On passive damping in machine tool hybrid structural parts

Hybrid materials combining steel or cast iron with fibre or particle composites have a good potential for lightweight machine tool structural design with high damping ratio. These materials are analyzed in the paper with a focus on damping improvement of structural components and machine tool assemblies. Fibre composites and particle composites were selected as the lightweight elements for the hybrid machine tool structure. The fibre composites were designed as low-density, high stiffness-oriented reinforcements, which were bonded to build metal structural parts conventionally. The particle composites were applied as filler materials into the hollows of the metal structural parts. Both composite structures presented a possibility to reduce the mass of the component due to the reduction of wall thickness (fibre composite) or removal of heavy ribbing (particle composites) and to influence the parts’ static and dynamic stiffness. Hybrid structures, combining the light-weight elements with cast iron or welded steel, were designed and tested in case studies using experimental modal analysis methods. Experimental modal analysis was used as the main approach for identification of the damping ratio on a basic coupon level, followed by testing of structural parts in a stand-alone configuration and ending with a structural part assemblies testing. Both particle composites and fibre composites were successful in improving the damping ratio of single structural parts. However, the damping ratio of the hybrid component mounted into an assembly configuration shows only less significant improvement. The presented results demonstrate importance of the damping caused in the connecting interfaces.