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Effect of specimen thickness on Mode II fracture toughness of rock

  • Rao Qiu-hua 
  • Sun Zong-qi 
  • Wang Gui-yao 
  • Xu Ji-cheng 
  • Zhang Jing-yi 
Article

Abstract

Anti-symmetric four-point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode II fracture test and study the effect of specimen thickness on Mode II fracture toughness of rock. Numerical calculations show that the occurrence of Mode II fracture in the specimens without guiding grooves (when the inner and outer loading points are moved close to the notch plane) and with guiding grooves is attributed to a favorable stress condition created for Mode II fracture, i.e. tensile stress at the notch tip is depressed to be lower than the tensile strength or to be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of Mode II fracture toughness KII C decreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness.

Key words

Mode II fracture toughness rock fracture stress analysis specimen thickness 

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Copyright information

© Central South University 2001

Authors and Affiliations

  • Rao Qiu-hua 
    • 1
  • Sun Zong-qi 
    • 1
  • Wang Gui-yao 
    • 2
  • Xu Ji-cheng 
    • 3
  • Zhang Jing-yi 
    • 3
  1. 1.College of Resources, Environment and Civil EngineeringCentral South UniversityChangshaChina
  2. 2.River and Sea DepartmentChangsha Communications UniversityChangshaChina
  3. 3.Open Lab of MechanicsCentral South UniversityChangshaChina

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