• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.421-427
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• 2010

이 논문은 필라멘트 와인딩 공법으로 제작된 복합재 lattice 구조물에 대한 연구이다. 복합재 lattice 구조물은 helical rib과 hoop rib 구조로 이루어져 있다. 이 구조는 탄소 섬유를 에폭시에 함침 시켜 섬유의 끊어짐이 없이 연속적으로 실리콘 고무 금형의 홈 안에 필라멘트 와인딩하여 제작한 것이다. 본 연구에서는 lattice 구조물의 helical rib의 각도, 두께, 폭, 간격등을 안전율에 대하여 최적화 하는 이론을 제시하였다. 그리고 lattice 구조물의 제작방법을 기술하고 해석 및 시험결과를 기술하였다.

• 한국농공학회논문집
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• 제46권3호
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• pp.73-81
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• 2004

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surfaces and coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and CFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.307-311
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• 2011

이 논문은 필라멘트 와인딩 공법으로 제작된 cone형 복합재 lattice 구조물에 대한 연구이다. cone형 복합재 lattice 구조물은 helical rib과 hoop rib 구조로 이루어져 있다. 이 구조는 탄소 섬유를 에폭시수지에 함침 시켜 섬유의 끊어짐이 없이 연속적으로 실리콘 고무 금형의 홈 안에 필라멘트 와인딩 하여 제작한 것이다. 본 연구에서 cone형 복합재 lattice 구조물에 대한 설계 개념과 제작방법에 대해 기술하였다.

• Geomechanics and Engineering
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• 제12권2호
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• pp.295-312
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• 2017

Cast in situ and grouted concrete helical piles with 150-200 mm diameter half cylindrical ribs have become an economical and effective choice in Shanghai, China for uplift piles in deep soft soils. Though this type of pile has been successful used in practice, the reinforcing mechanism and the contribution of the ribs to the total resistance is not clear, and there is no clear guideline for the design of such piles. To study the inclusion of ribs to the contribution of shear resistance, the shear behaviour between silty sand and concrete slabs with parallel ribs at different spacing and angles were tested in a large direct shear box ($600mm{\times}400mm{\times}200mm$). The front panels of the shear box are detachable to observe the soil deformation after the test. The tests were modelled with three-dimensional finite element method in ABAQUS. It was found that, passive zones can be developed ahead of the ribs to form undulated failure surfaces. The shear resistance and failure mode are affected by the ratio of rib spacing to rib diameter. Based on the shape and continuity of the failure zones at the interface, the failure modes at the interface can be classified as "punching", "local" or "general" shear failure respectively. With the inclusion of the ribs, the pull out resistance can increase up to 17%. The optimum rib spacing to rib diameter ratio was found to be around 7 based on the observed experimental results and the numerical modelling.

• Composites Research
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• 제31권4호
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• pp.161-170
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• 2018

원통형 복합재 격자 구조체는 필라멘트 와인딩 기법으로 제작되며 제작 공정에서 발생할 수 있는 섬유체적비 불균일과 수지응집층은 구조체의 강성도 및 강도에 영향을 줄 수 있다. 구조체의 주요 요소인 후프 및 헬리컬 리브의 단면 분석을 통해 섬유체적비 불균일 및 수지응집층의 존재 여부를 확인하였으며, 단면 분석 결과를 바탕으로 후프 및 헬리컬 리브에 대한 실험 및 이론적 접근을 통해 섬유체적비 불균일 및 수지응집층이 리브 요소의 강성도에 미치는 영향을 분석하였다. 섬유체적비 불균일이 후프 리브의 굽힘 거동에 영향을 미치는 것을 확인하였으며 헬리컬 리브의 경우 섬유체적비 불균일 및 수지응집층에 의해 강성도에 변화가 있음을 확인하였다.

• Steel and Composite Structures
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• 제24권2호
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• pp.249-264
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• 2017

In this paper free linear vibration of lattice composite conical shells will be investigated. Lattice composite conical shell consists of composite helical ribs and thin outer skin. A smeared method is employed to obtain the variable coefficients of stiffness of conical shell. The ribs are modeled as a beam and in addition to the axial loads, endure shear loads and bending moments. Therefore, theoretical formulations are based on first-order shear deformation theory of shell. For verification of the obtained results, comparison is made with those available in open literature. Also, using FEM software the 3D finite element model of composite lattice conical shell is built and analyzed. Comparing results of analytical and numerical analyses show a good agreement between them. Some special cases as variation of geometric parameters of lattice part, effect of the boundary conditions and influence of the circumferential wave numbers on the natural frequencies of the conical shell are studied. It is concluded, when mass and the geometrical ratio of the composite lattice conical shell do not change, increment the semi vertex angle of cone leads to increase the natural frequencies. Moreover for shell thicknesses greater than a specific value, the presence of the lattice structure has not significant effect on the natural frequencies. The obtained results have novelty and can be used for further and future researches.

• 대한기계학회논문집B
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• 제23권5호
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• pp.678-686
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• 1999

The purpose of this work is to Investigate the pressure drop and the heat transfer characteristics in the channel of plate heat exchanger with crossed-discrete ribs. The flow is assumed to be three-dimensional, laminar and periodically fully developed. Computations have been carried out for angles of attack from $0^{\circ}$ to $90^{\circ}$ and ratios of rib height from 0.15 to 0.46 for various values of Reynolds and Prandtl numbers. The heat transfer was improved by inclined ribs generating helical vortices and secondary flows. The results show that the pressure drop has a maximum value at $70^{\circ}$ and the heat transfer has a maximum value at $45^{\circ}$. As the rib height increases, the pressure drop and the heat transfer increase quadratically, and the increasing rate of pressure drop is higher than that of the heat transfer. As Reynolds number increases, the pressure drop increases in proportion to the square of Reynolds number and the heat transfer increases linearly.

• Archives of Plastic Surgery
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• 제47권4호
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• pp.317-323
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• 2020

Background Microtia with constricted features is characterized by a short helical length of variable severity, upper antihelical or scaphal deficiency, and a downfolded upper ear. No consensus has been reached regarding the most appropriate surgical method for this condition. In this study, we aimed to introduce a simple and safe surgical method for the correction or reconstruction of upper helix ear deformities. Methods Between February 2011 and June 2014, eight patients with microtia with constricted upper helix ear deformity underwent reconstruction of the ear deformity. The upper ear helical framework was constructed by carving and curving the eighth rib cartilage harvested from the ipsilateral chest wall, covering this cartilage with a superficial temporal fascial flap, and adjusting the skin graft to align with the ear contour. To evaluate their satisfaction, patients were asked to complete a questionnaire regarding ear shape, symmetry, position, color, and overall outcome scored on a 5-point scale at 12 months postoperatively. Results None of the patients experienced severe complications in the reconstructed ear. The preoperative and postoperative vertical ear length ratios were 0.88 and 1.02, respectively. And the mean patient satisfaction scores for shape, symmetry, position, color, and overall outcome were 4.2, 4.5, 4.7, 4.4, and 4.6 out of 5 points, respectively. All patients expressed a high level of satisfaction at 12 months postoperatively. Conclusions Our technique provides a good alternative method for the reconstruction of moderate constricted upper helix ear deformities in patients who meet the surgical indications with satisfactory outcomes and few complications.

• Composites Research
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• 제33권3호
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• pp.169-175
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• 2020

콘형 복합재 격자 구조체의 강성 평가를 위한 두 종류의 시편 단위 압축 및 인장 시험을 수행하였으며 유한요소해석 결과와 비교하였다. 구조체는 높이별로 반경이 변화하는 콘형이므로 단순 압축 및 인장 시험이 어려우므로 시험 수행이 가능한 형태의 시편 및 지그를 제작하여 시험을 수행하였다. 압축 시험이 가능하도록 단위 격자 구조체를 Subelement 형태로 가공하였으며, 압축 시험을 수행하여 측정된 섬유방향 압축 변형률을 유한요소해석 결과와 비교하여 헬리컬 리브의 강성을 확인하였다. 후프 리브의 강성 평가를 위해서는 구조체에서 후프 링 시편을 가공하여 인장 시험을 수행하였다. 후프 링에 인장 하중을 가하여 굽힘 변형이 크게 발생하도록 하였으며, 두께 방향 섬유체적비를 고려한 유한요소해석 결과와 비교하여 후프 리브의 강성을 확인하였다.

• 한국농공학회논문집
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• 제46권5호
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• pp.69-77
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• 2004

FRP rebar has low bond performance than steel rebar. Usually, FRP rebar has about 60% of bond strength of steel rebar. Without adequate bond to concrete, the full composite action between reinforcement and concrete matrix can not be achieved. Therefore, FRP rebars must also have surface deformations that provide good bond to concrete. The purpose of this research was decided an optimum surface deformation patterns through bond test of FRP rebar. Eighteen surface deformation patterns of FRP rebar with widely different geometries were investigated. Based on the test results, we established optimum surfale deformation pattern. Bond tests were performed for three types of surface deformation patterns of FRP rebar including sand coated rebar, ribbed rebar, and wrapped and sand coated rebar that commercially available, and two types of FRP rebar including CFRP, GFRP rebars that optimum surface deformation pattern is applied. According to bond test results, FRP rebars that optimum surface deformation pattern is applied were found to have better bond strength with concrete than currently using FRP rebar.