EDDY-CURRENT VARIABLE-FREQUENCY METHOD OF DETERMINATION MECHANICAL STRESS
Abstract
Using of multiparameter electromagnetic control methods of materials and products for
controlling the electrical and magnetic fields of conductive products, which can be used to determine the
strength parameters, hardness, mechanical stresses, temperature, and prevailing impurities, is practical
interest. The expediency of using electromagnetic transducers with a cylindrical solid product, because in
this case the functional connections between the signals of the converter and the product have been
determined in the absence of a mechanical stress, is shown. In the paper, further development of
electromagnetic methods and implementing converters in the direction of various practical applications and,
in particular, for the determination of mechanical stresses, forces, weight of loads, pressures, moments, etc.,
is considered. Applying the functional dependences of the amplitude and phase of the specific normalized
emf of the transformer converter with a cylindrical ferromagnetic product, amplitude and phase frequency
methods for determining the mechanical stresses are proposed. The emergence of mechanical stress in the
product can result in general to a change in both the values of the magnetic permeability and the specific
electric conductivity.
In order to increase the resolving power of a transformer electromagnetic converter when measuring
the magnitude of the mechanical stress in a wide range of their variations, the frequency amplitude and
phase methods should be used. The essence of both methods is that first, in the absence of a mechanical
stress of the product, the value of the frequency of the probe field is defined, corresponding to the maximum
steepness of the transformation function, which sets in at 1.5 <x <3. The errors in measuring the mechanical
forces by these methods don’t exceed 2%. Both methods were used in the developing of weighing apparatus
which having simple conversion function, the design of the elements and high sensitivity to the change in
mechanical stresses. These methods also have found application in installations for research of influence of
mechanical stresses, deformation on electric and magnetic parameters of products and the samples made of
various materials.