Papers by Keyword: Cyclic Stress

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Authors: Jaroslav Polák, Martin Petrenec, Jiří Man
Abstract: Austenitic stainless steel was cycled at a series of temperatures in the interval from 296 K to 113 K. Constant plastic strain amplitude loading at different levels of plastic strain amplitude and testing similar to multiple step test method were applied at different temperatures. The stress amplitude was continually recorded and selected hysteresis loops were stored and later analyzed using statistical theory of the hysteresis loop. Effective stress component and probability density function as a function of temperature were evaluated. The results were discussed in terms of the temperature dependence of the cyclic yield stress and its sources.
Authors: Hong Gun Kim
Abstract: A micromechanical model based on continuum analysis has been investigated by using finite element analysis (FEA) in discontinuous metal matrix composites (DMMC). To assess the tensile and compressive constitutive responses, a cyclic stress-strain behavior has been performed. For analysis procedure, the elastoplastic FEA and the regularly aligned axisymmetric single fiber model have been implemented to evaluate the internal field quantities. Accordingly, the fiber and matrix internal stresses were investigated for the constrained representative volume element (RVE). Further, the local plasticity in the matrix were described during loading and unloading precesses, which can predict the damage mechanisms as well as strengthening mechanisms. On the other hand, a thermoelasto- plastic analysis has been performed using FEA for the application to the continuum behavior in a discontinuous metal matrix composite. The internal field quantities of composite as well as overall composite behavior and an experiment was demonstrated to compare with the numerical simulation. As the procedure, the reasonably optimized FE mesh generations, the appropriate imposition of boundary conditions, and the relevant postprocessing such as elasto-plastic thermo-mechanical analysis were taken into account. For micromechanical model, the temperature dependent material properties and precipitation hardening effects have been employed to investigate field quantities. It was found that the residual stresses are induced substantially by the temperature drop during heat treatment and that the FEA results give a good agreement with experimental data.
Authors: Seok Jin Kwon, Kazuhiro Ogawa, Tetsuo Shoji
Abstract: In general, the S-N curve in railway axles was mainly carried out under 107-108 cycles, while the service area of a railway axle is 108-109 cycles. The strain gages using electrical resistance have been used to measure stresses in railway vehicle wheelsets. However, there are some problems with strain gages using electrical resistance for railway axles. For example, the measured data is for special or limited intervals only. Strain gage installation is complicated, that is, it requires lead wires for measurement. The design of railway axles makes use of data that was obtained many years ago. The applied stresses in wheelsets running for a long time and in new railway vehicle wheelsets have not been studied clearly yet. It is necessary to carry out stress monitoring for more than 108 cycles to evaluate the safety of railway wheelset. Therefore, it is necessary to develop new stress monitoring techniques that can easily measure the working stress of the wheelset. In the present paper, the stress measurement technique of copper electroplating is considered because of its high potential for this purpose.
Authors: Lei Wang, Tong Cui, Jun Ying Lü, Hong Cai Yang, Guang Pu Zhao
Abstract: Low-cycle fatigue property of superalloy GH4586 was investigated using a stress amplitude-controlled mode at 1023K. Fracture surface was examined with a scanning electronic microscopy. It was found that the cyclic life can be illustrated by Manson-Coffin at all strain levels. The fatigue cracks initiate primarily on the surface of the specimen. The plastic strain amplitude responded to the cyclic loading shows higher sensitivity than that of the elastic strain amplitude. It was demonstrated that the failure of the present alloy is in a manner of creep-fatigue feature.
Authors: Michal Lattner, Frantisek Holešovsky
Abstract: The paper deals with the influence of the properties surface layer of notched components. This material is widely used in the automotive industry. This material is subject to different kinds of processing, and therefore present a different quality of the surface layer. For many manufactured components, we find diverse types of notches, such as slots, recesses and holes. They are the place where is stress concentrated, so called the macroscopic stress concentrator. When we focus more on the surface profile, we find the diversity of technologies in the surface, which creates different sizes and shapes of microscopic notches. In these places, there is a higher risk of the destruction of the components. Many designers prescribe unnecessarily high surface quality. It is important to maintain adequate quality of the surface to achieved high durability.
Authors: Xue Ping Yi, Jiu Fa Wang
Abstract: At first, the unidirectional stress fatigue strength has been made the brief description, and the calculation methods about the fatigue stress under two cases also has been introduced, two cases are the symmetrical and asymmetrical cyclic stress fatigue strength. The calculation of fatigue strength is based on the fact that calculating safety factor is equal to or greater than the allowable safety coefficient. Finally, some alloy steel parts are taken as an example to carry on the fatigue strength calculation.
Authors: Jun Jie Yuan, Wei Min Zhang
Abstract: The magnetization induced by applied cyclic stresses on low carbon steel samples was studied through experiments by using a high sensitive magnetic sensor. The stress-magnetic coupling under cyclic tensile stress was researched during static, cyclic and fatigue loading process respectively. The results indicate the consistency and also some contradiction with existing conclusions of metal magnetic memory theory or magneto-mechanical researches. It is put forward that the stress induce magnetization is dependent on both applied stress and micro structure abnormality in ferromagnetic materials. Then the potential applications of the stress-magnetic coupling behavior were proposed.
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