Round Rods Research Articles

Visual experimental study on bubble characteristics near the heating wall in subcooled flow boiling

A visual experiment is conducted to study bubble dimension characteristics during subcooled flow boiling in vertical flow channel with a round heating rod in a squared channel. With the high speed camera, the bubble behavior is captured and bubble dimension characteristics near the heating wall are obtained. In this study, the system pressure is from 0.1 to 1.0 MPa, the mass flux is from 800 to 1900 kg/m2s and the inlet subcooling is from 10 to 30 K. The effect of working conditions on bubble behavior is discussed in detail, such as system pressure, are analyzed in detail. The bubble dimension increases with increasing heat flux, while decreases with system pressure, inlet subcooling and mass flux. In order to predict bubble dimension better, a model is proposed based on important dimensionless numbers in this paper and good agreement is achieved when comparing with the experimental result.

Design and experimental study of ginkgo leaf picking device

To achieve the purpose of Ginkgo biloba leaves continuous harvesting, a ginkgo leaf picking device is designed. The device is consisted of a picking executive composed from a round rod picking hand and a rotating drum, a frame, a motor, a motor base, a coupling, a bearing seat, a motor support frame, a deciduous box, and a connecting screw. And the picking theoretical analysis and calculation are carried out. Finally, the feasibility of the design is verified by adjusting the tilt angle and motor speed of the picking device. The experimental results show that when the inclination angle between the picking device and the horizontal plane is 30° and the motor speed is 120 r/min, the damage rate of Ginkgo biloba leaves is 1.52%. The net collection rate is 94.29%, and the damage degree of branch and stem is mild.

Creep characteristics of directionally solidified turbine blades based on the difference in original casting characteristics

Due to the difference between original material and the processed material for use in turbine blades, research that solely focuses on the original materials may not fully explain the performance of operational turbine blades. In order to ensure the maximum utilization rate of turbine blades, the study examines the creep properties and differences of different parts of the directional solidification of original casting turbine blades. In this article, a set of sampling fixtures from different parts of a turbine blade were proposed to quantitatively measure the difference in creep properties caused by the complex geometric factors created during the DS process. The special fixtures would cut the blades into five different parts, which were to be further processed into small samples. Creep tests under two different conditions (980 °C/245 MPa, 980 °C/267 MPa) were carried out. Round rod specimens (standard parts) were used for creep tests under the same conditions for comparison. By employing scanning electron microscopic (SEM) and creep tests on different parts of original casting turbine blades, the mechanism of microstructure evolution and the creep fracture behavior were proposed in this condition. In addition, the original microstructure of different parts of a blade was observed by scanning electron microscopy (SEM), and the characteristics of the different parts were simulated based on an improved two-parameter creep constitutive model. The results suggest that the creep life of the different parts of the original casting blade is different, which caused by the differences in microstructure and morphology of the different parts of the original casting blade. The creep property of standard parts is better than that of original casting blades. The creep life of original casting blades from small to large is as follows: CVS, DP, LE, CCS, TT. An improved two-parameter creep constitutive model was adopted to simulate the difference in creep properties (including creep life) resulted from different parts in a turbine blade. This difference needs to be considered in designing the structure and service life of turbine blades formed by directional solidification. The research results are of great significance for improving the design of directionally solidified turbine blades and for improving the directional solidification forming process.

Pemanfaatan Drainase (Saluran) Air Bekas Limbah Rumah Tangga sebagai Solusi untuk Penurunan Resistansi Pentanahan (Grounding)

This study aims to anticipate a high value of grounding resistance by utilizing drainage or waste water from household waste as a planting medium to reduce the value of grounding resistance. The research method used is an experimental method of testing and measuring at field locations. In this study, a round rod electrode is coated with copper, namely testing with one electrode rod and two electrode rods that are installed in parallel or better known as the use of a driven rod. The results showed a decrease in the value of the grounding resistance where the average value for 1 grounding rod was 18.32 ohms and 11.82 ohms for the measurement of 2 grounding rods installed in parallel. From the test results, there was a decrease in the resistance value of 59.52% for 1 electrode rod and a 51.75% decrease for 2 electrode rods, where the decrease in the resistance value in the field was caused by factors of water, humidity and used water minerals from household waste. In conclusion, housing with reddish yellow podzolic soil that is clay (high soil resistance) by utilizing water drainage is a solution to reduce grounding resistance.
 Keywords: Resistance, Drainage, Grounding (Grounding)

Damage Model Determination for Predicting Creep Rupture Time of 2 1/4Cr–1Mo Steel Weld Joints

In a creep damage analysis for a weld joint (WJ) using a damage model, it is important to select a damage model that properly reflects complex conditions of stress generated in the interface between the base metal and the heat-affected zone (HAZ). For 2 1/4Cr–1Mo steel, we examined what type of scalar stress is appropriate to properly reflects the conditions of stress generated around the HAZ for accurately predicting creep rupture time, in the framework of the time exhaustion rule, which evaluates damage as a function of stress. For a specimen of a round rod WJ through which an HAZ penetrates obliquely, we compared actual tests and finite element method (FEM) analysis, in temperature-stress ranges from 120 to 160 MPa at 823 K, and from 80 to 100 MPa at 873 K. Using FEM calculations, we evaluated the rupture time based on the time exhaustion rule, considering three types of scalar stress: the maximum principal stress, the equivalent stress, and the Huddleston stress. Comparing with the tests, we found that the scalar stress that gives an appropriate rupture time is the Huddleston stress. In this stress, the damage accumulation due to the creep deformation in the base metal (BM)-HAZ interface and the cavity formation due to the hydrostatic pressure are taken into account. Analyses of the stress distribution inside and outside of the HAZ and in the BM-HAZ interface indicated that, for the 2 1/4Cr–1Mo steel, the cavity formation due to the tensile hydrostatic pressure is also important when we evaluate damage. We optimized a parameter b, which regulates the balance in the Huddleston stress, so that the observed results are reproduced with the determination coefficient of R2 = 0.948, and we obtained the value of b as b = 0.34.

Inertial Separation of Particles Escaped from Electrostatic Precipitators.

For particles that escape from electrostatic precipitators (ESPs), inertial recapture is used to improve the efficiency of dust removal. A rod-grid inertial separator was designed. The electrostatic and fluid flow particle tracking modules were selected in the model established by the COMSOL software, and the dust removal efficiency of the proposed dust separator was evaluated. When the flue gas velocity was 20 m·s–1, the diameter of the round rod was 8 mm, and the spacing of the pipes was 15 mm, the removal efficiency of PM2.5 and PM10 reached 27.8 and 84.6%, respectively. Experiments were performed under laboratory conditions and actual working conditions in a coal-fired power plant flue. Results showed that an inertial separator can achieve more than 60% efficiency in recapturing fly ashes that have escaped from ESPs. It can effectively remove fine particles and aerosol pollutants represented by PM2.5 and PM10.

INVESTIGATION OF RESIDUAL STRESS FIELD IN THE CURVED SURFACE OF ROUND ROD SUBJECTED TO MULTIPLE LASER SHOCK PEENING

Laser shock peening (LSP) was employed to squeeze compressive residual stress (CRS) into the curved surface of the round rod with diameter of 16[Formula: see text]mm. The residual stress field was induced by nine laser shots irradiating at different locations along the specified path. The developing process of the residual stress field was investigated with finite element analysis, and the corresponding experiments were also carried out to validate the calculated results. Results demonstrate that multiple LSP with 50% overlapping rate can result in residual stress field with the maximum CRS varying from 155.2[Formula: see text]MPa to 198.8[Formula: see text]MPa along the direction of the rod axis. The peened surface appears wavy in shape and the maximum depth of plastic deformation in the curved surface is 13.41[Formula: see text][Formula: see text]m. The value of surface roughness increases from 3.87[Formula: see text][Formula: see text]m to 4.65[Formula: see text][Formula: see text]m.

Experimental and Fracture Model Study of Q690D Steel Under Various Stress Conditions

The fracture failure of high-strength steel has an important relationship with the stress state. In order to predict the fracture failure of high-strength steel under different stress conditions, based on the void growth model (VGM), a fracture model which comprehensively considers the effect of stress triaxiality and the Lode parameter on fracture failure is proposed and is called LVGM. A batch of Chinese Q690D high strength steel round rods and plate shaped specimens reflecting different stress states were processed, and the monotonic tensile tests, the scanning electron microscopy tests and the finite element calculation were carried out to study the crack initiation of the specimens. The microscopic mechanism of the fracture damage of the specimens was analyzed. Based on the fracture test results of the specimens and the corresponding finite element analysis, the LVGM parameters of the Q690D high strength steel were calibrated. Finally, the LVGM was used to predict the crack initiation and fracture failure process of the specimens with initial gap. The prediction results are in good agreement with the experimental results, and the LVGM has better prediction accuracy than the VGM.

The study of heat and mass transfer during dehydration of gelatin from waste products of hydrobionts

Fish processing waste is rich in collagen and promising as a source of raw materials for the production of gelatin. Gelatin today remains one of the most popular collagens in various industries, while the main share in the Russian gelatin market is occupied by imported products. Given there are structural, mechanical and foam structural characteristics of gelatin extract, including from fish processing waste, one of the ways to increase the effectiveness of dried gelatin technology will be its radiation dehydration in foamy form. The formation of a stable foam structure leads to a significant intensification of the moisture removal operation due to the growth of the phase contact surface during transfer and exchange of thermal energy and substance, a decrease in adhesion between the drying object and the working surface of the unit and, as a result, to simplification of the separation of the dehydrated material from it and the elimination of the energy-intensive crushing operation finished products. The purpose of this research was to develop rational drying regimes of gelatin extract based on the study of kinetic laws of choosing ways to intensify the process of moisture removal. Foamed gelatin extract was dried in the form of round rods with volumetric convective and convective-radiation energy supply. Based on the results of experimental and analytical studies of convective and convective-radiation foam drying of gelatin, practical recommendations are given on the hardware design of the drying process, including the design of a complex convective-radiation drying installation, which is applicable both to the production of dry gelatin and similar complex properties thermolabile elastic-viscous, gel-like and paste-like materials.

Bone formation at Ti‐6Al‐7Nb scaffolds consisting of 3D honeycomb frame and diamond‐like carbon coating implanted into the femur of beagles

We fabricated Ti-6Al-7Nb bone scaffolds with 5 mm diameter and 20 mm length comprise of a three-dimensional (3D) honeycomb frame structure of truncated octahedra created by selective laser sintering 3D printing. The honeycomb frame was then coated with 0.1μm thick diamond-like carbon (DLC) to increase biocompatibility. A round rod of Ti-6Al-7Nb alloy (ASTM F1295) was as a control material. They were implanted into the femur bones of beagles to evaluate bone morphometrics and to investigate changes in the transcriptome of the new bone tissue using DNA microarray analysis and real-time polymerase chain reaction (PCR). In the present report, the 3D honeycomb material with and without DLC film consisting of a-C:H is referred to as 3D_a-C:H and 3D_non, respectively. At 3 weeks after implantation, the 3D_non had more contact between the new and artificial bones compared with the control, and the 3D_a-C:H had more contact between the new and artificial bones compared with the control and 3D_non. Furthermore, 3D_a-C:H showed even more new bone compared with the control and 3D_non. At 8 weeks after implantation, more appeared lamellar bone with the 3D_a-C:H implant than those with the control and 3D_non. The real-time PCR results at 1week of implantation revealed higher expression levels of VEGF, RANKL, and NOTCH2 expression with 3D_a-C:H than with 3D_non and control. As a result of real-time PCR at 2 weeks of implantation, OPN and CTSK expressions were found to be higher with 3D_a-C:H and 3D_non than that with the control.

Application of Anisotropic Ductile Fracture Model for Prediction of Diagonal Cracks in Outer Rim of Flange-Shaped Parts

Inclined rotary forming (IRF) combines bending and axial compression with rotation and is employed for forming flange shaft-structured parts from round rod billets. Although the forming load is smaller than that in conventional processes, cracks may develop during this process. However, it is difficult to predict the onset of cracks using conventional ductile fracture prediction equations. In this paper, the ductile fractures were predicted using the anisotropic ductile damage equations that the present authors previously developed. The proposed equation was expressed as a second-rank tensor resulting from the product of the stress tensor and the strain increment tensor. Referring to previously published results on the compression of cylindrical specimens, the difference between diagonal and longitudinal sidewall cracks was assumed by considering the anisotropy of ductile damage. The proposed equation was then applied to the IRF process, where diagonal cracks developed at the outer rim of the flange. Consequently, it was found that the proposed anisotropic damage model can predict the onset of diagonal cracks on the outer rim and the effect of the lubrication condition on the onset of these cracks.

Thermomechanical analysis of nitinol memory alloy behavior

Shape memory alloys are functional materials characterized by the effect of shape memory and superelasticity. Due to these properties, they are widely used, particularly, in bioengineering, aeronautics, robotics and civil engineering. The temperatures of phase transformations and the influence of external temperature and strain rate on the functional and mechanical characteristics of Ni55.75Ti44.15 shape memory alloy are investigated in this paper. The temperature of alloy phase transformations is obtained by differential scanning calorimetry (DSC) in the temperature range from -70°C to 70°C. Diagrams of differential scanning calorimeters at different heating and cooling rates of Ni55.75Ti44.15 alloy is constructed and analyzed. Samples for mechanical tests are made of round rod 8 mm in diameter. The samples working area is 12.5 mm in length and 4 mm in diameter. Mechanical tests are carried out at temperatures close to the maximum value of the completion temperature of martensitic-austenitic transformation Af = 14.7°C. Diagrams of deformation under uniaxial tension are constructed and stresses of phase transformations, Young's modulus and relative elongations of transformation areas at different loading speeds and exterior temperatures are determined. Using Clausius-Clapeyron formula, it is shown that with simultaneous changes in temperature and strain rate, the stresses of phase transformations are largely due to changes in temperature rather than load rates. The coefficients of Clausius-Clapeyron equation for superelastic Ni55.75Ti44.15 alloy with shape memory, which are consistent with those known in the literature, are determined.

Zone Recrystallization of Zirconium and Hafnium

The work studied the possibility of obtaining of the high-purity samples of zirconium and hafnium by the method of zone recrystallization of round rods with electron-beam heating in a vacuum of 1∙10-4 Pa. Some meltings were carried out in a constant electric field with the variability of its connection. It is shown that the simultaneous passage of several refining processes (evaporation of highly volatile metallic impurities, zone recrystallization with directional displacement of impurities to the end of the sample, electrotransport) made it possible to efficient refining of zirconium both from metallic impurities and from interstitial impurities. The best degree of purification was achieved when zone melting carrying out in an electric field directed opposite to the zone movement. In this case, the displacement of interstitial impurity ions coincided with the direction of movement of the liquid zone. Samples of zirconium with a purity of 99.89 wt. % were obtained (the concentration of aluminum was reduced by 5, iron - 11, copper - 45, chromium - 75, silicon - 10, titanium - 2.5, oxygen - 3.3, nitrogen - 3, carbon - 2 times). The hafnium samples refined by the zone recrystallization method were characterized by a purity of 99.85 wt. %. The concentrations of both all metal impurities and interstitial impurities were significantly reduced (concentration in wt% oxygen was 0.011, carbon - 0.0018, nitrogen - 5∙10-5). A study of gas evolution from samples of iodide hafnium and refined hafnium was carried out. It was found that the maximum gas release peak fell on the temperature range of 500 ... 550 °C. The use of an integrated approach, including high-temperature heating, stages of zone melting at different rates, and thermal cycling in the range of the polymorphic transformation temperature, made it possible to obtain single-crystal hafnium samples. According to X-ray diffraction data, the parameters of the hafnium crystal lattice were determined: а = (0.31950 ± 5·10-5) nm and с = (0.50542 ± 5·10-5) nm (at 298 K), which corresponds to the density ρ = 13.263 g/cm3 and axial ratio с/a = 1.5819.

Coupling a Gaussian input beam to a quadrupole mass filter with round rods

We consider an input ion beam that has Gaussian distributions of the initial ion coordinates and transverse velocities at the entrance of a quadrupole mass filter (QMF) with round rods. To calculate the statistical QMF acceptance, an ion trajectory method has been used. The probability density functions of accepted points on phase planes of transverse ion positions and velocities in the X and Y directions are used to visualize the distributions of phase space points. To determine the statistical acceptances we calculate the second moments of the probability density functions. We define the statistical acceptance of the quadrupole mass filter as the area of an ellipse on the phase plane determined by the second moments. The values of the second moments characterize the efficiency of the coupling of the Gaussian ion source and the acceptance of a quadrupole rod set with round rods. The above approach is a supplement to a previously published theoretical model of QMF fields with circular electrodes.

Low loss and polarization-insensitive coupling length for a terahertz fiber directional coupler with symmetric dual-suspended core structure

In this work, a terahertz (THz) fiber directional coupler with a symmetric dual-suspended core structure has been proposed for realizing low loss and polarization-insensitive coupling length in the THz frequency region. The fiber core of the directional coupler consists of two round solid dielectric rods supported by two intersecting thin dielectric layers. Numerical simulations performed using the full-vector finite element method show that a short polarization-independent coupling length can be obtained by adjusting the geometric parameters of the fiber. Moreover, a low-loss THz fiber directional coupling performance can also be achieved at a central frequency of 1.00-THz and approximately 0.16 THz of bandwidth. For example, a coupler with a length of 0.421 cm has a transmission loss of 0.30 dB and 0.26 dB for the x- and y-polarization modes, respectively.

Magnetic Field Scattering of a Transformer Winding on a Round Rod for a Safety Relay

A model permitting simulation of the magnetic field scattering of a current-bearing winding on a round ferromagnetic rod is developed. The model is verified experimentally.

Stability of Shape Memory Alloy rods under reverse phase transformation in case of initial tensile phase-structural strains

Stability of a round cross section rod of Shape Memory Alloys under reverse phase transition where the initial strain was obtained with the help of reverse loading and subsequent unloading was investigated. It was shown that the additional structural transformation connected with buckling could not take place within the framework of a given model of the constitutive equations for Shape Memory Alloys. Numerical solutions in various problem statements and concepts were obtained.

A continuous damage model of Q690D steel considering the influence of Lode parameter and its application

Chinese Q690D high strength steel has begun to be applied in building structures in recent years, but researches on ductile fracture behavior of Q690D steel are still insufficient, and most of the mechanical fracture models based on micro fracture mechanics mechanism ignore shear effect. In this paper, the yield surface size of materials considered the shear effect through Lode parameter, and a continuous damage model (LCDM) was also provided to consider the effect of Lode parameter. A batch of Chinese Q690D high strength steel round rods and plate shaped specimens were designed to reflect different stress states, which were submitted to monotonic tensile loading. The micro fracture mechanism under different stress states was revealed by scanning electron microscopy tests. According to experimental results and finite element simulation results, LCDM parameters of Q690D steel were calibrated and crack initiation positions of various specimens were analyzed. Finally, the LCDM was used to predict crack initiation and fracture failure process of the cruciform joint specimen with initial gap. It is found that the load displacement curve, crack initiation and evolution law obtained from finite element simulation are in good agreement with the test, and the prediction accuracy based on LCDM is higher than that based on the model without considering the effect of Lode parameter.

RESIDUES OF THE PRODUCTION BUILDING ON KUDRYAVS’KA str. 24A IN KYIV

During the archaeological research of the Old Rus site on the Kudryavska st., 24A in Kyiv, in the historical area called «Kopyriv kinec», the remains of the manufactory building were discovered. The building has a frame-and-pillar structure, 4 Ч 4 m square, located in the eastern part of the excavation area. The stepped entrance adjoined the building from the southwest side. This building was cut in half by the modern building foundation. At its bottom, in addition to pits of different diameters, the small hearth was located. In the filling of the building a lot of various finds such as the fragments of various vessels, the objects from ferrous and non-ferrous metals, fragments of building materials, stone items, various slags, animal bones etc. were discovered. In the building filling the artifacts indicating its manufacture purpose have been discovered: the fragments of commercial copper — the raw materials for casting bronze products in the form of round rods with cross-sections with traces of chopping and riveting. Material for smelting followed by casting, like raw materials, used the colored scrap in the form of fragments of various copper or bronze products, melted and deformed under the influence of high temperature little bell, broken strips etc. Slag fragments, found in the building, clearly indicate the activity related to metal production and metal processing. Most likely, the main metallurgical workshop was placed nearby. Consequently, this manufactory building was probably the part of metallurgical complex. Obviously, it was engaged in the smelting of metal and the manufacture of non-ferrous metal items.

Achieving Grain Refinement of Upsized Al–3Mg–0.2Sc (mass%) Round Rods Using Multi-Pass High-Pressure Sliding (MP-HPS)

Achieving Grain Refinement of Upsized Al–3Mg–0.2Sc (mass%) Round Rods Using Multi-Pass High-Pressure Sliding (MP-HPS)