بررسی شکست نمونه‌های سنگی دارای شیار U شکل با استفاده از معیار تنش محیطی اصلاح شده (MTS-FEM) تحت مود یک

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشیار دانشگاه خوارزمی، دانشکده فنی و مهندسی، گروه مکانیک

2 کارشناسی ارشد، گروه مهندسی مکانیک، دانشکده فنی و مهندسی، دانشگاه خوارزمی، تهران، ایران

3 دانشیار، دانشکده علوم و فنون نوین، دانشگاه تهران

چکیده

در این مقاله به بررسی شکست نمونه­ های سنگی دارای شیار U شکل تحت بارگذاری مود یک خالص با استفاده از یک معیار جدید پرداخته می ­شود. معیار پیشنهادی بر پایه معیار بیشینه تنش محیطی (MTS) استوار می­باشد. بر اساس معیار MTS، شروع شکست هنگامی اتفاق می­افتد که میزان بیشینه تنش محیطی در شعاع بحرانی از نوک شیار به مقدار بحرانی خود برسد. با توجه به بزرگ بودن شعاع بحرانی در نمونه های سنگی، معیار بیشینه تنش محیطیِ کلاسیک که فقط جملات اول یا تکین از بسط سری تنش را مورد توجه قرار می­دهد، نمی­تواند توصیف صحیح و دقیقی از شروع شکست ارائه نماید. بنابراین، از تحلیل اجزای محدود برای محاسبه ­ی دقیق­تر تنش در روش پیشنهادی استفاده شده است. به منظور ارزیابی روش پیشنهادی که روش MTS-FEM نامیده می­شود، از داده­های آزمایشگاهی ارائه شده در تحلیل نمونه ­های خمش چهار نقطه ­ای با شیار U شکل لب ه­ای، تحت بارگذاری مود I خالص که در مقالات علمی گزارش شده است، استفاده می­گردد. نتایج حاصل از ارزیابی­ها نشان می­دهد که معیار MTS-FEM نه تنها نسبت به معیار MTS از دقت بهتری برخوردار است، بلکه می­تواند نتایج آزمایشگاهی را با دقت خوبی (زیر 13%) پیش ­بینی نماید.

کلیدواژه‌ها


عنوان مقاله [English]

MODE I FRACTURE ASSESSMENT OF U-NOTCHED ROCK SPECIMENS USING MTS-FEM CRITERION

نویسندگان [English]

  • Javad Akbardoost 1
  • Milad Sangsefidi 2
  • Ali Reza Torabi 3
1
2 Graduated MSc student, department of mechanical engineering, Kharazmi university, Tehran, Iran
3 Associate professor, department of mechanical engineering, University of Tehran, Tehran, Iran
چکیده [English]

In this paper, the fracture behavior of U-notched rock specimens under pure mode I loading has been investigated by means of a new criterion. The proposed approach is based on the maximum tangential stress (MTS) criterion which states that the onset of fracture takes place when the maximum tangential stress at the critical distance from the notch border attains a critical value. Due to the relatively large critical distance in quasi-brittle materials such as rock, the classical MTS criterion which considers only the first or singular terms of the stress series expansion around the notch border cannot provide an accurate estimation for the onset of fracture in rock-type notched samples. Therefore, it is proposed in this paper that the tangential stress component is determined directly form finite element (FE) analysis. Since the proposed approach is a combination of MTS criterion and the FE method, it is named the MTS-FEM criterion. In order to evaluate the MTS-FEM criterion, the experimental results reported in the previous studies for U-notched samples were employed. The comparison between the fracture loads predicted by MTS and MTS-FEM criteria and those reported in the previous studies revealed that the MTS-FEM criterion not only can provide more accurate estimates than the MTS criterion, but also in good agreements with the experimental results (less than 13%).

کلیدواژه‌ها [English]

  • Rock-type notched sample
  • modified maximum tangential stress (MTS-FEM)
  • four-point bending
  • pure mode I
  • finite element method
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