Jerzy Ejsmont

INFLUENCE OF TREAD PATTERN ON TIRE/ROAD NOISE

An indoor road-wheel facility at the Technical University of Gdansk was used to study the noise emission from a variety of tires with different tread patterns. The tires were run both on a smooth steel drum and a drum covered by a replica road surface. All tread patterns were hand-cut to generate several families of simple treads with regular pitch for a systematic study of how groove design influences noise. Most of the observed, tread influenced phenomena could be explained by generation mechanisms such as radial vibrations induced by tread block impact, pocket air pumping and pipe resonances in the grooves. For instance, it was observed that, when speed increases, sooner or later the tread block impact frequency will coincide with the pipe resonance frequency, and then generate excessive noise at that speed.

Road Texture Influence on Tire Rolling Resistance

Tire rolling resistance is one of the most important resistive forces acting on road vehicles. It depends on tire and surface characteristics as well as vehicle operating parameters. This paper deals with the influence of road surface texture on rolling resistance of passenger car tires. Results of road measurements performed on variety of road surfaces are presented.

Road texture influence on tyre rolling resistance

Tyre performance, one of the critical factors for vehicle users, is strongly related to the road surface characteristics, most notably to the pavement texture. Phenomena that occur at the tyre/road interface affect tyre friction (skid resistance), rolling resistance, tyre wear and tyre/road noise. This article deals with relationship between surface texture and rolling resistance of light and heavy vehicle tyres. Mean profile depth (MPD) is one of the most common descriptors of road surfaces and in many studies it is correlated with rolling resistance of tyres. Results of measurements performed by the Technical University of Gdańsk show that although the correlation exists, it is not very strong and regression between MPD and rolling resistance is not linear. The key reason for this is partial enveloping of the tyre tread interacting with pavement texture. The article presents results of laboratory and road measurements of rolling resistance performed on road surfaces characterised by MPD from 0.20 up to 4.75 mm and the correlation of the rolling resistance coefficient with MPD. Certain aspects of texture enveloping and influence of this phenomenon on rolling resistance are discussed.

Rolling resistance and tyre/road noise on rubberised asphalt pavement in Poland

The paper presents results of tyre/road noise and rolling resistance measurements performed on stone mastics asphalt (SMA) that contains rubberised asphalt, developed and produced by a refinery in Poland. Bituminous binder was modified with polymer and addition of crumb rubber. The first observations of asphalt mixture with the new kind of modified bitumen used on the field section are presented. Rolling resistance of passenger car tyres was measured by test trailer R2 Mk.2. Tyre/road noise was measured by a Tiresonic Mk.4 trailer using the close proximity method. Measurements were performed for 50 and 80 km/h and the results obtained on test and reference sections covered with conventional SMA 11 were compared.

Analysis of Rolling Resistance of Tires with Run Flat Insert

Run flat properties are required for tires intended for special applications like military or rescue vehicles. Run-Flat inserts make possible to drive a car or truck, with certain restrictions, also when inflation pressure is very low or non-existing (after tire damage). Rolling resistance of tires rolling on the inserts increases considerably in relation to the rolling resistance of properly inflated tires. This paper presents results of rolling resistance measurements for such conditions.

Directivity of tire/road noise emission for selected tires and pavements

Road traffic noise reduction of drainage pavement with small air gaps among grains is well known. However, traffic flow over many years fills those gaps with mud and sand, thereby degrading the noise reduction effect. To regain that effect, cleansing or reconstructing the pavement is necessary after precise assessment of the air gaps. For that purpose, acoustical diagnoses of drainage pavement are proposed and test results are introduced. One method is to check sound absorption of the pavement surface, which normally has high absorption near frequencies of 1 kHz, which is related to the reduction of road traffic noise. The use of a particle velocity sensor together with a microphone greatly simplifies measurements and judgments. Another analysis method is based on sound propagation through air gaps in the pavement. Transmission characteristics clearly indicate pavement conditions. Low-attenuation sound transmissions are shown in a wide frequency range below 1 kHz for sound air gaps, and weak transmissions in a narrow frequency range are shown when air gaps are filled. These acoustic diagnostic methods are effective in investigating porous drainage pavement.

Reduction of road traffic noise by source measures â–” present and future strategies

The current trend worldwide is less focused on reducing road traffic noise. This is in strong contrast to the severe impact of traffic noise to the general health and quality of life. A more holistic and combined strategy is needed. Current international rules and regulations regarding vehicles and tyres are not sufficient to reduce traffic noise levels in an effective way. Calculations show that these regulations will only yield a reduction of approximately 1.5 dB in Lden levels for urban traffic. Additional measures need to be implemented. By combining optimized tyres and road surfaces, a noise reduction of 4â–“6 dB can be achieved. Such tyres are currently being developed for electric and hybrid-electric vehicles. In addition to noise reduction, these tyres have less rolling resistance that can reduce vehicle energy consumption up to 15% on normal road surfaces. However, there are several obstacles still to be removed, such as the effectiveness of the EU tyre labeling system, and the implementation and durability of low-noise road surfaces. These challenges are discussed in the article.

Tyre rolling resistance and its influence on fuel consumption

Rolling resistance of tyres is one of the major resistive forces acting on any wheeled vehicle. Unfortunately, it is also one of the forces very difficult to measure. It is estimated that in certain traffic conditions (like for example constant speed driving with slow or moderate speed) so called Rolling Resistance Impact Factor may be as high as 0.3. This means that reduction of rolling resistance by 50% would lead to 15% of energy savings. The paper presents road measuring method of tyre rolling resistance and unique equipment used by the Technical University of Gdansk designed to perform measurements of passenger car tyres. It also discusses road pavement, tyre and environmental conditions influence on rolling resistance. Also selected data describing current situation related to rolling resistance on different road pavements and rolling resistance of modern passenger car tyres including tyres specially designed for electric and hybrid vehicles are presented.

Innovative run flat systems

One of the most essential threats to the mobility of wheeled vehicles is their relatively high sensitivity to tire damage. Tires can be damaged as a result at vehicle-targeting fire, after running on a mine or an improvised charge. The purpose of the article is to analyze the current technical solutions in wheeled vehicle tires, allowing for the unobstructed use of the vehicle despite the damage of one or several tires (RUN FLAT systems). Since RUN FLAT systems have become increasingly popular in passenger cars as well, the article contains partial references to civilian solutions. One should remember that RUN FLAT systems are not only to guarantee vehicle mobility following the loss of pressure in the tire in straight-line motion, but also crew safety providing sufficient driving level and stability at longer distances. The article presents solutions of this type, applied not only in military vehicles, but also considers research-structural works implemented by ROSOMAK S.A. in cooperation with other centres. The works presented in this article were financed by ROSOMAK S.A. and National Research and Development Centre (NCBiR) (project SPB – RolRes, agreement no PBS1/A6/1/2012).

RESEARCH ON OPERATIONAL CHARACTERISTICS OF TYRES WITH RUN FLAT INSERT

The paper describes results of research on heavy vehicle tyre with Run Flat VFI insert. The experiment has included the determination of heat generation, rolling resistanceand radial stifnessof two different tyre designes (textile and steel carcass). The results have been used for the purpose of ewalution of tyre operating characteristics. The study included research on non-inflated tyre properties. The purpose of the paper is nto determine chracteristics of the tyres equipped with inserts, which are essenical for driving wheeled APCs. The inserts are composed of polymer rings mounted on rims inside the tyres. If the inflation pressure of the tyres is very low or of there is no inflation pressure at all, the rings transfers the loads imposed on the tyre to the run. Usually in such a case, there is coctact of the ring and inn er surdace of the tyre tread area. Laboratory facility for surveys of heavy vehicles tyres summary characteristicsof radial stiffness and histeresis of the tyres, temperature destribution on the external surface of the test tyre, comparison of radial characteristics of the tyres tested, example of stiffness characteristics, destribution of the temperature on the side of tyre during the road test and carcass damages on the flat tyre are presented in the paper.