P. Wiewiórski

Magnetovisual method for monitoring thermal demagnetization of permanent magnets used in magnetostrictive actuators

Abstract The design and measuring potential of the latest generation of the magnetic scanner called Magscanner-Maglab System (MMS) was presented. It enabled the fast acquisition of 3D signals from magnetic sensors and their visualization as digitalized magnetic images. This system was used for monitoring of a thermal demagnetization process of permanent magnets. The original method and measurement devices were capable for examination of magnetic, mechanical and thermal defects in cylindrical rods made of NdFeB and non-rare earth components. Effectiveness of the method and device was tested for the reference demagnetized magnet dedicated for magnetostrictive actuators.

3D Magnetovision Scanner as a Tool for Investigation of Magnetomechanical Principles

The study was aimed at designing a system for measuring the distribution of magnetic field around different magnetic objects including Smart Magnetic Materials. A new type of 3D camera for monitoring the magnetic field intensity was constructed. The measurement principle is based on internal magnetics properties of materials and the reverse magnetostriction effect (also called the Villari effect). No external magnetizing field is assumed; the entire magnetic effect is due to magnetomechanical principles. A new generation of Honeywell magnetosensors were applied to measure field intensity in 3D. Small size of measurement area (1.5 mm3) allows quasi-local measurement of magnetic field. In the measurement head also Hall probes were alternately used. The aim of this stage of research was to construct the set for measurement of strength of a very weak magnetic field (10 A/m) around the magnetic objects. In scanner construction three axes for displacement in directions consistent with sensor axis were applied, which permits measuring magnetic field vector in geometrical coordination. Specialized software for data acquisition, processing and visualization of magnetic field vector has been written. In preliminary parts of the work magnetic scanner system allows determination of correspondence between mechanical and magnetic quantities. Main applications for this type of system are: reverse magnetostriction and magnetostriction in smart magnetic materials and composites, martensitic transformation induces plastic strain in shape memory alloys, NDT investigation, identification of local plastic deformation and texture of ferromagnetic materials, magnetic polygraphy and others. Measuring system may be used both as an entirely autonomous system as well as an integrated one, also through joint control with a typical mechanical testing systems for static and fatigue tests.

Application of Vibration for Energy and Data Transfer in Mechanical Constructions; Energy Harvesting

The work presents a method of at once power and information transmission through pair of rails using SURPS (Smart Ultrasonic Resonant Power System). The solution allows to (electrically) feed sensors located in hardly accessible places of mechanical constructions with simultaneous half-duplex data transmission (e.g. measurement “question-response”), when conventional power supply (requiring e.g. electricity networks, storage batteries, batteries, etc.) is eliminated. The mechanism of power transmission consists in “sending” of mechanical energy through an actuator in a form of “pure” sinusoidal ultrasonic wave and next “receiving” it and transforming into useful electrical current by a harvester. Both magnetostrictive and piezoelectric harvesters/actuators were used. For information transfer F2F (frequency - double frequency) procedures were used, they are a kind of FM (Frequency Modulation). To optimise transmission (the highest possible efficiency and acceptably low noise level), software allowing to select the right type of an actuator, modulation and the recommended frequency band was developed. Additionally it is possible to determine resonance frequency for each construction which is to be used for information and power transfer.

Power generating by high pulse mechanical stimulation of magnetic coupled NdFeB and Terfenol-D

Rising requirements for a new constructions, devices and machines force engineers to monitor them all day long. An attractive solution seems to be applications of wireless sensors. However, there is a barrier limiting their application, which is the need to supply them with an electrical power over extended period of time without using additional wiring or batteries. The potential solution of this problem seems to be an energy harvesting. Most methods of obtaining the energy from the external sources e.g. vibrations, is to use piezoelectric materials. However, the amount of energy generated by piezoelectric materials is smaller than most electronic devices need. Therefore a new method for generating a pulse of energy and conditioning for other loads devices must be developed. This paper proposes a new energy harvesting device based on magnetostrictive material. In the course of the experiments with using Terfenol-D rods as actuators and sensors it has been observed interesting phenomenon. Mechanical impact (e.g.energy between 1J and 10J in infinite time) to magnetic core based on Terfenol-D rod (diameter 5mm, length 10 mm), NdFeB permanent magnets and coil allowed get electric power signal enough to supply device of 100 Ohm load on their active state (typical low power controller). In comparison to the same magnetic circuit built with other typical ferromagnetic materials e.g. Armco iron, showed effect 10 times lower or none. Tests and experiments showed the important role of coupling Terfenol-D and NdFeB permanent magnets, their configuration and variable coil parameters determined this effect. In regard to the results the authors proposed the construction of a new impulse harvesting method based on Terfenol-D material for low impedance load.

The Use of Magnetostrictive Cores for the Vibrations Generation and Energy Harvesting from Vibration, in the Selected Frequencies of Work

The paper presents research on use of magnetostrictive cores for the recovery of energy from vibrations and its use to power low-power electronics. To achieve this goal a test stand was constructed to generate and to receive the vibrations in the measurement system at the same time. Selection of an appropriate magnetomechanical parameters of the system was an important element influencing end results. The most important were values of the prestress and magnetising field for actuators and harvesters. As a result of the investigation the device operating in a wide frequency range (up to 40 KHz) and a system for energy transportation through mechanical vibrations were developed. Moreover it was shown that the proposed solution allow information transfer in a short bursts over the same system as energy transfer.

High Power Actuator Based on Magnetostrictive Composite Core with Temperature Drift Compensation

The paper presents an actuator based on a coil placed in the casing, with specially prepared connection rods. The construction allows installation of the fiber Bragg grating sensors inside the coil. It allows to measure deformation of the composite that is located in the core of the coil. Thanks to the signal generation with use of DASYLab software, it is possible to precisely control the frequency, value of amplitude excitation and to send the signal to the system with use of the measurement card. The main goal of the experiment is to keep constant value of deformation, by means of a feedback loop with use of PID control, and to change the initial conditions of the test by change of the external force. The system is designed to return to the initial settings by appropriate control of the intensity of magnetic field, and thus the deformation of the sample.

Testing Mechanical and Electrical Defects in Piezoceramic Materials Resulting from Ultrasonic Vibrations

The work presents recommendations related to the selection and installation of high power piezo ceramic rings dedicated to simultaneous power supply and data transmission for the purpose of extending life in their operation. Mechanical and electrical defects in piezoceramic elements of conical actuators were presented. The issue is important in the case when energy and information are transmitted at the same time using upper acoustic waves to autonomic wireless measurement nodes (WMN) in mechanical construction elements. A laboratory ultrasonic actuator was made and used to test ceramic rings. Additionally a dedicated vibration sensor was made and a measurement system for determination of frequency response of high power actuators was developed. Identification of the material used to make the ceramic rings and feeding electrodes was conducted. Next calibration tests of conical piezoelectric actuators were conducted and their defects were tested.

Evaluation of Possibilities of Electroactive Polymers Application in Bio-inspired Adaptronic System

The paper presents an original design of 3-segments adaptronic analogue of units of mammal’s vertebrae based on 8 actuators using dielectric electro-active polymer (DEAP). The way of preparation took into account the tendency of the DEAP material to local breakdowns, caused by degradation of the internal structure. The cross effects of phase response on a given electrical stimulus under high voltage were identified as well. The degrees of freedom of the analogue segments were determined, taking into account biological significance of vertebral endplates which a simplified form is included in the model. The work is to propose a bio-inspired techniques to build robots with many degrees of freedom using DEAP materials.

Magnetovision Method for Determining the Martensite Phase in the Austenite in Cylindrical and Spherical Objects as a Result of the Cyclic Loads

The subject of the study was to investigate the application potential of the magnetovision method for detecting martensitic transformation in solid samples (3D). The main goal of this research was to develop a system for tracking changes on the surface of the material during cyclic loading (fatigue of the material) and visualization of the results. As a part of that work a dedicated software GR2R-Mag was developed. It was designed to support experiments with use of a goniometer adapted for magnetic measurements. Based on the obtained results it was shown that the proposed testing method is useful for determination of the martensite phase in austenite in spherical objects during cyclic loading. By adaptation of the goniometer for magnetic field measurements, it was possible to measure the value of magnetic field around the spherical and cylindrical objects in a polar coordinates.

The advanced magnetovision system for Smart application

An original method, measurement devices and software tool for examination of magneto-mechanical phenomena in wide range of SMART applications is proposed. In many Hi-End market constructions it is necessary to carry out examinations of mechanical and magnetic properties simultaneously. Technological processes of fabrication of modern materials (for example cutting, premagnetisation and prestress) and advanced concept of using SMART structures involves the design of next generation system for optimization of electric and magnetic field distribution. The original fast and higher than million point static resolution scanner with mulitsensor probes has been constructed to measure full components of the magnetic field intensity vector H, and to visualize them into end user acceptable variant. The scanner has also the capability to acquire electric potentials on surface to work with magneto-piezo devices. Advanced electronic subsystems have been applied for processing of results in the Magscaner Vison System and the corresponding software - Maglab has been also evaluated. The Dipole Contour Method (DCM) is provided for modeling different states between magnetic and electric coupled materials and to visually explain the information of the experimental data. Dedicated software collaborating with industrial parametric systems CAD. Measurement technique consists of acquiring a cloud of points similarly as in tomography, 3D visualisation. The actually carried verification of abilities of 3D digitizer will enable inspection of SMART actuators with the cylindrical form, pellets with miniature sizes designed for oscillations dampers in various construction, for example in vehicle industry.