Transient Analysis of Engine Parts under Engine Loads and Random Road Vibration for Fatigue Evaluation

Some of the engine components are connected both to the chassis and to the engine. These parts are subject to vibrational loads coming from the road and the engine. Engine loads are generally considered to be deterministic, whereas the road load is random and conventional methods such as steady state forced frequency analysis, or PSD approach usually focus on engine and road loads separately. Since phase information is lost during PSD conversion, it is not possible to superimpose the results of these analyses without making additional assumptions such as creating random phase data for stress results, which would be a questionable technique. Consequently, these approaches generally result in delivering incomplete information for fatigue evaluation. In this study, both of the engine and road loads are considered simultaneously. Direct transient analysis technique is utilized in order to obtain overall stress values on the parts. Up to 40% difference in the stress values are seen in the selected bracket of interest, and it is concluded that ignoring one of the sources of vibration, either the road or the engine, may result in misinterpretation of fatigue durability of the part.