Gear Root Stress Optimization Using Photoelastic Optimization Techniques

An important factor influencing the strength of spur gear teeth is the fillet profile. In the fillet area bending stress and local geometry changes result in stresses and stress concentrations that can, under high loading conditions, lead to failure. This study was conducted to determine if an optimum fillet profile existed, what the shape of the optimum profile is, if the profiles are similar for different pressure angles and the magnitude of improvement that could be expected. New manufacturing techniques such as full-form grinding, near net formed gear blanks and powered metallurgy technology allow the gear designer to put different forms in the root area than the usual trochoid produced by the tip of a hob generating the gear. With the application of these techniques the fillet profiles could be optimally formed leading to strength improvements of up to 40%, with reductions in rotating mass.