TY - JOUR
T1 - Finite element analysis of the modified ring test for determining mode I fracture toughness
AU - Fischer, M. P.
AU - Elsworth, D.
AU - Alley, R. B.
AU - Engelder, T.
N1 - Funding Information:
Acknowledgements--The work presented herein resulted from experiments to determine the fracture toughness of ice and tim. Firn for the project was provided via the Polar Ice Coring Office, the GISP2 Science Management Office, and the 109th New York Air National Guard. We would like to thank A. R. Ingraffea for providing the finite element program FRANC. T. Bittencourt, D. Swenson and P. Wawrzynek provided excellent technical support during our use of the program. S. Anandakrishnan and G. Woods provided valuable advice and assistance during this project. We thank P. J. Lemiszki for reviewing an early version of this manuscript. Funding for this project was provided by the David and Lucille Packard Foundation, and NSF grants DPP-8822027, and DPP-8915995 to R. B. Alley.
PY - 1996
Y1 - 1996
N2 - Plane strain fracture toughness (KIc) values are determined for the modified ring (MR) test through numerical simulation of crack growth to highlight the sensitivity of MR KIc values on applied displacement or force boundary conditions, slip conditions at the specimen-platen interface, and the Poisson ratio (ν) of the test material. Numerical calculation of fracture toughness in the MR test is traditionally conducted assuming a uniform force along the specimen loading surfaces and no slip between the specimen and the loading platens. Under these conditions KIc increases by 30-40% as ν decreases from 0.4 to 0.1. When slip is allowed at the specimen-platen interface under a uniform force, KIc values are independent of ν, and for any given ν, are 5-25% less than those determined under a no-slip boundary condition. Under a uniform displacement of the specimen loading surfaces, KIc is essentially independent of ν, regardless of specimen-platen interaction. Moreover, although KIc values determined under uniform displacement and no-slip boundary conditions are always higher than those determined under uniform displacement and slip-allowed boundary conditions, the average difference in KIc for these two methods is less than 5% for the two specimen geometries examined. This suggests that under uniform displacement conditions, KIc is essentially independent of specimen-platen interaction. Because KIc values determined from MR testing are strongly dependent on the modeling procedure, future reports KIc determined from this test should be accompanied by detailed reports of the modeling procedure. Until further testing reveals the most accurate simulation technique, we advocate use of a uniform displacement formulation for KIc determination from MR testing because results from this method are insensitive to most modeling parameters. Numerical results from models conducted under uniform force, no-slip boundary conditions should be viewed as an upper bound to KIc.
AB - Plane strain fracture toughness (KIc) values are determined for the modified ring (MR) test through numerical simulation of crack growth to highlight the sensitivity of MR KIc values on applied displacement or force boundary conditions, slip conditions at the specimen-platen interface, and the Poisson ratio (ν) of the test material. Numerical calculation of fracture toughness in the MR test is traditionally conducted assuming a uniform force along the specimen loading surfaces and no slip between the specimen and the loading platens. Under these conditions KIc increases by 30-40% as ν decreases from 0.4 to 0.1. When slip is allowed at the specimen-platen interface under a uniform force, KIc values are independent of ν, and for any given ν, are 5-25% less than those determined under a no-slip boundary condition. Under a uniform displacement of the specimen loading surfaces, KIc is essentially independent of ν, regardless of specimen-platen interaction. Moreover, although KIc values determined under uniform displacement and no-slip boundary conditions are always higher than those determined under uniform displacement and slip-allowed boundary conditions, the average difference in KIc for these two methods is less than 5% for the two specimen geometries examined. This suggests that under uniform displacement conditions, KIc is essentially independent of specimen-platen interaction. Because KIc values determined from MR testing are strongly dependent on the modeling procedure, future reports KIc determined from this test should be accompanied by detailed reports of the modeling procedure. Until further testing reveals the most accurate simulation technique, we advocate use of a uniform displacement formulation for KIc determination from MR testing because results from this method are insensitive to most modeling parameters. Numerical results from models conducted under uniform force, no-slip boundary conditions should be viewed as an upper bound to KIc.
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U2 - 10.1016/0148-9062(95)00043-7
DO - 10.1016/0148-9062(95)00043-7
M3 - Article
AN - SCOPUS:0029750090
SN - 0148-9062
VL - 33
SP - 1
EP - 15
JO - International Journal of Rock Mechanics and Mining Sciences and Geomechanics
JF - International Journal of Rock Mechanics and Mining Sciences and Geomechanics
IS - 1
ER -