Determination of Local Constitutive Properties of Aluminum using Digital Image Correlation: A Comparative Study Between Uniform Stress and Virtual Fields

A proper understanding of material mechanical properties is important in designing and modelling of components.  As a part of a study on the structural integrity, the Digital Image Correlation technique was used to obtain the fullfield strain distribution during a tensile test of the specimens. In this study, the elastic and plastic properties of Al6061 alloy has been carried out using both the uniform stress method and the virtual fields method involving digital image correlation technique. In uniform stress methodology, full range stress–strain curves are obtained using the whole field strain measurement using Digital Image Correlation. Recently, the virtual fields method is gaining a lot of popularity in domain characterization as it is robust, accurate and faster. Young’s modulus, Poisson’s ratio, yield strength, strength coefficient and strain hardening exponent are the parameters extracted using both uniform stress method and virtual fields method. The parameter variation obtained by both uniform stress method and the virtual fields method are compared very well. The Virtual Fields Method provides a theoretically sound basis for developing robust optimization constructs to estimate local material properties, including spatial variations in hardening exponent and strength coefficient. Due to various advantages associated with virtual fields method, it is generally recommended for material mechanical properties extraction.