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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Welding and Joining
Journal Basic Information
Journal DOI :
The Korean Welding and Joining Society
Editor in Chief :
Volume & Issues
Volume 33, Issue 6 - Dec 2015
Volume 33, Issue 5 - Oct 2015
Volume 33, Issue 4 - Aug 2015
Volume 33, Issue 3 - Jun 2015
Volume 33, Issue 2 - Apr 2015
Volume 33, Issue 1 - Feb 2015
Selecting the target year
The Current State, Outcome and Vision of Additive Manufacturing
Terner, Mathieu ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 1~5
DOI : 10.5781/JWJ.2015.33.6.1
Additive Manufacturing defines the fabrication of objects by successive consolidation of materials, layer by layer, according to a three-dimensional design. The numerous technologies available today were recently standardized into seven categories based on the general method. Each technology has its own set of advantages and limitations. Though it very much depends on the field of application, major assets of additive manufacturing compared to conventional processing routes are the ability to readily offer complexity (in terms of intricate shape and customization) and significant reduction of waste. On the other hand, additive manufacturing often suffers of relatively low production rates. Anyhow, additive manufacturing technologies is being given outstanding attention. In particular, metal additive manufacturing emerges as of great significance in industries like aerospace, automotive and tooling. The trend progresses toward full production of high value finished products.
Effect of Restraint Stress on the Precipitation Behavior and Thermal Fatigue Properties of Simulated Weld Heat Affected Zone in Ferritic Stainless Steel
Han, Kyutae ; Kang, Yongjoon ; Lee, Sangchul ; Hong, Seunggab ; Jeong, Hongchul ; Lee, Changhee ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 6~12
DOI : 10.5781/JWJ.2015.33.6.6
Thermal fatigue life of the automobile exhaust manifold is directly affected by the restraint force according to the structure of exhaust system and bead shape of the welded joints. In the present study, the microstructural changes and precipitation behavior during thermal fatigue cycle of the 18wt% Cr ferritic stainless steel weld heat affected zone (HAZ) considering restraint stress were investigated. The simulation of weld HAZ and thermal fatigue test were carried out using a metal thermal cycle simulator under complete constraint force in the static jig. The change of the restraint stress on the weld HAZ was simulated by changing the shape of notch in the specimen considering the stress concentration factor. Thermal fatigue properties of the weld HAZ were deteriorated during cyclic heating and cooling in the temperature range of
due to the decrease of Nb content in solid solution and coarsening of MX type precipitates, laves phase,
with coarsening of grain and softening of the matrix. As the restraint stress on the specimen increased, the thermal fatigue life was decreased by dynamic precipitation and rapid coarsening of the precipitates.
Effect of Initial (Reference) Welding Current for Adaptive Control and It's Optimization to Secure Proper Weld Properties in Resistance Spot Welding
Ashadudzzaman, Md. ; Choi, Il-Dong ; Kim, Jae-Won ; Nam, Dae-Geun ; Park, Yeong-Do ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 13~20
DOI : 10.5781/JWJ.2015.33.6.13
Many automotive companies are endeavoring to improve the quality of resistance spot welding by updating body-in-white (BIW) production line with adaptive control spot welding system to compensate the process disturbances such as gap, electrode wear, oxidized surfaces, poor fit up and adhesive etc. Most of the commercial adaptive weld controllers require proper "Initial Welding Schedule" or "Reference weld" to achieve compensation in welding parameters during real time welding. In this study, the compensation of a commercial adaptive weld controller had been observed and analyzed thoroughly for various process disturbances to find optimal initial welding schedule. It was observed that 90 percent of the expulsion current in constant current control as reference welding schedule conferred the maximum button diameter in adaptive control welding. Finally, effects of each disturbance in combined field disturbances system with adaptive control had also been confirmed with the design of experiment (DOE) by minitab(R)16 for combined disturbances situation and suitability of optimum initial weld current had also established with real body part validation test.
Effects of Phosphorus and in-situ Post-heat Pulse Conditions on Resistance Spot Weldability of High Si DP980 Steel Sheet
Choi, Du-Youl ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 21~26
DOI : 10.5781/JWJ.2015.33.6.21
Recently, application of UHSS(Ultra High Strength Steels) whose tensile strength is over 1000MPa to car body structure are growing due to great needs for light weighting and improved crash worthiness. However, their poor weldability is one of obstacles to expand selecting to car body. In this study, effect of Phosphorus contents on resistance spot weldability of high elongation DP980 steel whose Si content is over 1% was investigated. The cross tension strength (CTS) was decreased showing partial interface fracture as Phosphorus content increase because of solidification segregation of Phosphorus. In order to improve resistance spot weldability by modification of welding condition, in-situ post-weld heating pulse was introduced after main pulse. The optimum cooling time between main and post pulse and post-pulse current condtion were determined through FEM welding simulation and DOE tests. The CTS was increased about 1.5 time showing plug fracture. The decrease of Phosphorus segregation was found to be a major reason for weld ductility and CTS improvement.
A Study on HAZ Softening Characteristics of Fiber Laser Weldment for High-Strength Steel
Park, Min-Ho ; Kim, Ill-Soo ; Lee, Jong-Pyo ; Jin, Byeong-Ju ; Kim, Do-Hyeong ; Kim, In-Ju ; Kim, Ji-Sun ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 27~35
DOI : 10.5781/JWJ.2015.33.6.27
Laser welding sector in the automotive industry has been widely recognized as one of the most important bonding processes, such as parts welding. Efforts to improve productivity and weld quality have been progressing steadily. In addition, laser welding is suitable for welding process that can produce high-quality welds suitable for flexible production and small quantity batch productions. In order to ensure the rigidity of the material, high strength material are applied to more than 1 GPa class body parts and automotive bumper beams. However, not only the situation is that the trend of domestic research, but also development is based on product molding considering freedom of shape where reinforcement is applied to meet the safety regulations and high-speed crash performance, despite the use of high strength materials. The tendency for heat-affected zone (HAZ) softening phenomenon common in areas of laser welded high tensile steel welding confirmed the occurrence of weld softening effect according to the process parameters. Based on this, range of process parameters could be selected for ensuring weld quality.
Development of Reinforcement Side Outer Using TWB Hot Stamping Process
Kim, Soyoun ; Kong, Hoyoung ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 36~41
DOI : 10.5781/JWJ.2015.33.6.36
In the automotive industry, TWB hot stamping process is broadly adapted to reduce weight of the car and improve fuel efficiency. However, the process faces a problem of weakened strength of the welded zone after hot stamping process, due to the fact that Al-Si elements of the coating layer penetrating the welded zone. In this study, filler wires with high percentages of carbon and manganese is adapted during laser welding process to secure the strength of the fusion zone. In addition, wire feeding speed and laser welding speed are optimized by sample test.
Fatigue Damage Behavior in TIG Welded Joint of F82H Steel under Low Cycle Fatigue Loading
Kim, Dong-Hyun ; Park, Ki-Won ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 42~48
DOI : 10.5781/JWJ.2015.33.6.42
Reduced activation ferritic/martensitic steels are recognized as the primary candidate structural materials for fusion blanket systems. Welding is an inevitable for breeding blanket for pressure tightness and radioisotope confinement. Especially, TIG welding was chosen for sealing because it has the largest gap allowance compared to the other welding methods, and its properties are controllable by feed wire and welding conditions. In this study, the low cycle fatigue test using two-type gage such as extensometer and strain gage was applied to the TIG welded joint of F82H steel, for evaluating fatigue damage accumulation behavior of the HAZs. As the result, the over-tempered HAZ have shown a higher fatigue damage accumulation compared with other materials at all the testing conditions.
Fatigue Life Prediction of Non-Load-Carrying Cruciform Welded Joint using Master S-N Curve based on Structural Stress Approach
Kwak, Si-Young ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 49~54
DOI : 10.5781/JWJ.2015.33.6.49
Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.
Design of Helical SPR for Joining Advanced High Strength Steel and Aluminum Alloy Sheets
Kim, Dongbum ; Kim, Kwan-Woo ; Cho, Hae-Yong ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 55~59
DOI : 10.5781/JWJ.2015.33.6.55
Self-piercing riveting (SPR) is a sheet-joining method that can be used for materials that are difficult or unsuitable for weld, such as aluminum alloys and other steel sheet metals. The increased application of lightweight materials has initiated many investigations into new SPR conditions for riveting dissimilar materials. However, buckling of the semi-tubular rivet occurs during the riveting of AHSS. In this study, a helical SPR was designed for the riveting of AHSS and Al-alloy. In addition, the reinforced helical SPR which has straight parts was designed. The riveting of AHSS and Al-alloy was simulated. Simulated results were verified by comparison with experimental ones.
Finite Element Analysis on the Improvement of Residual Deformation of the Part After Pulse Laser Welding of Circular Cover
Kim, Kwan-Woo ; Cho, Hae-Yong ;
Journal of Welding and Joining, volume 33, issue 6, 2015, Pages 60~66
DOI : 10.5781/JWJ.2015.33.6.60
Molten zone shape of pulse laser welding is affected by welding conditions such as beam power, beam speed, irradiation time, pulse frequency, etc. and is divided into conduction type and keyhole type. It is necessary to design heat source model for irradiation of laser beam in the pulse laser welding. Shape variables and the maximum energy density value of the heat source model are different depending on the molten zone shape. In this paper, pulse laser welding simulation for joining of cylindrical part and circular cover was carried out. The heat source model for pulse laser beam with circular path was applied to the heat input boundary condition, radiative and conductive heat transfer were considered for the thermal boundary condition. For each phase, thermal and mechanical properties according to temperature were also applied to analysis. Analytical results were in good agreement with the molten zone size of specimen under the same welding conditions. So, the reliability of the welding simulation was verified. Finally, the improvements for reducing residual deformation after cover welding could be reviewed analytically.