Road Load Identification and Accelerated Life Testing of Engine Mounts

Internal combustion engine mounts in a ground vehicle experience a very complicated loading situation. The loads mainly depend on the combination of engine vibration, engine torque, and vehicle motion especially in irregular road and maneuver conditions. Fatigue life estimation of rubber components is more complicated than metal components because of nonlinear viscoelastic behavior of rubber. Hence, analytical and numerical methods to estimate the loading and fatigue life of engine mount rubber components are not employed as often as in metal components. A new approach has been proposed to validate engine mount rubber components using accelerated fatigue life testing. Accurate identification of service loads is the key factor for a successful engine mount development and validation process. A multi-axial load sensor was developed to measure the engine mount loading in six degrees of freedom for a rear wheel drive heavy duty truck. Developed load sensors were installed onto a heavy duty truck and engine mount loading was measured during vehicle durability test. Measured loading data were processed using rainflow cycle counting technique to generate the accelerated fatigue life test profile. Failure of the engine mount rubber observed in vehicle durability test was successfully replicated in accelerated life test. This approach can also be employed for validation of different rubber components available in suspension and driveline sub-systems.