چكيده به لاتين
Nowadays, hyperelastic materials (like rubbers and elastomers) have attracted many attentions due to their unique mechanical properties, including high deformation and almost complete retrieval during unloading. However, presence of any kinds of stress concentration factors in rubbers decreases the optimal performance of these materials. Hence, researchers have studied the fracture behavior of these types of materials and presented some criteria. Average Strain Energy Density (ASED) criterion is one of the high precision criteria utilized recently for the fracture assessment of hyperelastic materials in the presence of a crack.
On the other hand, U-shaped notch is one of the most available notches in the rubber components. Due to the existence of high stresses, the regions near the tip of this notch are known as the most likely areas for rupture initiation. So far, the fracture behavior of the rubber parts in the presence of the U-shaped notch has not been investigated. Therefore, prediction of the fracture load of rubber samples containing a U-shaped notch has been investigated in this study using the ASED criterion.
To do this, some experiments were carried out for rubber materials in the presence of the U-shaped notch with different radii and depths of the notch. The analysis of the ruptured samples showed that the rupture of the components has nearly initiated from the tip of the notch. Also, the rupture path is horizontal and perpendicular to the loading direction. Afterward and by using finite element modeling, a hyperelastic material model which has the best agreement with the uniaxial tensile data was assigned to the target rubber. Then, the almost uniaxial state of the stress fields near the notch tip and the crescent shape of control volume around the U-shaped notch were proved. Finally, the ASED criterion was extended to be used in the hyperelastic materials weakened by a U-shaped notch. By comparing the estimations of the ASED criterion with the corresponding experimental data, it was found that the average discrepancies for the small-radius notches (i.e., 1 and 1.5mm) was about 7% which indicated the efficacy of the ASED criterion for these samples. However, the predictions of the criterion for U-notches with larger radius (i.e., 2.5mm) was inefficient. The reason for the inefficiency is the elimination of the notch effect due to the high elongation of the rubber materials.
Keywords:
Average Strain Energy Density (ASED) criterion, Hyperelastic material, Rubber, U-shaped notch, Finite element modeling.
