Design Variation Simulation of Tliicl(-walled Cylinders

Introduction The design of a product requires knowledge of how the product will be used, how it will be manufactured, and of what materials it is made. Successful design practices also attempt to compensate for aging processes such as wear and corrosion. The factor-of-safety method of design is one such design practice, where allowable stresses or factors of safety are specified on the basis of experience or recognized design codes. While such design factors may comfort a design engineer by providing "rules of thumb," these arbitrary limits often lead to overly conservative designs. Probabilistic methods, however, can provide more quantitative and qualitative design evaluations, leading to higher product functionality, quality and overall value. Probablistic methods are deeply rooted in the fertile fields of worst case analysis, random variable algebra and Monte Carlo simulation. Worst case analysis is a simple, but effective approach to analyzing alternatives with respect to performance criteria. The design engineer merely poses the appropriate what-if questions, such as what if the load is doubled, will the machine element fail? What if the actual yield strength is only 90 percent of the nominal strength? And so on. Assuming that the right what-if questions are asked, the resulting worst cases reveal the design's weaknesses. A more systematic approach couples the worst-case of all the design variables, thereby describing the impact of simultaneous variations The random variable algebra approach incorporates statistics such as the mean value and standard deviation of the design variables and parameters. The statistics characteriz