B • Nylon 6, due to its low melt viscosity, is weldable only at lower rotation rates. Therefore, a 300 rev/min rotation speed and 25-mm/min feed rate has given comparatively good weld results at 0-deg tool angle. • At higher rotation rates, squeezing out of excess plasticized material and defects formation in the weld zone were observed. • A small-diameter shoulder, on the other hand, reduced the amount of flash by reducing the primary heat. • The processing temperatures, measured 1 mm below the pin plunged zone, were quite below the thermal degradation temperature of Nylon 6 (350°C). Thus, it is assumed the Nylon 6 in the stirring zone did not undergo extreme thermal degradation, although minor reduction in molecular Fig. 14 — A — Specimen before welding with marker material perpendicular to the WD; B — horizontal cross section of postweld specimens when marker material is on the AS; C — weld interface; D — RS. weight due to smoke evolution is believed to have occurred. • The tensile strength of all joints was quite lower than that of the base material. • As the result of microstructure observation in the weld zone regions, relatively smooth and uniform microstructure was observed at the optimum set of parameters. • DSC results showed the crystallinity of the weld zone decreased compared to base material. Moreover, the retreating side compared to the advancing side was found to have low crystallinity. • During tensile tests, all specimens fractured at the interface of the weld zone on the retreating side. It can be attributed to the lack of bonding at the interface of the weld zone on the WELDING RESEARCH retreating side, and low crystalline content in the retreating side region. • Material flow examination revealed large (more than pin diameter) backward displacement of plasticized material. However, overall a uniformly mixed distinct isolated pin plunged zone was found. Acknowledgments The authors would like to thank Universiti Teknologi PETRONAS for the research facilities and financial support. 1. A Guide to nylon. Available: ptsllc.com/intro/Nylon_intro.aspx. 2. Magnus, C. Feasibility Study of Metal to Polymer Hybrid Joining. 2012. 3. Liu, F. C., Liao, J., and Nakata, K. 2014. Joining of metal to plastic using friction lap welding. Materials & Design 54(2): 236–244. 4. Arici, A., and Sinmazçelýk, T. 2005. Effects of double passes of the tool on friction stir welding of polyethylene. Journal of Materials Science 40(6): 3313–3316. 5. Pirizadeh, M., Azdast, T., Ahmadi, S. R., Shishavan, S. M., and Bagheri, A. Friction stir welding of thermoplastics using a newly designed tool. Materials & Design 54(2): 342–347. 6. Olabisi, O., and Adewale, K. 1997. Handbook of Thermoplastics. Vol. 41. CRC press. 7. Aydin, M. 2010. Effects of welding parameters and pre-heating on the friction JUNE 2016 / WELDING JOURNAL 217-s Fig. 13 — A — Specimen before welding with a marker material parallel to the WD; B — vertical cross section of postweld specimens when marker material is on the RS; C — the AS. Fig. 15 — Specimens before welding with marker material at the bottom, middle, and top of the following: A — AS; B — RS; C — longitudinal section of postweld specimen AS; D — RS. References A B C A C D A B C D
Welding Journal | June 2016
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