Modified Method for Dynamic Stress-Strain Curve Determination of Closed-Cell Foams

Abstract

The paper presents a modified method for the non-linear dynamic stress-strain curve determination with the use of cushion curves provided by the manufacturers of closed-cell foams. This method consists of two main stages: stage 1 – the cushion curves transformation to the coordinate system of dynamic stress-energy density, combined with the cubic b-spline curve approximation, and stage 2 – development of the dynamic stress-strain curve considering that the area under the curve is equal to the energy density of a collision. The stress-strain curves are one of the basic parameters of the foam material models used to describe the collision process, in the modelling environments of finite element method (FEM), e.g. LS-DYNA. Performed verification consisting in the reconstruction of cushion curves using LS-DYNA showed that the proposed method of the dynamic stress-strain curves determination is efficient and effective. Taking into account that access to the stress-strain curves is hindered (cushioning material manufacturers do not publish them), and the access to charts of cushion curves is easier, the proposed method for determining the stress-strain curves can relevantly shorten the process of preparing the input data, which are required during modelling of spatial structures using FEM. Copyright © 2016 John Wiley & Sons, Ltd.