Weibull stress method to determine the minimum required strength to improve the actual reliability

Abstract

The method to determine the minimum strength that a product must present to improve the product's reliability from its actual R(t) to a desired R(t2) index are given. The method can be performed in both the normal and accelerated scenarios. It can be done by using either complete failure time data or based only on the applied stress range. The addressed minimum strength that corresponds to the R(t2) index is then used in the stress/strength reliability function to determine the corresponding reliability R(t/S,s) index. From the comparison between the R(t2) and R(t/S,s) indices, we found they are similar only for high reliability indices (say R(t) > 0.90). For lower indices their difference is significant, implying more research must be undertaken. In the application a zero accelerated test plan (ZATP) is performed to experimentally demonstrate the improved product presents the desired R(t2) index. Finally, because by applying the proposed method we always can reproduce the product's average, then the formulation to determine the capability Cp and ability Cpk indices of the R(t2) index is also given.