Abstract
Fiducial grids have been applied to measure micro-deformation near interfaces in aluminum bicrystals and to study mechanisms of fatigue crack transfer across the interface under loading in a scanning electric microscope (SEM). Three types of aluminum bicrystals were designed to allow the primary slip to induce different incompatible plastic strain at the interface. An inclined notch was spark cut along the primary slip band on one edge of each specimen to initiate a crack smoothly. This paper also describes the means to produce fiducial grids of evaporated gold with 7-μm square mesh size and 0.3-μm line width in a place of interest on a specimen surface, usually ahead of a crack tip near the interface. Interface cracking and width increase of persistent slip band (PSB) induced by an approached transvese crack have been identified by comparing two photos of fiducial grid patterns taken, respectively, at maximum and minimum cyclic stress in a SEM. Grids were also used to measure both cyclic shear strain at a crack tip and crack growth rate, which decreases as the crack approaches an incompatible interface.
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Li, C.S., Orlecky, L.J. Fiducial grid for measuring microdeformation ahead of fatigue crack tip near aluminum bicrystal interface. Experimental Mechanics 33, 286–292 (1993). https://doi.org/10.1007/BF02322143
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DOI: https://doi.org/10.1007/BF02322143