Eigen-line in welded structures of thermoplastic polymers |
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| Institution: | 1. Institute of Process Equipment, Zhejiang University, Hangzhou, PR China;2. State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, PR China;3. Georgia Tech Manufacturing Institute and School of Industrial & Systems Engineering, Georgia Institute of Technology, Atlanta, GA, United States;1. Polymer Processing and Flow (P-PROF) Group, School of Energy, Environment and Materials, King Mongkut''s University of Technology Thonburi (KMUTT), 126 Pracha Uthit Rd., Bang Mod, Thung Khru, Bangkok, 10140, Thailand;2. Department of Materials Engineering, Faculty of Engineering, Kasetsart University, 50 Ngamwongwan Rd., Ladyao, Chatuchak, Bangkok, 10900, Thailand;2. Department of Civil Engineering, Federal University of São Carlos, Brazil;3. Federal Centre for Technological Education of Minas Gerais, Department of Civil Engineering, Brazil;4. Advanced Composites Centre for Innovation and Science, University of Bristol, UK;1. CEITEC – Central European Institute of Technology, Brno University of Technology, Purkynova 656/123, 612 00 Brno, Czechia;2. Unipetrol RPA, Ltd., Polymer Institute Brno, Tkalcovska 36/2, 656 49 Brno, Czechia;3. Ratiochem, Ltd., Tkalcovska 36/2, 602 00 Brno, Czechia;1. Department of Railway Engineering, School of Civil Engineering, Central South University, Changsha, Hunan 410075, China;2. Trelleborg Industrial Anti-Vibration Systems, Leicester LE4 2BN, UK;1. Department of Power Mechanical Engineering, National Formosa University, Yunlin 632, Taiwan;2. Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, Keelung, Taiwan;3. Electronics and Optoelectronics Research Laboratories (EORL), Industrial Technology Research Institute (ITRI), Taiwan |
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| Abstract: | Welding is widely used as a joining method for thermoplastics, and it is imperative to ensure the joining quality, particularly for critical applications. In a previous work by the authors, an Eigen-line was found in the electrofusion joint of polyethylene (PE) pipes based on ultrasonic tests and it could be used to detect and assess cold welding defects. However, the nature of the Eigen-line and reasons for the Eigen-line's existence in ultrasonic images have not yet been fully understood, which limited its applications. In this paper, Eigen-lines were observed in other thermoplastics including polypropylene (PP), polyamide 6 (PA 6), polyoxymethylene (POM) and polyethylene terephthalate (PET), suggesting that Eigen-lines have common existence. Microindentation tests were conducted on specimens cut from electrofusion joints and butt joints of PE pipes. It was found that a significant change of elastic modulus exists around the Eigen-line, which can partly explain the appearance of an Eigen-line in ultrasonic images. Scanning electron microscopy (SEM) and reflective optical microscopy were also employed to explore the nature of the Eigen-line. The results showed that an Eigen-line is a thin layer with polymer chain orientation between base material and welded zone. |
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| Keywords: | Cold welding Eigen-line Microindentation |
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