Measurement of deformations for copper/aluminum clad under tension with digital speckle correlation

To measure the deformation of copper/aluminum clad metals made by explosive welding technique,a new full-field three-dimensional deformation measurement method based on the digital speckle correlation method and binocular stereovision was proposed and implemented.The related key technologies including image correlation matching,three-dimensional coordinates,displacement and strain reconstruction were investigated.Then a deformation measurement system and corresponding software were developed based on the VC++6.0 platform.To validate the feasibility of the proposed method,a precision test and a copper/aluminum clad tensile test were conducted,and the experimental data of the test and the numerical simulation using Abaqus software were compared.Experimental results show that the accuracy of strain measurement is not lower than 0.5%,very close to that of the extensometer.The extreme strain distribution based on digital speckle correlation method is coincident with that the finite element simulation well.Furthermore,the simulated curves of plastic stress-strain are in agreement with the experimental data before necking the sheet metal,and the tendency of simulated curves of displacement-load is consistent with the experimental data in the whole tensile processes.Moreover,the relative errors of simulated ultimate load are from 0.06% to 2.25%.It demonstrates that the digital speckle correlation method is an effective tool to obtain the full-field strain of sheets accurately.