• Title/Summary/Keyword: PFC2D & PFC3D

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DEM analysis of the anisotropy effects on the failure mechanism of the layered concretes' specimens with internal notches

  • Jinwei Fu;Vahab Sarfarazi;Hadi Haeri;Mohammad Fatehi Marji
    • Computers and Concrete
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    • v.33 no.6
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    • pp.659-670
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    • 2024
  • The mechanical behaviour of layered concrete samples containing an internal crack was numerically studied by modelling the geo-mechanical specimens in the particle flow code in two dimensions (PFC2D). The numerical modelling software was calibrated with the experimental results of the Brazilian tensile strengths gained from the laboratory disc-type specimens. Then, the samples with the bedding layers and internal notch were numerically simulated with PFC2D under uniaxial compressive loading. In each specimen, the layers' thickness was 10 mm but the layer's inclination angle was changed to 0°, 30°, 60°, 90°, 120° and 150°. Of course, the layers'interfaces are considered to have very low strengths. The internal notch was kept at 3 cm in length however, its inclination angle was changed to 0°, 40°, 60° and 90°. Therefore, a total, of 24 numerical models were made to study the failure mechanism of the layered concrete samples. Considering these results, it has been concluded that the inclination angles of both internal crack and bedding layers affect the failure mechanism and uniaxial compressive strength of the concrete.

An Improved PFC & Low Noise Power Supply using Quasi-Resonant Mode Hybrid IC of STR-G9600 (의사공진형 Hybrid IC STR-G9600을 이용한 저 노이즈 역률 개선형 전원 장치)

  • Lee Myung Jun;Ahn Jun Young;Shin Ho Jun;Bae Jun Sung
    • Proceedings of the KIPE Conference
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    • 2002.07a
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    • pp.233-236
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    • 2002
  • The solution for PFC(Power Factor Correction), as a regulation in energy Policy, is becoming a hot Issue in every country because of the shortage of electrical energy. Therefore, a new improved idea for PFC problem has been introduced in this study. A lot of merits, effective cost by simple circuit, reduced PCB size, lighter than reactor in the view of weight, lower level of screen noise by leakage inductance in CTV applications, have been stated by comparing to the earlier method of using a Reactor. All test results in this statement were done by using a power device of STR-G9600 series based on the real load condition of color television. furthermore, the study shows that the test results also meets the IEC-1000-3-2 class D, which regulates the PFC when input power of a set is more than 75watts. More improved PFC in other applications hopes to be implemented by using the proposed method.

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Design and Analysis of an Interleaved Boundary Conduction Mode (BCM) Buck PFC Converter

  • Choi, Hangseok
    • Journal of Power Electronics
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    • v.14 no.4
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    • pp.641-648
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    • 2014
  • This paper presents the design considerations and analysis for an interleaved boundary conduction mode power factor correction buck converter. A thorough analysis of the harmonic content of the AC line current is presented to examine the allowable voltage gain (K value) for meeting the EN61000-3-2, Class D standard while maximizing efficiency. The results of the harmonic analysis are used to derive the required value of K and therefore the output voltage necessary to meet the class D requirements for a given AC line voltage. The discussed design consideration and harmonic current analysis are verified on a 300W universal line experimental prototype converter with an 80V output. The measured efficiencies remain above 96% down to 20% of the full load. The input current harmonics also meet the IEC61000-3-2 (class D) standard.

Investigation of ratio of TBM disc spacing to penetration depth in rocks with different tensile strengths using PFC2D

  • Sarfarazi, Vahab;Haeri, Hadi;Shemirani, Alireza Bagher;Hedayat, Ahmadreza;Hosseini, Seyed Shahin
    • Computers and Concrete
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    • v.20 no.4
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    • pp.429-437
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    • 2017
  • In this study, the effect of the tensile strength and ratio of disc spacing to penetration depth on the efficiency of tunnel boring machine (TBM) is investigated using Particle flow code (PFC) in two dimensions. Models with dimensions of $150{\times}70mm$ made of rocks with four different tensile strength values of 5 MPa, 10 MPa, 15 MPa and 20 MPa were separately analyzed and two "U" shape cutters with width of 10 mm were penetrated into the rock model by velocity rate of 0.1 mm/s. The spacing between cutters was also varied in this study. Failure patterns for 5 different penetration depths of 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm were registered. Totally 100 indentation test were performed to study the optimal tool-rock interaction. An equation relating mechanical rock properties with geometric characteristics for the optimal TBM performance is proposed. The results of numerical simulations show that the effective rock-cutting condition corresponding to the minimum specific energy can be estimated by an optimized disc spacing to penetration depth, which, in fact, is found to be proportional to the rock's tensile strength.

PFC Dual Boost Converter Based on Input Voltage Estimation for DC Inverter Air Conditioner

  • Park, Gwi-Geun;Kwon, Kee-Yong;Kim, Tae-Woong
    • Journal of Power Electronics
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    • v.10 no.3
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    • pp.293-299
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    • 2010
  • In this paper, a single-phase PFC (Power Factor Correction) dual boost converter based on input voltage estimation is studied for DC inverter air conditioner. It is focused on improving input power factor and power quality to satisfy the recent harmonic current regulation standards. Furthermore the input voltage estimation is introduced for price competitive products. A low cost and reasonable control system is implemented using a specified high-speed 32-bit microprocessor. Their effectiveness are verified through theoretical analysis and experiments.

Analysis of Fine Particle Transfer and Shear Strength Increase Using PFC in Permeation Grouting (PFC를 이용한 침투그라우팅시 미세입자의 이동 및 전단강도증가 해석)

  • Lee, Wan-Ho;Lim, Heui-Dae
    • Journal of the Korean Geotechnical Society
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    • v.23 no.11
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    • pp.49-58
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    • 2007
  • Numerical experiments using a distinct element code (PFC3D) were carried out for the analysis of grout-material transfer in soil layers and also for the analysis of increase in mechanical strength after permeation grouting. For rapid analysis, up-scaling analysis in length scale was adopted, and the following observations were made from the numerical experiments. Firstly, the relative size of grout material with respect to the in situ soil particles controlled the transfer distance of the grout particles. When the size of grout particle was 0.2 to 0.25 times of the in situ soil particles, clogging of pore spaces among the in situ soil particles occurred, resulting in restricted propagation of grout particles. It was also found that there was a threshold value in the size of grout particle. Below the threshold value, the transfer distance of the grout particle did not increase with the decrease of particle size of the grout material. Secondly, the increase in cohesion and internal friction angle was observed in the numerical specimen with grouting treatment, but not with the untreated specimen.

Surface roughness crushing effect on shear behavior using PFC (PFC를 이용한 평면 파쇄가 전단 거동에 미치는 효과)

  • Kim, Eun-Kyung;Jeong, Da-Woon;Lee, Seok-Won
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.14 no.4
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    • pp.321-336
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    • 2012
  • The shear behavior at the particle/surface interface such as rock joint can determine the mechanical behavior of whole structure. Therefore, a fundamental understanding of the mechanisms governing its behavior and accurately estimation of the interface strength is essential. In this paper, PFC, a numerical analysis program of discrete element method was used to investigate the effects of the surface roughness crushing on interface strength. The surface roughness was characterized by smooth, intermediate, and rough surface, respectively. Particle shape was classified into one ball model of circular shape and 3 ball model of triangular shape. The surface shape was modelled by wall model of non-crushing surface and ball model of crushing surface. The results showed that as the bonding strength of ball model decreases, lower interface strength is induced. After the surface roughness crushing was occurred, the interface strength tended to converge and higher bonding strength induced lower surface roughness crushing. Higher friction angle was induced in wall model and higher surface roughness induced the higher friction angle. From these findings, it is verified that the surface roughness and surface roughness crushing effect on the particle/surface interface shear behavior.

Infiltration behaviour of the slurry into tunnel face during slurry shield tunnelling in sandy soil (사질성 지반에서 이수식 쉴드 TBM 적용시 굴진면으로의 이수 침투특성에 대한 해석적 고찰)

  • Roh, Byoung-Kuk;Koh, Sung-Yil;Choo, Seok-Yeon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.14 no.3
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    • pp.261-275
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    • 2012
  • This paper presents numerical analysis of the mud cake infiltration behaviour which is influenced tunnel face stability during excavation by slurry shield TBM. This analysis method can make useful data to select proper shield TBM type and to set up the construction plan. But effective analysis did not proposed until now. In this paper, we carried out numerical analysis using by $PFC^{2D}$ fluid coupling simulation which is suitable for sandy soil modelling. As a analysis result, we checked that the slurry infiltration behaviour varied with soil permeability and slurry characteristic(specific weight, viscosity etc). This analysis method is helpful safety excavation through anticipating the proper slurry viscosity at the design stage and verifying the slurry quality at initial excavation stage.

Numerical Analysis on Cutting Power of Disc Cutter with Joint Distribution Patterns (절리분포 양상에 따른 디스크커터의 절삭력에 관한 수치해석적 연구)

  • Lee, Seung-Joong;Choi, Sung-O.
    • Tunnel and Underground Space
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    • v.21 no.3
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    • pp.151-163
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    • 2011
  • The LCM test is one of the most powerful and reliable methods for designing the disc cutter and for predicting the TBM (Tunnel Boring Machine) performance. It has an advantage to predict the actual load on disc cutter from the laboratory test on the real-size large rock samples, however, it also has a disadvantage to transport and/or prepare the large rock samples and to need an extra cost for experiment. Moreover it is not easy to execute the test for jointed rock mass, and sometimes the design model estimated from the test can not be applied to the real design of disc cutter. In order to break this critical point, lots of numerical studies have been performed. PFC2D can simulate crack propagation and rock fragmentation effectively, because it is useful in particle flow analysis. Consequently, in this study, the PFC2D has been adopted for numerical analysis on cutting power of disc cutter according to the different angle of joint, the different direction of joint, and the different space of joint with jointed rock mass models. From the numerical analyses, it was concluded that the bigger cutting power of disc cutter was needed for reverse cutting direction to joint rather than for forward direction, and the cutting power of disc cutter was increased with decreasing the dip angle of joint and decreasing the space of joints in reverse cutting direction. The more precise numerical model for disc cutter can be developed from comparison between the numerical results and LCM test results, and the resonable guideline is expected for prediction of TBM performance and disc cutter.

Interaction between opening space in concrete slab and non-persistent joint under uniaxial compression using experimental test and numerical simulation

  • Vahab Sarfarazi;Kaveh Asgari;Mehdi Kargozari;Pouyan Ebneabbasi
    • Computers and Concrete
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    • v.31 no.3
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    • pp.207-221
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    • 2023
  • In this investigation, the interaction between opening space and neighboring joint has been examined by experimental test and Particle flow code in two dimension (PFC2D) simulation. Since, firs of all PFC was calibrated using Brazilian experimental test and uniaxial compression test. Secondly, diverse configurations of opening and neighboring joint were provided and tested by uniaxial test. 12 rectangular sample with dimension of 10 cm*10 cm was prepared from gypsum mixture. One quarter of tunnel and one and or two joint were drilled into the sample. Tunnel diameter was 5.5 cm. The angularities of joint in physical test were 0°, 45° and 90°. The angularities of joint in numerical simulation were 0°, 30°, 60°, -30°, -45°, -60° and its length were 2cm and 4cm. Loading rate was 0.016 m/s. Tensile strength of material was 4.5 MPa. Results shows that dominant type of crack which took place in the model was tensile cracks and or several shear bands develop within the model. The Final stress is minimum in the cases where oriented angle is negative. The failure stress decrease by decreasing the joint angle from 30° to 60°. In addition, the failure stress decrease by incrementing the joint angle from -30° to -60°. The failure stress was incremented by decreasing the number of notches. The failure stress was incremented by decreasing the joint length. The failure stress was incremented by decreasing the number of notches. Comparing experimental results and numerical one, showed that the failure stress is approximately identical in both conditions.