L. Harasztosi

Correlation between the grain-shape and magnetic properties in nanocrystalline iron

Abstract Correlation between magnetic properties and time evolution of size (d) and shape of grains of pure nanocrystalline iron produced by ball-milling were investigated by Barkhausen-noise and lowfield magnetization measurements. Strong texture and elongated grain structure were developed after some hours milling time, and the thickness of elongated grains was in accordance with the grain size obtained from X-ray line broadening. After prolonged milling, disruption of the elongated grains and development of equiaxed grain structure was observed. There was a maximum in the Barkhausen-noise when the above lamellar structure was the most typical. It is shown that the coercive force (Hc) is not sensitive to the formation of the grain structure, but the course of the Hc(d) curve strongly depends on the initial and preparation conditions. In accordance with our previous results, the saturation magnetization was independent of the grain size.

Correlation between Barkhausen-noise and corrugation of railway rails

The magnetic Barkhausen-noise has been investigated on the running surface of a railway rail and a good correlation has been found between the noise and corrugation. The Barkhausen-noise showed minima and maxima at the hill and valley positions, respectively. This correlation can be used to observe or preindicate the corrugation process.

Correlation between Barkhausen noise and mechanical sensitivity in FINEMET-type materials

Measuring technique, developed at our Laboratory for the investigation of ferromagnetic industrial materials, experimental results obtained and their analysis are reviewed. The magnetic properties (permeability, mechanical sensitivity) of as received and heat treated Finemet type ribbons (Fe75Si15NbBCu) were measured with common industrial equipments. The above properties were correlated with magnetic Barkhausen noise parameters. The distributions of peak area A and peak noise energy E were analyzed and it was found that distribution of the noise parameters P(x) (where x = A or E), were in good agreement with the theory of self organized criticality (SOC), satisfying power laws in the form P(x) ~x. Useful correlation between the noise parameters and the mechanical sensitivity has been established. The noise did not considerably depend on the other parameters of ribbons.

Development and characterization of a new measurement technique for monitoring changes in acceleration during hippotherapy

Abstract The beneficial effects of hippotherapy lie in the transmission of the horses movements to the patient. The aim of our work was to create a measurement method for objective evaluation that can be used in natural settings without interfering with therapy. Methodology/Principal findings Our measurement system consists of three treble axis accelerometers connected to a data logger. Software was developed for data analysis and post processing. A commercial DVD recording camera was used to document the hippotherapy session. In this paper we present the results obtained in pilot measurements on ten children with cerebral palsy. For reference, a skilled rider was measured on the same horse using a passive following seat. Conclusions The acceleration diagrams show common characteristics useful to the interpretation of the movement transfer during hippotherapy as well as individual patterns indicating alterations in the movement reactions of different patients.

Temperature Dependence of Barkhausen Noise Parameters in Carbon Steel

Temperature dependence of different parameters (the position of the inflexion point and the saturation value on the root main square, RMS, values versus exciting field curves) of the Barkhausen noise is measured in structural steel (S 235 JRG1). It is shown that while the position of the inflexion point remained constant, the RMS value at the inflexion point and saturation value increased with the increasing temperature, T. Most interestingly the field required for saturation decreased with decreasing temperature and had a breakpoint at about 200K. Breakpoints at the same temperature on the critical exponents versus temperature functions (i.e. on the β(T) and α(T) curves, where β and α are the exponents of the probability distributions of peak heights and durations, respectively) were also observed. This temperature can be identified as the ductile-brittle transition temperature.