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- Wahlström, Jens, 1979-
(författare)
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Towards a simulation methodology for prediction of airborne wear particles from disc brakes
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During braking, both the rotor and the pads in disc brakes are worn. Since disc brakes are not sealed, some of the wear particles generated can become airborne. Several studies have found an association between adverse health effects and the concentration of particles in the atmosphere, so it is of interest to improve our knowledge of the airborne wear particles generated by disc brakes. However, in field tests it is difficult to distinguish these particles from others in the surrounding environment, so it may be preferable to use laboratory test stands and/or simulation models to study the amount of airborne wear particles generated. This thesis deals with a simulation methodology for prediction of airborne wear particles from disc brakes and three experimental methods for testing disc brake materials with focus on airborne wear particles. The four appended papers discuss the possibility to both measure and predict the number and size distribution of airborne wear particles that originate from the pad to rotor contact. The objective is to develop a simulation methodology that predicts the number and size distribution of airborne wear particles from disc brakes. Paper A describes how a modified pin-on-disc machine was used to study airborne wear particles originating from different disc brake materials. The results indicate that the test setup can be used to measure and rank the number concentration and size distribution of the airborne wear particles generated. Paper B describes a disc brake assembly test stand for measurements of airborne wear particles from disc brakes. The results indicate that the test setup can be used to measure the number concentration and size distribution of airborne wear particles generated from disc brake materials. The results also indicate a promising ability to rank different pad/rotor material combinations with respect to the number concentration of airborne wear particles. Paper C compares measurements made in passenger car field tests with measurements made in a disc brake assembly test stand and in a pin-on-disc machine. A promising correlation between the three different test methods is found. Paper D presents a simulation methodology for predicting the number and size distribution of airborne wear particles using finite element analysis (FEA). The simulated number distribution is compared with experimental measurements at component level. The result indicates that the proposed methodology may be used to predict the number concentration and size distribution of airborne particles generated in the pad-to-rotor contact.
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| 2. |
- Fullagar, Wilfred, et al.
(författare)
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A broadband laser plasma X-ray source for application in ultrafast chemical structure dynamics
- 2007
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 78:11, s. 1-115105
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Tidskriftsartikel (refereegranskat)abstract
- A plasma source free from characteristic emission lines is described, based on laser irradiation of a water jet in a helium atmosphere. Various key aspects of the laser interaction are presented along with practical characterization of the observed isotropic ~4–10 keV x-ray emissions, measurements of which indicate subpicosecond duration. Observations are consistent with a vacuum heating plasma mechanism at the helium-water interface and indicate strong potential for in-house ultrafast chemical structure dynamics application when coupled to contemporary detector developments.
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| 4. |
- Jansson, Anders, 1947-, et al.
(författare)
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Ultrafine particle formation from wear
- 2009
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Ingår i: Proceedings of Ventilation 2009, the 9th International Conference on Industrial Ventilation.
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Konferensbidrag (refereegranskat)abstract
- Much attention is given to the consequences of airborne particles on human health and well-being. Wear is one source of airborne particles and contributions in urban environments from wheel-to-rail contacts and disc brakes cannot be neglected. Traditionally mechanical wear has been associated with the generation of particles of diameters of some μm. However, we have also found ultrafine particle generation from wear processes. Particle generation from wear was measured under controlled laboratory conditions. The wear was created through sliding contact in a tribometer (type "pin-on-disc") with different materials and with different sliding velocities and pressures, to represent rail traffic and automobile disc braking. Particle concentrations and size distributions in the air were determined for particle diameters from 10 nm up to more than 10 μm. For most materials and conditions three particle size modes were found: one at 50-100 nm, one at a few hundred nm and one at a few μm particle diameter.
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| 5. |
- Leijon, Ola, et al.
(författare)
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Prevalence of self-reported neck-shoulder-arm pain and concurrent low back pain or psychological distress : time-trends in a general population, 1990-2006.
- 2009
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 34:17, s. 1863-1868
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: Analysis of repeated cross-sectional surveys. OBJECTIVE: To investigate the prevalence of neck-shoulder-arm pain and concurrent low back pain and psychological distress in a geographical area over a 16-year period. SUMMARY OF BACKGROUND DATA: A large number of studies have shown that nonspecific neck, shoulder, and arm pain is a very common symptom in the general population. However, few studies have followed the prevalence of neck-shoulder-arm pain within a geographical area, in order to investigate time-trends. METHODS: This study provides an analysis of questionnaire data collected every 4 years between 1990 and 2006 on the prevalence of neck-shoulder-arm pain and concurrent low back pain or psychological distress in the County of Stockholm, Sweden (response rate: 61%-69%). All individuals aged 21 to 64 years (n = 1976-26,611) were included in the study. RESULTS: Over the 16-year period, the prevalence of self-reported neck-shoulder-arm pain rose slightly, from 22.8% to 25.0% among females (prevalence rate ratio [PRR]: 1.10) and from 12.8% to 15.4% among males (PRR: 1.21). The prevalence of neck-shoulder-arm pain with concurrent low back pain also rose slightly, from 8.4% to 10.8% among females (PRR: 1.28) and from 5.3% to 6.6% among males (PRR: 1.24). In contrast, the prevalence of neck-shoulder-arm pain with concurrent psychological distress rose more substantially, from 4.4% to 8.5% among females (PRR: 1.91) and from 2.0% to 4.3% among males (PRR: 2.18). All prevalence rates rose between 1990 and 2002, and decreased in 2006 compared to 2002. The gender gap in prevalence did not change over time. CONCLUSION: Although the prevalence of neck-shoulder-arm pain and concurrent symptoms decreased in 2006 compared to 2002, it is still too early to conclude that we have reached and passed the peak of the "epidemic" of neck-shoulder-arm pain.
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| 10. |
- Söderberg, Anders, et al.
(författare)
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On Airborne Wear Particles Emissions ofCommercial Disc Brake Materials– A Pin on Disc Simulation
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A novel test method was used to study the concentration and size distribution of airborne wear particles from disc brake materials. A pin-on-disc tribometer equipped with particle counting instruments was used as test equipment. Four different nonasbestoses-organic (NAO) linings for the U.S. market and four different low metallic linings for the EU market were tested against material from gray cast iron rotors. The result indicates that the low metallic linings are more aggressive to the rotor material then the NAO linings, resulting in higher amount of wear and concentrations of airborne wear particles. But, although there are variations in the measured particle concentrations, similar size distributions were obtained regardless of lining material.
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