Pit Diameter Research Articles

Study on Milling Temperature of Titanium Alloy with Micro-Textured Ball End Milling Cutter under Radius of Blunt Edge

A high temperature is produced in the process of precision milling of titanium alloy, and the cutting temperature can be effectively reduced by placing a micro-texture on the tool surface. In order to study the milling temperature of micro-textured ball-end milling cutter in milling titanium alloy under the combined action of a blunt radius with different edges and a micro-texture with different parameters, a new method based on micro-element theory and the generation and transmission of cutting heat has been established. At the same time, the influence of different radii of blunt edges on the milling temperature is simulated by the finite element method and experimentally verified to explore the influence of different radii of a blunt edge and micro-texture parameters on the milling temperature. Taking the milling temperature as the evaluation index, the optimum parameters of micro-circular pit texture are as follows: the diameter of micro-circular pit is 40 micron, pit spacing is 225 micron, distance from cutting edge is 100 microns, and radius of the blunt edge is 60 microns.

‘Incognito’ dermal ring umbilicoplasty

Background. After using the standard umbilicoplasty techniques described for the white population, many of our dark-skinned patients developed prominent scars at the umbilical inset site. This prompted us to modify the technique to improve the aesthetic appeal of the translocated umbilicus. Objective. To describe a new umbilicoplasty technique aimed at reducing visible scarring, especially in keloid-prone patients. Methods. Between 2014 and 2019, 16 patients underwent abdominoplasty using this new technique. All patients were female, aged 30 - 45 years and with a body mass index of between 35 and 40. Thirteen patients were of Fitzpatrick skin type 6, and the remainder of type 4, 3 and 1, respectively. Umbilical detachment was done by keeping a de-epithelialised dermal ring outside the intact umbilical centre. The outer ring of dermis was attached to defatted area of the neo-umbilicus site of the abdominoplasty flap, followed by suturing of the borders of the T-shaped neo-umbilicus opening to the inner circle of the original umbilicus. The aim is to hide the umbilical suture line in the concavity of the umbilical pit, while maintaining the pit diameter with the dermal attachments. At the same time, extra support is given by the dermal ring sutures to prevent scar-widening. Results. All patients operated on using the new technique had less-visible scars, and no patient developed either scar hypertrophy or scar-widening, which was common in patients treated with the older technique. Keeping the epidermal section small allows partial effacement of the umbilicus, which allows easier cleaning. Ten patients were lost to long-term follow-up. Conclusion. Adding a peripheral de-epithelialised dermal ring, and keeping a small diameter of epithelialised umbilical stump, led to the suture line being under less tension, and resulted in a less-visible scar in the small cohort of the study. In addition, the smaller diameter allowed the umbilical walls to stretch open more to allow easier cleaning in patients with thick abdominal walls.

The control of thermal conductivity through coherent and incoherent phonon scattering in 2-dimensional phononic crystals by incorporating elements of self-similarity

In this letter, we report the theoretical study on phonon transport in monocrystalline silicon thin-films having unfilled or metal-filled circular holes (i.e., phononic crystals, PnCs) and show that the thermal conductivity, κ, at 1 K can be maximally reduced by using a multiscale structure, which allows us control over the porosity of the structure. The circular scatterers are placed in the square (SQ) and hexagonal (HX) pattern with a fixed 100 nm interhole spacing, and the pit diameter is varied between 10 and 90 nm. Each of the corresponding silicon PnCs shows reduced κ compared to the unpatterned film. The SQ-PnC having tungsten-filled pits shows the greatest reduction in κ when we consider only the effects of coherent scattering. Furthermore, we have computed κ for the PnC where the unit cell, of 100 nm and 500 nm sizes, comprises the Sierpinski gasket (SG) with circular holes of different diameters (depending on the fractal order) in the same cell. It is observed that the κ for the 2nd (100 nm cell) and 3rd order (500 nm cell) SG-PnC is comparable to the SQ- and HX-PnC with a pit diameter of 90 nm. When we add the effect of the diffuse boundary scattering in κ, there is a lowering in κ compared to that when only the coherent effects are considered. The additional κ-reduction due to boundary scattering for the SQ-PnC and HX-PnC (both with 90 nm diam) as well as the 2nd and 3rd order SG-PnCs is 47%, 40%, 80%, and 60%, respectively.

Icelandic Pit Chains as Planetary Analogs: Using Morphologic Measurements of Pit Chains to Determine Regolith Thickness

AbstractPit chains are distinctive geologic landforms present on planetary bodies across the solar system, which can be used to understand regolith properties and formation. If there is a direct relationship between pit diameter and the regolith depth, pit chains can be used to map regolith thickness across a planetary surface. Here, the morphology of individual pits within pit chains in northern Iceland was measured as a planetary analog to determine whether there is a direct relationship between individual pit diameters and pit depth, which is assumed to be a proxy for regolith depth. The morphology of pit chains and regolith thickness was measured in three different locations in northern Iceland, within two different substrates: unconsolidated floodplain sediments and more consolidated soils overlaying basaltic lava flows. There is a significant linear relationship between pit diameter and depth for pit chains located in the floodplain sediment, but not for pits located in basaltic materials. However, this depth‐diameter relationship does not correlate with regolith thickness. The depth of the pits in basaltic materials is more representative of the regolith depth than the pits in the floodplain sediments. If high‐resolution topography data are available, then the depth of pits in more consolidated materials can be used as a reliable estimate of regolith thickness. In more unconsolidated materials, the pit depth represents a minimum regolith depth. This ability to resolve regolith thicknesses may help resolve the processes by which regolith is emplaced and has implications for the thermal evolution of planetary bodies.

Effects of Oxygen Content on the Ablation Behavior of Silicone Rubber-Based Insulation Material

A self-designed oxygen-kerosene ablation system was employed to research the ablation properties of silicone rubber-based insulation material under different oxygen-rich conditions, that is, 0%, 5.00%, 7.71%, 17.01%, and 18.50%. The morphology of posttest specimens was analyzed via a scanning electron microscope (SEM), and the ablation rates were calculated. Experimental results showed that when the particle concentration was a fixed value, the mass and the linear ablation rates increased first and then decreased with the rise of oxygen content; the maximum values were 0.572 g/s and 0.933 mm/s, respectively. Under high oxygen-rich conditions, the formation of silicone rubber restricted the further increase of the ablation rates, filling more gaps of the reaction layer with liquid silicone rubber. Meanwhile, the thickness of the liquid glass layer attached to the surface was increased, which acted as a buffer against the impacts and erosion of particles and retarded the consumption and recession of materials. Excess oxygen spread to the edge of the ablation pit and reacted. Finally, these led to the increase in diameter of the ablation pit and the decrease of two types of ablation rates.

Spectroscopy of backscattered Cu ions detected by CR39 through grayness analysis of ion-etch tracks

The paper reports on a semi-automatic method for the detection and analysis of ion-etch pits generated on Solid State Nuclear Track Detectors (SSNTD) of the CR39 type. The CR39 detectors have been exposed to the elastically scattered Cun+ ions on a 50 nm Au layer deposited on a silicon substrate. After irradiations, foils have been chemically etched for 2 h in a 6.25 M NaOH solution to develop the ion-induced latent tracks. The detectors' surfaces have been analysed by Optical Microscopy (OM) and studied with the proposed method based on the measurements of both diameter and mean gray value of the ion-etched pits. The results are motivated by the future applications of these polymeric foils in the detection of charged particles in “harsh” environments, characterized by high dose and high radiation damage, e.g., in fusion experiments or in the diagnostic of plasma generated by lasers. A strong correlation between tracks’ characteristics (diameter and grayness) and the energy of the backscattered Cu ions has been obtained and empirical relationships between them are presented.

Evaluation of crack resistance of 38KhN3MFA-Sh structural steel by fracture properties and elastic wave velocities

The results of the study on the effects of tempering temperature on 38KhN3MFA-Sh steel static strength and crack resistance are given. The fractured surface texture has been studied after various heat treatment modes using electron-fractography analysis. Relationships between the fracture properties and the critical stress intensity factor have been established. The effect of tempering temperature on the velocities of ultrasonic bulk waves has been investigated. A linear relationship has been found between the velocity of elastic waves and the critical stress intensity factor of 38KhN3MFA-Sh steel. The dependence discovered allows us to estimate the changes in crack resistance of steel using a non-destructive test method with variations in tempering temperature. The method of electron fractography has been used to analyze specimen fractures having a crack in structural high-quality 38KhN3MFA-Sh steel. Investigations of the fractured surface texture subjected to various heat treatment modes have shown that the microrelief is represented by flattened cone-shape pits. An increase in tempering temperature is accompanied by an increase in the diameter of flattened cone pits on the fractured surface. A quadratic dependence has been established between the crack resistance parameter and the diameter of the pits. It is shown that the contribution of ferrite matrix structural condition to crack resistance value is much more significant than the contribution of isolated carbides. The velocities of elastic waves in steel have been measured; their values increase with the growth of tempering temperature. The characteristics of strength and crack resistance of structural steel exposed to hightemperature tempering have been predicted based on the values of transverse wave velocities. Deviation of the predicted values of crack resistance K1С and ultimate strength σb from the experimental values does not exceed 5.4% and 12.6%, respectively.

Tribological behavior of laser textured nodular cast iron surface

PurposePrevious publications were mainly focused on the effect of textures under lubrication. Under dry sliding, area ratio of surface texturing (pit area ratio) and diameter of pit affect the tribological behavior. This paper aims to investigate the effect of laser surface texturing on tribological behavior of nodular cast iron under dry sliding.Design/methodology/approachPit-like textures with different diameters and spaces were fabricated by laser on nodular cast iron (QT600-3). Using nodular cast iron (QT600-3) as the disc specimen and resin matrix composites (UCV018) as the pad specimen, the tribological test was performed with pin-on-disk reciprocating tribo-tester.FindingsThe coefficient of friction (COF) of the non-textured specimen was larger than that of the textured one. For the same pit diameter, a larger pit area ratio induced a slight decrease of COF, while wear volume decreased significantly. The pit diameter induced a slight decrease of COF as the pit area ratio, but its effect was weaker.Practical implicationsThe experimental studies will help to improve the brake system such as structure modeling of brake disc. Predicting the performance and life of the brake disc in vehicle based on tribological behavior checked in test, it was proved that pit-like texture had application value in vehicle brake system.Originality/valueThis paper showed that the effect of pit area ratio on friction and wear was greater than that of pit diameter. The experimental results will be useful to the design on safety brake disc.

Predictive modeling of grinding force in the inner thread grinding considering the effect of grains overlapping

Grinding force is an important factor to consider in the field of precision manufacturing. In this study, a model of the thread grinding force in inner thread grinding that takes into account the thread helix angle and effect of grains overlapping is presented. The average undeformed chip thickness of a single abrasive grain can be obtained based on the Rayleigh probability density function. The contact length is assumed to be the arc contact length and is calculated based on the movement of an active grain. In addition, the effective grain overlap coefficient can be defined as the ratio of the effective area removed by a single grain to the cutting area without overlapping grains. The normal force is generated by material deformation and friction. Similarly, the tangential force is produced by material deformation and tangential friction. The normal and tangential forces can be calculated by considering a micro abrasive grain. Experiments were conducted to calculate the coefficients of the grinding force model in order to validate the model. Scanning electron microscopy was performed to determine the relationship between the normal force and the largest pit on the inner thread surface. Normal and tangential forces were analyzed under different spindle speeds, workpiece speeds, grinding depths, and thread helix angles. The numerical results suggest that grinding force is affected by the thread helix angle and friction forces; moreover, grain overlap cannot be ignored. Finally, a linear relationship between the normal force and the largest pit diameter was derived and used to determine the optimal normal force for generating improved inner thread surfaces. The proposed model provides a theoretical basis for the optimization of high-speed high-precision inner thread grinding.

Stem anatomy diversity in Iresine (Amaranthaceae s.l.): an ecological interpretation

Iresine is an American genus that belongs to Amaranthaceae s.l. To understand its stem anatomy and correlation with the habit and habitat, a comparative study was carried out. We present the most extensive stem anatomical survey of Iresine to date. Our observations agree with wood descriptions for other Amaranthaceae having simple perforation plates, intervessel pits alternate and nucleated fibers. Few species showed distinctive growth rings. Rays are heterocellular, multiseriate with meristematic centers. The occurrence of rays with meristematic centers is not related to habit or habitat, but suggests that water and photosynthates movement is complex through the axial–radial system. Species studied have successive cambia in concentric bands or patches. Seven species have distinctive characters as for I. latifolia (M.Martens & Galeotti) Hook.f. with two or three pairs pith bundles, I. rzedowskii Zumaya, Flores Olv. & Borsch with a thick periderm and I. cassiniiformis S.Schauer with lignified pith. Not all quantitative wood features follow the trends expected with habit but significant differences exist (P > 0.05) for some as fiber length. The tree species has the widest vessel diameter (81 µm) and the longest fiber length (570 µm), and shrubs show the highest variation. Canonical correlation analysis allowed to identifying that mean annual temperature, longitude and annual rainfall have an impact in the wood of Iresine species, especially in vessel and fiber wall thickness, intervessel pit diameter and fiber length. Iresine wood appears to be more susceptible to changes of mean annual temperature and precipitation showing its plasticity.

Corrosion Evaluation of 316L Stainless Steel in CNT-Water Nanofluid: Effect of CNTs Loading.

Polarization resistance and potentiodynamic scan testing were performed on 316L stainless steel (SS) at room temperature in carbon nanotube (CNT)-water nanofluid. Different CNT loadings of 0.05, 0.1, 0.3 and 0.5 wt% were suspended in deionized water using gum arabic (GA) surfactant. Corrosion potential, Tafel constants, corrosion rates and pitting potential values indicated better corrosion performance in the presence of CNTs with respect to samples tested in GA-water solutions. According to Gibbs free energy of adsorption, CNTs were physically adsorbed into the surface of the metal, and this adsorption followed Langmuir adsorption isotherm type II. Samples tested in CNT nanofluid revealed a corrosion performance comparable to that of tap water and better than that for GA-water solutions. Among all samples tested in CNT nanofluids, the lowest corrosion rate was attained with 0.1 wt% CNT nanofluid, while the highest value was obtained with 0.5 wt% CNT nanofluid. At higher CNT concentrations, accumulated CNTs might form active anodic sites and increase the corrosion rate. SEM images for samples of higher CNT loadings were observed to have higher pit densities and diameters.

Experimental evaluation of the shear buckling behaviors of corrugated webs with artificial corrosion pits

Fifteen corrugated steel web I–beams were designed to investigate the shear buckling behavior and shear strength of corrugated steel webs with artificial corrosion pits. Different corrosion height, depth, and pit diameter, were considered in the shear loading tests. Critical buckling load and ultimate strength were compared with those calculated by existing formulas. In addition, Failure modes were discussed. Test results showed that corrosion volume decreased by 8% and bearing capacity decreased by nearly half compared with no corrosion. All corrugated steel webs were evenly sheared before the critical load was reached. Before reaching ultimate strength, the curve of vertical displacements and load is linear and the slope was affected by the corrosion. Perforation affected the failure modes of corrugated steel webs. Existing formulas yielded accurate and reliable results for uncorroded corrugated steel webs but cannot be used in the evaluation of the bearing capacity of corroded specimens. Corrosion volume, which was nonlinearly related to bearing capacity, was identified as an important factor that affects bearing capacity. Thus, corrosion volume must be considered in accordance with the actual working situation of corrugated steel webs. Future research should focus on the effect of perforation location and corrosion volume on ultimate strength to develop reliable designs for corrugated steel webs.

Stress and electrochemical corrosion of titanium produced by laser rapid forming

Objective: To investigate the stress corrosion and electrochemical corrosion resistance of titanium produced through laser rapid forming (LRF), and to provide a basis for their clinical application. Methods: Forged commercial pure titanium (CP-Ti) was used as control group and LRF pure titanium was used as LRF group. All samples were placed in acidic artificial saliva containing fluorine (pH=7), and loaded with a stress of 1.2 × σ(0.2) Pa (σ(0.2) represents the yield strength of material). Stress corrosion resistance of specimens that have been soaked for 30 days was analyzed by naked eye observation, X-ray diffraction analysis and scanning electron microscopy. For samples placed in artificial saliva, neutral fluoride solution (pH=7) and acidic fluoride solution (pH=3) (4 test pieces in each corrosive medium), and their electrochemical corrosion resistance was evaluated by free corrosion potential (Ecorr) measurements, corrosion current (Icorr), electrochemical impedance spectroscopy (EIS), and anodic polarization curves. Results: With the prolongation of immersion time, the corrosion products gradually increased. The stress corrosion of CP-Ti group was significantly more than that of LRF-Ti group, and the pit diameter was significantly larger than that of LRF-Ti group. The electrochemical corrosion results showed that the Ecorr (-469 mV) of LRF-Ti in artificial saliva was higher than that of CP-Ti (-555 mV), and the Ecorr (-925 mV) of LRF-Ti was higher than that of CP-Ti (-943 mV) in neutral fluoride solution. In acid fluoride solution, the Ecorr (-943 mV) of LRF-Ti was higher than that of CP-Ti (-956 mV). The Ecorr of the same metal was the highest in artificial saliva and the lowest in acid fluoride solution; the Icorr of the same metal was the lowest in artificial saliva and the highest in acid fluoride solution. Conclusions: Under the same corrosion conditions, LRF Ti demonstrated better stress and electrochemical corrosion resistance than CP-Ti.

Comparison of poly(butylene succinate) biodegradation by Fusarium solani cutinase and Candida antarctica lipase

Poly(butylene succinate) (PBS) was hydrolyzed by two different enzymes: cutinase from Fusarium sp. and lipase from Candida antarctica (Lipozyme CALB). The differences between the PBS residues degraded over time were investigated with respect to their morphology, crystallinity and chemical structures. The degradation mechanism of PBS films using the two enzymes was further investigated by establishing a model. The results show that the PBS weight loss when degraded by cutinase was higher than when degraded by Lipozyme CALB under the same conditions. The PBS degradation mechanisms by cutinase and Lipozyme CALB occur by surface erosion and bulk erosion, respectively. Scanning electron microscopy shows that the diameter of pits formed after degradation by cutinase was approximately 3 times larger than those formed by Lipozyme CALB. The change in crystallinity is related to the type of enzyme used during the degradation process. Following Lipozyme CALB degradation, the degree of PBS crystallinity decreased with increasing time, leading to increased weight loss of the PBS films. Conversely, the PBS crystallinity was nearly unchanged following cutinase degradation. Powder X-ray diffraction indicates that the crystalline structure does not change during enzymatic hydrolysis. Fourier transform infrared spectroscopy confirms that the resulting structure of the degraded PBS is similar when treated with cutinase and Lipozyme CALB. Mass-spectrometric analysis suggested an endo-type action mode for both the enzymes.

Precise control of surface texture on carbon film by ion etching through filter: Optimization of texture size for improving tribological behavior

Surface texture is a potential way to promote the tribological behavior of films with a range of tens to hundreds nanometers, but how to precisely control the texture size and find an optimal size for improving the tribological behavior is still challenging. In this paper, we proposed a method to fabricate pit texture with tunable size on the surface of carbon film by ion etching through a filter. The pit depth (10, 30 and 60 nm) was decided by the etching time and the pit diameter (10, 60 and 120 μm) was equal to the through-hole on the filter. The tribological properties of these carbon films were tested using a pin-on-disk tribometer. The results demonstrated that the friction coefficient and wear life were strongly affected by the texture parameter and there were an optimal pit depth and diameter under which the film exhibited the lowest friction coefficient and the longest wear life. The mechanism of the tribological property promotion was further discussed based on the variation of the transfer film structure and contact condition induced by the texture. These results provided an effective way to choose proper texture parameters for better tribological performance of the surface, which can be expected for expanding the texture techniques.

Calculation of Sound Insulation for Hybrid CLT Fabricated with Lumber and LVL and comparison with experimental data.

The insulated predictions were carried out for LVL, CLT and HCLT in order to evaluate their sound properties, in which the theoretical value of sound insulation was predicted by regarding the substances in wood cell wall as equivalence to specific medium based on Biot model, and the wood anatomical characteristics, such as the length and diameter of tracheid, diameter of pit, and porosity, were taken into account for determining the equivalent density and bulk modulus of elasticity of wood cell wall. By comparing the tested and predicted values of sound insulation, the conclusion were drawn as follows: the predicted values of sound insulation were significantly correlated with the tested values for LVL, CLT and HCLT. As for Masson pine and Southern pine, the adjacent of earlywood and latewood was considered as sandwich structure for the calculation of sound insulation. Meanwhile, the bonding interface was creatively introduced to improve the accuracy of sound insulation prediction. The transfer function involved in sound insulation prediction provide an effective method to characterize the sound insulation volume of wood composite in construction and decoration areas.

Study of the Electrical Properties of Porous Silicon Prepared by Electrochemical Etching Technique

In our work, a P-type porous silicon (PSi) with orientation (100) have been prepared using the chemical etching method; the goal is to study the electrical properties of PSi samples prepared with completely different etching current (7, 9, 11 and 13) mA and glued for (15 min) anodization time. Depending on the atomic force microscopy (AFM) investigation, we notice the roughness of Si surface increases with increasing etching current because of increases within the dimension (diameter) of surface pits. The electrical and optoelectronic properties of prepared PSi, specifically capacitance-voltage (C-V), current-voltage (I-V), responsivity and detectivity, are analyzed. It had been found that electrical characteristics of porous Si samples measured in dark (Id) and below illumination (IPh) will be fitted well by the equations of thermal emission. From this point of view, Schottky barrier height (ɸB) and ideality factor (n) of made-up photodetectors were calculated. We tended to determine from I-V characteristics of a dark, and illuminations that the pass current through the PSi layer reduced by increasing the etching current, as a result of increasing the electrical resistance of PSi layer and therefore the optimum value of ideality factor is (2.7), whereas from C-V characteristic we determined that in-built potential accumulated with increasing etching current. The results show that there are clear results for better performance of photodetectors.

Influence of the diameter of ground date pits on the technological properties of clay bricks

Abstract The main aim of this study was to evaluate the effect of diameter of ground date pits (GDP) on the technological properties of a clay brick. For this purpose, increasing amounts of GDP (0, 5, 10, 15 and 20 wt%) with different diameters were mixed with a clay to produce clay bricks by pressing, drying and then firing at 900 °C. The GDP diameter and content changed the water requirement for plasticity. The shrinkage, water absorption and apparent porosity of fired clay brick increased with the content and diameter of GDP. The compressive strength, apparent density and thermal conductivity of the samples decreased with the increase in diameter and content of GDP. With the help of SEM micrographs, it was observed that the combustion of added GDP in the mixture led to a reduction in the diameter of pores formed in the fired clay brick samples.

Influence of pitting corrosion on the bending capacity of thin-walled circular tubes

Thin-walled circular tubes (TWCTs) have been extensively used in space lattice structures and other industrial areas. Corrosion is inevitable for steel structures with regard to its service life, and it will remarkably reduce the loading capacity and critically threaten the structural safety. The present work aims to investigate the influence of pitting corrosion on the bending capacity of TWCT. A series of nonlinear numerical analyses was conducted to investigate the influences of corrosion pit shape, specification, corrosion thickness, diameter, and thickness of TWCT on bending capacity. Corrosion was simulated by reducing the thickness of shell element. Random corrosion distribution was generated, and its influence on bending capacity was estimated. The method for generating a random corrosion would provide a reference for the analysis of other structures with corrosion.

Numerical assessment of experiments on the ultimate strength of stiffened panels with pitting corrosion under compression

The ultimate strength of stiffened panels under compressive loads is assessed by numerical simulations, in order to compare with tests made to investigate the influence on the ultimate strength of varying pit location, pit diameter and pit depth. The validated model is them used for a numerical study on the influence of pitting on the residual ultimate strength of stiffened panels by a series of non-linear finite element analysis. The parameters of pit position, diameter, number, depth, and corroded volume loss will be investigated for the stiffened panels subjected to axial compressive load with initial deformations. It is found that the pits will induce the buckling failure of stiffened panels. All parameters discussed in this paper have significant influence on the residual ultimate strength of the pitting corroded stiffened panel. A formula was derived by introducing the reduction of plate slenderness and column slenderness.