ABSTRACT
Accelerated Life Testing (ALT) is commonly used in order to obtain reliability information about a product in a timely manner. Several stress loading designs have been proposed and recent research interests have emerged concerning the development of equivalent ALT plans.
Step-Stress ALT (SSALT) is one of the most commonly used stress loadings because it usually shortens the test duration and reduces the number of required test units. This paper considers two fundamental questions when designing a SSALT and provides formal proofs in answer to each. Namely: (1) Can a simple SSALT be designed so that it is equivalent to other stress loading designs? (2) When optimizing a multi-level SSALT, does it degenerate to a simple SSALT plan? The answers to both queries, under certain reasonable model assumptions, are shown to be a qualified YES. In addition, we provide an argument to support the rationale of a common practice in designing a SSALT, that is, setting the higher stress level as high as possible in a SSALT plan.
Keywords: Accelerated life test; Equivalent ALT plan; Optimum ALT plan; Step-stress ALT.
Step-Stress ALT (SSALT) is one of the most commonly used stress loadings because it usually shortens the test duration and reduces the number of required test units. This paper considers two fundamental questions when designing a SSALT and provides formal proofs in answer to each. Namely: (1) Can a simple SSALT be designed so that it is equivalent to other stress loading designs? (2) When optimizing a multi-level SSALT, does it degenerate to a simple SSALT plan? The answers to both queries, under certain reasonable model assumptions, are shown to be a qualified YES. In addition, we provide an argument to support the rationale of a common practice in designing a SSALT, that is, setting the higher stress level as high as possible in a SSALT plan.
Keywords: Accelerated life test; Equivalent ALT plan; Optimum ALT plan; Step-stress ALT.