PSI - Issue 56

Sergiu-Valentin Galațanu et al. / Procedia Structural Integrity 56 (2024) 138– 143 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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49 MPa. The white and black specimen groups have lower values of the maximum stress (about 47 MPa in the case of white samples, and about 46 MPa in the case of black samples respectively).

Fig. 3. (a) Average of the maximum stress, (b) Average of the strain at the maximum stress, (c) Average of the ultimate strain, and (d) and Young Modulus.

The highest values of the strain at the maximum stress were observed in the case of white samples, Fig. 3b; they tend to be more ductile than the other samples, even though the difference between the values is subtle. If we analyze the results, we can see that the white samples have the best repeatability, while the recycled samples have a higher spread of values. This may be due to the inhomogeneity, but also to the diameter variation for the extruded recycled wire. At the same time, in the case of the recycled and black samples, the results show us a large dispersion in terms of the ultimate strain. For a better understanding of this behavior, more specimens need to be analyzed in the future. However, with the exception of one specimen, all the black samples presented high ultimate strain values. The observed differences between the results recorded for the group of specimens with different wire colors also confirm that the color influences the mechanical tensile properties, Frunzaverde et al. (2023). In Fig. 3 d, it can be seen that the Young modulus obtained has similar values to those from the literature (about 2100 MPa both for the recycled and raw specimens).

Fig. 4. Displacement from DIC on the recycled specimen

Fig. 5. Displacement from DIC on the raw specimen

In Fig. 4 three displacement phases of the recycled specimen measured with DIC are depicted. The initial phase is presented in (a). This is the reference position for the measurement when the specimen is not loaded. Figure (b) shows an intermediary phase, the specimen was loaded, and the maximum deformation is located in the upper part of the specimen. The last figure shows the last phase before the crack appears; in this phase, the maximum displacement is 2.56 mm in the upper part of the specimen. Fig 5 presents the same thing but for the raw specimen. In this case, the first stage was no longer represented, only the second (b) and third (c) phases are displayed. Similar to the results recorded in the case of the recycled specimen the maximum displacement is about 2.32mm before the crack appears. If we compute the difference between the movement of the upper and lower point from the specimen in DIC, the maximum displacement in the recycled specimen is 1,39mm and 1,28mm for the raw specimen respectively until the crack appears. In Fig. 6 and 7 the true principal strain from DIC on the recycled and raw specimens, are presented. The initial phase (presented in Fig. 6a), the intermediate phase (Fig. 6b, Fig. 7b) and a phase close to the appearance of the crack (Fig. 6c and Fig. 7c) are presented. These images provide a better understanding in the distribution of true