innovative fe-analysis of the roller burnishing process for different ...

F. Klocke, V. Bäcker, H. Wegner and A. Timmer.
2 MODEL DEVELOPMENT
In the following sections the developed FE-models will be described (Figure 1).
Figure 1: Modelling of the roller burnishing process for different geometries
The determination of an accurate stress distribution in the rime zone requires a high
number of elements, which makes a simulation of the complete geometry impossible.
Therefore cut-out dimensions for each geometry were defined. This allows a robust and timeefficient
roller burnishing simulation. In order to ensure a minimal influence of the boundaries
on the stress development, symmetric boundary conditions were applied on these surfaces.
Each section was modelled as a deformable 3D-body. The roller burnishing tools were
simplified and modelled as rigid balls. This assumption is valid, because of the high hardness
of the tungsten carbide roller ball (~2400 HV) compared to the processed material (~450 HV).
Contact between tool and workpiece was modelled using a finite-sliding formulation where
separation and sliding of finite amplitude, and arbitrary rotation of the surfaces may arise. The
normal contact behaviour between the contact surfaces was modelled using the hard contact
formulation implemented in ABAQUS. The contact constraint is enforced with a Lagrange
multiplier representing the contact pressure in a mixed formulation. The friction was modelled
using an extended version of the classical isotropic Coulomb friction model. The extensions
include an additional limit on the allowable shear stress, anisotropy, and the definition of a
“secant” friction coefficient. Thereby, the friction model is able to consider stick-slip-effects,
which can occur during roller burnishing at high pressures.
The behaviour of the used materials, IN718 and Ti-6Al-4V, was modelled using the
implemented ABAQUS material models for metals subjected to cyclic loading. The elastic
material behaviour was described using a linear elasticity model, whereas for the plastic
behaviour a nonlinear, isotropic/kinematic hardening model was used. The model parameters
for the description of the elastic material behaviour and for the plastic hardening were
determined from material examinations and cyclic tests.
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