Вплив деформації на параметри магнетоакустичних сигналів

This paper presents results on the study of the effect of elastic and plastic deformation of low-carbon steel on magnetoacoustic emission (MAE) performed with the measuring system MAE-1L. Generally, the observed tendencies of reduction of MAE with deformation of iron-based alloys confirm those published in the literature. The reproducibility of measurements in the ealstic region is very high. As to the plastic region it demands further investigations. These measurements confirmed the perspectiveness of the method MAE for nondestructive evaluation (NDE) of plastically damaged parts of operated equipment or structures. MAE-1L system exhibited an appropriate service performance.Наведено результати досліджень впливу пружної та пластичної деформацій низьковуглецевої сталі на мегнетоакустичну емісію (МАЕ) із використанням вимірювальної системи MAE-1L. Виявлені тенденції зниження МАЕ із деформуванням сплавів на основі заліза загалом збігаються із опублікованими даними. Відтворюваність вимірювань на ділянці пружних деформацій є дуже висока. Щодо пластичної ділянки, необхідні подальші дослідження. Наведені результати підтверджують перспективність методу МАЕ для неруйнівного контролю ділянок діючого обладнання та споруд, які зазнали пластичного деформування. Система МАЕ-1L продемонструвала належну працездатність

Modeling of Hysteresis Losses in Ferromagnetic Laminations under Mechanical Stress

A novel approach for predicting magnetic hysteresis loops and losses in ferromagnetic laminations under mechanical stress is presented. The model is based on combining a Helmholtz free energy -based anhysteretic magnetoelastic constitutive law to a vector Jiles-Atherton hysteresis model. This paper focuses only on unidirectional and parallel magnetic fields and stresses, albeit the model is developed in full 3-D configuration in order to account also for strains perpendicular to the loading direction. The model parameters are fitted to magnetization curve measurements under compressive and tensile stresses. Both the hysteresis loops and losses are modeled accurately for stresses ranging from –50 to 80 MPa.Peer reviewe

Vibration energy harvesting using Galfenol based transducer

In this paper the novel design of Galfenol based vibration energy harvester is presented. The device uses Galfenol rod diameter 6.35 mm and length 50mm, polycrystalline, production grade, manufactured by FSZM process by ETREMA Product Inc. For experimental study of the harvester, the test rig was developed. It was found by experiment that for given frequency of external excitation there exist optimal values of bias and pre-stress which maximize generated voltage and harvested power. Under optimized operational conditions and external excitations with frequency 50Hz the designed transducer generates about 10 V and harvests about 0,45 W power. Within the running conditions, the Galfenol rod power density was estimated to 340mW/cm3. The obtained results show high practical potential of Galfenol based sensors for vibration-to-electrical energy conversion, structural health monitoring, etc

Investigation on magnetomechanical behavior of materials: instrumentation, measurement and modeling

Stress is one of the principal external factors affecting the magnetization of materials. Although some aspects of magnetoelasticity, such as magnetostriction, have been well documented in the scientific literature, other aspects such as the change in magnetization with stress remain almost undocumented. It is into this relatively unexplored territory that researchers began studies of magnetoelastic effects. This thesis reports on a number of studies into the effects of stress and field on magnetization. In particular it is concerned with the fundamental description of the behavior of magnetic materials as the stress is changed. For small stress, and hence small deviations of the spins from their easy axes, the behavior if linear and reversible and the net result is either a simple increase or decrease in magnetization (depending on the magnetostriction and the sign of the stress). This behavior can be described in terms of an effective field theory, which expresses the stress in terms of an equivalent magnetic field, which either increases or decreases the magnetization. However when the state of a material undergoes large changes as a result of being subjected to high levels of external influences, such as field, stress or temperature, the response eventually extends beyond the simple linear regime. Beyond this regime the description of the behavior becomes much more complicated and changes in magnetization become irreversible and cause dissipation of energy. Under these conditions it is also often found that the state of the material is no longer reversible. These phenomena are documented in the experimental literature. However the theoretical non-linear hysteretic description of the response of materials undergoing large changes is only at an early stage of development compared with linear reversible theories that are applicable to small changes. This thesis will show how the effective field theory can be combined with other hysteretic and anhysteretic concepts to provide a description of this behavior under higher stress excitation. Furthermore the limitations of these theories will be discussed