Strength represents mechanical tension σB on reaching which owing to influence regarding material begins to collapse. More correct term for this phenomenon accepted by state standard specification is definition the "temporary resistance to destruction" designating tension corresponding to maximum effort after which there will be a rupture of a prototype at the carried-out tests.
Instruction
1. Strength is defined, proceeding from that theory that any material is able to maintain infinitely long time static load of any force if it forms tension which quantity does not exceed temporary resistance. If on material resistance which to equally temporary tension, destruction of a prototype happens through an uncertain final period of time is shown.
2. Apply to measurement of strength also concepts of limits of fluidity, proportionality, endurance, etc. Value of temporary resistance to destruction on stretching of material and on its compression for different substances significantly differ. For fragile materials to which the ceramics belongs the strength is one compression more than its value on stretching, the opposite situation is characteristic of composite materials, and plastic and metals usually show identical strength in both directions.
3. To calculate strength, it is necessary to know force which arises in a body at deformation of a subject, and the area of influence regarding third-party force. Mechanical tension in a certain point is equal to the relation of internal force in newtons to unit of area in a certain point of section in sq.m. I.e. external influence is directed to change of provision of particles of substance rather each other, and that tension which arises in substance at the same time prevents this change of location and limit its distribution. Allocate the normal and tangent mechanical tension which differ in the direction of application of force.
4. FS where S is the area of influence, and F - the deformation force formed in a body is expressed as a formula σB as Q =. The greatest possible number of mechanical tension for concrete substance also is a limit of its durability. So 24000 MPas, and tension limit for nylon - 500 MPas will be a limit for steel.