2012 Volume 53 Issue 4 Pages 690-695
A new sensing method called “smart stress-memory patch” has been proposed for fatigue damage evaluation of structures. This patch estimates the number of cycles and stress amplitude using its crack length. In this study, fatigue crack growth behavior in thin pure copper sheet was investigated under strain-controlled testing to evaluate the sensor characteristics when the patch is attached to structure. Electrodeposited (ED) copper of 99.96% purity with an average grain size of 2 µm provided a stable crack propagation and easy observation of crack length. The relationship between stress intensity factor range and crack growth rate was fitted on one curve regardless of strain amplitude. The scattering in fatigue crack growth was evaluated by a stochastic model, and it demonstrated that the error of fatigue cycles estimated by the patch is small enough. Furthermore, stress transfer between the patch and structure was calculated on the simple assumption that the patch is perfectly bonded on the structure, and it was shown that the patch attached to structure can estimate the number of cycles and stress amplitude on the structures.