Friction Coefficient Resistance Research Articles

Study on Detection and Location of Mobile Oil Pipeline Leakage Based on Pressure Gradient Method

In the process of monitoring mobile oil pipeline system, it is hard to detect the exact leakage point. In order to solve this problem, a method based on pressure gradient is adopted to improve the accuracy of leakage detection. In the previous researches, the fluid friction resistance coefficient is supposed to be an invariable before and after the leakage of mobile oil pipeline, but the method based on pressure gradient can overcome this limitation and improve the accuracy of locating leakage point. Furthermore, it is indicated that the method is better by comparison with relevant literatures.

Properties of melt processable PTFE/PEEK blends: The effect of reactive compatibilization using electron beam irradiated melt processable PTFE

AbstractFor the first time, blends of melt processable polytetrafluoroethylene (MP PTFE) with polyetheretherketone (PEEK) in the MP PTFE/PEEK ratio of 100/0, 80/20, 50/50, 20/80, and 0/100 w/w were prepared and characterized. MP PTFE/PEEK blends are attractive materials due to the combination of low coefficient of friction and universal chemical resistance of MP PTFE with good wear resistance and mechanical strength of PEEK while maintaining high thermal stability of both. Miscibility, phase morphology, and mechanical properties of the new MP PTFE/PEEK blends were investigated. To improve their end‐use properties, an attempt of reactive compounding with the electron beam irradiated MP PTFE (e‐beam MP PTFE) was made. The reactive compounding was done in two steps, that is, the preparation of a masterbatch (MB) consisting of e‐beam MP PTFE/PEEK (50/50 w/w) and subsequent melt blending of MP PTFE/PEEK with varying concentrations of MB. The e‐beam irradiation of MP PTFE carried out in air atmosphere and at room temperature with a dose of 50 kGy results in its chain scission associated with formation of COF and COOH functional groups. Such modified MP PTFE can be used to compatibilize MP PTFE/PEEK blends. Reactive compatibilized blends exhibit improved phase morphology and mechanical properties. Especially for MP PTFE/PEEK 50/50 blends, a great improvement of almost 250% in strain at break, 40% in stress at break, and more than 600% in toughness was achieved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Tribological behavior of microwave processed copper–nanographite composites

Excellent properties offered by nanographite particles are exploited as a reinforcement to the copper matrix. The effects of graphite particle size, spatial distribution, normal load and sliding speed on the friction and wear performance of microwave sintered copper metal matrix composites were studied using a pin-on-disc tribometer. Copper–nanographite composites show higher wear resistance and low coefficient of friction compared to copper–graphite composites. High surface area of nanographite particles embedded in copper matrix exhibited high adherent graphite tribo-layer at the contact surface. Formed graphite layer reduces the sub-surface deformation of the composite by way of reduced frictional force.

Phase composition and tribological performance of molybdenum nitride coatings synthesized by IBAD

Molybdenum nitride coatings were synthesized by ion-beam-assisted-deposition (IBAD). The effects of nitrogen partial pressure and bombarding ion energy on the phase formation were investigated. The coefficient of friction and wear resistance of the coatings in different environments were studied.The stoichiometric ratio of nitrogen to Mo of the molybdenum nitride phases increases with the nitrogen partial pressure, and higher bombarding ion energy was helpful to form single MoN phase. Mo2N, MoN or mixture of the two phases could be prepared by controlling of the ratio of nitrogen/argon and ion energy. The hardness, coefficient of friction, wear and oxidation resistance of MoN were superior to that of Mo2N coating. The coefficient of friction decreased with the increase of testing temperature, yet the wear resistance became lower. The change of friction in non-oxidation atmosphere was reversed to that in the open air, indicating that the low friction of MoN at elevated temperature depends on oxidation. The tribological performance of the MoO3 phase formed by oxidation annealing showed much higher coefficient of friction than that of as-deposited MoN in all the testing conditions, and the oxygen deficient oxides were implied to be the lubricious phases.

DETERMINATION OF HEAD LOSSES IN PIPE-LINES LOSSES DURING HYDRAULIC CALCULATIONS FOR RINGED WATER NET

This paper provides the results of theoretical and experimental researches of head losses in industrial pipelines, which have technical coarseness. In the Nikuradzes researches values for frictional resistance coefficient were determined for artificial even-grained sandy roughness. The pipe-lines, which are used for water-supply in practice, have natural technical coarseness. The coarseness has different structure: it can have corrugated or saw-tooth surfaces and there can be also protective coat.The comparative analysis is provided for different methods of hydraulic losses calculations for head losses in pipe-lines for ringed water net. Recommendations for usage are also presented.

The modeling and validation of the flow and heat transfer models of pulsating flow in channels in rolling motion

The flow and heat transfer models of laminar flow and turbulent flow in rolling motion are established theoretically and modified with CFD results and experimental data. The correlations of frictional resistance coefficient and Nusselt number in pipes in rolling motion are obtained. The effect of rolling motion on the flow and heat transfer is mainly affected by the Reynolds number, angular acceleration and channel diameter. As the channel diameter is small, the effect of rolling motion on the flow and heat transfer is weak. The modified correlations of frictional resistance coefficient and Nusselt number in rolling motion could predict the flow and heat transfer in pipes in rolling motion correctly. The average discrepancy between theoretical correlations and experimental data is about 15%.

Effect of heat treatment on dry sliding wear of titanium-aluminum- vanadium (Ti-6Al-4V) implant alloy

Titanium and its alloys have very attractive properties that enable them to be used in the fields of aero space, biomedical, marine and also in many corrosive environments. The application of these alloys is more attractive today in the field of biomedical implant materials due to their superior biocompatibility and strength. These alloys have high coefficient of friction and poor abrasive wear resistance which results in the wear of the implant during its fixation in the body. Implant wear is a common phenomenon which results due to high friction between artificial implant materials when in contact with natural bone - this is much higher than healthy and natural joints that can withstand cyclic loads acting on them. The corresponding wear of the implant results in the accumulation of wear debris in the body tissues which results in inflammation, pain and loosening of implant resulting in shorter life period of the implant. Heat treatment of the alloy is one of the important techniques to improve the sliding wear properties of the alloy. The property of poor abrasive resistance can be altered by changing the microstructure of the alloy where the formation martensitic structure (acicular α or retained β) is resulted. The formation of martensitic structure in titanium alloy results in improved hardness value with a subsequent improvement in its sliding wear behavior. In this work, the implant material is subjected to heat treatment above its transformation temperature followed by slow cooling in furnace, air and water. These specimens were further aged and tested for dry sliding wear properties against hardened steel disc using a pin-on-disc apparatus using weight loss method with an optimal load of 50 N and a sliding distance of 500 m. An improvement of wear rate is reported under different heat treatment condition and an analysis of wear track of the specimens is done using scanning electron micrographs (SEM). Key words: Biomaterial, heat treatment, martensitic structure, dry sliding wear.

Enhancing the adhesive wear performance of polyetherimide composites through nano-particle treatment of the carbon fabric

Rare earth compound Ytterbium fluoride (YbF3) in nano-size (40–80 nm) was employed for surface treatment of carbon fabric (CF) to improve its wettability with polyetherimide matrix. Composites were developed based on untreated and surface-treated CF with three doses, 0.1, 0.3, and 0.5 wt%, of YbF3 in ethyl alcohol suspension. The composites were analyzed for interlaminar shear strength (ILSS). Improvement in ILSS was observed for treated fabric reinforced composites and it was maximum (61%) for 0.3 wt% dose of YbF3. The adhesive wear performance of composites was evaluated by sliding a pin of composite against mild steel disc under varying loads (200–600 N). The treated fabric composites exhibited lower coefficient of friction (μ) and higher wear resistance (W R). ILSS and W R showed good linear correlation. Both properties were highest for 0.3% YbF3 dosing. Increased roughness of fiber surface and adhesion of nano-particles on the fiber surface was observed in scanning electron microscopic (SEM) studies. SEM studies of worn surfaces of composites were performed to understand wear mechanisms. Atomic force microscopic studies indicated substantial increase in roughness value of CF.

Improving hardness and tribological characteristics of nanocrystalline Cr–C films obtained from Cr(III) plating bath using pulsed electrodeposition

Effect of pulsed electrodepostion on the nanocrystal size, composition, hardness, coefficient of friction and wear resistance was investigated for the Cr–C electrodeposits obtained from a trivalent chromium bath. The electrodeposits were shown to contain about 9% of carbon. Pulsed electrodeposition does not virtually affect the carbon content. At the same time, an increase in the off time duration leads to a decrease in the nanocrystals size. The hardness and wear parameters of the electrodeposits may be sufficiently improved when using pulsed current. For instance, at ton=toff=1s, the hardness reaches the values of ~1200÷1300 HV (meanwhile, it is close to 850÷950 HV at a steady-state electrolysis).

Theoretical model of laminar flow in tubes in rolling motion

The theoretical model of laminar flow in tubes in rolling motion is established. The velocity and temperature correlations are derived, and the frictional resistance coefficient and Nusselt number are also obtained. The oscillation of parameters is induced by the tangential force due to rolling motion. The effect of centrifugal and Coriolis forces on the flow is negligible. The tangential force does not effect on the average parameters. The oscillating amplitude of Nusselt number increase with the Prandtl number increasing. Both the oscillating amplitudes of frictional resistance coefficient and Nusselt number increase with the rolling frequency increasing.

Distributed parameters modeling for evaporation system in a once-through coal-fired twin-furnace boiler

In this paper, a distributed parameter model for the evaporation system of a subcritical once-through, coal-fired, twin-furnace boiler based on 3-D temperature field reconstruction is developed. The imaginary wall surface was put forward to simplify the twin-furnace problem. The mathematical model was formulated for predicting the transient distributions of parameters, such as the heat flux, the metal-surface temperature and the steam quality; while considering the non-uniform distributions of the surface heat transfer coefficient and frictional resistance coefficient. The model was based on the 3-D temperature distribution got by a flame image processing technique. The model was validated by some measurable parameters of the evaporation system at three typical loads. The results show that the heat flux and the temperature which are located at the overlapping region of the two tangential flames are higher than those in other corners. This distributed parameter model on evaporation system reflects the in-situ operating status of the power plant boiler, which may lead to the subsequent research on a supercritical boiler.

Experimental assessment of sliding materials for seismic isolation systems

Novel self-lubricating materials are currently being proposed to be used in sliding isolation systems such as the curved surface sliding isolator system, or pendulum bearing system, for the protection of buildings and structures. The current codes for anti-seismic devices are focused on the evaluation of the performance of the whole isolation system; as a consequence, a reliable procedure for the pre-assessment of the material combinations of sliding interfaces is currently missing. Therefore in this paper, an experimental methodology is proposed for the characterization of self-lubricating materials through tests on small-scale specimens performed using customized equipment able to reproduce the operational conditions of real isolation systems as per contact pressure, sliding velocity, temperature and slide path. The testing sequence has been designed in order to evaluate the sliding properties of the material in terms of static and dynamic coefficient of friction and wear resistance. Examples are reported for the assessment of two self-lubricating materials with different sliding characteristics. In order to validate the method and to confirm the reliability of extrapolating the results to real working conditions, prototypes of pendulum isolation systems incorporating the assessed materials have been tested according to the AASHTO (Guide specifications for seismic isolation design, 2nd edn. American Association of State Highway and Transportation Officials, Washington, DC, 1999) specifications and the relevant dynamic properties assessed from the Horizontal Load—Displacement loops. The experimental outcomes confirmed that the frictional characteristics provided by the proposed procedure can be reliably used in the design of seismically isolated structures.

The experimental and theoretical analysis of a natural circulation system in rolling motion

The natural circulation in rolling motion is investigated experimentally. The RELAP5/MOD3.3 code is modified by adding a module calculating the effect of rolling motion and introducing new flow and heat transfer models. The thermal hydraulic code in rolling motion is developed to simulate the natural circulation in rolling motion. The experimental data are used to validate the theoretical models and calculation results. It is shown that the new flow and heat transfer models could correctly predict the frictional resistance and heat transfer coefficients in rolling motion. The thermal hydraulic code is used to simulate a natural circulation system in rolling motion. The calculation results are in agreement with experimental data. The relative discrepancies between calculation results and experimental data are less than 5%.

The development and validation of a thermal hydraulic code in rolling motion

An advanced thermal hydraulic code is established on the basis of RELAP5/MOD3.3 code for the investigation of the thermal hydraulic behavior of nuclear power systems. The RELAP5 code is modified by adding a module calculating the effect of rolling motion and introducing new flow and heat transfer models. The experimental data are used to validate the theoretical models and calculation results. It is shown that the advanced flow and heat transfer models could correctly predict the frictional resistance and heat transfer coefficients in rolling motion. The thermal hydraulic code is used to simulate the operation of a natural circulation system in rolling motion. The calculation results are in good agreement with experimental data. The relative discrepancies between calculation results and experimental data are less than 5%.

Theoretical model of laminar flow in a channel or tube under ocean conditions

The theoretical model of laminar flow in a channel or tube under ocean conditions is established. The velocity and temperature correlations are derived, and the frictional resistance coefficient and Nusselt number are also obtained. The theoretical results are in agreement with experimental data. The oscillation of parameters is induced by the tangential force due to ocean conditions. The effect of centrifugal and Coriolis forces on the flow is negligible. The effects of several parameters on the frictional resistance coefficient and Nusselt number are investigated. The oscillating amplitude of Nusselt number increases with the increasing of Prandtl number. Both the oscillating amplitudes of frictional resistance coefficient and Nusselt number increase with the increasing of rolling frequency.

Role of Nano-YbF3-Treated Carbon Fabric on Improving Abrasive Wear Performance of Polyetherimide Composites

A method for surface treatment of carbon fabric with nano-particles of rare earth salt (ytterbium fluoride–YbF3) was tried first time in the authors’ laboratory to enhance the fiber–matrix interface, and has been reported here. In this article authors have reported on the performance evaluation of composites developed from the four fabrics treated with various doses viz. 0, 0.1, 0.3, and 0.5 wt% of YbF3. The abrasive wear performance of these composites was evaluated by abrading the composites against silicon carbide abrasive paper under varying loads. The treated fabric composites exhibited lower coefficient of friction and higher wear resistance as compared with untreated fabric composite. A linear correlation between ILSS (interlaminar shear strength) and wear resistance was observed. Both were the highest for 0.3% dosing of fabric. Since it was also desirable to compare the efficiency of this novel method of treatment of carbon fibers with conventional one, a few results of composites with plasma-treated carbon fabric were compared with the nano-particle-treated fabric composites. It was concluded that the latest method improved the abrasive wear resistance of composites almost two times more than the plasma-treated composites. Fiber–matrix interface was strengthened because of the treatment as observed from SEM studies, ILSS, and matrix pick-up studies. Increased roughness of fiber surface was observed in topographical analysis by SEM. Effect of treatment on fiber was also observed by adhesion test and fiber tow tension test. SEM studies of worn surfaces were performed to understand wear mechanisms.

Characteristics of DLC containing Ti and Zr films deposited by reactive magnetron sputtering

The purpose of this paper is to investigate metal doping effects on micro-structural, mechanical and corrosive behavior of the DLC film. Ti and Zr doped DLC films were prepared on NiTi alloys by reactive magnetron sputtering combined with plasma source ion implantation (PSII) technology used to improve the coherent strength, respectively. The mechanical properties of the doped DLC films were investigated by means of nano-indentation technique, microscratch and frictional wear testing. The potentiodynamic polarization measurement was employed to value the corrosion resistance of DLC with Ti and Zr films in Hank's simulated body fluid. It was found that Ti-doped DLC films embraced higher nano-hardness, somewhat lower coefficient of friction and better corrosion resistance than Zr-doped DLC films.

ESTUDO TRIBOLÓGICO DE REVESTIMENTOS DE DLC COM GASES REFRIGERANTES HFC134A E HC600A

This work aims to study the effect of refrigerant gases HFC134a and HC600a in components coated with DLC, Diamond-like Carbon, as well as is to establish a methodology for tribology evaluating of them. The tribological tests were conducted on a reciprocal motion. Balls of SAE 52100 steel and WC-Co were used as counter-body. The load was applied in a incremental way. The samples were prepared in SAE 1020 steel coated with DLC obtained from commercial suppliers. The characterization of samples was performed by optical interferometry and Scanning Electron Microscopy - SEM. It was verified a strong influence of the atmosphere through the in formation of a tribolayer at the interface between body and counter body. This influence showed disturbances in the coefficient of friction and contact resistance. Chemical analysis indicated that the tribolayer was formed by elements originated from the degradation of the refrigerants gases associated with of oxygen.

Research on Leakage Detection and Analysis of Leakage Point in the Gas Pipeline System

Recently, with large-scale use of natural gas and massive constructions of gas pipelines, more and more public concern is focused on pipeline leakage. The leakage caused by holes on gas pipelines generates economic losses to gas companies and causes risks to the environment and sometimes accidents. In order to detect and locate pipeline rupture immediately, the leakage detection method plays a key role in the overall integrity management in the pipeline system. One of the most important applications of transient simulation is dynamic leakage detection. A leakage detection model and the solution were proposed based on the three conservation laws in hydromechanics and the state equation, which includes transient simulation model and volume balance model. Dynamic parameters involved in the model such as pressure, flow and temperature can be acquired through SCADA (Supervisory Control And Data Acquisition) system. By analyzing the factors influencing leakage position, we came to a conclusion that leakage and outlet pressure are more important parameters compared to the coefficient of frictional resistance and pipeline diameter. The more leakage increases, the closer leakage point approaches pipeline outlet. Leakage location is closer to outlet when pipeline outlet pressure becomes bigger. Experiments were also carried out according to leakage percentage.

Reinforcement of Ball Shaped MoS<SUB>2</SUB> Nanoparticles in Epoxy Resin

The present work involves the synthesis of molybdenum disulfide (MoS2) nanoparticles by annealing the precursor obtained from simple reflux method. XRD, FESEM and HRTEM confirmed the formation of 2H-MoS2 with ball shaped particles, where some of them possess coalesced dumbbell morphology. The reinforcement of polysulphide modified epoxy resin (PSER) by MoS2 with varying amounts from 0.150 to 0.200 wt% provides unique combination of the improved thermal stability, tribological and mechanical properties. XRD studies indicate interaction between the sulphur containing nanoparticles and the epoxy resin. Maximum improvements in tensile strength (440%) and toughness (534%) are observed with ball shaped MoS2 nanoparticles (0.150 wt%)/PSER composite. Also the coefficient of friction and wear resistance show improvements of 60 and 78% respectively for 0.175 wt% loading in PSER compared to the neat resin matrix. Thermal stability is found to be improved maximum by 23 degrees C, when 5% weight loss is taken as a point of comparison. Similar studies on synthetic microcrystalline MoS2 filled PSER show that improvements in all these properties are very inferior.