Stability of Dynamically Propagating Cracks

	Stability of Dynamically Propagating Cracks K. Uenishi and H.P. Rossmanith Institute of Mechanics, Vienna University of Technology, Vienna, Austria

Summary

Dynamic crack propagation and bifurcation phenomena are investigated analytically by utilizing the strain energy density fracture criterion in the framework of catastrophe theory. The effect of biaxial stress, loading imperfections (mixed-mode loading), Poisson's ratio, state of stress as well as crack tip propagation speed on the crack path directional stability is analyzed. Special crack path stability charts for (un)stably propagating cracks are obtained and their connection with the experimentally recorded crack tip stress field is addressed. It is shown that slight change of the normal stress acting parallel to a crack at its tip (crack-parallel stress) may be able to affect the crack surface roughening and/or branching velocity considerably. It is also indicated that under small tensile crack-parallel stress, the crack propagation is stable only when the crack propagation speed is less than about 30% of the relevant shear wave speed. The crack becomes unstable and its surfaces roughen severely at a higher speed, and the crack bifurcates at the highest propagation speed, some 45% of the shear wave speed. It is suggested that superimposing mode-II (shear) loading will enhance the dynamic crack path stability while increasing crack propagation speed will reduce the stability of crack propagation. It is expected that under compressive crack-parallel stress, no crack surface roughening will occur before the crack stably bifurcates.

Keywords

Crack branching and bifurcation, Dynamic fracture, Crack propagation, Crack mechanics, Energy methods, Stability and bifurcation, Catastrophe theory, Loading imperfection.

Related Publications

Uenishi, K., and H.P. Rossmanith (2002). Stability of Dynamically Propagating Cracks in Brittle Materials. Acta Mech., 156(3-4), 179-192.
Uenishi, K., and H.P. Rossmanith (2000). The Effect of Crack-Parallel Stress and Mixed-Mode Loading on Dynamic Crack Path Instability. Eos Trans. AGU, 81(48), Fall Meet. Suppl., Abstract T22D-02.

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