• Journal of Advanced Marine Engineering and Technology
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• v.9 no.2
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• pp.126-142
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• 1985

The plane bending corrosiion fatigue test for the welded metal parats was performed in the air and in the natural sea water with and without applying cathodic protection. The specimens tested were the weld of SM41 steel plates, SM58 steel plates and of SM41 to SM58, which were all prepared by submerged arc welding. The main results obtained from the experiment are summarized as follows: (1) In case with SM41 and SM58 steel plates, lower value of impact strength, higher value of hardness and more noble electrode potential were observed in the welded metal part than in the HAZ and base metal. Also the lowest hardness zone in the HAZ was observed with SM58 which was not found with SM41. In case with weld specimen of SM41 to SM58, the impact strength and the electrode potential of the welded metal part showed again the lowest and most noble value but the hardness value was located between those of SM41 and SM58 base metal. (2) In the fatigue test, the specimens tested in the air and under the cathodic protection were both cracked in a purely mechanical mode, but the specimens tested without cathodic protection were cracked by the combination of mechanical fracture and electro-chemical corrosion. (3) The corrosion fatigue limit of the welded metal parts of the specimen was increased by the cathodic protection. As the protection potential was varied down to -800 mV vs. SCE the fatigue limit was increased to the value tested in the air, and the maximum fatigue limit appeared at the -1, 000 - -1, 200 mV vs. SCE. However, as the protection potential was further decreased below -1, 200 mV vs.SCE, the fatigue limit of weld of SM58 and of SM41-SM58 joining was decreased but the limit was almost constant in the case of weld of SM41. (4) It is suggested that when designing steel ship the corrosion fatigue limit of welded metal parts should be stressed as a designing strength of the structure of steel ship in addition to the conventional basis considering simply tensile strength of steel and safety factor.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.605-608
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• 1999

The objective of this research is to examine whether the determination of development length for high strength concrete by the ACI Building Code 318-95 could be applied and the upped limit of compressive strength, 700kg/$\textrm{cm}^2$ is suitable. Eight beam specimens were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The beams were loaded in positive bending with the splice in a constant moment region. The variables used here were compressive strength and the space of stirrup within splice length. The results indicated that for (c$\div$Ktr)/db of the range of 1.5-2.0 compressive strength up to 800kg/$\textrm{cm}^2$ is acceptable with regard to bond strength and ductility, thus the limit of compressive strength in ACI 318-95 may be extended to 800kg/$\textrm{cm}^2$.

• Steel and Composite Structures
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• v.12 no.1
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• pp.31-51
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• 2012

Local buckling can be ignored for hot-rolled ordinary strength steel equal angle compression members, because the width-to-thickness ratios of the leg don't exceed the limit value. With the development of steel structures, Q420 high strength steel angles with the nominal yield strength of 420 MPa have begun to be widely used in China. Because of the high strength, the limit value of the width-to-thickness ratio becomes smaller than that of ordinary steel strength, which causes that the width-to-thickness ratios of some hot-rolled steel angle sections exceed the limit value. Consequently, local buckling must be considered for 420 MPa steel equal angles under axial compression. The existing research on the local buckling of high strength steel members under axial compression is briefly summarized, and it shows that there is lack of study on the local buckling of high strength steel equal angles under axial compression. Aiming at the local buckling of high strength steel angles, this paper conducts an axial compression experiment of 420MPa high strength steel equal angles, including 15 stub columns. The test results are compared with the corresponding design methods in ANSI/AISC 360-05 and Eurocode 3. Then a finite element model is developed to analyze the local buckling behavior of high strength steel equal angles under axial compression, and validated by the test results. Following the validation, a finite element parametric study is conducted to study the influences of a range of parameters, and the analysis results are compared with the design strengths by ANSI/AISC 360-05 and Eurocode 3.

• Computers and Concrete
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• v.6 no.5
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• pp.357-376
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• 2009

In the design of concrete columns, it is important to provide some nominal flexural ductility even for structures not subjected to earthquake attack. Currently, the nominal flexural ductility is provided by imposing empirical deemed-to-satisfy rules, which limit the minimum size and maximum spacing of the confining reinforcement. However, these existing empirical rules have the major shortcoming that the actual level of flexural ductility provided is not consistent, being generally lower at higher concrete strength or higher axial load level. Hence, for high-strength concrete columns subjected to high axial loads, these existing rules are unsafe. Herein, the combined effects of concrete strength, axial load level, confining pressure and longitudinal steel ratio on the flexural ductility are evaluated using nonlinear moment-curvature analysis. Based on the numerical results, a new design method that provides a consistent level of nominal flexural ductility by imposing an upper limit to the axial load level or a lower limit to the confining pressure is developed. Lastly, two formulas and one design chart for direct evaluation of the maximum axial load level and minimum confining pressure are produced.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.461-471
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• 2000

This study evaluated the effect of degassing on the ceramic bond strength of two Ni-Cr alloys under varying holding time at the upper limit temperature and atmospheric conditions. Metal specimens were divided into 5 groups for each alloy according to degassing conditions prior to porcelain application no degassing, degassing under vacuum without hold, degassing under vacuum with hold for 5 min. and 10 min. respectively at the upper limit temperature and degassing in air. Total number of metal ceramic specimens was eighty and each group had eight specimens. The ceramic bond strength was measured by four-point flexural test using Instron and the fractured surface was examined under SEM. The results obtained were as follows. 1. Degassing in air improved the ceramic bond strength of Ni-Cr alloys. 2. In degassing under vacuum, hold at the upper limit temperature was advantageous to the ceramic bonding of Ni-Cr alloys. 3. After ceramic metal bond test, metal surfaces were partially covered with the thin porcelain layer, and the cohesive failures in porcelain were predominant in groups showing higher ceramic bond strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1444-1450
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• 2003

The fatigue life and tensile strength of JLF-1 steel (Fe-9Cr-2W-V-Ta) and its TIG weldment were investigated at the room temperature and $400^{\circ}C$. Four kinds of test specimens, which associated with the rolling direction and the TIG welding direction were machined. The base metal of JLF-1 steel represented almost anisotropy in the tensile properties for the rolling direction. And the base metal of JLF-1 steel showed lower strength than that of TIG weldment. Also, the strength of all materials entirely decreased in accordance with elevating test temperature. Moreover, the fatigue limit of weld metal was largely increase than that of base metal at both temperatures. The fatigue limit of JLF-1 steel decreased in accordance with elevating test temperature. The fatigue limit of JLF-1 steel decreased in accordance with elevating test temperature. The SEM fractography of tensile test specimen showed conspicuous cleavage fracture of a radial shape. In case of fatigue life test specimen, there were so many striations at crack initiation region, and dimple was observed at final fracture region as a ductile fracture mode.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.146-152
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• 2010

Recently, the applied frequency of composite materials was increased from the viewpoint of lightweight, high strength and low cost when a leisure boat and a fishing boatwere built. However, studies on the mechanical properties of composite material with ship are rare. Specially, a leisure boat and fishing boat with FRP had been built by hand lay-up method. However, the vacuum infusion method is rising recently for ship building. The manufactured these FRP plates were combined by using the adhesive. Therefore, in this study Cleavage peel strength, Shear strength and fatigue limit of adhesive bonds by tensileloading were estimated. From test results, the strengths of FRP specimens made by the vacuum infusion method are higher than that of the hand lay-up method.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.649-655
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• 2019

Fracture behaviors of SCM435 high strength bolt have been studied including macroscopic and microscopic fracture observation, Energy Dispersive X-ray Spectroscopy, Vickers hardness test and applied stress evaluation. cracks (ratchet marks) were generated by the repetitive loads acting on the bolts, initial stress of bolt and the stress concentration. The applied stress was found to be slightly higher than the fatigue limit of the material. The initial stress of bolt must be removed, and the mold temperature during the process must be maintained by room temperature. Bolts are recommended to be peened to improve fatigue limit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.19-26
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• 2010

In this paper, limit load analyses and fracture mechanics analyses were conducted via finite element analyses for the welded pipe with circumferential crack at the center of the weldment. Systematic changes for strength mismatch ratio, width of weldment, crack shape and thickness ratio of the pipe were considered to provide strength mismatch limit load. And J-integral calculations based on reference stress method were conducted for two materials, stainless steel and ferritic steel. Reference stress defined by provided strength mis-match limit load gives much more accurate J-integral.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.277-289
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• 2005

The study examines the limit strength for steel cable-stayed bridges. A case studies have been performed in order to evaluate the limit strength lot steel cable-stayed bridges using nonlinear inelastic analysis approach and bifurcation point instability analysis approach, effective tangent modulus $(E_f)$ method. To realize it, a practical nonlinear inelastic analysis condoling the initial shape is developed. In the initial shape analysis, updated structural configuration is introduced instead of initial member forces for beam-column members at every iterative step. Geometric and material nonlinearities of beam-column members are accounted by using stability function, and by using CRC tangent modulus and parabolic function, respectively Besides, geometric nonlinearity of cable members is accounted by using secant value of equivalent modulus of elasticity. The load-displacement relationships obtained by the proposed method are compared well with those given by other approaches. The limit strengths evaluated by the proposed nonlinear inelastic analysis for the proposed cable-stayed bridges with tee dimensional configuration compared with those by the inelastic bifurcation point instability analyses.