• Journal of the Korean institute of surface engineering
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• v.37 no.5
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• pp.279-288
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• 2004

This paper describes a three-dimensional transient finite element model for a laser cladding process. In the model, an adaptive finite element technique is used for dilution control. Using the proposed finite element model, the effects of process parameters such as scanning speed, laser's power, and preheating on the dilution of clad layer, the shape of melting pool, and the temperature distribution are calculated. It is also shown that the optimal process parameters for the required dilution can be determined from the proposed finite element model. An experiment is performed to validate the proposed model. The numerical results are compared with experimental ones.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.52-55
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• 2000

Investigated via a series of finite element process simulation is the effect of diverse process variables on some selected non-dimensional parameters characterizing the strip in hot strip rolling. Then on the basis of these parameters an on-line model is derived for the precise prediction of roll and roll power. The prediction accuracy of the proposed model is examined through comparison with predictions from a finite element process model.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.115-121
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• 2004

Hemming is the last farming process in stamping and determines external quality of automotive outer panels. Few numerical approaches using 3-dimensional finite element model have been applied to a hemming process due to small element size which is needed to express the bending behavior of the sheet around small die comer and comparatively big model size of automotive opening parts, such as side door, back door and trunk lid etc In this study, part model assembling method is suggested and applied to the 3-dimensional finite element simulation of flanging and hemming process far an automotive front hood.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.103-107
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• 2002

The 2nd forming process of flanging/hemming has recently many interest because it determines external quality of automobile. It is difficult to apply finite element simulation in flanging/hemming due to small element size which needs for expression of bending effect on the die corner and big model size of side door, back door, tank lid and like opening Parts. This paper shows the process of flanging/hemming simulation using finite element model for automotive panels. The explicit finite element program PAM-STAMP$\^$TM/ was used to simulate the flanging and hemming operations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.3 s.246
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• pp.310-317
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• 2006

Currently most practical vibration and structural problems in automotive suspensions require the use of the finite element method to obtain their structural responses. When the finite element model has a very large number of degrees of freedom the harmonic and dynamic analyses are computationally too expensive to repeat within a feasible design process time. To alleviate the computational difficulty, this paper presents a moment-matching based model order reduction (MOR) which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary simulations with the reduced-size models. The moment-matching model reduction via the Arnoldi process is performed directly to ANSYS finite element models by software mor4ansys. Among automotive suspension components, a knuckle is taken as an example to demonstrate the advantages of this approach for vibration simulation. The frequency and transient dynamic responses by the MOR are compared with those by the mode superposition method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.121-124
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• 2001

On-line prediction model which calculate roll force, roll power and forward slip of continuous hot strip rolling was built based on the results of plane strait rigid-viscoplastic finite element process model. Using the integrated FE process model, a series of finite element simulation was conducted over the process variables, and the influence of various process conditions on non-dimensional parameters was inspected. The prediction accuracy of the proposed on-line model under front and back tension is examined through comparison with predictions from a finite element process model over the various process conditions. In addition, we examined the validity of the on-line prediction model through comparison with roll force of experiment in hot rolling.

• Journal of KSNVE
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• v.9 no.1
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• pp.163-173
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• 1999

Precise and reasonable modelling is necessary and indispensable to the analysis of dynamic characteristics of mechanical structures. Also. the effective prediction of the change of modal properties due to the variation of design parameters is required especially for the application of finite element method to the structural dynamics problems. To meet those necessity and requirement, three model updating algorithms are proposed for finite element methods. Those algorithms are based on sensitivity analysis of the modal data obtained from experimental modal analysis(EMA) and analytical modal analysis(AMA). The adapted sensitivity analysis methods of the algorithms are 1)eigensensitivity(EGNS) method. 2)frequency response function sensitivity(FRFS) method. 3)sensitivity based element-by-element method (SBEEM), Singular value decomposition(SVD) is used for performing eigenanalysis and parameter estimation in the updating process. Those algorithms are applied to finite element of a plate and the updating capability of each algorithm is compared in terms of accuracy. reliability and stability of the updating process. It is shown that the model updating method using frequency response function is superior to the other methods in view of various updating capabilities.

• Transactions of Materials Processing
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• v.29 no.2
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• pp.89-96
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• 2020

The finite element method has been widely applied in the sheet metal forming process. However, the finite element method is computationally expensive and time consuming. In order to tackle this problem, surrogate modeling methods have been proposed. An artificial neural network (ANN) is one such surrogate model and has been well studied over the past decades. However, when it comes to ANN with two or more layers, so called deep neural networks (DNN), there is distinct a lack of research. We chose to use DNNs our surrogate model to predict the behavior of sheet metal in the deep drawing process. Thickness variation is selected as an output of the DNN in order to evaluate workpiece feasibility. Input variables of the DNN are radius of die, die corner and blank holder force. Finite element analysis was conducted to obtain data for surrogate model construction and testing. Sampling points were determined by full factorial, latin hyper cube and monte carlo methods. We investigated the performance of the DNN according to its structure, number of nodes and number of layers, then it was compared with a radial basis function surrogate model using various sampling methods and numbers. The results show that our DNN could be used as an efficient surrogate model for the deep drawing process.

• Transactions of Materials Processing
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• v.24 no.3
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• pp.161-166
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• 2015

The finite element method has been widely used in the analysis of ring rolling. For ring rolling it requires a high computational expense due to the non-steady state material flow characteristics of the process. The high computational expense causes the finite element analysis to be impractical for industrial applications. In the current study, we aim to develop a practical implicit finite element modeling method for ring rolling. This method uses a step-wise steady state assumption and is called the “Stepped method”. The stepped method divides the whole process time of unsteady-state flow model into a finite number of steady-state models. It then solves the process at several specific time steps until convergence is reached. In order to confirm the performance and validity of the newly proposed stepped method, the result from the stepped method were compared to the results from a Lagrangian finite element method and to results from experiments reported in the literature.

• Earthquakes and Structures
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• v.5 no.1
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• pp.111-127
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• 2013

This paper describes effects of infill walls on behavior of RC frame with low strength, including numerical modeling, modal testing and finite-element model updating. For this purpose full scaled, one bay and one story RC frame is produced and tested for plane and brick in-filled conditions. Ambient-vibration testis applied to identify dynamic characteristics under natural excitations. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to obtain experimental dynamic characteristics. A numerical modal analysis is performed on the developed two-dimensional finite element model of the frames using SAP2000 software to provide numerical frequencies and mode shapes. Dynamic characteristics obtained by numerical and experimental are compared with each other and finite element model of the frames are updated by changing some uncertain modeling parameters such as material properties and boundary conditions to reduce the differences between the results. At the end of the study, maximum differences in the natural frequencies are reduced on average from 34% to 9% and a good agreement is found between numerical and experimental dynamic characteristics after finite-element model updating. In addition, it is seen material properties are more effective parameters in the finite element model updating of plane frame. However, for brick in-filled frame changes in boundary conditions determine the model updating process.