PSI - Issue 53

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 53 (2024) 264–269

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Author name / Structural Integrity Procedia 00 (2023) 000–000

Since printing parameters have influence on the mechanical performance of 3D-printed parts, in this study, printing parameters such as feed rate, layer thickness, and fill density were kept constant in printing of all specimens to ensure consistent printing quality. The fabricated specimens were kept at room temperature for one week, they are named here ”unaged”. In this study, we printed 14 specimens for each geometry. Half of the specimens were artificially aged which is explained in the following section.

4. Experimental procedure

4.1. Accelerated thermal aging

Di ff erent mechanical parts might be subjected to various environmental conditions, investigation their behavior is necessary. In this context, accelerated thermal aging test is considered as an e ff ective experimental technique to assess the thermostability of the structural elements. Considering di ff erent applications of3D-printed parts, they encounter a variety of environmental conditions over their service life, but less focus has been placed on the e ff ects of thermal aging on the mechanical strength of 3D-printed components. It is noteworthy that there is a lack of standard or systematic procedure for e ff ects of thermal aging on 3D-printed parts, but elevated temperature is considered as a method of accelerated aging. In the present study, the specimens with three di ff erent geometries were subjected to the accelerated thermal aging using an environmental climate test chamber. Particularly, we used a floor standing model WK340 (manufactured by Weiss Technik) to simulate the natural environment. The utilized climate chamber works in the range of -45 ◦ Cto + 180 ◦ C. In this study, the test coupons were artificially aged in the temperature range of -5 ◦ C to + 35 ◦ C and each temperature was kept for 1 h. This aging cycle was continuously repeated in two weeks. Fig. 2 shows the specimens inside the climate chamber and details of thermal aging cycles.

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Fig. 2. Accelerated aging of the specimens in the heat chamber (left), and the applied cycles of thermal aging (right).

After accelerated thermal aging, the aged specimens were cooled to room temperature and then examined similarly to the unaged specimens. The weights of each specimen were measured before and after thermal aging, with an accuracy of ± 0.001 g. Moreover, length, width, and thickness of the specimens were measured precisely before and after aging process. There was no significant changes in weights and dimensions due to the conducted thermal aging.

4.2. Mechanical tests

A series of tensile tests under static loading conditions was performed on aged and unaged specimens using a hydraulic machine which was fitted with 15 kN load cell. All tests were carried out in the displacement control mode at a displacement rate of 5 mm / min according to ASTM D638 (ASTM D638, 2014). The utilized tensile machine was equipped with electronic control which monitors the applied load and movement of the top cross head. In experimental tests, no external extensometer was used for strain measurement and displacements on the specimens were measured by a linear variable displacement transducer. Fig. 3 shows a V-notched specimen under test conditions before and