Arbeiten des Laboratoriums für Technische Physik der Technischen Hochschule München

Meissner, W.; Heckeler, R.

doi:10.1007/bf02584989

Cited by 1 publication

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“…On a still finer scale, sudden microstructural rearrangements can also be detected by acoustic emission techniques. Typically, ultrasonic pulses in the band around 300 kHz with total energies as low as 10 −24 J or 6 × 10 −6 eV can be distinguished from the thermal phonon background [28]. The magnetic counterpart of these effects is Barkhausen emission [29].…”

Section: Magnetomechanical Effectsmentioning

confidence: 99%

Piezomagnetism and fatigue

Erber

Guralnick

Desai

et al. 1997

J. Phys. D: Appl. Phys.

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Piezomagnetism refers to a change in the intrinsic magnetization of a material subjected to mechanical actions such as tension or compression. In a ferromagnet such as a mild steel these effects are easily measured: typically a stress of or 140 MPa induces a magnetic moment of the order of emu or , resulting in flux densities in the range 10 mG or T in the vicinity of the specimen. Since piezomagnetic effects are due to interactions between the mechanical and magnetic mesostructure of materials microplastic processes that alter the arrangement of the ferromagnetic domain structure affect the intensity of the associated magnetic fields. The progressive degradation of such materials under cyclic loading can therefore be tracked by following the evolution of the piezomagnetic field. Specifically, if the measurements are displayed as loci in a three-dimensional stress - strain - field (B) space, the approach to fatigue failure is paralleled by a series of conspicuous geometric transformations of these curves. Complementary information also appears in continuous-time records of B(t): these magnetograms clearly show the abrupt incidence of `infarcts' (microcracks) and the cumulation of phase shifts as the material degrades.

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Section: Magnetomechanical Effectsmentioning

confidence: 99%