2,640 research outputs found

    Compensation of deep drawing tools for springback and tool-deformation

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    Manual tool reworking is one of the most time-consuming stages in the\ud preparation of a deep drawing process. Finite Elements (FE) analyses are now widely\ud applied to test the feasibility of the forming process, and with the increasing accuracy of the\ud results, even the springback of a blank can be predicted. In this paper, the results of an FE\ud analysis are used to carry out tool compensation for both springback and tool/press\ud deformations. Especially when high-strength steels are used, or when large body panels are\ud produced, tool compensation in the digital domain helps to reduce work and save time in the\ud press workshop. A successful compensation depends on accurate and efficient FE-prediction,\ud as well as a flexible and process-oriented compensation algorithm. This paper is divided in\ud two sections. The first section deals with efficient modeling of tool/press deformations, but\ud does not discuss compensation. The second section is focused on springback, but here the\ud focus is on the compensation algorithm instead of the springback phenomenon itself

    In vivo measurement of human brain elasticity using a light aspiration device

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    The brain deformation that occurs during neurosurgery is a serious issue impacting the patient "safety" as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians' experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an external camera. This paper describes the experimental setup as well as its use during a specific neurosurgery. The experimental data was used to calibrate a continuous model. We show that we were able to extract an in vivo constitutive law of the brain elasticity: thus for the first time, measurements are carried out per-operatively on the patient, just before the resection of the brain parenchyma. This paper discloses the results of a difficult experiment and provide for the first time in-vivo data on human brain elasticity. The results point out the softness as well as the highly non-linear behavior of the brain tissue.Comment: Medical Image Analysis (2009) accept\'

    Effects of biodiesel fuel temperature on performance and emissions of a compression ignition (CI) engine

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    Diesel engines are still widely needed and applicable to light duty passenger car and heavy duty vehicles. In recent years, limited supply of fossil fuel makes alternative sources of fuel especially biodiesel receiving a lot of attention in the automotive industry. However, in using biodiesel as fuel had created poor fuel-air mixing that generally will produce lower performance and higher emissions than diesel fuel. This is associated with the fuel properties especially viscosity that higher compared to diesel fuel. The aim of this present research was to investigate the effects of preheated biodiesel based crude palm oil (B5, B10 and B15) at 40oC, 50oC and 60oC on performance and emissions of diesel engine at three different load conditions, which are 0% load, 50% load and 100% load. A four-cylinder four strokes cycle, water cooled, direct injection engine was used for the experiments. The results showed that the maximum performance produced was at 0% load condition with the 60oC of heating temperature by B10 where the torque, flywheel torque and brake power increased by 11.55%, 11.42% and 4.16% respectively compared to diesel fuel. While for the emissions, the preheat temperature results on the decrement of CO emission for all load conditions and the maximum reduction recorded was 41.2%. However, the increment of fuel temperature promotes to the higher NOx emissions produced and the maximum increment recorded was 51.7%

    Multiphysics Modeling and Numerical Simulation in Computer-Aided Manufacturing Processes

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    The concept of Industry 4.0 is defined as a common term for technology and the concept of new digital tools to optimize the manufacturing process. Within this framework of modular smart factories, cyber-physical systems monitor physical processes creating a virtual copy of the physical world and making decentralized decisions. This article presents a review of the literature on virtual methods of computer-aided manufacturing processes. Numerical modeling is used to predict stress and temperature distribution, springback, material flow, and prediction of phase transformations, as well as for determining forming forces and the locations of potential wrinkling and cracking. The scope of the review has been limited to the last ten years, with an emphasis on the current state of knowledge. Intelligent production driven by the concept of Industry 4.0 and the demand for high-quality equipment in the aerospace and automotive industries forces the development of manufacturing techniques to progress towards intelligent manufacturing and ecological production. Multi-scale approaches that tend to move from macro- to micro- parameters become very important in numerical optimization programs. The software requirements for optimizing a fully coupled thermo-mechanical microstructure then increase rapidly. The highly advanced simulation programs based on our knowledge of physical and mechanical phenomena occurring in non-homogeneous materials allow a significant acceleration of the introduction of new products and the optimization of existing processes.publishedVersio

    Analýza odpružení výtažku nepravidelného tvaru z různých materiálů s využitím metody konečných prvků

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    Paper concerns drawing operation including related consequent springback of intricate shape stamping from thin sheet-metal – internal reinforcement of car bodyshell B-pillar in order to keep after drawing process the dimensions and tolerances of stamping after drawing process which are given in part drawing. Simulation of drawing process and consequent springback simulations were carried out in CAE software PAM-STAMP 2G 2011 which uses finite element method. In contribution the drawing process simulation of car bodyshell B-pillar is detailly described in this program, choice of suitable solver for separate drawing simulation stages, consequent springback simulations for four strip steels with the use of two mesh strategies and their mutual comparison. For given stamping shape the best strip steels were evaluated from point of view of drawability and reaching minimal springback size. In the end of the paper the method of tuning of sizes of drawing tool in order to achieve the state when final stamping deviations will correspond to tolerances specified at part drawing is described.Článek se týká řešení operace tažení včetně s tím souvisejícím následným odpružením výtažku nepravidelného tvaru z tenkého plechu – vnitřní výztuhy B-sloupku karosérie automobilu za účelem dosažení po procesu tažení rozměrů a tolerancí výtažku, které jsou předepsány na výkresu součásti. Simulace plošného tváření a následné simulace odpružení byly prováděny s využitím programu PAM-STAMP 2G 2011, který využívá metodu konečných prvků. V článku je podrobně popsána simulace procesu tváření B-sloupku karosérie automobilu v tomto programu, volba vhodného řešiče pro jednotlivé etapy simulace, následné simulace velikosti odpružení pro čtyři druhy pásových ocelí při použití dvou zvolených meshovacích strategií a jejich vzájemné porovnání. Pro daný typ výtažku byly vyhodnoceny nejvhodnější pásové oceli z hlediska lisovatelnosti a dosažení minimální velikosti odpružení. V závěru článku je popsán způsob ladění rozměrů tažného nástroje za účelem dosažení stavu, kdy tvarové odchylky konečného výtažku odpovídají předepsaným tolerancím na výkresu součásti

    Volume 2 – Conference: Wednesday, March 9

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    10. Internationales Fluidtechnisches Kolloquium:Group 1 | 2: Novel System Structures Group 3 | 5: Pumps Group 4: Thermal Behaviour Group 6: Industrial Hydraulic

    Fundamentals of lubricated friction in deep drawing of zinc coated sheet metal considering contacting surface morphology and chemistry

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    Die vorliegende Dissertation beschäftigt sich mit dem tribologischen System beim Tiefziehen, das sich aus verzinktem Stahlblech, Werkzeugstahl und flüssigem Schmierstoff bei Raumtemperatur zusammensetzt. Der Schwerpunkt der Arbeit liegt insbesondere auf dem Zusammenhang zwischen dem Reib- und Verschleißverhalten des Tribosystems und der Zusammensetzung und der Topologie der Kontaktflächen. Die Beschreibung des Tribosystems basiert auf der Annahme, dass die Reibung und der Verschleiß durch Adhäsion und Furchung entstehen. Die Untersuchungen folgen einem modularen experimentellen Rahmen, der tribologische Versuche, Oberflächenanalysen und mechanisches Testen verbindet. Die Arbeit beginnt mit einer umfangreichen Übersicht des Stands der Technik, in der die wichtigsten Ansätze bezüglich der Charakterisierung von Reibung und Verschleiß, der Theorie des Reibmechanismus, die bestehenden Reibungsmodellierungsverfahren und das Konzept des dritten Körpers betrachtet werden. Es folgt die Beschreibung der angewendeten Vorgehensweise und der für die Untersuchung genutzten Materialien. Im Hauptteil der Dissertation werden die Ergebnisse der Versuche vorgestellt. Zunächst wird der Einfluss der Oberflächentopologie auf die Reibung betrachtet. Hierbei hängt die Topographie der Werkzeugoberfläche im Wesentlichen von der Art und der Genauigkeit des Endbearbeitungsprozesses ab. Die Ausgestaltung der Blechoberfläche wird durch das dem Walzprozess folgende Dressieren bestimmt. Anhand der Untersuchungen konnten die wesentlichen Eigenschaften der Kontaktoberflächen, die das Reibverhalten des Tribosystems beeinflussen, ermittelt werden. Es wurden Bleche von einem Coil mit stufenweise unterschiedlichen Dressiergraden in Streifenzieh- und Stiftscheibeversuchen untersucht, wobei Werkzeuge mit unterschiedlichen Oberflächenbeschaffenheiten eingesetzt wurden. Ein wichtiger Teil der Arbeit stellt die anschließende Ermittlung des Anteils der Oberflächenstruktur am Reib- und Verschleißverhalten des Tribosystems dar. Bei einem Vergleich zweier unterschiedlicher Arten von Zinkbeschichtung, nämlich der reinen Zinkbeschichtung und der Zink-Magnesium-Beschichtung konnte beobachtet werden, dass eine Änderung der chemischen Zusammensetzung der Beschichtung einen erheblichen Unterschied im Verhalten des jeweiligen Tribosystems zur Folge hat. Diese Erkenntnis ermöglicht weitere Einsichten hinsichtlich des Hauptmechanismus der Reibung beim Tiefziehen

    Engineering for a changing world: 60th Ilmenau Scientific Colloquium, Technische Universität Ilmenau, September 04-08, 2023 : programme

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    In 2023, the Ilmenau Scientific Colloquium is once more organised by the Department of Mechanical Engineering. The title of this year’s conference “Engineering for a Changing World” refers to limited natural resources of our planet, to massive changes in cooperation between continents, countries, institutions and people – enabled by the increased implementation of information technology as the probably most dominant driver in many fields. The Colloquium, supplemented by workshops, is characterised but not limited to the following topics: – Precision engineering and measurement technology Nanofabrication – Industry 4.0 and digitalisation in mechanical engineering – Mechatronics, biomechatronics and mechanism technology – Systems engineering – Productive teaming - Human-machine collaboration in the production environment The topics are oriented on key strategic aspects of research and teaching in Mechanical Engineering at our university
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