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Oh S.K.,Daegu Mechatronics and Materials Institute | Lee K.K.,VP Korea | Suh C.H.,Daegu Mechatronics and Materials Institute | Jung Y.-C.,Daegu Mechatronics and Materials Institute | Kim Y.S.,Kyungpook National University
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

Because of their high flexibility and durability, multilayer bellows are manufactured for use in commercial vehicles, while single-layer bellows are manufactured for use in passenger vehicles. A study based on the finite element method (FEM) and shape optimization for the single-layer bellows has been actively performed; however, until now, a study based on the FEM has rarely been performed for the multilayer bellows with gaps between the layers. This paper presents a finite-element modeling scheme for the multilayer bellows to improve simulation reliability during the evaluation of stress and flexibility. For performing shape optimization for the multilayer bellows, DOE (design of experiment) and the Kriging metamodel followed by the D-optimal method are used. © 2011 The Korean Society of Mechanical Engineers.


Oh S.K.,Daegu Mechatronics and Materials Institute | Lee K.K.,VP Korea | Suh C.H.,Daegu Mechatronics and Materials Institute | Jung Y.-C.,Daegu Mechatronics and Materials Institute | Kim Y.S.,Kyungpook National University
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

The mechanical limited slip differential (LSD) in vehicles is being replaced by the electromagnetic LSD because of its fast response and better active control characteristics. The coil housing made of STS 304 is one of the most important parts in die solenoid assembly of the electromagnetic LSD. High geometrical accuracy is a prerequisite for the manufacture of such coil housings, but precision machining is difficult because of me use of STS 304 thin plate and the variance in machining variables. The aim of this study is to optimize the mean and variance of the shape accuracy in die coil housing by finding a robust solution for the machining process conditions. The mean and standard deviation of the jaw contact pressure, cutting speed, and feed rate are considered to be the major parameters for minimizing the geometrical mean and variance. The response surface model based on the second-order Taylor series is combined together to minimize the mean and variance of die shape accuracy of the coil housing. © 2011 The Korean Society of Mechanical Engineers.


Lee K.-K.,VP KOREA | Lee K.-H.,Korea University | Han S.-H.,Korea University
International Journal of Structural Integrity | Year: 2011

Purpose Approximation techniques were used instead of expensive computing analysis in a traditional parametric design optimization of a complex system. A Kriging meta-model was utilized, which enabled the fit of approximated design characteristics for a complex system such as turbine blades that incorporate a large number of design variables and non-linear behaviors. This paper aims to discuss these issues. Design/methodology/approach The authors constructed a Kriging meta-model with a multi-level orthogonal array for the design of experiments, which were used to optimize the fatigue life of turbine blades under cyclic rotational loads such as centrifugal force. By combining a seven-level orthogonal array with the Kriging model, the non-linear design space of fatigue life was explored and optimized. Findings A computer-generated multi-level orthogonal array provided a good representation of the non-linear design space information. The results show that not only was the fatigue life of the leading edge of the blade root significantly improved, but also that the computing analysis was effective. Originality/value To maximize the fatigue life of the turbine blade, the three-design variables with seven factor levels were optimized via a Kriging meta-model. As with the optimization technique, a desirability function approach was adopted, which converted multiple responses into a single response problem by maximizing the total desirability. © 2011 Emerald Group Publishing Limited. All rights reserved.


Lee K.K.,VP Korea | Han J.W.,System Engineering Research Division | Han S.H.,Dong - A University
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

The technique for order preference by similarity to ideal solution (TOPSIS) is regarded as a classical method of multiple attribute decision making (MADM), often used to solve various decision-making or selection problems. It is based on the concept that the chosen alternative should have the shortest distance from the positive ideal solution and the farthest distance from the negative ideal solution. The TOPSIS can be applied to a design process for carrying out multi-objective shape optimization wherein the best and worst alternatives are to be decided. In this paper, multi-objective shape optimization using the TOPSIS and Rational Bezier curve was applied to the funnel of a cathode-ray tube (CRT). In order to minimize the weight and first principal stress, a new multi-objective shape optimization meuiodology is proposed, wherein the relative-closeness coefficients of the TOPSIS are defined as the performance indices of a multi-objective function and evaluated by response surface models. This methodology enables the designer to decide on the best solution from a number of design specification groups by examining the various conflicts between the weight and the first principal stress. © 2011 The Korean Society of Mechanical Engineers.


Lee K.K.,VP Korea | Han S.H.,Dong - A University
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

In the current design process for the lower arm used in automobile parts, an optimal solution of its various design variables should be found through exploration of the design space approximated using the response surface model formulated with a first- or second-order polynomial equation. In this study, a multi-level computational DOE (design of experiment) was carried out to explore the design space showing nonlinear behavior, in terms of factors such as the total weight and applied stress of the lower arm, where a fractional-factorial orthogonal array based on the artificial neural network model was introduced. In addition, the tolerance robustness of the optimal solution was estimated using a tolerance optimization with six sigma constraints, taking into account the tolerances occurring in the design variables. © 2011 The Korean Society ot Mechanical Engineers.


Lee K.-K.,VP KOREA | Park C.-K.,Korea Railroad Research Institute | Han S.-H.,Dong - A University
Journal of Mechanical Science and Technology | Year: 2010

Robust design for the primary suspension of a railway vehicle was performed according to the optimization of 10 dynamic responses representing driving safety and ride comfort, in which response surface models (RSMs) from the design of experiments (DOEs) were applied. To evaluate the probabilistic feasibility of robustness, an intensive computational process is mandatory. In the present study, the authors utilized the first-order Taylor series expansion to reduce the computational burden associated with a probabilistic feasibility evaluation, thus easily obtaining both an individual mean and variance of constraints. To overcome the difficulty of optimizing the mean and probabilistic variances for the 10 dynamic responses, a process capability index (Cpk) was introduced, which shows the mean value and scattering of the product quality to a certain extent and normalizes the objective functions irrespective of varying dimensions. Consequently, the robust design to optimize the 10 dynamic responses minimized the Cpk subjected to the constraint of Cpk ≥ 2, which satisfied 6σ. The proposed method improved the Cpk that violated the constraints obtained by the RSMs from DOEs and minimized the variance of the Cpk. © KSME & Springer 2010.


Lee K.K.,VP KOREA | Han S.H.,Dong - A University
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2010

A complex system involves a large number of design variables, and its operation is non-linear. To explore the characteristics in its design space, a Kriging meta-model can be utilized; this model has replaced expensive computational analysis that was performed in traditional parametric design optimizatioa In this study, a Kriging meta-model with a computational orthogonal array for the design of experiments was developed to optimize the fatigue life of a turbine blade whose behavior under cyclic rotational loads is significantly non-linear. The results not only show that the maximum fatigue life is improved but also indicate that the accuracy of computational analysis is achieved. In addition, the robustness of the results obtained by six-sigma optimization can be verified by comparison with the results obtained by performing Monte Carlo simulations.


Park H.S.,Hyundai Motor | Chang Y.,Hyundai Motor | Jung J.H.,VP KOREA
Lecture Notes in Electrical Engineering | Year: 2013

Occupant protection during interior head impact is should be consider while designing the headliner. There is a Federal Motor Vehicle Safety Standard, FMVSS201 to ensure the occupant's safety during an interior head impact. Energy absorbing components are used to protect the occupant in the event of impact with components of upper passenger compartment. Automobile manufacturers have been developing suitable designs without Energy absorbing components because of cost issues. The objective of this study is to develop the design method without Energy absorbing components on the grip-handle areas. Grip-handles are located on upper roof in the vehicle where is impact zone that must meet the occupant safety requirement during interior head impact such as FMVSS201U. The head acceleration must be reduced to lower the Head Injury Criterion (HIC) to 1,000. To reduce the head acceleration without energy absorbing components, Grip-handles and related components should absorb the impact by themselves. Grip-handles are connected to brackets. The bracket is used to assemble the headliner with grip-handles. Griphandles and the brackets should endure the downward force. On the other hand, when FMH impact Roof trim, the bracket is deflecting upward and it will absorb the impact energy The bracket needs to meet two demands. In order to meet these demands, Experiment of design will be carried out with the help of CAE and DOE. © Springer-Verlag Berlin Heidelberg 2013.

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