• Journal of the Korean Society for Railway
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• v.4 no.4
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• pp.138-146
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• 2001

For the purpose of the effective maintenance of surface irregularities of rail, this paper investigates the rail service life to a bending fatigue failure of welding parts of rail on the slab track by the structures laboratory testing to derive S-N curves, a GTDAP(General Track Dynamic Analysis Program) to calculate the stresses and a modified Miner's rule to predict a fatigue life. The useful guides for maintenance of rail welded parts on the slab track are proposed in terms of a grinding period and the depth of rail surface irregularities. This study also proposed the guides for maintenance of rail welded part on the ballast track. The effects of fatigue service lives are compared one another.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.58-63
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• 2010

The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multibody dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structure with optimum arrangement of diaphragms was proposed. This work basically consists of the following two parts: part 1 focuses on multibody dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.61-66
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• 2011

The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multi-body dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structures with optimum arrangement of diaphragms was proposed. This work mainly consists of the following two parts: part 1 focuses on multi-body dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.33-42
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• 1999

In the present study, crack initiation criteria, static failure and tensile mode fatigue behavior for a rail steel are evaluated to assure the railway vehicle's safety. The transverse fissure, which is the most critical damage in the rail, is initiated by the maximum shear stress and its location is subsurface. In addition, the possibility of transition from the shear mode to the mixed mode increases with increasing the length of subsurface crack. Because of the brittleness by the welding, the fracture toughness of the welded part is lower than of the base metal. For low ${\Delta}K$, the stage II fatigue crack growth rates of the welded part is slower than of the base metal but, for high ${\Delta}K$, this different behavior for fatigue crack growth rate is nearly diminished. These trends are more remarkable for low stress ratio, R=0.1. It is believed that this behavior is caused by the change of the microstructure which that of the welded part is coarser than of base metal.

• Laser Solutions
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• v.18 no.2
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• pp.5-10
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• 2015

A tailor welded blank (TWB) is a welded blank comprised of two or more sheets with different properties - thickness, strengths or formabilities. TWBs are applied to the body panels to reduce weight and cost of the part. In this research, ultra high strength steel and high ductility steel were joined and laser tailor welded blanks were implemented. Yb:YAG laser welding tests were conducted with various welding conditions, and mechanical and geometrical characteristics of weldments were evaluated.

• Economic and Environmental Geology
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• v.18 no.2
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• pp.125-134
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• 1985

The Chisulryoung Volcanic Formation comprises a thick sequence of pyroclastic flow deposits. Six members are distinguished, each representing separate flow units, comprising weakly to intensely welded acidic tuffs. A stock of welded acidic tuff, 1 km in diameter, intrudes hornblende granodiorite and sediments of Late Cretaceous age and the lower part of the Chisulryoung Volcanic Tuff Formation and may represent the vent through which the upper flows of the Chisulryoug Volcanic Formation were erupted.

• Journal of Power System Engineering
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• v.21 no.1
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• pp.57-62
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• 2017

The flexible joint with bellows and flange is made by welding bellows and flange in general. The welded parts cause a crack or demage in the flexible joint due to continuous vibration and fatigue limit. This paper is concerned with development of flexible joint with non-welded, free rotation of flange and non-packing to improve fatigue failure condition between bellows and flange. The support box and support plate that are components of press part are designed to compress fore-end of bellows only without demage of bellows. The production system of flexible joint is designed with piston attached on the compression side. The simulation is performed using Deform 3D software. As the result of simulation, the shape of compressed bellows was most proper in the compression power of $157kg{\cdot}f$ and any deformation has not occurred at a part besides fore-end. The result show that the production possibility of the designed flexible joint.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.28-33
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• 2014

Vibro ripper worked by high frequency vibration is developed to do rock fragmentation and work of ripper is the different concept with other existing breakers. The gear box-shank welded joint of vibro ripper is very important part to deliver vibromotive force to tooth, so this part should endure high frequency vibration environments. The purposes of this study are to choose the optimal welding conditions for fatigue strength. The conditions were made using three kind of shank materials and two kind of filler metals. Shank materials are Hadox-hituf, Posten80 and AR400, and filler metals are CSF-71T and CSF-81T. The fatigue test was conducted each condition. Fracture surface was observed to estimate fracture characteristics of welded joint using SEM.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.1-7
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• 1996

The stress concentration factor gives the significant effect the fatigue strength of welded joints. The model used herein is the type of the load carrying fillet welded cruciform joint with full or partial penetration. In order to obtain the stress concentration factor at the weld toe of fillet joint, the reasonable element size of the toe part is investigated and the stress analysis for the series models by FEM under tensile load is performed. On the basis of the calculation results, the estimated formulae for the stress concentration factor(Kt) at weld toe part of the fillet welded joint, which the effect of toe radius, flank angle and other parameters are taken into account, is derived.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.793-799
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• 2004

In track a third weakness point is joint part, turnout part, curve part. One of them joint part of rail have been known to the most weak point by loosen of joint bar and fish bolt due to impulse and vibration by wheel contact at times. In addition happen to deformation and failure at end of rail, failure and miniature of ballast gravel. Finally impact between wheel and rail become origin cause of a welded rail, noise and vibration. riding condition deterioration, besides track failure. In the present domestic, Thermite and Gas pressure weldings have been used to continuous welded rail(CWR), however stiffness and confidence in quality is lower than Flash butt welding method. FRW have the excellent capacity, however have a shortcoming large scale of machine and power equipment. Therefore we will introduce Mobile Flash Butt Welder can weld in track.