Q235钢细观损伤声发射源动态观测实验研究

金属材料细观损伤过程伴随有瞬态应力波的释放,利用声发射检测技术可采集到应力波的信息,但由于缺少直观可视的手段,利用声发射信息定量评价金属材料的细观损伤存在困难。本文将SEMtester1000原位拉伸试验机、MZ1000正置显微镜和PCI-2型声发射检测系统相结合,搭建了声发射源动态观测实验系统。以Q235钢可视化原位拉伸实验为例,获取了晶体的滑移和夹杂物的断裂两种典型声发射源图像及对应的声发射信号。通过对不同声发射源信号的分析可知,滑移是一个持续的过程,复杂的滑移活动会产生多类型的声发射信号。夹杂物断裂是瞬态过程,产生典型的突发型声发射信号,能量较滑移信号更高。依据声发射源动态观察结果及图像分析,建立了基于声发射机制的Q235钢细观损伤模型。

Experimental study on dynamic observation of acoustic emission source for mesoscopic damage of Q235 steel

The mesoscopic damage process of metal materials is accompanied with the release of transient stress waves,which can be collected by acoustic emission testing technology.However,due to the lack of directly visual means,it is difficult to evaluate the mesoscopic damage of metal materials quantitatively by acoustic emission information.In this work,the SEMtester1000 in-situ tensile testing machine,MZ1000 microscope and PCI-2 acoustic emission detection system are combined to build up an experimental system for acoustic source dynamic observation.Taking the Q235 steel as an example,two typical acoustic emission sources including the slip of the crystals and the fracture of the inclusions are obtained,and the corresponding acoustic emission information is collected.The experimental results show that the slip of the crystals is a continuous process,and the complex slip activity produces multiple types of acoustic emission signals.The fracture of the inclusions is a transient process,which produces typical sudden acoustic emission signals.The comparison between the two sources reveals that the signal energy generated by the fracture of the inclusions is higher.Based on the results of acoustic emission signal analysis and image analysis,a model is established to describe the mesoscopic damage mechanism of the tensile process of Q235 steel.