Evaluation of Equivalent Initial Flaws for Damage Tolerance Analysis
Final rept. 30 Sep 1977-30 Sep 1978
BATTELLE COLUMBUS DIV OH
Pagination or Media Count:
An experimental investigation was conducted to establish whether the size of the so-called equivalent initial flaw can be rationalized on the basis of the size of intermetallic particles or clusters of such in the material. Fatigue experiments were conducted on flat specimens with a central hole cut from 7075-T73 Al alloy plate. The size and number of intermetallic particles were measured in the regions where crack initiation was anticipated. Assuming the existence of an equivalent initial flaw the fatigue life of the specimens was calculated by means of crack growth analysis. In this manner the size of the equivalent initial flaw was determined as the flaw that needs to be assumed present from the beginning to give a crack propagation life equal to the observed life of the specimen. The sizes of equivalent initial flaws so calculated did not show a correlation with number or size of intermetallic particles.
- Metallurgy and Metallography