PSI - Issue 39

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

Figure 12. Material flow behind the pin, during FSW.

Additional masse flow M EX, may be considered when rotating speed reaches a critical value; this flow comes from the shoulder zone III to the advancing zone I, Figure 12. For dissimilar polymeric materials, the difference in density and rheology of the two materials must lead to additional factors conditioning the material flow. For the present case, the retreating side was imposed to ABS polymer, which has slightly higher density compared to PP. Mass flow in the retreating side is higher compared to advancing side for a large range of rotating speed, leading to tunnel defect, as illustrated in Figures 3 and 4. Finally, a good compromise was found concerning the process parameters and the resulting mechanical-physical properties of these two thermoplastics, joined using FSW: 2000 rpm for rotating speed, 1.5 – 3 mm/min of advanced speed, 2.5 mm/min of penetration speed, cylindrical pin and contact between mobile shoulder and plastic material.

5. Conclusions The following conclusions can be drawn from the present work:

Friction stir welding joining has been performed in two polymeric dissimilar materials: ABS and PP. The process parameters were obtained for the higher joining efficiency, attaining close to 90% of tensile strength, compared to parent materials. Hardness profiles along and across the testing specimens were obtained, revealing systematically decrease of this property at the stir zone. Mechanical bonding was predominant for the joining of dissimilar ABS-PP consisting of molecular diffusion, following material flows patterns illustrated in Figure 12. Joining results show a good compromise between some obtained process parameters and the joining efficiency; nevertheless, additional investigations are needed to advance in the complexity of mass flow during FSW and its impact in the mechanic physical obtained properties, together with the rheological and physical properties of dissimilar polymers and its effects on the resulting joining. The last should be accompanied with the effects of the process parameters and new techniques and modalities of FSW of dissimilar polymers: imposed initial and process temperatures, fixed shoulders, pin profiles, addition of reinforcement elements, etc. Acknowledgements The authors express their special mention of gratitude to CONACYT (The National Council for Science and Technology, Mexico), for the financial support destined to this study. An additional mention of gratitude to the University of Michoacán in Mexico for the received support in the development of this work.