Displacement measurements at the connector contact interface employing a novel thick film sensor

One of the key failure mechanisms for wiring and connector systems used in the automotive industry is fretting and fretting corrosion at the contact interface of connectors. For many years, procedures have been carried out under laboratory controlled conditions to investigate both thermal and vibration fretting effects using environmental chambers and fretting tests. Both optical and visual inspections have also been adopted to observe the movement at the contact interface. However, these methods can be considerably inconvenient and costly. Furthermore, their suitability for field applications is limited. In order to study the fretting degradation at the actual interface for in-situ measurement effectively, a novel position sensor is designed to monitor the relative displacement. Thick film techniques are employed to fabricate miniaturised and cost effective resistive devices. The sensor is assembled into a connector sample by taking the place of the male component. When the interface experiences movement, the relative displacement of the contact point would cause a corresponding linear change of resistance measured across the male and female connection. The sensors are validated by a series of experiments and subsequently used in a field test to establish the relationships between the fretting effects with temperature, humidity and differential pressure. It is found that variation in differential pressure dominates the behaviour of movement at the contact interface of the well-sealed connector sample while temperature and humidity have negligible influences on the measured relative displacement.