NOTCH BEHAVIOR IN METALS.
Final rept. 1 Jul 65-31 May 66,
BATTELLE MEMORIAL INST COLUMBUS OHIO
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Measurements of the shape and size of the plastic zone, delineating the transverse strain field and the corresponding crack-tip displacements as a function of stress level, under on-load conditions are described. The measurements were done on notched sheet coupons of 4330-M steel and 2219-T87 and 7075-T6 aluminum, with the aid of a replicating technique. The extent of the plastic zone and internal cracking is shown to be connected. In this way, the progress of slow crack growth in the interior of the sheets is reconstructed. A correlation of the experimental values of crack-tip displacements with the prediction of the DM model Dugdale-Muskhelishvili, in the presence of a slowly growing internal crack, is noted and discussed. The analysis of the DM model is extended to the case of a crack in a plate of finite width and is solved numerically, using a point-matching technique. The calculations show that in the case of a plate containing a crack one-sixth of the plate width, loaded to one-half of the yield stress, the plastic zone size for finite-plate analysis was 3 percent higher over the corresponding size for infinite DM plate analysis. When the crack length was one-half of the plate width and the load was one-third of the yield stress, the finite-plate analysis gave a plastic zone size that was approximately twice the value given by infinite-plate analysis. Author
- Metallurgy and Metallography