مهدي كاظمي

Due to the special mechanical characteristics, like high flexibility and non-linear elastic behavior, rubbers are used in various industries. The presence of cracks as a stress concentration factor in rubbery samples with complex behavior, causes more complexity in their behavior. Therefore, in order to obtain more information about the elastomers, it is important to eva‎luate the behavior of cracked rubbery specimens. In this research, the presence of crack on the behavior of NBR filled with 15 phr carbon black, which has high deformability, was investigated under mixed-mode (I/II) loading. In the experimental part of study, simple tensile test and fracture tests were performed on dumbbell-shaped samples and various SEC specimens with different crack angles and crack lengths, respectively. The result of experiments showed that in the cracked large deformation rubbers, after the initial crack blunting, the crack effect is nearly removed and the component is deformed in such a way that almost no sign of stress concentration factor is observed in the sample. Also, specimen after a while ruptured rapidly, like a uniaxial tensile test sample. As a result, the rupture of high deformation rubbers in the current study is divided into two separate phases; named here as the crack removal phase and the final rupture phase. Then for each separate phase, a separate criterion was developed to predict the corresponding load of cracked rubbers. In the numerical part of study, using finite element software, the introduced criteria for both phases were examined. The comparison between the theoretical and experimental data for all samples has shown that the results are in good agreement. Furthermore, the state of the stress field around the crack tip as well as other issues about cracked rubbery samples, were also investigated for the rubber used in this research.

لاستيك داراي تغيير شكل زياد , مكانيك شكست , مواد هايپرالاستيك , لاستيك‌هاي ترك‌دار , ترك

Large deformation rubber , Fracture mechanics , Hyperelastic materials , Cracked rubber , Crack

Mehdi Kazemi

Majid Reza Ayatollahi