Energy absorption characteristics of axially compressed double wall foam filled and empty square tubes

Abstract

Occupant safety has become increasingly important in recent times. This can be achieved either using active safety or passive safety. Crash worthiness is one of the primary passive seafty methods to protect the occupants in the event of an accident. Structures with high energy absorption can provide better occupant safety at the instance of collision.

Thin walled tubes are widely used as energy absorbers in automobiles and other structures. Several strategies have been adopted thus far to improve the energy absorption characteristics of thin walled structures by conducting experiments at the laboratory scale and extending the results to full structure. These include use of foam filled tubes which absorb higher energy compared to empty thin walled tubes. Earlier studies focused on insertion of rib walls as reinforcements at specified locations (as a function of crumple zone side) to enhance the specific energy absorption during compression testing.

In present work, crashworthiness characteristics of double wall empty and double wall foam filled tubes are investigated experimentally and through numerical simulation. Commercially available extruded thin wall aluminium square tubes were used in this study. Two square tubes having a nominal dimension of 1” x 1” (as inner tube) and 2” x 2” (as outer tube) were selected. The tubes were either placed in parallel side wall configuration or placed with an offset angle of 45˚ (referred to as diamond configuration) to enhance the stiffness. Polymer foam was used as filler material between two tubes to fabricate double wall foam filled tube. The effect of different densities of polyurethane foam on the crushing of foam filled tubes was examined. Densities of polyurethane foam used in this study are 40Kg/m^3^, 80 Kg/m^3^, 140Kg/m^3^. All the specimens were compressed at a displacement rate of 100 mm/min. Crushing of different configurations were numerically analyzed using nonlinear finite element tool LS-Dyna.

Double wall empty tube diamond configuration absorbed more energy compared to parallel configuration due to interaction between inner and outer tubes. Results indicate that foam filling with each density improves energy absorption. Compared to double wall tubes maximum increase in energy absorption of over 50% is observed in foam filled tubes. Computer Tomography (CT) scan of specimens suggests that foam filling alters crushing behaviour of the inner and outer tube.

Keywords: Energy absorption, Crashworthiness, Thin walled tubes, Double wall tubes, Foam-filled tubes. 


Energy Absorption Characteristics of Axially Compressed Double Wall Foam Filled and Empty Square Tubes

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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