Effect Of Material Damping Research Articles

Torsional Vibration of Viscoelastic Foundations

Simple approximate solutions are presented for the steady-state response of rigid circular foundations which are supported at the surface of a linear viscoelastic half space and are excited by a harmonically varying torque. The half space is idealized either as a standard Voigt solid or as a constant hysteretic solid. Comprehensive data are presented and their significance analyzed. It is shown that the principal effects of material damping are to increase the damping capacity of the system and to reduce its natural frequency. The increase in damping and the associated reduction in response may be of considerable practical consequence. Some attention is also given to the response of foundations subjected to transient excitations, and a procedure is recommended for interrelating the responses of systems for the two models of viscoelastic action investigated. It is shown that, provided the parameters of the two viscoelastic models are selected as recommended, the maximum transient responses of the two models are for most practical purposes equal.

Effect of time‐dependent material properties on dynamic response

AbstractBy representing the time‐dependent material properties by mechanical models, i.e. the generalized Maxwell and/or Voigt (or Kelvin) models, it is possible to formulate a consistent procedure to analyse the effect of material damping on dynamic response. As a continuation of the previous work which concerned the creep and relaxation of viscoelastic materials, the present paper applies this representation to the harmonic response analysis. The harmonic solution can be obtained by decomposing the relevant forces and displacements into real and imaginary parts and it is shown that the modal analysis by an appropriate eigensolution procedure is useful for obtaining the dependence of vibration amplitude on frequencies of sinusoidal external excitations.

Vibration of viscoelastic foundations

AbstractSimple approximate solutions are presented for the steady‐state response of a massless, rigid disk, which is supported at the surface of a linear viscoelastic halfspace and is excited by a harmonically varying horizontal or vertical force, or by a harmonically varying moment about an axis in the plane of the disk. The halfspace is idealized either as a standard Voigt solid or as a constant hysteretic solid. The solution for the massless disk is then applied to the analysis of foundations with mass, and for each mode of excitation, comprehensive numerical data are presented to illustrate the effects of viscoelastic action on the response of both the massless disk and of foundations with massIt is shown that the principal effects of material damping are to increase the damping capacity of the foundation and to reduce its ‘natural’ frequency. In the mathematically equivalent representation of the elastically supported massless disk as a spring‐dashpot combination without mass, it is shown that the effective stiffness of the spring may become negative over significant ranges of the exciting frequency, and that it is preferable to model the disk‐halfspace system as an oscillator with mass, taking its spring constant equal to the static stiffness of the original system.