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Fatigue damage calculations are traditionally based on the time domain approach. Acceleration time history inputs are used to excite the system and the outputs are in a form of stress time history. This transient dynamic approach, as time history is intuitive to understand, provides straightforward and reasonable result. Nevertheless, a typical automotive proving ground test consists of 20 to 30 road events, it is not only computationally intensive but could be also a grueling process for an engineer to carry out as it requires several iterations for each event in the schedule before fatigue calculation. Alternatively, a frequency domain fatigue calculation is widely used. In this approach, both the dynamic loading and response are expressed in terms of Power Spectral Density (PSD) functions and the dynamic structure is treated as a linear transfer function. The transfer function is then multiplied with the event PSD to get the PSD of the stress.

Traditionally, fatigue calculations are based on the time domain approach. Acceleration time history inputs are used to excite the system. Through the element stress time history output and rainflow cycle count algorithm, fatigue damage can be calculated through the Palmgren-Miner cumulative damage rule. Nevertheless, it can be a daunting process for CAE analysts as it requires iteration for each individual event in the schedule before calculating the fatigue life. The alternative approach is frequency domain fatigue calculation. In this approach, both the dynamic loading and response are expressed in terms of Power Spectral Density (PSD) functions and the dynamic structure is treated as a linear transfer function. The stress PSD is then obtained by multiplying the transfer function with the PSD load. The objective of this paper is to present a CAE based virtual shaker table procedure for an automotive exhaust component and subjecting it to PSD for fatigue life prediction.