Measurement of the mixed mode fracture strength of green sandstone using three-point bending specimens

Yifan Li, Shiming Dong and Martyn J. Pavier

Abstract

Three-point bending specimens have been used to investigate the mixed mode fracture of green sandstone. Dimensionless stress intensity factors and T-stresses were calculated first by using the finite element method for various crack lengths, crack angles and span to length ratios. It is shown that three-point bending specimens can provide the whole range of mode mixities from pure mode I to pure mode II, provided suitable values are chosen for the crack angle and span to length ratio. The fracture test results were also used to compare with predictions of different criteria. These comparisons show that modified criteria including the influence of the T-stress agree better with experiment than the conventional criteria but that no one criterion matches perfectly the test results.

Key Words

sandstone; fracture; T-stress; three-point bending; different criteria

Address

Yifan Li: 1.) Department of Mechanical Engineering, University of Bristol, Queens Building, University Walk, Bristol BS8 1TR, U.K. 2.) College of Architecture and Environment, Sichuan University, Chengdu 610065, China Shiming Dong: College of Architecture and Environment, Sichuan University, Chengdu 610065, China Martyn J. Pavier:Department of Mechanical Engineering, University of Bristol, Queens Building, University Walk, Bristol BS8 1TR, U.K.

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