Research On Explosive Dispersal Process Based On Peridynamics

Explosive dispersal is an extremely efficient driving method.It was born as a chemical weapon in World War I.Due to its high lethality,explosive dispersal immediately became a research hotspot in military neighborhoods.With the development of science and social progress,explosive dispersal not only shines brightly in the military field,but also is widely used in civil engineering.Currently,numerical simulation research on explosive dispersal mainly uses finite element methods,which can effectively predict most of the cracks in materials.However,based on traditional continuum mechanics,the finite element method has certain limitations in the study of complex crack problems such as crack merging,crack branching,and arbitrary three-dimensional cracks.The Peridynamics based on nonlocal theory avoids the problem of discontinuous displacement fields in traditional continuum mechanics methods,overcomes the difficulties of mesh dependency and failure criterion selection in finite element and extended finite element methods,and has good applicability to crack initiation,propagation,and various complex crack problems.Based on the Peridynamic bond theory,a two-dimensional near field dynamic model of explosive dispersal was proposed in this paper.A corresponding numerical calculation program had been developed,and its effectiveness in predicting shell cracking and the distribution of propellant cloud had been verified.The effects of different shell structures and central charge structures on the explosive dispersion results were further studied.The main research contents are as follows:(1)On the basis of reasonable assumptions,an explosion dispersion model based on Peridynamics was proposed using Peridynamic bond theory,and relevant numerical calculation programs were developed using the Matlab platform.In order to determine the appropriate Peridynamic parameters in the explosive dispersal model,different Peridynamic parameters were selected to conducted two-dimensional square explosive dispersal research,matching the literature results while considering simulation efficiency.Finally,determined the time step parameter:(35)t =1E-8s,the material point spacing coefficient: m=5,the near-field range parameter:d =5.015 mm.(2)A numerical simulation study was conducted on a two-dimensional square explosive dispersal device.First of all,ignoring the dispersion of the propellant,only the cracking behavior of the shell under explosive load was studied,and the simulation results agree with the experimental results.Secondly,ignoring the shell constraints,only the dispersion of the propellant under explosive load was studied.The simulated cloud distribution of the propellant is only slightly similar to the experimental results.Finally,the overall research of the square explosive dispersal device was conducted,and the results showed that the shell cracking pattern and the distribution of dispersal clouds were in good agreement with the experimental results.The effectiveness of the model in predicting shell cracking and the distribution of propellant cloud has been demonstrated.(3)Two dimensional explosive dispersal devices with different shell shapes under circular charges were studied,and two types of explosive dispersal devices,circular and square,were installed.The simulation results showed that the location of shell cracking,the size of shell fragments after cracking,and the distribution of shell fragments are different under different shell shapes.The distribution of pesticide cloud is different under different shell shapes.The circular shell is more conducive to the dispersion of pesticide,and the distribution of pesticide cloud is more uniform.(4)A study was conducted on two-dimensional explosive dispersal devices with different shell thicknesses under circular charges.Four types of explosive dispersal devices,including circular shells with 3mm and 6mm thicknesses and square shells with 3mm and 6mm thicknesses,were numerically simulated and analyzed.The simulation results showed that:(a)For a square shell,the shell thickness does not change the crack location and distribution of the shell fragments,but affects the size of the shell fragments after the shell cracks.As the thickness of the shell increases,the distribution of cloud and mist is basically consistent,and the diffusion rate of cloud and mist decreases.(b)For circular shells: Increasing the thickness of a circular shell changes the location of shell cracks and the size of shell fragments,but does not change the distribution of shell fragments.As the thickness of the shell increases,the distribution of cloud and mist is basically consistent,and the diffusion rate of cloud and mist decreases.(5)Research was conducted on explosive dispersal devices with different central charge shapes.Numerical simulation analysis was conducted on four types of explosive dispersal devices,namely,circular shells with circular and square charges and square shells with circular and square charges.The simulation results showed that:(a)For square shells,different charge shapes have a small impact on the cracking shape of the shell,but they will affect the size of the cracked shell fragments.The cracked shell fragments under square charges are significantly larger than those under circular charges.Different central charge shapes will affect the cloud distribution shape of the dispersal charge,and the cloud distribution of the dispersal charge under the square charge is more uneven.The square charge is similar to a square,while the circular charge is similar to a diamond.(b)For circular shells,different central charge shapes will directly affect the crack location and shell fragment distribution of the circular shell.Different central charge shapes will affect the density of the cloud distribution of the dispersal charge,and there is a significant gap in the cloud distribution of the square charge in the central area of the dispersal charge.Overall,the distribution of cloud and mist scattered by the explosion under the circular shell of the circular charge is the best.