Bs. Henry et al., ELASTIC-PLASTIC FRACTURE-MECHANICS ASSESSMENT OF LOW CONSTRAINT ALUMINUM TEST SPECIMENS, International journal of fracture, 81(3), 1996, pp. 217-234
Recent studies have shown that the near crack-tip stress field at a gi
ven J value is dependent on geometry. This dependence has been linked
to the degree of constraint in the geometry, with low constraint geome
tries losing J dominance at very low deformation levels. New approache
s centred on the use of a two-parameter description (e.g. J-T and J-Q)
of the crack-tip stress-strain state have emerged. However, there is
a serious lack of experimental and numerical results for low constrain
t geometries to quantify the T-stress and Q-value in the literature. T
his paper describes details of an experimental and numerical program c
arried out on low and high constraint geometries (CCT and TPB) fabrica
ted from an aluminium alloy. The results show that the experimental an
d numerical fracture toughness values (J,) agree within +/-10 percent.
The T-stress and Q-value two-parameter methodologies are successful a
t indexing the fracture toughness, ordering the data into a systematic
trend of decreasing fracture toughness with increasing T or Q, albeit
with some scatter. This allows the use of practical two-parameter fai
lure criteria, in the form of J-T and J-Q loci, to predict the behavio
ur of cracked components, without the conservatism associated with the
use of high constraint test geometries.