• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.208-211
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• 2005

This paper describes the development process of steering system for reduce idle vibration through the data level of frequency and sensitivity. High stiffness and light weight vehicle is a major target in the refinement of passenger cars to meet customers' contradictable requirements between NVH performance and fuel economy. The target frequency of the steering system is set by benchmarking of a competitive vehicle and the vibration mode map is used to separate steering column modes from resonance of body structure and engine idle rpm. This paper descirbes the analysis approach process for high stiffness of steering system and the design guideline is suggested about steering column and support system by using mother car at initial design stage. We used a patent map in order to analyze accurately a technical trend and suggested the design process using dynamic damper of steering system considering sensitivity. And we established techniques of analysis on steering system and evaluated the level of accuracy of analysis through correlating the test and analysis results. It makes possible to design the good NVH performance vehicle at initial design stage and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

• 한국유체기계학회 논문집
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• 제15권6호
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• pp.39-45
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• 2012

This paper describes the outcome of the design of a 200 kW class micro gas turbine and the sensitivity of its performance (efficiency and power) to the variations in major design parameters. The reference design parameters were set up based on the best available component technologies. The resulting net electricity generation efficiency of the micro gas turbine package was found to be competitive to those of other systems in the market. The sensitivities of power and efficiency to the variations in compressor and turbine efficiencies, pressure ratio, turbine inlet temperature, recuperator effectiveness, secondary air ratio, pressure loss ratios of both the cold and hot sides of the recuperator were estimated. Based on the sensitivity data, a simplified method to predict the variation in system performance responding to the combinations of small changes in all design parameters were set up and validated.

• 대한조선학회논문집
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• 제51권1호
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• pp.78-87
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• 2014

Recently the offshore wind turbine development is requested to be installed off south-west coast and Jeju island in Korea. Reliable and robust support structures are required to meet the demand on the offshore wind turbine in harsh and rapidly varying environmental conditions. Monopile is the most preferred substructure in shallow water with long term experiences from the offshore gas and oil industries. This paper presents an optimum design of a monopile connection with grouted transition piece (TP) for the reliable and cost-effective design purposes. First, design loads are simulated for a 5 MW offshore wind turbine in site conditions off the southwest coast of Korea. Second, sensitivity analysis is performed to investigate the design sensitivity of geometry and material parameters of monopile connection based on the ultimate and fatigue capacities according to DNV standards. Next, optimization is conducted to minimize the total mass and resulted in 30% weight reduction and the optimum geometry and material properties of the monopile substructure of the fixed offshore wind turbine.

• Smart Structures and Systems
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• 제18권2호
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• pp.293-315
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• 2016

Seismic isolation is often used in protecting mission-critical structures including hospitals, data centers, telecommunication buildings, etc. Such structures typically house vibration-sensitive equipment which has to provide continued service but may fail in case sustained accelerations during earthquakes exceed threshold limit values. Thus, peak floor acceleration is one of the two main parameters that control the design of such structures while the other one is peak base displacement since the overall safety of the structure depends on the safety of the isolation system. And in case peak base displacement exceeds the design base displacement during an earthquake, rupture and/or buckling of isolators as well as bumping against stops around the seismic gap may occur. Therefore, obtaining accurate peak floor accelerations and peak base displacement is vital. However, although nominal design values for isolation system and superstructure parameters are calculated in order to meet target peak design base displacement and peak floor accelerations, their actual values may potentially deviate from these nominal design values. In this study, the sensitivity of the seismic performance of structures equipped with linear and nonlinear seismic isolation systems to the aforementioned potential deviations is assessed in the context of a benchmark shear building under different earthquake records with near-fault and far-fault characteristics. The results put forth the degree of sensitivity of peak top floor acceleration and peak base displacement to superstructure parameters including mass, stiffness, and damping and isolation system parameters including stiffness, damping, yield strength, yield displacement, and post-yield to pre-yield stiffness ratio.

• 감성과학
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• 제15권2호
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• pp.317-327
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• 2012

This paper uses the sensibility engineering method to find the model of automobile most appealing to buyers in the $4^{th}$ and $5^{th}$ tier cities of China. Samples of class A & A0 cars were shown to 96 subjects in those cities to investigate their responses in relation to the concepts 'modern' and 'smart'. The result shows that even though men tend to be more sensitive to automobile models in general than women are, both genders showed similar responses to specific models when they were asked to identify a model 'magnificent', 'modern', 'lively', 'smart' or 'cute'. This implies that despite the gender differences in terms of aesthetic sensitivity, both men and women share similar taste in relation to the appearance of cars. Apart from aesthetics, however, men tend to pay a greater attention to the details of design and material used for the cars, while women tend to pay attention to higher priced and better looking cars.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.580-585
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• 2001

A response surface method(RSM) is utilized for structural optimization and implemented on a parametric CAD platform. Once an approximation of the performance function is made, no formal design sensitivity analysis is necessary. The approximation gives the designer the sensitivity information and furthermore intuition on the performance functions. The scheme for the design of experiment chosen for the RSM has a large influence on the accuracy of converged solutions and the amount of computation. The D-optimal design criterion as implemented in this paper is found efficient for the structural optimization. The program is developed on a parametric CAD platform and tested using several shape design problems of such as a torque arm and a belt clip. It is observed that the RSM used provides a faster convergence than other approximation methods for design sensitivity.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2833-2842
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• 1996

This paper is to practice optimal rigidity design by the strain energy density estimation method for static buckling and sizing design sensitivity analysis for dynamic buckling of a nonlinear vehicle frame structure from those results. Using these sizing design sensitivity resutls, an optimization of a nonlinear vehicle frame structure with dynamic buckling constraint is carrried out with the graient projection method.

• 한국생산제조학회지
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• 제7권5호
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• pp.106-112
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• 1998

Experience and experiments show that in many cases the buckling limit is reached at a much smaller load level than is predicted by linear buckling analysis. In this paper, it is considered linear and nonlinear of plane vehicle structure and estimates design sensitivity of the cross sectional area that is composed plane vehicle structure and performs optimal design. It compares linear vehicle structure with nonlinear vehicle structure for optima design result that is selected constraint condition of buckling load.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.359-369
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• 1999

The paper describes the study of concurrent subspace optimization(CSSO) for coupled multidisciplinary design optimization (MDO) techniques in mechanical systems. This method is a solution to large scale coupled multidisciplinary system, wherein the original problem is decomposed into a set of smaller, more tractable subproblems. Key elements in CSSO are consisted of global sensitivity equation(GSE), subspace optimization (SSO), optimum sensitivity analysis(OSA), and coordination optimization problem(COP) so as to inquiry valanced design solutions finally, Automatic differentiation has an ability to provide a robust sensitivity solution, and have shown the numerical numerical effectiveness over finite difference schemes wherein the perturbed step size in design variable is required. The present paper will develop the automatic differentiation based concurrent subspace optimization(AD-CSSO) in MDO. An automatic differentiation tool in FORTRAN(ADIFOR) will be employed to evaluate sensitivities. The use of exact function derivatives in GSE, OSA and COP makes Possible to enhance the numerical accuracy during the iterative design process. The paper discusses how much influence on final optimal design compared with traditional all-in-one approach, finite difference based CSSO and AD-CSSO applying coupled design variables.

• International Journal of Railway
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• 제8권1호
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• pp.5-9
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• 2015

Reliability based limit state design method is replacing traditional deterministic designs such as allowable stress design and/or ultimate strength design methods in world trends. European design code(Eurocode) has adopted limit state design, and Korea road bridge design standard has also recently been transferred to limit state design method. In this trend, Korea railroad design standard is also preparing for adopting the same design concept. While safety factors are determined empirically in traditional design, load combinations as well as load factors are determined by solving limit state equations. General partial safety factors are evaluated by using AFORM(Advanced First Order Reliability Method) in the reliability based limit state design method. In this study sensitivity analysis is carried out for a dead load factor and a live load factor. Relative precisions of the dead load and the live load factors are discussed prior to the AFORM analysis. Furthermore the sectional forces of design and the material quantities required by two different design methods are compared for a PSC box girder railway bridge.