A modification of J-Q theory and its applications

To more effectively quantify constraint effects on crack-tip fields and fra cture resistances in ductile materials, a modification of the J-Q theory (O 'Dowd and Shih, 1991) is proposed by introducing a parameter Q*. Results sh ow that Q* is a load-independent constraint parameter under LSY or fully pl astic deformation. The validity of J-Q* description has been demonstrated b y three applications to: (a) predict crack-tip fields without further FEA c alculations; (b) rank constraint levels for different fracture specimens; ( c) predict constraint-corrected J-R curves.