Advanced Machine Technology
　Advanced Mechanical Technologies are essential not just for development of the field of Mechanical Engineering itself, but also for progress in almost every other field of industrial engineering and science.
　
　Research in the Department of Advanced Machinery, carried out in close cooperation with other departments in the laboratory, aims to develop these technologies and includes work in the following areas:
　
1) Investigations into the basic properties of mechanical components and machines, with a view to creating completely new designs and mechanisms. This work includes the development of mechanisms for micromachines, and the design of high precision mechanical components.
2) Development of new processing methods and technologies for measurement and evaluation of processing results. Here, we are working on ion-beam and hybrid processing techniques, and methods for nondestructive testing and process evaluation.
3) General improvements in mechanical devices and systems. This includes work towards improving safety and reliability (for example; predictive maintenance), and sound and vibration control.
　
Some specific projects are described in more detail below.
　
Laser guided discharge
　A new method of guiding low-pressure electrical discharges using a laser beam has been developed. Thermoelectrons are emitted from a metal plasma, generated by the laser beam, and the discharge path is controlled by the flight path of the thermoelectrons. The Figure (Fig.1) shows a spectacular demonstration of the method, where a discharge between facing anode and cathode is guided from the anode, through a hole in the cathode, and round to the back of the cathode. A feasibility study has been made on a new technique for electric-dis-charge machining using this method.
　
Fig.1 Example of guided discharge through a electrode hole.
　
Molecular dynamics of ice crystal growth
　Slurry ice is often used in air-conditioning systems. Addition of Antifreeze Protein (AFP) helps create needle crystals which are resistant to recrystallisation and therefore help storage and transportation. The influence of AFP on ice crystal surfaces has been observed using a Scanning Tunnelling Microscope (STM), and the mechanism of crystal growth when AFPs are adsorbed onto the crystal surface has been investigated by a molecular dynamics simulation. It was found that crystal growth does not easily occur close to the AFP, but rather at sites where water molecules can easily create at least two hydrogen bonds onto the crystal lattice. The result is a curved ice surface, which corresponds well with STM observations. A Silane coupling agent has been experimentally approved as a substitute additive for making ice slurry, providing molecules of artificially high molecular weight.
　
Fig.2 Convex Structure of Ice Crystal based on Molecular Dynamics Simulation.
　
Elastohydrodynamic Lubrication characteristics of Electrorheological fluids
　Electrorheological fluids (ER fluids) are new materials which undergo fast reversible changes in viscosity on application of an external electric field (electro-rheology). They have potential application in industrial tribology problems - particularly those where control of tribological characteristics is desirable.
　A ball-on-disk tribo-testing machine was made to observe the thickness and shape of an Elastohydrodynamic Lubrication (EHL) film, and to investigate the possibility of control of triboelement performance using ER fluids. A liquid crystal was used as the lubricant and the Figure shows results obtained during the experiment which confirm that an applied electric field causes changes in the tribological conditions. These results indicate that there is potential for control of triboperformance using ER fluids.
　
Fig.3 Interference Fringe of EHL Film: (a) Without Voltage (b) With 1000V.
　
Smart structures for active noise control
　Work is in progress to develop novel active noise control systems for sound fields carried by three-dimensional structures. This project began with the introduction of a new parameter: the "acoustic power mode", initially intended for application to flat planar strctures, and obtained by grouping structural vibration modes in order of acoustic radiation efficiency. The parameter allows the noisiest modes to be targeted for suppression, and will theoretically make it possible to guarantee that overall suppression in the spectrum of interest will be optimum. A new type of distributed parameter sensor using a PVDF film with an optimised shape has been developed, which gives an output voltage proportional to the acoustic power mode amplitude, together with a compact actuator incorporating PZT ceramic stacks and steel columns which is capable of applying bending moments. Because the structure condition may change with time, an adaptive controller which minimises sensor output using DSP techniques with a filterde-x LMS algorithm has also been devised.
　
　This project is one stage in the development of smart structures incorporating distributed parameter sensors, bending moment actuators, and adaptive control algorithms. Although the development of smart structures initially began with work on large space structures, we anticipate these ideas will find new application in achieving a quiet everyday environments.
　
Fig.4 Smart sensors and bending moment-type actuators for active noise control.

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produced by General Research Counselor