• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.240-244
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• 2017

Experimental verification in the rig test stage for component development is a vital link between the aeromechanical design and structural integrity validation process. Based on this premise, Non-Intrusive Stress Measuring System was adopted on the axial compressor test rig to measure the static and dynamic tip deflection of all blades by using tip-timing sensors. Through analyzing vibration characteristics, we evaluated the vibratory stresses seen on the blades fatigue critical location; detected synchronous resonances which are the source of High Cycle Fatigue (HCF) in blades; presented non-synchronous vibration response by aerodynamic excitation and individual blade mis-tuning patterns.

• Advances in materials Research
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• v.6 no.3
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• pp.279-301
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• 2017

Thermo-mechanical vibration characteristics of in homogeneousporous functionally graded (FG) micro/nanobeam subjected to various types of thermal loadings are investigated in the present paper based on modified couple stress theory with consideration of the exact position of neutral axis. The FG micro/nanobeam is modeled via a refined hyperbolic beam theory in which shear deformation effect is verified needless of shear correction factor. A modified power-law distribution which contains porosity volume fraction is used to describe the graded material properties of FG micro/nanobeam. Temperature field has uniform, linear and nonlinear distributions across the thickness. The governing equations and the related boundary conditions are derived by Extended Hamilton's principle and they are solved applying an analytical solution which satisfies various boundary conditions. A comparison study is performed to verify the present formulation with the known data in the literature and a good agreement is observed. The parametric study covered in this paper includes several parameters such as thermal loadings, porosity volume fraction, power-law exponents, slenderness ratio, scale parameter and various boundary conditions on natural frequencies of porous FG micro/nanobeams in detail.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.569-576
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• 2003

Based on the equivalent uniform stress concept Presented by Seed and Idriss, sinusoidal cyclic loads which simplified earthquake loads have been applied in evaluating the liquefaction resistance strength experimentally. However, the liquefaction resistance strength of soil based on the equivalent uniform stress concept can not exactly reflect the dynamic characteristics of the irregular earthquake motion. The liquefaction assessment method which was invented by using the equivalent uniform stress concept is suitable for the severe earthquake region such as Japan or USA, so the proper method to Korea is needed. In this study, estimation of the resistance to liquefaction was conducted by applying real earthquake loading to the cyclic triaxial test. From the test results, the characteristics of the fine sand under moderate earthquake were analyzed and compared with the results under strong earthquakes. Typically real earthquake loads used in this study are divided into two types - impact type and vibration type. Furthermore, results of the liquefaction resistance strength based on the equivalent uniform stress concept and tile concept using real earthquake loading were compared.

• Explosives and Blasting
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• v.17 no.1
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• pp.27-55
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• 1999

The excavation works for deep foundation in urban areas have recently increased complaints of blasting vibration and settlement of ground level. Foundation must be excavated approximately up to 24-28m depths from the surface. The roads and subway line pass through the excavation area. The Dae-chung station is also located at the nearest distance 5-35m from the working site. To protect subway station and adjacient some structures from blasting and settlement, the level of ground vibration, displacements and stress were monitored and analyzed. The results can be summarized as follows ; 1. An empirical particle velocity equation were obtained by test blasts at Nassan Missi 860 Office tel construction site. $V{\;}={\;}K(D/\sqrt{W})^{-n}$, where the values for n and k are estimated tobe 0.371 and 1.551. From this ground vibration equation, the max. charge weight per delay time against distance from blasting point is calculated. Detailed blasting method is also presented. 2. To measure the horizontal displacement in directions perpendicular to the borehole axis, 6 inclinometers installed around working sites. The displacement at the begining was comparatively high because the installation of struts was delayed, but after its installation the values showed a stable trend. Among them, the displacement by 3 inclinometers installed on a temporary parking area showed comparatively high values, for example, the displacement measured at hole No. IC-l recoded the max. 47.04mm for 6 months and at hole No. IC-2 recorded the max. 57.33mm for 7 months. So, all of these data was estimated below a safe standard value 103mm. 3. Seven strain gauge meter was installed of measure the magnitude and change of stress acted on structs. The measured value of maximum stress was $-465{\;}kgf/\textrm{cm}^2,{\;}-338.4{\;}kgf/\textrm{cm}^2,{\;}302.3{\;}kgf/\textrm{cm}^2$ respectively. In compareto the allowable stress level of steel, they are estimated to be safe.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.108-115
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• 2015

Electro-mechanical actuator installed on aircraft consists of a decelerator which magnifies the torque in order to rotate an axis connected with aircraft control surface, a control section which controls the motor assembly through receiving orders from cockpit and a motor assembly which rotates the decelerator. Electro-mechanical actuator controls aircraft altitude, position, landing, takeoff, etc. It is an important part of a aircraft. Aircraft maneuvering causes vibrations to electro-mechanical actuator. Vibrations may result in structural fatigue. For that reason, it is necessary to analyze the system structural safety. In order to analyze the system structural safety. It is needed reasonable finite element model and structural response stress closed to real value. In this paper, analytic model is derived by using the simplified finite element model, and damping ratio which is closely related to response stress is derived by using modal test. So, we developed analytic model in less than 10 % error rate, compared with modal test. Vibration response stress close to real value was estimated from analytic model modified with modal experimental damping ratio. Estimation method for damping ratio with empirical formula was suggested partly. Finally, It was proved that electro-mechanical actuator had reasonable structure margin of safety at environmental random $3{\sigma}$ stress during life cycle.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.69-78
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• 2009

Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.70-76
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• 2013

This study investigates structural durability through the analyses of stress, fatigue life and vibration damage at bike carrier basket. As model 2 has less stress and deformation than model 1 on static structural analysis, model 2 becomes more durable than model 1. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. The amplitude deformations become highest at maximum response frequency of 2400Hz in cases of models 1 and 2. As the values of maximum equivalent stresses become within the allowable material stresses at two holes at the upper parts on models 1 and 2, these models become safe. The structural result of this study can be effectively utilized with the design of bike carrier basket by investigating prevention and durability against fatigue or vibration damage.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.147-154
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• 2003

Radial Dual Mass Flywheel(RDMF) is designed to reduce torsional vibration and noise occurring in automotive powertrain. In this paper, finite element method is used to evaluate stress level and critical area of the torsional spring box, a major part of RDNF system. In finite element analysis, both static and dynamic loadings are considered and it is found that the most critical spot is the welded zone of spring box. Also, fatigue test is performed and fractured surfaces are examined to find fatigue stress level by experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.434-438
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• 2006

The purpose of this paper is that investigates the Natural Frequency behavior characteristic of Wind Turbine Jacket Type Tower model, and calculated that the stress values of Thrust Load, Wave Load, Wind Load, Current Loda, Gravity Load, etc., environment evaluation analysis during static Operating Wind Turbine Jacket Type Tower model, carried out of Natural Frequency analysis of total load case to stress matrix, Frequency calculated that calculated Add Natural Frequency to stiffness matrix for determinant to stress results. The finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.819-822
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• 2006

This paper has the objects of deciding dynamic instability regions of thick plates on inhomogeneous Pasternak foundation by finite element method and providing kinematic design data for mats and slabs of building structures. In this paper, dynamic stability analysis of tapered opening thick plate is done by use of Serendipity finite element with 8 nodes considering shearing strain of plate. To verify this finite element method, buckling stress and natural frequencies of thick pate with or without in-plane stress are compared with existing solutions. The results are as follow that this finite element solutions with $4{\times}4$ meshes are shown the error of maximum 0.56% about existing solutions, and the larger foundation parameters, the farther dynamic instability regions are from vertical axis of graph presented relation of ${\beta}\;and\;\overline{\omega}/\omega$.