| This study investigates the nature of energy dissipation in axial crushing of High Molecular Weight High Density Polyethylene (HMW/HDPE) circular tubes. In the process, formulas are developed for the prediction of peak and mean crushing loads including the effects of strain-hardening, strain-rate, and inelastic behavior. Possibility of using nested tubes for optimal performance as energy dissipation device is considered.;The prediction of peak axial crushing load of tubes is carried out by buckling and post-buckling analyses. The equivalent column approach is used in buckling analysis, and inelastic and strain-hardening effects are considered.;An upper-lower bound method is proposed to predict the mean crushing load. The upper bound of axial crushing load of tubes is predicted by post-buckling analysis, whereas the lower bound is predicted by plastic analysis. The mean axial crushing load is taken as the average of upper and lower bounds of the axial crushing load. It is found that the mean crushing load is affected not only by tube's geometric parameter, ;HMW/HDPE was found to be a strain-rate sensitive material and the constitutive relationship for it can be expressed either by Cowper and Symonds' equation or, in the logarithmic form. The strain rates of tubes in axial crushing in both circumferential and axial directions were found to be significant and hence needed to be accounted for in the prediction of effective strain rate. It was also found that strain rate does not vary linearly with the loading speed, as multiple folds are formed simultaneously under a high loading speed.;Energy dissipation characteristics of a group of nested tubes was found to be superior to that of a simple tube. The honeycomb arrangement avoids global buckling of long tubes, and concentrically nested tubes with different lengths enhance the mean crushing load and reduce the peak crushing load improving energy dissipation efficiency. The honeycomb structure with nested tubes is proposed for energy dissipation devices. The honeycomb structure with nested tubes is considered to be best suited for optimal design of energy dissipation devices based on axial crushing of tubes. Further study of this topic is needed. |
