NDTnet 1998 Aug, Vol.3 No.8

Abstract

The article deals with the idea of new non-destructive method of exact determination of Poisson's ratio for constructional materials using of the magnetic Barkhausen-noise. The relative strain () in the direction forming the angle with the direction of applied load can be described by the following formula:



Having used Barkhausen-effect so-called magnetic parameter MP (RMS of Barkhausen-noise, number of impulses per unit time) as a function of the angle between the direction of applied load and the magnetization direction of the material for two values of external load can be experimentally determined (Fig. 1).

Fig. 1. Magnetic parameter versus magnetization angle

Having found extreme of the curve under the load (A) and the point (B) of intersection of the curves with and without load one easily determines the angle. The squared cotangent of these angle is simply equal to Poisson's ratio.

The advantage of the described method is that the value of Poisson's ratio can be obtained directly from geometrical parameters of the MP-angle-curves. Knowledge of geometrical sizes of the examined sample, values of loading forces and other parameters is not required. The accuracy of determination of Poisson's ratio depends only on the accuracy of determination of the angle. There has been invented a special measuring head allowing to establish the magnetization direction with the pitch of 0.0015°. In the case of non-ferromagnetic materials a thin iron foil should be cemented to the surface of the sample being tested.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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