Alperm (also alfenol or alfer ) is a class of alloys comprising 83-90% of iron and 10-17% of aluminium . The most widely used composition is with 16% Al.
53-580: An alloy with 13% Al is also sometimes referred to as alfer . It exhibits large magnetostriction and it is used in magnetoelastic sensors. Later during the WW2, Japanese used the alloy with 12.7-12.9% aluminium as a replacement of nickel for the magnetostrictive transducers used in their Type 93 model 5, Type 3, and Simple naval sonars . Alperm is magnetically soft and exhibits high magnetic permeability . The material can be produced in 0.5 mm thick sheets, as well as 50-60 μm thick ribbons. The coercivity
106-475: A H 2 S atmosphere. Thus, single-crystal-like texture (~90% {011} grain coverage) is attainable, reducing the interference with magnetic domain alignment and increasing microstrain attainable for polycrystalline alloys as measured by semiconducting strain gauges . These surface textures can be visualized using electron backscatter diffraction (EBSD) or related diffraction techniques. For actuator applications, maximum rotation of magnetic moments leads to
159-427: A the acceleration of the object and the distance traveled by the accelerated object in time t , we find with v = a t {\displaystyle v=at} for the velocity v of the object The work done in accelerating a particle with mass m during the infinitesimal time interval dt is given by the dot product of force F and the infinitesimal displacement d x where we have assumed
212-410: A body's mass, inertia, and total energy. In fluid dynamics , the kinetic energy per unit volume at each point in an incompressible fluid flow field is called the dynamic pressure at that point. Dividing by V, the unit of volume: where q {\displaystyle q} is the dynamic pressure, and ρ is the density of the incompressible fluid. The speed, and thus the kinetic energy of
265-405: A change in the material's dimensions is a consequence of magnetocrystalline anisotropy ; it takes more energy to magnetize a crystalline material in one direction than in another. If a magnetic field is applied to the material at an angle to an easy axis of magnetization, the material will tend to rearrange its structure so that an easy axis is aligned with the field to minimize the free energy of
318-410: A changing magnetic field. Internally, ferromagnetic materials have a structure that is divided into domains , each of which is a region of uniform magnetization. When a magnetic field is applied, the boundaries between the domains shift and the domains rotate; both of these effects cause a change in the material's dimensions. The reason that a change in the magnetic domains of a material results in
371-460: A helical anisotropy of the susceptibility of a magnetostrictive material when subjected to a torque and the Wiedemann effect is the twisting of these materials when a helical magnetic field is applied to them. The Villari reversal is the change in sign of the magnetostriction of iron from positive to negative when exposed to magnetic fields of approximately 40 kA/m . On magnetization,
424-512: A low magnetic-anisotropy field strength, H A , of less than 1 kA/m (to reach magnetic saturation ). Metglas 2605SC also exhibits a very strong ΔE-effect with reductions in the effective Young's modulus up to about 80% in bulk. This helps build energy-efficient magnetic MEMS . Cobalt ferrite , CoFe 2 O 4 (CoO·Fe 2 O 3 ), is also mainly used for its magnetostrictive applications like sensors and actuators, thanks to its high saturation magnetostriction (~200 parts per million). In
477-555: A magnetic material undergoes changes in volume which are small: of the order 10 . Like flux density , the magnetostriction also exhibits hysteresis versus the strength of the magnetizing field. The shape of this hysteresis loop (called "dragonfly loop") can be reproduced using the Jiles-Atherton model . Magnetostrictive materials can convert magnetic energy into kinetic energy , or the reverse, and are used to build actuators and sensors . The property can be quantified by
530-622: A pure element at 60 microstrains . Among alloys, the highest known magnetostriction is exhibited by Terfenol-D , (Ter for terbium , Fe for iron , NOL for Naval Ordnance Laboratory , and D for dysprosium ). Terfenol-D, Tb x Dy 1− x Fe 2 , exhibits about 2,000 microstrains in a field of 160 kA/m (2 kOe) at room temperature and is the most commonly used engineering magnetostrictive material. Galfenol , Fe x Ga 1− x , and Alfer , Fe x Al 1− x , are newer alloys that exhibit 200-400 microstrains at lower applied fields (~200 Oe) and have enhanced mechanical properties from
583-402: A single object is frame-dependent (relative): it can take any non-negative value, by choosing a suitable inertial frame of reference . For example, a bullet passing an observer has kinetic energy in the reference frame of this observer. The same bullet is stationary to an observer moving with the same velocity as the bullet, and so has zero kinetic energy. By contrast, the total kinetic energy of
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#1732794554001636-449: A system of objects cannot be reduced to zero by a suitable choice of the inertial reference frame, unless all the objects have the same velocity. In any other case, the total kinetic energy has a non-zero minimum, as no inertial reference frame can be chosen in which all the objects are stationary. This minimum kinetic energy contributes to the system's invariant mass , which is independent of the reference frame. The total kinetic energy of
689-421: Is dissipated in various forms of energy, such as heat, sound and binding energy (breaking bound structures). Flywheels have been developed as a method of energy storage . This illustrates that kinetic energy is also stored in rotational motion. Several mathematical descriptions of kinetic energy exist that describe it in the appropriate physical situation. For objects and processes in common human experience,
742-460: Is done by the object when decelerating from its current speed to a state of rest . The SI unit of kinetic energy is the joule , while the English unit of kinetic energy is the foot-pound . In relativistic mechanics , 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} is a good approximation of kinetic energy only when v is much less than
795-446: Is equal to where: The kinetic energy of any entity depends on the reference frame in which it is measured. However, the total energy of an isolated system, i.e. one in which energy can neither enter nor leave, does not change over time in the reference frame in which it is measured. Thus, the chemical energy converted to kinetic energy by a rocket engine is divided differently between the rocket ship and its exhaust stream depending upon
848-419: Is equal to 1/2 the product of the mass and the square of the speed. In formula form: where m {\displaystyle m} is the mass and v {\displaystyle v} is the speed (magnitude of the velocity) of the body. In SI units, mass is measured in kilograms , speed in metres per second , and the resulting kinetic energy is in joules . For example, one would calculate
901-602: Is given the credit for coining the term "kinetic energy" c. 1849–1851. William Rankine , who had introduced the term "potential energy" in 1853, and the phrase "actual energy" to complement it, later cites William Thomson and Peter Tait as substituting the word "kinetic" for "actual". Energy occurs in many forms, including chemical energy , thermal energy , electromagnetic radiation , gravitational energy , electric energy , elastic energy , nuclear energy , and rest energy . These can be categorized in two main classes: potential energy and kinetic energy. Kinetic energy
954-430: Is hypothesized to be due to a "jump" in initial alignment of domains perpendicular to applied stress and improved final alignment parallel to applied stress. These materials generally show non-linear behavior with a change in applied magnetic field or stress. For small magnetic fields, linear piezomagnetic constitutive behavior is enough. Non-linear magnetic behavior is captured using a classical macroscopic model such as
1007-418: Is simply the sum of the kinetic energies of its moving parts, and is thus given by: where: (In this equation the moment of inertia must be taken about an axis through the center of mass and the rotation measured by ω must be around that axis; more general equations exist for systems where the object is subject to wobble due to its eccentric shape). A system of bodies may have internal kinetic energy due to
1060-550: Is the movement energy of an object. Kinetic energy can be transferred between objects and transformed into other kinds of energy. Kinetic energy may be best understood by examples that demonstrate how it is transformed to and from other forms of energy. For example, a cyclist uses chemical energy provided by food to accelerate a bicycle to a chosen speed. On a level surface, this speed can be maintained without further work, except to overcome air resistance and friction . The chemical energy has been converted into kinetic energy,
1113-461: Is usually below 5 A/m (for alfer it is around 50 A/m) and permeability 55 000 (for alfer 4000). Saturation flux density is 0.8 T (for alfer 1.28 T). The addition of Al increases electrical resistivity of alloy up to 140 μΩm, which is almost four times the value in commonly used 3% SiFe electrical steel . For this reason alperm can be used in higher frequency range. However, because of the Al content
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#17327945540011166-538: The Preisach model and Jiles-Atherton model. For capturing magneto-mechanical behavior, Armstrong proposed an "energy average" approach. More recently, Wahi et al. have proposed a computationally efficient constitutive model wherein constitutive behavior is captured using a "locally linearizing" scheme. Kinetic energy In physics , the kinetic energy of an object is the form of energy that it possesses due to its motion . In classical mechanics ,
1219-433: The ingot . For a polycrystalline alloy, an established formula for the magnetostriction, λ, from known directional microstrain measurements is: λ s = 1/5(2λ 100 +3λ 111 ) During subsequent hot rolling and recrystallization steps, particle strengthening occurs in which the particles introduce a “pinning” force at grain boundaries that hinders normal ( stochastic ) grain growth in an annealing step assisted by
1272-558: The living force or vis viva . Willem 's Gravesande of the Netherlands provided experimental evidence of this relationship in 1722. By dropping weights from different heights into a block of clay, Gravesande determined that their penetration depth was proportional to the square of their impact speed. Émilie du Châtelet recognized the implications of the experiment and published an explanation. The terms kinetic energy and work in their present scientific meanings date back to
1325-479: The speed of light . The adjective kinetic has its roots in the Greek word κίνησις kinesis , meaning "motion". The dichotomy between kinetic energy and potential energy can be traced back to Aristotle 's concepts of actuality and potentiality . The principle of classical mechanics that E ∝ mv is conserved was first developed by Gottfried Leibniz and Johann Bernoulli , who described kinetic energy as
1378-469: The absence of rare-earth elements, it is a good substitute for Terfenol-D . Moreover, its magnetostrictive properties can be tuned by inducing a magnetic uniaxial anisotropy. This can be done by magnetic annealing, magnetic field assisted compaction, or reaction under uniaxial pressure. This last solution has the advantage of being ultrafast (20 min), thanks to the use of spark plasma sintering . In early sonar transducers during World War II, nickel
1431-466: The brittle Terfenol-D. Both of these alloys have <100> easy axes for magnetostriction and demonstrate sufficient ductility for sensor and actuator applications. Another very common magnetostrictive composite is the amorphous alloy Fe 81 Si 3.5 B 13.5 C 2 with its trade name Metglas 2605SC. Favourable properties of this material are its high saturation-magnetostriction constant, λ, of about 20 microstrains and more, coupled with
1484-480: The chosen reference frame. This is called the Oberth effect . But the total energy of the system, including kinetic energy, fuel chemical energy, heat, etc., is conserved over time, regardless of the choice of reference frame. Different observers moving with different reference frames would however disagree on the value of this conserved energy. The kinetic energy of such systems depends on the choice of reference frame:
1537-458: The energy of motion, but the process is not completely efficient and produces heat within the cyclist. The kinetic energy in the moving cyclist and the bicycle can be converted to other forms. For example, the cyclist could encounter a hill just high enough to coast up, so that the bicycle comes to a complete halt at the top. The kinetic energy has now largely been converted to gravitational potential energy that can be released by freewheeling down
1590-432: The formula 1 / 2 mv given by classical mechanics is suitable. However, if the speed of the object is comparable to the speed of light, relativistic effects become significant and the relativistic formula is used. If the object is on the atomic or sub-atomic scale , quantum mechanical effects are significant, and a quantum mechanical model must be employed. Treatments of kinetic energy depend upon
1643-399: The game of billiards , the player imposes kinetic energy on the cue ball by striking it with the cue stick. If the cue ball collides with another ball, it slows down dramatically, and the ball it hit accelerates as the kinetic energy is passed on to it. Collisions in billiards are effectively elastic collisions , in which kinetic energy is preserved. In inelastic collisions , kinetic energy
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1696-454: The highest possible magnetostriction output. This can be achieved by processing techniques such as stress annealing and field annealing. However, mechanical pre-stresses can also be applied to thin sheets to induce alignment perpendicular to actuation as long as the stress is below the buckling limit. For example, it has been demonstrated that applied compressive pre-stress of up to ~50 MPa can result in an increase of magnetostriction by ~90%. This
1749-439: The hill than without the generator because some of the energy has been diverted into electrical energy. Another possibility would be for the cyclist to apply the brakes, in which case the kinetic energy would be dissipated through friction as heat . Like any physical quantity that is a function of velocity, the kinetic energy of an object depends on the relationship between the object and the observer's frame of reference . Thus,
1802-467: The kinetic energy of a non-rotating object of mass m traveling at a speed v is 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} . The kinetic energy of an object is equal to the work , force ( F ) times displacement ( s ), needed to achieve its stated velocity . Having gained this energy during its acceleration , the mass maintains this kinetic energy unless its speed changes. The same amount of work
1855-428: The kinetic energy of an 80 kg mass (about 180 lbs) traveling at 18 metres per second (about 40 mph, or 65 km/h) as When a person throws a ball, the person does work on it to give it speed as it leaves the hand. The moving ball can then hit something and push it, doing work on what it hits. The kinetic energy of a moving object is equal to the work required to bring it from rest to that speed, or
1908-445: The kinetic energy of an object is not invariant . Spacecraft use chemical energy to launch and gain considerable kinetic energy to reach orbital velocity . In an entirely circular orbit, this kinetic energy remains constant because there is almost no friction in near-earth space. However, it becomes apparent at re-entry when some of the kinetic energy is converted to heat. If the orbit is elliptical or hyperbolic , then throughout
1961-424: The magnetostrictive coefficient, λ, which may be positive or negative and is defined as the fractional change in length as the magnetization of the material increases from zero to the saturation value. The effect is responsible for the familiar " electric hum " ( Listen ) which can be heard near transformers and high power electrical devices. Cobalt exhibits the largest room-temperature magnetostriction of
2014-497: The magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron . Magnetostriction applies to magnetic fields, while electrostriction applies to electric fields. Magnetostriction causes energy loss due to frictional heating in susceptible ferromagnetic cores, and is also responsible for the low-pitched humming sound that can be heard coming from transformers, where alternating currents produce
2067-427: The material is more susceptible to oxidation . The alloy was first synthesized and characterized by Japanese researchers H. Masumoto and Hideo Saito in 1939. Magnetostriction Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization . The variation of materials' magnetization due to the applied magnetic field changes
2120-447: The mechanical properties ( ductility ) of magnetostrictive alloys can be significantly improved. Targeted metallurgical processing steps promote abnormal grain growth of {011} grains in galfenol and alfenol thin sheets, which contain two easy axes for magnetic domain alignment during magnetostriction. This can be accomplished by adding particles such as boride species and niobium carbide ( NbC ) during initial chill casting of
2173-496: The mid-19th century. Early understandings of these ideas can be attributed to Thomas Young , who in his 1802 lecture to the Royal Society, was the first to use the term energy to refer to kinetic energy in its modern sense, instead of vis viva . Gaspard-Gustave Coriolis published in 1829 the paper titled Du Calcul de l'Effet des Machines outlining the mathematics of kinetic energy. William Thomson , later Lord Kelvin,
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2226-453: The molecular or atomic level, which may be regarded as kinetic energy, due to molecular translation, rotation, and vibration, electron translation and spin, and nuclear spin. These all contribute to the body's mass, as provided by the special theory of relativity. When discussing movements of a macroscopic body, the kinetic energy referred to is usually that of the macroscopic movement only. However, all internal energies of all types contribute to
2279-411: The orbit kinetic and potential energy are exchanged; kinetic energy is greatest and potential energy lowest at closest approach to the earth or other massive body, while potential energy is greatest and kinetic energy the lowest at maximum distance. Disregarding loss or gain however, the sum of the kinetic and potential energy remains constant. Kinetic energy can be passed from one object to another. In
2332-412: The other side of the hill. Since the bicycle lost some of its energy to friction, it never regains all of its speed without additional pedaling. The energy is not destroyed; it has only been converted to another form by friction. Alternatively, the cyclist could connect a dynamo to one of the wheels and generate some electrical energy on the descent. The bicycle would be traveling slower at the bottom of
2385-409: The reference frame that gives the minimum value of that energy is the center of momentum frame, i.e. the reference frame in which the total momentum of the system is zero. This minimum kinetic energy contributes to the invariant mass of the system as a whole. The work W done by a force F on an object over a distance s parallel to F equals Using Newton's Second Law with m the mass and
2438-408: The relationship p = m v and the validity of Newton's Second Law . (However, also see the special relativistic derivation below .) Applying the product rule we see that: Therefore, (assuming constant mass so that dm = 0), we have, Since this is a total differential (that is, it only depends on the final state, not how the particle got there), we can integrate it and call
2491-575: The relative motion of the bodies in the system. For example, in the Solar System the planets and planetoids are orbiting the Sun. In a tank of gas, the molecules are moving in all directions. The kinetic energy of the system is the sum of the kinetic energies of the bodies it contains. A macroscopic body that is stationary (i.e. a reference frame has been chosen to correspond to the body's center of momentum ) may have various kinds of internal energy at
2544-434: The relative velocity of objects compared to the fixed speed of light . Speeds experienced directly by humans are non-relativisitic ; higher speeds require the theory of relativity . In classical mechanics , the kinetic energy of a point object (an object so small that its mass can be assumed to exist at one point), or a non-rotating rigid body depends on the mass of the body as well as its speed . The kinetic energy
2597-523: The result kinetic energy: This equation states that the kinetic energy ( E k ) is equal to the integral of the dot product of the momentum ( p ) of a body and the infinitesimal change of the velocity ( v ) of the body. It is assumed that the body starts with no kinetic energy when it is at rest (motionless). If a rigid body Q is rotating about any line through the center of mass then it has rotational kinetic energy ( E r {\displaystyle E_{\text{r}}\,} ) which
2650-521: The system. Since different crystal directions are associated with different lengths, this effect induces a strain in the material. The reciprocal effect, the change of the magnetic susceptibility (response to an applied field) of a material when subjected to a mechanical stress, is called the Villari effect . Two other effects are related to magnetostriction: the Matteucci effect is the creation of
2703-434: The work the object can do while being brought to rest: net force × displacement = kinetic energy , i.e., Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force. As a consequence of this quadrupling, it takes four times
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#17327945540012756-435: The work to double the speed. The kinetic energy of an object is related to its momentum by the equation: where: For the translational kinetic energy, that is the kinetic energy associated with rectilinear motion , of a rigid body with constant mass m {\displaystyle m} , whose center of mass is moving in a straight line with speed v {\displaystyle v} , as seen above
2809-531: Was used as a magnetostrictive material. To alleviate the shortage of nickel, the Japanese navy used an iron - aluminium alloy from the Alperm family. Single-crystal alloys exhibit superior microstrain, but are vulnerable to yielding due to the anisotropic mechanical properties of most metals. It has been observed that for polycrystalline alloys with a high area coverage of preferential grains for microstrain,
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