Deformation. Types of deformations of solid bodies
deformation
Change in size, shape of a solid body under the action of external forces (usually without changing its mass).
Any change deviation of something. from the norm.
Encyclopedic Dictionary, 1998
deformation
DEFORMATION (from Latin deformatio - distortion)
change in the relative position of the points of a solid body, in which the distance between them changes, as a result external influences. The deformation is called elastic if it disappears after removal of the action, and plastic if it does not completely disappear. Most simple views deformations - stretching, compression, bending, torsion.
In a figurative sense - a change in form, a distortion of the essence of something (for example, deformation of the social structure).
Deformation
(from Latin deformatio ≈ distortion), a change in the relative position of body particles associated with their movement. D. is the result of a change in interatomic distances and a rearrangement of blocks of atoms. D. is usually accompanied by a change in the magnitude of interatomic forces, the measure of which is elastic stress. The simplest types of D. of the body as a whole: tension ≈ compression, shear, bending, torsion. In most cases, the observed D. represents several D. at the same time. Ultimately, however, any dynamic can be reduced to the two simplest ones: extension (or compression) and shear. The motion of a body is completely determined if the displacement vector of each of its points is known. D. solids in connection with structural features the latter is studied by solid state physics, while the motions and stresses in deformable solids are studied by the theory of elasticity and plasticity. In liquids and gases, the particles of which are easily mobile, the study of displacement is replaced by the study of the instantaneous distribution of velocities. D. of a solid body can be the result of phase transformations associated with a change in volume, thermal expansion, magnetization (magnetostrictive effect), the appearance of an electric charge (piezoelectric effect), or the result of the action of external forces. D. is called elastic if it disappears after the removal of the load that caused it, and plastic if after the removal of the load it does not disappear (at least completely). All real solids in D. have plastic properties to a greater or lesser extent. Under certain conditions, the plastic properties of bodies can be neglected, as is done in the theory of elasticity. Solid with sufficient accuracy can be considered elastic, i.e., not revealing noticeable plastic D., until the load exceeds a certain limit. The nature of plastic D. can be different depending on the temperature, the duration of the load, or the speed of D. With a constant load applied to the body, D. changes with time; this phenomenon is called creep (see Creep of materials). With increasing temperature, the creep rate increases. Relaxation and elastic aftereffect are particular cases of creep. Relaxation is the process of a spontaneous decrease in internal stress over time at a constant voltage. The process of spontaneous growth of stress over time at a constant voltage is called an aftereffect. One of the theories explaining the mechanism of plastic dislocation is the theory of dislocations in crystals. In the theory of elasticity and plasticity, bodies are considered as "solid". Continuity, that is, the ability to fill the entire volume occupied by the material of the body without any voids, is one of the main properties attributed to real bodies. The concept of continuity also applies to elementary volumes into which a body can be mentally divided. The change in the distance between the centers of each two adjacent infinitesimal volumes in a body that does not experience discontinuities must be small compared to the initial value of this distance. The simplest elementary D. is the relative elongation of some element: e = (l1≈ l)/l, where l1 ≈ the length of the element after the D., l ≈ the initial length of this element. In practice, small D. are more common, so e<<
D. is measured either in the process of testing materials in order to determine their mechanical properties, or in the study of a structure in kind or on models in order to judge the magnitude of stresses. Elastic D. are very small, and their measurement requires high accuracy. The most common method for studying deformation is with the help of strain gauges. In addition, resistance strain gauges, the polarization-optical method for studying stress, and X-ray structural analysis are widely used. To judge local plastic D., knurling on the surface of a mesh product, coating the surface with an easily cracking varnish, etc. is used.
Lit .: Rabotnov Yu. N., Strength of materials, M., 1950; V. D. Kuznetsov, Solid State Physics, vol. 2≈4, 2nd ed., Tomsk, 1941≈47; Sedov L.I., Introduction to continuum mechanics, M., 196
Wikipedia
Deformation
Deformation- change in the relative position of the particles of the body, associated with their movement relative to each other. Deformation is the result of a change in interatomic distances and a rearrangement of blocks of atoms. Usually, deformation is accompanied by a change in the values of interatomic forces, the measure of which is the elastic mechanical stress.
Deformations are divided into reversible. Elastic deformations disappear after the end of the action of the applied forces, while irreversible ones remain. Elastic deformations are based on reversible displacements of metal atoms from the equilibrium position.
Plastic deformations are irreversible deformations caused by changes in stresses. Creep deformations are irreversible deformations that occur over time. The ability of materials to plastically deform is called plasticity. During plastic deformation of a metal, a number of properties change simultaneously with a change in shape - in particular, during cold deformation, strength increases.
Examples of the use of the word deformation in the literature.
It tossed and turned awkwardly near Adrastea, trembling, plasma pulsed erratically in the nozzles, a shirt of discharges appeared on the body, swellings and deformations.
Professor Mayer from Bonn considered it to be the skeleton of a Cossack who died in 1814, Wagner from the University of Göttingen thought it was the skeleton of an ancient Dutchman, the Parisian scientist Prüner-Bey claimed that it was the skeleton of an ancient Celt, and the famous physician Virchow, whose too hasty judgments more than once slowed down scientific thought, authoritatively stated that this skeleton belongs to modern man, but bears traces of senile deformations.
Orthopedics is a branch of medicine that studies congenital and acquired deformations and dysfunctions of the musculoskeletal system and developing methods for their treatment and prevention.
Gender reassignment acts as the final stage deformations body, as a diagrammatic sign of bodily inversion, begun by eating someone else's voice.
The monstrosity of such an eversion, such an unimaginable deformations is the diagrammatic trace of the machine of chimerical corporeality.
Particular signs of the foot include curvature of the foot along the axial line, fusion of individual fingers, absence of individual fingers, significant protrusion of individual fingers, shape, size and location deformations skin, structural features of papillary lines.
Both physically and geometrically, warming up means breaking or deformation connections.
Since it has been suggested that hypermetropia is due to congenital deformation of the eyeball, and until relatively recently it was suggested that in most cases astigmatism also represents a congenital condition, little effort was made to find explanations for their origin or preventive measures against them - they simply did not think about it.
In dubbing, facial expressions are already initially distorted in relation to sound, the face is already subjected to barely visible deformations.
There would be a theater of the absurd without linguistic invention, deformations words, Jarry's cruel pun.
Strong freezing of the soil, countless deep cracks in it, in the absence of snow since autumn, leads to a strong deformations soil, which causes mechanical damage to the tillering node and roots of winter wheat.
It is when a ripple passes over the water surface that the reflection of the mascaron appears here, and the paradoxicality of the mirror system built by Rastrelli becomes especially obvious: the sculpture captures its own deformation in a water mirror, the object includes mirror defects.
It is believed that deformations and displacements are elastic and inelastic - this also applies to the continuum Universe, each layer of which has its own mass, and hence its own inertia.
Exceeding the maximum G-force during dive recovery may result in deformations aircraft structure, and, in addition - to the exit to supercritical angles of attack with subsequent stall.
The novel, built as a story of a crime based on everyday motives, developed into a philosophical narrative concerning painful issues associated with deformations the American moral ideal of the individual who asserts himself in the struggle for happiness and justifies his own individualism with this goal.
Shear, torsion, bending deformation is a change in the volume and shape of a body when an additional load is applied to it. In this case, the distances between molecules or atoms change, leading to the appearance. Consider the main and their characteristics.
Compression and stretching
Tensile deformation is associated with relative or absolute elongation of the body. An example is a homogeneous rod, which is fixed at one end. When a force acting in the opposite direction is applied along the axis, the rod is stretched.
The force applied towards the fixed end of the rod leads to compression of the body. In the process of compression or stretching, a change in the cross-sectional area of the body occurs.
Tensile deformation is a change in the state of an object, accompanied by a displacement of its layers. This view can be analyzed on a model of a solid body consisting of parallel plates, which are interconnected by springs. Due to the horizontal force, the plates are shifted at some angle, while the volume of the body does not change. In the case between the force applied to the body and the shear angle, a directly proportional relationship was revealed.
bending deformation
Consider examples of this type of deformation. In the case of bending, the convex part of the body is subjected to some tension, and the concave fragment is compressed. Inside the body subjected to this type of deformation, there is a layer that does not experience either compression or tension. It is commonly called the neutral region of the deformable body. Near it, you can reduce the area of \u200b\u200bthe body.
In engineering, examples of this type of deformation are used to save materials, as well as to reduce the weight of structures being erected. Solid bars and rods are replaced with pipes, rails, I-beams.
Torsional deformation
This longitudinal deformation is a non-uniform shear. It arises under the action of forces directed parallel or opposite to the rod, which has one end fixed. Most often, various parts and mechanisms used in structures and machines undergo complex deformations. But due to the combination of several variants of deformations, the calculation of their properties is greatly facilitated.
By the way, in the process of significant evolution, the bones of birds and animals adopted a tubular version of the structure. This change contributed to the maximum strengthening of the skeleton at a certain body weight.
Deformations on the example of the human body
The human body is subjected to serious mechanical stress from its own efforts and weight, which appear as physical activity. In general, deformation (shift) is characteristic of the human body:
- Compression is experienced by the spine, integuments of the feet, lower limbs.
- Ligaments, upper limbs, muscles, tendons are stretched.
- The bend is characteristic of the limbs, pelvic bones, vertebrae.
- The neck is subjected to torsion during rotation, and the hands are tested during rotation.
But if the indicators are exceeded, a rupture is possible, for example, the bones of the shoulder, thigh. In ligaments, the tissues are connected so elastically that they can be stretched twice. By the way, shear deformation explains all the dangers of moving women in high heels. The weight of the body will be transferred to the fingers, which will lead to an increase in the load on the bones by a factor of two.
According to the results of medical examinations conducted in schools, out of ten children, only one can be considered healthy. How are deformities related to children's health? Shear, torsion, compression are the main causes of posture disorders in children and adolescents.
Strength and deformation
Despite the diversity of the living and non-living world, the creation of numerous material objects by man, all objects and living beings have a common property - strength. It is commonly understood as the ability of a material to persist for a long time period without visible damage. There is the strength of structures, molecules, structures. This characteristic is appropriate for blood vessels, human bones, brick columns, glass, water. Shear deformation is a variant of testing a structure for strength.
The use of different types of deformations by man has deep historical roots. It all started with the desire to connect a stick and a sharp tip to each other in order to hunt ancient animals. Already in those distant times, man was interested in deformation. Shift, compression, stretching, bending helped him create dwellings, tools, and cook food. With the development of technology, mankind has managed to use various types of deformations so that they bring significant benefits.
Hooke's law
Mathematical calculations necessary in construction, technology, allowed to apply for shear deformation. The formula showed a direct relationship between the force applied to the body and its elongation (compression). Hooke used the coefficient of rigidity, showing the relationship between the material and the possibility of its deformation.
With the development and improvement of technical means, apparatus and instruments, the development of the theory of resistance, serious studies of plasticity and elasticity were carried out. The results of the fundamental experiments carried out began to be applied in building technology, the theory of structures, and theoretical mechanics.
Thanks to an integrated approach to the problems associated with various types of deformation, it was possible to develop the construction industry, to carry out the prevention of correct posture in the younger generation of the country.
Conclusion
The deformations considered in the course of school physics affect the processes occurring in the living world. In human and animal organisms, torsion, bending, stretching, and compression are constantly occurring. And in order to carry out timely and complete prevention of problems associated with posture or overweight, doctors use the dependencies identified by physicists during fundamental research.
For example, before carrying out prosthetics of the lower extremities, a detailed calculation of the maximum load for which it should be calculated is performed. Prostheses are selected for each person individually, as it is important to take into account the weight, height and mobility of the latter. For violations of posture, special correction belts are used, based on the use of shear deformation. Modern rehabilitation medicine could not exist without the use of physical laws and phenomena, including without taking into account the laws of various types of deformations.
Details Category: Molecular-kinetic theory Posted on 11/17/2014 18:20 Views: 10012Under the influence of external forces, solid bodies change their shape and volume, i.e. are deformed.
As a result of the action of forces applied to the body, the particles of which it consists move. The distances between atoms and their mutual arrangement change. This phenomenon is called deformation .
If, after the termination of the force, the body returns to its original shape and volume, then such a deformation is called elastic , or reversible . In this case, the atoms again take the position in which they were before the force began to act on the body.
If we squeeze a rubber ball, it will change shape. But he will immediately restore it as soon as we let him go. This is an example of elastic deformation.
If, as a result of the action of a force, the atoms are displaced from their equilibrium positions by such distances that the interatomic bonds no longer act on them, they cannot return to their original state and occupy new equilibrium positions. In this case, irreversible changes occur in the physical body.
Squeeze a piece of plasticine. He will not be able to return to his original form when we stop working on him. It has deformed irreversibly. This deformation is called plastic , or irreversible .
Irreversible deformations can also occur gradually over time if the body is subjected to a constant load, or under the influence of various factors, mechanical stress arises in it. Such deformations are called creep deformations .
For example, when parts and assemblies of some units experience serious mechanical loads during operation, and are also exposed to significant heat, creep deformation is observed in them over time.
Under the influence of the same force, a body can experience elastic deformation if the force is applied to it for a short time. But if the same force acts on the same body for a long time, then the deformation may become irreversible.
The amount of mechanical stress at which the deformation of the body will still be elastic, and the body itself will restore its shape after the load is removed, is called elastic limit . At values above this limit, the body will begin to collapse. But destroying a solid body is not so easy. It resists. And this property is called strength .
When two vehicles connected by a tow cable start moving, the cable is deformed. It stretches, and its length increases. And when they stop, the tension is released, and the length of the cable is restored. But if the cable is not strong enough, it will simply break.
Types of deformation
Depending on how the external force is applied, there are tensile-compressive deformations, shear, bending, torsion.
Tensile-compressive deformation
Tensile-compressive deformation caused by forces that are applied to the ends of the beam parallel to its longitudinal axis and directed in different directions.
Under the action of external forces, the particles of a solid matter, oscillating about their equilibrium position, are displaced. But this process is being prevented by the internal forces of interaction between the particles, trying to keep them in their original position at a certain distance from each other. Forces that prevent deformation are called elastic forces .
Tensile deformation is experienced by a stretched bowstring, a towing cable of a car during towing, coupling devices of railway cars, etc.
When we climb stairs, the steps are deformed by our gravity. This is a compression strain. The same deformation is experienced by the foundations of buildings, columns, walls, a pole with which an athlete jumps.
Shear deformation
If an external force is applied tangentially to the surface of the bar, the lower part of which is fixed, then shear strain . In this case, the parallel layers of the body seem to shift relative to each other.
Imagine a rickety stool on the floor. We apply a force to it tangentially to its surface, that is, we simply pull the upper part of the stool towards ourselves. All its planes parallel to the floor will shift relative to each other by the same angle.
The same deformation occurs when a sheet of paper is cut with scissors, a wooden beam is sawn with a saw with sharp teeth, etc. All fasteners connecting surfaces - screws, nuts, etc. - undergo shear deformations.
bending deformation
Such a deformation occurs if the ends of a beam or rod lie on two supports. In this case, it is subjected to loads perpendicular to its longitudinal axis.
Bending deformation is experienced by all horizontal surfaces laid on vertical supports. The simplest example is a ruler lying on two books of the same thickness. When we put something heavy on top of it, it will bend. In the same way, a wooden bridge thrown over a stream sags when we walk along it.
Torsional deformation
Torsion occurs in a body when a couple of forces are applied to its cross section. In this case, the cross sections will rotate around the axis of the body and relative to each other. Such deformation is observed in the rotating shafts of machines. If you manually wring out (twist out) wet laundry, it will also be subjected to torsion deformation.
Hooke's law
Observations of various types of deformation showed that the amount of deformation of the body depends on the mechanical stress arising under the action of forces applied to the body.
This dependence is described by a law discovered in 1660. English scientist Robert Hooke , who is called one of the fathers of experimental physics.
It is convenient to consider the types of deformation on the beam model. This is a body, one of the three dimensions of which (width, height or length) is much larger than the other two. Sometimes instead of the term "beam" the term "rod" is used. The length of the rod is much greater than its width and height.
Let us consider this dependence for tensile-compressive deformation.
Let us assume that the rod initially has a length L . Under the action of external forces, its length will change by the value ∆l . It is called absolute elongation (compression) of the rod .
For tensile-compressive deformation, Hooke's law has the form:
F - the force that compresses or stretches the rod; k - coefficient of elasticity.
The elastic force is directly proportional to the elongation of the body up to a certain limit value.
E - modulus of elasticity of the first kind, or Young's modulus . Its value depends on the properties of the material. This is a theoretical value introduced to characterize the elastic properties of bodies.
S - cross-sectional area of the rod.
The ratio of absolute elongation to the original length of the rod is called elongation or relative deformation .
When stretched, its value is positive, and when compressed, it is negative.
The ratio of the modulus of the external force to the cross-sectional area of the rod is called mechanical stress .
Then Hooke's law for relative values will look like this:
Voltage σ directly proportional to relative strain ε .
It is assumed that the force tending to lengthen the rod is positive ( F˃0 ), and the force shortening it has a negative value ( F ˂ 0 ).
Deformation measurement
When designing and operating various mechanisms, technical objects, buildings, bridges and other engineering structures, it is very important to know the amount of deformation of materials.
Since elastic deformations are small, the measurements must be carried out with very high accuracy. For this purpose, devices called strain gauges .
The strain gauge consists of a strain gauge and indicators. It may also include a recording device.
Depending on the principle of operation, strain gauges are optical, pneumatic, acoustic, electrical and X-ray.
Optical strain gauges are based on measuring the deformation of a fiber optic thread glued to the object of study. Pneumatic strain gauges record the change in pressure during deformation. In acoustic strain gauges, piezoelectric sensors measure the values by which the speed of sound and acoustic damping change during deformation. Electrical strain gauges calculate strain based on changes in electrical resistance. X-ray determine the change in interatomic distances in the crystal lattice of the studied metals.
Until the 1980s, sensor signals were recorded by recorders on ordinary paper tape. But when computers appeared and modern technologies began to develop rapidly, it became possible to observe deformations on monitor screens and even give control signals to change the mode of operation of the tested objects.
Plastic deformation
Diagram showing the relationship between the applied force and the deformation of a ductile metal.
Continuity
In the theory of elasticity and plasticity, bodies are considered as "solid". Continuity, that is, the ability to fill the entire volume occupied by the material of the body without any voids, is one of the main properties attributed to real bodies. The concept of continuity also applies to elementary volumes into which a body can be mentally divided. The change in the distance between the centers of each two adjacent infinitesimal volumes in a body that does not experience discontinuities must be small compared to the initial value of this distance.
The simplest elementary deformation
The simplest elementary deformation is the relative elongation of some element:
- l 1 - element length after deformations;
- l is the initial length of this element.
In practice, small deformations, so e<< 1.
Deformation measurement
Measurement deformations It is produced either in the process of testing materials in order to determine their mechanical properties, or when studying a structure in kind or on models to judge the magnitude of stresses. elastic deformations are very small, and their measurement requires high accuracy. The most common research method deformations- using tensiometers. In addition, resistance strain gauges, the polarization-optical method for studying stress, and X-ray structural analysis are widely used. To judge local plastic deformations knurling is used on the surface of the mesh product, surface coating with easily cracking varnish, etc.
Notes
Literature
- Rabotnov Yu. N., Strength of materials, M., 1950;
- V. D. Kuznetsov, Solid State Physics, vol. 2-4, 2nd ed., Tomsk, 1941-47;
- Sedov L.I., Introduction to continuum mechanics, Moscow, 1962.
Wikimedia Foundation. 2010 .
Deformations are divided into reversible (elastic) and irreversible (plastic, creep). Elastic deformations disappear after the end of the action of the applied forces, while irreversible ones remain. Elastic deformations are based on reversible displacements of metal atoms from the equilibrium position (in other words, atoms do not go beyond the limits of interatomic bonds); irreversible ones are based on irreversible displacements of atoms at considerable distances from the initial equilibrium positions (that is, going beyond the framework of interatomic bonds, after removing the load, reorientation to a new equilibrium position).
Plastic deformations are irreversible deformations caused by changes in stresses. Creep deformations are irreversible deformations that occur over time. The ability of materials to plastically deform is called plasticity. During plastic deformation of a metal, a number of properties change simultaneously with a change in shape - in particular, during cold deformation, strength increases.
Types of deformation
The simplest types of deformation of the body as a whole:
In most practical cases, the observed deformation is a combination of several simultaneous simple deformations. Ultimately, however, any deformation can be reduced to the two simplest ones: tension (or compression) and shear.
Deformation study
The nature of plastic deformation can be different depending on the temperature, the duration of the load, or the strain rate. With a constant load applied to the body, the deformation changes with time; this phenomenon is called creep. With increasing temperature, the creep rate increases. Relaxation and elastic aftereffect are particular cases of creep. One of the theories explaining the mechanism of plastic deformation is the theory of dislocations in crystals.
Continuity
In the theory of elasticity and plasticity, bodies are considered as "solid". Continuity (that is, the ability to fill the entire volume occupied by the material of the body, without any voids) is one of the main properties attributed to real bodies. The concept of continuity also applies to elementary volumes into which a body can be mentally divided. The change in the distance between the centers of each two adjacent infinitesimal volumes in a body that does not experience discontinuities must be small compared to the initial value of this distance.
The simplest elementary deformation
The simplest elementary deformation is the relative elongation of some element:
In practice, small deformations are more common - such that .
Deformation measurement
Deformation is measured either in the process of testing materials in order to determine their mechanical properties, or when studying a structure in kind or on models to judge the magnitude of stresses. Elastic deformations are very small, and their measurement requires high accuracy. The most common method for studying deformation is with the help of strain gauges. In addition, resistance strain gauges, the polarization-optical method for studying stress, and X-ray diffraction analysis are widely used. To judge local plastic deformations, knurling on the surface of a mesh product, coating the surface with easily cracking varnish or brittle gaskets, etc. is used.
Notes
Literature
- Rabotnov Yu. N., Strength of materials, M., 1950;
- V. D. Kuznetsov, Solid State Physics, vol. 2-4, 2nd ed., Tomsk, 1941-47;
- Sedov L.I., Introduction to continuum mechanics, Moscow, 1962.
see also
Links
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Synonyms:- Beta (letter)
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See what "Deformation" is in other dictionaries:
deformation- deformation: Distortion of the shape of a bar of soap compared to that provided in the technical document. Source: GOST 28546 2002: Solid toilet soap. General technical conditions original document De ... Dictionary-reference book of terms of normative and technical documentation
DEFORMATION- (fr.) Ugliness; shape change. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. DEFORMATION [lat. deformatio distortion] change in the shape and size of the body under the influence of external forces. Dictionary of foreign words. Komlev … Dictionary of foreign words of the Russian language
DEFORMATION Modern Encyclopedia
Deformation- - change in the shape and / or dimensions of the body under the influence of external forces and various kinds of influences (changes in temperature and humidity, settlement of supports, etc.); in the strength of materials and the theory of elasticity, a quantitative measure of dimensional change... Encyclopedia of terms, definitions and explanations of building materials
Deformation- (from the Latin deformation distortion), a change in the relative position of the particles of a substance, due to any external or internal causes. The simplest types of deformation of a solid body: tension, compression, shear, bending, torsion. ... ... Illustrated Encyclopedic Dictionary
DEFORMATION- (from lat. deformatio distortion) 1) change in the relative position of the points of a solid body, in which the distance between them changes, as a result of external influences. The deformation is called elastic if it disappears after the removal of the impact, and ... ... Big Encyclopedic Dictionary
deformation- Cm … Synonym dictionary
DEFORMATION- (from lat. deformatio distortion), a change in the configuration of c.l. object resulting from external. influences or internal forces. D. may experience TV. bodies (crystal, amorphous, organic origin), liquids, gases, physical, living fields ... ... Physical Encyclopedia
deformation- and, well. deformation f. lat. deformatio distortion. 1. Changing the size, shape of a solid body under the influence of external forces (usually without changing its mass). BAS 1. || In the visual arts, a deviation from the natural perceived by the eye ... ... Historical Dictionary of Gallicisms of the Russian Language
deformation- deformation, deformed. Pronounced [deformation], [deformed] and obsolete [deformation], [deformed] ... Dictionary of pronunciation and stress difficulties in modern Russian
Deformation- rocks (from lat. deformatio change in shape, distortion * a. rock deformafion; n. Deformation von Gesteinen; f. deformation des roches; i. deformacion de las rocas) a change in the relative position of rock particles, causing a change ... Geological Encyclopedia
Books
- Plastic deformation of metals, R. Honeycombe, For engineering and scientific workers of factories and research institutes, university professors, graduate students and senior students. Reproduced in original… Category: