Past Event: Oden Institute Seminar

Development of a constitutive model for viscoelastic particulate composites under large deformation and it’s implementation for finite element analysis of solid propellants

Birkan Tunc, Post-Doctoral Fellowm Oden Institute, UT Austin

Abstract

In this study, a complete pathway to construct a constitutive model well suited for finite element analysis of viscoelastic media, in particular solid propellants, undergoing large deformation and damage is described. Damage is assumed to initiate by failure of the particle-binder bond or failure in the binder itself. Opening of the micro-cracks resulting from either failure is associated with the evolution of damage. Stress softening during unloading and reloading is captured via a cyclic function modifying the viscoelastic stress. The model accounts for the effect of temperature, pressure as well. The constitutive model was implemented in commercial software Abaqus for finite element analysis. Numerical algorithm used for implementation was explained in great detail. The model was validated using a set of solid propellant test data. Uniaxial and cyclic loading tests was used for calibration of both viscoelastic model and damage parameters. Both stress as dilatation responses of the material were investigated. The distributions of these parameters were found to be consistent with the stress–strain field predictions of the rocket motor analysis, indicating efficiency and stability of the computational algorithm. A three-dimensional stress analysis of a rocket motor under cyclic temperature loading was performed. The results were compared to the test data. It was concluded that the formulation and its implementation enable realistic stress analysis of solid rocket motors under general loading and environmental conditions, providing valuable information for their life assessment. Co-Authors: Birkan Tunc (Post-Doctoral Fellow at Oden Institute), Sebnem Ozupek (Associate Professor at Bogazici University, Istanbul, Turkey) Bio Birkan Tunc recieved his PhD in 2017 from mechanical engineering from Bogazici University, Istanbul with a focus on the constitutive modelling and finite element analysis of viscoelastic materials undergoing large deformations and damage. At the same time, he worked for research and development departments of international companies such as Ford Motor Company on the design of vehicle body structures using finite element analysis. He was a visiting scholar at ICES between 2018-20119 and since the beginning of 2019 he has been working as a post-doctoral fellow at Oden Institute on the modelling of brain cancer tumor growth.