Study on Fatigue Life of Engine-Exhaust Pipe Flexible Couplings

Flexible couplings (bellows) located between the exhaust manifold of the car engine and exhaust pipe play an important role in thwarting vibration and engine motion to the automotive body and structure. However, this part experiences harsh cyclic thermo-mechanical loadings which could considerably reduce its effective life. In present research, the fatigue life of the bellows under one type of real road maneuver (Road Load Data Acquisition -RLDA) is taken into account. Based on the data recorded from the RLDA tests, relative three-dimensional position of two ends of the bellows is measured. The fatigue characteristics of the part material are derived based on a 3-DOF test bench under purely reversible loading. These data are used to construct an empirical Wohler fatigue diagram. In the next step, in order to calculate the fatigue life of coupling under real road time histories, a numerical study is conducted in which a FE model from the bellows is used for stress analysis. Then in the fatigue code, real time history is introduced to the model and tolerable life of flexible coupling is estimated.