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Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding

Procedia CIRP 2022年 111卷 397-400页

作者： Nasim Bakir Ömer Üstündag Andrey Gumenyuk Michael Rethmeier Fraunhofer Institute for Production Systems and Design Technology Pascalstraße 8-9 10587 Berlin Germany Institute of Machine Tools and Factory Management Technische Universität Berlin Pascalstraße 8-9 10587 Berlin Germany

Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root.

关键词： Laser beam welding (LBW) solidification cracking partial penetration weld pool shape

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Harmonization of Heterogeneous Asset Administration Shells

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Procedia CIRP 2022年 107卷 95-100页

作者： Nikolaos-Stefanos Koutrakis Varun Gowtham Wenzel Baron Pilar von Pilchau Thomas Josef Jung Julian Polte Jörg Hähner Marius-Iulian Corici Thomas Magedanz Eckart Uhlmann Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstr. 8-9 10587 Berlin Germany Fraunhofer FOKUS Kaiserin-Augusta-Allee 31 10589 Berlin Germany University of Augsburg Am Technologiezentrum 8 86159 Augsburg Germany Robert Bosch GmbH Robert-Bosch-Campus 1 71272 Renningen Germany Technische Universität Berlin Institute for Machine Tools and Factory Management (IWF) Pascalstr. 8-9 10587 Berlin Germany

In the era of digital transformation of the manufacturing and process industry, heterogeneity of assets is one of the most challenging issues towards digitally integrating components within the Industrial Internet of Things. In this context every participant relies on its proprietary digitalization approach envisioned by Plattform Industrie 4.0. To consolidate these heterogeneous data exchange interfaces, e.g. communication protocols, data formats etc., an intermediate step of harmonization is required. Our contribution provides an architecture based on the Asset Administration Shell standard to bring heterogeneous Cyber-Physical-systems together. We illustrate the functionality through an abstract use-case.

关键词： Asset Administration Shell Digital Twin Virtual Sensor Sensor Networks IIoT I4.0 MQTT OPC UA

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Introducing readiness scales for effective reuse of open source hardware

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Procedia CIRP 2022年 109卷 635-640页

作者： Robert Mies Martin Häuer Mehera Hassan Technische Universität Berlin Institute for Machine Tools and Factory Management PTZ 3 Pascalstr. 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology Digital engineering Pascalstr. 8-9 10587 Berlin Germany

Open source hardware (OSH) describes physical products that allow for "anyone to study, modify, produce, and distribute them". While OSH principles aim to support design reuse, recent studies have challenged whether this is properly applied in practice. Therefore, this article delivers an assessment scheme that allows to identify the readiness of OSH designs for reuse. Testing the scheme on OSH ventilator designs collected by the Publnv ventilator project showed overall good usefulness of the scheme and emphasised the need of unambiguous assessment scales based on common standards. Less than two thirds of Publnv’s listed projects fulfilled minimum criteria for openness.

关键词： open innovation open source hardware open source product development technology readiness documentation readiness design reuse

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Pressure conditions during the immersed tumbling process

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Procedia CIRP 2021年 101卷 198-201页

作者： E. Uhlmann J. Polte M. Polte Y. Kuche Institute for Machine Tools and Factory Management (IWF) Technische Universität Berlin Pascalstraße 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstraße 8-9 10587 Berlin Germany

An approach to improve the tool wear behaviour of milling tools made of cemented carbide is a defined cutting edge preparation usingthe immersed tumbling process. One significant factor that influences cutting edge preparation is the effective pressure generated by the relative movement of the cutting tools and the abrasive particles. However, the development and influence of the process pressure has been discussed almost exclusively based on machining and preparation results. For a profound process understanding a wireless force measurement system was designed and the pressure forces of two media were examined. The influences of the used lapping media, the velocityas well as the depth of immersion using a simplified linear movement were analysed. The results provide information about the pressure conditions that change in the real process.

关键词： Cutting edge Finishing Force Measurement

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Boron-doped monocrystalline diamond as cutting tool for temperature measurement in the cutting zone

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Procedia CIRP 2021年 101卷 258-261页

作者： E. Uhlmann J. Polte M. Polte T. Hocke Institute for Machine Tools and Factory Management (IWF) Technische Universität Berlin Pascalstraße 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstraße 8-9 10587 Berlin Germany

Ultra-precision machining is a key technology for manufacturing optical surfaces in a broad range of automotive and aerospace applications. At the state of the art, no precise methods for analysing the temperatures in the cutting zone of a monocrystalline diamond tool are available. Precise cutting temperatures are required for a detailed analysis of the wear behaviour. High response times and low measurement accuracies are still challenges. In this work, a new approach for a precise temperature measurement using boron-doped diamonds is shown. The sensor properties of boron-doped diamonds were analysed and experimental investigations to show the suitability were carried out. First results show a great potential as measurement method for real time temperatures during the cutting process.

关键词： temperature sensor diamond tool measurement system ultra-precision machining

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Holistic Concept Towards a Reference Architecture Model for Predictive Maintenance

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Procedia CIRP 2021年 104卷 1430-1433页

作者： Eckart Uhlmann Julian Polte Nikolaos-Stefanos Koutrakis Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstraße 8-9 10587 Berlin Germany Institute for Machine Tools and Factory Management (IWF) Technische Universität Berlin Pascalstraße 8-9 Berlin 10587 Germany

In the era of digital transformation of factories, one of the most challenging applications of the Industrial Internet of Things (IIoT) is predictive maintenance. This paper presents a holistic concept for predictive maintenance together with a reference architecture that includes data acquisition on the sensor level, edge computing and digital twin applications. For that purpose, condition-based maintenance, lifecycle monitoring and digital assistance systems are integrated to develop application-specific digital twins based on the proposed architecture, integrating heterogenous data sources in order to enhance the accuracy of the machine learning models. The concept is illustrated through an experimental use case.

关键词： Analytics Reference Architecture Digital Twin Predictive Maintenance IIoT Machine Learning

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Simulation of metal cutting with cutting fluid using the Finite-Pointset-Method

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Procedia CIRP 2021年 101卷 98-101页

作者： Eckart Uhlmann Enrico Barth Tobias Seifarth Maximilian Höchel Jörg Kuhnert Almut Eisenträger Institute for Machine Tools and Factory Management (IWF) Technische Universität Berlin Pascalstr. 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstr. 8-9 10587 Berlin Germany Fraunhofer Institute for Industrial Mathematics ITWM Fraunhofer-Platz 1 67663 Kaiserslautern Germany

Despite the common use of cutting fluids in metal cutting, most simulations of these processes only consider dry conditions. This is largely due to limitations in conventional simulation methods, such as the Finite Element Method (FEM), regarding fast changing computational domains. In this paper, a simulation model of metal cutting with cutting fluid based on the Finite Pointset Method (FPM) is presented. This approach allows to simulate the Fluid-Structure-Interactions (FSI) within the same simulation method. For different orthogonal turning processes, the simulations are compared with experiments for dry and wet conditions. The simulation results illustrate the cooling effect numerically.

关键词： Simulation Fluid Turning

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Dry-ED milling of micro-scale contours with high-speed rotating tungsten tube electrodes

Dry-ED milling of micro-scale contours with high-speed rotat...

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20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020

作者： Uhlmann, E. Perfilov, I. Yabroudi, S. Mevert, R. Polte, M. Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 Berlin10587 Germany

This paper presents machining results for dry-ED milling of micro-scale contours by use of a new machine tool, including a relaxation generator, designed for dry-EDM. To implement the dry-ED milling process tungsten tube electrodes were used. The gas is injected through the tubular tool electrode under high pressure. Additionally, a high-speed EDM spindle was used to overcome process instabilities and increase the material removal rate due to better flushing conditions. Further, fluid simulations of the flushing conditions are presented in this paper. It is found that the use of gaseous dielectrics enables much better machining results in terms of shape accuracy and tool wear. The simulations provide new insights in the flushing conditions when using gaseous dielectrics. The calculated fluid flow pattern shows a great agreement with the observed depositions of reattached molten material on the tool and workpiece surface. The results presented as well as the hardware introduced enable the industrial application of dry-EDM for the first time. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ISEM 2020

关键词： Computational fluid dynamics

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design and hard machining of a high performance ceramic impeller 20

Design and hard machining of a high performance ceramic impe...

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20th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2020

作者： Uhlmann, E. Polte, J. Koprowski, S. Kochan, J. Borsoi Klein, T. Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 Berlin10587 Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Pascalstr. 8-9 Berlin10587 Germany

ISBN: (纸本)9780995775176

The constant development and improvement of mechanical and chemical properties of high performance ceramics allows the expansion of its actual applications. In comparison to metal materials, the use of novel high performance components can offer numerous advantages. In turbomachinery, a full ceramic impeller can fulfil the requirements of efficiency and high turbine inlet temperatures combined with lower cooling requirements, reduced combustion emissions and fuel consumption. This is feasible not only thanks to the properties of the ceramics, but also by the interaction of this with simulation, design optimization, manufacturing processes and a high quality finishing by hard machining. However, the machining of brittle material components with complex geometries remains a challenge in terms of resultant surface characteristics, tribological properties, geometric accuracy and process costs. In this scenario, 5-axis grinding with mounted points and innovative strategies provide new possibilities for the manufacturing of these complexes components. The current work aims at a practice-oriented design and the following hard machining of a hot isostatically pressed silicon nitride (HIPSN) impeller with complex geometry and high requirements, gathering low geometrical deviations, reduced brittle fractures and roughness at the ground part. To achieve these objectives, different machining strategies and parameters are tested and correlated with the resulting quality of the component. Simulation techniques are also shown to ensure optimum operating conditions for the ceramic component. Copyright © Proceedings of the 20th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2020. All rights reserved.

关键词： Silicon nitride

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Determination of critical local straining conditions for solidification cracking at laser beam welding by experimental and numerical methods

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PAMM 2024年第2期24卷

作者： Nasim Bakir Andrey Gumenyuk Michael Rethmeier Bundesanstalt für Materialforschung und prüfung (BAM) Berlin Germany Technische Universität Berlin Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Berlin Germany

The phenomenon of solidification cracking has been the subject of numerous research projects over the years. Great efforts have been made to understand the fundamentals of hot cracking. It is generally agreed that solidification cracks form in the solidification range between the liquidus and solidus temperatures under the combination of thermal, metallurgical and mechanical factors. There is still a need to determine the time-resolved strain distribution in the crack-sensitive region in order to analyse the local critical conditions for solidification cracking phenomena. This was a strong motivation for the development of a measurement system used in this study to estimate the local strains and strain rates in the zone where the solidification crack is expected to occur. The laser beam welding experiments were conducted using the Controlled-Tensile-Weldability test (CTW test) to apply an external strain condition during welding to generate solidification cracks. The CTW test is a test method for investigating the susceptibility of laser-welded joints to solidification cracking, in which the sample can be subjected to a defined strain at a defined strain rate during welding. In combination with experimental investigations, numerical simulations provide spatially detailed and time-dependent information about the strain development during the welding process, especially regarding the critical conditions for solidification cracking. Therefore, this tool was also used in the present study to evaluate the accuracy of measurement methods and to estimate experimentally derived values and their concrete influence on the formation of solidification cracks. By integrating experimental methods and numerical simulations, this study investigates the spatially resolved and temporally changing development of strain during welding, with a particular focus on the critical conditions that lead to the formation of solidification cracks. The use of numerical simulations serves a dual p

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