Search

This paper refines the two-regime transient theory developed by Romano et al. [Romano L, Bruzelius F, Jacobson B. Unsteady-state brush theory. Vehicle Syst Dyn. 2020;59:11–29. DOI: .] to include the effect of combined slip. A nonlinear system is derived that describes the non-steady generation of tyre forces and considers the coupling between the longitudinal and lateral characteristics. The proposed formulation accounts for both the carcass and the bristle dynamics, and represents a generalisation of the single contact point models. A formal analysis is conducted to investigate the effect of the tyre carcass anisotropy on the properties of the system. It is concluded that a fundamental role is played by the ratio between the longitudinal and lateral relaxation lengths. In particular, it is demonstrated that the maximum slip that guarantees (partial) adhesion conditions does not coincide with the stationary value and decreases considerably for highly anisotropic tyres. The dissipative nature of the model is also analysed using elementary tools borrowed from the classic theory for nonlinear systems. A comparison is performed against the single contact point models, showing a good agreement especially towards the full-nonlinear one. Furthermore, compared to the single contact point models, the two-regime appears to be able to better replicate the exact dynamics of the tyre forces predicted by the complete brush theory. Finally, the transient model is partially validated against experimental results. [ABSTRACT FROM AUTHOR]

Author(s): Sergey Kubatkin [1]; Andrey Danilov [1]; Mattias Hjort [2]; Jérôme Cornil [2, 3]; Jean-Luc Brédas [2, 3, 5]; Nicolai Stuhr-Hansen [4]; Per Hedegård [4]; Thomas Bjørnholm (corresponding author) [4] [...]

For at least 50 years, the interest in understanding and reducing the rolling resistance of pneumatic tyres has been growing. This interest is driven by the need to reduce vehicle fuel consumption and CO2-emissions, for environmental and economic reasons. The amount of rolling resistance generated depends on the vehicle type, tyre properties and operating conditions. The main objective of this literature review is to provide an overview of the most influential operating conditions with respect to rolling resistance, their effects and their connection to different measurement techniques. The examined operating conditions are the inflation pressure, the temperature, the curvature of the test surface, the load, road surface, speed, torque, slip angle and camber angle. In addition, the definition of rolling resistance is investigated, which shows lack of harmony in the literature. There are important areas where little research can be found and where further research would be valuable. Examples of such areas are effects of the torque, slip angle and camber angle on rolling resistance, thorough comparison between flat-surface and drum measurements, effects of temperature difference between laboratory measurements and actual driving on rolling resistance and evaluation of Unrau's formula for temperature correction of rolling resistance measurements. [ABSTRACT FROM AUTHOR]

REDD+ is a forest conservation and carbon trading scheme seeking to incentivise a reduction in emissions through payments. This article draws on Foucault's governmentality concept and Dean's analytics of government framework to analyse the REDD+ negotiations under the UNFCCC. It argues that negotiators perceived forest inhabitants as malleable subjects whose conduct can and should be "improved" through disciplinary techniques instantiated in forest monitoring practices. Forest inhabitants are not powerless or passive recipients of discipline, but these techniques foster a conduct that only values carbon at the expense of other ecological and cultural values and, further, encourage conservation purely based on cost-benefit reasoning. The article also interrogates the negotiations of safeguards meant to ensure that REDD+ does no social or ecological harm. It argues that the safeguards appear to allow forest inhabitants to decide on REDD+ implementation and governance, and protect their existing forest governance practices should they elect to do so. However, the safeguards are formulated in a voluntary manner, casting doubts on their ability to offer suitable protection. The article concludes by reflecting on the current demand for carbon credits from REDD+ projects and the implications this has for the disciplinary techniques and the conduct they foster. [ABSTRACT FROM AUTHOR]

This article analyses the rationale for and impacts of Conservative Party overseas volunteering projects from 2007 to 2017. Using interview data and participant observation, we uncover aims of project founders and explore impacts of volunteering on Party members and policy. We make three substantial contributions. The first focuses on the survival of Conservative Party modernisation strategies launched under David Cameron. Support for development, particularly Party pledges to spend 0.7% of UK gross national income on aid, are poorly explained by existing research. We argue that a focus on volunteering helps explain the survival of this commitment. Second, we argue that volunteering experience may support sustained Party policy change by enhancing 'issue ownership'. Our final contribution is providing the first analysis of political parties as development-volunteer sending communities. Through new data and distinctive contributions, we demonstrate that understanding Party-supported volunteering promotes improved explanations of Party modernisation persistence and policy change. [ABSTRACT FROM AUTHOR]

Tyre modelling is an important part of understanding and estimating the tyre–road friction. In this paper a basic steady-state tyre model for the combined-slip case is derived. The model is intended to be used in friction estimations applications, where the model complexity is of high priority. The model, described using only two parameters, is validated with measured data from various conditions and tyre types using mobile measurement equipment. The performance from the measurements suggests that only two parameters are sufficient for the combined-slip case. [ABSTRACT FROM AUTHOR]

This paper evaluates an approach for predicting rut formation in asphalt concrete (AC) layers. The approach is based on a linear viscoelastic model for predicting permanent vertical strain in AC layers subjected to a moving load. The input data are tyre pressure, loading speed, lateral wandering of loading wheel, shear modulus and phase angle of AC layer. The analytical approach takes into consideration the change in material characteristics in respect of temperature and changes in the air void content of AC layers due to repeated loading. The approach is verified by a full-scale accelerated loading test at different temperatures. The approach has shown good agreement as regards the prediction of flow rutting in AC layers. In addition, the approach is capable of calculating rutting profiles including the upheaval, which is important for estimating rut depth. [ABSTRACT FROM PUBLISHER]

With today’s advanced measurement equipment for monitoring road condition, it is possible to measure road geometry at high precision within a large span of wavelengths. Detailed information about the roads longitudinal and lateral profile, including macro texture, would in theory be sufficient for a realistic reproduction of road induced vibration and noise in a driving simulator. Especially, it would be possible to create a direct connection between the visual information of the road condition and the ride experience, which would increase the level of realism in the simulation. VTI has during three years performed an internal project called SHAKE with the aim to develop and implement models in VTI driving simulator III that use measured road data for generating realistic vibrations and audible road noise connected to the visual impression presented on the projection screen. This has indeed resulted in a more realistic driving experience and a validation study with test persons driving both in the simulator and in the field, has been undertaken. The OpenDRIVE standard is used as a framework for describing the road properties (e.g., visual, vibrations, and noise). For this purpose some augmentations to the OpenDRIVE standard had to be made. This paper describes the technical implementations in the driving simulator, along with results from test drives on the implemented road sections. [ABSTRACT FROM AUTHOR]