Electrical Wear Research Articles

Chaotic dynamic analysis of electrical contact resistance measured in sliding current-carrying friction

This work explores the dynamic laws of electrical contact resistance (ECR) signals measured in the sliding current-carrying friction tests based on chaos theory. It is found that ECR time series have a chaotic nature, strongly verified by the positive largest Lyapunov exponent λ1. The chaos may originate from the combined friction effects on short and long timescales. Phase space analysis indicates that the ECR phase trajectory adheres to the “convergence–stability” evolution law over time, which pertains closely to energy dissipation. Hence, the chaotic attractor exists during current-carrying friction. Strikingly, wear surfaces confirm that the ECR phase trajectory evolution process corresponds to the stages of “formation–keeping” of the chaotic attractor, and also agrees with the electrical wear stages of “running-in–steady-state”. Further, the chaos quantifier variation is consistent with the phase space analysis results to identify wear transition quantitatively.

Understanding Electric Current Effects on Tribological Behaviors of Instantaneous Current-Carrying Pair with Recurrence Plot

Abstract Armature-rail instantaneous current-carrying friction in electromagnetic launchers refers to a sliding electric-mechanical impact friction and transition-induced arc erosion on a millisecond time scale. To reveal the electric current (50 to 300 A) effects on friction behavior and wear mechanism, the instantaneous current-carrying friction tests were performed with Al 1060 and Brass H62. Given the short nonlinear friction-induced signals, the friction behavior, including the time-domain information and system state, was comprehensively analyzed via frictional sound pressure (FSP), recurrence plot (RP), and recurrence quantification analysis (RQA). The wear topography was observed, and characterized by the multifractal spectrum. Recurrence analyses demonstrate that as the current increases, the nonstationarity of the system state weakens, and the complexity and unpredictability enhance. Higher currents reduce the FSP amplitude, i.e., enhance the interfacial lubrication effect, but intensify electrical wear and surface roughness. This signifies a wear mechanism transition from abrasive wear and slight adhesive wear to arc ablation, fatigue wear, and severe adhesive wear. The widening spectrum width implies that the irregularity and fluctuation of the topography are enhanced with the current. RP patterns and RQA quantifiers correlate with the wear damage state. The results provide a reference for anti-wear design and online degradation tracking of the rail.

Experimental study of the effect of contact line profiles on the wear mechanism of a skateboard

Using an experimental approach, the researchers investigated the wear of a skateboard according to different profile contact lines. A high-speed current-carrying test machine was used to simulate underground railway operational conditions and obtain parameters such as the coefficient of friction, arc discharge energy, temperature increase, current-carrying efficiency, and offline rate of friction pairs comprising a skateboard and contact lines with varying profiles. The researchers analysed the impact of experimental parameters on skateboard wear matched with the different contact lines, as well as the wear mechanism of the skateboard. The experimental results revealed the following order for the total skateboard wear when matched with different contact lines: oblique contact line > pitted contact line > normal contact line. For the total skateboard wear with oblique contact line, the electrical wear of the skateboard predominantly contributed to the overall wear. Across all experiments, the total skateboard wear when matched with the oblique and pitted contact lines reached 10.291 g and 5.537 g, respectively, which was approximately 3.232 and 1.739 times the wear observed when matched with the normal contact line (3.184 g). With other experimental parameters held constant, the skateboard wear was directly proportional to current and sliding velocity, but inversely proportional to the normal load. The effect of sliding velocity on skateboard wear, arc energy, offline rate, etc., was less significant than the impact of current and normal load, especially at low speeds.

Current-carrying wear behavior and the interface evolution of the Cu/Al tribological pair

Cu/Al tribological pairs play a crucial role in maintaining the efficient operation of a wide range of engineering components. However, their durability is often compromised by wear-induced damage, which involves the accumulation of material at the Cu/Al friction interface. This study investigates the intricate wear behavior of Cu/Al tribological pairs under electrical current, with a specific emphasis on material transfer events occurring at the interface. Our findings reveal that the applied electric current exerts a lubricating effect on the sliding contact friction, resulting in reduced adhesive wear. However, it concurrently exacerbates fatigue-induced delamination, abrasive wear, and electrical wear. Through detailed analysis of interface temperatures and microstructure characterizations, we demonstrate that Al deposit adhesion occurs through interfacial metal mixing and nanoscale diffusion in the presence of only mechanical friction. Conversely, at high electrical currents, interfacial melting transpires, resulting in robust adhesion facilitated by the formation of an intermetallic compound. Our findings offer valuable insights into the microscopic adhesion events occurring in Cu/Al tribological pairs and provide guidance for developing innovative coating systems aimed at reducing material deposition in Cu/Al current-carrying friction interfaces.

Comparative Investigation Into the Current-Carrying Wear Properties of Two Kinds of Carbon Skateboard/Wire Contact Under Different Conditions

The poor matching performance of a carbon skateboard and contact wire leads to abnormal wear of a rigid pantograph–catenary system. However, an effective response strategy for reducing the frequency of abnormal wear of the arch network has not been achieved. In this article, the friction and wear properties of pure carbon and copper-impregnated carbon skateboards are used to investigate and compare the friction properties under different working conditions. The experimental results show that the contact resistance of the pure carbon skateboard/contact wire increases from 12 mΩ to 45 mΩ with increasing current and shows an overall low friction coefficient. The contact resistance of the copper-impregnated carbon skateboard/contact wire fluctuates in the range of 4 mΩ to 16 mΩ, with a relatively high friction coefficient. A high current density accelerates the electrical wear behavior and temperature increase of the interface of the pure carbon skateboard/contact wire. A matching strategy of carbon skateboard and contact wire is proposed by comparing the friction coefficient, contact resistance, and wear rate.

Experimental study on the wear mechanism of the contact line in rigid pantograph-catenary systems

An experimental study was conducted to assess the wear mechanism of the commonly used contact lines in rail services. A high-speed sliding electrical contact wear test machine was applied to pantograph-catenary systems (PCS). The friction coefficient, arc discharge energy, current-passing efficiency, contact resistance, and contact loss rate were recorded or calculated. The impact of the test parameters on the wear of the contact line was analyzed. Our results showed that the wear rate of the contact line was inversely proportional to the normal force and directly proportional to the sliding speed. The wear of the contact line at constant current mainly included mechanical and electrical wear. With declining system stability, electrical wear gradually became the key to determining total contact line wear. When the normal force and sliding speed were maintained constant, the wear rate of the contact line fluctuated with changes in the current. Under non-current conditions, mostly mechanical wear occurred in the contact line, and the total wear was the highest. When the current (I) was maintained at 250 A, the electrical wear of the contact line was the highest, and the total wear was the highest under current-carrying conditions. However, at I = 350 A, the electrical and mechanical wear of the contact line were both at a low level, and the total wear of the contact line was the lowest. When I was increased to 450 A, the total wear of the contact line contributed to material transfer wear based on electrical and mechanical wear. In all tests, the maximum wear rate of the contact line (6.9712 × 10−3 g/km) was 3.138 times the minimum wear rate of the contact line (2.2215 × 10−3 g/km).

Sliding electrical contact properties of highly oriented copper fiber brush

Metal fiber brush is a new electrical brush that has a promising application in high current density and non-lubricating conditions owing to its unique structure. The copper fiber brush comprised of highly oriented and uniformly distributed fibers was prepared by the knitting method with a packing fraction of 20%. The influence of current on the sliding electrical contact properties of the copper fiber brush as sliding against the steel disc was investigated. The worn surfaces of the copper fiber brushes and the steel discs were characterized to reveal the involved wear mechanisms. The results show that the static contact resistance decreases significantly from 55 to 18 mΩ with the gradual increase of contact force from 1 to 8 N, which is attributed to the elastic contact of multiple fibers and good compressive performance. The sliding contact resistance and electrical noise decrease with the increase of current, which is attributed to the micro-welding of contact spots induced by an electric arc. The wear rate of copper fiber brush increases significantly from 1.2 × 10−5 to 5.7 × 10−5 mm3/N·m with the increase of current from 0 to 8 A. The electrical wear caused by arc erosion becomes the dominant wear mechanism, which is more profound than mechanical wear under high currents.

Effects of material transfer evolution on tribological behavior in CuCrZr alloy paired with 7075 Al alloy under current-carrying

This study investigated the effects of material transfer evolution on the tribological behavior of a CuCrZr alloy paired with the 7075 Al alloy under current-carrying using a self-developed block-pin wear tester. The microstructure, material transfer behavior, tribological characteristics, and wear mechanism of the worn surfaces were examined. The results indicated that mechanical and electrical wear were the primary wear mechanisms, and a large amount of the Al alloy material was transferred to the worn surface. The material transfer was caused by the adhesion of debris and the splashing of the Al alloy sample. The material transfer process affected the tribological behavior; the final stable Al alloy layer on the worn surface reduced and stabilized the coefficient of friction.

Modelling on the synergy of mechanical and electrical wear in a current line/catenary-pantograph system

The metro system of electrified rolling stock is an important vehicle for partly solving the metropolitan transportation and carbon emission problems. This study aims to analyse the wear of current collector/catenary-pantograph system in the rolling stock. A theoretical wear rate model between the conductor wire and the current collector of the pantograph system was adopted from the literature and further decomposed into mechanical load, electrical current, current arc erosion, and the synergy components. Based on the decomposed model, an experimental protocol for finding the curve-fitted parameters for the theoretical model was proposed. The numerical data adopted from a previous literature was employed in the decomposed model to discuss the effects of mechanical loading, electrical current, and vehicle speed on the wear rate components. From the decomposed wear rate model, the so-called electrical current lubrication on the total wear rate due to the applied electrical current could be observed directly. Moreover, the nonlinear couplings among the control factors in the operation of the system manifested significantly. Thus, in the design phase the optimization analysis should be performed on the control parameters using the theoretical wear rate model to extend the life and reliability of this catenary-pantograph system.

Evaluation of the Useful and Residual Life of a Class of Relay-Based Centralised Traffic Control

Currently in Bulgaria, the main railway lines (corridors) are being modernised to increase train speed up to 160/200 km/h, which necessitates adoption of modern European traffic control systems (ERTMS/ETCS, classified as so-called class A systems). The remaining sections continue to operate mainly relay-based systems for ensuring safety of train traffic (the so-called class B systems). These systems include, first, station centralised traffic control systems, most of which are currently route relay-based ones. On the railways of Bulgaria, two classes of route relay-based centralised traffic control systems (RRCTCS) are operated, using respectively, the relays of so called «first class of reliability», and the relays of the so called «not first class of reliability». The inevitable increase in the age of RRCTCSs makes it necessary to assess their technical condition and technical suitability to clarify strategies for their further operation. Such an assessment is difficult due to the lack, first, of statistical data on the failures and reliability parameters during operation as per types of systems and their constituent elements and, second, of manufacturers’ recommendations on the service life of RRCTCS. The service life and residual service life, as well as the useful and residual life of RRCTCSs could, in the author’s opinion, be assessed according to the following criteria: • Electrical and mechanical useful life/wear of the components. • Reliability parameters of the relay components. • Electrical and mechanical useful life or the condition of the external and internal cabling. • Operating costs required to maintain RRCTCS within the range of predefined technical parameters. The article analyses and evaluates the average useful life and the average residual life of RRCTCS based on the first two criteria. It is concluded that neither electrical nor mechanical wear resistance of components is among leading characteristics for assessing useful and residual life. Two approaches are used to consider some of reliability parameters of the relay components: deterministic and probabilistic one, which are based on the «intensity of dangerous failures» characteristic of the relay of the first reliability class. Based on that characteristic, the probability of a dangerous failure of the first-class relays in operation was calculated for 58 Bulgarian RRCTCSs of N-68 type with non-routed manoeuvres, as well as the probability of their safe operation; the latter probability is proposed to be used to calculate the average residual life of the relay, and based on that, to calculate the average residual life of RRCTCSs of that type. By early 2021, the estimated maximum of the latter is 11 years. The consequences of implementing two strategies in subsequent years are considered: a) «nothing is done» and b) «RRCTCS useful life/age management» (based on the program of gradual decommissioning of N-68 type RRCTCSs and of re-equipment of relevant stations). This is also a prerequisite for safety management of train traffic. It is argued that an average useful life of RRCTCS could be estimated as no more than 60 years in operation. Considering additional factors, this period should be understood as a predicted value of the expected time after which the corresponding RRCTCS will reach the limit state and will be decommissioned. The average useful life and the average residual life should be considered the best guideline for the expected age limit for this type of RRCTCS.

Damage mechanism of crown spring for the EMU traction Motor’s connector

The electrical connector of the traction motor is an important device to ensure the stable operation of the electronic system of the EMU. Damage to the crown spring inside the connector will cause the traction motor to lose power supply. In this work, the damage morphology, composition and damage depth of the crown spring damage area were systematically analyzed using macroscopic and microscopic analysis equipment.Results show that the coating of the slightly damaged reeds was oxidized. Moderately damaged reeds have severe mechanical wear that caused the coating to disappear. Severely damaged reeds are caused by the combined action of mechanical wear, electrical wear and oxidative wear. At this stage, the connector joint heats up rapidly, which causes the crown spring to melt. The results show that the failure of the crown spring is the result of the combined effect of mechanical wear, electrical wear, and oxidative wear.

Electrical wear performance of copper matrix composites reinforced with hybrid CNTs and TiB2 particles

PurposeCopper matrix composites are widely used in high-voltage switches, electrified railways and other electric friction fields. The purpose of this study is to improve its wear resistance and investigate the effect of hybrid carbon nanotubes (CNTs) and titanium diboride (TiB2) particles reinforced copper matrix composites on electrical wear performance.Design/methodology/approachCNTs and TiB2 particles were introduced into copper matrix simultaneously by powder metallurgy combined with electroless copper plating. Electrical wear performance of the composites was studied on self-made pin on disk electrical wear tester.FindingsThe results show that the friction coefficient and wear rate of (1CNTs–4TiB2)/Cu composite are respectively reduced by 40% and 25.3%, compared with single TiB2/Cu composites. The micron-sized TiB2 particles can hinder the plastic deformation of composites, and bear part of the load to weaken the wear rate of composites. CNTs with the self-lubricating property can form lubricating layer to reduce the friction coefficient of composites.Originality/valueThis work can provide a design method for further improving the wear properties of TiB2/Cu composites.

The wear resistance of Al–Si–Re alloys for electrical contact applications

We prepared aluminum–silicon–rare earth (Al–Si–Re) elements alloys for electrical contact applications. Three Si weight percentages (wt.%) — 10%, 20% and 30% — were used, and rare earth (Re) elements were kept at 0.35 wt.%. The spraying forming process was adopted, and high-pressure hot isostatic pressing (HIP) was conducted to obtain the bulk materials from the as-deposited billets. The electrical conductivity of alloys with 10% and 20% Si reached 40% International Annealed Copper Standard (IACS). The hardness of Al–Si alloys significantly increased with Si content and HIP processing times. The hardness of alloy with 30% Si reached [Formula: see text]90 HV. Meanwhile, HIP reduced weight loss in the wear resistance by reducing the microcracks and materials removal. The current study proposes an approach to manufacture Al–Si alloys with high electrical conductivity and high wear resistance.

Modernization of Electrode Composite Material Based on Copper Powder for Electrical Discharge Machining of High-Strength Alloys

As a result of implemented modernization of known electrode composite material based on Cu-3% wt BN copper powder successfully used for electrical discharge machining of high-strength alloys, composite material (Cu - 3% wt BN) – 0.5 % wt Al – 0.25 % wt in the form of high-density long thin-wall plates for operations of electrical discharge cutting and piercing of hard-to-machine materials was obtained. The new material was obtained with the use of the method of reactionary mechanical alloying of initial powder components in the attritor. Tool electrodes made of the new material during electrical discharge piercing of rectangular holes in titanium alloy sheets ensure a 1.6 times higher machining rate comparing to tool electrodes made of the Cu-3% wt BN prototype material. After replacement of rolled copper in tool electrodes with the new composite material the machining rate will increase 4.1 times. The tool electrodes made of this material have significantly lower electrical discharge wear comparing to the wear of tool electrodes made of the prototype material and rolled copper.

A research on the electrical sliding behavior wear of dual-scale particulate reinforced copper matrix composites

This work aims to investigate the electrical sliding wear behavior of the dual-scale particulate reinforced copper matrix composites by a self-developed pin-on-disk wear tester. Cu-xCr-0.3Zr-1ZrB2 (x = 0, 0.5, 1.0) composites were fabricating by casting and cold rolling. The microstructure of worn surfaces was examined using scanning electron microscopy (SEM) and laser scanning confocal microscope to unravel the wear mechanisms. The results indicated that the combined effect of mechanical wear and electrical wear dominated the wear process with an increase in the apparent normal load. Amplifying the electrical current increased the wear loss of the sliding pair, in the meantime alleviated the fluctuation of the friction coefficient with marginal changes in the average values. After introducing Cr element and ZrB2 particles, the wear rate decreased from 0.197 mg/m to 0.141 mg/m under moderate operating test conditions. Adhesive wear and abrasive wear occupied an important position in the wear mechanism of the Cu-1wt%Cr-0.3wt%Zr-1wt%ZrB2 composite under electrical current due to the elevation of thermal stability and the formation of a tribolayer introduced by these reinforcements.

Logical-probabilistic assessment of the occurrence of destruction during intersystem interactions in the electrical system of the seaport

This article solves the problem of a quantitative assessment of the occurrence of destruction in the intersystem interactions of the transport system and the electrical system of the seaport, in the conditions of the technological process in the seaport, which indicates its significant impact on the electrical system, as a result of which the reliability of the berthing power line is significantly reduced. The intersystem interactions that occur during the implementation of the technological process, as experience shows, are the causes of critical situations that occur at the border of areas of different physical nature, and the consequences are recorded, in the case under consideration, in the electrical system. A mathematical model describing intersystem destruction in quantitative form is presented in this paper using a logical-probabilistic model that reflects internal and external relationships. In the object under study, the destructive cause (collision) and the consequence (accumulation of electrical damage in the insulation of the cable line) are in the same object (the mooring power supply unit), and this is limited to the effects of intersystem destruction. In such a statement, the object of power supply of the technological process and equipment is considered as a composite object containing a cable line and an electric contact column. The problem being formulated is an important and relevant scientific task, which includes not only the question of identifying the causes of increased electrical wear of the power line, but also the development of methods for obtaining quantitative results, and in practical terms also involves the diagnosis of the technical condition of electrical equipment and timely preventive maintenance.

Mathematical model of the evolution of operating parametersof dielectrics in the marine power supply system when forcing certain factors

The paper addresses the issue of development of a mathematical model for the evolution of operating parameters of dielectrics in the marine power supply system when forcing certain factors. The paper addresses a comprehensive problem in comparison with the classical problem of the wear theory. With regard to the given details, factors that cause a decrease in the operating time were introduced to determine the operating time before electrical wear of the power supply unit. The study employs methods of the fuzzy (uncertain) set theory. The uncertainty of quantities in the fuzzy set theory is set by the membership function, which determines the degree of its fuzziness. In accordance with fuzzy set methods, a membership function is constructed to estimate fuzziness of the function of a shrinking time resource of operating time before wear. In Mathcad, the authors have developed a computational module for estimating the fuzzy time (due to inaccuracy of the initial data) subtracted from the total operating time before electrical wear of the berthing power supply unit. To improve the reliability of power supply to seaports and reduce accidents, new technical and organizational measures are being developed. Therefore, the task is formulated to ensure serviceability of the power supply system with due regard to its interactions with various subsystems.

Sub-Microstructure of Surface and Subsurface Layers after Electrical Discharge Machining Structural Materials in Water

The material removal mechanism, submicrostructure of surface and subsurface layers, nanotransformations occurred in surface and subsurface layers during electrical discharge machining two structural materials such as anti-corrosion X10CrNiTi18-10 (12kH18N10T) steel of austenite class and 2024 (D16) duralumin in a deionized water medium were researched. The machining was conducted using a brass tool of 0.25 mm in diameter. The measured discharge gap is 45–60 µm for X10CrNiTi18-10 (12kH18N10T) steel and 105–120 µm for 2024 (D16) duralumin. Surface roughness parameters are arithmetic mean deviation (Ra) of 4.61 µm, 10-point height (Rz) of 28.73 µm, maximum peak-to-valley height (Rtm) of 29.50 µm, mean spacing between peaks (Sm) of 18.0 µm for steel; Ra of 5.41 µm, Rz of 35.29 µm, Rtm of 43.17 µm, Sm of 30.0 µm for duralumin. The recast layer with adsorbed components of the wire tool electrode and carbides was observed up to the depth of 4–6 µm for steel and 2.5–4 µm for duralumin. The Levenberg–Marquardt algorithm was used to mathematically interpolate the dependence of the interelectrode gap on the electrical resistance of the material. The observed microstructures provide grounding on the nature of electrical wear and nanomodification of the obtained surfaces.

Enhancement in corrosion and electrical wear resistance of copper via laser surface alloying with NiTi

With a 2.3-kW high-power diode laser, laser surface alloying of a commercially pure copper (cp Cu) with NiTi powder was carried out to attain higher corrosion and electrical wear resistances. Potentiodynamic polarization was conducted in simulated acid rain (SAR) at 25 °C for simulating the corrosive environment. In the SAR, corrosion potentials of all laser-alloyed samples are found to be nobler than those of cp Cu and NiTi alloy and their corrosion current densities are lower than that of cp Cu although their oxide layers are less uniform. Electrical wear tests were also carried out in both dry and wet conditions with a pin-on-disc tribometer. The electrical wear resistances of the laser-alloyed samples in wet condition are higher than in dry condition due to lubrication effect and reduction in frictional heat. The electrical wear resistances of all laser-alloyed samples were improved as compared with cp Cu owing to the presence of pseudo-plasticity of B19′ and hard IMPs, and work hardening effect during electrical wear. The contribution of electrical wear in SAR is mainly mechanical wear, and wear-corrosion synergism up to 36.1%, while corrosion is negligible. Compared with cp Cu, the interfacial contact resistance of the laser-alloyed samples at 50 N/cm 2 has increased from 3.5 to 7.2 times. • Pure copper is successfully laser-surface alloyed with NiTi powder • Compared to cp Cu, corrosion potentials of laser-alloyed samples are nobler and corrosion current densities are lower • Their electrical wear resistances are improved due to pseudo-plasticity of B19’, hard IMPs and work hardening effect • Contribution of electrical wear in SAR is mainly mechanical wear and wear-corrosion synergism up to 36.1% • Compared to cp Cu, interfacial contact resistance of laser-alloyed samples is increased from 3.5 to 7.2 times

Research on the wear and life of copper tungsten alloy contacts of high voltage SF6 circuit breakers

Three phase short circuit and two phase short circuit grounding fault of power system have a significant influence on the electrical life of circuit breaker contact. In this paper, the mathematical model of each component is established by Power System Analysis Software Package (PSASP), and the simulation model is built to simulate the dynamic state of the circuit breaker after different short-circuit faults. The simulated result confirms that contact electrical wear quantity related to the type of short circuit fault and the position of short circuit point. The size of short circuit current will directly impact electrical wear quantity and electrical life of circuit breaker contact.