U-shaped Groove Research Articles

Interlaminar Microstructure and Mechanical Properties of Narrow Gap Laser Welding of 40-mm-Thick Ti-6Al-4V Alloy.

Narrow gap laser welding (NGLW) is a common solution for the welding of thick structures. NGLW was carried out on narrow-gap butt joints of 40 mm-thick Ti-6Al-4V alloy plates with a U-shaped groove. The distribution characteristics of the interlaminar microstructure in different height ranges of the joint were investigated, and the evolution behavior and formation mechanism of the interlaminar microstructure of the joint were also revealed. This showed that a large amount of short needle martensite nucleated and grew up near the fusion line and the upper boundary of the remelting zone. The "softening" phenomenon occurred in all welds except the cover layer weld. The microstructure evolution and defect migration, induced by multiple welding thermal cycles in the upper weld forming process, were the main reasons for the "softening" of the lower weld. The tensile strength of each sample changed in the range of 920~990 MPa; the fracture mode of the sample belongs to a transgranular ductile fracture. In addition, compared with the upper part of the joint, the plasticity and toughness of the weld area in the lower part of the joint was improved.

Broadband Contactless 90° Waveguide Transition With a U-Shaped Choke Groove

This letter presents a broadband 90° bent waveguide transition that is suitable for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -plane split-blocks technique. In this transition, imperfect metal connections will not cause unacceptable transmission loss by employing a novel U-shaped choke groove and a groove gap waveguide. Such contactless waveguide transitions are advantageous as they allow for easy interconnection and packaging of millimeter-wave and terahertz circuitry. A 90° bent waveguide operating over the WR-4.3 waveguide frequency band (170–260 GHz) is designed, and the transition with a different air gap between the top and bottom parts is measured. The measured results show that the transmission losses are about 0.2 dB with good consistency.

Laser ablation on coated metal gravures for roll-to-roll printed electronics

Ultrafast laser micromachining plays an important role in the manufacturing of electronics. Especially, rotogravure processing produces high-resolution patterns for roll-to-roll printed electronic circuits. However, this technique still poses some limitations. This study introduces a new technique for coating gravures on a “soft” metal to improve the precision of rotogravure processing for manufacturing roll-to-roll electronics. The coating is termed “soft” because it has a lower ablation threshold fluence than the metal gravure core. The resulting U-shaped grooves offer several advantages over the V-shaped grooves typically formed through laser ablation on a single-layer material. Conductive ink transfers more completely from the U-shaped grooves, offering increased precision with respect to the resulting parts and saving ink.

Numerical Investigation of the Flexural Performance of Slender CFST Beams with Varied Shapes of External Stiffeners

The concrete-filled steel tube (CFST) beams are recommended for adopting in the modern composite structure since it achieves a higher load capacity and ductility behaviour than the conventional structural members. Using CFST beams with slender steel cross-section led to reduce the overall cost of the structures compared to those with compact cross-sections; however, it is more likable to buckle under the compression stress. Therefore, providing external stiffeners along the four sides of CFST beams expected to reduce the overall self-weight also can provide more stiffening to the steel’s section that led to improve the loading capacity. In this study, a finite element (FE) method was adopted for numerically investigated the flexural performance of the square CFST beams stiffened with different shapes of external grooves that provided along the beam’s sides. The FE software named ABAQUS was adopted for this purpose where the original model of CFST beam analysed and verified with the corresponding tested specimen. After that, additional CFST model have been built and analysed to investigate further parameters including the effects of varied tube’s thickness, steel yielding strength, concrete compressive strength and different external grooves shape (V-shaped, U-shaped, C-shaped, double V-shaped). The results established from the numerical analyses showed that the ultimate bending capacity (Mu) of the stiffened CFST models was generally enhanced by increasing their concrete strength, steel yield strength and tube’s thickness but in varied percentages. For example, increasing the tube thickness from 1.5 mm to 3.0 mm achieved an improvement in Mu values of about 72.3\%. while fewer improvement percentages have been recorded of about 11.9\% when only the core concrete strength increased from 25 MPa to 55 MPa. Furthermore, the shape and number of grooves have positive impact on the bending capacity of stiffened CFST models, where using U-shape, C-shape and V-shape external grooves were led to improve the Mu value of about 2.8\%, 10.7\%, and 11.1\%, respectively. Thus, the energy absorption of these models was improved accordingly.

Design of new infrared nano sensor based on surface plasmon resonance photonic crystal fibers

In this paper, five different surface plasmon resonance photonic crystal fiber (SPR-PCF) structures are proposed and evaluated by numerical modeling. The structures are based on photonic crystal fibers with defects rods of air, Au, and TiN in the background of silica. In the fourth and fifth designs, two grooves coated with gold layers are considered to improve the functionality of the structures and help the analyte to become closer to the fiber core. The effects of geometrical parameters like radius, thickness, and width on the loss spectrum are also investigated, and the results are presented. Finally, a double D-shaped SPR-PCF sensor with ITO belts and U-shaped grooves covered with gold is proposed. The proposed sensor can detect a low RI change from 1.4 to 1.6 with a maximal sensitivity factor around 6000 (nm/RIU). The proposed SPR-PCF sensor can be an appropriate candidate in nano-optical integrated circuits (for different applications) due to its compact size and high sensitivity factor.

Double U-groove temperature and refractive index photonic crystal fiber sensor based on surface plasmon resonance.

Based on double U-groove photonic crystal fiber (PCF), a surface plasmon resonance sensor with dual parametric detection of temperature and refractive index is proposed. The birefringence of PCF is increased by using germanium ions doped in the core and introducing U-shaped notches on both sides of the D-shaped fiber. The polished surface of the PCF is coated with gold film and PDMS as a temperature sensing channel, and the U-shaped groove is coated with gold film as a refractive index sensing channel. Through the design of the sensor, it is finally possible to achieve independent measurement of the two parameters. The sensor has a maximum wavelength sensitivity of 4715 nm/RIU in the analyte refractive index range of 1.32-1.4, and maximum wavelength sensitivity of 18 nm/°C in the ambient temperature range of -30∘C-50∘C. The proposed sensor has broad application prospects in scenarios such as blood analysis, DNA hybridization analysis, and microenvironmental cell interactions.

Structural basis for the acetylation mechanism of the Legionella effector VipF.

The pathogen Legionella pneumophila, which is the causative agent of Legionnaires' disease, secrets hundreds of effectors into host cells via its Dot/Icm secretion system to subvert host-cell pathways during pathogenesis. VipF, a conserved core effector among Legionella species, is a putative acetyltransferase, but its structure and catalytic mechanism remain unknown. Here, three crystal structures of VipF in complex with its cofactor acetyl-CoA and/or a substrate are reported. The two GNAT-like domains of VipF are connected as two wings by two β-strands to form a U-shape. Both domains bind acetyl-CoA or CoA, but only in the C-terminal domain does the molecule extend to the bottom of the U-shaped groove as required for an active transferase reaction; the molecule in the N-terminal domain folds back on itself. Interestingly, when chloramphenicol, a putative substrate, binds in the pocket of the central U-shaped groove adjacent to the N-terminal domain, VipF remains in an open conformation. Moreover, mutations in the central U-shaped groove, including Glu129 and Asp251, largely impaired the acetyltransferase activity of VipF, suggesting a unique enzymatic mechanism for the Legionella effector VipF.

Shafts with U-shaped circumferential grooves: design charts for stress concentration factors, radial displacement and Poisson’s ratio influence

Shafts with U-shaped circumferential grooves subjected to internal normal force and bending moment are investigated on the basis of finite element analysis. The classical problem of the stress concentration factors (SCFs) identification is addressed. SCF charts are provided, adopting the maximum equivalent von Mises stress in the SCF definition. The discrepancy between the uniaxial SCFs extracted from the standard reference books and the multiaxial SCF obtained by finite element increases from 5% up to 20%. The intersections between the SCF curves are studied, which reveal a non-monotonic profile of the SCFs with respect to the outer and inner diameter ratio of the notched shaft. The radial displacement at the notch root is examined and design charts of ample validity and prompt access are compiled. It is found that the radial displacement sign and magnitude are largely dependent on the geometry of the notch. Furthermore, the strain and stress state of extremely shallow grooves are analysed, and a critical discussion on their SCFs using the von Mises criterion is presented. The influence of Poisson’s ratio is considered. A simplified method for the evaluation of a multiaxial SCF is proposed to account for the Poisson’s ratio effect. Thanks to the employment of few dedicated diagrams, and the present method allows an accurate evaluation of the SCF for U-grooved shafts, when Poisson’s ratio differs from the common 0.3 value.

The Design of Large-aperture HFCVD Diamond-coated Drawing Die Preparation System and Experimental Study on Its Application

As a new type of die, HFCVD diamond-coated drawing die registers a great application prospects and market potential because of its performance advantages. This study mainly focuses on the preparation system of diamond coating for large-aperture drawing die. According to the finite element analysis of the temperature field of the die base on HFCVD process, hot filament parameters on the temperature distribution of the die base is studied. And on the basis of the sdudy, a new HFCVD coating mold preparation system with rotating U-shape groove is designed, which can produce more uniform coating. The deposition experiments were carried out on the inner wall of the drawing die by the HFCVD coating mold preparation system. The cross-sectional morphology, surface morphology and Raman spectrogram of the diamond coating show that the thickness of the diamond coating is uniform and the quality is satisfactory. This provides reference for the application of the large-aperture diamond-coated drawing die.

Effect of the Axial Casing Groove Geometry on the Production and Distribution of Reynolds Stresses in the Tip Region of an Axial Compressor Rotor

AbstractStereo-PIV data are used for investigating the effect of axial casing groove (ACG) geometry on the distribution, evolution, and production rates of turbulent kinetic energy (TKE) and Reynolds stresses near a rotor tip. The ACGs delay the onset of stall by entraining the tip leakage vortex (TLV) and cause periodic changes to incidence angle. These effects are decoupled using semicircular, U-shaped, and S-shaped grooves that have similar inlets, but different outflow directions. Most TKE distribution trends can be explained by the local turbulence production rates, elucidating the different mechanisms involved and providing a unique database for turbulence modeling. Interaction of the tip flow with the ACGs modifies the highly anisotropic and inhomogeneous passage turbulence. In all cases, the TKE is high in the TLV center and shear layer connecting the TLV to the rotor tip. At prestall flowrate, TLV entrainment reduces the passage turbulence level, but introduces elevated turbulence in the corner vortex formed at the downstream corner of grooves, and in shear layers developing at the exit from grooves. The location of peaks and the dominant components vary among grooves. Near the best efficiency point, interactions of the TLV with the circumferentially negative outflow from the U and semicircular ACGs generate high turbulence levels, which extend deep into the passage. In contrast, interactions with S grooves are limited, resulting in a substantially lower turbulence level. Accordingly, the S groove maintains the untreated endwall efficiency, while the U and semicircular grooves reduce the peak efficiency.

Hybrid Fiber-Optic Sensor for Seawater Temperature and Salinity Simultaneous Measurements

In this letter, we propose a compact hybrid fiber-optic sensor for seawater temperature and salinity simultaneous measurements. The device consists of a hollow-core fiber (HCF)-based Fabry-Perot interferometer (FPI) and no-core fiber (NCF)-based anti-resonance (AR) structure. A U-shaped groove is inscribed in the HCF by femtosecond laser for liquid inflow and salinity sensing. A section of the polymer coating is retained on the NCF to excite the AR effect for temperature measurement. The incident light is partially reflected at the HCF fusion end-faces and forms the FPI reflection spectrum, while the transmission light in the NCF cladding is coupled to the polymer coating and forms the AR phenomenon. In theoretical modeling, the temperature and salinity responses of the hybrid sensor are analyzed separately, and the corresponding sensitivities are calculated theoretically. In the experiment, the results show that the temperature and salinity sensitivities are -4.948 nm/ and 0.235 nm/, respectively. In addition, the calibration test, time stability, and repeatability of the sensor are also evaluated by the experiments. The construction method of this hybrid sensing structure is flexible and accurate, so it is expected to be applied in the seawater parameter measurements.

DESIGN AND EXPERIMENT OF THE SEED DELIVERY DEVICE WITH A ROTATING BRUSH WHEEL FOR PRECISION SEEDER

In high speed seeding operation, the random collisions of seeds in the seed delivery tube seriously affect the seeding accuracy. In order to improve seeding uniformity and stability in high speed operation, the seed delivery device with a rotating brush wheel was designed, including U-shaped groove seed tube and flexible brush wheel. The optimization experiment was carried out by quadratic-regression rotatable orthogonal design method in JPS-12 seeding performance test bench. The three main factors were the rotate speed of seed metering device, the brush wheel diameter and the brush wheel speed. The evaluation indexes were the qualified rate of seeding spacing, miss seeding rate and coefficient of variation of seeding spacing. The results showed that the optimal parameters were rotate speed of seed metering device of 30 r/min, brush wheel diameter of 66 mm and brush wheel speed of 850 r/min. Finally, the verification experiment was carried out. The test results showed that the working performance of seed delivery device with a rotating brush wheel was obviously better than that of common seed delivery tube, especially at the forward speed of 15 km/h and above. The research provides a reference for the innovative design for a high speed precision seeder.

Machining fused silica surface by continuous-wave CO2 laser beams and their nanostructure characterizations

Fused silica surface machined using continuous-wave CO2 laser beams with an energy density of 0.5 J/mm2 presented U-shaped grooves (approximately 47 μm-deep and 250 μm-wide) and asymmetrical craters (2–5 μm high). The fully reacted valley in the groove center exhibited porous microstructures and agglomerated silica nanoparticles in the size of 33–118 nm; whereas, the less reacted peak in the groove edge only presented uneven solidified films from silica ablations. Distinct morphologies in the valley and peak areas were supposed to result from the Gaussian energy distribution of laser beams. The selected area electron diffraction pattern suggested that the laser-reacted silica nanostructures were still amorphous with no obvious composition change. The x-ray photoelectron spectrometric results showed that both Si 2p and O 1s peaks shifted to higher energy sides, implying a more oxidized state of Si4+ and absorbed oxygen or hydroxides on nanostructured silica after CO2 laser machining.

Effects of U-shaped two-step throttling groove parameters on cavitation erosion characteristics

Effects of U-shaped two-step throttling groove parameters on cavitation erosion characteristics

Design and research of a miniaturized four notch UWB antenna

In order to effectively suppress the interference of narrow-band communication systems such as WiMAX band, international satellite band, X band and the ITU band, this paper designs a miniature ultra wideband (UWB) antenna. The improved rectangle is used as the radiation patch. The semicircular groove is dug in the upper part of the rectangle and the two corners below are cut off. The long triangle is also cut on both sides of the end of the microstrip line. The fish bone groove is well modified in the middle of the rectangular ground plate to obtain the perfect ultra wideband characteristics. By digging a semi-circular groove on the radiation patch to introduce T-shaped branches, and opening an inverted U-shaped groove in the center of the radiation patch, introducing symmetrical C-shaped open branches on both sides of the feeder line and etching U-shaped narrow gaps on the feeder line, four band notch characteristics of 3.24−3.8 GHz, 4.5−4.97 GHz, 7.24−7.76 GHz and 8.0−8.54 GHz are produced, which better suppresses the interference in the notch band, shows that the antenna can work normally in the frequency band of 3.0−13.09 GHz, and the four notch baud property of the antenna also expands the application field, which is suitable for many ultra wideband communication systems.

Edge/direct-lit hybrid mini-LED backlight with U-grooved light guiding plates for local dimming.

Current mini-LED backlights improve high-dynamic-range liquid crystal displays (LCDs) by using tens of thousands of direct-lit sources for local dimming. However, relative thick profile and high power consumption are the inherent limitations while compared with edge-lit backlights. By synthesizing edge- and direct-lit advantages, we propose a novel hybrid mini-LED backlight equipped with a specially designed integrated light guiding plate (LGP) for large-area displays. This LGP is seamlessly spliced by multiple physically segmented sub-LGPs with a scattering dot array on the bottom and U-shaped grooves at the corners. Each sub-LGP is a single local dimming zone that can be independently controlled. Scattering dot distribution can be numerically calculated even from multiple edge-lit sources. High optical performance and satisfactory local dimming effect are verified and analyzed via both simulation and experiment. The experimental spatial illuminance uniformity and the light extraction efficiency reach 81% and 83% while the crosstalk can be well suppressed below 0.2% between adjacent local dimming zones. The significant advantages of our design towards state-of-the-art mini-LED backlights include the zero optical distance for an ultra-thin profile, low mini-LED amount for local dimming, high optical efficiency, and infinite extension of zone number, which is expected to have a broad application prospect in the near future.

Evaluation of the Cross-Sectional Shape of μ-Grooves Produced in Stainless Steel 304 by Laser-Induced Etching Technique.

The variation in cross-sectional profile of a microgroove fabricated with focused and diverging laser irradiation is demonstrated with ray tracing. To verify the result of ray tracing, stainless-steel 304 microgrooves were manufactured utilizing the conventional lens-based and optical fiber-based laser-induced etching techniques in phosphoric acid solution. Three distinctive groove geometries, i.e., a flat surface with no groove, an intermediate stage groove, and a fully developed V-groove, were rendered for numerical analysis. For focusing mode, the first and second reflections were caused by high laser intensity and the second reflected beam could lead to variation in the groove shape such as a U-shaped groove or a V-shaped groove in accordance with etchant concentration. On the contrary, a weak laser entirely distributed at the groove sidewall could not induce a chemical reaction, leading to a V-shaped groove. The effect of process variables such as laser power (intensity) and etchant concentration on the cross-sectional profiles of a groove are closely examined through the computed simulation results.

Effect of groove microstructure on slurry erosion in the liquid-solid two-phase flow

Different from the traditional research and design of new materials and coatings, three types of surface microstructures including V-shape, U-shape, and ring-shape groove microstructures were performed to enhance the slurry erosion resistance. Slurry erosion experiments were carried out on a home-made rotating disc erosion rig on the conditions of the velocity of 8.25 m/s and sand containing 5 wt%. Mass loss measurements, micro-morphology, and roughness observation combined with flow field analysis were employed to reveal the erosion mechanism. The results showed that the erosion rate of the V-shape groove microstructure was approximately 69% and 93% of the U-shape, and ring-shape groove microstructures respectively. The most severe slurry erosion occurred on the incident flow surfaces of the V-shape and U-shape grooves, and the bottom surface of the ring-shape groove. Vortex flow in the grooves contributed to the erosion difference on the grooved surfaces and the top surface in the way of changing impingement velocity and angle.

Pressure impact characteristic of vane type continuous rotary motor under different buffer structures

In order to solve the problem of pressure shock on the continuous rotary electro-hydraulic servo motor, the mathematical models of pressure gradient under the structure of pre-compressed chamber and U-shaped groove were established. The optimal structure dimensions of the pre-compressed chamber and the U-shaped groove were determined. The fluid models were established by Solidworks under the four structures of triangular groove, triangular groove with pre-compression chamber, U-shaped groove and U-shaped groove with pre-compression chamber. Simulation analysis of depressurization process of fluid models was performed based on FLUENT. The pressure nephograms of different buffer structures were compared and analyzed, and the pressure change curves and pressure gradient change curves in the process of depressurization were obtained. The results show that the optimal edge length of the pre-compressed chamber of continuous rotary electro-hydraulic servo motor is 20 mm in the process of decompression. The pressure reduction effect is the best when the width of the U-shaped groove is 1.5 mm and the depth is 1.65 mm. The U-shaped groove structure with pre-compression chamber is more conducive to alleviate the pressure shock phenomenon of the motor compared with different combine buffer structures.

Design of Filtering Power Divider with Wide Stopband Based on QMSIW

A miniaturized filtering power divider with wide stopband based on quarter-mode substrate integrated waveguide (QMSIW) is proposed. The physical size of the QMSIW is reduced by 3/4 comparing with the traditional SIW structure, which can achieve miniaturization, and its electromagnetic field distribution has little effect. Using the metal interference column and the etched U-shaped groove to adjust the resonance frequency, so that the main mode and the first higher mode form a passband, meanwhile, suppressing the second higher mode. The simulation results show that the center frequency is 4.42 GHz with insertion loss of 0.45 dB, the 3-dB bandwidth is 4.12-4.63 GHz with a fractional bandwidths of 9.7%, and there is a great stopband up to 11 GHz with 15 dB rejection level. Besides, the return loss of passband is better than 17.5 dB. To verify the validity of this design, a prototype is fabricated and measured. The measured results demonstrate that it has a good agreement with the design simulations.