This Engineering Probabilistic Methods report presents a comprehensive review of probabilistic methods that can be implemented in engineering practice. This establishes a new SAE standard on the use of probabilistic methods in industry. A theoretical review provides the knowledge for understanding this new paradigm by practicing engineers. Current implementation is also discussed. It is addressed to practicing design engineers as well as theorists and researchers at the forefront of technology.
Engineers design safe products by subjectively accounting for uncertainty. In the design phase, load, geometry and material strength are all imprecisely defined at best. In operation, the order and magnitude of these critical inputs are random and unpredictable. Strength and stress are both random variables. To negate these uncertainties engineers use factors of safety, the ratio of minimum strength to maximum stress. Safety factors do not necessarily predict the actual safety of a design. Catastrophic accidents have demonstrated that subjective engineering judgment can be insufficient. Societal pressures drive revised design standards and quality assurance requirements to improve product safety. Lacking rigorous methods of evaluation, engineers previously increased safety factors to prevent failures. In other words, engineers increased cost, weight or both yielding an unknown and unpredictable improvement in product safety.