This chapter presents various introductory aspects of engineering reliability.

This is a well-known concept used to represent failure behavior of various engineering items because the failure rate of such items is a function of time (i.e., it changes with time). A bathtub hazard rate curve is shown in Figure 3.1. It is divided into three regions (i.e., Region I, Region II, and Region III). Region I is known as the burn-in region, debugging region, infant mortality region, or break-in region. During this period or region the item hazard rate (i.e., time-dependent failure rate) decreases because of failures occurring for reasons such as listed in Table 3.1 [2]. Region II is referred to as the “useful life period,” during which the item hazard rate remains constant. Some of the reasons for the occurrence failure in this region are presented in Table 3.1. Region III is known as the “wear-out period,” during which the hazard rate increases because of failures occurring for reasons such as presented in Table 3.1.