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.

Dynamic characteristics of machining systems are analysed for improved understanding of both structural and process properties. The thesis stresses the use of testing methods under operational like conditions as these are more representative of closed loop systems, such as machining systems, as compared to conventional testing methods.

The test instrument proposed is a contactless excitation and response system, developed for testing of machine tool spindles under load and with rotating spindle. The instrument uses electromagnetic excitation and displacement sensors for analysis of rotating milling tools subject to load. A graphical tool for displaying and analysing rotor displacement was developed in conjunction with this.

A modelling procedure for both off-line and on-line estimation of dynamic properties of mechanical structure and process information is presented. The proposed auto-regressive moving average models enable calculation of operational dynamic parameters and they can be estimated in a recursive manner, thus enabling real-time monitoring. The discrimination between stable and unstable processes, both in turning and milling, was performed by analysing the damping obtained from the operational dynamic parameters.