Dynamic propagation stress intensity

Nuclear Regulatory Commission and the Electric Power Research Institute to understand and develop tools for managing rapid crack propagation and crack arrest [2,3]. In this effort, methods such as optical caustics and dynamic photoelasticity were used to measure directly the instantaneous stress intensity at the tip of a rapidly propagating and arresting crack. The relationship between crack tip stress intensity and crack velocity (Figure 1) was established as the material property governing crack behavior in a structure. This relationship was later confirmed by Zehnder and Rosakis [4]. 

Zehnder, A.T. and Rosakis, A.J. (1990). Dynamic Fracture Initiation and Propagation in 4340 Steel under Impact Loading, International Journal of Fracture, 43, pp. 271-285. Kalthoff, J.F., Beinert, J. and Winkler, S. (1977). Measurements of Dynamic Stress Intensity Factors for Fast Running and Arresting Cracks in Double-Cantilever-Beam Specimens. n Fast Fracture and Crack Arrest, ASTMSTP 627, pp. 161-176, Hahn, G.T. and Kanninen, M.F. (Eds.). American Society for Testing and Materials. 

In this paper we have calculated the three dimensional stress fields at the tip of the crack associated with the standing waves across the plate, assuming the waves modulate the stress intensity factor of the crack. Thus the present analysis takes account of these important experimental observations for the microcrack branching instability described above. We are unable, however, to clarify the direct cause of this instability but we have pointed out that the transient interference pattern of the standing waves could enhance the stress fields at the tip of the crack, as shown in Fig. 5, and possibly change the dynamics of the propagating crack. 

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