Reliability Curves Mechanical failure can occur at any point in a product life cycle. These can be divided into infant mortality, constant failure rate, and wear out. As shown in the diagram, which is a plot of failure rate as a function of time, the individual curves of these three different classes of failure mechanisms sum together to form the classic bathtub curve of observed failure rate. Infant Mortality Infant mortality occurs early during product use. The failure rate declines as a function of time, so reliability actually increases until a point is reached where the constant failure rate becomes dominant and the infant rate becomes negligible. The Weibull Distribution is used to model the infant mortality period. A wear-in or burn-in period may be used to screen out …
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