基于圆弧底试件的动态裂纹扩展及止裂规律研究

为了研究脆性材料的动态裂纹扩展及止裂规律，设计了一种带圆弧形底边的梯形开口边裂纹（trapezoidal opening crack with arc bottom，TOCAB）构型的试件。在落锤冲击设备加载下，对圆心角为0°、60°、90°和120°的TOCAB试件进行了冲击实验，并采用裂纹扩展计(crack propagation gauge，CPG)监测裂纹起裂和扩展时间，从而获得裂纹扩展速度。采用有限差分软件AUTODYN对落锤冲击设备和试件进行数值模拟，研究了裂纹的动态扩展过程及止裂规律。还基于实验和数值方法，计算了裂纹的临界动态应力强度因子。实验和数值结果均表明:3种弧度的TOCAB试件都可以实现运动裂纹止裂，该构型可用于研究动态裂纹止裂问题；数值计算的裂纹扩展路径与实验结果基本一致，验证了数值模型的有效性；裂纹起裂和止裂时刻的临界动态应力强度因子大于裂纹动态扩展过程中的临界动态应力强度因子。

Dynamic crack growth and crack arrest law based on arc bottom specimen

In order to study the crack growth and crack arrest law of the brittle materials, a large-sized trapezoidal opening crack with arc bottom (TOCAB) configuration specimen was proposed. The impact tests were carried out on the TOCAB specimens with radians of 0°, 60°, 90° and 120° under the drop hammer impact device. The crack growth speed was obtained by using the distance between the two resistance wires divided by the break time of the resistance wire of the crack propagation gauge, and crack propagation gauge (CPG) was used to monitor the crack initiation time and expansion time. The crack growth behavior of the TOCAB specimen was numerically simulated by using the finite difference software AUTODYN. And the crack growth process and the crack arrest law were numerically studied. The critical dynamic stress intensity factor of the moving crack was calculated based on the experimental-numerical method and the finite element software ABAQUS. Both experimental and numerical results show that the three arc-bottom specimens have a crack-stopping effect on the moving crack, andthe TOCAB configuration specimen is suitable for studying the crack arrest problem. And the crack growth path obtained in the numerical calculation is basically consistent with the experimental results, which verifies the validity of the numerical model. And the critical dynamic stress intensity factor at the time of crack initiation and crack arrest is greater than that at the time of the crack growth.