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.
In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs
Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.