Failure rate model of components with the number of load application as life parameter

The failure rate model of components with the number of load application as life parameter is developed in this paper. Taking static strength failure and fatigue failure as the backgrounds, the dynamic reliability models of components under random repeated load without strength degradation and those with strength degradation are derived, respectively. Then, the failure rate model of components with the number of load application as life parameter is derived without strength degradation and those with strength degradation are derived, respectively. The relationship between reliability and the number of load application, and that between failure rate and the number of load application are discussed in different cases. The result shows that even though when strength doesn't degenerate, both reliability and failure rate of components decrease as the number of load application increases, and the failure rate curve has the partial character of bathtub curve with early failure period and random failure period. When strength degenerates with the number of load application, the reliability of components decreases more obviously, and the failure rate curve of components is bathtub-shaped.