Method for Fatigue Life Analysis in Road Implement Chassis from Power Spectral Densities

Abstract

<div class="section abstract"><div class="htmlview paragraph">This paper presents the development of a method for the fatigue life analysis in chassis of road implements from power spectral densities, bringing a new possibility for fatigue analysis and reducing the probability of a prototype having fatigue failure. The method was executed by deploying triaxial and uniaxial accelerometers at various points on the road implement chassis, and performing finite element analysis, while it was driven on various road surfaces. Within the proposed method, three types of analyzes were performed: the operational modal analysis; harmonic and modal analysis; and fatigue life analysis. To perform the operational modal analysis, the signals were treated with low-pass and window filters and converted to the frequency domain. As a result, the modal data referring to the implement are inserted as properties of a virtual chassis model in finite elements to obtain frequency response functions through harmonic and modal analysis. A matrix of power spectral densities was also created from the accelerations obtained so that, together with the frequency response functions and, from stress calculation techniques, the spectral moments are obtained. To calculate the fatigue life, the Dirlik or Tovo-Benasciutti methods were employed using spectral moments to obtain the probability density functions. These functions, along with S-N curves, were then utilized to determine the fatigue life. The fatigue life was calculated both in the time and frequency domains for two chassis models, one simplified and the other being a full representation. The simplified model presented approximate results in both domains, in the time domain, the worst life presented itself at 11.200 km and, in the frequency domain, 8.900 km. The complete model showed a variation in the results, 847.000 km in the time domain, and 0.05 km in the frequency domain.</div></div>