Effects of Hardness on the Lifetime of Graphite Brushes Used for Aircraft Starter Generators

2012 ◽  
Author(s):  
R. Asmatulu ◽  
M. J. Holle ◽  
H. E. Misak
Keyword(s):  
Wear Rate ◽  
Surface Morphology ◽  
Optical Microscope ◽  
Excess Carbon ◽  
Wear Rates ◽  
Key Factor ◽  
Generating Mode ◽  
Starter Generator ◽  
The Relationship ◽  
Morphology Changes

This study is focused on the relationship between the hardness of three different carbon/graphite brushes (A, B and C), the wear rate of the brushes and heat generated within a 400 Amp starter generator. The method being proposed was to alternate the starter generator from the starting mode and the generating mode, and run each carbon/graphite brush in the starter generator for a set time and document the wear rates, heat generations and surface morphology changes. The hypothesis was that either excess carbon dust caused arcing, or the energy required to form the carbon dust was releasing too much heat, and thus the brush was too hard. An optical microscope, AFM, and SEM were used in the analysis of the surfaces. It was found that as the hardness of the brush went up, the wear rate decreased while the overall heat on the inside of the starter generator increased. From this research, it is evident that the hardness of the brushes is the key factor for heat, wear and morphology changes in the starter generator.

Tribological Characteristics of Deformed Magnesium Alloy AZ61 Under Dry Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Abdel-Wahab El-Morsy ◽  
A. Abouel-Kasem
Keyword(s):  
Magnesium Alloy ◽  
Wear Rate ◽  
Deformation Process ◽  
Wear Behavior ◽  
Sliding Velocity ◽  
Wear Rates ◽  
Power Spectral ◽  
Dry Conditions ◽  
The Relationship ◽  
Applied Stresses

The wear behavior of deformed magnesium alloy AZ61 under dry conditions was evaluated. Two types of AZ61 alloy were used, extruded and rolled samples, to investigate the effect of deformation process on the wear behavior. The experiments were performed using a pin-on-ring type wear apparatus against a stainless-steel counterface under applied stresses in the range of 3–7 MPa, and within a sliding velocity range of 0.2–1.8 m/s. The topographical images of the eroded surfaces at different sliding velocity for extruded and rolled samples were quantified using fractal analysis. The results revealed that for all applied stress, the wear rates increased with increasing the sliding velocity of both samples. The wear rate of the rolled samples is greater than that of the extruded samples at the stress range from 3 to 5 MPa. However, when the stress is increased to 7 MPa the wear rate of the rolled samples is lower than that of the extruded samples. The variation of fractal value of slope of linearized power spectral density (PSD) with the sliding velocity is largely similar to the relationship between the wear rate and the sliding velocity.

Contact Temperature and Its Effects in an Oscillatory Sliding Contact

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
F. E. Kennedy ◽  
S. C. Cullen ◽  
J. M. Leroy
Keyword(s):  
Wear Rate ◽  
Polyethylene Wear ◽  
Contact Temperature ◽  
Element Analysis ◽  
Wear Rates ◽  
Transfer Films ◽  
Model Predictions ◽  
The Relationship ◽  
Ultra High Molecular Weight ◽  
Good Agreement

The relationship between contact temperature, friction coefficient, and wear rate was studied here for the case of dry sliding between pin and flat in small amplitude oscillatory motion. In the first part of the study, infrared radiation pyrometry and finite element analysis techniques were used to measure and model surface temperatures in an oscillatory contact. Good agreement was achieved between model predictions and experimental measurements. The model was then applied to an oscillating contact between an ultra-high molecular weight polyethylene pin and a rough stainless steel flat. Temperature predictions for that case were correlated with measured friction coefficients and wear rates. It was found that the polyethylene wear rate decreased as the contact temperature increased. The uniformity and thickness of the transfer films which formed on both counterface and polymer pin were found to be affected by contact temperature. Transfer film behavior was deemed responsible for the influence of contact temperature on wear rate.

Strategies of maintenance and repair of agricultural machinery

2020 ◽  
pp. 38-48
Author(s):  
Aleksey S. Dorokhov ◽  
Aleksandr V. Denisov ◽  
Aleksey A. Solomashkin ◽  
Valeriy S. Gerasimov
Keyword(s):  
Wear Rate ◽  
Technical Condition ◽  
Research Purpose ◽  
Agricultural Machinery ◽  
Maintenance And Repair ◽  
Wear Rates ◽  
Urgent Task ◽  
Machine Parts ◽  
Current Value ◽  
Agricultural Machines

Modern machines are subject to progressive wear that occurs at different rates, which leads to unpredictable failures that reduce the reliability and durability of machines. The strategy of maintenance and repair is aimed at eliminating these problems. (Research purpose) The research purpose is in analyzing the basic principles of the strategy of maintenance and repair of agricultural machinery in order to ensure control of the technical condition of machine parts. (Materials and methods) When resource diagnostics is used, , the allowable value of the parameter is set in advance for a part . This value is the tolerance that corresponds to a certain wear rate of the part. The tolerance is set based on the condition that if the current value of the controlled resource parameter during the next diagnosis is less than the set value, then such a part at the current value of the wear rate can be finalized until the next inter-control check. Taking into account the wear rate of the same type of parts from the group when determining the allowable wear during their resource diagnostics becomes an urgent task. (Results and discussions) As a result of research, the article presents "Methodology for determining the main indicators of reliability of parts of agricultural machines with different wear rates" and "Methodology for determining the tolerance system of parts of agricultural machines with different wear rates". (Conclusions) The article presents the tolerance system that reduces the probability of failure of machine parts in operation. During resource diagnostics, those parts whose resource parameters exceed the tolerance are rejected.

scholarly journals Surface Forming Criteria of Ti-6AL-4V Titanium Alloy under Laser Loading

2021 ◽  
Vol 11 (12) ◽  
pp. 5406
Author(s):  
Fei Yin ◽  
Xia Ye ◽  
Hongbing Yao ◽  
Pengyu Wei ◽  
Xumei Wang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Surface Morphology ◽  
High Speed ◽  
Yttrium Aluminum Garnet ◽  
Laser Energy ◽  
Target Material ◽  
Nanosecond Laser ◽  
Laser Shock ◽  
Shock Condition ◽  
Key Factor

In order to study the spallation phenomenon of titanium alloy under the shock of nanosecond laser, the Neodymium-Yttrium-Aluminum Garnet laser was used to carry out laser shock experiments on the surface of titanium alloy. By observing and measuring the surface morphology of the target material, the forming factors and the changes of the surface morphology under different parameter settings, the forming criteria of the titanium alloy were obtained. The results show that under the single variable method, the change of laser energy can affect the target shape variable, and there is a positive correlation between them. When the thickness was greater than or equal to 0.08 mm, no obvious cracks were found in the targets. Moreover, the number of impact times was the key factor for the target deformation; with the growth of impact times, the target deformation gradually became larger until the crack appeared. The larger the diameter of the spot, the more likely the target was to undergo plastic deformation. The surface of titanium alloy with a thickness of 0.08 mm appeared to rebound under specific laser shock condition. The changes in the back of the target material were observed in real time through a high-speed camera, and the plasma induced by the laser was observed in the process. This study is based on the results of previous studies to obtain the titanium alloy forming criteria, which provides a basis for the setting of laser parameters and the thickness of the target when the nanosecond laser impacts the Ti-6AL-4V target.

scholarly journals Estimation of resistance force at steady-state sinkage for cylindrical wheel-typed lunar/planetary exploration rovers with function of push–pull locomotion

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Daisuke Fujiwara ◽  
Naoki Tsujikawa ◽  
Tetsuya Oshima ◽  
Kojiro Iizuka
Keyword(s):  
Steady State ◽  
Estimation Method ◽  
Planetary Exploration ◽  
Experimental Result ◽  
Resistance Force ◽  
Estimation Model ◽  
Loose Soil ◽  
Key Factor ◽  
The Relationship ◽  
Resistance Forces

Abstract Planetary exploration rovers have required a high traveling performance to overcome obstacles such as loose soil and rocks. Push-pull locomotion rovers is a unique scheme, like an inchworm, and it has high traveling performance on loose soil. Push-pull locomotion uses the resistance force by keeping a locked-wheel related to the ground, whereas the conventional rotational traveling uses the shear force from loose soil. The locked-wheel is a key factor for traveling in the push-pull scheme. Understanding the sinking behavior and its resistance force is useful information for estimating the rover’s performance. Previous studies have reported the soil motion under the locked-wheel, the traction, and the traveling behavior of the rover. These studies were, however, limited to the investigation of the resistance force and amount of sinkage for the particular condition depending on the rover. Additionally, the locked-wheel sinks into the soil until it obtains the required force for supporting the other wheels’ motion. How the amount of sinkage and resistance forces are generated at different wheel sizes and mass of an individual wheel has remained unclear, and its estimation method hasn’t existed. This study, therefore, addresses the relationship between the sinkage and its resistance force, and we analyze and consider this relationship via the towing experiment and theoretical consideration. The results revealed that the sinkage reached a steady-state value and depended on the contact area and mass of each wheel, and the maximum resistance force also depends on this sinkage. Additionally, the estimation model did not capture the same trend as the experimental results when the wheel width changed, whereas, the model captured a relatively the same trend as the experimental result when the wheel mass and diameter changed.

scholarly journals Sliding Wear of Conventional and Suspension Sprayed Nanocomposite WC-Co Coatings: An Invited Review

2021 ◽  
Author(s):  
R. Ahmed ◽  
O. Ali ◽  
C. C. Berndt ◽  
A. Fardan
Keyword(s):  
Wear Rate ◽  
Thermal Spray ◽  
Sliding Wear ◽  
Failure Modes ◽  
Thermal Spray Coatings ◽  
Annual Growth Rate ◽  
Total Energy Consumption ◽  
Wear Performance ◽  
Wear Rates ◽  
Spray Coatings

AbstractThe global thermal spray coatings market was valued at USD 10.1 billion in 2019 and is expected to grow at a compound annual growth rate of 3.9% from 2020 to 2027. Carbide coatings form an essential segment of this market and provide cost-effective and environmental friendly tribological solutions for applications in aerospace, industrial gas turbine, automotive, printing, oil and gas, steel, and pulp and paper industries. Almost 23% of the world’s total energy consumption originates from tribological contacts. Thermal spray WC-Co coatings provide excellent wear resistance for industrial applications in sliding and rolling contacts. Some of these applications in abrasive, sliding and erosive conditions include sink rolls in zinc pots, conveyor screws, pump housings, impeller shafts, aircraft flap tracks, cam followers and expansion joints. These coatings are considered as a replacement of the hazardous chrome plating for tribological applications. The microstructure of thermal spray coatings is however complex, and the wear mechanisms and wear rates vary significantly when compared to cemented WC-Co carbides or vapour deposition WC coatings. This paper provides an expert review of the tribological considerations that dictate the sliding wear performance of thermal spray WC-Co coatings. Structure–property relationships and failure modes are discussed to grasp the design aspects of WC-Co coatings for tribological applications. Recent developments of suspension sprayed nanocomposite coatings are compared with conventional coatings in terms of performance and failure mechanisms. The dependency of coating microstructure, binder material, carbide size, fracture toughness, post-treatment and hardness on sliding wear performance and test methodology is discussed. Semiempirical mathematical models of wear rate related to the influence of tribological test conditions and coating characteristics are analysed for sliding contacts. Finally, advances for numerical modelling of sliding wear rate are discussed.

An Empirical Research on the Relationship between Real Estate Prices and Inflation

2011 ◽  
Vol 55-57 ◽  
pp. 1992-1996
Author(s):  
Tie Qun Li
Keyword(s):  
Real Estate ◽  
Stock Prices ◽  
Test Analysis ◽  
Social Demand ◽  
The Real Estate ◽  
Key Factor ◽  
Negative Effect ◽  
Labor Service ◽  
Real Estate Prices ◽  
The Relationship

The former researches referring to inflation and real estate prices concentrated mainly on the stock prices rather than the real estate prices. Owing to the enlarging ratio of real estate industry in national economy with each passing day, as well as the overheating real estate prices in recent years, the relationship between real estate prices and inflation is particularly vital to the monetary policy making for the monetary authorities. According to the test analysis of data from 2001 to 2009, it is found that real estate prices is Granger Cause of inflation while inflation is not the Granger Cause of real estate prices in this paper. Through the Effects of Wealth, Credit and Tobin, real estate prices drive the growth of social consumption and investments and expand the total social demand which possess an positive effect on inflation; nevertheless the rising of real estate prices causes the rising of currency for real estate purchasing, which, under the circumstance of that currency supply remains, will inevitably bring about the reduction of currency for other consumption and investments and restrain the total social demand which would mean a suppression of continuous rising of prices of other commodity and labor service. All these show that real estate also has a negative effect on inflation. The cancellations between the two effects make the long-term influence real estate bearing on inflation is not obvious. The experimental results indicate that when the price of real estate rises 1%, inflation only rises 0.058%. Consequently, a strict controlling of the amount of money issued is the key factor for keeping the over rapid rising of real estate prices from leading to inflation.

Synthesis and characterization of silver nanoparticle nanocomposite thin films with thermally induced surface morphology changes

2015 ◽  
Vol 159 ◽  
pp. 118-121 ◽  
Author(s):  
Ernandes T. Tenório-Neto ◽  
Marcos R. Guilherme ◽  
Manuel E.G. Winkler ◽  
Lucio Cardozo-Filho ◽  
Stéphani C. Beneti ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Silver Nanoparticle ◽  
Synthesis And Characterization ◽  
Thermally Induced ◽  
Nanocomposite Thin Films ◽  
Morphology Changes
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