Experimental investigation of torsional strengths of aluminum alloys: Circular and rectangular solid sections

Abstract

An experimental investigation of aluminum alloy rods and bars subjected to torsional loading is presented. The test specimens were 6061-T6 and 5050-H32 alloys with solid circular and solid rectangular cross-sections. The test plan included torsion tests until rupture, for 5 sets of 6061-T6 specimens with circular and rectangular cross-sections, and 4 sets of 5050-H32 specimens with rectangular cross-sections. Each test series included six specimens, for a total of 54 torsion tests. Experimental torque and angular deformation data were recorded and subsequently analyzed to investigate the torsional stiffness, strength, and ductility of the specimens, including consideration of initial-yield, full-yield, and rupture strengths, as well as total angular deformation at failure. A methodology was developed to estimate the full plastic torque, associated with yielding throughout the cross-section, from the measured experimental data. Results were compared with nominal strengths predicted using the material properties required within the Aluminum Association’s Specification for Aluminum Structures (SAS). Use of these properties in conjunction with SAS’s first-yield criterion produced results that were overly conservative in general, demonstrating the importance of exploring changes to the Specification. Recommendations are made for adjustments and extensions to the SAS, which support an ultimate strength approach consistent with its strength limit states design methodology.