Analysis of Relative Motion and Contact Resistance of an Automotive Electrical Connector by Coupling Vibrations and Temperature

Relative motion between the pin and the clip of a semi-permanent connector, caused by vibration and temperature variations, is well known to be the main cause of fretting-corrosion failure in electrical connectors. Displacements induced by temperature variations are generally of low amplitude and very low frequency, in the order of a milli-hertz. These are difficult to measure with a motion sensor, which tends to drift over time. This study aims to quantify the relative displacements in the contact point of the pin and clip of an automotive electrical connector due to temperature variations. An original test bench was designed allowing coupling vibrations and temperature variations. A series of tests were carried out. Firstly, temperature cycles on static terminals were carried out at 100 °C and 180 °C for 6 days, at a rate of 8 hours per day. Hysteresis loops revealed that the electrical contact resistance (ECR) behaved differently during the heating and cooling phases and its areas are related to Joule losses. Secondly, the relative motion transfer function (RMFT) of the connector with all its components, established over a frequency range of 100 to 1000 Hz with an acceleration of 20G at room temperature (RT) and 120 °C, showed a significant variation in relative motion. Finally, a long duration fretting test carried out on the terminals, when a nominal current of 10A is imposed with voltages of 16 VDC, shows that the erosion and perforation of the fretting track of the pin are due to the occurrence of arcing in the contact point and not to resistive heating.