A Simple Determination of Von Karman Critical Velocities
The ductility of non-brittle engineering metals and alloys has been shown by Hoppmann to be a function of deformation velocity. The ductility increases to some maximum at the Karman Critical Velocity and thereafter diminishes. This implies that the volume of the plastic zone at the tip of the crack will vary as a function of deformation velocity, and that at the Karman velocity the character of the material drastically changes toward a brittle material. An analysis of this phenomena is presented. A tensile test is generally required to determine the critical value. This technique is simplified by using the non-destructive characterization of the scleroscope hardness which is shown to rank the critical velocities in a reproducible manner. The reasons for this relationship are analyzed by using the Pond — Glass method of critical velocity determination.
KeywordsWave Speed Critical Velocity OFHC Copper Cold Extrude Dynamic Elastic Limit
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