New methodology for accelerating the four-post testing of tractors using wheel hub displacements

Durability tests of tractor prototypes need substantial financial and time commitments. The duration and cost of tests could be reduced using accelerated tests able to reproduce on the structural part of the tractor, the same damage produced on the tractor during its real life but over a reduced time period. It has been recently demonstrated how it is possible to speed up the tests using automotive proving grounds. However a complete prototype with all its components is necessary to perform tests on proving grounds, but to test only the structural durability is possible the use of a 4-post bench. A 4-post bench is able to reproduce a specific vehicle response, with the possibility of applying fatigue editing techniques to remove the non-damaging portions of the load signals. These techniques are usually applied to load signals measured with strain gauges during tests on proving grounds. However, strain gauge installations and data validation of the acquired signals are time-consuming. Here a new method, able to calculate the displacements on the wheel hub starting with acceleration measurements, applying fatigue editing techniques and defining drive files to command the actuators of a 4-post bench is described. The method proposed has an acceleration factor for the test of 5.3 together with a more rapid procedure to fit the transducers and to analyse the data obtained from the accelerometers compared to those obtained from the strain gauges.