Deformation of shear, torsion, bending is a change in the volume and shape of the body when exposed to additional load. In this case, the distances between molecules or atoms change, leading to the appearance of elastic forces. Consider the main types of deformations and their characteristics.
Compression and stretching
Tensile deformation is associated with relative or absolute elongation of the body. As an example, we can give a homogeneous rod, which is fixed at one end. When a force is applied along the axis acting in the opposite direction, 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 extension, 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 type can be analyzed on a model of a solid body consisting of parallel plates that are interconnected by springs. Due to the horizontal force, the plates are shifted by an angle, the body volume does not change. In the case of elastic deformations between the force applied to the body and the shear angle, a directly proportional relationship is revealed.
Bending strain
Consider examples of deformation of this type. In the case of bending, the convex part of the body undergoes some stretching, and the concave fragment is compressed. Inside the body undergoing this variant of deformation, there is a layer that does not experience compression or tension. It is commonly called the neutral part of the deformable body. Near it, you can reduce the body area.
In the technique, examples of this type of deformation are used to save materials, as well as to reduce the weight of structures being constructed. Solid bars and rods are replaced by pipes, rails, I-beams.
Torsion strain
This longitudinal deformation is an inhomogeneous shift. It occurs under the action of forces directed parallel or opposite to the rod, at which one end is fixed. Most often, various details and mechanisms used in structures and machines are subjected to complex deformations. But thanks to a combination of several deformation options, 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. Such a change contributed to the maximum hardening of the skeleton at a certain body weight.
Deformations on the example of the human body
The human body is subjected to serious mechanical stresses from its own efforts and weight, which appear during physical activity. In general, deformation (shift) is characteristic of the human body:
- Compression experiences the spine, integument of the feet, lower limbs.
- Ligaments, upper limbs, muscles, tendons are stretched.
- Bending is characteristic of limbs, pelvic bones, vertebrae.
- It undergoes torsion during rotation of the neck, while rotating it, hands are tested.
But if excess stress indicators are exceeded , a gap may occur, for example, bones of the shoulder, thigh. In the ligaments, the tissues are connected so elastically that they can be stretched twice. By the way, shear deformation explains the whole danger of the movement of women in high heels. Body weight will be transferred to the fingers, which will increase the load on the bones by half.
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? Shift, torsion, compression are the main causes of poor posture in children and adolescents.
Strength and deformation
Despite the diversity of the living and nonliving world, and the creation by man of numerous material objects, all objects and living things have a common property - strength. It is commonly understood by it as the ability of a material to remain for a long time period without visible damage. There is the strength of structures, molecules, structures. This characteristic is relevant for blood vessels, human bones, brick columns, glass, water. Shear deformation is an option for checking the 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 between themselves to hunt ancient animals. Already in those distant times, man was interested in deformation. Shear, compression, stretching, bending helped him create homes, tools, 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
The mathematical calculations necessary in construction and engineering made it possible to apply Hooke's law for shear strain. The formula showed a direct relationship between the force applied to the body and its extension (compression). Hook used the stiffness coefficient, 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 began to be applied in construction equipment, construction theory, 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 prevent the correct posture of 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 humans, animals, torsion, bending, stretching, and compression constantly occur. And in order to carry out timely and complete prevention of problems associated with posture or overweight, physicians use the dependencies identified by physicists in conducting basic research.
For example, before performing prosthetics of the lower extremities, a detailed calculation of the maximum load for which it should be designed is performed. Dentures are selected for each person individually, since 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.