Observation of optical interferometric band structure representing plastic deformation front under cyclic loading

An interferometric band structure previously observed under monotonic tensile loading has been observed under cyclic loading as well. Like the previous monotonic loading case, the band structure is found to represent the plastic deformation front, indicating that it can be used for visualization of stress concentration. Observed correlation between the motions of the plastic deformation front and the test machine's crosshead indicates that the plastic deformation front moves in proportion to the strength of the displacement field induced by the test machine. This is consistent with a previous report that the propagation speed of the plastic deformation front varies in proportion to the monotonic loading speed.