Extruded aluminium profiles with a variety of different cross-sections are mainly used in lightweight structures for transportation means. Examples are stringer profiles in the fuselage of airplanes or profiles in chassis of trains and cars. Nowadays, the mass reduction of a lightweight structure is an important issue to achieve lower fuel consumption and CO2 emissions. With an increased portion of aluminium profiles the mass of structures can be reduced considerably in contrast to the application of steel parts, due to the lower density of aluminium. However, this is coupled with disadvantages such as the lower specific stiffness and strength of the material. One possibility to improve the mechanical properties of aluminium profiles without a considerable increase of their weight is the embedding of reinforcing elements during the extrusion process. Special porthole extrusion dies are used to feed reinforcing elements in form of high strength steel wires separate from the aluminium material flow. In the welding chamber of the die both materials bond together to a composite profile. To achieve a high advantage of the technology for lightweight applications a high reinforcing volume of aluminium profiles is targeted. A comparatively high reinforcing volume can be reached either by a high number of reinforcing elements or through a reduction of the profile wall thickness. A high number of reinforcing elements leads to a small distance between the single elements in the profile cross-section. The paper will show the results of an experimental and numerical analysis which were carried out to determine the minimum distance between the reinforcing elements as well as the minimum profile thickness. In the trials different arrangements of the elements in the profile cross-section and profile thicknesses were considered. Main parameters which have an influence on the process stability were analyzed and a process window for the manufacture of thin profiles with high reinforcing volume was deduced.
In this paper experimental investigations aimed at measuring the die deformations during aluminum extrusion process is presented and discussed. A two-holes die generating two U-shape profiles with different supporting legs was produced and tested under strictly monitored conditions. The influence of die deformation on the speed, temperature distribution and distortion of the two profiles is reported and analyzed. AA6082 alloy was used as deforming material while H-13 hot-work tool steel was selected as die material. The experiments were repeated at least three times in the same conditions in order to achieve a statistical distribution of the acquired data: such data are then used as a reference for the 2009 edition of the extrusion benchmark.
Abstract. Extruded aluminum profiles are essential for lightweight constructions in contemporary transport and automotive applications. The reinforcement of such aluminum-based profiles with high-strength materials offers a high potential for weight reduction and an improvement of functional and mechanical properties. In comparison to conventional composite extrusion using fiber or particle reinforced billets, the alternatively developed process for the embedding of endless reinforcing elements provides enormous advantages regarding extrusion forces, load-adapted reinforcement, and tool abrasion. In this extrusion process with conventional billets, modified tools with portholes are used to position reinforcing elements from outside the pressing tool and to embed them into the material flow during the pressing operation. This composite extrusion process is part of the research work started in 2003 and carried out within the scope of the Collaborative Research Center SFB/TR10. To increase the potential of composite extrusion with endless reinforcing elements, the manufacture of composite extrusion profiles with high-strength non-metallic alumina wires is planned. Due to the wires' specific properties, e.g. high stiffness, their deflection behavior must be analyzed to guarantee a stable feeding-in process. In this paper the specific behavior of alumina reinforcing elements regarding the feeding-in process is analyzed by experimental investigations. The main influencing factors are determined and a process window is deduced.
Aluminum matrix composite extrusions reinforced with wires made of high strength stainless steel represent an innovative material concept for lightweight structures. The use of reinforcing elements should improve the mechanical properties and the performance of lightweight structures. This study deals with the process chain of extrusion and die forging to manufacture steel-reinforced products. The production of discontinuously-reinforced, semi-finished aluminum profiles by co-extrusion is in focus on the extrusion part. The material flow is analysed in order to understand, and further to influence, where the steel-reinforcements are appear in the strand. For the forging part the extruded profiles are continuous-reinforced by means of steel wires as well as partially by means of steels elements. For the process design the geometry of the forging die cavity and the material flow are of vital importance. A Finite Element Analysis is carried out in order to predict the position of the elements in the forging parts depending on the position in the extrusions.
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