Simulation model and experimental validation for estimation of fatigue damage due to random vibration

In nature, there are many mechanical components that are subjected to vibrations. When they are applied, the material is loaded by a certain level of stress, depending on their amplitude and their frequency. If those vibrations endure for long time, a possible structural failure could occur. Such type of failure, called also fatigue failure, happens as a result of accumulated damage. Most of the vibrations are non-deterministic vibrations or, so called, random vibrations. They are non-deterministic excitations, a type of oscillation whose behavior is non predictable and without repeatability. The unpredictable behavior of those vibration makes the work of the designer complicated. Fortunately, many methods of predicting the vibration response of mechanical and structural systems, to fluctuating external forces, have grown rapidly in importance over the last century. However, the results of available methods are just an approximation, and for being sure of how big the useful residual life of the specimen is, a lot of experimental tests must be executed. The negative side of the tests are the costs they need for being executed. That is the reason for which the simulation models are required nowadays. The purpose of this work is to create a Finite Element Method (FEM)-model whose goal is to predict with a good accuracy the fatigue damage and the residual useful life of a AISI 304 specimen loaded with a PSD load. The load profile used has been an incremental load. The specimen has been subject to a constant PSD-load, over a narrow frequency band centered around the second frequency resonant for a constant time-duration. Completed the time load, the PSD has been gradually increased of a fixed increment, till the component has have a failure. Experimental tests have been conducted with the aim of calibrating and validating the simulations with the help of an electrodynamic shaker. The simulation’s results seem to represent with good precision both the mechanical characteristics of the material and the durability of the specimen.