Kaiser Effect in Sandstone in Triaxial Compression with Multistage Rotation of an Assigned Stress Ellipsoid
I. A. Panteleev1, V. A. Mubassarova1, A. V. Zaitsev2, N. I. Shevtsov3, Yu. F. Kovalenko3, V. I. Karev3
1Institute of Continuum Mechanics, Ural Branch, Russian Academy of Sciences, Perm, 614013 Russia
2Perm National Research Polytechnic University, Perm, 614990 Russia
3Ishlinsky Institute for Problems in Mechanics, Moscow, 119526 Russia
Keywords: Эффект Кайзера, акустическая эмиссия, истинное трехосное нагружение, вращение эллипсоида заданных напряжений, эффект деформационной памяти, испытательная система, Kaiser effect, acoustic emission, true triaxial loading, assigned stress ellipsoid rotation, deformation memory effect, test system
Abstract
The authors examine Kaiser effect in sandstone in nonproportional triaxial cyclic compression tests with stage rotation of an assigned stress ellipsoid through an angle of 90°. The load program consists of three pairs of cycles such that the maximal nominal stress of the second cycle exceeds the first cycle stress by 20 MPa at the constant side support. Cyclic loading is applied to sandstone in three orthogonal directions, with two cycles in each direction. Kaiser effect only appears in the second loading in the same direction, and activation of acoustic emission upon the change in the active loading direction is independent of the earlier reached stress level. This fact points at the orientation-driven nature of Kaiser effect, which means the material remembers its lattermost internal damaged structure.
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