Multi-physics experimental investigation into stator-housing contact interface

The shrink-fitting of housings on to electrical machine stators is a common, semi-permanent and low-cost method of assembly. As the stator-housing interface lies in the main heat extraction path, an ideal shrink-fit should provide the necessary holding torque, present minimal thermal contact resistance and remain mechanically and thermally stable over the operating temperature range and life of the electrical machine. The optimal design of such a shrink-fit represents a multi-physics problem requiring, among other data, accurate coefficient of friction and thermal contact conductance information. However, these parameters are influenced by many factors including interface pressure, surface preparation and temperature, and are therefore difficult to predict unless experimental methods are adopted. To this end, this paper presents two independent experimental apparatus designed to measure the pressure dependent coefficient of friction and thermal contact conductance between typical housing and electrical steel materials under in-service conditions.