bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Far Infrared Emission from Mineral Tourmaline Fine Powders
Authors: Han Li Jun , Liang Jin Sheng
Published: March 2009

The little disturbance theory in quantum mechanics was used to research the frequency and the high emissivity of far infrared emission from natural black tourmaline on basis of the electric dipole model. Comparing the theoritical and the experimental value of the frequency we found that they are in match case. So we testified that the tourmaline partical is really composed of lots of crystal electric dipole. At the same time we explained the curves of infrared absorption analysis of natural black tourmalines at room temperature are simillar despite of their diversification in chemistry component and producing area, and they have high infrared emissivity from the theory point of view. Finally we pointed out the condition under which the high infrared emissivity of tourmaline can be obtained theoritically.
Surface Modification of Diamonds in Diamond/Al-Matrix Composite
Authors: Edtmaier C. , Weber Ludger , Tavangar Reza
Published: March 2009

Fe- or Mn-powders were mixed with the diamonds and the mixtures were heat treated under different gas atmospheres like hydrogen or argon gas and at varying temperatures in order to roughen the surface of the diamond particles. Subsequently the reaction layers are removed by the addition of aqueous solutions of HCl. The modified surface structure after the etching process is investigated by electron microscopy showing increased roughening of the formerly flat faces of the diamond particles with increasing heat treatment temperature. After drying the diamonds, composites were prepared by gas pressure infiltration with pure Al. For treatments in the temperature range from 750 to 850°C the thermal conductivity can be improved by up to 20 percent compared to composites based on un-treated powders.
Carbon Nanotubes as Highly Conductive Nano-Fillers in Metallic Matrices
Authors: Edtmaier C. , Janhsen T. , Hula R.C. , Pambaguian Laurent , Wulz Hans Georg , Forero Stefan , Hepp F.
Published: March 2009

. A baseline electroless deposition processes for Cu on CNTs has been developed. This process results in the formation of copper particles of few tens of nanometres. Using this process in a CNT loaded solution it is possible to obtain a homogeneous distribution of CNTs and Cu, even for volume fraction of CNTs as high as 17 v%. By the application of wet chemical processing it is possible to penetrate the natural felt-like structure of the CNTs and to fill the gaps with copper particles. Variations of the baseline deposition process have been established, allowing adding small amount of nickel on the CNT prior to the copper deposition to strengthen the interfacial bonding between matrix and CNTs. Hot pressing of the highly CNT loaded metal matrix composites has been developed; it allows producing bulk material that can be handled. The microstructure of these materials has been investigated and samples have been machined for further testing, i.e. mechanical characterization and thermo-physical properties.
Influence of Different Deposition Parameters on the Performance of a Ti-Ta-C Interface Layer in SiC-Fiber Reinforced Copper Matrix Composites
Authors: Köck Thomas , Herrmann Aurelia , Brendel Annegret , Bolt Harald
Published: March 2009

The mechanical properties of a SiC-fiber/copper matrix composite, reinforced with SCS-0 SiC-fibers ( 140µm, Specialty Materials), can significantly be increased by applying a Ti-Ta-C multilayer between fiber and matrix. This interlayer is deposited with a magnetron sputter device directly on the single fibers. By changing the deposition parameters of this sputter process the Ti-Ta-C interlayer can be optimized regarding fiber strength and fiber/matrix adhesion. Experiments with different deposition pressures, bias voltages and layer thickness’ were performed to increase the bond strength and the ultimate tensile strength when compared to the Ti-Ta-C reference sample.
Fabrication and Properties of Copper/Carbon Composites for Thermal Management Applications
Authors: Schubert Thomas , Weißgärber T. , Kieback Bernd
Published: March 2009

The ideal thermal management material working as heat sink and heat spreader should have a high thermal conductivity combined with a reduced and tailorable thermal expansion. To meet these market demands copper composites reinforced with diamond particles were fabricated by a powder metallurgical method (powder mixing with subsequent pressure assisted consolidation).
In order to design the interfacial behaviour between copper and the reinforcement different alloying elements, chromium or boron, were added to the copper matrix. The produced composites exhibit a thermal conductivity up to 700 W/mK combined with a coefficient of thermal expansion (CTE) of 7-8 x 10-6/K. The copper composites with good interfacial bonding show only small decrease in thermal conductivity and a relatively stable CTE after the thermal cycling test.
Interface Design in Copper-Diamond Composite by Using PVD and CVD Coated Diamonds
Authors: Neubauer Erich , Kladler G. , Eisenmenger-Sittner C. , Hell J. , Prentice C. , Angerer P. , Ciupiński Łukas
Published: March 2009

One of the key problems in copper-diamond composites is the interface between the metal matrix and the diamond reinforcement. In order to take advantage of the high thermal conductive diamond filler in a composite the design of the interface is crucial. One approach to minimize the thermal contact resistance between metal and diamond reinforcement is to coat the diamonds with functional layers, e.g. Mo or W. For coating of diamonds PVD and CVD have been used followed by characterization of coating thickness by different methods. The coated diamonds were used for composite manufacturing and the thermal diffusivity of the compacted materials was measured.
Nanocomposite Coatings Produced by Friction Cladding
Authors: Popov Vladimir A. , Tulupov S.A. , Skryleva E.A. , Chuvilin Andrey L. , Kaiser Ute , Khodos Igor I. , Kovalchuk M.N.
Published: March 2009

Copper matrix nanocomposites (materials for coatings) and reinforcements from
nanodiamonds, nanosilica or diatomite were fabricated by mechanical alloying, and coatings were
produced by the friction cladding method. Investigations included the study of material at all steps
of the technological scheme: formation of granules during mechanical alloying; distribution of
nanoparticles in the copper matrix after consolidation of granules; structure of coatings and
distribution of reinforcements in the coatings. As the result of these investigations, optimal
technological conditions of treatment were developed.
Ab-Initio Modelling of Point Defect-Impurity Interaction in Tungsten and other BCC Transition Metals
Authors: Nguyen-Manh Duc
Published: March 2009

Ab-initio calculations have been performed to investigate systematically defect-impurity interaction in Tungsten and other bcc transition metals. It is found that the most stable configuration of C and N atoms is the octahedral interstitial site whereas O and H atoms are located in the tetrahedral configuration. For the particular case of bcc-W, the binding energies formed by the carbon and nitrogen atoms located at octahedral sites, and mono-vacancy on a nearest neighbor site are very large, 1.39 eV and 1.91 eV, respectively. Implication of these results of diffusion of point defects in tungsten is discussed and compared with the case of bcc-Fe.
Microstructure and Properties of SiC Nanowire-Reinforced SiCf/SiC Composites
Authors: Kim Weon Ju , Kang Seok Min , Park Ji Yeon
Published: March 2009

Microstructure and mechanical/thermal properties of SiCf/SiC composites additionally reinforced with SiC nanowires were investigated. SiC nanowires could be grown successfully within the SiC fiber preform by a chemical vapor infiltration (CVI) process through a control of the deposition parameters. The incorporation of the SiC nanowires into the fiber perform was clearly shown to be effective in increasing the efficiency of the matrix infiltration, and thus resulted in a higher density in a shorter CVI time. The modification of the pore structure and the reduction of the macro-pores in the composite resulted in higher mechanical and thermal properties than the conventional CVI counterpart. The matrix deposition on both surfaces of the SiC fibers and nanowires induced smaller matrix grains in the nanowire-reinforced composite, and thus a higher hardness and elastic modulus than the conventional one after an ion irradiation.
Multi-Axial Thermo-Mechanical Fatigue of a Near-Gamma TiAl-Alloy
Authors: Brookes Stephen Peter , Kühn Hans Joachim , Skrotzki Birgit , Klingelhöffer Hellmuth , Sievert Rainer , Pfetzing Janine , Peter Dennis , Eggeler Gunther F.
Published: March 2009

A material family to replace the current superalloys in aeronautical gas turbine engines is considered to be that of gamma Titanium Aluminide (-TiAl) alloys. Structural components in aeronautical gas turbine engines typically experience large variations in temperatures and multiaxial states of stress under non-isothermal conditions. The uniaxial, torsional and bi-axial thermo-mechanical fatigue (TMF) behaviour of this -TiAl alloy have been examined at 400 – 800oC with strain amplitudes from 0.15% to 0.7%. The tests were conducted at both in-phase (IP) and out-of-phase (OP). The effects of TMF on the microstructure were also investigated. For the same equivalent mechanical strain amplitude uniaxial IP tests showed significantly longer lifetimes than pure torsional TMF tests. The non-proportional multiaxial OP test showed the lowest lifetimes at the same equivalent mechanical strain amplitude compared to the other types of tests.
High Heat Flux Testing of TiC-Doped Isotropic Graphite for Plasma Facing Components
Authors: López-Galilea I. , Pintsuk Gerald , García-Rosales C. , Linke Jochen
Published: March 2009

The technical design solution for the future thermonuclear fusion reactor, ITER, must guarantee a reasonable lifetime from a safety and economical point of view. Carbon fibre reinforced carbon (CFC) is envisaged as a corrective material solution for the strike point area of ITER divertor due to its high thermal shock resistance necessary to withstand excessive heat loads during transient thermal loads; in particular plasma disruptions that can deposit energy densities of several ten MJm-2 with a typical timescale in the order of milliseconds. In this work, as potential alternative to CFCs new finely dispersed TiC-doped isotropic graphites with high thermal conductivity and mechanical strength, manufactured using synthetic mesophase pitch “AR” as raw material, have been evaluated under typical disruption conditions using an energetic electron beam at the JUDITH facility.
Machining of Carbon Fibre-Reinforced Silicon-Ccarbide Composites
Authors: Biermann Dirk , Jansen T. , Feldhoff M.
Published: March 2009

A growing demand for fibre-reinforced ceramics necessitates effective ways for machining these materials. In this paper, different tool concepts are presented for an efficient machining of carbon fibre-reinforced silicon carbide. Drill hole machining, slot machining and first investigations of free-form surface machining are presented.
Features of Technological Layout of Manufacture of Unique Mono-Block Large-Dimension Plates
Authors: Kobelev O.A. , Tsepin M.A. , Skripalenko M.M. , Popov Vladimir A.
Published: March 2009

Blank punch was applied for manufacturing of hollow billets by press piercing. Analysis of piercing by different punches was carried out. Data showing fluctuating of load during piercing and changing of billet’s shape was received.
Al Si Oxide Coating as Ttritium Penetration Barrier on 316L Stainless Steel Prepared by a Combined Process
Authors: Liu Hong Bing , Tao Jie , Xu Jiang , Chen Zhao Feng , Sun Xian Jun
Published: March 2009

Based on the favorable effect of the elements Al and Si on the improvement in reducing hydrogen permeability, a new combined process of simultaneous aluminizing and siliconizing, followed by oxidizing treatments using double glow plasma technology on 316L substrate was developed in this work. Microstructure and phase structure of as- prepared coating was examined by scanning electronic microscopy (SEM), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the simultaneous aluminizing and siliconizing coating consisted of an outer aluminide layer (dissolved Si) and a diffusion zone. After a combined process, a continuous and compact Al2O3-rich coating was formed at the outermost surface. SiO2 was also detectable in the oxide coating.
Comparison of Material Behavior and Economic Effects of Cold and High Temperature Forming Technologies Applied to High-Strength Steels
Authors: Neugebauer Reimund , Göschel Angela , Sterzing Andreas , Kurka Petr , Seifert Michael
Published: March 2009

The focus of forming high-strength steel at elevated temperature is to improve its
forming properties like elongation and to reduce the power requirements during the forming process in opposite to cold forming. Because of the undefined and large spring-back effects parts made by cold forming are not able to achieve the demanded dimensional accuracy, which is necessary for laser welding operations in car body assembly. The reduction of the spring-back behavior is another advantage of the temperature controlled forming technology. On the other side the forming at
elevated temperatures requires increased costs for forming tools and tempering equipment. For a fundamental evaluation of this technology, expenditures for the complete process chain have to be considered.
Manufacturing of High Strength Steel and Aluminum for a Mixed Material Body in White
Authors: Pfestorf Markus
Published: March 2009

Sophisticated materials like high strength steel or even multi phase steel as well as
aluminum require more efforts within the manufacturing process than conventional steel sheets as they have been used in the body in white recently. The manufacturing process itself as well as engineering of the parts, material of the forming tools as well as cold and warm joining technologies must be regarded separately. For forming tools coated steel inserts or sometimes even cooling is
essential in terms of high-volume car series production. In mixed material solutions using steel in combination with aluminum, the common used resistance spot welding process does not work any more. To maintain high process stability of cold joining technologies combined with adhesive bonding a new process must have been developed. Other items for weight and cost savings are tailored rolled blanks or sophisticated joining technologies. Regarding the manufacturing costs, a cost effective combination of the mentioned high-sophisticated alloys with conventional material should be achieved. Developing a design concept due to crash, stiffness and driving performance, basic requirements have to be considered. This aims to check the high potential of cost intensive materials wherever high functional benefit is necessary under commercial aspects.
Use of Zinc-Alloys for Low Temperature Soldering of Zinc Coated Steels
Authors: Wilden J. , Bergmann Jean-Pierre , Dolles M. , Reich Sebastian
Published: March 2009

Zinc coated steels are nowadays used for different applications as for example for
household appliances, automotive or offtakes. Due to the boiling temperature of zinc (907°C), which is lower than the steel melting point, the welding of zinc coated steel sheets presents many difficulties. As a result of the violent evaporation of zinc, pores in the weld seam are present after solidification and the zinc coating near the weld is damaged. Brazing of zinc coated steels with CuSi-alloys offers some advantages, as the joining temperature is about 950-1000°C. Nevertheless the high melting point of these filler materials requires very restricted process strategies and
damaging of the zinc coating near the brazing seam can’t be avoided. Although laser-, plasma- and MIG-joining with CuSi and CuAl are performed nowadays. ZnAl-alloys are characterized through low melting temperature, which are comparable to the melting point of zinc, so that the damaging of the zinc coating can be reduced.
In this paper investigations carried out with ZnAl-materials for joining zinc coated steel sheets as DC04ZE75/75 and DX56Z (thickness 0,9 mm) are reported. First investigations were performed by resistance spot soldering and show that using low temperature melting materials leads to a lower damaging of the zinc coating. Further the process reliability of laser soldering with ZnAl-alloys and a Nd:YAG as well as a
diode laser is reported and confirms the suitability of these alloys for a damaging free joining zinc coated steels. The low surface tension leads to a wide bearing section, so that advantageous properties are expected. The mechanical properties of edge welds are evaluated in this paper through tensile tests as well.
Flux-Less Joining Technique of Aluminium with Zinc-Coated Steel Sheets by a Dual-Spot-Laser Beam
Authors: Laukant H. , Wallmann C. , Korte M. , Glatzel Uwe
Published: March 2009

Joining of iron with aluminium in the liquid phase is complicated due to the formation of
brittle intermetallics within Fe-Al melts. In this work we present the technology of a laser weldingbrazing (LWB) process to join zinc-coated steel and aluminium sheets in an overlap geometry. The process is divided into welding of the aluminium sheet and brazing of filler material and molten aluminium sheet onto the zinc-covered steel sheet to avoid the liquid stage of iron. It is possible to join those materials with a single laser beam. However, with a second laser beam, the melt flow can be controlled more effectively and the wetting behaviour can be improved by preheating the zinc-covered steel sheet surface. This is beneficial since the process works without any flux agent. Wetting lengths increase by using this technique and generate a joint that exceeds the tensile strength of the base material. Due to the zinc cover on the steel sheet there are two possible filler materials that have
miscibility with zinc as well as aluminium. Zinc based filler materials have the advantage of a lower melting point and thus lower process temperatures. And aluminium based filler wires result in more ductile brazed seams, making it possible to deform such joints in a later application as tailored blanks.
Influence of Magnetic Fields on Dilution during Laser Welding of Aluminium
Authors: Thomy Claus , Vollertsen Frank
Published: March 2009

In order to minimize the occurrence of hot-cracking phenomena in laser welding of hotcracking sensitive aluminum alloy sheets, it is a common technique to introduce silicon-containing filler wire into the weld metal. However, to achieve an optimum result, a homogenous distribution of not less than 2 % of silicon throughout the weld metal is strongly recommendable. Under certain circumstances, this may be a difficult task. One potential solution to achieve sufficient dilution and, consequently, a very homogenous silicon distribution might be the application of alternating magnetic fields. In foundry technology, the use of magnetic fields to influence melt flow is a wellestablished method. For TIG welding, a process called magnetic stirring was first investigated in the 1970s. It was sufficiently demonstrated by the help of an alternating magnetic field coaxial with the arc axis, that, among other effects, the degree of dilution can be increased and a refined grain structure is achieved. Since the late 1990s, some efforts have been taken to apply constant magnetic fields to laser welding processes. However, neither alternating fields nor potential effects on dilution have been in the focus of these investigations. To help this situation, basic studies on magnetically influencing melt flow during laser welding of aluminum have been conducted. To that end, alternating fields have been coaxially applied with magnetic flux densities up to 60 mT and frequencies in the range of 0 to 20 Hz. It was demonstrated by the help of a specially developed method that, depending on the parameters chosen, such fields are indeed capable of influencing melt flow and weld pool dilution, thus “stirring” the weld metal.
Rapid Parametric Process Design Using FEM Analysis
Authors: Tisza Miklós , Lukács Zsolt
Published: March 2009

During the recent years, due to the rapid development in Finite Element modeling, as well as the rapid evolution of computer techniques, numerical modeling has become an important everyday tool not only for process analysis and process optimization but for die design and rapid die manufacturing, as well. The Department of Mechanical Technology at the University of Miskolc is regarded as the leading research centre for Computer Aided Engineering of sheet metal forming processes in Hungary. The activity of the department covers the computer aided technological and tool design, the development and application of knowledge based expert systems for process planning and process optimization and die design using sophisticated FEM packages. In this latter activity, the AutoForm Engineering GmbH is a strategic partner of the department for several years. In this paper, the concept for an integrated computer aided die design system specialized for the rapid design of parametric die faces using finite element simulation technique will be presented.
Trends and Developments in Intelligent Computer Aided Design of Progressive Dies
Authors: Kumar S. , Singh R.
Published: March 2009

This paper discusses the trends and developments in intelligent CAD of progressive die. The research efforts reviewed reveal the growing importance and relevancy of particular AI techniques for automation of progressive die design activities. Based on the knowledge base approach of AI, an intelligent CAD framework is developed and presented in this paper. The proposed intelligent CAD framework comprises different knowledge base modules for automating progressive die design process. The procedure for the development of various knowledge base modules of the proposed intelligent CAD system is described through module CCKBS which has been designed for assessing manufacturability of sheet metal parts. An illustrative example has been included for demonstrating the usefulness of the developed module CCKBS. The system framework is flexible enough to accommodate new acquired knowledge for each module. The modules of the system framework are implementable on a PC and thus can be affordable by small and medium size enterprises.
Tolerance Analysis of Sheet Metal Assemblies with Focus on Non-Rigid Geometry
Authors: Lustig R. , Hochmuth R. , Meerkamm H.
Published: March 2009

Tolerance analysis is nowadays a modern and efficient tool to simulate toleranced
assemblies. As a result the designer gets the closing tolerance as well as to the priority of influencing tolerances. The closing tolerance can be calculated in worst-case or in statistical manner. These methods and tools have in common that only rigid, non-deformable geometry can be integrated. Many application cases in industry have tolerances as well as the influence of elastic deformations of components to be considered. Effects as spring-back of deformed components for
assembly are reality. In this paper a method will be presented which allows a tolerance analysis of non-rigid geometry, especially for sheet metal assemblies.
A Framework for Automatic Tool Selection in Integrated CAPP for Sheet Metal Bending
Authors: Nguyen T.H.M. , Duflou Joost R. , Kruth Jean Pierre
Published: March 2009

Sheet metal bending is a metal forming process, in which flat sheets are bent along
straight bend lines in a specific bending sequence to form three-dimensional parts. A large number of tools with different characteristics can be used in this process. The task to choose the right tooling for a requested sheet metal part is however one of the bottle necks in process planning. An inefficient tool selection may result in failure of finding a feasible bending sequence. In previous work, methodologies for tool selection and optimization have been proposed. The presented paper describes a framework to implement these methodologies into a system that allows automatic tool
selection in consistent consideration of bend sequencing. As a result, automated and optimized tool selection for sheet metal bending is achieved, as illustrated by performance test results for a robust software implementation.
Finite Element Analysis for Deep Drawing of Tailored Heat Treated Blanks
Authors: Kerausch M. , Merklein Marion , Staud Detlev
Published: March 2009

Aluminum alloys, due to their low density compared to steels, are an important group of materials, in particular for light weight construction of transport vehicles. However, aside from their low specific weight, drawing of car body components made from aluminum alloys is limited by an inferior formability. To enable a modern car body design, it is necessary to enhance the formability of aluminum sheet metal. One basic approach to reach this aim is to adapt the mechanical properties of the blank for the drawing process. The general idea is to soften the deformation zone relative to the force transferring zone, which results in an improved material flow and thus to larger drawing depths. In this paper the process sequence consisting of local induction heat treatment followed by deep drawing of precipitation hardenable aluminum alloy is presented. Using an induction system, it is possible to change the mechanical properties of the 6xxx aluminum blanks in a restricted area by influencing the precipitation structure. Tensile tests characterize the conversion from the stable naturally aged condition T4 to reversible solution heat treated W conditions of AA6016 as function of temperature and time. This effect leads to a reduction of flow stress, which is used to design an material property distribution adapted for the subsequent deep drawing process. A process characterization study provides detailed information concerning induction heating parameters, to
improve the deep drawing of cylindrical cups, which results in a decisive increase of the limiting drawing ratio. Accompanying the experimental investigations, a finite element analysis approach is realized as a process design and optimization tool. Following the presented strategy, it is possible to enhance the forming capability of aluminum alloys. This leads to advanced manufacturing processes, which extend the field of applications for aluminum car body parts.
Hydromechanical Deep Drawing Simulations: Model Development and Process Parameters Investigation
Authors: Ceretti Elisabetta , Giardini Claudio , Contri C. , Bortot Paolo
Published: March 2009

Numerical simulation conducted by Finite Element Method is one of the most powerful
tools for analyzing metal forming processes. Among them, Hydromechanical Deep Drawing (HDD) is, probably, the process which has gained the major interest in industries in the last few years. In this paper a numerical study of HDD of a can box is presented. The influence of geometrical features of a pressure chamber in terms of the gap with the punch is discussed, together with the main process parameters, such as counter-pressure and Blank Holder Force (BHF). The pressure path was found to be the key parameter for a successful HDD. The pressure, in fact, has to be increased very quickly in the first part of the process in order to obtain a minimum friction between the blank and the die entrance radius. The BHF is determined by the pressure path and so a simple way for understanding the correct force was developed. The results are presented in terms of thinning and wrinkles of the final product. Thickness was found to decrease in the first half of the simulation and then it remains constant; wrinkles take place in the last steps of the simulation and they depend on the BHF and on sheet metal anisotropy. The FEM commercial code Pam Stamp 2000 with Aquadraw function was utilized.
Die Surface Structures and Hydrostatic Pressure System for the Material Flow Control in High-Pressure Sheet Metal Forming
Authors: Krux Rainer , Homberg Werner , Kalveram M. , Trompeter Michael , Kleiner Matthias , Weinert Klaus
Published: March 2009

A promising approach to control the material flow within deep drawing and workingmedia based forming processes is the structuring of the tool surfaces in the contact zones between workpiece and die. In order to obtain a sufficient and an optimised material flow respectively – especially for non-symmetric or non-uniform workpiece geometries – a locally adapted distribution of surface structures is a practicable solution. The macroscopic, and also the microscopic surface structures can be manufactured sufficiently by means of a high-speed cutting process. The shape of the tool surface structure has a significant influence on the tribological conditions between workpiece and die. To adjust the surface structure distribution to the required material flow distribution, detailed knowledge about the correlation of the material flow from the tribological conditions between sheet and the forming tool is required. A further innovative approach, particularly for decreasing the friction coefficient, is the use of an innovative hydrostatic pressure system using fluid ducts. Its functional principle is based on the reduction of the contact shear stress at the sheet surface in the contact zone with the forming tool by means of locally applying a
hydrostatic fluid pressure. To obtain information about the correlation of the material flow from the tool surface structures and from the parameters of the hydrostatic pressure system respectively, fundamental investigations have been carried out. In order to optimise the material flow, these toolbased approaches can be used as stand-alone solution, or in addition to other systems. If the surface structures and a hydrostatic pressure system are used in combination with the multi-point blank
holder, which has already been qualified for the high-pressure sheet metal forming (HBU), a powerful system for the material flow control is available.
Integrated Manufacturing by Hydroforming, Laser Welding and Cutting
Authors: Kreis O. , Celeghini M. , Merklein Marion
Published: March 2009

The shortening of process chains and the combination of innovative manufacturing
technologies offer the possibility to enhance the complexity of technical products. The presented work describes the development of a process chain for the manufacturing of complex hollow parts out of double sheets and tubes with a big variation of the cross section, e.g. for A-pillars in the automotive sector. Two blanks and a tube are inserted in a hydroforming tool by a handling robot. The processes forming of blanks and tubes as well as joining by clinching are integrated in this tool.
After these steps, the handling robot places the part in a laser station, where integrated laser welding and cutting processes take place. This paper focuses on special solutions developed both in the hydroforming and in the laser processing. In particular, the connection between blanks and tube is extremely problematic with regard to the sealing in the hydroforming process and the welding operations due to an existing gap. The requested tightness is reached by reinforcing the tube in the
connection area with a ring insert, by placing sealing profiles on the outer surface of the tube and particularly by adding a sealing medium to the hydroforming fluid. In laser operations, special challenges result from complex welding and cutting paths, contaminations of the blanks with hydroforming media and lubricants, gaps between the blanks that occur due to residual stresses after forming and burr formation.
Non-Thermal Laser Stretch-Forming
Authors: Schulze Niehoff H. , Vollertsen Frank
Published: March 2009

A new process technology for stretch-forming of thin sheet metals is presented within
this paper. This new technology is based on shock waves as a source for the forming energy, which are created through laser pulses. The results of some preliminary experiments show, that stretchforming with laser pulses is possible. The influence of parameters like defocussing, power density, pulse energy, number of pulses and material are worked out with excimer-laser pulses. The results show, that uniform shaped domes with a dome height over 250 µm with diameters of 1.4 mm could be produced. More recent studies show that even better results can be reached through the use of TEA-CO2-Lasers, since no confinement is needed and ablation at the surface is avoided. The absence of ablation at the surface makes this new technology even more interesting, since not only the surface remains accurate, but also since several pulses can be applied at one point and thus higher forming degrees can be reached without increasing the power density.
Incremental Sheet Forming with an Industrial Robot – Forming Limits and Their Effect on Component Design
Authors: Lamminen L.
Published: March 2009

Incremental sheet forming (ISF) has been a subject of research for many research groups before. However, all of the published results so far have been related to either commercial ISF machines or ISF forming with NC mills or similar.
The research reported in this paper concentrates on incremental sheet forming with an industrial robot. The test equipment is based on a strong arm robot and a moving forming table, where a sheet metal blank is attached. The tool slides on the surface of the sheet and forms it incrementally to the desired shape. The robot is capable of 5-axis forming, which enables forming of inwards curved forms. In this paper the forming limit diagram (FLD) for ISF with the robot is presented and it is compared with conventional forming limit diagrams. It will be shown that the conventional FLD
does not apply to incremental forming process. Geometrical accuracy of sample pieces is also studied. Cones of different shapes are formed with the robot equipment and their correspondence with the 3D CAD model is evaluated. The results are compared with other results of accuracy of incremental sheet forming, reported earlier by other researchers. The third issue covered in this article is a product development point of view to incremental sheet forming. In addition to fast prototyping and low volume production of sheet metal parts, ISF brings new possibilities to sheet metal component design and manufacturing. These possibilities can only be exploited if design rules, that will take the possibilities and limitations of the method into account are created for ISF.
New Approach for Process Planning and Optimization in Sheet Metal Spinning
Authors: Göbel R. , Kleiner Matthias , Henkenjohann N.
Published: March 2009

Due to the high complexity and the large number of possible geometries to be formed, a systematic design of the sheet metal spinning process is, up to now, difficult and time consuming. Sustainable models of the spinning process do not exist so far. Due to this, a new approach for the systematic design and optimization of the spinning process has been developed. In a first step of the planning sequence, a prediction of initial parameter settings is given by a case-based-reasoning approach. A first adaptation of the pre-selected parameters is then realized on a fuzzy-based model. In the next step, a model based optimization using statistical design of experiments is performed. For this, a new statistical approach has been developed being optimized regarding the requirements of the spinning process. In this paper, the methods used and the implementation of the approach in a process planning software are described. The approach is verified by the example of setting up a
process to manufacture a cylindrical model workpiece.
Finite Element Modeling of Incremental Forming of Aluminum Sheets
Authors: He S. , Van Bael Albert , van Houtte Paul , Duflou Joost R. , Szekeres Alexander , Henrard Christophe , Habraken Anne Marie
Published: March 2009

Incremental forming is an innovative and flexible sheet metal forming technology for
small batch production and prototyping, which does not require any dedicated die or punch to form a complex shape. This paper investigates the process of single point incremental forming of an aluminum cone with a 50-degree wall angle both experimentally and numerically. Finite element models are established to simulate the process. The output of the simulation is given in terms of final geometry, the thickness distribution of the product, the strain history and distribution during
the deformation as well as the reaction forces. Comparison between the simulation results and the experimental data is made.
Comparison of FEM Simulations for the Incremental Forming Process
Authors: Henrard Christophe , Habraken Anne Marie , Szekeres Alexander , Duflou Joost R. , He S. , Van Bael Albert , van Houtte Paul
Published: March 2009

Incremental forming is an innovative and highly flexible sheet metal forming technology for small batch production and prototyping that does not require any adapted dies or punches to form a complex shape. The purpose of this article is to perform FEM simulations of the forming of a cone with a 50-degree wall angle by incremental forming and to investigate the influence of some crucial computational parameters on the simulation. The influence of several parameters will be discussed: the FEM code used (Abaqus or Lagamine, a code developed at the University of Liège), the mesh size, the potential simplification due to the symmetry of the part and the friction coefficient. The output is given in terms of final geometry (which depends on the springback), strain history and distribution during the deformation, as well as reaction forces. It will be shown that the deformation is localized around the tool and that the deformations constantly remain close to a plane strain state for this geometry. Moreover, the tool reaction clearly depends on the way the contact is taken into account.
Lubrication of Aluminium Sheet Metal within the Automotive Industry
Authors: Meiler M. , Jaschke H.
Published: March 2009

The production of automotive body parts and panels is a very complex process, starting with the raw materials and ending in the paint shop. Due to the fact that aluminium sheet metal has to be lubricated before forming, all of the following processes have to be considered. Lubricants, such as oils, dry-film lubricants or recently introduced hotmelts have to protect the material’s surface, reduce friction whilst drawing the panels and should not compromise further treatments [1].
Different types of lubricants show different characteristics. This difference is especially noticeable when comparing liquid and dry-film lubricants. As dry-film lubricants do not run off the blanks’ surface and are distributed homogeneously, they show different tribological properties compared to conventional liquid lubricants. The effect on friction of aluminium sheet metal is shown through several basic experiments [2, 3]. In addition, the paper shows the effect of further operations within the production chain. The advantages and disadvantages not only for drawing, but also for assembly lines and the painting process are described in this paper. Assembly issues are carried out on stability testings of riveted and clinched assemblies. These trials show how the assembly process is affected by different
proceedings. The fact that every car body has to be completely free of grease before painting, signifies the necessity to get lubrication off the car body’s surface before painting. The interactions between lubrication and paint shop are shown on typical process parameters. Most typical characteristics considering bonding and riveting were tested out on a hood assembly of the current BMW 7-series. In addition to that, experiences made in the press shop at BMW’s Dingolfing plant were figured out and carried over to a long-term strategy of pre-lubrication of
aluminium sheet metal. This includes adhesive compatibility as well as the above mentioned assembly process.
Surface Inspection System for Large Sheet Metal Parts
Authors: Denkena Berend , Berg F. , Acker W.
Published: March 2009

In this paper a measuring system that allows an automatic detection of waviness and form errors in sheet metal parts is introduced. The system is based on a stripe projection method using a high resolution line scan camera. Particular focus is put on achieving a short measuring time and a high resolution in depth, aiming at a reliable automatic recognition of dents and waviness of 10 µm on large curved surfaces of approximately 1 m width. On smoothly curved surfaces a spatial frequency analysis is used to detect dents. By combining this spatial frequency analysis with a CAD
model, more complex parts can be inspected, too. Using an objective 100% inspection of all parts, a quality improvement can be achieved by controlling the forming process.
Measuring and Quantifying the Surface-Roughness Anisotropy of Modeled and Industrially Produced Surfaces
Authors: Wichern C.M. , Rasp W.
Published: March 2009

‘Three-dimensional surface profilometry’ when used for analysis and product
specification reports roughness parameters that provide an average surface description over a relatively large area. Many commercial sheet steels are produced with special textured surfaces for tribological benefits or appearance benefits. These surfaces, as well as others, may demonstrate high levels of roughness anisotropy that is not quantifiable by simple three dimensional surface parameters. This anisotropy can play an important role in the surface appearance of the finished
product and in the tribological behaviour during forming. The current work presents a method for quantifying surface-roughness features as a function of angular orientation with respect to rolling direction. The measurement methodology was applied to several model surfaces and one industrially produced electron-beam textured-surface (EBT). This methodology extracts multiple surface-height profiles of the same angular orientation from a single surface and calculates an
average roughness parameter for the orientation angle based on the multiple profiles. Particularly interesting results were the large number of profiles necessary to obtain repeatable values for the roughness variation with respect to direction and the strong influence of surface feature size on the repeatability of said results. These results indicate that care must be taken when using a single extracted profile to represent a ‘three-dimensional’ surface.
Novel Concept of Experimental Setup for Characterisation of Plastic Yielding of Sheet Metal at Elevated Temperatures
Authors: Geiger Manfred , van der Heyd G. , Merklein Marion , Hussnätter Wolfgang
Published: March 2009

In times of highest significance of process modelling and numerical simulation characterisation of material properties is of special importance for tools’ and components’ dimensioning. But in general material properties depend on many different influencing variables, e.g. temperature, humidity and many others. Especially in fields of sheet metal forming the mechanical behaviour of components highly differs according to real stress condition. In particular yield loci combine the
information of beginning of yielding with a biaxial stress condition, but nevertheless for many materials they have not been determined yet. For all others the existing values are available only at room temperature. In this paper a novel concept of the experimental setup is shown, with which plastic yielding of sheet metal can be examined also at elevated temperatures. In usual biaxial tension tests cruciform
specimen are drawn in plane. The new machine-concept, which is presented in this paper, is based on a punch-load moving perpendicular to the sheet. By clamping the specimen restoring forces are induced, which cause in dependence of special developed tool and work piece geometries defined stress conditions. Using an optical measurement system for determination of strains with CCDcameras
of very high frame rate allows exact identification of starting plastification by offline analysis. Experiments at elevated temperatures are realised by local heating with a diode laser and a special optical system to reach a homogenous distribution of temperatures in the forming zone. On the one hand these investigations are necessary for many materials to achieve further information on characteristic properties in warm forming, because their data are only known at room temperature. On the other hand some materials, e.g. magnesium wrought alloys, are mostly formed
at elevated temperatures (here in the range of 200°C to 250°C), because of its significant higher formability. Thus, material behaviour must be characterised at these temperatures.
Solution Heat Treatment and Cold Die Quenching in Forming AA 6xxx Sheet Components: Feasibility Study
Authors: Garrett R.P. , Lin J. , Dean Trevor A.
Published: March 2009

To overcome the major problems in forming aluminium sheet components, such as
springback, low formability and microstructure variation a novel process is proposed in this paper. That is combined Solution Heat Treatment (SHT) hot stamping followed by cold die quenching. To determine the feasibility of such process a series of thermal-mechanical tests have been designed and carried out on aluminium alloy AA6082. Three aspects of the forming process are investigated and represented in the paper. The first is to investigate the effects of SHT proportions on the mechanical properties of the material. The second is the effects of quenching rates on the mechanical properties after SHT. The third is the effect of predeformation after the SHT and the quenching rate on the mechanical properties of the formed parts. Summaries are given for each aspect of the study. These tests are to investigate the effects of Solution Heat Treatment time proportion. Variables are also introduced during the cold die quenching, including clearance between the testpiece and dies as well as the applied load. Finally the relationship between quench rate and predeformation is investigated.
Thermal Imaging Analysis of Stimulated Heat Diffusion in Sheet Metal for Non-Destructive Metrology and Testing
Authors: Spellenberg B. , Zettner J. , Hierl T. , Haller M. , Lenzi T.
Published: March 2009

Recent developments in infrared camera technology, testing methods and data processing algorithms have brought significant progress for high resolution spatial and temporal analysis of thermal radiation. Together with industry standard automation technology and specific infrared image data processing it became possible to non destructively inspect laser welded seams and other types of joints using heat flux analysis subsequent to thermal stimulation. High thermal diffusion
coefficients of the usually metallic samples under test make the availability of high-speed infrared cameras as a key hardware component indispensable. Since high-speed infrared cameras with frame rates of at least 500 Hz have become available for commercial applications, non-destructive testing systems with a new class of performance were designed, manufactured, and implemented at industrial sites. Heat flux analysis as a new and robust method of non-destructive testing has been
implemented for various types of equipment, ranging from off-line tools for laboratory use to automated robot based systems enabling fast and operator-free in-line inspection. Depending on environment, implementation surroundings, and geometry of objects to be inspected, different types of pulsed or continuous operating heat sources (e.g. flash light, laser, … ) are selected. Due to its outstanding industrial relevance non-destructive testing of laser welded seams in automobile manufacturing is shown in detail in this paper.