Papers by Keyword: Bending Fatigue

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Authors: Kook Jin Lee, Jae Heon Lee, Tae Kun Lee, Seong Kyun Cheong
Abstract: In this paper the life extension of automobile drive plates will be investigated. The material of specimen is a high carbon steel treated by shot peening, which is most important in the manufacturing process of drive plates. The optimum shot peening condition was investigated by changing the feeding speed and exposure time. The fatigue crack was observed at the fracturing surface of specimens by using scanning electron microscopy (SEM). The distribution of compressive residual stress induced by shot peening process was investigated by using X-ray diffraction. The number of cycles to failure increases at the beginning of exposure. The life cycle decreases after passing some interval of exposure, which will be called as optimum peening zone. Experimental results show that the residual stress distribution and the number of cycles to failure of a drive plate are greatly affected by peening process.
Authors: Ivo Černý, Ivan Fürbacher, Dagmar Mikulová, Jiří Sís
Abstract: The paper deals with an investigation of surface laser hardening characteristics on contact and bending fatigue resistance of a 42CrMo4 steel, being often used for manufacture of gear wheels. The aim of the experimental programme was to simulate the complex service loading of fairly large gears by two separate investigations, namely contact fatigue performed on a special, so called analogon machine and bending fatigue performed on high cycle fatigue resonance machines using three-point-bend (3PB) fairly large specimens. It was shown that after optimising the methodology and parameters of the laser hardening technology, contact fatigue resistance is very good, comparable with very expensive and time consuming thermochemical high-depth surface treatments. Bending endurance limit can be increased. The role of residual stresses resulting from the laser treatment was shown as decisive.
Authors: Jai Won Byeon, S.I. Kwun, Kae Myung Kang
Abstract: Acoustic emission (AE) technique was applied to evaluate both tensile deformation of 316L stainless steel and bending-fatigue damage of socket-welded pipe. AE activity was monitored during tensile deformation of plate-type specimens subjected to various heat treatments. Variation in RMS voltage of AE signal was correlated with the amount of strain-induced martensite phase. Secondly, actual size of socket-welded pipe specimen was bending-fatigued under various stresses. Crack initiation was determined by observing an abrupt increase in AE count, and confirmed by radiographic examination before and after the crack initiation cycle. Potentials of AE technique for monitoring fatigue crack initiation were discussed.
Authors: P. Manikandan, G. Sudarsana Rao, J. Srinath, V.M.J. Sharma, P. Ramesh Narayanan, S.C. Sharma, Koshy M. George
Abstract: Gimbaling the engine nozzle within a specified angle through hydraulic actuator modules is commonly used to control the trajectory path of satellite launch vehicles. During one of the hot test of a liquid engine stage, a drop in system pressure in actuator module was noticed due to cracking of case drain plumbing inside the ferrule. The tensile and fatigue (axial and bending) test of the tube material was carried out to understand the cause of failure, simulating the actual service conditions such as strength and bending moment in assembled tube. Findings of the metallurgical investigation along with the fatigue test results were presented in this paper.
Authors: Srečko Glodež, Marko Šori
Abstract: The paper discusses the computational and experimental approach for determination of the PM gears service life concerning bending fatigue in a gear tooth root. A proposed computational model is based on the stress-life approach where the stress field in a gear tooth root is determined numerically using FEM. The experimental procedure was done on a custom made back-to-back gear testing rig. The comparison between computational and experimental results has shown that the proposed computational approach is appropriate calculation method for service life estimation of sintered gears regarding tooth root strength. Namely, it was shown that in the case of proper heat treatment of tested gears, the tooth breakage occurred inside the interval with 95 % probability of failure, which has been determined using proposed computational model.
Authors: K.I. Kang, J.P. Jung, Woong Ho Bang, J.H. Park, Kyu Hwan Oh
Abstract: Bending fatigue behavior of eutectic Sn-3.5Ag solder bump bonded on FR4-PCB was characterized by experimental and finite element method (FEM). To investigate an effect of stress state on bump failure, which had not been weighed in conventional Coffin-Manson model of Nf=K ⋅εp -1~-2, ‘fatigue frequency variable’ and ‘bump viscoplasticity’ were included in analysis procedure. As experimental results, with increasing fatigue cycles from 3,000 to 10,000, bond strength decreased from 98.9% to 76.5%, and from 97.5% to 67.1% at the fatigue frequencies of 2.5Hz and 5.0Hz, respectively. Stress state could be critical components to determine fatigue life, which should be combined in Coffin-Manson criteria. FEM calculation showed that higher bending frequency led to higher normal stress development at the solder and IMC interface, but smaller plastic strain in bump. However, bending fatigue experiment revealed discrepant results from that of Coffin-Manson criteria. Higher bending frequency, which was predicted to give rise to smaller εp at solder, showed dramatic bond deterioration of solder bump on UBM (under bump metallurgy). This was confirmed experimentally through SEM (scanning electron microscopy) observation as cracks were found at the solder bump and UBM interfacial IMC, Ni3Sn4, in case of the higher bending frequency.
Authors: Guo Jun Wang, Mei Hua Jiang, Shi Shun Zhu, An Tao Xu
Abstract: Bending fatigue is one of the main failure modes of gears. The method of gear fatigue design was discussed in many papers. Most of them are based on GB/T3480-83.But study shows that the method current widely used only fits for the single side loaded gear. For double sides loaded gear, only a mean stress modification coefficient is concerned compared to single side loaded gear. A new formula based on fatigue theory is given to modify the mean stress in consideration of the load character of doubled sides loaded gear. The method given in the paper is an addition to the traditional gear design method.
Authors: Taehyung Nam, Sung Ho Choi, Tae Hun Lee, Kyung Young Jhang, Chungseok Kim
Abstract: The bending fatigue of Al6061 alloy has been evaluated by the acoustic nonlinearity of laser-generated surface wave. The surface wave is very attractive for field applications since it enables to pulse and receive signals at the same surface of materials, and has strong acoustic nonlinear effects on the surface. A relative acoustic nonlinear parameter was measured successfully on the surface of fatigue-damaged aluminum 6061 alloy. The results show that the acoustic nonlinear parameter increased with fatigue damage accumulation in relation to dislocation evolution. Consequently, this study suggests that the acoustic nonlinearity technique of a laser-generated surface wave can be potentially used to characterize surface damage resulting from bending fatigue.
Authors: Ke Bao, Ri Dong Liao
Abstract: The influence of residual stesses must be considered in bending fatigue life prediction of fillet rolling crankshafts. In this paper, the stress/strain distributions near fillet during fatigue tests are calculated by finite element method. In residual stress computation, the three dimensional flexible contact model is adopted, and in bending strain computation, the static analysis are selected. Then, bending fatigue life prediction is performed by local stress-strain approach based on the residual stess and bending strain amplitude, and the results agree with the bending fatigue test.
Authors: Yuan Yuan Ma, Li Yang Xie
Abstract: Taking the local parts of high-speed training service as the research object, the static form of the finite element model is established, and the dangerous parts of the stress distribution under different load form corresponding to loading and displacement conditions applied in experimental test is calculated. Fatigue life of the same welding parts of the different forms due to the state of the uniaxial tensile and the bending is respectively tested in the lab, the life distribution and characteristics of their statistics are obtained; Compared to the stress distribution of dangerous parts and data of the test, analysis that the similar parameters of life and failure forms can be received if it choose the reasonable load parameters in different form and loading in the test.
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