Strain distribution measurement in laminated martensitic/austenitic steel during a compression test by the electron moiré method

Abstract

The strain distribution in a multi-layered steel composed of brittle martensitic steel (WT-780C) and ductile austenitic steel (SUS304) during a compressive test was measured by the electron moiré method. A very fine model grid with 5 μm spacing was fabricated using electron lithography techniques on the surface of the specimen and an electron beam scan in which spaces are almost the same as those of the model grid can be used for the master grid. The difference between the amounts of secondary electrons per primary electron causes moiré fringes that consist of bright and dark parts. The spacing of the electron moiré fringe was measured, and the strain on the specimen was calculated by using the spacing of the electron moiré fringe and the spacing of the electron beam scan. The strain distribution was not uniform for each steel sheet and the boundaries. The strain near the boundary between the different steel sheets is larger than that in the SUS304 sheet and that in the WT-780C sheet.