstream elbow: The role of Dean vortices in thermal fatigue

    International Nuclear Information System (INIS)

    Tunstall, R.; Laurence, D.; Prosser, R.; Skillen, A.

    2016-01-01

    Highlights: • A T-Junction with an upstream bend is studied using wall-resolved LES and POD. • The bend generates Dean vortices which remain prominent downstream of the junction. • Dean vortex swirl-switching results in an unsteady secondary flow about the pipe axis. • This provides a further mechanism for near-wall temperature fluctuations. • Upstream bends can have a crucial role in T-Junction thermal fatigue problems. - Abstract: Turbulent mixing of fluids in a T-Junction can generate oscillating thermal stresses in pipe walls, which may lead to high cycle thermal fatigue. This thermal stripping problem is an important safety issue in nuclear plant thermal-hydraulic systems, since it can lead to unexpected failure of the pipe material. Here, we carry out a large eddy simulation (LES) of a T-Junction with an upstream bend and use proper orthogonal decomposition (POD) to identify the dominant structures in the flow. The bend generates an unsteady secondary flow about the pipe axis, known as Dean vortex swirl-switching. This provides an additional mechanism for low-frequency near-wall temperature fluctuations downstream of the T-Junction, over those that would be produced by mixing in the same T-Junction with straight inlets. The paper highlights the important role of neighbouring pipe bends in T-Junction thermal fatigue problems and the need to include them when using CFD as a predictive tool.

  19. Effect of couple-stress on the pure bending of a prismatic bar

    International Nuclear Information System (INIS)

    Tzung, F.; Kao, B.; Ho, F.; Tang, P.

    1981-02-01

    An evaluation of the applicability of the couple-stress theory to the stress analysis of graphite structures is performed by solving a pure bending problem. The differences between solutions from the couple-stress theory and from the classical theory of elasticity are compared. It is found that the differences are sufficient to account for the inconsistencies which have often been observed between the classical elasticity theory and actual behavior of graphite under bend and tensile loadings. An experimental procedure to measure the material constants in the couple-stress theory is also suggested. The linear couple-stress theory, the origins of which go back to the turn of the last century, adds linear relations between couple-stresses and rotation gradients to the classical stress-strain law. By adopting the classical assumption that the plane cross section remains plane after deformation, the pure-bending problem is reduced to a plane couple-stress problem with traction-free boundary conditions. A general solution for an isotropic elastic prismatic bar under pure bending is then obtained using the Airy stress function and another stress function wich accounts for the couple-stresss. For a cylindrical bar, it reduces to a simple series solution. The moment-curvature and stress-curvature relations derived for a cylindrical bar from the general solution are used to examine the effect of couple-stresses. Numerical compilation of relations indicates that the couple stress parameters can be practically determined by measuring the moment-curvature ratio of various diametered specimens under bending. Although there is not sufficient data for such evaluation at present, it appears that the theory is consistent with the limited bend and tensile strength data of cylindrical specimens for H-451 graphite

  20. Corrosion fatigue of steels

    International Nuclear Information System (INIS)

    Spaehn, H.; Wagner, G.H.

    1976-01-01

    Corrosion fatigue phenomena can be classified into two main groups according to the electrochemical state of the metal surface in the presence of electrolytes: the active and the passive state with an important sub-group of corrosion fatigue in the unstable passive state. The allowable stress for structures exposed to the conjoint action of corrosion and fatigue is influenced by many factors: kind of media, number of cycles, frequency, mean stress, size, notches, loading mode, alloy composition and mechanical strength. A critical literature review shows contradictory results if a classification by the electrochemical surface state is not applied. Case histories and counter measures illustrate the practical importance of corrosion fatigue in many branches of industry as well as the urgent need for a better knowledge about the mutual influence of the phenomena to get rules by which the engineer can appraise the risk of corrosion fatigue. (orig.) [de

  1. Examining fatigue in COPD

    DEFF Research Database (Denmark)

    Al-Shair, Khaled; Muellerova, Hana; Yorke, Janelle

    2012-01-01

    ABSTRACT: INTRODUCTION: Fatigue is a disruptive symptom that inhibits normal functional performance of COPD patients in daily activities. The availability of a short, simple, reliable and valid scale would improve assessment of the characteristics and influence of fatigue in COPD. METHODS......: At baseline, 2107 COPD patients from the ECLIPSE cohort completed the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) scale. We used well-structured classic method, the principal components analysis (PCA) and Rasch analysis for structurally examining the 13-item FACIT-F. RESULTS: Four items...... were less able to capture fatigue characteristics in COPD and were deleted. PCA was applied to the remaining 9 items of the modified FACIT-F and resulted in three interpretable dimensions: i) general (5 items); ii) functional ability (2 items); and iii) psychosocial fatigue (2 items). The modified...

  2. Symmetric bends how to join two lengths of cord

    CERN Document Server

    Miles, Roger E

    1995-01-01

    A bend is a knot securely joining together two lengths of cord (or string or rope), thereby yielding a single longer length. There are many possible different bends, and a natural question that has probably occurred to many is: "Is there a 'best' bend and, if so, what is it?"Most of the well-known bends happen to be symmetric - that is, the two constituent cords within the bend have the same geometric shape and size, and interrelationship with the other. Such 'symmetric bends' have great beauty, especially when the two cords bear different colours. Moreover, they have the practical advantage o

  3. Combined simulation of fatigue crack nucleation and propagation based on a damage indicator

    Directory of Open Access Journals (Sweden)

    M. Springer

    2016-10-01

    Full Text Available Fatigue considerations often distinguish between fatigue crack nucleation and fatigue crack propagation. The current work presents a modeling approach utilizing one Fatigue Damage Indicator to treat both in a unified way. The approach is implemented within the framework of the Finite Element Method. Multiaxial critical plane models with an extended damage accumulation are employed as Fatigue Indicators. Locations of fatigue crack emergence are predicted by these indicators and material degradation is utilized to model local material failure. The cyclic loading is continued on the now degraded structure and the next location prone to material failure is identified and degradation modeled. This way, fatigue crack propagation is represented by an evolving spatial zone of material failure. This propagating damage zone leads to a changing structural response of the pristine structure. By recourse to the Fatigue Damage Indicator a correlation between the number of applied load cycles and the changing structural behavior is established. Finally, the proposed approach is exemplified by cyclic bending experiments in the Low Cycle Fatigue regime

  4. High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S. [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P., E-mail: pentti.karjalainen@oulu.fi [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland)

    2010-08-20

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 10{sup 6} cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  5. Fatigue behaviour of friction welded medium carbon steel and austenitic stainless steel dissimilar joints

    International Nuclear Information System (INIS)

    Paventhan, R.; Lakshminarayanan, P.R.; Balasubramanian, V.

    2011-01-01

    Research highlights: → Fusion welding of dissimilar metals is a problem due to difference in properties. → Solid state welding process such as friction welding is a solution for the above problem. → Fatigue life of friction welded carbon steel and stainless steel joints are evaluated. → Effect of notch on the fatigue life of friction welded dissimilar joints is reported. → Formation of intermetallic is responsible for reduction in fatigue life of dissimilar joints. -- Abstract: This paper reports the fatigue behaviour of friction welded medium carbon steel-austenitic stainless steel (MCS-ASS) dissimilar joints. Commercial grade medium carbon steel rods of 12 mm diameter and AISI 304 grade austenitic stainless steel rods of 12 mm diameter were used to fabricate the joints. A constant speed, continuous drive friction welding machine was used to fabricate the joints. Fatigue life of the joints was evaluated conducting the experiments using rotary bending fatigue testing machine (R = -1). Applied stress vs. number of cycles to failure (S-N) curve was plotted for unnotched and notched specimens. Basquin constants, fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated for the dissimilar joints. Fatigue strength of the joints is correlated with microstructure, microhardness and tensile properties of the joints.

  6. Crack Propagation Calculations for Optical Fibers under Static Bending and Tensile Loads Using Continuum Damage Mechanics

    Science.gov (United States)

    Chen, Yunxia; Cui, Yuxuan; Gong, Wenjun

    2017-01-01

    Static fatigue behavior is the main failure mode of optical fibers applied in sensors. In this paper, a computational framework based on continuum damage mechanics (CDM) is presented to calculate the crack propagation process and failure time of optical fibers subjected to static bending and tensile loads. For this purpose, the static fatigue crack propagation in the glass core of the optical fiber is studied. Combining a finite element method (FEM), we use the continuum damage mechanics for the glass core to calculate the crack propagation path and corresponding failure time. In addition, three factors including bending radius, tensile force and optical fiber diameter are investigated to find their impacts on the crack propagation process and failure time of the optical fiber under concerned situations. Finally, experiments are conducted and the results verify the correctness of the simulation calculation. It is believed that the proposed method could give a straightforward description of the crack propagation path in the inner glass core. Additionally, the predicted crack propagation time of the optical fiber with different factors can provide effective suggestions for improving the long-term usage of optical fibers. PMID:29140284

  7. Constructing kinetics fatigue diagrams using testing results obtained on a machine with rigid loading for specimens of various thickness

    International Nuclear Information System (INIS)

    Simin'kovich, V.N.; Gladkij, Ya.N.; Deev, N.A.

    1981-01-01

    Bending tests of 40KhS steel specimens, tempered at 200 and 500 deg C, are conducted to investigate the possible effects of specimen thickness on fatigue crack growth. Kinetic fatigue diagrams are constructed using the investigation results. An increase in crack growth with thickness is observed only in high-tempered specimens. Changes in specimen thickness do not affect crack growth in 40KhS low-tempered steel [ru

  8. Needle puncture in rabbit functional spinal units alters rotational biomechanics.

    Science.gov (United States)

    Hartman, Robert A; Bell, Kevin M; Quan, Bichun; Nuzhao, Yao; Sowa, Gwendolyn A; Kang, James D

    2015-04-01

    An in vitro biomechanical study for rabbit lumbar functional spinal units (FSUs) using a robot-based spine testing system. To elucidate the effect of annular puncture with a 16 G needle on mechanical properties in flexion/extension, axial rotation, and lateral bending. Needle puncture of the intervertebral disk has been shown to alter mechanical properties of the disk in compression, torsion, and bending. The effect of needle puncture in FSUs, where intact spinal ligaments and facet joints may mitigate or amplify these changes in the disk, on spinal motion segment stability subject to physiological rotations remains unknown. Rabbit FSUs were tested using a robot testing system whose force/moment and position precision were assessed to demonstrate system capability. Flexibility testing methods were developed by load-to-failure testing in flexion/extension, axial rotation, and lateral bending. Subsequent testing methods were used to examine a 16 G needle disk puncture and No. 11 blade disk stab (positive control for mechanical disruption). Flexibility testing was used to assess segmental range-of-motion (degrees), neutral zone stiffness (N m/degrees) and width (degrees and N m), and elastic zone stiffness before and after annular injury. The robot-based system was capable of performing flexibility testing on FSUs-mean precision of force/moment measurements and robot system movements were elastic zone stiffness in flexion and lateral bending. These findings suggest that disk puncture and stab can destabilize FSUs in primary rotations.

  9. Finite Element Analysis for Bending Process of U-Bending Specimens

    Energy Technology Data Exchange (ETDEWEB)

    Park, Won Dong; Bahn, Chi Bum [Pusan National University, Busan (Korea, Republic of)

    2015-10-15

    ASTM G30 suggests that the applied strain can be calculated by dividing thickness by a bend radius. It should be noted, however, that the formula is reliable under an assumption that the ratio of thickness to bend radius is less than 0.2. Typically, to increase the applied stress/strain, the ratio of thickness to bend radius becomes larger than 0.2. This suggests that the estimated strain values by ASTM G30 are not reliable to predict the actual residual strain state of the highly deformed U-bend specimen. For this reason, finite element analysis (FEA) for the bending process of Ubend specimens was conducted by using a commercial finite element analysis software ABAQUS. ver.6.14- 2;2014. From the results of FEA, PWSCC initiation time and U-bend specimen size can be determined exactly. Since local stress and strain have a significant effect on the initiation of PWSCC, it was inappropriate to apply results of ASTM G30 to the PWSCC test directly. According to results of finite element analysis (FEA), elastic relaxation can cause inaccuracy in intended final residual stress. To modify this inaccuracy, additional process reducing the spring back is required. However this additional process also may cause uncertainty of stress/strain state. Therefore, the U-bending specimen size which is not creating uncertainty should be optimized and selected. With the bending radius of 8.3 mm, the thickness of 3 mm and the roller distance of 32.6 mm, calculated maximum stress and strain were 670 MPa and 0.21, respectively.

  10. Multiaxial low cycle fatigue life under non-proportional loading

    International Nuclear Information System (INIS)

    Itoh, Takamoto; Sakane, Masao; Ohsuga, Kazuki

    2013-01-01

    A simple and clear method of evaluating stress and strain ranges under non-proportional multiaxial loading where principal directions of stress and strain are changed during a cycle is needed for assessing multiaxial fatigue. This paper proposes a simple method of determining the principal stress and strain ranges and the severity of non-proportional loading with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. This study also discusses properties of multiaxial low cycle fatigue lives for various materials fatigued under non-proportional loadings and shows an applicability of a parameter proposed by author for multiaxial low cycle fatigue life evaluation

  11. Natural Frequncies of Coupled Blade-Bending and Shaft-Torsional Vibrations

    Directory of Open Access Journals (Sweden)

    B.O. Al-Bedoor

    2007-01-01

    Full Text Available In this study, the coupled shaft-torsional and blade-bending natural frequencies are investigated using a reduced order mathematical model. The system-coupled model is developed using the Lagrangian approach in conjunction with the assumed modes method to discretize the blade bending deflection. The model accounts for the blade stagger (setting angle, the system rotating speed and its induced stiffening effect. The coupled equations of motion are linearized based on the small deformation theory for the blade bending and shaft torsional deformation to enable calculation of the system natural frequencies for various combinations of system parameters. The obtained coupled eignvalue system is ready for use as a reference for comparison for larger size finite element simulations and for the use as a fast check on natural frequencies for the coupled blade bending and shaft torsional vibrations in the design and diagnostics processes. Some results on the predicted natural frequencies are graphically presented and discussed pertinent to the coupling controlling factors and their effects. In addition, the predicted coupled natural frequencies are validated using the Finite Element Commercial Package (Pro-Mechanica where good agreements are found.

  12. Ab initio study on mechanical-bending-induced ferroelectric phase transition in ultrathin perovskite nanobelts

    International Nuclear Information System (INIS)

    Li, H.F.; Zhang, G.H.; Zheng, Yue; Wang, Biao; Chen, W.J.

    2014-01-01

    Based on first-principles calculations, we systematically investigated the structural, ferroelectric (FE), energetic and electronic properties of bended ultrathin PbTiO 3 and BaTiO 3 nanobelts in between flat sheet and nanotube configurations. It is found that both PbTiO 3 and BaTiO 3 ultrathin nanobelts can possess axial antiferrodistortive structural distortion (AFD distortion), and the magnitude of the AFD rotation angle is obviously determined by the bending curvature of the nanobelts. Meanwhile, spontaneous polarization can be retained in these single-unit-cell-thick nanobelts with contributions from the axial improper ferroelectricity and the radial flexoelectricity, which indicates that ultrathin perovskite nanobelts do not have a critical thickness. On the other hand, we found that the AFD distortion is stable and significant in PbTiO 3 nanobelts while it is metastable in BaTiO 3 nanobelts in comparison with the stable non-AFD structure without AFD distortion. This is due to the competition between AFD distortion and circumferential lattice extension in releasing the elastic energy in BaTiO 3 material. Moreover, we found that the electronic structure and bandgap of the nanobelts can be tuned by the bending curvature, indicating potential control of transport properties by mechanical bending. Our results gave more insight into the inherence of improper ferroelectricity in low-dimensional perovskite ferroelectrics

  13. Fatigue evaluation algorithms: Review

    Energy Technology Data Exchange (ETDEWEB)

    Passipoularidis, V.A.; Broendsted, P.

    2009-11-15

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Puck, to model the degradation caused by failure events in ply level. Residual strength is incorporated as fatigue damage accumulation metric. Once the typical fatigue and static properties of the constitutive ply are determined,the performance of an arbitrary lay-up under uniaxial and/or multiaxial load time series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a wind turbine rotor blade construction. Two versions of the algorithm, the one using single-step and the other using incremental application of each load cycle (in case of ply failure) are implemented and compared. Simulation results confirm the ability of the algorithm to take into account load sequence effects. In general, FADAS performs well in predicting life under both spectral and block loading fatigue. (author)

  14. Prolonged unexplained fatigue in paediatrics

    NARCIS (Netherlands)

    Bakker, R.J.

    2010-01-01

    Prolonged Unexplained Fatigue in Paediatrics. Fatigue, as the result of mental or physical exertion, will disappear after rest, drinks and food. Fatigue as a symptom of illness will recover with the recovering of the illness. But when fatigue is ongoing for a long time, and not the result of

  15. Incomplete (bending) fractures of the mandibular condyle in children

    International Nuclear Information System (INIS)

    Ahrendt, D.; Swischuk, L.E.; Hayden, C.K. Jr.; Texas Univ., Galveston

    1984-01-01

    Incomplete, bending or bowing fractures of the mandibular condyle in children frequently go undetected. The reason is that the bending deformity often is subtle and passes for normal. This is especially true if the fractures are bilateral. (orig.)

  16. Bending properties of Ce-TZP/A nanocomposite clasps for removable partial dentures.

    Science.gov (United States)

    Urano, Shinjiro; Hotta, Yasuhiro; Miyazaki, Takashi; Baba, Kazuyoshi

    2015-01-01

    Ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) has excellent fracture toughness and bending strength that could be useful for partial denture framework application. The aim of this study was to investigate the effects of three-dimensional (3D) geometry on the bending and fatigue properties of a model simulation of Ce-TZP/A clasps. Half oval-shaped Ce-TZP/A rods were prepared in six 3D designs. Specimens were either of standard (width divided by thickness: 2.0/1.0 mm) or flat type (2.5/0.8 mm) cross-sectional areas with taper ratios of 1.0, 0.8, or 0.6. As a comparison, cobalt-chromium (Co-Cr) alloy rods of the same shape as the Ce-TZP/A standard shape rod were prepared. All specimens were subjected to the cantilever test and loaded until fracture. They were also cyclically loaded 106 times with various constant displacements, and the maximum displacement prior to fracture was determined for each specimen. Three-dimensional finite element analysis (3D FEA), simulating the cantilever test, was performed to determine the stress distribution during loading. Specimens with the standard cross-sectional shape exhibited higher rigidity and higher fracture loads than the flat specimens by the cantilever test. In addition, lower taper ratios were consistently associated with larger displacements at fracture. Fatigue tests revealed that the maximum displacement prior to fracture of Ce-TZP/A specimens was comparable to that of Co-Cr alloy specimens. The 3D FEA showed that specimens with a taper ratio of 0.6 had the least stress concentration. Ce-TZP/A clasp specimens with a standard cross-sectional shape and a 0.6 taper ratio exhibited the best bending properties among those tested.

  17. Modelling of convective heat and mass transfer in rotating flows

    CERN Document Server

    Shevchuk, Igor V

    2016-01-01

     This monograph presents results of the analytical and numerical modeling of convective heat and mass transfer in different rotating flows caused by (i) system rotation, (ii) swirl flows due to swirl generators, and (iii) surface curvature in turns and bends. Volume forces (i.e. centrifugal and Coriolis forces), which influence the flow pattern, emerge in all of these rotating flows. The main part of this work deals with rotating flows caused by system rotation, which includes several rotating-disk configurations and straight pipes rotating about a parallel axis. Swirl flows are studied in some of the configurations mentioned above. Curvilinear flows are investigated in different geometries of two-pass ribbed and smooth channels with 180° bends. The author demonstrates that the complex phenomena of fluid flow and convective heat transfer in rotating flows can be successfully simulated using not only the universal CFD methodology, but in certain cases by means of the integral methods, self-similar and analyt...

  18. A Study on U-bending Technology using Rotary Draw Bending

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ok-gyu; Kim, Won-seok [BHI Co., Gyunsang-Namdo (Korea, Republic of); Ku, Tae-wan [Pusan National Univ., Busan (Korea, Republic of)

    2014-10-15

    In the steam generator, heat transfer phenomenon for producing the steam between the primary system of the nuclear reactor and the secondary one occurs around the heat transfer tube. That is, the primary coolant with high temperature(320 .deg.. C) and high pressure(157Kgf/cm2) derived from the reactor flows in the heat transfer tube, and the secondary one runs out that tube. Therefore, it is able to mention that the heat transfer tube itself is a boundary of the heat transfer phenomenon. The heat transfer tube bundle of each steam generator used for the PWR and the PHWR(Pressurized Heavy Water Reactor) is generally composed of about 8,000-13,000 U-tubes. And these tubes are the core component as the structural and heat transfer material in the steam generator, which is in charge of cooling about 70% of the cooling surface of the primary system. For achieving the U-bending process with the thin walled tube, generally, a mandrel could be inserted in the tube according to the bending radius. But when the bending radius is small, the tube U-bending process could be also performed without the mandrel. In this study, numerical and experimental investigations on the U-bending process for producing the heat transfer tubes by using the straight and long tubes were carried out with the consideration of the elastic recovery after the U-bending. In the numerical approach, finite element analysis scheme was adopted with a commercial code, ABAQUS Implicit/Explicit. As the precedent study, the related experiment was also performed to verify the predicted results on the ovality and the minimum wall thickness of the U-bending heat transfer tube. Furthermore, its bending process was also conducted to analyze the deformation behavior for the Alloy 690 tube. In this study, the U-bending process was considered to simulate and manufactured the heat transfer tube used for the steam generator. To investigate the deformation behavior of the U-bending process, and a series of the

  19. Prediction of fatigue damage in tapered laminates

    DEFF Research Database (Denmark)

    Raeis Hosseiny, Seyed Aydin; Jakobsen, Johnny

    2017-01-01

    Effective implementation of ply-drops configurations substantially improve the damage tolerant design of flexible and aero-elastic wind turbine blades. Terminating a number of layers for an optimized blade design creates local bending effects. Inter-laminar stress states in tapered areas give rise...... to delamination and premature structural failure. Precise calculation of the stress levels for embedded ply-drops is required to predict failure initiation within acceptable limits. Multi-axial stress states in orthotropic laminates subjected to diverse loading mechanisms nucleate microscopic cracks....... By increasing the cracks density, damage occurs when residual material properties reduce to a critical level. Residual strength and stiffness of simple laminates are assigned in a set of fatigue failure criteria to assess the remaining life of the components by increasing number of loading cycles. The mode...

  20. Thermal Analysis of Bending Under Tension Test

    DEFF Research Database (Denmark)

    Ceron, Ermanno; Martins, Paulo A.F.; Bay, Niels

    2014-01-01

    during testing is similar to the one in the production tool. A universal sheet tribo-tester has been developed, which can run multiple tests automatically from coil. This allows emulating the temperature increase as in production. The present work performs finite element analysis of the evolution......The tribological conditions in deep drawing can be simulated in the Bending Under Tension test to evaluate the performance of new lubricants, tool materials, etc. Deep drawing production with automatic handling runs normally at high rate. This implies considerable heating of the tools, which...... sometimes can cause lubricant film breakdown and galling. In order to replicate the production conditions in bending under tension testing it is thus important to control the tool/workpiece interface temperature. This can be done by pre-heating the tool, but it is essential that the interface temperature...

  1. Vortex breakdown in simple pipe bends

    Science.gov (United States)

    Ault, Jesse; Shin, Sangwoo; Stone, Howard

    2016-11-01

    Pipe bends and elbows are one of the most common fluid mechanics elements that exists. However, despite their ubiquity and the extensive amount of research related to these common, simple geometries, unexpected complexities still remain. We show that for a range of geometries and flow conditions, these simple flows experience unexpected fluid dynamical bifurcations resembling the bubble-type vortex breakdown phenomenon. Specifically, we show with simulations and experiments that recirculation zones develop within the bends under certain conditions. As a consequence, fluid and particles can remain trapped within these structures for unexpectedly-long time scales. We also present simple techniques to mitigate this recirculation effect which can potentially have impact across industries ranging from biomedical and chemical processing to food and health sciences.

  2. Nuclear fuels accounting interface: River Bend experience

    International Nuclear Information System (INIS)

    Barry, J.E.

    1986-01-01

    This presentation describes nuclear fuel accounting activities from the perspective of nuclear fuels management and its interfaces. Generally, Nuclear Fuels-River Bend Nuclear Group (RBNG) is involved on a day-by-day basis with nuclear fuel materials accounting in carrying out is procurement, contract administration, processing, and inventory management duties, including those associated with its special nuclear materials (SNM)-isotopics accountability oversight responsibilities as the Central Accountability Office for the River Bend Station. As much as possible, these duties are carried out in an integrated, interdependent manner. From these primary functions devolve Nuclear Fuels interfacing activities with fuel cost and tax accounting. Noting that nuclear fuel tax accounting support is of both an esoteric and intermittent nature, Nuclear Fuels-RBNG support of developments and applications associated with nuclear fuel cost accounting is stressed in this presentation

  3. Effect of confinements: Bending in Paramecium

    Science.gov (United States)

    Eddins, Aja; Yang, Sung; Spoon, Corrie; Jung, Sunghwan

    2012-02-01

    Paramecium is a unicellular eukaryote which by coordinated beating of cilia, generates metachronal waves which causes it to execute a helical trajectory. We investigate the swimming parameters of the organism in rectangular PDMS channels and try to quantify its behavior. Surprisingly a swimming Paramecium in certain width of channels executes a bend of its flexible body (and changes its direction of swimming) by generating forces using the cilia. Considering a simple model of beam constrained between two walls, we predict the bent shapes of the organism and the forces it exerts on the walls. Finally we try to explain how bending (by sensing) can occur in channels by conducting experiments in thin film of fluid and drawing analogy to swimming behavior observed in different cases.

  4. Measuring device for bending of beryllium reflector

    International Nuclear Information System (INIS)

    Nishida, Seiri; Sakamoto, Naoki.

    1994-01-01

    The device of the present invention can measure bending of a beryllium reflector formed in a reactor core of a nuclear reactor by a relatively easy operation. Namely, a sensor portion comprises a long-support that can be inserted to a fuel element-insertion hole disposed in the reactor and a plurality of distance sensors disposed in a longitudinal direction of the support. A supersonic wave sensor which is advantageous in the heat resistance, the size and the accuracy and can conduct measurement in water relatively easily is used as the distance sensors. However, other sensors, instead of the sensor described above, may also be used. The plurality of distance sensors detect the bending amount of the beryllium reflector in the longitudinal direction by such an easy operation of inserting such a sensor portion to the fuel element-insertion hole upon exchange of fuel elements. (I.S.)

  5. Molecular Origin of Model Membrane Bending Rigidity

    International Nuclear Information System (INIS)

    Kurtisovski, Erol; Taulier, Nicolas; Waks, Marcel; Ober, Raymond; Urbach, Wladimir

    2007-01-01

    The behavior of the bending modulus κ of bilayers in lamellar phases was studied by Small Angle X-ray Scattering technique for various nonionic C i E j surfactants. The bilayers are either unswollen and dispersed in water or swollen by water and dispersed in dodecane. For unswollen bilayers, the values of κ decrease with both an increase in the area per surfactant molecule and in the polar head length. They increase when the aliphatic chain length increases at constant area per surfactant molecule. Whereas for water-swollen membranes, the values of κ decrease as the content of water increases converging to the value of the single monolayer bending modulus. Such a behavior results from the decoupling of the fluctuations of the two surfactant membrane monolayers. Our results emphasize the determinant contribution of the surfactant conformation to κ

  6. Holey fibers for low bend loss

    Science.gov (United States)

    Nakajima, Kazuhide; Saito, Kotaro; Yamada, Yusuke; Kurokawa, Kenji; Shimizu, Tomoya; Fukai, Chisato; Matsui, Takashi

    2013-12-01

    Bending-loss insensitive fiber (BIF) has proved an essential medium for constructing the current fiber to the home (FTTH) network. By contrast, the progress that has been made on holey fiber (HF) technologies provides us with novel possibilities including non-telecom applications. In this paper, we review recent progress on hole-assisted type BIF. A simple design consideration is overviewed. We then describe some of the properties of HAF including its mechanical reliability. Finally, we introduce some applications of HAF including to high power transmission. We show that HAF with a low bending loss has the potential for use in various future optical technologies as well as in the optical communication network.

  7. Foam topology. Bending versus stretching dominated architectures

    International Nuclear Information System (INIS)

    Deshpande, V.; Ashby, M.; Fleck, N.

    2000-01-01

    Cellular solids can deform by either the bending or stretching of the cell walls. While most cellular solids are bending-dominated, those that are stretching-dominated are much more weight-efficient for structural applications. In this study we have investigated the topological criteria that dictate the deformation mechanism of a cellular solid by analysing the rigidity (or otherwise) of pin-jointed frameworks comprising inextensional struts. We show that the minimum node connectivity for a special class of lattice structured materials to be stretching-dominated is 6 for 2D foams and 12 for 3D foams. Similarly, sandwich plates comprising of truss cores faced with planar trusses require a minimum node connectivity of 9 to undergo stretching-dominated deformation for all loading states. (author)

  8. Hydrodynamic processes in sharp meander bends and their morphological implications

    NARCIS (Netherlands)

    Blanckaert, K.

    2011-01-01

    The migration rate of sharp meander bends exhibits large variance and indicates that some sharply curved bends tend to stabilize. These observations remain unexplained. This paper examines three hydrodynamic processes in sharp bends with fixed banks and discusses their morphological implications:

  9. Effects of laser bending on the microstructural constituents

    CSIR Research Space (South Africa)

    Tshabalala, L

    2012-01-01

    Full Text Available This article will illustrate the correlation between microstructural and microhardness changes in high-strength-low-alloy steel that occur as a result of laser-bending. Laser bending is a process of bending metal shapes using the laser beam...

  10. Metal-bending brake facilitates lightweight, close-tolerance fabrication

    Science.gov (United States)

    Ercoline, A. L.; Wilton, K. B.

    1964-01-01

    A lightweight, metal bending brake ensures very accurate bends. Features of the brake that adapt it for making complex reverse bends to close tolerances are a pronounced relief or cutaway of the underside of the bodyplate combined with modification in the leaf design and its suspension.

  11. Characterization and study of photonic crystal fibres with bends

    International Nuclear Information System (INIS)

    Belhadj, W.; AbdelMalek, F.; Bouchriha, H.

    2006-01-01

    Analysis of a photonic crystal fibre (PRCF) with bends is presented. Using the versatile finite difference time domain method, the modal characteristics of the PCFs are found. Possibilities of employing PCFs with bends in sensing are discussed. It is found that a large evanescent field is present when the bend angle exceeds 45 o

  12. Smoothed particle hydrodynamics simulations of flow separation at bends

    NARCIS (Netherlands)

    Hou, Q.; Kruisbrink, A.C.H.; Pearce, F.R.; Tijsseling, A.S.; Yue, T.

    2014-01-01

    The separated flow in two-dimensional bends is numerically simulated for a right-angled bend with different ratios of the channel widths and for a symmetric bend with different turning angles. Unlike the potential flow solutions that have several restrictive assumptions, the Euler equations are

  13. Smoothed particle hydrodynamics simulations of flow separation at bends

    NARCIS (Netherlands)

    Hou, Q.; Kruisbrink, A.C.H.; Pearce, F.R.; Tijsseling, A.S.; Yue, T.

    2013-01-01

    The separated flow in two-dimensional bends is numerically simulated for a right-angled bend with different ratios of the channel widths and for a symmetric bend with different turning angles. Unlike the potential flow solutions that have several restrictive assumptions, the Euler equations are

  14. AA, assembly of wide bending magnet

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    The very particular lattice of the AA required 2 types of dipoles (bending magnets; BST, short and wide; BLG, long and narrow). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see the copper coils being hoisted onto the lower half of a BST. See also 7811105, 8006050. For a BLG, see 8001044.

  15. Closed-form plastic collapse loads of pipe bends under combined pressure and in-plane bending

    International Nuclear Information System (INIS)

    Oh, Chang Sik; Kim, Yun Jae

    2006-01-01

    Based on three-dimensional (3-D) FE limit analyses, this paper provides plastic limit, collapse and instability load solutions for pipe bends under combined pressure and in-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide plastic collapse loads (using the twice-elastic-slope method) and instability loads. For the bending mode, both closing bending and opening bending are considered, and a wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and collapse load solutions for pipe bends under combined pressure and bending are proposed

  16. First multi-bend achromat lattice consideration

    Energy Technology Data Exchange (ETDEWEB)

    Einfeld, Dieter, E-mail: dieter.einfeld@maxlab.lu.se [Lund University, PO Box 118, Lund SE-221 00 (Sweden); Plesko, Mark [COSYLAB, Teslova ulica 30, Ljubljana SI-1000 (Slovakia); Schaper, Joachim [HAWK University of Applied Sciences and Arts, Hohnsen 4, D-31134 Hildesheim (Germany)

    2014-08-27

    The first proposed lattice for a ‘diffraction-limited light source’ is reported. This approach has now more or less been used for the MAX IV project. By the beginning of 1990, three third-generation synchrotron light sources had been successfully commissioned in Grenoble, Berkeley and Trieste (ESRF, ALS and ELETTRA). Each of these new machines reached their target specifications without any significant problems. In parallel, already at that time discussions were underway regarding the next generation, the ‘diffraction-limited light source (DLSR)’, which featured sub-nm rad electron beam emittance, photon beam brilliance exceeding 10{sup 22} and the potential to emit coherent radiation. Also, at about that time, a first design for a 3 GeV DLSR was developed, based on a modified multiple-bend achromat (MBA) design leading to a lattice with normalized emittance of ∊{sub x} = 0.5 nm rad. The novel feature of the MBA lattice was the use of seven vertically focusing bend magnets with different bending angles throughout the achromat cell to keep the radiation integrals and resulting beam emittance low. The baseline design called for a 400 m ring circumference with 12 straight sections of 6 m length. The dynamic aperture behaviour of the DLSR lattice was estimated to produce > 5 h beam lifetime at 100 mA stored beam current.

  17. The multi-bend achromat storage rings

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Mikael [MAX IV Laboratory Ole Römers v. 1 22100 Lund Sweden (Sweden)

    2016-07-27

    Not very long ago, the 3{sup rd} generation storage ring technology was judged as mature. Most of the 3{sup rd} generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA) concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.

  18. BENDING BEHAVIOUR OF MAGNETIC COTTON YARNS

    Directory of Open Access Journals (Sweden)

    LUPU Iuliana G.

    2017-05-01

    Full Text Available Magnetic yarns are composite yarns, i.e. they combine elements of various natures and properties, with proven potential for electromagnetic interference (EMI shielding. In this paper, different mixtures of hard and soft magnetic powder were chosen to cover materials made of cotton yarn. The physical properties and bending behavior of the produced composite yarns were investigated in order to evaluate the yarns for further textile processing.The cotton yarn used as base material was covered with hard (barium hexaferrite BaFe12O19 and soft (Black Toner magnetic particles. An in-house developed laboratory equipment has been used to cover the twist cotton yarns with seven mixtures having different amounts of magnetic powder (30% – 50%. The bending behavior of the coated yarns was evaluated based on the average width of cracks which appeared on the yarn surface after repeated flexural tests. The obtained results revealed that usage of a polyurethane adhesive in the coating solution prevents crack formation on the surface of hard magnetic yarns after flexural tests. At the same time, the higher the mass percentage of hard magnetic powder in the mixture, the higher was the cracks’ width. The soft magnetic yarns are more flexible and a smaller crack width is observed on their surface. Both the coating solution composition and the powder diameter are expected to influence the bending behavior of coated yarns.

  19. The multi-bend achromat storage rings

    International Nuclear Information System (INIS)

    Eriksson, Mikael

    2016-01-01

    Not very long ago, the 3"r"d generation storage ring technology was judged as mature. Most of the 3"r"d generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA) concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.

  20. Forming and bending of metal foams

    International Nuclear Information System (INIS)

    Nebosky, Paul; Tyszka, Daniel; Niebur, Glen; Schmid, Steven

    2004-01-01

    This study examines the formability of a porous tantalum foam, known as trabecular metal (TM). Used as a bone ingrowth surface on orthopedic implants, TM is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. This research aims to develop bend and stretch forming as a cost-effective alternative to net machining and EDM for manufacturing thin parts made of TM. Experimentally, bending about a single axis using a wiping die was studied by observing cracking and measuring springback. It was found that die radius and clearance strongly affect the springback properties of TM, while punch speed, embossings, die radius and clearance all influence cracking. Depending on the various combinations of die radius and clearance, springback factor ranged from .70-.91. To examine the affect of the foam microstructure, bending also was examined numerically using a horizontal hexagonal mesh. As the hexagonal cells were elongated along the sheet length, elastic springback decreased. This can be explained by the earlier onset of plastic hinging occurring at the vertices of the cells. While the numerical results matched the experimental results for the case of zero clearance, differences at higher clearances arose due to an imprecise characterization of the post-yield properties of tantalum. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams

  1. Emittance growth of bunched beams in bends

    International Nuclear Information System (INIS)

    Carlsten, B.E.; Raubenheimer, T.O.

    1995-01-01

    Talman [Phys. Rev. Lett. 56, 1429 (1986)] has proposed a novel relativistic effect that occurs when a charged particle beam is bent in the magnetic field from an external dipole. The consequence of this effect is that the space-charge forces from the particles do not exhibit the usual inverse-square energy dependence and some part of them are, in fact, independent of energy. This led to speculation that this effect could introduce significant emittance growth for a bending electron beam. Subsequently, it was shown that this effect's influence on the beam's transverse motion is canceled for a dc beam by a potential depression within the beam (to first order in the beam radius divided by the bend radius). In this paper, we extend the analysis to include short bunch lengths (as compared to the beam pipe dimensions) and find that there is no longer the cancellation for forces both transverse to and in the direction of motion. We provide an estimate for the emittance growth as a function of bend angle, beam radius, and current, and for magnetic compression of an electron bunch

  2. Insomnia and Fatigue

    Science.gov (United States)

    ... week at work or a busy day of hiking or chasing a toddler. Fatigue related to cancer ... Coworkers About Your Diagnosis Work Accommodations and Disability Benefits Offsetting the “Hidden Costs” of Breast Cancer Getting ...

  3. Brain Tumors and Fatigue

    Science.gov (United States)

    ... Subscribe for e-updates Please leave this field empty Fatigue SHARE Home > Treatment and Care > Side Effects ... take-out food tends to be high in calories, fat and sodium and low in energy-boosting ...

  4. Hyperthermia and fatigue

    DEFF Research Database (Denmark)

    Nybo, Lars

    2008-01-01

    The present review addresses mechanisms of importance for hyperthermia-induced fatigue during short intense activities and prolonged exercise in the heat. Inferior performance during physical activities with intensities that elicit maximal oxygen uptake is to a large extent related to perturbation...... of the cardiovascular function, which eventually reduces arterial oxygen delivery to the exercising muscles. Accordingly, aerobic energy turnover is impaired and anaerobic metabolism provokes peripheral fatigue. In contrast, metabolic disturbances of muscle homeostasis are less important during prolonged exercise...... in the heat, because increased oxygen extraction compensates for the reduction in systemic blood flow. The decrease in endurance seems to involve changes in the function of the central nervous system (CNS) that lead to fatigue. The CNS fatigue appears to be influenced by neurotransmitter activity...

  5. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    This review describes when fatigue may develop during soccer games and the potential physiological mechanisms that cause fatigue in soccer. According to time?-?motion analyses and performance measures during match-play, fatigue or reduced performance seems to occur at three different stages......, acidity or the breakdown of creatine phosphate. Instead, it may be related to disturbances in muscle ion homeostasis and an impaired excitation of the sarcolemma. Soccer players' ability to perform maximally is inhibited in the initial phase of the second half, which may be due to lower muscle...... concentrations in a considerable number of individual muscle fibres. In a hot and humid environment, dehydration and a reduced cerebral function may also contribute to the deterioration in performance. In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different...

  6. A new hydrocarbon empirical potential in angle bending calculation for the molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ping, Tan Ai; Hoe, Yeak Su [Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor Darul Takzim (Malaysia)

    2014-07-10

    Typically, short range potential only depends on neighbouring atoms and its parameters function can be categorized into bond stretching, angle bending and bond rotation potential. In this paper, we present our work called Angle Bending (AB) potential, whereas AB potential is the extension of our previous work namely Bond Stretching (BS) potential. Basically, potential will tend to zero after truncated region, potential in specific region can be represented by different piecewise polynomial. We proposed the AB piecewise potential which is possible to solve a system involving three atoms. AB potential able to handle the potential of covalent bonds for three atoms as well as two atoms cases due to its degeneracy properties. Continuity for the piecewise polynomial has been enforced by coupling with penalty methods. There are still plenty of improvement spaces for this AB potential. The improvement for three atoms AB potential will be studied and further modified into torsional potential which are the ongoing current research.

  7. A comparative study on free vibration analysis of delaminated torsion stiff and bending stiff composite shells

    International Nuclear Information System (INIS)

    Dey, Sudip; Karmakar, Amit

    2013-01-01

    This paper presents a finite element method to compare the effects of delamination on free vibration of graphite-epoxy bending stiff and torsion stiff composite pretwisted shallow conical shells. The generalized dynamic equilibrium equation is derived from Lagrange's equation of motion neglecting the Coriolis effect for moderate rotational speeds. An eight noded isoparametric plate bending element is employed incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. The multipoint constraint; algorithm is utilized to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The standard eigen value problem is solved by applying the QR iteration algorithm. Mode shapes for typical configurations are also depicted. Numerical results obtained are the first known non-dimensional frequencies which could serve as reference solutions for the future investigators.

  8. Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

    DEFF Research Database (Denmark)

    Keller, Stephan Urs; Haefliger, D.; Boisen, Anja

    2010-01-01

    SU-8 cantilevers with a thickness of 2 mu m were fabricated using a dry release method and two steps of SU-8 photolithography. The processing of the thin SU-8 film defining the cantilevers was experimentally optimized to achieve low initial bending due to residual stress gradients. In parallel......, the rotational deformation at the clamping point allowed a qualitative assessment of the device release from the fluorocarbon-coated substrate. The change of these parameters during several months of storage at ambient temperature was investigated in detail. The introduction of a long hard bake in an oven after...... development of the thin SU-8 film resulted in reduced cantilever bending due to removal of residual stress gradients. Further, improved time-stability of the devices was achieved due to the enhanced cross-linking of the polymer. A post-exposure bake at a temperature T-PEB = 50 degrees C followed by a hard...

  9. Improved Formula for the Stress Intensity Factor of Semi-Elliptical Surface Cracks in Welded Joints under Bending Stress

    Science.gov (United States)

    Peng, Yang; Wu, Chao; Zheng, Yifu; Dong, Jun

    2017-01-01

    Welded joints are prone to fatigue cracking with the existence of welding defects and bending stress. Fracture mechanics is a useful approach in which the fatigue life of the welded joint can be predicted. The key challenge of such predictions using fracture mechanics is how to accurately calculate the stress intensity factor (SIF). An empirical formula for calculating the SIF of welded joints under bending stress was developed by Baik, Yamada and Ishikawa based on the hybrid method. However, when calculating the SIF of a semi-elliptical crack, this study found that the accuracy of the Baik-Yamada formula was poor when comparing the benchmark results, experimental data and numerical results. The reasons for the reduced accuracy of the Baik-Yamada formula were identified and discussed in this paper. Furthermore, a new correction factor was developed and added to the Baik-Yamada formula by using theoretical analysis and numerical regression. Finally, the predictions using the modified Baik-Yamada formula were compared with the benchmark results, experimental data and numerical results. It was found that the accuracy of the modified Baik-Yamada formula was greatly improved. Therefore, it is proposed that this modified formula is used to conveniently and accurately calculate the SIF of semi-elliptical cracks in welded joints under bending stress. PMID:28772527

  10. The effects of Nitinol phases on corrosion and fatigue behavior

    Science.gov (United States)

    Denton, Melissa

    The purpose of these studies was to provide a detailed understanding of Nitinol phases and their effects on corrosion and fatigue life. The two primary phases, austenite and martensite, were carefully evaluated with respect to material geometry, corrosion behavior, wear, and fatigue life. Material characterization was performed using several techniques that include metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray photoelectron spectrum (XPS), and Auger electron spectroscopy (AES). Uniaxial tensile tests were conducted to determine the mechanical properties such as elongation, ultimate tensile strength, modulus, transformation strain, and plateau stress. In addition, accelerated wear testing and four point bend fatigue testing were completed to study the fatigue life and durability of the material. The corrosion of Nitinol was found to be dependent on various surface conditions. Electrochemical corrosion behavior of each phase was investigated using cyclic potentiodyamic polarization testing. The corrosion response of electropolished Nitinol was found to be acceptable, even after durability testing. Stress-induced martensite had a lower breakdown potential due to a rougher surface morphology, while thermally induced martensite and austenite performed similarly well. The surface conditioning also had a significant effect on Nitinol mechanical properties. Electropolishing provided a smooth mirror finish that reduced localized texture and enhanced the ductility of the material. Quasi-static mechanical properties can be good indicators of fatigue life, but further fatigue testing revealed that phase transformations had an important role as well. The governing mechanisms for the fatigue life of Nitinol were determined to be both martesitic phase transformations and surface defects. A new ultimate dislocation strain model was proposed based on specific accelerated step-strain testing.

  11. The Recognition Of Fatigue

    DEFF Research Database (Denmark)

    Elsass, Peter; Jensen, Bodil; Mørup, Rikke

    2007-01-01

    Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87......Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87...

  12. The fatigue life and fatigue-crack-through-thickness behavior of a surface-cracked plate, 3

    International Nuclear Information System (INIS)

    Nam, Ki-Woo; Matsui, Kentaro; Ando, Kotoji; Ogura, Nobukazu

    1989-01-01

    The LBB (leak-before-break) design is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, LNG carriers and various other structures. In the LBB design, it is necessary to evaluate precisely the lifetime of steel plate. Furthermore, the change in crack shape that occurs during the propagation after through thickness is of paramount importance. For this reason, in a previous report, the authors proposed a simplified evaluation model for the stress intensity factor after cracking through thickness. Using this model, the crack propagation behavior, crack-opening displacement and crack shape change of surface-cracked smooth specimens and surface-cracked specimens with a stress concentration were evaluated quantitatively. The present study was also done to investigate the fatigue crack propagation behavior of surface cracks subjected to combined tensile and bending stress. Estimation of fatigue crack growth was done using the Newman-Raju formula before through thickness, and using formula (7) and (8) after through thickness. Crack length a r at just through thickness increases with increasing a bending stress. Calculated fatigue crack shape showed very good agreement with experimental one. It was also found that particular crack growth behavior and change in crack shape after cracking through thickness can be explained quantitatively using the K value based on Eqs. (7) and (8). (author)

  13. Fabrication of topology optimized photonic crystal waveguide Z-bend displaying large bandwidth with very low bend loss

    DEFF Research Database (Denmark)

    Harpøth, Anders; Frandsen, Lars Hagedorn; Kristensen, Martin

    2004-01-01

    We have designed, simulated and fabricated a photonic crystal waveguide Z-bend, which displays a total bend loss of ~1dB per bend in a wavelength range of more than 200nm. The fabricated component performs in excellent agreement with 3D finite-difference time-domain calculations....

  14. 76 FR 81992 - PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption

    Science.gov (United States)

    2011-12-29

    ... License Application for Bell Bend Nuclear Power Plant; Exemption 1.0 Background PPL Bell Bend, LLC... for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant (BBNPP... based upon the U.S. EPR reference COL (RCOL) application for UniStar's Calvert Cliffs Nuclear Power...

  15. Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

    International Nuclear Information System (INIS)

    Keller, Stephan; Boisen, Anja; Haefliger, Daniel

    2010-01-01

    SU-8 cantilevers with a thickness of 2 µm were fabricated using a dry release method and two steps of SU-8 photolithography. The processing of the thin SU-8 film defining the cantilevers was experimentally optimized to achieve low initial bending due to residual stress gradients. In parallel, the rotational deformation at the clamping point allowed a qualitative assessment of the device release from the fluorocarbon-coated substrate. The change of these parameters during several months of storage at ambient temperature was investigated in detail. The introduction of a long hard bake in an oven after development of the thin SU-8 film resulted in reduced cantilever bending due to removal of residual stress gradients. Further, improved time-stability of the devices was achieved due to the enhanced cross-linking of the polymer. A post-exposure bake at a temperature T PEB = 50 °C followed by a hard bake at T HB = 90 °C proved to be optimal to ensure low cantilever bending and low rotational deformation due to excellent device release and low change of these properties with time. With the optimized process, the reproducible fabrication of arrays with 2 µm thick cantilevers with a length of 500 µm and an initial bending of less than 20 µm was possible. The theoretical spring constant of these cantilevers is k = 4.8 ± 2.5 mN m −1 , which is comparable to the value for Si cantilevers with identical dimensions and a thickness of 500 nm.

  16. Fatigue Evaluation of Recycled Asphalt Mixture Based on Energy-Controlled Mode

    Directory of Open Access Journals (Sweden)

    Tao Ma

    2017-01-01

    Full Text Available The fatigue properties of asphalt mixtures are important inputs for mechanistic-empirical pavement design. To understand the fatigue properties of asphalt mixtures better and to predict the fatigue life of asphalt mixtures more precisely, the energy-controlled test mode was introduced. Based on the implementation theory, the laboratory practice for the energy-controlled mode was realized using a four-point-bending fatigue test with multiple-step loading. In this mode, the fatigue performance of typical AC-20 asphalt specimens with various reclaimed asphalt pavement (RAP contents was tested and evaluated. Results show that the variation regulation of the dissipated energy and accumulative energy is compatible with the loading control principle, which proves the feasibility of the method. In addition, the fatigue life of the asphalt mixture in the energy-controlled mode was between that for the stress-controlled and strain-controlled modes. The specimen with a higher RAP content has a longer fatigue life and better fatigue performance.

  17. Recent developments in bend-insensitive and ultra-bend-insensitive fibers

    Science.gov (United States)

    Boivin, David; de Montmorillon, Louis-Anne; Provost, Lionel; Montaigne, Nelly; Gooijer, Frans; Aldea, Eugen; Jensma, Jaap; Sillard, Pierre

    2010-02-01

    Designed to overcome the limitations in case of extreme bending conditions, Bend- and Ultra-Bend-Insensitive Fibers (BIFs and UBIFs) appear as ideal solutions for use in FTTH networks and in components, pigtails or patch-cords for ever demanding applications such as military or sensing. Recently, however, questions have been raised concerning the Multi-Path-Interference (MPI) levels in these fibers. Indeed, they are potentially subject to interferences between the fundamental mode and the higher-order mode that is also bend resistant. This MPI is generated because of discrete discontinuities such as staples, bends and splices/connections that occur on distance scales that become comparable to the laser coherent length. In this paper, we will demonstrate the high MPI tolerance of all-solid single-trench-assisted BIFs and UBIFs. We will present the first comprehensive study combining theoretical and experimental points of view to quantify the impact of fusion splices on coherent MPI. To be complete, results for mechanical splices will also be reported. Finally, we will show how the single-trench- assisted concept combined with the versatile PCVD process allows to tightly control the distributions of fibers characteristics. Such controls are needed to massively produce BIFs and to meet the more stringent specifications of the UBIFs.

  18. Influence of flock coating on bending rigidity of woven fabrics

    Science.gov (United States)

    Ozdemir, O.; Kesimci, M. O.

    2017-10-01

    This work presents the preliminary results of our efforts that focused on the effect of the flock coating on the bending rigidity of woven fabrics. For this objective, a laboratory scale flocking unit is designed and flocked samples of controlled flock density are produced. Bending rigidity of the samples with different flock densities are measured on both flocked and unflocked sides. It is shown that the bending rigidity depends on both flock density and whether the side to be measured is flocked or not. Adhesive layer thickness on the bending rigidity is shown to be dramatic. And at higher basis weights, flock density gets less effective on bending rigidity.

  19. Permanent bending and alignment of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)

    2011-07-01

    Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.

  20. Tunable waveguide bends with graphene-based anisotropic metamaterials

    KAUST Repository

    Chen, Zhao-xian; Chen, Ze-guo; Ming, Yang; Wu, Ying; Lu, Yan-qing

    2016-01-01

    We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.

  1. Tunable waveguide bends with graphene-based anisotropic metamaterials

    KAUST Repository

    Chen, Zhao-xian

    2016-01-15

    We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.

  2. Performance of 3Y-TZP bioceramics under cyclic fatigue loading

    Directory of Open Access Journals (Sweden)

    Renato Chaves Souza

    2008-03-01

    Full Text Available In this work, the static mechanical properties and cyclic fatigue life of 3 mol. (% Y2O3-stabilized tetragonal zirconia polycrystalline (3Y-TZP ceramics were investigated. Pre-sintered samples were sintered in air at 1600 °C for 120 minutes, and characterized by X ray diffraction and scanning electronic microscopy. Hardness and fracture toughness were determined by Vicker's indentation method, and Modulus of Rupture was determined by four-point bending testing. Fully dense sintered samples, near to 100% of theoretical density, presented hardness, fracture toughness and bending strength of 13.5 GPa, 8.2 MPa.m½ and 880 MPa, respectively. The cyclic fatigue tests were also realized using four-point bending testing, within a frequency of 25 Hz and stress ratio R of 0.1. The increasing of load stress lead to decreasing of the number of cycles and the run-out specimens number. The tetragonal-monoclinic (t-m ZrO2-transformation observed by X ray diffraction contributes to the increasing of the fatigue life. The 3Y-TZP samples clearly presents a range of loading conditions where cyclic fatigue can be detected.

  3. Coupling between shear and bending in the analysis of beam problems: Planar case

    Science.gov (United States)

    Shabana, Ahmed A.; Patel, Mohil

    2018-04-01

    The interpretation of invariants, such as curvatures which uniquely define the bending and twist of space curves and surfaces, is fundamental in the formulation of the beam and plate elastic forces. Accurate representations of curve and surface invariants, which enter into the definition of the strain energy equations, is particularly important in the case of large displacement analysis. This paper discusses this important subject in view of the fact that shear and bending are independent modes of deformation and do not have kinematic coupling; this is despite the fact that kinetic coupling may exist. The paper shows, using simple examples, that shear without bending and bending without shear at an arbitrary point and along a certain direction are scenarios that higher-order finite elements (FE) can represent with a degree of accuracy that depends on the order of interpolation and/or mesh size. The FE representation of these two kinematically uncoupled modes of deformation is evaluated in order to examine the effect of the order of the polynomial interpolation on the accuracy of representing these two independent modes. It is also shown in this paper that not all the curvature vectors contribute to bending deformation. In view of the conclusions drawn from the analysis of simple beam problems, the material curvature used in several previous investigations is evaluated both analytically and numerically. The problems associated with the material curvature matrix, obtained using the rotation of the beam cross-section, and the fundamental differences between this material curvature matrix and the Serret-Frenet curvature matrix are discussed.

  4. Experiences of Fatigue at Sea

    DEFF Research Database (Denmark)

    Zhao, Zhiwei; Jepsen, Jørgen Riis; Chen, Zhonglong

    2016-01-01

    Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T-test t......-test to compare strata of seafarers to analyse work and sleep patterns in global seafaring. Qualitative analysis are also employed to explore the impacts of fatigue on seafarer’s occupational health and safety.......Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T...

  5. Standard test methods for bend testing of material for ductility

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen. 1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregu...

  6. The elastic plastic behaviour of a 1/2% Cr Mo V steam turbine steel during high strain thermal fatigue

    International Nuclear Information System (INIS)

    Murphy, M.C.; Batte, A.D.; Stringer, M.B.

    1979-01-01

    High strain fatigue problem in steam turbine. Cyclic stress strain hysteresis loops and stress relaxation behaviour in 16 h dwell period tests. Variation of stress and strain during tests under nominally strain controlled conditions. Definition of test conditions and of criteria for crack initiation and failure. Comparison of reverse bend and push pull failure data. (orig.) 891 RW/orig. 892 RKD [de

  7. Relationship between microhardness and fatigue strength after glass micro-bead peening and ion implantation

    International Nuclear Information System (INIS)

    Lunarski, J.; Zielecki, M.

    1989-01-01

    Results of tests on fatigue strength and condition of the surface layer, produced by ion implantation or/and glass micro-bead peening for E1961Sz and 12H2N4MAZ steels and WT3-1 titanium alloy are reported. In the tests the following characteristics are measured: Knoop hardness, residual stresses (by etching method), surface roughness, and oscillatory bending fatigue limit at the resonance frequency of the specimen. The test results indicate that for the examined steels there is a strong correlation between surface microhardness and fatigue limit, in spite of various surface treatments. This fact enables to predict changes in the fatigue limit, basing on the results of surface microhardness measurements, which are inexpensive and easy to perform. (author)

  8. Evaluation of Work Fatigue in Loading Workers Using Muscle Fatigue Assessment Method (MFA: A Case Study in a Brick Factory

    Directory of Open Access Journals (Sweden)

    Haji Omid Kalte

    2016-09-01

    Full Text Available Introduction and purpose: Work fatigue is one of the main causes of workrelated musculoskeletal disorders and reduced productivity in industry. Therefore, it is vital to evaluate work fatigue, especially muscle fatigue, to determine the permissible workload. This study aimed to evaluate muscle fatigue of brick field workers. Methods: This cross-sectional study was conducted on transportation sector workers in Pey Dezh Brick Production Company, Golestan, Iran in 2015. In this research, the qualitative of Muscle Fatigue Assessment (MFA method was used to assess the level of fatigue. Duration of each task and frequency of efforts were determined using the level of effort to obtain a numerical result for comparison with the standard level. Results: The evaluated task was to remove paired bricks from the conveyor and transfer them to trailer truck by workers. The final results revealed that lower back tolerated the most amount of pressure (score=323, followed by the shoulders and wrist of the right hand (scores=313, which were assigned to the fatigue level. Therefore, the highest total fatigue of workload was imposed on these body parts. Conclusion: According to the results of this study, the upper limbs of workers incurred the highest burden in lifting bricks, and there was a in risk of WMSDS due to high workload. Therefore, it is recommended that working systems be improved through rotating work and reducing the number of transferred bricks to avoid risks caused by accumulation of fatigue.

  9. Thermal fatigue. Materials modelling

    International Nuclear Information System (INIS)

    Siegele, D.; Fingerhuth, J.; Mrovec, M.

    2012-01-01

    In the framework of the ongoing joint research project 'Thermal Fatigue - Basics of the system-, outflow- and material-characteristics of piping under thermal fatigue' funded by the German Federal Ministry of Education and Research (BMBF) fundamental numerical and experimental investigations on the material behavior under transient thermal-mechanical stress conditions (high cycle fatigue V HCF and low cycle fatigue - LCF) are carried out. The primary objective of the research is the further development of simulation methods applied in safety evaluations of nuclear power plant components. In this context the modeling of crack initiation and growth inside the material structure induced by varying thermal loads are of particular interest. Therefore, three scientific working groups organized in three sub-projects of the joint research project are dealing with numerical modeling and simulation at different levels ranging from atomistic to micromechanics and continuum mechanics, and in addition corresponding experimental data for the validation of the numerical results and identification of the parameters of the associated material models are provided. The present contribution is focused on the development and experimental validation of material models and methods to characterize the damage evolution and the life cycle assessment as a result of thermal cyclic loading. The individual purposes of the subprojects are as following: - Material characterization, Influence of temperature and surface roughness on fatigue endurances, biaxial thermo-mechanical behavior, experiments on structural behavior of cruciform specimens and scatter band analysis (IfW Darmstadt) - Life cycle assessment with micromechanical material models (MPA Stuttgart) - Life cycle assessment with atomistic and damage-mechanical material models associated with material tests under thermal fatigue (Fraunhofer IWM, Freiburg) - Simulation of fatigue crack growth, opening and closure of a short crack under

  10. Fatigue properties of dissimilar metal laser welded lap joints

    Science.gov (United States)

    Dinsley, Christopher Paul

    This work involves laser welding austenitic and duplex stainless steel to zinc-coated mild steel, more specifically 1.2mm V1437, which is a Volvo Truck Coiporation rephosphorised mild steel. The work investigates both tensile and lap shear properties of similar and dissimilar metal laser welded butt and lap joints, with the majority of the investigation concentrating on the fatigue properties of dissimilar metal laser welded lap joints. The problems encountered when laser welding zinc-coated steel are addressed and overcome with regard to dissimilar metal lap joints with stainless steel. The result being the production of a set of guidelines for laser welding stainless steel to zinc-coated mild steel. The stages of laser welded lap joint fatigue life are defined and the factors affecting dissimilar metal laser welded lap joint fatigue properties are analysed and determined; the findings suggesting that dissimilar metal lap joint fatigue properties are primarily controlled by the local stress at the internal lap face and the early crack growth rate of the material at the internal lap face. The lap joint rotation, in turn, is controlled by sheet thickness, weld width and interfacial gap. Laser welded lap joint fatigue properties are found to be independent of base material properties, allowing dissimilar metal lap joints to be produced without fatigue failure occurring preferentially in the weaker parent material, irrespective of large base material property differences. The effects of Marangoni flow on the compositions of the laser weld beads are experimentally characterised. The results providing definite proof of the stirring mechanism within the weld pool through the use of speeds maps for chromium and nickel. Keywords: Laser welding, dissimilar metal, Zinc-coated mild steel, Austenitic stainless steel, Duplex stainless steel, Fatigue, Lap joint rotation, Automotive.

  11. Rupture prediction for induction bends under opening mode bending with emphasis on strain localization

    International Nuclear Information System (INIS)

    Mitsuya, Masaki; Sakanoue, Takashi

    2015-01-01

    This study focuses on the opening mode of induction bends; this mode represents the deformation outside a bend. Bending experiments on induction bends are shown and the manner of failure of these bends was investigated. Ruptures occur at the intrados of the bends, which undergo tensile stress, and accompany the local reduction of wall thickness, i.e., necking that indicates strain localization. By implementing finite element analysis (FEA), it was shown that the rupture is dominated not by the fracture criterion of material but by the initiation of strain localization that is a deformation characteristic of the material. These ruptures are due to the rapid increase of local strain after the initiation of strain localization and suddenly reach the fracture criterion. For the evaluation of the deformability of the bends, a method based on FEA that can predict the displacement at the rupture is proposed. We show that the yield surface shape and the true stress–strain relationship after uniform elongation have to be defined on the basis of the actual properties of the bend material. The von Mises yield criterion, which is commonly used in cases of elastic–plastic FEA, could not predict the rupture and overestimated the deformability. In contrast, a yield surface obtained by performing tensile tests on a biaxial specimen could predict the rupture. The prediction of the rupture was accomplished by an inverse calibration method that determined the true stress-strain relationship after uniform elongation. As an alternative to the inverse calibration, a simple extrapolation method of the true stress-strain relationship after uniform elongation which can predict the rupture is proposed. - Highlights: • A method based on FEA that can predict the displacement at the rupture is proposed. • The yield surface shape and the true stress–strain have to be defined precisely. • The von Mises yield criterion overestimated the deformability. • The ruptures are due to the

  12. Limit loads for pipe bends under combined pressure and in-plane bending based on finite element limit analysis

    International Nuclear Information System (INIS)

    Oh, Chang Sik; Kim, Yun Jae

    2006-01-01

    In the present paper, approximate plastic limit load solutions for pipe bends under combined internal pressure and bending are obtained from detailed three-dimensional (3-D) FE limit analyses based on elastic-perfectly plastic materials with the small geometry change option. The present FE results show that existing limit load solutions for pipe bends are lower bounds but can be very different from the present FE results in some cases, particularly for bending. Accordingly closed-form approximations are proposed for pipe bends under combined pressure and in-plane bending based on the present FE results. The proposed limit load solutions would be a basis of defective pipe bends and be useful to estimate non-linear fracture mechanics parameters based on the reference stress approach

  13. The mechanics of fault-bend folding and tear-fault systems in the Niger Delta

    Science.gov (United States)

    Benesh, Nathan Philip

    This dissertation investigates the mechanics of fault-bend folding using the discrete element method (DEM) and explores the nature of tear-fault systems in the deep-water Niger Delta fold-and-thrust belt. In Chapter 1, we employ the DEM to investigate the development of growth structures in anticlinal fault-bend folds. This work was inspired by observations that growth strata in active folds show a pronounced upward decrease in bed dip, in contrast to traditional kinematic fault-bend fold models. Our analysis shows that the modeled folds grow largely by parallel folding as specified by the kinematic theory; however, the process of folding over a broad axial surface zone yields a component of fold growth by limb rotation that is consistent with the patterns observed in natural folds. This result has important implications for how growth structures can he used to constrain slip and paleo-earthquake ages on active blind-thrust faults. In Chapter 2, we expand our DEM study to investigate the development of a wider range of fault-bend folds. We examine the influence of mechanical stratigraphy and quantitatively compare our models with the relationships between fold and fault shape prescribed by the kinematic theory. While the synclinal fault-bend models closely match the kinematic theory, the modeled anticlinal fault-bend folds show robust behavior that is distinct from the kinematic theory. Specifically, we observe that modeled structures maintain a linear relationship between fold shape (gamma) and fault-horizon cutoff angle (theta), rather than expressing the non-linear relationship with two distinct modes of anticlinal folding that is prescribed by the kinematic theory. These observations lead to a revised quantitative relationship for fault-bend folds that can serve as a useful interpretation tool. Finally, in Chapter 3, we examine the 3D relationships of tear- and thrust-fault systems in the western, deep-water Niger Delta. Using 3D seismic reflection data and new

  14. Bending of light in quantum gravity.

    Science.gov (United States)

    Bjerrum-Bohr, N E J; Donoghue, John F; Holstein, Barry R; Planté, Ludovic; Vanhove, Pierre

    2015-02-13

    We consider the scattering of lightlike matter in the presence of a heavy scalar object (such as the Sun or a Schwarzschild black hole). By treating general relativity as an effective field theory we directly compute the nonanalytic components of the one-loop gravitational amplitude for the scattering of massless scalars or photons from an external massive scalar field. These results allow a semiclassical computation of the bending angle for light rays grazing the Sun, including long-range ℏ contributions. We discuss implications of this computation, in particular, the violation of some classical formulations of the equivalence principle.

  15. Structural analysis of suerconducting bending magnets

    International Nuclear Information System (INIS)

    Meuser, R.B.

    1980-05-01

    Mechanical stresses, displacements, and the effects of displacements upon aberrations of the magnetic field in the aperture have been calculated for a class of superconducting bending-magnet configurations. The analytical model employed for the coil is one in which elements are free to slide without restraint upon each other, and upon the surrounding structure. Coil configurations considered range from an idealized one in which the current density varies as cosine theta to more realistic ones consisting of regions of uniform current density. With few exceptions, the results for the more realistic coils closely match those of the cos theta coil

  16. Extension versus Bending for Continuum Robots

    Directory of Open Access Journals (Sweden)

    George Grimes

    2008-11-01

    Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.

  17. Minimum emittance of three-bend achromats

    International Nuclear Information System (INIS)

    Li Xiaoyu; Xu Gang

    2012-01-01

    The calculation of the minimum emittance of three-bend achromats (TBAs) made by Mathematical software can ignore the actual magnets lattice in the matching condition of dispersion function in phase space. The minimum scaling factors of two kinds of widely used TBA lattices are obtained. Then the relationship between the lengths and the radii of the three dipoles in TBA is obtained and so is the minimum scaling factor, when the TBA lattice achieves its minimum emittance. The procedure of analysis and the results can be widely used in achromats lattices, because the calculation is not restricted by the actual lattice. (authors)

  18. Clinical bending of nickel titanium wires

    Directory of Open Access Journals (Sweden)

    Stephen Chain

    2015-01-01

    Full Text Available Since the evolution and the involvement of Nickel Titanium wires in the field of Orthodontics. The treatment plan has evolved with the use of low force Nickel Titanium wires. Because of their high springback, low stiffness, they are the key initial wires in leveling and alignment but have poor formability. Since poor formability limits its ability to create variable arch forms thus; limits the form of treatment. We have devised a method to bend the Nickel Titanium wires to help in our inventory but also customized the wire according to the treatment.

  19. Electrothermally-Actuated Micromirrors with Bimorph Actuators—Bending-Type and Torsion-Type

    Directory of Open Access Journals (Sweden)

    Cheng-Hua Tsai

    2015-06-01

    Full Text Available Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA. A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively.

  20. Laser Doppler measurements of laminar and turbulent flow in a pipe bend

    Science.gov (United States)

    Enayet, M. M.; Gibson, M. M.; Taylor, A. M. K. P.; Yianneskis, M.

    1982-01-01

    The streamwise components of velocity in the flow through a ninety degree bend of circular cross section for which the ratio of radius of curvature to diameter is 2.8 were measured. The development of strong pressure driven secondary flow in the form of a pair of counter rotating vortices in the steamwise direction is shown. Refractive index matching at the fluid wall interface was not employed; the displacement of the measurement volume due to refraction is allowed for in simple geometrical calculations.

  1. The effect of surface corrosion damage on the fatigue life of 6061-T6 aluminum alloy extrusions

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Matthew; Eason, Paul D.; Özdeş, Hüseyin; Tiryakioğlu, Murat, E-mail: m.tiryakioglu@unf.edu

    2017-04-06

    An investigation was performed where 6061-T6 extrusions were exposed to a 3.5% NaCl solution at pH 2 for 2 days and 24 days to create distinct surface flaws. The effect of these flaws on the rotating beam fatigue life was then investigated and analyzed by using Wöhler curves, Weibull statistics and scanning electron microscopy (SEM). It was determined that corrosion damage reduced the fatigue life significantly and specimens corroded for both 2-days and 24-days exhibited similar fatigue lives. Statistical analyses showed that fatigue life of all three datasets followed the 3-parameter Weibull distribution and the difference between the fatigue lives of two corroded datasets was statistically insignificant. Analysis of fracture surfaces showed that sizes of pits that led to fatigue crack initiation were very different in the two corroded datasets. Implications of the similarity in fatigue lives despite disparity in surface condition are discussed in detail in the paper.

  2. Multi-parameter crack tip stress state description for evaluation of nonlinear zone width in silicate composite specimens in component splitting/bending test geometry

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Frantík, P.; Sopek, J.; Malíková, L.; Seitl, Stanislav

    2015-01-01

    Roč. 38, č. 2 (2015), s. 200-214 ISSN 8756-758X R&D Projects: GA ČR(CZ) GAP104/11/0833 Institutional support: RVO:68081723 Keywords : near-crack tip fields * Williams series * higher-order terms * stress field * failure criterion * nonlinear zone * quasi-brittle fracture * splitting-bending geometry Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.838, year: 2015

  3. Influence of Deposition Conditions on Fatigue Properties of Martensitic Stainless Steel with Tin Film Coated by Arc Ion Plating Method

    Science.gov (United States)

    Fukui, Satoshi; Yonekura, Daisuke; Murakami, Ri-Ichi

    The surface properties like roughness etc. strongly influence the fatigue strength of high-tensile steel. To investigate the effect of surface condition and TiN coating on the fatigue strength of high-strength steel, four-point bending fatigue tests were carried out for martensitic stainless steel with TiN film coated using arc ion plating (AIP) method. This study, using samples that had been polished under several size of grind particle, examines the influence of pre-coating treatment on fatigue properties. A 2-µm-thick TiN film was deposited onto the substrate under three kinds of polishing condition. The difference of the hardness originated in the residual stress or thin deformation layer where the difference of the size of grinding particle of the surface polishing. And it leads the transformation of the interface of the substrate and the TiN film and improves fatigue limit.

  4. Normalizing effect on fatigue crack propagation at the heat-affected zone of AISI 4140 steel shielded metal arc weldings

    Directory of Open Access Journals (Sweden)

    B. Vargas-Arista

    2013-01-01

    Full Text Available The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughness and critical crack length, and a transgranular brittle final fracture with an area fraction of dimple zones connecting cleavage facets. A fractographic analysis proved that as the normalizing time increased the crack length decreased. The increase in the river patterns on the fatigue crack propagation in zone II was also evidenced and final brittle fracture because of transgranular quasicleavage was observed. Larger grains induced a deterioration of the fatigue resistance of the HAZ.

  5. Validation of Analytical Damping Ratio by Fatigue Stress Limit

    Science.gov (United States)

    Foong, Faruq Muhammad; Chung Ket, Thein; Beng Lee, Ooi; Aziz, Abdul Rashid Abdul

    2018-03-01

    The optimisation process of a vibration energy harvester is usually restricted to experimental approaches due to the lack of an analytical equation to describe the damping of a system. This study derives an analytical equation, which describes the first mode damping ratio of a clamp-free cantilever beam under harmonic base excitation by combining the transverse equation of motion of the beam with the damping-stress equation. This equation, as opposed to other common damping determination methods, is independent of experimental inputs or finite element simulations and can be solved using a simple iterative convergence method. The derived equation was determined to be correct for cases when the maximum bending stress in the beam is below the fatigue limit stress of the beam. However, an increasing trend in the error between the experiment and the analytical results were observed at high stress levels. Hence, the fatigue limit stress was used as a parameter to define the validity of the analytical equation.

  6. Thermal stratification and fatigue stress analysis for pressurizer surge line

    International Nuclear Information System (INIS)

    Yu Xiaofei; Zhang Yixiong

    2011-01-01

    Thermal stratification of pressurizer surge line induced by the inside fluid results in the global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to avoid a costly three-dimensional computation, a combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line of QINSHAN Phase II Extension Nuclear Power Project in this paper, using the computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor are obtained. The results indicate that the stress and fatigue intensity considering thermal stratification satisfies RCC-M criterion. (authors)

  7. Thermal fatigue of beryllium

    International Nuclear Information System (INIS)

    Deksnis, E.; Ciric, D.; Falter, H.

    1995-01-01

    Thermal fatigue life of S65c beryllium castellated to a geometry 6 x 6 x (8-10)mm deep has been tested for steady heat fluxes of 3 MW/m 2 to 5 MW/m 2 and under pulsed heat fluxes (10-20 MW/m 2 ) for which the time averaged heat flux is 5 MW/m 2 . These tests were carried out in the JET neutral beam test facility A test sequence with peak surface temperatures ≤ 600 degrees C produced no visible fatigue cracks. In the second series of tests, with T max ≤ 750 degrees C evidence for fatigue appeared after a minimum of 1350 stress cycles. These fatigue data are discussed in view of the observed lack of thermal fatigue in JET plasma operations with beryllium PFC. JET experience with S65b and S65c is reviewed; recent operations with Φ = 25 MW/m 2 and sustained melting/resolidification are also presented. The need for a failure criterion for finite element analyses of Be PFC lifetimes is discussed

  8. Rotator cuff exercises

    Science.gov (United States)

    ... 25560729 . Read More Frozen shoulder Rotator cuff problems Rotator cuff repair Shoulder arthroscopy Shoulder CT scan Shoulder MRI scan Shoulder pain Patient Instructions Rotator cuff - self-care Shoulder surgery - discharge Using your ...

  9. Fatigue reduction during aggregated and distributed sequential stimulation.

    Science.gov (United States)

    Bergquist, Austin J; Babbar, Vishvek; Ali, Saima; Popovic, Milos R; Masani, Kei

    2017-08-01

    Transcutaneous neuromuscular electrical stimulation (NMES) can generate muscle contractions for rehabilitation and exercise. However, NMES-evoked contractions are limited by fatigue when they are delivered "conventionally" (CONV) using a single active electrode. Researchers have developed "sequential" (SEQ) stimulation, involving rotation of pulses between multiple "aggregated" (AGGR-SEQ) or "distributed" (DISTR-SEQ) active electrodes, to reduce fatigue (torque-decline) by reducing motor unit discharge rates. The primary objective was to compare fatigue-related outcomes, "potentiation," "variability," and "efficiency" between CONV, AGGR-SEQ, and DISTR-SEQ stimulation of knee extensors in healthy participants. Torque and current were recorded during testing with fatiguing trains using each NMES type under isometric and isokinetic (180°/s) conditions. Compared with CONV stimulation, SEQ techniques reduced fatigue-related outcomes, increased potentiation, did not affect variability, and reduced efficiency. SEQ techniques hold promise for reducing fatigue during NMES-based rehabilitation and exercise; however, optimization is required to improve efficiency. Muscle Nerve 56: 271-281, 2017. © 2016 Wiley Periodicals, Inc.

  10. BOHICA; bend over, here it comes again… construction and test of a change fatigue instrument

    NARCIS (Netherlands)

    Elving, Wim; Hansma, Lindy; de Boer, Merel

    2011-01-01

    Within change literature, pace and frequency of organizational change are reoccurring topics. The pace is experienced as high and the frequency of change within organizations appears to be growing exponentially. This lead to study to more extent ‘change fatigue’ that already received attention in

  11. Fatigue analysis of flexible pipes using alternative element types and bend stiffener data

    OpenAIRE

    Chen, Minghao

    2011-01-01

    The flexible pipe is a vital part of a floating production system. The lifetime of a flexible riser system is crucial for the Health Safety and Environment (HSE) management. As a result of this, it is very necessary to carry out research on the lifetime of flexible pipe. In this thesis we formalized analysis on flexible pipes, utilizing the finite element analysis software BFLEX 2010, developed by MARINTEK. Chapter 1 describes basic knowledge about flexible pipe and relevant facilities. C...

  12. Far-infrared high resolution synchrotron FTIR spectroscopy of the ν11 bending vibrational fundamental transition of dimethylsulfoxyde

    Science.gov (United States)

    Cuisset, Arnaud; Nanobashvili, Lia; Smirnova, Irina; Bocquet, Robin; Hindle, Francis; Mouret, Gaël; Pirali, Olivier; Roy, Pascale; Sadovskií, Dmitrií A.

    2010-05-01

    We report the first successful high resolution gas phase study of the 'parallel' band of DMSO at 380 cm -1 associated with the ν11 bending vibrational mode. The spectrum was recorded with a resolution of 0.0015 cm -1 using the AILES beamline of the SOLEIL synchrotron source, the IFS 125 FTIR spectrometer and a multipass cell providing an optical path of 150 m. The rotational constants and centrifugal corrections obtained from the analysis of the resolved rotational transitions reproduce the spectrum to the experimental accuracy.

  13. Efficient Fatigue Analysis of Helix Elements in Umbilicals and Flexible Risers: Theory and Applications

    Directory of Open Access Journals (Sweden)

    Geir Skeie

    2012-01-01

    Full Text Available Fatigue analysis of structural components such as helix tensile armors and steel tubes is a critical design issue for dynamic umbilicals and flexible pipes. The basis for assessment of fatigue damage of such elements is the long-term stress cycle distribution at critical locations on the helix elements caused by long-term environmental loading on the system. The long-term stress cycle distribution will hence require global dynamic time domain analysis followed by a detailed cross-sectional analysis in a large number of irregular sea states. An overall computational consistent and efficient fatigue analysis scheme is outlined with due regard of the cross-sectional analysis technique required for fatigue stress calculation with particular attention to the helix elements. The global cross-section is exposed to pure bending, tensile, torsion, and pressure loading. The state of the different cross-section elements is based on the global response. Special emphasis is placed on assessment of friction stresses caused by the stick-slip behavior of helix elements in bending that are of special importance for fatigue life assessments. The described cross-sectional analysis techniques are based on an extensive literature survey and are hence considered to represent industry consensus. The performance of the described calculation scheme is illustrated by case studies.

  14. Modafinil May Alleviate Poststroke Fatigue

    DEFF Research Database (Denmark)

    Poulsen, Mai Bang; Damgaard, Bodil; Zerahn, Bo

    2015-01-01

    was randomized, double-blinded, and placebo-controlled. Patients were treated with 400-mg modafinil or placebo for 90 days. Assessments were done at inclusion, 30, 90, and 180 days. The primary end point was fatigue at 90 days measured by the Multidimensional Fatigue Inventory-20 general fatigue domain......BACKGROUND AND PURPOSE: Poststroke fatigue is common and reduces quality of life. Current evidence for intervention is limited, and this is the first placebo-controlled trial to investigate treatment of poststroke fatigue with the wakefulness promoting drug modafinil. METHODS: The trial....... Secondary end points included the Fatigue Severity Scale, the Montreal Cognitive Assessment, the modified Rankin Scale and the Stroke-specific quality of Life questionnaire. Adult patients with a recent stroke achieving a score of ≥12 on the Multidimensional Fatigue Inventory-20 general fatigue domain were...

  15. Fatigue design 1998

    Energy Technology Data Exchange (ETDEWEB)

    Marquis, G.; Solin, J. [eds.] [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    These preprints contain the presentations to be delivered at the Fatigue Design 1998 symposium held on May 26-29, 1998 in Espoo. Fatigue Design 1998 is the tenth in a series of VTT symposia addressing the challenge of fatigue of materials, components and structures. Previous international events were in 1992 and 1995. The key theme of the current meeting is `RELIABILITY`. The two volumes (VTT symposium 181-182) represent 56 contributions by authors representing 26 countries. Emphasis has been given to application oriented research topics that report new technologies, new uses of existing methods and case studies. The objective of the symposium is to bring together researchers and engineers to share experiences and new innovations in designing reliable components to resist alternating loads. (orig.)

  16. Near threshold fatigue testing

    Science.gov (United States)

    Freeman, D. C.; Strum, M. J.

    1993-01-01

    Measurement of the near-threshold fatigue crack growth rate (FCGR) behavior provides a basis for the design and evaluation of components subjected to high cycle fatigue. Typically, the near-threshold fatigue regime describes crack growth rates below approximately 10(exp -5) mm/cycle (4 x 10(exp -7) inch/cycle). One such evaluation was recently performed for the binary alloy U-6Nb. The procedures developed for this evaluation are described in detail to provide a general test method for near-threshold FCGR testing. In particular, techniques for high-resolution measurements of crack length performed in-situ through a direct current, potential drop (DCPD) apparatus, and a method which eliminates crack closure effects through the use of loading cycles with constant maximum stress intensity are described.

  17. Peripheral Protein Unfolding Drives Membrane Bending.

    Science.gov (United States)

    Siaw, Hew Ming Helen; Raghunath, Gokul; Dyer, R Brian

    2018-06-20

    Dynamic modulation of lipid membrane curvature can be achieved by a number of peripheral protein binding mechanisms such as hy-drophobic insertion of amphipathic helices and membrane scaffolding. Recently, an alternative mechanism was proposed in which crowding of peripherally bound proteins induces membrane curvature through steric pressure generated by lateral collisions. This effect was enhanced using intrinsically disordered proteins that possess high hydrodynamic radii, prompting us to explore whether membrane bending can be triggered by the folding-unfolding transition of surface-bound proteins. We utilized histidine-tagged human serum albumin bound to Ni-NTA-DGS containing liposomes as our model system to test this hypothesis. We found that reduction of the disulfide bonds in the protein resulted in unfolding of HSA, which subsequently led to membrane tubule formation. The frequency of tubule formation was found to be significantly higher when the proteins were unfolded while being localized to a phase-separated domain as opposed to randomly distributed in fluid phase liposomes, indicating that the steric pressure generated from protein unfolding is directly responsible for membrane deformation. Our results are critical for the design of peripheral membrane protein-immobilization strategies and open new avenues for exploring mechanisms of membrane bending driven by conformational changes of peripheral membrane proteins.

  18. Fatigue Resistant Bioinspired Composite from Synergistic Two-Dimensional Nanocomponents.

    Science.gov (United States)

    Wan, Sijie; Zhang, Qi; Zhou, Xiaohang; Li, Dechang; Ji, Baohua; Jiang, Lei; Cheng, Qunfeng

    2017-07-25

    Portable and wearable electronics require much more flexible graphene-based electrode with high fatigue life, which could repeatedly bend, fold, or stretch without sacrificing its mechanical properties and electrical conductivity. Herein, a kind of ultrahigh fatigue resistant graphene-based nanocomposite via tungsten disulfide (WS 2 ) nanosheets is synthesized by introducing a synergistic effect with covalently cross-linking inspired by the orderly layered structure and abundant interfacial interactions of nacre. The fatigue life of resultant graphene-based nanocomposites is more than one million times at the stress level of 270 MPa, and the electrical conductivity can be kept as high as 197.1 S/cm after 1.0 × 10 5 tensile testing cycles. These outstanding properties are attributed to the synergistic effect from lubrication of WS 2 nanosheets for deflecting crack propagation, and covalent bonding between adjacent GO nanosheets for bridging crack, which is verified by the molecular dynamics (MD) simulations. The WS 2 induced synergistic effect with covalent bonding offers a guidance for constructing graphene-based nanocomposites with high fatigue life, which have great potential for applications in flexible and wearable electronic devices, etc.

  19. Quantitative Acoustic Emission Fatigue Crack Characterization in Structural Steel and Weld

    Directory of Open Access Journals (Sweden)

    Adutwum Marfo

    2013-01-01

    Full Text Available The fatigue crack growth characteristics of structural steel and weld connections are analyzed using quantitative acoustic emission (AE technique. This was experimentally investigated by three-point bending testing of specimens under low cycle constant amplitude loading using the wavelet packet analysis. The crack growth sequence, that is, initiation, crack propagation, and fracture, is extracted from their corresponding frequency feature bands, respectively. The results obtained proved to be superior to qualitative AE analysis and the traditional linear elastic fracture mechanics for fatigue crack characterization in structural steel and welds.

  20. Compression fatigue of Wind Turbine Blade composites materials and damage mechanisms

    DEFF Research Database (Denmark)

    Fraisse, Anthony; Brøndsted, Povl

    According to the new IEC 61400-5-rev0 recommendation, which is under preparation it will be required to qualify wind turbine blade (WTB) composite materials in fatigue at R=0.1, R=-1, and R=10. As a minimum fatigue at R=-1 is required. This is a consequence of the ever-growing blades, where gravity...... driven edgewise bending introduces significant fully reversed cycling at the leading and trailing edges. Therefore, material manufacturer and WTB manufacturer demand test results of highest reliability and reproducibility. However, these equirements for compression-compression and tensioncompression...

  1. Experimental evaluation of the fretting fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2013-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. A method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires along the length of the monostrand. The experimental data....... Moreover, the paper provides relevant information about the monostrand bending stiffness and the extent of relative displacement between core and outer wires of the monostrand undergoing flexural deformations. The results presented herein are of special interest for the fatigue analysis of modern stay...

  2. The cyclic fatigue behavior of a Nicalon/SiC composite

    Energy Technology Data Exchange (ETDEWEB)

    Miriyala, N.; Liaw, P.K.; McHargue, C.J. [Univ. of Tennessee, Knoxville, TN (United States); Snead, L.L. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Cyclic fatigue tests were performed at ambient temperature on a Nicalon/SiC composite to study the effects of fabric orientation on the mechanical behavior. Four-point bend specimens were loaded either parallel or normal to the braided fabric plies. The maximum stresses chosen during the fatigue tests were 60, 70, and 80% of the monotonic strengths, respectively, in both orientations. Specimen failure did not occur in any case even after one million loading cycles. However, it was observed that much of the decrease in the composite modulus occurred in the first few (<10) cycles, and the fabric orientation did not significantly affect the effective modulus or midspan deflection trends.

  3. Rotary bending as a mean for improving micro-cleanliness of stainless steels for high demanding applications

    Directory of Open Access Journals (Sweden)

    Sourisseau Thomas

    2018-01-01

    Full Text Available Stainless steels are used for automotive or medical applications which require a high fatigue resistance correlated to a high level of micro-cleanliness. A methodology based on rotary bending tests carried out on wires or bars has been defined to determine the material’s endurance limit (after 100 millions cycles and identify the largest subcutaneous inclusions or precipitates where failures initiate. This methodology has been applied to EN 1.4568 spring wires. Failures were found to initiate both at oxide inclusions and AlN precipitates. For the same size, AlN precipitates were observed to be more critical towards crack initiation than oxide inclusions, due to their angular shape and lower thermal expansion at high temperatures. However, oxide inclusions larger than the AlN maximum size strongly impact the material’s fatigue limit, and their density and size should be reduced.

  4. Fatigue Strength of Weathering Steel

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Klusák, Jan

    2012-01-01

    Roč. 18, č. 1 (2012), s. 18-22 ISSN 1392-1320 Grant - others:GA MPO(CZ) FT/TA5/076 Institutional support: RVO:68081723 Keywords : fatigue of weathering steel * corrosion pits * fatigue notch factor Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.522, year: 2012

  5. Knee and hip sagittal and transverse plane changes after two fatigue protocols

    Science.gov (United States)

    Lucci, Shawn; Cortes, Nelson; Van Lunen, Bonnie; Ringleb, Stacie; Onate, James

    2013-01-01

    Fatigue has been shown to alter the biomechanics of lower extremity during landing tasks. To date, no study has examined the effects of two types of fatigue on kinetics and kinematics. Objectives This study was conducted to assess biomechanical differences between two fatigue protocols [Slow Linear Oxidative Fatigue Protocol (SLO-FP) and Functional Agility Short-Term Fatigue Protocol (FAST-FP)]. Design Single-group repeated measures design. Methods Fifteen female collegiate soccer players had to perform five successful trials of unanticipated sidestep cutting (SS) pre- and post-fatigue protocols. The SLO-FP consisted of an initial VO2peak test followed by 5-min rest, and a 30-min interval run. The FAST-FP consisted of 4 sets of a functional circuit. Biomechanical measures of the hip and knee were obtained at different instants while performing SS pre- and post-fatigue. Repeated 2 × 2 ANOVAs were conducted to examine task and fatigue differences. Alpha level set a priori at 0.05. Results During the FAST-FP, participants had increased knee internal rotation at initial contact (IC) (12.5 ± 5.9°) when compared to the SLO-FP (7.9 ± 5.4°, p < 0.001). For hip flexion at IC, pre-fatigue had increased angles (36.4 ± 8.4°) compared to post-fatigue (30.4 ± 9.3°, p = 0.003), also greater knee flexion during pre-fatigue (25.6 ± 6.8°) than post-fatigue (22.4 ± 8.4°, p = 0.022). Conclusion The results of this study showed that hip and knee mechanics were substantially altered during both fatigue conditions. PMID:21636322

  6. Fatigue data compilation and evaluation of fatigue on design

    International Nuclear Information System (INIS)

    Nyilas, A.

    1985-05-01

    The aim of this report is a review of the available fatigue data of various materials necessary for the design of large superconducting magnets for fusion. One of the primary objectives of this work is to present a broad outline of the low temperature fatigue data of relevant materials within the scope of available data. Besides the classical fatigue data of materials the fatigue crack propagation measurements are outlined widely. The existing recommendations for the design of cryogenic structures are described. A brief introduction of fracture mechanics as well as a historical background of the development of our present day understanding of fatigue has been done. (orig.) [de

  7. Characteristic of improved fatigue performance for Zr-based bulk metallic glass matrix composites

    International Nuclear Information System (INIS)

    Qiao, J.W.; Huang, E.W.; Wang, G.Y.; Yang, H.J.; Liang, W.; Zhang, Y.; Liaw, P.K.

    2013-01-01

    Zr 58.5 Ti 14.3 Nb 5.2 Cu 6.1 Ni 4.9 Be 11.0 bulk metallic glass matrix composites exhibit improved four-point-bending fatigue endurance with a fatigue limit of 567 MPa, compared to that under the tension–tension fatigue, due to the high-volume-fractioned dendrites, which can effectively blunt the fatigue-induced cracks. Illuminated by high-energy synchrotron X-ray at 200 and 100 K, the corresponding diffraction peaks, such as (110), (200), and (211) shift rightward to small lattice spacings, compared to those at 298 K. However, the peak widths at 100 K and 200 K are almost identical to that of room temperature. Since an identical fatigue specimen was measured under room temperature, 200 K, and 100 K, the invariant of the peak widths reveal the fact of the irreversible microstructure developments induced by fatigue. Even if the fatigue fracture stress is distinguishingly lower than the yielding strength, the deformation of dendrites locally prevails, evidenced by the occurrence of dislocations

  8. Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

    Science.gov (United States)

    Sivan, Shiril; Di Prima, Matthew; Weaver, Jason D.

    2017-09-01

    Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F2129 are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential. However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life. Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

  9. Effects of residual stress on fatigue strength of small diameter welded pipe joint

    International Nuclear Information System (INIS)

    Yamashita, Tetsuo; Hattori, Takahiro; Nomoto, Toshiharu; Iida, Kunihiro; Sato, Masanobu

    1996-01-01

    A power plant consists of many welded components, therefore, it is essential in establishing the reliability of the power plant to maintain the reliability of all welded components. The fatigue failure caused by mechanical vibrations of small diameter welded joints, which is represented by socket welded joints, is one of the major causes of trouble for the welded parts of the power plant. Here, bending fatigue tests were conducted to investigate the fatigue strength of small diameter socket welded pipe joints. In the most cases of large diameter socket joints, a fatigue crack started from the root of the fillet weld though the stress amplitude at the root was smaller than that at the toe of fillet weld. Additionally, the fatigue strength was affected by the weld bead sequence. The residual stress was considered to be one of the important parameters governing fatigue strength, therefore, its effects were investigated. In several types of pipe joints, the local stress and residual stress distributions were calculated by finite element analysis. The residual stresses were compressive at the toe and tensile at the root of the socket welded joints. Based on these results, the effects of residual stresses on the fatigue strength are discussed for small diameter welded pipe joints in the present work

  10. Corrosion-fatigue studies of the Zr-based Vitreloy 105 bulk metallic glass

    International Nuclear Information System (INIS)

    Horton Jr, Joe A.; Morrison, M.L.; Buchanan, R.A.; Liaw, Peter K.; Green, B.A.; Wang, G.Y.

    2007-01-01

    The purpose of this study was to characterize the stress-life behavior of the Vitreloy 105 BMG alloy in the four-point bending configuration in a 0.6 M. NaCl electrolyte. At high stress amplitudes, the corrosion-fatigue life was similar to the fatigue lives observed in air. The environment became increasingly detrimental with decreases in stress, and the corrosion-fatigue endurance limit decreased to about 50 MPa, an 88% decrease relative to testing in air. Similar to the tests conducted in air, oxide particles were found on the fracture surfaces but did not appear to significantly affect the corrosion-fatigue lives. However, wear and the resultant corrosion at the outer loading pins resulted in crack initiation in most of the samples. Thus, these results are considered conservative estimates of the corrosion-fatigue behavior of this BMG alloy. Monitoring of the samples and the open-circuit potentials revealed that the onset of significant crack growth occurred at an average of 92% of the total fatigue life. The mechanism of corrosion-fatigue degradation was found to be anodic dissolution

  11. Vertical jump fatigue does not affect intersegmental coordination and segmental contribution

    Directory of Open Access Journals (Sweden)

    Gleber Pereira

    2014-09-01

    Full Text Available The aim of this study was to describe the intersegmental coordination and segmental contribution during intermittent vertical jumps performed until fatigue. Seven male visited the laboratory on two occasions: 1 the maximum vertical jump height was determined followed by vertical jumps habituation; 2 participants performed intermittent countermovement jumps until fatigue. Kinematic and kinetic variables were recorded. The overall reduction in vertical jump height was 5,5%, while the movement duration increased 10% during the test. The thigh segment angle at movement reversal significantly increased as the exercise progressed. Non-significant effect of fatigue on movement synergy was found for the intersegmental coordination pattern. More than 90% of the intersegmental coordination was explained by one coordination pattern. Thigh rotation contributed the most to the intersegmental coordination pattern, with the trunk second and the shank the least. Therefore, one intersegmental coordination pattern is followed throughout the vertical jumps until fatigue and thigh rotation contributes the most to jump height.

  12. Usage of information safety requirements in improving tube bending process

    Science.gov (United States)

    Livshitz, I. I.; Kunakov, E.; Lontsikh, P. A.

    2018-05-01

    This article is devoted to an improvement of the technological process's analysis with the information security requirements implementation. The aim of this research is the competition increase analysis in aircraft industry enterprises due to the information technology implementation by the example of the tube bending technological process. The article analyzes tube bending kinds and current technique. In addition, a potential risks analysis in a tube bending technological process is carried out in terms of information security.

  13. Bending of conjugated molecular wires and its effect on electron conduction properties

    International Nuclear Information System (INIS)

    Das, Bidisa

    2010-01-01

    The electronic structure and electron transport properties of simple conjugated molecular wires like oligophenylene ethynylene (OPE) and oligophenylene vinylene (OPV) are studied under compression. If artificially confined to a given shorter length, the oligomers tend to bend and bending causes a loss in the overlap of the conjugated molecular orbitals. Theoretical modeling of electronic transport has been carried out for all undistorted and compressed OPE/OPV oligomers. OPV exists in step-like or V-like conformations and they have the same stability with very similar frontier molecular orbitals. The conductances of these molecular wires are calculated when inserted between two gold probes and the conductances for OPV are found to be comparable to OPE when the interfaces are same. The conductance decreases with bending due to the gradual loss in overlap of the molecular orbitals. It is also found that the conductances of the molecular wires decrease very strongly if the terminal sulfur atom is simultaneously bonded to hydrogen and a gold surface, thus reflecting the importance of the interface in determining the conductance in two-probe systems. From the conductance studies it may be concluded that if one or more benzene rings of OPE are rotated from coplanar conditions, the orthogonal molecular orbitals may completely block the electronic transport, rendering the molecule insulating.

  14. Laser-Doppler measurements of laminar and turbulent flow in a pipe bend

    Energy Technology Data Exchange (ETDEWEB)

    Enayet, M.M.; Gibson, M.M.; Taylor, A.M.K.P.; Yianneskis, M.

    1982-12-01

    Laser-Doppler measurements are reported for laminar and turbulent flow through a 90/sup 0/ bend of circular cross-section with mean radius of curvature equal to 2.8 times the diameter. The measurements were made in cross-stream planes 0.58 diameters upstream of the bend inlet plane, in 30, 60, and 75/sup 0/ planes in the bend and in planes one and six diameters downstream of the exit plane. Three sets of data were obtained: for laminar flow at Reynolds numbers of 500 and 1093 and for turbulent flow at the maximum obtainable Reynolds number of 43 000. The results show the development of strong pressure-driven secondary flows in the form of a pair of counter-rotating vortices in the streamwise direction. The strength and character of the secondary flows were found to depend on the thickness and nature of the inlet boundary layerd, conditions which could not be varied independently of Reynolds number. The quantitative anemometer measurements are supported by flow visualization studies. Refractive index matching at the fluid-wall interface was not used; the measurements consist, therefore, of streamwise components of mean and fluctuating velocities only, supplemented by wall pressure measurements for the turbulent flow. This displacement of the laser measurement volume due to refraction is allowed for in simple geometrical calculations. The results are intended for use as benchmark data for calibrating flow calculation methods.

  15. Fatigue and thermal fatigue of Pb-Sn solder joints

    International Nuclear Information System (INIS)

    Frear, D.; Grivas, D.; McCormack, M.; Tribula, D.; Morris, J.W. Jr.

    1987-01-01

    This paper presents a fundamental investigation of the fatigue and thermal fatigue characteristics, with an emphasis on the microstructural development during fatigue, of Sn-Pb solder joints. Fatigue tests were performed in simple shear on both 60Sn-40Pb and 5Sn-95Pb solder joints. Isothermal fatigue tests show increasing fatigue life of 60Sn-40Pb solder joints with decreasing strain and temperature. In contrast, such behavior was not observed in the isothermal fatigue of 5Sn-95Pb solder joints. Thermal fatigue results on 60Sn-40Pb solder cycled between -55 0 C and 125 0 C show that a coarsened region develops in the center of the joint. Both Pb-rich and Sn-rich phases coarsen, and cracks form within these coarsened regions. The failure mode 60Sn-40Pb solder joints in thermal and isothermal fatigue is similar: cracks form intergranularly through the Sn-rich phase or along Sn/Pb interphase boundaries. Extensive cracking is found throughout the 5Sn-95Pb joint for both thermal and isothermal fatigue. In thermal fatigue the 5Sn-95Pb solder joints failed after fewer cycles than 60Sn-40Pb

  16. Fatigue approach for addressing environmental effects in fatigue usage calculation

    Energy Technology Data Exchange (ETDEWEB)

    Wilhelm, Paul; Rudolph, Juergen [AREVA GmbH, Erlangen (Germany); Steinmann, Paul [Erlangen-Nuremberg Univ., erlangen (Germany). Chair of Applied Mechanics

    2015-04-15

    Laboratory tests consider simple trapezoidal, triangle, and sinusoidal signals. However, actual plant components are characterized by complex loading patterns and periods of holds. Fatigue tests in water environment show, that the damage from a realistic strain variation or the presence of hold-times within cyclic loading results in an environmental reduction factor (Fen) only half that of a simple waveform. This study proposes a new fatigue approach for addressing environmental effects in fatigue usage calculation for class 1 boiler and pressure vessel reactor components. The currently accepted method of fatigue assessment has been used as a base model and all cycles, which have been comparable with realistic fatigue tests, have been excluded from the code-based fatigue calculation and evaluated directly with the test data. The results presented show that the engineering approach can successfully be integrated in the code-based fatigue assessment. The cumulative usage factor can be reduced considerably.

  17. The Nature of Fatigue in Chronic Fatigue Syndrome.

    Science.gov (United States)

    Olson, Karin; Zimka, Oksana; Stein, Eleanor

    2015-10-01

    In this article, we report the findings of our study on the nature of fatigue in patients diagnosed with chronic fatigue syndrome. Using ethnoscience as a design, we conducted a series of unstructured interviews and card sorts to learn more about how people with chronic fatigue syndrome describe fatigue. Participants (N = 14) described three distinct domains: tiredness, fatigue, and exhaustion. Most participants experienced tiredness prior to diagnosis, fatigue during daily life, and exhaustion after overexertion. We also discuss participants' ability to adapt to a variety of stressors and prevent shifts to exhaustion, and relate our findings to stress theory and other current research. Primary strategies that promoted adaptation to stressors included pacing and extended rest periods. These findings can aid health care professionals in detecting impending shifts between tiredness, fatigue, and exhaustion and in improving adaptive strategies, thereby improving quality of life. © The Author(s) 2015.

  18. Fatigue approach for addressing environmental effects in fatigue usage calculation

    International Nuclear Information System (INIS)

    Wilhelm, Paul; Rudolph, Juergen; Steinmann, Paul

    2015-01-01

    Laboratory tests consider simple trapezoidal, triangle, and sinusoidal signals. However, actual plant components are characterized by complex loading patterns and periods of holds. Fatigue tests in water environment show, that the damage from a realistic strain variation or the presence of hold-times within cyclic loading results in an environmental reduction factor (Fen) only half that of a simple waveform. This study proposes a new fatigue approach for addressing environmental effects in fatigue usage calculation for class 1 boiler and pressure vessel reactor components. The currently accepted method of fatigue assessment has been used as a base model and all cycles, which have been comparable with realistic fatigue tests, have been excluded from the code-based fatigue calculation and evaluated directly with the test data. The results presented show that the engineering approach can successfully be integrated in the code-based fatigue assessment. The cumulative usage factor can be reduced considerably.

  19. Influence of cold rolling and fatigue on the residual stress state of a metal matrix composite

    International Nuclear Information System (INIS)

    Hanus, E.; Ericsson, T.; Lu, J.; Decomps, F.

    1993-01-01

    The large difference in the coefficient of thermal expansion between the matrix alloy and the particle in a metal matrix composite gives rise to residual stresses in the material. In the present work the effect of cold rolling and four-point bending fatigue on the residual stress state of a silicon carbide particle reinforced aluminium alloy (AA 2014) has been investigated. The three dimensional stress state measured in both phases: matrix and reinforcement, has been determined by using an X-ray diffraction technique. It was found that cold rolling induces surface compressive macrostresses of about -250 MPa, with a penetration depth around 2 mm. The absolute values of the pseudomacrostresses in both phases are significantly reduced due to the single track rolling. Stress relaxation occurs during four-point bending fatigue. (orig.)

  20. Fatigue strength of Al2O3 and Si3N4 ceramics

    International Nuclear Information System (INIS)

    Sonsino, C.M.

    1992-01-01

    Various Al 2 O 3 ceramics and random samples of two Si 3 N 4 ceramics were examined, with all specimens differing in terms of material and manufacturing parameters. Of the Al 2 O 3 ceramics, randomly selected specimens were tested for their banding strength at room temperature, and three specifically selected specimens were tested for their compressive strength at room temperature, at 800 C and at 1200 C. A number of specimen variants were examined by cyclic fatigue tests at room temperature and 800 C, and at 1200 C in one case, the specimens used being slightly notched specimens (α n = 1,02 and 1,08), or more heavily notched speciments (α n = 1.77, 1.90 and 2.24), with bending loads being either cyclic or growing. The Si 3 N 4 specimens were randomly chosen for bending tests and cyclic fatigue tests, at room temperature. (orig./MM) [de

  1. X-ray diffraction study of microstructural changes during fatigue damage initiation in steel pipes

    Energy Technology Data Exchange (ETDEWEB)

    Pinheiro, B., E-mail: bianca@lts.coppe.ufrj.br [Laboratory of Mechanics of Lille (LML), UMR CNRS 8107, University of Lille 1, Boulevard Paul Langevin, Cite Scientifique, 59655 Villeneuve d' Ascq (France); Lesage, J. [Laboratory of Mechanics of Lille (LML), UMR CNRS 8107, University of Lille 1, Boulevard Paul Langevin, Cite Scientifique, 59655 Villeneuve d' Ascq (France); Pasqualino, I. [Subsea Technology Laboratory (LTS), Ocean Engineering Department, COPPE/Federal University of Rio de Janeiro, PO Box 68508, Cidade Universitaria, CEP 21945-970, Rio de Janeiro/RJ (Brazil); Benseddiq, N. [Laboratory of Mechanics of Lille (LML), UMR CNRS 8107, University of Lille 1, Boulevard Paul Langevin, Cite Scientifique, 59655 Villeneuve d' Ascq (France); Bemporad, E. [Interdepartmental Laboratory of Electron Microscopy (LIME), University of Rome TRE, Via Della Vasca Navale 79, 00146 Rome (Italy)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer In this work we study the fatigue damage evolution in an API 5L X60 steel. Black-Right-Pointing-Pointer Microstructural changes and residual stresses are evaluated during fatigue tests. Black-Right-Pointing-Pointer Microdeformations and macro residual stresses are estimated by X-ray diffraction. Black-Right-Pointing-Pointer Results are discussed in view of an indicator of fatigue damage initiation. Black-Right-Pointing-Pointer This indicator could allow the prediction of residual life before macrocracking. - Abstract: Steel pipes used in the oil and gas industry undergo the action of cyclic loads that can cause their failure by fatigue. A consistent evaluation of the fatigue damage during the initiation phase should fundamentally be based on a nanoscale approach, i.e., at the scale of the dislocation network, in order to take into account the micromechanisms of fatigue damage that precede macrocrack initiation and propagation until the final fracture. In this work, microstructural changes related to fatigue damage initiation are investigated in the API 5L X60 grade steel, used in pipe manufacturing. Microdeformations and macro residual stress are evaluated using X-ray diffraction in real time during alternating bending fatigue tests performed on samples cut off from an X60 steel pipe. The aim of this ongoing work is to provide ground for further development of an indicator of fatigue damage initiation in X60 steel. This damage indicator could allow a good residual life prediction of steel pipes previously submitted to fatigue loading, before macroscopic cracking, and help to increase the reliability of these structures.

  2. Fatigue behaviour of T welded joints rehabilitated by tungsten inert gas and plasma dressing

    International Nuclear Information System (INIS)

    Ramalho, Armando L.; Ferreira, Jose A.M.; Branco, Carlos A.G.M.

    2011-01-01

    Highlights: → This study addresses the use of improvement techniques for repair T welded joints. → TIG and plasma arc re-melting are applied in joints with fatigue cracks at weld toes. → Plasma dressing provides reasonable repair in joints with cracks greater than 4 mm. → TIG dressing produces a deficient repair in joints with cracks greater than 4 mm. → TIG dressing provides good repair in joints with fatigue cracks lesser than 2.5 mm. -- Abstract: This paper concerns a fatigue study on the effect of tungsten inert gas (TIG) and plasma dressing in non-load-carrying fillet welds of structural steel with medium strength. The fatigue tests were performed in three point bending at the main plate under constant amplitude loading, with a stress ratio of R = 0.05 and a frequency of 7 Hz. Fatigue results are presented in the form of nominal stress range versus fatigue life (S-N) curves obtained from the as welded joints and the TIG dressing joints at the welded toe. These results were compared with the ones obtained in repaired joints, where TIG and plasma dressing were applied at the welded toes, containing fatigue cracks with a depth of 3-5 mm in the main plate and through the plate thickness. A deficient repair was obtained by TIG dressing, caused by the excessive depth of the crack. A reasonable fatigue life benefits were obtained with plasma dressing. Good results were obtained with the TIG dressing technique for specimens with shallower initial defects (depth lesser than 2.5 mm). The fatigue life benefits were presented in terms of a gain parameter assessed using both experimental data and life predictions based on the fatigue crack propagation law.

  3. Fatigue fracture of steel after mechanical and ultrasonic strengthening

    International Nuclear Information System (INIS)

    Stotskij, I.M.

    1978-01-01

    Fatigue fracture surfaces of samples after mechanical and ultrasonic strengthening have been studied metallographically and by electron fractography. Studied was the 40Kh steel hardened from 850 deg and then tempered at 180 deg or at 550 deg C. The ultrasound power was 25 kWt, the frequency was 20 kHz, the sample rotation velocity was 39.5 m/min. Mechanical and ultrasonic treatment was found to cause structural changes (formation of a white layer) and deformation of the material under the layer. The fatigue cracks were extending beyond the white layer; their propagation involved generation and coalescence of microcracks on account of segregation of carbides. It is concluded that mechanical and ultrasonic treatment should be used for increasing the fatigue strength of low and average strength materials rather than hardened or low-tempered ones

  4. Fatigue of dental ceramics.

    Science.gov (United States)

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-12-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, M.M.; Tops, M.

    2003-01-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support

  6. Chronic fatigue syndrome.

    NARCIS (Netherlands)

    Prins, J.B.; Meer, J.W.M. van der; Bleijenberg, G.

    2006-01-01

    During the past two decades, there has been heated debate about chronic fatigue syndrome (CFS) among researchers, practitioners, and patients. Few illnesses have been discussed so extensively. The existence of the disorder has been questioned, its underlying pathophysiology debated, and an effective

  7. Incompatibility and Mental Fatigue

    Science.gov (United States)

    Herzog, Thomas R.; Hayes, Lauren J.; Applin, Rebecca C.; Weatherly, Anna M.

    2011-01-01

    A straightforward prediction from attention restoration theory is that the level of incompatibility in a person's life should be positively correlated with that person's level of mental (or directed attention) fatigue. The authors tested this prediction by developing a new self-report measure of incompatibility in which they attempted to isolate…

  8. Rotational motion in nuclei

    International Nuclear Information System (INIS)

    Bohr, A.

    1977-01-01

    History is surveyed of the development of the theory of rotational states in nuclei. The situation in the 40's when ideas formed of the collective states of a nucleus is evoked. The general rotation theory and the relation between the single-particle and rotational motion are briefly discussed. Future prospects of the rotation theory development are indicated. (I.W.)

  9. Are nurses able to assess fatigue, exertion fatigue and types of fatigue in residential home patients?

    NARCIS (Netherlands)

    Tiesinga, L.J.; Dijkstra, Ate; Dassen, T.W.N.; Halfens, R.J.G.; van den Heuvel, W.J.A.

    Although fatigue is recognized as a subjective, generalized, extensive and disabling health care problem with a relatively high prevalence among the chronically ill, there have been no studies to show whether nurses caring for fatigued subjects are able to accurately assess the level of fatigue that

  10. Muscle Deoxygenation Causes Muscle Fatigue

    Science.gov (United States)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D.

    1999-01-01

    Muscle fatigue is a common musculoskeletal disorder in the work place, and may be a harbinger for more disabling cumulative trauma disorders. Although the cause of fatigue is multifactorial, reduced blood flow and muscle oxygenation may be the primary factor in causing muscle fatigue during low intensity muscle exertion. Muscle fatigue is defined as a reduction in muscle force production, and also occurs among astronauts who are subjected to postural constraints while performing lengthy, repetitive tasks. The objectives of this research are to: 1) develop an objective tool to study the role of decreased muscle oxygenation on muscle force production, and 2) to evaluate muscle fatigue during prolonged glovebox work.

  11. Fatigue testing of controlled memory wire nickel-titanium rotary instruments.

    Science.gov (United States)

    Shen, Ya; Qian, Wei; Abtin, Houman; Gao, Yuan; Haapasalo, Markus

    2011-07-01

    To improve the fracture resistance of nickel-titanium (NiTi) files, manufacturers have introduced new alloys to manufacture NiTi files and developed new manufacturing processes. This study was aimed to examine the fatigue behavior of NiTi instruments from a novel controlled memory NiTi wire (CM Wire). Instruments of ProFile, Typhoon (TYP), Typhoon CM (TYP CM), DS-SS0250425NEYY (NEYY), and DS-SS0250425NEYY CM (NEYY CM) (DS Dental, Johnson City, TN) all size 25/.04 were subjected to rotational bending at the curvature of 35° and 45° in air at the temperature of 23° ± 2°C, and the number of revolutions to fracture (N(f)) was recorded. The fracture surface of all fragments was examined by a scanning electron microscope. The crack-initiation sites, the percentage of dimple area to the whole fracture cross-section, and the surface strain amplitude (ε(a)) were noted. The new alloy yielded an improvement of over three to eight times in N(f) of CM files than that of conventional NiTi files (P wire (58%-100%) had one crack origin. The values of the fraction area occupied by the dimple region were significantly smaller on CM NiTi instruments compared with conventional NiTi instruments (P wire at both curvatures (P Wire had a significantly higher N(f) and lower surface strain amplitude than the conventional NiTi wire files with identical design. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  12. Bending of pipes with inconel cladding

    Energy Technology Data Exchange (ETDEWEB)

    Nachpitz, Leonardo; Menezes, Carlos Eduardo B; Vieira, Carlos R. Tavares [Primus Processamento de Tubos S.A. (PROTUBO), Macae, RJ (Brazil)

    2009-07-01

    The high-frequency induction bending process, using API pipes coated with Inconel 625 reconciled to a mechanical transformation for a higher degree of resistance, was developed through a careful specification and control of the manufacturing parameters and inherent heat treatments. The effects of this technology were investigated by a qualification process consisting of a sequence of tests and acceptance criteria typically required by the offshore industry, and through the obtained results was proved the effectiveness of this entire manufacturing process, without causing interference in the properties and the quality of the inconel cladding, adding a gain of resistance to the base material, guaranteed by the requirements of the API 5L Standard. (author)

  13. Design Study: ELENA Bending Magnet Prototype

    CERN Document Server

    Schoerling, D

    2013-01-01

    The ELENA bending magnet prototype shall prove that the proposed design meets the requirements set by the ELENA beam dynamics. The following points will be discussed in detail: (i) production process of a magnetic yoke diluted with stainless steel plates, (ii) the stability and repeatability of the field homogeneity of such a yoke over the full working range, (iii) choice of soft magnetic steel, (iv) hysteresis effects, (v) mechanical deformations, (vi) thermal insulation to intercept heat load from baking for activation of NEG coating in the vacuum chamber, (vii) end shim design. In order to verify these points the following measurements will be performed: (i) Hall probe scanning, (ii) integrated field homogeneity measurement (DC), (iii) integrated field homogeneity measurement (AC).

  14. Rotational motion in nuclei

    International Nuclear Information System (INIS)

    Bohr, A.

    1976-01-01

    Nuclear structure theories are reviewed concerned with nuclei rotational motion. The development of the deformed nucleus model facilitated a discovery of rotational spectra of nuclei. Comprehensive verification of the rotational scheme and a successful classification of corresponding spectra stimulated investigations of the rotational movement dynamics. Values of nuclear moments of inertia proved to fall between two marginal values corresponding to rotation of a solid and hydrodynamic pattern of an unrotating flow, respectively. The discovery of governing role of the deformation and a degree of a symmetry violence for determining rotational degrees of freedon is pointed out to pave the way for generalization of the rotational spectra

  15. Strength tests of thin-walled elliptic duralumin cylinders in pure bending and in combined pure bending and torsion

    Science.gov (United States)

    Lundquist, Eugene E; Stowell, Elbridge Z

    1942-01-01

    An analysis is presented of the results of tests made by the Massachusetts Institute of Technology and by the National Advisory Committee for Aeronautics on an investigation of the strength of thin-walled circular and elliptic cylinders in pure bending and in combined torsion and bending. In each of the loading conditions, the bending moments were applied in the plane of the major axis of the ellipse.

  16. Load tests with a pipe bend DN 425, applying slowly changing bending loads up to occurrence of leak

    International Nuclear Information System (INIS)

    Uhlmann, D.; Hunger, H.

    1990-01-01

    The experimental program deals with the formation of incipient cracks and subsequent crack growth of axially oriented cracks at a pipe bend with a nominal width of DN 425. The pipe bend consists of the ferritic material 20MnMoNi55. The numerical experiments by means of 3 D-FE analyses concentrate on determining the influence of the asymmetric crack depths at the two bend halves, and of the multiple crack fields, on the effective crack strain. (DG) [de

  17. Experimental investigation of high cycle thermal fatigue in a T-junction piping system

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, P. Karthick; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    High cycle thermal fatigue damage of structure in the vicinity of T-junction piping systems in nuclear power plants is of importance. Mixing of coolant streams at significant temperature differences causes thermal fluctuations near piping wall leading to gradual thermal degradation. Flow mixing in a T-junction is performed. The determined factors result in bending stresses being imposed on the piping system ('Banana effect').

  18. On the accuracy of analyses for in-plane bending of smooth pipe bends with end constraints

    International Nuclear Information System (INIS)

    Thomson, G.; Spence, J.

    1985-01-01

    The accuracy of theoretical analyses for in-plane bending of smooth pipebends with end constraints is discussed and investigated with a view to explaining and reducing the differences between the major works. An earlier theory of the authors is improved to give more accurate answers for bends with rigid flanges. Flanged bends are then examined in some detail, quantifying for the first time the important influence of the flange rigidity on the bend flexibility and stresses. A summary of some finite element analyses is presented from which it is clear that further work is desirable. (orig.)

  19. Application and assessment of multiscale bending energy for morphometric characterization of neural cells

    Science.gov (United States)

    Cesar, Roberto Marcondes; Costa, Luciano da Fontoura

    1997-05-01

    The estimation of the curvature of experimentally obtained curves is an important issue in many applications of image analysis including biophysics, biology, particle physics, and high energy physics. However, the accurate calculation of the curvature of digital contours has proven to be a difficult endeavor, mainly because of the noise and distortions that are always present in sampled signals. Errors ranging from 1% to 1000% have been reported with respect to the application of standard techniques in the estimation of the curvature of circular contours [M. Worring and A. W. M. Smeulders, CVGIP: Im. Understanding, 58, 366 (1993)]. This article explains how diagrams of multiscale bending energy can be easily obtained from curvegrams and used as a robust general feature for morphometric characterization of neural cells. The bending energy is an interesting global feature for shape characterization that expresses the amount of energy needed to transform the specific shape under analysis into its lowest energy state (i.e., a circle). The curvegram, which can be accurately obtained by using digital signal processing techniques (more specifically through the Fourier transform and its inverse, as described in this work), provides multiscale representation of the curvature of digital contours. The estimation of the bending energy from the curvegram is introduced and exemplified with respect to a series of neural cells. The masked high curvature effect is reported and its implications to shape analysis are discussed. It is also discussed and illustrated that, by normalizing the multiscale bending energy with respect to a standard circle of unitary perimeter, this feature becomes an effective means for expressing shape complexity in a way that is invariant to rotation, translation, and scaling, and that is robust to noise and other artifacts implied by image acquisition.

  20. 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.

  1. The role of pores and microstructural heterogeneity on the tooth root fatigue strength of sintered spur gears

    Directory of Open Access Journals (Sweden)

    Benedetti Matteo

    2018-01-01

    Full Text Available The automotive industry employs a considerable amount of sintered parts, mainly as transmission and engine components. Gears are the parts that mostly benefit, in terms of cost saving, from the near net shape P/M technology. However, the porosity along with the heterogeneous microstructure can detrimentally affect the mechanical behaviour, especially the fatigue strength. The possibility of increasing sintered density up to 90% and more, the use of high strength alloys, as well as post sintering treatments have been extensively investigated obtaining consistent increases in the fatigue strength. The present study focuses on the effects of porosity and microstructure on tooth root bending fatigue of small module spur gears. The aim is to investigate the synergistic contribution of pore morphology and microstructure heterogeneity to the initiation of fatigue cracks and to the following crack paths. High density parts produced by high strength pre-alloyed powders were studied. Part of the specimens was case-hardened to obtain a martensitic/bainitic microstructure in the surface layer. Bending fatigue tests up to a fatigue endurance of three million cycles were performed. A careful fractographic analysis was conducted. The obtained results were discussed using the fracture mechanics approach of Murakami, considering the pores as pre-existing defects, whose propagation strongly depends on the microstructural heterogeneity.

  2. Crack initiation life analysis in notched pipe under cyclic bending loads

    International Nuclear Information System (INIS)

    Lee, Joon Seong; Kwak, Sang Log; Kim, Young Jin; Park, Youn Won

    2001-01-01

    In order to improve leak-before-break methodology, more precisely the crack growth evaluation, a round robin analysis was proposed by the CEA Saclay. The aim of this analysis was to evaluate the crack initiation life, penetration life and shape of through wall crack under cyclic bending loads. The proposed round robin analysis is composed of three main topic; fatigue crack initiation, crack propagation and crack penetration. This paper deals with the first topic, crack initiation in a notched pipe under four point bending. Both elastic-plastic finite element analysis and Neuber's rule were used to estimate the crack initiation life and the finite element models were verified by mesh-refinement, stress distribution and global deflection. In elastic-plastic finite element analysis, crack initiation life was determined by strain amplitude at the notch tip and strain-life curve of the material. In the analytical method, Neuber's rule with the consideration of load history and mean stress effect, was used for the life estimation. The effect of notch tip radius, strain range, cyclic hardening rule were examined in this study. When these results were compared with the experimental ones, the global deformation was a good agreement but crack initiation cycle was higher than the experimental result

  3. Crack initiation life analysis in notched pipe under cyclic bending loads

    International Nuclear Information System (INIS)

    Goak, S. R.; Kim, Y. J.; Lee, J. S.; Park, Y. W.

    2000-01-01

    In order to improve LBB(Leak-Before-Break) methodology, more precisely the crack growth evaluation, a benchmark problem was proposed by the CEA Saclay. The aim of this benchmark analysis was to evaluate the crack growth in a notched pipe under cyclic bending loads. The proposed benchmark analysis is composed of three main topic; fatigue crack initiation, crack propagation and crack penetration. This paper deals with the first topic, crack initiation in a notched pipe under four point bending. Both elastic-plastic finite element analysis and Neuber's rule were used to estimate the crack initiation life and the finite element models were verified by mesh-refinement, stress distribution and global deflection. In elastic-plastic finite element analysis, crack initiation life was determined by strain amplitude at the notch tip and strain-life curve of the material. In the analytical method, Neuber's rule with the consideration of load history and mean stress effect, was used for the life estimation. The effect of notch tip radius, strain range, cyclic hardening rule were examined in this study. When these results were compared with the experimental ones, the global deformation was a good agreement but the crack initiation cycle was higher than the experimental result

  4. Deformation and fatigue behavior of hot dip galvanized coatings

    International Nuclear Information System (INIS)

    Camurri, Carlos P.; Benavente, Raul G.; Roa, Isidoro S.; Carrasco, Claudia C.

    2005-01-01

    This paper reports on the results of a study of the effect of static and dynamic stresses on hot dip galvanized coatings on SAE 1020 steel substrates. Galvanizing was performed using baths maintained at 450 deg. C, the zinc containing 0.16% Ti and 0.02% Fe and with Al and Ni in the ranges 0-0.20% and 0-0.30%, respectively. Static three-point bend tests were conducted with applied stresses in the range 428-790 MPa. Dynamic bend-fatigue tests involved stresses in the range 228-578 MPa at a cyclic frequency of 0.25 Hz for up to 700 cycles. The total crack density in the coatings was measured before and after the tests using light optical and electron microscopy. The results showed that the crack density increased as the applied stress increased and crack propagation was promoted perpendicular to the substrate. The number of cycles had no effect on the crack density and propagation at stresses lower than 386 MPa. At higher stresses the number of applied cycles contributed only to crack propagation. It was concluded that the best bath composition for preventing fatigue crack propagation is one that minimized the formation of thinner brittle layers in the galvanized coatings

  5. The effect of cracks on the limit load of pipe bends under in-plane bending

    International Nuclear Information System (INIS)

    Griffiths, J.E.

    1976-06-01

    The limit analysis of the in-plane bending of curved tubes had received attention previously, but the effect of defects in the tube has not been considered. A lower bound has been established which, with no defects present, is in agreement with previous theoretical work. The method of linear programming allows cracks to be introduced into analysis, and results have been obtained for various geometries of defect. The results show that the presence of cracks in the pipe bend can have a marked effect on the theoretical limit load: a part-through crack penetrating only half the wall thickness will reduce the limit moment by up to 10%. The worst possible case of a through-crack may reduce the limit load by 60%. (author)

  6. The effect of cracks on the limit load of pipe bends under in-plane bending

    International Nuclear Information System (INIS)

    Griffiths, J.E.

    1976-06-01

    The limit analysis of the in-plane bending of curved tubes had received attention previously, but the effect of defects in the tube has not been considered. A lower bound is established, which, with no defects present, is in agreement with previous theoretical work. The method of linear programming allows cracks to be introduced into the analysis. and results have been obtained for various geometries of defect. The results show that the presence of cracks in the pipe bend can have a marked effect on the theoretical limit load: a part-through crack penetrating only half the wall thickness will reduce the limit moment by up to 10%. The worst possible case of a through-crack may reduce the limit load by 60% (author)

  7. Deflections and Strains in Cracked Shafts due to Rotating Loads: A Numerical and Experimental Analysis

    Directory of Open Access Journals (Sweden)

    N. Bachschmid

    2004-01-01

    Full Text Available In this article, the deflections of a circular cross-section beam presenting a transverse crack of different depths, due to different loads (bending, torsion, shear, and axial loads, are analyzed with the aid of a rather refined 3-D model, which takes into account the nonlinear contact forces in the cracked area. The bending and shear loads are applied in several different angular positions, in order to simulate a rotating load on a fixed beam, or, by changing the reference system, a fixed load on a rotating beam. Torsion and axial loads are instead fixed with respect to the beam.

  8. Deflections and Strains in Cracked Shafts Due to Rotating Loads: A Numerical and Experimental Analysis

    Directory of Open Access Journals (Sweden)

    Nicolò Bachschmid

    2003-01-01

    Full Text Available In this article the deflections of a circular cross-section beam presenting a transverse crack of varying depths caused by various loads (bending, torsion, shear, and axial loads are analyzed with the aid of a rather refined three-dimensional model that takes into account the nonlinear contact forces in the cracked area. The bending and shear loads are applied in several different angular positions in order to simulate a rotating load on a fixed beam or, by changing the reference system, a fixed load on a rotating beam. Torsion and axial loads are fixed with respect to the beam.

  9. Mechanical Fatigue Testing of High-Burnup Fuel for Transportation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Wang, Hong [ORNL

    2015-05-01

    This report describes testing designed to determine the ability of high burnup (HBU) (>45 GWd/MTU) spent fuel to maintain its integrity under normal conditions of transportation. An innovative system, Cyclic Integrated Reversible-bending Fatigue Tester (CIRFT), has been developed at Oak Ridge National Laboratory (ORNL) to test and evaluate the mechanical behavior of spent nuclear fuel (SNF) under conditions relevant to storage and transportation. The CIRFT system is composed of a U-frame equipped with load cells for imposing the pure bending loads on the SNF rod test specimen and measuring the in-situ curvature of the fuel rod during bending using a set up with three linear variable differential transformers (LVDTs).

  10. The effects of localised fatigue on upper extremity jump shot kinematics and kinetics in team handball.

    Science.gov (United States)

    Plummer, Hillary A; Oliver, Gretchen D

    2017-01-01

    Team handball is a popular sport worldwide that requires numerous throws to be made throughout the course of a game. Because of the upper extremity demands of repetitive throwing, it is possible that fatigue can alter the mechanics of a shot. The purpose of this study was to determine the influence of localised fatigue on jump shot kinematics and kinetics. Eleven male team handball players (23.1 ± 3.1 years; 185.1 ± 8.3 cm; 89.7 ± 12.2 kg) volunteered. An electromagnetic tracking system was used to examine the jump shot prior to and following localised fatigue. The fatiguing protocol consisted of throwing a 2.2 kg medicine ball into a rebounder until volitional fatigue. No significant kinematic or kinetic differences were observed following fatigue. Shoulder external rotation was -74.8 ± 14.9° prior to and -79.0 ± 14.7° following fatigue at MER. Scapula, external rotation at ball release (BR) prior to fatigue was -2.2 ± 7.0° and -3.2 ± 11.1° following fatigue. Scapular internal rotation, at maximum shoulder internal rotation (MIR), changed from 18.4 ± 11.2° to 20.4 ± 11.8°. Ball velocity decreased from19.8 m · s -1 to 18.8 m · s -1 (P = 0.12). Accuracy percentage in the pre-fatigue trials was 60.8 ± 14.1% and 52.8 ± 12.7% following fatigue (P = 0.20). While no significant changes were observed, it is possible that other fatiguing protocols that more closely represent the aerobic and throwing demands of the sport may have a greater effect on the kinematics and kinetics of the jump shot.

  11. Effect of Bend Radius on Magnitude and Location of Erosion in S-Bend

    Directory of Open Access Journals (Sweden)

    Quamrul H. Mazumder

    2015-01-01

    Full Text Available Solid particle erosion is a mechanical process that removes material by the impact of solid particles entrained in the flow. Erosion is a leading cause of failure of oil and gas pipelines and fittings in fluid handling industries. Different approaches have been used to control or minimize damage caused by erosion in particulated gas-solid or liquid-solid flows. S-bend geometry is widely used in different fluid handling equipment that may be susceptible to erosion damage. The results of a computational fluid dynamic (CFD simulation of diluted gas-solid and liquid-solid flows in an S-bend are presented in this paper. In addition to particle impact velocity, the bend radius may have significant influence on the magnitude and the location of erosion. CFD analysis was performed at three different air velocities (15.24 m/s–45.72 m/s and three different water velocities (0.1 m/s–10 m/s with entrained solid particles. The particle sizes used in the analysis range between 50 and 300 microns. Maximum erosion was observed in water with 10 m/s, 250-micron particle size, and a ratio of 3.5. The location of maximum erosion was observed in water with 10 m/s, 300-micron particle size, and a ratio of 3.5. Comparison of CFD results with available literature data showed reasonable and good agreement.

  12. Gender differences in variability patterns of forward bending

    DEFF Research Database (Denmark)

    Villumsen, Morten; Madeleine, Pascal; Jørgensen, Marie Birk

    2016-01-01

    The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure.......The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure....

  13. Disk-bend ductility tests for irradiated materials

    International Nuclear Information System (INIS)

    Klueh, R.L.; Braski, D.N.

    1984-01-01

    We modified the HEDL disk-bend test machine and are using it to qualitatively screen alloys that are susceptible to embrittlement caused by irradiation. Tests designed to understand the disk-bend test in relation to a uniaxial test are discussed. Selected results of tests of neutron-irradiated material are also presented

  14. System effects influencing the bending strength of timber beams

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager; Källsner, B.

    1998-01-01

    A stochastic model of hierarchical series system type for the bending strength of spruce beams isdefined from the anticipation that the bending failure takes place at a cross-section with a defect cluster formed by knots or grain irregularities. The parameters of the model are estimated from meas...

  15. Bends in nanotubes allow electric spin control and coupling

    DEFF Research Database (Denmark)

    Flensberg, Karsten; Marcus, Charles Masamed

    2010-01-01

    We investigate combined effects of spin-orbit coupling and magnetic field in carbon nanotubes containing one or more bends along their length. We show how bends can be used to provide electrical control of confined spins, while spins confined in straight segments remain insensitive to electric...

  16. Spontaneous bending of 2D molecular bottle-brush

    NARCIS (Netherlands)

    Subbotin, A; Jong, J; ten Brinke, G

    Using a scaling approach we consider a 2D comb copolymer brush under bending deformations. We show that the rectilinear brush is locally stable and can be characterized by a persistence length lambda increasing with the molecular weight of grafting side chains as lambda similar to M-3. A bending

  17. High-sensitivity bend angle measurements using optical fiber gratings.

    Science.gov (United States)

    Rauf, Abdul; Zhao, Jianlin; Jiang, Biqiang

    2013-07-20

    We present a high-sensitivity and more flexible bend measurement method, which is based on the coupling of core mode to the cladding modes at the bending region in concatenation with optical fiber grating serving as band reflector. The characteristics of a bend sensing arm composed of bending region and optical fiber grating is examined for different configurations including single fiber Bragg grating (FBG), chirped FBG (CFBG), and double FBGs. The bend loss curves for coated, stripped, and etched sections of fiber in the bending region with FBG, CFBG, and double FBG are obtained experimentally. The effect of separation between bending region and optical fiber grating on loss is measured. The loss responses for single FBG and CFBG configurations are compared to discover the effectiveness for practical applications. It is demonstrated that the sensitivity of the double FBG scheme is twice that of the single FBG and CFBG configurations, and hence acts as sensitivity multiplier. The bend loss response for different fiber diameters obtained through etching in 40% hydrofluoric acid, is measured in double FBG scheme that resulted in a significant increase in the sensitivity, and reduction of dead-zone.

  18. Fatigue of cord-rubber composites for tires

    Science.gov (United States)

    Song, Jaehoon

    Fatigue behaviors of cord-rubber composite materials forming the belt region of radial pneumatic tires have been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction . Using actual tires, it was found that interply shear strain is one of the crucial parameters for damage assessment from the result that higher levels of interply shear strain of actual tires reduce the fatigue lifetime. Estimated at various levels of load amplitude were the fatigue life, the extent and rate of resultant strain increase ("dynamic creep"), cyclic strains at failure, and specimen temperature. The interply shear strain of 2-ply 'tire belt' composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs. symmetric 4-ply configuration. Reflecting their matrix-dominated failure modes such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. The increase of interply rubber thickness lengthens their fatigue lifetime at an intermediate level of stress amplitude. However, the increase in the fatigue lifetime of the composite laminate becomes less noticeable at very low stress amplitude. Even with small compressive cyclic

  19. Resident fatigue in otolaryngology residents: a Web based survey.

    Science.gov (United States)

    Nida, Andrew M; Googe, Benjamin J; Lewis, Andrea F; May, Warren L

    2016-01-01

    Resident fatigue has become a point of emphasis in medical education and its effects on otolaryngology residents and their patients require further study. The purpose of our study was to evaluate the prevalence and nature of fatigue in otolaryngology residents, evaluate various quality of life measures, and investigate associations of increased fatigue with resident safety. Anonymous survey. Internet based. United States allopathic otolaryngology residents. None. The survey topics included demographics, residency structure, sleep habits and perceived stress. Responses were correlated with a concurrent Epworth Sleep Scale questionnaire to evaluate effects of fatigue on resident training and quality of life. 190 residents responded to the survey with 178 completing the Epworth Sleep Scale questionnaire. Results revealed a mean Epworth Sleep Scale score of 9.9±5.1 with a median of 10.0 indicating a significant number of otolaryngology residents are excessively sleepy. Statistically significant correlations between Epworth Sleep Scale and sex, region, hours of sleep, and work hours were found. Residents taking in-house call had significantly fewer hours of sleep compared to home call (p=0.01). Residents on "head and neck" (typically consisting of a large proportion of head and neck oncologic surgery) rotations tended to have higher Epworth Sleep Scale and had significantly fewer hours of sleep (p=.003) and greater work hours (potolaryngology residents are excessively sleepy. Our data suggest that the effects of fatigue play a role in resident well-being and resident safety. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Fatigue Experiences Among OCD Outpatients.

    Science.gov (United States)

    Pasquini, Massimo; Piacentino, Daria; Berardelli, Isabella; Roselli, Valentina; Maraone, Annalisa; Tarsitani, Lorenzo; Biondi, Massimo

    2015-12-01

    Patients with OCD are impaired in multiple domains of functioning and quality of life. While associated psychopathology complaints and neuropsychological deficits were reported, the subjective experience of general fatigue and mental fatigue was scarcely investigated. In this single-center case-control study we compared 50 non-depressed OCD outpatients consecutively recruited and 50 panic disorder (PD) outpatients, to determine whether they experienced fatigue differently. Assessment consisted of structured clinical interview for DSM-IV criteria by using the SCID-I and the SCID-II. Symptom severity was assessed using the Yale-Brown Obsessive-Compulsive Scale, the Hamilton Anxiety Rating Scale, the Hamilton Depression Rating Scale, the Clinical Global Impressions Scale, severity and the Global Assessment of Functioning Scale. Fatigue was assessed by using the Multidimensional Fatigue Inventory (MFI). Regarding MFI physical fatigue, an OR of 0.196 (95 % CI 0.080-0.478) was found, suggesting that its presence is associated with lower odds of OCD compared to PD. The same can be said for MFI mental fatigue, as an OR of 0.138 (95 % CI 0.049-0.326) was found, suggesting that its presence is associated with lower odds of OCD. Notably, OCD patients with OCDP co-morbidity reported higher scores of mental fatigue. In this study fatigue, including mental fatigue, seems not to be a prominent experience among adult non-depressed OCD patients.

  1. Formulation of Forming Load in V-Bending

    Directory of Open Access Journals (Sweden)

    Koumura Yuki

    2016-01-01

    Full Text Available A novel method is described to calculate the forming load in V-bending by a press brake. The data of forming load are collected by FEM analysis. With an increase of the punch stroke in V-bending, the forming load increases gradually after the elastic limit, and then decreases after showing the maximum value. The proposal formulation to trace the variations in the forming load curve includes the calculating method of the load of the elastic limit, the maximum load in air bending and the variations of the forming load before/after the bending stroke of the maximum load. The calculated precision is confirmed by comparing with the measured load-stroke curves in V-bending with a press brake.

  2. Caffeine, fatigue, and cognition.

    Science.gov (United States)

    Lorist, Monicque M; Tops, Mattie

    2003-10-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support the general belief that caffeine acts as a stimulant. Studies using ERP measures indicate that caffeine has an effect on attention, which is independent of specific stimulus characteristics. Behavioural effects on response related processes turned out to be mainly related to more peripheral motor processes. Recent insights in adenosine and dopamine physiology and functionality and their relationships with fatigue point to a possible modulation by caffeine of mechanisms involved in the regulation of behavioural energy expenditure.

  3. Fatigue 󈨛. Volume 1,

    Science.gov (United States)

    1987-06-01

    277 FATIGUE 87 da/dn (m/ ciclo ) 10 - 07 10 - 08 10 - 0 9 R=0.5 S* • -Long Crack 10-10 e Smax = 195 MPa *Smax = 205 MPa 1Smax = 225 MPa 0.5 1 5 10 AK...MPa/m) Figure 1 Crack growth rate vs stress intensity factor range 10 . da/dn (m/ ciclo ) i0 - ° 09 i0-o -Long crack 10 . ° Smax = 10 Pa 10 Smax...120 NPa Smax = 145 NlPa 0.5 I 10 AKN~~)50 Figure 2 Crack growth rate vs stress intensity factor range 278 FATIGUE 87 da/dn (m/ ciclo ) 10- 10- 0 7 % 10

  4. Rotationally invariant correlation filtering

    International Nuclear Information System (INIS)

    Schils, G.F.; Sweeney, D.W.

    1985-01-01

    A method is presented for analyzing and designing optical correlation filters that have tailored rotational invariance properties. The concept of a correlation of an image with a rotation of itself is introduced. A unified theory of rotation-invariant filtering is then formulated. The unified approach describes matched filters (with no rotation invariance) and circular-harmonic filters (with full rotation invariance) as special cases. The continuum of intermediate cases is described in terms of a cyclic convolution operation over angle. The angular filtering approach allows an exact choice for the continuous trade-off between loss of the correlation energy (or specificity regarding the image) and the amount of rotational invariance desired

  5. A bend thickness sensitivity study of Candu feeder piping

    International Nuclear Information System (INIS)

    Li, M.; Aggarwal, M.L.; Meysner, A.; Micelotta, C.

    2005-01-01

    In CANDU reactors, feeder bends close to the connection at the fuel channel may be subjected to the highest Flow Accelerated Corrosion (FAC) and stresses. Feeder pipe stress analysis is crucial in the life extension of aging CANDU plants. Typical feeder pipes are interconnected by upper link plates and spacers. It is well known that the stresses at the bends are sensitive to the local bend thicknesses. It is also known from the authors' study (Li and et al, 2005) that feeder inter linkage effect is significant and cannot be ignored. The field measurement of feeder bend thickness is difficult and may be subjected to uncertainty in accuracy. Hence, it is desirable to know how the stress on a subject feeder could be affected by the bend thickness variation of the neighboring feeders. This effect cannot be evaluated by the traditional 'single' feeder model approach. In this paper, the 'row' and 'combined' models developed in the previous study (Li and et al, 2005), which include the feeder interactions, are used to investigate the sensitivity of bend thickness. A series of random thickness bounded by maximum and minimum measured values were applied to feeders in the model. The results show that an individual feeder is not sensitive to the bend thickness variation of the remaining feeders in the model, but depends primarily on its own bend thickness. The highest stress at a feeder always occurs when the feeder has the smallest possible bend thickness. A minimum acceptable bend thickness for individual feeders can be computed by an iterative computing process. The dependency of field thickness measurement and the amount of required analysis work can be greatly reduced. (authors)

  6. Small fatigue cracks; Proceedings of the Second International Conference/Workshop, Santa Barbara, CA, Jan. 5-10, 1986

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, R.O.; Lankford, J.

    1986-01-01

    Topics discussed in this volume include crack initiation and stage I growth, microstructure effects, crack closure, environment effects, the role of notches, analytical modeling, fracture mechanics characterization, experimental techniques, and engineering applications. Papers are presented on fatigue crack initiation along slip bands, the effect of microplastic surface deformation on the growth of small cracks, short fatigue crack behavior in relation to three-dimensional aspects and the crack closure effect, the influence of crack depth on crack electrochemistry and fatigue crack growth, and nondamaging notches in fatigue. Consideration is also given to models of small fatigue cracks, short crack theory, assessment of the growth of small flaws from residual strength data, the relevance of short crack behavior to the integrity of major rotating aero engine components, and the relevance of short fatigue crack growth data to the durability and damage tolerance analyses of aircraft.

  7. Recovery from Fatigue

    Science.gov (United States)

    1973-06-30

    functioning to replace sleep or recover from fatigue. Possibly the hypnagogic period of descending Stage I, apparently perceived differently S-1 of...partly to quality of mentation during the Stage I hypnagogic period. It may well be that nappers belong to the group described by Foulkes, Spear, and...Symonds (1966) who engage in hypnagogic mentation, and this is clearly perceived by them as different from sleep. The present study suggests that napping

  8. Fatigue life determination by damage measuring in SAE 8620 specimens steel subjected to multiaxial experiments in neutral and corrosive environment

    International Nuclear Information System (INIS)

    Silva, Luiz L. da; Filho, Nelson do N.A.; Gomes, Paulo de T.V.; Rabello, Emerson G.; Mansur, Tanius R.

    2013-01-01

    Fatigue is the fail phenomenon of a material subjected to cyclic loads. This phenomenon affects any component under loads (forces, temperatures, etc.) that changes in time. When there is a combined load, originating multiaxial fatigue, which is the most of the real loads, worst is the situation. Before the component fail, the fatigue phenomenon produces damages to its material and this is a cumulative process that could not be reduced. In the continuum mechanic context, material damage is defined as a parameter that reduces the component resistance and this could cause its fail. The process of damage measuring by changes in electrical resistance is used in this work, and from experimental results of SAE 8620 steel specimens subjected to multiaxial fatigue in corrosive and neutral environment, the remaining specimen time life could be determined. Each specimen has its initial electrical resistance measured and after a certain number of fatigue cycles stopping points, its electrical resistance was measured again. In order to study multiaxial fatigue in specimens, a machine that induces simultaneously bending and torsional loads in the specimen was developed. Air at the temperature range of 18 deg C and 20 deg C was considered neutral environment. The corrosive environment was a NaCl solution with a concentration of 3,5% in weigh. The experimental results showed that the measuring fatigue damage using the changes in electrical resistance is efficient and that is possible to estimate the effect of a corrosive environment in the fatigue damage. (author)

  9. 3-D analysis of fatigue crack behaviour in a shot peened steam turbine blade material

    Energy Technology Data Exchange (ETDEWEB)

    He, B.Y., E-mail: Binyan.he@soton.ac.uk [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Katsamenis, O.L. [muVIS X-ray Imaging Centre, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Mellor, B.G.; Reed, P.A.S. [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-08-26

    Serial mechanical sectioning and high resolution X-ray tomography have been used to study the three-dimensional morphology of small fatigue cracks growing in a 12 Cr tempered martensitic steam turbine blade material. A range of surface conditions has been studied, namely polished and shot peened (with varying levels of intensity). In the polished (unpeened) condition, inclusions (alumina and manganese sulphide) played an important role in initiating and controlling early fatigue crack behaviour. When fatigue cracks initiated from an alumina stringer, the crack morphology was normally dominated by single stringers, which were always in the centre of the fatigue crack, indicating its primary role in initiation. Manganese sulphide inclusion groups however seemed to dominate and affect the crack path along both the surface and depth crack growth directions. The more intensely shot peened condition did not however evidence inclusion or stringer affected fatigue crack initiation or growth behaviour; sub-surface crack coalescence being clearly observed by both serial sectioning and computed tomography (CT) imaging techniques at a depth of about 150–180 μm. These sub-surface crack coalescences can be linked to both the extent of the compressive residual stress as well as the depth of the plastic deformation arising from the intense shot peening process. Shot peening appears to provide a different defect population that initiates fatigue cracks and competes with the underlying metallurgical defect populations. The most beneficial shot peening process would in this case appear to “deactivate” the original metallurgical defect population and substitute a known defect distribution from the shot peening process from which fatigue cracks grow rather slowly in the strain hardened surface layer which also contains compressive residual stresses. A benefit to fatigue life in bending, even under Low Cycle Fatigue (LCF) conditions, has been observed in these tests if a

  10. Performance Demands in Softball Pitching: A Comprehensive Muscle Fatigue Study.

    Science.gov (United States)

    Corben, Jeffrey S; Cerrone, Sara A; Soviero, Julie E; Kwiecien, Susan Y; Nicholas, Stephen J; McHugh, Malachy P

    2015-08-01

    Monitoring pitch count is standard practice in minor league baseball but not in softball because of the perception that fast-pitch softball pitching is a less stressful motion. To examine muscle fatigue after fast-pitch softball performances to provide an assessment of performance demand. Descriptive laboratory study. Bilateral strength measurements (handheld dynamometer) were made on 19 female softball pitchers (mean age [±SD], 15.2 ± 1.2 years) before and after pitching a game (mean number of pitches, 99 ± 21; mean innings pitched, 5 ± 1). A total of 20 tests were performed on the dominant and nondominant sides: forearm (grip, wrist flexion/extension, pronation/supination, elbow flexion/extension), shoulder (flexion, abduction/adduction, external/internal rotation, empty can test), scapula (middle/lower trapezius, rhomboid), and hip (hip flexion/extension, abduction/adduction). Fatigue (percentage strength loss) was categorized based on bilateral versus unilateral presentation using paired t tests: bilateral symmetric (significant on dominant and nondominant and not different between sides), bilateral asymmetric (significant on dominant and nondominant but significantly greater on dominant), unilateral asymmetric (significant on dominant only and significantly greater than nondominant), or unilateral equivocal (significant on dominant only but not different from nondominant). Bilateral symmetric fatigue was evident for all hip (dominant, 19.3%; nondominant, 15.2%) and scapular tests (dominant, 19.2%; nondominant, 19.3%). In general, shoulder tests exhibited bilateral asymmetric fatigue (dominant, 16.9%; nondominant, 11.6%). Forearm tests were more variable, with bilateral symmetric fatigue in the elbow flexors (dominant, 22.5%; nondominant, 19.2%), and wrist flexors (dominant, 21.6%; nondominant, 19.0%), bilateral asymmetric fatigue in the supinators (dominant, 21.8%; nondominant, 15.5%), unilateral asymmetric fatigue in the elbow extensors (dominant, 22

  11. Fatigue crack propagation in additively manufactured porous biomaterials.

    Science.gov (United States)

    Hedayati, R; Amin Yavari, S; Zadpoor, A A

    2017-07-01

    Additively manufactured porous titanium implants, in addition to preserving the excellent biocompatible properties of titanium, have very small stiffness values comparable to those of natural bones. Although usually loaded in compression, biomedical implants can also be under tensional, shear, and bending loads which leads to crack initiation and propagation in their critical points. In this study, the static and fatigue crack propagation in additively manufactured porous biomaterials with porosities between 66% and 84% is investigated using compact-tension (CT) samples. The samples were made using selective laser melting from Ti-6Al-4V and were loaded in tension (in static study) and tension-tension (in fatigue study) loadings. The results showed that displacement accumulation diagram obtained for different CT samples under cyclic loading had several similarities with the corresponding diagrams obtained for cylindrical samples under compression-compression cyclic loadings (in particular, it showed a two-stage behavior). For a load level equaling 50% of the yield load, both the CT specimens studied here and the cylindrical samples we had tested under compression-compression cyclic loading elsewhere exhibited similar fatigue lives of around 10 4 cycles. The test results also showed that for the same load level of 0.5F y , the lower density porous structures demonstrate relatively longer lives than the higher-density ones. This is because the high bending stresses in high-density porous structures gives rise to local Mode-I crack opening in the rough external surface of the struts which leads to quicker formation and propagation of the cracks. Under both the static and cyclic loading, all the samples showed crack pathways which were not parallel to but made 45 ° angles with respect to the notch direction. This is due to the fact that in the rhombic dodecahedron unit cell, the weakest struts are located in 45 ° direction with respect to the notch direction

  12. Results of fatigue tests and prediction of fatigue life under superposed stress wave and combined superposed stress wave

    International Nuclear Information System (INIS)

    Takasugi, Shunji; Horikawa, Takeshi; Tsunenari, Toshiyasu; Nakamura, Hiroshi

    1983-01-01

    In order to examine fatigue life prediction methods at high temperatures where creep damage need not be taken into account, fatigue tests were carried out on plane bending specimens of alloy steels (SCM 435, 2 1/4Cr-1Mo) under superposed and combined superposed stress waves at room temperature and 500 0 C. The experimental data were compared with the fatigue lives predicted by using the cycle counting methods (range pair, range pair mean and zero-cross range pair mean methods), the modified Goodman's equation and the modified Miner's rule. The main results were as follows. (1) The fatigue life prediction method which is being used for the data at room temperature is also applicable to predict the life at high temperatures. The range pair mean method is especially better than other cycle counting methods. The zero-cross range pair mean method gives the estimated lives on the safe side of the experimental lives. (2) The scatter bands of N-bar/N-barsub(es) (experimental life/estimated life) becomes narrower when the following equation is used instead of the modified Goodman's equation for predicting the effect of mean stress on fatigue life. σ sub(t) = σ sub(a) / (1 - Sigma-s sub(m) / kσ sub(B)) σ sub(t); stress amplitude at zero mean stress (kg/mm 2 ) σ sub(B); tensile strength (kg/mm 2 ) σ sub(m); mean stress (kg/mm 2 ) σ sub(a); stress amplitude (kg/mm 2 ) k; modified coefficient of σ sub(B) (author)

  13. Equilibria and Free Vibration of a Two-Pulley Belt-Driven System with Belt Bending Stiffness

    Directory of Open Access Journals (Sweden)

    Jieyu Ding

    2014-01-01

    Full Text Available Nonlinear equilibrium curvatures and free vibration characteristics of a two-pulley belt-driven system with belt bending stiffness and a one-way clutch are investigated. With nonlinear dynamical tension, the transverse vibrations of the translating belt spans and the rotation motions of the pulleys and the accessory shaft are coupled. Therefore, nonlinear piecewise discrete-continuous governing equations are established. Considering the bending stiffness of the translating belt spans, the belt spans are modeled as axially moving beams. The pattern of equilibria is a nontrivial solution. Furthermore, the nontrivial equilibriums of the dynamical system are numerically determined by using two different approaches. The governing equations of the vibration near the equilibrium solutions are derived by introducing a coordinate transform. The natural frequencies of the dynamical systems are studied by using the Galerkin method with various truncations and the differential and integral quadrature methods. Moreover, the convergence of the Galerkin truncation is investigated. Numerical results reveal that the study needs 16 terms after truncation in order to determine the free vibration characteristics of the pulley-belt system with the belt bending stiffness. Furthermore, the first five natural frequencies are very sensitive to the bending stiffness of the translating belt.

  14. Large Deformation Dynamic Bending of Composite Beams

    Science.gov (United States)

    Derian, E. J.; Hyer, M. W.

    1986-01-01

    Studies were conducted on the large deformation response of composite beams subjected to a dynamic axial load. The beams were loaded with a moderate eccentricity to promote bending. The study was primarily experimental but some finite element results were obtained. Both the deformation and the failure of the beams were of interest. The static response of the beams was also studied to determine potential differences between the static and dynamic failure. Twelve different laminate types were tested. The beams were loaded dynamically with a gravity driven impactor traveling at 19.6 ft/sec and quasi-static tests were conducted on identical beams in a displacement controlled manner. For laminates of practical interest, the failure modes under static and dynamic loadings were identical. Failure in most of the laminate types occurred in a single event involving 40% to 50% of the plies. However, failure in laminates with 30 deg or 15 deg off-axis plies occured in several events. All laminates exhibited bimodular elastic properties. Using empirically determined flexural properties, a finite element analysis was reasonably accurate in predicting the static and dynamic deformation response.

  15. Field measurement for large bending magnets

    International Nuclear Information System (INIS)

    Lazzaro, A.; Cappuzzello, F.; Cunsolo, A.; Cavallaro, M.; Foti, A.; Orrigo, S.E.A.; Rodrigues, M.R.D.; Winfield, J.S.

    2008-01-01

    The results of magnetic field measurements of the large bending magnet of the MAGNEX spectrometer are presented. The experimental values are used to build an Enge function by the least-squares method. The resulting field is compared to the measured one, showing too large deviation for application to ray reconstruction techniques. Similarly, the experimental values are compared with results from a three-dimensional finite elements calculation. Again the deviations between measured and calculated field are too large for a direct application of the latter to ray reconstruction, while its reliability is sufficient for analysis purposes. In particular, it has been applied to study the effect of the inaccuracies in the probe location and orientation on the precision of field reconstruction, and to establish the requirements for the field interpolation. These inaccuracies are found to be rather important, especially for the transversal components of the field, with the consequence that their effect on the reconstructed field should be minimized by special interpolation algorithms

  16. Occipital bending (Yakovlevian torque) in bipolar depression.

    Science.gov (United States)

    Maller, Jerome J; Anderson, Rodney; Thomson, Richard H; Rosenfeld, Jeffrey V; Daskalakis, Zafiris J; Fitzgerald, Paul B

    2015-01-30

    Differing levels of occipital lobe asymmetry and enlarged lateral ventricles have been reported within patients with bipolar disorder (BD) compared with healthy controls, suggesting different rates of occipital bending (OB). This may exert pressure on subcortical structures, such as the hippocampus, reduced among psychiatric patients. We investigated OB prevalence in 35 patients with BD and 36 healthy controls, and ventricular and occipital volumes. Prevalence was four times higher among BD patients (12/35 [34.3%]) than in control subjects (3/36 [8.3%]), as well as larger lateral ventricular volumes (LVVs). Furthermore, we found OB to relate to left-to-right ventricular and occipital lobe volume (OLV) ratios. Those with OB also had reduced left-to-right hippocampal volume ratios. The results suggest that OB is more common among BD patients than healthy subjects, and prevalent in both BD Type I and Type II patients. We posit that anomalies in neural pruning or ventricular enlargement may precipitate OB, consequently resulting in one occipital lobe twisting around the other. Although the clinical implications of these results are unclear, the study suggests that asymmetrical ventricular volume matched with a pattern of oppositely asymmetrical occipital volume is related to OB and may be a marker of psychiatric illness. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  17. Effects of tanalith-e impregnation substance on bending strengths and modulus of elasticity in bending of some wood types

    Directory of Open Access Journals (Sweden)

    Hakan Keskin

    2016-04-01

    Full Text Available The aim of this study was to investigate the effects of impregnation with Tanalith-E on the bending strengths and modulus of elasticity in bending of some wood types. The test samples prepared from beech, oak, walnut, poplar, ash and pine wood materials - that are of common use in the forest products industry of TURKEY - according to TS 345, were treated with according to ASTM D 1413-76 substantially. Un-impregnated samples according to impregnated wood materials, the bending strengths in beech to 6.83%, 5.12% in ash, 5.93% in pine, the elasticity module values to 7.15% in oak and ash, at a rate of 6.58% in the higher were found. The highest values of bending strengths and modulus of elasticity in bending were obtained in beech and ash woods impregnated with Tanalith-E, whereas the lowest values were obtained in the poplar wood.

  18. Probabilistic Fatigue Damage Program (FATIG)

    Science.gov (United States)

    Michalopoulos, Constantine

    2012-01-01

    FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes. This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user. It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

  19. Improve the material absorption of light and enhance the laser tube bending process utilizing laser softening heat treatment

    Science.gov (United States)

    Imhan, Khalil Ibraheem; Baharudin, B. T. H. T.; Zakaria, Azmi; Ismail, Mohd Idris Shah B.; Alsabti, Naseer Mahdi Hadi; Ahmad, Ahmad Kamal

    2018-02-01

    Laser forming is a flexible control process that has a wide spectrum of applications; particularly, laser tube bending. It offers the perfect solution for many industrial fields, such as aerospace, engines, heat exchangers, and air conditioners. A high power pulsed Nd-YAG laser with a maximum average power of 300 W emitting at 1064 nm and fiber-coupled is used to irradiate stainless steel 304 (SS304) tubes of 12.7 mm diameter, 0.6 mm thickness and 70 mm length. Moreover, a motorized rotation stage with a computer controller is employed to hold and rotate the tube. In this paper, an experimental investigation is carried out to improve the laser tube bending process by enhancing the absorption coefficient of the material and the mechanical formability using laser softening heat treatment. The material surface is coated with an oxidization layer; hence, the material absorption of laser light is increased and the temperature rapidly rises. The processing speed is enhanced and the output bending angle is increased to 1.9° with an increment of 70% after the laser softening heat treatment.

  20. Development of a Very High Cycle Fatigue (VHCF multiaxial testing device

    Directory of Open Access Journals (Sweden)

    M. Vieira

    2016-07-01

    Full Text Available The very high cycle region of the S-N fatigue curve has been the subject of intensive research on the last years, with special focus on axial, bending, torsional and fretting fatigue tests. Very high cycle fatigue can be achieved using ultrasonic exciters which allow for frequency testing of up to 30 kHz. Still, the multiaxial fatigue analysis is not yet developed for this type of fatigue analyses, mainly due to conceptual limitations of these testing devices. In this paper, a device designed to produce biaxial fatigue testing using a single piezoelectric axial exciter is presented, as well as the preliminary testing of this device. The device is comprised of a horn and a specimen, which are both attached to the piezoelectric exciter. The steps taken towards the final geometry of the device are presented. Preliminary experimental testing of the developed device is made using thermographic imaging, strain measurements and vibration speeds and indicates good behaviour of the tested specimen.

  1. Experimental evaluation of torsional fatigue strength of welded bellows and application to design of fusion device

    International Nuclear Information System (INIS)

    Takatsu, Hideyuki; Yamamoto, Masahiro; Shimizu, Masatsugu; Suzuki, Kazuo; Sonobe, Tadashi; Hayashi, Yuzo; Mizuno, Gen-ichiro.

    1984-01-01

    Torsional fatigue strength of the welded bellows was evaluated experimentally, aiming the application to a port of a fusion device. The welded bellows revealed elastic torsional buckling and spiral distorsion even under a small angle of torsion. Twisting load never leads the welded bellows to fracture easily so far as the angle of torsion is not excessively large, and the welded bellows has the torsional fatigue strength much larger than that expected so far. Two formulae were proposed to evaluate the stress of the welded bellows under the forced angle of torsion; shearing stress evaluation formula in the case that torsional buckling does not occur and the axial bending stress evaluation formula in the case that torsional buckling occurs. And the results of the torsional fatigue experiments showed that the former is reasonably conservative and simulates the actual behavior of the welded bellows better than the latter in the high cycle fatigue region and vice versa in the low cycle fatigue region from the viewpoint of the mechanical design. The present evaluation method of the torsional fatigue strength was applied to the welded bellows for the port of the JT-60 vacuum vessel and its structural integrity was confirmed under the design load condition. (author)

  2. Fatigue damage behavior of a surface-mount electronic package under different cyclic applied loads

    Science.gov (United States)

    Ren, Huai-Hui; Wang, Xi-Shu

    2014-04-01

    This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fatigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are based on experimental investigations using scanning electron microscopy (SEM) in-situ technology and nonlinear finite element modeling, respectively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.

  3. Shrinkages in heavy-sized cast components of nodular cast iron – NDT and fatigue

    Directory of Open Access Journals (Sweden)

    Bleicher Christoph

    2014-06-01

    Full Text Available Material defects like shrinkages, dross, pores and chunky graphite are likely to occur in thick-walled castings and are a challenge for the foundries and their customers. These defects are mostly detected with handheld ultrasonic testing (UT or X-ray analysis. Within a research project done at the Fraunhofer Institute for Structural Durability and System Reliability LBF, the fatigue of Dross, shrinkages and chunky graphite in thick-walled cast material GGG-40 was estimated based on X-ray and fatigue tests on bending specimens. High fatigue reductions were received for the different material imperfections. Based on these impressions a further research project was executed at the Fraunhofer LBF to get an estimation of the informational value of UT in relation to fatigue of shrinkages in thick-walled castings of the material EN-GJS-400-18U-LT, EN-GJS-450-18 and EN-GJS-700-2. With the help of X-ray analysis and the UT technique Sampling Phased Array (SPA information about geometry and density were derived for a numerical analysis of shrinkages in thick-walled castings concerning fatigue. The following text summarizes the fatigue results achieved in the two research projects with the help of the X-ray and UT analysis.

  4. Experimental study on fatigue crack propagation rate of RC beam strengthened with carbon fiber laminate

    Science.gov (United States)

    Huang, Peiyan; Liu, Guangwan; Guo, Xinyan; Huang, Man

    2008-11-01

    The experimental research on fatigue crack propagation rate of reinforced concrete (RC) beams strengthened with carbon fiber laminate (CFL) is carried out by MTS system in this paper. The experimental results show that, the main crack propagation on strengthened beam can be summarized into three phases: 1) fast propagation phase; 2) steady propagation and rest phase; 3) unsteady propagation phase. The phase 2-i.e. steady propagation and rest stage makes up about 95% of fatigue life of the strengthened beam. The propagation rate of the main crack, da/dN, in phase 2 can be described by Paris formula, and the constant C and m can be confirmed by the fatigue crack propagation experiments of the RC beams strengthened with CFL under three-point bending loads.

  5. Estimation of fatigue strength enhancement for carburized and shot-peened gears

    Science.gov (United States)

    Inoue, Katsumi; Kato, Masana

    1994-05-01

    An experimental formula has been proposed to estimate the bending fatigue strength of carburized gears from the hardness and the residual stress. The derivation of the formula is briefly reviewed, and the effectiveness of the formula is demonstrated in this article. The comparison with many test results for carburized and shot-peened gears verifies that the formula is effective for the approximate estimation of the fatigue strength. The formula quantitatively shows a way of enhancing fatigue strength, i.e., the increase of hardness and residual stress at the fillet. The strength is enhanced about 300 MPa by an appropriate shot peening, and it can be improved still more by the surface removal by electropolishing.

  6. Development of piezoelectric ceramics driven fatigue testing machine for small specimens

    International Nuclear Information System (INIS)

    Saito, S.; Kikuchi, K.; Onishi, Y.; Nishino, T.

    2002-01-01

    A new fatigue testing machine with piezoelectric ceramics actuators was developed and a prototype was manufactured for high-cycle fatigue tests with small specimens. The machine has a simple mechanism and is compact. These features make it easy to set up and to maintain the machine in a hot cell. The excitation of the actuator can be transmitted to the specimen using a lever-type testing jig. More than 100 μm of displacement could be prescribed precisely to the specimen at a frequency of 50 Hz. This was sufficient performance for high-cycle bend fatigue tests on specimens irradiated at the SINQ target in Paul Scherrer Institute. The relationship of a displacement applied to the specimen and the strain of the necking part were obtained by experimental methods and by finite element method (FEM) calculations. Both results showed good agreement. This fact makes it possible to evaluate the strain of irradiated specimens by FEM simulations

  7. Crack growth and fracture in fiber reinforced concrete beams under static and fatigue loading

    International Nuclear Information System (INIS)

    Jeanfreau, J.; Arockiasamy, M.; Reddy, D.V.

    1987-01-01

    The paper presents the results of a two-phase experimental investigation on the fatigue and fracture of six different types of concrete: plain, 0.5%, 1.0%, 1.5%, and 2.0% steel fibers and 0.5% kevlar fibers. In the first phase the J-integral was evaluated for different types of concrete from load-displacement curves. The value shows a marked increase in the energy required to fracture concrete when fibers are added. The values did not vary substantially for different notch depths. In the second phase concrete beams were subjected to fatigue by applying a pure bending on the notch. The effect of fiber addition was examined with emphasis on the crack propagation and the increase in the fatigue strength. The crack pattern was mainly influenced by the presence, amount, and the distribution of the fibers in the concrete. (orig./HP)

  8. A study on the effects of artifacts on fatigue limit of ductile cast iron with ferritic structure

    International Nuclear Information System (INIS)

    Kim, Jin Hak; Kim, Min Gun

    2000-01-01

    In this study, fatigue tests were performed to examine the effects of micro drill hole on fatigue limit of as cast and Austempered Ductile cast Iron (ADI) using the rotary bending fatigue tester. As results, micro drill holes (diameter≤0.4mm) did not influence the fatigue limit of ADI, compared to annealed ductile cast iron; the critical defect size of crack initiation, in ADI was larger than as cast. If the √areas of micro drill hole and graphite nodule in ADI are comparable, crack initiates at the graphite nodule. When the ruggedness develops through austempering treatment process, microstructure on crack initiation at micro drill hole is tougher than that of as cast ductile cast iron

  9. The influence of end constraints on smooth pipe bends

    International Nuclear Information System (INIS)

    Thomson, G.; Spence, J.

    1981-01-01

    With present trends in the power industries towards higher operating temperatures and pressures, problems associated with the design and safety assessment of pipework systems have become increasingly complex. Within such systems, the importance of smooth pipe bends is well established. The work which will be presented will attempt to clarify the situation and unify the results. An analytical solution of the problem of a linear elastic smooth pipe bend with end constraints under in-plane bending will be presented. The analysis will deal with constraints in the form of flanged tangents of any length. The analysis employs the theorem of minimum total potential energy with suitable kinematically admissible displacements in the form of Fourier series. The integrations and minimisation were performed numerically, thereby permitting the removal of several of the assumptions made by previous authors. Typical results for flexibilities will be given along with comparisons with other works. The differences in some earlier theory are clarified and other more recent work using different solution techniques is substantiated. The bend behaviour is shown to be strongly influenced by the pipe bend parameter, the bend angle, the tangent pipe length and the bend/cross-sectional radius ratio. (orig./GL)

  10. Bending-Tolerant Anodes for Lithium-Metal Batteries.

    Science.gov (United States)

    Wang, Aoxuan; Tang, Shan; Kong, Debin; Liu, Shan; Chiou, Kevin; Zhi, Linjie; Huang, Jiaxing; Xia, Yong-Yao; Luo, Jiayan

    2018-01-01

    Bendable energy-storage systems with high energy density are demanded for conformal electronics. Lithium-metal batteries including lithium-sulfur and lithium-oxygen cells have much higher theoretical energy density than lithium-ion batteries. Reckoned as the ideal anode, however, Li has many challenges when directly used, especially its tendency to form dendrite. Under bending conditions, the Li-dendrite growth can be further aggravated due to bending-induced local plastic deformation and Li-filaments pulverization. Here, the Li-metal anodes are made bending tolerant by integrating Li into bendable scaffolds such as reduced graphene oxide (r-GO) films. In the composites, the bending stress is largely dissipated by the scaffolds. The scaffolds have increased available surface for homogeneous Li plating and minimize volume fluctuation of Li electrodes during cycling. Significantly improved cycling performance under bending conditions is achieved. With the bending-tolerant r-GO/Li-metal anode, bendable lithium-sulfur and lithium-oxygen batteries with long cycling stability are realized. A bendable integrated solar cell-battery system charged by light with stable output and a series connected bendable battery pack with higher voltage is also demonstrated. It is anticipated that this bending-tolerant anode can be combined with further electrolytes and cathodes to develop new bendable energy systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Tingkat Kelelahan Pengemudi Bus Rapid Transport (BRT Jakarta Berdasarkan Swedish Occupational Fatigue Index (SOFI

    Directory of Open Access Journals (Sweden)

    Rida Zuraida

    2015-06-01

    Full Text Available Fatigue is a common situation experienced by everyone, but until now a simple measuring tools universally accepted is not exist. Fatigue measurement instrument most widely used is an instrument-based questionnaire. This study used the Swedish Occupational Fatigue Index (SOFI as one of the instrument to measure BRT driver’s fatigue. The aim is to evaluate physical mental, and shift work fatigue and provide an overview of fatigue levels experienced by the driver BRT on two different shifts. Hopefully it can be used for driver fatigue management by a company. The study was conducted for two different shifts (morning and afternoon, with a total participants are 30 drivers. Results showed that motivation level of shift 2-driver is lower after they finish their work compared to shift1-driver. In shift 1, generally available time to rest,socializing and hanging out with family is longer than available time for shift 2-driver. Perception of loss of energy after work is also higher in shift 2 compared to shift 1, especially the perception of feeling exhausted. Similar results were obtained in the physical aspect and the physical exertion and physical discomfort. Therefore we can conclude the work shift has affected fatigue level experienced by the driver's BRT, and shift rotation is suggested to help the driver to recuperate.

  12. Parameterization of rotational spectra

    International Nuclear Information System (INIS)

    Zhou Chunmei; Liu Tong

    1992-01-01

    The rotational spectra of the strongly deformed nuclei with low rotational frequencies and weak band mixture are analyzed. The strongly deformed nuclei are commonly encountered in the rare-earth region (e. g., 150 220). A lot of rotational band knowledge are presented

  13. Rotating reactors : a review

    NARCIS (Netherlands)

    Visscher, F.; Schaaf, van der J.; Nijhuis, T.A.; Schouten, J.C.

    2013-01-01

    This review-perspective paper describes the current state-of-the-art in the field of rotating reactors. The paper has a focus on rotating reactor technology with applications at lab scale, pilot scale and industrial scale. Rotating reactors are classified and discussed according to their geometry:

  14. Fatigue Life of High-Strength Steel Offshore Tubular Joints

    DEFF Research Database (Denmark)

    Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

    1996-01-01

    In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength......In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high......-strength steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... from Ø 324-610 mm tubes, and the joints were loaded in in-plane bending. Both fatigue tests under constant amplitude loading and tests with a stochastic loading that is realistic in relation to offshore structures, are included in the investigation.A comparison between constant amplitude and variable...

  15. Preparation and Fatigue Properties of Functionally Graded Cemented Carbides

    International Nuclear Information System (INIS)

    Liu Yong; Liu Fengxiao; Liaw, Peter K.; He Yuehui

    2008-01-01

    Cemented carbides with a functionally graded structure have significantly improved mechanical properties and lifetimes in cutting, drilling and molding. In this work, WC-6 wt.% Co cemented carbides with three-layer graded structure (surface layer rich in WC, mid layer rich in Co and the inner part of the average composition) were prepared by carburizing pre-sintered η-phase-containing cemented carbides. The three-point bending fatigue tests based on the total-life approach were conducted on both WC-6wt%Co functionally graded cemented carbides (FGCC) and conventional WC-6wt%Co cemented carbides. The functionally graded cemented carbide shows a slightly higher fatigue limit (∼100 MPa) than the conventional ones under the present testing conditions. However, the fatigue crack nucleation behavior of FGCC is different from that of the conventional ones. The crack nucleates preferentially along the Co-gradient and perpendicular to the tension surface in FGCC, while parallel to the tension surface in conventional cemented carbides

  16. Fatigue life prediction of oil ducts under service loads

    Energy Technology Data Exchange (ETDEWEB)

    Meggiolaro, Marco A.; Castro, Jaime T.P. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)

    2003-07-01

    A methodology to calculate the residual initiation and propagation lives of fatigue cracks in oil pipelines with corrosion-like defects is proposed and applied to predict the residual life of an old duct made of API 5L Gr. B steel, in service for more than 40 years. Since its inauguration, this pipeline has carried several heated products under variable temperatures and pressures. The calculated (nominal) service stresses are very high, due to thermal loads that induce significant bending in curved parts of the duct, with peaks close to the yield strength of the steel. The elastic- plastic fatigue damage at a notch or a corrosion pit root is calculated using the {epsilon}N method, and the effects of surface semi-elliptical cracks in its internal (or external) wall is studied considering appropriate stress intensity factor expressions and the actual service loads. In the presence of surface flaws associated to stress concentration factors of the order of three, a fatigue crack likely will initiate in the pipeline. However, if these surface cracks are small compared to the duct wall thickness, their predicted propagation rates are very low. (author)

  17. Piezo films with adjustable anisotropic strain for bending actuators with tunable bending profiles

    International Nuclear Information System (INIS)

    Wapler, Matthias C; Stürmer, Moritz; Brunne, Jens; Wallrabe, Ulrike

    2014-01-01

    We present a method to produce in-plane polarized piezo films with a freely adjustable ratio of the strains in orthogonal in-plane directions. They can be used in piezo bending actuators with a tunable curvature profile. The strains are obtained as mean strains from a periodic polarization pattern produced by a suitable doubly interdigitated electrode structure. This mechanism is demonstrated for several examples using PZT sheets. We further discuss how this tuning and the parameters of the electrode layout affect the overall magnitude of the displacement. (paper)

  18. Numerical simulation of laser bending of AISI 304 plate with a ...

    African Journals Online (AJOL)

    Keywords: laser bending; process modeling; bending angle; response surface models. ... (Shi et al., 2007) presented numerical simulation of bending for with different shapes of laser ..... Matlab 2011a application code is used to develop and.

  19. Flow patterns and hydraulic losses in quasi-coil pipes : The effects of configuration of bend cross section, curvature ratio and bend angle

    OpenAIRE

    Shimizu, Yukimaru; Sugino, Koichi; Yasui, Masaji; Hayakawa, Yukitaka; Kuzuhara, Sadao

    1985-01-01

    Pipes with bend combinations are much used in the heat exchangers, since the curved path in the bends promotes the mixing in flow for active heat transfer. In the present paper, one of the pipes with bend combinations, namely, quasi-coiled pipes composed of many bend elements are investigated, and the relationships between the hydraulic loss and the secondary flow are studied experimentally. The configurations of the cross sections, the bent angles and the curvature ratios of the bend element...

  20. Monitoring fatigue loads on wind turbines using cycle counting data acquisition systems

    Energy Technology Data Exchange (ETDEWEB)

    Soeker, H; Seifert, H [Deutsches Windenergie-Institut (Germany); Fragoulis, A; Vionis, P; Foussekis, D [Center for Renewable Energy Sources (Greece); Dahlberg, J A; Poppen, M [The Aeronautical Research Institue of Sweden (Sweden)

    1996-09-01

    As in any industrial application, the duration of a wind turbine`s life is a key parameter for the evaluation of its economic potential. Assuming a service life of 20 years, components of the turbine have to withstand a number of load cycles of up to 10{sup 8}. Such numbers of load cycles impose high demands on the fatigue characteristics of both, the used materials and the design. Nevertheless, fatigue loading of wind turbine components still remains a parameter of high uncertainty in the design of wind turbines. The specific features of these fatigue loads can be expected to vary with the type of turbine and the site of operation. In order to ensure the reliability of the next generation of larger scale wind turbines improved load assumptions will be of vital importance. Within the scope of the presented research program DEWI, C.R.E.S. and FFA monitored fatigue loads of serial produced wind turbines by means of a monitoring method that uses on-line cycle counting techniques. The blade root bending moments of two pitch controlled, variable speed wind turbines operating in the Hamswehrum wind farm, and also that of a stall controlled, fixed speed wind turbine operating in CRES` complex terrain test site, were measured by DEWI and CRES. In parallel FFA used their database of time series measurements of blade root bending moments on a stall controlled, fixed speed turbine at Alsvik Windfarm in order to derive semi-empirical fatigue load data. The experience gained from application of the on-line measurement technique is discussed with respect to performance, data quality, reliability and cost effectiveness. Investigations on the effects of wind farm and complex terrain operation on the fatigue loads of wind turbine rotor blades are presented. (au)