• Journal of Welding and Joining
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• v.5 no.4
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• pp.36-46
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• 1987

The impact toughness and SCC resistance of duplex stainless steel weldment made by GTAW, GMAW and SMAW processes was studied. The impact toughness of GTA weld metal was higher than that of GMA weld metal which contained more ferrite phase than GTA weld metal. The impact toughness of SMA weld metal was the lowest due to the harmful effect of inclusions inspite of richness of more ductile austenite phase. From these facts, it can be concluded that the important factors determining the weld metal toughness were the amount of ferrite phase and the cleaness of weld metal. While the SCC resistance of SMA weld metal was lower than that of base metal and nay other weld metal, the SCC resistance of GMA and GTA weld metal was higher than that of base metal but that of all the HAZ's were lower than that of base metal. Therefore, the impact toughness and SCC resistance of GTA and GMA weldment was pretty good as long as phase ratio was propertly controlled. Although the phase ratio was controlled, SMA weld metal could not get a good combination because the lack of shielding from the environment results in a high content of inclusions in weld metal.

• Journal of Welding and Joining
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• v.29 no.3
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• pp.76-81
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• 2011

Recently, the structural failures due to fatigue occur frequently with the increase of size of ships and offshore structures. In this respect, the assessment of fatigue life and the residual strength are very important. Currently, the smart materials technology has demonstrated a variety of possibilities for a diagnosis of structural strength and structural health condition for large structures. The benefits and feature of the MFC sensor are more flexible, durable and reliable than conventional smart material. In this study, Micro Fiber Composite (MFC) sensor for the measurement of stress intensity factor (SIF) of two dimensional cracks induced in a structure is developed. Two MFC sensors are placed in the vicinity of the crack tip close to each other with the crack tip in between them. The SIFs of Mode I($K_I$) as well as of Mode II($K_{II}$) based on the piezoelectric constitutive law and fracture mechanics are calculated. In this study, the SIF values measured by MFC sensors are compared with the theoretical results and measured value.

• Journal of the Korean Society of Costume
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• v.42
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• pp.223-230
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• 1999

Dressmaking which is defined as the process of changing two-dimensional cloth into three-dime-nsional clothes needs a lot of joining parts. Particularly sleeve needs a more curved surface than other joining parts owing to shape of the top of arms. Easing is used to control the fullness along the seam-line to create the fullness curved shape of the sleeves and it plays an important role in increasing three-dimensional constru-ction power. unfortunately sufficient data regarding effective easing conditions to increase three-dimensional construction power of sleeve are not available. Therefore the author tried to investigate the effective easing conditions to increase three-dimensional construction power of sleeve by cap height. Easing construction power of sleeve by cap height. Easing contraction made by different angles on the sleeve cap curve line previous work were examined and the effective easing conditions according to the variation of angles were determined. This study contains the following objectives. Firstly to obtain the easing contraction ratio in sleeve according to the above easing conditions. Secondly to investigate the three-dimensional construction power or sleeve by the factors of easing contraction. Thirdly to determine for each sleeve the effective easing conditions on the basis of the calcuative easing contraction ratio in the sleeve patterns by cap heights.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.311-316
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• 2001

This paper presents that the affecting factors to the solderability and initial reliability. It is the factor that the coefficient of thermal expansion between package and PCB(Printed Circuit Board), the quantity of solder paste and reflow condition, and Au thickness of the solder ball pad on polyimide tape. As the reflow soldering condition for 48 ${\mu}BGA$ is changed, it is estimated that the quantity of Au diffusion at eutectic Sn-Pb solder surface and initial bonding strength of eutectic Sn-Pb solder and lead free solder. It is the result that quantitative measurement of Au diffusion quantity is difficult, but the shear strength of eutectic Sn-Pb solder joint is 842 mN at first reflow and increases 879 mN at third reflow. The major failure mode in solder is judged solder fracture. So, Au diffusion quantity is more affected by reflow temperature than by the reflow times.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.77-85
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• 2010

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of a railroad car and vehicles structure.However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weld, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, $({\Delta}{\sigma}_a)_R-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test(ALT) was conducted. From the experimental results, an acceleration model was derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.7-14
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• 2013

The legitimacy of dominating factor in the high accuracy prediction of welding distortion was investigated for butt welding and fillet welding. When out-of-plane distortion was measured by the experiment objecting to butt welding, if tack welding was easily performed, the position of a neutral axis was variously changed by the irregularity. Then, there have been a case that out-of-plane distortion was generated in the unexpected direction. This case should be especially noted. New model for the experiment was proposed so as to solve this problem. As it was elucidated by the case of fillet welding, it was verified that the analysis should be carried out with satisfying the yield condition (especially at high temperature above 700 degree Celsius) and with closely simulating the penetration shape (heat input in weld metal) in order to solve the proposition that is the high accuracy prediction of welding distortion. It was confirmed that residual stress is highly predicted because welding distortion is highly predicted, too.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.55-65
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• 1999

Metallurgical factors influencing toughness of the Intercritically Reheated Coarse-Grained Heat Affected Zone (ICCG HAZ) of multiple welded SA508-cl.3 Reactor Pressure Vessel Steel were evaluated. The recrystallized austenite formed along the prior austenite grain boundaries and late interfaced on heating to the intercritical range was transformed to bainite and/or martensite during cooling. The newly formed martensite always included some retained austenite(M-A constituents). The characteristics(amount, hardness, density, and size) of M-A constituents were found to be strongly associated with both peak temperature and cooling time(△t8/5(2)) of last pass. Toughness in the ICCG HAZ was deteriorated with increasing amount of M-A constituents which was increased with increasing the last peak temperature within the intercritical temperature range. Meanwhile, for the same intercritical peak temperature, toughness was decreased with increasing cooling time. When cooling time was short, the dominant factor influencing toughness of the ICCG HAZ was amount of M-A constituents. However, when cooling time was lengthened, the hardness difference between M-A constituents and softened matrix(tempered martensite) was found to be the dominant factor.

• Journal of Welding and Joining
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• v.1 no.1
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• pp.37-46
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• 1983

This paper describes a study of fillet welded joint stressed perpendicular to the weld line. The finite element method was used to determine the stress intensity factor for cruciform joint at weld toe and root cracks according to variation of H/Tp, weld angle and main plate thickness. But, in this study, weld angle was fixed at 45.deg., since the variation of weld angle affect the stress intensity factor little, also main plate thickness was fixed. Pulsating tension fatigue test was done at the second phase of experiment. The work using the concepts of the fracture mechanics on the stable crack growth, was in the correlation of the experimental fatigue stress-life behavior because the fatigue behaviors of various joint geometries are related to the stress intensity factors calculated by F.E.M. analysis. Main results obtained are summarized as follows. 1) According to the propagation of toe crack, the variation of the stress intensity factor at root crack is obvious as H/Tp is smaller. 2) According to the propagation of root cracks, the change of the stress intensity factor of the toe is very large with propagation of root crack. 3) The calculation formula of the stress intensity factor of crack propagation at the root crack was obtained. 4) The calculation formula of the stress intensity factor at the toe cracks was obtained in similar manner. 5) From the results of experiment, the velocity of fatigue crack propagation at the weld toe and root was estimated.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.22-27
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• 2014

In the past, cold crack was commonly observed in the HAZ(heat affected zone) of high-strength steels. Applying to TMCP(thermo-mechanical controlled process) and HSLA(high strength low alloy) steels, cold crack tends to increase the occurrence in the weld metal. It is generally understood that cold crack occurs when the following factors are present simultaneously : diffusible hydrogen in the weld metal, a susceptible microstructure and residual stress. In particular, many studies investigated the microstructural effect on the cold crack in HAZ and the cold crack in weld metals starts to receive the special attendance in modern times. The purpose of the study is to review the effect of weld microstructures (grain boundary ferrite, Widm$\ddot{a}$nstatten ferrite, acicular ferrite, bainite and martensite) on cold crack in the weld metals. Among various microstructures of weld metals, acicular ferrite produced the greatest resistance to the cold crack due to the fine interlocking nature and high-angle grain boundary of the microstructure.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.34-39
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• 2011

Nickel-based austenitic alloys such as Alloy 82 and 182 had been employed as the weld metals in nuclear power plants (NPPs) due to their high corrosion resistance as well as good mechanical properties. However, since the 2000s, the occurrence of primary water stress corrosion cracking has been reported in conjunction with these alloys in domestic and oversea NPPs. In the present work, we assumed an imaginary crack at the inner surface of a surge nozzle weld that had previously experienced the outside repair welding, and constructed its finite element model. Finite element analysis was performed with respect to the heat transfer, and then to the residual stress for obtaining the total applied stress distributions. These stress distributions were finally converted to the stress intensity factors for estimating crack growth rate. From the comparison of crack growth rate curves for the cases of no repair welding and outside repair welding, it was found that the outside repair welding did not exhibit negative effect on the crack growth for the surge nozzle under consideration in this work; in both cases, the cracks stopped growing before they became the through-wall cracks.