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Vibrations
Vibration () is a mechanical phenomenon whereby oscillations occur about an equilibrium point. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. the periodic motion of a pendulum), or random if the oscillations can only be analysed statistically (e.g. the movement of a tire on a gravel road). 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. In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations could be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. Careful designs usually minimize unwanted vibrations. The studies of sound and vibration are closely related (both fall under acoustics). Sound, or pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Damping Ratio
In physical systems, damping is the loss of energy of an oscillating system by dissipation. Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see Viscosity, viscous Drag (physics), drag), Friction, surface friction, radiation, Electrical resistance and conductance, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators. Damping not based on energy loss can be important in other oscillating systems such as those that occur in ecology, biological systems and Bicycle_and_motorcycle_dynamics#Lateral_motion_theory, bikes (ex. Suspension (mechanics)). Damping is not to be confused with friction, which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium. A mass su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Wave
In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a travelling wave; by contrast, a pair of superposition principle, superimposed periodic waves traveling in opposite directions makes a ''standing wave''. In a standing wave, the amplitude of vibration has nulls at some positions where the wave amplitude appears smaller or even zero. There are two types of waves that are most commonly studied in classical physics: mechanical waves and electromagnetic waves. In a mechanical wave, Stress (mechanics), stress and Strain (mechanics), strain fields oscillate about a mechanical equilibrium. A mechanical wave is a local deformation (physics), deformation (strain) in some physical medium that propa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Oscillation
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum and alternating current. Oscillations can be used in physics to approximate complex interactions, such as those between atoms. Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science: for example the beating of the human heart (for circulation), business cycles in economics, predator–prey population cycles in ecology, geothermal geysers in geology, vibration of strings in guitar and other string instruments, periodic firing of nerve cells in the brain, and the periodic swelling of Cepheid variable stars in astronomy. The term ''vibration'' is precisely used to describe a mechanical oscillation. Oscillation, especially rapid oscillation, may be an undesirable phenomenon in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Machining Vibrations
In machining, vibrations, also called chatter, are the relative movements between the workpiece and the cutting tool. The vibrations result in waves on the machined surface. This affects typical machining processes, such as turning, milling and drilling, and atypical machining processes, such as grinding. A chatter mark is an irregular surface flaw left by a wheel that is ''out of true'' (off-center) in grinding, or regular marks left when turning a long piece on a lathe, due to machining vibrations. As early as 1907, Frederick W. Taylor described machining vibrations as the most obscure and delicate of all the problems facing the machinist, an observation still true today, as shown in many publications on machining. The explanation of the machine tool regenerative chatter was made by Tobias. S. A. and W. Fishwick in 1958, by modeling the feedback loop between the metal cutting process and the machine tool structure, and came with the stability lobes diagram. The structure s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Drum Vibration Mode21
The drum is a member of the percussion instrument, percussion group of musical instruments. In the Hornbostel–Sachs classification system, it is a membranophones, membranophone. Drums consist of at least one Acoustic membrane, membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player's hands, or with a percussion mallet, to produce sound. There is usually a resonant head on the underside of the drum. Other techniques have been used to cause drums to make sound, such as the thumb roll. Drums are the world's oldest and most ubiquitous musical instruments, and the basic design has remained virtually unchanged for thousands of years. Drums may be played individually, with the player using a single drum, and some drums such as the djembe are almost always played in this way. Others are normally played in a set of two or more, all played by one player, such as bongo drums and timpani. A number of different drums together ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tuning Fork
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs ( ''tines'') formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone once the high overtones fade out. A tuning fork's pitch depends on the length and mass of the two prongs. They are traditional sources of standard pitch for tuning musical instruments. The tuning fork was invented in 1711 by British musician John Shore, sergeant trumpeter and lutenist to the royal court. Description A tuning fork is a fork-shaped acoustic resonator used in many applications to produce a fixed tone. The main reason for using the fork shape is that, unlike many other types of resonators, it produces a very pure tone, with most of the vibrational energy at the fundamental frequency. The reason for this is that the frequency of the first overtone is about ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of the processes involved is called tribology, and has a history of more than 2000 years. Friction can have dramatic consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Another important consequence of many types of friction can be wear, which may lead to performance degradation or damage to components. It is known that frictional energy losses account for about 20% of the total energy expenditure of the world. As briefly discussed later, there are many different contributors to the retarding force in friction, ranging from asperity deformation to the generation of charges and changes in local structure. When two bodies in contact move relative to each other, due to these variou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Reed (music)
A reed (or lamella) is a thin strip of material that vibrates to produce a sound on a musical instrument. Most woodwind instrument reeds are made from '' Arundo donax'' ("Giant cane") or synthetic material. Tuned reeds (as in harmonicas and accordions) are made of metal or synthetics. Musical instruments are classified according to the type and number of reeds. The earliest types of single-reed instruments used idioglottal reeds, where the vibrating reed is a tongue cut and shaped on the tube of cane. Much later, single-reed instruments started using heteroglottal reeds, where a reed is cut and separated from the tube of cane and attached to a mouthpiece of some sort. By contrast, in an uncapped double reed instrument (such as the oboe and bassoon), there is no mouthpiece; the two parts of the reed vibrate against one another. Single reeds Single reeds are used on the mouthpieces of clarinets and saxophones. The back of the reed is flat and is placed against the mouthpiece. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Random Vibration
In mechanical engineering Mechanical engineering is the study of physical machines and mechanism (engineering), mechanisms that may involve force and movement. It is an engineering branch that combines engineering physics and engineering mathematics, mathematics principl ..., random vibration is motion which is non-deterministic, meaning that the exact behavior at a future point in time cannot be predicted, but general trends and statistical properties can be known. The randomness is a characteristic of the excitation or input, not the normal modes, mode shapes or natural frequencies. Some common examples include an automobile riding on a rough road, wave height on the water, or the load induced on an airplane wing during flight. Structural response to random vibration is usually treated using statistical or probabilistic approaches. Mathematically, random vibration is characterized as an ergodic and stationary process. A measurement of the acceleration spectral density (ASD) is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Machine
A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems. Renaissance natural philosophers identified six simple machines which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today as mechanical advantage. Modern machines are complex systems that consist of structural elements, mechanisms and contr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Ear Drum
In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pressure of sound from the air to the ossicles inside the middle ear, and thence to the oval window in the fluid-filled cochlea. The ear thereby converts and amplifies vibration in the air to vibration in cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles. Rupture or perforation of the eardrum can lead to conductive hearing loss. Collapse or retraction of the eardrum can cause conductive hearing loss or cholesteatoma. Structure Orientation and relations The tympanic membrane is oriented obliquely in the anteroposterior, mediolateral, and superoinferior planes. Consequently, its superoposterior end lies lateral to its anteroinferior end. Anatomically, it relates superiorly to the middle cranial fos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Vocal Cords
In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when breathing and vibrating for speech or singing, the folds are controlled via the recurrent laryngeal nerve, recurrent laryngeal branch of the vagus nerve. They are composed of twin infoldings of mucous membrane stretched horizontally, from back to front, across the larynx. They vibration, vibrate, modulating the flow of air being expelled from the lungs during phonation. The 'true vocal cords' are distinguished from the 'false vocal folds', known as vestibular folds or ''ventricular folds'', which sit slightly superior to the more delicate true folds. These have a minimal role in normal phonation, but can produce deep sonorous tones, screams and growls. The length of the vocal fold at birth is approximately six to eight millimeters and grows t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
