Experimental creep buckling of aluminum cylinders in axial compression

Creep-buckling tests were conducted on aluminum alloy 2024-0 circular cylinders in axial compression at 500° F having nominalR/t values of 90 and 50. Creep-buckling times for a variety of applied creep-stress values were compared with theoretical predictions of Gerard's unified theory of creep buckling of columns, plates and shells. In this theory, creep-buckling solutions are analogous to plastic-buckling solutions, provided that the material parameters used in the theoretical relation are developed from constant-strain-rate stress-strain data derived by a graphical process from compressive-creep data. The theoretical data were evaluated using appropriate classical plastic-buckling theory and previously obtained creep data on the 2024-0 aluminum material at 500° F. End shortening of the cylinders was autographically recorded during the tests and creep-buckling times were obtained from an analysis of the end-shortening record. A comparison of theory and test data indicated that the theory was somewhat conservative in predicting creep-buckling times. The discrepancy may have been due, in part, to the uncertainty in determining the precise time at which the experimental cylinders buckled. The cylinders withR/t～90 buckled in the axisymmetric mode for the lower creep stresses while, forR/t～50, all buckling occurred in the axisymmetric mode.