Arc Method Research Articles

NUMERICAL ANALYSIS OF STRESS AND STRAIN STATE IN MEMBRANE WALLS WELD JOINTS PERFORMED BY SUBMERGED ARC WELDING

The article presents investigation on stress and strain state in weld joints of boiler membrane wall by performing numerical analysis (finite element method). The main purpose was to create 3D model which will correspond to real membrane wall geometry under consideration, which will allow to perform strength simulation of numerical models considering variable parameters depending on the temperature. The model was fragment of boiler membrane wall made of X10CrMoVNb9-1 pipe and 10CrMo9-10 flat bar welded with submerged arc method. The research included the assumption of boundary conditions such as temperature cycles, welding method, type of mounting and base materials or heat treatment cycle. Three simulations have been performed depended on base material and temperature cycle adopted. As a result of the simulations, the distribution of temperature, displacement and stress in analyzed cases were obtained. The numerical simulation in dissimilar welded joints X10CrMoVNb9-1 pipe and 10CrMo9-10 flat bar heat treated afterwards, showed that the differences in linear expansion coefficients favour the development of cracks in the welds caused by increased level of stress. In parallel materials used for boiler membrane walls are the reason for difficulties in determine the proper technology of welding, preheating temperature and post-weld heat treatment parameters. Simulations indicated that the state of stress in weld joint is dependent on type of parameters adopted, and in closest scenario to real conditions, simulation showed that post-weld heat treatment had no positive effect on the stress state caused by discrepancy in linear expansion coefficients of both base materials.

Postbuckling Behavior of Compressed Bars with Nonlinearly Elastic Supports

Supercritical bending of a rod compressed by a longitudinal force and having a non-linearly elastic resistance to rotation of its axis in hinged supports is considered. Hooke's law is adopted for the rod material. The deflection is presented as a trigonometric series, in which only the first three terms are left. Through this row, the angle of inclination of the axis of the rod is expressed. It is chosen as the desired function, with respect to which a resolving nonlinear integro-differential equation is obtained. To simplify it, the case is considered when the bent axis of the rod is a gentle curve. It is revealed that the usual approach, in which the compressive force is given, leads to a trivial solution with zero values for the coefficients of this series. Therefore, the first coefficient of the series, through which the deflection is represented, was chosen as the initial parameter. The equation containing the remaining desired coefficients and load was solved by the simple collocation method, since the use of the predetermined collocation method is impossible due to the nonlinearity of the resulting system of equations. The calculation results were analyzed depending on the choice of collocation points, which showed a small difference between the obtained solutions (the quadratic discrepancy between the calculated values did not exceed one percent, which indicates sufficient accuracy of the deflection approximation in the form proposed in the work). In contrast to the usual approach used in numerical methods, here it is not necessary to enter any parameter of the loading process (such as the length of the arc in the arc method) to pass the limit points. An approach is presented for an approximate calculation of the compliance of the considered rods in compression, taking into account their supercritical bending. The results of numerical studies of the supercritical behavior of rods for various geometric and mechanical characteristics of rods and supports are presented, and dependences between various parameters of the stress-strain state are obtained. Their analysis made it possible to reveal a number of features in the behavior of the considered rods depending on the properties of the nonlinear elastic resistance of the supports. In particular, it was found that under the considered parameters of the system under consideration, the compression force and the angle of inclination of the rod on the support are related by a relationship close to linear, the compliance of the compressible rod can increase by tens or more times depending on the stiffness of the springs, the rod can lose stability by snap at some values parameters of nonlinear elastic supports.

Ni, Co and Ni-Co-Modified Tungsten Carbides Obtained by an Electric Arc Method as Dry Reforming Catalysts

Dry reforming of methane (DRM), to produce synthesis gas, is one of the most important chemical reactions used for the industrial production of hydrogen and leads to the synthesis of hydrocarbons (liquid fuels) and other valuable products. A cost-effective alternative to active and stable noble metal DRM catalysts, with comparable catalytic performance, can be composite materials based on nickel, cobalt and transition metal carbides. In this line, the present work proposes a non-standard way to obtain dry reforming catalysts of Ni, Co and Ni-Co-modified tungsten carbide (WC) produced by an electric arc method. Different amounts of nickel, cobalt and their mixtures were deposited on tungsten carbide by deposition-precipitation with NaOH (DP) and incipient wetness impregnation (IWI) methods. The resulting materials were characterized by N2 adsorption-desorption, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and their performance was evaluated in DRM. The composition and preparation method of catalysts predetermined their structural, textural and electronic properties, playing a decisive role in their activity for DRM. DP-prepared 20%Ni/WC material remained resistant to oxidation, both that of the active metal (nickel) and of the tungsten carbide, as well as to coking during DRM. This sample proved to be the most active and stable among all studied materials. Possibly, the resistance to oxidation and coking was due to a more efficient implementation of the oxidation/(re)carbonization cycle on the surface of this catalyst.

NON-DESTRUCTIVE CONTROL OF PVD COATING SURFACE DEFECTS

Nanostructured ZrN coatings were deposited by the vacuum arc method with partial separation of the plasma flow from macroparticles using a curvilinear magnetic filter. With the proposed deposition parameters, a ZrN coating with an fcc lattice and (111) texture is formed. Theoretical studies are carried out to assess the defects of the surface layer in the presence of an adsorbed impurity of an fcc lattice with the surface orientation plane (111), and the characteristics of surface waves in the ZrN coating are considered. Equations are obtained for the dispersion laws and parameters of the splitting off of the surface wave from the zone of bulk vibrations in the nearest-neighbor approximation.

Synthesis of Cobalt-Nickel Aluminate Spinels Using the Laser-Induced Thermionic Vacuum Arc Method and Thermal Annealing Processes.

To obtain highly homogeneous cobalt-nickel aluminate spinels with small crystallite sizes, CoNiAl alloy thin films were primarily deposited using Laser-induced Thermionic Vacuum Arc (LTVA) as a versatile method for performing processing of multiple materials, such as alloy/composite thin films, at a nanometric scale. Following thermal annealing in air, the CoNiAl metallic thin films were transformed into ceramic oxidic (Co,Ni)Al2O4 with controlled composition and crystallinity suitable for thermal stability and chemical resistance devices. Structural analysis revealed the formation of (Co,Ni)Al2O4 from the amorphous CoNiAl alloys. The mean crystallite size of the spinels was around 15 nm. Thermal annealing induces a densification process, increasing the film thickness together with the migration process of the aluminum toward the surface of the samples. The sheet resistance changed drastically from 200-240 Ω/sq to more than 106 Ω/sq, revealing a step-by-step conversion of the metallic character of the thin film to a dielectric oxidic structure. These cermet materials can be used as inert anodes for the solid oxide fuel cells (SOFCs), which require not only high stability with respect to oxidizing gases such as oxygen, but also good electrical conductivity. These combination metal-ceramics are known as bi-layer anodes. By controlling the crystallite size and the interplay between the oxide/metal composite, a balance between stability and electrical conductivity can be achieved.

Synthesis and oxidation behavior of the materials based on carbon fibers and ultra-high temperature binary and high-entropy carbides

The paper reports the results obtained in the experimental studies of the oxidation behavior of powders based on carbon fibers (graphite) and carbides of metals of groups IV and V of the periodic table, including high-entropy carbide (HEC) TiZrNbHfTaC5. The materials were synthesized by vacuum-free electric arc method using X-ray fibrous amorphous carbon and metal oxides as a starting material. X-ray diffractometry of the synthesis products identified graphite, titanium, zirconium, niobium, hafnium, and tantalum carbides, and HEC TiZrNbHfTaC5. Scanning electron microscopy of the synthesis products showed carbon fibers with the surface modified by the above-mentioned carbides. Differential thermal analysis was performed to determine the parameters of the oxidation process of these materials; the main difference between the synthesized materials is the oxidation rate, with the lowest one demonstrated by the high-entropy carbide containing material.

Plasma electrolytic oxidation of as-cast and heat-treated binary Al-Ni alloys

In this study, the effect of nickel addition on the plasma electrolytic oxidation (PEO) behavior of pure Al was investigated. Binary Al-Ni alloys containing 1, 3, 5 and 7 at. % Ni were produced by two step vacuum arc and induction melting methods. Produced alloys and pure Al as a reference were PEO coated in a silicate-based alkaline electrolyte through a bipolar power source under constant voltage mode for 45 min. The samples were characterized by XRD, SEM-EDS and Vickers microhardness tester before and after PEO. All alloys were consisted of Al and Al3Ni phases. Fine rod-like eutectic structure was evident for 1 (hypoeutectic) and 3 (eutectic) at. % Ni containing alloys while further addition of Ni resulted in the coarsening of eutectic Al3Ni precipitates. All coatings contained γ-Al2O3 phase while additionally, α-Al2O3 phase formed on pure Al and Al-1Ni alloy. Despite the presence of Ni in the coatings, a Ni-based oxide phase was not evident. Ni, as an alloying element, is found to decrease microhardness and thickness of the coatings, induced a thickness variation between the regions close to the edge and center of the samples. This edge effect was maximum on eutectic alloy, which consisted of homogeneously distributed fine Al3Ni precipitates. To investigate the relationship between eutectic precipitate size and the edge effect, Al-3Ni alloy was heat-treated at 620 °C for 168 h and subsequently coated by PEO. Heat-treatment almost eliminated the edge effect, increased the average coating thickness and promoted the α-Al2O3 formation. Fine eutectic morphology in Al-Ni alloys is found to be detrimental for the coatings produced by PEO.

Production and 3D Printing of a Nanocellulose-Based Composite Filament Composed of Polymer-Modified Cellulose Nanofibrils and High-Density Polyethylene (HDPE) for the Fabrication of 3D Complex Shapes

This work aims to produce a 3D-printable bio-based filament composed of high-density polyethylene (HDPE) and chemically modified cellulose nanofibrils. Printing using HDPE as a raw material is challenging due to its massive shrinkage and warping problems. This paper presents a new method to overcome those difficulties by enhancing the mechanical properties and achieving better print quality. This was achieved using modified cellulose nanofibrils (CNFs) as fillers. Firstly, CNF was converted to a CNF-based macroinitiator through an esterification reaction, followed by a surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) of the hydrophobic monomer stearyl acrylate. Poly stearyl acrylate-grafted cellulose nanofibrils, CNF-PSAs, were synthesized, purified and characterized with ATR-FTIR, 13C CP-MAS NMR, FE-SEM and water contact angle measurements. A composite was successfully produced using a twin-screw extruder with a CNF-PSA content of 10 wt.%. Mechanical tests were carried out with tensile testing. An increase in the mechanical properties, up to 23% for the Young’s modulus, was observed. A morphologic analysis also revealed the good matrix/CNF compatibility, as no CNF aggregates could be observed. A reduction in the warping behavior for the composite filament compared to HDPE was assessed using a circular arc method. The 3D printing of complex objects using the CNF-PSA/HDPE filament resulted in better print quality when compared to the object printed with neat HDPE. Therefore, it could be concluded that CNF-PSA was a suitable filler for the reinforcement of HDPE, thus, rendering it suitable for 3D printing.

One step synthesis of 10B-enriched 10BPO4 nanoparticles for effective boron neutron capture therapeutic treatment of recurrent head-and-neck tumor

Recurrent head-and-neck (H&N) cancer is one of the most malignant cancers in the world. Various treatment modalities, such as radiation therapy, chemotherapy, and surgery were adopted to treat H&N cancer, but recurrence of H&N tumor always occurs again, leading to poor prognosis and low 5-year survival rate. Recently, boron neutron capture therapy (BNCT) emerges an alternative modality for curing recurrent tumors. Presently, boron phenylalanine-fructose (BPA-F) and sodium borocaptate (BSH) are the two best BNCT molecular drugs, which, however, have poor therapeutic efficacies and are lack of tumor-targeting ability. In this study, 10B-riched (98.5% 10B) boron phosphate nanoparticles (10BPO4 NPs) of ∼100 nm in size were prepared in a single step using a unique microwave arcing method. The 10B-enriched 10BPO4 NPs were surface-modified with anti-EGFR antibody to endow the targeting ability toward H&N cancer cells. In in-vivo xenograft mice model, a large amount (∼63 μg 10B/g cancer cells) of 10B atoms could be effectively accumulated at the H&N tumor sites using 10BPO4 NPs as BNCT reagents. In in-vitro neutron irradiation experiments, 72% cell deaths were observed from anti-EGFR-10BPO4 NPs-treated H&N cancer cells, which is ∼2.4 folds higher than that (30%) treated with the most effective molecular drug, BPA-F. We demonstrated that upon neutron irradiation, the anti-EGFR-10BPO4 NPs could exert a much higher extent of destruction of H&N tumor, as well as effective suppression of the probability of H&N tumor recurrence, as compared to the most effective molecular drug, BPA-F. The median survival of the BNCT treated mice with anti-EGFR-10BPO4 NPs extends beyond 75 days, which is far better than the mice treated with BPA-F (33 days), blank + NR mice (25), and blank mice (23 days).

Optical and surface properties of Gd-doped ZnO thin films deposited by thermionic vacuum arc deposition technology

In this paper, Zinc oxide (ZnO) was doped with Gadolinium (Gd) and it was deposited onto the glass and silicon substrates by thermionic vacuum arc (TVA) method to examine its morphological, compositional, and optical properties. The results show that the substrates strongly affect the morphological structures of the thin films. According to the obtained information, the surface roughness was found to be 38 nm and 6 nm for silicon and glass respectively. The images showed that the surface onto the glass had more symmetry and more regular grains. The optical properties of the nano composite on the glass substrate were analyzed with an optical interferometer and UV–Vis spectrophotometer. Absorbance, transparency, and refractive index of the thin film were obtained. It also had a relatively high refractive index. Furthermore, it was found that the band gap of ZnO decreased. The band gap of the deposited thin film was found 3.3 eV.

Development of Ultra-Low Specific Speed Centrifugal Pumps Design Method for Small Liquid Rocket Engines

With the growth of the satellite industry, the demand for a propulsion system for small launch vehicles and spacecraft has increased. Small liquid rocket engines may require Ultra-Low specific speed centrifugal pumps due to the low required thrust and volumetric flow rate and high combustion chamber pressure. Therefore, in this study, a design method of Ultra-Low specific speed centrifugal pumps for several hundred Newton class small liquid rocket engines was developed by combining various empirical formulas. In addition, centrifugal pump impellers were designed using the Stepanoff method, which is typically used in pump design, and the circular arc method. The most appropriate method for designing Ultra-Low specific speed centrifugal pumps was determined through a comparative analysis with other methods and validated through CFD. As a result, the pump designed using the proposed method exhibited a performance of pumping and suction superior to the Stepanoff method. Although the number of arcs did not considerably influence the pump performance, the single arc method was confirmed to be the most appropriate design approach in terms of the design productivity and simplicity.

Corrosion Testing of CrNx-Coated 310 H Stainless Steel under Simulated Supercritical Water Conditions.

The paper’s aim is the assessment of corrosion behaviour of a CrNx-coated 310 H stainless steel under simulated supercritical water conditions (550 °C and 25 MPa) for up to 2160 h. The CrNx coating was obtained by the thermionic vacuum arc (TVA) method. The oxides grown on this coating were characterized using metallographic and gravimetric analysis, SEM with EDS, and grazing incidence X-ray diffraction (GIXRD). A diffusion mechanism drives oxidation kinetics because it follows a parabolic law. By XRD analysis, the presence of Cr2O3 and Fe3O4 on the surface of the autoclaved CrNx-coated 310 H samples were highlighted. Corrosion susceptibility assessment was performed by electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization. EIS impedance spectra show the presence of two capacitive semicircles in the Nyquist diagram, highlighting both the presence of the CrNx coating and the oxide film formed during autoclaving on the 310 H stainless steel. Very low corrosion rates, with values up to 11 nm × year−1, obtained in the case of autoclaved for 2160 h, CrNx-coated samples indicated that the oxides formed on these samples are protective and provide better corrosion resistance. The determination of micro hardness Vickers completed the above investigation.

The Comparative Analysis of the Fe–Cr–C–Ti–Al Coatings Synthesized by Laser, Arc and Hybrid Cladding Methods

The Comparative Analysis of the Fe–Cr–C–Ti–Al Coatings Synthesized by Laser, Arc and Hybrid Cladding Methods

Self-Lubricating Property of TiB2-Ni Coating in the Hot Forging Die of Aluminum Alloy

Hot die forging is a forging forming method widely used in the automobile industry, shipbuilding, and the aerospace industry. In the hot die forging process of aluminum alloy, the “mold sticking” defect often occurs and results in low productivity and short die life. Herein, we prepared TiB2 reinforced nickel-based coatings by the combined use of a plasma transferred arc and plasma melt injection method, and investigated the morphology and properties of composite coatings in hot forging die conditions. The results showed that the nickel-based coating reinforced with TiB2 generated boron-rich self-lubricating products during the sliding with aluminum alloy, and the adhered aluminum alloy on a coating surface has significantly reduced quantity and transformed morphology from rough plough to smooth layer with the increase of TiB2, which is beneficial to the surface quality of the aluminum alloy counterface. The results of this research provide valuable guidelines for the design and preparation of the coatings applied in the mold in hot die forging of aluminum alloys.

Construction optimization and settlement analysis of Pile Beam Arc method in subway station

Subway stations are generally built in areas with dense buildings, heavy traffic, or dense pipelines. In this case, the control of land subsidence and building deformation is very strict. The Pile Beam Arc (PBA) method has its unique advantages in these aspects, and it is especially suitable for northern China. In this research, the Zhongjie subway station of Shenyang Metro Line 1 is taken as the research object, and MIDAS GTS NX software is used to simulate the various stages of the PBA method construction of the subway station. In this paper, the optimal construction scheme of the subway station is analyzed by numerical simulation. This study also uses the monitoring data provided by the construction site to analyze the influence and distribution law of the subway station on the ground surface deformation in each construction stage. In this paper, the results of numerical simulation are compared with the field monitoring data, and the most dangerous construction stage is obtained. The conclusions of this study can provide accurate supporting scheme and control measures for the subsequent construction.

Tunable thermochromism in V2O5 films deposited by cathodic vacuum arc method by tailoring the oxygen deficiency

Theromochromism and electrochromic coatings have promising applications in smart windows, IR sensors, and bio-medical devices. In this paper, we report the growth of vanadium oxide films using cathodic vacuum arc method for thermochromic application. Successive annealing of the as grown film shows the formation of yellow color V2O5 films. The color of the as grown films suggest the growth of highly disordered black VxOy film which after annealing gets converted into yellow V2O5 as confirmed by the X-ray diffraction and Raman spectroscopy. The scanning electron microscopy equipped with energy dispersive X-ray analysis was used to investigate the morphology and chemical composition of V2O5 phase. Although, the films gets completely converted into the stable phase after annealing but heating cycling of temperature significantly changes the color of the films in a reversible manner that confirms the thermochromic behavior. We propose a breathing of oxygen (tailoring of Oxygen within the films) responsible for such reversible change in the color. These studies open new pathways for investigating these films to electrochromic properties by locally heating the materials through electric current (through Joule heating) and change the optical properties.

Synthesis and characterization of some C-Ti based multilayer and composite nanostructures

Carbon-Titanium multilayer and composite thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisted by a carbon base layer and seven alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. By changing of substrate temperature, and on the other hand the bias potential up to –700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Grazing Incidence X-ray Diffraction (GIXRD) and Electron Microscopy technique (TEM). The measurements show that increase of the substrate temperature reveal the changes in TixCy lattice parameters. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively and a Bruker Hystrion TI 980 TriboIndenter. Was found that the coefficient of friction depends on the synthesis temperature, bias voltage and also by the C content, Ti content and amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedeman-Frantz law was obtained the thermal conductivity.

Research on the position and attitude control method of the spatial arc for a five-axis hybrid tapping robot

Automatic rubber harvesting can not only reduce the cost of latex production, but also stabilize the output and improve the production efficiency. In order to lay the foundation for the movement of the robot around the tapping trajectory and meet the performance requirements of the robot in the tapping operation, this paper studies the position and attitude interpolation algorithm of the spatial arc for a five-degree-of-freedom hybrid tapping robot to realize the synchronous motion of the spatial arc pose control. In the verification test, the tip of the pen installed at the end of the robot draws a coherent clear arc in the space. The end vector is perpendicular to the normal vector of the arc trajectory and keeps pointing to the center of the trajectory at the same time, which verifies the correctness of the position and attitude control method.

The Synergistic Effect of the Laser Beam on the Thermionic Vacuum Arc Method for Titanium-Doped Chromium Thin Film Deposition

Laser-Induced Thermionic Vacuum Arc (LTVA) provides a better way to produce uniform metallic thin films than the classical Thermionic Vacuum Arc (TVA) method. In Ti-doped chromium thin films produced using LTVA, the amorphous chromium is superimposed with small bcc chromium nanoparticles. These amorphous/crystalline structures with small crystallites induce lower roughness and electrical resistivity, reducing electron–phonon scattering and increasing charge transport across LTVA thin films. A significant shift in resistivity for the LTVA samples is observed due to electron scattering on the phonon–crystalline structures in the TVA samples which exhibit larger crystallites. Meanwhile, the wettability measurements reveal a higher contact angle, resulting in a lower surface free energy and consecutively lower dissociation energy for the LTVA-produced thin films than the TVA samples.

Effects of carbon short-range structure and Co-based catalyst on solid-phase synthesis of calcium carbide at moderate temperatures

Owing to the thermodynamic and kinetics restrictions, traditional electric arc method for calcium carbide (CaC2) synthesis is operated at very high temperature (∼2200 ​°C), which is an energy intensive (∼4000 ​kW·h/(t CaC2)) process and brings strict requirements to reactor design. Herein, to improve the calcium oxide (CaO) conversion rate, the short-range structure tailored active carbon (AC) material and CoOx as a catalyst were used for solid-phase synthesis of CaC2. It was found that the conversion of CaO could be increased by about 4-fold when using tailored AC with decreased impurity of H, S, N heteroatoms, increased content of disordered carbon atoms, expanded (002) crystal facet and C–C bond length. Compared with blank test, 5 ​wt% Co3O4 as a cobalt catalyst precursor that added into CaO-AC mixture can further increase the CaO conversion by ∼20% under optimal conditions and the onset temperature of solid-phase reaction decreases to ∼1620 ​°C. This catalytic function is assumed to be related with the enhanced chemical reaction at the solid-solid interface of CaO and AC reactants, increased mixed ionic and electric conductivity (MIEC) of bulk. Our work demonstrates that the short-range structure of carbon material is an essential factor to determine its reactivity and the catalytic function is still necessary and important in solid-phase synthesis of CaC2 even at high temperatures.