抄録
We expressed the general fracture criterion which has been proposed in Part I for quasi-ductile fracture type in the form of the first order of σ_3, σ_<eq> and σ_m as following. U=a+bσ_3+cσ_<eq>+dσ_m……(1) √<U>=a′+b′σ_3+c′σ_<eq>+d′σ_m……(2) where U=elastic shear strain energy. Equation (1) is the fracture criterion represented by the elastic shear strain energy, and equation (2) is the fracture criterion represented by the general shear stress. Modiffied Griffith criterion was here adopted for the local fracture criterion by reason of simplicity The fracture criterion for tri-axial compressive stress states was gained as following. 1/3{(σ_1-σ_2)^2+(σ_1-σ_3)^2+(σ_2-σ_3)^2}=a+bσ_1+cσ_3+d(σ_1+σ_2+σ_3)/3……(3) √<1/3{(σ_1-σ_2)^2+(σ_1-σ_3)^2+(σ_2-σ_3)^2}>=a′+b′σ_1+c′σ_3+d′(σ_1+σ_2+σ_3)/3……(4) Eq. (3), (4) were too represented in x-y-m coordinate given by x=(σ_1+σ_2+σ_3)/3, y=√<2J′_2> and m=Lode's parameter, as following. y^2=a+(b+c+d)x+(3(b-c)-m(b+c))/(√<b(3+m^2)>)y……(5) [numerical formula]……(6) These equation well agreed with the all most experimental results in tri-axial and bi-axial compressive stress states. Finaly, the fracture surfaces was illustrated from the fracture criterion proposed in Part I and Part II.
