• 대한금속재료학회지
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• 제49권8호
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• pp.649-656
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• 2011

The present study evaluated the microstructures and mechanical properties of severely deformed Ni-30Cr alloys. Cross-roll rolling (CRR) process was introduced as a severe plastic deformation (SPD), and Ni-30Cr alloy sheets were cold rolled to 90% thickness reduction and subsequently annealed at $700^{\circ}C$ for 30 min to obtain the recrystallized microstructure. Electron back-scattering diffraction (EBSD) was introduced to analyze grain boundary character distributions (GBCDs). The application of CRR to the Ni-30Cr alloy was effective in enhancing the grain refinement through heat treatment; consequently, the average grain size was significantly refined from $33{\mu}m$ in the initial material to $0.6{\mu}m$. This grain refinement directly improved the mechanical properties, in which yield and tensile strengths significantly increased relative to those of the initial material. We systematically discuss the grain refinement and accompanying improvement of the mechanical properties, in terms of the effective strain imposed by CRR relative to conventional rolling (CR).

• 한국표면공학회지
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• 제52권4호
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• pp.227-232
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• 2019

Mo-N based coatings have been studied for enhancing mechanical characteristics of thin films. In the case of Mo-X-N coatings, the microstructure and mechanical properties can be affected by the addition of the third element. In this work, Mo-Cu-N coatings were successfully fabricated with varying the Cu content from 4.5 at% to 31 at% by the co-sputtering method. Thus, properties of the coatings were analyzed by EDS, SEM, XRD, AFM, nano indentation and scratch test techniques. From observed results, MoxN bonds were made in a nitrogen atmosphere and Cu elements were present at grain boundaries. In addition, coatings with the Cu content above 14 at% had a Cu3N peak in the XRD results. Thus, it is suggested that the formation of Cu3N phase affected the microstructure and mechanical properties of Mo-Cu-N coatings. Mechanical properties of Mo-Cu-N coatings were found to be relatively better at Cu content of about 12 at%.

• 한국재료학회지
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• 제20권2호
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• pp.104-110
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• 2010

The characteristics of all polymer composites containing carbon materials are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape. As a consequence, in this paper we discuss the aspects of the mechanical, electrical and thermal properties of composites with different fillers of carbon black, carbon nanotube (CNT), graphene and graphite and focus on the relationship between factors and properties, as mentioned above. Accordingly, we fabricate rubber composites that contain various carbon materials in carbon black-based and silica based-SBR matrixes with dual phase fillers and use scanning electron microscopy, Raman spectroscopy, a rhometer, an Instron tensile machine, and a thermal conductivity analyzer to evaluate composites' mechanical, fatigue, thermal, and electronic properties. In mechanical properties, hardness and 300%-modulus of graphene-composite are sharply increased in all cases due to the larger specific surface. Also, it has been found that the thermal conductivity of the CNT-composite is higher than that of any of the other composites and that the composite with graphene has the best electrical properties.

• 한국기계가공학회지
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• 제19권11호
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• pp.35-41
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• 2020

The structure of the femur bone was analyzed. Moreover, the mechanical strength of the bone was determined by considering two parameters, namely, the outer wall thickness and inner filling density to realize the 3D printing of a cortical bone and spongy bone by using a fused deposition modeling type 3D printer and ABS material. A basic experiment was conducted to evaluate the variation trend in the mechanical strength of the test specimens with the change in the parameters. Based on the results, the parameters corresponding to the highest mechanical strength were selected and applied to the artificial bone, and the mechanical strength of the artificial bones was examined under a load. Moreover, we proposed an approximation method for the 3D printing parameters to enable the comparison of the actual bones and artificial bones in terms of the strength and weight.

• 터널과지하공간
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• 제22권2호
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• pp.93-105
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• 2012

균열암반의 등가역학적 물성을 수치해석적으로 결정할 때 2차원 및 3차원 해석을 비교하였다. 수직균열모델과 암반균열망(DFN) 모델이 균열암반의 형상으로 이용되었으며 3차원 모델으로부터 다양한 방향으로 2차원 모델을 절단하여 역학적 물성을 비교하였다. 본 연구의 지질데이터는 영국 셀라필드 지역의 자료를 기본으로 사용하였다. 직교균열모델에서는 컴플라이언스텐서의 변환을 이용한 해석적 방법이 물성결정을 위해 이용되었으며 암반균열망모델에서는 수치실험이 실시되었다. 2차원 모델에서는 균열이 항상 모델평면과 직교한다고 가정하기 때문에 탄성계수는 항상 3차원보다 크게 계산이 되었다. 2차원 해석에서의 포아송비는 3차원 해석보다 큰 값을 나타내는 경향이 있었으나 반대의 경향도 관찰되었다. 본 논문은 3차원 형상을 단순화시켜 사용하는 2차원 해석의 한계를 정량적으로 고찰하였다는데 의의가 있다.

• Composites Research
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• 제34권2호
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• pp.96-100
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• 2021

The lightweight industry continuously demands reliable near-net-shape fabrication where the preform just out-of-machine is close to the final shape. In this study, different half-finished preforms are made π-beams. Then the preforms are unfolded to make a 3D shape with integrated structure of fibers, providing easier handling in the further processing of composites. Several 3D textile preforms are made using weaving technique and are examined after resin infusion for mechanical properties such as inter-laminar shear strength, compressive strength and tensile strength. Considering that the time and labor are important parameters in modern production, 3D weaving technique reduces the manufacturing steps and therefore the costs, such as hand-lay up of textile layers, cutting, and converting into preform shape. Hence this 3D weaving technique offers many possibilities for new applications with efficient composite production.

• 소성∙가공
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• 제22권3호
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• pp.123-132
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• 2013

Hot stamping, which is the hot pressing of special steel sheet using a cold die, can combine ease of shaping with high strength mechanical properties due to the hardening effect of rapid quenching. In this paper, a thermo-mechanical analysis of hot stamping using the finite element method in conjunction with phase transformations was performed in order to investigate the plastic deformation behavior, temperature history, and mechanical properties of the stamped car part. We also conducted a fully coupled thermo-mechanical analysis during the stamping and rapid quenching process to obtain the mechanical properties with the consideration of the effects of plastic deformation and phase transformation on the temperature histories at each point in the part. The finite element analysis could provide key information concerning the temperature histories and the sheet mechanical properties when the phase transformation is properly considered. Such an analysis can also be used to determine the effect of cyclic cooling on the tooling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.419-423
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• 2001

It is important to know the mechanical properties of the materials under dynamic load. The mechanical properties of most materials are influenced to some extent by strain rate. One of the reliable test device for determining the mechanical properties of materials at high strain rate is Split Hopkinson Pressure bar. In this paper, we conducted the mechanical properties test for the aluminium alloy 6063 and 6061 using the SHPB device.

• 한국의류산업학회지
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• 제16권6호
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• pp.1008-1016
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• 2014

This study aims to analyze the changes in the mechanical properties of woven fabrics(cotton, linen, wool, silk, and polyester) by bonding fusible interlinings with varying deniers(10D, 20D, and 30D) for a 3D virtual try-on system(one that a user to try garments through screens using Avatar) developed over the last decade. We experimented with four mechanical properties and thicknesses of twenty-three specimens of interlining bonded fabrics including face fabrics and interlinings by using the KES-FB-AUTO system. The results showed that the tensile property increased(LT and RT increased and WT decreased) as the denier of the interlining increased; however, the change was slight. In contrast, the bending and shear properties increased significantly as the denier of the interlining increased on both the warp and the weft. This showed evidence that the interlining gives the fabrics size stability. The compression property was slight changed as the tensile property varies depending on the fibers and the denier of interlining. As expected, the thickness increased by bonding the interlining as the denier of interlining increased. From these results, we conclude that 3D users need to reflect these changes of woven fabrics by bonding interlinings when they try screen fittings to accurately express the fabric reality of manufactured garment.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.292-295
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• 2002

In this paper, an analytical model for the prediction of the elastic properties of multi-axial warp knit fabric (MWK) composites is proposed. The geometric limitation, effect of stitching fibers and design parameters of MWK composites are considered in the model. The elastic behavior of MWK composites was conducted by using an averaging method. The predicted elastic properties are in reasonably good agreement with experimental values. Finally the effect of stitching in the MWK composites are discussed.