very old ultrasonic cleaning bath- current needed!

Might be nickel rods and magnetostriction indeed.

Magnetostriction can peel nickel plate

drill here

http://www.google.ca/#hl=en&source=hp&q=nickel+%2Bmagnetostriction&btnG=Google+Search&meta=&aq=f&oq=nickel+%2Bmagnetostriction&fp=7cb5519368a1228f

Dear contributors,

your answers helped very much, but still some questions remaining.

In: Introduction to Magnetic Materials; B. D. Cullity, C. D. Graham, (found in the link) there are two interesting plots:

A.: Magnetostriction in Nickel is parabolic if excited (plotted) by flux-density.

A1.: Symmetric with saturation if excited by field-strength (amperes-turns).

B.: Magnetostriction is enhanced by 50% at tensile stress of 120 MPa and totally suppressed at a compressive stress of -120 MPa.

So if excited with a sinusoidally changing current there will be a changing length of twice the exciting frequency plus higher order (even only) frequency-components.

By the resulting stress level this may be changed to unsymmetric behaviour if the stress is above 10 ? MPa.

This is highly or total nonlinear behaviour so no linear oscillator-circuitry can be used.

Pre-straining in tension or equivalent magnetisation will establish a working point, near this working point a linear oscillator is existing that may be used with feedback to establish a stable oscillation that is self regulating, changing its frequency if coupling or other effects causes the natural frequency to drift.

I assume -but not sure- that the objects to be cleaned in the bath will change the part of the water that is coupled to the oscillations and are thus part of the oscillator and its characteristics.

So one suggestion from you: use an external frequency generator and an audio-amplifier will certainly work. I will try if I can get sufficient excitation.

I would like better a self tuning oscillator, but mechanical prestress is not suitable and if a magnetic prestress can be introduced is not clear as I do not know the direction of the magnetic field lines inside the 4 bars of the "transformer".

If you have additional comments I would be happy.

Thank you, any results will be posted here.

RHABE

Your curves are for FeCo alloy [Permalloy]. Although it is also magnetostrictive, its properties are very different from Nickel. I'm going to have to do some thinking to try to answer the rest of your questions, but suggest you use data for nickel.

If you excite the transducer symmetricaly around a zero magnetic field, you will find many complications. This is the primary reason for the DC bias current. When properly biased, most of the problems you mention, disappear.