Number Of Friction Cycles Research Articles

Preparation of Ceramic Fiber Threads with Enhanced Abrasion Resistance Performance.

Ceramic fiber thread is one of the key components in flexible external thermal insulation blankets, and it has been applied in various fields as a flexible ceramic fibrous material with excellent deformability and high-temperature resistance. However, ceramic fiber threads are often subjected to reciprocating friction motion at specific bending angles, making them highly susceptible to abrade and fracture. Enhancing the abrasion resistance performance of ceramic fiber threads under bending conditions is the future trend and remains a significant challenge. Hence, we design and construct a novel polyurethane-modified coating on the ceramic fiber threads to improve their abrasion resistance performance. The effects of the types and concentrations of modifiers on the microstructure, abrasion resistance property, and tensile property of ceramic fiber threads are systematically investigated. The ceramic fiber threads, after modification with hexamethylene diisocyanate waterborne polyurethane (HDI-WPU) with a concentration of 3%, exhibit excellent abrasion resistance properties. The number of friction cycles at fracture of the modified ceramic fiber thread is more than three times, and the tensile strength is more than one and a half times, that of the original ceramic fiber thread, demonstrating the great potential of the HDI-WPU modifier for enhancing the abrasion resistance performance of ceramic fiber threads.

Control Charts for Statistical Process Control of the Tribocharging of Polymer Slabs in Frictional Sliding Contact

Besides the nature and condition of the surfaces in contact, several factors influence the triboelectric charging of polymer slabs in frictional sliding contact: pressure load and relative velocity between the two bodies, number of friction cycles, ambient temperature, and humidity. This paper is aimed at pointing out the peculiarities of the statistic control of such a process. Thirty experiments were performed for the optimal combination of factor values (i.e., normal force: 10 N; sliding speed: 55 mm/s; number of sliding cycles: 10) that maximize the absolute value of the average potential at the surface of the tribocharged materials: 1600 V. The capability index calculated from the experimental data was satisfactory and two Shewart charts were established for the statistical control of the process. Two out-of-control situations were simulated, in order to test the efficiency of the charts.

Tribological Behavior of Rice Bran Ceramics in a Vacuum Environment

ABSTRACTIn this study, we investigated the friction and wear of rice bran (RB) ceramics—hard porous carbon materials made from rice bran—in a vacuum environment. Sliding friction tests for RB ceramic pin–RB ceramic disk contact were performed using a pin-on-disk-type friction tester installed in a vacuum chamber. The ambient pressure was controlled at 0.02, 0.6, 30, and 105 Pa (i.e., atmospheric pressure). The normal load was 0.49 or 2.94 N, the sliding velocity was 0.01 or 0.1 m/s, and the number of friction cycles was 50,000. The friction coefficient tended to decrease with decreasing ambient pressure for all combinations of normal load and sliding velocity; by contrast, the specific wear rate of the RB ceramic pin and disk specimens tended to increase with decreasing ambient pressure. The friction coefficient exhibited a low value of 0.05 or less at 0.02 Pa. The results suggested that the reduced surface roughness and graphitization of the sliding surface of the RB ceramic pin and disk due to induced friction, as well as the increased ratio between the partial pressure of water vapor and the ambient pressure, are related to the reduction in the friction of RB ceramic–RB ceramic dry sliding contact under vacuum conditions.

Tribology Study of High-Technological Composite Coatings Applied Using High Velocity Oxy-Fuel

In the work are studied the differential parameters of wear and wear resistance of high-tech composite coatings of powder superalloys with nickel matrix, WC-12Co and mixed compositions. Coatings were created and applied to a substrate of steel with a different flame velocity - 700 m/s and 1000 m/s without preheating the substrate and with preheating the substrate to 650° C. The wear is carried out with a "thumb-disk" tribotester under dry surface friction with fixed black corundum abrasive particles. Comparative results were obtained for the microstructure and texture of the pre- and post- friction coating, the porosity, roughness, hardness, the dependence of mass wear, the speed and wear intensity and the wear resistance of the coatings on the number of friction cycles. Influence of the flame rate and substrate temperature on wear resistance and differential wear parameters has been determined.

Optimization of continuous triboelectrification process for polymeric materials in dry contact

Triboelectrification (i.e., generation of electric charge by friction between two materials) is a complex process. Besides the nature and condition of the surfaces in contact, several factors can have an influence on charge generation: pressure load and relative velocity between the two bodies, number of friction cycles, ambient temperature and humidity, condition and type of material surface. This paper aims at demonstrating that associating the experimental response surface methodology and genetic algorithms is an effective technique for the optimisation of triboelectrification process. The quadratic model derived from the experiments is used in a genetic algorithm program to find the optimal combination of factor values (10 sliding cycles; normal force: 10 N; sliding speed: 55 mm/s) that maximize the average potential at the surface of the tribocharged materials: -1633 V. A final experiment confirmed the prediction of the genetic algorithm. The conclusions of this experimental study can be applied to the optimisation of industrial triboelectrification processes, and contribute to the reduction of the related maintenance, energy and raw-material costs.

Coating hardness effect on the critical number of friction cycles for wear particle generation in carbon nitride coatings

Wear particle generation in carbon nitride coatings by a spherical diamond counterpart in repeated sliding contacts has been studied with an emphasis on the effect of coating hardness, through varying two nitrogen incorporation conditions of ion acceleration energy (I.A.E.) and ion current density (I.C.D.). With a pin-on-disk type apparatus installed in the chamber of an environmental scanning electron microscope (E-SEM), the motivation of this paper is to show the direct evidence of when and where the wear particles of non-conductive carbon nitride coatings deposited onto silicon substrates do generate under controllable relative humidity, rather than infer that how wear particle generation do occur from post-testing observation. Based on the in situ examination, the shape transition maps for generated wear particles have been obtained for various nitrogen incorporation conditions. The results show that the critical number of friction cycles, Nc, for detecting a cluster of wear particles is observed to be generally decreasing with an increase in both ion acceleration energy and ion current density. However, the effect of ion acceleration energy seems to be somewhat bigger than that of ion current density, not only on the critical number of friction cycles, Nc, but also on the coating characteristics, such as surface roughness, nano-indentation hardness and internal stress. It is found further that the critical number of friction cycles, Nc, is showing a linearly increasing behavior with an increase in nano-indentation hardness, which is determined by both ion acceleration energy and ion current density during an ion beam assisted deposition process.

Boundary lubrication and shear properties of thin solid films of dioctadecyl dimethyl ammonium chloride (TA 100)

The friction and shear strength behaviour of thin films of a surfactant dioctadecyl dimethyl ammonium chloride (TA100) has been extensively studied. These films were of different types, such as Langmuir-Blodgett (LB), hexane-retracted, self-assembly and 'melt'; they were deposited on clean soda-lime glass and sapphire flats. The frictional force required to slide spheres of soda-lime glass and sapphire on these flats was measured. The parameters investigated were (i) the contact pressure (in the range of 100-1900 MPa) between the sliding sphere and the flat, (ii) the number of friction cycles (up to 104), (iii) the substrate temperature (range: 290-380 K), and (iv) the sliding velocity (range: 0.01-0.3 mm s-1). If was found that even a single monolayer of LB film of this material causes a dramatic reduction of the friction between a glass slider and a coated glass flat: for a dean glass sphere sliding on a clean glass slide, the coefficient of dynamic friction was 0.9, whereas it dropped to a low value of 0.05-0.06 when there was a single monolayer on it. On the g)ass, films of TA100 have been shown to be considerably more durable and tenacious than those of stearic acid; even after 10000 to-and-fro friction cycles on a single track, the coefficient of dynamic friction remained at a low value of approximately 0.06. The various results obtained by varying different parameters have been satisfactorily explained using Eyring's shear flow model.

The transitions between microscopic wear modes during repeated sliding friction observed by a scanning electron microscope tribosystem

In order to analyse the microscopic wear mechanism in repeat-pass sliding, the wear process was observed successively over ten cycles of sliding in a newly developed scanning electron microscope tribosystem. The wear process was recorded with a video tape recorder. The type of wear test was pin-on-disk. The pin specimen was made of tungsten carbide. The hemispherical pin tip radius was 30 μm. The disk specimen was made of SUS 304 stainless steel. The sliding velocity was 40 μm s −1. The normal load could be varied from 0.07 to 1.5 N. The following principal results were obtained. 1. (1) Wear mode transition during repeated sliding progresses from cutting, to wedge forming, to shear-tongue forming and then to ploughing. 2. (2) The critical conditions for the transitions between wear modes are expressed as follows: 0.27 < D p cutting; 0.09 < D p < 0.27 wedge forming; 0.06 < D p < 0.09 shear-tongue forming; D p < 0.06 ploughing; where D p is the ratio of the depth of penetration to the length of contact parallel to the sliding direction. It is expressed as a function of normal load, disk specimen hardness, pin specimen radius and number of friction cycles. 3. (3) The conditions for wear mode transition can be explained theoretically by using a wear mode diagram.