Método para a análise de vida em fadiga em chassi de implementos rodoviários a partir de densidades espectrais de potência

Abstract

This dissertation presents the development of a method for the fatigue life analysis in chassis of road implements out of power spectral densities. For this, triaxial and uniaxial accelerometer signals were used, which were positioned at ten points of a chassis of a road implement, covering various types of tracks. A finite element model of the chassis was also used, which was made available by the sponsoring company to carry out the research. Within the proposed method, three types of analysis were performed: modal operational analysis; harmonic and modal analysis; and fatigue life analysis. To perform the modal operational analysis, the signals obtained were treated with low-pass and window filters and converted to the frequency domain. As a result, modal data referring to the implement are entered as properties of a virtual finite element chassis model to obtain frequency response functions through harmonic and modal analysis. A power spectral density matrix was also created from the accelerations obtained so that, together with the frequency response functions and, from stress calculation techniques (von Mises and Critical Plane), the spectral moments are obtained. To obtain density probability functions, Dirlik or Tovo-Benasciutti methods are used using the spectral moments so that the fatigue life is calculated from the density probability functions together with S-N curves. Fatigue life was calculated in the time and frequency domain for two chassis models, one simplified and one complete. 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. Future work to obtain more accurate results includes: more collections in durability tests including strain gauges; modal experimental analysis in controlled scenarios; and residual stress assessments. [resumo fornecido pelo autor]