NACA-WR-L-67

Abstract

INTRODUCTION <br>The curved metal skin of a modern airplane in flight is subject to stresses that may cause the skin to buckle, and proper design of airplane structures requires a knowledge of the stress conditions under which buckling will occur. The ability to estimate the buckling point under combined loading conditions is of particular importance. <br>In order to determine the effect that normal pressures or air loads, might have on the critical stress for curved sheet, two preliminary tests were made (references 1 and 2). A pronounced increase in critical stress with increase in normal pressure was found, and the subsequent interest shown by the aircraft industry in this subject indicated the desirability of further Study. <br>No well-established theories for buckling of curved-sheet panels either In torsion or under hydrostatic pressure are available; however, satisfactory theories for buckling of complete cylinders under these loadings have been advanced (references 3 and 4). In order to effect some correlation between theory and experiments therefore, an investigation was made of the influence of internal pressure on the critical stresses of thin cylinders in torsion. Experiments were conducted to determine the critical shear stresses for four cylinder lengths at a number of different internal pressures. The theories and the experimental data were used in conjunction to determine an Interaction formula for the buckling of cylinders of moderate length under the combined action of torsion and internal pressure.