Further Development of a Computational Shear Band Model.
Final rept. May 77-Sep 78,
SRI INTERNATIONAL MENLO PARK CA
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Experimental and analytical work was performed to improve the computational model for adiabatic shear band nucleation and growth SNAG. A series of contained fragmenting cylinder experiments were performed with 4340 steel treated to hardness of R sub c 40, R sub c 52, and R sub c 21. The resulting damage ranged from homogeneous plastic deformation to extensive shear banding and resulting fragmentation. The results showed strong positive correlation between shear banding damage and material hardness for identical loading conditions. A simplified method of damage quantification was used to obtain shear band density, size and orientation distributions for all of the R sub c 40 experiments. Preliminary computer simulations were performed to determine plastic shear strain rate histories in the direction of the predominant shear banding orientation mode, and the computations were compared with experimental data to yield first estimates for the values of the nucleation and growth parameters. A shear band nucleation criterion based on measurable material properties was proposed and tested against the experimental data the criterion was seen to be promising although not yet conclusive. Several experimental techniques for characterizing the shear banding resistance of materials were evaluated and compared. The contained fragmenting cylinder experiment was concluded to be the best single technique, although the dynamic punch test has special value for armor penetration applications.
- Metallurgy and Metallography