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1
Cronje, M. "Finite element modelling of shielded metal arc welding." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/2649.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005.This study involved the modelling and verification of the Shielded Metal Arc Welding of mild steel with the focus on displacement and temperature distribution prediction of welded plates. The project was divided into three phases namely; the literature survey into finite element modelling of welding processes, the modelling of a welding process and verification of the modelling with experimental results. A working welding model was created using a commercial finite element software package with the capabilities to model welding processes. The welding model was systematically developed from a two-dimensional model into a threedimensional full physics process model. Experimental measured welding heat input parameters were applied in the model, temperature dependent material properties were applied and actual structural restraints from the experiments were modelled. Displacement and temperature distributions were measured on mild steel plates welded with the Shielded Metal Arc Welding process. The plate temperature was measured at various locations with K-type thermocouples spot welded onto the plates. Plate deformation was measured at various stages of the manufacturing process. Tendencies in plate displacement were investigated with a change in certain welding parameters. The finite element model was verified and good correlations were found, especially for the temperature distribution in the welded plates.
2
Lindmark, Terese. "Welding parameter window for Tandem gas-shielded metal arc welding and fatigue in welded T-joints." Thesis, University West, Department of Technology, Mathematics and Computer Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-828.
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Miller, Jay. "The development of a curriculum for a course in manipulative skills for shielded metal arc welding." CSUSB ScholarWorks, 1997. https://scholarworks.lib.csusb.edu/etd-project/1188.
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Du, Plessis John. "Control of diffusible weld metal hydrogen through arc chemistry modifications." Diss., Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-05152007-131110.
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Grantham, Jesse A. "Fundamental study of interfacial tension effects on weld bead profile in the shielded metal arc welding process /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487779914826799.
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Greene, Michael K. "The effects of titanium on the mechanical properties of shielded metal arc welding (SMAW) of C-Mn steels." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8297.
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Approved for public release; distribution is unlimitedThe strength and toughness of low alloy steel shielded metal arc weld (SMAW) metal is markedly improved by the presence of the microconstituent acicular ferrite. Since acicular ferrite is nucleated by the non-metallic inclusions present in the weld metal. Its presence is determined by the size, number, distribution and chemical composition of these inclusions. Previous work has shown that inclusions containing no titanium are usually ineffective as nucleates of acicular ferrite in some C-Mn steel weld metal whereas inclusions containing small amounts (less than 5%) of titanium or more can produce a microstructure containing as much as 70% of acicular ferrite
7
Sowards, Jeffrey William. "Development of a chromium-free consumable for joining stainless steel." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1237845645.
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Liang, Dong. "Environmental and Alloying Effects on Corrosion of Metals and Alloys." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243995273.
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9
Keenan, Patrick Joseph. "Thermal insulation of wet shielded metal arc welds." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37182.
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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Sciences & Engineering, 1994.Includes bibliographical references (leaf 55).
by Patrick Joseph Keenan.
M.S.
Nav.E.
10
Jönsson, Pär Göran. "Arc parameters and metal transfer in gas metal arc welding." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12470.
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Kim, Yong-Seog. "Metal transfer in gas metal arc welding." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14199.
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Liratzis, Theocharis. "Tandem gas metal arc pipeline welding." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/5686.
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Energy consumption has grown by 2% per year worldwide over the past ten years. In 2005 worldwide 900,000 barrels of oil and 7.6 billion cubic metre of natural gas were produced daily. The exploitation of fields to meet the increased demands in energy requires the presence of adequate infrastructures. High strength pipeline steels(X100) have been developed to operate at higher pressures allowing a greater volume of fuel to be transported. Additional advantages arising from the reduction in wall thickness contribute to reduction in construction costs and steel volume.
13
Talkington, John Eric. "Variable polarity gas metal arc welding." Connect to resource, 1998. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1130352747.
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Thesis (M.S.)--Ohio State University, 1998.Advisor: Richard W. Richardson, Welding Engineering Program. Includes bibliographical references (leaves 111-113). Available online via OhioLINK's ETD Center
14
Goodarzi, Massoud. "Mathematical modelling of gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27936.pdf.
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Erener, Yavuz. "Analysis Of Welding Parameters In Gas Metal Arc Welding By A Welding Robot." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607766/index.pdf.
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ANALYSIS OF WELDING PARAMETERS IN GAS METAL ARC
WELDING BY A WELDING ROBOT
Erener, Yavuz
M.S., Department of Mechanical Engineering
Supervisor : Prof. Dr. R. Tuna Balkan
Co-Supervisor : Prof. Dr. M. A. Sahir Arikan
September 2006, 130 pages
In Robotic Gas Metal Arc Welding process, the welding parameters controlled by the welder (travel speed of the welding torch, wire feed speed, current, voltage, wire diameter, etc.) should be considered to obtain a desired welding quality. To design an appropriate welding model for the used equipment, the effects of each parameter should be studied by carrying out an adequate number of experiments. The welding process is described by analyzing the experimental data to define the relationships between the welding parameters and process variables. Various regressional models can be suggested to establish the analytical relationships.
In this study, the relationship between bead geometry and voltage, current, travel speed and wire feed speed is established by using a specific computer program developed for this purpose.
16
Wang, Ge. "NUMERICAL ANALYSIS OF METAL TRANSFER IN GAS METAL ARC WELDING." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/538.
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In gas metal arc welding (GMAW), metal transfer plays a crucial role in determining the quality of the resultant weld. In the present dissertation, a numerical model with advanced computational fluid dynamics (CFD) techniques has been developed first in order to provide better numerical results. It includes a two-step projection method for solving the incompressible fluid flow; a volume of fluid (VOF) method for capturing free surface; and a continuum surface force (CSF) model for calculating surface tension. The Gauss-type current density distribution is assumed as the boundary condition for the calculation of the electromagnetic force. The droplet profiles, electric potential and velocity distributions within the droplet are calculated and presented for different metal transfer modes. The analysis is conducted to find the most dominant effects influencing the metal transfer behavior. Comparisons between calculated results and experimental results for metal transfer under constant current are presented and show good agreement. Then, our numerical model is used to study a proposed modified pulsed current gas metal arc welding. This novel modified pulsed current GMAW is introduced to improve the robustness of the welding process in achieving a specific type of desirable and repeatable metal transfer mode, i.e., one drop per pulse (ODPP) mode. This new technology uses a peak current lower than the transition current to prevent accidental detachment and takes advantage of the downward momentum of the droplet oscillation to enhance the detachment. The calculations are conducted to demonstrate the effectiveness of the proposed method in achieving the desired metal transfer process in comparison with conventional pulsed current GMAW. Also, the critical conditions for effective utilization of this proposed method are identified by the numerical simulation. The welding operational parameters and their ranges are also calculated and the calculated results further demonstrate the robustness of this new GMAW technique in achieving high quality welding.
17
Jones, Lawrence Anthony. "Dynamic electrode forces in gas metal arc welding." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11287.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 306-313).
by Lawrence Anthony Jones.
Ph.D.
18
Robertson, Tommy. "Investigation of possibility to use spectrometry for monitoring the plasma in gas shielded arc welding." Thesis, KTH, Industriell produktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-49972.
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Investigation of the plasma arc by using optical spectrometry has been performed in TIG and MAG welding. Two different spectrometer setups were tested. The aim was to detect defects such asporosity (gas flow variations), bad penetration, burn through defects and undercuts etc. by using spectrometry. Important factors for the setup and measurement procedure are investigated; also problems with the methods and proposal for improvements and future work are discussed. Specific material lines were identified and compared to results from other independent institutes, attempts to calculate the plasma temperature were made as well as calculation methods based on the intensity balance between UV, Visible and IR ranges. Some correlation between poor gas flow and information in the plasma arc could be established. Burn through could also be detected by calculating the plasma temperature. Current and voltagevariations could also be detected. More research is necessary to conclude on best setup and the full monitoring possibilities.
19
Ludick, Mark. "Experimental sensitivity analysis of welding parameters during transition from globular to spray metal transfer in gas metal arc welding." Thesis, Peninsula Technikon, 2001. http://hdl.handle.net/20.500.11838/1269.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, Cape Town, 2001Since the discovery of arc welding at the beginning ofthe century, metal transfer has been a topic ofresearch interest. Metal transfer can, in fact be related to weld quality, because it affects the arc stability. Furthermore, it determines the weld spatter, penetration, deposition rate and welding position. Gas Metal Arc Welding (also known as Metal Inert Gas- or MIG welding) is the most co=on method for arc welding steels and aluminurn alloys. Approximately 40% of the production welding in the country is accomplished by this process in which the thermal phenomena and melting ofthe solid electrode are coupled to the plasma arc and the weld pool. Thus the therrno- fluid behaviour of the electrode and detaching drops can have significant effects on the subsequent weld quality and production rate. The knowledge of how metal transfer affects this arc welding process is important for welding control and process automation, as well as in the development of improved welding consumables. Gas metal arc welding has a distinct feature, indicated by the results of Lesnewich [24], [23], that for most gases, there is a discrete metal droplet formation change between low and high current operations. Naturally the droplet size will have a significant influence on the properties ofthe welds. In globular transfer which occurs at low current, the welding electrode melts and produces large droplets (usually larger in diameter than the electrode wire diameter). This mode of transfer is associated with high spatter levels and thus undesirable in terms of welding economics. An increase in welding current will, for most welding! shielding gases, produce metal transfer with smaller droplets, which is termed spray transfer. This mode oftransfer is associated with high voltage and amperage settings, thus producing high deposition rates limited to the flaUhorizontal position.
20
Shen, Hao. "Seam position detection in pulsed gas metal arc welding." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20040823.125740/index.html.
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Liu, Xiaopei. "Dual Bypass Gas Metal Arc Welding Process and Control." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/664.
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GMAW (Gas Metal Arc Welding) is one of the most important arc welding processes being adopted in modern manufacturing industry due to its advantages in productivity, energy efficiency and automation. By monitoring and improving some of the important properties of GMAW such as production rate, metal transfer and base metal heat input, researchers could bring the process efficiency and stability to a new level. In recent years, some innovative modifications of GMAW such as Twins, Tandem and laser-MIG hybrid welding have been adopted into many industrial applications for better productivity.
In this dissertation, a novel GMAW called DB-GMAW (Dual Bypass Gas Metal Arc Welding) using two GTAW torches and one GMAW torch to construct a welding system, is proposed and developed. In DB-GMAW, two GTAW torches perform the bypass system which decouples the total welding current into base metal current and bypass current after the melt down of filler wire. Compared to conventional GMAW, DB-GMAW has many advantages in droplet formation, base metal heat input and penetration achievement due to its unique characteristics in welding arc and current flow. In the first place of the research, experimental system of DB-GMAW is constructed. Then, sufficient experiments under different parameters are performed to provide us a good understanding of the behaviors and characteristics of this novel GMAW process. Observation about metal transfer formation and base metal heat input is studied to verify its theoretical analysis. Full penetration of work piece via DB-GMAW is achieved based on a series of parameter testing experiments. Moreover, image processing techniques are applied to DB-GMAW to monitor the welding process and construct a feedback system for control.
Considering the importance of maintaining stable full penetration during many welding applications, a nonlinear model of DB-GMAW full penetration is developed in this dissertation. To do that, we use machine vision techniques to monitor the welding profile of the work piece. A control algorithm based on the nonlinear model using adaptive control technique is also designed. The achievement of this dissertation provides a fundamental knowledge of a novel welding process: DB-GMAW, and a good guidance for further studies about DBGMAW.
22
Khalaf, Gholam Hossein. "Neuro-fuzzy control modelling for gas metal arc welding process." Thesis, Loughborough University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263585.
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Hansen, James Christopher. "Rotating Electrode Pulse Gas Metal Arc Welding for Improved Aluminum Shipbuilding Quality." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1606991932450895.
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Mazidi, Aimal. "Comparison of a new, high precision, energy efficient welding method with the conventional Gas Metal Arc Welding on high carbon steel base metal." Thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-6860.
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CMT+P welding is less susceptible to hot cracking than the MAG welding process due to use of low heat input properties. Solidification cracking was found in all weld specimens that had greater 0.39KJ/mm heat inputs. Cracking occurs because of the contraction stresses generates during cooling. Hydrogen cracking is found in HAZ with low heat input parameters, this type of cracking occurred because of very rapid cooling and therefore not enough time to allow the hydrogen to dissipate from the specimen. To eliminate this type of cracking the experiment could be repeated by adding heating during welding to control and reduce the cooling rate. Due to high carbon content in the steel and very fast cooling the microstructure of the weld is martensitic in the base metal as well as the HAZ. Microstructure in the weld and base metal is martensitic due to high carbon con-tent and rapid cooling. At low heat inputs dilution is less and therefore lower carbon content in weld pool. Better weld appearance and weld quality is achieved with CMT+P welding process than the conventional GMA welding processes because of the new wire movement technology during welding
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Davies, Mark H. "Numerical modelling of weld pool convection in gas metal arc welding /." Title page, contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phd2563.pdf.
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Smailes, Allan J. "Thermal modelling of gas metal arc welding using finite element analysis /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09ENS/09enss635.pdf.
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Tam, Joseph. "Methods of Characterizing Gas-Metal Arc Welding Acoustics for Process Automation." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/859.
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Recent developments in material joining, specifically arc-welding, have increased in scope and extended into the aerospace, nuclear, and underwater industries where complex geometry and hazardous environments necessitate fully automated systems. Even traditional applications of arc welding such as off-highway and automotive manufacturing have increased their demand in quality, accuracy, and volume to stay competitive. These requirements often exceed both skill and endurance capacities of human welders. As a result, improvements in process parameter feedback and sensing are necessary to successfully achieve a closed-loop control of such processes. One such feedback parameter in gas-metal arc welding (GMAW) is acoustic emissions. Although there have been relatively few studies performed in this area, it is agreed amongst professional welders that the sound from an arc is critical to their ability to control the process. Investigations that have been performed however, have been met with mixed success due to extraneous background noises or inadequate evaluation of the signal spectral content. However, if it were possible to identify the salient or characterizing aspects of the signal, these drawbacks may be overcome.
The goal of this thesis is to develop methods which characterize the arc-acoustic signal such that a relationship can be drawn between welding parameters and acoustic spectral characteristics. Three methods were attempted including: Taguchi experiments to reveal trends between weld process parameters and the acoustic signal; psycho-acoustic experiments that investigate expert welder reliance on arc-sounds, and implementation of an artificial neural network (ANN) for mapping arc-acoustic spectral characteristics to process parameters.
Together, these investigations revealed strong correlation between welding voltage and arc-acoustics. The psycho-acoustic experiments confirm the suspicion of welder reliance on arc-acoustics as well as potential spectral candidates necessary to spray-transfer control during GMA welding. ANN performance shows promise in the approach and confirmation of the ANN?s ability to learn. Further experimentation and data gathering to enrich the learning data-base will be necessary to apply artificial intelligence such as artificial neural networks to such a stochastic and non-linear relationship between arc-sound and GMA parameters.
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Modenesi, P. J. "Statistical modelling of the narrow gap gas metal arc welding process." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/831.
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The J-laying technique for the construction of offshore pipelines requires a fast welding process that can produce sound welds in the horizontal-vertical position. The suitability of narrow gap gas metal arc welding (NG-GMA W) process for this application was previously demonstrated. The present programme studied the influence of process parameters on the fusion characteristics of NG-GMA welding in a range of different shielding gas compositions and welding positions. Statistical techniques were employed for both designing the experimental programme and to process the data generated. A partial factorial design scheme was used to investigate the influence of input variables and their interaction in determining weld bead shape. Modelling equations were developed by multiple linear regression to represent different characteristics of the weld bead. Transformation of the response variable based on the Cox-Box method was commonly used to simplify the model format. Modelling results were analysed by graphical techniques including surface plots and a multiplot approach was developed in order to graphically assess the influence of up to four input variables on the bead shape. Conditions for acceptable bead formation were determined and the process sensitivity to minor changes in input parameters assessed. Asymmetrical base metal fusion in horizontalvertical welding is discussed and techniques to improve fusion presented. At the same time, the interaction between the power supply output characteristic and the bead geometry was studied for narrow gap joints and the effect of shielding gas composition on both process stability and fusion of the base metal was assessed. An arc instability mode that is strongly influenced by arc length, power supply characteristic and shielding gas composition was demonstrated and its properties investigated. An optimized shielding gas composition for narrow gap process was suggested.
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Pitrun, Miroslav. "The effect of welding parameters on levels of diffusible hydrogen in weld metal deposited using gas shielded rutile flux cored wires." Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050202.153920/index.html.
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Jilla, Abhinay. "Evaluation of Total Fume and Heavy Metal Emission Factors Applicable to Gas Metal Arc Welding." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2612.
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Welding is a metal joining process widely used in many manufacturing facilities around the world. It involves the process of heating the base and filler metals to a high temperature that leads to the formation of fumes. Welding emissions consist of gaseous pollutants and micron and sub-micron particles consisting of different heavy metals. Health risks associated with exposures to weld fume is well recognized in the literature. This research evaluates emissions and emission factors applicable to gas metal arc welding (GMAW) on AH 36 (mild steel) and 316 L (stainless steel). Emission factors evaluated consisted, total fume, chromium, cobalt, lead, manganese, and nickel. A weld fume chamber is used to capture the welding fumes onto a filter and then further analyzed to quantify the total fume and heavy metal emissions. Critical operating parameters such as current, voltage, shielding gas, welding speed, and contact tube to work distance (CTWD) were considered while evaluating emissions and emission factors. The parameters with greater influence on emissions are selected, and then the heavy metal emissions are quantified by varying those parameters using inductively coupled plasma atomic emission spectrometry (ICP-AES) and portable XRF (X-Ray Fluorescence) analyzer. The heavy metal results from the ICP-AES and XRF are compared to explore the feasibility of using XRF analyzer in quantifying the heavy metals in welding fumes. Using the heavy metal emissions, the lifetime carcinogenic and non-carcinogenic risks are evaluated for the GMAW process. The mild steel (MS) and stainless steel (SS) statistical analysis results indicate current and voltage are most influencing parameters in generating the fumes in GMAW. This research found a significant linear relationship between ICP-AES and XRF heavy metal results. The lifetime carcinogenic and non-carcinogenic risks results indicate high potential health risks if not properly managed.
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Xu, Jun. "Dynamic thermal tensioning for welding induced distortion control /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/7145.
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Azar, Amin S. "Dry Hyperbaric Gas Metal Arc Welding of Subsea Pipelines : Experiments and Modeling." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-17721.
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Ambitions in exploration of oil and gas fields at deeper water depth require continuous investigation and maintenance. The transportation pipelines laid in deep waters are both subjected to corrosion and buckling due to environmental phenomena. They may also often undergo branching (namely hot tapping) to redirect (or add to) the transportation paths. Mechanical joints and welding are both considered as available alternatives when sectioning and replacement of the pipes at shallow waters is necessary, yet, welding is more promising for deep waters where remote operation is central. Fusion welding on the other hand comprises several technological detractions for sound operations under high ambient pressures disregarding its low cost and flexibility. The foremost detracting phenomenon in the arc welding is called ‘arc root constriction’, which is defined as arc geometry shrinkage under the increased pressure. Consequently, the power delivery to the weld pool at different pressure levels is a major worry. Effects of ionization and dissociation energies of different gases and mixtures, partial pressure of environmental gases including hydrogen and oxygen, gasification and degasification of the weld metal, inclusions that affect the phase transformation, absorption and desorption kinetics, oxidation and deoxidation reactions and many more are the phenomena that can possibly be altered by the gas type and ambient pressure level. Spattering and fume generation is a problematic issue since the arc is rather unstable under high pressure. Thus, seeking the effect of different chamber gas mixtures on welding parameters, final microstructure and mechanical properties is the main objective of this work. Statistical analysis of the collected voltage and current waveforms is carried out to identify the source of arc misbehavior and instability (discussed in Paper I). The stochastic parameters is related to the electrical stability and resolved into a number of varying welding parameters. The datasets are representing the effects of using pure argon under 14 incrementally increased pressure levels. Fast Fourier Transformation (FFT) is used to characterize the frequency domain of the waveforms. Auto-correlation Function (AF) and Power Spectral Density (PSD) were calculated assuming the Wiener-Khinchin theorem. Considering the AF, it is possible to visualize the deteriorating stability of the arc. The rate of stability degradation is quite gentle after 20 bar, though, huge differences were observed from 1 to 20 bar. The characteristic frequencies of 100-150 Hz and 350-400 Hz were observed. The first range can be associated with the mass transfer or molten droplet launch frequency and the latter range is representative of the rectified mains. The spread of large low-frequency peaks at higher pressures is illustrating the mass transfer deterioration. The aforementioned peaks were found above 125 bar where the range of the characteristic frequency peaks in voltage and current waveforms started to deviate. The calculated arc power is higher at high-pressure range while the weld bead geometry was barely varied. It implies that the arc efficiency factor decreases at high pressures. The heat source dimensions and heat efficiency factor are two major inputs for finite element (FE) simulations of the weld. However, a systematic classification of these factors was hardly available prior to this work. Additionally, to the best of author’s knowledge, the direct high-speed observation of the arc inside the hyperbaric welding chamber has not been investigated in detail by far due to several technological issues. The varying bead-on-plate welds including the end crater appearance can possibly be good candidates to categorize the FE heat source dimensions. Double-ellipsoidal heat source (Goldak’s Model) was implemented in WeldSimS® FE code that is used in this study. Since the model incorporates two superimposed reference heat sources, the amount of dissipated heat from each source should be differentiated. An intermediate heat source model was employed for this purpose. The latter model is after Myhr and Grong that is called distributed point heat sources. This model can be accurately fit to the weld cross section geometry if calibrated accurately. The calibrated parameters were found to be very close to the ones required by Double-ellipsoidal heat source model. By using this approach, not only the effect of welding parameters on weld bead geometry can be categorized, but also the spent time for double-ellipsoidal heat source adjustments will be cut by 90%. A Gaussian heat source was also employed for welding thermal cycle simulations. Accompanying experiments suggested that the thermal gradients hardly change as pressure elevates. However, it was found that the increased pressure level might not necessarily result in higher or lower cooling rates despite the geometrical changes. In a parallel investigation, the metallurgical effect of different shielding environments on phase transformation and mechanical properties of the bead-onplate weld samples was studies. Electron backscattered diffraction (EBSD) and orientation imaging microscopy (OIM) techniques were used to identify the effect of five different shielding environments on the phase transformation. Argon and Helium chamber gases offer the conditions that facilitate the highest amount of acicular ferrite transformation, yet, they show some differences in a number of crystallographic details. CO2 gas provided conditions for a lot of porosity in addition to the dominant polygonal ferrite/bainite transformation. He+½CO2 mixture resulted in bainite transformation that was found to follow the maximum heat flow direction in terms of crystallographic orientations. Very small sized tensile and single-edged notch bending (SENB) samples were machined from the weld metal material. The tests revealed that the best mechanical properties are associated with the He chamber gas and the poorest properties were presented by the samples welded in He+½CO2 shielding environment. It was also observed that there is a good correlation between the acquired acoustic signals and the fracture properties of the weld samples
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Ogunbiyi, T. E. B. "Process monitoring and adaptive quality control for robotic gas metal arc welding." Thesis, Cranfield University, 1995. http://dspace.lib.cranfield.ac.uk/handle/1826/4604.
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The aim of this research was to develop an adaptive quality control strategy for robotic gas metal arc welding of thin steel sheets. Statistical methods were used to monitor and control the quality of welds produced. The quality of welds cannot be directly measured during welding. It can however be estimated by correlating weld quality parameters to relevant process variables. It was found sufficient to do this using welding current and voltage transient signals only. The strategy developed was problem solving oriented with emphasis on quality assurance, defect detection and prevention. It was based on simple algorithms developed using multiple regression models, fuzzy regression models and subjective rules derived from experimental trials. The resulting algorithms were used to control weld bead geometry; prevent inadequate penetration; detect and control metal transfer; assess welding arc stability; optimise welding procedure; prevent undercut; detect joint geometry variations. Modelling was an integral part of this work, and as a feasibility study, some of the models developed for process control were remodelled using 'Backpropagation' Artificial Neural Networks. The neural network models were found to offer no significant improvement over regression models when used for estimating weld quality from welding parameters and predicting optimum welding parameter. As a result of the work a multilevel quality control strategy involving preweld parameter optimisation, on line control and post weld analysis was developed and demonstrated in a production environment. The main emphasis of the work carried out was on developing control models and means of monitoring the process on-line; the implementation of robotic control was outside the scope of this work. The control strategy proposed was however validated by using post weld analysis and simulation in software.
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Ribeiro, A. F. M. "Automated off-line programming for Rapid Prototyping using Gas Metal Arc Welding." Thesis, Cranfield University, 1995. http://dspace.lib.cranfield.ac.uk/handle/1826/10430.
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Rapid Prototyping is a recent CAD/CAM based manufacturing technique which
produces prototypes of components in a fraction of the time normally required. This
technique normally involves drawing the part as a 3 Dimensional solid model using a
CAD
program and then 'printing' it in 3 Dimensions. The raw material can be a
photopolymer or thermoplastic which solidifies when in contact with light. Other
materials are available
although producing the final parts a 100% metal is not very
usual.
Some disadvantages of these techniques are:
a) 100% metal prototypes cannot normally be made directly.
b) only prototypes can be produced instead of the final component.
c) machine size limits the size of the final component.
d) very thin layers are deposited. This makes the build up more time consuming and
mostly suitable to small components.
The main
objective of this work was to overcome these disadvantages by creating a new
Rapid Prototyping technique using Robot Fusion Welding.
In the
pre-production phase, it is important to make a prototype not only for
visualisation but also to test and assess it in its real function. Therefore, prototyping in
resin a component which is going to be made in metal has no use for assessing purposes.
This
technique, besides making the prototype in metal can also be used as a production
technique to make the real usable final component. It even allows the use of different
metals
along its structure in the welding filler wire is changed. This makes it possible to
have different structural characteristics in the same component a required.
None of the
slicing algorithms developed for other Rapid Prototyping processes were
applicable to this new technique and therefore a new slicing concept (and routine) was
created
specifically. I addition, an interface for off-line programming and quality
documentation was evolved. The technique developed has been tested by fabricating
several 'test'
components and both the dimensional accuracy and component integrity
have been evaluated and proved to be successful.
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de, Souza Nayara. "Total Fume Emissions and Emission Factors Applicable to Gas Metal Arc Welding." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2603.
Full textAbstract:
Welding is a common industrial practice that has the potential to emit air pollutants. Emission factors are useful indicators to help in the understanding of the extent of pollution from a process and managing them to reduce or minimize health impacts. The objective of this thesis is to determine emission factors applicable to the gas metal arc welding (GMAW), under varying current and voltage conditions. The most used base metals and an electrode for the shipbuilding industry were considered. A weld fume chamber was used to achieve the project goals along with standard sampling and analytical procedures. Three test runs were performed for each sampling scenario to ensure repeatability. The EPA EF average for MS experiments with the ER70S-6 electrode is 5.2 g/kg, and for SS experiments with the ER316L-Si electrode is 3.2 g/kg, while the average results for this study were 6.81 g/kg and 3.28 g/kg respectively.
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Posinasetti, Praveen. "Process modelling and control of pulse gas metal arc welding of aluminum." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16530/1/Praveen_Posinasetti_Thesis.pdf.
Full textAbstract:
Recent developments in materials and material joining [specifically Aluminum and Pulse Gas Metal Arc Welding (GMAW-P) technology] have increased the scope and extent of their areas of application. However, stern market demand for the improved weld quality necessitates the need for automation of the welding processes. As a result, improvements in the process parameter feedback, sensing and control, are necessary to successfully develop the automated control technology for the welding processes. Hence, several aspects of the GMAW-P process have been investigated in this study in order to improve its control techniques.
Welding was conducted on 6XXX aluminium, using 1.2 mm diameter 4047 aluminum electrode and argon shielding gas. An extensive collection of high speed camera pictures were taken over a wide range of pulse parameters and wire feed rates using a xenon shadowgraph setup to improve understanding of the physics of GMAW-P process. Current and voltage signals were recorded concurrently too.
This investigation explores the effects of different process parameters namely pulsing parameters (Peak current (IP), Base Current (IB), Peak time (TP), Base Time (TB)) and wire feed rate on metal transfer phenomena in GMAW-P. Number of drops per pulse, arc length and droplet diameter were measured for aluminium electrodes by high speed videography. The pulsing parameters and wire feed rate were varied to investigate their effect on the metal transfer behaviour. Analysis showed that transition between the different metal transfer modes is strongly influenced by the electrode extension. Lower electrode extension reduced the number of droplets detached per pulse, while at higher electrode extension, spray mode is observed due to increased influence of the resistance heating.
Analysis of the current and voltage signals were correlated with the high speed films. A simple derivative filter was used to detect the sudden changes in voltage difference associated with metal transfer during GMAW-P. The chosen feature for detection is the mean value of the weld current and voltage. A new algorithm for the real time monitoring and classification of different metal transfer modes in GMAW-P has been developed using voltage and current signals. The performance of the algorithm is assessed using experimental data. The results obtained from the algorithm show that it is possible to detect changes in metal transfer modes automatically and on-line.
Arc stability in the GMAW-P has a close relationship with the regularity of metal transfer, which depends on several physical quantities (like voltage, current, materials, etc.) related to the growth and transfer of the metal droplet. Arc state in GMAW-P can be assessed quantitatively in terms of number of drops per pulse, droplet diameter and arc length. In order to assess the arc state in GMAW-P quantitatively, statistical and neural network models for number of drops/pulse, droplet diameter and arc length were developed using different waveform factors extracted from the current waveform of GMAW-P. To validate the models, estimated results were compared to the actual values of the number of drops per pulse, droplet diameter and arc length, observed during several welding conditions.
Determination of stable one drop per pulse (ODPP) parametric zone containing all the combinations of peak current (IP), base current (IB), peak time (TP), and base time (TB) that results in stable operation of GMAW-P, is one of the biggest challenges in GMAW-P. A new parametric model to identify the stable ODPP condition in aluminium which also considers the influence of the background conditions and wire feed has been proposed.
Finally, a synergic control algorithm for GMAW-P process has been proposed. Synergic algorithm proposed in this work uses the sensing and prediction techniques to analyse state of the arc and correct the pulsing parameters for achieving the stable ODPP. First arc state is estimated using the signal processing techniques and statistical methods to detect the occurrence of short circuit, unstable ODPP or multiple drops per pulse (MDPP) in GMAW-P system. If the arc state is not stable ODPP, then parametric model and genetic algorithm (GA) is used to assess the deviation of the existing pulsing parameters from the stable operation of GMAW-P process and automatically adjust pulsing parameters to achieve stable ODPP.
37
Posinasetti, Praveen. "Process modelling and control of pulse gas metal arc welding of aluminum." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16530/.
Full textAbstract:
Recent developments in materials and material joining [specifically Aluminum and Pulse Gas Metal Arc Welding (GMAW-P) technology] have increased the scope and extent of their areas of application. However, stern market demand for the improved weld quality necessitates the need for automation of the welding processes. As a result, improvements in the process parameter feedback, sensing and control, are necessary to successfully develop the automated control technology for the welding processes. Hence, several aspects of the GMAW-P process have been investigated in this study in order to improve its control techniques.
Welding was conducted on 6XXX aluminium, using 1.2 mm diameter 4047 aluminum electrode and argon shielding gas. An extensive collection of high speed camera pictures were taken over a wide range of pulse parameters and wire feed rates using a xenon shadowgraph setup to improve understanding of the physics of GMAW-P process. Current and voltage signals were recorded concurrently too.
This investigation explores the effects of different process parameters namely pulsing parameters (Peak current (IP), Base Current (IB), Peak time (TP), Base Time (TB)) and wire feed rate on metal transfer phenomena in GMAW-P. Number of drops per pulse, arc length and droplet diameter were measured for aluminium electrodes by high speed videography. The pulsing parameters and wire feed rate were varied to investigate their effect on the metal transfer behaviour. Analysis showed that transition between the different metal transfer modes is strongly influenced by the electrode extension. Lower electrode extension reduced the number of droplets detached per pulse, while at higher electrode extension, spray mode is observed due to increased influence of the resistance heating.
Analysis of the current and voltage signals were correlated with the high speed films. A simple derivative filter was used to detect the sudden changes in voltage difference associated with metal transfer during GMAW-P. The chosen feature for detection is the mean value of the weld current and voltage. A new algorithm for the real time monitoring and classification of different metal transfer modes in GMAW-P has been developed using voltage and current signals. The performance of the algorithm is assessed using experimental data. The results obtained from the algorithm show that it is possible to detect changes in metal transfer modes automatically and on-line.
Arc stability in the GMAW-P has a close relationship with the regularity of metal transfer, which depends on several physical quantities (like voltage, current, materials, etc.) related to the growth and transfer of the metal droplet. Arc state in GMAW-P can be assessed quantitatively in terms of number of drops per pulse, droplet diameter and arc length. In order to assess the arc state in GMAW-P quantitatively, statistical and neural network models for number of drops/pulse, droplet diameter and arc length were developed using different waveform factors extracted from the current waveform of GMAW-P. To validate the models, estimated results were compared to the actual values of the number of drops per pulse, droplet diameter and arc length, observed during several welding conditions.
Determination of stable one drop per pulse (ODPP) parametric zone containing all the combinations of peak current (IP), base current (IB), peak time (TP), and base time (TB) that results in stable operation of GMAW-P, is one of the biggest challenges in GMAW-P. A new parametric model to identify the stable ODPP condition in aluminium which also considers the influence of the background conditions and wire feed has been proposed.
Finally, a synergic control algorithm for GMAW-P process has been proposed. Synergic algorithm proposed in this work uses the sensing and prediction techniques to analyse state of the arc and correct the pulsing parameters for achieving the stable ODPP. First arc state is estimated using the signal processing techniques and statistical methods to detect the occurrence of short circuit, unstable ODPP or multiple drops per pulse (MDPP) in GMAW-P system. If the arc state is not stable ODPP, then parametric model and genetic algorithm (GA) is used to assess the deviation of the existing pulsing parameters from the stable operation of GMAW-P process and automatically adjust pulsing parameters to achieve stable ODPP.
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Tipaji, Pradeep Kumar. "E-design tools for friction stir welding: cost estimation tool." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Tipaji_09007dcc8043f642.pdf.
Full textAbstract:
Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 29-31).
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Åstrand, Erik. "A Framework for optimised welding of fatigue loaded structures : Applied to gas metal arc welding of fillet welds." Doctoral thesis, Högskolan Väst, Forskningsmiljön produktionsteknik(PTW), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-9339.
Full textAbstract:
Welding is a key process for heavy steel structures, but it is also a weak link in the structure since fatigue fractures in welds are a common cause of failure. This thesis proposes several changes in order to improve the fatigue properties in acost effective way, enabling reduced weight and reduced cost of welded structures. The main idea is to adapt the weld requirements and welding procedures to the load conditions of the weld. This approach ensures that the main focus in the welding process is the critical characteristics of the welds fatigue life properties. The fatigue life critical properties are most often related to the geometrical factors of the weld such as the radius at the weld toe or the penetration in the root. The thesis describes a holistic view of the subject and covers fatigue, weld quality, weld requirements and welding procedures. It becomes evident that the traditional way of working without a direct connection to fatigue is not the best. With an adaptation to the load conditions and fatigue, it is possible to enhance the fatigue life and reduce the welding cost. The main challenge is to connect the welding process, weld requirements and fatigue life properties. It is needed for an optimised welding process of heavy structures subjected to fatigue and toget a predictable fatigue life. Welds optimised for enhanced fatigue life properties are not necessary accepted according to the requirements in a current standard. Several welding procedures are proposed for improving the fatigue life properties of the weld, which indicate a high potential for enhanced fatigue lifeof fillet welds. The idea is to replace the "standard" fillet weld with three different weld types: (i) Welds with deep penetration, (ii) Welds with large weld toe radius and (iii) Welds produced with low cost. Together with customised requirements and reduced over-welding there is a vast potential for reduced weight, reduced cost and increased productivity.The main contribution of this thesis work is the cross-functional studies including design, analysis, production and quality control. This gives a framework for improvements supporting reduced cost and reduced weight of VIII welded structures without reducing the fatigue strength. Many shortcomings have been highlighted to change the welding from a state where welds are done in a way as they "always" have, by tradition, to a more contemporary situation where weld requirements and welding procedures are actively chosen to match the load conditions of the weld. This result in requirements and welding procedures which actually are connected to the fatigue properties as defined by the loading conditions, and where auditors with high probability can say that an accepted weld actually is better than a rejected weld.
40
Cho, Min Hyun. "Numerical simulation of arc welding process and its application." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155741113.
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da, Costa Pépe Nuno Vasco. "Advances in gas metal arc welding and application to corrosion resistant alloy pipes." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4501.
Full textAbstract:
According to recent estimations, the construction of pipelines will continue to increase during the next thirty years, in particular as a result of oil and gas discoveries in remote locations. Significant advances in welding technology during the last ten years have potential to provide improvements in productivity, quality and structural integrity of pipe girth welds. In this thesis, several new processes Lincoln STT, Lincoln RapidArc, Fronius CMT, Fronius CMT-P and Kemppi FastROOT have been compared the first time to the GMAW-P to understand how these new waveforms operate for pipe welding. The process setting parameters have been analysed to understand their effect on metal transfer and arc stability control, and on bead shape characteristics. Although all waveforms present similar burn-off ratios, individual waveforms differ considerably, and especially the arc voltage waveform. This leads to considerable differences in the mechanism of metal transfer and the stability of the processes under similar experimental conditions. Understanding of these new waveforms in terms of the effect of setting parameters in the mechanism of metal transfer, process stability and melting phenomena provides a basis for assessing the potential of these processes for a range of applications, and in particular application to CRA pipe root welding Since the arc energy is the overall energy delivered from the power source at the contact tip of the torch, and part of that energy is not absorbed by the workpiece, research was performed to measure the process efficiency associated with some of these waveforms and process setting conditions. The study led to a better understanding of the potential errors in calculating process efficiency. The results obtained show that all the short-circuiting waveforms analysed (i.e. CMT, STT and FastRoot) had a similar process efficiency of 90±3%, while pulse spray waveforms (GMAW-P, CMT-P and RapidArc) are characterized by lower process efficiency, approximately 78±3%. The application of these waveforms to the welding a narrow groove pipe with a “J” groove design was investigated. These analyses were focused on the variation of bead shape characteristics and welding quality performance based on the analysis of the conditions that result in lack of penetration and top bead defects, such as lack of side wall fusion or undercutting. It was observed that RapidArc and CMT-P are able to satisfy the quality requirements, i.e. full penetration and absence of defects for the specific conditions described in this thesis. High welding speeds (up to 1m/min) were achieved with these processes, four times the typical speed 0.25m/min. Finally, the shielding gas plays an important role in terms of quality and weld bead performance. This led to an optimization of the shielding gas composition used, based on mixtures of carbon dioxide, argon and helium. Statistical modelling was undertaken to optimize the shielding gas mixtures using RapidArc and CMT-P waveforms. In parallel, a new purging shielding gas device was designed to achieve a weld root free of oxidation.
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Jones, Steven Alan. "Refinement of TI-6%AL-4%V weld metal structures during gas-tungsten arc welding." Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288987.
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Gaal, Brian. "Development of a Coating Formulation Procedure for Ni-base Shielded Metal Arc Electrodes with Varying Core Wire Composition." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354481846.
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Hamed, Maien. "Vision-guided tracking of complex tree-dimensional seams for robotic gas metal arc welding." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1428.
Full textAbstract:
Automation of welding systems is often restricted by the requirements of spatial information of the seams to be welded. When this cannot be obtained from the design of the welded parts and maintained using accurate xturing, the use of a seam teaching or tracking system becomes necessary. Optical seam teaching and tracking systems have many advantages compared to systems implemented with other sensor families. Direct vision promises to be a viable strategy for implementing optical seam tracking, which has been mainly done with laser vision. The current work investigated direct vision as a strategy for optical seam teaching and tracking. A robotic vision system has been implemented, consisting of an articulated robot, a hand mounted camera and a control computer. A description of the calibration methods and the seam and feature detection and three-dimensional scene reconstruction is given. The results showed that direct vision is a suitable strategy for seam detection and learning. A discussion of generalizing the method used as an architecture for simultanious system calibration and measurement estimation is provided.
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Carvalho, G. C. "An adaptive control system for off-line programming in robotic gas metal arc welding." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/4597.
Full textAbstract:
The aim of this work was to develop an integration concept for using off-line programming in robotic gas metal arc welding of thin sheet steel. Off line-welding parameter optimization and on-line monitoring and adaptive control of process stability and torch-to-workpiece relative distance were used to ensure weld consistency. The concept developed included four main aspects: a) the use of a CAD system to design the workpiece; b) the use of a welding off-line programming system to design the welds, generate the welding parameters and to extract geometrical information from the CAD models to generate a robot program; c) the use of a graphical simulation system to simulate the robot movements; and d) the use of monitoring and adaptive control for ensuring that the required weld quality is delivered. The CAD system was chosen to be the basis for the development of the welding off-line programming system. The generation of optimized welding parameters was based on empirical welding models and the robot program generation was based on on-line programming experience. A PC based monitoring and control system was developed to provide on-line position and process control. The position control was carried out by pre-weld adjusting the initial position of the workpiece using a wire touch sensor and on-line adjusting the torch-to-workpiece distance by moving the workpiece based on the information provided by a through-the-arc sensor. The process control was carried out by automatically trimming the welding voltage such that the most stable process could be obtained. The stability of the process was estimated by using previously established monitoring indices. It was assumed that the off-line welding parameter optimization would provide the deposition rate necessary to produce the required weld quality. Successful welding control trials were performed showing the effectiveness of the adaptive control strategy. An off-line programming system has been developed and the programs generated have been tested by simulation. This showed that simulated positioning errors, produced by deliberate wrong path data, were successfully compensated for by the control system developed in this work.
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Walters, Jon D. "Microchemical analysis of non-metallic inclusions in C-MN steel shielded metal arc welds by analytical transmission electron microscopy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA350613.
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Mortazavi, Seyed Bagher. "Inter-relationship between ultraviolet, ozone and hexavalent chromium in metal inert gas (MIG) welding process." Thesis, University of Bradford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324614.
Full textAbstract:
Welding is a common metal fabrication process within industry. Epidemiology suggests that welders as an occupational group demonstrate slight, but significant, increased risks of respiratory ill-health. This might be expected as welding processes often present high levels of occupational exposure to oxidising gasses and weld fumes which are often inadequately controlled through local exhaust ventilation or personal respiratory protection because of high costs and the burden of worker participation. Fundamental control strategies of occupational hygiene encourage development and use of engineering controls as the best means to optimally control occupational exposure. However, engineering controls have not yet been successfully developed to control occupational exposure to welding fume and gases. This thesis investigates the interrelationships between ultra-violet radiation (UV). ozone (0:;). and hexavalent chromium (CrVI) in metal inert gas (MIG) welding in order to investigate possible methods to control occupational exposure to welding fume and gases by engineering contro!' Past studies of occupational ill-health in welders are reviewed as is the currently understanding of the physico-chemical principles by which the various components of welding fume evolves. Experiments were designed to investigate the mechanisms of formation of UV, 0 3 and CrVI formation from which a number of possible control strategies were developed further. Among these results emerge two process modifications with exciting potential to reduce two toxic components. 0, and CrVI , in stainless steel welding fume and gas. The addition of trace amounts of Zinc to chromium containing steel wires virtually eliminates all 0, and significantly reduces hexavalent chromium within the weld plume. As Zn is a volatile metal, it does not contaminate weld quality but increases the zinc oxide le\els in the fume slightly. A second method developed in this thesis involves the addition of a dual shield gas shroud containing reducing gases such as C2H .. to remove 0, and consequently. reduce Cr(VI) levels. Preliminary results suggest that these methods can be used separately. or in combination, to provide a practical means of controlling occupational exposure to two of the more toxic components of welding fume and gases. This thesis describes in details the experiments and results culminating in successful preliminary development of engineering controls for 0 3 and CrVI through process modification of the stainless steel MIG welding process. Further work for further development of these methods is outlined and funding to extend this area of applied research is being actively pursued with the support of major UK industry.
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Siminski, Michael. "Weld path optimisation for rapid prototyping and wear replacement by robotic gas metal arc welding." Faculty of Engineering, 2003. http://ro.uow.edu.au/theses/399.
Full textAbstract:
Rapid prototyping (RP) is a large and rapidly growing industry with many different processes either under development or already available commercially. These processes offer fast and flexible production of objects from a wide range of materials. They vary from being able to produce only prototypes of products, through to being suitable for production of finished products ready for service. Rapid prototyping by robotic gas metal arc welding (GMAW) uses metal deposited by the GMAW process to build metal products with engineering properties suitable for service conditions. Wear replacement (WR) involves the repair of worn metal surfaces through the deposition of weld metal, and can also be performed using robotic GMAW. Since both rapid prototyping and wear replacement by robotic GMAW involve the building up of metal objects from metal deposited by the GMAW process, it is possible to combine research in this area. Rapid prototyping and wear replacement using the robotic GMAW process may however give rise to stability problems. Geometric and thermal instability can be an inherent feature of the process, resulting in relatively poor dimensional accuracy and surface quality. Various research directions have been taken in the past in order to address these problems, however the effects of weld path design on process stability have not yet been well researched. The objective of this thesis was to study what effects weld path design can have on the stability of rapid prototyping and wear replacement by GMAW, in order to test whether weld path design could be used to improve process stability and performance. The hypothesis adopted in this thesis was that improved geometric and thermal stability should be possible if the material and heat input are optimised by control of the weld path through weld path design. It was found that the stability of the rapid prototyping and wear replacement by GMAW process is very sensitive to weld path design and that optimised open-loop weld path design can be used to greatly improve process stability and performance. A number of different mechanisms were identified through which the weld path design impacts on the stability and performance of the process and corresponding recommendations for weld path design were presented. The suitability of various weld path designs for different types of applications was assessed and the most optimal weld path designs for an expected wide range of applications were identified. By using one of the most recommended path strategies, rapid prototyping and wear replacement by GMAW systems can enjoy improved geometric and thermal stability and fewer problems with weld defects, through the choice of weld path. It was predicted that the most successful commercial rapid prototyping and wear replacement by robotic GMAW systems would utilise a flexible and multi-faceted approach, using a combination of technologies, in order to best address the various needs of the process as required for key areas of industrial application.
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Sgro, Sergio Domenico. "The efficacy of teaching oxyacetylene welding prior to gas metal arc welding for introductory materials and process courses in industrial technology." [Ames, Iowa : Iowa State University], 2006.
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ALVES, Sérvulo José Ferreira. "Estudo dos fumos e gases gerados no processo de soldagem Gas Metal Arc Welding (GMAW) em duas empresas do segmento metal mecânico de Pernambuco." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/17933.
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Na união de materiais metálicos, sobretudo nos aços, os processos de soldagens são predominantes e com grande destaque para soldas ao arco elétrico. E dentre os processos de soldas ao arco elétrico há no segmento metal mecânico mundial uma enorme utilização do GMAW que necessita de gases de proteção que evitam a contaminação das áreas soldadas pelos gases presentes na atmosfera, em especial o nitrogênio, o oxigênio e o hidrogênio. O GMAW por sua vez é subdividido em dois tipos de processos de soldagens que dependem das características físicas e químicas dos gases de proteção, bem como, do metal de base a ser soldado. O primeiro deles quando se usa como gás de proteção um gás inerte como o argônio e o hélio ou uma mistura de gases inertes sendo denominado então MIG. Já o segundo tipo ocorre quando no gás de proteção há a presença de um gás ativo como o oxigênio ou o dióxido de carbono ou uma mistura de gases ativos e inertes e é conhecido como MAG. Foi realizada a coleta e a análise em Pernambuco dos fumos (particulados) e gases gerados na soldagem GMAW, no soldador, em duas empresas do segmento metal mecânico de Pernambuco de acordo com a NR-15 e a ACGIH. A caracterização dos fumos foi obtida por ICP-OES enquanto, a dos gases ocorreu por cromatografia em fase gasosa. O objetivo deste trabalho foi coletar e analisar qualitativa e quantitativamente os fumos e os gases gerados no soldador no processo de soldagem GMAW. E desenvolver uma metodologia eficiente e de baixo custo na coleta e acondicionamento das amostras dos gases no soldador de duas empresas do segmento metal mecânico de Pernambuco. A conclusão deste trabalho se baseou nas análises dos fumos e dos gases, em cada um dos soldadores. E indicou que nas duas empresas, cada soldador não estava exposto a fumos acima dos limites da NR-15 e da ACGIH. As análises do CO2 e do CO, indicaram que o soldador da empresa “A” não excedia os limites toleráveis da ACGIH e da NR-15. O soldador da empresa “B” ficou exposto apenas ao CO acima do limite da ACGIH e quanto ao CO2 não excedeu os limites da NR-15 e da ACGIH.
In the union of metallic materials, mainly in steel, welding processes are predominant and with great emphasis on the electric arc welds. And among the processes of arc welding to metal segment in the world there is a huge mechanical use of GMAW that requires shielding gas to prevent contamination of the welded areas by gases present in the atmosphere, in particular nitrogen, oxygen and hydrogen. The GMAW is in turn subdivided into two types of welding processes that depend on the physical and chemical characteristics of shielding gases, as well, as the base metal being welded. The first of them when used as a shielding gas as an inert gas argon and helium or a mixture of inert gases then being called MIG. The second type occurs when there is the presence of an active gas such as oxygen or carbon dioxide or a mixture of active and inert gas in the shielding gas and is known as MAG. Was performed the collection and analysis in Pernambuco of the fumes (particulate) and gases generated in GMAW welding, in the welder, in two companies of Pernambuco mechanical metal segment of according to NR -15 and the ACGIH. The aim of this work was to collect and analyze qualitatively and quantitatively the fumes and gases, in the welder, in GMAW welding process. And develop an efficient methodology and low cost in the collection and packaging of the samples of gases, in the welder, in the GMAW welding in two metal mechanic segment companies Pernambuco. The characterization of the smoke was obtained by ICP-OES while the gases occurred by gas chromatography. The conclusion of this work was based on analysis of the fumes and gases in each of the welders. And indicated that the two companies, each welder was not exposed to fumes and gases or CO and CO2 above the limits of the NR-15 and ACGIH. Analyses of CO2 and CO indicated that the welder of the company "A" did not exceed the tolerable limits of the ACGIH and NR-15. Welder the company "B" was exposed only to CO above the ACGIH limit and how much CO2 has exceeded the scope of the NR-15 and ACGIH.