PSI - Issue 53

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 53 (2024) 264–269 Author name / Structural Integrity Procedia 00 (2023) 000–000

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after loading. All tests were performed at room conditions: 23 ± 3 ◦ C and 50 ± 50% temperature and relative humidity, respectively. A pre-load of 5 N was applied to the specimen prior to the test start to take up the slack.

Fig. 3. A V-notched specimen under test conditions; prior to the loading (left), and after applied load (right).

It is noteworthy that we used a rigid fixture for the experimental setup not only to fix each specimen on the tensile machine, but also to avoid any unwanted movement. In this study, the experiments were repeated seven times fro each group of the specimens (aged and unaged) to confirm that the experimental findings are reliable. After tensile tests, the examined specimens were released from the fixture for further crack evaluation.

5. Results and analysis

In the tensile tests, the load-displacement curves were recorded for each specimen. The load corresponding to frac ture initiation (i.e., the maximum load) has been considered as critical load. Fig. 4 shows the force-displacement curves of unagd and aged specimens with di ff erent geometries. Based on the results, unaged smooth specimens indicated the highest fracture load compared to their counterparts (dumbbell-shaped and V-notched specimens).

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V-notch Smooth Dumbbell-shaped

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Fig. 4. Force-displacement curves of examined specimens; unaged (left) and aged (right).

The highest and lowest fracture loads in unaged specimens are 1980.5 N and 1356.7 N belong to the smooth and dumbbell-shaped specimens, respectively. Although accelerated thermal aging has led to a reduction in the fracture load, the results indicated that the smooth specimens showed the highest fracture load and sti ff ness after accelerated thermal aging compared to other aged specimens. Based on the experiments, the lowest fracture load was 1112.8 N obtained from tests on the dumbbell-shaped specimens. Although physical appearance of the test coupons are not changed after accelerated thermal ageing, their load carrying capabilities are influenced.