灰岩拉伸过程中细观结构演化的分形特征

岩石损伤演化的本质在于内部微细观结构发生了不可逆的劣化,它会在岩石表面体现出来。通过带扫描电镜的伺服试验机对岩石进行了拉伸试验,实时采集了岩石变形破坏过程中表面细观形貌的SEM照片。试验表明岩石在变形破坏过程中表面形貌将发生不可逆的演化直至最终出现宏观拉伸裂纹。针对SEM照片,借助数字图像处理的方法进行了阈值分割及边缘检测,计算出SEM数字图像的分形维数作为描述岩石表面细观形貌的参数。研究表明,随着载荷的增大,岩石表面的分形维数也逐渐增大,岩石的损伤程度加剧。

Fractal characterization of meso-structural evolution during tension of limestone

The essential of rock damage evolution is the deterioration of rock’s meso-structure, which also appears on the surface of rock. The tension tests of limestone samples were employed in the test machine assembled with scanning electronic microscope, and simultaneously the SEM image of sample surface was captured while the sample is being loaded. It is observed that the surface pattern of rock transforms irreversibly and eventually macro cracks appear on the surface due to tension. Moreover the SEM image is analyzed by the method of digital image processing, which includes threshold partition and edge detection, and then the fractal dimension of rock surface is calculated as a parameter to characterize the meso surface pattern of rock. It is concluded that the fractal dimension increases with the increasing of load, and at the same time damage become more severe.