Fatigue and fracture of cylindrical shells containing a circumferential crack

Abstract

The cylindrical shells containing a circumferential crack subjected to axial tensaon are considered. For a uniform stress away from the crack the membrane and bending components of the stress intensity factor are obtained within the confines of an eight order linear shallow shell theory. By subjecting 6061-T4 aluminum cylinders to axial fatigue, crack propagation data are collected. Using two different empirical models the shell data are analyzed along with the plate data and it is shown that the fatigue crack propagation behavior of shells can be predicted from that of flat plates with the same material and thickness. The shells are then subjected to static rupture tests. Due to the difference in the nature of plastic deformations in shells and plates, a direct comparison of the rupture results in the two cases, smailar to that of fatigue results, does not seem to be possible.

Crack problems in cylindrical and spherical shells

“…In add ition to linear elasticity, in the existing solutions [e.j., [1][2][3][4][5][6][7][8][9][10][11][12][13] it is as sumed that the shell is "infinitely" large, the curvatures are constant (i.e., the shell is a circular cylinder or a sphere), the crack is along a principal plane of curvature, and the material is isotropic and homogeneous. If these assumptions are disregarded, mathematically the problem does not seem to be tractable.…”

Plasticity and the crack opening displacement in shells

“…Comparison of the results given in [9] and [13] indicates that the effect of curvature on the stress intensity factor in cylindrical shells with a circumferential crack is small compared to that in cylindrical shells with an axial crack and spherical shells with a meridional crack.…”

“…Figure 14 shows the calculated crack opening displacement ^, obtained from the same data. Comparing the trend of the data as presented in Figure 14 with that of Figures 12 and 13 The solution of the problems for symmetrically loaded cylindrical and spherical shells containing a crack can be reduced to that of a system of singular integ^*al equations of the following form [9][10][11][12][13]: '…”

“…In the calculation of the plastic zone size, the striess intensity ratios A m (a p ) and A b (X p ) shown in equation (z) were obtained by letting N Y S -N o and M y C 0 in (A2) and by following the p r ocedure outlined in [13] and [9 ]. For The integration "quantity" arising from (A4) is a constant and is determined from v(+ 1, 0) = 0.…”

Nonlinear bulging factors for longitudinal and circumferential cracks in cylindrical shells subjected to combined loads

“…Many studies have been conducted to characterize bulging cracks, and both analytical [1][2][3][4][5][6][7][8] and empirical formulas [9][10][11][12][13][14] for the bulging factor have been developed. Analytical expressions for the bulging factor in shells were first developed by Folias using a formulation based on linear shallow shell theory.…”