Dynamic crack growth across an interface
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The growth of a crack first in an elastic solid, then across an interface and into an elastic-viscoplastic solid is analyzed numerically. The analyses are carried out within a framework where the continuum is characterized by two constitutive relations; one that relates stress and strain in the bulk material, the other relates the traction and separation across a specified set of cohesive surfaces. Crack initiation, crack growth and crack arrest emerge naturally as outcomes of the imposed loading, without any ad hoc assumptions concerning crack growth or crack path selection criteria. Full transient analyses are carried out using two characterizations of strain rate hardening for the viscoplastic solid; power law strain rate hardening and a combined power law-exponential relation that gives rise to enhanced strain rate hardening at high strain rates. Results are presented for two values of interface strength. For the higher strength interface the crack grows straight through the interface into the elastic-viscoplastic solid, while for the lower strength interface the crack deflects into the interface.