M. Kulisiewicz

Identification of Nonlinear Damping Using Energy Balance Method with Random Pulse Excitation

This paper presents the application of the energy balance equation to the identification of nonlinear damping in complex multi-degree-of-freedom systems subjected to excitations in the form of a random series of impulses. It is proven that the proposed procedure makes it possible to determine damping characteristics irrespective of the form of purely elastic interactions and the occurrence of the so-called mixed term. The procedure was verified experimentally, using a system with two degrees of freedom. The effect of the intensity with which impulses appear (pulse rate) on the quality of the obtained results is examined. The presented method can be applied to investigate the damping of vibrations of selected elastodamping elements in real vibrating systems.

The Method of Determining Certain Parameters of Energy Absorption in Materials Under Complex Dynamic Excitations

The paper presents the method to identify the dissipative properties of the materials with a clear hysteresis loop under the quasi-static loads. Because of the fact that for low values of velocity, the resisting forces related to the speed are minimal, it is not possible to determine these forces as the functions of velocity in the quasi-static deformations. It results in the need to develop such methods for identification, which use the responses of the tested system to the cyclic loading with a high frequency. This paper presents such a method. Its application may be useful in the area of constructing the effective and modern ballistic shields.

Identification of nonlinear dynamical systems under random impulse excitations

A solution relating to the identification of dynamical systems subjected to excitations in the form of a series of random impulses is discussed. The existing relevant methods are applicable to one-degree-of-freedom systems subjected to determinate random stationary excitations. In the present article an important contribution to the identification of non-linear restitutive interaction is made through the use of suitably modified so-called power balance equation. The proposed solution has been verified experimentally by applying it to a non-linear system with two degrees of freedom. This method can be used to investigate the elasto-damping properties of structural materials (or elastic machine elements) and discover changes of these properties under sustained dynamic loads.