bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of Motion-Capture Techniques Applied to Tube Bending
Authors: Simonetto Enrico , Ghiotti Andrea , Bruschi Stefania
Published: July 2015

Tube bending is one of the most relevant manufacturing processes for the production of structural elements, but it suffers from the problem of springback that requires the tuning of the process parameters at every launch of new production batches. Off-line optimization approaches can be found in literature, but they often require complex characterization of the material properties or the application of approaches based on numerical simulation analyses. So, the development of new and more flexible on-line approaches to measure and correct the springback is crucial especially for highly automated machines as for example the tube benders. The paper presents a new measurement approach, based on the application of motion-capture techniques, to provide real-time measurements of the bent tube orientation, in order to decrease the time for the set-up of the main process parameters. A new methodology as well as a new experimental apparatus for the in-line monitoring of the tube springback is presented, as well as the evaluation of its accuracy when applied to the industrial process. An Inertial Measurement Unit (IMU) is linked to the tube during bending and the measurements from three gyroscopes and three accelerometers are used to perform the computation of the tube orientation in the 3D space. The proposed approach appeared promising for the evaluation of the springback through the measurement of the final angular configuration reached after bending.
Shape Factors and Feasibility of Sheet Metal Hydroformed Components
Authors: Primo Teresa , Papadia Gabriele , Del Prete Antonio
Published: July 2015

The authors have investigated, in other paper, the problem related to the definition of a “set of shape factors” in order to declare the feasibility of a product through sheet hydroforming. In particular the defined shape factors are three different a-dimensional coefficients by which it is possible to declare the feasibility of a product through the calculation, in different sections, of the three previous shape factors. The robustness of this methodology is related to the correct calculation of the “limit value” of each shape factor. In fact the feasibility is reached if, in any section, the calculated shape factors are higher than their respective limit values. In this paper the authors have performed an extensive numerical and experimental campaign, taking into account a different geometry respect to that of the first paper, in order to: re-calculate the limit value for each shape factor and, then, verify the correctness of the limit values exposed in the previous first paper. The numerical campaign has been used, after the evaluation of the accuracy of the numerical model, in order to study the feasibility of the product without engaging the hydroforming machine. Finite Element Analysis (FEA) has been extensively used in order to investigate and define each shape factor with a proper comparison to the macro feasibility of the chosen component geometry. The limit values that have been calculated by the authors in this paper are slightly different from those calculated in the first paper. From this point of view it is possible that, although the shape factors are a-dimensional coefficients, they are affected by different choices of the users as, for example, the dimensions of the initial blank. Anyway, the small differences in the shape factors limit values do not adversely affect the use of the shape factors in order to predict the feasibility of the product.
High Strain Rate Behaviour of AA7075 Aluminum Alloy at Different Initial Temper States
Authors: Sasso Marco , Forcellese Archimede , Simoncini Michela , Amodio Dario , Mancini Edoardo
Published: July 2015

The aim of this work is to study the mechanical properties of alloy AA7075 in both T6 and O temper states, in terms of visco-plastic and fracture behavior. Tension and compression tests were carried out starting from the quasi-static loading condition 10-3 up to strain rates as high as 2 x 103 s-1. The high strain rate tests were performed using a Split Hopkinson Tension-Compression Bar (SHTCB) apparatus. The tensile specimens were also subjected to micro-fractography analysis by Scanning Electronic Microscope (SEM) to evaluate the characteristics of the fracture. The results show a different behavior for the two temper states: AA7075-O showed a significant sensitivity to strain rate, with a ductile behavior and a fracture morphology characterized by coalescence of microvoids, whilst AA7075-T6 is generally characterized by a less ductile behaviour, both as elongation at break and as fracture morphology. Brittle cleavage is accentuated with increasing strain rate. The Johnson-Cook viscoplastic model wad also used to fit the experimental data with an optimum matching.
Numerical – Experimental Correlation of Sheet Hydroformed Component
Authors: Spagnolo Alessandro , Primo Teresa , Papadia Gabriele , Del Prete Antonio
Published: July 2015

Sheet hydroforming has gained increasing interest in the automotive and aerospace industries because of its many advantages such as higher forming potentiality, good quality of the formed parts which may have complex geometry. The main advantage is that the uniform pressure can be transferred to any part of the formed blank at the same time. This paper reports numerical and experimental correlation for symmetrical hydroformed component. Experimental tests have been carried out through the hydroforming cell tooling, designed by the authors thanks to a research project, characterized by a variable upper blankholder load of eight different hydraulic actuators. The experimental tests have been carried out following a factorial plane of two factors, with two different levels for each factor and three replicates for each test with a total of 12 tests. In particular two process parameters have been considered: blank holder force, die fluid pressure. Each factor has been varied between an High (H) and Low level (L). The order in which have been conducted the tests has been established through the use of the Minitab software, in order to ensure the data normality and the absence of auto-correlation between the tests. An ANOVA analysis has been performed, in addition, with the aim of evaluating the influence of process parameters on the thickness distribution of the component, its formability and feasibility. Finally, finite element analysis (FEA) was used to understand the formability of a material during the hydroforming process. In this paper, the commercial finite element code LS-Dyna was used to run the simulations. A good numerical – experimental correlation has been obtained.
Numerical and Experimental Investigations of Multistage Sheet-Bulk Metal Forming Process with Compound Press Tools
Authors: Behrens Bernd-Arno , Bouguecha Anas , Vucetic Milan , Hübner Sven , Rosenbusch Daniel , Koch S.
Published: July 2015

Sheet-bulk metal forming is a manufacturing technology, which allows to produce a solid metal component out of a flat sheet. This paper focuses on numerical and experimental investigations of a new multistage forming process with compound press tools. The complete process sequence for the production of this solid metal component consists of three forming stages, which include a total of six production techniques. The first forming stage includes deep drawing, simultaneous cutting and following wall upsetting. In the second forming stage, flange forming combined with cup bottom ironing takes place. In the last stage of the process sequence, the component is sized. To investigate and to improve process parameters such as plastic strain distribution, resulting dimensions and process forces, FEA is performed. Based on these results the developed process is designed.
Hot Deformation Behavior of a 3rd Generation Advanced High Strength Steel with a Medium-Mn Content
Authors: Steineder Katharina , Dikovits Martina , Beal Coline , Sommitsch Christof , Krizan Daniel , Schneider Reinhold
Published: July 2015

Medium-Mn steels are one of the promising candidates to achieve the desired mechanical properties in the 3rd generation of cold rolled advanced high strength steels (AHSS) for automotive applications. Their duplex microstructure consists of a ferritic matrix with a substantial amount of metastable retained austenite, which transforms to strain-induced martensite upon forming. This strengthening mechanism, well known as the TRansformation Induced Plasticity (TRIP) effect, provides the steel an excellent combination of high strength and elongation with a product of RmxA80 up to 30.000 MPa%. As hot rolling is one of the crucial steps during their production, the hot deformation behavior of Medium-Mn steels has to be thoroughly evaluated during their development stage.Therefore, the present contribution studied the hot deformation response of a 0.1 %C 5.5 %Mn steel by means of hot compression tests using a Gleeble® 3800 device. The influence of different deformation temperatures (900-1100 °C) and strain rates (0.1-10 s-1) on the stress-strain behavior was investigated. The flow curves were analyzed and corrected by the effects of adiabatic heating.Furthermore, the strain rate sensitivity m of the material was determined by evaluating stress values at different strain rates for given temperatures and strains. The m-values can be used to predict the deformation behavior of the material within the investigated range of parameters.Lastly, the hot working behavior of an alternative steel concept for a 3rd Generation AHSS with significantly lower Mn-content was comparatively investigated.
Tool Wear Prediction in Machining Process Using a Microstructure-Based Finite Element Model
Authors: Sáez-de-Buruaga Mikel , Poveda Ibon , Arrazola Pedro José
Published: July 2015

The microstructure of materials has a significant influence on tool life, however most of the research in modelling to date considers the material as homogeneous. This research aims to develop a microstructure-based Finite Element Model in order to qualitatively analyze the influence of the scale of the microstructure on the generated tool wear. In particular, this paper is focused on the orthogonal cutting process of a ferrite-pearlite dual-phase steel using uncoated carbide tools. Based on individual mechanical properties of these phases, a 3D coupled Eulerian Lagrangian heterogeneous model was developed. An empirical tool wear rate prediction model was implemented by a user subroutine in both models (heterogeneous and homogeneous) to predict wear and wear rate values. A comparison between the microstructure-base model (heterogeneous) and the homogeneous model considering wear and wear rate values was made. The results demonstrate the validity of microstructure-based Finite Element Model for an improved prediction of the wear phenomena.
Agile Multiscale Modelling of the Thermo-Mechanical Processing of an Aluminium Alloy
Authors: Macioł Piotr , Bureau Romain , Poletti Cecilia , Sommitsch Christof , Warczok Piotr , Kozeschnik Ernst
Published: July 2015

The multiscale modelling of the behaviour of metal alloys during processing is often limited by the computing power required to run them. The Agile Multiscale Methodology was conceived to enhance the designing and controlling of complex multiscale models through an automatic run-time adaptation of its constitutive sub-models. This methodology is used to simulate the behaviour of an 6082 aluminium alloy during its thermomechanical treatment. The macroscopic deformation, the work-hardening and the state of precipitation are computed in different modules, allowing the coupling of several software solutions (DEFORMTM2D and © MatCalc) through an external storage of the relevant data.
Inverse Analysis Procedure to Determine Flow Stress and Friction Data for Metal Cutting Finite Element Modeling
Authors: Franchi Rodolfo , del Prete Antonio , Umbrello Domenico , Mariano Emilia
Published: July 2015

This paper describes an automated procedure developed for the identification of Johnson-Cook (JC) law material parameters and Coulomb friction coefficient at the tool-chip interface, in the specific case of metal cutting FE analysis. The procedure has been developed in iSight environment, through the integration between AdvantEdge metal cutting FE code and an appropriately selected optimization algorithm. The identification of JC and friction parameters, in fact, has been performed considering it as an optimization problem, in which the objective function is the numerical/experimental error function minimization (in the specific case, it is related to the forces and temperatures responses). The calibration and validation phases have been performed using forces and temperatures experimental data, collected in orthogonal cutting test on SAF2507 superduplex steel.
Numerical Optimization of Current Parameters in Combined Electromagnetic-Classical Forming Processes
Authors: Kiliclar Yalin , Rozgic̀ Marco , Reese Stefanie , Stiemer Marcus
Published: July 2015

A method for the virtual process design of combined quasi-static and electromagnetic forming processes based on a thorough process simulation is developed. Its flexibility is demonstrated by means of an identification problem for process parameters yielding a minimum bottom edge radius in round cup forming. Particularly, an optimum double exponential current pulse is identified. This class of pulses is parameterized as an example for pulses with mono-directed current employed to reduce the wear of the tool coil.
Numerical Modelling of Explosive Welding on the Basis of the Coupled Eulerian Lagrangian Approach
Authors: Madej Lukasz , Perzynski Konrad , Paul Henryk
Published: July 2015

The main goal of the paper is development of a numerical model for explosive welding involving geometry and properties of major process components, i.e. base plate, flyer plate and explosive material. To properly replicate material behavior under these severe conditions the Coupled Eulerian Lagrangian (CEL) approach is used. Series of numerical simulations are realized based on the developed model in order to relate the process variables to the physical parameters. That will be used in further work to establish how these can be used to predict whether or not bonding will occur.
Effect of Geometric Parameters in the Upsetting and Extruding Riveting Process on the Quality of Riveted Joints
Authors: Li Wei Jia , Yang Lian Fa
Published: July 2015

Upsetting and extruding riveting is a new joining method, which is mainly used to join castings. In order to investigate the effect of geometric dimensions of punch and upper sheet hole diameter on the quality of joints, models with different geometric parameters were simulated via ABAQUS. According to the simulation results, the riveting process could be divided into five stages. Besides, diameter difference on rivet tail and interference value on upper sheet hole wall were selected as indicators to evaluate quality of joints. And a group of parameters is obtained for a better quality of joints. Finally, the simulation results were validated through experiments.
Basic Investigations on Joining of Metal and Fibre Components Based on the Semi-Solid Forming Process
Authors: Marx Lukas , Liewald Mathias , Riedmüller Kim Rouven
Published: July 2015

The trend towards lightweight construction in automotive engineering causes additional effort and higher expense in vehicle manufacturing, because new materials or, respectively, new material combinations require adapted production and processing methods. Various combinations of metallic and fibre-based structures (GRP-/ CFRP components) presuppose convenient joining methods. In this context, an innovative joining method for combining sheet metals with carbon textiles is going to be developed at the Institute for Metal Forming Technology (IFU, University of Stuttgart / Germany). The goal of this research work is motivated by the prevention of any damage of the used textile fibre structures during the joining process (compared to mechanical joining methods like screwing or riveting). Based on the semi-solid forming technology, the new joining process is going to be developed to create a material integrated interlock between fibres and metallic components.This paper deals with the first fundamental investigations, conducted at IFU, which have already shown the technical feasibility of this new type of joining technique. The research work to be carried out comprises the usage of different sheet alloys: the combinations steel-aluminium, aluminium-aluminium and steel-steel are to be joined with layers of carbon fibre fabrics. By this innovative joining method, a firmly bonded and non-aging connection between textile and metallic materials is to be produced, without the need of any adhesive materials or associated preparative cleaning methods.
Adhesive Distribution and Global Deformation between Hybrid Joints
Authors: Landgrebe Dirk , Mayer Bernd , Niese Stephan , Fricke Holger , Neumann Ivo , Ahnert Maik , Falk Tobias
Published: July 2015

In multi-material-design, e.g. in the automotive industry, mechanical joining processes like self-pierce riveting are well established, because of their amount of advantages. However, adhesive bonding with one-component structural adhesives is increasingly being used. The combination of the specific advantages of both joining techniques in the form of hybrid joints leads to synergies of quality and reliability, such as high corrosion resistance and better damping properties. A critical issue is the generation of global deformations of the different parts of the mechanical joints. These global deformations of the sheet metal between two or more mechanical connectors (e.g. rivets) are caused by the formation of adhesive bags during the riveting process, before the adhesive curing takes place. This research focuses on the time-dependent formation process of these bags. The aim is to achieve a reduction of global deformations based on detailed knowledge of the adhesive flow during the manufacturing of the joint by means of experiments and simulations. For this purpose experimental techniques and measurement methods for deformations over time are presented for different setups of hybrid joint types of self-piercing rivets in combination with adhesive bonding. The challenge is to track rapid and small surface deformations very accurately in the ongoing mechanical joining process. High-speed optical measurement technology like Point-Tracking and surface scanning are used to track the resulting deformations experimentally. Numerical investigations, which include the interaction of the solid matter influenced in the mechanical joining process and the fluid adhesive, are presented. On the basis a fully coupled fluid-structure interaction simulation of a single hybrid joint, a surrogate model for a multi-point hybrid joint is developed. The comparison of experimental data with simulations allows deriving the pressure distribution and flow velocities inside the adhesive layer. The influence of various parameters can be interpreted based on the physics of the interacting system, ultimately resulting in optimization helpful to the automotive industry.
FEA-Based Optimisation of a Clinching Process with a Closed Single-Part Die Aimed at Damage Minimization in CR240BH-AlSi10MnMg Joints
Authors: Behrens Bernd-Arno , Bouguecha Anas , Vucetic Milan , Hübner Sven , Yilkiran Deniz , Jin Yi Lin , Peshekhodov Ilya
Published: July 2015

The paper presents results of FEA-based optimisation of the tool design of a clinching process with a closed single-part die. The studied materials are the bake-hardening steel CR240BH, 1.5 mm thick, on the punch side and the die-cast aluminium alloy AlSi10MnMg, 2.95 mm thick, on the die side. The optimisation was aimed at suppression of cracks that appear at the bottom of the clinch joint in AlSi10MnMg in the case of using conventional tool designs. By varying geometry parameters of the tools it was possible to reduce crack probability, though along with slightly worse, but still acceptable geometry parameters of the clinch joint.
Inverse Thermal Analysis of Melting Pool in Selective Laser Melting Process
Authors: van Belle Laurent , Agazzi Alban
Published: July 2015

The Selective Laser Melting (SLM) process of metallic powder is an additive technology. It allows the production of complex-shaped parts which are difficult to obtain by conventional methods. The principle is similar to Selective Laser Sintering (SLS) process: it consists, from an initial CAD model, to create the desired part layer by layer. The laser scans a powder bed of 40 μm thick. The irradiated powder is instantly melted and becomes a solid material when the laser moves away. A new layer of powder is left and the laser starts a new cycle of scanning. The sudden and intense phase changing involves high thermal gradients which induce contraction and expansion cycles in the part. These cycles results in irreversible plastic strains. The presence of residual stresses in the manufactured part can damage the mechanical properties, such as the fatigue life. This study focuses on the thermal and mechanical modelling of the SLM process. One of the key points of the mechanical modelling is the determination of the heat source generated by the laser in order to predict residual stresses. This work is divided in three parts. In a first part, an experimental protocol is established in order to measure the temperature variation during the process. In the second part, a thermal model of the process is proposed. Finally, an inverse method to determine the power and the shape of the heat source is developed. Experimental and computational results are fitted. The influence of several geometries of the heat source is investigated.
Simplified Rheocasting of Al-Si Alloys Sheared by Mechanical Stirring
Authors: Hernández Alfredo , Chávez J. Federico , Hernández Raquel E.
Published: July 2015

A rheocasting prototype for the semi-solid processing of Al-Si alloys was designed and assembled at laboratory scale, this is the first attempt for the development of S2P equipment in Mexico. This work describes the simplified method of mechanical stirring and the calculation of the theoretical parameters for the operation of the experimental device in order to provide shear rate into the slurry by a stainless steel impeller inside a crucible made of hot work steel. Moreover, a vertical pressure die-rheocasting system it is applied with the semi-solid alloy flowing counter the position of the injector during the displacement of the crucible in order to fill the mold. New design is applied in this rheocasting equipment.The semi-solid state with thixotropic behavior is produced in the stirred AlSi7Mg alloy; this condition allows the non-dendritic morphology because the intensively stirring at the beginning of the solidification produces the trimming of dendrites, growing so the primary solid (α) in globular shape surrounded by eutectic microstructure. Preliminary microstructural characterization was performed.
Mechanical Properties of Thixoformed 7075 Feedstock Produced via the Direct Thermal Method
Authors: Ahmad Asnul Hadi , Naher Sumsun , Brabazon Dermot
Published: July 2015

Abstracts: This paper presents an overview of measured mechanical properties of thixoformed aluminium 7075 feedstock produced by the direct thermal method (DTM). The DTM feedstock billets were processed with a pouring temperature of 685 °C and holding periods of 20 s, 40 s and 60 s before being quenched and subsequently thixoformed. A conventionally cast feedstock billet was produced with a pouring temperature of 685 °C and was allowed to solidify without quenching. The feedstock billets were later formed by an injection test unit in the semi-solid state. Tensile testing was then conducted on the thixoformed feedstock billets. Tensile properties for 7075 DTM thixoformed feedstock billets were found significantly influenced by the thixoformed component density. Samples with longer holding times were found to have higher density and higher tensile strength.
Anisotropic Behavior in Plasticity and Ductile Fracture of an Aluminum Alloy
Authors: Lou Yan Shan , Yoon Jeong Whan
Published: July 2015

Anisotropic mechanical behavior is investigated for an aluminum alloy of 6K21-IH T4 both in plastic deformation and ductile fracture. Anisotropic plastic deformation is characterized by uniaxial tensile tests of dog-bone specimens, while anisotropy in ductile fracture is illustrated with specimens with a central hole, notched specimens and shear specimens. All these specimens are cut off at every 15º from the rolling direction. The r-values and uniaxial tensile yield stresses are measured from the tensile tests of dog-bone specimens. Then the anisotropic plasticity is modeled by a newly proposed J2-J3 criterion under non-associate flow rule (non-AFR). The testing processes of specimens for ductile fracture analysis are simulated to extract the maximum plastic strain at fracture strokes as well as the evolution of the stress triaxiality and the Lode parameter in different testing directions. The measured fracture behavior is described by a shear-controlled ductile fracture criterion proposed by Lou et al. (2014. Modeling of shear ductile fracture considering a changeable cut-off value for stress triaxiality. Int. J. Plasticity 54, 56-80) for different loading directions. It is demonstrated that the anisotropic plastic deformation is described by the J2-J3 criterion with high accuracy in various loading conditions including shear, uniaxial tension and plane strain tension. Moreover, the anisotropy in ductile fracture is not negligible and cannot be modeled by isotropic ductile fracture criteria. Thus, an anisotropic model must be proposed to accurately illustrate the directionality in ductile fracture.
A Comparative Study of the Identification Methods for Tube Hydroforming Process
Authors: Zribi Temim , Khalfallah Ali , Salah Hedi Belhadj
Published: July 2015

The present paper aims to assess the accuracy of identification methods used in the evaluation of the flow stress relationship of tubular materials for hydroforming applications. Based on experimental data acquired from home designed and manufactured experimental tool and results collected from literature, flow stress parameters are determined using both analytical and inverse identification methods. The obtained results are coped to experimental measurements to validate the proposed approaches. It is shown from the analysis based on the comparative assessment of flow stress inferred from tube bulge test that, inverse parameter identification method is the appropriate methodology that contribute to a more accurate tube hydroforming characterization.
Numerical Modeling of Thermal Evolution in Hot Strip Rolling of Magnesium Alloy
Authors: Nam Alexander , Prüfert Uwe , Eiermann Michael , Kawalla Rudolf
Published: July 2015

This paper introduces a concept for the simulation of temperature distribution in reversing hot rolling of magnesium strip. The technological chain consists of reheating the casted rough strip, carrying the coil form furnace to coiler, setting down on mandrel, and hot reversing rolling. The paper represents the current state of work. The numerical calculation is based on an object-oriented FEM toolkit written in MATLAB™ and is carried out in three spatial dimensions and time.
A Comparative Study of Forming Limit Diagrams Predicted by Two Different Plasticity Theories Involving Vertex Effects
Authors: Akpama Holanyo K. , Bettaieb Mohammed , Abed-Meraim Farid
Published: July 2015

The main objective of this contribution is to compare the Forming Limit Diagrams (FLDs) predicted by the use of two different vertex theories. The first theory is micromechanical and is based on the use of the Schmid law, within the framework of crystal plasticity coupled with the Taylor scale-transition scheme. The second theory is phenomenological and is based on the deformation theory of plasticity. For both theories, the mechanical behavior is formulated in the finite strain framework and is assumed to be isotropic and rate-independent. The theoretical framework of these approaches will be presented in details. In the micro-macro modeling, the isotropy is ensured by considering an isotropic initial texture. In the phenomenological modeling, the material parameters are identified on the basis of micro-macro simulations of tensile tests.
Metallurgical Evolutions in Hot Forging of Dual Phase Titanium Alloys: Numerical Simulation and Experiments
Authors: Ducato Antonino , Buffa Gianluca , Astarita Antonello , Squillace Antonino , Fratini Livan , Micari Fabrizio
Published: July 2015

Titanium forging has been encountering a growing interest in the scientific and industrial communities because of the distinct advantages it provides with respect to machining, in terms of both mechanical properties of the product and material waste, thus significantly reducing the Buy to Fly ratio. In the paper, a numerical FE model, based on a tri-coupled approach and able to predict the microstructural evolutions of the workpiece during the process, is developed and set up. Calculated results are compared to experiments for a few industrial case studies. The final phases distribution in the forged parts is experimentally measured and compared to the FE model output finding satisfying overlapping.
Speed Idle Roll Law Optimization in a Ring Rolling Process
Authors: Giorleo Luca , Ceretti Elisabetta , Giardini Claudio
Published: July 2015

Ring Rolling is a complex hot forming process where different rolls are involved in the production of seamless rings characterized by extreme dimensions (i.e. external diameter higher more than 1m). Because each roll can be independently controlled from the other ones different speed laws must be set; usually, in the industrial environment, a milling curve is introduced to monitor the shape of the workpiece during the deformation in order to ensure a correct ring production. In former works the authors focused their attention on the influence of different milling curves for an industrial case and the results underlined that a ring produced with a good quality and lower loads and energy could be obtained imposing a linearly descending trend to the Idle roll speed law. However different approaches could be used in order to evaluate the mentioned speed law.In this work the authors enhanced the knowledge about the optimization of the Idle roll speed law: different Idle roll speed laws were designed and simulated and the results were compared in order to identify the best speed law that guarantees a good quality ring with lower loads and energy required for manufacturing.
Design of Rotary Extrusion Process Using Simulation Techniques to Save Raw Material in Hollow Components
Authors: Mangas Ángela , Santos Maite , Zarazua Jose Ignacio , Pérez Iñaki
Published: July 2015

The forging process plays an important role in the automotive industry thanks to the good mechanical properties of the forged parts. Nowadays, due to the European policy of increasing efficiency in raw material and energy usage, the metal forming sector is demanding new innovative technologies. In this context, rotary extrusion technology is a very promising metal forming alternative to the drilling techniques after forging processes.The presented work is focused on hollow shafts that are usually manufactured using a combination of forming and metal cutting techniques. Deep drilling is the most common technique to obtain internal holes in the automotive hollow parts, but it is an expensive process in terms of material usage. In this framework, rotary extrusion appears as an alternative technology that leads to the reduction of material usage and process time. The tubular shape is formed with the combination of two forming processes: flow forming and backward extrusion.This paper presents the development of a simulation methodology, the process design for a hollow part, the specifications of the experimental unit, and the manufactured prototypes in order to validate the simulation model. Also the incremental process is improved thanks to a sensitivity study of the rollers geometry. Rotary extrusion experiments are done using a modified flow forming machine and 20% material saving is achieved when obtaining the deep hole in comparison to the current deep drilling technology. The process design and numerical model tasks carried out try to provide the industry manufacturers an alternative technology to drilled parts considering the advantages of rotary extrusion parts.
Effect of Stress State and Temperature on the Kinetics of Martensitic Phase Transformation in TRIP-Assisted Steel
Authors: Kim Hwi Geon , Lee Jin Woo , Barlat Frédéric , Kim Dae Yong , Lee Myoung Gyu
Published: July 2015

The effects of the stress state and temperature on the martensitic phase transformation behavior in TRIP 780 steel were investigated using multi-axial experimental techniques. Various mechanical experiments are performed to differentiate the stress state and temperature effects. For this purpose, five different stress states were considered; i.e., uniaxial tension, uniaxial compression, equibiaxial tension, plane strain tension and simple shear. A temperatures both 25 and 60 °C for each stress state condition except the simple shear test were investigated. In-situ magnetic measurements were performed to mesure the evolution of the martensite content throughout each experiment. Finally, a new martensitic transformation kinetics model for the TRIP 780 steel is proposed to take the effect of stress state and temperature into account.
Modelization of the Rolling Mill with a FE Code
Authors: Chevalier Damien , Cezard Pierre , Langlois Laurent , Bigot Régis
Published: July 2015

To reduce production costs and to improve performances of hot rolled products, it is necessary to optimize the production line. The rolling mill is one of the major factors which affect the internal quality. In fact the process tends to reduce the size of defects during the strain. The production line consisting of 24 stands has been modeled with a commercial FE-code FORGE®. First, a model has been developed and adjusted according to industrial data. Then a parametric study was carried out in order to estimate the influence of the process parameters on the internal quality of the rolled material.
Investigation of the Operational Reliability of the Rolled Rails According to the Various Technologies
Authors: Kolbasnikov N.G. , Zotov Oleg G. , Lukyanov Aleksey A.
Published: July 2015

Based on experimental studies of the complex mechanical properties and microstructure, as well as simulation of rails rolling modes made from different steel manufacturers are shown the main technological approaches to obtain rails with high operational reliability . Found that, under the current production technology of domestic steel rails the adjustment of the chemical composition, temperature-deformation modes of rolling and cooling speed rate of the rails is suitable for reducing the negative free ferrite influence on rails durability.
A Novel Method for Determining the Stiffness of a Composite Structure Resulting from the Manufacturing Process Using a Discrete Mesoscopic Finite Element Model
Authors: Mitchell Cynthia J. , Sherwood James A. , Dangora Lisa M. , Gorczyca Jennifer L.
Published: July 2015

This paper presents a methodology for extending the use of the beam-shell forming model to predict the structural properties of the composite part. After the forming simulation has been performed, the material definition will be changed such that the beam elements will represent the fiber reinforcements and the shell elements will represent the resin. The methodology behind the entire approach will be demonstrated using a stitched uniaxial glass fabric. The methodology for characterizing the fabric behavior will be discussed. After the part has been formed, it will be infused with resin. The methodology for characterizing the composite behavior will be introduced. The finite element model will be compared with experimental data to validate the methodology.
A Contribution on Manufacturing Process Development for Composite Material Forming
Authors: Mayer Philippe , Perrin Henri , Becker Eric , Langlois Laurent , Bigot Régis
Published: July 2015

The author presents an approach to study an innovative manufacturing process developed to produce composite parts with new geometrical possibilities. The aim of this first study is to understand the motions of fibers during the forming of this kind of composite parts and to explore the feasibility of this forming process by an experimental analysis and FEM simulations with Forge3©. The reliability of the simulation tool and its potential, never exploited in this area, will be evaluated.
Experimental Test and FEA of a Sheet Metal Forming Process of Composite Material and Steel Foil in Sandwich Design Using LS-DYNA
Authors: Behrens Bernd-Arno , Vucetic Milan , Neumann A. , Osiecki Tomasz , Grbic Nenad
Published: July 2015

A structural concept in multi-material design is used in the automotive industry with the aim of achieving significant weight reductions of conventional car bodies. In this respect, the specific use of steel foils and continuous fiber-reinforced thermoplastics represents an interesting material combination for the production of hybrid parts in sandwich design. This contribution deals with the experimental and numerical analysis of a conventional sheet metal forming process using a composite material based on Polyamide 6 (PA6) with unidirectional endless glass fiber reinforcement and HC220Y+ZE steel foil. A unidirectional composite plate is positioned between two steel foils in sandwich design and formed under appropriate temperature conditions. For the numerical analysis of the forming process the software LS-DYNA is used.
Path Definition for Tailored Fiber Placement Structures Using Numerical Reverse Draping Approach
Authors: Bohler Patrick , Carosella Stefan , Goetz Christopher , Middendorf Peter
Published: July 2015

The properties of fiber reinforced materials are depending on the fiber direction. During draping processes - which are necessary to form complex structures - the fiber direction and therefore the resulting properties of the final part are changing.To ensure that the fibers in the final complex structure are placed exactly in the direction needed, a new approach is investigated.The idea is to define the orientation of the reinforcement fibers based on the distribution of forces in a complex structure under certain loading determined by a structural simulation. Best lightweight behavior is achievable in the final complex structure. A three-dimensional mesoscopic model of the directed fibers is created using FEM-software. In reverse draping simulations the three-dimensional fibers are formed from complex shape to a two-dimensional flat sheet.In manufacturing the two-dimensional patches can be created using the tailored fiber placement process. With this process it is possible to place the fibers orientated to the required paths. The patches are formed to the necessary three-dimensional shape by a real draping process. The relative sliding behavior of crossing fibers can be achieved by varying the stitch during the TFP process.Using that approach it is possible to create lightweight structures in which fibers are orientated directly along the load paths of the three-dimensional application.
Nano-Structured Tungsten Carbide Coating Reduces Wear of Tooling for Extrusion and Abrasive Materials Forming
Authors: Zhuk Yuri
Published: July 2015

This paper presents the applications of advanced CVD Tungsten Carbide coating to extend the life of tooling used for forming abrasive and corrosive materials.Hardide nanostructured Tungsten Carbide coating combines high hardness (70-77Rc) with excellent toughness. Unlike other hard coatings Hardide can produce a conformal coating layer on complex-shaped tools, including internal surfaces of extrusion die cavities and moulds. In ASTM G65 test the Hardide coating abrasion resistance exceeded WC/Co (9%) cemented carbide by a factor of 4X, and D2 tool steel by 10X. Thus the coating can significantly increase the life of D2 steel tooling used for forming abrasive materials and by maintaining better dimensional tolerances and surface finish of the tool it will manufacture better quality products.The Hardide coating has enhanced resistance to corrosion and aggressive media, including acids; this makes the coating especially suitable for the tooling used in forming uPVC, PTFE and other corrosive materials.The Hardide coating has been tested on extrusion and pelletizing dies processing abrasive and corrosive slurries and typically showed a 3X increase in the life of the tooling. Similar results were achieved by the coating of powder compaction punch/die sets for pharmaceuticals tableting.
Investigation of the Suitability of Surface Treatments for Dry Cold Extrusion by Process-Oriented Tribological Testing
Authors: Teller Marco , Bambach Markus , Hirt Gerhard , Ross Ingo , Temmler André , Poprawe Reinhart , Bolvardi Hamid , Prünte Stephan , Schneider Jochen M.
Published: July 2015

In cold extrusion of aluminum alloys adhesive wear can be prevented by an excessive lubrication of the process. While this causes additional process steps also environmental risks have to be addressed. Hence, dry metal forming, i.e. avoiding lubrication by means of coatings and topography modifications is highly desirable. In this paper first results concerning the behavior of tailored surfaces under dry metal forming conditions for pure aluminum are presented. Different surface treatments (laser polishing and Mo2BC coating) of the tool steel AISI H11 are tested in a compression-torsion-tribometer under conditions adapted from cold extrusion. Normal stresses six times higher than the initial yield stress of the tested workpiece material pure aluminum (AA1050-O) are applied. Furthermore, a strategy for the characterization of aluminum adhesions to the tool is introduced. The influences of different topographies and the presence of a coating on the loss of material due to adhesive wear are investigated.
Implicit Stress Integration and Consistent Tangent Matrix for Yoshida’s 6th Order Polynomial Yield Function Combined with Yoshida-Uemori Kinematic Hardening Rule
Authors: Hamasaki Hiroshi , Yoshida Fusahito , Uemori Takeshi
Published: July 2015

This paper describes fully implicit stress integration scheme for Yoshida’s 6thorder yield function combined with Yoshida-Uemori kinematic hardening model and its consistent tangent matrix. Cutting plane method was employed for accurate integrations of stress and state variables appeared in Yoshida-Uemori model. In the present scheme, equivalent plastic strain, stress tensor and all the state variables are treated as independent variables in order to handle the 6th order yield function which is not the J2 yield function, and the equilibriums for each variables are solved for the stress integration. Subsequently, exact consistent tangent matrix which is necessary for implicit static finite element simulation was obtained. The proposed scheme was implemented into finite element code LS-DYNA and deep drawing process for aluminum alloy sheet was calculated. The earing appearance after drawing was compared with the experiment.
Prediction of 3D Microstructure and Plastic Deformation Behavior in Dual-Phase Steel Using Multi-Phase Field and Crystal Plasticity FFT Methods
Authors: Yamanaka Akinori
Published: July 2015

The plastic deformation behavior of dual-phase (DP) steel is strongly affected by its underlying three-dimensional (3D) microstructural factors such as spatial distribution and morphology of ferrite and martensite phases. In this paper, we present a coupled simulation method by the multi-phase-field (MPF) model and the crystal plasticity fast Fourier transformation (CPFFT) model to investigate the 3D microstructure-dependent plastic deformation behavior of DP steel. The MPF model is employed to generate a 3D digital image of DP microstructure, which is utilized to create a 3D representative volume element (RVE). Furthermore, the CPFFT simulation of tensile deformation of DP steel is performed using the 3D RVE. Through the simulations, we demonstrate the stress and strain partitioning behaviors in DP steel depending on the 3D morphology of DP microstructure can be investigated consistently.
Application of Rheological Model of Material with Microdefects and Nanodefects with Hydrogen in the Case of Cyclic Loading
Authors: Yakovlev Yuri  A. , Belyaev Alexander , Polyanskiy Vladimir
Published: July 2015

The paper deals with the example of application of the two continuum rheological model of materials with microdefects, nanodefects and solute hydrogen for calculation of stress and strain in cylindrical specimen under periodic loading. The model suggested allows one to relate the mechanical characteristics with the hydrogen concentration.The stability analysis of the system metal-hydrogen is carried out. The influence of parameters of the mechanical loading, hydrogen concentration and parameters of sorption and desorption of hydrogen from the surface of the internal defects (traps) of various nature on the system stability is performed.It is shown that influence of hydrogen can be considered as parametric instability of a continuous medium under mechanical deformation.This can be important during forming or plastic deformation of materials and nanomaterials containing hydrogen.
Advances in Level-Set Modeling of Recrystallization at the Polycrystal Scale - Development of the Digi-μ Software
Authors: Scholtes Benjamin , Shakoor Modesar , Bozzolo Nathalie , Bouchard Pierre-Olivier , Settefrati Amico , Bernacki Marc
Published: July 2015

The mechanical and thermal properties of metallic materials are strongly related to theirmicrostructure. An accurate and quantitative prediction of microstructural evolutions is then crucialwhen it comes to optimize the forming process. Recently a new full field approach, based on a Level-Set (LS) description of interfaces in a finite element (FE) context has been introduced to model 2D and3D primary recrystallization (ReX), including the nucleation stage [1, 2], and has been extended to takeinto account the grain growth (GG) stage [3, 4]. The ability of this approach to model also the Zenerpinning (ZP) phenomenon without any assumption concerning the shape of second phase particleswas also demonstrated [5]. Moreover, recent developments have also illustrated the capability of thisapproach to take into account the characteristics of twin interfaces during grain boundary motion [6,7]. Current work concerns also the improvement of the numerical cost of this new approach [8]. Allthese developments are necessary to account for the microstructural complexity of ReX phenomenon.
Investigation of Deformation Induced Martensitic Transformation during Incremental Forming of 304 Stainless Steel Wires
Authors: Kuhfuss Bernd , Moumi Eric , Clausen Brigitte , Epp Jeremy , Koehler Bernd
Published: July 2015

Wires with 1 mm initial diameter have been reduced between 10 and 64 percent at different temperatures and strain rates by infeed rotary swaging, which is an incremental cold forming process mainly used for rods and pipes. The volume fraction of martensite in the deformed wires has been determined by X-Ray diffraction and by magnetic induction for different processing parameters. Measurements show that for already small percentage of reduction, martensite is present in the wires and its amount changes with the strain rate and temperature. While for smaller strain rates at room temperature the formation of martensite is promoted, it is restrained for higher strain rates and higher temperatures. Results also reveal that the martensite distribution in the sample is inhomogeneous. Further investigations have been made to analyze the microstructure by optical microscopy and to determine mechanical properties by tensile testing.