Hole Surface Research Articles

Fleas and lesions in armadillo osteoderms.

Armadillos are bitten by several species of flea. Females of the genus Tunga penetrate the epidermis and when in place are fertilised by males, after which the abdomen swells enormously to form a 'neosome'. Within the penetrans group, T. perforans, makes lesions that perforate the osteoderms within the integument to form ~3 mm diameter cavities occupied by a discoid neosome. We examined these lesions in carapace material from animals which had died in the wild to see whether we could recruit evidence as to how they may be generated, either by the insect or by the host. We studied one species without such lesions, the nine-banded armadillo Dasypus novemcinctus, and two species with, the greater hairy armadillo Chaetophractus villosus and the southern three-banded armadillo Tolypeutes matacus, both showing the characteristic 'flea bite' holes in the external surfaces of the osteoderms. Samples were studied by three-dimensional backscattered electron mode scanning electron microscopy and X-ray microtomography. Both methods showed resorption pit complexes in the external surfaces of the osteoderms characteristic of those made by osteoclasts in active bone resorption. Lesions involved both the syndesmoses (sutures) between adjacent bones and the central regions of the osteoderms. Many lesions showed extensive repair by infilling with new bone. We conclude that the T. perforans neosome creates a local host response which causes bone resorption, creating the space in which it can grow.

Visual Spatial Attention and Proprioceptive Data-Driven Reinforcement Learning for Robust Peg-in-Hole Task Under Variable Conditions

Anchor-bolt insertion is a peg-in-hole task performed in the construction field for holes in concrete. Efforts have been made to automate this task, but the variable lighting and hole surface conditions, as well as the requirements for short setup and task execution time make the automation challenging. In this study, we introduce a vision and proprioceptive data-driven robot control model for this task that is robust to challenging lighting and hole surface conditions. This model consists of a spatial attention point network (SAP) and a deep reinforcement learning (DRL) policy that are trained jointly end-to-end to control the robot. The model is trained in an offline manner, with a sample-efficient framework designed to reduce training time and minimize the reality gap when transferring the model to the physical world. Through evaluations with an industrial robot performing the task in 12 unknown holes, starting from 16 different initial positions, and under three different lighting conditions (two with misleading shadows), we demonstrate that SAP can generate relevant attention points of the image even in challenging lighting conditions. We also show that the proposed model enables task execution with higher success rate and shorter task completion time than various baselines. Due to the proposed model's high effectiveness even in severe lighting, initial positions, and hole conditions, and the offline training framework's high sample-efficiency and short training time, this approach can be easily applied to construction.

Sustainable cooling/lubrication induced thermo-mechanical effects on ultrasonic vibration helical milling of CFRP/Ti–6Al–4V stacks

Sustainable cooling/lubrication strategies including dry, minimum quantity lubrication (MQL), cryogenic (LN2) and hybrid (MQL and LN2) were used in ultrasonic vibration helical milling (UVHM) machining to improve the performance of hole-making for CFRP/Ti–6Al–4V stacks. The machining temperatures and forces were measured to characterize the thermo-mechanical effects on UVHM with different cooling/lubrication conditions. The machining temperatures at cryogenic conditions were −146 °C, −170 °C and −53 °C at CFRP layer, interface and Ti–6Al–4V layer, respectively. Axial and radial resultant forces at different conditions were highly related to the cutting temperature. Fiber removal mechanism at different conditions was analyzed according to the cutting temperatures, forces and the kinematic analysis in UVHM. Effects of sustainable cooling strategies and ultrasonic vibration on the hole surface texture of Ti–6Al–4V alloy were discussed. The amplitudes at different conditions varied approximately from 3.5 to 7 μm due to the variation of the forces. High precision of the exit geometry was achieved, as the height of hole exit burrs at Ti–6Al–4V layer were less than 40 μm except for the cryogenic condition. Diameters at the MQL and hybrid conditions were closer to the target diameter (ϕ10 mm), and the precision of the cylindricity of the machined holes of the stacks with the MQL and hybrid cooling conditions was higher than those at other conditions. Tool wear at different conditions were analyzed according to the SEM and EDS results. This work provided the fundamental understand of the hybrid process with sustainable cooling/lubrication strategy in UVHM machining. High quality of holes in CFRP/Ti–6Al–4V stacks were achieved by the hybrid processes.

Chloride Adsorbates Enhance the Photocarrier Separation and Promote the Bio-Syngas Evolution.

Photocarrier separation and migration to the surface are vital for photocatalysis. However, the mobility of the surface holes and electrons makes them easily recombine before participating in the surface reaction, which constrains the photocatalytic efficiency. Targeting this problem, herein, it is reported that chloride adsorbates enhance the photocarrier separation and promote the bio-syngas evolution. Chloride, adsorbed on the surface of CdS(CdS-Cl), can increase the internal electric field and enhance the charge separation and migration to the surface. Moreover, compared with pristine CdS where holes are mobile and distributed on all the surface atoms, CdSCl can reduce the hole mobility via delocalization on specific sites and thus prolong the photocarrier lifetime. This contributes to an 11-fold enhanced photocatalytic syngas evolution from glycerol. This study reports the pivotal effect of surface adsorbates on photocarrier separation and offers a convenient strategy to prohibit surface holes and electrons recombination for solar energy utilization.Chloride absorbates on CdS contribute to enhanced photocatalytic syngas evolution from glycerol by increasing the internal electric field.

Assessment of surface integrity and hole quality in graphene-based NMQL Micro-drilling of ceramic-coated Nimonic 90 for gas turbine applications

Nickel-based superalloys have superior strength properties at higher temperature ranges and thus have become increasingly important in manufacturing gas turbine components for aerospace industry. However, the desire for a larger thrust-weight ratio has raised the typical operating temperature in a gas turbine; thus, thermal barrier coatings are essential. The present work compares the micro-drilling performance of ceramic-coated Nimonic 90 nickel superalloy under dry, flood and 0.5% graphene-based NMQL conditions. The biodegradable acid oil was used as a base oil, and the assessment comprised surface integrity in terms of surface roughness inside the hole and micro-crack formation and hole quality based on the diametrical overcut and taper ratio. Spindle speed (1000, 2000 and 3000 rpm) and feed rate (3, 6, and 9 μm/rev) were changed in three levels, and Taguchi L9 array was applied for the design and analysis of the experiments. Ti-Al-N coated tungsten carbide drill of diameter 700 μm was used, and Analysis of variance (ANOVA) revealed that spindle speed was the utmost important parameter impacting surface roughness, while speed and feed rate both influenced overcut and taper ratio. 0.5% Graphene-based NMQL lubrication condition significantly diminished the surface roughness by 52.67%, overcut by 46.86% and the taper ratio by 48.87% as compared to dry condition. Furthermore, in the NMQL condition, micro-crack development and ceramic layer damage were minimized, resulting in better surface integrity. In addition, burr development was minimized at the hole periphery, and tool wandering was not seen in the NMQL condition. Hence the hole quality was superior in NMQL conditions as compared to the dry and flood lubrication.

Material removal and surface damage mechanisms in micro drilling of Nd:YAG material

Neodymium-doped Yttrium Aluminum garnet (Nd:YAG) materials enable the vital applications in both industrial and military fields. In this study, the nanoscratch and micro drilling tests were conducted to investigate the material removal and surface damage mechanisms of Nd:YAG. The brittle-ductile transformation and intermittent edge breaking mechanisms were elaborated in the nanoscratch tests. After the scratch load exceeded 37 mN, the material removal mechanism transforms from elastic-plastic deformation to brittle fracture. Subsequently, the various material removal and surface damage mechanisms were observed on the hole surface and hole wall in micro drilling, which was consistent with the scratch test results. On the hole surface, the discontinuous edge-breaking defects with a petal shape are the primary surface damages, which encircle the hole surface to form a sunflower shape. However, the hole wall quality primarily depends on the proportion of flaky exfoliation and the brittle fracture zones on the hole wall, and the hole wall roughness increased with the drilling speed and feed rate. This study aims to understand the material removal mechanisms and optimise the machining parameters in micro drilling of hard and brittle materials.

Correlating Surface and Downhole Perforation Entry Hole Measurements Leads to Development of Improved Perforating Systems

Summary Studies have shown that achieving a consistent perforation hole size in casing (i.e., entry hole) and zero-phase perforation gun orientation led to improved treatment distribution among multiple perforation clusters in plug-and-perf limited entry treatments. In addition to reducing variation in the perforation entry hole by establishing uniformity in gun clearance and the angle of incidence of the perforation jet at the wall of the casing, oriented perforating has been shown to minimize the tendency of proppant to separate from the fracturing fluid while traveling across the perforated intervals (inertial effect) and mitigate nonuniform entry hole erosion due to gravity-induced proppant stratification. The primary goal of this study was to determine the controllable perforating gun elements and accessories that effect the accuracy of gun orientation and entry hole dimensions. Surface tests were conducted at manufacturing facilities for determining the characteristics of the entry holes in pipe produced by shaped explosive charges using various system configurations and the robustness of various gun orientation devices. Promising perforating systems were then used in wellbores to create calibration entry holes (downhole tests) that were measured for equivalent diameter and orientation accuracy using high-resolution acoustic imaging before conducting treatments. This process enabled components of the perforating system influencing entry hole size and gun orientation to be evaluated and modified, as necessary. Elements of the perforating system and downhole environment that influenced entry hole size and consistency included casing type, cement sheath characteristics, perforating gun clearance and orientation, perforating charge type and density, packing arrangement of multiple charges, charge tube and charge carrier design, gun detonation system, hydrostatic pressure, and locking devices. Achieving tight control of these elements significantly reduced variation in entry hole size. Deviations from surface and downhole testing results were commonly attributed to using perforating system elements in the field that differed from those used by the manufacturer in surface testing. Factors affecting gun orientation accuracy and consistency included weight bar type, gun string length, weight, and stiffness, the presence of modified standoff bands, progressive gun deformation during firing, wellbore tortuosity, and self-orienting devices. Several orientation systems were found that achieved orientation within the target 20°-window. To assess the value of this workflow process, the paper includes information on the results of diagnostic tests for evaluating the accuracy of the ultrasonic measuring device, the derivation process used for determining coefficients for a two-component perforation erosion model, and the use of the derived erosion rate coefficients for computing the mass of proppant that enters each perforation and perforation cluster during a fracturing treatment.

Experimental and Numerical Studies on Interaction Mechanism between Joints and a Hole in Rock-like Materials under Uniaxial Compression

To investigate the influence of joints on the stability of underground opening, uniaxial compression tests and FE analyses based on a microplane damage model for rocks has been conducted for rock-like models with a circular hole and a set of non-persistent joints. It was found that the peak strength and Young’s modulus decrease with the increase in joint continuity factor k, and variation of them with joint inclination angle β are W or V-shaped curves with the minima and maxima at β = 30° and 90°, respectively. The failure modes of the specimens and the collapse modes of the hole can be related to crack coalescence between the hole and the joints or matrix. Numerical simulation can reproduce the main features of macroscopic mechanical behavior and explain the anisotropic damage mechanism. The strong interaction between the hole and the nearest joint was revealed. During the elastic stage, stress concentration around the hole will be altered by the presence of the joints, and the effect may be strengthened with the increase in k. At the peak strength, the current stress concentration areas will be transferred from the hole surface to the interior due to stress loosening in damage localization bands/zones, and a higher hoop stress concentration factor may lead to lower strength.

Impact of polyethylene glenoid cementation technique on cement mantle integrity and stability after cyclic loading: a computed tomography and biomechanical study.

There are no generally accepted guidelines for polyethylene (PE) glenoid component cementation techniques. In particular, it is not known whether the backside of a PE glenoid should be fully or partially cemented-or not cemented at all. We hypothesized that cementing techniques would have an impact on cement mantle volume and integrity, as well as biomechanical stability, measured as micromotion under cyclic loading. To address our hypothesis, 3 different cementation techniques using a single 2-peg PE glenoid design with polyurethane foam were compared regarding (1) the quality and quantity of the cement mantle and (2) biomechanical stability after cyclic loading invitro. Eight identically cemented glenoids per group were used. Group A underwent cement application only into the peg holes, group B received additional complete cement mantle application on the backside of the glenoid, and group C received the same treatment as group B but with additional standardized drill holes in the surface of the glenoid bone for extra cement interdigitation. All glenoids underwent cyclic edge loading by 105 cycles according to ASTM F2028-14. Before and after loading, cement mantle evaluation was performed by XtremeCT and biomechanical strength and loosening were evaluated by measuring the relative motion of the implants. The cement mantle at the back of the implant was incomplete in group A as compared with groups B and C, in which the complete PE backside was covered with a homogeneous cement mantle. The cement mantle was thickest in group C, followed by group B (P=.006) and group A (P<.001). We did not detect any breakage of the cement mantle in any of the 3 groups after testing. Primary stability during cyclic loading was similar in all groups after the "running-in" phase (up to 4000 cycles). Gross loosening did not occur in any implant. Coverage of the PE glenoid with cement was reproducible in the fully cemented groups (ie, groups B and C) as compared with relevant cement defects in group A. The addition of cement to the back of the PE glenoid and additional drill holes in the glenoid surface did not improve primary stability in the tested setting.

Investigation of Flux Transfer along Ferrite Core of Probe Coil for Eddy Current Nondestructive Evaluation

Abstract A probe coil with a T-core above a layered conductor with surface hole is investigated for magnetic flux transfer along the ferrite core and enhancement of eddy currents in conductor. The cylindrical coordinate system is adopted and an artificial boundary is added to the solution domain with radius b, and the general formula for calculating the impedance of the T-core coil is derived using the truncated region eigenfunction expansion (TREE) method. For four special cases with different probe configurations, coil impedance changes due to the layered conductor and defect are calculated with Mathematica software over a frequency change ranging from 100 Hz to 20 kHz. The analytical results are in good agreement with those obtained by the finite element method and experimental measurements. The results show that under the same lift-off height and excitation frequency, the impedance change caused by the conductor or defect in the coil of long core column is greater than that of the short core column coil. It indicates that the probe coil with a long core column can transfer magnetic flux to the conductor, thereby enhancing eddy currents in the conductor.

Surface passivation decoration of amorphous cobalt silicate on molybdenum-doped bismuth vanadate for efficient photoelectrochemical water oxidation

Such a subtly strategy greatly promoted the surface holes consumption rate and made composite photoanode dramatically achieve in 2.82 mA /cm2 at 1.23 VRHE (4.7 - fold higher than BiVO4) with a negative onset potential offset of 207 mV. The amorphous Co - species decoration tremendously enhanced surface charge injection efficiency to almost 90 % at 1.23 VRHE. And the biggest photovoltage and lowest charge recombination kinetics of composite photoanode also presented that the amorphous Co species had the potential ability to be passivation layer which were characterized by OCP and IMPS test.

Study on the modification effect and mechanism of tailings powder on coal gangue-based mining cementitious filling material.

Based on the problems of high carbon emission and high cost of traditional mining methods and filling materials, the tailings powder modified Coal Gangue-based Cementitious Backfill Material (CGCBM) was used for paste filling mining. In this study, the samples were prepared with different tailings powder content and different curing ages. The compressive strength test, XRD, SEM test, and NMR test were used to explore the changes of macroscopic strength and microstructure of the material. The results show that adding 50% tailings powder has the most obvious optimization effect on the performance of CGCBM. Tailings powder particles fill the surface holes of the fine aggregate of coal gangue in the early cement hydration process, reduce the water absorption of the aggregate. In addition, the active substances such as Ca2SiO4 play the pozzolanic effect, stimulate the secondary hydration of slurry, make the microstructure closely, and thus improve the macroscopic mechanical strength.

Drilling Response of Carbon Fabric/Solid Lubricant Filler/Epoxy Hybrid Composites: An Experimental Investigation

Carbon-fiber-reinforced epoxy composite (CEC) has gained widespread acceptance as a structural material in various applications. Drilled holes are essential for assembling composite material components. Reducing drilling-induced damage and temperature effects is crucial for improved surface quality and integrity of the drilled composite. In the present work, drilling experiments were conducted on CEC, hexagonal-boron nitride (h-BN) dispersed CEC, and molybdenum disulfide (MoS2) dispersed CEC at three different levels of spindle speed, feed, and drill diameter using solid carbide twist drills. The filler concentrations used in this study were 4, 6, and 8 wt%. Analysis of variance (ANOVA) was used to determine the significance of input factors (feed, spindle speed, drill diameter, and filler concentration) on the drilling responses such as thrust force, temperature, arithmetic mean surface roughness (Ra), and push-out delamination factor (DFexit). The average drilling temperature, Ra, and DFexit of MoS2 dispersed CEC were reduced by 24.7, 46.5, and 11.3%, respectively, when compared to neat CEC. In h-BN dispersed CEC, the average drilling temperature, Ra, and DFexit were reduced by 25.2, 40.9, and 13.2%, respectively, compared to neat CEC. The lubricating properties and high thermal conductivity of filler added to epoxy are responsible for the lower temperature and improved hole surface finish. The improved delamination resistance in filler-loaded CEC is due to the strengthening of the matrix and fiber–matrix interface. Scanning electron microscopy (SEM) was used to examine the morphology of the drilled composite surface. The spindle speed of 5500 rpm, feed of 0.03 mm.rev−1, and filler loading of 4 wt% produced the minimum Ra and DFexit. The response surface method (RSM) was applied to determine the input parameters based on multi-response optimum criteria.

Plant-Insect Interactions on Aquatic and Terrestrial Angiosperms from the Latest Albian (Early Cretaceous) of Estercuel (Northeastern Spain) and Their Paleoenvironmental Implications.

Fossils of plant-insect interactions are direct evidence of paleoecological relationships between these two dominant groups in terrestrial ecosystems. We present a variety of plant-insect interactions from the late Early Cretaceous (latest Albian) in the Estercuel locality in northeastern Spain (Iberian Peninsula), affecting two types of terrestrial angiosperms and the basal eudicot Klitzschophyllites, which is one of the oldest putative members of aquatic Ranunculales found to date. The study of these interactions revealed 23 different damage types belonging to eight functional feeding groups (hole feeding, margin feeding, skeletonization, surface feeding, piercing and sucking, mining, oviposition and galling), suggesting these angiosperms were an important source of food and lodging for insects in the Iberian ecosystems during the late Early Cretaceous. Notably, the diversity of damage in the leaves of angiosperms suggests a diverse community of herbivorous insects and a variety of strategies of interactions with plants at the end of the Early Cretaceous in the southwestern Tethys realm.

Kinetic Difference in Water Photooxidation between TiO2 and WO3 Electrodes by Rate Law Analysis

The photocarrier interfacial kinetics is often considered to be a bottleneck for water photooxidation on semiconductors and has attracted extensive attention in recent years. Although tremendous efforts have been devoted into the kinetic study for a certain semiconductor, there are few works focused on the dynamic differences in water oxidation between various kinds of semiconductors. In this study, the kinetics of water oxidation on WO3 and TiO2 electrodes was investigated by a combination of photoelectrochemical techniques and then compared using the electrodes’ rate law. It was found that the water oxidation on WO3 is faster than the that of TiO2 electrodes under the same surface hole density and the basic origin for this kinetic difference is attributed to greater charger transfer rate constant (kct). The greater kct is due to the fact that the WO3 electrodes have a smaller Helmholtz layer capacitance (CH), a larger space charge layer capacitance (CSC), and a greater charge transfer rate constant at flatband potential (kct0). These finding provide a better understanding of the photocarrier transfer dynamics and may enlighten rational design on exploiting the metal oxide semiconductors to achieve a higher solar conversion efficiency.

Helical Milling of CFRP/Ti6Al4V Stacks Using Nano Fluid Based Minimum Quantity Lubrication (NF-MQL): Investigations on Process Performance and Hole Integrity.

The structural components in the aeronautical industry require CFRP/Ti6Al4V stacks to be processed together, which results in poor hole integrity due to the thermal properties of the materials and challenges related to processability. These challenges include quality variation of the machined holes because of the limitations in process properties. Therefore, a novel solution through helical milling is investigated in the study using nano fluid based minimum quantity lubrication (NF-MQL). The analysis of variance shows, for Ti6Al4V, eccentricity (PCR = 28.56%), spindle speed (Ti) (PCR = 42.84%), and tangential feed (PCR = 8.61%), and for CFRP, tangential feed (PCR = 40.16%), spindle speed (PCR = 28.75%), and eccentricity (PCR = 8.41%) are the most significant parameters for diametric error. Further on, the rise in the circularity error is observed because of prolonged tool engagement at a higher value of tangential feed. Moreover, the surface roughness of Ti was reduced with an increasing percentage of MoS2 in the lubricant. The spindle speed (37.37%) and lubricant (45.76%) have a potential influence on the processing temperature, as evident in the analysis of variance. Similarly, spindle speed Ti (61.16%), tangential feed (23.37%), and lubrication (11.32%) controlled flank wear, which is critical to tool life. Moreover, the concentration of MoS2 decreased edge wear from ~105 µm (0.5% concentration) to ~70 µm (1% concentration). Thorough analyses on process performance in terms of hole accuracy, surface roughness, processing temperature, and tool wear are carried out based on the physical science of the process for cleaner production. The NF-MQL has significantly improved process performance and hole integrity.

Wire electrochemical finishing of wire electrical discharge machined surface of highly alloyed materials with insoluble precipitates

Wire electrochemical machining (WECM) using bipolar pulse current with scanning wire electrode can be effectively applied to mirror-finish the wire electrical discharge machined surfaces of stainless steel. However, highly alloyed materials with insoluble precipitates such as cold tool steel and nickel-based superalloy are hard to finish, due to their non-uniform phase. This study aimed to finish these highly alloyed materials, by optimizing the duty factor. The machined depth, surface roughness, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) observation, bending strength, and edge roundness of WECMed surface of these materials were investigated. As a result, the duty ratio of 30% for cold tool steel and 40% for Inconel 718 were most effective to smoothen the surface uniformly. Furthermore, the shape accuracy of WECMed surfaces of small holes and thicker workpieces was also reviewed. The inner surface of small holes made in stainless steel with 0.5 mm in diameter was finished to surface roughness of Ra 0.088 µm, which is almost the same roughness as obtained with plane surfaces. Even a workpiece of 120 mm thickness was finished successfully with a straightness smaller than 2 µm.

Noisy Surfaces: Vulnerability and Art in Human–Ocean Relations

At the shoreline, human and ocean activities often act in unproductive tension with one another. This article draws from encounters between the modernist architecture in the port city of Toamasina in Madagascar and the activities of the Indian Ocean at that location to sense how human–ocean binary lines might become more porous. The first part of the article sketches a material-discursive theory of the weathered hole in modernist architectural surfaces. It explores the hole as a vital collective of queer otherings to the specific land-centred individualistic subject-hood of modernist Man, a specific figuration of a human who draws binary lines to separate itself out from the “natural world”. The second part of the article argues that artistic inquiry is well positioned to sense into the activities of the hole. It looks to how the hole at the surface of modernist Man can co-shape the specific human–ocean relationship that forms at this shoreline. Such inquiry is explored through my solo exhibition titled Static Drift, held at the Wits Art Museum in Johannesburg in 2021. Sensing, the exhibition reveals, has the potential for listening to binary lines as they erect a surface that both pushes away yet also receives what has been pushed. In Static Drift, being vulnerable through human perceptions was highlighted as a critical mode for sensory attunement to the relationships that form at such surfaces. This article argues that the sonic is a useful sensory mode for opening perceptions toward what is not yet perceived in surface–hole relationships. The sonic opens sites for ontological thinking into human–ocean relations by sensing into the re-orienting potentials that noise offers for thinking about disrupting binaried surfaces.

Progressive damage induced degradation of mechanical properties in the hole surfaces during drilling processes of CFRP

This paper presents a novel 3D numerical model of drilling CFRP to evaluate the degradation of mechanical properties in the hole surfaces. It can be used to determine the change of functional performance induced by accumulated damage. This function is realized through introducing damage evolution laws of the plies as well as the interfaces into the model. The damage level within plies leads to the degradation of stiffness of the hole surfaces. The simulation results are validated against cutting forces, torques and delamination, then the degradation of stiffness matrix is evaluated through prediction. This model is the first to merge different progressive damage evolution laws in drilling CFRP, which is beneficial for understanding the damage mechanisms in hole surfaces, and can be used to optimize CFRP drilling processes by reducing damage, delamination, and subsequent degradation of the workpiece stiffness.

High-performance p-type transparent conducting CuI–Cu2O thin films with enhanced hole mobility, surface, and stability

We employed reactive magnetron sputtering and iodination process at room temperature to deposit CuI–Cu2O films with enhanced hole mobility, surface, and stability.