ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

used the PAC constitutive constants (obtained from the study by Jin et al. [15]) that
correspond to the tissue relaxed state: 1) Matrix Young’s modulus E=26.4 kPa; 2) Fibre
constants (defined as in [14] and [15]), C3=56 kPa, C4=11, C5=8.45 MPa,
C6=-8.39 MPa ; and 3) The stretch value where the fibers are straightened * =1.32.
Edge A Edge B
4. RESULTS
Fig. 4 Meshless model applied when
modelling the experiments on elongation of
samples of pia-arachnoid-complex tissue
conducted by Jin et al. [13]. Dimensions:
height (along Y axis) of 12.7 mm, length
(along X axis) of 20.0 mm, thickness of
0.0246 mm. Edge A was rigidly constrained,
and Edge B was subjected to elongation in X
(horizontal) axis direction.
4.1 Verification of meshless algorithm for soft tissue fragmentation modelling
The results obtained using our meshless algorithm with visibility criterion for
fragmentation modelling were very close to those calculated by the ABAQUS finite
element solver. The maximum difference in the nodal displacements along X axis was
0.37 mm (i.e. less than 2% of the total model elongation) and occurred in the vicinity of
the notch tip where the finite element mesh exhibited large distortion (Fig. 5). The
average absolute difference in the nodal displacements was order of magnitude smaller
than the maximum difference and equaled 0.029 mm (which is only 0.15% of the total
model elongation).
Fig. 5 Results of verification of the
meshless algorithm in modelling of
discontinuities (crack) due to tissue
fragmentation. The model set-up used in
this verification is shown in Fig. 3.
Distribution of the absolute differences (in
metres) in nodal displacements in X
direction between the meshless algorithm
and ABAQUS finite element solver overimposed
on deformed meshless grid for
elongation of 20% of the initial length of
the model. Model dimensions are in metres.
4.2 Evaluation of meshless algorithm performance: Modelling of pia-arachnoid complex
rupture
The nominal stress–strain relationship of the PAC sample predicted by the model
implemented using our meshless algorithm with visibility criterion was within the
envelope of the experimental responses (Fig. 6). Overall deformation of the sample
predicted by the model agreed well with that observed in the experiments (Fig. 7).