# Stress and strain

## Stress and strain

Related terms defining the intensity of internal reactive forces in a deformed body and associated unit changes of dimension, shape, or volume caused by externally applied forces. Stress is a measure of the internal reaction between elementary particles of a material in resisting separation, compaction, or sliding that tend to be induced by external forces. Total internal resisting forces are resultants of continuously distributed normal and parallel forces that are of varying magnitude and direction and are acting on elementary areas throughout the material. These forces may be distributed uniformly or nonuniformly. Stresses are identified as tensile, compressive, or shearing, according to the straining action.

Strain is a measure of deformation such as (1) linear strain, the change of length per unit of linear dimensions; (2) shear strain, the angular rotation in radians of an element undergoing change of shape by shearing forces; or (3) volumetric strain, the change of volume per unit of volume. The strains associated with stress are characteristic of the material. Strains completely recoverable on removal of stress are called elastic strains. Above a critical stress, both elastic and plastic strains exist, and that part remaining after unloading represents plastic deformation called inelastic strain. Inelastic strain reflects internal changes in the crystalline structure of the metal. Increase of resistance to continued plastic deformation due to more favorable rearrangement of the atomic structure is strain hardening.

A stress-strain diagram is a graphical representation of simultaneous values of stress and strain observed in tests and indicates material properties associated with both elastic and inelastic behavior (see illustration). It indicates significant values of stress-accompanying changes produced in the internal structure. See Elasticity

References in classic literature ?
He felt the stress and strain of life, its fevers and sweats and wild insurgences - surely this was the stuff to write about
In addition, at lower stress and higher stress level, the relationship between peak stress and strain rate is described by exponential function and power exponent function, respectively.
These combined multiaxial cyclic loadings induce complex stress and strain paths during a loading cycle.
To ensure that the sub-sized samples were cut from a domain where the strain distribution was as homogeneous as possible, the stress and strain fields of the large specimens were simulated with ABAQUS/Standard software.
It is important to remember that even if a data sheet gives stress and strain values at both yield and break, these simply represent points on a curve, just as the modulus we discussed last month is a point on a curve.
Hence we define the stress and strain value at the failing moment as failure stress and strain.
1 : great worry and concern or physical effort <Perhaps, the pressures of everyday stress and strain had gotten her down.
The finite-element method analysis also shows that during triaxial, oedometer, shear box tests distribution of stress and strain in the sample is non-uniform.
Some more parameters such as Von Mises stress and strain energy values of belt edges for both types of analysis have been reported in table 4, keeping in mind that this region is highly prone to failure during service.
Finite element analysis was used in order to get deeper insight into stress and strain distribution and to identify positions for strain gages.
By summing the relative standard uncertainties in quadrature, the combined standard uncertainty of the stress and strain measurements is about 4%.
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