| 1. |
- Carlsson, Daniel, 1982-
(författare)
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Effects of cold and hand-arm vibration on the peripheral neurosensory and vascular system : an occupational perspective
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background In Swedish working life, exposure to cold and exposure to hand-arm vibration (HAV) are two common health hazards. Health effects of HAV in the neurosensory, vascular and musculoskeletal systems are collectively denoted hand-arm vibration syndrome (HAVS), and have been thoroughly studied. Effects of cold exposure in terms of effects on the peripheral neurosensory and vascular system are on the contrary limited, especially in an occupational setting. Effects of cold exposure or cold injury have not previously been assessed with quantitative sensory testing (QST). Commonly reported symptoms after exposure to HAV and after cold injuries, includes cold sensitivity and sensation of cold. Cold sensitivity can also occur without previous exposure to vibration or cold and may have a major impact on quality of life. Other possible risk factors for cold sensitivity need to be assessed. Sensation of cold hands could theoretically imply an early manifestation of damage to the neurosensory or vascular system, and therefore be of importance to enable early detection of vascular and neurosensory HAVS. The purpose of this thesis was to increase the knowledge about health effects from cold and HAV on the peripheral neurosensory and vascular system, with an occupational perspective. The aims were: first, to identify and evaluate health effects and sequelae in the peripheral neurosensory and vascular system due to cold injury and cold exposure; second, to investigate if sensation of cold hands is a predictor for future onset of Raynaud's phenomenon or paresthesia; and third, to identify possible risk factors associated with cold sensitivity.Methods A case series on 15 military conscripts with local cold injuries in the hands or feet, involving QST and symptom descriptions, was conducted to investigate the hypothesis that cold injuries can result in similar neurosensory and vascular impairments as in HAVS. To assess health effects of cold exposure, a cohort study on 54 military conscripts in cold winter military training, with cold exposure assessments, was conducted. Possible health effects were assessed after 14 months of military training, containing considerable cold exposure, by means of QST, Finger systolic blood pressure after local cooling (FSBP) and a questionnaire. To investigate if sensation of cold hands is a predictor for vascular or neurosensory HAVS we investigated a cohort of 178 employees at a manufacturing company where HAV was a common exposure. The cohort was followed during 21 years and both vibration exposure and health outcomes were assessed regularly. Questionnaire items were used to assess sensations of cold hands as well as signs of Raynaud’s phenomenon and paresthesia. To identify risk factors for cold sensitivity a case-control study was conducted involving 997iiiparticipants from the general population in northern Sweden. The study was cross-sectional and explored possible risk factors for cold sensitivity.Results Cold injuries and cold exposure were associated with reduced sensibility in QST and increase severity and prevalence of neurosensory and vascular symptoms. Our results did not show any impairment in peripheral blood flow due to cold exposure, detectable by FSBP. The risk of developing Raynaud's phenomenon was increased for workers previously reporting sensation of cold hands (OR 6.3, 95% CI 2.3-17.0). No increased risk for paresthesia in relation to a sensation of cold hands was observed. The identified risk factors for cold sensitivity were frostbite in the hands, rheumatic disease, nerve injury in upper extremities or neck, migraine and vascular disease. When analysing women and men separately, women’s risk factors were frostbite in the hands, rheumatic disease, migraine and cold exposure. Men’s risk factors were frostbite in the hands, vibration exposure and nerve injury in upper extremities or neck. BMI > 25 was a protective factor for both men and women.Conclusion Cold injury and cold exposure are associated with impairments in the neurosensory system, detectable by QST. Symptoms such as sensation of cold hands and white fingers indicate vascular involvement, even though no vascular impairments due to cold exposure could be detected by objective measurements. A sensation of cold hands is a risk factor for development of Raynaud´s phenomenon, but not for paresthesia. At the individual level, reporting cold hands does not appear to be useful information when considering the possibility of a future development of Raynaud’s phenomenon. Frostbite in the hands is a risk factor for cold sensitivity among both women and men. For women rheumatic disease, migraine and cold exposure are also independent risk factors, and for men, exposure to HAV. Being overweight is a protective factor for both women and men.
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| 2. |
- Stjernbrandt, Albin, 1985-
(författare)
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Cold exposure and health : A study on neurological and vascular hand symptoms in northern Sweden
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Living in a cold climate is associated with several adverse health effects. The main purpose of this thesis was to describe cold exposure characteristics in northern Sweden, and investigate the associations between such exposure and the reporting of neurological and vascular hand symptoms. One common cold-related hand symptom is Raynaud’s phenomenon, defined as episodic attacks of acral pallor or cyanosis. There is evidence to suggest that cold exposure can act both as a causal factor and a trigger for such vasospastic symptoms. Other important associated factors include exposure to hand-arm vibration and the presence of rheumatic disease. A somewhat similar clinical entity, cold sensitivity, is defined as a collection of acquired symptoms, resulting in an abnormal aversion to cold, with pain, sensory alterations, stiffness, or color changes, which may occur after a traumatic injury. The condition is hypothesized to mainly originate from nerve injury. The effects of cold exposure on hand function, the occurrence of cold sensitivity in the general population, the link between cold exposure and cold sensitivity, as well as the interface between cold sensitivity and Raynaud’s phenomenon are not fully understood. Therefore, this thesis was also intended to expand the knowledge on Raynaud’s phenomenon and cold sensitivity.Methods: Postal surveys were sent to a sample of men and women between 18 and 70 years of age, living in Norrbotten, Västerbotten, Västernorrland, and Jämtland, drawn from the national Swedish population register. The first survey collected data on 12,627 subjects, and the results were used to describe cold exposure characteristics, and broadly investigate the statistical associations with different neurological and vascular hand symptoms (Paper I). A follow-up survey was sent to a subset of responders, to form nested case–control studies on cold sensitivity (N=1,230; Paper II) and Raynaud’s phenomenon (N=1,400; Paper III). Subjects with cold sensitivity (N=12) from Paper II were subsequently recruited to a laboratory study, to investigate the vascular and neurosensory function of the hands, by means of physical examination, laser speckle contrast analysis before and after cold stress testing, and thermal quantitative sensory testing (Paper IV). Finally, healthy controls (N=1,239) from the case–control studies were used as a reference population for the Cold intolerance symptom severity questionnaire, to establish a cut-off for abnormal cold sensitivity (Paper V).Results: In Paper I, cold exposure was commonly reported, both during work and leisure time. Exposure was most pronounced in alpine regions, generally higher among men than women, and decreased with age. Highly cold-exposed occupational groups were militaries; agricultural, forestry and fishery workers; and crafts and related trades workers (e.g. construction workers). The correlation between occupational and leisure-time cold climate exposure was low. Men reported more occupational exposure to hand-arm vibration than women, but the correlation between occupational cold and vibration exposure was low. A range of neurological and vascular hand symptoms were statistically associated with high cold exposure, such as decreased perception to touch, warmth, and cold, as well as Raynaud’s phenomenon. In Paper II, cold sensitivity was significantly associated with previous frostbite affecting the hands, rheumatic disease, upper extremity nerve injury, migraine, vascular disease, and high body mass index (inversely), in a multiple conditional logistic regression model. In Paper III, Raynaud’s phenomenon was significantly associated with previous frostbite affecting the hands, first degree heredity, and high body mass index (inversely), in a similar model. Previous upper extremity nerve injury was suggested as a separating trait between Raynaud’s phenomenon and cold sensitivity. In Paper IV, laser speckle contrast analysis indicated disturbances in microvascular regulation, while physical examination and thermal quantitative sensory testing mainly yielded normal results. In Paper V, the 95th percentile for the Cold intolerance symptom severity score was 49.5 for men, and 53.0 for women.Conclusions: Cold exposure in the working-age population of northern Sweden varied with age, gender, occupation, and place of residence. Cold exposure was related to the reporting of neurological and vascular hand symptoms in the population as a whole. There was a major overlap between reporting cold sensitivity and Raynaud’s phenomenon, and the conditions shared several associated factors. Previous upper extremity nerve injury was suggested to be a separating trait, supporting the neurosensory pathophysiological hypothesis for cold sensitivity. Cold sensitivity was not effectively assessed by physical examination or thermal quantitative sensory testing. However, laser speckle contrast analysis could prove a useful tool in further studies on cold sensitivity. A Cold intolerance symptom severity score above 50 could be considered to indicate abnormal cold sensitivity, and be used to guide further care.
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| 3. |
- Wahlström Edling, Cecilia, 1959-
(författare)
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Besvär i rörelseorganen hos musiklärare och deras syn på musikelevers hälsa : visioner och verklighet på kollisionskurs
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of the licentiate thesis was to reach a better understanding of music teachers' health, with focus on musculoskeletal disorders, and music teachers' view on young music students' health, from a gender perspective.A cross-sectional study was directed to music teachers employed at a municipality music- and culture school, in order to investigate the relationship between physical workload and work-related disorders among music teachers. Out of 61 music teachers 47 agreed to participate. The study group was divided into two groups depending on if they had an asymmetric or symmetric upper extremity and back playing posture. Musculoskeletal disorders were frequent among the music teachers. Women music teachers reported significantly more musculoskeletal disorders than their male collegues and music teachers with asymmetric work posture had significantly higher amount of musculoskeletal disorders than those who had a symmetric playing posture.A qualitative interview study with semi-structured interviews with 18 music teachers were conducted to explore music teachers' experiences of health and gender among young music students. An interview guide was used, with topic areas concerning experiences and perceptions of positive health aspects and health problems among young music students, taking part in music education. The interviews were analysed with qualitative content analysis according to Graneheim and Lundman. The analysis resulted in an overarching theme "Visions and reality in contradiction" and three categories: "Music making to feel good", "Pressure on girls, acceptance for boys" and "Blame on the individual".Music teachers at music- and culture schools seem to be at high risk of developing musculoskeletal disorders, especially music teachers playing an instrument that requires an asymmetric playing position. Young musicians' teachers need a better knowledge in the field of prevention of music students' health problems and physiotherapists and ergonomists may assist and collaborate in this. A gender perspective in music medicine research may contribute to a better understanding of musicians' health.
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| 4. |
- Riva, Gabriele, 1988-
(författare)
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A methodology to simulate automotive disc brake tribology and emissions
- 2020
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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.
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| 5. |
- Svedmark, Åsa, 1961-
(författare)
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Neck pain in women : effect of tailored treatment and impact of work environment
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Musculoskeletal pain is a common problem in the working population. In Sweden, 40% of women and 30% of men report suffering from neck and shoulder pain weekly. The underlying cause for neck pain is often not known and the treatment is commonly guided by the individual’s symptoms. However, there is a lack of knowledge on how to receive the best effect based on the individual’s symptoms and functional limitations, and therefore this has been scarcely evaluated in research. Furthermore, the impact of work exposure and stress on long-term treatment for persons with neck pain is not clear.Aims: To develop (paper 1) and to evaluate a decision model for tailored treatment in women with neck pain (paper 2). Moreover, to determine if risk factors at work and stress influence intermediate and long-term treatment results (paper 3). Further, to investigate if changes in self-reported pain and disabilities are associated with changes of physical test outcomes of the neck and shoulder region after treatment (paper 4).Methods: In an RCT, 120 working women with non-specific neck pain were randomized to three different groups – tailored treatment (TT), non-tailored treatment (NTT) or treatment-as-usual (TAU) for an 11 weeks intervention with short-term, intermediate-term and long-term follow-ups. The TT group was guided by a decision model with cut-off levels to indicate impairments. The NTT group received two established treatment components randomly from those not indicated, and TAU group did not receive any treatment within the study. The RCT primary outcomes were self-reported neck pain and neck disability. A linear mixed model was used for analysing the effects. One week after the end of intervention work exposure and stress were assessed at a work-place visit and associations to treatment results were tested for, and mixed models were used to estimate longitudinal associations. Associations between self-reported neck problems and physical outcomes were estimated with univariate and multiple regressions analysis.Results: No differences between TT and NTT were revealed for neck pain and disability. In comparison to TAU, the TT and NTT groups both showed improvements at short-term follow-up, but not at intermediate and long-term follow-up. High stress level and low self-estimated control at work were associated with more pain and disability at the intermediate and long-term follow-ups. After intervention and at the intermediate-term follow-up, reduced neck pain, disability and frequency of symptoms were associated with increased peak speed of head rotation and cervical range of motion.Conclusion: Tailored treatment according to the decision model was not superior to the non-tailored treatment in women with non-specific neck pain. One explanation for this can be the weak relationships found between neck pain and disability and physical test outcomes. Further, perceived stress and psychosocial work exposure were associated with self-reported neck problems and should be taken into account to optimize the effects in neck pain rehabilitation.
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| 6. |
- Alemani, Mattia, et al.
(författare)
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Scaling effects of measuring disc brake airborne particulate matter emissions – A comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions
- 2018
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : Sage Publications. - 1350-6501 .- 2041-305X. ; 232:12, s. 1538-1547
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Tidskriftsartikel (refereegranskat)abstract
- An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use inertia dynamometer benches; although they are quite expensive to run. Pin-on-disc tribometers, on the other hand, are relatively cheap to run, but simplify the real system. The literature indicates promising correlations between these two test stands with regard to measured airborne number distribution. Recent studies also show a strong dependency between the airborne number concentration and the disc temperature. However, a direct comparison that also takes into account temperature effects is missing. The aim of this paper is, therefore, to investigate how the transition temperature is affected by the different test scales, under dragging conditions, and the effects on total concentration and size distribution. New and used low-steel pins/pads were tested against cast iron discs/rotors on both the aforementioned test stands, appositely designed for particulate emission studies. A constant normal load and constant rotational velocity were imposed in both test stands. Results show that a transition temperature can always be identified. However, it is influenced by the test scale and the frictional pair status. Nevertheless, emissions are assessed similarly when an equivalent frictional pair status is analysed (e.g. run-in). Further investigations for fully run-in samples on the pin-on-disc should be performed in order to finally assess the possibility of using the tribometers for the initial assessment of different friction materials.
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| 7. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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A Friction, Wear and Emission Tribometer Study of Non-Asbestos Organic Pins Sliding Against AlSiC MMC Discs
- 2018
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Ingår i: Tribology in Industry. - : Faculty of Engineering, University of Kragujevac. - 0354-8996 .- 2217-7965. ; 40:2, s. 274-282
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Tidskriftsartikel (refereegranskat)abstract
- The friction, wear and particle emission from an AlSiC MMC brake disc/non-asbestos organic brake pad system is studied using a pin-on-disc tribometer. The results show that this unconventional AlSiC MMC brake disc system presents friction performance as good as a conventional cast iron brake disc system. During braking, brake pad materials are transferred to the brake disc surface to form a protective third body tribo-layer, resulting in a negative specific wear rate of the brake disc. A higher contact load is likely to make it easier to generate the tribo-layer. The tribo-layer also seems to depend on the disc surface grinding features and the contact temperature during braking. By reusing an AlSiC MMC disc where the tribo-layer is already formed, the airborne emission in terms of mass is about 50% lower and in terms of number about the same as the conventional brake contact pair under a similar braking condition. Further full-scale studies are suggested to determine the validity of the findings.
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| 8. |
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| 9. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures
- 2019
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; , s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- Most freight wagons in the EU use cast iron brake blocks. Cast iron brake blocks have a stable braking capability in different environmental conditions, but wear down the wheel tread quickly. Therefore, there is a need to understand the tribology of other brake block materials. A pin-on-disc tribometer placed in a temperature-controlled chamber is used to investigate the tribology of cast iron, sinter and composite railway brake blocks at low ambient temperatures. Pins made from different brake blocks are tested with discs made from steel wheels. Both friction coefficient and wear are evaluated at five different temperatures from + 10 to − 30 °C. The cast iron block demonstrated the greatest wear at − 10 and − 20 °C, due to the ductile-to-brittle transition at low temperatures. The worn graphite from cast iron is likely to become a solid lubricant, reducing the friction at − 10 and − 20 °C. For the composite brake block, a gradual decrease in friction with decreasing temperature was found. The sinter brake block was not sensitive to changes in ambient temperature. The sliding speed in the current study is relatively low and further study at higher speed is suggested in order to evaluate the tribological performance of different brake blocks.
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| 10. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Friction, wear and airborne particle emission from Cu-free brake materials
- 2020
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 141
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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.
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| 11. |
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| 12. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Recycling of worn out brake pads impact on tribology and environment
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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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.
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| 13. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Tribology and airborne particle emission of laser-cladded fe-based coatings versus non-asbestos organic and low-metallic brake materials
- 2021
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Laser cladding is a promising surface treatment for refurbishing worn-out cast-iron brake rotors. Previous studies on laser-cladded brake rotors have demonstrated their extensively higher wear and greater airborne particle emissions, compared with traditional cast iron rotors. In order to overcome this, a commercial non-asbestos organic (NAO) brake material is tested against Fe-based laser-cladded and traditional cast-iron brake rotors. Two low-metallic brake pad materials are also tested as references. The materials’ coefficients of friction, specific wear rates and particle number concentrations are evaluated. The results indicate that the NAO brake material showed lower wear and had fewer particle emissions than the low-metallic brake materials when deployed against both cast iron and laser-cladded brake rotors. The NAO/laser-cladding friction pairing showed wear, particle concentration and fraction of fine particles (sub 1 µm) equivalent to those of the low-metallic/cast-iron friction pairing, creating significant potential for application in refurbishing worn-out cast-iron brake rotors.
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| 14. |
- Ma, Jijie, et al.
(författare)
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A Comparison of Airborne Particles Generated from Disk Brake Contacts : Induction Versus Frictional Heating
- 2020
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Ingår i: Tribology letters. - : SPRINGER/PLENUM PUBLISHERS. - 1023-8883 .- 1573-2711. ; 68:1
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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.
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| 15. |
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| 16. |
- Matejka, Vlastimil, et al.
(författare)
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Airborne Wear Particle Emissions Produced during the Dyno Bench Tests with a Slag Containing Semi-Metallic Brake Pads
- 2020
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Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 11:11
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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
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| 17. |
- Olofsson, Ulf, 1962-, et al.
(författare)
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Laser Cladding Treatment for Refurbishing Disc Brake Rotors : Environmental and Tribological Analysis
- 2021
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Ingår i: Tribology letters. - New York : Springer Nature. - 1023-8883 .- 1573-2711. ; 69:2
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Tidskriftsartikel (refereegranskat)abstract
- In this study, grey cast iron disc brake rotors are refurbished by adding a surface layer through laser cladding. Current methods to deal with replaced rotors mainly include remelting, with a minority fraction disposed in landfill. Both approaches result in a huge waste of resources and an increase in CO2 footprint. From a sustainable point of view, this study aims to evaluate the feasibility of refurbishing brake rotors by a combined environmental and tribological performance approach. A streamlined life cycle assessment is conducted to compare the environmental impacts between producing virgin grey cast iron brake rotors and refurbishing replaced brake rotors by laser cladding. It turns out that the energy consumption and CO2 footprint of the laser cladding refurbished brake rotors are 80% and 90% less than the virgin brake rotors. The results show that the refurbished brake rotor yields higher friction compared to the original cast iron utilizing the same pad material. The wear and particle emissions of the disc brake contact are in this study higher for the laser-cladded one compared to the original cast iron one.
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| 18. |
- Perricone, Guido, et al.
(författare)
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A proposed driving cycle for brake emissions investigation for test stand
- 2020
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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
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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.
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| 19. |
- Perricone, Guido, 1973-, et al.
(författare)
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Towards a test stand for standardized measurements of the brake emissions
- 2016
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Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : Sage Publications. - 0954-4070 .- 2041-2991. ; 230:11, s. 1521-1528
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Tidskriftsartikel (refereegranskat)abstract
- Brake-related particulate matter contributes considerably to the non-exhaust emissions of the transport sector in urban areas of the world. The airborne particle emissions from automotive brakes currently lack any proper regulations. Future regulations require test stands, test cycles and particle instruments to be suitable for measuring the brake emissions. This present work focuses on the design of a novel test stand for reliable measurements of the brake emissions with a high sampling efficiency. A test stand in the form of an inertial disc brake dynamometer was redesigned to allow control of the cleanness of the incoming air and to assure isokinetic sampling. The cleanness of the incoming air, together with an over-pressurized chamber around the brake assembly, ensures that all the particles measured originate from the brake materials. In order to evaluate the novel design, the number and size distributions of the brake emissions are measured online with and without control of the cleanness of the intake air. The results reveal that this test stand can be proposed as a standard test stand to assess objectively the emissions of airborne brake particles in future regulations.
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| 20. |
- Riva, Gabriele, et al.
(författare)
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A CFD study of a pin-on-disc tribometer setup focusing on airborne particle sampling efficiency
- 2017
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Ingår i: ECOTRIB 2017.
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Konferensbidrag (refereegranskat)abstract
- One of the most important measures to evaluate air quality is the presence of particles. Pin-on-disc tribometers are used to study airborne wear particles originating from different sliding contacts in a controlled laboratory environment. One important aspect when measuring airborne particles is to ensure isokinetic sampling conditions. Another important aspect is that the concentration and the particles distribution entering the sampling probe are representative for the emissions generated. It is therefore important to have an estimation of the sampling efficiency of the test system. The aim of this paper is to investigate the particle sampling efficiency of a pin-on-disc tribometer setup. In addition, a modified sampling setup that allows isokinetic sampling is investigated. CFD simulations to investigate air and particle motion were performed for both the existing and the modified configuration. The results show that the velocity field at the outlet does not allow isokinetic sampling for the existing configuration. In the modified configuration a sampling pipe is used to make isokinetic sampling possible. A comparison between the two configurations show that the modified configuration increases the sampling efficiency with almost 40% for ultrafine particles and about 20% for fine and coarse particles. It remains to validate the CFD simulations with experiments.
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| 21. |
- Riva, Gabriele, et al.
(författare)
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A Multi-Scale Simulation Approach to Investigate Local Contact Temperatures for Commercial Cu-Full and Cu-Free Brake Pads
- 2019
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Ingår i: Lubricants. - Basel : MDPI. - 2075-4442. ; 7:9
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Tidskriftsartikel (refereegranskat)abstract
- Copper from vehicles disc brakes is one main contributor of the total copper found in the environment. Therefore, the U.S. Environmental Protection Agency (EPA) and the automotive industries started the Copper-Free Brake Initiative. The pad friction material is essentially composed of a binder, fillers, reinforcing fibres and frictional additives. Copper and brass fibres are the most commonly used fibres in brake pads. There is a need to understand how the contact temperature distribution will change if copper-based fibres are changed to steel fibres. The aim of this work is, therefore, to investigate how this change could influence the local contact temperatures. This is done by developing a multi-scale simulation approach which combines cellular automaton, finite element analysis (FEA) and computational fluid dynamics (CFD) approaches with outputs from inertia brake dyno bench tests of Cu-full and Cu-free pads. FEA and thermal-CFD are used to set the pressure and the temperature boundary conditions of the cellular automaton. The outputs of dyno tests are used to calibrate FEA and CFD simulations. The results of the study show lower peaks in contact temperature and a more uniform temperature distribution for the Cu-free pad friction material.
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| 22. |
- Riva, Gabriele, et al.
(författare)
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A NUMERICAL STUDY OF DISC BRAKES WEAR DEPENDENCE OF ROTOR SURFACE COATING
- 2018
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Konferensbidrag (refereegranskat)abstract
- Airborne emissions from disc brakes adversely affect the air quality in urban areas of EU. The emissions come from the wear of the pads and rotors in disc brakes. The wear of disc brakes depends on the contact situation between the pads and rotors. During braking, secondary contact plateaus are created on both the pads and rotors contact surfaces. Literature reports numerical studies of the creation of contact plateaus on the pad surface but no numerical studies known to the authors have taken into consideration the creation of contact plateaus on the rotor surface. Furthermore, experimental studies reported in the literature shows that secondary plateaus are created in the low-lands of the rotor contact surface and that this affects the wear performance. In particular, it has been reported that the creation of secondary plateaus on coated rotors have a relatively large affect the wear and emissions. The aim of this study is therefore to numerically investigate how the creation of contact plateaus on the rotor surface could affect the disc brake wear performance. This is done by expanding an existing simulation tool used for simulation of friction, wear and particle emission, which takes into account the creation of contact plateaus on the pad surface, to include creation of contact plateaus on the rotor surface. One rotor surface that corresponds to a cast iron rotor is compared with one rotor surface that corresponds to a coated rotor. The results are qualitatively in line with observations done in pin-on-disc tribometer tests. It remains to validate the numerical results with data obtained in experiments.
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| 23. |
- Riva, Gabriele, 1988-, et al.
(författare)
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An FEA approach to simulate disc brake wear and airborne particle emissions
- 2019
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 138, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- Emissions from disc brake wear adversely affect the air quality in cities. Finite Element Analysis (FEA) approaches focussing on the macroscopic wear of pads and rotors can be found in the literature, but none of these take the wear and emission dependence of the local contact pressure and sliding speed into account. The aim of the present study is to further develop an FEA approach for simulation of macroscopic wear and airborne emission to include the dependences of local contact pressure and sliding speed by implementing wear and emission maps obtained by pin-on-disc tribometer tests. Results from a dyno bench test are compared with simulated results. The simulated rotor and pads wear, and airborne emissions are in line with the measured values.
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| 24. |
- Riva, Gabriele, et al.
(författare)
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Simulation of Contact Area and Pressure Dependence of Initial Surface Roughness for Cermet-Coated Discs Used in Disc Brakes
- 2019
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Ingår i: Tribology in Industry. - : Faculty of Engineering, University of Kragujevac. - 0354-8996 .- 2217-7965.
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Tidskriftsartikel (refereegranskat)abstract
- Friction, wear, and emission performance strongly depend on the contact pressure and area at the interface of the pad and disc. The contact situation at the pad-to-disc interface can be explained by the formation and destruction of mesoscopic sized contact plateaus on the pad surface. Experimental studies report that the initial surface roughness of cermet-coated discs strongly affects friction, wear and emission performance. This is explained by the formation of secondary plateaus on the disc surface. The aim of this work is to extend an existing cellular automaton approach to include the formation of secondary plateaus on the disc surface in order to explain experimental results reported in the literature. First, to investigate the validity of the novel simulation approach, a cermet-coated cast iron disc is tested against a low-met pad material with a pin-on-disc tribometer. The same conditions are used as input in a simulation. Then, the initial disc roughness influence on contact pressure and area of the same cermet-coated disc is compared with results reported in the literature. The topographies of the measured and simulated disc surfaces are qualitatively in line. An initial rougher disc surface results in a considerably lower contact area than does a smother surface.
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| 25. |
- Tu, Minghui, et al.
(författare)
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A comparison of airborne wear particle emission models based on metro station measurements
- 2019
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Ingår i: Proceedings of 10th International Scientific Conference BALTTRIB 2019. - : Vytautas Magnus University. - 2424-5089. ; , s. 150-157
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Konferensbidrag (refereegranskat)abstract
- The main sources of non-exhaust particles around metro systems are the wear from wheel-rail contact, brake contact and the contact between mechanical parts in electric power systems. In order to predict the PM10 levels on underground metro platforms, the relation among time, train frequency and PM10 level should be investigated. Two types of particle emission models have previously been published to determine the PM10 level on underground train platform; these are the linear model and the conservation model. The aim of this study is to compare the results from the two models with a set of field measurements PM10. In 2016, a set of field measurements are performed on four underground metro platforms in Stockholm. The predicted PM10 values from the two models are compared with the measurement data. The accuracy of the two models is analysed and the behaviours of the two models in high and low train frequency regions are separately discussed.
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| 26. |
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| 27. |
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| 28. |
- Tu, Minghui, et al.
(författare)
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Towards a two-part train traffic emissions factor model for airborne wear particles
- 2019
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Ingår i: Transportation Research Part D. - : Elsevier Ltd. - 1361-9209 .- 1879-2340. ; 67, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- In 2017 a new railway tunnel containing two stations opened in Stockholm, Sweden. A series of field measurements were carried out on the platforms in this tunnel before and after it was opened for normal traffic. These measurements were used to investigate the contribution of airborne particle emissions from wear processes to total train emissions. This field data was used to develop a two-part train traffic emission factor model for PM10. The two parts are the accumulative effect term (relating to operating distance such as wheel-rail contact and overhead electric line sliding contact) and a brake effect term (relating to the number of braking operations such as brake disc and brake pad contact). The results show that operating a single trial train at a higher than normal frequency on an otherwise empty platform increases the platform particulate concentration until the concentration reaches a steady value. The model suggests that brake emissions account for about 50% of the total emissions measured in the tunnels.
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| 29. |
- Wahlström, Jens, PhD/Docent, 1979-
(författare)
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A pin-on-disc tribometer study of friction at low contact pressures and sliding speeds for a disc brake material combination
- 2019
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Ingår i: Results in Engineering. - : Elsevier. - 2590-1230. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Disc brake creep groan is a stick-slip phenomenon which results in a low frequency noise in road vehicles that could occur at low vehicle speeds and brake torques. Simulation approaches are used predict the stick-slip phenomena for disc brakes. These approaches depend on the friction model used. Tribometers can be used to map how the local coefficient of friction (CoF) depends on the contact pressure (p) and sliding speed (v). A CoF pv-map can be used as friction model in simulation approaches. There is a lack of CoF maps at low contact pressures and sliding speeds are reported in the literature. The aim of the presented study is to map the CoF for a disc brake material combination at low contact pressures (0.03–0.28 MPa) and sliding speeds (0–3.8 mm/s). The result shows that the friction decreases with increased contact pressure and sliding speed for the specific material combination tested and the test conditions used. More studies are needed to further investigate the validity of the results.
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| 30. |
- Wahlström, Jens, PhD/Docent, 1979-, et al.
(författare)
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A Study of the Effect of Brake Pad Scorching on Tribology and Airborne Particle Emissions
- 2020
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Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 11:5
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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.
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