bluuebunny/crossref_metadata_2025 huggingface dataset:
Democracy within Norwegian Political Parties
Authors: Saglie Jo , Heidar Knut
Published: June 2004

How democratic are the political parties in Norway? We use survey data from Norwegian party members (1991 and 2000) and Congress delegates (2000-1) to discuss two main questions: how do party members and Congress delegates evaluate the state of intra-party democracy? And what kind of intra-party democracy do they prefer? The analyses do not support the thesis of an increasing centralization of party decision making. Members were reasonably satisfied with the leadership, but those in positions of power were more satisfied than the grassroots. Participants at all levels preferred the present delegatory type of democracy to more direct democratic procedures. The attitudes of the participants do not indicate any strong pressure for organizational change, but declining membership and lack of legitimacy may still bring changes to intra-party decision-making.
Food, Health and Psychology: Competing Recipes for Research and Understanding
Authors: Smith John L.
Published: June 2004

Mainstream and post-postivist approaches to psychological research are compared with regard to healthy eating and eating disorders. The tendency of the mainstream operationally to define key concepts is contrasted with the post-positive preference for conceptual analysis and an example of this is considered in relation to theory of planned behaviour research. The reason why the search for a causal mechanism for major eating disorders such as anorexia nervosa has proved unfruitful becomes transparent once the phenomena are construed as action, as opposed to behaviour. Some of the methodological problems and issues arising within the post-positivist approaches are discussed using illustrative examples of autoethnographic research into eating episodes.
Good for ‘You’: Generic and Individual Healthy Eating Advice in Family Mealtimes
Authors: Wiggins Sally
Published: June 2004

Healthy eating is one of the main concerns for health organizations in the UK, and has been widely promoted in recent decades. Yet despite the amount of nutritional information available, levels of obesity, heart disease and other food-related diseases remain high. Existing research in this area often uses individual accounts of consumption to examine the reasons why people may not be eating ‘healthily’. An alternative way to approach this issue is to examine how healthy eating advice is constructed and used in everyday interaction. This research uses tape-recorded family mealtimes to examine instances where nutritional advice is embedded and managed in conversational activities. A distinction between generic and individually focused healthy eating talk is illustrated, and the implications for further research are discussed.
Nutritional Health Messages in Women’s Magazines: A Conflicted Space for Women Readers
Authors: Madden Helen , Chamberlain Kerry
Published: June 2004

Media representations of food are ubiquitous in contemporary society, and healthy eating features predominantly in such texts. This study explores the discursive construction of food and healthy eating in texts appearing in popular women’s magazines, and examines the variety of positions and subjectivities offered to women readers of these texts. We find that such texts present quite complex constructions of nutritional health, based on scientific and biomedical discourses of nutrition interwoven with discourses of morality, feminine beauty and mothering. We conclude that these texts offer a conflictual space for women to traverse in efforts to position themselves as good mothers and moral and healthy eaters.
Organizational Pathologies in Police Intelligence Systems
Authors: Sheptycki James
Published: June 2004

During the 1990s serious and organized crime moved to the top of the agenda for policing internationally. This shift took place during the same period that new information and communications technologies were being adopted across the policing sector in most European countries, a shift known in some places as the rise of ‘intelligence-led policing’. Discussion of intelligence-led policing against serious and organized crime has tended to focus on formal models of intelligence systems. The purpose of this paper is to contribute to the vocabulary of intelligence-led policing by providing the terms for describing the organizational problems that bedevil the organization of police information systems. It is based on original empirical research in the United Kingdom and a number of other countries and provides a lexicon of 11 organizational pathologies. The paper ends by arguing that strategic intelligence forecasts about future trends in organized and serious crime that emanate from the police sector are not as strategic or as comprehensive as they appear to be.
On Not Abolishing Faith Schools
Authors: Groothuis Douglas
Published: June 2004

This article finds Michael’s Hand’s argument for the abolition of faith schools to be deficient because key premises of his argument seem false. I argue that the concept of knowledge that Hand employs in arguing that no religious proposition is known to be true is overly strict. I reject Siegel’s attempt to amend Hand’s argument to make it stronger because Siegel employs a false construal of ‘faith’. I further argue that Hand’s premise that students in faith schools will not take their teachers to be religious authorities is very weak. Finally, I note that the abolishing of faith schools does not follow from either Hand’s or Siegel’s argument.
The Master Settlement Agreement and African Americans: Opinions About the Allocation of Resources
Authors: King Gary , Mallett Robyn K. , Bendel Robert L. , Noubary Farzad , Nahata Sunny
Published: June 2004

This article analyzes demographic, attitudinal, and behavioral variables that predict African Americans’ opinions about state distribution of funds received from the Master Settlement Agreement (MSA). The sample consisted of 1,000 randomly selected African Americans from 10 U.S. congressional districts represented by African Americans. Descriptive analysis revealed that 38.7% of respondents favored dispersing funds evenly between tobacco control and other state functions, and 63% of respondents favored specifically directing MSA funds to African American communities. Cumulative logit regression analysis showed that age, education, geographic region, and smoking status were significant predictors of opinions about spending MSA funding on antismoking initiatives. Multiple logistic regression analysis revealed that opinions about targeted MSA funds to African Americans varied by homeownership, views on tobacco excise taxes, the fairness of tobacco taxes to African Americans, and the association between smoking and racism in U.S. society.
The Effect of Enforcement of the Master Settlement Agreement on Youth Exposure to Print Advertising
Authors: Lieberman Alan
Published: June 2004

Enforcement of the Master Settlement Agreement’s (MSA) prohibitions on youth targeting and the use of cartoons has resulted in a significant reduction in youth exposure to tobacco advertising. The MSA between the states and the tobacco companies has provided state officials with a new and powerful tool to address tobacco company marketing practices that may promote underage smoking. In the area of print advertising, enforcement of the MSA’s prohibitions on youth targeting (MSA III[a]) and on the use of cartoons (MSA III[b]) has resulted in a significant reduction in youth exposure to tobacco advertising. The recent court decisions finding that R. J. Reynolds violated the youth targeting prohibition in its tobacco advertising in national magazines affirm the viability of the MSA’s various restrictions and its enforcement mechanisms as a key way that state Attorneys General are responding to a range of tobacco company practices affecting youth.
Analytical solutions for heat flow in multiple pass welding
Authors: Suzuki R.N. , Trevisan R.E. , Trevisan O.V.
Published: June 2004

The purpose of this paper is to present analytical solutions for the heat distribution in the base metal during and after serial heating in multiple pass arc welding. Recent literature on welding heat transfer has covered extensively numerical models for different aspects of the process. Most of these aspects are non-linear problems in heat flow, e.g. varying thermal properties, inclusion of radiative transfer in the arc, and/or convective flow in the welding pool. The basic analytical models in use were established long ago in classical papers, but these refer to single heat cycles. The present paper addresses the circumstances of multiple cycles. In these cases, depending on the bead length and the interpass time, as shown by the proposed solution, the thermal effects of each successive pass will accumulate. When modelling the heat transfer in each pass, the effects of previous passes enter into the differential equations as non-homogeneous initial conditions. The complexity introduced by these conditions requires special treatment: an analytical solution employing the Green's function method was used. The main focus in this work is on welding of thin plates. Simple changes to the models take account of the convective heat loss to the surroundings and enable temperature dependent properties to be calculated. The solutions were checked against experimental results obtained from a specially designed laboratory setup. Thermal cycles provided by the analytical solutions compare well with temperature histories measured at different locations during three pass gas metal arc welding of a 0.5 in (∼1 cm) AISI 304 stainless steel plate. Measured data and model results show very good agreement. The analytical solutions are also extended to the geometries of moderately thick plates.
Modelling creep rupture strength of ferritic steel welds
Authors: Cole D. , Martin-Moran C. , Sheard A.G. , Bhadeshia H.K.D.H. , MacKay D.J.C.
Published: June 2004

Recent changes in the design of steam turbine power plant have necessitated the replacement of bolted flanges with welded joints. The design process therefore requires a knowledge of the creep rupture strength of the weld metal consumed in the welding process. This paper presents a method which can be used to estimate the creep rupture strength of ferritic steel weld metals, from a knowledge of the creep strength of wrought plates. The method is validated using published data.
Study of all position electron beam welding process for pipeline joints
Authors: Koga S. , Inuzuka M. , Nagatani H. , Iwase T. , Masuda H. , Ushio M.
Published: June 2004

For the purpose of applying the electron beam (EB) welding process to the site welding of natural gas pipelines, the authors investigated fundamental all position EB welding characteristics for 19 mm thick API 5L–X65 steel pipe. To establish appropriate welding conditions for satisfactory weld bead formation, the study was separated into two steps. First, appropriate welding parameter ranges were investigated in eight representative welding positions by rotating the test pipe in which the electron gun was fixed. Second, based on the investigation in the first step, all position continuous welding was carried out successfully by rotating the gun in a vertical plane. The influence of edge misalignment and mismatch on weld bead formation was investigated and the dimensional tolerances needed to obtain acceptable weld beads were clarified. Solidification cracking in the weld metal of a pipeline steel was investigated and it was determined that sulphur was the most harmful element in terms of promoting cracking. Some mechanical properties of the weld joint were also examined.
Optimisation of welding using two Nd–YAG laser beams combined at workpiece surface
Authors: Narikiyo T. , Fujinaga S. , Takenaka H. , Ohmori A. , Inoue K.
Published: June 2004

Two Nd–YAG laser beams were combined at a certain point on the workpiece surface to increase weld penetration depth. One of the beams was a pulsed laser beam, and the other was a continuous wave laser beam or a modulated laser beam. Using this combination of laser beams, a wide range of welding conditions, such as average power, peak power, and power density, could be selected. A high peak power pulsed laser beam would play a significant role in forming a keyhole, but a severe spatter loss problem could be encountered under high peak power laser conditions, thus the conditions necessary to prevent spatter loss were investigated. The greatest penetration depth is obtained under the critical conditions for spatter loss. Critical conditions for spatter loss are controlled by the peak power of a pulsed laser beam, thus deeper weld penetration is obtained using a pulsed laser beam with higher average power, that is, of longer pulse width and/or a higher repetition rate within the limit of the oscillator output. Moreover, spatter loss is reduced under conditions providing large molten zones in the weld, thus a higher peak power pulsed laser beam can be employed under such conditions. Large molten zones are obtained using a modulated laser beam of a high average power and/or low welding speeds.
Visualisation of material flow in autogenous friction stir welds
Authors: Reynolds A.P.
Published: June 2004

Material flow in friction stir welds has been visualised using embedded marker materials. The fidelity of the visualisation technique has also been demonstrated. Results from the flow visualisation show that the friction stir welding process can be roughly described as an in situ extrusion process wherein the tool shoulder, the weld backing plate, and the cold base metal outside the weld zone form an ‘extrusion chamber’ which moves relative to the workpiece. Deviation from this description occurs primarily at the top surface of the weld where significant material transport occurs owing to the action of the rotating tool shoulder. The transport caused by the shoulder leads to a small amount of circulation about the longitudinal axis of the weld with material moving primarily from trailing to leading sides at the top of the weld and primarily from leading to trailing near the middle and bottom of the weld.
Estimation of mechanical properties of ferritic steel welds. Part 1: Yield and tensile strength
Authors: Lalam S.H. , Bhadeshia H.K.D.H. , MacKay D.J.C.
Published: June 2004

The yield strength and ultimate tensile strength of ferritic steel weld metal have been expressed as functions of chemical composition, the heat input during welding, and the heat treatment given after welding is completed. The method involved a neural network analysis of a vast and fairly general database assembled from publications on weld metal properties. The outputs of the model have been assessed in a variety of ways, including specific studies of model predictions for the so called C–Mn and 2.25Cr–1Mo systems. Where possible, comparisons have also been made with corresponding methods which use simple physical metallurgical principles. The models created are believed to have been trained on the largest weld metal database to date, and are shown to capture vital metallurgical trends. The computer programs associated with the work have been made freely available on the World Wide Web.
Estimation of mechanical properties of ferritic steel welds. Part 2: Elongation and Charpy toughness
Authors: Lalam S.H. , Bhadeshia H.K.D.H. , MacKay D.J.C.
Published: June 2004

Previous work presented models which can be used to estimate the yield and ultimate tensile strengths of ferritic steel welds. The present paper deals with properties that are much more difficult to predict: the elongation and Charpy impact toughness. While the models are found to be useful and emulate expectations from current physical metallurgy principles, it is clear that much more systematic experimental data are needed before the predictability becomes as good as the strength models of Part 1.
Microstructure and toughness of intercritically reheated heat affected zone in reactor pressure vessel steel weld
Authors: Kweon K.S. , Kim J.H. , Hong J.H. , Lee C.H.
Published: June 2004

This study is concerned with correlating the metallurgical factors and the toughness of the intercritically reheated coarse grained heat affected zone (ICCGHAZ) of multipass welded SA508–cl. 3 reactor pressure vessel steel. The influence on toughness was investigated by means of a simulated heat affected zone test. Toughness and other properties of the ICCGHAZ were strongly influenced by metallurgical factors such as high concentration of carbon martensitic islands (secondary phase, martensite–austenite constituents) formed along the prior austenite grain boundaries and martensite lath interfaces, and a softened matrix (tempered martensite or bainite). The characteristics (amount, hardness, and size) of the islands were found to be strongly correlated with both peak temperature and the cooling time of the previous pass. The toughness of the ICCGHAZ deteriorated with increasing amounts of martensite–austenite constituents, which were made more abundant by increasing the final peak temperature within the intercritical temperature range. Meanwhile, for the same intercritical peak temperature, toughness decreased with increased cooling time. When the cooling time was short, the dominant factor influencing toughness of the ICCGHAZ was the amount of martensitic islands. However, when the cooling time was long, the hardness difference between the martensitic islands and the softened matrix (tempered martensite) was found to be the dominant factor.
Microstructure of martensite–austenite constituents in heat affected zones of high strength low alloy steel welds in relation to toughness properties
Authors: Lambert A. , Lambert A. , Drillet J. , Gourgues A.F. , Sturel T. , Pineau A.
Published: June 2004

Microstructure and fracture properties relationships have been investigated in the heat affected zones (HAZs) of a high strength low alloy steel used for offshore applications. Metallographic examinations of simulated HAZ microstructures were conducted to investigate the detailed microstructure of the martensite–austenite (M–A) constituents. Using scanning and transmission electron microscopy, various microstructures were found for the M–A constituents. In mixed particles, retained austenite was located at the periphery of the islands. Chemical and/or mechanical effects could possibly account for the stabilisation of this austenite phase. In situ cooling experiments in the transmission electron microscope showed that stacking faults play an important role in the thermal stability of austenite. Impact properties of simulated HAZ microstructures are strongly affected by both the bainitic microstructure and M–A constituents. In particular, freshly transformed high carbon martensite was shown to be much more deleterious than retained austenite.
Investigation into arc constriction by active fluxes for tungsten inert gas welding
Authors: Howse D.S. , Lucas W.
Published: June 2004

Mechanisms by which active fluxes increase the penetration of conventional tungsten inert gas (TIG) welds (so called A-TIG welds) are reviewed. The most dominant mechanism for increased penetration is considered to be arc constriction rather than a change in the surface tension of the molten pool. An experimental programme of work was carried out using A-TIG flux in combination with a number of welding processes. The plasma process was investigated as it gives greater penetration than conventional TIG welding by increasing current density. The CO2 laser and electron beam processes which do not rely on a current carrying arc as the heat source for welding were also investigated. Macrosections taken from the welds made by these processes showed that the A-TIG flux was only effective when the weld pool was produced by an arc or plasma. Where there was no arc or plasma present, the flux had little effect.
Selection of welding process to fabricate cruciform joints using analytic hierarchic process based on qualitative factors
Authors: Balasubramanian V. , Guha B. , Swamidas A.S.J. , Seshadri R.
Published: June 2004

Selection of a welding process is an unstructured decision problem involving multiple attributes (factors). To provide decision support for the welding engineer, an all encompassing analysis of multiple attributes is necessary. The present paper reports a new procedure using an analytic hierarchic process for the selection of a welding process to fabricate cruciform joints of ASTM 517 ‘F’ grade steels, based on the qualitative factors of the welding processes, when the quantitative factors appear to be equal.
Numerical modelling of temperature distribution during multipass welding of plates
Authors: Murugan S. , Gill T.P.S. , Kumar P.V. , Raj B. , Bose M.S.C.
Published: June 2004

Welding is a reliable, cost effective, and efficient metal joining process. Manual metal arc welding (MMAW) is a widely used welding process in industry and multipass welding is very frequently used in the MMAW process. The temperature distribution that prevails during multipass welding affects the material microstructure and hardness of the regions near the weld, and the residual stresses that will be present in the material after cooling to room temperature. These changes will consequently affect the performance of the welded joint. In the present work, a computer model based on the control volume method has been developed to predict the temperature distribution during multipass welding of plates using the MMAW process. To validate the computer model, the temperature distribution was measured experimentally in a 12 mm thickness stainless steel weld pad during multipass welding. The welding parameters were used as input data for the computer model. The computer predictions and the experimentally measured temperature distributions agree well.
Stability of droplets in gas metal arc welding
Authors: Murray P.E.
Published: June 2004

A method is developed to compute the stability of droplets detaching from the consumable electrode in gas metal arc welding. An aluminium electrode is used as the model system. Theoretical predictions and supporting experiments are used to ascertain the rate of transfer of droplets for a range of current encompassing globular and spray transfer, and to examine the transition between these distinct modes of metal transfer. The method uses dimensional analysis to correlate the mass, rate of transfer, and force acting to detach droplets. The correlation is found to undergo a notable change in slope at the transition between globular and spray transfer. The accuracy of the correlation is assessed by comparing the theoretical and measured rate of transfer of droplets in gas metal arc welding using aluminium electrodes of variable diameter.
Mapping transfer modes for stainless steel gas metal arc welding
Authors: Scotti A.
Published: June 2004

A methodology for the construction of transfer mode maps for stainless steel gas metal arc welding, with argon and argon–oxygen shielding gases, is presented. A back lighting laser and high speed video camera were used for visualisation and measurement of droplets and electrode extension. The reasons for the use of a groove, instead of the traditional bead on plate method, and of same volume beads are discussed and the results assessed. Unlike in other mapping procedures, mapping was conducted as a function of welding current and arc length. In addition, transfer rate v. welding current or wire feedrate curves were plotted. The results show the importance of the use of both maps and curves for identification and quantification of the shielding gas effects on the transfer mode. The results also suggest that an increase in oxygen content in the shielding gas reduces the values of transition current and transition wire feedrate (as expected), but also that it reduces the transfer rate and droplet size at the globular–spray transition.
Microstructure and properties of as welded duplex stainless steel
Authors: McPherson N.A. , Li Y. , Baker T.N.
Published: June 2004

Butt welds of duplex stainless steel plate (grade 2205) have been produced using grade 2209 consumables for a variety of welding processes employed in the shipbuilding industry. The welding processes were used initially with interpass temperatures in the range 250–350°C. When the interpass temperature was controlled to below 150°C, the average ferrite content increased in the weld metal and in the heat affected zone (HAZ). Controlling the interpass temperature did not dramatically affect the properties in the mechanical tests performed. Heat inputs were in some instances higher than those used previously, but this did not adversely affect weld metal and HAZ properties. No evidence of intermetallic phase precipitation was found, by TEM of thin foils, in any of the weld metal in the processes used. There was evidence of fine particle precipitation of M23C6 in the HAZ regions. The level of precipitation observed is acceptable for the final application as all the mechanical test and corrosion test requirements were comfortably met. There was evidence that the HAZ was an area of higher strain: dislocation density was high and deformation bands, twinning, and stacking faults were present.
Analysis of angular distortion in weldments using laminated plate theory
Authors: Son K.J. , Yang Y.S. , Beom H.G.
Published: June 2004

The problems of distortion and residual stresses in and around a welded joint are of major concern in heavy industry. In the present work, a formula for weld induced angular distortion, in terms of weld parameters such as heat input and plate thickness, is developed analytically using an infinite laminated plate theory to consider an elliptical cylindrical inclusion with an eigenstrain. The source of angular distortion in weldments is the plastic strains that are caused by non-uniform temperature gradient. The distributions of the plastic strain corresponding to the eigenstrain are determined using Rosenthal's solution, which describes temperature distributions. Comparison of the calculated results with the experimental data shows the accuracy and validity of the proposed method.
Occurrence of bay area in submerged arc welds
Authors: Lee C.S. , Chandel R.S. , Seow H.P.
Published: June 2004

An experimental study has been carried out to evaluate the effect of submerged arc welding parameters on the formation of a bay area in the heat affected zone of bead on plate welds in ASTM A36 steel. It was observed that the formation of weld beads having a bay area is influenced by the heat distribution from the arc, which in turn is determined by the welding conditions. The effect of the welding parameters on the weld bead formation is discussed in terms of the arc operation modes and the resulting heat distributions.
Combined effect of inoculation and magnetic arc oscillation on microstructure and tensile behaviour of type 2090 Al–Li alloy weld fusion zones
Authors: Sundaresan S. , Janaki Ram G.D. , Murugesan R. , Viswanathan N.
Published: June 2004

In the development of Al–Li alloys for aerospace structures, their behaviour during welding plays an important role. One way of improving weldability is to refine weld solidification structures, which can be achieved by a variety of means. In this work, a type 2090 Al–Li alloy was gas tungsten arc welded with two different filler materials corresponding to types 2319 (Al–6.3Cu) and 4043 (Al–5.2Si). Inoculation with titanium together with arc oscillation through an imposed alternating magnetic field was used to refine the weld fusion zone microstructures. Post-weld aging and tensile testing were employed to assess possible improvements in performance. It was found that the combined treatment of inoculation and magnetic oscillation resulted in fully equiaxed, fine grained structures and that this led to a noticeable increase in aging response and tensile properties, especially ductility.
Laser beam welding of wrought aluminium alloys
Authors: Ion J.C.
Published: June 2004

Laser beam welding is now a common manufacturing method for a wide range of steel products from automobiles to razor blades. However, the process has only recently been approved for critical applications involving aluminium alloys, notably in the aerospace and automotive industries. The properties of aluminium alloys influence the interaction between the beam and the material to a far greater extent than for steels. The challenge of developing industrial welding procedures has therefore been considerable. The present review describes the effects of CO2 and Nd–YAG laser beam processing parameters and the properties of the most common wrought aluminium alloys on the characteristics of welded joints. Porosity, solidification cracking, and poor weld bead geometry are shown to be the most frequently encountered imperfections. These can be eliminated through the use of appropriate filler materials, process gases, material preparation, and in some instances, adaptive control systems. Very little work has been reported on the corrosion properties of laser welded aluminium alloys. Experimental processing parameters are presented and compared using an analytical model, which can also be employed for predictive purposes. A number of industrial applications are described. These demonstrate that, for specific alloys, the process is now sufficiently well understood to be approved for high volume production, particularly in the transport industries.
Grain growth behaviour and high strain rate tensile properties of gas tungsten arc welds in iridium alloy DOP–26
Authors: McKamey C.G. , Lee E.H. , Cohron J.W. , Goodwin G.M. , George E.P.
Published: June 2004

The high strain rate tensile ductilities of gas tungsten arc welds in an Ir–0.3 wt-%W alloy containing 60 wt-ppm Th (designated DOP–26) have been determined at test temperatures of 900–1200°C. Within this temperature range, the welded specimens of DOP–26 exhibited tensile ductilities of 9–15%, independent of the test temperature. These values are comparable to those of unwelded DOP–26 tensile specimens tested at temperatures below 1000°C, but significantly lower than (approximately half) those of unwelded DOP–26 tested above 1000°C. Elongation measurements at points along the gauge length of tensile tested specimens indicated that ductility was fairly uniform across the base metal and weld regions. At a tensile test temperature of 900°C, fracture occurred in the base metal with a mixed intergranular–transgranular failure mode. At 980°C and above, fracture occurred along the grain boundaries in the centreline of the weld. Scanning electron microscopy of fracture surfaces revealed the presence of numerous secondary phase particles along grain boundaries in the weld region. These particles were rich in thorium and were identified as an Ir–Th eutectic phase (melting point ∼2080°C) that formed as the weld pool cooled. These particles, and the larger grain size of the fusion zone compared with the base metal, contributed to the lower tensile ductilities of the welded specimens compared with unwelded specimens. Because high strain rate tensile ductility in this alloy is strongly dependent on grain size, the grain growth behaviour of welded specimens of the alloy was also studied. In as welded specimens, the average grain diameters (measured through the thickness of the specimens in a plane perpendicular to the welding direction) in the base metal, weld centreline, and fusion zone were ∼21, 41, and 72 µm respectively. For annealing times up to 1065 h at 1400°C and up to 100 h at 1500°C, grain sizes in the weld centreline and in the fusion zone did not change significantly. For these same anneals the base metal grain size increased gradually to 45 and 58 µm for 1400 and 1500°C annealing respectively. The base metal grain sizes were comparable to previous data from unwelded specimens of this alloy. However, excessive grain growth for an annealing time of 250 h at 1500°C was observed and as yet is unexplained.
Weld geometry and tensile strength in laser welded thin sheet metals
Authors: Du J. , Longobardi J. , Latham W.P. , Kar A.
Published: June 2004

Weld geometries and their effects on the ultimate tensile strength (UTS) of welded specimens were studied experimentally for type 316 stainless steel sheets. Bead on plate welding with 0.1 and 0.2 mm thick workpieces and lap welding with 0.1 mm thick workpieces were carried out. The results showed that the strength of lap welds is influenced by the weld geometry to a large extent. A three-dimensional quasi-steady state heat conduction model was developed to understand the heat flow mechanism during laser welding of sheet metals of finite thickness. The temperature distribution and weld geometry were calculated using the mathematical model and the theoretical results were found to compare well with experimental data. More energy is used to produce melt pools in thinner workpieces than in thicker ones. The model can be used to select suitable process parameters to achieve a predetermined UTS by controlling the weld geometry.
Effects of absorptivity, shielding gas speed, and contact media on sheet metal laser welding
Authors: Tanriver U. , Longobardi J. , Latham W.P. , Kar A.
Published: June 2004

A three-dimensional quasi-steady state heat conduction model is developed for laser welding of sheet metals. The heat flux at the surface of the workpiece is considered to be due to a moving Gaussian laser beam. An analytical expression is obtained for the temperature distribution by solving the conduction problem using the Fourier integral transform technique. This expression is used to locate the melting temperature isotherm, and thereby determine the weld depth and width. Experimental and theoretical results for the weld depths and widths are illustrated for different welding parameters such as the laser power, absorptivity, welding speed, and shielding gas speed. The theory and experiment are found to agree reasonably well. The effects of absorptivity, shielding gas speed, and heat loss due to different contact media at the bottom surface of the workpiece are also investigated, and are found to be significant for thin metal laser welding.
Determination of weld pool shape and temperature distribution by solving three-dimensional phase change heat conduction problem
Authors: Guo W. , Kar A.
Published: June 2004

A quasi-steady state heat conduction model considering phase change for laser welding of sheet metals is presented. The method of least squares was used to solve the governing equation in the liquid phase. The solution provides the weld pool shape and the temperature distribution in the weld pool. Results for stainless steel were compared with experimental data and fairly good agreement was obtained between the theoretical predictions and the experimental data.
Gas metal arc welding process monitoring and quality evaluation using neural networks
Authors: Wu C.S. , Polte T. , Rehfeldt D.
Published: June 2004

To ensure product quality, it is essential to ensure process quality. Thus, early monitoring and detection of process disturbances in welding production lines are of great significance. The present paper introduces a neural network system for process monitoring and quality evaluation in gas metal arc welding. The system is based only on the measured and statistically processed data for welding voltage and short circuiting time. It is a self-organising feature map Kohonen network which can automatically recognise and classify process disturbances occurring during welding.
Tensile properties and fracture toughness of 18Ni (250 grade) maraging steel weldments
Authors: Shamantha C.R. , Narayanan R. , Iyer K.J.L. , Radhakrishnan V.M. , Seshadri S.K. , Sundararajan S. , Sundaresan S.
Published: June 2004

Gas tungsten arc welding was performed on 18Ni (250 grade) maraging steel sheet using two different filler wires: one of the same composition as the base material and the other containing more cobalt and aluminium and less molybdenum and titanium. Weld specimens were then aged under four different sets of conditions. After metallographic characterisation, mechanical properties including hardness, tensile strength and ductility, and fracture toughness were evaluated. Results showed that use of the matching filler material led to lower strength but higher ductility than in the other case; this was attributed to the presence of reverted austenite in the former (caused by segregation, especially of molybdenum) at the fusion zone substructure boundaries. In both types of weld metal, a re-solution treatment followed by aging at 480°C resulted in optimum tensile properties. Fracture toughness of the aged weldments was in general close to that of the parent material aged at 480°C; some deterioration occurred only when welds with pronounced segregation were made at high temperature.
Joining issues for new constructional steels
Authors: Dolby R.E.
Published: June 2004

Joining and related fabrication issues that must be considered in modern steel development are described. The fabricator's view is presented in relation to the received steel quality, productivity and fabrication issues, and flaw avoidance using existing and newly developed welding processes. The designer's view is then linked to potential issues for modern steels concerning joint strength, toughness, fatigue strength, and corrosion. Finally, implications for the steel developer are presented, including some recommendations related to the protection of the environment.
Fatigue and fracture issues of welds in civil structures
Authors: Miki C.
Published: June 2004

Fatigue and fracture events occurring in bridge structures built in the 1960s and 1970s are reviewed and methods used to repair damaged structures are outlined. One of the most important factors is the design lifetime of structures, usually considered to be more than 100 years. The means of guaranteeing the performance of structures throughout their lives with minimum cost is an engineering issue of increasing importance.
Formation mechanism of vermicular and lacy ferrite in austenitic stainless steel weld metals
Authors: Inoue H. , Koseki T. , Ohkita S. , Fuji M.
Published: June 2004

Solidification and subsequent transformation of austenitic stainless steel weld metals that solidified in the ferritic–austenitic mode were investigated from the viewpoint of crystallography. The formation mechanisms for the vermicular and lacy ferrite observed in the weld metals were clarified. The ferrite morphology is determined by both the crystallographic orientation relationship between ferrite and austenite established at the stage of ferrite nucleation and the relationship between the welding heat source direction and the preferential growth directions of ferrite and austenite. In particular, for the formation of continuous lacy ferrite, it is necessary that the ferrite continues to grow with the Kurdjumov–Sachs orientation relationship with austenite that is established at the stage of ferrite nucleation.
Gas hollow tungsten arc characteristics under simulated space environment
Authors: Nishikawa H. , Yoshida K. , Maruyama T. , Ohji T. , Suita Y. , Masubuchi K.
Published: June 2004

A feasibility study has been conducted to determine whether gas hollow tungsten arc (GHTA) welding can be used for welding in space. As described in a previous paper by the present authors, the GHTA method has been tested in a simulated space environment using aircraft. The test result shows that the method is most promising as a welding process in space. In the present paper, some fundamental characteristics of the GHTA in a vacuum chamber, such as discharge characteristics and plasma properties, have been elucidated and the results of melting tests on stainless steel plate using the GHTA method have been compared with those obtained via a conventional gas tungsten arc method under atmospheric pressure.
Laser welding with activating flux
Authors: Kuo M. , Sun Z. , Pan D.
Published: June 2004

The effect on laser welding of activating flux, originally developed to improve penetration depth for tungsten inert gas welding, was investigated. Both mild and stainless steels were tested. Results show that weld penetration capability relates closely to the laser power level and welding speed of the process. Significant improvement in penetration was only observed when laser welding was performed in the conduction mode (i.e. weld aspect ratio <1). For the range of parameters studied, the best penetration capability improvements achievable for mild steel, type 304 stainless steel, and duplex stainless steel were found to be 41, 53, and 63% respectively. These data are of use in the selection of parameters for laser welding with activating flux.
Properties of as welded and heat treated pure titanium–7075 Al–Zn–Mg alloy friction weld joints
Authors: Fuji A. , Ameyama K. , Kokawa H. , Satoh Y. , North T.H.
Published: June 2004

The effects of joining conditions and an age hardening post­weld heat treatment (PWHT) at 120°C for 24 h on the tensile strength and metallurgical properties of dissimilar friction joints between pure titanium and age strengthened 7075 Al–Zn–Mg alloy were investigated. Highest strength was achieved using intermediate friction pressure (150 MPa), short friction time (0.5 s), and high upsetting (forging) pressure (400 MPa). The joint tensile strength decreased when the joint diameter was increased from 8 to 16 mm. The joint tensile strength of as welded (AW) dissimilar joints was similar to that of PWHT joints with diameters of 8, 12, and 16 mm. Detailed TEM confirmed that there was a negligible difference in the thickness of the intermetallic layer formed at the dissimilar joint interface for AW and PWHT joints. While the intermetallic phases formed at the joint interface comprised Al3Ti, τ (Ti2Mg3Al18), and Al in AW joints, they consisted of Al+ τ or Mg2Al3+ τ+Al in PWHT joints. Softened regions were generated in 7075 base material immediately next to the interface in AW joints. Post­weld heat treatment increased the hardness of the softened region almost to that of as received 7075–T6 base material in 12 and 16 mm diameter joints. In contrast, the hardness of the softened region in 8 mm diameter joints could not be recovered to that of the as received material. This was a result of overaging and coarse precipitates in the softened region produced during the friction welding operation.
Solidification and microstructure modelling of welds in aluminium alloys 5754 and 6111
Authors: Babu S.S. , David S.A. , Vitek J.M. , Reed R.W.
Published: June 2004

A solidification and microstructure modelling approach has been developed to predict weld metal and heat affected zone (HAZ) characteristics. The freezing range and phase evolution in the weld metal region were predicted using thermodynamic and diffusion controlled growth calculations. The calculated freezing range was correlated with the weld solidification cracking tendency. A simplified analytical model was suggested to describe thermal cycles that are experienced by the HAZ. This analytical model was coupled with a published microstructure model for age hardenable alloys to predict the hardness variations across the HAZ. The above integrated approach was evaluated using experimental welds made on non­age hardenable 5754 (Al–Mg) and age hardenable 6111 (Al–Mg–Si) alloys using gas tungsten arc, electron beam, and gas metal arc welding processes.
Methodology for development of welding procedures and empirical weld process models based on principal component analysis techniques
Authors: Biglou J. , Weckman D.C. , Bennett G.W. , Kerr H.W.
Published: June 2004

With the increased automation of welding processes, there is a necessity for experimental design techniques that will permit rapid and efficient definition of the range of welding process parameters that may be used to produce acceptable welds for each new application. Such techniques are also required during development of empirical weld process models. In the present study, an experimental design technique based on principal component analysis (PCA) has been developed and shown to be more efficient than the traditional fractional factorial approach to experiment design, weld procedure development, and development of weld process models. Gas tungsten arc (GTA) welding of corner joint sheet steel was selected to exemplify the application of the technique. The boundary of a three­dimensional domain of weld process parameters (welding current, speed, and electrode gap) which could be used to produce acceptable welds when using either flush or edge touch corner joint configurations was satisfactorily approximated using only 25 welds. The PCA based technique was able to resolve differences between the procedural domains of these two joint geometries. The procedural field for the edge touch configuration was found to have a larger range of acceptable welding conditions than that for the flush configuration. Empirical weld process models for these joint configurations were developed using standard multivariable regression analysis techniques and only 25 further welds. Finally, an empirical model for weld width prediction in corner joint GTA welding was developed which includes the effect of current, voltage, torch travel speed, and sheet metal fitup. This model had an R2 value of 86%, with all statistical tests yielding acceptable results.
Microresistance spot welding of Kovar, steel, and nickel
Authors: Ely K.J. , Zhou Y.
Published: June 2004

Microresistance spot welding of 0.2–0.5 mm thickness Kovar, steel, and nickel using different types of power supply was investigated. The effects of process parameters (welding current/pulse energy, electrode force, and welding time/pulse width) on joint strength and nugget diameter were studied. The maximum values of welding current and nugget diameter that did not result in weld metal expulsion and/or electrode–sheet sticking were determined. The difference between micro- and ‘large scale’ resistance spot welding was also considered. It was noted that the difference between micro- and large scale resistance spot welding is due not only to the difference in the scale of the joints, but also to the fundamental difference in the electrode forces (pressures) used. Based on the results of the present work, nominal process parameters are recommended for microresistance spot welding of Kovar, steel, and nickel when using different power supplies.
Line Gauss heat source model: An efficient approach for numerical welding simulation
Authors: Cai Z. , Wu S. , Lu A. , Zhao H. , Shi Q.
Published: June 2004

In view of the characteristics of the welding heat source, a new heat source model based on an established Gauss model, termed the line Gauss heat source, is developed to improve calculation efficiency. A typical welding process is simulated using both Gauss and line Gauss source models. The results show that using the new model, analysis time can be reduced greatly while high precision is maintained, and this method renders three-dimensional simulation of some real welding structures containing long welds practical. The cutting processes for the side plate of a bridge crane beam are simulated using the line Gauss source model, and the results agree fairly well with real measurements.