Damage to thick steel sheet in cyclic plastic flexure

The laminar development of damage in thick 10Г2С1 steel sheet during cold plastic deformation by cyclic flexure is investigated. The steel is subjected to pure flexure in a symmetric cycle, with strain of amplitude 5.5%. The variation in steel strength indicates the damage kinetics in the plastic deformation. In the region of reversible damage, the rate of change in the strength increases to a maximum and then declines. In the region of irreversible damage there is no further change in strength of steel before failure occurs. An upper limit is proposed for the damage of the steel: 20–30% of N f , where N f is the number of cycles to failure in cyclic extension–compression. In structural terms, the upper limit of reversible damage is assumed to correspond to the transformation of cellular dislocation structure to band structure.