Auxiliary acceleration factor for sequential Accelerated Life Tests: A case study

Accelerated life testing (ALT) has been extensively used in manufacturing industry so as to quickly obtain information about product reliability. However, when stress levels are low, failures can still be elusive. To mitigate this problem, a common remedy is to specify a minimum number of failures which may result in long test time and/or excessive extrapolation. In this paper, an auxiliary acceleration factor, with its effect well defined, is employed to amplify the failure probability at low stress levels. Particularly, it is proposed that the auxiliary stress is loaded under a step-stress loading pattern so that the initial stress level will not be too harsh for the product. Based on Weibull failure time and time censoring (type-I) scheme, we demonstrate an approach for embedding an auxiliary acceleration factor into the design of sequential constant-stress ALT through a case study.