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 full-field strain distribution during a tensile test of the specimens. The displacement maps were analyzed using Matlab scripts to compute local stress-strain variations. Consequently the local proof stress values were extracted. In this study, the local extraction of 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. The parameters investigated are Young s modulus, Poisson s ratio, yield strength, strain hardening exponent and strength coefficient. 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 compares very well. Due to various advantages associated with virtual fields method, it is generally recommended for material mechanical properties extraction.

Keywords:

Constitutive properties , Digital image correlation , Strain hardening exponent , Strength coefficient introduction , Virtual fields method