• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.189-194
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• 2006

In this paper, an automated adaptive mesh generation scheme, based on an advancing-front-Delaunay method, is presented fur finite element simulation of three dimensional bulk metal farming processes. Basic approach is introduced in detail, including a surface meshing and volume meshing technique and a mesh density control scheme. The presented approach is applied to automatic forging simulation in order to evaluate the effect of the developed schemes. Comparison shows a good agreement between required mesh density and generated mesh density, implying that the presented approach is appropriate for automatic mesh generation in metal forming simulation.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.109-116
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• 1998

The three-dimensional profile of a solder fillet is predicted by minimizing the surface tension and gravity energies of the solder joint using finite element modeling. Geometric complexity stemming from the inclined plane of the gullwing lead is resolved by employing three element types. These element types are used to describe the joint profile formed on the vertical, inclined and interfacial planes. The predicted solder joint profiles show good agreements with the experimental data provided that the solder volume is adjusted considering the wicking effects. Effects of the pad length, inclined lead angle and solder volume on joint profiles are also investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.203-208
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• 2005

In this paper, an automated adaptive mesh generation scheme, based on an advancing-front-Delaunay method, is developed for finite element simulation of three dimensional bulk metal forming processes. During the simulation, the finite element mesh system is adaptively remeshed whenever the mesh is unacceptable. Several schemes are developed such as curvature compensation scheme to minimize volume loss, optimal smoothing scheme to improve element quality, etc. The presented approach is evaluated and applied to automatic forging simulation in order to demonstrate the effect of the developed schemes.

• Proceedings of the ESK Conference
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• 1993.04a
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• pp.18-26
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• 1993

When designing workplaces, controls should be placed within the reach of operator's arm or foot to guarantee effective performance. The aviation industry is perhaps the chief user of anthropometric data for its need to weight minimization and space optimization. In designing a workplace which must cater to a wide range of operator size, it might be sufficient to plan only for the 'average person'. Static arm reach measurements which are taken in conventional, standardized positions provide the necessary information, but they cannot be directly applied to dynamic situations. In this research, an approximate algorithm to generate the workspace of the human body including foot reach and trunk motion is proposed and tested. The robot kinematics was employed to represent the human body as a multi-link system.

• Steel and Composite Structures
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• v.48 no.5
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• pp.583-597
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• 2023

This paper introduces a novel approach to multi-material topology optimization (MTO) targeting in-plane bi-directional functionally graded (IBFG) non-uniform thickness Reissner-Mindlin plates, employing an alternative active phase approach. The mathematical formulation integrates a first shear deformation theory (FSDT) to address compliance minimization as the objective function. Through an alternating active-phase algorithm in conjunction with the block Gauss-Seidel method, the study transforms a multi-phase topology optimization challenge with multi-volume fraction constraints into multiple binary phase sub-problems, each with a single volume fraction constraint. The investigation focuses on IBFG materials that incorporate adequate local bulk and shear moduli to enhance the precision of material interactions. Furthermore, the well-established mixed interpolation of tensorial components 4-node elements (MITC4) is harnessed to tackle shear-locking issues inherent in thin plate models. The study meticulously presents detailed mathematical formulations for IBFG plates in the MTO framework, underscored by numerous numerical examples demonstrating the method's efficiency and reliability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.591-599
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• 1994

A design system for power transmission bevel gears(straight, zerol, and spiral) is developed, in which the strength and durability of bevel gears can be estimated and the size of bevel gears can be minimized by introducing optimal techniques. The size of bevel gear pair as the object function to be minimized is the volume of equivalent spur gear pair at mean normal section, and the design variables to be determined are considered as the number of teeth, face width, diametral pitch, and spiral angle in spiral bevel gear. The strength(bending strength, pitting resistance) according to the AGMA standards, geometrical quantities, and operating characteristics(interference of pinion, contact ratio, etc.) are considered as the constraints in design optimization. The optimization with these constraints becomes nonlinear problem and that is solved with ALM(Augmented Lagrange Multiplier) method. The developed design method is applied to the example designs of straight, zerol, and spiral bevel gears. The design results are acceptable from the viewpoint of strength and durability within the design ranges of all other constraint, and the bevel gears are designed toward minimizing the size of gear pair. This design method is easily applicable to the design of bevel gears used as power transmitting devices in machineries, and is expected to be used for weight minimization of bevel gear unit.

• Journal of the Korean Magnetics Society
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• v.6 no.1
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• pp.40-47
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• 1996

In this paper, the optimal design rrethod of the electropermanent magnetic lifter is proposed. The electromag-netic performances at the states of attraction and release are calculated by the means of the equivalent magnetic circuit rrethod. The magnetic flux flow, the magneto-rrntive force and the aJronnt of lifting force correspond to the electromagnetic performances. As the optimization algorithm, the evolution strategy(ES) is applied for the maximization of the electromagnetic force at the state of attraction and for the minimization of the volume within the alJowable electomagnetic force range.[3] At this rrnrrent, the optimization satisfy the minimization of the electromagnetic force at the state of release. The validity of the proposed optimization rrethod is verified by the comparison between the optimization result and the FEM result (this FEM result is obtained from MAXWELL).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.469-475
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• 2010

The objective of this study is to integrate reliability analysis into shape optimization problem using the evolutionary structural optimization (ESO) in the application example. Reliability-based shape optimization is formulated as volume minimization problem with probabilistic stress constraint under minimization max. von Mises stress and allow stress. Young's modulus, external load and thickness are considered as uncertain variables. In order to compute reliability index, four methods, i.e., reliability index approach (RIA), performance measure approach (PMA), single-loop singlevector (SLSV) and adaptive-loop (ADL), are used. Reliability-based shape optimization design process is conducted to obtain optimal shape satisfying max. von Mises stress and reliability index constraints with the above four methods, and then each result is compared with respect to numerical stability and computing time.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.591-602
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• 2009

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.62-70
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• 2000

The design of gear train is a kind of mixed problems which have to determine various types of design variables; i,e., continuous, discrete, and integer variables. Therefore, the most common practice of optimum design using the derivative of objective function has difficulty in solving those kinds of problems and the optimum solution also depends on initial guess because there are many sophisticated constrains. In this study, the Genetic Algorithm is introduced for the optimum design of gear trains to solve such problems and we propose a genetic algorithm based gear design system. This system is applied for the geometrical volume(size) minimization problem of the two-stage gear train and the simple planetary gear train to show that genetic algorithm is better than the conventional algorithm solving the problems that have continuous, discrete, and integer variables. In this system, each design factor such as strength, durability, interference, contact ratio, etc. is considered on the basis of AGMA standards to satisfy the required design specification and the performance with minimizing the geometrical volume(size) of gear trains