Non-local stress approach to fracture initiation in laboratory experiments with a tensile stress gradient

The paper discusses the stress distribution and the fracturing in diametrically loaded discs in which a hole has been drilled at some distance from the loaded diameter. A linear elastic analysis of the problem indicates that the maximum tensile stress at the hole is up to four times the tensile stress along the loaded diameter. For the configurations in which the tensile stress gradients at the hole are large, the discs nevertheless fail unstably along the loaded diameter, without a sign of fracturing at the hole. A non-local stress approach to fracture initiation satisfactorily explains this behaviour, A similar analysis of fracture initiation on the same type of limestone in other configurations with a stress gradient yields similar values for the characteristic length and for the non-local tensile strength. (C) 2001 Elsevier Science Ltd. All rights reserved.