• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.356-359
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• 2004

Above all Ni-alloys Inconel 625 is used widely in plate of welding structural materials such as turbine case, a combustor of liner. In general, weldability of Inconel 625 is not well because of poorly liquids of weld metal also it have a broken probability oj the welding crack. In case of FCAW weld process, it is not easy to develope of welding materials, because it is possible only fillet welding at view position of look down except for butt welding. But recently, though it is more used by FCAW process, owing to welding materials worked at the vertical position. the study for FCAW weld of Inconel 625 is actively not yet worked. In this study, the weldability and weld characteristics(mechanical characteristics, corrosive property) of Inconel 625 are considered in FC4W weld associated with the several shielding gases$80\%Ar\;+\;20\%\;CO_2,\;50\%Ar\;+\;50\%\;CO_2,\;100\%\;CO_2$ in viewpoint of welding productivity. The results of impact test are follows; It was evaluated 70J at shielding gase of $100\%\;CO_2$, and obtained about 35J at the other shielding gases. If it was used for parts be required the impact value at the extremely low temperature, it is expected to have the advantage of using the $100\%\;CO_2$ shield gase than the others.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.401-402
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• 2009

• Journal of Welding and Joining
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• 제21권5호
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• pp.561-567
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• 2003

For construction of I-beam steel structures, a fillet welding is one of the main manufacturing process. However, this welding process cause some problems associated with welding residual stress and welding deformation that are harmful to the safety of structures. Accordingly, this study clarified the creation mechanism of the welding deformation on I-beam steel structure from the experimental results given by the FEM method. To prevent or minimize the longitudinal bending deformation, first of all, a field supervision is necessary to observe the optimal groove design. Secondly, the welding order for cooling weld zone is needed.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.422-432
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• 2001

There are many analysis formulas for determining the resultant shear force in welds. However, there is no general procedure which is applicable to a joint with all six possible loadings exerted simultaneously. A numerical methodology and computer program for such a problem were developed, and they are capable of analyzing a weld of any shape composed of straight or circular line segments. The computer program developed in this study can also display the design procedures and results using computer graphics. The development of such a design procedure and an interactive computer program for weldments analysis will lead to lower cost.

• 대한조선학회논문집
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• 제46권4호
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• pp.417-423
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• 2009

This paper is concerned with the fatigue behaviour of welded joints by the notch stress approach. The actual welded shape is complex and 3-dimensional that may influence greatly the fatigue strength. The purpose of the paper is to present a way of modelling the actual weld bead shape by using a 3-D Laser scanner for experimental models of steel plates with longitudinal fillet welds, and applying its results to a proper notch stress method for the fatigue strength. The present approach to assess the fatigue strength is quite promising with application to a variety of welded joints and effects of weld profiling to fatigue strength.

• 산업기술연구
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• 제20권A호
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• pp.169-178
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• 2000

The 4-point bending tests have been performed In order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

• Journal of Welding and Joining
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• 제31권5호
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• pp.15-19
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• 2013

In order to reduce a grand compute time in prediction of welding distortion and residual stress by 3D thermal elastic plastic analysis, idealization of welding that is methods to heat input simultaneously in all weld metal on the same welding direction is carried out on two weld joints(butt welding and fillet welding). Then, the accuracy of acquired results is investigated through the comparison of the high accuracy prediction results. The thermal conduction analysis results by idealization of welding, the temperature is raised accompany with beginning of heat input because all of weld metal is heated input at the same time. On the other side, the temperature witch predicted with high accuracy is raised at the moment heating source passes the measuring points. So, there is difference of time between idealization of welding and considering of moving heat source faithfully. However, temperature history by idealization of welding is well simulated a high accuracy prediction results.

• 한국해양공학회지
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• 제18권6호
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• pp.79-83
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• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• Journal of Welding and Joining
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• 제15권4호
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• pp.63-69
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• 1997

Welding distortion is more serious problem than any other problems caused by welding process, especially, in the heavy-industrial place. These welding distortions are caused by nonuniform heating and cooling of metal during and after welding operations. And these distortion quantities are must be known to worker in production line because distorions are important role in assembling part. Therefore an analytical model to explain and predict the welding distortion are needed. A numerical analysis of welding distortion which is inelastic behavior of weldment would require the three dimensional calculation. But computing time and memory would be very large, and the resulting cost might be unacceptable. Therefore we use a numerical technique for two dimensional analysis in the section normal to the weld direction of weldment under an assumption of quasi-stationary conditions. But the result of the calculation under two dimensional(plane strain) assumption was not satisfied as compared with experimental result. This paper proposed a technique for analysing the welding angular distortion by using a constraint boundary condition on the two dimensional finite element model. The simulation results revealed that the constraint boundary model could more reasonably describe the welding distortion than the plane strain model did.

• 소성∙가공
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• 제27권5호
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• pp.296-300
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• 2018

T-type and H-type section steels were generally used in shipbuilding and offshore plants and were produced by welding technology. These section steels were produced by handwork, and the supplying amounts can't satisfy the demand amounts of the fabrication companies. In case of fillet welding, there are some gaps in weld-joint region due to no groove preparation processing and it can occur crack initiation in the welded region. It is important to evaluate the microstructural and mechanical properties of welded zone to solve these problems. To satisfy the demand amounts of T-bar parts, automatic welding technology was introduced and several conditions as a function of welding speeds were carried out to improve the manufacturing speed. Heat-affected zone may be affected by variation of heat input and cooling rate through automatic welding speed and welding speed is necessary to be optimized. In this study, fusion zone and heat-affected zone were investigated by microstructural and mechanical analysis and were evaluated whether the welded parts were sound or not.