Optimal Burn-in Test Strategy For Two-dimensional Warranted Products

Burn-in test is used to simulate the actual or accelerated working conditions for a certain duration to screen out potential problems and boost product quality along with improvement measures.Too little investment in Burn-in may lead to infant mortalities,while over-investment obviously increases test cost and accelerates product aging,both of which will generate additional warranty claims and costs.Therefore,the trade-off between Burn-in and warranty is important.Meanwhile,heterogeneities of Burn-in test rate and customer usage rate significantly affect the virtual age of two-dimensional(2D)warranted products which are sensitive to usage rate.Previous literature mainly focuses on the optimization of Burn-in test time,which may cause inaccurate decision-making for their trade-off problems.Therefore,this dissertation studies optimal Burn-in test strategies for 2D warranted products as follows.First,the optimal Burn-in strategy for 2D warranted products considering preventive maintenance(PM)is studied.With harsher Burn-in,infant mortalities can be removed,but meanwhile product aging is accelerated.PM within warranty can mitigate these negative effects.The consideration of PM has increased the complexities of the trade-off between Burn-in and the 2D warranty.This dissertation constructs joint optimization models to minimize warranty claims and total costs based on accelerated failure time techniques,and obtain the optimal Burn-in strategy.Meanwhile,the impacts of the relation of accelerated coefficients between aging and infant mortalities and PM policies on optimal Burn-in strategy are proved.In addition,the sensitivity analysis is used to study the influence of the usage heterogeneity on the optimal strategy.Second,the reliability and 2D warranty cost of multi-component systems with failure interactions are studied.To study the optimization between Burn-in and two-dimensional warranty from components or black-box products to multi-component systems,accurate calculation of the reliability and warranty cost of the system must be realized.This problem requires not only the complex structure of the system but also the impact of failures interactions to be considered.The analysis of failure interactions has always been a difficult problem.In this dissertation,the failure interactions have been described by the failure dependence probability matrix.Compared with the related research of series,parallel and two-component systems,a recursive algorithm is used to calculate the reliability and 2D warranty cost for a more generalized multi-component system,namely k-out-of-n system.Meanwhile,through applying the convolution theorem and Laplace transform and its inversion to a special case of exponential distribution,the corresponding analytical solutions are obtained to simplify the calculation.In addition,sensitivity analysis is conducted to study the impacts of failure interactions and 2D warranty policies on system reliability and warranty costs.Third,the optimal Burn-in strategy for 2D warranted multi-component system with failure interactions is studied.On the one hand,most of the products requiring Burn-in are multi-component systems with complex structures.On the other hand,even if the components of a multi-component system have been individually burnt-in,there are still potential assembly or design flaws after assembling into a system.Therefore,research on the system Burn-in test is necessary.Previous literature neither considers the trade-off between Burn-in test and 2D warranty of the multi-component system,nor considers the influence of failure interactions.Therefore,this dissertation first realizes the recursive algorithm of system reliability and cost considering the failure interactions under Burn-in test for k-out-of-n system,and then combines the research on reliability and 2D warranty cost of multi-component systems,so as to minimize warranty claims or total cost and achieve the optimal Burn-in strategy.Sensitivity analysis shows that Burn-in can help to reduce warranty claims and total costs,especially for low-level redundant systems or systems with low critical maintenance level.Except for the series system,the failure interactions have significant impacts on the reliability,total cost,and optimal Burn-in strategy of other structural systems.Fourth,the optimal multi-phase Burn-in strategy for 2D warranted products considering failure mode improvement is studied.For the trial products that can be repeatedly improved,Burn-in test can improve the reliability of these products by combining the failure mode identification and improvement measures after each test.At present,there is no overall consideration of the cost trade-off between the multi-phase test strategy and 2D warranty.Therefore,this dissertation studies the joint cost optimization model of multi-phase Burn-in test strategy and 2D warranty for the trial products.Under the constraints of MTBF target,an optimal multi-phase test strategy is obtained.The result shows that the multi-phase optimal Burn-in test strategy can effectively reduce the total cost.In addition,the optimal combination of test rates shows an upward trend to expose the more hard-to-discover failure modes,which is consistent with the actual application and can help provide better theoretical support.