应用微相关技术研究裂端弹塑性变形

Study of Elasto-plastic Deformation around Crack-tip by Micro-correlation Technique

测量裂端附近区域的弹塑性变形,对于研究材料的损伤或微裂纹的产生,获得材料早期的损伤信息,为预防宏观裂纹的产生及扩展具有十分重要的意义。本文用A3钢材料制作边缘带裂纹的显微拉伸试件,试件表面进行了金相处理。试件是用由计算机控制的显微拉伸台进行加载试验。在加载过程中,利用环境扫描电镜对裂端附近的显微结构进行原位观察以及扫描记录。应用数字散斑相关技术对扫描电子显微镜记录的显微结构图进行分析处理,求出裂端附近的弹塑性变形。借助扫描电子显微镜,不仅可以定性观察应力集中区微裂纹的萌生及扩展过程,还可以结合数字散斑相关技术,对微区内的弹塑性变形进行测试,是研究微区域内材料变形的一个有效手段。

Measurement of the elasto-plastic deformation around crack-tip for studying material damage or micro-crack initiation and obtaining early damage information of material is important for preventing micro-crack initiation and propagation. In this study, a micro-tensile specimen with boundary-crack was fabricated from an A3 steel and the surface of the specimen was treated by metallographic etching. The specimen was then loaded by a computer-controlled micro-tensile instrument. Under loading, the microstructure around crack-tip was observed in-situ and recorded by an Environmental Scanning Electron Microscope. The patterns of the microstructure recorded by ESEM were processed by digital speckle correlation technique to yield the elasto-plastic deformation around the crack-tip. Utilization of the ESEM is capable of not only qualitatively observing the process of the micro-crack initiation and propagation in the stress concentration area but also quantitatively measuring the local elasto-plastic deformation by combining with the digital speckle correlation technique; thus has proved to be an effective means to investigate the material deformation in a micro region.