PSI - Issue 53

P.N.B. Reis et al. / Procedia Structural Integrity 53 (2024) 309–314 P.N.B. Reis / Structural Integrity Procedia 00 (2019) 000–000

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velocity of 2 mm/min. The applied load was acquired using a 10 kN load cell and the strain by an extensometer with 20 mm gauge length. As shown in Fig. 2, cyclic tests were also performed using constant and variable amplitude loading. Successive loads and unloads were applied at a constant displacement rate and in a range between 0 and 90% of the maximum average load obtained from the monotonic tensile tests (Fig.2a). Finally, as shown in Fig. 2b, progressive load-unload tests were also carried out in the range between 0 and 90% of the maximum average load and with incremental steps of 500 N (keeping the displacement rate constant of 2 mm/min). This resulted in 14 load-unload steps.

b)

a)

Fig. 2. Geometric representation of the repeated load cycles with: a) Constant load-unload values; b) Progressive load-unload values.

3. Results and discussion Fig. 3 shows the average stress-strain curve obtained from the monotonic tests, where good repeatability of the results can be observed, measured through the low dispersion of the curves (illustrated by the shaded area). The main static properties, in terms of average values and standard deviation (sdev), are 14.3 (0.85) MPa for the maximum tensile strength and 1.54 (0.58) % for the strain at the maximum tensile stress. The test was stopped before failure because the branch of the curve after maximum load is not relevant to this study.

Fig. 3. Monotonic stress-strain curve and its repeatability (illustrated by the shaded area).