• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.175-183
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• 2004

In hot strip rolling, a capability for precisely predicting roll force is crucial for sound process control. In the past, on-line prediction models have been developed mostly on the basis of Orowan's theory and its variation. However, the range of process conditions in which desired prediction accuracy could be achieved was rather limited, mainly due to many simplifying assumptions inherent to Orowan's theory. As far as the prediction accuracy is concerned, a rigorously formulated finite element(FE) process model is perhaps the best choice. However, a FE process model in general requires a large CPU time, rendering itself inadequate for on-line purpose. In this report, we present a FE-based on-line prediction model applicable to precision process control in a finishing mill(FM). Described was an integrated FE process model capable of revealing the detailed aspects of the thermo-mechanical behavior of the roll-strip system. Using the FE process model, a series of process simulation was conducted to investigate the effect of diverse process variables on some selected non-dimensional parameters characterizing the thermo-mechanical behavior of the strip. Then, it was shown that an on-line model for the prediction of roll force could be derived on the basis of these parameters. The prediction accuracy of the proposed model was examined through comparison with measurements from the hot strip mill.

• Structural Engineering and Mechanics
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• v.49 no.5
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• pp.569-595
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• 2014

In this paper, a novel semi-energy finite strip method (FSM) is developed based on the concept of first order shear deformation theory (FSDT) in order to attempt the post-buckling solution for thin and relatively thick functionally graded (FG) plates under uniform end-shortening. In order to study the effects of through-the-thickness shear stresses on the post-buckling behavior of FG plates, two previously developed finite strip methods, i.e., semi-energy FSM based on the concept of classical laminated plate theory (CLPT) and a CLPT full-energy FSM, are also implemented. Moreover, the effects of aspect ratio on initial post-buckling stiffness of FG rectangular plates are studied. It has been shown that the variation of the ratio of initial post-buckling stiffness to pre-buckling stiffness ($S^*/S$) with respect to aspects ratios is quite independent of volume fractions of constituents in thin FG plates. It has also been seen that the universal curve representing the variation of ($S^*/S$) with aspect ratio of a FG plate demonstrate a saw shape curve. Moreover, it is revealed that for the thin FG plates in contrast to relatively thick plates, the variations of non-dimensional load versus end-shortening is independent of ceramic-metal volume fraction index. This means that the post-buckling behavior of thin FG plates and the thin pure isotropic plates is similar. The results are discussed in detail and compared with those obtained from finite element method (FEM) of analysis. The study of the results may have a great influence in design of FG plates encountering post-buckling behavior.

• Ocean Systems Engineering
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• v.3 no.3
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• pp.219-236
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• 2013

The accurate prediction of motion in waves of a marine vehicle is essential to assess the maximum sea state vs. operational requirements. This is particularly true for small crafts, such as Autonomous Surface Vessels (ASV). Two different numerical methods to predict motions of a SWATH-ASV are considered: an inviscid strip theory initially developed at MIT for catamarans and then adapted for SWATHs and new a hybrid strip theory, based on the numerical solution of the radiation forces by an unsteady viscous, non-linear free surface flow solver. Motion predictions obtained by the viscous flow method are critically discussed against those obtained by potential flow strip theory. Effects of viscosity are analyzed by comparison of sectional added mass and damping calculated at different frequencies and for different sections, RAOs and motions response in irregular waves at zero speed. Some relevant conclusions can be drawn from this study: influence of viscosity is definitely non negligible for SWATH vessels like the one presented: amplitude of the pitch and heave motions predicted at the resonance frequency differ of 20% respectively and 50%; in this respect, the hybrid method with fully non-linear, viscous free surface calculation of the radiation forces turns out to be a very valuable tool to improve the accuracy of traditional strip theories, without the burden of long computational times requested by fully viscous time domain three dimensional simulations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.837-845
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• 1987

In the research of the rolling of strip, producing the strip with a close tolerance of thickness over the rolling direction was a principal object. But it was solved by the contribution of two-dimensional theory of rolling and the development of automatic gauge control system. And new requirements for the study of flatness, crown of rolled strip and edge drop grow up recently. These phenomena are closely related with the thickness distribution along the lateral direction of rolled strip. To analyse the thickness distribution of rolled strip along the lateral direction, elastic deformation of rolls and plastic deformation of work material must be discussed simultaneously. In this report, an approximate three-dimensional analysis based on Tozawa's three dimensional approach was applied to 12 cases of different rolling conditions and the numerical results were investigated. Especially stresses were laid upon the investigation of optimal boundary position between the three-dimensional analysis region and the plane strain analysis region.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.854-859
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• 2003

In this paper, we examine the singular stresses and electric fields in a functionally graded piezoelectric ceramic strip containing an eccentric crack off the center line under anti-plane shear loading with the theory of linear piezoelectricity. It is assumed that the properties of the functionally graded piezoelectric ceramic strip vary continuously along the thickness. Fourier transforms are used to reduce the problem to the solution of two pairs of dual integral equations, which are then expressed to a Fredholm integral equation of the second kind. Numerical values on the stress intensity factor and the energy release rate are obtained.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.75.5-75
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• 2001

In this paper, we study design of a ILQ(Inverse Linear Quadratic optimal control) looper control system for hot strip mills. The looper which is placed between stands plays an important role in controlling strip width by regulating strip tension variation generated from the velocity difference of main work rolls. A Looper servo controller is designed by ILQ control theory which is an inverse problem of LQ(Linear Quadratic optimal control) control. The mathematical model for looper system is obtained by Taylor´s linearization of nonlinear differential equations. Then we designed linear controller for linearization model by using the ILQ control algorithm. Thereafter this controller is applied to the nonlinear model for model identification. As a result, we show the controller´s robustness for the model error, external disturbance and sensor noise.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.224-228
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• 2000

The piercing and blanking of thin sheet metal working is specified division in press die design and making. In order to prevent the detects, the optimum design of the production part, strip process layout, die design, die making and try out etc. re necessary the analysis of effective factors. For example, theory and practice of metal shearing process and its phenomena, die structure, machine tool working for die making, die materials and its heat treatment, metal working in industrial and its know how etc. In this study, we analyzed whole of data base, theoretical back ground of metal working process, and then performed the progressive die tryout with the screw press. This study regards to the aim of small quantity of production part's press working. Part 1 of this study reveals with production part and strip process layout design.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.302-312
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• 1994

In this study, a fuzzy theory is introduced to control the cross-sectional strip shape in cold rolling. A fuzzy controller is developed based on the production data and the operational knowledge. The cold rolled products are characterized into several types based on their irregularities. For each type of irregular strip shape, fuzzy controller calculates the changes of bender forces of work and intermediate rolls using fuzzy control algorithm. To simulate the continuous shape control, fuzzy controller is linked with emulator which is developed using neural network. The developed fuzzy controller and emulator simulate the cold rolling process until the irregularities converge to the tolerable range to produce unifrom cross-sectional strip shape. The results from this simulation are reasonable for various irregular strip shapes.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.101-111
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• 1998

This study presents test results of RC beams strengthened by carbon fiber sheet(CFS), carbon fiber reinforced plastics(CFRP) or glass fiber reinforced plastics(GFRP) for increasing shear resistance. Nineteen specimens were tested, and the test was performed with different parameters including the type of strengthening materials(CFS, GFRP, CFRP), shear-strengthening methods(wing type, jacket type, strip type), strip-spacing, strengthening direction of FRP. The test results show that shear-damaged RC beams strengthened by FRP(CFS, GFRP, CFRP) have more improved the shear capacity. The mathematical model based on plastic theory was also developed to predict shear strength of shear-damaged RC beams strengthened by FRP. The predictions using the mathematical model. are agreed with the observations from the observed shear strengths for 19 test beams.

• The Journal of the Acoustical Society of Korea
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• v.3 no.2
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• pp.23-29
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• 1984

In this paper surface acoustic wave beam track changers using symmetric multistrip coupler are designed on the basis of the perturbation theory, and its characteristics are studied. SAW beam track changers, which have the configuratio of the periodic array of metal strips, are designed with the following specifications ; the number of strips : 140, the strip period: 0.25λ, the ratios of the strip width to the period a/p: 0.5, 0.375, 0.25, respectively, and approximately consistent with the theoretical values, and also the bulk wave mode and the 2nd-order effects are suppressed by these track changers.