Determining the dynamic stress intensity factor with strain gages using a crack tip locating algorithm

Abstract Recent experimental studies have shown that strain gages can be employed to determine either static or dynamic stress intensity factors K I , with relatively simple experiments. This paper describes an analysis method for determining K ID (t) associated with a propagating crack. The analysis is based on a three parameter representation of the strain field near the crack tip. An algorithm is developed where triangulation is used to precisely locate the crack tip position. The algorithm also includes an iteration scheme which permits an accurate determination of two key parameters in the series representation of the strain field. The new method of analysis is demonstrated in a dynamic experiment with a high strength 4340 alloy steel.