| 1. |
- Riva, Gabriele, 1988-
(författare)
-
A methodology to simulate automotive disc brake tribology and emissions
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Airborne particle emissions from road vehicles are one of the main issues affecting urban air quality. Vehicle disc brakes are one of the most important sources of non-exhaust emissions, which have recently been considered to be as important as exhaust emissions. In disc brakes, the pads are pushed against the rotating disc to slow down the vehicle. The contact surfaces of the disc and pads are worn, some of the debris becomes airborne and can be harmful to human health if inhaled. Particle emissions from disc brakes are influenced by a greater amount of contact phenomena at the sliding interfaces, e.g. friction, wear, contact temperature, contact pressure and surface topography. Due to the difficulty in accessing the pad-to-disc contact in the brake system during testing, it is hard to study contact phenomena. Moreover, experiments need the friction material and brake system to be produced at least in their prototype configuration. The aim of this thesis is to develop a methodology based on simulation to better understand contact phenomena and to evaluate the tribological and emission performance of friction material and brake systems in the early design phase.Different simulation approaches can be adopted, depending on what is to be evaluated. A macro-scale approach based on finite element analysis (FEA) can be used to evaluate wear, particle emission and the coefficient of friction (COF) of the entire brake system. A meso-scale approach based on cellular automaton (CA) simulation can be used to evaluate the local contact behaviour on the disc and pad surfaces, and the influence of the single components of the friction mixture. These two different-scale simulation approaches can be integrated to generate an overall multi-scale simulation procedure to investigate and predict the contact phenomena in brake systems.
|
|
| 2. |
- Lyu, Yezhe, 1987-, et al.
(författare)
-
Friction, wear and airborne particle emission from Cu-free brake materials
- 2020
-
Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 141
-
Tidskriftsartikel (refereegranskat)abstract
- Cu is required to be abated in brake pads due to its toxicity. There are on the market several Cu-free brake pads. These Cu-free brake pads are only evaluated regarding their friction and wear performance, whereas, their airborne particle emissions are not considered. A pin-on-disc tribometer is used to evaluate the friction, wear and airborne particle emission from two Cu-free commercial brake pads used in the Europe. Moreover, a commercial brake pad containing Cu is evaluated as a reference. The results indicate that Cu-free brake pads yield comparable coefficient of friction as the Cu-contained brake pad. All three brake materials result in similar wear to the mating brake rotor. Cu-free brake pads generate more airborne particles than Cu-contained brake pad.
|
|
| 3. |
- Lyu, Yezhe, 1987-, et al.
(författare)
-
Recycling of worn out brake pads impact on tribology and environment
- 2020
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- Disc brake systems are widely used on commercial vehicles for braking. The brake pads are usually replaced by new ones before being totally worn out. Current methods to deal with the replaced brake pads include landfill and combustion, resulting in a huge waste of resources and increase of CO2 footprint. From a sustainable point of view, this study aims to evaluate the feasibility of recycling replaced brake pads by addressing a protocol recycling procedure. The results show that the recycled brake pads yield similar friction, wear and airborne particle emission to virgin brake pads. A streamlined life cycle assessment is conducted to compare the environmental impacts between producing virgin brake pads and recycling replaced brake pads. Energy consumption and CO2 footprint of the recycled brake pads are 36% and 34% less than virgin brake pads, indicating that recycling could be a promising method of handling replaced brake pads.
|
|
| 4. |
- Ma, Jijie, et al.
(författare)
-
A Comparison of Airborne Particles Generated from Disk Brake Contacts : Induction Versus Frictional Heating
- 2020
-
Ingår i: Tribology letters. - : SPRINGER/PLENUM PUBLISHERS. - 1023-8883 .- 1573-2711. ; 68:1
-
Tidskriftsartikel (refereegranskat)abstract
- Volatile emissions of vehicle brakes relate to the high temperature of the brake friction pair. However, as a passive parameter of braking applications, temperature is usually studied together with other parameters such as sliding speed and load. Heating tests that increase the friction pair temperature with an induction heater instead of friction are proposed in this study to imitate the rise in temperature in friction tests. Non-friction airborne particles produced solely by the high temperature in heating tests were studied in comparison with friction tests. The results confirmed the existence of non-friction airborne particles and they can represent about 4.5% of the total airborne particles in friction tests. The high-temperature behaviour as well as the composition of the non-friction airborne particles is also presented.
|
|
| 5. |
- Matejka, Vlastimil, et al.
(författare)
-
Airborne Wear Particle Emissions Produced during the Dyno Bench Tests with a Slag Containing Semi-Metallic Brake Pads
- 2020
-
Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of the present paper is to investigate the level of airborne wear particles released during the dyno-bench tests with the brake pads consisting of alkali-activated slag as an abrasive. Airborne wear particles are generated with a full-scale dyno-bench adapted for airborne wear particles emission studies. The tested disc brake is equipped with two semi-metallic brake pads and a grey cast iron brake disc. A reduced Los Angeles City Traffic (LACT) driving cycle, developed within the LOWBRASYS project (European Union's Horizon 2020 research and innovation programme), is used to mimic city driving. The same friction pair is used six times with reduced LACT cycle. The weight loss and thickness of the pads and disc are registered after each test cycle ends. The amount of the airborne wear particles emissions released during each test cycle are characterized using a PM10 impactor and electric low-pressure impactor. The obtained data of wear particle emissions are correlated with the parameters of the brake stops. The maximum disc temperature was indicated as the parameter having the largest influence on the production of particle emissions together with the duration of the brake event
|
|
| 6. |
- Perricone, Guido, et al.
(författare)
-
A proposed driving cycle for brake emissions investigation for test stand
- 2020
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : Sage Publications. - 0954-4070 .- 2041-2991. ; 234:1, s. 122-135
-
Tidskriftsartikel (refereegranskat)abstract
- Particulate matter emission factors from vehicle brakes are difficult to assess directly from the field. Moreover, there is a lack of a standardized cycle and test stand for evaluating brake emissions. For these reasons, a test cycle was developed from real driving data collected from a car. This new test cycle was implemented on an inertia disc brake dynamometer appositely designed for brake particle emission studies. Results reveal that, for the brake system used as an example, the obtained emission factors for the urban driving conditions studied are comparable to EURO 6 regulations in terms of particle number and comparable to EURO 4 levels in terms of mass with brake emission factors equal to 4.37-6.46 x 10(11) particles/km and 44-48 mg/km, respectively.
|
|
| 7. |
- Wahlström, Jens, PhD/Docent, 1979-, et al.
(författare)
-
A Study of the Effect of Brake Pad Scorching on Tribology and Airborne Particle Emissions
- 2020
-
Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 11:5
-
Tidskriftsartikel (refereegranskat)abstract
- Non-exhaust wear emissions from disc brakes affect the air quality in cities throughout the world. These emissions come from the wear of the contact surfaces of both the pads and disc. The tribological and emissions performance of disc brakes strongly depend on the contact surface characteristics of the pads and discs. The surfaces of conventional pads are scorched by heating it to several hundred degrees to make the resin carbonize down to a few millimetres deep into the pad. This is done to have a shorter run-in period for new pads. It is not known how scorching will affect the amount of airborne particle emissions. Therefore, the aim of the present study is to investigate how pad scorching influence the airborne particle emissions. This is done by comparing the pin-on-disc tribometer and inertia dyno bench emission results from a Cu-free friction material run against a grey cast iron disc. Three types of modified friction material surfaces have been tested: scorched, extra-scorched and rectified. The results show that the level of scorching strongly affects the airborne particle emissions in the initial phase of the tests. Even if the scorched layer is removed (rectified) before testing, it seems like it still has a measurable influence on the airborne particle emissions. The results from the tribometer tests are qualitatively in line with the inertia dyno bench test for about the first forty brake events; thereafter, the airborne particle emissions are higher for the scorched pads. It can be concluded that it seems that the level of scorching has an adverse influence on both the tribological performance and level of particle emissions.
|
|
