Using the Upper Bound Technique for Calculating the Strain Rate Intensity Factor

Abstract

The strain rate intensity factor is the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. This factor can be used to describe the generation of fine grain layers in the vicinity of friction surfaces in metal forming processes. However, a difficulty is that the strain rate intensity factor follows from singular solutions and commercial finite element packages are not capable of finding this factor. In the present paper, the upper bound technique is used for this purpose. The kinematically admissible velocity field chosen accounts for the exact asymptotic expansion of the equivalent strain rate. Therefore, an approximate value of the strain rate intensity factor can be found from this field.