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Search Results: 1 - 10 of 405053 matches for " I.S. Kim "
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Interaction model for predicting bead geometry for Lab Joint in GMA welding process
D.T. Thao,I.S. Kim
Archives of Computational Materials Science and Surface Engineering , 2009,
Abstract: Purpose: The prediction of the optimal bead geometry is an important aspect in robotic welding process. Therefore, the mathematical models that predict and control the bead geometry require to be developed. This paper focuses on investigation of the development of the simple and accuracy interaction model for prediction of bead geometry for lab joint in robotic Gas Metal Arc (GMA) welding process.Design/methodology/approach: The sequent experiment based on full factorial design has been conducted with two levels of five process parameters to obtain bead geometry using a GMA welding process. The analysis of variance (ANOVA) has efficiently been used for identifying the significance of main and interaction effects of process parameters. General linear model and regression analysis has been employed as a guide to achieve the linear, curvilinear and interaction models. The fitting and the prediction of bead geometry given by these models were also carried out. Graphic results display the effects of process parameter and interaction effects on bead geometry.Findings: The fitting and the prediction capabilities of interaction models are reliable than the linear and curlinear models and it was found that welding voltage, arc current, welding speed and 2-way interaction CTWD welding angle have the large significant effects on bead geometry.Research limitations/implications: The these models developed are extended to shielding gas composition, weld joint position, polarity and many other parameters which are not included in this research in order to establish a closed loop feedback control system to minimize possible errors from uncontrolled variations.Practical implications: The developed models apply real-time control for bead geometry in GMA welding process and perform the Design of Experiments (DOE) analysis steps in order to solve optimisation problems in GMA welding process.Originality/value: The interaction factors, welding voltage arc current, CTWD welding angle, also imposes a significant effect on bead geometry. With the experimental data of this study, the interaction models have a more reliable fitting and better predicting than that of linear and curvilinear models.
Control of welding process for BV-AH 32 steel
H.H. Kim,I.S. Kim,I.J. Kim,B.Y. Kang
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The GMA welding process involves large number of interdependent variables, which may affect product quality, productivity and cost effectiveness. With the combination of sensors and mathematical models, increased effectiveness in control of the automatic welding process was achieved. In this study, it focuses on development of mathematical models for the selection of process parameters using BV-AH32 steel for shipbuilding industry.Design/methodology/approach: The base material used for this study was the BV-AH32 steel with12 mm in thickness for multi-pass butt welding. A curvilinear regression analysis was performed with the predictors that were found to be statistically significant against bead geometry based on the results from the above factorial design. The adequacy of the models and the significance of coefficients were tested by applying the analysis of variance technique and T-test respectively.Findings: From the above resultant equation for estimation of bead geometry, the sensitivity equations are obtained by differentiation with respect to process parameters of interest such as arc current, welding voltage and welding speed that are explored.Practical implications: Sensitivity analysis has been investigated to represent the effectiveness of the processing parameters on these empirical equations and showed that the change of process parameters affects the bead width and bead height more strongly than penetration relatively.Originality/value: These models are extended to shielding gas composition, weld joint position, polarity and many other parameters which are not included in this research in order to establish a closed loop feedback control system to minimize possible errors from uncontrolled variations.
An experimental study on the prediction of back-bead geometry in pipeline using the GMA welding process
J.S. Kim,I.S. Kim,J.H Lee,S.M. Jung
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: of this research paper is to select optimal welding condition for a root-pass welding for pipeline and to provide a best process for desirable welding quality.Design/methodology/approach: In this study, a variety of welding experiments were carried out to optimize an automated welding process using a GMA (Gas Metal Arc) process, these has been applied for root-pass welding. Welding current, welding speed, wire feed speed and torch angle were chosen as input parameters, while back-bead geometry representing quality of root-pass welding as output parameter.Findings: Based on the results from welding experiments, optimal welding conditions were selected after analyzing correlation between welding parameters and back-bead geometry such as back-bead width and back-bead height. Moreover, not only effectiveness of empirical models developed was compared and analyzed. The optimized empirical models were finally developed for predicting back-bead geometry by analyzing the main effect of each factor and their influence on interaction.Research limitations/implications: This research was concentrated on the developed empirical models that can predict back-bead width and height for root-pass welding in pipeline.Originality/value: This study is intended to define correlations between process parameters and back-bead geometry as welding quality and eventually select optimal welding condition by performing root-pass welding experiment under various conditions.
Quality control for the continuous casting process using electromagnetic transducers
I.S. Kim,J.S. Son,H.J. Kim,B.S. Sung
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The continuous casting process is controlled automatically because various sensors and control unitsare connected to the mold and lower tundish roll. The solidification point in the process has a major factor onthe quality of products, but the point has been predicted depending on the inaccurate calculated results from acomputer simulation until now. Therefore, the objective of this paper is to develop the EMAT sensors for themeasurement of the solidification point made by a through transmission technique based on the relationshipbetween ultrasonic speed and measured temperature.Design/methodology/approach: The EMAT sensor is composed of an Elongated Spiral (ES) forming an eddycurrent and a permanent magnetic core generating a static magnetic field. ES coils of the sensor to measure0.08mm, 0.2mm and 0.45mm as solidification points were employed respectively. Probes for receiving andtransmitting which included 4 permanent magnets measuring 5 ×5 ×10mm, were placed together in one unit.Each coil was used to magnetic cores measuring 0.08mm and 0.45mm wound around it forty three times. TheAI 75 ×75mm and 75 ×100mm simulators to identify whether the solidification point can be detected using anEMAT sensor, were machined with 2mm, 4mm, 8mm, 16mm and 32mm holes in diameter respectively.Findings: The electromagnetic interaction decreases in a high sphere of lift-off. Solidification point in acontinuous casting processing could be detected through a series of tests with the use of a fabricated probe andthe amplitude extent of ultrasonic wave decreases as the hole diameter of the simulators increases, Furthermore,the sensor developed is useful for measuring things such as lift-off.Research limitations/implications: A considerable amount of time and energy for miniaturization of the sensorand construction of an on-line system for a field installation should be saved by reducing mistake ratio andcurtailing unnecessary processes.Originality/value: The solidification point in a continuous casting processing could be detected through a seriesof tests with the use of the developed EMAT sensor.
Development of a mathematical model to study on variation of shielding gas in GTA welding
I.S. Kim,J.S. Son,H.J. Kim,B.A. Chin
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: Generally discrete alternate supply of shielding gas is a new technology which alternately supplies thedifferent kinds of shielding gases in weld zone. In this study, welding characteristics under variation of alternatesupply method of shielding gases in austenite stainless steel using a GTA welding process have been investigatedand found the relationship between different types of shielding gas and shielding gas supply.Design/methodology/approach: 2-D axisymmetric heat and fluid mathematical model about weld pool has beendeveloped for verifying the effect of alternate supply of shielding gas. The developed models were solved using ageneral thermofluid-mechanics computer program, PHOENICS code, which is based on SIMPLE algorithm.Findings: The computed results showed that the developed computational models are very adequate to predictin the weld pool and bead geometry, and the technique of alternate supply of shielding gas should be useful toincrease higher productivity, cost savings and better quality in arc welding.Research limitations/implications: The effect of alternate supply of shielding gas should be useful to apply fora narrow-gap welding process.Originality/value: The range of molten metal at the top of weld pool for supply of He shielding gas becamewider than that for supply of Ar shielding gas. The developed computational models are very adequate to predictin the weld pool and bead geometry.
A study on numerical analysis of the resistance spot welding process
H. Zhigang,I.S. Kim,J.S. Son,H.H. Kim
Journal of Achievements in Materials and Manufacturing Engineering , 2005,
Abstract: Purpose: Over the last few years, there has been a growing interest in quantitative representation of heat transfer and fluid flow phenomena in weld pools in order to study relationships between the processing variables and the quality of the weldment produced and to use this information for the optimization and mobilization of the welding process.Design/methodology/approach: A 2D axisymmetric Finite Element Method (FEM) model has been developed to analyze the transient thermal behaviors of Resistance Spot Welding (RSW) process. In this model, the temperature dependent material properties, phase change and convectional boundary conditions were taken account for the improvement of the calculated accuracy, but the determination of the contact resistance at the surface is moderately simplified in order to reduce the calculating time through the analysis.Findings: The developed model has been employed the thermal history of the whole process (including cooling) and temperature distributions for any position in the weldmentResearch limitations/implications: Future research in the field of RSW processing could focus on analysis of the stress and strain distributions as well as deformation in the weldment.Originality/value: It can be concluded that the maximum temperature was up to 1346°C, nearly the molten point of mild steel, and verified by the observation of the surface of the weldment after welding
A study on variation of shielding gas in GTA welding using finite element method
I.S. Kim,J.S. Son,H.J. Kim,B.A. Chin
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: Generally discrete alternate supply of shielding gas is a new technology which alternately supplies the different kinds of shielding gases in weld zone. In this study, welding characteristics under variation of alternate supply method of shielding gases in austenite stainless steel using a GTA welding process have been investigated and found the relationship between welding distortions and welding speed and different types of shielding gas and shielding gas supply.Design/methodology/approach: 2-D axisymmetric heat and fluid mathematical model about welding arc and weld pool has been developed for verifying the effect of alternate supply of shielding gas. The developed models were solved using a general thermofluid-mechanics computer program, PHOEINCS code, which is based on SIMPLE algorithm.Findings: The computed results showed that the developed computational models are very adequate to predict in the weld pool and bead geometry, and the technique of alternate supply of shielding gas should be useful to increase higher productivity, cost savings and better quality in arc welding.Research limitations/implications: The effect of alternate supply of shielding gas should be useful to apply for a narrow -gap welding process.Originality/value: The range of molten metal at the top of weld pool for supply of He shielding gas became wider than that for supply of Ar shielding gas. The developed computational models are very adequate to predict in the weld pool and bead geometry.
A study on electromagnetic transducers for the continuous casting process
I.S. Kim,J.S. Son,H.J. Kim,B.A. Chin
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: One of the areas in the continuous casting process that has not been definitively instrumented is a method for reliably locating the part of a continuously cast strand that remains liquid for a period after the outer portion has solidified. Therefore, this paper is focused on the measurement of the solidification point made by a through transmission technique based on the relationship between ultrasonic speed and measured temperature using an EMAT sensor.Design/methodology/approach: An EMAT (Electro Magnetic Acoustic Transducer) has been designed and fabricated with an elongated spiral coil and a permanent magnetic core. Al75×75mm and 75×100mm simulators with 2, 4, 8, 16 and 32 mm holes were produced and demonstrated that the location of the final solidification point during the continuous casting process can be monitored using a 1.0 MHz frequency.Findings: The solidification point in a continuous casting bloom could be detected through a series of tests with the use of a fabricated probe and the amplitude extent of ultrasonic wave decreases as the hole diameter of the simulators increases. Furthermore, through a test of lift-off effect it was found that the extent of amplitude decreases as lift-off increases, thus one of the most important factors for a field application.Research limitations/implications: As cutting speed and cutting length can be predicted from a miniaturization of the sensor and construction of an on-line system for a field installation, a considerable amount of time and energy can be saved by reducing mistake ratio and curtailing unnecessary processes.Originality/value: The measured ultrasonic waves allow for prediction of the casting speed necessary to correctly locate the liquid core and thereby maximize the benefits of soft reduction and the productivity of the machine.
Weldability of 440 MPa galvanized steel with inverter DC resistance spot welding process
I.S. Hwang,H.J. Yoon,M.J. Kang,D.C. Kim
Archives of Materials Science and Engineering , 2010,
Abstract: Purpose: This paper comparatively analyzes resistance spot weldability depending on whether or not 440 MPa-grade steel is galvanized at inverter DC spot welding.Design/methodology/approach: To compare the resistance spot weldability depending on whether or not the steel is galvanized, an inverter DC welding system was designed. Then, using this system, both tensile strength testing and macro-section testing were conducted on SPRC440 (uncoated steel) and SGARC440 (galvanized steel), and weldability was evaluated. Suitable welding conditions were calculated using the resistance spot welding variables such as electrode force, welding time and lobe diagram on the welding current. The low limit of the lobe diagram was set to the low limit of the tensile strength of 440 MPa-grade steel while the high limit was set depending on whether or not expulsion was detected.Findings: Compared to uncoated steel, galvanized steel had lower suitable welding current conditions anda narrower lobe diagram.Research limitations/implications: This paper compared resistance spot weldability and lobe diagram depending on whether or not 440 MPa-grade steel is galvanized.Practical implications: This paper confirms the weldability of galvanized steel by comparing resistance spot weldability depending on whether or not steel is galvanized.Originality/value: For analysis of resistance spot weldability depending on whether or not steel is galvanized, weldability was compared between SPRC440 (uncoated steel) and SGARC440 (galvanized steel) under the same welding conditions. As a result, compared to uncoated steel, galvanized steel had lower suitable welding current conditions and a narrower lobe diagram.
Inverter DC resistance spot welding of magnesium alloy AZ31
I.S. Hwang,D.C. Kim,M.J. Kang
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: The welding lobes of AC resistance spot welding and inverter DC resistance spot welding for the magnesium alloy sheet AZ31 were compared and analyzed.Design/methodology/approach: Using the welding lobe in terms of electrode force, weld time, and weld current which are process variables of the resistance spot welding, optimal welding conditions were determined. The lower limit of the range of the optimal welding condition was decided by minimum shear tension strength for the magnesium alloy sheet AZ31, and the upper limit was decided by whether an expulsion occurs or not.Findings: It was found that the range of the optimal welding condition of the inverter DC resistance spot welding was larger than the AC resistance spot welding and that the nugget width of inverter type resistance spot welding was larger in the same welding condition.Research limitations/implications: A comparison was between the welding lobes for AC and inverter DC resistance spot welding of magnesium alloy sheet AZ31.Practical implications: In this study, by comparing the range of the acceptable welding condition of the resistance spot welding between AC type and inverter DC type power supplies, the effect of the types of power supplies on welding lobes could be confirmed.Originality/value: This study compared the characteristics of the resistance spot welding between the AC type and inverter DC type power sources. It was confirmed that the range of acceptable welding conditions of the inverter DC resistance spot welding was larger than AC type.
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