• Title, Summary, Keyword: Thickness of model

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Technology of Dimensional Control for Different Thickness Strip in Hot Strip Finishing Mills (열간 마무리압연에서 이종두께 강판의 치수제어기술)

  • Lee, Sang Ho;Park, Hong Bae;Park, Cheol Jae
    • Journal of Institute of Control, Robotics and Systems
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    • v.21 no.8
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    • pp.735-741
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    • 2015
  • In this paper, we suggest a dimensional controller to produce a different thickness strip without adding production facilities at the same steel. We describe the model for the non-linear thickness and speed setup, and drive a variation of the speed and thickness with Talyor expansion. The control algorithm is composed of 8 steps and the transient condition is added in order to maintain a mass flow between stands. A simulator is developed in order to verify the algorithm, and includes a non-linear rolling model, the tension model, AGC model, the disturbance model, and so on. From the simulation results by disturbances, we show that the thickness, tension and looper angle are converged to the set condition when we change the rolling conditions.

Improvement and Validation of an Overlay Design Equation in Seoul (서울형 포장설계식 개선 및 검증)

  • Kim, Won Jae;Park, Chang Kyu;Son, Tran Thai;Phuc, Le Van;Lee, Hyun Jong
    • International Journal of Highway Engineering
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    • v.19 no.5
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    • pp.49-58
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    • 2017
  • PURPOSES : The objective of this study is to develop a simple regression model in designing the asphalt concrete (AC) overlay thickness using the Mechanistic-empirical pavement design guide (MEPDG) program. METHODS : To establish the AC overlay design equation, multiple regression analyses were performed based on the synthetic database for AC thickness design, which was generated using the MEPDG program. The climate in Seoul city, a modified Hirsh model for determining dynamic modulus of asphalt material, and a new damaged master curve approach were used in this study. Meanwhile, the proposed rutting model developed in Seoul city was then used to calibrate the rutting model in the MEPDG program. The AC overlay design equation is a function of the total AC thickness, the ratio of AC overlay thickness and existing AC thickness, the ratio of existing AC modulus and AC overlay modulus, the subgrade condition, and the annual average daily truck traffic (AADTT). RESULTS : The regression model was verified by comparing the predicted AC thickness, the AADTT from the model and the MEPDG. The regression model shows a correlation coefficient of 0.98 in determining the AC thickness and 0.97 in determining AADTT. In addition, the data in Seoul city was used to validate the regression model. The result shows that correlation coefficient between the predicted and measured AADTT is 0.64. This indicates that the current model is more accuracy than the previous study which showed a correlation coefficient of 0.427. CONCLUSIONS:The high correlation coefficient values indicate that the regression equations can predict the AC thickness accurately.

Determination of Thin Film Thickness by EDS Analysis and its Modeling (EDS 분석과 모델링에 의한 박막두께 측정 방법에 관한 연구)

  • Yun, Jae-Jin;Lee, Won-Jong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.8
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    • pp.647-653
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    • 2011
  • In this study, a method to measure the thickness of thin film by EDS (energy dispersive spectroscopy) is suggested. We have developed a model which calculates the thickness of thin film from the characteristic x-ray intensity ratio of the elements in thin film and substrate by considering incident electron beam energy, x-ray generation curve, backscattering and absorption of x-ray, take-off angle of x-ray and tilt angle of the sample. We obtained the relation curve between the film thickness measured experimentally and the x-ray intensity ratio of elements. The film thicknesses calculated from the model agrees quite well with those measured experimentally. Therefore, the thin film thickness can be measured rapidly and accurately by using the model developed in this study and the x-ray intensity ratio obtained in EDS analysis.

The New Calculation Model of Film Thickness to Evaluat Asphalt Mixtures (아스팔트혼합물을 평가하기 위한 유효아스팔트 함량의 새로운 계산 모델)

  • Kim, Sung-Ho;Kim, Boo-Il
    • International Journal of Highway Engineering
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    • v.9 no.1
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    • pp.57-67
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    • 2007
  • Many researches have recently discussed about the film thickness as a good substitute or supplement for VMA or other volumetric criteria in the design procedure. Some researchers have not only proposed the specific number for the recommended film thickness, but also introduced the new calculation procedures or concepts. Each model (index model and the virtual model) has its own advantages and disadvantages in terms of the ability to account for the volumetric properties of the mixture. In this paper, the modified virtual model was proposed to combine advantages from both models. However, it cannot be disregarded the way to determine the appropriate particle shape factors for different sources and sizes of aggregates. In order to evaluate the different calculation methods, mixtures with two aggregate sources and eight gradations were designed based on the dominant aggregate size range (DASR) porosity concept. Superpave indirect tensile test (IDT) and asphalt pavement analyzer (AEA) test were used to describe the performance of mixtures. Test results indicated that the virtual model, which is the same to the modified virtual model for sphere 1:1 case, is better than the conventional standard model to define the range of the film thickness to have better performance of asphalt mixtures.

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Influence of slice thickness of computed tomography and type of rapid protyping on the accuracy of 3-dimensional medical model (CT절편두께와 RP방식이 3차원 의학모델 정확도에 미치는 영향에 대한 연구)

  • Um Ki-Doo;Lee Byung-Do
    • Imaging Science in Dentistry
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    • v.34 no.1
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    • pp.13-18
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    • 2004
  • Purpose : This study was to evaluate the influence of slice thickness of computed tomography (CT) and rapid protyping (RP) type on the accuracy of 3-dimensional medical model. Materials and Methods: Transaxial CT data of human dry skull were taken from multi-detector spiral CT. Slice thickness were 1, 2, 3 and 4 mm respectively. Three-dimensional image model reconstruction using 3-D visualization medical software (V-works /sup TM/ 3.0) and RP model fabrications were followed. 2-RP models were 3D printing (Z402, Z Corp., Burlington, USA) and Stereolithographic Apparatus model. Linear measurements of anatomical landmarks on dry skull, 3-D image model, and 2-RP models were done and compared according to slice thickness and RP model type. Results: There were relative error percentage in absolute value of 0.97, 1.98,3.83 between linear measurements of dry skull and image models of 1, 2, 3 mm slice thickness respectively. There was relative error percentage in absolute value of 0.79 between linear measurements of dry skull and SLA model. There was relative error difference in absolute value of 2.52 between linear measurements of dry skull and 3D printing model. Conclusion: These results indicated that 3-dimensional image model of thin slice thickness and stereolithographic RP model showed relative high accuracy.

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Estimation of Empirical Fatigue Crack Propagation Model of AZ31 Magnesium Alloys under Different Specimen Thickness Conditions (AZ31 마그네슘합금의 시편두께 조건에 따른 실험적 피로균열전파모델 평가)

  • Choi, Seon Soon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.2
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    • pp.646-652
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    • 2014
  • It is the primary aim of this paper to propose the empirical fatigue crack propagation model fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions. The empirical models estimated are Paris-Erdogan model, Walker model, Forman model, and modified-Forman model. The parameters of each model are estimated by maximum likelihood method. The statistical crack growth data needed for an estimation of empirical models are obtained by fatigue crack propagation tests under the three cases of specimen thickness. It is found that the good empirical models fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions are Paris-Erdogan model and Walker model. It is also verified that a fatigue crack growth rate exponent of a empirical model may be a material constant at the specimen thickness conditions of 4.75mm and 6.60mm.

Numerical and Experimental Analysis of Laminated-Film Thickness Variation in Vacuum-Assisted Thermoforming (열진공성형에서 적층필름 두께변화에 대한 수치 및 실험적 해석)

  • Lee, H.S.;Yoo, Y.G.
    • Transactions of Materials Processing
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    • v.22 no.3
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    • pp.171-177
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    • 2013
  • Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding (FIM) to make parts of complex shape. If the thickness distribution of the formed film is non-uniform, then cracking, deformation, warpage, and wrinkling can easily occur at the injection molding stage. In this study, the simulation of thermoforming was performed to predict the film thickness distribution, and the results were compared with experiments. Uniaxial tensile tests with a constant crosshead speed for various high temperatures were conducted to investigate the stress-strain behavior. An instance of yielding occurred at the film temperature of $90^{\circ}C$, and the film stiffness increased with increasing crosshead speed. Two types of viscoelastic models, G'Sell model, K-BKZ model, were used to describe the measured stress-strain relationship. The predicted film thickness distributions were in good agreement with the experimental results.

Effect of Boundary Layer Thickness on the Flow Characteristics around a Rectangular Prism (직사각형 프리즘 주위의 유동특성에 대한 경계층 두께의 영향)

  • Ji, Ho-Seong;Kim, Kyung-Chun
    • Proceedings of the KSME Conference
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    • pp.306-311
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    • 2001
  • Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer$(\delta=270mm)$ was the natural turbulent boundary layer at the test section with fully long developing length(18m). The thin boundary layer with 36.5mm thickness was generated by on a smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity and the height of the model was $7.9{\times}10^3$. The mean velocity vector fields and turbulent kinetic energy distribution were measured and compared. The effect of boundary layer thickness is clearly observed not only in the length of separation bubble but also in the reattachment points. The thinner boundary layer thickness, the higher turbulent kinetic energy peak around the model roof. It is strongly recommended that the height ratio between model and approaching boundary layer thickness should be a major parameter.

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Analysis of Fatigue Crack Growth with Thickness Ratio in Weldments (두께比를 考廬한 鎔接部의 疲勞龜裂傳播 解釋)

  • 차용훈;방한서;김덕중
    • Journal of Welding and Joining
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    • v.14 no.5
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    • pp.69-77
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    • 1996
  • This study aims to analyze the S. I. F. K value upon Mode I cracks in a finite-width plate of varying thickness, which is expressed in terms of width ratio ($\omega$), thickness ratio ($\beta$) and non-dimensional crack length (λ) by using the 2-dimensional finite element method. Then, by comparing the effectiveness of the results obtained by the two finite element methods, it is seen that the 2-dimensional finite element method can be used in order to analyse the S. I. F. K values upon a various thickness model. A model is developed in order to analyze the effects of initial residual stress upon the fatigue crack growth behavior in various thickness welded specimens. In this model, crack growth rate da/dN appears to be come small as the thickness ratio with the same ΔK is increased. Also, in the initial step, as ΔK is increased with crack growth rate is decreased and then increased because the repeated compressive residual stress retards crack growth rate.

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Analysis of Chip Thickness Model in Ball-end Milling (볼엔드밀 가공의 칩두께 모델 해석)

  • Sim Ki-Joung;Mun Sang-Don
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.2
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    • pp.73-80
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    • 2006
  • This paper describes a analysis on the chip thickness model required for cutting force simulation in ball-end milling. In milling, cutting forces are obtained by multiplying chip area to specific cutting forces in each cutting instance. Specific cutting forces are one of the important factors for cutting force predication and have unique value according to workpiece materials. Chip area in two dimensional cutting is simply calculated using depth of cut and feed, but not simply obtained in three dimensional cutting such as milling due to complex cutting mechanics. In ball-end milling, machining is almost performed in the ball part of the cutter and tool radius is varied along contact point of the cutter and workpiece. In result, the cutting speed and the effective helix angle are changed according to length from the tool tip. In this study, for chip thickness model analysis, tool and chip geometry are analyzed and then the definition of chip thickness and estimation method are described. The resulted of analysis are verified by compared with geometrical simulation and other research. The proposed chip thickness model is more precise.