bluuebunny/crossref_metadata_2025 huggingface dataset:
High factor VIII (FVIII) levels in venous thromboembolism: role of unbound FVIII
Authors: Grossmann Ralf , Zonnur Sarah , Berger Mario , Teuchert Kathleen , Spahn Alois , Walter Ulrich , Schambeck Christian
Published: June 2004

Theoretically, von Willebrand factor (VWF) should be capable of binding all factor VIII (FVIII), but an unbound FVIII (uFVIII) plasma fraction remains. In patients’ status post deep-vein thrombosis (DVT), an altered uFVIII fraction and high FVIII levels might be indicative of dysfunctional FVIII regulation. Out of 928 consecutive DVT patients, 321 were found to have high FVIII levels. After excluding 183 patients with known causes for high FVIII levels, plasma samples with unexplainably high FVIII levels were available from 84 patients. To capture the FVIIIVWF-complex, superparamagnetic polystyrene beads with covalently attached streptavidin were coated with biotinylated anti-rabbit Ig and incubated with rabbit anti-human VWF-Ig. Slowly thawed plasma samples were added to cooled beads, which were then separated by a magnetic particle concentrator. The uFVIII fraction was calculated by dividing the FVIII activity in the supernatant of the FVIII-VWF-complex-free sample by the FVIII activity in the supernatant of the control sample. Additionally, the VWF residuum in the supernatant was determined. Compared to age- and sex-matched blood donors, thrombosis patients showed a significantly higher plasma FVIII/VWF ratio (median: 1.3 vs. 1.0, p<0.001). uFVIII fraction data were adjusted for VWF residuum. After forward stepwise logistic regression, uFVIII had an odds ratio of 0.48 (95% CI 0.34 – 0.65), i. e. the uFVIII fraction was reduced in thrombosis patients. Analysis of covariance confirmed these results: In thrombosis patients, the estimated mean of the uFVIII fraction was significantly lower (6.34% vs. 7.58%, p<0.001). In conclusion, thrombosis patients with high FVIII levels showed a higher FVIII/VWF ratio, similar to mice with defective FVIII clearance.The clearly reduced uFVIII fraction lends further support to the hypothesis of a modified FVIII clearance.
Mutation in the leucine-rich repeat C-flanking region of platelet glycoprotein Ibβ impairs assembly of von Willebrand factor receptor
Authors: Tang Jingrong , Stern-Nezer Sara , Liu Po-Ching , Matyakhina Ludmila , Riordan Michael , Luban Naomi , Steinbach Peter , Kaler Stephen
Published: June 2004

We describe a syndrome of thrombocytopenia, bleeding episodes, congenital heart disease and facial dysmorphism in a newborn infant, and trace the cause to mutations on chromosome 22 that involve the gene for platelet glycoprotein Ibβ (GPIbβ, Human Genome Organisation gene symbol GPIBB), a critical component of the von Willebrand factor (vWF) receptor. Fluorescence in situ hybridization in transformed lymphoblasts revealed hemizygous microdeletion of 22q11.2 containing the GP1BB locus. DNA sequencing revealed a C to T transition in the patient’s remaining GP1BB allele, predicting a novel proline to serine substitution (Pro96Ser) in the carboxyterminal flanking domain of a leucine-rich repeat. We characterized the mutant GP1BB allele by expression in a cell line (CHOαIX) that stably expresses two other components of the vWF receptor, GPIbα and GPIX. Flow cytometry and confocal imaging of transfected CHOαIX cells demonstrated that P96S GPIbβ abrogates surface assembly of the complex, consistent with platelet flow cytometry studies in the patient. Based on sequence homology to the known crystal structures of two other leucine-rich repeat proteins, the human Nogo receptor and GPIbα, we propose a new structural model of GPIbβ. The model refutes earlier assumptions about cysteine-cysteine interactions in the amino-terminal region of GPIbβ, and predicts a hydrophobic patch the burial of which may contribute to proper conformation of the fully assembled vWF receptor complex.
Periodontal disease, but not edentulism, is independently associated with increased plasma fibrinogen levels
Authors: Völzke Henry , Robinson Daniel , Luedemann Jan , Bernhardt Olaf , Gesch Dietmar , John Ulrich , Kocher Thomas , Schwahn Christian
Published: June 2004

The systemic response to periodontal disease was analyzed in the cross-sectional Study of Health in Pomerania (SHIP). The completed data of 2,738 subjects aged 20 to 59 years were used for logistic regression analysis with an increased plasma fibrinogen level (≥3.25 g/L according to Clauss) as the dependent variable. Participants were divided into four groups according to the number of periodontal pockets ≥ 4mm (0, 1-7, 8-14, ≥15 pocketing). An additional group comprised the 52 edentulous subjects. The adjusted odds ratio (OR) of ≥15 periodontal pockets for increased plasma fibrinogen levels was 1.88 (95% CI: 1.25-2.83). Edentulism per se was not associated with increased plasma fibrinogen levels but was contained in a two-way interaction with the number of cigarettes/day in current smokers (p = 0.031). For edentulous nonsmokers the adjusted OR was 1.10 (95% CI: 0.51-2.39). Furthermore, body mass index, the interaction between gender and body mass index, serum LDL cholesterol, medication, the interaction between LDL cholesterol and medication, aspirin, smoking, school education, chronic bronchitis, and the interaction between alcohol consumption and chronic gastritis were associated with plasma fibrinogen levels. Our results show that periodontal disease but not edentulism per se is associated with an increased plasma fibrinogen level.
CD14+CD16+ monocytes in coronary artery disease and their relationship to serum TNF-α levels
Authors: Blankenberg Stefan , Espinola-Klein Christine , Dopheide Joern , Bickel Christoph , Lackner Karl , Iz Mete , Meyer Juergen , Darius Harald , Rupprecht Hans , Schlitt Axel , Heine Gunnar
Published: June 2004

Monocytes play a central role in the inflammatory disease atherosclerosis. CD14+CD16+ monocytes are considered proinflammatory monocytes, as they have an increased capacity to produce proinflammatory cytokines, such as TNF-α, and are elevated in various inflammatory diseases. We hypothesized that patients with coronary artery disease (CAD) have increased levels of CD14+CD16+ monocytes, and that CD14+CD16+ monocytes are associated with inflammation markers. We investigated CD14+CD16+ monocytes in 247 patients with CAD and 61 control subjects using flow cytometry. In addition serum concentrations of TNF-α, IL-6, and Hs-CRP were assessed. Patients with CAD had higher levels of CD14+CD16+ monocytes than controls (13.6% versus 11.4%; p<0.001). Logistic regression analysis including quartiles of CD14+CD16+ monocytes showed that CD14+CD16+ monocytes were associated with prevalence of CAD (OR 4.9, 95% CI 2.5–19.1, for subjects in the fourth quartile in comparison to subjects in the first quartile). The association between CD14+CD16+ monocytes and CAD remained independently significant after adjustment for most potential confounders (OR 5.0, 95% CI 1.2-20.0). Serum concentrations of TNF-α were elevated in subjects within the highest quartiles of CD14+CD16+ monocytes (p=0.018). Our study showed that increased numbers of CD14+CD16+ monocytes are associated with coronary atherosclerosis and TNF-α. In accordance, recent animal studies suggest a possibly important role of these monocytes in the development of atherosclerosis.
In vitro studies, pharmacokinetic studies and clinical use of a high purity double virus inactivated FVIII/VWF concentrate (Immunate) in the treatment of von Willebrand disease
Authors: Ver Elst Kristien , van Vliet Huub , Kappers-Klunne Mies , Leebeek Frank
Published: June 2004

Patients with type 2 and 3 von Willebrand disease (VWD) are treated with factor VIII/VWF concentrate in case of bleeding or surgery. Immunate® (Baxter, Vienna, Austria) is a double virus inactivated FVIII/VWF concentrate and is registered in several countries for patients with VWD with reduced FVIII levels.We performed an in vitro, a pharmacokinetic and a clinical study to evaluate Immunate in VWD. In vitro studies showed a significant variation in VWF levels in 9 different batches. The median (range) values (in IU/mL) were 1.10 (0.98-1.30) for FVIII:C, 1.34 (0.95-1.61) for VWF:Ag, 0.60 (0.27-1.08) for VWF:CBA and 0.73 (0.59-0.94) for VWF:RCo. The relatively low VWF activity is mainly due to the lack of high molecular weight multimers (HMWM), as determined by electrophoresis. A pharmacokinetic study showed, based on a content of FVIII:C of 1 U/mL, in vivo recoveries (%) of 106 (56-150) (median and range) for FVIII:C, 105 (62-187) for VWF:Ag, 25 (7-41) for VWF:CBA and 43 (11-76) for VWF:RCo. Half-lives were 14.1 h (7.4-36.9) for FVIII:C, 10.8 h (7.7-26.2) for VWF:Ag, 15.3 h (7.8-44.6) for VWF:CBA and 16.4 h (4.2-26.5) for VWF:RCo. In a clinical study efficacy was determined after infusion given before surgery or dental extractions in ten patients. In two patients the hemostatic response was classified as inadequate. In conclusion, there is a wide variability in VWF concentration and activity in various batches of Immunate®. In the clinical study in which the dosage was based on FVIII:C contents of the concentrate, two out of ten patients had an insufficient haemostatic response. Therefore dosing of Immunate dosing should not be based on FVIII:C levels, but should be based on VWF activity of the individual batches. Future studies using a VWF activity-guided dosage regimen have to be performed to establish the efficacy of Immunate in the treatment of von Willebrand disease.
Neural networks for online prediction of quality in gas metal arc welding
Authors: Li X. , Simpson S.W. , Rados M.
Published: June 2004

Modern welding equipment often features a rather complex operator interface that can make it somewhat difficult, even for an experienced welder, to determine optimum settings for a given welding job. For example, the joint fitup may vary, or some form of unexpected contamination may occur. In addition, in welding tasks for which a procedure has been specified, and in automated welding, changes in welding conditions may mean that some adjustment to the pre-established welding parameters is desirable. With online signal inputs from the welding process, artificial neural networks offer the possibility of providing signals that can be used for control, either indirectly by advising the operator of problems when the system conditions have deviated from satisfactory operation, or by direct feedback control of the welding equipment. This paper reports the development of a prototype which takes arc voltage data as online input, and applies the data to a neural network. The neural network has been trained to output the welding metal transfer mode, and whether the operating regime is satisfactory from the point of view of producing a good quality final weld. Various data preprocessing schemes have been investigated, and it has been found that, with suitable processing, accurate quality prediction is possible for both shortcircuiting and spray metal transfer mode.
Criteria for hot cracking evaluation in austenitic stainless steel welds using longitudinal varestraint and transvarestraint tests
Authors: Shankar V. , Gill T.P.S. , Mannan S.L. , Sundaresan S.
Published: June 2004

The longitudinal varestraint test (LVT) and transvarestraint test (TVT) are widely used for assessment of weld metal cracking susceptibility. The TVT is preferred over the LVT for study of weld metal cracking. However, few reports exist that discuss the relative merits of the two tests for evaluating cracking susceptibility. This investigation was carried out to compare weldability assessments using the two tests and the relevant criteria for weldability evaluation. Several stainless steels solidifying in the austenitic and ferritic solidification modes were tested. The study shows that the LVT can be used for evaluation of fusion zone cracking through a maximum cracking distance criterion. This parameter correlated well with the maximum crack length in the TVT, traditionally used to derive the brittleness temperature range (BTR). The study further indicates that the total crack length can be related to the BTR by considering the area density of cracking.
Influence of weld size on fatigue life prediction for flux cored arc welded cruciform joints containing lack of penetration defects
Authors: Balasubramanian V. , Guha B.
Published: June 2004

Fracture mechanics equations have been developed to predict the fatigue life of flux cored arc welded cruciform joints between pressure vessel grade steels, containing lack of penetration defects. These equations have been developed by combining the Paris law and Δ K i (initial stress intensity factor range) endurance equations. The initiation life and the propagation life of the joints were accounted for, to obtain the total fatigue life. The initiation life was obtained experimentally and the propagation life was evaluated using the numerically developed equations. The accuracy of the developed equations was tested by comparing the predicted data with the experimental data and the correlation was found to be fairly close. Further, the influence of weld size on fatigue life has been analysed in detail.
Liquid infiltrated powder interlayer bonding: A process for large gap joining
Authors: Zhuang W.D. , Eagar T.W.
Published: June 2004

The liquid infiltrated powder interlayer bonding (LIPIB) process is proposed to make large gap, transient liquid phase joints. Some basic aspects of the LIPIB process are discussed. In the LIPIB process, a joint with high mechanical properties requires a low volume fraction of porosity in the powder interlayer and low concentrations of melting point depressants in the joint. To achieve the fully infiltrated large gap joint, it is essential to maintain an open pore structure at the initial stage of infiltration, while allowing complete elimination of pores behind the infiltration front. Approximate analytical solutions are applied to describe dissolution of capillaries and isothermal diffusional solidification during infiltration. Calculations based on the Cu–Ag binary system show that infiltration kinetics are strongly affected by the geometry of the capillaries. When the effective capillary size is smaller than the critical effective capillary radius at a certain infiltration temperature, the isothermal solidification time will be less than the time required for full infiltration, leading to an incompletely infiltrated powder interlayer. Full infiltration of powder compacts requires tight control of the rearrangement rate of the particles such that a relatively large capillary radius can be maintained to prevent diffusional solidification before full infiltration. Meanwhile, the rearrangement should be able to close the pores behind the infiltration front. Small amounts of chromium or nickel powder addition into spherical copper powders were found to affect the rearrangement significantly, whereas little effect was observed for irregular copper powders. Copper–copper square joints with clearance up to 22 mm have been successfully made.
Thermomechanical and isothermal fatigue behaviour of type 316 stainless steel base metal, weld metal, and joint
Authors: Yoshihisa E. , Ganesh Sundara Raman S.
Published: June 2004

In phase thermomechanical fatigue (TMF) in the temperature range 573–973 K (300–700°C) and isothermal fatigue behaviour at 973 K in air were studied for type 316 stainless steel using smooth cylindrical specimens machined from base metal, weld metal, and the weld joint (cross-weld). In all joint specimens, fatigue failure occurred in the weld metal region. The lifetimes of weld metal and joint specimens were almost equal and were always inferior to those of base metal specimens. In the base metal, the effect of strain rate on the isothermal fatigue life was not very significant. Although TMF lifetimes were always a little shorter than the isothermal fatigue lifetimes in base metal, the difference was small for the same mechanical strain range and similar strain rate. This may be because the fracture mode for both types of loading was of a similar mixed type. Conversely, a dramatic reduction in lifetime was observed in weld metal and joint specimens under TMF in comparison with isothermal fatigue. This was attributed to the additional damage caused by many independent subsurface cracks at σ phase boundaries and linkage of these cracks with the surface crack, leading to rapid crack propagation. The δ ferrite in the weld metal completely transformed to σ phase in both the isothermal fatigue and TMF tests.
Influence of spot welding on fracture behaviour of Al–6.6Mg alloy
Authors: Jiang D.M. , Kang S.B. , Kim H.W. , Ko H.S.
Published: June 2004

The influence of spot welding on the microstructure and fracture behaviour of an Al–6.6Mg alloy has been investigated. Results showed that dendrites were formed with porosity and cracks in the nugget. Grain boundary melting occurred in the heat affected zone and wide grain boundaries appeared. Spot welding increased the tendency towards intergranular fracture. Tensile shear fracture was mixed with dimples and intergranular fracture. Fatigue fracture was transgranular with striations at the surface. However, the alloy sheet without welding showed dimpled tensile fracture and fatigue fracture mixed with intergranular and transgranular fracture.
Progress in real time laser process monitoring: Theory and practice
Authors: Farson D.F.
Published: June 2004

Real time detection of defects in laser welds has been the subject of substantial research and development efforts. In this review, the state of progress in developing so called emission based monitoring systems is described. These monitors collect and analyse various forms of energy radiated from the laser–material interaction site as the weld is being formed. The most common emissions that have been used for monitoring purposes include optical and near optical wavelength electromagnetic radiation, audible and ultrasonic airborne acoustic waves, and integrated charged particle flux. The various system configurations and the weld quality characteristics that have been measured with these emissions are summarised. As researchers continue to refine these systems, there has been increasing interest in the mechanisms by which the signals are produced and their relationship to the various physical processes occurring in the laser weld keyhole. A review of the current literature pertinent to the sources of electromagnetic, acoustic, and plasma charge emissions is given. Finally, results illustrating the relationships between the various emissions signals are presented.
Heat conduction analysis of bidirectional multipass welding with short bead lengths
Authors: Kasuya T. , Hashiba Y. , Ohkita S. , Fuji M.
Published: June 2004

A heat conduction analysis is considered for multipass welding conducted in a forward–reverse manner. When the welding is conducted continuously and the bead is short, the interpass temperature sometimes exceeds 500°C. To predict the thermal histories, a heat conduction model is examined using the analytical solution of a moving point heat source in a wide plate of finite thickness. In the model, point heat sources, some of which are moving in one direction and others in the opposite direction, are considered. Comparison of the calculated and experimental results reveals that the proposed model can predict the thermal histories fairly well. This is followed by calculation of the equivalent arc energy, defined as the apparent arc energy which gives either the same cooling time from 800 to 500°C or the same kinetic strength of the heat cycles with no preheating (the concept of kinetic strength has been developed to estimate austenite grain growth in the heat affected zone region), and examination of the effect of maximum interpass temperatures on the equivalent arc energy. When the interpass temperature is greater than 500°C, its effect can be to increase the equivalent arc energy from 2.5 kJ mm-1 to between 6 and 14 kJ mm-1.
Bruscato factor in temper embrittlement of welds
Authors: Lalam S.H. , Bhadeshia H.K.D.H. , MacKay D.J.C.
Published: June 2004

Published experimental data on the tendency for 2.25Cr–1Mo to undergo impurity induced temper embrittlement have been analysed quantitatively. The results indicate strong effects owing to phosphorus, silicon, manganese, and molybdenum concentrations, but the influence of tin, antimony, and arsenic cannot be perceived because of the overwhelming effects of the other elements. A computer model for the calculations is obtainable freely over the World Wide Web.
Electron beam welding characteristics of high strength aluminium alloys for express train applications
Authors: Lee C.H. , Kim S.W. , Yoon E.P.
Published: June 2004

The basic characteristics of electron beam (EB) welding of high strength aluminium alloys for express train applications were evaluated. The aluminium alloys tested were non-heat treatable A5083–O, heat treatable A6N01–T6, and A7N01–T6. Principal welding process parameters, such as accelerating voltage, beam current, welding speed, and chamber pressure were investigated. The dimensions and microstructures of welds were evaluated using optical light microscopy and SEM (EDAX). In addition, variation in weldability (in terms of formation of cracking and porosity) owing to process parameters was evaluated. Electron beam welds showed discontinuities such as cracks, cold shuts, porosities, and spikes; the tendency to form weld discontinuities was strongly dependent on the EB process parameters and chemistry. Although the three aluminium alloys were welded using the same conditions, alloying elements had an important effect on the dimensions of the weld and thus on weldability. Alloy A6N01 showed a lower depth than the other alloys and variation in the weld depth was found to be sensitive to the vaporisation tendency of the alloying elements. Silicon, which is a major element of A6N01, is more difficult to vaporise than other elements (such as aluminium, magnesium, and zinc). The degree of cracking in the EB fusion zone appeared to be affected mainly by aspect ratio (depth/width), such that as aspect ratio increased the cracking tendency also increased. The alloying element itself may also affect the hot cracking resistance, but its role is considered to be an indirect effect, such that the relatively higher vaporisation pressures for zinc and magnesium give deeper weld penetration and thus result in a greater tendency towards cracking.
Microstructure and mechanical properties of friction stir welded aluminium alloys with special reference to AA 5083 and AA 6082
Authors: Svensson L.-E. , Karlsson L. , Larsson H. , Karlsson B. , Fazzini M. , Karlsson J.
Published: June 2004

Aluminium alloys AA 5083 and AA 6082 have been friction stir welded and the mechanical properties and microstructures of the welds have been evaluated. Alloy AA 5083 mainly fractured near the centre of the weld, while fracture in AA 6082 mainly occurred in the heat affected zone. The tensile strength of welded joints in AA 6082 was lower than the base material strength, but still met classification societies’ requirements. Hardness was approximately constant across the welded zone in AA 5083, while a minimum in hardness was found in the AA 6082 welds. The location of the fracture closely matched the minimum hardness region. Very fine scale precipitation in AA 6082 was significantly affected by the weld thermal cycle. In the zone of lowest hardness, the hardening precipitate ( β″-Mg5Si6) had transformed to the non-hardening β′-Mg1.7Si. This is probably the main reason for the minimum in hardness, the fracture location, and the decreased tensile strength. Results are compared to a similar investigation of aluminium alloy AA 7075.
Systematic approach to solution of welding problems in STX21 project: Aiming for remarkable advances in welded joints
Authors: Shiga C.
Published: June 2004

Research activities, as part of the Japanese STX21 project, involving welding of 800 MPa high strength steels with reduced carbon equivalents achieved through grain refinement are described. Results from tests of spray coating to impart corrosion resistance and from creep cracking tests in the heat affected zones of heat resistant steels are also briefly introduced.
Weldability of X100 linepipe
Authors: Thewlis G.
Published: June 2004

Research has been carried out to identify weld metal compositions and microstructures capable of meeting high strength and toughness requirements for X100 seam welded linepipe. Single pass, multiwire submerged arc welds were made in experimental, high strength low alloy steel plates using consumables to give a wide range of weld metal alloying. Work has shown that the optimum strength and toughness are obtained in Mo–B–Ti alloyed weld metals with P cm values between 0.218 and 0.250. Weld metal microstructures were almost fully acicular ferrite with an ultrafine grain size (1–2 µm). Dilatometric studies demonstrated that at typical weld cooling rates the optimised welds transformed at significantly lower temperatures than those reported for X65 plate deposits, which contain acicular ferrite in the form of idiomorphic primary ferrite and intragranular Widmanstätten ferrite. The maximum rate of transformation in the optimised welds occurred between 515 and 570°C, which indicates that the acicular ferrite in this case consisted of intragranular Widmanstätten ferrite and/or bainite. The ferrite would appear to have a fine plate morphology growing from large as well as small inclusions, but not very far before the onset of hard impingement, thereby ensuring an ultrafine grain size. Tensile strengths of 708–784 MPa were achieved with an 80 J Charpy impact transition temperature toughness between -68 and -115°C. More highly alloyed weld metals containing 2–3%Mn and 1.5%Si transformed at lower temperatures and showed increased strength, but there was a substantial loss of toughness, attributed to the relatively unimpeded growth of large ferrite plates from larger inclusions, and the replacement of ultrafine acicular ferrite between these plates by blocks of martensite–austenite. One pass per side, multiwire submerged arc welds manufactured to the optimum weld metal chemistry confirmed their applicability for thin section X100 linepipe.
Effect of sulphur on hot ductility and heat affected zone microfissuring in Inconel 718 welds
Authors: Guo H. , Chaturvedi M.C. , Richards N.L.
Published: June 2004

The influence of sulphur on microfissuring has been studied by characterising the hot ductility and heat affected zone (HAZ) microfissuring in welded wrought Inconel 718. A series of Inconel 718 base alloys, with sulphur concentrations in the range 7–110 wt-ppm and with the lowest possible concentrations of carbon, boron, and phosphorus were used in the study. The hot ductility of the alloys was measured using a Gleeble 1500 system, and their weldability was evaluated by bead on plate electron beam welding. The effect of sulphur on microfissuring in the weld HAZ was compared with that of boron in boron containing, but sulphur free, alloys. Sulphur reduced the weldability of the material, but its influence was very moderate in comparison with that of boron. The rate of increase of the brittle temperature range hot ductility parameter with increasing sulphur concentration was significantly smaller compared with that with increasing boron concentration. This may be because sulphur and boron seem to influence grain boundary liquation in the HAZ differently during welding of these alloys. Sulphur influences the weld HAZ microfissuring mainly by reducing the solidus temperature of liquid films during the cooling part of the welding cycle. Boron, however, not only reduces the solidus temperature, but also promotes grain boundary liquation during the heating part, and is therefore more effective than sulphur in promoting HAZ microfissuring.
Effects of activating flux on arc phenomena in gas tungsten arc welding
Authors: Tanaka M. , Shimizu T. , Terasaki T. , Ushio M. , Koshi­ishi F. ,   Yang C.-L.
Published: June 2004

Dramatic increases in the depth of weld bead penetration have been demonstrated by welding stainless steel using the gas tungsten arc (GTA) process with activating fluxes consisting of oxides and halides. However, there is no commonly agreed mechanism for the effect of flux on the process. In order to clarify the mechanism, behaviour of the arc and weld pool in the GTA process with activating flux was observed in comparison with a conventional GTA process. A constricted anode root was found in the GTA process with activating flux, while a diffuse anode root was found in the conventional process. Furthermore, it is suggested that these anode roots are strongly related to metal vapour from the weld pool, which is also related to temperature distributions on the weld pool surface.
High temperature soldering of SiC particulate aluminium matrix composites (series 2000) using Zn–Al filler alloys
Authors: Urena A. , Gil L. , Escriche E. , Gómez de Salazar J.M. , Escalera M.D.
Published: June 2004

The present paper evaluates the solderability of three discontinuously reinforced aluminium matrix composites. The tested composites were an aluminium alloy of the 2000 series (AA2014) reinforced with different percentages of silicon carbide particles (6, 13, and 20 vol.-% respectively). A similar study was carried out on the unreinforced aluminium alloy for comparative purposes. Three low temperature filler alloys of the Zn–Al system were used for soldering. Drop formation tests were performed to evaluate the wettability of the molten filler alloys and sample joints (single overlap specimens) were produced to determine solder penetration in the joint clearance. Microstructural studies of the joints were carried out to determine the effects of the solid reinforcement particles on molten pool behaviour and solidification mechanisms.
Dynamic model for electrode melting rate in gas metal arc welding process
Authors: Bingul Z. , Cook G.E. , Strauss A.M.
Published: June 2004

A model has been developed that correlates the anode temperature profile with the dynamic melting rate in gas metal arc welding. The components of this model are the electrode melting rate, the temperature dependent resistivity of the electrode, and the arc voltage. The differential equations describing the dynamic behaviour of the electrode extension were derived from the mass continuity and energy relations. The temperature of the electrode extension was determined by analysing conductive heat transfer and Joule heating effects. One­dimensional solutions for the temperature and heat content were used to obtain the dynamic melting rate equation. The purpose of the present paper is to provide quantitative analyses, concentrating on the thermal behaviour and the electrical characteristics of the arc welding system, to aid in achieving a fundamental understanding of the process, and to develop a dynamic model that can be used in adaptive control. The model is tested by comparison with experimental results.
Simulation of hydrogen induced cold cracking using electrolytic precharging procedure
Authors: Wildash C. , Cochrane R.C. , Gee R.
Published: June 2004

A simple electrolytic cell can be used to charge hydrogen into steel samples. The present paper investigates the validity of this procedure for simulating hydrogen induced cold cracking in steel weld metal, as compared with weld metal containing hydrogen originating from the welding process. The simulation procedure has been investigated since a potential advantage is its ability to provide improved understanding of the quantitative relationships between hydrogen, microstructure, and cracking susceptibility when applied to mechanical test specimens. The intention of the present study was to verify that the distribution of hydrogen was uniform in test samples. Various experiments were therefore carried out which showed how, with care, the hydrogen concentration could be controlled to simulate that expected during welding. This has been further verified using a simple model of diffusion. In addition, it has been shown that the procedure can simulate the same microstructural mechanisms of crack initiation and propagation that are observed in welds containing hydrogen originating from the welding process.
Microstructure and properties following welding of duplex stainless steel using coated electrodes
Authors: Petronius I. , Bamberger M.
Published: June 2004

The effects of the type of electrode coating – basic or rutile – on the microstructure, and strength and impact properties of a welded structure constructed from duplex stainless steel UNS–S31803 were investigated. It was found that the use of a rutile coated electrode leads to considerable porosity and a higher nitrogen content but lower oxygen, and hence less ε-Fe2O3 is created compared with weldments produced using an electrode having a basic coating. These phenomena, in turn, cause a higher volume fraction of austenite and thus a higher low temperature impact energy, as well as improved ductility; however, the yield strength is reduced compared with that following basic coated electrode welding.
Influence of copper on amorphous nickel based brazing alloy
Authors: Zhang G.D. , Yu S.F. , Li Z.Y. , Fu C.Y. , Lu W.J.
Published: June 2004

Brazing of stainless steel using nickel based alloys has sometimes been avoided, in spite of its various advantages, because it is a somewhat unreliable process in terms of the mechanical characteristics and corrosion resistance of the brazed joints. Addition of copper to amorphous Ni–Cr–B–Si brazing alloys has been shown to be a promising method of improving the performance of joints. Because copper can form a solid solution with nickel at any concentration, addition of copper has a great effect on the microstructures of the nickel based filler metal and braze seam, by improving the volume ratio of nickel based solid solution to the embrittled intermetallic compounds. As a result, a significant increase in the critical brazing clearance (CBC) was obtained in the present work. Furthermore, copper might increase the electrode potential of nickel based solid solution, so that addition of copper could improve the corrosion resistance of the brazed joints. The results show that an appropriate copper addition to the present Ni–Cr–B–Si group amorphous brazing foil provides an effective method of overcoming the weaknesses of joints brazed using conventional nickel based filler metals, such as low value of CBC and low corrosion resistance.
CO2 and Nd–YAG laser beam welding of 5754–O aluminium alloy for automotive applications
Authors: Ramasamy S. , Albright C.E.
Published: June 2004

Federal regulations have recently been enacted to reduce significantly the atmospheric pollution caused by motor vehicles. This has compelled automotive manufacturers to improve the fuel efficiency of cars and light trucks by using lightweight materials such as aluminium. The focus of the present work is to develop welding procedures for autogenous CO2 (continuous mode) and Nd–YAG (continuous mode) laser beam welding of 5754–O aluminium alloy. The mechanical and microstructural characteristics of the welded joints were evaluated using tensile tests, microhardness tests, optical microscopy, and chemical analysis. Results indicate that this alloy can be autogenously laser welded with full penetration, minimum surface discontinuities, and little if any loss of magnesium through vaporisation from the fusion zone. The total elongation (all weld metal) in the longitudinal direction for 5754–O laser welds produced using 5 kW CO2 and 3 kW continuous wave (CW) Nd–YAG shows a slight decrease with increasing travel speed. Studies indicate that the decreasing tendency is probably due to the orientation of the grains with respect to the loading direction. The welds produced using the 5 kW CO2 laser at travel speeds between 127 and 212 mm s-1 displayed a total longitudinal elongation of 19.13–15.12% and those produced using the 3 kW CW Nd–YAG laser at travel speeds between 85 and 148 mm s-1 displayed a total longitudinal elongation of 22.6–18.15%, compared with the base metal value of 28.1%. An observation of great interest was that the weld surface condition did not have any effect on the ductility of the 5754–O aluminium alloy studied in the present investigation.
Study on lamellar tearing generated by corner joint welding in box column of ultrathick plate
Authors:   Bang H.-S.,   Kim J.-M.,   Ro C.-S.,   Kim S.-J.,   Chang W.-S.
Published: June 2004

In an attempt to reduce the risk of lamellar tearing during welding of ultrathick plates, the present study has evaluated the susceptibility to lamellar tearing of steel structures in relation to welding stress rather than metallurgical properties, and eventually attempted to determine the optimum groove shape and welding procedure by computer simulation based on the finite element method. Based on the simulation, it has been identified that controlling the shape of the deposited weld metal in the anticipated position of the occurrence of lamellar tearing is the most favourable method of preventing lamellar tearing by minimising welding residual stress and strain. Owing to the difference in weld deposited area, the cooling rate for the partial penetration condition is more rapid than for full penetration. Furthermore, in terms of welding residual stress, the full penetration condition is preferable to the partial penetration condition.
Solid state diffusion bonding of Inconel 718
Authors: Zhang G. , Chandel R.S. , Seow H.P.
Published: June 2004

Solid state diffusion bonding of Inconel 718 has been studied. Mechanical tests and metallographic examinations were used to evaluate the joint quality. The effect of bonding time, temperature, and pressure on the joint integrity was assessed. The results showed thatpartial recrystallisation occurs in joints bonded attemperatures lower than 970°C. In addition, large amounts of δ phase precipitates were also found and both the ductility and the tensile strength were poor. Nevertheless, the joint strength was comparable to thatof the parent metal when bonding was carried outat temperatures greater than 970°C. When bondingwas carried out at 1000°C, a pressure of 32 MPa, and a bonding time of 30 min, the joint tensile strength obtained was 874 MPa. There was no further improvement with increasing bonding time beyond 240 min.
Coupled thermomechanical analysis of friction stir welding process using simplified models
Authors: Dong P. , Lu F. , Hong J.K. , Cao Z.
Published: June 2004

It is widely recognised that the fundamental mechanisms associated with the weld formation process and their relationships with welding parameters are complex and remain to be fully understood. The present paper reports a series of general findings based on a set of simplified numerical models that were designed to elucidate various aspects of the complex thermomechanical phenomena associated with friction stir welding. The following phenomena were investigated in separate numerical models: (i) coupled friction heat generation; (ii) plastic flow slip zone development; and (iii) three-dimensional heat and material flow. The friction induced heat generation model was used to quantify the contributions of coupled thermomechanical friction heating, including non-linear interfacial phenomena between the tooling (e.g. stir pin) and material being welded. The plastic work induced heating effects were also examined. The plastic slip formation mechanisms were then investigated by considering contributions from various heating mechanisms. Finally, a simplified three-dimensional heat and material flow model, based on the observations from the coupled friction heat generation model, was used to establish some initial insight regarding the heat and material flow. The results from the three subproblem areas were then generalised in the form of a simple parametric relationship between welding variables (i.e. travel and rotating speeds) and weld formation conditions. A series of assumptions were made in constructing these individual models since there exists little information on actual material behaviour under friction stir welding conditions. However, the findings from the present study not only illuminate some of the important weld formation mechanisms in friction stir welding, but also provide an effective framework for more focused investigations into some of the fundamental phenomena identified in the three subproblem areas: such investigations will be reported separately in a future publication.
Effect of aging on elevated temperature ductile fracture toughness of type 316LN stainless steel/alloy 800 weldment
Authors: Bhaduri A.K. , Sathe D.B. , Ray S.K. , Gill T.P.S. , Rodriguez P.
Published: June 2004

A type 316LN stainless steel/alloy 800 dissimilar metal weld, welded using Fe–16Cr–8Ni–2Mo (wt-%) filler metal, was subjected to accelerated aging heat treatments at 873 K for up to 5000 h to simulate long term service exposures, and was characterised for elevated temperature service at 773 K. The analysis included, apart from conventional structure–property correlation, characterisation in terms of the empirical parameters Γf and ηf determined at 773 K. The parameters Γf and ηf characterise the resistance to ductile fracture and are determined from tensile tests of smooth cylindrical transverse weld specimens. The results show that the present weldment has adequate stability against elevated temperature aging, and should therefore show stable behaviour on exposure at the service temperature.
Analysis of microstructure and mechanical properties in alloy 690 weldments using filler metals I-82 and I-52
Authors: Lee H.T. , Kuo T.Y.
Published: June 2004

This work investigated the weldability and mechanical properties of weldments made with Inconel filler metals I-52 and I-82 in the welding of Inconel alloy 690. Gas tungsten arc welding was used with different multipass sequences. The microstructures of the fusion and heat affected zones were examined and weldment properties were compared by tensile, hardness, and impact tests. Fracture surfaces were examined by scanning electron microscopy. Experimental results indicate that the subgrain structure near the fusion zone centreline was dominated by equiaxed dendrites in I-82 weldments but by columnar dendrites in I-52 weldments. In addition, the I-82 weldments had a finer subgrain structure near the fusion zone centreline and smaller cellular spacing near the fusion line than I-52 weldments. Mechanical test results demonstrate that the I-82 weldments had higher tensile strength (622–630 MPa) with rupture occurring in the base metal. In comparison, the I-52 weldments had lower tensile strength (568–578 MPa) and rupture occurred in the fusion zone. Filler metal I-52 showed better welding performance and greater impact toughness with only slight sensitivity to the number of passes. However, a gradual increase in the hardness of the weld was observed as the number of passes increased.
Effects of shielding gases on weld diffusible hydrogen contents using cored wires
Authors: Mirza R.M. , Gee R.
Published: June 2004

Cored wire welding is widely used for joining thick steel sections, where a high integrity weld is required. The shielding gases selected for cored wire welding depend on the type of filling constituents of the wire. Weld properties, deposit chemistry, bead shape, deposition rates, and the operational characteristics of weld ing are greatly affected by the shielding gases. In the present work, studies have been carried out to observe the effects of wide ranging shielding gases on the diffusible hydrogen contents of welds using cored and solid metal inert gas (MIG) welding wires. The hydrogen present in the weld metal has been determined by the method described in British Standard BS 6693: 1988. For flux and metal cored wires, it was observed that an increase in shielding gas CO2 content has a marked effect on diffusible hydrogen and, for both consumables, the diffusible hydrogen content decreases as the CO2 content increases in Ar–CO2 mixtures. The effects of weld penetration and metal transfer, by changing the shielding gas, on hydrogen content of the weld metal have also been studied and reported.
Pressureless diffusion bonding of ferritic stainless steel foil controlled by metal evaporation
Authors: Takahashi Y. , Inoue K.
Published: June 2004

Bond formation of thin ferritic stainless steel foils containing 20Cr–5Al (wt-%) was observed under near vacuum pressure of ∼10-3 Pa. Debonded (peeled off) surfaces exhibited a white scaly morphology after bonding above 1400 K. No bond formation was observed below 1400 K, so the critical temperature for bond formation must exist around 1400 K. The critical temperature also depends on the surface roughness of the foil (the thickness of the gap between foils), which can be explained in terms of aluminium evaporation behaviour between foils. A theoretical model is proposed to estimate the effect of aluminium evaporation on the critical temperature. It is also suggested that aluminium evaporation between foils can protect the bonding surface from the residual oxygen gas.
Pressureless solid state diffusion bonding of ferritic stainless steel honeycomb matrix
Authors: Takahashi Y.
Published: June 2004

A honeycomb matrix was prepared by winding a corru gated foil and a flat foil fabricated from 5Al–20Cr (wt-%) ferritic stainless steel. The interconnection between the corrugated foil and the flat foil was initiated as small bond islands which developed along the peaks of the corrugated foil because of the surface roughness of the foils. Each island gradually grew and united with others during diffusion bonding. The growth of the bond islands was controlled by two independent processes. One growth process was in the y direction, parallel to the contact zone between the corrugated foil and the flat foil. The other was in the x direction, perpendicular to the contact zone. It is suggested that the bonding is achieved by diffusional transport. The rate determining step of the y direction growth is controlled by volume diffusion in the high temperature region (>1473 K) but is replaced by another diffusional process as temperatures decrease below 1473 K. The dominant mechanism at low temperature (<1473 K) is suggested to be based on surface and interface selfdiffusion. It was found that the y direction bond growth process is much more important than the x direction neck growth sintering process in producing the honeycomb interconnection.
Analysis of effect of dynamic compositional fluctuation on weld metal creep based on laminate composite simulation
Authors: Wang S.H. , Matlock D.K. , Olson D.L.
Published: June 2004

The high temperature properties of wrought materials of uniform composition are different from those of materials exhibiting compositional fluctuation, which is generally caused by differences in materials processing. Roll bonded laminate composites of nickel with Cu–Ni solid solutions containing 8·9, 18·9, 28·6, 37·3, and 48·3 at.-%Cu were fabricated to simulate physically the microsegregation occurring in solidified Monel 400 weld metal. The results show that the creep behaviour is strongly influenced by the degree of interdiffusion and amplitude of the compositional fluctuation, as a result of the driving force of the simulated microsegregation. The apparent activation energy Q is dependent on the applied stress. As stresses increase, the deformation mechanisms suggested vary from short circuit diffusion, to thermal lattice selfdiffusion, to high atomic mobility selfdiffusion which is attributed to the athermal excess vacancies. Changes in stress exponent n, Q, and the structure dependent constant A with time are correlated with the dynamic interdiffusion due to the homogenisation process.