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In this paper, we use a phenomenological model based on the Jiles-Atherton-Sablik model of stress affecting the magnetic hysteresis of magnetic materials as modified when stress goes past the yield stress We use this to show that (1) the model produces sharp shearing of hysteresis curves, as seen experimentally and that (2) it also produces a step in the hysteresis loss at small residual plastic strain. We also find that the step in the hysteresis loss can be fitted to a power law, and find that the power law can be fitted by the power m=0.270, different from the mechanical Ludwik Law exponent, and reasonably close to the experimental 0.333 and 0.202. We will also suggest a method of measuring how plastically deformed the material is by suggesting how the dislocation density can be measured. [ABSTRACT FROM AUTHOR]

A new nondestructive eddy current technique is described for testing for incipient creep damage in austenitic steel boiler tubing in power plants. It is used because as incipient creep damage is formed, a magnetic oxide scale forms on the outside of the boiler tube in concentration proportional to the incipient creep damage; simultaneously in the base metal under the scale, a magnetic ferrite phase also forms in the grains and grain boundaries, which is in smaller concentration, but which is also in concentration proportional to the incipient creep damage. The eddy current signal can be processed in such a way that it varies monotonically and nearly linearly with the magnetic phase concentration and monotonically and nearly linearly with the incipient creep damage. Various aspects of the measurement are analysed and discussed—for example, liftoff, wall thickness, and diameter dependence. Using a zero point value to assess oxide layer permeability and dependence on conductivity is also discussed. Comparison is made between measurements and finite element modelling results. [ABSTRACT FROM AUTHOR]

The statistical energy analysis method is applied to a beam network in a building structure. A method of taking structural resonances into account is introduced into the analysis via the use of discretized modal densities. Transfer functions computed from the model beam network are compared over a wide frequency range to experimentally measured transfer functions from an equivalent beam network in an existing building structure in which one of the beams is vibrationally excited.

Provides information on a study which established a correlation between magnetoacoustic emission properties, magnetic properties, and microstructure for incipient stages of creep damage. Methods; Results; Discussion.

Provides information on a study that presents finite element simulations for worst case relative permeabilities for base metal, heat-affected zone and weld material. Physical model for creep-induced magnetic changes; Improved finite element computation for seam welds; Results; Conclusion.

Using appropriately modified magnetization curves for each element of creep-damaged material, a finite element calculation has been carried out to simulate magnetic detection of non-uniform creep damage around a seam weld in a 2.25 Cr 1 Mo steam pipe. The magnetization curves for the creep-damaged elements were obtained from an earlier model for the magnetic effect of a uniformly creep-damaged material as given by Chen, et al. In the finite clement calculation, a magnetic C-core with primary and secondary coils was placed with its pole pieces flush against the specimen in the vicinity of the weld. The secondary emf was shown to be reduced when creep damage was present inside the pipe wall at the cusp of weld and in the vicinity of the cusp. The C-core detected the creep damage best if it completely spanned the weld seam width. Also, the current in the primary needed to be such that the C-core was not magnetically saturated. [ABSTRACT FROM PUBLISHER]

Abstract: The paper presents the results of a complementary study including magnetic hysteresis loops B(H), magnetic Barkhausen noise (MBN) and magnetoacoustic emission (MAE) signals measurements for plastically deformed Fe–2%Si samples. The investigated samples had been plastically deformed with plastic strain level (εp ) up to 8%. The properties of B(H) loops are quantified using the coercivity HC and maximum differential permeability μrmax as parameters. The MBN and MAE voltage signals were analysed by means of rms-like voltage (Ub and Ua, respectively) envelopes, plotted as a function of applied field strength. Integrals of the Ub and Ua voltages over half of a period of magnetization were then calculated. It has been found that HC and integrals of Ub increase, while μrmax decreases monotonically with increasing εp . The MAE (Ua) peak voltage at first decreases, then peaks at εp ≈1.5% and finally decreases again. The integral of the Ua voltage at first increases for low εp and then decreases for εp >1.5%. All those various dependence types suggest the possibility of detection of various stages of microstructure change. The above-mentioned results are discussed qualitatively in the paper. Some modelling of the discussed dependency is also presented. [Copyright &y& Elsevier]