Proceedings of SerbiaTrib '13

etween friction clutch components and byconvection to environment, in addition to thethermal effect due to the slipping there is other loadcondition which is the pressure contact betweencontact surfaces. In the second period, there arethree types of load conditions the temperaturedistribution from the last period (slipping period),the pressure between contact surfaces due to theaxial force of diaphragm spring and the centrifugalforce due to the rotation of the contacts parts.Figure 2 shows the load conditions during theengagement cycle of the clutch, where t s is theslipping time and T is the transmitted torque byclutch.3. FINITE ELEMENT FORMULATIONThis section presented the steps to simulate thecontact elements of friction clutch using ANSYSsoftware. Moreover it gives more details about thetypes of contacts and algorithms which are used inthis software.The first step in this analysis is the modelling;due to the symmetry in the geometry (frictionallining without grooves) and boundary conditions ofthe friction clutch (take into the consideration theeffect of the pressure and centrifugal force loads,and neglected the effect of thermal load due to theslipping), two-dimensional axisymmetric FEM canbe used to represent the contact between the clutchelements during the steady-state period as shown infigure 3.There are three basic types of contact used inAnsys software single contact, node-to-surfacecontact and surface-to-surface contact. Surface-tosurfacecontact is the most commonly type ofcontact used for bodies that have arbitrary shapeswith relative large contact areas. This type ofcontact is most efficient for bodies that experiencelarge values of relative sliding such as block slidingon plane or sphere sliding within groove [9].Surface-to-surface contact is the type of contactassumed in this analysis because of the large areasof clutch elements in contact.In this work, it has been assumed two types ofload conditions effects on the clutch system duringthe steady-state period (full engagement period) thecontact pressure between clutch elements due to theaxial force by diaphragm spring and the centrifugalforce due to the rotation.The elements used for contact model are: “Plan13” used for all elements of theclutch (flywheel, clutch disc and pressureplate). “Conta172” used for contact surfaces thatare the upper and lower surfaces of clutchdisc. “Targe169” used for the target surfacesthat are the lower surface of the flywheeland the upper surface of the pressure plate.Figure 4 shows the details about schematic for allelements that has been used in this analysis.zTarge169rThe frictional liningFlywheelPressure plateAxialFigure 3. The Contact model for clutch systemPlane13FlywheelClutch discConta172Pressure plateFigure 4. Schematic elements used for the friction clutchelementsThe stiffness relationship between contact andtarget surfaces will decide the amount of thepenetration. Higher values of contact stiffness willdecrease the amount of penetration, but can lead toill-conditioning of the global stiffness matrix andconvergence difficulties. Lower values of contactstiffness can lead to certain amount of penetrationand low enough to facilitate convergence of thesolution. The contact stiffness for an element ofarea A is calculated using the following formula[10]: f e f i iTFkn dA(1)The default value of the contact stiffness factorFKN is 1, and it is appropriate for bulkdeformation. If bending deformation dominates thesolution, a smaller value of KKN = 0.1 isrecommended.There are five algorithms used for surface-tosurfacecontact type are: Penalty method: this algorithm used constant“spring” to establish the relationship betweenthe two contact surfaces (figure 5). The contact212 13 th International Conference on Tribology – Serbiatrib’13