Thin walled structures are widely used as energy absorbing devices during accidents, collisions in various transportation systems. Designing an energy absorbing device requires proper combination of geometry and material. The deformation behavior and collapse modes of these structures are complex. Simple geometries with square, polygonal or circular cross section deform with various collapse modes for energy absorption in these structures. In the present work, square extruded Aluminum tubes are axially compressed under quasistatic loading. Infra-red thermal imaging is done to measure the rise in surface temperature during axial compression of the square tube. Post experimental investigations have been conducted using Scanning Electron Microscope (SEM) and Computerized Tomography (CT) scan to understand the deformation behavior at micro level. The out of plane displacement after progressive buckling is measured using a Coordinate Measuring Machine (CMM). Full field 3D Digital image correlation (DIC) technique has been used to measure the surface strain. The results indicate a good correlation between displacements measured by DIC technique and CMM. Strain field developed during progressive buckling suggests large strains at crumple zones. SEM investigations suggest material pile-up at severely compressed regions with thinning on tensile deformation edges. Copyright © 2016 by ASME.