Drive Shaft Instrumentation for Torque Evaluation in a 4-Square Endurance Test Rig

Drive shafts endurance tests performed in 4-square test rigs often presents different levels of wear on samples of the same test, and the most damaged joints usually comes from positions 3 and 4 of the machine. These results are evidences of an unequal torque distribution between the tested parts. In order to analyze this effect on the equipment, four half shafts prepared for torque measurement are proposed. These parts are put in the machine and a simulated test is performed, while the torque applied to each rig position is measured simultaneously. The effect of the applied torque, speed and joint bending angles can so be evaluated to the influence on test results. Through this test it is possible to conclude that variations on applied torque is related more to the applied speed than to the other studied factors. It happens because the speed of half shafts in positions 1 and 2 is clockwise direction, while the parts on positions 3 and 4 are subjected to anti-clockwise speed, and torque is applied in clockwise direction on all four samples. So, parts on positions 3 and 4 are always subjected to a higher torque than the others, what may influence their performance on the test. Instead of existing, the maximum difference between the machine positions is no more than 3% of the test nominal torque.