Small Groove Research Articles

Liquid droplet impingement erosion on groove roughness

A study of erosion mechanism during the liquid droplet impingement (LDI) on a rough surface was conducted using both numerical simulation and experiments. The numerical simulation was carried out for the LDI on single groove roughness utilizing the two-phase full Eulerian approach based on the high-resolution finite volume method to understand the evolution of the droplet deformation and the wall pressure distribution. The numerical results for the LDI on a large groove roughness showed that the first and the second impacts occurred close to the first contact location of the droplet on the wall, which was similar to the LDI on a smooth surface. The largest impact occurred by the third impact at the groove bottom, which was caused by the side-jet focusing and droplet focusing generated from the contact edge of the droplet. It was also found that the maximum wall pressure at the groove bottom increased with the increase in the groove roughness parameter that represented the geometrical ratio of the groove depth to the droplet diameter. In addition to the numerical studies, the erosion behavior of LDI on single groove roughness was observed experimentally using a Scanning Electron Microscope (SEM) after spray jet impingement on an aluminum specimen with various groove roughness parameter. The experimental results showed that the LDI erosion on the large groove roughness started from the groove bottom, while the LDI erosion on the small groove roughness started from the groove edge and the groove bottom. These experimental findings are well correlated with the maximum wall pressure distributions obtained from the numerical results.

Electrical Contacts in SOI MEMS Using Aerosol Jet Printing

In this paper, an additive method to make electrical contacts in SOI MEMS devices with aerosol jet printing is introduced. Small grooves were etched to the frame of MEMS accelerometer in the same step with the active structure release. Aluminum ink was jetted to the trenches in wafer-level to bridge the device layer to the handle wafer with the minimum amount of material. After subsequent annealing, ohmic contacts between p-type device layer and p-type handle silicon were verified by I – V measurements. The via resistance less than 4 $\Omega $ per via is measured. The method demonstrated in this paper provides simple and low-cost approach for SOI handle contact where additional packaging of wafer process steps can be avoided.

Topology Analysis of Bicycle Rim Brake Pad to Improve Braking Performance

Various parameters of rubber brake pad tribology will affect the braking performance of a rim brake system of a bicycle. Out of those, three main parameters are contact length of brake pad, surface topology of friction surface, and the thickness of rim brake pad. the goals of this study are to improve the braking performance of rim brakes to have better friction performance while retaining its simplicity of manufacturing and to investigate the effect on friction performance through the modifications of external dimensions and surface topology of rim brakes. Moreover, through this study, it can reveal which topology modifications of the rubber brake pad will have the most significance effect towards friction performance. Experimental measurement is used to obtain the friction properties and then parametric study was carried out numerically to obtain the braking performance of the rubber brake pad. the parametric study was simulated in ANSYS Transient Structural analysis. Taguchi design method was used for quantitatively identifying the right inputs and parameter levels. the results showed that smaller groove and smaller width contribute to higher friction performance. Stress concentration occurs at the edge of groove; hence, by reducing number of groove, it allows higher braking force to be generated. Location of groove concentration appears to have insignificance effect to the friction performance. Through the topology modifications, it improves the braking performance by 3%. As for external dimension, thick rubber brake pad will not demonstrate any improvement and longer contact length will demonstrate higher friction force. However, it has to be bounded by the practicality of the dimension. Upon modifications at the external dimension, it has an improvement of 64% in braking performance.

Structural characterization of SpoIIIAB sporulation-essential protein in Bacillus subtilis.

Endospore formation in the Gram-positive bacterium Bacillus subtilis initiates in response to nutrient depletion and involves a series of morphological changes that result in the creation of a dormant spore. Early in this developmental process, the cell undergoes an asymmetric cell division that produces the larger mother cell and smaller forespore, the latter destined to become the mature spore. The mother cell septal membrane then engulfs the forespore, at which time an essential channel, the so-called feeding-tube apparatus, is thought to cross both membranes to create a direct conduit between the cells. At least nine proteins are required to form this channel including SpoIIQ under forespore control and SpoIIIAA-AH under the mother cell control. Several of these proteins share similarity to components of Type-II, -III and -IV secretion systems as well as the flagellum from Gram-negative bacteria. Here we report the X-ray crystallographic structure of the cytosolic domain of SpoIIIAB to 2.3 Å resolution. This domain adopts a conserved, secretion-system related fold of a six membered anti-parallel helical bundle with a positively charged membrane-interaction face at one end and a small groove at the other end that may serve as a binding site for partner proteins in the assembled apparatus. We analyzed and identified potential interaction interfaces by structure-guided mutagenesis in vivo. Furthermore, we were able to identify a remarkable structural homology to the C-subunit of a bacterial V-ATPase. Collectively, our data provides new insight into the possible roles of SpoIIIAB protein within the secretion-like apparatus essential to bacterial sporulation.

A submerged tooth possibly caused by biting on a tracheal tube in hospital due to cerebral hemorrhage in childhood

We report the case study of a 17-year-old boy with cerebral-hemorrhage sequelae including intellectual disability, who presented with a severe, submerged first deciduous molar in his mandibular alveolar bone. It was believed that his condition was caused by biting on a tracheal tube during hospitalization after a fall that he experienced at the onset of a cerebral hemorrhage when he was 6 years old. His school dentist referred him to us, but he did not notice the submerged deciduous molar at that time. We found that the patient had 26 permanent teeth, with two congenitally missing lateral mandibular incisors, and there was some space with a small groove between his left first and second premolars. Panoramic radiography revealed the crown of his deciduous first molar lodged in the mandibular alveolar bone. Oral surgery to extract this tooth was performed under general anesthesia, with an additional aim of improving his oral hygiene. Additionally, a part of his extracted tooth was examined histopathologically, and was found to have no sign of ankylosis around its root. This case suggests that medical staff should pay attention to patients’ teeth in the hospital, especially because a tracheal tube has the potential to affect the teeth. This case also confirms the importance of dental treatment for people with special needs to improve their oral hygiene and quality of life.

Electron backscatter diffraction-analysis of deformed micro-milled commercially pure-titanium specimens at different strain values

Abstract The surface structuring process micro-milling introduces small grooves, which act as geometrical notches and influence the mechanical properties of the component, into the surface. The mechanical behaviour depends on the relation of the notch size to the grain size. Micro-milling processes were applied to improve the functional properties of component surfaces. They are used in mechanically loaded environments as well as in biotechnological applications. Therefore, commercially-pure-titanium is a favoured material of investigation. To determine the effect of the notches, a detailed analysis of the deformation behaviour of the structured material is indispensable. In the present work, structured specimens were tested under quasi-static loading. The testing was interrupted at different strain values. The micro-sections of the specimens were characterized by means of electron backscatter diffraction analysis to obtain information about the first indication of plastic deformation and the development of the deformation features. The results show inhomogeneous deformation behaviour of the material. The deformation mechanisms, the development of small angle and high angle grain boundaries as well as twinning are shown.

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

AbstractMechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.

Comparison Between Cemented Carbide and PCD Tools on Machinability of a High Silicon Aluminum Alloy

The high content of silicon of aluminum casting alloys challenges the tool life of conventional cemented carbide inserts, and polycrystalline diamond (PCD) tools appear as an interesting material to machine these alloys because they improve substantially the durability of cutting tools and consequently the productivity of machining. However, the surface roughness, cutting forces and chip morphology are equally important factors in machining evaluation. Therefore, an experimental study is performed aiming at comparing the performance of cemented carbide and PCD tools taking into account cutting forces, surface roughness and chip morphology, under dry longitudinal turning, performed for the AlSi9Cu3 alloy produced by permanent mold casting process. Different chip breaker geometries were also considered, and their influence on the referred parameters was also investigated. Analysis of variance was employed to study the different contributions of inserts, cutting speed, feed rate, depth of cut and their interactions in machinability performance. The results show low cutting forces and better results for surface roughness for uncoated cemented carbide tools, with simpler chip breakers and flat rake face PCD tool, but an efficient chip control was obtained for inserts with small grooves with high cutting forces and power consumption. Nevertheless, the feed rate and depth of cut have the highest influence on the machinability performance of the alloy under investigation.

Wall-climbing robot for non-destructive evaluation using impact-echo and metric learning SVM

The impact-echo (IE) acoustic inspection method is a non-destructive evaluation technique, which has been widely applied to detect the defects, structural deterioration level, and thickness of plate-like concrete structures. This paper presents a novel climbing robot, namely Rise-Rover, to perform automated IE signal collection from concrete structures with IE signal analyzing based on machine learning techniques. Rise-Rover is our new generation robot, and it has a novel and enhanced absorption system to support heavy load, and crawler-like suction cups to maintain high mobility performance while crossing small grooves. Moreover, the design enables a seamless transition between ground and wall. This paper applies the fast Fourier transform and wavelet transform for feature detection from collected IE signals. A distance metric learning based support vector machine approach is newly proposed to automatically classify the IE signals. With the visual-inertial odometry of the robot, the detected flaws of inspection area on the concrete plates are visualized in 2D/3D. Field tests on a concrete bridge deck demonstrate the efficiency of the proposed robot system in automatic health condition assessment for concrete structures.

Separation control over a grooved surface inspired by dolphin skin

Over many decades the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow which appear on surfaces such as shark skin, have been well documented. However the skin of dolphins is embedded with sinusoidal grooves that run perpendicular or transverse to the flow over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus acting as a potential mechanism to reduce flow separation and thus pressure drag. In an attempt to test this hypothesis and study these effects, an adverse pressure gradient was induced above a flat plate resulting in a controlled region of flow separation occurring within a tripped, turbulent boundary layer. Small transverse grooves of both rectangular and sinusoidal shape were 3D printed and mounted to the plate to measure their effect on the boundary layer flow. The results were compared to a flat plate without grooves using digital particle image velocimetry (DPIV). The strength of the adverse pressure gradient was varied, and the observed control in flow separation and other effects upon the boundary layer are discussed.

Efficacy of Palatal Applications on Fracture Resistance of Reattached Maxillary Central Incisors: AnIn VitroStudy

The purpose of this study was to evaluate the effects of different palatal applications on fracture strength of the fractured anterior tooth. Sixty caries-free human maxillary incisors were used. Endodontic treatments of the teeth were performed. Then, the teeth were divided randomly into five groups (n = 12). Crowns of all teeth in groups A–D were cut with diamond discs at a fixed distance of 3 mm from the incisal margin in a plane normal to the buccal surface. In all groups, coronal fragments were reattached to the remaining teeth by bonding with hybrid composite resin. After then, the teeth were restored to the following; group A, bonding and palatal laminate; group B, bonding and creation of a vertical groove; group C, bonding and creation of two slot grooves; group D, bonding only; and group E, intact tooth. It was lesser in group B than in groups C and E (p = 0.007 and p = 0.006, resp.) and lesser in group D than in groups A, C, and E (p = 0.002, p < 0.001, and p < 0.001, resp.). Within the limitations of this in vitro study, it can be concluded that methods employing palatinal laminate and small grooves are clinically feasible for the reattachment of tooth fragments to incisors.

EXPERIMENTAL STUDY ON THE COLLABORATIVE DRAG REDUCTION PERFORMANCE OF A SURFACTANT SOLUTION IN GROOVED CHANNELS

Abstract Turbulence with a relatively larger vortex is obtained in drag-reducing surfactant solution, which provides an excellent condition for the application of small scale grooves. In this work, the coupling drag reduction performance of surfactant solution and grooves was experimentally investigated to explore the complementary possibility between their drag reduction mechanisms. The cationic surfactant cetyltrimethyl ammonium chloride (CTAC) mixed with the counterion salt sodium salicylate (NaSal) was experimented in smooth or grooved channel, respectively, at the mass concentrations of 50-150 ppm. It was found that the surfactant solutions gave more effective drag reduction in the grooved channel by the interaction between the restriction effect and peak effect of grooves. Moreover, the critical temperature and critical Reynolds number of the surfactant solution were smaller in the grooved channel, and the friction factor in the grooved channel increased much more rapidly than that in the smooth channel when Re is larger than a critical value.

A new species of the genus Paramesotriton (Caudata: Salamandridae) from Fujian, southeastern China.

New amphibian species have been constantly discovered throughout southern China, including from areas close to heavily populated cities that remain poorly surveyed for amphibian diversity. We describe a new species of the newt genus Paramesotriton from Fujian, a developed province on the southeastern coast of mainland China. The mitochondrial genealogy suggests that the new species is the sister taxon to Paramesotriton hongkongensis, separated by an uncorrected pairwise distances of 5.8% at the ND2 gene fragment analyzed. In addition to the genetic divergence, the new species can be readily differentiated from its congeners by having: a very rough skin; a continuous, orange, vertebral ridge; few warts on each side of the vertebral ridge; numerous small irregular orange-red or yellow spots on the chin, venter, underside of axillae, flanks, lateral side of the tail, base of limbs and cloaca; a small groove at the base of the vomerine tooth series; relatively long tail, relatively flat cloaca in females; normally developed eyes, and the absence of vestigial gills and gill filaments in adults.

Tribological and Corrosion Properties of Nickel/TiC Bilayered Coatings Produced by Electroless Deposition and PACVD

Ni/TiC bilayered coatings are deposited on hot-working steel (H11) by plasma-assisted chemical vapor deposition and electroless technique. The TiC layer is deposited at 490 °C using a gas mixture of TiCl4, CH4, H2, and Ar, and a dense nanostructured TiC coating with minimum excessive carbon phases and low chlorine concentration is produced. The effects of the Ni intermediate layer on the microstructure, tribology, and corrosion behavior of the nanostructured TiC coating are investigated. The friction coefficient of the Ni/TiC bilayered coating (Ni thickness = 4 µm) at 500 cycles is much smaller than that of the coating without the Ni intermediate layer. The smallest friction coefficient is about 0.2, and the hardness values of the Ni/TiC bilayered samples with three different Ni layer thicknesses of 2, 4, and 6 µm are 2534, 3070, and 2008 Hv, respectively. The wear mechanism of the Ni/TiC bilayered coatings is abrasive induced by plastic deformation and fatigue during the sliding process. The smaller groove width on the 4-µm electroless nickel-Ni3P/TiC bilayered coating correlates with the larger H/E ratio and the 4-µm nickel/TiC bilayered sample shows the better wear resistance. The polarization resistance of the 6-µm electroless nickel-Ni3P/TiC coating in 0.05 M NaCl and 0.5 M H2SO4 increases by about 8 and 15 times, respectively. The Ni intermediate layer increases the toughness of the coating and adhesion between the hard coating and steel substrate thereby enhancing the tribological properties and corrosion resistance.

Computational analysis of aeroacoustic noise generated from a rotating tire with a longitudinal groove

It is known that acoustic waves which is higher than 1000 Hz are generated from a rotating tire, and one possibility of their generation mechanism is aeroacoustic effect. The main objective of this study is to understand the generation mechanism and acoustic wave characteristic for realization of low noise tire. For this main objective, the effects of a longitudinal groove shape on acoustic field are investigated in the present study. Three cases, without a groove case (slick tire), a small longitudinal groove and large longitudinal groove are analyzed by large eddy simulations. The result shows that compression or expansion of the vortex is alleviated and weaken sound source by attaching a groove on tire surface. On the other hand, we also confirm that a groove contributes generation of new fluctuation and affects the spread of fluctuations. It can be considered that acoustic fields of front side of tire are affected by a tradeoff between the effect of compression or expansion of the vortex and those of the spread of fluctuation.

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding.

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process.

Effect of Insert Groove Geometry on Chip Breaking Performance

AbstractThe insert groove geometry is an important part of turning tool design. In this article, a systematic design approach is presented for the chip breaker design in turning. The chip breaking ability of various groove geometry of a turning insert is investigated. The ratio of chip thickness to chip curl radius is taken as the index of chip breaking performance. Taguchi method is applied to analyze the contribution to chip breaking performance of each geometric parameter. Response surface methodology is then used to construct a predictive model evaluating the effect of turning conditions and groove geometry on chip breaking performance. The result of this study shows that the feed rate significantly affects chip breaking performance, and that insert with larger land angle, higher back wall and smaller groove is more effective in chip breaking. Among the parameters of the insert groove, the width of the groove has the greatest contribution to chip breaking than the others. The simulation results and predictions are validated by turning experiments.

A new Maldane species and a new Maldaninae genus and species (Maldanidae, Annelida) from coastal waters of China.

Paramaldane, new genus, with type species Paramaldane glandicincta sp. n., and Maldane adunca sp. n. (Maldanidae, Polychaeta) are described based on material from the coast of south China. The new genus Paramaldane is similar to Maldane Grube, 1860 and Sabaco Kinberg, 1867, but it clearly differs from all genera within the subfamily Maldaninae by a unique combination of characters: the cephalic plate is almost circular with low, entire and smooth cephalic rim, nuchal grooves small and crescentic, lacking a collar on chaetiger 1, short companion notochaetae, a collar-like glandular band on the anterior part of the sixth chaetiger, and a well-developed anal valve. Paramaldane glandicincta sp. n. is characterised by having a glandular band on the anterior part of the sixth chaetiger, an almost circular cephalic plate, an entire and smooth cephalic rim, and small crescentic nuchal grooves. Maldane adunca sp. n. is characterised by a low cephalic rim, nuchal grooves with a strongly curved anterior part and isolated from the cephalic rim. Finally, a taxonomic key to genera of Maldaninae and a comparative table to species of Maldane are provided.

Cranial anatomy of Paleogene Micromomyidae and implications for early primate evolution

Paleogene micromomyids are small (∼10–40 g) euarchontan mammals with primate-like molars and postcrania suggestive of committed claw-climbing positional behaviors, similar to those of the extant arboreal treeshrew, Ptilocercus. Based primarily on evidence derived from dental and postcranial morphology, micromomyids have alternately been allied with plesiadapiforms, Dermoptera (colugos), or Primatomorpha (Primates + Dermoptera) within Euarchonta. Partial crania described here of Paleocene Dryomomys szalayi and Eocene Tinimomys graybulliensis from the Clarks Fork Basin of Wyoming are the first known for the family Micromomyidae. The cranium of D. szalayi exhibits a distinct, small groove near the lateral extreme of the promontorium, just medial to the fenestra vestibuli, the size of which suggests that the internal carotid artery was non-functional, as has been inferred for paromomyid and plesiadapid plesiadapiforms, but not for Eocene euprimates, carpolestids, and microsyopids. On the other hand, D. szalayi is similar to fossil euprimates and plesiadapoids in having a bullar morphology consistent with an origin that is at least partially petrosal, unlike that of paromomyids and microsyopids, although this interpretation will always be tentative in fossils that lack exhaustive ontogenetic data. Micromomyids differ from all other known plesiadapiforms in having an inflated cochlear part of the bony labyrinth and a highly pneumatized squamosal and mastoid region with associated septa. Cladistic analyses that include new cranial data, regardless of how bullar composition is coded in plesiadapiforms, fail to support either Primatomorpha or a close relationship between micromomyids and dermopterans, instead suggesting that micromomyids are among the most primitive known primates.

GAP/CL-20-Based Compound Explosive: A New Booster Formulation Used in a Small-Sized Initiation Network

ABSTRACTWith ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and glycidyl azide polymer (GAP) as the solid filler and binder, respectively, GAP/CL-20-based compound explosives were designed and prepared. Using micro injection charge technology, the compound explosives were packed into small grooves to explore their application in a small-sized initiation network. The detonation reliability, detonation velocity, mechanical sensitivity, shock sensitivity, and brisance of the explosive were measured and analyzed. The results show that when the solid content of CL-20 is 82 wt%, the explosive charged in the groove has a smooth surface from a macroscopic view. From a microscopic view, a coarse surface is bonded with many CL-20 particles by GAP binder. The GAP/CL-20-based explosive charge successfully generates detonation waves in a groove larger than 0.6 mm × 0.6 mm. When the charge density in the groove is 1.68 g·cm−3 (90% theoretical maximum density), the detonation velocity reaches 7,290 m·s−1. Moreover, this kind of explosive is characterized by low impact and shock sensitivity.