Optimal simple step stress accelerated life test design for reliability prediction

Numerical Methods for Reliability and Safety Assessment

“…Li and Fard (2007) proposed an optimum step-stress accelerated life test for two stress variables which include censored data. Fard and Li (2009) derived a simple Step-stress ALT (SSALT) model to determine the optimal hold time at which the stress levels changed; they assumed a Weibull distribution for failure time. In Fig.…”

Reference optimality criterion for planning accelerated life testing

“…Consequently, robustness of such optimal plans should be studied according to different initial values. See Fard and Li (2009) and Tsai et al (2012). Besides, V-optimality criterion and D-optimality criterion are based on large sample approximations, while ALTs are usually subject to the constraint that the available number of test units has to be small either because of high cost of the units, or availability of prototype units.…”

Bayesian Analysis of Step-Stress Accelerated Life Tests and Its Use in Planning

“…DeGroot and Goel (1979) and Leu and Shen (2007) consider planning assuming an exponential lifetime distribution. Fard and Li (2009) and Yuan, Liu, and Kuo (2012) consider two or three step-stress plans to determine optimal switching times; that is, the times to switch from the current step to the next step, and use an approximate variance of a specified lifetime distribution quantile; these articles use the same Weibull distribution parameterization as we use in this article but employ a loglinear model for the Weibull scale parameter as a function of stress instead of a power law. In this article, we consider the number of units for multiple step durations in an 11-step plan motivated by the cryogenic cable example in Nelson (1990, ch.…”