• 소성∙가공
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• 제20권2호
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• pp.154-159
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• 2011

The roll die forming (RDF) process is a new manufacturing technique for producing gear parts such as clutch drum and clutch hub in automotive transmission. In the RDF process, the material is deformed by a roll installed on a die set. Excellent productivity, low forming load and improved dimensional accuracy have quantitatively been shown to be the benefits of the RDF. In this study, the RDF process is applied to manufacture a clutch hub with a gear shaped part. A finite element (FE) analysis was performed in order to investigate the material strain field and dimension of the final product. Based on the result of the FE analysis, a RDF experiment was performed and the dimensional accuracy of the final product was validated. This work demonstrates that RDF is a process capable of producing a sound clutch hub.

• 한국정밀공학회지
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• 제26권12호
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• pp.94-101
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• 2009

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. The sleeve spring type damper is one of the preventive measures for reducing the torsional vibration. In this study, 2-roll bending process was proposed to manufacture sleeve spring; The program to calculate the initial radius including springback effect was developed and the FEA method to analyze elasto-plastic problem was verified through analysis of 90 degree bending process. The elasto-plastic analysis of 2-roll bending process was carried out by the FEA method verified to set a new criterion, and the new process design parameter(contact angle) in the 2-roll bending process was proposed.

• 한국정밀공학회지
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• 제30권10호
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• pp.1087-1093
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• 2013

In this study, a measurement method of double ball-bar is proposed to measure the geometric errors of an ultra-precision roll mold machine tool. A volumetric error model of the machine tool is established to investigate the effects of the geometric errors to a radius error and a cylindricity of the roll mold. A measurement path is suggested for the geometric errors, and a ball-bar equation is derived to represent the relation between the geometric errors and a measured data of the double ball-bar. Set-up errors, which are inevitable at the double ball-bar installation, also are analyzed and are removed mathematically for the measurement accuracy. In addition, standard uncertainty of the measured geometric errors is analyzed to determine the experimental condition. Finally, the proposed method is tested and verified through simulation.

• Tribology and Lubricants
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• 제33권3호
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• pp.98-105
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• 2017

A pin-on-disk test is performed to measure the wear volume of a ductile cast iron (DCI) roll when it wears down using a high carbon steel and two alloy steels at different sliding velocities between the roll and the material (steel). Normal pressure is set as constant and test temperatures are 400, 500 and $600^{\circ}C$. In addition, thermal softening behavior of the DCI roll is examined using a high-temperature micro-hardness tester and the surface hardness variation of the DCI roll is expressed in terms of temperature and heating time. Based on experimental data, a wear coefficient used in Archard's wear model for each material is obtained. The wear volume is clearly observed when the test temperature is $400^{\circ}C$ and sliding velocity varies. However, it is not measured at temperatures of $500^{\circ}C$ and $600^{\circ}C$ even with variations in sliding velocity. From the optical photographs of the pin and disk, the abrasive wear is observed at $400^{\circ}C$ clearly, but no at $500^{\circ}C$ and $600^{\circ}C$. At higher temperatures, the pin surface is not smooth and has many tiny caves distributed on it. It is found that wear volume is dependent on the carbon contents rather than alloy contents. Results also reveal that the variations of wear coefficients are almost linearly proportional to the carbon contents of the material.

• Elastomers and Composites
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• 제6권1호
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• pp.71-81
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• 1971

The intention of this study is to investigate the properties of polymer blend, NBR/PVC vulcanizates and blending procedures such as roll-mixing temperatures and sequences for polymer blending of NBR and PVC(resin type). The results obtained are as follows: 1. The roll temperature applied for polymer blending is around $150^{\circ}C$. At this temperature region, the degradation of rubber stock, which may be caused by heat, can be minimized and mill processing in practical application in industries can also be facilitated. 2. It is obviously necessary that a small amount of plasticizers should be added to the stock for improving processibility of roll mixing and physical properties. 3. On roll-mixing sequence, it is more effective that PVC compounded with plasticizer is added to NBR milled on hot roll. 4. The vulcanizates of the blends with different degree of polymerization of PVC ale similar to one another in properties. 5. NBR/PVC(70/30) blends shows the better physical characters than eve,-made foreign latex blend except abrasion-resistance. 6. As PVC addition ratio is increased, the physical properties such as resistance to ozone, tear, heat and oil and tensile strength, modulus, hardness have also improved, on the other hand, tension set and rebound character decreased. 7. The curve of ultimate elongation have point of inflection at the ratio of $30\sim40$ part of PVC. 8. While CR is blended, the physical properties such as brittle point, rebound and resistance to oil in high temperature have improved. 9. Polymer blend of NBR and domestic PVC is applied for the industrial utility such as rubber sole and heel, electric wire cover and oil-resistant packing, coating and gasket, printing roll, film for food packing etc.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.517-524
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• 2019

오버드라이버 허브클러치는 자동차 6단 자동 변속기 미션에 장착되어 엔진의 여유출력을 이용해 연료사용을 절감시켜주는 부품이다. 본 연구에서는 오버드라이버 허브클러치 제품에 대해 피어싱 공정 중 펀치에 가해지는 하중 및 소재 처짐량을 최소화 하고자 한다. 공정 중 펀치의 하중과 처짐량에 영향을 줄 수 있는 다이 클리어런스(die clearance)와 전단각도(shear angle) 그리고 마찰계수(friction coefficient)를 설계 변수로 설정했다. 또한 펀치의 하중과 소재 처짐량에 대해 각 설계 변수들의 영향도를 확인하기 위해 민감도 분석(sensitivity analysis)을 진행했다. 그 결과 전단 각도, 마찰 계수, 다이 클리어런스 순으로 하중 및 처짐량에 대해 민감한 것으로 조사되었다. 이를 통해 펀치의 하중과 소재 처짐량을 목적함수로 설정하고, 반응표면법(Response Surface Method)을 통해 각 설계 변수들과 목적함수의 방정식을 도출했다. 이를 통해 설정된 설계 변수들의 최적 값을 도출해 유한요소해석에 적용한 결과 펀치의 하중 및 소재의 처짐량이 기존대비 22.14% 개선됐다.

• 대한조선학회논문집
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• 제45권2호
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• pp.109-123
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• 2008

The present paper presents the CFD result for a beam wave test case. An ONR tumblehome ship model with bilge keels is used. The beam wave test is for zero forward speed and roll and heave 2DOF with wave slope $a_k=0.156$ and wavelength ${\lambda}=1.12L_{PP}$, with $L_{PP}$ the ship length. The problems is solved numerically with an unsteady Reynolds averaged Navier-Stokes approach. The free surface flow is computed using a single-phase level-set method and the motions in each time step are integrated using a predictor-corrector iteration approach which uses dynamic overset grids moving with relative ship motion. The predicted CFD results for motions and forces are compared with experimental data, showing a reasonable agreement.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문
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• pp.101-109
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• 1996

Mini-mill process which is one of the new steel -marking technologies to be able to produce the hot rolled coils by thin slab caster of ISP(In-Line Strip Production) type, will be completed in the Kwangyang Steel Works of POSCO in August, 1996, SEt-Up Model of finishing mill which consists of 5 stands is the most basic and essential in mini-mill plant. Therefore, the simulation program of Finishing-mill Set-Up model were developed in this research , using new temeprature prediction model, roll gap model and rolling physical model. Using the developed FSU program , pass schedules to produce the strips with target strip thickness of 1.8mm, 2.0mm, 2.3mm, 2.7mm an d3.0mm were also determined respectively.

• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.32-45
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• 2007

The T-50 advanced supersonic jet trainer employs the Relaxed Static Stability (RSS) concept to improve the aerodynamic performance while the flight control system stabilizes the unstable aircraft and provides adequate handling qualities. The T-50 flight control laws employ a proportional-plus-integral type controller based on a dynamic inversion method in longitudinal axis and a proportional type controller based on a blended roll system with simple roll rate feedback and beta-betadot feedback system. These control laws are verified by flight tests with various maneuver set flight envelopes and the control laws are updated to resolve flight test issues. This paper describes several concepts of flight control laws used in T-50 to resolve those flight test issues. Control laws for solving the roll-off problem during pitch maneuver in asymmetric loading configurations, improving the departure resistance in negative angle of attack conditions and enhancing the fine tracking performance in air-to-air tracking maneuvers are described with flight test data.

• 소성∙가공
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• 제26권6호
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.