工程力学第六章杆件的应力..ppt

线应变: 角应变 观察到下列现象: (1)各圆周线的形状、大小以及两圆周线间的距离没有变化 (2)纵向线仍近似为直线, 但都倾斜了同一角度γ （3）表面方格变为菱形。 1.变形几何关系 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 平面假设： 变形前为平面的横截面变形后仍为平面，它像刚性平面一样绕轴线旋转了一个角度。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 横截面上距形心为?的任一点处应变 在外表面上 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 根据剪切胡克定律, 当剪应力不超过材料的剪切比例极限时 剪应力方向垂直于半径 2. 物理关系 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 3.静力学关系 —截面的极惯性矩 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 于是再由物理关系得 二、 最大扭转切应力 当 ? ＝ ? max 时，? ＝ ? max ? 抗扭截面系数 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 6-6 极惯性矩和抗扭截面系数 一、 实心圆截面 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 二、 空心圆截面 ?=d / D Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 已知：P1＝14kW, n1= n2= 120r/min, z1=36, z3=12; d1=70mm, d 2 =50mm, d3=35mm. 求: 各轴横截面上的最大剪应力。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. N1=14kW, N2=N3= N1/2=7 kW n1=n2= 120r/min n3= n1 z3 z1 =120? 36 12 =360r/min T1=1114 N.m T2=557 N.m T3=185.7 N.m ?max(C)= = 21.98 MPa T3 Wp3 ?max(H)= = 22.69 MPa T2 Wp2 ?max(E)= T1 Wp1 = 16.54 MPa Evaluation only. Created with Aspose.Slides for .NET 3.5 C