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Experimental and numerical investigation of the effect of the combined mechanism of circumferential expansion and folding on energy absorption parameters

Abolfathi M., Nia A. A., Attar A. A., Abbasi M.

Archives of Civil and Mechanical Engineering

2018

Vol. 18, no. 4

1464--1477

In this research, in order to increase energy absorption of thin-walled tubes, a combined deformation mechanism is proposed which involves the simultaneous combination of circumferential expansion and folding. Such a combined mechanism was not concerned in the literature. The study is carried out both experimentally and numerically. A special device was designed and made to conduct experimental tests on tubes. The samples were made of aluminum, and quasi-static loading was applied at two different speeds of 10 and 200 mm/min. Energy absorption parameters including specific energy absorption (SEA), crushing mean force, initial peak force, the deformation mode and crush force efficiency (CFE) were studied. Experimental results showed that combined mechanism (without lubrication) could increase absorbed energy up to 123% compared to the folding mechanism. If the lubricant is used, the increase will be up to 97%. The combined deformation mechanism (without lubrication) increases absorbed energy up to 94% compared to the circumstantial expansion. This value will be 107% with lubrication. In addition, the initial peak force in the combined mechanism decreases between 8% and 36% relative to the folding mechanism. The circumstantial expansion in the proposed mechanism is complete and the expansion stroke length is 100%, while this stroke was less in the previous researches due to design restrictions. Numerical simulations were conducted using LS-Dyna software and there is good agreement between the numerical results and experimental data.

The effect of different layouts in internal and external stiffeners on the energy absorption of thin-walled structures with square sections

Nia A. A., Attar A. A.

Archives of Civil and Mechanical Engineering

2017

Vol. 17, no. 4

997--1010

This study attempted to examined the energy absorption and the mechanical behavior of thin-walled aluminum structures with square section, which are connected to the structural wall by either internal or external stiffeners and then exposed to axial quasi-static loading. The features of energy absorption examined in these structures included specific energy absorption, mean crush force, initial maximum force, deformation style and returns to crush force efficiency. The impact of stiffener layout on energy absorption was evaluated through several primary simulations through LS-DYNA for hypothetical models. Finally, a few different samples of the primary models were developed and tested experimentally. In experimental studies after annealing and determining the mechanical properties of aluminum 1100, the energy absorption properties under quasi-static pressure were found. The results of numerical and experimental studies showed good consistency. The results showed that the specific energy absorption of square thin-walled structures enhances as the number of stiffeners increases, which depends on the position of the stiffeners. The experimental tests proved that the layout of stiffeners according to the proposed model can increase specific energy absorption (SEA) by up to 65% compared to samples without stiffeners. Moreover, the crush force efficiency (CFE) during the test amounted desirably to 0.69.