NATIONAL TRIBOLOGY CONFERENCE 24-26 September 2003 THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, TRIBOLOGY 2003 ISSN 1221-4590 243 INFLUENCE OF COMMANDING PARAMETERS ON THE SURFACE QUALITY FOR ROLLER - ROLLER TRIBOMODEL Nicolae Diaconu, Lorena Tomescu, Minodora Rîp ă , Iulian Gabriel Bîrsan University “Dunărea de Jos” of Galaţi, Romania nicolae.diaconu@ugal.ro ABSTRACT This paper presents the influence of commanding parameters as load and relative sliding speed, on the surface characteristics. Tests were done on roller- roller tribomodels. There were studied the influence of load, relative sliding speed and lubricant on the skewness and the kurtosis of the surface profile but also on common parameters as Ra and Rz. Such a study may be used for selecting a suitable lubricant (especially grease), after test under severe conditions, very close to the actual ones. KEYWORDS: surface characteristics, surface profile, tribomodel, grease, friction, wear. 1. INTRODUCTION Traditional roughness parameters as Ra and Rq, deal only with relative vertical distance of asperities to the mean line and they give no infor- mation on shape, slope and asperities magnitude, on their appearance frequency on the profile length [2]. This paper will analysed parameters defined in table 1 and figure 1. The parameters Ra, Rt, Rz, Rtm, Rq, Rmax give the magnitude on the profile height but it is recommended to use distribution moment for obtain information on asperities’shape [2], [4], [6]. For evaluating the quality of a surface, the most useful are the moment of second, third and fourth order, symbolised by Rq, Rsk, Rku, respectively. The shape of the asperities is adequate represented by Rsk and Rku. Fig. 1 Profile characterisation. 2. METHODOLOGY Tests were done on tribomodels roller – roller as coded in table 2 (TR – heat-treated steel and grinded, N – untreated steel). Rollers 6E and 6F were kept as witness samples and they were made of steel grade OLC25/OLC 45, treated and grinded. Profile parameters were recorded and cal- culated by the help of Surtronic 3+ and Talyprof (Taylor-Hobson®). Analysed length was ~4mm or ~8mm for every measurement, the cut-off length being 0.8mm. The parameter values were calculated for the non-filtered profiles. For every roller, there were done Table 1. Analysis Parameters Profile Parameter Relationship The arithmetic mean of the departures of the profiles from the mean line (µm) ∑ = ≅ n i i a y n R 1 1 The maximum depth of the profile under the mean line (µm) Rv The maximum height of the profile above the mean line within the assessment length (µm) Rp The maximum peak to valley height, in the assessment length (µm) Rt The RMS corresponding to Ra (µm) ∑ = = n i i y n Rq 1 2 ) ( 1 Skewness (measure of symmetry of the amplitude distribution curve about the mean line) ( ) ∑ = = n i i y n Rq Rsk 1 3 3 1 1 Kurtosis (a measure of the sharpness of the amplitude distribution curve) ( ) ∑ = = n i i y n Rq Rku 1 4 4 1 1 The mean distance between two consecutive peaks (µm) RS The mean spacing between profile peaks at the mean line (µm) RSm