Cracks in Three-Dimensional Polycrystals with Microstructural Stresses

Jingchun Guo, M.S.
Department of Engineering Mechanics
University of Nebraska - Lincoln
Advisor:  Dr. M.S. Wu

Date:  Friday, September 18, 1998
Time:  3:30 p.m.
Place:  W196 Nebraska Hall


IA three-dimensional sector crack within a random polycrystal subjected to a remote stress is investigated through the development of a topologically correct Poisson-Voronoi model. The microstructural stresses due to the elastic anisotropy of the crystals are determined within the polycrystal. The mode I stress intensity factor of the crack is computed using the microstructural stresses.

The algorithm to generate 1,139 Poisson-Voronoi crystals is proven to be effective. The statistical analysis shows that the model is successful and can be used for analysis of polycrystals.

The stress field within the polycrystal is computed using the Eshelby’s method. Microstructural stress components are found to depend strongly on material properties and crystal orientation. It is also found that the microstructural stress magnitude depends on the degree of anisotropy of the material and the variation of the stress field over most part of the crystal face is small.

The mode I stress intensity factor of the sector crack subjected to remote tension is computed numerically using the body force method. The effects of the microstructural stress on the stress intensity factor are investigated. It is found that the stress intensity factor changes significantly with the anisotropy of the single crystal, the crystal orientation and the remote stress state.