MT-1620 al.2002 Unit 19 General Dynamic Considerations Reference: Elements of Vibration Analysis, Meirovitch, McGraw-Hill, 1975 Paul A Lagace, Ph. D Professor of aeronautics Astronautics and Engineering Systems Paul A Lagace @2001
MIT - 16.20 Fall, 2002 Unit 19 General Dynamic Considerations Reference: Elements of Vibration Analysis, Meirovitch, McGraw-Hill, 1975. Paul A. Lagace, Ph.D. Professor of Aeronautics & Astronautics and Engineering Systems Paul A. Lagace © 2001
MT-1620 al.2002 VI.(Introduction to Structural dynamics Paul A Lagace @2001 Unit 19-2
MIT - 16.20 Fall, 2002 VI. (Introduction to) Structural Dynamics Paul A. Lagace © 2001 Unit 19 - 2
MT-1620 al.2002 Thus far have considered only static response. However, things also move, this includes structures Can actually identify three "categories" of response A.(Quasi)-Static [quasi because the load must first be applied B. Dynamic C. Wave propagation What is the key consideration in determining which regime one is in? the frequency of the forcing function EXample: Mass on a Spring Figure 19.1 Representation of mass on a spring F t多 Paul A Lagace @2001 Unit 19-3
MIT - 16.20 Fall, 2002 Thus far have considered only static response. However, things also move, this includes structures. Can actually identify three “categories” of response: A. (Quasi) - Static [“quasi” because the load must first be applied] B. Dynamic C. Wave Propagation What is the key consideration in determining which regime one is in? --> the frequency of the forcing function Example: Mass on a Spring Figure 19.1 Representation of mass on a spring Paul A. Lagace © 2001 Unit 19 - 3
MT-1620 al.2002 A) push very slowly Figure 19.2 Representation of force increasing slowly with time t time The response is basically determined by f=k F(t F q k k Figure 19.3 Deflection response versus time for mass in spring with loads slowly increasing with time F/k)at any point Paul A Lagace @2001 Unit 19-4
qt MIT - 16.20 Fall, 2002 A) Push very slowly Figure 19.2 Representation of force increasing slowly with time t = time The response is basically determined by: F = k q Ft ⇒ () = () ≈ F k k Figure 19.3 Deflection response versus time for mass in spring with loads slowly increasing with time (F/k) at any point Paul A. Lagace © 2001 Unit 19 - 4
MT-1620 al.2002 B)Push with an oscillating magnitude Figure 19.4 Representation of force with oscillating magnitude 七 The response also oscillates Figure 19.5 Representation of oscillating response Paul A Lagace @2001 Unit 19-5
MIT - 16.20 Fall, 2002 B) Push with an oscillating magnitude Figure 19.4 Representation of force with oscillating magnitude The response also oscillates Figure 19.5 Representation of oscillating response Paul A. Lagace © 2001 Unit 19 - 5