Stribeck curves characterization of lubricants for. E ect of friction, when relative velocity between the two contact surfaces is zero, cannot be described by the static friction model. Characterization of lubricants for research and development, quality control and application engineering. Historical background and the discovery of the hydrodynamic effect. The load characteristics of a flow regulator have a profound influence on the working quality of a ducted rocket. The importance of the stribeck curve in the minimisation of engine. Pdf stribeck curve under friction of copper samples in the. The stribeck curve is a graphical representation of the friction coefficient as a function of the ratio. Stribeck curve starved lubrication mixed lubrication film thickness oil layer thickness over roughness ratio. Development of a set of stribeck curves for conformal. Evaluating the potential applications of lubricants with the umt tribolab and stribeck curves. Controlling stickslip noise generation with lubricants. Tribology 101 introduction to the basics of tribology. At present there is no standard published test method that can be used for generating a stribeck curve, either in unidirectional motion or in reciprocating motion.
It can be seen from figure 2 that when the liquid film thickness, sliding speed, normal force. On the stribeck curves for lubricated counterformal contacts of rough surfaces article pdf available in journal of tribology 72 april 2015 with 1,228 reads how we measure reads. Influence of tribology size effect on stribeck curve in micro deep drawing. Characterizing food by tribology r heology has been used for many years to characterize the flow prop erties of foods and beverages, and rheological measurements have been well correlated with results of sensory evaluation. Consideration of stribeck diagram parameters in the. Boundary, mixed and fluidfilm lubrication, shown by the three classic regions on an idealized stribeck curve, were all demonstrated using metalonmetal joints in a hip simulator. The stribeck curve is an overall view of friction variation in the entire range of lubrication, including the hydrodynamic, mixed, and boundary lubrication. Furthermore, a dynamometer brake test was conducted to determine the characteristic system parameters of the 7dof vibration model. Bearing number can be defined as sliding velocity, what we are talking. On the stribeck curves for lubricated counterformal contacts of. The stribeck curve is a more advanced model of friction as a function of velocity. Engineering tribology pdf free download free ebook engineering tribology pdf free download free ebook. Surface roughness for specified values of surface pattern number is generated assuming a gaussian height distribution and stribeck type.
Stribeck curve is a discontinuous nonlinear function. Stribeck curve for starved concentrated contacts springerlink. The effect of surface pattern on frictional characteristics of lubricated contact is studied. Friction coefficient increases with increasing bearing characteristic number in stribeck curve. The discovery and underlying research is usually attributed to richard stribeck and mayo d. Analyses concerning the wear coefficient by archard equation were also.
How to measure, prevent, and eliminate stickslip and. Hersey, who studied friction in journal bearings for railway wagon. Pdf the effect of cu grain size on transition from ehl. The following calculations were made using the friction coefficients at the breakaway point m. The surface roughness of the journal and the bearing and material. Generating a stribeck curve in a reciprocating test. Wear 263 2007 592597 case study tribological characterization of electroless nip coatings lubricated with biolubricants a. An algorithm based on the loadsharing concept is developed which assumes that the total transmitted load is carried by the asperities as well as the fluid film. Pdf on the stribeck curves for lubricated counterformal. Pdf experimental and numerical investigations of the stribeck. This paper discusses a mixed lubrication model in order to predict the stribeck curve for starved lubricated line contacts.
The lambda ratio is the ratio of the predicted minimum film thickness to the combined surface roughness of the articulating surfaces 19. In the stribeck curve the friction coefficient is plotted as function of the hersey number he, which is defined as. Using the nanovea tribometer advanced stepless speed control, from 15000 to 0. The stribeck curve was plotted according to the velocity and friction, and then a genetic algorithm was used to acquire the model parameter basis on the stribeck curve in reference. Although it is still valid only in steady state, it includes the model of coulomb and viscous friction as builtin elements. A 7degreeoffreedom dof vibration model of a fixedcaliper disc brake system was developed herein based on the stribeck effect. The variables were speed, load, temperature and lubricant composition. The stribeck curve based on the thermodynamic model was simulated and experimentally confirmed by friction tests on silicon wafer substrates modified with different free energies. Pdf the friction and wear of a pure copper block 99. While rheology has been used for many decades, tribologythe science and technology related to fric. The stribeck type curves obtained show clear differences due to rheological properties. During whirl, the friction torque is higher and has a positive slope. The stribeck curve is an overall view of friction variation over the entire spectrum of lubrication, including the boundary, mixed, and fullfilm hydrodynamic or. One way of depicting these regimes is by use of the stribeck curve shown in figure 1.
By means of the stribeck curve the transitions from boundary lubrication to mixed lubrication and the transitions from mixed. The effect of cu grain size on transition from ehl to bl regime stribeck curve. Pdf the stribeck curve shows the friction coefficient as a function of speed, viscosity and load. Tribological properties of ionic liquids intechopen. Tribology is the science and technology of interacting surfaces in relative motion. The different modes of lubrication prevalent in the joints resulted in wear rates spanning two orders of magnitude between joints differing principally in diameter. Aade17ntce100 evaluation of measurement techniques. Pdf prediction of the stribeck curve under fullfilm. Effect of internal clearance on load distribution and life of radially loaded ball and roller bearings. For rolling to sliding contacts, three lubrication regimes are distinguished. When the surface roughness varies, the shape and the position of the stribeck curve will also change. Pdf the stribeck curve is an important means to demonstrate the frictional behavior of a lubricated interface during the entire. Zhang1,2 1complex and intelligent system laboratory, school of mechanical and power engineering, east china university of science and technology, shanghai, china.
Stribeck curves generated using reciprocating test mode. The stribeck curve shows friction as a function of viscosity. Meanwhile, the stribeck curve of the lubrication system presents transition lubrication regime with minimum friction coefficients, namely, valley zone. The stribeck curve plays an important role in identifying boundary, mixed, elastohydrodynamic, and hydrodynamic lubrication regimes. The stribeck curve the stribeck curve indicates friction as a function of linear or rotational speed. Case study tribological characterization of electroless.
Stribeck curve is only valid when roughness of the rubbing surfaces remains the same. Thermodynamics model for stribeck curve and experiments. Effect of surface pattern on stribeck curve springerlink. Based on friction experiments on bearings, stribeck expressed the relationship between the friction coefficient f, viscosity of the lubricating oil. The tests allow the conclusion that stickslip occurs solely in the declining branch of the stribeck curve fig. The translational friction block represents friction in contact between moving bodies. It shows that friction in fluidlubricated contacts is a nonlinear function of the contact load, the lubricant viscosity and the lubricant entrainment speed. During stickslip vibration, the friction curve shows a stribeck effect, which explains the instability of steady rotation. Additional standard reciprocating test capabilities. Please use one of the following formats to cite this article in your essay, paper or report. The bulk flow properties of the liquid play little or no part in the friction and wear behavior.
The viscosity of the lubricant also plays a critical role in defining the characteristic form of the stribeck curve. It includes the study and application of the principles of friction, lubrication and wear. Evaluating the potential applications of lubricants with. Consideration of stribeck diagram parameters in the investigation on wear and friction behavior in lubricated sliding this paper deals with an experimental study of both wear and friction responses of lubricated sliding tests, considering both responses in stribeck diagram. Peter jost in england in 1966 the jost report, provided to the british parliament. Boundary lubrication is lubrication by a liquid under conditions where the solid surfaces are so close together that appreciable contact. Friction force corresponds to shear resistance of fluid film between two bodies. Influence of tribology size effect on stribeck curve in micro deep. Tribology is the science and engineering of interacting surfaces in relative motion. This curve brilliantly captures the characteristics of various lubrication regions, including i boundary. Results indicate that certain aspects of the stribeck curve can offer an insight into the correlation between the frictional behaviour of food to their sensory feel. This model is based on a combination of the contact model of greenwood and williamson and the elastohydrodynamic ehl film thickness for starved line contacts.
Load characteristics and modeling methods for the flow. This model was developed to study the effects of braking conditions, such as disc rotational speed and brake pressure on brake noise. Load journal bearing thick film thin film, mixed boundary. Space tribology is a subset of the lubrication field dealing with the reliable performance of satellites and spacecraft including the space station. Research article dynamic friction parameter identification. The friction force is simulated as a function of relative velocity and is assumed to be the sum of stribeck, coulomb, and viscous components, as shown in the following figure. The stribeck curve is a fundamental concept in the field of tribology. Stribeck curve is basically a curve between coefficient of friction and bearing number. Stribeck curves during the slowdown phase of the system. This paper presents the results of research on the friction of a journalbearing conformal contact system in the form of stribeck curves through numerical simulation. Two solid bodies are completely separated by fluid film. The hydrodynamic range represents the ideal operating conditions for sintered sliding bearings. This chapter covers the changes in frictional processes encountered in passing from boundary lubrication at the start of motion, to mixed film lubrication at the lowest surface speeds, and finally to lift off with development of a.