不同裂纹高度的三点弯曲梁动态焦散线实验

Dynamic Caustic Line Experiment of Three-point Bending Beam with Different Crack Heights

为了探究不同高度条形缺陷的梁构件动态裂纹扩展规律,在三点弯曲梁中设计高度分别为22 mm、28.5 mm、35 mm的条形缺陷,通过数字激光动态焦散线实验系统和落锤冲击试验系统进行研究。结果表明:不同高度条形缺陷的三点弯曲梁在落锤冲击实验中,裂纹扩展速度和应力强度因子受缺陷高度影响分两个阶段。第一阶段随着缺陷高度的增加,裂纹最大扩展速度分别为247.49 m/s、292.49 m/s与284.99 m/s,呈现先上升后趋于稳定的态势,起裂应力强度因子随着缺陷高度的增加而变大,分别为1.480 MPa/m^(3/2)、1.665 MPa/m^(3/2)、1.812 MPa/m^(3/2);第二阶段随着缺陷高度的增加,裂纹起裂扩展速度逐步减小分别为634.42 m/s、524.97 m/s、377.67 m/s,KⅠ型起裂应力强度因子逐步减小分别为3.281 MPa/m^(3/2)、3.192 MPa/m^(3/2)、2.876 MPa/m^(3/2),KⅡ型起裂应力强度因子逐步增大分别为1.254 MPa/m^(3/2)、1.319 MPa/m^(3/2)、1.398 MPa/m^(3/2),KⅠ-KⅡ复合型应力强度因子经偏转化为KⅠ型应力强度因子。研究结果可为不同形状和不同位置的缺陷构件的动态响应问题提供理论参考。

In order to explore the dynamic crack propagation law of beam members,bar defects with the heights of 22 mm,28.5 mm and 35 mm were designed in a three-point bending beam,and then tested by the digital laser dynamic caustic line experiment system and the drop weight impact test system.The results show that the crack propagation rate and stress intensity factor are affected by the defect height in two stages in the drop weight impact experiment.In the first stage,the maximum growth rates of crack propagation have a trend of first rising and then stabilizing as 247.49 m/s,292.49 m/s and 284.99 m/s with the increase of defect height,and the cracking stress intensity factor was respectively 1.480 MPa/m^(3/2),1.665 MPa/m^(3/2) and 1.812 MPa/m^(3/2),which increased with the increase of defect height.Meanwhile,the crack initiation and propagation rates respectively decreased by 634.42 m/s,524.97 m/s and 377.67 m/s,the cracking stress intensity factors of KⅠtype respectively decreased by 3.281 MPa/m^(3/2),3.192 MPa/m^(3/2) and 2.876 MPa/m^(3/2),and the cracking stress intensity factors of KⅡtype respectively increased by 1.254 MPa/m^(3/2),1.319 MPa/m^(3/2),and 1.398 MPa/m^(3/2).Furthermore,the KⅠ-KⅡcomposite stress intensity factor was transformed into a KⅠtype stress intensity factor by deflection.