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The usage of ultra-high strength aluminium alloys (EN AW-7000 series) offers a great weight saving potential due to the high rigidity and specific strength values. Various heat assisted forming technologies have been developed in order to improve the limited formability at room temperature and thus to be able to increase the geometrical complexity of such sheet metal parts. In this study the forming behaviour of EN AW-7021 sheet metal alloy is described as a function of the forming process and the corresponding temperature profile. The forming limit curves (FLCs) are obtained by experimental Nakajima tests using the Warmforming, Hotforming, extended Hotforming and W-Temper process route. For this purpose, a Nakajima testing tool is designed according to ISO 12004 standard which allows operating temperatures of up to 200 °C.

Silicon carbide is a superior material for the manufacturing of semiconductors. This is where the project on the gaseous phase synthesis of SiC components made of carbon precursors comes in. On the basis of graphite substrates and a reaction with thermally evaporated silicon monoxide in the CVI process (chemical vapor infiltration), silicon carbide with strongly process dependent structural composition is formed. The process can be used for the coating of C substrates as well as for the manufacturing of complex components. With the help of new approaches in process development and via detailed materialographic microstructural analysis, the understanding of gaseous phase synthesis was promoted. The transition of different carbon structures in equivalent silicon carbide structures was verified.

The surface finish of an injection mould influences the quality of the moulded polymer optic parts. In order to improve and control the surface finish of the mould it is important to be able to predict the material removal during the polishing process of this mould. The aim of this work is to predict the material removal during the polishing process, comparing the results obtained from polishing attempts on steel samples and the results obtained from a simulation model. A simulation model is developed with the abrasive wear Holm-Archard equation in ANSYS. This simulation model will help to eliminate the iterative trial and error polishing, therefore facilitating the steel mould production.

Polishing as a step of the manufacturing process is not only used in the finishing of optical elements made out of glass. An increasing number of applications needs shiny or glossy surfaces. For these parts, the specified roughness has to be achieved by a final polishing step while keeping or improving the final shape. The goal of the presented research is to predict the material removal that occurs during the polishing process by a simulation based on finite element modelling (FEM). The presented finite element simulation model for PMMA is based on the material parameters for workpiece and polishing tool. Compared to previous research on aspherical elements made out of glass [1], the model allows the description of the process based on material parameters get out the data sheets. The data derived from the finite element modelling is compared with the polishing results on plastic materials (PMMA). Results of the polishing tests compared with the simulated values will be reported.

Ophthalmic lenses, sensors, and sunglasses, among other things, are commonly made of polymer materials. Therefore, polymer optics is a growing market mainly for medium quality but also for precision optics. Polymer optics are usually produced in an injection molding process. Due to high quality requirements on the final product, the manufacturing process of the molds has to be very accurate and precise. Thus the master tool has to be fabricated to a high quality with regard to shape accuracy and roughness. The focus of this article is on the process chain for the fabrication of molds for polymer optics and the finite element simulation of this process. The typical existing process chains contain steps like nickel plating, diamond machining and manual polishing. Some of these steps are expensive and require very experienced staff. In the new process chain, an industrial robot with special tools is used for lapping and polishing. Robot polishing replaces the former nickel plating, diamond machining, and man...

This paper investigates the mechanical properties of a new type of hollow sphere structure. For this new type, the sphere shell is perforated by several holes in order to open up the inner sphere volume and surface. The mechanical behaviour of perforated sphere structures under large deformations and strains in a primitive cubic arrangement is numerically evaluated by using the finite element method for different hole diameters and different joining techniques.

Hollow sphere structures are a new group of advanced lightweight materials for multifunctional applications. Within the scope of this paper, the uniaxial deformation behaviour in the regime of large deformations is investigated. Appropriate computational models are developed to account for the deformation mechanisms occurring under high deformations. Macroscopic stress-strain curves are derived and the influence of different material parameters is investigated.

Hydroforming or internal high pressure (IHP) forming is a manufacturing process which involves the use of internal pressure and axial loads to reshape components in a specially designed die piece. The internal pressure and axial force are defined as a function of time, and usually referred to as load-curves. This paper describes the principles involved in the design of load-curves for the simulation and production of a component part using IHP.

Currently one difficulty presented in the induction melting and casting of Pu is stirring of the metal during melting. Stirring is typically performed mechanically by an operator, who plunges a stir rod into the melt, or by a complex mechanical system. These methods have several inherent problems; vacuum degradation associated with mechanical actuation through containment and plunging of impurity rich skull back into the melt which has been shown to introduce casting defects.

This paper investigates the effect of cooling rate on the grain size and microstructure of Mg AZ31B alloy cast at a superheat of 8°C using the Magnetic Suspension Melting (MSM) process, which is capable of melting and casting at superheats less than 5°C. In this study, the Mg alloy was unidirectionally solidified in a bottom-chill mold with stainless steel and copper chill blocks. The solidification parameters, namely growth velocity (V) and temperature gradient (G), were determined from numerical simulation of the cooling curves, which was found to be in good agreement with measurements. For the investigated solidification rates, metallographic examination showed globular solidification morphology, and the grain size was inversely proportional to the square root of the cooling rate. Microprobe analysis of the cast ingots also showed that Al segregation occurs primarily at the grain boundaries, and the solidification rate affects the size and distribution of both the secondary α phase and the intermetallic Mg17Al12 phase.

Bislang benotigten FT-ICR-Systeme grose, kryogen gekuhlte Magneten. Ein neues, hochauflosendes Gerat, welches auf 1 Tesla starken Permanentmagneten basiert, ist nur noch so gros wie ein Rollcontainer.

Magnesium is the lightest of all structural metals and offers significant weight savings compared to traditional automotive materials. This paper describes the macrostructure and the micro structure of Mg AZ31B alloy produced via the Magnetic Suspension Melting (MSM) technique at a low superheat of 5°C. It was found that casting at this low superheat produced a fine globular grain structure in comparison to a dendritic structure in conventionally cast alloys. The intermetallic phases were analyzed in detail and compared with the conventionally cast alloy. In the MSM cast alloy, the Mg17Al12 phase formed mainly at the grain boundaries, in contrast to typical dendritic entrapment of this phase within the grains in conventional castings. The formation of the Al-rich secondary-α phase during solidification was investigated. The effects of this morphology change on mechanical and fracture behavior of this material are presented. These results are discussed relative to conventionally cast Mg alloys.

Forming complex parts out of high and ultra-high strength aluminium alloys has proved to be more challenging in comparison to the currently used deep drawing steels. The novel "Warmforming-Process" offers the potential to produce light and highly integrated one-piece components out of such aluminium alloys at elevated temperatures. When considering aluminium alloys in the 7000 group, which can reach strength values (UTS) far above 600 MPa, crash components such as side impact bars would offer a suitable field of application. It is important when taking into consideration the geometric design of structural components to utilise their load bearing characteristics in an efficient manner. This structural optimisation lends itself well to computational simulation techniques, which are essential in the evaluation of appropriate geometry and sizing of complex structures with challenging load scenarios. Crash simulations using the nonlinear finite element method (FEM) of side impact protection beams have been used to demonstrate the weight saving potential of high and ultra-high strength aluminium alloys. A beam design formed from a 7000 series alloy was taken as a reference. Substituting various materials, inter alia press hardened steel (phs), and benchmarking against the original beam's crash performance, by changing the material thickness, equivalent beams were produced. The thicknesses of the beam geometries have been evaluated by "sizing optimisation" and their possible mass reduction are compared against each other. The nonlinear FEM simulations show good agreement with a corresponding set of experimental results. It was seen that for a common crash performance the ultra-high strength aluminium alloys outperform press hardened steel components in terms of their weight. Thus, there is a significant weight saving potential to be realised if crash components are manufactured using 7000 series aluminium alloys. In this work, the weight saving potential was found to be in the region of 20 - 25%.