Comparison of procedures for experimental and theoretical durability approval of a truck axle

The durability approval of truck axles is performed on proving grounds with well defined road characteristics as well as in laboratory test facilities simulating these loading conditions. These proof out tests are supposed to reproduce within a reasonable time the customer usage conditions which are expected during the life of a vehicle taking into account the large scatter of service. The programs and requirements are based on extensive measurements as well as long term experience. However, the development of vehicles for specific mission profiles as well as the introduction of components from new light weight material and innovative manufacturing technologies with different durability properties, requires procedures for the evaluation of the programs themselves. Within this paper the procedure of a comparative damage evaluation of test track and laboratory test programs with respect to an appropriated mission profile is demonstrated as example on a truck axle. Starting with road load measurements with the wheel force transducer VELOS for heavy trucks on a proving ground, the design load conditions are derived and design load spectra are established based on experience with many years of measurements and testing on different heavy trucks. Referring the program and requirement on the proving ground and in laboratory testing to the design spectra in a comparative damage calculation, allows the evaluation of the durability approval itself.