Abstract: Smoothed particle hydrodynamics (SPH) method has been applied widely to the calculation of impacts with large deformations in the fields of aeronautics and astronautics. Numerical fractures are often encountered in SPH computations which can seriously reduce the computational accuracy. First, by extending the method of preventing numerical fractures for regulardistribution particle models to irregulardistribution particle models in SPH, an inserting particle method of preventing numerical fracture is obtained for irregulardistribution model. Second, the method is validated by the bending of a 3D cantilever beam with numerical fractures. Finally, the method of preventing numerical fractures for irregular particle models is applied to the calculation of impacts of the projectile on the aircraft skin, and the results obtained from regular particle models, irregular particle models and the experiment are compared and analyzed. The results show that numerical fractures can be effectively prevented for irregular particle models， the computational accuracy can be improved, and the method can be applied widely.

Key words: moothed particle hydrodynamics, fracture, numerical fracture, irregular particle model, inserting particle method, aircraft skin