In Situ Investigation and Image-Based Modelling of Aluminium Foam Compression Using Micro X-Ray Computed Tomography - Visual Computing: Scientific Visualization and Imaging Systems - page 185

Fig. 10.3 Experimental and
numerical stress-strain
curves of the compressed
foam
when the stress approaches its maximum during the early compression stage,
which is followed by a plateau regime showing prolonged deformation at almost
constant stress. After considerably more deformation the stress rapidly rises with
strain, reflecting the cell interaction in the densification regime. The numerical
prediction generally overestimates the stress level and does not precisely mimic
the experimental stress-strain curve. Nevertheless, it successfully captures the
essential trend of the stress variation, i.e. the stress almost remains constant in the
plateau regime. Unfortunately, the simulation of the densification stage cannot be
achieved in the present model due to extensive element distortion associated with
the large deformations. The predicted modulus of the linear part of the stress-
strain curve is also larger than the experimental one, but is close to the unloading
modulus of the same foams measured in previous experiments [ 9 ]. The discrep-
ancy between the numerical and experimental results can be attributed to the
numerical errors caused by the use of linear elements to discretize the cell walls
and possibly an insufficient number of elements over the thin solid walls, as well as
the inhomogeneous properties of the cell-wall material [ 10 ]. To improve the
numerical precision further, more elements would be required which was not
possible in this case due to the limited computational power available for over 15
million elements. Furthermore, the increased relative density after meshing and the
lack of reliable homogenised material models for the cell walls also hinder more
accurate prediction. Nevertheless, the effect of the real meso-scale geometry on the
compressive behaviour has been captured in the FE model. Therefore, the current
simulation should be regarded as qualitative and capable of providing insights into
the compressive behaviour of foams.