Ductile fracture criteria would be a very useful engineering tool in predicting failure of metals in practical deformation processes.
In the present study, a ductile fracture criterion for a cracked plate of n-th power strain hardening material has been investigated theoretically and experimentally under plastic uniaxial tension.
The relation between the critical strain far from a crack at fracture and a crack length was derived theoretically based on the energy conservation law and by analytical estimation of the strain energy for a cracked plate. The experiment on 0.80%C steel was conducted to compare with theory. Also, the strain and stress distributions near a crack tip were discussed.
The following conclusions were obtained:
(1) The total strain energy I
for a cracked plate is expressed as the sum of I∞
without a crack and Ic
due to a crack, where Ic
is represented by the product of I∞
, square of a crack length C2
and constant α, that is, Ic
(2) The relation between the critical strain ε∞
and a crack length is given by ε∞
(3) The experimental results are in good agreement with theory.
(4) The strain distribution ε near a crack tip is predicted as follows,
: strain far from a crack, r
: radial coordinate)