Teruo Kishi1, Yasuhide Sakakibara2, Yoshihiko Obata3 and Ryo Horiuchi1
1Institute of Space and Aeronautical Science, The University of Tokyo, Tokyo
An experimental estimate was made of the amplitude distribution for acoustic emission peak due to the Bauschinger effect. It was found that the backward yielding occured inhomogeneously during the strain region of this Bauschinger AE peak region and the number of backward yielding sites could be given by analysing the peak profile. From these results, a new method was proposed to obtain the mean back stress component in flow stress, which controls the Bauschinger effect and/or fatigue hardening. The obtained mean back stress was 15∼16% of the flow stress in Al and Cu, 22% in α -Brass and 37% in SUS 304, independent of the amount of pre-strain and strain rate. The same experimental result on the mean back stress was obtained in single crystals. The low temperature annealing resulted in an decrease of the mean back stress without affecting other hardening causes. It can be suggested that the origin of back stress is connected with the primary slip dislocations around some inhomogeneities such as cell boundaries, sessile dislocations and precipitates.
Please do not copy without permission.