Groove Structure Research Articles

Finite Element Simulation of Jet Fracture and Distribution of Grooving Charge Cover on Inner Surface

According to the analysis of the application of grooves on the inner surface of the conical charge cover in JET warhead, when the charging structure of the conical charge cover and the caliber of the charge cover are determined, Ansys LS-DYNA explicit finite element analysis software was used to study the JET fracture time, JET granulation and JET distribution caused by the groove depth and groove spacing of the inside surface of the charge cover of five groups. On this basis, parallel group experiments were conducted to analyze the data structure of the five groups. The influence law of groove structure on jet after effect on the inner surface of conical drug cover was obtained. It was found that when groove depth was 0.1mm, the effect on jet after effect was good, while the effect on jet after effect was poor when groove depth was 0.2mm. Reducing groove spacing on the inner surface would optimize jet fracture.

Suppression of hot electron effect in AlGaN/GaN HEMT with multi-grooves barrier-etched structure

A multi-grooves barrier-etched structure between barrier layer and passivation layer is proposed in this paper to suppress the hot electron effect at the gate edge on the drain side in the p-GaN gate AlGaN/GaN high-electron-mobility transistor. In the TCAD simulations, the groove structure induces extra electric field concentration region and AlGaN/SiN interface area, which can lower the high electric field peak and electron temperature in the channel at the gate edge, leading to the alleviated capture and release of hot electrons. The static I–V characteristic and dynamic switching performance and breakdown characteristic show that the multi-grooves barrier-etched structure improves the current collapse and switching time and breakdown voltage. Our work exhibits the great potential of multi-grooves barrier-etched structure on the stability and reliability of the AlGaN/GaN HEMT.

Cost‐effective fast prototyping using a dry film photoresist for micromixers towards point‐of‐care devices

AbstractThis paper deals with a novel structure of serpentine micromixer with its high mixing efficiency and its fabrication of soft photolithography molds using dry film photoresist as an alternative to the conventional liquid photoresist, such as SU‐8. This method provides simplification, significant time‐savings, low cost due to non‐cleanroom setting and less toxic developer solution. In this paper, the design, simulation, fabrication and experimental analysis of the passive micromixers have been presented. The mixing efficiency of the chip was implemented by using of micro‐barrier structure along its meander microchannel. The serpentine structures with and without embedded grooves on their micro sidewalls were designed and compared together in order to prove good mixing performance. Experimental measurements were introduced using white and green food dyes as the mixing fluids. The mixing efficiencies of micromixers were determined and compared in the analytical model and the mixing test. It was found that grooved structures significantly enhanced the performance of the serpentine micromixers due to induce perturbations in the flow field. By optimizing the design of the serpentine micromixers equipped with embedded grooves under its simple fabrication method making this study a promising solution for a wide variety of application.

Structure improvement and parameter optimization of micro flow control valve

Aiming at the sticking phenomenon between the valve core and the valve sleeve when the valve core moves, and to solve the problem that the torque required to drive the valve core to rotate is large, the fluid–solid coupling simulation analysis of the valve core is carried out in this study, and then the valve core structure of the valve core is improved and its parameters are optimized based on the bird colony algorithm. The combination structure of the valve sleeve and valve core is studied, and the fluid–solid coupling model is established by Ansys WorkBench, and the static structure simulation analysis of valve sleeve and valve core before and after structural improvement and parameter optimization is performed. The mathematical models of triangular buffer tank, U-shaped buffer tank and combined buffer tank are established, and the structural parameters of the combined buffer tank are optimized by bird swarm optimization. The results demonstrate the triangular buffer tank has good depressurization effect but great impact, the pressure of the U-shaped buffer tank is stable and gentle but the depressurization effect is not ideal, while the combined buffer tank has obvious depressurization effect and good stability. At the same time, the optimal structural parameters of the combined buffer tank are cut-in angle of 72, plane angle of 60 and depth of 1.65 mm. The excellent structure and parameters of the combined buffer groove are obtained, so that the pressure buffer of the regulating valve at the key position of the valve port achieves the best effect, and an effective solution is provided for solving the sticking problem of the valve core of the regulating valve when working.

Numerical and experimental investigation on the performances of a liquid metal bearing with spiral groove structures

Liquid metal is a perfect lubricant due to its low melting point, good fluidity at room temperature, higher thermal conductivity and high temperature stability. In this work, the novel hydrodynamic liquid metal bearing with spiral grooves is studied. Influences of the eccentricity, the bearing radius clearance, and the groove structural parameters on the pressure distributions and the load carrying capacity of journal liquid metal bearing are deeply numerically investigated. Meanwhile, the bearing clearance and the structure parameter of herringbone grooves on pressure distribution and load carrying capacity of thrust liquid metal bearing are also numerically conducted and experimentally validated. Numerical studies are conducted based on the finite element method. Results show that the pressure distribution and the load carrying capacity of journal liquid metal bearing are significantly affected by the eccentricity, the bearing clearance and the groove structural parameters. Specifically, for journal bearing, the load carrying capacity increases with the growth of the eccentricity and the groove spacing, while it decreases with the increase of radius clearance, the groove depth and the groove ridge ratio. Besides, it turns out that when the spiral angle is larger than 37.5 degree, the increase of the groove spiral angle results in a decrease of the load carrying capacity, while when the spiral angle is lower than 37.5 degree, the value of load carrying capacities at different spiral angle depends on the specific value of eccentricity. As for thrust bearing, the load carrying capacity increases with the decrease of bearing clearance, and the increase of groove depth. Besides, the groove numbers of 13 and the angle between two vertices of herringbone groove of 13 degree are beneficial for improving the load carrying capacity of thrust liquid metal bearings. Based on the above observations, optimal design parameter sets are selected to obtain much higher load carrying capacities up to four times for both journal and thrust bearings compared with the bearings with original parameters.

Nonlinear Contact Stiffness and Damping Identification of a Tenon Connection Structure Based on Its Dynamic Characteristics

A tenon connection structure is widely used for the blade-disk connection in turbomachinery, and its contact stiffness and contact damping have caused nonlinear dynamic characteristics. The nonlinear dynamic characteristics of a blade-disk structure are mainly affected by its contact stiffness and damping characteristics, which are difficult to accurately predict and affected by many factors such as the operating speed and the centrifugal force caused by the rotation speed. Based on a single blade and tenon groove structure and the use of the dynamic characteristics experiments and simulations, the influence law of the contact stiffness and damping of the tenon connection structure with the change of the blade root compression force on the dynamic characteristics of the structure is obtained. The average relative error of identifying the contact stiffness is 0.48%; thus, identification of the nonlinear contact stiffness and damping of multiple pairs of contact curved surfaces is realized.

Focusing enhancement of terahertz surface plasmon polaritons

Subwavelength-sized metallic structures exhibit extraordinary responses to electromagnetic waves due to their geometry, generating surface plasmon polaritons (SPPs) at the metal–dielectric interface. The development and application of terahertz (THz) science, which is an emerging science, can be advanced by studying SPPs in the THz band. Because the field strength of SPPs gradually weakens in the propagation direction, a coherent phase-matched THz SPP enhancement structure was designed. Here, we demonstrated an asymmetrical circular groove structure. And using this structure, THz SPPs can be excited and can be focused and enhanced under the illumination of linearly polarized THz pulses, generating a subwavelength-sized focal spot. These functions are achieved via phase matching. Furthermore, the original structure was modified by controlling the propagation phase of the THz SPPs and a periodic enhancement structure was designed. Compared to the original structure, the periodic enhancement structure has a stronger focusing effect on THz SPPs. Moreover, we imaged the THz SPPs by using a THz real-time near-field spectral imaging system and verified the feasibility of the designed structure by comparing with the simulation results. The study results are of great significance to the application of THz SPPs and the fabrication of related devices.

Biomimetic high toughness Si3N4 ceramics with inverse-bouligand structure

Inspired by the Bouligand structure in nature, a kind of Inverse-Bouligand structure was designed. Different from the bionic Bouligand structure of a one-dimensional material unit, the inverse-Bouligand structure is obtained by stacking and twisting the ceramic layer with a parallel groove structure. The grooves arranged in parallel are first etched on the ceramic green body and then sintered after stacking and twisting. After sintering, the groove structure can still be maintained, so the resulting laminated twisted groove structure in the bulk forms an inverse-Bouligand structure, which can promote crack deflection and improve the toughness of the material during the fracture process. After testing different twist angles, the results show that when the twist angle is 15°, the toughness of the material can reach 11.22 ± 1.77 MPa m1/2, and high strength can be guaranteed. The synergistic effect of interlayer crack deflection and regional crack twist is the main mechanism for the improvement of material toughness.

Drag Reduction Performance of Triangular (V-groove) Riblets with Different Adjacent Height Ratios

Surface structure is used to interfere with the turbulent boundary layer in the groove drag reduction, which is important to the endurance and stability of high-speed and ultrahigh-speed aircraft. The size of the groove structure directly affects the flow in the turbulent boundary layer and changes the drag reduction effect. The drag reduction characteristics of bionic triangular (V-groove) riblets were studied through Particle Image Velocimetry (PIV) experiment and Finite Volume Method (FVM) simulation. Triangular riblets with adjacent height ratios (AHR) of 1.00, 1.74, and 3.02 were considered in this research, and the influence of these groove structures on the flow characteristics of turbulence near the wall is compared with those of the smooth plates. The distribution of time-averaged velocity, turbulence intensity, and coherent structures of turbulent boundary layer on the riblet surface is analyzed to document the effects of the geometric parameters of various groove structures on drag reduction rates. Results showed that the best drag reduction is obtained using the V-groove riblets with adjacent height ratio of 1:1 under the low free-stream velocity. The results can be used as a reference for further optimization of drag reduction structures with surface grooves.

The effect of laser surface textures on the adhesion strength and corrosion protection of organic coatings - Experimental assessment using the pull-off test and the shaft load blister test

Adhesion is necessary for an effective corrosion protection of metallic surfaces through organic coatings. Even the best anticorrosive coatings fail if it is not well adhered to the substrate. Laser surface texturing (LST) process has been widely used for enhancing adhesion between coatings and steel surfaces in various applications. In addition, recent researches have proven that LST is an effective option for pretreatment of steel surfaces prior to organic coating deposition. This work reports an investigation on the adhesion strength of organic coatings deposited onto AISI-A36 carbon steel laser-textured surfaces. Nanosecond LST via the direct laser writing (DLW) method was used to fabricate V-shaped grooves on the steel surfaces. The distance between consecutive grooves was varied to obtain different surface topographies with controlled surface textured area (TA) ranging from 10 % to 60 %. Conventional bead-blasted surfaces were used as a reference. Surface morphology and topography were characterized through roughness and tortuosity. The frequently used pull-off test (ISO 4624) and a shaft load blister test (SLBT) were used to determine the adhesion of the epoxy coating. In addition, accelerated corrosion tests were carried out to assess the effects of the laser textured surface conditions on the corrosion propagation. After running the pull-off test, all the surfaces' conditions exceeded the minimum pull-off strength value of 5 MPa stated in ISO 12944-9. The results for the SLBT showed that the adhesive strength is highly influenced by the laser-textured area. The geometrical aspects of the groove structure promote phenomena such as mechanical interlock and mechanical hooking of the coating, which affect the adhesion failure mechanism of the organic coating during the test. For lower TA, the crack propagation occurs mainly at the coating/steel interface. However, increasing the TA shows that the crack propagation is stopped near the V-shaped grooves due to the complex shape and must deviate inside the coating for further propagation. Finally, adhesion strength results were correlated with coating delamination rates and an indirect relationship was found.

Bionic Ring Grooves Design and Experiment of the Suction Cup Applied in Oil-Immersed Substrate

The vacuum suction cup is often used as an end effector and widely used in wall-climbing operations. However, there are few vacuum suction cup designs and applications for oil-immersed substrates. Inspired by the surface morphology of the octopus sucker, bionic suction cups with different numbers, diameters, and spacings of the ring grooves were designed. Their normal adsorption force was evaluated on the untreated and polished steel plate in oil. The test results showed that ring grooves positively affected the adsorption force. The bionic suction cup with a groove number of 3, a diameter of 0.5 mm, and a spacing of 3 mm was the most excellent in the test. It achieved normal adsorption forces of 54.83 ± 0.48 N and 43.89 ± 0.69 N on the untreated and polished steel plate. Compared with the standard suction cup, it increased by 32.31% and 12.28% on the untreated and polished steel plate. The regression model between the normal adsorption force and design factors was established based on the adsorption force test results, and the influence law of the ring groove structure parameters on the adsorption force of suction cups on oil-immersed substrates was analyzed. The order of significant effects of groove design parameters on normal adsorption forces was groove diameters, spacings, and numbers. The finite element analysis (FEA) results show that the ring grooves could significantly increase the contact pressure, frictional stress, and sliding distance between the suction cup and the substrate. The ring groove structure effectively improves the adsorption force of the suction cup on the oil-immersed surface by forming a more effective seal and increasing the friction force and adsorption area. This study could provide a reference for developing the actuator of the oil-immersed or lubricated climbing machine.

Chitosan from crab shell waste for soft lithography of bioplastic diffraction gratings.

Bioplastic diffraction gratings are fabricated from chitosan prepared from crab shells through a soft lithography replication process. Atomic force microscopy and diffraction experiments with the chitosan grating replicas indicate the successful copying of periodic nanoscale groove structures corresponding to densities of 600 and 1200lines/mm. First-order efficiency of bioplastic gratings is comparable to the output of elastomeric grating replicas.

Fabrication and mechanism analysis of wavy fins using a novel machining method

This research proposed a novel plowing extrusion-cutting (PE-C) method for efficiently fabricating 3D functional fins with novel wavy-shaped structures, which could be applied for electronics cooling, chemical reaction, and other energy applications. PE-C sequentially involved three critical stages: preheating, plowing extrusion (PE), and cutting. During PE, the preheated metal was adequately shaped into grooved structures. The cutting stage was the core procedure for the whole PE-C, in which grooved structures were multi-folded into arrays of wavy fins. Comprehensive experiments were conducted to investigate the forming performance of PE-C. Subsequently, an in-depth comparative analysis was performed to clarify their forming mechanism and geometric model. Results show that the tool rake angle γc, cutting velocity Vc, and relative cutting thickness tpd were critical parameters to control wavy fins' geometry (shape and size). Small γc, Vc, and tpd contributed to fabricating wavy fins with large amplitude As, while the period width Pw of wavy fins remained basically stable under variable parameters. During the cutting stage, the forming process of the fin top and its bottom had a velocity difference due to the different stacking deformation. Accordingly, the established geometric model showed good agreement with the experimental results. In addition, PE-C could be applied in conventional rough-cutting procedures to reduce waste chips. Therefore, PE-C was a feasible and efficient process for direct fabricating geometrically advanced fins instead of waste chips during machining, exhibiting great potential in fabricating 3D fins and recycling chips.

Sealing performance and mechanical response of mud pump piston

In order to explore the effect of piston cup structure on its sealing characteristics and mechanical properties, a numerical simulation model of the piston cup in the BW-160 mud pump was established. Effects of work load, friction coefficient and cup structure parameters on the sealing and mechanical properties of the piston were discussed under mud discharge condition. The results show that stress concentration on the root and lips of the cup is becoming more and more obvious with the working load increases. The average contact pressure increases with the friction coefficient increases, but an excessive friction coefficient accelerate the wear of the cup and the heat generation. Effect of the piston lip interference and thickness on the sealing performance of the cup is greater than that of the inner wall width. The piston with groove structure can effectively improve the sealing performance of the piston. The mechanical properties of triangular groove cup are better than that of semicircular and trapezoidal groove cup.

Enhanced Terahertz Fingerprint Sensing Mechanism Study of Tiny Molecules Based on Tunable Spoof Surface Plasmon Polaritons on Composite Periodic Groove Structures

Highly sensitive detection of enhanced terahertz (THz) fingerprint absorption spectrum of trace-amount tiny molecules is essential for biosensing. THz surface plasmon resonance (SPR) sensors based on Otto prism-coupled attenuated total reflection (OPC-ATR) configuration have been recognized as a promising technology in biomedical detection applications. However, THz-SPR sensors based on the traditional OPC-ATR configuration have long been associated with low sensitivity, poor tunability, low refractive index resolution, large sample consumption, and lack of fingerprint analysis. Here, we propose an enhanced tunable high-sensitivity and trace-amount THz-SPR biosensor based on a composite periodic groove structure (CPGS). The elaborate geometric design of the spoof surface plasmon polaritons (SSPPs) metasurface increases the number of electromagnetic hot spots on the surface of the CPGS, improves the near-field enhancement effect of SSPPs, and enhances the interaction between THz wave and the sample. The results show that the sensitivity (S), figure of merit (FOM) and Q-factor (Q) can be increased to 6.55 THz/RIU, 4234.06 1/RIU and 629.28, respectively, when the refractive index range of the sample to measure is between 1 and 1.05 with the resolution 1.54×10-5 RIU. Moreover, by making use of the high structural tunability of CPGS, the best sensitivity (SPR frequency shift) can be obtained when the resonant frequency of the metamaterial approaches the biological molecule oscillation. These advantages make CPGS a strong candidate for the high-sensitivity detection of trace-amount biochemical samples.

Influence of spherical triggers on axial collapse of tapered tubes

Thin-walled structures are widely used in the design of energy absorbers due to their excellent performance on crashworthiness. Various designs and optimisations on the internal and external structures, materials, and fillers of thin-walled structures are intensively studied. However, traditional thin-walled structures often exhibit excessive initial peak crushing force (IPCF) and large fluctuations in the force-displacement curve under axial load. This paper optimises the traditional thin-walled structure from the perspective of biological structure and proposes a new tapered structure that mimics the shape of a conch shell, named ‘Conch tube’ (CT), which aims to stabilise the crushing process and improve energy absorption capacity. Numerical simulations are used to study the effects of thread pitch and groove width on the deformation mode and performance on crashworthiness of the CT. The results show that the deformation mode of the CTs can be changed from the spiral groove trigger mode to the progressive mode by controlling the thread pitch and groove width. Therefore, by controlling the pitch and groove width, the CT can obtain a lower IPCF. Finally, multi-objective optimisation based on active learning is used to obtain the best CT structure. Compared with the traditional conical tube, the CT has an excellent crashworthiness performance. The effectiveness of the spiral groove structure in enhancing energy absorption and reducing IPCF is confirmed.

Thermal-Fluid-Solid Coupling Simulation and Oil Groove Structure Optimization of Wet Friction Clutch for High-Speed Helicopter

Wet friction clutch is the key functional component of the high-speed helicopter variable-speed transmission system, which is used to change the power transmission path. In the engagement process of wet friction clutch, the driving/driven disc will produce drag torque under the shearing of lubricating oil, which reduces the transmission efficiency. This unnecessary drag torque reduces efficiency and increases clutch temperature. The temperature increase promotes the wear of gears and bearings and the aging deformation of friction plates, which leads to local wear and reduces the service life of the clutch. From the principle of wet friction clutch, the oil groove structure is directly related to the drag torque and the temperature rise of friction disc. It is very important for the long-distance flight and service life of high-speed helicopters to obtain the groove structure with low drag torque and low temperature rise. In order to solve this problem, taking the wet friction clutch of a high-speed helicopter as the research object, based on the radial and annular compound groove, the thermal-fluid-solid coupling simulation model of the wet friction clutch is established to obtained the flow characteristics and temperature field distribution of the lubricating oil in the friction disc oil groove, and to analyze the influence law of the oil groove structure parameters on the drag torque and temperature field. In order to improve the transmission efficiency and the service life of friction disc, Taguchi experiment and non-dominated neighborhood immune algorithm were used to optimize the structural parameters of the oil grooves. The comparison results show that the optimized structural can effectively reduce the drag torque and the temperature rise. This work can provide a theoretical reference for the structure design of a wet friction clutch.

Efficient removal of condensate droplets from the surface with microgroove composite structures

Due to the increasing scarcity of global water resources, water collection based on structural functional materials has become one of most potential ways to relieve the crisis. However, water collection functional surface with the high efficiency still encounters a bottleneck. In this paper, we constructed a rough surface with micro groove and nano grass composite structures on the copper substrate, and studied the influence of micro groove spacing on the falling radius of condensate droplets. The results show that the micro groove structure increases the nucleation of droplets, and the nano needle accelerates the removal of condensate droplets. The composite structure reduces the droplet shedding diameter, and the droplet nucleation first occurs at the edge of the micro groove. Therefore, reducing the tank spacing is conducive to the condensation and removal of droplets. In addition, the water collection experiment shows that the surface with micro/nano composite structures has higher collection efficiency than the smooth surface. These findings are useful for designing condensate collection systems with high performance.

Cooling characteristics of array jet impinging on grooved target surface imitating blue whale skin

In this paper, based on the idea of bionics and imitating the groove structure of the blue whale skin surface, a composite cooling structure with array jet impinging on groove target surface is proposed for the cooling of combustion chamber. For the working conditions of high Reynolds number (Re = 10,000 to 70,000) and high heat flux (q = 10 kW·m-2), this paper firstly explores the heat transfer characteristics of the flat target surface and the grooved target surface under different Re through experiments. The flow characteristics of the array jet impinging on groove target surface are studied by numerical simulation, and the influence of the existence of grooves on the flow field is analyzed. The research results show that the presence of grooves enhances the fluid disturbance near the wall, and the use of grooved target surfaces can significantly reduce the target surface temperature, increase Nu, and reduce the friction factor f. Compared with the flat target surface, the average temperature of the groove target surface decreases by 2.13%, the average Nusselt number Nuave increases by 43.3%, and the average friction factor f decreases by 3.79%. In addition, the comprehensive heat transfer factor F of the grooved target surface is all greater than 1.06, which indicates that the comprehensive heat transfer performance of the groove target surface is better. In addition, with the increase of Re, the target surface Nuave increases and the friction factor f decreases. When Re increases from 10,000 to 70,000, the Nuave of the groove target surface increases by 85.9%, and f decreases by 6.16%.

Design and analysis of grooved heat pipe

AbstractA heat pipe is a heat conduction program that utilizes both heat permeability and regime shift concepts to transport heat effectively between 2 different lines. A heat pipe is made up of a pipe or tube and a base fluid. In practice, the heat pipe is poured into a mould that is compatible with the cooling media. These devices have found uses in a variety of fields, including space apparatus, solar energy systems, electronic equipment, and air conditioning systems, due to their simplicity of design and ease of manufacture and maintenance. Thermal performance improvement being the major concern in our project we researched different techniques. The heating surface area has a direct impact on heat transfer. Therefore, we have focused on heat enhancement by introducing grooves. Alongside we also considered using different materials for the pipe. At the end of our research, we are going to produce groove structure models with different materials and analyze them using ANSYS software and propose the best structures with highest thermal efficiency for different applications of heat pipes. This is an attempt to increase heat transmission in response to various material and structural changes. Heat transmission is improved with grooved heat pipes as well as heat transmission various with different types materials used in heat pipe.