Effect of flank angle and friction coefficient on contact stress of turbine rotor

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J.Cent.South Univ.(2013)20：1792-1796DoI：10.1007/sl1771-O13.1674.9Effect offlank angle and friction coe垒Springercient on contact stress of turbine rotorwu Xiao-zan(伍晓赞)，TAO Qing-bin(陶庆斌)，CHEN An-ping(陈安平)，XU Hui(徐慧)1.School of Physics Science and Technology，Central South University，Changsha 4 1 0083，China；2.School ofMaterials Science and Engineering，Central South University，Changsha 410083，China◎ Central South University Press and Springer·Verlag Berlin Heidelberg 20 1 3Abstract：In order to simulate the stress Of turbine rotor in aeroengine.based on the ANSYS.the simplifcation model of the turbinerotor was built up.By applying the simplifcation mode1.the contact stress of turbine rotor was computed.The maximum contactstress appears at the chamfer below the flank.which agrees with experiment result.At tl1e same time.the contact stress changing withthe flank angle and friction coeficient was calculated.The results show that the contact stress in the flank increases slowly with theincrease of flank angle；with the friction coefi cient increasing.the contact stress in flank 1ength decreases；the contact stress wil notchange when the friction coefficient is over 0.25。

Key words：aeroengine；contact stress；ANSYS；optimization designl Intr0ductiOnAs a critical component of aeroengine.turbine rotoris more complex.High stress and strain wil1 aDpear inloca1 area when it works which easily leads to al kindsof failures.Through the stress anabrsis on the turbinerotor.failure 1ocation and the maximum stress point canbe determined.Strain-gaga electrical logging method，optical fiber grating test method and photoelastic methodare widely used in the determination of the stress and thestrain.but these methods are not good in the economicrespect and safety.So.it is necessary that the computersimulation method is used in the structural design of theturbine rotor. The analytic method 1]，boundarycoordination method2-5]，finite element method6-81，boundary element method，mechanics method，weightfunction method9-1 2]and 1inear spring mode1 can beused as the theoretica1 foundation of computer simulation。

W ith the growth in computing power of currentcomputers，computationally expensive finite element(FE)method has become a common and important techniquein the product development process.which is necessaryin the optimization of flank angle.flank 1ength andfriction coemcient of turbine rotor.PAPANIKOS et al[1 3-1 61 have used nonlinear finite element method andexperimental methods to research the distribution oftwo-dimension and three.dimension models of the stressfield.ZBOINSKI1 7-1 81 has found that the max stressgradient appears close to the chamfer of the circulargears by the finite element method.HE and RUIZ[1 9]has predicted several danger point and positions of theinitial cracks through the smal1 size sample.LUCJAN[20]has analyzed the turbine contact stress by the MSCsoftware，from which six danger points of the turbinewere found.D G et al 21] have analyzed thethree.dimensional nonlinear cyclic stress and strain ofturbine rotor，considering the aeolotropies of the bladematerial，the contact between turbine gear and blade，thecomposites elastic.plastic deformation.the non.uniforlTltemperature and many other nonlinear factors。

Previous studies were conducted on the simulationsof contact stress and failure on the turbine rotor，butrarely focused on the effect of contact stress by flankangle flank length and friction coefi cient.In this work，the contact stress of the simplifying model of turbinerotor changing with the flank angle and frictioncoefi cient was calculated by the finite element sofiwareANSYS.The results wil provide guidelines for theoptimization design and fatigue analysis of the turbinerotorinthefuture。

2 Simplification model of turbine rotor andfinite element model2.1 Simplification model of turbine rotorThe turbine rotor works in a bad and complexworking condition with high temperature and high speedand its structure is more complex.The structure ofFoundation item：Project(1774-107101027)supposed by the National Defense Fund of China；Project(1343-74236000006)supposed by the GraduateFoundation of Hunan Province，ChinaReceived date：2012-03-13：Accepted date：2012-07 01Corresponding author：XU Hui，Professor，PhD；Tel：86 731-88836762；E-mail：cmpxhg###CSU edu.cnJ.Cent.South Univ.(2013)20：1792-1796 1795maximum contact stress is calculated at the flank anglesof 45。，50。，55。，60。，65。，70。and 75。.Table 2 gives themaximum contact stress changing with flank angle，including the maximum contact stress at the flank anglesof 45。，50。，55。，60。，65。，70。and 75。.W hen the flankangle increases.the blade assemble in the turbine discbecomes untwisted and runs away easily. So，themaximum contact stress increases with the increase offlank angle。

that：1、The contact stress of the flank decreases with theincrease of仔iction coeficient；2、The contact stressdecreases more and more slowly when frictioncoefi cient is over 0.25.This is because when the frictioncoefi cient increases to certain degree，the blade becomesfirm enough in the turbine disc.When the frictioncoeficient increases again，the contact stress changeslittle。

Table 3 Maximum contact stress changing with frictionTable 2 Maximum contact stress chanzinwith flank anle coe衔 cientFigure 7 shows the contact stress changing withflank length at different flank angles.It is shown that：1、According to mechanical principles， higher stressappears at the end of flank length.So，the contact stressincreases greatly with the increase of the flank 1ength nomatter what the flank angle is：21 The contact stress ofthe flank increases slowly with the increase of flankangle and increases significantly when the flank angle isover 70。。

山 2Flank length/mmFig.7 Contact stress changing with flank length at differentflank angles3.2.2 M aximum contact stress changing with frictioncoeficientSimilarly，the friction coeficient also has greatinfluence on the contact stress among the parameters ofthe turbine rotor.Table 3 gives the maximum contactstress changing with friction coefi cient，including themaximum contact stress at the friction coeficients of0.01，0.05，0.1，0.15，0-20，0.25 and 0-30.W hen thefriction coeficient increases.the blade assemble in theturbine disc becomes firm and runs away dificultly.So。

the maximum contact stress decreases with the increaseof friction coefficient。

Figure 8 shows the contact stress changing withflank length at different friction coefficients.It is shown萋黑∽ Flank length/mmFig.8 Contact stress changing with flank length at differentfriction coefHcientsFrom these analyses above，we can see that thecontact stress of the turbine rotor will change greatlywith the flank angle，the friction coefficient and otherkey parameters.On optimization design of turbine rotorin the furore，we can refer to the calculation result andselect the optimal materia1 whose flank angle and frictioncoefi cient are suitable。

4 Conclusions1、 The maximum contact stress appears at thechamfer below the flank (the end of the contact element)，where the fracture failure can easily emerge。

2、The contact stress in the flank increases with theincrease of f1ank angle。

31 W ith the friction coeficient increasing.thecontact stress in flank 1ength decreases。

4、The contact stress will not change when thefriction coeficient is over 0.25。

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