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
A Study on Damping Capacity of a Jointed Cantilever Beam : 2nd Report, Comparison between Theoretical and Experimental Values
The large-sized machine tools are often made of welded steel and to increase their damping capacity a jointed beam or a damping joint is often used. The behaviour of the damping capacity relating to the first, second and third modes of vibration of the jointed beam had experimentally been studied in the previous report, however, the method for the theoretical calculation of damping capacity of it has not been established yet. In this paper, the relationships between the slip ratio and the damping capacity have been theoretically investigated considering the first and second modes of vibration of the jointed cantilever beams used in the previous study. Through comparison between the experimental values obtained from the previous study and the theoretical values, it has been confirmed that the damping capacity of a jointed cantilever beam can be well estimated by using a method proposed here.
Contact stresses in a moderately thin strip (with particular reference to fretting experiments)
This paper uses Fourier transform methods to calculate the stress field in a strip of finite thickness under normal contact loading. The geometry is relevant to a number of common fretting fatigue experiments. It is demonstrated that the stress component induced parallel to the free surface differs significantly from that predicted for a half plane. Further, it is shown that the use of half-plane expressions will significantly underestimate the severity of the stress state induced in fretting experiments. This has important implications for the development of initiation and propagation models in fretting fatigue.