Effect of the nature of the stressed state on ductility and failure in structural steels

Conclusions

• 1. Formation and development of plastic strain zones inductile steel testpieces with circular notches markedly depend on the stressed state of the material.

• 2. During transition from the elastic to plastic regions (up to 3%) the nature of the distribution of the stressed state stiffness coefficient Π in the minimum cross section of the testpiece does not vary, which distinguishes it from the stress concentration coefficient, since with increasing plastic strain the region of stress concentration is displaced within the testpiece.

• 3. The sensitivity of material ductility to changes in the stressed state (inclination of the curves ε_ψ-П and β-Π to the Π axis) depends on the supply of initial, ductility ε_ψ and the stressed state range under consideration; Sec. I is strongly sensitive with П>П_cr, Sec. II is weakly sensitive with П>П_cr.

• 4. The point of failure in structural steels, and also the type of fracture, depend not only on absolute values of active normal stresses, but on the overall nature of the stress state, i.e., on the values of II, since the latter determine the ratio of normal to tangential stresses, the ratio of specific energy consumed in changing the shape and volume of the body, and naturally, on the state of crack initiation and growth.