• Title, Summary, Keyword: Net shape

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Process Development to Form Net-Shape Nosing Shells by the Backward Tracing Scheme of the Rigid-Plastic FEM and Its Experimental Confirmation (강-소성 유한요소법의 역추적기법을 이용한 정밀정형 쉘 노우징 부품의 성형공정 개발과 실험적 증명)

  • Kim, Sang-Hyeon;Lee, Jin-Hui;Im, Hak-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.7
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    • pp.2118-2133
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    • 1996
  • A preform is designed by the backward tracing scheme of the rigid-plastic finite element method(FEM) for net-shape shell nosing components without machining after forming. The current process of the shell nosing requires cost-consuming machining to produce final products. Here, the backward tracing scheme of the rigid-plastic FEM, a novel method for preform design of metal forming processes, derives a sound preform for net-shape shell nosing product. The current process is simulated by the rigid-plastic finite element analysis to check the metal flow involved in the forming with a trial preform and its modified preform. The two preforms are found to be inadequate for net-shape shell nosing product. The first application of the back ward tracing scheme derives a preform producing a not-shape shell nosing product. The first application of the backward tracing scheme derives a preform producing a net-shape product numerically, but it is difficult to be formed economically as a preform. Thus an improved preform is designed by the badkward tracing scheme, which is suitable for net-shape manufacturing of the shell nosing components in view of economy of production and forming characteristics of the product. The preform in the current process and a modified preform are confirmed by a series of experiments and the results give the same deformation with the numerical ones. Finally the newly designed preform by the FEM was experimentally proved to be adequate in obtaining net-shape products.

Fundamental Studies on the Net-Shape of the Drag Net ( III ) - The Relationship between the Section Shape and the Porosity of Netting in the Bag Net - (저예망의 어구형상에 관한 기초적 연구 III)

  • 이주희
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.21 no.2
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    • pp.89-98
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    • 1985
  • As a primary step in studying the effects of the netting porosity on the net-shape in the four-seam trawling net, a series of experiments were performed changing the porosity of each panel, with the simplified mo:iel of the bag net made of porous vinyl film and that ma:ie of net webbing. These models were suspended horizontally in circularly flowing water, with two pairs of susp~nding threais to four points of symetry at the border of the bag mouth in place of both wing nets. And then, the section shape of the bag mouth photographed and the tensions on both pairs of suspending threads were measured with two load cells in circularly flowing water. From the results, the auther estimated an experimental equation from the relationship between the porosity of each panel in the bag net and the section shape of the bag mouth, h/w=k (l-Pr_u/lPr_s)

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Process Design in Shell Nosing for Net-Shape Product by the Backward Tracing Schme of the Rigid-Plastic FEM (유한요소법의 역추적기법을 활용한 정밀정형 노우징 부품의 성형 공정설계)

  • 김상현;이진희;강범수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.224-232
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    • 1995
  • A process is designed by the backward tracing scheme of the rigid-plastic FEm for net-shape shell nosing component without machining after forming. The current process of the shell nosing industry requires cost-consuming machining to produce final product . The backward tracing scheme of the rigid-plastic FEM, a novel method in preform design of metal forming processes , derives a sound preform for net-shape shell nosing product . The current process is simulated to check the metal flow involved informing with a trial preform and its modified preform. It is found that the two preforms are not suitable for net-shape shell nosing product. Finally, a preform is desinged by the backward tracing scheme, which is suitable for net-shape manufacturing of the shell nosing component.

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Billet Treatment and Die Design for Net-Shape Forming of Gear by Cold Forging (정밀정형 냉간단조 기어성형을 위한 소재처리와 다이설계)

  • Kang K.G.J.;Park H.J.;Yun J.C.;Kim J.;Kang B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.87-90
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    • 2004
  • In this paper, net-shape forming of an automobile gear is investigated. Barrel, a component of automobile start motor, is adopted as a net-shape forming. In order to accomplish the goal of net-shape forming without cutting of tooth and cam after forming, forming ability is raised through billet treatment and die design. As a technique of billet treatment spheroidizing annealing of billet to get low hardness and molybdenum disulphide coating to get low contact friction between billet and die is carried out. One of critical points of die design, fillet radii variation of tooth of die is applied to get smooth surface of barrel after cold forging. As a measurement of tooth accuracy, distance between two pins and lead-tooth alignments are investigated. Cam profile accuracy is checked with a 3D measuring instrument. Results obtained from the tests revealed reasonable result with respect to design goal. By these results, the paper shows that reasonable results can be obtained by billet treatment and die design for net-shape forming.

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Shape of the model pound net affected by wave and fish behavior to the net - Shape and tension of the model pound net affected by wave - (파동에 의한 모형정치망의 형상변화와 어류대망행동 - 파동에 의한 모형정치망의 형상과 장력변화 -)

  • Lee, Ju-Hee;Kwon, Byeong-Guk;Yun, Il-Bu;Kim, Sam-Kon;Yoo, Je-Bum;Kim, Boo-Young;Kim, Byung-Soo;Lee, Hye-Ok
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.43 no.2
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    • pp.101-115
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    • 2007
  • The pound net fishery is very important one in Korean coastal fishery and it need to grasp the characteristics of the net affected by many factors. It is considered that the structure and the shape of the pound net can be changed by the direction and speed of current, wave height, depth and conditions of sea bed. However, most of all, the speed of current and wave height influence more upon the pound net than any other factors to deform and flutter. In this study, author carried out the experiments with a model of double one-side pound net made by the similarity law as 1:100 scales at a real experimental area, and additionally the model net experiments were conducted in the circulating water channel in Pukyong National University. The author analyzed the data of transformation of shape and tension of the model pound net to recognize the characteristics of the current and wave acting on it. Regardless of the direction of flow affecting on the fish court net or bag net, the deformed angle and depth to the side panel and bottom of box nets becomes bigger as the wave gets higher and the period of wave is faster. The tension in both upward or downward tends to be changed by the speed of wave. Those value of changes occurred similarly in either fish court net or bag net. Generally, when bag net is located at upward of flow, the value of tension was bigger 10% than any other location or nets. Regardless of the setting direction, the tension of the pound net is increased in proportion to flow speed, wave height and period of wave, and it becomes bigger about 15-30% at upward to flow than downward. Where the flow is upward in the court net, the tension in the wave increased to 37% compared to the one in the flow only in the condition of flow of 0.1-0.3m/s. Where the flow is upward in the bag net, the tension in the wave increased to 52% in the flow of 0.1m/s, and the tension increased to 48% in the flow of 0.2-0.3m/s.

Resistive Net Computing Shape from Shading (명암 변화에서 형상을 재현하기 위한 저항 신경망)

  • 차국찬;최종수
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.6
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    • pp.972-981
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    • 1990
  • Many researchers have been interested in whether complex computational problems can be solved by the neural net or not. Especially, problems of early vision are integrated by Tikhonov's regularization theory. Regularization technique can be realized in resistive net. In this paper, we suggest the resistive net with upper and lower thresholder to be able to compute shape from shading and to solve its discontinuous problem. We simulate three algorithms-Horn's algorithm, resistive net and up-low thrwsholding net -with respect to three cases-fully boundary, boundary losing partly and noisy image. As being able to cope with crease and discontinuous parts, we get the good 3D shape from shading.

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Geometry of the Model Purse Seine in Relation to Enclosed Volume during Hauling Operation

  • Kim Yong-Hae
    • Fisheries and Aquatic Sciences
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    • v.3 no.2
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    • pp.156-162
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    • 2000
  • Model experiments for a purse seine were carried out in order to measure the geometry of net shape and to estimate an enclosed volume by using 1177 scale model purse seine of 12.62m float line from an offshore mackerel purse seine. A model purse seine was set from a net box of shooting equipments and then pursing and hauling net by hauling equipment. The 3- D geometry shape of the purse seine net during hauling operation was measured by video image processing and tension of purse line by load cell. The 3-D geometry of the model purse seine during hauling operation could be represented with variables such as a ratio of shooting diameter or maximum net depth and a ratio of hauling operation time. Horizontal shapes of float line and lead line were varied from a circle after shooting to an ellipse with pursing and hauling. Projected lateral shape of purse line was observed and formulated as a shape of a water drop. The cross sectional shapes of curved net from two directions were varied such as sine function or polynomial curves. Therefore, enclosed volume of a purse seine in relation to fish school behaviour can be approximated using two main variables from relevant equations.

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Model test on the net mouth shape of a gape net according to current speeds in Jindo area, Korea (전남 진도지역 낭장망의 유속에 따른 망구형상 변화에 관한 모형실험)

  • Kim, Seonghun;Lee, Donggil;Lim, Jihyun;Park, Seongwook
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.51 no.1
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    • pp.146-153
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    • 2015
  • A model net experiment of the gape net for anchovy in Jindo, Jeollanam-do was carried out to investigate the net shape and hydrodynamic resistance using circulating water channel. The model net was made 1/33 down scale by Tauti's similarity method and the range of experimental current speed was from 0.5 knot to 3.5 knot (increasing 0.5 knot interval). The net mouth height in 0.5 knot of the minimum experiment current speed was shown 26.0 cm (full-scale conversion value 8.58 m). The net mouth height and mouth area in 1.5 knot of the same current speed with a gape net fishing ground were shown 20.0 cm (full-scale conversion value : 6.60 m) and about $507.9cm^2$ (full-scale conversion value : $55.31m^2$). The net mouth height and area were decreased with increase the experimental current speed. The hydrodynamic resistance of the model net in 1.5 knot current speed was shown 1.11 kgf and the value of full-scale conversion by Tauti's method was shown 3.996 ton.

A Planting Study on the Development of Eco-friendly Reinforced Earth-Retaining Wall Using Planting Green Net (환경친화형 그린넷 보강토 옹벽 개발을 위한 식생시험 연구)

  • Chung, Dae-Seouk
    • Journal of Environmental Science International
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    • v.16 no.9
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    • pp.1099-1102
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    • 2007
  • This paper presents eco-friendly planting method to overcome the problems of existing concrete retaining wall and gabion retaining wall, respectively, based on the examination on existing concrete and gabion retaining wall. Prior to doing this, proper design method was provided through pull out test. Planting method using gabion metal net and L shape green net retaining wall were compared and analyzed. According to this study, it is confirmed that reduction of construction period and economical profit in construction can be achieved by both manufacturing at the factory and self procurement at the job site as well as the use of metal net, which is applied as a substitution of existing strengthening material. For the effect of planting method, the use of L shape green net retaining wall shows superiority to environment-friendly gabion retaining wall in its ability to rootage and germination of the grass. The L shape green net retaining wall had excellent performance in helping rootage of grass and prevention of soil leakage, and even if raining period, remarkable damage of planting mat does not occur when planting mat is applied.