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由裂纹顶端应变开裂判据ε_(max)=ε_c可知,裂纹体、切口体和光滑体的开裂判据应是一致的,故三种试样所测得的断裂韧性之间必有内在联系,本文通过对广义缺口顶端应变场的理论分析和实验研究,运用松弛滑移的概念,得到裂纹和切口张开位移δ之表达式。同时,在探讨裂纹当量曲率半径ρ_f物理本质的基础上,得到ρ_f与材料中的夹杂物或第二相质点的平均间距λ大致相等的经验关系。从而得到切口断裂韧性与裂纹断裂韧性之间的换算关系:((δ_c)_f)/(δ_c)_n=((δ_(pc))_f)/((δ_(pc))_n)=((δ_(ec)~*)_f)/((δ_(ec)~*)_n)=(ρ_f/ρ_n)~(1/2)=(λ/ρ_n)~(1/2)并通过实验进行了初步验证.
From the crack tip crack resistance criterion ε max max = ε c, it can be seen that the cracking criterion of crack body, incision body and smooth body should be consistent. Therefore, the fracture toughness measured by the three kinds of specimens must have an intrinsic relationship, In this paper, through the theoretical analysis and experimental study of the strain field at the top of generalized notch, the expression of crack and notch open displacement δ is obtained by using the concept of relaxation slip. At the same time, on the basis of exploring the physical nature of crack equivalent radius of curvature ρ_f, an empirical relationship between ρ_f and the average spacing λ of inclusions or second-phase particles in the material is obtained. (Δ_c) _f) / (δ_c) _n = (δ_ (pc)) _f) / (δ_ (pc)) _ n) = ((δ_ (ec) ~ *) _f) / (δ_ (ec) ~ *) _n) = (ρ_f / ρ_n) ~ (1/2) = (λ / ρ_n) ~ (1/2) verification.