Improved method for demagnetisation of naval vessels and Preisach analysis T. M. Baynes, G. J. Russell and A. Bailey University of New South Wales, Sydney Australia Maritime Operations Division D.S.T.O. Australia
Demagnetisation (from Chikazumi 1967) Anhysteretic magnetisation
Z Coil X Coil
Problems with Flash D • Redundancy • Time consuming • Predicting deperm outcome
DMR (H1 , H2 ) = f(-H1 ).f(H2 ) MR initial(H) =1/2 f(H) 2
Conclusions: • laboratory simulation allows experiments into alternative deperm procedures. • Anhysteretic deperm produces more reliable vertical magnetisation AND allows for theoretical modelling. Flash D can not be modelled easily. • Preisach model used to describe bulk magnetisation changes in tube. • It’s possible to use just use the initial remanent magnetisation curve to predict deperm results. • Stage 1 data from previous deperms on submarines can be used as approximation for initial curve – can also predict deperm results.