ENB331 Lecture Notes - Lecture 5: Ductility, Manganese, Fracture Mechanics
Document Summary
A balance between surface energy and strain energy. Kic is a measure of a materials resistance to brittle fracture when a crack is present. S = specific surface energy a = half the internal crack length. = design stress a = allowable flaw size or ndt flaw detection. Stress distribution around crack tip in a thin infinite plate. A uniaxial stress gives rise to a triaxial state of strain. Effect of material thickness on local stresses and strains. If a plate is very thin, only local stresses x and y (biaxial tension) are induced. No localized tensile stress along the z-axis ( z = 0) and is called plane stress as one of the principal stresses is zero. From equation 6, the local stresses cause a negative strain at the crack root. Negative strain means thinning of the plate (free contraction) near the crack tip due to the high value of x and y.
