bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of normal metal-superconductor interface on the statistics of conductance and shot noise power in a non-ideal chaotic quantum dot
Authors: Duarte-Filho Gerson C , Almeida Francisco A G
Published: January 2021

In this paper, we apply Andreev’s reflection to study the sub-gap coherent transport properties for a quantum dot attached to normal metal and superconductor reservoirs via non-ideal leads. We use the random matrix theory to obtain numerically the conductance and shot noise power probability densities varying the transparencies and the number of open scattering channels in each lead for the three Wigner–Dyson ensembles. We obtain results from the extreme quantum limit (where the conductance is of the order of 2e
2/h, the quantum of conductance) to the semiclassical regime (conductance much larger than 2e
2/h). We observe the appearance of non-analyticities in these probability densities and an interesting invariance break under the operation of exchanging the lead labels when time-reversal symmetry is absent.
Radiative MHD unsteady Casson fluid flow with heat source/sink through a vertical channel suspended in porous medium subject to generalized boundary conditions
Authors: Asifa  , Kumam Poom , Shah Zahir , Watthayu Wiboonsak , Anwar Talha
Published: January 2021

Unsteady, incompressible flow of Casson fluid between two infinitely long upward heated walls nested in a porous medium is analyzed in this work. The mass diffusion and heat transfer phenomena are also studied in the presence of thermal radiation, magnetic field, and heat source/sink. The generalized boundary conditions in terms of continuous time-dependent functions are considered for mass, energy, and momentum fields. Fick’s law, Fourier’s law, and momentum conservation principle are adopted to formulate the mathematical equations. Analytic solution for the concentration equation is established first by adding certain unit-less quantities and then by using the Laplace method of transformation. Semi-analytic solutions are calculated by means of Stehfest’s numerical Laplace inversion algorithm for energy and velocity equations. To demonstrate the verification of those solutions, a tabular comparison is drawn. Graphical illustrations along with physical descriptions are provided to discuss the essential contribution of thermo-physical parameters in heat and mass transfer and flow of the Casson fluid. The numerical computations of Sherwood number, Nusselt number, and skin friction for various inputs of related parameters are organized in tables to investigate mass transfer rate, heat transfer rate, and shear stress respectively. It is observed that porosity of the medium and buoyancy force tend to accelerate the flow. The heat and mass transfer rates are appreciated by Prandtl and Schmidt numbers respectively. Furthermore, radiation parameter and Grashof number significantly minimize the shear stress.
Kalman filter based demodulation in a dual-pulse phase-OTDR
Authors: Alekseev A E , Gorshkov B G , Bashaev A V , Potapov V T , Taranov M A , Simikin D E
Published: January 2021

In the present paper, we propose an approach based on the Kalman filter for demodulation in a dual-pulse phase-OTDR. Although the Kalman filter is well-developed and widely used method for the state estimation of a dynamic system, its use for demodulation in a phase-OTDR is proposed for the first time, to our best knowledge. Two main algorithms are considered and described in detail: the extended Kalman filter (EKF) and the unscented Kalman filter (UKF), the first one is fast and simple, but the second one is more accurate. A qualitative comparison of these algorithms with the differentiate and cross-multiply (DCM) algorithm is performed. The efficiency of the EKF and the UKF algorithms is experimentally verified.
Nonequilibrium free energy and information flow of a double quantum-dot system with Coulomb coupling*
Authors: Lin Zhiyuan , Fu Tong , Xiao Juying , Su Shanhe , Chen Jincan , Zhang Yanchao
Published: January 2021

We build a double quantum-dot system with Coulomb coupling and aim at studying connections among the entropy production, free energy, and information flow. By utilizing concepts in stochastic thermodynamics and graph theory analysis, Clausius and nonequilibrium free energy inequalities are built to interpret local second law of thermodynamics for subsystems. A fundamental set of cycle fluxes and affinities is identified to decompose two inequalities by using Schnakenberg’s network theory. Results show that the thermodynamic irreversibility has energy-related and information-related contributions. A global cycle associated with the feedback-induced information flow would pump electrons against the bias voltage, which implements a Maxwell demon.
Dynamics of k-essence in loop quantum cosmology *
Authors: Shi Jiali , Wu Jian-Pin
Published: January 2021

In this paper, we study the dynamics of k-essence in loop quantum cosmology (LQC). The study indicates that the loop quantum gravity (LQG) effect plays a key role only in the early epoch of the universe and is diluted in the later stages. The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker (FRW) cosmology. For most of the attractor solutions, the stability conditions in LQC are in agreement with those for the standard FRW universe. For some special fixed points, however, tighter constraints are imposed thanks to the LQG effect.
Study properties of Eigenvalues, Eigenvectors and Eigenspace of matrices by using MatLab
Authors: Abbas Muntaha Khudair
Published: January 2021

The aim of this paper is to study the properties of eigenvalues with types (real, Repeated, complex) of matrices (2x2), (3x3), (4x4), eigenvectors and eigenspace of matrices by using Matlab. It also investigates the left and right eigenvectors, characteristic equation, existence and multiplicity of eigenvalues, gives some examples about the computation of eigenvalues, eigenvectors, and solves the Dynamic Systems of First Order Linear Differential Equations of (2 dim and 3 dim) as well as the Numerical solution to Dynamic systems by using program Matlab.
Influence of the limited room space on inlet conditions and fan operation at the rotating test rig
Authors: Sieradzki A , Łukasik B
Published: January 2021

The limited space of the laboratory room allows maintaining the selected ambient air parameters in the required ranges. It can be, however, a source of many problems in the case of rotating test rigs that blow a large amount of air. The aim of the paper is to examine the influence of limited space and its shape on the working conditions of axial fans test stand. The focus was particularly on the conditions prevailing at the inlet to the test rig and their potential impact on the tested fan operation. The article presents the results of CFD simulations for two rooms of different volumes and the results of experimental measurements carried out for the smaller one. Good qualitative agreement between the simulations and the experiment was obtained. The limited space around the test rig causes the unsteadiness of the axial velocity profile and introduces an unsteady swirl at the inlet. This leads, in turn, to local changes in the angle of attack of the fan blades and the resulting consequences related to the off-design working conditions. The paper proves the need to minimise the effects of the induced airflow in the test room and proposes some methods to accomplish this task.
Hydrodynamic advantages of in-line schooling
Authors: Saadat Mehdi , Berlinger Florian , Sheshmani Artan , Nagpal Radhika , Lauder George V , Haj-Hariri Hossein
Published: January 2021

Fish benefit energetically when swimming in groups, which is reflected in lower tail-beat frequencies for maintaining a given speed. Recent studies further show that fish save the most energy when swimming behind their neighbor such that both the leader and the follower benefit. However, the mechanisms underlying such hydrodynamic advantages have thus far not been established conclusively. The long-standing drafting hypothesis—reduction of drag forces by judicious positioning in regions of reduced oncoming flow–fails to explain advantages of in-line schooling described in this work. We present an alternate hypothesis for the hydrodynamic benefits of in-line swimming based on enhancement of propulsive thrust. Specifically, we show that an idealized school consisting of in-line pitching foils gains hydrodynamic benefits via two mechanisms that are rooted in the undulatory jet leaving the leading foil and impinging on the trailing foil: (i) leading-edge suction on the trailer foil, and (ii) added-mass push on the leader foil. Our results demonstrate that the savings in power can reach as high as 70% for a school swimming in a compact arrangement. Informed by these findings, we designed a modification of the tail propulsor that yielded power savings of up to 56% in a self-propelled autonomous swimming robot. Our findings provide insights into hydrodynamic advantages of fish schooling, and also enable bioinspired designs for significantly more efficient propulsion systems that can harvest some of their energy left in the flow.
The land use legacy effect: looking back to see a path forward to improve management
Authors: Martin Sherry L , Hamlin Quercus F , Kendall Anthony D , Wan Luwen , Hyndman David W
Published: January 2021

Water quality has suffered as humans have increased nutrient inputs across the landscape. In many cases, management actions to reduce nutrient inputs have not been met with concomitant ecosystem responses. These missed expectations are partly due to the continued slow delivery of nutrient-enriched groundwater pre-dating input reductions resulting from management actions. Land use legacies as expressed through this time lag are important to quantify in order to adjust management expectations. We present a novel coupling of nitrogen source maps with groundwater transport times to create a high-resolution (120 m) fully distributed estimate of the timing and magnitude of groundwater nitrogen deliveries to surface water across Michigan’s Lower Peninsula. This new view of the landscape has been designed around common management timelines for: elected officials looking to make a difference for re-election (<5 years), career managers hoping to see the fruits of their labor (5–30 years), and advocacy groups whose work can span generations (>30 years). One striking result is that after 100 years, in our study area, approximately 50% of the nitrogen that enters the groundwater system remains in transit. This means that actions taken now may not show the expected lower nitrogen loads to receiving ecosystems for decades to centuries. We show that differences in groundwater travel times create a heterogeneous patchwork over which managers can prioritize actions to best match their targeted response times. Across the highest nitrogen inputs in our study region, less than 10% had short enough groundwater legacies to match the management timeline of most government and agency work. Agricultural practices (manure and chemical fertilizer) are the main nitrogen contributors across the top three management classes; however, human contributions through septic tank effluent and lawn fertilizers contribute 5%–8% of nitrogen.
‘Fair’ inequality, consumption and climate mitigation
Authors: Millward-Hopkins Joel , Oswald Yannick
Published: January 2021

Economic inequality and climate change are pressing issues that have climbed high up the political agenda, yet action to mitigate both remains slow. As income is a key determinant of ecological impacts, the Global North—and wealthier classes elsewhere—are the primary drivers of global carbon emissions, while the least well off have contributed the least yet are set to be hit hardest by climate impacts. These inequalities are clearly unjust, but the interrelations between economic inequality and ecological impacts are complex, leaving open the question of whether reducing the former would mitigate the latter, in the absence of reductions in total economic output. Here, we contribute to these debates by estimating the carbon-footprint implications of reducing income (and hence expenditure) inequalities within 32 countries of the Global North to the levels people consider to befair; levels that are substantially smaller than currently exist. We find that realising these levels of economic inequality brings comparable reductions in carbon-footprint inequalities. However, in isolation, implementingfairinequalities has a negligible impact upon total emissions. In contrast, recomposing consumption—by reducing inequalities in household expenditure and the overall levels, then reallocating the reductions to public services—reduces carbon footprint by up to 30% in individual countries and 16% overall and, crucially, still allows the consumption of those at the bottom to rise. Such reductions could be significant on a global level, and they would be additional to the full range of conventional technological and demand-side measures to reduce carbon emissions.
Simulation of heat transfer processes in a diesel engine equipped with pistons coated by using Galvanic-plasma Method
Authors: Al-Bdeiri M S , Krasilnikov V V , Sergeyev S V
Published: January 2021

The methodology for analyzing the thermodynamics and heat transfer of the combustion chambers of a diesel engine is presented. The work is devoted to the modified quasi-steady method (MQM) for the analysis of a diesel engine piston coated with an aluminum alloy. The oxide-coated piston using a galvanic-plasma modification (GPM) depending on the thickness of the coating, including comparison with the results for uncoated piston temperature, to achieve higher characteristics of the Cummins KTA-50 diesel engine. In thermodynamic modeling of a diesel engine, instantaneous gas temperatures and convective heat exchanges are first predicted. The time-dependent boundary conditions are then applied to the gas-blown surfaces of two-dimensional, transitional finite element models of the components of the combustion chamber. Further, the predictions on the finite elements of the instantaneous heat flux passing through each surface of the component are used to determine when the engine goes into quasi-stationary operation. The results show that our path in methodology can identify the complex transition paths of the heat process in the engine combustion chamber and significantly improve heat conduction and convection heat models when modeling a diesel engine.
A new combined SPD technique to improve mechanical properties and electrical conductivity of long-sized billets
Authors: Bobruk E V , Botkin A V , Murashkin M Yu , Raab G I
Published: January 2021

As a result of computer simulation carried out using the DEFORM 3D software package, the influence of the shape of the extrusion die-set, combined with equal-channel angular pressing with parallel channels (ECAP-PC), on the stress-strain state of cylindrical billets of an aluminum alloy was established. The obtained data made it possible to manufacture an experimental die-set for extrusion, combined with ECAP-PC, and to produce in it a cylindrical long-sized UFG billet from the 6063 alloy. It was established that one cycle of direct extrusion combined with ECAP-PC in the matrix with a non-axisymmetric deforming section for direct extrusion leads to a significant microstructure refinement and an improvement of mechanical properties of the alloy.
Portevin-Le Chatelier effect in austenitic steel Fe-18%Cr-8%Ni
Authors: Borisova Yu , Yuzbekova D , Mogucheva A
Published: January 2021

The study of the mechanical behavior of the austenitic Fe-18% Cr-8% Ni steel was carried out in the temperature range of 530°C - 680°C at a strain rate of 1×10−3 s−1, as well as at a temperature of 620°C and strain rates of 1×10−2 s−1 - 1×10−4 s−1. At these conditions, the PLC effect was observed. Type A serrations were observed in the temperature range 530 - 680°C. A decrease in the strain rate at a temperature of 620°C leads to a change in the type of serrations from type A to type B.
Influence of ECAP on the structure and properties of Ti18Zr15Nb and Ti10Mo8Nb6Zr alloys for medical application
Authors: Churakova A A , Gunderov D V , Raab G I , Prokoshkin S D , Sheremetyev V A , Filho Paulo N Lisboa , Pedro João , Claro Ana Paula Rosifini Alves
Published: January 2021

Studies of the influence of ECAP on the structure and properties of the metastable β-Ti alloys Ti18Zr15Nb and Ti10Mo8Nb6Zr have been carried out. The XRD data shows that the BCC β is the main phase in the initial alloys and alloys after ECAP. As a result of ECAP, the strength and yield stress of the alloys increases significantly due to the refinement of the structure. After ECAP, UTS and YS of the Ti10Mb8Nb8Zr alloy increase more noticeably than the Ti18Zr15Nb alloy, but after 7 ECAP cycles according to the regimes used (n = 6 T 250 °C + n = 1 350 °C), the Ti10Mb8Nb8Zr alloy becomes brittle. The increment in the yield point of the Ti18Zr15Nb alloy after ECAP processing together with the preservation of the β-state, allows one to expect an increase in the functional properties of the alloy.
Effect of thermomechanical treatment on the microstructure and mechanical properties of a low-carbon low-alloy steel
Authors: Dolzhenko A S , Belyakov A N , Kaibyshev R O
Published: January 2021

The effect of thermomechanical treatment on the microstructure, tensile strength and impact toughness of low-carbon low-alloy steel is considered. The developed microstructure is characterized by grain elongation along the rolling direction. Both the yield strength and the ultimate tensile strength increase with a decrease in test temperature. The ultimate strength at room temperature is 797 MPa, and at 77 K the ultimate strength increases to 1198 MPa. The steel samples subjected to tempforming exhibit impact toughness of KCV = 410 J/cm2 at room temperature. A decrease in the test temperature to 233 K leads to a slight decrease in the KCV value to 340 J/cm2. It should be noted that the impact specimens are not completely fractured even at a test temperature of 233 K, suggesting higher real values of impact toughness.
Evolution of strengthening factors during long-term aging at 650 °C in advanced 10% Cr heat-resistant steel
Authors: Dudova N , Mishnev R , Kaibyshev R
Published: January 2021

The effect of long-term aging for 1000…∼40,000 h at 650 °C on the tensile strength at ambient temperature was studied in a low-nitrogen and high-boron 10%Cr martensitic steel. In order to establish the reason for increasing the yield stress and ultimate tensile strength after 10,000 h of aging, the evolution of strengthening factors was analyzed. A decrease in the substructure and solid solution strengthening during long-term aging is compensated by an increase in the dispersion strengthening due to the precipitation of V-rich MX carbonitrides.
Evolution of the tempered lath structure of the 12%Cr steels with low N and high B contents during creep
Authors: Fedoseeva A E , Nikitin I S , Fedoseev A E , Kaibyshev R O
Published: January 2021

9-12%Cr martensitic steels are promising materials for elements of boilers, tubes, pipes, heaters and steam blades for fossil power plants, which are able to operate at ultra-supercritical parameters of steam. Creep tests were carried out for two 12%Cr and 9%Cr steels at 650°C. After tempering at 750-770°C, a tempered lath structure was revealed in all the steels studied. The 12%Cr-Ta steel had the smallest lath width among the steels studied that provided the longest creep rupture time after creep test at 650°C/120 MPa. During creep, the applied stress causes the lath growth and the formation of subgrains instead of martensitic laths. The experimental sizes of subgrains and equilibrium subgrains, calculated on balance of driving and retarding forces and using the dependence of the size of subgrains on the applied stress during creep, were compared to estimate the contributions of secondary particles and applied stress to the growth of subgrains during tempering and creep in the different steels.
B2 precipitates formation in Al-containing CoCrFeMnNi-type high entropy alloy
Authors: Klimova M , Shaysultanov D , Semenyuk A , Zherebtsov S , Salishchev G , Stepanov N
Published: January 2021

The non-equiatomic Al7.5Co21.75Cr5.5Fe21.75Mn21.75Ni21.75 high entropy alloy was studied. After cold rolling and annealing at 700-900 °C, a dual-phase ultrafine-grained structure composed of the partially recrystallized fcc matrix and B2 particles was produced; complete recrystallization of the fcc phase was observed after annealing at 1000 °C. The B2 precipitates formation provided a significant strengthening of the alloy in comparison with the single-phase state. The alloy demonstrated an attractive combination of mechanical properties, presenting yield and ultimate tensile strengths of 900 MPa and 1200 MPa, respectively, along with a ductility of 22%.
Development of n-body interatomic potentials for calculating the thermodynamic characteristics of V-Nb-Mo-W alloys
Authors: Maksimenko V N , Lipnitskii A G
Published: January 2021

New interatomic potentials for Mo and binary systems V-Nb, V-Mo, Nb-Mo, Nb-W and Mo-W are constructed taking into account the angular dependencies of interatomic interactions. Together with the potentials constructed earlier in the same approach, a complete set of potentials for modeling alloys of the V-Nb-Mo-W system at any component concentrations is obtained. A tendency to narrow the range of values of the calculated enthalpy of formation and the volume of formation in equiatomic alloys of the V-Nb-Mo-W system with an increase in the number of components was found. Deviations from the Vegard’s rule in the volume of formation of these alloys are shifted to the negative range of values when the number of components is more than two.
Modelling of the Rolling Process of Titanium Alloy Tube Billets in Laboratory Conditions on a RSP 14-40 Rolling Mill
Authors: Martynov K G , Negodin D A , Klimenko D N , Gladkov Yu A , Zherebtsov S V
Published: January 2021

The development of screw rolling technology for the production of hot-deformed tubes over Ø250 mm on a SVP-500 rolling mill faces a number of challenges that influence the quality of tubes, such as: the screw trace formed on the external surface of tubes and bending of tubes that makes impossible subsequent manufacturing operations. The following experimental and laboratory research was performed to solve these problems: a number of experimental tube billets with and without mandrels were rolled to various strains on a RSP 14-40 laboratory rolling mill to obtain the best ratio of wall thickness to the external diameter. The temperature field distribution and the strain intensity in the deformation area of tube billets rolling were analyzed. A quality assessment of the influence of the section of the calibrating rolls used in industrial technology on the external surface of hot-deformed tubes was also carried out at the modeling stage. The angle changing options of the calibrating rollers section of the screw rolling mill were analyzed for the subsequent tool improvement.
Investigation of an early stage of the abnormal grain growth in the friction-stir welded 6061-T6 aluminum alloy
Authors: Vysotskiy I , Malopheyev S , Mironov S
Published: January 2021

In this work, quasi in-situ electron backscatter diffraction (EBSD) was applied to study an early stage of the abnormal grain growth occurring in the friction-stir welded 6061 aluminium alloy during post-weld solution heat treatment. It was found that the catastrophic grain growth completed during the heating stage of the annealing treatment, and further static storage at the solutionsizing temperature provided almost no microstructural changes.
On the local variation of mechanical properties in friction-stir welded 6061 aluminum alloy
Authors: Kalinenko A , Kim K , Vysotskiy I , Malopheyev S , Mironov S
Published: January 2021

In this work, digital image correlation technique was applied to investigate local variations of mechanical properties in friction-stir welded 6061 aluminium alloy. A pronounced strain concentration in the bottom section of stir zone was revealed during transverse tensile tests. This effect was suggested to be associated with residual stress generated in this microstructural region during friction-stir welding.
Effect of tempering temperature on the microstructure and creep resistance of a 10%Cr martensitic steel
Authors: Mishnev R V , Dudova N R , Kaibyshev R O
Published: January 2021

The tempered martensite lath structure of a 10% Cr martensitic steel after normalizing and tempering at 750 °C was studied. The effect of reducing the tempering temperature from 770 by 20 °C on the microstructural parameters in steel was shown. Tempering at a lower temperature of 750 °C provides thinner laths and finer M23C6 particles (55 nm) than tempering at 770 °C. Such structural changes do not affect the creep rupture time at 650 °C and applied stresses of 180 and 160 MPa, whereas the positive effect occurs at 140 MPa, the time to rupture increases by more than two times from 1426 to 3909 hours.
Microstructure of a low alloyed Cu-Cr-Zr alloy after ECAP-Conform
Authors: Morozova A , Lugovskaya A , Pilipenko A , Tkachev M , Raab G , Belyakov A , Kaibyshev R
Published: January 2021

The microstructure of a Cu-0.1%Cr-0.1%Zr alloy after annealing or aging and equal channel angular pressing with conform (ECAP-C) process was investigated. ECAP-C led to formation of strain induced low-angle boundaries (LAB) which transformed in high-angle boundaries (HAB) during deformation. Deformation microbands developed after 1 ECAP-C pass, leading to new ultrafine grain formation in the microbands upon further processing. Average grain size gradually decreased with strain while dislocation density increased. After 8 ECAP-C passes average grain size achieved 1 μm. Maximum of LAB density occurred after 4 ECAP passes and then LAB density decreased with strain while HAB density gradually increased during ECAP-C. Relationships between dislocation density, grain size, and density of crystallite boundaries were discussed.
Effect of the deformation temperature on the deformation behavior of a Cu-Cr-Zr alloy
Authors: Morozova A , Tkachev M , Pilipenko A , Lugovskaya A , Belyakov A , Kaibyshev R
Published: January 2021

The mechanical properties and deformation behavior of a Cu-Cr-Zr alloy after solution treatment (ST) or aging (ST+AT) and equal channel angular pressing (ECAP) at elevated temperature were investigated. ECAP at elevated temperature led to strengthening and degradation of plasticity compared with the initial state. The deformation behavior of the alloy after 1 and 2 ECAP passes at 200 °C was almost the same. An increase in ECAP temperature promoted uniform strain and plasticity. An increase in the number of ECAP led to a gradual increase in strength. YS and UTS in ST+AT condition were higher than in ST samples regardless of the ECAP temperature and the number of passes. The maximum values of YS and UTS were obtained after 4 ECAP passes at 400 °C and achieved 525 MPa and 600 MPa in ST and 570 MPa and 650 MPa in ST+AT condition, respectively. The effect of deformation strain and ECAP temperature on work hardening rate and recovery were discussed in terms of the Voce equitation.
Studying the Impact of Blast Treatment on the Structure and Mechanical Properties of Carbon Steel
Authors: Nagicheva G S , Nokhrin A V , Berendeev N N , Melekhin N V , Piskunov A V , Sysoev A N , Gryaznov M Y
Published: January 2021

The study has covered the effects of blast treatment on the microstructure parameters and mechanical performance of carbon steel. The calculation results of examining the structure and properties of carbon steel in its initial state and after explosive hardening in various sections of cylindrical carbon steel workpieces have been verified with the finite-element analysis using the ANSYS Workbench software environment. Blast treatment has been demonstrated to lead to a perceptible change in the structural state of carbon (cementite) in steel.
Cracking of Ti2AlNb-based alloy after laser beam welding
Authors: Panov D O , Naumov S V , Sokolovsky V S , Volokitina E I , Kashaev N , Ventzke V , Dinse R , Riekehr S , Povolyaeva E A , Alekseev E B , Nochovnaya N A , Zherebtsov S V , Salishchev G A
Published: January 2021

Crack formation process in the Ti-23Al-23Nb-1.4V-0.8Zr-0.4Mo-0.4Si (at.%) alloy based on orthorhombic titanium aluminide (Ti2AlNb), especially in the weld zone (WZ), heat-affected zone (HAZ), and base metal (BM), during laser beam welding (LBW) at room temperature was considered. It was determined that the crack spread in the WZ throughout the crystallites of β-phase. In the HAZ, cracks spread throughout the globular β-phase crystals body and along the edges of globular α2- and O-phases. The cracking stopped in BM due to a mechanism similar to shear ligament toughening. Cracking can be effectively suppressed by increasing the LBW temperature.
Studying Corrosion Resistance of Weld Joints of Ultrafine-Grained Titanium Alloys
Authors: Nokhrin A V , Andreev P V , Likhnitskii C V , Vostokov M M , Kopylov V I , Chuvil’deev V N , Gudz’ D A , Chegurov M K , Murashov A A
Published: January 2021

Ultrafine-grained (UFG) samples of PT-3V near-α titanium alloy were subjected to diffusion welding using the Spark Plasma Sintering system. It has been shown that the destruction of welded UFG samples under hot salt corrosion (HSC) is two-staged – first, intercrystalline corrosion is manifested, which then graduates to pitting corrosion. It has been established that the corrosion resistance of weld joints is determined by vanadium concentration at the grain boundaries, the size and volume ratio of β-phase particles and the presence of pores in the weld joints. It has been shown that welded UFG samples possess higher hardness and corrosion resistance than coarse-grained samples.
Effect of carbon on microstructure and mechanical properties of titanium
Authors: Ozerov M S , Klimenko D N , Rtishcheva L P , Kopylov V N , Stepanov N D , Zherebtsov S V
Published: January 2021

The microstructure and mechanical properties of cold rolled titanium with 0.0, 0.1 and 0.2 wt.% of carbon were studied after annealing in a temperature range of 500-800 °C. The addition of carbon resulted in slower grain growth kinetics and less intensive softening during annealing of the cold rolled alloys in the temperature range 500-800 °C. Besides, the alloys with carbon are considerably stronger in comparison with pure titanium; cold rolling resulted in an increase in the yield stress from 540 MPa for titanium to 630 and 605 MPa for Ti-0.1C and Ti-0.2C, respectively. However, ductility of the carbon doped titanium was also found to be decreased to ∼32% in comparison with 40% for pure titanium.
The effect additives of magnesium, titanium and zirconium oxides additives on the densification kinetics and structure of alumina during spark plasma sintering
Authors: Popov A A , Boldin M S , Nokhrin A V , Chuvil’deev V N
Published: January 2021

The results of an experimental study of the effect of metal oxide additives on the sintering kinetics of systems based on alumina by the method of spark plasma sintering (SPS) are presented. The influence of additives at the stage of intensive compaction of powder pressing and at the stage of intensive growth of ceramic grains is analyzed. A qualitative explanation of the mechanism of the effect of magnesium oxide additives on the stabilization of the grain structure of aluminum oxide is given.
Effect of solid-solution treatment on the microstructure and mechanical properties of high-nitrogen FeMnCrNiCo high entropy alloys
Authors: Reunova K A , Astafurova E G , Melnikov E V , Astafurov S V , Panchenko M Yu , Moskvina V A
Published: January 2021

The effect of solid-solution treatment on the microstructure and tensile properties of high-nitrogen and nitrogen-free high entropy alloys (FeMnCrNiCo and FeMnCrNiCoN, N=0.36 mass.% and N=0.44 mass.%) has been investigated. It has been established that all materials under study possess an fcc crystal lattice, the lattice parameter of which increases with increasing nitrogen content. In comparison with the cast state, which is characterized by a coarse-grained dendritic microstructure, the alloys after solid-solution treatment show a more homogeneous microstructure. Solid-solution treatment does not significantly affect the mechanical characteristics of the alloys and their fracture micromechanisms.
Studying Thermal Stability of Cast and Microcrystalline Alloys Al-(2.5, 4)%Mg-Sc-Zr
Authors: Shadrina I S , Nokhrin A V , Kopylov V I , Chuvil’deev V N , Bobrov A A , Likhnitskii C V
Published: January 2021

The article presents the results of experimental studies of the structure and mechanical properties of cast and microcrystalline (MC) aluminum alloys Al-(2.5, 4)%Mg-Sc-Zr with a total content of Sc+Zr = 0.32%. The Sc content was varied from 0.10% to 0.22% at an interval of 0.02%, with the Zr concentration in the alloy being changed proportionally. In their initial state, cast alloys are characterized by a homogeneous coarse-grained macrostructure. The structure of the alloy structure presents single submicron particles Al3 (Sc,Zr) that are formed during crystallization of the alloys. It has been demonstrated that the recrystallization onset temperature in MC alloys depends on the scandium-to-zirconium ratio.
Structural-phase features of WC-based ceramics obtained by the spark plasma sintering method
Authors: Smetanina K E , Andreev P V , Lantsev E A , Vostokov M M , Malekhonova N V , Murashov A A
Published: January 2021

Ceramics obtained by spark plasma sintering of tungsten carbide powder were studied by X-ray diffraction layer-by-layer analysis. The surface of the ceramic samples was mechanical grinded and polished in several stages. The distribution of crystal phases by the depth of ceramics was investigated.
Effect of microstructure on the oxidation behavior of a β-solidified γ-TiAl based alloy after nitrogen ion implantation
Authors: Panov D O , Sokolovsky V S , Stepanov N D , Zherebtsov S V , Novikov V Y , Nochovnaya N A , Panin P V , Salishchev G A
Published: January 2021

The microstructure of the oxide layer of a β-solidifying γ-TiAl alloy (Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B) after nitrogen ion implantation was studied after cyclic oxidation tests at 800 °C. Oxidation resulted in the formation of the continuous oxide scale, consisting of thin inner and outer TiO2, dense Al2O3 and mixed Al2O3 + TiO2 layers. It was revealed that the nitrogen ion implantation considerably inhibited the growth of the oxide scale, internal oxidation and Al-depleted zones. Thick Al-depleted zones and a mixture of Al2O3 and TiO2 were formed along the colony boundaries. Tooth-shaped Al-depleted zones propagated along the lamella boundaries. In addition, the presence of Gd-rich particles in the oxide scale promoted the formation of Al2O3 particles in surrounding areas and increased the depth of the oxide scale around.
The new indicator coating to detect the place of barely visible impacts on aircraft composite structures
Authors: Buslaeva O S , Sapozhnikov S B , Bezmelnitsyn A V , Ignatova A V , Kudryavtsev A
Published: January 2021

There was developed indicator coating made of epoxy resin filled with hollow glass spheres of the volume fraction up to 50% on GFRP substrates. This coating has a high sensitivity to local impacts changing light reflection by the failure of epoxy and glass spheres in the contact area. Mechanical behaviours of the coating are close to the pure epoxy resin but the density is twice less. We also provided experimental data concerning the contact traces under barely visible impact and the numerical model to predict residual traces onto indicator coating with GFRP substrate.
Solvent-free process for the synthesis of highly stretchable piezoresistive sensors based on polydimethylsiloxane filled with graphene nanoplatelets and carbon nanotubes
Authors: Piscitelli F. , Lo Gatto M. L. , Rollo G. , Filippone G. , Lavorgna M.
Published: January 2021

This work reports on the design, the development, and a preliminary characterization of highly stretchable polydimethylsiloxane (PDMS) elastomers as matrices for piezoresistive composites with graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) applicable to aircrafts with morphing shape changes. The strategy adopted for the formulation of the polymeric matrices was to use precursors at low molecular weights, in order to avoid the use of solvents, and functionalized with lateral phenyl groups, to improve the filler dispersion and the filler-polymer interactions. The nanocomposites show high deformability (90%), high conductivity (0.85-0.9S/m), and piezoresistive behavior (Gauge Factor equal to 0.75). Additionally, CNT and GNP show a synergistic effect in the electrical conductivity, since the percolative threshold of hybrid nanocomposites is lower than those observed with CNT or GNP separately.
Multilayer and high-entropy alloy-based protective coatings for solving the issue of critical raw materials in the aerospace industry
Authors: Postolnyi Bogdan , Buranich Vladimir , Smyrnova Kateryna , Araújo João Pedro , Rebouta Luís , Pogrebnjak Alexander , Rogoz Vladyslav
Published: January 2021

Aerospace is an actively developing industry that continuously requires the implementation of modern technologies. The rapid growth in new vehicle production demands much support. Hence, the problem of resources with complicated supply and distribution is always of current interest. These critical raw materials (CRMs) are involved in almost all areas of aerospace manufacturing and service. An efficient and profitable solution to the problem of critical materials can be found in protective coatings, especially in such advanced concepts as multilayer and high-entropy alloy (HEA)-based coatings. In this paper, we study both ways of manufacturing effective coatings. We have shown that multilayer CrN/MoN coatings with exceptional toughness and hardness could find promising applications in the aerospace industry. The developed strategy for the novel materials screening based on the prediction of their properties has been demonstrated on the example of the refractory HEA-based coatings. A brief state of the art of the EU critical raw materials and their place in the aerospace/defence industry has been given.
Numerical procedure for electro-thermal anti-icing system simulation coupling internal thermal analysis and external multi-physic code
Authors: Carozza A. , Petrosino F. , Mingione G.
Published: January 2021

The present work has the aim of coupling two codes, one able to perform icing simulations and another one capable to simulate the performance of an electro-thermal anti-icing system in an integrated fashion. In fact, the classical tool chain of icing simulation (aerodynamics, water catch and impact, mass and energy surface balance) is coupled to the thermal analysis through the surface substrate and the ice thickness. In general, the substrate consists of a multi-layered composite with different properties for each layer and embedded heaters (resistors) at interfaces between layers. In the present approach, the ice protection simulation is not decoupled from the ice accretion simulation, but a single computational workflow is considered. Validation results obtained on benchmark test cases from NASA database will be detailed as well as comparison with numerical results from other authors.
Comparison of lightning strike damage in bolted and bonded CFRP joints using a coupled electro-thermal FE model
Authors: Alexandros Sofianos , Konstantinos Tserpes
Published: January 2021

Carbon Fiber Reinforced Plastics (CFRPs) composite structures are widely used in aeronautical structures. Due to the semiconducting nature of CFRPs, lightning strikes can cause significant damages in aircraft components made from such materials. In CFRP laminates joined by mechanical fasteners or adhesive bonding, the damage induced by lightning strikes is a complex multiphysics coupling process. In the present work, in order to study the effects of the different lightning current components on CFRP joints due to the Joule heat flux phenomenon, a coupled electro-thermal FE model has been developed using the ANSYS commercial FE code. Two case studies are considered, i.e. a bolted single-lap joint and an adhesively bonded single-lap joint of CFRP laminates. The model is based on the SOLID5 coupled field solid element and applies a non-linear, time-transient analysis. The main input to the model are the thermal-electrical properties of the CFRP material which vary with temperature. Three electrical lightning strikes of low, medium, and high peak intensity have been applied according to the SAE ARP 5412 standard. The numerical results reveal the detrimental effect of the lightning strike on the bolted joint of the riveted case as the electro-thermal conditions on the bolt facilitated the through-the-thickness degradation of the CFRP material, as opposed to the adhesively bonded joint where the increase of the peak intensity has led to an escalation of the area and penetration of matrix thermal damage (pyrolysis) as well as to the increase of fiber damage (deterioration and ablation). Through static mechanical analysis, the residual joint stiffness has been also predicted.
Finite Element Analysis of Composite Matrix Material with Micro-damage Healing Ability
Authors: Smojver I. , Ivanćevič D. , Brezetič D.
Published: January 2021

A novel constitutive model for modelling of polymer composite matrix material is proposed. Investigated material is an advanced ethylene/methacrylic acid (E/MAA) copolymer, DuPont™ Surlyn® 8940 thermoplastic resin, which exhibits intrinsic self-healing ability. The model incorporates damage evolution and healing model, and the von Mises linear isotropic hardening plasticity model and is validated with static tensile and two-cycle tensile tests on pure Surlyn® 8940 specimens. The concept of nominal and healing configurations is used in the development and numerical implementation of the model, which is additionally streamlined by the application of the strain equivalence hypothesis. Developed constitutive model enables accurate prediction of Surlyn® 8940 behaviour under tensile loading and precise prediction of accumulated plastic strain.
Investigation on Electrically-Assisted Rolling Process of Surface Texture for Drag Reduction
Authors: Xu Zhenhai , Xue Shaoxi , Wang Chunju , Liu Baosheng , Shan Debin , Guo Bin
Published: January 2021

Surface texture is employed for drag reduction in the aviation and aerospace, since it has a positive effect on boundary layers of flow. In this paper, the triangular surface texture was formed via the rolling process. The effects of the roll gap, sheet thickness, the space and size of the triangular shape on the forming quality of the surface texture were studied. The simulation indicates that a small roll gap is benefit for forming full profile. With the decrease of sheet thickness, the forming height is greater, but the sheet flatness is poorer. The size and space of riblet have significant effects on the stress and strain distribution and forming height. When the electric current is introduced into the rolling process, the formed surface texture shows greater forming profile and better flatness. It is concluded that the electrically-assisted rolling process is a promising way of forming surface texture on metal sheets.
TOD – Thermoplastics on Doors: Development of full scale innovative composites doors, surrounds and sub-structure for Regional Aircraft Fuselage barrel on-ground demonstrators. Innovative overall manufacturing and assembly approach and preliminary results obtained at the early stage of the project
Authors: Miraglia A , Felline F , Rocco C , Ceresa A , Raganato Umberto , Zavala-Arredondo M , Flipo B , Liaptsis G , Riise J , Cui X , Wu M , Sampethai S
Published: January 2021

Thermoplastic composites can reduce cost and save weight in airplane structures. Currently on the market there is no thermoplastic door available for commercial aircraft. The overall goal of TOD project is to demonstrate and validate the manufacturing process of thermoplastic door components, induction welding assembly process, additive manufacturing and metallic parts of door mechanism, metallic and thermoset parts of surrounding structure of the passenger and service door of an aircraft. The activities of TOD project have received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement number 821192.
Experimental investigation of damage detection on structures with friction stir welding (FSW) junctions
Authors: Sorrentino A , Chiariello A , Di Palma L , De Fenza A
Published: January 2021

A Structural Health Monitoring system for damage detection is proposed in this paper. The Probability Ellipses method (PE) is a non-destructive method based on Guided waves. This method estimates a global index called Damage Index (DI), that represents a way to measure how much critical is the related sensing-path (actuator-sensor). The DI is high when the damage is closer to the sensing-path and it increases again when the damage severity grows. The work is being developed in the framework of the Clean Sky 2 specifically for More Affordable Small Aircraft Manufacturing (SAT-AM) project, whose main goal is the development of new technologies to be employed in the development of next generation of small aircrafts category responding to CS/FAR-23 certification specification Rules. The Friction Stir Welding (FSW) is one of key technologies to reduce cost, time and manufacturing costs. Conversely, the low historical data on structural degradation of FSW joints require a conservative approach during design stage. A possible answer to the lack of structural knowledge behavior could be overpassed by using structural health monitoring system that periodically evaluates the born of any criticalities of the FSW structures. Preliminary experimental investigations of the ET method, applied to structures with Friction Stir Welding (FSW) junctions, are illustrated. Aluminum panels were joined with FSW technique and damage was produced in the junctions. The structures were instrumented with piezoelectric actuators and sensors. The Guided waves were acquired on both undamaged and damaged configurations and the PE method was applied to identify the damage position.
The dependence of the speed of sound in the Earth’s atmosphere on its density and the correction of Mach’s number
Authors: Kirtskhalia V.
Published: January 2021

According to the modern theory of sound, its speed in the Earth’s atmosphere depends only on temperature and does not depend on its density (height). The report shows a significant dependence of the speed of sound on the density of the atmosphere and, consequently, the requirement to adjust the Mach number, which plays an important role in determining the aerodynamic parameters of an aircraft.
Energy approach to transonic flutter and LCO with shock waves movement
Authors: Kuzmina S , Ishmuratov F , Karas O
Published: January 2021

The paper briefly describes the main features of the used mathematical model of aerodynamic forces in transonic flow. The model is based on the Euler equations in various approximations, the boundary layer theory and viscous-inviscid interaction. Structural elastic deformations are described by equations in modal coordinates. The algorithm for computation of dynamic aeroelasticity characteristics in transonic flow has been developed on the base of energy method.

The problem of transonic self-oscillations and their relationship with the pressure distribution peculiarities and shock waves motion is numerically investigated using the CAST wing section as example. The dependence of aeroelastic stability characteristics on the distributed work of aerodynamic forces along the wing chord is shown. An approach to the creation of a numerical modeling methodology is developed for LCO processes in the time domain.