Abrasive Tip Research Articles

Machining mechanism and residual stress of AlCuCrFeNi alloy

This investigation utilizes molecular dynamics simulations to explore the mechanical response of the AlCuCrFeNi high-entropy alloy to nano-scraping employing an abrasive tip traversing the workpiece surface. This study investigates the influence of various parameters, such as grain size, pressing depth, alloy composition, temperature, and sliding distance, on plastic deformation, frictional behavior, dislocation density, wear mechanisms, and von Mises stress. The results reveal that increasing grain size leads to augmented force and hardness, indicative of a reverse Hall-Petch relationship. Moreover, scraping and indentation forces escalate with decreasing aluminum concentration and temperature. The analysis underscores the pivotal role of grain boundaries in impeding stress and strain propagation. Stress and strain concentrations are particularly evident at the interface between the scraping tool and the substrate and near the grain boundaries. Grain boundary slipping, bending, and grain merging are pivotal mechanisms contributing to the distortion of polycrystalline materials, culminating in solid dislocations within grain boundaries. Furthermore, heightened compression depth and sliding distance exacerbate plastic deformation and subsurface damage. Notably, the presence of copper atoms enhances the HEA's resistance to deformation. This research enhances comprehension of the nano-scraping behavior and deformation mechanisms in AlCuCrFeNi HEA during ultra-precision processing.

Effect of cooling rate on microstructure, mechanical and wear properties of Mg-2Zn and Mg-2Zn-1Mn alloys

ABSTRACT In this study, the wear characteristics of Mg-2Zn and Mg2Zn-1Mn alloys in both dry and corrosive conditions, as well as their mechanical properties dependent on cooling rate, were examined. It has been determined that MgZn, Mg2Zn3 and MgZn2 phases are formed together with the α-Mg main matrix in the microstructure of the alloys. The highest tensile strength (188.6 MPa) was observed in section B of Mg-2Zn alloy. With this, section A of the Mg-2Zn-1Mn alloy showed the lowest wear value (0.00144 mm3/N.m) following dry wear. However, under corrosive wear conditions, the lowest wear rate (0.0008 mm3/N.m) was exhibited at B section in Mg-2Zn-1Mn alloy. In the SEM images of the abrasive tips used in the wear tests, it was determined that the scratches occurred along the wear direction, and as a result of the EDX analysis, alloying elements were transferred from the alloys to the abrasive tip.

Interfacial and Tribological Characteristics of MoS2 on Ni Under Nanoindentation and Nanoscratch

With the rapid development of science and technology, microscale machining has become an important topic, and lubricants play a vital role in machining. Solid lubricants are suitable for a variety of precision machining better than liquid lubricants. Molybdenum disulfide (MoS2) in 2D‐layered nanomaterials is a promising candidate for use as a solid lubricant. Herein, molecular dynamics (MD) simulations are performed to study the effects of scratch depth, speed, and temperature on the mechanical properties of Ni‐based MoS2 thin films. The results show that atom stacking and extrusion around the abrasive tip increase the friction coefficient in the indentation and scratch phases. The higher value of scratch depths, speeds, and temperatures can lead to higher friction coefficients and wider dislocation distributions. Moreover, Shockley dislocation appears in all cases at all effects, and the total dislocation length increases with the higher value of scratch depths, speeds, and temperatures.

Surgical technique for removing vitreous cortex remnants using a diamond-dusted membrane scraper.

The purpose of this paper is to present a new surgical technique to remove vitreous cortex remnants. Non-consecutive retrospective interventional case series. When the posterior vitreous is split, its outermost layer may remain attached to the retina, developing vitreoschisis-induced vitreous cortex remnants (VCR). Their role in macular pathology etiopathogenesis has been well documented; however, recently, it has been proposed that VCR also play a crucial role in proliferative vitreoretinopathy and consequent retinal redetachment. The prevalence of VCR is underestimated because triamcinolone acetonide is not routinely used for vitreous staining. Vitreous cortex remnants (VCR) removal is challenging, and several surgical techniques have been proposed. However, they require sclerotomy enlargement, material that may not be readily available, and manual fashioning. Alternatively, a diamond-dusted membrane scraper (DDMS), already widely used in macular pathology treatment, can follow the contour of the retina, as it is a silicone tube, and remove VCR with its abrasive tip. A DDMS may also be introduced in the vitreous cavity through a standard trocar. Finally, the use of a DDMS provides predictable feedback, making the learning curve short. In this case series, 34 eyes affected by primary rhegmatogenous retinal detachment were enrolled. The retinal redetachment rate was 2.9% at six months of follow-up, below the average literature value of 21%. No adverse events were reported. A DDMS can be suitable for use in VCR removal, although further studies are warranted to understand the indications and extent of this surgical technique for improving the management of rhegmatogenous retinal detachment.

Durable Abrasive Tip Design for Single Crystal Turbine Blades

Abstract In order to create and maintain peak efficiency in turbine stages, it is useful to minimize hot air leakage over blade tips. For unshrouded blades, this means creating minimal clearance over the airfoil tip with rub-tolerate zero-gap materials systems. In this study, a refractory abrasive tip material (ABT) was developed and applied to a plain turbine blade tip to work in conjunction with an abradable coating on the tip-shoe. Process development efforts resulted in abrasive material that could be as much as 2 mm thick. Further, the abrasive media included imbedded grits that would remain in back-up until such time as they were exposed and were pressed into service. Application methods of both furnace brazing and induction brazing were explored as were pre- and post-consolidation net shaping. Evaluation testing included compatibility for the application process onto single-crystal blades. Performance testing included rub-rig testing and long-term oxidation testing. Service testing included commercial engine operation for 14,000 h followed by metallurgical reevaluation. Service performance was mechanically successful, although some material transfer from the tip-shoe was observed which decreased the abrasive nature of the tip. Metallurgically, some intergranular oxidation was observed, but the grits themselves were well retained and were sufficiently refractory to avoid microstructural or oxidation degradation. A production implementation of the coating by an induction heating process is shown.

Mechanism-Independent Manipulation of Single-Wall Carbon Nanotubes with Atomic Force Microscopy Tip.

Atomic force microscopy (AFM) based nanomanipulation can align the orientation and position of individual carbon nanotubes accurately. However, the flexible deformation during the tip manipulation modifies the original shape of these nanotubes, which could affect its electrical properties and reduce the accuracy of AFM nanomanipulation. Thus, we developed a protocol for searching the synergistic parameter combinations to push single-wall carbon nanotubes (SWCNTs) to maintain their original shape after manipulation as far as possible, without requiring the sample physical properties and the tip-manipulation mechanisms. In the protocol, from a vast search space of manipulating parameters, the differential evolution (DE) algorithm was used to identify the optimal combinations of three parameters rapidly with the DE algorithm and the feedback of the length ratio of SWCNTs before and after manipulation. After optimizing the scale factor F and crossover probability Cr, the values F = 0.4 and Cr = 0.6 were used, and the ratio could reach 0.95 within 5–7 iterations. A parameter region with a higher length ratio was also studied to supply arbitrary pushing parameter combinations for individual manipulation demand. The optimal pushing parameter combination reduces the manipulation trajectory and the tip abrasion, thereby significantly improving the efficiency of tip manipulation for nanowire materials. The protocol for searching the best parameter combinations used in this study can also be extended to manipulate other one-dimensional nanomaterials.

Influences of grain size and temperature on tribological characteristics of CuAlNi alloys under nanoindentation and nanoscratch

The mechanical response of CuAlNi nanocrystalline under the nanoscratch through an abrasive tip sliding on the workpiece is investigated using molecular dynamics (MD) simulation. The influences of the grain size, alloy composition, temperature and scratch speed on the plastic deformation characteristic and wear mechanism are surveyed. The results represent that increasing the grain size leads to higher force and hardness, which suggests the reverse Hall-Petch relationship. Meanwhile, the indentation and scratch forces tend to increase when reducing the Cu content and temperature, increasing the scratch speed. The deformation behavior exhibits that grain boundaries play a key role in inhibiting the spread of strain and stress. The results show that the stress and strain are concentrated not only in the contact region between the abrasive tip and substrate but also in the grain boundary and adjacent grain boundary areas. Notably, the sliding, twisting of grain boundary and the fusion of grains are a significant mechanism in the deformation behavior of polycrystalline, resulting in the dislocation is strongly developed in the grain boundary. Furthermore, the movement of atoms in various directions leads to different morphology of pile-up. From quantitative results of the special wear rate show that the ability to lose material volume is larger with Cu86Al11Ni3 alloy and at a temperature of 600 K, as well as the polycrystalline is higher than the single-crystalline. Finally, the residual depth ratios exhibit more strain recovery at the grain size of 6.17 nm and lower temperature.

Two-Body Abrasion Behaviors Characterization of White Cast Iron with Various Chromium Concentrations

As-cast white cast iron specimens with chromium concentrations of 0, 2, and 4 wt% were prepared by melting and casting. Scanning electron microscopy and X-ray diffractometry results indicate that the composite phase consists of a hard phase (cementite) and a toughness matrix (pearlite) with a 28.8 ± 2% cementite volume fraction, which is a typical hypoeutectic structure. The cementite and pearlite microhardness increased with a higher chromium content. The maximum cementite microhardness was 1,054.23 HV. Two-body abrasive wear was measured under a higher impact load using a pin-on-disc tribometer. The effect of chromium content on the wear behavior of the cementite groove depth and width, roughness, chip peel off on the worn surfaces, and mass loss were investigated at an applied pressure of 1.83 MPa. With increasing Cr content, the roughness and mass loss decreased by 10.7 and 15.9%, respectively, and the wear resistance increased visibly. The break in abrasive SiO2 resulted in abrasive tip passivation during wear. As a result, the ratio of the depth–width of the parallel groove and the length–width of the worn chip decreased significantly.

Reconstruction of undersampled atomic force microscope images using block-based compressive sensing

Atomic force microscope (AFM) is a high-precision instrument to research surface topography of various samples. Nevertheless, the standard AFM procedure takes excessively long time to acquire high-resolution images. Moreover, too much interaction between a probe tip and a specimen potentially leads to tip abrasion and sample damage. Compressive sensing (CS) has been employed to realize high-speed AFM (HS-AFM). However, a considerably large-sized image may be hard to be reconstructed through the common CS method with some ordinary algorithms, due to the high computational complexity and hardware costs. Thus, block-based compressive sensing (BCS) is adopted as an alternative means. In our work, three scanning patterns were utilized to generate undersampled AFM images at various sampling rates for five samples with different surface appearance. Each image block was reconstructed through one of six representative algorithms. Finally, an optimal measurement scheme for BCS-HS-AFM was put forward based on the analysis of experimental results, which consisted of sampling rate, scanning pattern, block mode and reconstruction algorithm. BCS was compared with other CS methods in terms of the computational complexity and image reconstruction effect to reveal its superior performance. In brief, BCS can be applied to effectively realize the high-resolution and low-damage HS-AFM imaging.

Tip wear and tip breakage in high-speed atomic force microscopes

Tip abrasion is a critical issue particularly for high-speed atomic force microscopy (AFM). In this paper, a quantitative investigation on the tip abrasion of diamond-like-carbon (DLC) coated tips in a high-speed metrological large range AFM device has been detailed. Wear tests are conducted on four different surfaces made of silicon, niobium, aluminum and steel. During the tests, different scanning speeds up to 1 mm/s and different vertical load forces up to approximately 33.2 nN are applied. Various tip characterization techniques such as scanning electron microscopy (SEM) and AFM tip characterizers have been jointly applied to measure the tip form change precisely. The experimental results show that tip form changes abruptly rather than progressively, particularly when structures with steep sidewalls were measured. This result indicates the increased tip breakage risk in high-speed AFM measurements. To understand the mechanism of tip breakage, tip-sample interaction is modelled, simulated and experimentally verified. The results indicate that the tip-sample interaction force increases dramatically in measurement scenarios of steep surfaces.

Mathematical model of thrust force for rotary ultrasonic drilling of brittle materials based on the ductile-to-brittle transition phenomenon

Modelling the thrust force of rotary ultrasonic drilling (RUD) is an important aspect for optimizing the process parameters and predicting the material cracking and edge chipping. Mainly, the material removal of brittle material occurs mainly through the brittle mode, while the ductile mode occurs in case of micro or nano-depth of cut. This paper introduces a mathematical model for thrust force based on the two material removal modes. The mathematical model correlates the thrust force with the material characteristics and the machining parameters as feed rate, spindle speed, ultrasonic amplitude, frequency and tool abrasive size, tip angle, and concentration. Complete hole drilling and scratch-drilling with depth of 10-μm experiments are conducted in soda glass to verify the model. Thrust force measurement and microstructure features are used to verify the model. The predicted model results agree with the experimental results. The model predicts that the range of feed rate and spindle speed produce the ductile mode cutting.

Abrasion phenomena of the contact tip in consumable electrode arc welding

ABSTRACTIn GMA welding, presently, fluctuation of the tip of welding wire has been able to restrain precisely, and metal transfer also has been able to regulate periodically, that is stable arc-like TIG welding has been realized. Then at this stage, reduction of contact tip abrasion is the most important subject to maintain arc stability for a long time. In this investigation, many factors are evaluated with abrasion amount, and new material of contact tip is recommended. Results obtained are as follows. Using uncoated welding wire increases contact tip abrasion rapidly as to Cu-coated welding wire. On the contrary, other welding conditions concerning contact point have almost no influence. Under the same current, the abrasion of contact tip is reduced accordingly as welding wire feeding rate becomes higher. Therefore, the abrasion is accelerated violently at the time of arc ignition because of heat accumulation at the contact point by wire stopping and high current which is needed for arc ignition. That is the welding wire which is induced to contact point with room temperature has considerable influence to cool the contact point. As a measure to reduce the abrasion at arc ignition, shortening the period of high current is effective. To cool the contact point positively, thermoelectromotive force was applied. Constantan (Cu-455Ni) has low thermoelectromotive force and high melting point than Fe. So, Cu–Ni alloy (Cu-43.3%Ni-0.92%Mn) was selected and examined as the contact tip material. The abrasion of Cu–Ni alloy contact tip becomes less than about two-tenth of the abrasion of Cu–Cr contact tip. As the conclusion, the best mixed measures which are effective to reduce the contact tip abrasion are using Cu-coated welding wire, wire retract type arc ignition and Cu–Ni alloy contact tip.

The wear mechanisms of reaction bonded silicon carbide under abrasive polishing and slurry jet impact conditions

A study of the wear mechanism on a reaction bonded silicon carbide (RB-SiC) subjected to fixed abrasive polishing and loose abrasive waterjet (AWJ) impact conditions is presented. It is found that the wear of the material is characterised by different mechanisms in its silicon and silicon carbide constituents. The surface polished by diamond abrasives appears with brittle fractures on the silicon carbide phase, while the silicon phase is found to be plastically deformed and embedded onto the surface of the fractured silicon carbide. Sub-micrometer surface finish can be obtained by polishing using silicon carbide abrasives, and the process is initiated through the penetration of abrasive tips into the softer silicon matrix. Since the progressive wear flattens the tips of abrasives, the penetration depth of abrasives into the material gradually decreases. When the penetration depth is below a critical value, ductile material removal mode becomes dominant in the removal process. When abrasives that are softer than the silicon carbide grains are sufficiently introduced onto the material surface by a slurry jet, wear can occur even at a pressure below the critical value for phase transformation of the silicon constituent. Wear takes place mainly through weakening the Si bond by erosion and wedging, which eventually releases the SiC grain from the material structure. It is feasible to use a relatively low-pressure alumina slurry jet to machine RB-SiC without causing any surface damage and the processed surface quality depends mainly on the material structure.

Material wear map for ground-engaging steels based on scratch tests

The present work examines the scratch resistances of a series of candidate ground-engaging steels. A range of microstructures is considered: tempered martensite, nano-bainite, pearlite, and austenite. Scratch testing was performed using tungsten carbide and diamond spherical tip sliders with tip radii ranging between 25 µm and 1.3 mm. Wear grooves were analysed and material loss determined. A material property wear map based on hardness and ‘scratch ductility’ is introduced. The map is analogous to those frequently employed in the literature to compare the strength and ductilities of structural alloys. A simple analytical wear model is developed and this is employed to enable comparison between candidate materials for differing scratching conditions. It is seen that the role of hardness dominates over that of ductility for high loads and smaller abrasive tip radii. This leads to a number of striking changes in relative wear rates of the candidate materials examined and these are effectively captured in the proposed map. The groove geometry due to the plastic flow of the material was also found to be the key parameter of the wear model and prediction of the wear mechanism.

Effect of different polishing methods on surface roughness of provisional prosthetic materials

Purpose:To evaluate the surface roughness of bis-acrylic and acrylic resins submitted to different methods of polishing.Materials and Methods:Fifty samples of each provisional restorative material (Structur 2, Protemp 4, Duralay, and Dencrilay) were fabricated (10 mm × 2 mm) and divided into five groups (n = 10): (1) positive control group – polyester strip; (2) negative control – unpolished; (3) abrasive tips (Exa-Technique-Edenta); (4) goat hair brush and diamond polishing paste; and (5) silicone tips (Enhance). Each material was mixed and polymerized according to manufacturer's instructions. The parameter evaluated was the arithmetic mean of the surface roughness (Ra) determined using the rugosimeter SJ 301 (Mitutoyo, Japan). The data were analyzed with two-way analysis of variance (post hoc Tukey's test) (P < 0.05).Results:The lowest surface roughness values (0,22–0,90 μm) were observed in the Group 4 – goat hair brush and diamond paste, while the highest values (1,17–1,44 μm) were found in the Group 5 – silicone tips (enhance), with statistically significant differences between them, except for Dencrilay acrylic resin. There was statistically significant difference between bis-acrylic and acrylic resins in the Groups 1, 2, and 4.Conclusions:Within the limitations of this study, it was concluded that the most effective polishing system was the goat hair brush with diamond paste for both bis-acrylic and acrylic resins. The bis-acrylic resins exhibited significantly smoother surfaces than the acrylic resins.

A small badge of longevity: opposing survival selection on the size of white and black wing markings

According to handicap principle, exaggerated ornamental traits are supposed to exert costs on their bearers. However, there is much less theoretical and practical consensus about whether and under which conditions ornament expression should positively correlate with survival. We measured age‐related variation and survival selection on the size of white wing patches and black wing tips in a long‐lived monogamous seabird, the common gull Larus canus. Males had larger white patches than females but patch size showed concave relationship with age irrespective of sex, suggesting that white patch size was prone to senescence in both sexes. Extent of wing tip abrasion correlated negatively with the size of white patch, suggesting, in agreement with the Zahavian handicap hypothesis that only individuals with largest ornaments are able of maintaining them and not paying cost of displaying them. Areas of white wing patches and black wing tips correlated negatively. Irrespective of sex, survival selection favored birds with larger white wing patches and smaller black wing tips, which suggests that white and black wing markings may have coevolved as reverse components of a single ornament. Altogether, our results provide an evidence for the case where survival selection on ornamental traits in females is not weaker than in males. Absence of sex differences with respect to most of observed patterns is consistent with a prediction that among monogamous long‐lived species with biparental care, mutual mate choice leads to evolution of elaborate ornamental traits in both sexes.

Detailed description of the Ócsa Bird Ringing Station, Hungary

Abstract The present paper acts as an introduction to a series that will describe the exploratory analyses of migration phenology and morphometrics of the most common passerine species at the Ócsa Bird Ringing Station. This station is situated in the Ócsa Landscape Protection Area that belongs to the Duna–Ipoly National Park, Hungary. The area is somewhat cooler and more humid than the surrounding agricultural fields and tree plantations, covered by a mosaic of diverse hygrophilous vegetation patches. Bird trapping is mostly based on Japanese mist-net lines crossing different plant communities. During the period of 1984–2015, a total of 422,862 birds were trapped and ringed here, while 202,739 local, 1,235 within country, and 443 foreign recaptures were also recorded. Each bird is characterized by the following data: location and time of capture, species, age, sex, scores of fat, pectoral muscle, wing tip abrasion, and moult, length of wing, 3rd primary, and tail, and body mass. After subjected to a rigorous quality check, digital data are deposited in the archive of the Hungarian Bird Ringing Centre, and the EURING data base. From time to time, other research projects also utilized the accessibility of wild birds captured here, thus collection of blood samples, ecto- and endoparasites was carried out at the station. The relatively long time span, large number of species and individuals, and the readily available environmental (weather, vegetation, etc.) data makes the avian data collected here a suitable base for studies of various disciplines like capture methodology, habitat preferences, breeding, migration, and wintering, effects of weather and climate change, and epidemiology of viruses and parasites.

Effects of different polishing systems on the surface roughness of two ceromers

Objective: This in vitro study evaluated the effects of three polishing systems on the surface roughness of two ceromers. Material and Methods: 96 specimens (8 mm in diameter and 2 mm thick) were prepared in a metal mold using two restorative materials: CERAMAGE (Shofu, Japan) and VMLC VITA (VITA Zahnfabrik, Germany). The specimens were divided into 4 groups (n=12): G1: positive control, Mylar strip; G2: abrasive tips, Edenta system; G3: silicon tips, Enhance system; and G4: abrasive tips, Shofu system. The parameter evaluated was the average surface roughness (Ra) determined by using a profilometer SJ 301 (Mitutoyo, Japan), followed by photographic evaluation images through Scanning Electron Microscopy (SEM), with a 1000x magnification range. The data was subjected to statistical analysis for comparison between the groups (ANOVA, Tukey and Student T-tests), with a significance level of 5%. Results: there was a statistically significant difference between the silicone tip Enhance and the other groups for both ceromers with higher values of surface roughness. There was no statistically significant difference between the ceromers, except for the Shofu system, which showed lower values of surface roughness for Vita VMLC. Conclusion: Within the limitations of this study, it was concluded that the Edenta and Shofu abrasive tips are more effective in reducing the surface roughness of ceromers compared with the Enhance silicone tip.Keywords: Resins; Surface roughness; Dental polishing.

Time-dependent degradation of Pt/ZnO nanoneedle rectifying contact based piezoelectric nanogenerator

A piezoelectric nanogenerator based on the platinum rectifying contact on ZnO nanoneedle arrays (NNA) has been successfully fabricated on silicon substrate by using the thermal evaporation deposition technique. It is demonstrated that the rectifying platinum contact on ZnO NNA can efficiently convert nanoscale mechanical energy into electrical energy by exploiting the piezoelectric and semiconducting properties of ZnO. The effect of key parameters such as scanning speed, force on scanning tip, and tip abrasion on the nanogenerator has been studied along with long-time stability of the piezoelectric nanogenerator. The study reveals that the nanogenerator output degrades with time primarily due to degradation of the rectifying contact with time and abrasion of the tip caused by repeated scanning. The results of the study are expected to provide quantitative ideas about the long-time stability of ZnO NN based nanogenerators.

Advances in the Development of Carbidic ADI

Carbidic ADI (CADI) is a new type of Austempered Ductile Iron containing free carbides in the microstructure, providing a particular combination of wear resistance and impact toughness. In this work, four CADI variants were evaluated, in which carbides were promoted by alloying with chromium. Tests performed under the low stress abrasion condition imposed by the ASTM G65 standard show that CADI can increase the wear resistance up to 100 % when compared with conventional ADI austempered at the same temperature. The carbide content must be higher than 10 % to promote a considerable reinforcing effect. However, at this carbide content level, the impact toughness varies between 7 and 11 J/cm2 for unnotched samples. These values are much lower than those of conventional ADI, but higher than those of other abrasion resistant materials, like white irons. Some CADI variants were also evaluated in field tests, producing abrasion under either low stress or high stress conditions. For this purpose, two CADI prototype parts were studied: screw segments for animal food extruders (low stress abrasion) and wheel loader bucket edges (high stress abrasion). The results gathered showed that CADI behaves satisfactorily under low stress abrasion, but the performance is not so good under high stress conditions. To analyze the differences in the abrasion response, scratch tests were performed in order to evaluate the interaction between the abrasive tip and the microstructure.