Numerical Prediction of Residual Stress and Deformation of Cannon Tubes
Final rept. Dec 2000-Jan 2002
EUROPEAN RESEARCH OFFICE LONDON (UNITED KINGDOM)
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An experimental program involving uniaxial testing of candidate gun steels was undertaken at Benet Laboratory. One striking feature is a very significant reduction in elastic modulus during load reversal. These data were then fitted numerically using a new variant of the non-linear kinematic hardening model. Numerical fits to the uniaxial behavior were incorporated into a non-linear numerical stress analysis program. Residual stress profiles for each of the candidate gun steels were then calculated because of the combined influence of strain hardening, unloading modulus and Bauschinger effect the optimum residual stress field is not provided by the strongest material. Residual bore hoop stress values were fitted using a numerical procedure. These were employed in calculating predicted pressures for the re-yielding of tubes subjected to high pressure after autofrettage. Additional work, beyond contract requirements, was undertaken as follows 1 The behavior of a current gun steel was used to determine, with Bauschinger effect, residual stresses in a swage-autofrettaged gun tube. 2 An initial study of the mechanics of a specific wear process was undertaken. 3 A simple procedure was devised to test the general assumption that the Bauschinger effect is isotropic. Using two uniaxial tests, undertaken by Mr. E Troiano of Benet Laboratory, it has been demonstrated that the Bauschinger effect exhibits significant an isotropy.