Role of the friction coefficient in the frictional heating ignition of explosives

1981 ◽  
Vol 6 (1) ◽  
pp. 17-23 ◽  
Author(s):  
W. H. Andersen
Keyword(s):  
Friction Coefficient ◽  
Frictional Heating

Abrasive wear response of Al-Si–SiCp composite: Effect of friction heat and friction coefficient

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Raj Kumar Singh ◽  
Amit Telang ◽  
Satyabrata Das
Keyword(s):  
Heat Treatment ◽  
Friction Coefficient ◽  
Abrasive Wear ◽  
Applied Load ◽  
Frictional Heating ◽  
Matrix Alloy ◽  
Composite Effect ◽  
Friction Heat ◽  
Wear Response ◽  
Abrasive Size

Abstract The effects of friction heat and friction coefficient on the abrasive wear response of Al-7.5Si–SiCp composite against low-cost hypereutectic (Al-17.5Si) alloy were investigated as functions of the abrasive size and applied load in both as-cast and after heat-treatment conditions. Experiments were performed on pin-on-disc apparatus at 38 –80 μm abrasive size, 5 – 20 N applied load, 100 –400 m abrading (sliding) distances and 1 m s–1 constant sliding speed. The frictional heating of as-cast and heat-treated composite was superior compared to the matrix alloy and hypereutectic alloy, whereas the trend reversed for the friction coefficient. The frictional heating and friction coefficient of the materials increased with the abrasive size and applied load in both as-cast and after heat-treatment. The worn surface and wear debris particles were examined by using field emission scanning electron microscopy to understand the wear mechanism.

scholarly journals Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere

2020 ◽  
Vol 637 ◽  
pp. A97
Author(s):  
B. Snow ◽  
A. Hillier
Keyword(s):  
Solar Atmosphere ◽  
Mode Conversion ◽  
Frictional Heating ◽  
Fast Mode ◽  
Compressional Waves ◽  
Pressure Scale ◽  
Velocity Drift ◽  
Two Fluid ◽  
Lower Solar Atmosphere

Context. The plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly made up of ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfvén speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. The way the energy is distributed between the two modes depends on the angle of magnetic field. Aims. We aim to investigate the separation of neutral and ionised species in a gravitationally stratified atmosphere. The role of two-fluid effects on the structure of the shocks post-mode-conversion and the frictional heating is quantified for different levels of collisional coupling. Methods. Two-fluid numerical simulations were performed using the (PIP) code of a wave steepening into a shock in an isothermal, partially-ionised atmosphere. The collisional coefficient was varied to investigate the regimes where the plasma and neutral species are weakly, strongly, and finitely coupled. Results. The propagation speeds of the compressional waves hosted by neutral and ionised species vary and, therefore, velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fast-mode shock. We find that the collisional coefficient drastically impacts the features present in the system, specifically the mode conversion height, type of shocks present, and the finite shock widths created by the two-fluid effects. In the finitely-coupled regime, fast-mode shock widths can exceed the pressure scale height, which may lead to a new potential observable of two-fluid effects in the lower solar atmosphere.

A Mechanism of Sliding on the Nanometer-Thick Ag Layers

2005 ◽  
Author(s):  
F. Honda ◽  
M. Goto
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
High Vacuum ◽  
High Energy ◽  
Thin Layers ◽  
Ultra High Vacuum ◽  
Wear And Friction ◽  
Thickness Measurements

Tribological performance of sub-nano to nanometer-thick Ag layers deposited on Si(111) have been examined to understand the role of surface thin layers to the wear and friction characteristics. The slider was made of diamond sphere of 3 mm in radius. Sliding tests were carried out in an ultra-high vacuum environment (lower than 4 × 10−8 Pa) and analyzed in-situ by Auger electron spectroscopy (AES) for the quantitative thickness-measurements, by reflection high-energy electron diffraction (RHEED) to clarify the substrate cleanliness and crystallography of the Ag films, and by scanning probe microscopy (SPM) for the morphology of the deposited/slid film surfaces. As the results, a minimum of the friction coefficient 0.007 was observed from the film thickness range of 1.5–10 nm, and exactly no worn particles were found after 100 cycles of reciprocal sliding. Results have directly indicated that solid Ag(111) sliding planes allowed to reduce the friction coefficient very low without any detectable wear particles, and Ag nanocrystallites in Ag polycrystalline layers increase the size to 20–40 nm order, during sliding. The friction coefficient was slightly dependent to the normal load. Results were discussed on the role of the surface atoms to the friction, and a mechanism of sliding on Ag thin layers.

The fate of garnet during (deep-seated) coseismic frictional heating: The role of thermal shock

Geology ◽  
2018 ◽  
Vol 46 (5) ◽  
pp. 471-474 ◽  
Author(s):  
Simone Papa ◽  
Giorgio Pennacchioni ◽  
Ross J. Angel ◽  
Manuele Faccenda
Keyword(s):  
Thermal Shock ◽  
Frictional Heating

scholarly journals Rubber Wear and the Role of Transfer Films on Rubber Friction on Hard Rough Substrates

2021 ◽  
Vol 69 (2) ◽  
Author(s):  
A. Tiwari ◽  
N. Miyashita ◽  
B. N. J. Persson
Keyword(s):  
Friction Coefficient ◽  
Sliding Friction ◽  
Present Theory ◽  
Concrete Surface ◽  
Relative Importance ◽  
Rubber Compound ◽  
Transfer Films ◽  
Rubber Compounds ◽  
Rubber Friction

AbstractWe study the influence of rubber transfer films on the sliding friction between rectangular rubber blocks and a concrete surface. We present experimental results for the friction coefficient for a rubber compound sliding on a concrete surface contaminated by another rubber compound, for two different pairs (A, B) and (C, D) of rubber compounds. For the same rubber compounds, we present theory results which illustrate the relative importance of the viscoelastic and adhesive contribution to the sliding friction. We correlate the calculated rubber friction with the nature of the observed transfer films (or wear processes). Graphical Abstract

scholarly journals Dependency of Rubber Friction on Normal Force or Load: Theory and Experiment

2017 ◽  
Vol 45 (1) ◽  
pp. 25-54 ◽  
Author(s):  
Gaetano Fortunato ◽  
Vincenzo Ciaravola ◽  
Alessandro Furno ◽  
Michele Scaraggi ◽  
Boris Lorenz ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Frictional Heating ◽  
Measured Temperature ◽  
Load Theory ◽  
Time Integral ◽  
Rubber Friction ◽  
Pressure Dependency ◽  
Road Surfaces ◽  
Good Agreement

ABSTRACT In rubber friction studies, it is often observed that the kinetic friction coefficient μ depends on the nominal contact pressure p. We discuss several possible origins of the pressure dependency of μ: (1) saturation of the contact area (and friction force) due to high nominal squeezing pressure; (2) nonlinear viscoelasticity; (3) nonrandomness in the surface topography, in particular the influence of the skewness of the surface roughness profile; (4) adhesion; and (5) frictional heating. We show that in most cases the nonlinearity in the μ(p) relation is mainly due to process (5), frictional heating, that softens the rubber, increases the area of contact, and (in most cases) reduces the viscoelastic contribution to the friction. In fact, because the temperature distribution in the rubber at time t depends on the sliding history (i.e., on the earlier time t′ < t), the friction coefficient at time t will also depend on the sliding history, that is, it is, strictly speaking, a time integral operator. The energy dissipation in the contact regions between solids in sliding contact can result in high local temperatures that may strongly affect the area of real contact and the friction force (and the wear-rate). This is the case for rubber sliding on road surfaces at speeds above 1 mm/s. Previously, we derived equations that described the frictional heating for solids with arbitrary thermal properties. Here, the theory is applied to rubber friction on road surfaces. Numerical results are presented and compared to experimental data. We observe good agreement between the calculated and measured temperature increase.

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