Increase Of Groove Depth Research Articles

Fault detection in rotor system by discrete wavelet neural network algorithm

This study identifies a method for detection of irregularities such as open cracks or grooves on a rotating stepped shaft with multiple discs, based on the wavelet transforms. Cracks are represented as reduction in diameter of shaft (groove) with small width. Single as well as multiple grooves are considered on stepped shaft at locations of stress concentration. Translational or rotational response curves/mode shapes are extracted from finite element analysis of rotors with and without grooves. Discrete and continuous 1D wavelet transforms are applied on resultant response curve or mode shapes. The results show that rotational response curves or mode shapes are more sensitive to shaft cracks and key contributors to identify the location of cracks than translation response curves or mode shapes. Discrete wavelet transforms are accurate enough to locate the groove of smaller size. Effectiveness of detection by wavelets transforms is analysed for single as well as multiple grooves with increase in groove depth. Increase in groove depth can be quantified by increase in wavelet coefficient, and it can be an indicator. White Gaussian noise with low signal-to-noise ratio is added to response curves and analysed for crack location identification. Intelligent techniques such as artificial neural networks are used to quantify the location and depth of crack. Discrete wavelet transforms coefficients are provided as input to the neural network. Feed forward artificial neural networks are trained with Levenberg–Marquardt back propagation algorithm. Trained networks are able to quantify the crack location and depth accurately.

In situ reflection electron microscopy for investigation of surface processes on Bi2Se3(0001)

The sublimation and van der Waals (vdW) epitaxy on Bi2Se3(0001) surface have been first visualized using in situ reflection electron microscopy. When Bi2Se3(0001) surface was exposed to a Se molecular beam (up to 0.1 nm/s) and heated to ∼400°C, we observed ascending motion of atomic steps corresponding to congruent Bi2Se3 sublimation. During the sublimation, grooves made by probe lithography act as sources of atomic steps: groove depth increases and generates atomic steps that move in the ascending direction away from the source. We used this phenomenon to create self-organized regularly-spaced zigzag atomic steps having 1 nm height on the Bi2Se3(0001) surface. The deposition of Bi (up to ∼0.01 nm/s) onto the Bi2Se3(0001) surface at constant Se flux (up to ∼0.1 nm/s) reversed the direction of the step flow, and vdW epitaxy was observed. The deposition of In and Se onto the Bi2Se3(0001) surface at ∼400°C led to the epitaxial growth of layered In2Se3. This vdW heteroepitaxy started with 2D island nucleation and, after 3–5 nm growth, continued with a screw-dislocation-driven formation of 3D islands. Ex situ Raman scattering measurements have shown that the grown 20-nm-thick In2Se3 film exhibits vibrational modes that originate from the β-In2Se3 crystal phase.

Effects of interfacial trapezoidal grooves on the mechanical properties of coatings by laser cladding

Inspired by the micro-wavy interface of high-strength and high-toughness biological tissues, this study conducted laser cladding on 1045 steel substrates with isosceles trapezoidal grooved-textures by using Fe-based powder. The results showed that the cladding layer exhibited a satisfactory metallurgical bond with the substrate. When the loading direction was parallel to the grooves, the maximum impact energy was 23 J at a groove depth of 0.9 mm; when the loading direction was perpendicular to the grooves, the maximum impact energy reached 26 J at a groove depth of 0.6 mm. The ultimate tensile strength also increased because of the presence of groove texture. The coordinate deformation ability of the substrate-clad layer structure, interface stress concentration, and microscopic defects competed, resulting in the complex tendencies of the toughness and strength of the specimen with an increase in groove depth. When the groove depth was 0.6 mm, the actual depth of the texture groove was equivalent to the preset effective thickness of the upper cladding layer. Within the parameter range of this study, the optimal comprehensive performance of the specimen with groove depth of 0.6 mm was realized.

Dynamic Analysis of Multi Disc Rotating Stepped Shaft Through Signal Processing

This study identifies a method for detection of irregularities like open cracks or grooves on a rotating stepped shaft with multiple discs, based on the Wavelet Transforms. Cracks are represented as reduction in diameter of shaft (groove) with small width. Single as well as multiple grooves are considered on stepped shaft at locations of stress concentration. Translational or rotational response curves/mode shapes are extracted from finite element analysis of rotor with and without grooves. Discrete and continuous 1D wavelet transforms applied on resultant response curve or mode shapes. The results show that rotational response curves or mode shapes are more sensitive to shaft cracks and key contributors to identify the location of cracks than translation response curves or mode shapes. Discrete Wavelet Transforms are accurate enough to locate the groove of smaller size. Effectiveness of detection by Wavelets Transforms is analyzed for Single as well as Multiple grooves with increase in grove depth. Increase in groove depth can be quantified by increase in wavelet coefficient and it can be an indicator.

Investigation on groove depth of artificial dam of underground reservoir in coal mines

Water storage in underground reservoirs serves as an important means of water resource protection in coal mines in Western China. The groove depths of the artificial dam required plays an important role in the design of these underground reservoirs. The underground reservoir of the Wulanmulun coal mine was examined in this study using theoretical analysis and similar simulation experiment, and the groove depth was optimized using FLAC3D based on the results obtained. According to the theoretical calculation model of the groove depth, the safe groove depth was determined to be 0.2 m. It was found that the groove was the weakest point in the reservoir with the most serious seepage and maximum likelihood of failure. The variation curve of the volume of the plastic zone followed a U-shaped distribution. The side, roof, and floor depths corresponding to the minimum volume of the plastic zone were determined to be 0.6 m, 0.2 m, and 0.3 m, respectively. The analysis indicates that increasing the groove depth within a certain range can enhance the stability of the reservoir; however, as the groove depth exceeds a critical value, the increase in groove depth was unfavorable for the stability of the reservoir. Moreover, increasing the side groove depth above the critical value was more effective in enhancing the stability of the reservoir than increasing the roof and floor groove depths.

A computational study of heat transfer and material removal in picosecond laser micro-grooving of copper

A 2D two-temperature model (TTM) is developed for picosecond laser micro-grooving of copper (Cu) and discretized using the finite difference scheme, to explore the temperature evolution and groove formation process. For lattice and electron subsystems, as well as the coupling strength between them, comprehensive temperature-dependent properties are employed and updated in real time to make the calculation more accurate. The model verification is then conducted and a reasonable good agreement has been found between predicted and measured groove depths. Using the verified model, computational studies of temperature field evolution are carried out in different fluence levels. For low fluence of around 0.283 J/cm2, phase change can be neglected, and the temperature difference between two subsystems decreases with an increase in pulse width and can be neglected when the pulse width is over 200 ps. In contrast, for high fluence of about 10.61 J/cm2, the maximum lattice temperature increases rapidly to boiling point within 3 ps, and the peak electron temperature is around 10 times higher, leading to material removal via evaporation. Under this high fluence level, groove depth around 0.25 μm is obtained within a 12 ps single pulse irradiation. In addition, thermal diffusion occurs from the residual hot zone adjacent to groove edge towards surrounding area during the off-pulse period, as the heat affected zone depth is up to 1 μm after 500 ps and over 4 μm after 6 ns, and the peak residual lattice temperature drops to about 396 K from boiling point within 53 ns. Moreover, the groove depth and groove profile show a periodically evolving manner with respect to scanning times, and for each scanning, a slow-fast-slow pattern has been observed in groove depth increase and profile development.

Effect of Oil Groove Depth on Friction Performance of Copper based Friction Materials with Different Graphite Content

Copper-based friction materials with different oil groove depth and graphite content were prepared by powder metallurgy process. The effect of oil groove depth on the friction performance of copper based friction materials with different graphite content at different linear velocities was studied. The results show that the dynamic friction coefficient of material decreases with the increase of oil groove depth at low linear velocity of 16.5m/s, and increases with the increase of oil groove depth when linear velocity is ≥ 20m / s. With the increase of oil groove depth and graphite content, the heat resistance of the friction material increases and the wear rate decreases.

Effects of surface texturing on nanotribological properties and subsurface damage of monocrystalline GaN subjected to scratching investigated using molecular dynamics simulation

Surface nanotribological properties and subsurface damage of flat and textured gallium nitride (GaN) substrates during both linear and circular nanoscratching processes are investigated using molecular dynamics simulation. Results show that the surface texture can remarkably reduce not only the surface friction and wear but also the scratching-induced subsurface damage regardless of the tip radius and penetration depth. Tangential force and friction coefficient decreased with an increase in groove width or depth primarily due to the reduced contact area. The effect of texturing on stress distribution can affect the development of dislocation to alleviate the nanoscale material deformation and removal and thereby reduce surface wear and subsurface damage. Increasing tip radius can reduce the friction coefficient and surface wear, but it promotes subsurface damage. By contrast, increasing tip penetration depth can increase the friction, wear, and subsurface damage for flat and textured GaN substrates. Compared with the c-plane, the m-plane GaN substrate exhibits higher friction but lower material wear, and it has a considerably thicker subsurface damage layer due to the difference in their dislocation networks. This work can provide useful insights into the design of GaN-based material with antifriction and wear properties through the surface texturing treatments.

Deformation, fragmentation and acceleration of a controlled fragmentation charge casing

Abstract Two different finite element software, LS-DYNA and Impetus, have been evaluated to test their ability to predict the deformation, fragmentation and acceleration of a controlled fragmentation charge casing. The general-purpose program LS-DYNA was used with a multi-material ALE formulation and a mass-preserving erosion criterion coupled to a Johnson-Cook fracture criterion. In the Impetus simulations, a third order Lagrangian element formulation was used for the casing and a node-splitting element erosion treatment coupled to a Cockcroft-Latham failure criterion was used to describe casing fracture. The high-explosive gases were described by a discrete particle formalism. In order to acquire data to validate our computational tools and constitutive models, a series of experiments have been performed using a laboratory charge with an internal grooved casing. In the test series, the charge geometry was fixed except that the groove depth were varied from very shallow to very deep resulting in different deformation patterns, fracture modes and terminal velocities. Various diagnostic tools captured the different stages of the expansion and fragmentation of the casing. A high-speed framing camera depicted the deformation pattern before fragmentation and was used to determine the moment when the casing failed. Three different complementary techniques were used to follow the acceleration of the fragments; a Photon Doppler velocimetry to determine the initial acceleration of the casing, double exposed radiographs to estimate the fragment velocity after break-up and a high-speed video to determine the terminal velocity of the fragment after leaving the fireball. In addition, the fragments were soft recovered in a set of sawdust pit tests and their final shape and weight were measured. A SEM was used to characterise the fracture surfaces and to determine the modus of fracture (tensile or shear failure). Comparisons to experiments show that both software can predict the change in deformation behaviour when the groove depth increases, from tangential necking for shallow grooves to radial punching for deep groves. Both software could also reasonable well predict the acceleration of the fragments, though both overestimates the terminal velocity for the charge with the deepest grooves.

Experimental study of cavitation characteristic of single-row reverse spiral groove liquid-film seals

Abstract A series of experiments is conducted to study the cavitation in the single-row reverse spiral groove liquid-film seals. The experimental system withstanding internal pressure consists of a transparent rotating ring mating with a stationary ring textured with grooves. Liquid-film seals with different groove parameters under different operating conditions are tested, acquiring the distribution and evolution of cavitation and fitting the experimental relations of cavitation boundaries. Results indicate that cavitation occurs in the grooves and many protruding bubbles appear near the liquid-film reformation boundary. Increasing pressure effectively reduces the cavitation but for speed, it's opposite. Although the increase of groove depth and the decrease of spiral angle reduces the cavitation area, effects of them on the cavitation boundaries are different.

Drop impact on a superhydrophobic surface with single groove

In this paper, we systematically studied droplets with different velocities impact on grooves with different depths. In the experiment, there are four morphological changes of droplets due to the influence of the impact velocity and the groove depth. Different morphological changes show different spreading characteristics. When the groove depth remains unchanged, the increase of impacting velocity promotes the spreading of droplets in the X (perpendicular to the groove) and Y (parallel to the groove) directions. However, when the impact velocity keeps uniform, the increase of groove depth only promotes the spreading of droplets in the Y direction and has little effect on the maximum spread diameter of the droplet in the X direction. The experimental results also show that the contact time is related to the change of droplet morphology, and their relationship is explained at last.

TC4/Ag Metal Matrix Nanocomposites Modified by Friction Stir Processing: Surface Characterization, Antibacterial Property, and Cytotoxicity in Vitro.

Numerous antibacterial biomaterials have been developed, but a majority of them suffer from poor biocompatibility. With the purpose of reducing biomaterial-related infection and cytotoxicity, friction stir processing (FSP) was employed to embed silver nanoparticles (Ag NPs) in a Ti-6Al-4V (TC4) substrate. Characterization using scanning electron microscopy, transmission electron microscopy, and three-dimensional atom probe tomography illustrates that NPs are distributed more homogeneously on the surface of TC4 as the groove depth increases, and silver-rich NPs with a size from 10 to 20 nm exist as metallic silver diffused into the substrate, where the silver content is 4.3-5.6%. Electrochemical impedance spectroscopy shows that both FSP and the addition of silver have positive effects on corrosion resistance. The modified samples effectively inhibit both Staphylococcus aureus and Escherichia coli strains and slightly reduce their adhesion while not displaying any cytotoxicity to bone mesenchymal stem cells in vitro. The antibacterial effect is independent of Ag-ion release and is likely due to the number of embedded silver NPs on the surface, which directly contact and subsequently destroy the cell membrane. Our study shows that the TC4/Ag metal matrix nanocomposite is a potential infection-related biomaterial and that embedding Ag NPs tightly on a biomaterial surface is an effective strategy for striking a balance between the antibacterial effect and biocompatibility, providing an innovative approach for accurately controlling the cytotoxicity of infection-related biomaterials.

Analysis of Oil Film Characteristics of Two-Axial Groove Sleeve Bearings

Abstract Based on the finite finite difference method, the Reynolds equation, the flow equilibrium relationship of oil film gradient, and the oil film thickness equation are solved for different groove locations and depths in two-axial groove sleeve bearings. The oil film pressure, extent of the cavitation zone, and carrying capacity of two-axial groove sleeve bearings are computed at different oil groove locations and depths. With the increase of oil groove depth, the oil film pressure of two-axial groove sleeve bearings decreases noticeably, and the bearing capacity decreases gradually. It can be concluded that the maximum oil film pressure and bearing capacity of two-axial groove sleeve bearings are lower than that of the common sleeve bearing. With the groove position moving along the circumferential direction, the oil film pressure peak heights and bearing capacities decrease and then increase. The oil film pressure peak heights and load capacities reach maximum when the position of the two-axial oil groove is about 20° and 200°. It has been proven that different positions of oil grooves show different influences on the extent of the cavitation zone. The first oil groove is always located in the full oil film region, and the second oil groove may be located in the full oil film region or the cavitation region because of the change of distance from the convergent wedge of the bearing. The cavitation area firstly decreases and then increases with the movement of the groove in the circumferential direction.

Fretting wear and fatigue in press-fitted railway axle: A simulation study of the influence of stress relief groove

In this paper, a finite element model for the prediction of fretting fatigue crack initiation in the full-scale railway axle was proposed, which took into account the influence of the stress redistribution due to fretting wear on the fretting fatigue. Then, this model was used to investigate the influence of stress relief groove on the fretting wear and fatigue of the railway axle. The simulation results show that the stress concentration at the contact edge is gradually relieved with an increase in fretting cycles due to the fretting wear, while a new stress concentration appears at the edge of fretting wear scar, which gradually increases and moves towards the inner side of the contact area. The stress concentration in the inner side is considered to cause the fatigue crack initiation. Either the increase in groove depth or the decrease in groove radius can reduce the fretting wear and improve the fretting fatigue strength through relieving the stress concentration. Accompanying the improvement of fretting fatigue strength, the potential site of crack initiation gradually moves towards the contact edge. The simulation results stated above agree with the published experimental results.

The effects of laser patterning 10CeTZP-Al2O3 nanocomposite disc surfaces: Osseous differentiation and cellular arrangement in vitro

Customized square grid arrangements of different groove depths (1.0, 1.5 and 3.0 µm) and separations (10 and 30 µm) were successfully laser patterned, using a nanosecond pulsed fibre laser, on the surface of 10 mol% ceria-stabilized zirconia and alumina (10CeTZP-Al2O3) nanocomposite discs (diameter: 10 mm; thickness: 1.5 mm). The patterned surfaces and the in vitro biological response of osteoblasts (SAOS-2) towards them were thoroughly analysed. In terms of composition, the laser treatment was found to cause superficial monoclinic-tetragonal zirconia phase transformation and alumina evaporation. In vitro, the most effective grid configuration for osseous differentiation was found to be 1.5 µm groove depth and 10 µm groove separation, and confocal microscopy revealed that the cells show a tendency to be sorted as groove depth increases. It is thought that custom-made patterns could be produced to guide cell attachment in vivo, which could favour implant integration and reduce healing time.

Characteristics of interaction between single-layer graphene on copper substrate and groove

The two-dimensional material graphene is usually required to be transferred on the target substrate for some special applications, thus it is important to understand the adsorption properties in the graphene transferring and stripping processes. In this paper, the adsorption properties of a single-layered graphene on the grooved copper substrate are investigated using molecular dynamics simulations. The influence of geometric characteristic size of the groove on the adsorption force of the graphene deriving from the substrate is explored. For the fixed boundary conditions of the graphene, the adsorption force increases up to maximum and then decreases with reducing the distance between the graphene and substrate in the adsorbing process. The maximum adsorption force increases with groove depth increasing, with the groove width kept constant. Nevertheless, as the groove depth increases continuously, the adsorption force decreases greatly until the graphene cannot be adsorbed into the groove. In the graphene stripping process, the critical force that can strip the graphene completely from the substrate increases first and then decreases with the increase of the groove depth, which is also dependent on the steady adsorbing configuration of the system before stripping. With the groove depth kept constant, the magnitude of the adsorption force between the graphene and substrate is determined by the steady adsorbing configuration of the graphene in the groove region. The adsorption force versus the distance between the graphene and the grooved substrate can be divided into two groups according to whether the graphene can be adsorbed into the groove. In both adsorbing and stripping processes, the adsorption force for the graphene adsorbed into the groove is obviously larger than that for the graphene covered on the groove. Moreover, the influence of the boundary condition of the graphene on the adsorption properties in the groove region on the substrate is considered preliminarily. It indicates that the tensile plane stress within the graphene sheet induced by the fixed boundaries can hinder the graphene from being adsorbed into the groove. The findings may be helpful for the graphene-based fabrication of nano-apparatus and functionalized surface modification.

Numerical Modelling and Analysis of Hydrostatic Thrust Air Bearings for High Loading Capacities and Low Air Consumption

The paper presents a numerical simulation study on hydrostatic thrust air bearings to assess the load capacity, compressed air consumptions, and the dynamic response. Finite Difference Method (FDM) and Finite Volume Method (FVM) are combined to solve the non-linear Reynolds equation to find the pressure distribution of the air bearing gas film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, supplied pressure, depth of the groove and external load, are investigated based on the proposed FDM model. The simulation results show that the thrust air bearings with a groove have a higher load capacity and air consumption than without a groove, and the load capacity and air consumption both increase with the depth of the groove. Bearings without the groove are better damped than those with the grooves, and the stability of thrust bearing decreases when the groove depth increases. The stability of the thrust bearings is also affected by their loading.

Anchorage Performance and Interfacial Mechanics Transfer Characteristics of a Composite Anchor Bolt with Different Surface Shape

To solve the deficiency of steel anchor blot in corrosion resistance and flaw of GFRP anchor bolt in fracture resistance, our research group develops a new composite anchor bolt made of steel strands wrapped up with compound fiber resin. To improve the cohesion performance of the composite anchor bolt, pull-out tests of different composite anchor bolts with different groove intervals and depths were made and analyzed. The results show that the pulling resistance of the composite anchor bolt increases with the increase of groove interval and depth, but groove interval and depth have optimal value. Based on elastic mechanics, the cohesion between anchor bolts and anchor bodies and its distribution characteristics caused by axial tension are analyzed and cohesion formula is obtained. By contrast, the experimental result is consistent with the theoretical analysis. Therefore, the surficial change of anchor colts could influence the performance of the composite anchor bolt. The cohesion force and anchorage performance can be improved by changing the surface of anchor bolts. Research results show that the new composite anchor bolt is high-performance material in the civil engineering.

Property of the PVC Dust Collecting Plate Used in Wet Membrane Electrostatic Precipitator

This paper investigates the water distribution performance, discharging characteristics, and dust collecting efficiency of a wet membrane electrostatic precipitator, in which the collecting electrode is made of polyvinyl chloride (PVC) grooved plate. The film ratio of each horizontal-grooved plate is higher than the untreated PVC plate, and increases with the increase of groove depth and width under the same water flow; film ratio of vertical-grooved plate is higher than the untreated PVC plate in smaller groove width and depth, while it decreases with an increase in the groove width and depth. At the same voltage, corona current and dust collection efficiency increase with the increase of groove width and depth of horizontal-grooved plate, while it decreases with the increase of groove size of the vertical-grooved plate; with the same collecting plate, corona current increases with the increase of feed water flow and decreases with the increase of powder amount at the same voltage. The film ratio and discharge current reach the best value with the horizontal groove depth, width and interval of 6, 3, and 2 mm, respectively, resulting in the collection efficiency of 99.8% for a particle size of less than 1 μm.

Effects of groove on behavior of flow between hydro-viscous drive plates

The flow between a grooved and a flat plate was presented to investigate the effects of groove on the behavior of hydro-viscous drive. The flow was solved by using computational fluid dynamics (CFD) code, Fluent. Parameters related to the flow, such as velocity, pressure, temperature, axial force and viscous torque, are obtained. The results show that pressure at the upstream notch is negative, pressure at the downstream notch is positive and pressure along the film thickness is almost the same. Dynamic pressure peak decreases as groove depth or groove number increases, but increases as output rotary speed increases. Consequently, the groove depth is suggested to be around 0.4 mm. Both the groove itself and groove parameters (i.e. groove depth, groove number) have little effect on the flow temperature. Circumferential pressure gradient induced by the groove weakens the viscous torque on the grooved plate (driven plate) greatly. It has little change as the groove depth increases. However, it decreases dramatically as the groove number increases. The experiment results show that the trend of experimental temperature and pressure are the same with numerical results. And the output rotary speed also has relationship with input flow rate and flow temperature.