Microstructural investigation of ice surfaces after rubber–ice and sand–ice sliding friction tests

The dual process of etching and replicating technique revealing lattice dislocations, dislocation cells, grain and sub-grain boundaries, etc., in ice has been applied to investigate the microstructure of freshly deformed ice surfaces after rubber–ice and sand–ice sliding friction tests. Features related to the generation, multiplication and mobility of dislocations were observed in ice subjected to rubber–ice friction even at high speeds and high ice temperatures, involving low friction. During sand–ice friction, deformation took place at the surfaces as well as deeper within the ice by ploughing sand particle, and was accompanied with recrystallization. The deformation features in ice found in the laboratory were also observed in full-scale tire–ice interactions on ice covered runway pavements.     

The effect of hydrogen on friction and wear of Ni–P electroless coating

The effects of charging and outgassing on friction and wear of Ni–P amorphous and nanocrystalline coating have been studied under ambient humidity and temperature. The results indicate that charging can improve the wear durability for Ni–P amorphous coating and inhibit formation of wear crack for brittle Ni–P nanocrystalline, which is due to atomic hydrogen because the wear behavior will restore after outgassing. Maybe, atomic hydrogen absorbed on the surface of the charged sample lubricates the surface in contact, resulting in reducing the friction coefficient and improving the wear durability.     

Formation of transfer layer and its effect on friction and wear of carbon–graphite face seal under dry,water and steam environments

The present work aims to explore the friction and wear characteristics of antimony-impregnated-carbon–graphite material used in steam rotary joint and to study the transfer of graphite films from seals to mating metal surfaces. An experimental facility consisting of a 1.3 MPa capacity boiler to supply saturated steam, a torque sensor, a displacement sensor, two thermocouples, a data acquisition system, a bakelite coupling to insulate the torque sensor, a 2237 W (3 hp) A.C. motor with frequency drive to control the rotational speed of shafts, and actual rotary joint has been developed to measure the instant friction losses and calculate the wear loss of four seals used in rotary joint. Wear loss, friction torque and surface temperature of sealing surfaces have been measured under dry, water and steam lubrication conditions. The obtained results are tabulated and plotted for quick understanding of experimental findings. Discussions on the excessive wear rate due to the presence of abundant water, misalignment and closing force are presented. Finally design changes to enhance the seal life are recommended.     

The influence of friction and wear on the generation of surface microprofile of steel–sintered friction powder based on copper in the course of operation in lubricated medium

The development of new compositions of sintered friction powders based on copper that operate in lubricated states should be based on deep knowledge of peculiar features of break-in and wear mechanisms of both counterbody and friction material. The obtained data have enabled the determination of the existence of the transferred bronze layer of friction material, the peculiarities of the generation of the surface microprofile of the counterbody during operation, these data can be useful upon assessing the thermal loading of the friction zone.     

Prediction of friction and heat flow in machining incorporating thermophysical properties of the coating–chip interface

This paper deals with an experimental and analytical investigation into the thermodynamically activated effects influencing the behaviour of the multi-layered coated tool rake face during orthogonal cutting of ferromagnetic and paramagnetic steels. Temperature measurements on the tool rake face using a thermocouple-based technique and identification of the contact zone by means of computer image processing were carried out. New methodology for assessing friction and the amount of thermal energy generated when machining with a coated tool insert with natural and restricted contact coupled with a metallic chip, using thermophysical properties of the sliding materials is developed in this study. The dependence of the material properties on the contact temperature makes the predictive models more realistic. It was proven, based on the heat flux analysis, that the use of advanced coatings with an intermediate Al₂O₃ layer could substantially improve the heat flow into the chip at distinctly lower temperatures than other commercially available coatings. The data obtained can be used for the optimisation of tool selection with respect to friction and heat transfer and for maintaining the recommended contact temperature.     

Experimental and theoretical analysis of friction stir welding of Al–Cu joints

This paper presents a study of friction stir welding of aluminium and copper using experimental work and theoretical modelling. The 5083-H116 aluminium alloy and pure copper were successfully friction-stir-welded by offsetting the pin to the aluminium side and controlling the FSW parameters. A theoretical analysis is presented along with key findings. The process temperatures are predicted analytically using the inverse heat transfer method and correlated with experimental measurements. The temperature distribution in the immediate surroundings of the weld zone is investigated together with the microstructures and mechanical properties of the joint. This was supported by a finite element analysis using COMSOL Multiphysics. In this study, two rotational speeds were used and a range of offsets was applied to the pin. The microstructure analysis of the joints was undertaken. This revealed some particles of Cu inclusion in the nugget zone. The energy dispersive spectroscopy showed a higher diffusion rate of aluminium towards the interface while copper maintained a straight base line.     

Stress–strain behavior and specific friction of toric rubber-cord casings of flexible couplings

The results of experimental studies of stress–strain behavior during hardening stages, as well as the stabilization and strength degradation of the rubber-cord casings during the static loading mode have been given. The influence of measurements of these characteristics on the drive dynamic loading has been shown. The physical processes of specific friction in the coupling flexible element have been considered. Dependence diagrams of the specific friction on dynamic torque, vibration frequency, torsion angles, and casing temperature have been made.     

Research on swing friction lubrication mechanisms and the fluid load support characteristics of PVA–HA composite hydrogel

Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate fluid load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and fluid load support. The friction coefficient increases with contact load and swing angle. The fluid flow has an important effect on the fluid load support, which decreases with an increase in contact load and swing angle. The fluid load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.     

Analysis of a steel disk surface running in tandem with the metal–ceramic friction material MK-5 under the conditions of boundary friction of a hydromechanical transmission

The development of metal–ceramic copper-based materials that operate under lubrication requires experience in operation under normal conditions, as well as with disruption of operation. The exclusion of a component or substitutions in the material composition is an important issue when taking into account that the component belongs to a group of hazardous substances that contain lead in MK-5 metal–ceramic copper-based friction materials.     

Effective wind speed estimation: Comparison between Kalman Filter and Takagi–Sugeno observer techniques

Advanced model-based control of wind turbines requires knowledge of the states and the wind speed. This paper benchmarks a nonlinear Takagi–Sugeno observer for wind speed estimation with enhanced Kalman Filter techniques: The performance and robustness towards model-structure uncertainties of the Takagi–Sugeno observer, a Linear, Extended and Unscented Kalman Filter are assessed. Hence the Takagi–Sugeno observer and enhanced Kalman Filter techniques are compared based on reduced-order models of a reference wind turbine with different modelling details. The objective is the systematic comparison with different design assumptions and requirements and the numerical evaluation of the reconstruction quality of the wind speed. Exemplified by a feedforward loop employing the reconstructed wind speed, the benefit of wind speed estimation within wind turbine control is illustrated.     

Fabrication,characterization and evaluation of the effect of PLGA and PLGA–PEG biomaterials on the proliferation and neurogenesis potential of human neural SH-SY5Y cells

In recent years with regard to the development of nanotechnology and neural stem cell discovery, the combinatorial therapeutic strategies of neural progenitor cells and appropriate biomaterials have raised the hope for brain regeneration following neurological disorders. This study aimed to explore the proliferation and neurogenic effect of PLGA and PLGA–PEG nanofibers on human SH-SY5Y cells in in vitro condition. Nanofibers of PLGA and PLGA–PEG biomaterials were synthesized and fabricated using electrospinning method. Physicochemical features were examined using HNMR, FT-IR, and water contact angle assays. Ultrastructural morphology, the orientation of nanofibers, cell distribution and attachment were visualized by SEM imaging. Cell survival and proliferation rate were measured. Differentiation capacity was monitored by immunofluorescence staining of Map-2. HNMR, FT-IR assays confirmed the integration of PEG to PLGA backbone. Water contact angel assay showed increasing surface hydrophilicity in PLGA–PEG biomaterial compared to the PLGA substrate. SEM analysis revealed the reduction of PLGA–PEG nanofibers' diameter compared to the PLGA group. Cell attachment was observed in both groups while PLGA–PEG had a superior effect in the promotion of survival rate compared to other groups (p < .05). Compared to the PLGA group, PLGA–PEG increased the number of Ki67⁺ cells (p < .01). PLGA–PEG biomaterial induced neural maturation by increasing protein Map-2 compared to the PLGA scaffold in a three-dimensional culture system. According to our data, structural modification of PLGA with PEG could enhance orientated differentiation and the dynamic growth of neural cells.     

Influence of valence electron concentration over the friction behaviors of quasicrystal and B2‐type approximants in Al–Cu–Fe ternary system

Quasicrystals and their approximants are Hume–Rothery compounds having similar valence electron concentration. According to the valence electron concentration criterion for approximants, some B2 superstructures can be regarded as a special group of approximants. The present paper reports on an investigation of dry friction behavior of this group of phases. The results are compared with the data from quasicrystalline and related crystalline phases with similar composition. Specifically, we show that samples containing the B2 structure and its superstructures exhibit friction coefficients that decrease with increasing e/a and reach a minimum at 1.86, the value of the quasicrystal. Therefore, quasicrystals and B2‐based approximants belong to one group of phases whose surface properties are mainly determined by electronic structure characteristics rather than crystal structures. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of nitrogen concentration on microstructure and ultra-low friction behaviour of Fe–N thin films

The influence of nitrogen concentration on the microstructure, chemical and electronic properties of Fe–N thin films and their tribological behaviour are studied. Increasing the nitrogen concentration from 5% to 12%, results in the decrease in friction coefficient from 0.14 to 0.04, while wear life increases significantly. However, increase in nitrogen concentration to 32% results in the increase in friction coefficient to 0.1 and decrease in wear life. Therefore, lowest friction and longest wear life is observed in the film with 12% nitrogen, which is due to the formation of ε-Fe₂N phase having high bond strength and chemically passive surface.     

The effect of calibration equations on the uncertainty of UV–Vis spectrophotometric measurements

The effect of adequateness of the calibration equations on measurement uncertainty was not mentioned by EURACHEM. In this work, we investigate the sources of uncertainty when measuring glucose concentration with a UV–Vis spectrophotometer. The effect of two calibration equations on the uncertainty was compared. The sources of the glucose concentration measurement uncertainty include purity, volume of flasks, mass and the calibration equations. The effects of two calibration equations, linear and polynomial equation, on the uncertainty source were evaluated using the inverse calibration equation. The results indicated that the uncertainty components from purity were the smallest. The volumes of the volumetric flasks had only modest effect on the uncertainty, while the mass was an important source of the uncertainty. The contribution of the calibration equation to the total relative measurement uncertainty was 59.39% for the linear equation and 30.34% for the polynomial equation. With the selection of the adequate equation, the uncertainty source of the calibration equation could be reduced significantly.     

On the role of sliding load and heat input conditions in friction stir processing on tribology of aluminium alloy–alumina surface composites

ABSTRACT

Aluminium (AA5083)-alumina surface composites are prepared by friction stir processing in two conditions of heat input. The low heat (LH) input conditions is achieved at a rotational speed of 710?rpm and a traverse speed of 100?mm/min, and high heat (HH) input conditions are achieved at a rotational speed of 1400?rpm and a traverse speed of 40?mm/min. The tribological characteristics of aluminium alloy, friction stir processed (FSPed) alloy and FSPed surface composites against steel ball are studied at 5, 10 and 20?N load. While no significant influence is found on frictional behaviour, wear resistance of FSPed composites is superior to FSPed alloys. FSPed composites fabricated at HH input conditions exhibited improved wear resistance as compared to LH input condition. Adhesion and delamination are dominant wear mechanisms at 20?N. Debris particles are reduced in size and hydroxidated in sliding of surface composites.     

Low-pass filter without the end effect for estimating transmission characteristics—Simultaneous attaining of the end effect problem and guarantee of the transmission characteristics

A Gaussian filter (GF) is the most commonly used low-pass filter of measuring surface roughness. However, undesirable distortions, called “end effects," occur near the end points of the data ends in GF. The transmission characteristics are one of the most important indicators that show the quality of a filter. Previously, it was only possible to obtain theoretical values for the transmission characteristics of filters whose weights were given by an explicit function. In recent years, it has also become possible to obtain the transmission characteristics of a filter whose weights are given by an implicit function. However, this method has a problem in that the values near the end points of the measurement data become significantly different from each other. The consequence is that end effects may occur in the filter outputs due to side effects of the periodic extension. In the case of a spline filter (SF) applied to open profiles, the transmission characteristics of a periodic SF with an end effect can be obtained uniquely. However, the transmission characteristics of a nonperiodic SF, which has no end effect, cannot be uniquely obtained. This results in a trade-off between the two states: end effects exist in a filter whose transmission characteristics can be obtained, and the transmission characteristics of a filter without end effects cannot be uniquely obtained. To address this problem, we propose a method for the GF processing that uses shearing, point symmetric extension, and periodic extension, and produces no end effect but allows the transmission characteristics to be obtained. Previously, there was a problem with the proposed method in that the rationale was unclear regarding how to determine the reference points for point symmetric extension. We resolved this and optimized the reference points. As a result, the proposed method was shown to be successful in not only resolving the end effects in the GF, but also obtaining the transmission characteristics.