Full Field Deformation Research Of Single Inclusion Problem

Inclusion problem is very important for mechanics and materials science. To accuratety obtain the deformation field around inclusion is a significant problem for experimental mechanics. Digital Volume Correlation (DVC) is the only method that can realize the internal full field measurement of three dimensional (3D) displacements and strains. However, DVC method obtains large errors around inclusion boundaries, because DVC is based on continuum mechanics.An improved DVC method is proposed in this study to overcome the boundary problems of the traditional method. The results of two numerical tests demonstrate that the improved method is effective in dealing with the boundary problems. In the mode I crack test, the maximum value of absolute error of improved DVC methods is forty times smaller than the traditional method. For the numerical test of the spherical inclusion problem, the absolute error on the displacement decreased from 0.08 voxel to 0.02 voxel by using the improved method in the vicinity of the inclusion.The improved DVC method is used to study the deformation behavior of a larger pore inner a foam concrete. The improved DVC method not only get a more precise displacement field, but also capture the real strain distribution around pore boundary. In the process of foam concrete shrinkage, the shrinkage degree around pore is much greater than that of the other positions, the maximum principal strain reached 0.062 around the pore, and the far field strain value is only about 0.002.DVC method is used to detect micro cracks which CT data could not "see" directly. A method to determine the crack location based on the strain field is proposed, and the 3D crack shape is extracted using this method. Furthermore, the improved DVC method is applied to recalculate the 3D CT data. The improved DVC method obtains a gradual displacement field near the crack, where traditional DVC methods only gets a fuzzy displacement field. The crack opening displacement (COD) is further calculated, which is irregular and in the range of 0.02-0.08 voxel. The crack detect ability of this method depends on the precision of DVC, and it is 0.02 voxel in this study, i.e.1.3 micrometer with voxel size of 63 micrometer.