• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.20-26
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• 2012

The objective of this study is to assess plastic deformation in aluminium alloy by acoustic nonlinearity of laser-generated surface waves. A line-arrayed laser beam made by high-power pulsed laser and mask slits is utilized to generate the narrowband surface wave and the frequency characteristics of laser-generated surface waves are controlled by varying the slit opening width and slit interval of mask slits. Various degrees of tensile deformation were induced by interrupting the tensile tests so as to obtain aluminum specimens with different degrees of plastic deformation. The experimental results show that the acoustic nonlinear parameter of a laser-generated surface wave increased with the level of tensile deformation and it has a good correlation with the results of micro-Vickers hardness test and electron backscatter diffraction (EBSD) test. Consequently, acoustic nonlinearity of laser-generated surface wave could be potential to characterize plastic deformation of aluminum alloy.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.113-123
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• 2006

An experimental investigation on the behavior of reinforced concrete coupling beams is presented. The test variables are the span-to-depth ratio, the ratio of flexural reinforcements and the ratio of shear rebars. The distribution of arch action and truss action which compose the mechanism of shear resistance is discussed. The increase of plastic deformation after yielding transforms the shear transfer by arch action into by truss action. This study proposes the deformation model for reinforced concrete coupling beams considering the bond slip of flexural reinforcement. The strain distribution model of shear reinforcements and flexural reinforcements based on test results is presented. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. The flexural-shear failure mechanism determines the ultimate state of RC coupling beams. It is expected that this model can be applied to displacement-based design methods.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.51-61
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• 2002

In this research, a numerical algorithm is developed for the response analysis of burined pipelines considering longitudinal permanent ground deformation(PGD) due to liquefaction induced lateral spreading. Buried pipelines and surrounding soil are modeled as continuous pipelines using the beam elements and a series of elasto-plastic springs represented for equivalent soil stiffness, respectively. Idealized various PGD patterns based on the observation of PGD are used as a loading configuration and the length of the lateral spread zone is considered as loading parameter. Numerical results are verified with other research results and efficient applicability of developed procedure is shown. Analyses are performed by varying different parameters such as PGD pattern, pipe diameter and pipe thickness. Through these procedures, relative influences of various parameters on the response of buried pipeline subject to longitudinal PGD are investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2021-2026
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• 2013

In this study, the effect on the welding angle distortion was reviewed by carrying out a thermal elastic-plastic analysis while changing the cooling condition(width, length, and distance from weld torch to cooling torch) the back of the welding zone for the butt weld joint. The review results revealed that maximum 57% of reduction in the angle distortion was achieved when the distance between weld torch and cooling tip of 25mm, cooling length of 80mm, and cooling width of 30mm were maintained.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.561-570
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• 2003

This study evaluate the characteristics of stainless steel for the use of stainless steel tubes as structural members. The strength of stainless steel tube was compared with that of steel tube stub-columns through tensile experiment and compressed experiment. The selected experimental parameters were diameter (width)-thickness and section shape. The results of tests showed that stainless steel tubes could be predicted as superior to steel tubes in terms of tensile strength, yield ratio, elongation percentage, and absorption ability of energy. The yield strength of stainless steel tubes were found to be higher than the Korean Standards ($Fy=2.1tf/cm^2$) and the design strength of SIJ-ASD($Fy=2.4tf/cm^2$). It was also higher then the yield strength of steel tubes. The plastic deformation of stainless steel tubes was found to beto that of steel tubes.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.169-179
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• 1994

Recently the construction of residential buildings faces many difficulties due to the shortage of building materials and works. Simplifying the stage of processing and assembling reinforcing rods and increasing the efficiency of them in reinforced concrete construction can be used to settle the difficulties. In the respect, structural wire-fabric and loop wire-fabric is utilized. The purpose of this study, on condition of being $210kg/cm^2$ concrete strength, is to analyze the structural and flexural properties of one-way concrete slabs by testing with different reinforcing type, tensile steel ratio based with minimum steel ratio, boundary condition and splice length which affect the maximum width of crack and ductility factor. From the test results, the ductility factor is approved that the slabs using deformed bar were much better than that using wire-fabric, and 30D of splice length was appropriate in the slabs as splice length. In the control of the maximum crack width the slabs using wire-fabric and loop wire-fabric were much better than that using deformed bar.

• Transactions of Materials Processing
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• v.1 no.2
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• pp.32-39
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• 1992

대형 강괴의 자유단조 공정 중에서 코깅(cogging)작업은 강괴 단조의 초기에 단면을 줄이면서 길이 방향으로 늘리는 작업이다. 코깅 작업의 역활은 주조시 발생하는 강괴 내부의 기공을 압착시켜 제거하며 주조 조직을 파괴하여 물성치를 균질화하고 향상시키는 것이다. 그러나 대형강괴의 작업에는 제약조건이 많이 있고 작업공정에서 공정변수도 여러가지 이다. 따라서 본 논문에서는 변형해석과 온도해석을 할 수 있는 3차원 열-점소성 유한요소해석 프로그램을 개발하고, 코깅공정에서 다이의 형상과 다이폭, 다이 겹침과 엇갈리기, 강괴의 온도 구배, 압하 깊이와 패스 설계등의 여러 공정 변수의 영향을 해석하여, 단조 효과를 최대화하는 최적의 단조 공정을 예측하여 공정개선에 적용하는 것이 목적이다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.285-299
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• 1993

The objective of the present study is to analyze material flow in the metal forming processes by using computer simulation and experiment with model material, plasticine. A UBET program is developed to analyze the bulk flow behaviour of various metal forming problems. The elemental strain-hardening effect is considered in an incremental manner and the element system is automatically regenerated at every deforming step in the program. The material flow behavior in closed-die forging process with rib-web type cavity are analyzed by UBET and elastic-plastic finite element method, and verified by experiments with plasticine. There were good agreements between simulation and experiment. The effect of corner rounding on material flow behavior is investigated in the analysis of backward extrusion with square die. Flat punch indentation process is simulated by UBET, and the results are compared with that of elastic-plastic finite element method.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.625-632
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• 2008

In the companion paper (Model Development), an analytical model estimating the available rotation capacity of fully restrained beam-column connections in special steel moment-resisting frames was proposed. In this paper, two limit states were considered as the connection rotation capacity criteria: (i) strength degradation failure when the strength falls below the nominal plastic strength due to the local buckling of the beam's cross-section and (ii) low-cycle fatigue fracture caused by plastic strain accumulation at the buckled flange after only a few cycles of high-amplitude deformation. A series of analyses are conducted using the proposed model with two limit states under monotonic and cyclic loadings. Beam section geometric parameters, such as flange and web slenderness ratios, varied over the practical ranges of H-shapedbeams to observe their effect on the rotation capacity and low-cycle fatigue life of pre-qualified WUF-W connections.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.104-111
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• 2020

The purpose of this study is to investigate the flexural behavior and plastic hinge of reinforced concrete-ECC composite beams. Ordinary portland cement was used as a binder, and high volume fly ash was also used to improve the properties of ECC. An ECC designed in this study showed high tensile strain capacity of 3.0%. Three types of beams were manufactured according to the replacement length of concrete with ECC. From the bending tests, it was found that load-bearing capacity as well as ductility of beam increased with an increase in the replacement length of concrete with ECC. Curvature ductility and plastic hinge length of beam were also increased.