Electrical Wear Research Articles

Laser fabrication of W-reinforced Cu layers: II. Electrical wear behavior in air and synthetic acid rain

In order to enhance the electrical sliding wear resistance and hence the lifespan of cp Cu for applications in electrical contacts, W-reinforced Cu layers were fabricated by laser surface modification on cp Cu. Compared with cp Cu, the hardness of the laser-fabricated layers with 55–60 wt% W was improved from 70 to 150 HV0.2 while electrical wear resistances in dry and wet conditions were improved by 3 orders of magnitude despite the increase in the interfacial contact resistance of the layers. The main contribution of electrical wear in synthetic acid rain is mechanical wear, with contribution of corrosion-wear synergism up to 32.8%, while corrosion alone is negligible.

Effect of Al2O3 Particle Size on Electrical Wear Performance of Al2O3/Cu Composites

ABSTRACTAl2O3/Cu composites (1.0 vol%) reinforced with different size of α-Al2O3 particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al2O3 particle size on electrical wear performance of the Al2O3/Cu composite was studied, and the wear mechanism of the Al2O3/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A12O3/Cu composite are closely related to the mechanical properties. With an increase in Al2O3 particle size, the wear rates of A12O3/Cu composites have a reverse variation with hardness of A12O3/Cu composites. In the range of 50–100 nm, Al2O3/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al2O3/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic deformation area on the pin sample of the frictional end depends on the electrical wear resistance of A12O3/Cu composites.

전동차 주습판(Pantograph Slider) 재질개선 및 실차 적용에 관한 연구

A slider of the pantograph undergoes uneven and abnormal wear due to sliding contact with the catenary. In the case of rain, the loss of lubricant increases the frictional resistance for the reciprocating motion between the catenary and the slider, accelerating local wear. The slider in the winter should have good wear resistance, which can be achieved through alloy design. Uneven and abnormal wear were not observed in the results of a driving test using a wear resistant slider. It was found that the increased density of the slider enhanced the corrosive effects of Fe-Ti, preventing the occurrence of abnormal wear by maintaining the wear and arc resistance in the rainy season. Also, mechanical and electrical wear did not affect the composition of the slider, and this improved the wear resistance. Inaddition, the slider was applied to an entire train and was tested during driving; ananalysis of the correlation of the catenary was performed, including during the rainy season and the winter season.

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.

Structural Changes in the Surface Layer of Carbon Steels Under Friction and Current Loading in Air and in Liquid Media

The current dependence of the electrical conductivity and wear intensity of a sliding electrical contact in air, glycerin, or electrolyte under electrolysis conditions at a contact current density of 100 A/сm2 is presented. The structural characteristics of the steel surface layer are shown to change due to the formation of the γ-iron and ferric carbide phases. Low phase content is found to cause higher wear intensity of the sliding contact.

Identification of the sources of PM10 in a subway tunnel using positive matrix factorization

The level of particulate matter of less than 10 μm diameter (PM10) at subway platforms can be significantly reduced by installing a platform screen-door system. However, both workers and passengers might be exposed to higher PM10 levels while the cars are within the tunnel because it is a more confined environment. This study determined the PM10 levels in a subway tunnel, and identified the sources of PM10 using elemental analysis and receptor modeling. Forty-four PM10 samples were collected in the tunnel between the Gireum and Mia stations on Line 4 in metropolitan Seoul and analyzed using inductively coupled plasma–atomic emission spectrometry and ion chromatography. The major PM10 sources were identified using positive matrix factorization (PMF). The average PM10 concentration in the tunnels was 200.8 ± 22.0 μg/m3. Elemental analysis indicated that the PM10 consisted of 40.4% inorganic species, 9.1% anions, 4.9% cations, and 45.6% other materials. Iron was the most abundant element, with an average concentration of 72.5 ± 10.4 μg/m3. The PM10 sources characterized by PMF included rail, wheel, and brake wear (59.6%), soil combustion (17.0%), secondary aerosols (10.0%), electric cable wear (8.1%), and soil and road dust (5.4%). Internal sources comprising rail, wheel, brake, and electric cable wear made the greatest contribution to the PM10 (67.7%) in tunnel air.ImplicationsWith installation of a platform screen door, PM10 levels in subway tunnels were higher than those on platforms. Tunnel PM10 levels exceeded 150 μg/m3 of the Korean standard for subway platform. Elemental analysis of PM10 in a tunnel showed that Fe was the most abundant element. Five PM10 sources in tunnel were identified by positive matrix factorization. Railroad-related sources contributed 68% of PM10 in the subway tunnel.

The Use of Infrared Thermography in the Analysis of Engineered Cementitious Composites

Non-destructive testing using infrared thermography has been used in civil construction basically in situations involving electrical conductors or mechanical wear that normally generate heat. In the specific case of materials, the application of thermography to metal stud is well documented, but there are few reports in the literature covering thermography in concrete; these are usually limited to the inspection of cracks and to the localization of water infiltration in prefabricated concrete structures. The present report evaluates the potential of the active infrared thermography method in the detection of changes in the macrostructure of engineering cementitious composite, as well as in order to estimate its thermal performance. The results show that thermography is able to detect changes in the macrostructure and is sensitive to temperature differences among the constituents of concrete.

Effect of the Thermal Expansion Characteristics of Reinforcements on the Electrical Wear Performance of Copper Matrix Composite

Copper matrix composites reinforced with MgO, Al2O3, SiO2, and SiC nanoparticles were fabricated by powder metallurgy. The tribological properties of the composites were examined using a self-made pin-on-disk electrical wear tester. Thermal expansion properties of the prepared composites were evaluated by their coefficient of thermal expansion from 50 to 500°C. The effect of the thermal expansion characteristics of reinforcements on the electrical wear performance of the composites was also studied. The results showed that the wear rates of MgO/Cu and Al2O3/Cu composites were lower than those of SiC/Cu and SiO2/Cu composites, which were also consistent with the difference between the coefficient of thermal expansion of the copper matrix and reinforcements. The relationship was analyzed by calculation of the thermal stress at the copper matrix–reinforcement interface in the electrical sliding process. Microstructural observation revealed that the wear mechanisms of the copper matrix composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage.

Preparation and Properties of Cf-Ti<sub>3</sub>SiC<sub>2</sub>-Cu-Graphite Composites

Copper-plated short carbon fiber/copper-plated Ti3SiC2-Cu-graphite composite, copper-plated short carbon fiber/Ti3SiC2-Cu-graphite composite with the same carbon fiber content and copper-plated Ti3SiC2-Cu-graphite composite were prepared by the powder metallurgy method. Physical and mechanical properties of these composites were tested. The dry friction tests of the composites under sliding velocity of 10m/s and load of 4.9N were conducted for 36 hours. The results show that the properties of the Cf-copper-plated Ti3SiC2-Cu-graphite composite such as electric conductivity, bending strength and wear resistance are remarkably increased than those of either Cf-Ti3SiC2-Cu-graphite or copper-plated Ti3SiC2-Cu-graphite composites.

Active control strategy on a catenary–pantograph validated model

Dynamic simulation methods have become essential in the design process and control of the catenary–pantograph system, overall since high-speed trains and interoperability criteria are getting very trendy. This paper presents an original hardware-in-the-loop (HIL) strategy aimed at integrating a multicriteria active control within the catenary–pantograph dynamic interaction. The relevance of HIL control systems applied in the frame of the pantograph is undoubtedly increasing due to the recent and more demanding requirements for high-speed railway systems. Since the loss of contact between the catenary and the pantograph leads to arcing and electrical wear, and too high contact forces cause mechanical wear of both the catenary wires and the strips of the pantograph, not only prescribed but also economic and performance criteria ratify such a relevance. Different configurations of the proportional-integral-derivative (PID) controller are proposed and applied to two different plant systems. Since this paper is mainly focused on the control strategy, both plant systems are simulation models though the methodology is suitable for a laboratory bench. The strategy of control involves a multicriteria optimisation of the contact force and the consumption of the energy supplied by the control force, a genetic algorithm has been applied for this purpose. Thus, the PID controller is fitted according to these conflicting objectives and tested within a nonlinear lumped model and a nonlinear finite element model, being the last one validated against the European Standard EN 50318. Finally, certain tests have been accomplished in order to analyse the robustness of the control strategy. Particularly, the relevance or the plant simulation, the running speed and the instrumentation time delay are studied in this paper.

Electric Contact Stability and Wear Durability at a Nanoscale Sliding Electric Contact

Electric Contact Stability and Wear Durability at a Nanoscale Sliding Electric Contact

Correlation analysis of brush temperature in brush-type DC motor for predicting motor life

Some critical components of motors and generators have sliding electrical contacts. Electrical brushes are usually used in these contact points to conduct current between the stationary part and the moving part of the motor. In this paper, studies on brush wear against copper commutators are briefly reviewed. The main influential factors in brush wear are associated with both mechanical wear and electrical wear. Brush wear is affected by various factors, including temperature, material properties, sliding speed, contact force, and interfacial as well as environmental conditions. The mechanical wear of brushes is proportional to brush spring pressure and sliding speed, and the electrical wear of brushes is associated with current and contact voltage drop. For characterization, a brush wear test machine is designed, and influential factors, such as electrical contact resistance, temperature, wear mass loss, and so on, are measured. The wear tests are processed using a small brush-type automotive DC motor. The study primarily aims to investigate the effects of the wear behavior of copper-graphite brushes on small brush-typed DC motors. The variable conditions of electrical current are obtained by changing the brush spring pressure and the sliding speed. The results are electrical contact resistance, voltage drop, brush surface temperature rise, and so on. Brush wear is greatly changed by electrical current, which indicates that high current itself not only produces more Joule heating but also causes an increase in voltage drop that will result in additional Joule heating.

Preparation and Properties of Cf-TiB2-Cu-Graphite Composites

Copper-plated TiB2-Cu-graphite composite, Cf-TiB2-Cu-graphite composite and Cf-copper-plated TiB2-Cu-graphite composite with the same TiB2 content were prepared by the powder metallurgy method. Physical and mechanical properties of these composites were tested. The dry friction tests of the composites under sliding velocity of 10m/s and load of 4.9N were conducted for 36h. The results show that the properties of the Cf-copper-plated TiB2-Cu-graphite composite such as electric conductivity, hardness, bending strength and wear resistance are increased remarkably than those of either Cf-TiB2-Cu-graphite or copper-plated TiB2-Cu-graphite composites.

Effect of pv factor on sliding friction and wear of copper-impregnated metallized carbon

In this paper, the effect of pv factor on the tribological behavior of a copper-impregnated metallized carbon brush sliding against a CuCrZr ring was investigated. Friction and wear tests were conducted on a brush-on-slip ring type wear tester. The tests were performed at two electrical currents (0 and 20A) and seven different combinations of contact pressure (p) and sliding velocity (v), herein referred to as the pv factor to study the relationship between electrical and mechanical wear. The results show that mechanical wear aggravates electrical wear. Higher interfacial temperatures appear to be responsible for the higher wear rate. Worn surfaces of brush specimens were observed and analyzed by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS). It is apparent that the degree of tribo-oxidation at the brush increases with an increase in pv, which has a significant influence on the tribological behavior of the brush specimen.

Mechanism of Undulating Wear Formation of Overhead Rigid Conductor Line Related to Dynamic Characteristics of Pantographs

When there is an undulating wear on overhead rigid conductor line, arc due to contact loss is generated between the conductor line and a pantograph. The arcs cause extreme wear of contact lines and contact strips of the pantograph. However the mechanism of the undulating wear formation has not been clarified. This paper to make clear the mechanism of the formation of the undulating wear through on-site investigation of overhead rigid conductor lines and excitation tests of the pantograph. It was been clarified that the dynamic characteristics of pantograph and the distance between pantograph heads play a causal role in the undulating wear formation. Firstly, a periodic unevenness is generated by mechanical wear that is caused due to the dynamic characteristics of pantograph, especially anti-resonance phenomenon of pantograph. When the wear amplitude of unevenness grows to the extent with which pantographs cannot comply, arc due to contact loss occurs between overhead rigid conduct line and the pantograph. By this arc, electric wear is generated in a hollow of unevenness, then the undulating wear of which wavelength is related to the interval of pantograph head grows.

Electroless Coating of Silver on Multiwall Carbon Nanotubes

Silver reinforced with carbon nanotubes, instead of graphite, would increase both the electrical conductivity, hardness and wear resistance of the electrical brush materials. The effective utilization of carbon nanotubes in the Ag/CNT composite depends strongly on its uniform distribution and strong interfacial adhesion to the silver matrix and thus demands for its surface modification. In order to carry out the surface modification of carbon nanotubes, electroless coating was given to them after liquid phase oxidation, sensitization and activation process. The room-temperature chemical treatment results in a nominally complete coating over the entire outer surface of multiwall carbon nanotube. The surface morphology of the carbon nanotubes after each step has been studied using TGA, DSC, XRD, FTIR and SEM.

Variations in the properties of the friction zone of metallic composites under the effect of electric current and Pb-Sn melt in the contact gap

The paper deals with study of the wear rate and specific surface electric resistance of the contact of metallic composites in dry friction at a high current density. Friction induced structures are shown to appear in the surface layer of the composites. The specific electric resistance of the friction induced structures is estimated quantitatively. It is found that their specific electric resistance is similar to that of the known electrographites and carbon graphites, resulting in a high contact resistance. The electric resistance and wear rate of the friction zone are diminished by the introduction of a Pb-Sn melt. The possibility of developing of an efficient sliding electric contact of two metallic composites with a metal melt between their friction surfaces is noted.

Wear Behavior of Cr<sub>2</sub>O<sub>3</sub>/Cu Composite under Electrical Sliding

The Cr2O3/Cu composites with different Cr2O3-content performed in this paper were prepared by surface internal oxidation of Cu-Cr solid alloy. The Cr2O3/Cu composite wires were slid against a copper-based powder metallurgy strip under unlubricated conditions. The wear behavior of Cr2O3/Cu composite was researched under different currents from 0-50A and sliding distance from 0-72Km. Worn surfaces of the Cr2O3/Cu composite were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results indicate that the wear rate of Cr2O3/Cu composite increases with the increase in electrical current and sliding distance. The wear rate increases abruptly at the beginning and smoothly subsequently. And the variety of electrical currents has slight influence on the wear rate. The wear rate of the Cr2O3/Cu composites decreases with the increase in Cr2O3-content. The wear rate of 0.478 Cr2O3/Cu composite is 2-3 times that of 1.25Cr2O3/Cu composite at the same experimental conditions. Abrasive wear and electrical erosion wear are the dominant wear mechanisms during the electrical sliding wear processes.

Influence of Adding Carbon Nanotubes and Graphite to Ag-MoS2 Composites on the Electrical Sliding Wear Properties

Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ◦C and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.

An analysis of the main factors on the wear of brushes for automotive small brush-type DC motor

Some critical components in motors and generators have sliding electrical contacts. Electrical brushes are commonly used in those contact points to conduct current between the stationary and moving parts of a motor. Brushes are exposed both to mechanical and electrical loading. In this paper, studies on the wear of brushes against copper commutator were briefly reviewed. The main influential factors of brush wear are associated with both mechanical and electrical wear. Brush wear is affected by various factors including temperature, material properties, sliding speed, contact force, and interfacial and environmental conditions. The mechanical wear of brushes is proportional to the brush spring pressure and sliding speed, while the electrical wear of brushes is associated with current and contact voltage drop. To characterize the wear, a brush wear test machine was designed, and influential factors were measured such as electrical contact resistance, temperature, wear mass loss, and so on. The wear tests were processed using a small brush type automotive DC motor. The main objective of this study is to investigate the effects of the wear behavior of copper-graphite brushes in a small brush-type DC motor. The variable conditions are with and without electrical current by changing the brush spring pressure and sliding speed, and the results are electrical contact resistance, voltage drop, brush surface temperature rise, and so on. Brush wear greatly changes with electrical current. This shows that the high current not only produces more Joule heating but also causes an increase in voltage drop, which will result in additional Joule heating.