【摘要】 岩石试件表面的数字图像可作为试件表面变形或裂纹扩展的信息载体。为从加载过程中记录的数字图像中分析出定量的信息,提出一种新的分析方法:计算两幅图像灰度的相关性,用灰度相关性的分布表征变形和破裂的发展。介绍了图像灰度相关性的计算方法,并用模拟的变形和破裂图像验证了灰度相关性在表征变形与破裂上的有效性,最后用此方法对一个岩石结构加载过程中的图像序列进行分析。结果表明,图像灰度相关性分布的演化与结构的变形局部化演化在空间和时间上都存在对应关系。因此,试件表面数字图像灰度相关性可作为描述岩石材料损伤演化的一种工具。更多还原

【Abstract】 Damage evolution of rock under loading can be expressed to some extent by the deformation and crack propagation of the specimen surface,which could be observed or analyzed with the digital images recorded from the specimen surface during loading.However,current methods to evaluate deformation from digital images are either qualitative(semi-qualitative) or quantitative,and very complicated computation and special software are demanded(for example,digital speckle correlation method).In this paper,a very simple quantitative analysis method for digital images recorded from loaded rock specimen to evaluate its damage evolution is proposed.To realize the method,a reference image is firstly selected from the series of digital images;and then the gray correlation of all other images is calculated using a pre-defined calculation scheme.When the image coordinate is fixed,the deformation will change the pixel aray,therefore,the correlation will decrease when there is a large deformation.Likewise,intensity of crack position will change sharply because of the existence of new exposure part by crack,then there is a sharp decrease of the gray correlation.Therefore,the distribution of gray correlation will reveal the damage distribution.The validity of this evaluation method is verified through two simulated image pairs,one deformation and one crack.Then,a series of surface images recorded from an en-echelon rock structure are analyzed using this method.The result shows that the spatial and temporal parallelism exists between the evolution of the gray correlation and the deformation localization.Therefore,gray correlation is expected to be a useful tool to evaluate the damage evolution of rock.更多还原