PSI - Issue 47

Mario A. Sánchez Miranda et al. / Procedia Structural Integrity 47 (2023) 310–324 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Some investigations have been devoted to investigate individually the FSW joint of these two thermoplastics, [25, 30-32]; nevertheless, in the best knowledge of the authors, no results are available for the joining of these two dissimilar thermoplastics using FSW. The main purpose of present investigation has been to advance the knowledge of mechanical behaviour of the joint UHMWPE-PP, obtained by FSW. Three pins profiles were tested in the beginning of this research: hexagonal, cylindrical and conical; nevertheless, the hexagonal profile has given better results and consequently, it was retained for the following FSW tests. Figure 1 shows the three tested profiles for welding UHMWPE-PP, with the corresponding dimensions. In order to carry out FSW on these two thermoplastics, plates of dimensions: 6 cm width, 16 cm length, and 2.5 cm thickness, were machined, as shown in Figure 2. The disposition of these two plates was as follows: PP plate was placed always in the advancing side, due to its higher melting temperature, and UHMWPE was placed always at the retreating side.

Figure 2. Plates of UHMWPE and PP machined to carry out the FSW union of these two thermoplastics.

With aim to improve the FSW joint of these two dissimilar thermoplastics, a stationary shoulder was manufactured with an aluminium alloy (AA6061-T6). It was an aluminium structure in which is machined a central circular depression, intended to accommodate a circular bearing, allowing free motion for the pin and restricting motion for the stationary shoulder. Figure 3a illustrates the hexagonal pin inserted in the circular bearing, allowing free rotation for the pin; whereas Figure 3b presents the fixed aluminium shoulder with the corresponding circular depression where de bearing is fitted. Under these conditions, the central part of bearing rotates together with the hexagonal pin, and the outside of bearing is fixed within the stationary aluminium shoulder. During the FSW tests, the stationary shoulder moves simultaneously with traverse speed, but does not rotate and does no generate heat dissipation related to rotation.

Figure 3. a) Pin tool inserted into bearing, b) Aluminium plate (AA6061-T6) with the circular depression.