A multi-discipline Finite element model to study friction resistance capability at the interference fit at an elevated temperature

Paper #:
  • 2017-01-0453

  • 2017-03-28
Considered in this study by the use of finite element model is a unit of assembled stator and one-way clutch (OWC) whose inner chamber is maintained at a given temperature of 150 degree C while its exterior housing surfaces are exposed to the room temperature. Two key components of dissimilar metals are assembled, as usual, at the room temperature, through the conventional interface fitting, to form a secured joint by the means of internal friction forces so that torque loads are capable to be transmitted. Due to the dissimilar materials and resulting difference in their thermal expansion coefficients, an outer component of aluminum from this joint tends to expand more than the inner component of steel when the temperature rises. This work is indented to demonstrate that using a combined thermal and structural FEA can play a pivoting role in designing not only a robust product, but also a vital test procedure that can really captures how the product functions. Studied in this work are two simulations of test setup whose primary purpose is to evaluate the capability of slip torques between the surfaces on the outer member (i.e., aluminum stator) and OWC's hardened racer (acting as an inner member), both of which are interference-fit at the room temperature. In the first setup, the outer rim of a spoke-like stator is rigidly connected to a bulky and thick cylinder of steel whose inner wall is surrounded by hot fluid with a temperature maintained at 150C and whose outer wall is exposed to the room temperature. As expected and seen from the FEA simulation involving a combination of thermal and structural fields, the thick steel cylinder with much colder temperature prevents the aluminum stator from freely expanding radially when elevated to 150C. As a consequence, the interference force between the interface of stator and OWC racer is not decreased dramatically. In the contrast, in the second simulated test setup, the outer rim of aluminum stator is no longer radially connected to the thick steel cylinder acting as the housing to contain the hot fluid. As the result, at the thermal steady-state, the aluminum stator can fairly freely expand without much mechanical restriction. The FEA model will demonstrate that the The interference effects at its contact force can be dramatically diminished. In the worst case, the contact force could be totally lost depending on the amount of initial interference and the difference in temperature between the inner chamber and outside air.
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