机械振动噪声学一.ppt

Power units in every kinds of vessels may cause vibrations 控制方法：新的保护罩用打孔金属薄板和金属丝网制成。 Class 1 Thank you and have a nice day! Thank you and have a nice day! Mass element 质量元件 Inelastic, rigid body，kinetic energy storage elements 是无弹性的刚体,储存动能的元件 Translation平移： Force力, mass质量 & acceleration加速度 Units量纲: N、kg、m/s 2。 Rotation旋转： Moment力矩, moment of inertia转动惯量 & angular acceleration角加速度 Units量纲: Nm、kg m 2、rad / s 2 2.1.1.2 Discretized mechanical system 2.1.1 Mechanical Model of Physical System 2. 1 Differential Equation of Vibration Spring (elastic) element 弹性元件 Potential energy storage elements 是势能储存元件 Force力, stiffness刚度 &displacement位移Units量纲: N, N/m & m Moment力矩, torsion stiffness扭转刚度 & angle角位移Units量纲: Nm, Nm/rad & rad Translation平移： Rotation旋转： 2.1.1.2 Discretized mechanical system 2.1.1 Mechanical Model of Physical System 2. 1 Differential Equation of Vibration Damping element 阻尼元件 Energy dissipation elements 耗能元件 Force力, damping coefficient阻尼系数& velocity速度Units量纲: N, Ns/m & m/s 。 Moment力矩, torsion damping coefficient扭转阻尼系数& angular velocity角速度 Units量纲: Nm, Nms/rad & rad/s Translation平移： Rotation旋转： 2.1.1.2 Discretized mechanical system 2.1.1 Mechanical Model of Physical System 2. 1 Differential Equation of Vibration (1) Force method 2.1.2 Methods to Establish Differential Equation Steps： 1. Generalized coordinate 建立广义坐标 2. Draw a diagram of equilibrium of forces of the mass element作质量元件的隔离体受力分析图 . Normal form of the vibration equation 建立振动微分方程并整理成标准的形式 2. 1 Differential Equation of Vibration (1) Force method Example 2-2 SDOF damping system Generalized coordinate .建立广义坐标 (direction方向,origin原点) Mechanics principle 力学定律 2. 1 Differential Equation of Vibration 2.1.2 Methods to Establish Differential Equation Equilibrium of forces at the mass element质量受力的平衡 single pendulum Generalized coordinate θ. (direction,origin) Equilibrium of moments at the joint D’Alembert Principle (1) Force method Example 2-3 2. 1 Differenti