관수로 부정류 마찰항 보정을 위한 Levenberg Marquardt 방법의 적용연구

박조은,김상현 한국수자원학회 2013 한국수자원학회논문집 Vol.46 No.4

In this study, a conventional pipeline unsteady friction model has been integrated into Levenberg Marquardt method to calibrate friction coefficient in a pipeline system. The method of characteristics has been employed as the modeling platform for the frequency dependant model of unsteady friction. In order to obtain Hessian and Jacobian matrix for optimization, the direct differentiation of pressure to friction factor was calculated and sensitivities to friction for heads and discharges were formulated for implementation to the integration constant in the characteristic method. Using a hypothetical simple pipeline system, time series of pressure, introduced by a sudden valve closure, were obtained for various Reynolds numbers. Convergency in fiction factors were evaluated both in steady and unsteady friction models. The comparison of calibration performance between the proposed method and genetic algorithm indicates that faster and stabler behaviour of Levenberg Marquardt method than those of evolutionary calibration. 이 논문에서는 관망시스템의 마찰항을 보정하기 위해서, 부정류 마찰 모형과 Levenberg Marquardt 방법을 합성하였다. 부정류 마찰항을 고려하기 위한 방법으로 빈도 의존 마찰항을 사용하였으며, 특성선 방법을 모형 개발의 기반으로 하였다. 최적화에 필요한 Hessian과 Jacobian 행렬을 구하기위해서 수압을 직접 마찰항에 미분한 항을 계산하였으며, 특성선 방법상에서의 다양한 수압과 유량에 대한 마찰계수의 민감도를 수식으로 유도하였다. 간단한 관망을 가정한 뒤, 갑작스런 밸브의 거동으로 도입된 수압의 시계열을 확보하였고, 이를 이용하여 정상류 마찰 모형과 부정류 마찰모형의 마찰항 보정을 수행하였다. 제안된 방법과 진화 연산 알고리즘의 마찰항 수렴거동을 비교하였으며, Leveberg Marquardt방법의 안정적이고 신속한 수렴결과를 확인하였다.

자동변속기 클러치 디스크 마찰특성의 실험적 분석

정규홍(Gyu Hong Jung),박동훈(Dong Hoon Park),나두현(Doo Hyun Na) 유공압건설기계학회 2018 드라이브·컨트롤 Vol.15 No.3

Wet clutches in an automatic transmission enable the transmission of the engine power by the frictional torque experienced and noted between disk and plates. Since the clutch frictional torque considerably affects the shift quality of an automatic transmission as well as the durability of the machinery, its friction characteristics must be carefully examined to meet the design requirements. The SAE No. 2 friction test machine is a well-known standard to evaluate mainly the friction characteristics of plate clutches along with the required automatic transmission fluids. This paper reviews the experimental analysis of the wet clutch friction characteristics by using the exclusively developed clutch test machine which is capable of controlling the clutch test procedure, in accordance with the applicable test standard and processing of the experimental data automatically. As the clutch test machine is designed for the accommodation of dual clutches which is applied to the real transmission, it can evaluate not only the clutch friction characteristics, but also an actuation performance of a measured clutch piston. In respect to friction characteristics involving dynamic friction coefficients, the energy absorbed in a clutch disk and the recorded temperatures of clutch plates during braking actions and procedures are also investigated. Additionally, the change of friction coefficients by the use of the repeated clutch application is also observed with the endurance test functions of an accurately calibrated and dedicated clutch test machine.

유압구동재의 마찰에 미치는 전류의 영향

전성재,강인혁,류미라,조연상,박홍식 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-

Generally, Oxidization film are generated by friction and wear in lubricant oil. It is effect that the heat and pressure act on contact area. Because the electrons movement progress the oxidization, if the electrons movement be regulated, the thickness of oxidization film can be regulated and friction characteristics can be improved. But electronic current can deteriorate friction characteristics, so various characteristics must be investigated on transforming of electronic current. Therefor, using the Norton equation, short current were transformed between ball and disk. Also, an experiment was carried out using ball on disk type tester. So, we studied up on effect of current for friction characteristics.

윤활하에서의 마찰 특성에 미치는 전류의 영향

전성재(S. H. Jun),강인혁(I. H. Kang),류미라(M. R. Lyu),조연상(Y. S. Cho),박흥식(H. S. Park) 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.35 No.-

Generally, Oxidization film are generated by friction and wear in lubricant oil. It is effect that the heat and pressure act on contact area. Because the electrons movement progress the oxidization, if the electrons movement be regulated, the thickness of oxidization film can be regulated and friction characteristics can be improved. But electronic current can deteriorate friction characteristics, so various characteristics must be investigated on transforming of electronic current. Therefor, using the Norton equation, short current were transformed between ball and disk. Also, an experiment was carried out using ball on disk type tester. So, we studied up on effect of current for friction characteristics.

관내마찰저항 시험장치를 활용한 콘크리트의 관내 유동 및 마찰저항 특성의 평가에 관한 연구

김형래,조호규,권대훈,Kim, Hyung-Rae,Jo, Ho-Kyoo,Kwon, Dae-Hun 대한건축학회 2011 대한건축학회논문집 Vol.27 No.11

The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for the evaluation of concrete pumping performance for high speed construction of super-tall building. So, this study focuses on quantitative evaluation of concrete fluid characteristics and surface friction resistance under the change of concrete mix proportion and pumping condition. For this, we developed temporary horizontal pumping evaluation system to measure pipe pressure and surface friction characteristics. And, relations between concrete mix proportion and pressure characteristics was investigated by experiment. As the result of the experiment, high regression between the surface friction and pressure gradient was confirmed. And, It means that it is able to evaluate the friction resistance between concrete and pipe by means of the pumping system that includes frictional resistance testing pipe.

마찰진자형 지진격리받침의 설계 특성 전산 해석 방법 비교

홍동의 ( Hong Dong Uie ),이재석 ( Lee Jae Seok ) 충북대학교 건설기술연구소 2020 建設技術論文集 Vol.39 No.2

이 논문에서는 교량의 내진설계에 사용되는 마찰진자형 지진격리 받침의 설계 특성치에 대하여 해석모델과 해석 방법을 달리하여 유한요소해석을 기반으로 한 전산해석을 수행하고 결과를 비교함으로써 해석모델과 해석방법의 타당성과 효율성을 검토하였다. 해석모델을 교량에 설치되는 형상과 유사한 경우, 실물시험에서의 시험기 받침들까지 같이 고려한 경우 그리고 실물시험과 배치형상은 같지만 시험기 받침들을 고려하지 않은 경우들에 대하여 실제 교량에서의 거동을 모사할 수 있도록 경계조건을 부과한 후 해석을 수행한 결과 유효강성 및 EDC의 경우 유사하게 발생됨을 확인할 수 있었고 주요 부재의 최대발생응력도 모두 허용응력 이내로 나타나 어느 해석 모델이라도 실물시험에 대한 대안으로 활용될 수 있음을 확인하였다. 해석모델을 교량에 설치되는 형상과 유사하게 모사한 경우가 다른 해석 모델에 비해 마찰판의 응력을 상대적으로 크게 예측하므로 안전여유 측면에서 유리하고 또한 해석 모델이 단순해 해석 효율성이 높으며 해석 모델의 형상과 구속 방법이 실제 교량과 유사하므로 상대적으로 효율적이라고 판단된다. A comparative study on the enhancement of the computational method for the evaluation of the design characteristics of the friction pendulum bearings is presented. The computational method is based on the finite element approach and the commercial finite element analysis package, MIDAS is used in this study. Friction pendulum bearings are widely used in the bridge and building structures to mitigate the structural response due to earthquake. Typically, the performance of the friction pendulum bearing is evaluated through the full-scale test which is time-consuming and expensive. Recently, the computer simulation based on finite element analysis method is regarded as an alternative of the full-scale test to evaluate the performance of the friction pendulum bearings. Through the computer simulations, not only the energy dissipation characteristics but also the stresses and strains at the crucial points of the friction pendulum bearings which can not be available in the full-scale test can be traced. In this paper, a comparative study is presented to enhance the computational method for the evaluation of the design characteristics of the friction pendulum bearings. Three relatively realistic modeling cases are compared to finalize the reasonable computational method for the evaluation of the design characteristics of the friction pendulum bearings.

관내마찰저항 시험장치를 활용한 콘크리트의 관내 유동 및 마찰저항 특성의 평가에 관한 연구

김형래(Kim, Hyung-Rae),조호규(Jo, Ho-Kyoo),권대훈(Kwon, Dae-Hun) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.11

The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for the evaluation of concrete pumping performance for high speed construction of super-tall building. So, this study focuses on quantitative evaluation of concrete fluid characteristics and surface friction resistance under the change of concrete mix proportion and pumping condition. For this, we developed temporary horizontal pumping evaluation system to measure pipe pressure and surface friction characteristics. And, relations between concrete mix proportion and pressure characteristics was investigated by experiment. As the result of the experiment, high regression between the surface friction and pressure gradient was confirmed. And, It means that it is able to evaluate the friction resistance between concrete and pipe by means of the pumping system that includes frictional resistance testing pipe.

토크컨버터 록업클러치용 마찰재의 내구성에 미치는 작동조건의 영향

박지열(Jiyeol Park),김명식(Myungsik Kim),장영기(Yeunggi Jang),장재덕(Jaeduk Jang),주인식(Insik Joo) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Friction plate which is main torque transfer element in lock-up clutch system is made of wet friction material that is consisted of synthetic fiber. Factors that decide characteristics of friction material are material composition, apply pressure, rotation speed and ATF temperature. Particularly, special condition control for friction durability is required because apply pressure and rotation speed become a important factor for friction characteristics and durability of friction material. The analysis of friction durability of friction material is investigated by using SAE No.2 test machine. This study provides applicable basic data for lock-up clutch system.

입경․비중 겸용 밭작물 곡물 선별기의 설계 요인 분석

하유신,최병준,권기영,송대빈 경상대학교 농업생명과학연구원 2013 농업생명과학연구 Vol.47 No.6

본 연구에서는 입경·비중 겸용 밭작물 곡물 선별기 개발을 위한 전 단계로서, 밭작물 곡물의 완전립과 불량립의 기하학적, 공기역학적, 마찰 특성을 측정하고, 선별기 설계에 적용하기 위한 선별 요인을 분석하였다. 측정된 곡물의 기하학적 특성 결과(길이, 폭, 두께)를 이용하여 스크린의 치수와 형상을 결정하여 선별기를 제작하여 선별시험을 한 결과 선별효율은 콩의 경우 94.7%, 커피는 92.0%, 아몬드는 74.5%, 옥수수는 90.0%로 나타났다. 측정된 곡물의 마찰 특성 결과를 이용한 고무벨트 선별 시험 결과 콩의 경우 벨트 속도 0.5 m/s, 벨트 각도 5˚ 일 때 선별효율이 88.2%로 가장 높게 나타났다. 측정된 곡물의 공기역학적 특성 결과, 종말속도는 콩의 경우 4.4∼6.0 m/s, 커피는 3.2∼4.4 m/s, 아몬드는 3.5∼5.1 m/s, 옥수수는 4.7∼6.0 m/s의 범위로 나타났다. This study was implemented to develop a separator based on particle size, shape and gravity for upland cereal crops as a preliminary research. The geometric, friction and aerodynamic characteristics of perfect and imperfect grains were tested, and separation factors were analyzed for separator design. The geometric properties of the measured cereals showed that 8.20 mm long, 7.49 mm wide and 6.24 mm thick for soybean, 9.57 mm long, 7.30 mm wide and 3.93 mm thick for coffee 21.77 mm long, 12.04 mm wide, and 7.55 mm thick for almond, and 8.12 mm long, 7.80 mm wide and 5.64 mm thick for corn. The size and shape of the screen for the separator were determined by these factors. The separation efficiency with the separator was 94.7%, 92.0%, 74.5% and 90.0% for soybean, coffee, almond and corn, respectively. Friction properties of the cereals were tested with different velocities and angles in a rubber belt. The measured friction coefficients were 0.432 for perfect-shaped soybean, 0.371 for round-surfaced coffee, 0.356 for perfect-shaped almond, and 0.665 for round-surfaced corn. The friction coefficients of the imperfect grain showed large differences in the rubber belt. In the separation efficient test, soybean showed the highest efficiency as 88.2% at a belt velocity of 0.5m/s and angle of 5°. Aerodynamic characteristics for the cereals were tested, and the results showed that the terminal velocity was 4.4 to 6.0 m/s for soybean, 3.2 to 4.4 m/s for coffee, 3.5 to 5.1 m/s for almond, and 4.7 to 6.0 m/s for corn. With the analyzed results, it was possible to determine hole size and shape for size-based selection, friction materials, conveying velocity and angle for shape-based selection, and air velocity for gravity separation.

ABS 마찰 특성을 고려한 제동 특성 검증에 관한 연구

오염락(Yumrak Oh),이호종(Hojong Lee),박영필(Youngpil Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Braking performance is one of the important performances of the vehicle tests because that is related to the driver and pedestrian security, ABS(Anti-lock Brake System) can improve vehicle braking/stability performance, So nowadays many of cars are equipped ABS basically, ABS braking performance is determined from optimum combination of ABS logic, tire traction and friction characteristics of brake pad. In this paper, we developed performance measurement index to predict ABS braking, To do this, we measured vehicle characteristics such as load transfer and ABS working slip ratio during braking with V-BOX and measured tire characteristics like longitudinal friction with Flat-trac Ⅲ test machine, And then, considering both vehicle and tire characteristics, finally we predicted ABS braking performance, This index has high correlation with ABS braking distance and can give us intuition to tune the tire design to improve the braking performance.