Fatigue Damage Equivalence of Field and Simulated Vibrational Environments.

Abstract : A method is developed for comparing the fatigue damage equivalence of field and laboratory simulated vibration environments. It involves the use of a model hardware specimen which is instrumented to record typical strain-time histories that occur in a given environment. The device is used to acquire data from both the field and corresponding laboratory simulation. The resulting strain-time histories are analyzed for fatigue damage potential. This analysis is based on the use of fatigue life gages. A mission ratio is defined for each pair of strain histories so that the degree of simulation achieved can be expressed in terms of the number of equivalent missions experienced. The technique is applied to OH-58A Helicopter, M-35 Truck, and M-113 Armored Personnel Carrier vehicle environments and their simulations. It is found that a typical uniaxial test simulation provides a rather poor duplication of the actual multi-axial field environments.