• Title, Summary, Keyword: design sensitivity

### A Design Using Sensitivity Information (민감도 정보를 이용한 설계 방법)

• Kim, Y.I.;Yi, J.W.;Park, G.J.
• Proceedings of the KSME Conference
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• pp.1248-1253
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• 2003
• Sensitivity information has been used for linearization of nonlinear functions in optimization. Basically, sensitivity is a derivative of a function with respect to a design variable. Design sensitivity is repeatedly calculated in optimization. Since sensitivity calculation is extremely expensive, there are studies to directly use the sensitivity in the design process. When a small design change is required, an engineer makes design changes by considering the sensitivity information. Generally, the current process is performed one-by-one for design variables. Methods to exploit the sensitivity information are developed. When a designer wants to change multiple variables with some relationship, the directional derivative can be utilized. In this case, the first derivative can be calculated. Only small design changes can be made from the first derivatives. Orthogonal arrays can be used for moderate changes of multiple variables. Analysis of Variance is carried out to find out the regional influence of variables. A flow is developed for efficient use of the methods. The sensitivity information is calculated by finite difference method. Various examples are solved to evaluate the proposed algorithm.

### Development of Nonlinear Static Design Sensitivity Analysis Based ANSYS (ANSYS 비선형 정적설계민감도해석 외부모듈 개발)

• Choi, Byung-Nam;Jung, Jae-Jun;Yoo, Jung-Hoon;Lee, Tae-Hee
• Proceedings of the KSME Conference
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• pp.543-547
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• 2001
• CAE has been settled down to an indispensable tool for the simulation of a mechanical system according to the development of computer-aided analysis rapidly. Particularly finite element programs have advanced to the one of most valuable things in the filed of CAE due to the remarkable progress in the implementation. But since this analysis tool mostly provides the result of the analysis, it cannot satisfy designers who are seeking for information to improve their designs. Therefore, design sensitivity analysis or optimization module has been incorporated into commercial FEA programs to satisfy the desire of designers since 1990s. Design sensitivity analysis is to compute the rate of change of response with respected to design variable. Design sensitivity analysis is classfied into static design sensitivity analysis, Eigenvalue design sensitivity analysis and dynamic design sensitivity analysis. In this research, it will be presented to nonlinear static design sensitivity analysis formulation and nonlinear static design sensitivity analysis external module based ANSYS have been developed and illustrated an example to verify the developed module.

### Augmented Displacement Load Method for Nonlinear Semi-analytical Design Sensitivity Analysis (준해석적 비선형 설계민감도를 위한 개선된 변위하중법)

• Lee, Min-Uk;Yoo, Jung-Hun;Lee, Tae-Hee
• Proceedings of the KSME Conference
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• pp.492-497
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• 2004
• Three methods for design sensitivity such as numerical differentiation, analytical method and semi-analytical method have been developed for the last three decades. Although analytical design sensitivity analysis is exact, it is hard to implement for practical design problems. Therefore, numerical method such as finite difference method is widely used to simply obtain the design sensitivity in most cases. The numerical differentiation is sufficiently accurate and reliable for most linear problems. However, it turns out that the numerical differentiation is inefficient and inaccurate because its computational cost depends on the number of design variables and large numerical errors can be included especially in nonlinear design sensitivity analysis. Thus semi-analytical method is more suitable for complicated design problems. Moreover semi-analytical method is easy to be performed in design procedure, which can be coupled with an analysis solver such as commercial finite element package. In this paper, implementation procedure for the semi-analytical design sensitivity analysis outside of the commercial finite element package is studied and computational technique is proposed, which evaluates the pseudo-load for design sensitivity analysis easily by using the design variation of corresponding internal nodal forces. Errors in semi-analytical design sensitivity analysis are examined and numerical examples are illustrated to confirm the reduction of numerical error considerably.

### A Design Methodology and Software Development with Sensitivity Information (민감도 정보를 이용한 설계 방법 및 소프트웨어의 개발)

• 김용일;이정욱;윤준용;박경진
• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2092-2100
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• 2003
• Sensitivity information has been used for linearization of nonlinear functions in optimization. Basically, sensitivity is a derivative of a function with respect to a design variable. Design sensitivity is repeatedly calculated in optimization. Since sensitivity calculation is extremely expensive, there are studies to directly use the sensitivity in the design process. When a small design change is required, an engineer makes design changes by considering the sensitivity information. Generally, the current process is performed one-by-one for design variables. Methods to exploit the sensitivity information are developed. When a designer wants to change multiple variables with some relationship, the directional derivative can be utilized. In this case, the first derivative can be calculated. Only small design changes can be made from the first derivatives. Orthogonal arrays can be used for moderate changes of multiple variables. Analysis of Variance is carried out to find out the regional influence of variables. A flow is developed for efficient use of the methods. A software system with the flow has been developed. The system can be easily interfaced with existing commercial systems through a file wrapping technique. The sensitivity information is calculated by finite difference method. Various examples are solved to evaluate the proposed algorithm and the software system.

### Design Sensitivity Analysis of Eigen Problem Using NASTRAN (NASTRAN을 이용한 고유치 문제의 설계 민감도 해석)

• 윤광수;이태희
• Proceedings of the Korean Society of Precision Engineering Conference
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• pp.508-512
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• 1997
• Design sensitivity analysis of Eigen Problem give systematic design improvement information for noise and vibration of a system. Based on reliable results form commercial FE code(UAI/NASTRAN), three computational procedures for design sensitivity analysis of eigen problem are suggested. Those methods are finite difference,design sensitivity analysis using external module and design sensitivity analysis running with NASTRAN. To verify the suggested methods, a numerical example is given and these results are compared with the results from UAI/NASTRAN eigen sensitivity option. We can conclude that design sensitivity coefficient of eigen proplems can be computed outside of the FE code as easy as inside of the FE code.

### DESIGN SENSITIVITY ANALYSIS AND OPTIMIZATION OF ZWICKER'S LOUDNESS (Zwicker 라우드니스에 대한 설계 민감도 해석 및 최적화)

• Kang, Jung-Hwan;Wang, Se-Myung
• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• pp.149-154
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• 2004
• The design sensitivity analysis of Zwicker's loudness with respect to structural sizing design variables is developed. The loudness sensitivity in the critical band is composed of two equations, the derivative of main specific loudness with respect to 1/3-oct band level and global acoustic design sensitivities. The main specific loudness is calculated by using FEM, BEM tools. i.e. MSC/NASTRAN and SYSNOISE. And global acoustic sensitivity is calculated by combining acoustic and structural sensitivity using the chain rule. Structural sensitivity is obtained by using semi-analytical method and acoustic sensitivity is implemented numerically using the boundary element method. For sensitivity calculation, sensitivity analyzer of loudness (SOLO), in-house program is developed. A 1/4 scale car cavity model is optimized to show the effectiveness of the proposed method.

### Displacement-Load Method for Semi-Analytical Design Sensitivity Analysis (준해석 설계민감도를 위한 변위하중법)

• Yoo Jung Hun;Kim Heung Seok;Lee Tae Hee
• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1590-1597
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• 2004
• Three methods of design sensitivity analysis for structures such as numerical method, analytical method and semi-analytical method have been developed for the last three decades. Although analytical design sensitivity analysis can provide very exact result, it is difficult to implement into practical design problems. Therefore, numerical method such as finite difference method is widely used to simply obtain the design sensitivity in most cases. The numerical differentiation is sufficiently accurate and reliable fur most linear problems. However, it turns out that the numerical differentiation is inefficient and inaccurate in nonlinear design sensitivity analysis because its computational cost depends on the number of design variables and large numerical errors can be included. Thus the semi-analytical method is more suitable for complicated design problems. Moreover, semi-analytical method is easy to be performed in design procedure, which can be coupled with an analysis solver such as commercial finite element package. In this paper, implementation procedure fur the semi-analytical design sensitivity analysis outside of the commercial finite element package is studied and the computational technique is proposed for evaluating the partial differentiation of internal nodal force, so called pseudo-load. Numerical examples coupled with commercial finite element package are shown to verify usefulness of proposed semi-analytical sensitivity analysis procedure and computational technique for pseudo-load.

### Optimization of the Path of Inner Reinforcement for an Automobile Hood Using Design Sensitivity Analysis (설계민감도해석을 이용한 자동차후드 보강경로 최적설계)

• Lee, Tae-Hui;Lee, Dong-Gi;Gu, Ja-Gyeom;Han, Seok-Yeong;Im, Jang-Geun
• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1
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• pp.62-68
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• 2000
• Optimization technique to find a path of an inner reinforcement of an automobile hood is proposed by using design sensitivity informations. The strength and modal characteristics of the automobile hood are analyzed and their design sensitivity analyses with respect to the thickness are carried out using MSC/NASTRAN. Based on the design sensitivity analysis, determination of design variables and response functions is discussed. Techniques improving design from design sensitivity informations are suggested and the double-layer method is newly proposed to optimize the path of stiffener for a shell structure, Using the suggested method, we redesign a new inner reinforcement of an automobile hood and compare the responses with the original design. It is confirmed that new design improved in the frequency responses without the weight increasement.

### An Efficient Algorithm for Design Sensitivity Analysis of railway Vehicle Systems (철도차량의 설계 민감도 해석을 위한 효율적인 알고리즘 개발)

• 배대성;조희제;백성호;이관섭;조연옥
• Proceedings of the KSR Conference
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• pp.299-306
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• 1998
• Design sensitivity analysis of a mechanical system is an essential tool for design optimization and trade-off studies. This paper presents an efficient algorithm for the design sensitivity analysis of railway vehicle systems, using the direct differentiation method. The cartesian coordinate is employed as the generalized coordinate. The governing equations of the design sensitivity analysis are formulated as the differential equations. Design sensitivity analysis of railway vehicle systems is performed to show the validity and efficiency of the proposed method.

### Configuration sensitivity analysis of mechanical dynamics

• Bae, Daesung
• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.112-119
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• 2001
• Design sensitivity is an important is an important device in improving a mechanical system design. A continuum design consists of the shape and orientation design. This research develops the shape and orientation design sensitivity method. The configura-tion design variables of multibody systems define the shape and orientation changes. The equations of motion are directly differentiated to obtain the governing equations for the design sensitivity. The governing equation of the design sensitivity is formulated as an over determined differential algebraic equation and treated as ordinary differential equations on mani-folds. The material derivative of a domain functional is performed to obtain the sensitivity due to shape and orientation changes. The configuration design sensitivities of a fly-ball governor system and a spatial four bar mechanism are obtained using the proposed method and are validated against those obtained from the finite difference method.