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
Effect of Welding on the Slip Damping of Layered and Jointed Structures
A mathematical model has been presented for the mechanism of interfacial slip damping in layered and jointed cantilever beams with continuous and tack welds. The pressure distribution at the interfaces, number of contacting layers, techniques of welding, length and thickness of the beam specimen, and amplitude and frequency of vibration are found to be the dominating factors influencing the damping capacity of such welded structures. The results can be exploited positively in the design of machine tools, aircraft, spacecraft, satellites, automobiles, missile systems, etc. for maximizing their damping capacity.
Considerations on the improvement of the stiffness of bolted joints in machine tools.
The present paper deals with an improvement of the stiffness of bolted joints in machine tools. In the design of bolted joints, the stiffness, the bolt axial force and the distribution of the contact stress are important characteristics, and they have been investigated by many researchers. But the effects of the tightening position of the thread in a base, the height of clamped parts and the configuration of contact surfaces are not taken into consideration sufficiently. Thus, in the present paper, the effects of the tightening position of the thread in the base on the stiffness and the distribution of the contact stress are examined experimentally in the case where a beam is fastened partially to the base with tap bolts. As a result, it is shown that these effects contribute to the improvement of the stiffness of bolted joints.