Thomas Kloppenborg

Experimental and Numerical Analysis of Material Flow in Porthole Die Extrusion

The design of porthole dies for aluminum extrusion processes is very complex. For the accurate design, fundamental knowledge about material flow is of major importance. To gain these information, numerical methods are increasingly utilized. The accuracy of the simulation results depends mainly on the precision of the used boundary conditions in the model. Therefore, visioplastic analyses of the material flow inside a porthole die are presented in this paper. A special modular tool concept was developed to prepare and visualize the material flow inside the process. The results of the experimental analysis were used for the verification of numerical results which were calculated with the commercial software codes Deform3D and HyperXtrude.

Numerical Optimization of Bearing Length in Composite Extrusion Processes

The decrease of the bearing length in extrusion processes results in increasing of the material flow and offers, through this, the possibility for manipulation and optimization. This paper presents a simulation based optimization technique which uses this effect for optimizing the material flow in direct extrusion processes. Firstly, the method is used in a multi-extrusion process with equal pitch circle profiles, then in an extrusion process of an asymmetric profile. Furthermore, a composite extrusion process is analyzed where endless wires of high strength steel are embedded in a base material of aluminum. The insertion of reinforcement elements into the base material flow, especially within the small ratio between profile thickness and the reinforcement diameter, can lead to significant local disturbances inside the die, which result in undesirable profile defects. Hence, the simulation-based optimization method is especially used to optimize inhomogeneous wall thicknesses in composite profiles.

Accurate Welding Line Prediction in Extrusion Processes

In contrast to conventional extrusion processes, where a lot of research is done on in the welding quality, in composite extrusion, research is investigated into the welding line positioning. As a result of the process principle, the reinforcing elements are embedded into the longitudinal welding line. Hence, an undefined material flow inside the welding chamber induces reinforcement deflection, which can lead to reduced mechanical properties, as momentum of inertia. Therefore and to reduce costly experimental investigations, a new method of an automated numerical welding line prediction was developed. The results form HyperXtrude finite element calculations are used for special particle tracing simulations to predict the welding line in the profile cross section accurately. The procedures of segmentation and characteristic extraction are presented to approximate the welding line by cubic spline functions. The method was fully programmed in the Java program language, and works well for all HyperXtrude process models consisting of tetrahedral elements.

Finite Element Based Determination and Optimization of Seam Weld Positions in Porthole Die Extrusion of Double Hollow Profile with Asymmetric Cross Section

Finite elemente analysis (FEA) allows to reduce development time during the die design stage as well as costly extrusion trials with prototypes. Therefore, it is essential that FEA computation provides reliable results. Among other output quantities such as temperature, load, or die stress, the prediction of material flow is one of the most essential ones. Especially in porthole dies, the material flow can be very complex and thus the position of the seam welds in the profile may be uncertain. In this study the particle tracing method was utilized to determine and finally adjust the seam weld positions in a double hollow profile with varying wall thicknesses over the cross section. The seam weld positions resulting from the original die design were determined by Eulerian FEA computation in the first step. Subsequently, the seam weld positions were adjusted by changing the die geometry. The simulation results were verified by means of extrusion tests, which were conducted under industrial conditions. In addition, Lagrangian and Eulerian FEA was utilized to analyze the evolution of the seam weld positions by evaluation of material flow as well as pressure distribution during the transient initial stage and the steady-state stage of the extrusion process. It was demonstrated that steady state process simulation and the particle tracing method can be used for the prediction of seam weld positions in complex hollow cross sections.

Extrusion Benchmark 2013 - Experimental Analysis of Mandrel Deflection, Local Temperature and Pressure in Extrusion Dies

A bridge die was designed for the simultaneous extrusion of two rectangular profiles and used in a strictly monitored aluminum extrusion process. Experimental investigations aimed at the measurement of the mandrel deflection, the local die temperature, and the pressure inside the welding chamber by means of special measurement equipment. AA6082 alloy was used as extrusion material. The influence of the extrusion speed on the aforementioned objectives is reported. The experiments were repeated at least three times under the same conditions in order to achieve a statistical validation of the acquired data. These data are provided as reference for the 2013 edition of the Extrusion Benchmark.

Integrated simulation of the process chain composite extrusion–milling–welding for lightweight frame structures

Generally, the manufacturing of lightweight frame structures involves various processes that yield the final product. Simulation methods can be used to optimise the different process steps. When chaining these process steps together in the simulation, software interfaces become necessary to realise an integrated virtual process chain. In this paper two approaches are presented that solve this issue and demonstrate it for an exemplary part. Different software tools with appropriate interfaces and the use of only one software tool for the simulation of the whole process chain are investigated respectively. The results of both approaches are analysed and relevant conclusions are deduced.

Optimization of the Die Topology in Extrusion Processes

This paper presents the results of investigations on topology optimizations in extrusion dies. The change of material viscosity of finite elements in the numerical model is utilized to allow or to block the material flow through the finite elements in simplified two-dimensional extrusion models. Two different optimization procedures are presented. In the first part of the paper dead zones in a flat and in a porthole die were improved by enhance the streamlining of the extrusion die. In the second part an evolutionary optimization algorithm has been used to optimize the extrusion die topology in order to reduce the difference between the strand exit velocities in a multi extrusion process. Finally, both methods were sequentially combined.

Preparation and Etching Methods for a Light-Optical Microscopy Analysis of Extrusion Seams and Microstructural Contrasting for Aluminum Alloys EN AW-6063 and EN AW-6082

Abstract To begin with, a visualization of the seam location as well as of the microstructure of the entire profile cross-section is necessary in order to evaluate the stability of extrusion processes and the resulting relationships between process, microstructure, and properties of extrusion profiles characterized by an extrusion seam. The investigations aim at determining appropriate preparation and etching methods for a light-optical microscope analysis of the longitudinal as well as the transversal extrusion seam in the alloys EN AW-6063 and EN AW-6082 and – in the best case – a simultaneous microstructural contrasting. For this purpose, different chemical etching techniques have been applied. A reliable uncovering of the seam was possible for both alloys using a HF solution. Etching with Wecks reagent after NaOH pre-etching turned out to be a promising method for microstructural contrasting of the EN AW-6063 alloy. The transversal extrusion seam could not be rendered visible by means of conventional etching methods. In this context, extrusion of both alloys (EN AW-6082 and EN AW-6063) applying the billet-to-billet extrusion method in line with visioplastic analyses allowed for an indirect representation of the extrusion seam.

Numerical Approach for the Evaluation of Seam Welding Criteria in Extrusion Processes

The accurate simulation and the optimization of extrusion processes can be a helpful technique to ensure producibility of complex aluminum profiles, for example for the automobile industry. Currently, the die designing is based on expert’s knowledge and cost-intensive prototyping. The paper deals with numerical investigations based on finite element simulations as well as experimental investigations of an industrial extrusion process. A newly developed method for longitudinal seam weld prediction is applied to analyze the position of the longitudinal welding line and the welding quality.

Numerical Material Flow Optimization of a Multi-Hole Extrusion Process

The decrease of the bearing length in the aluminum extrusion processes results in an increase of the material flow and offers, through this, the possibility for correction and optimization. This study presents a simulation-based optimization technique which uses this effect for optimizing the material flow in a direct multi-hole extrusion process. First the extrusion process was numerically calculated to simulate the production of three rectangular profiles with equal cross sections. Here, the die orifices were arranged at various distances to the die centre, which lead to different profile exit speeds. Based on the initial numerical calculation, an automated optimization of the bearing length with the adaptive-response-surface-method was set up to achieve uniform exit speeds for all profiles. Finally, an experimental verification carried out to show the influence of the optimized die design.