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Agglomerations of oxide films are some of the typical defects of friction stir welding. The structure of such defects and their small opening do not allow finding them using the conventional ultrasonic nondestructive testing methods (in particular, by the pulse-echo technique), among other things because of their low reflectivity. We have proposed a technique of artificial introduction of oxide films into a welded joint. We have shown that, to reveal such defects, it is promising to use the diffraction methods of ultrasonic nondestructive testing. The diffraction methods make it possible to detect signals from defects with minimum opening as well as from defects with a partially metallic bonding, which are semitransparent to ultrasonic waves and revealing of which is impossible using other methods of ultrasonic testing, in particular, the pulse-echo technique, along with X-ray testing.

A model is developed to describe the refraction of an elastic transverse wave by an immersed concave cylindrical surface. The wave may be incident on the liquid surface at any angle. Immersional monitoring of a small-diameter pipeline is considered.

The behavior of Al2O3 ceramics having a 50% volume of pore space under compression is studied. The porous structure includes three types of pores: large porosity with an average size of 120 μm, small porosity with an average size of 2 μm, and extended porous channels (about 150 μm) formed as a result of zonal separation during sintering. It is shown that at a load of ceramics with such a multilevel pore structure, the microdamage accumulates over the entire volume of the sample. It causes decreasing the scale level of fracture from microscopic (in the case of ceramics with unimodal pore structure) to meso- and microscale (for ceramics with a multilevel pore structure). Residual deformation in such material appears at small loads of about 0.3σc due to displacements of blocks and their groups during deformation before the ultimate strength.

The evolution of the manifestation of levels of defects in h-BN in tunneling through graphene/h-BN/graphene heterostructures with various degrees of perfection, from completely defectless to those with several tens of levels in the band gap of h-BN, has been studied. It has been shown that the behavior of these levels is related to the motion of Dirac points and the chemical potentials of graphene layers at change in the bias and gate voltages, which is described by the electrostatic model of an ideal defectless heterostructure. The density of states of graphene in a magnetic field has been studied by its probing by the level of a single defect with a sensitivity allowing the detection of splitting of the zeroth Landau level caused by the lifting of the spin and valley degeneracy already at B ∼ 4 T.

According to powder X-ray diffraction data, the crystal structures of compounds SrLnCuS3 (Ln = Er, Yb) have been refined by minimizing the derivative difference in the anisotropic approximation for all atoms. Crystals are orthorhombic, space group Cmcm, structure type KZrCuS3: a = 3.93128(3) A, b = 12.9709(1) A, c = 10.1161(1) A, V = 515.843(9) A3, ρcalc = 5.337 g/cm3, Z = 4, RDDM = 3.73%, RF = 2.06% (SrErCuS3); a = 3.91448(4) A, b = 12.9554(1) A, c = 10.0332(1) A, V = 508.842(8) A3, ρcalc = 5.487 g/cm3, Z = 4, RDDM = 3.56%, RF = 1.48% (SrYbCuS3). The structure of SrLnCuS3 is described by [LnCuS3] twodimensional layers formed by distorted CuS4 tetrahedra and LnS6 octahedra with Sr2+ ions residing between the layers. The compounds are transparent for IR radiation in the range 3200–1800 cm–1.

The influence of tungsten carbide and titanium nitride nanoparticles on the structure and properties of the weld metal of welded joints made by automatic twin submerged arc welding is considered. The nanoparticles have been introduced into the weld pool as a part of the “master alloy” based on nickel powder (PNE-1 according to GOST 9722). It has been shown that modifying the weld metal with tungsten carbide nanoparticles holds promise for enhancing the impact strength. In addition, it has been found that titanium nitride is prone to dissociation under the same conditions. However, microalloying with titanium, which is due to the release of titanium from the nitride, leads to an increase in the impact strength of the weld metal.

Results of the tomographic inspection of a prototype sample additive manufactured by selective laser alloying have been evaluated. Specific features of revealing “incomplete fusion” flaws and the influence of various parameters of inspection on its results are considered.

The possibilities and limitations of applying head and surface waves to ultrasonic inspection of articles manufactured by selective laser alloying are considered. The optimum angles have been determined for the generation of head and surface waves in a product made of the domestic EP648 powder. The peculiarities of revealing crack-like flaws by the ultrasonic echo method are demonstrated.

Advances in nanotechnology have made it possible to use nanosized particles for the modification of metals and alloys both in metallurgy and in welding. This article discusses the thermodynamic stability of titanium nitride nanosized particles in a molten pool on the basis of theoretical analysis and experiments. It is demonstrated that, upon the addition of titanium nitride to a molten pool, its dissociation should be expected in the overall temperature range; this has been confirmed experimentally.

The compaction behavior is studied in Al2O3 ceramics with a pore space volume in the range from 35 to 60% and with the following three types of hierarchical pore structure: coarse porosity with a size of 80 to 100 μm, fine porosity with a size of 14 to 15 μm, and intermediate interblock porosity comprised of elongated (110–120 μm) porous microchannels formed as a result of zonal isolation during sintering. It is shown that the obtained hierarchical porous structure causes the formation of a hierarchical deformation structure in the volume of ceramics and leads to a decrease in the extent of destruction processes from the macroscopic scale in the case of unimodal ceramics to the microscale destruction comparable with the sizes of the blocks formed during sintering.

Results of ultrasonic testing of parts that are fabricated by selective laser melting are assessed using radiography and X-ray computed tomography. Peculiarities of revealing incompletefusion flaws with the above methods are considered.

Possibilities, application domains, advantages, and limitations are considered for currently used physical methods of nondestructive testing of additive manufactured parts. The methods are classified according to the physical principle of operation.

The results of studies on determining the nucleation moment of microcracks in fiberglass are presented on the basis of a full-strength glassfiber mat and vinyl ether binder by the acoustic emission method in uniaxial tension. The research was carried out by continuous monotonic loading of samples under uniaxial tension until failure with simultaneous recording of the parameters of acoustic emission signal. Qualitative dependences of the parameters of acoustic emission signals on the stress value in the sample are revealed. It is found that, at a stress value of about 40% of the ultimate strength of material (about 420 MPa), microfracture processes—cracking of the polymer matrix—begin.

Peculiarities of additive technologies are considered, and the most typical flaws are listed. The possibility of layer-by-layer nondestructive testing of parts immediately in the course of additive manufacturing is demonstrated. Based on the review of domestic and international publications, possibilities that are offered by various physical methods of nondestructive evaluation are analyzed and potential of their usage is reviewed.

The contrast of extended defects representing dislocations and grain boundaries has been calculated for the X-ray-beam-induced current (XBIC) method. It is established that the maximum contrast increases with the diffusion length of excess charge and decreases with increasing X-ray beam width. The simulated XBIC profile contrasts are compared to experimentally measured patterns.

A high narrow peak in the interlayer differential tunnel conductance has been observed in heterostructures with two closely located electron layers at low temperatures. Analysis of the experimental results suggests that this peak is due to the interlayer phase coherence, which appears in the system under investigation owing to the Bose condensation of indirect excitons, i.e., pairs of electrons and holes from different layers in the absence of the magnetic field.

A long adaptation of Microsporidia to intracellular development supposes the host-derived ATP dependence of merogony and sporogony stages. To prove this assumption the activities of ten carbohydrate and energy metabolism enzymes were compared in the microsporidia Nosema grylli intracellular stages and mature spores. This species infects the fat body of crickets Gryllus bimaculatus. We have demonstrated lower activities of glycolytic enzymes, phosphoglucomutase and glucose-6-PhDH in the metabolically active meronts and sporonts than in the dormant mature spores. Low glycolysis level indicates that carbohydrate catabolism is not a principal mechanism of ATP supply in the N. grylli intracellular stages. Furthermore, we have not revealed a preferable expenditure of glycogen in comparison with triglycerides in infected cricket fat bodies. The N. grylli infection causes an equal reduction of glycogen and lipid content approximately in 2-3 times. Microsporidia have not mitochondria, Krebs cycle and electron-transport chain. Therefore they are not able to utilise fat reserves for ATP production. It seems to be proposed that microsporidia consume exogenous ATP which is produced by host cell metabolic system. The N. grylli infection provokes an increase of ATP content and ratio of ATP/ADP concentrations in cricket fat bodies approximately in 4 times. These data indicates a rise of host cell energy metabolism rate during the infection.

The Waldman e. a. (1986) method of separation of Cryptosporidium spp. oocysts from feces by using a percoll discontinuous density gradient appeared a method of choice for obtaining large numbers of oocysts of C. parvum free of fecal contamination. Feces of 7-12 day old calves, spontaneously infected with C. parvum, were concentrated and purified by the above technique. The purified oocysts were shown to be infectious by inoculation of 6-9 day old rats with an average dose of 20,000 oocysts per animal. The rats shed oocysts after 4 days. At necropsy on day 4 postinoculation, the pattern of endogenous development appeared normal, when examined on frozen sections of fresh tissue, using the Bright cryostat, stained with hematoxylin and eosin. Samples of the clean sediment, presumably containing only oocysts of C. parvum, were smeared and stained with carbol fuchsin after Ziehl-Neelsen, and with gentian violet after Sidorenko (1988). With the latter technique, an intense gentian violet staining screened all the constituents of the smear, except the oocysts, which being "negatively stained" looked as small transparent spheres 4-5 mkm in diameter. But of special interest was the reaction of the smeared organisms with carbol fuchsin. Some organisms stained dark red and had a variable number of dark granules, seemingly on the surface; whereas others stained light reddish, if at all, and appeared as transparent spheres. It does not seem unlikely that the sediment, resulting from the final step of percoll separation, may contain, besides oocysts, some other endogenous stages (meronts, gamonts, thin-walled oocysts) that appeared in the lumen of the intestine because of an intense flow of diarrheal fluid during cryptosporidiosis. Unlike the thick walled oocysts, other endogenous stages are not covered with protective walls and thus fail to absorb acid fast staining. Segmented meronts were obviously observed on the rat fecal smears 96 hours after infection. This observation enables us to propose that newly infected hosts-recipients may obtain, with diarrheal fecal masses of infected donors, not only sporulated oocysts, but also some earlier developmental stages. Merozoites, released from the segmented meronts, could start in the intestine asexual rounds, thus shortening the resulting prepatent period. Fluctuations in prepatent period duration are characteristic of Cryptosporidium spp., and the above observation may be one of its explanations.