An Analytic Method for Quantity of Spare Parts in Typical System Consisted of Units with Exponential Distribution

Most electronic products can be viewed as the typical systems consisted of units with exponential distribution,and thus it's of great significance to determine the quantity of spare parts.However,how to acquire the needed quantity of spare parts exactly and quickly is a problem in engineering.Suppose that the replacement time is neglected,an integral expression of failure probability is given by using Poisson process,based on which an analytic method is proposed for downtime and average unavailability of the system.Since the formula is expressed as analytical solution in form of series,it has the characteristics of high calculation speed and high accuracy,which can avoid complicated computation of Monte Carlo simulation.Therefore,it provides a practical method for spare part determination.