Parametric design of multi-cell thin-walled structures for improved crashworthiness with stable progressive buckling mode. (October 2018) - Kenyon, Daneesha
Abstract: Thin-walled single and multi-cell structures are an ongoing topic of interest in the field of crashworthiness, due to their wide range of applications in automotive and aerospace industry as lightweight energy-absorbing structures in crash environments. This work presents a new five-cell cross-section that merges high performance multi-cell and twelve-edge cross-sections from previous research, and compares its performance to four- and nine-cell square cross-sections. Super Folding Element (SFE) theory and Finite Element Analysis (FEA) in LS-DYNA are used to analyze cross-sections and found to have good agreement. The LS-DYNA environment is validated with physical testing. The geometry of the cross-sections is varied in order to find maximal values of the performance parameters specific energy absorption ( SEA ) and crush force efficiency ( CFE ) under stable progressive buckling mode and constraints for manufacturability. The nine- and five-cell cross-sections ultimately out-perform the four-cell cross-section, with the nine-cell having the highest SEA and CFE, though the five-cell design has a significantly lower (47%) mean crush force ( P m ) for only an 11% and 14% loss in SEA and CFE respectively. As a final refinement, the geometry was varied across these two high-performing cross-sections to create equivalent mean crush forces to the four-cell cross-section, which showed the five-cell cross-section to have an improved SEA and better mass efficiency over the nine-cell under a mean crush force constraint. Abstract : Highlights: Identifying stable/transitional buckling regimes enables optimal design selection. Manufacturability constraints ensure mass producibility for automotive industry. 9-cell outperforms 5-cell but increases mass by 2.2X for 11–14% performance gain. 5-cell becomes top performer in automotive application after force normalization.