The inductive sensors for high resolution eddy current non-destructive testing

Продемонстровано виготовлені індуктивні сенсори високої роздільної здатності для вихрострумових перетворювачів. Сенсори були досліджені для визначення їх роздільної здатності в скануючому дефектоскопі. Отримано двовимірні магнітні образи системи модельних дефектів, на яких визначено реальну роздільну здатність сенсорів. Реальна роздільна здатність сенсорів становить менше 50 мікрон. Типові розміри індуктивних сенсорів складають приблизно 1 мм у діаметрі при довжині близько 5 мм. Наведено фото сенсорів на різних етапах виготовлення, а також фото системи модельних дефектів та їх двовимірний магнітний образ. Також продемонстровано реальне магнітне зображення зварного шва в алюмінії, отримане таким сенсором за допомогою скануючого дефектоскопа. Зроблено висновок про перспективність використання сенсорів такого типу в новітніх розробках вихрострумових дефектоскопів скануючого та матричного типів.This paper presents the novel inductive sensors for the high-resolution eddy current scanning heads used for non-destructive testing of the welded joints and material non-uniformities. The inductive coils, used for magnetic excitation and detection of the inductive response, were wounded with 20 μm copper wire on the ferrite core with diameter down to 300 μm. In this work we present the description of the inductive sensors fabrication procedure, as well as their dimensions and pictures. The fabricated eddy current sensors were fixed on the sensor holder, mounted on the computer controlled industrial 2D scanning system with nominal spatial motion precision of 25 μm. The 2D magnetic images, obtained by recording sensor signal in each point of the scanning range, were used to determine the sensor’s ultimate resolution in detection of material non-uniformities (defects). The test samples, specially designed for this purpose, have artificially created test defects with various dimensions and depth. The test samples were designed to model cracks and corrosion pinholes in magnetic (steel) and non-magnetic (aluminum alloy) materials The two-dimensional magnetic image of the test samples reveals the actual spatial resolution of the sensors, found to be less than 50 micrometers Moreover, the sensitivity of the developed inductive sensor is high enough not only to image point like inclusions but also to image the therma stress zone in the aluminum welded joint, as shown in the paper. The small size of the sensors, typically ~1 mm in diameter and ~5 mm in length, allows dense packaging of multiple sensors into the compact multisensory scanning head of the matrix type. The size and sensitivity of the presented eddy current sensors make them a promising candidate for application in the latest non-destructive scanning diagnostics systems.

Core-Core Dynamics in Spin Vortex Pairs

We investigate magnetic nano-pillars, in which two thin ferromagnetic nanoparticles are separated by a nanometer thin nonmagnetic spacer and can be set into stable spin vortex-pair configurations. The 16 ground states of the vortex-pair system are characterized by parallel or antiparallel chirality and parallel or antiparallel core-core alignment. We detect and differentiate these individual vortex-pair states experimentally and analyze their dynamics analytically and numerically. Of particular interest is the limit of strong core-core coupling, which we find can dominate the spin dynamics in the system. We observe that the 0.2 GHz gyrational resonance modes of the individual vortices are replaced with 2-6 GHz range collective rotational and vibrational core-core resonances in the configurations where the cores form a bound pair. These results demonstrate new opportunities in producing and manipulating spin states on the nanoscale and may prove useful for new types of ultra-dense storage devices where the information is stored as multiple vortex-core configurations

DEVELOPING A MODEL OF COOKING GRAIN BATCH

Summary. By batch cooking of grain accumulated considerable experimental and production material. However, the theory of this process has not been developed to the desired extent. It is shown that the mathematical modeling of the process of cooking the grain batch can be used as a basis for non-stationary diffusion equation and its numerical solution based on the grid method. It is shown that in addition to non-stationary diffusion process by using the grid method can take into account the temperature processes and the theory of swelling of the starch granules. The values of the activation energy of diffusion bound moisture in grains and the pre-exponential value were determined. To describe the swelling of the starch granules used solutions sufficiently numerous studies, and the selected model based on chemical reaction kinetics of the second order. Elaboration of the model of cooking done on experimental data for wheat grits, and concluded the need to address the gap of the starch granules during swelling and separation of layers of material adjacent to the liquid phase during the entire process until the complete cooking of cereal grits. An enlarged under a microscope photos edge dry and tenderized particles showing swelling of the starch granules and the isolation of the outer layer of the particle. Simultaneously taken into account in the model dynamics of temperature changes during heating and mixing the grain of cooking. The simulation results are identified according to a pilot study of cooking barley grits. Found that the developed model accurately describes the results of the pilot study. It is shown that the mathematical model based on the non-stationary diffusion equation, excluding the effects of temperature and swelling of the starch granulestheory gives too high of cooking time

Сlinical Case of Macular Hole Recurrence after Surgical Treatment with Platelet-Rich Plasma

Purpose: presentation of a clinical case of an idiopathic macular hole (IMH) recurrence after its successful closure augmented with platelet-rich plasma (PRP) and the results of repeated surgical treatment.Methods. The patient underwent clinical examination and optical coherence tomography (OCT) of the retina before and after surgical treatment. А 2-stage surgical treatment of the left eye with an interval of 7 days: phacoemulsification (PE) followed by microinvasive vitrectomy with Internal limiting membrane peeling (ILM) and closure with the use of PRP. The patient was discharged with improved visual acuity and closure of the macular hole (MH). After 2 weeks vision deterioration was noted by the patient in the operated eye. Clinical examination revealed macular edema (ME) and recurrence of MH. Topical steroid eye drops were used to no avail, with increase of ME and MH via OCT control. Revision of the vitreal cavity augmented with PRP was performed.Results. In follow-up a complete closure of the MH, resolution of ME and improvement in visual acuity after repeated surgery was confirmed.Conclusions. A case of recurrent MH after primary closure with PRP is described. The case suggests a possibility of clinical improvement after repeated MH closure augmented with PRP. The causes and mechanisms of the recurrence of MH are still not clear. Despite the positive results of surgery subsequent OCT retina examination is necessary

Influence of plasticity on the magnetic-field-induced bending deformation in a magneto-active elastomer with superparamagnetic nanoparticles

The influence of residual plastic deformation on the bending deformation of a magnetoactive elastomer (MAE) beam with non-coercive superparamagnetic manganite (La0.6Ag0.2Mn1.2O3) nanoparticles induced by a transverse uniform magnetic field has been studied. It was found that the MAE bending induced by the magnetic field switching-on/switching-off is mainly cyclic elastic. Plastic deformation leads to the emergence of residual bending and hysteresis in the field dependence of the bending. It was shown that the residual bending that appears after the first magnetic field switch-on eliminates the uncertainty of the bending direction at the next magnetization. Due to the residual plastic deformation, the bending direction of the superparamagnetic MAE with nanoparticles does not change when the direction of the applied magnetic field is inverted, in contrast to the MAE with microparticles where the uncertainty of the bending direction is eliminated due to the residual magnetization of weakly coercive ferromagnetic microparticles; therefore, the bending direction changes its sign with magnetic field reversion. In the low fields, the bending value for the MAEs with superparamagnetic particles is proportional to the square of the magnetic field strength. Model estimates on the residual deformation influence on the beam bending at beam magnetization reversal were obtained