Spinning Gear

Application ID: 407

One way to fasten a gear to a shaft is by thermal interference. In preparation of the assembly, the shaft diameter is oversized and the gear thermally expanded in a heat-treating oven. At an appropriate expansion state, the gear is removed from the oven, slid onto the shaft, and allowed to cool.

As the gear temperature drops, the gear shrinks and comes into contact with the shaft before it reaches its original shape. From this point on, additional gear shrinkage results in hoop stresses in the gear as well as normal compression of the shaft. At thermal equilibrium, a bond between the two components is reached.

Such an assembly can operate safely in many situations. However, there are operating conditions under which the fastening stresses become insufficient - for instance, when spinning the assembly at high RPM.

The goal of this analysis is to determine the critical spinning frequency at which gear and shaft separate. It is done through a parametric analysis and an optimization study.