Cyclic Deformation and Proof Evaluation of an Automotive Torque Converter

The cyclic deformation of a torque converter (T/C) assembly for automatic transmission motor vehicles was studied to evaluate the endurance under constant-amplitude cyclic internal pressure. An electric-hydraulic servo controlled endurance test machine was developed to estimate the cyclic deformation by monitoring the volume of hydraulic fluid supplied to T/C assembly. The cyclic volume expansion of T/C assembly from 0 MPa to the test pressure in each cycle was obtained from the supplied hydraulic fluid. The volume expansion decreased first and increased with increasing cycle, followed by the oil leakage. The number of cycles at the minimum of the volume expansion corresponded with the cycles to the crack initiation inside the T/C assembly. Since the life of crack growth has a good relation with that of crack initiation, the total life could be evaluated in term of the life of the crack initiation. This suggested that the timesaving endurance test should be possible for T/C assembly.