Proving Ground Durability Simulations

Abstract: Virtual durability simulations have been explored in the automotive industry to complement physical testing in designing durable vehicles. Simulations are useful to check the validity of the design before even building the prototype of the vehicle. They are also useful in checking the effect of changes in vehicle design to the durability of the vehicle. Buses are designed and tested for durability before they are sold to customers. Bus manufacturers use special test tracks consisting of different kinds of maneuvers/obstacles to test the buses for durability. Proving ground durability test schedules defines the combination of different test track maneuvers/obstacles at which the bus is to be run. The test schedules are created to achieve accelerated fatigue damage in the bus comparable with the fatigue damage occurring in typical customer usage. This thesis is an attempt to check if a proving ground durability test schedule can be simulated in a computer. A Multibody dynamic model of the bus with its constituent subsystems is modeled in a multibody simulation software MSC ADAMS. Sub-systems like bus chassis frame and axle are modeled as flexible as their dynamic properties are assumed to influence the simulation results. The virtual bus is run on the virtual version of the test tracks. Loads at suspension torque rods, anti-roll bars, axles and displacement of dampers are extracted from the simulation. The load signals are post-processed to derive fatigue damage. The simulation model is compared with the test results of a single standard test track maneuver. The simulation model is tuned by adjusting the parameters to match with the test results of the given maneuver. Finally, the tuned model is used to run the bus in a test schedule. Results achieved at the end of the thesis shows that well-tuned simulation model is necessary for simulating test schedules with enough accuracy. Comparison with test results are to be treated with caution as the conditions of the test bus should be exactly same as the simulation model; which is difficult to achieve. Future extension of the work involves improving the accuracy of simulations and using simulations to iterate new kinds of maneuvers/obstacles to improve existing test schedules.