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This research deals with both experimental testing and numerical modeling of the cutting deformation associated with aluminum AA6061-T6 round extrusions as possible energy absorbing structures. For the experimental portion of this research, round extruded specimens of length 200 mm with a nominal wall thickness of 3.175 mm and an external diameter of 50.8 mm were considered. A heat treated 4140 steel alloy cutter was designed and manufactured with four cutting blades of approximate average thickness of 1.00 mm to penetrate through the round AA6061-T6 extrusions. Results from the experimental tests showed that the cutting deformation mode exhibited a high average crush force efficiency of 0.95 compared to average values of 0.66 and 0.20 for progressive folding and global bending deformation modes respectively. An almost constant cutting force was observed during the cutting deformation process.

A plethora of applications in the transportation industry for both vehicular and roadside safety hardware, especially seatbelts, harnesses and restraints, rely on tensile loading to dissipate energy and minimize injury. There are disadvantages to the current state-of-the-art for these tensile energy absorbers, including erratic force-displacement responses and low tensile force efficiencies (TFE). Axial cutting was extensively demonstrated by researchers at the University of Windsor to maintain a stable reaction force, although exclusively under compressive loading. A novel apparatus was investigated in this study which utilized axial cutting under a tensile loading condition to absorb energy. A parametric scope was chosen to include circular AA6061 extrusions in both T4 and T6 temper conditions with an outer diameter of 63.5 mm and wall thickness of 3.18 mm.

This research focused on the energy absorption capabilities of axially loaded structures fabricated from aluminum alloy extruded tubing with a square cross section. Quasi-static compressive testing was used to examine the effects of dual centrally-located circular hole discontinuities on the energy absorption characteristics of the extrusion test specimens. In addition to previously characterized progressive buckling and global bending modes, collapse modes involving cracking and splitting were observed in several experimental tests. For this reason, finite element models of each test specimen were developed using a material model incorporating damage mechanics. The suitability of using shell elements versus solid elements to model these relatively thick walled structures was investigated. A good correlation was observed between the results of the experimental quasi-static compressive tests and the results of the finite element simulations conducted using LS-DYNA.

The axial cutting deformation mode is a novel alternative to progressive folding, the current state-of-the-art, where the cutting scheme exhibits more favorable mechanical performance. By splitting the extrusion into multiple evenly spaced and near-identical petals a highly consistent force response can be achieved. Maximizing the energy absorbing capacity of a sacrificial energy absorber is a fundamental design challenge in the field of crashworthiness. Generating hybrid deformation modes by simultaneously combining multiple deformation mechanisms into a single safety system is a promising technique to achieve high capacity energy dissipation. However, these systems tend to be susceptible to transitioning deformation modes (e.g. from progressive folding to global bending) since the sacrificial material is often loaded at or near its capacity.

Experimental and numerical studies have been completed on the deformation behaviour of round AA6061-T6 aluminum extrusions during an axial cutting deformation mode employing both curved and straight deflectors to control the bending deformation of petalled side walls. Round extrusions of length 200 mm with a nominal wall thickness of 3.175 mm and an external diameter of 50.8 mm were considered. A heat treated 4140 steel alloy cutter and deflectors, both straight and curved, were designed and manufactured for the testing considered. The four blades of the cutter had an approximate average thickness of 1.00 mm which were designed to penetrate through the round AA6061-T6 extrusions. Experimental observations illustrated high crush force efficiencies of 0.82 for the extrusions which experienced the cutting deformation mode with the deflectors. Total energy absorption during the cutting process was approximately 5.48 kJ.