• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.63-68
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• 2001

SG-365 steel is an important material and used for manufacturing a pressure vessel which the gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the an unloading compliance method according to the ATM E813-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the $J_IC. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides, it improves the accuracy of toughness values, decreases the scattering of them and tunneling and shear lip by the side groove.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.519-523
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• 2008

Poisson's ratio is one of elastic constants of elastic solids. However, it has not attracted attention due to its narrow range and difficult measurement. Transverse wave velocity as well as longitudinal wave velocity should be measured for nondestructive measurement of Poisson's ratio. Hard couplant for transverse wave prevents transducer from scanning over specimen. In the present work, a novel measurement of Poisson's ratio distribution was proposed. Immersion method was employed for the scanning over the specimen. Echo signals of normal beam longitudinal wave were collected. Transverse wave modes generated by mode conversion were identified. From transit time of longitudinal and transverse waves, Poisson's ratio can be determined without information of specimen thickness. This technique was demonstrated for aluminum and steel specimens.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.111-118
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• 2007

Hydroforming is a cost-effective way of shaping malleable metals such as steel into lightweight, structurally stiff and strong pieces. With the increased use of the hydroformed components in automotive and aerospace industries, it is important to know the variations of the mechanical properties in the hydroforming process far the safe and durable design purposes. The principal goal of this paper is to suggest a procedure to evaluate the variations of tensile and fatigue properties before and after a hydroforming process. A miniature specimen, which is 0.2 mm thick and 2.3 mm wide, is devised and tested to measure local mechanical properties. The effects of specimen size, defects, surface roughness, and hydroforming on the tensile and fatigue behaviors are discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1091-1096
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• 2001

Generally, in a steel girder and the concrete slab act as a composite structure, the connectors must have adequate strength and stiffness. If there are no horizontal or vertical separations at the interface, the connectors are described as rigid, and complete interaction can be said to exist under these idealized circumstances. In previous study, it was considered that the strength of stud is affected by the stud diameter, height of stud and compressive strength of concrete. The differences between previous study and this study are variables, which are shank diameter of shear connector, the spacing of shear connector, the size of specimen and the row of shear connector. So this paper, as a study on the strength of shear connector with the spacing of shear connector, size of specimen (block-out size), row of shear connector and shank diameter of shear connector resulted from the push-out specimen are conducted with ABAQUS program. It is to investigate the effects of characteristics of these factors. The load-slip relations obtained from the experiments are compared with those of analyses. From these results, the trends of stress are stress estimated and compared with push-out test.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.175-180
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• 2002

Regardless of the carbonation of concrete is one of the importants causes of corrosion of reinforing steel in concrete with the cloride attack and the frost damage, the investigacion about the carbonation of concrete is limited and each investigator experiments under different condition. In this paper, the effect of temperature, relative humidity, concentration of $CO_2$, type of specimen, etc., were investigated according to the accelerated carbonation test. The principal conclusions from this research were as follows: 1) The carbonation of concrete is higher in olden of, under environmental condition(temperature-relative humidity, concentration of $CO_2$, ) of 40-40-10＞40-50-10＞40-60-5＞20-60-5. 2) Under same environmental condition, the carbonation of concrete in $\Phi$10$\times$20cm cylinder specimen is 2-8% higher then 10$\times$10$\times$40cm specimen.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.139-144
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• 2004

Dynamic crack initiation in ductile steel is investigated by means of impact loaded 3 point bend(PB) specimens. Results from non-viscoplastic and viscoplastic materials are compared. Their materials are applied with various impact velocities and static strain rates. The specimen has the size 320${\times}$750 mm with a thickness of 10 mm. A modified 3PB specimen design with reduced width at the ends has been developed in order to avoid the initial compressive load of the crack tip and also to avoid the uncertain boundary conditions at the impact heads. Numerical simulations are made by using the FEM code ABAQUS. Therefore, their results are plotted by shapes of the von Mises plastic stress and equivalent plastic strain of the specimens applied by various impact velocities.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.216-218
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• 2000

In case of hardfaced wrapping roll, beadmark shape appear at wrapping roll surface due to irregular wear between weld bead. Irregular wear of this is caused by difference of hardness between weld bead. This study aims at investigating which matrix is good for removing of beadmark at wrapping roll surface. So, we make specimen with martensitic matrix and austenitic matrix. The hardfacing alloys were deposited 4 times on a SS41 steel plate using self-shielding flux cored arc welding method. Difference of hardness between weld bead of specimen with matrix of martensite was higher than specimen with matrix of austenite both as-welded and after heat treatment. Therefore, austenitic matrix is better than martensitic matrix for removing of beadmark of wrapping roll surface.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.178-179
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• 2014

Corrosion is very serious problem in RC structure under ocean environment. There is no enough experiment information using the reinforced geo polymer concrete applied by electo chemical protection system. Three condition, such as tidal zone, submerged zone and crack were simulated to geo polymer specimen. Corrosion rate and natural electrode potential were measured through accelerated test. Anti corrosion property of geo polymer was better than OPC regardless of specimen condition and applied time.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.408-415
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• 1997

Bond strength of reinforcing bar to high-performance concrete using Belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that for the group with portland cement I using superplasticizer additional slump does not decrease the bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfy the modification factor for top reinforcement. The result also show that bond strength is function of square root of concrete compressive strength and cover thickness. More detailed evaluation will be conducted from the test specimen with high strength concrete using the belite cement.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.52-57
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• 1997

Electronic Speckle Pattern Interferometry(ESPI) using the Model 95 Ar. laser, a video system and an image processor was applied to the in-plane displacement measurements. Unlike traditional strain gauges or Moire method, ESPI method requires no special surface preparation or attachments and can be measured in-plane displacement with no special surface preparation or attachments and can be measured in-plane displacement with no contact and real time. In this experiment specimen was loaded in parallel with a loadcell. The specimen was the cold rolled steel sheet of 2mm thickness, which was attached strain gauges. The study provides an example of how ESPI have been used to measure strain displacement in this specimen. The results measured by ESPI compare with the data which was measured by strain gauge method in tensile testing.