Implementation of a Material Model for Adhesives in Abaqus
Examensarbete för masterexamen
Applied mechanics (MPAME), MSc
In recent years it has become more common to use adhesive bonded multi-material
structures in the automotive industry. These structures are however prone to distortions
during the Electrocoat-oven process. These distortions are partly generated
due to the curing of the adhesive, in combination with different coefficients of thermal
expansion of the materials joined together (Δα). One way to predict these
distortions is through FE-simulation.
To be able to get accurate results from FE-simulations, a material model that
accurately describes the degree of cure and its impact on the mechanical behaviour
is required. Volvo Cars is therefore part of the research project MADBOND, in
which a material model for adhesives has been developed and implemented in the
In this master’s thesis, the adhesive material model developed in the MADBOND
project has been implemented as a user material model in the FE-solver
Abaqus, which is the preferred solver for Δα-simulations at Volvo Cars.
The Abaqus implementation was evaluated against both the existing implementation
in LS-DYNA and a physical test.
In the evaluation, the results from Abaqus were within the defined error tolerance
of 10% for the residual stresses and residual deformations, when compared to
LS-DYNA. In the comparison with the physical test, the same buckling behaviour
was noted in the results from both the Abaqus simulation and the test. Significant
differences in the magnitudes of the residual displacements was however seen, which
in some regions was 10 times larger in the test case. The differences were to a large
extent explained by adhesive failure in the test, which was an aspect not included
in the simulation model.
A convergence study was conducted for the material model, and it showed that
the time increment size had a significant impact on the results, both in LS-DYNA
and Abaqus. It was also discovered that the Abaqus implementation was not compatible
with parallel execution. It was therefore recommended that these aspects
are taken into consideration in any future work at Volvo Cars in order to perform
accurate Δα-simulations for large structures.
Multi-material structures , Adhesive , Δα , UMAT , Abaqus , LS-DYNA , CAE , FEA