溶接構造用圧延鋼板のバウシンガー効果に関する研究

抄録

The effect of pre-strain and low temperature annealing on the behaviours of Bauschinger effect was studied to establish the quantitative relation of yield stress decrease due to Bauschinger effect in rolled steel plates for welded structure. In this paper, Bauschinger strain and Bauschinger stress, which is a difference between applied stress and 0.1% proof stress in stress reversal, are used to indicate the amount of Bauschinger effect. The results are summarized as follows:
(1) Both Bauschinger strain and stress increase with the increase of pre-strain, but the ratio of these indicators to the amount of strain hardening decreases rapidly with the amount of pre-strain and reaches constant at 2-3% pre-train.
(2) The following relationship is well established between Bauschinger stress σ_B and pre-strain ε_P,
σ_B=k·ε^m_P
where k and m are material constants.
(3) The Bauschinger effect disappear gradually in low temperature annealing treatment. The activation energy of 18000-20000 cal/mol was obtained in the process, which means that the recovery process of Bauschinger effect is controlled by strain aging due to C and N solute atoms.
(4) The back stress component which controls the Bauschinger effect was estimated. These values increase with pre-strain, however, they are about 30% of flow stress over the wide range of pre-strain.
The pre-strain dependence of Bauschinger effect can be understood very well by the aspect of the back stresses.