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Sample records for high-cycle fatigue life

  1. A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

    Science.gov (United States)

    Pejkowski, Łukasz; Skibicki, Dariusz

    2016-08-01

    This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The criterion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are: function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S-N curves: tension-compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promising. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the non-proportionality of loading.

  2. A Modified Fatigue Damage Model for High-Cycle Fatigue Life Prediction

    Directory of Open Access Journals (Sweden)

    Meng Wang

    2016-01-01

    Full Text Available Based on the assumption of quasibrittle failure under high-cycle fatigue for the metal material, the damage constitutive equation and the modified damage evolution equation are obtained with continuum damage mechanics. Then, finite element method (FEM is used to describe the failure process of metal material. The increment of specimen’s life and damage state can be researched using damage mechanics-FEM. Finally, the lifetime of the specimen is got at the given stress level. The damage mechanics-FEM is inserted into ABAQUS with subroutine USDFLD and the Python language is used to simulate the fatigue process of titanium alloy specimens. The simulation results have a good agreement with the testing results under constant amplitude loading, which proves the accuracy of the method.

  3. A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain

    Directory of Open Access Journals (Sweden)

    M. Malnati

    2014-04-01

    Full Text Available A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.

  4. High-cycle Fatigue Life Extension of Glass Fiber/Polymer Composites with Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Christopher S Grimmer; C K H Dharan

    2009-01-01

    The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites.

  5. The Effect of Drive Signal Limiting on High Cycle Fatigue Life Analysis

    Science.gov (United States)

    Kihm, Frederic; Rizzi, Stephen A.

    2014-01-01

    It is common practice to assume a Gaussian distribution of both the input acceleration and the response when modeling random vibration tests. In the laboratory, however, shaker controllers often limit the drive signal to prevent high amplitude peaks. The high amplitudes may either be truncated at a given level (socalled brick wall limiting or abrupt clipping), or compressed (soft limiting), resulting in drive signals which are no longer Gaussian. The paper first introduces several methods for limiting a drive signal, including brick wall limiting and compression. The limited signal is then passed through a linear time-invariant system representing a device under test. High cycle fatigue life predictions are subsequently made using spectral fatigue and rainflow cycle counting schemes. The life predictions are compared with those obtained from unclipped input signals. Some guidelines are provided to help the test engineer decide how clipping should be applied under different test scenarios.

  6. Accelerated multiscale space-time finite element simulation and application to high cycle fatigue life prediction

    Science.gov (United States)

    Zhang, Rui; Wen, Lihua; Naboulsi, Sam; Eason, Thomas; Vasudevan, Vijay K.; Qian, Dong

    2016-08-01

    A multiscale space-time finite element method based on time-discontinuous Galerkin and enrichment approach is presented in this work with a focus on improving the computational efficiencies for high cycle fatigue simulations. While the robustness of the TDG-based space-time method has been extensively demonstrated, a critical barrier for the extensive application is the large computational cost due to the additional temporal dimension and enrichment that are introduced. The present implementation focuses on two aspects: firstly, a preconditioned iterative solver is developed along with techniques for optimizing the matrix storage and operations. Secondly, parallel algorithms based on multi-core graphics processing unit are established to accelerate the progressive damage model implementation. It is shown that the computing time and memory from the accelerated space-time implementation scale with the number of degree of freedom N through ˜ O(N^{1.6}) and ˜ O(N), respectively. Finally, we demonstrate the accelerated space-time FEM simulation through benchmark problems.

  7. Influence Of Surface Roughness On Ultra-High-Cycle Fatigue Of Aisi 4140 Steel.

    OpenAIRE

    Daniel Januário Cordeiro Gomes.; Ernani Sales Palma

    2015-01-01

    Low and high-cycle fatigue life regimes are well studied and are relatively well understood. However, recent fatigue studies on steels have shown that fatigue failures can occur at low amplitudes even below the conventional fatigue limit in the ultra-high-cycle fatigue range (life higher than 107 cycles). Fatigue life in the regime of 106 to 108 cycles-to-failure in terms of the influence of manufacturing processes on fatigue strength is examined. Specifically, the influe...

  8. High cycle fatigue properties of inconel 690

    International Nuclear Information System (INIS)

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

  9. Very High Cycle Fatigue Failure Analysis and Life Prediction of Cr-Ni-W Gear Steel Based on Crack Initiation and Growth Behaviors

    Directory of Open Access Journals (Sweden)

    Hailong Deng

    2015-12-01

    Full Text Available The unexpected failures of structural materials in very high cycle fatigue (VHCF regime have been a critical issue in modern engineering design. In this study, the VHCF property of a Cr-Ni-W gear steel was experimentally investigated under axial loading with the stress ratio of R = −1, and a life prediction model associated with crack initiation and growth behaviors was proposed. Results show that the Cr-Ni-W gear steel exhibits the constantly decreasing S-N property without traditional fatigue limit, and the fatigue strength corresponding to 109 cycles is around 485 MPa. The inclusion-fine granular area (FGA-fisheye induced failure becomes the main failure mechanism in the VHCF regime, and the local stress around the inclusion play a key role. By using the finite element analysis of representative volume element, the local stress tends to increase with the increase of elastic modulus difference between inclusion and matrix. The predicted crack initiation life occupies the majority of total fatigue life, while the predicted crack growth life is only accounts for a tiny fraction. In view of the good agreement between the predicted and experimental results, the proposed VHCF life prediction model involving crack initiation and growth can be acceptable for inclusion-FGA-fisheye induced failure.

  10. Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF range based on inclusion population

    Directory of Open Access Journals (Sweden)

    Kolyshkin A.

    2014-06-01

    Full Text Available The VHCF behaviour of metallic materials containing microstructural defects such as non-metallic inclusions is determined by the size and distribution of the damage dominating defects. In the present paper, the size and location of about 60.000 inclusions measured on the longitudinal and transversal cross sections of AISI 304 sheet form a database for the probabilistic determination of failure-relevant inclusion distribution in fatigue specimens and their corresponding fatigue lifes. By applying the method of Murakami et al. the biggest measured inclusions were used in order to predict the size of failure-relevant inclusions in the fatigue specimens. The location of the crack initiating inclusions was defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. Reasonable agreement was obtained between modeling and experimental results.

  11. 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.

  12. 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.

  13. High-cycle Fatigue Properties of Alloy718 Base Metal and Electron Beam Welded Joint

    Science.gov (United States)

    Ono, Yoshinori; Yuri, Tetsumi; Nagashima, Nobuo; Sumiyoshi, Hideshi; Ogata, Toshio; Nagao, Naoki

    High-cycle fatigue properties of Alloy 718 plate and its electron beam (EB) welded joint were investigated at 293 K and 77 K under uniaxial loading. At 293 K, the high-cycle fatigue strength of the EB welded joint with the post heat treatment exhibited somewhat lower values than that of the base metal. The fatigue strengths of both samples basically increased at 77 K. However, in longer life region, the EB welded joint fractured from a blow hole formed in the welded zone, resulting in almost the same fatigue strength at 107 cycles as that at 293 K.

  14. Very high cycle fatigue of duplex stainless steels and stress intensity calculations

    OpenAIRE

    Tofique, Muhammad Waqas

    2014-01-01

    Very high cycle fatigue (VHCF) is generally considered as the domain of fatigue lifetime beyond 10 million (107) load cycles. Few examples of structural components which are subjected to 107-109 load cycles during their service life are engine parts, turbine disks, railway axles and load-carrying parts of automobiles. Therefore, the safe and reliable operation of these components depends on the knowledge of their fatigue strength and the prevalent damage/failure mechanisms. Moreover, the fati...

  15. High-cycle fatigue / low-cycle fatigue interactions in Ti-6Al-4V

    OpenAIRE

    Knipling, Keith Edward

    2002-01-01

    The largest single cause of failure in fan and compressor components in the cold frontal sections of commercial and military gas turbine engines has been attributed to high cycle fatigue (HCF). Additionally, both high-cycle fatigue (HCF) and low-cycle fatigue (LCF) loadings are widely recognized as unavoidable during operation of these components and because the classic Linear Damage Rule (LDR) neglects to account for the synergistic interaction between these damage contributors, dangerous o...

  16. 核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的研究%Study on Crack Propagation Life under Low Cycle Fatigue and High Cycle Fatigue of Nuclear Steam Turbine Rotors

    Institute of Scientific and Technical Information of China (English)

    史进渊

    2015-01-01

    提出核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的计算与评定方法.介绍核电汽轮机转子的低周疲劳与高周疲劳的应力幅与应力范围、低周疲劳裂纹扩展寿命与高周疲劳扩展寿命的计算方法.给出了核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展日历寿命的计算与评定方法,以及1 000 MW级核电汽轮机焊接低压转子疲劳裂纹扩展日历寿命的计算与改进的应用实例.结果表明,高周疲劳对汽轮机转子疲劳裂纹扩展日历寿命有比较大的影响,新研制核电汽轮机的转子结构设计和在役核电汽轮机的转子安全性评定,需要评估转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命.%The calculation and assessment methods for the crack propagation life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors is presented. The low high fatigue cycle stress amplitude and stress range as well as the crack propagation life calculation methods for low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are introduced. The calculation and assessment methods for the crack propagation calendar life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are given together with an application example for calculation and improvement of the fatigue crack propagation calendar life of a low pressure welded rotor for 1 000 MW nuclear steam turbines. The example results indicate that effect of the high cycle fatigue on the fatigue crack propagation calendar life of nuclear steam turbine rotors is bigger, it is necessary that assessment for the crack propagation life under low cycle fatigue and high cycle fatigue of rotors in the rotor structure design of new development for nuclear steam turbine and the rotor safety assessment for operation steam turbine for nuclear power plants.

  17. 核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的研究%Study on Crack Propagation Life under Low Cycle Fatigue and High Cycle Fatigue of Nuclear Steam Turbine Rotors

    Institute of Scientific and Technical Information of China (English)

    史进渊

    2015-01-01

    The calculation and assessment methods for the crack propagation life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors is presented. The low high fatigue cycle stress amplitude and stress range as well as the crack propagation life calculation methods for low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are introduced. The calculation and assessment methods for the crack propagation calendar life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are given together with an application example for calculation and improvement of the fatigue crack propagation calendar life of a low pressure welded rotor for 1 000 MW nuclear steam turbines. The example results indicate that effect of the high cycle fatigue on the fatigue crack propagation calendar life of nuclear steam turbine rotors is bigger, it is necessary that assessment for the crack propagation life under low cycle fatigue and high cycle fatigue of rotors in the rotor structure design of new development for nuclear steam turbine and the rotor safety assessment for operation steam turbine for nuclear power plants.%提出核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的计算与评定方法.介绍核电汽轮机转子的低周疲劳与高周疲劳的应力幅与应力范围、低周疲劳裂纹扩展寿命与高周疲劳扩展寿命的计算方法.给出了核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展日历寿命的计算与评定方法,以及1 000 MW级核电汽轮机焊接低压转子疲劳裂纹扩展日历寿命的计算与改进的应用实例.结果表明,高周疲劳对汽轮机转子疲劳裂纹扩展日历寿命有比较大的影响,新研制核电汽轮机的转子结构设计和在役核电汽轮机的转子安全性评定,需要评估转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命.

  18. Very high cycle fatigue behavior of SAE52100 bearing steel by ultrasonic nanocrystalline surface modification.

    Science.gov (United States)

    Cho, In Shik; He, Yinsheng; Li, Kejian; Oh, Joo Yeon; Shin, Keesam; Lee, Chang Soon; Park, In Gyu

    2014-11-01

    In this paper, the SAE52100 bearing steel contained large quantities of cementite dispersed in ferrite matrix was subjected to the ultrasonic nanocrystalline surface modification (UNSM) treatment that aims for the extension of fatigue life. The microstructure and fatigue life of the untreated and treated specimens were studied by using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM), and a developed ultra-high cycle fatigue test (UFT). After UNSM treatment, the coarse ferrite grains (- 10 μm) were refined to nanosize (- 200 nm), therefore, nanostructured surface layers were fabricated. Meanwhile, in the deformed layer, the number density and area fraction of cementite were increased up to - 400% and - 550%, respectively, which increased with the decrease in depth from the topmost treated surface. The improvement of hardness (from 200 Hv to 280 Hv) and high cycles fatigue strength by - 10% were considered the contribution of the developed nanostructure in the UNSM treated specimen. PMID:25958512

  19. High Cycle Fatigue (HCF) Science and Technology Program

    Science.gov (United States)

    Bartsch, Thomas M.

    2002-05-01

    This fifth annual report of the National Turbine Engine High Cycle Fatigue (HCF) Program is a brief review of work completed, work in progress, and technical accomplishments. This program is a coordinated effort with participation by the Air Force, the Navy, and NASA. The technical efforts are organized under seven action teams Materials Damage Tolerance Research, Forced Response Prediction, Component Analysis, Instrumentation, Passive Damping Technology, Component Surface Treatments, and Engine Demonstration and two Programs Test and Evaluation, and Transitions (ENSIP).

  20. Competition between microstructure and defect in multiaxial high cycle fatigue

    Directory of Open Access Journals (Sweden)

    F. Morel

    2015-07-01

    Full Text Available This study aims at providing a better understanding of the effects of both microstructure and defect on the high cycle fatigue behavior of metallic alloys using finite element simulations of polycrystalline aggregates. It is well known that the microstructure strongly affects the average fatigue strength and when the cyclic stress level is close to the fatigue limit, it is often seen as the main source of the huge scatter generally observed in this fatigue regime. The presence of geometrical defects in a material can also strongly alter the fatigue behavior. Nonetheless, when the defect size is small enough, i.e. under a critical value, the fatigue strength is no more affected by the defect. The so-called Kitagawa effect can be interpreted as a competition between the crack initiation mechanisms governed either by the microstructure or by the defect. Surprisingly, only few studies have been done to date to explain the Kitagawa effect from the point of view of this competition, even though this effect has been extensively investigated in the literature. The primary focus of this paper is hence on the use of both FE simulations and explicit descriptions of the microstructure to get insight into how the competition between defect and microstructure operates in HCF. In order to account for the variability of the microstructure in the predictions of the macroscopic fatigue limits, several configurations of crystalline orientations, crystal aggregates and defects are studied. The results of each individual FE simulation are used to assess the response at the macroscopic scale thanks to a probabilistic fatigue criterion proposed by the authors in previous works. The ability of this criterion to predict the influence of defects on the average and the scatter of macroscopic fatigue limits is evaluated. In this paper, particular emphasis is also placed on the effect of different loading modes (pure tension, pure torsion and combined tension and torsion on

  1. High-cycle fatigue characterization of titanium 5Al-2.5Sn alloy

    Science.gov (United States)

    Mahfuz, H.; Xin, Yu T.; Jeelani, S.

    1993-01-01

    High-cycle fatigue behavior of titanium 5Al 2.5Sn alloy at room temperature has been studied. S-N curve characterization is performed at different stress ratios ranging from 0 to 0.9 on a subsized fatigue specimen. Both two-stress and three-stress level tests are conducted at different stress ratios to study the cumulative fatigue damage. Life prediction techniques of linear damage rule, double linear damage rule and damage curve approaches are applied, and results are compared with the experimental data. The agreement between prediction and experiment is found to be excellent.

  2. A Very High-Cycle Fatigue Test and Fatigue Properties of TC17 Titanium Alloy

    Science.gov (United States)

    Jiao, Shengbo; Gao, Chao; Cheng, Li; Li, Xiaowei; Feng, Yu

    2016-03-01

    The present work studied the very high-cycle fatigue (VHCF) test and fatigue properties of TC17 titanium alloy. The specimens for bending vibration were designed using the finite element method and the VHCF tests were conducted by using the ultrasonic fatigue testing system. The results indicated that there is no the fatigue limit for TC17 titanium alloy, and the S-N curve shows a continuously descending trend. The fatigue crack initiates at the specimen surface within the range of VHCF and the VHCF lives follow the log-normal distribution more closely.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-08-20

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

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

    International Nuclear Information System (INIS)

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 106 cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  5. Effects of foreign object damage from small hard particles on the high-cycle fatigue life of titanium-(6)aluminum-(4)vanadium

    Science.gov (United States)

    Hamrick, Joseph L., II

    Thin rectangular samples of Ti-6Al-4V were damaged by four methods to represent foreign object damage found in turbine engine blades: (1) impact with 2 mm. and 5 mm diameter glass spheres at 305 m/s, (2) impact with 2 mm and 4 mm diameter steel spheres at 305 m/s, (3) quasi-static displacement controlled indentation using steel chisels with 1 mm, 2 nun and 5 mm diameter tips and (4) shearing notches with a 2 mm. diameter chisel point under a quasi-static loading condition. Finite element analysis was used to study the relationship between the stress state created by the plastic damage and the fatigue strength. A new method of quantifying the amount of plastic damage from multiple methods was developed. The fatigue strength required for crack initiation at 10E7 cycles was found to be a function of the total depth from the edge of the undeformed specimen up to the end of the plastically deformed zone. For damage depths less than 1750 mum, the reduction in fatigue strength is proportional to the depth of total damage. For depths > 1750 mum, there appears to be a threshold value of fatigue strength.

  6. MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

    Directory of Open Access Journals (Sweden)

    Grzegorz SZALA

    2014-03-01

    Full Text Available In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF, high cycle fatigue (HCF, fatigue limit (FL and giga cycle fatigue (GCF appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys.

  7. Investigation of High Cycle Fatigue Life of MW Grade Wind Turbine Ductile Iron Hub%兆瓦级风电轮毂球铁高周疲劳寿命研究

    Institute of Scientific and Technical Information of China (English)

    刘佳; 曲迎东; 李荣德; 马广辉; 白彦华; 姜珂; 邱克强; 尤俊华; 王瑞春

    2012-01-01

    为了获得MW级风机轮毂QT350-22LT的高周疲劳寿命.通过拉-拉高周疲劳试验获得其疲劳极限,并通过数值模拟的方法确定QT350-22LT是否能够作为轮毂材料.疲劳试验在PW3-10程序控制高频万能疲劳试验机进行,采用实际生产的附铸试块进行拉-拉高周疲劳试验.试验结果表明:获得的兆瓦级风电轮毂QT350-22LT的疲劳极限值为250MPa,根据数据绘制的S-N曲线的拐点在290MPa;疲劳源的位置不同,所产生的瞬断区断口形貌也有所差别.对轮毂本身所能承受的最大应力进行有限元分析,得到最大应力为156MPa.应力集中部位的值没有超过材料的疲劳极限,这证明球铁QT350-22LT能够满足风机轮毂设计的应力要求.%The main purpose of this paper is to obtain high cycle fatigue life of MW grade the wheel hub (QT350-22 LT). Through the pull-pull high cycle fatigue tests, the fatigue limit is determined. The numerical simulation method was used to determine whether QT3 50-22 LT is able to be the hub material or not. The fatigue test equipment and materials are PW3-10 program control high frequency universal fatigue test machine and the practical production casting blocks, respectively. The results show that fatigue limit of the MW grade wind turbine hub QT350-22 LT is 250 MPa and inflection point of S-N curve draw according to data is 290 MPa; the morphologies of the transient breaking fracture are different due to the different crack sources. The maximum tensile stress of the hub is 156 MPa, which is obtained by the finite element analysis. The value of tensile stress concentration position is no more than the fatigue limit of the material, which proves that the ductile iron hub (QT350-22 LT) can satisfy the design requirement of stress.

  8. Problems of the high-cycle fatigue of the materials intended for the parts of modern gas-turbine engines and power plants

    Science.gov (United States)

    Petukhov, A. N.

    2010-10-01

    The problems related to the determination of the life of the structural materials applied for important parts in gas-turbine engines and power plants from the results of high-cycle fatigue tests are discussed. Methods for increasing the reliability of the high-cycle fatigue characteristics and the factors affecting the operational reliability are considered.

  9. High cycle fatigue properties of die-cast magnesium alloy AZ91D-1%MM

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The high cycle fatigue properties of the die-cast magnesium alloy AZ91D containing 1%mischmetal(mass fraction)at a fatigue ratio of 0.1 were investigated.The difference in the microstructure between the skin and core region of the die-cast magnesium alloy was analyzed by optical microscopy.The mechanical property tests indicate that the values of the tensile strength,elongation and hardness are 185 MPa,1.5%and HBS 70±3 at room temperature,respectively.The p-S-N curve(p=50%)of the die-cast magnesium alloy AZ91D-1%MM is determined and the mean fatigue strength corresponding to 3.8×105cycles is 70 MPa.A linear relation between S and Np in log scale between 103 and 106 cycles is written with a equation.The mechanical properties are influenced by the casting defects.The fatigue life of the samples with minor defects is near to the upper limit of the fatigue life data.The fatigue fracture surface of the samples with minor defects possesses the mixed characteristics of quasi-cleavage,lacerated ridge and dimple and it is briule fracture mode as a whole.

  10. High cycle fatigue property of Ti-600 alloy at ambient temperature

    International Nuclear Information System (INIS)

    Research highlights: Ti-600, developed by Northwest Institute for Nonferrous Metal Research (NIN) in China, is a near alpha titanium alloy designed for components used in turbine engines up to 600 deg. C. Mechanical behavior of the alloy at ambient temperature and its service temperature has widely been studied, the fatigue property for the alloy has never been systematically discussed. Smooth axial fatigue tests were taken for solutioned plus aged alloy, and the fractographies were observed. In order to get the damage mechanism, OM and TEM microstructures were also investigated. - Abstract: Smooth axial fatigue tests were carried out at ambient temperature on one kind of near alpha titanium alloy named after Ti-600 at a frequency of 120-130 Hz and with two kinds of load ratios. The high cycle fatigue (HCF) strength for the solutioned and aged alloy is found to be 475 MPa fatigued with a load ratio R of 0.1, and which is 315 MPa with a load ratio R of -1. The observed high HCF strength for the samples fatigued with a load ratio R of 0.1 is attributed to its overlapping fine and thin plate like α + β phase microstructure. During the crack propagation region, at the same stress of 600 MPa, the sample with a fatigue life of 1.78 x 106 cycles has a better fatigue resistance than that of the sample with a fatigue life of 8.61 x 105 cycles, because of its smaller striation distance, its well-developed secondary cracks, more wider and coarsened α lathes precipitated at grain boundaries, and the heavily arranged interlacing transformed β microsructures. The average grain size of rare earth phases varies from several micrometers to 0.2 μm, no cracks corresponding to rare earth particles can be initiated.

  11. 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.

  12. Fatigue crack initiation life prediction of railroad

    International Nuclear Information System (INIS)

    Study of multiaxial high-cycle fatigue initiation life prediction for railroad is done in this paper. Using ANSYS 11.0 software three dimensional elasto-plastic finite element model of rail/wheel contact is constructed and fine mesh technique in contact region is used to achieve both computational efficiency and accuracy. Stress analysis is performed and fatigue damage in railroad is evaluated numerically using multiaxial fatigue crack initiation model. Using the stress history during one loading cycle and fatigue damage model, the effects of vertical loading, material hardness material fatigue properties and wheel/rail contact situation on fatigue crack initiation life are investigated.

  13. The significance of crack initiation stage in very high cycle fatigue of steels

    Energy Technology Data Exchange (ETDEWEB)

    Bergstroem, J. [Department of Materials Engineering, Karlstad University (Sweden); Burman, C.; Kazymyrovych, V.

    2010-04-15

    Different stages of the Very High Cycle Fatigue (VHCF) crack evolution in tool steels have been explored using a 20 kHz ultrasonic fatigue testing equipment. Extensive experimental data is presented describing VHCF behaviour, strength and crack initiating defects in an AISI H11 tool steel. Striation measurements are used to estimate fatigue crack growth rate, between 10{sup -8} and 10{sup -6} m/cycle, and the number of load cycles required for a crack to grow to critical dimensions. The growth of small fatigue cracks within the ''fish-eye'' is shown to be distinctively different from the crack propagation behaviour of larger cracks. More importantly, the crack initiation stage is shown to determine the total fatigue life, which emphasizes the inherent difficulty to detect VHCF cracks prior to failure. Several mechanisms for initiation and early crack growth are possible. Some of them are discussed here: crack development by local accumulation of fatigue damage at the inclusion - matrix interface, hydrogen assisted crack growth and crack initiation by decohesion of carbides from the matrix. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  14. Effect of severe shot peening on ultra-high-cycle fatigue of a low-alloy steel

    International Nuclear Information System (INIS)

    Highlights: • Severe shot peening was applied to obtain a nanostructured surface of 50Crmo4 steel. • An nanocrystalline structured is generated by severe shot peening. • Ultra-high-cycle fatigue test results show the remarkable effect of severe shot peening. • The results were discussed in the light the surface modifications induced by SSP. - Abstract: It is well known that shot peening is able to increase the fatigue strength and endurance of metal parts, especially with a steep stress gradient due to a notch. This positive effect is mainly put into relation with the ability of this treatment to induce a compressive residual stress state in the surface layer of material and to cause surface work hardening. Recently the application of severe shot peening (shot peening performed with severe treatment parameters) showed the ability to obtain more a remarkable improvement of the high cycle fatigue strength of steels. In this paper severe shot peening is applied to the steel 50CrMo4 and its effect in the ultra-high cycle fatigue regime is investigated. Roughness, microhardness, X-ray diffraction residual stress analysis and crystallite size measurement as well as scanning electron microscopy (SEM) observations were used for characterizing the severely deformed layer. Tension–compression high frequency fatigue tests were carried out to evaluate the effect of the applied treatment on fatigue life in the ultra-high cycle region. Fracture surface analysis by using SEM was performed with aim to investigate the mechanism of fatigue crack initiation and propagation. Results show an unexpected significant fatigue strength increase in the ultra-high cycle region after SSP surface treatment and are discussed in the light of the residual stress profile and crystallite size

  15. 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.

  16. High cycle thermal fatigue issues in PWR nuclear power plants, life time improvement of some austenitic stainless steel components; Cas de fatigue thermique a grand nombre de cycles dans des generateurs PWR, allongement de la duree de vie de pieces en acier inoxydable

    Energy Technology Data Exchange (ETDEWEB)

    Le Duff, J.A.; Lefrancois, A.; Meyzaud, Y. [AREVA NP, Materials and Technology Dept., 92 - Paris La Defense (France); Vernot, J.Ph.; Martin, D. [AREVA NP, Fluids and Structural Mechanics Dept., 92 - Paris La Defense (France); Mendez, J.; Lehericy, Y. [Ecole Nationale Superieure de Mecanique et d' Aerotechnique (ENSMA), 86 - Poitiers (France)

    2007-03-15

    Examples of high cycle thermal fatigue (HCTF) damage cases on PWR austenitic stainless steel components are reported. High cycle thermal fatigue risk is primarily due to mixing of cold and hot water, unexpected leaks of cold water through check valves or to turbulent penetration of hot water running in a main pipe into a connected line. When such thermal fatigue issues are identified in PWR power plants, manufacturing improvement such as inner surface polishing of austenitic stainless steel parts can be performed to increase the fatigue resistance of the components. (authors)

  17. Effects of high mean stress on the high-cycle fatigue behavior of PWA 1480

    International Nuclear Information System (INIS)

    PWA 1480 is a potential candidate material for use in the high-pressure fuel turbine blade of the Space Shuttle Main Engine. As an engine material it will be subjected to high-cycle fatigue loading superimposed on a high mean stress due to combined centrifugal and thermal loadings. This paper describes results obtained in an ongoing program to determine the effects of a high mean stress on the high-cycle fatigue behavior of this material

  18. Shakedown based model for high-cycle fatigue of shape memory alloys

    Science.gov (United States)

    Gu, Xiaojun; Moumni, Ziad; Zaki, Wael; Zhang, Weihong

    2016-11-01

    The paper presents a high-cycle fatigue criterion for shape memory alloys (SMAs) based on shakedown analysis. The analysis accounts for phase transformation as well as reorientation of martensite variants as possible sources of fatigue damage. In the case of high-cycle fatigue, once the structure has reached an asymptotic state, damage is assumed to become confined at the mesoscopic scale, or the scale of the grain, with no discernable inelasticity at the macroscopic scale. Using a multiscale approach, a high-cycle fatigue criterion analogous to the Dang Van model (Dang Van 1973) for elastoplastic metals is derived for SMAs obeying the Zaki–Moumni model for SMAs (Zaki and Moumni 2007a). For these alloys, a safe domain is established in stress deviator space, consisting of a hypercylinder with axis parallel to the direction of martensite orientation at the mesoscopic scale. Safety with regard to high-cycle fatigue, upon elastic shakedown, is conditioned by the persistence of the macroscopic stress path at every material point within the hypercylinder, whose size depends on the volume fraction of martensite. The proposed criterion computes a fatigue factor at each material point, indicating its degree of safeness with respect to high cycle fatigue.

  19. A very high cycle fatigue thermal dissipation investigation for titanium alloy TC4

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

    2014-04-01

    Titanium alloy TC4 is widely used in aeronautics applications where it is subjected to high frequency fatigue loads. Tests are performed to investigate the alloy fatigue behavior sustaining ultrasonic fatigue load in Very High Cycle Fatigue (VHCF) regime. Thermal dissipation for the alloy in 20 kHz frequency is studied and a model is proposed to describe the temperature increment in the framework of thermodynamics by estimation of the anelastic and inelastic thermal dissipation at microscopic active sites in the reference element volume. The failure probability prediction method is used to evaluate the VHCF dispersion based on the two scale model and fatigue thermal dissipation analysis.

  20. Effect of microstructure on high-cycle fatigue properties of Alloy718 plates

    Science.gov (United States)

    Ono, Y.; Yuri, T.; Nagashima, N.; Ogata, T.; Nagao, N.

    2015-12-01

    Effect of microstructure on high-cycle fatigue properties of Alloy718 were investigated at 77 K by using samples with three different microstructures; fine-grained (FG), coarse-grained (CG) and bimodal-grained (BG) ones. The BG sample consisted of FG and CG microstructural regions and grain sizes of those regions were close to those of the FG and the CG samples, respectively. High-cycle fatigue strength of the FG sample was higher than that of the CG sample. High-cycle fatigue strength of the BG sample was clearly lower than that of the FG sample and almost the same as that of the CG one. Flat area (facet) was found at fatigue crack initiation site in all specimens. Facet size was similar to the grain size and found to be almost same in the CG and the BG samples. Observations of the microstructure beneath the fatigue crack initiation site of the BG sample revealed that the facet corresponds to transgranular cracking in the course grain, meaning that fatigue crack initiated at the coarse grain in the BG sample. It is deduced that the high-cycle fatigue strength of Alloy 718 with the BG microstructure is strongly affected by that of the CG region in that material.

  1. Effects of δ-ferrite and welding structure on high-cycle fatigue properties of austenitic stainless steels weld metals

    International Nuclear Information System (INIS)

    We studied the effects of δ-ferrite and welding structure on high-cycle fatigue properties for austenitic stainless steel weld metals at cryogenic temperatures. SUS304L and SUS316L weld metals contained 0% δ-ferrite (0% material) and 10% δ-ferrite (10% material) were prepared. High-cycle fatigue tests were carried out at 293, 77 and 4 K. The S-N curves of those weld metals shifted towards higher stress levels, i.e., the longer life side, with decreasing test temperature. The ratios of 106-cycles fatigue strength (FS) to tensile strength (TS) of 0% material decreased from 0.8 to 0.45 and those of 10% material decreased between 0.35 to 0.65 with decreasing test temperature. Fatigue crack initiation sites of SUS304L 10% material were almost at blowholes, and those of SUS316L 10% material were at weld pass interface boundaries. On the other hand, those of 0% materials were considered to be due to the interface of the solidification structure. Although δ-ferrite reduces toughness at cryogenic temperatures in austenitic stainless steel weld metals, the effects of δ-ferrite on high-cycle fatigue properties are not significant

  2. Fatigue performance of laser additive manufactured Ti-6Al-4V in very high cycle fatigue (VHCF regime up to 109 cycles

    Directory of Open Access Journals (Sweden)

    Eric eWycisk

    2015-12-01

    Full Text Available Additive manufacturing technologies are in the process of establishing themselves as an alternative production technology to conventional manufacturing such as casting or milling. Especially laser additive manufacturing (LAM enables the production of metallic parts with mechanical properties comparable to conventionally manufactured components. Due to the high geometrical freedom in LAM the technology enables the production of ultra-light weight designs and therefore gains increasing importance in aircraft and space industry. The high quality standards of these industries demand predictability of material properties for static and dynamic load cases. However, fatigue properties especially in the very high cycle fatigue regime until 109 cycles have not been sufficiently determined yet. Therefore this paper presents an analysis of fatigue properties of laser additive manufactured Ti-6Al-4V under cyclic tension-tension until 107 cycles and tension-compression load until 109 cycles.For the analysis of laser additive manufactured titanium alloy Ti-6Al-4V Woehler fatigue tests under tension-tension and tension-compression were carried out in the high cycle and very high cycle fatigue regime. Specimens in stress-relieved as well as hot-isostatic-pressed conditions were analyzed regarding crack initiation site, mean stress sensitivity and overall fatigue performance. The determined fatigue properties show values in the range of conventionally manufactured Ti-6Al-4V with particularly good performance for hot-isostatic-pressed additive-manufactured material. For all conditions the results show no conventional fatigue limit but a constant increase in fatigue life with decreasing loads. No effects of test frequency on life span could be determined. However, independently of testing principle, a shift of crack initiation from surface to internal initiation could be observed with increasing cycles to failure.

  3. Fatigue performance of laser additive manufactured Ti-6Al-4V in very high cycle fatigue (VHCF) regime up to 109 cycles

    Science.gov (United States)

    Wycisk, Eric; Siddique, Shafaqat; Herzog, Dirk; Walther, Frank; Emmelmann, Claus

    2015-12-01

    Additive manufacturing technologies are in the process of establishing themselves as an alternative production technology to conventional manufacturing such as casting or milling. Especially laser additive manufacturing (LAM) enables the production of metallic parts with mechanical properties comparable to conventionally manufactured components. Due to the high geometrical freedom in LAM the technology enables the production of ultra-light weight designs and therefore gains increasing importance in aircraft and space industry. The high quality standards of these industries demand predictability of material properties for static and dynamic load cases. However, fatigue properties especially in the very high cycle fatigue regime until 109 cycles have not been sufficiently determined yet. Therefore this paper presents an analysis of fatigue properties of laser additive manufactured Ti-6Al-4V under cyclic tension-tension until 107 cycles and tension-compression load until 109 cycles. For the analysis of laser additive manufactured titanium alloy Ti-6Al-4V Woehler fatigue tests under tension-tension and tension-compression were carried out in the high cycle and very high cycle fatigue regime. Specimens in stress-relieved as well as hot-isostatic-pressed conditions were analyzed regarding crack initiation site, mean stress sensitivity and overall fatigue performance. The determined fatigue properties show values in the range of conventionally manufactured Ti-6Al-4V with particularly good performance for hot-isostatic-pressed additive-manufactured material. For all conditions the results show no conventional fatigue limit but a constant increase in fatigue life with decreasing loads. No effects of test frequency on life span could be determined. However, independently of testing principle, a shift of crack initiation from surface to internal initiation could be observed with increasing cycles to failure.

  4. Influence of neodymium on high cycle fatigue behavior of die cast AZ91D magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    杨友; 李雪松

    2010-01-01

    High cycle fatigue behavior of die cast AZ91D magnesium alloy with different Nd contents was investigated.Axial mechanical fatigue tests were conducted at the stress ratio R=0.1 and the fatigue strength was evaluated using up-to-down load method on specimens of AZ91D with different Nd contents.The results showed that the grain of AZ91D alloy was refined,the size and amount of β-Mg17Al12 phase decreased and distributed uniformly with increasing Nd content.At the number of cycles to failure,Nf=107,the fatigue...

  5. High cycle fatigue crack propagation resistance and fracture toughness in ship steels (Short Communication

    Directory of Open Access Journals (Sweden)

    R.S. Tripathi

    2001-04-01

    Full Text Available In this paper, two grades of steel, viz., plain carbon steel and low alloy steel used in naval ships have been selected for studies on high cycle fatigue, crack propagation, stress intensity and crack opening displacement (COD. Specimen for high cycle fatigue was prepared as per IS: 1608. High cycle fatigue was carried out up to 50,000 cycles at 1000 kgfto 2000 kgfloads. Up to 2000 kgfloads, both the materials were observed within elastic zones. A number of paran1eters, including stress, strain and strain range, which indicate elastic behaviour of steels, have been considered. Low alloy steel specimen was prepared as per ASTM standard: E-399 and subjected to 5,00,000 cycles. Crack propagation, COD, stress intensity, load-cycle variations, load-COD relation, and other related paran1eters have been studied using a modem universal testing machine with state-of-the-art technology

  6. Non-local high cycle fatigue criterion for metallic materials with corrosion defects

    OpenAIRE

    May Mohamed El; Saintier Nicolas; Palin-Luc Thierry; Devos Olivier

    2014-01-01

    Designing structures against corrosion fatigue has become a key problem for many engineering structures evolving in complex environmental conditions of humidity (aeronautics, civil engineering …). In this study, we investigate the effect of corrosion defects on the high cycle fatigue (HCF) strength of a martensitic stainless steel with high specific mechanical strength, used in aeronautic applications. A volumetric approach based on Crossland equivalent stress is proposed. This can be applied...

  7. The role of high cycle fatigue (HCF) onset in Francis runner reliability

    International Nuclear Information System (INIS)

    High Cycle Fatigue (HCF) plays an important role in Francis runner reliability. This paper presents a model in which reliability is defined as the probability of not exceeding a threshold above which HCF contributes to crack propagation. In the context of combined Low Cycle Fatigue (LCF) and HCF loading, the Kitagawa diagram is used as the limit state threshold for reliability. The reliability problem is solved using First-Order Reliability Methods (FORM). A study case is proposed using in situ measured strains and operational data. All the parameters of the reliability problem are based either on observed data or on typical design specifications. From the results obtained, we observed that the uncertainty around the defect size and the HCF stress range play an important role in reliability. At the same time, we observed that expected values for the LCF stress range and the number of LCF cycles have a significant influence on life assessment, but the uncertainty around these values could be neglected in the reliability assessment.

  8. 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

  9. Biaxial high cycle fatigue: experimental investigation and two-scale damage model

    International Nuclear Information System (INIS)

    This research thesis first describes the multi-axial fatigue phenomenon in the cases of mechanical and complex loadings, discusses multi-axial fatigue criteria, and presents the approach of fatigue by incremental damage mechanics. Then, it reports an experimental investigation of fatigue crack initiation under biaxial polycyclic fatigue in 304L austenitic stainless steel and in titanium alloy. The author presents a probabilistic two-scale damage model, and then reports the assessment of multi-axial fatigue life by means of this model

  10. High Cycle-life Shape Memory Polymer at High Temperature

    Science.gov (United States)

    Kong, Deyan; Xiao, Xinli

    2016-01-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g−1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously. PMID:27641148

  11. High Cycle-life Shape Memory Polymer at High Temperature

    Science.gov (United States)

    Kong, Deyan; Xiao, Xinli

    2016-09-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g‑1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously.

  12. The effect of low cycle fatigue cracks and loading history on high cycle fatigue threshold

    Science.gov (United States)

    Moshier, Monty Allen

    High cycle fatigue (HCF) has been of great concern of late in light of the many HCF gas turbine engine failures experienced by the U.S. Air Force. Due to the high frequency, failures occur rapidly when components sustain damage from other sources. Low cycle fatigue (LCF) can initiate cracks that produce such damage. This study investigates the HCF threshold of Ti-6A1-4V when naturally initiated small surface cracks (2a = 25 mum--600 mum) are present. Small surface cracks are initiated in notched specimens using two different LCF loading histories at room temperature and 10 Hz. Direct current potential difference (DCPD) is used to detect crack initiation. Surface crack measurements are made using a scanning electron microscope prior to HCF testing. Heat tinting prior to HCF testing is used to mark the crack front to allow for post fracture crack measurements. HCF thresholds at R = 0.1 and R = 0.5 are determined for each specimen using step loading at room temperature and 600 Hz. Additionally, the HCF threshold is measured at R = 0.1 for specimens with small cracks that have been stress relief annealed to eliminate residual stresses and load history. Long crack thresholds are determined using a similar step loading procedure at R = 0.1 and R = 0.5 for specimens which have been precracked using a range of Kmax. Long crack threshold measurements are also determined for specimens which have been precracked using a range of Kmax, but stress relief annealed prior to testing. Comparisons show that HCF threshold measurements, when naturally initiated small cracks are present, are dependent on the load histories that are used to initiate the cracks. Further comparisons show that the measured small crack thresholds follow similar trends for load history effects which occur in the long crack threshold data. Additionally, it is found that thresholds can be measured free of load history effects by using a stress relief annealing process after the precracking and prior to the

  13. High-Cycle Fatigue Resistance of Si-Mo Ductile Cast Iron as Affected by Temperature and Strain Rate

    Science.gov (United States)

    Matteis, Paolo; Scavino, Giorgio; Castello, Alessandro; Firrao, Donato

    2015-09-01

    Silicon-molybdenum ductile cast irons are used to fabricate exhaust manifolds of internal combustion engines of large series cars, where the maximum pointwise temperature at full engine load may be higher than 973 K (700 °C). In this application, high-temperature oxidation and thermo-mechanical fatigue (the latter being caused by the engine start and stop and by the variation of its power output) have been the subject of several studies and are well known, whereas little attention has been devoted to the high-cycle fatigue, arising from the engine vibration. Therefore, the mechanical behavior of Si-Mo cast iron is studied here by means of stress-life fatigue tests up to 10 million cycles, at temperatures gradually increasing up to 973 K (700 °C). The mechanical characterization is completed by tensile and compressive tests and ensuing fractographic examinations; the mechanical test results are correlated with the cast iron microstructure and heat treatment.

  14. Development of a Very High Cycle Fatigue (VHCF multiaxial testing device

    Directory of Open Access Journals (Sweden)

    M. Vieira

    2016-07-01

    Full Text Available The very high cycle region of the S-N fatigue curve has been the subject of intensive research on the last years, with special focus on axial, bending, torsional and fretting fatigue tests. Very high cycle fatigue can be achieved using ultrasonic exciters which allow for frequency testing of up to 30 kHz. Still, the multiaxial fatigue analysis is not yet developed for this type of fatigue analyses, mainly due to conceptual limitations of these testing devices. In this paper, a device designed to produce biaxial fatigue testing using a single piezoelectric axial exciter is presented, as well as the preliminary testing of this device. The device is comprised of a horn and a specimen, which are both attached to the piezoelectric exciter. The steps taken towards the final geometry of the device are presented. Preliminary experimental testing of the developed device is made using thermographic imaging, strain measurements and vibration speeds and indicates good behaviour of the tested specimen.

  15. Experimental study on properties of high cycle thermal fatigue. Outline and test plan of high cycle fatigue test equipment on sodium

    International Nuclear Information System (INIS)

    At a nuclear power plant, where fluids of high and low temperature flow into each other, it is necessary to prevent structural failure damage caused by high cycle thermal fatigue (thermal striping phenomenon). High cycle fatigue test equipment on thermal can be develop by modifying the thermal transient test facility for structure (TTS) in order to clarify the effect of temperature fluctuation induced by the thermal striping phenomenon on crack initiation and their propagation behavior. The test equipment has the following characteristic. (1) Fluid is controlled by a circulation pump, and by continuously changing the flow quantity ratio of high and low temperature Sodium, sinusoidal temperature fluctuations at various period of the test samples can be taken. (2) Mixing is done by the jet flow mix, thus it can generate axisymmetric temperature fluctuations by accelerating the mixing process of high and low temperature Sodium. (3) It can also control the temperature fluctuation, in which short and long term changes are superimposed. (4) Because the test sample cylinder is hollow, analysis of thermal stress and data from crack initiation to crack propagation can easily be obtained. Sinusoidal temperature fluctuations, random temperature fluctuations, and strength testing of the weld zone by test samples made of stainless steel are planned in the next stage. (author)

  16. Energy Approach-Based Simulation of Structural Materials High-Cycle Fatigue

    Science.gov (United States)

    Balayev, A. F.; Korolev, A. V.; Kochetkov, A. V.; Sklyarova, A. I.; Zakharov, O. V.

    2016-02-01

    The paper describes the mechanism of micro-cracks development in solid structural materials based on the theory of brittle fracture. A probability function of material cracks energy distribution is obtained using a probabilistic approach. The paper states energy conditions for cracks growth at material high-cycle loading. A formula allowing to calculate the amount of energy absorbed during the cracks growth is given. The paper proposes a high- cycle fatigue evaluation criterion allowing to determine the maximum permissible number of solid body loading cycles, at which micro-cracks start growing rapidly up to destruction.

  17. Effects of load ratio, R, and test temperature on high cycle fatigue behavior of nano-structured Al-4Y-4Ni-X alloy composites

    Energy Technology Data Exchange (ETDEWEB)

    El-Shabasy, Adel B., E-mail: ashabasy@hotmail.com [Department of Design and Production Engineering, Faculty of Engineering, Ain Shams University, Cairo 11517 (Egypt); Hassan, Hala A. [Department of Design and Production Engineering, Faculty of Engineering, Ain Shams University, Cairo 11517 (Egypt); Lewandowski, John J. [Department of Material' s Science and Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)

    2012-12-15

    Nanostructured Al-4Y-4Ni-X composites created by extruding atomized amorphous powders at different extrusion ratios were tested under high cycle bending fatigue at load ratios, R=0.1, 0.33 and -1 at room temperature, 149 Degree-Sign C and 260 Degree-Sign C. Increasing the extrusion ratio generally improved the fatigue life and the fatigue limits were well in excess of that obtained on conventional aluminum alloys at all temperatures tested. The fatigue limits obtained in this work were also compared to previously reported values for a nanostructured composite Al-Gd-Ni-Fe alloy produced via similar means.

  18. Strength calculation of NPP equipment and pipelines during operation. Low- and high-cycle corrosion fatigue

    International Nuclear Information System (INIS)

    This paper presents empirical equations and design curves for structural steels employed in nuclear power facilities with light water reactors. These equations allow to take into account the effects of cycle asymmetry, water coolant and ductility decrease during operation. The fatigue curves cover the low-cycle and high-cycle regions (up to 1012 cycles). The equations include the mechanical characteristics of steels under static tension. The coolant effect on steel fatigue is allowed for using a model developed at the Argonne National Laboratory

  19. Experimental investigation of high cycle thermal fatigue in a T-junction piping system

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, P. Karthick; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    High cycle thermal fatigue damage of structure in the vicinity of T-junction piping systems in nuclear power plants is of importance. Mixing of coolant streams at significant temperature differences causes thermal fluctuations near piping wall leading to gradual thermal degradation. Flow mixing in a T-junction is performed. The determined factors result in bending stresses being imposed on the piping system ('Banana effect').

  20. Effects of High Mean Stress on High-cycle Fatigue Behavior of PWA 1480

    Science.gov (United States)

    Majumdar, S.; Antolovich, S. D.; Milligan, W. W.

    1985-01-01

    PWA 1480 is a potential candidate material for use in the high-pressure fuel turbine blade of the space shuttle main engine. As an engine material it will be subjected to high-cycle fatigue loading superimposed on a high mean stress due to combined centrifugal and thermal loadings. The present paper describes the results obtained in an ongoing program at the Argonne National Laboratory, sponsored by NASA Lewis, to determine the effects of a high mean stress on the high-cycle fatigue behavior of this material. Straight-gauge high-cycle fatigue specimens, 0.2 inch in diameter and with the specimen axis in the 001 direction, were supplied by NASA Lewis. The nominal room temperature yield and ultimate strength of the material were 146 and 154 ksi, respectively. Each specimen was polished with 1-micron diamond paste prior to testing. However, the surface of each specimen contained many pores, some of which were as large as 50 micron. In the initial tests, specimens were subjected to axial-strain-controlled cycles. However, very little cyclic plasticity was observed.

  1. High-cycle fatigue behavior of Ti-5Al-2.5Sn ELI alloy forging at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio; Demura, Masahiko [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Matsuoka, Saburo [Kyushu University, 744, Motooka, Nishi-ku, Fukuoka, Fukuoka 819-0395 (Japan); Sunakawa, Hideo [Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan)

    2014-01-27

    High-cycle fatigue properties of Ti-5Al-2.5Sn Extra Low Interstitial (ELI) alloy forging were investigated at low temperatures. The high-cycle fatigue strength at low temperatures of this alloy was relatively low compared with that at ambient temperature. The crystallographic orientation of a facet formed at a fatigue crack initiation site was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to understand the fatigue crack initiation mechanism and discuss on the low fatigue strength at low temperature. Furthermore, in terms of the practical use of this alloy, the effect of the stress ratio (or mean stress) on the high-cycle fatigue properties was evaluated using the modified Goodman diagram.

  2. Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures

    CERN Document Server

    Heikkinen, Samuli; Wuensch, Walter

    2010-01-01

    In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

  3. Damage estimates for European and U.S.sites using the U.S. high-cycle fatigue data base

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, H.J. [Wind Energy Technology, Sandia National Lab., Albuquerque, NM (United States)

    1996-09-01

    This paper uses two high-cycle fatigue data bases, one for typical U.S. blade materials and one for European materials, to analyze the service lifetime of a wind turbine blade subjected to the WISPER load spectrum for northern European sites and the WISPER protocol load spectrum for U.S. wind farm sites. The U.S. data base contains over 2200 data points that were obtained using coupon testing procedures. These data are used to construct a Goodman diagram that is suitable for analyzing wind turbine blades. This result is compared to the Goodman diagram derived from the European fatigue data base FACT. The LIFE2 fatigue analysis code for wind turbines is then used to predict the service lifetime of a turbine blade subjected to the two loading histories. The results of this study indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a U.S. wind farm site, i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a U.S. wind farm site. Further, the analysis demonstrate that the European and the U.S. fatigue material data bases are in general agreement for the prediction of tensile failures. However, for compressive failures, the two data bases are significantly different, with the U.S. data base predicting significantly shorter service lifetimes than the European data base. (au) 14 refs.

  4. Simulation of Delamination Under High Cycle Fatigue in Composite Materials Using Cohesive Models

    Science.gov (United States)

    Camanho, Pedro P.; Turon, Albert; Costa, Josep; Davila, Carlos G.

    2006-01-01

    A new thermodynamically consistent damage model is proposed for the simulation of high-cycle fatigue crack growth. The basis for the formulation is an interfacial degradation law that links Fracture Mechanics and Damage Mechanics to relate the evolution of the damage variable, d, with the crack growth rate da/dN. The damage state is a function of the loading conditions (R and (Delta)G) as well as the experimentally-determined crack growth rates for the material. The formulation ensures that the experimental results can be reproduced by the analysis without the need of additional adjustment parameters.

  5. High Cycle Fatigue Crack Initiation Study of Case Blade Alloy Rene 125

    Science.gov (United States)

    Kantzos, P.; Gayda, J.; Miner, R. V.; Telesman, J.; Dickerson, P.

    2000-01-01

    This study was conducted in order to investigate and document the high cycle fatigue crack initiation characteristics of blade alloy Rene 125 as cast by three commercially available processes. This alloy is typically used in turbine blade applications. It is currently being considered as a candidate alloy for high T3 compressor airfoil applications. This effort is part of NASA's Advanced Subsonic Technology (AST) program which aims to develop improved capabilities for the next generation subsonic gas turbine engine for commercial carriers. Wrought alloys, which are customarily used for airfoils in the compressor, cannot meet the property goals at the higher compressor exit temperatures that would be required for advanced ultra-high bypass engines. As a result cast alloys are currently being considered for such applications. Traditional blade materials such as Rene 125 have the high temperature capabilities required for such applications. However, the implementation of cast alloys in compressor airfoil applications where airfoils are typically much thinner does raise some issues of concern such as thin wall castability, casting cleaningness, and susceptibility to high-cycle fatigue (HCF) loading.

  6. Evaluation of the Effect of Surface Finish on High-Cycle Fatigue of SLM-IN718

    Science.gov (United States)

    Lambert, D. M.

    2016-01-01

    The surface finish of parts produced by additive manufacturing processes is much rougher than the surface finish generated by machining processes, and a rougher surface can reduce the fatigue strength of a part. This paper discusses an effort to quantify that reduction of strength in high-cycle fatigue for selective laser melt (SLM) coupons. A high-cycle fatigue (HCF) knockdown factor was estimated for Inconel 718, manufactured with the SLM process. This factor is the percentage reduction from the maximum stress in fatigue for low-stress ground (LSG) specimens to the maximum stress of those left with the original surface condition at the same fatigue life. Specimens were provided by a number of vendors, free to use their "best practice"; only one heat treat condition was considered; and several test temperatures were characterized, including room temperature, 800F, 1000F, and 1200F. The 1000F data had a large variance, and was omitted from consideration in this document. A first method used linear approximations extracted from the graphs, and only where data was available for both. A recommended knockdown factor of the as-built surface condition (average roughness of approximately 245 micro-inches/inch) versus low-stress ground condition (roughness no more than 4 micro-inches/inch) was established at approximately 1/3 or 33%. This is to say that for the as-built surface condition, a maximum stress of 2/3 of the stress for LSG can be expected to produce a similar life in the as-built surface condition. In this first evaluation, the knockdown factor did not appear to be a function of temperature. A second approach, the "KP method", incorporated the surface finish measure into a new parameter termed the pseudo-stress intensity factor, Kp, which was formulated to be similar to the fracture mechanics stress intensity factor. Using Kp, the variance seemed to be reduced across all sources, and knockdown factors were estimated using Kp over the range where data occurred. A

  7. Low-cycle fatigue/high-cycle fatigue (LCF/HCF) interaction studies using a 10- to 40-kHz HCF loading device

    Science.gov (United States)

    Matikas, Theodore E.

    1999-02-01

    To simulate the testing conditions experienced by aircraft engine turbine blades, a new experimental facility was developed capable of providing interactive low cycle fatigue (LCF)/high cycle fatigue (HCF) loading. The new facility is based on a HCF cell that can operate in the 10-40 kHz frequency range. This HCF testing cell can also be interfaced to a servo-hydraulic load frame, which provides a second fatigue cycle. Sample geometry is critical for the HCF cell to produce the desired applied load on the specimen. The objective of this research is to develop analytical modeling necessary for the design of test coupons to be used in the new HCF testing cell operating at ultrasonic frequencies, and also to demonstrate the capabilities of the new device by performing LCF/HCF interaction studies in Ti-6Al-4V. The results of these studies clearly showed the effect of the HCF component of the load in spite the fact that the HCF component was only 15-19 percent of the overall load. It was also found that the HCF component of the load was the major cause of observed damage with the LCF component having much less effect. Eliminating the HCF component completely resulted in increasing the fatigue life at least an order of magnitude.

  8. Effect of thermo-mechanical loading histories on fatigue crack growth behavior and the threshold in SUS 316 and SCM 440 steels. For prevention of high cycle thermal fatigue failures

    International Nuclear Information System (INIS)

    High cycle thermal fatigue failure of pipes induced by fluid temperature change is one of the interdisciplinary issues to be concerned for long term structural reliability of high temperature components in energy systems. In order to explore advanced life assessment methods to prevent the failure, fatigue crack propagation tests were carried out in a low alloy steel and an austenitic stainless steel under typical thermal and thermo-mechanical histories. Special attention was paid to both the effect of thermo-mechanical loading history on the fatigue crack threshold, as well as to the applicability of continuum fracture mechanics treatment to small or short cracks. It was shown experimentally that the crack-based remaining fatigue life evaluation provided more reasonable assessment than the traditional method based on the semi-empirical law in terms of 'usage factor' for high cycle thermal fatigue failure that is employed in JSME Standard, S017. The crack propagation analysis based on continuum fracture mechanics was almost successfully applied to the small fatigue cracks of which size was comparable to a few times of material grain size. It was also shown the thermo-mechanical histories introduced unique effects to the prior fatigue crack wake, resulting in occasional change in the fatigue crack threshold. (author)

  9. Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel

    DEFF Research Database (Denmark)

    Carstensen, J.V.; Mayer, H.; Brøndsted, P.

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained...

  10. Evaluation of the Effect of Surface Finish on High-Cycle Fatigue for SLM-IN718

    Science.gov (United States)

    Lambert, Dennis M.

    2016-01-01

    A high-cycle fatigue (HCF) knockdown factor was estimated for Inconel 718, manufactured with the selective laser melt (SLM) process. This factor is the reduction at a common fatigue life from the maximum stress in fatigue for low-stress ground (LSG) specimens to the maximum stress of those left with the original surface condition. Various vendors provided specimens. To reduce the number of degrees-of-freedom, only one heat treat condition was evaluated. Testing temperatures included room temperature, 800F, 1000F, and 1200F. The two surface conditions were compared at constant lives, where data was available. The recommended knockdown factor of the as-built surface condition (average roughness of approximately 245 micro-inches/inch) versus low-stress ground condition (roughness <= 4 micro-inches/inch) is approximately 1/3 or 33%. This is to say that for the as-built surface condition, a maximum stress of 2/3 of the stress for LSG can be expected to produce the same life in the as built surface condition. As an alternative method, the surface finish was incorporated into a new parameter with the maximum stress. The new parameter was formulated to be similar to the fracture mechanics stress intensity factor, and it was named the pseudo stress intensity factor, Kp. Using Kp, the variance seemed acceptable across all sources, and the knockdown factor was estimated over the range of data identified by Kp where data occurred. A plot of the results suggests that the knockdown factor is a function of temperature, and that for low lives the knockdown is greater than the knockdown observed above about one million cycles, where it stabilizes. One data point at room temperature was clearly different, and the sparsity of data in the higher life region reduces the value of these results. The method does appear to provide useful results, and further characterization of the method is suggested.

  11. Very-High-Cycle-Fatigue of in-service air-engine blades, compressor and turbine

    Science.gov (United States)

    Shanyavskiy, A. A.

    2014-01-01

    In-service Very-High-Cycle-Fatigue (VHCF) regime of compressor vane and turbine rotor blades of the Al-based alloy VD-17 and superalloy GS6K, respectively, was considered. Surface crack origination occurred at the lifetime more than 1500 hours for vanes and after 550 hours for turbine blades. Performed fractographic investigations have shown that subsurface crack origination in vanes took place inspite of corrosion pittings on the blade surface. This material behavior reflected lifetime limit that was reached by the criterion VHCF. In superalloy GS6K subsurface fatigue cracking took place with the appearance of flat facet. This phenomenon was discussed and compared with specimens cracking of the same superalloy but prepared by the powder technology. In turbine blades VHCF regime appeared because of resonance of blades under the influenced gas stream. Both cases of compressor-vanes and turbine blades in-service cracking were discussed with crack growth period and stress equivalent estimations. Recommendations to continue aircrafts airworthiness were made for in-service blades.

  12. Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

    2001-01-01

    Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high-cycle

  13. Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dong-Ming; Miller, Robert A.

    1998-01-01

    Ceramic thermal barrier coatings have attracted increased attention for diesel engine applications. The advantages of using the ceramic coatings include a potential increase in efficiency and power density and a decrease in maintenance cost. Zirconia-based ceramics are the most important coating materials for such applications because of their low thermal conductivity, relatively high thermal expansivity and excellent mechanical properties. However, durability of thick thermal barrier coatings (TBCS) under severe temperature cycling encountered in engine conditions, remains a major question. The thermal transients associated with the start/stop and no-load/full-load engine cycle, and with the in-cylinder combustion process, generate thermal low cycle fatigue (LCF) and thermal high cycle fatigue (HCF) in the coating system. Therefore, the failure mechanisms of thick TBCs are expected to be quite different from those of thin TBCs under these temperature transients. The coating failure is related not only to thermal expansion mismatch and oxidation of the bond coats and substrates, but also to the steep thermal stress gradients induced in the coating systems. Although it has been reported that stresses generated by thermal transients can initiate surface and interface cracks in a coating system, the mechanisms of the crack propagation and of coating failure under the complex LCF and HCF conditions are still not understood. In this paper, the thermal fatigue behavior of an yttria partially stabilized zirconia coating system under simulated LCF and HCF engine conditions is investigated. The effects of LCF and HCF on surface crack initiation and propagation are also discussed.

  14. Influence of microstructure on high-cycle fatigue of Ti-6Al-4V: Bimodal vs. lamellar structures

    Science.gov (United States)

    Nalla, R. K.; Ritchie, R. O.; Boyce, B. L.; Campbell, J. P.; Peters, J. O.

    2002-03-01

    The high-cycle fatigue (HCF) of titanium alloy turbine engine components remains a principal cause of failures in military aircraft engines. A recent initiative sponsored by the United States Air Force has focused on the major drivers for such failures in Ti-6Al-4V, a commonly used turbine blade alloy, specifically for fan and compressor blades. However, as most of this research has been directed toward a single processing/heat-treated condition, the bimodal (solution-treated and overaged (STOA)) microstructure, there have been few studies to examine the role of microstructure. Accordingly, the present work examines how the overall resistance to high-cycle fatigue in Ti-6Al-4V compares between the bimodal microstructure and a coarser lamellar ( β-annealed) microstructure. Several aspects of the HCF problem are examined. These include the question of fatigue thresholds for through-thickness large and short cracks; microstructurally small, semi-elliptical surface cracks; and cracks subjected to pure tensile (mode I) and mixed-mode (mode I+II) loading over a range of load ratios (ratio of minimum to maximum load) from 0.1 to 0.98, together with the role of prior damage due to sub-ballistic impacts (foreign-object damage (FOD)). Although differences are not large, it appears that the coarse lamellar microstructure has improved smooth-bar stress-life (S-N) properties in the HCF regime and superior resistance to fatigue-crack propagation (in pure mode I loading) in the presence of cracks that are large compared to the scale of the microstructure; however, this increased resistance to crack growth compared to the bimodal structure is eliminated at extremely high load ratios. Similarly, under mixed-mode loading, the lamellar microstructure is generally superior. In contrast, in the presence of microstructurally small cracks, there is little difference in the HCF properties of the two microstructures. Similarly, resistance to HCF failure following FOD is comparable in the

  15. Influence of HVOF sprayed WC/Co coatings on the high-cycle fatigue strength of mild steel

    International Nuclear Information System (INIS)

    HVOF thermally sprayed WC/Co coatings are applied onto components which are exposed to wear caused by abrasion, erosion, fretting and sliding. Beside wear attacks and static stresses in lots of cases alternating mechanical stresses caused by dynamic loads occur additionally. Therefore, the fatigue resistance of WC/Co 88/12 and WC/Co 83/17 coated specimens was investigated by high-cycle fatigue tests (HCF). The results of the fatigue tests were documented in statistically ascertained Woehler-diagrams (S-N-curves). Furthermore, the mechanisms of failure are discussed

  16. 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.

  17. High Cycle Fatigue Properties of Die-Cast Magnesium Alloy AZ91D with Addition of Different Concentrations of Cerium

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium al-loy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and fatigue strength was evaluated using up-and-down loading method. The results show that the grain size of AZ91D alloy is remarkably refined, and the amount of porosity decreases and evenly distributes with the addition of Ce. The fatigue strength of AZ91D alloy at room temperature increases from 96.7 up to 116.3 MPa (1% Ce) and 105.5 MPa (2% Ce), respectively, at the number of cycles to failure, Nf = 1 × 107. The fatigue crack of AZ91D alloy initiates at porosities and inclusions, and propagates along grain boundaries. The fatigue striations on fractured surface appear with Ce addition. The fatigue fracture surface of test specimens shows mixed-fracture characteristics of quasi-cleavage and dimple.

  18. Ultrasonic evaluation of the effects of compressive residual stresses on aircraft engine turbine blades subjected to high cycle fatigue

    Science.gov (United States)

    Bray, Don E.; Suh, Ui; Hough, C. L. ``Mickey''

    2002-05-01

    Experiments conducted on titanium (Ti-64) turbine blades with the LCR ultrasonic wave at 20 MHz showed significant differences in untreated blades and blades treated to increase the subsurface compressive residual stress. Group 1 showed significant differences in the treated and untreated areas, the top and bottom of the blades, high cycle fatigue and cracked and uncracked conditions. Group 2 blades showed significant difference between untreated and treated travel-times at probes located at the blade leading edge.

  19. Ultrasonic evaluation of the effects of compressive residual stresses on aircraft engine turbine blades subjected to high cycle fatigue

    International Nuclear Information System (INIS)

    Experiments conducted on titanium (Ti-64) turbine blades with the LCR ultrasonic wave at 20 MHz showed significant differences in untreated blades and blades treated to increase the subsurface compressive residual stress. Group 1 showed significant differences in the treated and untreated areas, the top and bottom of the blades, high cycle fatigue and cracked and uncracked conditions. Group 2 blades showed significant difference between untreated and treated travel-times at probes located at the blade leading edge

  20. Structure-phase states evolution in Al-Si alloy under electron-beam treatment and high-cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Konovalov, Sergey, E-mail: konovserg@gmail.com; Alsaraeva, Krestina, E-mail: gromov@physics.sibsiu.ru; Gromov, Victor, E-mail: gromov@physics.sibsiu.ru; Semina, Olga, E-mail: gromov@physics.sibsiu.ru [Siberian State Industrial University, Novokuznetsk, 654007 (Russian Federation); Ivanov, Yurii, E-mail: yufi55@mail.ru [Institute of High-Current Electronics SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    By methods of scanning and transmission electron diffraction microscopy the analysis of structure-phase states and defect substructure of silumin subjected to high-intensity electron beam irradiation in various regimes and subsequent fatigue loading up to failure was carried out. It is revealed that the sources of fatigue microcracks are silicon plates of micron and submicron size are not soluble in electron beam processing. The possible reasons of the silumin fatigue life increase under electron-beam treatment are discussed.

  1. Digital Micromirror Device (DMD-Based High-Cycle Torsional Fatigue Testing Micromachine for 1D Nanomaterials

    Directory of Open Access Journals (Sweden)

    Chenchen Jiang

    2016-03-01

    Full Text Available Fatigue behavior of nanomaterials could ultimately limit their applications in variable nano-devices and flexible nanoelectronics. However, very few existing nanoscale mechanical testing instruments were designed for dedicated fatigue experiments, especially for the challenging torsional cyclic loading. In this work, a novel high-cycle torsion straining micromachine, based on the digital micromirror device (DMD, has been developed for the torsional fatigue study on various one-dimensional (1D nanostructures, such as metallic and semiconductor nanowires. Due to the small footprint of the DMD chip itself and its cable-remote controlling mechanisms, it can be further used for the desired in situ testing under high-resolution optical or electron microscopes (e.g., scanning electron microscope (SEM, which allows real-time monitoring of the fatigue testing status and construction of useful structure-property relationships for the nanomaterials. We have then demonstrated its applications for testing nanowire samples with diameters about 100 nm and 500 nm, up to 1000 nm, and some of them experienced over hundreds of thousands of loading cycles before fatigue failure. Due to the commercial availability of the DMD and millions of micromirrors available on a single chip, this platform could offer a low-cost and high-throughput nanomechanical solution for the uncovered torsional fatigue behavior of various 1D nanostructures.

  2. The Effect of Ballistic Impacts on the High Cycle Fatigue Properties of Ti-48Al-2Nb-2Cr (at.%)

    Science.gov (United States)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Austin, C. M.; Erdman, O.

    2000-01-01

    The ability of gamma - TiAl to withstand potential foreign and/or domestic object damage is a technical risk to the implementation of gamma - TiAl in low pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high cycle fatigue strength of gamma - TiAl simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy had the largest influence on the response of gamma - TiAl to ballistic impacting. Backside crack length was the best predictor of remnant fatigue strength for low energy impacts (fatigue strength. For the fatigue design stresses of a 6th stage LPT blade in a GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.

  3. Study on high cycle thermal fatigue in mixing tee. Evaluation of transfer characteristics of temperature fluctuation from fluid to structure

    International Nuclear Information System (INIS)

    Thermal striping is observed at a point where hot and cold fluids are mixing. Evaluation of high cycle thermal fatigue on structural components is a significant issue for the reactor safety design. Japan Atomic Energy Agency (JAEA) has conducted experimental and numerical investigations to establish a quantitative evaluation method of high cycle thermal fatigue in a sodium-cooled fast reactor, based on the nature of the phenomena. A water experiment WATLON (as Water Experiment of Fluid Mixing in T-pipe with Long Cycle Fluctuation) has been conducted to clarify the thermal striping phenomena in a mixing tee area. In this study, water experiments WATLON were carried out to clarify the unsteady behavior of heat transfer under wall jet condition. In experiments, heat transfer coefficients between fluid and wall in the mixing region were obtained from temperature measurements using thermocouples (movable tree type in fluid and embedded type in wall). To clarify the relation between the local velocity and the wall temperature, those were measured simultaneously by the Particle Image Velocimetry (PIV) and the thermocouple measurement, respectively. Sampling time of the velocity by the PIV and the temperature by the thermocouple were synchronized in the measurement. The experimental results showed that the heat transfer coefficient was 2∼6 time larger than the reference value predicted by the Dittus-Boelter correlation in straight pipes and was increased as the local velocity near the wall. A CD-ROM is attached as an appendix. (J.P.N.)

  4. Experimental study on properties of high cycle thermal fatigue. 3. Results of sinusoidal temperature fluctuation test at 20 second cycle

    International Nuclear Information System (INIS)

    In a nuclear power plant, it is necessary to be attentive to fatigue fracture of the structural material caused by cyclic thermal stress due to the mixing of temperature different fluids. The purpose of this study is to obtain data to demonstrate high cycle thermal fatigue evaluation methods by applying the effects of the frequency of temperature fluctuation. A sinusoidal temperature fluctuation test of with a 20 second period was conducted using high cycle fatigue test equipment (SPECTRA). A SUS304 steel pipe was used as the test sample, at an average sodium temperature of 425 deg C, fluctuation amplitude of 200 deg C and a sodium flow rate of 300 l/min in the test pipe. The results obtained are as follows: (1) Valid strength data to verify evaluation methods could be obtained by applying a 20 second cycle temperature fluctuation to the test sample with SPECTRA. A Crack penetrated at about 157,150 cycles. (2) Numerous cracks in an axial direction were observed on the inner surface of the test sample in the upper flow area. An air fatigue test demonstrated the difference in the strength of the test sample between axial direction and circumferential direction, revealing that cracks were distributed in an axial direction since anisotropic influences easily appear on the high cycle side. (3) An approximated curve obtained by the common relation of crack and axial direction distance indicates that the boundary of a crack would be located about 430 mm downstream from the tapered end of the test sample with the upper flow. (4) Crack occurring on the inner surface progressed to a depth of 1 to 2 mm in the crystal grain, then progressed along the crystal grain boundary. Striations were formed on areas of the fracture surface in the grain, but were not found on the fracture surface of the grain boundary. Sinusoidal temperature fluctuation tests at the periods of 2, 5, 10, and 40 seconds are planned to confirm the influence of fluctuation frequency responsiveness on

  5. Design and realization of a multisamples rotating high cycle fatigue machine

    OpenAIRE

    Massimo Martorelli; Domenico Gentile

    2012-01-01

    In this work the design and the technical characteristic of a Moore rotating bending machine are presented. The machine has been realized at the University of Cassino in order to run tests on multiple specimens at different temperature. The user can choose independently the load and the temperature for each specimen. The machine has been designed to produce in short time a several numbers of data of materials fatigue strength at low costs. The machine is in assembling step at the Laboratory o...

  6. Dynamic speckle interferometry of high-cycle material fatigue: Theory and some experiments

    Science.gov (United States)

    Vladimirov, A. P.

    2016-06-01

    The objective of this paper was theoretical analysis of speckle dynamics in the image plane of a thin transparent object. It was suggested that speckle dynamics develops in simultaneous periodic motion of the sample, micro- and macro-variations of its refraction index and its translational motion. The results of the theory were contrasted with the data obtained in the fatigue tests with transparent object.

  7. High Cycle Fatigue of Al and Cu Thin Films by a Novel High-Throughput Method

    OpenAIRE

    Burger, Sofie

    2013-01-01

    In the last two decades, the reliability of small electronic devices used in automotive or consumer electronics gained researchers attention. Thus, there is the need to understand the fatigue properties and damage mechanisms of thin films. In this thesis a novel high-throughput testing method for thin films on Si substrate is presented. The specialty of this method is to test one sample at different strain amplitudes at the same time and measure an entire lifetime curve with only one experiment.

  8. How to deal with very high cycle fatigue (VHCF) effects in practical applications?

    Energy Technology Data Exchange (ETDEWEB)

    Bacher-Hoechst, Manfred; Issler, Stephan [Robert Bosch GmbH, Stuttgart (Germany). Corporate Research and Advance Engineering, Materials and Process Engineering Metals

    2012-07-01

    Fatigue designing of high-stressed engine components is a key factor for reliable power train systems in automotive industry. In this context load assumptions are very important since this is attended with a pre-designing of important machine elements. Load analyses are usually performed by using experimental methods since the accuracy of load simulations are often not precise enough. An example for VHCF problems occurs in modern high pressure pumps for gasoline direct injection systems, which have load spectra with a large amount of cycles up to 10{sup 9} including a very powerful shape of the spectra. At the same time it is necessary to consider the properties of fuels in service since they might affect the fatigue strength significantly. For example, ethanol-based gasoline fuels are used in a lot of countries worldwide and especially their additives may lead to significant corrosion fatigue effects. In addition, it is well known that material inclusions play an important role for the VHCF behaviour especially for high-strength steels. This paper deals with possibilities to avoid VHCF problems of components in service to maintain reliable systems. (orig.)

  9. A constitutive high cycle fatigue damage model - based on the interaction between microplasticity and local damage

    Energy Technology Data Exchange (ETDEWEB)

    Flaceliere, L. [Futurscope (France); Morel, F.; Dragon, A.

    2006-07-01

    This paper presents a new model that accounts, on a local scale, for the coupling between plasticity due to gliding in shear bands and damage occurring when the accumulated plastic strain has reached a threshold value. The irreversible thermodynamics with internal state variables is employed to keep a middle way between extensive description of plastic and damage flow and application of accessibility requirements. Plasticity and damage are governed by their proper complementary rules (yield functions and potentials). At the same time, a coupling occurs between the damage variable and the hardening parameters. A large experimental database relative to the fatigue behavior of a mild steel C36 submitted to different loading modes (tension, torsion, combined proportional tension and torsion) proves the efficiency of such a model. The prediciton of Woehler curves for cyclic complex stress states can be readily done, but the main feature of this approach is to ensure a clear link between mesoscopic parameters like the hardening behavior of individual grains and the subsequent local damage.

  10. Evolution of structural phase states of 08Cr18Ni10Ti steel subjected to high-cycle fatigue with electrostimulation

    Institute of Scientific and Technical Information of China (English)

    Molotova; K.Ye.; Konovalov; S.V.; Kozlov; E.V.; Ivanov; Yu.F.; Gromov; V.E.

    2005-01-01

    This work contains analysis results from the study of defective substructure and phase state of steel subjected to fatigue loading and pulse current action in order to increase its fatigue life.……

  11. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel; Endommagement et cumul de dommage en fatigue dans le domaine de l'endurance limitee d'un acier inoxydable austenitique 304L

    Energy Technology Data Exchange (ETDEWEB)

    Lehericy, Y

    2007-05-15

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  12. Coating pre-cracking effect on the LCF fatigue life of superalloys for gas turbine blades

    Energy Technology Data Exchange (ETDEWEB)

    Filippini, M.; Foletti, S. [Politecnico di Milano, Milan (Italy); Pasquero, G. [AVIO SpA, Rivalta di Torino (Italy)

    2009-07-01

    Low cycle fatigue (LCF) strain controlled experimental fatigue tests were conducted on the nickel superalloy MAR-M002 used in the construction of gas turbine blades. The aim of the study was to compare dwell times and high cycle fatigue (HCF) and LCF combined cycle fatigue test conditions. The study focused on investigating the potentially detrimental effect of coating cracking. A fatigue test system was equipped with an induction furnace and a high temperature extensometer. A procedure was developed to generate controlled cracking in the coating prior to fatigue testing. Loading modes used in the tests were representative of loads experienced by the superalloy turbine blades when in operation. HCF amplitudes were superimposed on major LCF cycles. It was concluded that coating cracks do not significantly impact the LCF fatigue life of aluminized investment casting nickel superalloy MAR-M002. 7 refs., 1 tab., 12 figs.

  13. Effect of vanadium on the high-cycle fatigue fracture properties of medium-carbon microalloyed steel for fracture splitting connecting rod

    International Nuclear Information System (INIS)

    Highlights: • Effect of V up to 0.45% on fatigue property of medium carbon MA steel was studied. • Fatigue strength and fatigue strength ratio increase with increasing V content. • Excellent fatigue properties can be obtained when V is higher than ∼0.28%. • Strengthening ferrite is the key to improve fatigue property of MA steel. • The fatigue crack growth behavior is similar for the MA steel with exponent m ≈ 3.5. - Abstract: The present investigation effort was made to study the effect of V up to 0.45% on the high-cycle fatigue properties of medium-carbon microalloyed (MA) steel 37MnSiVS, for the development of new crackable MA forging steel with excellent fatigue properties. The results show that the amount of V(C,N) precipitates increases with increasing V content and most of the precipitates are less than 5 nm. Owing to the significant precipitation strengthening effect of these nanosized particles, the hardness increase of ferrite with increasing V content is higher than that of pearlite and accordingly a decrease of pearlite/ferrite hardness ratio. Therefore, both fatigue strength and fatigue strength ratio increase with increasing V content and excellent fatigue properties could be obtained when V content is higher than about 0.28%. The fatigue crack growth (FCG) behavior is similar for all the three 37MnSiVS samples with an exponent m ≈ 3.5. It is concluded that V can improve the fatigue properties of ferrite–pearlite steel mainly through precipitation strengthening and therefore it is anticipated that MA steel’s fatigue property could be further improved as well as more fine V(C,N) particles be obtained

  14. EFFECT OF HALLOYSITE NANOTUBE ON THE FATIGUE LIFE OF GLASS FIBER REINFORCED EPOXY COMPOSITES.

    OpenAIRE

    Ramamoorthi, R; P.S. SAMPATH

    2015-01-01

    Glass fiber polymer composites have high strength, low cost but frequently suffer from poor performance in fatigue. This investigation shows that the addition of small fraction of halloysite nanotubes (HNTs) in the matrix results in a significant increase in high-cycle fatigue life. Thermosetting epoxy polymer was modified by incorporating 4wt% of well dispersed Halloysite nano tube(HNT). The neat and HNT modified epoxy resins were used to fabricate glass fiber reinforced plastic (GFRP) compo...

  15. Multiscale Fatigue Life Prediction for Composite Panels

    Science.gov (United States)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Arnold, Steven M.

    2012-01-01

    Fatigue life prediction capabilities have been incorporated into the HyperSizer Composite Analysis and Structural Sizing Software. The fatigue damage model is introduced at the fiber/matrix constituent scale through HyperSizer s coupling with NASA s MAC/GMC micromechanics software. This enables prediction of the micro scale damage progression throughout stiffened and sandwich panels as a function of cycles leading ultimately to simulated panel failure. The fatigue model implementation uses a cycle jumping technique such that, rather than applying a specified number of additional cycles, a specified local damage increment is specified and the number of additional cycles to reach this damage increment is calculated. In this way, the effect of stress redistribution due to damage-induced stiffness change is captured, but the fatigue simulations remain computationally efficient. The model is compared to experimental fatigue life data for two composite facesheet/foam core sandwich panels, demonstrating very good agreement.

  16. LIFE PREDICTION APPROACH FOR RANDOM MULTIAXIAL FATIGUE

    Institute of Scientific and Technical Information of China (English)

    Wang Lei; Wang Dejun

    2005-01-01

    According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results.

  17. On the effect of deep-rolling and laser-peening on the stress-controlled low- and high-cycle fatigue behavior of Ti-6Al-4V at elevated temperatures up to 550?C

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, IAltenberger, RKNalla, YSano LWagner, RO

    2012-04-01

    The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed) condition. Although the fatigue resistance of the Ti-6Al-4V alloy declined with increasing test temperature regardless of surface condition, deep-rolling and laser-shock peening surface treatments were found to extend the fatigue lives by factors of more than 30 and 5-10, respectively, in the high-cycle and low-cycle fatigue regimes at temperatures as high as 550?C. At these temperatures, compressive residual stresses are essentially relaxed; however, it is the presence of near-surface work hardened layers, with a nanocystalline structure in the case of deep-rolling and dense dislocation tangles in the case of laser-shock peening, which remain fairly stable even after cycling at 450?-550?C, that provide the basis for the beneficial role of mechanical surface treatments on the fatigue strength of Ti-6Al-4V at elevated temperatures.

  18. Experimental study of cyclic creep and high-cycle fatigue of welded joints of St3 steel by the DIC technique

    Energy Technology Data Exchange (ETDEWEB)

    Kibitkin, Vladimir V., E-mail: vvk@ispms.tsc.ru; Solodushkin, Andrey I., E-mail: s.ai@sibmail.com; Pleshanov, Vasily S., E-mail: vsp@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    In the paper the mechanisms of plastic deformation and fracture of welded joints of steel St3 were investigated at high-cycle fatigue and cyclic creep by the digital image correlation (DIC) technique. The evolution of strain rate is studied for the following regions: base metal, HAZ, and fusion zone. This strain rate evolution can be considered as a mechanical response of material. Three stages of deformation evolution are shown: deformation hardening (I), fatigue crack initiation (II), and the last stage is related to main crack (III). Two criteria are offered to evaluate the current mechanical state of welded joints.

  19. EFFECT OF HALLOYSITE NANOTUBE ON THE FATIGUE LIFE OF GLASS FIBER REINFORCED EPOXY COMPOSITES.

    Directory of Open Access Journals (Sweden)

    RAMAMOORTHI R

    2015-06-01

    Full Text Available Glass fiber polymer composites have high strength, low cost but frequently suffer from poor performance in fatigue. This investigation shows that the addition of small fraction of halloysite nanotubes (HNTs in the matrix results in a significant increase in high-cycle fatigue life. Thermosetting epoxy polymer was modified by incorporating 4wt% of well dispersed Halloysite nano tube(HNT. The neat and HNT modified epoxy resins were used to fabricate glass fiber reinforced plastic (GFRP composite laminates by hand layup followed by hot compression moulding technique. The stress- controlled tensile fatigue behaviour at a were performed on these composites; the fatigue life of GFRP composite was increased by about two times due to HNT. Cyclic hysteresis measured over each cycle in real time during testing is used as a sensitive indicator of fatigue damage. It was observed that when HNTs are present hysteresis growth with cycling is suppressed.

  20. Effect of Thickness on Very High Cycle Bending Fatigue Properties of 5083 Aluminum Alloy Sheet%厚度对5083铝合金薄板超高周弯曲疲劳性能的影响

    Institute of Scientific and Technical Information of China (English)

    梁凌宇; 王弘; 董轩成

    2016-01-01

    在超声振动载荷下,对2 mm 和5 mm 厚5083铝合金薄板进行了超高周弯曲疲劳试验,研究了铝合金薄板厚度对其超高周弯曲疲劳性能的影响。结果表明:5083铝合金薄板的 S-N曲线呈连续下降特征,试样在109周次处仍会发生断裂,与一般铝合金的疲劳特征一致,即传统的疲劳极限并不存在;受尺寸效应影响,2 mm 厚薄板的弯曲疲劳强度高于5 mm 厚薄板的;尺寸效应在高周阶段对薄板疲劳性能的影响最大,超高周阶段的影响逐渐减弱;试样的疲劳裂纹起源于表面,表现为多源萌生;同应力幅值下不同厚度的5083铝合金薄板断口具有相同的解理特征。%Very high cycle bending fatigue test was carried out on 5083 aluminum alloy sheet with thickness of 2 mm and 5 mm at ultrasonic vibratory load,and the effect of thickness of aluminum alloy sheet on very high cycle bending fatigue properties of the sheet was studied.Results show that the S-N curves of the sheet exhibited continuous decline characteristics,the specimens fractured in the life cycle of 10 9 .There was no traditional fatigue limit in the testing as conventional aluminum alloys used to be.Bending fatigue strength of the sheet with thickness of 2 mm was higher than that of the sheet with thickness of 5 mm,this was the result of size effect.In high cycle stage,the effect of size effect on fatigue property was the largest,and the effect gradually weakened in very high cycle stage.It was found that all fatigue cracks emanated from the specimen surface,and the crack was multiple sources.5083 aluminum alloy sheet with different thicknesses had the same cleavage fracture characteristics at the same stress amplitude.

  1. A study on the role of grain boundary engineering in promoting high-cycle fatigue resistance and improving reliability in nickel base superalloys for propulsion systems

    Science.gov (United States)

    Gao, Yong

    High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a commercial polycrystalline nickel base gamma/gamma' superalloy, ME3, as a typical engine disk material, sequential thermomechanical processing, involving alternate cycles of strain and annealing, is used to (i) modify the proportion of special grain boundaries, and (ii) interrupt the connectivity of the random boundaries in the grain boundary network. The processed microstructures are then subjected to fracture-mechanics based high cycle fatigue testing to evaluate how the crack initiation and small- and large-crack growth properties are affected and to examine how the altered grain boundary population and connectivity can influence growth rates and overall lifetimes. The effect of such grain-boundary engineering on the fatigue-crack-propagation behavior of large (˜8 to 20 mm), through-thickness cracks at 25, 700, and 800°C was examined. Although there was little influence of an increased special boundary fraction at ambient temperatures, the resistance to near-threshold crack growth was definitively improved at elevated temperatures, with fatigue threshold-stress intensities some 10 to 20% higher than at 25°C, concomitant with a lower proportion (˜20%) of intergranular

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

    International Nuclear Information System (INIS)

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

  3. Assessment of fatigue life of remanufactured impeller based on FEA

    Science.gov (United States)

    Xu, Lei; Cao, Huajun; Liu, Hailong; Zhang, Yubo

    2016-09-01

    Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.

  4. 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.

  5. Crack path for run-out specimens in fatigue tests: is it belonging to high- or very-high-cycle fatigue regime?

    OpenAIRE

    A. Shanyavskiy

    2015-01-01

    Fatigue tests run-out specimens up to 106 – 5x107 load cycles are used to determine the stress level named “fatigue limit”. Nevertheless, it is not clear what kind of fatigue cracking takes or will take place in these specimens. To discuss this problem, fatigue tests of titanium alloy VT3-1 specimens have been performed under tension with different values of R-ratio and under rotating-bending after various thermo-mechanical treatments (tempering, surface hardening and their combin...

  6. Effect of stress ratio on long life fatigue behavior of Ti-Al alloy under flexural loading

    Institute of Scientific and Technical Information of China (English)

    XUE Hong-qian; TAO Hua; SHAO Ren-ping; B.CLAUDE

    2008-01-01

    A new ultrasonic three-point bending fatigue test device was introduced to investigate fatigue life ranging up to 1010 cycles and associated fracture behavior of Ti-Al alloy. Tests were performed at a frequency of 20kHz with stress ratio R=0.5 and R=0.7 at ambient temperature in air. Three groups of specimens with different surface roughness were applied to investigate the effect of surface roughness on fatigue life. Furthermore, optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructure characteristic and fracture surface analysis. The S-N curves obtained show that fatigue failure occurs in the range of 105-1010 cycles, and the asymptote of S-N curve inclines slightly in very high cycle regime, but is not horizontal for R=0.5. Fatigue limit appears after 108 cycles for R=0.7. Surface roughness (the maximum roughness is no more than 3μm) has no influence on the fatigue properties in the high cycle regime. A detailed investigation on fatigue fracture surface shows that the Ti-Al alloy studied here is a binary alloy in the microstructure composed of α2-Ti3Al and γ-Ti-Al with fully lamellar microstructure. Fractography shows that fatigue failures are mostly initiated on the surface of specimens, also, in very high cycle regime, subsurface fatigue crack initiation can be found. Interlamellar fatigue crack initiation is predominant in the Ti-Al alloy with fully lamellar structure. Fatigue crack growth is mainly in transgranular mode.

  7. Fatigue life of metal treated by magnetic field

    Institute of Scientific and Technical Information of China (English)

    Liu Zhao-Long; Hu Hai-Yun; Fan Tian-You; Xing Xiu-San

    2009-01-01

    This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statis-tical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the dynamic equation of microcrack growth, where the influence of magnetization is described by an additional term in the potential energy of microcrack. The statistical value of fatigue life of metal under magnetic field is derived, which is expressed in terms of magnetic field and macrophysical as well as microphysical quantities. The fatigue life of AISI 4140 steel in static magnetic field from this theory is basically consistent with the experimental data.

  8. Simulation Methods for High-Cycle Fatigue-Driven Delamination using Cohesive Zone Models - Fundamental Behavior and Benchmark Studies

    DEFF Research Database (Denmark)

    Bak, Brian Lau Verndal; Lindgaard, Esben; Turon, A.;

    2015-01-01

    A novel computational method for simulating fatigue-driven delamination cracks in composite laminated structures under cyclic loading based on a cohesive zone model [2] and new benchmark studies with four other comparable methods [3-6] are presented. The benchmark studies describe and compare the...... traction-separation response in the cohesive zone and the transition phase from quasistatic to fatigue loading for each method. Furthermore, the accuracy of the predicted crack growth rate is studied and compared for each method. It is shown that the method described in [2] is significantly more accurate...... than the other methods [3-6]. Finally, studies are presented of the dependency and sensitivity to the change in different quasi-static material parameters and model specific fitting parameters. It is shown that all the methods except [2] rely on different parameters which are not possible to determine...

  9. Investigation of ultra-high cycle fatigue behavior of TC17 alloy at a frequency of 20kHz%20kHz下TC17钛合金超高周疲劳性能研究

    Institute of Scientific and Technical Information of China (English)

    高潮; 程礼; 彭桦; 申景生; 邱辰霖; 刘延杰

    2012-01-01

    The bending fatigue system was developed using the piezoelectric ultrasonic fatigue testing technology and experimental investigation of the ultra-high cycles fatigue life for TC17 alloy subjected to bending fatigue deformation has been conducted.The experimental resultes show that the specimens were tested to failure in the range of 107-109 cycles and the fatigue limit decreases with the increasing number of cycles between 107 and 109 for R=-1.0 and there was no obvious fatigue limit.The S-N curve for TC17 is a continuous decline curve between 107 and 109 cycles.The fractographic study showes that fatigue failures are mostly initiated at the surface of the test specimens.When there are subsurface inclusions,fatigue cracks initiated from subsurface inclusions,and the composition of inclusions is mainly oxides of aluminums.%应用基于压电超声疲劳试验技术开发的20kHz弯曲疲劳试验系统,完成了室温下TC17合金超高周疲劳试验.结果表明:在疲劳循环大于107周次时,试样仍会发生疲劳断裂,疲劳强度随循环次数的增加而下降,并不存在明显的疲劳极限.TC17合金的应力-寿命(S-N)曲线在107~109周次的范围内为连续下降型.光学显微镜发现,TC17合金的疲劳破坏主要起源于试样表面.当存在夹杂物时,疲劳裂纹从距离表面很近的夹杂物处萌生,能谱分析表明夹杂物的成分主要是铝的氧化物.

  10. Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

    International Nuclear Information System (INIS)

    Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×107 cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature

  11. Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qingjun [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Yuming; Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China)

    2014-10-06

    Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×10{sup 7} cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature.

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

    International Nuclear Information System (INIS)

    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 (Rm) and fatigue limit strength after 109 cycles (σw9) and in the non-failed condition were 1688 MPa and 875 MPa, respectively such that σw9/Rm 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

  13. A study at understanding the mechanisms governing the high cycle fatigue and final fracture behavior of the titanium alloy: Ti-4Al-2.5V

    International Nuclear Information System (INIS)

    In this research paper, the cyclic stress amplitude-controlled high cycle fatigue properties and fracture behavior of a titanium alloy are presented and discussed. The material chosen for this study is a Ti-Al-V-Fe-O2 alloy that is marketed under the trade name ATI 425TM. This alloy was initially developed and put forth for use as a ballistic material but through the last few years it gained in stature for use in other areas due to a healthy combination of physical and mechanical properties. Test specimens were prepared, in conformance with the ASTM E-8 standard, from the as-received sheet stock, which was cold rolled and mill annealed, with the rolling direction both parallel (longitudinal) and perpendicular (transverse) to the length of the sheet. The test specimens were cyclically deformed at three different load ratios (R = 0.1, R = 0.3 and R = 0.033) and the cycles-to-failure (Nf) was recorded. The fatigue fracture surfaces were examined in a scanning electron microscope to examine the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of magnitude of applied stress-microstructural feature interactions in governing failure.

  14. 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.

  15. MULTIAXIAL CREEP-FATIGUE LIFE EVALUATION UNDER PROPORTIONAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Y.Noguchi; M.Miyahara

    2004-01-01

    A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading.Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue loadings.

  16. Forecasting method of fatigue life test data for metal materials

    Institute of Scientific and Technical Information of China (English)

    张怀亮; 邱显焱; 谭冠军

    2001-01-01

    GM(1, 1) model of grey system theory is used to forecast fatigue life test data for metal materials. The method can reduce test time and save test cost, and reliability indexes of metal materials can be obtained quickly. The results of an example show that grey system theory has a high precision for forecasting fatigue life test data for metal materials. A valuable method is put forward, which can effectively reduce the fatigue life test time for metal materials.

  17. Fatigue life of automotive rubber jounce bumper

    Energy Technology Data Exchange (ETDEWEB)

    Sidhu, R S [Automotive Engineering Unit, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM Serdang, Selangor (Malaysia); Ali, Aidy, E-mail: aidy@eng.upm.edu.my [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor (Malaysia)

    2010-05-15

    It is evident that most rubber components in the automotive industry are subjected to repetitive loading. Vigorous research is needed towards improving the safety and reliability of the components. The study was done on an automotive rubber jounce bumper with a rubber hardness of 60 IRHD. The test was conducted in displacement-controlled environment under compressive load. The existing models by Kim, Harbour, Woo and Li were adopted to predict the fatigue life. The experimental results show strong similarities with the predicted models.

  18. Towards a unified fatigue life prediction method for marine structures

    CERN Document Server

    Cui, Weicheng; Wang, Fang

    2014-01-01

    In order to apply the damage tolerance design philosophy to design marine structures, accurate prediction of fatigue crack growth under service conditions is required. Now, more and more people have realized that only a fatigue life prediction method based on fatigue crack propagation (FCP) theory has the potential to explain various fatigue phenomena observed. In this book, the issues leading towards the development of a unified fatigue life prediction (UFLP) method based on FCP theory are addressed. Based on the philosophy of the UFLP method, the current inconsistency between fatigue design and inspection of marine structures could be resolved. This book presents the state-of-the-art and recent advances, including those by the authors, in fatigue studies. It is designed to lead the future directions and to provide a useful tool in many practical applications. It is intended to address to engineers, naval architects, research staff, professionals and graduates engaged in fatigue prevention design and survey ...

  19. High-Strength Bolt Corrosion Fatigue Life Model and Application

    Directory of Open Access Journals (Sweden)

    Wang Hui-li

    2014-01-01

    Full Text Available The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

  20. High Cycle Fatigue Properties of Hot-rolled TC1 and TC2 Titanium Alloys%轧制变形TC1和TC2钛合金的高周疲劳性能

    Institute of Scientific and Technical Information of China (English)

    吕伟; 陈立佳; 车欣; 刘正

    2011-01-01

    Through performing the stress-controlled fatigue tests, the high-cycle fatigue properties of hot-rolled TC1 and TC2 titanium alloy plates at different testing temperature were investigated, and the fatigue properties of two alloy plates were compared. The results show that, at the same maximum cyclic stress, the fatigue lives of both TC1 and TC2 alloy plates decrease with the increase of temperature. At the same testing temperature, the fatigue life of TC2 alloy plate is longer than that of TC1 alloy plate, In addition, both TC1 and TC2 alloy plates show lower fatigue limit at higher testing temperature. At different temperature, the fatigue limit of TC2 alloy plate is higher than that of TC1 alloy plate.%通过进行应力控制的疲劳试验,研究了TC1和TC2钛合金热轧板材在不同试验温度下的高周疲劳性能,并对两类钛合金板材的疲劳性能进行了比较.结果表明,在相同的最大循环应力下,TC1和TC2钛合金板材的高周疲劳寿命均随着温度的升高而降低,且当温度相同时,TC2钛合金板材的疲劳寿命均高于相同轧制方向的TCl钛合金板材.此外,实验温度越高,TC1和TC2钛合金板材的疲劳极限越低,且在不同温度下,TC2钛合金板材的疲劳极限均明显高于相同轧制方向的TC1钛合金板材.

  1. Fatigue life evaluation of mechanical components using vibration fatigue analysis technique

    International Nuclear Information System (INIS)

    Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration's direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition

  2. High-temperature fatigue life prediction of turbopump turbine

    International Nuclear Information System (INIS)

    In general, many components are able to be operated under severe thermal conditions. The turbopump turbine is operated under these environments like high temperature and high centrifugal force due to high rotating velocity during operating time. Because these conditions may often cause low-cycle fatigue problem, strain life method is applied to predict low-cycle fatigue life of turbopump turbine. In this paper, strain life method is used to analyze low-cycle fatigue. First of all, to obtain strain history, thermal stress analysis is practised by ABAQUS/CAE. Considering elasticity and plasticity strain's effect, Coffin-Manson' equation is used. S.W.T's method is used to consider the mean stress effect. Low-cycle fatigue analysis is done for turbopump turbine which may have FCL(Fracture Critical Location). MSC.Fatigue is used to analyze low-cycle fatigue life of turbopump turbine.

  3. High cycle thermal fatigue: benchmark at a Te junction piping system of the nuclear power plant Phenix; Fatigue a grand nombre de cycles: benchmark d'un te de tuyauterie de la centrale Phenix

    Energy Technology Data Exchange (ETDEWEB)

    Gelineau, O.; Simoneau, J.P. [NOVATOME, a Div. of Framatome, 69 - Lyon (France); Roubin, P. [CEA Cadarache, DER, 13 - Saint-Paul-lez-Durance (France)

    2001-07-01

    This paper presents the studies of the benchmark concerning a high cycle thermal fatigue problem. This benchmark is based on an industrial case, a Te junction piping system of the french FBR Phenix. The main objectives were the comparison of the different methods used by the participants and the analysis of the damage evaluation methods capacity compared to the observed phenomena. This study took place in an international framework with the United Kingdom, Italy, Japan, Korea, Russia, India and France. (A.L.B.)

  4. Fatigue life and damage evolution of martensitic steels for low-pressure steam turbine blades in the VHCF regime

    International Nuclear Information System (INIS)

    Low-pressure steam turbine blades are usually made of martensitic steels with Cr contents between 9 and 12%, which combine good corrosion resistance, high mechanical strength and sufficient ductility. The inhomogeneous flow field behind the vanes generates high-frequency oscillations above 1 kHz. In addition, the blades with lengths up to 1.5 m are operated at rotational speeds up to 3000 rpm, resulting in large centrifugal forces leading to the superposition of extremely high mean stresses. Also resonance oscillations during start-up and shutdown cannot be completely excluded. Currently, the components are designed using high safety factors against S-N curves with an assumed asymptotic fatigue limit above 107 load cycles. Nevertheless, fatigue cracks are observed even at high number of cycles, starting from the blade root without pre-damage by erosion or steam droplet impingement. While fatigue failure usually occurs at the surface, fatigue cracks at very high number of cycles (> 108) initiate at oxides or intermetallic inclusions below the surface. This transition between both failure mechanisms in the Very High-Cycle Fatigue (VHCF) regime is in the focus of numerous current research activities, because numbers of cycles above 108 can be attained in a viable period of time using the recently developed high-frequency testing techniques operated at 20 kHz. Also for wind turbines, gas turbines, bearings, springs, etc. VHCF issues become increasingly important. Within this work, the fatigue life and damage behavior of a martensitic Cr-steel during fatigue loading with and without high mean stresses at number of cycles to failure above 108 was analyzed. On the one hand, the studies gave insights into the relation between fatigue life and fatigue damage evolution of the investigated group of high-strength steels in the very high cycle fatigue regime (up to 2·109). In particular, the influence of high mean stresses on the VHCF behavior (fracture origin, crack growth

  5. High-cycle fatigue of nickel-base superalloy Rene 104 (ME3): Interaction of microstructurally small cracks with grain boundaries of known character

    International Nuclear Information System (INIS)

    High-cycle fatigue (HCF), involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency cyclic loading, has been identified as one of the leading causes of turbine engine failures in aircraft. In this work, we consider the feasibility of using grain-boundary engineering to improve the HCF properties of a polycrystalline nickel-base superalloy, Rene 104 (also known as ME3), through systematic modification of the grain-boundary distribution. In particular, we investigate the growth of microstructurally small fatigue cracks at ambient temperature in microstructures with varying proportions of 'special' vs. 'random' boundaries, as defined by coincident-site lattice theory. Specifically, we examine the interaction of propagating small (∼10-900 μm) surface cracks with grain boundaries of known character, with respect both to any deflection in crack trajectory that occurs at or near the boundary, and more importantly to any local changes in crack-growth rates. In addition, finite-element calculations are performed to evaluate the effective driving force and plastic-zone profile for such small-crack propagation, incorporating information from both the local microstructure (from electron backscattering diffraction scans) and the surface crack-path profile

  6. K495高温合金的高周疲劳性能%High Cycle Fatigue Properties of K495 Superalloy

    Institute of Scientific and Technical Information of China (English)

    王荣; 何向明; 周鹏杰

    2012-01-01

    The high cycle fatigue properties of K495 alloy at 700 ℃ and 900 ℃ were investigated. The fatigue curve was tested, the loading cycle was sinusoidal, and the ratio of stress was 0.1. The test results show that K495 has good fatigue properties under those two temperatures, the fatigue limit is 322 MPa and 314MPa, respectively. At 700 ℃, when the stress is low, the fatigue crack initiates from the accumulation of PSB on the grain boundary; when the stress is high, the crack originates from the inner defects of specimen, such as solidification pores , inclusions and a BCC structured Y rich phase. With the increase of maximum stress, the crack origins switch from single point into multiples sites. At 900 ℃, the crack originates from the inner metallurgical defects near the surface.%研究了K495合金在700、900℃的高周疲劳性能.测试的疲劳为拉伸疲劳曲线,采用正弦波,应力比R=0.1.结果表明,K495合金在这两个温度下都具有较好的疲劳性能,其疲劳强度极限分别为322、314MPa.在700℃时,当应力较小时,其疲劳裂纹由驻留滑移带在晶界的冲击而产生;当应力较大时,其疲劳裂纹萌生于试样的冶金缺陷处,如凝固缩孔和夹杂物处和一种体心立方结构的富Y相;随最大应力的增加,裂纹源由单一裂纹源向多裂纹源转变;在900℃,裂纹产生于靠近表面的冶金缺陷处.

  7. Experimental Study on High-Cycle Fatigue Property of Elastic Support with Multiple Squirrel-Cages%串联式鼠笼弹性支承高周疲劳性能试验

    Institute of Scientific and Technical Information of China (English)

    粟勇; 杨正兵; 李光辉; 王继成

    2014-01-01

    To evaluate the high cycle fatigue performance of elastic support, a set of test specimen and ex-periment method have been designed based on the structure of elastic support system with multiple squirrel cages on an aero-engine. The testing results show that simulated rotor can better simulate the true stress with elastic support. The load adjustment and control during the test are more direct and convenient which provide support for fatigue life design of elastic support.%为评估弹性支承高周疲劳性能,根据某航空发动机串联式鼠笼弹性支承系统结构,设计了一套弹性支座疲劳试验件和试验参数测试方法,对弹性支座的高周疲劳性能进行试验研究。经试验验证,所设计的试验方案可以更好地模拟发动机工作状态下弹性支座的受力状态,试验过程中的载荷调节和控制更直接、便捷,为发动机弹性支承的疲劳寿命设计提供了方法支持。

  8. Fatigue life estimation of ultrasonic spot welded Mg alloy joints

    International Nuclear Information System (INIS)

    Highlights: • Fatigue life test of USWed similar Mg alloy was investigated. • USW joints exhibited a superior fatigue life compared with other welding processes. • Life prediction model agreed fairly well with the obtained experimental results. • The fatigue failure mode changed with decreasing cyclic load level. - Abstract: Lightweight magnesium alloys are increasingly used in automotive and other transportation industries for weight reduction and fuel efficiency improvement. The structural application of magnesium components requires proper welding and fatigue resistance to guarantee their durability and safety. The objective of this investigation was to identify failure mode and estimate fatigue life of ultrasonic spot welded (USWed) lap joints of an AZ31B-H24 magnesium alloy. It was observed that the solid-state USWed joints exhibited a superior fatigue life compared with other welding processes. Fatigue failure mode changed from interfacial failure to transverse-through-thickness crack growth with decreasing cyclic load level, depending on the welding energy. Fatigue crack initiation and propagation occurred from both the notch tip inside the faying surface and the edge of sonotrode indentation-footprints due to the presence of stress concentration. A life prediction model for the spot welded lap joints developed by Newman and Dowling was adopted to estimate the fatigue lives of the USWed magnesium alloy joints. The fatigue life estimation, based on the fatigue crack growth model with the global and local stress intensity factors as a function of kink length and the experimentally determined kink angle, agreed fairly well with the obtained experimental results

  9. A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen

    Science.gov (United States)

    Appleby, A. J.; Dhar, H. P.; Kim, Y. J.; Murphy, O. J.

    1989-01-01

    The nickel-hydrogen secondary battery system, developed in the early 1970s, has become the system of choice for geostationary earth orbit (GEO) applications. However, for low earth orbit (LEO) satellites with long expected lifetimes the nickel positive limits performance. This requires derating of the cell to achieve very long cycle life. A new system, rechargeable MnO2-Hydrogen, which does not require derating, is described here. For LEO applications, it promises to have longer cycle life, high rate capability, a higher effective energy density, and much lower self-discharge behavior than those of the nickel-hydrogen system.

  10. Fatigue life improvement in fatigue-aged fastener holes using the cold expansion technique

    OpenAIRE

    Zhang, Xiang; Wang, Z.

    2003-01-01

    The use of cold expansion process as a life extension technique on aircraft structural joints was investigated. The primary focus was an experimental test programme consisting of open-hole and low-load transfer joint specimens made of 2024-T351 aluminium alloy and pre-fatigued to 25, 50 and 75% of the baseline fatigue life for plain holes. The FALSTAFF loading spectrum was applied. The results indicate that significant life improvements can be obtained through cold expansion...

  11. Numerical Analysis of Rolling Contact Fatigue Crack Initiation and Fatigue Life Prediction of the Railway Crossing

    NARCIS (Netherlands)

    Xin, L.; Markine, V.L.; Shevtsov, I.

    2015-01-01

    The procedure for analysing rolling contact fatigue crack initiation and fatigue life prediction of the railway turnout crossing is developed. A three-dimensional finite element (FE) model is used to obtain stress and strain results, considering the dynamic effects of wheel-crossing rolling contact.

  12. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations....... The fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the deck structure of the Farø Bridges...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  13. Fatigue Life Prediction under Service Load Considering Strengthening Effect of Loads below Fatigue Limit

    Institute of Scientific and Technical Information of China (English)

    ZHAO Lihui; ZHENG Songlin; FENG Jinzhi

    2014-01-01

    Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule (PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule (MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are –3.78% and –1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

  14. Residual fatigue life estimation using a nonlinear ultrasound modulation method

    International Nuclear Information System (INIS)

    Predicting the residual fatigue life of a material is not a simple task and requires the development and association of many variables that as standalone tasks can be difficult to determine. This work develops a modulated nonlinear elastic wave spectroscopy method for the evaluation of a metallic components residual fatigue life. An aluminium specimen (AA6082-T6) was tested at predetermined fatigue stages throughout its fatigue life using a dual-frequency ultrasound method. A modulated nonlinear parameter was derived, which described the relationship between the generation of modulated (sideband) responses of a dual frequency signal and the linear response. The sideband generation from the dual frequency (two signal output system) was shown to increase as the residual fatigue life decreased, and as a standalone measurement method it can be used to show an increase in a materials damage. A baseline-free method was developed by linking a theoretical model, obtained by combining the Paris law and the Nazarov–Sutin crack equation, to experimental nonlinear modulation measurements. The results showed good correlation between the derived theoretical model and the modulated nonlinear parameter, allowing for baseline-free material residual fatigue life estimation. Advantages and disadvantages of these methods are discussed, as well as presenting further methods that would lead to increased accuracy of residual fatigue life detection. (paper)

  15. Studies of Microtexture and Its Effect on Tensile and High-Cycle Fatigue Properties of Laser-Powder-Deposited INCONEL 718

    Science.gov (United States)

    Qi, Huan; Azer, Magdi; Deal, Andrew

    2012-11-01

    The current work studies the microstructure, texture, and mechanical properties of INCONEL 718 alloy (IN718) produced by laser direct metal deposition. The grain microstructure exhibits an alternative distribution of banded fine and coarse grain zones as a result of the rastering scanning pattern. The effects of the anisotropic crystallographic texture on the tensile and high-cycle fatigue (HCF) properties at room temperature are investigated. Tensile test results showed that the tensile strength of laser-deposited IN718 after direct aging or solution heat treatment is equivalent to the minimum-forged IN718 properties. The transverse direction (relative to the laser scanning direction) produces >10 pct stiffer modulus of elasticity but 3 to 6 pct less tensile strength compared to the longitudinal direction due to the preferential alignment of grains having and directions parallel to the tensile loading direction. Laser-deposited IN718 with good metallurgical integrity showed equivalent HCF properties compared to the direct-aged wrought IN718, which can be attributed to the banded grain size variation and cyclic change of inclining grain orientations resulted from alternating rastering deposition path.

  16. A Methodology to Predict Uniform Material Fatigue Life of Cast Iron: Law for Cast Iron%A Methodology to Predict Uniform Material Fatigue Life of Cast Iron: Law for Cast Iron

    Institute of Scientific and Technical Information of China (English)

    Sinan Korkmaz

    2011-01-01

    Mechanical, physical and manufacturing properties of east iron make it attractive for many fields of application, such as cranks and cylinder holds. As in design of all metals, fatigue life prediction is an intrinsic part of the design process of structural sections that are made of cast iron. A methodology to predict high-cycle fatigue life of cast iron is proposed. Stress amplitude-strain amplitude, strain amplitude-number of loading cycles relationships of cast iron are investigated. Also, fatigue life prediction in terms of Smith, Watson and Topper parameter is carried out using the proposed method. Results indicate that the analytical outcomes of the proposed methodology are in good accordance with the experimental data for the two studied types of cast iron: EN-GJS-400 and EN-GJS-600.

  17. An investigation on fatigue life of borided AISI 1010 steel

    Directory of Open Access Journals (Sweden)

    O.N. Celik

    2009-01-01

    Full Text Available Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made in rotating-bend test device. Separate S-N diagram has been formed for each boriding condition and then their results were compared with the results of the specimens on which any heat treatment has not been made.Findings: As a result it has been seen that boriding has no positive effect on fatigue life of AISI 1010 steel materials. And also it has been determined that fatigue life of the materials on which boriding heat treatment applied, decreases in between 14 %-55 %.Research limitations/implications: It can be noted that the reasons of short fatigue life determination are the boride layer’s much higher hardness than the substrate material’s, and the micro cracks existed between boride phases formed onto the surface.Originality/value: The investigations on fatigue life of borided AISI 1010 steel were made.

  18. Enhanced Prediction of Gear Tooth Surface Fatigue Life Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Sentient will develop an enhanced prediction of gear tooth surface fatigue life with rigorous analysis of the tribological phenomena that contribute to pitting...

  19. 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%.

  20. Studies on fatigue life enhancement of pre-fatigued spring steel specimens using laser shock peening

    International Nuclear Information System (INIS)

    Highlights: • Laser peening significantly extended fatigue life of pre-fatigued spring steel. • Increase in fatigue life of laser peened specimens was more than 15 times. • Black PVC tape is an effective coating for laser peening of ground surfaces. • Repeat peening repaired local surface melted regions on laser peened surface. • Technique is effective for life extension of in-service automobile parts. - Abstract: SAE 9260 spring steel specimens after enduring 50% of their mean fatigue life were subjected to laser shock peening using an in-house developed 2.5 J/7 ns pulsed Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser for studying their fatigue life enhancement. In the investigated range of process parameters, laser shock peening resulted in the extension of fatigue life of these partly fatigue damaged specimens by more than 15 times. Contributing factors for the enhanced fatigue life of laser peened specimens are: about 400 μm thick compressed surface layer with magnitude of surface stress in the range of −600 to −700 MPa, about 20% increase in surface hardness and unaltered surface finish. For laser peening of ground steel surface, an adhesive-backed black polyvinyl chloride (PVC) tape has been found to be a superior sacrificial coating than conventionally used black paint. The effect of repeated laser peening treatment was studied to repair locally surface melted regions and the treatment has been found to be effective in re-establishing desired compressive stress pattern on the erstwhile tensile-stressed surface

  1. FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE

    Directory of Open Access Journals (Sweden)

    A.G.A. Rahman

    2012-12-01

    Full Text Available Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components.

  2. GENERALIZED FATIGUE CONSTANT LIFE CURVE AND TWO-DIMENSIONAL PROBABILITY DISTRIBUTION OF FATIGUE LIMIT

    Institute of Scientific and Technical Information of China (English)

    熊峻江; 武哲; 高镇同

    2002-01-01

    According to the traditional fatigue constant life curve, the concept and the universal expression of the generalized fatigue constant life curve were proposed.Then, on the basis of the optimization method of the correlation coefficient, the parameter estimation formulas were induced and the generalized fatigue constant life curve with the reliability level p was given.From P-Sa-Sm curve, the two-dimensional probability distribution of the fatigue limit was derived.After then, three set of tests of LY11 CZ corresponding to the different average stress were carried out in terms of the two-dimensional up-down method.Finally, the methods are used to analyze the test results, and it is found that the analyzedresults with the high precision may be obtained.

  3. Fatigue life estimation for internal threads in class 1 components

    International Nuclear Information System (INIS)

    7eat exchangers, steam generators and other pressure vessels in nuclear power plants are equipped with bolted closures for the purpose of in service inspection and maintenance. The ASME Boiler and Pressure Vessel Code specifies that all Class 1 components meet the fatigue life requirements for Level A and B Service Conditions. In the case of bolted closures, it is often found that the bolt/stud is the most critical part. In many situations, the bolts fail to meet the fatigue requirements for the design life of the equipment. In such cases, the bolts can be replaced after certain duration based upon their fatigue life. However, the mating threads in the flange (which is an integral part of the vessel) are still a concern. While the replacement of the bolts is relatively easy and inexpensive, the corrective action (e.g. replacement or repair) for the flange is usually difficult and expensive, or impossible. Hence, it is important to have a reasonable estimate of the fatigue life of internal threads to alleviate or minimize the concern. In this paper, a simplified approach is presented for this purpose. Considering various bolt sizes, commonly used thread series and typical Class 1 component materials, it is shown that the fatigue life of the internal threads is about three times the fatigue life of the bolt threads. This conclusion greatly reduces or eliminates the concern for in service replacement or repair of the components with internal threads. (orig.)

  4. Ultra-high Cycle Fatigue Behaviors of Directionally Solidified Superalloy DZ125 at a Frequency of 20kHz%20kHz频率下DZ125定向凝固高温合金的超高周疲劳行为研究

    Institute of Scientific and Technical Information of China (English)

    顾玉丽; 刘昌奎; 何玉怀; 陶春虎

    2011-01-01

    The ultra-high cycle fatigue behavior of DZ12S alloy was studied using the ultrasonic fatigue testing technique under the load frequency of 20kHz and load ratio of R =- 1. The results show that DZ125 alloy still failed after 108 cycles. The analysis of the failed specimens using scaning electron microscopy ( SEM ) reveals that all ultra-high cycle fatigue cracks initiated at the surface of the specimens. Quantitative estimation of the fracture initiation life is 97. 3% of the total life. Using electron backscatter diffraction ( EBSD) technique, the crystal orientation change during the ultra-high cycle fatigue of superalloy DZ12S after conventional heat treatments, the crystal rotation angle will be slightly increased with the increase of the applied stress amplitude, the depth of deformation is minimum near the final fracture zone. After the frequency correction, the ultra-high cycle fatigue S-N curve is good agreement with the traditional fatigue S-N curve.%采用超声疲劳试验技术,研究了DZ125定向凝固高温合金在频率20kHz、载荷比R=-1下的超高周疲劳失效行为.结果表明:DZ125合金在循环周次大于108下仍发生了疲劳断裂;扫描电镜观察表明,DZ125合金的超高周疲劳裂纹均起源于试样的表面,经疲劳断口定量计算,超高周疲劳的萌生寿命约占总寿命的97.3%;电子背散射衍射(EBSD)分析表明,在超声振动应力的作用下,DZ125合金晶体发生了旋转,外加应力幅越大,晶体旋转的角度会略微增大,疲劳变形区域也略微增大,接近疲劳瞬断区的变形层深度最低;超高周疲劳试验结果经频率修正后,S-N曲线与常规低频疲劳的S-N曲线能很好地衔接.

  5. Fatigue Life of High-Strength Steel Offshore Tubular Joints

    DEFF Research Database (Denmark)

    Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

    1996-01-01

    In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength......In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high...... from Ø 324-610 mm tubes, and the joints were loaded in in-plane bending. Both fatigue tests under constant amplitude loading and tests with a stochastic loading that is realistic in relation to offshore structures, are included in the investigation.A comparison between constant amplitude and variable...... 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 in...

  6. Analysis of fatigue life for tube trailer cylinders

    Directory of Open Access Journals (Sweden)

    Xinqi YU

    2015-08-01

    Full Text Available Risk of fatigue failure exists in the tube trailer cylinders under the condition of internal pressure variation and inertial load caused through road transport. In order to estimate the safety state of the cylinders under the action of alternating load, the model of certain geometry sizes is built based on the widely used tube trailer cylinders. The fatigue analysis of tube trailer gas cylinders is made aiming at the action of the internal pressure and the inertial load. The fatigue life distribution of cylinders is obtained under the condition of different loads through the numerical simulation by ANSYS Workbench. The analysis results show that under internal pressure, gas cylinders have limited fatigue life, but can satisfy the requirements; when the inertial load exceeds a certain value, natural gas cylinders of tube trailer is under finite life state, which does not meet the requirements of strength, therefore the inertial load should be controlled.

  7. Thermomechanical fatigue life prediction of high temperature components

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, Thomas; Hartrott, Philipp von; Riedel, Hermann; Siegele, Dieter [Fraunhofer-Inst. fuer Werkstoffmechanik (IWM), Freiburg (Germany)

    2009-07-01

    The aim of the work described in this paper is to provide a computational method for fatigue life prediction of high temperature components, in which the time and temperature dependent fatigue crack growth is a relevant damage mechanism. The fatigue life prediction is based on a law for microcrack growth and a fracture mechanics estimate of the cyclic crack tip opening displacement. In addition, a powerful model for nonisothermal cyclic plasticity is employed, and an efficient laboratory test procedure is proposed for the determination of the model parameters. The models are efficiently implemented into finite element programs and are used to predict the fatigue life of a cast iron exhaust manifold and a notch in the perimeter of a turbine rotor made of a ferritic/martensitic 10%-chromium steel. (orig.)

  8. Dramatic increase in fatigue life in hierarchical graphene composites.

    Science.gov (United States)

    Yavari, F; Rafiee, M A; Rafiee, J; Yu, Z-Z; Koratkar, N

    2010-10-01

    We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries. PMID:20863061

  9. Dramatic increase in fatigue life in hierarchical graphene composites.

    Science.gov (United States)

    Yavari, F; Rafiee, M A; Rafiee, J; Yu, Z-Z; Koratkar, N

    2010-10-01

    We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.

  10. Study on the Ultra High Cycle Bending Vibration Fatigue Test of Titanium Alloys%钛合金超高周弯曲振动疲劳性能试验

    Institute of Scientific and Technical Information of China (English)

    申景生; 李全通; 吴晓峰; 高潮; 刘青川

    2011-01-01

    Based on the three-point bending method, an ultra high cycle bending vibration fatigue system is developed and the design method of fatigue test specimens is introduced too. The S - N curve of titanium alloy TC17 is determined by the ultra high cycle dissymmetrical bending fatigue system (20 kHz). The result shows that when stress ratio(R) is -1, the S - N curve of titanium alloy TC17 is a continuously declining curve, The specimens continue to fail over 107 stress cycles. In 107 weeks time, the samples don' t happen the fatigue damage, so it does not exist in the traditional sense fatigue limit.%在三点弯曲超高周疲劳试验的基础上,开发了悬臂梁式弯曲振动超高周疲劳试验系统,并介绍了疲劳试验试片的设计方法.利用超高周弯曲疲劳试验系统(20 kHz)测定了钛合金TC17的S-N曲线,结果表明,当应力比R=-1时TC17钛合金的S-N曲线是一条连续下降型曲线,在107周次以后,试样仍未发生疲劳破坏,不存在传统意义上的疲劳极限.

  11. Surface Fatigue Life of High Temperature Gear Materials

    Science.gov (United States)

    Townsend, Dennis P.

    1994-01-01

    Three high temperature gear materials were evaluated using spur gear surface fatigue tests. These materials were, VASCO max 350, VASCO matrix 2, and nitralloy N and were evaluated for possible use in high temperature gear applications. The fatigue life of the three high temperature gear materials were compared with the life of the standard AISI 9310 aircraft gear material. Surface fatigue tests were conducted at a lubricant inlet temperature of 321 K (120 F), a lubricant outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), a speed of 10,000 rpm, and with a synthetic paraffinic lubricant. The life of the nitralloy N was approximately the same as the AISI 9310, the life of the VASCO max 350 was much less than the AISI 9310 while the life of the VASCO matrix 2 was several times the life of the AISI 9310. The VASCO max 350 also showed very low fracture toughness with approximately half of the gears failed by tooth fracture through the fatigue spall. The VASCO matrix 2 had approximately 10-percent fracture failure through the fatigue spalls indicating moderate to good fracture toughness.

  12. a Study on the Fretting Fatigue Life of Zircaloy Alloys

    Science.gov (United States)

    Kwon, Jae-Do; Park, Dae-Kyu; Woo, Seung-Wan; Chai, Young-Suck

    Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr, and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

  13. A self-healing polymer composite for extended fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Brown, E. N. (Eric N.); Jones, A. S. (Alan S.); White, S. R. (Scott R.); Sottos, Nancy R.

    2004-01-01

    A novel approach is explored for improving the fatigue life of thermosetting polymers through the addition of self-healing functionality. Thermosetting polymers are used in a wide variety of applications, but are susceptible to the initiation and propagation of small cracks deep within the structure where detection is difficult and repair is virtually impossible. The material under investigation is an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. A propagating crack exposes particles of catalyst and ruptures the microcapsules, which release healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with the catalyst. Fatigue crack retardation and arrest from self-healing functionality result from crack-tip shielding mechanisms, such as hydrodynamic pressure and artificial-crack closure. In situ healing is observed to significantly extended fatigue life or permanently arrested fatigue crack growth over a wide range of loading conditions.

  14. Rolling contact fatigue life of ion-implanted GCr15

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Presents an experimental research into the rooling contact fatigue life of GCr15 steel with Tix N, TiX N + Ag and Tix N + DLC layers ion-implanted using the plasma ion-implantation technology on a ball-rod style high-speed con tact fatigue tester, and concludes with test results that the fatigue life increases to varying degrees with Tix N, Tix N + Ag, and Tix N + DLC layers implanted, and increases 1.8 times with Tix N + Ag layer implanted, hairline cracks grow continuously into fatigue pits under the action of shear stress in the superficial layer of material, and ion-implantation acts to prevent initiation of cracks and slow down propagation of cracks.

  15. Bayesian inference model for fatigue life of laminated composites

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der; Berggreen, Christian

    2016-01-01

    A probabilistic model for estimating the fatigue life of laminated composite plates is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configurations. Model parameters are estimated by Bayesian inference....... The reference data used consists of constant-amplitude cycle test results for four laminates with different layup configurations. The paper describes the modeling techniques and the parameter estimation procedure, supported by an illustrative application....

  16. Fatigue life prediction modeling for turbine hot section materials

    Science.gov (United States)

    Halford, G. R.; Meyer, T. G.; Nelson, R. S.; Nissley, D. M.; Swanson, G. A.

    1989-01-01

    A major objective of the fatigue and fracture efforts under the NASA Hot Section Technology (HOST) program was to significantly improve the analytic life prediction tools used by the aeronautical gas turbine engine industry. This was achieved in the areas of high-temperature thermal and mechanical fatigue of bare and coated high-temperature superalloys. The cyclic crack initiation and propagation resistance of nominally isotropic polycrystalline and highly anisotropic single crystal alloys were addressed. Life prediction modeling efforts were devoted to creep-fatigue interaction, oxidation, coatings interactions, multiaxiality of stress-strain states, mean stress effects, cumulative damage, and thermomechanical fatigue. The fatigue crack initiation life models developed to date include the Cyclic Damage Accumulation (CDA) and the Total Strain Version of Strainrange Partitioning (TS-SRP) for nominally isotropic materials, and the Tensile Hysteretic Energy Model for anisotropic superalloys. A fatigue model is being developed based upon the concepts of Path-Independent Integrals (PII) for describing cyclic crack growth under complex nonlinear response at the crack tip due to thermomechanical loading conditions. A micromechanistic oxidation crack extension model was derived. The models are described and discussed.

  17. Experimental Study on High Cycle Fatigue Behavior andγ-P-S-N Curves of Bridge Steel Q345qD%Q345qD桥梁钢高周疲劳性能及γ-P-S-N曲线试验研究

    Institute of Scientific and Technical Information of China (English)

    贾单锋; 廖小伟; 崔佳

    2016-01-01

    针对桥梁钢Q345qD的力学性能及高周疲劳特性,分别使用直径10,mm的圆棒试件和沙漏型试件进行了轴向拉伸试验及轴向疲劳试验,得到 Q345qD 完整的材性数据及应力-寿命曲线(S-N 曲线)。考虑到材料疲劳寿命离散性较大,为了便于工程应用,采用单侧容限统计方法,研究在给定置信度下各应力水平对应的 Q34qD 的安全疲劳寿命,得出了同时考虑置信度和存活率的设计疲劳曲线。研究结果表明桥梁钢 Q345qD 在常温下具有较好的疲劳性能,随应力水平的降低疲劳寿命明显增大,疲劳寿命曲线迅速趋于水平,疲劳极限在Smax=273~278,MPa之间。%The mechanical properties and high cycle fatigue behavior of bridge steel Q345qD were studied.A number of axial tensile tests and axial fatigue tests were conducted using 10,mm-diameter round bar specimens and hourglass specimens respectively.The accurate data of material properties and stress-life curve(S-N curve)were ob-tained.Taking into account the large discreteness of material fatigue life,in order to facilitate engineering applica-tions,unilateral tolerance statistical methods were adopted to study the Q345qD safety fatigue life at a given confi-dence level for each stress level.The safe life fatigue curves with confidence and survival rate were also obtained.The results show that the bridge steel Q345qD has good fatigue properties at room temperature.The fatigue life increases significantly with the decrease of stress level and the fatigue curve tends to reach the horizontal level quickly.The fatigue limit lies within the range ofSmax=273—278,MPa.

  18. 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.

  19. Creep fatigue life prediction for engine hot section materials (isotropic)

    Science.gov (United States)

    Moreno, Vito; Nissley, David; Lin, Li-Sen Jim

    1985-01-01

    The first two years of a two-phase program aimed at improving the high temperature crack initiation life prediction technology for gas turbine hot section components are discussed. In Phase 1 (baseline) effort, low cycle fatigue (LCF) models, using a data base generated for a cast nickel base gas turbine hot section alloy (B1900+Hf), were evaluated for their ability to predict the crack initiation life for relevant creep-fatigue loading conditions and to define data required for determination of model constants. The variables included strain range and rate, mean strain, strain hold times and temperature. None of the models predicted all of the life trends within reasonable data requirements. A Cycle Damage Accumulation (CDA) was therefore developed which follows an exhaustion of material ductility approach. Material ductility is estimated based on observed similarities of deformation structure between fatigue, tensile and creep tests. The cycle damage function is based on total strain range, maximum stress and stress amplitude and includes both time independent and time dependent components. The CDA model accurately predicts all of the trends in creep-fatigue life with loading conditions. In addition, all of the CDA model constants are determinable from rapid cycle, fully reversed fatigue tests and monotonic tensile and/or creep data.

  20. Deformation heterogeneities and their role in life-limiting fatigue failures in a two-phase titanium alloy

    International Nuclear Information System (INIS)

    is presented. The hypothesis invokes the concept of hierarchy of fatigue deformation heterogeneities, which is suggested to develop within the first few fatigue cycles. The deformation heterogeneity is suggested to be linked to the underlying randomness and hierarchy in the microstructural arrangements. This hypothesis appears to explain the occurrence of crack-growth-lifetime-dominated, life-limiting failures in the regime of high-cycle fatigue, as shown in this study, and suggests a probability of occurrence of such failures even in the very-high-cycle fatigue regime, although with diminishing probability as the stress level is decreased

  1. Practical methodology to evaluate the fatigue life of seam welded joints

    OpenAIRE

    K.C.Goes; G.F. Batalha; M.V. Pereira; A.F. Camarao

    2011-01-01

    Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. A tube-to-plate specimen was submitted to a combined cyclic loadi...

  2. The effect of plasma electrolytic oxidation on the mean stress sensitivity of the fatigue life of the 6082 aluminum alloy

    Science.gov (United States)

    Winter, L.; Morgenstern, R.; Hockauf, K.; Lampke, T.

    2016-03-01

    In this work the mean stress influence on the high cycle fatigue behavior of the plasma electrolytic oxidized (PEO) 6082 aluminum alloy (AlSi1MgMn) is investigated. The present study is focused on the fatigue life time and the susceptibility of fatigue-induced cracking of the oxide coating and their dependence on the applied mean stress. Systematic work is done comparing conditions with and without PEO treatment, which have been tested using three different load ratios. For the uncoated substrate the cycles to failure show a significant dependence on the mean stress, which is typical for aluminum alloys. With increased load ratio and therefore increased mean stress, the fatigue strength decreases. The investigation confirms the well-known effect of PEO treatment on the fatigue life: The fatigue strength is significantly reduced by the PEO process, compared to the uncoated substrate. However, also the mean stress sensitivity of the fatigue performance is reduced. The fatigue limit is not influenced by an increasing mean stress for the PEO treated conditions. This effect is firstly shown in these findings and no explanation for this effect can be found in literature. Supposedly the internal compressive stresses and the micro-cracks in the oxide film have a direct influence on the crack initiation and growth from the oxide film through the interface and in the substrate. Contrary to these findings, the susceptibility of fatigue-induced cracking of the oxide coating is influenced by the load ratio. At tension-tension loading a large number of cracks, which grow partially just in the aluminum substrate, are present. With decreasing load ratio to alternating tension-compression stresses, the crack number and length increases and shattering of the oxide film is more pronounced due to the additional effective compressive part of the load cycle.

  3. On Fatigue Life Under Stationary Gaussian Random Loads (A)

    DEFF Research Database (Denmark)

    Talreja, R.

    1973-01-01

    Power spectra are taken to represent stationary Gaussian random loads. Location, scale, and shape parameters are defined for power spectra and proposed as a convenient set of load parameters for random loads. The center frequency of a power spectrum, defined as its weighted average frequency......, is proposed as a measure of fatigue life. A servohydraulic closed loop testing machine is used to load specimens of carbon steel under six different power spectral shapes. Test results are utilized to evaluate a fatigue life function formulated in terms of the load parameters. The concept of a shape operator...

  4. Fatigue life prediction of crankshaft repaired by twin arc spraying

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guo-qing; WANG Cheng-tao; PU Geng-qiang

    2005-01-01

    This paper used Baumel Jr. and Seeger's approach estimating fatigue parameters of 48MnV with 3Cr13coatings. The fatigue life of the crankshaft of a six-cylinder engine, repaired by twin arc spraying 3cr13 deposits, is respectively calculated using different damage model such as S-N method, normal strain approaches, SWT-Bannantine approaches, shear strain approaches, and fatemi-Socie method based on dynamical simulation and FE analysis of crankshaft. The results indicate that the traditional calculation is conservative and that the life of crankshaft repaired by arc spraying is sufficient.

  5. 汽轮机转子初始裂纹高周疲劳安全性分析方法及其在焊接转子中的应用%High Cycle Fatigue Safety Analysis for Steam Turbine Rotors with Initial Cracks and Its Application to a Welded Rotor

    Institute of Scientific and Technical Information of China (English)

    史进渊; 邓志成; 汪勇; 杨宇; 刘岩; 刘霞; 王争艳; 杨彦磊

    2013-01-01

    An introduction is being presented to the design method of high cycle fatigue life of steam turbine rotors, together with descriptions to analytical methods for high cycle fatigue safety of turbine rotors with initial cracks, and to calculation methods for the mean stress σm ,stress amplitude σA and the range △KI of stress intensity factors as well as to an experience formula for the fatigue crack growth threshold △KRth of the rotor material. Meanwhile, an analysis method and the assessment criteria for high cycle fatigue safety of steam turbine rotors with initial cracks are given, with an application example listed for high cycle fatigue safety analysis of a welded low-pressure rotor for a half-speed steam turbine in a 1 000 MW nuclear power station. Results show that the analytical methods may be used for safety evaluation and structural optimization of steam turbine rotors, so as to guarantee safety operation of relevant power plants.%介绍了汽轮机转子高周疲劳寿命的设计方法.提出了汽轮机转子初始裂纹高周疲劳安全性的分析方法,转子高周疲劳的平均应力σm、应力幅σA和应力强度因子范围AKI的计算方法以及转子钢疲劳裂纹扩展门槛值△KR的经验计算公式.给出了汽轮机转子初始裂纹高周疲劳安全性的分析思路、分析方法、评价判据以及半转速1 000 MW核电汽轮机焊接低压转子的高周疲劳安全性分析应用实例.结果表明:转子初始裂纹高周疲劳分析方法能够应用于汽轮机转子的安全性评价,并可以为汽轮机转子的结构优化和长周期安全运行提供依据.

  6. Fatigue life of ablation-cast 6061-T6 components

    Energy Technology Data Exchange (ETDEWEB)

    Tiryakioglu, Murat, E-mail: m.tiryakioglu@unf.edu [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Eason, Paul D. [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Campbell, John [Department of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT (United Kingdom)

    2013-01-01

    The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si-Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.

  7. Prediction of corrosion fatigue life using DCPD method

    International Nuclear Information System (INIS)

    In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities and corrosion fatigue life considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The potential difference due to the crack growth behavior in 25 deg. C, 3.5wt.% NaCl solution is very susceptible. And it was found that stress amplitude has a linear relationship with the critical potential. Therefore, it is expected that the corrosion fatigue life of TMCP steel can be nondestructively predicted using the DCPD method

  8. Multi-Axial Damage Index and Accumulation Model for Predicting Fatigue Life of CMC Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The fatigue life of CMCs must be well characterized for the safe and reliable use of these materials as integrated TPS components. Existing fatigue life prediction...

  9. Survey on damage mechanics models for fatigue life prediction

    NARCIS (Netherlands)

    Silitonga, S.; Maljaars, J.; Soetens, F.; Snijder, H.H.

    2013-01-01

    Engineering methods to predict the fatigue life of structures have been available since the beginning of the 20th century. However, a practical problem arises from complex loading conditions and a significant concern is the accuracy of the methods under variable amplitude loading. This paper provide

  10. Relationship between fatigue life in the creep-fatigue region and stress-strain response

    Science.gov (United States)

    Berkovits, A.; Nadiv, S.

    1988-01-01

    On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the two more pairs of stress strain parameters must be ascertained.

  11. Fatigue Life Assessment of Selected Engineering Materials Based on Modified Low-Cycle Fatigue Test

    Directory of Open Access Journals (Sweden)

    M. Maj

    2013-01-01

    Full Text Available In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade.The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF, which enables the determination of parameters resulting fromthe Manson-Coffin-Morrow relationship.The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidalgraphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties, confirmed also smallvariations in the geometrical parameters of graphite related with its content and morphological features.

  12. Fatigue Life Analysis of Rolling Bearings Based on Quasistatic Modeling

    OpenAIRE

    Wei Guo; Hongrui Cao; Zhengjia He; Laihao Yang

    2015-01-01

    Rolling bearings are widely used in aeroengine, machine tool spindles, locomotive wheelset, and so forth. Rolling bearings are usually the weakest components that influence the remaining life of the whole machine. In this paper, a fatigue life prediction method is proposed based on quasistatic modeling of rolling bearings. With consideration of radial centrifugal expansion and thermal deformations on the geometric displacement in the bearings, the Jones’ bearing model is updated, which can pr...

  13. Fatigue Life Analysis of Rolling Bearings Based on Quasistatic Modeling

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2015-01-01

    Full Text Available Rolling bearings are widely used in aeroengine, machine tool spindles, locomotive wheelset, and so forth. Rolling bearings are usually the weakest components that influence the remaining life of the whole machine. In this paper, a fatigue life prediction method is proposed based on quasistatic modeling of rolling bearings. With consideration of radial centrifugal expansion and thermal deformations on the geometric displacement in the bearings, the Jones’ bearing model is updated, which can predict the contact angle, deformation, and load between rolling elements and bearing raceways more accurately. Based on Hertz contact theory and contact mechanics, the contact stress field between rolling elements and raceways is calculated. A coupling model of fatigue life and damage for rolling bearings is given and verified through accelerated life test. Afterwards, the variation of bearing life is investigated under different working conditions, that is, axial load, radial load, and rotational speed. The results suggested that the working condition had a great influence on fatigue life of bearing parts and the order in which the damage appears on bearing parts.

  14. Simulation work of fatigue life prediction of rubber automotive components

    Energy Technology Data Exchange (ETDEWEB)

    Samad, M S A [Automotive Engineering Unit, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM Serdang, Selangor (Malaysia); Ali, Aidy, E-mail: aidy@eng.upm.edu.my [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor (Malaysia)

    2010-05-15

    The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

  15. Fatigue Life of Postbuckled Structures with Indentation Damages

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of each stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 32 millimeters to 56 millimeters were tested quasi-statically and in fatigue, and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  16. Fatigue Life of Postbuckled Structures with Indentation Damage

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of the stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 37 millimeters to 56 millimeters were tested in fatigue and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  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 is...

  18. The Reliability Life of 7B04 Aluminum Alloy under Alternate Action of Corrosion and Fatigue

    Directory of Open Access Journals (Sweden)

    Changfan Li

    2016-01-01

    Full Text Available Experiment of alternate action of corrosion and fatigue on 7B04 aluminum alloy was carried out in this paper and fatigue life was obtained. One of the characteristics about fatigue life is that it is not always decreasing with the increasing of corrosion time. The surface splits caused by the corrosion of intruding and extruding slip steps on the surface and decreasing of stress concentration around corrosion pits were the main reasons. Single side allowance factor k was proposed to calculate reliability fatigue life with both reliability and confidence. Reliability, confidence, and specimen number had affection on the value of k. The reliability influences more greatly the reliability fatigue life compared to the confidence. The safe fatigue life is smaller than median life and it was safe to administrate aircraft life using safe fatigue life.

  19. Time-dependent fatigue--phenomenology and life prediction

    International Nuclear Information System (INIS)

    The time-dependent fatigue behavior of materials used or considered for use in present and advanced systems for power generation is outlined. A picture is first presented to show how basic mechanisms and phenomenological information relate to the performance of the component under consideration through the so-called local strain approach. By this means life prediction criteria and design rules can be formulated utilizing laboratory test information which is directly translated to predicting the performance of a component. The body of phenomenological information relative to time-dependent fatigue is reviewed. Included are effects of strain range, strain rate and frequency, environment and wave shape, all of which are shown to be important in developing both an understanding and design base for time dependent fatigue. Using this information, some of the current methods being considered for the life prediction of components are reviewed. These include the current ASME code case, frequency-modified fatigue equations, strain range partitioning, the damage function method, frequency separation and damage rate equations. From this review, it is hoped that a better perspective on future directions for basic material science at high temperature can be achieved

  20. Advances in fatigue life prediction methodology for metallic materials

    Science.gov (United States)

    Newman, J. C., Jr.

    1992-01-01

    The capabilities of a plasticity-induced crack-closure model to predict small- and large-crack growth rates, and in some cases total fatigue life, for four aluminum alloys and three titanium alloys under constant-amplitude, variable-amplitude, and spectrum loading are described. Equations to calculate a cyclic-plastic-zone corrected effective stress-intensity factor range from a cyclic J-integral and crack-closure analysis of large cracks were reviewed. The effective stress-intensity factor range against crack growth rate relations were used in the closure model to predict small- and large-crack growth under variable-amplitude and spectrum loading. Using the closure model and microstructural features, a total fatigue life prediction method is demonstrated for three aluminum alloys under various load histories.

  1. A State-of-the-Art Review on Fatigue Life Assessment of Steel Bridges

    Directory of Open Access Journals (Sweden)

    X. W. Ye

    2014-01-01

    Full Text Available Fatigue is among the most critical forms of damage potentially occurring in steel bridges, while accurate assessment or prediction of the fatigue damage status as well as the remaining fatigue life of steel bridges is still a challenging and unsolved issue. There have been numerous investigations on the fatigue damage evaluation and life prediction of steel bridges by use of deterministic or probabilistic methods. The purpose of this review is devoted to presenting a summary on the development history and current status of fatigue condition assessment of steel bridges, containing basic aspects of fatigue, classical fatigue analysis methods, data-driven fatigue life assessment, and reliability-based fatigue condition assessment.

  2. Comparison between tensile, stiffness and fatigue life tests results

    OpenAIRE

    Silva, Hugo Manuel Ribeiro Dias da; Pais, Jorge C.; Pereira, Paulo A. A.

    2003-01-01

    A laboratory mechanical test is being implemented in the University of Minho to evaluate the asphalt-aggregate interaction. This test measures the tensile properties of the bituminous mixture in the interface between the asphalt and the aggregates. By using the tensile test it is intended to observe how the asphalt-aggregate interaction influences the mechanical properties of the bituminous mixtures, namely, stiffness modulus and fatigue life. The tensile test results must have a good correla...

  3. 海洋隔水管对接环焊缝接头高周疲劳性能研究%Research on High Cycle Fatigue Property for Butt Circumferential Weld of Marine Riser

    Institute of Scientific and Technical Information of China (English)

    余钊辉; 党恩; 朱安达; 杨龙; 张建勋

    2013-01-01

    The four-point bend fatigue test method was used to measure the high cycle fatigue property of marine riser X80/X80J butt circumferential weld. The influence on crack initiation location of stress concentration,microstructure and hardness was analyzed comprehensively. The results showed that the fatigue crack of welded joint with weld reinforcement initiates from toes, and then extends to the heat affected zone from the weld reinforcement,while the crack initiates from weld and propagates along the weld without reinforcement. The stress concentration caused by the weld reinforcement is the main factor to reduce the welded joint fatigue performance. The fatigue limit of welded joint is 216 MPa for with reinforcement and 400 MPa for without the weld reinforcement.%采用四点弯曲疲劳试验法,测试了海洋隔水管道X80/X80J对接环焊缝高周疲劳性能。综合分析了应力集中、显微组织和硬度对裂纹萌生位置的影响。结果表明,有余高焊接接头疲劳裂纹在焊趾处萌生并向热影响区扩展,去除余高的焊接接头疲劳裂纹从焊缝处萌生并沿焊缝扩展;焊缝余高引起的应力集中是降低焊接接头疲劳性能的主要因素,有余高焊接接头的疲劳极限为216 MPa,去除余高的焊接接头疲劳极限为400 MPa。

  4. TiAl 合金择优取向层片组织的高周疲劳行为%High-cycle Fatigue Behavior of TiAl Alloy Containing Preferentially Oriented Lamellar Microstructures

    Institute of Scientific and Technical Information of China (English)

    万文娟; 韩波; 韩伟; 张继

    2016-01-01

    采用旋转弯曲的加载方式,评价了 Ti-47.5Al-2.5V-1.0Cr-0.2Zr (原子分数/%)合金择优取向层片组织的高温高周疲劳性能,并对疲劳断口进行了扫描电镜分析。结果表明:该合金表现出符合 Basquin 方程的平直 S-N 曲线,750℃条件疲劳极限相当于其抗拉强度的60%;断口观察发现,所有试样中的疲劳裂纹均以穿层片方式扩展,表明该种组织的界面对疲劳裂纹扩展具有较高的抗力。%The high-cycle fatigue performance of Ti-47.5Al-2.5V-1 .0Cr-0.2Zr (at.%)alloy with a preferentially oriented lamellar microstructure has been evaluated by means of load-controlled rotating bending fatigue tests at elevated temperature,and fracture sur-faces of fatigue specimens were also analyzed by scanning electron microscope.The results show that it exhibits a flat S-N curve fitted by Basquin equation,and its fatigue limit is equal to 60% of the ultimate tensile strength at 750 ℃.The fracture surface observation proves that all of the fatigue crack propagation in the studied samples is indeed presented with a typical translamellar mode,and indica-ting the high resistance of this microstructure to crack propagation.

  5. A real time neural net estimator of fatigue life

    Science.gov (United States)

    Troudet, T.; Merrill, W.

    1990-01-01

    A neural network architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopumps blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high-frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines.

  6. Study on effect of mean stress on fatigue life prediction of thin film structure

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Myung Soo [Ahtti Co., Seongnam (Korea, Republic of); Park, Jun Hyu [Tongmyong University, Busan (Korea, Republic of); Kim, Jung Yup [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2016-04-15

    This paper describes the effect of mean stress on fatigue life prediction of structure made with thin film. It is well known that the mean stress influences fatigue life prediction of mechanical structure. We investigated a reasonable method for considering mean stress when fatigue strength assessment of micro structure of thin film should be performed. Fatigue tests of smooth specimen of beryllium-copper (BeCu) thin film were performed in ambient air at R = 0.1 with 5 Hz. A micro probe was designed and made with BeCu thin film by the precision press process. Fatigue tests of micro structure were performed with 5 Hz frequency, in ambient air to verify the fatigue life predicted by computer simulation through FE analysis. The fatigue life predicted by the Sa -N curve modified by Goodman method with principal stress through FE analysis shows a more reasonable result than other methods.

  7. Fatigue

    Science.gov (United States)

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

  8. On the effect of deep-rolling and laser-peening on the stress-controlled low- and high-cycle fatigue behavior of Ti-6Al-4V at elevated temperatures up to 550?C

    OpenAIRE

    Ritchie, IAltenberger, RKNalla, YSano LWagner, RO

    2013-01-01

    The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed...

  9. Effects of temperature change on fatigue life of carbon steel in high temperature water

    International Nuclear Information System (INIS)

    Strain controlled fatigue tests of a carbon steel in oxygenated high temperature water were carried out under the condition of combined and synchronized mechanical and thermal strain cycling. The effects of temperature change on environmental fatigue life were investigated, showing basic conceptual data to evaluate the fatigue damage under the condition of transient temperature change of actual plant components

  10. Development of Fatigue Life Improvement Technology of Butt Joints Using Friction Stir Processing

    OpenAIRE

    Jeong-Ung Park; GyuBaek An; Heung-ju Kim; Jae-hyouk Choi

    2014-01-01

    Burr grinding, tungsten inert gas (TIG) dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, improving the bead shape, or causing compressive residual stress. This study proposes a new postweld treatment method improving the weld bead shape and metal structure at the welding zone using friction stir processing (FSP) to enhance fatigue life. For that, a pin-shape...

  11. Fatigue Life Methodology for Tapered Composite Flexbeam Laminates

    Science.gov (United States)

    Murri, Gretchen B.; O''Brien, T. Kevin; Rousseau, Carl Q.

    1997-01-01

    The viability of a method for determining the fatigue life of composite rotor hub flexbeam laminates using delamination fatigue characterization data and a geometric non-linear finite element (FE) analysis was studied. Combined tension and bending loading was applied to nonlinear tapered flexbeam laminates with internal ply drops. These laminates, consisting of coupon specimens cut from a full-size S2/E7T1 glass-epoxy flexbeam were tested in a hydraulic load frame under combined axial-tension and transverse cyclic bending loads. The magnitude of the axial load remained constant and the direction of the load rotated with the specimen as the cyclic bending load was applied. The first delamination damage observed in the specimens occurred at the area around the tip of the outermost ply-drop group. Subsequently, unstable delamination occurred by complete delamination along the length of the specimen. Continued cycling resulted in multiple delaminations. A 2D finite element model of the flexbeam was developed and a geometrically non-linear analysis was performed. The global responses of the model and test specimens agreed very well in terms of the transverse flexbeam tip-displacement and flapping angle. The FE model was used to calculate strain energy release rates (G) for delaminations initiating at the tip of the outer ply-drop area and growing toward the thick or thin regions of the flexbeam, as was observed in the specimens. The delamination growth toward the thick region was primarily mode 2, whereas delamination growth toward the thin region was almost completely mode 1. Material characterization data from cyclic double-cantilevered beam tests was used with the peak calculated G values to generate a curve predicting fatigue failure by unstable delamination as a function of the number of loading cycles. The calculated fatigue lives compared well with the test data.

  12. Thermal fatigue of pipes induced by fluid temperature change. Effect of multiaxial pre-loading on fatigue strength

    International Nuclear Information System (INIS)

    This study investigates an effect of pre-inelastic multiaxial loading on failure lives in a followed high cycle fatigue test for SUS316 steel. In the multiaxial low cycle fatigue test for the pre-loading, two types of strain paths were employed which are a push-pull straining and a circle straining. The circle straining is the non-proportional loading in which axial strain ε and shear strain γ has 90 degree phase difference. Using the specimen fatigued in the pre-loading test, high cycle fatigue test was conducted by a rotating bending fatigue testing machine. Based on the obtained results, property of fatigue life in high cycle fatigue which received pre-loading under non-proportional loading is discussed. (author)

  13. In-situ fatigue life prognosis for composite laminates based on stiffness degradation

    Data.gov (United States)

    National Aeronautics and Space Administration — In this paper, a real-time composite fatigue life prognosis framework is proposed. The proposed methodology combines Bayesian inference, piezoelectric sensor...

  14. Low Cycle Fatigue Behavior and Life Prediction of a Cast Cobalt-Based Superalloy

    Science.gov (United States)

    Yang, Ho-Young; Kim, Jae-Hoon; Yoo, Keun-Bong

    Co-base superalloys have been applied in the stationary components of gas turbine owing to their excellent high temperature properties. Low cycle fatigue data on ECY-768 reported in a companion paper were used to evaluate fatigue life prediction models. In this study, low cycle fatigue tests are performed as the variables of total strain range and temperatures. The relations between plastic and total strain energy densities and number of cycles to failure are examined in order to predict the low cycle fatigue life of Cobalt-based super alloy at different temperatures. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

  15. Vortex-induced vibration effect on fatigue life estimate of turbine blades

    Science.gov (United States)

    Lau, Y. L.; Leung, R. C. K.; So, R. M. C.

    2007-11-01

    An analysis of a turbine blade fatigue life that includes the physics of fluid-structure interaction on the high cycle fatigue (HCF) life estimate of turbine blades is carried out. The rotor wake excitation is modeled by rows of Karman vortices superimposed on an inviscid uniform flow. The vortex-induced vibration problem is modeled by a linear cascade composed of five turbine blades and the coupled Euler and structural dynamics equations are numerically solved using a time-marching boundary element technique. The analysis can be applied to any blade geometries; it is not limited to the blade geometry considered here. Two major design parameters have been identified; the ratio of blade spacing to blade chord length s/ c of the stator, and the normalized frequency parameter c/ d which is related to the wake passing frequency of the rotor. For a rigid cascade, it is found that aerodynamic resonance prevails at the resonant c/ d values corresponding to an isolated blade while s/ c is responsible for the level of the aerodynamic response. If the central blades were elastic, the parameter s/ c plays a different role in the fluid-structure interaction problem. With a c/ d that could lead to structural resonance for an isolated blade, changing s/ c would stabilize the aerodynamic and structural response of the elastic blade in a cascade. On the contrary, an improper choice of s/ c might turn the elastic blade response into structural resonance even though the oncoming c/ d is non-resonant. The results of the nonlinear effects of c/ d and s/ c could be used together with the Campbell diagram to obtain an improved HCF design of rotor-stator pair.

  16. 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.

  17. Prediction of Fatigue Life of a Continuous Bridge Girder Based on Vehicle Induced Stress History

    Directory of Open Access Journals (Sweden)

    V.G. Rao

    2003-01-01

    Full Text Available The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge-vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.

  18. 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

  19. 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

    OBJECTIVES: To examine associations of fatigue in midlife and later life with physical performance and strength in early old age. METHODS: Data on approximately 1800 men and women from the UK Medical Research Council National Survey of Health and Development with data on fatigue at ages 43 and 60...... to 64 years were used. Fatigue was defined as perceived tiredness and was assessed prospectively at ages 43 and 60 to 64 years. At both ages, participants were categorized as having no, occasional, or frequent fatigue. Physical performance and strength were measured at age 60 to 64 years using four...... life. These findings indicate that it is not just fatigue but fatigue sustained across adulthood that has implications for later life functioning....

  20. Experimental fatigue life investigation of cylindrical thrust chambers

    Science.gov (United States)

    Quentmeyer, R. J.

    1977-01-01

    The thrust chambers studied in the investigation have been designed for a possible use in the Space Shuttle main engine. An annular combustion chamber configuration was used, consisting of an annular injector, a liquid hydrogen cooled outer cylinder, which served as the test section, and a contoured water cooled centerbody which formed the throat. Twenty-two cylinders were fabricated by milling cooling channels into liners fabricated from the material to be evaluated. The three materials chosen for the liners include OFHC copper, Amzirc, and NARloy-Z. The cylinders were cyclically tested until failure occurred due to fatigue cracks in the hot-gas-side wall. It was found that cylinders with liners fabricated from NARloy-Z and aged Amzirc had the best cyclic life characteristics.

  1. Fatigue life assessment for pipeline welds by x-ray diffraction technique

    International Nuclear Information System (INIS)

    The objective of this study is to estimate the feasibility of X-ray diffraction method application for fatigue life assessment of the high-temperature pipeline steel such as main steam pipe, re-heater pipe and header etc. in power plant. In this study, X-ray diffraction tests using various types of specimen simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages such as 1/4, l/2 and 3/4 of fatigue life, respectively. As a result off-ray diffraction tests for specimens simulated fatigue damages, we conformed that the variation of the full width at half maximum intensity decreased in proportion to the increase of fatigue life ratio. And also, He ratio of the full width at half maximum intensity due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.

  2. 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.

  3. Study on Contact Fatigue Life and Failure Mechanism of Subquenched 42CrMo Steel

    Institute of Scientific and Technical Information of China (English)

    HE Bo-lin; YU Ying-xia; SHAO Er-yu

    2004-01-01

    The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.

  4. A prediction of biaxial fatigue life of cast stainless steels(CF8M) by degradation

    International Nuclear Information System (INIS)

    The multiaxial fatigue test under in-phase and out-of-phase load were performed to study what degradation phenomenon affects fatigue life with virgin and 3600 hrs degraded materials. The various kind of fatigue data for fatigue life prediction were acquired under pure axial and pure torsional load of fully reversal condition. The models which was investigated are: 1) the von Mises equivalent strain range, 2) the critical shear plane approach method of Fatemi-Socie(FS) parameter, 3) the modified Smith-Watson-Topper(SWT) parameter. The result showed that, fatigue life by material degradation are decreased and life prediction which was used the FS parameter is not conservative but the best result

  5. Study on fatigue life evaluation of structural component based on crack growth criterion

    International Nuclear Information System (INIS)

    As one of the practical application of fracture mechanics, fatigue life evaluation method based on crack growth criterion has been diffusing in various field of technology in order to determine the rational and reliable life of structural components. The fatigue life by this method is evaluated based on the fatigue crack growth analysis from defects, while many problems, such as the influence of residual stress on the crack growth behavior, the effect of overloading, and evaluation method for multiple surface cracks, are not sufficiently solved yet. In this paper, the above problems are treated, and based on some exprimental data some simple mehtods for fatigue life evaluation are proposed regarding the above problems. Verification of the proposed methods are shown in the paper by comparing with some experimental results, and the applicability of the proposed method is also examined by the fatigue test of pipes with cracks in the inner surface. (author)

  6. Transverse Tension Fatigue Life Characterization Through Flexure Testing of Composite Materials

    Science.gov (United States)

    OBrien, T. Kevin; Chawan, Arun D.; Krueger, Ronald; Paris, Isabelle

    2001-01-01

    The transverse tension fatigue life of S2/8552 glass-epoxy and IM7/8552 carbon-epoxy was characterized using flexure tests of 90-degree laminates loaded in 3-point and 4-point bending. The influence of specimen polishing and specimen configuration on transverse tension fatigue life was examined using the glass-epoxy laminates. Results showed that 90-degree bend specimens with polished machined edges and polished tension-side surfaces, where bending failures where observed, had lower fatigue lives than unpolished specimens when cyclically loaded at equal stress levels. The influence of specimen thickness and the utility of a Weibull scaling law was examined using the carbon-epoxy laminates. The influence of test frequency on fatigue results was also documented for the 4-point bending configuration. A Weibull scaling law was used to predict the 4-point bending fatigue lives from the 3-point bending curve fit and vice-versa. Scaling was performed based on maximum cyclic stress level as well as fatigue life. The scaling laws based on stress level shifted the curve fit S-N characterizations in the desired direction, however, the magnitude of the shift was not adequate to accurately predict the fatigue lives. Furthermore, the scaling law based on fatigue life shifted the curve fit S-N characterizations in the opposite direction from measured values. Therefore, these scaling laws were not adequate for obtaining accurate predictions of the transverse tension fatigue lives.

  7. Methodology of determination the influence of corrosion pit on decrease of hydro turbine shaft fatigue life

    OpenAIRE

    Mitrović, Radivoje; Atanasovska, Ivana; MOMČILOVIĆ, Dejan; Vuherer, Tomaž

    2015-01-01

    This paper describes the influence of corrosion on stress concentration factor and crack initiation at shaftflange transition section. The case study of hydraulic turbine shaft failure is used as the basis for this research. The quantification of the stress concentrators was accomplished by the usage of Theory of critical distances (TCD) in the prediction of high-cycle fatigue behavior in machine parts and systems. The stresses obtained by Finite Element Analysis, was used as an entry values ...

  8. Thermomechanical Fatigue Life Prediction for a Marine Diesel Engine Piston considering Ring Dynamics

    OpenAIRE

    Tao He; Xiqun Lu; Dequan Zou; Yibin Guo; Wanyou Li; Minli Huang

    2014-01-01

    A newly designed marine diesel engine piston was modeled using a precise finite element analysis (FEA). The high cycle fatigue (HCF) safety factor prediction procedure designed in this study incorporated lubrication, thermal, and structure analysis. The piston ring dynamics calculation determined the predicted thickness of lubrication oil film. The film thickness influenced the calculated magnitude of the heat transfer coefficient (HTC) used in the thermal loads analysis. Moreover, the gas pr...

  9. Aspects of fatigue life in thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, H.

    2001-08-01

    Thermal barrier coatings (TBC) are applied on hot components in airborne and land based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment. Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO{sub 2} + 6-8% Y{sub 2}O{sub 3}. Below the top coat there is a metallic bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% Yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions, have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal barrier coatings fail. As a final outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's. In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the bond coat due to inter-diffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed

  10. FATIGUE LIFE AND CRACK GROWTH BEHAVIOR IN ANNEALED AND NORMALIZED 0.83% CARBON STEEL

    OpenAIRE

    CHOBIN MAKABE; SHINYA YAMAZAKI; TATSUJIRO MIYAZAKI; MASAKI FUJIKAWA

    2015-01-01

    The variations of fatigue limit and fatigue life of a plain specimen of annealed and normalized 0.83% carbon steel were investigated. This material is used for cutting tools and the original microstructure includes a spherical microstructure. After heat treatment under some conditions, the microstructure changed to a lamellar microstructure. However, the fatigue lives of the plain specimens of this material showed almost the same tendency even after heat treatment under some conditions. In th...

  11. A review on fatigue life prediction methods for anti-vibration rubber materials

    Directory of Open Access Journals (Sweden)

    Xiaoli WANG

    2016-08-01

    Full Text Available Anti-vibration rubber, because of its superior elasticity, plasticity, waterproof and trapping characteristics, is widely used in the automotive industry, national defense, construction and other fields. The theory and technology of predicting fatigue life is of great significance to improve the durability design and manufacturing of anti-vibration rubber products. According to the characteristics of the anti-vibration rubber products in service, the technical difficulties for analyzing fatigue properties of anti-vibration rubber materials are pointed out. The research progress of the fatigue properties of rubber materials is reviewed from three angles including methods of fatigue crack initiation, fatigue crack propagation and fatigue damage accumulation. It is put forward that some nonlinear characteristics of rubber under fatigue loading, including the Mullins effect, permanent deformation and cyclic stress softening, should be considered in the further study of rubber materials. Meanwhile, it is indicated that the fatigue damage accumulation method based on continuum damage mechanics might be more appropriate to solve fatigue damage and life prediction problems for complex rubber materials and structures under fatigue loading.

  12. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

    Directory of Open Access Journals (Sweden)

    Nuha Salim Mashaan

    2014-01-01

    Full Text Available Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test, dynamic creep (repeated load creep, and fatigue test (indirect tensile fatigue test at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa. Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

  13. Evaluation of fatigue life of CRM-reinforced SMA and its relationship to dynamic stiffness.

    Science.gov (United States)

    Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati; Koting, Suhana

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

  14. Statistical analysis of fatigue strain-life data for carbon and low-alloy steels

    International Nuclear Information System (INIS)

    The existing fatigue strain vs life (S-N) data, foreign and domestic, for carbon and low-alloy steels used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. A statistical model has been developed for estimating the effects of the various test conditions on fatigue life. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by applying design margins for size, geometry, and surface finish to crack initiation curves estimated from the model

  15. Laser Shock Peening of Aluminum Alloy 7050 for Fatigue Life Improvement

    Institute of Scientific and Technical Information of China (English)

    Qian; Ming; Lian; Ying; Zou; Shikun; Gong; Shuili

    2007-01-01

    The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction stress measurement shows that LSP results in prominent increase of surface compressive stress,quasi-symmetrically distributed in the laser peened region.The fatigue life of the alloy 7050 in rivet fastener hole structure is notably improved owing to LSP.The sequence of LSP and fastener hole preparation also influence the fatigue cycle life of the alloy.

  16. Relation between Shot Peening Process and Fatigue Life in the Case of Hardening Steels

    Institute of Scientific and Technical Information of China (English)

    SHIGEYOSHI HAGA; HARUSHIGE TSUBAKINO; YASUNORI HARADA

    2004-01-01

    Nowadays, in the auto industry, the need for improvement of fuel efficiency is getting increased more and more in terms of the global warming, as well as the need of light-weighting of gears, transmission parts. Hence, we've studied the relation between the shot peening working conditions and factors for improvement of gear's fatigue life, and also the relation between the factors for improvement and the fatigue life, applying shot peening to a gear of SNCM220. Also, we examined the relation between the fatigue life and arc height that is utilized as a substitute characteristic for shot peening working conditions, adding its observation here.

  17. A Simple Fatigue Life Prediction Algorithm Using the Modified NASGRO Equation

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2016-01-01

    Full Text Available A simple fatigue life prediction algorithm using the modified NASGRO equation is proposed in this paper. The NASGRO equation is modified by introducing the concept of intrinsic effective threshold stress intensity factor (SIF range ΔKeffth. One advantage of the proposed method is that the complex growth behavior analysis of small cracks can be avoided, and then the fatigue life can be calculated by directly integrating the crack growth model from the initial defect size to the critical crack size. The fatigue limit and the intrinsic effective threshold SIF range ΔKeffth are used to calculate the initial defect size or initial flaw size. The value of ΔKeffth is determined by extrapolating the crack propagation rate curves. Instead of using the fatigue limit determined by the fatigue strength at the specific fatigue life, the fatigue limit is selected based on the horizontal tendency of the S-N curve. The calculated fatigue lives are compared to the experimental data of two different alloys. The predicted S-N curves agree with the test data well. Besides, the prediction results are compared with that calculated using the FASTRAN code. Results indicate that the proposed life prediction algorithm is simple and efficient.

  18. Probabilistic Modelling of Fatigue Life of Composite Laminates Using Bayesian Inference

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der

    2014-01-01

    A probabilistic model for estimating the fatigue life of laminated composite plates subjected to constant-amplitude or variable-amplitude loading is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configurations...

  19. Fatigue and quality of life in breast cancer survivors: temporal courses and long-term pattern

    NARCIS (Netherlands)

    Schmidt, M.E.; Chang-Claude, J.; Vrieling, A.; Heinz, J.; Flesch-Janys, D.; Steindorf, K.

    2012-01-01

    INTRODUCTION: Fatigue is a frequent problem during and after cancer treatment. We investigated different courses of fatigue from pre-diagnosis, through therapy, to long-term survivorship and evaluated potential implications on long-term quality of life (QoL). METHODS: Breast cancer patients diagnose

  20. Fatigue Life of High Performance Grout for Wind Turbine Grouted Connection in Wet or Dry Environment

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Westhof, Luc; Yde, Elo;

    at varying levels of cyclic frequency and load. The fatigue tests were performed in two series: one with the specimens in air and one with the specimens submerged in water during the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when...

  1. Fatigue, mood and quality of life improve in MS patients after progressive resistance training

    DEFF Research Database (Denmark)

    Dalgas, U; Stenager, E; Petersen, T;

    2010-01-01

    Fatigue occurs in the majority of multiple sclerosis patients and therapeutic possibilities are few. Fatigue, mood and quality of life were studied in patients with multiple sclerosis following progressive resistance training leading to improvement of muscular strength and functional capacity. Fa...

  2. Fatigue life prediction in composites using progressive damage modelling under block and spectrum loading

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Philippidis, T.P.; Brøndsted, Povl

    2010-01-01

    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...

  3. Effects of LWR environments on fatigue life of carbon and low-alloy steels

    International Nuclear Information System (INIS)

    SME Boiler and Pressure Vessel Code provides construction of nuclear power plant components. Figure I-90 Appendix I to Section III of the Code specifies fatigue design curves for structural materials. While effects of environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A 106-Gr B carbon steel and A533-Gr B low-alloy steel in water

  4. Damage study of an austenitic stainless steel in high cycle multiaxial fatigue regime;Etude de l'endommagement d'un acier inoxydable austenitique par fatigue multiaxiale a grand nombre de cycles

    Energy Technology Data Exchange (ETDEWEB)

    Poncelet, M. [CEA Saclay, DEN, SRMA, 91 - Gif-sur-Yvette (France); Barbier, G.; Raka, B.; Vincent, L.; Desmorat, R. [LMT Cachan, ENS Cachan/CNRS/UPMC/PRES Univ. Sud Paris, 94 - Cachan (France); Barbier, G. [EDF R and D / LaMSID, 92 - Clamart (France)

    2010-02-15

    Biaxial fatigue tests are performed up to 1 000 000 cycles at room temperature. Cross specimens of 304L steel thinned in their centre to initiate crack, are loaded by a biaxial testing machine. The strain at the centre of the sample is measured during loading using a stroboscopic Digital Image Correlation (DIC) technique, and crack initiation on the whole gauge zone is early detected by a second DIC-based measurement. A special optical assembly is designed to allow for simultaneous measurements. Three types of loadings are performed: equi-biaxial with a loading ratio R = 0.1, equi-biaxial with loading ratio R = -1, pseudo uniaxial (cyclic loading at R 0.1 in one direction and constant loading in the other). First results are commented. (authors)

  5. Impact of Radiotherapy Treatment on Jordanian Cancer Patients’ Quality of Life and Fatigue

    Directory of Open Access Journals (Sweden)

    Kholoud Abu Obead

    2013-11-01

    Full Text Available Background: The distressing treatment of cancer whether chemotherapy or radiotherapy is associated with fatigue and has negative impact on patient quality of life (QOL. Objectives: The purposes of this study were to examine the impact of radiotherapy treatment on Jordanian cancer patients’ QOL and fatigue, and to explore the relationship between fatigue and QOL. Methods: One group quasi-experimental correlational design was used with 82 patients who had been diagnosed with cancer and required radiotherapy treatment. QOL was measured using the Functional Assessment of Cancer Therapy-General (FACT-G. Fatigue was measured using Piper Fatigue Scale (PFS. Data were collected over a period of three months, and analyzed using Pearson Product Moment Correlation, descriptive statistics and paired-sample t-test. Results: Significant differences were found between pre- and post- radiotherapy QOL mean total scores (t=19.3, df=79, P<0.05, as well as physical, emotional, sexual, and functional wellbeing dimensions. Statistically significant differences were found between pre- and post- radiotherapy fatigue mean total scores (t=-8.95, df=79, P<0.05, as well as on behavioral, affective, sensory, and cognitive dimensions of PFS. Quality of life total scores correlated significantly and negatively with total fatigue scores (P<0.01. Conclusions: Exposure of cancer patient to radiotherapy treatment increased their fatigue level and decreased their QOL.  Nurses should assess cancer patients before, during, and after their treatment to design proper interventions to reduce fatigue and enhance QOL.

  6. Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams

    Science.gov (United States)

    Murri, Gretchen B.; Schaff, Jeffery R.; Dobyns, Alan L.

    2002-01-01

    Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

  7. Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

    Science.gov (United States)

    urri, Gretchen B.; Schaff, Jeffery R.

    2006-01-01

    Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

  8. Fatigue life prediction of magnetorheological elastomers subjected to dynamic equi-biaxial cyclic loading

    International Nuclear Information System (INIS)

    Prediction of fatigue life is of great significance in ensuring that dynamically loaded rubber components exhibit safety and reliability in service. In this text, the dynamic equi-biaxial fatigue behaviour of magnetorheological elastomer (MREs) using a bubble inflation method is described. Wöhler (S–N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range of stress amplitudes (σa) between 0.75 MPa and 1.4 MPa. Changes in physical properties, including variation in stress–strain relations and complex modulus (E*) during the fatigue process were analysed. It was found that the complex modulus of MRE samples decreased throughout the entire fatigue test and failure took place at a limiting value of approximately 1.228MPa ± 4.38% for isotropic MREs and 1.295 ± 10.33% for anisotropic MREs. It was also determined that a dynamic stored energy criterion can be used as a plausible predictor in determining the fatigue life of MREs. - Highlights: • The first Wöhler curves for MREs subjected to equi-biaxial loading were presented. • Anisotropic MREs exhibited higher fatigue resistance than isotropic MREs. • There is a limiting value of complex modulus (E*) at which fatigue failure will occur. • The dynamic stored energy criterion can be used as a fatigue life predictor

  9. Extreme Environment Damage Index and Accumulation Model for CMC Laminate Fatigue Life Prediction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Materials Research & Design (MR&D) is proposing in the SBIR Phase II an effort to develop a tool for predicting the fatigue life of C/SiC composite...

  10. Prediction of the fatigue life distribution for aluminum through its mechanical characteristics

    Science.gov (United States)

    Ramadan, S. Z.; Zaid, Adnan I. O.

    2016-08-01

    A novel and reliable theoretical model based on the Birnbaum-Saunders (BISA) distribution is presented from which the fatigue life can be determined. Experimental verification of the model is in progress and will be published in due course.

  11. Modeling the effects of control systems of wind turbine fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, K.G.; Laino, D.J. [Univ. of Utah, Salt Lake City, UT (United States)

    1996-12-31

    In this study we look at the effect on fatigue life of two types of control systems. First, we investigate the Micon 65, an upwind, three bladed turbine with a simple yaw control system. Results indicate that increased fatigue damage to the blade root can be attributed to continuous operation at significant yaw error allowed by the control system. Next, we model a two-bladed teetered rotor turbine using three different control systems to adjust flap deflections. The first two limit peak power output, the third limits peak power and cyclic power output over the entire range of operation. Results for simulations conducted both with and without active control are compared to determine how active control affects fatigue life. Improvement in fatigue lifetimes were seen for all control schemes, with increasing fatigue lifetime corresponding to increased flap deflection activity. 13 refs., 6 figs., 2 tabs.

  12. What roles do team climate, roster control, and work life conflict play in shiftworkers' fatigue longitudinally?

    Science.gov (United States)

    Pisarski, Anne; Barbour, Jennifer P

    2014-05-01

    The study aimed to examine shiftworkers fatigue and the longitudinal relationships that impact on fatigue such as team climate, work life conflict, control of shifts and shift type in shift working nurses. We used a quantitative survey methodology and analysed data with a moderated hierarchical multiple regression. After matching across two time periods 18 months apart, the sample consisted of 166 nurses from one Australian hospital. Of these nurses, 61 worked two rotating day shifts (morning & afternoon/evening) and 105 were rotating shiftworkers who worked three shifts (morning afternoon/evening and nights). The findings suggest that control over shift scheduling can have significant effects on fatigue for both two-shift and three-shift workers. A significant negative relationship between positive team climate and fatigue was moderated by shift type. At both Time 1 and Time 2, work life conflict was the strongest predictor of concurrent fatigue, but over time it was not.

  13. Influence of Subgrade and Unbound Granular Layers Stiffness on Fatigue Life of Hot Mix Asphalts - HMA

    OpenAIRE

    Hugo A. Rondón-Quintana; Wilmar D. Fernández-Gómez; Jesús A. Hernández-Noguera

    2013-01-01

    The mainly factors studied to predict fatigue life of hot mix asphalt-HMA in flexible pavements are the loading effect, type of test, compaction methods, design parameters of HMA (e.g., particle size and size distribution curve, fine content, type of bitumen) and the variables associated with the environment (mainly moisture, temperature, aging). This study evaluated through a computer simulation, the influence of the granular layers and subgrade on the fatigue life of asphalt layers in flexi...

  14. The prediction technology study of fatigue life for key parts of a tracked vehicle's suspension system

    Institute of Scientific and Technical Information of China (English)

    WANG Hongyan; RUI Qiang; HE Xiaojun

    2007-01-01

    In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software-ADAMS. Node force and stress results of the torsion bar from last step simu- lation were acquired; taking into account the material charac- teristics and influential factors, fatigue life of the flexible body. of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.

  15. Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle

    OpenAIRE

    V.K.Aher; R. A. Gujar; Wagh, J. P.; P.M.Sonawane

    2012-01-01

    The Leaf spring is widely used in automobiles and one of the components of suspension system. It needs to have high fatigue life. As a general rule, the leaf spring is regarded as a safety component as failure could lead to severe accidents. The purpose of this paper is to predict the fatigue life of steel leaf spring along with analytical stress and deflection calculations. This present work describes static and fatigue analysis of a steel leaf spring of a light commercial vehicle (LCV). Th...

  16. Fatigue Life and Short Crack Behavior in Ti-6Al-4V Alloy; Interactions of Foreign Object Damage, Stress, and Temperature

    Science.gov (United States)

    Majidi, Behzad

    2008-04-01

    High-cycle fatigue (HCF) failures associated with foreign object damage (FOD) in turbine engines of military aircrafts have been of major concern for the aeronautic industry in recent years. The present work is focused on characterizing the effects of FOD on crack initiation and small crack growth of a Ti-6Al-4V alloy at ambient and also elevated temperatures. Results show that the preferred crack initiation site depends on applied stress and temperature as maximum fractions of cracks emanating from the simulated damage site, and naturally initiated cracks are observed at 25 °C under the maximum stress of 700 MPa and at 300 °C under the maximum stress of 300 MPa. The fatigue crack growth rate is influenced by increasing temperature, and the FCG rate at 300 °C is higher than that at room temperature under the same Δ K, whereas this effect for FOD-site initiated cracks is not so remarkable. This observation seems to be due to the effect of stress relaxation at 300 °C. Results also indicate that fatigue crack initiation life ( N i ) and fatigue life ( N f ) are expressed by three-parameter Weibull distribution function.

  17. Fatigue

    Science.gov (United States)

    Bennett RM. Fibromyalgia, chronic fatigue syndrome, and myofascial pain. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 274. Thames TA, Karrh ...

  18. Low-Cycle Fatigue Life Prediction in GTD-111 Superalloy at Elevated Temperatures

    International Nuclear Information System (INIS)

    The Ni-base super-heat-resistant alloy, GTD-111, is employed in gas turbines because of its high temperature strength and oxidation resistance. It is important to predict the fatigue life of this superalloy in order to improve the efficiency of gas turbines. In this study, low-cycle fatigue tests are performed as variables of total strain range and temperature. The relationship between the strain energy density and number of cycles to failure is examined in order to predict the low-cycle fatigue life of the GTD-111 superalloy. The fatigue life predicted by using the strain-energy methods is found to coincide with that obtained from the experimental data and from the Coffin-Manson method

  19. Low-Cycle Fatigue Life Prediction in GTD-111 Superalloy at Elevated Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ho Young; Kim, Jae Hoon [Chungnam National University, Daejeon (Korea, Republic of); Yoo, Keun Bong; Lee, Han Sang [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); You, Young Soo [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2011-07-15

    The Ni-base super-heat-resistant alloy, GTD-111, is employed in gas turbines because of its high temperature strength and oxidation resistance. It is important to predict the fatigue life of this superalloy in order to improve the efficiency of gas turbines. In this study, low-cycle fatigue tests are performed as variables of total strain range and temperature. The relationship between the strain energy density and number of cycles to failure is examined in order to predict the low-cycle fatigue life of the GTD-111 superalloy. The fatigue life predicted by using the strain-energy methods is found to coincide with that obtained from the experimental data and from the Coffin-Manson method.

  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. Empirical modeling of environment-enhanced fatigue crack propagation in structural alloys for component life prediction

    Science.gov (United States)

    Richey, Edward, III

    1995-01-01

    This research aims to develop the methods and understanding needed to incorporate time and loading variable dependent environmental effects on fatigue crack propagation (FCP) into computerized fatigue life prediction codes such as NASA FLAGRO (NASGRO). In particular, the effect of loading frequency on FCP rates in alpha + beta titanium alloys exposed to an aqueous chloride solution is investigated. The approach couples empirical modeling of environmental FCP with corrosion fatigue experiments. Three different computer models have been developed and incorporated in the DOS executable program. UVAFAS. A multiple power law model is available, and can fit a set of fatigue data to a multiple power law equation. A model has also been developed which implements the Wei and Landes linear superposition model, as well as an interpolative model which can be utilized to interpolate trends in fatigue behavior based on changes in loading characteristics (stress ratio, frequency, and hold times).

  2. Effect Of Solidification Speed On Fatigue Properties

    Science.gov (United States)

    Mccay, M. H.; Schmidt, D. D.; Hamilton, W. D.; Alter, W. S.; Parr, R. A.

    1989-01-01

    Fast solidification increases fatigue life, but failure distribution becomes less predictable. Report describes effects of rate of solidification on nickel-based super-alloy MAR-M246(Hf) used in turbine blades. Based on experiments in which specimens directionally solidified at 5 cm/h and 30 cm/h, then tested for high cycle fatigue. Specimens also inspected by energy-dispersive x-ray (EDX) analysis and optical and electron microscopy.

  3. Review of creep–fatigue endurance and life prediction of 316 stainless steels

    International Nuclear Information System (INIS)

    The effects of different factors on the creep–fatigue endurance of 316 stainless steel are reviewed in this paper. The factors include hold period, strain range, stress range at half-life and stress relaxation behavior. The strength and limitation of different creep–fatigue life prediction methods are also summarized from the available data. It is found that each method shows some agreement with prediction with a specific set of testing data. Standard deviations of different prediction methods are calculated to evaluate the prediction capacity of these methods. It is showed that ductility exhaustion model exhibits highest accuracy at two different temperatures. - Highlights: • Effects of different factors on the creep–fatigue endurance of 316 SS are reviewed. • Tensile hold period produces more damage than compressive hold period of 316 SS. • The 316 SS exhibits cyclic-hardening characteristics under creep–fatigue conditions. • Different creep–fatigue life prediction methods are summarized. • The creep–fatigue life prediction capacities are evaluated

  4. An Integrated Approach to Fatigue Life Prediction of Whole System for Offshore Platforms

    Institute of Scientific and Technical Information of China (English)

    方华灿; 段梦兰; 许发彦; 吴永宁; 樊晓东

    2001-01-01

    The failure of one or even more components usually does not lead to the collapse of the whole structure. Most of theanalysis of fatigue is centered on only a single component which the researchers are interested in or much attentionshould be paid to. However, the collapse of a structure is the result of failure of a series of components in a specific orderor path. This paper proposes an integrated approach to fatigue life prediction of whole structural system for offshoreplatforms, mainly describing the basic principles and prediction method. A method is presented for determining the fail-ure path of the whole structure system and calculating the fatigue life in the determined failure path. The correspondingfinal collapse criteria for the whole structure system are discussed. A simple method of equivalent fatigue stress range cal-culation and a mathematical model of structural component fatigue life estimation in consideration of sea wave and seaice loads are provided. As an application of the proposed approach, a fixed production platform Bohai No. 8 is chosenfor the predication of fatigue life of the whole structure system by means of the software OSFAC developed based on thepresent methods.

  5. Effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy

    Institute of Scientific and Technical Information of China (English)

    何晓; 岳俊; 沈保罗; 曹建玲; 邱绍宇; 邹红

    2003-01-01

    Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy by means of section-varied samples. Results reveal that the fatigue life of the materials with (116~280)×10-6 hydrogen is higher than that of natural hydrogen material provided that the fatigue load Δσ is over 550MPa. At higher Δσ, the content of hydrogen has small effects on fatigue life within (116-280)×10-6 hydrogen. For material containing 280×10-6 hydrogen, fatigue cracks tend to initiate at sample edges at higher load, in contrast, to initiate at sites of hydrides at lower load. The interstitial hydrogen atoms softening the persistent slip bands(PSB) and hydrides separating from the body become the cause of decrease in fatigue life. Hydrides resolved into the body is observed at lower Δσ for material with 280×10-6 hydrogen, which is the result of concentration of hydrogen atoms at crack tips and stress-induced re-precipitation of hydrides.

  6. Fatigue life improvements of the AISI 304 stainless steel ground surfaces by wire brushing

    Science.gov (United States)

    Ben Fredj, Nabil; Ben Nasr, Mohamed; Ben Rhouma, Amir; Sidhom, Habib; Braham, Chedly

    2004-10-01

    The surface and subsurface integrity of metallic ground components is usually characterized by an induced tensile residual stress, which has a detrimental effect on the fatigue life of these components. In particular, it tends to accelerate the initiation and growth of the fatigue cracks. In this investigation, to deliberately generate compressive residual stresses into the ground surfaces of the AISI 304 stainless steel (SS), wire brushing was applied. It was found that under the experimental conditions selected in this investigation, while the surface roughness was slightly improved by the brushing process, the surface residual stress shifted from a tensile stress (σ‖=+450 MPa) to a compressive stress (σ‖=-435 MPa). On the other hand, the work-hardened deformation layer was almost two times deeper after wire brushing. Concerning the fatigue life, an improvement of 26% in terms of endurance limit at 2×106 cycles was realized. Scanning electron microscope (SEM) observations of the fatigue fracture location and size were carried out to explain the fatigue life improvement. It was found that the enhancement of the fatigue strength could be correlated with the distribution and location of the fatigue fracture nucleation sites. Concerning the ground surfaces, it was seen that the fatigue cracks initiated at the bottom of the grinding grooves and were particularly long (150-200 µm). However, the fatigue cracks at the brushed surfaces were shorter (20-40 µm) and appeared to initiate sideways to the plowed material caused by the wire brushing. The results of the wire-brushed surface characterization have shown that significant advantages can be realized regarding surface integrity by the application of this low-cost process compared to shot peening.

  7. Quality of life, fatigue, depression and cognitive impairment in Lyme neuroborreliosis.

    Science.gov (United States)

    Dersch, Rick; Sarnes, Antonia A; Maul, Monika; Hottenrott, Tilman; Baumgartner, Annette; Rauer, Sebastian; Stich, Oliver

    2015-11-01

    The prognosis and impact of residual symptoms on quality of life in patients with Lyme neuroborreliosis (LNB) is subject to debate. The aim of this study was to assess quality of life, fatigue, depression, cognitive impairment and verbal learning in patients with definite LNB and healthy controls in a case-control study. We retrospectively identified all patients diagnosed with definite LNB between 2003 and 2014 in our tertiary care center. Healthy controls were recruited from the same area. Patients and healthy controls were assessed for quality of life [Short Form (36) with subscores for physical and mental components (PCS, MCS)], fatigue (fatigue severity scale), depression (Beck depression inventory), verbal memory and learning and cognitive impairment (mini-mental state examination). 53 patients with definite LNB could be identified, of which 30 partook in the follow-up assessment. Estimates for quality of life, fatigue, depression, verbal memory and cognitive impairment did not differ statistically significantly between 30 patients with LNB and 35 healthy controls. Patients with residual symptoms had lower scores for quality of life (PCS) compared to patients without residual symptoms. Our results do not support the hypothesis that a considerable proportion of patients with antibiotically treated LNB develop a 'post Lyme syndrome' consisting of debilitating fatigue or cognitive impairment or have severe limitations of quality of life. However, some patients experience residual symptoms of LNB.

  8. The effects of fibre architecture on fatigue life-time of composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Zangenberg Hansen, J.

    2013-09-15

    Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation methodologies in order to be assessed. Furthermore, numerical evaluation and predictions of the fatigue damage evolution are decisive in order to make future improvements. The present work is focused around two central themes: fibre architecture and fatigue failure. The fibre architecture is characterised using real material samples and numerical simulations. Experimental fatigue tests identify, quantify, and analyse the cause of failure. Different configurations of the fibre architecture are investigated in order to determine and understand the tension-tension fatigue failure mechanisms. A numerical study is used to examine the onset of fatigue failure. Topics treated include: experimental fatigue investigations, scanning electron microscopy, numerical simulations, advanced measurements techniques (micro computed tomography and thermovision), design of test specimens and preforms, and advanced materials characterisation. The results of the present work show that the fibre radii distribution has limited effect on the fibre architecture. This raises the question of which

  9. Comparing Fatigue Life Estimations of Composite Wind Turbine Blades using different Fatigue Analysis Tools

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro; Lennie, Matthew; Branner, Kim;

    2015-01-01

    suggested by the IEC 61400-1 standard were studied employing different load time intervals and by using two novel fatigue tools called ALBdeS and BECAS+F. The aeroelastic loads were defined thought aeroelastic simulations performed with both FAST and HAWC2 tools. The stress spectra at each layer were...

  10. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    WANG Qingyuan (王清远); N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials,loading,and environmental conditions.A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e.the pit nucleation and growth,pit-crack transition,short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size,corrosion pitting current,and material properties due to the scatter found in the experimental data.Monte Carlo simulations were performed to define the failure probability distribution.Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.

  11. FATIGUE LIFE PREDICTION OF COMMERCIALLY PURE TITANIUM AFTER NITROGEN ION IMPLANTATION

    Directory of Open Access Journals (Sweden)

    Nurdin Ali

    2013-06-01

    Full Text Available Prediction of fatigue life has become an interesting issue in biomaterial engineering and design for reliability and quality purposes, particularly for biometallic material with modified surfaces. Commercially pure titanium (Cp-Ti implanted with nitrogen ions is a potential metallic biomaterial of the future. The effect of nitrogen ion implantation on fatigue behavior of Cp-Ti was investigated by means of axial loading conditions. The as-received and nitrogen-ion implanted specimens with the energy of 100 keV and dose of 2 × 1017 ions cm-2, were used to determine the fatigue properties and to predict the life cycle of the specimens. The effect of nitrogen ion implantation indicated revealed improved the tensile strength due to the formation of nitride phases, TiN and Ti2N. The fatigue strength of Cp-Ti and Nii-Ti was 250 and 260 MPa, respectively. The analytical results show good agreement with experimental results.

  12. A comparison of some methods to estimate the fatigue life of plain dents

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Ricardo R.; Noronha Junior, Dauro B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2009-12-19

    This paper describes a method under development at PETROBRAS R and D Center (CENPES) to estimate the fatigue life of plain dents. This method uses the API Publication 1156 as a base to estimate the fatigue life of dome shaped plain dents and the Pipeline Defect Assessment Manual (PDAM) approach to take into account the uncertainty inherent in the fatigue phenomenon. CENPES method, an empirical and a semi-empirical method available in the literature were employed to estimate the fatigue lives of 10 plain dents specimens of Year 1 of an ongoing test program carried out by BMT Fleet Technology Limited, with the support of the Pipeline Research Council International (PRCI). The results obtained with the different methods are presented and compared. Furthermore some details are given on the numerical methodology proposed by PETROBRAS that have been used to describe the behavior of plain dents. (author)

  13. Design characteristics that improve the fatigue life of threaded pipe connections

    OpenAIRE

    Van Wittenberghe, Jeroen; DE BAETS, Patrick; De Waele, Wim; Galle, Timothy; Bui, Tien Thanh; De Roeck, Guido

    2011-01-01

    Threaded pipe connections are commonly used to connect risers, tendons, drill pipes and well casing strings. In these applications fatigue resistance plays an important role. A large variety of patented design features exist, all claiming to improve the connection’s fatigue life. However, patent documents only contain claims and numerical or experimental data about these connection’s performance is generally not published. This makes it hard to make a quantitative comparison between different...

  14. 基于ANSYS-FATIGUE的曲轴疲劳寿命计算%Calculation of Crankshaft Fatigue Life Based on ANSYS - FATIGUE

    Institute of Scientific and Technical Information of China (English)

    叶晓琰; 张军辉; 蒋小平; 丁亚娜

    2011-01-01

    基于有限元通用软件ANSYS的疲劳寿命分析方法,运用ANSYS的FATIGUE模块,将有限元方法和疲劳寿命分析理论相结合,对往复泵曲轴进行三维参数化建模,并编制APDL命令流,建立疲劳分析文件对往复泵曲轴进行累积损伤系数计算,计算曲轴的疲劳寿命为26年.并对机组进行扩容10%、15%后,计算出曲轴的疲劳寿命分别为年18年和14.7年.%Adopting the fatigue life analysis method based on ANSYS, which combines the finite element method with the fatigue life analyzing theory by using FATIGUE module of ANSYS. A three dimensional parameter model for crank-shaft has been established. The APDL command stream being compiled, and the documents for fatigue life analysis being built, and then the fatigue life of crank-shaft has been analyzed. Results show that the fatigue life of crank - shaft is 26 years. After machine's plunger force was expanded 10% and 15%, the fatigue life of the crankshaft is 18 and 14.7years.

  15. FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guoqing; PU Gengqiang; WANG Chengtao

    2006-01-01

    S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper (SWT)-Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis (FEA) of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life.

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

    NARCIS (Netherlands)

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

    2013-01-01

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

  17. Probabilistic Fatigue Life Prediction of Turbine Disc Considering Model Parameter Uncertainty

    Science.gov (United States)

    He, Liping; Yu, Le; Zhu, Shun-Peng; Ding, Liangliang; Huang, Hong-Zhong

    2016-06-01

    Aiming to improve the predictive ability of Walker model for fatigue life prediction and taking the turbine disc alloy GH4133 as the application example, this paper investigates a new approach for probabilistic fatigue life prediction when considering parameter uncertainty inherent in the life prediction model. Firstly, experimental data are used to update the model parameters using Bayes' theorem, so as to obtain the posterior probability distribution functions of two parameters of the Walker model, as well to achieve the probabilistic life prediction model for turbine disc. During the updating process, Markov Chain Monte Carlo (MCMC) technique is used to generate samples of the given distribution and estimating the parameters distinctly. After that, the turbine disc life is predicted using the probabilistic Walker model based on Monte Carlo simulation technique. The experimental results indicate that: (1) after using the small sample test data obtained from turbine disc, parameter uncertainty of the Walker model can be quantified and the corresponding probabilistic model for fatigue life prediction can be established using Bayes' theorem; (2) there exists obvious dispersion of life data for turbine disc when predicting fatigue life in practical engineering application.

  18. 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 .

  19. A Fatigue Life Prediction Model of Welded Joints under Combined Cyclic Loading

    Science.gov (United States)

    Goes, Keurrie C.; Camarao, Arnaldo F.; Pereira, Marcos Venicius S.; Ferreira Batalha, Gilmar

    2011-01-01

    A practical and robust methodology is developed to evaluate the fatigue life in seam welded joints when subjected to combined cyclic loading. The fatigue analysis was conducted in virtual environment. The FE stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. The measurement or modelling of the residual stresses resulting from the welded process is not part of this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly through fatigue curves corrections in the samples investigated. A tube-plate specimen was submitted to combined cyclic loading (bending and torsion) with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.

  20. 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.

  1. Fatigue life prediction of fiber reinforced concrete under flexural load

    DEFF Research Database (Denmark)

    Zhang, Jun; Stang, Henrik; Li, Victor

    1999-01-01

    This paper presents a semi-analytical method to predict fatigue behavior in flexure of fiber reinforced concrete (FRC) based on the equilibrium of force in the critical cracked section. The model relies on the cyclic bridging law, the so-called stress-crack width relationship under cyclic tensile...

  2. Evaluation of Fatigue Life Reliability of Steering Knuckle Using Pearson Parametric Distribution Model

    Directory of Open Access Journals (Sweden)

    E. A. Azrulhisham

    2010-01-01

    Full Text Available Steering module is a part of automotive suspension system which provides a means for an accurate vehicle placement and stability control. Components such as steering knuckle are subjected to fatigue failures due to cyclic loads arising from various driving conditions. This paper intends to give a description of a method used in the fatigue life reliability evaluation of the knuckle used in a passenger car steering system. An accurate representation of Belgian pave service loads in terms of response-time history signal was obtained from accredited test track using road load data acquisition. The acquired service load data was replicated on durability test rig and the SN method was used to estimate the fatigue life. A Pearson system was developed to evaluate the predicted fatigue life reliability by considering the variations in material properties. Considering random loads experiences by the steering knuckle, it is found that shortest life appears to be in the vertical load direction with the lowest fatigue life reliability between 14000–16000 cycles. Taking into account the inconsistency of the material properties, the proposed method is capable of providing the probability of failure of mass-produced parts.

  3. Effect of grinding conditions on the fatigue life of titanium 5Al-2.5Sn alloy

    Science.gov (United States)

    Rangaswamy, P.; Terutung, H.; Jeelani, S.

    1991-01-01

    An investigation into the effect of grinding conditions on the fatigue life of titanium 5Al-2.5Sn is presented. Damage to surface integrity and changes in the residual stresses distribution are studied to assess changes in fatigue life. A surface grinding machine, operating at speeds ranging from 2000 to 6000 fpm and using SiC wheels of grit sizes 60 and 120, was used to grind flat subsize specimens of 0.1-in. thickness. After grinding, the specimens were fatigued at a chosen stress and compared with the unadulterated material. A standard profilometer, a microhardness tester, and a scanning electron microscope were utilized to examine surface characteristics and measure roughness and hardness. Increased grinding speed in both wet and dry applications tended to decrease the fatigue life of the specimens. Fatigue life increased markedly at 2000 fpm under wet conditions, but then decreased at higher speeds. Grit size had no effect on the fatigue life.

  4. Prevalence of fatigue in patients with multiple sclerosis and its effect on the quality of life

    Directory of Open Access Journals (Sweden)

    Karthik Nagaraj

    2013-01-01

    Full Text Available Objective: This prospective study was carried out to observe the prevalence of fatigue in patients with multiple sclerosis (MS and its effect on quality-of-life (QoL. Study Design and Setting: Prospective observational study in a University Tertiary Research Hospital in India. Patients and Methods: A total of 31 patients (25 females with definite MS according to McDonald′s criteria presented in out-patient/admitted in the Department of Neurology (between February 2010 and December 2011 were included in the study. Disease severity was evaluated using the Kurtzke′s expanded disability status scale (EDSS. Fatigue was assessed using Krupp′s fatigue severity scale (FSS. QoL was assessed by the World Health Organization QoL-BREF questionnaire. Results: The mean age of patients was 30.1 ± 9.1 years. The mean age at first symptom was 25.23 ± 6.4 years. The mean number of relapses was 4.7 ± 3.6 in the patients. The mean duration of illness was 4.9 ± 4.4 years. The mean EDSS score was 3.5 ± 2.2. Mean fatigue score was 38.7 ± 18.5 (cut-off value 36 in FSS. The prevalence of fatigue in patients with MS was 58.1% (18/31. MS patients with fatigue were significantly more impaired (P < 0.05 on all QoL domains (i.e., physical, psychosocial, social, and environment than MS patients without fatigue. Conclusion: Prevalence of fatigue was found to be high in the MS patients in the study. All four domains of QoL were significantly more impaired in the group with fatigue than in those without fatigue.

  5. Fatigue and Quality of Life of Women Undergoing Chemotherapy or Radiotherapy for Breast Cancer

    Institute of Scientific and Technical Information of China (English)

    Winnie K.W.So; Gene Marsh; W.M.Ling; F.E Leung; Joe C.K.Lo; Maggie Yeung; George K.H.Li

    2009-01-01

    OBJECTIVE To examine fatigue and quality of life (QOL) in breast cancer patients undergoing chemotherapy or radiotherapy.METHODS A self-report survey derived from the Chinese version of Brief Fatigue Inventory, the Functional Assessment of Chronic Illness Therapy for Breast Cancer, and the Medical Outcomes Study Social Support Survey. Descriptive statistics was used to examine the intensity of fatigue and the prevalence of severe fatigue. Multivariate analysis of variance was used to determine factors that affect the five domains of QOL among the participants.RESULTS The majority of the participants (n = 261) perceived a mild level of fatigue, but 35.6% of them suffered severe fatigue. Fatigue had a significantly negative association with all domains of QOL except social/family wellbeing. The participants who were receiving chemotherapy, undergoing curative treatment and having inadequate social support were more likely to have poorer QOL in all five domains (after adjustment for age).CONCLUSION Although the majority of the participants experienced a mild level of fatigue, there was a substantial group of breast cancer patients who perceived their fatigue as severe. The findings of this study showed that fatigue had a detrimental effect on the various aspects of the participants'QOL. Demographic and clinical characteristics of breast cancer patients who were at risk of getting poorer QOL were identified. The results of the study demonstrate that we should enhance healthcare professionals' awareness of the importance of symptom assessment, and provide them with information for planning effective symptom-management strategies among this study population.

  6. Major Effects of Nonmetallic Inclusions on the Fatigue Life of Disk Superalloy Demonstrated

    Science.gov (United States)

    Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Bonacuse, Peter J.; Barrie, Robert L.

    2002-01-01

    The fatigue properties of modern powder metallurgy disk alloys can vary because of the different steps of materials and component processing and machining. Among these variables, the effects of nonmetallic inclusions introduced during the powder atomization and handling processes have been shown to significantly degrade low-cycle fatigue life. The levels of inclusion contamination have, therefore, been reduced to less than 1 part per million in state-of-the-art nickel disk powder-processing facilities. Yet the large quantities of compressor and turbine disks weighing from 100 to over 1000 lb have enough total volume and surface area for these rare inclusions to still be present and limit fatigue life. The objective of this study was to investigate the effects on fatigue life of these inclusions, as part of the Crack Resistant Disk Materials task within the Ultra Safe Propulsion Project. Inclusions were carefully introduced at elevated levels in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were then performed on extracted test specimens at 650 C. Analyses were performed to compare the low-cycle fatigue lives and failure initiation sites as functions of inclusion content and fatigue conditions. Powder of the nickel-base superalloy U720 was atomized in argon at Special Metals Corporation, Inc., using production-scale high-cleanliness powder-processing facilities and handling practices. The powder was then passed through a 270-mesh screen. One portion of this powder was set aside for subsequent consolidation without introduced inclusions. Two other portions of this powder were seeded with alumina inclusions. Small, polycrystalline soft (Type 2) inclusions of about 50 mm diameter were carefully prepared and blended into one powder lot, and larger hard (Type 1) inclusions of about 150 mm mean diameter were introduced into the other seeded portion of powder. All three portions of powder were

  7. Practical methodology to evaluate the fatigue life of seam welded joints

    Directory of Open Access Journals (Sweden)

    K.C.Goes

    2011-11-01

    Full Text Available Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life method. A tube-to-plate specimen was submitted to a combined cyclic loading (bending and torsion with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.Findings: The finite element model was validated due to laboratory results. The analytical stress result presented upper value due to the approach used that considered the fillet weld supported all work. The model presented a good representation of failure and load correlation.Research limitations/implications: The measurement or modelling of the residual stresses resulting from the welding process was not included in this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly with regard to the corrections performed in the fatigue curves obtained from the investigated samples.Practical implications: Integrating fatigue analysis and finite elements, it is possible to analyse several welded joint configurations in the design phase, providing development time and cost reduction, increasing the project reliability.Originality/value: This methodology will permit, in further studies, the modelling of both stresses, in-service and residual stresses, acting together, which seem

  8. Accelerated ultrasonic fatigue testing applications and research trends

    Energy Technology Data Exchange (ETDEWEB)

    Cho, In Sik; Shin, Choongshig; Kim, Jong Yup; Jeon, Yongho [Ajou Univ., Gyeonggi (Somalia)

    2012-06-15

    Very high cycle fatigue (VHCF) behavior of aerospace components has emerged much attention due to their long service life. In this study, a piezoelectric ultrasonic fatigue testing (UFT) system has been developed by Mbrosiatec Co., Ltd. to study the high cycle fatigue (HCF) strength of Ti 6Al 4V alloy. Hourglass shaped specimens have been investigated in the range from 10'6' to 10'9' cycles at room temperature under completely reversed R=-1 loading conditions, Scanning electron microscopy (SEM) analysis revealed that failures occurred in the entire range up to the gigacycle regime, and the fractures have been found to be initiated from the surface, unlike in steels. However, it was found from the SEM microgprahs that microcracks transformed into intergranular fractures. Thus, it can be concluded from according to the results that this test method can be applicable to commercialized automotive and railroad parts that require high cycle fatigue strength.

  9. Effects of sodium tartrate anodizing on fatigue life of TA15 titanium alloy

    Directory of Open Access Journals (Sweden)

    Fu Chunjuan

    2015-08-01

    Full Text Available Anodizing is always used as an effective surface modification method to improve the corrosion resistance and wear resistance of titanium alloy. The sodium tartrate anodizing is a new kind of environmental anodizing method. In this work, the effects of sodium tartrate anodizing on mechanical property were studied. The oxide film was performed on the TA15 titanium alloy using sodium tartrate as the film former. The effects of this anodizing and the traditional acid anodizing on the fatigue life of TA15 alloy were compared. The results show that the sodium tartrate anodizing just caused a slight increase of hydrogen content in the alloy, and had a slight effect on the fatigue life. While, the traditional acid anodizing caused a significant increase of hydrogen content in the substrate and reduced the fatigue life of the alloy significantly.

  10. Fatigue assessment and its impact in the quality of life of patients with ankylosing spondylitis.

    Science.gov (United States)

    Schneeberger, Emilce Edith; Marengo, María Florencia; Dal Pra, Fernando; Maldonado Cocco, José Antonio; Citera, Gustavo

    2015-03-01

    The most frequently reported symptoms by patients with ankylosing spondylitis (AS) are pain, stiffness, and fatigue. Previous studies have estimated a 63% prevalence of fatigue in AS, with a low correlation of fatigue with pain and functional capacity. The objective of this study is to assess fatigue prevalence in AS patients and establish the main associated factors. A case-control study including AS patients according to New York modified criteria was carried out. The control group included individuals of the general population without rheumatic conditions, matched by gender, age, and socioeconomic level. Disease-related variables were recorded. Functional capacity, disease activity, and quality of life were assessed using Bath Ankylosing Spondylitis Funcional Index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and ankylosing spondylitis quality of life (ASQoL). CES-D questionnaire was used to evaluate depression and fatigue severity scale (FSS) to evaluate fatigue. Sixty-four consecutive AS patients and 95 controls were included. Patients' median age was 44 years (interquartile range (IQR), 33.25-53), 89.1% were male, and had a median disease duration of 17 years (IQR, 10.3-25). Fatigue prevalence in AS was 73.4% compared to 30.5% in the control group (p < 0.001; OR, 2.08 (95% CI, 1.53-2.83)). Furthermore, fatigue in AS correlated with ASQoL (r = 0.65), BASFI (r = 0.52), BASDAI (r = 0.52), and depression (r = 0.51), whereas no correlation with age or disease duration was found. In the linear regression analysis using fatigue as the dependent variable, depression was the only associated variable (p = 0.01). No association with age, gender, disease duration, BASDAI, BASFI, or presence of comorbidities was found. Finally, BASDAI fatigue question correlated with the FSS (r = 0.55). Fatigue was significantly more prevalent in AS than in healthy controls. The main determinant factor of fatigue was the presence of

  11. The effects of fibre architecture on fatigue life-time of composite materials

    DEFF Research Database (Denmark)

    Hansen, Jens Zangenberg; Østergaard, Rasmus

    Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre...... decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation...... methodologies in order to be assessed. Furthermore, numerical evaluation and predictions of the fatigue damage evolution are decisive in order to make future improvements. The present work is focused around two central themes: fibre architecture and fatigue failure. The fibre architecture is characterised using...

  12. Influences of size and position of defects on the fatigue life of electron beam welded-aluminum alloy joints

    Institute of Scientific and Technical Information of China (English)

    LU Li; ZHAO Haiyan; CAI Zhipeng; CUI Xiaofang

    2007-01-01

    Defects such as pores influence the fatigue life of electron beam-welded aluminum alloy joints. In this paper,the influences of pore size and position on the fatigue life of aluminum overlap joint are studied. A finite element model (FEM), combined with experimental data, is established to evaluate the fatigue life of overlap joints. By employing this FE model, the effects of pore size and position on fatigue lives of overlap joints are investigated and discussed. From the present study, when pore position is closer to the weld bead tip or the faying surface, the fatigue life decreases. Also, there is a critical size for the pore; when the pore size is larger than the critical value, the fatigue strength decreases sharply.

  13. Structural integrity and fatigue crack propagation life assessment of welded and weld-repaired structures

    Science.gov (United States)

    Alam, Mohammad Shah

    2005-11-01

    Structural integrity is the science and technology of the margin between safety and disaster. Proper evaluation of the structural integrity and fatigue life of any structure (aircraft, ship, railways, bridges, gas and oil transmission pipelines, etc.) is important to ensure the public safety, environmental protection, and economical consideration. Catastrophic failure of any structure can be avoided if structural integrity is assessed and necessary precaution is taken appropriately. Structural integrity includes tasks in many areas, such as structural analysis, failure analysis, nondestructive testing, corrosion, fatigue and creep analysis, metallurgy and materials, fracture mechanics, fatigue life assessment, welding metallurgy, development of repairing technologies, structural monitoring and instrumentation etc. In this research fatigue life assessment of welded and weld-repaired joints is studied both in numerically and experimentally. A new approach for the simulation of fatigue crack growth in two elastic materials has been developed and specifically, the concept has been applied to butt-welded joint in a straight plate and in tubular joints. In the proposed method, the formation of new surface is represented by an interface element based on the interface potential energy. This method overcomes the limitation of crack growth at an artificial rate of one element length per cycle. In this method the crack propagates only when the applied load reaches the critical bonding strength. The predicted results compares well with experimental results. The Gas Metal Arc welding processes has been simulated to predict post-weld distortion, residual stresses and development of restraining forces in a butt-welded joint. The effect of welding defects and bi-axial interaction of a circular porosity and a solidification crack on fatigue crack propagation life of butt-welded joints has also been investigated. After a weld has been repaired, the specimen was tested in a universal

  14. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, W., E-mail: wyman.zhuang@dsto.defence.gov.au [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Liu, Q.; Djugum, R.; Sharp, P.K. [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Paradowska, A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2232 (Australia)

    2014-11-30

    Highlights: • Deep surface rolling as a post-repair enhancement technology was applied to the laser cladded 7075-T651 aluminium alloy specimens that simulated corrosion damage blend-out repair. • The residual stresses induced by the deep surface rolling process were measured. • The deep surface rolling process can introduce deep and high magnitude compressive residual stresses beyond the laser clad and substrate interface. • Spectrum fatigue test showed the fatigue life was significantly increased by deep surface rolling. - Abstract: Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface.

  15. Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle

    Directory of Open Access Journals (Sweden)

    V.K.Aher

    2012-06-01

    Full Text Available The Leaf spring is widely used in automobiles and one of the components of suspension system. It needs to have high fatigue life. As a general rule, the leaf spring is regarded as a safety component as failure could lead to severe accidents. The purpose of this paper is to predict the fatigue life of steel leaf spring along with analytical stress and deflection calculations. This present work describes static and fatigue analysis of a steel leaf spring of a light commercial vehicle (LCV. The dimensions of the leaf spring of a LCV are taken and are verified by design calculations. The non-linear static analysis of 2D model of the leaf spring is performed using NASTRAN solver and compared with analytical results. The preprocessing of the model is done by using HYPERMESH software. The stiffness of the leaf spring is studied by plotting load versus deflection curve for various load applications. The simulation results are compared with analytical results. The fatigue life of the leaf spring is predicted using MSC Fatigue software.

  16. Perkiraan Fatigue Life pada Bracket Kapal Tanker Berdasarkan Common Structural Rules

    Directory of Open Access Journals (Sweden)

    Dita septiana

    2012-09-01

    Full Text Available Umur kelelahan (fatigue life dari struktur kapal dianalisis dengan menggunakan standar pada Common Structural Rules for Double Hull Oil Tanker. Kapal tanker single hull direncanakan akan dikonversi menjadi FPSO sehingga perlu diketahui sisa fatigue life konstruksinya. Dalam penelitian ini, fokus analisis dilakukan pada konstruksi bracket karena bracket sebagai salah satu penopang yang esensial pada kapal ini. Oleh karena itu, perlu diketahui letak bracket dengan tegangan paling besar dan besar fatigue lifenya. Kapal tersebut dimodelkan menggunakan softwareMSC Pastran sebagai pre-processor dan MSC Nastran sebagai processor. Bagian kapal yang dimodelkan adalah 3 ruang muat pada midship. Ruang muat pada bagian tengah dari ketiga ruang muat tersebut adalah ruang muat yang paling besar. Fatigue life yang dianalisa merupakan pengaruh dari beban lingkungan (beban gelombang air laut dan beban internal (beban tangki. Kondisi pembebanan yang dilakukan ada 6 macam load cases sesuai dengan ketentuan CSR. Tegangan pada bracket yang didapat dari pemodelan diambil tegangan yang paling besar untuk dianalisa fatigue lifenya. Hasil perhitungan menunjukkan bahwa bracket dengan tegangan paling besar terjadi pada web frame 7 pada ruang muat tengah dan pada kondisi pembebanan A2 didapat umur kapal yang paling rendah yaitu sebesar 26 tahun.

  17. A computational approach for thermomechanical fatigue life prediction of dissimilarly welded superheater tubes

    Energy Technology Data Exchange (ETDEWEB)

    Krishnasamy, Ram-Kumar; Seifert, Thomas; Siegele, Dieter [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

    2010-07-01

    In this paper a computational approach for fatigue life prediction of dissimilarly welded superheater tubes is presented and applied to a dissimilar weld between tubes made of the nickel base alloy Alloy617 tube and the 12% chromium steel VM12. The approach comprises the calculation of the residual stresses in the welded tubes with a multi-pass dissimilar welding simulation, the relaxation of the residual stresses in a post weld heat treatment (PWHT) simulation and the fatigue life prediction using the remaining residual stresses as initial condition. A cyclic fiscoplasticity model is used to calculate the transient stresses and strains under thermocyclic service loadings. The fatigue life is predicted with a damage parameter which is based on fracture mechanics. The adjustable parameters of the model are determined based on LCF and TMF experiments. The simulations show, that the residual stresses that remain after PWHT further relax in the first loading cycles. The predicted fatigue lives depend on the residual stresses and, thus, on the choice of the loading cycle in which the damage parameter is evaluated. It the first loading cycle, where residual stresses are still present, is considered, lower fatigue lives are predicted compared to predictions considering loading cycles with relaxed residual stresses. (orig.)

  18. Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 °C

    Science.gov (United States)

    Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L., III; Busby, Jeremy T.; Mo, Kun; Stubbins, James F.

    2013-01-01

    Creep-fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep-fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep-fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep-fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep-fatigue life. The linear damage summation could predict the creep-fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep-fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep-fatigue life prediction results for both materials.

  19. Experimental and modeling results of creep–fatigue life of Inconel 617 and Haynes 230 at 850 °C

    International Nuclear Information System (INIS)

    Creep–fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep–fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep–fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep–fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep–fatigue life. The linear damage summation could predict the creep–fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep–fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep–fatigue life prediction results for both materials.

  20. Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

    International Nuclear Information System (INIS)

    Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.

  1. Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang [ORNL; Sokolov, Mikhail A [ORNL; Sham, Sam [ORNL; ERDMAN III, DONALD L [ORNL; Busby, Jeremy T [ORNL; Mo, Kun [ORNL; Stubbins, James [ORNL

    2013-01-01

    Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.

  2. Deformation behaviour and fatigue life of the alloy PE 16 under creep stress

    International Nuclear Information System (INIS)

    The service life of components subject to combined creep and fatigue stress in general is shorter than that of components affected only by one or the other. In the presence of both types of stress, their interactive effects lead to creep fatigue, which has to be taken into account in assessing the service life of turbine blades or turbine disks in a power plant or aircraft. The investigations reported in the paper have shown that the mechanisms of interaction between dislocations and precipitations have an effect on the stress curve in case of low-cycle fatigue stress. Introducing a holding time in case of LCF stress induces an additional solidification and shortens the service life of the material. This additional solidification is caused by a rearrangement of the distribution of dislocations. The reduction of service life observed at the smallest strain amplitude is mainly due to grain boundary damage. At larger strain amplitudes, fatigue damage seems to also contribute to the shortening of the material's service life. (orig./RHM)

  3. Effect of pre-deformation on the fatigue crack initiation life of X60 pipeline steel

    International Nuclear Information System (INIS)

    It is impossible to keep petroleum and natural gas transmission pipelines free from defects in the manufacturing, installation and servicing processes. The damage might endanger the safety of pipelines and even shorten their service life; gas or petroleum release due to defects may jeopardise the surrounding ecological environments with associated economic and life costs. Pre-tensile deformation of X60 steel is employed to experimentally simulate the influence of dents on the fatigue crack initiation life. The investigation indicates that the fatigue crack initiation life of pre-deformed X60 pipeline steel can be assessed by a previously proposed energetic approach. The threshold for crack initiation increases with the pre-deformation due to a strain hardening effect, while the fatigue resistant factor exhibits a maximum with pre-deformation owing to its special dependence on fracture strain and fracture strength. The result is expected to be beneficial to the understanding of the effect of damage on the safety of pipelines and fatigue life prediction

  4. A Study on the Effects of Ball Defects on the Fatigue Life in Hybrid Bearings

    Science.gov (United States)

    Tang, Ching-Yao; Foerster, Chad E.; O'Brien, Michael J.; Hardy, Brian S.; Goyal, Vinay K.; Nelson, Benjamin A.; Robinson, Ernest Y.; Ward, Peter C.; Hilton, Michael R.

    2014-01-01

    Hybrid ball bearings using silicon nitride ceramic balls with steel rings are increasingly being used in space mechanism applications due to their high wear resistance and long rolling contact fatigue life. However, qualitative and quantitative reports of the effects of ball defects that cause early fatigue failure are rare. We report on our approach to study these effects. Our strategy includes characterization of defects encountered in use, generation of similar defects in a laboratory setting, execution of full-scale bearing tests to obtain lifetimes, post-test characterization, and related finite-element modeling to understand the stress concentration of these defects. We have confirmed that at least one type of defect of appropriate size can significantly reduce fatigue life. Our method can be used to evaluate other defects as they occur or are encountered.

  5. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    王清远; N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials axe known to have a considerablescatter due to the random nature of materials, loading, and environmental conditions. A probabilisticapproach for predicting the pitting corrosion fatigue life has been investigated which captures the effectof the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigueprocess (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pittingcurrent, and material properties due to the scatter found in the experimental data. Monte Carlo simu-lations were performed to define the failure probability distribution. Predicted cumulative distributionfunctions of fatigue life agreed reasonably well with the existing experimental data.

  6. Bi-variable damage model for fatigue life prediction of metal components

    Institute of Scientific and Technical Information of China (English)

    Miao Zhang; Qing-Chun Meng; Xing Zhang; Wei-Ping Hu

    2011-01-01

    Based on the theory of continuum damage mechanics, a bi-variable damage mechanics model is developed, which, according to thermodynamics, is accessible to derivation of damage driving force, damage evolution equation and damage evolution criteria. Furthermore, damage evolution equations of time rate are established by the generalized Drucker's postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations, and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise, for notched specimens under the repeated loading with constant strain amplitude, the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus, the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1, 2 and 3.

  7. The fatigue life of a cobalt-chromium alloy after laser welding.

    Science.gov (United States)

    Al-Bayaa, Nabil Jalal Ahmad; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

    2011-03-01

    The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p < 0.001). Consequently, the technique may not be appropriate for repairing cobalt chromium clasps on removable partial dentures. Scanning electron microscopy indicated the presence of cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld. PMID:21528682

  8. An analytical method on evaluation of creep-fatigue life with long-time strain hold

    International Nuclear Information System (INIS)

    Evaluation of creep-fatigue life with long-time strain hold is a very important problem for structural design of FBR. But, these creep-fatigue tests are very difficult because of test techniques and costs. Therefore, the life prediction for long-time must be based on analytical approach by which the extrapolation to the range of longer hold time effect can be evaluated and justified. In this paper, an analytical method is proposed, which is based on generalized relaxation analysis, creep damage analysis, total damage evaluation per cycle and the diagram of creep-fatigue interaction effect. By this method, it is expected that the prediction is simplified and the evaluation is conservative. (author)

  9. Fatigue, fracture, and life prediction criteria for composite materials in magnets

    International Nuclear Information System (INIS)

    An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77 degree K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior

  10. Thermomechanical fatigue – Damage mechanisms and mechanism-based life prediction methods

    Indian Academy of Sciences (India)

    H-J Christ; A Jung; H J Maier; R Teteruk

    2003-02-01

    An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy IMI 834 and dispersoidstrengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinforced conditions was used to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown that the cyclic -integral ($\\Delta J_{\\text{eff}}$ concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep–fatigue damage parameter $\\Delta_{C\\ F}$ introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law. Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account.

  11. Fatigue Life of Haynes 188 Superalloy in Direct Connect Combustor Durability Rig

    Science.gov (United States)

    Gabb, TIm; Gayda, John; Webster, Henry; Ribeiro, Greg

    2007-01-01

    The Direct Connect Combustor Durability Rig (DCR) will provide NASA a flexible and efficient test bed to demonstrate the durability of actively cooled scramjet engine structure, static and dynamic sealing technologies, and thermal management techniques. The DCR shall be hydrogen fueled and cooled, and test hydrogen coolded structural panels at Mach 5 and 7. Actively cooled Haynes 188 superalloy DCR structural panels exposed to the combustion environment shall have electrodischarge machined (EDM) internal cooling holes with flowing liquid hydrogen. Hydrogen combustion could therefore produce severe thermal conditions that could challenge low cycle fatigue durability of this material. The objective of this study was to assess low cycle fatigue capability of Haynes 188 for DCR application. Tests were performed at 25 and 650 C, in hydrogen and helium environments, using specimens with low stress ground (LSG) and electro-discharge machined (EDM) surface finish. Initial fatigue tests in helium and hydrogen indicate the low cycle fatigue life capability of Haynes 188 in hydrogen appears quite satisfactory for the DCR application. Fatigue capability did not decrease with increasing test temperature. Fatigue capability also did not decrease with EDM surface finish. Failure evaluations indicate retention of ductility in all conditions. Additional tests are planned to reconfirm these positive trends.

  12. Compassion Fatigue, Compassion Satisfaction, and Burnout: Factors Impacting a Professional's Quality of Life

    Science.gov (United States)

    Sprang, Ginny; Whitt-Woosley, Adrienne; Clark, James J.

    2007-01-01

    This study examined the relationship between three variables, compassion fatigue (CF), compassion satisfaction (CS), and burnout, and provider and setting characteristics in a sample of 1,121 mental health providers in a rural southern state. Respondents completed the Professional Quality of Life Scale as part of a larger survey of provider…

  13. SHM-Based Probabilistic Fatigue Life Prediction for Bridges Based on FE Model Updating.

    Science.gov (United States)

    Lee, Young-Joo; Cho, Soojin

    2016-03-02

    Fatigue life prediction for a bridge should be based on the current condition of the bridge, and various sources of uncertainty, such as material properties, anticipated vehicle loads and environmental conditions, make the prediction very challenging. This paper presents a new approach for probabilistic fatigue life prediction for bridges using finite element (FE) model updating based on structural health monitoring (SHM) data. Recently, various types of SHM systems have been used to monitor and evaluate the long-term structural performance of bridges. For example, SHM data can be used to estimate the degradation of an in-service bridge, which makes it possible to update the initial FE model. The proposed method consists of three steps: (1) identifying the modal properties of a bridge, such as mode shapes and natural frequencies, based on the ambient vibration under passing vehicles; (2) updating the structural parameters of an initial FE model using the identified modal properties; and (3) predicting the probabilistic fatigue life using the updated FE model. The proposed method is demonstrated by application to a numerical model of a bridge, and the impact of FE model updating on the bridge fatigue life is discussed.

  14. Effect of Defects Distribution on Fatigue Life of Wind Turbine Components

    DEFF Research Database (Denmark)

    Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard

    2015-01-01

    by a Poisson process / field where the defects form clusters that consist of a parent defect and related defects around the parent defect. The fatigue life is dependent on the number, type, location and size of the defects in the component and is therefore quite uncertain and needs to be described...

  15. Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

    Directory of Open Access Journals (Sweden)

    Takamoto Itoh

    2015-10-01

    Full Text Available This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of λ=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. λ is a principal stress ratio and is defined as λ=II/I, where I and II are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at λ=0 is a uniaxial loading test and that at λ=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing λ induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

  16. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

    2011-01-01

    The cementitious material in grouted connections of offshore monopile wind turbine structures is subjected to very high oscillating service stresses. The fatigue capacity of the grout therefore becomes essential to the performance and service life of the grouted connection. In the present work...

  17. SELF-REPORTED FATIGUE AND PHYSICAL FUNCTION IN LATE MID-LIFE

    NARCIS (Netherlands)

    Boter, Han; Manty, Minna; Hansen, Ase Marie; Hortobagyi, Tibor; Avlund, Kirsten

    2014-01-01

    Objective: To determine the association between the 5 sub-scales of the Multidimensional Fatigue Inventory (MFI-20) and physical function in late mid-life. Design: Cross-sectional study. Subjects: A population-based sample of adults who participated in the Copenhagen Aging and Midlife Biobank popula

  18. Fatigue Life Improving of Drill Rod by Inclusion Control

    Science.gov (United States)

    Wang, Linzhu; Yang, Shufeng; Li, Jingshe; Liu, Wei; Zhou, Yinghao

    2016-08-01

    Large and hard inclusions often deteriorate the service performance and reduce the fatigue lifetime of drill rods. In this paper, the main reasons of the rupture of drill rods were analyzed by the examination of their fracture and it is found that the large inclusions were the main reason of breakage of rod drill. The inclusions were high of Ca content or Al2O3 rich. Smaller and better deformability inclusions were obtained by the optimization of refining slag, calcium treatment process and the flow control devices of tundish. Results of industrial experiment after optimization show that total oxygen content of drill rods decreased by more than 50%, macro-inclusions weight fraction decreased from about 4 mg/10 kg to about 0.3 mg/10 kg and the micro-inclusions average size decreased from 6 to 3.6 μm. The average using times of drill rods after optimization were increased by about 60%.

  19. Load Identification of Offshore Platform for Fatigue Life Estimation

    DEFF Research Database (Denmark)

    Perisic, Nevena; Kirkegaard, Poul Henning; Tygesen, Ulf T.

    2014-01-01

    of the structure and the discrete Kalman filter which recursively estimates unknown states of the system in real time. As a test-case, the algorithm is designed to estimate the equivalent total loading forces of the structure. The loads are estimated from noised displacement measurements of a single location......The lifetime of an offshore platform is typically governed by accumulated fatigue damage. Thus, the load time history is an essential parameter for prediction of the lifetime of the structure and its components. Consequently, monitoring of structural loads is of special importance in relation to re......-assessment of offshore platforms. Structural monitoring systems (SMSs) on offshore structures typically consist of a set of sensors such as strain gauges, accelerometers, wave radars and GPSs, however direct measuring of the actual loading is usually not feasible. One approach is to measure the loads indirectly...

  20. Numerical Estimation of Fatigue Life of Wind Turbines due to Shadow Effect

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Pedersen, Ronnie; Nielsen, Søren R.K.

    2009-01-01

    The influence of tower design on damage accumulation in up-wind turbine blades during tower passage is discussed. The fatigue life of a blade is estimated for a tripod tower configuration and a standard mono-tower. The blade stresses are determined from a dynamic mechanical model with a delay...... effect included in the normal coefficient used to compute the transverse load. Furthermore, the rotational effect of the turbulence spectrum is included in the model. The proposed tripod configuration of the tower limits the damage accumulation in the turbine blades significantly when compared...... to the fatigue of a blade from a monotower wind turbine....

  1. GH4169镍基高温合金的超高周疲劳性能%Very High Cycle Fatigue Properties of GH4169 Ni-based Superalloy

    Institute of Scientific and Technical Information of China (English)

    燕怒; 韩晓琪; 余泳华; 游敏; 彭文杰

    2016-01-01

    在室温下使用超声疲劳试验机对GH4169镍基高温合金进行了105~108周次的疲劳试验,获得了S-N曲线并观察了疲劳断口形貌.结果表明:S-N曲线呈逐渐下降的趋势,没有出现疲劳极限,在超过107周次的循环后试样仍发生疲劳破坏;疲劳裂纹的萌生位置并未随S-N曲线的下降呈现出规律性,裂纹主要萌生于试样表面,少量萌生于试样内部;在超声疲劳载荷作用下试样同时存在塑性和脆性两种破坏方式.%The fatigue tests in 105-108 cycles of GH4169 Ni-based superalloy were carried out at ambient temperature by the ultrasonic fatigue tester, and then the S-N curve was obtained and the fatigue fracture morphology was observed.The results show that the S-N curve exhibited a descending trend and the fatigue limit was not observed.The fatigue fracture of the specimen still occurred when the number of cycles exceeded 107 .The fatigue crack initiation positions didn′t show the regularity with the S-N curve descending.The fatigue cracks mostly initiated from the surface and few from internal of the specimen.Under the ultrasonic load the plastic and brittle failure modes were both found in the specimen.

  2. Influence of Subgrade and Unbound Granular Layers Stiffness on Fatigue Life of Hot Mix Asphalts - HMA

    Directory of Open Access Journals (Sweden)

    Hugo A. Rondón-Quintana

    2013-11-01

    Full Text Available The mainly factors studied to predict fatigue life of hot mix asphalt-HMA in flexible pavements are the loading effect, type of test, compaction methods, design parameters of HMA (e.g., particle size and size distribution curve, fine content, type of bitumen and the variables associated with the environment (mainly moisture, temperature, aging. This study evaluated through a computer simulation, the influence of the granular layers and subgrade on the fatigue life of asphalt layers in flexible pavement structures. Mechanics parameters of granular layers of subgrade, base and subbase were obtained using the mathematical equations currently used for this purpose in the world. The emphasis of the study was the city of Bogotá, where the average annual temperature is 14°C and soils predominantly clay, generally experience CBR magnitudes between 1% and 4%. General conclusion: stiffness of the granular layers and subgrade significantly affect the fatigue resistance of HMA mixtures. Likewise, the use of different equations reported in reference literature in order to characterize granular layers may vary the fatigue life between 4.6 and 48.5 times, varying the thickness of the pavement layers in the design.

  3. Split mandrel versus split sleeve coldworking: Dual methods for extending the fatigue life of metal structures

    Science.gov (United States)

    Rodman, Geoffrey A.; Creager, Matthew

    1994-01-01

    It is common practice to use split sleeve coldworking of fastener holes as a means of extending the fatigue life of metal structures. In search of lower manufacturing costs, the aerospace industry is examining the split mandrel (sleeveless) coldworking process as an alternative method of coldworking fastener holes in metal structures. The split mandrel process (SpM) significantly extends the fatigue life of metal structures through the introduction of a residual compressive stress in a manner that is very similar to the split sleeve system (SpSl). Since the split mandrel process is significantly less expensive than the split sleeve process and more adaptable to robotic automation, it will have a notable influence upon other new manufacture of metal structures which require coldworking a significant number of holes, provided the aerospace community recognizes that the resulting residual stress distributions and fatigue life improvement are the same for both processes. Considerable testing has validated the correctness of that conclusion. The findings presented in this paper represent the results of an extensive research and development program, comprising data collected from over 400 specimens fabricated from 2024-T3 and 7075-T651 aluminum alloys in varied configurations, which quantify the benefits (fatigue enhancement and cost savings) of automating a sleeveless coldworking system.

  4. Influence of shrinkage porosity on fatigue performance of iron castings and life estimation method

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2016-01-01

    Full Text Available Shrinkage porosity exists more or less in heavy castings, and it plays an important role in the fatigue behavior of cast materials. In this study, fatigue tests were carried out on the QT400-18 cast iron specimens containing random degrees of shrinkage porosity defect. Experimental results showed that the order of magnitude of life scattered from 103 to 106 cycles when the shrinkage percentage ranged from 0.67% to 5.91%. SEM analyses were carried out on the shrinkage porosity region. The inter-granular discontinuous, micro cracks and inclusions interfered with the fatigue sliding or hindering process. The slip in shrinkage porosity region was not as orderly as the ordinary continuous medium. The shrinkage porosity area on fracture surface (SPAFS and alternating stress intensity factor (ASIF were applied to evaluate the tendency of residual life distribution; their relationship was fitted by negative exponent functions. Based on the intermediate variable of ASIF, a fatigue life prediction model of nodular cast iron containing shrinkage porosity defects was established. The modeling prediction was in agreement with the experimental results.

  5. Probabilistic fatigue life of balsa cored sandwich composites subjected to transverse shear

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Berggreen, Christian

    2015-01-01

    model are obtaining characteristic S–Ncurves corresponding to a given survival probability, and calibrating partial safety factorsfor material fatigue. The latter is demonstrated by a calibration performed using reliability analysis with the first-order reliability method. The measured variance in balsa...... shearproperties, for both static strength and fatigue failure, is higher than the variance normallyobserved in the properties for fiber-reinforced polymer composite laminates. This could be attributed to the fact that end-grain balsa wood is the product of a naturally occurringgrowth process, which cannot...... be controlled to the same extent as an industrial manufacturing processes. The large variance in the probabilistic model for fatigue life is reflected in the corresponding calibrated partial safety factors, which are higher thanthe factors usually associated with synthetic materials such as fiber...

  6. Method to calculate fatigue fracture life of control fissure in perilous rock

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong-kai; TANG Hong-mei

    2007-01-01

    Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰ and model-Ⅱ stress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters(C and m)of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.

  7. Prediction of Fatigue Life of Gear Subjected to Varying Loads

    Directory of Open Access Journals (Sweden)

    D. Hanumanna

    1998-07-01

    Full Text Available Structural members and components of a vehicle during service are subjected to varying loads which are random in nature. For structural members subjected to loads of constant amplitude, it is possible to describe the load with explicit mathematical relationship, and thereby, the life span can be estimated. Whereas, for structural members subjected to varying loads with time, there is no satisfactory method to estimate their life span. This paper describes a method for the estimation of life span of a gear in the gear box of a fighting vehicle subjected to fluctuating loads. For this purpose, it is assumed that the load spectrum corresponds to Gaussian (normal distribution, and the life has been worked out by applying linear cumulative damage theory.

  8. The Effect of Sequence of Operations on Fatigue Life of LSP Treated Open-hole Aluminium Specimens

    OpenAIRE

    Ivetic, G.; Meneghin, I.; E. Troiani; Molinari, G.; Lanciotti, A.; Ocaña Moreno, Jose Luis; Ristori, V.; Morales Furió, Miguel; Porro González, Juan Antonio; Plaisier, J.; Lausi, A.

    2011-01-01

    Fastener holes in aeronautical structures are typical sources of fatigue cracks due to their induced local stress concentration. A very efficient solution to this problem is to establish compressive residual stresses around the fastener holes that retard the fatigue crack nucleation and its subsequent local propagation. Previous work done on the subject of the application of LSP treatment on thin, open-hole specimens [1] has proven that the LSP effect on fatigue life of treated specimens ...

  9. 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.

  10. Evaluation for probabilistic distributions of fatigue life of marine propeller materials by using a Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Han Yong; Zhang, Jian Wei [Mokpo National University, Muan (Korea, Republic of)

    2008-12-15

    Engineering materials have been studied and developed remarkably for a long time. But, few reports about marine propeller materials are presented. Recently, some researchers have studied the material strength of marine propellers. However, studies on parametric sensitivity and probabilistic distribution of fatigue life of propeller materials have not been made yet. In this study, a method to predict the probabilistic distributions of fatigue life of propeller materials is presented, and the influence of several parameters on the life distribution is discussed.

  11. Influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates

    DEFF Research Database (Denmark)

    Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi;

    2016-01-01

    It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...... specimen that fails in the gauge section. The second objective was to compare fatigue performance of two laminates, one having a newly developed UD powder-bound fabric as a reinforcement and the other having a quasi-UD stitched non-crimp fabric as a reinforcement. In the first phase, a rectangular specimen...... a significant effect on the failure mode and measured fatigue life of the laminates. A significantly higher fatigue life was measured for the laminate with the powder-bound fabric reinforcement when compared to the laminate with the stitched reinforcement....

  12. Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J; Huang, M; Niu, X; soboyejo, W

    2006-10-09

    In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces. They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).

  13. Optimal Shot Peening Treatments to Maximize the Fatigue Life of Quenched and Tempered Steels

    Science.gov (United States)

    Llaneza, V.; Belzunce, F. J.

    2015-07-01

    The search for the optimal Almen intensity to use in shot peening treatments to maximize the fatigue life of industrial steel components involves many different variables and physical phenomena. In this paper, the optimal peening intensity of different steel grades obtained from an AISI 4340 steel through heat treatments has been determined. Six different steel grades were subjected to shot peening treatments, which were performed under full coverage, but employing diverse Almen intensities, shot sizes and air pressures. The role of the mechanical properties of the treated steel and the applied Almen intensity on the shot peening effects were studied to understand the results obtained by means of rotating bending fatigue tests. Each steel has a specific Almen intensity value able to optimize its fatigue life, thereby allowing an optimal balance between the positive and negative effects induced by shot peening. This value, or range of values, is dependent on the mechanical properties of the treated steel, increasing with increasing steel properties up to a certain point and then decreasing for stronger steels. In these cases, over peening treatments produce sufficiently large surface defects to induce relaxation of the surface residual stress and facilitate the initiation of surface fatigue cracks.

  14. Assessment of Surface Treatment on Fatigue Life of Cylinder Block for Linear Engine using Frequency Response Approach

    Directory of Open Access Journals (Sweden)

    M. M. Rahman

    2009-01-01

    Full Text Available Objectives: This study was focused on the finite element techniques to investigate the effect of surface treatment on the fatigue life of the vibrating cylinder block for new two-stroke free piston engine using random loading conditions. Motivation: An understanding of the effects related to the random loading is necessary to improve the ability of designers to accurately predict the fatigue behavior of the components in service. An internal combustion engine cylinder block is a high volume production component subjected to random loading. Problem statement: Proper optimization of this component that is critical to the engine fuel efficiency and more robustly pursued by the automotive industry in recent years. A detailed understanding of the applied loads and resulting stresses under in-service conditions is demanded. Approach: The finite element modeling and analysis were performed utilizing the computer aided design and finite element analysis codes respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis code. Aluminum alloys were considered as typical materials in this study. Results: The frequency response approach was applied to predict the fatigue life of cylinder block using different load histories. Based on the finite element results, it was observed that the fatigue life was significantly influenced for the nitriding treatment. The obtained results were indicated that the nitrided treatment produces longest life for all loading conditions. Conclusion: The nitriding process is one of the promising surface treatments to increase the fatigue life for aluminum alloys linear engine cylinder block.

  15. Prediction of fatigue life of high-heat-load components made of oxygen-free copper by comparing with Glidcop

    International Nuclear Information System (INIS)

    By using the strain-range partitioning method, the fatigue life of high-heat-load components made of oxygen-free copper have been successfully predicted within a factor of two. Following a successful study on the prediction of fatigue life of high-heat-load components made of Glidcop, the thermal limitation of oxygen-free copper (OFC), which is used more commonly than Glidcop, has been studied. In addition to its general mechanical properties, the low-cycle-fatigue (LCF) and creep properties of OFC were investigated in detail and compared with those of Glidcop. The breaking mode of OFC, which was observed to be completely different from that of Glidcop in a fatigue fracture experiment, clarified the importance of considering the creep–fatigue interaction. An additional LCF test with compressive strain holding was conducted so that the creep–fatigue life diagram for out-of-phase thermal fatigue could be obtained on the basis of the strain-range partitioning method. The life predicted from elasto-plastic creep analysis agreed well with that determined from the void ratio estimated in the fatigue fracture experiment

  16. Fatigue life prediction of casing welded pipes by using the extended finite element method

    Directory of Open Access Journals (Sweden)

    Ljubica Lazić Vulićević

    2016-03-01

    Full Text Available The extended finite element (XFEM method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to verify numerical results with the experimental ones. After successful verification, the XFEM was used to simulate fatigue crack growth, position axially in the pipe, and estimate its remaining life.

  17. Comparison of Fatigue Life Estimation Using Equivalent Linearization and Time Domain Simulation Methods

    Science.gov (United States)

    Mei, Chuh; Dhainaut, Jean-Michel

    2000-01-01

    The Monte Carlo simulation method in conjunction with the finite element large deflection modal formulation are used to estimate fatigue life of aircraft panels subjected to stationary Gaussian band-limited white-noise excitations. Ten loading cases varying from 106 dB to 160 dB OASPL with bandwidth 1024 Hz are considered. For each load case, response statistics are obtained from an ensemble of 10 response time histories. The finite element nonlinear modal procedure yields time histories, probability density functions (PDF), power spectral densities and higher statistical moments of the maximum deflection and stress/strain. The method of moments of PSD with Dirlik's approach is employed to estimate the panel fatigue life.

  18. Formulation and Validation of Multidisciplinary Design Problem on Wear and Fatigue Life of Lead Screw Actuators

    OpenAIRE

    Krishna Meruva; Zhuming Bi; Donald Mueller; Bongsu Kang

    2013-01-01

    Multidisciplinary design optimization has been widely applied in the optimization of large-scale complex system and also in the design and optimization of components, which are involved in multidisciplinary behaviors. The wear and fatigue life of lead screw actuators is a typical multidisciplinary problem. The wear behaviors of actuators closely relate to many factors such as loads, lubrications, materials properties, surface properties, pressures, and temperature. Therefore, the wear and fat...

  19. Development of a device to study fatigue life of fixed partial dentures

    OpenAIRE

    Gutiérrez Rubert, Santiago Carlos; Meseguer Calas, María Desamparados

    2012-01-01

    Fixed partial dentures can be fabricated by means of different materials and with different manufacturing processes. In order to establish possible differences among them, their behaviour, as fatigue life or cement shear bond strength, have to be evaluated. This article presents a modular, economic and robust device to evaluate fixed partial dentures and dental crowns. A base to support the fixed partial dentures and a device to simulate masticatory loads have been developed. T...

  20. Effect of Pre-corrosion on Fatigue Life of High Strength Steel 38CrMoAl

    Institute of Scientific and Technical Information of China (English)

    LIU Jianhua; HAO Xuelong; LI Songmei; YU Mei

    2011-01-01

    The effect of pre-corrosion on fatigue behavior of high strength steel 38CrMoAl was investigated with a fatigue test method using the accelerated pre-corrosion specimen in the neutral salt spray environment.The methods of weight-loss and energy dispersive spectrum(EDS)were adopted.The corrosion weight-loss rate was fitted with the test time using power law,and the relationship between the corrosion weight-loss rate and the time was formulated.Moreover,the fatigue behaviors of the steel for different pre-corrosion time were investigated by the axis-direction tensile fatigue test.The fatigue life distribution characteristics of the pre-corrosion specimens were studied using the statistical probability methods,and the mathematical expectations and the standard tolerances of the material fatigue lives after different pre-corrosion time were obtained.It was found that the crack initiation of the high strength steel was accelerated by the preferential corrosion at the local plastic deform areas.The fatigue life obeys the lognormal distribution perfectly.Furthermore,within the common time range of the engineering,the standard tolerances of the logarithm of the fatigue life were independent of the pre-corrosion time.

  1. The impact of disability, fatigue and sleep quality on the quality of life in multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Ghaem Haleh

    2008-01-01

    Full Text Available Background: Only few papers have investigated the impact of multiple sclerosis (MS, especially MS-related fatigue and the impact of the quality of sleep on the quality of life (QoL in MS patients. Objective: The objective of this study was to measure the quality of life in MS patients and the impact of disability, fatigue and sleep quality, using statistical modeling. Materials and Methods: A cross-sectional study was conducted and data was collected from 141 MS patients, who were referred to the Mottahari Clinic, Shiraz, Iran, in 2005. Data on health-related quality of life (MSQoL-54, fatigue severity scale (FSS, and Pittsburgh sleep quality Index (PSQI were obtained in the case of all the patients. Epidemiology data concerning MS type, MS functional system score, expanded disability status scale (EDSS etc. were also provided by a qualified neurologist. Spearman a coefficient, Mann-Whitney U test, and linear regression model were used to analyze the data. Results : The mean ±SD age of 141 MS patients was 32.6±9.6 year. Thirty five (24.8% of them were male and the others were female. Eighty two (58.1% of the patients had EDSS score of ≤ 2, 36 (25.5% between 2.5 and 4.5, and 23 (16.3% ≥ 5. As per PSQI scores, two (1.4% of the patients had good sleep, 16 (11.3% had moderate sleep and 123 (87.2% had poor sleep. There was a significant high positive correlation between the quality of mental and physical health composite scores (r = 0.791, P < 0.001. There was a significant negative correlation between the quality of physical score and age (r = -0.88, P < 0.001, fatigue score (r = -0.640, P < 0.001, EDSS score (r = -0.476, P < 0.001 and PSQI (sleep quality r = -0.514, P < 0.000. Linear regression analysis showed that PSQI score, EDSS, and fatigue score were predictors in the model between the quality of physical score and covariates ( P < 0.001. Linear regression model showed that fatigue score and PSQI were predictors in the model between the

  2. Shot-peening process for fatigue-life delay effect of laser welding

    International Nuclear Information System (INIS)

    At present, welding technology is not only emphasized in the development of manufacturing technology but also application is expanding. In these systems, application of SUS as high-temperature material which is used for special purposes is attempted, and improvement of manufacturing technologies bear watching together with increase of using rate. Specifically, Wings with surface of three-dimensional shape usually applied to Fastener with purpose of light weight. However, due to development of welding technology, methods of existing assembly tend to be replaced by welding, recently. Specifically, if laser welding techniques is applied, it minimizes heat-affected zone than other welding techniques. However, in the case of these special welding, residual stress is raised, and it fatally affects fatigue life. In order to remove residual stress and delay effect of fatigue life, shot-peening is executed; it executes shot-peening and verifies delayed effects of fatigue life. The intention of this study is to obtain the optimal conditions of shot-peening.

  3. 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.

  4. Laser Peening and Shot Peening Effects on Fatigue Life and Surface Roughness of Friction Stir Welded 7075-T7351 Aluminum

    Science.gov (United States)

    Hatamleh, Omar; Lyons, Jed; Forman, Royce

    2006-01-01

    The effects of laser peening, shot peening, and a combination of both on the fatigue life of Friction Stir Welds (FSW) was investigated. The fatigue samples consisted of dog bone specimens and the loading was applied in a direction perpendicular to the weld direction. Several laser peening conditions with different intensities, durations, and peening order were tested to obtain the optimum peening parameters. The surface roughness resulting from various peening techniques was assessed and characterized. The results indicate a significant increase in fatigue life using laser peening compared to shot peened versus their native welded specimens.

  5. 确定高周应力疲劳S-N曲线的方法研究%Method for Reducing Stress-life Curve of High Cycle Fatigue

    Institute of Scientific and Technical Information of China (English)

    李骋; 张国栋; 许超; 苏彬

    2008-01-01

    基于三参数幂函数法处理高周疲劳S-N曲线,提出了一种在短寿命区采用低周疲劳试验数据、长寿命区采用高周疲劳试验数据联合确定材料高周疲劳S-N曲线的方法.联合处理方法的应用在有效利用低周疲劳数据、节约试验经费和缩短试验周期的同时,获得了理想的S-N曲线.用FGH95合金500℃单晶合金DD3[001]取向850℃的高、低周疲劳数据对该方法进行了验证,结果表明:联合处理方法不仅在长寿命区与单纯用高周疲劳数据处理得到的S-N曲线吻合很好,而且将S-N曲线延伸到中、低寿命区,有效地保证了S-N曲线的完整,联合处理方法可以用来确定材料的高周S-N曲线.

  6. Method and data analysis example of fatigue tests

    International Nuclear Information System (INIS)

    In the design and operation of a nuclear fusion reactor, it is important to accurately assess the fatigue life. Fatigue life is evaluated by preparing a database on the relationship between the added stress / strain amplitude and the number of cycles to failure based on the fatigue tests on standard specimens, and by comparing this relationship with the generated stress / strain of the actual constructions. This paper mainly chooses low-cycle fatigue as an object, and explains standard test methods, fatigue limit, life prediction formula and the like. Using reduced-activation ferrite steel F82H as a material, strain controlled low-cycle fatigue test was performed under room temperature atmosphere. From these results, the relationship between strain and the number of cycles to failure was analyzed. It was found that the relationship is asymptotic to the formula of Coffin-Manson Law under high-strain (low-cycle condition), and asymptotic to the formula of Basquin Law under low-strain (high-cycle condition). For F82H to be used for the blanket of a nuclear fusion prototype reactor, the arrangement of fatigue life data up to about 700°C and the establishment of optimal fatigue design curves are urgent tasks. As for fusion reactor structural materials, the evaluation of neutron irradiation effect on fatigue damage behavior and life is indispensable. For this purpose, it is necessary to establish standardized testing techniques when applied to small specimens. (A.O.)

  7. An all-in-one numerical methodology for fretting wear and fatigue life assessment

    Directory of Open Access Journals (Sweden)

    I. Llavori

    2016-07-01

    Full Text Available Many mechanical components such as, bearing housings, flexible couplings and spines or orthopedic devices are simultaneously subjected to a fretting wear and fatigue damage. For this reason, the combined study on a single model of wear, crack initiation and propagation is of great interest. This paper presents an all-in-one 2D cylinder on flat numerical model for life assessment on coupled fretting wear and fatigue phenomena. In the literature, two stages are usually distinguished: crack nucleation and its subsequent growth. The method combines the Archard wear model, a critical-plane implementation of the Smith-Watson- Topper (SWT multiaxial fatigue criterion coupled with the Miner-Palmgren accumulation damage rule for crack initiation prediction. Then, the Linear Elastic Fracture Mechanics (LEFM via eXtended Finite Element Method (X-FEM embedded into the commercial finite element code Abaqus FEA has been employed to determine the crack propagation stage. Therefore, the sum of the two stages gives a total life prediction. Finally, the numerical model was validated with experimental data reported in the literature and a good agreement was obtained.

  8. NiCrMoV型转子钢焊接接头组织与高周疲劳性能研究%INVESTIGATION ON THE STRUCTURE AND HIGH CYCLE FATIGUE PROPERTY OF THE WELDED JOINT MADE OF NiCrMoV ROTOR STEEL

    Institute of Scientific and Technical Information of China (English)

    刘鹏; 刘霞; 芦凤桂; 高玉来

    2013-01-01

    采用应力比R=-1的拉压高周疲劳实验,研究了汽轮机焊接模拟转子试样的高周疲劳裂纹的萌生与扩展过程,并通过扫描电子显微镜(SEM)和能谱(EDS)观察与分析了疲劳断口的形貌特征和微区成分.结果表明:疲劳裂纹常在夹杂物和气孔等缺陷处萌生,进而以此为裂纹源,逐渐发生扩展,直至材料最终断裂失效.对于30Cr2Ni4MoV转子钢,夹杂物性质主要为氧化物(如CaO、SiO2、Al2O3和MgO等),因此应严格控制钢中O、A1、Si、Mg、Ca等元素的含量.%The initiation and propagation of fatigue crack of the simulation rotor used in steam turbine was investigated by employing the repeated high cycle tension and compression test with stress ratio R = - 1. The fatigue fracture morphology was observed by the scanning electron microscope ( SEM) , and the composition was analyzed by the energy dispersive spectroscopy ( EDS). The results showed that the fatigue crack was initiated in the zone where inclusion and/or pores existed, and then the fatigue crack propagated until its fracture failure. In particular, the inclusions in 30Cr2Ni4MoV rotor steel mainly consisted of oxides such as CaO, SiO2, A12O3 and MgO etc. So the content of O、 Al、Si、Mg and Ca element in rotor steel should be controlled strictly.

  9. Effects of pitting corrosion on fatigue life of aluminum alloy Y 12CZ based on initial discontinuity state

    Institute of Scientific and Technical Information of China (English)

    YU Da-zhao; CHEN Yue-liang; HU Jia-lin; YANG Mao-sheng

    2006-01-01

    Based on initial discontinuity state (IDS) of material, a preliminary analytical model was presented to evaluate the effect of interaction of pitting corrosion and fatigue loading on the residual fatigue life of aluminum alloy LY12CZ. A life prediction was carried out using constant and variable amplitude loading for various pitting corrosion levels, and the prediction agreed reasonably with the available test data. The results suggest that the combination of a pit and IDS can be treated as the initial crack size. Pitting corrosion causes a significant decrease in fatigue lives with small corrosion depths. But the effect of pit on fatigue life is gradually reduced with increasing pit size. A pit with a constant depth can be applied to the model for long exposure structure. A preliminary recommendation for the pit depth is about 1 mm for LY12CZ. At last the effect of multiple-site corrosion damage (MSCD) on fatigue life was also studied, and the result shows that MSCD can decrease substantially fatigue life compared with that of a single crack.

  10. Study on creep-fatigue failure mechanism and life evaluation for stainless steels

    International Nuclear Information System (INIS)

    For the achievement of high reliability on long-term extrapolation of creep-fatigue life, failure mechanism was investigated for Type 304 stainless steel, and it is clarified that creep damage is related to metallographical influence such as grain boundary sliding, creep cavity nucleation and growth. Then on the basis of ductility exhaustion rule, primary creep strain could be recoverable in cyclic loading and the conventional estimation would give excessive damage. If secondary creep deformation is dominant for grain boundary sliding, both of creep rupture and creep-fatigue failure can be represented by unified ductility criterion, and the rule on stress basis which are practically used in engineering applications can be derived. The evaluation method proposed by PNC gives good prediction and reliable extrapolation results to long time test data. It is in prospect that the rationalization of evaluation procedures in present structural design guide and the application to 316FR stainless steel are achievable. (author)

  11. Reconstruction of probabilistic S-N curves under fatigue life following lognormal distribution with given confidence

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yong-xiang; YANG Bing; PENG Jia-chun

    2007-01-01

    When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except for the special levels. Therefore, the wide applied curves are expected. Monte Carlo reconstruction methods of the test data and the curves are investigated under fatigue life following lognormal distribution. To overcome the non-conservative assessment of existent man-made enlarging the sample size up to thousands, a simulation policy is employed to address the true production where the sample size is controlled less than 20 for material specimens, 10 for structural component specimens and the errors matching the statistical parameters are less than 5 percent. Availability and feasibility of the present methods have been indicated by the reconstruction practice of the test data and curves for 60Si2Mn high strength spring steel of railway industry.

  12. Stochastic Analysis of the Influence of Tower Shadow on Fatigue Life of Wind Turbine Blade

    DEFF Research Database (Denmark)

    Pedersen, Ronnie; Nielsen, Søren R.K.; Thoft-Christensen, Palle

    2012-01-01

    Fatigue damage accumulation in upwind turbine blades is primarily influenced by turbulence in the inflow. However, the stress reversals during blade passages through the stagnating and deflected mean wind field in front of the tower also contributes significantly. In the paper the lower order...... statistical moments of the fatigue life of a blade are estimated and compared for a turbine with a tripod tower and a standard mono-tower, respectively. The stagnation zones for each of the legs of the tripod are narrower than for the mono-tower, and hence the stress reversals will be comparable smaller...... that the expected damage accumulation per unit of time in the turbine blades are reduced significantly for the tripod when compared to the damage in a comparable mono-tower design....

  13. Service Life Of Main Piping Component Due To Low Thermal Stresses.Fatigue

    International Nuclear Information System (INIS)

    The paper deals with estimating the service life of the power station Main piping component and describing the repair process for extending of its service life. After a long period of service, several circular fatigue cracks have been discovered at the bottom of the Main piping component chamber. Finite element analyses of transient thermal stresses, caused by power station startup, are carried out in the paper. The calculation results show good agreement between the theoretical locations of the maximum stresses and the actual locations of the cracks. There is a good agreement between theoretical evaluation and actual service life, as well. The possibility of machining out the cracks in order to prevent their growing is examined here. The machining enables us to extend the power station component's life service

  14. A Study on the Unified Damage Model for Creep-Fatigue Interacted Life Prediction of Nickel-base Superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Won; Kang, Dong Hwan [Hanyang Univ., Seoul (Korea, Republic of); Yeom, Jong Taek; Park, Nho Kwang [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2007-07-01

    A methodology for creep-fatigue interacted life prediction of nickel-base superalloy at high temperature is presented enabling the experimentally measured life to be compared with the model predictions. Continuum damage mechanics has been employed to determine the accumulation of damage during the deformation by means of the unified damage model, which is coupled with the material behavior analysis. Several types of low cycle fatigue test at high temperature have been carried out, and thus the effect of plastic strain range together with the relaxed stress to the life can be investigated. Good agreements between the interacted model's predictions and experimental data of the life were obtained.

  15. Effect of induction hardening on high-cycle fatigue property of medium-carbon microalloyed steel for semi-axle%感应淬火对半轴用非调质钢高周疲劳性能的影响

    Institute of Scientific and Technical Information of China (English)

    胡芳忠; 惠卫军; 雍歧龙; 张英建; 鹿云

    2012-01-01

    利用旋转弯曲疲劳试验方法对比研究了一种半轴用铁素体+珠光体型非调质钢感应淬火前后高周疲劳性能的变化。结果表明,试验钢试样感应淬火后表层形成了厚度约1.2 mm、平均显微硬度约650 HV0.3的马氏体组织淬硬层。该淬硬层具有较高的残余压应力和十分细小的原奥氏体晶粒。感应淬火处理后,试验钢的疲劳耐久极限从420 MPa提高到716 MPa。疲劳断口的SEM观察表明,未经感应淬火试样的疲劳裂纹均起源于试样的表面基体,而经表面感应淬火后的疲劳裂纹则起裂于淬硬层边界附近的内部基体。%High-cycle fatigue property for semi-axle made of a medium-carbon microalloyed steel before and after induction hardening was investigated by using rotating bending fatigue test. The results show that a martensitic hardened layer with a thickness of about 1.2 mm and an average microhardness of about 650 HV0. 3 is formed after induction hardening. This harden layer has relatively higher compressive residual stress and much finer prior austenite grain. The fatigue endurance limit stress of the tested steel increases from 420 MPa to 716 MPa after induction hardening. Further SEM observations of fatigue fracture surface reveals that all the fatigue cracks of the specimen without induction hardening initiate from specimen shallow subsurface, whereas all the fatigue cracks of the specimen with induction hardening initiate under the depth of about 1.2 mm.

  16. Slow Crack Growth and Fatigue Life Prediction of Ceramic Components Subjected to Variable Load History

    Science.gov (United States)

    Jadaan, Osama

    2001-01-01

    Present capabilities of the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code, which has also been modified to have the ability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.

  17. Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

    Institute of Scientific and Technical Information of China (English)

    RAHMAN M.M.; ARIFFIN A.K.; JAMALUDIN N.; HARON C.H.C.

    2006-01-01

    This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine's components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.

  18. Effects of regenerative heat treatment on creep behaviour and on life with fatigue stresses

    International Nuclear Information System (INIS)

    This dissertation is intended to make a contribution to the modelling of pore shrinking in regenerative heat treatment of materials under fatigue stresses and to the knowledge of the regeneration capacity of austenitic steels. Starting from the models for describing the speed of growth of grain boundary pores during a high temperature fatigue stress test, mechanisms are used to describe a healing process during an interposed heat treatment without external stress. Apart from the pore shrinking by diffusion, a model is derived for pore shrinking by creep back due to the effect of internal stresses and due to the stress field induced by surface tension. The effect of an additional external hydrostatic pressure is also taken into account. The effects of intermediate annealing after creep stress to the tertiary range on creep behaviour and the remaining life were examined on austenitic X 8 Cr NiMoNb 16 16 and X 6 CrNi 18 11 steels. The damage occurring in the fatigue test and the regeneration effect are followed up by metallographic and electron microscope investigations and by measurements of density. (orig.)

  19. Multifrequency Eddy Current Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life

    Science.gov (United States)

    Okafor, A. C.; Natarajan, S.

    2007-03-01

    Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.

  20. Ti–6Al–4V welded joints via electron beam welding: Microstructure, fatigue properties, and fracture behavior

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoguang [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Co-Innovation Center for Advanced Aero-Engine, Beijing 100191 (China); Li, Shaolin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Qi, Hongyu, E-mail: qhy@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Co-Innovation Center for Advanced Aero-Engine, Beijing 100191 (China)

    2014-03-01

    The effect of microstructural characteristics on the fatigue properties of electron beam-welded joints of forged Ti–6Al–4V and its fracture behavior were investigated. Tensile tests and fatigue tests were conducted at room temperature in air atmosphere. The test data were analyzed in relation to microstructure, high-cycle fatigue properties, low-cycle fatigue properties, and fatigue crack propagation properties. The high-cycle fatigue test results indicated that the fatigue strength of the joint welded via electron beam welding was higher than that of the base metal because the former had a high yield strength and all high-cycle fatigue specimens were fractured in the base metal. Although the joint specimens had a lower low-cycle fatigue life than the base metal, they mainly ruptured at the fusion zone of the joint specimen and their crack initiation mechanism is load-dependent. The fatigue crack propagation test results show that the joint had a slower crack propagation rate than the base metal, which can be attributed to the larger grain in the fusion zone.

  1. Ti–6Al–4V welded joints via electron beam welding: Microstructure, fatigue properties, and fracture behavior

    International Nuclear Information System (INIS)

    The effect of microstructural characteristics on the fatigue properties of electron beam-welded joints of forged Ti–6Al–4V and its fracture behavior were investigated. Tensile tests and fatigue tests were conducted at room temperature in air atmosphere. The test data were analyzed in relation to microstructure, high-cycle fatigue properties, low-cycle fatigue properties, and fatigue crack propagation properties. The high-cycle fatigue test results indicated that the fatigue strength of the joint welded via electron beam welding was higher than that of the base metal because the former had a high yield strength and all high-cycle fatigue specimens were fractured in the base metal. Although the joint specimens had a lower low-cycle fatigue life than the base metal, they mainly ruptured at the fusion zone of the joint specimen and their crack initiation mechanism is load-dependent. The fatigue crack propagation test results show that the joint had a slower crack propagation rate than the base metal, which can be attributed to the larger grain in the fusion zone

  2. Creep fatigue life prediction for engine hot section materials (isotropic): Fourth year progress review

    Science.gov (United States)

    Nelson, Richard S.; Schoendorf, John F.

    1986-01-01

    As gas turbine technology continues to advance, the need for advanced life prediction methods for hot section components is becoming more and more evident. The complex local strain and temperature histories at critical locations must be accurately interpreted to account for the effects of various damage mechanisms (such as fatigue, creep, and oxidation) and their possible interactions. As part of the overall NASA HOST effort, this program is designed to investigate these fundamental damage processes, identify modeling strategies, and develop practical models which can be used to guide the early design and development of new engines and to increase the durability of existing engines.

  3. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons.

    Science.gov (United States)

    Hassanpour-Dehkordi, Ali; Jalali, Amir

    2016-07-01

    Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly's quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly's quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions). In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual's demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly's quality of life. PMID:27424013

  4. Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials

    Science.gov (United States)

    Townsend, D. P.

    1985-01-01

    Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

  5. 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

  6. 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

  7. Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

    Institute of Scientific and Technical Information of China (English)

    CHEN Jiping; DING Zhiping

    2007-01-01

    The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system.By taking account of the coupling effects,formulas of equivalent stress and strain for cubic single crystal materials are cited.Using the equivalent strain and equivalent stress for such material and a variable k,which is introduced to express the effect of asymmetrical cyclic loading on fatigue life,a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed.On the basis of the yield criterion and constitutive model of cubic single crystal materials,a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed.The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680℃ was analyzed.Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis.The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient.A power law exists between k and the failure cycle.The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys.All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens,respectively.

  8. Fatigue Properties of Cast Magnesium Wheels

    Science.gov (United States)

    Li, Zhenming; Luo, Alan A.; Wang, Qigui; Peng, Liming; Zhang, Peng

    2016-08-01

    This paper investigates the fatigue properties and deformation behavior of a newly developed Mg-2.96Nd-0.21Zn-0.39Zr magnesium alloy wheel in both as-cast and T6 conditions. Compared with the as-cast alloy, the T6-treated alloy shows a significant increase in fatigue strength and cyclic stress amplitude. This is believed to be attributed to the change of defect type from porosity to oxides and the increased matrix strength in the T6 (peak-aged) condition. For the as-cast alloy wheel, fatigue failure mainly originated from the cast defects including porosity, oxide film, and inclusion at or near the sample surface. In the T6-treated alloy, however, oxides and inclusions or slip bands initiate the fatigue cracks. Solution treatment appears to reduce or eliminate the shrinkage porosity because of grain growth and dissolution of as-cast eutectic phases in the grain boundaries. The cyclic stress amplitude of the as-cast alloy increases with increasing the number of cycles, while the T6-treated alloy shows cyclic softening after the stress reaches a maximum value. The Coffin-Manson law and Basquin equation can be used to evaluate the life of low cycle fatigue. The developed long crack model and multi-scale fatigue (MSF) models can be used to predict high-cycle fatigue life of the Mg-2.96Nd-0.21Zn-0.39Zr alloys with or without casting defects.

  9. Fatigue Properties of Cast Magnesium Wheels

    Science.gov (United States)

    Li, Zhenming; Luo, Alan A.; Wang, Qigui; Peng, Liming; Zhang, Peng

    2016-05-01

    This paper investigates the fatigue properties and deformation behavior of a newly developed Mg-2.96Nd-0.21Zn-0.39Zr magnesium alloy wheel in both as-cast and T6 conditions. Compared with the as-cast alloy, the T6-treated alloy shows a significant increase in fatigue strength and cyclic stress amplitude. This is believed to be attributed to the change of defect type from porosity to oxides and the increased matrix strength in the T6 (peak-aged) condition. For the as-cast alloy wheel, fatigue failure mainly originated from the cast defects including porosity, oxide film, and inclusion at or near the sample surface. In the T6-treated alloy, however, oxides and inclusions or slip bands initiate the fatigue cracks. Solution treatment appears to reduce or eliminate the shrinkage porosity because of grain growth and dissolution of as-cast eutectic phases in the grain boundaries. The cyclic stress amplitude of the as-cast alloy increases with increasing the number of cycles, while the T6-treated alloy shows cyclic softening after the stress reaches a maximum value. The Coffin-Manson law and Basquin equation can be used to evaluate the life of low cycle fatigue. The developed long crack model and multi-scale fatigue (MSF) models can be used to predict high-cycle fatigue life of the Mg-2.96Nd-0.21Zn-0.39Zr alloys with or without casting defects.

  10. Verification of recursive probabilistic integration (RPI) method for fatigue life management using non-destructive inspections

    Science.gov (United States)

    Chen, Tzikang J.; Shiao, Michael

    2016-04-01

    This paper verified a generic and efficient assessment concept for probabilistic fatigue life management. The concept is developed based on an integration of damage tolerance methodology, simulations methods1, 2, and a probabilistic algorithm RPI (recursive probability integration)3-9 considering maintenance for damage tolerance and risk-based fatigue life management. RPI is an efficient semi-analytical probabilistic method for risk assessment subjected to various uncertainties such as the variability in material properties including crack growth rate, initial flaw size, repair quality, random process modeling of flight loads for failure analysis, and inspection reliability represented by probability of detection (POD). In addition, unlike traditional Monte Carlo simulations (MCS) which requires a rerun of MCS when maintenance plan is changed, RPI can repeatedly use a small set of baseline random crack growth histories excluding maintenance related parameters from a single MCS for various maintenance plans. In order to fully appreciate the RPI method, a verification procedure was performed. In this study, MC simulations in the orders of several hundred billions were conducted for various flight conditions, material properties, and inspection scheduling, POD and repair/replacement strategies. Since the MC simulations are time-consuming methods, the simulations were conducted parallelly on DoD High Performance Computers (HPC) using a specialized random number generator for parallel computing. The study has shown that RPI method is several orders of magnitude more efficient than traditional Monte Carlo simulations.

  11. High-Cycle-Life Lithium Cell

    Science.gov (United States)

    Yen, S. P. S.; Carter, B.; Shen, D.; Somoano, R.

    1985-01-01

    Lithium-anode electrochemical cell offers increased number of charge/ discharge cycles. Cell uses components selected for compatibility with electrolyte solvent: These materials are wettable and chemically stable. Low vapor pressure and high electrochemical stability of solvent improve cell packaging, handling, and safety. Cell operates at modest temperatures - less than 100 degrees C - and is well suited to automotive, communications, and other applications.

  12. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    Science.gov (United States)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-09-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  13. Fatigue life prediction method for sucker rods based on local concept; Verfahren zur Lebensdauerabschaetzung der Tiefpumpgestaenge nach dem oertlichen Konzept

    Energy Technology Data Exchange (ETDEWEB)

    Ulmanu, V. [Universitatea Petrol-Gaze, Ploiesti (Romania); Ghofrani, R. [Technische Univ. Clausthal, Clausthal-Zellerfeld (DE). Inst. fuer Erdoel- und Erdgastechnik (ITE)

    2001-04-01

    The paper presents a model to calculate the sucker rod fatigue life based on the 'local concept' and on the 'crack propagation concept'. Typical crack initiation site for sucker rods is the upset or body area close to the upset. The fatigue life of Grade C and Grade D - 25,4 mm diameter sucker rods is calculated, considering the rod with surface transverse discontinuities tolerated by API Standards. The crack initiation S-N (Woehler) curve is calculated based on the experimentally determined fatigue characteristics and on the Neuber's rule for describing the material behaviour at the root of the notch. The fatigue crack propagation life is calculated by numerical integration of the Paris law using an estimation for the stress intensity factor for cylindrical bars with an edge crack. The estimated fatigue life is in good agreement with the Woehler diagramm obtained from the failure analysis of rod fractures in the oil field. (orig.)

  14. Influence of Working Environment on Fatigue Life Time Duration for Runner Blades of Kaplan Turbines

    Directory of Open Access Journals (Sweden)

    Ana-Maria Budai

    2010-10-01

    Full Text Available The paper present an analytical analyzes refer to influence of working environment on life time duration in service of runner blades of Kaplan turbines. The study are made using only analytical method, the entry dates being obtained from measurements made in situ for a Kaplan turbine. To calculate the maximum number of stress cycles whereupon the runner blades work without any damage it was used an analytical relation known in specialized literatures under the name of Morrow’s relation. To estimate fatigue life time duration will be used a formula obtained from one of most common cumulative damage methodology taking in consideration the real exploitation conditions of a specified Kaplan turbine.

  15. Investigation of Bearing Fatigue Damage Life Prediction Using Oil Debris Monitoring

    Science.gov (United States)

    Dempsey, Paula J.; Bolander, Nathan; Haynes, Chris; Toms, Allison M.

    2011-01-01

    Research was performed to determine if a diagnostic tool for detecting fatigue damage of helicopter tapered roller bearings can be used to determine remaining useful life (RUL). The taper roller bearings under study were installed on the tail gearbox (TGB) output shaft of UH- 60M helicopters, removed from the helicopters and subsequently installed in a bearing spall propagation test rig. The diagnostic tool was developed and evaluated experimentally by collecting oil debris data during spall progression tests on four bearings. During each test, data from an on-line, in-line, inductance type oil debris sensor was monitored and recorded for the occurrence of pitting damage. Results from the four bearings tested indicate that measuring the debris generated when a bearing outer race begins to spall can be used to indicate bearing damage progression and remaining bearing life.

  16. Effects of Spot Diameter and Sheets Thickness on Fatigue Life of Spot Welded Structure based on FEA Approach

    Directory of Open Access Journals (Sweden)

    M. M. Rahman

    2009-01-01

    Full Text Available This study presents the effect of the spot weld and sheets thickness on the fatigue life of the of the spot-weld joints to predict the lifetime and location of the weakest spot-welds due to the variable amplitude loading conditions. A simple model was used to illustrate the technique of spot-weld fatigue analysis. Finite element model and analysis were carried out utilizing the finite element analysis commercial codes. Linear elastic finite element analysis was carried out to predict the stress state along the weld direction. It can be seen from the results that the predicted life greatly influence the sheet thickness, nugget diameter and loading conditions of the model. Acquired results were shown the predicted life for the nugget and the two sheets around the circumference of the spot-weld at which angle the worst damage occurs. The spot-welding fatigue analysis techniques are awfully essential for automotive structure design.

  17. Experimental analysis of the fatigue life of threaded pipe connections under cyclic bending

    OpenAIRE

    Van Wittenberghe, Jeroen; Galle, Timothy; De Waele, Wim; DE BAETS, Patrick

    2012-01-01

    When subjected to cyclic loads, fatigue cracks can cause failure of pipe systems joined by threaded pipe connections. In this study, the effect of contact conditions and coupling geometry is investigated experimentally. Fatigue tests under cyclic bending are carried out on three different threaded connection configurations. The resulting fatigue lives are compared and fracture surfaces are investigated. The fatigue cracks are found to initiate at the last engaged thread of the pin and fatigue...

  18. The Effects of Mechanical Properties on Fatigue Behavior of ECAPed AA7075

    Science.gov (United States)

    Kaya, Hasan; Uçar, Mehmet

    2016-03-01

    In this study, the effects of equal channel angular pressing (ECAP) on high-cycle fatigue and fatigue surface morphology of AA7075 have been investigated at a constant temperature (483 K) and the "C" route for four passes at ECAP process. ECAPed and as-received specimens were tested by four-point bending fatigue device. Fatigue tests were carried out by using 100, 120 and 140 MPa strength values. ECAPed specimens were characterized for each pass with optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectroscope (EDS), transmission electron microscope (TEM), selected area electron diffraction (SAED) and hardness measurements. Fracture surfaces of the specimens were also characterized with SEM. The results show that the highest hardness values (137 HV) and the best fatigue life (5.4 × 107 for 100 MPa) were measured in ECAPed four-pass sample. For this reason hardness values and fatigue life were increased with increasing number of severe plastic deformation (SPD) process.

  19. A New Ductility Exhaustion Model for High Temperature Low Cycle Fatigue Life Prediction of Turbine Disk Alloys

    Science.gov (United States)

    Zhu, Shun-Peng; Huang, Hong-Zhong; Li, Haiqing; Sun, Rui; Zuo, Ming J.

    2011-06-01

    Based on ductility exhaustion theory and the generalized energy-based damage parameter, a new viscosity-based life prediction model is introduced to account for the mean strain/stress effects in the low cycle fatigue regime. The loading waveform parameters and cyclic hardening effects are also incorporated within this model. It is assumed that damage accrues by means of viscous flow and ductility consumption is only related to plastic strain and creep strain under high temperature low cycle fatigue conditions. In the developed model, dynamic viscosity is used to describe the flow behavior. This model provides a better prediction of Superalloy GH4133's fatigue behavior when compared to Goswami's ductility model and the generalized damage parameter. Under non-zero mean strain conditions, moreover, the proposed model provides more accurate predictions of Superalloy GH4133's fatigue behavior than that with zero mean strains.

  20. Comparison of fatigue life prediction based on local strains and nominal stresses respectively

    International Nuclear Information System (INIS)

    Fatigue life predictions based on local strains and nominal stresses respectively have been performed for notched cylindrical bending test specimens (Ksub(t)=1.4, 2.2, 3.3) made of steel 42 Cr Mo 4, Ck 45 and 49 Mn CS 3 under random loading. The results of calculation are compared with relevant test results. The accuracy of the life prediction based on local strains increases the more informations of the notched specimen (e. g. endurance limit, S-N-curve etc.) will be taken into consideration for the life calculation. In the main the accuracy of life prediction based on nominal stresses is dependent on the slope of the S-N-curve assumed to be valid below the endurance limit. By application of relative Miner's rule life prediction can be improved if relevant test results are available. The comparison of the two prediction methods investigated reveals no favour for one of them. Hence, the decision which method should be applied depends on the special problems to be solved. (orig.)

  1. Analytical Method to Estimate Fatigue Life Time Duration in Service for Runner Blade Mechanism of Kaplan Turbines

    Directory of Open Access Journals (Sweden)

    Ana – Maria Budai

    2010-10-01

    Full Text Available The paper present an analytical method that can be used to determianted fatigue life time duration in service for runner blade mechanism of Kaplan turbines. The study was made for lever button of runer blade mechanism using two analytical relation to calculate the maximum number of stress cycles whereupon the mechanism work without any damage. To estimate fatigue life time duration will be used a formula obtained from one of most comon cumulative damage methodology taking in consideration the real exploatation conditions of a specified Kapaln turbine.

  2. 高温条件下NiCrMoV转子钢焊接接头的高周疲劳性能研究%INVESTIGATION ON HIGH TEMPERATURE HIGH CYCLE FATIGUE PROPERTY OF THE WELDING JOINT FOR NiCrMoV ROTOR STEEL

    Institute of Scientific and Technical Information of China (English)

    刘鹏; 芦凤桂; 刘霞; 高玉来

    2013-01-01

    The fatigue crack initiation and propagation of the simulated rotor (30Cr2Ni4MoV) used in steam turbine was investigated by the repeated high-cycle tensile and compressive test with stress ratio R =-1.The fatigue fracture morphology was observed by the scanning electron microscope (SEM),and the composition of the selected zone was analyzed by the energy dispersive spectroscopy (EDS).For the welded rotor steel of 30Cr2Ni4MoV,the inclusions basically consisted of oxides,such as Al2O3,CaO,MgO and SiO2,etc.The results revealed that the fatigue crack generally occurred at the inclusions and pores,leading to fish-eye propagation around the defects.In addition,the effective projected area parameter model was applied to calculate the critical size of the defect causing crack initiation.Based on the present results,in order to improve the fatigue property of rotor steel,some effective measures should be adopted to control the size,shape and distribution of the defects.%通过应力比R=-1的拉压高周疲劳实验,研究了在370℃条件下汽轮机转子模拟件焊接接头的高周疲劳裂纹的萌生和扩展过程.通过扫描电子显微镜(SEM)和能谱(EDS)分析了疲劳断口的形貌特征和微区成分.研究结果表明:对于30Cr2Ni4MoV转子钢焊接接头而言,夹杂物主要成分为氧化物(Al2O3、CaO、MgO和SiO2等),疲劳裂纹往往萌生于夹杂物和气孔等内部缺陷.采用有效投影面积模型计算出母材和焊缝区域组织对应的临界缺陷尺寸,建立了夹杂物尺寸和疲劳裂纹萌生区域之间的关系.基于该研究结果,采取适当措施减少其内部的缺陷尺寸,并优化其形态和分布,以提高转子钢材料的抗疲劳性能.

  3. Fatigue Crack Growth Threshold Testing of Metallic Rotorcraft Materials

    Science.gov (United States)

    Newman, John A.; James, Mark A.; Johnson, William M.; Le, Dy D.

    2008-01-01

    Results are presented for a program to determine the near-threshold fatigue crack growth behavior appropriate for metallic rotorcraft alloys. Four alloys, all commonly used in the manufacture of rotorcraft, were selected for study: Aluminum alloy 7050, 4340 steel, AZ91E Magnesium, and Titanium alloy Ti-6Al-4V (beta-STOA). The Federal Aviation Administration (FAA) sponsored this research to advance efforts to incorporate damage tolerance design and analysis as requirements for rotorcraft certification. Rotorcraft components are subjected to high cycle fatigue and are typically subjected to higher stresses and more stress cycles per flight hour than fixed-wing aircraft components. Fatigue lives of rotorcraft components are generally spent initiating small fatigue cracks that propagate slowly under near-threshold cracktip loading conditions. For these components, the fatigue life is very sensitive to the near-threshold characteristics of the material.

  4. Microstructural Influence on Deformation and Fatigue Life of Composites Using the Generalized Method of Cells

    Science.gov (United States)

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

    2015-01-01

    A fully coupled deformation and damage approach to modeling the response of composite materials and composite laminates is presented. It is based on the semi-­-analytical generalized method of cells (GMC) micromechanics model as well as its higher fidelity counterpart, HFGMC, both of which provide closed-form constitutive equations for composite materials as well as the micro scale stress and strain fields in the composite phases. The provided constitutive equations allow GMC and HFGMC to function within a higher scale structural analysis (e.g., finite element analysis or lamination theory) to represent a composite material point, while the availability of the micro fields allow the incorporation of lower scale sub­-models to represent local phenomena in the fiber and matrix. Further, GMC's formulation performs averaging when applying certain governing equations such that some degree of microscale field accuracy is surrendered in favor of extreme computational efficiency, rendering the method quite attractive as the centerpiece in a integrated computational material engineering (ICME) structural analysis; whereas HFGMC retains this microscale field accuracy, but at the price of significantly slower computational speed. Herein, the sensitivity of deformation and the fatigue life of graphite/epoxy PMC composites, with both ordered and disordered microstructures, has been investigated using this coupled deformation and damage micromechanics based approach. The local effects of fiber breakage and fatigue damage are included as sub-models that operate on the microscale for the individual composite phases. For analysis of laminates, classical lamination theory is employed as the global or structural scale model, while GMC/HFGMC is embedded to operate on the microscale to simulate the behavior of the composite material within each laminate layer. A key outcome of this study is the statistical influence of microstructure and micromechanics idealization (GMC or HFGMC) on

  5. Fatigue Life Prediction of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures. Part I: Experimental Analysis

    Science.gov (United States)

    Longbiao, Li

    2016-04-01

    This paper presents an experimental analysis on the fatigue behavior in C/SiC ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply and 2.5D woven, at room and elevated temperatures in air atmosphere. The experimental fatigue life S - N curves of C/SiC composites corresponding to different stress levels and test conditions have been obtained. The damage evolution processes under fatigue loading have been analyzed using fatigue hysteresis modulus and fatigue hysteresis loss energy. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different peak stress, fiber preforms and test conditions have been estimated. It was found that the degradation of interface shear stress and fibres strength caused by oxidation markedly decreases the fatigue life of C/SiC composites at elevated temperature.

  6. Pre-crack fatigue life assessment of relevant aircraft materials using fractal analysis of eddy current test data

    Science.gov (United States)

    Schreiber, Jürgen; Cikalova, Ulana; Hillmann, Susanne; Meyendorf, Norbert; Hoffmann, Jochen

    2013-01-01

    Successful determination of residual fatigue life requires a comprehensive understanding of the fatigue related material deformation mechanism. Neither macroscopic continuum mechanics nor micromechanic observations provide sufficient data to explain subsequent deformation structures occurring during the fatigue life of a metallic structure. Instead mesomechanic deformation on different scaling levels can be studied by applying fractal analysis of various means of nondestructive inspection measurements. The resulting fractal dimension data can be correlated to the actual material damage states, providing an estimation of the remaining residual fatigue life before macroscopic fracture develops. Recent efforts were aimed to apply the fractal concept to aerospace relevant materials AA7075-T6 and Ti-6Al-4V. Proven and newly developed fractal analysis methods were applied to eddy current (EC) measurements of fatigued specimens, with the potential to transition this approach to an aircraft for an in-situ nondestructive inspection. The occurrence of mesomechanic deformation at the material surface of both AA7075-T6 and Ti-6Al-4V specimens could be established via topography images using confocal microscopy (CM). Furthermore, a pulsed eddy current (PEC) approach was developed, combined with a sophisticated new fractal analysis algorithm based on short pulse excitation and evaluation of EC relaxation behavior. This paper presents concept, experimental realization, fractal analysis procedures, and results of this effort.

  7. Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

    Directory of Open Access Journals (Sweden)

    Bendouba Mostefa

    2012-12-01

    Full Text Available Hole cold expansion (HCE is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model.

  8. Improvements in the microstructure and fatigue behavior of pure copper using equal channel angular extrusion

    Institute of Scientific and Technical Information of China (English)

    J Nemati; GH Majzoobi; S Sulaiman; BTHT Baharudin; MAAzmah Hanim

    2014-01-01

    In this study, annealed pure copper was extruded using equal channel angular extrusion (ECAE) for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life con-tinued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses (or high-cycle fatigue), a maximum increase in fatigue resistance of approximately 500%was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000%was obtained for high-applied stresses (or low-cycle fatigue). Optical microscopic examinations revealed grain refinements in the range of 32 to 4 µm. A maximum increase in impact energy absorption of 100%was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the ex-truded material during fatigue tests.

  9. Fatigue life prediction method for gas turbine rotor disk alloy FV 535. Gas turbine yo rotor disk zai FV 535 gokin no hiro jumyo suitei ho

    Energy Technology Data Exchange (ETDEWEB)

    Horikawa, Takeshi; Okada, Tomonobu; Tsunenari, Toshiyasu (Ryukoku Univ., Faculty of Science and Technology, Otsu (Japan) Kawasaki Heavy Industries Ltd., Kobe (Japan))

    1990-01-15

    A rotor disk of jet engine and/or gas turbine has serrated parts and bolt holes which are the most important parts necessary for fatigue strength evaluation. Fatigue life prediction method for serrated parts have been studied with carbon steel and some kinds of alloyed steel, but it is not verified yet whether the method may be adaptible to gas turbine rotor alloys. Fatigue tests were carried out for a smooth specimen and a notched specimen made of the rotor disk material to study the adaptability of the already proposed fatigue crack initiation life prediction method. The following conclusions were obtained from the experimental study. The fatigue crack initiation life of a notched specimen under constant stress amplitude can be well predicted by Koe {prime} s or Neuber {prime} s method. The proposed fatigue life prediction method may well predict the fatigue life of a smooth specimen in the region of higher stress level than the fatigue limit by using the interaction coefficient of C = 0.3. On the other hand, the method predicted very conservative life and the coefficient C was more than 5 in the region of stress near the fatigue limit. 12 refs., 7 figs., 4 tabs.

  10. Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 Degree-Sign C

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xiang, E-mail: chenx@ornl.gov [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States); Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Sokolov, Mikhail A.; Sham, Sam; Erdman III, Donald L.; Busby, Jeremy T. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Mo, Kun; Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

    2013-01-15

    Creep-fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 Degree-Sign C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep-fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep-fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep-fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep-fatigue life. The linear damage summation could predict the creep-fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep-fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep-fatigue life prediction results for both materials.

  11. The characteristics of fatigue symptoms and their association with the life style and the health status in school children.

    Science.gov (United States)

    Okamoto, M; Tan, F; Suyama, A; Okada, H; Miyamoto, T; Kishimoto, T

    2000-07-01

    In order to evaluate the characteristics of fatigue symptoms and their association with the life style and the health status, we examined using data accumulated by the longitudinal surveys from 1992 to 1998, in 118 six-year primary school children and 129 second-year junior high school children. The complaints of "drowsiness and dullness", such as "become drowsy" (71%), "give a yawn" (59%) and "want to lie down" (51%), respectively, were most frequently observed. The proportion of these complaints was high before the first morning class, but decreased when the children leave school. Notably, the complaints of "difficulty in concentration" annually have increased. Children with undesirable eating habits, particularly those who often eat salty foods, or poor life style, such as staying up late at night tended to have more complaints of fatigue symptoms. By correlation analysis, these complaints were significantly related to the obesity degree, blood pressure, HDL cholesterol and atherogenic index. These results support the hypothesis that fatigue symptoms increase or are associated with life style and health status. Consequently, it is necessary to improve the life style such as dietary habits and rhythm of life for the reduction of fatigue symptom. PMID:10959606

  12. Analysis of Fatigue Crack Growth in Longitudinals of Ship Hull and Fatigue Life%船体纵骨疲劳裂纹扩展及寿命分析

    Institute of Scientific and Technical Information of China (English)

    何文涛; 刘敬喜; 解德

    2015-01-01

    Based on ABAQUS in python scripting language, and combined with virtual crack closure technique, a program (FCG-System) is developed to simulate the growth of fatigue crack. The crack in a typical longitudinal connection of an oil tanker is simulated. Crack growth path and fatigue life is discussed under lateral pressure load and axial tension load respectively. Results indicate that crack growth paths are different under these two load conditions and the fatigue lives before the fractures of face-plate occupy a large proportion in total life.%基于有限元软件 ABAQUS,结合虚拟裂纹闭合法、裂纹扩展判据及子结构技术,应用脚本语言 Python开发了模拟疲劳裂纹扩展的程序(FCG-System)。对含初始裂纹的油船纵骨节点疲劳裂纹扩展进行数值模拟,并探讨侧向压力和轴向拉力这两种载荷对疲劳裂纹扩展路径和疲劳寿命的影响。结果表明,两种加载方式下裂纹扩展路径不同,且面板断裂前的疲劳寿命在总寿命中占据很大的成分。

  13. A case study on relation between roughness, lubrication and fatigue life of rolling bearings

    Science.gov (United States)

    Balan, M. R.; Tufescu, A.; Cretu, S. S.

    2016-08-01

    A spherical roller bearing under high radial loading, constant speed and imposed roughness for the contacting surfaces was chosen as case study. Different lubrication regimes were obtained by varying oil viscosity through the operating temperature. For bearings with especially machined contacting surfaces, λ-ratio is firstly determined and its value is used to estimate the particular value of the lubrication parameter κ. Using the λ-ratio approach the paper reveals the relationship between roughness amplitude and the modified rating life of rolling bearings. The roughness values corresponding to good manufacturing practice are possible to be determined for each particular case. Three groups of random Gaussian roughness were generated with the same values for the Ra parameter as used in the modified lives investigations. For medium and especially high radial loads, the contacts between rough surfaces develop, inside the shallow layer, von Mises equivalent stresses higher than the fatigue limit stress. For condition of lack of lubricant or starved lubrication, these findings explain the initiation of the rolling contact fatigue in the shallow layer, close to contacting surfaces.

  14. EFFECTS OF MODIFICATION OF THE CARBIDE CHARACTERISTICS THROUGH GRAIN BOUNDARY SERRATION ON CREEP-FATIGUE LIFE IN AUSTENITIC STAINLESS STEELS

    Institute of Scientific and Technical Information of China (English)

    K.J.Kim; H.U.Hong; K.S.Min; S.W.Nam

    2004-01-01

    Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides vere observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample vith planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.

  15. Comparative Study of Fatigue Damage Models Using Different Number of Classes Combined with the Rainflow Method

    Directory of Open Access Journals (Sweden)

    S. Zengah

    2013-06-01

    Full Text Available Fatigue damage increases with applied load cycles in a cumulative manner. Fatigue damage models play a key role in life prediction of components and structures subjected to random loading. The aim of this paper is the examination of the performance of the “Damaged Stress Model”, proposed and validated, against other fatigue models under random loading before and after reconstruction of the load histories. To achieve this objective, some linear and nonlinear models proposed for fatigue life estimation and a batch of specimens made of 6082T6 aluminum alloy is subjected to random loading. The damage was cumulated by Miner’s rule, Damaged Stress Model (DSM, Henry model and Unified Theory (UT and random cycles were counted with a rain-flow algorithm. Experimental data on high-cycle fatigue by complex loading histories with different mean and amplitude stress values are analyzed for life calculation and model predictions are compared.

  16. Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720

    Science.gov (United States)

    Gabb, T. P.; Telesman, J.; Kantzos, P. T.; Bonacuse, P. J.; Barrie, R. L.

    2002-01-01

    The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.

  17. Specimen Design for Fatigue Testing at Very High Frequencies

    Science.gov (United States)

    MATIKAS, T. E.

    2001-11-01

    Components in rotational machinery such as turbine blades used in military aircraft engines are subjected to low-amplitude, high-frequency loads in the kHz range. Under high cycle fatigue (HCF), the initiation state of a crack consumes most of the life of the component. Vibratory stresses may therefore result in unexpected failures of the material. Hence, there is a need for HCF studies to address HCF-related failures of turbine engines and to develop a life prediction methodology. Ultrasonic fatigue provides accelerated HCF testing enabling the simulation of realistic loading conditions for testing materials used in structural components subjected to vibratory stresses. Specimen design is critical for optimum ultrasonic fatigue testing. The objective of this study is therefore to develop analytical modelling necessary for the design of test coupons to be fatigue tested at ultrasonic frequencies.

  18. Fatigue properties of ductile cast iron containing chunky graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ferro, P., E-mail: ferro@gest.unipd.it [Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, I-36100 Vicenza (Italy); Lazzarin, P.; Berto, F. [Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, I-36100 Vicenza (Italy)

    2012-09-30

    Highlights: Black-Right-Pointing-Pointer Experimental determination of high cycle fatigue properties of EN-GJS-400. Black-Right-Pointing-Pointer Evaluation of the influence of chunky graphite morphology on fatigue life. Black-Right-Pointing-Pointer Metallurgical analysis and microstructural parameters determination. Black-Right-Pointing-Pointer Nodule counting and nodularity rating. - Abstract: This work deals with experimental determination of high cycle fatigue properties of EN-GJS-400 ductile cast iron containing chunky graphite. Constant amplitude axial tests were performed at room temperature under a nominal load ratio R = 0. In order to evaluate the influence of chunky graphite morphology on fatigue life, fatigue tests were carried out also on a second set of specimens without this microstructural defect. All samples were taken from the core of a large casting component. Metallurgical analyses were performed on all the samples and some important microstructural parameters (nodule count and nodularity rating, among others) were measured and compared. It was found that a mean content of 40% of chunky graphite in the microstructure (with respect to total graphite content) does not influence significantly the fatigue strength properties of the analysed cast iron. Such result was attributed to the presence of microporosity detected on the surface fracture of the specimens by means of electron scanning microscope.

  19. The life estimation of turbine rotor through fracture mechanics and fatigue analysis

    International Nuclear Information System (INIS)

    Stress analysis for High Pressure Turbine Rotor of Korea Nuclear Power Unit 9/10 was carried out by finite element method. And, using the greatest value of stress output, the maximum allowable non-metallic inclusion size and the operating cycle limit at bore surface were calculated through linear elastic fracture mechnics and low cycle fatigue theory respectively; the inclusion smaller than 14.3mm in length was safe from brittle fracture regardless of its existing position and crack initiating life was 3886 cycles under the most severe starting condition. FEM program TDROTOR(Temperature Distribution of was developed to calculate temperature distribution of Rotor by heat transfer from hot steam, and centrifugal, thermal and total stress components were calculated by SAROTOR(Stress Analysis of ROTOR). Both FEM codes used axi-symmetric, quadrilateral element, and plasticity was not considered. (Author)

  20. The effect of corrosion on the fatigue life of aluminum alloys

    Science.gov (United States)

    Dalla, P. T.; Tragazikis, I. K.; Exarchos, D. A.; Matikas, T. E.

    2016-04-01

    The corrosion behavior of metallic structures is an important factor of material performance. In case of aluminum matrix composites corrosion occurs via electrochemical reactions at the interface between the metallic matrix and the reinforcement. The corrosion rate is determined by equilibrium between two opposing electrochemical reactions, the anodic and the cathodic. When these two reactions are in equilibrium, the flow of electrons from each reaction type is balanced, and no net electron flow occurs. In the present study, aluminum alloy tensile-shape samples are immersed in NaCl solution with an objective to study the effect of the controlled pitting corrosion in a specific area. The rest of the material is completely sealed. In order to investigate the effect of pitting corrosion on the material performance, the specimens were subjected to cyclic loading. The effect of corrosion on the fatigue life was assessed using two complimentary nondestructive methods, infrared thermography and acoustic emission.

  1. Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect...... on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries...... (Spain and Germany) with high wind energy penetration it is mandatory or under bonus to retrofit these fixed speed wind turbines and provide ride through capability. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generators poorly damped...

  2. Development of a device to study fatigue life of fixed partial dentures

    Science.gov (United States)

    Gutierrez, S. C.; Meseguer, M. D.; Estal, R.; Folguera, F.; Vidal, V.

    2012-04-01

    Fixed partial dentures can be fabricated by means of different materials and with different manufacturing processes. In order to establish possible differences among them, their behaviour, as fatigue life or cement shear bond strength, have to be evaluated. This article presents a modular, economic and robust device to evaluate fixed partial dentures and dental crowns. A base to support the fixed partial dentures and a device to simulate masticatory loads have been developed. The device has got a simple design. It is based on a pneumatic piston, with a pressure regulator to control masticatory loads. On a first stage, only vertical forces have been taking into account. However, the device will allow simulating tangential masticatory loads on the other axis, studying the behaviour of the fixed partial dentures submerged in a solution similar to saliva, changing masticatory load application, etc. with little modifications.

  3. Standard test method for ambient temperature fatigue life of metallic bonded resistance strain gages

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2003-01-01

    1.1 This test method covers a uniform procedure for the determination of strain gage fatigue life at ambient temperature. A suggested testing equipment design is included. 1.2 This test method does not apply to force transducers or extensometers that use bonded resistance strain gages as sensing elements. 1.3 Strain gages are part of a complex system that includes structure, adhesive, gage, leadwires, instrumentation, and (often) environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further complication is that strain gages, once installed, normally cannot be reinstalled in another location. Therefore, it is not possible to calibrate individual strain gages; performance characteristics are normally presented on a statistical basis. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices ...

  4. Magnitude of fatigue in cancer patients receiving radiotherapy and its short term effect on quality of life

    Directory of Open Access Journals (Sweden)

    Janaki M

    2010-01-01

    Full Text Available Background : Fatigue is one of the most common, ongoing symptoms reported by patients undergoing radiotherapy and has profound effects on the quality of life. Aims : This study attempts to identify the magnitude of fatigue and its implication on the quality of life during radiotherapy. Methods and Materials : A prospective study was conducted from March 2004 to September 2005, on 90 patients with histologically proven cancer, receiving radiotherapy. Pretreatment and weekly assessment of fatigue and QOL was done during radiation treatment using Brief Fatigue Inventory Scale and EORTC QLQ C30 respectively and repeated one month after completion of radiotherapy. All the scores were measured in the 0 to 100 scale. Statistical Methods Used : Trimean, SPSS 11.0 and Sysstat 8.0 were used for statistical analysis. Results : Fatigue was present in 87.8% of patients initially and increased gradually over the course of radiotherapy and peaked in the last week. However at follow up it was nearing the pretreatment level. There was significant reduction in the functional scores ( P < 0.001 of QOL (physical, role and emotional function, which returned to pretreatment level at follow up. In the seventh week impairment of cognitive function (P=0.059 was noted. Significant reduction of social function (P < 0.001 at second week and global health status (P < 0.001 at fifth week was noted while financial difficulty was seen from second week onwards. Conclusion : Fatigue is transiently increased by radiotherapy before reaching pretreatment level after few weeks of completion of radiotherapy. QOL is also affected by fatigue which follows the same pattern.

  5. Sleep, Fatigue and Quality of Life: A Comparative Analysis among Night Shift Workers with and without Children

    Science.gov (United States)

    Fernandes-Junior, Silvio Araújo; Ruiz, Francieli Silva; Antonietti, Leandro Stetner; Tufik, Sergio; Túlio de Mello, Marco

    2016-01-01

    Introduction The reversal of the natural cycle of wakefulness and sleep may cause damage to the health of workers. However, there are few studies evaluating sleep, fatigue and quality of life of night shift workers considering the influence of small children on these variables. Aims Evaluate the sleep time, fatigue and quality of life of night shift workers and verify the relationship between these variables with the presence or absence of children in different age groups. Methods Were evaluated 78 mens shiftworkers, with or without children. Group 1, workers without children (G1-NC), group 2, workers with children pré-school age (G2-PS) and group 3, workers with children school age (G3-S). The sleep time (ST), sleep efficiency (SE), sleep latency (SL) and maximum time awake (MTA) were recorded by actigraphy. The risk of being fatigued at work was estimated by risk index for fatigue (RIF). Results The G1-NC showed a longer ST on working days and when evaluated only the first nights shift, after day off (pMTA on day off was lower in the workers from G2-PS. The RIF was lower on G1-NC in the first nights shift compared to the other groups. Conclusion In this research, workers without children had higher sleep time during the working days. These workers also were less likely to feel fatigued during night work than workers with children, regardless of age these children. PMID:27391478

  6. STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A cyclic plasticity model is used into finite element (FE) method to obtain the details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteria in multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue lives are in favorable agreement with the experimental results for machined bolts.

  7. Ultrasonic fatigue testing in the scanning electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Soeker, Marcus; Krupp, Ulrich [University of Applied Sciences, Osnabrueck (Germany). Inst. of Materials Design and Structural Integrity; Galster, Michael [Novelis Inc., Goettingen (Germany); Doenges, Benjamin [Siegen Univ. (Germany)

    2016-02-01

    The continuing trend to increase the performance and durability of machines requires the use of materials, whose structural integrity must be ensured far beyond the classical fatigue limit. In this so-called ''very high cycle fatigue'' regime (VHCF), the materials show a strong scatter in fatigue life, which makes life service assessment difficult. Present studies on austenitic-ferritic duplex steel 1.4462 (X2CrNiMoN22-5-3) have shown that the reason of this scatter in fatigue life can be found in the microstructural length scale mainly due to the barrier effect of grain and phase boundaries. The integration of an ultrasonic fatigue testing system in a high-resolution scanning electron microscope allows observing and evaluating the active microstructural mechanisms of fatigue crack initiation and early crack propagation, such as the formation and propagation of slip bands, during the majority of VHCF life. Additional micro texture measurements by electron backscatter diffraction (EBSD) provide data for the development of a mechanism-oriented numerical short crack simulation. In the context of crack initiation and propagation in the VHCF regime in duplex stainless steel, the focus of the present paper is put on the technical realization of the in-situ ultrasonic fatigue testing in the scanning electron microscope.

  8. Ultrasonic fatigue testing in the scanning electron microscope

    International Nuclear Information System (INIS)

    The continuing trend to increase the performance and durability of machines requires the use of materials, whose structural integrity must be ensured far beyond the classical fatigue limit. In this so-called ''very high cycle fatigue'' regime (VHCF), the materials show a strong scatter in fatigue life, which makes life service assessment difficult. Present studies on austenitic-ferritic duplex steel 1.4462 (X2CrNiMoN22-5-3) have shown that the reason of this scatter in fatigue life can be found in the microstructural length scale mainly due to the barrier effect of grain and phase boundaries. The integration of an ultrasonic fatigue testing system in a high-resolution scanning electron microscope allows observing and evaluating the active microstructural mechanisms of fatigue crack initiation and early crack propagation, such as the formation and propagation of slip bands, during the majority of VHCF life. Additional micro texture measurements by electron backscatter diffraction (EBSD) provide data for the development of a mechanism-oriented numerical short crack simulation. In the context of crack initiation and propagation in the VHCF regime in duplex stainless steel, the focus of the present paper is put on the technical realization of the in-situ ultrasonic fatigue testing in the scanning electron microscope.

  9. Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

    Energy Technology Data Exchange (ETDEWEB)

    Dorman, M. [Department of Aerospace Engineering, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Toparli, M.B. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Smyth, N.; Cini, A. [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Fitzpatrick, M.E. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Irving, P.E., E-mail: p.e.irving@cranfield.ac.uk [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer Effect of laser peen intensity on local residual stress fields in 2024 aluminium. Black-Right-Pointing-Pointer Peening induces significant changes in surface topography and local hardness. Black-Right-Pointing-Pointer Residual stress at peen spot centre in tension, spot overlap in compression. Black-Right-Pointing-Pointer Notched fatigue lives increased; crack morphology correlated to residual stress field. Black-Right-Pointing-Pointer Large peening power densities can cause fatigue life reduction in notched samples. - Abstract: Laser peening at a range of power densities has been applied to 2 mm-thick sheets of 2024 T351 aluminium. The induced residual stress field was measured using incremental hole drilling and synchrotron X-ray diffraction techniques. Fatigue samples were subjected to identical laser peening treatments followed by scribing at the peen location to introduce stress concentrations, after which they were fatigue tested. The residual stresses were found to be non-biaxial: orthogonal to the peen line they were tensile at the surface, moving into the desired compression with increased depth. Regions of peen spot overlap were associated with large compression strains; the centre of the peen spot remaining tensile. Fatigue lives showed moderate improvement over the life of unpeened samples for 50 {mu}m deep scribes, and slight improvement for samples with 150 {mu}m scribes. Use of the residual stress intensity K{sub resid} approach to calculate fatigue life improvement arising from peening was unsuccessful at predicting the relative effects of the different peening treatments. Possible reasons for this are explored.

  10. The relationship between cough-specific quality of life and abdominal muscle endurance, fatigue, and depression in patients with COPD

    Science.gov (United States)

    Arikan, Hulya; Savci, Sema; Calik-Kutukcu, Ebru; Vardar-Yagli, Naciye; Saglam, Melda; Inal-Ince, Deniz; Coplu, Lutfi

    2015-01-01

    Background Cough is a prevalent symptom that impacts quality of life in COPD. The aim of this study was to assess the relationship between cough-specific quality of life, abdominal muscle endurance, fatigue, and depression in stable patients with COPD. Methods Twenty-eight patients with COPD (mean age 60.6±8.7 years) referred for pulmonary rehabilitation participated in this cross-sectional study. Sit-ups test was used for assessing abdominal muscle endurance. Leicester Cough Questionnare (LCQ) was used to evaluate symptom-specific quality of life. Fatigue perception was evaluated with Fatigue Impact Scale (FIS). Beck Depression Inventory (BDI) was used for assessing depression level. Results The LCQ total score was significantly associated with number of sit-ups; BDI score; FIS total; physical, cognitive, and psychosocial scores (P<0.05). Scores of the LCQ physical, social, and psychological domains were also significantly related with number of sit-ups, FIS total score, and BDI score (P<0.05). FIS total score and number of sit-ups explained 58% of the variance in LCQ total score (r=0.76, r2=0.577, F(2–20)=12.296, P<0.001). Conclusion Chronic cough may adversely affect performance in daily life due to its negative effect on fatigue and decrease abdominal muscle endurance in patients with COPD. Decreased cough-related quality of life is related with increased level of depression in COPD patients. Effects of increased abdominal muscle endurance and decreased fatigue in COPD patients with chronic cough need further investigation. PMID:26379433

  11. Thermal fatigue of pipes induced by fluid temperature change (18). Applicability of crack growth law based on continuum fracture mechanics criterion to small fatigue cracks

    International Nuclear Information System (INIS)

    High cycle thermal fatigue failure of pipes induced by fluid temperature change is one of the interdisciplinary issues to be concerned for long term structural reliability of high temperature components in energy systems. In order to explore advanced life assessment methods to prevent the failure, fatigue crack propagation tests were earned out in an austenitic stainless steel. Special attention was paid to the applicability of continuum fracture mechanics treatment to small or short cracks. It was shown exponentially that the crack propagation analysis based on continuum fracture mechanics was almost successfully applied, to the small fatigue cracks of which size was comparable to a few times of material grain size. (author)

  12. Predictions for fatigue crack growth life of cracked pipes and pipe welds using RMS SIF approach and experimental validation

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Punit, E-mail: punit@barc.gov.in [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Singh, P.K.; Bhasin, Vivek; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Pukazhendhi, D.M.; Gandhi, P.; Raghava, G. [Structural Engineering Research Centre, Chennai 600 113 (India)

    2011-10-15

    The objective of the present study is to understand the fatigue crack growth behavior in austenitic stainless steel pipes and pipe welds by carrying out analysis/predictions and experiments. The Paris law has been used for the prediction of fatigue crack growth life. To carry out the analysis, Paris constants have been determined for pipe (base) and pipe weld materials by using Compact Tension (CT) specimens machined from the actual pipe/pipe weld. Analyses have been carried out to predict the fatigue crack growth life of the austenitic stainless steel pipes/pipes welds having part through cracks on the outer surface. In the analyses, Stress Intensity Factors (K) have been evaluated through two different schemes. The first scheme considers the 'K' evaluations at two points of the crack front i.e. maximum crack depth and crack tip at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor (K{sub RMS}) at deepest and surface points. Crack growth and the crack shape with loading cycles have been evaluated. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipe and pipe welds with part through circumferential crack. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor (K{sub RMS}) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme. Fatigue crack growth in pipe weld (Gas Tungsten Arc Welding) can be predicted well using Paris constants of base material but prediction is non-conservative for pipe weld (Shielded Metal Arc Welding). Further, predictions using fatigue crack growth rate curve of ASME produces conservative results for pipe and GTAW pipe welds and comparable results for SMAW pipe welds. - Highlights: > Predicting fatigue crack growth of Austenitic Stainless Steel pipes and pipe welds. > Use of RMS-SIF and

  13. Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach,Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN/MSC.NASTRAN and fatigue life prediction was carried out using MSC.FATIGUE software. Based on the finite element results, different frequency response approach was applied to predict the cylinder block fatigue life. Results for different load histories and material combinations are also discussed. Results indicated great effects for all surface finish and treatment. It is concluded that polished and cast surface finish conditions give the highest and lowest cylinder block lives, respectively; and that Nitrided treatment leads to longest cylinder block life. The results were used to draw contour plots of fatigue life and damage in the worst or most damaging case.

  14. Effect of Surface Nanocrystallization on Fatigue Behavior of Pure Titanium

    Science.gov (United States)

    Wang, Qi; Sun, Qiaoyan; Xiao, Lin; Sun, Jun

    2016-01-01

    The high-cycle fatigue behavior was investigated in pure titanium after surface nanocrystallization (SNC Ti). Compared with the coarse-grained titanium (CG Ti) samples, the SNC Ti samples exhibit an improved fatigue life. The SNC has a remarkable influence on the fatigue cracks initiation and growth of pure titanium. The results show that, because the free-surface cracking is suppressed by the surface nanogradient structure in the SNC Ti, the fatigue cracks initiation sites change from the free surface to the subsurface. Meanwhile, the fatigue crack growth rate decreases due to the microstructural feature and residual compressive stress. The deformation twins in the subsurface of SNC Ti have a marked effect on the fatigue crack initiation and the crack growth. The former effect is due to the twin boundaries being preferential sites for crack initiation, while the latter is associated with the barriers that the twin boundaries pose to the propagation of dislocations. Furthermore, microstructural analysis indicates that the dislocation distribution in SNC Ti gradually becomes homogenous as fatigue processes. This homogeneous microstructure is also beneficial to the improvement of fatigue life.

  15. Multi-scale analysis of behavior and fatigue life of 304L stainless under cyclic loading with pre-hardening

    International Nuclear Information System (INIS)

    This study investigates the effects of loading history on the cyclic stress-strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension-compression tests were performed on the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after pre-loading and their evolution during the fatigue cycles were characterized by TEM. The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction. (author)

  16. An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis.

    Science.gov (United States)

    Akay, M; Aslan, N

    1995-01-01

    A fracture mechanics approach was applied to estimate the life of a prosthesis injection moulded from short carbon fibre reinforced poly ether ether ketone. Flexural modulus and strength, fracture toughness, fatigue endurance limit, fatigue crack growth rate and threshold stress intensity factor were determined. The dimensions of the test pieces were selected to yield fibre orientation and fibre length distributions similar to those obtained in the prosthesis. Stress levels generated in the prosthesis under different activities were estimated by conducting three-dimensional finite element analysis. It was shown by a fracture mechanics approach that a fatigue failure due to the propagation of an embedded elliptical slit, under these stresses, would be unlikely for a crack length smaller than 1.85 mm. However, the cement would fail under the same conditions, irrespective of the type of the prosthesis employed.

  17. Finite element analysis of sucker rod couplings with guidelines for improving fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, E.L. [Sandia National Labs., Albuquerque, NM (United States). Engineering and Structural Mechanics Div.

    1997-09-01

    The response of a variety of sucker rod couplings to an applied axial load was simulated using axisymmetric finite element models. The calculations investigated three sucker rod sizes and various combinations of the slimhole, Spiralock, and Flexbar modifications to the coupling. In addition, the effect of various make-ups (assembly tightness) on the performance of coupling was investigated. An axial load was applied to the sucker rod ranging from {minus}5 ksi to 40 ksi, encompassing three load cycles identified on a modified Goodman diagram as acceptable for indefinite service life of the sucker rods. The simulations of the various coupling geometries and make-ups were evaluated with respect to how well they accomplish the two primary objectives of preloading threaded couplings: (1) to lock the threaded coupling together so that it will not loosen and eventually uncouple, and (2) to improve the fatigue resistance of the threaded connection by reducing the stress amplitude in the coupling when subjected to cyclic loading. Perhaps the most significant finding in this study was the characterization of the coupling parameters which affect two stress measures. The mean hydrostatic stress, which determines the permissible effective alternating stress, is a function of the coupling make-up. Whereas, the alternating effective stress is a function of the relative stiffnesses of the pin and box sections of the coupling and, as long as the coupling does not separate, is unaffected by the amount of circumferential displacement applied during make-up. The results of this study suggest approaches for improving the fatigue resistance of sucker rod couplings.

  18. A STUDY OF FATIGUE LIFE OF ASPHALT CONCRETE BASED ON SHUNGITE MINERAL POWDER

    Directory of Open Access Journals (Sweden)

    D. I. Chernousov

    2011-11-01

    Full Text Available Problem statement. Shortage of mineral powder stimulates seeking of new materials and technologiesby which traditional ones can be replaced without deterioration of their operating properties. Thatis why a study of mineral powder from shungite and development of new technologies of arrangementof high quality and durable asphalt concrete pavement based on shungite is an actual problem.Results. Bearing capacity and service life of asphalt concrete pavement is most completely characterizedby modulus of elasticity and tensile bending strength. To forecast operating properties ofasphalt concrete, 4×4×16 cm beams were tested on vibrostand УВ 70/100, which enables one toobtain frequency and amplitude of oscillations continuously adjustable during operation. The techniqueuses analytical relationships which allow one to determine durability of operating period undersimulation of axis load of 6 and 10 tons. Comparison of the relationships obtained shows thatmodulus of elasticity, bending and comparison strength of involved asphalt concrete mixes markedlydecrease. However, this decrease is more pronounced with reference asphalt concretes.Conclusions. The use of shungite mineral powder provides for increasing fatigue life of asphaltconcrete, which can be related to higher adhesion activity of shungite powder compared with limestonepowder.

  19. Creep-fatigue life prediction for engine hot section materials (isotropic)

    Science.gov (United States)

    Moreno, V.

    1982-01-01

    The objectives of this program are the investigation of fundamental approaches to high temperature crack initiation life prediction, identification of specific modeling strategies and the development of specific models for component relevant loading conditions. A survey of the hot section material/coating systems used throughout the gas turbine industry is included. Two material/coating systems will be identified for the program. The material/coating system designated as the base system shall be used throughout Tasks 1-12. The alternate material/coating system will be used only in Task 12 for further evaluation of the models developed on the base material. In Task II, candidate life prediction approaches will be screened based on a set of criteria that includes experience of the approaches within the literature, correlation with isothermal data generated on the base material, and judgements relative to the applicability of the approach for the complex cycles to be considered in the option program. The two most promising approaches will be identified. Task 3 further evaluates the best approach using additional base material fatigue testing including verification tests. Task 4 consists of technical, schedular, financial and all other reporting requirements in accordance with the Reports of Work clause.

  20. Influence of grain orientation on evolution of surface features in fatigued polycrystalline copper: a comparison of thermal and uniaxial mechanical fatigue results

    CERN Document Server

    Aicheler, M

    2010-01-01

    Surface state plays a major role in the crack nucleation process of pure metals in the High-Cycle-Fatigue (HCF) as well as in the Ultra-High-Cycle-Fatigue (UHCF) regime. Therefore, in studies dealing with HCF or UHCF, special attention is paid to the evolution of surface degradation during fatigue life. The accelerating structures of the future Compact Linear Collider (CLIC) under study at CERN will be submitted to a high number of thermal-mechanical fatigue cycles, arising from Radio Frequency (RF) induced eddy currents, causing local superficial cyclic heating. The number of cycles during the foreseen lifetime of CLIC reaches 2x10(11). Fatigue may limit the lifetime of CLIC structures. In order to assess the effects of superficial fatigue, specific tests are defined and performed on polycrystalline Oxygen Free Electronic (OFE) grade Copper, a candidate material for the structures. Surface degradation depends on the orientation of near-surface grains. Copper samples thermally fatigued in two different fatigu...

  1. Creep-fatigue life prediction for different heats of Type 304 stainless steel by linear-damage rule, strain-range partitioning method, and damage-rate approach

    Energy Technology Data Exchange (ETDEWEB)

    Maiya, P.S.

    1978-07-01

    The creep-fatigue life results for five different heats of Type 304 stainless steel at 593/sup 0/C (1100/sup 0/F), generated under push-pull conditions in the axial strain-control mode, are presented. The life predictions for the various heats based on the linear-damage rule, strain-range partitioning method, and damage-rate approach are discussed. The appropriate material properties required for computation of fatigue life are also included.

  2. Fatigue Failure of Space Shuttle Main Engine Turbine Blades

    Science.gov (United States)

    Swanson, Gregrory R.; Arakere, Nagaraj K.

    2000-01-01

    Experimental validation of finite element modeling of single crystal turbine blades is presented. Experimental results from uniaxial high cycle fatigue (HCF) test specimens and full scale Space Shuttle Main Engine test firings with the High Pressure Fuel Turbopump Alternate Turbopump (HPFTP/AT) provide the data used for the validation. The conclusions show the significant contribution of the crystal orientation within the blade on the resulting life of the component, that the analysis can predict this variation, and that experimental testing demonstrates it.

  3. 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.

  4. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

    OpenAIRE

    Nuha Salim Mashaan; Mohamed Rehan Karim; Mahrez Abdel Aziz; Mohd Rasdan Ibrahim; Herda Yati Katman; Suhana Koting

    2014-01-01

    Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weigh...

  5. The relationship between cough-specific quality of life and abdominal muscle endurance, fatigue, and depression in patients with COPD

    Directory of Open Access Journals (Sweden)

    Arikan H

    2015-09-01

    Full Text Available Hulya Arikan,1 Sema Savci,2 Ebru Calik-Kutukcu,1 Naciye Vardar-Yagli,1 Melda Saglam,1 Deniz Inal-Ince,1 Lutfi Coplu31Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Hacettepe University, Ankara, Turkey; 2School of Physiotherapy and Rehabilitation, Dokuz Eylul University, Izmir, Turkey; 3Department of Chest Medicine, Faculty of Medicine, Hacettepe University, Ankara, TurkeyBackground: Cough is a prevalent symptom that impacts quality of life in COPD. The aim of this study was to assess the relationship between cough-specific quality of life, abdominal muscle endurance, fatigue, and depression in stable patients with COPD.Methods: Twenty-eight patients with COPD (mean age 60.6±8.7 years referred for pulmonary rehabilitation participated in this cross-sectional study. Sit-ups test was used for assessing abdominal muscle endurance. Leicester Cough Questionnare (LCQ was used to evaluate symptom-specific quality of life. Fatigue perception was evaluated with Fatigue Impact Scale (FIS. Beck Depression Inventory (BDI was used for assessing depression level.Results: The LCQ total score was significantly associated with number of sit-ups; BDI score; FIS total; physical, cognitive, and psychosocial scores (P<0.05. Scores of the LCQ physical, social, and psychological domains were also significantly related with number of sit-ups, FIS total score, and BDI score (P<0.05. FIS total score and number of sit-ups explained 58% of the variance in LCQ total score (r=0.76, r2=0.577, F(2–20=12.296, P<0.001.Conclusion: Chronic cough may adversely affect performance in daily life due to its negative effect on fatigue and decrease abdominal muscle endurance in patients with COPD. Decreased cough-related quality of life is related with increased level of depression in COPD patients. Effects of increased abdominal muscle endurance and decreased fatigue in COPD patients with chronic cough need further investigation.Keywords: cough, quality of

  6. The fatigue life of contoured cobalt chrome posterior spinal fusion rods.

    Science.gov (United States)

    Nguyen, T-Q; Buckley, J M; Ames, C; Deviren, V

    2011-02-01

    Intraoperative contouring of posterior rods in lumbar arthrodesis constructs introduces stress concentrations that can substantially reduce fatigue life. The sensitivity of titanium (Ti) and stainless steel (SS) to intraoperative contouring has been established in the literature; however, notch sensitivity has yet to be quantified for cobalt chrome (CoCr), which is now being advocated for use in posterior arthrodesis constructs. The goal of this study is to evaluate the sensitivity of CoCr rods to intraoperative contouring for posterior lumbar screwrod arthrodesis constructs. In this paper lumbar bilateral vertebrectomy models are constructed based on ASTM F1717-01 with curved rods (26-30 degrees total curvature) and poly-axial pedicle screws. Three types of constructs are assembled: first, 5.5 mm SS rods with SS screws (6.5 x 35 mm), second, 6.0 mm Ti rods with Ti screws (7.5 x 35 mm), and third, 6.0 mm CoCr rods with Ti screws (7.5 x 35 mm). All specimens are tested at 4 Hz in dynamic axial compression-bending with a load ratio of ten and maximum load levels of 250, 400, and 700 N until run-out at 2 000 000 cycles. Results are presented that show that the fatigue life of CoCr constructs tend to be greater than Ti constructs at all levels. At the 400 N maximum loading, CoCr lasts an average of 350 000 cycles longer than the Ti constructs. The CoCr constructs are able to sustain the 250 N load until run-out at 2 000 000 cycles but they fail at high load levels (maximum 700 N). The CoCr constructs fail at the neck of the Ti screw at high loads whereas Ti screws fail at the notch induced by contouring. Since CoCr is compatible with magnetic resonance imaging and has high static strength characteristics, the results of this study suggest that it may be an appropriate substitute for Ti. PMID:21428153

  7. Effect of twinning, slip, and inclusions on the fatigue anisotropy of extrusion-textured AZ61 magnesium alloy

    International Nuclear Information System (INIS)

    Highlights: → Twinning and detwinning was observed in the hysteresis loops of the AZ61 mg alloy. → Fatigue cracks incubated from fractured intermetallic particles in the AZ61 mg alloy. → Inclusions were more important in determining fatigue life than microstructure. → The model predicted the different fatigue lives in the two orientations tested. - Abstract: In this study, experiments were conducted to quantify structure-property relations with respect to fatigue of an extruded AZ61 magnesium alloy using a MultiStage Fatigue (MSF) model. Experiments were conducted in the extruded and transverse directions under low and high cycle strain control fatigue conditions. The cyclic behavior of this alloy displayed varying degrees of twinning and slip depending on the strain amplitude as observed in the hysteresis loops of both directions. Under low cyclic conditions, asymmetrical stress strain response was observed for both orientations. However, systematic stabilization of the hysteresis occurred by half-life due to subsequent twinning and detwinning mechanisms. In addition, under high cycle fatigue, pseudo-elasticity was observed at the first and at half-life cycles. Structure-property relations were quantified by examining the fracture surfaces of the fatigued specimens using a scanning electron microscope. In terms of crack incubation, fatigue cracks were found to initiate from intermetallic particles (inclusions) that were typically larger than the mean size. Quantified sources of fatigue crack incubation, microstructurally small cracks, and cyclic stress-strain behavior were correlated to the MSF model. Based on the specific material parameters, the MSF model was able to predict the difference in the strain-life results of the AZ61 magnesium alloy in the extruded and extruded transverse directions including the scatter of the experimental results. Finally, the MSF model revealed that the inclusion size was more important in determining the fatigue life than

  8. Perception of fatigue and quality of life in patients with COPD

    NARCIS (Netherlands)

    Breslin, E; van der Schans, C; Breukink, S; Meek, P; Mercer, K; Volz, W; Louie, S

    1998-01-01

    Introduction: Although dyspnea is considered the primary activity-limiting symptom in patients with COPD, other symptoms, such as fatigue, are frequently reported, The purpose of this study was to determine the relationship between fatigue and pulmonary function, exercise tolerance, depression, and

  9. Effect of Cryorolling and Aging on Fatigue Behavior of Ultrafine-grained Al6061

    Science.gov (United States)

    Yadollahpour, M.; Hosseini-Toudeshky, H.; Karimzadeh, F.

    2016-05-01

    The effects of cryorolling (rolling at liquid nitrogen temperature) and heat treatment on tensile and high-cycle fatigue properties and fatigue crack growth rate of Al6061 alloy have been investigated in the present work. First, the solid solution-treated bulk Al6061 alloy was subjected to cryorolling with 90% total thickness reduction and subsequent short annealing at 205°C for 5 min and peak aging at 148°C for 39 h to achieve grain refinement and simultaneous improvement of the strength and ductility. Then, hardness measurements, tensile tests, fatigue life, and fatigue crack growth rate tests including fractography analyses using scanning electron microscopy were performed on bulk Al6061 alloy, cryorolled (CR), and cryorolled material followed by peak aging (PA). The PA specimen showed improved yield strength by 24%, ultimate tensile strength by 20%, and ductility by 12% as compared with the bulk Al6061 alloy. It is shown that the fatigue strength of both CR and PA specimens under a high-cycle fatigue regime are larger than that of the bulk Al6061 alloy. Also, fatigue crack growth rates of the CR and PA specimens show significant enhancement in fatigue crack growth resistances as compared with the bulk Al6061 alloy, as a result of grain refinement.

  10. Self-reported fatigue and physical function in late mid-life

    DEFF Research Database (Denmark)

    Boter, Han; Mänty, Minna; Hansen, Åse Marie;

    2014-01-01

    population cohort (n = 4,964; age 49-63 years). Methods: Self-reported fatigue was measured using the MFI-20 comprising: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Handgrip strength and chair rise tests were used as measures of physical function. Multiple...... ratio (OR) 0.75 (95% confidence interval (CI) 0.66-0.86); p ≤ 0.001) and reduced motivation (adjusted OR 0.85 (95% CI 0.75-0.96); p ≤ 0.05), but not with the other subscales. After these adjustments, the chair rise test was associated with physical fatigue (adjusted OR 0.61 (0.53-0.69); p ≤ 0...

  11. Life Management Technique of Thermal Fatigue for SMST Boiler Tube at Different Heating Zone Using Smithy Furnace

    OpenAIRE

    Shekhar Pal; Pradeep Suman

    2014-01-01

    This paper highlights on the evaluation of thermal fatigue failure for SMST (Salzgitter Mannesmann strain less boiler tube) DMV 304 HCu boiler tube using life management technique by using of smithy furnace. Boiler tubes are highly affected by operating conditions like, high temperature and high pressure. So it needs periodic checking for the purpose of safety and health assessment of the plant. So using this technique we can identify the degradation of tubes at microstructure...

  12. Influence of phosphorus content and quenching/tempering temperatures on fracture toughness and fatigue life of SAE 5160 steel

    OpenAIRE

    Danilo Borges Villarino de Castro; Jaime Milan Ventura; Cassius Olivio Figueiredo Terra Ruckert; Dirceu Spinelli; Waldek Wladimir Bose Filho

    2010-01-01

    This study investigates the influence of quenching/tempering temperatures on the fracture toughness and fatigue life of SAE 5160 steel, considering different phosphorus contents. Quenching and tempering treatments were applied to samples removed from different bars of commercial SAE 5160 steel with different P content. Three different austenitizing temperatures for quenching: 850, 900 and 1000 ºC and a constant holding time of 15 minutes were used. The oil temperature for quenching was kept a...

  13. The effect of allergic rhinitis on the degree of stress, fatigue and quality of life in OSA patients.

    Science.gov (United States)

    Park, Cheol Eon; Shin, Seung Youp; Lee, Kun Hee; Cho, Joong Saeng; Kim, Sung Wan

    2012-09-01

    Both allergic rhinitis (AR) and obstructive sleep apnea (OSA) are known to increase stress and fatigue, but the result of their coexistence has not been studied. The objective of this study was to evaluate the amount of stress and fatigue when AR is combined with OSA. One hundred and twelve patients diagnosed with OSA by polysomnography were enrolled. Among them, 37 patients were diagnosed with AR by a skin prick test and symptoms (OSA-AR group) and 75 patients were classified into the OSA group since they tested negative for allergies. We evaluated the Epworth sleepiness scale (ESS), stress score, fatigue score, ability to cope with stress, and rhinosinusitis quality of life questionnaire (RQLQ) with questionnaires and statistically compared the scores of both groups. There were no significant differences in BMI and sleep parameters such as LSAT, AHI, and RERA between the two groups. However, the OSA-AR group showed a significantly higher ESS score compared to the OSA group (13.7 ± 4.7 vs. 9.3 ± 4.8). Fatigue scores were also significantly higher in the OSA-AR group than in the OSA group (39.8 ± 11.0 vs. 30.6 ± 5.4). The OSA-AR group had a significantly higher stress score (60.4 ± 18.6 vs. 51.2 ± 10.4). The ability to cope with stress was higher in the OSA group, although this difference was not statistically significant. RQLQ scores were higher in the OSA-AR group (60.2 ± 16.7 compared to 25.1 ± 13.9). In conclusion, management of allergic rhinitis is very important in treating OSA patients in order to eliminate stress and fatigue and to minimize daytime sleepiness and quality of life. PMID:22207526

  14. Sleep, Fatigue and Quality of Life: A Comparative Analysis among Night Shift Workers with and without Children

    Science.gov (United States)

    Fernandes-Junior, Silvio Araújo; Ruiz, Francieli Silva; Antonietti, Leandro Stetner; Tufik, Sergio; Túlio de Mello, Marco

    2016-01-01

    Introduction The reversal of the natural cycle of wakefulness and sleep may cause damage to the health of workers. However, there are few studies evaluating sleep, fatigue and quality of life of night shift workers considering the influence of small children on these variables. Aims Evaluate the sleep time, fatigue and quality of life of night shift workers and verify the relationship between these variables with the presence or absence of children in different age groups. Methods Were evaluated 78 mens shiftworkers, with or without children. Group 1, workers without children (G1-NC), group 2, workers with children pré-school age (G2-PS) and group 3, workers with children school age (G3-S). The sleep time (ST), sleep efficiency (SE), sleep latency (SL) and maximum time awake (MTA) were recorded by actigraphy. The risk of being fatigued at work was estimated by risk index for fatigue (RIF). Results The G1-NC showed a longer ST on working days and when evaluated only the first nights shift, after day off (p<0,005). This sample, the age of the children did not influence the sleep time these workers. The MTA on day off was lower in the workers from G2-PS. The RIF was lower on G1-NC in the first nights shift compared to the other groups. Conclusion In this research, workers without children had higher sleep time during the working days. These workers also were less likely to feel fatigued during night work than workers with children, regardless of age these children. PMID:27391478

  15. The influence of temperature on low cycle fatigue behavior of prior cold worked 316L stainless steel (II) : life prediction and failure mechanism

    International Nuclear Information System (INIS)

    Tensile and low cycle fatigue tests on prior cold worked 316L stainless steel were carried out at various temperatures from room temperature to 650 deg. C. Fatigue resistance was decreased with increasing temperature and decreasing strain rate. Cyclic plastic deformation, creep, oxidation and interactions with each other are thought to be responsible for the reduction in fatigue resistance. Currently favored life prediction models were examined and it was found that it is important to select a proper life prediction parameter since stress-strain relation strongly depends on temperature. A phenomenological life prediction model was proposed to account for the influence of temperature on fatigue life and assessed by comparing with experimental result. LCF failure mechanism was investigated by observing fracture surfaces of LCF failed specimens with SEM

  16. Relationship between fatigue life of asphalt concrete and polypropylene/polyester fibers using artificial neural network and genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    Morteza Vadood; Majid Safar Johari; Ali Reza Rahai

    2015-01-01

    While various kinds of fibers are used to improve the hot mix asphalt (HMA) performance, a few works have been undertaken on the hybrid fiber-reinforced HMA. Therefore, the fatigue life of modified HMA samples using polypropylene and polyester fibers was evaluated and two models namely regression and artificial neural network (ANN) were used to predict the fatigue life based on the fibers parameters. As ANN contains many parameters such as the number of hidden layers which directly influence the prediction accuracy, genetic algorithm (GA) was used to solve optimization problem for ANN. Moreover, the trial and error method was used to optimize the GA parameters such as the population size. The comparison of the results obtained from regression and optimized ANN with GA shows that the two-hidden-layer ANN with two and five neurons in the first and second hidden layers, respectively, can predict the fatigue life of fiber-reinforced HMA with high accuracy (correlation coefficient of 0.96).

  17. Determination of the fatigue life of the AD33-V composite under conditions of low-cycle loading in pure bending

    Energy Technology Data Exchange (ETDEWEB)

    Utkin, V.S.; Salibekov, S.E.; Chubarov, V.M.

    1986-06-01

    Specimens of AD33-V, an aluminum/boron composite, were tested in cyclic bending to determine the dependence of accumulated damage and fatigue life on the stress amplitude under conditions of pure bending. It is shown that the fatigue life of the composite is proportional to its ultimate strength. Conditional endurance limits are determined as a function of the permissible amount of accumulated damage.

  18. High-temperature fatigue in metals - A brief review of life prediction methods developed at the Lewis Research Center of NASA

    Science.gov (United States)

    Halford, G. R.

    1983-01-01

    The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed. Previously announced in STAR as A83-12159

  19. The effect of intravenous vitamin C on cancer- and chemotherapy-related fatigue and quality of life

    Directory of Open Access Journals (Sweden)

    Anitra C. Carr

    2014-10-01

    Full Text Available Cancer patients commonly experience a number of symptoms of disease progression and the side effects of radiation therapy and adjuvant chemotherapy, which adversely impact on their quality of life. Fatigue is one of the most common and debilitating symptoms reported by cancer patients and can affect quality of life more than pain. Several recent studies have indicated that intravenous vitamin C alleviates a number of cancer- and chemotherapy-related symptoms, such as fatigue, insomnia, loss of appetite, nausea and pain. Improvements in physical, role, cognitive, emotional and social functioning, as well as an improvement in overall health, were also observed. In this mini review we briefly cover the methods commonly used to assess health-related quality of life in cancer patients, and describe the few recent studies examining the effects of intravenous vitamin C on cancer- and chemotherapy-related quality of life. We discuss potential mechanisms that might explain an improvement in quality of life and also considerations for future studies.

  20. Stress analysis and life prediction of gas turbine blade

    Science.gov (United States)

    Hsiung, H. C.; Dunn, A. J.; Woodling, D. R.; Loh, D. L.

    1988-01-01

    A stress analysis procedure is presented for a redesign of the Space Shuttle Main Engine high pressure fuel turbopump turbine blades. The analysis consists of the one-dimensional scoping analysis to support the design layout and the follow-on three-dimensional finite element analysis to confirm the blade design at operating loading conditions. Blade life is evaluated based on high-cycle fatigue and low-cycle fatigue.

  1. Fatigue Life Prediction of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures. Part II: Experimental Comparisons

    Science.gov (United States)

    Longbiao, Li

    2015-12-01

    This paper follows on from the earlier study (Part I) which investigated the fatigue behavior of unidirectional, cross-ply and 2.5D C/SiC composites at room and elevated temperatures. In this paper, a micromechanics approach to predict the fatigue life S-N curves of fiber-reinforced CMCs has been developed considering the fatigue damage mechanism of interface wear or interface oxidation. Upon first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. The two-parameter Weibull model is used to describe fibers strength distribution. The stress carried by broken and intact fibres on the matrix crack plane under fatigue loading is determined based on the Global Load Sharing (GLS) criterion. The fibres failure probabilities under fatigue loading considering the degradation of interface shear stress and fibres strength have been obtained. When the broken fibres fraction approaches critical value, the composite would fatigue fail. The fatigue life S-N curves of unidirectional, cross-ply and 2.5D C/SiC composites at room and elevated temperatures have been predicted. The predicted results agreed with experimental data.

  2. Fatigue life prediction and experiment research for composite laminates with circular hole

    Institute of Scientific and Technical Information of China (English)

    齐红宇; 温卫东; 孙联文

    2004-01-01

    Based on the fatigue prediction model of exponential function and Whitney-Nuismer(WN) criterion of static strength for the composite material laminate with a circular hole, the stress correct factor (β) was put forward and a new fatigue prediction model for composite material laminate was set up. T300/KH304, which is recently studied and is a high capability composite material, was used as the raw material. In order to gain the factorβ, the fatigue experiments of the laminates with holes in different diameters and the same ratio of width to diameter were conducted. The fatigue analysis and tests of the laminates with a hole 5 mm in diameter are carried out at different stress levels, and the results meet the engineering requirement. The simple, prompt and practical method is provided for the prediction of S-N curve of composite laminate with a circular hole.

  3. Rolling Contact Fatigue Life of Steel Rollers Treated by Cavitation Peening and Shot Peening

    Science.gov (United States)

    Seki, Masanori; Soyama, Hitoshi; Kobayashi, Yuji; Gowa, Daisuke; Fujii, Masahiro

    The purpose of this study is to investigate the influence of peening on the rolling contact fatigue (RCF) life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings. In particular, they were most increased by the FPP. On the other hand, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the RCF tests, the RCF lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the pmax - N curves and the [A(σy/√3 HV)]max - N curves, the improvement in RCF lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the RCF were equivalent under the same surface roughness and the same surface hardness. It follows from these that the surface treatment condition should be selected according to the rolling contact conditions and the failure modes of machine elements.

  4. Study of the Fatigue Life and Weight Optimization of an Automobile Aluminium Alloy Part under Random Road Excitation

    Directory of Open Access Journals (Sweden)

    A. Saoudi

    2010-01-01

    Full Text Available Weight optimization of aluminium alloy automobile parts reduces their weight while maintaining their natural frequency away from the frequency range of the power spectral density (PSD that describes the roadway profile. We present our algorithm developed to optimize the weight of an aluminium alloy sample relative to its fatigue life. This new method reduces calculation time; It takes into account the multipoint excitation signal shifted in time, giving a tangle of the constraint signals of the material mesh elements; It also reduces programming costs. We model an aluminium alloy lower vehicle suspension arm under real conditions. The natural frequencies of the part are inversely proportional to the mass and proportional to flexural stiffness, and assumed to be invariable during the process of optimization. The objective function developed in this study is linked directly to the notion of fatigue. The method identifies elements that have less than 10% of the fatigue life of the part's critical element. We achieved a weight loss of 5 to 11% by removing the identified elements following the first iteration.

  5. DETERMINATION OF VEHICLE COMPONENTS FATIGUE LIFE BASED ON FEA METHOD AND EXPERIMENTAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Arif Senol SENER

    2012-01-01

    Full Text Available In this study, construction and standardization of a track for performing fatigue and reliability test of light commercial vehicles is described. For the design and process verification of the company’s vehicles one test track is defined. A questionnaire was used to determine the average usage of light commercial vehicles in Turkey. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads and this article focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from the accelerated test route. Fatigue analysis and estimated lifespan of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When the customer profile is taken into consideration; Turkish customer automotive usage profile, the aim of usage of this kind of vehicle (LCV, fatigue characteristics of Turkish roads for this vehicle were determined and around Bursa one accelerated test tracks were formed for the reliability and fatigue test for the related company, linear analysis executed on the FEA of the spring was more convenient were obtained.

  6. Service life prediction. Development of models for predicting the service life of power plant components subject to thermomechanical creep fatigue; Lebensdauervorhersage. Entwicklung von Modellen zur Lebensdauervorhersage von Kraftwerksbauteilen unter thermisch-mechanischer Kriechermuedungsbeanspruchung. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Cui, L.; Scholz, A. [Technische Univ. Darmstadt (Germany). Institut fuer Werkstoffkunde; Hartrott, P. von; Schlesinger, M. [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

    2009-07-01

    Extensive use is made of massive components of heat resistant and highly heat resistant materials in installations of the power and heating industry. These components are exposed to varying thermomechanical stress as a result of ramping-up and down processes. In this research project two computer-assisted methods of predicting service life until crack initiation were extended to include cases of thermomechanical multi-axis stress conducive to creep fatigue and of superposition of high-cycle stress on power plant components. Investigations were limited to rotor steel of type X12CrMoWVNbN10-1-1. Complex thermomechanical multi-axis experiments were performed on round, notched and cruciform test specimens of close-to-life dimensions in order to demonstrate by experiment the validity of these models. The results of these calculations showed an acceptable degree of agreement between experiment and simulation for both models. Calculations on earlier TMF experiments performed at IfW on hollow specimens of 1%CrMoNiV showed good predictability for both the SARA and the ThoMat programme. Calculations on experiments performed at MPA Stuttgart on model bodies consisting of the same 1%CrMoNiV showed a predictability of acceptable variability considering the complexity of the stresses involved. A further outcome of this project is that the use of SARA appears universally suitable for the construction of new plants and in the service area, while the use of ThoMat appears suited for detail optimisation in the development process.

  7. Effects from fully nonlinear irregular wave forcing on the fatigue life of an offshore wind turbine and its monopile foundation

    DEFF Research Database (Denmark)

    Schløer, Signe; Bredmose, Henrik; Bingham, Harry B.;

    2013-01-01

    The effect from fully nonlinear irregular wave forcing on the fatigue life of the foundation and tower of an offshore wind turbine is investigated through aeroelastic calculations. Five representative sea states with increasing significant wave height are considered in a water depth of 40 m....... The waves are both linear and fully nonlinear irregular 2D waves. The wind turbine is the NREL 5-MW reference wind turbine. Fatigue analysis is performed in relation to analysis of the sectional forces in the tower and monopile. Impulsive excitation of the sectional force at the bottom of the tower is seen...... when the waves are large and nonlinear and most notably for small wind speeds. In case of strong velocities and turbulent wind, the excitation is damped out. In the monopile no excitation of the force is seen, but even for turbulent strong wind the wave affects the forces in the pile significantly...

  8. Predicting Fatigue Life Based on the Behavior of Short Fatigue C rack%基于疲劳短裂纹行为的疲劳寿命估算方法

    Institute of Scientific and Technical Information of China (English)

    吕文阁

    2001-01-01

    The process of forming short fatigue crack was di vided into short fatigue crack initiation phase and short fatigue crack propagat ion phase. The theory of continuously distributed dislocations of crack was app l ied to analyze the early growth and the effect of microstructure of short fatigu e crack. The dislocations model of crack under cyclic stress was built based on the analysis of the equilibrium condition for dislocations when the applied stre ss was reduced. The reverse plastic displacement at the crack-tip was adjusted to discribe the growth of fatigue crack. The model was used in short fatigue cr a ck initiation with the physical background of the diceleration behavior of early growth of short fatigue crack. A fatigue limit diagram of hyperbola was derive d from the threshold stress condition of short fatiuge crack determined by the an alysis of interactions between early growth of short fatigue crack and grain bou ndary. The equation of short fatiuge crack growth rate was presented from the m o del related to the threshold stress condition of short fatigue crack. The ellip s oidal inhomogeneity method was applied to the study on elastic-plastic fractrue problem, and then the analytical expressions of crack-tip extension displaceme nt were found. The method in which crack-tip extension displacement range was u tilized to describe the rate of short fatigue crack propagation was presented. I t was found that the propagation rate of short fatigue cracks. Based on the beh a vior of initiation and propagation of short fatigue cracks, a method of predicti ong fatiuge life was proposed. The predicting result shows that this method was accurate enough.%在疲劳短裂纹形成和扩展行为研究基础上,提出了一种疲劳 寿命估算方法。计算结果表明,该方法具有满意的预测精度。

  9. A study on the influence of microstructure on small fatigue cracks

    Science.gov (United States)

    Castelluccio, Gustavo M.

    In spite of its significance in industrial applications, the prediction of the influence of microstructure on the early stages of crack formation and growth in engineering alloys remains underdeveloped. The formation and early growth of fatigue cracks in the high cycle fatigue regime lasts for much of the fatigue life, and it is strongly influenced by microstructural features such as grain size, twins and morphological and crystallographic texture. However, most fatigue models do not predict the in uence of the microstructure on early stages of crack formation, or they employ parameters that should be calibrated with experimental data from specimens with microstructures of interest. These post facto strategies are adequate to characterize materials, but they are not fully appropriate to aid in the design of fatigue-resistant engineering alloys. This thesis considers finite element computational models that explicitly render the microstructure of selected FCC metallic systems and introduces a fatigue methodology that estimates transgranular and intergranular fatigue growth for microstructurally small cracks. The driving forces for both failure modes are assessed by means of fatigue indicators, which are used along with life correlations to estimate the fatigue life. Furthermore, cracks with meandering paths are modeled by considering crack growth on a grain-by-grain basis with a damage model embedded analytically to account for stress and strain redistribution as the cracks extend. The methodology is implemented using a crystal plasticity constitutive model calibrated for studying the effect of microstructure on early fatigue life of a powder processed Ni-base RR1000 superalloy at elevated temperature under high cycle fatigue conditions. This alloy is employed for aircraft turbine engine disks, which undergo a thermomechanical production process to produce a controlled bimodal grain size distribution. The prediction of the fatigue life for this complex

  10. Fatigue properties of weathering steel

    OpenAIRE

    Zavadilová, Petra

    2012-01-01

    This work deals with the influence of atmospheric corrosion on high-cycle fatigue properties of a weathering steel ATMOFIX B. New experimental data on fatigue strength of a steel exposed for 20 years to an atmospheric corrosion were compared to those characterizing the base material. Reduction of the fatigue lifetime of the exposed material compared with the base material was predicted on the basic of fractographic examination of fracture surfaces and the influence of surface notches on fatig...

  11. Standard practice for statistical analysis of linear or linearized stress-life (S-N) and strain-life (ε-N) fatigue data

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice covers only S-N and ε-N relationships that may be reasonably approximated by a straight line (on appropriate coordinates) for a specific interval of stress or strain. It presents elementary procedures that presently reflect good practice in modeling and analysis. However, because the actual S-N or ε-N relationship is approximated by a straight line only within a specific interval of stress or strain, and because the actual fatigue life distribution is unknown, it is not recommended that (a) the S-N or ε-N curve be extrapolated outside the interval of testing, or (b) the fatigue life at a specific stress or strain amplitude be estimated below approximately the fifth percentile (P ≃ 0.05). As alternative fatigue models and statistical analyses are continually being developed, later revisions of this practice may subsequently present analyses that permit more complete interpretation of S-N and ε-N data.

  12. Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures

    Science.gov (United States)

    Longbiao, Li

    2016-10-01

    In this paper, the comparison of fatigue life between C/SiC and SiC/SiC ceramic-matrix composites (CMCs) at room and elevated temperatures has been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S-N curves and fatigue limits of cross-ply, 2D and 3D C/SiC and SiC/SiC composites at room temperature, 550 °C in air, 750 °C in dry and humid condition, 800 °C in air, 1000 °C in argon and air, 1100 °C, 1300 °C and 1500 °C in vacuum, have been predicted. At room temperature, the fatigue limit of 2D C/SiC composite with ECFL of 20 % lies between 0.78 and 0.8 tensile strength; and the fatigue limit of 2D SiC/SiC composite with ECFL of 20 % lies between 0.75 and 0.85 tensile strength. The fatigue limit of 2D C/SiC composite increases to 0.83 tensile strength with ECFL increasing from 20 to 22.5 %, and the fatigue limit of 3D C/SiC composite is 0.85 tensile strength with ECFL of 37 %. The fatigue performance of 2D SiC/SiC composite is better than that of 2D C/SiC composite at elevated temperatures in oxidative environment.

  13. Prediction of low-cycle fatigue-life by acoustic emission—1: 2024-T3 aluminum alloy, and —2: 7075-T6 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Baram, J. [Ben-Gurion Univ. of the Negev, Beer Sheva (Israel). Materials Engineering Division; Rosen, M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials and Molecular Research Division

    1981-01-01

    1: In this paper, low-cycle fatigue tests were conducted by tension-tension until rupture, on a 2024-T3 aluminum alloy sheet. Initial crack sizes and orientations in the fatigue specimens were found to be randomly distributed. Acoustic emission was continuously monitored during the tests. Every few hundred cycles, the acoustic signal having the highest peak-amplitude, was recorded as an extremal event for the elapsed period. This high peak-amplitude is related to a fast crack propagation rate through a phenomenological relationship. The extremal peak amplitudes are shown by an ordered statistics treatment, to be extremally distributed. The statistical treatment enables the prediction of the number of cycles left until failure. Predictions performed a posteriori based on results gained early in each fatigue test are in good agreement with actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress appears to be a promising nondestructive method of predicting fatigue life. 2: In this paper, low cycle high stress fatigue tests were conducted by tension-tension on an Alclad 7075-T6 aluminum sheet alloy, until rupture. Initial crack sizes and orientations in the fatigue specimens were randomly distributed. Acoustic emission was continuously monitored during the tests. Extremal peak-amplitudes, equivalent to extremal crack-propagation rates, are shown to be extremally Weibull distributed. The prediction of the number of cycles left until failure is made possible, using an ordered statistics treatment and an experimental equipment parameter obtained in previous experiments (Part 1). The predicted life-times are in good agreement with the actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress has been proven to be a feasible nondestructive method of predicting fatigue life.

  14. The study on the factors affecting the high temperature continuous low-cycle fatigue life of the welded 316LN stainless steel by GTAW

    International Nuclear Information System (INIS)

    The influence of weld defect on the continuous low cycle fatigue property for type 316LN stainless steel base metal and weldment was investigated with a strain rate of 4x10-3/sec in air atmosphere. Low cycle fatigue test were conducted at temperature of 823K and 873K. Total strain amplitude was controlled to be 0.4-0.6%. The 308L stainless steel was used as the welding rod. The welding was done by the GTAW process with the welding direction perpendicular to the rolling direction of the base metal. The microstructures of the base metal and weldment are γ phase γ/δ duplex-ferrite, respectively. The fatigue lives of the base metal had twice higher than those of weldment having no visible defect. From the tensile result, the uniform elongation of the base metal had twice higher than that of the weldment. For the base metal and HAZ, the fatigue lives at the same condition were reliable. But some results of the fatigue lives in the weldment had the lowest fatigue life at the same condition. From the observation of the fracture surface after fatigue tests, there were porosities and welding defects. For weldments having the many porosities and welding defects, the fatigue lives decreased 50% and 60-70%, respectively. From the observation of the microstructure near the internal crack, the internal weld defects was existed at the interface among the dendrites grown along the different direction

  15. Combined Cycle Fatigue Investigation Based on Energy Principle

    Directory of Open Access Journals (Sweden)

    Kalynenko Mykyta

    2016-01-01

    Full Text Available We present a modified energy-principle based model of fatigue damage accumulation in high temperature alloys usually used in gas turbine engine under combined high cycle fatigue and low cycle fatigue (LCF/HCF loading conditions. Our model is based on the energy principle which includes a modified approximation formula that describes fatigue crack origin depending on the relative amplitude of stress intensity in the ranges of both high- and low-cycle fatigue under non-isothermal loading. Functional dependence that presents the influence of HCF mechanisms on a fatigue life of our structural material is gradual and it has not breaks of the curve that yields a possibility to rewrite the equation of the S-N curve with taking into account combined cycle fatigue loading. We used the same number of parameters as the initial model. Note, that new parameter interpretation gives clear physical picture. The proposed model is verified by comparing the computed results with the experimental data for one high temperature alloy GH4133.

  16. Quality of life, fatigue and local response of patients with unstable spinal bone metastases under radiation therapy - a prospective trial

    International Nuclear Information System (INIS)

    To evaluate the local response according to stability after radiotherapy (RT) with a special focus on quality-of-life (QoL), fatigue, pain and emotional distress in patients with unstable spinal bone metastases. In this prospective trial, 30 patients were treated from September 2011 until March 2013. The stability of osteolytic metastases in the thoracic and lumbar spine was evaluated on the basis of the Taneichi-score after three and six months. EORTC QLQ-BM22, EORTC QLQ-FA13, and QSC-R10 were assessed at baseline, and three months after RT. After 3 months, 25% (n = 6) and after 6 months 33.3% (n = 8) were classified as stable. QoL, fatigue, and emotional distress showed no difference over the course. The pain response 3 months after RT showed a significant difference (p < 0.001). Pathological fractures occurred in 8.3% of the patients (n = 2) within six months following RT. Our trial demonstrated that RT can improve stability in one third of patients over a 6-months period with unstable spinal metastases. Importantly, for these patients pain relief was detected but RT had no impact on QoL, fatigue, and emotional distress

  17. Effect of Application of Short and Long Holds on Fatigue Life of Modified 9Cr-1Mo Steel Weld Joint

    Science.gov (United States)

    Shankar, Vani; Mariappan, K.; Sandhya, R.; Mathew, M. D.; Jayakumar, T.

    2013-11-01

    Modified 9Cr-1Mo steel is a heat-treatable steel and hence the microstructure is temperature sensitive. During welding, the weld joint (WJ) is exposed to various temperatures resulting in a complex heterogeneous microstructure across the weld joint, such as the weld metal, heat-affected zone (HAZ) (consisting of coarse-grained HAZ, fine-grained HAZ, and intercritical HAZ), and the unaffected base metal of varying mechanical properties. The overall creep-fatigue interaction (CFI) response of the WJ is hence due to a complex interplay between various factors such as surface oxides and stress relaxation (SR) occurring in each microstructural zone. It has been demonstrated that SR occurring during application of hold in a CFI cycle is an important parameter that controls fatigue life. Creep-fatigue damage in a cavitation-resistant material such as modified 9Cr-1Mo steel base metal is accommodated in the form of microstructural degradation. However, due to the complex heterogeneous microstructure across the weld joint, SR will be different in different microstructural zones. Hence, the damage is accommodated in the form of preferential coarsening of the substructure, cavity formation around the coarsened carbides, and new surface formation such as cracks in the soft heat-affected zone.

  18. Fatigue Life Prediction of Fiber-Reinforced Ceramic-Matrix Composites with Different Fiber Preforms at Room and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Longbiao Li

    2016-03-01

    Full Text Available In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional, 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL was introduced to describe the fiber architecture of preforms. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Under cyclic fatigue loading, the fiber broken fraction was determined by combining the interface wear model and fiber statistical failure model at room temperature, and interface/fiber oxidation model, interface wear model and fiber statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfies the Global Load Sharing (GLS criterion. When the broken fiber fraction approaches the critical value, the composites fatigue fracture.

  19. FATIGUE LIFE PREDICTION BASED ON MACROSCOPIC PLASTIC ZONE ON FRACTURE SURFACE OF AISI-SAE 1018 STEEL

    Directory of Open Access Journals (Sweden)

    G.M. Domínguez Almaraz

    2010-06-01

    Full Text Available This paper deals with rotating bending fatigue tests at high speed (150 Hz carried out on AISI-SAE 1018 steel with a high content of impurities (non metallic inclusions, for which the high experimental stress inside the specimen is close to the elastic limit of the material. Simulations of rotating loading are obtained by Visual NASTRAN software in order to determine the numerical stresse and strain distributions inside a hypothetical homogeneous specimen; later, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed and then, the experimental results are presented and discussed according the observed failure origin related to the non metallic inclusions and the associated high stress zones. Finally, a simple model is proposed to predict the fatigue life for this non homogeneous steel under high speed rotating bending fatigue tests close to the elastic limit, based on the rate between the visual macro-plastic deformation zone at fracture surface and the total fracture surface, together with the crack initiation inclusion (or inclusions located at this zone.

  20. Effects of geometry and materials on low cycle fatigue life of turbine blades in LOX/hydrogen rocket engines

    Science.gov (United States)

    Ryan, R. M.; Gross, L. A.

    1986-01-01

    This paper presents the results of an advanced turbine blade test program aimed at improving turbine blade low cycle fatigue (LCF) life. A total of 21 blades were tested in a blade thermal tester. The blades were made of MAR-M-246(Hf)DS and PWA-1480SC in six different geometries. The test results show that the PWA-1480SC material improved life by a factor of 1.7 to 3.0 over the current MAR-M-246(Hf)DS. The geometry changes yielded life improvements as high as 20 times the baseline blade made of PWA-1480SC and 34 times the baseline MAR-M-246DS blade.

  1. Determination of remaining fatigue life of welded stud details on overhead aluminum sign panels in Virginia

    OpenAIRE

    Cousins, Thomas E.; Lucas, Jeremy L.

    2005-01-01

    Some overhead highways signs in Virginia using a specific welded threaded stud and clip connection have failed while in service. From inspection of the signs it was determined that the failure was caused by fatigue of the weld connecting the threaded stud to the back of the sign panel. It was also observed that lower edge connections failed first and the failures progressed upwards in an unzipping pattern. A combination of natural and truck-induced wind gusts is the cause for the fatigue fail...

  2. Effect of Fe ion concentration on fatigue life of carbon steel in aqueous CO2 environment

    DEFF Research Database (Denmark)

    Rogowska, Magdalena; Gudme, J.; Rubin, A.;

    2016-01-01

    In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ex...... of Fe2+ marginally above the solubility limit of FeCO3 compared to the samples tested in highly supersaturated solution of Fe2+. Results revealed that the impact of the alternating stresses on the corrosion behaviour of samples reduces with lowering the applied stresses. At the stress range of 100 MPa...

  3. Influence of phosphorus content and quenching/tempering temperatures on fracture toughness and fatigue life of SAE 5160 steel

    Directory of Open Access Journals (Sweden)

    Danilo Borges Villarino de Castro

    2010-12-01

    Full Text Available This study investigates the influence of quenching/tempering temperatures on the fracture toughness and fatigue life of SAE 5160 steel, considering different phosphorus contents. Quenching and tempering treatments were applied to samples removed from different bars of commercial SAE 5160 steel with different P content. Three different austenitizing temperatures for quenching: 850, 900 and 1000 ºC and a constant holding time of 15 minutes were used. The oil temperature for quenching was kept at 66 ºC and the tempering conditions were 470, 500 and 530 ºC with the necessary time for a final hardness of 45 ± 3 HRC. Therefore, the heat treatments cycles were applied to specimens containing low (0.012 wt. (%, medium (0.017 wt. (% and high (above 0.025 wt. (% phosphorus contents, in order to observe the effects of this element on the susceptibility of these steels to enhance quench and tempering embrittlements. The Charpy tests results showed that the phosphorus content analyzed in this work has caused embrittlement, even in the bars with the lowest P content, leading to intergranular fracture. However, if the nucleation life is taken into consideration, this embrittlement has no effect on the nucleation fatigue life of the component.

  4. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, M. H.; Sørensen, John Dalsgaard; Kroon, I. B.

    1993-01-01

    This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue...

  5. Fatigue behavior of high-Mn TWIP steels

    International Nuclear Information System (INIS)

    Fatigue behavior of three high-Mn TWIP steels with the grain sizes between 4.5 and 55 μm were investigated in reversed plane bending in the high-cycle regime. Crack initiation and propagation stages were examined by optical, scanning electron and atom force microscopy. It was found that the fatigue limit, which is the stress amplitude leading to fatigue life beyond 2 x 106 cycles, is quite high, about 400 MPa, for these steels. This value is between 0.42 and 0.48 of the tensile strengths, similarly as for austenitic stainless steels. Refining the grain size still increases the fatigue resistance. Neither martensite is formed nor mechanical twinning takes place in the course of cycling, but intense slip bands are created with extrusions and intrusions. Fatigue cracks tend to nucleate at an early stage of fatigue life, and preferentially on grain and twin boundaries, especially in the intersection sites of slip bands and boundaries, besides slip bands. However, the crack propagation takes place mainly transgranularly creating ductile striations and protrusions on fracture surfaces.

  6. Life Management Technique of Thermal Fatigue for SMST Boiler Tube at Different Heating Zone Using Smithy Furnace

    Directory of Open Access Journals (Sweden)

    Shekhar Pal,

    2014-06-01

    Full Text Available This paper highlights on the evaluation of thermal fatigue failure for SMST (Salzgitter Mannesmann strain less boiler tube DMV 304 HCu boiler tube using life management technique by using of smithy furnace. Boiler tubes are highly affected by operating conditions like, high temperature and high pressure. So it needs periodic checking for the purpose of safety and health assessment of the plant. So using this technique we can identify the degradation of tubes at microstructure level, So that one create the current situation of the component and give respective result.

  7. Effect of rare earth Ce on the fatigue life of SnAgCu solder joints in WLCSP device using FEM and experiments

    International Nuclear Information System (INIS)

    With the addition of 0.03 wt% rare earth Ce, in our previous works, the properties of SnAgCu solder were enhanced obviously. Based on the Garofalo–Arrhenius creep constitutive model, finite element method was used to simulate the stress–strain response during thermal cycle loading, and combined with the fatigue life prediction models, the fatigue life of SnAgCu/SnAgCuCe solder joints was calculated respectively, which can demonstrate the effect of the rare earth Ce on the fatigue life of SnAgCu solder joints. The results indicated that the maximum stress–strain can be found on the top surface of the corner solder joint, and the warpage of the PCB substrate occurred during thermal cycle loading. The trends obtained from modeling results have a good agreement with the experimental data reported in the literature for WLCSP devices. In addition, the stress–strain of SnAgCuCe solder joints is lower than that of SnAgCu solder joints. The thermal fatigue lives of solder joints calculated based on the creep model and creep strain energy density model show that the fatigue life of SnAgCuCe solder joints is higher than the SnAgCu solder joints. The fatigue life of SnAgCuCe solder joints can be enhanced significantly with the addition of Ce, is 30.2% higher than that of SnAgCu solder joints, which can be attributed to the CeSn3 particles formed resisting the motion of dislocation; moreover, the refinement of microstructure and the IMC sizes also contribute to the enhancement of fatigue life, which elucidates that SnAgCuCe solder can be utilized in electronic industry with high reliability replacing the SnAgCu solder

  8. Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution%Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution

    Institute of Scientific and Technical Information of China (English)

    SHA Yun-dong; GUO Xiao-peng; LIAO Lian-fang; XIE Li-juan

    2011-01-01

    As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings, an effective method for predicting the fatigue life of a structure under random loadings was studied. Firstly, the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied, analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution. The formula for calculating Weibull parameters were given. Based on the Miner linear theory, the method for predicting the random sonic fatigue life based on the stress probability density was developed, and the model for fatigue life prediction was constructed. As an example, an aero-engine combustor liner structure was considered. The power spectrum density (PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM (finite element method/boundary element method) model, the fatigue life was estimated by using the constructed model. And considering the influence of the wide frequency band, the calculated results were modified. Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend. The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.

  9. Lap shear strength and fatigue life of friction stir spot welded AZ31 magnesium and 5754 aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, S.H. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3 (Canada); Chen, D.L., E-mail: dchen@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3 (Canada); Bhole, S.D. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3 (Canada); Cao, X.; Wanjara, P. [Aerospace Manufacturing Technology Centre, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec, Canada H3T 2B2 (Canada)

    2012-10-30

    Lightweighting is today considered as one of the key strategies in reducing fuel consumption and anthropogenic greenhouse gas emissions. The structural applications of lightweight magnesium and aluminum alloys in the transportation industry inevitably involve welding and joining while guaranteeing the safety and reliability of motor vehicles. This study was aimed at evaluating lap shear strength and fatigue properties of friction stir spot welded (FSSWed) AZ31B-H24 Mg and 5754-O Al alloys in three combinations, i.e., similar Mg-to-Mg, Al-to-Al, and dissimilar Al-to-Mg joints. The Mg/Mg similar weld had a nugget-shaped stir zone (SZ) around the keyhole where fine recrytallized equiaxed grains were observed. While the hardness profile of the Mg/Mg similar weld exhibited a W-shaped appearance, the lower hardness values appeared in the TMAZ and HAZ of both Mg/Mg and Al/Al similar welds. In the Al/Mg dissimilar weld, a characteristic interfacial layer consisting of intermetallic compounds (IMC) Al{sub 12}Mg{sub 17} and Al{sub 3}Mg{sub 2} was observed. Both Mg/Mg and Al/Al similar welds had significantly higher lap shear strength, failure energy and fatigue life than the Al/Mg dissimilar weld. While the Al/Al weld displayed a slightly lower lap shear strength than the Mg/Mg weld, the Al/Al weld had higher failure energy and fatigue life. Three types of failure modes were observed. In the Mg/Mg and Al/Al similar welds, at higher cyclic loads nugget pullout failure occurred due to fatigue crack propagation circumferentially around the nugget, while at lower cyclic loads fatigue failure occurred perpendicular to the loading direction caused by the opening of keyhole through crack initiation in the TMAZ and HAZ. In the Al/Mg dissimilar weld nugget debonding failure mode was observed because of the presence of an interfacial IMC layer.

  10. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  11. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    International Nuclear Information System (INIS)

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented

  12. Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models

    Science.gov (United States)

    Gangloff, Richard P.; Kim, Sang-Shik

    1993-01-01

    This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on 'stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

  13. Probabilistic fatigue life updating accounting for inspections of multiple critical locations

    NARCIS (Netherlands)

    Maljaars, J.; Vrouwenvelder, A.C.W..

    2014-01-01

    Many steel structures contain multiple fatigue sensitive details that have similar geometries and are subjected to similar load fluctuations. Examples are orthotropic (bridge) decks and stiffened (ship) hulls where tens to thousands of similar details are present in one structure. Generally only vis

  14. Research on the Fatigue Property of HFW Pipe Welded Seam and Fatigue Life Forecast Method%HFW钢管焊缝疲劳特性与疲劳寿命预测方法研究

    Institute of Scientific and Technical Information of China (English)

    韩军; 高惠临; 韩新利

    2011-01-01

    受停输启用和供需变动的影响,油气管道的输送压力会发生周期性的变化,疲劳失效问题异常突出.特别是对于含有裂纹缺陷的管道,在疲劳载荷的作用下,若管道的应力强度因子幅超过疲劳裂纹扩展门槛值,裂纹就会发生疲劳扩展.当裂纹扩展到一定程度,超过管道运行压力下所能承受的临界缺陷极限尺寸,管道就会发生疲劳失效,从而影响到管道的使用寿命.采用高频疲劳试验机测试了X80钢级HFW焊管焊缝的疲劳裂纹扩展门槛值与疲劳裂纹扩展速率,结合API 579《适用性评价规范》中推荐的失效评估图技术(FAD)和Miner线性疲劳损伤积累理论,考虑了多种应力比对管道疲劳寿命的影响,建立了双参数HFW管道的疲劳寿命预测方法.%The transportation pressure of oil and gas pipeline can change periodically because of restart and supply change, so the fatigue failure problems stand out exceptionally. Especially for pipeline with crack defect, when the value of stress intensity factor exceeds fatigue crack expansion threshold value under fatigue load, the crack will expand; when crack expansion exceed critical defect extreme dimension under pipeline operation pressure, the fatigue failure of pipeline will happen, this will affect useful life of pipeline. In this article, the fatigue crack expansion threshold value of X80 HFW pipe welded seam and fatigue crack propagation rate were tested by using high-frequency fatigue testing machine, combined with the failure assessment diagram (FAD) recommended in API 579 Fitness-for-service Specification and the Miner's linear cumulative damage theory, considering the effect of combined stress ratio on pipeline fatigue life, the fatigue life forecast method for two-parameter HFW pipeline was established.

  15. Numerical simulation of the fatigue behavior of additive manufactured titanium porous lattice structures.

    Science.gov (United States)

    Zargarian, A; Esfahanian, M; Kadkhodapour, J; Ziaei-Rad, S

    2016-03-01

    In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1-0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-life approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45° to the loading direction. PMID:26706539

  16. Stress Analysis and Fatigue Analysis of Front Axle of Heavy-Duty Truck using ANSYS Ncode Design Life for Different Loading Cases

    Directory of Open Access Journals (Sweden)

    Hemant L. Aghav

    2016-06-01

    Full Text Available Front axle of heavy duty truck is the important component of vehicle and needs good design under the various loading conditions of the complete vehicle. Aim of the project is to stress analysis and predict the life of front axle for vertical, and vertical and braking loading case. The fatigue life of front axle is generally estimated by stress life approach and strain life approach method. Front axle beam assembly was modeled in the NX cad software. Meshing and Stress analysis is performed by ANSYS workbench and fatigue analysis is performed by NCODE design life ANSYS tool under different loading cases. Fatigue life of axle obtained by FEA method is more than 2 x 105 cycles, which is considered as safe for vertical loading case. Similarly, Fatigue life of axle obtained is more than 4 x 103 cycles, which is considered as safe for vertical and braking loading case. The max stress region is below spring pad of axle for vertical loading and in the goose neck of axle for vertical and braking loading case

  17. Fatigue behaviour and crack growth rate of cryorolled Al 7075 alloy

    International Nuclear Information System (INIS)

    Highlights: → High cycle fatigue of cryorolled Al 7075 alloy has been investigated. → Cryorolled Al alloy showed significant enhancement in fatigue strength. → FCGR resistance of the ufg Al alloy is higher at higher values of applied stress. - Abstract: The effects of cryorolling (CR) on high cycle fatigue (HCF) and fatigue crack growth rate behaviour of Al 7075 alloy have been investigated in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic (liquid nitrogen) temperature and its tensile strength, fatigue life, and fatigue crack growth mechanism were studied by using tensile testing, constant amplitude stress controlled fatigue testing, and fatigue crack growth rate testing using load shedding (decreasing ΔK) technique. The microstructural characterization of the alloy was carried out by using Field emission scanning electron microscopy (FESEM). The cryorolled Al alloy after 70% thickness reduction exhibits ultrafine grain (ufg) structure as observed from its FESEM micrographs. The cryorolled Al 7075 alloys showed improved mechanical properties (Y.S, U.T.S, Impact energy and Fracture toughness are 430 Mpa, 530 Mpa, 21 J, 24 Mpa m1/2 for 40CR alloy) as compared to the bulk 7075 Al alloy. It is due to suppression of dynamic recovery and accumulation of higher dislocations density in the cryorolled Al alloys. The cryorolled Al alloy investigated under HCF regime of intermediate to low plastic strain amplitudes has shown the significant enhancement in fatigue strength as compared to the coarse grained (CG) bulk alloy due to effective grain refinement. Fatigue crack growth (FCGR) resistance of the ufg Al alloy has been found be higher, especially at higher values of applied stress intensity factor ΔK The reasons behind such crack growth retardation is due to diffused crack branching mechanism, interaction between a propagating crack and the increased amount of grain boundaries (GB), and steps developed

  18. Reliability analysis for aeroengine turbine disc fatigue life with multiple random variables based on distributed collaborative response surface method

    Institute of Scientific and Technical Information of China (English)

    高海峰; 白广忱; 高阳; 鲍天未

    2015-01-01

    The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables, such as applied load, working temperature, geometrical dimensions and material properties. In order to ameliorate reliability analysis efficiency without loss of reliability, the distributed collaborative response surface method (DCRSM) was proposed, and its basic theories were established in this work. Considering the failure dependency among the failure modes, the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables. Then, the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion. Finally, the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method. Through the comparison of DCRSM, Monte Carlo method (MCM) and the traditional response surface method (RSM), the results show that the computational precision for DCRSM is more consistent with MCM than RSM, while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions. Thus, DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables, and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.

  19. Multimodal intervention improves fatigue and quality of life in subjects with progressive multiple sclerosis: a pilot study

    Directory of Open Access Journals (Sweden)

    Bisht B

    2015-02-01

    Full Text Available Babita Bisht,1 Warren G Darling,2 E Torage Shivapour,3 Susan K Lutgendorf,4–6 Linda G Snetselaar,7 Catherine A Chenard,1 Terry L Wahls1,8 1Department of Internal Medicine, Carver College of Medicine, University of Iowa, 2Department of Health and Human Physiology, College of Liberal Arts and Sciences, University of Iowa, 3Department of Neurology, Carver College of Medicine, University of Iowa, 4Department of Psychology, College of Liberal Arts and Sciences, University of Iowa, 5Department of Obstetrics and Gynecology, Carver College of Medicine, University of Iowa, 6Department of Urology, Carver College of Medicine, University of Iowa, 7Department of Epidemiology, College of Public Health, University of Iowa, 8Department of Internal Medicine, VA Medical Center, Iowa City, IA, USA Background: Fatigue is a disabling symptom of multiple sclerosis (MS and reduces quality of life. The aim of this study was to investigate the effects of a multimodal intervention, including a modified Paleolithic diet, nutritional supplements, stretching, strengthening exercises with electrical stimulation of trunk and lower limb muscles, and stress management on perceived fatigue and quality of life of persons with progressive MS. Methods: Twenty subjects with progressive MS and average Expanded Disability Status Scale (EDSS score of 6.2 (range: 3.5–8.0 participated in the 12-month phase of the study. Assessments were completed at baseline and at 3 months, 6 months, 9 months, and 12 months. Safety analyses were based on monthly side effects questionnaires and blood analyses at 1 month, 3 months, 6 months, 9 months, and 12 months. Results: Subjects showed good adherence (assessed from subjects' daily logs with this intervention and did not report any serious side effects. Fatigue Severity Scale (FSS and Performance Scales-fatigue subscale scores decreased in 12 months (P<0.0005. Average FSS scores of eleven subjects showed clinically significant reduction (more than

  20. Thickness dependent fatigue life at microcrack nucleation for metal thin films on flexible substrates

    Science.gov (United States)

    Sun, X. J.; Wang, C. C.; Zhang, J.; Liu, G.; Zhang, G. J.; Ding, X. D.; Zhang, G. P.; Sun, J.

    2008-10-01

    For polymer-supported metal thin films used in flexible electronics, the definition of the fatigue lifetime at microcrack nucleation (FLMN) should be more physically meaningful than all the previous definitions at structural instability. In this paper, the FLMN of Cu films (with thickness from 100 nm to 3.75 µm) as well as Al thin films (from 80 to 800 nm) was experimentally characterized at different strain ranges and different thicknesses by using a simple electrical resistance measurement (ERM). A significant thickness dependence was revealed for the FLMN and a similar Coffin-Manson fatigue relationship observed commonly in bulk materials was found to be still operative in both the films. Microstructural analyses were carried out to verify the feasibility of ERM correspondingly.

  1. Evolution of a laser shock peened residual stress field locally with foreign object damage and subsequent fatigue crack growth

    International Nuclear Information System (INIS)

    Foreign object damage (FOD) can seriously shorten the fatigue lives of components. On the other hand, laser shock peening improves fatigue life by introducing deep compressive residual stress into components. In this paper we examine how the non-uniform steep residual stress profile arising from FOD of laser peened aerofoil leading edges varies as a function of fatigue crack growth under high cycle fatigue and mixed high and low cycle fatigue conditions. The ballistic FOD impacts were introduced by impacting a cube edge head-on (at an angle of 0°) to the leading edge. The residual stress distributions have been mapped by synchrotron X-ray diffraction prior to cracking and subsequent to short (∼1 mm) and long (up to 6 mm) crack growth. The results suggest that the local residual stress field is highly stable even to the growth of relatively long cracks

  2. Dynamic Properties and Fatigue Life of Stone Mastic Asphalt Mixtures Reinforced with Waste Tyre Rubber

    Directory of Open Access Journals (Sweden)

    Nuha Salim Mashaan

    2013-01-01

    Full Text Available Today, virgin polymer modified asphalt mixes are comparatively more expensive for road pavement. One way to reduce the expense of such construction and to make it more convenient is the application of inexpensive polymer, such as waste polymer. The primary aim of this study was to investigate the effect of adding waste tyre rubber (crumb rubber modifier (CRM on the stiffness and fatigue properties of stone mastic asphalt (SMA mixtures. Various percentages of waste CRM with size of 0.60 mm were added to SMA mixtures. Indirect tensile stiffness modulus test was conducted at temperatures of 5, 25, and 40°C. Indirect tensile fatigue test was conducted at three different stress levels (2000, 2500, and 3000 N. The results show that the stiffness modulus of reinforced SMA samples containing various contents of CRM is significantly high in comparison with that of nonreinforced samples, and the stiffness modulus of reinforced samples is in fact less severely affected by the increased temperature compared to the nonreinforced samples. Further, the results show that CRM reinforced SMA mixtures exhibit significantly higher fatigue lives compared to the nonreinforced mixtures help in and promotion of sustainable technology by recycling of waste materials in much economical and environmental-friendly manner.

  3. Damage repair in CMSX-4 alloy without fatigue life reduction penalty

    Science.gov (United States)

    Okazaki, Masakazu; Ohtera, Issei; Harada, Yoshio

    2004-02-01

    The microstructural changes in a single-crystal Ni-base superalloy, CMSX-4, that might occur during the processes of repair and recoating of hot section components for advanced gas turbines were studied. It is shown that the cellular γ/γ‧ microstructure is formed when the material is subjected to local plastic straining, followed by the reheat treatments during the course of damage recovery. The formation of cellular microstructure in the material led to the remarkably reduced fatigue strength. In order to reduce or prevent the preceding undesirable effect resulting from cellular microstructure, a new method based on applying overlay coating technique was developed. The method is based on an idea that the alloying elements that are depleted in base alloys could be supplemented via the overlay coating. An X alloy, which contains grain boundary strengthening elements, was selected and coated on the CMSX-4 with the cellular microstructure by low-pressure plasma spraying. The fatigue tests on the coated CMSX-4 specimens demonstrated the effectiveness of the method. The observations of the crack initiation site, the fatigue fracture mode, the crack density in the cellular transformed area, and the crack propagation morphologies near the prior interface strongly supported the validity of this approach. The method is expected to build a road to a so-called damage cure (or recovery) coating.

  4. Applications of a new magnetic monitoring technique to in situ evaluation of fatigue damage in ferrous components

    International Nuclear Information System (INIS)

    This project consisted of research into the use of magnetic inspection methods for the estimation of fatigue life of nuclear pressure vessel steel. Estimating the mechanical and magnetic properties of ferromagnetic materials are closely interrelated, therefore, measurements of magnetic properties could be used to monitor the evolution of fatigue damage in specimens subjected to cyclic loading. Results have shown that is possible to monitor the fatigue damage nondestructively by magnetic techniques. For example, in load-controlled high-cycle fatigue tests, it has been found that the plastic strain and coercivity accumulate logarithmically during the fatigue process. Thus a quantitative relationship between coercivity and the number of fatigue cycles could be established based on two empirical coefficients, which can be determined from the test conditions and material properties. Also it was found that prediction of the onset of fatigue failure in steels was possible under certain conditions. In strain-controlled low cycle fatigue, critical changes in Barkhausen emissions, coercivity and hysteresis loss occurred in the last ten to twenty percent of fatigue life

  5. Applications of a new magnetic monitoring technique to in situ evaluation of fatigue damage in ferrous components

    Energy Technology Data Exchange (ETDEWEB)

    Jiles, D.C.; Biner, S.B.; Govindaraju, M.R.; Chen, Z.J. [Iowa State Univ. of Science and Technology, Ames, IA (United States). Center for Nondestructive Evaluation

    1994-06-01

    This project consisted of research into the use of magnetic inspection methods for the estimation of fatigue life of nuclear pressure vessel steel. Estimating the mechanical and magnetic properties of ferromagnetic materials are closely interrelated, therefore, measurements of magnetic properties could be used to monitor the evolution of fatigue damage in specimens subjected to cyclic loading. Results have shown that is possible to monitor the fatigue damage nondestructively by magnetic techniques. For example, in load-controlled high-cycle fatigue tests, it has been found that the plastic strain and coercivity accumulate logarithmically during the fatigue process. Thus a quantitative relationship between coercivity and the number of fatigue cycles could be established based on two empirical coefficients, which can be determined from the test conditions and material properties. Also it was found that prediction of the onset of fatigue failure in steels was possible under certain conditions. In strain-controlled low cycle fatigue, critical changes in Barkhausen emissions, coercivity and hysteresis loss occurred in the last ten to twenty percent of fatigue life.

  6. EFFECTS OF STRAIN RATIO ON THERMAL-MECHANICAL CYCLIC STRESS-STRAIN RESPONSE AND FATIGUE LIFE IN DS SUPERALLOY DZ125

    Institute of Scientific and Technical Information of China (English)

    G.D. Zhang; S.L. Liu; Y.H. He; R.Z. Chen

    2004-01-01

    The effects of strain ratio on thermal-mechanical cyclic stress-strain response and fatigue life in DS superalloy DZ125 have been studied by performing tests at various strain ratio experiments, under strain-controlled and temperature cycling from 550to 1000 C. It is shown that thermal-mechanical cyclic stress-strain response behavior not only depend on magnitude of strain, and temperature-loading phase angle, but also strain ratio. Fatigue life at strain ratio Re=-0.3 is longer than that of strain ratio Rε=-1. 0, under in-phase thermal-mechanical loading. However, Fatigue life at strain ratio Rε=-0. 3 is shorter than that of strain ratio Rε=-1.0, under out-of-phase thermal-mechanical loading. The thermal-mechanical fatigue (TMF) damage model was discussed. Results of fractography show that fatigue, creep and oxidation damage always occur during TMF. The main damage mode depends on loading wave, strain ratio and magnitude of strain.

  7. Effect of grinding on the fatigue life of titanium alloy (5 Al-2.5 Sn) under dry and wet conditions

    Science.gov (United States)

    Rangaswamy, Partha; Terutung, Hendra; Jeelani, Shaik

    1989-01-01

    The principal factors in the performance of aerospace materials are strength-to-weight ratio, fatigue life, fracture toughness, survivability and, of course, reliability. Machining processes and, in particular, grinding under adverse conditions have been found to cause damage to surface integrity and affect the residual stress distribution in the surface and subsurface region. These effects have a direct bearing on the fatigue life. In this investigation the effects of grinding conditions on the fatigue life of Titanium 5 Al-2.5Sn were studied. This alloy is used in ground form in the manufacturing of some critical components in the space shuttle's main engine. It is essential that materials for such applications be properly characterized for use in severe service conditions. Flat sub-size specimens 0.1 inch thick were ground on a surface grinding machine equipped with a variable speed motor at speeds of 2000 to 6000 rpm using SiC wheels of grit sizes 60 and 120. The grinding parameters used in this investigation were chosen from a separate study. The ground specimens were then fatigued at a selected stress and the resulting lives were compared with that of the virgin material. The surfaces of the specimens were examined under a scanning electron microscope, and the roughness and hardness were measured using a standard profilometer and microhardness tester, respectively. The fatigue life of the ground specimens was found to decrease with the increase in speed for both dry and wet conditions. The fatigue life of specimens ground under wet conditions showed a significant increase at the wheel speed of 2000 rpm for both the grit sizes and thereafter decreased with increase profilometry, microhardness measurements and scanning electron microscopic examination.

  8. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    Science.gov (United States)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  9. Mechanical and transport properties of IBAD/EDDC-SmBCO coated conductor tapes during fatigue loading

    Science.gov (United States)

    Shin, Hyung-Seop; Dedicatoria, Marlon J.

    2011-06-01

    In electrical devices like superconducting motor, generator and SMES, HTS coated conductor (CC) tapes will be subjected to alternating stress or strain during manufacturing and operation. The repeated loading will affect the mechanical integrity and eventually the electrical transport property of CC tapes. Therefore in such applications, electro-mechanical property of CC tapes should be evaluated. In this study, the endurance of an IBAD/EDDC-SmBCO CC tape under high-cycle fatigue loading has been evaluated. Applied maximum stress and fatigue life ( S-N) relation was obtained at 77 K. The mechanical properties and the critical current, I c, of the sample under fatigue loading were investigated at 77 K. Considering the practical operating environment, the effect of the stress ratio R, on the degradation behavior of I c under fatigue loading was also examined.

  10. Multiaxial fatigue criterion based on parameters from torsion and axial S-N curve

    Directory of Open Access Journals (Sweden)

    M. Margetin

    2016-07-01

    Full Text Available Multiaxial high cycle fatigue is a topic that concerns nearly all industrial domains. In recent years, a great deal of recommendations how to address problems with multiaxial fatigue life time estimation have been made and a huge progress in the field has been achieved. Until now, however, no universal criterion for multiaxial fatigue has been proposed. Addressing this situation, this paper offers a design of a new multiaxial criterion for high cycle fatigue. This criterion is based on critical plane search. Damage parameter consists of a combination of normal and shear stresses on a critical plane (which is a plane with maximal shear stress amplitude. Material parameters used in proposed criterion are obtained from torsion and axial S-N curves. Proposed criterion correctly calculates life time for boundary loading condition (pure torsion and pure axial loading. Application of proposed model is demonstrated on biaxial loading and the results are verified with testing program using specimens made from S355 steel. Fatigue material parameters for proposed criterion and multiple sets of data for different combination of axial and torsional loading have been obtained during the experiment.

  11. Dynamic Properties and Fatigue Life of Stone Mastic Asphalt Mixtures Reinforced with Waste Tyre Rubber

    OpenAIRE

    Nuha Salim Mashaan; Ali, Asim H.; Suhana Koting; Mohamed Rehan Karim

    2013-01-01

    Today, virgin polymer modified asphalt mixes are comparatively more expensive for road pavement. One way to reduce the expense of such construction and to make it more convenient is the application of inexpensive polymer, such as waste polymer. The primary aim of this study was to investigate the effect of adding waste tyre rubber (crumb rubber modifier (CRM)) on the stiffness and fatigue properties of stone mastic asphalt (SMA) mixtures. Various percentages of waste CRM with size of 0.60 mm ...

  12. 钢筋混凝土桥面板疲劳寿命评估%Fatigue life estimation for reinforced concrete bridge deck

    Institute of Scientific and Technical Information of China (English)

    王春生; 吴全友; 缪文辉

    2013-01-01

    In order to ensure the service safety, it is necessary to evaluate the fatigue life of concrete bridge decks. The fatigue life estimation and prediction models for concrete bridge decks were proposed based on the theory of cumulative fatigue damage, wheel loading test data and the correlation coefficient of actual bridge deck fatigue life and tested fatigue life. Based on the fatigue life estimation model of concrete bridge decks, the effects of the different standard fatigue vehicles in BS5400, Eurocode, AASHTO design codes and truck overload were evaluated. The results show that the technical parameters of the different standard fatigue vehicles have obvious effect on the fatigue life, so a special fatigue vehicle model for concrete bridge decks should be developed; wheel live load spectrum value of BS5400 is the preferred choice under no traffic detection data; the fatigue life of concrete bridge decks decreases greatly at truck overload of 20% , and the fatigue life is less than 10 years at truck overload of 40%. So the trucks with 20% overload must be strictly prohibited to pass the operation concrete bridges. 4 tabs, 4 figs, 17 refs.%为确保桥梁使用安全,对混凝土桥面板进行疲劳寿命评估十分迫切.基于疲劳损伤累积理论和混凝土桥面板车轮移动疲劳加载下试验数据,并引入模型相关系数,用来考虑桥面板实际寿命和试验寿命的差异,建立了混凝土桥面板疲劳寿命预测模型,对混凝土桥面板的疲劳寿命进行评估.分析比较了采用英国BS5400、欧洲规范Eurocode和美国AASHTO规范中标准疲劳车评价混凝土桥面板疲劳寿命的差异性,以及车辆超载对桥面板使用寿命的影响.计算结果表明:疲劳标准车技术参数对混凝土桥面板的疲劳寿命影响较大,应研发适用于桥面板疲劳分析的车辆荷载模型;在没有实桥调查数据情况下,建议优先采用BS5400规定的车轮活载频谱值;当车辆超载20%以上

  13. 玉米收获机底盘车架疲劳寿命研究%Study on fatigue life of frame for corn combine chassis machine

    Institute of Scientific and Technical Information of China (English)

    陈志; 周林; 赵博; 梁学修

    2015-01-01

    提出一种玉米收获机底盘车架疲劳寿命预测方法.利用ANSYS软件对玉米收获机底盘车架进行有限元分析,得到最大模态变形位置和静应力分析条件下的应力分布;在有限元分析数据基础上,粘贴应变片,组建应力测量系统,实测田间及道路条件下的应变时间历程;对采集的应变数据开展预处理,初步分析其受力情况及动载荷特征,采用nCode软件完成疲劳寿命预测.试验结果表明,车身横梁疲劳寿命为24.1万h、支撑部件寿命为16 500万h,满足使用要求,但支撑部件强度设计过剩,采用workbench的shape optimization对该部件开展轻量化设计,在满足疲劳可靠性条件下,减少了该部件质量24%.%The chassis frame is the installed base of the corn combine harvester, which bears a lot of force from the longitudinal bending, torsion, lateral bending, horizontal rhombic and their combined loads. The frame has obvious dynamic load characteristics, therefore the static strength check is not enough and research on the fatigue life is needed. As the lack of basic research, the key data accumulation is insufficient, the tradition design method is relatively limited, many Chinese products lack the necessary fatigue strength in design, and the reliability is poor. Experience in the automotive industry has proved that the combination of fatigue load spectrum and CAE technology can greatly improve the forecasting ability. Fatigue strength study of the corn combine harvester is the foundation of improving the reliability and an important method to reduce the structural mass. In order to reduce the structural weight and improve the fatigue reliability of the corn combine harvester, this paper studies a method to evaluate fatigue life of the main frame. Firstly, using ANSYS software, the stress distribution of the corn harvester chassis frame was analyzed, and the stress distribution of the maximum modal deformation position and under static stress

  14. TiNi-based films for elastocaloric microcooling— Fatigue life and device performance

    Science.gov (United States)

    Ossmer, H.; Chluba, C.; Kauffmann-Weiss, S.; Quandt, E.; Kohl, M.

    2016-06-01

    The global trend of miniaturization and concomitant increase of functionality in microelectronics, microoptics, and various other fields in microtechnology leads to an emerging demand for temperature control at small scales. In this realm, elastocaloric cooling is an interesting alternative to thermoelectrics due to the large latent heat and good down-scaling behavior. Here, we investigate the elastocaloric effect due to a stress-induced phase transformation in binary TiNi and quaternary TiNiCuCo films of 20 μm thickness produced by DC magnetron sputtering. The mesoscale mechanical and thermal performance, as well as the fatigue behavior are studied by uniaxial tensile tests combined with infrared thermography and digital image correlation measurements. Binary films exhibit strong features of fatigue, involving a transition from Lüders-like to homogeneous transformation behavior within three superelastic cycles. Quaternary films, in contrast, show stable Lüders-like transformation without any signs of degradation. The elastocaloric temperature change under adiabatic conditions is -15 K and -12 K for TiNi and TiNiCuCo films, respectively. First-of-its-kind heat pump demonstrators are developed that make use of out-of-plane deflection of film bridges. Owing to their large surface-to-volume ratio, the demonstrators reveal rapid heat transfer. The TiNiCuCo-based devices, for instance, generate a temperature difference of 3.5 K within 13 s. The coefficients of performance of the demonstrators are about 3.

  15. Combined Cycle Fatigue Investigation Based on Energy Principle

    OpenAIRE

    Kalynenko Mykyta

    2016-01-01

    We present a modified energy-principle based model of fatigue damage accumulation in high temperature alloys usually used in gas turbine engine under combined high cycle fatigue and low cycle fatigue (LCF/HCF) loading conditions. Our model is based on the energy principle which includes a modified approximation formula that describes fatigue crack origin depending on the relative amplitude of stress intensity in the ranges of both high- and low-cycle fatigue under non-isothermal loading. Func...

  16. Response Surface Approximation for Fatigue Life Prediction and Its Application to Multi-Criteria Optimization With a Priori Preference Information

    International Nuclear Information System (INIS)

    In this paper, a versatile multi-criteria optimization concept for fatigue life prediction is introduced. Multi-criteria decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability

  17. Influence of process parameters on rolling-contact-fatigue life of ion plated nickel-copper-silver lubrication

    International Nuclear Information System (INIS)

    In this paper, we present a connection between argon ion flux, element-mixing, and rolling contact fatigue (RCF) life of a thin film nickel-copper-silver lubricant on ball bearings. The film is deposited on the balls using an ion plating process and tested for RCF in high vacuum. The ion flux is measured using a Langmuir probe and the plane stress within the film during deposition is calculated using a thin film model. Experiments reveal that there is an inverse relationship between ion flux and RCF life for most deposition voltage and pressure combinations tested, specifically, 15.5-18.5 mTorr and 1.5-3.5 kV. For voltages up to 2.5 kV, RCF life decreases as ion flux increases due to increased compressive stress within the film, reaching as high as 2.6 GPa. For voltages between 2.5 and 3.5 kV, interlayer mixing of nickel and copper with the silver layer reduces RCF life due to contamination, even as ion flux and corresponding film compressive stress are reduced. A Monte Carlo-based simulation tool, SRIM is used to track collision cascades of the argon ions and metal atoms within the coating layers. At process voltages above 2.5 kV we observe elemental mixing of copper and nickel with the silver layer using Auger electron spectroscopy of coated steel and Si3N4 balls. The authors conclude that an ion flux greater than 5.0 x 1014 cm-2 s-1 leads to reduced RCF life due to high film stress. In addition, process voltages greater than 2.5 kV also reduce RCF life due to contamination and interlayer mixing of nickel and copper within the silver layer.

  18. Fatigue limit investigation of 6061-T6 aluminum alloy in giga-cycle regime

    International Nuclear Information System (INIS)

    In order to investigate the fatigue limit micro-mechanism of a precipitation-hardened Al–Mg–Si alloy (6061-T6), the alloy was subjected to very-high-cycle fatigue (VHCF) of over 109 cycles by an ultrasonic fatigue method. Two kinds of specimens, one with smooth surface and the other with a small artificial hole on the surface, were compared. The smooth specimens showed no distinct fatigue limit. Conversely, the holed specimens showed clear fatigue limit which had been generally deemed to be absent in non-ferrous alloys. In addition to the conventional fatigue crack growth (FCG) observation by replica technique, metallographically critical analyses by electron backscattered diffraction (EBSD) and cross-sectional focused ion beam (FIB) were conducted to reveal the micro-plasticity associated with FCG. It was found that the fatigue life of smooth specimens at low stress amplitude was controlled by an unstoppable FCG mechanism mediated by persistent slip bands (PSBs). On the other hand, the emergence of distinct fatigue limit in holed specimens was attributed to a non-propagating crack having mode I characteristics in essence. No coaxing effect was, however, confirmed for such non-propagating cracks. The above results, which were somewhat different from previous ones obtained by rotating bending under normal frequency, were discussed in terms of both metallurgical and mechanical points of view

  19. Androgen deficiency in male patients diagnosed with ANCA-associated vasculitis : A cause of fatigue and reduced health-related quality of life?

    NARCIS (Netherlands)

    Tuin, Janneke; Sanders, Jan-Stephan F.; Buhl, Birgit M.; van Beek, Andre P.; Stegeman, Coen A.

    2013-01-01

    Introduction: Low testosterone levels in men are associated with fatigue, limited physical performance and reduced health-related quality of life (HRQOL); however, this relationship has never been assessed in patients with anti-neutrophil cytoplasmic antibodies (ANCA) -associated vasculitides (AAV).

  20. Fatigue of stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Solin, J. (VTT Technical Research Centre of Finland, Espoo (Finland))

    2010-05-15

    The 2009b update of ASME III introduces a new set of fatigue design curves. The new curve for austenitic stainless steels is exactly matching with the one endorsed in 2007 by the US NRC for new designs only. This has a notable effect in usage factor calculation at strain amplitudes below 0.5 %. However, experimental results clearly demonstrate that a new air curve would not be needed for the studied stainless steel grades. Our current results suggest arguments for use of stabilized stainless steels in NPP piping components, where high cycle fatigue (epsilon{sub a}<=0.5%) is a concern. (orig.)

  1. Probabilistic Rotor Life Assessment Using Reduced Order Models

    OpenAIRE

    Beachkofski, Brian K.

    2009-01-01

    Probabilistic failure assessments for integrally bladed disks are system reliability problems where a failure in at least one blade constitutes a rotor system failure. Turbine engine fan and compressor blade life is dominated by High Cycle Fatigue (HCF) initiated either by pure HCF or Foreign Object Damage (FOD). To date performing an HCF life assessment for the entire rotor system has been too costly in analysis time to be practical. Although the substantial run-time has previously precluded...

  2. Micromechanical study of the effect of inclusions on fatigue failure in a roller bearing

    DEFF Research Database (Denmark)

    Cerullo, Michele; Tvergaard, Viggo

    2015-01-01

    Purpose - The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings. Design/methodology/approach - The local stress concentrations around an inclusion are determined from a characteristic unit cell...... of the most commonly used bearing steels, AISI 52100, and two different types of inclusions are considered. The macroscopic stress histories applied correspond to either a Hertzian or an elastohydrodynamic (EHL) contact pressure distribution under the rollers. Findings - The paper shows that sub-surface...... to work in the very high cycle regime (N>109 cycles). This paper develops a micromechanical study that provides a deeper understanding on effect of inclusions on the fatigue life, according to one of the most used multiaxial fatigue criteria....

  3. Structural health monitoring for fatigue life prediction of orthotropic brdige decks

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Lotfollah Pahlavan, P.; Paulissen, J.H.; Hakkesteegt, H.C.; Jansen, T.H.

    2013-01-01

    Infrastructure asset owners are more and more confronted with structures reaching the end of their structural life. Structural Health Monitoring (SHM) systems should provide up-to-date information about the actual condition, as well predict the structural life and required maintenance of the assets

  4. Effect of Thermal Shock Process in Accelerated Environment Spectrum on the Fatigue Life of 7B04-T6 Aluminum Alloy

    Institute of Scientific and Technical Information of China (English)

    CUI Tengfei; LIU Daoxin; ZHANG Xiaohua; YU Shouming

    2016-01-01

    The effect of thermal shock, in an accelerated-corrosion environment spectrum, on the fatigue and corrosion behavior of 7B04-T6 aluminum alloy, was determined. The environment spectrum consists of two modules, namely: salt-spray corrosion and thermal shock. The effect of thermal shock on the mechanical properties was determined via tensile tests; SEM, DCS, and XRD were used to determine the effect of thermal shock on the corrosion products. In addition, the corrosion resistance of the products was ascertained through electrochemical testing. The results show that the mechanical properties and fatigue life of the aluminum alloy will decline with prolonged thermal shock time. The thermal shock process may result in denser surface corrosion products than those formed on the no thermal shock specimens, and transformation of some Al (OH)3 into AlOOH. AlOOH may have resulted in improved corrosion resistance and hence a lower decrease in the fatigue life after corrosion, compared with that of the no thermal shock specimen. Repeated corrosion/thermal shock may have delayed further decease in the fatigue life. Therefore, selection of an appropriate equivalent thermal shock temperature and time was essential for designing the environmental spectrum.

  5. Experimental Study of Fatigue Life of Tractor PTO Gear%拖拉机动力输出齿轮疲劳寿命的试验研究

    Institute of Scientific and Technical Information of China (English)

    王风雨; 陈振

    2012-01-01

    为了研究现有工艺下拖拉机动力输出被动齿轮的疲劳寿命,选取共振式高频疲劳试验机,对随机选取的某一型号拖拉机动力输出齿轮进行弯曲疲劳试验,测得齿轮的疲劳极限载荷和S-N曲线。通过试验取得的数据,为拖拉机齿轮的可靠性设计和寿命评估模型的构建提供依据。%In order to investigate the fatigue life of tractor PTO' s passive gear under the actual technics, the fatigue experiments were performed by syntonic high-frequency test-bed. The tractor PTO' s passive gear was selected at random,and the bending fatigue tests were done. The gear' s fatigue life limit and S-N curve were gained. The experimental data can be acted as the data for the tractor gear' s reliable design and the construction of the model for evalu;,ting life.

  6. Impact of partial versus whole breast radiation therapy on fatigue, perceived stress, quality of life and natural killer cell activity in women with breast cancer

    International Nuclear Information System (INIS)

    This pilot study used a prospective longitudinal design to compare the effect of adjuvant whole breast radiation therapy (WBRT) versus partial breast radiation therapy (PBRT) on fatigue, perceived stress, quality of life and natural killer cell activity (NKCA) in women receiving radiation after breast cancer surgery. Women (N = 30) with early-stage breast cancer received either PBRT, Mammosite brachytherapy at dose of 34 Gy 10 fractions/5 days, (N = 15) or WBRT, 3-D conformal techniques at dose of 50 Gy +10 Gy Boost/30 fractions, (N = 15). Treatment was determined by the attending oncologist after discussion with the patient and the choice was based on tumor stage and clinical need. Women were assessed prior to initiation of radiation therapy and twice after completion of radiation therapy. At each assessment, blood was obtained for determination of NKCA and the following instruments were administered: Perceived Stress Scale (PSS), Functional Assessment of Cancer Therapy-Fatigue (FACT-F), and Functional Assessment of Cancer Therapy-General (FACT-G). Hierarchical linear modeling (HLM) was used to evaluate group differences in initial outcomes and change in outcomes over time. Fatigue (FACT-F) levels, which were similar prior to radiation therapy, demonstrated a significant difference in trajectory. Women who received PBRT reported progressively lower fatigue; conversely fatigue worsened over time for women who received WBRT. No difference in perceived stress was observed between women who received PBRT or WBRT. Both groups of women reported similar levels of quality of life (FACT-G) prior to initiation of radiation therapy. However, HLM analysis revealed significant group differences in the trajectory of quality of life, such that women receiving PBRT exhibited a linear increase in quality of life over time after completion of radiation therapy; whereas women receiving WBRT showed a decreasing trajectory. NKCA was also similar between therapy groups but additional

  7. Fatigue Life Analyzing of A Semi-trailer Skeleton Based on AWE%基于AWE某半挂车车架疲劳寿命分析

    Institute of Scientific and Technical Information of China (English)

    赵轩

    2014-01-01

    The UG software was used to establish model and through AWE software analysis, From the cloud diagram of fatigue life generated by result of the fatigue simulation,we can directly and clearly determine the dangerous areas where the fatigue takes place,Therefore, these data can be used for the optinization design of skeleton to improve the quality.%采用UG软件建立了三维模型,并应用AWE软件完成了该产品试验的疲劳分析,从仿真分析计算所得到的疲劳寿命云图中,可直观的判断出车架的疲劳发生危险区域,为其改进设计提供了依据。

  8. 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.

  9. Creep fatigue life prediction for engine hot section materials (isotropic): Two year update

    Science.gov (United States)

    Moreno, V.

    1984-01-01

    Requirements for increased durability of gas turbine hot section components have placed a greater degree of importance on accurate structural analysis and life prediction. Various life prediction approaches for high temperature applications were investigated. Basic models were selected and developed for simple-cycle, isothermal loading conditions. Models will be developed which address thermomechanical cycling, multiaxial conditions, cumulative loading, environmental effects, and cyclic mean stress. Verification tests of models will be conducted on an alternate material and coating system.

  10. Reciprocal relationship between acute stress and acute fatigue in everyday life in a sample of university students.

    Science.gov (United States)

    Doerr, Johanna M; Ditzen, Beate; Strahler, Jana; Linnemann, Alexandra; Ziemek, Jannis; Skoluda, Nadine; Hoppmann, Christiane A; Nater, Urs M

    2015-09-01

    We investigated whether stress may influence fatigue, or vice versa, as well as factors mediating this relationship. Fifty healthy participants (31 females, 23.6±3.2 years) completed up to 5 momentary assessments of stress and fatigue during 5 days of preparation for their final examinations (exam condition) and 5 days of a regular semester week (control condition). Sleep quality was measured by self-report at awakening. A sub-group of participants (n=25) also collected saliva samples. Fatigue was associated with concurrent stress, stress reported at the previous measurement point, and previous-day stress. However, momentary stress was also predicted by concurrent fatigue, fatigue at the previous time point, and previous-day fatigue. Sleep quality mediated the association between stress and next-day fatigue. Cortisol and alpha-amylase did not mediate the stress-fatigue relationship. In conclusion, there is a reciprocal stress-fatigue relationship. Both prevention and intervention programs should comprehensively cover how stress and fatigue might influence one another. PMID:26143479

  11. Fatigue Life Prediction of Mooring Chains for a Floating Tidal Current Power Station

    Institute of Scientific and Technical Information of China (English)

    Fengmei Jing; Liang Zhang; Zhong Yang

    2012-01-01

    As a kind of clean and renewable energy,tidal current energy is becoming increasingly popular all over the world with the shortage of energy and environmental problems becoming more and more severe.A floating tidal current power station is a typical type of tidal current power transformers which can sustain the loads of wind,waves,and current,and even the extreme situation of a typhoon.Therefore,the mooring system must be reliable enough to keep the station operating normally and to survive in extreme situations.The power station examined in this paper was installed at a depth of 40 m.A 44 mm-diameter R4-RQ4 chain was chosen,with a 2 147 kN minimum break strength and 50 kN pretension.Common studless link chain was used in this paper.Based on the Miner fatigue cumulative damage rule,S-N curves of chains,and MOSES software,a highly reliable mooring system was designed and analyzed.The calculation results show that the mooring system designed is reliable throughout a 10-year period.It can completely meet the design requirements of American Petroleum institution (API).Therefore,the presented research is significant for advancing the design of this kind of power station.

  12. A Study on Variations of the Low Cycle Fatigue Life of a High Pressure Turbine Nozzle Caused by Inlet Temperature Profiles and Installation Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hur, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Seo, Do Young [Pusan National Univ., Busan (Korea, Republic of)

    2015-11-15

    High pressure components of a gas turbine engine must operate for a long life under severe conditions in order to maximize the performance and minimize the maintenance cost. Enhanced cooling design, thermal barrier coating techniques, and nickel-base superalloys have been applied for overcoming them and furthermore, material modeling, finite element analysis, statistical techniques, and etc. in design stage have been utilized widely. This article aims to evaluate the effects on the low cycle fatigue life of the high pressure turbine nozzle caused by different turbine inlet temperature profiles and installation conditions and to investigate the most favorable operating condition to the turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and its results were the input for the assessment of low cycle fatigue life at several critical zones.

  13. A study on variations of the low cycle fatigue life of a high pressure turbine nozzle caused by inlet temperature profiles and installation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Aero-propulsion Research Office, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Seo, Do Young [School of Mechanical and Aerospace Engineering, Pusan National University, Busan (Korea, Republic of)

    2015-11-15

    High pressure components of a gas turbine engine must operate for a long life under severe conditions in order to maximize the performance and minimize the maintenance cost. Enhanced cooling design, thermal barrier coating techniques, and nickel-base superalloys have been applied for overcoming them and furthermore, material modeling, finite element analysis, statistical techniques, and etc. in design stage have been utilized widely. This article aims to evaluate the effects on the low cycle fatigue life of the high pressure turbine nozzle caused by different turbine inlet temperature profiles and installation conditions and to investigate the most favorable operating condition to the turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and its results were the input for the assessment of low cycle fatigue life at several critical zones.

  14. Influence of Ply Waviness on Fatigue Life of Tapered Composite Flexbeam Laminates

    Science.gov (United States)

    Murri, Gretchen B.

    1999-01-01

    Nonlinear tapered flexbeam laminates, with significant ply waviness, were cut from a full-size composite rotor hub flexbeam. The specimens were tested under combined axial tension and cyclic bending loads. All of the specimens had wavy plies through the center and near the surfaces (termed marcelled areas), although for some of the specimens the surface marcels were very obvious, and for others they were much smaller. The specimens failed by first developing cracks through the marcels at the surfaces, and then delaminations grew from those cracks, in both directions. Delamination failure occurred in these specimens at significantly shorter fatigue lives than similar specimens without waviness, tested in ref. 2. A 2D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. In addition, the FE model duplicated the waviness observed in one of the test specimens. The model was analyzed using a geometrically nonlinear FE code. Modifications were made to the original model to reduce the amplitude of the marcels near the surfaces. The analysis was repeated for each modification. Comparisons of the interlaminar normal stresses, sigma(sub n), in the various models showed that under combined axial-tension and cyclic-bending loading, for marcels of the same aspect ratio, sigma(sub n) stresses increased as the distance along the taper, from thick to thin end, increased. For marcels of the same aspect ratio and at the same X-location along the taper, sigma(sub n) stresses decreased as the distance from the surface into the flexbeam interior increased. A technique was presented for determining the smallest acceptable marcel aspect ratio at various locations in the flexbeam.

  15. Quality of life, depression and fatigue among persons co-infected with HIV and hepatitis C: outcomes from a population-based cohort.

    Science.gov (United States)

    Braitstein, P; Montessori, V; Chan, K; Montaner, J S G; Schechter, M T; O'Shaughnessy, M V; Hogg, R S

    2005-05-01

    The objective of the study was to describe the additional burden generated by hepatitis C (HCV) infection among HIV-infected individuals as measured by self-reported quality of life, depression and fatigue. The provincial HIV/AIDS Drug Treatment Program (DTP) distributes all antiretroviral medication in the province of British Columbia. Eligibility for accessing antiretrovirals is based on published guidelines commensurate with the International AIDS Society. Each participant is asked to complete a self-administered mailed questionnaire that includes patient sociodemographic information, quality of life measures (Medical Outcomes Study-Short Form (MOS-SF), mental health issues (Centre for Epidemiological Studies Depression scale (CESD) and fatigue information. HIV-HCV co-infected individuals were compared to HIV mono-infected individuals using parametric and nonparametric methods. Multivariate logistic regression was used to examine the impact of hepatitis C on quality of life, depression and fatigue, after controlling for sociodemographics and HIV-specific clinical characteristics. Of the 4,134 individuals who were sent a HIV/AIDS DTP survey in 1999, 2000 or 2001, 484 participants both returned one and had an HCV-antibody test result on file. Of the 484 participants eligible for this analysis, 105 (22%) were HCV-positive. In comparison to the 379 (78%) patients testing negative for HCV, a larger proportion of co-infected patients were female (18% versus 3%, p<0.001), aboriginal (20% versus 3%, p<0.001), had ever injected drugs (79% versus 5%, p<0.001), were unemployed (91% versus 49%, p<0.001) and lived in unstable housing (19% versus 1%, p<0.001) at the time they completed the survey. Co-infected patients reported more symptoms consistent with depression, increased fatigue and poorer quality of life. However, using multivariate modeling, it was determined that the impact of HCV on quality of life, depression and fatigue was better explained by the

  16. Improvement in Fatigue, Sleepiness, and Health-Related Quality of Life with Bright Light Treatment in Persons with Seasonal Affective Disorder and Subsyndromal SAD

    Directory of Open Access Journals (Sweden)

    Cecilia Rastad

    2011-01-01

    Full Text Available Objective. To investigate the effects of bright light treatment for secondary outcome measures and to explore and validate empirically derived subgroups and treatment effects in subgroups. Methods. A descriptive design. A sample of forty-nine persons (mean age of 45.8 with clinically assessed seasonal affective disorder (SAD or subsyndromal SAD (S-SAD participated in a two-group clinical trial evaluating the effects of treatment with bright light therapy. A person-oriented cluster analysis was applied to study treatment effects in subgroups. Results. For the merged group, sleepiness (Epworth Sleepiness Scale, fatigue (fatigue questionnaire, and health-related quality of life (SF-36 were improved at posttreatment, and results were maintained at the one-month followup. Three distinct subgroups had a high level of fatigue in common, while the level of excessive daytime sleepiness and depressed mood differed between the subgroups. Over time, all subgroups improved following ten days treatment in a light room. Conclusion. Fatigue, excessive daytime sleepiness, and health-related quality of life improve in a similar way as depressed mood following treatment with bright light. The treatment was effective irrespective of the severity of the disorder, that is, for persons with SAD and subsyndromal SAD.

  17. 空冷风机桥架疲劳寿命分析%Analysis of fatigue life for air-cooling fan bridges

    Institute of Scientific and Technical Information of China (English)

    徐亚洲; 白国良

    2013-01-01

    Based on the in-situ tested vibration responses of an air-cooling fan bridge,the dynamic analysis is performed with modulation amplitude disturbing force model of draught fans.Rainflow method is used to count stress cycles and the fatigue load spectrum of air-cooling fan bridges is then programmed combined with investigation results of running frequencies of different operation modes per year.Fatigue damage to the air-cooling fan bridge is calculated in terms of Miner' s cumulative damage rule and design p-S-N curve.After giving the damage threshold corresponding to fatigue failure,the predicted fatigue life of the fan bridge is longer than the designed service life.Furthermore,the fatigue life slightly decreases as effects of mean stress are taken into consideration by Goodman' s,Gerber' s and Soderberg' s models.%基于现场实测风机桥架振动响应,采用风机调幅扰力模型进行结构动力响应分析.根据不同工况下疲劳危险点的名义应力时程,采用雨流计数法和各工况年运行频次调查结果编制疲劳载荷谱.通过Miner损伤累积准则和p-S-N关系对风机桥架进行疲劳损伤分析,给定疲劳破坏的损伤阈值,所得疲劳寿命满足设计使用年限的要求.采用Goodman、Gerber和Soderberg模型考虑平均应力影响时的疲劳寿命略有降低.

  18. Effect of corrosion on the fatigue service-life on steel and reinforced concrete beams

    NARCIS (Netherlands)

    Veerman, R.P.; van Breugel, K.; Koenders, E.A.B.

    2015-01-01

    Chloride-induced corrosion is a point of big concern in reinforced concrete (RC) structures. To monitor the actual health and to predict the remaining service-life of structures, it is important to understand the structural behaviour and the failure mechanism of structures exposed to chlorides under

  19. Compassion fatigue in nurses.

    Science.gov (United States)

    Yoder, Elizabeth A

    2010-11-01

    Compassion fatigue, trigger situations, and coping strategies were investigated in hospital and home care nurses. The Professional Quality of Life Scale measured compassion fatigue, compassion satisfaction, and burnout. Narrative questions elicited trigger situations and coping strategies. Compassion fatigue scores were significantly different between nurses who worked 8- or 12-hour shifts. Fifteen percent of the participants had scores indicating risk of the compassion fatigue. There were significant differences in compassion satisfaction, depending on the unit worked and time as a nurse. The most common category of trigger situations was caring for the patient. Work-related and personal coping strategies were identified. PMID:21035028

  20. A STUDY OF FATIGUE LIFE OF ASPHALT CONCRETE BASED ON SHUNGITE MINERAL POWDER

    OpenAIRE

    D. I. Chernousov; Vl. P. Podolsky; E. V. Trufanov; B. A. Bondarev

    2011-01-01

    Problem statement. Shortage of mineral powder stimulates seeking of new materials and technologiesby which traditional ones can be replaced without deterioration of their operating properties. Thatis why a study of mineral powder from shungite and development of new technologies of arrangementof high quality and durable asphalt concrete pavement based on shungite is an actual problem.Results. Bearing capacity and service life of asphalt concrete pavement is most completely characterizedby mod...