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A Comparative Study of Polarity-related Effects in Single Discharge EDM of Titanium and Iron Alloys

Procedia CIRP 2018年 68卷 52-57页

作者： F. Klocke M. Mohammadnejad M. Holsten L. Ehle M. Zeis A. Klink Laboratory for Machine Tools and Production Engineering WZL of RWTH Aachen University Steinbachstrasse 19 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstrasse 17 52074 Aachen Germany Central Facility for Electron Microscopy (GFE) RWTH Aachen University Ahornstrasse 55 52074 Aachen Germany

In comparison to steel, titanium alloys react differently to the choice of process parameters in sinking electrical discharge machining (EDM), especially concerning the applied electrical polarity of the tool. With an anodic tool polarity, sinking EDM removal on titanium Ti6Al4 V is scarce due to titanium carbide formation, while on steel removal occurs as expected. To understand the behavior of titanium alloys, a comparative study between titanium and iron alloys in single and successive discharge experiments is performed. Ironically, single discharge removal is scarce with an anodic tool on both iron and titanium alloys. However, in ten successive discharges experiments, removal with an anodic tool increases disproportionately. Finally, the continuous EDM process with an anodic tool stops to be effective for the Ti6Al4 V machining while for steel is effective as well as efficient in terms of low tool wear. The explanation proposed is the recast layer that has a lower thermal conductivity on which successive discharges would remove material more easily. As a result, the formation of titanium carbide in Ti6Al4 V machining is likely not occurring in single discharges due to lack of continuous heat needed for carbon transfer.

关键词： Electrical discharge machining EDM single discharges polarity material removal

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Comparative Integrated Manufacturing Efficiency in Production Engineering

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Procedia CIRP 2017年 63卷 527-532页

作者： A.P. Kuznetsov H.-J. Koriath A.V. Kalyashina Moscow State University of Technology “STANKIN” 127055 Moscow Russia Fraunhofer Institute for Machine Tools and Forming Technology IWU 09126 Chemnitz Germany Kazan National Research Technical University Kazan Russia

At present a plurality of manufacturing methods, different manufacturing processes and manufacturing equipment are known in order to produce and customize work pieces and products. A new systematic approaches for the analysis and evaluation of manufacturing methods bases on the energy-information model as a conceptual approach to the comparative integrated manufacturing efficiency in production engineering. The integrated manufacturing efficiency is equal to the product of the efficiencies of matter, energy and information. The Comparative Integral Manufacturing Efficiency is the product of Quality rate, Effectiveness, Availability, devided by the product of (used Energy, used material, Emission ratio). A case study compares additive and removal process efficiencies for the production of a hollow cylinder. Proposed method for comparative integrated manufacturing efficiency will offer resource-efficient strategies for the creation and optimization of processes and technology applications.

关键词： manufacturing efficiency technological process

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Multiscale Multiphysics Simulation of a Pulsed Electrochemical Machining Process with Oscillating Cathode for Microstructuring of Impact Extrusion Punches

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Procedia CIRP 2017年 58卷 257-262页

作者： Ingo Schaarschmidt Mike Zinecker Matthias Hackert-Oschätzchen Gunnar Meichsner Andreas Schubert Professorship Micromanufacturing Technology Faculty of Mechanical Engineering Chemnitz University of Technology D-09107 Chemnitz Germany Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 D-09126 Chemnitz Germany

The pulsed electrochemical machining (PECM) with oscillating cathode is a manufacturing technology which is used for shaping and surface structuring of different workpieces, e.g. impact extrusion punches. The principle behind the ECM-process is the controlled anodic dissolution of the workpiece material without any thermal or mechanical impact and independent from workpiece material hardness. In this study, a new multi-scale approach for the modelling of PECM with oscillating cathode was created integrating the short and long time scale physical phenomena. In the short time scale simulation step (t < 0.02 s) the physical processes (current density distribution, motion of cathode, heat and hydrogen generation) during one single oscillation were analyzed. An averaged dissolution speed at the anode boundary over the small time range was calculated. The averaged values were imported as initial and boundary conditions into the long times scale simulation step (t > 10 s). Within this simulation step, the anodic dissolution was simulated by deforming the geometry. This approach allows simulations for long overall time ranges (t > 1000 s) while considering the short times scale processes in combination with a relatively small computational effort. This multiscale and multiphysics model helps to analyze the differences between front and lateral working gap and supports the process design for the pulsed electrochemical machining with oscillating cathode.

关键词： Electro chemical machining (ECM) Material removal Multiscale-multiphysics-modelling

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Characterization of an Electrochemical Machining Process for Precise Internal Geometries by Multiphysics Simulation

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Procedia CIRP 2017年 58卷 175-180页

作者： Matthias Hackert-Oschätzchen Raphael Paul Michael Kowalick Danny Kuhn Gunnar Meichsner Mike Zinecker Andreas Schubert Professorship Micromanufacturing Technology Faculty of Mechanical Engineering Chemnitz University of Technology D-09107 Chemnitz Germany Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 D-09126 Chemnitz Germany

In several fields of mechanical engineering internal precision geometries are applied. For this, application requirements like high shape accuracy, sufficient stability, high wear resistance or an increase of life time have to be fulfilled. However, there is also a demand on quick and precise manufacturing processes that are flexible in machining various internal geometries. Electrochemical machining (ECM) is a process which meets these requirements. This process allows surface structuring and shaping of metal components with high shape accuracy independently of the materials strength and hardness [1] . This study presents investigations on a developed process design for manufacturing internal precision geometries by pulsed electrochemical machining (PECM) with help of multiphysics simulations. The peculiarity of this process is the shaping of the workpiece by the lateral working gap. Multiphysics simulations were carried out to understand the respective interactions between several physical phenomena. Especially, fluid dynamical effects are described in detail within the developed model. Furthermore, Joule heating and cathodic hydrogen formation are included. The fluid flow ensures the removal of heat and hydrogen and a continual supply with fresh electrolyte, respectively. The electrical conductivity of the electrolyte is modeled as a function of hydrogen volume concentration and temperature. Hence, both effects, Joule heating and hydrogen formation, influence the current density distribution which in turn determines the material removal.

关键词： Electrochemical machining (ECM) Finite element method (FEM) Multiphysics Simulation

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Principle and setup for characterization of material parameters for high speed forming and cutting

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Procedia Engineering 2017年 207卷 2000-2005页

作者： Marc Tulke Christian Scheffler Verena Psyk Dirk Landgrebe Alexander Brosius Chair of Forming and Machining Processes (FF) Technische Universität Dresden 01062 Dresden Germany Fraunhofer Institute of Machining Tools and Forming Technology 09126 Chemnitz Germany

Velocity effects in production technology provide technological and economic advantages, but at the same time they necessitate consideration of strain rate dependent material behavior in process modelling. This paper proposes an innovative approach for material characterization in terms of strain rate dependent flow curves and failure describing parameters. Two driving concepts for high velocity testing, which can be used for examining the material behavior under different load cases by considering different specimen geometries, are presented: a pneumatic one for plastic strain rates up to 1,000 s -1 and an electromagnetic one for strain rates of 5·10 2 s -1 up to 10 5 s -1 . Compared to the Split-Hopkinson-Bar-Test normally used, there are some advantages regarding achievable strain rates and achieved measurement data. In principle, knowledge about the strain paths, stress paths and local distributions of stress and strain in the specimen is essential for identifying material characteristics. Short process times, fast changes of the measurement values, small specimen size and frequently limited accessibility of the specimen during the test hinder directly measuring these parameters at high velocity testing. Therefore, here auxiliary test parameters, which are easier to measure, are recorded and used as input data for an inverse numerical simulation that provides the desired material characteristics as a result. For a first evaluation of the test arrangement, the concept was investigated in a numerical sensitivity study and the measuring principle was verified experimentally in a drop tower test.

关键词： High strain rates Parameter identification Material characterisation Sheet metal

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Embedding electronics into additive manufactured components using laser metal deposition and selective laser melting

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Procedia CIRP 2018年 74卷 168-171页

作者： Torsten Petrat Robert Kersting Benjamin Graf 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

The paper deals with the integration of a light emitting diode (LED) into an additive manufactured metal component. Selective laser melting (SLM) and laser metal deposition (LMD) are used. The material used is the chrome-nickel steel 316L. The basic component is manufactured by means of SLM and consists of a solid body and an area with grid structure. The solid body includes a duct in the shape of a groove with a recess for the positioning of the power cable. The LED is embedded in the grid structure via an inlet from the solid body. In further processing, the groove is filled with LMD. Two strategies with different parameter combinations were investigated. It shows that a high energy input near the power cable leads to its destruction. By using multiple parameter combinations during the manufacturing process, this destruction can be prevented. There was a comparison of both strategies with regard to the necessary number of tracks and duration of welding time.

关键词： additive manufacturing condition monitoring process chain laser-metal-deposition selektive-laser-melting embedded electronics

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Laser-plasma-cladding as a hybrid metal deposition-technology applying a SLM-produced copper plasma nozzle

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Procedia CIRP 2018年 74卷 738-742页

作者： Christian Brunner-Schwer Robert Kersting Benjamin Graf 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

Laser-Metal-Deposition (LMD) and Plasma-Transferred-Arc (PTA) are well known technologies which can be used for cladding purposes. The prime objective in combining LMD and PTA as a Hybrid Metal Deposition-technology (HMD) is to achieve high deposition rates at low thermal impact. Possible applications are coatings for wear protection or repair welding for components made of steel. The two energy sources (laser and plasma arc) build a joint process zone and are configurated to constitute a stable process at laser powers between 0.4-1 kW (defocused) and plasma currents between 75-200 A. Stainless steel 316L serves as filler material. For this HMD process, a plasma Cu-nozzle is designed and produced by powder bed based Selective Laser Melting. The potential of the HMD technology is investigated and discussed considering existing processes. This paper demonstrates how the interaction of the two energy sources effects the following application-relevant properties: deposition rate, powder efficiency and energy input.

关键词： Laser-Metal-Deposition Plasma-Transferred-Arc SLM printed plasma torch Laser-Plasma-Hybrid

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Automated hole expansion test with pneumatic crack detection

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IOP Conference Series: Materials Science and Engineering 2019年第1期480卷

作者： A Leonhardt V Kräusel U Paar Chemnitz University of Technology / Institute for Machine Tools and Production Processes / Professorship for Forming and Joining / Reichenhainer Straße 70 / 09126 Chemnitz / Germany Volkswagen Sachsen GmbH / Serienplanung Presswerk / Glauchauer Straße 40 / 08058 Zwickau / Germany

The hole expansion test according to ISO 16630:2009 is a widely used method for determining the edge crack sensitivity, e. g. for advanced high strength steels (AHSS). However, the optical crack detection causes a subjective stop of the test, which is also difficult to automate. These existing disadvantages are eliminated by a newly developed method to stop the hole expansion test using pressure drop at an edge crack through the entire sheet thickness. The pneumatic crack detection ensures a high degree of objectivity and automation. The functionality of the new stopping method was experimentally proven by the comparison with the optical method, the investigation of the influence of different parameters and by testing of good part and reject batches from series production. The pneumatic method stops the test when through-thickness cracks are less pronounced up to a hole expansion ratio λ of approx. 35%, i. e. for materials sensitive to edge cracks. Thus, this variant provides more objective results than the optical method. The test results between the two methods are comparable in the range of λ ≤ 100%.

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Precision enhancement technologies for multi-axis ultra precision machining of freeform optical elements with variable micro/nano structures

Precision enhancement technologies for multi-axis ultra prec...

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ASPEN/ASPE 2017 Spring Topical Meeting on Manufacture and Metrology of Structured and Freeform Surfaces for Functional Applications

作者： Uhlmann, E. Kühne, S. Jagodzinski, M. Widemann, R. Haskic, K. Institute for Machine Tools Factory Management IWF Technische Universität Berlin Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Berlin Germany LT ULTRA-PRECISION TECHNOLOGY GmbH Herdwangen-Schönach Germany

Aspherical and freeform optics receive uprising attention, due to their advantages in terms of aberrations and reduction of system volume, for example in spectroscopic applications. An additional surface structuring e... 详细信息

ISBN: (纸本)9781510853546

关键词： Enhancement Technologies Optical Component precision machining aberrations MULTIAXIAL surface structure reduction Precision

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Resource-efficient development of thermally highly resistant engine components of hybrid metal composites – experiments and numerical analysis

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Procedia Engineering 2017年 207卷 884-889页

作者： Dirk Landgrebe Lutz Krüger Nadine Schubert Eric Jentsch Tim Lehnert Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 09126 Chemnitz Germany Institute for Materials Engineering TU Bergakademie Freiberg Gustav-Zeuner-Straße 5 09599 Freiberg Germany

Requirements for protection of environment and climate, increasing energy cost and security demands form the basis for research activities in the maritime sector. Within the scope of the joint project »INKOV – development of innovative piston and valve solutions for composites in ship engines« metallic composites are developed and investigated. Their application in large engines powered by heavy fuel oil shall reduce nitrogen oxide emissions. The investigations of the publicly funded research project intend to generate high-strength components made of a hybrid composite material while simultaneously increasing resource efficiency. The focus of the research and development activities lies on components for large engines which are subject to extremely high dynamic, thermal and corrosive loads. Using conventional heat-resistant and wear-resistant steels, the wear related to the conditions of the application site can hardly be controlled. High-performance alternatives are necessary. The goal of the approach is to specifically apply a nickel-base alloy to a locally limited area by using a selected thermal joining process. Thus, a layer composite is to be produced, which corresponds to the solid material of a nickel-base alloy regarding its properties of thermal resistance and corrosion resistance. Currently, criteria for excluding the integration of these materials include high prices as well as their partly limited availability despite of their reported suitability for high-temperature applications. Using hybrid materials should open up their considerable potential in terms of increasing strength and high-temperature resistance while simultaneously reducing wear-related downtimes to a minimum. An aim of the project is to implement forming processes of hybrid composites by means of simulation as a basis for optimizations in terms of joining materials, joining processes or geometrical dimensions. Furthermore, the basic behavior of hybrid materials and their interface shal

关键词： hybrid composite material resource efficiency FEM bulk metal forming

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