This work presents the results of the experimental investigation of the compressive damages in the volume of angle-ply laminates with a various central ply of 0 degrees or 90 degrees fiber orientation. Layer-by-layer observation of volume microstructure damages was performed using high-frequency acoustic microscopy. The ultrasound imaging revealed the location of matrix cracking, fiber fracture and interlayer delaminations in laminates with [f45 degrees 2/ 0 degrees]S and [f45 degrees 2/90 degrees]S layup. Experimental results were supplemented numerical modeling of the development of the fracture process. According to the ultrasound imaging of the volumetric microstructure, we highlighted several typical damage in laminates and assumed the role of central ply in process of damage appearance and evolution in angle-ply laminates under compression. It was found that damage in laminates with a central 90 degrees ply was predominantly multiple small-scale delaminations, united by a mesh of matrix cracks that formed during smooth plastic deformation; while the central 0 degrees ply, on the contrary, provided rigidity of the structure, which led to the fracture of fibers and the growth of extended delaminations.

The article presents the results of computational and experimental studies of the strength and damageability of a connecting composite part in a metal-composite joint of isogrid and anisogrid structures made of polymer composite material under tension. The assessment of the minimal cross-sectional area of the connecting part was performed based on design calculations, taking into account strengthening during extrusion of the excess binder. The onset of failure in the contact zone with the steel element of the metal-composite joint was predicted based on experimental studies using model samples. A comparison was made between the calculation results for the tensile loading diagram, considering the physical nonlinear behavior of composite material in the joint zone, and the readings of strain gauges after testing the metal-composite joint. Damages and deformation of the connecting composite part under the tensile load was imaged using acoustic microscopy.

The in situ study of fractal microstructure in nanocarbon polymers is an actual task for their application and for the improvement in their functional properties. This article presents a visualization of the bulk structural features of the composites using pulsed acoustic microscopy and synchrotron X-ray microtomography. This article presents details of fractal structure formation using carbon particles of different sizes and shapes—exfoliated graphite, carbon platelets and nanotubes. Individual structural elements of the composite, i.e., conglomerations of the particles in the air capsule as well as their distribution in the composite volume, were observed at the micro- and nanoscale. We have considered the influence of particle architecture on the fractal formation and elastic properties of the composite. Acoustic and X-ray imaging results were compared to validate the carbon agglomeration.

Fracture processes in carbon fiber reinforced plastics significantly depend on the architecture of the laminate reinforcement. For ± 45° angle-ply laminates of carbon fiber reinforced plastics, mechanical loading is accompanied by pseudo-ductility. This mechanism is characterized by the nonlinear stress-strain behavior under unidirectional loads. Bending stress combines compressive and tensile stresses. A transition between them is not linear, and destruction processes in carbon fiber reinforced plastic structure having layers angled at ± 45°, are interesting and not completely understood. The paper presents the experimental results of bending damage of a laminate with stacking sequences of [(± 45°)2/0°]S and [(± 45°)2/90°]S. High-frequency acoustic microscopy is used to visualize the bending damage development. Layer-by-layer ultrasound imaging shows localization of fiber fractures, microcrack nucleation, growth and association with interlayer delamination.

The kinetics of microcracks accumulation and fracture at various stages of tension of grade 20 steel samples with coarse-grained and ultrafine-grained (UFG) structure obtained by equal-channel angular pressing (ECAP) has been studied. To research the effect of mechanical degradation, a part of the samples were subjected to preliminary cycling to a relative lifetime of 50%, followed by tensile tests, during which the parameters of acoustic emission and deformation fields obtained by digital image correlation were evaluated, and the intensity of the residual magnetic field was measured. The length and density of surface microcracks were measured by optical microscopy using computer image analysis. It is established that pre-cycling causes hardening of the material and a decrease in its plasticity. The fracture stages were revealed, and the origins of fatigue cracks were found on the internal delaminations of samples with a UFG structure after preliminary cyclic loading. It is shown that the formation of the UFG structure after the ECAP of samples made of grade 20 steel leads to hardening and reduction of the fracture work, the area of the plastic zone, maximum major deformations and damage, as well as to an increase in the number of AE signals and the intensity of the residual magnetic field.

Abstract—The influence of reinforcement with basalt fibers in an amount of 0.6 vol

In this work, new devices and tools for minimally invasive endoscopic surgery are considered, which were developed by Mechanical Engineering Research Institute of the Russian Academy of Sciences, together with the Central Clinical Hospital, Russian Academy of Sciences. Experimental samples of the devices and tools are presented.

The effect of reinforcement by basalt fiber in an amount of 0.6% (vol.) has been investigated concerning the manifestation of the size effect for concrete made from Portland cement CEM II / A-K (Sh-I) 42.5N (GOST 31108-2016). To do this, tests for a three-point bend of geometrically similar samples with the length L = 1075, 465 and 215 mm and the width D = 40, 93 and 215 mm, respectively, that had a central incision with a length a0 were carried out. For all samples conditions L / D = 5, a0 / D ≈ 0.3 were met. The mechanical properties, parameters of acoustic emission, characteristics of the local deformed state, estimated by the correlation method of digital images, the size of the destruction process zone in the top of the incision, determined using ultrasonic flaw detection, were studied. According to data of a change in the parameters of acoustic emission and the main deformations, the stages of fracture was analyzed in the top of the incision. The nominal strength decreased with an increase in the size of the sample. The influence of the size of the sample was also noted on the parameters of acoustic emission, the value of the main deformations and the size of the zone of the fracture process. It was established that the introduction of basalt fiber into concrete reduced its nominal strength, increased the energy of fracture, and reduced the size effect.

Pulsed acoustic microscopy (100–200 MHz) is used to study layers of pyrolytic graphite with a thickness of 40 μm on a glass substrate comparable to the wavelength of the probing sound. The mechanism of the natural enhancement of acoustic contrast while visualizing this type of structures is analyzed. The interpretation of images of the inhomogeneous structure of the layer-substrate contact is supported by a quantitative assessment of acoustic impedances.

The investigation of destruction processes in composite materials is a current problem for their structural application and the improvement of their functional properties. This work aimed to visualize structural changes induced in layered carbon fiber reinforced plastics (CFRP) with the help of synchrotron X-ray microtomography. This article presents the details of destructive processes in the early stages of the deformation of reinforced polymers under uniaxial stretching, investigated at the micro level. Individual structural elements of the composite–filaments, parallel fiber bundles, the nonuniformity of the polymer binder distribution, and continuity defects—were observed under an external load. We have considered the influence of the material architecture and technological defects on fracture evolution in cross-ply and quasi-isotropic fiber-reinforced plastics. The results indicate the sequence of irreversible structural changes before the destruction of the material.

В статье рассмотрены новые устройства и инструменты для малоинвазивной эндоскопической хирургии, разработанные Институтом машиноведения им. А.А. Благонравова РАН совместно с Центральной клинической больницей Российской академии наук. Представлены экспериментальные образцы устройств и инструментов.

This work presents the results of the experimental investigation of the bending damage evolution in the volume of laminate with a stacking sequence of [0 degrees /90 degrees ]4S and thickness of 4.32 mm. Damage formation under the stepby-step loading (three iterations) was detected by acoustic emission (AE) and was visualized by high-frequency acoustic microscopy. The acoustic emission method revealed the moments of the fiber breakage, formation of cracks and delaminations in the process of bending. AE activity and the energy of AE pulses were related to drops and slope of the loading curves, which corresponded to the damage in the composite volume. The layer-by-layer ultrasound imaging revealed the location of matrix cracking, fiber fracture and interlayer delaminations. We presented the scheme of the step-by-step damage development in the laminate volume, based on experimental data.

The kinetics of damage accumulation in a D16ch sheet aluminum alloy (Al–Cu–Mg system) at various stages of static loading is investigated using a combined technique, which includes the detection of acoustic emission (AE) signals, structural studies, and the determination of electrical resistance and an eddy-current parameter. The dependences of these characteristics on the relative strain demonstrate the presence of four stages of specimen fracture. Correlation exponential dependences of the electrical resistance and the eddy-current parameter on damage are obtained, and they can be used to diagnose the state of the material.

The fracture toughness which reflects change in the elastic deformation energy of the structural element with an increase in the crack area per unit at the onset of straining is one of the crack resistance parameters of carbon fiber plastics (CFRPs). When studying the fracture toughness, the position of the crack front is determined: both the initial one and that obtained as a result of crack growth. Currently existing test standards (STO TsAGI, ASTM D7905) determine the viscosity by the shear mode GIIc using the samples with a crack initiator. However, the method does not reflect the real conditions of crack initiation in CFRPs structures and can lead to a decrease in the accuracy of determining the load of crack initiation. A new technique of the fracture viscosity determination free of the standard delamination initiator has been developed in TsAGI. We present the results of developing the proposed methodology. The GIIc values were determined for a shear crack under three-point bending conditions after wedging. To determine the position and shape of the crack front, as well as to assess the dynamics of its propagation under subsequent loads, we used ultrasonic methods — ultrasonic flaw detection (ultrasonic NDT) and acoustic microscopy instead of the standard visual observation of the crack boundaries from the end surface of the samples. It is shown that acoustic microscopy at a frequency of 50 MHz provides determination of the crack front position in CFRP samples at a depth of 3.0 – 3.5 mm with a high resolution about 100 μm. The features of the crack growth under shear conditions are discussed. The results of the study show that high accuracy of acoustic microscopy in comparison with traditional ultrasonic NDT diagnostics is strongly sought for determining the shape of the cracks, as well as for analyzing the dynamics of crack growth and revealing the mechanisms of interlayer crack propagation in a composite material.

The mechanical and physical properties of X70 pipeline steels produced in France and Japan are comprehensively studied using tensile and impact bending tests, analysis of the fracture reliefs of specimens, and the estimation of acoustic emission parameters, the attenuation coefficient of longitudinal ultrasonic waves, and the residual magnetic field intensity. A correlation between the mechanical and physical characteristics during tensile tests is revealed. After long-term operation, the yield strength and the ultimate tensile strength are shown to decrease and the plasticity and impact characteristics are shown to increase in comparison with the initial values from pipelines sertificates for both studied steels. The predominant mechanism of these changes is associated with the presence of a large number of delaminations, which cause fracture energy dissipation and hide the true picture of changes in the estimated strength characteristics.

In the work, the first results of in situ ultrasound observation of microstructure changes in the volume of carbon fiber reinforced composites under tension are presented. The results depict the mechanical behavior of the laminate with stacking sequences of [−45°/0°/+45°/90°/+45°/0°/−45°]. Ultrasound visualization of volume microstructure is carried out with a controlled stepwise increase in deformation of the loaded specimens. Data of ultrasound investigation are compared with optical microphotograph and strain–stress curves of controlled and tested specimens. This approach makes it possible to visualize in dynamics the processes of appearance, growth, and transformation of microstructural damages in the volume with a resolution of tenth microns.

The problem of eye pathologies, such as age-related macular dystrophy and children's myopia, is becoming increasingly relevant every year. The influence of the spectral composition of artificial lighting that accompanies a person from birth to maturity is becoming more noticeable. To identify this pattern, experimental studies are carried out using an effective animal model: the Japanese quail Coturnix japonica, whose domesticated population is widely used as a laboratory animal in ophthalmology and biomedical disciplines. To reveal the difference in the development of eye tissues under everyday light with different spectral characteristics, chicks and adult birds are studied. Optical coherence tomography is used to observe the structure of the anterior part of the eye, as well as the thickness and structure of the retinal-choroidal complex. Data on age-related changes in the eyeball, cornea, anterior chamber, lens, vitreous body, chorioretinal complex, and sclera are obtained using ultrasound methods. The content of melatonin in the tissues of the eye is measured.

Pulsed acoustic microscopy in the 50–100 MHz range is used to study the effect mechanical treatment has on the bulk structure of carbon fiber reinforced plastic composites (CFRPs). Acoustic images of composite samples reveal areas of interlayer damage more than 50 × 50 μm in size near the edge of a hole. Acoustic visualization allows estimation of the size, nature, and location of defects.