Measurement of crack tip strains using neutron diffraction

Residual elastic strains and plastic zones near fatigue cracks and monotonically loaded fatigue cracks in compact tension specimens of AISI 4340 steel were measured using neutron diffraction. Compressive residual strain fields were observed close to the crack tip. Further from the crack tip the residual strains were tensile, reaching a maximum within 5 mm from the crack. Mode I stress intensity factors required to compensate for the residual …