Yong Zhen Zhang

Study of the Friction and Wear of Electrified Copper against Copper Alloy under Dry or Moist Conditions

The frictional and wear characteristics of electrified copper sliding against a QCr0.5 copper alloy under moist and dry conditions were investigated utilizing a special pin-on-disc apparatus. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to observe the morphology of the copper pin contact surface and analyze its compositions, respectively. The results indicate that the wear rate and frictional coefficient of the copper are reduced as a result of the cooling and lubricating effect of water compared with dry sliding condition. However, both the frictional coefficient and wear rate of the copper material increases with an increase in electrical current under either moist or dry conditions and the frictional coefficient varies within narrow limits under wet conditions. In addition, there is a greater amount of oxygen associated with the surface under wet conditions than dry.

Tribological Properties of PTFE Nanocomposites Filled with Alumina Nanoparticles

Polytetrafluoroethylene (PTFE) nanocomposites filled with alumina nanoparticles were prepared by compression molding and follow-up sintering. The tribological behaviors of PTFE nanocomposites sliding against GCr15 steel were evaluated using ball-on-disk tribology test rig. The worn surfaces of the unfilled and filled PTFE nanocomposite were investigated using a scanning electron microscope (SEM). The wear behavior of the PTFE nanocomposites was explained in terms of the topography of worn surfaces. It was found that the addition of alumina nanoparticles was effective in enhancing the wear resistance of the PTFE nanocomposite.

Friction and Wear Behavior of Copper-Graphite Composite Material in High-Speed Sliding with Current

In the present study, the friction and wear behaviors of copper-graphite composite against GCr15 steel in high-speed sliding with current were investigated. The worn surfaces and wear debris were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the wear mechanisms were discussed. It shows that the current plays an important role in the high-speed dry sliding of copper-graphite composite against GCr15 steel. With increasing current, the friction coefficient decreases, and the wear rate increases. The wear mechanisms of the copper-graphite composite are main abrasion and fatigue without current, and that of with current are main fatigue, arc ablation.

Research on Frictional Wear Properties of C/C Composite with Electric Current

Using C/C composite and chrome bronze as a friction couple, the frictional wear properties of C/C composite with electric current is studied in this paper. The results have shown that current, velocity and load are important factors to affect the frictional wear properties of C/C composite with electric current. The coefficient of friction and the wear rate increase with the increase of velocity when the electric current is constant of 100A. The coefficient of friction increases but the wear rate decreases with the increase of load when the electric current is constant at 100A. The coefficient of friction decreases but the wear rate increases with the increase of current when the load is constant of 80N. Comparing with no electric current, the coefficient of friction of C/C composite with electric current decreases but the wear rate of that increases obviously. The wear mechanism of C/C composite is mainly of electric wear caused by arc erosion under the condition of current-carrying.

Study of Dry Sliding Friction and Wear Characteristic of High-Speed Steel / 40CrMoA Steel under Direct Steady Magnetic Field

The influence of DC steady magnetic field on dry-sliding Friction and wear characteristics of friction pair of high-speed steel (HSS) ring and 40CrMoA pin is studied by use of improved MPV-1500 type Friction and wear tester under normal temperature. Experiments show that, The wear loss of both HSS ring and 40CrMoA pin decreases gradually, along with the enhancement of the magnetic field intensity, under the load of 250N and the friction velocity of 0.6m/s; The wear loss of the sample HSS ring keeps low comparing with that of the sample 40CrMoA steel pin; The trend of friction coefficients decreases quickly and then slowly; Magnetic field can accelerate oxidization; Oxidation and adhesion occur mainly in friction surface.

Influence of DC Steady Magnetic Field on Friction and Wear Characteristics of Friction Pair of High-Speed Steel / 2Cr13 Stainless Steel

The influence of DC steady magnetic field on dry-sliding Friction and wear characteristics of friction pair of high-speed steel (HSS) ring and 2Cr13 pin is studied by use of improved MPV-1500 type Friction and wear tester under normal temperature. Experiments show that, The wear loss of both HSS ring and 2Cr13 pin decreases gradually, along with the enhancement of the magnetic field intensity, under the load of 250N and the friction velocity of 0.6m/s; The phenomenon of negative wear loss appears to the HSS ring. The wear loss of the sample HSS ring keeps low comparing with that of the sample 2Cr13 stainless steel pin; The trend of friction coefficients decreases quickly and then slowly; Magnetic field can accelerate oxidization.

Effect of Surface Roughness on Slip Resistance of Rubber

In order to decrease accidents of slips and falls, COFs of rubber samples with different surface roughness were measured by Brungraber Mark II. And the correlation coefficients between roughness parameters and COF were calculated. The rusults have shown that the COF increases with surface roughness and the correlation coefficient between Sq and COF is highest. In general, almost all the roughness parameters used in the study have high correlation with COF. Parameters had the highest correlation with COF depends on the materials used and test conditions.

Study on the Tribological Performance of Copper-Based Powder Metallurgical Friction Materials with Cu-Coated or Uncoated Graphite Particles as Lubricants

The tribological performance of copper-based powder metallurgical material is much influenced by the interfacial bonding between the components and matrix. By adding Cu-coated or uncoated graphite particles as a lubricant, two types of copper-based powder metallurgical materials were prepared via spark plasma sintering (SPS). The hardness, relative density, and thermal conductivity of the two specimens were firstly measured. Using an inertial braking test bench and temperature measuring instrument, the average friction coefficients, instantaneous friction coefficients, and friction temperatures of the two specimens were tested under different test conditions, and the wear rates were calculated accordingly. Based on the analysis of surface morphologies and elements distribution after the tests, the mechanisms of wear and formation of friction films were discussed. The results show that with the lubricant of Cu-coated graphite, the hardness, relative density, thermal conductivity, and interfacial bonding between the graphite and matrix can be greatly improved. Under the same test condition, the average friction coefficient, wear rate, and friction temperature of the specimen with added Cu-coated graphite are both lower than those of the specimen with added uncoated graphite. The two specimens show different variation trends in the instantaneous friction coefficient during the tests, and the variation of the instantaneous friction coefficient at a high initial test speed is also different from that at a low initial test speed for each specimen. The two specimens also show differences in the continuity of friction film and the content of graphite and oxide in the friction film.

Study of Friction and Wear Behavior of C/C Composite under Electrical Sliding

Using C/C composite and chrome bronze as a friction couple, the frictional wear properties of C/C composite with electric current is studied in this paper. The results have shown that current, velocity and load are important factors to affect the frictional wear properties of C/C composite with electric current. Wear rate of C/C composite increases with the increase of arc energy .The coefficient of friction and the wear rate increase with the increase of velocity when the electric current is constant of 100A. The coefficient of friction increases but the wear rate decreases with the increase of load when the electric current is constant at 100A. The coefficient of friction decreases but the wear rate increases with the increase of current when the load is constant of 80N. Comparing with no electric current, the coefficient of friction of C/C composite with electric current decreases but the wear rate of that increases obviously. The wear mechanism of C/C composite is mainly of electric wear caused by arc erosion under the condition of current-carrying.

Tribological Behavior of PTFE Nanocomposites Reinforced with PBA Grafted Alumina Nanoparticles

Polybutyl acrylate (PBA) grafted alumina nanoparticles were synthesized. Polytetrafluoroethylene (PTFE) nanocomposites reinforced with PBA grafted nanoparticles were prepared by compression molding. The effects of PBA grafted nanoparticles on the tribological behavior of the PTFE nanocomposites were investigated on a tribometer. The abrasion mechanisms of the PTFE nanocomposites were investigated by scanning electron microscopy (SEM) of the abraded surfaces. The results show that the addition of PBA grafted nanoparticles maintains low friction coefficient and improves the wear resistance of the PTFE nanocomposites.