Shoulder Fillets

The shoulder fillets are representative of the most common types of stress concentrations that are encountered in machine design practice. The majority of stress concentration factors (SCFs) for the fillets under tension and bending are from photoelastic tests, and the rest are found from finite element analyses. For torsion, the SCFs for the fillets are from a mathematical analysis. One of the problems occurring in the design of shafting, rotors, and other relevant parts, is how to reduce the concentrated stresses at a shoulder fillet while maintaining the positioning line and dimensions. This can be done in a number of ways. By cutting into the shoulder, a larger fillet radius can be obtained without developing interference with the fitted member. A ring insert could be used, but this needs an additional part. A similar result could be obtained except that a smooth fillet surface is more difficult to realize.