Increasing Groove Depth Research Articles

Dicing Process for 4H-SiC Wafers by Plasma Etching Using High-Pressure SF<sub>6</sub> Plasma with Metal Masks

Since SiC is hard and brittle, dicing by normal grinding process not only requires a long time for processing, but also reduces chip strength due to microcracks. The use of highly efficient and damage-free etching with high-pressure plasma as a chemical processing method for dicing rather than mechanical processing was investigated. The results of groove processing using a combination of a metal mask with slit-like apertures and plasma etching with high-pressure SF6 plasma showed that the processing speed decreased with decreasing slit width and increasing groove depth. The results of electrostatic field calculations suggest that this is due to a decrease in plasma intensity caused by electric field decreasing.

Investigation on the effect of different groove depth and width on the tip clearance leakage flow of hydrofoil

Abstract Due to the complexity of axial-flow hydraulic machinery structure and the difficulty of flow field analysis, this paper takes three-dimensional hydrofoil as the research object to analyse the flow characteristics of clearance flow and carry out research on clearance leakage control. The 3-D hydrofoil model with two kinds of gap widths was calculated by using the numerical model method, and compared with the experiment; the influence law of different groove depth and width on the gap leakage flow characteristics and energy characteristics was studied. The results show that with the increase of groove depth, the clearance leakage increases, the lift-drag ratio decreases, and the pressure coefficient increases. Higher axial velocity is shown with increasing groove depth under the small tip clearance, while the opposite is true for large gaps. The optimal groove depth is determined to be D=1mm. When the groove width is 2mm, the pressure coefficient of the hydrofoil is the highest and the vorticity coefficient is the smallest, so the hydrofoil has better performance. In summary, when groove depth D=1mm and groove width W=2mm, the clearance leakage flow rate is smaller and the lift-drag ratio is higher. This study provides a new method for improving the flow field and running stability of turbine-machines with tip clearance in practical engineering.

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.

Experimental and numerical simulation study on the effect of granite grooving characteristics on PDC cutter cutting performance

How to improve drill bit working efficiency in deep drilling has been a wide concerned issue in petroleum industry. Utilizing ultra-high-pressure water jet to groove the bottom hole rock and reconfiguration the stress field is considered an effective method to improve the rock breaking efficiency and improve rate of penetration. However, there is currently no relevant report available on the effect of groove characteristics, which are important factors affecting rock break efficiency. Therefore, this study combines lab test with numerical simulations to analyze the effects of rock groove characteristics under the simultaneous action of confining pressure and hydrostatic pressure on cutting force, energy consumption of rock breaking, cutting size, cutting trajectory morphology, stress distribution characteristics, crack characteristics, and failure modes. The research results show that increasing groove depth and number significantly reduce cutting force, enhance rock fragmentation mass, and significantly improve rock breaking efficiency. There exists a threshold for specific energy consumption of rock breaking under different groove characteristics, with a 35.17% decrease in energy consumption of rock breaking at a cutting depth of 15 mm, and the lowest energy consumption of rock breaking when the number of grooves is 2. The reduced compressive effect of the confining pressure on the rock after grooving decreases the inhibitory effect on internal crack propagation and the increase in internal cracks and the higher percentage of tensile failure contribute to the increased rock breaking efficiency. This study provides theoretical and technical guidance for ultra-high-pressure water jet drilling technology.

Experimental Investigation and Statistical Modeling of the Effective Parameters in Charpy Impact Test on AZ31 Magnesium Alloy with V-shape Groove Using Taguchi Method

Today, the charpy impact test is required as a general quality control test in various industries. Several industrial standards have been formulated to perform the test accurately. It is important to determine the dynamic fracture energy in the charpy impact test and its relation to the fracture toughness through semi-empirical equations. In the present study, the charpy impact test on AZ31 magnesium alloy with standard ASTM E23 sample size is measured by the effect of groove depth, temperature and angle of groove on fracture energy. Taguchi and L18 arrays have been used to design the experiments and obtain the optimal state according to the number of factors studied. The effect of each input variable on the target parameter was analyzed by using ANOVA and the values of input parameters were extracted to maximize the amount of fracture energy by signal to noise method. The results showed that the groove depth has the greatest effect on the fracture energy and decreased with increasing groove depth. Also the best combination to maximize fracture energy was obtained in the non-grooved sample at -10 °C with a groove angle of 60 °.

Investigation into the effect of wheel groove depth and width on grinding performance in creep-feed grinding

This work presents an investigation into the effects of different groove depths and groove widths on grinding performance in creep-feed grinding using grinding wheels with spiral-shaped circumferential grooves inscribed around their surface. These grooves had constant widths of 3.2 mm and 1.7 mm, respectively, allowing for the decoupling of groove depth effects from groove width effects. Force, power, and surface roughness data was acquired for each experiment. There were only small differences between the results for force, power, and workpiece surface roughness for both groove widths. It was found that the grinding forces and spindle power initially decreased with increasing groove depth but the reductions in forces and power decreased and eventually leveled off as groove depths increased. For the experimental conditions of this research, it was found that there is little benefit in grooving deeper than ~ 400 μm. Groove depth did not appear to influence workpiece surface roughness significantly. The changes in grinding performance observed at different groove depths were attributed to changes in coolant flow. It was discovered that the coolant-induced force resulting from hydrodynamic pressure in the grinding zone decreased with respect to increasing groove depth up until about 400 μm which is consistent with the results observed for forces and power. The decrease in coolant-induced force signifies an increase in useful flowrate which was believed to be responsible for the improved grinding performance observed at different groove depths.

Experimental study on EHD effects on wetting characteristics of liquid in open rectangular microgrooves

Liquid wetting characteristics under EHD (Electrohydrodynamic) effects as a function of heat flux, voltages, microgroove inclination and dimensions in open rectangular microgrooves have been experimentally investigated. Two planar electrodes were used to generate electric fields. Wetting length was captured by a camera and it was determined according to the locations of marking lines that were measured by a caliper. The uncertainties of the heat loss and wetting length are 11.11% and 7.46%, respectively. Results indicate that higher heat flux can be achieved by electric fields effects. Wetting length increases notably by EHD pumping at a lower inclination. It is observed that microgrooves with smaller depth/width ratio perform a more pronounced increase of wetting length in the presence of electric fields. In addition, theoretical analyses show that the wetting length under electric field effects increases with the increasing groove depth while decreases as the groove width increases. Besides, both the threshold and optimal voltage are smaller for microgrooves with larger depth/width ratio. Moreover, the threshold voltage decreases with the increase of the depth/width ratio linearly. The findings are useful for the design of the EHD augmented grooved microfluidic devices with considering the fair geometrical dimensions and electric field voltages.

Residual heat generated during laser processing of CFRP with picosecond laser pulses

Abstract One of the major reasons for the formation of a heat-affected zone during laser processing of carbon fiber-reinforced plastics (CFRP) with repetitive picosecond (ps) laser pulses is heat accumulation. A fraction of every laser pulse is left as what we termed residual heat in the material also after the completed ablation process and leads to a gradual temperature increase in the processed workpiece. If the time between two consecutive pulses is too short to allow for a sufficient cooling of the material in the interaction zone, the resulting temperature can finally exceed a critical temperature and lead to the formation of a heat-affected zone. This accumulation effect depends on the amount of energy per laser pulse that is left in the material as residual heat. Which fraction of the incident pulse energy is left as residual heat in the workpiece depends on the laser and process parameters, the material properties, and the geometry of the interaction zone, but the influence of the individual quantities at the present state of knowledge is not known precisely due to the lack of comprehensive theoretical models. With the present study, we, therefore, experimentally determined the amount of residual heat by means of calorimetry. We investigated the dependence of the residual heat on the fluence, the pulse overlap, and the depth of laser-generated grooves in CRFP. As expected, the residual heat was found to increase with increasing groove depth. This increase occurs due to an indirect heating of the kerf walls by the ablation plasma and the change in the absorbed laser fluence caused by the altered geometry of the generated structures.

Suppression of bulk waves in surface acoustic wave filter

Introduction. One of the dominant second order effects in devices based on surface acoustic waves (SAW) is the excitation of parasitic bulk acoustic waves (BAW). Attention is drawn to the lack of effectiveness of traditional BAW suppression ways. Traditional ways of suppressing the bulk acoustic waves. Provides an overview of how suppression of parasitic BAW to SAW filters. One way allows to reach a record level of BAW suppression (−65 dB) due to the significant mechanical weakening of the acoustic line of the filter. Narrowband surface acoustic wave filter. It is found that in the SAW filter with an extremely high level of out-of-band suppression (−72 dB) traditional ways do not provide the required level of suppression of BAW. Wave heterogeneity of special shape. Tested the effectiveness of the authors proposed way of BAW suppression in a narrow-band SAW filter with an extremely high level of out-of-band suppression. A deep closed groove which is cut in the lower surface of the acoustic line of filter reduces the level of BAW to −70 dB, and the strength of the acoustic line of filter is almost not reduced. The dependence of suppression the bulk acoustic waves from the parameters of the wave heterogeneity. The dependence of the relative level (B) of suppression the slow quasi-shear bulk acoustic waves from the depth of the closed groove was investigated. It was found a monotonic increase in the level of B with increasing groove depth. Level B = −70 dB was obtained when the thickness of the gap between the bottom of the groove and the working surface of the acoustic line was (for different filter samples). Conclusion. The effectiveness of the authors proposed way of suppression the slow quasi-shear BAW in SAW filters is proved. A deep closed groove which is cut into the bottom surface of the acoustic line of filter can suppress slow quasi-shear BAW to a level of −70 dB.

Fretting fatigue behavior and life prediction of automotive steel bolted joint

Fatigue tests of bolted joints of SAPH400 automotive steel plate were carried out. Effect of groove on fretting fatigue strength was investigated by introducing various geometries of grooves at contact edge. The fretting fatigue strength was improved by introducing groove: the fatigue strength increased with increasing groove depth. As the next step, the applicability of the tangential stress range–compressive stress range diagram to the bolted joints was investigated using the tangential stress range–compressive stress range diagram obtained from conventional laboratory-type SAPH400 steel specimens. The result showed that the fretting fatigue strength of actual component, i.e. the bolted joint could be successfully predicted based on the tangential stress range–compressive stress range diagram.

Tri-helical gravure roll coating

A mathematical model is presented and solved for the fluid flow within the coating bead of a tri-helical gravure roll coater, operating in reverse mode. A variety of rolls etched circumferentially with grooves of different cross-sectional shape and aligned at non-zero angles of pitch are investigated. Predictions of fluid pick-out from the grooves are compared with complementary experimental data. Quantitative agreement between the two is found to be very good, showing a linear increase in pickout as a function of web-to-roll speed ratio and groove depths up to the point at which streaking, as observed experimentally, occurs and beyond which the model is no longer valid. In regions of parameter space for which there is no experimental data available for comparison purposes the model predicts that: (i) fluid pick-out decreases with increasing groove depth while the film thickness tends to increase and (ii) an increase in groove aspect ratio leads to a reduction in both pick-out and film thickness for a given land width and groove cross-sectional shape.

Power loss characteristics of a sensing element based on a grooved polymer optical fiber under elongation

This study conducts a numerical and experimental investigation into the effects of elongation on the power attenuation characteristics of grooved polymer optical fibers (POFs). POFs with groove depths ranging from 0 to 1.1 mm are tensile tested. The load–elongation data are then used to compute the corresponding average plastic energy density (APED). An elastic–plastic three-dimensional finite element model is used to simulate the deformation which takes place near the grooved region of the elongated POF in order to clarify the experimental results. In general, the results show that the change rate of the power ratio or the sensitivity increases with increasing elongation and increasing groove depth. By applying a curve-fitting technique, an empirical expression is developed to relate the power ratio to the APED and the groove depth. It is found that the difference between the predicted values obtained from the proposed equation and the experimental results is less than 7%, thus confirming the APED to be a meaningful index with which to evaluate the sensitivity of POF sensors.

Scattering of backward spin waves in a one-dimensional magnonic crystal

Scattering of backward volume magnetostatic spin waves from a one-dimensional magnonic crystal, realized by a grating of shallow grooves etched into the surface of an yttrium iron garnet film, was experimentally studied. Rejection frequency bands were clearly observed. The rejection efficiency and the frequency width of the rejection bands increase with increasing groove depth. A theoretical model based on the analogy of a spin-wave film waveguide with a microwave transmission line was used to interpret the obtained experimental results.

Anisotropic Wetting Behavior Arising from Superhydrophobic Surfaces: Parallel Grooved Structure

It has been found experimentally that superhydrophobic surfaces exhibit strong anisotropic wetting behavior. This study reports a simple but robust thermodynamic methodology to investigate the anisotropic superhydrophobic behavior for parallel grooved surfaces. Free energy and its barrier and the corresponding contact angle and its hysteresis for various orientations of the groove structure are calculated based on the proposed thermodynamic model. It is revealed that the strong anisotropy of equilibrium contact angle (ECA) and contact angle hysteresis (CAH) is shown in the noncomposite state but almost isotropic wetting properties are exhibited in the composite state. Furthermore, for the noncomposite state, decreasing groove width and spacing or increasing groove depth can amplify the anisotropy for ECA. Meanwhile, decreasing groove width and increasing depth can amplify the anisotropy for CAH, while varying groove spacing can barely influence CAH. For the composite state, however, the surface geometry hardly leads to the anisotropic behavior. In addition, using a fitting approximation, a simple quantitative correlation between wettability and orientation can be established well, which is consistent with the numerical calculations.

Sub‐micron and nanoscale feature depth modulates alignment of stromal fibroblasts and corneal epithelial cells in serum‐rich and serum‐free media

Topographic features are generally accepted as being capable of modulating cell alignment. Of particular interest is the potential that topographic feature geometry induces cell alignment indirectly through impacting adsorbed proteins from the cell culture medium on the surface of the substrate. However, it has also been reported that micron-scale feature depth significantly impacts the level of alignment of cellular populations on topography, despite being orders of magnitude larger than the average adsorbed protein layer (nm). In order to better determine the impact of biomimetic length scale topography and adsorbed protein interaction on cellular morphology we have systematically investigated the effect of combinations of sub-micron to nanoscale feature depth and lateral pitch on corneal epithelial cell alignment. In addition we have used the unique properties of a serum-free media alternative in direct comparison to serum-rich medium to investigate the role of culture medium protein composition on cellular alignment to topographically patterned surfaces. Our observation that increasing groove depth elicited larger populations of corneal epithelial cells to align regardless of culture medium composition and of cell orientation with respect to the topography, suggests that these cells can sense changes in topographic feature depths independent of adsorbed proteins localized along ridge edges and tops. However, our data also suggests a strong combinatory effect of topography with culture medium composition, and also a cell type dependency in determining the level of cell elongation and alignment to nanoscale topographic features.

The effect of combined cyclic mechanical stretching and microgrooved surface topography on the behavior of fibroblasts

Under the influence of mechanical stress, cultured fibroblasts have a tendency to orient themselves perpendicular to the stress direction. Similar cell alignment can be induced by guiding cells along topographical clues, like microgrooves. The aim of this study was to evaluate cell behavior on microgrooved substrates, exposed to cyclic stretching. We hypothesized that cellular shape is mainly determined by topographical clues. On basis of earlier studies, a 10-microm wide square groove, and a 40-microm wide V-shaped groove pattern were used. Smooth substrates served as controls. Onto all substrates fibroblasts were cultured and 1-Hz cyclic stretching was applied (0, 4, or 8%) for 3-24 h. Cells were prepared for scanning electron microscopy, immunostaining of filamentous actin, alignment measurements, and PCR (collagen-I, fibronectin, alpha1- and beta1-integrins). Results showed that cells aligned on all grooved surfaces, and fluorescence microscopy showed similar orientation of intracellular actin filaments. After 3 h of stretch, cellular orientation started to commence, and after 24 h the cells had aligned themselves almost entirely. Image analysis showed better orientation with increasing groove depth. Statistical testing proved that the parameters groove type, groove orientation, and time all were significant, but the variation of stretch force was not. Substrates with microgrooves perpendicular to the stretch direction elicit a better cell alignment. The expression of beta1-integrin and collagen-I was higher in the stretched samples. In conclusion, we can maintain our hypothesis, as microgrooved topography was most effective in applying strains relative to the long axis of the cell, and only secondary effects of stretch force were present.

Articular chondrocyte passage number: Influence on adhesion, migration, cytoskeletal organisation and phenotype in response to nano- and micro-metric topography

The isolation and culture of articular chondrocytes is a prerequisite of their use in tissue engineering, but prolonged culture and passaging is associated with de-differentiation. In this paper we studied the influence of nanometric and micrometric grooves (85 nm to 8 microm in depth and 2 microm to 20 microm in width) on 1st and 2nd passage ovine chondrocytes since our earlier findings indicate that primary cells are not affected by such features. 1st and 2nd passage chondrocytes cultured on grooved substrata showed a polarisation of cell shape parallel to the groove long axis and F-actin condensations were evident at groove ridge boundaries. An increase in cell migration with increasing groove depth was observed. Both passages of chondrocytes maintained type II collagen expression, but to a lesser degree in 2nd. This study demonstrates that passage number alters the response of chondrocytes to micrometric and nanometric topography, and could be important in ex vivo cartilage engineering.

Microstructure and Properties of Groove-Shaped Artificial Pinning Centers Introduced by Microfabrication

Effective flux pinning centers are required for the development of practical superconductors in order to achieve high critical current density. In the case of metallic superconductors, a drawing process introduces artificial pinning centers in metallic superconductors. However, artificial pinning centers cannot be introduced into high-Tc superconductors through the drawing process because these superconductors are brittle. We consider the microfabrication technique, instead of the drawing process, in order to introduce artificial pinning centers into the superconductors. Groove-shaped artificial pinning centers are introduced into a 0.5 /spl mu/m thick evaporated Nb film on a sapphire substrate by photolithography. The groove-shaped pattern with a spacing of 4 /spl mu/m was introduced by etching on a 0.9 /spl times/ 0.9 mm region of the Nb film. Nb films with varying groove depths were prepared, and the groove depth dependence on critical current density was investigated for the width of the hysteresis curve of the magnetic moment. The hysteresis curves of the specimens with grooves were measured with a SQUID magnetometer. The width of the hysteresis curve decreases with an increasing groove depth for over 70% of the film thickness.

Competitive Guidance Cues Affect Fibroblast Cell Alignment: Electric Fields vs. Contact Guidance

ABSTRACTWhen bovine ligament fibroblast cells were cultured on parallel micro-grooved surfaces, they aligned their long axes parallel to the groove direction. This alignment was dependent on the groove depth, with increasing groove depth increasing guided cell alignment. When cells were cultured in a physiological dc electric field (EF) on non-grooved, flat surfaces, the cells aligned in response to the EF, with their long axes perpendicular to the EF vector. This response was EF strength dependent, increasing EF strength (from 20 to 200mV/mm) increased cell alignment, perpendicular to the EF vector. These two guidance cues were applied simultaneously, so that the EF vector was parallel to the groove direction. At high but still physiological EF strengths (200mV/mm) cells ignored the topography and were guided by the EF alone, aligning perpendicular to the EF vector, as on non-grooved surfaces. At low field strengths (20mV/mm) cells responded only to the topographic guidance cue, with cells aligning parallel to the grooves and therefore also to the EF vector. Intermediate field strengths (50 to 100mV/mm) produced a mixed response, with cells responding to both guidance cues. The effect of removing serum from the culture medium on the EF and topographical guidance of fibroblast cells was studied and the results were compared to cells on non-grooved surfaces. Removal of serum produced a small but significant decrease in the angle of cell alignment for cells on non-grooved surfaces, from 78 to 63 degrees, relative to the EF vector, but did not completely suppress the EF guidance cue. In contrast, the EF guidance of cells on grooved substrates was suppressed almost completely by the absence of serum, with cells responding only to the grooved topography, aligning their long axis parallel to the grooves and the EF vector. These results imply that alignment of fibroblasts by topography is serum-independent, but alignment by EFs is serum-dependent. In addition they demonstrate that the alignment of fibroblast cells can be tailored by the dual guidance cues of topography and electric fields.

The Effect of Asperity Array Geometry on Friction and Pull-Off Force

The friction and pull-off forces between regular asperity arrays with various heights on a silicon wafer and a scanning probe of an atomic force microscope (AFM) were measured. We used two-dimensional periodic asperity arrays. The arrays were created by using a focused ion beam (FIB) to mill patterns on a silicon plate and on a platinum layer deposited on a silicon plate. For both materials, the distance between adjacent peaks was about 240 nm and the groove depth ranged from about 3 to 49 nm. The probe of the AFM was a square flat, 0.7 × 0.7 μm2. For the silicon array, the pull-off force decreased with increasing groove depth and was proportional to the radius of curvature of the asperity. The friction force also decreased with asperity height and was proportional to both the asperity curvature and the pull-off force. For the platinum asperity array, although both the pull-off and friction forces also decreased with groove depth, the friction coefficient (calculated by dividing the friction force by the pull-off force) was about half that of the silicon asperity array.