Papers by Keyword: Random Process

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Authors: Zhi Li Sun, Yun Feng Zhang, Yu Tao Yan
Abstract: The wear volume is obtained by means of experiment and the wear random process model is established according to the result. The Carbon steel material is used and the samples are grouped five after surface treatment, each group tests six times under the same condition. The wear volume under each wear time shows big dispersion. The additional study indicates that the sample has the large wear volume is in the serious wear state from the beginning, and the wear of running-in phase is inflected by the work velocity and the state condition of the surface of the samples. The wear process which the mean value is a constant and the standard deviation is different is a normal process generally, it is a stationary normal process if the standard deviation has no relation to the start of the wear time, or a Wiener process if the standard deviation is liner with the wear time, it is valuable to forecast the wear reliability.
Authors: C.C. Ni
Abstract: The study is focused on the formulation of a proposed polynomial stochastic fatigue crack growth model. Assuming the fatigue crack growth rate equal to a deterministic polynomial function in terms of fatigue crack size multiplied by a stationary lognormal random factor accounting for the statistical scatter of the fatigue crack growth, the analytical solutions of fatigue crack growth function and median crack growth function in term of model parameters were derived. Two extreme cases, lognormal random variable and lognormal white noise, of the proposed model were also investigated, and the analytical solutions of the distribution function of the random crack size at any service time and distribution function of random time to reach a specified crack size were obtained.
Authors: Xiao Jin Zhang, Li Yang Xie, Ying Wu, Yu Zhang, Ming Yang Zhao, Shi Zhe Xu
Abstract: A novel time-variant reliability model is developed after studying the traditional dynamic performance of mechanism. The expression of reliability is given based on stochastic process. A two-dimensional description of the error generating process is established by studying mechanism output kinematic accuracy. The reliability of mechanism output kinematic accuracy can be obtained according to this description. The model proposed can be used to calculate the reliability of mechanism directly, if the distribution of mechanism output kinematic accuracy is known.
Authors: Jing Ke Zhang, Wen Wu Chen, Fa Guo He, Guang Pin Sun, Qing Lin Guo
Abstract: Deformation behavior of endangered earthen heritage slope makes sense to scientific conservation of earthen architecture. It realizes qualitative and quantitative description of diseases. Based on random process and description theory, deformation behavior of endangered earthen heritage slope (Jiaohe Ruins) is studied using high-accuracy, real-time, dynamic information obtained by deformation monitoring appliance. Research result indicates that mathematic model can be established by use of modern mathematic method. The mathematic model of Jiaohe slope proves that short-term deformation behavior owns periodicity (36h) and occasional mutation. Simultaneously, tendency deformation performs weakly. The conclusion lays foundation for the research on quantitative deformation behavior and the following forecasting of similar earthen heritage slope damages.
Authors: Feng Du, Zhi Wei Guan, Yi Zhou
Abstract: For those large-scale and complex mechanical products, considering economy and applicability, these products are impossible to be discarded as soon as they take place malfunction. Generally, they can be reused again and again after be repaired repeatedly, that is, they usually have multi-lifespan. Accordingly, it is very necessary to establish a kind of proper reliability evaluation mode for these complex repairable products. In this paper, the treatment procedure of the reliability test data for these repairable products is researched based on the repairable reliability theory, and the method of model identification about failure distributions law is proposed. In addition, how to reasonably determine or predict product lives by using random process model is also introduced. Finally, an analysis case for putting this mean into practice is expounded. This method for product reliability analysis is suitable to most large-scale and complex mechanical products.
Authors: Jun Wang, Hong Guang Ji, Juan Juan Wang, Zi Jian Zhang
Abstract: Scientific prediction the residual life of existing reinforced concrete elements is an important basis for assessment the structures. The resistance probabilistic density function of reinforced concrete elements was proposed by analyzing the random processes of resistance attenuation of concrete and steel bars. Since the factors of concrete durability damaged and materials deterioration , considered practical conditions of service structures and durability failure criteria of concrete members, a method of calculation the residual life was given, which is verified reasonable through the engineering case.
Authors: Ming Liu, Wei Guang An
Abstract: Dynamic reliability of supercavity vehicle is investigated. The vehicle is modeled as thin shells, using eight-node super-parametric shell elements. To deal with the tail of supercavity vehicle structures subjected to stationary random excitations, and the wave passage effect must be considered, an efficient method, the Pseudo Excitation Method, is suggested. The stationary random excitation is transformed into a deterministic transient excitation. The response can be obtained by Newark method, at last dynamic reliability of supercavity vehicle can be got base on the rule of first excursion failure. Examples show that this method is simple, efficient and has good precision.
Authors: Z.Y. Hu, Li Yang Xie
Abstract: A model of the optimal maintenance period for repairable product after warranty expiration under renewing warranty is proposed. In the process to fulfilling warranty, the failures of product within warranty period happen randomly, the replacements of products successively failed with warranty period form a renewing process. Given failure rate of product, the period of fulfilling warranty is function of warranty period. User purchasing a product is considered an investment; the period of fulfilling warranty and the maintenance period after warranty make up the life cycle of product investment. Taking various cost factors into account, making model of the cost rate in life cycle of product investment under renewing warranty, the cost rate is function of maintenance period. Give the failure rate of product is an increasing function, it is derived that there is unique optimal maintenance period minimizing the cost rate. Finally, numerical example is given for illustration.
Authors: Zhao Ning Zhang, Ai Ping Jia
Abstract: Using the method of stochastic differential equations to analysis two aircrafts and to establish the aircraft flight collision risk model. First the relative position and speed of the aircraft on the joint distribution density should be confirmed, and convert it into a Gaussian density to simplify the calculation of nonlinear filtering theory, and then use the method of stochastic differential equation to establish flight collision risk model, and also includes the introduction of how the CNS performance of random factors, human factors and avoidance system performance affect the flight collision. After verifying the collision risk in the example, the results show that the model is feasible.
Authors: Shi Lin Yan, Yong Jing Lee, De Quan Lee, Fei Yan, Jun Xia Wang
Abstract: This paper uses FLOTRAN to estimate the resin flow permeability of fiber tow in RTM. Nine models of different fractions varies from 0.4~0.75 have been built, and the random process of the fiber’s distribution is realized by APDL code. The results show that the dispersion of fiber determines the fluid flow channels, which effect the pressure and velocity’s distribution; the FLOTRAN can be used to estimate the transverse permeability of the fiber bundles.
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