• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.11 s.254
• /
• pp.1439-1446
• /
• 2006

The fatigue test of the fillet weldments was executed with different beveling angles and porosities. The beveling angles of $0^{\circ}$, $45^{\circ}$ and $55^{\circ}$ were compared with fatigue lives. After the fillet weldment failure, the porosities which found at the fractured surface were observed to account the effect on fatigue life. Finite element analysis was performed to correlate the fatigue strength and the sizes and the locations of porosities. The stress-strain field was severely affected by the length of notch and the sizes and locations of porosities. Based on the quantitative analysis of porosity effect, the total volume of porosities was a key factor for fatigue strength of the fillet weldment.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.11 no.1
• /
• pp.52-60
• /
• 1991

The importance and role of preservice and inservice inspection(PSI/ISI) for nuclear power plant components are intimately related to plant design, safety, reliability and operation etc.. The Korea Atomic Energy Research Institute(KAERI) has been performing PSI/ISI in Korea since the PSI of Kori nuclear power plant, unit 1 had been performed in 1977. KAERI has localized PSI/ISI technology and has done much experience in ultrasonic flaw detection, evaluation and its excavation on the weldments of large pressure vessels. The results of flaw estimation using ultrasonic examination are compared with the actual flaw sizes revealed by field excavation. KAERI's experience regarding PSI/ISI was described and some discussions were added.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.2
• /
• pp.9-16
• /
• 2007

The fatigue test of the fillet weldments were executed with different groove angles and porosity. The groove angles of $90^{\circ}$, $45^{\circ}$ and $55^{\circ}$ were compared with fatigue lives. After the fillet weldment failure, the porosity which found at the fractured surface were observed to account the effect on fatigue life. Finite element analysis were performed to correlate the fatigue strength and the size & the location of porosity. The stress-strain field were severely affected by the length of notch and the size & location of porosity. Based on the quantitative analysis of porosity effect, the total volume of porosity was key factor for fatigue strength of the fillet weldment.

• Proceedings of the KWS Conference
• /
• 1998.10a
• /
• pp.11-24
• /
• 1998

The invention of fusion wilding technology has brought on a revolutionary change in manufacturing industry which enables the construction of large scale high temperature plants in chemical, petrochemical and power generation industries. However, among the failure cases of high temperature components, premature failures of weldments have taken a large percentage that indicates the detrimental effect of welding on structural integrity. The accurate prediction of the high temperature behaviour of welded components is thus becoming increasingly important in order to realise an optimised design and maintenance of a plant life. In the present paper, recent research activities on high temperature behaviour of welded structures are briefly summarised. A local deformation measuring technique is proposed to determine the creep properties of weldment constituents. A damage mechanics approach is introduced to study the life reduction and ductility reduction due to the presence of a weld in high temperature structures. Finally, the high temperature creep crack growth in weldments is discussed.

• Journal of Welding and Joining
• /
• v.4 no.3
• /
• pp.32-42
• /
• 1986

In this study, the influence of carbon equivalents on friction welds of dissimilar steels was investigated. Four types of carbon steels with 10mm diameter were welded to a high-speed tool steel SKH 9. Main experimental results could be summarized as follows (1) Under constant friction pressure, the friction time increased almost linearly with the increasing burn-off length, while the forge length decreased almost linearly. (2) The maximum hardness in carbon steels increased almost linearly with the increasing carbon equivalent, but was much lower than that in the high speed steel. (3) After quenching and tempering of dissimilar steel friction welds, the hardness in carbon steel weldments became similar as that in the base metal, while the hardness in SKH 9 weld was still higher that of the base metal. (4) Relative movement in the friction phae occurred not at the interface of the weldments, but in the high speed steed steel near the interface. (5) For considered material combinations and welding parameters, most of fractures in tension and twisting tests occurred in the base metal. And welds with so high strength could produced in a wide range of welding parameters.

• Journal of Welding and Joining
• /
• v.4 no.3
• /
• pp.58-71
• /
• 1986

Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1997.04a
• /
• pp.143-149
• /
• 1997

the horizontal corrosion fatigue tester has been developed for investigating environmental strength. Using this tester, we investigated about corrosion fatigue caracteristic for A106 GrB steel weldments in 3.5% synthetic seawater and room temperature. Considered parameter is only frequency of 1,3 and 5Hz. and Corrosion fatigue crack length was measured by DC potential difference method. From the results, we could find that the horizontal corrosion fatiued tester could be well applied to estimation of fatigue strength. and In case of 5Hz, corrosion fatigue crack growth path of A106 GrB steel weldment was transgranular, and of 1 and 3Hz showed that transgranular and intergranular was mixed. Also, Corrosion fatigue crack growth caracteristic values estimated in each frequency were C=9.33 x 10-9 and m=2.93 in 1Hz, C=9.77x10-10 and m=3.47 in 3Hz, C=1.02x10-10 and m=4.05 in 1Hz

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1996.11a
• /
• pp.167-176
• /
• 1996

Flaw classification and sizing are very essential issues in quantitative ultrasonic nondestructive evaluation of various materials and structures including weldments. For performing of these tasks in an automated fashion, we are developing an intelligent ultrasonic evaluation system with a multi-axis portable scanner which can do consistent and efficient acquisition and processing of ultrasonic flaw signals. Here we present our efforts to develop of this intelligent system including design of the portable scanner, acquisition and processing of ultrasonic flaw signals, display of pseudo 3-D image of flaws, and classification and sizing of flaws in weldments.

• Proceedings of the KAIS Fall Conference
• /
• 2011.05b
• /
• pp.679-682
• /
• 2011

The effects of heat input(1.5~3.6kJ/mm) and postweld heat treatment(PWHT, $600^{\circ}C$, 40hr.) on the TMCP HSB600 steel weldments made by GMAW process were investigated. The tensile strength and CVN impact energy of as-welded specimens decreased with increasing heat input. The fine-grained acicular ferrite was mainly formed in the low heat input while polygonal and side plate ferrites were dominated in the high inputs. Meanwhile, tensile strength and hardness of PWHT weldments decreased due to the coarsening of microstructure and reduction of residual stresses.

• Journal of Welding and Joining
• /
• v.20 no.2
• /
• pp.59-64
• /
• 2002

When the vehicle travels in an actual road, resistance spot weldments of the vehicle structure are exposed to complex loading state. Since the fatigue strength in resistance spot weldment of vehicle body can be determined by effect of residual stresses and loading state of driving, estimating actual loading state and considering residual stress effect are needed. In this study, Fatigue stress-fatigue life relation concerned residual stress effect was obtained by thermo elastic plastic finite element analysis. And applied loading in resistance spot weldments of vehicle body was calculated by dynamic analysis. Presumption of fatigue life was performed using proposed method