理论力学教学课件PPT静力学基础.ppt

多媒体双语授课系统,一、理论力学的研究对象,理论力学是研究：物体机械运动一般规律的科学。所谓机械运动是指：物体在空间的位置随时间而发生变化的一种运动形式。例如：地球的运转，车辆的行使，机器的运转等。物体的静止是机械运动的特殊形式。,二、理论力学的性质和任务,在工科院校它是一门理论性较强的技术基础课。理论力学既不是一门专业课，也不是一门单纯的基础课，在工科院校它是一门理论性较强的技术基础课，也就是说，它的理论在工程技术中有广泛的应用，凡搞工程技术的人一般都要学习这门课程。,性质:,主页,任务：（即：作用）（1）是学习后续课程（如材料力学、机械原理、机械设计等）的基础；（2）应用理论力学基本理论，结合专业知识解决工程实际问题。,三、理论力学的内容具体分为三部分：静力学、运动学、动力学静力学：研究力系的简化合成与平衡条件；运动学：用几何的观点研究点和刚体的运动规律；动力学：研究力的作用和机械运动变化之间的关系。,主页,statics,kinematics,dynamics,fundamentalsofanalyticalmechanics,fundamentalknowledgeofvibration,examples,主页,basisofstatics,statics,导言,第一篇：静力学,basicforcesystems,generalcoplanarforcesystems,forcesystemsinspaceandthecenterofgravity,equilibriumproblemswithfriction,statics,1.静力学基础,2.基本力系,3.平面力系,4.空间力系与重心,5.摩擦平衡问题,introduction,静力学,主页,本章学习指导,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,本章学习指导,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,在静力学中，可以把物体处于“平衡”理解为物体相对于地面保持静止或相作匀直线运动。例如：图1-1静止的建筑物图1-2匀速行使的汽车这些都是平衡的例子，平衡是机械运动的特殊情况。,图1-1,图1-2,equilibrium,rigidbodydoesnotdeformunderload,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,但我们知道：任何物体受力都会发生变形。例如：车床主轴在切削过程中发生弯曲变形；车辆驶过一座桥时，桥梁发生弯曲变形，桥墩发生压缩变形；因此，“刚体”实际上是不存在的，它是一种抽象化的力学模型，至于在一个问题中能否将物体视为刚体，不仅取决于变形的大小，还取决于问题的要求。,equilibrium,rigidbody,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,图1-3,力是物体间的相互机械作用，这种作用使物体的形态或者运动状态发生变化。,外效应：力使物体运动状态发生改变的效应-理论力学课程中研。内效应：力使物体形状发生改变的效应-材料力学等课程中研究。,equilibrium,rigidbodydoesnotdeformunderload,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,definitionofaforce,effectofaforce,equilibrium,rigidbodydoesnotdeformunderload,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,力是物体间的相互机械作用，这种作用使物体的形态或者运动状态发生变化。,外效应：力使物体运动状态发生改变的效应-理论力学课程中研。内效应：力使物体形状发生改变的效应-材料力学等课程中研究。,definitionofaforce,effectofaforce,equilibrium,rigidbodydoesnotdeformunderload,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,力是物体间的相互机械作用，这种作用使物体的形态或者运动状态发生变化。,外效应：力使物体运动状态发生改变的效应-理论力学课程中研。内效应：力使物体形状发生改变的效应-材料力学等课程中研究。,definitionofaforce,effectofaforce,主页,力的三要素：大小、方向、作用点（或作用）。我们可以用如图所示的矢量f表示力。或者用数学分析式表示力:其中：f1,f2,f3表示力沿直角坐标轴上的分力，它们是矢量。x、y、z表示力在直角坐标轴上的投影，它们是代数量。,equilibrium,rigidbodydoesnotdeformunderload,definitionofaforce,effectofaforce,representationofaforce,力的表示法,力的效应,力的定义,刚体,平衡,basisofstatics,静力学基础,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,representationofaforce,思考：分力大小=投影？,axiomofadditionandsubtractionequilibriumforcesystems,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,axiomoftwoforcesequilibrium,静力学基础,刚化公理,axiomofrigidization,axiomofrigidization,力的平行四边形公理,parallelogramaxiom/law,transmissibilityofforce,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,1.4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,axiomofadditionandsubtractionequilibriumforcesystems,主页,静力学基础,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,注:此公理是研究力系合成和力的分解的基础。,parallelogramaxiom/law,主页,静力学基础,答1：合力不一定大于分力。,2.力的分力与力的投影是否相等？,1.合力是否一定大于分力？,思考,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,答2：在直角坐标系下分力与投影大小相等，非直角坐标系下二者不相等。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,静力学基础,思考,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,axiomofactionandreaction,主页,静力学基础,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,axiomofrigidization,静力学基础,思考,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,静力学基础,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,transmissibilityofforce,主页,静力学基础,axiomofequilibriumofthreeforces,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,静力学基础,思考：,axiomofadditionandsubtractionequilibriumforcesystems,axiomofrigidization,刚化公理,transmissibilityofforce,parallelogramaxiom/law,axiomofactionandreaction,axiomofequilibriumofthreeforces,作用力与反作用力公理,三力平衡定理,力的可传性,力的平行四边形公理,加减平衡力系公理,两力平衡公理,axiomoftwoforcesequilibrium,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,主页,静力学基础,自由体：在空间可作任意位移的物体称为自由体。非自由体：在空间位移受到限制的物体称为非自由体。,约束：限制非自由体位移的物体称为该非自由体的约束。约束反力：约束作用于非自由体(被约束体)的力，称为约束反力。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,主页,freebodyandnon-freebody,constraints/supportsandconstraintforce,contactonfrictionlesssurface,静力学基础,例如：火车运行时受轨道的约束，轨道对火车车轮施加约束反力；物品放在行李架上不会掉下来，受支架的约束，支架对物品施加约束反力；车床主轴转动时受轴承的约束，那么轴承对轴施加约束反力。静力学中的主要问题之一，就是要确定约束反力的大小和方向，下面介绍几种工程中常见的几类约束，重点说明如何确定约束反力的方向(约束力的大小由后面平衡方程求解)。,约束特性：只能承受拉力，能阻碍物体沿绳索伸长方向的位移。约束反力：方位沿绳索本身，指向背离物体，使物体受拉。例如：电棒用链条悬挂，受力如图所示：起吊机用钢丝绳起吊重物，受力如图所示。皮带轮受皮带拉力，受力如图所示,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,主页,flexiblecablecordofnegligibleweight,contactonfrictionlesssurface,静力学基础,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,约束特性：只能承受拉力，能阻碍物体沿绳索伸长方向的位移。约束反力：方位沿绳索本身，指向背离物体，使物体受拉。例如：电棒用链条悬挂，受力如图所示：起吊机用钢丝绳起吊重物，受力如图所示。皮带轮受皮带拉力，受力如图所示,flexiblecablecordofnegligibleweight,主页,contactonfrictionlesssurface,静力学基础,约束特性：只能阻碍物体沿着接触点公法线朝向约束的位移,而不能阻碍物体沿接触点切线方向的位移。约束反力:方向沿接触点的公法线而指向被约束物体。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,contactonfrictionlesssurface,主页,静力学基础,约束结构：两个物体a、b上钻同样大小的圆孔，并用圆柱销钉c穿入圆孔,将两个物体连接起来.约束特性：不能阻碍绕销钉轴线相对转动，可以阻碍沿半径方向（垂直于轴线的任何方向）的任何位移。约束反力：在垂直于销钉轴线的平面内并通过圆心，但方位和指向不能确定。一般画受力图时用f，表示，或者用两个正交分力fx,fy表示，如图1-17所示。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,主页,cylindricalhingewithfrictionless,静力学基础,注意：在画受力图时，一般将a、b两物体分开并将销钉c与其中的一个物体相连。,约束结构：两个物体a、b上钻同样大小的圆孔，并用圆柱销钉c穿入圆孔,将两个物体连接起来.约束特性：不能阻碍绕销钉轴线相对转动，可以阻碍沿半径方向（垂直于轴线的任何方向）的任何位移。约束反力：在垂直于销钉轴线的平面内并通过圆心，但方位和指向不能确定。一般画受力图时用f，表示，或者用两个正交分力fx,fy表示，如图所示。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,主页,cylindricalhingewithfrictionless,静力学基础,注意：在画受力图时，一般将a、b两物体分开并将销钉c与其中的一个物体相连。,约束结构：两个物体a、b上钻同样大小的圆孔，并用圆柱销钉c穿入圆孔,将两个物体连接起来.约束特性：不能阻碍绕销钉轴线相对转动，可以阻碍沿半径方向（垂直于轴线的任何方向）的任何位移。约束反力：在垂直于销钉轴线的平面内并通过圆心，但方位和指向不能确定。一般画受力图时用f，表示，或者用两个正交分力fx,fy表示，如图1-17所示。注意：在画受力图时，一般将a、b两物体分开并将销钉c与其中的一个物体相连。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,主页,cylindricalhingewithfrictionless,静力学基础,约束结构:两端用光滑铰链与其他物体相连的杆件(直的或弯的),并且假设其自重不计。约束性质：可承受拉力或压力.因此链杆属于二力构件(在两力作用下处于平衡的构件）。约束反力:沿着两端铰链中心的连线,等值、方向、共线。如图所示：,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,主页,atwo-forcebody,静力学基础,图1-22,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,约束结构:两端用光滑铰链与其他物体相连的杆件(直的或弯的),并且假设其自重不计。约束性质：可承受拉力或压力.因此链杆属于二力构件(在两力作用下处于平衡的构件）。约束反力:沿着两端铰链中心的连线,等值、方向、共线。如图1-22、1-23所示：,主页,atwo-forcebody,图1-23,静力学基础,图1-22,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,约束结构:两端用光滑铰链与其他物体相连的杆件(直的或弯的),并且假设其自重不计。约束性质：可承受拉力或压力.因此链杆属于二力构件(在两力作用下处于平衡的构件）。约束反力:沿着两端铰链中心的连线,等值、方向、共线。如图1-22、1-23所示：,主页,atwo-forcebody,图1-23,静力学基础,约束结构:由一物体的球部嵌入另一物体的球窝构成。约束特性:允许物体a绕球心o转动,不能沿半径移动。约束反力:通过球心o,方向不能预先确定,通常用三个正交分力fx，fy，fz来表示。,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contactonfrictionlesssurface,ball-and-socketjointwithfrictionless,主页,静力学基础,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,约束特点:与光滑接触面相似.约束反力:垂直于支承面,在单面约束的条件下,指向被约束体,如图所示。注：在双面约束的情况下,指向不能事先确定。,contactonfrictionlesssurface,rollersupport,主页,静力学基础,约束特点:与光滑圆柱铰链类同.约束反力:方向不定,可以假设用f，或用两个正交分力fx，fy表示,basisofstatics,fundamentalconceptsofstatics,1静力学基本概念,axiomofstatics,commonsupportsinengineering,4受力图画法,methodsofdrawingfree-bodydiagrams,3工程中常见约束,2静力学公理,pinsupport,rollersupport,ball-and-socketjointwithfrictionless,flexiblecablecordofnegligibleweight,constraints/supportsandconstraintforce,freebodyandnon-freebody,自由体与非自由体,约束与约束反力,柔索,光滑接触面,光滑圆柱铰链,二力杆,光滑球铰链,滚动支座,固定铰链支座,颈轴承与推轴承,链杆约束,固定端约束,cylindricalhingewithfrictionless,atwo-forcebody,sliderradialbearingorhingeandthrustbearingorhinge,hingestaff-atwo-forcebody,built-in(cantilever)support,contact