Number Of Grooves Research Articles

Influence of the preparation design on the retentive strength of resin-bonded attachments

ObjectivesThe study investigated the influence of retention grooves and material thickness of the retainer wing on the retentive strength of resin-bonded attachments (RBAs).Materials and methodsSixty-four extracted human molars were used. Each tooth received a preparation limited to the enamel for the retainer wings of the RBAs. The specimens were divided into eight groups, each containing eight specimens. The groups varied based on the number of conical retention grooves (0, 1, 2, or 4) and the thickness of the CoCr retainer wings (0.4 mm and 0.8 mm). Before testing the retentive strength of the RBAs, the specimens underwent 37,500 thermal cycles followed by dynamic loading of 1,200,000 cycles on the RBAs’ patrices using a chewing simulator. The debonding test was conducted using a universal testing machine at a crosshead speed of 2 mm/min.ResultsThe mean retentive strength ranged from 326 ± 96 N to 440 ± 77 N. Only a small portion of specimens (10.9%) exhibited adhesive failure, while the remainder demonstrated cohesive failure within the tooth structure. Neither the number of retention grooves, the thickness of the retainer wings, nor the size of the bonding surface significantly affected retentive strength.ConclusionsThe findings suggest that reducing the number of retention grooves and the material thickness does not influence the retentive strength of RBAs.Clinical relevanceThe retention of RBAs appears promising, supporting the clinical application of this treatment modality.

Numerical and experimental analysis of Al/GFRP joint for optimization of adhesive bonding strength using response surface method by considering surface patterning of the joints

Nowadays, adhesive bonding of metals and composites is widely used in the aerospace, automotive and military industries. In the present research, the finite element analysis (FEA) and response surface method (RSM) are used to optimize adhesive bonding strength between aluminum (Al) and glass fiber reinforced polymer (GFRP). For this purpose, the influence of the parameters of joint type, groove shape, groove number, and groove angle was investigated on the bonding strength. The joint type includes Al/Al, Al/GFRP and GFRP/GFRP, the groove shape includes V-shape, square and concave, the groove number includes 1, 3 and 5 grooves, and the groove angle includes 0, 45 and 90º. In order to model the crack growth in the simulation of adhesive bonding, the cohesive zone model was applied. Finally, the optimal sample is fabricated to examine its strength in temperature-humidity environmental conditions. The results of simulation and optimization indicated that the bonding strength improved in Al/Al mode with one square groove at 0° groove angle. The stress-strain diagram obtained from the simulation and optimization results was in good agreement with the sample made under optimal conditions. Moreover, the tensile strength of the optimal sample at temperature-humidity conditions was higher than the tensile force of the sample without groove.

Analysis and optimization of a high-speed generator’s cooling structure based on Taguchi method

To increase the power density of the original generator, it is desired to boost the generator’s power to 1.2 times its original capacity. However, the cooling structure of the original generator cannot meet the heat dissipation requirements of the upgraded power level. It necessitates a redesign of the cooling structure. For the stator, water pipes through the stator core yoke are added; for the rotor, a novel rotor cooling structure is designed. The structure includes the groove bottom vent beneath the rotor excitation winding and the radial auxiliary grooves on the sides. The airflow passes through the groove bottom vent and then follows the radial auxiliary grooves until it reaches the air gap. It can efficiently remove the heat from the rotor excitation winding. The results of the new scheme are discussed. When comparing the new scheme with the original one, the highest temperature of the stator winding decreases by 20.6k, while the one of the rotor excitation winding does by 23.7K. To further improve the cooling structure, the Taguchi method is employed. The optimization variables include the area of the stator back vent, the number of radial auxiliary grooves, and the height of the groove bottom vent. The optimization objectives are the highest temperature of the stator winding, the highest temperature of the rotor excitation winding, the air friction loss, and the inlet-outlet static pressure difference. By analyzing the variance and range of the results, the improved scheme is obtained. Comparing the improved scheme with the new one, the temperature distribution difference between them is negligible. The improved scheme reduces the air frictional loss by 10.7%, but increases the inlet-outlet static pressure difference by 8.0%.

The Effect of Air–Water Mixture on the Dynamic Response of a Hydrodynamic Journal Bearing With Inclined Grooves

Abstract Water-lubricated hydrodynamic journal bearings with deep inclined grooves are often used to support radial loads and dampen pump vibrations in nuclear power plants. The inclined grooves increase the pumping effect of the lubricant thus reducing wear and friction during rotor startup and coast-down. The deep grooves also facilitate the removal of debris without damaging the bearing. The load capacity and the stability of this type of bearing are studied in the present work. A sensitivity study of the impact of the number of grooves on bearing performance underlined the superiority of the journal bearing with two inclined grooves. Moreover, these journal bearings may operate with a mixture of water and air. This compressible two-phase lubricant will modify the load capacity and the stability of the journal bearing. The impact of the ingested volume fraction of air is therefore investigated. A physical model of the homogeneous air–water mixture linking the local air volume fraction with the pressure was used in conjunction with the numerical solution of the compressible Reynolds equation on an unstructured grid. It was found that the air ingestion in the two-inclined grooves journal bearing decreases the load capacity but improves the stability for mild and low loads.

Enhancing the electrochemical performance of graphite sheet electrodes for ketamine detection

Flexible graphite sheets (GS) have been a promising material for developing electrochemical sensors. In this work, we showed that the electrochemical activation protocol (+1.4 V followed by -1.0 V vs. Ag|AgCl|KCl(sat.) both at 200 s) in alkaline medium (0.5 mol l-1 NaOH) enhances the electrochemical activity of GS. Before the treatment, cyclic voltammetric profile of inner-sphere [Fe(CN)6]3-/4- redox couple at 50 mV s-1 exhibited an ill-defined voltammetric profile (ΔEp = 800 mV) while an increase in the reversibility was achieved (ΔEp = 225 mV) after the treatment. Additionally, the lower charge transfer resistance (Rct) measured by Electrochemical Impedance Spectroscopy (EIS) and a higher heterogeneous electron transfer constant (k0) corroborate with the enhancement in the electrochemical performance of treated GS electrodes. The SEM images revealed an irregular pattern with number of grooves, indicating a partially surface exfoliation and AFM analysis displayed an increase in the roughness. These findings agreed with the estimation of electroactive area which increased 3-times after the treatment. As proof of concept, ketamine (KET), an anesthetic often used as drug of abuse, was determined in synthetic saliva and veterinary pharmaceutical samples using treated GS electrodes and square wave voltammetric measurements. Linear range of 5.0–100.0 µmol l-1 with a limit of detection value of 2.1 µmol l-1 was obtained for KET. Appropriate recovery values (∼105 %) for the analysis of samples were achieved.

Torque and heat transfer characteristics in Taylor–Couette turbulence with an axially grooved cylinder

To describe the aerodynamic and thermal effects in the flow between the slotted stator and rotor of electric motors, we have conducted direct and large eddy simulations using the lattice Boltzmann method. The flow between the stator and rotor is influenced by turbulence and Taylor–Couette (TC) vortices. Axial grooves (slots) are incorporated either on the stationary outer cylinder or the rotating inner cylinder. These groove shapes and numbers are designed based on the groove geometry of drive motors used in commercial electric vehicles. The radius ratio of the TC flow configuration in this study is 0.955, and the simulated bulk Reynolds numbers reach up to 21000 which corresponds to the Taylor number of Ta=4.63×108. The characteristics of torque and heat transfer are analysed by comparing cases with and without grooves. Regardless of the groove placement, it is suggested that while the grooved surface effects are not significant on torque and heat transfer performance at Taylor numbers Ta≤107, where Taylor vortices are still evident, the effects become pronounced at Ta≥108 as the flow transitions to the ultimate regime.

Effect of some design parameters on the performance of side access nozzle and grooved plate of centre pivot sprinkler

This research evaluates the effect of various heights, pressures, nozzle size and groove numbers on the uniformity distribution of a developed pivot sprinkler. The experiment was set up at an open space in Niger State College of Agriculture Mokwa. The wind speed and temperature during the experiment were at an average of 2.2mph and 25°C. A nozzle of size 6mm, and deflection plate of 6 curved grooves were used in a centre pivot spray unit. In evaluating the performance of the spray unit components i.e. the nozzle and deflection plate, three different pressures of 5, 10, and 15 Psi and heights of 1, 1.2, and 1.5mm were used. The support structure for the experiment is an inverted U-shaped frame designed to support a spray sprinkler at different heights. The water source was a reservoir with a capacity of 3m3and a 1.5hp electric centrifugal pump was used. The volumetric or bucket method was used to measure flow rate. The application rate was measured using catch can method. The duration of each test was approximately 30min. The data obtained from the measurements were statistically analyzed with line graphs using Excel. Relationships were also established between discharge and pressure. The highest index of jet break up was 4.89 at 15Psi and 3.74 at 10Psi. The result shows that as the pressure increases with height the CU also increases. The highest uniformity of 79.4% was obtained at 1.5m height and 15Psi.

Study on the groove geometry of pad in water dissolution polishing of soft brittle materials based on trajectory analysis

During the water dissolution polishing process of soft brittle materials, the pad's groove geometry plays a significant role in determining the performance. This not only affects the flow of the slurry but also directly impacts the overall distribution of the water core on the pad surface, thereby influencing the polishing effect. A trajectory model of the water core on the workpiece surface was established through kinematic analysis and the characteristics and effects of the pad's groove geometry in circular, radial, composite, and grid were studied combined with the trajectory analysis. The coefficient of variation and power spectral density were established to evaluate the trajectory uniformity. The trajectory density distribution was quantitatively analyzed to obtain a better understanding of the material removal uniformity. The simulation and experiment results indicated that the existence of groove geometry will greatly affect the flow of slurry and the surface quality. The grid groove had a better distribution of water core, which means better material removal. There exists a tradeoff between the number of grooves and their spacing. These insights offer a fresh perspective and serve as a valuable reference for further research and analysis into the groove characteristics of pads.

Aerodynamic characteristics of axisymmetric boattail models with different number of longitudinal groove cavities

Reducing aerodynamic drag and increasing flying object performance is an important task in aerospace engineering. The high drag occurs for blunt base models, which are not only for missiles, and projectiles but also for building, bridges. This study presents numerical results regarding subsonic flow characteristics over axisymmetric boattail models equipped with longitudinal grooves, with the number of grooves ranging from 2 to 12. The standard model has a fixed boattail length of 0.7D and an angle 22°. The investigation employs numerical simulation methods utilizing the Reynolds-averaged Navier-Stokes (RANS) equations with the k-ω SST turbulent model. The boundary layer was captured well by the current simulation. The numerical results are initially validated against both simulated and experimental data from previous studies, ensuring accuracy and reliability. The findings indicate that an increase in the number of grooves from 0 to 4 results in a slight increment in drag. However, as the number of grooves is further increased from 6 to 12, a significant reduction in the model's drag is observed. Additionally, the flow patterns around the boattail model are visually depicted and analyzed to explain the drag trend of the model with different groove configurations

Multi-objective optimization of liquid metal bearing based on NSGA-II

Due to their exceptional static and dynamic properties along with high-temperature resistance, liquid metal bearings are extensively employed in challenging environments. This paper carried out a multi-objective optimization work for spiral groove journal liquid metal bearings (JLMB) by using a NSGA-II. The clearance of bearing C, spiral angle a, groove depth hg, groove ridge ratio β, groove number N, and groove spacing P were chosen as design variables to maximize the load-carrying capacity and the effective stiffness of liquid metal bearing. During optimization process, the Latin hypercube sampling was adopted to generate 41 sample points, and the Kriging surrogate model was used to establish the correlations between design variables and objective functions. The Pareto front with optimal structures was obtained after optimization. Subsequently, optimal parameters were determined from the Pareto front by using the TOPSIS decision method. Finally, a comparative analysis of bearing performance was conducted between the journal liquid metal bearings with optimal parameters and the original parameters. The results indicated that the optimal JLMB parameters are given as follows: C = 10 μm, a = 26°, hg = 5.2 μm, β = 0.7, P = 11.1 mm, N = 10. The static and dynamic performance of optimized JLMB has been significantly improved. Specifically, the load carrying capacity increased to 2781.2N, making a 1313% enhancement over the JLMB with original parameters. While the effective stiffness of the optimized JLMB surged to 1.86 × 108 N/m, a more than 20-fold increase.

Designing an imaging spectrometer with high resolution using manufacturable gradient-index (MGRIN) lenses with a linear distribution of refractive index.

In this work, an imaging spectrometer with a diffraction-limited resolution of 0.043nm is designed by using two manufacturable gradient-index (MGRIN) lenses with a linear refractive index distribution to suppress the aberrations. The MGRIN lenses are made from a combination of two separate base materials that their refractive indices are determined by the fractional composition of each base material at any point. The volume fraction of each base material in both lenses changes linearly from the front edge to the rear vertex of the lens. The input light to the spectrometer originates from a single-mode fiber with a core diameter of 9μm and a numerical aperture of 0.1. The parallel rays after passing through the collimator are diffracted by a diffraction grating with a number of grooves of 1200 g/mm. The criteria determining the quality of the image show that the aberrations of the image have been optimally controlled. Comparing the results of this design with some similar studies done by other researchers shows that the root-mean-square radius of the spot diagram and Airy disk radius are significantly smaller than those designs. In addition, the modulation transfer function diagram has a better fit with the diffraction limit curve. These results make our proposed spectrometer have a stronger resolution than those in previous studies.

The impact of filling procedure for labial augmentation (FPLA) therapy on the stability of lip print: A longitudinal study

Lip print identification is one of the forensic identification tools recognized a long time ago. Few studies investigated the stability of lip prints, particularly the changes attributed to time or aging. To our knowledge, no previous studies speculated the changes in lip print following lip augmentation therapy, which has increased over the last few years. Therefore, the current study aimed to investigate the effect of lip augmentation therapy on lip print stability. The current study was a prospective longitudinal study that enrolled female volunteers who underwent a filling procedure for labial augmentation. A total of 24 volunteers' prints were analyzed using Suzuki and Tsuchihashi classification. Participants showed a mean age of 27.5 ± 6.0 years. The current study showed that no two lips exhibited the same pattern. Moreover, although the filling procedure for labial augmentation (FPLA) therapy preserved the predominant groove pattern, it significantly influenced the frequency of lip patterns in all lip quadrants. A significant decline in the number of lip grooves, notably Types I and I' was noticed. However, the predominant groove pattern was preserved. Quadrants A and D were the least affected lip parts. Type I′ was the predominant lip pattern over the study population, representing 83.3 %, followed by Type I, representing 16.7 % before and 12.5 % after augmentation without a statistically significant difference (p = 0.317). On the other side, Type III was the least presented pattern. The upper lip score had decreased significantly after augmentation from 71.5 ± 10.8–65.8 ± 10.2, and the lower lip score had decreased significantly from 67.4 ± 13.7–64.9 ± 13.5. Consequently, the overall lips score had decreased significantly from 139.0 ± 22.9–130.7 ± 21.1 after augmentation (p < 0.001). So, we recommend adopting more than one criterion to report a reliable, repeatable lip print, including the frequency of lip lines besides the predominant pattern. However, we advise giving more attention to the distinguished lip patterns (Types II, III, IV, and V) and considering the FPLA as one of the lip print modifiers.

Impact of helical grooves on drag force and flow-induced noise of a cylinder under subcritical Reynolds numbers

The drag force and flow-induced noise of underwater vehicles significantly affect their hydrodynamic and stealth performance. This paper investigates the impact of helical grooves on the drag force and flow-induced noise of underwater vehicles through numerical simulations of the flow around cylinders with two types of helical grooves under various subcritical Reynolds numbers. The simulation scheme employs the large-eddy simulation framework combined with the Lighthill acoustic analogy method. The results show that the helical-groove structure can achieve reductions of up to 30% in drag and 5 dB in noise. These helical grooves have a significant effect in terms of suppressing the formation of a Karman vortex street downstream of the cylinder. Under subcritical Reynolds numbers, the drag-reduction effect of the helically grooved cylinder decreases as the number of helical grooves increases, while the noise-reduction effect increases with increasing number of helical grooves.

Design of herringbone grooved thrust bearing for locomotive turbocharger rotor

The herringbone texture exhibited excellent tribological performance to minimize friction and wear. However, the application of this texture in the development of grooved thrust bearings is limited. Therefore, in this study, an attempt was made to design an oil-lubricated herringbone grooved thrust bearing for high-speed locomotive turbochargers. The designed bearing accommodates the axial load generated due to the pressure difference between the turbine and compressor wheel. The bearing design starts with applying Newton’s second law to predict the thrust load acting on the locomotive turbocharger rotor. The thrust load is calculated analytically and is found to be 4.54 kN for a design rotor speed of 1,00,000 rpm. Further, the herringbone grooved thrust bearing has been modeled numerically using non-linear Reynolds equation. The modified Reynolds equation is discretized using the finite volume method (FVM) and solved by successive over-relaxation (SOR) methodology to determine the static characteristics over the bearing surface. The developed HGTB is found to have a suitable load-carrying capacity of 4.6 kN, frictional torque of 0.25 N.m, and power loss of 2.98 kW. Further, a parametric analysis has been carried out to study the influence of design parameters such as the number of grooves, helix angle, angular groove width, groove depth, and speed on load-carrying capacity, frictional torque, and power loss.

Enhancing heat transfer in various grooved annular for Taylor-Couette-Poiseuille flow

The present study investigated the impact of various parameters on pressure drop, Nusselt number, and friction factor in grooved annular channels, which have practical applications in cooling electric motors and generators. The parameters studied include the effective Reynolds number, Taylor number, groove aspect ratio, number of grooves, and groove angle. The k-ω SST turbulence model was employed in CFD simulations for various parameter ranges. These ranges include an effective Reynolds number spanning from 4.42 × 103to 1.6 × 104, Taylor number of 0–2.24 ×106, the groove aspect ratio of 0 to 2, the number of grooves ranging from 5 to 20, and the groove angle ranging from 70° to 130°. As the effective Reynolds and Taylor numbers increase within the ranges noted above, the Nusselt number exhibits a corresponding increase of 9.16 % and 1.77 %, respectively. However, the effective Reynolds number plays a more significant role. Various design factors, including the number of grooves, the aspect ratio, and the groove angle, also influenced the heat transfer enhancement. As any of these factors increase within the specified ranges, the corresponding Nusselt number values increase by 2.35 %, 3.62 %, and 6.09 %, respectively.

Thermal Cavitation Effect on the Hydrodynamic Performance of Spiral Groove Liquid Face Seals.

Cavitation in micro-scale lubricating film could be determined by the fluid's thermal properties, which impacts the hydrodynamic lubrication capacity dramatically. This study aimed to novelly investigate the impact of the thermal cavitation effect on the hydrodynamic performance of liquid face seals, employing the compressible cavitation model, viscosity-temperature effect, and energy equation. The finite difference method was adopted to analyze the thermal cavitation by calculating the pressure and temperature profiles of the lubricating film. The working conditions and geometric configuration of liquid face seals under different thermal cases were further studied to explore their effects on sealing performance. The results showed that thermal cavitation could reduce the temperature difference of liquid film at high speeds, and cavitation would be weakened under temperature gradients, which further dropped off the hydrodynamic performance. Contrary to the leakage rate, the opening forces tended to be lower with the increasing seal pressure and film thickness under high-temperature gradients. Furthermore, apart from the spiral angle of grooves, the hydrodynamic performance exhibited significant variation with increasing groove depth, number, and radius at high-temperature gradients, which meant that the thermal cavitation effect should be considered in the design of geometric grooves to obtain better hydrodynamic performance.

Multidisciplinary design and optimization of journal bearing for high-power wind turbine speed increaser

With the increasing power of wind turbine generators (WTG), the failure rate of rolling bearings in wind turbines due to insufficient bearing capacity increases with the increase of bearing size. To overcome these challenges, this paper proposes a design optimization method for the rectangular groove elliptical sliding bearing (RGEB) of the WTG output shaft. This method can maximize the radial bearing capacity under the premise of ensuring that the oil film pressure is large, the end leakage and the temperature rise are small. The multidisciplinary design and modeling of RGEB are carried out according to the structure and working conditions of WTG. Based on computational fluid dynamics (CFD), the influence of the number of rectangular dynamic pressure grooves on the bearing performance is analyzed. The kriging model, BP neural network model, and SSA-BP model are constructed for each performance index of RGEB, to establish a high-precision combined surrogate model based on global error criterion. After establishing the optimization equation, the PSO and SQP combined optimization algorithm is used to optimize the optimal structural parameters. The results show that the bearing capacity of the optimized RGEB is 95.9% higher than that of the ordinary elliptical bearing (EB) without increasing the size and quality of the bearing. In addition, the combined surrogate model can effectively replace the expensive finite element model to deal with the WTG sliding-bearing optimization problem.

Thermal aging behavior and heat resistance mechanism of ultraviolet crosslinked ultra‐high molecular weight polyethylene fiber

AbstractAs advances in heat resistant ultrahigh molecular weight polyethylene (UHMWPE) fiber via ultraviolet (UV) crosslinking, it is worth paying attention to its thermal aging behavior and heat resistance mechanism. UHMWPE fibers in different forms, the fully drawn yarn (FDY) and the UV crosslinked FDY (UVFDY), are subjected to isothermal aging at 135°C. The effects of thermal aging on their surface morphology and mechanical properties are studied and compared initially. The results demonstrate that UVFDY is a kind of a heat‐resistant fiber. Subsequently, to reveal the heat resistance mechanism of UVFDY, its crystalline and orientation structure evolution during thermal aging are further studied. It is indicated that the formation of dense‐packing crystals and disorientation behavior lead to fiber shrink, so that a number of grooves appear on the fiber surface. Since the crosslinked stucture of UVFDY hinders its molecules movement, the crystallization and disorientation behavior of UVFDY are weaker than those of FDY, resulting in UVFDY possesses slighter thermal shrinkage (Ts), fewer grooves and better mechanical properties than those of FDY. Therefore, the heat resistance of the fiber improves effectively after UV crosslinking. This work provides insights into the structure–property relationship of UVFDY during thermal aging, and offers basis data for its application in specific conditions.

Pool boiling heat transfer enhancement induced by capillary wicking from radial gradient structures: A lattice boltzmann study

With the aid of a three-dimensional lattice Boltzmann model built in the lab, the boiling state on the surface with gradient groove structure is investigated. The emphasize is placed on the impact brought by the wicking capability from the gradient structure on boiling performance. Besides the roles of distribution, number, width and depth of the grooves in the boiling process discussed in detail, the effects of wall superheat and wettability on boiling heat transfer are also explored. The results show that the wicking force generated by the gradient grooves can improve the boiling performance to an extent. Adjusting the geometry of grooves can enhance heat flux by up to 27.46% compared to a flat competitor. However, there exists a limit for the gradient defined in this study. Pursuing larger gradient values can extend the pit region at the center of surface. Upon TPCL being trapped within the pit region, it causes a negative effect on the boiling performance. The wicking capability has a positive relationship with surface wettability at a given groove number and size. In regards to the parametric effects of groove, the heat flux first increases but then declines with increasing the groove width at a fixed Jacob number. Despite the enhanced boiling performance with increasing the groove number and depth, the enhancement has an upper limit. But, the groove distribution has a minor effect on the boiling performance if TPCL is outside the pit region. This study provides quantitative evidence for the fact that wicking can promote boiling from the numerical view.

Machining performance of micro-pit and micro-groove composite textured tools in tungsten alloy turning

Tungsten alloys are widely used in aerospace because of their high-temperature resistance, corrosion resistance, high strength, and other excellent comprehensive properties. But tungsten alloys are typical hard-to-machining materials. Surface micro-textures can improve friction properties, such as preparing micro-textures on the surface of cutting tools for tungsten alloys, which is expected to enhance the cutting performance of tungsten alloys. Still, the relevant cutting laws need to be further studied. A combination texture of micro-pit and micro-groove was designed, and the micro-textured tool surface was prepared by laser machining. Compared with non-textured tools, micro-pit and micro-groove composite textured tools can effectively improve the processing quality of tungsten alloys. It happened because textures on the tool’s surfaces enhance machining performance by reducing the actual contact area between the tool and the chip and storing lubrication medium. At the same time, comparative experiments of micro-textured tools and non-textured tools were carried out. The results showed that when cutting W93NiFe alloys with textured and non-textured tools, the maximum reduction in resultant cutting forces with textured tools was 9%. The maximum reduction in surface roughness was 39.3%, the surface burr height of the tungsten alloy workpiece was lower, the number of surface grooves was lesser, and the surface was more flat. The research results are significant in achieving the efficient processing and high-quality manufacturing of tungsten alloys.