• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.104-107
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• 2003

The ageing cause in many porcelain suspension insulators which occur on transmission and distribution line with dead-end stings is mechanical stress in interface between porcelain and cement materials. It is known that the principal mechanical stress which give electrical failure is the results of the displacement is due to cement growth. We studied an analysing method to find out a deformation of brittle porcelain with a thermal expansion of cement for suspension insulator. These simulation analysis and experimental results show that cement volume growths affect severely to be mechanical failure ageing. These simulation analysis and experimental results show that axial loading affects of Porcelain insulators severely to be mechanical failure ageing.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.446-449
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• 2006

Several experimental investigations have been carried out to study the behavior of reinforced concrete columns with short lap splices. However, very few analytical models have been developed for the analysis of such columns subjected to earthquakes. As nonlinear analysis procedures become more common in practice (such as those outlined in the Guidelines for Seismic Rehabilitation of Buildings published by the Federal Emergency Management Agency in the United States), the need for an accurate and reliable representation of the nonlinear response of strength degrading systems becomes more important. In this study, an analytical model for estimating the complete response of reinforced concrete columns with short lap splices is presented. The model is based on local bond stress-slip relationships and is validated against independent experimental data from cyclic loading tests on reinforced concrete columns with typical construction details of the 1960s. In this paper a simple equation for calculating the bar stress at splice failure is presented. Use of the proposed equation resulted in excellent agreement between the measured and calculated strength at splice failure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2072-2081
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• 1992

Theoretical fringe patterns were calculated and regenerated by using power series type Williams equations and coefficients estimated from the photoelastic data. Results of calculated values were evaluated by comparing experimental data points with the regenerated theoretical fringe loops. Statistical accuracy evaluation between regenerated fringe values and experimental ones showed that standard deviation was minimum and correlation coefficient was maximum when the first four terms of Wiliams equations were used.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.104-109
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• 1998

This document is a experimental study on fatigue life of brace mounting weld joint. A brace is used to put sub-frame together on the main frame with high strength bolts. It has low fatigue life so a patch is in need for improving a fatigue characteristics of welded joint in brace mounting This paper presents the most pertinent patch size for truck. For this, a critical stress is computed at the point of fatigue crack occurred on truck frame by finite Element Analysis. Using by this critical stress. Designers are able to determin whether fatigue crack is occurred and are able to select a pertinent patch type. And then, with a selected patch type, structural joint stiffness was estimated to compare to the conventional and other patch type or brace mounting Finally, fatigue test were performed to prove a suitability of selected prototype compare with the conventional and other patch type or brace mounting.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.77-81
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• 2008

Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Generally, the operating frequency is designed at more than resonance frequencies. When a vibrating structure starts or stops, the structure has to pass through a resonance frequency, which results in large stress concentration. This paper presents the transient thermoelastic stress analysis of vibrating cantilever beam using infrared thermography and finite element method (FEM). In FEM, stress concentration factor at the 2nd resonance vibration mode is calculated by the mode superposition method of ANSYS. In experiment, stress distributions are investigated with infrared thermography and dynamic stress concentration factor is estimated. Experimental result is agreed with FEM result within 10.6%. The advantage of this technique is a better immunity to contact problem and geometric limitation in stress analysis of small or micro structures.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.2
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• pp.79-88
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• 2001

This paper suggests to predict the failure of helical gear extrusion die. The basic assumption that constitutes the frame-work for any combined stress failure theory is that failure is predicted to occur when the maximum value of stress becomes equal to or exceeds the value of the same modulus that produces failure in a simple uniaxial stress test using the same material. The stresses which were calculated to each critical points are applied maximum normal stress theory and distor-tion energy theory. The theroretical analysis and experimental results for Samanta process and New process dies were com-pared.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.75-83
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• 2023

For three-dimensional finite element welding residual stress simulation, several methods are available. Two widely used methods are the moving heat source model using heat flux and the temperature boundary condition model using the temperature profile of the welded beads. However, each model has pros and cons in terms of calculation times and difficulties in determining welding parameters. In this paper, a new method using the moving temperature profile model is proposed to perform efficiently 3-D FE welding residual stress analysis for large structures. Comparison with existing experimental residual stress measurement data of two-pass welding pipe and SNL(Sandia National Laboratories) mock-up canister shows the accuracy and efficiency of the proposed method.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.753-762
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• 2012

The ratcheting characteristics of cylindrical shell under cyclic axial loading are investigated. The specimens are subjected to stress-controlled cycling with non-zero mean stress, which causes the accumulation of plastic strain or ratcheting behavior in continuous cycles. Also, cylindrical shell shows softening behavior under symmetric axial strain-controlled loading and due to the localized buckling, which occurs in the compressive stress-strain curve of the shell; it has more residual plastic strain in comparison to the tensile stress-strain hysteresis curve. The numerical analysis was carried out by ABAQUS software using hardening models. The nonlinear isotropic/kinematic hardening model accurately simulates the ratcheting behavior of shell. Although hardening models are incapable of simulating the softening behavior of the shell, this model analyzes the softening behavior well. Moreover, the model calculates the residual plastic strain close to the experimental data. Experimental tests were performed using an INSTRON 8802 servo-hydraulic machine. Simulations show good agreement between numerical and experimental results. The results reveal that the rate of plastic strain accumulation increases for the first few cycles and then reduces in the subsequent cycles. This reduction is more rapid for numerical results in comparison to experiments.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.35-41
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• 2000

Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.77-82
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• 1999

Resistance spot welding process is completed in very short time and there are many factors affecting on the generation of heat. It is difficult to control these experimental factors and monitor distribution of the temperature and stresses in the experimental analysis case. and too much time and expense are required for the experimental trials to fine proper welding condition. So numerical analyses have been attempted steadily, but most numerical analyses on the resistance spot welding are mainly focused on thermal behavior. Therefore, in this paper, the numerical analysis of mechanical behavior as well as heat conduction is carried out for the spot welding process. For this numerical analysis, axial symmetric computer program for the spot welding analysis by F.E.M. has been developed considering heat conduction and thermal elastic-plastic theory. Material properties depending on temperature such as density, heat conductivity, heat expansion coefficient, specific heat, yield stress, elastic modulus, and specific resistance are considered. Using the results of temperature distribution obtained from heat conduction analysis, the thermal elastic-plastic analysis is carried out to clarify mechanical behavior of spot welded specimen. In order to evaluate the effect of residual stresses, numerical analyses are carried out under tension-shear load in two cases respectively; one with residual stress, the other without residual stresses.