تحلیل تجربی و عددی اثر شار الکتریکی فرعی بر اتّصالات جوش نقطه ای مقاومتی آلیاژ آلومینیوم 2219

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی مکانیک، دانشگاه تهران، تهران، ایران

چکیده

شار الکتریکی فرعی در جوش نقط های هنگامی رخ می­دهد که جریان الکتریکی از طریق نقطه جوش موجود عبور می­کند. مقدار این شار به تعداد، فاصله و اندازه دکمه (های) قبلی وابسته بوده، باعث تغییرات ابعادی و متالورژیکی دکمه جوش پایانی می ­شود. در این مطالعه، اثر شار الکتریکی فرعی به کمک یک مدل الما ن محدود مورد بررسی قرار گرفته، نتایج آن با آزمایشات تجربی روی ورق ­های آلومینیوم 2219 مورد مقایسه قرار گرفته است. در این راستا، پارامترهای فاصله و جریان جوشکاری جهت کشف اثر شار الکتریکی فرعی بر کیفیت دکمه جوش مورد بررسی قرار گرفته ­اند. در بخش تجربی، طراحی آزمایش سه عاملی به منظور تشخیص اهمیّت عوامل مؤثّر و اعتبارسنجی مدل المان محدود استفاده شده است. در مدل المان ­محدود، تمامی اثرات متقابل الکترو-ترمال و مکانیکی مد نظر قرار داده شده، خواص جنس بصورت تابعی از دما وارد شده ­اند. نتایج تجربی و عددی از مطابقت قابل قبولی برخوردار هستند. عدم تقارن توزیع دما به همراه ابعاد نقطه­ جوش تحت اثر عامل مذکور توسّط مدل المان­ محدود پیش بینی شده، توسّط نتایج تجربی اعتبارسنجی شده است. همچنین تاثیر شار الکتریکی فرعی بر کاهش عمق نفوذ، گرایش منطقه ی متاثّر از حرارت به نقطه جوش قبلی و تمرکز عناصر آلیاژی در مرز دانه ­های منطقه متاثر از حرارت به اثبات رسیده است

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Shunting Effect in Resistance Spot Welded Joints of Aluminum Alloys

نویسندگان [English]

  • M. Jafari Vardanjani
  • A. Araee
Department of Mechanical Engineering, University of Tehran, Tehran, Iran
چکیده [English]

Shunting effect occurs in RSW when the electrical current passes through previous spot welds. Value of this current depends mostly on distance, number, and size of previous spot welds. This will cause some dimensional and metallurgical changes in welding nugget as well as heat affected zone (HAZ). In this study, shunting effect of RSW is considered in a finite element analysis (FEA) model and the results are compared to experiments performed on aluminum alloy 2219. Weld spacing together with welding current and time are considered to discover the effect of shunting current in the final quality of nugget. A three factor experiment design has been performed to find the significance of factors and interactive effects, as well as FEA model verification. Electrothermal and mechanical interactions are considered in the FEA model. Experimental and numerical solutions have yielded comparable similar results in terms of welding nugget properties. Asymmetry in electrical potential, temperature, and stress distribution and geometry of shunted nugget are predicted and verified directly or indirectly. Intense effect of shunting current on nugget height, asymmetric growth of heat affected zone (HAZ) toward previous welding nugget, as well as concentration of alloying elements along grain boundaries are also discovered.

کلیدواژه‌ها [English]

  • Resistance spot welding
  • Shunting
  • Finite element analysis
  • Experiment

مراجع

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نشریه مهندسی مکانیک امیرکبیر
دوره 50، شماره 3
مرداد و شهریور 1397
صفحه 561-576

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