Shrink Fit Shafts

Shrink and press fitting can be effective ways to join cylindrical structures. The cylinders are initially sized so that a specified radial interference exists at room temperature. The inner cylinder outer radius is larger than outer cylinder inner radius by a specified amount. If the cylinders are then forced together by applying sufficient axial force to overcome the friction, then the cylinders will be joined by a radial interface pressure. Instead of forcing the cylinders with a press-fit, the outer cylinder could be expanded by heating, or the inner cylinder could be shrunk by cooling, so that the cylinders can be joined with no axial force required.

Figure 2 shows a pair of cylinders that are joined in this manner. Concyl can be used to determine the interface stresses for systems of such cylinders with multiple materials by applying the proper radial thermal strains to the cylinders to account for the initial radial interference between the cylinders. This amounts to determining the proper stress-free temperature for each cylinder to achieve the radial displacements needed to fit the cylinders together.