Probabilistic Design for Reliability and the Factor of Safety

Producing a reliable product requires planning for reliability from the earliest stages of product design. This chapter covers basic models and principles to quantify and evaluate reliability during the design stage. One way to quantify reliability during design and to design for reliability is the probabilistic approach to design. The chapter presents the probabilistic design approach and relationships between reliability and safety factor. It also discusses the relationship between tolerances on the characteristics of the parts and reliability. Probabilistic design requires analysis of the functions of random variables. Since both strength and stress are random variables, the engineers designing a product must determine which measures of strength or the stress should be used in the computation of the factor of safety based on probability. Following the steps for probabilistic design can result in the production of a product that will achieve the desired level of reliability in its application environment.