材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
き裂を有するぜい性材料の静疲労試験結果の解析法
野島 武敏加藤 秀輝
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1993 年 42 巻 482 号 p. 1331-1337

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By assuming that the time-to failure Tf in static fatigue tests of ceramics is controlled by the subcritical crack growth in Region I of trimodal KI-a curve, where loganlogKI holds (a; the crack velocity, KI; the stress intensity factor and n: a constant), Evans formulated a simple but quite convenient formula for static data analysis (σanTf=constant). However, because not only oxide-ceramics show the trimodal curve but also logKI-loga relations are not always linear in non-oxide ceramics, the formula necessarily has some limitations in its applications.
In the present paper, the applied load Po-Tf relations are formulated for bi-linear or tri-linear relation between logKI and loga, and the Po-Tf relation is numerically simulated for the trimodal curve. The simulation shows that a gap between Region I and Region III still appears in the logPo-logTf diagram, although the gap gets a little gentle. It is also cleared through the formulation that static fatigue data for various specimen geometries, sizes and initial crack length can be analyzed quite well by using a newly introduced “normalized time of failure”, (Tf)N=[Tf/(W/a*)]/∫1x0[√x0F(x0)/√xF(x)]ndx, where x0; the initial crack length, F(x); the geometry factor of the specimen and W; the specimen width.

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