“…For the application of energy approach to dynamic fracture problems, Nakamura et al [3] developed the following 2-D integral expression for dynamic energy release rate of a plane crack in a linear elastic body advancing in the x 1 (1) direction (normal to the crack tip): (2) where U is the strain energy density, T is the kinetic energy density, σ ij are the components of stress, u i are the components of displacements, ρ is the mass density of the material, n j are the components of the unit normal vector to a contour Γ 0 around the crack tip which begins on one crack face and ends on the opposite face, and A 0 is the area enclosed by Γ 0 , another contour Γ around the crack tip but closer, and a portion of crack faces between the end points of the contours. The contours and area are shown in figure (1).…”