NACA-ARR-3J02

Abstract

Cut-outs In wings or fuselages produce stress concentrations that present a serious problem to the stress analyst. As a partial solution of the general problem, this paper presents formulas for calculating the stress distribution around rectangular cut-outs in axially loaded panels. The formulas are derived by means of the substitute-stringer method of shear-lag analysis. <br>In a previous paper published under the same title as the present one, the analysis had been based on a substitute structure containing only two stringers. The present solution is based on a substitute structure containing three stringers and is more complete as well as more accurate than the previous one. It was found that the results could be used to improve the accuracy of the previous solution without appreciably reducing the speed of calculation. Details are given of the three-stringer solution as well as of the modified two-stringer solution. <br>In order to check the theory against experimental results, stringer stresses and shear stresses were measured around a systematic series of cut-outs. In addition, the stringer stresses measured in the previous investigation were reanalyzed by the new formulas. The three-stringer method was found to give very good accuracy in predicting the stringer stresses. The shear stresses cannot be predicted with a comparable degree of accuracy; the discrepancies are believed to be caused by local deformations taking place around the most highly loaded rivets and relieving the maximum shear stresses.