Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
Knowledge of tire-road friction characteristics is essential for the proper performance of\nmost relevant vehicle active safety systems. Therefore, its determination is necessary to improve the\neffectiveness of these systems and to avoid or reduce the consequences of traffic accidents. For this\nreason, there is a great deal of literature concerning methods and devices for measuring and modeling\ntire-road friction. Most of these methods have focused on determining the road friction resistance,\ntaking only road composition and making measurements in wet conditions into account. However,\nfriction forces are also dependent on the tire type, since the contact is established between the tire and\nthe road in real driving conditions. Thus, the type and characteristics of the tire have to be considered\nin the study of the interaction between the vehicle and the road. The aim of this work is to unify\nthe study of the friction coefficient, taking into consideration the two existing bodies involved in the\ncontact, i.e., the tire and road and the main factors that influence the forces in the contact. To this\nend, a modification of the Pacejka Magic Formula is proposed to include the effects of the main\nparameters that influence the contact, such as road composition and its state, tire type, vehicle speed,\nand slip between the tire and the road. To do so, real tests have been conducted on several roads\nand with different operating conditions. As a result, a more accurate tire-road friction model has\nbeen obtained....
In this study, we analyze the deficiencies of specific frictional resistance in heating engineering. Based on economic specific\nfrictional resistance,we put forward the concept of comprehensive specific frictional resistance,which considers themultiple factors\nof technology, economy, regulation modes, pipe segment differences, and medium pressure. Then, we establish a mathematical\nmodel of a heating network across its lifespan in order to develop a method for determining the comprehensive specific frictional\nresistance. Relevant conclusions can be drawn from the results. As an application, we have planned the heating engineering for\nYangyuan County in China, which demonstrates the feasibility and superiority of the method....
An ultra-thin water film plays the decisive role in steelââ?¬â??ice friction in bobsleighing.\nThe water film has a thickness on the order of nanometers and results from the superposition of an\nexisting quasi-liquid layer and additional surface water generated by frictional heat. When friction is\nmeasured as function of sliding velocity, the coefficients decrease according to the typical Stribeck\nbehavior. However, for highest sliding velocities, it is still unknown whether friction decreases\nfurther or shows an increase due to viscous drag. Both tendencies are essential for the construction of\nsafe bobsleighs and bobsleigh tracks. This contribution presents results of high-speed experiments\nup to 240 km/h for a steel slider on a disk of ice at different ice temperatures. In addition, using\nthe friction model of Makkonen, friction coefficients were calculated as function of sliding velocity\nand ice temperature. The significant correlation between experimental results and model calculation\nsupports the model conception of frictional melting and viscous shearing....
Hydroxyl groups play an important role in friction of graphene oxides. In this paper,\nthe influence of hydroxyl groups on friction of graphene is investigated by molecular dynamics\nsimulation. The results show that the friction does not always go up with the rising of hydroxyl\ngroups ratio, and reaches the maximum when the hydroxyl groups ratio between interfaces is about\n10%. The reason is that hydrogen bonds tend to form in interlayers when the hydroxyl groups\nratio is high. The formed hydrogen bonds between interfaces are closely related to the friction.\nHowever, the analysis of the component of van derWaals, Coulomb�s forces and hydrogen bonds\ninteraction between interfaces indicates that van der Waals forces are dominant in friction, which can\nbe attributed to the influence of interface distance on friction....
The aim of this work is to investigate the durability of tool steels for hot stamping by comparing the wear resistance of three hot\nwork tool steels. Friction and wear behaviours of different tool steels sliding against a 22MnB5 uncoated steel at elevated\ntemperatures were investigated using a high-temperature version of the Optimol SRV reciprocating friction and wear tester at\ntemperatures of 40 and 200�°C. Our results show that friction decreased with increasing temperature, whereas wear of the tool steel\nincreased with temperature for the second and the third tested tool steels. The slightly better wear behaviour of steel specimen 1\ncomes from the hardness of the carbides in the martensitic microstructure, which are rich in vanadium....
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