چكيده به لاتين
Abstract
Nowadays, hyperelastic materials such as rubbers and elastomers have become increasingly important in research and industry. A network-like structure consisting of polymer chains has led to unique properties such as high deformation, purely elastic deformation, and entropic-driven elasticity behavior in these materials. In this regard, investigators have studied the behavior of these materials in conjunction with the brittle ones in the presence of a factor of stress concentration, so that some criteria for rupture assessment of rubbers have been presented during the last decade.
On the other hand, one of the energy-based criteria, which has attracted many attentions due to its convenience in use and high precision, is the averaged energy density criterion (ASED). This criterion, which is mostly used for brittle materials, has been recently extended to be used in cracked rubber samples. By examining of the previous studies, it can be concluded that despite the importance of rounded V-shaped notch, no research has been carried out in the presence of this type of stress concentration in hyperelastic materials. As a consequence, the target of this thesis is to investigate the rupture of rubbers containing a rounded V-shaped notch using the ASED criterion.
To this end, some experiments and numerical studies are performed. In the experimental phase, by changing the depth, opening angle, and end radius of the notch, a total number of 54 fracture tests are carried out. It is seen that the rupture in the samples are initiated from the end region of the notch and in a nearly horizontal path (perpendicular to the loading direction). Furthermore and in the numerical phase of the research, a hyperelastic material model which has the best agreement with the tensile test data is selected. Afterwards, by confirming the necessary requirements for the application of the ASED criterion in hyperelastic materials (e.g. the nearly uniaxial state of stress field near the notch tip and crescent-shape of control volume around the notch tip), the main parameters of the criterion (i.e., the values of critical strain energy density and critical radius) are determined. Finally, the critical displacements of the rubber samples estimated by the ASED criterion are compared with the corresponding experimental data and then, a mean discrepancy of less than 10% is achieved for the samples with the small end-notch diameter (i.e., 2 and 3 mm). This finding indicates the accuracy of the criterion for the samples with small end-notch radius. In addition, it is observed that for the samples with a larger end-notch diameter (i.e., 5 mm), the estimations of the criterion are inefficient. It is then justified that for the samples with the end-notch diameter of 5 mm, the notch is practically lost and does not have an effect on the rubber specimen.
Keywords:
Rubber components, Rounded V-shaped notch, Hyperelastic material model, Averaged strain energy density criterion, Finite element modeling.
