تأثیر مدل‎سازی سه بعدی بر رفتار تنش مسطح یا کرنش مسطح در اطراف نوک ترک در نمونه کشش-فشار (CT)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 نویسنده مسئول

2 استاد

چکیده

بررسی مسائل شکست و گسترش ترک در مواد مختلف همواره مورد توجه محققین بوده است. لذا بررسی شکست فولاد ساختمانی به عنوان یکی از پرکاربردترین مواد در صنعت امری ضروری به ­نظر می­آید. مدل‎سازی‌های عددی همواره مکملی برای تحلیل نمونه­های آزمایشگاهی محسوب می­ شوند. یکی از مسائل مهم، بررسی رفتار نمونه ­های آزمایشگاهی با توجه به ابعاد آنها می ­باشد، این امر در مسائل شکست از اهمیت بیشتری برخوردار است، در این تحقیق بصورت عددی تأثیر اندازه ضخامت نمونه بر رفتار نوک ترک بررسی گردید. معمولاً برای بررسی شکست مواد شکل­ پذیر از نمونه استاندارد فشار-کشش (CT) استفاده می ­شود. رفتار نوک ترک در طول ضخامت نمونه های آزمایشگاهی ترکیبی از رفتار تنش مسطح و کرنش مسطح می­باشد، از این رو در این بررسی با اعتبارسنجی نتایج عددی رفتار نمونه ­های عددی در طول ضخامت بررسی گردید، تا به عنوان مکملی برای نتایج آزمایشگاهی مورد استفاده قرار گیرد. با مدل‎سازی و تحلیل نمونه­ های عددی با ضخامت­ های مختلف مشاهده شد با پیشروی از مرکز ضخامت نمونه به سمت لبه ­های آزاد رفتار از کرنش مسطح به تنش مسطح تغییر می­ کند، برای نمونه استاندارد CT با طول ترک 25 میلی­متر، ضخامت نمونه­هایی با بیش از 15 میلی­متر رفتار تقریباً به کرنش مسطح میل می­ کند، و می­توان به نتایج اعتماد کرد. در ادامه با تحلیل­های بیشتر و در نظر گرفتن پارامترهای وابسته به ابعاد نمونه، مقدار بارگذاری و تنش- کرنش در راستای عمود بر صفحه معادله­ایی ارائه گردید، که می­توان با استفاده از آن تشخیص داد تا چه طولی از لبه آزاد نمونه CT رفتار بصورت تنش مسطح یا کرنش مسطح می­ باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Three-Dimensional Modeling on the Behavior of Plane Strain or Plane Stress around Crack Tip in Compact-Tension (CT) Specimen

نویسندگان [English]

  • ali permanoon 1
  • Amir Hoshang Akhaveissy 2
1 Author
2 1Associate professor, Department of Civil Engineering, Faculty of Engineering, Razi University, , Kermanshah, Iran
چکیده [English]

An analysis of the two concepts the failure and crack propagation in various materials has always been of interest to researchers. Thus, it is of necessity to investigate the failure of construction steel as one of the most widely used materials in the industry. Numerical modeling is always a compliment to the analysis of laboratory samples. One important issue, particularly in failure problems, is to study the behavior of laboratory samples according to their dimensions. In the current research, the effect of sample thickness size on crack tip behavior is numerically examined. A standard CT specimen is commonly used to evaluate the failure of ductile materials. The crack tip behavior along the thicknesses of the laboratory samples is a combination of plane stress and plane strain behavior. Accordingly, in the present study, the effect of thickness on the numerical samples was investigated via the numerical result validation. The validated results then were used as a complement to the experimental results. Modeling and analysis of the numerical samples of varying thicknesses indicated that, with progression from the sample thickness center towards the free edges, the behavior shifts from plane strain to plane stress. In the case of the standard CT specimen with 25 mm crack length, the samples with greater than 15 mm thickness have an almost plane strain behavior, and the results are proved to be reliable. Then, with further analysis and taking into account the parameters dependent on sample size, loading value, and stress-strain values perpendicular to the equation plane, an equation was presented which can be used to realize to what extent the behavior in the free edge of the CT specimen operates in the form of plane stress or plane strain.
 

کلیدواژه‌ها [English]

  • Crack
  • Ductile material
  • J-Integral
  • finite element
  • Thickness
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