悬臂弯曲加载方式的应变控制方法研究

Research for Strain Controlling Method of Cantilever Bend Loading

本文将COD位移规引进悬臂弯曲加载方式,从而替代传统的应变片实现裂纹前缘的应变控制。借助有限元数值模拟,研究了COD位移规装卡刀口的位置和形状对悬臂弯曲加载试样(GROSS试样)本身对称性的影响。结果表明:COD位移规装卡刀口开度越大,刀口造成的监控点应变非对称畸变越小;而装卡刀口宽度一定时,监控点应变对称性受到的扰动强度随COD位移规装卡刀口尖端角度的减小而降低。考虑到现有COD位移规量程及装卡的稳定性,最终选择实际试样中COD规装卡刀口宽度为10 mm,刀口尖端根部取15°。通过COD规进行应变控制试验时,其装卡刀口相对位移-监控点应变遵从线性关系,因此,这种悬臂弯曲加载方式应变控制方法的改进是合理可靠的,且控制稳定,操作简单。

This paper introduced COD gage instead of traditional strain gage to control the strain in front of the crack for cantilever bend loading style.Through the FEM analysis,the influence of COD gage's fixing position and form to the symmetry of cantilever bend loading specimen(GROSS specimen) was researched.The results indicated that the greater the COD gage's edge opening was,the smaller the monitor points' unsymmetrical strain aberration showed;if the edge's width was fixed,the perturbation strength of the monitor points' symmetrical strain would be reduced along with the decrease of the edge peak's angle.Considering the measuring range and stability of the COD gage,the actual specimen was designed as 10 mm for the width of the COD gage's fixing edge,15° for the root segment.The linearity relationship was obeyed for the fixing edge's relative displacement and monitor points' strain by using COD gage to achieve strain controlling test.Therefore,it was considered that this improvement for strain controlling method of cantilever bend loading was reliable,reasonable,stable for controlling and convenient for operation.