• Journal of Mechanical Science and Technology
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• 제14권2호
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• pp.197-206
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• 2000

A boundary integral equation method in the shape design sensitivity analysis is developed for the elasticity problems with axisymmetric non-homogeneous bodies. Functionals involving displacements and tractions at the zonal interface are considered. Sensitivity formula in terms of the interface shape variation is then derived by taking derivative of the boundary integral identity. Adjoint problem is defined such that displacement and traction discontinuity is imposed at the interface. Analytic example for a compound cylinder is taken to show the validity of the derived sensitivity formula. In the numerical implementation, solutions at the interface for the primal and adjoint system are used for the sensitivity. While the BEM is a natural tool for the solution, more generalization should be made since it should handle the jump conditions at the interface. Accuracy of the sensitivity is evaluated numerically by the same compound cylinder problem. The endosseous implant-bone interface problem is considered next as a practical application, in which the stress value is of great importance for successful osseointegration at the interface. As a preliminary step, a simple model with tapered cylinder is considered in this paper. Numerical accuracy is shown to be excellent which promises that the method can be used as an efficient and reliable tool in the optimization procedure for the implant design. Though only the axisymmetric problem is considered here, the method can be applied to general elasticity problems having interface.

• 한국전산구조공학회논문집
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• 제19권1호
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• pp.27-37
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• 2006

모사풀림(SA)의 특징적인 Metropolis 규준을 단순 유전자 알고리즘(SGA)의 재생산 연산과정에 도입함으로써 Metropolis 유전자 알고리즘(MGA)이 개발되고, 구조 설계 최적화에 응용되었다. 이러한 결합을 통하여 MGA는 개체의 다양성을 유지하며, 초기 세대에서 나타날 수 있는 유용한 유전자 정보가 보존될 수 있다. 따라서 이 연구에서 제안된 MGA는, 국부적 최적해로 조기 수렴하게 되는 SGA의 단점과 정밀한 전역적 최적해를 찾기 위해 수없이 많은 계산을 해야 하는 SA의 단점을 극복하게 되었다 수치예를 통하여 MGA의 성능과 적용성을 재래의 알고리즘들과 비교하고 평가하였다. 특히 MGA의 성능 신뢰성과 강건성을 평가하는 데는 집단 크기와 최대 반복세대수의 효과를 인용하였다. 이론적 고찰과 수치예의 결과로부터, 이 연구에서 개발된 MGA가 효율성과 신뢰성을 갖춘 구조 설계 최적화의 도구로서 평가되었다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.629-634
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• 2000

Generally, the accuracy of motion control systems is strongly influenced by both the mechanical characteristics and servo characteristics of feed drive systems. In the fed drive systems of machine tools that consist of mechanical parts and electrical parts, a torsional vibration is often generated because of its elastic elements in torque transmission. Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed drive system. In this paper, based on the simplifies feed drive system model, radius errors due to position gain mismatch and servo response characteristic have been developed and an optimal criterion for tuning the gain of speed controller is discussed. The proportional and integral parameter gain of the feed drive controller are optimal design variables for the gain tuning of PI speed controller. Through the optimization problem formulation, both proportional and integral parameter are optimally tuned so as to compensate the radius errors by using the genetic algorithm. As a result, higher performance on circular profile tests has been achieved than the one with standard parameters.

• 지식경영연구
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• 제20권3호
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• pp.39-47
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• 2019

Response surface methodology (RSM) is a group of statistical modeling and optimization methods to improve the quality of design systematically in the quality engineering field. Its final goal is to identify the optimal setting of input variables optimizing a response. RSM is a kind of knowledge management tool since it studies a manufacturing or service process and extracts an important knowledge about it. In a real problem of RSM, it is a quite frequent situation that considers multiple responses simultaneously. To date, many approaches are proposed for solving (i.e., optimizing) a multi-response problem: process capability function approach, desirability function approach, loss function approach, and so on. The process capability function approach first estimates the mean and standard deviation models of each response. Then, it derives an individual process capability function for each response. The overall process capability function is obtained by aggregating the individual process capability function. The optimal setting is given by maximizing the overall process capability function. The existing process capability function methods usually use the arithmetic mean or geometric mean as an aggregation operator. However, these operators do not guarantee the Pareto optimality of their solution. Moreover, they may bring out an unacceptable result in terms of individual process capability function values. In this paper, we propose a maximin-based process capability function method which uses a maximin criterion as an aggregation operator. The proposed method is illustrated through a well-known multiresponse problem.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.29-34
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• 2017

본 논문에서는 압연 공정을 통해 리드용 와이어를 생산할 때 생산성을 향상시키기 위해 와이어의 직진 속도를 증가시키는 방법을 연구했다. 직진 속도를 증가시킬 때 가장 중요한 점은 와이어가 원래의 목적을 바르게 수행할 수 있는 것이다. 즉, 와이어의 직진 속도가 증가함과 동시에 균열이 발생하지 않으며, 치수 공차를 만족시켜야 한다. 하지만 와이어의 직진속도를 증가시키게 되면 기존의 압하량 보다 더 큰 수치를 주어야 하고 이는 와이어에 보다 큰 손상을 주어 표면에 무리를 주게 된다. 따라서 기존의 2단계 평압연 공정을 통해 생산되었던 와이어의 필요스펙을 충족시키면서 생산성 향상까지 도모할 수 있는 3단계 평압연 공정에 관해 연구하였다. 본 연구에서는 3단계 평압연 롤러의 압하량만을 변수로 가정하고 다른 조건은 현장 조건과 일치시킨다. 상용 PIDO(Process Integration and Design Optimization) 툴인 PIANO (Process Integration, Design and Optimization)를 통해 지정한 변수 3가지를 조작하면서 실험점을 분포하고 이를 바탕으로 최적설계를 진행하여 와이어의 생산성을 향상시킴과 동시에 필요 스펙인 최대 응력의 최소화가 가능하도록 설계되었다.

• 한국항공우주학회지
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• 제42권11호
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• pp.903-910
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• 2014

선풍기는 유도 전동기에 의해 구동되는 축류형 날개를 가진 기계이다. 본 연구에서는 기본 설계된 선풍기의 날개를 바탕으로 스태킹 라인의 최적 설계를 통해 선풍기의 성능 향상을 목표로 하였다. 전산 해석을 위해 상용 툴인 Ansys 사(社)의 CFX 14.5를 이용하였고, 난류 모델은 k-${\omega}$ SST 를 사용하였다. 설계 변수는 스윕 각과 기울기 각으로 설정하였고, 유량과 토크를 목적함수로 설정하여 스태킹 라인의 최적화를 수행하였다. 최적화 결과 풍량이 증가하였고, 토크가 감소함을 확인 하였다. 최적화된 모델과 기본 모델은 KS C 9301을 이용하여 측정되었으며, 전산 해석 결과를 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.81-87
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• 1998

In this paper, a global acoustic design sensitivity analysis (DSA) of field point pressure with respect to structural sizing design variables is developed. Firstly acoustic sensitivity is formulated and implemented numerically. And it is combined with continuum structural sensitivity to obtain the global acoustic, design sensitivity. For this procedure, GASA (global acoustic design sensitivity analyzer) has been developed. A half scale of automobile cavity model is considered in this paper. In order to confirm accuracy of the results of global acoustic DSA obtained by GASA, it is compared with the result of central finite difference method. In order to reduce computation time, Rayleigh approximated solution is evaluated and compared with the solution which used every nodal velocities. Also the acoustic optimization procedure is performed using design sensitivities. From these numerical studies, it can be shown that global acoustic DSA is a useful tool to improve acoustic problems.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.34-39
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• 2001

The median barrier is one of the roadside hardware to prevent severe human and property damage from highway traffic accidents. The foreign standard of concrete median barrier was introduced and implemented without modification fitting to domestic vehicle and highway condition. In a car accident, median barrier doesn't protect vehicle effectively, especially for heavy vehicle such as bus and heavy truck. The purpose of this study is to develop the optimal performance design of concrete median barrier using the design of experiment with crash simulation analysis which is done by Pam-Crash that is one of the commercial crash simulation software. As a result of this study, an optimal design of concrete median barrier is obtained considering von Mises stress, volume and COG acceleration of truck.

• 한국항공우주학회지
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• 제30권1호
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• pp.132-138
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• 2002

오늘날 여러 가지 측면에서 전략적으로 고성능의 위성 본체를 개발하는 것은 매우 중요하다. 본 연구에서는 부분구조합성법의 하나인 구속모드법을 이용한 연성하중해석 기법 및 모달 과도해석법을 사용하여 위성체 구조부재에 대한 최적화를 수행하였다. 제안된 방법은 초기 설계시, 일반적으로 사용되고 있는 준정적 하중을 이용하지 않고, 동종의 발사체에 대해 유사한 위성과의 연성하중해석 자료를 이용함으로써, 각 구조부재에 대해 보다 정확한 결과를 얻을 수 있는 장점이 있다. 예제를 통해 제안된 기법이 초기단계의 위성체 구조 부재의 효율적인 최적설계 및 중량 감소를 위해 적용될 수 있음을 확인하였다.

• Computers and Concrete
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• 제28권5호
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• pp.465-478
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• 2021

On the premise of ensuring that the static performance of the concrete spreader is met, the first-order natural frequency of the concrete spreader is increased, and the weight of the main beam is reduced. ANSYS is used as an analysis tool to perform modal analysis on the concrete spreader. The natural frequency, mode shape and modal test verification will be obtained to ensure the accuracy of finite element model analysis. Using the ANSYS designxplorer module, the size of the main beam is set, and the response surface model between the parameter variables and the optimization objective is established according to the experimental design points. Screening algorithm and MOGA algorithm are used to multi-optimize the stress, first-order natural frequency and girder weight, and the optimal solution is obtained by comparison. The results of modal analysis are consistent with those of the experiment, and a set of optimal solutions is obtained through the optimization algorithm. The optimal solution obtained can meet the purpose of increasing the first-order natural frequency of the concrete spreader and reducing the weight of the main beam under the premise of ensuring the overall dynamic and static performance of the concrete spreader.