• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.87-92
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• 2008

In the load-carrying fillet weldments, which are common in ship structures, fatigue cracks can occur at the weld root, in addition to the weld toe. In particular, fatigue cracks originating from the weld root are difficult to detect and cause a significant reduction in the fatigue strength of a weldment. Therefore, it is important to note the fatigue failure mode of load-carrying fillet weldment. In this study, a series of fatigue test was carried out for the fatigue strength evaluation of longi-web connections that are typical kinds of the load-carrying fillet weldment.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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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.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.476-483
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• 2006

Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane bending load have been carried out by using both hot spot stress and structural stress methods. In this study, a derivation for the structural stress method using shell element models is discussed in detail. Finite element analysis using shell element models have been performed for the assessment of fatigue strength. As a result of the fatigue strength evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with structural stress method and measurement. Hot spot stress, however, estimated for the load carrying longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. On the other hand, drawbacks and doubts associated with applying the structural stress method such as the guidance of virtual node method have been discussed.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.31-38
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• 2001

For the horizontal fillet welding with one plate in a vertical position, there will be a higher tendency of weld metal falling down rather than for the butt-welding in flat position. Such phenomenon could bring about the overlap or deflection of weld pool, and consequently induce the poor mechanical strength of weldments. Therefore, a precise position control of welding torch in conjunction with the weld qualify plays an important role in welding robot applications. In the present study, an experimental method was proposed for deriving a mathematical model between the leg length and the welding conditions. Finally, an algorithm was proposed for weld seam tracking and improvement of the weld quality. The reliability of the proposed algorithm was evaluated through various experiments, which showed that the proposed algorithm can be very effective for tracking the weld line and simultaneously achieving the sound weld bead.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.53-61
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• 1993

One of the most interesting and promising steel groups considered for the rocket motor case, aircraft and aerospace component is the maraging(martensitic plus aging) nickel steel, developed by International Nickel Company in 1960. This material attains a very high strength with good fracture toughness by simple heat treatments which do not involve a quenching. Full strength can be obtained by "maraging" at 480.deg. for 3 hours for the 18% Ni maraging steel. The effect of heat treatments was considered on the residual stress field of 18% Ni maraging steel weldments. In experiments, various heat treatments such as stress relieve heat treatment, aging and solution heat treatment were carried out of the GTA weldments and the residual stresses were measured by using the hole drilling method. Whereas the conventional pattern of residual stress shows the stresses to be maximum along the weld centerline with tensile stress extending into the heat affected zone, the pattern in maraging steels shows the centerline stress to be compressive. After welding, a series of aging, solution heat treatment and solution heat treatment plus aging treatment were carried out and the residual stresses were measured to reveal that these heat treatments almost completely remove the welding residual stresses.

• Journal of Welding and Joining
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• v.9 no.4
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• pp.50-59
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• 1991

Large steel water pipes in Korea are joined prevalently by bell end method and welded at inside as well as outside of the pipes with the length of leg which is same as or larger than the thickness of pipes. This results in an excessive consumption of material and labor compared with foreign counturies such as USA, so that in our recent situation of requiring a number of water pipes such consumption is very ineffective and an improvement in weld design of water pipes is urgently necessary. In this experimental study, the possibility of reducing the length of leg to 85% of the pipe thickness was investigated through observations of microstructure and cross section of weldments, the tensile test, and the impact test of the field and laboratory specimens. As the results of this study, it was revealed that water pipes which have the leg of fillet about 0.8xthickness show a good weldability, have a greater strength than the base metal and absorb the enough energy to be safe in the working condition of the pipes.