Proceedings of SerbiaTrib '13

Advantages and disadvantages of traditional andmodern approaches of surface analysis based onconcepts of roughness and texture are discussed inthe paper [3]. Authors considered that traditionalconcept of rough surface based mainly on profileparameters is not fully satisfied modern trends intribology. This paper presents a review of theproblems of rough surfaces analysis in theirevolution from statistical height and stepparameters of profiles to dimensionless and scaleinvariant representation of surface texture. Theyconcluded that texture analysis can be efficientlyapplied for solving practical tribological problemsin micro/nanoscale.Paper [4] presents a study on the surface qualitypointing out the influence of relative sliding on thetopography parameters. A comparative study of thesurface topography, obtained by changing a singleparameter during the tests, may reveal at least aqualitative influence of this parameter that could beuseful for practicians.The authors in paper [5] investigated theboundary friction model, which is built up by thesurface topography. The model contained the effectof boundary film, adhesion, plough and lubrication.Based on the model, a coefficient for weakeningplough for the lubrication was proposed. Themodified model could fit for the working conditionof wet friction elements.In the paper [6] authors indicate that staticfriction is necessary for vehicle starting and runningand show comparative information of static frictionexperiment of prismatic steel samples slip andtribology studies of the wheel-rail contact.The new friction coefficient calculationprocedure based on the Molecular-mechanicaltheory of friction is proposed in the paper [7]. Thisprocedure considers roughness parameters andhardness of contact surfaces, as well as therelationship between the deformation component ofthe static friction coefficient and the total staticfriction coefficient determined experimentally forspecific tribological conditions. Studied tribologicalconditions in the research are related to the press fitjoints of railway vehicles drive unit components.The proposed model considers experimentalresearch of tribomechanical pairs at which plasticdeformations exist in the real area of contact.A review of standards and methods of slipresistance measuring provided by flooring andfootwear suppliers in United Kingdom is presentedin paper [8]. It can be seen that a lot of suppliersdidn’t specify date about the slip resistance of theirproducts.The lack of international standards for the slipresistance of ceramic tiles is stated in the paper [9].The paper considers recent and current potentialdevelopments in the international standardization ofslip resistance. It identifies some limitations of wetbarefoot ramp test, and suggests that changesshould be made.The paper [10] researches the friction betweenrubber and metal which can significantly influencesdamping characteristics of the rubber-metal springs.In the framework of the experimental research thathas being conducted the coefficient of the staticfriction between the rubber and metal has beenestablished in different contact conditions.Moreover, compressions of rubber-metal springsare also performed and force-deflection diagramsare recorded. In this way, the mutual influence ofthe static friction between the rubber and the metalpad and the accumulated/absorbed energy within arubber-metal spring is analyzed.Tribological approach of the contact footwearflooris the subject of research that has started atFaculty of Mechanical Engineering in Niš.Experimental research of static friction of footwearrubber samples and different types of floormaterials is presented in this paper.2. STATIC FRICTIONIn order to achieve vehicle wheel turning on theroad, it is necessary to have the drive torque as wellas a force of resistance in the wheel-road contact.Similarly, in order to make walking on the floorpossible, a drive force delivered by the legs and aforce of resistance in the footwear-floor contact areneeded. This resistance is the static force of slidingfriction. So, wheel rolling is achieved through thestatic friction force of sliding. Likewise, pedestriancan walk with the help of static friction force.Friction represents a resisting force that opposesrelative motion of bodies’ surfaces that are incontact. According to the state of moving, i. e. tothe resultant tangential force that induces movingthere are two types of friction. The static friction orthe stationary state friction that exists when theresultant tangential force is lower than thesummation of all resistances that oppose movingand the kinetic friction or the moving state frictionwhen the force that induces moving is greater thanthe summation of resistant forcesThe diagram F(s) in Fig. 1 shows that the forceincreases from the point O to the point A, where themaximal value of the force is achieved. That is thestatic friction force (Fs). The static friction forcerepresents a maximal tangential resistant force thatacts during so called boundary relativedisplacement. Boundary displacement (preslidingmovement) can be defined as a micro moving offrictional surfaces that goes before visible or macromoving of surfaces in mutual contact (the part OA13 th International Conference on Tribology – Serbiatrib’13 303