• Journal of Welding and Joining
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• v.19 no.5
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• pp.548-554
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• 2001

The restraint force is required an accurate measurement and analysis to protect weldment from residual stress. Also, this residual stress caused by clacks in weldments are often observed in the weldments of large size nozzles or radial tanks after welding. This paper is preformed on the study of evaluation of welding restraint forces using load cell with STS thin plate which are using pressure vessel steel in the industry field. As a result of this study, as the welding currents are higher and the welding speeds are more slowly, the magnitude of restraint force in process of the flat plate welding hows to be more large. Also, the temperature in process of melting is increasingly rising, then the restraint forces exhibit the compressive forces, whereas the restraint forces during cooling represent extensional force.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.8-13
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• 2004

The purpose of this paper is to investigate the welding residual stress distribution according to the constraint or non-constraint welding condition with titanium commonly using power station, aircraft, and ship. The measuring method of the residual stress was applied stress release rating method with strain gages and a potable strain meter. The x direction residual stress generally showed the tensile residual stress in case of res03int welding. On the other hand, the x direction residual stress under non-restraint welding were changed tensile stress into compressive stress on 15mm away from welding bead center. Also, the y direction residual stress generally showed the tensile residual stress in case of non-restraint welding and the y direction residual stress under restraint welding were changed tensile stress into compressive stress about 60mm away from welding bead center.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.14-20
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• 2003

In this paper, a practical design criteria for judgement of crack occurrence in weldments is presented as a function of typical welding parameters, such as diffusible hydrogen, restraint intensity, and preheating temperature. The elastic analyses using the finite element techniques are employed in order to quantify the restraint intensities, numerically. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.86-93
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• 2007

The restraint force is required for the accurate measurement and analysis to protect weldment from residual stress. Also, this residual stress caused by cracks in weldments is often observed in the weldments of large size nozzles or radial tanks after welding. This paper is preformed to evaluate the welding restraint forces using load cell with STS304 thin plate which is used as the pressure vessel steel in the industry field. As a result, as the welding currents are higher and the welding speeds are more slowly, the magnitude of restraint force in process of the flat plate welding shows to be more large.

• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.38-45
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• 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 Welding and Joining
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• v.6 no.3
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• pp.21-26
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• 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
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• v.30 no.5
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• pp.51-56
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• 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 KWS Conference
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• 2002.10a
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• pp.396-401
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• 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.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.1-7
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• 2003

The objective of this paper was to investigate the welding characteristics according to the restraint condition. the pass number, and the shield gas quantity with titanium commonly using in power stations, aircrafts, ships, and so forth. The residual stress distribution was measured under restraint and nonrestraint welding conditions. The tensile strength and elongation of the 4 pass welded specimen were shown higher about 10% and 30% than those of the 7 pass welded specimen at the same welding conditions respectably. Also, the more shield gas quantity and the shorter natural cooling time, the higher tensile strength and the lower elongation.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.6-12
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• 2015

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 $200^{\circ}C$ to $900^{\circ}C$ due to the decrease of Nb content in solid solution and coarsening of MX type precipitates, laves phase, $M_6C$ 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.