き裂を有するぜい性材料の静疲労試験結果の解析法

概要

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By assuming that the time-to failure T_f in static fatigue tests of creamics is controlled by the subcritical crack growth in Region I of trimodel K_I-a curve,where loga∝nlogK_I holds (a;the crack velocity,K_I;the stress intensity factor and n:a constant),Evans formulated a simple but quite convenient formula for static data analysis (σ_a^nT_f=constant).However,because not only oxide-ceramics show the trimodal curve but also logK_I-loga relations are not always linear in non-oxide ceramics,the formula necessariy has some limitations in its applications.In the present paper,the applied load P_o-T_f relations are formulated for bi-linear or tri-linear relation betweem logK_I and loga,and the P_o-T_f relation is numerically simulated for the trimodal curve.The simulation shows that a gap between Region I and Region III still appears in the logP_o-logT_f diagram,although the gap gets a little gentle.It is also cleared through the formulation that static fatigue data for various specimen geometries,sizea and initial crack length can be analyzed quite well by using a newly introduced "normalized time of failure",(T_f)_N=[T_f/(W/a^*)]/∫^1_x0[√<x_0>F(x_0)/√<x>F(x)]^ndx,where x_0;the initial crack length,F(x);the geometry factor of the specimen and W;the specimen width.
社団法人日本材料学会の論文
1993-11-15