材料力学课件：第1章 材料力学基本概念.ppt

材 料 力 学 第1章 材料力学基本概念 1.1 材料力学的基本任务 1.2 变形固体的基本假设 1.3 杆件的内力与截面法 1.4 应力与应变的概念 1.5 材料力学简史 1.1 材料力学的基本任务 构件分类 载荷的分类 杆件变形的基本形式 材料力学的基本任务 * 材料的机械（力学）性质 返回 构件分类 * 轴线 返回 载荷的分类 * 按作用方式分 集中力 分布力 * 按作用性质分 静载（荷） 动载（荷） 返回 杆件变形的基本形式 轴向 拉压 剪切 扭转 弯曲 杆 轴 梁 返回 在满足强度、刚度、稳定性的 要求下，以最经济的代价，为构件 确定合理的形状和尺寸，选择适宜 的材料，而提供必要的理论基础和 计算方法。 返回 材料力学的基本任务 * 强度 抵抗断裂或过量 塑性变形的能力 返回 图2 桩断裂的典型裂纹 图1 砌体结构房屋破坏的实例 桥梁下部结构的严重损伤是引起桥梁倒塌 返回 返回 * 刚度 抵抗弹性变形的能力 返回 立式弯曲中心lsw32 固特机械 76S大半径自由成型弯曲 桥面弯曲成w形 返回 南京一处楼房开裂 房屋变形鉴定显示“安全” 返回 Fig. 1. Schematic of the piezoelectric microcantilever motion.Note that the light gray microcantilever is inequilibrium, while the darkgray microcantilever is not sample Piezoelectric layer Atomic Force Microscopy (AFM) AFM tip Fig. 1. Schematic representation of a piezoelectric nanoelectromechanical resonator. 压电纳米机电谐振器 Nanoelectromechanical resonator They can be applied in the detection of amyloid(淀粉体) growth , quantum ground state and spin manipulation piezoelectric laminated micro system Fig. 1. (a) A schematic view of the micro system ,(b)deflected element of micro system beam,and (c)System crosssection when 0xlp Fig. 1. (A) Schematic model of a decagonal Al-Ni-Co quasicrystal, showing the orientation of decagonal and twofold planes. The 2-fold plane is periodic along the 10-fold direction and aperiodic along the 2-fold direction. (B) Schematic of the cantilever and the scanning geometry during friction studies Strong friction anisotropy is found when the twofold surface of an atomically clean aluminum-nickel-cobalt quasicrystal slides against a thiol-passivated titanium-nitride tip. Friction along the aperiodic direction is one-eighth as much as that along the periodic direction. This anisotropy, which is about three times as large as the highest value observed in anisotropic crystalline surfaces, disappears after the surface is oxidized in air. These results reveal a strong connection between interface atomic structure and the mechanisms by which energy