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Rheopectic
In continuum mechanics, rheopecty or rheopexy is the rare property of some non-Newtonian fluids to show a time-dependent increase in viscosity ( time-dependent viscosity); the longer the fluid undergoes shearing force, the higher its viscosity. Rheopectic fluids, such as some lubricants, thicken or solidify when shaken. The opposite and much more common type of behaviour, in which fluids become less viscous the longer they undergo shear, is called thixotropy. Examples of rheopectic fluids include gypsum pastes and printer inks. In the body synovial fluid exhibits the extraordinary property of inverse thixotropy or rheopexy. There is ongoing research into new ways to make and use rheopectic materials. There is great interest in possible military uses of this technology. Moreover, the high end of the sports market has also begun to respond to it. Body armor and combat vehicle armor are key areas where efforts are being made to use rheopectic materials. Work is also being done to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oobleck (non-Newtonian Fluid)
A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid. Many salt solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as custard, toothpaste, starch suspensions, corn starch, paint, blood, melted butter, and shampoo. Most commonly, the viscosity (the gradual deformation by shear or tensile stresses) of non-Newtonian fluids is dependent on shear rate or shear rate history. Some non-Newtonian fluids with shear-independent viscosity, however, still exhibit normal stress-differences or other non-Newtonian behavior. In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, passing through the origin, the constant of proportionality being the coefficient ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-Newtonian Fluid
A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid. Many salt solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as custard, toothpaste, starch suspensions, corn starch, paint, blood, melted butter, and shampoo. Most commonly, the viscosity (the gradual deformation by shear or tensile stresses) of non-Newtonian fluids is dependent on shear rate or shear rate history. Some non-Newtonian fluids with shear-independent viscosity, however, still exhibit normal stress-differences or other non-Newtonian behavior. In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, passing through the origin, the constant of proportionality being the coefficie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the internal frictional force between adjacent layers of fluid that are in relative motion. For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's axis than near its walls. Experiments show that some stress (such as a pressure difference between the two ends of the tube) is needed to sustain the flow. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion. For a tube with a constant rate of flow, the strength of the compensating force is proportional to the fluid's viscosity. In general, viscosity depends on a fluid's state, such as its temperature, pressure, and rate of deformation. However, the dependence on some of these properties is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-dependent Viscosity
In continuum mechanics, time-dependent viscosity is a property of fluids whose viscosity changes as a function of time. The most common type of this is thixotropy, in which the viscosity of fluids under continuous Shearing (physics), shear decreases with time; the opposite is rheopecty, in which viscosity increases with time. Thixotropic fluids Some Non-Newtonian fluid, non-Newtonian Power-law fluid, pseudoplastic fluids show a time-dependent change in viscosity and a non-linear stress-strain behavior in which the longer the fluid undergoes shear stress, the lower its viscosity becomes. A thixotropic fluid is one that takes time to attain viscosity equilibrium when introduced to a step change in shear rate. When shearing in a thixotropic fluid exceeds a certain threshold, it results in a breakdown of the fluid's microstructure and the exhibition of a shear thinning property. Certain gels or fluids that are thick (viscous) under static conditions will begin to thin and flow as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuum Mechanics
Continuum mechanics is a branch of mechanics that deals with the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles. The French mathematician Augustin-Louis Cauchy was the first to formulate such models in the 19th century. Explanation A continuum model assumes that the substance of the object fills the space it occupies. Modeling objects in this way ignores the fact that matter is made of atoms, and so is not continuous; however, on length scales much greater than that of inter-atomic distances, such models are highly accurate. These models can be used to derive differential equations that describe the behavior of such objects using physical laws, such as mass conservation, momentum conservation, and energy conservation, and some information about the material is provided by constitutive relationships. Continuum mechanics deals with the physical properties of solids and fluids which are independent of any particular coordinate sys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transportation
Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations. Transport enables human trade, which is essential for the development of civilizations. Transport infrastructure consists of both fixed installations, including roads, railways, airways, waterways, canals, and pipelines, and terminals such as airports, railway stations, bus stations, warehouses, trucking terminals, refueling depots (including fueling docks and fuel stations), and seaports. Terminals may be used both for interchange of passengers and cargo and for maintenance. Means of transport are any of the different kinds of transport facilities used to carry people or cargo. They may include vehicles, riding animals, and pack animals. Vehicl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dilatant
A dilatant (, ) (also termed shear thickening) material is one in which viscosity increases with the rate of shear strain. Such a ''shear thickening fluid'', also known by the initialism ''STF'', is an example of a non-Newtonian fluid. This behaviour is usually not observed in pure materials, but can occur in suspensions. A dilatant is a non-Newtonian fluid where the shear viscosity increases with applied shear stress. This behavior is only one type of deviation from Newton’s Law, and it is controlled by such factors as particle size, shape, and distribution. The properties of these suspensions depend on Hamaker theory and Van der Waals forces and can be stabilized electrostatically or sterically. Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation. A large portion of the properties of these systems are due to the surface chemistry of particles in dispersion, known as colloids. This can readily be seen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornstarch
Corn starch, maize starch, or cornflour (British English) is the starch derived from corn (maize) grain. The starch is obtained from the endosperm of the kernel. Corn starch is a common food ingredient, often used to thicken sauces or soups, and to make corn syrup and other sugars. Corn starch is versatile, easily modified, and finds many uses in industry such as adhesives, in paper products, as an anti-sticking agent, and textile manufacturing. It has medical uses as well, such as to supply glucose for people with glycogen storage disease. Like many products in dust form, it can be hazardous in large quantities due to its flammability—see dust explosion. When mixed with a fluid, corn starch can rearrange itself into a non-Newtonian fluid. For example, adding water transforms corn starch into a material commonly known as oobleck while adding oil transforms corn starch into an electrorheological (ER) fluid. The concept can be explained through the mixture termed "c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dual-use Technology
In politics, diplomacy and export control, dual-use items refers to goods, software and technology that can be used for both civilian and military applications.''Exporting dual-use goods.'' European Commission (accessed Aug 2022) More generally speaking, dual-use can also refer to any goods or technology which can satisfy more than one goal at any given time. Thus, expensive technologies that would otherwise benefit only civilian commercial interests can also be used to serve military purposes if they are not otherwise engaged, such as the . The "dual-use dilemma" was first noted with the discovery of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shock Absorption
A shock absorber or damper is a mechanical or hydraulic device designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typically heat) which is then dissipated. Most shock absorbers are a form of dashpot (a damper which resists motion via viscous friction). Description Pneumatic and hydraulic shock absorbers are used in conjunction with cushions and springs. An automobile shock absorber contains spring-loaded check valves and orifices to control the flow of oil through an internal piston (see below). One design consideration, when designing or choosing a shock absorber, is where that energy will go. In most shock absorbers, energy is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid heats up, while in air cylinders, the hot air is usually exhausted to the atmosphere. In other types of shock absorbers, such as electromagnetic types, the dissipated energy can be s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Footwear
Footwear refers to garments worn on the feet, which typically serves the purpose of protection against adversities of the environment such as wear from ground textures and temperature. Footwear in the manner of shoes therefore primarily serves the purpose to ease locomotion and prevent injuries. Footwear can also be used for fashion and adornment as well as to indicate the status or rank of the person within a social structure. Socks and other hosiery are typically worn additionally between the feet and other footwear for further comfort and relief. Cultures have different customs regarding footwear. These include not using any in some situations, usually bearing a symbolic meaning. This can however also be imposed on specific individuals to place them at a practical disadvantage against shod people, if they are excluded from having footwear available or are prohibited from using any. This usually takes place in situations of captivity, such as imprisonment or slavery, where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parachuting
Parachuting, including also skydiving, is a method of transiting from a high point in the Atmosphere of Earth, atmosphere to the surface of Earth with the aid of gravity, involving the control of speed during the descent using a parachute or parachutes. For human skydiving, it may involve a phase of more or less free-falling (the skydiving segment) which is a period when the parachute has not yet been deployed and the body gradually accelerates to terminal velocity. For cargo parachuting, the parachute descent may begin immediately, such as a parachute-airdrop in the Troposphere, lower atmosphere of Earth, or be significantly delayed, such as in a planetary atmosphere where an object is descending "under parachute" following atmospheric entry from outer space, space, and may begin only after the hypersonic entry phase and initial deceleration that occurs due to aerodynamic drag, friction with the thin upper atmosphere. History Common uses Parachuting is performed a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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