Preliminary Investigation On Spall Fracture With Peridynamics

Spall fracture is shock-induced fracture phenomenon in which material is impacted under high speed and failure occurs,and spall fracture is exist in the military,aerospace and various engineering fields.Hopkinson was the first to observe spall fracture a century before.Considerable research work has been conducted based on experimental,analytical and numerical methods and made huge progress.With the development of computer technology,numerical simulation attracted more attention from the scientific community.But due to the material discontinuity in the process of spallation,there is a difficulty of using numerical methods based on classical continuum mechanics to simulate spall fracture.Paradynamics proposed more than ten years ago abandon the hypothesis of continuum.And the basic equation of Paradynamics is the differential(time)–integral(space)equation,which is more suitable to solve non-continuous problems such spell fracture and explosion.Hence,peridynamics is adopted to study spallation caused by high speed impacting.The main research content is as follows:1.Deformation gradient of continuum mechanics was adopted to approximate the deformation gradient in state based peridynamic theory.So that a linkage between state-based peridynamic theory and continuum mechanics could be made and the peridynamic constitutive relation has been developed.The basic equations used in peridynamics were those from the available literature and tuned it to describe problems in high speed impacting.2.Based on the equation developed above,computational scheme and flow chart was developed followed by the development of computer code.To verify the model developed,two numerical examples were considered,the first one is target impacted by flyer(material is LY12 Al)and the other is without considering the flyer.The simulation results are in good agreement with and even superior to the results from FEM,so that the present computational tool to study spallation is more realistic and reliable.3.The model of target impacted by flyer is adopted to study the effect of spacing between points,different influence functions and the different horizon size.Results show that the case of the first near-neighbor is the better,the averaging weight function is better forthe first near-neighbor and the small space between points is4.The material with void impacted by flyer was simulated,and the void evolution in the process of impacting was captured and the material behavior effected by void wheninitial spall fracture happened.