Finite element modeling of microstructurally small cracks using single crystal plasticity

Abstract Finite element simulations of small fatigue cracks were performed using crystal plasticity theory to describe the deformation behavior near the crack tip. A rate-independent small strain formulation from crystal plasticity theory was implemented. Constant amplitude loads were applied, with a load ratio of R =0.3. Crack opening stresses and crack tip opening displacement ranges were simulated as the crack grew in a single grain, as well as when the crack grew toward a grain boundary. Crack growth in single grains indicated that stabilization of the crack opening stresses occurs relatively rapidly (5–10 μm of crack growth). Studies of crack growth toward a grain boundary revealed that, depending on the orientation of the adjacent grain, the crack growth rate is significantly affected. If the angle of misorientation between the two adjacent grains is small, the neighboring grain can increase the growth rate near the grain boundary. If the misorientation angle is high, the fatigue crack growth rate will be significantly slowed near the grain boundary.

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