Wearout

Wearout is the final phase of a component’s life in reliability engineering, during which the probability of failure increases as time or usage accumulates. It is part of the commonly described bathtub curve, which also includes an initial high-failure period (infant mortality) and a middle period of relatively constant failure rate (normal life). In the wearout phase, aging, material degradation, and cumulative damage raise the hazard rate.

Causes of wearout failures vary by component but typically include fatigue and wear of materials, corrosion, creep, thermal cycling, lubrication breakdown, and environmental stress. As components approach the end of their useful life, unchecked wear can lead to performance decline and sudden failures if not addressed.

Modeling and measurement often involve analyzing the hazard rate, which tends to rise during wearout. Reliability data may be described by distributions such as the Weibull with a shape parameter greater than one. Field failure data and accelerated life testing are used to estimate time-to-failure and to inform replacement or maintenance planning.

Management strategies focus on extending useful life or mitigating wearout risk. These include preventive replacement schedules, condition-based maintenance, redesigns with more durable materials, improved lubrication or coatings, maintenance redundancy, and early detection of wear through monitoring and prognostics.

Common examples of wearout failures occur in mechanical bearings, gears, and tires, where wear or fatigue increases the likelihood of failure with mileage or usage. Batteries and capacitors can also exhibit wearout behavior as performance degrades with cycles and aging.

See also: bathtub curve, reliability engineering, maintenance strategy, prognostics.