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  • 1
    Online Resource
    Online Resource
    Investigation of Snow Milling Mechanics to Optimize Winter Tire Traction
    The Tire Society ; 2017
    In:  Tire Science and Technology Vol. 45, No. 3 ( 2017-07-01), p. 162-174
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 45, No. 3 ( 2017-07-01), p. 162-174
    Abstract: A detailed understanding of effects occurring in the contact patch between tire tread and snow surface is needed to maximize tire grip in winter conditions. The main focus of this study is quantifying the snow milling effects of individual tire tread block elements during sliding. Tests are carried out using the high-speed linear friction tester (HiLiTe), located at the Institute of Dynamics and Vibration Research at Leibniz University of Hannover, Germany. Test tracks are prepared using artificially produced snow. To solely investigate snow milling effects and exclude material properties of rubber, in a first instance the tread block samples are made of polytetrafluoroethylene (PTFE). Because PTFE is at the same time rigid and hydrophobic, known friction mechanisms such as adhesion and hysteresis can be neglected, leaving only the tread pattern milling mechanics to transmit frictional forces to the snow track. The PTFE samples are shaped in such a way that they mimic the geometry of different siped rubber tread blocks under load, varying the sipes' number, shape, and tilt angle. Results show the benefit of multiple sipes and give information on the evolution of transmittable forces with respect to sliding distance. It is found that the block element shape and tilt angle are directly linked to the frictional force, showing a distinct optimum for specific angle and shape combinations. In addition, forces are not depending on sliding speed, but on sliding distance. The snow milling results of PTFE block elements are then compared to siped rubber block samples. Corresponding high-speed videos show that PTFE sample snow milling mechanics can be directly applied to rubber samples.
    Type of Medium: Online Resource
    ISSN: 0090-8657 , 1945-5852
    URL: Article
    DOI: 10.2346/tire.17.450302
    Language: English
    Publisher: The Tire Society
    Publication Date: 2017
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Wear and Related Topology of Rubber Surface
    The Tire Society ; 2014
    In:  Tire Science and Technology Vol. 42, No. 4 ( 2014-10-01), p. 200-215
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 42, No. 4 ( 2014-10-01), p. 200-215
    Abstract: The wear mechanism of rubber is complex, and the direct experimental observations of wear are limited. The understanding of the wear mechanism and its prevention are important aims and fields of investigation in the tire industry. The most straightforward way to quantify wear is a measurement of the mass loss after wear experiments. The different mass loss of different rubber materials is used to classify the wear performance of the materials. An additional way to obtain information about the different wear behavior of different compounds and the mechanism is to take a look of the worn surface of the wheels. After wear experiments with real tires on the street or small rubber wheels in laboratory, microstructures normal to the slip direction occur, the so called Schallamach waves. The kinematic analysis of these structures can lead to a deeper understanding of the wear mechanism. The surfaces of four compounds with a different wear performance are investigated in this paper with the aim of distinguishing them not just through the measured mass losses but also through an analysis of the surface and the extraction of a characteristic. This characteristic is recognized as the lateral displacement of the surface structures. It is quantified using a new evaluation technique based on the particle image velocimetry (PIV) method. The lateral displacement is compound specific and is observed parallel to the lowering of the altitude due to mass loss. In addition, the observed microstructures are used to add a new aspect of local plasticization to the well-established wear mechanism theory.
    Type of Medium: Online Resource
    ISSN: 1945-5852 , 0090-8657
    URL: Article
    DOI: 10.2346/tire.14.420401
    Language: English
    Publisher: The Tire Society
    Publication Date: 2014
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    Online Resource
  • 3
    Online Resource
    Online Resource
    An Analytical Thermodynamic Approach to Friction of Rubber on Ice
    The Tire Society ; 2012
    In:  Tire Science and Technology Vol. 40, No. 2 ( 2012-04-01), p. 124-150
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 40, No. 2 ( 2012-04-01), p. 124-150
    Abstract: The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.
    Type of Medium: Online Resource
    ISSN: 0090-8657 , 1945-5852
    URL: Article
    DOI: 10.2346/1945-5852-40.2.124
    Language: English
    Publisher: The Tire Society
    Publication Date: 2012
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Winter Tires: Operating Conditions, Tire Characteristics and Vehicle Driving Behavior
    The Tire Society ; 2010
    In:  Tire Science and Technology Vol. 38, No. 2 ( 2010-06-01), p. 119-136
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 38, No. 2 ( 2010-06-01), p. 119-136
    Abstract: The modern development process of winter tires not only requires intense subjective and objective evaluation of the tire properties on the vehicle, but also requires knowledge about the influence of relevant tire characteristics on vehicle driving behavior. It is important to understand the influences of ambient conditions, such as temperature, track surface (asphalt vs corundum) and tire inflation pressure on tire behavior. Tire characteristic results of a parametric study, using a fully climate-controlled interior drum test stand will be presented. The effect on tire characteristics and the resulting vehicle behavior will be discussed using vehicle dynamics simulation. Furthermore the consequences for an optimal design of modern high performance winter tires will be presented.
    Type of Medium: Online Resource
    ISSN: 1945-5852 , 0090-8657
    URL: Article
    DOI: 10.2346/1.3428961
    Language: English
    Publisher: The Tire Society
    Publication Date: 2010
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Investigations of Road Wear Caused by Studded Tires
    The Tire Society ; 2014
    In:  Tire Science and Technology Vol. 42, No. 1 ( 2014-01-01), p. 2-15
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 42, No. 1 ( 2014-01-01), p. 2-15
    Abstract: The use of studded tires has been a subject of controversy from the time they came into market. While studded tires contribute to traffic safety under severe winter conditions by increasing tire friction on icy roads, they also cause damage to the road surface when running on bare roads. Consequently, one of the main challenges in studded tire development is to reduce road wear while still ensuring a good grip on ice. Therefore, a research project was initiated to gain understanding about the mechanisms and influencing parameters involved in road wear by studded tires. A test method using the institute's internal drum test bench was developed. Furthermore, mechanisms causing road wear by studded tires were derived from basic analytical models. These mechanisms were used to identify the main parameters influencing road wear by studded tires. Using experimental results obtained with the test method developed, the expected influences were verified. Vehicle driving speed and stud mass were found to be major factors influencing road wear. This can be explained by the stud impact as a dominant mechanism. By means of the test method presented, quantified and comparable data for road wear caused by studded tires under controllable conditions can be obtained. The mechanisms allow predicting the influence of tire construction and variable operating conditions on road wear.
    Type of Medium: Online Resource
    ISSN: 1945-5852 , 0090-8657
    URL: Article
    DOI: 10.2346/tire.14.420101
    Language: English
    Publisher: The Tire Society
    Publication Date: 2014
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    Online Resource
  • 6
    Online Resource
    Online Resource
    Tire ABS-Braking Prediction with Lab Tests and Friction Simulations
    The Tire Society ; 2015
    In:  Tire Science and Technology Vol. 43, No. 4 ( 2015-10-01), p. 260-275
    Details
    In: Tire Science and Technology, The Tire Society, Vol. 43, No. 4 ( 2015-10-01), p. 260-275
    Abstract: The invention and application of antilock braking systems (ABS) has resulted in a significant improvement of traffic safety and a reduction of stopping distance, especially on wet roads [1]. The reason for this success is rather clear: ABS is designed to steer the braking process in the most efficient way by keeping an optimal level of tire slip. At the same time, it must be clear that ABS uses braking forces generated in the tire footprint, and really good braking is possible only with high-performance tires. The best way to probe tire performance is to build tires and test them. This is, however, a long and an expensive procedure, so prediction of ABS performance based on results of some simple experiments is a very attractive supplement to the development process. Tire-braking performance is related to the friction of rubber on a surface. Relevant friction mechanisms can include adhesion, rubber hysteresis, and various kinds of viscous friction. All of these phenomena depend on the local sliding velocity, load, and temperature of tread rubber. Tire blocks pass the footprint area of a braking tire very rapidly, but their dynamics are indeed influenced by ABS. All of these aspects make the problem of ABS-braking prediction very intricate. In this publication, we present an approach for prediction of the ABS-braking performance. The approach links friction measurements conducted in laboratory to tire tests results. The friction of six specially designed compounds was measured on dry and wet surfaces using a high-speed linear friction test rig. Obtained experimental results are analyzed with the aid of rubber friction theory [2,3] involving both surface and rubber as input parameters. It is demonstrated that lab friction test procedures can be used for prediction of ABS wet braking performance.
    Type of Medium: Online Resource
    ISSN: 1945-5852 , 0090-8657
    URL: Article
    DOI: 10.2346/tire.15.430401
    Language: English
    Publisher: The Tire Society
    Publication Date: 2015
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