A method of ruling circular diffraction gratings and their use in the moiréa technique of strain analysis

Abstract

A method is described for ruling circular diffraction gratings and of using such gratings as strain gauge rosettes suitable for measuring principal strains and indicating principal strain directions. The technique for ruling such gratings is both simple and efficient and can be used to produce good quality gratings with up to 2500 lines per radial inch. With such gratings, strains of 0.01 per cent and upwards should be capable of measurement over a wide range of temperatures.