Effects of Cold-Straining on Structural Sheet Steels

Tension and compression tests, transverse to and in the direction of plastic prestretching, indicate that cold stretching has pronounced effects on the mechanical properties of structural sheet steels. The effects are strongly directional and different for various types of structural steels. Increases in yield strength and ultimate strength and decreases in ductility are approximately proportional to the amount of prior cold stretching. The Bauschinger effect is present in the direction of prestretching whereas an inverse Bauschinger effect exists in the direction transverse to that of prestretching. Strain aging increases the yield strength and ultimate strength, decreases the ductility, and converts the stress-strain curve from gradual to sharp yielding. Current concepts of the crystalline nature of metals and dislocation theories are used to examine experimental observation regarding strain hardening, the Bauschinger effect, and strain aging.