• 한국재료학회지
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• 제2권5호
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• pp.366-374
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• 1992

S-2유리섬유직물과 폴리에스터 수지로 구성된 적충복합재료를 케블라 49 Thread로 1/2인치, 1인치 2인치 간격으로 스티칭하여 스티칭 간격에 따른 물성과 충격 강도의 변화로부터 최적스티칭 조건을 구하였으며 또한 스티칭하지 않은 적층복합재료와의 물성차를 비교연구하였다. 인장실험과 3점굽힘실험을 통해 시편의 종류별 기본 물성을 알아보았고, 234.7J의 충격에너지를 가해 시편의 파단 현상과 에너지 흡수 능력을 조사하였다. 파단에너지의 약 50% 정도인 110.2J의 충격에너지로 3회 반복실험하여 시편의 손상정도와 충격강도를 비교 검토하였다. 인장실험과 굽힘 실험의 결과 1인치 간격으로 스티칭한 시편이 가장 높은 강도를 보였으며, 충격실험에서도 가장 뛰어난 에너지 흡수능력 및 손상에 대한 저항을 보였다. 반복충격 실험의 결과 스티칭하지 않은 시편은 현저한 충격강도의 감소를 보인 반면 스티칭한 시편은 반복충격에도 에너지 흡수능력이 우수하게 유지되었다. C-scanning으로 손상부위를 관찰한 결과 스티칭으로 인해 손상영역의 확산이 억제되어 현저히 감소함을 보여주었다. 스티칭 간격이 너무 조밀한 경우 강도의 향상보다는 스티칭으로 인한 손상이 더 커져서 1/2인치 간격으로 스티팅한 시편의 경우는 인장강력이나 충격에너지 흡수가 스티칭하지 않은 시편에 비해 오히려 감소하는 결과를 나타내었다. 그러나 이러한 감소에도 불구하고 외부충격에 의한 손상영역의 확산은 효과적으로 억제되어 국부적인 손상만이 발생함을 알 수 있었다.

• Journal of Welding and Joining
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• 제13권4호
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• pp.103-112
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• 1995

This study was performed to optimize friction welding conditions of Cr-Mo steel bars used for hydraulic of pneumatic valve spools and to realize the real-time evaluation of weld quality by acoustic emission method. SNCM220, SCM435, SCAM645, and SCM415 steel bars were tested to find optimum conditions of friction welding. Auantitative equations which exhibit the relations of tensile strength, elongation, reduction of area and energy absorption with friction heating time were obtained by the experiment. Acoustic emission was also performed in the friction weldig process, and the real-time evaluation was enabled to find the optimum range of weld strength. Finally, the strength and toughness of welded joints were interpreted by the sem analysis of tensile fracture surfaces.

• 펄프종이기술
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• 제44권1호
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• pp.58-64
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• 2012

As a first step to apply PVAm (polyvinylamine) on packaging paper by surface treatment, three types of linerboards were impregnated with PVAm solution. The effect of PVAm pick-up on strength properties of linerboard was investigated. The pick-up of PVAm was controlled by varying concentration of PVAm solution. It was found that dry tensile strength, tensile energy absorption, burst strength and compressive strength of linerboard were increased by applying PVAm. In addition, wet tensile strength was significantly improved with increasing PVAm pick-up. However, folding endurance was found to be decreased with increasing PVAm pick-up.

• Structural Engineering and Mechanics
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• 제81권6호
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• pp.729-736
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• 2022

Earth is facing a serious problem of pollution and scarcity of energy sources. The synthetic fibers used in automobile and Aerospace manufacturing sectors are non-renewable and harmful to environment. International Agency such as FAA and SAE is forcing for green fuel, green materials and structures. Further exploration is much needed to understand its potential in structural applications. In the current study, hemp and Jute fibre based composites were developed and tested for assessing their suitability for possible applications in automobile and aerospace sectors. Composites were undergone tensile test, water absorption test, and fatigue analysis to understand its behavior under various loading conditions. The finite element analysis has been carried out to understand the fatigue behaviour of composites. The results revealed that the usage of hemp and jute fibre reinforced composites can improve mechanical properties and have shown a viable alternative to replace synthetic fibres such as glass fibres for specific applications. Hemp reinforced bio-composites have shown better performance as compared to Jute reinforced bio-composites while water resistance characteristics for hemp is poorer to jute fibres.

• Structural Engineering and Mechanics
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• 제46권2호
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• pp.295-322
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• 2013

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.

• 폴리머
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• 제32권6호
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• pp.598-602
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• 2008

본 연구에서는 리튬이차전지용 상용 분리막에 전자선을 조사하여 가교구조를 지닌 내열성이 향상된 분리막을 제조하였고 조사선량에 의한 열적, 기계적 특성들을 평가하였다. 전자선 조사된 분리막의 열수축률은 조사선량이 증가할수록 감소하였고 AC impedance를 이용한 shutdown거동 연구 결과 전자선 조사를 하지 않은 분리막보다 우수한 shutdown 특성을 갖는 것으로 확인하였다. 또한, 전자선 조사선량이 증가할수록 분리막의 모듈러스는 향상되는 반면 인장강도와 파단 연신율은 감소됨이 관찰되었다.

• 방사선산업학회지
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• 제6권3호
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• pp.211-215
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• 2012

In this study, crosslinked polyethylene (PE) foam sheets were prepared through gamma-ray irradiation. PE foam sheets were prepared through a foaming process using sodium bicarbonate as a blowing and foaming agent. The prepared PE foam sheets were then crosslinked through gamma-ray irradiation. The crosslinking degree was increased to 86.0% with an increase in the absorption dose. The tensile strength of the crosslinked PE foam sheets was increased with an increase in the absorption dose. However, the elongation-at-break of the crosslinked PE foam sheets was decreased. The thermal decomposition temperature of the crosslinked PE foam sheets was increased to $421.2^{\circ}C$ with an increase in the absorption dose. The SEM analysis revealed that the morphology was not changed significantly after the crosslinking through gamma-ray irradiation.

• 방사선산업학회지
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• 제4권3호
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• pp.271-276
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• 2010

Epoxy resin has wide application in various industrial fields because of their good mechanical strength, superiority adhesion and low shrinkage etc. And the typical curing method for epoxy resins is thermal and press compaction. However, a curing method was used electron beam process in this study. Epoxy acrylate was fabricated from mixture of epoxy, acrylic acid, tetraphenylporphyrin (TPP) and hydroquinone monomethyl ether (MEHQ) with mole ratios. Then electron beam irradiation effect on the curing of the epoxy acrylate resin was investigated various absorption dose in nitrogen atmospheres at room temperature. The dynamic mechanical and thermal properties of the irradiated epoxy acrylate resins were characterized using dynamic mechanical analysis (DMA) and thermogravimetric analyzer (TGA). And the tensile and flexural strength were measured by an universal tensile machine (UTM).

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.133-151
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• 2016

Self-Compacting Concrete (SCC) has been originally developed in Japan to offset a growing shortage of skilled labors, is a highly workable concrete, which is not needed to any vibration or impact during casting. The utilizing of fibers in SCC improves the mechanical properties and durability of hardened concrete such as impact strength, flexural strength, and vulnerability to cracking. The purpose of this investigation is to determine the effect of steel fibers on mechanical performance of traditionally reinforced Self-Competing Concrete beams. In this study, two mixes Mix 1% and Mix 2% containing 1% and 2% volume friction of superplasticizer are considered. For each type of mixture, four different volume percentages of 60/30 (length/diameter) fibers of 0.0%, 1.0%, 1.5% and 2% were used. The mechanical properties were determined through compressive and flexural tests. According to the experimental test results, an increase in the steel fibers volume fraction in Mix 1% and Mix 2% improves compressive strength slightly but decreases the workability and other rheological properties of SCC. On the other hand, results revealed that flexural strength, energy absorption capacity and toughness are increased by increasing the steel fiber volume fraction. The results clearly show that the use of fibers improves the post-cracking behavior. The average spacing of between cracks decrease by increasing the fiber volume fraction. Furthermore, fibers increase the tensile strength by bridging actions through the cracks. Therefore, steel fibers increase the ductility and energy absorption capacity of RC elements subjected to flexure.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.435-446
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• 2024

The use of cold-formed steel members is increasing day by day, especially in regions where earthquake effects are intensively experienced. Among cold-formed steel members (CFS), "channel" members are used more than other crosssectional members, especially in buildings or industrial structures. In recent years, several studies have been carried out on the axial load and flexural performance of these members under monotonic loading. In this study, CFS beam-column members were cyclically and monotonically loaded under combined axial load and biaxial bending moments, and their buckling behavior, load bearing capacity, stiffness, ductility, and energy absorption capacity were determined. For this purpose, monotonic and cyclic loading experiments were carried out on 30 CFS channel members at 15 different eccentricities. Then, material properties were determined by axial monotonic tensile and very low cycle fatigue tests for use in numerical studies. From the experimental results, the buckling modes, bearing capacities, ductility, stiffness, and energy absorption capacities of the members were obtained. The characteristics of the members were compared according to the stress state of the lips. According to the data obtained from the displacement transducer placed on the lips and on the back of the web, information about the buckling mode and curvature of the members was obtained. Finally, monotonic, and cyclic loading results were compared to determine the differences in the buckling behavior of the members.