1. Modal Theory of Multiple Degree of Freedom System Dept. of Mechanical Engineering Yungpeng Wang 南臺科技大學 STUST

2. Modal Theory of Multiple Degree of Freedom System 1. Theory 2. Solution of Eigenvalue Problem 3. Weighted Orthogonality of Modal Vectors 4. Modal Vector Scaling Example 5. Principal Coordinates - Modal Coordinates 6. Proportional Damping 7. Modal Vectors from the System Matrix 南臺科技大學 STUST

3. Theory 1. Equation of Motion: Multiple degree of freedom system, a set of 2 nd order differential equations, matrix form. 2. Eigenvalue Problem 南臺科技大學 STUST

4. Solution of Eigenvalue Problem 1. Characteristic Equation 2. Computation of Eigenvalues and Eigenvectors 南臺科技大學 STUST

5. Weighted Orthogonality of Modal Vectors 南臺科技大學 STUST 1. Modal Mass 2. Modal Stiffness 3. Orthonormal Modal Vector

6. Modal Vector Scaling Example 南臺科技大學 STUST 1. Example of Two Degrees of Freedom System

7. Principal Coordinates - Modal Coordinates 南臺科技大學 STUST 1. principal coordinates, normal coordinates or modal coordinates 2. transformation matrix 3. modal matrix or matrix of modal vectors 4. Modal Mass, Generalized Mass 5. Modal Stiffness, Generalized Stiffness

8. Proportional Damping 南臺科技大學 STUST Structural Damping, Viscous Damping, Coulomb Damping, Hysteretic Damping

9. Modal Vectors from the System Matrix 南臺科技大學 STUST The evaluation of modal vectors is very useful in relating measured frequency response function data to the system modal vectors. The residues of a frequency response function for a particular pole ( r ) are directly related to the elements of a modal vector. Also, the symmetry of the adjoint matrix is the justification for not needing to evaluate the complete frequency response function matrix.