Geometrical Dimensions Research Articles

Analytical investigation on the rotational behavior of dovetail mortise–tenon joints between beams and columns in traditional Chinese timber frames

We theoretically analyzed the rotational behavior of beam–column dovetail joints in traditional Chinese timber frames in this study. An analytical model of dovetail joints at both the column head and body was designed by clarifying the moment generation mechanism and effect of rotational embedment yielding in timber perpendicular to the grain on the rotational behavior of joints. An asynchronous manifestation of rotational embedment deformation across the column surface, tenon cheeks, and upper and lower surfaces of the tenon head was analyzed, and the corresponding characteristic yield points and consequent reduction in rotational stiffness were derived in the model. The Inayama embedment theory was used to clarify the effect of rotational embedment with varying end lengths on the movement of the joint rotation center and asymmetric moment generated in different rotation directions of the column head joint. The precision of the analytical model was validated through a comparative analysis by involving nine sets of experimental data, for estimating the initial stiffness, post-yield stiffness, and identified yield points. The implications of the parameters, including the initial gap between the tenon and mortise, geometric dimensions of the dovetail tenon, and friction coefficient, were also discussed. Controlling the ratio of the initial gap and tenon height within 0.01 to ensure a certain rotational resistance of dovetail beam–column joints within the collapse limits of traditional timber frames is recommended considering the significant effect of the initial gap on the initial sliding angle and moment reduction.

Calorimetric Measurements of a High-Power RF Signal

Development of a high-power RF signal meter based on the method of calorimetric measurements, which in some cases is the only possible one is presented. The device is as a system of elements exchanging either energy or information, the operation and interconnection of which ensures the stability of its functioning. The main elements of the device are: a coordinated load and a two-circuit water-air cooling system that convert RF energy first into thermal electrical energy, and then into internal energy of the coolant (working fluid). The measurement and control system provides information display on the monitor and generation of internal control signals. The work focuses on the process of converting electromagnetic energy into internal energy of the coolant, since the matched RF load is integrated into the cooling system and requires special design and technological solutions to ensure efficient operation. A cooling and measurement system has been designed to test the developed RF absorber with a power of up to 5 kW. The parameters of the cooling system were determined based on minimizing the time to achieve thermal equilibrium (time to establish readings) and the set parameters (input temperature no more than 35 °С, temperature difference no more than 40 °С). Based on calculations of the electrodynamic model constructed by the partial domain method, the geometric dimensions were determined at which the voltage standing wave ratio of the load in the operating frequency range (from DC to 1300 MHz) will be the smallest. The article presents the results of designing a high-frequency wattmeter cooled by a liquid (water), examines the thermophysical processes occurring in it and the influence of the presence of a coolant in the cooling circuit.

Design and experiment of a deviation information detection mechanism for sugar beet harvesters based on agricultural machinery and agronomy integration

To address large geometric shape differences, poor ridge distribution straightness and the uncertain spatial distribution of beet roots during the harvesting period, as well as damage caused by the inaccurate row correction detection mechanisms of combine harvesters, this study conducts a design analysis and performance tests of deviation information detection mechanisms based on the integration of agricultural machinery and agronomy. The agronomic process of mechanized sugar beet production was analyzed, the geometric dimensions of root tubers under typical planting patterns of typical varieties in main sugar beet production areas were measured, and a three-dimensional geometric model of beet root tubers was established. A device for measuring ridge shape and root tuber distribution was designed, and agronomic parameters during the harvesting period, such as plant spacing, ridge height, unearthed height, and deviation distance of beet root tubers, were measured and analyzed. A spatial model of ridge shape and beet root tuber growth distribution on the ridge during harvesting was established. The overall structure of the deviation information detection mechanism was analyzed and designed, and the structural forms and key parameters of key mechanisms, such as left‒right swing detection and up‒down floating profiling, were designed on the basis of agronomic parameter analysis. Using the missed detection rate as the evaluation index, field performance tests of the deviation information detection mechanism were conducted. The results revealed that when the average forward speed of the harvester was 0.84 m/s, the average missed detection rate of the deviation information detection mechanism was 0.56%. This method has high adaptability and detection accuracy and achieves a high level of integration for agricultural machinery (detection spatial region of the detection mechanism) and agronomy (beet root distribution spatial region). This study provides a technical basis and methodological reference for improving the quality and efficiency of automatic row correction combined with harvesting operations for crops such as sugar beets.

АНАЛИЗ ПРОИЗВОДИТЕЛЬНОСТИ ХМЕЛЕСУШИЛКИ С ЧАСТИЧНОЙ РЕКУПЕРАЦИЕЙ ТЕПЛОВОЙ ЭНЕРГИИ

Drying is an integral part of the technological process of commercial hop production. Depending on the production volume and the level of automation of the process, there are several ways to dry hop cones, including convective, microwave and sublimation. At the same time, dryers have different ratios of quality and productivity. Reducing energy costs for drying hops is an important area in the development of hop growing. In this regard, modernization and analysis of the productivity of hop dryers is a pressing issue in the current conditions of rising production costs. The aim of the research is to analyze the productivity of the MXS-25 hop dryer, modernized by installing a heat pump in the air circulation circuit and having adjustable heat recovery. The air temperature in the drying chamber was successfully controlled in the range of 60 ± 2 ° C. The preheating time required to achieve the air temperature was approximately 0.5 hours, which corresponds to approximately 5% of the total hop drying time. Comparison of the measured and calculated energy consumption values showed that the experimental values were in the range of 10.2 kWh to 11.5 kWh, averaging approximately 10.85 kWh during the experiment. Accordingly, the calculated values were in the range of 8.9 kWh and 10.2 kWh, averaging 9.55 kWh. A series of experiments comparing the drying performance using partial recovery showed that with an increase in the ambient temperature to 24 °C, the maximum relative moisture separation rate reached 6.23 kg/(kWh) with a bypass ratio of 0.86, which was higher than that of 5.54 kg/(kWh) for drying with full recovery. The partial heat recovery system is superior to the full recovery system in terms of energy efficiency and increased hop drying performance.

Mechanical Performance Analysis Method for Ribbed H-Section Aluminum Alloy Members with Initial Curvature and Torsion Angle

In this study, an experimental investigation was conducted on the axial compression performance of ribbed H-section aluminum alloy members with initial curvature and torsion angle under varying boundary conditions, including one end hinged with the other rigidly connected, and both ends rigidly connected. Ultimate bearing capacity and failure modes were identified under real loads and subsequently compared with previous findings from our research group on members with hinged ends. To account for initial imperfections introduced during processing and transportation, 3D scanning technology was utilized to capture the precise geometrical dimensions, constructing an accurate numerical simulation model. The experimental results were corroborated with numerical simulations, leading to the proposal of an analytical method for members with initial curvature and torsion angle. Furthermore, extensive parametric analysis elucidated the impact of initial curvature, torsion angle, and slenderness ratio on the ultimate bearing capacity, culminating in the formulation of the stability factor and calculated length factor based on numerical outcomes. The study discovered significant variances in bearing capacity under different boundary conditions, with one-end hinged and one-section rigidly connected, and two-end rigidly connected conditions exhibiting 1.4 and 2.1 times the capacity of the hinged-at-both-ends scenario. Under different boundary conditions, the axial compression members were subjected to flexural-torsional buckling failure. Moreover, when the ultimate bearing capacity was reached, the lower flange of the member and the web near the lower flange appeared obvious buckling phenomenon. The numerical analysis aligned well with experimental data, validating the simulation method's reliability and revealing the stress distribution and evolution during member failure. These findings offer vital theoretical insights and technical support for engineering design and practical applications.

DETERMINATION OF OPTIMAL CONDITIONS FOR HERMETIC WELDING OF THIN FOILS WHEN USED IN MEMBRANE-TYPE STRUCTURES

Purpose. Development of optimal technology for welding thin-walled shells mode of 12Х18Н10Т steel (δ=0.15 mm), working at alternating loads. Research methods. Research methods. For welding automatic argon-arc welding (AAAW) equipment was used for of orbital welding, which includes a MW 2600 current source (FRONIUS) with software control unit and welding head of closed type MW40. Research warks showed that this type of welding is not enough for such small thicknesses concentration of the welding arc, which does not allow stable forming of the bath and obtaining solid uniform seam. A special robotic complex was used for microplasma welding STARWELD 190H, which includes: a power source for the regular arc INV 50; source main arc power supply INV 190; SIEMENS Simatic S 7-300 control unit; robot CR3-535M (MITSUBISHI); manipulator and HPH 80 plasmatron. Welding quality control was carried out by visual inspection and metallographic examination. Taking into account the conditions of operation of the parts, according to the technical conditions of the drawing, it was also provided pneumohydraulic control method. Obtained results. Visual inspection the outer surface of the welds showed the absence of defects in the form of pores, cracks, shells, no fusions, undercuts, etc. The geometric dimensions of the weld met the requirements of the standard documentation valid at the enterprise. Metallographic studies of the boxes membranes, welded by microplasma welding, gave a positive result. Defects of metallurgical character were not found in the welds. Practical value. The optimal method of welding that can be applied is determined for the manufacture of thin-walled membrane structures, from the point of view of manufacturability and economy expediency It has been established that microplasma welding allows obtaining a hermetically tight seam, when the thickness of parts to be welded is about 0.15 mm. The performance of welded membrane boxes is confirmed in the barostatic valve of an aircraft engine. It is established that micro plasma welding can be used in the manufacture of thin-walled shells made of 12X18H10T steel (δ=0.15 mm), which work at variable loads. The technological process of welding is introduced into the series production.

Design of a CPW-Based SSPP Band-Pass Filter with Reflectionless Notch

Abstract This work proposes a band-pass filter (BPF) with a reflectionless notch based on spoof surface plasmon polaritons (SSPPs), utilizing interdigital coupling structures and novel transmission line unit cells. This filter efficiently transmits signals within the 0.67 GHz - 4.06 GHz frequency range. By analyzing the equivalent LC circuit of the novel transmission line unit cell, its dispersion relation is derived using microwave network theory, with a cutoff frequency of 4.11 GHz. By comparing its dispersion relation with that of the conventional transmission line unit cell, the miniaturization capability of the proposed unit cell can be verified. In the BPF, loading a zigzag groove onto the central transmission line can be equivalently represented as an interdigital coupling structure, generating a stopband in the low-frequency range near 0 GHz. By deriving and analyzing its S-parameters, it is shown that the bandwidth of the low-frequency stopband can be flexibly adjusted by modifying the geometric dimensions of the zigzag groove. Additionally, loading another set of interdigital coupling structures onto the transmission line generates a notch at its resonant frequency of 3.4 GHz. It is noteworthy that in this configuration, the interdigital coupling structures along with the central transmission line can be represented equivalently as a set of CPW antennas. At the resonant frequency, the atructure radiates signals into free space, forming a reflectionless notch. Based on the simulations, a physical filter was fabricated and tested, showing excellent agreement between simulations and measurements.

CWGA-Net: Center-Weighted Graph Attention Network for 3D object detection from point clouds

The precision of 3D object detection from unevenly distributed outdoor point clouds is critical in autonomous driving perception systems. Current point-based detectors employ self-attention and graph convolution to establish contextual relationships between point clouds; however, they often introduce weakly correlated redundant information, leading to blurred geometric details and false detections. To address this issue, a novel Center-weighted Graph Attention Network (CWGA-Net) has been proposed to fuse geometric and semantic similarities for weighting cross-attention scores, thereby capturing precise fine-grained geometric features. CWGA-Net initially constructs and encodes local graphs between foreground points, establishing connections between point clouds from geometric and semantic dimensions. Subsequently, center-weighted cross-attention is utilized to compute the contextual relationships between vertices within the graph, and geometric and semantic similarities between vertices are fused to weight attention scores, thereby extracting strongly related geometric shape features. Finally, a cross-feature fusion Module is introduced to deeply fuse high and low-resolution features to compensate for the information loss during downsampling. Experiments conducted on the KITTI and Waymo datasets demonstrate that the network achieves superior detection capabilities, outperforming state-of-the-art point-based single-stage methods in terms of average precision metrics while maintaining good speed.

18F RADIOISOTOPE YIELD OF POLYTETRAFLUOROETHYLENE ACTIVATION ON THE M-30 MICROTRON

The experimental and modeled values of the yield of the 18F radioisotope formed during the irradiation of polytetrafluoroethylene (Teflon) with bremsstrahlung photons at the maximum energy of 17.5 MeV are presented. The output was determined using the induced activity method. The activation process was carried out on the M-30 microtron of the Institute of Electronic Physics of the National Academy of Sciences of Ukraine. The yields of the 18F radioisotope for the optimized scheme of stimulation of (γ,n)-reactions were modeled by the GEANT4 toolkit, taking into account the technical characteristics of the M-30 microtron electron output unit. The effectiveness of using the formed beam of bremsstrahlung photons for forming the 18F radioisotope was evaluated, taking into account the reaction cross-section for the optimized irradiation scheme. The possibilities of increasing the output of the 18F radioisotope by optimizing the activation time of the samples and their geometric dimensions were analyzed. The proposed approach can be used to optimize photonuclear reaction stimulation schemes at the M-30 microtron for a wide range of nuclei and predict the yields of the radioisotopes formed.

A generalized framework for identification and geometrical feature extraction of circular and polygonal shaped prisms

Abstract This paper introduces a versatile framework crucial for robotic applications such as object manipulation, mobile robot navigation, and pole climbing. It addresses the identification of geometric shapes and dimensions of diverse objects found in varied environments. The proposed method utilizes LiDAR scanning to capture objects from different angles, generating point clouds merged through transformations and superimpositions. After filtering and slicing, intersections are isolated and projected onto a chosen datum plane. The framework employs Non-Linear Least Square fitting via Gauss Newton iterative approach, utilizing pseudo-inverse Jacobian of a hypotrochoid to approximate polygons. The algorithm consecutively fits polygon prisms, determining the best fit with the least norm of error. Results indicate an average least square error of less than 9% for radius fitting and a high f-score for shape identification.

Nondestructive differential eddy current testing for corrosion detection on coated aluminium alloys

PurposeThe objective of this study is to use non-destructive testing of corrosion on coated aluminium alloys using differential eddy current detection (DECD), with the aim of elucidating the relationship between the characteristics of corrosion defects and the detection signal.Design/methodology/approachPitting corrosion defects of varying geometrical dimensions were fabricated on the surface of aluminium alloy plates, and their impedance signals were detected using DECD to investigate the influence of defect diameter, depth, corrosion products and coating thickness on the detection signals. Furthermore, finite element analysis was used to ascertain the eddy current distributions and detection signals under different parameters.FindingsThe size of the defect is positively correlated with the strength of the detection signal, with the defect affecting the latter by modifying the distribution and magnitude of the eddy current. An increase in the diameter and depth of corrosion defects will enhance the eddy current detection (ECD) signal. The presence of corrosion products in the corrosion defects has no significant effect on the eddy current signal. The presence of a coating results in a decrease in the ECD signal, with the magnitude of this decrease increasing with the thickness of the coating.Originality/valueThe objective is to provide experimental and theoretical references for the design of eddy current non-destructive testing equipment and eddy current testing applications.

Cellular Automata-Based Experimental Study on the Evolution of Corrosion Damage in Bridge Cable Steel Wire

Cable-stayed bridges have become the preferred bridge type for large-span bridges due to their unique advantages, and the long-term performance of the cable under the extreme conditions has been facing great challenges. An accelerated corrosion test was carried out using in-service cable, and the evolution model of the etch pit was established based on cellular automata to study the evolution law of corrosion damage to steel wire. This study showed that with the increase in the number of dry-wet cycles in the electrified accelerated corrosion, the macro- and micromorphology of the steel wire showed more serious corrosion damage, the tensile strength decreased, the ductility index decreased, and the tensile strength of the steel wire after corrosion decreased by nearly 5%; the geometric dimension of the steel wire etch pits all met a right-skewed distribution with a broader range of etch pit depth, mainly consisting of shallow spherical etch pits and deep ellipsoidal etch pits. The length, width, and depth sizes were mainly distributed in the range of 0.005 mm to 0.015 mm, 0.005 mm to 0.02 mm, and 0 mm to 0.04 mm; at the early stage of corrosion, the etch pits were first developed along the longitudinal direction. As the corrosion process progressed, the iron matrix participated in the electrochemical reaction, leading to the rapid expansion of the etch pits’ dimensions. The stress concentration effect at the bottom of the etch pit caused the maximum stress to approach 1800 MPa, with a stress concentration coefficient of more than 3.0; when the cable anchorage system was located in the connecting sleeve and the threaded splice seam, where corrosion protection was prone to failure, the outer steel wire bore most of the corrosive effects, and the internal cable was less eroded by the corrosive medium.

Simulation and experimental study on surface modification of 6061‐T651 aluminum alloy by machine hammer peening

AbstractMachine hammer peening is a surface treatment technique employed to enhance the surface properties of the treated samples. In this present work, the theoretical analysis, finite element simulation and experiment of single peening are carried out to investigate the relationship between the machine hammer peening force and geometric dimensions of the single peening indentation deformation, including diameter and depth. The single peening experimental results are in accordance with theoretical and simulation analysis. The machine hammer peening experiment with grate tool path are done and the results including surface topography, surface roughness, surface hardness, x‐ray diffraction analysis and wear resistance are discussed. This work seeks to explore the effects of process parameters like machine hammer peening force, indentation and pitch spacing on surface roughness and hardness. The results reveal that the surface hardness and roughness are positively associated with machine hammer peening force and small indentation and pitch spacing lead to high hardness. The x‐ray diffraction analysis validate machine hammer peening is a mechanical treatment without new compound generated. The friction test results in an enhancement in wear resistance of treated samples.

Modified Easley formula for elastic critical global shear buckling stress of corrugated steel webs considering real boundary conditions

The real juncture between corrugated steel webs (CSWs) and flanges follows a multi-segmented line, distinct from that of flat steel webs. Classic methods may yield significant deviations in predicting the elastic global shear buckling capacity of CSWs of various scales due to their failure to consider real boundary constraints. Therefore, a universally applicable formula for calculating the elastic critical global shear buckling stress of CSWs, which accounts for real boundary conditions, is proposed. This formula is pertinent to both large-scale engineering CSWs and small-scale testing CSWs. This study commenced with a comprehensive reassessment of the elastic global shear buckling calculation method. Subsequently, the influence of geometric parameter ratios on the elastic critical global buckling stress was examined. The primary parameter was identified and employed to improve the global buckling coefficient. The proposed calculation method was validated using different corrugation configurations, including 1000-type, 1200-type, 1600-type, 1800-type, and 2000-type CSWs, as well as other CSWs used in experimental settings. These results were compared with those obtained from other reference methods. Findings indicate that the accuracy of the classic theoretical method is affected by variations in both boundary conditions and geometric dimensions due to the constraint effect of real boundary conditions. Under the real boundary conditions, the elastic critical global shear buckling stress of CSWs with simply supported boundary conditions is close to that of CSWs with consolidated boundary conditions. The ratio of web height to corrugation depth primarily affects the elastic global shear buckling capacity, which decreases as the ratio increases. The Easley formula can be modified based on the web height to corrugation depth ratio. Comparisons of numerous numerical and theoretical results reveal that the proposed calculation method exhibits commendable computational precision. In comparison to alternative formulas, the proposed method demonstrates enhanced consistency for calculating CSWs with varying geometric dimensions and boundary conditions, thereby demonstrating its favorable applicability. These conclusions provide valuable reference for the shear design of CSWs.

Design optimization for enhancing performances of integrated planar inductor for power electronics applications

Goal. In this work, the performance of an integrated planar inductor with a square geometric shape using different materials for the substrate: Ni-Fe, Mn-Zn and Ni-Zn have been analyzed and investigated in order to assess the impact of the substrate material on the performance of the integrated planar inductor and to determine the optimal material in the various applications of power modules in power electronics. Methods. To this end, we carried out an in-depth analysis of the geometric dimensions of the integrated planar inductor, by calculating all the geometric parameters of the proposed structure, to establish an equivalent physical model of the integrated planar inductor in order to evaluate its different electrical specifications. The numerical simulation, based on the three-dimensional mathematical model of the system using Maxwell’s equations, was realized by COMSOL Multiphysics software. Results show the importance of the substrate material for the performance of the integrated planar inductor, and specify that the use of Ni-Fe ferrite as a substrate of the integrated planar inductor gives very interesting performance compared to other materials studied. The presented results provide valuable information on the influence of substrate material on the performance of embedded integrated planar inductor and can help to design and optimize these components for use in power electronic systems. Practical value. These results are significant for a wide range of applications, where the integrated planar inductor performance and efficiency can have a significant impact on the overall performance and cost-effectiveness of the power electronic device. References 37, tables 2, figures 7.

Silage harvesting for small farms by using vacuum sealing in flexible polymer containers on a converted trailer

The article presents an analysis of milk production in Kazakhstan and identifies the reason for its low level, which is due to deficient feed, especially in small farms and in the private sector. The difficulty of saving the limited silage volume is due to the lack of preparation technology for preventing spoilage. The objective of this work is to complete the necessary equipment of a mobile tractor-trailer to reduce the specific energy consumption when preparing silage in flexible containers using a vacuum seal to increase the productivity of dairy cattle farming in smallholder and the private sector of the Republic. The basic rational parameters for sealing the silage by vacuum in the field on a mobile tractor-trailer for ease of transport and storage are obtained: silage weight in a flexible container – 769.6 kg, geometric dimensions of the sealed container by height (0.90 m), width (0.85 m) and length (0.85 m). The efficiency of the specific energy consumption of the proposed method for silage preparation is established at 35% compared with the traditional method. The recommended technology of silage preparation in flexible containers will be possible when conventional tractor-trailers are retrofitted with standard portable equipment (internal combustion engine-based (ICE) electric generator, vacuum pump, film welder).

Конструкционные плиты из гидродинамически активированной коры сосны (Pinus sylvestris) без связующих веществ

Bark is a large-tonnage waste in a number of wood processing technologies requiring efficient use. One of the promising areas of bark use is the production of boards without synthetic binders. Research has been conducted on the production of structural boards from Pinus sylvestris bark without a binder. The method is based on preliminary hydrodynamic activation of bark. The initial bark undergoes primary crushing in a hammer mill. After that, it is mixed with water at a concentration of 6 %. Then the resulting mass is activated in a rotary pulsation disperser, a carpet is formed from it, cold pressing is carried out, and then hot pressing. As a criterion for assessing the degree of mass activation, water-retaining capacity is adopted. The dependencies have been determined between the duration of treatment and water-retaining capacity, as well as the strength of the boards and water-retaining capacity. The latter made it possible to obtain the optimal value of the water-retaining capacity equal to 290 %. A multifactorial experiment has been conducted to develop the optimal hot pressing mode. As a result, the optimal mode for pressing the boards has been determined: temperature – 190 °C; specific process duration – 2.8 min/mm; pressing pressure – 4.4 MPa. The properties of the boards produced in this mode are: density – 980 kg/m 3 ; bending strength – 24 MPa; swelling during soaking for 24 hours – 5 %; water absorption – 9 %. After soaking and subsequent drying to a moisture content of 5 %, the boards retain 75 % of their before soaking. In this case, the geometric dimensions return to the original ones. The resulting boards can be used as a sheet finishing and structural material, in house-building (as a base for floor and roofing materials), in furniture production, especially in severe temperature and humidity conditions. The conducted research shows the possibility of producing board materials with high performance properties from pine bark without binders.

Modeling and evaluation of ivermectin release kinetics from 3D-printed tablets.

Aim: This study focused on evaluating the influence of geometric dimensions on the drug release kinetics of 3D-printed tablets.Materials & methods: An ink based on Gelucire 50/13 was prepared to print ivermectin-loaded tablets. The ink was characterized physicochemically and tablet dissolution tests were carried out.Results: The results confirmed the suitability of the ink for 3D printing at a temperature >46°C. Changes in the crystallinity of ivermectin were observed without chemical interactions with the polymer. 3D printed tablets with varied proportional sizes showed dual behavior in their release profiles, while tablets with only thickness reduction exhibited zero-order kinetics.Conclusion: These findings highlight the versatility of 3D printing to create systems with specific and customized release profiles.

Wide-angle low-scattering transmitarray antenna based on transmit-reflect selective metasurface

Abstract A high-gain transmitarray antenna with low radar cross section (RCS) properties is presented in this paper. Compared with conventional high-profile multilayer designs, we introduce a transmit-reflect selective metasurface integrated with high-gain transmission and random scattering functions, achieving a reduced thickness of 0.13 λ 0 (where λ 0 is the wavelength at the center frequency). For the meta-atom design, we combine geometric rotation and dimension optimization to realize 1-bit independent transmit and reflection phase modulation, respectively. Moreover, in metasurface coding strategy, we employ an initial phase optimization method and a simulated annealing algorithm to determine the optimal coding matrices. The experimental results demonstrate high-performance radiation characterized by the peak gain of 23.6 dB, maximum aperture efficiency of 28.5%, and 3 dB gain bandwidth of 18.4%. For x-polarization, measured 10 dB RCS reduction bandwidth under transverse magnetic (TM) 0°-45° and transverse electric (TE) 0°-20° incidence are 9.02–11.36 GHz. For y-polarization, 10 dB RCS reduction bandwidth under TM 0–60° and TE 0–30° incidence is 8.82–10.96 GHz.

Numerical Investigation of Film Formation Characteristics and Mechanisms through Airless Spraying on Spherical Surfaces

This paper focuses on key engineering issues, particularly the overall turbulent transport of paint spray and coating film distribution characteristics, in the process of airless spraying film formation. By deeply considering the geometric features of spherical surfaces and their impact on the near-wall region of the flow field, an airless spraying film formation model consisting of the Eulerian multiphase model, the realizable k–ε turbulence model, and the Eulerian Wall Film model was established. Through numerical simulations of static spraying on the inner and outer walls of spherical surfaces with different radii, the influence of geometric features on the spray flow field and film formation characteristics on spherical surfaces was investigated. Subsequently, based on numerical simulations of dynamic spraying on different nozzle trajectories, the film formation characteristics were analyzed, and the optimal spray trajectory planning method was determined. Additionally, this study examined the coating distribution characteristics during dynamic spraying on spherical surfaces with varying geometric dimensions. Finally, a kind of chlorinated rubber anti-corrosion primer was chosen to carry out spraying experiments, which validated that the airless spray coating model and the corresponding numerical simulation methods established in this paper were reasonable and feasible for investigating the film formation characteristics on spherical surfaces. This work is expected to further promote the application of airless spray techniques in machinery, automotive, shipbuilding, and aviation industries.