John Perkins has vast experience in power ultrasonics. Here he starts with the basics, covering the design and construction of piezo sandwich transducers and sonotrodes, before giving a detailed description of sonochemistry principles - cavitation, energy-density, monitoring power and amplitude.
(Now updated with a new link to NASA Telerobotics Program Plan, since the old page has been removed.)
An interesting page about research at MIT to develop a high torque-density solid-state actuator for use in the NASA/JPL Mars Micro Lander manipulator arm. It includes a general explanation of the principles of ultrasonic motors, and some cool animations! Note the use of dynamic and time-averaged ESPI (electronic speckle pattern interferometry) to evaluate the vibration modes.
Canon's brief description of their development of ultrasonic motors for use in camera auto-focus lenses. Their explanation of the arrangement of piezoelectric elements is particularly good. There are two sets of elements, offset by a quarter-wavelength, each generating a standing wave. Superimposing the offset standing waves creates a traveling wave that drives the rotor.
Ultrasound in liquids creates cavitation bubbles, which as they collapse can generate immense temperatures and pressures, and brief faint flashes of light - called sonoluminescence. It's a strange phenomenon, not yet fully understood but very reproducible. This article gives a clear account of the equipment required to generate and study sonoluminescence - a surprisingly simple set up suitable for a high-school laboratory.
The subject of metal welding seems to attract high-quality articles from equipment suppliers. While not as comprehensive as Stapla's book, this article from AmTech gives a good introduction to the theory and practice of welding metals, aimed particularly at wire-joining applications.
Using liquid carbon dioxide as a cleaning solvent offers some great environmental advantages. Compared to conventional chlorinated solvents and detergents it is very clean, with no harmful emissions. Separating the liquid from the dissolved contaminants is easy - just reduce the pressure and allow the CO2 to boil off (after which it can be trapped and recycled). However the pressure required to maintain CO2 in liquid form (>60 bar) does present some challenges for ultrasonic tank design...
A new online ultrasonics components store has just opened at www.UltrasonicsWorld.com. Check their amazing prices for replacement ultrasonics components, fully compatible with the major manufacturers' originals at a fraction of the cost.
Miodrag Prokic is an independent consultant, developer of new ultrasonics applications (such as ultrasonic cleaning in liquid CO2) and supplier of special ultrasonic systems for cleaning, sonochemistry and other applications. This is the new site I've just built for him, which includes a variety of technical articles and photos of modern ultrasonic cleaning systems.
Located in Neuchatel, Switzerland, with partner organisations in Russia and India, Progress Ultrasonics Group develops technology-intensive ultrasonic equipment for oil and gas condensate production, processing and transport.
In trials, oil beds in Russia and Romania demonstrated successful results with an overall average efficiency of 200% oil flow compared to normal (double the flow rate).