Abstract
In this paper, we develop a procedure to design, fabricate, and verify pulse shapers using elastic metamaterials under impact excitation as applied to the Split Hopkinson Pressure Bar (SHPB) test. The SHPB test, a fundamental dynamic test for over 70 years, has incorporated pulse shaping as a key feature which we re-examine through the use of elastic metamaterials. Elastic metamaterials, which exhibit properties atypical of their constitutive elements, hold promise for expanding on conventional pulse shaping abilities and improve the capabilities of the SHPB test. We first design the pulse shaper by numerically optimizing its geometry using finite element analysis. The pulse shaper consists of repeated unit cells which are based on a combination of a phononic crystal and a local resonator. Then, we fabricate and test pulse shaper candidates to validate the procedure efficacy. We incorporate an iterative element to this procedure such that we learn from inaccuracies in input force and material properties to converge on an appropriate pulse shaper. We carry-out this procedure by designing pulse shapers fabricated from 3D-printed PLA to achieve an extended dwell acceleration pulse shape. In experimental impact tests, we verify that the procedure results in ramp-up, acceleration dwell, and ramp-down comparable to that predicted, effectively confirming the efficacy of the presented procedure.
