Papers by Author: 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.

Abstract: In order to improve reliability of automobile transmission system and its running stability, this paper raises a reliability assessment calculation method. This method considers dependent failure of the parts, material strength degradation with increasing load times and uncertainty of load times in micro and macro scopes to explore main factors affecting the system reliability. The feasibility of this method has been validated by the example analysis. As a result , material properties of each gear parts, torques and load times play key parts in reliability of the system.

Abstract: A maintenance policy model based on time-variant reliability is put forward upon those mechanical systems which can carry on multiple maintenance in the whole life period, and the recurrence relations of the preventive maintenance intervals and reliability benefits is established. Two kinds of devices, one device’s mean time to failure complies with exponential distribution and another device’s mean time to failure meets the Weibull distribution, are taken as examples to get the approximate function expressions of the system's maintainability parameters of these devices through the curve fitting for data, analyze the system’s maintainability parameters and get the equipment’s maintenance policy model based on time-variant reliability. Examples verify the feasibility of the model.

Abstract: In view of analyzing the whole side crashworthiness, based on C-NCAP side impact regulations, this study has analyzed the structural characteristics influencing the side impact of car, and proposed the corresponding structural optimization case. According to FEM, the body optimization case has been simulated and contrasted with the real results. As a result, a good side crashworthiness of the car has been obtained, which helps reduce the cost and the quality of the car. Besides, the study has also done simulation work of the rigidity and modal of the body-in-white and compared it with the real results, which has further tested the correctness of optimization model and helped achieve effective approaches to the design of the car side crashworthiness.

Abstract: The three-dimensional solid modeling is built based on some Automobile gearbox Product, the dangerous working conditions of static load are analyzed. On the basis of ADAMS, transient dynamic loads of gearbox at different working gears are found out. The finite element analysis modeling of gearbox casing is built. The static displacement and the stress distribution of gearbox casing are obtained, and the static strength and stiffness are evaluated. The eigenvalues of vibration of gearbox casing are solved, the coupling relationship of the excitation frequency and the gearbox casing natural frequency is analyzed. Based on the transient dynamic analysis of gearbox casing at the first gear and the reverse gear, the evaluations of the dynamic strength and dynamic stiffness are obtained and the weak position of structure is found out, which provides the beneficial information for the further study on the design of the fatigue and reliability of gearbox casing.

Abstract: Failure rate functions were usually constructed in terms of life distribution. The present paper defines “discrete failure rate”, analyzes the dependence of failure rate curve shape on the probabilistic property of load-strength interaction, and develops load-strength-interaction based system failure rate model. For the majority of mechanical equipment, operation load is normally a random process, components are subjected to a large number of stochastic load actions during its service life. Meanwhile, material property degrades continuously owing to the failure mechanisms such as fatigue. It is the ever changing load-strength relationship that yields the variation in failure rate. Based on the criterion that failure occurs when a load higher than the relevant strength appears, failure rate model is developed based on the interaction mechanism between load and residual strength, and their statistical characteristics as well. Based on the interpretation to the variation of failure rate in terms of load uncertainty and strength uncertainty, the effect of statistical risk of load and the effect of strength degradation on failure rate curve shape are highlighted.

Abstract: With the scenario of reliability estimation, a geometrically complex mechanical/structural component with multiple damage sites should be treated as a system, since there are many links (damage sites) of similar failure probabilities on any of such a component and the failures of the individual damage sites are not perfectly dependent of each other. Conventional system reliability model is not applicable to such a system because of the statistical dependence among the element (damage site) failures. To estimate the reliability of a mechanical system (or a complex component) in which element (damage site) failure dependence plays an important role, a model capable of reflecting the effect of element failure dependence is necessary. The present paper develops models which can deal with multiple damage sites and multiple failure mechanisms, reflect the dependence among element failure events and that among different failure modes. Such models are applicable to both typical mechanical systems and various components.

Abstract: With structural reliability assessment as the scenario, a structural part made of foam material was treated as a series k-out-of-n system. The strength random variable of a large-size part was characterized by the strength random variables of virtual elements with certain size, as well as the number of the elements determined by part size. Specially, the statistical dependence among element failures was expounded with respect to the virtual elements. A series k-out-of-n system failure probability model was presented, and the failure probability of a structural part of foam material was described in terms of the size parameters of the part in two dimensions: the number of elements in width direction and that in length direction. It was shown that strong dependence among element failures exists, the failure probability of a large-size part will approaches to an upper bound with the increase in part length.