衝撃力による鋼材内のき裂成長開始 : 静的予荷重および温度の影響

概要

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The purpose of this paper is to ascertain the mechanical condition and the microstructural aspect of a crack growth in structural steel when an impact load is imposed on it. Impact tensile experiments were carried out using precracked specimens at 77 K. And the effect of superposition static pretension was also examined at room temperature and 77 K. The effect of static and impact stresses on crack growth is discussed, based on the stress intensity factor (K_I)_<pre> and the dynamic stress σ_<cd> at the moment of precrack growth. The summation of both effects is expressed by D_f, and it increased with the increase of (K_I)_<pre> when static prestress was applied at room temperature. On the other hand, D_f decreased with the increase of (K_I)_<pre> when static prestress was applied at 77 K. In addition, when only an impact load was applied to a specimen, D_f was smaller for shorter length specimens and for larger values of a/W, where a and W are the precrack length and the half width of a specimen, respectively. The size of the plastic region near the prearack tip was measured after fracture, and was independent of the loading type and about three times the grain diameter. The distribution of dislocations near the precrack tip by TEM was observed after fracture. This results showed the different aspects for impact fracture and impact fracture under static pretension.
社団法人日本機械学会の論文
1986-05-25