INVESTIGATION OF THE DURABILITY TRANSFER CONCEPT FOR VEHICLE PROGNOSTIC APPLICATIONS

Vehicle prognostics are used to estimate the remaining useful life of components or subsystems, based on a limited number of measured vehicle parameters. Ideally, sensors would be available for every component and failure mode of interest, such that accurate data could be measured and used in prognostic estimates. However, this is impractical in terms of the number of sensors required and the costs to install such a system and maintain its integrity. A better solution is to relate the loading on a specific component to more generic vehicle behavior. This paper reviews a methodology referred to as the “Durability Transfer Concept”, which suggests that damage, or severity of usage, at various points of interest on a vehicle can be predicted simply from measured accelerations at some nominal location – a wheel axle, for example. Measured accelerations are double integrated to get displacements. Those displacements are then filtered using the Rupp or Lalanne method. A transfer function is devised that relates nominal displacements to local damage on critical components. The results show good correlation between measured acceleration on a vehicle and damage at a remote location. However, correlation does depend on coherence; therefore, it is important to select representative locations for the accelerometers relative to the critical components. For best results, the transfer function requires a good range of usage conditions – i.e., representative terrain roughness, speed profile and vehicle weight conditions. In conclusion, the Durability Transfer Concept offers a good solution for predicting severity of usage for structural components on a vehicle, including chassis, steering and suspension components. The Rupp filtering method is preferable in this case where damage is attributable to low frequency terrain induced fatigue.