• Composites Research
• /
• 제23권1호
• /
• pp.37-43
• /
• 2010

이 연구에서는 볼트로 겹침이음된 펄트루젼 복합재의 접합부에 대한 구조적 거동을 실험적 연구를 통해 조사하였다. 펄트루젼 복합재 접합부의 구조적 거동 조사에 앞서 재료의 역학적 성질을 파악하기 위해 펄트루젼 복합재의 인장 및 전단실험을 수행하였고, 이를 바탕으로 볼트의 수와 배열을 변수로 3종류의 겹침이음 시편을 제작하였다. 겹침이음 접합부 실험은 접합부를 중심으로 인장하중이 작용하도록 하중을 재하하였고, 하중증가에 따른 접합부의 구조적 거동 및 파괴모드를 조사하였다. 실험결과 접합부에 대한 파괴는 대부분 전단파괴로 나타났으며, 실험을 통해 얻어진 데이터를 분석하여 설계를 위한 기초자료로 활용될 수 있도록 하였다.

• Steel and Composite Structures
• /
• 제24권4호
• /
• pp.399-408
• /
• 2017

Of high strength bolts, the torque shear type bolt is known to be clamped normally when pin-tails are broken. Sometimes the clamping loads on slip critical connections considerably fluctuate from the required tension due to variation of torque coefficient. This is why the viscosity of lubricant affects the torque coefficient by temperature. In this study, the clamping tests of high strength bolts were performed independently at laboratory conditions and at outdoor environment. The temperatures of outdoor environment candidates were ranged from $-11^{\circ}C$ to $34^{\circ}C$ for six years. The temperature at laboratory condition was composed from $-10^{\circ}C$ to $50^{\circ}C$ at each $10^{\circ}C$ interval. At outdoor environment conditions, the clamping load of high strength bolt was varied from 159 to 210 kN and the torque value was varied from 405 to 556 Nm. The torque coefficients at outdoor environment were calculated from 0.126 to 0.158 when tensions were measured from 179 to 192 kN by using tension meter. The torque coefficients at outdoor environment conditions were analyzed as the range from 0.118 to 0.152. From these tests, the diverse equations of torque coefficient, tension dependent to temperature can be acquired by statistic regressive analysis. The variable of torque coefficient at laboratory conditions is 0.13% per each $1^{\circ}C$ when it reaches 2.73% per each $1^{\circ}C$ at outdoor environment conditions. When the results at laboratory conditions and at outdoor environment were combined to get the revised equations, the change in torque coefficient was modified as 0.2% per each $1^{\circ}C$ and the increment of tension was adjusted as 1.89 % per each $1^{\circ}C$.

• 센서학회지
• /
• 제5권6호
• /
• pp.35-42
• /
• 1996

본 논문에서는 전기자동차에서 사용할 수 있는 모델 기반 잔존용량계(model based battery indicator)를 개발했다. 제안된 방법을 이용하면 잔존용량을 측정하는 데 전지의 전압과 전류만 측정하면 되고, 초기 잔존용량값의 영향을 받지 않으며, 전기자동차와 같이 부하가 급변하는 상태에서도 정확하게 계측할 수 있을 뿐 아니라, 그에 따라 주행 가능 거리를 계산하여 예측할 수 있다. 전지의 방전 특성 데이터를 이용해 수학적인 모델링을 한 후, 전압과 전류를 검출하여 이를 모델링한 식에 대입하면, 추정된 전지 전압을 얻을 수 있다. 이 추정 전압과 측정 전압의 차이가 최소가 되도록 하는 잔존용량의 반화량을 이용히여 잔존용량을 추정한다. 실험에서는 제작한 충방전장치와 PC를 이용하여 전지의 전압과 전류를 계측하여 수학적으로 모델링을 하고, 실제의 전기자동차에 탑재 가능한 스탠드 얼론(stand alone)타입의 마이크로 콘트롤러에 모델식 및 알고리즘을 장착하여 모델 기반 잔존용량계를 실제 검증하여 그 유용성을 입증하였다.

• 한국공간구조학회논문집
• /
• 제19권2호
• /
• pp.35-42
• /
• 2019

The purpose of this paper is to evaluate the structural performance of joints between modules with steel plate press forming type non-symmetric cross section. The main experimental variables are direction of load, whether vertical bolts are fastened, and whether the concrete inside the column is filled. A total of three experiments were performed for each variable. Experimental results show that the behavior of the joints dominated by the local buckling deformation of the upper and lower beam flanges of the module joints, and the final failure was the fracture of the column-beam welds. In case of short side direction, it is possible to secure the performance of intermediate moment frame (0.02 rad). In case of long side direction, it is evaluated that the performance of special moment frame (0.04 rad) is secured regardless of whether or not concrete is infilled in the column.

• Geomechanics and Engineering
• /
• 제34권1호
• /
• pp.51-67
• /
• 2023

In this research, the degradation rate of physical properties of the Angouran pit bedrock (calc-schist) is first investigated under the specific numbers of freeze-thaw (F-T) cycles. Then, the durability of calc-schist specimens against the F-T cycle number (N) is examined considering the mechanical parameters, and using the decay function and half-time techniques. For this purpose, point load strength (I_S(50)), second durability index (I_d2), Brazilian tensile strength (BTS), and compressive (V_P) and shear (V_S) wave velocities of calc-schist specimens are measured after 0, 7, 15, 40, and 75 N. For comparing the degradation rate of mechanical properties of available rock types on the Angouran mine walls, these tests are also carried out on the limestone and amphibolite schist specimens beside the calc-schist. According to test results, the exponential regression models are developed between the mechanical parameters of rock specimen's and N variable. Also, the long-term durability of each rock type versus N is studied using the decay function and half-time techniques. Results indicated that the degradation rate differs for the above rock types in which amphibolite schist and calc-schist specimens have the highest and least resistance against the N, respectively. The obtained results from this study can play a key role in the optimal design of the mine's final walls.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.967-972
• /
• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• 설비공학논문집
• /
• 제22권2호
• /
• pp.78-85
• /
• 2010

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• 설비공학논문집
• /
• 제4권1호
• /
• pp.33-47
• /
• 1992

Experimental investigation on the performance of a heat pump system using refrigerant mixtures is done. The condenser and the evaporator are double pipe heat exchangers of counter flow type and the compressor is driven by a variable speed motor. The refrigerant mixture used in the experiment is R22/R142b. Experiments are performed by changing the compressor speed, composition on ratio of mixture, and the average temperatures of condenser and evaporator. The compressor work, heating capacity and the coefficient of performance are calculated. Results show that the heating capacity can be changed by varying the mass flow rate of refrigerant mixtures to meet the heating load. It is shown that the capacity control by changing the composition ratio is more effective than by changing the compressor speed. Under the condition where the external conditions are fixed and the heating loads are equal, the coefficient of performance has its maximum value near 50 : 50 mass fraction of the refrigerant mixture in this study.

• 전기학회논문지
• /
• 제63권2호
• /
• pp.237-244
• /
• 2014

In this paper, we presented a study on the design of permanent magnet rotor for exterior rotor type brushless direct current(BLDC) motor. To reduce the cogging torque and torque ripple, the specific shape and magnetization pattern of permanent magnets in BLDC motors are suggested. Firstly, four permanent magnet models with different shapes and magnetization arrays are presented. The results from the finite element method(FEM), the most effective model for reducing cogging torque and torque ripple was presented. In addition, to confirm the steady state performance, the torque-speed characteristic analysis has been performed with variable speed and load. Finally, the best permanent magnet model for reducing cogging torque and torque ripple with appropriate torque-speed performance was selected through the comparison according to the device volume.

• Journal of Electrical Engineering and Technology
• /
• 제13권3호
• /
• pp.1123-1130
• /
• 2018

Voltage stabilization is an essential component of power quality in low voltage DC (LVDC) microgrid. The microgrid demands the interconnection of a number of small distributed power resources, including variable renewable generators. Therefore, the voltage can be maintained in a stable manner through the control of these distributed generators. In this study, we did research on the new advanced operating method for a photovoltaic (PV) simulator in order to achieve interconnection to a bipolar LVDC microgrid. The validity of this voltage stabilization method, using the distributed generators, is experimentally verified. The test LVDC microgrid is configured by connecting the developed PV simulator and DC load, DC line, and AC/DC rectifier for connecting the main AC grid. The new advanced control method is applied to the developed PV simulator for the bipolar LVDC grid in order to stabilize the gird voltage. Using simulation results, the stabilization of the grid voltage by PV simulator using the proposed control method is confirmed the through the simulation results in various operation scenarios.