Entrance Edge Research Articles

Experimental and numerical optimization study on CNTs/Al composites drilling based on response surface methodology

Carbon nanotube reinforced aluminum (CNTs/Al) composites have been widely used in the aviation field due to their excellent properties, but there are still problems in their drilling, such as unclear damage mechanisms and poor hole quality. This study investigates the removal mechanism of CNTs/Al composites during drilling by finite element simulation and single factor experiments, and the impact of process parameters on hole wall morphology and the quality of the entrance edge is revealed. Optimal process parameter combinations are determined based on the response surface methodology (RSM) and multiobjective optimization via the NSGA-II genetic algorithm, with method verification. The results show that during the drilling process of CNTs/Al composites, CNTs primarily experience fragmentation, rebound, and pull-out, while the Al matrix exhibits partial tearing and interfacial separation. The coating of the Al matrix and CNT agglomeration contribute to defects like burrs and microcracks. Entrance damage is notably more severe than exit damage, characterized by higher tearing factor values, longer side burrs, and increased trajectory scratch areas. The main process parameter that affects surface roughness and entrance tear is feed rate. The results of multiobjective optimization are n = 3830 r/min, f = 0.0674 m/min, h = 2.0558 mm, with Ra = 6.327 μ,m and LD1 = 1.01732. Experimental validation shows Ra = 6.331 μm and LD1 = 1.01743, with errors of 0.063% and 0.011%, respectively.

Evolution features and a prediction model of casing perforation erosion during multi-staged horizontal well fracturing

Large-displacement high-intensity sanding hydraulic fracturing operations often cause casing perforation erosion and thus temporary plugging failures, exacerbate the unevenness of fracture initiation and expansion, and induce casing damage. In order to clarify the dynamic evolution of perforation erosion and predict perforation diameter, the effects of different types of proppants, the viscosity of sand-carrying liquids, and large sand-passing quantities on perforation erosion rate were experimentally explored in the study. The evolution of perforation erosion and the particle size distribution of quartz sand and ceramsite were analyzed in the experiment and a prediction model for perforation erosion under various fracturing parameters was established. Compared to ceramsite, quartz sand had the more significant effect on perforation erosion and the more serious particle abrasion and fragmentation under the same sand-passing quantity. Increasing the viscosity of the sand-carrying liquid slowed down perforation erosion and made the edge of perforation entrance more uniform. As the sand-passing quantity through the perforation increased, perforation erosion in the initial stage was concentrated at the perforation edge. Then, the inner wall of the perforation was also eroded, but the average erosion rate was reduced. A prediction model of perforation erosion considering multiple fracturing parameters was established based on the principle of fluid similarity. The errors between predicted values and downhole eagle-eye observation values were less than 15 %. The model provides an important basis for the optimization of fracturing parameters and downhole casing strength design.

Dimethicone-assisted interlaced scanning compound cutting for regulating thermal damage in CFRP laser cutting by synergistic suppression of coupled heat effect

Carbon fiber reinforced polymer (CFRP) is prone to produce significant thermal damage such as heat-affected zone (HAZ) during laser cutting, which seriously affects the processing quality. In this paper, a new method of dimethicone-assisted interlaced scanning mode (DISM) compound cutting is proposed to regulate the surface damage of CFRP nanosecond UV laser hole cutting. Based on the simulation and experimental testing analysis, the coupling effect of heat conduction and heat accumulation during the laser cutting process, as well as the suppression mechanism of heat effects by compound cutting methods have been described. Compared to the default cutting method, DISM can effectively reduce the damage of CFRP laser hole cutting. The average matrix recession (MR) width of the hole entrance edge is reduced by 47.54% for DISM, while eliminating the heat-damaged matrix (HDM) zone, resulting in a comprehensive reduction of HAZ by 85.2%. The most obvious parameter combination for the reduction of MR width is 50 kHz, 1000 mm/s, and 0.06 mm, where the MR is reduced by 61.31% (37.61 μm→14.55 μm). Interlaced scanning mainly reduces MR width, while dimethicone-assisted processing exhibits suppression of HDM. The compound cutting method significantly reduces thermal damage and improves CFRP mechanical properties.

Scour hole reduction at a diversion channel junction using different entrance edge shapes

In the current study, the effect of the entrance edge shape on the scour hole in the diversion junction region was experimentally investigated. The investigation has considered three entrance models-rounded edge shapes on one or both sides of the diversion channel entrance-with five different inlet edge radius ratios (rr) of 25%, 37.5%, 50%, 62.5%, and 75% and five different diversion discharge ratios (Qr) of 7.5%, 12.5%, 17.5%, 22.5%, and 30%. The results have found the direct relation between Qr and the scour depth to the diversion channel water depth ratio (ds/yb). Moreover, the use of a rounded edge shape on one or both sides of the diversion channel entrance instead of a sharp shape results in a reduction in scour depth to diversion channel water depth ratio (ds/yb) when the Qr is greater than 20%. The results also indicated that the largest decrease in the scour coefficient (Kds) for the model with a rounded downstream edge compared with the sharp edge diversion channel entrance shape was 22% at a discharge ratio of 22.5% and an edge radius ratio of 37.5%. In addition, the entrance shape model with a rounded edge at the upstream outperformed other models in scour reduction with an average of all experiments of 5.77%. Finally, empirical relations for estimating scour depth for different rounded edge models in terms of the effective dimensionless parameters were established with coefficients of determination (R2) of not less than 0.853.

Last stage stator blade profile improvement for a steam turbine under a non-equilibrium condensation condition: A CFD and cost-saving approach

Non-equilibrium phenomena and related damages have always been one of the great concerns among researchers, designers, and industry managers. In power plants, the overhaul of turbines during a pre-planned schedule includes checking, repairing, and replacing damaged parts, which always challenge industry investors with variable costs. In this study, a modified profile for the stationary cascade blades of a 200 MW steam turbine is predicted by help of the Computational Fluid Dynamics (CFD) according to a cost-saving approach for a power plant. Wet steam model is used to investigate the flow behavior between the turbine blades, due to the sonication and non-equilibrium phenomena. The numerical model based on the Eulerian-Eulerian approach accounts the turbulence caused by the presence of droplets, condensation shocks and aerodynamics. At first, such model has been carefully validated against the available experimental data. Then, the entrance edge of the blade is designed considering different shapes and sizes. The flow behavior at the entrance edge region has been fully investigated. Finally, according to the criteria for measuring the non-equilibrium flow phenomena (erosion rate, Mach number, entropy, exergy destruction and transfer of mass and heat between flow phases), a modified model for the steam turbine blade considering the economic aspects has been presented. The modified blade model exhibits 88%, 0.13% and 7% reduction in the erosion rate, entropy generation and exergy destruction, respectively. Furthermore, the application of this modified blade profile save 456$ of the total monthly maintenance costs.

STUDY OF THE TECHNOLOGICAL POSSIBILITIES OF THE BALL PROCESSING METHOD IN THE MAGNETIC FIELD OF BLADES WITH OPERATIONAL DAMAGE

Purpose. To conduct a study of the technological possibilities of the method of treatment with balls in the magnetic field of the pen of vanes that have operational damage. Research methods. A mechanical method for the study of residual stresses, developed by аcad. Davydenkov, an experimental method for determining the endurance of blades, stepwise regression methods for building regression models. Results. The study of the geometry of the blade feathers shows that the biggest change in the geometry of the blades occurs in the peripheral zone (intersections A7-A7 and A8-A8). The measurement results show that the microhardness of the surface on the side of the trough is significantly lower than on the backs, and the highest values of roughness are recorded in the peripheral zone of the trough on the side of the entrance edge, which corresponds to the place of maximum operational damage. The parameters of the surface layer were studied and the scheme and optimal mode of processing blades with steel balls in a magnetic field was determined, which leads to a 39% increase in the endurance limit compared to blades that have experience in operation. Regression models of self-oscillation frequencies and blade run-in were built for two engines operated under the same conditions, but with different run-in. Special attention should be paid to measures that can minimize erosive wear of blade edges and increase the service life of engines. Scientific novelty. A new method of processing the blade feathers with balls in a magnetic field is proposed, which allows differential processing of the blade feathers: only the edge or the entire feather. Also, the method allows you to process blade feathers with operational damage, which leads to increased durability of blades. Practical value. The conducted studies allow us to recommend the use of the method of processing blade feathers with steel balls in a magnetic field as a technological operation for the restoration of compressor blades that have operational damage in the form of potholes on the inlet edges.

Study on Smoothing of Hole Wall Surface by Electron Beam Polishing under Control of Magnetic Field

A surface finishing method by large-area electron beam (EB) irradiation called EB polishing has been developed recently. Highly efficient surface smoothing of mold steels with planar shape can be performed by the EB polishing. However, it is difficult to smooth wall and bottom surfaces in hole shape by the EB polishing, since the EB tends to concentrate on entrance edge or upper inside wall of hole, and the energy density of EB on the wall and bottom surface of hole may decrease. Our previous study showed that the bottom surface could be smoothed by EB polishing under control of magnetic field around the workpiece. It is highly expected that EB can be also guided to the whole area of hole wall surface under appropriate control of magnetic field there.In this study, smoothing of hole wall surface by EB polishing under control of magnetic field around the workpiece was proposed. As a basic study for smoothing of hole wall surface, L-shaped workpiece was prepared by combining two stainless steel plates, and magnet was set under the workpiece. The electromagnetic field analysis results suggested that EB could be guided to the whole area of side surface by setting magnet under appropriate setting position, since magnetic force lines are uniformly distributed on whole area of side surface. In addition, magnetic flux destiny on the side surface more increases by setting a yoke made of steel on the magnet. The experimental results show that smoothed area with the surface roughness of less than 1.5μmRz can be obtained on the whole area of side surface. Therefore, the whole area of side surface can be uniformly smoothed by guiding the EB to the side surface under appropriate control of magnetic field.

The Effect of Entrance Edges Shape of the Diversion Channel on the Dividing Streamlines Behavior at the Junction Region

Diversion channels are used in irrigation networks and many of water resource projects. Due to the diversion of a portion of the water, a ratio of the main flow streamlines is deflected to the diversion channel (on the diversion side). The ratio of dividing streamlines increases from the surface to the bottom due to the high momentum of the flow upper layers,which resists its diversion. This negatively affects the quality of diversion water, as the largest proportion of it comes from the high sediment concentration of the lower layers. In this study, the effect of changing the sharp edge of the diversion channel entrance to a circular edge (at upstream, downstream or both sides) on the behavior of dividing streamlines. The study considered five different percentages of the diversion discharge ratio (between 7.5% and 30% of the total discharge) with five different diameters of the circular edge. The results indicated that there is a noticeable improvement of the dividing streamlines uniformity along the flow depth when using the upstream and downstream circular edge, as well as when using large diameter of the upstream circular edge only. In addition, increasing the discharge ratio reduces the regularity of the flow lines.

Drilling of CFRP plates with adjustable pulse duration fiber laser

ABSTRACT CFRP plates are important advanced material used in the aerospace field, high-quality and high-efficiency drilling is the main application processing demand of CFRP. In this paper, a 532 nm nanosecond fiber laser with adjustable pulse duration is used and the scanning path was planned as Z-direction up-bottom incremental cutting, and X-Y direction concentric circle cutting scanning mode to realize the CFRP plates hole drilling, and obtain high drilling performance. The mechanisms of material removal for CFRP plates hole drilling under 532 nm nanosecond laser is explored, and it is mainly attributed to thermal evaporation accompanied by certain heating carbonization. The results show that a narrow width of HAZ can be obtained with short pulse duration, the minimum value of HAZ width at hole entrance edge is 18.74 µm, and the matrix material damage near the HAZ becomes small. Reducing the pulse duration also helps to decrease the drilling taper (minimum taper value 0.046), the taper of the drilling hole is smaller than that of the drilling dicing. But the drilling efficiency is reduced due to the low pulse energy with short pulse duration.

Research on Operation Stability of Standard Orifice Plate in Nuclear Power Plant KME System

In order to promote the power stability of nuclear power units, the KME thermal balance principle is used to further analyze the factors affecting the flow of the standard orifice plate of the nuclear power plant KME system (Test Instrumentation). The high-accuracy three-coordinate measuring machine is used to detect the arc radius of the entrance edge of the standard orifice plate and the inner diameter of the standard orifice plate. Analysis the operation history data of the standard orifice plate of the nuclear power plant KME system. Study the running radius of the entrance edge of the same orifice plate and the inner diameter of the standard orifice plate under different operating units. Obtain the influence of the arc radius of the entrance edge of the standard orifice plate and the inner diameter of the standard orifice plate of different types of units.

Study on the variation of recast layer in laser trepan drilling by millisecond Nd:YAG laser

Recast layer (RL) is a major defect in laser drilling of micro holes. In this study, some methods to reduce RL in micro-hole drilling were carried out by using a pulsed Nd:YAG laser (λ = 1.06 µm) on a type 304 stainless steel. Based on the previous optimization of laser parameters, trepanning velocity and rotation number in laser trepan drilling were specially studied of their effect on RL. Single-factor experiment and orthogonal experiment were both employed in the experimental research. It was found that the thickness of RL dropped rapidly with lower trepanning velocity and fewer beam rotations. However, when the two factors deviated from some range, cracks might emerge on entrance edges and inner walls, and the further they deviated, the more serious the cracks became. An equation was constructed to evaluate the optimizing effect simultaneously considering four factors: (a) the total volume of RL in a hole; (b) the sum of entrance crack length (CL); (c) the sum of inner CL; and (d) drilling efficiency. Eventually, in this article, an optimum set of parameters was obtained, which might generate micro-holes almost free of RL.

Investigation of the Machinability of the Inconel 718 Superalloy during the Electrical Discharge Drilling Process

The properties of the Inconel 718 superalloy are used in the manufacturing of aircraft components; its properties, including high hardness and toughness, cause machining difficulties when using the conventional method. To circumvent this, non-conventional techniques are used, among which electrical discharge machining (EDM) is a good alternative. However, the nature of removing material using the EDM process causes the thermophysical properties of Inconel 718 to hinder its machinability; thus, a more extensive analysis of the influence of these properties on the EDM process, and a machinability analysis of this material in a wider range, using more process parameters, are required. In this study, we investigated the drilling of micro-holes into the Inconel 718 superalloy using the EDM process. An experiment was conducted to evaluate the impact of five process parameters with a wide range of values (open voltage, time of the impulse, current amplitude, the inlet dielectric fluid pressure, and tube electrode rotation) on the process’s performance (drilling speed, linear tool wear, the side gap thickness, and the aspect ratio of holes). The analysis shows that the thermal conductivity of this superalloy significantly influences the effective drilling of holes. The combination of a higher current amplitude (I ≥ 3.99 A) with an extended pulse time (ton ≥ 550 µs) can provide a satisfactory hole accuracy (side gap thickness ≤ 100 µm), homogeneity of the hole entrance edge without re-solidified material, and a depth-to-diameter ratio of about 19. Obtaining a high dimensional shape accuracy of holes has an enormous effect on their usability in the structure of the components in the aviation industry.

Effect of Ultrasonic Impact Treatment on the Fatigue Performance of Cold Expanded AA6061-T6 Hole

Cold expansion is widely used to improve the fatigue life of fastener holes. However, fatigue crack often initiates at the entrance edge of the hole due to lower compressive or tensile residual stress as a result of cold expansion. In the current study, the entrance edge of the cold expanded hole has been ultrasonically impacted with a specially designed pin, and comparative fatigue tests are performed to evaluate the influence of the ultrasonic impact treatment on the fatigue performance of the cold expanded holes. The findings show that the ultrasonic impact treatment imparted a larger compressive residual stress and created a fillet arc at the entrance edge, which resulted in an obvious reduction in the fatigue crack propagation rate in the earlier stage of the fatigue crack growth and extended the fatigue life of the cold expanded holes further.

Ablation characteristics of picosecond laser single point drilling of Si3N4 under dry and water medium

Single point laser ablation of Si3N4 under dry and water medium is investigated and analysed. The experiments were conducted based on the one-factor-at-a-time strategy considering various input parameters such as piercing time, focus point position and water layer thickness. The effects of process inputs on the ablated hole’s geometrical features including the ablation depth and diameter, hole taper, and hole edge roundness under presence and absence of water as an intermediate medium are studied. The laser focus point position was determined and varied during the investigation. It was found that, compared to the dry condition, the maximum ablation depth under wet condition is much more sensitive to the position of the laser focus point. It was also observed that the ablation depth is directly influenced by the piercing time in both dry and under water conditions. Picosecond laser single point ablation under a water layer with a thickness of 0.6 mm could increase the ablation depth up to 23%, compared to the dry condition. However, the ablation depth was significantly decreased by increasing the water layer thickness. Additionally, the hole entrance edge was rounded with increasing the water layer thickness. The hole taper was significantly influenced by the water layer thickness.

Enhancing the Efficiency of Small-Scale and Microhydroturbines Using Nature-Imitation Technologies for the Development of Autonomous Energy Sources

The issues of developing small-scale and microhydropower generation under present-day conditions as one of the renewable energy sources that do not aggravate environmental problems are considered. Some of the most effective approaches to designing microhydropower plants and small-scale and microhydroturbines that meet the environmental friendliness and high-energy efficiency requirements are outlined. The results of a computational study of a microturbine prototype with a blade system modified according to a principle of biomimetics (nature-imitation technologies) have been validated experimentally. Two modified configurations of the blade system are considered and compared with the original version under identical conditions. To increase the reliability of the findings, the experiment with the original and modified impellers of the microhydroturbine was repeatedly conducted. The energy characteristics of a microhydroturbine based on experimental data that demonstrate the best repeatability with an error not exceeding 10% are presented. Based on the calculated and experimental data, a comparative assessment of the turbine’s energy characteristics with the original and modified impellers is made. It has been established that the use of the so-called “growths” on the entrance edge of the impeller blades contributes to streamlining the flow pattern in the interblade channel. This, in turn, leads to a decrease in hydraulic drag and, consequently, to a decrease in hydraulic losses when flowing around the blade system. As shown by quantitative assessment of the energy characteristics, the energy efficiency of a microhydroturbine is increased by 20%, which proves the viability of the chosen direction for developing smallscale and microhydropower generation as well as the effectiveness of the approaches used in the design of the working bodies of microhydroturbines. Further ways of improving the approaches under study and obtaining new developments in this field of hydropower generation are scheduled and set forth.

Derived muscle arrangements and their shared innervation patterns of external and internal cheek pouches in rodents.

Cheek pouches have evolved from the oral cavity in rodents and act as temporary food storage repositories. There are two types of opening, internal and external. Details about the complex cutaneous muscles controlling the pouches have still not been fully elucidated. To understand the shared and derived traits of the muscles surrounding the cheek pouch and their innervation, we carried out an evolutionary morphological study using two desert kangaroo rats (Dipodomys deserti) and three plains pocket gophers (Geomys bursarius) from each of the two families equipped with external cheek pouches, and four Syrian hamsters (Mesocricetus auratus) with internal cheek pouches. The most conspicuous derived trait of the muscles between the external and internal cheek pouches, the sphincter sacculi, surrounds almost all of the edge of the outer entrance of the pouch. It is present in both species with external pouches, but not in hamsters, which have internal pouches. Our neurological findings demonstrate that most pouch muscles are innervated by both the facial and the cervical nerves, regardless of the pouch type. In these dually innervated muscles, the ventromedial part of the muscles tends to be innervated dominantly or uniquely by the cervical nerves, which usually enter from the superficial or lateral aspect. As a trait shared with the cervical nerves innervating the propatagial muscles in aerodynamic mammals such as bats and flying squirrels, and panniculus carnosus in most mammals, our neurological evidence suggests that the cervical nerve has the potential to innervate derived cutaneous muscles in the cervicofacial region.

Development of a gas filled magnet for FIPPS phase II

The Fission Product Prompt γ-ray Spectrometer (FIPPS) is a new instrument of the Institut Laue-Langevin (ILL) for the spectroscopy of nuclei produced after neutron induced reactions. The future upgrade of the instrument aims to explore the neutron-rich region of the nuclear chart with higher selectivity by identifying the fragments produced after neutron induced fission. The Gas-Filled-Magnet (GFM) technique has been chosen in order to obtain a good mass separation (<4 amu at A = 150) and a large geometrical and momentum acceptance (>50 msr and Δ P/P > 10%). A GFM design consisting of a 1/r magnetic field index and Thales circle-shaped entrance and exit magnet edges is proposed. The characteristic of the magnet is presented with realistic magnetic field calculations and Monte-Carlo simulations.

Material for Strengthening of Entrance Edges of Work Blades of Stream Turbines

Material for Strengthening of Entrance Edges of Work Blades of Stream Turbines

Study of the Effect of Heat Supply on the Hydrodynamics of the Flow and Heat Transfer in Capillary Elements of Mixing Heads Jet Thrusters

The article presents the results of experimental studies of hydrodynamics and those of loobman single-phase and two-phase flows in capillary nozzle elements propellant thrusters and the proposed method of their calculation. An experimental study was performed in capillaries with a sharp entrance edge of the internal diameter of 0.16 and 0.33 mm and a relative length 188 and 161, respectively, in pouring distilled water and acetone in the following range of parameters Reynolds number Re = (0,3 ... 10) · 103, Prandtl number Pr = (2 ... 10), pressure p = (0,1 ... 0,3) MPa, the heat flux q = (0...2)×106 W/m2, the difference of temperature under-heating of liquid Δtn = (5 ... 80)K. The dependences for calculation of single phase boundaries, the undeveloped and the developed surface of the bubble and film key singing of subcooled liquid. It is shown theoretically and experimentally confirmed the virtual absence of areas of undeveloped nucleate boiling in laminar flow. The dependence for calculation of hydraulic resistance and heat transfer in the investigated areas of current. It is shown that in the region of nucleate boiling surface in the flow in capillary tubes, influence of the formed vapor phase on the hydrodynamics and heat transfer substantially higher than in larger diameter pipes.

Magnetic fixtures for enhancement of smoothing effect by electron beam melting

In large-area electron beam (EB) irradiation method developed recently, high energy density EB can be obtained without focusing the beam. Therefore, large-area EB of 60mm in diameter can be used for instant melting and evaporation of the wide area material surface, and high efficient surface finishing is possible. However, if the workpiece has a hole shape, the EB concentrates in the entrance edge or inside wall of the hole. Thus, it is difficult to smooth the hole bottom surface. Previous study showed that the surface smoothing and micro-deburring effects for non-magnetic workpiece could be improved by setting a magnetic block under the workpiece, since the electrons tend to concentrate the magnetic block along magnetic lines. In this study, smoothing of hole bottom surface was experimentally investigated by setting a magnetic block under a workpiece in large-area EB irradiation. Expansion of smoothing area of the bottom surface was also tried by setting a through hole at the center of the magnetic block. It was clarified that wide area of hole bottom surface could be smoothed by large- area EB irradiation by setting the magnetic block under workpiece. The surface roughness decreased to less than 3.0μmRz at the area of hole bottom surface. When the hole diameter was 20mm and hole depth was less than 40mm, smoothing area of 10mm in diameter was obtained by using the magnetic block. Moreover, the smoothing area was sufficiently expanded by setting a through hole with an appropriate diameter in magnetic block.