A physical approach for determining the optimum random-vibration screening duration

The authors propose a physical approach for the determination of the optimum random-vibration screening duration. This approach is based on a newly-proposed bimodally-distributed P-S-N diagram, for the fatigue strength of nonscreened units, and its corresponding threshold S-N curve for fatigue defect precipitation. Equations, for mean and variance of the cumulative damage and fatigue-defect precipitation time distributions, and for the optimum random-vibration screening duration, under both stationary narrow-band and stationary wide-band random stressing, are derived in terms of the parameters of the structure-inherent bimodally-distributed P-S-N diagram and of the stress response spectrum which corresponds to the applied acceleration power spectral density (PSD) function. A numerical example is given to illustrate the application of the proposed approach.