تعیین پارامترهای شکست یک استوانه جدار نازک تحت فشار در حضور تنش‏های پسماند جوشکاری

نوع مقاله: مقاله پژوهشی

نویسندگان

1 عضو هیات علمی / دانشکدة مهندسی صنایع، دانشگاه علم و صنعت ایران

2 کارشناس ارشد / دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران

چکیده

در این مقاله ابتدا فرایند جوشکاری قوس تنگستن یک پوستة آلومینیومی با درز جوش طولی به‏صورت سه‏بعدی در نرم‏افزار آباکوس مدلسازی شده و توزیع تنش پسماند ناشی از فرایند جوشکاری به‏دست می‏آید. تمامی خواص مکانیکی و حرارتی پوسته وابسته به دما در نظر گرفته شده و برای مدلسازی شار حرارتی و فلز جوش از مدل دو بیضی‏گون گلداک و روش تولد و مرگ المان استفاده می‏شود. مقدار تنش پسماند در اطراف خط جوش و در ناحیه متأثر از حرارت به مقدار قابل ملاحظه‏ای کششی می‏باشد که می‏تواند سبب بروز و رشد ترک در ناحیة خط جوش شود. سپس یک ترک سه‏بعدی نیم‏بیضوی با طول‏های مختلف در امتداد خط جوش و در جدارة پوستة آلومینیومی به‏صورت طولی در نظر گرفته می‏شود و پس از محاسبة ضریب شدت تنش مود I آن تحت بارگذاری فشار داخلی منحنی‏های تغییرات ضریب شدت تنش در سرتاسر جبهة ترک و برای طول ترک‏های مختلف ارائه می‏شود. در نهایت با در نظر گرفتن تأثیر حوزة تنش پسماند اطراف جوش در ضریب شدت تنش و تکرار تحلیل‏های اجزاطی محدود نشان داده می‏شود که تأثیر همزمان فشار داخلی و تنش پسماند کششی موجود در اطراف جوش می‏تواند شرایط رشد ترک در پوسته را تسهیل نمایند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Fracture parameter determination for a thin walled pressurized cylinder under the influence of residual stress induced by welding process

نویسندگان [English]

  • Mohammad Reza Mohammad Aliha 1
  • Hussain Gharehbaghi 2
چکیده [English]

In the first part of this paper, the gas tungsten-arc welding process of a thin cylinder made of Al6061-T6 alloy is simulated using 3-D finite element model in the ABAQUS code and the distribution of residual stress is obtained. Temperature dependent thermo-mechanical properties are considered for the aluminum alloy and for simulating the heat source of tungsten arc welding, Goldak's double ellipsoid model is also employed. Based on the finite element results, the value of residual stress is considerably positive around the weld line and HAZ area which can increase the risk of crack initiation and propagation in the weldment zone. Hence, in the second part of the numerical analyses of this research a longitudinal semi elliptical crack is considered in the wall of internally pressurized aluminum cylinder and its mode I stress intensity factor (KI) is determined numerically for different crack geometries. Finally the influence of both residual stress field and internal pressure is taken into account on the value of KI. It is observed that the effects of combined internal pressure and tensile residual stresses around the crack can facilitate required conditions for crack propagation in the analyzed cracked thin cylinder.

کلیدواژه‌ها [English]

  • Finite element modeling
  • welding simulation
  • Residual Stress
  • cracked thin cylinder
  • semi elliptical crack

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