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Totally found 258 items.

  • [会议] CFD Analysis of Carbon Fiber Reinforced Polytetrafluoroethylene (PTFE) Hydrodynamic Journal Bearing Using Optimization Technique
    This work focuses on study of tribological behavior of a commercially available polytetrafluoroethylene (PTFE) and carbon fiber reinforced PTFE hydrodynamic journal bearing. The purpose of selection of this material is due to its low coefficient of friction and enhancement of the self lubricating properties. Performance parameters like pressure distribution, load carrying capacity and deformation of bearing are studied for various eccentricity ratios and speeds. Fluid structure interaction (FSI) coupled with Response surface optimization technique is used to get numerical results which are compared with experimental results. This approach provides a platform to predict accurate performance of hydrodynamic journal bearings considering realistic conditions. It is observed that CFD-FSI method provides a useful platform to study the combined effect of hydrodynamics and elastic behavior of the bearing. It is concluded that the deformations of the bearing are significant and should be considered in order to predict accurate performance of the hydrodynamic journal bearings.
    关键词: Composite bearing;fluid structure;hydrodynamic journal bearing;PTF;Optimization
  • [会议] Vibration Analysis of Polytetrafluoroethylene(PTFE)Deep Groove Ball Bearing
    Polymer matrix composites have shown the ability to balance traditional polymer properties such as low weight and ease of processability with the strength and stiffness of reinforcing agents. Ball bearings are broadly used in industry from home appliances to aerospace industry. In order to prevent catastrophic damages,the proper functioning of these machine elements is extremely important. Therefore,it is important to examine the condition of the bearings and to know the severity of the defects prior to they cause severe catastrophic damages. Hence,the study of vibrations produced by these defects plays a significant role in quality check as well as for condition monitoring of the ball bearing/machine element. In this paper,an attempt is made to study the performance of polymer ball bearings made with Polytetrafluoroethylene(PTFE)material using vibration analysis on different components of the bearing structure using the time and frequency domain parameters. This paper investigates the relationship between vibration frequency,RMS,amplitude and kurtosis for different speeds on new and defective ball bearing conditions.
    关键词: -
  • [会议] Magnetohydrodynamic Analysis of Polytetrafluoroethylene Thermal Arc Coupled with P-1 Radiative Analysis
    Radiative heat transfer plays an important role in energy balance of thermal arcs in gas circuit breakers (GCBs) especially at high current. At high interrupting current, it is known that the polytetrafluoroethylene (PTFE) walls of nozzles in GCBs are ablated and the nozzles are temporarily filled with pure PTFE vapor. The authors performed magnetohydrodynamic analysis of a model GCB coupled with radiative analysis called P1 approximation to calculate radiative heat transfer under PTFE-100% and CO_2-100% environments. The radiative heat loss for PTFE vapor in arc core region is larger than that for CO_2 at the peak current point due to the smaller absorption (κG) of PTFE than that of CO_2. In contrast to arc core region, the radiative heat loss for PTFE near the nozzle surface is smaller than that for CO_2. This is because the absorption is small compared to the emission (4πε) and the emission for PTFE is smaller than that for CO_2 near the nozzle surface. The net absorption regions for PTFE vapor and CO_2 are different due to the different temperature profiles. In these regions, the absorption is caused by different species between PTFE and CO_2.
    关键词: Gas Circuit Breaker;PTFE;Arc;Radiation;P1 approximation;Numerical Simulation
  • [会议] Effect of Surface Charges on the Surface-breakdown Characteristics of Polytetrafluoroethylene
    Under the DC electric field, surface charge accumulates on the surface of PTFE and increases the risk of surface insulation failure. On the basis of self-built surface potential measurement system, the DC voltage of 2.5kV~4kV was applied to the needle electrode for non-contact charge injection on the surface of PTFE, a Kelvin probe was used to measure the surface potential of PTFE. The relationship between the surface charge distribution and the applied voltage were obtained. Then the effect of surface charges on the flashover voltage was studied. Experimental results showed that the surface charge of PTFE was concentrically circularly distributed. The surface charge density increased with the increase in applied voltage. When the surface charge was injected on the discharge channel, the positive charge enhanced the electric field near the cathode so as to reduce the negative streamer inception voltage. Similarly, the negative charges also reduced the electric field near the anode and decreased positive streamer inception voltage. Therefore, when the average surface charge density of the accumulating charges was 16.7 pC/mm 2 , the flashover voltage decreased by 5.9\%. When the average surface charge density is -17.2 pC/mm 2 , the flashover voltage decreased by 6.8\%.
    关键词: Surface discharges;Electric fields;Flashover;Electrodes;Needles;Discharges (electric);Electric potential
  • [会议] Microwave dielectric properties of SrAl2Si2O8 filled Polytetrafluoroethylene composites
    The properties of Polytetrafluoroethylene (PTFE) filled with SrA12Si208 (SAS) and alkali-free glass fiber (GF) were investigated. The content of GF is 1 vol. %, and the content of SAS varied form 10 vol. % to 50 vol. %. The SAS was modified by silane coupling agent to improve interaction between SAS and PTFE, and the composites were prepared through SMECH (include Sigma Mixing (SM), Extrusion (E), Calendering (C) and Hot pressing (H) ) process. XRD was used to testify the phase purity of SAS. FTIR was used to analyze the surface of modified SAS. The SAS/PTFE composite material exhibited a near-zero dielectric constant temperature coefficient (τε=5.1 ppm/°C) while achieving a low dielectric constant (e,.=3.21) and a low dielectric loss (tanδ<5=0.00136) at 40 vol. % SAS filling. The SAS/PTFE composites are potential candidates for microwave substrates applications.
    关键词: -
  • [会议] Performance Analysis of Polytetrafluoroethylene as Journal Bearing Material
    In this study, the friction and wear behaviour of solid lubricant polytetrafluoroethylene (PTFE) reinforced with carbon, MoS2, glass fiber, polyether ether ketone (PEEK) particles are tested as journal bearing material with respect to varying high loads, under dry and wet condition against AISI SS 304 stainless steel using a pin-on-disc arrangement. Compared with pure PTFE, introduction of the fillers made composites have longer wear life. Among the all PTFE composites under experimental investigation due to friction and wear mechanism the lowest wear loss is observed for the composite of PTFE composite reinforced with 15% Glass fiber + 5% MoS2 particles by weight for the values of loads and sliding velocity.
    关键词: Polytetrafluoroethylene;Wear;Composites
  • [会议] Surface Electrical Performance of Polytetrafluoroethylene and Epoxy Resin under Arc Ablation
    The resistance performance under arc ablation is a critical factor to determine the surface electrical performance of the break of HVDC circuit breaker. In order to study the effects of arc energy on the surface electrical performance of polytetrafluoroethylene (PTFE) and epoxy resin (EP) insulation, an arc ablation test platform was set up to simulate the arc ablation process during the operation of HVDC circuit break. And the surface microtopography of two insulations under arc ablation was analyzed using atomic force microscope (AFM). The results show that DC flashover voltage of PTFE and EP insulation decreased by 16.0\% and 64.7\% respectively when the arc energy is equal to 156.5 J. The decrease in surface electrical performance is closely related to the changes of surface microtopography. Compared with PTFE, a plenty of drastic fluctuations and random defects appeared on EP surface after ablating. These defects can distort the surface electric field and thereby promote the development of flashover process, which is considered as one of the likely reasons that drastically decrease the surface electrical performance of EP insulation.
    关键词: Insulation;Surface morphology;Surface treatment;Flashover;Rough surfaces;Surface roughness;Conductivity
  • [会议] Fabrication of superhydrophobic polyvinylidene fluoride membranes with polytetrafluoroethylene nano-film surface coatings
    In this work, we used pulsed laser deposition (PLD) to coat polyvinylidene fluoride (PVDF) substrates with polytetrafluoroethylene (PTFE) thin films at room temperature. Modifying a PVDF membrane with a superhydrophobic nano-coating of PTFE has been shown to enhance the membrane's self-cleaning ability. The PTFE was deposited at different deposition times (15, 30, 45, 60, and 90 min). The surface roughness increased as deposition time increased up to 45 minutes. The highest water contact angle, 155° with negligible contact angle hysteresis, was observed for the sample with 45-minute deposition time. This study produced a superhydrophobic PVDF membrane with outstanding self-cleaning properties using a convenient, one-step, non-polluting technique without a wetting step.
    关键词: pulsed laser depostion;superhydrophobic;PVDF;surface roughness;self-cleaning
  • [会议] Surface Electrical Performance of Polytetrafluoroethylene and Epoxy Resin under Arc Ablation
    The resistance performance under arc ablation is a critical factor to determine the surface electrical performance of the break of HVDC circuit breaker. In order to study the effects of arc energy on the surface electrical performance of polytetrafluoroethylene (PTFE) and epoxy resin (EP) insulation, an arc ablation test platform was set up to simulate the arc ablation process during the operation of HVDC circuit break. And the surface microtopography of two insulations under arc ablation was analyzed using atomic force microscope (AFM). The results show that DC flashover voltage of PTFE and EP insulation decreased by 16.0\% and 64.7\% respectively when the arc energy is equal to 156.5 J. The decrease in surface electrical performance is closely related to the changes of surface microtopography. Compared with PTFE, a plenty of drastic fluctuations and random defects appeared on EP surface after ablating. These defects can distort the surface electric field and thereby promote the development of flashover process, which is considered as one of the likely reasons that drastically decrease the surface electrical performance of EP insulation.
    关键词: Insulation;Surface morphology;Surface treatment;Flashover;Rough surfaces;Surface roughness;Conductivity
  • [会议] Mechanical and operational properties of boron nitride-modified polytetrafluoroethylene
    Rational conditions for composite formation based on polytetrafluoroethylene with the increased wear resistance were defined. The influence of ultrasonic treatment parameters on mechanical and tribotechnical properties of polymeric composite material based on polytetrafluoroethylene was determined. A new PTFE-based composite material with high load capacity and wear resistance providing operation of friction units without lubrication was developed. The synthesis technology of polymer composite material based on PTFE modified with boron nitride was proposed for the production of sliding bearings.
    关键词: -
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