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Welding Process (welding + process)

Distribution by Scientific Domains

Polymers and Materials Science	60%
Engineering	33%

Selected Abstracts

Influence of Filler Composition on the Microstructure and Mechanical Properties of Steel,Aluminum Joints Produced by Metal Arc Joining,

ADVANCED ENGINEERING MATERIALS, Issue 5 2009
Leonardo Agudo Jácome
Chemical joining of aluminum to steel parts is one of the main challenges in the automotive industry to achieve sound economical solutions for required automobile weight reduction. The cold metal transfer (CMT) is a fusion welding process developed to meet that challenge. It is shown in this paper how the choice of proper filler materials can yield appropriate mechanical performance of specially designed dissimilar CMT butt joints by improving the seam characteristics and weld bead properties. [source]

Fatigue crack initiation life estimation in a steel welded joint by the use of a two-scale damage model

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2009
N. LAUTROU
ABSTRACT This work deals with the fatigue behaviour of S355NL steel welded joints classically used in naval structures. The approach suggested here, in order to estimate the fatigue crack initiation life, can be split into two stages. First, stabilized stress,strain cycles are obtained in all points of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. This calculation takes account of: base metal elastic,plastic behaviour, variable yield stress based on hardness measurements in various zones of the weld, local geometry at the weld toe and residual stresses if any. Second, if a fast elastic shakedown occurs, a two-scale damage model based on Lemaitre et al.'s work is used as a post-processor in order to estimate the fatigue crack initiation life. Material parameters for this model were identified from two Wöhler curves established for base metal. As a validation, four-point bending fatigue tests were carried out on welded specimens supplied by ,DCNS company'. Two load ratios were considered: 0.1 and 0.3. Residual stress measurements by X-ray diffraction completed this analysis. Comparisons between experimental and calculated fatigue lives are promising for the considered loadings. An exploitation of this method is planned for another welding process. [source]

Fracture analysis of strength undermatched Al-Alloy welds in edge cracked tensile panels using FITNET procedure

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2008
S. CICERO
ABSTRACT This paper presents a methodology for the assessment of the remaining load carrying capacity of thin-walled components under tension containing highly strength undermatched welds and edge cracks. The analysis is based on the strength mismatch option of the fracture module, part of the newly developed European fitness-for-service (FFS) procedure FITNET. The mismatch option of the FITNET fracture module allows weld features such as weld tensile properties and weld geometry to be taken into account in the fracture analysis of cracked welded components. The methodology described was verified for centre cracked Al-alloy large tensile panels containing undermatched welds in Ref. [1] and hence the present work provides validation with experimental results of the single edge cracked (SEC) and double edge cracked (DEC) panels. The material used is an age-hardening aluminium alloy 6013 in T6 temper condition used in welded airframe components. The welds in the form of butt joints were produced using the CO2 laser beam welding process. The results show that by using the FITNET FFS methodology with an appropriate selection of the input parameters, safe acceptable predictions of the maximum load carrying capacity of the welded panels can be obtained. It should also be noted that one of the main difficulties that engineers encounter when applying mismatch analysis for first time is its apparent complexity. A step-by-step analysis is proposed here in order to provide guidance for this kind of assessments. [source]

Adaptive mesh technique for thermal,metallurgical numerical simulation of arc welding processes

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008
M. Hamide
Abstract A major problem arising in finite element analysis of welding is the long computer times required for a complete three-dimensional analysis. In this study, an adaptative strategy for coupled thermometallurgical analysis of welding is proposed and applied in order to provide accurate results in a minimum computer time. The anisotropic adaptation procedure is controlled by a directional error estimator based on local interpolation error and recovery of the second derivatives of different fields involved in the finite element calculation. The methodology is applied to the simulation of a gas,tungsten-arc fusion line processed on a steel plate. The temperature field and the phase distributions during the welding process are analyzed by the FEM method showing the benefits of dynamic mesh adaptation. A significant increase in accuracy is obtained with a reduced computational effort. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Ultrasonic welding of advanced thermoplastic composites: An investigation on energy-directing surfaces

ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2010
Irene Fernandez Villegas
Abstract Ultrasonic welding is considered as one of the most promising welding techniques for continuous fiber-reinforced thermoplastic composites. Intermolecular friction within the bulk, resulting from the application of ultrasonic waves applied on the surfaces, generates the heat required for welding to take place at the interface of the joining members via the so-called "energy directors" (EDs). Energy directors consist of resin protrusions or artificially produced asperities on the composite surfaces and play an important role both in the welding process and in the quality of the resulting welds. This paper presents the results of a study on the effects of configuration of different EDs on the ultrasonic welding of carbon fiber/polyetherimide advanced thermoplastic composites in a near-field setup. Triangular EDs were molded on the surface of consolidated composite laminates with a hot platen press. Single lap-shear-welded samples were produced to investigate the influence of the orientation of the EDs with respect to the load direction, as well as the configuration of multiple EDs. The results indicate that the configuration of multiple transverse EDs was more effective in covering the overlap area, once the resin has melted, causing only a minimum fiber disruption at the welding interface. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:112,121, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20178 [source]

Intergranular corrosion on Nd:YAG laser-welded A653 steel for automotive application

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2004
Y. M. Looi
Abstract Laser welding techniques produce a narrower heat-affected zone than other conventional welding methods. However, laser welding is not exempt from high heat input during the welding process. This high heat input results in changes of the material properties including its corrosion behaviour; the formation of the heat affected zone increases the susceptibility of the material to intergranular attack. The residue of zinc at the weld due to condensation and splashing during the welding process may also influence adversely the corrosion behaviour of the material. The degree of susceptibility to corrosion strongly depends on the welding parameters. Electrochemical and microstructure characterisation were employed to study the influence of Nd:YAG (neodymium yttrium aluminium garnet) laser-welding on an A653 galvanized steel at different welding parameters. [source]

Fortschritte beim Rührreibschweißen von Aluminium, Magnesium und Stahl

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 9 2006
S. Sheikhi Dr.-Ing.
Friction Stir Welding; Aluminium; Magnesium; Steel; Tailored welded blanks Abstract Das Rührreibschweißen (Friction Stir Welding (FSW)) stellt einen innovativen Schweißprozess zum Fügen von Leichtmetallen insbesondere von Aluminiumlegierungen dar. Die Herstellung von Aluminiumverbindungen mit konventionellen Schmelzschweißverfahren erfüllt nicht immer und nicht bei jeder Legierung die von der Industrie gestellten Qualitätsanforderungen. Das Rührreibschweißen stellt eine Alternative zu den Schmelzschweißverfahren dar. Die entstehenden Schweißnähte weisen gute mechanische Eigenschaften auf, das Verfahren ist robust und seine Reproduzierbarkeit sehr gut. Im Rahmen dieser Arbeit wird der Einsatz des Rührreibschweißens zum Fügen von Aluminium- und Magnesiumlegierungen erläutert. Dabei werden artgleiche und artungleiche Verbindungen und deren mechanische Eigenschaften beschrieben. Das Rührreibschweißen von Stahl mit seinen besonderen Anforderungen an das Schweißwerkzeug wird ebenfalls vorgestellt. Progresses on the friction stir welding of aluminium, magnesium and steel Friction Stir Welding (FSW) represents an innovative welding process for joining light metal, especially, aluminium and its alloys. Friction Stir Welding offers an attractive alternative to conventional fusion welding processes because of the excellent properties (particularly ductility), reproducibility, robustness, and surface finish obtained with the process. Within the scope of this work the Friction Stir Welding-Process with its possible joint configurations is explained. The focus of this work concentrates on weldability studies concerning cladded aluminium alloys, aluminium cast alloys, aluminium tailored welded blanks both from similar and dissimilar joints produced in aluminium, magnesium and steel. The mechanical properties of the welded samples will be discussed. [source]

Laserstrahlschweißen von Titanwerkstoffen unter Berücksichtigung des Einflusses des Sauerstoffes

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 9 2004
J. P. Bergmann
titanium; colorations; laser welding; shielding device Abstract Im Rahmen dieses Aufsatzes wird erstmalig ein innovatives Konzept zum Laserstrahlschweißen von Titan für die Serienfertigung dargestellt und validiert. Durch den neuartigen Einsatz eines 6-lagigen Metallgewebes ist es möglich, die Strömung vom Schutzgas so stark zu beruhigen, dass die beim Schweißen schädlichen Verwirbelungen vermieden werden können. Der Einbau eines derartigen Gewebes als Boden einer offenen Schweißkammer ermöglicht sowohl das mechanisierte als auch das vollautomatisierte Schweißen von hochreaktiven Werkstoffen, wie zum Beispiel Titanwerkstoffen, unter atmosphärischen Druckbedingungen und unter inerter Abdeckung. Damit wird der für eine industrielle Fertigung, insbesondere für Industrieroboter, notwendige Freiheits- und Zugänglichkeitsgrad zur Fügestelle im Vergleich zu konventionellen geschlossenen WIG-Schweißhauben gewährleistet. Von weitgehender Bedeutung für die Schweißtechnik von Titanwerkstoffen ist es, dass auch die Bereiche, die in der Praxis mittels einer Nachschleppdüse vom Schutzgas nicht erreichbar wären, wie z.,B. die Überlappgebiete bei der Überlappnaht, erfolgreich durch das Prinzip der wirbelfreien Schweißkammer geschützt werden können. Mit Hilfe dieser neuartigen Vorgehensweise und eines modernen Fügeverfahrens, wie dem Nd:YAG-Laserschweißen, konnten erstmalig systematische Grundlagenuntersuchungen zum Einfluss von Sauerstoff in der Schweißumgebung auf die Mikrostruktur und auf die mechanisch-technologischen Eigenschaften einer Modellschweißverbindung durchgeführt werden. Durch die Validierung des gesamten Systems konnte bewiesen werden, dass im Vergleich zum konventionellen WIG-Verfahren geringere Anforderungen an die Reinheit des Schutzgases, um Anlauffarben und unzulässige Aufhärtungen zu vermeiden, gerichtet werden können. Für das Laserstrahlschweißen kann ein maximaler Restsauerstoffgehalt von 1000 ppm in der Schweißumgebung unbedenklich toleriert werden. Für das WIG-Schweißen gilt dagegen ein Höchstwert von etwa 30 ppm. Ferner konnte nachgewiesen werden, dass die Qualitätsmerkmale der derzeitigen Regelwerke für das WIG-Schweißen für die Luft- und Raumfahrttechnik auf das Verfahren Laserstrahlschweißen mit Nd:YAG-Quellen übertragen werden können. Influence of the oxygen content in the shielding gas on microstructure and mechanical properties of laser welds of titanium and titanium alloys In the present work, a new tool concept for laser welding of titanium in high volume production has been presented and evaluated. Through the innovative application of a six-layer metal web it is possible to calm the argon gas flow and avoid pernicious turbulences during welding. The integration of the mentioned metal web at the base of an open welding chamber allows the automated welding of highly reactive materials, such as titanium, under atmospheric pressure and inert shielding conditions. The higher density of argon relative to air offers the unique possibility to leave the chamber open on the top, so that a higher degree of flexibility than gas shielding devices for TIG welding, especially for industrial robots, is attained and can be successfully used for industrial mass production. Furthermore this device is important for welding three-dimensional contours or to shield the regions of overlap (in overlapped joints) where shielding gas trailers are unsuccessful. By means of the presented gas shielding procedure and a modern laser welding process such as Nd:YAG laser welding, systematic investigations on the effect of oxygen on the microstructure as well as on the mechanical properties of reference bead-on-plate weldments could be performed for the first time. As a result of these welding trials it can be concluded that in order to avoid discolorations and hardness increase, lower restrictions to the purity of the shielding gas, in comparison to TIG welding condition, can be allowed. The maximum tolerable value of oxygen in the welding atmosphere was found to be approximately 1000 ppm for laser welding. On the contrary the maximum value for TIG welding is about 30 ppm. Further investigations on the microstructural and mechanical properties of the joints confirm that the optical quality assurance criteria for TIG welding due to the standards of aircraft construction transferable to Nd:YAG welding are. [source]

Effects of the shape of the energy director on far-field ultrasonic welding of thermoplastics

POLYMER ENGINEERING & SCIENCE, Issue 1 2000
Yew Khoy Chuah
An energy director is widely used in ultrasonic welding to increase the welding speed and quality. In the present work, three different types of energy directors were studied,namely, a triangular, a rectangular, and an innovative semicircular energy director. Experiments were performed using far-field test samples made of amorphous-type (ABS) and semicrystalline-type (PE) thermoplastics. It was found that the weld time is an important parameter of ultrasonic welding for the three types of energy directors studied. Weld pressure has different effects for the types of plastics tested. Increasing the weld pressure will decrease the welding efficiency for ABS. But for PE, increasing the weld pressure to four bars will increase the welding efficiency. The shape of the energy director was found to significantly affect the welding efficiency. In comparison, a semicircular shape was found to yield the highest welding efficiency under the same welding conditions and the triangular shape the lowest. Temperature measurements at the triangular energy director during the welding process indicate that the energy director absorbed 48.5% of the welding energy for ABS and 21.1% for PE. The different energy absorption rates are probably due to the difference in elasticity and viscosity between amorphous (ABS) and semicrystalline (PE) plastics. [source]

Determination of stability of MIG/MAG welding processes

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2001
Marjan Suban
Abstract The paper treats several methods of evaluating the stability of MIG/MAG welding processes, which are based on measurement of time-varying welding-current intensity and welding voltage. The stability of the welding process is affected by numerous parameters. The most unfavourable result of poor stability are spatters, which are problematic in terms of material losses and extension of production times due to cleaning, as well as appearance. The experimental part of the paper is based on stability analyses carried out with three different gas-shielding atmospheres. Two different welding domains were compared. The first was short-circuit material transfer, and the second spraying material transfer. The results obtained in the analysis of the signals measured indicate a more stable short-circuit material transfer in the case of welding with the pure CO gas, and a more stable spray material transfer in the case of welding with the transferred ionized molten energy mixture. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Ultrasonically Welded Aluminium Foams/Sheet Metal , Joints,

ADVANCED ENGINEERING MATERIALS, Issue 9 2006
C. Born
Abstract The ultrasonic welding technology enables to produce high-strength joints between sheet metal and aluminium foam sandwich (AFS) without melting of the metal or any damage of the foam structure. In the investigations the used welding processes and different factors influencing the weldability were varied. The achievable mechanical properties for ultrasonically welded metal joints, especially under monotonic and cyclic load, will be discussed. Additionally, results of microscopic investigations of the bonding zone and possible applications are presented. [source]