다분야 최적설계를 위한 파라메트릭 구조해석 방법 연구

정효식 경상대학교 대학원 2006 국내석사

For the design optimization of the whole system, disciplines like aerodynamics and structure have been optimized sequentially and independently. This kind of sequential and independent approach does not solve the actual problem, so the approach is not good enough for the complex system design like airplane design. To overcome this limitation, we need a MDO(Multi-Disciplinary Optimization) concept, which is the method for system optimization based on disciplinary base analysis. The purpose of this paper is constructing base system for 3-dimensional wing shape optimization using advanced optimization method which integrates and concurrently optimize aerodynamics and structure. Base system are consist of aerodynamics shape design, aerodynamics mesh generation, aerodynamics analysis, structure finite element model generation, structure analysis and load transfer from aerodynamics to structure. Each part is modulized and automized.

점성효과를 고려한 스테이터와 움직이는 로터 케스케이드의 비선형 유체/구조 연계해석

오세원 경상대학교 대학원 2007 국내석사

In this study, nonlinear fluid/structure coupling analyses have been conducted for a stator and moving rotor cascade configuration. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed static and dynamic responses of general stator-rotor cascade configurations. Especially, effects of relative motions of the rotor cascade with respect to the stator cascade are considered in numerical analyses. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming techniques. Unsteady, Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras (S-A) and SST - turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the cascades for fluid-structure interaction (FSI) problems. For the purpose of validation of the developed FSI analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. Also, flow-induced vibration (FIV) analyses for the single blade row cascade models have been conducted. Detailed static and dynamic FSI responses for stator-rotor interaction flow conditions are presented to show the physical performance and vibration characteristics in the time-domain.

카플란수차에서 발생하는 진동현상 연구

피인섭 경상대학교 대학원 2006 국내석사

Changing output of the power from 1000kW to 7000kW by 1000kW stages, We measured the vibration of Nam-gang hydropower by using a kaplan turbine of the vertical bulb type. In the range of measurement, we used a stay-vane part for the generator and set up the standardds of axiality and radius direction of runner's casing part for the turbine by using an accelerometer. We measured 0~5kHz of frequency per 5minutes and performed vibrational tests, we realized that the cavitation phenomena caure vibrations as we raised the power in the analysis of the FFT. The value off the RMS means that not only the size of the vibrations but also possibilities of the cavitation's occurrence. Also it makes cavitation phenomena front and rear of 3.5kHz high -frequency range as the result. We measured the shape of runner to research into the cazitation,s effect accurately. After inspecting runner's surface accurately, we detected that cavities had been generated intensively from the upstream of the tuunner, grom the leading edge to the vicinity(20~60cm) inthe runner root Cavity which is genetated is 1/8~1/4 of dimension and is designed to getting incidence of angle of attack from aviewpoint of the runner character. Since there wasn't reasonable operations related tho the increased height of Nam-gang dam, the runner malfunctioned and after all it occurred the cavitation. It needs to decide output limit ranges according to changing water level. because the vibrations occurred in cavitation are differ from the water level. Also, it is required the shape of downstream gate, penstock, guide vane, runner to judge water flow conditions accurately. On the assumption that the water level of Nam-gang dam could be changed from the high water level to low water level for safety operation, there are 3 variables that Nam-gang hydropower can choose. 1. Adjusting method of guide vane's rotation angle 2. Adjusting method of runner vane's rotation angle 3. Adjusting method of water level of downstream It is required to carry out vibration tests with changing power at each water level in order to have a safety operation-maintenance. Also calculating water flow and judging cavitations according to three variables above are needed. As you can see in total vibration curves of each output of the power, operating below 6500KW was very recommended method to reduce vibrations and noises. Hereafter, the result which we obtained from status diagnosis is needed to present normal operating range. And it will be used as a reference design of the horizontal kaplan turbine.

보 이론을 이용한 복합재 풍력 블레이드의 구조해석

정성훈 경상대학교 2007 국내석사

This thesis is about structural analysis of composite wind turbine blade based on beam theory. The general idea of wind turbine blade including design process, coordinate system, material property, laminate plan, structural concept and load applications were studied to analysis wind turbine blade. The classical laminated plate theory, modulus weighted centroid and Euler's beam theory were investigated to get a section property and structural analysis of wind turbine blade. The calculated section properties and structural analysis results by the developed code were verified and compared with commercial structural analysis code, PATRAN as a pre/post processor and ABAQUS as a solver. Flapwise stiffness and deflection which is critical to wind turbine design showed good agreement with commercial software. However, there are some deviations in edgewise stiffness and deflection, especially in inboard section due to the geometrical shape. Stress results showed similar stress distribution tendency along the blade length as the commercial software but stress level had some differences.

로터-낫셀 시스템의 훨플러터 특성 연구

양용준 경상대학교 대학원 2006 국내석사

In this study, simplified whirl flutter analyses using quasi-steady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters for rotor-nacelle system are considered and the effects of whirl flutter stability have been investigated for various design parameters.

공력효과를 적용한 복합재 풍력 터빈블레이드의 정적/동적 해석 연구 : Static and Dynamic Analysis of a Composite Wind Turbine Blade including Aerodynamic Effect

알랙산드바비 경상대학교 2007 국내석사

The work in this thesis can be divided into two domains. First work deals with the static and dynamic analysis of a composite horizontal axis wind turbine blade including the aerodynamic effects. The finite element model for simulation of the static and dynamic responses of a composite wind turbine blade has been developed. The simulations are performed using commercial finite element software SAMCEF, which is a program developed for general analysis, linear as well as non-linear, static as well as dynamic. The aerodynamic model, used to transform the wind flow field to loads on the blade, is a CFD model. The CFD grid is constructed using the GAMBIT module of the Fluent software. The result for aerodynamic analysis shows that the static pressure on the front surface of the blade is higher than that on the back surface of the blade. The static and dynamic analysis results show that the composite blade is met the design requirements. Second work deals with the development of Blade Element Momentum code using MATLAB. The code is made with the purpose of the aerodynamic loads calculations on the wind turbine blade. The main algorithm is based on classical Blade Element Momentum theory from Glauert. For the verification purpose, the generic wind turbine blade example from BLADED software was used as a reference model. The results for generic wind turbine blade model from BEM code show a good agreement with that from BLADED software

복합재-금속 접착 단일겹침 체결부의 전단강도 특성에 관한 연구

김태환 경상대학교 대학원 2007 국내석사

Failure loads of bonded joints are very sensitive to the adherend material and bonding conditions. It is commonly found that the bonding strength of practical joint is much lower than that of adhesive provided by manufacturer. In this study, a parametric study on the adhesively bonded carbon composite-to-aluminum single-lap joints was conducted by experiment. A high strength adhesive FM73m by Cytec was used for bonding. The main objective of this study is to investigate the effect of various parameters, such as overlap length (i.e. bonded area), curing pressure for bonding, the thickness of two adherends, and stacking sequence of composite adherend, on the failure load and mode of the joint with dissimilar materials. While the metal bonded joints generally fail in adhesive layer, the final failure modes of all the tested bonded joints with dissimilar materials were delamination of composite adherend. Bonding strengths of the tested joints were lower than the metal-to-metal bonded joint strength. Failure loads of the joint did not increase at the bonding length longer than 35 mm. In terms of the bonding pressure, specimens bonded under the pressure of 4 and 6 atm induced higher failure loads than pressure of 3 atm which is within the range of the manufacturer-recommended curing pressure. In case of stacking sequence change of laminate in composite adherend, the strength of the joint with woven prepreg was lower than that of joint with all unidirectional prepreg. because the joint with all unidirectional prepreg was failed with mixed delamination of ±45°, 90° and 0° layers. Increasing adherend thickness was not linearly proportional to the failure loads. Changing stacking sequence was confirmed to induce the change of interlaminar stresses and failure loads.

압축기 밸브의 유체- 구조 연계 및 비선형충돌 해석 : Flow Structure Interaction and Nonlinear Impact Analysis of Compressor Valves

레사 옥타비안티 경상대학교 대학원 2007 국내석사

Discharge valve failure is a common problem which causes compressor of refrigerator failed to operate. There are several problems contribute in this failure as of wear, overstress, fatigue, corrosion, and combination of these factors. In order to attain the 3 years lifetime-cycle of discharge valve before performing major maintenance, discharge valve configuration need to operate without failure. In this thesis, discharge valve of reciprocating compressor for small hermetic refrigerator has been analyzed to simulate its dynamics motion during its operation. The numerical model of discharge valve has been constructed to conduct different types of analyses, such as contact analysis, flow structure interaction analysis, and impact analysis. The analyses are carried out for several type of discharge valve configuration. Three type of compressor model are scrutinized to give the insight to comparatively examine the discharge valve configuration which prone to have fatigue failure during its operational period. Flow structure interaction analysis is conducted using commercial software (ADINA Ver.8.3) in order to obtain velocity profile for further analysis. The specified flow-structure interaction domain is merely emphasized on discharge valve structure. Therefore, the impact analyses based on velocity result obtained in flow-structure interaction analysis are conducted in order to preliminarily estimate the limit cycling stress region as of impact results to its supported structure over discharge valve.

틸트로터 허브 동하중을 고려한 복합재 스마트 무인기 진동해석

정세운 경상대학교 대학원 2006 국내석사

In this study, structural analyses of a composite smart unmanned aerial vehicle (UAV) have been conducted considering the dynamic hub-loads of tilt-rotor. Unsteady hub-loads of tilt field is divided into a moving zine with rotating blades and a stationary zone containing wing, nacelle and fuselage configurations. Dynamic hub-loads ate calculated for three different flight modes: helicopter, transition,and airplane. Computational structural dynamic techique based on the finite element nethod is practically applied using MSC/NASTRAN. The present smart UAV structural model is constructed as a full 3D configuration with composite materials. Modal based transient and frequency response analyses are used to efficiently investigate vibration transition flight mode corresponding to the case of 80-deg tilting angle is most critical to the induced vibration level of major electronic equipments installed in the front body of the SUAV model.

클로즈 몰드 공정의 PMI 폼 두께 영향성 연구

최상민 경상대학교 대학원 2009 국내박사

Close mold or matched metal die molds are used to produce composite parts, which are controlled outside surface with high tolerance such as a helicopter rotor blade. The objective of this study is to investigate the effect of oversized thickness of crushable PMI(Polymetacrylimide) foam, Rohacell 51WF, that is co-cured with thermoset composite material, Hexel 913 Carbon/Epoxy prepreg, in a closing mold process. Close mold process using crushable foam is analyzed in three phases including initial mold phase, foam relaxation phase and thermal expansion phase. A parametric study is performed using a simplified specimen which is manufactured using the close mold process, with different foam heights and oversized thicknesses of crushable foam. Mechanical and physical tests are carried out on the cut-off specimen, from the upper and lower skins of each cured specimen, to compare the effect of parameters and to examine the quality of process. Flexural, short beam shear, resin content and Tg-DMA test are performed. SEM and lightmicroscope inspections are performed for upper and lower skin interface, between skin and foam. Uniaxial compression test of PMI foam are also conducted to investigate the behavior and deformation mechanism of the foam, with different crosshead speed and different temperature. PMI foam stress-strain curve has an initial elastic behavior, followed by a long plateau regime in which the stress is almost constant at a densification regime. The compression strength of PMI foam decreases as the temperature rises and increase as the crosshead speed increase. Numerical analysis is performed to simulate behavior of foam. Test results show that oversizing the PMI foam in linear elastic region gives the best quality and mechanical performance of the sandwich structure by the close mold process. It is also found that the oversized thickness beyond the elastic region squeezes out the resin too much from the skin and consequently results in the increase of foam weight.