# 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

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.
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.
Suppose a linear distribution for the stress and strain at any point y below the top fibre of the cross-section at time t, then,
Bao, "Dependence of ductile crack formation in tensile tests on stress triaxiality, stress and strain ratios," Engineering Fracture Mechanics, vol.
Caption: FIGURE 5: Stress and strain curves for the sandstone under dynamic loading with (a) impact at 0.6 MPa pressure under a confining pressure of 5 MPa, (b) impact at 0.7 MPa pressure under a confining pressure of 5 MPa, (c) impact at 0.6 MPa pressure under a confining pressure of 10 MPa, and (d) impact at 0.7 MPa pressure under a confining pressure of 10 MPa.
As all the Cr atoms in [Cr.sub.2][O.sub.3] are structurally equivalent, the variation of location of defect will not vary the maximum tensile stress and strain of the system.
The low stiffness makes the stress wave too low to achieve uniform loading in the specimen, which challenges the uniform assumptions of stress and strain in the specimen.
Figure 1 contains the key points that we customarily obtain from the data sheet; the yield stress and strain as well as the modulus.
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