Question

How can the Griffith crack equation be modified to describe crack propagation in ductile materials? Why is the correction necessary?

Answer 1

* Griffith Crack equation Cequation A suggesty good results for glass. = C A where; E Young's Modules of material (Pa) == $uofoce energy density of material (Ilm). C= constant and *Modification of Griffith crack equation for ductile material is represented by equation (a) The dissipation energy, includes plastic dissipation (Cap) and surface energy density of material (20). a = diqgipation energy (J/m2) 20= Surface energy dripod density (Jlm 2) ap = plastic dissipation (m2) a is given by :- a= Qrt apol - B Modified Griffith equation for ductile matericel :- Ex Ch = constante 1 (Angesen ㅈ cohere ; E - Young's Modules of material (Pa) a= Diegipation Energy (m2) IS cause * cony this correction necessary ? ? The correction was necesary because of following reasons: - (1) In actual structeercl mcclesials; the amount of energy needed fracture is higher than a surface energy (ii) an actual structural material, there is always come inelastic deformations around the crack is present. (Angwer)