走査型電子顕微鏡を用いたモアレ法による微視的変形挙動の観察

Abstract

A new Moiré method using a scanning electron microscope has been developed for the measurements of micro-deformation. In this method, the model grid is fine parallel lines of metal deposited on a specimen, and as a master grid, the electron beam of a SEM is used. The scanning of electron beam on the specimen with the model grid constructs a Moiré fringe. This fine Moiré fringe in a small area makes it possible to determine the distribution of strain around a small notch, the deformation within a grain and grain boundary sliding.For demonstrative experiments, tensile and creep tests of polyimide resin and pure copper specimens were carried out. In the tensile test of a polyimide resin specimen with a small hole, an observation of the electron beam Moiré fringe was performed in-situ in a SEM during loading. The Moiré fringes for copper specimens were observed after high temperature tensile test (673K) and interrupted creep test (723K and 30MPa). It is found that electron beam Moiré fringes are fine and clear enough to measure the strain distribution in a small area (about 500μm square) around a hole in a polyimide resin specimen. The strain distribution around a small hole was calculated from an analysis of the fringes and a strain contour map was constructed.The Moiré fringe in the copper specimens shows complicated patterns due to some metallurgical behaviours. The pattern was analysed. Grain boundary sliding could be measured with high accuracy from the displacement of Moiré fringe at grain boundary, and deformation in a grain and coarse slip bands could be observed from change in the Moiré fringe patterns in relation to micro-deformation modes. Also inhomogenious deformations at triple points and rotation caused by grain boundary slidings in a crept specimen were observed using this method.