• Journal of Welding and Joining
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• 제18권5호
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• pp.84-89
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• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• 시멘트 심포지엄
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• 28호
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• pp.54-62
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• 2001

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.90-96
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• 2009

Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. Today, injection molded parts have been increased dramatically the demand for high strength and quality applications. This report investigates that the optimum injection molding condition for minimum of shrinkage. Molding shrinkage is occurred by several reasons such as thermal shrinkage, a hardening process and compressibility. This report concentrate on shrinkage by a hardening process. As Change a holding pressure and holding time, checked deflections of X, Y, Z directions by shrinkage based on same condition. In conclusion, it was found that holding pressure is stronger and holding time is longer, the deflection by shrinkage is smaller because injection molding needs enough time for cooling and high density. The FEM Simulation CAE tool. Moldflow, is used for the analysis of injection molding process.

• Design & Manufacturing
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• 제15권2호
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• pp.36-41
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• 2021

The 3 dimensional Pipe (Annular) Shaped Products was selected as a test sample, then a attribute of a molding shrinkage according to the parameters of a injection process was examined with PC, which is the typical engineering plastic. Both the inside and the outside diameter of the Pipe (Annular) sample were shrank into the inner direction of the part. And then the comparative analysis of the samples proved that a increasing thickness led a bigger shrinkage rate in the equal outside diametric samples, and a decreasing outside diameter caused a bigger shrinkage rate in the same thickness samples. The comparative study of the cushion volume of a injection machine showed that the molding shrinkage was most affected by the pressure strength among the resin temperature, the maintenance pressure strength and the maintenance pressure duration time. Each of the shrinkage rates according to the measuring direction and the gate position was different. As a result, the injection molded sample had not a typical circular shape.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.814-821
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• 2015

본 연구에서는 섬유를 혼입한 지하층 누름콘크리트의 균열 저감 특성에 관하여 분석되었다. 섬유의 최적 혼입량과 종류를 알아보기 위해 공기량, 슬럼프, 압축강도, 인장강도 및 소성수축시험을 실시하였다. 공기량 시험결과, 섬유를 혼입한 시편들이 플레인에 비하여 높은 공기량이 나타났다. 그리고 유동성 측정결과, 섬유를 혼입한 시편들이 플레인에 비하여 40-80%낮은 슬럼프를 나타냈다. 강토 특성에서는 섬유를 혼입한 시편들이 무근콘크리트에 비하여 높은 압축 및 인장강도를 나타냈다. 소성수축 시험결과 섬유를 혼입한 시편들이 플레인에 비하여 균열발생이 감소하였으며, 특히 NY섬유를 혼입한 시편의 경우에는 균열이 발생하지 않았다. 결과적으로 NY섬유를 0.6% 혼입하였을 때 누름 콘크리트에 최적의 특성을 나타내는 것을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.118-121
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• 2000

CFRD (Concrete Faced Rockfill Dam) face slab concrete has a much capability to occur crack due to drying shrinkage, hydration heat and bas compaction etc. Because of crack of concrete induce structural problem and decrease durability of concrete, it is need to reduce crack of concrete. This is an experimental study to analyze the Control Property of Plastic Shrinkage Crack for CFRD face slab concrete. For this purpose, it was investigated and analyzed the engineering properties of plain concrete and using admixtures (polypropylene fiber, fly-ash) according to test result As the result, it was found that crack width and area of concrete using admixtures less than of plain concrete.

• 한국건축시공학회지
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• 제7권3호
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• pp.83-90
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• 2007

This study is to investigate the effects of nylon(NY) and cellulose(CEL) fiber contents on the mechanical properties of the concrete. The results were summarized as following. Test showed that increase of NY and CEL fiber contents decreased fluidity of fresh concrete, so the loss of the fluidity would be considered when they were over added. Air contents were slight increased, but they satisfied the target air content. Bleeding capacity of concrete containing fiber significantly was declined. In addition, concrete containing higher amounts of fiber retarded setting time remarkably. Plastic shrinkage crack was reduced with the use of fiber due to increasing fiber contents and changing fiber classes, and NY fibers to prevent the plastic shrinkage crack effectively. Compressive and tensile strength of almost specimens were increased when air contents of the fresh concrete were fixed according to fiber contents, and flexural strength was increased according to fiber contents. For the impact strength of specimens, the specimen containing $0.6kg/m^3$ of NY fibers, showed the most favorable impact strength, The fiber reinforced concrete using NY fibers exhibited superior mechanical performance, and it was considered that $0.6kg/m^3$ of was desirable as the most favorable adding amount.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.11-12
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• 2014

In this study, fundamental properties of concrete mixed with fiber has been analysed. Compressive strength, tensile strength and plastic shrinkage has been tested to conduct the optimum addition ratio of fiber. Effect to control press concrete's cracking has been tested. The following results could be made as the conclusion. For the flowability, slump decreased about 41-79% when all types of fiber used in the concrete. When the addition ratio of fiber is 1.2%, the slump of concrete decreased about 45%. For the strength properties. all the specimens with different addition ratio of fiber shown higher compressive strength comparing with Plain. Comparing with Plain, cracking decreased when the fiber added. Especially, when NY fiber used in the concrete, the plastic shrinkage did not occurred. In addition, Latex modified concrete(LMC) has improved superior physical and chemical properties. The properties of latex, combined with the low water-cement ratio, produce a concrete that has improved flexural, tensile, and bond strength, lower modulus of elasticity, increased freeze-thaw resistance, and reduced permeability compared to conventional concrete of similar mix design.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.112-118
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• 1999

Shrinkage behavior was investigated to obtain more accurate dimensions of injected molding parts for free and restricted shrinkage conditions. various parameters for metal inserted injection process, such as thickness of resin, holding pressure and time, mo이 temperature and restriction condition of mold, were considered for the analysis of shrinkage phenomena. For numerical analysis, MOLDFLOW software was used to find the deterministic parameters of filling time, temperature, pressure and holding time. Also , experimental shrinkage effects were measured through actual injection molding process and the resin thickness was under controlled as 3 mm , 5 mm, and 7mm for the shapes of plastic gear made of Polymide(PA) and Polyxymethlene(POM). The main parameters of these injection processes were found to be holding pressure, holding time and mold temperature in the case of metal inserted molding.

• 토지주택연구
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• 제7권4호
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• pp.323-328
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• 2016

아파트의 슬래브에는 전기등박스 매입을 위한 소형 박스 개구부가 존재한다. 이 박스 개구부 주변에는 건조수축으로 인한 균열을 방지하기 위하여 일부에서는 용접철망이나 플라스틱 링 등으로 보강한 상세를 적용하고 있다. 이러한 보강의 타당성을 검토하고 경제적인 대안을 모색하기 위하여 여러 가지 대안으로 보강을 한 슬래브 전기박스 주변의 건조 수축량을 측정하여 분석하였다. 등박스 주변의 보강방법 대안은 기존에 여러 건설사에서 사용되고 있는 용접철망보강안과 플라스틱링 보강안 및 보강을 하지 않은 무보강안 3가지로 하여 비교 분석하였다. 여기서 대상으로 한 아파트는 전용면적 $59m^2$ 이하의 소형평형을 대상으로 하였고 거실 등의 슬래브 하부에 전등박스 주변에 신축량 측정용 팁을 부착하고 컨텍게이지로 신축량을 측정하여 분석하였다. 측정 결과 3가지 대안들에서 상호간의 유의미한 차이가 나타나지 않았고 전반적인 변형량은 $-264{\mu}{\varepsilon}{\sim}+216{\mu}{\varepsilon}$의 범위에 있는 것으로 나타났다. 측정한 변형량의 추이는 거푸집 탈형일 기준치에서 3~5주까지는 조금씩 증가(+)하다가 그 이후 감소하여 수축(-)하는 경향을 띠고 있으며, 한두번의 측정을 제외하고는 변형률이 $+120{\mu}{\varepsilon}$ 이내의 범위에 있는 것으로 나타내고 있어, 콘크리트의 인장 균열 발생 가능성이 매우 거의 없었다.