• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.5
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• pp.62-73
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• 2005

The objects of this research are to establish the criteria of peel occurrence considering the shape of bond terminus and to compare the strength properties of adhesive joint of different three type such as butt joint, T-shape, and single lap Joints. The criteria of peel occurrence at the bond terminus was suggested. Peel loads of three type adhesive joint (butt Joint, T-shape specimen, single lap joint) were determined from tensile tests. Principal stress distributions of these joints were determined from finite element method analysis. Then, peel occurrence was estimated with stress singularity factor$(K_{prin})$ when the terminus shape was square, with average principal stress when the terminus shape was rounded. The conclusions are summarized as follows; (1) In the non-filleted model(e.g., butt joint, T-shape specimen), principal stress shows singularity at the bond terminus, intensity of stress(principal stress) singularity $(K_{prin})$ can use as the criteria of peel occurrence at the bond terminus. (2) In the filleted model(e.g., single lap joint), principal stress has not affected singularity at the bond terminus. Average principal stress$(K_{av})$ can use as the criteria of peel occurrence at the bond terminus.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.52-63
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• 1985

Fillet welded joints, specially in ship structure, are well known the critical part where stress concentrate or crack initiates and grows. This paper is concerned with the study of the behavior of fatigue crack growth t the root and toe of load carrying cruciform fillet welded joints under three points bending by the determination of stress intensity factor from the J-Integral, using the Finite Element Method. The stress intensity factor was investigated in accordance to the variation of the weld size (H/Tp). weld penetration (a/W) and plate thickness (2a'/Tp). As mixed mode is occurred on account of shearing force under the three points bending, Stern's reciprocal theory is applied to confirm which mode is the major one. The main results may be summarized as follows 1) The calculation formula of the stress intensity factor at the both of root and toe of the joint was obtained to estimate the stress intensity factor in the arbitrary case. 2) The change of stress field around crack tip gives much influence on each other at the roof and toe as H/Tp decreases. 3) Mode I is a major mode under the three points bending.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.79-86
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• 2014

The purpose of this study is to determine the proper fillet weld size for the stiffeners on hull bottom plate of crude oil tanker. To achieve it, the effective notch stress and hot spot stress of the fillet weld with leg length specified in the rule were evaluated by using comprehensive FE analyses. Based on the results, the fatigue damages at each location of weld were calculated. Meanwhile the transitional behavior of initial welding distortion in the hull bottom plate under the design conditions was investigated by using a non-linear FEA. Welding distortion and residual stress introduced during fabrication process were considered as initial imperfections. According to FE analysis results, if the fillet leg length satisfies the design criteria of the classification society, the concern on the root failure at the fillet welds in the bottom hull plate during the design life can be negligible. In addition, considering the transitional behavior of the distortion during the service life, the fillet leg length should be minimized.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.275-284
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• 1991

Fatigure crack growth from surface defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, ship hulls and other various structures. This paper attempts to analysis some practical or general problems such as the estimation of crack growth life to penetrate the plate thickness, based on fatigure crack growth from a single surface flaw and the interaction of multiple flaws. An experiment on the coalescence of multiple undercuts was carried out under cyclic tension condition as a attempt to the analysis of multiple crack problems. It is noted that the fracture strength is characterized by the analogy to that in a single crack growth.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.561-565
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• 2010

Stainless steel sheets are widely used as structural materials for the manufacture of railroad cars and commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For the fatigue design of gas welded joints such as fillet joints and plug joints, it is necessary to obtain information on the stress distribution at the weldment and the fatigue strength of the gas welded joints. Moreover the influence of the geometrical parameters corresponding to the gas welded joints on the stress distribution and fatigue strength must be evaluated. ${\Delta}P-N_f$ curves were obtained from the data recorded in fatigue tests. Using these results, the ${\Delta}P-N_f$ curves were rearranged according the relation between $\Delta\sigma-N_f$ and the maximum stress at the edge of the fillet welded joint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1207-1212
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• 2015

A vibro ripper utilizes high-frequency vibration for rock fragmentation. This concept is different from those used by other existing breakers. The gearbox-shank welded joint of a vibro ripper is a very important part. Because it delivers the vibromotive force to the tooth, it is important to predict its soundness. This study was conducted to predict the fatigue life under welding conditions. The shank materials were Hardox-Hituf and AR400, and the filler metals were CSF-71T and CSF-81T. Fatigue tests were conducted under each set of conditions. P-S-N curves are presented based on the statistical testing method recommended by JSME-S002, and a comparison is made of the results under each set of conditions. The life was estimated using a P-S-N curve.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.127-138
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• 1991

A gear forming method by cold extrusion and an analytical method with its numerical solution program based on the upper bound method were developed. In the analysis the involute curve was as a shape of die and the upper bound method was used to calculate energy dissipation rate. By this method the power requirement and optimum conditions necessary for extruding helical(spur) gear were successfully calculated. These numerical solutions are in good agreement with experimental data. In the experiment, 4-6 class helical gear of KS standard for automobile transmission was successfully manufactured.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.551-556
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• 2007

High pressure storage of the agent gas in fire suppression system was composed of tank, main valve and safety valve, which prevents the fracture of the high pressure storage. The safety valve has circular thin plate as fracture plate that was destroyed over fracture pressure. When inner pressure of the storage is reached the fracture pressure, the safety valve discharges gas and degrades simultaneously the inner pressure of the storage. There are design variables such as flow path diameter, inner diameter of the plastic packing ring, thickness of plate and fillet radius. In this variables, thickness of plate is set to be a value of 0.2mm. The main effect of variables on the inner pressure, has been decided using factorial design and statistical analysis. Therefore, the relation of variables are expressed by regression equation. It is disclosed results that the difference of fracture pressures between the equation and experiment has $2{\sim}5%$. Finally, using response surface method, the optimal design of the safety valve could be decided with safety pressure of 25MPa, where the fracture occurs on circular thin plate.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.779-788
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• 1998

This paper presents the results of the experimental and analytical investigation for the fatigue strength of welded details frequently used in steel bridges, especially for the details with relatively lower fatigue strength. Considering the measured stress fatigue cracking initiated at toe of the transverse fillet weld joining the gusset plates to the web because of the stress concentration that developed as a result of the geometric conditions and the greater probability of microscopic discontinuities at the fillet weld toe A comparison was made of the stress calculated by considering geometric aspect of bead and measured at same position. They indicate that the geometric conditions of the weld toe result in similar stress concentration on both FEM models and test results. The test results were compared with the fatigue criteria of AASHTO, JSSC specifications. Specimens of 80 and 150mm gusset plate configuration tested either respectively equaled or exceeded the fatigue resistance provided by category D and E of the AASHTO specification. It also satisfied the category F and G of JSSC. Both WG1 and WG3 specimen tend to provide S-N curves with a store near -0.3 less than AASHTO and JSSC.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.547-556
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• 2001

This study presents new method in which to derive the constraint coefficient from the quantity of angular deformation by welding measured by varying the shape of welded joints and the magnitude of constraints by varying the shape of welded joints and the magnitude of constraints by experiment and from the result analyzed by elastic FEM method and then to decide equivalent load with it The numerical analysis results by this new method verified the validity by agreeing with the experimental result on specimen. In addition These results are applicable to the prediction of the quantity of welding deformation for large structures regardless of the size and the shape While in the effects of the constraints based on the shape of welded joints in the case of Butt welding when the constraint coefficients are not considered the deformed quantity is produced larger than one by the experiment and consequently is largely affected by the constraints But in the case of Fillet welding the deformed quantity is seldom affected regardless of considering the constraint coefficients or not.