J. Frischkorn

A new method of intelligent control for system stabilization in process-integrated powder coating by radial axial rolling of rings

Process-integrated powder coating by radial axial rolling of rings represents a novel hybrid production process to apply powder metallurgical coatings on large ring-shaped parts. The goal is to noticeably improve resistance against abrasive wear. To investigate important quantities such as e.g. the residual porosity in the layer and the stress states in the rolling zone, the versatile use of the finite element method (FEM) is crucial. Therefore, a parameterized FE model is developed on the basis of a finite strain viscoplastic material formulation. Reasonably controlling the movement of the guide rollers is an important task. It will be shown that the development of a mathematical formulation for the analytical design of such a control system based on Apollonian mutually orthogonal circles is necessary. The paper will be concluded by simulation results of the ring rolling process and comparisons with experimental results.

Stability of Mixed Finite Element Formulations – A New Approach

To guarantee stability of non-linear mixed finite element formulations is still an unsolved problem. In the present contribution firstly a unified finite element technology for linear-elastic problems is described where the effect of locking can be well explained and the issue of instability is not relevant. The extension to large deformation models reveals the difficulty of differentiating between physcially relevant and artificial bifurcations. Powerful finite element technologies should be able to exhibit the first kind but not show the second kind of bifurcations. In the paper a strategy is developed to detect and to avoid such non-physical instabilities.

Coupled Thermo-Mechanical Analysis of Process-Integrated Powder Coating by Means of Hot Rolling

In this paper, a new hybrid production technique is presented. It exploits the advantage of high temperatures and high forces in the ring rolling process. This manufacturing technique is not only suitable to increase the ring’s diameter but also to apply and compact powder metallurgical multi-functional coatings onto solid substrate rings with the same process. In order to design this new process parameterized 2D and 3D FE models are created in ABAQUS/EXPLICIT on the basis of a viscoplastic material model formulation. The control capability of the conventional control mechanisms are based on the assumption of volume consistency. However, this assumption is not well applicable for a ring furnished by multi-functional surfaces with non-isochoric plastic deformation behavior. Therefore, this paper deals with the implementation of a new control mechanism. Finally the paper is concluded with the integration of heat treatment of the rolled ring into the subsequent cooling process.

Finite element modelling of process-integrated powder coating by radial axial rolling of rings

The process‐integrated powder coating by radial axial rolling of rings represents a new hybrid production technique applied in the manufacturing of large ring‐shaped work pieces with functional layers. It is thought to break some limitations that come along with the hot isostatic pressing (HIP) which is used nowadays to apply the powdery layer material onto the rolled substrate ring. Within the new process the compaction of the layer material is integrated into the ring rolling and HIP becomes dispensable. Following this approach the rolling of such compound rings brings up some new challenges. The volume of a solid ring stays nearly constant during the rolling. This behaviour can be exploited to determine the infeed of the rollers needed to reach the desired ring shape. Since volume consistency cannot be guaranteed for the rolling of a compound ring the choice of appropriate infeed of the rollers is still an open question. This paper deals with the finite element (FE) simulation of this new process. Firs...