No abstract

In the radial motion of an elastic cylindrical shell following impulsive pressure all round, imperfections in the uniformity can cause development of flexure through interaction of (fluctuating) circumferential force with flexural curvature. Flexural modes of rather high order (several nodes in the circumference) can be strongly excited, especially those having a frequency one half that of the breathing mode (nonlinear autoparametric excitation). Almost all the original energy can be transferred, over a number of cycles, from the breathing mode to one or two high flexural modes.

The linear thermoelastic problem is solved for a uniform heat flow disturbed by a hole of ovaloid form, which includes the ellipse and circle as special cases. Results for stress and displacement are found in closed form, by reducing the problem to one of boundary loading solvable by a method of Muskhelishvili.

Solutions of the equation of elasticity are applied to investigate the disturbing effect of small spherical and cylindrical inclusions on an otherwise uniform stress distribution. Numerical results are found for gaseous inclusions (flaws), perfectly rigid inclusions, and for systems roughly representing slag globules in steel and reinforcing rods in concrete.

A theory is postulated to explain the dynamic plastic buckling of cylindrical shells in sustained axial compressive flow. Tube impact experiments are described in which uniform axisymmetric waves were produced. Predicted and experimental wavelengths are in satisfactory agreement. According to the theory presented, wavelengths do not depend strongly on strain-hardening modulus and, based on results for two aluminum alloys, neither do experimental wavelengths. This result is shown to apply also to slow plastic buckling.