The Measurement of Elastic Strain Fields and Line-Broadening Near Cracks in Loaded Bars of HY-80 Steel
Defence Research Establishment Atlantic Dartmouth, Nova Scotia Canada
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The elastlc strain fields in the neighbourhood of 6 mm and 20 mm deep cracks in bars loaded in three-point bending were measured by neutron diffraction. Calculations of the elastic strain field under the known loads included a stress-concentration contribution approximated by linear elastic fracturemechanics LEFM. Close to the crack tip, the calculated load-induced strains with the LBFM contribution are in reasonable agreement with the measurements although the agreement is not good far from the crack. The diffraction linewidths can be related to the plastic deformation within the region of measurement. A 20 increase in linewidth occurred ahead of and behind the crack tip, and near the uncracked surface adjacent to the central support for the three-point bending. The radius of the enhanced linewidth region was about 5 mm near the crack tip.