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15th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2015

作者： Börner, Richard Scholz, Peter Kühn, Ralf Schubert, Andreas Zeidler, Henning Müller, Roland Technische Universität Chemnitz Prof. Micromanufacturing Technology Chemnitz09107 Germany Fraunhofer Institute for Machine Tools and Forming Technology IWU Chemnitz09126 Germany

ISBN: (纸本)9780956679079

Sheet metal forming is characterised by strong frictional forces involving an increase of the temperature and a tendency to adhesion. Consequently, use of lubricants is essential yet, especially for forming of Aluminium alloys. Furthermore, lubricant reduces tool wear. However, for economical and ecological reasons, dry forming is highly desired. Avoiding the application of lubrication requires a reduction of the coefficient of friction and the tendency for adhesion in dry forming processes. One approach is to increase the nominal surface pressure by micro structuring the tool. Additionally, different carbon based layers (a-C:H:Si and CVD diamond) are applied on the tool to reduce wear and tendency to adhesion. For using a a-C:H:Si layer, uncoated steel drawing tools are micro structured with calottes by milling. Because of a higher thickness of CVD diamond layers, calottes have to be generated directly in the coating using ablating processes like electrical discharge machining. To emulate the tribological system of a sheet metal forming process and characterise it, strip drawing tests are done. For a-C:H:Si coated drawing tools, the test results show a significant reduction of the coefficient of friction in micro structured, compared to polished drawing tools. To further increase the wear resistance of the tool it is intended to apply CVD diamond layers on steel tools as soon as the process is operational.

关键词： Metals

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Formability enhancement in incremental forming for an automotive aluminium alloy using laser assisted incremental forming

Formability enhancement in incremental forming for an automo...

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16th International Conference on Sheet Metal, SheMet 2015

作者： Mohammadi, Amirahmad Vanhove, Hans Van Bael, Albert Weise, Dieter Duflou, Joost R. KU Leuven Department of Mechanical Engineering Belgium KU Leuven Department of Materials Engineering Belgium Fraunhofer-Institut for Machine Tools and Forming Technology IWU Department Sheet Metal Processing and Basics Chemnitz Germany

ISBN: (纸本)9783038354505

The aim of this study is to establish general guidelines for minimizing the number of tests required to determine optimum process parameters in terms of formability for laser assisted single point incremental forming (LASPIF). An automotive aluminium alloy (AA5182-O) is selected and the room temperature failure angle of this material is determined experimentally. The straining behaviour as well as sheet thinning of the test part (at its maximum forming angle) is studied using an experimentally validated finite element model. From the thinning rate of the sheet metal and the shape of the contact zone between tool and sheet it is concluded that continuous straining of the sheet on the wall region of the contact area is responsible for extra thinning and failure. Based on the size and position of the contact zone, different laser tool positioning strategies have been used to achieve the highest forming angle. It is concluded that due to an elongated shape of the contact zone in steep wall angle parts and considering a small deviation of the forming robot, the selection of a large spot diameter is necessary in terms of maximum obtainable wall angle. It has been observed that the maximum forming angle is still achievable using a large forward offset. It is concluded that the partial stress-relief annealing of the deformed geometry during the approach of the forming tool, is responsible for this formability enhancement. © 2015 Trans Tech Publications, Switzerland.

关键词： Finite element method

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Adhesive distribution and global deformation between hybrid joints 18th

Adhesive distribution and global deformation between hybrid ...

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18th International ESAFORM Conference on Material forming, ESAFORM 2015

作者： Landgrebe, D. Mayer, B. Niese, S. Fricke, H. Neumann, I. Ahnert, M. Falk, T. Fraunhofer Institute for Machine Tools and Forming Technology IWU Nöthnitzer Straße 44 Dresden01189 Germany Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM Wiener Straße 12 Bremen28359 Germany

ISBN: (纸本)9783038354710

In multi-material-design, e.g. in the automotive industry, mechanical joining processes like self-pierce riveting are well established, because of their amount of advantages. However, adhesive bonding with one-component structural adhesives is increasingly being used. The combination of the specific advantages of both joining techniques in the form of hybrid joints leads to synergies of quality and reliability, such as high corrosion resistance and better damping properties. A critical issue is the generation of global deformations of the different parts of the mechanical joints. These global deformations of the sheet metal between two or more mechanical connectors (e.g. rivets) are caused by the formation of adhesive bags during the riveting process, before the adhesive curing takes place. This research focuses on the time-dependent formation process of these bags. The aim is to achieve a reduction of global deformations based on detailed knowledge of the adhesive flow during the manufacturing of the joint by means of experiments and simulations. For this purpose experimental techniques and measurement methods for deformations over time are presented for different setups of hybrid joint types of self-piercing rivets in combination with adhesive bonding. The challenge is to track rapid and small surface deformations very accurately in the ongoing mechanical joining process. High-speed optical measurement technology like Point-Tracking and surface scanning are used to track the resulting deformations experimentally. Numerical investigations, which include the interaction of the solid matter influenced in the mechanical joining process and the fluid adhesive, are presented. On the basis a fully coupled fluid-structure interaction simulation of a single hybrid joint, a surrogate model for a multi-point hybrid joint is developed. The comparison of experimental data with simulations allows deriving the pressure distribution and flow velocities inside the adhesive layer.

关键词： Automotive industry

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Resource Networks: Decentralised Factory Operation Utilising Renewable Energy Sources

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Procedia CIRP 2015年 26卷 486-491页

作者： Johannes Stoldt Enrico Franz Andreas Schlegel Matthias Putz Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 09126 Chemnitz Germany

Striving for sustainability, most industrialised countries make increasing use of renewable energy sources to meet their energy demands. This causes power generation to become more decentralised and volatile, making flexibility in production (i.e. energy demand) a fundamental necessity for manufacturing companies. Hence, it is to be expected that companies which attain a symbiosis of renewable energy applications, efficient technologies, and innovative approaches to production organisation will have a competitive advantage in the future. The EU funds research in this direction as part of the REEMAIN project, amongst others. In particular, a concept for Resource Networks is developed. These networks aim to manage production using renewable energy sources by dividing a complex factory into smaller subsystems including energy suppliers and consumers, as well as storages to reach this symbiosis. This paper explains the concept and its application within fraunhofer IWU's E 3 -Research Factory.

关键词： Energy efficiency Manufacturing system Production Renewable energy sources Sustainable development

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Improving the ramp-up process of a body-construction line by numerical supported design of clamping devices and FEM based tolerance prognosis 18th

Improving the ramp-up process of a body-construction line by...

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18th International ESAFORM Conference on Material forming, ESAFORM 2015

作者： Landgrebe, Dirk Ackert, Patrick Grützner, Raik Weber, Johannes Mauermann, Reinhard Tegtmeier, André Fraunhofer Institute for Machine Tools and Forming Technology Nöthnitzer Straße 44 Dresden01187 Germany Porsche Leipzig GmbH Porschestraße 1 Leipzig04158 Germany

ISBN: (纸本)9783038354710

Car body manufacturing begins with sheet metal forming, while in subsequent steps the inner structures of the vehicle are assembled and connected to the outer skin by hemming. The use of FEM (finite element method) to assistant in ramp-up processes of car body construction lines is increasing, thanks to developments in recent years. Several methods to predict the distortion of joining and the dimensional effect of clamping during the assembly process were presented and validated. Dimensional effects of the clamping process are basically the result of a deliberate alignment, other than the given values of construction to compensate dimensional inaccuracy of single parts from the body shop. These deliberate alignments are generally effected through a translation of clamps and pins in the clamping device. Until now, most of the methods of clamping and joining simulation presented have been verified using academic samples. In this report, the quality of forecasting in real problems during a ramp-up process will be verified and expanded. As part of a national project, co-funded by Sächsische Aufbaubank (SAB), the potential of FEM to assist in the ramp-up process were reviewed in a cooperative effort between Porsche Leipzig GmbH and fraunhofer institute for machine tools and forming technology (IWU). Furthermore, it will be shown that developed methods are able to represent the influence of deliberate positioning of clamps in complex samples. © (2015) Trans Tech Publications, Switzerland.

关键词： Finite element method

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Dry forming of aluminium sheet metal: Influence of different types of forming tool microstructures on the coefficient of friction 18th

Dry forming of aluminium sheet metal: Influence of different...

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18th International ESAFORM Conference on Material forming, ESAFORM 2015

作者： Scholz, Peter Richard, Börner Kühn, Ralf Müller, Roland Schubert, Andreas Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany Technische Universität Chemnitz Reichenhainer Str. 70 09126 Germany

ISBN: (纸本)9783038354710

In the sheet metal forming industry lubricants are applied in forming processes to expand the technological boundaries by reducing friction and wear. The friction between tool and sheet metal is crucial to the deep drawing process. Due to economic and ecological reasons the aim of the manufacturers is to reduce or even avoid the use of lubricants. Consequently, this approach enables both a shortening of the process chains and an essential saving of resources. The advantages of structured forming tools in lubricated processes concerning the reduction of the coefficient of friction by the appearance of lubricating micro pockets are well-known. However, without using any lubricant this effect does not work. In this case the contact area is reduced by structuring the forming tool which affects the tribological system. In this paper the influence of microstructures with different geometries and surface treatments (uncoated / a-C: H: Si-coating) on the coefficient of friction in dry metal forming of the alloy AA5182 is compared to the frictional behaviour of unstructured forming tools using lubricant as reference. Before coating, the forming tools are machined by milling to generate tribologically effective microstructures. With the use of a strip drawing plant the effects of different surface microstructures and materials on the coefficient of friction are investigated. © (2015) Trans Tech Publications, Switzerland.

关键词： Lubricants

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Challenge of machining aluminium matrix composites reinforced by diamonds 15

Challenge of machining aluminium matrix composites reinforce...

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15th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2015

作者： Schubert, Andreas Zeidler, Henning Flemmig, Sebastian Penzel, Michael Krönert, Maik Meichsner, Gunnar Essel, Shai Prof. Micromanufacturing Technology Technische Universität Chemnitz Chemnitz09107 Germany Fraunhofer Institute for Machine Tools and Forming Technology Chemnitz09126 Germany Israel Institute of Metals Technion Haifa Israel

ISBN: (纸本)9780956679079

To increase the efficiency of heat transfer and cooling systems, high thermally conductive materials have to be developed. Using Aluminium reinforced by Diamond particles, thermal conductivity and heat dissipation can be enhanced in correspondence to particle size. Due to the high hardness of diamond the machinability decreases. A cutting machining process is not feasible because of the high tool wear. In this study two possible ablating techniques, Pulsed Electrochemical Machining (PECM) and Micro Electro Discharge Machining (μEDM) are assessed. It is shown that with both methods machining and shaping of AMCs, reinforced by monocrystalline diamonds, is possible. Due to the chemical stability of the diamond particles only the base material of Aluminium has been electrochemical machined. Similar to PECM, and also for μEDM, ablating is a selective machining process, but here an approach for further ablating possibilities is given. The achieved surface roughness is dependant on the particle size of the Diamond.

关键词： Thermal conductivity

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Laser Metal Deposition as Repair technology for a Gas Turbine Burner Made of Inconel 718

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Physics Procedia 2016年 83卷 761-768页

作者： Torsten Petrat Benjamin Graf Andrey Gumenyuk Michael Rethmeier Fraunhofer Institut for Production Systems and Design Technology Pascalstraße 8-9 10587 Berlin Germany Federal Institute for Materials Research and Testing Unter den Eichen 87 12205 Berlin Germany Technical University Berlin Institute of Machine Tools and Factory Management Pascalstraße 8-9 10587 Berlin Germany

Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition.

关键词： Laser metal deposition Inconel 718 additive manufacturing maintenance repair and overhaul

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Investigation of tribological properties of AlMg4,5Mn0,7 in a warm forming process using the barrel compression test 18th

Investigation of tribological properties of AlMg4,5Mn0,7 in ...

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18th International ESAFORM Conference on Material forming, ESAFORM 2015

作者： Müller, Benedikt Jahn, Stephan F. Fang, Ru Schubert, Andreas Technische Universität Chemnitz Reichenhainer Str. 70 Chemnitz09107 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

ISBN: (纸本)9783038354710

Within the German Collaborative Research Center 39 PT-PIESA the forming of micro cavities into aluminum sheets is one challenging task. During this forming process high forces and stresses occur which lead to a high tool wear. Hence, the actually applied cold forming process should be replaced by a warm forming process. This paper shows the tribological investigations for the warm forming process. Within the experiments the barrel compression test [1] is used to determine the friction conditions by varying the size of the cylindrically shaped samples of AlMg4,5Mn0,7, the forming degree and the lubrication condition (dry, graphite, forming oil). The flat punches were made from hardened steel 1.3343. The friction factor was calculated, and surface roughness was evaluated by 3D-laser microscopy. The experiments show that the friction factor increases, especially at forming degrees below 1 and for small specimen size, compared to cold forming processes [2]. In addition to that, an influence of the lubrication condition onto the surface roughness was observed. For experiments conducted with graphite, the surface roughness is significantly higher than for samples, which were formed dryly or with forming oil. © (2015) Trans Tech Publications, Switzerland.

关键词： Graphite

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Optical micro-metrology of structured surfaces micro-machined by jet-ECM 15

Optical micro-metrology of structured surfaces micro-machine...

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15th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2015

作者： Quagliotti, Danilo Tosello, Guido Islam, Aminul M. Hansen, Hans N. Zeidler, Henning Martin, André Schubert, Andreas Brandao, Carla Riemer, Oltmann Technical University of Denmark Department of Manufacturing Engineering Kgs. Lyngby2800 Denmark Chemnitz University of Technology Faculty Mechanical Engineering Institute for Machine Tools and Production Processes Chemnitz09107 Germany Fraunhofer Institute for Machine Tools and Forming Technology IWU Chemnitz09126 Germany University of Bremen Laboratory for Precision Machining Bremen28359 Germany

ISBN: (纸本)9780956679079

A procedure for statistical analysis and uncertainty evaluation is presented with regards to measurements of step height and surface texture. Measurements have been performed with a focus-variation microscope over jet electrochemical micro-machined surfaces. Traceability has been achieved using as reference contact measurements from a calibrated stylus instrument. A statistical analysis has been carried out and the method of least squares has been implemented to correct for systematic behaviours. The combined uncertainty has been evaluated accordingly and the expanded uncertainty has been finally calculated as the confidence interval of 95 %. Results show that agreement within single digit micrometre (dimensional measurements) and tenths of micrometre (surface parameters measurements) can be achieved with the proposed methodology.

关键词： Least squares approximations

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