Effect of Local Strain on Low Cycle Fatigue Measured by ESPI System
Low cycle fatigue cracks are mainly detected at discontinuous welded locations with high stresses under repeated cyclic static loads due to cargo loading and unloading. Theoretical and analytical methods have been used to estimate the local stress and strain, which affect the prediction of fatigue life, but these methods have difficulties considering stress concentration at notched locations and complicated material behavior of welded joints or heat affected zones. Electronic speckle pattern interferometry(ESPI) system is a nondestructive and non-contact measurement system, which can provide relatively accurate full field strain at critical positions such as welded zones and structurally discontinuous locations. In this study, local strain was measured by ESPI system at the welded cruciform joint, and then low cycle fatigue test was performed. Effect of local strain on low cycle fatigue life was examined by using the strain value measured by ESPI. In order to verify the relations between local strains and fatigue lives, after theoretical local strains and stresses were calculated by using Neuber’s rule, the measured local strains corresponding the experimental fatigue lives were compared with the results of Neuber’s rule and established codes of the British standard and DNV curve.
Seung-Seok Lee, Joon Hyun Lee, Ik Keun Park, Sung-Jin Song, Man Yong Choi
K. S. Kim, K. S. Kim, K. H. Lee, J. M. Kwon, S. M. Park, N. H. Lee, "Effect of Local Strain on Low Cycle Fatigue Measured by ESPI System", Key Engineering Materials, Vols. 321-323, pp. 678-683, 2006