Rapid Method for Determining Stress Concentrations for Autofrettaged TubesContaining Multiple Axial Perforations Within the Wall

摘要

A simple method is developed for the determination of the stress concentrationfactor (SCP) arising from multiple, periodic, axial, elliptical holes within the wall of a gun tube. The model is based upon a simple superposition procedure with capping of any stresses that exceed yield magnitude, and is able to incorporate autofrettage residual stresses. By plotting the ratio of stress ranges due to firing at two potential failure locations, taking account of pressure entering bore cracks, straightforward design plots of stress range ratio permit the selection of optimum radial hole location. This location is found to vary with the eccentricity of the hole's elliptical shape. The choice of ideal ellipse eccentricity depends upon Rn, percentage overstrain, and ratio of firing pressure/yield strength. A near optimum value for the case Rn/R1 = 1/4 is provided by the circular hole. A straightforward design procedure is proposed which requires only standard compendia in order to optimize hole shape.