Vibration control requires high dynamic stiffness in mechanical structures for a reliable performance under extreme conditions. Dynamic stiffness composes the parameters of stiffness (K) and damping (η) that are usually in a trade-off relationship. This thesis study aims to break the trade-off relationship.

After identifying the underlying mechanism of damping in composite materials and joint interfaces, this thesis studies the deposition technique and physical characteristics of nano-structured HDS (high dynamic stiffness) composite thick-layer coatings. The HDS composite were created by enlarging the internal grain boundary surface area through reduced grain size in nano scale (≤ 40 nm). The deposition process utilizes a PECVD (Plasma Enhanced Chemical Vapour Deposition) method combined with the HiPIMS (High Power Impulse Magnetron Sputtering) technology. The HDS composite exhibited significantly higher surface hardness and higher elastic modulus compared to Poly(methyl methacrylate) (PMMA), yet similar damping property. The HDS composites successfully realized vibration control of cutting tools while applied in their clamping interfaces.

Compression preload at essential joint interfaces was found to play a major role in stability of cutting processes and a method was provided for characterizing joint interface properties directly on assembled structures. The detailed analysis of a build-up structure showed that the vibrational mode energy is shifted by varying the joint interface’s compression preload. In a build-up structure, the location shift of vibration mode’s strain energy affects the dynamic responses together with the stiffness and damping properties of joint interfaces.

The thesis demonstrates that it is possible to achieve high stiffness and high damping simultaneously in materials and structures. Analysis of the vibrational strain energy distribution was found essential for the success of vibration control.

Vibration problems are still the major constraint in modern machining processes that seek higher material removal rate, shorter process time, longer tool life and better product quality. Depending on the process, the weaker structure element can be the tool/tool holder, workpiece/fixture or both. When the tool/tool holder is the main source of vibration, the stability limit is determined in most cases by the ratio of length-to-diameter. Regenerative chatter is the most significant dynamic phenomenon generated through the interaction between machine tool and machining process. As a rule of thumb, the ratio between the tool’s overhang length and the tool’s diameter shouldn’t exceed 4 to maintain a stable machining process while using a conventional machining tool. While a longer tool overhang is needed for specific machining operations, vibration damping solutions are required to ensure a stable machining process. Vibration damping solutions include both active and passive damping solutions. In the passive damping solutions, damping medium such as viscoelastic material is used to transform the vibration strain energy into heat and thereby reduce vibration amplitude. For a typical cantilever tool, the highest oscillation displacement is near the anti-node regions of a vibration mode and the highest oscillation strain energy is concentrated at the node of a vibration mode. Viscoelastic materials have been successfully applied in these regions to exhibit their damping property. The node region of the 1st bending mode is at the joint interfaces where the cantilever tools are clamped. In this thesis, the general method that can be used to measure and characterize the joint interface stiffness and damping properties is developed and improved, joint interfaces’ importance at optimizing the dynamic stiffness of the joint interface is studied, and a novel advancing material that is designed to possess both high young’s modulus and high damping property is introduced. In the joint interface characterization model, a method that can measure the joint interface’s stiffness and damping over the full frequency range with only the assembled structure is presented. With the influence of a joint interface’s normal pressure on its stiffness and damping, an optimized joint interface normal pressure is selected for delivering a stable machining process against chatter with a boring bar setting at 6.5 times overhang length to diameter ratio in an internal turning process. The novel advancing material utilizes the carbon nano particles mixed in a metal matrix, and it can deliver both high damping property and high elastic stiffness to the mechanical structure.