Master thesis and internship[BR]- Master's thesis : Towards a new constitutive model for gelatin impacts modelling[BR]- Integration Internship

Abstract

A new constitutive model is proposed for ballistic gelatin, considered as a bird surrogate, to simulate bird ingestion in new generation aircraft engines using LS–DYNA. The stress– strain relation is an isotropic hyperelastic model with a Mooney–Rivlin strain energy function and an uncoupled volumetric/deviatoric response. Gelatin quasi–incompressibility is actually treated with a multiplicative decomposition of the deformation gradient. The latter aims at to remove the hypothesis and limitations of the current hydrodynamics model used. It considers gelatin as an actual solid instead of a fluid. Since this material model does not exist natively in LS–DYNA, it is programmed in a user–material Fortran subroutine as part of the software’s user–defined–features. The implementation is validated by comparing simulation results with their analytical solutions. An influence study is conducted on the material constants and on the parameters of the numerical method used: the smoothed–particle hydrodynamics. The goal being to identify their effects on the responses, stability, robustness, computation time, etc. A correlation with a real test is performed, and the results are compared with the previous material model. This new constitutive model presents interesting results, and offers a more physical response of the gelatin on certain points compared to the hydrodynamics. Indeed, this material model adds more cohesion in the material, which may enable a better representation of multiple impacts simulations. However, a proper calibration and identification of its parameters are still required