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Air spring systems are increasingly used on suspensions for commercial vehicles. To prove their durability a reliable test procedure is necessary: to be applied already in the development stage to be used to qualify individual air spring manufacturers and to assure manufacturing quality. In this paper the test procedure, the test facility and some test results are presented. In the test facility the air spring is mounted on a fixture and is loaded by a servohydraulic actuator. The mounting of the air spring allows to simulate all operational deformations, being decisive for the durability. Based on the extensive measurements on proving ground and public roads the test program was worked out. The test program includes besides the loading and deformations during driving also kneeling operations as well as high and low temperatures. The accelerated laboratory tests deliver results which correspond to the existing experience at the service usage.

Validation of the complex wheel/hub assembly has been carried out in the Biaxial Wheel/Hub Test Facility since the early ‘1980’s, developed at Fraunhofer LBF. This test procedure was applied as standard at most of the European vehicle producers and wheel suppliers and was also introduced as SAE wheel standard J 2562, for wheels of passenger cars, issued in 2003. By extensive test series and investigations a suitable load file has been developed which is able to create fatigue failures and damages on wheel bearings, comparable to real service failures within an acceptable testing time and so far to prove their operational durability. The load program is based on the existing test program for durability approval of wheels and hubs, simulating different driving sections such as straight ahead driving, cornering and, if required, off-road driving and braking operations. The influence of different load programs on the bearing damage is described in this paper.

The method of fatigue life evaluation and validation testing under operational conditions is a prerequisite to achieve optimal designs with respect to weight and long-term durability of the structure considered. Criteria like driving behavior and braking performance, influenced by global stiffness as well as fatigue life evaluation were taken into account when optimizing a forged 6.5 front axle beam of a heavy truck. The procedure for weight optimization includes the following steps: Stress analysis e.g. using strain gage techniques and/or Finite Element Method, Road load data acquisition and derivation of design spectrum describing customer usage, Fatigue testing under constant amplitude and/or variable amplitude loading to establish component related SN-curves and/or fatigue life curves, Fatigue life evaluation using damage accumulation hypothesis (Miner's Rule), Optimization and weight reduction (in this case 14% weight savings were achieved) based on fatigue life evaluation.