Constitutive parameters for powder liner in shaped charge:An inversion study
[Objective]Powder liners,a new type of liner with superior performance compared with conventional liners,have been recently widely used in perforation operations.However,accurately determining the constitutive parameters that reflect the behavior of powder liners under perforating detonation conditions remains challenging.This limitation hinders the optimization of perforating charge structures and further study of the perforating process.The complex fabrication processes(pressing and sintering)and high strain rates of metal jets during perforation make conventional material property experiments unsuitable for this application.To precisely depict the mechanical behavior of powder liners under elevated temperatures,intense pressures,and substantial deformations and to render them suitable for numerical simulations of perforation,herein,we propose a constitutive parameter inversion method based on ground perforating experiments,finite element simulation,and multiobjective optimization.[Methods]First,a shooting experiment using 45 steel was conducted to provide data support for subsequent parameter inversion and to verify the effect of parameter inversion through projectile flow imaging in a shaped charge.Subsequently,a dynamic simulation using ANSYS/LS-DYNA was conducted to analyze the process of shaped charge penetration into a steel target.Building upon this foundation,we systematically examined the influence of constitutive parameters on perforation depth and perforation aperture.Through this comprehensive analysis,three parameters were identified as having the most substantial impact on the perforation simulation results.To improve inversion efficiency,this study fixed the values of other constitutive parameters with insignificant effects according to the literature.Only three main control parameters were selected as inversion variables,with perforation depth and aperture as target variables.The response surface method was used to derive a reliable representation of the target variable concerning the inversion variable.Subsequently,an iterative solution approach using a multiobjective genetic algorithm was applied to obtain an optimal distribution(Pareto solution)of the target variable.Based on the experimental results of the ground shooting experiment conducted on 45 steel,the optimal solution closely approximated the average value obtained from the experiments.Consequently,we have derived the Johnson-Cook constitutive parameters for the powder liner.[Results]The numerical simulation of the perforating process,based on the retrieved constitutive parameters,was compared with the experimental results.The findings demonstrated that the discrepancy between simulated and experimental results for perforation depth and aperture was below 5%,compared with errors greater than 30% when traditional constitutive parameters were used.In addition,jet morphology and velocity showed excellent agreement with experimental results.[Conclusions]The proposed method effectively circumvents the limitations of experimentally fitting constitutive parameters by integrating experiments,finite element simulations,and multiobjective optimization.This approach enhances the simplicity and reliability of acquiring such parameters while accurately reflecting the deformation and flow behavior of powder liners during perforation.The method achieves the desired outcome and establishes the groundwork for further investigation into the mechanism of perforation.
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