ABSTRACT
The design engineer can estimate a part’s reliability in its new condition. Part reliability based on time-to-failure data using the exponential probability distribution assumes that part reliability is constant over its useful life-a best-practices approach for electronics and digital parts. Weibull failure distributions based on time-to-failure data suppose that the degradation of structural and dynamic part reliability can be modeled over the useful life; however, one must ask what practical application that information serves. More important to the design and sustainment engineer is the blunt fact that time does not cause part failure: Failure mechanisms cause part failure!
