Residual Storage Life Prediction Of Long-storage Product With Periodical Inspection

For products undergone long storage before usage,residual storage life(RSL)is an important index reflecting the reliability of a product.Accurate prediction of RSL is of significant help for the evaluation of reliability,optimal maintenance,and lifetime health management,and serve as a reference for integrated support decision making as well.This paper study on product inspected periodically during storage,the storage life time of those products can be divided into natural storage stage and inspection stage.During natural storage stage,product suffers stress from temperature and humidity,while during inspection stage,the electricity current or mechanical stress may largely influence the RSL of product.In this paper,related issues are researched from unit to subsystem based on practical experience,and main achievements are listed as follows:(1)Method of RSL prediction for units without maintenance.Firstly the storage process for units with periodical inspection is modeled.Based on Wiener process model,the difference of stress in different storage stages are described by different drift coefficient,the diffusion coefficient is considered the same in different stage.Secondly,based on the two-stage liner Wiener process,the parameters are estimated by Bayesian method,and RSL is defined as the first passage time of the process crossing the failure threshold.The probability distribution of RSL is calculated by simulation.Lastly,Point estimation and interval estimation are carried out for predicting RSL.(2)Method of RSL prediction for units with preventive maintenance.Preventive maintenance would be carried out for some units,including parameter adjustment and replacement.Storage states of units are modeled,and the effect of maintenance is described.By probability decomposition and convolution,the RSL distribution of unit with uncertain maintenance times is calculated by simulation.RSL of units with preventive maintenance is predicted.(3)Method of RSL prediction for entire product.The unit-subsystem-product hierarchy structure is built.RSL distributions of different reliability structures are obtained by simulation.Result of RSL prediction for entire product is provided fusing RSL distributions of different reliability structures.Lastly,the present method is valid for units for different distributions and is convenient for engineering application.