PSI - Issue 21

Amir H. Benvidi et al. / Procedia Structural Integrity 21 (2019) 12–20 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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By identifying two important factors of the ASED criterion, one can utilize this criterion to calculate the rupture displacement of other relevant samples. As can be concluded form previous explanations, in order to apply the ASED criterion for rupture assessment of rounded-tip V-notched components made of rubber, the nearly uniaxial nature of the stress field around the notch tip should be evaluated. Then, after determining the values of and for a typical sample with rounded V-shape notch, the rupture displacement of the other samples will be predicted by using the ASED criterion. 3. Experimental procedure In order to experimentally investigate the rupture of rubber specimens containing a rounded v-shaped notch, some samples made of ethylene propylene diene monomer (EPDM) rubber were prepared. The dimensions and schematic of these samples are shown in Fig. 2. Totally, by changing the radius and depth of samples and by considering three repetitions for each case, 12 tests were performed for notched samples. This included two different notch depths (a) of 5 and 10 mm, two different notch tip diameters (d) of 2 and 3 mm, and a notch opening angle ( ) of 30 °. Furthermore, to obtain the stress-strain results of target EPDM under the uniaxial tensile test, some dumbbell-shaped samples were prepared which their geometry and dimensions are shown in the following figure.

20 mm

Fig. 2. Dimensions and schematic of EPDM rubber samples

The notched and dumbbell-shaped samples were loaded at the rate of 2 mm/min. The accurate measurement of strain values during the testing of dumbbell-shaped samples in hyperelastic materials is one of the most important factors in the experiments. For this purpose, as shown in Fig. 3, five points were painted at a distance of 5 mm from each other on the surface of rubber specimens and the motion of sample at specified time intervals was captured using a Canon camera. After the test, utilizing an image analysis method, the distance between these points was measured in each photograph and the strain was calculated in each certain time intervals.

Fig. 3. Dumbbell-shaped sample rupture in simple tensile test

4. Results and Discussion As stated in the previous sections, in order to perform numerical modeling, the hyperelastic material model in accordance with the rubber specimen behavior should be determined. After the curve fitting of some various