焊接结构损伤区细观裂纹扩展的分形特征及其多尺度损伤表征  

Fractal behavior of cracking in damaged zone of welded structures and its multi-scale characterization

作　　者：赵超凡[1] 李兆霞[2] 

机构地区：[1]东南大学土木工程学院,南京210096 [2]东南大学江苏省工程力学分析重点实验室,南京210096

出　　处：《东南大学学报（自然科学版）》2013年第5期1039-1044,共6页Journal of Southeast University：Natural Science Edition

基　　金：国家自然科学基金资助项目(11072060)

摘　　要：为了研究焊接结构破坏过程中的宏细观损伤演化特征及其表征方法,以含细观裂纹的焊接构件为对象,采用X-CT(X射线计算机断层扫描)和电测技术同步记录试样内部细观结构和宏观力学性能变化过程.实验发现,试样变形过程中试样在弹性模量减小的同时,其内部细观裂纹不断萌生、扩展和聚合,扩展形态表现出显著的分形特征,且分形维数随试样塑性变形呈线性增加的趋势.综合考虑裂纹扩展形态的分形维数度量与裂纹扩展的物理意义,提出了一种多尺度损伤表征方法,以同时描述结构宏观损伤特性与内部细观裂纹扩展特性,并用传统的损伤量化方法进行验证.结果表明,新的多尺度损伤表征方法能够很好地描述细观裂纹到宏观损伤的多尺度演化过程.This paper aims to explore behavior of cracking and develop the method for of multi-scale damage characterization. A welded specimen with meso-cracks was taken as research objects. X-CT （Micro focus X-ray Computed Tomography System） was employed to record the tomograms of cracking and macro-scale response was measured synchronously using electrical measurement device. The experimental results show that the specimen＇s modulus decreases on the same time when mesocracks initiation, propagation and coalescence happens during the deformation process. The behavior of crack growth shows typical fractal pattern, and the fractal dimension is linearly increasing along with plastic strains of the specimen. Considering both the fractal dimension measurement of crack growth morphology and the physical significance of crack growth, a new multi-scale damage charac- terization method is proposed to describe the behavior of damage both in meso- and macro-scale of cracking. The proposed method was verified by current theories of damage mechanics. The results show that, the new method can well describe multi-scale damage evolution process in which damage starts from meso-cracks to macroscopic crack.

关 键 词：X射线计算机断层扫描 分形维数 塑性变形 细观裂纹 多尺度损伤表征 

分 类 号：O346.5[理学—固体力学]