![]() ![]() Generally, one or more "input" or "control" points located on the DUT-side of a vibration fixture is kept at a specified acceleration. For higher frequencies (typically 5 Hz to 2000 Hz), electrodynamic shakers are used. Squeak and rattle testing is performed with a special type of quiet shaker that produces very low sound levels while under operation.įor relatively low frequency forcing (typically less than 100 Hz), servohydraulic (electrohydraulic) shakers are used. The measured response may be ability to function in the vibration environment, fatigue life, resonant frequencies or squeak and rattle sound output ( NVH). Vibration testing is performed to examine the response of a device under test (DUT) to a defined vibration environment. Alternately, a DUT (device under test) is attached to the "table" of a shaker. Vibration testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker. Active vibration isolation involves sensors and actuators that produce disruptive interference that cancels-out incoming vibration. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibration isolation is the prevention of transmission of vibration from one component of a system to others parts of the same system, as in buildings or mechanical systems. An example of this type of vibration is the vehicular suspension dampened by the shock absorber. The vibrations gradually reduce or change in frequency or intensity or cease and the system rests in its equilibrium position. For linear systems, the frequency of the steady-state vibration response resulting from the application of a periodic, harmonic input is equal to the frequency of the applied force or motion, with the response magnitude being dependent on the actual mechanical system.ĭamped vibration: When the energy of a vibrating system is gradually dissipated by friction and other resistances, the vibrations are said to be damped. Examples of these types of vibration include a washing machine shaking due to an imbalance, transportation vibration caused by an engine or uneven road, or the vibration of a building during an earthquake. The periodic input can be a harmonic or a non-harmonic disturbance. ![]() The disturbance can be a periodic and steady-state input, a transient input, or a random input. The mechanical system vibrates at one or more of its natural frequencies and damps down to motionlessness.įorced vibration is when a time-varying disturbance (load, displacement, velocity, or acceleration) is applied to a mechanical system. Examples of this type of vibration are pulling a child back on a swing and letting it go, or hitting a tuning fork and letting it ring. Machining vibrations are common in the process of subtractive manufacturing.įree vibration or natural vibration occurs when a mechanical system is set in motion with an initial input and allowed to vibrate freely. Car suspension: Designing vibration control is undertaken as part of acoustic, automotive or mechanical engineering. One of the possible modes of vibration of a circular drum (see other modes). Hence, attempts to reduce noise are often related to issues of vibration. vocal cords) these pressure waves can also induce the vibration of structures (e.g. Sound, or pressure waves, are generated by vibrating structures (e.g. The studies of sound and vibration are closely related (both fall under acoustics). Careful designs usually minimize unwanted vibrations. Such vibrations could be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound. ![]() ![]() Vibration can be desirable: for example, the motion of a tuning fork, the reed in a woodwind instrument or harmonica, a mobile phone, or the cone of a loudspeaker. the movement of a tire on a gravel road). the periodic motion of a pendulum), or random if the oscillations can only be analysed statistically (e.g. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. Vibration (from Latin vibrō 'to shake') is a mechanical phenomenon whereby oscillations occur about an equilibrium point. ![]()
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