• Steel and Composite Structures
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• 제23권4호
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• pp.465-472
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• 2017

This paper presents an experimental study, investigating the compressive behavior of glass-fibre reinforced and unreinforced cementitious material-filled square steel tubular (GFCMFST and CMFST) columns. The specimens were manufactured by using high performance cementitious materials without using coarse aggregate. The influence of adding glass-fibres to the mix on the behavior of both axially and eccentrically loaded columns is considered. It was found that adding glass fibre improvesthe confinement behavior, the axial compressive strength, the stiffness and the toughness of both axially and eccentrically loaded columns. The compressive strength of axially loaded columns is compared with strength predictions according to EC4 and the AISC specification. It was found that the design predictions according to EC4 and the AISC codes provide conservative results for CMFST and GFCMFST columns. Alternatively, the axial load-bending moment interaction diagrams specified in theEC4 are conservative for the eccentrically tubular CMFST and GFCMFST tested columns.

• 반도체디스플레이기술학회지
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• 제17권2호
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• pp.61-66
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• 2018

The objective of this research study is to investigate the optimal process parameters of electrical discharge machining (EDM) on SCM440 steel with copper as a tool electrode. The effect of various process parameters on machining performance is investigated in this study. Modern ED machinery is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, etc. This paper reports the results of an experimental investigation by Taguchi method carried out to study the effects of machining parameters on material surface roughness in electric discharge machining of SCM440 steel. To predict the optimal condition, the experiments are conducted by using Taguchi's L27 orthogonal array. The work material was ED machined with copper electrodes by varying the pulsed current, pulse on-time, voltage, servo speed and spark speed. Investigations indicate that the surface roughness is strongly depend on pulsed current.

• 한국정밀공학회지
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• 제10권3호
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• pp.31-40
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• 1993

The vibration-proof material normally used in structural components of precision machinery or measuring instruments requires higher damping in vibration and better characteristics in dimensional stability and rigidity to accomplish the quality assurance of the products. In this study the ferrite-resin material, which is the mixture of epoxy resin and the oxidized steel (Fe$_{3}$O$_{4}$: ferrite) in consideration of characteristics of aggregator and binder, is developed and investigated as one of vibration-proof materials. Four kinds of composite plates for experiments are made by adding another filler materials such as steel powder, granite powder and carbon-fiber sheet to the basic ferrite-resin matrix. Their characteristics are compared with a cast iron specimen which has the same bending rigidity as other specimens. The ferrite-resin material gives the best damping effect in the motor-induced vibration test. Therefore, the material can be applied to the manufacturing industry for vibration damping of machine elements.

• 한국강구조학회 논문집
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• 제28권3호
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• pp.173-183
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• 2016

본 연구에서는 HSA800 강재의 7종의 각종 시험을 실시하여 다양한 소재특성을 확인하였으며, 강도에 대한 균질성의 정량적 기준을 제안하였다. 또한 HSA800 강재가 강도에 대한 균질성의 기준을 만족하는지 검토하였다. 시험결과 HSA800 강재의 1/4지점의 소재 특성은 KS를 만족하며, 우수한 방향성, 저온에서의 내충격성이 나타났다. 또한, 제안한 강재의 강도에 대한 균질성의 기준을 만족하였다. 그러나, 마이크로조직시험 결과 2/4 지점에서 일부의 경우 조직이 뭉쳐있는 형태로 확인되어 주의가 요망된다.

• Journal of Welding and Joining
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• 제26권2호
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• pp.75-84
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• 2008

With the development of surface roughness textured steel for automotive body-in-white assemble, one of key issues is to understand the role of the surface roughness in textured steel sheets. To investigate effect of surface roughness on weldability in prepared steels, electrode force was varied. Steel sheets (T-H) with high surface roughness ($Ra\;=\;1.94\;{\mu}m$) reduced electrode life. It was attributed to the higher contact resistance at the electrode-sheet interface in the presence of the high surface roughness. The increased electrode diameter decreased current density, therefore reducing weld electrode life due to small weld button size. When an increased electrode force was used, a significant increase in the electrode life was observed in welding of high surface roughness steel sheet. This study suggested that contact resistance at the electrode-sheet interface was the dominant factor, as compared to the sheet-sheet interface for determining electrode life in welding of surface roughness textured steel.

• Steel and Composite Structures
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• 제33권6호
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• pp.823-836
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• 2019

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiral-welded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'_c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

• Journal of Welding and Joining
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• 제32권2호
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• pp.29-36
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• 2014

Recently, in order to enhance the function and usefulness of products, cladding of dissimilar materials that maximizes the performance of the material is being widely used in all areas of industry as an important process. Clad steel plate, produced by cladding stainless steel plate, an anticorrosive material, on carbon steel plate, is being used to produce pressure vessels. Stainless steel plate has good corrosion resistance, and carbon steel plate has good rigidity and strength; clad steel can satisfy all of these qualities at once. This study aims to find the ${\delta}$-ferrite behavior, mechanical properties, structure change, integrity and reliability of clad steel weld on hot rolled steel plates. For this purpose, multi-layer welding, repair welding and post weld heat treatment were implemented according to welding procedure specifications (WPS). In order to observe the mechanical properties and toughness of clad steel weld zone, post weld heat treatment was carried out according to ASME Sec. VIII Div.1 UW-40 procedure for post weld heat treatment. With heat treatment at $625^{\circ}C$, the hold time was used as the process variable, increased by intervals that were doubled each time, from 80 to 1,280 min. The structure of weld part was typical cast structure; localized primary austenite areas appeared near central vermicular ferrite and fusion line. The heat affected zone showed rough austenite structure created by the weld heat input. Due to annealing effects of heat treatment, the mechanical properties (tensile strength, hardness, impact value) of the heat affected area tended to decrease. From the results of this study, it is possible to conclude the integrity of clad steel welds is not affected much in field welding, repair welding, multi-layer welding, post weld heat treatment, etc.

• 대한소아치과학회지
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• 제26권3호
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• pp.528-537
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• 1999

Stainless steel crown은 소아치과 영역에서 가장 효과적이면서 신뢰할 수 있는 수복방법으로 그 사용이 확대되는 추세이다. 선학들의 연구에 의하면, stainless steel crown의 장착에 있어서 시멘트를 사용한 경우가 사용하지 않은 경우보다 8배 이상의 유지력을 얻을 수 있으므로, stainless steel crown 시술에 있어서 시멘트는 중요한 부분이라고 할 수 있다. 본 연구는 stainless steel crown의 접착을 위하여 임상적으로 흔히 사용되는 인산아연 시멘트, 폴리카복실레이트 시멘트, 접착용 글래스 아이오노머 시멘트의 접착력을 비교분석 할 목적으로 시도되었다. 인산아연 시멘트로 FLECK'S, 폴리카복실레이트 시멘트로는 HY-Bond, 접착용 글래스 아이오노머 시멘트로는 Vitremer, stainless steel로는 Sun-Platinum plate를 사용하였다. Bovine teeth, 글래스 아이오노머 시멘트(Fuji II LC), 아말감(Valiant)상에 3종의 시멘트로 형성된 기둥을 세워 양자간의 접착력을 측정하였고, 한편으로는 stainless steel plate 상에 3종의 시멘트 기둥을 세워 또한 양자간의 인장접착 강도를 만능시험기로 측정하였다. 측정치를 ANOVA와 Student t-test로 통계 처리하여 다음과 같은 결과를 얻었다. 1. Stainless steel crown에 대해 글래스 아이오노머 시멘트와 폴리카복실레이트 시멘트가 인산아연 시멘트보다 높은 인장결합강도를 보였고, 글래스 아이오노머 시멘트와 폴리카복실레이트 시멘트 사이에는 차이가 없었다. 2. Bovine teeth와 수복용 글래스 아이오노머 시멘트에 대해서는, 접착용 글래스 아이오노머 시멘트가 가장 높은 인장결합강도를 보였고, 다음으로 폴리카복실레이트 시멘트와 인산아연 시멘트의 순이었다. 3. 아말감 수복재에 대해서는, 폴리카복실레이트 시멘트와 글래스 아이오노머 시멘트가 인산아연 시멘트보다 높은 인장결합강도를 보였고, 폴리카복실레이트 시멘트와 글래스 아이오노머 시멘트 사이에는 유의한 차이가 없었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.77-78
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• 2006

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.380-381
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• 2005