Bathtub-type and roller-coaster-type failure rates modeling

摘要

Failure rate curves take on a variety of patterns, such as bathtub shape, roller-coaster shape, etc. The present paper investigates the mechanisms by which the different types of failure rate curves are produced. The basic idea is that, for the majority of engineering structures and mechanical components, the operating load is usually a random process, material property degrades with the loading experience, and the continuously changing load-strength relationship yields the variation in failure rate over time or over load history. In load amplitude domain, the situation can be described as one in which the structure or component is subjected to multiple actions of stochastic load, and the material property degrades continuously, and failure is caused by a load higher than strength. Through analyzing the interaction between the statistically-increasing load level and the degrading strength property, as well as the competing failure modes, a dynamic load-strength interference model is developed and both the bathtub-type failure rate curve and the roller-coaster type failure rate curve are illustrated.