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1、Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2 构件的受力分析 2.0.1 研研讨背景背景 任何构件任何构件 任何任何时候候 外力作用外力作用 本身本身变形形2.0.2 研研讨对象象 构件构件, 刚体体: 恣意两点恣意两点间的的间隔隔坚持持不不变2.0.3 研研讨内容和目的内容和目的 1) 物体平衡概念和静力平衡的根本物体平衡概念和静力平衡的根本规律；律； 2) 运用静力平衡的运用静力平衡的规律，求解未知力。律，
2、求解未知力。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.1 静力学的根本概念2.1.1 力的根本概念力的根本概念定义: 力是物体之间相互的机械作用.单位和换算：1 kgf=9.8N1pound=0.4536 kgf三要素: 大小,方向,作用点.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyr
3、ight 2019-2019 Aspose Pty Ltd.2.1 静力学根本概念其他概念：其他概念：等效能系合力平衡力系平衡形状Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.1.2 静力学公理静力学公理b.二力平衡公理a. 二力平衡实例二力平衡实例1.二力平衡公理Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2
4、.0.0.Copyright 2019-2019 Aspose Pty Ltd.c. 二力杆件2.1.2 静力学公理静力学公理d. 作用力与反作用力定律 和二力平衡公理的区别Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2. 加减力系公理FF推论:力的可传性Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.C
5、opyright 2019-2019 Aspose Pty Ltd.3.平行四边形法那么平行四边形法那么表示图Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.4.三力平衡汇交定律三力平衡汇交Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2
6、.2 约束、约束反力和受力图约束反力：限制物体运动的力；主 动 力：引起物体运动和运动趋势的力；被 动 力：由自动力的作用而引起的力约 束：对于某一物体的活动起限 制造用的其它物体；2.2.1约束和约束反力约束和约束反力Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.2.2 约束的根本类型约束的根本类型约束反力的作用线沿着被拉直的柔性物体中心线且背叛物体运动趋势方向。WT1. 柔性柔性约束束Evaluation
7、only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2. 光滑面约束光滑面约束约束反力经过接触点，并沿公法线，指向与物体运动趋势方向相反即恒指向被约束的物体)WNEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.3. 固定铰链约束固定铰链约束约束反力的指向随杆件受力情
8、况的不同而相应地变化。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.4. 活动铰链活动铰链(辊轴支座辊轴支座)约束约束约束反力的指向必定垂直于支承面，并经过铰链中心。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.5. 固定端约束固定端约
9、束限制物体三个方向运动，产生三个约束反力。NAXEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.例1.画人口盖的受力图NxNyFWF2.2.3 受力图受力图Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.3 平面汇交力系的合成及平衡条件
10、2.3.0 平面汇交力系假设作用于刚体上的力系位于同一平面内,且汇交于一点,那么成之为平面汇交力系.2.3.1 平面汇交力系的合成 几何法(平面四边形法) 解析法(投影法)Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.3 平面汇交力系的合成及平衡条件Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Cop
11、yright 2019-2019 Aspose Pty Ltd.合力投影定理Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.多个力多个力时合力投影定理Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.3.2 平面汇交力系的平衡条件静力平衡
12、条件静力平衡条件两个独立的方程,求解两个未知数!Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.例2 求AB、BC杆的受力BNBCTWNABEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created wi
13、th Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.4 平面力偶的合成和平衡条件FEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.4.1力矩与合力矩定理力矩合力矩定理平面汇交力系的合力对于平面内恣意点的力矩等于各分力对于该点的力矩的代数和.Evaluation only.Created
14、with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.力偶：作用在物体上一对大小相等、 方向相反不共作用线的平行力 作用：使物体发生转动；力偶矩：力的数值与力臂的乘积 MF.d 规定：反时针转向的力偶矩为正2.4.2力偶与力偶矩Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.本质：力偶中两个力
15、对平面上恣意点的代数和；等效能偶：同一平面内,两个力偶只需M相等方向一样，即为等效能偶。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.4.3 力偶系的合成和平衡条件力偶系的合成方法Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.M1=
16、F1d1,M2=F2d2将M2化为等效能臂为d1的等效能K2，那么K2M2/d1合力：RF1K2合力偶：M=Rd1=M1+M2Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.4.3 力偶系的合成和平衡条件1.力偶系的合成2.力偶系的平衡条件Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright
17、 2019-2019 Aspose Pty Ltd.2.5 平面普通力系的合成和平衡条件2.5.1力系的平移原理2.5.0 根本力系:平面汇交力系和平面力偶系Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.5.2 平面普通力系向知点的简化根据力线平移定理,平面普通力系的各力可以平移到作用面的恣意一点, 从而将原力系简化为一个平面汇交力系和一个平面力偶系,该点记为C,称为简化中心. 简化后的力系可以表示为Evalu
18、ation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.2.5.3 平面普通力系的平衡条件处置方法：将平面普通力系转化为一组汇交力系和一组力偶系平衡条件：Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.例3 求D点的反力和BD杆的受力Evaluation o
19、nly.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.以E为支点：Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.BD为二力杆Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5
20、.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.今日作业复习复习: 例题例题1 思索思索: 5,6,11,13,习题习题: 2-2，7，13，14预习预习: 第三章第三章Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.习题2-11(a)NAyNAxNBNB=7.05KN，NAX14.1KN，NAY=7.05KNEvaluation only.Created with Aspose.
21、Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.三力平衡定律Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.习题2-11(b)NAyNAxNBNB=10KN，NAX21.15KN，NAY=7.01KNEvaluation only.Created with Aspose.Slides for .NET 3.5
22、Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.习题1-22(a)NAyNAXNBEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.习题 1-22(b)NAyNAXNBEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019
23、-2019 Aspose Pty Ltd.等效能系 假设两个力系对同一刚体分别作用时,产生的效果完全一样,那么称此二力系为等效能系.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.合力 假设一个力与某一力系对同一刚体分别作用时,产生的效果完全一样,那么称此力系为该力系的合力.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5
24、.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.平衡力系 假设某一力系可以使得刚体坚持平衡形状,那么称此力系为平衡力系.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.平衡形状 假设物体相对于某一惯性参考系坚持静止或作匀速直线运动,称此该物体处于平衡形状.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client P
25、rofile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.二力平衡公理 作用于刚体上的两个力使作用于刚体上的两个力使得刚体坚持平衡的必要和充分得刚体坚持平衡的必要和充分条件是这两个力的大小相等条件是这两个力的大小相等,方方向相反向相反,且作用在同不断线上且作用在同不断线上.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with
26、 Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.backEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-20
27、19 Aspose Pty Ltd.加减平衡力系公理 在一刚体上恣意加上或减去一个平衡力系,不会改动原力系对刚体的作用效果,这个公理称为加减平衡力系公理.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.力的可传性原理 作用于刚体上的力可以沿其作用线上挪动,而不会改动原力系对刚体的作用效果,这个原理称为力的可传性原理.Evaluation only.Created with Aspose.Slides for .NET
28、 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.平行四边形法那么 作用于某一点的两个力,其合力的作用线必然经过该点,合力的大小与方向可以由这两个力矢为邻边的平行四边形的对角线来表示.这个法那么称为力的平行四边形法那么.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.三力平衡汇交定律 当刚体在三个力的作用下处于平衡形状时,假设其中两个力的作用
29、线相交于一点,那么第三个力的作用线必然经过该点,且三力共面.这个定律称为三力平衡汇交定律.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.力线的平移定理 作用在刚体上A点的力可以平移到的B点,但必需附加一个力偶,这个附加力偶的矩等于原来的力对新作用点的矩.这个定理称为力线平移定理.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profil
30、e 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2019-2019 Aspose Pty Ltd.
