Kang-Yul Bae

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.

Effects of Inductor Shape in Steel Forming Process with High Frequency Induction Heating

Because of high intensity and easy controllability of the heat source, high frequency induction heating has been concerned and studied for the steel forming process in the ship building industry. However, the heating and forming characteristics have to be further properly modelled and analyzed for the process to be utilized with its optimal working parameters. In this study, a modelling with thermo-elasto-plastic analysis is performed using the FEM to study heat flow and deformation of the steel plate during the forming process with the electro-magnetic induction heating. The numerical model is then used to study the effect of the inductor shape on the magnitude of angular deformation of the plate during the forming process. It is revealed that the square shape of inductor induces the largest deformation among the rectangular inductors.

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.

Prediction of Heating Line for Plate Forming in Induction Heating Process Using Artificial Neural Network

)를신경망의입력요소값으로취한다출력요소는변형된강판형상을생성하.기위한가열변수로 가열위치 가열면전면또는후, , (면 속도등으로구성된다하나의가열위치는가열면), .과가열속도를포함하는가열선이된다.출력층에서각요소의출력값은이진 값으(binary)로부호화되어있고각가열선은 개의파라미터로예, 4측된다 파라미터 은가열여부를나타내어 값이 이. 1 , 1면 해당가열선에가열이수행되어야함을의미하며, ,0 . 2이면가열되지않음을나타낸다 파라미터 는값이1 , 0이면전면에가열을수행하고 이면후면을가열하게됨을의미한다 파라미터 은이진값의조합으로. 3 5,10, 15, 20m/s 4 .의 가지가열속도를나타낸다 이를위해신경망의출력값은다음과같이한계값과비교하여결정된다.

The Development of an Artificial Neural Network Model to Predict Heating-Line Positions for Plate Forming in Induction Heating Process

Abstract An artificial neural network model can help manufacturers determine the positions of induction heating lines and their heating parameters to form a desired shape of plate. The vertical displacements of a deformed plate are considered as the input parameters and the selected induction heating lines as output parameters to develop the model. The training patterns of neural network are obtained using an analytical solution that is derived from the plate theory to predict plate deformations in induction heating process. The plastic region in the analytical solution of the angular deformation of a steel plate is obtained from the thermal analysis of the plate with the heat input calculated from the electro-magnetic analysis of the induction heating process.

Analysis of Strengthening Structures of Steel Manhole Cover

Manhole cover, which is usually made of grey cast iron and consists of frame and cover, should have enough strength to support the heavy traffic load. The manhole cover made of cast iron has heavy weight to handle manually and is vulnerable to impact force with its brittle characteristics. Moreover, its production process of casting has been regulated in terms of environmental pollution. In this study, steel manhole cover is proposed to substitute the cast cover with a series of structural analyses to confirm its strength to support the test load for manhole cover. The cover of the proposed steel manhole cover is made of thin circular pate and stiffeners below the plate. Rectangular columns and hollow circular plate were selected for the shape of the stiffener. In order to give enough strength for the cover to behave within elastic range in the loading, strengthening structures of the cover were varied with increasing the number and the size of the stiffeners. The results of the analyses revealed that when both the hollow circular stiffener and cross stiffeners were additionally applied at the same time to the steel cover with longitudinal stiffeners, the maximum stress level in the cover could be reduced to that level presented in the cast cover.

Numerical analysis of heat flow in oxy-ethylene flame cutting of steel plate

To manufacture a steel structure, in the first step, raw steel plate needs to be cut into proper sizes. Oxy-fuel flame is widely used in the cutting process due to its flexibility with respect to accessibility, plate thickness, cost, and material handling. However, the deformation caused by the cutting process frequently becomes a severe problem for the next process in the production of steel product. To decrease the deformation, the thermo-elasto-plastic behavior of the steel plate in the cutting process should be analyzed in advance. In this study, heat sources in oxy-ethylene flame cutting of steel plate were modeled first, and the heat flow in the steel plate was then analyzed by the models of the heat sources using a numerical simulation based on the finite element method. To verify the analysis by the numerical simulation including the models, a series of experiments were performed, and the temperature histories at several points on the steel plate during the cutting process were measured. Moreover, the predicted sizes of the heat-affected zone by the numerical simulations according to the variation in the cutting parameters were compared to the experimental results. The power functions of the relationship between the sizes of the heat-affected zone and cutting parameters were obtained by the recursion analysis using the correlation between the results and parameters. The results of the numerical simulation showed good agreement with those of the experiments, indicating that the proposed models of the heat sources and thermal analysis were feasible to analyze the heat flow in the steel plate during the cutting process.

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.

Analysis of Welding Distortion of Large Steel Plate by Using Analytical Solution of Temperature Distribution and Finite Element Method

Welding distortions of large steel structures had mainly been estimated with some simplified formula obtained by lots of experience and numerical analyses for small steel structures. However, the large structures would have different characteristics of distortion with welding because of their own stiffness coming from the size itself. Therefore, in order to find some measures for preventing welding distortion of large structure, it is requite in advance to precisely analysis thermal stress and distortion during welding of the structure. Numerical analysis for larger structure has been known to take large amount of calculation time and have a poor convergency problem during the thermo-elasto-plastic calculation. In this study, a hybrid method is proposed to analysis the thermal stress and distortion of a large steel plate with the finite element analysis by incorporating with temperature distribution of the plate calculated by an analytical solution. The proposed method revealed that the thermo-mechanical analysis for welding of the large structure could be performed with a good convergence and produced precise results with much reduced time consumption.