Some contributions to optimal reliability test plans and estimation

Abstract

Design of optimal system reliability test plan has numerous advantages in product newlinemanufacturing industry as it helps to evaluate the system reliability and thereby newlinedemonstrates that the system will perform satisfactorily, prior to its deployment to newlinethe concerned field. The failure data and prior information available on failure rates newline newlineof units will help manufacturers to develop higher warranty periods and better ser- newlinevice facilities to customers. Thus, a Bayesian approach can be adopted to obtain a newline newlinegood reliability estimates and cost-effective optimal test plans. In systems that are newlinedesigned to achieve very high reliability (e.g., missiles, rockets, etc.), it is difficult to newlineobtain good estimate of system reliability. This is due to either the data recorded newlinecontain only a small number of failures or lack of availability of sufficient testing time newlineto observe failures. In such circumstances, a better alternative for obtaining data newlinequickly is the application of accelerated life tests (ALTs) or partially accelerated life newlinetests (PALTs). In both of these testing procedures, units are subjected to perform newlineunder higher stress than the normal stress level, whereas in PALT, some units are newlineallowed to perform under normal stress. Both testing procedures are destructive in newlinenature, i.e., one has to destroy some units to obtain lifetime quickly. Thus, in most of newlinethe existing reliability estimation method, failure time data are obtained from either newlineclassical life test or accelerated testing. In most of such situations, observing data is newlinetime-consuming, expensive or impracticable. One can make use of readily available newline newlinedegradation data enclosing information about system failure. For example, a fluo- newlinerescent lamp is considered as a failed one, when its luminosity falls below a certain newline newlinelevel, where an interesting feature of this experiment is the periodic monitoring of newlinethe luminosity. Hence degradation data, which are obtained during the lifetime of units can be utilized to get reliability estimate saving time and money.