材料力学第三章扭转.ppt

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1、1CHAPTER3TORSIONMechanicsofMaterials2第三章扭转材料力学3§3–1SUMMARY§3–2EXTERNALTORQUEOFATRANSMISSIONSHAFTINTERNALTORQUEANDDIAGRAMS§3–3TORSIONOFTHIN-WALLEDHOLLOWSHAFTS§3–4STRESSESOFCIRCULARSHAFTSINTORSION·STRENGTHCONDITIONS§3–5DEFORMATIONSOFACIRCULARSHAFTINTORSION·RIGIDITYCONDITIONS§3–6STATICALLYINDETERMIN

2、ATEPROBLEMSOFCIRCULARSHAFTSINTORSION§3–7STAINENERGYOFCIRCULARSHAFTSINTORSION§3–8STRESSESANDDEFORMATIONSOFNONCIRCULARSHAFTSINFREETORSION§3–9STRESSESOFOPENEDANDCLOSEDRODSWITHTHINWALLEDSECTIONSINFREETORSIONCHAPER3TORSION4§3–1概述§3–2传动轴的外力偶矩.扭矩及扭矩图§3–3薄壁圆筒的扭转§3–4等直圆杆在扭转时的应力·强度条件§3–5等直圆杆在扭转时的变形·刚度条件§3–

3、6等直圆杆的扭转超静定问题§3–7等直圆杆在扭转时的应变能§3–8非圆截面等直杆在自由扭转时的应力和变形§3–9开口和闭口薄壁截面杆在自由扭转时的应力第三章扭转5§3–1SUMMARYShaft：Inengineeringthemembersofwhichdeformationsaremainlytorsion.Suchastransmissionshaftsinmachines,drillrodsinoil-drillingrigsetc.Torsion：Resultantoftheexternalforcesisaforcecoupleanditsactingplaneisperpe

4、ndiculartotheaxisoftheshaft.Underthiscasethedeformationoftherodistorsion.ABOmmOBATORSION6扭转§3–1概述轴：工程中以扭转为主要变形的构件。如：机器中的传动轴、石油钻机中的钻杆等。扭转：外力的合力为一力偶，且力偶的作用面与直杆的轴线垂直，杆发生的变形为扭转变形。ABOmmOBA7Theangleoftwist()：Theangleofrotationofonesectionwithrespecttoanother.Shearingstrain()：Thechangeofarightangl

5、ebetweentwostraightlines.mmOBATORSION8扭转扭转角（）：任意两截面绕轴线转动而发生的角位移。剪应变（）：直角的改变量。mmOBA9TORSIONPracticalexamplesinengineeringTransmissionshaft10扭转工程实例11§3–2EXTERNALTORQUEOFATRANSMISSIONSHAFTINTERNALTORQUEANDITSDIAGRAM1、ExternaltorqueofatransmissionshaftTherelationbetweenthetransmissionpower,revo

6、lutionandexternaltorqueofthetransmissionshaft：where：P-power,unit:kilowatt(kW)n–rotationalspeed,unit:r/minor（rpm）where：P-power,unit:horsepower(PS)n–rotationalspeed,unit:r/minor（rpm）where：P-power,unit:kilowatt(HP)n–rotationalspeed,unit:r/minor（rpm）1PS=735.5N·m/s,1HP=745.7N·m/s,1kW=1.36PSTORSION12扭转

7、§3–2传动轴的外力偶矩·扭矩及扭矩图一、传动轴的外力偶矩传递轴的传递功率、转数与外力偶矩的关系：其中：P—功率，千瓦（kW）n—转速，转/分（rpm）其中：P—功率，马力（PS）n—转速，转/分（rpm）其中：P—功率，马力（HP）n—转速，转/分（rpm）1PS=735.5N·m/s,1HP=745.7N·m/s,1kW=1.36PS133)Signconventionsforinternaltorque：“T”willbeco