Crack Propagation In Microstructures Research Articles

Microscopic cracking simulation of nanocomposite ceramic tool materials under the consideration of residual stress

In this paper, the numerical simulation of crack propagation in microstructures of Al2O3/SiCn nanocomposite ceramic tool materials is carried out by means of a micromechanical model based on the Voronoi tessellation and the cohesive element theory in order to explore the relationship between microstructure morphologies and mechanical properties. The residual stress initiated due to the mismatch of thermal expansion coefficients and elastic modulus between matrix grains and nanoparticles is considered in the simulation. The effects of microstructure types and nanoparticle volume content on the residual stress field and the fracture behavior are analyzed, respectively.

Mesoscale Mechanical Model for Intergranular Stress Corrosion Cracking and Implications for Microstructure Engineering

The resistance of polycrystalline materials to intergranular cracking can be influenced by the microstructure. In sensitized stainless steels, for example, the grain boundaries prone to sensitization form paths of low resistance for intergranular stress corrosion cracking. The nonsensitized grain boundaries, such as twin boundaries, have been observed to encourage the formation of crack bridging ligaments. Computational models of intergranular cracking have been developed to investigate the consequences of crack bridging, through its effects on crack propagation in microstructures with different fractions of nonsensitized boundaries. This paper introduces the recently developed two-dimensional model for intergranular cracking with crack bridging, and reports its application to investigate the effect of grain size. It is shown that the size of the crack bridging zone depends on the grain size, and the shielding contribution depends on the relative size of the bridging zone compared to the crack length. It is concluded that both grain refinement and increase in the fraction of resistant boundaries can improve microstructure resistance to intergranular cracking. These observations are consistent with the effects of grain boundary engineering on stress corrosion cracking resistance in sensitized stainless steels.