Proceedings of SerbiaTrib '13

to obtain the temperature distributions and thestresses. The results show the significant effect ofthe thermal load on the temperatures and stresses;therefore it is desirable to increase the thickness ofthe pressure plate as much as possible to increasethe thermal capacity of the pressure plate to reducethe thermal stresses. High stress intensity valueoccurs around the fillet region of the window in thehub plate.Shahzamanian et al. [3] used numericalsimulation to study the transient and contactanalysis of functionally graded (FG) brake disk.The material properties vary in the radial directionfrom full-metal at the inner radius to that of fullceramicat the outer radius. The coulomb contactfriction is considered between the pad and the brakedisk.Two-dimensional finite element model used inthe work to obtains the pressure distribution, totalstresses, pad penetration, friction stresses, heat fluxand temperature during the contact for differentvalues of the contact stiffness factor. It was found,that the contact pressure and contact total stressincrease when the contact stiffness factor increasesand the gradation of the metal–ceramic hassignificant effect on the thermo-mechanicalresponse of FG brake disks. Also, it can beconcluded when the thickness of the pad increasesthe contact status between pad and disc changesfrom sticking to contact and then to near contact.Abdullah and Schlattmann [4-8] investigated thetemperature field and the energy dissipated of dryfriction clutch during a single and repeatedengagement under uniform pressure and uniformwear conditions. They also studied the effect ofpressure between contact surface when varyingwith time on the temperature field and the internalenergy of clutch disc using two approaches heatpartition ratio approach to compute the heatgenerated for each part individually whereas thesecond applies the total heat generated for thewhole model using contact model. Furthermore,they studied the effect of engagement time andsliding velocity function, thermal load anddimensionless disc radius (inner disc radius/outerdisc radius) on the thermal behavior of the frictionclutch in the beginning of engagement.In this paper the finite element method used tostudy the contact pressure and stresses during thefull engagement period of the clutches usingdifferent contact algorithms. Moreover, sensitivitystudy for the contact pressure is presented toindicate the importance of the contact stiffnessbetween contact surfaces.2. FUNDAMENTAL PRINCIPLESThe main system of the friction clutch consistsof pressure plate, clutch disc and flywheel as shownin figure 1.TTorqueFlywheelFigure 1. The main parts of clutch systemThermal +Contact pressureSlipping period(Transient case)Thermal +Contact pressure+Centrifugal effectFull engagementperiod(Steady-statecase)TimeFigure 2. The load conditions during theengagement cycle of the clutchWhen the clutch starts to engage the slippingwill occur between contact surfaces due to thedifference in the velocities between them (slippingperiod), after this period all contacts parts arerotating at the same velocity without slipping (fullengagement period). A high amount of the kineticenergy converted into heat energy at interfacesaccording to the first law of thermodynamics duringthe slipping period and the heat generated betweencontact surfaces will be dissipated by conductiont sClutch discPressure plate13 th International Conference on Tribology – Serbiatrib’13 211