In situ neutron diffraction study of internal strain evolution around a crack tip under variable-amplitude fatigue-loading conditions

In situ neutron diffraction measurements were performed to investigate the lattice-strain evolution around a fatigue crack under five different loading conditions (i.e. fatigued, tensile overloaded, compressive underloaded, tensile overloaded–compressive underloaded, and compressive underloaded–tensile overloaded) during fatigue crack growth. The results show that different crack-growth behaviors are closely related to the distinct strain distributions developed near the crack tip under the various loading conditions.