In the paper a new approach for the investigation of the dielectric properties of dielectric material will be described, with implementation of artificial metamaterial structure over the aperture of waveguide sensor in order to increase the sensing properties of classical waveguide sensor. The aim is to achieve the optimal design of metamaterial structure for waveguide sensor tuning in microwave X-band. The possibility of metamaterial structure used for upgrading properties of classical waveguide sensor will be emphasized. The numerical simulation of 2D metamaterial structure properties and experimental results for dielectric properties dielectric materials are carried out, resulting in the possible applications of metamaterials to improve the sensing of classical microwave devices, so that metamaterials open a new degrees of freedom in sensor design like a sensitivity increasing in the area of measurement of dielectric properties of materials, which changes can be the indicator of new properties that could lead in some cases to the material failure. In a large range of applications, the information about dielectric properties are required, but not only these, sometimes, for natural dielectric as wood, the direction of the wood grain that is changing from point to point, making the permittivity tensor to become a random values. Wood being a heterogeneous material, it has variable properties that can be a bottleneck in some industrial applications where the material properties should be strictly defined to assure prime quality. Over the past decades the traditional use of wood as construction material evolved to a modern, widely differentiated application domains, as sonic barriers or components in small wind turbine blades, etc. The purpose of the paper was to apply a modern microwave measurement method to determine the dielectric properties of wood samples and validate the results with Dynamic Mechanical Analysis.

    

   

As about 50 years have passed since the high economic growth period, the aging of metal parts such as the corrosion and cracks is becoming a serious problem, which are used in the highways, bridges and buildings. Thus, a technology to detect the aging of metal parts is required. We have developed magnetic nondestructive evaluation (NDE) technologies for the steel structures. Some highways and brigdes have steel plate under the asphalt or concrete, such as the steel floor slabs of roads. In the NDE of highway and birdge, it is required to inspect the steel material with a distance between the sensor and steel structure (high lift-off). In the high lift-off, the signal from crack is small, and the noise peculiar to the magnetic material makes the signal detection difficult. Therefore, the influence of the magnetic noise should be reduced. In order to reduce the influence of the magnetic noise, in this study, a detection coil of a secondary differential coil combining two differential coils was developed. By arranging two sets of differential coils in layers, it is possible to reduce the magnetic noise and improve the signal to noise ratio (SNR) by reducing the influence of the applied magnetic field. Beacause of the increase in SNR, a weak signal from the sample with a high lift-off is expected to detect. In addition, the induction coil was also prepared by connecting two coils in reverse, and it can generate a dipole-like induced current under the center of the coil. The induction / detection coil and various power supplies were implemented to a hand cart and this enabled to move the measurement system easily above the sample. To obtain the mapping of magnetic signal, the hand cart was moved from the edge to edge of sample (1 line scan), and the data of nine lines with 30 mm intervals was measured for imaging. We used two steel plates (SM490A) with a crack as a test sample which is 0.7 m in width, 1.0 m in length and 6 mm in thickness. Each sample has surface cracks of 50 and 100 mm in size and 4 mm in depth. In addition, the distance between the sample and the detection coil was 20, 50, and 80 mm, and the angle of the induction coil to the slit was also changed. As a result, it was found that the applied dipole-like current was particularly effective for detecting the slit when the direction of current was orthogonal to the slit. From this result, the proposed induction and detection coil configuration is expected to detect the cracks in steel structures located under the asphalt or concrete.

    

   

Some NDT methods advantageously use spectral analysis using DFT. These are e.g. methods of nonlinear ultrasonic spectroscopy, resonance spectroscopy but also some others. Despite its indisputable advantages, the use of DFT spectral analysis brings some problems. A major problem is the leakage effect, which is evident in cases where we cannot provide a coherent DFT with synchronous sampling. Related to this is the problem of insufficiently accurate determination of frequencies of dominant harmonic components, which is manifested e.g. in detection of change of resonant frequencies during non-linear effects of tested systems. A common solution to these problems is the use of new methods for very accurate determination of the frequency of the dominant harmonic signal. This also allows the suppression of the leakage effect in spectral analysis, so that the spectrum obtained is accurate and without the leakage effect in a significantly higher dynamic range than the use of known window functions. The paper shows the possibilities of solving the mentioned problems.

    

   

Acoustic emission from the fast dislocations emitted from an edge crack in 3D bcc iron crystal is studied via atomistic simulations by molecular dynamics technique. Acoustic emission patterns arising from the fast dislocation motion in molecular dynamics are visualized via the local kinetic energies of individual atoms and further modeled as a moving source of the stress waves in the anisotropic continuum.

    

   

Micro defects occur on the surface or inside metal materials during their production, processing for a metal structure, or caused by the aged deterioration. Therefore, a non-destructive testing that can inspects and evaluates the micro defect of early stage is required. In the conventional eddy current testing, a combination of an induction and a detection coil is widely used. Recently, the magnetic sensor which has high sensitivity and spatial resolution even at low frequencies have been used instead of the detection coil. In this study, the optimization of applied magnetic field for detecting various shapes of defect generated in both magnetic and non-magnetic materials was examined using the eddy current testing with a highly sensitive magnetic sensor. The measurement system consisted of an oscillator, an induction coil, a nanogranular tunnel magneto resistive (TMR) sensor, an X-Y automatic scanning stage, a lock-in amplifier, a differential amplifier, and PC. The magnetic signals were lock-in detected by synchronizing them with the reference signal generated by the oscillator which was also used to drive the induction coil. An alternating magnetic field was applied to the test sample using the induction coil to induce an eddy current. In this study, various shapes of induction coil, such as solenoid, tangential and wire type, were used and the characteristics of response to each coil were compared. The test samples were the aluminum (non-magnetic) and the steel (magnetic) plate with various shapes of defects (pit, slit shape). The eddy current distribution generated from various shapes of defects using various induction coil were also analyzed by the simulation. From the simulation results, it was found that the signal waveform of magnetic field depended on the defect and coil shape, and these results agreed with the measured values when the magnetic signal was scanned over the defect. In the case of wire type, the change of the magnetic field distribution generated by the eddy current was large when the TMR sensor was placed above the induction wire. In the case of solenoid type, the detection sensitivity increased when the TMR sensor was close to the edge of coil which is apart from the center of the coil. In addition, it was found that the signal change was different between the magnetic and non-magnetic materials. For the non-magnetic material, as the frequency increased, the signal to noise ratio of the detected defect signal increased because the signal is generated from only the eddy current. On the other hand, for the magnetic material, there was an optimum frequency for detecting the defect because the signal is generated due to both the magnetization and the eddy current. As a results, the optimum method of applying the magnetic field for the eddy current testing using magnetic sensor could be clarified.

    

   

Values of a residual magnetic induction change as a result of the work of a steel wire, i.e. its bending, stretching or twisting. The value of the induced magnetic field in the wire is also affected by the damage occurring. Under the influence of cyclically changing work loads, due to the effects of magnetomechanics, changes in electromagnetic properties occur both in the wires and in the entire steel wire rope. Anomalies of the residual magnetic field are used to identify imperfections of steel wire ropes such as broken wires, deformations, wear and corrosion. The most common method of non-destructive testing of steel wire ropes is the active magnetic method, which uses imperfections leaked by a strong, formatted by an external source, magnetic field. In this case, the steel wire rope is magnetised only before or during the test, thus losing important diagnostic information. An increasingly popular method using a residual magnetic field leakage does not require pre-magnetization. Magnetic flux leakage (MFL) detection has the advantages of accurate positioning obvious target defect. The MFL information on the surface of the wire rope can be converted into magnetic images so that the circumferential and axial position of the wire rope defects can be displayed more intuitively. By fusing the visible and magnetic images, it is possible to use of their information and the defect recognition rate can be improved. The article focuses on the very process of magnetization and demagnetization. In detail, the magnetomechanical effects are discussed: direct and inverse. As far as the measurement is concerned, it is presented as follows. Three identical, new steel wire samples from the production line, were subjected to the processes: one of them was magnetized with a strong magnetic field (like in a active method), the other was subjected to a demagnetization process (passive method), while the third was left unchanged. A diagnostic signal was recorded for each of these samples using the SpinMeter-3D sensor. The signal was measured in the three axes of the Cartesian system. Then, each of these samples was subjected to two-way bending until breaking. Diagnostic signals for each of these samples were registered again and next obtained results were compared very closely. The results obtained allowed for the formulation of certain conclusions and dependencies.

    

   

Biodegradable materials are used as alternative implants for orthopedic applications due suitable strength, fatigue resistance, ductility and biocorrosion resistance which are features for biodegradable implants. Mechanical properties can be improved by adding alloying elements. The decrease of the corrosion rate of Mg can be induced by modifying the structure and phase distribution. Thus, Mg alloys have been designed to meet the requirements of bone repair implant materials by adding Calcium and Yttrium. Usually Ca is added to control corrosion rate of Mg alloys and thinning grain boundaries. Rare earths are often used as addition elements to improve alloys properties as biocompatibility and creep resistance. Mg based alloy with Ca and Y had been proved to be a biocompatible material, osteoconductive and biodegradable and can be used in bone repairs. The system is defined as Mg100-(n+x) Ca(n) RE(x), varying the RE concentration in order to slow the degradation process. Beside morphological characterization with SEM, EDX, non-invasive testing is required to be carried out the determination of mechanical characteristics. The interest in this study is to analyse the influence of Yttrium over elastic properties of these alloys in order to choose the best values appropriate with human bones, using Resonant Ultrasound Spectroscopy and ultrasound method.

    

   

CFRP are used in most wide domains due their low density, lack of mechanical fatigue phenomena and high strength -to weight ratio. Low strength to impact on the normal direction to fiber's plane, leads to delamination and fiber breaking and these must be nondestructive evaluated in order to avoid further damage propagation. Also, the behavior of interlaminar fractures of composites is investigated numerically and experimental, the test being carried out with Arcan specimens that offer the possibility to use a single type of specimen in order to extract the fracture properties. The variation of loading direction between 00 and 900 towards the fibers direction allows the obtaining of different complex state of stress. From electromagnetic point of view, CFRP structure represents an inhomogeneous structure of electric conductive fibers embedded into a dielectric material, thus an electromagnetic configurable architecture (CA) can be used to evaluate the materials. Starting from apriori knowledge about Iosipescu specimen, the modelling will be carried in FEM software to optimize the shape of the specimen, in order to obtain more uniform stresses in cross section. A FEM is performed for Iosipescu specimen, designed for pure shear, when it is mounted in Arcan device and loaded in order to obtain some complex states of stress as close as possible to those encountered in practice. The studied material is Carbon Fiber Reinforced Plastics used in aerospace industry. In order to adopt an appropriate form of the specimens, an analysis is required before the tests are carried out.

    

   

During the development process of MPI equipment it is very helpful to know the detection ability of MPI process. Such an ability depends on material properties of the body under test, applied magnetic field, defect shape and size, and detection particle properties. There is not enough information published, so that in-house experiments are justified. An experimental setup for MPI sensitivity measurement is presented in this paper. The setup consists of four coils and a two steel plates attached to the coils. The steel plates are magnetized by the flux generated by the coils. The coils are situated at the vertices of a square and the opposite coils are electrically connected in series therefore the setup can be fed by two independent current waveforms. These current waveforms generate two perpendicular magnetic field components on the plates therefore it is possible to generate arbitrary tangential magnetization on the surfaces of the steel plates. A standard QQI gauge is placed on the steel plate in the middle of the coils. If the setup is fed by two sine waveforms of the same frequency and arbitrary phase shift the tangential magnetization of the steel plates is elliptical polarized. The coils are fed from a pair of arbitrary-waveform generators amplified by a pair of power amplifiers. Using this setup the sensitivity of MPI can be measured for a various parameters. Measurement setup as well as first experimental results are presented in this paper.

    

   

Corrosion of pre-stressing strands causes a deterioration of condition of civil engineering structures like bridges, therefore periodic inspections are necessary to prevent collapse of such structures. The corrosion of steel is a slow process however it can be well reproduced in the lab using accelerated corrosion process. Monitoring the amount of corrosion in a sample is of great importance to predict the integrity and the residual life-time of structures. The ultrasonic techniques were proposed as valid methods of analysing the data recorded during the monitoring. In this paper we show results of our experimental study and the application potential of ultrasonic techniques to analyse the effect of damage induced by accelerated corrosion on the linear and nonlinear elastic behaviour of a steel strands. These initial results show the possibility for the application of nonlinear ultrasonic testing methods for monitoring of condition of strands which are built into bridge girders.

    

   

The aging of steel pipes used for lighting and sign poles that are a part of social infrastructure is becoming a problem. This aging is often caused by the corrosion of steel pipes generated near ground which is located several tens of millimeters from the ground line. The accident that the structure collapses has been reported due to the growth of ground corrosion defects. Currently, a general maintenance inspection is visual inspection performed by excavating the ground. However, it is difficult to detect the corrosion defects near the ground quickly and quantitatively with such an inspection method. We have developed the integrated magnetic sensor probe with two tilted sensors for the extremely low-frequency eddy current testing (ELECT) in order to detect the corrosion near the ground from the ground surface. Using this probe, a correlation could be obtained between the signal attenuation due to the corrosion near ground and the thinning rate. In this study, the inclination angle of the magnetic sensor probe and the distance between two sensors were optimized by measuring a test sample, and the quantitative evaluation of the thinning rate and the corrosion position that has not been clarified until now were investigated. When the inclination angle of the sensor probe was decreased, the change rate of the signal intensity increased, and the corrosion at a deep position could be also detected. Under this conditions, the distance dependence which is the relationship between the signal intensity and the defect position from the sensor was measured and the obtained data was normalized with the signal intensity measured at the uncorroded area. As a result, it was possible to clearly extract the difference between the signal intensity at the uncorroded area and the corrosion defect. In addition, when the samples with different thinning rates were measured, the signal intensity depended on the thinning rate, and it was possible to evaluate the thinning rate of corrosion defects quantitatively. Furthermore, a method to estimate the position of corrosion defects was examined using the measured data of two magnetic sensors. The improvement of the change rate in signal intensity acquired by the two sensors was attempted by reducing the distance between sensors. Since the signal intensity changed with the distance between the sensors and the defect, it was also possible to estimate the position of the corrosion defect quantitatively. Therefore, the developed system can be applied to various shapes of corrosion defects generated in the actual social infrastructure.

    

   

During the operation of machines and mechanical devices, there is a risk of damaging critical elements that may result in serious failures, unplanned downtimes, financial losses, and damage to the health of personnel or third parties. In order to reduce the above-mentioned hazards, periodic non-destructive tests (NDT) are performed and/or the work parameters and structural health are monitored (CM, SHM). The effectiveness of preventive actions, described by the probabilities of diagnosis POD, is the resultant of the expected diagnostic symptoms (knowledge about the process and accompanying phenomena), the choice of observation method (NDT, SHM), the quality of the measurement path, software quality and diagnostic criteria used for numerical analysis. The article presents the project for the use of magnetic magnetometers in the 0 - 500 Hz band for remote, non-contact monitoring of object operation and assessment of the technical condition of ferromagnetic elements and systems. At the beginning, the theoretical foundations of passive magnetic tests and applied magnetometers (multi channels 3 D system) have been presented. Next, selected results of laboratory tests and applied measurement data analysis methods are presented. Then selected results of tests carried out on the real object are presented, among others Kaplan turbine and turbine jet engine. Finally, discussing the results of research, the strengths and weaknesses of the magnetic state observer were pointed out. It has been experimentally demonstrated that a remote magnetic state observer provides qualitative and quantitative diagnostic information that can be used in NDT and SHM.