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Eigenmodes for 3-cell and 7-cell specimens that are chosen to perturb the mesh for explicit FE simulations. Mode A corresponds to the lowest eigenmode and mode B is chosen corresponding to higher buckling load.
This and the next image are from:
Royan J. D’Mello, Sophia Guntupali, Lucas R. Hansen and Anthony M. Waas, “Dynamic axial crush response of circular honeycombs”, We May 2012, Royal Society Publishing,
http://royalsocietypublishing.org/content/early/2012/05/22/rspa.2011.0722 DOI: 10.1098/rspa.2011.0722
ABSTRACT: The dynamic axial crush response of circular cell polycarbonate honeycombs was studied for 3-cell and 7-cell specimens experimentally and through finite-element (FE) simulation. The experiments were conducted using two loading methods: (i) the wave loading device (WLD) method and (ii) the direct impact method (DIM). The specimens were subjected to crush velocities of about 12000 mm per second in the WLD method and 5000 mm per second in the DIM. The two methods were used to obtain a fairly wide range of input velocities. The collapse sequence and displacement information of the specimens were captured using a high-speed camera. The mode of collapse was through progressive concertina-diamond fold formation over a fairly constant state of load, which is referred to as the crush load. The crushing was simulated using an explicit FE analysis using ABAQUS, with geometrically imperfect 3-cell and 7-cell honeycomb models that incorporated the rate-dependent properties of polycarbonate. The FE results were found to agree well with the experimental results in terms of overall force-displacement plots, thus providing a basis to extract energy absorption estimates from the models and to draw comparisons between the 3-cell and 7-cell response behaviour. Moreover, the dynamic crush results were compared against a quasi-static axial crush response to demonstrate the presence of rate effects.
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