Vibration tests on spherical shell caps

Fabrication and testing of vibrations in small-scale, electroplated nickel, spherical shell caps which are clamped on their open boundaries, are briefly described. Comparisons with theoretical predictions show that with low levels of excitation energy, for which displacements in the resonant response are considerably less than the shell thickness, classical thin shell theory provides a close description of observed resonance in both axisymmetric and non-axisymmetric modes. For larger excitation energies, for which resonant displacements are of the same order as the shell thickness, tests are reported to show the possible need to include in analysis the effects of geometric non-linear, modal interactions.