[材料力学复习与例题.ppt

Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 组合变形的判断 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. ?—长度系数（或约束系数）。 ? l —相当长度 欧拉公式 两端铰支 一端固定一端铰支 两端固定 一端固定一端自由 μ=1 μ= 0.7 μ=0.5 μ=2 细长压杆临界压力 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. A.减小压杆长度 l B.减小长度系数μ（增强约束） C.增大截面惯性矩 I （合理选择截面形状） D.增大弹性模量 E（合理选择材料） 欧拉公式 越大越稳定 提高压杆稳定性的措施 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. ——动荷系数 动静法： 能量法 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. 一、交变应力：构件内一点处的应力随时间作周期性变化，这种应力称为交变应力。 二.疲劳破坏的特点 1 2 3 交变应力的破坏应力值一般低于静载荷作用下的强度极限值,有时甚至低于材料的屈服极限. 无论是脆性还是塑性材料,交变应力作用下均表现为 脆性断裂,无明显塑性变形. 断口表面可明显区分为光滑区与粗糙区两部分. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 影响因素 构件外形 构件表面 质量 构件尺寸 影响持久极限的因素 提高疲劳强度的措施 减缓应力集中 提高表面质量 增加表层强度 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 绪论 1.构件所受的外力可以是各式各样的，有时是很复杂的。材料力学根据构件的典型受力情况及截面上的内力分量可分为（ ）四种基本变形。 A.拉伸或压缩（拉压）、剪切、扭转、弯曲 B.拉伸、压缩、扭转、弯曲 C.拉伸、挤压、扭转、弯曲 D.拉伸和压缩、挤压、剪切、扭转 √ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 研究构件在外力作用下变形和破坏的规律；在保证构件满足强度