温度对Ⅱ型加载断裂韧性的影响规律

EFFECT OF TEMPERATURE ON THE FRACTURE MODES OF BHW-35 STEEL UNDER MODE- Ⅱ LOADING

探讨纯Ⅱ型加载BHW－35钢断裂韧性随温度的变化规律．有限元分析及实验研究表明：Ⅱ型加载下存在两种类型的裂纹扩张方式-滑开型与张开型；温度的变化导致裂纹扩张方式的改变．文中对两种扩张方式的临界J积分随温度的变化规律以及裂纹扩张方式转变临界温度作了进一步讨论．

Finite e1ement method(FEM) has been used to analyze the stress and strain fields and the stress triaxial levels around the tip of the crack under mode- Ⅱ loading. The results show that: under mode-Ⅱ loading, the direction of the maximum tensile stress and the direction of the maximum triaxial levels (R.) exist at an angle of - 75. 3° from the original crack plane; the direction of the maximum shear stress and R.= 0 exist along the original crack plane.Mode- Ⅱ loading experiment using BHW-35 steel at different temperatures showed that there were two kinds of fracture mode, opening mode (or tensile mode ) and sliding mode (or shear mode). The decrease in temperature caused the fracture mode to change from shear mode to tensile mode. For BHW-35 steel this critical temperature is about - 90℃ Actually, under any kind of loading mode (modeⅠ, modeⅡ mode Ⅲor mixed mode), there always exist severaI kinds of potential fracture modes (for example, opening mode, sliding mode, tearing mode or mixed mode). The effect of temperature under mode-Ⅱ loading is actually related to the change of the elastic-plastic properties of the material.