 | 2008 |
Abstract:
At present, there is a worldwide competition between products made of aluminum and al-ternative materials, for example carbon fiber reinforced plastic (CFK), and their application in aerospace engineering. In order to promote the advantages of aluminum extrusion products, innovative production processes like composite extrusion have been developed in recent years. The continuous reinforcement of aluminum profiles enables an increase in strength and stiffness and, furthermore, ensures safety against crack growth or a reduction of profile weight depending on the choice of reinforcement material [1, 2]. Special bridge dies are utilized to divide the aluminum base material into different feeders and to supply the reinforcement in between the material flow at the moment when the mate-rial rejoins in the welding chamber. Thus, the reinforcement is embedded in the longitudinal seam weld of the composite profile. However, with the insertion of reinforcement, a problem can occur which is negligible in the conventional extrusion process. Namely, depending on the material flow conditions in the die, reinforcing elements are deflected horizontally and vertically in relation to the supply position, which yields a change in the mechanical proper-ties like moment of inertia. In [2] Schomäcker analyzed the main effects of the positioning failures. He examined the process experimentally and found out that the position of the elements is mainly influenced by the press on, the temperature distribution, the forming velocity, the die design and the position of the supply channels. It is obvious that the degree of difficulty to predict the material flow rises with the complexity of the die. Hence, for high-quality die designing, technical know-how is necessary, which has to be acquired over long time. But the process comprehension is limited so that cost intensive trial-and-error experiments are often essential. In case of com-posite extrusion, Schomäcker established that an experimental analysis of all influencing pa-rameters on reinforcement positioning exceeds the economic efficiency of the die develop-ment process. For this reason, the use of numerical simulations becomes more interesting. Especially, in the course of the process, the proceedings in the inaccessible die, such as distribution of the material flow, temperature, and pressure, can be visualized [3]. In [4] Schikorra presented two methods to predict the longitudinal seam weld. It could be shown that the effective strain rate or the equivalent strain and the particle tracings are the criteria for the longitudinal seam weld position and concluded that these criterions can be helpful to improve reinforcement positioning. However, the determination of the seam weld position was mainly performed optically and thus implies a more qualitative character. In order to substantiate these criteria it is necessary to predict the longitudinal seam weld more accurately and in an automated way. Especially in case of an automated process optimization, it can be helpful to approximate the seam weld, for example, by polynomials. The polynomials can than be useful as an optimiza-tion criterion. In the present paper, an automated detection of the longitudinal seam weld using particle tracing is presented. Furthermore, the first results in method development will be introduced. The method is illustrated on a double-T shaped profile and applied on parameter variations by means of die temperature distribution and feeder cross-section variation.