• Journal of Welding and Joining
• /
• v.6 no.3
• /
• pp.21-26
• /
• 1988

The behavior of angular distortion in butt joint wleding of thin plate structure is investigated with an experimental model and partially with a computational model. The experimental model studying the effects of specimene size and degree of restraint on the angular distorion offers a good method for analyzing the behavior of the distrotion. In addition, the distrotion during welding was demonstrated by both experimental measurement and numericla prediciton. The facts evealed in this study are as follows : 1) distrotion angles were changed with variations of specimene wldth. 2) With the restraint, angular distrotion was reduced to 20% to that of free joint. 3) After the restraint being removed, the effect of restraint was also remained. 4) Same heat input per unit thickness caused same amount of distortion. 5) The mode of angular distortion was expected to be changed with expected to be changed with time, i.e. convex movement during heating and concave one during cooling.

• Journal of Welding and Joining
• /
• v.18 no.6
• /
• pp.83-88
• /
• 2000

Variation of welded-joint hardness and tensile strength of a accelerated-cooled fine-grained ferritic-pearlitic steel with heat input was investigated. In a weld heat-affected zone, a softened zone was formed and it had lower hardness than that of a base metal. While the width of a softened zone increased continuously with an increase of heat input up to 100kJ/cm. the minimum hardness in a softned zone was almost constant after a continuos decrease up to 60KJ/cm. Because of a softened zone, the welded-joint was fractured in the HAZ and its maximum reduction of tensile strength was about 20%. Measured welded-joint tensile strength and calculated minimum tensile strength in a welded-joint was almost same, which means that the plastic restraint of a softened zone did not occur in this experiment. It is believed that as a softened zone width-to-specimen thickness ratio is as high as 2~6 in this experiment, the plastic restraint effect does not occur. Theoretical analysis shows that the plastic restraint effect occurs only when the ratio is below 0.5.

• Advances in concrete construction
• /
• v.14 no.2
• /
• pp.139-151
• /
• 2022

Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

• Journal of Korean Clinical Nursing Research
• /
• v.17 no.1
• /
• pp.90-100
• /
• 2011

Purpose: This paper was to develop an elbow restraint which can reduce the side effects of the wrist restraint which was frequently used in an intensive care unit and to evaluate its application. Methods: A nonequivalent control group non-synchronized design was used. Subjects were 38 patients (elbow restraint group: 18, wrist restraint group: 20) and 20 nurses who used both restraints in medical intensive care unit at G National University Hospital. Restraints were applied to subjects for 72 hours. Data were collected from December 1, 2009 through March 31, 2010. The data collected were analyzed using $x^2-test$, Fisher's exact test, t-test, and ANCOVA using SPSS 12.0 program. Results: Elbow restraint significantly decreased range of wrist motion reduction, swelling and significantly increased the convenience of wearing restraint compared to wrist restraint. Conclusion: The new elbow restraint are more efficient than the old wrist restraint, which have been used in an intensive care unit, in terms of convenience of restraint application, range of joint motion and prevention of swelling.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.396-401
• /
• 2002

A practical method for evaluating the possibility of the occurrence of cracking in actual thick-plate T-joint weldments is presented in this study. Systematic experiments based on the method of the design of experiment are conducted in order to investigate the crack tendency in relation to typical welding parameters such as diffusible hydrogen, restraint intensity, preheating temperature and so on. The elastic analysis using the [mite element techniques is employed to quantify the restraint intensities of the specimens. The defined restraint intensities are treated in numerical way for the sake of considering the most uncertain factor among some major factors that govern the cracking phenomena due to welding. The critical plane for judgment of the crack occurrence or crack density is presented as a function of typical welding parameters including determined restraint intensities. The results of numerical estimation by the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problem having extensive uncertainties.

• International Journal of Korean Welding Society
• /
• v.4 no.1
• /
• pp.38-45
• /
• 2004

A practical method for evaluating the possibility of the occurrence of cracking in actual thick-plate T-joint weldments is presented in this study. Systematic experitrients based on the method of the design of experiment are conducted in order to investigate the crack tendency in relation to typical welding parameters such as diffusible hydrogen, restraint intensity, preheating temperature and so on. The elastic analysis using the fmite element techniques is employed to quantify the restraint intensities of the specimens. The defined restraint intensities are treated in numerical way for the sake of considering the most uncertain factor among some major factors that govern the cracking phenomena due to welding. The critical plane for judgment of the crack occurrence or crack density is presented as a function of typical welding parameters including determined restraint intensities. The results of numerical estimation by the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problem having extensive uncertainties.

• Journal of Ocean Engineering and Technology
• /
• v.13 no.3 s.33
• /
• pp.49-56
• /
• 1999

Welding is a reliable process and is mainly adopted for fabricating heavy structures. Recently, transverse cracks in the weld metal is serious problem, and they affect cost, efficiency, safety and joint reliability for various welded structures. In this view of point, this study investigated the potential factors for weld metal transverse crack. The main results obtained are as follows; 1) The content of diffusible hydrogen in the commercial flux cored are welding wire was remarkable change by manufacturer. 2) The diffusible hydrogen content was thd main factor for weld metal transverse cracks. 3) Weld metal was immune to transverse cracking under the condition of low diffusible hydrogen content of high restraint condition. 4) The factors for weld metal transverse crack would be the content of diffusible hydrogen and restraint of weld joint.

• Journal of Welding and Joining
• /
• v.30 no.5
• /
• pp.51-56
• /
• 2012

The purpose of this study is to evaluate the distortion and the residual stress of GTA tubular welds between tube and head. In order to do it, the heat input model for GTA welding process was first developed by experiment and FE analyses. The welding distortion and the residual stress distribution of the tubular welds according to welding pass and various restraint degrees were evaluated by using FEA with the heat input model. From FEA results, it was found that the residual stress and the radial distortion at the weld toe of tube part decrease with a decrease in the number of welding pass. However, the maximum residual stresses in each direction of tubular welds are almost constant regardless of the external restraint degree. It was mainly due to the high internal restraint of the welds.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.1057-1064
• /
• 2004

For New In-Cheon Airport. South Approach Section of Young long Great Bridge is to be special concerned to CWR due to substructure was already constructed former railroad bridge design specification. So we applied maintenance free system and CWR (Continuous Welded Rail) by ZLR(Zero Longitudinal Restraint) at bridge expansion joint part. This thesis generally introduce for CWR by ZLR at South Approach Section of Young long Great Bridge.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.43-46
• /
• 2005

Precast prestressed concrete hollow slab bridge is one of segmented bridge which can be long span, so that the structural behavior of joints of adjacent segment should be evaluated by the analysis as well as experiment. In this study, small scaled beam tests were carried out to determine joint shear key shape and restraint stress by prestressing. From the tests and the analysis, it was found that the joint key shape and the restraint stress affect the behavior of segments and the segments which has the height to the width of shear key as 1/3 possess maximum shear resistance.