Based on the principle of finite life design, the influencing factors on the fracture resistance and fatigue life of drill rod are analyzed according to wave mechanics and dynamics of percussive drilling. A thin-wall tubular drill rod is thus suggested to improve its fracture resistance by low stress distribution. With the purpose of no extra consumption of drill steel but improving the fracture resistance of drill rod by reducing its cyclic stress, the outer diameter of drill rod is remarkably increased. T...