Fracture Toughness for Brittle Fracture of Elastic and Plastic Materials

Abstract

The crack energy density causes a new expression of fracture toughness for brittle fracture, together with the concept of Barenblatt’s characteristic distance d_c of cohesive zone at the edge of the crack. The Griffith’s formula for fracture toughness is modified by the ratio of σ_T/Σ_T, which σ_T is the true fracture stress and Σ_T the maximum strength of the material obtainable by ordinary processing. The fracture toughness of elastic-plastic material, K_Ic^* for brittle fracture is described by the product of σ_T and the root of the observed absorption energy by Charpy impact test corrected for instrumental effect, \sqrt\smashI_cp^corrected\mathstrut . The characteristic distance d_c depends linearly on the released elastic energy, which is the physical basis of above-mentioned estimation formula.