The influence of imperfect contact conditions between layers of a hollow sandwich sphere on its natural frequencies is studied. It is assumed that the materials of face layers are the same, but different from the core layer material. Each layer is made of a homogeneous isotropic material and has a constant thickness. Investigations are performed using a piecewise homogeneous body model with the use of exact three-dimensional equations and relations of elastodynamics. The solution of the corresponding equations of motion of the hollow sandwich sphere is presented through the Helmholtz potentials in spherical coordinates. Numerical results for the influence of imperfect contact conditions between layers on the natural frequencies of the sphere are presented and discussed. It is established that an imperfect contact between sphere layers can decrease its natural frequencies significantly.

中文翻译：

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空心夹心球层间不完全接触条件对其自然频率的影响

研究了空心夹层球层之间的不完美接触条件对其固有频率的影响。假设面层材料相同，但与芯层材料不同。每层均由均质各向同性材料制成并具有恒定厚度。使用分段均质体模型进行研究，并使用精确的三维方程和弹性动力学关系。通过球坐标中的亥姆霍兹势，给出了空心夹层球相应运动方程的解。提出并讨论了层间不完美接触条件对球体固有频率影响的数值结果。