بررسی تجربی و تئوری چقرمگی شکست مود 2 خالص برای قطعات نرم ترک‌دار با کرنش- سختی بالا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 علم و صنعت

2 گروه آموزشی هوافضا، دانشکده علوم و فنون نوین دانشگاه تهران

چکیده

هدف از این پژوهش، بررسی تجربی و تئوری چقرمگی شکست صفحات مربعی شیاردار همراه با پیش‌ترک مرکزی تحت بارگذاری مود 2 خالص است. این صفحات از فولاد ضد زنگ 316- ال با خاصیت چکش‌خواری و کرنش- سختی بالا ساخته شده‌اند. به منظور تعیین تئوری چقرمگی شکست این قطعات، از مفهوم ماده فرضی استفاده شده است. با استفاده از این مفهوم می‌توان بدون نیاز به تحلیل‌های پیچیده الاستیک- پلاستیک و تنها با بکارگیری تحلیل‌های مکانیک شکست الاستیک خطی، چقرمگی شکست مواد چکش‌خوار را پیش‌بینی کرد. به عبارت دیگر، براساس فرضیات مفهوم ماده فرضی می‌توان ماده ترد فرضی با خاصیت الاستیک خطی را جایگزین فولاد 316- ال کرد. سپس با ترکیب مفهوم ماده فرضی با معیارهای تنش میانگین، تنش میانگین تعمیم یافته، بیشینه تنش مماسی، بیشینه تنش مماسی تعمیم یافته، چگالی انرژی کرنشی و چگالی انرژی کرنشی تعمیم یافته، مقادیر چقرمگی شکست قطعات مورد نظر تخمین زده می‌شود. به منظور تأیید مقادیر چقرمگی شکست تخمین زده شده، آز‌مون‌های شکست بر روی نمونه‌های آزمایشگاهی مورد نظر انجام شده است. مشاهدات تجربی نشان می‌دهد که این قطعات در آستانه رشد ترک، تغییر شکل پلاستیک زیادی را تجربه می‌کنند. مقایسه نتایج نشان می‌دهد که معیارهای ترکیبی بررسی شده می‌توانند بخوبی نتایج تجربی را پیش‌بینی کنند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental and Theoretical Assessment of Mode II Fracture Toughness for Cracked Ductile Specimens with High Strain-Hardening

نویسندگان [English]

  • Hadi Sadeghian 1
  • Majid Reza Ayatollahi 1
  • Ali Reza Torabi 2
1 IUST
2 Faculty of New Science and Technologies, University of Tehran
چکیده [English]

In this research, the mode II fracture toughness of O-notched diagonally loaded square plate samples with pre-existing cracks which are made of stainless steel 316L with specifications of highly ductile behavior and great strain hardening is investigated theoretically and experimentally. For this purpose, several fracture tests are carried out on the pre-cracked specimens to determine the fracture toughness experimentally. The experimental observations and the load-displacement curves obtained from the fracture tests illustrate that the pre-cracked specimens undergo large plastic deformations at the onset of crack propagation. Afterward, the fictitious material concept is used to estimate the values of fracture toughness achieved experimentally. By using the fictitious material concept, the fracture toughness of pre-cracked specimens fabricated from stainless steel 316L could be estimated without the need for complicated and time-consuming elastic-plastic failure analysis and by performing only linear elastic analysis. For this purpose, the fictitious material concept is simply combined with mean stress, generalized mean stress, maximum tangential stress, generalized maximum tangential stress, strain energy density, and generalized strain energy density criteria. It is shown that the combination of fictitious material concepts with four linear elastic brittle fracture criteria is quite successful in predicting the mode II fracture toughness of ductile pre-cracked specimens. 

کلیدواژه‌ها [English]

  • Fictitious Material Concept
  • crack propagation
  • Mode II loading
  • Elastic fracture mechanics
  • Fracture Toughness
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