Bathtub curve

A graph that shows the relationship between elapsed time and failure rate of equipment or components. It is also called a failure rate curve and is named because its shape resembles a bathtub. After the start of use, the failure rate is high due to initial failures, but it decreases over time. Eventually, it enters a random failure period where the failure rate remains low and stable. After the random failure period, it enters the wear-out failure period, where failures increase due to aging and deterioration. The lifespan of equipment or components is often set based on the time before entering this wear-out failure period.