• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.340-343
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• 2007

This paper introduces a new approach to consider the bending history in finite element inverse analysis of the cylindrical cup drawing. A modified membrane element is adopted to add the bending-unbending energy to the total plastic energy on the bending-unbending region predicted from the geometry of the final shape and tools. The algorithm suggested was applied to a cylindrical cup deep drawing process. The blank shape and the distribution of the thickness strain are compared with those obtained from incremental finite element analysis. The comparison demonstrates the algorithm proposed reduces the difference between the results from inverse analysis and those from incremental analysis when the bending history is considered.

• Transactions of Materials Processing
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• v.16 no.8
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• pp.590-595
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• 2007

This paper introduces a new approach to take account of bending history in finite element inverse analysis during sheet metal forming process. A modified membrane element was adopted for finite element inverse analysis so that bending-unbending energy was additionally imposed in the total plastic energy, predicting bending-unbending regions using the geometry of the final shape and tools. An algorithm was applied to a cylindrical cup deep drawing process. The blank shape and the distribution of the thickness strain were compared with those obtained from the incremental finite element analysis in order to evaluate the effect of the bending history. The algorithm reduced the difference between the results of the inverse analysis from those of the incremental analysis due to bending history. The analysis was also carried out with the variation of the thickness of the initial blank to investigate the effect of bending deformation. The results showed that the difference was remarkably reduced as the thickness of the initial blank increased. This indicates that the finite element inverse analysis cooperated with the suggested scheme is useful to obtain more accurate results, especially when bending effects are significant.

• Smart Structures and Systems
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• v.17 no.4
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• pp.611-629
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• 2016

This study presents a new approach of surrogate modeling for time-consuming finite element analysis. A surrogate model is widely used to reduce the computational cost under an iterative computational analysis. Although a variety of the methods have been widely investigated, there are still difficulties in surrogate modeling from a practical point of view: (1) How to derive optimal design of experiments (i.e., the number of training samples and their locations); and (2) diagnostics of the surrogate model. To overcome these difficulties, we propose a sequential surrogate modeling based on Gaussian process model (GPM) with self-adaptive sampling. The proposed approach not only enables further sampling to make GPM more accurate, but also evaluates the model adequacy within a sequential framework. The applicability of the proposed approach is first demonstrated by using mathematical test functions. Then, it is applied as a substitute of the iterative finite element analysis to Monte Carlo simulation for a response uncertainty analysis under correlated input uncertainties. In all numerical studies, it is successful to build GPM automatically with the minimal user intervention. The proposed approach can be customized for the various response surfaces and help a less experienced user save his/her efforts.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.737-750
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• 2022

Timber-Concrete Composite construction system consists of combining timber beam or deck and concrete with different connectors. Different fastener types are used in Timber-Concrete Composite systems. In this paper, the effects of two types of fasteners on structural behavior are compared. First, the notches were opened on timber beam, and combined with reinforced concrete slab by fasteners. This system is called as Notched Connection System. Then, timber beam and reinforced concrete slab were combined by new type designed fasteners in another model. This system is called as Notched-Slab Approach. Two laboratory models were constructed and bending tests were performed to examine the fasteners' effectiveness. Bending test results have shown that heavy damage to concrete slab occurs in Notched Connection System applications and the system becomes unusable. However, in Notched-Slab Approach applications, the damage concentrated on the fastener in the metal notch created in the slab, and no damage occurred in the concrete slab. In addition, non-destructive experimental measurements were conducted to determine the dynamic characteristics. To validate the experimental results, initial finite element models of both systems were constituted in ANSYS software using orthotropic material properties, and numerical dynamic characteristics were calculated. Finite element models of Timber-Concrete Composite systems are updated to minimize the differences by manual model updating procedure using some uncertain parameters such as material properties and boundary conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.338-341
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• 2009

In this paper, three-dimensional finite element approach to determining the number of blows in hammer forging is presented. Energy efficiency which is a major factor affecting the number of blows in hammer forging is assumed to decrease linearly as die-material contact area increases. The approach is applied to predicting the number of blows in counterblow hammer forging of large crank shaft for medium sized ship engine.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.473-480
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• 1999

This paper presents the results of a parametric study on the behavior of mechanically stabilized earth retaining wall. It has been recognized that the currently available design guidelines, which is base on the limit equilibrium approach, cannot properly account the interaction effect between the components, construction sequence, and foundation settlement which may impose a significant influence on the wall behavior. A parametric study using finite element analysis was performed to investigate the behavior of MSE wall under different construction conditions and the applicability of the current design approach. In the parametric analysis, the effects of the construction sequence, the surcharge, and the foundation stiffness were studied and a detailed finite element modeling for various components of the system were employed. The results, such as wall displacement and earth pressure distributions, reinforcement forces, vertical stress distribution were then thoroughly analyzed to investigate the effect of construction details on the wall behavior.

• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.29-36
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• 2005

In this paper, a useful rigid-plastic finite element method with various numerical schemes is presented for simulation of an orbital forming process. A new approach to reduce volume change during simulation is presented and an approximation method to reduce computational time is also presented. An actual orbital forming process found in a bearing making industry is simulated by the presented approach. The simulated results of the orbital forming process are compared with the experimental results.

• Structural Engineering and Mechanics
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• v.30 no.1
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• pp.77-97
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• 2008

In this paper, a strut-and-tie model approach has been proposed to directly calculate the amount of reinforcements in deep beams, and the force transfer mechanisms for this approach were investigated using linear finite element analysis. The proposed strut-and-tie model provides quite similar force transfer mechanisms to the results of linear finite element analysis for the 28 deep beams. The load-carrying capacities calculated from the proposed method are both accurate and conservative with little scatter or trends for the 214 deep beams. The deep beams have different concrete strengths including high-strength, various combinations of web reinforcements, and wide range of and a/d ratios. Good accuracy was also obtained using VecTor2, nonlinear finite element analysis tool based on the Modified Compression Field Theory. Since the proposed method provides a safe and reliable means for design of deep beams, this can serve to improve design provisions in future adjustments and development of design guidelines.

• Transactions of Materials Processing
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• v.7 no.4
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• pp.347-353
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• 1998

A new approach of elastic finite element to die stress analysis in forging is presented in this paper. The die set analysis problem is formulated by considering contact problems under both mechanical and thermal loads. In the approach, amount of shrink fit is controlled by thermal load i.e., temperature difference between die insert and shrink fits. The loading conditions are extracted automatically from a forging simulator. The predicted solution is compared with analytical one and it has been shown that the predicted results are in excellent agreement with the analytical ones. An application example is given, which was found in a cold forging company.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.353-358
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• 2006

A three-dimensional finite element approach to process analysis and design for joining the socket with the ball by a kind of the rotary forging processes is presented in this paper. The rigid-plastic finite element method is employed and its results are used to reduce the number of process design tryouts. The approach is applied to developing a concave piston assembly for a high pressure hydraulic pump. Experiments show that the developed piston assembly satisfies the quality requirement on geometrical tolerance.