Reza Kebriaei

A Cohesive Zone Model for Simulation of the Bonding and Debonding in Metallic Composite Structures - Experimental Validations

Flexible and economic production of composite structures which include functional layersrequires new manufacturing techniques. Joining by plastic deformation is a powerful technique whichis widely used in production processes to create metal composites [1]. The use of plastic deformationin joining processes offers improved accuracy, reliability and environmental safety [2]. The presentstudy deals with modeling of the bonding and debonding behavior in metallic composite structures.Therefore, a general cohesive zone element formulation in the framework of zero-thickness interfaceelements is developed. This enables the accurate and efficient modeling of the interface based on aninterfacial traction-separation law. The paper is concluded by a detailed description of the processsimulation and a comparison of its results with experimental data.

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.

Experimental Chemo-Mechanical Characterization and Multiscale Modeling of the Alloys Al1050, Al2024 and Al5754

In the last decades, manufacturing of layered composite materials has become an interesting topic in industrial development. Joining properties of adhesively bonded materials are characterized by a complex interaction of plastic deformation, thermo-mechano-chemical coupling effects, adhesion and diffusion. Additionally, the interactions between the microstructures involved in the process have to be taken into account. In this paper the microstructure of materials (as e.g. Al1050, Al2024 and Al5754), which have a wide range of applications in engineering structures, is numerically and experimentally investigated. The results are compared with experimental data.

Material Modeling and Numerical Analysis of the Heat Treatment in High Carbon Steels-Application to Ring Rolling

Numerical modeling of the heat treatment is developed over the past 30 years and connected to the industrial applications. This requires a good insight in the thermal, mechanical and metallurgical behavior of steels and the coupling effects among these physical phenomena. To describe these effects, a suitable material model is developed. Additionally, the thermo-mechanical behavior of multi-phase steel during the phase transformation is investigated. Furthermore, the material model is applied to describe the plastic behavior of the steel during the cooling process in process-integrated powder coating which is a new kind of ring-rolling process. It takes advantages of the high temperatures and high forces of the ring rolling process. This is not only to increase the rings diameter, but also to integrate powder metallurgical multi-functional coatings within the same process. In order to increase the strength and wear properties of investigated steels, an appropriate heat treatment should be done. Therefore, the heat treatment after the rolling process is discussed which goes along with phase transformations. The paper is concluded by a detailed description of the process simulation and a comparison of its results with experimental data.

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...