Elasticityability of a deformed material body to return to its original shape and size when the forces causing the deformation are removed. A body with this ability is said to behave or respond elastically.
To a greater or lesser extent, most solid materials exhibit elastic behaviour, but there is a limit to the magnitude of the force and the accompanying deformation within which elastic recovery is possible for any given material. This limit, called the elastic limitis the maximum stress or force per unit area within a solid material that can arise before the onset of permanent deformation. Stresses beyond the elastic limit cause a material to yield or flow.
For such materials the elastic limit marks the end of elastic behaviour and the beginning of plastic behaviour. For most brittle materials, stresses beyond the elastic limit result in fracture with almost no plastic deformation. The elastic limit depends markedly on the type of solid considered; for example, a steel bar or wire can be extended elastically only about 1 percent of its original length, while for strips of certain rubberlike materials, elastic extensions of up to 1, percent can be achieved.
Steel is much stronger than rubber, however, because the tensile force required to effect the maximum elastic extension in rubber is less by a factor of about 0. The elastic properties of many solids in tension lie between these two extremes. The different macroscopic elastic properties of steel and rubber result from their very different microscopic structures. The elasticity of steel and other metals arises from short-range interatomic forces that, when the material is unstressed, maintain the atoms in regular patterns.
Under stress the atomic bonding can be broken at quite small deformations. By contrast, at the microscopic level, rubberlike materials and other polymers consist of long-chain molecules that uncoil as the material is extended and recoil in elastic recovery.
The mathematical theory of elasticity and its application to engineering mechanics is concerned with the macroscopic response of the material and not with the underlying mechanism that causes it.
The value of E depends on the material; the ratio of its values for steel and rubber is aboutIt expresses, in terms of macroscopic quantities, something about the nature or constitution of the material. This theory is commonly applied in the analysis of engineering structures and of seismic disturbances.
The elastic limit nearly coincides with the proportional limit for some elastic materials, so that at times the two are not distinguished; whereas for other materials a region of nonproportional elasticity exists between the two.
The linear theory of elasticity is not adequate for the description of the large deformations that can occur in rubber or in soft human tissue such as skin. It is available for transfer into other forms of energy—for example, into the kinetic energy of a projectile from a catapult. In this way, the elastic response of any solid in tension can be characterized by means of a stored-energy function. An important aspect of the theory of elasticity is the construction of specific forms of strain-energy function from the results of experiments involving three-dimensional deformations, generalizing the one-dimensional situation described above.
Strain-energy functions can be used to predict the behaviour of the material in circumstances in which a direct experimental test is impractical. In particular, they can be used in the design of components in engineering structures. For example, rubber is used in bridge bearings and engine mountings, where its elastic properties are important for the absorption of vibrations.
Steel beams, plates, and shells are used in many structures; their elastic flexibility contributes to the support of large stresses without material damage or failure. The elasticity of skin is an important factor in the successful practice of skin grafting. Within the mathematical framework of the theory of elasticity, problems related to such applications are solved.
The results predicted by the mathematics depend critically on the material properties incorporated in the strain-energy function, and a wide range of interesting phenomena can be modeled.
Gases and liquids also possess elastic properties since their volume changes under the action of pressure. See also deformation and flow. Article Media.
Info Print Cite. Submit Feedback. Thank you for your feedback. The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree See Article History. Read More on This Topic.Elasticity is a physical property of a material whereby the material returns to its original shape after having been stretched out or altered by force.
Substances that display a high degree of elasticity are termed "elastic. The causes of elasticity vary depending on the type of material. Polymersincluding rubber, may exhibit elasticity as polymer chains are stretched and then subsequently return to their original form when the force is removed.
Metals may display elasticity as atomic lattices change shape and size, again, returning to their original form once energy is removed. Examples: Rubber bands and elastic and other stretchy materials display elasticity. Modeling clay, on the other hand, is relatively inelastic and retains a new shape even after the force that caused it to change is no longer being exerted.
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Micellar structures and nanoporous patterns formed after beta-turn structures were present via changes in either the thermal or the mechanical inputs. A model is proposed to explain the super elasticity and energy conversion mechanisms of resilin, providing important insight into structure—function relationships for this protein.
Furthermore, this model offers a view of elastomeric proteins in general where beta-turn-related structures serve as fundamental units of the structure and elasticity. Resilin functions as a 'super elastic rubber' in specialized cuticle regions of most insects where extension and retraction are needed millions of times over the lifetime of the animals 1.
Naturally, crosslinked resilin exhibits high resilience, large strain and low moduli. As to the unique mechanical properties of resilin, several studies have been reported to understand the relationships between structure and function of this protein system, as well as providing options for potential applications for biomaterials with super elasticity 45. For example, a partial clone of resilin rec1-resilinfrom the first exon of Drosophila melanogasterprovided the major source of elasticity via unstructured amorphous features 36.
This rec1-resilin was not sufficient to store energy for jumping or flying of insects and must act as constituent of a composite with other domains in the resilin, such as the chitin-binding domain 57.
This result suggested a clue that the full-length resilin may function in both elasticity and energy storage. However, the mechanisms responsible for the storage of elastic potential energy in response to external stress remain unclear. Full-length resilin in D. Despite progress in experimental and theoretical studies, thus far no model has been developed to enable a comprehensive understanding of the role of the two fundamental constituents derived from exon I and III of full-length resilin that is, the resilin fibril nanostructure as shown in Fig.
This progress has partly been hindered due to a lack of a thorough understanding of the molecular mechanism for resilin elasticity at the nanoscale. The resilin fibrils with crosslinking consist of two major unstructured peptides derived from exon I and III of full-length resilin. The scale bar is 5 mm. Recently, we cloned and expressed the recombinant full-length resilin as a soluble protein in Escherichia coli 7.
To probe the molecular mechanism of resilin elasticity, we also produced the individual exon I and III polypeptides of resilin with a similar cloning strategy Fig. Furthermore, we have previously shown that a similar fluorescence signature was confirmed for full-length resilin as previously reported for pro-resilin Fig. In this paper, a new mechanistic model was developed to describe the elastic mechanisms of resilin, with contributions from the individual protein domains towards the behaviour of the full-length protein.
Temperature-modulated differential scanning calorimetry TM-DSC techniques were first performed to measure the transition temperatures for the full-length resilin, exon I and III samples Fig. The results indicated a two-step transition in the bound water-resilin system.
This difference indicated a specific three-dimensional functional conformation for bound water in both exons with a quick 'melting' or 'relaxation' behaviour. The non-reversing impact in thermal properties, such as the thermal contribution of water evaporation and other non-reversing transitions, are thereby eliminated for the precise identification of the two-step transitions by this technique.This patent application claims priority from German Patent Application No.
The invention relates to a power transmission mechanism, comprising at least one input and one output, a hydrodynamic component and a device for at least partially bridging over the transmission of power through the hydrodynamic component with a control device 12 assigned to the latter, comprising an actuating mechanism 13 that is actuatable by means of a chamber 15 that can be charged with a pressurizing agent.
Power transmission mechanisms that can be implemented between a drive machine and a gear component in drive trains, particularly for mobile applications, and even more particularly for motor vehicles, are known in a multitude of versions from the existing art.
These generally comprise an input and at least one output, where the input is coupleable with the drive machine directly or indirectly through additional transmission elements, and at least one output, which is connected to a gear component positioned after the power transmission mechanism, normally a manual gear-changing unit or a continuously variable transmission, and is formed by a transmission input shaft.
The latter includes at least one primary wheel that functions as a pump wheel when power is being transmitted from the input to the output, and one secondary wheel that functions in this power transmission direction as a turbine wheel.
US8220605B2 - Power transmission mechanism - Google Patents
To bridge over the hydrodynamic component, a device is provided that is also known as a lockup clutch. The latter is normally designed as a switchable clutch operating on the principle of friction, and includes a first clutch part and a second clutch part, which may be brought into operative connection with each other, at least indirectly. The lockup clutch serves here as a coupling between the input and the output, in particular as the coupling in the connection between the input and pump wheel with the turbine wheel, or the connection between turbine wheel and output.
Actuation of the switchable clutch is accomplished by way of a control device, which in its simplest form comprises an actuating device in the form of a piston element chargeable with a pressurizing agent. If the power transmission mechanism is designed as a three-channel unit, it includes at least three connections: a first connection which is coupled with the working chamber of the hydrodynamic component; a second connection which is coupled with the interior of the power transmission mechanism; and, a third connection which is coupleable with a chamber that is chargeable with a pressurizing agent, which chamber is assigned to the actuating device and through which the pressure in the actuating chamber is freely adjustable.
In this design of three-channel construction, the control device is subjected to a separately controllable pressure. The flow-through direction of the hydrodynamic component is controlled through the other connections to the working chamber of the hydrodynamic component and the intermediate spaces between the hydrodynamic component and the lockup clutch or the control device.
Power transmission mechanisms of this type are normally operated in two different operating modes, which differ in the flow of force through two different power branches; overlapping operation in both power branches is also possible.
There the transmission of power in a first power branch takes place via the hydrodynamic component. In this case the lockup clutch is deactivated and the pump wheel is coupled with the input, while the turbine wheel is connected to the output in a rotationally fixed connection. For bridging, the lockup clutch is activated and the hydrodynamic component is removed from the power stream.
However, that is normally accompanied by a strong engagement impact, which is caused in part by the non-equilibrium of the centrifugal oil pressures on the piston element of the control device for the lockup clutch.
Furthermore, the switchable clutch device can be closed actively by pressurizing the pressure chamber assigned to the control device, which is normally realized by a filling pulse in the hydraulics. This causes a relatively high volume flow, whereby the control device, in particular the piston element, is brought beyond the air space to bear against the individual clutch parts, in particular in the form of lamellae, and the necessary torque for the transmission is built up.
At the same time it is necessary, however, that the filling pulse be controlled so that the flow volume becomes zero exactly at the moment when the piston element, i. Otherwise there will be a strong pressure rise, which is manifested in an engagement impact.
In another case the control device is not in contact, and the engagement impact follows when an attempt is made to build up pressure on the converter clutch. This system is very sensitive to influences of tolerances and the environment, in particular friction, temperature and the centrifugal oil pressures, and thus is dependent on parameters that change during operation.
The bridging clutch is path-controlled in the transition from the disengaged state to the power transmitting state, and is power-controlled in the power transmitting state.
A disadvantage of the systems known heretofore is in particular the engagement impact, which has a negative impact on the driving behavior and also promotes wear. Such a design of a power transmission mechanism is described by way of example in published patent DE 52 A1.In hydraulics only liquids are considered, and for hydraulics in civil engineering, water is the prime subject of study.
Civil engineers have to design the water supply system, drainage system, irrigation canals, and dams. To do all this design and analysis a civil engineer should have a sound understanding of the basic properties of fluids.
Fluid is a substance which can flow. Technically the flow of any substance means a continuous relative motion between different particles of the substance. Now, how and why does a fluid flow? A fluid can deform under shear stress indefinitely without returning to its original position. The term fluid includes both liquid and gases. The main difference between a liquid and a gas is that the volume of a liquid remains definite because it takes the shape of the surface on or in which it comes into contact, whereas a gas occupies the complete space available in the container in which it is kept.
In hydraulics in civil engineering, the fluid for consideration is liquid, so, we will examine some terms and properties of the liquids. Mass Density : It is the mass of the fluid per unit volume. It unit is kg per cubic meter. Specific Weight : It is the weight per unit volume of the fluid. This quantity depends on the gravitational force of the place where the fluid is kept. The units for it are newton per cubic meter. Specific Volume : It is the volume occupied by the unit mass of the fluid.
Its unit is cubic meter per kg. Relative Density or Specific Gravity : It is defined as the ratio of mass density of the fluid concerned and the mass density of water at standard pressure and temperature, i. Viscosity : Viscosity is the property of fluid which defines the interaction between the moving particles of the fluid. It is the measure of resistance to the flow of fluids.
The viscous force is due to the intermolecular forces acting in the fluid. The flow or rate of deformation of fluids under shear stress is different for different fluids due to the difference in viscosity. Fluids with high viscosity deform slowly. Compressibility : When pressure is applied on a fluid, its volume decreases.
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This property of a fluid is called compressibility.Subclass G01N covers investigating, i. G01H covers the combination of generation and measurement of mechanical and other vibrations while subclass G01M covers determining unbalance by oscillating or rotating the body to be tested.
G01R covers instruments for measuring electrical variables, which can be used for balancing machines or devices but not specially adapted for this purpose. H04R covers electromechanical transducers producing acoustic waves or variations of electric variables current or voltage while G01M covers determining unbalance by converting vibrations due to unbalance into electric variables.
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:.
Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude. Correcting- or balancing-weights or equivalents means for balancing rotating bodies, e. By using thermal means, pigs or moles, fluid or vacuum, tracer materials, infrasonic, sonic, or ultrasonic vibrations, pressure or flow or level detector, light or by using other electric means, e. G01B covers apparatus, which can be used for investigating the elasticity of structures but not specially adapted for this purpose, e.
G01H covers measurement of mechanical vibrations in general. Measuring speed of fluids, e. Also covered is parachute canopy testing, testing using infrared camera, chimney testing, space conditions, simulation, testing of autopilots, heat conversion, balancing of propellers.
Partial details of wind tunnels, measurements arrangements, investigation properties, like acoustic or wind distribution, wall arrangements, wind or smoke or hot gas production, production of environmental conditions, supersonic flow generators, high speed plasma generators, holding or support devices of the object under test, vibration absorbers, isolation, high pressure wave generator.
Theoretical arrangements for aerodynamic measuring, constructions in combination with visualisation methods of flow profiles, simulation, space conditions, turbulators on airfoils for transient simulation, balances incorporated in test object. Theoretical models and model construction for aerodynamic measurements or observing or form creation. Hydrodynamic testing and arrangements therefore, e. Testing of optical apparatus, e.
Testing of headlights. Testing structures by optical methods not otherwise provided for. This group also covers theoretical articles, calibration arrangements not otherwise provided, parts of testing systems, like power meters, testing resistance to radiation, end face monitoring, photo acoustic methods.
This group is residual place for classifying testing of optical devices or apparatus not provided for in any other subclass of the CPC. Testing of particular optical devices or apparatus is often covered by the respective subclass provided for that optical devices or apparatus. Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e. In general, this group covers the testing of optical by measuring one or more given physical parameters; however, if it concerns the use of fibre for determining one or more physical parameters, see the corresponding fields for instance G01L for force measurement, G01K for temperature measurement Testing of light fibers with light source and detector on the same end, measuring connectors, optical switches, splitter in optical transmission lines, measuring end shape of fiber backscatter of cw for power measurements.
Localisation of attenuation or faults by use of single pulses and direct detection of delay-time and intensity, like OTDR, averaging, box-car, references fibers, dummy fibers, photon counting. Measurements on doped fibers, measurements using stimulated Raman or Brillouin scattering, or using laserloops or ringlasers for generating stimulated backscatter. Also refractive index profile measurements of fibers, fiber core diameter or shape or excentricity measurements, and also transversal camera monitoring.
Testing of machine parts, such as: sealing rings, gearings, power-transmitting couplings or clutches, power-transmitting endless, e. G01L covers instruments which can be used for testing of machine parts, e. G01N covers investigating, i. Devices for measuring, signaling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles.
Devices for determining the value of power, e. Means for indicating positions or pistons or cranks of internal-combustion engines by measuring pressure. Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency. Also testing of power transmitting rotating elements, like gearings, driveshaft, differentials, vehicle power transmissions, coupling, belt drives, temperature or pressure or other adaptation means, gear shifting, control tests of automatic transmission, life usage, shaft adjustments, rotation angle measurements, tests of synchronizers.We present a tractable heterogeneous-agent version of the New Keynesian model that allows us to study the interaction between inequality and monetary policy.
When prices are sticky and wages flexible, as in the textbook representative-agent model, monetary policy affects the distribution of consumption, but has no effect on output as workers choose not to change their hours worked in response to wage movements. First, the lower profits induced by higher wages raise labor supply through a wealth effect and, secondly, the mere presence of profits reduces the negative income effect of a wage rise.
When wages are rigid, in contrast, our model exhibits plausible responses of output and hours worked to monetary policy shocks. Most users should sign in with their email address. If you originally registered with a username please use that to sign in. To purchase short term access, please sign in to your Oxford Academic account above.
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Close mobile search navigation Article Navigation. Volume Oxford Academic. Google Scholar. Niels-Jakob Harbo Hansen. Per Krusell. Krusell iies.
Select Format Select format. Permissions Icon Permissions. Abstract We present a tractable heterogeneous-agent version of the New Keynesian model that allows us to study the interaction between inequality and monetary policy. Issue Section:. You do not currently have access to this article.
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