Advanced Materials Research Vol. 10

Abstract: The production of continuously reinforced profiles by use of aluminium as base material and a reinforcement made of steel or carbon offers a great potential for modern lightweight constructions. Within this scope, they present the potential for an increase in usage of space frame constructions in automotive or aerospace engineering. But with the insertion of reinforcement in the material flow of the extrusion process some problems can occur that are negligible in thee conventional extrusion processes: in the composite development area a significant local perturbation of the material flow is induced that can lead to the induction of high tensile stresses into the reinforcement. Due to this, failures like cracking of the reinforcement elements during the extrusion process has been detected in experimental investigations. A second problem occurring is the necessity of prediction of the seam weld position and prediction of the seam weld quality. The reinforcement can only be induced by bridge dies between two strands and due to this it is always positioned in a seam weld. While in conventional extrusion the seam weld positions is often only an aesthetical problem, now this position mainly influences the extruded profiles properties like moment of inertia. This paper deals with the problem of determination of seam weld position on the example of a double-t-profile extrusion. By use of a coupled thermo-mechanical finite element simulation with the commercial FE code HyperXtrude from Altair the velocity fields of an extrusion process with and without reinforcement were calculated and the resulting material flow was analysed. The numerical results went along with experimental investigations to verify the calculated results.

Abstract: Lightweight structures are an important element in today’s production industry. For the multi-axis milling of these structures some aspects have to be considered to achieve a good surface quality and to prevent damaging the milling machine during the machining process. In this article methods to determine suitable feed rates for the milling process, to identify parts of the workpiece with too much heat build-up, and to avoid collisions between workpiece and machine parts are presented. For this purpose a milling simulation based on a multi-dexel field workpiece model has been developed, in which two types of feed rate adaptation have been integrated. Work on a built-in temperature development simulation and collision control is in progress.

Abstract: Most technical components applied in industrial practice are subjected to metal cutting operations during their production process. However, this leads to undesirable thermal and mechanical loads affecting the machined workpiece, which can result in an impairment of its serviceability. Due to their small wall thickness lightweight hollow profiles are highly susceptible to the inevitable machining loads and thermal stresses during drilling processes. For the virtual optimization of the machining process and in order to ensure a suitable process strategy, a finite element simulation of cutting operations for thin-walled light metal profiles is conducted. Due to the flexibility within creating drill holes of different diameters without tool changes circular milling represents a promising alternative to the application of conventional drilling tools for variable process strategies to handle batch sizes down to one piece efficiently. Hence, this article gives an insight into the investigations regarding the modeling concepts of the mechanical and thermal loads induced into the thin-walled lightweight frame structure during the circular milling process. Furthermore, process reliability aspects as well as the correlation of the calculated and the measured results will be discussed on the basis of experimental investigations. Finally, this article compares Finite Element Analysis aspects of circular milling processes with conventional drilling processes.

Abstract: This paper describes the analysis of thermal and mechanical effects during welding and the following cooling-phase on a welded structure. An off-the-shelf aluminum-profile, as used in other simulation sub-projects of the research center, was chosen as a sample part for the simulation tests. Taking up an important production scenario of lightweight-production, the frontal closing of two profiles is modeled. The development of residual stresses and the distortion is investigated by a thermo-mechanical FE-simulation. The virtually examined process is provided by a hybrid, bifocal laser system consisting of both an Nd:YAG-laser and a high power diode laser (HPDL). For comparison, a single Nd:YAG-process was simulated, too. The theoretically different generation of residual stresses can be verified within the simulation.

Abstract: An optimization approach is derived from typical design problems of hybrid material structures, which provides the engineer with optimal designs. Complex geometries, different materials and manufacturing aspects are handled as design parameters using a genetic algorithm. To take qualitative information into account, fuzzy rule based systems are utilized in order to consider all relevant aspects in the optimization problem. This paper shows results for optimization tasks on component and structural level.

Abstract: With a novel extrusion process which is investigated in the Collaborative Research Center Transregio 10 (SFB/TR10), it is possible to manufacture spatially curved aluminum profiles. This process is the base for an automated small and medium size batch production of light-weight frame structures. For the handling and machining of the spatially curved profiles, highly flexible machines and manufacturing equipment are needed. Today’s automated process chains do not reach a sufficient flexibility. This article introduces a new approach to handle and machine spatially curved profiles using a flexible gripping and clamping system. Firstly, the requirements concerning the process comprehensive gripping technology, which have to be fulfilled for a flexible small and medium batch production of light-weight frame structures, are specified. Subsequently, the function and design of a flexible gripping and clamping system are described. Furthermore, metrological processes to maintain a once reached condition of order during the entire process chain are depicted.

Abstract: The importance of rigid and self supporting space frame structures for the automotive and aerospace industry continually increases. To meet the market requirements for a flexible and competitive small batch production, innovative machine concepts must be investigated. By integrating handling and machining capabilities into one machine structure, redundant degrees of freedom can be reduced and a former idle economic potential can be made use of. This paper introduces a systematic approach to reveal synergetic potentials that emerge by integrating two different fields of function, the handling and the machining. Therewith a matrix with technical solutions for a combination of handling and machining is generated. These solutions are the base for new machine concepts that fulfill both tasks with a minimal number of machine axes. The authors present a machine concept which is combined out of a four-axes parallel kinematics and a conventional serial kinematics. The two kinematic structures collaborate and allow the product flexible handling and machining of three dimensional rounded extrusions with a minimal technical effort. The machine concept is dimensioned and optimized for a maximal stiffness by the coupling of a multi body simulation to an external parameter optimization software. The optimization results show that the stiffness of the machine concept could be explicitly improved. This paper is based on investigations of the collaborative research centre SFB/TR10 which is kindly supported by the German Research Foundation (DFG).