The variable-radius notch: Two new methods for reducing stress concentration

Geometrical features such as notches and corners give rise to stress concentrations. In industrial components these features are often designed with a constant radius, however it is already known that a more complex shape, having a variable radius, can have a much lower stress concentration factor. In this paper we describe two new approaches for obtaining useful variable-radius notches. The first approach, which we call the Local Curvature Method (LCM) involves post-processing results of a stress analysis conducted on a constant-radius notch, altering the local curvature as a function of the local surface stress. This method is being described here for the first time: it was found to be very successful, reducing the maximum stress at a 90° fillet by about a factor of 2. The second approach involved using commercial software (modeFrontier) to carry out a more systematic search of possible variable-radius designs using multiple finite element models. This approach, though much more expensive in terms of computing resources, was able to find slightly better solutions. Our findings were verified by conducting experimental tests to measure brittle fracture strength and high-cycle fatigue strength.