Optimum time-censored simple ramp-stress accelerated life test sampling plan for the log-logistic distribution

Abstract

Purpose -Acceptance sampling plans are designed to decide about acceptance or rejection of a lot of products on the basis of sample drawn from it. Accelerating the life test helps in obtaining information about the lifetimes of high reliability products quickly. The purpose of this paper is to formulate an optimum time censored acceptance sampling plan based on ramp-stress accelerated life test (ALT) for items having log-logistic life distribution. The log-logistic life distribution has been found appropriate for highly reliable components such as power system components and insulating materials. Design/methodology/approach -The inverse power relationship has been used to model stress-life relationship. It is meant for analyzing data for which the accelerated stress is nonthermal in nature, and frequently used as an accelerating stress for products such as capacitors, transformers, and insulators. The method of maximum likelihood is used for estimating design parameters. The optimal test plan is obtained by minimizing variance of test-statistic that decides on acceptability or rejectibility of lot. The optimal test plan finds optimal sample size, stress rates, sample proportion allocated to each stress and lot acceptability constant such that producer's risk and consumer's risk is satisfied. Findings -Asymptotic variance plays a pivotal role in determining the sample size required for a sampling plan for deciding the acceptance/rejection of a lot. The sample size is minimized by optimally designing a ramp-stress ALT so that the asymptotic variance is minimized. Originality/value -The model suggested is of use to quality control and reliability engineers dealing with highly reliable items.

Optimum reliability acceptance sampling plan using Type-I generalized hybrid censoring scheme for products under warranty

“…Another alternative approach followed in the literature for finding RASPs is to minimize the asymptotic variance V (Srivastava and Sharma, 2015;Wook Chung et al., 2006). As mentioned in Section 2, the asymptotic variance of test statistic is obtained as V ¼ ' 11 ðθÞ þ k 2 ' 22 ðθÞ − 2k' 12 ðθÞ where ' 11 , ' 22 and ' 12 are elements of variance-covariance matrix of the likelihood estimates of the parameters.…”

“…Wook Chung et al (2006) obtained RASPs for failure censored accelerated life tests (ALTs). Srivastava and Sharma (2015) formulated time-censored sampling plans for product lifetimes following log-logistic distribution under an accelerated setting. Using Rama distribution, Al-Omari et al (2019) developed a new acceptance sampling plan for time truncated life tests.…”

Optimal design of reliability acceptance sampling plan based on constant‐stress accelerated life testing considering the uncertainty of accelerated factor

“…The AASPs are designed to save the test resources effectively in reliability demonstration tests, but they are often not the optimal ones in existing works 21 . Consequently, to improve the test efficiency and save the test cost furtherly, the optimum AASPs can be designed by establishing an optimization model.…”

“…The AASPs are designed to save the test resources effectively in reliability demonstration tests, but they are often not the optimal ones in existing works. 21 Consequently, to improve the test efficiency and save the test cost furtherly, the optimum AASPs can be designed by establishing an optimization model. In general, the design process mainly consists of three steps: identifying decision variables, formulating the objective function and constraints, and implementing model computations.…”

Estimation and Optimal Plans of Multiple Ramp-Stress Accelerated Life Tests for the Generalized Half-Normal Distribution

“…Unfortunately, there are a few studies on the optimal design of ramp-stress ALTs as compared to constant and step-stress planning. Furthermore, the most recent studies on the optimal design of ramp-stress ALT considering the simple ramp-stress ALT; see for instance, Bai et al [35], and Srivastava and Sharma [36]. Thus, designing an effective multiple ramp-stress ALT for GHN distribution is required and of great attention.…”