Probabilistic Random Vibration Fatigue

Industrial components subjected to random vibration fatigue (loading with a power spectral density, PSD, or a sinusoidal spectrum) are frequently designed by the use of numerical simulations to estimate the lifetime and ensure the mechanical system behavior.Finite element simulations need the use of a significant amount of input parameters to solve the problem (material properties such as Young's modulus, density, stiffness of joints between components, model element choice.). Some of these parameters are identified from tests with unavoidable uncertainty and others are subjected to inherent variability. It is important to know the influence of this variability/uncertainty on model responses. Innovative methods have been developed to determine the sensitivity of model responses to uncertain parameters in order to study the robustness of the design.Then, the identification of the most influential parameters, associated with the study of their variations, allow to determine result dispersions for the modal analysis (eigen frequencies, mode shapes), the calculation of random vibration (RMS constraints) and damage calculation.This methodology provides an estimation of the probability of system failure instead of a binary result obtained by a deterministic design method.