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Sample records for notch fatigue strength

  1. Notch Fatigue Strength of a PM Disk Superalloy

    Science.gov (United States)

    Gayda, John; Gabb, Timothy P.; Telesman, Jack

    2007-01-01

    New powder metallurgy (PM) disk superalloys, such as ME3, LSHR, and Alloy 10, have been developed in recent years which enable rim temperatures in turbine disk applications to approach 1300 F. Before these alloys can be utilized at 1300 F their long term durability must be ensured. One of the key requirements for disk rims is notch fatigue strength. This issue is extremely important and is a direct result of the blade attachment geometry employed at the disk rim. Further, the imposition of a dwell at maximum load, associated with take off and landing, can also affect notch fatigue strength. For these reasons a study has been undertaken to assess the notch dwell fatigue strength of a modern PM disk alloy through spin pit evaluation of a prototypical disk. The first element of this program involves screening potential heat treatments with respect to notch fatigue strength at 1300 F utilizing a conventional notch fatigue specimen with a stress concentration factor (K(sub t)) of 2 and a 90 sec dwell at peak load. The results of this effort are reported in this paper including the downselect of an optimal heat treatment, from a notch fatigue standpoint.

  2. Multiaxial fatigue strength of severely notched titanium grade 5 alloy

    Directory of Open Access Journals (Sweden)

    F. Berto

    2015-07-01

    Full Text Available The multiaxial fatigue strength of severely notched titanium grade 5 alloy (Ti-6Al-4V is investigated. Experimental tests under combined tension and torsion loading, both in-phase and out-of-phase, have been carried out on axisymmetric V-notched specimens considering different nominal load ratios (R = -1, 0. All specimens are characterized by a notch tip radius less than 0.1 mm, a notch depth of 6 mm and a notch opening angle equal to 90 degrees. The experimental data from multiaxial tests are compared with those from pure tension and pure torsion tests on un-notched and notched specimens, carried out at load ratio ranging from R = -3 to R = 0.5. In total, more than 160 new fatigue data are examined, first in terms of nominal stress amplitudes referred to the net area and then in terms of the local strain energy density averaged over a control volume surrounding the V-notch tip. The dependence of the control radius on the loading mode is analysed showing a very different notch sensitivity for tension and torsion. For the titanium alloy Ti-6Al-4V, the control volume is found to be strongly dependent on the loading mode

  3. Notch sensitivity jeopardizes titanium locking plate fatigue strength.

    Science.gov (United States)

    Tseng, Wo-Jan; Chao, Ching-Kong; Wang, Chun-Chin; Lin, Jinn

    2016-12-01

    Notch sensitivity may compromise titanium-alloy plate fatigue strength. However, no studies providing head-to-head comparisons of stainless-steel or titanium-alloy locking plates exist. Custom-designed identically structured locking plates were made from stainless steel (F138 and F1314) or titanium alloy. Three screw-hole designs were compared: threaded screw-holes with angle edges (type I); threaded screw-holes with chamfered edges (type II); and non-threaded screw-holes with chamfered edges (type III). The plates' bending stiffness, bending strength, and fatigue life, were investigated. The stress concentration at the screw threads was assessed using finite element analyses (FEA). The titanium plates had higher bending strength than the F1314 and F138 plates (2.95:1.56:1) in static loading tests. For all metals, the type-III plate fatigue life was highest, followed by type-II and type-I. The type-III titanium plates had longer fatigue lives than their F138 counterparts, but the type-I and type-II titanium plates had significantly shorter fatigue lives. All F1314 plate types had longer fatigue lives than the type-III titanium plates. The FEA showed minimal stress difference (0.4%) between types II and III, but the stress for types II and III was lower (11.9% and 12.4%) than that for type I. The screw threads did not cause stress concentration in the locking plates in FEA, but may have jeopardized the fatigue strength, especially in the notch-sensitive titanium plates. Improvement to the locking plate design is necessary. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Notch fatigue behavior: Metallic glass versus ultra-high strength steel

    Science.gov (United States)

    Wang, X. D.; Qu, R. T.; Wu, S. J.; Duan, Q. Q.; Liu, Z. Q.; Zhu, Z. W.; Zhang, H. F.; Zhang, Z. F.

    2016-01-01

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities. PMID:27752136

  5. Notch fatigue behavior: Metallic glass versus ultra-high strength steel

    Science.gov (United States)

    Wang, X. D.; Qu, R. T.; Wu, S. J.; Duan, Q. Q.; Liu, Z. Q.; Zhu, Z. W.; Zhang, H. F.; Zhang, Z. F.

    2016-10-01

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities.

  6. Fatigue strength of Al7075 notched plates based on the local SED averaged over a control volume

    Science.gov (United States)

    Berto, Filippo; Lazzarin, Paolo

    2014-01-01

    When pointed V-notches weaken structural components, local stresses are singular and their intensities are expressed in terms of the notch stress intensity factors (NSIFs). These parameters have been widely used for fatigue assessments of welded structures under high cycle fatigue and sharp notches in plates made of brittle materials subjected to static loading. Fine meshes are required to capture the asymptotic stress distributions ahead of the notch tip and evaluate the relevant NSIFs. On the other hand, when the aim is to determine the local Strain Energy Density (SED) averaged in a control volume embracing the point of stress singularity, refined meshes are, not at all, necessary. The SED can be evaluated from nodal displacements and regular coarse meshes provide accurate values for the averaged local SED. In the present contribution, the link between the SED and the NSIFs is discussed by considering some typical welded joints and sharp V-notches. The procedure based on the SED has been also proofed to be useful for determining theoretical stress concentration factors of blunt notches and holes. In the second part of this work an application of the strain energy density to the fatigue assessment of Al7075 notched plates is presented. The experimental data are taken from the recent literature and refer to notched specimens subjected to different shot peening treatments aimed to increase the notch fatigue strength with respect to the parent material.

  7. Effect of Notch Location on Fatigue Life Prediction of Strength Mismatched HSLA Steel Weldments

    Institute of Scientific and Technical Information of China (English)

    S. Ravi; V. Balasubramanian; S. Nemat Nasser

    2004-01-01

    Welding of high strength low alloy steels (HSLA) involves usage of Iow, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM)joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0). A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.

  8. Notch strength of composites

    Science.gov (United States)

    Whitney, J. M.

    1983-01-01

    The notch strength of composites is discussed. The point stress and average stress criteria relate the notched strength of a laminate to the average strength of a relatively long tensile coupon. Tests of notched specimens in which microstrain gages have been placed at or near the edges of the holes have measured strains much larger that those measured in an unnotched tensile coupon. Orthotropic stress concentration analyses of failed notched laminates have also indicated that failure occurred at strains much larger than those experienced on tensile coupons with normal gage lengths. This suggests that the high strains at the edge of a hole can be related to the very short length of fiber subjected to these strains. Lockheed has attempted to correlate a series of tests of several laminates with holes ranging from 0.19 to 0.50 in. Although the average stress criterion correlated well with test results for hole sizes equal to or greater than 0.50 in., it over-estimated the laminate strength in the range of hole sizes from 0.19 to 0.38 in. It thus appears that a theory is needed that is based on the mechanics of failure and is more generally applicable to the range of hole sizes and the varieties of laminates found in aircraft construction.

  9. FATIGUE STRENGTH OF HIGH-STRENGTH STEEL,

    Science.gov (United States)

    coldhardened by deforming to 83%. It was found that it has low static notch sensitivity (lower than that of heat-treated steels), that static strength ...is raised appreciably by increased cold plastic deformation, and that its fatigue strength is raised substantially by mechanical polishing. (Author)

  10. On the Notch Effect in Low Temperature Carburized Stainless Steel under Fatigue

    Directory of Open Access Journals (Sweden)

    Minak G.

    2010-06-01

    Full Text Available The present paper describes the fatigue behaviour of carburized notched AISI 316 austenitic stainless steel specimens. Rotary four point bending fatigue tests have been performed using carburized smooth specimens with two different values of surface rugosity and notched specimen with two different stress concentration factors Kt, of 3.55 and 6.50 and the effects of carburizing on fatigue strength and notch sensitivity were discussed. Results show a general improvement of the fatigue life due to the treatment for all the series with an apparent notch sensitivity lower than one in the case of blunt notches due to secondary effects that were singled out.

  11. On the Notch Effect in Low Temperature Carburized Stainless Steel under Fatigue

    Science.gov (United States)

    Minak, G.

    2010-06-01

    The present paper describes the fatigue behaviour of carburized notched AISI 316 austenitic stainless steel specimens. Rotary four point bending fatigue tests have been performed using carburized smooth specimens with two different values of surface rugosity and notched specimen with two different stress concentration factors Kt, of 3.55 and 6.50 and the effects of carburizing on fatigue strength and notch sensitivity were discussed. Results show a general improvement of the fatigue life due to the treatment for all the series with an apparent notch sensitivity lower than one in the case of blunt notches due to secondary effects that were singled out.

  12. Experience with the Notch Stress Approach for Fatigue Assessment of Welded Joints

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters; Mouritsen, Ole Ø.; Hansen, Michael Rygaard

    2010-01-01

    In this paper, fatigue assessment using the notch stress approach is discussed based on re-analysis of many fatigue test results and experience from practical application. Three topics are treated; evaluation of the fatigue strength for as-welded details (FAT225) in the notch stress system......, problems regarding assessment of mild-SCF details and a novel proposal for extension of the notch stress approach for use with post-weld treated details....

  13. Fatigue life estimation for different notched specimens based on the volumetric approach

    Directory of Open Access Journals (Sweden)

    Esmaeili F.

    2010-06-01

    Full Text Available In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

  14. The Variability of Fatigue in Notched Bars of IN100 (Preprint)

    Science.gov (United States)

    2012-08-01

    conducted having nominally 40 m micro-notches machined using focused ion beam ( FIB ) in the geometric center of the two notches. These micro-notches... FIB crack starters in the notch and replicated to measure the small crack growth rates. This also allows a comparison of the small crack growth...ID JAI19045. 8) M. Aratani and J.F. Knott , “The Growth of Short Fatigue Cracks Ahead of a Notch in High Strength Steel,” Eng. Failure. Anal., 17

  15. Biaxial Fatigue Cracking from Notch

    Science.gov (United States)

    2013-03-04

    Leevers (reference 11) noticed that the variation in  from 0 to 2 has little effect on the da/dN in PVC ( polyvinyl - chloride ), but reduces the da/dN...under biaxial rotating and bending. Ahmad (reference 2) formulated a model for the biaxial fatigue crack growth in aggressive environment, outlined by...1962, Vol. 90, pp. 238-239. 20. ASM Handbook , Vol. 12 Fractography: 1992, p. 430, 438. 21. Metals Handbook , Vol. 9 Fractography and Atlas of

  16. Notched strength of beryllium powder and ingot sheets.

    Science.gov (United States)

    Moss, R. G.

    1972-01-01

    The effects of notches in thin beryllium sheets were studied as functions of material variables and notch severity. Double edge notched samples having stress concentration factors of 1.0 to 15.4 were prepared by milling to size, etching, and electrical discharge machining the notches. Strength was not reduced greatly by sharp notches, and duller notches were more deleterious than sharp notches. The trend was for reduced strength for dull notches, increased strength for sharper notches, and reduced strength for very sharp notches. Differences in material purity or source of the sheet had little affect on notch sensitivity. The most important factors appear to be oxide content and directionality of the sheet microstructure; high oxide content and highly directional microstructure tend to give more notch sensitivity than low oxide content, and more bidirectional microstructure. Postulated causes of the change in notched/unnotched strength are given.

  17. Influence of laser treatment on the fatigue of notched bar

    Institute of Scientific and Technical Information of China (English)

    ZhangHui; LingWeiye; JiangShouwei

    2003-01-01

    Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.

  18. Corrosion Fatigue Crack Growth Behavior at Notched Hole in 7075-T6 Under Biaxial and Uniaxial Fatigue with Different Phases

    Science.gov (United States)

    2015-09-17

    CORROSION FATIGUE CRACK GROWTH BEHAVIOR AT NOTCHED HOLE IN 7075-T6 UNDER BIAXIAL AND UNIAXIAL FATIGUE WITH DIFFERENT PHASES... CORROSION FATIGUE CRACK GROWTH BEHAVIOR AT NOTCHED HOLE IN 7075-T6 UNDER BIAXIAL AND UNIAXIAL FATIGUE WITH DIFFERENT PHASES THESIS...UNLIMITED AFIT-ENY-MS-15-S-065 CORROSION FATIGUE CRACK GROWTH BEHAVIOR AT NOTCHED HOLE IN 7075-T6 UNDER BIAXIAL AND UNIAXIAL FATIGUE WITH

  19. Some considerations about improvement for fatigue strength of structures; Shatai kozobutsu no hiro kyodo kojo ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Kimoto, H.; Toyama, K.; Maruyama, H.; Magara, S. [Press Kogyo Co. Ltd., Kanagawa (Japan)

    1997-10-01

    To reduce weight, higher tensile strength and/or thinner plate are used or considered in vehicle structures. In general, welded or notch sections, fatigue strength decreases because of increasing concentrated stress or effect of notch sensitivity and so on. In this paper, some methods are studied to improve fatigue strength and obtain a long life. 2 refs., 11 figs., 5 tabs.

  20. Holding time effect of pack carburizing on fatigue characteristic of v-notch shaft steel specimens

    Science.gov (United States)

    Supriyono, Jamasri

    2017-06-01

    The objective of this research is to study the effect of the holding times of pack carburizing process on fatigue characteristic of v-notch shaft steel specimens. The carbon source was taken from charcoal of unused mahogany. The holding times were 2, 3 and 4 hours. The fatigue tests were conducted on rotary bending machine. The specimens were made of low carbon steel of 0.17% carbon content. Pack carburizing was conducted to the specimens at 930°C. V-notch was made to present the stress concentration on the specimens. To see the effects of the carburizing in changing the material properties, the micro-structures and hardness tests along the cross sectional area of the specimens were carried out. The results showed that the holding time of the carburizing process influences the fatigue strength of the material. The longer the holding time will be the higher the fatigue strength. The increase of the fatigue strength is due to the carbon content on the surface. It was confirmed by the micro-structures and the hardness tests results. The cross sectional area of carburized material is divided into two zones i.e. surface zone and core zone. The surface zone consists of hypereutectoid, eutectoid, and hypo eutectoid sub-zone. The core zone is the same as raw material. The longer the holding time will be the deeper the surface zone.

  1. IIW guidelines on weld quality in relationship to fatigue strength

    CERN Document Server

    Jonsson, Bertil; Hobbacher, A F; Kassner, M; Marquis, G

    2016-01-01

    This book presents guidelines on quantitative and qualitative measures of the geometric features and imperfections of welds to ensure that it meets the fatigue strength requirements laid out in the recommendations of the IIW (International Institute of Welding). Welds that satisfy these quality criteria can be assessed in accordance with existing IIW recommendations based on nominal stress, structural stress, notch stress or linear fracture mechanics. Further, the book defines more restrictive acceptance criteria based on weld geometry features and imperfections with increased fatigue strength. Fatigue strength for these welds is defined as S-N curves expressed in terms of nominal applied stress or hot spot stress. Where appropriate, reference is made to existing quality systems for welds.In addition to the acceptance criteria and fatigue assessment curves, the book also provides guidance on their inspection and quality control. The successful implementation of these methods depends on adequate training for o...

  2. Fatigue Analysis of Notched Laminates: A Time-Efficient Macro-Mechanical Approach

    Science.gov (United States)

    Naghipour, P.; Pineda, E. J.; Bednarcyk, B. A.; Arnold, S. M.; Waas, A. M.

    2016-01-01

    A coupled transversely isotropic deformation and damage fatigue model is implemented within the finite element method and was utilized along with a static progressive damage model to predict the fatigue life, stiffness degradation as a function of number of cycles, and post-fatigue tension and compression response of notched, multidirectional laminates. Initially, the material parameters for the fatigue model were obtained utilizing micromechanics simulations and the provided [0], [90] and [plus or minus 45] experimental composite laminate S-N (stress-cycle) data. Within the fatigue damage model, the transverse and shear properties of the plies were degraded with an isotropic scalar damage variable. The damage in the longitudinal (fiber) ply direction was suppressed, and only the strength of the fiber was degraded as a function of fatigue cycles. A maximum strain criterion was used to capture the failure in each element, and once this criterion was satisfied, the longitudinal stiffness of the element was decreased by a factor of 10 (sup 4). The resulting, degraded properties were then used to calculate the new stress state. This procedure was repeated until final failure of the composite laminate was achieved or a specified number of cycles reached. For post-fatigue tension and compression behavior, four internal state variables were used to control the damage and failure. The predictive capability of the above-mentioned approach was assessed by performing blind predictions of the notched multidirectional IM7/977-3 composite laminates response under fatigue and post-fatigue tensile and compressive loading, followed by a recalibration phase. Although three different multidirectional laminates were analyzed in the course of this study, only detailed results (i.e., stiffness degradation and post-fatigue stress-train curves as well as damage evolution states for a single laminate ([30/60/90/minus 30/minus 60] (sub 2s)) are discussed in detail here.

  3. Prediction of multiaxial fatigue life for notched specimens of titanium alloy TC4

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. R.; Li, Z. X. [Southeast University, Nanjing (China); Hu, X. T.; Song, Y. D. [Nanjing University, Nanjing (China)

    2016-05-15

    Both the proportional and nonproportional multiaxial fatigue tests were conducted on two kinds of notched specimens of titanium alloy TC4. The multiaxial fatigue critical area of notched specimen is considered as the location experiencing the maximum damage. It is unsatisfactory to predict the multiaxial fatigue life with the local stress and strain in the fatigue critical area. The critical distance concepts are employed in the multiaxial life prediction method for notched specimens. The proposed method was checked by the test data of TC4 notched specimens. The prediction results are almost within a factor of three scatter band of the test results.

  4. Notch Corrosion Fatigue Behavior of Ti-6Al-4V

    Directory of Open Access Journals (Sweden)

    Sergio Baragetti

    2014-06-01

    Full Text Available The aim of this paper is to map the corrosion fatigue characteristics of Ti-6Al-4V alloy through the evaluation of the corrosion fatigue initiation and failure mechanisms. The study included the effect of the stress concentration factor at very high Kt values and the role of different inert or corrosive environments. This alloy is widely used in naval-structures and aero-engine communities and the outcomes of the work will have direct relevance to industrial service operations. Axial fatigue tests (R = 0.1; 2 × 105 cycles; f = 10 Hz were carried out on smooth and high notched (Ktmax = 18.65 flat specimens in laboratory air, paraffin oil, laboratory air + beeswax coating, recirculated 3.5% NaCl solution. The step loading procedure was used to perform the fatigue tests and the surface replica method and crack propagation gages were used to check crack nucleation and propagation until failure. Log-Log plots of σmax vs. Kt showed a bilinear behavior and enabled the demonstration of the presence of a threshold stress intensity factor (Kt = 8–9, after which the environment has no effect on the fatigue damage for all the tested environments.

  5. Notch Corrosion Fatigue Behavior of Ti-6Al-4V.

    Science.gov (United States)

    Baragetti, Sergio

    2014-06-11

    The aim of this paper is to map the corrosion fatigue characteristics of Ti-6Al-4V alloy through the evaluation of the corrosion fatigue initiation and failure mechanisms. The study included the effect of the stress concentration factor at very high Kt values and the role of different inert or corrosive environments. This alloy is widely used in naval-structures and aero-engine communities and the outcomes of the work will have direct relevance to industrial service operations. Axial fatigue tests (R = 0.1; 2 × 10⁵ cycles; f = 10 Hz) were carried out on smooth and high notched (Ktmax = 18.65) flat specimens in laboratory air, paraffin oil, laboratory air + beeswax coating, recirculated 3.5% NaCl solution. The step loading procedure was used to perform the fatigue tests and the surface replica method and crack propagation gages were used to check crack nucleation and propagation until failure. Log-Log plots of σmaxvs.Kt showed a bilinear behavior and enabled the demonstration of the presence of a threshold stress intensity factor (Kt = 8-9), after which the environment has no effect on the fatigue damage for all the tested environments.

  6. Local strain energy density to assess the multiaxial fatigue strength of titanium alloys

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-07-01

    Full Text Available The present paper investigates the multiaxial fatigue strength of sharp V-notched components made of titanium grade 5 alloy (Ti-6Al-4V. Axisymmetric notched specimens have been tested under combined tension and torsion fatigue loadings, both proportional and non-proportional, taking into account different nominal load ratios (R = -1 and 0. All tested samples have a notch root radius about equal to 0.1 mm, a notch depth of 6 mm and an opening angle of 90 degrees. The fatigue results obtained by applying multiaxial loadings are discussed together with those related to pure tension and pure torsion experimental fatigue tests, carried out on both smooth and notched specimens at load ratios R ranging between -3 and 0.5. Altogether, more than 250 fatigue results (19 S-N curves are examined, first on the basis of nominal stress amplitudes referred to the net area and secondly by means of the strain energy density averaged over a control volume embracing the V-notch tip. The effect of the loading mode on the control volume size has been analysed, highlighting a wide difference in the notch sensitivity of the considered material under tension and torsion loadings. Accordingly, the control radius of the considered titanium alloy (Ti-6Al-4V is found to be strongly affected by the loading mode.

  7. Averaged strain energy density-based synthesis of crack initiation life in notched steel bars under torsional fatigue

    Directory of Open Access Journals (Sweden)

    Filippo Berto

    2016-10-01

    Full Text Available The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the crack nucleation life was reduced with increasing stress concentration, on the other hand the crack propagation life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue crack propagation phase, such as sliding contact and/or friction between fracture surfaces, crack initiation life has been considered in the present work. In the original paper, initiation life was defined in correspondence of a 0.1÷0.4-mm-deep crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and cracked specimens at NA = 2 million loading cycles

  8. Matrix fatigue crack development in a notched continuous fiber SCS-6/Ti-15-3 composite

    Science.gov (United States)

    Hillberry, B. M.; Johnson, W. S.

    1990-01-01

    In this study the extensive matrix fatigue cracking that has been observed in notched SCS-6/Ti-15-3 composites is investigated. Away from the notch a uniform spacing of the fatigue cracks develops. Closer to the notch, fiber-matrix debonding which occurs increases the crack spacing. Crack spacing and debond length determined from shear-lag cylinder models compare favorably with experimental observations. Scanning electron microscope (SEM) fractography showed that the principal fatigue crack initiation occurred around the zero degree fibers. Interface failure in the 90 degree plies does not lead to the development of the primary fatigue cracking.

  9. 14 CFR 23.627 - Fatigue strength.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fatigue strength. 23.627 Section 23.627 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of...

  10. Fatigue Strength of Weathering Steel

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    Ludvík KUNZ

    2012-03-01

    Full Text Available Fatigue behaviour of Atmofix 52 steel (comparable to COR-TENâ steel exposed to atmospheric corrosion for 20 years was investigated. S-N curves for load symmetrical cycling and cycling with stress ratio R = 0 were determined on specimens detracted from a failed transmission tower. The data were compared with those on material without a rust layer. The fracture surfaces and, in particular, the sites of fatigue crack initiation were analyzed. Substantial decrease of fatigue life and fatigue limit due to corrosion exposition was found. Based on observation of surface layer with corrosion products and on fractographic analysis of failed specimens conclusions on fatigue damage mechanism were drawn. No grain boundary corrosion, which can be responsible for fatigue crack initiation, was observed. Initiation of fatigue cracks was related to surface roughness and took place exclusively on corrosion dimples.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1335

  11. Fatigue behaviour of high strength AA 7012 aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Di Russo, E.; Ragazzini, R.; Buratti, M.; Ferrarin, C. (Aluminia-ISML, Novara (Italy) Caproni Vizzola costruzioni aeronautiche, Somma Lombarda (Italy))

    1990-02-01

    The alloy 7012 (Al, 6.2% Zn, 2% Mg, 1% Cn, 0.13% Mn, 0.14% Zn, 0.04% Ti) belongs to the 7XXX family of high mechanical resistance alloys containing Zr as the principal additive. Produced in the form of extrusions, sheets and forgings, the alloy finds application in the defense, transportation and power industry fields. This paper presents the results of experimental fatigue tests (10/sup 7/ cycles) on 7020 in the T6 and T73 temper conditions and draws comparisons with corresponding test results on 7075 and 2024 type alloys. A comparative analysis of S-N curves obtained from plane bending and axial fatigue tests on smooth and notched specimens evidences the superior performance of 7020 in terms of higher strength and corrosion cracking resistance.

  12. Notch fatigue of ultrahigh molecular weight polyethylene (UHMWPE) used in total joint replacements.

    Science.gov (United States)

    Ansari, Farzana; Gludovatz, Bernd; Kozak, Adam; Ritchie, Robert O; Pruitt, Lisa A

    2016-07-01

    Ultrahigh molecular weight polyethylene (UHMWPE) has remained the primary polymer used in hip, knee and shoulder replacements for over 50 years. Recent case studies have demonstrated that catastrophic fatigue fracture of the polymer can severely limit device lifetime and are often associated with stress concentration (notches) integrated into the design. This study evaluates the influence of notch geometry on the fatigue of three formulations of UHMWPE that are in use today. A linear-elastic fracture mechanics approach is adopted to evaluate crack propagation as a function of notch root radius, heat treatment and Vitamin E additions. Specifically, a modified stress-intensity factor that accounts for notch geometry was utilized to model the crack driving force. The degree of notch plasticity for each material/notch combination was further evaluated using finite element methods. Experimental evaluation of crack speed as a function of stress intensity was conducted under cyclic tensile loading, taking crack length and notch plasticity into consideration. Results demonstrated that crack propagation in UHMWPE emanating from a notch was primarily affected by microstructural influences (cross-linking) rather than differences in notch geometry.

  13. Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys

    Science.gov (United States)

    Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

    2011-01-01

    The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

  14. Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach

    Directory of Open Access Journals (Sweden)

    Giovanni Meneghetti

    2017-07-01

    Full Text Available The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD technique. Based on the results obtained from the potential drop technique, the crack initiation life has been defined in correspondence of a relative potential drop increase V/V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the crack initiation life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests

  15. Microstructure-Sensitive Fatigue Design of Notched Components

    Science.gov (United States)

    2015-01-26

    Materials , World journal of mechanics (05 2013) TOTAL: 2 Books Number of Manuscripts: Patents Submitted Patents Awarded Awards Graduate Students...Received Book TOTAL: Received Book Chapter TOTAL: PERCENT_SUPPORTEDNAME FTE Equivalent: Total Number: Discipline Oluwamayowa Okeyoyin 1.00 Li Shi 1.00...complexity of realistic microstructures. Notch size effects and notch root inelastic behavior are combined with probability distributions of

  16. Effects of varying Notch1 signal strength on embryogenesis and vasculogenesis in compound mutant heterozygotes

    Directory of Open Access Journals (Sweden)

    Ge Changhui

    2010-03-01

    Full Text Available Abstract Background Identifying developmental processes regulated by Notch1 can be addressed in part by characterizing mice with graded levels of Notch1 signaling strength. Here we examine development in embryos expressing various combinations of Notch1 mutant alleles. Mice homozygous for the hypomorphic Notch112f allele, which removes the single O-fucose glycan in epidermal growth factor-like repeat 12 (EGF12 of the Notch1 ligand binding domain (lbd, exhibit reduced growth after weaning and defective T cell development. Mice homozygous for the inactive Notch1lbd allele express Notch1 missing an ~20 kDa internal segment including the canonical Notch1 ligand binding domain, and die at embryonic day ~E9.5. The embryonic and vascular phenotypes of compound heterozygous Notch112f/lbd embryos were compared with Notch1+/12f, Notch112f/12f, and Notch1lbd/lbd embryos. Embryonic stem (ES cells derived from these embryos were also examined in Notch signaling assays. While Notch1 signaling was stronger in Notch112f/lbd compound heterozygotes compared to Notch1lbd/lbd embryos and ES cells, Notch1 signaling was even stronger in embryos carrying Notch112f and a null Notch1 allele. Results Mouse embryos expressing the hypomorphic Notch112f allele, in combination with the inactive Notch1lbd allele which lacks the Notch1 ligand binding domain, died at ~E11.5-12.5. Notch112f/lbd ES cells signaled less well than Notch112f/12f ES cells but more strongly than Notch1lbd/lbd ES cells. However, vascular defects in Notch112f/lbd yolk sac were severe and similar to Notch1lbd/lbd yolk sac. By contrast, vascular disorganization was milder in Notch112f/lbd compared to Notch1lbd/lbd embryos. The expression of Notch1 target genes was low in Notch112f/lbd yolk sac and embryo head, whereas Vegf and Vegfr2 transcripts were increased. The severity of the compound heterozygous Notch112f/lbd yolk sac phenotype suggested that the allelic products may functionally interact. By

  17. Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

    Science.gov (United States)

    Telesman, J.; Gabb, T. P.; Yamada, Y.; Ghosn, L. J.; Jayaraman, N.

    2012-01-01

    A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

  18. Multiaxial fatigue assessment of welded joints using the notch stress approach

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters

    2016-01-01

    This paper presents an evaluation of the safety involved when performing fatigue assessment of multiaxially loaded welded joints. The notch stress approach according to the IIW is used together with 8 different multiaxial criteria, including equivalent stress-, interaction equation- and critical...

  19. The effects of pack carburizing using charcoal of unused mahogany on fatigue characteristic of v-notch shaft steel specimens

    Science.gov (United States)

    Supriyono, Jamasri

    2017-04-01

    The aim of this research is to study the fatigue characteristic of v-notch shaft steel specimens before and after pack carburizing. The carbon source is taken from charcoal of unused mahogany. The fatigue test is conducted on rotary bending machine. The specimens are made of low carbon steel of 0.17% carbon content. Pack carburizing is conducted to the specimens at 930°C. V-notch is made to present the stress concentration factor on the specimens. To see the effects of the carburizing in changing the material properties, micro-structures before and after carburizingare looked and micro hardness measurements along the cross sectional area are carried out. The results show that the carburizing process increases fatigue strength of the material. The micro-structures of the raw material are ferrite and pearlite. The carburized material is divided into two zones i.e. surface zone and core zone. The surface zone consists of hypereutectoid, eutectoid, and hypoeutectoid sub-zone. The core zone is the same as raw material

  20. Effect of vibration loading on the fatigue life of part-through notched pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Rahul [Nuclear Power Corporation of India Limited, Mumbai (India); Singh, P.K., E-mail: singh_pawank@yahoo.com [Bhabha Atomic Research Centre, Mumbai (India); Pukazhendi, D.M. [Structural Engineering research Centre, Chennai (India); Bhasin, V.; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Mumbai (India)

    2011-10-15

    A systematic experimental and analytical study has been carried out to investigate the effect of vibration loading on the fatigue life of the piping components. Three Point bend (TPB) specimens machined from the actual pipe have been used for the evaluation of Paris constants by carrying out the experiments under vibration + cyclic and cyclic loading as per the ASTM Standard E647. These constants have been used for the prediction of the fatigue life of the pipe having part-through notch of a/t = 0.25 and aspect ratio (2c/a) of 10. Predicted results have shown the reduction in fatigue life of the notched pipe subjected to vibration + cyclic loading by 50% compared to that of cyclic loading. Predicted results have been validated by carrying out the full-scale pipe (with part-through notch) tests. Notched pipes were subjected to loading conditions such that the initial stress-intensity factor remains same as that of TPB specimen. Experimental results of the full-scale pipe tests under vibration + cyclic loading has shown the reduction in fatigue life by 70% compared to that of cyclic loading. Fractographic examination of the fracture surface of the tested specimens subjected to vibration + cyclic loading have shown higher presence of brittle phases such as martensite (in the form of isolated planar facets) and secondary micro cracks. This could be the reason for the reduction of fatigue life in pipe subjected to vibration + cyclic loading. - Highlights: > Vibration loading affects fatigue crack growth rate. > Crack initiation life depends on crack tip radius. > Crack initiation life depends on the characteristic distance. > Characteristic distance depends on the loading conditions. > Vibration + cyclic load gives lower fatigue life.

  1. Fatigue strength tests of layered steel

    Directory of Open Access Journals (Sweden)

    Michal Černý

    2013-01-01

    Full Text Available The work deals with original measurement of fatigue properties of formed layered steel material – damask steel. This is a material that exhibits a fine micro-structure as well as a regular composition of many material layers with complementary properties. The article experimentally verifies high-cycle fatigue properties of layered steel and evaluates them from the point of view of fatigue tests of conventional steel materials and a parallel application of a non-destructive – acoustic emission – testing. Finally, it discusses the influence of production on fatigue strength and the possibilities of using multi-layered steel materials in technological practice. A serious result of this pilot experiment is the fact documented no only by the fractographic observation, but mainly by the AE records that the fatigue service life of this material is high if it its not stressed by tension approximating the yield point Re. However, such stress is not common in practical use of tools made of damask steel and thus under common bending stress an exceptionally long service life of tools made of this type of material is demonstrable. The fact that damask steel behaves like a homogeneous material is mainly confirmed by the records of the AE signal at lower values of stress σa. When stressed by higher amplitudes of tension σa damask responds in AE records similarly to a laminate material that is stressed by bending.

  2. Biaxial fatigue tests of notched specimens for AISI 304L stainless steel

    Directory of Open Access Journals (Sweden)

    G. Beretta

    2016-07-01

    Full Text Available High cycle fatigue tests were conducted for stainless steel AISI 304L. The geometry was a thin walled tube with a passing through hole. The tests were axial, torsional and in-phase axial-torsional, all of them under load control with R = −1. The S-N curves were constructed following the ASTM E739 standard and the fatigues limits were calculated following the method of maximum likelihood proposed by Bettinelli. The crack direction along the surface was analysed, with especial attention to the crack initiation zones. The notch fatigue limits for different hole diameters were compared with the predictions done with a microstructural fracture mechanics model.

  3. An elasto-plastic approach to estimate lifetime of notched components under variable amplitude fatigue loading: a preliminary investigation

    Directory of Open Access Journals (Sweden)

    N. Zuhair Faruq

    2016-07-01

    Full Text Available The present paper is concerned with the formulation of an elasto-plastic strain based approach suitable for assessing fatigue strength of notched components subjected to in-service variable amplitude cyclic loading. The hypothesis is formed that the crack initiation plane is closely aligned with the plane of maximum shear strain amplitude, its orientation and the associated stress/strain quantities being determined using the Maximum Variance Method. Fatigue damage is estimated by applying the Modified Manson-Coffin Curve Method (MMCCM along with the Point Method (PM. In the proposed approach, the required critical distance is treated as a material property whose value is not affected either by the sharpness of the notch being assessed or by the profile of the load spectrum being applied. The detrimental effect of non-zero mean stresses and degree of multiaxiality of the local stress/strain histories is also considered. The accuracy and reliability of the proposed design methodology was checked against several experimental data taken from the literature and generated under different uniaxial variable amplitude load histories. In order to determine the required local stress/strain states, refined elasto-plastic finite element models were solved using commercial software ANSYS®. This preliminary validation exercise allowed us to prove that the proposed approach is capable of estimates laying within an error factor of about 2. These preliminary results are certainly promising, strongly supporting the idea that the proposed design strategy can successfully be used to assess the fatigue lifetime of notched metallic components subjected to in-service multiaxial variable amplitude loading sequences.

  4. A unifying approach to fatigue design in presence of defects and notches subject to uniaxial loading

    Directory of Open Access Journals (Sweden)

    Atzori Bruno

    2014-06-01

    Full Text Available In the recent past, Atzori and Lazzarin proposed a diagram able to include the geometrical effects on the fatigue limit of defects, short cracks, long cracks and U-shaped notches of whatever severity. The diagram shows that defect sensitivity and notch sensitivity can be considered as two sides of the same medal, thus creating a bridging between Linear Elastic Fracture Mechanics and Notch Mechanics. The fundamental material parameter, dependent on the load ratio, necessary to define the diagram is the El Haddad-Smith-Topper length parameter a0 defined by the plain material fatigue limit and the threshold value of the mode I stress intensity factor for long cracks. It is worth noting that a0 does not contain any geometry-related parameter. The diagram has been validated in the past against a number of experimental results and has been subsequently extended to sharp and blunt V-shaped notches, dependent on their absolute dimensions. After summarising the theory supporting the approach, some application examples relevant to both defect and notch sensitivity will be given

  5. Notched Strength Allowables and Inplane Shear Strength of AS4/VRM-34 Textile Laminates

    Science.gov (United States)

    Grenoble, Ray W.; Johnston, William M.

    2013-01-01

    Notched and unnotched strength allowables were developed for a textile composite to provide input data to analytical structural models based on the Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS) concept. Filled-hole tensile strength, filled-hole compressive strength, and inplane shear strength along stitch lines have been measured. The material system evaluated in this study is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. All specimens were tested in as-fabricated (dry) condition. Filled-hole strengths were evaluated with and without through-thickness stitching. The effects of scaling on filled-hole tensile strength were evaluated by testing specimens in two widths, but with identical width / hole-diameter ratios. Inplane shear specimens were stitched in two configurations, and two specimen thicknesses were tested for each stitch configuration.

  6. Effect of V Notch Shape on Fatigue Life in Steel Beam Made of AISI 1037

    Directory of Open Access Journals (Sweden)

    Qasim Bader

    2014-04-01

    Full Text Available The present work encompasses effect of V notch shape with various geometries and dimensions on fatigue life behavior in steel beam made of Medium Carbon Steel AISI 1037 which has a wide application in industry. Fatigue life of notched specimens is calculated using the fatigue life obtained from the experiments for smooth specimens (reference and by use Numerical method (FEA.The fatigue experiments were carried out at room temperature, applying a fully reversed cyclic load with the frequency of (50Hz and mean stress equal to zero (R= -1, on a cantilever rotating-bending fatigue testing machine. The stress ratio was kept constant throughout the experiment. Different instruments have been used in this investigation like Chemical composition analyzer type (Spectromax ,Tensile universal testing machine type (WDW-100E ,Hardness tester type (HSV- 1000 , Fatigue testing machine model Gunt WP 140, Optical Light Microscope (OLM and Scanning Electron Microscope (SEM were employed to examine the fracture features . The results show that there is acceptable error between experimental and numerical works .

  7. Re-analysis of fatigue data for welded joints using the notch stress approach

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters; Mouritsen, Ole Ø.; Hansen, Michael Rygaard

    2010-01-01

    Experimental fatigue data for welded joints have been collected and subjected to re-analysis using the notch stress approach according to IIW recommendations. This leads to an overview regarding the reliability of the approach, based on a large number of results (767 specimens). Evidently......-welded joints agree quite well with the FAT 225 curve; however a reduction to FAT 200 is suggested in order to achieve approximately the same safety as observed in the nominal stress approach....

  8. Effect of Notches on Creep-Fatigue Behavior of a P/M Nickel-Based Superalloy

    Science.gov (United States)

    Telesman, Jack; Gabb, Timothy P.; Ghosn, Louis J.; Gayda, John, Jr.

    2015-01-01

    A study was performed to determine and model the effect of high temperature dwells on notched low cycle fatigue (NLCF) and notch stress rupture behavior of a fine grain LSHR powder metallurgy (PM) nickel-based superalloy. It was shown that a 90 second dwell applied at the minimum stress (min dwell) was considerably more detrimental to the NLCF lives than similar dwell applied at the maximum stress (max dwell). The short min dwell NLCF lives were shown to be caused by growth of small oxide blisters which caused preferential cracking when coupled with high concentrated notch root stresses. The cyclic max dwell notch tests failed mostly by a creep accumulation, not by fatigue, with the crack origin shifting internally to a substantial distance away from the notch root. The classical von Mises plastic flow model was unable to match the experimental results while the hydrostatic stress profile generated using the Drucker-Prager plasticity flow model was consistent with the experimental findings. The max dwell NLCF and notch stress rupture tests exhibited substantial creep notch strengthening. The triaxial Bridgman effective stress parameter was able to account for the notch strengthening by collapsing the notched and uniform gage geometry test data into a singular grouping.

  9. Mechanical behaviors of notched composite laminates

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Presents the study on the mechanical behaviors of composite laminates with both static and fatigue tests per formed with different notched specimens and concludes with experimental results that ultimate strength and initial stiff ness of various notched composite laminates is almost as same as un-notched ones but the fatigue life of notched speci mens is much higher than un-notched ones. Compared with metals, composite materials are notch insensitive. The properties measured by using bar type specimens can not represent the real properties of composite laminates. Notches on the free edge may be helpful to the structure. The fatigue life can be predicted through theoretical models estab lished using the residual stiffness model.

  10. Residual Tensile Strength of Plain Concrete Under Tensile Fatigue Loading

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The functional relation between the residual tensile strength of plain concrete and number of cycles was determined. 99 tappered prism specimens of plain concrete were tested under uniaxial tensile fatigue loading. Based on the probability distribution of the residual tensile strength, the empirical expressions of the residual tensile strength corresponding to the number of cycles were obtained. The residual tensile strength attenuating curves can be used to predict the residual fatigue life of the specimen under variable-amplitude fatigue loading. There is a good correlation between residual tensile strength and residual secant elastic modulus.The relationship between the residual secant elastic modulus and number of cycles was also established.

  11. IIW recommendations for the HFMI treatment for improving the fatigue strength of welded joints

    CERN Document Server

    Marquis, Gary B

    2016-01-01

    This book of recommendations presents an overview of High Frequency Mechanical Impact (HFMI) techniques existing today in the market and their proper procedures, quality assurance measures and documentation. Due to differences in HFMI tools and the wide variety of potential applications, certain details of proper treatments and quantitative quality control measures are presented generally. An example of procedure specification as a quality assurance measure is given in the Appendix. Moreover, the book presents procedures for the fatigue life assessment of HFMI-improved welded joints based on nominal stress, structural hot spot stress and effective notch stress. It also considers the extra benefit that has been experimentally observed for HFMI-treated high-strength steels. The recommendations offer proposals on the effect of loading conditions like high mean stress fatigue cycles, variable amplitude loading and large amplitude/low cycle fatigue cycles. Special considerations for low stress concentration welded...

  12. Corrosion Fatigue of High-Strength Titanium Alloys Under Different Stress Gradients

    Science.gov (United States)

    Baragetti, Sergio; Villa, Francesco

    2015-05-01

    Ti-6Al-4V is the most widely used high strength-to-mass ratio titanium alloy for advanced engineering components. Its adoption in the aerospace, maritime, automotive, and biomedical sectors is encouraged when highly stressed components with severe fatigue loading are designed. The extents of its applications expose the alloy to several aggressive environments, which can compromise its brilliant mechanical characteristics, leading to potentially catastrophic failures. Ti-6Al-4V stress-corrosion cracking and corrosion-fatigue sensitivity has been known since the material testing for pressurized tanks for Apollo missions, although detailed investigations on the effects of harsh environment in terms of maximum stress reduction have been not carried out until recent times. In the current work, recent experimental results from the authors' research group are presented, quantifying the effects of aggressive environments on Ti-6Al-4V under fatigue loading in terms of maximum stress reduction. R = 0.1 axial fatigue results in laboratory air, 3.5 wt.% NaCl solution, and CH3OH methanol solution at different concentrations are obtained for mild notched specimens ( K t = 1.18) at 2e5 cycles. R = 0.1 tests are also conducted in laboratory air, inert environment, 3.5 wt.% NaCl solution for smooth, mild and sharp notched specimens, with K t ranging from 1 to 18.65, highlighting the environmental effects for the different load conditions induced by the specimen geometry.

  13. Concepts for estimating the fatigue strength of sintered steel components

    Directory of Open Access Journals (Sweden)

    Götz Sebastian

    2014-06-01

    Full Text Available The fatigue notch effect can be estimated using fracture mechanics-based support factors. Stress intensity factors for cracks in notches must therefore be calculated. There is a problem of transferability when 2D reference geometries are used for this. This can be avoided when modelling 3D cracks in the notch of the actual part to be assessed. This is more laborious, but leads to better results, which will be shown in this presentation. The questions of aspect ratio and to point on the crack front, where stresses are evaluated, will be discussed. The approach is validated using a broad database of different sintered steels. The statistical evaluation shows an almost exact prediction of the mean value with a relatively small scatter.

  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...... 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...... amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained...

  15. Indoor mobility-related fatigue and muscle strength in nonagenarians

    DEFF Research Database (Denmark)

    Mänty, Minna; Ekmann, Anette; Thinggaard, Mikael

    2014-01-01

    significantly (P muscle strength during the entire study period. Longitudinal analyses indicated slightly slower decline in muscle strength among participants with fatigue compared to those without; however, observed selective dropout of participants with fatigue and poor performance at baseline...... needs to be considered when interpreting the results. Accordingly, participants without fatigue had significantly higher chances of being alive and having muscle strength above gender-specific median at first (RR 1.32, 95 % CI 1.07-1.58), second (RR 1.51, 1.06-1.96) and third (RR 1.39, 1......BACKGROUND AND AIMS: Mobility-related fatigue is an important indicator of functional decline in old age, however, very little is known about fatigue in the oldest old population segment. The aim of this study was to examine the association between indoor mobility-related fatigue and muscle...

  16. Experimental Evaluation of Fatigue Crack Initiation from Corroded Hemispherical Notches in Aerospace Structural Materials

    Science.gov (United States)

    Garcia, Daniel B.; Forman, Royce; Shindo, David

    2010-01-01

    A test program was developed and executed to evaluate the influence of corroded hemispherical notches on the fatigue crack initiation and propagation in aluminum 7075-T7351, 4340 steel, and D6AC steel. Surface enhancements such as shot peening and laser shock peening were also incorporated as part of the test effort with the intent of improving fatigue performance. In addition to the testing, fracture mechanics and endurance limit based analysis methods were evaluated to characterize the results with the objective of challenging typical assumptions used in modeling fatigue cracks from corrosion pits. The results specifically demonstrate that the aluminum and steel alloys behave differently with respect to fatigue crack initiation from hemispherical corrosion pits. The aluminum test results were bounded by the fracture mechanics and endurance limit models while exhibiting a general insensitivity to the residual stress field generated by shot peening. The steel specimens were better characterized by the endurance limit fatigue properties and did exhibit sensitivities to residual stresses from the shot peening and laser shock peening

  17. Arterial Elasticity, Strength, Fatigue, and Endurance in Older Women

    Directory of Open Access Journals (Sweden)

    Gary R. Hunter

    2014-01-01

    Full Text Available Arterial health may influence muscle function in older adults. Study purpose was to determine whether arterial elasticity is related to strength, central and peripheral fatigue, fatigue at rest, and treadmill endurance. Subjects were 91 healthy women aged >60. Treadmill endurance and maximal oxygen uptake (VO2 max were measured. Peripheral and central fatigue for the knee extensors were evaluated using two isometric fatigue tests (one voluntary and one adding electrical stimulation. Arterial elasticity was determined using radial artery pulse wave analysis. Linear multiple regression was used in statistical analysis. Large artery elasticity was associated with central fatigue (P<0.01 and treadmill endurance (P<0.02 after adjusting for VO2 max and knee extension strength. Subjective fatigue at rest was related to large artery elasticity after adjusting for ethnic origin (<0.02. Strength was significantly related to small artery elasticity after adjusting for ethnic origin, leg lean tissue, age, and blood pressure. Arterial elasticity is independently related to strength and fatigue in older women, especially in the central nervous system where arterial elasticity is independently related to perceptions of fatigue at rest and central fatigue. These results suggest that arterial health may be involved with the ability of the central nervous system to activate muscle in older women.

  18. Notched multiaxial fatigue of Al7050-T7451: on the need for an equivalent process zone size

    Directory of Open Access Journals (Sweden)

    J.L.A Ferreira

    2017-07-01

    Full Text Available The aim of this work is to investigate stress gradient effects on the fatigue life estimation of notched Al 7050-T7451 specimens under combined torsion and push-pull loading conditions. Initially, simple push-pull and torsion fatigue tests in plain and notched specimens were independently conducted not only to obtain the material properties necessary to calibrate a standard multiaxial critical plane based model, but also to raise the critical distance versus life curves in tension (L  – Nf and in torsion (L  – Nf. This latter step also required a Finite Element Elastic Stress Analysis of the notched specimens tested in the medium high-cycle fatigue regime. Then, proportional multiaxial fatigue tests were carried out using this same notched geometry. The combination of a multiaxial model with the theory of critical distance (TCD was applied to estimate fatigue lives. For this aluminium alloy, neither the use of the L  – Nf nor L  – Nf combined with the predictive multiaxial model was able to estimate lives in an accurate way.

  19. AISI/DOE Technology Roadmap Program: Characterization of Fatigue and Crash Performance of New Generation High Strength Steels for Automotive Applications

    Energy Technology Data Exchange (ETDEWEB)

    Brenda Yan; Dennis Urban

    2003-04-21

    A 2-year project (2001-2002) to generate fatigue and high strain data for a new generation of high strength steels (HSS) has been completed in December 2002. The project tested eleven steel grades, including Dual Phase (DP) steels, Transformation-Induced Plasticity (TRIP) steels, Bake Hardenable (BH) steels, and conventional High Strength Low Alloy (HSLA) steels. All of these steels are of great interest in automotive industry due to the potential benefit in weight reduction, improved fuel economy, enhanced crash energy management and total system cost savings. Fatigue behavior includes strain controlled fatigue data notch sensitivity for high strength steels. High strain rate behavior includes stress-strain data for strain rates from 0.001/s to 1000/s, which are considered the important strain rate ranges for crash event. The steels were tested in two phases, seven were tested in Phase 1 and the remaining steels were tested in Phase. In a addition to the fatigue data and high st rain rate data generated for the steels studied in the project, analyses of the testing results revealed that Advanced High Strength Steels (AHSS) exhibit significantly higher fatigue strength and crash energy absorption capability than conventional HSS. TRIP steels exhibit exceptionally better fatigue strength than steels of similar tensile strength but different microstructure, for conditions both with or without notches present

  20. Notched Strength of Woven Fabric Kenaf Composite Plates with Different Stacking Sequences and Hole Sizes

    Directory of Open Access Journals (Sweden)

    Hans Romayne Anders

    2016-01-01

    Full Text Available Advantages of using kenaf fibres over synthetic fibres in composites manufacturing are relatively cheap, less abrasive and hazardous during handling, and renewable materials. Current work investigates parametric effects on notched strength of woven fabric kenaf polymer composites plates with variation of lay-up types, notch sizes and plate thickness. Testing coupons are prepared using hand lay-up technique and circular notch were drilled prior to mechanical testing. Stress concentration at the notch edge promotes micro-damage event as tensile loading was applied leading to crack initiation and propagations across the plate width. It is suggested that woven fabric kenaf polymer composites are potentially used in low and medium load bearing applications.

  1. 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...

  2. Fatigue life of high strength steel for cold forming

    Directory of Open Access Journals (Sweden)

    R. Ulewicz

    2017-01-01

    Full Text Available The article presents the results of fatigue tests carried out on STRENX-type high-strength cold forming steel. For high-cycle fatigue tests carried out using low cycle loading frequencies of around 30 Hz, a ROTOFLEX machine was used. For ultra high-cycle tests, a KAUP-ZU testing machine was employed, which enables fatigue tests to be performed with symetric specimen loading (R = -1 and at a frequency of f ≈ 20 kHz. The relationships σa = f(N were determined experimentally in the high and ultra high-cycle region for STRENX high-strength steel. To determine the fatigue crack initiation mechanism, the fractographic analysis of fatigue fractures was made.

  3. Fatigue Properties of Galvanized Higher-Strength Steel Sheets

    Directory of Open Access Journals (Sweden)

    Buršák, M.

    2007-01-01

    Full Text Available The paper analyzes the fatigues properties of galvanized microalloyed steel sheets H220LAD and H380LAD. Under flat bending conditions and the symmetrical cycle, the fatigue limit of the H220LAD sheet is σCo = ± 152 MPa and that of the H380LAD sheet is σCo = ±188 MPa, and the fatigue limit to tensile strength ratio is 0,41 and 0,37, respectively. During fatigue tests with an increasing number of cycles or an increasing stress value, the degradation of the zinc coating increases (relief formation, damage of integrity. As a result, local corrosion, but also continuation of fatigue damage after 107 cycles, and hence corrosion fatigue, can take place during operation.

  4. A comparison of conventional local approach and the short crack approach to fatigue crack initiation at a notch

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, Narayanaswami; Leroy, Rene; Tougui, Abdellah [Laboratoire de Mecanique et Rheologie, Universite Francois Rabelais de Tours, Polytech Tours, Departement Mecanique et Conception de Systemes, Tours (France)

    2009-09-15

    Methods to estimate fatigue crack initiation life at a notch tip are compared. The methods used determine the strain amplitudes at the notch tip using Neuber's or Glinka's approximation. In conventional approaches, equivalent-damage levels are determined, using appropriate strain-life relationships coupled with damage-summation models. In the short-crack approach, a crack-like defect is assumed to exist at the notch tip. It is shown that the short-crack concept can be successfully applied to predict crack-initiation behavior at a notch. Model predictions are compared with carefully designed experiments. It is shown that model predictions are very close to experimentally measured lives under an aircraft-wing loading spectrum. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  5. Fatigue strength of hybrid VHSS-Cast steel welded plates.

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    Very high strength steels (VHSS) have been made available by the steel industry for many years. In a fatigue loaded VHSS structure absolute and relative stress variation will be higher compared to stresses in structures made of lower grade steels. Cast steel, also available up to yield strength of 1

  6. Effects of Changes in Test Temperature on Tensile Properties and Notched Vs Fatigue Precracked Toughness of a Zr-Based BMG Composite

    Science.gov (United States)

    Clinton, Jessica A.; Morrison, Rachel L.; Carter, Jennifer L. W.

    2017-07-01

    Tensile and fracture toughness behavior of a Zr-based bulk metallic glass matrix composite (BMGMC) containing a body-centered cubic crystalline phase was examined over temperatures from 77 K to 653 K (-196 °C to 380 °C). The BMGMC exhibited tensile plasticity at all test temperatures. The sample tested in tension at 173 K (-100 °C) exhibited work hardening but the remaining samples tested at higher temperatures exhibited work softening. EBSD analysis of the crystalline phase after tensile testing provides insight into active deformation mechanisms in the crystalline phase. At 603 K (330 °C), the dendrites exhibit significant plastic strain, with the dendrites oriented {101} parallel to the loading direction exhibiting the least amount of strain. Schmid factor analysis leads to the hypothesis that {110} dislocation mechanisms are active at this temperature. Additionally, measurements of dendrite shape as a function of macroscopic strain state in the tension experiments provide insight into cooperative deformation mechanisms in the composite. At low temperatures, the fracture toughness of the notch toughness samples exceeded that of fatigue precracked samples; but at and above room temperature, the toughness values of notched and fatigue precracked samples converge. These observations are rationalized based on the changes to the flow and fracture behavior of the glass and the crystalline phases over this temperature range. At low temperatures, the crystalline phase is sensitive to defects and changes in stress state that reduce its energy absorbing ability. At higher temperatures, both constituents possess lower strength and are less sensitive to defects, enabling more significant crack tip blunting in the fatigue precracked samples. This produces toughness values that are similar to those obtained for the notched samples.

  7. Fatigue Strength and Residual Stress Analysis of Deep Rolled Crankshafts

    Directory of Open Access Journals (Sweden)

    Imran M Quraishi

    2012-12-01

    Full Text Available The endurance life of an engine crankshaft is closely related to its fatigue strength, in addition to other material properties and shape parameters. Deep rolling, moreover, enhances the fatigue limit by applying compressive residual stress within the fillet radius area as a major surface hardening technique. The objective of this paper isto maximize fatigue life of engine through crankshaft design optimization by quantifying fatigue strength for microalloyed steels versus Cr-Mo alloy steel, and to examine the effects of deep rolling load and rolled fillet geometry. Fatigue tests have been made with standard rotary bending test samples from both bar and forged blanks. Rig tests for actual crankshafts have been made to show how the fatigue strength correlates with different sample types. A correlation of stress distribution with bending moment was demonstrated by applying a strain gauging technique on crankshaft specimens. Therefore, an analysis of combined stresses could be made by considering the effect of static residual stress in addition to the applied dynamic bending stress. Optimum conditions for rolling load, fillet geometry and material were identified. Consequently, these results will be adapted to CAE analysis database to enable an optimization of safety factors.

  8. Modulating the strength and threshold of NOTCH oncogenic signals by mir-181a-1/b-1.

    Directory of Open Access Journals (Sweden)

    Rita Fragoso

    Full Text Available Oncogenes, which are essential for tumor initiation, development, and maintenance, are valuable targets for cancer therapy. However, it remains a challenge to effectively inhibit oncogene activity by targeting their downstream pathways without causing significant toxicity to normal tissues. Here we show that deletion of mir-181a-1/b-1 expression inhibits the development of Notch1 oncogene-induced T cell acute lymphoblastic leukemia (T-ALL. mir-181a-1/b-1 controls the strength and threshold of Notch activity in tumorigenesis in part by dampening multiple negative feedback regulators downstream of NOTCH and pre-T cell receptor (TCR signaling pathways. Importantly, although Notch oncogenes utilize normal thymic progenitor cell genetic programs for tumor transformation, comparative analyses of mir-181a-1/b-1 function in normal thymocyte and tumor development demonstrate that mir-181a-1/b-1 can be specifically targeted to inhibit tumor development with little toxicity to normal development. Finally, we demonstrate that mir-181a-1/b-1, but not mir-181a-2b-2 and mir-181-c/d, controls the development of normal thymic T cells and leukemia cells. Together, these results illustrate that NOTCH oncogene activity in tumor development can be selectively inhibited by targeting the molecular networks controlled by mir-181a-1/b-1.

  9. Two-step phase shifting interferometry technique for evaluation of fatigue process zone parameters in notched specimens

    Science.gov (United States)

    Muravsky, Leonid I.; Picart, Pascal; Kmet', Arkady B.; Voronyak, Taras I.; Ostash, Orest P.; Stasyshyn, Ihor V.

    2016-08-01

    A new two-step phase shifting interferometry technique for evaluation of a fatigue process zone (FPZ) in notched metal and alloy specimens is proposed. In comparison with well-known destructive and nondestructive methods evaluating FPZ, this technique possesses higher accuracy and performance and allows defining the FPZ size for notched specimens made of metals and alloys with low, moderate or high plasticity. The technique is fulfilled by retrieval of a total surface relief of a studied notched specimen, extraction of surface roughness and waviness phase maps from the retrieved surface relief, calculation of a surface roughness parameter Ra spatial distribution and definition of the FPZ size by using an extracted surface roughness phase map. Obtained experimental results have confirmed assumption that the surface roughness of notched specimens after cyclic loading reaches its maximum values at the FPZ boundary. This boundary is produced as the narrow strip containing pixels possessing the maximum values on the spatial distribution of the roughness parameter Ra near a notch root. The basic distances d* defining the FPZ sizes were measured for notched specimens made of a low-carbon steel and aluminum alloys 2024-T6 and 7075-T3. Results of the distances d* measurement are very close to respective results obtained with the help of other methods for the FPZ evaluation.

  10. Fatigue strength of welded connections made of very high strength cast and rolled steels

    NARCIS (Netherlands)

    Pijpers, R.J.M.

    2011-01-01

    Although Very High Strength Steels (VHSS) with nominal strengths up to 1100 MPa have been available on the market for many years, the use of these steels in the civil engineering industry is still uncommon. The main objective of the research is the determination of the fatigue strength of welded con

  11. Fatigue Crack Propagation from Notched Specimens of 304 SS in elevated Temperature Aqueous Environment

    Energy Technology Data Exchange (ETDEWEB)

    Wire, G. L.; Mills, W. J.

    2002-08-01

    Fatigue crack propagation (FCP) rates for 304 stainless steel (304SS) were determined in 24 degree C and 288 degree C air and 288 degree C water using double-edged notch (DEN) specimens of 304 stainless steel (304 SS). Test performed at matched loading conditions in air and water at 288 degree C with 20-6- cc h[sub]2/kg h[sub]2O provided a direct comparison of the relative crack growth rates in air and water over a wide range of crack growth rates. The DEN crack extension ranged from short cracks (0.03-0.25 mm) to long cracks up to 4.06 mm, which are consistent with conventional deep crack tests. Crack growth rates of 304 SS in water were about 12 times the air rate. This 12X environmental enhancement persisted to crack extensions up to 4.06 mm, far outside the range associated with short crack effects. The large environmental degradation for 304 SS crack growth is consistent with the strong reduction of fatigue life in high hydrogen water. Further, very similar environmental effects w ere reported in fatigue crack growth tests in hydrogen water chemistry (HWC). Most literature data in high hydrogen water show only a mild environmental effect for 304 SS, of order 2.5 times air or less, but the tests were predominantly performed at high cyclic stress intensity or equivalently, high air rates. The environmental effect in low oxygen environments at low stress intensity depends strongly on both the stress ratio, R, and the load rise time, T[sub]r, as recently reported for austenitic stainless steel in BWR water. Fractography was performed for both tests in air and water. At 288 degree C in water, the fracture surfaces were crisply faceted with a crystallographic appearance, and showed striations under high magnification. The cleavage-like facets on the fracture surfaces suggest that hydrogen embrittlement is the primary cause of accelerated cracking.

  12. Sharply notch cylindrical tension specimen for screening plane-strain fracture toughness. I - Influence of fundamental testing variables on notch strength. II Applications in aluminum alloy quality assurance of fracture toughness

    Science.gov (United States)

    Jones, M. H.; Bubsey, R. T.; Brown, W. F., Jr.; Bucci, R. J.; Collis, S. F.; Kohm, R. F.; Kaufman, J. G.

    1977-01-01

    A description is presented of studies which have been conducted to establish an improved technology base for a use of the sharply notched cylindrical specimen in quality assurance tests of aluminum alloy products. The results are presented of an investigation of fundamental variables associated with specimen preparation and testing, taking into account the influence of the notch root radius, the eccentricity of loading, the specimen diameter, and the notch depth on the sharp notch strength. Attention is given to the statistical procedures which are necessary to establish correlations between the sharp notch strength and the plane-strain fracture toughness for high-strength aluminum alloys.

  13. Determination of Tensile Strength and Fracture Toughness of Granite Using Notched Three-Point-Bend Samples

    Science.gov (United States)

    Wang, Yusuo; Hu, Xiaozhi

    2017-01-01

    Direct tensile strength and fracture toughness of rock and concrete, important properties for many applications, are cumbersome to measure directly. In this study, granite is chosen as an example to show how the tensile strength and fracture toughness can be measured from small three-point-bend samples of a single size but with different notches. An existing fracture mechanics model has been extended to include the stable fictitious crack growth before peak loads, which is then linked to the granite grain size. Both tensile strength and fracture toughness of granite can be estimated by the maximum load measurements from those notched three-point-bend samples. In total, 72 three-point-bend granite samples with different notches have been tested, and the estimated tensile strength and fracture toughness are compared with those available in the literature. The modified fracture mechanics model is then used to predict the fracture behaviour of smaller samples of the same granite. The theoretical prediction is confirmed by the experimental results of those smaller samples. Finally, the fracture model and its relation with the American Society for Testing and Materials (ASTM) standard on fracture toughness are discussed.

  14. Fatigue strength testing of LTCC and alumina ceramics bonds

    Science.gov (United States)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  15. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

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

    2002-01-01

    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...

  16. Creep-Rupture and Fatigue Behavior of a Notched Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature

    Science.gov (United States)

    2008-06-01

    ultrasonic bath of deionized water to remove any excess debris and then dried in an oven at 90°C for 30 minutes. 16 Figure 9. Specimen dimensions...Figure 107. 155 MPa Fatigue (right) 100 Bibliography 1. “3M Ceramic Fiber Typical Properties,” Nextel™ Ceramic Textiles Technical Notebook... ultrasonic C-scans,” Composites Science and Technology, 61[11], 1561-1570 (2001). 20. Kramb, Victoria A., Reji John and Larry P. Zawada. “Notched

  17. Fatigue Strength Prediction of Drilling Materials Based on the Maximum Non-metallic Inclusion Size

    Science.gov (United States)

    Zeng, Dezhi; Tian, Gang; Liu, Fei; Shi, Taihe; Zhang, Zhi; Hu, Junying; Liu, Wanying; Ouyang, Zhiying

    2015-12-01

    In this paper, the statistics of the size distribution of non-metallic inclusions in five drilling materials were performed. Based on the maximum non-metallic inclusion size, the fatigue strength of the drilling material was predicted. The sizes of non-metallic inclusions in drilling materials were observed to follow the inclusion size distribution rule. Then the maximum inclusion size in the fatigue specimens was deduced. According to the prediction equation of the maximum inclusion size and fatigue strength proposed by Murakami, fatigue strength of drilling materials was obtained. Moreover, fatigue strength was also measured through rotating bending tests. The predicted fatigue strength was significantly lower than the measured one. Therefore, according to the comparison results, the coefficients in the prediction equation were revised. The revised equation allowed the satisfactory prediction results of fatigue strength of drilling materials at the fatigue life of 107 rotations and could be used in the fast prediction of fatigue strength of drilling materials.

  18. Modal characteristics and fatigue strength of compressor blades

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Kook [Doosan Heavy Industries and Construction, Changwon (Korea, Republic of); Lee, Young Shin [Chungnam National University, Daejeon (Korea, Republic of)

    2014-04-15

    High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. The modal characteristics and endurance strength of a 5 MW gas turbine engine blade developed by Doosan Heavy Industries and Construction Co., Ltd. in HCF fracture were verified through analysis and tests to determine the reliability of the compressor blade. A compressor blade design procedure that considers HCF life was performed in the following order: airfoil and blade profile design, modal analysis, stress distribution test, stress endurance limit test, and fatigue life verification. This study analyzed the Campbell diagram and estimated resonance risk on the basis of the natural frequency analysis and modal test of the compressor blade to guarantee safe and operational reliability. In addition, the maximum stress point of the compressor blade was determined through stress distribution analysis and test. The bonding point of the strain gage was determined by using fatigue test. Stress endurance limit test was performed based on the results of these tests. This research compared and verified the modal characteristics and endurance strengths of the compressor blades to prevent HCF fracture, which is among the major causes of gas turbine engine damage. A fatigue life design procedure of compressor blades was established. The 5 MW class gas turbine compressor blade is well designed in terms of resonance stability and fatigue endurance limit.

  19. Effects of Core-Musculature Fatigue on Maximal Shoulder Strength.

    Science.gov (United States)

    Rosemeyer, James R; Hayes, Bradley T; Switzler, Craig L; Hicks-Little, Charlie A

    2015-11-01

    Core stability has been shown to affect lower-extremity motion, but activation of the core has also been observed just before movements of the upper extremity. However, there is limited evidence regarding the effects that core musculature has on upper-extremity strength. To determine the effects of core fatigue on maximal shoulder strength. Crossover study. Sports-medicine research laboratory. 23 participants (15 male and 8 female, age 21.3 ± 2.5 y, height 174.5 ± 10.3 cm, weight 71.3 ± 12.0 kg). All participants performed maximal voluntary isometric contractions in 3 different planes (sagittal, frontal, transverse) of shoulder-joint motion. A core-fatiguing protocol was conducted, and the same 3 shoulder-strength tests were repeated and compared with the initial measurements. Strength measures were recorded in kilograms with a dynamometer. Results showed a significant decrease in strength in the frontal (-0.56 ± 1.06 kg, P = .020) and transverse (-0.89 ± 1.49 kg, P = .012) planes but not in the sagittal plane (-0.20 ± 0.98 kg, P > .05). Furthermore, regardless of the specific strength test measured, results revealed that the 1st (-7.05% ± 11.65%, P = .012) and 2nd (-5.71% ± 12.03%, P = .042) strength-test measurements after the fatiguing protocol were significantly decreased, while the 3rd strength-test measurement (-4.19% ± 12.48%, P = .140) did not show statistical significance. These results indicate that decrease in core stability may have an influence on shoulder strength. The literature suggests that the core is designed for endurance, and this study helps validate its recovery properties. Further research is needed to determine the significance of this effect and how injury rates coincide.

  20. Prediction for multiaxial fatigue strength with small defects

    Directory of Open Access Journals (Sweden)

    Yanase Keiji

    2014-06-01

    Full Text Available As an extension of previous studies, this paper further examine the applicability and characteristics of the predictive method, in particular, for the case of proportional loading. The predictive method is based on the \\vec{area} See Formula in PDF -parameter model and Endo’s biaxial fatigue failure criterion. The present study manifests that the critical plane is normal to the direction of maximum principal stress, and the fatigue strength is dictated by both the maximum and minimum principal stresses.

  1. Bending Fatigue Strength of Austempered Ductile Iron Spur Gears

    Science.gov (United States)

    Yamanaka, Masashi; Tamura, Ryo; Inoue, Katsumi; Narita, Yukihito

    This paper deals with an experimental evaluation of bending fatigue strength for austempered ductile iron (ADI) spur gears. The module is 2.5 and the number of teeth is 26 in the test gears. The material of the test gears corresponds to Japan Industrial Standard (JIS) FCAD1100-15. Some gears are processed by one of two types of fine particle bombarding (FPB). The surface roughness is slightly increased by FPB. The obtained strengths are 623 MPa for the as-austempered gears, and 1011 and 1085 MPa for the gears after FPB. The strength is expressed by the fillet stress level, which is calculated by FEM. The strength of a gear with the same dimensions made of carburized SCr420H alloy steel is 1205 MPa, and the strength of the ADI gear is approximately half that of the carburized steel gear. The FPB process has a significant effect on the ADI gear, improving its strength by 62-74%.

  2. Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

    Science.gov (United States)

    Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

    2012-01-01

    Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a

  3. Surface Studies of Ultra Strength Drilling Steel after Corrosion Fatigue in Simulated Sour Environment

    Energy Technology Data Exchange (ETDEWEB)

    M. Ziomek-Moroz; J.A. Hawk; R. Thodla; F. Gui

    2012-05-06

    The Unites States predicted 60% growth in energy demand by 2030 makes oil and natural gas primary target fuels for energy generation. The fact that the peak of oil production from shallow wells (< 5000 m) is about to be reached, thereby pushing the oil and natural gas industry into deeper wells. However, drilling to depths greater than 5000 m requires increasing the strength-to weight ratio of the drill pipe materials. Grade UD-165 is one of the ultra- high yield strength carbon steels developed for ultra deep drilling (UDD) activities. Drilling UDD wells exposes the drill pipes to Cl{sup -}, HCO{sub 3}{sup -}/CO{sub 3}{sup 2-}, and H{sub 2}S-containig corrosive environments (i.e., sour environments) at higher pressures and temperatures compared to those found in conventional wells. Because of the lack of synergism within the service environment, operational stresses can result in catastrophic brittle failures characteristic for environmentally assisted cracking (EAC). Approximately 75% of all drill string failures are caused by fatigue or corrosion fatigue. Since there is no literature data on the corrosion fatigue performance of UD-165 in sour environments, research was initiated to better clarify the fatigue crack growth (FCGR) behavior of this alloy in UDD environments. The FCGR behavior of ultra-strength carbon steel, grade UD-165, was investigated by monitoring crack growth rate in deaerated 5%NaCl solution buffered with NaHCO{sub 3}/Na{sub 2}CO{sub 3} and in contact with H{sub 2}S. The partial pressure of H{sub 2}S (p{sub H2S}) was 0.83 kPa and pH of the solution was adjusted by NaOH to 12. The fatigue experiments were performed at 20 and 85 C in an autoclave with surface investigations augmented by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. In this study, research focused on surface analyses supported by the fatigue crack growth rate measurements. Fig. 1 shows an SEM micrograph of the crack that propagated from the

  4. Effect of Microstructure on Fatigue Strength of Bovine Compact Bones

    Science.gov (United States)

    Kim, Jong Heon; Niinomi, Mitsuo; Akahori, Toshikazu; Takeda, Junji; Toda, Hiroyuki

    Despite its clinical importance in developing artificial bone, limited information is available regarding the microstructure with respect to the fatigue characteristics of bones. In this study, the fatigue characteristics of the bovine humerus and femur were investigated with respect to microstructures. Fatigue tests were conducted on the bovine humerus and femur at a stress ratio of 0.1 and a frequency of 10Hz. The fatigue strength of the plexiform bone is slightly greater than that of the haversian bone. This is because the volume fraction of voids in the haversian bone, which is the site of stress concentration, is higher than that of voids in the plexiform bone. Several microcracks are observed on the fatigue fracture surface of the haversian bone. The microcracks are short and their propagation directions are random. However, the number of the microcracks in the plexiform bone is very small. The microcracks are relatively long and their propagation directions are parallel to the longitudinal direction of the lamellar bone. Therefore, the crack requires relatively more energy to propagate across the lamella in the plexiform bone.

  5. Evaluation of fatigue process zone dimensions in notched specimens by two-step phase shifting interferometry technique

    Science.gov (United States)

    Muravsky, Leonid I.; Picart, Pascal; Kmet', Arkady B.; Voronyak, Taras I.; Ostash, Orest P.; Stasyshyn, Ihor V.

    2016-10-01

    A method for evaluation of fatigue process zone (FPZ) dimensions near a notch root in metal and alloy specimens by using a two-step phase shifting interferometry (TS PSI) technique is proposed. In comparison with other destructive and nondestructive methods evaluating the FPZ dimensions, it possesses higher accuracy and performance. The method uses a criterion for the FPZ dimensions definition based on an assumption that the surface roughness of notched specimens after cyclic loading reaches its maximum values at the FPZ boundary. To realize this method, first, a phase map (PM) of a total surface relief near a notch root is retrieved; second, roughness and waviness PMs are extracted from the retrieved total surface relief PM by using the TS PSI; and finally, a surface roughness parameter Ra spatial distribution is calculated according to the offered criterion and the FPZ size d* is defined. The FPZ size was measured for specimens made of low-carbon steel and aluminum alloys 2024-T6 and 7075-T3. Obtained experimental results have shown that the proposed criterion allows defining the FPZ size for notched specimens made of metals and alloys possessing high, moderate, and low plasticity.

  6. Effect of cyclic high loading rates on the fatigue strength of aluminum-based composites

    Science.gov (United States)

    Calderon Arteaga, Hermes Eskander

    The study of fatigue under high loading rates is of great interest in the complete characterization of a new series of composites with Al-Cu-Mg matrix reinforced with AlB2 dispersoids. Homogeneous and functionally graded composites were prepared via gravity and centrifugal casting, respectively. Through centrifugal casting a gradual variation of the volume fraction of reinforcing particles along the cross section was obtained. In specific fabrication conditions, even complete segregation of the reinforcement particles was achieved. Charpy impact tests as well as hardness tests were conducted to assess the composite strength as a function of the weight percent of boron. The tensile properties of gravity cast samples were obtained. Then for both casting conditions, simple edge-notched bend SE(B) specimens were tested under fatigue conditions (three-point bending). The results from impact and hardness tests allowed identifying an interaction between the Mg dissolved in the matrix and the diborides. This interaction, which has never been reported before, was responsible for the strength reduction observed. It was assumed that a substitutional diffusion of Al by Mg atoms in the hp3 structure of diboride was causing the strength reduction, and three approaches were developed to estimate the amount of Mg depleted from the matrix by the diborides during the composite processing. Gravity cast samples were more sensitive to monotonic damage due to fatigue loads where compared with functionally-graded composites. Contrary to the centrifugal cast samples, gravity samples were also affected by the loading rate. The Mg-AlB2 interaction was also responsible for the reduction in the fatigue resistance as the weight percent of boron increased in both types of composites; regression models were obtained to predict the crack growth curve slope change as function of the boron level. The particle distribution showed to affect the crack growth behavior of the FGMs, decreasing the

  7. Measurement of In-Plane Shear Strength of Carbon/Carbon Composites by Compression of Double-Notched Specimens

    Science.gov (United States)

    Yan, K. F.; Zhang, C. Y.; Qiao, S. R.; Song, C. Z.; Han, D.; Li, M.

    2012-01-01

    The compression of a double-notched specimen was used to determine the in-plane shear strength (IPSS) of a carbon/carbon composite in the paper. The effects of the notch distance ( L), thickness ( T), and notch width ( W) and supporting jig on the IPSS of the double-notched specimens were investigated numerically and experimentally. The fracture surfaces were examined by a scanning electron microscope. It was found that the IPSS varied with L. Thin specimen yielded low strength. W has little effect on IPSS. The main failure modes include the matrix shear cracking, delamination, fracture and pullout of fibers or fiber bundles. Meanwhile, a supporting jig can provide lateral support and prevent buckling, therefore lead to the failure in a shear mode.

  8. High-cycle Fatigue Fracture Behavior of Ultrahigh Strength Steels

    Institute of Scientific and Technical Information of China (English)

    Weijun HUI; Yihong NIE; Han DONG; Yuqing WENG; Chunxu WANG

    2008-01-01

    The fatigue fracture behavior of four ultrahigh strength steels with different melting processes and therefore different inclusion sizes were studied by using a rotating bar two-point bending fatigue machine in the high-cycle regime up to 107 cycles of loading. The fracture surfaces were observed by field emission scanning electron microscopy (FESEM). It was found that the size of inclusion has significant effect on the fatigue behavior.For AISI 4340 steel in which the inclusion size is smaller than 5.5 μm, all the fatigue cracks except one did not initiated from inclusion but from specimen surface and conventional S-N curve exists. For 65Si2MnWE and Aermet 100 steels in which the average inclusion sizes are 12.2 and 14.9 μm, respectively, fatigue cracks initiated from inclusions at lower stress amplitudes and stepwise S-N curves were observed. The S-N curvedisplays a continuous decline and fatigue failures originated from large oxide inclusion for 60Si2CrVA steel in which the average inclusion size is 44.4 μm. In the case of internal inclusion-induced fractures at cycles beyond about 1×106 for 65Si2MnWE and 60Si2CrVA steels, inclusion was always found inside the fish-eye and a granular bright facet (GBF) was observed in the vicinity around the inclusion. The GBF sizes increasewith increasing the number of cycles to failure Nf in the long-life regime. The values of stress intensity factor range at crack initiation site for the GBF are almost constant with Nf, and are almost equal to that for the surface inclusion and the internal inclusion at cycles lower than about 1×106. Neither fish-eye nor GBF was observed for Aermet 100 steel in the present study.

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

    Science.gov (United States)

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

    1998-01-01

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

  10. Consideration on fatigue strength of corroded steel plates; Fushoku suimo koban no hiro kyodo ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, M.; Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1996-10-01

    Discussions were given on fatigue strength of corroded steel plates taken from a hull of a ship seventeen years old after construction. The steel plates have had their original thickness of 13 mm reduced to 5.3 to 8.3 mm. After having been cut by a machine, the steel plates were used for tests as ground plates after going through grinding and as corroded plates with rust remaining on them. The fatigue test was performed in artificially made sea water at a temperature of 25{degree}C and in air with axial power pulsating tensile load and at iterative loading velocities of 3 to 5 Hz. The corroded material test verified that corrosion pits exist innumerably on the test piece surface and fatigue cracks have been developed and grown from bottoms of the pits. The stress concentration coefficient of the corrosion pits was about 1.9. Good agreement with the test result was found in the S-N chart in which the number of iteration of fracture was regarded as the number of iteratively generated cracks, and notch coefficient was estimated as 1.9. These results proved that the fatigue strength assessing method for virgin materials can be applied also to steel plates which have been exposed to corrosive environment for extended periods of time. 5 refs., 7 figs., 1 tab.

  11. Anomolous Fatigue Crack Growth Phenomena in High-Strength Steel

    Science.gov (United States)

    Forth, Scott C.; James, Mark A.; Johnston, William M., Jr.; Newman, James C., Jr.

    2004-01-01

    The growth of a fatigue crack through a material is the result of a complex interaction between the applied loading, component geometry, three-dimensional constraint, load history, environment, material microstructure and several other factors. Previous studies have developed experimental and computational methods to relate the fatigue crack growth rate to many of the above conditions, with the intent of discovering some fundamental material response, i.e. crack growth rate as a function of something. Currently, the technical community uses the stress intensity factor solution as a simplistic means to relate fatigue crack growth rate to loading, geometry and all other variables. The stress intensity factor solution is a very simple linear-elastic representation of the continuum mechanics portion of crack growth. In this paper, the authors present fatigue crack growth rate data for two different high strength steel alloys generated using standard methods. The steels exhibit behaviour that appears unexplainable, compared to an aluminium alloy presented as a baseline for comparison, using the stress intensity factor solution.

  12. Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques

    Science.gov (United States)

    Chan, Kwai S.

    2015-12-01

    Rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti-6Al-4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%-75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.

  13. Fatigue strength of truss girders made of very high strength steel

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.

    2010-01-01

    An effective application of Very High Strength Steel (VHSS) in civil engineering structures is expected in stiff, truss like structures, typically made of Circular Hollow Sections (CHS). Use of castings in combination with CHS could be promising for the design of highly fatigue resistant joints. Cas

  14. Effect of load ratio, testing frequency, temperature, moisture, notch and stacking sequence on the fatigue resistance of woven CFRP laminates

    OpenAIRE

    Lani, Frédéric; 6th International Conference on Fatigue of Composite ICFC2015

    2015-01-01

    A woven CFRP composite laminate has been thoroughly characterized under fatigue. Over 150 tests were performed in order to address the effect of sample geometry (Open Hole Tension, Open Hole Compression, Plain Compression, …), testing frequency (5Hz, 30Hz) with and without cooling system, load ratio (R=10., R=-1., R=0.1), temperature (RT and 120°C), moisture intake (50% RH and 85+% RH at RT), notch (Open Hole Vs. Plain Specimen), stacking sequence (3 different stacking sequences) on the measu...

  15. Fatigue Analysis and Life Prediction of Dumpers with Cumulative Fatigue Damage Approach

    Institute of Scientific and Technical Information of China (English)

    LI Shouju; LIU Yingxi; SUN Huiling

    2004-01-01

    A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.

  16. The Effect of Residual Stress State in the Notch Root Region Caused by the Hold Period of the Overload to the Fatigue Life

    OpenAIRE

    Anindito Purnowidodo; Ari Wahyudi; Rudy Soenoko; Khairul Anam

    2015-01-01

    In the present study, the effect of the overload together with the hold period of the overload to the fatigue life associating with the crack emerging from the notch root region is investigated because the region is vulnerable to the plastic deformation. The result of the study shows that the fatigue life is affected by the residual stress state in front of the notch root, and the state of the residual stress depends on the constant amplitude load condition following of the overload. The resi...

  17. Modeling and fatigue assessment of weld start-end locations based on the effective notch stress approach

    Energy Technology Data Exchange (ETDEWEB)

    Malikoutsakis, M. [Aristotle University of Thessaloniki, Faculty of Mechanical Engineering, Laboratory of Machine Elements Machine Design, 54124 Thessaloniki (Greece); Savaidis, G.

    2011-04-15

    The present paper contains a methodology for modeling and life assessment of fatigue loaded welded components providing distinct weld start and end locations. The proposed methodology follows the IIW recommendation regarding modeling and finite element meshing of weld toe and root by means of an effective notch radius and uses the corresponding Woehler curve (FAT class) to assess the durability. Geometrical singularities and, therewith, numerical discontinuities, can be overcome especially when 3D weld root problems are treated. The fatigue life assessment is performed on the basis of normal stresses acting at the failure-critical weld toe and root locations. Comprehensive experimental database containing stress and fatigue life results derived from motor truck's hypoid rear axles providing complex 3D welds subject to vertical, longitudinal, and torsional loading is used to verify the calculation accuracy of the proposed methodology. The agreement between experimentally determined and calculated fatigue results is satisfactory. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. High-cycle fatigue investigations of notched Glare under different stress ratio's in various environments

    National Research Council Canada - National Science Library

    Bhat, Sunil; Narayanan, Sockalingam

    2014-01-01

    Notched Glare 4A-3/2 laminates, comprising thin 2014-T6 aerospace aluminum alloy sheets alternately bonded with unidirectional E-glass fiber-based composite prepregs, are tested under tensile-tensile...

  19. The fatigue strength of base material and butt welds made of S690 and S1100

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2007-01-01

    Modern steel manufacturing techniques make it possible to produce steel with nominal strengths up to 1100 MPa (very high strength steels, VHSS). For the design of cyclic loaded slender VHSS structures, the fatigue strength of both base material and welded components should be known. In a VHSS fatigu

  20. The effect of yield strength and ductility to fatigue damage

    Science.gov (United States)

    Yeh, H. Y.

    1973-01-01

    The cumulative damage of aluminium alloys with different yield strength and various ductility due to seismic loads was studied. The responses of an idealized beam with a centered mass at one end and fixed at the other end to El Centro's and Taft's earthquakes are computed by assuming that the alloys are perfectly elastoplastic materials and by using numerical technique. Consequently, the corresponding residual plastic strain can be obtained from the stress-strain relationship. The revised Palmgren-Miner cumulative damage theorem is utilized to calculate the fatigue damage. The numerical results show that in certain cases, the high ductility materials are more resistant to seismic loads than the high yield strength materials. The results also show that if a structure collapse during the earthquake, the collapse always occurs in the very early stage.

  1. Neuromuscular fatigue during dynamic maximal strength and hypertrophic resistance loadings.

    Science.gov (United States)

    Walker, Simon; Davis, Lisa; Avela, Janne; Häkkinen, Keijo

    2012-06-01

    The purpose of this study was to compare the acute neuromuscular fatigue during dynamic maximal strength and hypertrophic loadings, known to cause different adaptations underlying strength gain during training. Thirteen healthy, untrained males performed two leg press loadings, one week apart, consisting of 15 sets of 1 repetition maximum (MAX) and 5 sets of 10 repetition maximums (HYP). Concentric load and muscle activity, electromyography (EMG) amplitude and median frequency, was assessed throughout each set. Additionally, maximal bilateral isometric force and muscle activity was assessed pre-, mid-, and up to 30 min post-loading. Concentric load during MAX was decreased after set 10 (Pmuscle activity during HYP loading. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Low cycle fatigue behavior of high strength gun steels

    Institute of Scientific and Technical Information of China (English)

    Maoqiu Wang; Han Dong; Qi Wang; Changgang Fan

    2004-01-01

    The low cycle fatigue (LCF) behavior of two high strength steels, with nominal chemical compositions (mass fraction, %)of 0.40C-1.5Cr-3Ni-0.4Mo-0.2V (PCrNi3MoV) and 0.25C-3Cr-3Mo-0.8Ni-0.1Nb (25Cr3Mo3NiNb), was investigated by using the smooth bar specimens subjected to strained-controlled push-pull loading. It is found that both steels show cyclic softening, but 25Cr3Mo3NiNb steel has a lower tendency to cyclic softening. 25Cr3Mo3NiNb steel has higher fatigue ductility, and its transition fatigue life is almost three times that of PCrNi3MoV. 25Cr3Mo3NiNb steel also shows higher LCF life either at a given total strain amplitude above 0.5% or at any given plastic strain amplitude, despite its lower monotonic tensile strength than that of PCrNi3MoV.It also means that 25Cr3Mo3NiNb steel can endure higher total strain amplitude and plastic strain amplitude at a given number of reversals to failure within 104. 25Cr3Mo3NiNb steel is expected to be a good gun steel with high LCF properties because only several thousand firings are required for gun barrel in most cases.

  3. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

    Science.gov (United States)

    Bast, Callie Corinne Scheidt

    1994-01-01

    This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

  4. Fatigue in Welded High-Strength Steel Plate Elements under Stochastic Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1999-01-01

    The present project is a part of an investigation on fatigue in offshore structures in high-strength steel. The fatigue life of plate elements with welded attachments is studied. The material used has a yield stress of ~ 810-840 MPa, and high weldability and toughness properties. Fatigue test...... series with constant amplitude loading and with various types of stochastic loading have been carried through on test specimens in high-strength steel, and - for a comparison - on test specimens in conventional offshore structural steel with a yield stress of ~ 400-410 MPa.A comparison between constant...... amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those...

  5. Fracture strength of all-ceramic restorations after fatigue loading

    Science.gov (United States)

    Baladhandayutham, Balasudha

    Fracture strength of monolithic and bilayered LAVA and e. max lower molar crowns after load cycling was measured and compared. The study included three groups (n = 8) from LAVA zirconia and three groups from e. max lithium disilicate to compare influences of different layers, thicknesses and manufacturing techniques. Prefabricated anatomically designed crowns were cemented to dies made from Z 100 composite resin using Rely X Luting Plus resin modified glass ionomer cement. Cemented crowns were stored at 37° C for 24 hours then cyclic loaded to test fatigue properties. The crowns were loaded to 200,000 cycles at 25N at a rate of 40 cycles / minute to simulate oral function. Subsequently, fracture properties for each group were measured using an Instron Universal Testing machine. Microscopic evaluation of the surface of fatigued samples did not reveal micro-cracks at the end of 50,000 cycles but minor wear facets were observed at the site of contact from the steatite ball antagonist. Crowns from LAVA bilayered groups showed step by step fractures while crowns from all other groups fractured as a single event as observed by the high speed camera. Zirconia bilayered crowns showed the highest loads to fracture while lithium disilicate monolithic crowns showed the lowest, within the limitations of the study. The study also showed that monolithic zirconia crowns of 0.6mm thickness resulted in relatively high magnitude for forces at fracture.

  6. Maintained ship hull girder ultimate strength reliability considering corrosion and fatigue

    DEFF Research Database (Denmark)

    Hu, Yong; Cui, W.; Pedersen, Preben Terndrup

    2004-01-01

    The prupose of this paper is to propose a methodology to assess the time-variant ultimate strength of ship hull girder under the degradations of corrosion and fatigue. The effects of fatigue cracks on the tensile and compressive residual ultimate strength of stiffened panels and unstiffened plate...

  7. Influence of fretting on the fatigue strength at the vise clamp–specimen interface

    Indian Academy of Sciences (India)

    Abdulhaqq A Hamid; Rafi K Yahya

    2003-12-01

    Fretting fatigue is one of the most important phenomena for inducing a significant reduction of fatigue strength and consequently, leading to unexpected failure accidents of the engineering structures even at very low stresses. In the present study, both plain and fretting fatigue tests with zero mean stress were carried out on two different types of steel, low-carbon steel and martensitic stainless steel, by means of a reversed bending fatigue testing machine. The drop in the fatigue strengths through fretting at vise clamp–specimen interface were significant for both tested steels. The fretting processes produced a reduction in fatigue strength of about 27% for low-carbon steel and 16% for martensitic stainless steel.

  8. Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males.

    Science.gov (United States)

    Kroll, Walter; And Others

    1980-01-01

    There is a degree of uniqueness in fatigue patterns, particularly between different levels of absolute maximum strength. Caution should be used when analyzing fatigue curves among subjects with unspecified strength levels. (CJ)

  9. A Model of the Fatigue Life Distribution of Composite Laminates Based on Their Static Strength Distribution

    Institute of Scientific and Technical Information of China (English)

    Wu Fuqiang; Yao Weixing

    2008-01-01

    The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article.It is concluded that the inner original defects,which derived from the manufacturing process of composite laminates,are the common and major reason of causing the random distributions of the static strength and the fatigue life.And there is a correlative relation between the two distributions.With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material,the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained.And then the model which is used to describe the distributions of fatigue life of composites,based on their distributions of static strength,is set up.This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates.The experimental data of three kinds of composite laminates are employed to verify this model,and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.

  10. Fatigue Induced Alteration of the Superficial Strength Properties of 2024 Aluminum Alloy

    Institute of Scientific and Technical Information of China (English)

    K.-D. Bouzakis; I. Mirisidis; Sp. G. Pantelakis; A.N. Chamos

    2011-01-01

    aluminum alloy 2024 T3 specimens have been subjected to constant amplitude fatigue loading at R=0.1. During fatigue, an appreciable increase of the surface hardness of the material at the meso-scale can be observed and captured by means of nanoindentations. Surface hardness increases with increasing fatigue stress amplitude and advancing number of applied fatigue cycles. Observed increase of specimen surface hardening degree during fatigue causes an evolution of superficial mechanical strength properties of the alloy. Stress-strain curves associated with the evoluting superficial mechanical properties are derived, employing a developed finite element method (FEM)-supported evaluation procedure of nanoindentation experimental results.

  11. Strength Training Improves Fatigue Resistance and Self-Rated Health in Workers with Chronic Pain

    DEFF Research Database (Denmark)

    Sundstrup, Emil; Jakobsen, Markus Due; Brandt, Mikkel;

    2016-01-01

    -rated health and pain. Time to fatigue, muscle strength, hand/wrist pain, and self-rated health improved significantly more following strength training than usual care (all P ... (Spearman's rho = -0.40; P = 0.01). In conclusion, specific strength training improves muscular fatigue resistance and self-rated health and reduces pain of the hand/wrist in manual workers with chronic upper limb pain. This trial is registered with ClinicalTrials.gov NCT01671267....

  12. Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints

    Directory of Open Access Journals (Sweden)

    Kittima Sillapasa

    2017-02-01

    Full Text Available Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = −1 = 1.68 HV (σa is in MPa and HV has no unit. It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints.

  13. A New Perspective on Fatigue Performance of Advanced High- Strength Steels (AHSS) GMAW Joints

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [ORNL; Chiang, Dr. John [Ford Motor Company; Kuo, Dr. Min [MIttal Steel; Jiang, Cindy [AET Integration, Inc; Sang, Yan [AET Integration, Inc

    2008-01-01

    Weld fatigue performance is a critical aspect for application of advanced high-strength steels (AHSS) in automotive body structures. A comparative study has been conducted to evaluate the fatigue life of AHSS welds. The material studied included seven AHSS of various strength levels - DP 600, DP 780, DP 980, M130, M220, solution annealed boron and fully hardened boron steels. Two conventional steels, HSLA 590 and DR 210, were also included for baseline comparison. Lap fillet welds were made on 2-mm nominal thick sheets by the gas metal arc welding process (GMAW). Fatigue test was conducted under a number of stress levels to obtain the S/N curves of the weld joints. It was found that, unlike in the static and impact loading conditions, the fatigue performance of AHSS is not influenced by the HAZ softening in AHSS. There are appreciable differences in the fatigue lives among different AHSS. Changes in weld parameters can influence the fatigue life of the weld joints, particularly of these of higher strength AHSS. A model is developed to predict the fatigue performance of AHSS welds. The validity of the model is benchmarked with the experimental results. This model is capable to capture the effects of weld geometry and weld microstructure and strength on the fatigue performance experimentally observed. The theoretical basis and application of the newly developed fatigue modeling methodology will be discussed.

  14. Advanced methods of fatigue assessment

    CERN Document Server

    Radaj, Dieter

    2013-01-01

    The book in hand presents advanced methods of brittle fracture and fatigue assessment. The Neuber concept of fictitious notch rounding is enhanced with regard to theory and application. The stress intensity factor concept for cracks is extended to pointed and rounded corner notches as well as to locally elastic-plastic material behaviour. The averaged strain energy density within a circular sector volume around the notch tip is shown to be suitable for strength-assessments. Finally, the various implications of cyclic plasticity on fatigue crack growth are explained with emphasis being laid on the DJ-integral approach.   This book continues the expositions of the authors’ well known reference work in German language ‘Ermüdungsfestigkeit – Grundlagen für Ingenieure’ (Fatigue strength – fundamentals for engineers).

  15. The influence of rolling practice on notch toughness and texture development in high-strength linepipe

    Energy Technology Data Exchange (ETDEWEB)

    Baczynski, G.J.; Jonas, J.J.; Collins, L.E.

    1999-12-01

    The mechanical properties and notch toughnesses of an X80 linepipe steel were determined for various test directions in the plane of sheet that had been finish rolled in the {gamma} and in the intercritical ({alpha} + {gamma}) regions. The anisotropies of yield strength (YS) and of impact energy are correlated to the presence of various texture components, as detected by the use of an orientation distribution function (ODF) analysis. The final microstructures were similar and consisted of polygonal and acicular ferrite. The textures were also similar; however, after rolling in the ({alpha} + {gamma}) region, the intensity of the texture was significantly higher. These textures were mainly comprised of two fibers, the rolling direction (RD), {l{underscore}angle}110{r{underscore}angle}//RD, and the normal direction (ND), {l{underscore}angle}111{r{underscore}angle}//ND, fibers. The observations show that the RD fiber centered at {l{underscore}brace}112{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} and the {l{underscore}brace}10{r{underscore}brace}{l{underscore}angle}001{r{underscore}angle} orientation were responsible for the YS anisotropy. The relationships between notch toughness and texture were considered for the brittle or cleavage ({minus}196 C), mixed brittle-ductile ({minus}60 C), and ductile (room temperature (RT)) modes of fracture. This work shows that the anisotropy of impact energy associated with ductile fracture at the higher temperatures is caused by the {l{underscore}brace}112{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} component, and that the {l{underscore}brace}001{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} and {l{underscore}brace}110{r{underscore}brace}{l{underscore}angle}001{r{underscore}angle} components (if present) are responsible for the anisotropy of the impact energy associated with cleavage at low temperatures. The lack of anisotropy of the impact energy observed at {minus}196 C and

  16. Effects of structure and defect on fatigue limit in high strength ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hak; Kim, Min Gun [Kangwon National Univ., Chunchon (Korea, Republic of)

    2000-05-01

    In this paper, the influence of several factors such as hardness, internal defect and non-propagating crack on fatigue limits was investigated with three kinds of ductile iron specimens. From the experimental results the fatigue limits were examined in relation with hardness and tensile strength in case of high strength specimens under austempering treatment; in consequence the marked improvement of fatigue limits were not showed. The maximum defect size was an important factor to predict and to evaluate the fatigue limits of ductile irons. And, the quantitative relationship between the fatigue limits({sigma}{sub {omega}}) and the maximum defect size({radical}area{sub max}) was expressed as {sigma}{sub {omega}}{sup n} {center_dot} {radical}area{sub max}=C{sub 2}. Also, it was possible to explain the difference for the fatigue limits in three ductile irons by introduction of the non-propagating crack rates.

  17. Structural strength analysis and fatigue life prediction of traction converter box in high-speed EMU

    Science.gov (United States)

    Tan, Qin; Li, Qiang

    2017-01-01

    The method of building the FEA model of traction converter box in high-speed EMU and analyzing the static strength and fatigue strength of traction converter box based on IEC 61373-2010 and EN 12663 standards is presented in this paper. The load-stress correlation coefficients of weak points is obtained by FEA model, applied to transfer the load history of traction converter box to stress history of each point. The fatigue damage is calculated based on Miner's rule and the fatigue life of traction converter box is predicted. According to study, the structural strength of traction converter box meets design requirements.

  18. Crack growth behavior under creep-fatigue conditions using compact and double edge notch tension-compression specimens

    Science.gov (United States)

    Narasimha Chary, Santosh Balaji

    The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially address these shortcomings of the load-controlled tests for which the C(T) geometry is unsuitable. A double edge notch tension-compression, DEN(T-C), specimen to perform displacement controlled creep-fatigue crack growth testing is developed and optimized with the help of finite element and boundary element analyses. Accurate expressions for estimating the fracture mechanics crack tip parameters such as the stress intensity parameter, K, the crack mouth opening displacement (CMOD), and the load-line displacement (LLD) are developed over a wide range of crack sizes for the DEN(T-C) specimen. A new compliance relationship for use in experimental testing has been developed by using the compliance form available in ASTM E-647 standard. Experimentally determined compliance value compared well with the new relation for C15 steel (AISI 1015) and P91 steel tested at room and elevated temperature conditions respectively. Fatigue crack growth rate data generated using the DEN(T-C) specimens on the two metallic materials are in good agreement with the data generated using standard compact specimens; thus validating the stress-intensity factor and the compliance equation for the double edge notch tension-compression specimen. The testing has shown that the DEN(T-C) specimen is prone to crack asymmetry issues. Through

  19. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

    Science.gov (United States)

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-06-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials.

  20. Optical Tweezers Studies on Notch: Single-molecule Interaction Strength is Independent of Ligand Endocytosis

    Science.gov (United States)

    Shergill, Bhupinder; Meloty-Kapella, Laurence; Musse, Abdiwahab A.; Weinmaster, Gerry; Botvinick, Elliot

    2012-01-01

    SUMMARY Notch signaling controls diverse cellular processes critical to development and disease. Cell surface ligands bind Notch on neighboring cells yet require endocytosis to activate signaling. The role ligand endocytosis plays in Notch activation has not been established. Here we integrate optical tweezers with cell biological and biochemical methods to test the prevailing model that ligand endocytosis facilitates recycling to enhance ligand interactions with Notch necessary to trigger signaling. Specifically, single-molecule measurements indicate that interference of ligand endocytosis and/or recycling does not alter the force required to rupture bonds formed between cells expressing the Notch ligand Delta-like1 (Dll1) and laser-trapped Notch1-beads. Together, our analyses eliminate roles for ligand endocytosis and recycling in Dll1-Notch1 interactions, and indicate that recycling indirectly affects signaling by regulating the accumulation of cell-surface ligand. Importantly, our study demonstrates the utility of optical tweezers to test a role for ligand endocytosis in generating cell-mediated mechanical force. PMID:22658935

  1. Fatigue Strength Improvement of Welded Joint by Ultrasonic Peening in Ultra-Fine Grain Steel

    Institute of Scientific and Technical Information of China (English)

    TIAN Zhi-ling; ZOU Gang; HE Chang-hong; ZHANG Xiao-mu

    2003-01-01

    The ultrasonic peening of weld toes in ultra-fine grain steel was applied to enhance the fatigue behavior. The test results show that the ultrasonic treatment remarkably shifts the S-N curve to the right. The FAT (fatigue strength at 106 cycles) is increased by 66 %. The fatigue life at Δσ=200 MPa is extended by 58 times. The mechanism of fatigue strength improvement by ultrasonic treatment was studied. It is shown that two mechanisms improve the fatigue strength of welded joint by ultrasonic treatment: one is the decrease of the stress concentration ratio at weld toes, and the other is the building-up of a compressive residual stress at the weld.

  2. Fatigue properties of high-strength materials used in cold-forging tools

    DEFF Research Database (Denmark)

    Brøndsted, P.; Skov-Hansen, P.

    1998-01-01

    In the present work classical analytical models are used to describe the static stress–strain curves, low-cycle fatigue properties and fatigue crack growth behaviour of high-strength materials for use in tools for metal-forming processes such as cold forging and extrusion. The paper describes...

  3. Assessment of Fatigue Strength of An Offshore Floating Production and Storage Unit

    Institute of Scientific and Technical Information of China (English)

    刘建成; 顾永宁

    2002-01-01

    The procedure of assessment of structural fatigue strength of an offshore floating production and storage and offloadingunit(FPSO) in this paper. The emphasis is placed on the long-term prediction of wave induced loading, the refined finite el-ement model for hot spot stress calculation, the combination of stress components, and fatigue damage assessment based onS-N curve.

  4. The fatigue strength of base material and butt welds made of S690 and S1100

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2007-01-01

    Modern steel manufacturing techniques make it possible to produce steel with nominal strengths up to 1100 MPa (very high strength steels, VHSS). For the design of cyclic loaded slender VHSS structures, the fatigue strength of both base material and welded components should be known. In a VHSS

  5. Effects of thermal fatigue on shear punch strength of tooth-colored restoratives

    Directory of Open Access Journals (Sweden)

    Fam Mei Shi Melody

    2016-01-01

    Conclusions: The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The “sculptable” composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the “flowable” injectable hybrid giomer was intermediate between the composite and GICs.

  6. Experimental and theoretical research on residual strength of plain concrete under compressive fatigue loading

    Institute of Scientific and Technical Information of China (English)

    MENG Xian-hong; SONG Yu-pu

    2008-01-01

    To investigate the residual strength of concrete under fatigue loading, experiments were conducted to determine the functional relation between residual strength and the number of cycles. 80 100mm×100mm×100ram specimens of plain concrete were tested under uniaxial compressive fatigue loading. Based on probabili-ty distribution of the residual strength of concrete under fatigue loading, the empirical expressions of the residual strength corresponding to the number of cycles were obtained. There is a good correlation between residual strength and residual secant elastic modulus. Thus the relationship between residual secant elastic modulus and the number of cycles is established. A damage variable based on the longitudinal maximum strain is defined, and a good linearity relationship between residual strength and damage is found out.

  7. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    OpenAIRE

    Etube, L. S.

    1998-01-01

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to 70OMPa. These steels are thought to exhib...

  8. NUMERICAL AND ANALYTICAL PROBLEMS OF FATIGUE STRENGTH IN ROLLING BEARINGS

    Directory of Open Access Journals (Sweden)

    Paweł ROMANOWICZ

    2014-06-01

    Full Text Available The aim of the work is to create an algorithm of fatigue life prediction for typical rolling bearings. The proposed approach makes use of various, well established hypothesis for multiaxial fatigue applied in engineering calculations. In the first part of the work the theoretical solutions for different contact problems are compared with the numerical ones. The respective numerical results are obtained with the use of finite element modelling (ANSYS software. Then, an algorithm for fatigue life prediction is demonstrated. The results of the proposed analysis are compared with those given in rolling bearings catalogue

  9. Fatigue failure of hydrogen embrittled high strength steels

    Science.gov (United States)

    Kim, Y. G.; Aleszka, J.

    1975-01-01

    Results of an experimental investigation are presented concerning the fracture behavior of cathodically charged, quenched and tempered martensitic steels under cyclic load conditions. Introduction of H2 by cathodic charging reduced fatigue life by as much as 60%. It is proposed that subsurface transverse fatigue cracks nucleate simultaneously at multiple sites, such as at microcracks, voids, or inclusions. Fatigue crack growth then occurs on planes perpendicular to the major applied stress axis in the presence of the critical combination of applied external stress and hydrogen.

  10. Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

    Science.gov (United States)

    Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

    2016-03-01

    In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

  11. Effect of Water on Ductility and Fatigue Strength of Austempered Ductile Cast Iron (adi)

    Science.gov (United States)

    Yakushiji, Terutoshi; Ferguson, W. George; Goto, Masahiro

    In order to study the mechanism of decreasing tensile strength and elongation of Austempered Ductile Cast Iron (ADI) in the wet condition, various tension tests and impact tests were carried out. Three point bending fatigue tests were carried out on ADI and annealed 0.55% carbon steel to clarify the influence of water on fatigue strength. The main conclusions are as follow. Embrittlement by water begins when plastic deformation starts in a tension test. The fatigue limit of ADI in water showed a lower value than that in air. The influence of a water environment on fatigue behaviour was similar to that of annealed 0.55% carbon steel. Embrittlement such as that in a tension test was not observed in a fatigue test.

  12. An Investigation on Fatigue in High-Strength Steel Offshore Structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Lopez Martinez, L.

    1997-01-01

    In the present investigation, the fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa, and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading....... In the experimental part of the investigation, fatigue test series have been carried through on both full-scale tubular joints and smaller welded plate test specimens, in high-strength steel as well as in conventional offshore structural steel. The present document gives a summary of the main results presented in two......, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  13. The fatigue strength of graphite and carbon materials for HTTR core components

    Energy Technology Data Exchange (ETDEWEB)

    Eto, Motokuni [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Arai, Taketoshi; Konishi, Takashi

    1998-03-01

    Room temperature fatigue tests were carried out on graphite and carbon materials, which are used for the components in the core region of the HTTR, in the applied stress condition that R (={sigma} min / {sigma} max)=-3, -1, 0 (PGX graphite), =-1, 0 (ASR-ORB carbon) and =-1 (IG-11 graphite). The data were analyzed by Price`s method, homologous stress method and P-T-S diagram method to investigate which is the most appropriate to derive design S-N curves. Fatigue tests were also carried out at 980degC in vacuo on IG-11 graphite to clarify the effect of temperature on its fatigue strength. The results indicated: (1) Price`s method was the most appropriate to analyze the data for a design S-N curve. (2) Fatigue strength decreased with decreasing R-value, with the less pronounced tendency for ASR-ORB. (3) Design S-N curves were obtained on PGX and ASR-ORB on the basis of the data analyzed by Price`s method. (4) Fatigue strength of IG-11 at 980degC appeared to be almost the same as that for the room temperature fatigue strength, if the applied stress was normalized to the mean tensile strength at room temperature in vacuo. (author)

  14. An Investigation on the Wear Resistance and Fatigue Behaviour of Ti-6Al-4V Notched Members Coated with Hydroxyapatite Coatings

    Directory of Open Access Journals (Sweden)

    Reza H Oskouei

    2016-02-01

    Full Text Available In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor of the uncoated titanium decreased from 0.31 to 0.06, through a fluctuating trend, after 50 cycles of wear tests. However, the friction factor of both the coated samples (10 and 50 µm gradually decreased from 0.20 to 0.12 after 50 cycles. At the end of the 50th cycle, the penetration depth of the 10 and 50 µm coated samples were 7.69 and 6.06 µm, respectively. Fatigue tests showed that hydroxyapatite coatings could improve fatigue life of a notched Ti-6Al-4V member in both low and high cycle fatigue zones. It was understood, from fractography of the fracture surfaces, that the fatigue zone of the uncoated specimens was generally smaller in comparison with that of the coated specimens. No significant difference was observed between the fatigue life of coated specimens with 10 and 50 µm thicknesses.

  15. Degradation in the Fatigue Strength of Dentin by Cutting, Etching and Adhesive Bonding

    Science.gov (United States)

    Lee, H.-H.; Majd, H.; Orrego, S.; Majd, B.; Romberg, E.; Mutluay, M.M.; Arola, D.

    2014-01-01

    The processes involved in placing resin composite restorations may degrade the fatigue strength of dentin and increase the likelihood of fractures in restored teeth. Objective The objective of this study was to evaluate the relative changes in strength and fatigue behavior of dentin caused by bur preparation, etching and resin bonding procedures using a 3-step system. Methods Specimens of dentin were prepared from the crowns of unrestored 3rd molars and subjected to either quasi-static or cyclic flexural loading to failure. Four treated groups were prepared including dentin beams subjected to a burr treatment only with a conventional straight-sided bur, or etching treatment only. An additional treated group received both bur and etching treatments, and the last was treated by bur treatment and etching, followed by application of a commercial resin adhesive. The control group consisted of “as sectioned” dentin specimens. Results Under quasi-static loading to failure there was no significant difference between the strength of the control group and treated groups. Dentin beams receiving only etching or bur cutting treatments exhibited fatigue strengths that were significantly lower (p≤0.0001) than the control; there was no significant difference in the fatigue resistance of these two groups. Similarly, the dentin receiving bur and etching treatments exhibited significantly lower (p≤0.0001) fatigue strength than that of the control, regardless of whether an adhesive was applied. Significance The individual steps involved in the placement of bonded resin composite restorations significantly decrease the fatigue strength of dentin, and application of a bonding agent does not increase the fatigue strength of dentin. PMID:24985539

  16. Fatigue of concrete under compression: Database and proposal for high strength concrete

    NARCIS (Netherlands)

    Lantsoght, E.O.L.

    2014-01-01

    The compressive strength of concrete decreases as an element is subjected to cycles of loading. In a typical fatigue test for the concrete compressive strength, a concrete specimen (typically a cylinder) is loaded between a lower and upper stress limit. These limits are expressed as a fraction of th

  17. Fatigue of concrete under compression: Database and proposal for high strength concrete

    NARCIS (Netherlands)

    Lantsoght, E.O.L.

    2014-01-01

    The compressive strength of concrete decreases as an element is subjected to cycles of loading. In a typical fatigue test for the concrete compressive strength, a concrete specimen (typically a cylinder) is loaded between a lower and upper stress limit. These limits are expressed as a fraction of

  18. Comparison of Fatigue Properties and Fatigue Crack Growth Rates of Various Implantable Metals

    Directory of Open Access Journals (Sweden)

    Yoshimitsu Okazaki

    2012-12-01

    Full Text Available The fatigue strength, effects of a notch on the fatigue strength, and fatigue crack growth rate of Ti-15Zr-4Nb-4Ta alloy were compared with those of other implantable metals. Zr, Nb, and Ta are important alloying elements for Ti alloys for attaining superior long-term corrosion resistance and biocompatibility. The highly biocompatible Ti-15Zr-4Nb-4Ta alloy exhibited an excellent balance between strength and ductility. Its notched tensile strength was much higher than that of a smooth specimen. The strength of 20% cold-worked commercially pure (C.P. grade 4 Ti was close to that of Ti alloy. The tension-to-tension fatigue strength of an annealed Ti-15Zr-4Nb-4Ta rod at 107 cycles was approximately 740 MPa. The fatigue strength of this alloy was much improved by aging treatment after solution treatment. The fatigue strengths of C.P. grade 4 Ti and stainless steel were markedly improved by 20% cold working. The fatigue strength of Co-Cr-Mo alloy was markedly increased by hot forging. The notch fatigue strengths of 20% cold-worked C.P. grade 4 Ti, and annealed and aged Ti-15Zr-4Nb-4Ta, and annealed Ti-6Al-4V alloys were less than those of the smooth specimens. The fatigue crack growth rate of Ti-15Zr-4Nb-4Ta was the same as that of Ti-6Al-4V. The fatigue crack growth rate in 0.9% NaCl was the same as that in air. Stainless steel and Co-Cr-Mo-Ni-Fe alloy had a larger stress-intensity factor range (ΔK than Ti alloy.

  19. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws.

    Science.gov (United States)

    Hou, Sheng-Mou; Wang, Jaw-Lin; Lin, Jinn

    2002-01-01

    To investigate the effects of the design and microstructure on the mechanical strength of tibial locking devices. The mechanical strength of two prototypes of specially developed locking devices (a both-ends-threaded screw and an unthreaded bolt) was tested and compared with that of five types of commercially available tibial locking screws (Synthes, Howmedica, Richards, Osteo AG, and Zimmer) with similar dimensions. The devices were inserted into a polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life were then measured. Failure analysis of the fractured screws was performed to investigate the microstructure and potential causes of the fatigue fracture. Test results showed that both yielding strength and fatigue life were closely related to the section modulus of the inner diameter of screws. Among the threaded screws, the both-ends-threaded screws had a higher yielding strength and longer fatigue life than the Osteo AG, Howmedica, Richards, and Zimmer screws. The unthreaded bolts had a lower yielding strength than Synthes screws, but they demonstrated the longest fatigue life among all. In failure analysis of broken screws, no metallurgical or manufacturing defects were found except for surface microimperfections. The implants investigated in this study are manufactured with high-quality materials and manufacturing processes. The main cause of hardware failure was mechanical overloading. The five commercially used tibial locking screws had a relatively short fatigue life under high loading. Removing the screw threads might substantially increase the fatigue life of the locking devices. In unthreaded bolts, this increase might be tenfold to a hundredfold.

  20. Fatigue behavior of press hardened Al-Si coated high strength steel

    Institute of Scientific and Technical Information of China (English)

    Wang Zijian; Gui Zhongxiang; Zhang Yisheng

    2014-01-01

    The fatigue behavior of press hardened Al-Si coated high strength steel has been investigated,and the fatigue strength turns out to be about 1 000 MPa. Surface morphology of fractured and non-fractured speci-men has been observed,and the coating shows significant influence on the fatigue behavior. The difference of elastic modulus between coating and substrate led to the main cracks perpendicular to the loading direction. The coating close to fracture exfoliated thinly,while the coating far away from the fracture kept integrated. Though the specimen was polished to obtain high surface quality,3 types of cracks occurred during the fatigue test. What’s more,inclusion particles were proved to play a crucial role in causing these cracks.

  1. Influence of laser treatment on the fatigue of notched bar%激光处理对切口棒料疲劳性能的影响

    Institute of Scientific and Technical Information of China (English)

    张辉; 凌维业; 蒋寿伟

    2003-01-01

    Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.%疲劳断料是一种新的分离材料方法.通过对棒料进行切口并施加旋弯载荷,可人为制造疲劳.为了进一步提高断裂的效率,采用激光对棒料切口的根部进行了处理,处理后的棒料疲劳周次大大降低.通过分析实验结果得到:棒料的疲劳受硬化区形状影响,具有较小轴向尺寸和较大径向尺寸的硬化区会促进疲劳.硬化区的形状可以通过调整激光处理参数来控制.

  2. The Effect of Shot Peening on the Fatigue Strength of Pure Titanium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-bin; FAN Ding; YU Shu-rong

    2004-01-01

    The changes of the substructure, the residual stress and the surface roughness of shot peened pure titanium were analyzed by means of SEM, TEM, XRD and surface roughness measurements in this paper. The results show that shot peening increased the fatigue strength of pure titanium. The substructures of shot peened pure titanium consist of dislocations, deformation twins and deformation bands. Fatigue loading will relax the compressive residual stress and decrease the strengthening effect. The increased surface roughness has negative effects.

  3. Factors that affect the fatigue strength of power transmission shafting and their impact on design

    Science.gov (United States)

    Leowenthal, S. H.

    1986-01-01

    A long standing objective in the design of power transmission shafting is to eliminate excess shaft material without compromising operational reliability. A shaft design method is presented which accounts for variable amplitude loading histories and their influence on limited life designs. The effects of combined bending and torsional loading are considered along with a number of application factors known to influence the fatigue strength of shafting materials. Among the factors examined are surface condition, size, stress concentration, residual stress and corrosion fatigue.

  4. Simple Predicting Method for Fatigue Crack Growth Rate Based on Tensile Strength of Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Three types of fatigue tests for an annealed carbon steel containing carbon of 0.42 % were carried out on smooth specimens and specimens with a small blind hole in order to investigate the fatigue crack growth law. A simple predicting method for crack growth rates has been proposed involving strength σb and the relation between cyclic stress and strain. The validity of proposed method has been confirmed by experiments on several carbon steels with different loadings.

  5. Mobility-Related Fatigue, Walking Speed, and Muscle Strength in Older People

    DEFF Research Database (Denmark)

    Mänty, Minna; Mendes de Leon, Carlos F.; Rantanen, Taina

    2012-01-01

    Background. Fatigue is an important early marker of functional decline among older people, but the mechanisms underlying this association are not fully understood. The purpose of the present study was to examine the association between mobility-related fatigue and walking speed and to test...... the degree to which muscle strength accounts for this association. Methods. The study is based on baseline (n = 523) and 5-year follow-up data (n = 292) from a cohort of 75-year-old persons. Standardized assessments include self-report measures of mobility-related fatigue (score range 0–6) and medical...

  6. Fatigue reliability based on residual strength model with hybrid uncertain parameters

    Institute of Scientific and Technical Information of China (English)

    Jun Wang; Zhi-Ping Qiu

    2012-01-01

    The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model.By solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness,the fatigue reliability with hybrid parameters can be obtained.The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters.A comparison among the presented hybrid model,non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples.The results show that the presented hybrid model,which can ensure structural security,is effective and practical.

  7. Fatigue strength of a Ti-6Al-4V alloy produced by selective laser melting

    Science.gov (United States)

    Gerov, M. V.; Vladislavskaya, E. Yu.; Terent'ev, V. F.; Prosvirnin, D. V.; Kolmakov, A. G.; Antonova, O. S.

    2016-10-01

    The fatigue properties and the fracture mechanisms of the Ti-6Al-4V alloy produced by selective laser melting (SLM) from a powder of an CL41TiELI titanium alloy have been studied. Cylindrical blanks were grown at angles of 90° and 45° to a platform. The best fatigue strength is observed in the samples the blanks of which were grown at an angle of 45°. It is found that the structure of the SLM material can contain portions with unmelted powder particles, which are the places of initiation of fatigue cracks.

  8. 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...

  9. Reliability analysis of stochastic structural system considering static strength, stiffness and fatigue

    Institute of Scientific and Technical Information of China (English)

    AN WeiGuang; ZHAO WeiTao; AN Hai

    2007-01-01

    Multi-failures are possible to appear in the process of using the structural system,such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation induced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reliability analysis considering static strength, fatigue and stiffness is given. A numerical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the paper, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.

  10. Reliability analysis of stochastic structural system considering static strength, stiffness and fatigue

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Multi-failures are possible to appear in the process of using the structural system, such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation in- duced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reli- ability analysis considering static strength, fatigue and stiffness is given. A nu- merical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the pa- per, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.

  11. Fatigue Performance of Advanced High-Strength Steels (AHSS) GMAW Joints

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [ORNL; Sang, Yan [AET Integration, Inc; Jiang, Cindy [AET Integration, Inc; Chiang, Dr. John [Ford Motor Company; Kuo, Dr. Min [MIttal Steel

    2009-01-01

    The fatigue performance of gas metal arc welding (GMAW) joints of advanced high strength steels (AHSS) are compared and analyzed. The steel studied included a number of different grades of AHSS and baseline mild steels: DP600, DP780, DP980, M130, M220, solution annealed boron steel, fully hardened boron steels, HSLA690 and DR210 (a mild steel). Fatigue testing was conducted under a number of nominal stress ranges to obtain the S/N curves of the weld joints. A two-phase analytical model is developed to predict the fatigue performance of AHSS welds. It was found that there are appreciable differences in the fatigue S/N curves among different AHSS joints made using the same welding practices, suggesting that the local microstructure in the weld toe and root region plays non-negligible role in the fatigue performance of AHSS welds. Changes in weld parameters can influence the joint characteristics which in turn influence fatigue life of the weld joints, particularly of those of higher strength AHSS. The analytical model is capable of reasonably predicting the fatigue performance of welds made with various steel grades in this study.

  12. Comparison of Post Weld Treatment of High Strength Steel Welded Joints in Medium Cycle Fatigue

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters; Mouritsen, Ole Ø.; Hansen, Michael Rygaard

    2010-01-01

    the stress range can exceed the yield-strength of ordinary structural steel, especially when considering positive stress ratios (R > 0). Fatigue experiments and qualitative evaluation of the different post-weld treatments leads to the selection of TIG dressing. The process of implementing TIG dressing......This paper presents a comparison of three post-weld treatments for fatigue life improvement of welded joints. The objective is to determine the most suitable post-weld treatment for implementation in mass production of certain crane components manufactured from very high-strength steel....... The processes investigated are: burr grinding, TIG dressing and ultrasonic impact treatment. The focus of this investigation is on the so-called medium cycle area, i.e. 10 000-500 000 cycles and very high stress ranges. In this area of fatigue design, the use of very high strength steel becomes necessary, since...

  13. An investigation on fatigue in high-strength steel offshore structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1998-01-01

    The fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading. In the experimental part...... of the investigation, fatigue test series were carried out on both full scale tubular joints and smaller welded plate test specimens in high-strength steel as well as in conventional offshore structural steel. This paper gives a summary of the main results presented in two recent research reports [15, 16], from...... specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  14. Associations of Midlife to Late Life Fatigue With Physical Performance and Strength in Early Old Age

    DEFF Research Database (Denmark)

    Mänty, Minna Regina; Kuh, Diana; Cooper, Rachel

    2015-01-01

    objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests. RESULTS: There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise, and TUG performance at 60 to 64 years. Furthermore, individuals reporting frequent...... fatigue at both ages had weaker grip strength (β = -4.09 kg, 95% confidence interval [CI] = -6.71 to -1.48) and slower chair rise (β = -4.65 repetitions/min, 95% CI = -6.65 to -2.64) and TUG (β = -4.22 cm/s, 95% CI = -12.16 to -2.28) speeds when compared with those who reported no fatigue at both time...

  15. Residual fatigue strength of 48MnV crankshaft based on safety factor

    Institute of Scientific and Technical Information of China (English)

    WANG Xiang; CHEN Ming; PU Geng-qiang; WANG Cheng-tao

    2005-01-01

    Residual fatigue strength of 48MnV crankshaft was studied and analyzed based on safety factor. Three different status crankshafts were used to the hop-up tests, which maintain new after 500 h hop-up tests and after 1 000 h hop-up tests. Then, crankshafts were cut into unit cranks. The unit cranks were used to do endurance bending tests to get the residual fatigue strength. Finally, the results were analyzed based on safety factor. The results show that safety factor of crankshaft descends a little with the increase of the running time, and the residual safety factor is still much bigger than the endurable safety factor. Furthermore, after the crankshaft accomplishes a full life cycle, the residual fatigue strength of the crankshaft is enough to remanufacture and fulfill the next life cycle.

  16. Proof of fatigue strength of ferritic and austenitic nuclear components

    Energy Technology Data Exchange (ETDEWEB)

    Roos, E.; Herter, K.H.; Schuler, X.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany)

    2009-07-01

    For the construction, design and operation of nuclear components and systems the appropriate technical codes and standards provide material data, detailed stress analysis procedures and a design philosophy which guarantees a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. For the fatigue design curves used as limiting criteria the influence of different factors like e.g., environment, surface finish and temperature must be taken into consideration in an appropriate way. Fatigue tests were performed with low alloy steels as well as with Nb- and Ti-stabilized German austenitic stainless steels in air and simulated high temperature boiling water reactor environment. The experimental results are compared and valuated with the mean data curves in air as well as with mean data curves under high temperature water environment published in the international literature. (orig.)

  17. FATIGUE STRENGTH OF A STRUCTURAL ELEMENT EXPOSED TO ICE LOADING

    Directory of Open Access Journals (Sweden)

    Uvarova Tat'yana Erikovna

    2012-10-01

    Full Text Available The cyclic nature of effects of ice loading contributes to the formation of non-reversible deformations and defects of structural elements that may cause loss of the bearing capacity of the structure due to the accumulation of fatigue damages in dangerous sections. The damages in question are caused by moderate loads of multiple repeatability. In order to assess the number of cycles of ice loading that the structure may be exposed to without any substantial damages, the authors have developed a simulation model of ice load formation that serves as the basis for the analysis of the loading pattern that the structure is exposed to. This loading pattern is the initial one for the purposes of calculation of the fatigue resistance of structural elements to ice load effects. In the research, the authors provide for the joint application of the simulation model of ice load formation and the model of accumulation of fatigue damages to assess the ice resistance of a platform and its reliability from the viewpoint of its failure.

  18. Comparison of Bending Fatigue Strength among Spur Gears Manufactured by Various Methods

    Science.gov (United States)

    Yamanaka, Masashi; Matsushima, Yu; Miwa, Shinji; Narita, Yukihito; Inoue, Katsumi; Kawasaki, Yoshiki

    This paper deals with an experimental evaluation of bending fatigue strengths for hobbed, forged, sintered and austempered ductile iron (ADI) spur gears. The module is 2.5 and the number of teeth is 26 in the test gears. The materials of the test gears are SCr420H for hobbed and forged gears, prealloyed powder metal with 1.5 wt.% Mo for sintered gears, and FCAD 1100-15 for ADI gears. All gears except ADI gears were carburized. The pulsator bending fatigue tests were carried out for the test gears. Then the relationship between the strength and the manufacturing cost is obtained. The forged gear has the high strength of 3% and low cost compared with the hobbed gear. It is the best among the four gears. The sintered and ADI gears have approximately half the strength and cost of the hobbed gear. These gears are effective when cost is a high priority. In the progress of the fatigue tests, comparisons of strength among gears having different tooth-root forms were needed. The nominal stress obtained from actual measured profile data using a noncontact-type measuring machine is suitable for comparing the fatigue strength in gears having different root forms.

  19. Fatigue strength of MAR-M509 alloy with structure refined by rapid crystallization

    Directory of Open Access Journals (Sweden)

    M. Mróz

    2010-07-01

    Full Text Available This study presents test results of high-cycle (N>2⋅107 fatigue bending strength of MAR-M-509 cobalt alloy samples, as cast and aftersurface refining with a concentrated stream of heat. Tests were conducted on samples of MAR-M59 alloy casts, obtained using the lostwax method. Cast structure refining was performed with the GTAW method in argon atmosphere, using the current I = 200 A andelectrical arc scanning velocity vs = 250 mm/min. The effect of rapid crystallization occurring after the fusion process is refinement of the MAR-M509 alloy cast microstructure and significant improvement in bending fatigue strength.

  20. STUDY ON THE METHOD OF FATIGUE STRENGTH DESIGN FOR DYNAMICALLY LOADED JOURNAL BEARING

    Institute of Scientific and Technical Information of China (English)

    FanXun; MengHuirong

    1996-01-01

    In this paper, a novel design method, which is different from the traditional and empirical one (i. e. , taking p and pv as the basic checking parameters) is presented for the fatigue strength design of dynamically loaded journal bearings. The method makes it possible that dynamically loaded bearings can be designed as same as other machine elements hy stress-strength criterion. The practical design results show that the method has high accuracy and reliability, and may open a new vista in bearing fatigue designs.

  1. Fatigue-induced damage of high-strength steels

    Science.gov (United States)

    Shetulov, D. I.; Myl'nikov, V. V.

    2014-03-01

    The issues on the estimation of the surface damage of the products produced from high-strength alloys are considered. Mathematical relationships for a numerical calculation of the surface damage are given. The peculiarities of the evaluation of the surface damage are investigated, as applied to high-strength alloys.

  2. 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.

  3. Damage formation, fatigue behavior and strength properties of ZrO2-based ceramics

    Science.gov (United States)

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

    2016-08-01

    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 ZrO2-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 105 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.

  4. Fatigue Performance of Microalloyed High-strength Rebar and Analysis of Fracture Mechanism

    Institute of Scientific and Technical Information of China (English)

    Peng-yan LU; Yu LIU; Hua-jie WU; Gang LIU; Xiang MENG; Yang XU

    2015-01-01

    Fatigue performance of hot-rolled ribbed-steel bar with the yield strength of 500 MPa (HRB500)was stud-ied with bend-rotating fatigue test at a stress ratio of R=-1 .It is determined by staircase method that its fatigue strength for 107 cycles is 451 MPa,which is higher than that of common carbon structural steel.This should be at-tributed to the fine-grain strengthening resulting from the high content of alloy element V and Thermo-Mechanical Control Process (TMCP).The S-N curve function is also obtained by nonlinear regression with three parameters power function.The fatigue fractures of the specimen were further analyzed with Scanning Electron Microscopy (SEM)and Energy Disperse Spectroscopy (EDS)to study the fracture mechanism.Taking into account microstruc-ture,hardness and cleanliness of the material,it implies that the fatigue fractures of HRB500 rebar all arise from surface substrates in which many brittle inclusions are contained,and that the fatigue crack propagation is principally based on the mechanism of quasi-cleavage fracture,because of the intracrystalline hard spots leading to stress con-centration and thus to the cracks.Moreover,the transient breaking area exhibits microvoid coalescence of ductile fracture due to the existing abundant inclusions.

  5. The influence of short-term strength on the notch sensitivity and crack growth resistance of the metal of rotors under creep conditions

    Science.gov (United States)

    Gladshtein, V. I.

    2014-06-01

    Comparative assessment of the effect the yield strength has on the characteristics of EI-415 steel under creep conditions is carried out based on the results from long-term (for more than 70000 h) tests of notched samples at an elevated temperature. The metal of three rotors (EI-415 steel) (one after it had been in operation for 137000 h and the other two in the delivery state with relatively increased and decreased levels of yield strength) was used as material under study. The notch sensitivity was evaluated from the ratio between the long-term strength of smooth samples and that of notched samples tested for long-term strength with recording the crack opening width. The resistances to crack incipience and to crack growth with a preset rate were determined from the lengths of cracks appeared at the end of two auxiliary notches of a smaller depth, and the creep fracture toughness was calculated from the break conditions. It is shown that the metal the properties of which are at the lower boundary of yield strength requirements is slightly more advantageous in the level of the above-mentioned characteristics.

  6. Analysis of Fretting Fatigue Strength of Integral Shroud Blade for Steam Turbine

    Science.gov (United States)

    Kaneko, Yasutomo; Tomii, Masayuki; Ohyama, Hiroharu; Kurimura, Takayuki

    To improve the reliability and the thermal efficiency of LP (Low Pressure) end blades of steam turbine, new standard series of LP end blades have been developed. The new LP end blades are characterized by the ISB (Integral Shroud Blade) structure. In the ISB structure, blades are continuously coupled by blade untwist due to centrifugal force when the blades rotate at high speed. One of the probable failure modes of the ISB structure seems to be fretting fatigue, because the ISB utilizes friction damping between adjacent shrouds and stubs. Therefore, in order to design a blade with high reliability, the design procedure for evaluating the fretting fatigue strength was established by the model test and the nonlinear contact analysis. This paper presents the practical design method for predicting the fretting fatigue strength of the ISB structure, and the some applications are explained.

  7. Strength training improves fatigue resistance and self-rated health in workers with chronic pain

    DEFF Research Database (Denmark)

    Sundstrup, Emil; Jakobsen, Markus Due; Brandt, Mikkel

    2016-01-01

    care ergonomic training (control). At baseline and follow-up, participants performed a handgrip muscular fatigue test (time above 50% of maximal voluntary contraction force) with simultaneous recording of electromyography. Additionally, participants replied to a questionnaire regarding self......Chronic musculoskeletal pain is widespread in the working population and leads to muscular fatigue, reduced work capacity, and fear of movement. While ergonomic intervention is the traditional approach to the problem, physical exercise may be an alternative strategy. This secondary analysis...... of a randomized controlled trial investigates the effect of strength training on muscular fatigue resistance and self-rated health among workers with chronic pain. Sixty-six slaughterhouse workers with chronic upper limb pain and work disability were randomly allocated to 10 weeks of strength training or usual...

  8. Fatigue and Muscle Strength Involving Walking Speed in Parkinson’s Disease: Insights for Developing Rehabilitation Strategy for PD

    Directory of Open Access Journals (Sweden)

    Ying-Zu Huang

    2017-01-01

    Full Text Available Background. Problems with gait in Parkinson’s disease (PD are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods. We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC, twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI and Fatigue Severity Scale (FSS. Results. The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion. Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force.

  9. Fatigue and Muscle Strength Involving Walking Speed in Parkinson's Disease: Insights for Developing Rehabilitation Strategy for PD

    Science.gov (United States)

    Chang, Fang-Yu; Liu, Wei-Chia; Chuang, Yu-Fen; Chuang, Li-Ling

    2017-01-01

    Background. Problems with gait in Parkinson's disease (PD) are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods. We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC), twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI) and Fatigue Severity Scale (FSS). Results. The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion. Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force. PMID:28321339

  10. INFLUENCE OF LASER CUTTING ON THE FATIGUE LIMIT OF TWO HIGH STRENGTH STEELS

    OpenAIRE

    Mateo García, Antonio Manuel; Fargas Ribas, Gemma; Calvo Muñoz, Jessica; Roa Rovira, Joan Josep

    2013-01-01

    Laser cutting is widely used in the metal industry, particularly when components of high strength steels sheets are produced. On the other hand, the roughness of cut - edges produced by laser differs from that obt ained by other methods, such as mechanical blank ing, and this fact influence s the fatigue performance. Moreover, thermal effects are another factor to consider. In the present investigation, specimens of two grades of high strength ...

  11. Fatigue strength of Co-Cr-Mo alloy clasps prepared by selective laser melting.

    Science.gov (United States)

    Kajima, Yuka; Takaichi, Atsushi; Nakamoto, Takayuki; Kimura, Takahiro; Yogo, Yoshiaki; Ashida, Maki; Doi, Hisashi; Nomura, Naoyuki; Takahashi, Hidekazu; Hanawa, Takao; Wakabayashi, Noriyuki

    2016-06-01

    We aimed to investigate the fatigue strength of Co-Cr-Mo clasps for removable partial dentures prepared by selective laser melting (SLM). The Co-Cr-Mo alloy specimens for tensile tests (dumbbell specimens) and fatigue tests (clasp specimens) were prepared by SLM with varying angles between the building and longitudinal directions (i.e., 0° (TL0, FL0), 45° (TL45, FL45), and 90° (TL90, FL90)). The clasp specimens were subjected to cyclic deformations of 0.25mm and 0.50mm for 10(6) cycles. The SLM specimens showed no obvious mechanical anisotropy in tensile tests and exhibited significantly higher yield strength and ultimate tensile strength than the cast specimens under all conditions. In contrast, a high degree of anisotropy in fatigue performance associated with the build orientation was found. For specimens under the 0.50mm deflection, FL90 exhibited significantly longer fatigue life (205,418 cycles) than the cast specimens (112,770 cycles). In contrast, the fatigue lives of FL0 (28,484 cycles) and FL45 (43,465 cycles) were significantly shorter. The surface roughnesses of FL0 and FL45 were considerably higher than those of the cast specimens, whereas there were no significant differences between FL90 and the cast specimens. Electron backscatter diffraction (EBSD) analysis indicated the grains of FL0 showed preferential close to orientation of the γ phase along the normal direction to the fracture surface. In contrast, the FL45 and FL90 grains showed no significant preferential orientation. Fatigue strength may therefore be affected by a number of factors, including surface roughness and crystal orientation. The SLM process is a promising candidate for preparing tough removable partial denture frameworks, as long as the appropriate build direction is adopted.

  12. Fatigue experiments on hybrid welded connections made of very high strength steels

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    In a fatigue loaded structure made of Very High Strength Steels (VHSS) absolute and relative stress variations will be higher compared to those in structures made of lower grade steels. Stress concentrations in joints reduce the advantage of VHSS under cyclic loading. A hybrid connection, consisting

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

    NARCIS (Netherlands)

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

    2009-01-01

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

  14. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

    Science.gov (United States)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  15. Improvement of the fatigue life of titanium alloys for biomedical devices through microstructural control.

    Science.gov (United States)

    Niinomi, Mitsuo; Akahori, Toshikazu

    2010-07-01

    A limited number of reports exist regarding the systematic investigation or comparison of the fatigue strength of titanium alloys for medical devices, including plain, fretting and notch fatigue, for improvement through various treatments and processes, with respect to related microstructures. This article focuses on the changes and improvements in fatigue strength of newly developed beta-type and practically used alpha + beta-titanium alloys for medical devices through heat treatments, thermomechanical treatments and surface modifications.

  16. Fatigue experiments on connections made of very high strength steels

    NARCIS (Netherlands)

    Pijpers, R.; Kolstein, H.; Bijlaard, F.

    2013-01-01

    An effective application of Very High Strength Steels (VHSS) can be expected in truss-like structures, typically made of hollow sections. Improved design of VHSS truss structures could incorporate the application of cast joints, since an appropriate design of cast joints limits the stress concentrat

  17. Evaluation of shot peening on the fatigue strength of anodized Ti-6Al-4V alloy

    Directory of Open Access Journals (Sweden)

    Costa Midori Yoshikawa Pitanga

    2006-01-01

    Full Text Available The increasingly design requirements for modern engineering applications resulted in the development of new materials with improved mechanical properties. Low density, combined with excellent weight/strength ratio as well as corrosion resistance, make the titanium attractive for application in landing gears. Fatigue control is a fundamental parameter to be considered in the development of mechanical components. The aim of this research is to analyze the fatigue behavior of anodized Ti-6Al-4V alloy and the influence of shot peening pre treatment on the experimental data. Axial fatigue tests (R = 0.1 were performed, and a significant reduction in the fatigue strength of anodized Ti-6Al-4V was observed. The shot peening superficial treatment, which objective is to create a compressive residual stress field in the surface layers, showed efficiency to increase the fatigue life of anodized material. Experimental data were represented by S-N curves. Scanning electron microscopy technique (SEM was used to observe crack origin sites.

  18. Analysis of methods for determining high cycle fatigue strength of a material with investigation of titanium-aluminum-vanadium gigacycle fatigue behavior

    Science.gov (United States)

    Pollak, Randall D.

    Today, aerospace engineers still grapple with the qualitative and quantitative understanding of fatigue behavior in the design and testing of turbine-driven jet engines. The Department of Defense has taken a very active role in addressing this problem with the formation of the National High Cycle Fatigue Science & Technology Program in 1994. The primary goal of this program is to further the understanding of high cycle fatigue (HCF) behavior and develop methods in order to mitigate the negative impact of HCF on aerospace operations. This research supports this program by addressing the fatigue strength testing guidance currently provided by the DoD to engine manufacturers, with the primary goal to investigate current methods and recommend a test strategy to characterize the fatigue strength of a material at a specified number of cycles, such as the 109 design goal specified by MIL-HDBK-1783B, or range of cycles. The research utilized the benefits of numerical simulation to initially investigate the staircase method for use in fatigue strength testing. The staircase method is a commonly used fatigue strength test, but its ability to characterize fatigue strength variability is extremely suspect. A modified staircase approach was developed and shown to significantly reduce bias and scatter in estimates for fatigue strength variance. Experimental validation of this proposed test strategy was accomplished using a dual-phase Ti-6Al-4V alloy. The HCF behavior of a second material with a very different microstructure (beta annealed Ti-6Al-4V) was also investigated. The random fatigue limit (RFL) model, a recently developed analysis tool, was investigated to characterize stress-life behavior but found to have difficulty representing fatigue life curves with sharp transitions. Two alternative models (bilinear and hyperbolic) were developed based on maximum likelihood methods to better characterize the Ti-6Al-4V fatigue life behavior. These models provided a good fit to the

  19. Residual strength evaluation of concrete structural components under fatigue loading

    Indian Academy of Sciences (India)

    A Rama Chandra Murthy; G S Palani; Nagesh R Iyer; Smitha Gopinath; B K Raghu Prasad

    2012-02-01

    This paper presents methodologies for residual strength evaluation of concrete structural components using linear elastic and nonlinear fracture mechanics principles. The effect of cohesive forces due to aggregate bridging has been represented mathematically by employing tension softening models. Various tension softening models such as linear, bilinear, trilinear, exponential and power curve have been described with appropriate expressions. These models have been validated by predicting the remaining life of concrete structural components and comparing with the corresponding experimental values available in the literature. It is observed that the predicted remaining life by using power model and modified bi-linear model is in good agreement with the corresponding experimental values. Residual strength has also been predicted using these tension softening models and observed that the predicted residual strength is in good agreement with the corresponding analytical values in the literature. In general, it is observed that the variation of predicted residual moment with the chosen tension softening model follows the similar trend as in the case of remaining life. Linear model predicts large residual moments followed by trilinear, bilinear and power models.

  20. Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep and thermal fatigue

    Science.gov (United States)

    Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

    1992-01-01

    This report presents the results of a fourth year effort of a research program, conducted for NASA-LeRC by the University of Texas at San Antonio (UTSA). The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subject to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 has been analyzed using the developed methodology.

  1. On the use of the Theory of Critical Distances to estimate the dynamic strength of notched 6063-T5 aluminium alloy

    OpenAIRE

    Yin, T; Tyas, A; PLEKHOV, O.; Terekhina, A.; L. Susmel

    2014-01-01

    In this paper the so-called Theory of Critical Distances is reformulated to make it suitable for estimating the strength of notched metals subjected to dynamic loading. The TCD takes as its starting point the assumption that engineering materials’ strength can accurately be predicted by directly post-processing the entire linear-elastic stress field acting on the material in the vicinity of the stress concentrator being assessed. In order to extend the used of the TCD to situation...

  2. CALCULATION OF FUZZY RELIABILITYIN THE CASE OF RANDOM STRESSAND FUZZY FATIGUE STRENGTH

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The fuzzy sets theory is introduced into the fatigue reliability analysis.The concepts of maximizing set and minimizing set are developed to decide the ordering value of each fuzzy number,and these values can be used to determine the order of the fuzzy numbers.On the basis of the works mentioned above,the membership function defining the fuzzy safety event can be calculated,and then the fuzzy reliability in the case of random stress and fuzzy fatigue strength is deduced.An example is given to illustrate the method.

  3. 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

    . 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......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...

  4. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    Science.gov (United States)

    Etube, Linus Sone

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to TOOMPa. These steels are thought to exhibit fatigue resistance properties which are different when compared with conventional fixed platform steels such as BS 4360 50D and BS 7191 355D. The difference in their behaviour was heightened by the discovery, in the late 80s and early 90s, of extensive cracking around the spud can regions of several Jack-ups operating in the North Sea. It was thought that these steels may be more susceptible to hydrogen cracking and embrittlement. There was the additional requirement to study their behaviour under realistic loading conditions typical of the North Sea environment. This thesis contains results of an investigation undertaken to assess the performance of a typical high strength weldable Jack-up steel under realistic loading and environmental conditions. Details of the methodology employed to develop a typical Jack-up Offshore Standard load History (JOSH) are presented. The factors which influence fatigue resistance of structural steels used in the construction of Jack-up structures are highlighted. The methods used to model the relevant factors for inclusion in JOSH are presented with particular emphasis on loading and structural response interaction. Results and details of experimental variable amplitude corrosion fatigue (VACF) tests conducted using JOSH are reported and discussed with respect to crack growth mechanisms in high strength weldable Jack-up steels. Different fracture mechanics models for VACF crack growth prediction are compared and an improved generalised methodology for fast

  5. Nickel multilayers and their effects on bend fatigue strength of leads

    Institute of Scientific and Technical Information of China (English)

    LIU Feihua; WANG Zhanhua; SHEN Zhuoshen

    2004-01-01

    Nickel is commonly coated on the outer leads for T8 metal package. The leads electrodeposited by conventional dull or bright nickel over 5 μm at direct current from Watt bath are hard to pass the bend fatigue test for three times. Nickel electrodeposited at multi waveform current including direct current, single and double pulse from sulfamate bath can improve the bend fatigue strength of leads. Such nickel plating has a multilayer structure, its morphology of sublayers can be clearly seen in its cross section with SEM. The electrochemical study shows that these sublayers have different corrosion potentials. The bend fatigue test of leads with such plating for T8 metal package shows that the number of bend increases with the decrease of average current density of multi waveform, which can be attributed to the reduction of every sublayer thickness and the increase of layer numbers under the same condition of total thickness.

  6. Strength distribution of fatigue crack initiation sites in an Al-Li alloy

    Science.gov (United States)

    Zhai, T.

    2006-10-01

    The stress-number of cycles to failure (S-N) curves were measured along the short-transverse (S) and rolling (L) directions of a hot-cross-rolled AA 8090 Al-Li alloy plate (45-mm thick). The alloy was solution heat treated, quenched in water, strained by 6 pct, and peak aged. Fatigue tests were carried out in four-point bend at room temperature, 20 Hz, R=0.1, in air. It was found that the fatigue limits in the S and L directions were 147 and 197 MPa, respectively. The crack population on the surface of a sample at failure increased with the applied stress level and was found to be a Weibull function of the applied maximum stress in this alloy. The strength distribution of fatigue weakest links, where cracks were initiated, was derived from the Weibull function determined by the experimental data. The fatigue weakest-link density was defined as the crack population per unit area at a stress level close to the ultimate tensile stress and can be regarded as a materials property. The density and strength distribution of fatigue weakest links were found to be markedly different between the L and S directions, accounting for the difference in fatigue limit between the directions in this alloy. They were also found to be different between S-L and S-T samples, and between L-T and L-S samples of this alloy, which could not be revealed by the corresponding S-N curves measured. These differences were due to the anisotropy of the microstructures in different directions in this alloy.

  7. Investigation of Contact Fatigue of High Strength Steel Gears Subjected to Surface Treatment

    Science.gov (United States)

    Dimitrov, L.; Michalopoulos, D.; Apostolopoulos, Ch. Alk.; Neshkov, T. D.

    2009-10-01

    In this paper the contact fatigue resistance of gearwheel teeth, subjected to shot-peening treatment, was investigated experimentally and analytically. The main objective was the evaluation and prediction of fatigue crack initiation, propagation, direction, and rate. A specially designed experimental rig was used to test a number of spur gears with the following characteristics: (a) unhardened, thermally untreated unpeened surfaces, (b) thermally treated unpeened surfaces, (c) unhardened peened surfaces, and (d) thermally treated peened surfaces. The theoretical model assumed initiation and propagation of surface cracks of gears operating in the elastohydrodynamic lubrication regime while loading was due to simultaneous rolling and sliding. Finite element modeling was used for the calculation of the stress field at the gear teeth. Comparison of the experimental and analytical results showed considerable improvement in the contact fatigue strength of thermally treated gear teeth and especially those that underwent shot peening, which increased surface durability. The residual stresses induced by shot peening are mainly effective in stopping microcrack propagation. When shot peening is applied on thermally untreated gear teeth surface, it increases the contact fatigue life of the material by 17% at 7 × 105 loading cycles. If shot peening is applied on carburized gear teeth surfaces, it increases the surface fatigue life by approximately 8% at 106 cycles. Contact fatigue and eventual pitting are treated as a normal consequence of the operation of machine elements. To study this failure process different types of testing machines have been designed. The purpose of this paper is the presentation and evaluation of a new design experimental rig for studying contact fatigue damage of gear teeth subjected to different load patterns.

  8. Clarification of strain limits considering the ratcheting fatigue strength of 316FR steel

    Energy Technology Data Exchange (ETDEWEB)

    Isobe, Nobuhiro [Hitachi Ltd. (Japan)], E-mail: nobuhiro.isobe.jk@hitachi.com; Sukekawa, Masayuki [Hitachi Ltd. (Japan); Nakayama, Yasunari [Kawasaki Heavy Industries Ltd. (Japan); Date, Shingo; Ohtani, Tomomi [Mitsubishi Heavy Industries Ltd. (Japan); Takahashi, Yukio [Central Research Institute of Electric Power Industry (Japan); Kasahara, Naoto [Japan Atomic Energy Agency (Japan); Shibamoto, Hiroshi; Nagashima, Hideaki; Inoue, Kazuhiko [Japan Atomic Power Company (Japan)

    2008-02-15

    The effect of ratcheting on fatigue strength was investigated in order to rationalize the strain limit as a design criterion of commercialized fast reactor systems. Ratcheting fatigue tests were conducted at 550 deg. Duration of the ratchet straining was set for a certain number of strain cycles taking the loading condition of fast reactors into account, and the number of cycles for strain accumulation was defined as the ratchet-expired cycle. Fatigue lives decrease as the accumulated strain by ratcheting increases. Mean stress increased during the ratcheting cycle and its maximum value depended on the accumulated strain and the ratchet-expired cycle. Fatigue life reduction was negligible when the maximum mean stress was less than 25 MPa, corresponding to an accumulated strain of 2.2%. Accumulated strain is limited to 2% in the present design guidelines and this strain limit is considered effective to avoid reducing fatigue life by ratcheting. Microcrack growth behaviors were also investigated in these tests in order to discuss the life reduction mechanisms in ratcheting conditions.

  9. Kic size effect study on two high-strength steels using notched bend specimens

    Science.gov (United States)

    Stonesifer, F. R.

    1974-01-01

    Five methods are used to calculate plane strain fracture toughness (K sub Q) values for bend-specimens of various sizes from two high-strength steels. None of the methods appeared to satisfactorily predict valid stress intensity factor (K sub IC) values from specimens of sizes well below that required by E399 standard tests.

  10. Effect of pulsed current welding on fatigue behaviour of high strength aluminium alloy joints

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, V. [Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar 608 002, Tamil Nadu (India)], E-mail: visvabalu@yahoo.com; Ravisankar, V. [Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar 608 002, Tamil Nadu (India); Madhusudhan Reddy, G. [Metal Joining Section, Defence Metallurgical Research Laboratory (DMRL), Kanchanbag (P.O), Hyderabad 560 058 (India)

    2008-07-01

    High strength aluminium alloys (Al-Zn-Mg-Cu alloys) have gathered wide acceptance in the fabrication of light weight structures requiring high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminium alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass welded joints. Single V butt joint configuration has been prepared for joining the plates. The filler metal used for joining the plates is AA 5356 (Al-5Mg (wt%)) grade aluminium alloy. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW) and (iv) pulsed current GMAW (PCGMAW) processes. Argon (99.99% pure) has been used as the shielding gas. Fatigue properties of the welded joints have been evaluated by conducting fatigue test using rotary bending fatigue testing machine. Current pulsing leads to relatively finer and more equi-axed grain structure in gas tungsten arc (GTA) and gas metal arc (GMA) welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Grain refinement is accompanied by an increase in fatigue life and endurance limit.

  11. Identification of low cycle fatigue parameters of high strength low-alloy (HSLA steel at room temperature

    Directory of Open Access Journals (Sweden)

    S. Bulatović

    2014-10-01

    Full Text Available Low cycle fatigue test was performed in ambient atmosphere at room temperature. Cycle loading of material, in case of High strength low-alloy steel, entails modifications of its properties and in this paper is therefore shown behavior of fatigue life using low cycle fatigue parameters. More precisely, crack initiation life of tested specimens was computed using theory of Coffin-Manson relation during the fatigue loading. The geometry of the stabilized hysteresis loop of welded joint HSLA steel, marked as Nionikral 70, is also analyzed. This stabilized hysteresis loop is very important for determination of materials properties.

  12. FATIGUE LIFE PREDICTION FOR NOTCHED SPECIMEN UNDER MULTIAXIAL LOADING%多轴载荷下缺口试件疲劳寿命预测研究

    Institute of Scientific and Technical Information of China (English)

    李静; 孙强; 李春旺; 张忠平; 乔艳江

    2011-01-01

    Based on the critical plane approach,the recently proposed multiaxial fatigue life prediction model applied to the smoothing tubular specimen is extended to assess the multiaxial fatigue life of notched one. Besides,with the aid of finite element analysis (FEA),the orientation of the critical plane and the effective cyclic parameter are determined by using the coordinate transformation principle. In the meantime,the proposed model is modified to take into consideration of the effect of mean stress when existing the mean stress.%基于临界平面法,在分析光滑薄壁圆管试件疲劳寿命预测模型的基础上,借助有限元应力应变分析,进一步将模型推广应用到了缺口试件的多轴疲劳寿命预测中,并利用坐标变换原理,明确了临界平面及有效循环变量的确定方法.在存在平均应力的情况下,分析了平均应力对疲劳寿命的影响,并对所建模型进行了平均应力修正.

  13. Strength Training Improves Fatigue Resistance and Self-Rated Health in Workers with Chronic Pain: A Randomized Controlled Trial

    Directory of Open Access Journals (Sweden)

    Emil Sundstrup

    2016-01-01

    Full Text Available Chronic musculoskeletal pain is widespread in the working population and leads to muscular fatigue, reduced work capacity, and fear of movement. While ergonomic intervention is the traditional approach to the problem, physical exercise may be an alternative strategy. This secondary analysis of a randomized controlled trial investigates the effect of strength training on muscular fatigue resistance and self-rated health among workers with chronic pain. Sixty-six slaughterhouse workers with chronic upper limb pain and work disability were randomly allocated to 10 weeks of strength training or usual care ergonomic training (control. At baseline and follow-up, participants performed a handgrip muscular fatigue test (time above 50% of maximal voluntary contraction force with simultaneous recording of electromyography. Additionally, participants replied to a questionnaire regarding self-rated health and pain. Time to fatigue, muscle strength, hand/wrist pain, and self-rated health improved significantly more following strength training than usual care (all P<0.05. Time to fatigue increased by 97% following strength training and this change was correlated to the reduction in fear avoidance (Spearman’s rho =-0.40; P=0.01. In conclusion, specific strength training improves muscular fatigue resistance and self-rated health and reduces pain of the hand/wrist in manual workers with chronic upper limb pain. This trial is registered with ClinicalTrials.gov NCT01671267.

  14. New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new welding electrode, low transformation temperatur e electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods.It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.

  15. Ultra-high cycle fatigue behavior of high strength steel with carbide-free bainite/martensite complex microstructure

    Institute of Scientific and Technical Information of China (English)

    Xue-xia Xu; Yang Yu; Wen-long Cui; Bing-zhe Bai; Jia-lin Gu

    2009-01-01

    The ultra-high cycle fatigue behavior of a novel high strength steel with carbide-free bainite/martensite (CFB/M) complex microstructure was studied. The ultra-high cycle fatigue properties were measured by ultrasonic fatigue testing equipment at a fre-quency of 20 kHz. It is found that there is no horizontal part in the S-N curve and fatigue fracture occurs when the life of specimens exceeds 107 cycles. In addition, the origination of fatigue cracks tends to transfer from the surface to interior of specimens as the fa-tigue cycle exceeds 107 , and the fatigue crack originations of many specimens are not induced by inclusions, but by some kind of "soft structure". It is shown that the studied high strength steel performs good ultra-high cycle fatigue properties. The ultra-high fa-tigue mechanism was discussed and it is suggested that specific CFB/M complex microstrueture of the studied steel contributes to itssuperior properties.

  16. Residual Strength of Stiffened LY12CZ Aluminum Alloy Panels with Widespread Fatigue Damage

    Institute of Scientific and Technical Information of China (English)

    Li Zhong; Ge Sen; Lu Guozhi; Chen Li; Ding Huiliang

    2008-01-01

    Experimental and analytical investigations on the residual strength of the stiffened LY12CZ aluminum alloy panels with widespread fatigue damage (WFD) are conducted. Nine stiffened LY12CZ aluminum alloy panels with three different types of damage are tested for residual strength. Each specimen is pre-cracked at rivet holes by saw cuts and subjected to a monotonically increasing tensile load until failure is occurred and the failure load is recorded. The stress intensity factors at the tips of the lead crack and the adjacent WFD cracks of the stiffened aluminum alloy panels are calculated by compounding approach and finite element method (FEM) respectively. The residual strength of the stiffened panels with WFD is evaluated by the engineering method with plastic zone linkup criterion and the FEM with apparent fracture toughness criterion respectively. The predicted residual strength agrees well with the experiment results. It indicates that in engineering practice these methods can be used for residual strength evaluation with the acceptable accuracy. It can be seen from this research that WFD can significantly reduce the residual strength and the critical crack length of the stiffened panels with WFD. The effect of WFD crack length on residual strength is also studied.

  17. Cryogenic Tensile Strength and Fatigue Life of Carbon Nanotube Multi-Yarn.

    Science.gov (United States)

    Misak, H E; Mall, S

    2016-03-01

    Carbon nanotube (CNT) multi-yarns, consisting of 30 yarns, were tested under monotonic tensile load and fatigue at the room temperature (298 K) and two cryogenic temperatures (232 and 123 K). Tensile stiffness increased with the decrease of temperature. The average ultimate tensile strength was higher at 123 K when compared to the higher temperatures (232 and 298 K). Failure mechanism changed from a combination of classical variant and independent fiber breakage at the two higher temperatures to mostly classical variant failure mechanism at the lower temperature. The CNT-yarn's fatigue life also increased with decreasing temperature. CNT-yarns have been shown to function well at lower temperatures making them usable for applications requiring operation at cryogenic temperatures, such as in satellites and high altitude aircraft.

  18. Modelling the Strength and Fatigue Life of a Unidirectional Fibrous Composite by Using Daniels' Sequence and Markov Chains

    Science.gov (United States)

    Paramonov, Yu.; Cimanis, V.; Varickis, S.; Kleinhofs, M.

    2013-11-01

    A review of the previous works of the authors dedicated to the use of Daniels' sequence (DS) for analyzing the relation between the distribution of the static strength of components of a unidirectional fibrous composite (UFC) and the distribution of its fatigue life is presented. A generalization of the DS which can be used to analyze the association of distribution of the static strength of composite components with distribution of the static strength of the UFC itself is given. In analyzing the fatigue life of a UFC, unlike in Daniels' model, the loading rate and randomness of the number of still workable components in the weak microvolume in which the destruction process takes place are taken into account. By analyzing the fatigue life, it is possible to explain the existence of the random fatigue strength and to calculate the maximum load at which the probability of absence of fatigue failure is great enough when the number of cycles of fatigue loading tends to infinity. Numerical examples of processing of experimental data are presented, and estimates for parameters of the corresponding nonlinear regression model, which can be interpreted as the strength parameters of UFC, are obtained.

  19. Effects of thermal fatigue on shear punch strength of tooth-colored restoratives

    Science.gov (United States)

    Melody, Fam Mei Shi; U-Jin, Yap Adrian; Natalie, Tan Wei Min; Elizabeth, Tay Wan Ling; Chien, Jessica Yeo Siu

    2016-01-01

    Aims: This study investigated the effect of thermal fatigue on the shear strength of a range of tooth-colored restorative materials including giomers, zirconia-reinforced glass ionomer cement (GIC), nano-particle resin-modified GIC, highly viscous GICs, and composite resin. Materials and Methods: Twenty specimens of each material were fabricated in standardized washers (17 mm outer diameter, 9 mm internal diameter, 1 mm thick). The specimens were cured, stored in 100% humidity at 37.5°C for 24 h, and randomly divided into two groups of 10. Group A specimens were nonthermocycled (NT) and stored in distilled water at 37°C for 168 h. Group B specimens were thermocycled (TC) for 10,000 cycles (168 h) with baths X, Y, and Z adjusted to 35°C, 15°C, and 45°C, respectively. Each cycle had dwell times of 28 s in X, and 2s in Y/Z in the order XYXZ. Specimens then underwent shear punch testing at a crosshead speed of 0.5 mm/min with a 2 kN load cell. Statistical analysis of shear strength was done using t-test and two-way ANOVA/Scheffe's post hoc test at significance level P composite resin (Filtek Z250XT) had the highest shear strength while the zirconia-reinforced (zirconomer) and a highly viscous GIC (Ketac Molar Quick) had the lowest. Conclusions: The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The “sculptable” composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the “flowable” injectable hybrid giomer was intermediate between the composite and GICs. PMID:27563182

  20. Asymmetric six-strand core sutures enhance tendon fatigue strength and the optimal asymmetry.

    Science.gov (United States)

    Kozono, N; Okada, T; Takeuchi, N; Hanada, M; Shimoto, T; Iwamoto, Y

    2016-10-01

    Under cyclic loading, we recorded the fatigue strength of a six-strand tendon repair with different symmetry in the lengths of suture purchase in two stumps of 120 dental rolls and in 30 porcine tendons. First, the strengths of the repairs with 1, 2, 3, 4 and 5 mm asymmetry were screened using the dental rolls. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm) in two tendon stumps, and shifting two other Kessler repairs by 1, 3 or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair. The core repairs with 3 mm or more asymmetry in suture purchases in two tendon ends showed significantly greater fatigue strength and significantly smaller gaps compared with 1 mm asymmetry in core suture repair. Our results support that asymmetric placement of core sutures in two tendon ends favour resisting gapping at the repair site and 3 mm or more asymmetry is needed to produce such beneficial effects. © The Author(s) 2016.

  1. Development of high-cycle fatigue design curves for a cast aluminum alloy

    Science.gov (United States)

    Cooper, R. A.

    1979-01-01

    Life prediction curves for rocket engine pump parts were developed from the results of high-cycle fatigue tests run on cast-aluminum specimens. Notched and smooth specimens were cyclically tested at different mean stress levels at -320 F (78 K). The notch size and mean stress enveloped the design operating conditions. Local stress computed in the groove of the notched specimen was used to represent its fatigue strength. The von Mises criterion was used to determine effective cyclic stresses. The Goodman rule was applied to determine equivalent reversed alternating stresses. The procedure permitted the notched and smooth data sets to each be described by a single curve. High-cycle fatigue life curves were provided for the stress state, mean stress, and stress concentration spanned by the data.

  2. Strength and fatigue limit of fabric base composites under combined static shear and cyclic compressive stresses

    Energy Technology Data Exchange (ETDEWEB)

    Limonov, V.A.; Razin, A.F.; Mikel`sons, M.Ya. [Central Research Institute of Special Engineering, Moscow (Russian Federation)

    1992-11-01

    Under real operating conditions, assemblies and products made of composites are subjected to combined static and cyclic loads. At the planning stage, an important problem is the selection of the materials to be used and an estimate of the load-bearing capacity by complex investigation of their physicomechanical properties. In the present work, the authors studied experimentally the characteristics of strength under static uniaxial and combined loading and the effect of static shear stresses on the compressive fatigue limit of glass-fabric reinforced plastic. 7 refs., 7 figs., 2 tabs.

  3. The Effect of Fine Non-Metallic Inclusions on the Fatigue Strength of Structural Steel

    Directory of Open Access Journals (Sweden)

    Lipiński T.

    2015-04-01

    Full Text Available The article discusses the results of a study investigating the effect of the number of fine non-metallic inclusions (up to 2 µm in size on the fatigue strength of structural steel during rotary bending. The study was performed on 21 heats produced in an industrial plant. Fourteen heats were produced in 140 ton electric furnaces, and 7 heats were performed in a 100 ton oxygen converter. All heats were desulfurized. Seven heats from electrical furnaces were refined with argon, and heats from the converter were subjected to vacuum circulation degassing.

  4. Calculation of low-cycle fatigue in accordance with the national standard and strength codes

    Science.gov (United States)

    Kontorovich, T. S.; Radin, Yu. A.

    2017-08-01

    Over the most recent 15 years, the Russian power industry has largely relied on imported equipment manufactured in compliance with foreign standards and procedures. This inevitably necessitates their harmonization with the regulatory documents of the Russian Federation, which include calculations of strength, low cycle fatigue, and assessment of the equipment service life. An important regulatory document providing the engineering foundation for cyclic strength and life assessment for high-load components of the boiler and steamline of a water/steam circuit is RD 10-249-98:2000: Standard Method of Strength Estimation in Stationary Boilers and Steam and Water Piping. In January 2015, the National Standard of the Russian Federation 12952-3:2001 was introduced regulating the issues of design and calculation of the pressure parts of water-tube boilers and auxiliary installations. Thus, there appeared to be two documents simultaneously valid in the same energy field and using different methods for calculating the low-cycle fatigue strength, which leads to different results. In this connection, the current situation can lead to incorrect ideas about the cyclic strength and the service life of high-temperature boiler parts. The article shows that the results of calculations performed in accordance with GOST R 55682.3-2013/EN 12952-3: 2001 are less conservative than the results of the standard RD 10-249-98. Since the calculation of the expected service life of boiler parts should use GOST R 55682.3-2013/EN 12952-3: 2001, it becomes necessary to establish the applicability scope of each of the above documents.

  5. Influence of High Strength Steel Microstructure on Fatigue Crack Growth Rate

    Directory of Open Access Journals (Sweden)

    Enefola S. Ameh

    2016-07-01

    Full Text Available This study examines the effect of high strength steel microstructure morphology on fatigue crack growth rate (FCGR. To achieve this aim, three different heat treatment methods (normalizing, austempering quenching and tempering were considered and all the steel specimens were initially heated to 9500C austenization temperature for ninety minutes and then processed via the different heat treatment methods before viewing the resultant microstructures under light optical microscope (LOM. Fatigue crack growth rate tests were conducted on the resultant microstructures with compact tension specimens at room temperature as prescribed by American standard testing method E647. Results of FCGR tests showed normalized microstructure has the lowest FCGR (6.2698E-06, followed by quenched and tempered (7.9519E-06, asreceived (8.15E-06 and austempered (9.6667E-06 microstructure considering a low stress intensity factor range. The trend of results showed insignificant effect of microstructure over the Paris regime growth indicating fatigue crack growth rate is not a reliable parameter for correlating rate of crack propagation to microstructure

  6. Corrosion Fatigue Crack Growth Behavior at Notched Hole in 7075 T6 Under Different Biaxial Stress Ratios

    Science.gov (United States)

    2016-08-18

    strain energy release rate I mode one (opening) K stress intensity factor (MPa*m^0.5) M molar mass R stress ratio for cyclic loading (unit less) r...Finally, 7 the third phase of the fatigue failure occurs when the resistance is exceeded, and a structure occurs, Figure 2.1 [30]. Figure 2.1...Alloy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 92 19a. NAME OF RESPONSIBLE PERSON Shankar

  7. Impact of Selected Parameters on the Fatigue Strength of Splices on Multiply Textile Conveyor Belts

    Science.gov (United States)

    Bajda, Mirosław; Błażej, Ryszard; Hardygóra, Monika

    2016-10-01

    Splices are the weakest points in the conveyor belt loop. The strength of these joints, and thus their design as well as the method and quality of splicing, determine the strength of the whole conveyor belt loop. A special zone in a splice exists, where the stresses in the adjacent plies or cables differ considerably from each other. This results in differences in the elongation of these elements and in additional shearing stresses in the rubber layer. The strength of the joints depends on several factors, among others on the parameters of the joined belt, on the connecting layer and the technology of joining, as well as on the materials used to make the joint. The strength of the joint constitutes a criterion for the selection of a belt suitable for the operating conditions, and therefore methods of testing such joints are of great importance. This paper presents the method of testing fatigue strength of splices made on multi-ply textile conveyor belts and the results of these studies.

  8. The effects of swimming fatigue on shoulder strength, range of motion, joint control, and performance in swimmers.

    Science.gov (United States)

    Matthews, Martyn J; Green, Daniel; Matthews, Helen; Swanwick, Emma

    2017-01-01

    To investigate the effects of training induced fatigue on shoulder strength, ROM, joint position sense, and stroke length in elite competitive swimmers. Seventeen national level swimmers performed maximum isometric strength (internal and external rotation), ROM, and joint position sense tests before and after a fatiguing 8 × 100 m training set. Stroke length, heart rate, blood lactate and blood glucose levels were recorded throughout. Peak blood lactate, blood glucose levels, and heart rate increased significantly (P swimming whereby a greater reduction in both external rotation range and joint position sense was observed in the dominant arm when fatigued. This has highlighted a relationship between fatigue and potential mechanism of shoulder pathology in swimmers. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Fatigue strength of bilayered ceramics under cyclic loading as a function of core veneer thickness ratios.

    Science.gov (United States)

    Dibner, Aurora Clark; Kelly, J Robert

    2016-03-01

    Minimal evidence is available concerning the appropriate thickness of each layer in bilayered ceramic systems. The purpose of this in vitro study was to examine the effect of core-veneer thickness ratios on the fatigue strength of a bonded bilayered ceramic system. Specimens of Ivoclar Porcelain System (IPS) e.max lithium disilicate were fabricated with core/veneer thicknesses of 0.5/1.0 mm, 0.75/0.75 mm, 1.0/0.5 mm, and 1.5/0.0 mm. All specimens were cemented to bases of a dentin-like material. Each specimen was cyclically loaded by a 2-mm-diameter G10 piston in water. Loads ranging from 10 N to the target load were applied at a frequency of 20 Hertz for 500,000 cycles. If cracked, the next specimen was cycled at a lower load; if not cracked, at a higher load (step size of 25 N). Mean and standard deviations of fatigue loads for the different core thicknesses were 0.5-mm core 610.94 N ±130.11; 0.75-mm core 600.0 N ±132.80; 1.0-mm core 537.50 N ±41.67; a Nd 1.5-mm core 501.14 N ±70.12. All veneered groups were significantly stronger than the full thickness group (ANOVA, Pcore groups (χ(2) test, Pcores increases the fatigue strength of the biceramic system. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  10. Strength and fatigue life evaluation of composite laminate with embedded sensors

    Science.gov (United States)

    Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

    2014-04-01

    Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

  11. Review: Gigacycle fatigue data sheets for advanced engineering materials

    Directory of Open Access Journals (Sweden)

    Koji Yamaguchi, Takayuki Abe, Kazuo Kobayashi, Etsuo Takeuchi, Hisashi Hirukawa, Yoshio Maeda, Nobuo Nagashima, Masao Hayakawa, Yoshiyuki Furuya, Masuo Shimodaira and Kensuke Miyahara

    2007-01-01

    Full Text Available Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 1010 cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 108 cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete.

  12. DOL behaviour of end-notched beams

    DEFF Research Database (Denmark)

    Gustafsson, P.J.; Hoffmeyer, Preben; Valentin, G.

    1998-01-01

    The long-term loading strength of end-notched beams made of glulam and LVL was tested. The beams were of various sizes, with and without a moisture sealing at the notch. Tests were conducted in open shelter climates, and at constant and cyclic relative humidity. The short-term strength was tested...... beams with a moisture sealing at the notch...

  13. Plasma immersion ion implantation on 15-5PH stainless steel: influence on fatigue strength and wear resistance

    Science.gov (United States)

    Bonora, R.; Cioffi, M. O. H.; Voorwald, H. J. C.

    2017-05-01

    Surface improvement in steels is of great interest for applications in industry. The aim of this investigation is to study the effect of nitrogen ion implantation on the axial fatigue strength and wear resistance of 15-5 PH stainless steel. It is well know that electroplated coatings, which are used to improve abrasive wear and corrosion properties, affects negatively the fatigue strength. It is also important to consider requirements to reduce the use of coated materials with electroplated chromium and cadmium, that produce waste, which is harmful to health and environment. The HVOF (High velocity oxygen fuel) process provides hardness, wear strength and higher fatigue resistance in comparison to electroplated chromium. Plasma immersion ion implantation has been used to enhance the hardness, wear, fatigue and corrosion properties of metals and alloys. In the present research the fatigue life increased twice for 15-5 PH three hours PIII treated in comparison to base material. From the abrasive wear tests a lower pin mass reduction was observed, associated to the superficial treatments. The improvement of fatigue and mechanical performance is attributed to a combination of nitrides phase structure and compressive residual stresses during the PIII treatment.

  14. Residual Stress and Fatigue Strength of Hybrid Laser-MIG-Welded A7N01P-T4

    Science.gov (United States)

    Wang, Qiuying; Chen, Hui; Qiu, Peixian; Zhu, Zongtao

    2017-02-01

    A7N01P-T4 aluminum alloy is widely used in some important welded components of high-speed trains. The hybrid laser-metal inert gas (MIG) welding process was studied to solve problems associated with the MIG welding process, such as low welding efficiency, high residual stress and deformation, and serious loss of strength. A high-speed camera, a voltage and current collection system, and NI DAQ were used to acquire arc profiles, welding voltage, and welding current simultaneously. Thermal cycle tests were carried out. Residual stresses induced by the welding process and fatigue strength of the joint were investigated. Large-size fatigue specimens were used in fatigue tests. The results show that the energy of the hybrid welding process is focused, and the power density of hybrid welding process is intense. The heat input per unit of the hybrid welding process is only half of that of the MIG welding process. Compared with the MIG welded joint, the overall residual stress level of the hybrid-welded joint is lower. The peak longitudinal stress of the hybrid-welded joint is reduced by 20 pct. The fatigue strength of hybrid joints is 14 pct higher than that of MIG-welded joints. Narrow weld and HAZ, weak softening behavior, and low residual stress level are the causes of the improvement of fatigue strength.

  15. Residual Stress and Fatigue Strength of Hybrid Laser-MIG-Welded A7N01P-T4

    Science.gov (United States)

    Wang, Qiuying; Chen, Hui; Qiu, Peixian; Zhu, Zongtao

    2016-09-01

    A7N01P-T4 aluminum alloy is widely used in some important welded components of high-speed trains. The hybrid laser-metal inert gas (MIG) welding process was studied to solve problems associated with the MIG welding process, such as low welding efficiency, high residual stress and deformation, and serious loss of strength. A high-speed camera, a voltage and current collection system, and NI DAQ were used to acquire arc profiles, welding voltage, and welding current simultaneously. Thermal cycle tests were carried out. Residual stresses induced by the welding process and fatigue strength of the joint were investigated. Large-size fatigue specimens were used in fatigue tests. The results show that the energy of the hybrid welding process is focused, and the power density of hybrid welding process is intense. The heat input per unit of the hybrid welding process is only half of that of the MIG welding process. Compared with the MIG welded joint, the overall residual stress level of the hybrid-welded joint is lower. The peak longitudinal stress of the hybrid-welded joint is reduced by 20 pct. The fatigue strength of hybrid joints is 14 pct higher than that of MIG-welded joints. Narrow weld and HAZ, weak softening behavior, and low residual stress level are the causes of the improvement of fatigue strength.

  16. Developing Fatigue Pre-crack Procedure to Evaluate Fracture Toughness of Pipeline Steels Using Spiral Notch Torsion Test

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Tan, Ting [ORNL; Jiang, Hao [ORNL; Zhang, Wei [ORNL; Feng, Zhili [ORNL

    2012-10-01

    The spiral notch torsion test (SNTT) has been utilized to investigate the crack growth behavior of X52 steel base and welded materials used for hydrogen infrastructures. The X52 steel materials are received from a welded pipe using friction stir welding techniques. Finite element models were established to study the crack growth behavior of steel SNTT steel samples, which were assumed to be isotropic material. A series SNTT models were set up to cover various crack penetration cases, of which the ratios between crack depth to diameter (a/D ratio) ranging from 0.10 to 0.45. The evolution of compliance and energy release rates in the SNTT method have been investigated with different cases, including different geometries and materials. Indices of characteristic compliance and energy release rates have been proposed. Good agreement has been achieved between predictions from different cases in the same trend. These work shed lights on a successful protocol for SNTT application in wide range of structural materials. The further effort needed for compliance function development is to extend the current developed compliance function to the deep crack penetration arena, in the range of 0.55 to 0.85 to effectively determine fracture toughness for extremely tough materials.

  17. In vitro bond strength and fatigue stress test evaluation of different adhesive cements used for fixed space maintainer cementation

    OpenAIRE

    Cantekin, Kenan; Delikan, Ebru; Cetin, Secil

    2014-01-01

    Objective: The purposes of this research were to (1) compare the shear-peel bond strength (SPBS) of a band of a fixed space maintainer (SM) cemented with five different adhesive cements; and (2) compare the survival time of bands of SM with each cement type after simulating mechanical fatigue stress. Materials and Methods: Seventy-five teeth were used to assess retentive strength and another 50 teeth were used to assess the fatigue survival time. SPBS was determined with a universal testing m...

  18. CORRELATIONS BETWEEN MUSCLE MASS, MUSCLE STRENGTH, PHYSICAL PERFORMANCE, AND MUSCLE FATIGUE RESISTANCE IN COMMUNITY-DWELLING ELDERLY SUBJECTS

    Directory of Open Access Journals (Sweden)

    Elizabeth

    2016-03-01

    Full Text Available Objective: To determine the correlations between muscle mass, muscle strength, physical performance, and muscle fatigue resistance in community-dwelling elderly people in order to elucidate factors which contribute to elderly’s performance of daily activities. Methods: A cross-sectional study was conducted on community-dwelling elderly in Bandung from September to December 2014. One hundred and thirty elderly, 60 years old or above, were evaluated using bioelectrical impedance analysis to measure muscle mass; grip strength to measure muscle strength and muscle fatigue resistance; habitual gait speed to measure physical performance; and Global Physical Activity Questionnaire (GPAQ to assess physical activity. Results: There were significant positive correlations between muscle mass (r=0,27, p=0,0019, muscle strength (r=0,26, p=0,0024, and physical performance (r=0,32, p=0,0002 with muscle fatigue resistance. Physical performance has the highest correlation based on multiple regression test (p=0,0025. In association with muscle mass, the physical activity showed a significant positive correlation (r=0,42, p=0,0000. Sarcopenia was identified in 19 (14.61% of 130 subjects. Conclusions: It is suggested that muscle mass, muscle strength, and physical performance influence muscle fatigue resistance.

  19. Strength and fatigue properties of three-step sintered dense nanocrystal hydroxyapatite bioceramics

    Science.gov (United States)

    Guo, Wen-Guang; Qiu, Zhi-Ye; Cui, Han; Wang, Chang-Ming; Zhang, Xiao-Jun; Lee, In-Seop; Dong, Yu-Qi; Cui, Fu-Zhai

    2013-06-01

    Dense hydroxyapatite (HA) ceramic is a promising material for hard tissue repair due to its unique physical properties and biologic properties. However, the brittleness and low compressive strength of traditional HA ceramics limited their applications, because previous sintering methods produced HA ceramics with crystal sizes greater than nanometer range. In this study, nano-sized HA powder was employed to fabricate dense nanocrystal HA ceramic by high pressure molding, and followed by a three-step sintering process. The phase composition, microstructure, crystal dimension and crystal shape of the sintered ceramic were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties of the HA ceramic were tested, and cytocompatibility was evaluated. The phase of the sintered ceramic was pure HA, and the crystal size was about 200 nm. The compressive strength and elastic modulus of the HA ceramic were comparable to human cortical bone, especially the good fatigue strength overcame brittleness of traditional sintered HA ceramics. Cell attachment experiment also demonstrated that the ceramics had a good cytocompatibility.

  20. 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.

  1. Effect of defect length on rolling contact fatigue crack propagation in high strength steel

    Directory of Open Access Journals (Sweden)

    T. Makino

    2015-10-01

    Full Text Available The objective of the present paper is to clarify the effect of defect length in depth direction on rolling contact fatigue (RCF crack propagation in high strength steel. RCF test and synchrotron radiation micro computed tomography (SR micro CT imaging were conducted. In the case of the defect with the 15 m diameter, flaking life decreased with increasing defect length. In a comparison of the CT image and the SEM view, the shapes of defects and the locations of the horizontal cracks were almost the same respectively. The mechanism of RCF crack propagation was discussed by finite element (FE analysis. Defects led to higher tensile residual stress than that without defects in the region where the defect exists. The shear stress range at 0.1 mm in depth on the middle line of the defect and the range of mode II stress intensity factor at the bottom of a vertical crack increased with increasing defect length.

  2. On the use of the Theory of Critical Distances to estimate the dynamic strength of notched 6063-T5 aluminium alloy

    Directory of Open Access Journals (Sweden)

    T. Yin

    2014-10-01

    Full Text Available In this paper the so-called Theory of Critical Distances is reformulated to make it suitable for estimating the strength of notched metals subjected to dynamic loading. The TCD takes as its starting point the assumption that engineering materials’ strength can accurately be predicted by directly post-processing the entire linear-elastic stress field acting on the material in the vicinity of the stress concentrator being assessed. In order to extend the used of the TCD to situations involving dynamic loading, the hypothesis is formed that the required critical distance (which is treated as a material property varies as the loading rate increases. The accuracy and reliability of this novel reformulation of the TCD was checked against a number of experimental results generated by testing notched cylindrical bars of Al6063-T5. This validation exercise allowed us to prove that the TCD (applied in the form of the Point, Line, and Area Method is capable of estimates falling within an error interval of ±20%. This result is very promising especially in light of the fact that such a design method can be used in situations of practical interest without the need for explicitly modelling the non-linear stress vs. strain dynamic behaviour of metals.

  3. Influence of rivet to sheet edge distance on fatigue strength of self-piercing riveted aluminium joints

    OpenAIRE

    Li, Dezhi; Han, Li; Thornton, M.; Shergold, M.

    2012-01-01

    Self-piercing riveting (SPR) is one of the main joining methods for lightweight aluminium automotive body structures due to its advantages. In order to further optimise the structure design and reduce the weight but without compromising strength, reduction of redundant materials in the joint flange area can be considered. For this reason, the influence of rivet to sheet edge distance on the fatigue strengths of self-piercing riveted joints was studied. Five edge distances, 5 mm, 6 mm, 8 mm, 1...

  4. Evaluation of Fatigue Strength Improvement by CFRP Laminates and Shot Peening onto the Tension Flanges Joining Corrugated SteelWebs

    Directory of Open Access Journals (Sweden)

    Zhi-Yu Wang

    2015-08-01

    Full Text Available Corrugated steel web with inherent high out-of-plane stiffness has a promising application in configuring large span highway bridge girders. Due to the irregularity of the configuration details, the local stress concentration poses a major fatigue problem for the welded flange plates of high strength low alloy structural steels. In this work, the methods of applying CFRP laminate and shot peening onto the surfaces of the tension flanges were employed with the purpose of improving the fatigue strength of such configuration details. The effectiveness of this method in the improvement of fatigue strength has been examined experimentally. Test results show that the shot peening significantly increases hardness and roughness in contrast to these without treatment. Also, it has beneficial effects on the fatigue strength enhancement when compared against the test data of the joints with CFRP strengthening. The stiffness degradation during the loading progress is compared with each treatment. Incorporating the stress acting on the constituent parts of the CFRP laminates, a discussion is made regarding the mechanism of the retrofit and related influencing factors such as corrosion and economic cost. This work could enhance the understanding of the CFRP and shot peening in repairing such welded details and shed light on the reinforcement design of welded joints between corrugated steel webs and flange plates.

  5. The effect of a resistance-training program on muscle strength, physical workload, muscle fatigue and musculoskeletal discomfort: An experiment

    NARCIS (Netherlands)

    Hamberg-Reenen, H.H. van; Visser, B.; Beek, A.J. van der; Blatter, B.M.; Dieën, J.H. van; Mechelen, W. van

    2009-01-01

    The aim of the study was to investigate the effectiveness of a resistance-training program on muscle strength of the back and neck/shoulder muscles, relative physical workload, muscle fatigue and musculoskeletal discomfort during a simulated assembly and lifting task. Twenty-two workers were randomi

  6. Acute Effects of Static vs. Ballistic Stretching on Strength and Muscular Fatigue Between Ballet Dancers and Resistance-Trained Women.

    Science.gov (United States)

    Lima, Camila D; Brown, Lee E; Wong, Megan A; Leyva, Whitney D; Pinto, Ronei S; Cadore, Eduardo L; Ruas, Cassio V

    2016-11-01

    Lima, CD, Brown, LE, Wong, MA, Leyva, WD, Pinto, RS, Cadore, EL, and Ruas, CV. Acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. J Strength Cond Res 30(11): 3220-3227, 2016-Stretching is used to increase joint range of motion, but the acute effects can decrease muscle strength. However, this may depend on the population or mode of stretching. The purpose of this study was to compare the acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. Fifteen resistance-trained women (age 23.8 ± 1.80 years, mass 67.47 ± 7.77 kg, height 168.30 ± 5.53 cm) and 12 ballet dancers (age 22.8 ± 3.04 years, mass 58.67 ± 5.65 kg, height 168.00 ± 7.69 cm) performed 5 days of testing. The first day was control (no stretching), whereas the other 4 days were static or ballistic stretching in a counterbalanced order. Range of motion, strength, and fatigue tests were also performed. Both groups demonstrated a significant decrease in hamstrings strength after static (102.71 ± 2.67 N·m) and ballistic stretching (99.49 ± 2.61 N·m) compared with control (113.059 ± 3.25 N·m), with no changes in quadriceps strength. For fatigue, only ballet dancers demonstrated a decrease from control (71.79 ± 4.88%) to ballistic (65.65 ± 8.19%), but no difference with static (65.01 ± 12.29%). These findings suggest that stretching decreases hamstrings strength similarly in ballet dancers and resistance-trained women, with no differences between modes of stretching. However, ballistic stretching only decreased muscular fatigue in ballet dancers, but not in resistance-trained women. Therefore, no stretching should be performed before strength performance. However, ballistic stretching may decrease acute muscular fatigue in ballet dancers.

  7. Proof of fatigue strength of nuclear components part II: Numerical fatigue analysis for transient stratification loading considering environmental effects

    Energy Technology Data Exchange (ETDEWEB)

    Kraetschmer, D.; Roos, E.; Schuler, X. [Materialpruefungsanstalt (MPA) Universitaet Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart (Germany); Herter, K.-H., E-mail: herter@mpa.uni-stuttgart.de [Materialpruefungsanstalt (MPA) Universitaet Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart (Germany)

    2012-04-15

    For the construction, design and operation of nuclear components and systems the appropriate technical codes and standards provide detailed analysis procedures which guarantee a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various mechanical and thermal loading histories and geometric complexities of the components. To consider effects of light water reactor coolant environments, new design curves included in report NUREG/CR-6909 for austenitic stainless steels and for low alloy steels have been presented. For the usage of these new design curves an environmental fatigue correction factor for incorporating environmental effects has to be calculated and used. The application of this environmental correction factor to a fatigue analysis of a nozzle with transient stratification loads, derived by in-service monitoring, has been performed. The results are used to compare with calculated usage factors, based on design curves without taking environmental effects particularly into account. - Highlights: Black-Right-Pointing-Pointer We model an nozzle for fatigue analysis und mechanical and thermal loading conditions. Black-Right-Pointing-Pointer A simplified as well as a general elastic-plastic fatigue analysis considering environmental effects is performed. Black-Right-Pointing-Pointer The influence of different factors calculating the environmental factor F{sub en} are shown. Black-Right-Pointing-Pointer The presented numerical evaluation methodology allows the consideration of all relevant parameters to assess lifetime.

  8. 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.

  9. Fatigue fracture of high-strength Al-Zn-Mg-Cu alloy

    Institute of Scientific and Technical Information of China (English)

    JIAN Hai-gen; JIANG Feng; WEN Kang; JIANG Long; HUANG Hong-feng; WEI Li-li

    2009-01-01

    X-ray diffractometry(XRD), optical microscopy(OM), scanning electron microscopy(SEM) were used to study the fatigue fracture of the T7451 Al-Zn-Mg-Cu alloy (470 ℃, 60 min+115 ℃, 8 h+165 ℃, 16 h). The study reveals mainly the microscopic structure of the alloy in the process of crack formation and crack growth. The fatigue fracture is characterized by three zones: fatigue crack source zone, fatigue crack propagation zone and fatigue fracture zone. The fatigue damage preferably incubates at the fractured inclusion particles at or near (about 25 μm) the specimen free surfaces, and these brittle Fe-rich intermetallic inclusion particles are (7-10) μm×(11-14) μm in size. Some features such as "feather-like", "river and range" and boundary extrusions can be observed in the fatigue propagation zone, and in the fatigue fracture zone the surface is rough and uneven.

  10. The effect of a resistance-training program on muscle strength, physical workload, muscle fatigue and musculoskeletal discomfort: an experiment.

    Science.gov (United States)

    Hamberg-van Reenen, Heleen H; Visser, Bart; van der Beek, Allard J; Blatter, Birgitte M; van Dieën, Jaap H; van Mechelen, Willem

    2009-05-01

    The aim of the study was to investigate the effectiveness of a resistance-training program on muscle strength of the back and neck/shoulder muscles, relative physical workload, muscle fatigue and musculoskeletal discomfort during a simulated assembly and lifting task. Twenty-two workers were randomized over an 8-week resistance-training group, and a control group. Isokinetic muscle strength was assessed using the Cybex dynamometer, muscle fatigue was measured using EMG, and perceived discomfort was measured using a 10-point scale. At the follow-up, we found no effect of the resistance-training program on isokinetic muscle strength of the back and shoulder muscles. Furthermore, we did not find any effect on EMG data, nor on musculoskeletal discomfort during the simulated work tasks. However, trained workers performed the lifting tasks for a longer time before reporting considerable discomfort than those in the control group.

  11. Rolling contact fatigue strength of successive austempered ductile cast iron; Chikuji austemper shori kyujo kokuen chutetsu no korogari hiro kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, T. [Yamaguchi University, Yamaguchi (Japan). Faculty of Engineering; Ogi, K. [Kyushu University, Fukuoka (Japan). Faculty of Engineering; Sawamoto, A. [Yamaguchi Univ., Yamaguchi (Japan). Faculty of Education

    1998-04-25

    The holding time of austempered spheroidal graphite cast iron material is allowed to vary in heat treatment especially at the lower bainite transformation zone during the process for the preparation of specimens different from each other in the amount of {gamma}-pool, and the specimens are tested for their rolling contact fatigue strength. The effects of the amount of {gamma}-pool, roughness of the bainite structure, and work-hardening, on the rolling fatigue strength are also studied. Findings obtained as the result of experiment are stated below. In the case of an austempered ductile cast iron specimen containing a {gamma}-pool amount that occupies a high rate of 6.52%, the rolling fatigue withstanding limit exhibits a relatively high level of 1310MPa, which becomes approximately 1245MPa when the holding time is extended in the lower bainite transformation zone. The limit rises to approximately 1320MPa at a stage where the {gamma}-pool virtually disappears. In a successive austempering treatment process that aims at improving on machinability and at allowing sufficient fatigue strength to be maintained, it is necessary to allow the holding time in the bainite zone to be long enough for the {gamma}-pool to disappear and for the lower bainite structure to grow sufficiently. 5 refs., 10 figs., 4 tabs.

  12. Fatigue strength evaluation of self-piercing riveted cold rolled steel joints under mixed mode loading conditions

    Directory of Open Access Journals (Sweden)

    KYUNG-MIN LEE

    2016-08-01

    Full Text Available Fatigue strength of cross-shaped specimens of SPR joints made of SPCC was evaluated at load angles of 0°, 45°, and 90°. For the static strength at load angles of 0°, 45°, and 90°, the maximum loads were determined to be 4890N, 1969N, and 1611N, respectively. Regarding for the relationship between the load amplitude and the number of cycles (Nf, the results were Pamp = 2209.3N−f 0.014 , = 8610.8 −0.199 Pamp N f , and = 3459.3 −0.149 Pamp N f for the load angle of 0°, 45°, and 90°, respectively. On the basis of the lifetime of 106 cycles, the load amplitudes which correspond to the fatigue limit for load angles of 0°, 45°, and 90° were 38%, 28%, and 29% of the static strength, respectively. The effective stress intensity factor was not found to be appropriate in the evaluation of the fatigue lifetime due to the different fatigue fracture behavior of these specimens.

  13. Assessment of Musculoskeletal Strength and Levels of Fatigue during Different Phases of Menstrual Cycle in Young Adults.

    Science.gov (United States)

    Pallavi, L C; D Souza, Urban John; Shivaprakash, G

    2017-02-01

    Some of the physiological factors and athletic performance might show variation along the phases of menstrual cycle. The alterations seen in these physiological parameters of various systems relating to oscillations in hormonal levels do affect the autonomic nervous system and metabolic functions. Former studies heave inconclusively about the influence of hormones on exercise performance, predominantly muscle strength and rate of fatigue during different phases of the menstrual cycle. Studies regarding influence of these variations during bleeding phase were not done. To evaluate the muscle strength variations and also the rate of fatigue during various phases of the menstrual cycle in young adults. This was a prospective study conducted among 100 healthy adult female volunteers aged 18-24 years, with normal regular menstrual cycles persistent between 26- 32 days (average of 28 days), for a minimum of last 6 months. Muscle strength was assessed by calculating the work done and fatigue rate using Mosso's ergograph and by handgrip dynamometer strength. Each subject was evaluated consecutively for two menstrual cycles in all three phases which were classified as Phase 1- Menstrual phase, Phase 2- Follicular phase and Phase 3- Luteal phase. The data obtained was analysed by statistical tool One-way ANOVA followed by a post-hoc Tukeys test. A p-value of ≤ 0.05 was considered significant. The amount of work done and handgrip strength was significantly higher in phase 2 (pmenstrual cycle. In terms of fatigue rate percentage, phase 2 showed significantly lesser values (pmenstrual cycle. We conclude that the cyclical variation in endogenous reproductive hormones increases the muscle strength in follicular phase of the menstrual cycle. Thus provide support for the influence of these hormones in regulation of these parameters in the premenopausal age group.

  14. Ductile and Compacted Graphite Iron Casting Skin -- Evaluation, Effect on Fatigue Strength and Elimination

    Science.gov (United States)

    Boonmee, Sarum

    Compacted graphite (CG) iron features a good combination of tensile strength, impact resistance, thermal conductivity and damping capacity. This combination makes CG iron a material of choice for various applications, especially for the automobile industry. The mechanical properties of CG iron listed in the standards (i.e. ASTM) are for machined specimens. However, since most iron castings retain the original casting surface (a.k.a. casting skin), the actual performance of the part could be significantly different from that of the machined specimens. Recent studies have shown the negative effect of the casting skin, but little quantification of its effect on mechanical properties is available. Further, the understanding of its mechanism of formation is at best incomplete. In this research, the effect of the casting skin on mechanical properties in CG and ductile irons (DI) is explored. The differences in tensile and fatigue properties between as-cast and machined samples were quantified and correlated to the casting skin features. It was found that the presence of the casting skin was accountable for 9% reduction of tensile strength and up to 32% reduction of fatigue strength (for CG iron with 40% nodularity). Several mechanisms of the casting skin formation are proposed in this research. The formation of ferritic and pearlitic rims is explained by decarburizing/carburizing reactions at the mold/metal interface. Mg depletion and solidification kinetics effect were identified as the formation mechanisms of the graphite degradation. A 2-D thermal diffusion model was formulated based on Mg depletion theory. The model can be used to predict the casting skin thickness when Mg depletion is the dominant mechanism. Furthermore, using the asymmetric Fe-Gr phase diagram, some instances of casting skin formation were explained based on solidification kinetics theory. The experimental microstructural evidence and the theoretical progress were conducive to the development of

  15. Influence of the number of cycles on shear fatigue strength of resin composite bonded to enamel and dentin using dental adhesives in self-etching mode.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Erickson, Robert L; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2017-09-28

    The influence of the number of cycles on shear fatigue strength to enamel and dentin using dental adhesives in self-etch mode was investigated. A two-step self-etch adhesive and two universal adhesives were used to bond to enamel and dentin in self-etch mode. Initial shear bond strength and shear fatigue strength to enamel and dentin using the adhesive in self-etch mode were determined. Fatigue testing was used with 20 Hz frequency and cycling periods of 50,000, 100,000 and 1,000,000 cycles, or until failure occurred. For each of the cycling periods, there was no significant difference in shear fatigue strength across the cycling periods for the individual adhesives. Differences in shear fatigue strength were found between the adhesives within the cycling periods. Regardless of the adhesive used in self-etch mode for bonding to enamel or dentin, shear fatigue strength was not influenced by the number of cycles used for shear fatigue strength testing.

  16. Mechanical fatigue of polysilicon: Effects of mean stress and stress amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)]. E-mail: harold.kahn@case.edu; Chen, L. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Ballarini, R. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)

    2006-02-15

    Polycrystalline silicon (polysilicon) fatigue specimens with micrometer-sized dimensions were fabricated and subjected to cyclic loading using an integrated electrostatic actuator. The fatigue effects were determined by comparing the single edge-notched beam monotonic bend strength measured after cyclic loading to the monotonic strength of 'virgin' specimens that had received no cycling. Both strengthening and weakening were observed, depending on the levels of mean stress and fatigue stress amplitude during the cyclic loading. Monotonic loading with similar sub-critical stress levels had no effect. The physical mechanisms responsible for this behavior are discussed, and a model based on grain boundary plasticity is presented for the strengthening behavior.

  17. Effects of Neuromuscular Fatigue on Quadriceps Strength and Activation and Knee Biomechanics in Individuals post Anterior Cruciate Ligament Reconstruction and Healthy Adults

    Science.gov (United States)

    Thomas, Abbey C.; Lepley, Lindsey K.; Wojtys, Edward M.; McLean, Scott G.; Palmieri-Smith, Riann M.

    2016-01-01

    Study design Laboratory based experiment using a pre/post-test design. Objectives To determine the effects of neuromuscular fatigue on quadriceps strength and activation and sagittal and frontal plane knee biomechanics during dynamic landing following anterior cruciate ligament reconstruction (ACLr). Background Impaired quadriceps central activation occurs post-ACLr, likely altering lower extremity biomechanics. Neuromuscular fatigue similarly reduces volitional muscle activation and impairs neuromuscular control. Upon return to full activity post-ACLr, individuals likely concurrently experience quadriceps central activation deficits and neuromuscular fatigue, though the effects of fatigue on muscle strength and activation and biomechanics post-ACLr are unknown. Methods Seventeen individuals 7–10 months post-ACLr and 16 controls participated. Quadriceps strength and central activation ratio were recorded pre-/post-fatigue, which was induced via sets of double-leg squats. Knee biomechanics were recorded during a dynamic landing activity pre-/post-fatigue. Results Both groups demonstrated smaller knee flexion (initial contact:P=.017; peak:P=.004) and abduction (initial contact:P=.005; peak:P=.009) angles post-fatigue. The ACLr group had smaller peak knee flexion angles (PKnee flexion moment was smaller in ACLr than controls pre- (Pknee flexion moments post-fatigue (P=.001). Knee abduction moment was smaller in both groups post-fatigue (P=.003). All participants demonstrated significantly lower strength (Pbiomechanics presented post-fatigue in both groups, confirming that neuromuscular fatigue may increase non-contact ACL injury risk. However, these changes were not exaggerated in ACLr participants, likely because they already demonstrated a stiff-legged landing strategy pre-fatigue. PMID:26471851

  18. The Influence of Microstructure on the Strength and Toughness and the Fatigue Crack Propagation in CrWMn Steels,

    Science.gov (United States)

    1986-01-24

    strength and toughness if a mixed ’ martensite structure with 50% bainite is obtained. It also can prolong the pregnant period of nucleation of fatigue crack...has high No and low da/dN. If the bainite is more than 90%, its fracture will show the characteristic of quasicleavage and da/dN increases remarkably...toughness simultaneously is an urgent problem needing to be solved. Recently, from the studies of mixed structures of bainite and ,.. martensite, it was

  19. Static, Fire and Fatigue Tests of Ultra High-Strength Fibre Reinforced Concrete and Ribbed Bars

    DEFF Research Database (Denmark)

    Hansen, Lars Pilegaard; Heshe, Gert

    2001-01-01

    - Densit Joint Cast ®. Also the connections between the columns and the slabs are made of this very strong concrete material. The paper describes some of the static tests carried out as well as some fire tests. Further, 2 chapters deal with some fatigue tests of the reinforcing bars as well as some fatigue...

  20. Fatigue life prediction and strength degradation of wind turbine rotor blade composites

    NARCIS (Netherlands)

    Nijssen, R.P.L.

    2006-01-01

    Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fat

  1. The effect of low temperatures on the fatigue of high-strength structural grade steels

    NARCIS (Netherlands)

    Walters, C.L.

    2014-01-01

    It is well-known that for fracture, ferritic steels undergo a sudden transition from ductile behavior at higher temperatures to brittle cleavage failure at lower temperatures. However, this phenomenon has not received much attention in the literature on fatigue. The so-called Fatigue Ductile-Brittle

  2. Impact of choice of stabilized hysteresis loop on the end result of investigation of high-strength low-alloy (HSLA steel on low cycle fatigue

    Directory of Open Access Journals (Sweden)

    S. Bulatović

    2014-10-01

    Full Text Available High strength low-alloy steel under low cycle fatigue at a certain level of strain controlled achieve stabilized condition. During the fatigue loading stabilized hysteresis loop is determined, which typical cycle of stabilization is calculated as half number of cycles to failure. Stabilized hysteresis loop is a representative of all hysteresis and it’s used to determine all of the parameters for the assessment of low cycle fatigue. This paper shows comparison of complete strain-life curves of low cycle fatigue for two chosen stabilized hysteresis loop cycles of base metal HSLA steel marked as Nionikral 70.

  3. Stomaching Notch

    Science.gov (United States)

    Yin, Xiaolei; Karp, Jeffrey M

    2015-01-01

    The self-renewal and differentiation of tissue stem cells must be tightly controlled. Unrestrained self-renewal leads to over-proliferation of stem cells, which may cause tumor formation, while uncontrolled differentiation leads to depletion of the stem cell pool. In this issue of The EMBO Journal, Demitrack et al (2015) show that the Notch pathway is a key regulator of Lgr5 antral stem cell self-renewal and differentiation. Notch signaling controls the proliferation and differentiation of stem cells as well as gastric tissue growth, while uncontrolled Notch activity in stem cells leads to polyp formation. PMID:26358838

  4. TIG-dressing of High Strength Butt Welded Connection. Part 2: Physical Testing and Modelling

    OpenAIRE

    Van Es, S.H.J.; Kolstein, M.H.; Pijpers, R.J.M.; Bijlaard, F.S.K.

    2014-01-01

    Weld improvement techniques are aimed at reducing the notch effects of welds and generally focus on two aspects: a change of geometry of the weld toe and a change of the weld residual stresses. In this paper, fatigue tests are discussed, performed on butt welded specimens in steel grades ranging from S460 to S1100 in the TIG-dressed condition. The test results are compared with modelled fatigue strength according to the notch stress theory and similar specimens in the as-welded condition. The...

  5. Assessment of Fatigue and Recovery in Male and Female Athletes After 6 Days of Intensified Strength Training.

    Science.gov (United States)

    Raeder, Christian; Wiewelhove, Thimo; Simola, Rauno Álvaro De Paula; Kellmann, Michael; Meyer, Tim; Pfeiffer, Mark; Ferrauti, Alexander

    2016-12-01

    Raeder, C, Wiewelhove, T, Simola, RÁDP, Kellmann, M, Meyer, T, Pfeiffer, M, and Ferrauti, A. Assessment of fatigue and recovery in male and female athletes after 6 days of intensified strength training. J Strength Cond Res 30(12): 3412-3427, 2016-This study aimed to analyze changes of neuromuscular, physiological, and perceptual markers for routine assessment of fatigue and recovery in high-resistance strength training. Fourteen male and 9 female athletes participated in a 6-day intensified strength training microcycle (STM) designed to purposefully overreach. Maximal dynamic strength (estimated 1 repetition maximum [1RMest]; criterion measure of fatigue and recovery); maximal voluntary isometric strength (MVIC); countermovement jump (CMJ) height; multiple rebound jump (MRJ) height; jump efficiency (reactive strength index, RSI); muscle contractile properties using tensiomyography including muscle displacement (Dm), delay time (Td), contraction time (Tc), and contraction velocity (V90); serum concentration of creatine kinase (CK); perceived muscle soreness (delayed-onset muscle soreness, DOMS) and perceived recovery (physical performance capability, PPC); and stress (MS) were measured before and after the STM and after 3 days of recovery. After completing the STM, there were significant (p ≤ 0.05) performance decreases in 1RMest (%[INCREMENT] ± 90% confidence limits, ES = effect size; -7.5 ± 3.5, ES = -0.21), MVIC (-8.2 ± 4.9, ES = -0.24), CMJ (-6.4 ± 2.1, ES = -0.34), MRJ (-10.5 ± 3.3, ES = -0.66), and RSI (-11.2 ± 3.8, ES = -0.73), as well as significantly reduced muscle contractile properties (Dm, -14.5 ± 5.3, ES = -0.60; V90, -15.5 ± 4.9, ES = -0.62). After days of recovery, a significant return to baseline values could be observed in 1RMest (4.3 ± 2.8, ES = 0.12), CMJ (5.2 ± 2.2, ES = 0.28), and MRJ (4.9 ± 3.8, ES = 0.32), whereas RSI (-7.9 ± 4.5, ES = -0.50), Dm (-14.7 ± 4.8, ES = -0.61), and V90 (-15.3 ± 4.7, ES = -0.66) remained

  6. Hybrid glass coatings for optical fibers: effect of coating thickness on strength and dynamic fatigue characteristics of silica fibers

    Science.gov (United States)

    Wojcik, A. B.; Matthewson, M. J.; Castelino, K. T.; Wojcik, J.; Walewski, A.

    2006-04-01

    Specialty optical fibers operating in harsh aerospace environments are typically exposed to high temperatures and elevated humidity. This calls for better performing protective coatings. Recently developed sol-gel derived inorganicorganic hybrid materials called hybrid glass offered improved protective performance as compared to standard dual polymer coated fibers [1]. In this paper we examine the effectiveness of online UV curing for the protective ability of hybrid glass coatings. For this purpose two types of UV-curable hybrid glass candidates representing two different concentrations of acrylate groups were applied online to silica fibers as single and dual coats. Samples of fibers were collected and subjected to dynamic fatigue testing by two-point bending. The stress corrosion parameter, n, as well as the strength of the fibers were determined. Both the strength and n were higher for fibers with two layers of coating as compared to single coatings even when the thickness of both one and two layer coatings was the same. This may be caused by the greater degree of cross linking of the inorganic component when the coating is exposed twice to the heat generated in the UV chamber. Coating materials with reduced acrylate group content had higher values of the fatigue parameter n but at the same time reduced strength.

  7. Fatigue and residual strength of concrete and other aging viscoelastic materials

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1996-01-01

    The DVM-theory (Damaged Viscoelastic Material) previously developed by the author to predict lifetime of non-aging viscoelastic materials (like wood) is generalized in this paper such that aging viscoelastic materials such as concrete subjected to variable load can also be considered. Lifetime...... criterion. A simple time criterion is much better. The theory is successfully compared with methods previously presented in the field of concrete fatigue. Algorithms and design graphs are developed which can be used in fatigue design of concrete products....

  8. Effect of microstructure on fatigue behavior of advanced high strength steels produced by quenching and partitioning and the role of retained austenite

    Energy Technology Data Exchange (ETDEWEB)

    Diego-Calderón, I. de, E-mail: irenedediego.calderon@imdea.org [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Rodriguez-Calvillo, P. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Lara, A. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Molina-Aldareguia, J.M. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Petrov, R.H. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); De Knijf, D. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Sabirov, I. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2015-08-12

    Despite the significant body of research on mechanical properties of quenched and partitioned (Q&P) steels, their fatigue behavior has not been investigated. This work focuses on the effect of microstructure on high cycle fatigue of Q&P steels and microstructural evolution during cyclic loading. It is demonstrated that increased content of retained austenite (RA) improves fatigue limit of Q&P steels that is related to delay of crack propagation due to austenite–martensite phase transformation. Increasing stress amplitude promotes austenite–martensite phase transformation during cycling loading. It is shown that size and crystallographic orientation of RA are the main factors determining its stability, whereas its shape and spatial distribution do not seem to affect it significantly. Fatigue crack initiation during fatigue testing with high stress amplitudes occurs by intergranular cracking, whereas transgranular cracking controls fatigue crack initiation during cycling loading with lower stress amplitudes. Transgranular crack propagation dominates in the second stage of fatigue at all stress amplitudes. The final stage of fatigue is also not affected by the stress amplitude. It is suggested that fatigue life of Q&P steels can be enhanced via improvement of strength of grain/interphase boundaries.

  9. Evaluation of Pressurization Fatigue Life of 1441 Al-li Fuselage Panel

    Science.gov (United States)

    Bird, R. Keith; Dicus, Dennis I.; Fridlyander, Joseph; Davydov, Valentin

    1999-01-01

    A study was conducted to evaluate the pressurization fatigue life of fuselage panels with skins fabricated from 1441 Al-Li, an attractive new Russian alloy. The study indicated that 1441 Al-Li has several advantages over conventional aluminum fuselage skin alloy with respect to fatigue behavior. Smooth 1441 Al-Li sheet specimens exhibited a fatigue endurance limit similar to that for 1163 Al (Russian version of 2024 Al) sheet. Notched 1441 Al-Li sheet specimens exhibited greater fatigue strength and longer fatigue life than 1163 Al. In addition, Tu-204 fuselage panels fabricated by Tupolev Design Bureau using Al-Li skin and ring frames with riveted 7000-series aluminum stiffeners had longer pressurization fatigue lives than did panels constructed from conventional aluminum alloys. Taking into account the lower density of this alloy, the results suggest that 1441 Al-Li has the potential to improve fuselage performance while decreasing structural weight.

  10. Cold-Drawn Bioabsorbable Ferrous and Ferrous Composite Wires: An Evaluation of Mechanical Strength and Fatigue Durability

    Science.gov (United States)

    Schaffer, Jeremy E.; Nauman, Eric A.; Stanciu, Lia A.

    2012-08-01

    Yield strengths exceeding 1 GPa with elastic strains exceeding 1 pct were measured in novel bioabsorbable wire materials comprising high-purity iron (Fe), manganese (Mn), magnesium (Mn), and zinc (Zn), which may enable the development of self-expandable, bioabsorbable, wire-based endovascular stents. The high strength of these materials is attributed to the fine microstructure and fiber textures achieved through cold drawing techniques. Bioabsorbable vascular stents comprising nutrient metal compositions may provide a means to overcome the limitations of polymer-based bioabsorbable stents such as excessive strut thickness and poor degradation rate control. Thin, 125- μm wires comprising combinations of ferrous alloys surrounding a relatively anodic nonferrous core were manufactured and tested using monotonic and cyclic techniques. The strength and durability properties are tested in air and in body temperature phosphate-buffered saline, and then they were compared with cold-drawn 316L stainless steel wire. The antiferromagnetic Fe35Mn-Mg composite wire exhibited more than 7 pct greater elasticity (1.12 pct vs 1.04 pct engineering strain), similar fatigue strength in air, an ultimate strength of more than 1.4 GPa, and a toughness exceeding 35 mJ/mm3 compared with 30 mJ/mm3 for 316L.

  11. Notch Antennas

    Science.gov (United States)

    Lee, Richard Q.

    2004-01-01

    Notch antennas, also known as the tapered slot antenna (TSA), have been the topics of research for decades. TSA has demonstrated multi-octave bandwidth, moderate gain (7 to 10 dB), and symmetric E- and H- plane beam patterns and can be used for many different applications. This chapter summarizes the research activities on notch antennas over the past decade with emphasis on their most recent advances and applications. This chapter begins with some discussions on the designs of single TSA; then follows with detailed discussions of issues associated with TSA designs and performance characteristics. To conclude the chapter, some recent developments in TSA arrays and their applications are highlighted.

  12. Equivalent hot spot stress approach for multiaxial fatigue strength assessment of complex welded joints%复杂焊接接头多轴疲劳强度评估的等效热点应力法

    Institute of Scientific and Technical Information of China (English)

    刘刚; 黄如旭; 黄一

    2012-01-01

    The current hot spot stress approach still has some limitations to the multiaxial fatigue strength assessment of complex welded joints.In this paper,an new stress estimation approach for the multiaxial fatigue strength assessment of complex welded joints is proposed,in which an equivalent hot spot stress is defined at a point(called Zero Point) in plate thickness direction where nonlinear distribution stress due to the notch effect of the weld is equal to zero.The proposed approach is based on that the nonlinear stress peak is not included in the hot spot stress and the nonlinear distribution stress is in self-equilibrium.First,influence factors and change laws of the Zero Point position were discussed,and a fitting equation for determining the Zero Point position was established.Then,published fatigue tests data and numerical stress results of some welded joints were used for comparison between the proposed equivalent hot spot stress approach and the current hot spot stress approach.The equivalent hot spot stress approach was verified to be consistent with the current hot spot stress approach and also have higher accuracy for considering the thickness effect on the fatigue strength to a certain extent.The merit of the proposed approach is that it can be used to estimate the multiaxial fatigue strength of welded joints through combining multiaxial fatigue theory.%基于焊缝本身引起的非线性分布应力自平衡的性质,在板厚方向非线性分布应力大小为零的位置(零点位置)定义等效热点应力,提出一种新的能够用于复杂焊接接头多轴疲劳应力评价方法.首先,分析了零点位置的影响因素和变化规律,建立了确定零点位置的拟合方程.然后,和公开发表的试验数据以及现有的热点应力法有限元计算结果进行了对比.结果表明,等效热点应力法和现有的热点应力法具有很好的一致性,而且能够在一定程度上考虑厚度效应对疲劳强度的影

  13. Modelling of ultrasonic impact treatment (UIT of welded joints and its effect on fatigue strength

    Directory of Open Access Journals (Sweden)

    K.L. Yuan

    2015-10-01

    Full Text Available Ultrasonic impact treatment (UIT is a remarkable post-weld technique applying mechanical impacts in combination with ultrasound into the welded joints. In the present work, a 3D simulation method including welding simulation, numerical modelling of UIT-process and an evaluation of fatigue crack growth has been developed. In the FE model, the actual treatment conditions and local mechanical characteristics due to acoustic softening are set as input parameters. The plastic deformation and compressive stress layer are found to be more pronounced when acoustic softening takes place. The predicted internal residual stress distributions of welded joint before and after UIT are compared with experimental results, showing a fairly good agreement with each other. Finally, simulated results of fatigue crack growth in various residual stress fields are well compared with test results, so that the proposed model may provide an effective tool to simulate UIT-process in engineering structures.

  14. Notch filter

    Science.gov (United States)

    Shelton, G. B. (Inventor)

    1977-01-01

    A notch filter for the selective attenuation of a narrow band of frequencies out of a larger band was developed. A helical resonator is connected to an input circuit and an output circuit through discrete and equal capacitors, and a resistor is connected between the input and the output circuits.

  15. A surface crosslinked UHMWPE stabilized by vitamin E with low wear and high fatigue strength.

    Science.gov (United States)

    Oral, Ebru; Ghali, Bassem W; Rowell, Shannon L; Micheli, Brad R; Lozynsky, Andrew J; Muratoglu, Orhun K

    2010-09-01

    Wear particle-induced periprosthetic osteolysis has been a clinical problem driving the development of wear resistant ultrahigh molecular weight polyethylene (UHMWPE) for total joint replacement. Radiation crosslinking has been used to decrease wear through decreased plastic deformation; but crosslinking also reduces mechanical properties including fatigue resistance, a major factor limiting the longevity of joint implants. Reducing UHMWPE wear with minimal detriment to mechanical properties is an unaddressed need for articular bearing surface development. Here we report a novel approach to achieve this by limiting crosslinking to the articular surface. The antioxidant vitamin E reduces crosslinking efficiency in UHMWPE during irradiation with increasing concentration, thus we propose to spatially control the crosslink density distribution by controlling the vitamin E concentration profile. Surface crosslinking UHMWPE prepared using this approach had high wear resistance and decreased crosslinking in the bulk resulting in high fatigue crack propagation resistance. The interface region did not represent a weakness in the material due to the gradual change in the crosslink density. Such an implant has the potential of decreasing risk of fatigue fracture of total joint implants as well as expanding the use of UHMWPE to younger and more active patients.

  16. Assessment of fatigue life for a crack emanated from a notch. ; Algorithm of fatigue life assessment by [delta]K[sub RP] approach without distinguishing between the crack Initiaion and the propagation. Kirikakitei kara hasseisuru bishi bisho kiretsu no hiro kiretsu jumyo hyokaho ni tsuite. ; Hassei to denpa no toitsu riron ni yoru jumyo yosoku no algorithm (RPG kijun ni yoru hiro kiretsu denpa kyodo no kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    Toyosada, M.; Niwa, T. (Kyushu University, Fukuoka (Japan). Faculty of Engineering)

    1993-08-01

    Fatigue life has been estimated as a sum of crack initiation life and crack propagation life, by using a fracture dynamical method. In order to make the method more reliable, a method is being discussed to estimate a growth curve for fatigue cracks from notch bottom under a unified theoretical system without a need of introducing the presence of initial cracks. Subsequently to the previous report, this paper describes a fatigue test that uses CT test pieces with the notch bottom finished in arc, an investigation on initiation and propagation behaviors of micro cracks, and discussions on their possibilities. From a large number of findings obtained, an algorithm was proposed to estimate the crack growth curve in approximation. The proposal was made by introducing a hypothesis that the growth of compressed plastic region is restricted by such a barrier as crystal particle boundaries until a developed crack can reach the first crystal particle boundary when the effective loading is maintained constant. The estimated curves and the experimental results have agreed well with each other. Stagnating crack phenomenon at a notch bottom and coaxing effect were explained qualitatively. 30 refs., 24 figs.

  17. In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

    Science.gov (United States)

    Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

    2015-06-01

    Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

  18. Evaluation of fatigue strength of WC cermet- and 13Cr steel-sprayed materials; WC cermet oyobi 13Cr ko yosha hifukuzai no hiro kyodo hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, T.; Tokaji, K.; Ejima, T. [Gifu University, Gifu (Japan); Kobayashi, Y.; Harada, Y. [Tocalo Co. Ltd., Kobe (Japan)

    1997-10-15

    Rotating bending fatigue tests have been conducted at room temperature in air using the specimens of medium carbon steel (S45C), low alloy steel (SCM435) and titanium alloy (Ti-6Al-4V) with HVOF sprayed coating of a cermet (WC-12%Co) and S45C with WFS sprayed coating of a 13Cr steel (SUS420 J2). The fatigue strength and fracture mechanisms were studied. The fatigue strength evaluated by nominal stress was strongly influenced by substrate materials and the thickness of sprayed coatings. Detailed observation of crack initiation on the coating surface and fracture surface revealed that microcracks initiated at the WC grain boundary coalesced, and then the crack grew rapidly in the coating. Cracks in the substrate were initiated by the stress concentration of the crack in the coating, which was modeled by finite element analysis. For the specimens tested in this study, the fatigue strength of sprayed specimens was dominated by that of sprayed coating. Thus, the fatigue strength could be evaluated uniquely by the true stress on the coating surface. 9 refs., 12 figs., 2 tabs.

  19. Fatigue experiments on very high strength steel base material and transverse butt welds

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    Very High Strength Steels (VHSS) with nominal strengths up to 1100 MPa have been available on the market for many years. However, the use of these steels in the civil engineering industry is still uncommon, due to lack of design and fabrication knowledge and therefore limited inclusion in codes. Mor

  20. Fatigue experiments on very high strength steel base material and transverse butt welds

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    Very High Strength Steels (VHSS) with nominal strengths up to 1100 MPa have been available on the market for many years. However, the use of these steels in the civil engineering industry is still uncommon, due to lack of design and fabrication knowledge and therefore limited inclusion in codes.

  1. Muscle strength and fatigue in newly diagnosed patients with myasthenia gravis

    DEFF Research Database (Denmark)

    Vinge, Lotte; Andersen, Henning

    2016-01-01

    significantly with manual muscle testing (MG Composite). Dynamometry revealed improved muscle strength of up to 50% (median 17%, range -1.8 - 49.8) despite no change in the MG Composite score. DISCUSSION: Dynamometry appears to be a more sensitive method of identifying changes in limb strength than MG...

  2. Notch-strengthening in two-dimensional foams

    NARCIS (Netherlands)

    Onck, P.R.

    2001-01-01

    Metallic foams show notch-strengthening behavior when analyzing double-edge notched specimen in compression and tension. A discrete microstructural model has been used to simulate the effect of notch depth and specimen size on the net-section-strength. The non-uniform deformation behavior is analyze

  3. Effect Of The Spacing Between Submicroscopic Oxide Impurities On The Fatigue Strength Of Structural Steel

    Directory of Open Access Journals (Sweden)

    Lipiński T.

    2015-09-01

    Full Text Available The article discusses the effect of distance between submicroscopic oxide impurities (up to 2 μm in size on the fatigue resistance coefficient of structural steel during rotary bending. The study was performed on 21 heats produced in an industrial plant. Fourteen heats were produced in 140 ton electric furnaces, and 7 heats were performed in a 100 ton oxygen converter. All heats were desulfurized. Furthermore seven heats from electrical furnaces were refined with argon, and heats from the converter were subjected to vacuum circulation degassing.

  4. Temperature effect on corrosion fatigue strength of coated ship structural steel; Zosen`yoko tosozai no fushoku hiro kyodo ni okeru ondo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Takanashi, M.; Fuji, A.; Kojima, M.; Kitagawa, M. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Kobayashi, Y. [Ship Research Inst., Tokyo (Japan); Kumakura, Y.

    1997-08-01

    The corrosion fatigue life was obtained using uncoated and tar epoxy resin specimens to clarify the temperature effect. The life curve for corrosion fatigue of machined and uncoated steel in the air and sea was obtained. The fatigue strength of uncoated steel largely decreases in the sea and breaks even in the nominal stress range of less than 1/2 of the fatigue limit in the air. The effect of temperature on the coated steel is represented by a corrosion coefficient. The steel coated at 25{degree}C is 1/1.03 to 1/1.13 at 40 to 60{degree}C. This showed that the fatigue strength decreases when the temperature exceeds 25{degree}C. However, it has not such tendency and significance that are represented quantitatively. There is a slight difference in the short-life area between the crack generation life and breaking life. However, the long-life area has no significance that influences the whole evaluation. In the long-life corrosion fatigue, the crack occurs from the corrosion pit due to the exposure below the coated film and progresses in the base material before the coated film is destroyed. The effect of the corrosion pit remarkably appears at a low-stress level. 14 refs., 14 figs., 4 tabs.

  5. Effect of HIP temperature on microstructure and low cycle fatigue strength of CuCrZr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishi, Hiroshi, E-mail: nishi.hiroshi88@jaea.go.jp [Japan Atomic Energy Agency, Naka-shi, Ibaraki-ken 311-0193 (Japan); Enoeda, Mikio [Japan Atomic Energy Agency, Naka-shi, Ibaraki-ken 311-0193 (Japan)

    2011-10-01

    In order to investigate the effect of the HIP cycle temperatures on the metallurgic degradation and the mechanical properties of CuCrZr alloy, assessments of the microstructure, tensile test, Charpy impact test and low cycle fatigue test are performed for various heat treated CuCrZr alloys, which were solution-annealed followed by water-quenched and aged state of CuCrZr with simulated HIP cycle at temperatures of 980 and 1045 deg. C. Grain growth occurred on 1045 deg. C HIP CuCrZr, though slightly on 980 deg. C HIP CuCrZr. Metallurgic degradation such as voids was not found by optical and SEM observations. There were coarse precipitates in all the CuCrZr and the precipitates did not easily dissolve at 980 deg. C. The low cycle fatigue strength of 1045 deg. C HIP CuCrZr was lower than that of other CuCrZr because of the metallurgic degradation caused by the heat cycle, while that of other CuCrZr was corresponding to the best fit curve of ITER MPH.

  6. An in vitro investigation into retention strength and fatigue resistance of various designs of tooth/implant supported overdentures.

    Science.gov (United States)

    Fatalla, Abdalbseet A; Song, Ke; Du, Tianfeng; Cao, Yingguang

    2012-02-01

    Previously, the choice of prosthetic implant-retained overdentures has depended on data from previous studies about the retention-fatigue strength of the attachment system selected. Little or no data have been available on the correlation between the attachment system selected and the overdenture support configuration. The purpose of the present study was to evaluate the retention force and fatigue resistance of three attachment systems and four support designs of overdenture prosthesis. Four lower edentulous acrylic models were prepared and eight combinations of attachments groups were investigated in the study. These included: O-Rings with mini-dental implants (MDIs), Dalbo elliptic with Dalbo Rotex and fabricated flexible acrylic attachments with both MDI and Dalbo Rotex. The study was divided into four test groups: groups A and B, controls, and groups C and D, experimental groups. Control group A contained three overdenture supports: two free standing MDIs in the canine region and at the midline, and one simulated tooth root with Dalbo Rotex screwed in. Control group B contained four overdenture support foundations: two free standing MDIs in the right canine region and the first premolar region, and two simulated tooth roots with Dalbo Rotex screwed in at the same MDI position, but on the left side of the model. Experimental group C contained three overdenture support foundations: two free standing MDIs in the canine region and at the midline, and one simulated tooth root with MDI screwed in. Experimental group D contained four overdenture support foundations: two free standing MDIs in the right canine region and the first premolar region, and two simulated tooth roots with MDIs screwed in at the same MDI position, but on the left side of the model. Each group was further divided into two subgroups according to attachment type used. Five samples were prepared for each group. Retention force (N) values were recorded initially (0 cycles) and after 360, 720, 1440

  7. Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

    Science.gov (United States)

    Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

    2011-01-01

    Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

  8. Incubating isolated mouse EDL muscles with creatine improves force production and twitch kinetics in fatigue due to reduction in ionic strength.

    Directory of Open Access Journals (Sweden)

    Stewart I Head

    Full Text Available BACKGROUND: Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. METHODS AND RESULTS: The extensor digitorum longus muscle from mice aged 12-14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i before fatigue; (ii immediately after a fatigue protocol; and (iii after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. CONCLUSION: Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca(2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation.

  9. The effect of the production process of medium-carbon steel on fatigue strength

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2010-04-01

    Full Text Available The experimental material comprised semi-finished, high grade, medium-carbon structural steel for the production of mining chains. Steel was melted in a 140 ton electric furnace and desulfurized (E. In the second analyzed variant, steel was additionally refined with argon (EA. In the third variant, steel was melted in a 100 ton converter. Secondary treatment involved vacuum circulation degassing. Specimens with a diameter of 10 mm were prepared by hardening and tempering at 200, 300, 400, 500 and 600°C. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were processed and presented in graphic form.

  10. Analysis of the fatigue strength under two load levels of a stainless steel based on energy dissipation

    Directory of Open Access Journals (Sweden)

    Ricotta M.

    2010-06-01

    Full Text Available In this paper the fatigue behaviour of a stainless steel AISI 304L is analysed. In the first part of the work the results obtained under constant amplitude fatigue are presented and synthesised in terms of both stress amplitude and energy released to the surroundings as heat by a unit volume of material per cycle, Q. Then some specimens have been fatigued in variable amplitude, two different load level tests: the first level was set higher while the second was lower than the constant amplitude fatigue limit. The Q values, evaluated during the second part of the fatigue test, have been compared with those calculated under constant amplitude fatigue at the same load level. The comparison allowed us to notice that the Q parameter is sensitive to the fatigue damage accumulated by the material during the first part of the fatigue test.

  11. Analysis of the fatigue strength under two load levels of a stainless steel based on energy dissipation

    Directory of Open Access Journals (Sweden)

    M. Ricotta

    2011-07-01

    Full Text Available In this paper the fatigue behaviour of a stainless steel AISI 304L is analysed. In the first part of the work the results obtained under constant amplitude fatigue are presented and synthesised in terms of both stress amplitude and energy released to the surroundings as heat by a unit volume of material per cycle, Q. Then some specimens have been fatigued in variable amplitude, two different load level tests: the first level was set higher while the second was lower than the constant amplitude fatigue limit. The Q values, evaluated during the second part of the fatigue test, have been compared with those calculated under constant amplitude fatigue at the same load level. The comparison allowed us to notice that the Q parameter is sensitive to the fatigue damage accumulated by the material during the first part of the fatigue test.

  12. Bending-fatigue damage-detection on notched-tooth spiral-bevel gears using the average-log-ratio, ALR, algorithm

    Science.gov (United States)

    Hines, Jason A.; Mark, William D.

    2014-02-01

    The frequency-domain ALR (average-log-ratio) damage-detection algorithm [MSSP 24 (2010) 2807-2823] is utilized to illustrate damage detection and progression on notched-tooth spiral-bevel gears. Use of equal weighting of increases or decreases of individual rotational-harmonic amplitudes caused by damage, for early ALR detections, is substantiated. Continuously improving statistical reliability of ALR is documented by using increasing numbers of rotational-harmonic amplitude-ratios and increasing numbers of waveforms in the synchronous averaging. Sensitivity of the ALR algorithm to incipient damage is observed to be comparable to that obtained from the kurtosis-based Figure of Merit 4 (FM4). In contrast to FM4, ALR is shown to monotonically increase with increasing damage and running time. Interestingly, this diagnostic technique can be implemented with remarkably low analog-to-digital conversion rates. Computation of ALR for differing torque levels shows strong indications of weakening tooth-stiffness and increasing tooth-plastic-deformation. ALR computation utilizing tooth-rotational-location windowing also is illustrated.

  13. Study on analyzing fatigue strength of welding structure based on ANSYS%基于ANSYS的焊接结构疲劳强度分析

    Institute of Scientific and Technical Information of China (English)

    耿新宇; 米彩盈

    2013-01-01

    针对焊接结构不同焊接接头具有不同的疲劳强度许用应力,根据焊接接头的形状与应力集中情况将焊缝与母材分为不同的等级,基于DIN15018-1报告给出的疲劳强度评定方法确定了不同等级的焊缝和母材的最大应力、最小应力、平均应力、应力比、应力幅和疲劳安全系数.提出了对于ANSYS平台的结果文件进行二次开发.通过FORTRAN语言编程提取出ANSYS结果二进制文件中所存储的方向应力,依据特定疲劳标准选行疲劳分析,并且将疲劳强度分析的结果数据放入ANSYS的结果文件中,实现在ANSYS平台的后处理模块中示疲劳强度的分析结果,提高疲劳强度分析结果的可视性.%In consider of the fact that different welding joints have different fatigue permissible stresses weld zone and metal base are divided into various levels depending on the shape of welding joints and the stress concentration situation.According to the method to evaluating fatigue strength which is given by DIN 15018-1 report,maximum stress,minimum stress,average stress,stress ratio,stress amplitude and factor of safety are calculated.The secondly development of the result file which is provided by ANSYS is raised.The nodal component stresses in result file are extracted and calculated by programming in FORTRAN language,according to specific fatigue design standard the results of analyzing fatigue strength are worked out,and the results of analyzing fatigue strength are written back into result file.The results of analyzing fatigue strength are displayed by post processing module of ANSYS.The second development which is described in this article has improved the visibility of the results of analyzing fatigue strength.

  14. Influence of surface finish on fatigue properties of metallic materials: a bibliographic study; Influence de l`etat de surface sur les proprietes de fatigue des materiaux metalliques: etude bibliographique

    Energy Technology Data Exchange (ETDEWEB)

    Akamatsu, M. [Electricite de France (EDF), Direction des Etudes et Recherches, 92 - Clamart (France)

    1997-12-31

    The investigation of a fatigue failed component very often shows that cracks initiated at the surface. It is actually well known that the surface finish notably influences the fatigue strength of a component. We have carried out a bibliographic study in order to clarify the influence of the different surface parameters. The analysis of the literature has shown that most of the data concerns high cycle fatigue. Three aspects of the surface finish have been examined: geometry (roughness), residual stresses and microstructure. In a general way, the influence of geometrical surface finish is tackled either empirically, with a factor assessing the fatigue limit decrease when the roughness and the tensile strength increase, or theoretically, with approaches modelling geometrical irregularities as notches or cracks. In all cases, the effect of roughness on fatigue strength depends on the material, through mechanical properties or microstructural features. The theoretical approaches seem particularly interesting, but their use is not straightforward and requires further development. The creation of residual stresses at the surface of a component can just as well reduce as improve its fatigue strength. In a first approach, these stresses can be regarded as a mean service stress. In fact, mechanical and metallurgical gradients near the surface have to be taken into account, which affect the relaxation of residual stresses during fatigue cycling. Actually, the effect of residual stresses can hardly be isolated, because these stresses are associated with geometrical and microstructural modifications. Microstructural features (metallurgical structure, grain size, inclusions, strain hardening) have an undoubted influence on fatigue strength, but the quantification of the effects remains tricky. The influence of the microstructure of surface layers on fatigue strength generally depends on the mechanical properties of materials. In short, fatigue strength predictions through a

  15. Notch sensitivity of ductile metallic foams : A computational study

    NARCIS (Netherlands)

    Mangipudi, K. R.; Onck, P. R.

    2011-01-01

    The role of notches in the fracture strength of metal foams has been studied using a multiscale model based on a two-dimensional Voronoi representation of the cellular architecture. The effect of the crack length to the specimen width ratio on the net section strength of double edge notch (DEN) spec

  16. The Effect of the Production Process and Heat Processing Parameters on the Fatigue Strength of High-Grade Medium-Carbon Steel

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2012-04-01

    Full Text Available The experimental material consisted of semi-finished products of high-grade, medium-carbon constructional steel with: manganese, chromium, nickel, molybdenum and boron. The experimental material consisted of steel products obtained in three metallurgical processes: electric and desulfurized (E, electric and desulfurized with argon-refined (EA and oxygen converter with vacuum degassed of steel (KP. The production process involved two melting technologies: in a 140-ton basic arc furnace with desulphurisation and argon refining variants, and in a 100-ton oxygen converter. Billet samples were collected to analyze: relative volume of impurities, microstructure and fatigue tests. The samples were quenched and austenitized at a temperature of 880oC for 30 minutes. They were then cooled in water and tempered by holding the sections at a temperature of 200, 300, 400, 500 and 600oC for 120 minutes and air-cooled. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were statistical processed and presented in graphic form. This paper discusses the results of microstructural analyses, the distribution of the relative volume of impurities in different size ranges, the fatigue strength characteristics of different production processes, the average number of sample- damaging cycles and the average values of the fatigue strength coefficient for various heat processing options.

  17. 焊缝余高对焊接接头疲劳强度的影响%INFLUENCE OF PILE HIGH ON FATIGUE STRENGTH OF WELDING JOINT

    Institute of Scientific and Technical Information of China (English)

    吕晓春; 张志毅; 李爱民

    2011-01-01

    The influence of pile high on fatigue strength of AQ400NH material weldment were studied by testing fatigue property of AQ400NH material and its smooth and pile high weldment, observing fracture, determining S -N curve, calculating stress with ANSYS. The results show that the weld defect is the main reason to influence fatigue strength of smooth weldment than the pile high is the main reason to influence fatigue strength of weldment with pile high. To measure true strain and ANSYS calculation give the same result that stress concentrate area is in weld toe, there is an linear relation between the strength of stress concentrate and pile high.%通过测定AQ400NH材料的光滑焊件、余高焊件的疲劳性能、观察断口形貌、绘制S-N曲线以及用AN-SYS有限元程序计算应力分布,研究余高对焊接接头疲劳强度的影响.结果发现,对于光滑焊件,焊接缺陷是影响疲劳强度的主要原因,对于有余高焊件,余高的高度是影响疲劳强度的主要原因,实际应变测量和有限元计算都表明,焊趾部位是应力集中区,应力集中的强度和余高间有线性关系.

  18. STUDY ON DOUBLE-NOTCH SHEAR STRENGTH OFGLASS CLOTH/EPOXY LAMINATES AT LOW TEMPERATURE%玻璃钢层合板的超低温双切口层间剪切强度研究

    Institute of Scientific and Technical Information of China (English)

    王瑞; 进藤裕英

    2000-01-01

    本文采用三维有限元法对双切口剪切试验测定玻璃钢层合板的超低温层间剪切强度进行了理论分析和研究,解析用的层合板有效弹性系数由组分材料的弹性系数和织物结构的代表体积单元求得。数值解析发现,当切口间隔与厚度之比较小时,双切口剪切试验片可产生较均匀的剪切应力分布。通过与二维有限元解析结果的对比分析,阐明了试验片三维形状对剪切应力分布的影响。%The double-notch shear test method for determining interlaminar shear strength of glass cloth/epoxy laminates at low temperature was studied using a three-dimensional finite element analysis. Effective e-lastic moduli were determined under the assumption of uniform strain inside the representative volume element. Double-notch shsar specimens with lower notch separation-to-thickness ratios were found to yield more uniform shear stress. The shear stress distribution was compared with the results provided by a plane-strain finite element analysis and the three-dimensional effects were examined.

  19. Notch sensitivity of space shuttle tile materials

    Science.gov (United States)

    Newman, J. C., Jr.

    1980-01-01

    Tests were conducted at room temperature to determine the notch sensitivity of the thermal protection tile for the space shuttle. Two types of RSI tile were studied: LI-900 and LI-2200. Three point bend specimens were cut from discarded tiles in the in-plane (ip) and through-the-thickness (ttt) directions. They were tested with or without a sharp notch. The LI-900 (ip and ttt) specimens were not very notch sensitive, but the LI-2200 (ip and ttt) specimens were. The LI-2200 material showed about a 35 percent reduction in strength due to the presence of the notch. This reduction in strength should be considered in the design of mechanically fastened tile concepts.

  20. The significance of ultrafine film-like retained austenite in governing very high cycle fatigue behavior in an ultrahigh-strength MN–SI–Cr–C steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: zhaoping12@mails.tsinghua.edu.cn [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhang, B.; Cheng, C. [Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China); Misra, R.D K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical and Materials Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968-0520 (United States); Gao, G., E-mail: gaogh@bjtu.edu.cn [Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China); Bai, B.; Weng, Y. [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China)

    2015-10-01

    We elucidate here the very high cycle fatigue (VHCF) behavior of an ultrahigh-strength medium carbon Mn–Si–Cr–C steel processed using the approach of bainite-based quenching and partitioning (BQ&P). The microstructure of BQ&P process comprised of bainite, carbon-depleted martensite, retained austenite (RA) and small amount of martensite/austenite island (M/A). The tensile strength (R{sub m}) and fatigue limit strength after 10{sup 9} cycles (σ{sub w9}) and in the non-failed condition were 1688 MPa and 875 MPa, respectively such that σ{sub w9}/R{sub m} exceeded conventional steels and was 0.52. Two types of failure modes were observed depending on the surface and microstructure, notably surface-induced failure and non-inclusion-induced failure, where the non-inclusion-induced failure was influenced by the microstructure. Inclusion-induced failure was absent. The study underscores that film-like retained austenite was the underlying reason for superior fatigue properties, hitherto not previously obtained.

  1. Effect of multiple passes treatment in waterjet peening on fatigue performance

    Science.gov (United States)

    Azhari, Azmir; Schindler, Christian; Godard, Claudia; Gibmeier, Jens; Kerscher, Eberhard

    2016-12-01

    The influence of waterjet peening on the residual stresses and fatigue performance of AISI 304 is investigated. The specimen surfaces were treated with multiple jet passes. The fatigue strength was evaluated using an alternating bending fatigue tester. The results of XRD measurements showed that a higher amount of compressive residual stresses is induced in the treated specimens. This strengthening layer is limited within the first 100 μm below the surface, which had been confirmed by micro hardness measurements. Even though the treated specimens showed compressive residual stresses the fatigue limit is lower than that of the untreated specimens. The roughness of the surface and the resulting notch effect seems to be stronger than the positive effect of the hardened layer.

  2. Behaviour of -glass fibre reinforced vinylester resin composites under impact fatigue

    Indian Academy of Sciences (India)

    Rita Roy; B K Sarkar; N R Bose

    2001-04-01

    An impact fatigue study has been made for the first time on 63.5% glass fibre reinforced vinylester resin notched composites. The study was conducted in a pendulum type repeated impact apparatus especially designed and fabricated for determining single and repeated impact strengths. A well-defined impact fatigue (S–N) behaviour, having a progressive endurance below the threshold single cycle impact fracture stress with decreasing applied stress has been demonstrated. Fractographic analysis revealed fracture by primary debonding having fibre breakage and pullout at the tensile zone, but a shear fracture of fibre bundles at the compressive zone of the specimen. The residual strength, modulus and toughness showed retention of the properties at high impact stress levels up to 1000 impacts followed by a sharp drop. Cumulative residual stresses with each number of impacts not withstanding the static fatigue failure at long endurances have been ascribed for the composite failures under the repeated impact stresses.

  3. Effects of thermal and mechanical fatigue on the flexural strength of G40-600/PMR-15 cross-ply laminates

    Science.gov (United States)

    Roberts, Gary D.; Ho, Barry Ping Hsiao; Wallace, John F.

    1993-01-01

    The effects of thermal and mechanical fatigue on the flexural strength of G40-600/PMR-15 cross-ply laminates with ply orientation of (0(2),90(2))2S and (90(2),0(2))2S are examined. The relative importance of shear and tensile stresses is examined by varying the span-to-depth ratios of flexural test specimens from 8 to 45. Acoustic emission signals are measured during the flexural tests in order to monitor the initiation and growth of damage. Optical microscopy is used to examine specimens for resin cracking, delamination, and fiber breaks after testing. Transverse matrix cracks and delaminations occur in all specimens, regardless of ply orientation, span-to-depth ratio, or previous exposure of specimens to thermal and mechanical fatigue. A small amount of fiber tensile fracture occurs in the outer 0 deg ply of specimens with high span-to-depth ratios. Because of the complex failure modes, the flexural test results represent the 'apparent' strengths rather than the true flexural or shear strengths for these cross-ply laminates. Thermal cycling of specimens prior to flexural testing does not reduce the apparent flexural strength or change the mode of failure. However, fewer acoustic events are recorded at all strains during flexural testing of specimens exposed to prior thermal cycling. High temperature thermal cycling (32 to 260 C, 100 cycles) causes a greater reduction in acoustic events than low temperature thermal cycling (-85 to +85 C, 500 cycles). Mechanical cycling (0 to 50 percent of the flexural strength, 100 cycles) has a similar effect, except that acoustic events are reduced only at strains less than the maximum strain applied during flexural fatigue.

  4. Effectiveness of a tailored neck training program on neck strength, movement, and fatigue in under-19 male rugby players: a randomized controlled pilot study.

    Science.gov (United States)

    Barrett, Matthew D; McLoughlin, Terence F; Gallagher, Kieran R; Gatherer, Don; Parratt, Michael Tr; Perera, Jonathan R; Briggs, Tim Wr

    2015-01-01

    To investigate the effect of a tailored neck muscle conditioning program on neck muscle strength, neck muscle fatigue, and range of neck movement in 16-18-year-old male rugby players. Thirty-four male rugby players were divided into forward and back playing positions and randomized within these groups. Seventeen players were randomly assigned to each group. The test group was given a tailored 6-week exercise regime based on their baseline measurements to be performed three times a week in addition to their normal training and playing. The control group trained and played as normal. The outcome measures used were cervical spine range of movement, neck strength, and neck muscle fatigability. There were no clinically relevant statistically significant differences between the two groups. Trends identified between the two groups suggest that a tailored neck exercise program increases neck strength, particularly neck extension, and increases resistance to fatigue, as well as influencing right- and left-sided neck muscle balance. A reduction in range of movement was also demonstrated in the test group. There was a great deal of variability in range of movement and strength within this age group. No previously undiagnosed neck conditions were detected, and there were no adverse events reported. This study has shown that neck strength, range of movement, and susceptibility of the neck muscles to fatigue can be influenced using a focused neck training regime. It forms an important basis for a larger, multicenter study to ensure the neck is given due attention in rugby training and receives the same focus of conditioning as other parts of the body.

  5. Benefits of thread rolling process to the stress corrosion cracking and fatigue resistance of high strength fasteners

    Energy Technology Data Exchange (ETDEWEB)

    Kephart, A.R.; Hayden, S.Z.

    1993-05-01

    Stress corrosion cracking (SCC) behavior of cut (machined) vice thread rolled Alloy X-750 and Alloy 625 fasteners in a simulated high temperature primary water environment has been evaluated. SCC testing at 360 and 338C included 157 small and 40 large 60{degree} Vee thread studs. Thread rolled fasteners had improved resistance relative to cut fasteners. Tests of fatigue resistance in air at room temperature and both air and primary water at 315C were conducted on smaller studs with both cut and rolled threads. Results showed rolled threads can have significantly improved fatigue lives over those of cut threads in both air and primary water. Fasteners produced by two different thread rolling methods, in-feed (radial) and through-feed (axial), revealed similar SCC initiation test results. Testing of thread rolled fasteners revealed no significant SCC or fatigue growth of rolling induced thread crest laps typical of the thread rolling process. While fatigue resistance differed between the two rolled thread supplier`s studs, neither of the suppliers studs showed SCC initiation at exposure times beyond that of cut threads with SCC. In contrast to rolling at room temperature, warm rolled (427C) threads showed no improvement over cut threads in terms of fatigue resistance. The observed improved SCC and fatigue performance of rolled threads is postulated to be due to interactive factors, including beneficial residual stresses in critically stressed thread root region, reduction of plastic strains during loading and formation of favorable microstructure.

  6. ON FATIGUE CRACK PATH DEVIATION AT ELEVATED TEMPERATURE IN ELECTRON BEAM REPAIRED WELDMENTS OF TURBINE DISK

    Institute of Scientific and Technical Information of China (English)

    H.Q. Zhang; H.Y. Zhao; Y.H. Zhang; L.H. Li; X.A. Zhang

    2004-01-01

    Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, HAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and hcat-affected-zone (HAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone.

  7. 高强度钻杆钢疲劳性能试验研究∗%Study on fatigue property of High-strength Drill Pipe Steels

    Institute of Scientific and Technical Information of China (English)

    刘飞; 邓天安; 周仕明; 曾德智

    2016-01-01

    In order to solve fatigue fracture of drilling tools, fatigue property of 165ksi and S135 drill pipe steels is studied by rotary bending fatigue test�Based on Basquin model, fatigue limit distribution of middle⁃long life zone is proposed for two high⁃strength drill pipe steels�Research results show that, under confidence level of 95% and reliability of 50%, 90% and 99%, the fatigue limit of 165ksi drill pipe steel is respectively 662�54, 645�92 and 632�28 MPa and that of S135 drill pipe steel is respectively 595�83, 541�87 and 529�73 MPa�In ad⁃dition, a complete stress⁃fatigue life S⁃N curve is obtained for two high⁃strength drill pipe steels�The results can provide basic data and theoretical basis for drill pipe material selection and reliability design of deep wells and ex⁃tradeep wells.%针对钻井过程中钻具疲劳断裂问题,采用旋转弯曲疲劳试验研究了S135和165ksi 2种高强度钻杆钢的疲劳性能。基于Basquin模型得出2种高强度钻杆钢中长寿命区的疲劳极限分布。研究结果表明,取95%的置信水平,则50%、90%和99%可靠度下的165ksi钻杆钢的疲劳极限分别为662�54、645�92和632�28 MPa, S135钻杆钢的疲劳极限分别为595�83、541�87和529�73 MPa,并得出了2种高强度钻杆钢完整的应力⁃疲劳寿命S⁃N曲线。试验结果可以为深井、超深井钻杆选材及可靠性设计提供基础数据和理论依据。

  8. Experimental examination of fatigue life of welded joint with stress concentration

    Directory of Open Access Journals (Sweden)

    Miodrag Arsic

    2016-03-01

    Full Text Available This paper presents results of experimental examinations of stress concentration influence to fatigue life of butt welded joints with K-groove, produced from the most frequently used structural steel S355J2+N. One group of experiments comprised examinations carried out on the K-groove specimens with stress concentrators of edged notch type. Specimens with short cracks (limited length of initial crack, defined on the basis of the experience from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and aimed to determine fatigue strengths for different lengths of initial crack and Relationship between fatigue strength and crack length. Other group of experiments comprised examinations of specimens with edge notch, prepared in accordance with ASTM E 399 for three points bending, in order to establish regularity between crack growth and range of exerted stress intensity factor aimed to determine resistance of welded joint to initial crack growth, namely fatigue threshold (ΔKth.

  9. Notch Inhibitors for Cancer Treatment

    OpenAIRE

    Espinoza, Ingrid; Miele, Lucio

    2013-01-01

    Notch signaling is an evolutionarily conserved cell signaling pathway involved in cell fate during development, stem cell renewal and differentiation in postnatal tissues. Roles for Notch in carcinogenesis, in the biology of cancer stem cells and tumor angiogenesis have been reported. These features identify Notch as a potential therapeutic target in oncology. Based on the molecular structure of Notch receptor, Notch ligands and Notch activators, a set of Notch pathway inhibitors have been de...

  10. Fatigue growth of a surface crack in a V-shaped notched round bar under cyclic tension%反复张力下V形切口圆条的表面裂纹的疲劳扩展

    Institute of Scientific and Technical Information of China (English)

    Devi CHANDRA; Judha PURBOLAKSONO; Yusoff NUKMAN; Haw-ling LIEW; Singh RAMESH; Mohsen-abdel HASSAN

    2014-01-01

    This paper presents modeling results for fatigue crack growths of a semi-elliptical surface crack in a V-shaped notched round bar under uniform cyclic tension. All the analyses were carried out by using a software package featuring the boundary element method. The J-integral technique was used to compute the stress intensity factors (SIFs), and the NASGRO crack growth rate was chosen to simulate the fatigue crack growths. Mechanical and fracture properties of AZ-6A-T5 magnesium alloy were used for our analysis. Crack shape evolutions for different crack aspect ratios and the corresponding SIFs may be correlated to study the behavior of crack growths. An unstable crack growth was observed when the evolving crack aspect ratio was between 0.6 and 0.7. Careful consideration should be taken if the cylinder contains a defect which has a straight shape on the crack front or a smaller crack aspect ratio.%研究目的:在相同的反复张力下,研究V形切口圆条表面裂纹的疲劳扩展规律。  研究方法:1.构建V形切口圆条模型(图1),基于线性二次元将模型表面离散成一个个网格点(图2);2.以AZ-6A-T5镁合金为例,利用J积分计算应力强度因数,利用NASGRO裂纹增长率模拟裂纹的疲劳扩展;3.通过研究不同的裂纹纵横比和对应的应力强度因数之间的相关性来研究裂纹的扩展。  重要结论:1.在裂纹扩展时裂纹纵横比的初始值对断裂形状的发展有重要影响;2.裂纹纵横比对疲劳负荷寿命的作用比缺口半径更加明显;3.当裂纹前缘演变成一条直线形时可观察到不稳定的裂纹扩展;4.裂纹深度一定时,断裂纵横比越小,疲劳负荷寿命越短;5.当裂纹纵横比为0.6-0.7时,出现了不稳定的裂纹扩展。

  11. Influence of non-metallic second phases on fatigue behaviour of high strength steel components; Efecto de segundas fases no metalicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.; Elvira, R.; Garcia de Andoin, A.; Pizarro, R.; Bertrand, C.

    2005-07-01

    To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of 100Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks.Two heats proceedings from different steelmaking routes were taken for the tests. The material were forged into ring shape components which were fatigue tested under compression-compression loads. Failures were analysed by SFEM (Scanning field Emission Microscopy), proving that most of failures at high loads were originated by manganese sulphides of small size (10-70 micros), while less than 40% of all fatigue cracks due to inclusions were caused by titanium carbonitrides and hard oxides. It has been demonstrated that once number and size of hard inclusions have been reduced, the hazardous effect of oxides and carbonitrides on the fatigue life decreases also. However, softer inclusions as manganese sulphides, currently considered as less hazardous, play a more relevant role as direct cause of fatigue failure and they should be taken into account in a deeper way in order to balance both machinability and fatigue life requirements in high strength steel components. (Author) 11 refs.

  12. Androgen signaling in myocytes contributes to the maintenance of muscle mass and fiber type regulation but not to muscle strength or fatigue.

    Science.gov (United States)

    Ophoff, Jill; Van Proeyen, Karen; Callewaert, Filip; De Gendt, Karel; De Bock, Katrien; Vanden Bosch, An; Verhoeven, Guido; Hespel, Peter; Vanderschueren, Dirk

    2009-08-01

    Muscle frailty is considered a major cause of disability in the elderly and chronically ill. However, the exact role of androgen receptor (AR) signaling in muscle remains unclear. Therefore, a postmitotic myocyte-specific AR knockout (mARKO) mouse model was created and investigated together with a mouse model with ubiquitous AR deletion. Muscles from mARKO mice displayed a marked reduction in AR protein (60-88%). Interestingly, body weights and lean body mass were lower in mARKO vs. control mice (-8%). The weight of the highly androgen-sensitive musculus levator ani was significantly reduced (-46%), whereas the weights of other peripheral skeletal muscles were not or only slightly reduced. mARKO mice had lower intra-abdominal fat but did not demonstrate a cortical or trabecular bone phenotype, indicating that selective ablation of the AR in myocytes affected male body composition but not skeletal homeostasis. Furthermore, muscle contractile performance in mARKO mice did not differ from their controls. Myocyte-specific AR ablation resulted in a conversion of fast toward slow fibers, without affecting muscle strength or fatigue. Similar results were obtained in ubiquitous AR deletion, showing lower body weight, whereas some but not all muscle weights were reduced. The percent slow fibers was increased, but no changes in muscle strength or fatigue could be detected. Together, our findings show that myocyte AR signaling contributes to the maintenance of muscle mass and fiber type regulation but not to muscle strength or fatigue. The levator ani weight remains the most sensitive and specific marker of AR-mediated anabolic action on muscle.

  13. Fatigue acceptance test limit criterion for larger diameter rolled thread fasteners

    Energy Technology Data Exchange (ETDEWEB)

    Kephart, A.R.

    1997-05-01

    This document describes a fatigue lifetime acceptance test criterion by which studs having rolled threads, larger than 1.0 inches in diameter, can be assured to meet minimum quality attributes associated with a controlled rolling process. This criterion is derived from a stress dependent, room temperature air fatigue database for test studs having a 0.625 inch diameter threads of Alloys X-750 HTH and direct aged 625. Anticipated fatigue lives of larger threads are based on thread root elastic stress concentration factors which increase with increasing thread diameters. Over the thread size range of interest, a 30% increase in notch stress is equivalent to a factor of five (5X) reduction in fatigue life. The resulting diameter dependent fatigue acceptance criterion is normalized to the aerospace rolled thread acceptance standards for a 1.0 inch diameter, 0.125 inch pitch, Unified National thread with a controlled Root radius (UNR). Testing was conducted at a stress of 50% of the minimum specified material ultimate strength, 80 Ksi, and at a stress ratio (R) of 0.10. Limited test data for fastener diameters of 1.00 to 2.25 inches are compared to the acceptance criterion. Sensitivity of fatigue life of threads to test nut geometry variables was also shown to be dependent on notch stress conditions. Bearing surface concavity of the compression nuts and thread flank contact mismatch conditions can significantly affect the fastener fatigue life. Without improved controls these conditions could potentially provide misleading acceptance data. Alternate test nut geometry features are described and implemented in the rolled thread stud specification, MIL-DTL-24789(SH), to mitigate the potential effects on fatigue acceptance data.

  14. Low-Cycle Fatigue Life and Fatigue Crack Propagation of Sintered Ag Nanoparticles

    Science.gov (United States)

    Shioda, Ryutaro; Kariya, Yoshiharu; Mizumura, Noritsuka; Sasaki, Koji

    2017-02-01

    The low-cycle fatigue life and fatigue crack propagation behavior of sintered silver nanoparticles were investigated using miniature specimens sintered at two different temperatures. The fatigue crack initiation life and fatigue crack propagation rate of sintered Ag nanoparticles were extremely sensitive to changes in the range of inelastic energy density and the cyclic J integral, exhibiting brittle characteristics, in contrast to tin-based lead-free solder alloys. With increasing sintering temperature, the fatigue crack propagation rate decreased. On the other hand, the effect of sintering temperature on the fatigue crack initiation life differed depending on the use of either a smooth specimen (low-cycle fatigue test) or notched specimen (fatigue crack propagation test). For the notched specimens, the probability of grain boundaries around the notch decreased due to increased sintering temperature. Therefore, the fatigue crack initiation life was increased with an increase in sintering temperature in the fatigue crack propagation test. In the smooth specimen, however, the fatigue life decreased with an increase in sintering temperature, as the elastic modulus of the specimen increased with increasing sintering temperature. In the low-cycle fatigue test, the specimen sintered with high internal stress started to develop crack initiation early, causing a decrease in the crack initiation life.

  15. Designing aluminium friction stir welded joints against multiaxial fatigue

    Directory of Open Access Journals (Sweden)

    L. Susmel

    2016-07-01

    Full Text Available The present paper investigates the accuracy of the Modified Wöhler Curve Method (MWCM in estimating multiaxial fatigue strength of aluminium friction stir (FS welded joints. Having developed a bespoke joining technology, circumferentially FS welded tubular specimens of Al 6082-T6 were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out using the experimental results have demonstrated that the MWCM applied in terms of nominal stresses, notch stresses, and also the Point Method is accurate in predicting the fatigue lifetime of the tested FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands.

  16. 船舶上层建筑端部实板厚疲劳试验研究%Real-thickness fatigue strength test of the ship superstructure end

    Institute of Scientific and Technical Information of China (English)

    任慧龙; 崔兵兵; 冯国庆; 成兵

    2015-01-01

    In order to research the fatigue characteristics of the ship superstructure end, the real⁃thickness four⁃point bending model tests were designed and actualized. The number of cycles to failure in the fatigue tests were ob⁃tained under different stress levels. The mid⁃value S-N curve and P-S-N curve were drawn through the fixed⁃slope maximum likehood method. The fatigue strength of the position was caculated and compared by testing P-S-N curve and the E curve of CCS codes. The research showed that the S-N curve obtained from fatigue tests can offer a reference for the design and analysis of ships in practice.%为研究船体上层建筑端部的疲劳特性,设计和实施了实板厚四点弯曲疲劳模型试验。获得疲劳试验中不同应力水平下的疲劳失效循环次数,并采用定斜率极大似然法拟合应力水平-疲劳失效循环次数得到中值S-N曲线和P-S-N曲线。分别采用试验P-S-N曲线和CCS规范E曲线计算和比较研究该部位的疲劳强度。结果表明,试验得到的S-N曲线可为实船设计和分析提供参考。

  17. Waveform frequency notching

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W.; Andrews, John

    2017-05-09

    The various technologies presented herein relate to incorporating one or more notches into a radar spectrum, whereby the notches relate to one or more frequencies for which no radar transmission is to occur. An instantaneous frequency is monitored and if the frequency is determined to be of a restricted frequency, then a radar signal can be modified. Modification can include replacing the signal with a signal having a different instantaneous amplitude, a different instantaneous phase, etc. The modification can occur in a WFS prior to a DAC, as well as prior to a sin ROM component and/or a cos ROM component. Further, the notch can be dithered to enable formation of a deep notch. The notch can also undergo signal transitioning to enable formation of a deep notch. The restricted frequencies can be stored in a LUT against which an instantaneous frequency can be compared.

  18. Effectiveness of a tailored neck training program on neck strength, movement, and fatigue in under-19 male rugby players: a randomized controlled pilot study

    Directory of Open Access Journals (Sweden)

    Barrett MD

    2015-05-01

    Full Text Available Matthew D Barrett,1 Terence F McLoughlin,2 Kieran R Gallagher,1 Don Gatherer,3 Michael TR Parratt,1 Jonathan R Perera,1 Tim WR Briggs1 1Royal National Orthopaedic Hospital, Stanmore, Middlesex, United Kingdom; 2Royal Liverpool University Hospital, Liverpool, Mersey Deanery, United Kingdom; 3The Gatherer Partnership, Aylesbury, United Kingdom Purpose: To investigate the effect of a tailored neck muscle conditioning program on neck muscle strength, neck muscle fatigue, and range of neck movement in 16–18-year-old male rugby players. Materials and methods: Thirty-four male rugby players were divided into forward and back playing positions and randomized within these groups. Seventeen players were randomly assigned to each group. The test group was given a tailored 6-week exercise regime based on their baseline measurements to be performed three times a week in addition to their normal training and playing. The control group trained and played as normal. The outcome measures used were cervical spine range of movement, neck strength, and neck muscle fatigability. Results: There were no clinically relevant statistically significant differences between the two groups. Trends identified between the two groups suggest that a tailored neck exercise program increases neck strength, particularly neck extension, and increases resistance to fatigue, as well as influencing right- and left-sided neck muscle balance. A reduction in range of movement was also demonstrated in the test group. There was a great deal of variability in range of movement and strength within this age group. No previously undiagnosed neck conditions were detected, and there were no adverse events reported. Conclusion: This study has shown that neck strength, range of movement, and susceptibility of the neck muscles to fatigue can be influenced using a focused neck training regime. It forms an important basis for a larger, multicenter study to ensure the neck is given due attention in

  19. Probability density evolution method of fatigue strength-life relationship%疲劳强度-寿命关系的概率密度演化方法

    Institute of Scientific and Technical Information of China (English)

    徐亚洲; 白国良

    2013-01-01

    Taking degradation of fatigue strength with increase in loading cycles into account, the joint probability density evolution equation of fatigue strength and random factors was derived using Euler description. A probability density S-N (p-S-N) surface was obtained with a numerical method, it was used to calculate the p-S-N curve with a given survivability. The analysis based on experimental fatigue data indicated that p-S-N curves with 95% survivability predicted by p-S-N, Monte Carlo simulation and S-N relation ship having parameters with a given fractile agree well; p-S-N provides a complete probability description of S-N relationship, independent of a probability distribution assumption.%基于疲劳强度随加载循环次数增加不断劣化的物理事实,采用Euler描述推导出疲劳强度与随机参数联合概率密度函数满足的演化方程.采用数值求解方法,给出疲劳强度-寿命概率密度曲面(probability density S-N),并可据此计算给定存活率的P-S-N曲线.基于疲劳试验结果的算例分析表明,疲劳强度-寿命概率密度曲面、MonteCarlo模拟及具有给定分位数参数的S-N关系三者计算的p-S-N曲线吻合良好.疲劳强度-寿命概率密度演化方法可不依赖分布假定给出S-N关系的完备概率描述.

  20. Complex-shaped hardened parts fatigue limit prediction according to the witness sample study results

    Science.gov (United States)

    Surgutanova, Yu N.; Mikushev, N. N.; Surgutanov, N. A.; Kiselev, P. E.; Shlyapnikov, P. A.; Meshcheryakova, A. A.

    2016-11-01

    The aim of this study is to investigate the possibility of assessment of the effect of preparatory surface plastic deformation by hydraulic shot blasting on the fatigue strength of cylindrical parts of different diameters (10-40 mm) of D16T alloy with circular notches of semicircular section, based on measurements of residual stress (initial deformations) of a witness sample. The residual stresses of smooth parts were used to calculate the residual stresses of parts with stress raisers. These were used to predict the increment of these parts fatigue limit caused by hardening hydraulic shot blasting. It was found that the highest compressive residual stresses in the smooth parts obtained through calculations differ from the observed values not more than by 7%, and in notched parts by 8%. Using the criterion of mean integral residual stresses, we calculate the increments of the fatigue limit of parts due to superficial hardening. The discrepancy between the experimental and calculated increment values of the fatigue limit of hardened parts with raisers does not exceed 17%.

  1. Notch signaling: its roles and therapeutic potential in hematological malignancies.

    Science.gov (United States)

    Gu, Yisu; Masiero, Massimo; Banham, Alison H

    2016-05-17

    Notch is a highly conserved signaling system that allows neighboring cells to communicate, thereby controlling their differentiation, proliferation and apoptosis, with the outcome of its activation being highly dependent on signal strength and cell type. As such, there is growing evidence that disturbances in physiological Notch signaling contribute to cancer development and growth through various mechanisms. Notch was first reported to contribute to tumorigenesis in the early 90s, through identification of the involvement of the Notch1 gene in the chromosomal translocation t(7;9)(q34;q34.3), found in a small subset of T-cell acute lymphoblastic leukemia. Since then, Notch mutations and aberrant Notch signaling have been reported in numerous other precursor and mature hematological malignancies, of both myeloid and lymphoid origin, as well as many epithelial tumor types. Of note, Notch has been reported to have both oncogenic and tumor suppressor roles, dependent on the cancer cell type. In this review, we will first give a general description of the Notch signaling pathway, and its physiologic role in hematopoiesis. Next, we will review the role of aberrant Notch signaling in several hematological malignancies. Finally, we will discuss current and potential future therapeutic approaches targeting this pathway.

  2. Fatigue Reliability under Random Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    , with the application of random loads, the initial homogeneous distribution of strength changes to a two-component distribution, reflecting the two-stage fatigue damage. In the crack initiation stage, the strength increases initially and then decreases, while an abrupt decrease of strength is seen in the crack...... propagation stage. The consequences of this behaviour on the fatigue reliability are discussed....

  3. Deer Antler Extract Improves Fatigue Effect through Altering the Expression of Genes Related to Muscle Strength in Skeletal Muscle of Mice

    Directory of Open Access Journals (Sweden)

    Jaw-Chyun Chen

    2014-01-01

    Full Text Available Deer antler is a well-known traditional Chinese medicine used in Asian countries for the tonic and the improvement of aging symptoms. The present study was designed to investigate the antifatigue effect and mechanism of Formosan sambar deer tip antler extract (FSDTAE. The swimming times to exhaustion of mice administered FSDTAE (8.2 mg/day for 28 days were apparently longer than those of the vehicle-treated mice in forced swim test. However, the indicators of fatigue, such as the reduction in glucose level and the increases in blood urea nitrogen and lactic acid levels, were not significantly inhibited by FSDTAE. Therefore, microarray analysis was further used to examine the anti-fatigue mechanism of FSDTAE. We selected genes with fold changes >2 or <−2 in skeletal muscle for pathway analysis. FSDTAE-affected genes were involved in 9 different signaling pathways, such as GnRH signaling pathway and insulin signaling pathway. All of the significantly expressed genes were classified into 8 different categories by their functions. The most enriched category was muscular system, and 6 upregulated genes, such as troponin I, troponin T1, cysteine and glycine-rich protein 2, myosin heavy polypeptide 7, tropomyosin 2, and myomesin family member 3, were responsible for the development and contraction of muscle. Real-time PCR analysis indicated that FSDTAE increased troponins mRNA expression in skeletal muscle. In conclusion, our findings suggested that FSDTAE might increase the muscle strength through the upregulation of genes responsible for muscle contraction and consequently exhibited the anti-fatigue effect in mice.

  4. Strength and fatigue testing of large size wind turbines rotors. Vol. II: Full size natural vibration and static strength test, a reference case

    Energy Technology Data Exchange (ETDEWEB)

    Arias, F.; Soria, E.

    1996-12-01

    This report shows the methods and procedures selected to define a strength test for large size wind turbine, anyway in particular it application on a 500 kW blade and it results obtained in the test carried out in july of 1995 in Asinel`s test plant (Madrid). Henceforth, this project is designed in an abbreviate form whit the acronym SFAT. (Author)

  5. In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

    OpenAIRE

    2015-01-01

    Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72...

  6. 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...... failure explanation under fatigue and static load conditions is observed. In the present study 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 between stiffness reduction...

  7. STUDY ON FATIGUE SHORT CRACK GROWTH LAW AND FATIGUE LIFE FOR MEDIUM CARBON STEELS

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels-35CrMo and 42CrMo are investigated under the different stress ratios R=0.1, 0.3) and three-point bending condition. The relationships between the maximum stress range at the notch root Δσmax and the number of cycles before fatigue crack initiation Ni are determined. The threshold stresses of fatigue crack initiation (Δσmax)th are got, and the smallcrack growth laws are obtained for these steels. An effective and convenient method is proposed for predicting the fatigue life of the notch specimens.

  8. The influence of fatigue loading on the quality of the cement layer and retention strength of carbon fiber post-resin composite core restorations.

    Science.gov (United States)

    Bolhuis, Peter; de Gee, Anton; Feilzer, Albert

    2005-01-01

    Clinical studies have shown that endodontically treated teeth restored with short posts or deficient ferrules show a high failure risk. This study. evaluated the influence of fatigue loading on the quality of the cement layer between prefabricated quartz coated carbon fiber posts with restricted length and the root canal wall in maxillary pre-molars. Two adhesive resin composite cements, chemical-cured Panavia 21 (Group 1) and dual-cured RelyX-ARC (Group 2), and one resin-modified glass-ionomer cement, chemical-cured RelyX (Group 3), delta were selected for this study. Post- and-core restorations were made on single-rooted human maxillary premolars from which the coronal sections were removed at the level of the proximal cemento-enamel junction (CEJ). Following endodontic treatment, a post-and-core restoration with 6-mm post length was prepared for each tooth. The posts were directly cemented into the root canal and, after applying an adhesive (Clearfil Photo Bond), they were built up with a core build-up composite (Clearfil Photo Core). For each group (n=8), half of the specimens were exposed to fatigue loading (10(6) load cycles) almost perpendicular to the axial axis (85 degrees), while the other half were used as the control. Three parallel, transverse root sections, 1.5-mm thick, were cut from each specimen at the apical, medial and coronal location. These sections were examined by Scanning Electron Microscopy (SEM) to evaluate the integrity of the cement layer, while the retention strength of the cemented post sections was determined with the push-out test. The multivariate results of MANOVA showed that the condition main effect (fatigue or control) was not significant (p=0.059); the two other main effects, type of cement and section location, were significant (p=0.001 and p=0.008). For both the push-out strength and SEM evaluation of the cement layer integrity, the results significantly improved from RelyX to RelyX-ARC to Panavia 21 and also from apical to

  9. 基于弹性模量的再生混凝土疲劳强度分析%On Fatigue Strength of Recycled Aggregate Concrete Based on Its Elastic Modulus

    Institute of Scientific and Technical Information of China (English)

    李宏; 肖建庄

    2012-01-01

    通过试验与分析,建立了再生混凝土弹性模量与其疲劳强度的回归公式,结果表明:由该回归公式计算出的再生混凝土受压疲劳强度与试验结果接近,可用来预测再生混凝土的受压疲劳强度,并指导工程实践;初步验证了GB 50010-2002《混凝土结构设计规范》中普通混凝土受压疲劳强度的取值方法对再生混凝土同样适用.%Based on the experiments and analysis, the relationship between the elastic modulus and the fatigue strength of recycled aggregate concrete(RAC) was established. The compressive fatigue strength calculated according to the formula suggested by this investigation is close to the experimental results, a reliable prediction for the compressive fatigue strength of RAC can be used to guide the engineering practice. And it is confirmed from this study that the method in code for GB 50010-2002 (Design of Concrete Structures> is suitable for the calculation of the compressive fatigue strength of RAC.

  10. Regulation of Notch signaling during T- and B-cell development by O-fucose glycans.

    Science.gov (United States)

    Stanley, Pamela; Guidos, Cynthia J

    2009-07-01

    Notch signaling is required for the development of all T cells and marginal zone (MZ) B cells. Specific roles in T- and B-cell differentiation have been identified for different Notch receptors, the canonical Delta-like (Dll) and Jagged (Jag) Notch ligands, and downstream effectors of Notch signaling. Notch receptors and ligands are post-translationally modified by the addition of glycans to extracellular domain epidermal growth factor-like (EGF) repeats. The O-fucose glycans of Notch cell-autonomously modulate Notch-ligand interactions and the strength of Notch signaling. These glycans are initiated by protein O-fucosyltransferase 1 (Pofut1), and elongated by the transfer of N-acetylglucosamine (GlcNAc) to the fucose by beta1,3GlcNAc-transferases termed lunatic, manic, or radical fringe. This review discusses T- and B-cell development from progenitors deficient in O-fucose glycans. The combined data show that Lfng and Mfng regulate T-cell development by enhancing the interactions of Notch1 in T-cell progenitors with Dll4 on thymic epithelial cells. In the spleen, Lfng and Mfng cooperate to modify Notch2 in MZ B progenitors, enhancing their interaction with Dll1 on endothelial cells and regulating MZ B-cell production. Removal of O-fucose affects Notch signaling in myelopoiesis and lymphopoiesis, and the O-fucose glycan in the Notch1 ligand-binding domain is required for optimal T-cell development.

  11. A mathematical approach regarding a better geometry of the root fillet of symmetric and asymmetric gears with the main scope of increasing the fatigue strength of gear teeth and avoiding the occurrence of cracks

    Science.gov (United States)

    Cazan, S.; Plesu, G.

    2016-08-01

    The main topic of the present paper consists of two main ideas: on one side, there is presented a mathematical approach on fatigue strength of a gear tooth and, on the other side, there is applied this mathematical approach on a particular case regarding a better fillet geometry of symmetric and asymmetric gears. In this mathematical approach, there is illustrated the planar curves theory and their planar contact. Then, there will be presented some theory regarding the gear failure and the appearance of cracks that generates tooth base fatigue. In the end, there will be presented some graphical results using Matlab programming language.

  12. Experimental Study of Gear Bending Fatigue Strength under Random Load with Gaussian Normal Distribution%服从正态分布随机载荷作用下齿轮弯曲疲劳试验研究

    Institute of Scientific and Technical Information of China (English)

    胡建军; 许洪斌; 祖世华; 高孝旺

    2013-01-01

    For the bending fatigue under the random load conditions with normal distribution,an equivalent load was analyzed and limiting value of gear bending fatigue strength was computed based on equivalent fatigue damage.The effect of load spectrum distributed parameter on equivalent load was analyzed,and load spectrum was compiled for luffing amplitude fatigue experiments.Then experiments of gear bending fatigue strength were achieved under random load according to normal distribution on MTS electro-hydraulic servo material fatigue tester,where the group method was used.The R-S-N curve was acquired in a concrete coefficient of variation.The tests prove that bending fatigue strength of gear under random load is less than that under constant load.By contrasting with the bending fatigue strength computed based on constant load,the theoretical results can agree with experimental ones.%根据齿轮传动过程中普遍承受的高斯分布载荷谱,编制了试验用随机变幅疲劳载荷谱,在MTS电液伺服疲劳试验机上利用成组试验方法完成了该随机载荷作用下全寿命齿轮弯曲疲劳试验,得到了特定变差系数高斯分布载荷谱下齿轮弯曲强度的R-S-N曲线.试验结果证明,随机变幅疲劳试验得出的轮齿疲劳寿命低于由疲劳载荷上限值取为载荷谱均值的恒载荷疲劳试验得出的疲劳寿命,因此,如果采用后者的试验结果去估算实际服役中的齿轮的弯曲疲劳寿命是非常危险的.对随机载荷下的齿轮设计的疲劳极限的理论值进行了预测,并与试验结果进行了比较.结果表明,理论分析结果与试验结果基本相符.

  13. 正交异性钢桥面板横隔板切口疲劳应力幅分析%ANALYSIS OF FATIGUE STRESS AMPLITUDE OF DIAPHRAGM NOTCH IN ORTHOTROPIC STEEL BRIDGE DECK

    Institute of Scientific and Technical Information of China (English)

    吉伯海; 田圆; 傅中秋; 徐汉江

    2014-01-01

    建立全桥模型和简化的钢桥面板局部节段模型,通过子模型法插值得到横隔板疲劳细节模型的边界条件,计算不同车轮横向分布对应的疲劳细节局部应力,研究横隔板参数变化对横隔板疲劳细节损伤的影响。结果表明:混合单元模型与钢桥面板简化模型对应的应力幅相差小于5.0%,采用钢桥面板简化模型分析横隔板疲劳细节受力简单合理。横隔板疲劳细节在车轮偏离中心位置150 mm时应力幅最大,随着车轮偏离中心位置距离的增大,应力幅下降明显。横隔板间距增大,横隔板疲劳细节应力幅上升,增加横隔板厚度可有效改善其疲劳受力性状。%The overall bridge FE model and simplified steel bridge deck FE model were built .The boundary conditions of diaphragm fatigue detail FEM were interpolated from the FEM of the steel bridge deck .The local stresses under variable wheels lateral distribution were calculated .Influence of diaphragm ’ s parameters on fatigue damage of diaphragm fatigue detail was investigated .The results showed that the differences of stress amplitude between the FEM of mixed-element and simplified steel bridge deck were less than 5.0%.It was simple and reliable to calculate the fatigue stress of diaphragm fatigue detail by using steel bridge deck model .Stress amplitude of diaphragm fatigue detail reached maximum when the off-center distance of wheel position was 150 mm, which decreased obviously with the increasing off-center distance of wheel position .Stress amplitude of diaphragm fatigue detail increased with the increasing interval of diaphragms .And increasing diaphragm ’ s thickness could improve the fatigue behavior of stress of steel bridge deck .

  14. Kick it up a notch: Notch signaling and kidney fibrosis

    OpenAIRE

    2014-01-01

    Notch is a critical regulator of kidney development, but the pathway is mostly silenced once kidney maturation is achieved. Recent reports demonstrated increased expression of Notch receptors and ligands both in acute and chronic kidney injury. In vivo studies indicated that Notch activation might contribute to regeneration after acute kidney injury; on the other hand, sustained Notch expression is causally associated with interstitial fibrosis and glomerulosclerosis. This review will summari...

  15. Are linear elastic material properties relevant predictors of the cyclic fatigue resistance of dental resin composites?

    Science.gov (United States)

    Belli, Renan; Petschelt, Anselm; Lohbauer, Ulrich

    2014-04-01

    The aim of this study was to measure the linear elastic material properties of direct dental resin composites and correlate them with their fatigue strength under cyclic loading. Bar specimens of twelve resin composites were produced according to ISO 4049 and tested for elastic modulus (Emod) in 3-point bending (n=10), flexural strength (FS) (n=15) and single-edge-notch-beam fracture toughness (FT) (n=15), both in 4-point bending. Using the same specimen geometry, the flexural fatigue strength (FFS) was determined using the staircase approach after 10(4) cycles at 0.5 Hz in 4-point bending (n=25). The observation of the fracture surface and fracture profiles was conducted using a scanning electron microscope in order to evaluate the respective fracture mechanisms according to the two different loading conditions. Materials were ranked differently according to the tested parameters. Only weak correlations were found between any of the initial properties and FFS or strength loss. The best correlation to FFS was found to be the Emod (r(2)=0.679), although only slightly. Crack path in both loading conditions was mainly interparticle, with the crack propagating mainly within the matrix phase for fatigued specimens and eventually through the filler/matrix interface for statically loaded specimens. Fracture of large particles or prepolymerized fillers was only observed in specimens of FS and FT. Initial properties were better associated with microstructural features, whereas the fatigue resistance showed to be more dependent on aspects relating to the matrix phase. Our results show that linear elastic properties such as elastic modulus, flexural strength and fracture toughness are not good descriptors of the fatigue resistance of dental resin composite under cyclic bending, and may therefore have limited clinical relevance. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Fatigue Strength of (Fe)-C-N Alloys After Precipitation Hardening%(Fe)-C-N合金经沉淀硬化后的疲劳强度

    Institute of Scientific and Technical Information of China (English)

    Aleksander Nakonieczny; Jan Tacikowski; Jerzy Michalski; Tomasz Babul

    2004-01-01

    为了寻求新的方法促进渗氮工艺在重型机械零件中的应用,渗氮层的硬化及通过对基体和心部进行进一步奥氏体化并快冷使其硬化的可能性引起了注意.本文给出了渗氮后的45钢(C-0.45%; Mn-0.65%)经沉淀硬化处理后的疲劳强度试验结果.试验结果表明经沉淀硬化后其近表层获得了不同的组织,可发现形态上与不同沉淀分散程度的贝氏体组织相似的纯马氏体区.渗氮后沉淀硬化有利于碳钢及其抗疲劳强度.本文还讨论了渗氮后沉淀硬化处理可替代渗碳或感应淬火.%In search for new solutions promoting expansion of nitriding application to heavy duty machine parts there has been drawn attention to a possibility of hardening of a nitrided layer, of hardening of its substrate and its core through further austenitizing connected with fast cooling. In the paper, there were given results of fatigue strength tests carried out on nitrided 45 carbon steel (C-0.45%; Mn-0.65%) after precipitation hardening. It was found that the near-surface zone obtained different structure after precipitation hardening. There could be found pure martensitic areas, morphologically similar to bainitic structure of various levels of precipitate dispersion. Research showed that nitriding followed by precipitation hardening beneficially affect carbon steel and fatigue strength. Discussed here nitriding process followed by precipitation hardening could create an alternative for carburising or induction hardening.

  17. 活性粉末混凝土疲劳后剩余抗压强度试验研究%Experimental study on residual compressive strength of RPC under fatigue loading

    Institute of Scientific and Technical Information of China (English)

    余自若; 安明喆; 郑帅泉

    2011-01-01

    In order to investigate the evolution law of residual compressive strength for reactive powder concrete ( RPC) under fatigue loading, the fatigue tests were carried out.24 cylinders were cast for testing and divided into 3 groups.By measuring the compressive strength of some RPC specimens, the relationship between initial compressive strength and resonance frequency was established firstly.On that basis, the constant amplitude and two-stage amplitude fatigue tests were carried and the residual compressive strength of RPC specimens were measured after fatigue.Experimental results show that the attenuation of post-fatigue residual compressive strength of RPC decreased with increase of recycle ratio.On the other hand, the attenuation rate increased with increase of recycle ratio.An fitting formula about the attenuation of post-fatigue residual compressive strength and recycle ratio was deduced.The calculated values which come from fitting formula are in good agreement with measured values.%为研究经受疲劳荷载作用后活性粉末混凝土(RPC)的剩余抗压强度变化规律,对3组共24个RPC圆柱体试件,进行疲劳试验研究.通过静载试验建立RPC抗压强度和谐振频率之间的关系,推算出各疲劳试件的初始抗压强度;在此基础上,对RPC试件进行轴压单级和两级疲劳加载试验,并实测试件在疲劳荷载作用一定次数后的剩余抗压强度.实测结果表明:RPC在单级疲劳后剩余抗压强度的衰减率随循环寿命比的增大而减小,而衰减速率则随着循环寿命比的增大而增大.根据实测值得到RPC单级和两级疲劳加载后剩余抗压强度衰减率与循环寿命比之间关系的拟合公式,计算结果与实测结果吻合良好.

  18. Notch Signaling in Pancreatic Development

    OpenAIRE

    2015-01-01

    The Notch signaling pathway plays a significant role in embryonic cell fate determination and adult tissue homeostasis. Various studies have demonstrated the deep involvement of Notch signaling in the development of the pancreas and the lateral inhibition of Notch signaling in pancreatic progenitor differentiation and maintenance. The targeted inactivation of the Notch pathway components promotes premature differentiation of the endocrine pancreas. However, there is still the contrary opinion...

  19. Stress concentration at notches

    CERN Document Server

    Savruk, Mykhaylo P

    2017-01-01

    This book compiles solutions of linear theory of elasticity problems for isotropic and anisotropic bodies with sharp and rounded notches. It contains an overview of established and recent achievements, and presents the authors’ original solutions in the field considered with extensive discussion. The volume demonstrates through numerous, useful examples the effectiveness of singular integral equations for obtaining exact solutions of boundary problems of the theory of elasticity for bodies with cracks and notches. Incorporating analytical and numerical solutions of the problems of stress concentrations in solid bodies with crack-like defects, this volume is ideal for scientists and PhD students dealing with the problems of theory of elasticity and fracture mechanics. Stands as a modern and extensive compendium of solutions to the problems of linear theory of elasticity of isotropic and anisotropic bodies with sharp and rounded notches; Adopts a highly reader-friendly layout of tables, charts, approximation ...

  20. Fatigue strength assessment of ship structures based on the crack propagation theory%基于裂纹扩展理论的船体结构疲劳评估

    Institute of Scientific and Technical Information of China (English)

    牛松; 任慧龙; 冯国庆

    2015-01-01

    Fatigue damage is one of main forms of ship structures destroyed. Every classification society and shipyard take fatigue assessment rules of ship structures as an instruction to assure fatigue strength of ship structures. Although these rules are based on the method of S-N curve, different fatigue lives of the same node are obtained with the help of different rules, because the disadvantages of S-N curve could not be avoided, such as neglect of initial objection of material. In this paper, fatigue strength assessment methods of ship structures are studied based on the facture propagation theory, and a detailed fatigue assessment method of ship structures is proposed, which is supposed to reference to predict fatigue life and preparation to perfect fatigue strength assessment of ship structures.%疲劳破坏是船舶结构的主要破坏形式之一。为了保证船舶结构有足够的疲劳强度,各国船级社、船厂等均建立了船舶结构疲劳强度校核规范作为船舶疲劳评估的指导性文件,尽管这些规范均是建立在S-N曲线方法基础上的,但由于S-N曲线方法存在自身无法克服的缺陷(如忽略材料的初始缺陷等),对同一节点进行计算得到的疲劳寿命大相径庭。该文作者在基于裂纹扩展理论的基础之上,给出了一套详细的船体结构疲劳评估方法,并应用此方法对大型船舶结构典型节点的疲劳寿命进行评估,以期能为完善船舶结构疲劳寿命的评估提供参考。

  1. Comparative Notched Box Plots.

    Science.gov (United States)

    1983-06-01

    provides a 95.1% confidence interval. See Noether (1976, Table E). Furthermore, this notch is not necessarily sym- metric about the sample median as in...distribution of the sign test). ( Noether 1976, Chapter 12; Lehmann 1975, Chapter 4; Hollander and Wolfe 1972, Chapter 3.) Thus, exact rather than approximate...binomial with parameters n and .5, i.e., b(n, .5). We will refer to dx as the notch depth. Noether (1978, Table E) provides the d. values; otherwise, they

  2. Exploring the effects of SiC reinforcement incorporation on mechanical properties of friction stir welded 7075 aluminum alloy: Fatigue life, impact energy, tensile strength

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Mohsen, E-mail: Mohsen.bahrami@aut.ac.ir [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Helmi, Nader [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Dehghani, Kamran [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Centre of Excellence in Smart Structures and Dynamical Systems (Iran, Islamic Republic of); Givi, Mohammad Kazem Besharati [Department of Mechanical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2014-02-10

    In the current research, the role of SiC nano-particles in improving the mechanical properties of friction stir welded (FSWed) 7075 aluminum alloy is investigated. To this end, friction stir welding (FSW) was conducted at 1250 rpm and 40 mm/min. The experiment carried out with and without incorporating SiC nano-particles along the joint line. Cross-sectional microstructures of the joints were characterized employing optical and scanning electron microscopy (SEM). Results achieved through X-ray diffraction (XRD) confirmed the presence of SiC powders. Moreover, it was discovered that the volume fraction of the reinforcement particles was 20%. Along with an excellent bonding between SiC nano-particles and aluminum matrix, SEM photograph demonstrated a good dispersion of SiC reinforcements. Atomic force microscopy (AFM) results were also in tight agreement with the recent SEM microstructure. Thanks to the presence of SiC nano-particles, tensile strength, percent elongation, fatigue life, and toughness of the joint improved tremendously. The fracture morphologies were in good agreement with corresponding ductility results.

  3. Effect of formoterol, a long-acting β2-adrenergic agonist, on muscle strength and power output, metabolism, and fatigue during maximal sprinting in men.

    Science.gov (United States)

    Kalsen, Anders; Hostrup, Morten; Backer, Vibeke; Bangsbo, Jens

    2016-06-01

    The aim was to investigate the effect of the long-acting β2-adrenergic agonist formoterol on muscle strength and power output, muscle metabolism, and phosphorylation of CaMKII Thr(287) and FXYD1 during maximal sprinting. In a double-blind crossover study, 13 males [V̇o2 max: 45.0 ± 0.2 (means ± SE) ml·min(-1)·kg(-1)] performed a 30-s cycle ergometer sprint after inhalation of either 54 μg of formoterol (FOR) or placebo (PLA). Before and after the sprint, muscle biopsies were collected from vastus lateralis and maximal voluntary contraction (MVC), and contractile properties of quadriceps were measured. Oxygen uptake was measured during the sprint. During the sprint, peak power, mean power, and end power were 4.6 ± 0.8, 3.9 ± 1.1, and 9.5 ± 3.2% higher (P power output during maximal sprinting is associated with increased rates of glycogenolysis and glycolysis that may counteract development of fatigue. Copyright © 2016 the American Physiological Society.

  4. An experimental study on the effects of compressive stress on the fatigue crack growth of low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D.P.; Hoppe, R.G. [Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.; Hechmer, J.L. [Babcock and Wilcox Co., Barberton, OH (United States); James, B.A. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgy

    1993-12-01

    A series of fatigue crack growth rate tests was conducted in order to study effects of negative stress ratio on fatigue crack growth rate of low-alloy steel in air. Four-point bend specimens were used to simulate linear stress distributions typical of pressure vessel applications. This type of testing adds to knowledge on negative stress ratio effects for low-alloy steels obtained in the past from uniform tension-compression tests. Applied bending stress range was varied over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. Crack geometries were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. Results are presented in terms of the stress intensity factor ratio R = K{sub MIN}/K{sub MAX}. The negative R-ratio test results were correlated to an equation of the form da/dN = C[{Delta}K/(A-R)]{sup n}, where A, C, and n are curve fitting parameters. It was found that effects of negative R-ratio on fatigue crack growth rates for even the high stress range tests could be bounded by correlating the above equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.

  5. Effect of shot peening and grain refinement on the fatigue life and strength of commercially pure Al and two of its alloys: Al-2024-T3 and Al-7075-T6

    Science.gov (United States)

    Qandil, A.; Zaid, Adnan I. O.

    2016-08-01

    Aluminum and its alloys are widely used materials in automobile, aircraft and space craft industries due to their high strength- to- weight ratio and corrosion resistance beside their other useful properties. They are the second materials in use after steel alloys. Most of the failures in parts of aircrafts and space vehicles are mainly caused by fatigue and stress corrosion cracking. In this paper, the effect of shot peening on the fatigue life of commercially pure aluminumand two of its alloys namely:Al-2024 and Al-7075-T6 is presented and discussed. Furthermore, the effect of addition of vanadium to Al and Al grain refined by Ti and Ti+Bon Its fatigue life and strengthis also presented and discussed using scanning electron microscope, SEM. It was that shot peening and the addition of V toAl and Al onAl grain refined by Ti and Ti+B have resulted in enhancement of the fatigue life and strength. Ffinally, the effect of shot peening on the surface quality of the peened parts is also presented and discussed.

  6. High-cycle notch sensitivity of alloy steel ASTM A743 CA6NM used in hydrogenator turbine components

    Directory of Open Access Journals (Sweden)

    José Alexander Araújo

    2010-10-01

    Full Text Available The presence of notches and other stress concentrations in turbine blades and other notch hydraulic components is a current problem in engineering. It causes a reduction of endurance limit of material. In that sense, specimens of the ASTM A743 CA6NM alloy steel using in several hydrogenator turbine components was tested. The specimens were tested under uniaxial fatigue loading with a load ratio equal to -1, and the considered stress concentration factors, Kt, values, calculated with respect to net area, were 1.55, 2.04 and 2.42. In order to determine the fatigue limit for such notch type, a reduction data method by Dixon and Mood, Staircase method was used. This approach is based on the assumed target distribution of the fatigue limit. For such geometry at least 8 specimens were tested. In addition, the Peterson and Neuber’s notch fatigue factor were compared through fatigue notch reduction factor, Kf, obtained from experimental data. According to results obtained it was possible to conclude that the tested material is less sensitive to notches than the prediction of the Peterson and Neuber’s empirical models.

  7. Electrochemical polishing of notches

    Science.gov (United States)

    Kephart, Alan R.; Alberts, Alfred H.

    1989-01-01

    An apparatus and method are disclosed for the selective electrochemical polishing of a lateral tip of a deep longitudinal notch in a work piece used to test crack initiation properties of materials. A DC power source is connected to the work piece and to an electrode disposed laterally along the distal end of an insulated body which is inserted in the longitudinal notch. The electrode and distal end of the body are disposed along the tip of the notch, but are spaced from the notch so as to provide a lateral passage for an electrolyte. The electrolyte is circulated through the passage so that the electrolyte only contacts the work piece adjacent the passage. Conveniently, the electrolyte is circulated by use of an inlet tube and an outlet tube provided at opposite ends of the passage. These tubes are preferably detachably located adjacent the ends of the passage and suitable seals are provided. A holding device including arms to which the tubes are attached is conveniently used to rapidly and easily locate the test specimen with the passage aligned with the tubes. The electrode is preferably a wire which is located in grooves along the distal end of the insulated body and up one side of the body or a plastic sheath insulated thin metal strip.

  8. Fatigue Strength of Portal Frame Beam in High-grade Dynamic Consolidation Construction%高能级强夯施工时门架横梁的疲劳强度验算

    Institute of Scientific and Technical Information of China (English)

    王红霞

    2014-01-01

    为避免高能级强夯施工时横梁断裂的事故发生,在此根据试验数据对横梁疲劳强度进行分析研究,以供参考。%To avoid the beam fracture in high-grade dynamic compaction ,this paper analyzed the fatigue strength of cross beam of portal frame according to the test data ,to provide reference for practice .

  9. Fatigue modelling for gas nitriding

    Directory of Open Access Journals (Sweden)

    H. Weil

    2016-10-01

    Full Text Available The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by the nitriding process. Simulations on rotating bending fatigue specimens are made in order to test the nitrided surfaces. The fatigue model is applied to the cyclic loading of a gear from a simulation using the finite element software Ansys. Results show the positive contributions of nitriding on the fatigue strength

  10. 蒸汽过滤器疲劳强度与寿命分析%Fatigue Strength and Life Analysis of Steam Superheater

    Institute of Scientific and Technical Information of China (English)

    赵静; 靳慧

    2015-01-01

    The steam superheater is a kind of pressure vessel which heats the steam from the saturation temperature to the superheat temperature in the boiler steam.The equipment was designed by ASME code,the test was done under 7.1 MPa of hydrostatic pressure in the normal temperature to ensure the bearing capacity.But the working temperature of the steam superheater is about 350 ℃ and the elastic modulus and yield stress would change a lot.The test at working temperature are difficult to realize.The safety and reliability cannot be guaranteed only rely on the experimental research at room temperature. Now the finite element calculations can simulate more condition and can guarantee the safety of steam generator.The steam superheater which is from a synthetic ammonia plant were taken as object of study. The three dimensional elastic-plastic finite element model of steam superheater was established,the dis-placement deformation of the intersection line between the nozzle and cylinder was presented by ANSYS calculating and compared with the experimental results,which verified that the finite element model can be used;Then the steam filter under the real operating conditions was simulated by finite element method, stress distribution and fatigue strength of open hole area were obtained;At last,fatigue evaluation results were compared between ANSYS fatigue calculation result(ASME Ⅷ -2)and the calculation result based on the Rssian Federation national standard ГОСТР25859.%蒸汽过热器是将蒸汽从饱和温度进一步加热至过热温度的一种压力容器。该设备是根据ASME 规范设计,在常温7.1 MPa 静水压力下经过测试确保轴承的能力。但蒸汽过热器的工作温度约为350℃,弹性模量和屈服应力都会发生很大的变化,在工作温度下的试验难于实现,此时可以借助有限元分析软件提供参考。对某20万吨合成氨厂的蒸汽过热器大开孔壳体建立了三维弹塑性有限元模型,

  11. 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...... is observed between stiffness reduction and accumulated creep. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and an explanation at a microstructural level...

  12. Mechano sorptive behaviour of notched beams in bending

    DEFF Research Database (Denmark)

    Jensen, Signe Kamp; Hoffmeyer, Preben

    1996-01-01

    Short term bending tests with end-notched beams at constant or varying moisture content have shown an apparent contradictory dependency between moisture content and strength. The higher the moisture content the higher the strength. Varying moisture results in particularly significant differences...... and by neglecting deformation due to shear. Compression stresses perpendicular to grain in excess of 6 MPa were found in the vicinity of the notch following a period of adsorption. Similarly, small tension stresses of the order 1 MPa were registered in this area when the specimens were at their most dry condition...

  13. Low cycle fatigue of irradiated LMFBR materials

    Energy Technology Data Exchange (ETDEWEB)

    Blackburn, L D

    1976-01-01

    A review of low cycle fatigue data on irradiated LMFBR materials was conducted and extensive graphical representations of available data are presented. Representative postirradiation tensile properties of annealed 304 and 316 SS are selected and employed in several predictive methods to estimate irradiated material fatigue curves. Experimental fatigue data confirm the use of predictive methods for establishing conservative design curves over the range of service conditions relevant to such CRBRP components as core former, fixed radial shielding, core barrel, lower inlet module and upper internals structures. New experimental data on fatigue curves and creep-fatigue interaction in irradiated 20 percent cold worked (CW) 316 SS and Alloy 718 would support the design of removable radial shielding and upper internals in CRBRP. New experimental information on notched fatigue behavior and cyclic stress-strain curves of all these materials in the irradiated condition could provide significant design data.

  14. Can a fatigue test of the isolated lumbar extensor muscles of untrained young men predict strength progression in a resistance exercise program?

    NARCIS (Netherlands)

    Helmhout, P.; Staal, B.; Dijk, J. van; Harts, C.; Bertina, F.; Bie, R. de

    2010-01-01

    AIM: The aim of this exploratory study was to investigate the predictive value of a fatigue test of the lumbar extensor muscles for training progression in a group of 28 healthy but predominantly sedentary male students, in an 8-week resistance exercise program. METHODS: A three-phased fatigue test

  15. Present Situation of the Anti-Fatigue Processing of High-Strength Steel Internal Thread Based on Cold Extrusion Technology: A Review

    Science.gov (United States)

    Miao, Hong; Jiang, Cheng; Liu, Sixing; Zhang, Shanwen; Zhang, Yanjun

    2017-03-01

    The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost and low energy consumption. It has vast application foreground in the field of aviation, spaceflight, high speed train and etc. The internal thread processing and anti-fatigue manufacture technology are summarized. In terms of the perspective of processing quality and fatigue serving life, the advantages and disadvantages of the processing methods from are compared. The internal thread cold-extrusion processing technology is investigated for the purpose of improving the anti-fatigue serving life of internal thread. The superiorities of the plastic deformation law and surface integrity of the metal layer in the course of cold extrusion for improving its stability and economy are summed up. The proposed research forecasts the development tendency of the internal thread anti-fatigue manufacturing technology.

  16. SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA

    Institute of Scientific and Technical Information of China (English)

    Z.X.Wu; X.C.Wu

    2001-01-01

    The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.

  17. On the microstructural basis of creep strength and creep-fatigue interaction in 9-12 % Cr steels for application in power plants

    Energy Technology Data Exchange (ETDEWEB)

    Chilukuru, H.

    2007-03-06

    As part of the efforts of preserving the environment it is necessary to reduce of the CO2 emissions from power plants. This can be done by increasing the plant efficiency. Research groups around the world are engaged in developing new steels capable of sustaining higher stresses and temperatures envisaged for high-efficiency power plants. Research carried out in Europe is organized within the COST Programme (Co-Operation in Science and Technology) aiming at replacing the conventional steels of type X20CrMoV121 by the new class of 9-12% Cr-steels with modified composition. The resistance of materials against deformation at elevated temperatures depends on their microstructure. Frequently in 9-12% Cr-steels improved short-term creep properties do not persist in the long-term service [1, 2, 3, 4, 5, 6]. This is related with insufficient microstructural stability. Hardening contributions in 9-12% Cr-steels come from solute atoms of the ferritic matrix, from dislocations, and from precipitates of foreign phases within the matrix. The term ''carbide stabilized substructure hardening'' of 9-12% Cr steels [7, 8] indicates that the hardening contributions are interdependent. The dislocations are the carriers of plastic deformation. They interact with each other, with solute atoms and with precipitates. The dislocation-dislocation interaction leads to formation of planar dislocation networks constituting low-angle boundaries. They form a subgrain structure within the grains. At present, a full and detailed understanding of the effects exerted by the different components of microstructure on creep strength is still lacking. The present work makes a contribution to the efforts of understanding the microstructural basis of creep strength and of creep-fatigue interaction by transmission electron microscopic structure investigations coupled with creep tests. Investigations by transmission electron microscopy (TEM) were carried out with regard to hardening by

  18. Idealization of a Gas Turbine Compressor Blade to a Rectangular Plate and Analyzing the Variation of Stress Concentration Factor for U-Notches

    Directory of Open Access Journals (Sweden)

    Mohammad Rafi Nadaf

    2014-01-01

    Full Text Available Aircraft turbine engines routinely experience the ingestion of debris resulting in "foreign object damage‟ FOD. The ingestion of foreign object into aircraft engines leads to severe structural damage of the fan or compressor blades. Foreign object damage by hard particles mostly occurs during motion of the aircraft on the airfield, during take-off and during landing. Typical objects ingested are stones and other debris; sizes in the millimeter regime form the airfield. The worst case condition is experienced during take-off maximum thrusts leads to maximum impact velocity. Typical impact velocities are in the regime of 100 – 400m/sec, depending on the types of engine and impact location on the blades. Foreign object damage does not always lead to sudden catastrophic failure, yet such damage can have a detrimental effect on the fatigue strength of fan and compressor aero foils. However complex stress fields and geometry of the aerofoil make it difficult to use of simple notch analysis. For finding the stress concentration factor on the notches grinded on the typical aerofoil FOD damaged gas turbine compressor blade closed form solutions are difficult proportion. In this paper a finite element analysis is carried out by idealization of the typical aerofoil to rectangular cantilever plate with single edge U-notches for finding the stress concentration factor and is then compared with the standard stress concentration data by R.E.Peterson. The study can then be extended to a typical aerofoil.

  19. Notch in Pathological Angiogenesis and Lymphangiogenesis

    Science.gov (United States)

    2012-05-01

    endothelial cells ( HUVEC ). Notch family receptors and ligands (Notch 1, Notch 4, Dll-4, Jag1) are present in HUVEC . Activation of Notch in HUVEC inhibits...associated gene, which is also repressed in HUVEC upon Notch activation) (data not shown). Figure 2a

  20. In-situ tensile testing of notched poly- and oligocrystalline 316L wires

    Energy Technology Data Exchange (ETDEWEB)

    Mitevski, Bojan [Materials Science and Engineering (ITM), Duisburg (Germany); Weiss, Sabine [Brandenburg Technical Univ., Cottbus-Senftenberg (Germany). Chair of Physical Metallurgy and Materials Science.; Fischer, Alfons [Duisburg-Essen Univ. (Germany). Materials Science and Engineering; Rush Univ. Medical Center, Chicago, IL (United States). Dept. of Orthopedics

    2017-03-01

    In-situ testing inside a scanning electron microscope is a helpful tool for detailed analyses of small sized specimens with respect to their mechanical properties and the correlated microstructural alterations. Thus, this test method is used to analyze the tensional properties of thin 316L (1.4441) wires used for microscale components, e.g., like coronary artery stents. Tensile tests were conducted on unnotched and circularly notched 316L wires (oe 0.95 mm) with a special focus on the number of grains within the cross section as well as the notch geometry. Four combinations of notch width (2 and 4 mm) and notch depth (diameter at notch root: 0.5 and 0.75 mm) were chosen. Notch depth and notch shape were adjusted by means of electrochemical polishing. Previous investigations showed, that oligocrystalline structures exhibit a different mechanical behavior compared to polycrystalline ones or single crystals. There are only a few data available on mechanical testing of oligocrystalline structures with respect to varying notch geometries. Depending on the notch geometry, grain size and, therefore, the number of grains within the notch cross section widely scattering yield- and tensile strength as well as failure elongation values were measured. However, the transition criterion between poly- and oligocrystalline behavior could be quantified to be 6 to 7 grains within the cross section.

  1. 巧克力裹包机正切型从动系统凸轮轴疲劳强度研究%Study on cam shaft fatigue strength of tangent type follower system of the chocolate bind chartered plane

    Institute of Scientific and Technical Information of China (English)

    常锋; 王振成; 刘瑞礼; 王欣

    2013-01-01

    Through the methods of trial for combining together with tired stress strain and theory analysis,the article studied the tangent type follower system of the chocolate bind chartered plane was studied on imitating 38GrMoAlA the high-quality alloy structure steel material guildert,under the situation on circulate operate stress of fatigue strength,Proposed the recognize method of fatigue strength tigen-value on tangent type follower system,gave the oval curve and equation on Limiting stress toge ther with the stress Oval equation on Octahedron fatigue limit,provided for reference and choice when engineering technical personnel design.%通过试验与疲劳应力应变理论分析相结合的方法,研究模拟38GrMoAlA优质合金结构钢材质的巧克力裹包机正切型从动系统凸轮轴,在循环工作应力条件下的疲劳强度;提出正切型从动系统凸轮轴疲劳强度特性值的确定方法;并给出它的极限应力椭圆曲线和方程及八面体疲劳极限应力椭圆方程,供工程技术人员设计时参考和选用.

  2. NOTCH FILTER USING SIMULATED INDUCTOR

    Directory of Open Access Journals (Sweden)

    D.SUSAN,

    2011-06-01

    Full Text Available The design of analog filters at low frequencies is not possible because the size of inductors becomes very large. In such cases, the simulated inductors using operational amplifiers are used. This paper deals with the implementation of notch filter using band pass filter which uses simulated inductor where the direct implementation of notch filter using simulated inductor is not possible because of floating inductor. The design of notch filter and the simulation done in PSPICE is presented.

  3. Notch Charge-Coupled Devices

    Science.gov (United States)

    Janesick, James

    1992-01-01

    Notch charge-coupled devices are imaging arrays of photodetectors designed to exhibit high charge-transfer efficiencies necessary for operation in ultra-large array, and less vulnerable to degradation by energetic protons, neutrons, and electrons. Main channel of horizontal register includes deep narrow inner channel (notch). Small packets of charge remain confined to notch. Larger packets spill into rest of channel; transferred in usual way. Degradation of charge-transfer efficiency by energetic particles reduced.

  4. Effect of service usage on tensile, fatigue, and fracture properties of 7075-T6 and 7178-T6 aluminum alloys

    Science.gov (United States)

    Everett, R. A., Jr.

    1975-01-01

    A study has been made to determine the effects of extensive service usage on some basic material properties of 7075-T6 and 7178-T6 aluminum alloy materials. The effects of service usage were determined by comparing material properties for new material (generally obtained from the literature) with those for material cut from the center wing box of a C-130B transport airplane with 6385 flight-hours of service. The properties investigated were notched and unnotched fatigue strengths, fatigue-crack-growth rate, fracture toughness, and tensile properties. For the properties investigated and the parameter ranges considered (crack length, stress ratio, etc.), the results obtained showed no significant difference between service and new materials.

  5. Fatigue endurance of Ti-6Al-4V alloy with electro-eroded surface for improved bone in-growth.

    Science.gov (United States)

    Janeček, Miloš; Nový, František; Stráský, Josef; Harcuba, Petr; Wagner, Lothar

    2011-04-01

    Ti-6Al-4V hour-glass shaped rotating beam specimens with duplex microstructure were processed by electric discharge machining (EDM). A comparatively high peak current of 29A was utilized in order to increase surface roughness for improved osteointegration. High cycle fatigue (HCF) tests were performed in rotating beam loading (R=-1) on these EDM specimens and results were compared with electrolytically polished specimens serving as reference. As expected, the HCF performance of EDM specimens was inferior to the electrolytically polished specimens. A detailed study of fatigue crack nucleation and microcrack growth was carried out on failed specimens by SEM. The poor HCF strength of EDM specimens is explained by early crack nucleation due to the high notch sensitivity of Ti-6Al-4V. In addition, process-induced residual tensile stresses and microstructural effects may also account for the drastic loss in HCF performance relative to the electropolished baseline.

  6. Application of Support Vector Machine in the Prediction of Fatigue Stress Concentration Factor%基于支持矢量机的疲劳应力集中系数预测模型研究

    Institute of Scientific and Technical Information of China (English)

    侯哲哲; 杜彦良; 赵维刚

    2012-01-01

    Fatigue stress concentration factors as fatigue limit of material fatigue resistance not only reflected the extent of fatigue stress concentration but also reflected for notch sensitive degree. The newly developed technical support vector machine(SVM) into the domain of fatigue stress concentration factor is introduced. Support vector machine theory is introduced, LIBSVM is used, and RBF is chosen as kernel function to build a mode. The input parameters are tensile strength, yield strength, fatigue strength, stress concentration factor, notch root radius, samples size and notch fatigue limit; Fatigue stress concentration factor is output. The calculations of SVM model, experimental formula Neural and Peterson are compared. The results show that the relative maximum predicting error is 0.7% under the condition of using a small quantity of samples to build the mathematical model. The accuracy and applicability for the present model are thus verified.%疲劳应力集中系数作为材料疲劳抗力指标的疲劳极限,不仅反映了疲劳应力集中的程度,还反映了材料对缺口的敏感程度,将近年来飞速发展的支持矢量机(Support vector machine,SVM)应用于疲劳应力集中系数的研究.介绍支持矢量机的基本原理,利用LIBSVM,选择高斯型径向基函数(Radial basis function,RBF)作为核函数,建立以材料的抗拉强度、屈服强度、光棒疲劳强度、理论应力集中系数、缺口根部半径、试样尺寸及缺口疲劳极限作为输入值,疲劳应力集中系数为输出值的模型,从而对疲劳应力集中系数进行分析和预测.同时,SVM模型与经验公式Neuber式和Peterson式的计算值进行比较.结果表明,在小样本条件下,应用SVM技术构建的数学模型,模型的拟合相对误差小于7.4%,从而证明该SVM模型的准确性和适用性.

  7. Fatigue Analysis of a Mono-Tower Platform

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune

    In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed thro...... of the natural period, damping ratio, current, stress Spectrum and parameters describing the fatigue strength. Further, soil damping is shown to be significant for the Mono-tower.......In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...

  8. Fatigue Reliability Analysis of a Mono-Tower Platform

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune

    1991-01-01

    In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed thro...... of the natural period, damping ratio, current, stress spectrum and parameters describing the fatigue strength. Further, soil damping is shown to be significant for the Mono-tower.......In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed...

  9. 夹杂物尺寸对汽车车轮用钢疲劳寿命的影响%Influence of Inclusion Size on Fatigue Life of High Strength Steel for Automobile Wheel

    Institute of Scientific and Technical Information of China (English)

    赵凤晓; 李会; 许晓嫦; 李良; 徐浩浩

    2013-01-01

    The fatigue life of high strength steel for automobile wheel was investigated by MTS858 electro-hydraulic servo fatigue testing, and then the fatigue fracture morphology was analyzed by Quanta 600 scanning electron microscope (SEM). Based on the preliminary analysis of the experimental data, the critical size of inclusions was calculated. According to the theory of normal distribution, fatigue life of the wheel steel was predicted. The results show that the fatigue cracks are all initiated from the internal and subsurface inclusions. The energy spectrum analysis indicates that the main components of the inclusions are oxides of calcium and aluminium. The measured size of most of the inclusions at the crack sources are larger than the critical size.%采用MTS858电液伺服疲劳实验机研究了高强度车轮用钢的疲劳寿命,并用Quanta 600环境扫描电子显微镜对疲劳断口形貌进行了观察.通过对实验数据分析,计算得出了夹杂物的临界尺寸,并根据正态分布理论对车轮钢的疲劳寿命进行了预测.研究结果表明,疲劳裂纹均是从内部或者亚表面的夹杂物处萌生;能谱分析表明:夹杂物的成分主要是钙铝的氧化物,测量所得裂纹源处夹杂物尺寸大部分超过了临界尺寸.

  10. Ubiquitination of Notch1 is regulated by MAML1-mediated p300 acetylation of Notch1

    Energy Technology Data Exchange (ETDEWEB)

    Popko-Scibor, Anita E.; Lindberg, Mikael J.; Hansson, Magnus L.; Holmlund, Teresa [Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, 171 77 Stockholm (Sweden); Wallberg, Annika E., E-mail: Annika.Wallberg@ki.se [Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, 171 77 Stockholm (Sweden)

    2011-12-16

    Highlights: Black-Right-Pointing-Pointer p300 acetylates conserved lysines within Notch1 C-terminal nuclear localization signal. Black-Right-Pointing-Pointer MAML1 and CSL, components of Notch transcription complex, increase Notch acetylation. Black-Right-Pointing-Pointer MAML1-dependent acetylation of Notch1 by p300 decreases the ubiquitination of Notch1. Black-Right-Pointing-Pointer CDK8 inhibits Notch acetylation and Notch transcription enhanced by p300. -- Abstract: Earlier studies demonstrated the involvement of the p300 histone acetyltransferase in Notch signaling but the precise mechanisms by which p300 might modulate Notch function remains to be investigated. In this study, we show that p300 acetylates Notch1 ICD in cell culture assay and in vitro, and conserved lysines located within the Notch C-terminal nuclear localization signal are essential for Notch acetylation. MAML1 and CSL, which are components of the Notch transcription complex, enhance Notch acetylation and we suggest that MAML1 increases Notch acetylation by potentiating p300 autoacetylation. Furthermore, MAML1-dependent acetylation of Notch1 ICD by p300 decreases the ubiquitination of Notch1 ICD in cellular assays. CDK8 has been shown to target Notch1 for ubiquitination and proteosomal degradation. We show that CDK8 inhibits Notch acetylation and Notch transcription enhanced by p300. Therefore, we speculate that acetylation of Notch1 might be a mechanism to regulate Notch activity by interfering with ubiquitin-dependent pathways.

  11. 威布尔分布随机载荷下齿轮弯曲疲劳试验分析%Experimental study of gear bending fatigue strength under random load according to three-parameter Weibull distribution

    Institute of Scientific and Technical Information of China (English)

    胡建军; 许洪斌; 高孝旺; 祖世华

    2012-01-01

    根据齿轮传动过程中普遍承受的三参数威布尔分布载荷谱,编制了试验用随机变幅疲劳载荷谱,在MTS电液伺服疲劳试验机上利用成组试验方法完成了该随机载荷作用下齿轮弯曲疲劳试验,得到了特定变异系数三参数威布尔分布载荷谱下齿轮弯曲强度的S-N曲线。试验结果证明,在服从三参数威布尔分布随机载荷谱下,随机变幅疲劳试验得出的轮齿疲劳寿命远低于恒载荷疲劳试验得出的疲劳寿命。对随机载荷下的齿轮设计的疲劳极限的理论值进行了预测,并与试验结果进行了比较。随机载荷下的理论值与试验结果相吻合,因此可以通过随机载荷谱的载荷比例系数去推断随机载荷下齿轮弯曲疲劳强度值。%Random-amplitude fatigue load spectrum for experiments is made according to the ubiquitous three-parameter Weibull distribution in gear transmission.Gear bending fatigue test under the random load is carried out on a MTS electro-hydraulic servo material fatigue tester by using group testing method,and the S-N curve of gear bending strength under three-parameter Weibull distribution with specific variation coefficients is obtained.The fatigue test results show the gear's endurance life under random load is far less than that under constant load when the load submits to three-parameter Weibull distribution random load spectrum.The theoretical value of fatigue limit for gear under random load is predicated and compared with test results.The theoretical value is in accordance with the test results.Therefore,the fatigue strength of gear bending under random load can be deduced according to the load ratio coefficient of random load spectrum.

  12. 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)

  13. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

    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...... 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...

  14. Notch as a tumour suppressor.

    Science.gov (United States)

    Nowell, Craig S; Radtke, Freddy

    2017-03-01

    The Notch signalling cascade is an evolutionarily conserved pathway that has a crucial role in regulating development and homeostasis in various tissues. The cellular processes and events that it controls are diverse, and continued investigation over recent decades has revealed how the role of Notch signalling is multifaceted and highly context dependent. Consistent with the far-reaching impact that Notch has on development and homeostasis, aberrant activity of the pathway is also linked to the initiation and progression of several malignancies, and Notch can in fact be either oncogenic or tumour suppressive depending on the tissue and cellular context. The Notch pathway therefore represents an important target for therapeutic agents designed to treat many types of cancer. In this Review, we focus on the latest developments relating specifically to the tumour-suppressor activity of Notch signalling and discuss the potential mechanisms by which Notch can inhibit carcinogenesis in various tissues. Potential therapeutic strategies aimed at restoring or augmenting Notch-mediated tumour suppression will also be highlighted.

  15. Bruton's Tyrosine Kinase Synergizes with Notch2 to Govern Marginal Zone B Cells in Nonobese Diabetic Mice1,2

    Science.gov (United States)

    Nyhoff, Lindsay E.; Steinberg, Hannah E.; Sullivan, Allison M.; Kendall, Peggy L.

    2015-01-01

    Expansion of autoimmune-prone marginal zone (MZ) B cells has been implicated in type 1 diabetes (T1D). To test disease contributions of MZ B cells in NOD mice, Notch2 haploinsufficiency (Notch2+/−) was introduced, but failed to eliminate the MZ, as it does in C57BL/6 mice. Notch2+/−/NOD have MZ B cell numbers similar to WT C57BL/6, yet still develop diabetes. To test whether BCR-signaling supports Notch2+/−/NOD MZ B cells, Bruton's tyrosine kinase (Btk)-deficiency was introduced. Surprisingly, MZ B cells failed to develop in Btk-deficient Notch2+/−/NOD mice. Expression of Notch2 and its transcriptional target, Hes5, were increased in NOD MZ B cells compared with C57BL/6 MZ B cells. Btk-deficiency reduced Notch2+/− signaling exclusively in NOD B cells, suggesting that BCR-signaling enhances Notch2 signaling in this autoimmune model. The role of BCR-signaling was further investigated using an anti-insulin transgenic BCR (125Tg). Anti-insulin B cells in 125Tg/Notch2+/−/NOD mice populate an enlarged MZ, suggesting that low level BCR signaling overcomes reliance on Notch2. Tracking clonotypes of anti-insulin B cells in H chain only VH125Tg/NOD mice showed that BTK-dependent selection into the MZ depends on strength of antigenic binding, while Notch2-mediated selection does not. Importantly, anti-insulin B cell numbers were reduced by Btk-deficiency, but not Notch2-haploinsufficiency. These studies show that: 1) Notch2-haploinsufficiency limits NOD MZ B cell expansion without preventing T1D, 2) BTK supports the Notch2 pathway in NOD MZ B cells, and 3) autoreactive NOD B cell survival relies on BTK more than Notch2, regardless of MZ location, which may have important implications for disease-intervention strategies. PMID:26034172

  16. Bruton's Tyrosine Kinase Synergizes with Notch2 To Govern Marginal Zone B Cells in Nonobese Diabetic Mice.

    Science.gov (United States)

    Case, James B; Bonami, Rachel H; Nyhoff, Lindsay E; Steinberg, Hannah E; Sullivan, Allison M; Kendall, Peggy L

    2015-07-01

    Expansion of autoimmune-prone marginal zone (MZ) B cells has been implicated in type 1 diabetes. To test disease contributions of MZ B cells in NOD mice, Notch2 haploinsufficiency (Notch2(+/-)) was introduced but failed to eliminate the MZ, as it does in C57BL/6 mice. Notch2(+/-)/NOD have MZ B cell numbers similar to those of wild-type C57BL/6, yet still develop diabetes. To test whether BCR signaling supports Notch2(+/-)/NOD MZ B cells, Bruton's tyrosine kinase (Btk) deficiency was introduced. Surprisingly, MZ B cells failed to develop in Btk-deficient Notch2(+/-)/NOD mice. Expression of Notch2 and its transcriptional target, Hes5, was increased in NOD MZ B cells compared with C57BL/6 MZ B cells. Btk deficiency reduced Notch2(+/-) signaling exclusively in NOD B cells, suggesting that BCR signaling enhances Notch2 signaling in this autoimmune model. The role of BCR signaling was further investigated using an anti-insulin transgenic (Tg) BCR (125Tg). Anti-insulin B cells in 125Tg/Notch2(+/-)/NOD mice populate an enlarged MZ, suggesting that low-level BCR signaling overcomes reliance on Notch2. Tracking clonotypes of anti-insulin B cells in H chain-only VH125Tg/NOD mice showed that BTK-dependent selection into the MZ depends on strength of antigenic binding, whereas Notch2-mediated selection does not. Importantly, anti-insulin B cell numbers were reduced by Btk deficiency, but not Notch2 haploinsufficiency. These studies show that 1) Notch2 haploinsufficiency limits NOD MZ B cell expansion without preventing type 1 diabetes, 2) BTK supports the Notch2 pathway in NOD MZ B cells, and 3) autoreactive NOD B cell survival relies on BTK more than Notch2, regardless of MZ location, which may have important implications for disease-intervention strategies. Copyright © 2015 by The American Association of Immunologists, Inc.

  17. Notch Signaling in Neuroendocrine Tumors

    Directory of Open Access Journals (Sweden)

    Judy Sue Crabtree

    2016-04-01

    Full Text Available Carcinoids and neuroendocrine tumors (NETs are a heterogeneous group of tumors that arise from the neuroendocrine cells of the GI tract, endocrine pancreas and the respiratory system. NETs remain significantly understudied with respect to molecular mechanisms of pathogenesis, particularly the role of cell fate signaling systems like Notch. The abundance of literature on the Notch pathway is a testament to its complexity in different cellular environments. Notch receptors can function as oncogenes in some contexts, and tumor suppressors in others. The genetic heterogeneity of NETs suggests that to fully understand the roles and the potential therapeutic implications of Notch signaling in NETs, a comprehensive analysis of Notch expression patterns and potential roles across all NET subtypes is required.

  18. 3D numerical analysis of crack propagation of heterogeneous notched rock under uniaxial tension

    Science.gov (United States)

    Wang, S. Y.; Sloan, S. W.; Sheng, D. C.; Tang, C. A.

    2016-05-01

    Macroscopic notches play an important role in evaluating the fracture process zone (FPZ) and the strengths of a heterogeneous rock mass. Crack initiation, propagation and coalescence for unnotched, single-notched and double-notched rock specimens are numerically simulated in a 3-D numerical model (RFPA3D). A feature of the code RFPA3D is that it can numerically simulate the evolution of cracks in three-dimensional space, as well as the heterogeneity of the rock mass. For the unnotched case, special attention is given to the complete stress-strain curve and the corresponding AE events for the failure process of rock specimen. By comparing with published experimental results, the simulation results from RFPA3D are found to be satisfactory. For the single-notched case, the effect of the length and the depth of the single notch and the thickness of the specimen on the failure mode and peak stress are evaluated. The 3D FPZ is very different from that in two dimensions. For the double-notched case, the effects of the separation distance and overlap distance of the double notches, as well as influence of the homogeneity index (m) are also investigated. As the overlap distance increases, the direction of the principal tensile stress at each notch-end changes from a perpendicular direction (tensile stress field) to a nearly parallel direction (compressive stress field), which affects the evolution of the cracks from the two notches.

  19. Notch sensitivity of hydrogenated oxygen-strengthened titanium

    Science.gov (United States)

    Wasz, M. L.; Ko, C. C.; Brotzen, F. R.; Mclellan, R. B.

    1990-01-01

    While earlier studies have shown that the tensile properties and fracture test intensity factors of oxygen-strengthened Ti remain nearly unaffected by the presence of about 70 ppm (weight) hydrogen, the Charpy V-notch test-determined impact properties of oxygen-bearing Ti are strongly affected by the presence of hydrogen. The present study establishes that, concurrently with the strengthening effect of oxygen, there is a substantial lowering of ductility. The presence of hydrogen has virtually no effect on the notch strength of Ti alloys of either low or high oxygen content, where hydrogen contents lie in the 25-80 range.

  20. Nanoparticle optical notch filters

    Science.gov (United States)

    Kasinadhuni, Pradeep Kumar

    Developing novel light blocking products involves the design of a nanoparticle optical notch filter, working on the principle of localized surface plasmon resonance (LSPR). These light blocking products can be used in many applications. One such application is to naturally reduce migraine headaches and light sensitivity. Melanopsin ganglion cells present in the retina of the human eye, connect to the suprachiasmatic nucleus (SCN-the body's clock) in the brain, where they participate in the entrainment of the circadian rhythms. As the Melanopsin ganglion cells are involved in triggering the migraine headaches in photophobic patients, it is necessary to block the part of visible spectrum that activates these cells. It is observed from the action potential spectrum of the ganglion cells that they absorb light ranging from 450-500nm (blue-green part) of the visible spectrum with a λmax (peak sensitivity) of around 480nm (blue line). Currently prescribed for migraine patients is the FL-41 coating, which blocks a broad range of wavelengths, including wavelengths associated with melanopsin absorption. The nanoparticle optical notch filter is designed to block light only at 480nm, hence offering an effective prescription for the treatment of migraine headaches.

  1. Thermal emission in fatigue described by power laws

    Directory of Open Access Journals (Sweden)

    Gallinatti A.E.

    2010-06-01

    Full Text Available In the present work, a theoretical model proposed by the literature and focused on the relationship between microplasticizations thermal behaviour and fatigue scatter is analysed and applied to fatigue test results of standard and notched steel specimens. The same experimental data are subjected to the TCM (Two Curves Method thermographic elaboration technique, in order to quickly evaluate fatigue limit values. TCM method has been modified, aiming at interpolating thermal data referred to the region of loads upper than fatigue limit with a non linear regression law having the same mathematical structure of the theoretical model equations (power laws.

  2. Fatigue Reliability under Multiple-Amplitude Loads

    DEFF Research Database (Denmark)

    Talreja, R.

    1979-01-01

    A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution...... for the initial tensile strength and the fatigue life, the probability distributions for the residual tensile strength in both the crack initiation and the crack propagation stages of fatigue are determined. The method is illustrated for two-amplitude loads by means of experimental results obtained by testing...

  3. Notch sensitivity of aliphatic polyketone terpolymers

    NARCIS (Netherlands)

    Zuiderduin, W.C.J.; Huetink, J.; Gaymans, R.J.

    2004-01-01

    The notch sensitivity of aliphatic polyketone (PK) terpolymers was investigated in this article. The notch-tip radius was varied between the size of an actual propagating crack tip of 1-2 m and the largest notch tip of 1000 m radius. The larger notch-tip radii (1000-15 m) were milled into the polyme

  4. Fatigue in Breakwater Concrete Armour Units

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    The reliability of rubble mound breakwaters depends on the hydraulic stability and the mechanical strength of the armour units. The paper deals with the important aspect of fatigue related to the strength of concrete armour units.......The reliability of rubble mound breakwaters depends on the hydraulic stability and the mechanical strength of the armour units. The paper deals with the important aspect of fatigue related to the strength of concrete armour units....

  5. Effect of the Content of Retained Austenite and Grain Size on the Fatigue Bending Strength of Steels Carburized in a Low-Pressure Atmosphere

    Science.gov (United States)

    Kula, P.; Dybowski, K.; Lipa, S.; Januszewicz, B.; Pietrasik, R.; Atraszkiewicz, R.; Wołowiec, E.

    2014-11-01

    The effect of the content of retained austenite and of the initial austenite grain size on high-cycle fatigue of two low-alloy steels 16MnCr5 and 17CrNi6-6 after carburizing in a low-pressure atmosphere (acetylene, ethylene and hydrogen) and subsequent high-pressure gas quenching is investigated.

  6. The influence of the notches on the natural frequencies

    Directory of Open Access Journals (Sweden)

    Dekýš V.

    2007-10-01

    Full Text Available The simplification of the FEM model (the missing of a notch or a crack generally means the modification of the natural frequencies. An analysis of these changes is matter of this paper. The direct and semicircle notches were made on the testing specimens (by cut depth in the specimens and the naturals frequencies were measured and computed. The results are compared.In the paper is discussed the choice of the FEM element for FEM model and the comparison with experiment is made too.The influence of the crack on the natural frequencies is discussed in the case of specimen for high cycle fatigue test. The changes of the first three frequencies are compared for specimens with and without crack.

  7. Progress in the Brittle Fracture and Fatigue of High Strength Steels and Their Welds%高强度钢材及其焊缝脆性断裂与疲劳性能的研究进展

    Institute of Scientific and Technical Information of China (English)

    王元清; 林云; 周晖; 张延年; 石永久

    2012-01-01

    The advantages and disadvantages of high strength steel as well as its application in the domestic and foreign construction engineering and bridge engineering were briefly described, as well as a number of practical engineering problems analyzed. Summing up the related research of domestic and foreign high strength steels and their welds on their brittle fracture and fatigue, the article raised the need for study on the fracture toughness and fatigue performance of high strength steel used in construction and its connection weld and the change law of influence factor. Low temperature, weld defects, increasing thickness of steel and high-frequency dynamic load were found greatly reducing the resistance capacity of brittle fracture of high strength steel and fatigue life; Other than these external factors,for mechanical properties and toughness due to special metallurgical processes,the application of high strength steel was limited.%简单阐述了高强度钢材的优、缺点以及在国内外建筑工程和桥梁工程中的应用情况,并分析了其实际工程中存在的若干问题.总结了国内外对高强度钢材及其焊缝的脆性断裂与疲劳破坏的相关研究,引出研究高强度建筑用结构钢材及其连接焊缝的断裂韧性和疲劳性能以及影响因素变化规律的必要性,得出了如下结论:低温、焊缝缺陷、钢材厚度的增加和高频动荷载极大降低了高强度钢材的抗脆断能力及疲劳寿命;同时高强度钢材由于特殊冶金工艺而具有的力学性能和韧性加上这些外因限制了其使用范围.

  8. The Effect of Contouring on Fatigue Strength of Spinal Rods: Is it Okay to Re-bend and Which Materials Are Best?

    Science.gov (United States)

    Slivka, Michael A; Fan, Yung K; Eck, Jason C

    2013-11-01

    Small-diameter spinal rods were tested in fatigue loading before and after contouring in pedicle screw constructs using dynamic testing machines. To characterize the change in fatigue performance of spinal rods resulting from contouring. Spine surgeons have a variety of rod materials to choose from, and selecting the best rod depends on patient characteristics and rod material properties, including fatigue performance. Four rod materials were tested, all 4.5 mm in diameter: titanium alloy (Ti), cobalt-chromium alloy (CoCr), and 2 different grades of stainless steel (SS and ultra SS). Three conditions were tested: straight (virgin rods), bent (rods bent to a radius of curvature of 100 mm), and re-bent (rods over-bent to a radius of 50 mm, then partially straightened to a 100-mm radius). Fatigue testing was conducted on unilateral vertebrectomy constructs with polyaxial screws. In all conditions, the endurance limit of the CoCr rods was at least 25% higher than the other materials but could not be determined because screw failure precluded rod failure. In the bent condition, the endurance limits of Ti, standard SS and ultra SS were reduced between 20% and 40%. In the re-bent condition, the endurance limit of Ti, standard SS, and ultra SS increased compared with the bent condition. Changes in fatigue performance are best explained by residual rod stresses induced during contouring. It appears safe to over-bend and then re-bend, for 1 cycle, small-diameter spinal rods made of the materials tested in this study using tube benders, and CoCr rods were clearly superior for all conditions. However, larger rods, multiple cycles of bending and re-bending, and rods bent using other instruments such as French benders were not studied and may result in different performance under the same conditions. Copyright © 2013 Scoliosis Research Society. Published by Elsevier Inc. All rights reserved.

  9. 焊接接头疲劳强度改善技术在海洋工程中的应用%Technology application for improving fatigue strength of welding joint to offshore engineering

    Institute of Scientific and Technical Information of China (English)

    时群超

    2011-01-01

    相对于船舶和普通海洋钢结构,深水和大型海洋工程结构面临的安全性更为重要.焊接结构很容易出现断裂问题,其中多数为疲劳失效,对于这个问题除了通过优化设计和提高质量要求之外,通过制造工艺对焊接接头疲劳强度进行改善也是很好的选择.在此结合部分海洋工程建造规范和应用实践,介绍了包括焊缝外观整体加工、焊趾打磨、TIG熔修和锤击等在内的海洋工程钢结构常用的焊接接头疲劳改善技术,提供了实用的操作细节和使用注意事项,并讨论了以上疲劳改善工艺在海洋工程建造应用中需解决的问题及其应用前景.%The safety of deepwater or large offshore structures is distinctly important than ship and other ordinary marine structures. Welded steel structures have high crack risk,especially fatigue cracks.In some cases,except good design and additional quality requirements,it is a good solution that uses manufacturing process to improve weld detail fatigue strength.Based on some offshore codes and engineering practice,this paper introduce some usual weld detail fatigue strength improvement methods,including weld profiling by machining and grinding,Weld toe grinding,TIC dressing,Hammer peening.sum up some practical process details and matters need attention.At last of this paper discuses some problems need solving, and analyze the application prospect forecast of weld detail fatigue strength improvement technique in offshore engineering.

  10. 高强度钢30Cr3SiNiMoVA的疲劳特性研究%Study of Fatigue Performance for High Strength Steel 30Cr3SiNiMoVA

    Institute of Scientific and Technical Information of China (English)

    李斌; 董万元; 王小兵; 梁强

    2012-01-01

    In order to obtain fatigue design data of high strength steel 30Cr3SiNiMoVA, the fatigue test of this steel material have been carried out. In the experiment the material conditional fatigue limit was tested by the up-and-down method, and other fatigue data were done by the group test method under four stress levels for the polished specimen and unpolished specimen of the material, respectively. Then a two-parameter least square method was used to fit the S-N curve, and the probability method was used to obtain the PS-N curve. By the comparisons between two S-N curves, it is seen that the fatigue life of unpolished samples is lower than that of polished samples under same fatigue load level, so 30Cr3SiNiMoVA's fatigue life is sensitive to the surface rough state of the specimen, and this sensitivity is increasing with the decreasing of fatigue load, and the fatigue limit of the polished specimen is about 1. 4 times of the unpolished specimen. It is suggested that the effective technology should be applied into improving the surface rough state of one type of this material. These data will provided a valuable support for the engineering applications of 30Cr3SiNiMoVA.%为了获得超高强度钢30Cr3SiNiMoVA的疲劳设计数据,对该材料进行了疲劳性能实验.分别对该材料的抛光和未抛光试样进行轴向拉压疲劳实验.用升降试验法测定材料的条件疲劳极限,用成组实验法在四级应力水平下测试其疲劳寿命.结合升降法所得的条件疲劳极限值和成组法实验数据,采用双参数最小二乘法拟合SN曲线,运用概率方法求得P-S-N曲线.通过对两种试样的SN曲线分析可知:未抛光试样的疲劳寿命要低于抛光试样的疲劳寿命,并且疲劳载荷级越低,两类试样之间的疲劳寿命差越大,抛光试样的疲劳极限大约是未抛光试样的1.4倍.相关实验现象表明30Cr3SiNiMoVA的疲劳寿命对试样表面粗糙状态非常敏感,建议该类材料在应用过

  11. 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

  12. Oncogenic programmes and Notch activity: an 'organized crime'?

    Science.gov (United States)

    Dominguez, Maria

    2014-04-01

    The inappropriate Notch signalling can influence virtually all aspect of cancer, including tumour-cell growth, survival, apoptosis, angiogenesis, invasion and metastasis, although it does not do this alone. Hence, elucidating the partners of Notch that are active in cancer is now the focus of much intense research activity. The genetic toolkits available, coupled to the small size and short life of the fruit fly Drosophila melanogaster, makes this an inexpensive and effective animal model, suited to large-scale cancer gene discovery studies. The fly eye is not only a non-vital organ but its stereotyped size and disposition also means it is easy to screen for mutations that cause tumours and metastases and provides ample opportunities to test cancer theories and to unravel unanticipated nexus between Notch and other cancer genes, or to discover unforeseen Notch's partners in cancer. These studies suggest that Notch's oncogenic capacity is brought about not simply by increasing signal strength but through partnerships, whereby oncogenes gain more by cooperating than acting individually, as in a ring 'organized crime'.

  13. Strength of Hard Alloys,

    Science.gov (United States)

    Partial replacement of titanium carbide by tantalum carbide in three-phase WC-TiC-Co alloys tends to have a favorable effect on mechanical properties such as fatigue strength under bending and impact durability.

  14. The Notch intracellular domain integrates signals from Wnt, Hedgehog, TGFβ/BMP and hypoxia pathways.

    Science.gov (United States)

    Borggrefe, Tilman; Lauth, Matthias; Zwijsen, An; Huylebroeck, Danny; Oswald, Franz; Giaimo, Benedetto Daniele

    2016-02-01

    Notch signaling is a highly conserved signal transduction pathway that regulates stem cell maintenance and differentiation in several organ systems. Upon activation, the Notch receptor is proteolytically processed, its intracellular domain (NICD) translocates into the nucleus and activates expression of target genes. Output, strength and duration of the signal are tightly regulated by post-translational modifications. Here we review the intracellular post-translational regulation of Notch that fine-tunes the outcome of the Notch response. We also describe how crosstalk with other conserved signaling pathways like the Wnt, Hedgehog, hypoxia and TGFβ/BMP pathways can affect Notch signaling output. This regulation can happen by regulation of ligand, receptor or transcription factor expression, regulation of protein stability of intracellular key components, usage of the same cofactors or coregulation of the same key target genes. Since carcinogenesis is often dependent on at least two of these pathways, a better understanding of their molecular crosstalk is pivotal.

  15. Notch1 and notch2 have opposite effects on embryonal brain tumor growth.

    Science.gov (United States)

    Fan, Xing; Mikolaenko, Irina; Elhassan, Ihab; Ni, Xingzhi; Wang, Yunyue; Ball, Douglas; Brat, Daniel J; Perry, Arie; Eberhart, Charles G

    2004-11-01

    The role of Notch signaling in tumorigenesis can vary; Notch1 acts as an oncogene in some neoplasms, and a tumor suppressor in others. Here, we show that different Notch receptors can have opposite effects in a single tumor type. Expression of truncated, constitutively active Notch1 or Notch2 in embryonal brain tumor cell lines caused antagonistic effects on tumor growth. Cell proliferation, soft agar colony formation, and xenograft growth were all promoted by Notch2 and inhibited by Notch1. We also found that Notch2 receptor transcripts are highly expressed in progenitor cell-derived brain tumors such as medulloblastomas, whereas Notch1 is scarce or undetectable. This parallels normal cerebellar development, during which Notch2 is predominantly expressed in proliferating progenitors and Notch1 in postmitotic differentiating cells. Given the oncogenic effects of Notch2, we analyzed its gene dosage in 40 embryonal brain tumors, detecting an increased copy number in 15% of cases. Notch2 gene amplification was confirmed by fluorescence in situ hybridization in one case with extremely high Notch2 mRNA levels. In addition, expression of the Notch pathway target gene Hes1 in medulloblastomas was associated with significantly shorter patient survival (P = 0.01). Finally, pharmacological inhibition of Notch signaling suppresses growth of medulloblastoma cells. Our data indicate that Notch1 and Notch2 can have opposite effects on the growth of a single tumor type, and show that Notch2 can be overexpressed after gene amplification in human tumors.

  16. PKCζ regulates Notch receptor routing and activity in a Notch signaling-dependent manner.

    Science.gov (United States)

    Sjöqvist, Marika; Antfolk, Daniel; Ferraris, Saima; Rraklli, Vilma; Haga, Cecilia; Antila, Christian; Mutvei, Anders; Imanishi, Susumu Y; Holmberg, Johan; Jin, Shaobo; Eriksson, John E; Lendahl, Urban; Sahlgren, Cecilia

    2014-04-01

    Activation of Notch signaling requires intracellular routing of the receptor, but the mechanisms controlling the distinct steps in the routing process is poorly understood. We identify PKCζ as a key regulator of Notch receptor intracellular routing. When PKCζ was inhibited in the developing chick central nervous system and in cultured myoblasts, Notch-stimulated cells were allowed to undergo differentiation. PKCζ phosphorylates membrane-tethered forms of Notch and regulates two distinct routing steps, depending on the Notch activation state. When Notch is activated, PKCζ promotes re-localization of Notch from late endosomes to the nucleus and enhances production of the Notch intracellular domain, which leads to increased Notch activity. In the non-activated state, PKCζ instead facilitates Notch receptor internalization, accompanied with increased ubiquitylation and interaction with the endosomal sorting protein Hrs. Collectively, these data identify PKCζ as a key regulator of Notch trafficking and demonstrate that distinct steps in intracellular routing are differentially modulated depending on Notch signaling status.

  17. Endosomal sorting of Notch receptors through COMMD9-dependent pathways modulates Notch signaling

    NARCIS (Netherlands)

    Li, H.; Koo, Y.; Mao, X.; Sifuentes-Dominguez, L.; Morris, L.L.; Jia, D.; Miyata, N; Faulkner, R.A.; Deursen, J.M.A. van; Vooijs, M.; Billadeau, D.D.; Sluis, B. van de; Cleaver, O.; Burstein, E.

    2015-01-01

    Notch family members are transmembrane receptors that mediate essential developmental programs. Upon ligand binding, a proteolytic event releases the intracellular domain of Notch, which translocates to the nucleus to regulate gene transcription. In addition, Notch trafficking across the endolysosom

  18. Relationship of mechanical characteristics and microstructural features to the time-dependent edge notch sensitivity of inconel 718 sheet

    Science.gov (United States)

    Wilson, D. J.

    1971-01-01

    Time-dependent notch sensitivity of Inconel 718 sheet was observed at 900 F to 1200 F (482 - 649 C). It occurred when edge-notched specimens were loaded below the yield strength and smooth specimen tests showed that small amounts of creep consumed large rupture life fractions. The severity of the notch sensitivity was reduced by decreasing the solution temperature, increasing the time and/or temperature of aging and increasing the test temperature to 1400 F (760 C). Elimination of time-dependent notch sensitivity correlated with a change in dislocation motion mechanism from shearing to by-passing precipitate particles.

  19. Notch2 and Notch3 Function Together to Regulate Vascular Smooth Muscle Development

    OpenAIRE

    Qingqing Wang; Ning Zhao; Simone Kennard; Brenda Lilly

    2012-01-01

    Notch signaling has been implicated in the regulation of smooth muscle differentiation, but the precise role of Notch receptors is ill defined. Although Notch3 receptor expression is high in smooth muscle, Notch3 mutant mice are viable and display only mild defects in vascular patterning and smooth muscle differentiation. Notch2 is also expressed in smooth muscle and Notch2 mutant mice show cardiovascular abnormalities indicative of smooth muscle defects. Together, these findings infer that N...

  20. Strengthening of old metallic structures in fatigue with prestressed and non-prestressed CFRP laminates

    DEFF Research Database (Denmark)

    Täljsten, Björn; Hansen, Christian Skodborg; Schmidt, Jacob Wittrup

    2009-01-01

    Test results and theoretical considerations on four different configurations of strengthened old steel plates with a centre notch loaded in fatigue are presented in this paper. The main interest of the research was to improve fatigue life by adhesive bonding of CFRP laminates on the steel surface...

  1. FOUR NOTCH ROADLESS AREA, TEXAS.

    Science.gov (United States)

    Houser, B.B.; Ryan, George S.

    1984-01-01

    A geologic and geochemical investigation of the Four Notch Roadless Area, Texas, was conducted. The area has a probable resource potential for oil and gas. There is, however, little promise for the occurrence of metallic mineral resources or other energy resources. Acquisition of seismic data and detailed comparisons with logs from wells from the vicinity of the Four Notch Roadless Area is necessary to better determine if the subsurface stratigraphy and structures are favorable for the accumulation of oil or gas.

  2. Titanium in fatigue critical military aircraft structure

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, F.

    1999-07-01

    This paper discusses the effect of fatigue requirements on titanium structure in military aircraft applications, specifically, fighter aircraft. The discussion covers how fatigue affects the design and analysis of detail parts, and how manufacturing processes affect the fatigue performance of titanium structure. Criteria for designing fighter aircraft have evolved from simple strength calculations to extremely complex computer generated analyses involving strength, durability, damage tolerance and fatigue. Fatigue life prediction is an important part of these analyses and dramatically affects the design and weight of fighter aircraft. Manufacturing processes affect fatigue performance both in a positive and negative manner. Designers must allow for the effect of these processes on titanium structure and consider the efficiency and economy of adding processes that increase fatigue life.

  3. Notch, lipids, and endothelial cells

    Science.gov (United States)

    Briot, Anaïs; Bouloumié, Anne; Iruela-Arispe, M. Luisa

    2017-01-01

    Purpose of review Notch signaling is an evolutionary conserved pathway critical for cardiovascular development and angiogenesis. More recently, the contribution of Notch signaling to the homeostasis of the adult vasculature has emerged as an important novel paradigm, but much remains to be understood. Recent findings Recent findings shed light on the impact of Notch in vascular and immune responses to microenvironmental signals as well as on the onset of atherosclerosis. In the past year, studies in human and mice explored the role of Notch in the maintenance of a nonactivated endothelium. Novel pieces of evidence suggest that this pathway is sensitive to environmental factors, including inflammatory mediators and diet-derived by-products. Summary An emerging theme is the ability of Notch to respond to changes in the microenvironment, including glucose and lipid metabolites. In turn, alterations in Notch enable an important link between metabolism and transcriptional changes, thus this receptor appears to function as a metabolic sensor with direct implications to gene expression. PMID:27454451

  4. 某汽车差速器齿轮的强度分析及疲劳寿命预测%A Car Differential Gear Strength Analysis and Fatigue Life Prediction

    Institute of Scientific and Technical Information of China (English)

    王良模; 刘飞; 夏汉关; 赵红军; 王小乾; 张艳伟

    2012-01-01

    运用现代设计方法进行了某汽车差速器齿轮静强度分析和疲劳寿命预测。将几何模型导入HyperMesh中,利用壳单元和实体单元划分网格,并建立合适的MPC单元以方便载荷和约束的施加。根据齿轮的对称性,建立了行星齿轮和半轴齿轮单齿的有限元模型。利用有限元分析软件ANSYS进行行星齿轮和半轴齿轮静强度分析。分析结果表明所设计的齿轮能满足强度要求。基于齿轮有限元分析结果,利用疲劳分析软件MSC.Fatigue得出行星齿轮和半轴齿轮寿命云图及最低疲劳寿命,均满足寿命要求。%Modern design method is used for a car differential gear static strength analysis and fatigue life prediction. The geometric model is imported to HyperMesh, the shell element and entity unit are used for division grid, and proper MPC unit are established for load and constraint applied. According to the gear of symmetry, planetary gear and axle side gear single tooth finite element model are established. Using finite element analysis software ANSYS, planetary gear and axle shaft gear static strength are analyzed, and the results show that the designed gears can meet the requirements. Based on gear finite element analysis results, planetary gear and axle shaft gear life nephogram and minimum fatigue life are analyzed by using fatigue analysis software MSC. Fatigue. Both gears can satisfy actual life requirement.

  5. Study on Rotation Capability and Fatigue Strength of Elliptical Flexure Spherical Hinge%椭圆型弹性球铰链转动性能及疲劳强度研究

    Institute of Scientific and Technical Information of China (English)

    李成刚; 尤晶晶; 吴洪涛

    2011-01-01

    基于卡氏第二定理,推导出椭圆型弹性球铰链柔度、精度的解析表达式.提出弹性球铰链柔度精度比的概念,并以此为性能指标对铰链的设计进行了优化.结果表明:铰链应选用弹性模量大、切变模量小的材料;在保证强度的前提下,应尽量减小椭圆广角、椭圆长短半轴之比以及铰链最小厚度与椭圆短半轴之比.指出在设计弹性铰链时不能仅追求转动性能,还需要考虑其疲劳强度,进而推导出弹性球铰链疲劳强度的校验公式.%Based on the Castigliano's second theorem, the equations were formulated for the compliance and precision of an elliptical flexure spherical hinge. A new concept of compliance accuracy ratio of flexure spherical hinge was proposed, which was used as the performance index of hinges. Optimization was done, and the results show that materials of hinges should be with high elastic modulus and low shear modulus; all of the wide-angle, the ratio of long half axis to short half axis and the ratio of the minimum thickness to short half axis of ellipse should be as little as possible on the premise of ensuring strength. A view point was proposed,that fatigue strength must also be considered except for improving performance while designing the flexure hinges, and the check formula of fatigue strength was derived.

  6. Notch1 and Notch2 receptors regulate mouse and human gastric antral epithelial cell homoeostasis.

    Science.gov (United States)

    Gifford, Gail B; Demitrack, Elise S; Keeley, Theresa M; Tam, Andrew; La Cunza, Nilsa; Dedhia, Priya H; Spence, Jason R; Simeone, Diane M; Saotome, Ichiko; Louvi, Angeliki; Siebel, Christian W; Samuelson, Linda C

    2017-06-01

    We tested the ability of Notch pathway receptors Notch1 and Notch2 to regulate stem and epithelial cell homoeostasis in mouse and human gastric antral tissue. Mice were treated with the pan-Notch inhibitor dibenzazepine (DBZ) or inhibitory antibodies targeting Notch1 and/or Notch2. Epithelial proliferation, apoptosis and cellular differentiation were measured by histological and molecular approaches. Organoids were established from mouse and human antral glands; growth and differentiation were measured after treatment with Notch inhibitors. Notch1 and Notch2 are the predominant Notch receptors expressed in mouse and human antral tissue and organoid cultures. Combined inhibition of Notch1 and Notch2 in adult mice led to decreased epithelial cell proliferation, including reduced proliferation of LGR5 stem cells, and increased apoptosis, similar to the response to global Notch inhibition with DBZ. Less pronounced effects were observed after inhibition of individual receptors. Notch pathway inhibition with DBZ or combined inhibition of Notch1 and Notch2 led to increased differentiation of all gastric antral lineages, with remodelling of cells to express secretory products normally associated with other regions of the GI tract, including intestine. Analysis of mouse and human organoids showed that Notch signalling through Notch1 and Notch2 is intrinsic to the epithelium and required for organoid growth. Notch signalling is required to maintain gastric antral stem cells. Notch1 and Notch2 are the primary Notch receptors regulating epithelial cell homoeostasis in mouse and human stomach. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  7. Fatigue of Fillet-welded Joint Assessment by the FEA Simulation of Damage Accumulation

    Directory of Open Access Journals (Sweden)

    Petinov S. V.

    2011-06-01

    Full Text Available Fatigue strength evaluation of non-continuous incomplete penetration fillet-welded joints transferring stress flow by the S-N criteria incorporating the «Hot-spot stress» or «Notch-stress» approaches is dubious since the characteristic stress at the crack initiation location is not established by the rules for fatigue design. Application of the linear fracture mechanics (LMF technique meets a problem of numerical modeling the crack three-dimensional shape and front extension, which becomes insoluble when the crack approaches the outer surface of weld bead and propagates along the seam. Apart from that, considering material plasticity beyond the initial phase of crack extensions from the cavity is off the frames of the principles of the LMF.An approach based on the FEA simulation of fatigue damage accumulation is suggested and applied to evaluate the crack initiation at the cavity and propagation in the non-continuous fillet-welded joint. The crack initiation at the cavity, its three-dimensional shape formation and evolution are simulated taking into account the elastic-plastic cyclic deformation of weld material until almost complete failure of the joint. The results of analysis are in good agreement with published experimental data.

  8. NOTCH1 and NOTCH2 regulate epithelial cell proliferation in mouse and human gastric corpus.

    Science.gov (United States)

    Demitrack, Elise S; Gifford, Gail B; Keeley, Theresa M; Horita, Nobukatsu; Todisco, Andrea; Turgeon, D Kim; Siebel, Christian W; Samuelson, Linda C

    2017-02-01

    The Notch signaling pathway is known to regulate stem cells and epithelial cell homeostasis in gastrointestinal tissues; however, Notch function in the corpus region of the stomach is poorly understood. In this study we examined the consequences of Notch inhibition and activation on cellular proliferation and differentiation and defined the specific Notch receptors functioning in the mouse and human corpus. Notch pathway activity was observed in the mouse corpus epithelium, and gene expression analysis revealed NOTCH1 and NOTCH2 to be the predominant Notch receptors in both mouse and human. Global Notch inhibition for 5 days reduced progenitor cell proliferation in the mouse corpus, as well as in organoids derived from mouse and human corpus tissue. Proliferation effects were mediated through both NOTCH1 and NOTCH2 receptors, as demonstrated by targeting each receptor alone or in combination with Notch receptor inhibitory antibodies. Analysis of differentiation by marker expression showed no change to the major cell lineages; however, there was a modest increase in the number of transitional cells coexpressing markers of mucous neck and chief cells. In contrast to reduced proliferation after pathway inhibition, Notch activation in the adult stomach resulted in increased proliferation coupled with reduced differentiation. These findings suggest that NOTCH1 and NOTCH2 signaling promotes progenitor cell proliferation in the mouse and human gastric corpus, which is consistent with previously defined roles for Notch in promoting stem and progenitor cell proliferation in the intestine and antral stomach. Here we demonstrate that the Notch signaling pathway is essential for proliferation of stem cells in the mouse and human gastric corpus. We identify NOTCH1 and NOTCH2 as the predominant Notch receptors expressed in both mouse and human corpus and show that both receptors are required for corpus stem cell proliferation. We show that chronic Notch activation in corpus stem

  9. Fatigue in Breakwater Concrete Armour Units

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    1985-01-01

    The reliability of rubble mound breakwaters depends on the hydraulic stability and the mechanical strength of the armour units. The paper deals with the important aspect of fatigue related to the strength of concrete armour units. Results showing significant fatigue from impact tests with Dolosse...... made of unreinforced and steel fibre reinforced flyash concrete are presented. Moreover universal graphs for fatigue in armour units made of conventional unreinforced concrete exposed to impact load and pulsating load are presented. The effect of fibre reinforcement and the implementation of fatigue...

  10. Subsea rigid jumper design and ⅤⅣ fatigue evaluation

    Institute of Scientific and Technical Information of China (English)

    Wang Jun

    2013-01-01

    The purpose of this paper is to present a design procedure for subsea rigid jumper system including strength and fatigue analysis.Special attention gives to a methodology based on DNV-RP-F105 to evaluate jumper fatigue damage caused by vortex induced vibration (ⅤⅣ).Jumper strength analysis is to determine the jumper configuration which can accommodate various load conditions and all possible span lengths driven by installation tolerances of connected subsea structures.Fatigue analysis includes two parts:thermal fatigue and ⅤⅣ fatigue.This paper presents the procedure of ⅤⅣ fatigue damage calculation.An example is given to illustrate above methodologies.

  11. Graded High-Strength Spring-Steels by a Special Inductive Heat T reatment

    Science.gov (United States)

    Tump, A.; Brandt, R.

    2016-03-01

    A method for effective lightweight design is the use of materials with high specific strength. As materials e.g. titanium are very expensive, steel is still the most important material for manufacturing automotive components. Steel is cost efficient, easy to recycle and its tensile strength easily exceeds 2,000 MPa by means of modern QT-technology (Quenched and Tempered). Therefore, lightweight design is still feasible in spite of the high density of steel. However, a further increase of tensile strength is limited, especially due to an increasing notch sensitivity and exposure to a corrosive environment. One solution is a special QT-process for steel, which creates a hardness gradient from the surface to the core of the material. This type of tailored material possesses a softer layer, which improves material properties such as fracture toughness and notch sensitivity. This leads to a better resistance to stress corrosion cracking and corrosion fatigue. Due to this optimization, a weight reduction is feasible without the use of expensive alloying elements. To understand the damage mechanism a comprehensive testing procedure was performed on homogeneous and gradient steels. Some results regarding the fracture mechanic behavior of such steels will be discussed.

  12. A Modified Constant-Stress Coupon for Enhanced Natural Crack Start during Fatigue Testing

    Science.gov (United States)

    2016-05-01

    UNCLASSIFIED UNCLASSIFIED A Modified Constant- Stress Coupon for Enhanced Natural Crack Start during Fatigue Testing Witold Waldman, Robert...modified constant- stress coupon for use in fatigue testing . This novel coupon design has a significantly greater surface area along the notch boundary...modified constant- stress coupon for use in fatigue testing . A constant- stress coupon is a novel design that has a significantly greater surface area along

  13. 基于焊接应力场的高强钢疲劳寿命研究%Analysis of high-strength steel fatigue based on welding stress field

    Institute of Scientific and Technical Information of China (English)

    王庆丰; 唐昌德; 郝寿军; 李永正

    2014-01-01

    运用 ANSYS APDL 语言编程,对船用高强钢 T 型试件的焊接过程进行了模拟,得到了其焊接残余应力场的分布规律。以预应力的方式将其应力场施加到结构的疲劳寿命计算过程中,得到了结构在焊接残余应力影响下的疲劳寿命。并通过与实验数据进行对比,较为直观地反映焊接残余应力对疲劳寿命的影响。%By using ANSYS APDL language,we simulated the welding process of T-joint test specimen made of ship high-strength steel. After obtaining the distribution of welding residual stress,it was used as pre-stress dur-ing the fatigue calculation. By comparing the FEM and test results,the influence of residual stress on fatigue life was visually reflected.

  14. Co-Ni超高强度钢的疲劳裂纹扩展行为与组织的关系%Relationship Between Fatigue Crack Growth Behaviour and Microstructures in Co-Ni Ultra-high Strength Steel

    Institute of Scientific and Technical Information of China (English)

    钟平; 凌斌; 王俊丽

    2001-01-01

    The relationship between fatigue crack growth behaviour and microstructures of 23NiCo steel was studied at the stress ratio R=0.1. 23NiCo steel showed slower fatigue crack growth rate than other steels with the same strength level,it is related to the characteristic of microstructures of 23NiCo steel.The absence of cementite and formation of reverted austenite at the plate boundaries tempered at 482℃ are the main factors.%研究了23NiCo钢应力比R=0.1的疲劳裂纹扩展行为与组织的关系。23NiCo钢比同一强度级钢具有较低的裂纹扩展速率的原因主要与钢的微观组织特征有关。23NiCo钢在482℃回火组织中板条边界形成薄膜状的逆转奥氏体和不存在渗碳体是主要的组织因素。

  15. An experimental study on the effects of compressive stress on the fatigue crack growth of low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D.P.; Hoppe, R.G. (Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.); Hechmer, J.L. (Babcock Wilcox Co., Barberton, OH (United States)); James, B.A. (Colorado School of Mines, Golden, CO (United States). Metallurgy Dept.)

    1994-08-01

    A series of fatigue crack growth rate tests was conducted in order to study the effects of negative stress ratio upon the fatigue crack growth rate of low-alloy steel in air environment. The tests used four-point bend specimens in order to simulate linear stress distributions typical of many pressure vessel applications. This type of testing adds to the knowledge on negative stress ratio effects for low-alloy steels that in the past have been obtained from uniform tension-compression tests. Additionally, the applied bending stress range was varied from low values of applied stress to high values of applied stress over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. The crack geometries involved were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. The results are presented in terms of the stress intensity factor ratio R = K[sub MIN]/K[sub MAX]. The negative R-ratio test results were correlated to an equation of the form da/dN = C[[delta]K/(A-R)][sup n] where A, C and n are curve-fitting parameters. It was found that the effects of negative R-ratio on the fatigue crack growth rates for even the high stress range tests could be bounded by correlating the foregoing equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.

  16. The Expression of Notch 1 and Notch 3 in Gallbladder Cancer and Their Clinicopathological Significance.

    Science.gov (United States)

    Liu, Luyao; Yang, Zhu-Lin; Wang, Chunwei; Miao, Xiongying; Liu, Zhiyu; Li, Daiqiang; Zou, Qiong; Li, Jinghe; Liang, Lufeng; Zeng, Guixiang; Chen, Senlin

    2016-07-01

    Gallbladder cancers (GBCs) are highly malignant gastrointestinal cancers. The biological makers for the prognosis and targeting therapy of GBCs have not been established. The protein expression of Notch 1 and Notch 3 in 46 squamous cell/adenosquamous carcinomas (SC/ASCs) and 80 adenocarcinomas (AC) was measured using immunohistochemistry. Positive Notch 1 and Notch 3 expression in both SC/ASC and AC was significantly associated with large tumor size, invasion, metastasis, and low surgical curability (P Notch 1 and Notch 3 expression was significantly associated with mean survival of SC/ASC and AC patients (P Notch 1 and Notch 3 expression, as well as low differentiation, large tumor size, high TNM stage, invasion, lymph node metastasis, and surgical curability are independent poor-prognostic factors in both SC/ASC and AC patients. Positive Notch 1 and Notch 3 expression is closely correlated with severe clinicopathological characteristics and poor prognosis in both SC/ASC and AC patients.

  17. Increasing Fatigue Lives of Laser-Cut Parts

    Science.gov (United States)

    Glick, Edward W.; Donovan, Michael H.

    1987-01-01

    Cut edges sanded to restore strength. Simple abrasion process removes transverse striations resulting from laser cutting of inconel 718 or equivalent alloy, increasing fatigue strengths of parts cut by laser beams. For stresses in range of 80 to 130 ksi (550 to 900 MPa) high cycle fatigue strengths restored to levels comparable to conventionally machined parts.

  18. Notch Signaling and Brain Tumors

    DEFF Research Database (Denmark)

    Stockhausen, Marie; Kristoffersen, Karina; Poulsen, Hans Skovgaard

    2011-01-01

    Human brain tumors are a heterogenous group of neoplasms occurring inside the cranium and the central spinal cord. In adults and children, astrocytic glioma and medulloblastoma are the most common subtypes of primary brain tumors. These tumor types are thought to arise from cells in which Notch...... signaling plays a fundamental role during development. Recent findings have shown that Notch signaling is dysregulated, and contributes to the malignant potential of these tumors. Growing evidence point towards an important role for cancer stem cells in the initiation and maintenance of glioma...

  19. Fatigue behavior of thin-walled grade 2 titanium samples processed by selective laser melting. Application to life prediction of porous titanium implants.

    Science.gov (United States)

    Lipinski, P; Barbas, A; Bonnet, A-S

    2013-12-01

    Because of its biocompatibility and high mechanical properties, the commercially pure grade 2 titanium (CPG2Ti) is largely used for fabrication of patient specific implants or hard tissue substitutes with complex shape. To avoid the stress-shielding and help their colonization by bone, prostheses with a controlled porosity are designed. The selective laser melting (SLM) is well adapted to manufacture such geometrically complicated structures constituted by struts with rough surfaces and relatively small diameters. Few studies were dedicated to characterize the fatigue properties of SLM processed samples and bulk parts. They followed conventional or standard protocols. The fatigue behavior of standard samples is very different from the one of porous raw structures. In this study, the SLM made "as built" (AB) and "heat treated" (HT) tubular samples were tested in fatigue. Wöhler curves were determined in both cases. The obtained endurance limits were equal to σD(AB)=74.5MPa and σD(HT)=65.7MPa, respectively. The heat treatment worsened the endurance limit by relaxation of negative residual stresses measured on the external surface of the samples. Modified Goodman diagram was established for raw specimens. Porous samples, based on the pattern developed by Barbas et al. (2012), were manufactured by SLM. Fatigue tests and finite element simulations performed on these samples enabled the determination of a simple rule of fatigue assessment. The method based on the stress gradient appeared as the best approach to take into account the notch influence on the fatigue life of CPG2Ti structures with a controlled porosity. The direction dependent apparent fatigue strength was found. A criterion based on the effective, or global, nominal stress was proposed taking into account the anisotropy of the porous structures. Thanks to this criterion, the usual calculation methods can be used to design bone substitutes, without a precise modelling of their internal fine porosity.

  20. Empirical formulas for description of the fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Rozumek, D. [Opole University of Technology, Faculty of Mechanical Engineering, Opole (Poland)

    2010-02-15

    The paper presents the test results obtained for fatigue crack growth in flat specimens subjected to bending. The tests were conducted for different loading amplitudes and different load ratios using the {delta}J parameter. Accuracy of description of the fatigue crack growth rate was tested with use of different empirical formulas. One-side restrained specimens made of 10HNAP steel were tested. In each tested specimen, there was the external notch 5 mm in depth, and the notch rounding radius was {rho}=0.2 mm. The tests were carried out at the fatigue test stand MZGS-100 under loading frequency 28.8 Hz. It has been found that the obtained results depend on the applied empirical formula. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  1. Eddy current monitoring of fatigue crack growth in Zr-2.5% Nb pressure tube

    Science.gov (United States)

    Krause, T. W.; Martin, A. E.; Sheppard, R. R.; Schankula, J. J.

    2000-05-01

    Zr-2.5% wt. Nb pressure tubes (PTs) form the core of the heat transport system in CANDU nuclear reactors. These 6 m long, 100 mm diameter tubes are operated at elevated temperatures (nominally 300 °C) and at pressures that produce hoop stresses that are 25% of the ultimate tensile strength of the PT (120 Mpa). Therefore, detection and characterization of flaws in these components becomes crucial for their continued pressure retaining integrity. If a flaw is detected, however, the cost of PT replacement is expensive. Periodic in-service inspection of a flaw that demonstrates no change in flaw characteristics can be used to allow a pressure tube to remain in-service. This requires confidence in the accuracy and reliability of methods used to inter flaw characteristics. Such confidence can only be developed by comparing nondestructive predictions with results from destructive examinations. In this work, eddy current testing was used to monitor the progressive stages of a fatigue crack, grown through pressure cycling from a notch on the inner surface of a PT. Results from a differential lift-off compensated eddy current probe were used to produce sizing estimates of the crack grown between 35% (base of notch) and 74% of the PT wall. A comparison with a destructive examination of the crack demonstrated sensitivity too changes in crack depth accurate to 5% of the tube wall thickness. Such results, combined with similar information obtained from ultrasonics will increase confidence in interpretation of PT inspection data.

  2. A Weakest-Link Approach for Fatigue Limit of 30CrNiMo8 Steels (Preprint)

    Science.gov (United States)

    2011-03-01

    used to predict the fatigue limit of notched and multiaxially loaded specimens of carburized steel [7]. The model was shown to be effective in... Carburized Steel 16mncrs5," Fatigue and Fracture of Engineering Materials and Structures, 28, pp. 983-995. [8] Bomas, H., Linkewitz, T., and Mayr, P., 1999

  3. Fatigue (PDQ)

    Science.gov (United States)

    ... of daily living . Better quality of life . More satisfaction with life. A greater sense of well-being. ... and decrease fatigue. The importance of eating enough food and drinking enough fluids. Physical therapy for patients ...

  4. Notch Signaling in Bone Regeneration

    Science.gov (United States)

    2011-10-01

    Notch delivery, a large animal model (e.g., sheep ) could be developed and tested in another 2 years. Within five years, we will have a product to...phenotype ( macrophage , endothelial cell, osteoblast, chondrocyte) using dual antibody labeling with antibodies for specific cell types. Additionally, we

  5. Notch Signaling and Brain Tumors

    DEFF Research Database (Denmark)

    Stockhausen, Marie; Kristoffersen, Karina; Poulsen, Hans Skovgaard

    2011-01-01

    Human brain tumors are a heterogenous group of neoplasms occurring inside the cranium and the central spinal cord. In adults and children, astrocytic glioma and medulloblastoma are the most common subtypes of primary brain tumors. These tumor types are thought to arise from cells in which Notch...

  6. Notch Signaling and Brain Tumors

    DEFF Research Database (Denmark)

    Stockhausen, Marie; Kristoffersen, Karina; Poulsen, Hans Skovgaard

    2011-01-01

    Human brain tumors are a heterogenous group of neoplasms occurring inside the cranium and the central spinal cord. In adults and children, astrocytic glioma and medulloblastoma are the most common subtypes of primary brain tumors. These tumor types are thought to arise from cells in which Notch...

  7. Effect of δ Phase on Hydrogen Embrittlement of Inconel 718 by Notch Tensile Tests

    Institute of Scientific and Technical Information of China (English)

    Liufa LIU; Chen LU; Wenjiang DING; Akio Hirose; Kojiro F.Kobayashi

    2005-01-01

    The effect of δ phase on the hydrogen embrittlement (HE) sensitivity of Inconel 718 was investigated by conducting notch tensile tests. Notch tensile specimens with various precipitation morphologies of δ phase were prepared with different heat treatments, and hydrogen was charged into the tensile specimens before tensile tests via a cathodic charging process. The loss of notch tensile strength (NTS) due to the charged hydrogen was used to evaluate the hydrogen embrittlement sensitivity. The results show that δ phase has deleterious effect on NTSs, and the fracture of hydrogen-charged specimens initiated near the notch surfaces. The loss of NTS caused by precharged hydrogen can be greatly decreased by dissolving δ phase. δ-free Inconel 718 alloy is proposed for the applications in hydrogen environments.

  8. Quantification of fatigue crack propagation of an austenitic stainless steel in mercury embrittlement

    Science.gov (United States)

    Naoe, Takashi; Yamaguchi, Yoshihito; Futakawa, Masatoshi

    2012-12-01

    Liquid metals are expected to be used as nuclear materials, such as coolant for nuclear reactors and spallation targets for neutron sources, because of their good thermal conductivity and neutron production. However, in specific combinations, liquid metals have the potential to degrade structural integrity of solid metals because of Liquid Metal Embrittlement (LME). In this study, the effect of mercury immersion on fatigue crack propagation rate in SUS316 was investigated through fatigue tests with a notched specimen under mercury immersion. FRActure Surface Topography Analysis (FRASTA) with the measurement of the notch opening distance was performed to estimate the fatigue crack growth rate in mercury. The results showed that the fatigue crack growth rate was slightly higher in mercury than that in the air in the low cycle fatigue region. This suggests that the crack propagation is accelerated by mercury immersion in high stress imposition regions.

  9. Anabolic actions of Notch on mature bone

    Science.gov (United States)

    Liu, Peng; Ping, Yilin; Ma, Meng; Zhang, Demao; Liu, Connie; Zaidi, Samir; Gao, Song; Ji, Yaoting; Lou, Feng; Yu, Fanyuan; Lu, Ping; Stachnik, Agnes; Bai, Mingru; Wei, Chengguo; Zhang, Liaoran; Wang, Ke; Chen, Rong; New, Maria I.; Rowe, David W.; Yuen, Tony; Sun, Li; Zaidi, Mone

    2016-01-01

    Notch controls skeletogenesis, but its role in the remodeling of adult bone remains conflicting. In mature mice, the skeleton can become osteopenic or osteosclerotic depending on the time point at which Notch is activated or inactivated. Using adult EGFP reporter mice, we find that Notch expression is localized to osteocytes embedded within bone matrix. Conditional activation of Notch signaling in osteocytes triggers profound bone formation, mainly due to increased mineralization, which rescues both age-associated and ovariectomy-induced bone loss and promotes bone healing following osteotomy. In parallel, mice rendered haploinsufficient in γ-secretase presenilin-1 (Psen1), which inhibits downstream Notch activation, display almost-absent terminal osteoblast differentiation. Consistent with this finding, pharmacologic or genetic disruption of Notch or its ligand Jagged1 inhibits mineralization. We suggest that stimulation of Notch signaling in osteocytes initiates a profound, therapeutically relevant, anabolic response. PMID:27036007

  10. NOTCH pathway inactivation promotes bladder cancer progression.

    Science.gov (United States)

    Maraver, Antonio; Fernandez-Marcos, Pablo J; Cash, Timothy P; Mendez-Pertuz, Marinela; Dueñas, Marta; Maietta, Paolo; Martinelli, Paola; Muñoz-Martin, Maribel; Martínez-Fernández, Mónica; Cañamero, Marta; Roncador, Giovanna; Martinez-Torrecuadrada, Jorge L; Grivas, Dimitrios; de la Pompa, Jose Luis; Valencia, Alfonso; Paramio, Jesús M; Real, Francisco X; Serrano, Manuel

    2015-02-01

    NOTCH signaling suppresses tumor growth and proliferation in several types of stratified epithelia. Here, we show that missense mutations in NOTCH1 and NOTCH2 found in human bladder cancers result in loss of function. In murine models, genetic ablation of the NOTCH pathway accelerated bladder tumorigenesis and promoted the formation of squamous cell carcinomas, with areas of mesenchymal features. Using bladder cancer cells, we determined that the NOTCH pathway stabilizes the epithelial phenotype through its effector HES1 and, consequently, loss of NOTCH activity favors the process of epithelial-mesenchymal transition. Evaluation of human bladder cancer samples revealed that tumors with low levels of HES1 present mesenchymal features and are more aggressive. Together, our results indicate that NOTCH serves as a tumor suppressor in the bladder and that loss of this pathway promotes mesenchymal and invasive features.

  11. Experimental Study of Stress Ratio to Fatigue Life of Steel Fiber Reinforced High-Strength Concrete Beams%应力比对钢纤维高强混凝土梁疲劳寿命影响的试验研究

    Institute of Scientific and Technical Information of China (English)

    李书群; 姬宏奎; 杨松

    2016-01-01

    通过对钢纤维钢筋高强混凝土梁不同应力比的弯曲疲劳荷载试验,研究了试件的疲劳寿命及疲劳强度。根据不同应力比作用下梁试件的疲劳寿命 N ,得出本次试件梁的 S - N 曲线,裂缝开展规律。应用 Miner 理论和科尔顿-多兰(Corten -Dolan)公式进行疲劳损伤计算、疲劳寿命分析及预测,最后采用断裂力学理论分析裂缝开展规律以预测疲劳寿命,并提出裂缝开展宽度计算公式。%Through the fatigue tests of steel fiber reinforced high strength concrete beams ,the impacts to the fatigue strength and fatigue life caused by the stress ratio was analized .Based on the fatigue life N under different stress ratios , this paper acquired the S -N curve of the beams .Miner theory and Colton - Dolan formula were used for fatigue damage calculation ,fatigue life analysis and prediction .Additionally the crack expanding law was carried out by the theory of fracture mechanics in order to predict the fatigue life and propose the crack width calculation formula .

  12. FATIGUE LIFE PREDICTION THEORY OF COMPOSITE LAMINATES AND EXPERIMENTAL VERIFICATION

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to traditional phenomenological fatigue methodology and modern continuum damage mechanics theory, dual fatigue cumulative damage rules to predict fatigue damage formation and propagation lives of the notched composite laminates are presented.A 3-dimensional damage constitutive equation of anisotropic composites is also established.Damage strain energy release rate is interpreted as a driving force of the fatigue delamination damage propagation.A new damage evolution equation and a damage propagation (a-(m-N( surface (stress amplitude-mean stress-life surface) are derived.Hence, using the method above, the fatigue life of composite components can be predicted.Finally, theoretically predicted results are compared with experimental data.It is found that the deviation of theoretic prediction from experimental results is about 22%.

  13. Combined deficiency of Notch1 and Notch3 causes pericyte dysfunction, models CADASIL, and results in arteriovenous malformations

    OpenAIRE

    Kofler, Natalie M.; Henar Cuervo; Uh, Minji K.; Aino Murtomäki; Jan Kitajewski

    2015-01-01

    Pericytes regulate vessel stability and pericyte dysfunction contributes to retinopathies, stroke, and cancer. Here we define Notch as a key regulator of pericyte function during angiogenesis. In Notch1 +/−; Notch3 −/− mice, combined deficiency of Notch1 and Notch3 altered pericyte interaction with the endothelium and reduced pericyte coverage of the retinal vasculature. Notch1 and Notch3 were shown to cooperate to promote proper vascular basement membrane formation and contribute to endothel...

  14. Effect of the Machining Processes on Low Cycle Fatigue Behavior of a Powder Metallurgy Disk

    Science.gov (United States)

    Telesman, J.; Kantzos, P.; Gabb, T. P.; Ghosn, L. J.

    2010-01-01

    A study has been performed to investigate the effect of various machining processes on fatigue life of configured low cycle fatigue specimens machined out of a NASA developed LSHR P/M nickel based disk alloy. Two types of configured specimen geometries were employed in the study. To evaluate a broach machining processes a double notch geometry was used with both notches machined using broach tooling. EDM machined notched specimens of the same configuration were tested for comparison purposes. Honing finishing process was evaluated by using a center hole specimen geometry. Comparison testing was again done using EDM machined specimens of the same geometry. The effect of these machining processes on the resulting surface roughness, residual stress distribution and microstructural damage were characterized and used in attempt to explain the low cycle fatigue results.

  15. Notching on Cancer’s Door: Notch Signaling in Brain Tumors

    OpenAIRE

    2015-01-01

    Notch receptors play an essential role in the regulation of central cellular processes during embryonic and postnatal development. The mammalian genome encodes for four Notch paralogs (Notch 1–4), which are activated by three Delta-like (Dll1/3/4) and two Serrate-like (Jagged1/2) ligands. Further, non-canonical Notch ligands such as epidermal growth factor like protein 7 (EGFL7) have been identified and serve mostly as antagonists of Notch signaling. The Notch pathway prevents neuronal differ...

  16. INVESTIGATION OF FRACTURE DESIGN FOR MEDIUM CARBON STEEL UNDER EXTRA-LOW CYCLIC FATIGUE IN AXIAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Youtang Li; Shuai Tan; Hongyan Duan

    2008-01-01

    The extra-low cyclic fracture problem of medium carbon steel under axial fatigue loading was investigated.Several problems,such as the relations of the cycle times to the depth and tip radius of the notch,loading frequency,loading range and the parameters of fracture design for medium carbon steel on condition of extra-low axial fatigue loading were discussed based on the experiments.Experimental results indicated that the tension-pressure fatigue loading mode was suitable for extra-low cyclic fatigue fracture design of medium carbon steel and it resulted in low energy consumption,fracture surface with high quality,low cycle times,and high efficiency.The appropriate parameters were as follows:loading frequency 3-5 Hz,notch tip radius r=(0.2-0.3)mm,opening angle α=60°,and notch depth t=(0.14-0.17)D.

  17. [Auditory fatigue].

    Science.gov (United States)

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

    Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.

  18. Chronic Fatigue Syndrome

    Science.gov (United States)

    Chronic fatigue syndrome (CFS) is a disorder that causes extreme fatigue. This fatigue is not the kind of tired feeling that ... activities. The main symptom of CFS is severe fatigue that lasts for 6 months or more. You ...

  19. Time-dependent edge notch sensitivity of Inconel 718 sheet in the temperature range 900 to 1400 F (482 to 760 C)

    Science.gov (United States)

    Wilson, D. J.

    1972-01-01

    Time-dependent notch sensitivity of Inconel 718 sheet occurred at 900 to 1200 F when notched specimens were loaded below the yield strength, and tests on smooth specimens showed that small amounts of creep consumed large fractions of creep-rupture life. The severity of the notch sensitivity decreased with decreasing solution treatment temperature and increasing time and/or temperature of the aging treatment. Elimination of the notch sensitivity was correlated with a change in the dislocation mechanism from shearing to by-passing precipitate particles.

  20. 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...

  1. Strength of Rewelded Inconel 718

    Science.gov (United States)

    Bayless, E.; Lovoy, C. V.; Mcllwain, M. C.; Munafo, P.

    1982-01-01

    Inconel 718, nickel-based alloy used extensively for high-temperature structural service, welded repeatedly without detriment to its strength. According to NASA report, tests show 12 repairs on same weld joint do not adversely affect ultimate tensile strenth, yield strength, fatigue strength, metallurgical grain structures, or ability of weld joint to respond to post weld heat treatments.

  2. Transforming the nature of fatigue through exercise

    DEFF Research Database (Denmark)

    Adamsen, L; Midtgaard, J; Andersen, C

    2004-01-01

    The objective of this study was to explore the nature of fatigue in cancer patients with advanced stages of disease undergoing chemotherapy and concurrently participating in a 6-week multidimensional exercise programme (physical exercise, relaxation, massage and body-awareness training). Semi...... the patients experienced exercise-induced fatigue, which they associated with a sense of increased physical strength, improvement in energy and physical well-being. This positive sense of fatigue can be seen as a contrast to the negative chemotherapy-induced fatigue, which is characterized by physical...

  3. DELAMINATION FORMATION AND DELAMINATION PROPAGATION OF COMPOSITE LAMINATES UNDER COMPRESSIVE FATIGUE LOADING

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Fatigue tests of the smooth composite laminates and the notched composite laminates under compressive cyclic loading have been carried out. The damage mechanism is discussed and analyzed. Damage evolution is monitored using stiffness decay. From these tests, it is found that the initial delamination occurs at the free boundary of smooth specimens, or the notch boundary of notched specimens, subjected to the compression-compression cyclic load. A point of view in relation to two-phases of compression fatigue delamination of composites is proposed, namely, compression-compression delamination consists of the delamination formation phase and the delamination propagation, and there is a "damage transition point" to separate this two-phases. Furthermore, an empirical modulus degradation formula and its parameters fitting method are presented. According to the test data handling results, it is shown that this formula is univocal and can fit the test data conveniently. In addition, two kinds of new anti-buckling devices are designed for these tests. At last, the E-N curves, the D-N curves and the S-N curve of the smooth carbon fiber reinforced composite laminates of T300/648C are determined to predict the fatigue life of the notched composite laminate. And the E-N curve of the notched specimens at the given load ratio R=10 and minimum load P min=-0.45 kN is also measured to verify the estimated result of fatigue life.

  4. Quantification of fatigue crack propagation of an austenitic stainless steel in mercury embrittlement

    Energy Technology Data Exchange (ETDEWEB)

    Naoe, Takashi, E-mail: naoe.takashi@jaea.go.jp [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Yamaguchi, Yoshihito [Nucelar Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Futakawa, Masatoshi [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The effect of mercury immersion on fatigue crack propagation rate in SUS316 was investigated through fatigue tests. Black-Right-Pointing-Pointer Fatigue crack growth rate in mercury was estimated by the FRActure Surface Topography Analysis (FRASTA). Black-Right-Pointing-Pointer The fatigue crack growth rate was slightly higher in mercury than that in the air in the low cycle fatigue region. Black-Right-Pointing-Pointer This suggests that the crack propagation is accelerated by mercury immersion in high stress imposition regions. - Abstract: Liquid metals are expected to be used as nuclear materials, such as coolant for nuclear reactors and spallation targets for neutron sources, because of their good thermal conductivity and neutron production. However, in specific combinations, liquid metals have the potential to degrade structural integrity of solid metals because of Liquid Metal Embrittlement (LME). In this study, the effect of mercury immersion on fatigue crack propagation rate in SUS316 was investigated through fatigue tests with a notched specimen under mercury immersion. FRActure Surface Topography Analysis (FRASTA) with the measurement of the notch opening distance was performed to estimate the fatigue crack growth rate in mercury. The results showed that the fatigue crack growth rate was slightly higher in mercury than that in the air in the low cycle fatigue region. This suggests that the crack propagation is accelerated by mercury immersion in high stress imposition regions.

  5. Notch Signaling Inhibits Axon Regeneration

    OpenAIRE

    Bejjani, Rachid El; Hammarlund, Marc

    2012-01-01

    Many neurons have limited capacity to regenerate their axons after injury. Neurons in the mammalian CNS do not regenerate, and even neurons in the PNS often fail to regenerate to their former targets. This failure is likely due in part to pathways that actively restrict regeneration; however, only a few factors that limit regeneration are known. Here, using single-neuron analysis of regeneration in vivo, we show that Notch/lin-12 signaling inhibits the regeneration of mature C. elegans neuron...

  6. Inclined defects and their effect on the fatigue limit and small crack growth

    Directory of Open Access Journals (Sweden)

    Roiko Andrew

    2014-06-01

    Full Text Available Small FIB (Focused Ion Beam milled notches were introduced in quenched and tempered 34CrNiMo6 steel to monitor initiation and growth of cracks in situ. The effect of the defects on the fatigue limit is discussed in terms of the √area model. Notches with projected √area of 30 to 56 μm normal to the applied stress were inclined by 0, 45, and 60 degrees. The effect of size and inclination on the small crack growth as well as the fatigue limit is discussed.

  7. HIGH CYCLE FATIGUE PROPERTIES OF NICKEL-BASE ALLOY 718

    Institute of Scientific and Technical Information of China (English)

    K.Kobayashi; K.Yamaguchi; M.Hayakawa; M.Kimura

    2004-01-01

    The fatigue properties of nickel-base Alloy 718 with fine- and grain-coarse grains were investigated. In the fine-grain alloy, the fatigue strength normalized by the tensile strengtn was 0.51 at 107 cycles. In contrast, the fatigue strength of the coarse-grain alloy was 0.32 at the same cycles, although the fatigue strengths in the range from 103to 105 cycles are the same for both alloys. The fracture appearances fatigued at around 106 cycles showed internal fractures originating from the flat facets of austenite grains for both alloys. The difference in fatigue strength at 107 cycles between the fine- and coarse-grain alloys could be explained in terms of the sizes of the facets from which the fractures originated.

  8. High cycle fatigue characteristics of 2124-T851 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    LI Xue; YIN Zhimin; NIE Bo; ZHONG Li; PAN Qinglin; JIANG Feng

    2007-01-01

    The fatigue crack growth rate, fracture toughness and fatigue S-N curve of 2124-T851 aluminum alloy at high cycle fatigue condition were measured and fatigue fracture process and fractography were studied using optical microscopy (OM), X-ray diffraction (XRD) technique, trans-mission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that at room tempera-ture and R = 0.1 conditions, the characteristics of fatigue fracture could be observed. Under those conditions, the fatigue strength and the fracture toughness of a 2124-T851 thick plate is 243 MPa and 29.64 MPa·m1/2,respectively.At high cycle fatigue condition, the higher the stress amplitude,the wider the space between fatigue striations, the faster the rate of fatigue crack developing and going into the intermittent fracture area, and the greater the ratio between the intermittent fracture area and the whole fracture area.

  9. The archetypal R90C CADASIL-NOTCH3 mutation retains NOTCH3 function in vivo.

    Science.gov (United States)

    Monet, Marie; Domenga, Valérie; Lemaire, Barbara; Souilhol, Céline; Langa, Francina; Babinet, Charles; Gridley, Thomas; Tournier-Lasserve, Elisabeth; Cohen-Tannoudji, Michel; Joutel, Anne

    2007-04-15

    Cerebral Autosomal Dominant Arteriopathy with Subcortical infarcts and Leukoencephalopathy (CADASIL) is the most prominent known cause of inherited stroke and vascular dementia in human adult. The disease gene, NOTCH3, encodes a transmembrane receptor primarily expressed in arterial smooth muscle cells (SMC). Pathogenic mutations lead to an odd number of cysteine residues within the NOTCH3 extracellular domain (NOTCH3(ECD)), and are associated with progressive accumulation of NOTCH3(ECD) at the SMC plasma membrane. The murine homolog, Notch3, is dispensable for viability but required post-natally for the elaboration and maintenance of arteries. How CADASIL-associated mutations impact NOTCH3 function remains a fundamental, yet unresolved issue. Particularly, whether NOTCH3(ECD) accumulation may titrate the ligand and inhibit the normal pathway is unknown. Herein, using genetic analyses in the mouse, we assessed the functional significance of an archetypal CADASIL-associated mutation (R90C), in vivo, in brain arteries. We show that transgenic mouse lines expressing either the wild-type human NOTCH3 or the mutant R90C human NOTCH3, at comparable and physiological levels, can rescue the arterial defects of Notch3-/- mice to similar degrees. In vivo assessment of NOTCH3/RBP-Jk activity provides evidence that the mutant NOTCH3 protein exhibits normal level of activity in brain arteries. Remarkably, the mutant NOTCH3 protein remains functional and does not exhibit dominant negative interfering activity, even when NOTCH3(ECD) accumulates. Collectively, these data suggest a model that invokes novel pathogenic roles for the mutant NOTCH3 protein rather than compromised NOTCH3 function as the primary determinant of the CADASIL arteriopathy.

  10. Assessment of correlation between knee notch width index and the three-dimensional notch volume

    NARCIS (Netherlands)

    van Eck, C.F.; Martins, C.A.Q.; Lorenz, S.G.F.; Fu, F.H.; Smolinski, P.

    2010-01-01

    This study was done to determine whether there is a correlation between the notch volume and the notch width index (NWI) as measured on the three most frequently used radiographic views: the Holmblad 45A degrees, Holmblad 70A degrees, and Rosenberg view. The notch volume of 20 cadaveric knees was me

  11. Involvement of notch signaling in wound healing.

    Directory of Open Access Journals (Sweden)

    Srinivasulu Chigurupati

    Full Text Available The Notch signaling pathway is critically involved in cell fate decisions during development of many tissues and organs. In the present study we employed in vivo and cell culture models to elucidate the role of Notch signaling in wound healing. The healing of full-thickness dermal wounds was significantly delayed in Notch antisense transgenic mice and in normal mice treated with gamma-secretase inhibitors that block proteolytic cleavage and activation of Notch. In contrast, mice treated with a Notch ligand Jagged peptide showed significantly enhanced wound healing compared to controls. Activation or inhibition of Notch signaling altered the behaviors of cultured vascular endothelial cells, keratinocytes and fibroblasts in a scratch wound healing model in ways consistent with roles for Notch signaling in wound healing functions all three cell types. These results suggest that Notch signaling plays important roles in wound healing and tissue repair, and that targeting the Notch pathway might provide a novel strategy for treatment of wounds and for modulation of angiogenesis in other pathological conditions.

  12. Notch Signaling Enhances Nestin Expression in Gliomas

    Directory of Open Access Journals (Sweden)

    Alan H. Shih

    2006-12-01

    Full Text Available Recent findings suggest that Notch signaling is active in brain tumors and stem cells, and that stem cells or cells with progenitor characteristics contribute to brain tumor formation. These stem cells are marked by expression of several markers, including nestin, an intermediate filament protein. We have studied how the Notch signaling pathway affects nestin expression in brain tumors. We find that Notch receptors and ligands are expressed in vitro and in human samples of glioblastomas, the highest grade of malignant gliomas. In culture, Notch activity activates the nestin promoter. Activation of the Notch pathway also occurs in a glioblastoma multiforme mouse model induced by Kras, with translational regulation playing a role in Notch expression. Combined activation of Notch and Kras in wild-type nestin-expressing cells leads to their expansion within the subventricular zone and retention of proliferation and nestin expression. However, activation of Notch alone is unable to induce this cellular expansion. These data suggest that Notch may have a contributing role in the stem-like character of glioma cells.

  13. Zebrafish phenotypic screen identifies novel Notch antagonists.

    Science.gov (United States)

    Velaithan, Vithya; Okuda, Kazuhide Shaun; Ng, Mei Fong; Samat, Norazwana; Leong, Sze Wei; Faudzi, Siti Munirah Mohd; Abas, Faridah; Shaari, Khozirah; Cheong, Sok Ching; Tan, Pei Jean; Patel, Vyomesh

    2017-04-01

    Zebrafish represents a powerful in vivo model for phenotype-based drug discovery to identify clinically relevant small molecules. By utilizing this model, we evaluated natural product derived compounds that could potentially modulate Notch signaling that is important in both zebrafish embryogenesis and pathogenic in human cancers. A total of 234 compounds were screened using zebrafish embryos and 3 were identified to be conferring phenotypic alterations similar to embryos treated with known Notch inhibitors. Subsequent secondary screens using HEK293T cells overexpressing truncated Notch1 (HEK293TΔE) identified 2 compounds, EDD3 and 3H4MB, to be potential Notch antagonists. Both compounds reduced protein expression of NOTCH1, Notch intracellular domain (NICD) and hairy and enhancer of split-1 (HES1) in HEK293TΔE and downregulated Notch target genes. Importantly, EDD3 treatment of human oral cancer cell lines demonstrated reduction of Notch target proteins and genes. EDD3 also inhibited proliferation and induced G0/G1 cell cycle arrest of ORL-150 cells through inducing p27(KIP1). Our data demonstrates the utility of the zebrafish phenotypic screen and identifying EDD3 as a promising Notch antagonist for further development as a novel therapeutic agent.

  14. 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...

  15. Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo

    NARCIS (Netherlands)

    Garcia-Godoy, F.; Frankenberger, R.; Lohbauer, U.; Feilzer, A.J.; Krämer, N.

    2012-01-01

    Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural

  16. Fatigue Technology Assessment and Strategies for Fatigue Avoidance in Marine Structures

    Science.gov (United States)

    1992-06-01

    Endurance, cycles Figure 9-4 Comparison of Fatigue Strength Improvement Techniques (From Reference 9.7) I- CA a :, ., a , a MS M w a us 4-4 4. 4.1 4- M...1991 SSC-365 Marine Structural Integrity Programs ( MSIP ) by Robert G. Bea 1992 SSC-366 Threshold Corrosion Fatigue of Welded Shipbuilding Steels by G

  17. Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo

    NARCIS (Netherlands)

    F. Garcia-Godoy; R. Frankenberger; U. Lohbauer; A.J. Feilzer; N. Krämer

    2012-01-01

    Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural str

  18. FATIGUE PROPERTIES OF SPRING REINFORCES POLYMER GEARS

    Directory of Open Access Journals (Sweden)

    Hilal CAN

    2005-03-01

    Full Text Available Failure of gears, occur surface pressure stress and fracture at base of teeth. For steel gears, it is known that process of carburizing increases fatigue strength. Internal stress on the surface increases of fracture fatigue strength. In this study fatigue properties of polypropylene gear reinforced with 1.2 mm wire diameter metallic springs was investigated. Extension springs were used as reinforcement element and placed into the mould and stretched before injection of polypropylene material into the mould. After injection of polypropylene, stretched springs were loosened in order to obtain pre-stressing. Fatigue tests were performed on the produced gear. Reinforcement increased the strength of gears. At result of experiments, pre-stressing increase in service life 12 times more than that of specimens without reinforcement.

  19. Upregulation of Notch pathway molecules in oral squamous cell carcinoma

    OpenAIRE

    2010-01-01

    The constitutive activation of the Notch pathway has been demonstrated in various types of malignancies. However, it remains unclear how the Notch pathway is involved in the pathogenesis of oral squamous cell carcinoma (OSCC). We investigated the expression of Notch pathway molecules in OSCC cell lines and biopsy specimens and examined the effect of Notch pathway inhibition. Reverse transcription-polymerase chain reaction revealed upregulation of Notch1, Notch2, Jagged1, HES1 and HEY1 in both...

  20. Fatigue 󈨛. Volume 1,

    Science.gov (United States)

    1987-06-01

    5] in their studies on HY80 steel . For a long crack, the value of AK., deter~ined using a careful wind-down sequence, at R = 0.35, wast4.6 MPam . In...with a value of AK = 4.8 MPam obtained by James and Knott [5] for HY80 steel quenched and tempered to similar yield strength, and R = 0.2. In the latter...of Fatigue-Crack Nucleation 53 in a Low-Alloy Steel under Fretting Conditions - J. BEARD AND P.F. THOMASON The Effects of Thin Anodic Films on the 63

  1. Fatigue Crack Growth Analysis Under Spectrum Loading in Various Environmental Conditions

    Science.gov (United States)

    Mikheevskiy, S.; Glinka, G.; Lee, E.

    2013-03-01

    The fatigue process consists, from the engineering point of view, of three stages: crack initiation, fatigue crack growth, and the final failure. It is also known that the fatigue process near notches and cracks is governed by local strains and stresses in the regions of maximum stress and strain concentrations. Therefore, the fatigue crack growth can be considered as a process of successive crack increments, and the fatigue crack initiation and subsequent growth can be modeled as one repetitive process. The assumptions mentioned above were used to derive a fatigue crack growth model based, called later as the UniGrow model, on the analysis of cyclic elastic-plastic stresses-strains near the crack tip. The fatigue crack growth rate was determined by simulating the cyclic stress-strain response in the material volume adjacent to the crack tip and calculating the accumulated fatigue damage in a manner similar to fatigue analysis of stationary notches. The fatigue crack growth driving force was derived on the basis of the stress and strain history at the crack tip and the Smith-Watson-Topper (SWT) fatigue damage parameter, D = σmaxΔɛ/2. It was subsequently found that the fatigue crack growth was controlled by a two-parameter driving force in the form of a weighted product of the stress intensity range and the maximum stress intensity factor, Δ K p K {max/1- p }. The effect of the internal (residual) stress induced by the reversed cyclic plasticity has been accounted for and therefore the two-parameter driving force made it possible to predict the effect of the mean stress including the influence of the applied compressive stress, tensile overloads, and variable amplitude spectrum loading. It allows estimating the fatigue life under variable amplitude loading without using crack closure concepts. Several experimental fatigue crack growth datasets obtained for the Al 7075 aluminum alloy were used for the verification of the proposed unified fatigue crack growth

  2. Fatigue crack initiation for Al-Zn-Mg alloy welded joint

    Institute of Scientific and Technical Information of China (English)

    Liang ZHANG; Xuesong LIU; Linsen WANG; Ping WANG; Hongyuan FANG

    2012-01-01

    To investigate fatigue crack initiation characteristics of A1-Zn-Mg alloy welded joint,notched specimens were used in fatigue test for the base metal,welding bead and heat affected zone (HAZ).The fatigue fracture surface near the fatigue crack initiation site was observed by scanning electron microscope (SEM).The results show that the differences of fatigue crack initiation life among base metal,welding bead and HAZ are not obvious.Inhomogeneity in microstructure and mechanical performance of HAZ influences the fatigue crack initiation life.The ratio of fatigue crack initiation life (Ni) to fatigue failure life (Nf) for the base metal,welding bead and HAZ of A7N01 aluminium alloy welded joint are 26.32%,40.21% and 60.67%,respectively.Fatigue crack initiation life can be predicted using a uniform model.Observation of fatigue fracture surfaces shows that for the welding bead a fatigue crack initiates from the smooth surface due to the welding process,the blowhole in HAZ causes fatigue crack and the crushed second phase particles play an important role in fatigue crack initiation for the base metal.

  3. Notch receptors in human choroid plexus tumors.

    Science.gov (United States)

    Beschorner, R; Waidelich, J; Trautmann, K; Psaras, T; Schittenhelm, J

    2013-08-01

    Notch signaling plays a role in development and formation of the normal choroid plexus (nCP), and in formation of various tumors in humans. Activation of Notch3 has been reported to promote tumor growth in invasive gliomas and to initiate formation of choroid plexus tumors (CPT) in mice. We investigated the expression of all currently known Notch receptors (Notch 1-4) in 55 samples of nCP and 88 CPT, including 61 choroid plexus papillomas (CPP), 22 atypical CPP and 5 choroid plexus carcinomas by immunohistochemistry. Notch expression was semiquantitatively evaluated separately for membranous/cytoplasmic and for nuclear staining. In addition, we examined Her2 expression (EGFR2, Her2/neu, ErbB2, CD340) because of its functional link to Notch signaling. All samples were negative for Notch3. Membranous/cytoplasmic expression of Notch1 (pnCP compared to CPT. Nuclear expression of Notch1, -2 and -4 was significantly higher in CPT compared to nCP (pnCP to a predominant nuclear expression in CPT. Her2 was weakly expressed in 42/84 CPT but only in 2/53 nCP (p=0.0001) and positively correlated with nuclear expression of Notch1, -2 and 4 in CPT. In summary, a shift between membranous/cytoplasmic (non-canonical signaling pathway) and nuclear expression (canonical signaling pathway) of Notch1, -2 and -4 and upregulation of Her2 indicate neoplastic transformation in human CP and may reveal new therapeutic approaches.

  4. Influence of water cavitation peening with aeration on fatigue behaviour of SAE1045 steel

    Science.gov (United States)

    Han, B.; Ju, D. Y.; Jia, W. P.

    2007-10-01

    Water cavitation peening (WCP) with aeration is a recent potential method in the surface enhancement techniques. In this method, a ventilation nozzle is adopted to improve the process capability of WCP by increasing the impact pressure, which is induced by the bubble collapse on the surface of components in the similar way as conventional shot peening. In this paper, fatigue tests were conducted on the both-edge-notched flat tensile specimens to assess the influences of WCP on fatigue behaviour of SAE1045 steel. The notched specimens were treated by WCP, and the compressive residual stress distributions in the superficial layer were measured by X-ray diffraction method. The tension-tension ( R = Smin/ Smax = 0.1, f = 10 Hz) fatigue tests and the fracture surfaces observation by scan electron microscopy (SEM) were conducted. The experimental results show that WCP can improve the fatigue life by inducing the residual compressive stress in the superficial layer of mechanical components.

  5. Notching on cancer’s door: Notch signaling in brain tumors

    Directory of Open Access Journals (Sweden)

    Marcin eTeodorczyk

    2015-01-01

    Full Text Available Notch receptors play an essential role in the regulation of central cellular processes during embryonic and postnatal development. The mammalian genome encodes for four Notch paralogs (Notch 1-4, which are activated by three Delta-like (Dll1/3/4 and two Serrate-like (Jagged1/2 ligands. Further, non-canonical Notch ligands such as EGFL7 have been identified and serve mostly as antagonists of Notch signaling. The Notch pathway prevents neuronal differentiation in the central nervous system by driving neural stem cell maintenance and commitment of neural progenitor cells into the glial lineage. Notch is therefore often implicated in the development of brain tumors, as tumor cells share various characteristics with neural stem and progenitor cells. Notch receptors are overexpressed in gliomas and their oncogenicity has been confirmed by gain- and loss-of-function studies in vitro and in vivo. To this end, special attention is paid to the impact of Notch signaling on stem-like brain tumor-propagating cells as these cells contribute to growth, survival, invasion and recurrence of brain tumors. Based on the outcome of ongoing studies in vivo, Notch-directed therapies such as γ secretase inhibitors and blocking antibodies have entered and completed various clinical trials. This review summarizes the current knowledge on Notch signaling in brain tumor formation and therapy.

  6. Active notch filter network with variable notch depth, width and frequency

    Science.gov (United States)

    Black, J. M. (Inventor)

    1980-01-01

    An active notch filter having independently adjustable notch frequency, width, and depth is provided by three equal capacitors connected in series with an operational amplifier (connected in a voltage follower configuration), a potentiometer across the series connected capacitors for notch depth adjustment, and a potentiometer (for notch frequency connected across the center capacitor); with its tap connected to receive a voltage feedback signal from a variable voltage divider comprised of another potentiometer for notch width. Adjusting the voltage dividing potentiometer will independently set the notch width, and adjusting the tap on the potentiometer across the center capacitor will independently adjust the notch frequency of the filter. A second operational amplifier connected in a voltage follower configuration may be used to connect the voltage divider output to the adjustable tap of the potentiometer across the center capacitor.

  7. Evidence of non-canonical NOTCH signaling

    DEFF Research Database (Denmark)

    Traustadóttir, Gunnhildur Ásta; Jensen, Charlotte H; Thomassen, Mads

    2016-01-01

    Dlk1(+/+) and Dlk1(-/-) mouse tissues at E16.5, we demonstrated that several NOTCH signaling pathways indeed are affected by DLK1 during tissue development, and this was supported by a lower activation of NOTCH1 protein in Dlk1(+/+) embryos. Likewise, but using a distinct Dlk1-manipulated (si...

  8. Targeting Notch to overcome radiation resistance.

    Science.gov (United States)

    Yahyanejad, Sanaz; Theys, Jan; Vooijs, Marc

    2016-02-16

    Radiotherapy represents an important therapeutic strategy in the treatment of cancer cells. However, it often fails to eliminate all tumor cells because of the intrinsic or acquired treatment resistance, which is the most common cause of tumor recurrence. Emerging evidences suggest that the Notch signaling pathway is an important pathway mediating radiation resistance in tumor cells. Successful targeting of Notch signaling requires a thorough understanding of Notch regulation and the context-dependent interactions between Notch and other therapeutically relevant pathways. Understanding these interactions will increase our ability to design rational combination regimens that are more likely to be safe and effective. Here we summarize the role of Notch in mediating resistance to radiotherapy, the different strategies to block Notch in cancer cells and how treatment scheduling can improve tumor response. Finally, we discuss a need for reliable Notch related biomarkers in specific tumors to measure pathway activity and to allow identification of a subset of patients who are likely to benefit from Notch targeted therapies.

  9. Identification of Domains for Efficient Notch Signaling Activity in Immobilized Notch Ligand Proteins.

    Science.gov (United States)

    Liu, Ledi; Wada, Hiroe; Matsubara, Natsuki; Hozumi, Katsuto; Itoh, Motoyuki

    2017-04-01

    Notch is a critical signaling pathway that controls cell fate and tissue homeostasis, but the functional characterization of Notch ligand domains that activate Notch receptors remains incomplete. Here, we established a method for immobilizing Notch ligand proteins onto beads to measure time-dependent Notch activity after the addition of Notch ligand-coated beads. A comparison between activities by the Notch ligand found on the cell surface to that of the ligand immobilized on beads showed that immobilized Notch ligand protein produces comparable signal activity during the first 10 h. Follow-up truncation studies showed that the N-terminal epidermal growth factor (EGF) repeat three region of delta like canonical Notch ligand 4 (DLL4) or jagged 1 (JAG1) is the minimum region for activating Notch signaling, and the DLL4 EGF repeat three domain may have a role in activation through a mechanism other than by increasing binding affinity. In addition, we found that reconstruction of the DLL4 delta and OSM-11 (DOS) motif (N257P) resulted in an increase in both binding affinity and signaling activity, which suggests that the role of the DOS motif is conserved among Notch ligands. Furthermore, active DLL4 protein on beads promoted T cell differentiation or inhibited B cell differentiation in vitro, whereas JAG1 proteins on beads did not have any effect. Taken together, our findings provide unambiguous evidence for the role of different Notch ligands and their domains in Notch signal activation, and may be potential tools for controlling Notch signaling activation. J. Cell. Biochem. 118: 785-796, 2017. © 2016 Wiley Periodicals, Inc.

  10. [Abnormal Notch-Hes Signaling Pathways and Acute Leukemia -Review].

    Science.gov (United States)

    Gu, Zhen-Yang; Wang, Li; Gao, Chun-Ji

    2017-02-01

    The abnormal activation of Notch signaling is closely related to the development of acute leukemia (AL). The core elements of the Notch signaling system include Notch receptors, Notch ligands, CSL DNA-binding proteins, and effectors like target genes. Any factors, which affect ligands, receptors, signal transducers and effectors, can influence the signal transduction of Notch signaling greatly. Based on the role of Notch signaling in AL, several targeted drugs against Notch upstream signaling have been developed. However, due to the complexity and pleiotropic effects of Notch upstream signaling, these targeted drugs display strong side effects. Thus, Hes (Hairy Enhancer of Split) factors as a primary Notch effector, also play an important role in the pathogenesis of AL. This review summarizes recent progresses on Notch-Hes signaling in AL, hopping to provide references for further excavation of the Notch-Hes signaling, and lay foundations for developing the next generation of targeted drugs.

  11. Corrosion Fatigue

    Science.gov (United States)

    1981-10-01

    the applied protection systems, (2) crevices for moisture entrapment, (3) galvanic couples when steel or titanium fasteners are used, and (4) fatigue...Activ Material Structure Exposed Normal Environment* Unexposed Atmosphere Aluminum alloys Steel 1.25 2.0 4.0 Titanium " Magnesium " (4.0) (8.0) (10.0...APPRNDIX - Chromic Acid Anodizing The surface treatment consists in the following process : D egreasing with trichlorethylene vapor, * Pickling , Composition

  12. Bending Fatigue of Carburized Steel at Very Long Lives

    Science.gov (United States)

    Nelson, D. V.; Long, Z.

    2016-01-01

    The bending fatigue behavior of two carburized steels is investigated for lives between approximately 105 and 108 cycles. Cracks are observed to start at sub-surface inclusions and develop features on fracture surfaces resembling "fish eyes" in appearance. This type of sub-surface cracking tends to govern fatigue strength at long lives. Previous studies of "fish eye" fatigue in carburized steel have been relatively few and have mainly considered failures originating at depths beneath a carburized case, where compressive residual stresses are minimal and hardness values approach those in the core. This study provides fatigue data for cracks originating within cases at various depths where compressive residual stresses are substantial and hardness is much higher than in the core. Fatigue strength is predicted by a simple model, accounting for the influence of residual stresses and hardness values at the different depths at which cracks started. Predictions of fatigue strength are compared with data generated in this study.

  13. Experimental and three-dimensional finite element investigation of fatigue

    Science.gov (United States)

    Bomidi, John A. R.

    Materials often fail at cyclic loads that are lower than their ultimate strength or even their yield strength due to progressive internal material degradation; commonly known as fatigue. Moreover, there is a wide scatter in observed fatigue lives of mechanical components operating under identical loading conditions. The randomness of fatigue failure is considered to be linked to basic microstructural effects such as random microstructure topology and the initiation/growth of cracks along inter/transgranular planes. Several modeling approaches have been previously presented ranging from 2D discrete element to 3D Finite Element methods with explicit representation of microstructure topology and continuum damage mechanics to capture dispersion in rolling contact fatigue life and fatigue spalling. There is, however, a need to compare the modeling approach with experimental fatigue test conditions in order to verify and as required enhance the modeling approach to capture observed fatigue failure. This dissertation presents experimental test results and three-dimensional modeling approach that capture fatigue failure. The three-dimensional modeling approach is enhanced according to the experimental observations to consider inter/trans granular failure, different modes of fatigue initiation and propagation and finally for considering effect of plasticity in fatigue of rolling contacts. The following phenomena have been investigated: (1) Fatigue of microbeams: (a )Results of fatigue life and failure from 3D modeling of intergranular fatigue in microbeams are compared with experimental observations reported in literature (2) Tensile fatigue of thin sheets: (a) A test rig with a new grip and alignment system is developed to address the challenges associated with thin sheet testing and conduct fatigue experiments. (b) The 3D fatigue model is enhanced to capture the dominant transgranular fatigue observed in the experiments. The observed and modeled fatigue life and failure

  14. Strength Modeling Report

    Science.gov (United States)

    Badler, N. I.; Lee, P.; Wong, S.

    1985-01-01

    Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements.

  15. The Notch pathway in colorectal cancer.

    Science.gov (United States)

    Vinson, Kaitlyn E; George, Dennis C; Fender, Alexander W; Bertrand, Fred E; Sigounas, George

    2016-04-15

    Colorectal cancer (CRC) is the third leading cause of cancer death worldwide. It is also the third most common cancer diagnosis among men, and the second most common cancer diagnosis among women. Globally, CRC can account for nearly 694,000 annual deaths. It is widely appreciated that CRC is the result of dysregulated cellular pathways that promote an inappropriate stem-cell-like phenotype, apoptotic resistance, unchecked proliferation and metastatic spread. While no single pathway is responsible for all of these attributes, an array of recent studies suggests a pivotal role for abnormal Notch-1 signaling in CRC, in part due to interconnectivity of Notch with other pathways. This review will summarize recent evidence for a role of Notch signaling in CRC, will consider interconnectivity between Notch and other pathways involved in CRC and will discuss the possible utility of targeting Notch as a CRC therapeutic.

  16. The Lead Crack Fatigue Lifting Framework

    Science.gov (United States)

    2010-04-01

    fracture properties of high strength aluminium and titanium alloys. ____________________ ________________________________________________ Russel...and the fatigue crack growth properties of high strength aluminium and titanium alloys. Russell and Simon have also collaborated on a chapter on...forms of machining damage (scratches, grooves, burrs, small tears and nicks); etch pits from surface treatments ( pickling , anodising); porosity

  17. Fatigue in cold-forging dies: Tool life analysis

    DEFF Research Database (Denmark)

    Skov-Hansen, P.; Bay, Niels; Grønbæk, J.;

    1999-01-01

    In the present investigation it is shown how the tool life of heavily loaded cold-forging dies can be predicted. Low-cycle fatigue and fatigue crack growth testing of the tool materials are used in combination with finite element modelling to obtain predictions of tool lives. In the models...... the number of forming cycles is calculated first to crack initiation and then during crack growth to fatal failure. An investigation of a critical die insert in an industrial cold-forging tool as regards the influence of notch radius, the amount and method of pre-stressing and the selected tool material...

  18. 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.

  19. High cycle fatigue properties of CLAM steel at 723 K and 823 K

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yanyun; Zhai, Xiangwei; Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn; Li, Chunjing; Huang, Qunying

    2015-11-15

    Highlights: • High cycle fatigue properties of CLAM steel were investigated at 723 K and 823 K. • The condition fatigue limit at N = 10{sup 7} were 275 MPa and 235 MPa at 723 K and 823 K. • Fatigue strength decreased when stress and temperature increased at 723 K and 823 K. • Dislocation density decrease and subgrain coarsening during the test process were the possible reasons for fatigue limit decrease. - Abstract: This paper highlights the results of a study on the high cycle fatigue strength and fracture mechanism of China Low Activation Martensitic (CLAM) steel. The high cycle fatigue test results showed that the fatigue strength of CLAM steel decreased with the temperature, and the condition fatigue strengths (N = 10{sup 7}) were 275 MPa and 235 MPa at 723 K and 823 K, respectively. The fractograph results indicated that the fractures were mainly initiated from the surface of the specimen.

  20. Improving fatigue performance of welded joints of X65 pipeline steel by UIT

    Institute of Scientific and Technical Information of China (English)

    Liu Jinming; Chen Tong; Zhang Yufeng

    2005-01-01

    Treating weld toes properly can improve the fatigue performance. Ultrasonic impact treatment (UIT) is a more effective and convenient method to enhance the fatigue strength of welded joints and suchlike structures. Fatigue tests were conducted on the specimens made of X65 pipeline steel. The test specimens were investigated on the fatigue strength and the fatigue life at the same stress range level by comparing the ones peened by UIT with the others without the treatment: the fatigue strength of the specimens as UIT, 90% of the fatigue strength of the base mental, is increased by 38% compared with that of as welded only; the fatigue life of the ones as UIT is prolonged by 11 multiples of the ones as welded only.

  1. Crack initiation behavior of notched specimens on heat resistant steel under service type loading at high temperature

    Directory of Open Access Journals (Sweden)

    Lu Cui

    2016-10-01

    Full Text Available Cracks at notches deserve special consideration in the design of steam turbine components. This work is addressed to investigate the crack initiation behavior a 10%Cr rotor steel with the help of notched specimens under service-type loading. A significant drifting down of the peak-values of axial deformation under constant amplitude load was observed. Crack initiation was evaluated with the help of the relationship between irreversible deformation energy and cycle number. Further, metallographic examinations were employed to characterize the superposition of creep and fatigue damage mechanisms. Both Neuber-hypothesis and von Mises equivalent strain at notch root were applied for lifetime prediction. Finally, the effectiveness of both methods is validated by comparing with experimental results

  2. Tunable Microwave Photonic Notch Filter Based on a high-birefringence linearly chirped fiber Bragg grating

    Energy Technology Data Exchange (ETDEWEB)

    Jin Yongxing; Dong Xinyong; Wang Jianfeng [Institute of Optoelectronic Technology, China Jiliang University, Hangzhou (China); Zhou Junqiang, E-mail: phyjyxin@gmail.com [Network Technology Research Centre, Nanyang Technological University (Singapore)

    2011-02-01

    In this paper, a continuously tunable microwave photonic notch filter is proposed and experimentally demonstrated. This filter is based on the differential group delay generated by a high-birefringence linearly chirped fiber Bragg grating. This microwave photonic filter belongs to the orthogonal polarization approach, polarization maintaining structure ensures the filter free from the random optical interference problem. Its response is induced by the differential group delay (DGD) of the Hi-Bi LCFBG and it can be varied by tuning the grating through adding gradient strength to the grating. Free spectral range tuning by 9.27 GHz with more than 35 dB notch rejection is achieved.

  3. Fatigue crack initiation and propagation in steels exposed to inert and corrosive environments. Final report, May 1, 1977--December 31, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Youseffi, K.; Finnie, I.

    1978-02-01

    The fatigue crack initiation life of AISI 1018 steel was investigated using compact tension specimens having sharp notch root radii. The data were analyzed using two methods for predicting initiation in strain cycling experiments. Also, another approach in which initiation is related to the stress intensity factor was developed. The next phase, that of propagation, was studied using AISI 1018 steel and a new high strength steel HY-180. The crack propagation data obtained for both steels tested in air can be described accurately by the power law first suggested by Paris, da/dN = C(..delta..K)/sup n/, where a is the crack length, N the number of cycles, and C and n are material constants. However, the exponent n was found to be two times larger for AISI 1018 steel than HY-180 steel.

  4. Characterization of Notch1 antibodies that inhibit signaling of both normal and mutated Notch1 receptors.

    Directory of Open Access Journals (Sweden)

    Miguel Aste-Amézaga

    Full Text Available Notch receptors normally play a key role in guiding a variety of cell fate decisions during development and differentiation of metazoan organisms. On the other hand, dysregulation of Notch1 signaling is associated with many different types of cancer as well as tumor angiogenesis, making Notch1 a potential therapeutic target.Here we report the in vitro activities of inhibitory Notch1 monoclonal antibodies derived from cell-based and solid-phase screening of a phage display library. Two classes of antibodies were found, one directed against the EGF-repeat region that encompasses the ligand-binding domain (LBD, and the second directed against the activation switch of the receptor, the Notch negative regulatory region (NRR. The antibodies are selective for Notch1, inhibiting Jag2-dependent signaling by Notch1 but not by Notch 2 and 3 in reporter gene assays, with EC(50 values as low as 5+/-3 nM and 0.13+/-0.09 nM for the LBD and NRR antibodies, respectively, and fail to recognize Notch4. While more potent, NRR antibodies are incomplete antagonists of Notch1 signaling. The antagonistic activity of LBD, but not NRR, antibodies is strongly dependent on the activating ligand. Both LBD and NRR antibodies bind to Notch1 on human tumor cell lines and inhibit the expression of sentinel Notch target genes, including HES1, HES5, and DTX1. NRR antibodies also strongly inhibit ligand-independent signaling in heterologous cells transiently expressing Notch1 receptors with diverse NRR "class I" point mutations, the most common type of mutation found in human T-cell acute lymphoblastic leukemia (T-ALL. In contrast, NRR antibodies failed to antagonize Notch1 receptors bearing rare "class II" or "class III" mutations, in which amino acid insertions generate a duplicated or constitutively sensitive metalloprotease cleavage site. Signaling in T-ALL cell lines bearing class I mutations is partially refractory to inhibitory antibodies as compared to cell

  5. Mechanistic aspects of fracture and fatigue in resin based dental restorative composites

    Science.gov (United States)

    Shah, Minalben B.

    For resin based dental restorative composites, one of the major challenges is to optimize the balance between mechanical and optical properties. Although fracture is the second leading cause of dental restorative failures, very limited mechanistic understanding exists on a microscopic level. In the present study, the fracture properties and mechanisms of two commercial dental resin composites with different microstructures are examined using double notched four point beam bending and pre-cracked compact-tension, C(T), specimens. Four point bend flexural strength was also measured using un-notched beam samples. The first material is a microhybrid composite that combines a range of nano and micro scale filler particles to give an average particle size of 0.6 mum, while the second is a nanofill composite reinforced entirely with nano particles and their agglomerates. The influences of 60 days water hydration and a post-cure heat treatment were also examined. Fracture resistance curve (R-curve) experiments have demonstrated the microhybrid composite to be more fracture resistant than the nanofill composite in both as-processed and hydrated conditions. Rising fracture resistance with crack extension was observed in all specimens, independent of the environmental conditions. Compared to the as-processed condition, a significant reduction in the peak toughness was observed for the nanofill composite after 60 days of water aging. Hydration lowered flexural strength of both composites which was attributed to hydrolytic matrix degradation with additional interfacial debonding causing larger strength decrease in the nanofill. Optical and SEM observations revealed an interparticle matrix crack path promoting crack deflection as a toughening mechanism in all cases except the hydrated nanofill which showed particle-matrix debonding. Crack bridging was another observed extrinsic toughening mechanism that was believed to be responsible for the rising fracture resistance curve (R

  6. Notch3/Jagged1 Circuitry Reinforces Notch Signaling and Sustains T-ALL

    Directory of Open Access Journals (Sweden)

    Maria Pelullo

    2014-12-01

    Full Text Available Deregulated Notch signaling has been extensively linked to T-cell acute lymphoblastic leukemia (T-ALL. Here, we show a direct relationship between Notch3 receptor and Jagged1 ligand in human cell lines and in a mouse model of T-ALL. We provide evidence that Notch-specific ligand Jagged1 is a new Notch3 signaling target gene. This essential event justifies an aberrant Notch3/Jagged1 cis-expression inside the same cell. Moreover, we demonstrate in Notch3-IC–overexpressing T lymphoma cells that Jagged1 undergoes a raft-associated constitutive processing. The proteolytic cleavage allows the Jagged1 intracellular domain to empower Notch signaling activity and to increase the transcriptional activation of Jagged1 itself (autocrine effect. On the other hand, the release of the soluble Jagged1 extracellular domain has a positive impact on activating Notch signaling in adjacent cells (paracrine effect, finally giving rise to a Notch3/Jagged1 auto-sustaining loop that supports the survival, proliferation, and invasion of lymphoma cells and contributes to the development and progression of Notch-dependent T-ALL. These observations are also supported by a study conducted on a cohort of patients in which Jagged1 expression is associated to adverse prognosis.

  7. Notched behavior of hybrid glass/aluminum/titanium fiber metal laminates

    Science.gov (United States)

    Zhang, Jipeng; Wang, Yue; Zhang, Jiazhen; Zhou, Zhengong

    2017-05-01

    A hybrid glass/aluminum/titanium fiber metal laminate (FML) based on the standard GLARE concept was proposed in present paper, and its notched behavior was investigated experimentally and numerically. Experimental results revealed that a special three-stage stress-stain curve was obtained by this reinforced GLARE, which was related to the transition of load bearing mechanism. As well as, improvements of notched strength and normalized notched strength were achieved benefiting from the high strength and ductile nature of titanium, where their maximum increments obtained at D/W=0.2 were 11.88% and 15.40%, respectively. In addition, numerical results indicated that the finite element model (FEM) predicted well the notched behavior of GLARE with incorporating the thermal residual stress effect. Moreover, the comparisons of internal energy and damage dissipation energy between standard GLARE and reinforced GLARE have facilitated in the understanding of reinforced effect of titanium. It is believed that the present investigation can provide some useful information for damage tolerance design of FMLs.

  8. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

    types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel with a yield stress of ~ 360-410 MPa or high-strength steel with a yield stress of ~ 810-1010 MPa. The fatigue tests and the fracture mechanics analyses......Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...... have been carried out using load histories, which are realistic in relation to the types of structures studied, i.e. primarily bridges, offshore structures and chimneys. In general, the test series carried through show a significant difference between constant amplitude and variable amplitude fatigue...

  9. Parallel monostrand stay cable bending fatigue

    DEFF Research Database (Denmark)

    Winkler, Jan Pawel

    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......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...... 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...

  10. Procedimiento para estimar la vida útil de engranajes cilíndricos de acero en base a la resistencia a la fatiga del material y norma AGMA 2101-D04. // A procedure for estimating expected fatigue life on steel cylindrical gears using strength-life theory a

    Directory of Open Access Journals (Sweden)

    G. González Rey

    2008-05-01

    Full Text Available En el trabajo se presenta un procedimiento, fórmulas y relaciones necesarias que permiten determinar un valor de vida útilde referencia previendo la rotura por fatiga de los dientes de acero en ruedas de engranajes cilíndricos de ejes paralelos ycontacto exterior. El procedimiento está fundamentado en considerar la resistencia a la picadura y a flexión de los dientesen engranajes cilíndricos. La base de las fórmulas y relaciones corresponden a la norma AGMA 2101-D04 dirigida alcálculo de la capacidad de carga de engranajes cilíndricos.Palabras claves: Engranaje cilíndrico, duración, fatiga, acero, AGMA 2101._______________________________________________________________________________Abstract.A procedure, formulas and information to estimate a value of expected fatigue life in case of steel cylindrical. Theprocedure is fixed taking into account the pitting resistance (surface fatigue failure and bending strength capacity(volumetric fatigue failure of spur and helical gears. Formulas are based in the AGMA Standard 2105-D04 forcalculation of the load capacity of cylindrical gears.Key words: cylindrical involute gears, lifetime, fatigue resistance, AGMA Standard 2105-D04.

  11. MANAGING FATIGUE IN SPORTS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Fatigue is a multifactorial process. Depletion of energy sources, including adenosine triphosphate (ATP), phosphocreatine (PCr), plus carbohydrates (CHO) like muscle glycogen and blood glucose can contribute to fatigue.

  12. Weld investigations by 3D analyses of Charpy V-notch specimens

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Needleman, Allan

    2005-01-01

    The Charpy impact test is a standard procedure for determining the ductile-brittle transition in welds. The predictions of such tests have been investigated by full three dimensional transient analyses of Charpy V-notch specimens. The material response is characterised by an elastic-viscoplastic ......The Charpy impact test is a standard procedure for determining the ductile-brittle transition in welds. The predictions of such tests have been investigated by full three dimensional transient analyses of Charpy V-notch specimens. The material response is characterised by an elastic...... parameters in the weld material differ from those in the base material, and the heat a®ected zone (HAZ) tends to be more brittle than the other material regions. The effect of weld strength undermatch or overmatch is an important issue. Some specimens, for which the notched surface is rotated relative...

  13. Notch signaling in acute promyelocytic leukemia.

    Science.gov (United States)

    Grieselhuber, N R; Klco, J M; Verdoni, A M; Lamprecht, T; Sarkaria, S M; Wartman, L D; Ley, T J

    2013-07-01

    Acute promyelocytic leukemia (APL) is initiated by the PML-RARA (PR) fusion oncogene and has a characteristic expression profile that includes high levels of the Notch ligand Jagged-1 (JAG1). In this study, we used a series of bioinformatic, in vitro, and in vivo assays to assess the role of Notch signaling in human APL samples, and in a PML-RARA knock-in mouse model of APL (Ctsg-PML-RARA). We identified a Notch expression signature in both human primary APL cells and in Kit+Lin-Sca1+ cells from pre-leukemic Ctsg-PML-RARA mice. Both genetic and pharmacologic inhibition of Notch signaling abrogated the enhanced self-renewal seen in hematopoietic stem/progenitor cells from pre-leukemic Ctsg-PML-RARA mice, but had no influence on cells from age-matched wild-type mice. In addition, six of nine murine APL tumors tested displayed diminished growth in vitro when Notch signaling was inhibited pharmacologically. Finally, we found that genetic inhibition of Notch signaling with a dominant-negative Mastermind-like protein reduced APL growth in vivo in a subset of tumors. These findings expand the role of Notch signaling in hematopoietic diseases, and further define the mechanistic events important for PML-RARA-mediated leukemogenesis.

  14. The role of Notch signaling in kidney podocytes.

    Science.gov (United States)

    Asanuma, Katsuhiko; Oliva Trejo, Juan Alejandro; Tanaka, Eriko

    2017-02-01

    The Notch signaling pathway is a basic cell-to-cell communication mechanism. This pathway is activated by the interaction between Notch receptors and the ligands of adjacent cells. Once activated, Notch receptors are cleaved and the intracellular domains translocate into the nucleus, where the transcription of target genes starts. In the mammalian kidney, Notch receptors are activated during nephrogenesis. Afterwards, in the mature glomeruli, the Notch pathway becomes silent. However, many researchers have reported the activation of Notch receptors in mature podocytes under pathological conditions. In this review, we discuss the role of Notch signaling in podocytes.

  15. Comparative analysis of Notch1 and Notch2 binding sites in the genome of BxPC3 pancreatic cancer cells

    OpenAIRE

    Liu, Hao; Zhou, Ping; Lan, Hong; Chen, Jia; Yu-xiang ZHANG

    2017-01-01

    Notch signaling plays a key role in the development of pancreatic cancer. Among the four identified Notch receptors, Notch1 and Notch2 share the highest homology. Notch1 has been reported to be an oncogene but some reports indicate that Notch2, not Notch1, plays a key role in pancreatic carcinogenesis. As both are transcription factors, examination of their genomic binding sites might reveal interesting functional differences between them. Notch proteins do not have DNA-binding domain. In the...

  16. Material fatigue in high pressure piping

    Energy Technology Data Exchange (ETDEWEB)

    Brunne, W.C. [Pro Novum, Research and Technological Services, Ltd, Katowice, (Poland)

    1998-12-31

    The present paper describes a type of damage to four-way cross pieces on live steam and reheated steam pipelines. The results of metallographic examination and strength tests are presented. The occurring mechanisms of material degradation, i.e. low-cycle fatigue and hydrogen corrosion are discussed. The both mechanisms result in the corrosion fatigue of the material causing the failure of cross pieces. A new design of cross piece was proposed. (orig.) 5 refs.

  17. 76 FR 22745 - Three Notch Railway, LLC-Acquisition and Operation Exemption-Three Notch Railroad Co., Inc.

    Science.gov (United States)

    2011-04-22

    ... Surface Transportation Board Three Notch Railway, LLC--Acquisition and Operation Exemption-- Three Notch Railroad Co., Inc. Three Notch Railway, LLC (TNRW), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from Three Notch Railroad Co., Inc. (TNHR) and to operate approximately...

  18. Study on unified fatigue strength assessment method for welded structure. Hot spot stress evaluating method for various combinations of plate thickness and weld leg length; Yosetsu kozo no toitsutekina hiro kyodo hyokaho ni kansuru kenkyu. Itaatsu to yosetsu ashinaga no kumiawase ni taisuru hot spot oryoku sanshutsu ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Nihei, K.; Inamura, F.; Koe, S. [Kawasaki Heavy Industries, Ltd., Kobe (Japan)

    1996-12-31

    There has been tried to apply unified assessment method using hot spot stress, which is effective to evaluate fatigue strength of fillet welded structures for ships and marine structures. This method can be applied to complicated structures and is independent of welding processes. In this study, first, stress analysis has been conducted for two-dimensional fillet welded joint models with various combinations of plate thickness and weld leg length of general fillet structures by means of boundary element method. Then, critical position, which is not affected by local stress concentration due to bead, was determined from the detailed stress distribution in the vicinity of weld toe. As a result, a general equation has been proposed to estimate the hot spot stress by one-point representative method. Second, the fatigue tests of typical fillet welded joints have been conducted by applying this method. Consequently, it was demonstrated that the unified fatigue strength can be evaluated by the S-N data based on hot spot stress range determined from the proposed equation, independent of structural stress concentration. 22 refs., 14 figs.

  19. Notch and the awesome power of genetics.

    Science.gov (United States)

    Greenwald, Iva

    2012-07-01

    Notch is a receptor that mediates cell-cell interactions in animal development, and aberrations in Notch signal transduction can cause cancer and other human diseases. Here, I describe the major advances in the Notch field from the identification of the first mutant in Drosophila almost a century ago through the elucidation of the unusual mechanism of signal transduction a little over a decade ago. As an essay for the GENETICS Perspectives series, it is my personal and critical commentary as well as an historical account of discovery.

  20. 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

  1. Relaxation of stress and density, strength (fatigue)

    CERN Document Server

    Gräfe, Wolfgang

    2015-01-01

    This treatment of ""Time-Dependent Mechanical Properties of Solids"" beginswith a phenomenological description of the transport of some unspecifiedentity. It is assumed that the transport is caused by mechanical stresses ortemperature fields. Using these assumptions, it is possible to deduceformulae for a theoretically based description of several phenomena withoutreferring to any specific process or entity. These theoretical results thenprovide the tools for performing methodologically better scientific work andfor a better analysis of data in the practical application of materials. Bypublish

  2. Fatigue test of carbon epoxy composite high pressure hydrogen storage vessel under hydrogen environment

    Institute of Scientific and Technical Information of China (English)

    Chuan-xiang ZHENG; Liang WANG; Rong LI; Zong-xin WEI; Wei-wei ZHOU

    2013-01-01

    A significant temperature raise within hydrogen vehicle cylinder during the fast filling process will be observed,while the strength and fatigue life of the cylinder will dramatically decrease at high temperature.In order to evaluate the strength and fatigue of composite hydrogen storage vessel,a 70-MPa fatigue test system using hydrogen medium was set up.Experimental study on the fatigue of composite hydrogen storage vessels under real hydrogen environment was performed.The experimental results show that the ultimate strength and fatigue life both decreased obviously compared with the values under hydraulic fatigue test.Furthermore,fatigue property,failure behavior,and safe hydrogen charging/discharging working mode of onboard hydrogen storage vessels were obtained through the fatigue tests.

  3. Influence of surface conditions on fatigue strength through the numerical simulation of microstructure; Etude par simulation numerique de la microstructure de l'influence de l'etat de surface sur la resistance a la fatigue d'un acier 304L

    Energy Technology Data Exchange (ETDEWEB)

    Le Pecheur, A.; Clavel, M.; Rey, C.; Bompard, P. [Laboratoire MSSMat, UMR 8579 CNRS, Ecole Centrale Paris (France); Le Pecheur, A.; Curtit, F.; Stephan, J.M. [Departement MMC, EDF RD, Site des Renardieres (France)

    2010-11-15

    A thermal fatigue test (INTHERPOL) was developed by EDF in order to study the initiation of cracks. These tests are carried out on tubular specimens under various thermal loadings and surface finish qualities in order to give an account of these parameters on crack initiation. The main topic of this study is to test the sensitivity of different fatigue criteria to surface conditions using a micro/macro modelling approach. Therefore a 304L polycrystalline aggregate, used for cyclic plasticity based FE modelling, have been considered as a Representative Volume Element located at the surface and subsurface of the test tube. This aggregate has been cyclically strained according to the results issued from FE simulation of INTHERPOL thermal fatigue experiment. Different surface parameters have been numerically simulated: effects of local microstructure and of grains orientation, effects of machining: metallurgical prehardening, residual stress gradient, and surface roughness. Three different fatigue criteria (Manson Coffin, Fatemi Socie and dissipated energy types), previously fitted at a macro-scale for thermal fatigue of 304L, have been computed at a meso scale, in order to show the surface 'hot spots' features and test the sensitivity of these three criteria to different surface conditions. Results show that grain orientation and neighbouring play an important role on the location of hot spots, and also that the positive effect of pre-straining and the negative effect of roughness on fatigue life are not all similarly predicted by these different fatigue criteria. (authors)

  4. Fatigue of weld ends under combined in- and out-of-phase multiaxial loading

    Directory of Open Access Journals (Sweden)

    E. Shams

    2016-10-01

    Full Text Available Weld start and end points are fatigue failure sensitive locations. Their fatigue behaviour especially in thin sheet structures under multiaxial load conditions is not sufficiently explored so far. Therefore, a research project was initiated to increase the knowledge concerning this topic, which is of special interest in the automotive industry. In the present study, fatigue tests on welded joints were conducted. In the numerical part of the study, notch stresses were calculated with an idealised weld end model. A numerical method which combines the geometrical and statistical size effect to an integrated approach was used, in order to consider the size effects

  5. Fatigue mechanisms in unidirectional glass-fibre-reinforced polypropylene

    DEFF Research Database (Denmark)

    Gamstedt, E.K.; Berglund, L.A.; Peijs, T.

    1999-01-01

    of interfacial strength on fatigue performance and on the underlying micromechanisms have been studied for these composite systems. Tension-tension fatigue tests (R = 0.1) were carried out on 0 degrees glass-fibre/PP and glass-fibre/ MA-PP coupons. The macroscopic fatigue behaviour was characterized in terms...... of stiffness reduction and fatigue-life curves. The results showed that the longitudinal Young's modulus degraded more rapidly for glass-fibre/PP, which was caused by a higher degree of damage growth and accumulation. The improvement in monotonic strength was negligible, but the fatigue life was prolonged...... by about one decade for the composite with the stronger interface by use of the maleic-anhydride grafted polypropylene matrix. During the fatigue testing, the microscopic mechanisms were monitored intermittently by a surface replication technique. From microscopic observations, it could be concluded...

  6. Notch Promotes Radioresistance of Glioma Stem Cells

    OpenAIRE

    Wang, Jialiang; Wakeman, Timothy P.; Latha, Justin D.; Hjelmeland, Anita B.; Wang, Xiao-Fan; White, Rebekah R.; Rich, Jeremy N.; Sullenger, Bruce A.

    2010-01-01

    Radiotherapy represents the most effective nonsurgical treatments for gliomas. Yet, gliomas are highly radioresistant and recurrence is nearly universal. Results from our laboratory and other groups suggest that cancer stem cells contribute to radioresistance in gliomas and breast cancers. The Notch pathway is critically implicated in stem cell fate determination and cancer. In this study, we showed that inhibition of Notch pathway with gamma-secretase inhibitors (GSIs) rendered the glioma st...

  7. Strength and toughness of structural fibres for composite material reinforcement.

    Science.gov (United States)

    Herráez, M; Fernández, A; Lopes, C S; González, C

    2016-07-13

    The characterization of the strength and fracture toughness of three common structural fibres, E-glass, AS4 carbon and Kevlar KM2, is presented in this work. The notched specimens were prepared by means of selective carving of individual fibres by means of the focused ion beam. A straight-fronted edge notch was introduced in a plane perpendicular to the fibre axis, with the relative notch depth being a0/D≈0.1 and the notch radius at the tip approximately 50 nm. The selection of the appropriate beam current during milling operations was performed to avoid to as much as possible any microstructural changes owing to ion impingement. Both notched and un-notched fibres were submitted to uniaxial tensile tests up to failure. The strength of the un-notched fibres was characterized in terms of the Weibull statistics, whereas the residual strength of the notched fibres was used to determine their apparent toughness. To this end, the stress intensity factor of a fronted edge crack was computed by means of the finite-element method for different crack lengths. The experimental results agreed with those reported in the literature for polyacrylonitrile-based carbon fibres obtained by using similar techniques. After mechanical testing, the fracture surface of the fibres was analysed to ascertain the failure mechanisms. It was found that AS4 carbon and E-glass fibres presented the lower toughness with fracture surfaces perpendicular to the fibre axis, emanating from the notch tip. The fractured region of Kevlar KM2 fibres extended along the fibre and showed large permanent deformation, which explains their higher degree of toughness when compared with carbon and glass fibres. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

  8. Fatigue life extension

    Science.gov (United States)

    Matejczyk, D. E.; Lin, J.

    1985-01-01

    Potential fatigue rejuvenation processes were carried out on fatigue-damaged material both with and without observable surface-connected fatigue cracks. The fatigue life of fatigue-damaged MAR-M246(Hf)(DS), a directionally solidified nickel-base superalloy used in turbine airfoils, was extended by reheat treatment. The fatigue life of fatigue-cracked Inconel 718, a wrought nickel-base superalloy used in a wide variety of advanced rocket engine components, was extended by electron-beam welding to close off the surface-connected crack, followed by hot isostatic pressing and reheat treatment.

  9. Fatigue Behaviors of Self-Piercing Rivets Joining Similar and Dissimilar Sheet Metals

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-01-01

    This paper summarizes the fatigue test results of self-piercing rivet (SPR) joints between similar and dissimilar sheet metals. The influences of material grades, material thickness, piercing direction and the use of structural adhesive on the rivet samples’ fatigue behaviors were investigated. Fatigue test results indicate that SPR joints have superior fatigue strength than resistance spot weld (RSW) joints for the same material combinations. The application of structure adhesive also significantly enhances the fatigue strength of the joint samples; this is particularly true for the lap shear loading configuration. In addition, different piercing directions for SPR joints have a noticeable effect on the static and fatigue strength of the joints. The joint fatigue results presented in this paper can offer design engineers with the durability data for SPR joints with these material combinations. Moreover, it will provide manufacturing engineers with some insights on the effects of different manufacturing parameters on the strength and durability of these joints.

  10. Restraint of fatigue crack growth by wedge effects of fine particles

    CERN Document Server

    Takahashi, I; Kotani, N

    2000-01-01

    Presents some experimental results which demonstrate restraint of fatigue crack growth in an Al-Mg alloy by wedge effects of fine particles. Fatigue test specimens were machined from a JIS A5083P-O Al-Mg alloy plate of 5 mm thickness and an EDM starter notch was introduced to each specimen. Three kinds of fine particles were prepared as the materials to be wedged into the fatigue cracks, i.e. magnetic particles and two kinds of alumina particles having different mean particle sizes of 47.3 mu m and 15.2 mu m. Particles of each kind were suspended in an oil to form a paste, which was applied on the specimen surface covering the notch zone prior to the fatigue tests. In order to make some fracture mechanics approaches, in situ observations of fatigue cracks were performed for the two cases using a CCD microscope, with a magnification of *1000. The crack length and the crack opening displacement (COD) at the notch root, delta , were measured. The crack retardation effect continues almost through the entire lifet...

  11. Notch Signaling in Vascular Smooth Muscle Cells.

    Science.gov (United States)

    Baeten, J T; Lilly, B

    2017-01-01

    The Notch signaling pathway is a highly conserved pathway involved in cell fate determination in embryonic development and also functions in the regulation of physiological processes in several systems. It plays an especially important role in vascular development and physiology by influencing angiogenesis, vessel patterning, arterial/venous specification, and vascular smooth muscle biology. Aberrant or dysregulated Notch signaling is the cause of or a contributing factor to many vascular disorders, including inherited vascular diseases, such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, associated with degeneration of the smooth muscle layer in cerebral arteries. Like most signaling pathways, the Notch signaling axis is influenced by complex interactions with mediators of other signaling pathways. This complexity is also compounded by different members of the Notch family having both overlapping and unique functions. Thus, it is vital to fully understand the roles and interactions of each Notch family member in order to effectively and specifically target their exact contributions to vascular disease. In this chapter, we will review the Notch signaling pathway in vascular smooth muscle cells as it relates to vascular development and human disease.

  12. Study of fatigue behavior of longitudinal welded pipes

    Science.gov (United States)

    Simion, P.; Dia, V.; Istrate, B.; Hrituleac, G.; Hrituleac, I.; Munteanu, C.

    2016-08-01

    During transport and storage of the various fluids, welded pipes are subjected to cyclic loading due to pressure fluctuations that often exceed the prescribed values for normal operation. These cyclic loading can significantly reduce the life of the pipes; as a result the design should be based on the fatigue strength not only on static resistance. In general the fatigue strength of pipes is dependent by strength, pipe geometry and surface quality. In case of the electric longitudinal welded pipes, the fatigue strength is significantly limited by concentration of residual stress and the size of existing defects in the weld seam. This paper presents the fatigue behaviour of the electric welded pipes by high frequency, under conditions that simulate real operating conditions pipes. Fatigue testing was performed on welded pipes made of micro alloyed carbon steels. Some of these pipes were previously subjected to a heat treatment of normalization, in order to also determine the influence of heat treatment on the fatigue strength of welded pipes. To determine and correlate the different factors affecting the fatigue strength, welded pipes were also subjected to various tests: tensile tests, impact tests, measurement of micro hardness, microstructural analysis by optical microscopy and scanning electron microscopy.

  13. 当量加速腐蚀条件下7 B04-T6高强度铝合金疲劳裂纹扩展规律研究%The fatigue crack growth rule of 7B04-T6 high strength aluminum alloy under equivalently accelerated corrosion environment

    Institute of Scientific and Technical Information of China (English)

    谭晓明; 王海东; 王刚

    2015-01-01

    Based on an accelerated corrosion testing spectrum complicated for the servicing field environment, the equivalently accelerated corrosion testing of high strength aluminum alloy 7B04-T6 specimens for critical structure were carried out. Corrosion damage under the field environment was successfully simulated and reappeared, and corrosion damage evolvement rule was obtained. By prior⁃corrosion fatigue testing and fractography quantitative analysis, the fatigue crack length (a) and fatigue cycles (N) were gotten, and relationship between fatigue crack growth rate (da/dN) and stress intensify factors rang (ΔK) was analyzed. Moreover the effect of different corrosion damage on fatigue crack growth behavior was quantitatively characterized. The result shows that there is obvious short crack growth behavior during early corrosion stage, the fatigue crack growth rate increases when the corrosion damage is more serious, and the fatigue performance is greatly degraded.%基于编制的机场环境加速试验谱,针对关键结构高强度铝合金件进行当量腐蚀试验,在实验室条件下成功地模拟和再现了服役环境条件的腐蚀损伤,借助复型法观测得到了腐蚀损伤的演化规律;通过预腐蚀疲劳试验和疲劳断口扫描电镜定量分析,得到了裂纹长度a与循环次数N数据集,分析了裂纹扩展速率da/dN与应力强度因子幅值ΔK的对应关系,定量表征了不同程度腐蚀损伤对疲劳裂纹扩展行为的影响规律。结果表明,在腐蚀初期,疲劳裂纹扩展过程中有经典的小裂纹扩展阶段;随着腐蚀损伤的加重,小裂纹行为不明显;腐蚀损伤越严重,疲劳裂纹扩展速率越快,结构抗疲劳性能显著退化。

  14. Comparison of fatigue property between friction stir and TIG welds

    Institute of Scientific and Technical Information of China (English)

    Xunhong Wang; Kuaishe Wang; Yang Shen; Kai Hu

    2008-01-01

    The alloy 5052 was welded by friction stir welding (FSW) and tungsten inert gas (TIG) welding. The effect of welding processes (FSW and TIG) on the fatigue properties of 5052 aluminum-welded joints was analyzed based on fatigue testing, and the S-N curve of the joints were established. The results show that the fatigue properties of FSW welded joints are better than those of TIG welded joints. The fatigue strength is determined as 65 Mpa under 106 cycling of fatigue life. The microstructure of joints is fine grains and narrow HAZ zone in FSW welds, which inhibit the growth of cracks and produce high fatigue life compared with that of TIG welds. Fracture morphologies also show that the fatigue fracture results from weld defects.

  15. Fatigue Performance of Composite Laminates After Low-velocity Impact

    Directory of Open Access Journals (Sweden)

    LIANG Xiao-lin

    2016-12-01

    Full Text Available Compression-compression fatigue tests were carried out on T300/5405 composite laminates after low-velocity impact, compression performance of the laminates with different impact damages was studied together with its fatigue life and damage propagation under different stress levels, then the effects of impact energy, stress level and damage propagation on fatigue life of laminates were discussed. The results indicate that impact damage can greatly reduce the residual strength of laminates; under low fatigue load levels, the higher impact energy is, the shorter the fatigue life of laminates with impact damage will be; damage propagation undergoes two stages during the fatigue test, namely the steady propagation and the rapid propagation, accounting for 80% and 20% of the overall fatigue life, respectively; damage propagation rate decreases with the reduction of stress level.

  16. Contrasty Tests on Fatigue Properties of Aluminum Alloys 2E12-T3 and 7050-T7451 in Pooding Environment of Fuel Tank

    Directory of Open Access Journals (Sweden)

    LI Kuang

    2017-01-01

    Full Text Available Fatigue properties in typical corrosion environments are the premise of fatigue life design for metallic structures in aircraft. Therefore, fatigue tests were performed on smooth and notched specimens subjected to constant amplitude loading in two environments of dry air and fuel tank ponding respectively to determine pure and corrosion fatigue properties of aluminum alloys 2E12-T3 and 7050-T7451. Corrosion fatigue properties in the two environments were analyzed and compared with each other, and the interaction mechanisms between corrosion and fatigue were deduced from fractographical studies by using scanning election microscope (SEM. It is showed that fuel tank ponding has a detrimental influence on fatigue properties and the adverse effect increases with the decreasing stress level. In addition, the notch of specimen enhances the severity of corrosion effects. Fatigue crack is easily initiate from the corrosion pits on the rough fatigue surface, and crack propagation is enhanced by the corrosion products and the hydrogen embrittlement effects at crack tips, thus the degradation of fatigue properties and the reduction of fatigue life are caused.

  17. The role of Notch in the cardiovascular system: potential adverse effects of investigational Notch inhibitors

    Directory of Open Access Journals (Sweden)

    Paola eRizzo

    2015-01-01

    Full Text Available Targeting the Notch pathway is a new promising therapeutic approach for cancer patients. Inhibition of Notch is effective in the oncology setting because it causes a reduction of highly proliferative tumor cells and it inhibits survival of cancer stem cells which are considered responsible for tumor recurrence and metastasis. Additionally, since Delta- like ligand 4 (Dll4- activated Notch signalling is a major modulator of angiogenesis, anti-Dll4 agents are being investigated to reduce vascularization of the tumor. Notch plays a major role in the heart during the development and, after birth, in response to cardiac damage. Therefore, agents used to inhibit Notch in the tumors (gamma secretase inhibitors and anti-Dll4 agents could potentially affect myocardial repair. The past experience with trastuzumab and other tyrosine kinase inhibitors used for cancer therapy demonstrates that the possible cardiotoxicity of agents targeting shared pathways between cancer and heart and the vasculature should be considered. To date, Notch inhibition in cancer patients has resulted only in mild gastrointestinal toxicity. Little is known about the potential long term cardiotoxicity associated to Notch inhibition in cancer patients. In this review we will focus on mechanisms through which inhibition of Notch signalling could lead to cardiomyocytes and endothelial dysfunctions. These adverse effects could contrast with the benefits of therapeutic responses in cancer cells during times of increased cardiac stress and/or in the presence of cardiovascular risk factor

  18. Tensile and fatigue properties of Inconel 718 at cryogenic temperatures

    Science.gov (United States)

    Malin, C. O.; Schmidt, E. H.

    1969-01-01

    Tests to determine the tensile and fatigue properties of Inconel 718 at cryogenic temperatures show that the alloy increases in strength at low temperatures, with very little change in toughness. The effect of surface finish and grain size on the fatigue properties was also determined.

  19. Physical and Model Uncertainty for Fatigue Design of Composite Material

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    The main aim of the present report is to establish stochastic models for the uncertainties related to fatigue design of composite materials. The uncertainties considered are the physical uncertainty related to the static and fatigue strength and the model uncertainty related to Miners rule...

  20. 14 CFR 29.571 - Fatigue evaluation of structure.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fatigue evaluation of structure. 29.571... § 29.571 Fatigue evaluation of structure. (a) General. An evaluation of the strength of principal... (including tolerance to flaws). The structure must be shown by analysis supported by test evidence and,...