《Vibration Lecture 2 Notes- Introduction to Vibration》.pdfVIP

MCG 4308 Lecture 2 Fundamentals of Vibration Text: sections 1.1-1.5 Why study vibrations? Design of machines, foundations, structures, engines, turbines, control systems Transmission of vibration to humans causes discomfort and loss of efficiency Can cause mechanical failure e.g. disk vibrations in turbines Cyclic variation of induced stress causes material fatigue Vibration causes more rapid wear of machine parts such as bearings gears Fasteners can become loose Engineering applications of vibrations Vibrations can be utilized in applications: Vibratory conveyors, hoppers, sieves, compactors, washing machines, electric toothbrush, dentist drill etc Vibration can improve efficiency of certain machining, casting, forging and welding processes The Tacoma Narrows The Tacoma Narrows Bridge or Galloping Gertie, fell only four months after its completion because winds caused the bridge to resonate and collapse. http://youtu.be/LMTyIR BXeyE Basic concepts of vibration Vibration or oscillation : any motion that repeats itself – periodic motion Example: swinging pendulum Elementary parts of vibrating systems Way to store kinetic energy (mass/inertia) ►required Way to store potential energy (spring/elasticity/gravity) ►required Ways energy is lost – not always modeled Vibration of a system Vibration of a system transfer of energy from kinetic energy to potential energy and back Energy may be lost Energy may be added Conservative system: energy is neither added nor lost. Energy is conserved. Some Terminology Free vibration: system initially disturbed and then left to vibrate on its own. Terminology Classifications Forced vibration: system subject to ex