Reliability, Maintainability and Risk, 8th Edition

Chapter 6. Variable Failure Rates and Probability Plotting

6.1. The Weibull Distribution

The bathtub curve in Figure 2.7 showed that, as well as random failures, there are distributions involving increasing or decreasing failure rate. In these variable failure rate cases there is no point in considering the failure rate since it is continually changing. Only reliability and MTBF are meaningful. In Chapter 2 we saw that:

Only the random failures case enabled us to simplify this to R(t)=e^−λt and to make use of the failure rate parameter. Since the relationship between failure rate and time can take many forms, and depends on the device/component in ...