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Magnetic stress analysis of structural steel


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Langman, RA 1986 , 'Magnetic stress analysis of structural steel', PhD thesis, University of Tasmania.

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The original aim of this project (on which the thesis is based) was to
design an instrument that would measure stress in steel nondestructively
by means of magnetic measurements, using the known fact that the
magnetic properties of most steels are significantly affected by stress. It
soon became apparent that there was a paucity of relevant magnetic theory,
and so the project was widened to include a (mostly experimental) study of
the effect of stress on the magnetisation curves of mild steel. These were
measured for magnetisation parallel and perpendicular to the stress and for
tensile and compressive stresses. The highest sensitivity to stress occurs
on the steepest part of the magnetisation curve, which is where the stressinstrument
is used, and is also where the theory is least satisfactory. Thus
another aim is to relate magnetisation measurements and theory at moderate
field strengths.
The thesis is in three parts: I A review of experimental magnetic stress analysis, for the period 1950-
1980; work by about 12 individuals or groups is included.
II An account of the author's experimental results, both for the
development of the instrument to measure stress (called the Rotation Rig)
and also for the more basic measurements of magnetic properties of steel
under stress. Some work is also included on the effect of plastic strain and
on the relation between Barkhausen noise and the rotation rig results.
III A review of magnetomechanical theory, including a contribution from
the author; theories or concepts that have some relevance are by Brown,
Goodenough, Ginsburg, Watson, and Jiles and Atherton.
The first aim, that of designing an instrument to measure stress, has
been achieved. Strictly, only the differences in principal stresses, and
their directions, can be measured. The results are analagous to photoelastic
modeling but working on the actual steel instead of a plastic model. The rotation rig is cheap, quick, and convenient to use, and has an error of
about lOMPa in optimum conditions.
The . second aim, that of producing a theory to explain quantitatively
the effect of stress on magnetisation at moderate magnetic fields, has not
been achieved. In fact the complexity of the magnetic behaviour of steel
makes any theory likely to be rather complicated. However, the symmetry of
the experimental results on mild steel are explained theoretically by the
Many of the measurements, especially those with biaxial stresses, have
not been made before, and are a framework on which to base further

Item Type: Thesis - PhD
Authors/Creators:Langman, RA
Keywords: Steel, Structural, Strains and stresses
Copyright Holders: The Author
Copyright Information:

Copyright 1986 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Bibliography: leaves 268-278. Thesis (PhD)--University of Tasmania, 1987

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