Axial Hole Research Articles

Know-How of the Effective Use of Carbon Electrodes with a through Axial Hole in the Smelting of Silicon Metal

This article describes elements of the know-how of using carbon electrodes produced using the technology of molding around a rod when smelting silicon metal. Application of our know-how will dramatically increase the competitiveness of silicon metal production. Experts’ concerns regarding the use of such electrodes were that such electrodes have a through axial hole. This significantly reduces the mechanical strength of such electrodes, which can presumably lead to problems associated with the breakage of the working side of the electrode, which is immersed in the smelting space of the furnace under the charge layer. Industrial testing of such electrodes was carried out in a 30 MVA furnace of “Tau-Ken Temir” LLP. During testing, we used an approach previously developed by our team for working with a furnace in the process of smelting silicon metal. In particular, we used an interval between top treatments of about 30 min and adhered to the principles of balanced smelting, i.e., provided a balance between the intensity of the uniform supply of the charge into the furnace and the current active electrical power. Industrial testing carried out over four weeks confirmed the stability of the operation of cheaper carbon electrodes with a through axial hole. The recovery of silicon into finished products was also improved to 88–89% and the specific energy consumption was reduced to 11.2–12.1 MWh/t of silicon metal from the initial value 14,752 MWh/t. Thus, we received additional evidence for the effectiveness of our approach in furnace operating compared to an approach based on the ultimate provision of gas and permeability of the furnace top due to excessively intense processing of the top and an uncontrolled, uneven supply of charge to the furnace.

Dynamic response mechanism of the hole subjected to the 3D point source disturbance in an isotropic formation

Accurate estimation of the effects of dynamic disturbances on stress concentration is crucial for the stability of rock engineering and the corresponding analytical approaches are needed. This study presents an analytical approach to calculate the relative stress distribution with a point source inside and outside a hole using the linear theory of elasticity. The Helmholtz potentials and Sommerfeld integral are employed to describe the displacement and stress components, and then formulate the equilibrium equations to solve the equivalent stress distribution around the hole. Numerical examples demonstrate the impact of model parameters on the equivalent stress, such as frequency, hole radius, source location, etc. It is found that sometimes high frequencies can make the equivalent stress greater far from the source than that close to the source. Additionally, when the ratio of the distance between the source and the hole axis to the hole radius exceeds ten, the equivalent stress distribution around the hole remains nearly constant. This approach can be used for the design and assessment of underground engineering structures' stability under dynamic disturbances.

Study on explosion impact pressure and damage distribution law of rock powder segmented charge

The charge structure is the critical to determine the bench blasting effect of rock slope. Through theoretical calculation, model testing, and numerical simulation, a formula for calculating the stress attenuation of the axial hole wall of the segmented charging structure is proposed. Moreover, the influence mechanism of the explosive ratio and interval packing length on the internal damage distribution of the concrete of concrete specimens under a segmented charging structure of the cuttings is described. Finally, the research results are applied to the mining of a rock slope in southwest China. The research results reveal the following: 1) The pressure at the charge section is highest when the rock debris interval charge is used, and with the increase in the charge section distance, the pressure markedly decreases—sharply first before stabilizing. In the upper filling interval charge section, the minimum pressure corresponded to approximately the midway point of the filling section, and the stress distribution on the axial hole wall is concave: high at both ends and low in the middle. 2) The ratio of the upper and lower sections of the explosive column determines the form of blasting damage, and the range of blasting damage increases first and then decreases with the increase in the length of the rock debris in the interval section. 3) The field test shows that compared with the traditional blasting charge structure, the optimized segmented charge structure can reduce the blasting block rate by 13.1%. 4) Using the optimized charge structure, the explosive unit consumption can be decreased from 0.27 kg/m3 to 0.24 kg/m3, which improves the economic benefits of mining and construction of related mines.

Effects of pressure relief holes on coal burst: Insights from true-triaxial unloading tests

Drilling pressure relief is one of the methods to reduce the risk of coal bursts in deep mines. However, the effect of the drill hole orientations has not been studied well enough to understand their impact on the burst failure mechanism. In this study, we investigated two designs of drill hole orientations. The first design includes drill holes located on the upper free face of the rectangular samples and labelled as upper hole (UH) and centre hole (CH) – the long axes of the drill holes are aligned with minor principal stress, σ3, direction. The second design includes drill holes at the top (TH) and the side (SH) of the rectangular samples in which the long axes of the drill holes are aligned with the maximum, σ1, and intermediate principal stress, σ2, directions, respectively. The coal samples with the proposed drill hole orientations were subjected to the true-triaxial unloading coal burst tests. The results show that the drill holes reduce the risk of coal bursts. However, we found that the intensity of coal burst was significantly reduced with the SH-type, followed by the CH-types. We also observed that the coal burst intensity is reduced better for the CH, UH, TH, and SH-type drilling patterns. However, it was found that the orientations of drill holes have little influence on the failure mode (splitting). The acoustic emission (AE) activities for coal with drill holes noticeably decreased, especially for the UH and CH layouts. The drill holes reduced the upper limit of the AE entropy (chaos of microcracks generation). However, regarding reducing the coal burst risk, the TH and SH are less effective than UH and CH.

Method of inclined hole axis adjustment based on geometric optimization and minimum zone theory

The machining accuracy of the axis position and spatial angle of the array microholes with high aspect ratio on the components of the high-end equipment manufacturing industry will directly affect the performance of the whole machine. A method of tilt hole axis adjustment is proposed in this paper. It utilizes geometric optimization and minimum zone theory to measure the position and spatial angle of the hole axis. This addresses the slight angle error that occurs after correcting the inclined hole axis using visual techniques. Based on the minimum zone criterion for the cylindricity error, the evaluation model is re-established through the inner and the outer loop and spatial projection, which includes roundness evaluation of the projection curve by an improved particle swarm optimization (PSO) algorithm and elliptic fitting by a geometric parameter method, so as to obtain the optimal solution of the axis vector and spatial angle. Experimental comparison with the theory above shows that the precision of the method proposed is better than that of the least squares method and the traditional PSO algorithm based on the minimum zone criterion. The research results indicate that the precision of the tilt angle is better than 0.03°, and simultaneously the rotation angle is better than 0.1° in the range of 1°. This experiment verifies the effectiveness and accuracy of the proposed method.

Error Analysis of Normal Surface Measurements Based on Multiple Laser Displacement Sensors.

The robotic drilling of assembly holes is a crucial process in aerospace manufacturing, in which measuring the normal of the workpiece surface is a key step to guide the robot to the correct pose and guarantee the perpendicularity of the hole axis. Multiple laser displacement sensors can be used to satisfy the portable and in-site measurement requirements, but there is still a lack of accurate analysis and layout design. In this paper, a simplified parametric method is proposed for multi-sensor normal measurement devices with a symmetrical layout, using three parameters: the sensor number, the laser beam slant angle, and the laser spot distribution radius. A normal measurement error distribution simulation method considering the random sensor errors is proposed. The measurement error distribution laws at different sensor numbers, the laser beam slant angle, and the laser spot distribution radius are revealed as a pyramid-like region. The influential factors on normal measurement accuracy, such as sensor accuracy, quantity and installation position, are analyzed by a simulation and verified experimentally on a five-axis precision machine tool. The results show that increasing the laser beam slant angle and laser spot distribution radius significantly reduces the normal measurement errors. With the laser beam slant angle ≥15° and the laser spot distribution radius ≥19 mm, the normal measurement error falls below 0.05°, ensuring normal accuracy in robotic drilling.

Testing a new technique for producing artillery cartridge cases from pipe workpiece by roughing with a friction tool

The object of this study is the technological process of manufacturing parts such as artillery shells using pressure treatment methods. The work is aimed at solving the current scientific and technical task to improve the technological processes for manufacturing parts such as cartridge cases based on the use of a tangential rolling operation with a friction tool, which ensures the production of hollow products with a bottom. Using the finite element method, modeling of the bottom rolling processes was carried out, which made it possible to establish the effective geometry of the processed workpieces and their heating temperature. Recommendations have been devised for the design of new technological processes for roughing bottoms, which consist of determining the wall thickness of the workpiece before deformation, the heating temperature of the workpieces, and the amount of supply of the workpiece to the friction tool. The resulting recommendations were verified by experimental studies. Roughing of spherical bottoms should be carried out for pipes with a relative wall thickness (D/s) in the range of 15...20, the homologous heating temperature should be 0.8, and the relative feed of the workpiece into the friction tool should be 0.9. Testing the established relationships under laboratory conditions confirmed the recommendations for changing the shape of spherical bottoms during the roughing process. The results of metallographic studies on full-scale products confirm the results of the theoretical study. It is recommended to use this technique for products that have an axial hole (artillery shells, hydraulic cylinders, etc.), which will allow removing axial defects in the bottom after drilling the axial hole. The results could be used at machine-building enterprises in the manufacture of dual-use parts

Changes in the Thermal and Stress-Strain State of the HPC Rotor of a Powerful NPP Turbine after the Blades Damage

In practice, during the operation of steam turbines, accidental damage to the blades of the rotors and stators of powerful steam turbines occurs. The main causes of emergency stops of steam turbines were vibration fatigue of the blades material, erosive damage to the blades body, and resonance problems during the power equipment operation. Based on this study, the assessment of changes in the thermal and stress-strain state of power equipment elements, which at nuclear power plants significantly affect the continued operation of the turbine after its damage, are quite relevant. Changes in the thermal and stress-strain state, which may occur after damage to the rotor of high-pressure cylinder (HPC rotor) of the K-1000-60/3000 turbine power unit of the LMZ in the station conditions, have been considered and analyzed and will provide an opportunity to assess the individual resource and continue the power unit operation. In the calculated assessment of changes in the thermal and stress-strain state of the HPC rotor, taking into account the data of the technical audit regarding damage, a geometric model of the rotor was created. Studies were conducted for three options of designs: the original option (five stages of the HPC rotor), the option without the blades of the last stage and the option without the fifth stage (with four first stages). For the project design, when working at the nominal parameters of the steam, the most stressed areas are the unloading holes of the 5th stage (σi=202.8 MPa), axial hole of the rotor in the area of the 5th stage (σi=195.2 MPa), as well as the 5th-degree welding fillet from the side of the end seals (σi=200.3 MPa) and unloading holes of the 4th and 3rd stages with a stress intensity of about 170–185 MPa. The high values of the stress intensity in the area of the 5th stage can be explained by the significant concentration of the mass of both the stage itself and its blades, which provoke significant centrifugal forces when working at the nominal rotation frequency. For a HPC rotor without blades of the 5th stage, there is a shift of the maximum stress intensity to the area of the unloading holes of the 4th and 3rd stages, as well as the axial hole of the shaft under the same stages. The maximum stress value is σi max=184.8 MPa. At the same time, the intensity of stresses in the area of unloading holes of the 5th degree decreased almost by half, to the level of 124 MPa.

Experimental study on the breakdown mechanism of high temperature granite induced by liquid nitrogen fracturing: An implication to geothermal reservoirs

To reveal the breakdown mechanism of dry hot rock (HDR) induced by liquid nitrogen (LN) fracturing, the laboratory tests were performed on high temperature granite using specialized apparatus. The breakdown pressure and fracture morphology of high temperature granites subjected to different heating temperatures and thermal treatments were analyzed. The results showed that the breakdown pressure of granite decreased with heating temperature increasing. As the heating temperature increased from 25 °C to 300 °C, the breakdown pressure of high temperature granite decreased by 40.63%. In addition, the failure mode mainly presented in the form of tensile fractures, which developed into bi-wing fractures along the hole axis. For heating temperature higher than 220 °C, the high temperature granite presented an increase in fracture complexity with the increased heating temperature. After pre-cooled with LN, the breakdown pressure was lowered and the fracture complexity was enhanced. For example, the breakdown pressure of LN-treated sample was 4.61%–27.70% lower than heated sample. Under cryogenic conditions induced by LN, the failure mode mainly presented in the form of randomly distributed tiny cracks and holes, which made the breakdown pressure decreased by 8.67%–59.46%. LN fracturing could cause multiple cracking effects including thermal fracturing (i.e., thermal shock, cryogenic damage and cryogenic cracking) and pressure-induced fracturing on HDR. Importantly, the thermal fracturing effect could reduce the breakdown pressure and improve the fracture complexity.

Detection of defects in polyethylene pipes using open microwave coaxial line resonator sensor

A new method using a microwave coaxial line resonator sensor for the non-destructive evaluation of defects in polyethylene pipes is presented. The sensor consists of a coaxial line section and an extended section of circular waveguide. One end is short-circuited and the other end is open to free space. The sensor aperture is designed to conform to the curvature of the pipe outer surface, so that the common problem of the standoff distance effect by open-ended waveguide scanning is well circumvented. The presence of defects causes local permittivity and volume changes, leading to variations of the resonance frequency and quality factor due to material perturbation. The detection principle is confirmed by electromagnetic simulation. From the experiments, it is shown that the proposed sensor can perform both detection and classification of flat-bottom holes. The minimum diameter of the hole that can be detected is 1 mm, which is lower than that of a hole required in the standard practice. This method can also effectively detect axial defects and determine the lengths. In addition, an open-ended waveguide is used to detect axial holes, and the results were compared with those of coaxial line resonator. The sensor system presented here has the advantages of low cost, convenience for on-site detection and quantitative analysis.

Cooling Optimization of a Large Duplex Forged Bar and Subsequent Improvement in Impact Toughness over Its Thickness

The machining of a central axial hole in a duplex stainless steel 2205 bar is sufficient to optimize cooling and thus to achieve the toughness requirements of the most demanding international standards. The cooling rates are obtained by finite element methodology simulation. The increased cooling rate in the central zone of the bar is directly related to the improvement of the Charpy impact toughness. Microstructure at different bar locations is characterized by optical microscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectrometry. In the absence of sigma phase precipitation, an austenite spacing over 45 μ provokes a decrease in absorbed energy close to 40 J. Moreover, the pierced bar complies with the international standards requirements in tensile with yield strength higher than 450 MPa and Rockwell hardness lower than 31 (HRC) over the section and along the bar. Finally, the resistance to pitting corrosion required is also satisfactory due to the absence of chromium nitrides.

A Cooling Efficiency Model and Numerical Research of Multiparameter Film Cooling

Abstract Based on the validated simulation method of film cooling and multiphase flow simulation method, a multi-level three-dimensional simulation of forward-leaning fan-shaped film hole, cylindrical film hole with different injection angles, and film hole containing water vapor are established to discuss the effects of film hole structure parameters, hole distance, blowing ratio, injection angle, and water vapor volume on film cooling efficiency. The cooling efficiency of forward-leaning fan-shaped film hole increases as the exit length of film hole increases. After adding water vapor, the cooling efficiency of fan-shaped film hole decreases, and the influence of hole axis length and exit length on cooling efficiency is weak. For the cylindrical film hole, the larger the injection angle of film hole, the larger the film coverage area under the same blowing ratio. After adding water vapor, with the increase of the blowing ratio, the film coverage area increases first and then decreases. However, the film coverage area decreases with the increase of cooling injection angle for film holes containing water vapor. The cooling efficiency of the film hole with and without water vapor is related to the vapor velocity in the rising direction and the velocity in the mainstream direction, respectively. A model of film cooling efficiency with air blowing ratio and injection angle is established and verified with experimental data, based on the law that the average cooling efficiency in the main flow direction grows exponentially with the sine of the injection angle.

Effect of high-speed steel screw drill geometry on cutting performance when machining austenitic stainless steel

Drilling into the solid material is one of the basic technological operations, which creates a cylindrical hole in an appropriate time with required quality. Drilling operation demands a favourable removal of chips from the cutting area because a creation of an undesirable shape of chips can impart a lower quality of the drilled hole corresponding with the generation of excess heat due to the intense contact of the chip with drill. The solution for a proper machining is a suitable modification of the drill geometry i.e., point and clearance angles as presented in current study. The tested drills are made of M35 high-speed steel characterized by a very thin core at the point of the drill. An interesting feature of the drills is the use of cutting speed higher than 30 m min−1, with the feed of 0.2 mm per revolution. The surface roughness (Ra and Rz lower than 1 µm and 6 µm respectively), cylindricity (0.045 mm), roundness (0.025 mm), perpendicularity of the hole axis (0.025 mm), diameters and position of the individual holes were achieved for a drill with point angle 138.32°and clearance angle 6.92 respectively. The increase of the drill point angle by 6° resulted in the decrease in the feed force of more than 150 N. In addition, an increase of the clearance angle by 1° resulted with a decrease in the feed force of 70 N. The results of the experiment showed that with the correct geometry of the tool the effective machining without using internal cooling can be realised.

Bending Deformation and Ultimate Moment Calculation of Screen Pipes in Offshore Sand Control Completion

Horizontal wells, extended-reach wells, and multi-branch wells were often used to exploit subsea oil and gas efficiently. However, during the sand control screen completion of those wells, the sand control screen pipe was easily deformed. Failure occurred when passing through the bending section due to the large bending section in the wellbore trajectory. A parametric analysis model of the screen pipe was established based on ABAQUS and Python software under pure bending load first. Then, deformation patterns and mechanisms were identified and discussed. The effects of parameters on the screen pipe bending deformation patterns and the ultimate moment were analyzed. Finally, an empirical formula for calculating the ultimate moment of the screen pipe was established. The results showed that the deformation of the screen pipe was complex, and three deformation patterns were related to the hole parameters. Due to an increase in the diameter and number of circumferential and axial holes, the ultimate moment of the screen pipe gradually decreased, and the circumferential holes had a more significant effect on the ultimate moment than the axial holes. The established empirical formula could accurately calculate the ultimate moment of the screen pipe, and the average difference between the formula and numerical simulation results was 3.25%.

A chiral microchip laser using anisotropic grating mirrors for single mode emission

Abstract A pair of nanostructured mirrors made of a diffraction grating inscribed in the top layer of a Bragg mirror are designed such that a phase shift near π and different reflected amplitudes exist between transverse electric (TE) and magnetic (TM) reflected polarization states at normal incidence. When a standing wave laser resonator is formed with two such mirrors and the two mirrors’ principal axes are twisted one with respect to the other, this phase shift condition suppresses multiple longitudinal mode emission arising from axial spatial hole burning. In addition, the different amplitudes of TE and TM reflected polarizations create polarization eigenstates with different round-trip losses, suppressing one polarization eigenstate. Laser experiments made with a Yb3+-doped Y3Al5O12 active material reveal enhanced purity of the emission spectrum compared to similar lasers using conventional laser mirrors. The proposed design enables a miniature single mode laser, replacing more complex designs usually needed to achieve that goal.

CFD studies of the effect of holes and angles of upstream duct of horizontal axis wind turbines

This work presents an approach to the analysis of duct-augmented wind turbines using Computational Fluid Dynamics (CFD). The main objective is to find the optimum duct shape and design that gives maximum boost to the performance of wind turbines. A duct surrounding the rotor is able to increase the power coefficient above the Betz limit, so it has attracted great attention for many years. In this work, an extensive analysis of the performance of duct augmented wind turbines is presented, considering the influence of various duct angles and axial holes in the diffuser on the efficiency, in which a new formulation for the far-wake velocity is proposed. This study consists of two main parts. The first part compares the experimental performance of a conventional wind turbine with the identical turbine modeled and solved using CFD. Once the CFD results are validated, the second part presents an extensive parametric study by integrating a convergent duct with different parametric designs into the wind turbine model. The study reveals that the CFD results are in close agreement with the experimental results. It is found that the presence of holes in the duct has a detrimental effect on performance. However, the increase in the angle of the duct enhanced the performance, and there was an average increase in power output by 96% with a duct angle of 20°.

Evolution of the Stress–Strain State of Porous Workpieces in Hot Extrusion Forging to Produce Axisymmetric Parts with an Axial Hole

Evolution of the Stress–Strain State of Porous Workpieces in Hot Extrusion Forging to Produce Axisymmetric Parts with an Axial Hole

Tensile behavior of a laminated magnesium-aluminum composite with axial elliptical holes

A 3D finite element simulation of the behavior of a prismatic sample of a magnesium-aluminum composite material AMg6-AD1-MA2-1 with an elliptical defect in the AD1 layer under axial tension was carried out, its strength and the change in the stress-strain state were determined when the thickness of the AD1 layer varied from 5 to 1, 25 mm. A change in the stress-strain state and strength during perforation transfer to the MA2-1 layer was revealed.

Microforce Sensing and Flexible Assembly Method for Key Parts of ICF Microtargets

Microassembly is one of the key techniques in various advanced industrial applications. Meanwhile, high success rates for axial hole assembly of thin-walled deep-cavity-type items remain a challenging issue. Hence, the flexible assembly approach of thin-walled deep-cavity parts is investigated in this study using the assembly of the key components, the microtarget component TMP (thermomechanical package) and the hohlraum in ICF (inertial confinement fusion) research, as examples. A clamping force-assembly force mapping model based on multisource microforce sensors was developed to overcome the incapacity of microscopic vision to properly identify the condition of components after contact. The ICF microtarget flexible assembly system, which integrates multisource microforce sensing and a six degrees of freedom micromotion sliding table, is presented to address the constraint that the standard microassembly approach is difficult to operate once the parts contact. This method can detect contact force down to the mN level, modify deviation of the component posture efficiently, and achieve nondestructive ICF microtarget assembly at the end.

Discrete Element Simulation of Fracture Evolution around a Borehole for Gas Extraction in Coal Seams.

The stability analysis of underground caverns, tunnels, and boreholes is of great significance to underground engineering. In order to study the stress change of the coal around a hole and the evolution law of fractures during the coal seam drilling process, the discrete element simulation of the coal seam drilling process was carried out by using the particle flow code (PFC2D). The results show that during the drilling process, under the influence of confining pressure and drilling disturbance, the coal stress field around the hole and the development of fractures around the hole have the characteristics of zoning and dynamic evolution. In the axial direction of the borehole, it is divided into front and rear areas, and in the vertical axial direction, it is divided into the drilling disturbance zone and the confining pressure main control zone. During the drilling process, the direction of the maximum principal stress in the front zone gradually changes from the vertical hole axis to the direction parallel to the hole axis, and tension fractures are mainly developed along the drilling direction. In the rear zone, the principal stress direction tends to be stable and the principal stress value undergoes dynamic changes, and a large number of vertical hole axis tension fractures are developed. The drilling disturbance zone appears near the hole wall and has an important influence on the stability of the hole wall, while the confining pressure main control zone determines the antireflection effect around the hole and the influence radius of the hole. This work helps the understanding of the damage range and failure characteristics of the surrounding rock during the drilling process and has great significance for the guidance of drilling design.