Oscillation

Oscillation. In physics , chemistry, and engineering , repeated movement back and forth around a central position, or equilibrium position . The route that consists of going from one extreme position to the other and returning to the first one, passing twice through the central position, is called a cycle. The number of cycles per second, or hertz (Hz), is known as the oscillation frequency .

When a pendulum is set in motion or a guitar string is plucked, the pendulum and string end up stopping if other forces do not act on them. The force that stops them from oscillating is called the damper. These forces are often friction forces, but other damping forces, for example electrical or magnetic, may exist in an oscillating system.

Natural frequency

Any oscillating object has a ‘natural frequency’, which is the frequency with which it tends to vibrate if not disturbed. For example, the natural frequency of a 1m long pendulum is 0.5 Hz, which means that the pendulum comes and goes once every 2 seconds. If the pendulum is given a slight boost every 2 seconds, the amplitude of the oscillation gradually increases until it becomes very large. The phenomenon by which a forceRelatively small applied repeatedly causes the amplitude of an oscillating system to become very large. It is called resonance. Many serious vibration problems in engineering are due to resonance. For example, if the natural frequency of a car body is the same as the engine’s speed when it rotates at a certain speed, the body may start to vibrate or jerk. This vibration can be avoided by mounting the engine on a damping material, for example rubber or rubber, to isolate it from the body.

Flaming

A dangerous type of vibration is sudden, violent oscillation known as flapping. This phenomenon occurs mainly on the control surfaces of aircraft, but it also occurs on electric cables covered with frost when the wind speed is high. One of the most spectacular flare cases in 1940 caused the collapse of a bridge in Tacoma, United States. The cause was a hurricane wind whose speed enhanced the vibration of the bridge.

In flare, the amplitude of vibration of a structure can increase so rapidly that it disintegrates almost instantaneously. Therefore, preventing flare is very important when designing bridges and airplanes. In the case of airplanes, the flare analysis is usually complemented by tests carried out with a model of the plane in an aerodynamic tunnel.

 

Leave a Comment