Elastoplastic Flexure of Round Steel Beams. 2. Residual Stress

Аннотация

Residual stress in metals may lead to shaping defects and the failure of metal structures in prolonged operation. It may arise on account of plastic metal flow on shaping (as in forging) or slow irreversible creep at elevated temperature, under the prolonged action of loads. In viscoelastic media, it may be due to ductile strain accumulating when a body is in a deformed state for a long time. Residual stress also affects the microstructure of metals and may be present within and around crystalline grains as residual microstress, sometimes known as latent elastic stress. Residual stress is also described as eigenstress, by analogy with the eigenfunctions introduced by mathematicians to denote functions corresponding to specific parameters (eigenvalues) in a differential equation with specified boundary conditions. The concept of internal stress has been proposed as a general term for stress created by the body itself. Residual stress is then confined to cases in which the internal stress is due to irreversible deformation. Besides the creation of a favorable residual stress system, local increase in strength will be noted in forged metal disks with pronounced strain hardening, as long as the Bauschinger effect does not cancel out such benefits. In the present work, extremal values of the residual stress in a straight cylindrical steel rod (beam) are studied, in the case of flexure.