Analysis of reliability data for mechanical systems

Case studies for the analysis of the reliability data for complex hydromechanical systems are presented. The case studies indicate that failure rate is dependent on unit age and that system reliability is usually limited by a few dominant failure modes which exhibit an increasing failure rate with age (wearout). Unless this characteristic of mechanical systems is recognized and made a part of the hypothesis for the analysis, the results are likely to be in error. One important technique in an analysis is a Weibull plot of the data. Observation of such a plot will reveal changes in failure rate with age as well as the basic failure rate characteristic. The author also refers to an analysis technique (called the bi-Weibull) using the combination of two Weibull plots to model complex hydromechanical system failures.<>