Stress characteristics and slip lines
Where the geometry of a problem makes their use possible, stress characteristics should give a better lower bound solution than the assumption of stress discontinuities, and in some very simple cases can give an exact solution. Stress characteristics may be straight or curved and must obey certain restraints. These restraints and the full theory of stress characteristics have been the subject of many publications (e.g. Hencky, 1923; Sokolovski, 1965; Abbot, 1966; Houlsby and Wroth, 1982; Atkinson, 1981). It is not intended here to repeat the full theory, but simply to show that Mohr circles can be used to obtain expressions for stress change along a characteristic by the summation of infinitesimally small stress discontinuities.