A Soft Contact Formulation For Modelling
Thin Coatings
Author(s)
N. Str¨omberg & J. F. Massana
Abstract
Today, high-performance machine components are often improved by coatings.
For instance, thin layers can increase the life-time by reducing friction and wear.
An example of this is the spline joint in the suspension system of a truck. This
joint, which is placed at the output of the gearbox, allows relative translation in the
axial direction. In order to improve performance, this spline can be coated with a
thin layer of polyamide. In such a manner, the life-time of the joint is increased by
decreasing friction and wear. This type of coatings may be optimized by performing
finite element contact analysis. However, when performing such an analysis, it
can be difficult to obtain a good mesh due to the very thin layer. An approach to
avoid this difficulty is to instead include the elastic properties of the coating in the
contact formulation. Such a soft contact formulation is suggested and solved in this
paper. The formulation is obtained by adding an elastic part to the free energy corresponding
to Signorini’s contact conditions. In such a manner a new soft contact
law is derived by taking the subdifferential of the free energy. In this law two new
constitutive parameters appear. The first parameter describes the elastic response
of the thin layer and the second one is taken to be equal to the thickness of the
layer. In the event, when the layer is completely penetrated, hard contact is developed
following a classical Lagrange formulation of Signorini.A numerical method
for solving the new contact formulation is also developed. The method is obtained
by following the augmented Lagrangian approach. In such a way an equivalent setting
of equations is derived which in turn is solved by using a non-smooth Newton
method. The method is implemented in a Matlab toolbox. The method is robust
and produces accurate results. This is shown by comparing numerical results with
solutions obtained by using a penalty formulation in Abaqus.
Keywords: soft contact, finite elements, Newton’s method.
Keywords
soft contact, finite elements, Newton’s method.
Related Book
Other papers in this volume
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