부산대학교 도서관

Fatigue crack growth in thick‐section metals is typically controlled by an internal plane strain region where strong triaxial constraint of the crack tip occurs. However, the crack tip stress state in this region is challenging to measure. We have used neutron diffraction to study the plane strain section of fatigue crack tips in situ. A stroboscopic form of neutron diffraction using a moving frame‐of‐reference was developed to measure crack tip strains as a function of phase in the fatigue loading cycle without interrupting the cyclic load. Using point measurements of near‐tip strain in 7475‐T7351 aluminium alloy in conjunction with finite element analysis, we can estimate the extent of the crack tip plastic zone, verifying that it is small for this material and set of loading conditions. Highlights: We demonstrate stroboscopic neutron diffraction with an Eulerian frame‐of‐reference.This measures strain at the interior of a fatigue specimen without interrupting a test.Cyclic crack tip strains during fatigue of a 7xxx aluminium alloy have been observed.This near‐tip strain information can be used to validate FEA models of fatigue. [ABSTRACT FROM AUTHOR]