Chung-Min Hyun

Derivation of Simplified Formulas to Predict Deformations of Plate in Steel Forming Process with Induction Heating

Recently, the electro-magnetic induction process has been utilizing to substitute the flame heating process in shipyard. However, few studies have been performed to exactly analyze the deformation mechanism of the heating process with mathematical model. This is mainly due to the difficulty of modeling the inductor travelling on plate during the process. In this study, heat flux distribution of the process is firstly numerically analysed with the assumption that the process has a quasi-stationary state and also with the consideration that the heat source itself highly depends on the temperature of base plate. With the heat flux, the thermal and deformation analyses are then performed with a commercial program for 34 combinations of heating parameters. The deformations obtained and heating parameters are synthesized with a statistical method to produce simplified formulas, which easily give the relation between the heating parameters and deformations. The formulas are well compared with results of experiment.

Development of Simplified Formulas to Predict Deformations in Plate Bending Process with Oxy-Propane Gas Flame

Simplified mathematical formulas are presented to predict deformations during the plate forming process when the heating parameters are given. To obtain the formulas, firstly, the thermal analysis for steel plate is performed, and the thermo-mechanical analysis is followed with actual heating conditions. The analyses have been carried out by the commercial software MARC, which is programmed based on the FEM. Secondary, the results of the mechanical analysis are synthesized with their variables for a statistical approach, which results in simplified formulas. The results of the analysis are well compared with those of experimental measurements.

Analysis for the angular deformation of steel plates in a high-frequency induction forming process with a triangle heating technique

A triangle heating technique with the use of a heat source of high-frequency induction heating to make a steel plate deformed into a curved shape was modeled and analyzed using the numerical analysis of the finite element method in order to predict the angular deformation of the steel plate formed by the technique. For the analysis of the deformation, heat generation by an electromagnetic field was first analyzed with consideration of the preheat effect, and heat flow using the heat generated from the plate as the heat source was then analyzed. Thermal history of the plate predicted by numerical analysis was compared with that measured in an experiment of triangle heating on a steel plate. Deformations of the plates were then analyzed with changes of heating parameters including heating dimensions and plate thickness. The analyses were also verified with a series of experiments. In order to derive a simplified equation to readily predict deformation from the triangle heating technique, deformations predicted by numerical analyses and measured by the experiments were synthesized in association with the heating parameters using a statistical method of recursion analysis. The equation was verified to be able to predict the deformations conversely and expected to be practically used in the industry to select the heating parameters for the desired shapes of curved plates.

A study on heat flow and thermal distortion in terms of air-carbon-arc gouging of steel plates

In groove design, a proper shape should be chosen during the preparation for the welding of thick plates of steel structures to minimize the potential for any welding deformations. While the effect of welding on both sides of the plate in terms of the deformation potential is a foremost consideration during the groove-design process, the effect of gouging is not included even though it involves the usage of a high-heat arc input that may significantly influence the welding-deformation potential. In this study, the effect of the air-carbon-arc gouging process on the deformation of steel plates was investigated using a numerical finite element method analysis. For this purpose, the heat input from the gouging torch was first modeled using an analytical solution that is based on the Rosenthal equation. The model was then used as a heat input for the thermo-mechanical steel-plate-gouging model that is proposed in this study to obtain deformation estimations during the gouging process. A series of numerical analyses were carried out to predict the deformations according to changes in the plate thickness. The results of the analyses were found to be in sound agreement with those of the experiments that were performed to verify the simulations. The comparison revealed that the models that are proposed in this study are feasible ways of estimating the deformation caused by the gouging on steel plates.