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Face seals are a category of products where there is no dynamic movement on the part of either the seal or the hardware surface.ISO 8434 specifies the general and dimensional requirements for the design and performance of O-ring face seal connectors made of steel for tube outside diameters or hose inside diameters of 6 mm through 38 mm, inclusive. These connectors are for use in fluid power and general applications where elastomeric seals can be used to prevent fluid leakage, including leakage caused by variations in assembly procedures. They are intended for the connection of tubes and hose fittings to ports in accordance with ISO 6149-1. | https://en.wikipedia.org/wiki/Face_seal |
In mechanical engineering, a fillet is a rounding of an interior or exterior corner of a part designed in CAD. An interior or exterior corner, with an angle or type of bevel, is called a "chamfer". Fillet geometry, when on an interior corner is a line of concave function, whereas a fillet on an exterior corner is a line of convex function (in these cases, fillets are typically referred to as rounds). Fillets commonly appear on welded, soldered, or brazed joints. | https://en.wikipedia.org/wiki/Fillet_(mechanics) |
Depending on a geometric modelling kernel different CAD software products may provide different fillet functionality. Usually fillets can be quickly designed onto parts using 3D solid modeling engineering by picking edges of interest and invoking the function. Smooth edges connecting two simple flat features are generally simple for a computer to create and fast for a human user to specify. It is pronounced as "fill-et" similarly like the Fillet in picture framing. Once these features are included in the CAD design of a part, they are often manufactured automatically using computer-numerical control. | https://en.wikipedia.org/wiki/Fillet_(mechanics) |
In mechanical engineering, a helix angle is the angle between any helix and an axial line on its right, circular cylinder or cone. Common applications are screws, helical gears, and worm gears. The helix angle references the axis of the cylinder, distinguishing it from the lead angle, which references a line perpendicular to the axis. Naturally, the helix angle is the geometric complement of the lead angle. The helix angle is measured in degrees. | https://en.wikipedia.org/wiki/Helix_angle |
In mechanical engineering, a jaw coupling is a type of general purpose power transmission coupling that also can be used in motion control (servo) applications. It is designed to transmit torque (by connecting two shafts) while damping system vibrations and accommodating misalignment, which protects other components from damage. Jaw couplings are composed of three parts: two metallic hubs and an elastomer insert called an element, but commonly referred to as a "spider". The three parts press fit together with a jaw from each hub fitted alternately with the lobes of the spider. Jaw coupling torque is transmitted through the elastomer lobes in compression. | https://en.wikipedia.org/wiki/Jaw_coupling |
In mechanical engineering, a key is a machine element used to connect a rotating machine element to a shaft. The key prevents relative rotation between the two parts and may enable torque transmission. For a key to function, the shaft and rotating machine element must have a keyway and a keyseat, which is a slot and pocket in which the key fits. | https://en.wikipedia.org/wiki/Key_(engineering) |
The whole system is called a keyed joint. A keyed joint may allow relative axial movement between the parts. Commonly keyed components include gears, pulleys, couplings, and washers. | https://en.wikipedia.org/wiki/Key_(engineering) |
In mechanical engineering, a kinematic chain is an assembly of rigid bodies connected by joints to provide constrained motion that is the mathematical model for a mechanical system. As the word chain suggests, the rigid bodies, or links, are constrained by their connections to other links. An example is the simple open chain formed by links connected in series, like the usual chain, which is the kinematic model for a typical robot manipulator.Mathematical models of the connections, or joints, between two links are termed kinematic pairs. Kinematic pairs model the hinged and sliding joints fundamental to robotics, often called lower pairs and the surface contact joints critical to cams and gearing, called higher pairs. | https://en.wikipedia.org/wiki/Kinematic_chain |
These joints are generally modeled as holonomic constraints. A kinematic diagram is a schematic of the mechanical system that shows the kinematic chain. The modern use of kinematic chains includes compliance that arises from flexure joints in precision mechanisms, link compliance in compliant mechanisms and micro-electro-mechanical systems, and cable compliance in cable robotic and tensegrity systems. | https://en.wikipedia.org/wiki/Kinematic_chain |
In mechanical engineering, a kinematic diagram or kinematic scheme (also called a joint map or skeleton diagram) illustrates the connectivity of links and joints of a mechanism or machine rather than the dimensions or shape of the parts. Often links are presented as geometric objects, such as lines, triangles or squares, that support schematic versions of the joints of the mechanism or machine.For example, the figures show the kinematic diagrams (i) of the slider-crank that forms a piston and crank-shaft in an engine, and (ii) of the first three joints for a PUMA manipulator. | https://en.wikipedia.org/wiki/Kinematic_diagram |
In mechanical engineering, a parallel force system is a situation in which two forces of equal magnitude act in the same direction within the same plane, with the counter force in the middle. An example of this is a see saw. The children are applying the two forces at the ends, and the fulcrum in the middle gives the counter force to maintain the see saw in neutral position. Another example are the major vertical forces on an airplane in flight (see image at right). | https://en.wikipedia.org/wiki/Parallel_force_system |
In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements (such as balls or rollers) between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding. One of the earliest and best-known rolling-element bearings are sets of logs laid on the ground with a large stone block on top. As the stone is pulled, the logs roll along the ground with little sliding friction. | https://en.wikipedia.org/wiki/Rolling-element_bearings |
As each log comes out the back, it is moved to the front where the block then rolls on to it. It is possible to imitate such a bearing by placing several pens or pencils on a table and placing an item on top of them. See "bearings" for more on the historical development of bearings. | https://en.wikipedia.org/wiki/Rolling-element_bearings |
A rolling element rotary bearing uses a shaft in a much larger hole, and spheres or cylinders called "rollers" tightly fill the space between the shaft and hole. As the shaft turns, each roller acts as the logs in the above example. However, since the bearing is round, the rollers never fall out from under the load. | https://en.wikipedia.org/wiki/Rolling-element_bearings |
Rolling-element bearings have the advantage of a good trade-off between cost, size, weight, carrying capacity, durability, accuracy, friction, and so on. Other bearing designs are often better on one specific attribute, but worse in most other attributes, although fluid bearings can sometimes simultaneously outperform on carrying capacity, durability, accuracy, friction, rotation rate and sometimes cost. Only plain bearings are used as widely as rolling-element bearings. | https://en.wikipedia.org/wiki/Rolling-element_bearings |
Common mechanical components where they are widely used are - automotive, industrial, marine, and aerospace applications. They are products of great necessity for modern technology. The rolling element bearing was developed from a firm foundation that was built over thousands of years. The concept emerged in its primitive form in Roman times; after a long inactive period in the Middle Ages, it was revived during the Renaissance by Leonardo da Vinci, developed steadily in the seventeenth and eighteenth centuries. | https://en.wikipedia.org/wiki/Rolling-element_bearings |
In mechanical engineering, a shaft is a rotating machine element, usually circular in cross section, which is used to transmit power from one part to another, or from a machine which produces power to a machine which absorbs power. | https://en.wikipedia.org/wiki/Shaft_(mechanical_engineering) |
In mechanical engineering, an eccentric is a circular disk (eccentric sheave) solidly fixed to a rotating axle with its centre offset from that of the axle (hence the word "eccentric", out of the center).It is used most often in steam engines, and used to convert rotary motion into linear reciprocating motion to drive a sliding valve or pump ram. To do so, an eccentric usually has a groove at its circumference closely fitted a circular collar (eccentric strap). An attached eccentric rod is suspended in such a way that its other end can impart the required reciprocating motion. A return crank fulfills the same function except that it can only work at the end of an axle or on the outside of a wheel whereas an eccentric can also be fitted to the body of the axle between the wheels. Unlike a cam, which also converts rotary into linear motion at almost any rate of acceleration and deceleration, an eccentric or return crank can only impart an approximation of simple harmonic motion. | https://en.wikipedia.org/wiki/Eccentric_(mechanism) |
In mechanical engineering, an end-face mechanical seal (often shortened to mechanical seal) is a type of seal used in rotating equipment, such as pumps, mixers, blowers, and compressors. When a pump operates, the liquid could leak out of the pump between the rotating shaft and the stationary pump casing. Since the shaft rotates, preventing this leakage can be difficult. Earlier pump models used mechanical packing (otherwise known as gland packing) to seal the shaft. | https://en.wikipedia.org/wiki/End-face_mechanical_seal |
Since World War II, mechanical seals have replaced packing in many applications. An end-face mechanical seal uses both rigid and flexible elements that maintain contact at a sealing interface and slide on each other, allowing a rotating element to pass through a sealed case. The elements are both hydraulically and mechanically loaded with a spring or other device to maintain contact. For similar designs using flexible elements, see radial shaft seal (or "lip seal") and O-ring. | https://en.wikipedia.org/wiki/End-face_mechanical_seal |
In mechanical engineering, an envelope is a solid representing all positions which may be occupied by an object during its normal range of motion. Another (jargon) word for this is a "flop". | https://en.wikipedia.org/wiki/Work_envelope |
In mechanical engineering, an overconstrained mechanism is a linkage that has more degrees of freedom than is predicted by the mobility formula. The mobility formula evaluates the degree of freedom of a system of rigid bodies that results when constraints are imposed in the form of joints between the links. If the links of the system move in three-dimensional space, then the mobility formula is M = 6 ( N − 1 − j ) + ∑ i = 1 j f i , {\displaystyle M=6(N-1-j)+\sum _{i=1}^{j}f_{i},} where N is the number of links in the system, j is the number of joints, and fi is the degree of freedom of the ith joint. | https://en.wikipedia.org/wiki/Overconstrained_mechanism |
If the links in the system move planes parallel to a fixed plane, or in concentric spheres about a fixed point, then the mobility formula is M = 3 ( N − 1 − j ) + ∑ i = 1 j f i . {\displaystyle M=3(N-1-j)+\sum _{i=1}^{j}f_{i}.} If a system of links and joints has mobility M = 0 or less, yet still moves, then it is called an overconstrained mechanism. | https://en.wikipedia.org/wiki/Overconstrained_mechanism |
In mechanical engineering, backlash is the striking back of connected wheels in a piece of mechanism when pressure is applied. Another source defines it as the maximum distance through which one part of something can be moved without moving a connected part. It is also called lash or play. In the context of gears, backlash is clearance between mating components, or the amount of lost motion due to clearance or slackness when movement is reversed and contact is re-established. | https://en.wikipedia.org/wiki/Pitch_plane |
In a pair of gears, backlash is the amount of clearance between mated gear teeth. Backlash is unavoidable for nearly all reversing mechanical couplings, although its effects can be negated. | https://en.wikipedia.org/wiki/Pitch_plane |
Depending on the application it may or may not be desirable. Reasons for requiring backlash include allowing for lubrication and thermal expansion, and to prevent jamming. Backlash may also result from manufacturing errors and deflection under load. | https://en.wikipedia.org/wiki/Pitch_plane |
In mechanical engineering, backlash, sometimes called lash, play, or slop, is a clearance or lost motion in a mechanism caused by gaps between the parts. It can be defined as "the maximum distance or angle through which any part of a mechanical system may be moved in one direction without applying appreciable force or motion to the next part in mechanical sequence."p. 1-8 An example, in the context of gears and gear trains, is the amount of clearance between mated gear teeth. It can be seen when the direction of movement is reversed and the slack or lost motion is taken up before the reversal of motion is complete. | https://en.wikipedia.org/wiki/Backlash_(engineering) |
It can be heard from the railway couplings when a train reverses direction. Another example is in a valve train with mechanical tappets, where a certain range of lash is necessary for the valves to work properly. Depending on the application, backlash may or may not be desirable. | https://en.wikipedia.org/wiki/Backlash_(engineering) |
Some amount of backlash is unavoidable in nearly all reversing mechanical couplings, although its effects can be negated or compensated for. In many applications, the theoretical ideal would be zero backlash, but in actual practice some backlash must be allowed to prevent jamming. Reasons for specifying a requirement for backlash include allowing for lubrication, manufacturing errors, deflection under load, and thermal expansion. A principal cause of undesired backlash is wear. | https://en.wikipedia.org/wiki/Backlash_(engineering) |
In mechanical engineering, it is one part of a rotating joint where a shaft (the trunnion) is inserted into (and turns inside) a full or partial cylinder. Often used in opposing pairs, this joint allows tight tolerances and strength from a large surface contact area between the trunnion and the cylinder.In airframe engineering, these are self-contained concentric bearings that are designed to offer fluid movement in a critical area of the steering. The term is also used to describe the wheel that a rotating cylinder runs on. For example, a lapidary (stone-polishing) cylinder runs on a pair of rollers, similar to trunnions. | https://en.wikipedia.org/wiki/Trunnion |
The sugar industry uses rotating cylinders up to 22 feet (7 m) in diameter, 131 ft (40 m) long, and weighing around 1,000 tons. These rotate at around 30 revolutions per hour. | https://en.wikipedia.org/wiki/Trunnion |
They are supported on a pathring, which runs on trunnions. Similar devices called rotary kilns are used in cement manufacturing. In mining, some refining plants utilise drum scrubbers in the process that are supported by a large trunnion and associated trunnion bearings at each end. | https://en.wikipedia.org/wiki/Trunnion |
In mechanical engineering, kinematic synthesis (also known as mechanism synthesis) determines the size and configuration of mechanisms that shape the flow of power through a mechanical system, or machine, to achieve a desired performance. The word synthesis refers to combining parts to form a whole. Hartenberg and Denavit describe kinematic synthesis as ...it is design, the creation of something new. | https://en.wikipedia.org/wiki/Kinematic_synthesis |
Kinematically, it is the conversion of a motion idea into hardware. The earliest machines were designed to amplify human and animal effort, later gear trains and linkage systems captured wind and flowing water to rotate millstones and pumps. Now machines use chemical and electric power to manufacture, transport, and process items of all types. | https://en.wikipedia.org/wiki/Kinematic_synthesis |
And kinematic synthesis is the collection of techniques for designing those elements of these machines that achieve required output forces and movement for a given input. Applications of kinematic synthesis include determining: the topology and dimensions of a linkage system to achieve a specified task; the size and shape of links of a robot to move parts and apply forces in a specified workspace; the mechanical configuration of end-effectors, or grippers, for robotic systems; the shape of a cam and follower to achieve a desired output movement coordinated with a specified input movement; the shape of gear teeth to ensure a desired coordination of input and output movement; the configuration of a system of gears, belts, and cable, or rope drives, to perform a desired power transmission; the size and shape of fixturing systems to provide precision in part manufacture and component assembly.Kinematic synthesis for a mechanical system is described as having three general phases, known as type synthesis, number synthesis and dimensional synthesis. Type synthesis matches the general characteristics of a mechanical system to the task at hand, selecting from an array of devices such as a cam-follower mechanism, linkage, gear train, a fixture or a robotic system for use in a required task. Number synthesis considers the various ways a particular device can be constructed, generally focussed on the number and features of the parts. Finally, dimensional synthesis determines the geometry and assembly of the components that form the device. | https://en.wikipedia.org/wiki/Kinematic_synthesis |
In mechanical engineering, limits and fits are a set of rules regarding the dimensions and tolerances of mating machined parts if they are to achieve the desired ease of assembly, and security after assembly - sliding fit, interference fit, rotating fit, non-sliding fit, loose fit, etc. Tolerances are typically specified in thousandths of an inch or hundredths of a millimetre. | https://en.wikipedia.org/wiki/Limits_and_fits |
In mechanical engineering, many terms are associated into pairs called duals. A dual of a relationship is formed by interchanging force (stress) and deformation (strain) in an expression. Here is a partial list of mechanical dualities: force — deformation stress — strain stiffness method — flexibility method | https://en.wikipedia.org/wiki/Duality_(mechanical_engineering) |
In mechanical engineering, mechanical efficiency is a dimensionless number that measures the efficiency of a mechanism or machine in transforming the power input to the device to power output. A machine is a mechanical linkage in which force is applied at one point, and the force does work moving a load at another point. At any instant the power input to a machine is equal to the input force multiplied by the velocity of the input point, similarly the power output is equal to the force exerted on the load multiplied by the velocity of the load. The mechanical efficiency of a machine (often represented by the Greek letter eta η {\displaystyle \eta } ) is a dimensionless number between 0 and 1 that is the ratio between the power output of the machine and the power input η = Power output Power input {\displaystyle \eta ={\frac {\text{Power output}}{\text{Power input}}}} Since a machine does not contain a source of energy, nor can it store energy, from conservation of energy the power output of a machine can never be greater than its input, so the efficiency can never be greater than 1. | https://en.wikipedia.org/wiki/Mechanical_efficiency |
All real machines lose energy to friction; the energy is dissipated as heat. Therefore, their power output is less than their power input Power output = Power input − Frictional power loss {\displaystyle {\text{Power output}}={\text{Power input}}-{\text{Frictional power loss}}} Therefore, the efficiency of all real machines is less than 1. A hypothetical machine without friction is called an ideal machine, such a machine would not have any energy losses, so its output power would equal its input power, and its efficiency would be 1. (100%) For hydropower turbines the efficiency is referred to as hydraulic efficiency. | https://en.wikipedia.org/wiki/Mechanical_efficiency |
In mechanical engineering, random vibration is motion which is non-deterministic, meaning that future behavior cannot be precisely predicted. The randomness is a characteristic of the excitation or input, not the 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. | https://en.wikipedia.org/wiki/Random_vibration |
Mathematically, random vibration is characterized as an ergodic and stationary process. A measurement of the acceleration spectral density (ASD) is the usual way to specify random vibration. The root mean square acceleration (Grms) is the square root of the area under the ASD curve in the frequency domain. | https://en.wikipedia.org/wiki/Random_vibration |
The Grms value is typically used to express the overall energy of a particular random vibration event and is a statistical value used in mechanical engineering for structural design and analysis purposes. While the term power spectral density (PSD) is commonly used to specify a random vibration event, ASD is more appropriate when acceleration is being measured and used in structural analysis and testing. Crandall is uniformly considered as the father of random vibrations (see also books by Bolotin, Elishakoff et al.). The dramatic effect of often neglected cross-correlations is elucidated in the monograph by Elishakoff. | https://en.wikipedia.org/wiki/Random_vibration |
In mechanical engineering, stressed skin is a type of rigid construction, intermediate between monocoque and a rigid frame with a non-loaded covering. A stressed skin structure has its compression-taking elements localized and its tension-taking elements distributed. Typically, the main frame has rectangular structure and is triangulated by the covering. | https://en.wikipedia.org/wiki/Stressed_skin |
In mechanical engineering, the Beale number is a parameter that characterizes the performance of Stirling engines. It is often used to estimate the power output of a Stirling engine design. For engines operating with a high temperature differential, typical values for the Beale number are in the range 0.11−0.15; where a larger number indicates higher performance. | https://en.wikipedia.org/wiki/Beale_number |
In mechanical engineering, the Denavit–Hartenberg parameters (also called DH parameters) are the four parameters associated with a particular convention for attaching reference frames to the links of a spatial kinematic chain, or robot manipulator. Jacques Denavit and Richard Hartenberg introduced this convention in 1955 in order to standardize the coordinate frames for spatial linkages.Richard Paul demonstrated its value for the kinematic analysis of robotic systems in 1981. While many conventions for attaching reference frames have been developed, the Denavit–Hartenberg convention remains a popular approach. | https://en.wikipedia.org/wiki/Denavit–Hartenberg_parameters |
In mechanical engineering, the cylinders of reciprocating engines are often classified by whether they are single- or double-acting, depending on how the working fluid acts on the piston. | https://en.wikipedia.org/wiki/Double_acting_cylinder |
In mechanical engineering, the thread angle of a screw is the included angle between the thread flanks, measured in a plane containing the thread axis. This is a defining factor for the shape of a screw thread. Standard values include: | https://en.wikipedia.org/wiki/Thread_angle |
In mechanical engineering, ultimate failure describes the breaking of a material. In general there are two types of failure: fracture and buckling. Fracture of a material occurs when either an internal or external crack elongates the width or length of the material. In ultimate failure this will result in one or more breaks in the material. | https://en.wikipedia.org/wiki/Ultimate_failure |
Buckling occurs when compressive loads are applied to the material and instead of cracking the material bows. This is undesirable because most tools that are designed to be straight will be inadequate if curved. If the buckling continues, it will create tension on the outer side of the bend and compression on the inner side, potentially fracturing the material. | https://en.wikipedia.org/wiki/Ultimate_failure |
In engineering there are multiple types of failure based upon the application of the material. In many machine applications any change in the part due to yielding will result in the machine piece needing to be replaced. Although this deformation or weakening of the material is not the technical definition of ultimate failure, the piece has failed. | https://en.wikipedia.org/wiki/Ultimate_failure |
In most technical applications, pieces are rarely allowed to reach their ultimate failure or breakage point, instead for safety factors they are removed at the first signs of significant wear. There are two different types of fracture: brittle and ductile. | https://en.wikipedia.org/wiki/Ultimate_failure |
Each of these types of failure occur based on the material's ductility. Brittle failure occurs with little to no plastic deformation before fracture. | https://en.wikipedia.org/wiki/Ultimate_failure |
An example of this would be stretching a clay pot or rod, when it is stretched it will not neck or elongate, but merely break into two or more pieces. While applying a tensile stress to a ductile material, instead of immediately breaking the material will instead elongate. The material will begin by elongating uniformly until it reaches the yield point, then the material will begin to neck. | https://en.wikipedia.org/wiki/Ultimate_failure |
When necking occurs the material will begin to stretch more in the middle and the radius will decrease. Once this begins the material has entered a stage called plastic deformation. Once the material has reached its ultimate tensile strength it will elongate more easily until it reaches ultimate failure and breaks. | https://en.wikipedia.org/wiki/Ultimate_failure |
In mechanical horology, a remontoire (from the French remonter, meaning 'to wind') is a small secondary source of power, a weight or spring, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as a mainspring. It was used in a few precision clocks and watches to place the source of power closer to the escapement, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction in the geartrain. In spring-driven precision clocks, a gravity remontoire is sometimes used to replace the uneven force delivered by the mainspring running down by the more constant force of gravity acting on a weight. In turret clocks, it serves to separate the large forces needed to drive the hands from the modest forces needed to drive the escapement which keeps the pendulum swinging. A remontoire should not be confused with a maintaining power spring, which is used only to keep the timepiece going while it is being wound. | https://en.wikipedia.org/wiki/Remontoire |
In mechanical interlocking plants, a locking bed is constructed, consisting of steel bars forming a grid. The levers that operate switches, derails, signals or other appliances are connected to the bars running in one direction. The bars are constructed so that if the function controlled by a given lever conflicts with that controlled by another lever, mechanical interference is set up in the cross locking between the two bars, in turn preventing the conflicting lever movement from being made. In purely mechanical plants, the levers operate the field devices, such as signals, directly via a mechanical rodding or wire connection. | https://en.wikipedia.org/wiki/Electronic_interlocking |
The levers are about shoulder height since they must supply a mechanical advantage for the operator. Cross locking of levers was effected such that the extra leverage could not defeat the locking (preliminary latch lock). The first mechanical interlocking was installed in 1843 at Bricklayers Arms Junction, England. : 7 | https://en.wikipedia.org/wiki/Electronic_interlocking |
In mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. An overdrive is sometimes mistakenly called a freewheel, but is otherwise unrelated. The condition of a driven shaft spinning faster than its driveshaft exists in most bicycles when the rider stops pedaling. | https://en.wikipedia.org/wiki/Overrunning_clutch |
In a fixed-gear bicycle, without a freewheel, the rear wheel drives the pedals around. An analogous condition exists in an automobile with a manual transmission going downhill, or any situation where the driver takes their foot off the gas pedal, closing the throttle: the wheels drive the engine, possibly at a higher RPM. In a two-stroke engine, this can be catastrophic—as many two stroke engines depend on a fuel/oil mixture for lubrication, a shortage of fuel to the engine starves oil from the cylinders, and the pistons can soon seize, causing extensive damage. Saab used a freewheel system in their two-stroke models for this reason and maintained it in the Saab 96 V4 and early Saab 99 for better fuel efficiency. | https://en.wikipedia.org/wiki/Overrunning_clutch |
In mechanical systems, the position coordinates and velocities of mechanical parts are typical state variables; knowing these, it is possible to determine the future state of the objects in the system. In thermodynamics, a state variable is an independent variable of a state function. Examples include internal energy, enthalpy, temperature, pressure, volume and entropy. | https://en.wikipedia.org/wiki/State_Variable |
Heat and work are not state functions, but process functions. In electronic/electrical circuits, the voltages of the nodes and the currents through components in the circuit are usually the state variables. In any electrical circuit, the number of state variables are equal to the number of (independent) storage elements, which are inductors and capacitors. The state variable for an inductor is the current through the inductor, while that for a capacitor is the voltage across the capacitor. In ecosystem models, population sizes (or concentrations) of plants, animals and resources (nutrients, organic material) are typical state variables. | https://en.wikipedia.org/wiki/State_Variable |
In mechanical typewriters, the shift key functions by mechanically shifting some component so an alternate row of characters on typebars hits the paper. In an electronic system, by contrast, there is no necessary connection between the code points of unshifted and shifted values, though implementation is simpler if the code points of unshifted and shifted keys are related, most simply by a single bit differing. In electromechanical systems, this makes a significant difference in ease of implementation, as shifting must be accomplished by some physical linkage. For this reason, among others (such as ease of collation), the ASCII standard strove to organize the code points so that shifting could be implemented by simply toggling a bit. | https://en.wikipedia.org/wiki/Bit-paired_keyboard |
This is most conspicuous in uppercase and lowercase characters: uppercase characters are in columns 4 (100) and 5 (101), while the corresponding lowercase characters are in columns 6 (110) and 7 (111), requiring only toggling the 6th bit (2nd high bit) to switch case; as there are only 26 letters, the remaining 6 points in each column were occupied by symbols or, in one case, a control character (DEL, in 127). This is also present, but less precisely, in the organization of digits and symbols in columns 2 (010) and 3 (011) – this discrepancy is the source of bit-paired layouts. Ideally the characters would have been ordered so that unshifted and shifted values of a typewriter key were in adjacent columns, allowing shifting to be implemented by toggling the 5th bit (1st high bit). | https://en.wikipedia.org/wiki/Bit-paired_keyboard |
Due to other concerns, this correspondence is inexact: for example, SP (Space) and 0 (zero) both have low bits 00000 (to ease collation for space and conversion to/from binary-coded decimal for 0), preventing 0 from lining up with ) (right parenthesis), its conventional value, and thus instead () corresponded to 89, instead of 90 as on typewriters. Further, while digits were placed in column 3, the characters ,-./ (conventionally unshifted) were placed in column 2, to ease collation, due to being used as separators, and the characters ;: (conventionally paired) were both placed in column 3. Other symbols also did not line up with their conventional digit pair, as detailed below. | https://en.wikipedia.org/wiki/Bit-paired_keyboard |
As a result, implementing an electromechanical keyboard that produced an ASCII encoding but had conventional typewriter key mappings would require significant complexity due to key-specific shift mechanisms for digits and symbol keys. This could be avoided by changing the key mappings to correspond to the ASCII table, which was notably done in the Teletype Model 33 (1963). Later keyboards continued to use this mapping, which was formalized in the American Standards Association X4.14-1971 standard and the European Computer Manufacturers' Association ECMA-23 standard, where it is referred to as logical bit pairing, and contrasted with typewriter pairing. In everyday usage these were referred to as bit-paired and typewriter-paired keyboards. | https://en.wikipedia.org/wiki/Bit-paired_keyboard |
In mechanical-shaker baghouses, tubular filter bags are fastened onto a cell plate at the bottom of the baghouse and suspended from horizontal beams at the top. Dirty gas enters the bottom of the baghouse and passes through the filter, and the dust collects on the inside surface of the bags. Cleaning a mechanical-shaker baghouse is accomplished by shaking the top horizontal bar from which the bags are suspended. Vibration produced by a motor-driven shaft and cam creates waves in the bags to shake off the dust cake. | https://en.wikipedia.org/wiki/Fabric_filter |
Shaker baghouses range in size from small, handshaker devices to large, compartmentalized units. They can operate intermittently or continuously. Intermittent units can be used when processes operate on a batch basis; when a batch is completed, the baghouse can be cleaned. | https://en.wikipedia.org/wiki/Fabric_filter |
Continuous processes use compartmentalized baghouses; when one compartment is being cleaned, the airflow can be diverted to other compartments. In shaker baghouses, there must be no positive pressure inside the bags during the shake cycle. Pressures as low as 5 pascals (0.00073 psi) can interfere with cleaning. The air-to-cloth ratio for shaker baghouses is relatively low, hence the space requirements are quite high. However, because of the simplicity of design, they are popular in the minerals processing industry. | https://en.wikipedia.org/wiki/Fabric_filter |
In mechanically controlled variable capacitors, the distance between the plates, or the amount of plate surface area which overlaps, can be changed. The most common form arranges a group of semicircular metal plates on a rotary axis ("rotor") that are positioned in the gaps between a set of stationary plates ("stator") so that the area of overlap can be changed by rotating the axis. Air or plastic foils can be used as dielectric material. By choosing the shape of the rotary plates, various functions of capacitance vs. angle can be created, e.g. to obtain a linear frequency scale. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
Various forms of reduction gear mechanisms are often used to achieve finer tuning control, i.e. to spread the variation of capacity over a larger angle, often several turns. Maximum capacitance is achieved when the plates are "meshed" together, that is, they are inter-laced. Minimum capacitance is achieved when the plates are "unmeshed", that is, they are not inter-laced. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
Measurement of the capacitance of a rotary capacitor A vacuum variable capacitor uses a set of plates made from concentric cylinders that can be slid in or out of an opposing set of cylinders (sleeve and plunger). These plates are then sealed inside of a non-conductive envelope such as glass or ceramic and placed under a high vacuum. The movable part (plunger) is mounted on a flexible metal membrane that seals and maintains the vacuum. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
A screw shaft is attached to the plunger; when the shaft is turned the plunger moves in or out of the sleeve and the value of the capacitor changes. The vacuum not only increases the working voltage and current handling capacity of the capacitor, it also greatly reduces the chance of arcing across the plates. The most common usage for vacuum variables are in high-powered transmitters such as those used for broadcasting, military and amateur radio, as well as high-powered RF tuning networks. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
Vacuum variables can also be more convenient; since the elements are under a vacuum, the working voltage can be higher than an air variable the same size, allowing the size of the vacuum capacitor to be reduced. Very cheap variable capacitors are constructed from layered aluminium and plastic foils that are variably pressed together using a screw. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
These so-called squeezers cannot provide a stable and reproducible capacitance, however. A variant of this structure that allows for linear movement of one set of plates to change the plate overlap area is also used and might be called a slider. This has practical advantages for makeshift or home construction, and may be found in resonant-loop antennas or crystal radios. Small variable capacitors operated by screwdriver (for instance, to precisely set a resonant frequency at the factory and then never be adjusted again) are called trimmer capacitors. In addition to air and plastic, trimmers can also be made using a solid dielectric, such as mica. | https://en.wikipedia.org/wiki/Air_gap_capacitor |
In mechanics and aerodynamics, the drag area of an object represents the effective size of the object as it is "seen" by the fluid flow around it. The drag area is usually expressed as a product C d A , {\displaystyle C_{d}A,} where A {\displaystyle A} is a representative area of the object, and C d {\displaystyle C_{d}} is the drag coefficient, which represents what shape it has and how streamlined it is. The drag coefficient plays a role in Reynold's drag equation, F d = 1 2 ρ C d A v 2 . {\displaystyle F_{d}={\frac {1}{2}}\ \rho \ C_{d}A\ v^{2}.} Here, F d {\displaystyle F_{d}} is the drag force, ρ {\displaystyle \rho } the density of the fluid, and v {\displaystyle v} the speed of the object relative to the fluid. | https://en.wikipedia.org/wiki/Drag_area |
In mechanics and construction a resonance disaster describes the destruction of a building or a technical mechanism by induced vibrations at a system's resonant frequency, which causes it to oscillate. Periodic excitation optimally transfers to the system the energy of the vibration and stores it there. Because of this repeated storage and additional energy input the system swings ever more strongly, until its load limit is exceeded. | https://en.wikipedia.org/wiki/Mechanical_resonance |
In mechanics and geology, pure shear is a three-dimensional homogeneous flattening of a body. It is an example of irrotational strain in which body is elongated in one direction while being shortened perpendicularly. For soft materials, such as rubber, a strain state of pure shear is often used for characterizing hyperelastic and fracture mechanical behaviour. Pure shear is differentiated from simple shear in that pure shear involves no rigid body rotation. The deformation gradient for pure shear is given by: F = {\displaystyle F={\begin{bmatrix}1&\gamma &0\\\gamma &1&0\\0&0&1\end{bmatrix}}} Note that this gives a Green-Lagrange strain of: E = 1 2 {\displaystyle E={\frac {1}{2}}{\begin{bmatrix}\gamma ^{2}&2\gamma &0\\2\gamma &\gamma ^{2}&0\\0&0&0\end{bmatrix}}} Here there is no rotation occurring, which can be seen from the equal off-diagonal components of the strain tensor. The linear approximation to the Green-Lagrange strain shows that the small strain tensor is: ϵ = 1 2 {\displaystyle \epsilon ={\frac {1}{2}}{\begin{bmatrix}0&2\gamma &0\\2\gamma &0&0\\0&0&0\end{bmatrix}}} which has only shearing components. | https://en.wikipedia.org/wiki/Pure_shear |
In mechanics and geometry, the 3D rotation group, often denoted SO(3), is the group of all rotations about the origin of three-dimensional Euclidean space R 3 {\displaystyle \mathbb {R} ^{3}} under the operation of composition.By definition, a rotation about the origin is a transformation that preserves the origin, Euclidean distance (so it is an isometry), and orientation (i.e., handedness of space). Composing two rotations results in another rotation, every rotation has a unique inverse rotation, and the identity map satisfies the definition of a rotation. Owing to the above properties (along composite rotations' associative property), the set of all rotations is a group under composition. Every non-trivial rotation is determined by its axis of rotation (a line through the origin) and its angle of rotation. | https://en.wikipedia.org/wiki/Set_of_3D_rotations |
Rotations are not commutative (for example, rotating R 90° in the x-y plane followed by S 90° in the y-z plane is not the same as S followed by R), making the 3D rotation group a nonabelian group. Moreover, the rotation group has a natural structure as a manifold for which the group operations are smoothly differentiable, so it is in fact a Lie group. | https://en.wikipedia.org/wiki/Set_of_3D_rotations |
It is compact and has dimension 3. Rotations are linear transformations of R 3 {\displaystyle \mathbb {R} ^{3}} and can therefore be represented by matrices once a basis of R 3 {\displaystyle \mathbb {R} ^{3}} has been chosen. Specifically, if we choose an orthonormal basis of R 3 {\displaystyle \mathbb {R} ^{3}} , every rotation is described by an orthogonal 3 × 3 matrix (i.e., a 3 × 3 matrix with real entries which, when multiplied by its transpose, results in the identity matrix) with determinant 1. | https://en.wikipedia.org/wiki/Set_of_3D_rotations |
The group SO(3) can therefore be identified with the group of these matrices under matrix multiplication. These matrices are known as "special orthogonal matrices", explaining the notation SO(3). The group SO(3) is used to describe the possible rotational symmetries of an object, as well as the possible orientations of an object in space. Its representations are important in physics, where they give rise to the elementary particles of integer spin. | https://en.wikipedia.org/wiki/Set_of_3D_rotations |
In mechanics and materials science, strain rate is the time derivative of strain of a material. Strain rate has dimension of inverse time and SI units of inverse second, s−1 (or its multiples). The strain rate at some point within the material measures the rate at which the distances of adjacent parcels of the material change with time in the neighborhood of that point. It comprises both the rate at which the material is expanding or shrinking (expansion rate), and also the rate at which it is being deformed by progressive shearing without changing its volume (shear rate). | https://en.wikipedia.org/wiki/Strain_rate |
It is zero if these distances do not change, as happens when all particles in some region are moving with the same velocity (same speed and direction) and/or rotating with the same angular velocity, as if that part of the medium were a rigid body. The strain rate is a concept of materials science and continuum mechanics that plays an essential role in the physics of fluids and deformable solids. In an isotropic Newtonian fluid, in particular, the viscous stress is a linear function of the rate of strain, defined by two coefficients, one relating to the expansion rate (the bulk viscosity coefficient) and one relating to the shear rate (the "ordinary" viscosity coefficient). In solids, higher strain rates can often cause normally ductile materials to fail in a brittle manner. | https://en.wikipedia.org/wiki/Strain_rate |
In mechanics and physics, shock is a sudden acceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation. Shock describes matter subject to extreme rates of force with respect to time. Shock is a vector that has units of an acceleration (rate of change of velocity). | https://en.wikipedia.org/wiki/Shock_(mechanics) |
The unit g (or g) represents multiples of the standard acceleration of gravity and is conventionally used. A shock pulse can be characterised by its peak acceleration, the duration, and the shape of the shock pulse (half sine, triangular, trapezoidal, etc.). The shock response spectrum is a method for further evaluating a mechanical shock. | https://en.wikipedia.org/wiki/Shock_(mechanics) |
In mechanics and physics, simple harmonic motion (sometimes abbreviated SHM) is a special type of periodic motion an object experiences due to a restoring force whose magnitude is directly proportional to the distance of the object from an equilibrium position and acts towards the equilibrium position. It results in an oscillation that is described by a sinusoid which continues indefinitely (if uninhibited by friction or any other dissipation of energy). Simple harmonic motion can serve as a mathematical model for a variety of motions, but is typified by the oscillation of a mass on a spring when it is subject to the linear elastic restoring force given by Hooke's law. | https://en.wikipedia.org/wiki/Simple_Harmonic_Motion |
The motion is sinusoidal in time and demonstrates a single resonant frequency. Other phenomena can be modeled by simple harmonic motion, including the motion of a simple pendulum, although for it to be an accurate model, the net force on the object at the end of the pendulum must be proportional to the displacement (and even so, it is only a good approximation when the angle of the swing is small; see small-angle approximation). Simple harmonic motion can also be used to model molecular vibration. Simple harmonic motion provides a basis for the characterization of more complicated periodic motion through the techniques of Fourier analysis. | https://en.wikipedia.org/wiki/Simple_Harmonic_Motion |
In mechanics and thermodynamics, thermal stress is mechanical stress created by any change in temperature of a material. These stresses can lead to fracturing or plastic deformation depending on the other variables of heating, which include material types and constraints. Temperature gradients, thermal expansion or contraction and thermal shocks are things that can lead to thermal stress. | https://en.wikipedia.org/wiki/Heat_load |
This type of stress is highly dependent on the thermal expansion coefficient which varies from material to material. In general, the greater the temperature change, the higher the level of stress that can occur. Thermal shock can result from a rapid change in temperature, resulting in cracking or shattering. | https://en.wikipedia.org/wiki/Heat_load |
In mechanics, "stiffening" beams brings anti-buckling, anti-wrinkling, desired shaping, reinforcement, repair, strength, enhanced function, extended utility, longer beam life, safety, etc. Stiffening of fluid or rigid beams is used in medical arts, aerospace, aviation, sports, bookbinding, art, architecture, natural plants and trees, construction industry, bridge building, and more. Mechanical methods for stiffening include tension stiffening, centrifugal stiffening, bracing, superstructure bracing, substructure bracing, straightening, strain stiffening, stress stiffening, damping vibrations, swelling, pressure increasing, drying, cooling, interior reinforcing, exterior reinforcing, wrapping, surface treating, or combinations of these and other methods. Beams under bending loads or compression invite stiffening to stop buckling or collapse while fulfilling desired functions, purposes, and benefits. | https://en.wikipedia.org/wiki/Stiffening |
In mechanics, Avicenna, in The Book of Healing, developed a theory of motion, in which he made a distinction between the inclination (tendency to motion) and force of a projectile, and concluded that motion was a result of an inclination (mayl) transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease. He viewed inclination as a permanent force whose effect is dissipated by external forces such as air resistance.The theory of motion presented by Avicenna was probably influenced by the 6th-century Alexandrian scholar John Philoponus. Avicenna's is a less sophisticated variant of the theory of impetus developed by Buridan in the 14th century. | https://en.wikipedia.org/wiki/Avicennian_logic |
It is unclear if Buridan was influenced by Avicenna, or by Philoponus directly.In optics, Avicenna was among those who argued that light had a speed, observing that "if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite." He also provided a wrong explanation of the rainbow phenomenon. Carl Benjamin Boyer described Avicenna's ("Ibn Sīnā") theory on the rainbow as follows: Independent observation had demonstrated to him that the bow is not formed in the dark cloud but rather in the very thin mist lying between the cloud and the sun or observer. | https://en.wikipedia.org/wiki/Avicennian_logic |
The cloud, he thought, serves as the background of this thin substance, much as a quicksilver lining is placed upon the rear surface of the glass in a mirror. Ibn Sīnā would change the place not only of the bow, but also of the color formation, holding the iridescence to be merely a subjective sensation in the eye. In 1253, a Latin text entitled Speculum Tripartitum stated the following regarding Avicenna's theory on heat: Avicenna says in his book of heaven and earth, that heat is generated from motion in external things. | https://en.wikipedia.org/wiki/Avicennian_logic |
In mechanics, Sommerfeld effect is a phenomenon arising from feedback in the energy exchange between vibrating systems: for example, when for the rocking table, under given conditions, energy transmitted to the motor resulted not in higher revolutions but in stronger vibrations of the table. It is named after Arnold Sommerfeld. In 1902, A. Sommerfeld analyzed the vibrations caused by a motor driving an unbalanced weight and wrote that "This experiment corresponds roughly to the case in which a factory owner has a machine set on a poor foundation running at 30 horsepower. He achieves an effective level of just 1/3, however, because only 10 horsepower are doing useful work, while 20 horsepower are transferred to the foundational masonry". First mathematical descriptions of Sommerfeld effect were suggested by I. Blekhman and V. Konenko. | https://en.wikipedia.org/wiki/Sommerfeld_effect |
In mechanics, a constant of motion is a quantity that is conserved throughout the motion, imposing in effect a constraint on the motion. However, it is a mathematical constraint, the natural consequence of the equations of motion, rather than a physical constraint (which would require extra constraint forces). Common examples include energy, linear momentum, angular momentum and the Laplace–Runge–Lenz vector (for inverse-square force laws). | https://en.wikipedia.org/wiki/Dirac_observables |
In mechanics, a couple is a system of forces with a resultant (a.k.a. net or sum) moment of force but no resultant force.A better term is force couple or pure moment. Its effect is to impart angular momentum but no linear momentum. | https://en.wikipedia.org/wiki/Couple_(mechanics) |
In rigid body dynamics, force couples are free vectors, meaning their effects on a body are independent of the point of application. The resultant moment of a couple is a special case of moment. A couple has the property that it is independent of reference point. | https://en.wikipedia.org/wiki/Couple_(mechanics) |
In mechanics, a cylinder stress is a stress distribution with rotational symmetry; that is, which remains unchanged if the stressed object is rotated about some fixed axis. Cylinder stress patterns include: circumferential stress, or hoop stress, a normal stress in the tangential (azimuth) direction. axial stress, a normal stress parallel to the axis of cylindrical symmetry. radial stress, a normal stress in directions coplanar with but perpendicular to the symmetry axis.These three principal stresses- hoop, longitudinal, and radial can be calculated analytically using a mutually perpendicular tri-axial stress system.The classical example (and namesake) of hoop stress is the tension applied to the iron bands, or hoops, of a wooden barrel. | https://en.wikipedia.org/wiki/Cylinder_stress |
In a straight, closed pipe, any force applied to the cylindrical pipe wall by a pressure differential will ultimately give rise to hoop stresses. Similarly, if this pipe has flat end caps, any force applied to them by static pressure will induce a perpendicular axial stress on the same pipe wall. Thin sections often have negligibly small radial stress, but accurate models of thicker-walled cylindrical shells require such stresses to be considered. | https://en.wikipedia.org/wiki/Cylinder_stress |
In thick-walled pressure vessels, construction techniques allowing for favorable initial stress patterns can be utilized. These compressive stresses at the inner surface reduce the overall hoop stress in pressurized cylinders. Cylindrical vessels of this nature are generally constructed from concentric cylinders shrunk over (or expanded into) one another, i.e., built-up shrink-fit cylinders, but can also be performed to singular cylinders though autofrettage of thick cylinders. | https://en.wikipedia.org/wiki/Cylinder_stress |
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