Marcel Graf

Marcel Graf
Technische Universität Chemnitz · Institute of Materials Science and Engineering

Dr.-Ing.

About

69
Publications
18,227
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255
Citations
Additional affiliations
May 2015 - present
Technische Universität Chemnitz
Position
  • Scientific assistant
October 2008 - June 2015
Technische Universität Bergakademie Freiberg
Position
  • Scientific assistant

Publications

Publications (69)
Article
Purpose This paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing. Design/methodology/approach The component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element a...
Article
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This paper presents an investigation of austenitic stainless steel grain growth kinetics of SS316L under different heating temperature ranges and holding times. The main variables such as apparent activation energy (Q), rate constant (K), and kinetic exponent (n) were analyzed to understand the grain growth kinetics in austenitic stainless steel. T...
Article
This fundamental research deals with the investigation of material property model influences on distortion induced by multi-layered Wire Arc Additive Manufacturing (WAAM) with synergic-pulsed gas metal arc welding (P-GMAW) process which was modelled and simulated by means of non-linear numerical computation. The material property models of stainles...
Chapter
This research focuses on investigating major imperfection in coupled processes of ““Welding-to-Forming”” and “Forming-to-Welding” which are frequently found in parts production in automotive industries. Finite Element Method (FEM) based Virtual Manufacturing (VM) approach is used to predict final dimensional change in both welding and forming proce...
Chapter
Wire-arc additive manufacturing (WAAM) complex components can be built-up layer by layer from metallic construction materials. In this investigation two different WAAM processes with high built-up rates (CMT and pulsed GMAW) were compared in terms of geometry formation and component properties. The reference is a rectangular thin-walled geometry ma...
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In this research, FEM simulation was created butt joint with weld filler 3D-solid geometry. The assigned substrate element type is created and modeled on a 9 mm thickness. The three-passes of butt joint was undergoing with using the MSC Marc / Mentat student version simulation and simufact welding simulation. The butt joint designed with three pass...
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This research aims to predict the grain size growth using numerical computation. The material to be investigated is stainless steel 316L (SS316L). The mathematical modeling is derived into two cases, namely with the absence of precipitate (free growth) and with the presence of growing precipitates. The numerical computation involves ordinary differ...
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As one of additive manufacturing (AM) technologies, selective laser melting (SLM) which uses higher energy input enabling fully molten powder bed materials is nowadays increasingly applied to build full dense components without post processing. In the present work, specimens made of stainless steel powder SS 316L were to be processed using SLM Solu...
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This paper investigates the capability of probabilistic FEM to predict grain size distributions due to thermal cutting process. The application of transient heat source causes non-uniform temperature distribution across the parent metal that can lead to non-uniform expansion and contraction during heating and cooling cycle. This phenomenon will ind...
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This paper describes the sensitive influence of material parameters on the final numerical simulation result of forming process as one of virtual manufacturing applications. Although existing commercial software system provide predefined material properties, these can nevertheless differ with the actual material which might result in inaccuracies....
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In this paper, a coupled forming-welding process is to be analyzed. Therefore, the process chain of a tube u-/o-bending process was combined with the longitudinal welding of slotted tubes. Both processes were conducted and evaluated experimentally as well as numerically. To verify the process in a wide range of experimental technologies, different...
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Additive Manufacturing is an established process group that includes various technologies. In contrast to subtractive methods, complex components can be produced by applying layers of construction materials. In accordance with the standard VDI Guideline 3405, additive manufacturing technologies can be differentiated into wire- and powder-based tech...
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The description and modelling of the forming behaviour is essential for the numerical prediction of material flow and the applied forming force. A representative stress state as well as comparable strain rate and temperatures should be considered during material characterization. In the presented investigations, an extruded aluminium alloy (EN AW-6...
Conference Paper
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The material combination of aluminum and plastics in a hybrid semi-finished product combines the advantages of both material classes. It is possible to produce a final component with a high strength (due to the use of light metal) and good damping properties (due to the use of plastic). The present paper focusses on the production of a hybrid semi-...
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p class="AMSmaintext"> Various ways are sought today to increase mechanical properties of steels while maintaining their good strength and ductility. Besides effective alloying strategies, one method involves preserving a certain amount of retained austenite in a martensitic matrix. The steel which was chosen as an experimental material for this in...
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A chained forming–welding process is to be investigated and analyzed using experimental verification and numerical simulation in which the material and mechanical properties are fully transferred between processes. The investigated part is in the form of a tube with dimension of 300 mm (l) × 20 mm (OD) × 1.5 mm (t) made of a low carbon steel materi...
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This paper examines how the initial austenite grain size in quench and partitioning (Q-P) processes influences the final mechanical properties of Q-P steels. Differences in austenite grain size distribution may result, for example, from uneven heating rates of semi-finished products prior to a forging process. In order to quantify this influence, a...
Conference Paper
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Dieses Tagungsband enthält die während des 11. Anwendertreffens am 26.03.2019 präsentierten Vorträge zu unterschiedlichen Themenstellungen aus den Bereichen CAD, Simulation und Berechnung. Von Experten aus Wirtschaft und Wissenschaft wurden neben Hinweisen zu neuen Simulationsfeatures auch Einblicke und Anregungen für eine effiziente Bauteilberechn...
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The characterization of materials is essential for process development and process optimization. As the virtual techniques are becoming increasingly common, the material data must be identified and modelled in consideration of the process-relevant parameters (forming temperature, strain rate, sample position, main stress state and orientation). In...
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In this research, Wire Arc Additive Manufacturing is modelled and simulated to determine the most suitable bead modelling strategy. This analysis is aimed to predict distortion by means of thermomechanical Finite Element Method (FEM). The product model with wire as feedstock on plate as substrate and process simulation are designed in form of multi...
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Additive manufacturing processes have been investigated for some years, and are commonly used industrially in the field of plastics for small- and medium-sized series. The use of metallic deposition material has been intensively studied on the laboratory scale, but the numerical prediction is not yet state of the art. This paper examines numerical...
Conference Paper
Die additiven Fertigungstechniken haben seit einigen Jahren an Beliebtheit gewonnen, da somit komplexe Geometrien erzeugt, als auch unterschiedliche metallische Werkstoffe und Werkstoffverbunde verarbeitet werden können. Mit dieser Technologie zur Herstellung von Bauteilen ist in der Regel eine lange Prozesszeit verbunden, wenn bspw. pulverbettba-s...
Conference Paper
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Additive-manufacturing technologies have been gaining tremendously in popularity for some years in the production of single-part series with complex, close-to-final-contour geometries and the processing of special or hybrid materials. In principle, the processes can be subdivided into wire-based and powder-based processes in accordance with the Ass...
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Virtual process design based on numerical methods is a tool that has been widely used for years to help estimate expected forces, stresses and temperatures. Current efforts to improve hardware performance also seek to take account of the material itself in the numerical simulation. The necessary models to describe the material flow or microstructur...
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The aim is to realize a Q&P (Quenching and Partitioning) process for a hot forged component made of low-alloyed advanced high-strength steel (AHSS) 42MnSiCr. One advantage of this steel is the low alloy concept which is cost-effective. After forging, the component is cooled down to room temperature with a subsequent heat treatment to achieve the ch...
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Within this study, a new method for the determination of the Taylor-Quinney coefficient is presented. The coefficient was identified by measuring the force-displacement-behavior as well as the temperature change resulting from an adiabatic compression test. In order to deduce the global temperature increasing of the specimen from the local measured...
Conference Paper
Full-text available
Virtual process design based on numerical methods is a tool that has been widely used for years to help estimate expected forces, stresses and temperatures. Current efforts to improve hardware performance also seek to take account of the material itself in the numerical simulation. The necessary models to describe the material flow or microstructur...
Conference Paper
Full-text available
Inner cavities in cast ingots have to be closed by means of open-die forging to guarantee the integrity of the forged components during usage. In the paper a differentiation is made between the macroscopic and the microscopic closing of natural inner cavities. Special attention is paid to the dendritic structure of the surfaces of inner cavities an...
Conference Paper
The aim is to realize a Q&P (Quenching and Partitioning) process for a hot forged component made of low-alloyed advanced high-strength steel (AHSS) 42MnSiCr. One advantage of this steel is the low alloy concept which is cost-effective. After forging, the component is cooled down to room temperature with a subsequent heat treatment to achieve the ch...
Article
Full-text available
Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of die and workpiece, and machine kinema...
Article
In this paper, three different finite element simulations of welded T-Joint are to be computed using 2D-shell and 3D-solid element types. The assigned element types are built and modelled on T-joint plate with thickness of 4 mm. The thermo-mechanical FEM simulation using MSC Marc/Mentat is implemented throughout the analysis. The angular distortion...
Article
This paper focuses on investigation of welding distortion that occurred due to GMAW process which can adversely affect the dimensional accuracy and aesthetical value of the welded structure. Distortion can lead to production delay and costly remedial work. Based on this fact, it is necessary to predict the welding distortion in advance in order to...
Article
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Developments in technology rely increasingly on the numerical simulation of single process steps up to whole process chains using commercially available or user-written software systems, mostly based on the finite element method (FEM). However, detailed simulations require realistic models. These models consider the relevant material-specific param...
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During mechanical joining processes, high equivalent plastic strains occur in the joint area (e.g., flat-clinching: φeqv> 3.0). This causes a high deformation energy within the forming zone. In cold bulk forming, approximately 80% of the plastic energy is converted into heat due to internal friction at the grain boundaries. Compared to other formin...
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With the focus of lightweight constructions, the process line from producing of semi-finished products up to the second processing step of forging was investigated for composite of plastic (PA6) and aluminium alloy (EN-AW6060). Especially the material or deformation behaviour were determined fundamentally. For analysing the temperature-dependent ma...
Conference Paper
Nowadays the design of single process steps and even of whole process chains is realized by the use of numerical simulation, in particular finite element (FE) based methods. A detailed numerical simulation of hot forging processes requires realistic models, which consider the relevant material-specific parameters to characterize the material behavi...
Article
In this paper, the influence of the tension-compression anomaly of magnesium alloys on the numerical accuracy is quantified for the first time. For this, flow curves were evaluated for a twin-roll cast, rolled and annealed AZ31 strip using tensile and compression tests at different temperatures and constant strain rate. This is necessary to take in...
Conference Paper
Die additiven Fertigungstechnologien erleben seit einigen Jahren einen enormen Zuspruch bei der Herstellung von Einzelteilserien mit komplexen, endkonturnahen Geometrien und der Verarbeitung von Sonder- oder hybriden Werkstoffen. Prinzipiell lassen sich die Verfahren gemäß VDI- Richtlinie 3404 in drahtbasierte und pulverbasierte unterteilen. Eine w...
Conference Paper
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Dieses Tagungsband enthält die während des 9. Anwendertreffens am 28.03.2017 präsentierten Vorträge zu unterschiedlichen Themenstellungen aus den Bereichen CAD, Simulation und Berechnung. Von Experten aus Wirtschaft und Wissenschaft wurden neben Hinweisen zu neuen Simulationsfeatures auch Einblicke und Anregungen für eine effiziente Bauteilberechnu...
Article
Full-text available
Due to increasing product requirements the numerical simulation has become a powerful tool for the effective and efficient design of individual process steps as well as entire process chains. In order to model hot forging processes with finite element based numerical methods realistic models are required which consider the detailed mathematical des...
Conference Paper
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Dieser Artikel beschäftigt sich mit den umformtechnischen Verfahrensgrenzen für die Halbzeugherstellung und Weiterverarbeitung von Metall-Kunststoff-Verbunden aus EN AW-6060 und PA6 sowie von Metall-Metall-Verbunden bestehend aus EN AW-6082 und AZ31. Dabei wurden die Grundarten des Schmiedens - Steigen, Brei-ten und Stauchen - betrachtet. Es konnte...
Conference Paper
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Der Beitrag zeigt einen Ansatz zur Fertigung schlauchförmiger triaxialer Halbzeuge bzw. Preforms mit gewebeartiger Bindungsstruktur. Als innovativer Kern der Forschungs- und Entwicklungsarbeiten ist das neuartige und zum Patent angemeldete Verlegeprinzip mit zugehörigem Vorrichtungskonzept hervorzuheben. Für die Gestaltung der optimalen Verlegung u...
Conference Paper
Eine effiziente und effektive Technologieentwicklung und –optimierungen im Bereich der Umform- und Fertigungstechnik erfolgt heutzutage fast ausschließlich rechnergestützt auf Basis der Finiten Elemente Methode (FEM) oder der Finiten Differenzen Methode (FDM). Die aktuellen Umformsimulationssysteme sind in der Lage die notwendige Energie der Anlage...
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Low cost Fe-Mn-Si based shape memory alloys (SMA) have drawn much attention during the last two decades as a cost-effective alternative to the expensive Ni-Ti based SMA. In particular, the alloy Fe-17Mn-5Si-10Cr-4Ni-1(V,C) (mass%), which has been developed at Empa shows very promising properties with regard to potential commercial applications in c...
Conference Paper
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Dieses Tagungsband enthält die während des 8. Anwendertreffens am 22.03.2016 präsentierten Vorträge zu unterschiedlichen Themenstellungen aus den Bereichen CAD, Simulation und Berechnung. Von Experten aus Wirtschaft und Wissenschaft wurden neben Hinweisen zu neuen Simulationsfeatures auch Einblicke und Anregungen für eine effiziente Bauteilberechnu...
Article
Magnesium and magnesium alloys offer high potential as lightweight materials. Current works are mainly focused on the metal forming technologies and material development for sheet and strips to provide magnesium flat products for industrial applications. However, the technology for the production of magnesium long products for fasteners or other co...
Chapter
Branchenübergreifend unterliegen heute weltmarkttaugliche Lösungen von Bewegungsaufgaben einem ganzheitlichen Systemansatz. Dieser ist geprägt durch das Zusammenspiel neuester Forschungsergebnisse und Innovationen der Antriebs- und Getriebetechnik, der Regelungs-, Steuerungs- und Automatisierungstechnik bis hin zur Werkstoff- und Konstruktionstechn...
Conference Paper
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The changes of ecological awareness of political initiatives give new rules for economy and industry with the aim to support environmental friendly technology. Research projects are focusing on lightweight designs especially in automotive and aerospace industry. This paper deals with the results of the application of lightweight materials, in detai...
Article
Full-text available
The static recrystallization (SRX) behaviour of twin-roll cast and annealed magnesium AZ31 strip during hot deformation was determined under deformation conditions corresponding to the hot strip rolling process used in the production of twin-roll cast magnesium coils. Plane strain compression tests were performed using double-hit schedules at tempe...
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The significance of light-weight construction in the automotive industry continues to increase. The reasons for this lie, for example, in the reduction of CO2 emissions achieved by fuel savings due to reductions in automobile weight. Low vehicle weights can be achieved through material substitution or improved topologies. Steel, however, remains th...
Conference Paper
Over the last decades light-metal design has received a high priority in the modern light weight constructions. Thereby the goal is on the use of lightweight materials and the substitution of component materials. The main research activities are focused at metal forming technologies for strips and sheets of different magnesium alloys. The aspects i...
Article
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The paper is focused on magnesium alloys with different initial states – cast or extruded – for forging operations at the example of a wheel hub. The different initial microstructures have an influence on the deformation behaviour and therefore on the final mechanical properties of the components. The forming process of this component was designed...
Article
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Metadynamic recrystallization takes place during isothermal annealing of materials in which an incomplete dynamic recrystallization occurred. In magnesium alloys this question has been investigated less until now. The metadynamic recrystallization behavior of twin-roll-cast and annealed AZ31 strip after hot deformation was investigated under condit...
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The utilization of modern simulation systems offers new ways for an environment- and resource-friendly research and development of materials and their production technologies. Nowadays, technological parameters, which are significantly influencing the material's behavior, such as temperature development and mechanical properties of a semi-finished...
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The paper presents a new method to describe and to predict the development of scale during metal forming processes, especially hot strip rolling processes. This is necessary because scale develops during all hot deformation processes over 600 °C and affects the mass loss of the raw weight as well as the surface quality of the semi-finished product....
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Für die Zunderentstehung ist ein hoher Grad an Materialverlust charakteristisch, weshalb aktuell die Beschreibung der Zunderkinetik stark in den Focus der Wissenschaft und Industrie rückt. Dazu ist es jedoch notwendig, die Umformeigenschaften der oxidischen Deckschicht auf Stahl besser und detaillierter zu beschreiben, denn Zunder lässt sich währen...
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With the introduction of numerous new materials concepts and always desired process optimization and consolidation of the process stream, the demands on the forming process for the production of semi-finished to finished parts increase. To meet these requirements, numerical simulation systems are mainly used for the process design, all of them acce...
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This paper describes the possibilities for identifying temperature-dependent mechanical and thermo-physical properties of oxide scale components which are a necessary data input for a numerical simulation. Scale develops on steel surfaces in oxidising atmospheres above 570 °C and influences the surface quality as well as the roughness of semi-finis...
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Scale is a reaction product between oxygen and steel, which is formed at a temperature above 570 C. Oxidation processes at the surface of metallic products affect the quality. The growing oxide scale effect an increase in surface roughness of semi-finished products. Typically the oxide scale is built up of three ferrous oxides of different stoichio...
Article
This paper provides the base for a multi-scale hot forming simulation of material flow as well as scale development during deformation. A new idea enables the description of the properties of the scale evolution applying iron powder with different oxygen contents. The powder was pressed in diverse geometry shapes and sintered under controlled atmos...
Article
The general objective of the work is to estimate the properties of the material in hot strip rolling process. The authors propose a modified inverse algorithm; to make direct use of the manufacturing process instead of conventional plastometric tests. This approach allows to reduce time and costs of identification. The rolling at 4‐stand pilot mill...