In the interaction of solids with various environmental factors, changes can occur - both internal and external. One example is the mechanical stress that appears in the bowels of the body. It determines the extent of possible changes due to damage.
Basic concepts in physics
Mechanical stress is a measure of the internal forces of an object that occurs under the influence of various factors. For example, when a deformation occurs, during which external forces try to change the relative position of the particles, and internal forces impede this process, limiting it to some specific value. Thus, we can say that mechanical stress is a direct consequence of the load on the body.
Two main types of mechanical stress can be distinguished:
- Normal - applied to a single section site along the normal to it.
- Tangent - attached to the section area tangential to it.
The combination of these stresses acting at one point is called the stress state at this point.
The mechanical stress measured in pascals (Pa): the calculation formula is presented below
Q = F / S,
Where Q is the mechanical stress (Pa), F is the force arising inside the body during deformation (N), S is the area (mm).
Properties of solids
Solids, like all others, are composed of atoms, but they have a very strong structure, which practically does not undergo deformation, i.e. volume and shape remain constant. Such objects have a number of unique properties that can be divided into two large groups:
- Physical.
- Chemical.
The following can be attributed to physical ones:
- Mechanical - they are studied using the appropriate effects on the body. These properties include elasticity, fragility, strength, i.e. everything related to the ability to resist deformation caused by external factors.
- Thermal - studied by the influence of different temperatures on the object. These include expansion when heated, thermal conductivity, heat capacity.
- Electrical - these properties are associated with the movement of electrons inside the body and their ability to assemble in an ordered flow when exposed to external factors. An example is electrical conductivity.
- Optical - are studied using light fluxes. These properties include light reflection, light absorption , diffraction.
- Magnetic - are determined by the presence of magnetic moments in the components of a solid. Negatively charged particles are responsible for them, just as for electric ones, due to their structure and certain motion.
Chemical properties include everything related to the reaction to exposure to the corresponding substances and processes that occur during this. An example is oxidation, decomposition. The structure of the crystal lattice also refers to these properties of the object.
You can also highlight a small group of
physico-chemical properties. These include those that are manifested both under mechanical and chemical effects. An example is combustion, during which changes occur according to the two above characteristics.