摘要
中心直裂纹巴西圆盘试样可以用于脆性材料在纯Ⅰ型、纯Ⅱ型以及Ⅰ-Ⅱ复合型载荷下的动态断裂韧度的测试.通过改变径向冲击的加载角θ(加载方向相对于裂纹的倾斜角),可以方便地实现不同的Ⅰ、Ⅱ型动态断裂实验.本文用有限元软件ANSYS对试样进行动态复合型断裂模拟分析,研究了不同载荷、不同材料以及不同试样尺寸对动态无量纲应力强度因子的影响,得到了纯Ⅱ型加载所对应的加载角θⅡ的近似计算公式.对于在斜坡载荷作用下的复合型断裂,Ⅰ、Ⅱ型应力强度因子具有相似的时间历程曲线,其比值逐渐趋近于一个常数.本文给出了不同无量纲裂纹长度的试样在不同加载角下对应的Ⅰ、Ⅱ型无量纲应力强度因子的比值KⅠ(t)/KⅡ(t)(该比值称为复合比),利用该复合比,可以通过应变能密度因子准则求出试样的起裂角β0,得到的结果与文献给出的试验结果吻合得很好.
The center - cracked Brazilian disc specimens can be used to measure dynamic fracture toughness under pure mode Ⅰ, pure mode Ⅱ, or mixed - mode loadings for brittle materials. The pure or differently mixed mode dynamic fracture test can be realized by changing the loading angle θ, which is the inclination angle of the loading diameter with respect to the center crack. The finite element software ANSYS was used to simulate the impact fracture tests of the specimens, and the effect of different types of loads, materials and specimen geometry on the dimensionless dynamic stress intensity factors were investigated. An approximate formula was proposed to calculate the loading angle θ Ⅱ for the pure mode Ⅱ loading. As for the mixed mode loading, when a ramp load was applied, the stress intensity factors of mode Ⅰ and mode Ⅱ had similar curves of time history, and the mixed -mode ratio of mode Ⅰ to mode Ⅱ stress intensity factor, i.e. KI（ t）/KⅡ （t）, was nearly a constant value. The ratios of specimens with different dimensionless crack length under different loading angle were presented. Using these values, the dynamic crack initiation angles β0 can be estimated based on the strain energy density factor criterion, and the estimation is in good agreement with the experimental results given in the references
出处
《动力学与控制学报》
2007年第1期75-82,共8页
Journal of Dynamics and Control
基金
国家自然科学基金资助项目(10472075)~~
