Analysis of the transient handling properties of a tyre, based on the coupling of a flexible carcass-belt model with a separate tread incorporating transient viscoelastic frictional properties, Vehicle SystemThe behaviour of tyres under transient handling manoeuvres is studied with the aid of a newly developed model. The model consists of a discretized flexible belt with damping and inertia, connected to the rim by viscoelastic elements representing the carcass. In the neighbourhood of the contact patch, the belt is connected to a separate discretized viscoelastic tread with inertia. A separate algorithm taking into account the radial deflection of the carcass elements is used for the calculation of the contact pressure distribution along the contact patch. Friction follows a stick -slip law taking into consideration the velocity of tread elements, the normal force and the unequal coefficients of friction in the lateral and longitudinal directions. The model seems capable of generating transient forces and moments including the phase lags observed under time-varying kinematic excitations.

Citation: CZECHOWICZ, M.P. and MAVROS, G., 2014. Analysis of vehicle rollover dynamics using a high-fidelity model. Vehicle System Dynamics, 52 (5), pp. 608636. At the same time experimental testing to improve safety is expensive and dangerous. Therefore multi-body simulation is used in this research to improve understanding of rollover dynamics. The majority of previous work uses low fidelity models. Here a complex and highly nonlinear multibody model with 165 degrees of freedom is correlated to vehicle kinematic and compliance measurements. The Magic Formula tyre model is employed. Design of experiment methodology is used to identify tyre properties affecting vehicle rollover. A novel, statistical approach is used to link suspension kinematic and compliance characteristics with rollover propensity. Research so far reveals that the tyre properties that have the greatest influence on vehicle rollover are friction coefficient, friction variation with load, camber stiffness, and tyre vertical stiffness. Key kinematic and compliance characteristics affecting rollover propensity are front and rear suspension rate, front roll stiffness, front camber gain, front and rear camber compliance and rear jacking force.

<div class="section abstract"><div class="htmlview paragraph">The primary function of automotive windscreen wipers is to remove excess water and debris to secure a clear view for the driver. Their successful operation is imperative to vehicle occupants’ safety. To avoid reliance on experimental testing there is a need to develop physics-based models that can quantify the effects of design-based decisions on automotive wipers. This work presents a suite of evaluative tools that can provide quantitative data on the effects of design decisions. We analyse the complex non-linear contact interaction between the wiper blade and the automotive screen using finite element analysis, assessing the impact of blade geometry on the contact distribution. The influence of the evolution of normal applied load by the wiper arm is also investigated as to how it impacts the contact distribution evolution. The dynamics of the blade are subsequently analysed using a multiple connected mass spring damper system. Additionally, we apply hydrodynamic lubrication theory to study the residual film thickness post wipe and assess the effect of wiper blade geometry and lubricant composition. Finally, the complete wiper system is studied using a lump dynamic model, and bifurcation analysis is applied to determine areas of instability due to friction induced vibrations. Additionally, the wiper dynamics modelling shows peak frequencies occurring at 30-50Hz, which agrees well with a documented range of chatter frequencies. The friction coefficients calculated within the hydrodynamic model fall within experimentally documented ranges of lubricated sliding friction, <i>μ</i> ≈ 0.1. Furthermore, the areas of operational stability predicted by our bifurcation model coincide with current experimentally determined optimal operational regions for automotive wipers.</div></div>

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Citation: BEKAKOS, C.-A., 2016. Off-road tire-terrain interaction: an analytical solution. SAE International Journal of Commercial Vehicles, 9 (2), pp. 244-251.Additional Information:• This paper was accepted for publication in the journal SAE In- INTRODUCTIONTire-road interaction is a highly complex dynamic phenomenon, which has been subject to extensive research and development within the automotive industry. The tire is the dominant link between a vehicle body and road surface dynamic interaction in terms of accelerating, braking and steering forces. On-road tires have attracted significant attention with regards to reducing rolling resistance and fuel consumption following several European and/or world guidelines. However, off-road tires-soil interaction occupies an equally important position within the tire industry not only for military purposes but also for the growth of agricultural-based countries' economies.The ability of tracked and wheeled vehicles to transverse certain types of soft soils is a complex, multivariable phenomenon and because of this, several assumptions have to be made in order to create accurate and yet computationally efficient off-road tire models. Finite element models can produce highly accurate time-domain solutions, taking into account the exact properties of the tire and soil surface, however, they are typically unsuitable as inputs for interactive, dynamic vehicle simulations as they operate far from real time. Semi-analytical and/or numerical simplified models have been created in the past where the soil is being regarded as an elasticperfectly plastic material [1] and the tire is being considered as a rigid wheel model, representative of a highly inflated tire rolling on a very soft soil [2]. To the best of the authors' knowledge, regardless of the assumptions involved, in most of the models published in the literature the off-road tire-soil interaction is studied in terms of two main effects. The first tries to capture the relationship between the normal load and vertical displacement (sinkage) of the wheel into the soil; the second has to do with the shear stress-shear displacement developed on the tire-soil interface.In a pioneering paper representative of the former effect [3], based on the observation that the main resistance in a tire's movement is due to the effort to create a rut in order to transverse, Bernstein proposed eq.(1), which was later extended in a more generalized version, i.e. eq. ABSTRACTA novel semi-analytical solution has been developed for the calculation of the static and dynamic response of an off road tire interacting with a deformable terrain, which utilizes soil parameters independent of the size of the contact patch (size-independent). The models involved in the solution presented, can be categorized in rigid and/or pneumatic tires, with or without tread pattern. After a concise literature review of related methods, a detailed presentation of the semi-analytical solution is presented, along with assumptions and limitations. A flowchart is pro...