Determination of dynamic rock Mode-I fracture parameters using cracked chevron notched semi-circular bend specimen

Abstract Rock dynamic fractures are common in many geophysical processes and engineering applications. Characterization of rock dynamic fracture properties such as the initiation fracture toughness, the fracture energy, and the fracture velocity, is thus of great importance in rock mechanics. A novel method is proposed in this work to measure dynamic Mode-I rock fracture parameters using a cracked chevron notched semi-circular bend (CCNSCB) specimen loaded by a split Hopkinson pressure bar (SHPB) apparatus. A strain gauge is mounted on the sample surface near the chevron notch to detect the fracture onset, and a laser gap gauge (LGG) is used to monitor the crack surface opening distance (CSOD) during the dynamic test. With dynamic force balance achieved in the tests, the stable–unstable transition of the crack propagation crack is observed and the initiation fracture toughness is calculated from the dynamic peak load. The average dynamic fracture energy as well as the fracture propagation toughness are calculated based on the first law of thermodynamics. The measured dynamic fracture properties of Laurentian granite using CCNSCB method are consistent with those reported in the literature using other methods.

[1]  Fangyun Lu,et al.  Determination of dynamic fracture parameters using a semi-circular bend technique in split Hopkinson pressure bar testing , 2009 .

[2]  B. Mohanty,et al.  Fracture toughness anisotropy in granitic rocks , 2008 .

[3]  M. Kuruppu.  Fracture toughness measurement using chevron notched semi-circular bend specimen , 1997 .

[4]  Hubert Maigre,et al.  A new approach to the experimental determination of the dynamic stress intensity factor , 1992 .

[5]  B. Mohanty,et al.  Experimental calibration of stress intensity factors of the ISRM suggested cracked chevron-notched Brazilian disc specimen used for determination of mode-I fracture toughness , 2006 .

[6]  K. Xia,et al.  Loading Rate Dependence of Tensile Strength Anisotropy of Barre Granite , 2010 .

[7]  Weinong W Chen,et al.  Pulse shaping techniques for testing brittle materials with a split hopkinson pressure bar , 2002 .

[8]  C. Atkinson,et al.  Combined mode fracture via the cracked Brazilian disk test , 1982, International Journal of Fracture.

[9]  I. L. Lim,et al.  Fracture testing of a soft rock with semi-circular specimens under three-point bending. Part 2—mixed-mode , 1994 .

[10]  Chun’an Tang,et al.  A new method for measuring dynamic fracture toughness of rock , 1990 .

[11]  Ernian Pan,et al.  Fracture Mechanics Analysis of Cracked Discs of Anisotropic Rock Using the Boundary Element Method , 1998 .

[12]  Chaoshui Xu,et al.  The Cracked Chevron Notched Brazilian Disc Test Geometrical Considerations For Practical Rock Fracture Toughness Measurement , 1993 .

[13]  L. C. Schmidt,et al.  Rock fracture-toughness determination by the Brazilian test , 1993 .

[14]  K. Vecchio,et al.  Evaluation of dynamic fracture toughness KId by Hopkinson pressure bar loaded instrumented Charpy impact test , 2004 .

[15]  R. Barsoum.  Triangular quarter‐point elements as elastic and perfectly‐plastic crack tip elements , 1977 .

[16]  B. Mohanty,et al.  Fracture Toughness Measurements and Acoustic Emission Activity in Brittle Rocks , 2006 .

[17]  Finn Ouchterlony,et al.  Suggested methods for determining the fracture toughness of rock , 1988 .

[18]  A. Bertram,et al.  Crack Propagation Toughness of Rock for the Range of Low to Very High Crack Speeds , 2003 .

[19]  Fengchun Jiang,et al.  Experimental investigation of dynamic effects in a two-bar/three-point bend fracture test. , 2007, The Review of scientific instruments.

[20]  Daniel Casem,et al.  A Four-Point Bend Technique to Determine Dynamic Fracture Toughness of Ceramics , 2006 .

[21]  H. Kolsky.  An Investigation of the Mechanical Properties of Materials at very High Rates of Loading , 1949 .

[22]  F. Ouchterlony.  On the background to the formulae and accuracy of rock fracture toughness measurements using ISRM standard core specimens , 1989 .

[23]  Daniel Rittel,et al.  A method for dynamic fracture toughness determination using short beams , 2000 .

[24]  K. Xia,et al.  A Semi-Circular Bend Technique for Determining Dynamic Fracture Toughness , 2010 .

[25]  Herbert Kolsky,et al.  Stress Waves in Solids , 2003 .

[26]  K. Xia,et al.  Rate dependence of the flexural tensile strength of Laurentian granite , 2010 .

[27]  K. P. Chong,et al.  New specimen for fracture toughness determination for rock and other materials , 1984 .

[28]  B. Mohanty,et al.  Effects of microstructures on dynamic compression of Barre granite , 2008 .

[29]  R. J. Fowell,et al.  Suggested method for determining mode I fracture toughness using Cracked Chevron Notched Brazilian Disc (CCNBD) specimens , 1995 .

[30]  Per-Arne Lindqvist,et al.  Effects of loading rate on rock fracture , 1999 .

[31]  Weinong Chen,et al.  Energy for Specimen Deformation in a Split Hopkinson Pressure Bar Experiment , 2006 .

[32]  Per-Arne Lindqvist,et al.  Effects of loading rate on rock fracture: fracture characteristics and energy partitioning , 2000 .

[33]  Ares J. Rosakis,et al.  Experimental Determination of Dynamic Crack Initiation and Propagation Fracture Toughness in Thin Aluminum Sheets , 1998 .

[34]  Hubert Maigre,et al.  An investigation of dynamic crack initiation in PMMA , 1996 .

[35]  W. Böhme,et al.  The behavior of notched bend specimens in impact testing , 1982 .

[36]  K. Xia,et al.  Dynamic cracked chevron notched Brazilian disc method for measuring rock fracture parameters , 2010 .

[37]  A. Ingraffea,et al.  STANDARDS FOR FRACTURE TOUGHNESS TESTING OF ROCK AND MANUFACTURED CERAMICS: WHAT CAN WE LEARN FOR CONCRETE? , 1997 .

[38]  Chengcheng Xu,et al.  The use of the cracked Brazilian disc geometry for rock fracture investigations , 1994 .