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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40522 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Naghdabadi, Reza; Sohrabpour, Saeed
- Abstract:
- Increasing the application of elastomeric structures in industries has caused an interest in the researchers for nonlinear elasticity and viscoelasticity of solids. Such materials which show large deformation and rate dependent behavior are treated by visco-hyperelastic constitutive equations. Based on visco-hyperelastic constitutive equations, total stress is divided into two parts: quasi-static and viscous stress. The method for determining the visco-hyperelastic constitutive equation is strictly dependent on the chosen rheological model. In this project, a new visco-hyperelasic constitutive equation in the integral form was introduced based on the Zener model. Also, based on the internal variable approach, differential constitutive equations were developed and a new viscosity function was introduced. For studying the rate dependency and nonlinear behavior of rubbers, simple tension and compression experiments were designed and performed in quasi-static condition and at high strain rates on silicon rubber specimens. Tensile experiments were carried out by the conventional tensile test apparatus in the range of 0-0.4 s-1. Also, compressive experiments at high strain rates were performed by the split Hopkinson pressure bar apparatus. Based on the results, the slope of stress-strain curves at high strain rates in small strains are higher than the slope of the quasi-static curves. For describing the behavior in the silicon rubber as observed in experiments, a strain energy function is proposed. The comparison of the experimental and theoretical results showed that the proposed energy function is suitable for using in the visco-hyperelastic relations. In addition, using the proposed constitutive equations, the tensile experimental data showed a better correlation than those of compressive ones. Furthermore, the constitutive equations were implemented in modeling the experimental data available in the literature. Comparison of the results of this work with the ones of the existing models showed a better correlation of the proposed relations. For example, the results of modeling the polyurea experimental compressive data via the former models resulted in about 14% of average error which was reduced to 4% in the proposed model
- Keywords:
- Rubber ; Energy Function ; Hyperelasticity ; High Strain Rate ; Visco-Hyperelastic Behaviour ; Quasi-Static Stress
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