This report is the first part on the theoretical studies of propagation of brittle fracture and deals with the axissymmetrical case of the radial crack around a circular hole propagating at Speed V in the stress field of uniform tensile stress p at infinity. An approximate solution of the dynamical stress field and the extended Griffith's conception were obtained.
The general conclusion obtained are as follows :
(1) The dynamical stress field is affected by the crack speed.
(2) The critical stress for brittle crack propagation is affected by the crack speed as the results of change in the released elastic strain energy and the kinetic energy with crack speed.
(3) There exist the minimum critical stress depending on the temperature, arresting transition temperature, the minimum and the maximum critical speeds for brittle crack propagation under the consideration of the plastic strain energy near the top of crack.