| 1. |
- Alemani, Mattia, et al.
(author)
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A study on emission of airborne wear particles from car brake friction pairs
- 2015
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In: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 9:1, s. 147-157
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Journal article (peer-reviewed)abstract
- The emission of airborne wear particles from friction material / cast iron pairs used in car brakes was investigated, paying special attention to the influence of temperature. Five low-metallic materials and one non-asbestos organic material were tested using a pin-on-disc machine. The machine was placed in a sealed chamber to allow airborne particle collection. The concentration and size distribution of 0.0056 to 10 μm particles were obtained by a fast mobility particle sizer and an optical particle sizer. The temperature was measured by a thermocouple installed in the disc. The experiments show that as the temperature increases from 100 to 300 °C the emission of ultrafine particles intensifies while that of coarse particles decreases. There is a critical temperature at which the ultrafine particle emission rate rises stepwise by 4 to 6 orders of magnitude. For the friction pairs investigated, the critical temperature was found to be between 165 and 190 °C. Below the critical temperature, fine particles outnumber coarse and ultrafine particles, although coarse particles make up the bulk of the particulate matter mass. The friction pairs differ in the ultrafine particle emission rate by 1 to 2 orders of magnitude. Above the critical temperature, ultrafine particles constitute almost 100% of the total particle number and their relative mass contribution can exceed 50%. Analysis of the particle size distributions revealed peaks at 0.19-0.29, 0.9 and 1.7 μm. Above the critical temperature, one more peak appears in the ultrafine particle range at 0.011-0.034 μm.
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| 2. |
- Belyakov, Nikolay, et al.
(author)
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Analytical solution of non-stationary heat conduction problem for two sliding layers with time-dependent friction conditions
- 2016
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In: International Journal of Heat and Mass Transfer. - : Elsevier. - 0017-9310 .- 1879-2189. ; 98, s. 624-630
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Journal article (peer-reviewed)abstract
- In this article we conduct an overview of various types of thermal contact conditions at the sliding interface. We formulate a problem of non-stationary heat conduction in two sliding layers with generalized thermal contact conditions allowing for dependence of the heat-generation coefficient and contact heat transfer coefficient on time. We then derive an analytical solution of the problem by constructing a special coordinate integral transform. In contrast to the commonly used transforms, e.g. Laplace or Fourier transforms, the one proposed is applicable to a product of two functions dependent on time. The solution is validated by a series of test problems with parameters corresponding to those of real tribosystems. Analysis shows an essential influence of both time-dependent heat-generation coefficient and contact heat transfer coefficient on the partition of the friction heat between the layers. The solution can be used for simulating temperature fields in sliding components with account of this influence.
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| 3. |
- Nosko, Oleksii, 1983-
(author)
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Analytical Study of Sliding Instability due to Velocity- and Temperature-Dependent Friction
- 2016
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In: Tribology letters. - : Springer-Verlag New York. - 1023-8883 .- 1573-2711. ; 61:2, s. 1-10
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Journal article (peer-reviewed)abstract
- The instability of sliding causes deterioration of performance characteristics of tribosystems and is undesired. To predict its occurrence, the motion of a body of a one-degree-of-freedom system with friction is investigated about the steady sliding equilibrium position. The motion equation is formulated with the friction coefficient dependent on the sliding velocity and contact temperature changing due to transient heat conduction in the body. An analytical expression for the body motion is derived using the Laplace integral transform. It is shown that the sliding instability can manifest in the form of deviation of the body from the equilibrium position or in the form of oscillation. The instability conditions containing the friction–velocity and friction–temperature slope coefficients are obtained. Positive friction–temperature slope results in the deviation of the body from the equilibrium position. At negative friction–temperature slope, both types of the sliding instability can occur. The proposed instability conditions agree well with existing theoretical concepts and can be useful when designing tribosystems.
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| 4. |
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| 5. |
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| 6. |
- Nosko, Oleksii, 1983-, et al.
(author)
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Effective density of airborne wear particles from car brake materials
- 2017
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In: Journal of Aerosol Science. - : Elsevier. - 0021-8502 .- 1879-1964. ; 107, s. 94-106
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Journal article (peer-reviewed)abstract
- People living in urban environments are subject to high health risks due to various anthropogenicsources of airborne particulate matter, including wear of transport vehicle brakes. Studies ofairborne particles often require an estimate of the effective particle density, a property thatallows correct matching of mass and size characteristics measured by different aerosolinstruments. In this study we investigated the effective density of airborne wear particles emittedfrom car brake materials. The particles were generated by a pin-on-disc machine located in asealed chamber. Two methods were used to determine the effective density. The first method isbased on measurements of PM10 and particle size distribution. The second method involvesmeasurements and subsequent fitting of the mobility size distribution and aerodynamic sizedistribution. Results from the two methods showed good agreement. It was found that theeffective density is 0.75±0.2 g/cm3. The particle emission, size distribution and effectivedensity are sensitive to temperature variations. An intensive emission of ultrafine particles isinitiated at the disc temperature of 185±16 °C. The effective density decreases with thetemperature in the interval 110–360 °C. There is a large difference between the effective densityand the density of the particle material, which suggests that the particles are porous.
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| 7. |
- Nosko, Oleksii, 1983-, et al.
(author)
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Emission of 1.3–10 nm airborne particles from brake materials
- 2017
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In: Aerosol Science and Technology. - : Taylor & Francis. - 0278-6826 .- 1521-7388. ; 51:1, s. 91-96
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Journal article (peer-reviewed)abstract
- Operation of transport vehicle brakes makes a significant contribution to airborne particulate matter in urban areas, which is subject of numerous studies due to the environmental concerns. We investigated the presence and number fractions of 1.3–10 nm airborne particles emitted from a low-metallic car brake material (LM), a non-asbestos organic car brake material (NAO) and a train brake cast iron against a cast iron. Particles were generated by a pin-on-disc machine in a sealed chamber and analyzed using a nano condensation nucleus counter, a CPC, and an FMPS. It was found that 1.3–4.4 nm particles are emitted during the friction. For the pairs with the LM and NAO, 1.3–4.4 nm particles predominate in number at temperatures above 160°C. The emission of the 1.3–4.4 nm particles precedes the emission of above 4.4 nm particles. For the cast iron pair, the number of 1.3–4.4 nm particles is smaller than the number of 4.4–10 nm particles. The findings suggest that brake materials produce a significant number of 1.3–4.4 nm airborne particles, and these particles should not be neglected in environmental and tribological studies.
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| 8. |
- Nosko, Oleksii, 1983-, et al.
(author)
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Friction-induced oscillations of a non-asbestos organic pin sliding on a steel disc
- 2015
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In: Acta Mechanica et Automatica. - : Walter de Gruyter GmbH. - 1898-4088 .- 2300-5319. ; 9:2, s. 84-88
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Journal article (peer-reviewed)abstract
- Friction-induced oscillations result in deterioration of performance of disc brakes and are generally undesired. We conduct experimental study of friction-induced oscillations in a non-asbestos organic material/steel pair used in disc brakes of motor vehicles. The tests are done by use of a pin-on-disc machine in which the pin sample is supported on a deformable beam. The adjustable friction parameters are the disc velocity, contact pressure and temperature. The tests show that the friction coefficient decreases with the sliding velocity and increases with the temperature. The friction-induced tangential oscillation of the pin sample occurs with a frequency equal to the first natural frequency of the beam. The effects of the disc velocity and temperature on the oscillation characteristics are investigated. The oscillation amplitude increases with the disc velocity on the interval of velocities below 2 m/s. Temperature changes of several tens of degrees Celsius lead to the oscillation occurrence/decay. The obtained results can be useful for prognostication of friction-induced oscillations in disc brakes with non-asbestos organic pads.
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| 9. |
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| 10. |
- Olofsson, Ulf, 1962-, et al.
(author)
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A pin-on-disc study of airborne wear particle emissions from studded tyre on concrete road contacts
- 2018
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In: Wear. - Amsterdam : Elsevier Ltd. - 0043-1648 .- 1873-2577. ; 410-411, s. 165-172
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Journal article (peer-reviewed)abstract
- Studded tyres wear surfaces of winter roads, generating inhalable airborne particles. In this study, four concrete road materials and two stud geometries were investigated in terms of wear, road material hardness and airborne particle concentration. The sliding contact between studded tyres and road materials was studied using a pin-on-disc machine in a clean chamber. The results show that the normal load and the stud size have a large influence on the wear and particle emission. It was found that the wear and particle concentration are inversely proportional to the hardness of the aggregate in the road material and proportional to the sliding distance. The particle size distribution has peaks at 0.2 µm, 1 µm and 2 µm.
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