Differential stress is the difference between the greatest and the least compressive stress experienced by an object. For both the geological and civil engineering convention is the greatest compressive stress and is the weakest,
.
In other engineering fields and in physics, is the greatest compressive stress and is the weakest, so
.
These conventions originated because geologists and civil engineers (especially soil mechanicians) are often concerned with failure in compression, while many other engineers are concerned with failure in tension. A further reason for the second convention is that it allows a positive stress to cause a compressible object to increase in size, making the sign convention self-consistent.
In structural geology, differential stress is used to assess whether tensile or shear failure will occur when a Mohr circle (plotted using and ) touches the failure envelope of the rocks. If the differential stress is less than four times the tensile strength of the rock, then extensional failure will occur. If the differential stress is more than four times the tensile strength of the rock, then shear failure will occur.
Famous quotes containing the words differential and/or stress:
“But how is one to make a scientist understand that there is something unalterably deranged about differential calculus, quantum theory, or the obscene and so inanely liturgical ordeals of the precession of the equinoxes.”
—Antonin Artaud (1896–1948)
“A society which is clamoring for choice, which is filled with many articulate groups, each urging its own brand of salvation, its own variety of economic philosophy, will give each new generation no peace until all have chosen or gone under, unable to bear the conditions of choice. The stress is in our civilization.”
—Margaret Mead (1901–1978)