円孔を有する複合材料の疲労切り欠き係数に及ぼす2軸組み合わせ応力比の影響

抄録

This paper describes the effect of the biaxially combined stress ratio on the notch factor of the hole notched composite. Specimen was subjected to the tension-torsion fatigue loading. The notch factor has a liner relation with cos (tan^-1α) in all numbers of loading cycles discussed in this study (α: biaxially combined stress ratio). An equation that can empirically predict the notch factor is proposed. The notch factor decreases with an increase of number of cycles, in the case of low applied shear stress. This is caused by the stress relaxation in the stress concentrated region near the hole due to fatigue damage. When, however, the shear component of the applied stress is high, slight decreasing of the notch factor is observed. Especially in the case of pure shear loading it increases with an increase of cyclic number, because the remarkably damaged area does not progress to the stress concentrated region but along the fiber bundle. In this case the stress concentration is aggravated in the fatigue process. This study proposes the stress relaxation and aggravation model which can explain the change of the notch factor under fatigue loading.