|
Dashpot Symbol
A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring. The process and instrumentation diagram (P&ID) symbol for a dashpot is . Types The two most common types of dashpots are linear and rotary. Linear damper Linear dashpots — or linear dampers — are used to exert a force opposite to a translation movement. They are generally specified by stroke (amount of linear displacement) and damping coefficient (force per velocity). Rotary damper Similarly, rotary dampers will tend to oppose any torque applied to them, in an amount proportional to their rotational speed. Their damping coefficients will usually be specified by torque per angular velocity. One can distinguish two kinds of viscous rotary dashpots: * Vane dashpots which have a limited angular ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carburetor
A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main metering circuit, however various other components are also used to provide extra fuel or air in specific circumstances. Since the 1990s, carburetors have been largely replaced by fuel injection for cars and trucks, however carburetors are still used by some small engines (e.g. lawnmowers, generators and concrete mixers) and motorcycles. Diesel engines have always used fuel injection instead of carburetors. Etymology The name "carburetor" is derived from the verb ''carburet'', which means "to combine with carbon," or in particular, "to enrich a gas by combining it with carbon or hydrocarbons." Thus a carburetor mixes intake air with hydrocarbon-based fuel, such as petrol or autogas (LPG). The name is spelled "carburetor" in American Eng ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin–Voigt Material
A Kelvin-Voigt material, also called a Voigt material, is the most simple model viscoelastic material showing typical rubbery properties. It is purely elastic on long timescales (slow deformation), but shows additional resistance to fast deformation. It is named after the British physicist and engineer Lord Kelvin and German physicist Woldemar Voigt. Definition The Kelvin-Voigt model, also called the Voigt model, is represented by a purely viscous damper and purely elastic spring connected in parallel as shown in the picture. If, instead, we connect these two elements in series we get a model of a Maxwell material. Since the two components of the model are arranged in parallel, the strains in each component are identical: : \varepsilon_\text = \varepsilon_S = \varepsilon_D. where the subscript D indicates the stress-strain in the damper and the subscript S indicates the stress-strain in the spring. Similarly, the total stress will be the sum of the stress in each compone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maxwell Material
A Maxwell material is the most simple model viscoelastic material showing properties of a typical liquid. It shows viscous flow on the long timescale, but additional elastic resistance to fast deformations. It is named for James Clerk Maxwell who proposed the model in 1867. It is also known as a Maxwell fluid. Definition The Maxwell model is represented by a purely viscous damper and a purely elastic spring connected in series, as shown in the diagram. In this configuration, under an applied axial stress, the total stress, \sigma_\mathrm and the total strain, \varepsilon_\mathrm can be defined as follows: :\sigma_\mathrm=\sigma_D = \sigma_S :\varepsilon_\mathrm=\varepsilon_D+\varepsilon_S where the subscript D indicates the stress–strain in the damper and the subscript S indicates the stress–strain in the spring. Taking the derivative of strain with respect to time, we obtain: :\frac = \frac + \frac = \frac + \frac \frac where ''E'' is the elastic modul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscoelastic
In materials science and continuum mechanics, viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like water, resist shear flow and strain linearly with time when a stress is applied. Elastic materials strain when stretched and immediately return to their original state once the stress is removed. Viscoelastic materials have elements of both of these properties and, as such, exhibit time-dependent strain. Whereas elasticity is usually the result of bond stretching along crystallographic planes in an ordered solid, viscosity is the result of the diffusion of atoms or molecules inside an amorphous material.Meyers and Chawla (1999): "Mechanical Behavior of Materials", 98-103. Background In the nineteenth century, physicists such as Maxwell, Boltzmann, and Kelvin researched and experimented with creep and recovery of glasses, metals, and rubbers. Viscoelasticity was further examin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Model (abstract)
A conceptual model is a representation of a system. It consists of concepts used to help people know, understand, or simulate a subject the model represents. In contrast, physical models are physical object such as a toy model that may be assembled and made to work like the object it represents. The term may refer to models that are formed after a conceptualization or generalization process. Conceptual models are often abstractions of things in the real world, whether physical or social. Semantic studies are relevant to various stages of concept formation. Semantics is basically about concepts, the meaning that thinking beings give to various elements of their experience. Overview Models of concepts and models that are conceptual The term ''conceptual model'' is normal. It could mean "a model of concept" or it could mean "a model that is conceptual." A distinction can be made between ''what models are'' and ''what models are made of''. With the exception of iconic m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dashpot Timer
The first automatic timer, the dashpot timer has been used in many different machines and has many variations. Pneumatic, hydraulic-action, and mercury displacement timers. Being used in a variety of things such as printing presses, motors, and even irrigation systems, the dashpot timer has seen many applications. Even in modern times with electrical and digital timers, these old mechanical timers are still in use due to their simplicity and ability to function in tough environments. Types The dashpot timer is a fluid time-on-timer that can be used in definite time motor acceleration starters and controllers. A dashpot timer is a container, a piston, and a shaft. The dashpot timer functions when a magnetic field forces a piston to move within a cylinder when the coil is energized. The movement of the piston is limited by fluid passing through an orifice on the piston. The amount of fluid passing through the orifice is controlled by a throttle value, which determines the delay. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overcurrent
In an electric power system, overcurrent or excess current is a situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible causes for overcurrent include short circuits, excessive load, incorrect design, an arc fault, or a ground fault. Fuses, circuit breakers, and current limiters are commonly used overcurrent protection (OCP) mechanisms to control the risks. Circuit breakers, relays, and fuses protect circuit wiring from damage caused by overcurrent. Related standards * IEC 60364-4-43: Electrical installations of buildings – Part 4-43: Protection for safety – Protection against overcurrent See also * Current limiting * Electrical fault * Electrical safety * Overvoltage When the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Switchgear
In an electric power system, a switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is directly linked to the reliability of the electricity supply. The earliest central power stations used simple open knife switches, mounted on insulating panels of marble or asbestos. Power levels and voltages rapidly escalated, making opening manually operated switches too dangerous for anything other than isolation of a de-energized circuit. Oil-filled switchgear equipment allows arc energy to be contained and safely controlled. By the early 20th century, a switchgear line-up would be a metal-enclosed structure with electrically operated switching elements using oil circuit breakers. Today, oil-filled equipment has largely been replaced by air-blast, vacuum, or SF6 equip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relay
A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof. Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays were first used in long-distance telegraph circuits as signal repeaters: they refresh the signal coming in from one circuit by transmitting it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations. The traditional form of a relay uses an electromagnet to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aircraft Carrier
An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a naval force to project air power worldwide without depending on local bases for staging aircraft operations. Carriers have evolved since their inception in the early twentieth century from wooden vessels used to deploy balloons to nuclear-powered warships that carry numerous fighters, strike aircraft, helicopters, and other types of aircraft. While heavier aircraft such as fixed-wing gunships and bombers have been launched from aircraft carriers, these aircraft have not successfully landed on a carrier. By its diplomatic and tactical power, its mobility, its autonomy and the variety of its means, the aircraft carrier is often the centerpiece of modern combat fleets. Tactically or even strategically, it replaced the battleship in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
