Investigation of DynamicJId for Alloy Steel Weldments Using the Split Hopkinson Bar

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Abstract
The fracture toughness parameter JId, under dynamic loading conditions, was determined for weldments of HY80 and QT28 alloy steels using a split Hopkinson bar technique. JId was obtained for the fusion zone, the heat-affected zone, and the base metal for these steels as a function of temperature in the range of −80 to 25°C and at loading rates of ˙K = 106 MPa√m s−1. Wedge loaded compact tension specimens were loaded in a split Hopkinson bar. The onset of stable crack growth was determined by using a strain gage that was attached ahead of a fatigue crack. The results show that, at −80°C, fracture with limited stable crack growth takes place, while for all other testing conditions considerable ductility precedes fracture of these alloys.