• 한국지반공학회논문집
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• 제20권8호
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• pp.181-191
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• 2004

옹벽의 벽면이 거친 경우에 강성옹벽에 작용하는 주동토압의 크기와 분포형태는 뒷채움재의 내부마찰각과 옹벽의 벽면마찰각 뿐만 아니라 뒷채움재에서 발생하는 아칭효과와 파괴면의 형상에도 영향을 받는다. 따라서 강성옹벽에 작용하는 주동토압의 크기와 비선형의 분포형태를 정확히 산정하기 위해서는 토압 산정 시 뒷채움재에서 발생하는 아칭효과와 실제적인 파괴면의 형상을 고려해야 한다. 본 연구에서는 강성옹벽이 옹벽의 정점을 중심으로 회전하는 경우에 대하여 뒷채움재에서의 아칭효과와 실제적인 비선형의 파괴면 형상을 고려함으로써 비선형의 주동토압을 산정할 수 있는 토압산정식을 제안하였다. 그리고 제안식에 대한 정확도를 검증하기 위하여 제안식으로부터 얻어진 예측치들을 기존의 모형시험 결과들과 비교한 결과 제안식은 만족스런 토압 예측치를 제공하는 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.749-752
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• 2005

In the industry, three-dimensional coloring has been needed for realistic prototype from rapid prototyping. Z-corporation developed a 3D printer which provides three-dimensional colored prototype. However, the existing process cannot be adopted to models from other rapid prototyping process. In addition, time and cost for manufacturing colored prototype still remain to be improved. In this study, a new coloring process using ink-jet head is proposed for color printing on three-dimensional prototype surface. Process parameters such as the angle and the distance between ink-jet nozzle and the three-dimensional surface should be investigated from experiments. The correction matrix according to sloped angle to minimize the distortion of 2D image was proposed by analysis of printing error. Therefore, approximated method for angle and discrete length according to the radius of curvature for printing on the curved surface was proposed. By printing image on the doubly curved surface, the method was verified. As a practical example, helmet was chosen for printing images on the curved surface. The character images were applied with approximated method for angle and discrete length and was printed on the helmet surface.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.286-291
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• 2004

The objective of this research work is to investigate the influence of process parameters, such as power of laser, travel speed of laser and material thickness, on roughness and striation of the cut surface for the case of cutting of CSP 1N sheet using high power Nd:YAG laser with continuous wave(CW). In order to find the practical cutting region and the relationship between process parameters on the roughness and the striation, several laser cutting experiments are carried out. From the results of experiments, the allowable cutting region and an optimal cutting speed for each cutting condition have been obtained to improve the quality of the cut surface. In addition, it has been shown that the surface roughness is related to the number of striation and depth of valley of the cut surface.

• 열처리공학회지
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• 제35권3호
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• pp.139-149
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• 2022

In the automobile and shipbuilding industries, various materials and components require superior surface strength, excellent wear resistance and good resistance to repeated loads. To improve the surface properties of the materials, various surface heat treatment methods are used, which include carburizing, nitriding, and so on. Among them, carburizing treatment is widely used for structural steels containing carbon. The effective carburizing thickness required for materials depends on the service environment and the size of the components. In general, however, there is a limit in evaluation of the surface properties with a standardized mechanical test method because the thickness or cross-sectional area of the carburized layer is limited. In this regard, the nanoindentation technique has lots of advantages, which can measure the mechanical properties of the material surface at the nano and micro scale. It is possible to understand the relationship between the microstructural change in the hardened layer by carburizing treatment and the mechanical properties. To be spread to practical applications at the industrial level, in this paper, the principle of the nanoindentation method is described with a representative application for analyzing the mechanical properties of the carburized material.

• 품질경영학회지
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• 제48권2호
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• pp.269-282
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• 2020

Purpose: The practical design for experiments with mixtures of q components is consisted in the four types of design points, vertex, center of edge, axial, and center points in a (q-1)-dimensional simplex space. We propose a sequential method for the successful construction of the design space in Quality by Design (QbD) by allowing the different number of replicates at the four types of design points in the practical design when the quadratic canonical polynomial model is assumed. Methods: To compare the mixture designs efficiency, fraction of design space (FDS) plot is used. We search for the practical mixture designs whose the minimal half-width of the tolerance interval per a standard deviation, which is denoted as d₂, is less than 4.5 at 0.8 fraction of the design space. They are found by adding the different number of replicates at the four types of the design points in the practical design. Results: The practical efficient mixture designs for the number of components between three and five are listed. The sequential method to establish a design space is illustrated with the two examples based on the simulated data. Conclusion: The designs with the center of edge points replications are more efficient than those with the vertex points replication. We propose the sample size of at least 23 for three components, 28 for four components, and 33 for the five components based on the list of efficient mixture designs.

• 실천공학교육논문지
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• 제8권2호
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• pp.121-128
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• 2016

사출 성형 공정에서 외관 품질 문제는 대부분의 성형품에서 발생한다. 금형의 열역학적 설계 중의 하나는 어떠한 위치에서 캐비티 표면 온도가 되도록 균일하게 상승하는 것으로 수행된다. 실험적인 평가를 바탕으로 최적의 사출 성형 조건에서 성형품의 미려한 외관 품질을 위해서 캐비티 벽 온도와 다듬질 가공된 캐비티 표면이 성형품의 외관 문제를 피할 수 있는 가장 중요한 요소이다. 또한 잘못된 게이트 형식과 위치 선택은 성형품의 품질에 상당한 영향이 있어서, 각 캐비티로 부터 올바른 러너 밸런스를 유지하는 것은 매우 중요하다. 실질적으로 생산 현장에서 이행될 수 있는 사출 성형 품질을 위한 최적의 금형 설계와 실무 금형 기술 능력 향상을 위해서 현장 교육을 위한 실무적인 금형기술 과정의 교육훈련 모델을 제시하였다.

• 한국건설관리학회논문집
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• 제4권4호
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• pp.88-95
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• 2003

탈수거푸집공법은 거푸집 표면에 잉여수를 배출시킬 수 있는 구멍을 뚫고 내측에 섬유포를 부착하여 콘크리트 타설시 잉여수 및 혼입공기를 배출시키는 공법으로 시공상의 워커빌리티를 확보하면서 콘크리트 표층부 품질을 강화시킬 수 있다. 따라서 제치장 콘크리트 표면의 강도를 극대화할 뿐만 아니라, 수밀한 콘크리트 표층부를 생성하기 때문에 물이나 공기, 염분 등이 침투하기 어려워 콘크리트의 내구성을 크게 향상시킬 수 있다. 그러나 현재 국내에서는 이론적으로는 제기되고 있으나, 관련규준 및 시공방법에 대한 연구가 부재해 공사현장에서 적용할 기회가 없는 실정이다. 이에 본 연구에서는 물성실험을 통해 탈수거푸집 설계를 위한 기초자료를 제공하고, 이를 바탕으로 한 현장적용실험을 통해 탈수거푸집공법의 실용화 방안을 제안하고자 한다.

• 접착 및 계면
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• 제4권2호
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• pp.1-9
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• 2003

Epoxy-amine liquid prepolymers are extensively applied onto metallic substrates and cured to obtain painted materials or bonded joint structures. Overall performances of such systems depend on the created interphase between the organic layer and the substrate. When epoxy-amine liquid mixtures are applied onto more or less hydrated metallic oxide layer, concomitant amine chemical sorption and hydroxide dissolution appear lending to the chelate formation. As soon as the chelate concentration is higher than the solubility product, these species crystallize as sharp needles. Moreover, intrinsic and thermal residual stresses are developed within painted or bonded systems. When residual stresses are higher than the organic layer/substrate adhesion, buckling, blistering, debonding may occur leading to a catastrophic drop of system performances. Practical adhesion can be evaluated with either ultimate parameters (Fmax or Dmax) or the critical strain energy release rate, using the three point flexure test (ISO 14679-1997). We observe that, for the same system, the ultimate load decreases while residual stresses increase when the liquid/solid time increases. Ultimate loads and residual stresses depend on the metallic surface treatment. For these systems, the critical strain energy release rate which takes into account the residual stress profile and the Young's modulus gradient remains quite constant whatever the metallic surface treatment was. These variations will be discussed and correlate to the formation mechanisms of the interphase.

• 대한조선학회논문집
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• 제36권1호
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• pp.70-81
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• 1999

선체주위의 점성유동을 계산하기 위해서는 수치계산을 위한 3차원 공간 격자계가 필요하다. 본 논문에서는 타원형 미분 방정식인 Poisson 방정식의 해를 이용하여 3차원 공간 격자계를 구성하는 방법을 개발하였다. 2차원에서 사용되던 Sorenson방법을 3차원으로 확장하여 격자계의 분포 및 교차 각도를 지정하는 함수를 정의하게 하였다. 미분방정식의 해는 weighting function scheme과 modified strongly implicit procedure를 사용하여 구하였고, 3차원 내부 격자계와 경계면과의 매끄러운 연결을 위해 trans-finite interpolation을 이용하였다. 적용예로서 컨테이너 운반선과 대형 유조선 주위의 난류유동 계산을 위한 공간 격자계를 보였다.

• 대한조선학회논문집
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• 제47권4호
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• pp.543-552
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• 2010

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient $C_j$ = 0.1 and the rudder angle ${\alpha}=10^{\circ}$.