Vibration Attenuation in Layered and Welded Beams with Unequal Thickness
In built-up structures, one of the effective ways o f dissipating unwanted vibration is to exploit the oc currence of slip at the interfaces of structural laminates. The present work focuses on the dynamic analysis of welded structures. A mathem atical formulation has been developed for the mechanism of slip damping in layered and welded mild steel beams with unequal thickness subjected to both periodic and non-periodic forces. It i observed that a number of vital parameters such as; thickness rat io, pressure distribution characteristics, relative slip and kin ematic co-efficient of friction at the interfaces, nature of exciting forc es, length and thickness of the beam specimen govern the damping c hara teristics of these structures. Experimental verification has bee n carried out to validate the analysis and study the effect of these parameters. The developed damping model for the structure is found to be in fairly good agreement with the measured data. Finally, the results of the analysis are discussed and rationalized. Keywords—Slip damping, tack welded joint, thickness ratio, i nplane bending stress
Theoretical Analysis for a Damping Ratio of a Jointed Cantibeam
The loss energy of a jointed cantibeam may be derived from a microscopic slip and a normal pressure on the interfaces. It is however very difficult to calculate theoretically the energy dissipation between the joint surfaces, because a characteristic of the micro-slip on the interfaces has not been fully clarified yet.In this study the mechanism of the energy dissipation and also the ways of theoretically calculating the damping ratio of the jointed cantibeam have been investigated by considering experimental results of the characteristic of static micro-slip between the jointed surfaces.From the results it is clarified that the damping ratio of the jointed cantibeam can be well calculated by using the equations proposed in this paper, and how the characteristic of micro-slip influences the behaviours of the damping ratio.
Experimental study of non-linear effects in a typical shear lap joint configuration
Although mechanical joints are integral parts of most practical structures, their modelling and their effects on structural dynamics are not yet fully understood. This represents a serious impediment to accurate modelling of the dynamics and to the development of reduced-order, finite element models capable of describing the effects of mechanical joints on the dynamics. In this work we provide an experimental study to quantify the non-linear effects of a typical shear lap joint on the dynamics of two structures: a beam with a bolted joint in its center; and a frame with a bolted joint in one of its members. Both structures are subjected to a variety of dynamical tests to determine the non-linear effects of the joints. The tests reveal several important influences on the effective stiffness and damping of the lap joints. The possibility of using Iwan models to represent the experimentally observed joint effects is discussed. r 2003 Elsevier Ltd. All rights reserved.