Analysis of sliding electric contact characteristics in augmented railgun based on the combination of contact resistance and sliding friction coefficient

Paper analyses the sliding friction coefficient of rubber on concrete, timber and ceramic tile surfaces depending on the weight of the sliding object and contact surface area. It has been established that increase in the weight of the object makes sliding friction coefficient to grow. In the case of increase in size of contact area, sliding friction coefficient between rubber and concrete also increases, but it decreases between rubber- timber and rubber- tile. The mathematical model for description of sliding friction process has been developed which can be used to determine optimal surface area and a pattern as well as optimal weight of the sliding object in order to provide sufficient sliding friction. Model has five independent constants. It includes the contact surface area, the weight and the velocity of the sliding object, sliding friction coefficient, temperature and time.

Download Full-text

Static Friction and Initiation of Slip at Magnetic Head-Disk Interfaces

Journal of Tribology ◽

10.1115/1.555349 ◽

1999 ◽

Vol 122 (1) ◽

pp. 246-256 ◽

Cited By ~ 14

Author(s):

S. Wang ◽

K. Komvopoulos

Keyword(s):

Surface Roughness ◽

Friction Coefficient ◽

Film Thickness ◽

Contact Resistance ◽

Friction Force ◽

Static Friction ◽

Electric Contact ◽

Magnetic Head ◽

Friction Coefficients ◽

Lubricant Films

The apparent friction force and electric contact resistance at the magnetic head-disk interface were measured simultaneously for textured and untextured disks lubricated with perfluoropolyether films of different thicknesses. The initial stick time, representing the time between the application of a driving torque and the initiation of interfacial slip, was determined based on the initial rise of the apparent friction force and the abrupt increase of the electric contact resistance. Relatively thin lubricant films yielded very short initial stick times and low static friction coefficients. However, for a film thickness comparable to the equivalent surface roughness, relatively long initial stick times and high static friction coefficients were observed. The peak value of the apparent friction coefficient was low for thin lubricant films and increased gradually with the film thickness. The variations of the initial stick time, static friction coefficient, and peak friction coefficient with the lubricant film thickness and surface roughness are interpreted in the context of a new physical model of the lubricated interface. The model accounts for the lubricant coverage, effective shear area, saturation of interfacial cavities, limited meniscus effects, and the increase of the critical shear stress of thin liquid films due to the solid-like behavior exhibited at a state of increased molecular ordering. [S0742-4787(00)03101-5]

Download Full-text

Research on Dynamic Model of Double Helical Gear Pair Based on TCA and LTCA

10.20855/ijav.2019.24.31302 ◽

2019 ◽

Vol 24 (3) ◽

pp. 476-484 ◽

Cited By ~ 1

Author(s):

Cheng Wang ◽

Shouren Wang ◽

Gaoqi Wang

Keyword(s):

Friction Coefficient ◽

Dynamic Model ◽

Dynamic Models ◽

Sliding Friction ◽

Helical Gear ◽

Tooth Surface ◽

Gear Pair ◽

Axial Vibration ◽

Sliding Friction Coefficient ◽

Helical Gear Pair

Numerous dynamic models of spur gears, helical gears, bevel gears, and face gears can be found in various studies. However, studies that focus on the dynamic model of a double helical gear pair are quite limited. The author proposed a model of a double helical gear pair by only considering the axial vibration. The author did not consider the friction and multiple backlashes in the proposed model. The friction force of the tooth surface and backlash are important factors that can cause complex non-linear phenomena in gear pairs. Therefore, a dynamic model of a double helical gear pair that takes into consideration the axial vibration, friction and multiple backlashes is proposed. Firstly, based on the tooth contact analysis (TCA) of a double helical gear pair, the path of contact and meshing time from engagement to disengagement are obtained. The formula for determining the sliding friction coefficient is introduced. Based on TCA and the dynamic meshing force provided by the subsequent dynamics model of double helical gear pair, the sliding friction coefficient of the tooth surface is calculated. Secondly, the stiffness excitation, gear-into impact excitation and error excitation (including the axial displacement caused by the errors of manufacture and installation under low speed) are calculated according to the existing research results. Following this, a dynamic model of a double helical gear pair that takes into consideration the axial vibration, friction and multiple backlashes is both built and solved. Finally, an example is presented to verify the corresponding results.

Download Full-text

Computation of Sliding Friction and Ratcheting Strain of Sintered and Hardened Steels Under Contact Fatigue Conditions

Journal of Tribology ◽

10.1115/1.2959107 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 2

Author(s):

N. Govindarajan ◽

R. Gnanamoorthy

Keyword(s):

Powder Metallurgy ◽

Friction Coefficient ◽

Sliding Friction ◽

Fatigue Behavior ◽

Contact Fatigue ◽

Sliding Contact ◽

Particle Analysis ◽

Hardened Steels ◽

Ratcheting Strain ◽

Sliding Friction Coefficient

Fatigue properties of powder metallurgy parts are affected mainly by the porosity fraction. Even though it has inferior mechanical and physical properties over the conventional materials, the application of powder metallurgy products in automotive fields is seen in recent trends. The rolling-sliding contact fatigue behavior of sintered and hardened steels has been investigated by performing experiments that represent practical sliding friction coefficient component prevailing in the medium- and heavy-duty bearings and gears. Introduction of sliding friction coefficient changes the typical failure pattern and wear rate of sintered and hardened steels. The sliding friction has been computed from available models and compared with the experimental data. The ratcheting strain has also been predicted for sintered and hardened steels for various contact pressures and sliding friction coefficients. The maximum value of this strain is responsible for surface crack initiation. The wear particle analysis is carried out for the sintered and hardened steels under rolling-sliding contact fatigue conditions. The ferrogram slides for pore free steel under the rolling-sliding contact fatigue conditions are also prepared to study the effect of porosity in wear mechanism. The characteristics of wear morphology and the size, shape, and concentration of worn particles for sintered and hardened steels are also analyzed for various rolling-sliding contact fatigue conditions.

Download Full-text

OPTIMAL SLIDING FRICTION COEFFICIENT FOR ISOLATED BRIDGES IN DIFFERENT SOIL CONDITIONS

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015) ◽

10.7712/120119.7273.19105 ◽

2019 ◽

Author(s):

Paolo Castaldo ◽

Marianela Ripani ◽

Rosa Lo Priore

Keyword(s):

Friction Coefficient ◽

Sliding Friction ◽

Soil Conditions ◽

Sliding Friction Coefficient ◽

Isolated Bridges

Download Full-text

A method for the experimental determination of the sliding friction coefficient between a liquid and a solid

Lettere al Nuovo Cimento ◽

10.1007/bf02790721 ◽

1977 ◽

Vol 20 (12) ◽

pp. 427-430 ◽

Cited By ~ 2

Author(s):

E. Minetti-Mezzetti

Keyword(s):

Friction Coefficient ◽

Experimental Determination ◽

Sliding Friction ◽

Sliding Friction Coefficient

Download Full-text

Coefficients of Friction

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100121285 ◽

1949 ◽

Vol 53 (468) ◽

pp. 1085-1094 ◽

Cited By ~ 5

Author(s):

E. C. Pike

Keyword(s):

Friction Coefficient ◽

Surface Texture ◽

Sliding Friction ◽

Rolling Resistance ◽

Aircraft Design ◽

Resistance Coefficient ◽

Surface Material ◽

Primary Object ◽

Different Types ◽

Sliding Friction Coefficient

SummaryA summary is presented of information collected on coefficients of friction (rolling and sliding) between rubber tyres and road or runway surfaces. Nearly all the data collected are from tests on automobile tyres and are limited to speeds of about 40 m.p.h. In some cases the primary object of the tests was to distinguish between good and bad roads, and not to determine absolute values of friction coefficients.The reasons for the importance of the information for aircraft design use are discussed and distinctions are made between coefficients measured in different ways.The results show the variation of sliding friction coefficient with various parameters at speeds up to 40 m.p.h. There is a set of American tests at speeds up to 110 m.p.h., and some estimates made by the Dunlop Rubber Company up to 120 m.p.h.It is concluded that for sliding friction coeficients differences in surface texture (as distinct from surface material) are significant, and that information can be given only in the form of limits within which the values can be expected to lie.Few results are available on the variation of rolling resistance coefficient, but it is felt that the approximate values quoted for different types of surface are sufficiently accurate.

Download Full-text