Hello,
With respect to classic power-law crack growth in brittle materials, the
critical limit is given by

K = Y
crack length (which is taken as a square root).

My question is : What is the true independent variable (i.e., stress or strain) that determines when the material fractures? This equation suggests that it is the stress, since the strain is not given, but that might be more for convenience since we tend to measure stress, not strain.

Assuming the stress-strain relationship were perfectly linear it wouldn't matter, but since materials fracture in a regime in which the stress-strain is not linear, it changes the interpretation of fracture data.

Thanks, Jay

K = Y

***S***a^1/2, where Y is a constant, S is the applied stress, and a is theMy question is : What is the true independent variable (i.e., stress or strain) that determines when the material fractures? This equation suggests that it is the stress, since the strain is not given, but that might be more for convenience since we tend to measure stress, not strain.

Assuming the stress-strain relationship were perfectly linear it wouldn't matter, but since materials fracture in a regime in which the stress-strain is not linear, it changes the interpretation of fracture data.

Thanks, Jay