Maximum energy absorbing capacity and structural stability for energy dissipation devices exploiting a hybrid cutting/clamping deformation mode

There is significant and accelerating demand for novel, lightweight sacrificial energy absorbers which can exceed the performance of the current state-of-the-art (i.e., axial crushing), however, the risks of structural instability, practical limitations and mitigation strategies are unexplored in the literature. High-capacity hybrid cutting/clamping deformation modes considering 10 or more blades were newly investigated for their potential to eclipse the mechanical performance of traditional progressive folding deformation under quasi-static loading conditions, with further emphasis on maximizing energy absorbing capacity without exceeding acceptable limits on stability. Analytical, numerical and experimental studies were conducted for circular AA6061 extrusions in T6 and T4 temper conditions with multiple diameter/wall thickness combinations to quantify the influence of these engineering parameters, and the number of blades, on unfavorable transitions from steady-state cutting to progressive folding. Transitions were attributed to two primary instability mechanisms: peak force saturation as the cutting force exceeded the maximum collapse force of an extrusion, and petalled sidewall binding followed by geometric transformations to unilateral lobes. Temper condition was the most sensitive parameter, 6061-T4 extrusions in multiple geometric configurations regularly experienced transitions to progressive folding compared to limits between 13 and 15 blades for complementary 6061-T6 extrusions. These limits were analytically predicted with an average tolerance of ±1 blades. Numerical modeling considering an Eulerian material-and-void approach was suitable to predict steady-state cutting/clamping forces with 11.8% average cumulative error. The extrusions subjected to cutting/clamping dissipated up to 65.3% more energy (28.9% average) compared to axial crushing before geometric instabilities were observed. •Analytical models utilized to predict maximum number of blades for cutting/clamping.•Quasi-static testing of AA6061 extrusions to validate maximum number of blades.•Deformation transitions due to excessive force identified for extrusions.•Deformation transitions resulting from geometric instability identified.