• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.126-129
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• 2005

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Journal of Welding and Joining
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• v.22 no.3
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• pp.56-61
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• 2004

Friction stir weldability of AZ31B Mg alloy was studied using microstructural observation and mechanical tests. Defect free joints was obtained under the condition of 2000rpm-100mm/min. In TMAZ, a lot of twin deformation were observed due to the mechanical effect of the FSW tool and thus relatively high hardness was obtained. In SZ, the twin deformation was disappeared by recovery and the hardness decreased because the. grain structure was coarsened by dynamic recrystallization and grain growth. The Al-Mn precipitates were observed throughout the joint regions. On the other hand, $$\beta$-Mg_{17}Al_{12}$ intermetallic compounds were not observed in either of the zone. The joint efficiency was about 80% and the impact value of the joint was almost equal to that of base metal.

• Journal of Welding and Joining
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• v.30 no.3
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• pp.51-56
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• 2012

Different microstructures in the weld zone of a metal structure including a fusion zone and heat affected zone are formed as compared to the base material. Thus, the mechanical properties in the weld zone are different from those in the base material. As the basic data for reliably understanding the structural characteristics of welded nuclear material, the mechanical properties in the weld zone and base material for a Zircaloy-4 strap and Hastelloy${(R)}$-X alloy strap are measured using an instrumented indentation technique (IIT) in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.1-7
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• 2021

In recent years, automated process technology has allowed for the rapid manufacturing of metal parts. Maintaining high product quality is of vital importance during the production of these parts. Surface defects occurring after processing can compromise their assembly precision and performance. In this study, a deburring tool was developed that can remove burrs generated from drilling. Through the evaluation of processing, burrs were completely removed at entrance and exit surfaces. Therefore, this newly developed deburring tool shows better performance than deburring tools currently in use.

• Structural Monitoring and Maintenance
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• v.5 no.4
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• pp.429-443
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• 2018

Fatigue is a principal failure mode for steel structures, and it is still less understood than any other modes of failure. Fatigue life estimation of metal bridges is a major issue for making cost effective decisions on the rehabilitation or replacement of existing infrastructure. The fatigue design procedures given by the standard codes are either empirical or based on nominal stress approach. Since the fatigue life estimation through field measurements is difficult and costly, more researches are needed to develop promising techniques in the fatigue analysis of bridges through Finite Element Analysis (FEA). This paper aims to develop a methodology for the Fatigue life estimation of railway steel bridge using FEA. The guidelines of IIW-1823-07 were used in the development of the methodology. The Finite Element (FE) package ANSYS and the programming software MATLAB were used to implement this methodology on an Indian Railway Standard (IRS) welded plate girder bridge. The results obtained were compared with results from published literature and found satisfactory.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.2
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• pp.191-199
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• 2019

In this paper, dissimilar friction welding were produced using 15 mm diameter solid bar in chrome molybedenum steel(SCM440) to stainless steel(STS316L) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=70 MPa, UP=140 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 8.6 mm. In addition, an acoustic emission technique was applied to evaluate the optimal friction welding condition. AE parameters including the cumulative count, amplitude and energy showed a various changes according to the friction condition. A continuous type waveforms and low frequency spectrum was presented in friction time. On the other hand, a burst type waveform and high frequency spectrum was exhibited in pressing time.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1357-1368
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• 2021

This paper presents thermal aging effect on fracture toughness properties of GTAW (gas tungsten arc welding) and SMAW (shielded metal arc welding) of 316L stainless steels, and investigates the applicability of the existing three thermal aging models for CASS (cast stainless steels). Thermal aging was carried out at 350 ℃ for up to 15,000h and at 400 ℃ up to 8,000h. After aging, tensile and fracture toughness tests using 0.5T C(T) specimens were carried out at room temperature and at 288 ℃. Comparing with the predictions using three (ANL, French and H3T) thermal aging models for CASS show that the predictions can be very non-conservative at operating temperature, and thus that the existing thermal aging models for CASS cannot be applied to the welded stainless steels.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.438-442
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• 1996

The design of the vacuum vessel of KT-2(a large-aspect-ratio, mid-size tokamak) is presented. The KT-2 vacuum vessel provides necessary environments to contain a plasma of double-null configuration with elongation of up to 1.8. The vacuum vessel is designed as an all-metal welded structure. Eddy currents are induced on the vessel during all stages of the plasma operation. Influences of the continuous vessel on the plasma were investigated. No significant effect of the vessel on the plasma in every aspect of null formation, plasma initiation, plasma control was found. Stresses and deformations in the vessel by atmospheric pressure and electromagnetic forces due to the eddy currents were calculated using 3D FEM code.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.8-16
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• 2003

A major concern in Gas Metal Arc (GMA) welding process is the determination of welding process variables such as wire diameter, gas flow rate, welding speed, arc current and welding voltage and their effects on the desired weld bead dimensions and shape. To successfully accomplish this objective, 81 welded samples from mild steel AS 1204 flats adopting the bead-on-plate technique were employed in the experiment. The experimental results were used to develop a mathematical model to predict the magnitude of bead geometry as follows; weld bead width, weld bead height, weld bead penetration depth, weld penetration shape factor, weld reinforcement shape factor, weld bead total area, weld bead penetration area, weld bead reinforcement area, weld bead dilution, length of weld bead penetration boundary and length of weld bead reinforcement boundary, and to establish the relationships between weld process parameters and bead geomery. Multiple regression analysis was employed for investigating and modeling the GMA process and significance test techniques were applied for the interpretation of the experimental data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.22-28
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• 2013

Robotic GMA (Gas Metal Arc) welding process is one of widely acceptable metal joining process. The heat and mass inputs are coupled and transferred by the weld arc to the molten weld pool and by the molten metal that is being transferred to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired quality of the weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. MD (Mahalanobis Distance) technique was employed for investigating and modeling the GMA welding process and significance test techniques were applied for the interpretation of the experimental data. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats. First, a set of weldments without any faults were generated in a number of repeated sessions in order to be used as references. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. Statistical models developed from experimental results which can be used to quantify the welding quality with respect to process parameters in order to achieve the desired bead geometry based on weld quality criteria.