Strain rate effects on steel strength

SteveO

I was wondering exactly how yield and tensile strength increases with increasing levels of strain rate for a typical steel grade? I understand dislocations are generated during straining (work hardening), but what happens at higher strain rates which increases the strength?

Astronuc

The effect of increasing yield and tensile strength with increasing strain/strain rate is observed in many, if not most, metals, and even polymers.

In metals, this would have to do with the rate of dislocation/defect generation and dislocation pile-up. The dislocations diffuse through the crystal structure (from inside grains to grain boundaries). If the rate of dilocation generation exceeds the rate at which the diffuse to gb, then the dislocation density has to increase, which causes an increase in strength.

In addition, dislocations may cancel, but if the do not diffuse fast enough, they will not cancel.

Try this paper Adams, Kenneth Hoyt (1965-05-21) Dislocation mobility and density in zinc single crystals