SIMPLE AND SENSITIVE METHOD OF MONITORING CRACK AND LOAD IN COMPACT FRACTURE MECHANICS SPECIMENS USING STRAIN GAGES.

The calibrated strain on the back face (the face opposite that from which the slot is machined) of compact tension (CT) and T-type wedge-opening-loading (WOL) specimens provides a method for measuring crack length when the load is known or for measuring load when the crack length is known. The method is simple, reliable, sensitive, and inexpensive. A good correlation was achieved between strain measurements on a CT specimen and values computed from a two-dimensional finite element analysis. The method has good potential for developing into a more sensitive crack length measurement technique than has previously been achieved.