Abstract
The purpose of this study is to propose a method of strain measurements under multi-axial stress condition. By adopting the cube specimen, we can apply the load different from each other in three directions. At the triaxial test, six steel brushes covered the specimen, and there was no space to put wire strain gages or displacement devices on the surfaces of the specimen. Therefore, the cube specimen with chamfered edges was selected to measure strains by utilizing the chamfered edges. Six pairs of displacement measuring devices were set on the chamfered edges of the specimen in three directions (α, β, γ) as shown in Fig.2. The deformation in a specific direction was measured as the sum of the outputs from a pair of displacement devices placed in the diagonal and opposite edges in the same direction of the specimen. The strains, ε_X, Ε_Y and E_Z in X, Y and Z directions can be written in the equation (10), as the terms higher than the second order are negligibly small. The experimental strains that were measured in the manner described above are compared with the strains that were measured with wire strain gages mounted on its sides, both in the uniaxial compression test of the same specimen. The stress-strain relations of the two were almost the same, so that the validity of the method of strain measurement proposed in this study is experimentally proved.
