A Comparison of the Mechanical Performance of AA6061-T6 Extrusions Subjected to Axial Crushing and Axial Cutting

Conventional axially loaded energy absorbers dissipate kinetic energy through progressive folding. The significant fluctuations in load and high risk of transition to global bending are drawbacks that engineers have attempted to mitigate through several methods. A novel energy dissipation mechanism, referred to as axial cutting, utilizes thin-walled extrusions and a strengthened cutting tool to absorb energy in an axial impact. Compared to progressive folding, this can be achieved with minimal fluctuations in load during the deformation process. Based upon estimates from finite element models, a series of test cases were postulated where, for 8 and 10-bladed cutting scenarios, greater total energy absorption could be achieved through axial cutting than with progressive folding of geometrically similar extrusions. The specimens were AA6061 extrusions having T6 temper conditions that possessed 63.5 mm outer diameters and 1.5 mm wall thicknesses. All tests were performed quasi-statically using a universal MTS testing machine at a crushing rate of 50 mm/min. The axially cut extrusions displayed an average of 22.8 % more energy absorption than their respective axially crushed test specimens with an improved crush force efficiency, greater by a factor of 2. Finite element models utilizing an Arbitrary Lagrangian-Eulerian mesh were developed and solved with LS-DYNA R8.0.0 to numerically replicate the load-displacement responses of the axially cut extrusions. The steady-state cutting force was typically predicted to within 10% of experimental values with corresponding validation metrics generally above 0.90.