He is noted for his research on the strength criteria and yield surfaces of isotropic materials.
[1][2][3][4] His unified strength theory (UST) has found acceptance as generalized classical strength theory.
[5][6] It contains the following strength theories (hypotheses) and criteria as a function of the equivalent stress
) criteria: the Mohr–Coulomb theory (Single-Shear-Theory (SST)), the Sdobyrev[10] (Pisarenko-Lebedev)[11][12] criterion, and the Twin-Shear-Theory (TST).
The Unified Yield Criterion (UYC) as a part of the UST is used in the theory of plasticity (physics).