常圧焼結窒化ケイ素の疲労強度に及ぼす応力波形効果

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It is diffcult to conduct cyclic tensile fatigue tests for fine ceramics because of its high brittleness, and a little eccentricity of loading axis and gripping device gives inaccurate strebgth date. So, a major part of cyclic fatigue tests have benn carried out under bendung load conditions, for the allowance of misalignment of loading axis is generous to some extent in the case of bending fatigue. Asis well known, fatigue strength together with other fracture strength is critically affected by pre-existing defects, and consequebtly, the distribution of fatigue lives is very large even at high sstress levels depending on the distribution characteristics of the defects. To evaluate precisely the correlation between the distribution features of the defects and lives, it is preferable to discuss the contribution of the defects and their distribution tothefatigue strength on the basis of the fatigue strength date under tensile load condition to exclude the influence of stress gradient in the specimen. In this paper, the results of static and cyclic fatigue tests under tensile and 3-point bending load conditions are disucussed, where self-aligning rings for loading axis developed by the authors are equipped to the gripping devices in the case of tensile fatigue tests. The fatigue date obtained in this study are evaluated with the initial stress intensity factor for pre existing defects at the fracture origination site, and the effects of stress pattern on fatigue strength is discussed from several points of view.
社団法人日本材料学会の論文
1990-06-15

常圧焼結窒化ケイ素の疲労強度に及ぼす応力波形効果

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