Finite element analysis, stress-strain distribution and size effects rise during nanoindentation of welded aluminum alloy

Purpose - The purpose of this paper is to investigate the use of nanoindentation with a Berkovich indenter as a method of extracting equivalent stress-strain curves for the base metal and the welded zone of a friction stir welded aluminum alloy.Design methodology approach - Friction stir welding is a solid-state joining process, which emerged as an alternative technique to be used in high strength alloys that were difficult to join with conventional joining techniques. This technique has a significant effect on the local microstructure and residual stresses combined with deformation. Nano- and micro-indentation are the most commonly used techniques to obtain local mechanical properties of engineering materials. In order to test the reliability of nanoindentation technique and to connect nanoscale with macroscale, the indentation hardness-depth relation established by Nix and Gao was applied on the experimental values.Findings - The predictions of this model were found to be in good agreement with classical hardness measurements on AA 6082-T6 aluminum alloy. Also, finite element method provides a numerical tool to calculate complex nanoindentation problems and in correlation with gradients theories forms a well-seried tool in order to take into account size effects.Originality value - By studying this alloy, the paper reviews fundamental principles such as stress-strain distribution, size effects rise during nanoindentation and the applicability of finite element method, in order to take into account these issues.