COMPUTATIONAL SIMULATION UNDER PSD FATIGUE LOADING

In the design of structures subjected to acoustic fatigue, excitations are usually non-deterministic. Power Spectral Density (PSD) is used to describe the frequency content and intensity of random vibration. Random excitations can be applied in the form of accelerations, pressures or forces. Degradation of a structure is usually represented by the reduction of natural frequency during the application of PSD loading. A computational tool is developed to simulate the degradation response of composite structures under a PSD fatigue loading condition. Quantitative predictions of damage initiation, damage progression and propagation to fracture are monitored. Computational simulation is based on a step-by-step update of time during damage progression under PSD loading. For each step of equilibrium point natural frequencies of the structure are computed. The degradation of frequency is determined with the increment of time steps. The Excitation level-Time relationship is predicted from the output of several simulations at different PSD levels. A PMC test coupon is simulated on a dynamic shaker by imposing the PSD of base accelerations. Failure mechanisms and their locations are identified.