Yield Pressure Measurements and Analysis for Autofrettaged Cannons
ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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Yield pressure for a small permanent strain was measured in quasi-static laboratory tests of autofrettaged ASTM A723 steel cannon pressure vessels. Yield pressure was found to be a consistent ratio of the yield strength measured in close proximity to the area of observed yielding. Comparable yield pressure measurements for cannons firing with typical 5-ms pressure pulse duration gave 14 higher yield pressures, attributed to strainrate effects on plastic deformation. Calculated von Mises yield pressure for the laboratory test conditions, including the Bauschinger-modified inner diameter residual stress and open- end vessel conditions, agreed with measured yield pressure within 3 to 5 . Calculated yield pressure was found to be insensitive to the value of axial residual stress, since it is typically the intermediate value in the von Mises yield criterion. A description of yield pressure normalized by yield strength was given for autofrettaged A723 open-end pressure vessels over a range of wall ratio and degree of autofrettage, including effects of Bauschinger-modified residual stress. This method for calculating yield pressure is proposed as a design procedure for cannons and other pressure vessels.
- Properties of Metals and Alloys