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Crashworthiness performance of thin-walled hollow and foam-filled prismatic frusta – FEM parametric studies – Part 1

Szklarek, Karol / Kotełko, Maria / Ferdynus, Mirosław

Abstract Structural members termed frusta (conical shells or tapered prismatic tubes) are used as energy absorbers due to the stable plastic behavior during axial crushing process and to the decrease of peak crushing load in comparison with cylindrical columns or parallelepiped-shaped thin-walled columns. The paper presents the parametric study into crashworthiness performance of prismatic steel thin-walled frusta of square base and various apex angles produced from two face to face channel section bars, both hollow and foam filled, subjected to axial impact load. Material used for filled frusta was the polypropylene foam. An influence of geometrical parameters : wall inclination angle (frustum apex angle), wall thickness and frustum height as well as influence of foam filling on energy absorption and crashworthiness performance is investigated. The parametric study is performed using Finite Element simulations. Two step analysis was carried out (the eigenvalue buckling analysis and subsequently the non-linear explicit dynamic analysis). Crushing behavior (buckling and failure modes) and load–shortening characteristics obtained on the basis of FE numerical results are discussed. Energy absorbing effectiveness is analyzed using crashworthiness indicators, namely Peak Crushing Force (PCF), Crash Load Efficiency (CLE) and Total Efficiency (TE). Effect of synergy in case of foam filled frusta is examined. On the basis of the analyses some conclusions are derived concerning the most effective configurations of geometrical parameters of frusta under investigation as well as some of the drawbacks and limitations of the applicability of indicators used in the analysis. Further research topics are presented, including an identification of new or modified crashworthiness indicators and multi-objective optimization of examined frusta.

Highlights • Thin-walled prismatic frustum, both hollow and foam-filled subject to axial impact load is investigated. • The comprehensive parametric study of influence of several factors (height, thickness and apex angle of frustum) upon the energy absorption effectiveness is analyzed. • Polypropylene foam filling improves the crashworthiness performance, synergy effect is observed. • A necessity to develop new crashworthiness indicators is discussed.