Abstract
The stress-strain behavior of annealed low carbon steel under cyclic straining was investigated, and the results obtained are as follows.
(1) Under cyclic straining of constant total strain ranges of 2, 3 and 4%, the stress range increased with the increase in cyclic number. On the other hand, it decreased when the mean strain of 10% was applied. However, the stress range had a tendency to saturate with increase of cycles in both cases.
(2) The stress σ'-plastic strain εp' relation in half cycle with the reference point at the tip of hysteresis loop was found to be composed of two linear portions on log-log plotting. The relation was described in the form of
σ'=K'{2εpoα1-α2-2/πtan-1(εp'-εpo'/a)+εpo'α1-α2/2}εp'{α1-α2/πtan-1(εp'-εpo'/p')+α2α1}/2
where α1 and α2 are the strain, hardening exponents according to the relation of plastic strain in value whether large or small respectively. εpo' is the plastic strain dividing the plastic strain in the semi-cycle into two portions.
(3) Strain range and the number of cycles seem to have little effect on the values of α1, α2 and εpo'. α1 and α2 were about 0.18 and 0.08, respectively, and the former was about twice as large as the latter. εpo' was in 0.6-0.9%. The mean strain produced larger value of α2 in the semi-cycle of straining reverse to the mean strain in its direction.
(4) The two different strain hardening exponents found in the semi-cycle may indicate that the elasto-plastic deformation occurs before plastic deformation during the semi-cycle.
(5) In the saturated hysteresis-loop shape of stress-strain at various strain range, the stress range and plastic strain range was related as follows;
Δσ=KoΔεpα0
with α0 of 0.19.
