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Stress measurements on components with nondestructive ferromagnetic methods

: Theiner, W.A.; Brinksmeier, E.; Stückner, E.; Nowack, H.

Macherauch, E.; Hauk, V.:
Residual stresses in science and technology. Vol.1
Oberursel, 1987
Book Article
Fraunhofer IZFP ()
3MA; Eigenspannung; Härte; Innenlochsägeblatt; Koerzitivfeldstärke; mikromagnetisches Barkhausenrauschen; Niederdruckturbinenschaufel; Prüfgerät

For rapid stress tests on components micromagnetic quantities can be used. Methods developed in the last years are: the magnetic and acoustic Barkhausen noise, the incremental permeability and the dynamic magnetostriction. The advantage of these methods is given by the fact that quantities can be used which are sensitive to stress, microstructure and texture. Combining several independent micromagnetic quantities it is possible to get unambiguous results even for superimposing residual stress and microstructure states. The nondestructive testing procedure used is called 3MA (micromagnetic multiparameter microstructure and residual stress analysis. Up to now results have shown that for industrial applications the magnetic Barkhausen noise (M) method as well as the incremental permeability (my Delta) can be used for rapid tests successfully. Scopes of 3MA are: Detection of different heat treatments, of residual stresses, hardness test in welds, determination of texture direction, tests o f hardness gradients (grinding, inductive, laser), determination of strength and toughness parameters. To achieve quantitative results, the 3MA system has to be calibrated by mechanical tests, x-ray measurements and hardness tests as well. Test time for one measuring point: hardness/stress value about 0.5 sec; hardness gradient 0.5 sec ....30 sec. (IZFP)