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Screening-based evidence of the impact of geometrical deviations on inner stresses on mechanical presses

Procedia Manufacturing 2019年 27卷 185-191页

作者： N. Wagner T. Päßler Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Straße 88 09126 Chemnitz Germany

In recent years various cases of damage analysis have shown an increasing number of overload scenarios resulting in failures of entire press structures. This happens in spite of manufacture-compliant utilization and a correct press design process based on state-of-the-art methods such as FEM simulation. This paper proves the hypothesis that geometrical tolerances, defined clearances and geometrical signs of wear have a significant impact on residual stress of a press, by conducting an empirical sensitivity analysis. The focus is on mechanical presses with four-point leverage actuation as an example for highly over-determined press structures. As proven by FEM simulation, the identified geometrical deviations result in a preload of the press structure, amounting up to 10% of its theoretical sustainable stress. The significant impact of geometrical deviations on the residual stress has been proven successfully for the empirically determined assumption.

关键词： Press Tolerancing Residual stress

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Production planning for optimal mass pre-distribution for axial feed cross rolling

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Procedia Manufacturing 2019年 27卷 192-196页

作者： N. Schubert J. Steger M. Gerlach B. Lorenz Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 09126 Chemnitz Germany

At present, the process selection, the selection of tools and tool materials are key functions for the economic efficiency of manufacturing lines. The continuous improvements in production technology, including the related machine and tooling technology, have made it possible to increase both economic efficiency and resource efficiency in production. As a result of the market demand for a high variety of products and the constant change in the demand structure, the requested volume of individual product types is reduced – the trend towards small-series production is constantly increasing. In hot bulk forming processes, it is usually not possible to produce the workpiece in just one forming step. As an alternative to the well-known machining processes for optimized preforms, the axial feed cross rolling process was developed from wedge cross rolling. Due to the all-purpose tools, the use of this process is already economical for very small batch sizes. In order to achieve optimum results with regard to optimized mass pre-distribution, the process parameters during rolling must be kept within close limits. If this is the case, axial feed cross rolling allows additional material savings of between 12% and 15% compared to other preforming processes. In order to achieve best results, the preform operation is designed by using FE simulation axial feed cross rolling.

关键词： Hot deformation Production planning Finite element method (FEM)

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Additive manufacturing technologies for next-generation powertrains

Additive manufacturing technologies for next-generation powe...

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International Electric Drives Production Conference (EDPC)

作者： Philipp Fiedler Sebastian Stelzer Nikolaus Milaev Robert Richter Frank Kaulfuß Thomas Windisch Jan Bräunig Fraunhofer Institute for Machine Tools and Forming Technology IWU Dresden Germany 3D-Printpetrol Großenhain Germany Fraunhofer Institute for Material and Beam Technology IWS Dresden Germany Division Engineering of Adaptive Systems Fraunhofer IIS/EAS Fraunhofer Institute for Integrated Circuits Dresden Germany

ISBN: (数字)9781728184586

ISBN: (纸本)9781728196145

The paper addresses the prototypical development and implementation of an innovative and functionally integrated gear stage for next-generation electric vehicles, produced by using Laser Beam Melting (LBM) and Fused Deposition Modeling (FDM). Two new design targets are addressed by our approach: Oil-free operation is achieved by innovative coating of gear teeth which enables almost maintenance-free operation. Furthermore, a higher damping of sound transmission from tooth mesh to bearings is implemented by an optimal wheel body geometry that is realized by a combination of printable carbon-containing polymers (flange) and steel (gear rim). The innovative approach is to extend components by areas that cannot be produced by milling and casting, e.g. complex structures, contour-following fluid-carrying cooling elements by means of LBM, thus creating a significant benefit compared to state-of-the-art gearboxes. Function integration made possible by additive manufacturing results in a very high component complexity. It is combined with gear grinding and final ta-C coatings ensuring maximum efficiency in dry operation, to achieve economically viable production processes. The increase in tooth mesh efficiency is achieved by optimization approaches in the design to minimize heat losses while at the same time maintaining highest possible strength and lowest noise emission.

关键词： Gears Wheels Production Three-dimensional printing Laser beams Coatings Next generation networking

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Improvements to a method for determining leg length following total hip arthroplasty

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Journal of Medical Engineering and technology 2020年第2期44卷 69-75页

作者： Wendler, Toni Heilemann, Martin Grunert, Ronny Möbius, Robert Schmidt, Michael Schleifenbaum, Stefan Prietzel, Torsten Centre for Research on Muscoskeletal Systems Leipzig University Leipzig Germany Faculty of Medicine Institute of Anatomy Leipzig University Leipzig Germany Department of Orthopaedic Trauma and Plastic Surgery Leipzig University Leipzig Germany Fraunhofer Institute for Machine Tools and Forming Technology Dresden Germany Department of Neurosurgery Leipzig University Leipzig Germany Department of Orthopaedic Trauma and Plastic Surgery Zeisigwaldkliniken Bethanien Chemnitz Chemnitz Germany

Discrepancy in leg length does frequently occur as a side effect of total hip arthroplasty and may lead to reduced patient satisfaction as well as injury in the sequalae. It is consequently important to reduce leg length discrepancy where-ever technically possible. This may be achieved by recording precise intraoperative measurements and using different sized implanted components. The aim of the given study was to improve the accuracy of a previously validated optic measurement system (OMS) to reduce leg length discrepancy. This pre-existing OMS was first trialled and based on these preliminary findings developed further. Using this improved system, measurements were taken in models and cadavers. Inter observer reliability of the improved OMS was assessed. The system is introduced in the given technical feasibility study. Its accuracy was greater in the model setup (swivel joint: 772.7 ± 1.5 mm;ball joint: 770.0 ± 3.7 mm;reference: 772 mm) compared to the trial using cadaveric tissues (588.8 ± 5.7 mm;reference: 586 mm). Results of two examiners were similar. The third one measured significantly shorter values (p=.011). The results of the measurements with the OMS indicate that a significant increase in accuracy (p = 2.076×10−6) has been achieved compared to the previously reported system, however, a further improvement to measurement accuracy is necessary for this to be applied clinically. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.

关键词： Arthroplasty

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Thermal errors in milling: Comparison of displacements of the machine tool, tool and workpiece

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Procedia CIRP 2019年 82卷 389-394页

作者： M. Putz J. Regel A. Wenzel M. Bräunig Chemnitz University of Technology 09010 Chemnitz Germany Fraunhofer-Institute for Machine Tools and Forming Technology IWU 09126 Chemnitz Germany

The paper describes an experimental method for quantifying the proportions of thermal errors of the machine tool, tool and workpiece in the total thermal error. For this purpose, the workpiece was subsequently measured and both the machine-internal and additionally built-in measuring sensors were used to quantify displacement errors. The static errors must also be detected. Based on the measured values, thermal states are calculated by regression analysis and included in the evaluation. The percentages of the single errors were calculated and gave a clear statement about the time sequences and the thermal influence of the components regarding to the total error in a milling process. The results allow an assessment of relevant areas that contribute to positioning errors.

关键词： experimental investigation thermal error machine tools milling

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Process development for self-pierce riveting with solid formable rivet of boron steel in multi-material design

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Procedia Manufacturing 2019年 29卷 271-279页

作者： Thomas Grimm Welf-Guntram Drossel Fraunhofer Institute for Machine Tools and Forming Technology IWU Nöthnitzer Straße 44 01187 Dresden Germany

Mechanical joining techniques are important joining processes for the implementation of lightweight structures in automotive engineering and other branches of industry. However, existing processes such as self-pierce riveting with semi-tubular rivet (SPR-ST) or solid rivet (SPR-S) reach their limits in certain applications, e.g. joining press-hardened boron steel sheets in multi-material constructions of automotive bodies. A new method to join these materials reliably and with high quality is the self-pierce riveting with solid formable rivet (SPR-SF). This paper shows different problems during the mechanical joining of press-hardened steel 22MnB5 by conventional SPR-S and illustrates the numerical as well as the experimental development of the new rivet concept: the solid formable rivet. On the basis of validated simulation models for conventional SPR-S numerical sensitivity analyses are carried out to investigate the correlations between the rivet properties (geometry parameters, material) and important quality characteristics of the joint like interlock, punching force and upsetting force for the new SPR-SF joining process. With the knowledge of these studies, specific rivet geometries are determined and prototypes manufactured for joining the material combination EN AW-6016 T4 ( t = 1.5 mm) into 22MnB5 ( t = 1.2 mm) in good quality. So, the application potential of the new SPR-SF is shown.

关键词： Self-pierce riveting Sensitivity analysis Boron steel Multi-material joining technology

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Parameter study on press hardened components with tailored properties

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IOP Conference Series: Materials Science and Engineering 2021年第1期1157卷

作者： M Nestler J Schönherr R Haase A Albert A Stoll V Kräusel Fraunhofer Institute for Machine Tools and Forming Technology Chemnitz Germany

In automotive industry, crash relevant parts are mainly manufactured by press hardening. An innovative process variant aims at producing components with tailored properties. For this purpose, the microstructural transformation is locally influenced to produce areas with lower strength. Hence, the forming tool is locally equipped with heating elements. Due to the non-uniform temperature distribution, the final part geometry results from a complex interaction of localized spring back, shrinkage and microstructure evolution. To achieve high geometric accuracy, a strong focus lies on the implementation of appropriate process parameters. A parameter study is performed in order to identify those process parameters, which mainly influence component distortion of a top hat profile. An automated test setup with a locally heated press hardening tool is used. As a result, the achieved hardness values and the geometric deviations are presented in dependence of the main influencing parameters.

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Considering energy-related factors in the simulation of logistics systems 19

Considering energy-related factors in the simulation of logi...

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Proceedings of the Winter Simulation Conference

作者： Moritz Poeting Bastian Prell Markus Rabe Tobias Uhlig Sigrid Wenzel TU Dortmund University Dortmund Germany Fraunhofer Institute for Machine Tools and Forming Technology IWU Chemnitz Germany Universität der Bundeswehr München Neubiberg Germany University of Kassel Kassel Germany

ISBN: (纸本)9781728132839

Traditionally, aspects such as emissions and energy consumption have to be taken into account for environmental and economic reasons when it comes to transport. In other areas of logistics, such as production logistics and intralogistics, the energy aspect is also becoming increasingly important. Existing literature has been recently reviewed in a contribution of the Arbeitsgemeinschaft Simulation (ASIM) to the Winter Simulation Conference 2018 (Uhlig et al. 2018) to develop a map of common approaches and best practices for manufacturing and logistics systems. In the paper presented here, as a complement we are focusing on the application of energy simulation in logistics to give a comprehensive overview and present exemplary case studies. Furthermore, we show a classification of approaches to combine energy aspects with simulation. Finally, we will discuss open questions and future trends in this field of research.

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Influence on the microstructure of powder metallurgical metal foam by means of mechanical alloying 22nd

Influence on the microstructure of powder metallurgical meta...

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22nd Symposium on Composites, 2019

作者： Siebeck, Steve Trautmann, Maik Hohlfeld, Jörg Hipke, Thomas Wagner, Guntram Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Straße 88 Chemnitz09126 Germany Chemnitz University of Technology Professorship of Composites and Material Compounds Erfenschlager Straße 73 Chemnitz09125 Germany

ISBN: (纸本)9783035714531

Due to the process, metal foams produced by powder metallurgy have an inhomogeneous pore structure. The pore size variations from a few tenths of a millimeter up to the centimeter range is so typical. This leads to inconstant properties and makes the predictability of metal foam based components difficult. The present work deals with the approach to precondition the feedstock powder for the production of metal foams by mechanical alloying. Thereby, the homogeneous distribution of the blowing agent TiH2 is already present in the so-called composite powder. In addition, there is the possibility to add reinforcement particles with regard to a further improvement of the mechanical properties. Overall, this leads to a rather wide range of possible influencing factors and parameters to be varied. Accordingly, the present work is only a preview of a broad experimental program, taking into account the design of experiments and is currently being processed. In this first study, an alloy AA6060 has been used as the matrix material. The evaluated method provides a finer pore structure associated with a modified foaming behavior. © 2019 Trans Tech Publications Ltd, Switzerland.

关键词： Pore structure

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Current Insights into the Investigations on a New Motor Principle with Radially Laminated Stator Sheets, Concentrated Windings and Flux Barriers

Current Insights into the Investigations on a New Motor Prin...

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International Electric Drives Production Conference (EDPC)

作者： Alena Babl Mirko Bach Katrin Schubert Dieter Gerling Verena Kräusel Michaela Gedan-Smolka Chair of Electrical Drives and Actuators Bundeswehr University Munich Neubiberg Germany Fraunhofer Institute for Machine Tools and Forming Technology Chemnitz Germany Institut Polymerwerkstoffe Leibniz-Institut für Polymerforschung Dresden e. V. Dresden Germany

ISBN: (纸本)9781665418102

In the wake of the Paris Climate Agreement and the world wide obligation to reduce CO 2 emissions, products and their manufacturing processes must be optimized in order to reduce resource consumption. This particularly concerns the topic of electric drives and machines. Regarding machines, one possibility to achieve this goal is the use of so-called flux barriers. This working concept offers further possibilities for structural optimization, such as radial lamination of the sheets, which then allows the use of grain-oriented electrical steel. Both mentioned principles increase the efficiency of the machine to a high degree and reduce manufacturing costs, as the iron losses are lessened and the material utilization is raised. This paper presents recent investigations of the use of grain-oriented electrical steel sheets for novel, radially laminated stators for electric motors with concentrated windings and flux barriers. The focus is on the analysis of the electromagnetic properties of the electrical sheets before and after forming, their coating and the operating characteristics of the planned demonstrator machine. Recent findings in the area of the technical implementation of the demonstrator machine and its electromagnetic design with the aid of FEM simulation are presented. Furthermore, challenges are evaluated with regard to eddy currents that arise due the innovative design. Finally, recommendations for further proceeding are derived and the next steps are explained.

关键词： Lamination Windings Production Stators Manufacturing Finite element analysis Steel

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