| 1. |
- Christensson, Bengt, et al.
(författare)
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Åtgärder för säker hantering av nanofibrer vid komposittillverkning
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inför användning av nanomaterial i en ny produkt, har mätningar gjorts för att studera hur nanopartiklar sprids i arbetsmiljön och vilka halter som kan förväntas vid användning av kolnanofibrer (främst kolnanotuber) och järnoxidnanopartiklar. Mätningarna har använts som underlag för utvärdering av åtgärder med målet att ge råd om säker hantering av nanofibrer och nanopartiklar. Kolnanotuber är små och tunna, liksom fibriller från asbest. Det finns misstankar om att kolnanotuber liksom asbest kan orsaka cancer, bland annat mesoteliom. Det är därför viktigt att kolnanotuberna hanteras på ett kontrollerat sätt. Gränsvärden har förslagits för kolnanofibrer i arbetsmiljön. Föreslagna gränsvärden varierar från 2,5 µg/m3 till 100 µg/m3. För kolnanofibrer föreslås dessutom ett gränsvärde baserat på antal fibrer 0,01 f/ml (fibrer/ml luft). Beroende på kolnanofibrernas struktur diskuteras olika gränsvärden. Mätningar vid hantering av små mängder nanofibrer och nanopartiklar visar att halterna kan hållas låga om kolnanofibrerna hanteras i glovebox som placerats i dragskåp eller liknande välventilerat utrymme. Föreslagna gränsvärden är så låga att sluten hantering krävs för att gränsvärdena inte ska överskridas. Vid slipning fångades damm och nanopartiklar in om det fanns effektiva integrerade utsug i kombination med platsventilation. Utan väl fungerande ventilation blev halten nanofibrer och -partiklar snabbt mycket hög. Vid sanering minskade damningen om saneringen utfördes vått och med tillsats av dammbindningsmedel. Vid ovarsam hantering kan halterna också bli höga liksom vid tillfälliga spill. Inom projektet har flera olika mätmetoder testats och använts parallellt. Mätningarna har gett en god förståelse för hur nanopartiklar kan mätas men även för hur mätdata kan tolkas samt betydelsen av att ha kontroll på andra nanopartikel-källor som kan störa mätningarna. Mätningarna visar också att produktutveckling pågår som minskar nanopartiklarnas tendens att agglomerera, vilket kan leda till ökande exponering för nanopartiklar.
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| 2. |
- Ejsmont, Jerzy, et al.
(författare)
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Comparision of tire rolling resistance measuring methods for different surfaces
- 2024
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Ingår i: International Journal of Automotive Technology. - Seoul : Springer Nature. - 1976-3832 .- 1229-9138.
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Tidskriftsartikel (refereegranskat)abstract
- The rolling resistance of car tires is one of the most important parameters characterizing tires today. This resistance has a very significant contribution to the energy consumption of wheeled vehicles. The climate crisis has forced tire and car manufacturers to place great emphasis on the environmental impact of their products. Paradoxically, the development of electric vehicles has led to an even greater importance of rolling resistance, because in electric vehicles a large part of the influence of grade resistance and inertial resistance has been eliminated due to re-generative braking, which resulted in rolling resistance and air resistance remain as the most important factors. What is more, electric and hybrid vehicles are usually heavier so the rolling resistance is increased accordingly. To optimize tires for rolling resistance, representative test methods must exist. Unfortunately, the current standards for measuring rolling resistance assume that tests are carried out in conditions that are far from real road conditions. This article compares the results of rolling resistance tests conducted in road conditions with the results of laboratory tests conducted on roadwheel facilities. The overview of results shows thatthe results of tests conducted in accordance with ISO and SAE standards on steel drums are very poorly correlated with more objective results of road tests. Significant differences occur both in the Coefficients of Rolling Resistance (CRR) and in the tire ranking. Only covering the drums with replicas of road surfaces leads to a significant improvement in the results obtained.For investigations of rolling resistance in non steady-state conditions, the flat track testing machine (TTF), equipped with asphalt cassettes, is shown to provide measurement data in agreement with the road test data.
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| 3. |
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| 4. |
- Ydrefors, Lisa, et al.
(författare)
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Comparison between tyre rolling resistance measurements on a flat track and a test drum under non-steady-state conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Rolling resistance has become one of the key parameters that the vehicle industry is focussing on in their efforts to make vehicles more energy-efficient. Rolling resistance is generally measured in steady-state on a test drum which results in a higher rolling resistance compared to flat track measurements for the same test settings due to the curvature of the drum which deforms the tyre more. Therefore, the drum steady-staterolling resistance is commonly converted with Clark’s formula, as suggested in the rolling resistance measurement standards. The accuracy of Clark’s formula has been questioned by Freudenmann et al who suggest an adjusted formula for steady-state measurements. The aim of this work is to compare drum and flat track measurements performed at the same inflation pressure and tyre temperature instead of at steadystate and investigate whether Clark’s or Freudenmann’s formula can be used to convert the drum measurement to a corresponding flat track level. Non-steady-state measurements have been performed on both test drum and flat track. As expected, Freudenmann’s formula is not good for the conversion at nonsteady-state settings, since it was empirically developed for steady-state. Clark’s formula works better for conversion of measurements performed at the same tyre temperature and inflation pressure compared to steady-state conversions reported in literature. However, the dependency of rolling resistance on temperature is not the same in the drum and flat track measurements, causing a difference between the results which increases as the tyre temperature decreases. Further research is needed to improve Clark’s formula by including the effects of tyre temperature
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| 5. |
- Ydrefors, Lisa, et al.
(författare)
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Development of a method for measuring rolling resistance at different tyre temperatures
- 2022
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Ingår i: 27th IAVSD Symposium, 2021, digital from St Petersburg, 17-19 august, 2021. - Cham : Springer Science and Business Media Deutschland GmbH. ; , s. 1026-1039
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Konferensbidrag (refereegranskat)abstract
- Measurement methods to determine the rolling resistance of tyres during different operation conditions are essential in the work towards more energy efficient vehicles. One of the influential parameters is the tyre temperature distribution, which has a large impact on the rolling resistance. Today, the standardised test procedure to measure rolling resistance is steady-state measurement on drums. However, the steady-state temperature on a drum is not the same as the temperature during ordinary driving conditions. The aim of this work is to develop a measuring method that enables to set a desired measurement temperature, which would create the possibility to study the relationship between tyre temperature and rolling resistance in more detail. The measurement method was developed by the use of a flat track equipment but should be applicable to other rolling resistance measurement equipment such as drums. The resulting method gives a repeatable tyre temperature and rolling resistance and can be used for measurements on tyres heated to a chosen measurement temperature.
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| 6. |
- Ydrefors, Lisa, et al.
(författare)
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Development of rolling resistance measurement set-up in order to enable energy optimisation of vehicle-road interaction taking into account safety and performance
- 2021
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Ingår i: Proceedings of the Resource Efficient Vehicles Conference - 2021. - 9789180400473 ; , s. 116-122
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Reducing the rolling resistance for future vehicle designs creates a possibility to reduce the fuel consumption and make the future vehicles more economical and ecological. For electric vehicles it is also an enabler to increase their driving range per charge. When optimising for reduced rolling resistance, contradictory requirements such as force generation for maintaining safety and performance need to be considered. Furthermore, it is important to include both the effects of road surface and vehicle, to avoid sub-optimisation regarding only the tyres. A cross-functional conflict on the component level is well known, in form of energy consumption versus wet grip (traffic safety). On the system level, different wheel settings to optimise energy consumption conflicts with vehicle dynamical properties related to traffic safety, such as stability or steer response. The long term vision of the work presented is to create tools for more energy efficient vehicles by reducing the rolling resistance during driving. The first part is to establish a credible measurement method for rolling resistance on road under controlled conditions (lab environment). Today’s existing measurement methods on rolling resistance under laboratory conditions commonly utilise a rotating drum, whose curved surface affects the results. Therefore, rolling resistance influence of vehicle settings such as camber or toe angles is difficult to assess using standard methods, and there is a need for measurements using a more realistic contact patch, which would need a flat surface. The existing unique tyre testing facility at the Swedish National Road and Transport Research Institute, VTI, is used as a base for developing the new rolling resistance set-up. The tyre test facility is today used to determine tyre characteristics such as brake and steering forces. The method to measure rolling resistance with this equipment under highly controlled conditions is under development, and some preliminary results are presented.
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| 7. |
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| 8. |
- Ydrefors, Lisa, et al.
(författare)
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Measurement and evaluation of rolling resistance of car tyres at low operating temperatures
- 2023
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Ingår i: Proceedings of the 28th IAVSD Symposium on Dynamics of Vehicles on Roads and Tracks, Ottawa, Canada, 21 - 25 Aug 2023.
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Konferensbidrag (refereegranskat)abstract
- In the strive towards more energy efficient vehicles, efforts are made to reduce rolling resistance as one of the main resistive forces. Within the European Union (EU) tyres are labelled to guide consumers to choose a tyre with low rolling resistance. The tyres are labelled based on a standardised rolling resistance test performed at 25 ⁰C on a test drum, where the tyre is run until it reaches steady-state conditions. However, due to the high ambient air temperature, steady-state conditions and the curved surface of the drum, the rolling resistance in a standardised test is commonly measured at a higher tyre temperature compared with many real driving situations. The overall aim with this work was to experimentally measure the rolling resistance at low operating temperatures on a flat surface, which better correlates to realistic operating conditions compared to the EU standard measurement method. The investigated tyre temperature range, 0 ⁰C to 35 ⁰C, was determined based on tyre temperature measurements on a car in traffic during springin Sweden. Rolling resistance measurements were performed on a flat track test equipment for four car tyres with the same dimensions but different rolling resistance labelling. For the tyre with the largest temperature influence, the rolling resistance increased by almost 80 % for a temperature reduction of 20 ⁰C. These results emphasise the importance of the tyre temperature influence on rolling resistance. Further research is needed to conclude whether, and then how, the standardised measurements should be updated to address this temperature influence.
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| 9. |
- Ydrefors, Lisa, et al.
(författare)
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Parametrisation of a rolling resistance model for extending the brush tyre model
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A rolling resistance model has been created and parametrised with the purpose of modelling tyre rolling resistance within complete vehicle dynamics simulations. The rolling resistance model is based on a combination of the Masing and Zener model to simulate the Payne effect and the viscoelastic properties of rubber. The parametrised model is able to recreate the relationship between the rolling resistance and the tyre deformation well and it has a low computational power requirement. Today the model is limited to simulation of free-rolling tyres on a flat surface, but it can be extended to also include the effects of changes in operating conditions such as wheel angles or road surface.
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| 10. |
- Ydrefors, Lisa, et al.
(författare)
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Parametrisation of a rolling resistance model for extending the brush tyre model
- 2024
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Ingår i: International Journal of Vehicle Design. - : Inderscience Publishers. - 0143-3369 .- 1741-5314. ; 94:1-2, s. 38-56
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Tidskriftsartikel (refereegranskat)abstract
- A rolling resistance model (RRM) has been created and parametrised with the purpose of modelling tyre rolling resistance within complete vehicle dynamics simulations. The RRM is based on a combination of the Masing and Zener models to simulate the Payne effect and the viscoelastic properties of rubber. The parametrised model is able to recreate the relationship between the rolling resistance and the tyre deformation well and it has a low computational power requirement. Today the model is limited to simulation of free-rolling tyres on a flat surface, but it can be extended to also include the effects of changes in operating conditions such as wheel angles or road surface.
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