The performance of Cu-based friction material in dry clutch engagement

2020 ◽  
pp. 135065012094428
Author(s):  
Kingsford Koranteng ◽  
Joseph-Shaahu Shaahu ◽  
Ma Chengnan ◽  
Heyan Li ◽  
Yun-Bo Yi
Keyword(s):  
Friction Coefficient ◽  
Friction Material ◽  
Outer Radius ◽  
Friction Torque ◽  
Thermal Buckling ◽  
Dynamic Friction ◽  
Sliding Speed ◽  
Thermoelastic Instability ◽  
Friction Disc ◽  
Dry Clutch

An enhanced Cu-based friction material was prepared by the powder metallurgy techniques and proposed for use in the dry clutch system. The friction characteristics and wear rate of this friction material sliding against 65Mn steel are obtained using Universal Material Tester-5. The friction pairs were subjected to two operating variables, which are sliding speed and temperature. The effect of these variables during the engagement process of the friction pairs is investigated. Knowing the normal applied force and dimension of the clutch disc, the dynamic friction coefficient was translated to friction torque capacity with time. It was found that instability can be excited at low operational conditions when the resulting friction coefficient is high. At 25 ℃, the dynamic friction torque oscillates with time likewise at 400 ℃. Generally, a more stable friction torque is obtained when the sliding speed is varied compared to varying the temperatures. Moreover, the influence of the operating temperatures and sliding speeds on thermal buckling and thermoelastic instability of the friction disc is the second consideration in this work. The onset of thermoelastic instability occurs when the sliding speed exceeded 200 r/min and the results for the growth rate of hot spots were found to agree well with the critical speed of the system. Also, thermal buckling was highly dependent on the temperature difference between the inner and outer radius of the friction disc.

Tribological and Mechanical Properties of Materials for Friction Pairs Used to Space Docking

2012 ◽  
Vol 538-541 ◽  
pp. 1929-1934 ◽  
Author(s):  
Ping Ping Yao ◽  
Ye Long Xiao ◽  
Hai Bing Zhou ◽  
Zong Xiang Jin
Keyword(s):  
Mechanical Properties ◽  
Friction Coefficient ◽  
Tribological Properties ◽  
Friction Material ◽  
Friction Torque ◽  
Operation Conditions ◽  
Mechanical Properties Of Materials ◽  
Properties Of Materials ◽  
Counterpart Material

The microstructures and tribological properties of materials for friction pairs used to space docking were investigated by optical metallographic microscope and a special home-made tribo-tester, respectively. The results demonstrate that friction material appears homogeneous and compact microstructure. Counterpart material presents temper sorbite which keeps martensite morphology and residues a small amount of blocky undissolved ferrite; the porosity of friction material is about 3.7%. Materials for space docking show favorable rigidity; during running-in, friction torque of friction pairs can be enhanced obviously; under different operation conditions, friction pairs for space docking possesses different friction coefficient.

Effect of Temperature on Thermoelastic Instability in Thin Disks

2002 ◽  
Vol 124 (3) ◽  
pp. 429-437 ◽  
Author(s):  
Coby L. Davis ◽  
Charles M. Krousgrill ◽  
Farshid Sadeghi
Keyword(s):  
Steady State Solution ◽  
Friction Material ◽  
Effect Of Temperature ◽  
Governing Equations ◽  
Sliding Speed ◽  
Thermoelastic Instability ◽  
Conservative Approximation ◽  
The Stability ◽  
Thin Disks ◽  
Axisymmetric Perturbations

A model of a thin annular plate sliding against an elastic foundation was developed and used to study thermoelastic instability (TEI) in clutches. The analysis examines the stability of the quasi-steady state solution of the governing equations by considering non-axisymmetric perturbations. The results indicate that above critical values of temperature and sliding speed the response of the plate becomes unstable and exhibits large deformations. Two mechanisms account for this behavior: thermal buckling and bending. It is shown that a conservative approximation of the stability boundaries can be constructed by computing only two points on the stability curve. The boundary between stable and unstable behavior depends on the material properties, geometry, and boundary conditions. The model was used to conduct a parametric study which indicates that stability of the sliding system can be improved by reducing the sliding speed, decreasing the modulus of elasticity of the plate, increasing the thermal conductivity, or increasing the thickness. In addition, for a range of sliding speeds, increasing the stiffness of the friction material improves the stability of the system. For speeds outside this range, increasing the stiffness makes the system less stable.

Bearing Friction Torque in Threaded Fasteners With Non-Flat Underhead Contact

2018 ◽  
Author(s):  
Sayed A. Nassar ◽  
Marco Gerini Romagnoli ◽  
Joon Ha Lee
Keyword(s):  
Friction Coefficient ◽  
Contact Pressure ◽  
Friction Torque ◽  
Sliding Speed ◽  
Friction Coefficients ◽  
Threaded Fasteners ◽  
Tension Testing ◽  
Contact Surfaces ◽  
Flat Contact ◽  
Bearing Friction

This study provides experimentally validated formulation of underhead bearing friction torque component during tightening of threaded fasteners with non-flat contact with the joint. Motosh model is utilized for spherical and conical contact surfaces for various scenarios of contact pressure. For each pressure scenario, a single non-dimensional 3-D graph is generated for the corresponding values of an effective bearing friction radius. A rotating sliding speed-dependent friction coefficient model is also investigated for its impact of the results of bearing friction radius. Torque-Tension testing is used to measure the bearing friction torque and the corresponding bearing friction coefficients using Motosh model, in which the newly formulated bearing friction radius expressions are entered. Obtained bearing friction coefficient values are then compared with those published by the threaded fastener manufacturer.

The calculation model of the friction torque on a dry clutch

2017 ◽  
Vol 231 (13) ◽  
pp. 1796-1805 ◽  
Author(s):  
Xiaohua Lin ◽  
Junqiang Xi ◽  
Shengqiang Hao
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Surface Temperature ◽  
Calculation Model ◽  
Friction Torque ◽  
Force Model ◽  
Clamping Force ◽  
Temperature Model ◽  
Load Characteristic ◽  
Dry Clutch

The influencing factors of the friction torque on a dry clutch are analysed, the load characteristic of a diaphragm spring is modified and the clutch clamping force model is established by using the modified load characteristic. Also, the friction coefficient model is analysed and established on the basis of the sliding speed, the pressure and the surface temperature of clutch plates using a designed friction coefficient bench. Then, the temperature model of the friction plates is obtained by the finite element programming method, and the calculation model of the friction torque on a dry clutch is constructed on the basis of the above-mentioned models. By using an automobile powertrain bench, it is verified that the friction torque calculation model helps to determine the accuracy of the friction torque on the clutch.

The Tribological Characteristics of Cu-Based Friction Pairs in a Wet Multidisk Clutch Under Nonuniform Contact

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Er-hui Zhao ◽  
Biao Ma ◽  
He-yan Li
Keyword(s):  
Friction Coefficient ◽  
Test Bench ◽  
Friction Torque ◽  
Thermal Buckling ◽  
Tribological Characteristics ◽  
Total Output ◽  
Contact Ratio ◽  
Output Torque ◽  
Wet Clutch ◽  
Comprehensive Test

This work is devoted to investigate the effects of thermal buckling on the tribological characteristics of a Cu-based wet clutch by artificially modifying friction pairs into different contact ratios. A thermal lubrication model is provided, and corresponding experiments are conducted on the wet clutch comprehensive test bench. The friction results from measurements and simulations for such modified friction pairs are analyzed. The results show that, as the contact ratio reduces, surface temperature rises obviously, and friction coefficient increases dramatically, so that local friction torque and total output torque grow significantly. In addition, the vibration of the output torque becomes more severe as the contact ratio reduces. Therefore, the nonuniform contact after thermal buckling exacerbates the friction characteristics of friction pairs severely and accelerates the failure of wet clutches.

Real-Time Measurement of Friction Coefficient in the Frictional Performance Test of Brake Disk

2008 ◽  
Vol 373-374 ◽  
pp. 484-487
Author(s):  
Xiao Jing Huo ◽  
Rui Qing Zhang ◽  
Hui Wang ◽  
Dong Ping Qian ◽  
Jia Xu Teng
Keyword(s):  
Friction Coefficient ◽  
Data Acquisition ◽  
Real Time ◽  
High Speed ◽  
Performance Test ◽  
Friction Material ◽  
Friction Torque ◽  
Time Data ◽  
Brake Disk ◽  
Frictional Performance

Development and optimizing of friction material formula, oriented to improve the service life and security of brake disk, is largely based on advanced measurement method to accurately provide the friction coefficient. In this study, virtual instrumentation technique was used to design an automation measurement system of friction coefficient. With proper sensors, data of four measured variables such as temperature, rotation speed, pressure and friction torque are acquired by the computer combined with a plug-in data acquisition board. The system work principle, selection of sensors, multi-channel sampling, signal processing and anti-jamming measures have been presented in detail. Those functions of the software such as real-time data acquisition, dynamic wave displaying, high-speed report saving and inquiry, and so on, have been realized by LabWindows/CVI 7.1. The system works safely with high accuracy and friendly user interface in practical operation.

Improving the Engagement Smoothness Through Multi-Variable Frictional Map in Automated Dry Clutch Control

2012 ◽  
Author(s):  
V. D’Agostino ◽  
N. Cappetti ◽  
M. Pisaturo ◽  
A. Senatore
Keyword(s):  
Friction Coefficient ◽  
Control Strategies ◽  
Control Unit ◽  
Operating Conditions ◽  
Production Costs ◽  
Sliding Speed ◽  
Gear Shift ◽  
Automatic Transmissions ◽  
Dry Clutch

An Automated Manual Transmission (AMT) is directly derived from a manual one through the integration of actuators; then, development and production costs are generally lower than other automatic transmissions, while the reliability and durability are at highest level. For high class sport cars, vehicle dynamic performances and driving quality can be strongly improved with respect to automatic transmissions [1]. AMTs systems are generally constituted by a dry or wet clutch assembly and a multi-speed gearbox, both equipped with electro-mechanical or electro-hydraulic actuators, which are driven by a control unit, the transmission control unit (TCU). The operating modes of AMTs are usually two: semiautomatic or fully automatic. In both cases, after the gear shift command, the TCU manages the shifting steps according to current engine regime, driving conditions and selected program. In this transmission type the quality of the vehicle propulsion as perceived by the driver is largely dependent on the quality of the control strategies. Furthermore, sensitivity analyses on control schemes for AMTs have shown that uncertainties in clutch torque characteristic can severely affect the performance of the clutch engagement: modeling in detail the torque transmitted by the specific clutch architecture is a crucial issue in order to design robust engagement control strategies [2, 3 and 4]. This paper aims at investigating the engagement performance of an actuated dry clutch by taking into account the inference of the pressure on the facing materials and the sliding speed. In fact, according to literature outcomes [5], the friction coefficient after a first rising behavior with the sliding speed shows an asymptotic value for a typical clutch facing; the same material exhibits a nearly linear dependence of the friction coefficient on the pressure. The simulations consider: reduced-order dynamic system for simulation of passenger car driveline, control algorithm, experimental maps of the n-D clutch transmission characteristic, and gear shift maneuvers in different operating conditions. The outcome of this analysis could provide valuable issues for designers of automated clutches and control engineers to overcome the well known poor engagement performances of open loop motion strategy of the throwout bearing where cost reason and complexity don’t permit the use of displacement sensor.

scholarly journals A Simple Mechanistic Model for Friction of Rough Partially Lubricated Surfaces

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
Gianluca Costagliola ◽  
Tobias Brink ◽  
Julie Richard ◽  
Christian Leppin ◽  
Aude Despois ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Friction Coefficient ◽  
Mechanistic Model ◽  
Applied Pressure ◽  
Real Contact Area ◽  
Experimental Measurements ◽  
Dynamic Friction ◽  
Real Contact ◽  
Dynamic Friction Coefficient ◽  
Direct Measurements

AbstractWe report experimental measurements of friction between an aluminum alloy sliding over steel with various lubricant densities. Using the topography scans of the surfaces as input, we calculate the real contact area using the boundary element method and the dynamic friction coefficient by means of a simple mechanistic model. Partial lubrication of the surfaces is accounted for by a random deposition model of oil droplets. Our approach reproduces the qualitative trends of a decrease of the macroscopic friction coefficient with applied pressure, due to a larger fraction of the micro-contacts being lubricated for larger loads. This approach relates direct measurements of surface topography to realistic distributions of lubricant, suggesting possible model extensions towards quantitative predictions.

Sliding wear characteristics of a-C:H:SiOx coatings

2021 ◽  
pp. 1-27
Author(s):  
Alexander Grenadyorov ◽  
Andrey Solovyev ◽  
Konstantin Oskomov
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Chemical Vapor ◽  
Indentation Load ◽  
Sliding Speed ◽  
Carbon Coatings ◽  
Wear Characteristics ◽  
Load Increase ◽  
Speed Up ◽  
Polymeric Carbon

Abstract The paper presents the experimental study of the friction and wear characteristics of amorphous carbon coating containing hydrogen and SiOx (a-C:H:SiOx) deposited onto WC-8Co cemented carbide substrates. A 5 μm thick a-C:H:SiOx coating was fabricated using plasma-assisted chemical vapor deposition. The tribological properties of the a-C:H:SiOx coating sliding in contact with WC–8Co, ZrO2, SiC, Si3N4 counter bodies, are examined using the ball-on-disc method at different normal loads and sliding speeds. Tribology testing shows that the minimum values of the friction coefficient (0.044) and the wear rate (9.3×10−8 mm3/Nm) are observed when using a counter body made of silicon nitride at a 5 N indentation load. The load increase from 5 to 12 N raises the friction coefficient up to 0.083 and the wear rate up to 46×10−8 mm3/Nm. When the sliding speed reaches its critical value, the coating friction provides the transition from sp3 hybridized to sp2 hybridized and polymeric carbon, which is accompanied by the reduction in the friction coefficient. The a-C:H:SiOx coating provides an increase in the critical sliding speed up to 50–75 mm/s, which exceeds that of non-alloyed (a-C and a-C:H) diamond-like carbon coatings as a result of doping by silicon and oxygen.

The Dependence of the Friction Coefficient on the Size and Course of Sliding Speed

2014 ◽  
Vol 693 ◽  
pp. 305-310 ◽  
Author(s):  
Eva Labašová
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Testing Machine ◽  
Current Component ◽  
Sliding Speed ◽  
Rectangular Shape ◽  
Coefficient Increase ◽  
The Coefficient Of Friction ◽  
Ring Method ◽  
Run Up

The coefficient of friction for the bronze material (CuZn25Al6) with insert graphite beds and other bronze material (CuSn12) are investigated in this paper. Friction coefficient was investigated experimentally by the testing machine Tribotestor`89 which uses the principle of the ring on ring method. The external fixed bushing was exposed to the normal load of the same size in all tests. Process of load was increased from level 50 N to 600 N during run up 300 s, after the run up the appropriate level of load was held. The internal bushing performed a rotational movement with constant sliding speed. The value of sliding speed was changed individually for every sample (v = 0.2 (0.3, 0.4) m.s-1). The forth test had a rectangular shape of sliding speed with direct current component 0.3 m.s-1 and the amplitude 0.1 m.s-1 period 300 s, the whole test took 2100 s. The obtained results reveal that friction coefficient increase with the increase of sliding speed.

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