Conditions controlling kink crack nucleation out of, and delamination along, a mixed-mode interface crack

Abstract

This paper analyzes the competition between kink nucleation and interface fracture for an interface crack (without a putative kink flaw) subject to mixed-mode loading. The simulations utilize a distributed cohesive zone approach that embeds cohesive elements throughout the entire mesh; dynamic crack path evolution occurs through a loss of cohesive traction associated with a critical separation between elements. The simulations identify mesh densities that lead to mesh-independent results for randomly oriented triangular meshes, and provide clear guidelines regarding parameters that recover toughness-controlled cracking (i.e. linear elastic fracture mechanics). The results demonstrate that, when the when the normalized bulk toughness is far from the transition between kinking and delamination, crack direction and critical loads are identical to those predicted by He and Hutchinson, who analyzed cracking from a putative flaw associated with the maximum energy release rate. Near the transition between fracture modes, kink nucleation depends on the relative size of the interface and bulk process zones, such that additional criteria are needed (beyond those postulated by He and Hutchinson). Regime maps are presented which indicate regions of kink nucleation versus delamination as a function of controlling cohesive parameters.

An integrated analysis of transport, oxidation, and creep during oxidation of interior pores in SiC

“…This includes the future incorporation of existing cohesive element frameworks to simulate fracture. (e.g., 5,6 ) In addition, this approach exploits the speed of highly optimized, open-sourced auto-matic meshing algorithms for triangular elements that offer highly adaptable spatial resolution and easily handle significant changes in the geometry. 22,23 The need to iteratively solve for creep relaxation that occurs over an increment in growth implies the fact that the costs of re-meshing are negligible.…”

“…3,4 , the current approach has the benefit of straightforward coding that can be easily adapted to various constitutive descriptions of oxidation and creep and facile integration with existing cohesive zone frameworks for simulating fracture. 5,6 The two physical models that form the core of the simulation framework are: (i) an oxide growth model that represents a generalization of the Deal-Grove model, 7 wherein the flux of oxidant arriving at the oxide/SiC interface dictates the interface velocity, and (ii) a nonlinear, Eyring-type creep description of the oxide. 8 These are described in Section 2, along with an analytical solution for the stresses in a flat, growing oxide film that integrates both models.…”

“…While naturally there are numerous alternatives (e.g 3,4 ,. the current approach has the benefit of straightforward coding that can be easily adapted to various constitutive descriptions of oxidation and creep and facile integration with existing cohesive zone frameworks for simulating fracture 5,6 …”