• Fibers and Polymers
• /
• 제1권2호
• /
• pp.103-110
• /
• 2000

Flow analysis of profile extrusion is essential for design and production of a profile extrusion die. Velocity, pressure, and temperature distribution in an extrusion die are predicted and compared with the experimental results. A two dimensional numerical method is proposed for three dimensional analysis of the flow field within the profile extrusion die by applying a modified cross-sectional numerical method. Since the cross-sectional shape of the die is varied gradually, it is assumed that the pressure is constant within a cross-sectional plane that is perpendicular to the flow direction. With this assumption, the velocity component in the cross-sectional direction is neglected. The exact cross-sectional shape at any position is calculated based on the geometry of standard cross-sections. The momentum and energy equations are solved with proper boundary conditions at a cross-section and then the same calculation is carried out for the next cross-section using the current calculated values. An L-shaped profile extrusion die is produced and employed for experimental investigation using a commercially available polypropylene. Numerical prediction for the varying cross-sectional shape provides better results than the previous studies and is in good agreement with the experimental results.

• 소성∙가공
• /
• 제23권6호
• /
• pp.369-375
• /
• 2014

Flexible roll forming allows profiles to have variable cross-sections. However, the profile may have some shape errors, such as, warping which is a major defect. The shape error is induced by geometrical deviations in both the concave zone and the convex zone. In the current study, flexible roll forming was modeled with FE simulations to analyze the shape error and the longitudinal strain distribution along the flange section over the profile. A distribution of analytically calculated longitudinal strains was used to develop relationships between the shape error and the longitudinal strain distribution as a function of the defined shape parameters for the profile. The FE simulations showed that the shape error is primarily affected by the deviations between the distribution of analytically calculated longitudinal strain and the longitudinal strain distribution of the profile. The results show that the shape error can be controlled by designing the shape parameters to control the geometrical deviations at the flange section in the transition zones.

• 소성∙가공
• /
• 제22권7호
• /
• pp.401-406
• /
• 2013

The use of roll-formed products increases every year due to its advantages, such as high production rates, reduced tooling cost and improved quality. However, till now, it is limited to part profiles with constant cross section. In recent years, the flexible roll forming process, which allows variable cross sections of profiles by adaptive roll stands, was developed. In this study, an attempt to optimize profile design for the flexible roll forming process was performed. An equation that predicts the longitudinal strain for part geometries with variable cross-sections was proposed. The relationship between geometrical parameters and the longitudinal strain was analyzed and investigations on the optimal profile design were performed. Experiments were conducted with a lab-scale roll forming machine to validate the proposed equation. The results show that the profile design method proposed in this study is feasible and parts with variable cross sections can be successfully fabricated with the flexible roll forming process.

• 대한조선학회논문집
• /
• 제42권4호
• /
• pp.421-426
• /
• 2005

Scattering center extraction schemes for radar cross section reduction of large complex targets, like warships, was developed, which are an 1-D radar image method(range profile), and a direct analysis based on an object precision method. The analysis result of partial dihedral model shows that the presented direct analysis method is more efficient than the 1-D radar image method for scattering center extraction of interested targets, in terms of radar cross section reduction design, not signal processing. In order to verify the accuracy of the direct analysis method, a scattering center analysis of an naval weapon system was carried out, and the result was coincident with that of another well-known RCS analysis program. Finally, an analysis result of RCS and its scattering center of an 120m class warship-like model presented that the direct analysis method can be an efficient and powerful tools for radar cross section reduction of large complex targets.

• Journal of the Korean Wood Science and Technology
• /
• 제28권2호
• /
• pp.19-24
• /
• 2000

본 논문에서는 목재시편의 횡단연적과 수분경사가 라디에타파인 심재와 번재의 초음파 전달속도에 미치는 효과를 조사하였다. 각 수분경사 모델시편은 함수율이 다른 다섯 개의 소편을 배합하여 만들었다. 횡단면적이 작아질수록 초음파 전달속도는 심재와 변재 모두 4~8% 감소하였다. 수분경사 모델시편을 투과한 초음파 신호를 분석한 결과, 횡단면적이 클수록 저주파 신호가 고주파 신호보다 분명한 주류률 이루었다. 평균 함수율이 같더라도 수분경사가 다르면 시편의 초음파 전달속도는 다르게 나타났다. 초음파 전달속도와 수분경사 모델시편의 내층 평균 함수율의 분포는 함수율에 따라 세 가지 서로 다른 형태를 나타냄이 밝혀졌다.

• 한국측량학회지
• /
• 제24권3호
• /
• pp.251-259
• /
• 2006

기존 철도의 전철화 사업 수행을 위해서는 노후 터널의 역학적 안정성 조사와 함께 건축한계의 확보가 필수적으로 이루어져야 한다. 건축한계가 확보되지 않으면 터널의 선형 개선을 토대로 한 재시공이 발생하므로 측량 자료가 요구된다. 본 연구에서는 영동선 구간의 3개 터널에 대하여 동일좌표체계의 정밀 측량을 실시하고 종횡단면도, 종단레일고, 레일경사, 횡단터널높이, 건축한계높이 등의 자료를 취득하여 직선 및 곡선 터널구간의 건축한계를 효율적으로 분석하였다. 종횡단 측량성과를 이용한 도면과 기존 설계값과 비교하여 건축한계를 분석하고 시공성을 파악할 수 있도록 전철화 설계의 안정성에 대한 평가자료로 제시할 수 있었으며, 향후에는 터널구조물의 실시간 모니터링 시스템 개발에 이의 운용성을 증대시키고자 한다.

• Elastomers and Composites
• /
• 제55권1호
• /
• pp.46-50
• /
• 2020

Material extrusion (ME)-type 3D printing is the most popular among the 3D printing processes. In this study, the cross-section morphologies of ME-type 3D printing manufactured specimens were observed with respect to the thermal properties of the material. The cross-section morphology of a specimen is related to the deposition strength, and the outside profile of the cross-section is related to the surface roughness. The filaments used in this study, with different thermal conductivities, were the acrylonitrile-butadiene-styrene (ABS), the high impact polystyrene (HIPS), the glycol-modified polyethylene terephthalate (PETG), and the polylactic acid (PLA). The cross-sections and the surfaces of the 3D manufactured specimens were examined. In ME-type 3D printing, the filaments are extruded through a nozzle and they form a layer. These layers rapidly solidify and as a result, they become a product. The thermal conductivity of the material influences the cooling and solidification of the layers, and subsequently the cross-section morphology and the surface roughness.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2001년도 학술발표회 발표논문집
• /
• pp.246-251
• /
• 2001

This study is aimed to develop system that can export height automatically with Hierarchical Delaunay Triangulation and finally provide profile of hydraulic channel using 3D terrain geometry model. In this study, by using the object-oriented technique, we developed the traverse and cross-section design system of agricultural facilities, which maintain a consistency in the irrigation design process. This system can design the traverse and cross-section profile for the line type facilities. The results of this study, as for the design based on geography, after carrying out the modeling by using TIN of which employs Delaunays algorithm, it was found that the latitudinal design of the facility is feasible. And, as for the formulation of TIN, we obtained more precise result from using contour, stream, and road data rather than using the contour by itself.

• 대한기계학회논문집
• /
• 제18권7호
• /
• pp.1643-1653
• /
• 1994

To facilitate the manufacturing of dull using CNC grinding machine, the simulation of helical groove machining with given wheel profile and setting condition is necessary. Considering the wheel as a collection of thin disks, the flute configuration is predicted in a cross section perpendicular to the axis and the grinding wheel profile is also predicted to machine the desired helical groove with given setting conditions. Two programs for these processes are developed. Using programs interactively, the helical groove machining process can be predicted more accurately. By clarifying the geometrical relation between the shape of cutting edge and the flute configuration in the cross section which is perpendicular to drill axis, it becomes possible to predict the necessary cross sectional shape of wheel for desired drill cutting edge shape. Some factors for the software are considered concerning prediction of accuracy and computing time.

• Nuclear Engineering and Technology
• /
• 제54권1호
• /
• pp.401-413
• /
• 2022

This paper provides a simple method by which to estimate the cross-section stress profiles for nozzles designed according to ASME Code Section III. Further, this method validates the effectiveness of earlier work performed by the authors on standard nozzles. The method requires only the geometric information of the pressure vessel and the attached nozzle. A PWR direct vessel injection nozzle, a PWR outlet nozzle, a PWR inlet nozzle and a BWR recirculation outlet nozzle are selected based on their corresponding specific designs, e.g., a varying nozzle radius, a varying nozzle thickness and an outlet nozzle boss. A cross-section stress profile comparison shows that the estimates are in good agreement with the finite element analysis results. Differences in stress intensity factors calculated in accordance with ASME BPVC Section XI Appendix G are discussed. In addition, a change in the dimensions of an alternate nozzle design relative to the standard values is discussed, focusing on the stress concentration factors of the nozzle inside corner.