Research On Optimal Design Of Multiple Stresses Accelerated Life Test Plan On Non-rectangle Test Region

Multiple stresses accelerated life test is a common technique to access product life rapidly in engineering. Two stress constant accelerated life test is designed mainly on the rectangle region formed by two stresses. However, sometimes one stress is limited by the other stress in engineering practice, that will induce the two stresses not to reach the highest stress levels simultaneously,and the test region becomes non-rectangle. For the two stress accelerated life test on the non-rectangle test region, the stress level points will locate outside the test region if designing the optimal test plan according to the ideas about traditional rectangle region test design, so we can not surely get a feasibility test plan. Then it is necessary to research the methods about optimal design of multiple stress constant accelerated life test plan on non-rectangle test region and ways to access the corresponding optimal test plan design.Aiming at linear-extreme value model, the paper proposed optimal design of multiple stress constant accelerated life test plan on non-rectangle region based on uniform,orthogonal and E-M design theory;gave out the corresponding ration evaluating indicator of test plan. It obtained the test plan design of optimal comprehensive performance on non-rectangle test region by computer simulation experiment and summarized the test planning selection criteria. This research provides the theory and method for two-stress optimal CSALT planning and assessment on non-rectangle test regions.This dissertation is composed of six chapters and the main content of each chapter is as follows:Chapter one described the background and the significance of the research; reviewed the ALT methods and its development trend; introduced the present research situation and existing problems of ALT statistical model,ALT optimal design and ALT data analysis; analyzed the research status and existing problems of multiple stress ALT on non-rectangle test region; proposed the research objectives and the main research content.In chapter two,aiming at the problem of hardly finding out the point of the maximum probability of failure on the complicated boundary curves when designed the optimal multiple stresses accelerated life test plan on the non-rectangle test region based on Escobar-Meeker method,minimum variance of product life estimated value at normal working stresses is taken as design object for constant stresses accelerated life test method. After selecting two stress level points as the highest level point and the lowest level point on the non-rectangle test region, the highest stress level,the lowest stress level of each accelerated factor an allocation proportion of test samples are adopted as design variables. Limited test stress points spaced evenly distributed in the rectangle test region formed by the highest stress level point and the normal working stress level point; Proposed the optimal design method of constant stresses accelerated life test plan based on uniform design theory;Simplified the test plan optimal method;Verified the feasibility of the design method by an example.In chapter three, minimum variance of product life estimated value at normal working stresses is taken an desing object for constant stresses accelerate life test method. After selecting two stress level points as the highest level point and the lowest level point on the non-rectangle test region,the highest stress level,the lowest stress level of each accelerated factor and allocation proportion of test samples were adopted as design variables.The test stress points were distributed in accordance with best combination of test stress points based on orthogonal design theory.The paper proposed the optimal design method of constant stresses accelerated life test plan based on orthogonal design theory and verified the feasibility of the design method by an example.It gave out another simple method of optimal design.In chapter four, minimum variance of product life estimated value at normal working stresses is taken as design object for constant stresses accelerated life test method. Two stresses of the lowest stress and allocation proportion of test samples in every stress level were adopted as design variables. Aimed the maximum failure probability point of the non-rectangle region has two situations of unique and non-unique, the paper proposed the best combination of stress points and the optimal test plan based on E-M design theory when the stress level equal 3,4,5 and perfected the E-M design theory on the non-rectangle region.Chapter five proposed some ration evaluating indicator of optimal test plan on the non-rectangle test region;established a comprehensive evaluation method based on evaluating indicator;compared the merits and demerits of optimal test plan under the optimal model(uniform,orthogonal,E-M) about the ration evaluating indicator and comprehensive performance by computer simulation experiment; obtained the test plan design of optimal comprehensive performance on non-rectangle test region and summarized selection criteria of optimal constant ALT on the non-rectangle; gived some guidances and suggestions for the optimal test plan selection on non-rectangle test region.At last,the chapter six summarized the whole work of this dissertation,analyzed the innovations,and gave some suggestions for future research.