Tensile-compression in the resistance of materials is a type of longitudinal deformation of a bar or bar that occurs if a load is applied to it along its longitudinal axis (the resultant of the forces acting on it is normal to the cross section of the bar and passes through its center of mass ).
Content
- 1 Details
- 2 Stresses in a stretched or compressed rod
- 3 notes
- 4 See also
Details
Also called uniaxial or linear stress state . It is one of the main types of stress state of the box . It can also be two- and three-axis [1] . It is called both by the forces applied to the ends of the rod, and by forces distributed over the volume (inertia and gravity).
Stretching causes elongation of the rod (rupture and permanent deformation are also possible), compression causes a shortening of the rod (loss of stability and longitudinal bending may occur).
In the cross sections of the beam, one internal force factor arises - the normal force. If the tensile or compressive force is parallel to the longitudinal axis of the beam, but does not pass through it, then the rod experiences the so-called. eccentric tension (compression). In this case, due to the eccentricity of the load application in the rod, in addition to tensile (compressive) stresses , bending stresses also arise.
The stress along the axis is directly proportional to the tensile or compressive force and inversely proportional to the cross-sectional area. Under elastic deformation between stress and relative deformation, it is determined by Hooke's law , while the transverse relative deformations are derived from the longitudinal ones by multiplying them by the Poisson's ratio . Plastic deformation preceding the destruction of a part of the material is described by nonlinear laws.
Stresses in a stretched or compressed rod
Consider a rectilinear rod of constant cross section, stretched (compressed) by two oppositely directed forces. Using the hypothesis of a uniform distribution of stresses, we consider the equilibrium of some part of the rod cut off by the plane aa , whose normal is inclined to the axis of the rod at an angle α . The external force F is balanced by stresses uniformly distributed over the area of the inclined section A α . Denoting the cross-sectional area perpendicular to the axis of the rod, for A 0 , for . Having compiled the equilibrium condition for the cut off part of the rod, we obtain: pA α −F = 0, whence the expression
We decompose the stress p into normal σ α and the tangent components ...
Notes
- ↑ Great Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
See also
- Static stretching
- Thermal expansion