Abstract
Constant stress accelerated life tests (ALTs) can be applied to obtain a high estimation accuracy of reliability measurements, but these are time-consuming tests. Progressive stress ALTs can yield failures more quickly but cannot guarantee the estimation accuracy of reliability measurements. In this paper, a progressive-constant combination stress ALT is proposed to combine the merits of both tests. The optimal plan, in which the design variables are the initial progressive stress level, the progressive stress ramp rate, the sample allocation proportion of the progressive stress and the constant stress level, is determined using the principle of minimizing the asymptotic variance of the maximum likelihood estimator of the natural log reliable life for the connectors. A comparison between the optimal PCCSALT plan and the CSALT plan with the same sample size and estimation accuracy shows that the test time is reduced by 13.59% by applying the PCCSALT.
Highlights
Accelerated life tests (ALTs) can yield life information of a product in a short time [1,2,3]
The compared simple Constant stress accelerated life tests (CSALTs) plan is defined in the following manner: the mid value of the progressive stress, namely, ξ1 = ξp + α·tm/2, is used as the low stress, while the sample allocation proportion, the high stress and the censored time are the same as those in the proposed plan
The estimation accuracy depends on the sample size and test time
Summary
Accelerated life tests (ALTs) can yield life information of a product in a short time [1,2,3]. Constant stress accelerated life tests (CSALTs) have the advantages of theory maturity and high statistical precision, but they require many samples and a long test time. Progressive stress accelerated life tests (PSALTs) [4] can generate results in a shorter test time and require a smaller sample size, but they are not widely used in practice because of the immature statistical method and the poor estimation accuracy [5, 6]. Prot [7] proposed the PSALT optimal design method for a Weibull distribution. Bai et al [8] optimized a time-censored simple ramp stress test plan for the power-Weibull model and proposed an optimum single ramp stress test plan [9], which is more
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