• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.66-71
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• 2022

Metal additive manufacturing (AM) has revolutionized several manufacturing industries. AM can generate large-scale metal components and produce complex geometries close to net-shapes. WAAM is an AM technology that has garnered considerable interest among industries owing to its economics and relatively high deposition rates. However, the heat accumulation in the weld bead during deposition triggers distortion and residual stress. To address these problems, various methods of interpass pressure rolling systems have been suggested in recent research. In addition, combining the rolling and WAAM processes can mitigate residual stresses. The constant-pressure rolling of the interlayer also affect the microstructure. The coarse microstructure of the as-deposited sample was altered to finer equiaxed grains via these methods. However, the bead-shape accuracy of the interlayer constant-pressure method does not consider the heat accumulation in each layer. Therefore, this study develops an interpass variable pressure rolling system that considers the heat accumulation of each layer. The interpass variable pressure rolling system comprises deposition, detection, pressure, and transport units. Finally, verification tests are performed on the interpass variable-pressure rolling system (at 500 kg) with the WAAM process, and the obtained results are discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.85-93
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• 1994

A new diagnosis method is developed in this paper, in which the fuzzy set theory is introduced to diagnose the defects of rolling element bearings. The selection of membership function and the fuzzy operation model are discussed in detail here. The system is successfully used for various defects diagnosis of rolling element bearings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2836-2844
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• 2000

Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. In this study, a modifying method of rolling force set-up with consideration of spread was developed to improve the thickness uniformity at the finishing rolling units in hot rolling. Through the analysis of real production data it was found that the accuracy of the rolling force determined from the finishing mill set-up (FSU) model dominantly governed the thickness uniformity in rolled plates at the front. Based on this analysis , several examples were selected to calculate the spread of rolled plate using three dimensional rigid thermo-viscoplastic finite element program. FE analysis results were used to train the neural network system that can predict the spread hot-rolled plate and the rolling force was modified based on the predicted value of spread. The modified rolling forces were closer to the measured rolling force so it can be expected that the accuracy of thickness uniformity of hot-rolled plate will be improved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1095-1105
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• 1993

Shape rolling processes to produce H-section beams are numerically simulated by the simplified three-dimensional finite element method. The 2-dimensional finite element method, used for the generalized plane strain condition, is combined with the slab method. Computer simulation results of the 19-passes in H-section beam rolling in practice include the grid distortions, the cross-sectional area changes, the roll separating forces, and the roll torques. Also, the amount of side spread can be found during the multi-pass rolling simulations. The finite element mesh system is remeshed with I-DEAS whenever the billet distorts severely. This study would contribute to CAD/CAM of shape rolling process through the optimal roll pass schedule.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.116-126
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• 2010

The Korean rolling stock safety regulation stipulates that the collision deceleration of a car body should be maintained under average 5g and maximum 7.5g during train collisions. One-dimensional dynamic model of a full rake train, which is made up of nonlinear springs/bars-dampers-masses, is often used to estimate the collision decelerations of car bodies in a basic design stage. By the way, the previous studies have often used some average force-deformation curve for energy absorbing structures in rolling stock. Through this study, we intended to analyse how much the collision deceleration levels are influenced by the initial peak force modeling in the one-dimensional force-deformation curve. The numerical results of the one-dimensional dynamic model for the Korean High-Speed Train show that the initial peak force modeling gives significant effect on the collision deceleration levels. Therefore the peak force modeling of the force-deformation curve should be considered in one-dimensional dynamic model of a full rake train to evaluate the article 16 of the domestic rolling stock safety regulations.

• Korean Journal of Materials Research
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• v.26 no.11
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• pp.628-634
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• 2016

The cold rolling workability and mechanical properties of two new alloys, designed and cast Al-5.5Mg-2.9Si and Al-7Mg-0.9Zn alloys, were investigated in detail. The two alloy sheets of 4 mm thickness, 30 mm width and 100 mm length were reduced to a thickness of 1 mm by multi-pass rolling at ambient temperature. The rolling workability was better for the Al-7Mg-0.9Zn alloy than for the Al-5.5Mg-2.9Si alloy; in case of the former alloy, edge cracks began to occur at 50% rolling reduction, and their number and length increased with rolling reduction; however, in the latter alloy, the sheets did not have any cracks even at higher rolling reduction. The mechanical properties of tensile strength and elongation were also better in the Al-7Mg-0.9Zn alloy than in Al-5.5Mg-2.9Si alloy. Work hardening ability after cold rolling was also higher in the Al-7Mg-0.9Zn alloy than in the Al-5.5Mg-2.9Si alloy. At the same time, the texture development was very similar for both alloys; typical rolling texture developed in both alloys. These differences in the two alloys can primarily be explained by the existence of precipitates of $Mg_2Si$. It is concluded that the Al-7Mg-0.9Zn alloy is better than the Al-5.5Mg-2.9Si alloy in terms of mechanical properties.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.634-637
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• 2000

A diagnosis system that provides early warnings regarding machine malfunction is very important for rolling mill so as to avoid great losses resulting from unexpected shutdown of the production line. But it is very difficult to provide early warnings in rolling mill. Because dynamics of rolling mill is non-linear. This paper shows a chaotic behaviour of vibration signal in rolling mill using embedding method. Not only phase plane and Poincare map are implemented but also FFT and histogram of vibration signal in rolling mill is presented by embedding method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.374-377
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• 2001

A diagnosis system that provides early warnings regarding machine malfunction is very important for rolling mill so as to avoid great losses resulting from unexpected shutdown of the production line. But it is very difficult to provide early warnings in rolling mill. Because dynamics of rolling mill is non-linear. This paper shows a chaotic behaviour of vibration signal in rolling mill using embedding method. Not only phase plane and Poincare map are implemented but also FFT and histogram of vibration signal in rolling mill is presented by embedding method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.4
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• pp.759-765
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• 2000

A diagnosis system that provides early warnings regarding machine malfunction is very important for rolling mill so as to avoid great losses resulting from unexpected shutdown of the production line. But it is very difficult to provide early warnings in rolling mill. Because dynamics of rolling mill is non-linear. This paper shows a chaotic behavior of vibration signal in rolling mill using embedding method. Not only phase plane and Poincare map are implemented but also FH and histogram of vibration signal in rolling mill is presented by embedding method.

• Transactions of Materials Processing
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• v.8 no.1
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• pp.65-77
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• 1999

In recent years, the quality requirements from the customers of hot rolled steel strip have been steadily increasing in diversity and strictness. To meet these quality requirements as well as to improve productivity, steel mills have been doing their efforts for developing high performance Automatic Gauge Control (AGC) system. However, it is very time consuming and also needs a lot of money to develop the new technologies of AGC in actual mill. So, there has been a demand for developing the Dynamic Hot Rolling Simulator since late 80's. It is a kind of software packages and can analyze the dynamic behaviors of hot finishing rolling process without laborious experiments in actual mill. It can also be used as a designing tool of Automatic Gauge Controller. In this work, the Dynamic Hot Rolling Simulator which is applicable to 6 sands hot strip mill rolling was developed. The MATLAB with SIMLINK was used as a software developer for making the main part of simulator because it is very powerful tool for modeling, integrating, controller design, and simulation. In this paper, the structures and the mathematical models of the simulator were briefly described and the results of simulation on the transient phenomena of hot rolling process with actual mill data were also presented.