Description Spring supports for mechanical systems are usually based on springs with linear or piecewise linear, or nonlinear springs, where the stiffness is in all cases positive. However it is also possible to design a Negative Stiffness Vibration Isolation Device (the NSVID) which has the potential to reduce significantly the fundamental frequency of the protected structure in order to minimise the force or displacement transmission, even for low- or ultra-low-frequency excitation cases, where traditional vibration isolators can be ineffective. The effectiveness of the NSVID is in its unique nonlinear characteristics, which enables it to reduce the vibration transmissibility from the source of vibration, and at the same time to maintain system stability by providing a sufficient load-carrying capacity. Key Objectives

1. To investigate the theoretical performance of an SDOF oscillator with a negative linear stiffness and then to extend that to a nonlinear model in which the stiffness is switcheable to give combinations of positive and negative linear stiffness and positive and negative nonlinear (cubic) stiffness.
2. Then to interpret the theoretical responses of the oscillator for different combinations and from that to devise a system that has the potential for an optimal vibration isolation characteristic.
3. Finally to synthesise a practical design for a system which could be built and then tested for vibration isolation across as wide a design parameter space as possible.