Analysis of Fatigue of Metals by Electronic Speckle Pattern Interferometry

Electronic Speckle Pattern Interferometry (ESPI) was applied to analysis of the fatigue of metals. The deformation behavior of stainless steel sheet specimen during high-cyclic fatigue tests was dynamically observed by ESPI. The effect of fatigue progress on the deformation behaviors was discussed by evaluating the change in the ESPI fringe pattern focusing on the fatigue stages of crack initiation and crack propagation. The deformation behavior observed in the fatigue test was changed due to the occurrence of crack, and this phenomenon was observed as the fringe concentration around the tip of crack. In addition, static tensile tests with ESPI were performed for specimens which were previously subjected to the fatigue cycle within the fatigue life. The effect of fatigue damage appeared in the deformation behavior near the yielding; the strain concentration behavior caused by local plastic deformation changed depending on the fatigue stage. It was found that the previous cyclic load promotes the local plastic deformation in the static tensile test.