Papers by Keyword: Fretting Fatigue

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Authors: Tae Gyu Kim, Hyun Soo Kim, In Duck Park, Hye Sung Kim
Abstract: In this study, we investigated the fatigue characteristics of SMA40 materials as a potential application in connecting rod material for an automobile. Average fatigue life of 168,700 cycles and fatigue limit of 437 MPa was determined from SMA40 specimens. However, when tested under fretting condition, decrease in fatigue lifetime was 20% and fatigue limit was reduced to 350 MPa.
279
Authors: Jae Do Kwon, Sang Jin Cho, Yong Tak Bae
Abstract: The aged degradation of material is observed when heat-resisting steel is exposed for long periods of time at high temperatures. In the present study, the degraded 1Cr-0.5Mo steel that is used for long periods of time at high temperature(about 515°C) and artificially reheat-treated materials are prepared. These materials were used to study the effect of aged degradation on fretting fatigue behavior. Through this experiment, it is found that the fretting fatigue strength of reheat-treated 1Cr-0.5Mo steel is approximately 46 percent lower than that of the plain fatigue strength of the same material. Furthermore, the fretting fatigue strength of degraded 1Cr-0.5Mo steel was less than 53 percent of the same material™s plain fatigue strength. The maximum value of fatigue strength difference is observed as 57 percent between the fretting fatigue of degraded material and plain fatigue of reheat-treated material. These results can be used as basic data in a structural integrity evaluation of heat-resisting steel considering aged degradation effects.
1221
Authors: H. Sepehri Amin, Ahmad Kermanpur, Saeed Ziaei-Rad, Hassan Farhangi, M. Mosaddeghfar
Abstract: Several premature failures were occurred in the high-pressure section of an industrial gas turbine compressor due to the fracture of Titanium blade roots. In this work, the failure process of the compressor blades was investigated based on the experimental characterisation. Macro/microfractographic studies were carried out on the fracture surfaces. Optical and scanning electron microscopy of the blade airfoil and root were performed. Mechanical properties of the blade alloy were also evaluated and compared with the standard specifications. The experimental results showed no metallurgical and mechanical defects for the blade materials. Microstructures of the blade root and airfoil as well as the hardness and tensile properties were all comparable with those reported in the standard specification AMS 4928Q. Fractography experiments showed clearly multiple crack initiation sites and fatigue beach marks. Debris particles were observed on the fracture surface of samples and in the mouth of initiated cracks. The blade surface in contact to the disc in the dovetail region showed a higher surface roughness than the other surfaces. Based on the results obtained, the fretting fatigue mechanism was proposed for the premature failures. It was concluded that the stress concentration has been caused by either unsuitable curvature ratio of the disk dovetail, incorrect design of the blade or insufficient distance between the blade root and the disk in dovetail region.
2241
Authors: Wen Li, Ri Dong Liao, Zheng Xing Zuo
Abstract: Fretting fatigue becomes a typical failure mode for engine cylinder block caused by the increasing of the gas pressure and rotating speed, but the mechanism of fretting fatigue under diesel engine load condition hasn’t been systematic studied. In this paper, the fretting behaviors are mainly discussed by using fretting friction work parameter W and crack initiation location parameter G.
986
Authors: Wen Li, Ri Dong Liao, Li Tao Liu, Zheng Xing Zuo
Abstract: Fretting fatigue cracks always initial at the tralling of contact region, because the stresses in the vicinity of the contact zone exhibit steep gradients. A fracture mechanics approach is usually used to estimate fretting fatigue propagation life. In this paper, extended finite element method combined with fracture mechanics is used to study fretting crack propagation behaviors. The computation results reveal that fretting crack nucleation is mainly decided by fretting, and the cycle bulk stress is the main reason for crack propagation. Also the X-FEM exhibits merits in fretting fatigue problem.
1162
Authors: Xiao Hua Zhang, Ding Gen Xiang, Dao Xin Liu
Abstract: Ion-beam-assisted deposition (IBAD) was investigated as a potential way to increase the fretting fatigue resistance of Ti-8Al-1Mo-1V alloy at elevated temperature. Three coating systems, hard TiN film with good toughness and soft Al film of low friction and Cu/Ni multilayer films with modulation period thickness of 20~600nm have been applied on the base material. Coefficients of friction and fretting fatigue lives of the specimens with and without film were compared. The film damage was characterized through scanning electron microscopy. The results indicate that the IBAD technique can prepare all films with high bonding strength and excellent lubricating properties. The fretting fatigue life of the Ti-8Al-1Mo-1V alloy with the TiN film was improved by a factor of 2.4 as compared to the uncoated substrate at elevated temperature because of the excellent wear and fatigue resistance and good toughness of the film. Excellent wear resistance and good anti-fatigue properties could be simultaneously obtained by a single hard film to control the fretting fatigue damage. The IBAD Al film significantly improved the fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy at elevated temperature for good lubricating property. The fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy was improved by all the Cu/Ni multilayer films. However, the fretting fatigue resistance did not increase monotonically with the modulation period of the films. Films with a modulation period of 200 nm had the highest fretting fatigue resistance among the multilayer films prepared owing to their high toughness and strength and good lubricating and anti-fatigue action. The fretting fatigue resistance of films with a modulation period of 20 nm was low because of the poor fracture toughness and crack propagation resistance, even though these films had the highest hardness and good fretting wear resistance. Thus, comprehensive properties, including high toughness and strength, must be considered for multilayer films used to improve the fretting fatigue resistance of titanium alloys.
346
Authors: Wei Tian, Xiao Hua Zhang
Abstract: Ion-beam-assisted deposition (IBAD) was investigated as a potential way to increase the fretting fatigue resistance of Ti-8Al-1Mo-1V alloy at elevated temperature. Three coating systems, hard TiN film, Al film and Cu/Ni multilayer films have been applied on the base material. Coefficients of friction and fretting fatigue lives of the specimens with and without film were compared. The results indicate that the IBAD technique can prepare all films with high bonding strength and excellent lubricating properties. The fretting fatigue life of the Ti-8Al-1Mo-1V alloy with the TiN film was improved by a factor of 2.4 as compared to the uncoated substrate at elevated temperature because of the excellent wear and fatigue resistance and good toughness of the film. The IBAD Al film significantly improved the fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy at elevated temperature for good lubricating property. The fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy was improved by all the Cu/Ni multilayer films. However, the fretting fatigue resistance did not increase monotonically with the modulation period of the films.
7
Authors: P.M. Wavish, Ian R. McColl, Sean B. Leen
Abstract: This paper describes the conceptual, embodiment and detailed design of a representative test specimen to mimic fretting variables in aero-engine splined couplings. A fretting bridge design was chosen for the multi-axial representative specimen from a set of four concepts evaluated. The test specimen was intended to facilitate more rapid testing for design against fretting fatigue and wear in the complex contact geometry of the spline coupling.
267
Authors: Dong Hyong Lee, Ha Young Choi, Chang Yong Song, Bong Gu Lee
Abstract: The objective of this study is to propose the effective method of reducing the maximum contact pressure at the contact edge of press-fitted shaft by optimizing the location and the size of stress relief groove in hub face. Finite element analysis was performed in order to determine the contact pressure and stress state on a press-fitted assembly and optimization were applied to select optimal size and location of stress relief groove. In order to reduce the cost of optimization design, approximation optimization method is used and the optimum results obtained by Sequential Quadratic Programming and genetic algorithm are compared. Optimized results show that the maximum contact pressure at the contact edge of press-fitted shaft with optimal stress relief groove decreased about 30%. And the both optimization algorithms can effectively reduced the maximum contact pressure at the contact edge of press-fitted shaft.
1339
Authors: Wei Ming Sun, Shui Sheng Chen, Li Qun Tu
Abstract: The effect of contact pressure on fretting fatigue in quenched and tempered 45-carbon steel is studied. With an increase in contact pressure, fretting fatigue life is decreased quickly at low contact pressures; however it almost unchanged at high contact pressures. With an increase in cyclic stress amplitude, fretting fatigue life decreased. In the test, concavity is formed at the fretted area accompanying wear. The main crack is initiated at the outer edge corner of the concavity at high contact pressures, and initiated at the middle portion of the fretted area at low contact pressures.
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