Inverse estimation of the elastic and anelastic properties of anisotropic foams - study of the static/dynamic separation

Invited paper

Siemens Industry Software

Tuesday 2 june, 2015, 18:00 - 18:20

0.7 Lisbon (47)

Abstract:

This paper investigates the modelling and characterisation of the porous frame of anisotropic open-cell foams. The main objective is to find a suitable model for describing the elastic and anelastic properties of the material by making as few assumptions as possible. The proposed model is based on a fractional differential equation, taking into account the deformation memory of the material in a versatile and compact manner. In the frequency domain, this results in an augmented Hooke's law, where the stiffness matrix of the porous frame consists of a superposition of a fully-relaxed, frequency-independent elastic part, and a dynamic, frequency-dependent anelastic part. Two separate experiments are performed. A static photometry setup is designed, where a cubic sample of material is compressed along each of the three directions of space while the deformation is recorded on the four exposed faces. Furthermore, a dynamic measurement of a set of transfer functions between each pair of opposed faces of the sample is performed. The characterisation methodology consists of an inverse estimation of the parameters of the model. This is acheved by replicating each experiment as a finite element simulation and fitting the model by using an optimisation algorithm. The model comprises 24 independent constants, which are obtained by this procedure. Their independence is investigated by means of different parameterisations of the constitutive model. In particular, the independence of the elastic and anelastic parts is discussed.