Measurement of Strain by Digital Shearography with a New Algorithm of Phase Calculation

In this paper, digital shearography method has been used to measure the in-plane strain. One intensity is being recorded before loading and four intensities have been gotten after loading with the phase shifting method. With the subtraction of first intensity from the four intensities of after loading, four new intensities being calculated which from them the needed phase calculated and with use of this phase in the strain formula, the strain can be calculate. For this work, the modified Michelson system as a shearing tool is used. Testing specimen was an aluminum plate with the dimension of 35×35×1mm which is clamped in the boundary and has been loaded in the center. For the loading, a fixture has been made which has the ability of 3-micron displacement creation. For illumination on the specimen from two mutual and same directions, two diode lasers with the wavelength of 630 nm are used as the optical source. Taking into account that in the experimental measurement the conditions are real but are ideal in the numerical analysis, behavior of two graph of experimental measurement and numerical analysis is approximately the same. In the part of error analysis, the amount of relative error is approximately 18% determined.