Papers by Keyword: Fatigue Reliability

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Authors: Li Yang Xie, Wen Qiang Lin, Feng Lu
Abstract: Based on the concept of multilevel statistics, mixed-effect fatigue reliability models are presented, by which fatigue reliability can be directly calculated according to stress distribution and fatigue life distribution function condition to stress. Mathematically, the fatigue reliability is estimated as the expectation of a conditional survival probability function to the stochastic stress history. Especially, such models are capable of estimating the fatigue reliability of a component with competing failure mechanisms such as conventional fatigue and giga-cycle fatigue, where two groups of P-S-N curves are involved.
Authors: Li Yang Xie, Xue Hong He
Abstract: The present paper interpreted the traditional stress-strength interference model as an equation expressing the statistical average of the probability of strength preponderating over stress. Thus, the same equation, which was traditionally applicable only in the situation of same-measure parameters, can be applied to more general situation of different-measure parameters. In other words, the traditional model was extended to the situation of any two variables, as long as one variable can be expressed as a function of the other. With a specific load amplitude distribution, the method is to calculate the statistical average of the probability that fatigue life random variable under the individual constant amplitude cyclic load is greater than an assigned value. The extended interference analysis method can be applied directly to calculate fatigue reliability under constant amplitude cyclic load with uncertainty in the stress range.
Authors: Bin Tuan Wang, Qingxiong Yang
Authors: Ji Kang Bo
Abstract: The high voltage valve bears repeated loads and impact in its working state. Fatigue failure or fatigue damage is the most common failure mode of high voltage valves. This work analyzes the working principle and working characteristics of a high voltage valve under a static rated load, and proposes the necessity of the fatigue analysis. The failure probability of the high voltage valve is presented and the service life of the entire valve obtained. To find the part prone to fail, the evaluation of the fatigue life of the high voltage valve is carried out. The fatigue life and safety factor of the high voltage valve is obtained. It is found that the edge joints are easy to fatigue failure, which provides a reference for the actual application and of maintenance the high voltage valve.
Authors: Li Rong Sha, Yue Yang
Abstract: The ANN-based optimization for considering fatigue reliability requirements in structural optimization was proposed. The ANN-based response surface method was employed for performing fatigue reliability analysis. The fatigue reliability requirements were considered as constraints while the weight as the objective function, the ANN model was adopted to establish the relationship between the fatigue reliability and geometry dimension of the structure, the optimal results of the structure with a minimum weight was reached.
Authors: Hong Qin Liang, Yong Xiang Zhao, Ping Bo Wu
Abstract: Nonlinear dynamics model of the C62 freight car was established firstly and the random load spectrum acted on the wheelset was obtained by the simulation of the freight car running on a typical line. Taking the cyclic constructive relation of LZ50 axle steel into account in the finite element analysis of the wheelset, the stress time histories of the key parts of the axle in some typical conditions were got. Furthermore, based on the stress spectrum analysis of the hazard sections of the axle, the probabilistic fatigue stress spectrums with given probability and confidence were obtained. Finally, combining with the linear cumulative damage rules, the stress distribution of RD2 axle was investigated, which is fundamental for the further prediction of the fatigue life of axle.
Authors: Bin Li, Zong De Liu, Peng Duan
Abstract: The elastic oil sump is commonly used as support parts in large-scale thrust bearing. It often operates under fluctuating load conditions during service. So, fatigue analysis of the material of the elastic oil sump is of great significance. In order to obtain the fatigue design data of the material of the elastic oil sump, the systematic tests on uniaxial tension-compression fatigue at room temperature are made. The fatigue limits and the fatigue life curves of the steel of the elastic oil sump are determined at different cyclic stress ratio. The P-S-N equations are calculated by the probabilistic methods. The test results provide a theoretical basis for the safety of life assessment of the elastic oil sump.
Authors: Jian Chun Ding, Fa Guo Sun
Abstract: The paper is to develop a new approach to analyze the reliability of pressure-reducing valve basing on commercial software Ansys. After introducing the work principle of the pressure-reducing valve containing membrane, the mechanical model of the membrane acted by pressure caused by turbulence is established, base on which the simulated model built in Ansys is made. For the stress response of the membrane is dealt as linear response, so the loads acting on the membrane which consist of two parts, one is constant pressure, and another is harmonic load, are taken as superposition of two parts, and the stress response can be taken as superposition of two kinds of cases in Ansys, that are static analysis and harmonic analysis. Then by mote simulation the statistical character of the stress response can be obtained, such as mean and variance. Using three- parameter S-N equation and constant life fatigue life curve, the equation of the equivalent mean fatigue life is established, basing on the equation and linear cumulative damage theory, the fatigue reliability during certain period can be gotten. At last an example is given to verify above approach.
Authors: Yan Li, Da Gang Lv, Hong Fei Sheng
Abstract: The existent studies on cable stays fatigue for the serviced cable-stayed bridge generally only considered traffic or wind load action respectively. The long span cable-stayed bridges are very sensitive to wind load, so the fatigue estimation of cable stays considering traffic and wind load simultaneously is very important for the bridge safety. In the present research, taking an actual bridge as an example, based on linear cumulative damage theory, fatigue reliability of cable stays is analyzed under combined load of vehicles and wind. Firstly, based on the long-term traffic survey and wind speed data, traffic and wind load probability distribution models for the bridge are built respectively. Secondly, an intensive computational work is performed to obtain stress time history of the stay cables in the typical time block by running self-compiled Bridge-Vehicle-Wind interaction dynamic response analysis program. Thirdly, the stress result is updated in accordance with traffic growth and extreme wind speed changing in service period. The stress amplitude and frequency are attained by rain-flow cycle counting method. Finally, the fatigue damage limit state function of cable stays is proposed based on linear cumulative damage theory, and solved by Monte-Carlo method. The analysis result shows that the effect of buffeting wind load on the fatigue reliability of cable stays is significant, the influence degree increases generally in accordance with the order from short cable to long cable. The fatigue life of cable under designed safety probability reduces by the range from 2% to 63%, average 50% compared to only considering traffic load. So fatigue assessment of stay cables should take traffic and wind loads together into account. The proposed analysis framework offers a referenced fatigue assessment approach for conventional long span bridges.
Authors: Zhao Qian Wang, Tian Biao Yu, Ye Zou, Chang Xin Wang, Hai Feng Zhao, Wan Shan Wang
Abstract: Tools of tunnel boring machine CAD models have been built by CAD software, it is analyzed static characteristics and fatigue characteristics by finite element analysis and obtaining the displacement in the poor stiffness conditions. Improving its structure to strengthen stiffness and fatigue life by the calculate result. The final result shows that the structure can satisfy its rigid command and can fit the soil conditions above 5%-10%. Damage frequency of tools is greatly deduced. It provides a theoretical basis for the actual design and product manufacturing.
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