Crack Tip Strain - A Comparison of FEM Calculations and Measurements.
SYRACUSE UNIV N Y GEORGE SACHS FRACTURE AND FATIGUE RESEARCH LAB
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Earlier crack tip strain measurements have shown a definitive three dimensional effect upon crack tip deformation. In this study, a pseudo three dimensional Finite element method FEM calculation is made with a composite stiffness matrix. The calculated strains agree exceedingly well with the experimental measurements. The degree of crack tip stiffening is equivalent to only 4 of the plane strain plastic zone along the crack front in a 14 inch thick aluminum speciment, and 8 for a 12 inch thick speciment. Both specimens are loaded considerably beyond general yielding. The results cast serious doubt upon the premise that the specimen, with extensive plastic deformation, can be used to determine plane strain fracture toughness.
- Metallurgy and Metallography