PSI - Issue 39

M.A. Sánchez Miranda et al. / Procedia Structural Integrity 39 (2022) 161–172 uthor name / Structural Integrity Procedia 00 (2019) 000–000

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Figure 4. Improved joining of dissimilar ABS-PP thermoplastic with the welding parameters of test 9, in Table 3.

In test 10 the advanced speed is reduced to 50% in regard the previous one; the welding seems acceptable, but the tunnel defect appears one again with the length of 1 cm; a decrease of initial mixing would be at the origin of this defect. Increase of rotating speed to 3000 rpm (test 11 in Table 3), induces a detrimental effect on welding, related to excess of heat dissipation and generation of discontinuities in the welding zone. Finally, tests 12, 13 and 14 in Table 3 were carried out with three specimens each one, changing only the advanced speed in order to evaluate the tensile strength of resulting dissimilar joints. Better results were obtained for tests 13 and 14. 3. Mechanical tests In order to validate the tensile strength of dissimilar ABS-PP joints, prismatic specimens were joined by friction stir welding according the parameters of tests 13 and 14 in Table 3. The testing specimens are shown in Figure 5, where the dark zone corresponding to ABS and the white to PP.

Figure 5. Dissimilar joints ABS-PP for tensile tests.

The dimensions of welded prismatic specimens destined to tensile tests were: 12 mm width, 65 mm long and 3 mm thickness. Tensile tests were carried out with the constant deformation speed of 1.5 mm/min. In Table 4 are listed the specimens subjected to tensile tests; whereas in Figure 6 are plotted the results of these tensile tests. According to investigations on thermoplastics joining by FSW [ 22 ] , the fracture under tensile tests occurs in five zones: a) Crack formed outside weld seam, b) Crack formed at the retreating interface, c) Crack formed in retreating side of weld seam, d) Crack formed at center of weld seam, and e) Crack formed in advancing side of weld seam.