• 터널과지하공간
• /
• 제21권6호
• /
• pp.480-493
• /
• 2011

암석의 동적물성은 내진설계의 동적해석에 필요한 물성이다. 본 연구에서는 충남 연기군 지역의 화강암 시험편을 대상으로 양단자유 공진주시험을 실시하여 동적물성인 동탄성계수, 동전단계수, 감쇠비 등의 특성을 분석하고, 역학적 물성과의 상관관계를 분석하였다. 탄성파속도를 기준으로 동적물성을 분석한 결과, 탄성파속도가 빠를수록 동탄성계수와 동전단계수는 선형적으로 증가하는 경향을 보였으며, 감쇠비는 비선형적으로 감소되는 것으로 조사되었다. 논문은 사인형태의 입사파에 대한 장점을 설명하고 또한 동하중에 대한 암석의 크기효과를 설명하고 있다.

• Geomechanics and Engineering
• /
• 제28권2호
• /
• pp.107-116
• /
• 2022

The steady state of unsaturated soil takes a long time to achieve. The soil seepage behaviours and hydraulic properties depend highly on the wetting/drying rate. It is observed that the soil-water characteristic curve (SWCC) is dependent on the wetting/drying rate, which is known as the dynamic effect. The dynamic effect apparently influences the scanning curves and will substantially affect the seepage behavior. However, the previous models commonly ignore the dynamic effect and cannot quantitatively describe the hysteresis scanning loops under dynamic conditions. In this study, a dynamic hysteresis model for SWCC is proposed considering the dynamic change of contact angle and the moving of the contact line. The drying contact angle under dynamic condition is smaller than that under static condition, while the wetting contact angle under dynamic condition is larger than that under static condition. The dynamic contact angle is expressed as a function of the saturation rate according to the Laplace equation. The model is given by a differential equation, in which the slope of the scanning curve is related to the slope of the boundary curve by means of contact angle. Empirical models can simulate the boundary curves. Given the two boundary curves, the scanning curve can be well predicted. In this model, only two parameters are introduced to describe the dynamic effect. They can be easily obtained from the experiment, which facilitates the calibration of the model. The proposed model is verified by the experimental data recorded in the literature and is proved to be more convenient and effective.

• Structural Engineering and Mechanics
• /
• 제23권6호
• /
• pp.635-649
• /
• 2006

The static and dynamic responses of guyed telecommunication towers can be determined by using two models, the space truss element model, and the equivalent beam-column element model. The equivalent beam-column analysis is based on the determination of the equivalent shear, torsion, and bending rigidities as well as the equivalent area of the guyed mast. In the literature, two methods are currently available to determine the equivalent properties of lattice structures, namely: the unit load method, and the energy approach. In this study, an equivalent beam-column analysis is introduced based on an equivalent thin plate approach for lattice structures. A finite-element modeling, using suitably modified ABAQUS software, is used to investigate the accuracy of utilizing the different proposed methods in determining the static and dynamic responses of a guyed tower of 364.5-meter high subjected to static and seismic loading conditions. The results from these analyses are compared to those obtained from a finite-element modeling of the actual structure using 3-D truss and beam elements. Good agreement is shown between the different proposed beam-column models, and the model of the actual structure. However, the proposed equivalent thin plate approach is simpler to apply than the other two approaches.

• 한국군사과학기술학회지
• /
• 제20권2호
• /
• pp.206-216
• /
• 2017

This paper studies on the dynamic properties of Ti-6Al-4V alloy. After forming the four different micro structures(equiaxed, lamellar, and 2 bimodals) through heat treatments, static and dynamic properties of each structure were investigated quantitatively. Dynamic behaviors of the alloy are observed by the compressive split Hopkinson pressure bar(SHPB) tests. In additon, parameters of Johnson-Cook equation were determined from the SHPB test results. In order to verify the suitability of the parameters, high velocity impact tests were performed and the results were compared with the numerical analysis results. Although the flow stress and the fracture strain of the bimodal structures were higher than those of the equiaxed structure at the static tests, the superior dynamic properties were observed at the equiaxed structure due to the effects of higher maximum flow stress and fracture strain. From the numerical analysis, J-C parameters which are determined on this study describe well the dynamic behavior of Ti-6Al-4V alloy. Experimental and analysis results are consistent with ${\pm}5%$ of an average error.

• 드라이브 ㆍ 컨트롤
• /
• 제20권3호
• /
• pp.42-49
• /
• 2023

In this study, the safety of fastening device for the agricultural by-product collector was evaluated according to the driving ground conditions by deriving the stress, static safety factor, and fatigue life using dynamic simulation. A 3D modeling of agricultural by-product collector was carried out, and simulation model was developed by applying the material properties. As a result of dynamic simulation, the magnitude of the maximum stress generated in the fastening device was the highest when driving on the flat off-road, followed by sloped pave-road and flat pave-road. Static safety factor and fatigue life were the highest when driving on the flat pave-road, followed by sloped pave-road and flat off-road. The safety of fastening device was confirmed that static safety factor was more than 1.0 and service life exceeded 9 years in all driving ground conditions.

• 제어로봇시스템학회논문지
• /
• 제10권1호
• /
• pp.60-65
• /
• 2004

A flexible tactile sensor away with 8 H 8 tactile elements is designed and fabricated. The material of the sensor is PVDF(polyvinylidene fluoride) film and flexible circuitry is used in the fabrication fur the flexibility of the sensor The experimental results on static and dynamic properties of the sensor are obtained and examined. The signals of a contact pressure to the sensor are sensed and processed in the DSP system in which the signals are digitalized and filtered. The processed signals of the sensor outputs are visualized in a personal computer for illustrating the shape and force distribution of a contact object. The reasonable performance for the detection of contact state is verified through sensing examples.

• 한국기계가공학회지
• /
• 제12권5호
• /
• pp.116-121
• /
• 2013

A high speed deburring machine was developed based on the analysis of magnetic contact force, forced vibration, stiffness and deformation of the structure. After 3 dimensional CATIA modelling, the stiffness and the deformation properties of the deburring machine in static and dynamic condition using finite element method were analyzed. Both static and dynamic simulation results showed that designed high speed deburring machine was well satisfied the stability properties at the operating condition. we have performance test program for the real system to evaluate the simulation results.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.656-661
• /
• 2004

Static and dynamic responses of micro double cantilever beam structures interacted by electrostatic forces are obtained employing Galerkin's method based on Euler beam theory. Variations of static and dynamic responses as well as natural frequencies are estimated for several sets of beam properties and applied voltages. It is shown that the variations of beam properties resulted by manufacturing process influence the deflections and the modal characteristics significantly. Such information can be usefully employed for the design of MEMS structures.

• Elastomers and Composites
• /
• 제35권2호
• /
• pp.138-148
• /
• 2000

EPDM 발포체의 정적/동적 특성을 측정하여 재료 특성과 진동 특성과의 연관성을 알아보고 이로부터 충격음 저감재로서의 적용 가능성을 검토하였다. 정적/동적 특성은 material test system (MTS)를 사용하여 시편의 형상, 두께, 초기하중, 발포도 등에 따라 정적 탄성계수, 동적 탄성계수, 전달율의 변화를 조사하였다. 정적 탄성계수와 동적 탄성계수의 경우, 형상이 단순하고 두께가 얇을수록 큰 값을 나타냈고, 전달율과 동적 탄성계수는 상호 비례 관계에 있음을 확인할 수 있었다. 특징적으로 동적 탄성계수가 증가하면, 전달율의 특성 피크치는 같은 주파수 영역에서의 증가 혹은 고주파수 영역으로의 전이의 형태로 일어나게 되는 것을 알 수 있었다. 실험실적 모사 시험장치를 통해 충격에 따른 주파수별 진동 속도측정과 유한 요소 해석 모델을 사용하여 mode shape에 의한 충격 해석 결과를 알아보았는데, EPDM 발포체를 사용함으로써 2.5-3.5배의 진동 속도 저감이 이루어짐을 알 수 있었고, mode shape의 경우 몰타르와 콘크리트만으로 구성된 구조물에 비해 진동 충격에 대한 변위가 급감함으로써 충격음 저감재로서의 EPDM 발포체의 적용 가능성은 상당히 높은 것을 확인할 수 있었다.

• 대한금속재료학회지
• /
• 제48권1호
• /
• pp.8-18
• /
• 2010

This study aimed at investigating quasi-static and dynamic torsional deformation behavior of three API X70 and X80 linepipe steels. Quasi-static and dynamic torsional tests were conducted on these steels. having different grain sizes and volume fractions of acicular ferrite and polygonal ferrite, using a torsional Kolsky bar. The test data were then compared via microstructures and adiabatic shear band formation,. The dynamic torsional test results indicated that the steels rolled in the single phase region had higher maximum shear stress than the steel rolled in the two phase region, because the microstructures of the steel rolled in the single phase region were composed mainly of acicular ferrites. In the X80 steel rolled in the single phase region, the increased dynamic torsional properties could be explained by a decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. The possibility of adiabatic shear band formation was analyzed from the energy required for void initiation and variation in effective grain size.