Abrasive Action Research Articles

The implications of COVID-19 legislation on chronic ailments patients: perspectives from Botswana

Purpose COVID-19 is one of the greatest public health challenges in the 21st century. The World Health Organisation recommended physical distancing to halt the upward trajectory of the infections. Countries including Botswana imposed lockdown for non-essential workers. This paper aims to argue that lockdown as imposed by the Government of Botswana was a necessary measure given the nature of transmission of COVID-19. Design/methodology/approach The paper uses exploratory research to unpack impacts of the novel COVID-19 regulations or be responsive to new concerns by breaking new ground through delving into new problem areas. The paper used a use case to explain a single outcome for a single case. Findings The restriction on the freedom of movement is necessary to protect citizens, particularly, those with chronic illness from contracting the deadly virus. The paper further observes that while the legislative intent of the GOB was to protect those with chronic illnesses from COVID-19, the lockdown resulted in near death experiences for some chronic ailment patients. These experiences result from unfettered discretion of functionaries who were policing and manning the streets and those who are conferred with authority to issue travel permits to seek and obtain medical assistance, lack of public transport and the processes of applications for the permits, which exposed citizens to COVID-19. Research limitations/implications The study was desk based. It may have yielded different results. Lockdowns limited mobility for non-essential services. The full impact of the restrictions and the attendant defaulting was yet to be fully realised. Observing the COVID-19 protocols and bureaucratic requirements for obtaining information from the government offices were major challenges. Practical implications Achieving total lockdown as an end in itself may amount to a pyrrhic victory – the authorities may successfully achieve total lockdown but with heavy costs on gains made in combating ailments. Botswana has fought many other pandemics and chronic illnesses still subsist and need to be catered for. For patients, there is not only the complexity of dealing with one chronic condition but also the work of trying to live “normal” lives in the face of co-morbidity, which can be overwhelming. The COVID-19 pandemic adds to the “work” that patients must do to manage and live with such health conditions and the psychological distress. Social implications Authorities need to be fully aware of the consequences of their actions. Abrasive actions may lead to a higher constituency of discontent. Botswana has had a good track record of being democratic, and this needs to be strengthened. Originality/value The implementation of the COVID-19 regulations particularly the requirement for a travel permit to seek health-care services may hinder access to essential health services and ultimately increase the pressure on emergency services or, at worst, increase mortality. Clear guidelines and sober interpretation of the regulations are necessary. This will also make it easier for the frontline security officers manning the streets to correctly understand the prevailing circumstances. In view of the massive gains garnered in combating chronic illnesses, it is important that such gains are not reversed, while the GOB fights COVID-19. People living with HIV/AIDS, the elderly and people with pre-existing health conditions are known to be at significantly higher risk of developing severe illness when contracting COVID-19. Achieving total lockdown as an end in itself may amount to a pyrrhic victory – the authorities may successfully achieve total lockdown but with heavy costs on gains made in combating other chronic ailments.

Investigation and analysis of EDM process – a new approach with Al2O3 nano powder mixed in sunflower oil

This study analyses the EDM process of AISI D2 steel with copper tungsten electrode along with Al2O3 powder mixed in sunflower oil as a dielectric fluid in place of EDM oil. AISI D2 steel is predominantly used in the manufacture of precision components of dies, press tools, automobiles, aircraft and space equipment. For that reason, it has been selected as work piece material. Based on the high conductivity nature of electrical and thermal characteristics of copper tungsten, it is used as an electrode in the process. Due to the easy availability and affordability, Al2O3 particles of 60 nano meter size is taken as catalyst for mixing with the sunflower oil and used as an alternate dielectric fluid in place of EDM oil. In order to reduce the harmful effects on the environment produced by the gases due to EDM oil, a vegetable oil namely, sunflower oil is used in its place. Flash point, fire point is higher than 300°C in sunflower oil when compared to conventional EDM oil. It is also eco-friendly and biodegradable. Input parameters of pulse interval, pulse duration, discharge voltage and peak current are compared with various output parameters of the process, namely, electrode wear rate, surface roughness and material removal rate. Experiments are conducted using Taguchi L9 experimental design and the effect of process input values over the output process response are analyzed using ANOVA method. The analysis leads to the conclusion that powder mixed EDM process (PMEDM), in which Al2O3nano particles mixed with sunflower oil yields a minimum surface roughness due to the better heat absorption. More removal of material along with a lesser tool wear is also noticed. Nano particles of Al2O3 improved the surface finish due to the abrasive action of the lowest discharge gap between particles.

Glicina e as suas aplicações na medicina dentária: uma revisão narrativa

Introduction: There are several minimally invasive treatments and sensitive clinical protocols which lead to the need to find an innovative alternative with different substances. Glycine, a non-essential amino acid with a simple structure and an important constituent in the extracellular structure of proteins such as collagen and elastin, has been used and tested in diverse dental medicine applications in the form of abrasive powder particles. Despite the mechanisms of action not being yet fully understood, it is believed to have anti-inflammatory therapeutic effects as well as helping in regulating the immune functions and synthesis of cytokines. Glycine is odorless, colorless and highly soluble in water. Objectives: To present the different glycine powder applications in dental medicine. Results: Different studies have been made to compare the glycine action with the use of various manual, rotary and polishing instruments, and with clinical protocols such as acid etching and pretreatment of the dentin structure. Glycine powder presents a reduced abrasive action, producing less damage to the teeth and gum surfaces. Its efficacy was observed in the removal of supra and subgingival biofilm, with reduced injury of the gingival structure when compared to the use of the sodium bicarbonate jet, root scraping and scaling. It achieved an excellent polishing and teeth surface smoothness, thus reducing the adhesion and maturation of the bacterial microflora. Conclusions: Glycine is nowadays regarded as an innovative substance in the world of dentistry and has been applied in the periodontics, polishing of dental surfaces, restorative material and in the pre-treatment protocol of dentin. Despite the good results obtained, further investigation is needed to validate these features and advantages.

On the Use of Microscale Abrasion Test for Determining the Particle Abrasivity

Abstract Particle abrasivity is an important concept for helping to select materials for pumps and for disc cutters in underground excavation, and specific ASTM standards are available for making these selections. However, for manufacturing processes in which abrasive action is their core, the particle size range is approximately a few micrometers. The evaluation of particle abrasivity using the microscale abrasion test matches this range of particles for this purpose, but relatively few investigations using this kind of method have been conducted. The aim of this investigation is to use the microscale abrasion test to evaluate the particle abrasivity, avoiding changes on the ball surface and on the particle size distribution. Samples of quenched AISI D2 tool steel were used for tests. The wear mode was dependent on the testing time. Alumina (Al2O3) particles presented a lower abrasiveness when compared to boron carbide (B4C) ones, confirmed by the higher wear coefficient found in the latter after reaching the steady-state regime. This behavior was evidenced by the number of active particles in the contact, which showed that there were a larger number of B4C particles than Al2O3 during the contact at all sliding distances. The particle abrasivity is discussed in terms of significant characteristics of slurries: particle shape, particle size distribution, hardness-to-elastic modulus ratio, zeta potential, and density. As the controlling of those characteristics seems to be very important, particle abrasivity is a concept that needs to be improved besides the test system used for that purpose.

Simulation of intermittent grinding for Ti-6Al-4V with segmented wheel

Abstract Titanium alloy-Ti-6Al-4V, in spite of all its superior mechanical characteristics and functional acceptance, is categorized as a difficult-to-cut super alloy. Major concerns associated with conventional surface grinding of Ti-6Al-4V is its poor thermal conductivity, grinding burn, high tendency of hardening during machining as well as chemical affinity with wheel materials. Higher magnitudes of grinding force and temperature reported during conventional grinding may lead to adverse burning effects and associated concerns such as micro-cracking etc. on the ground surface. Present paper is a simulation study to showcase the capability of intermittent-segmented grinding to eliminate such concerns. A comparison of intermittent segmented cutting with conventional abrasive action in continuous mode is presented through a 3D finite element model in ABAQUS. The effectiveness of intermittent-segmented cutting to control grinding temperature well below the critical limit to avoid burning effects on Ti-6Al-6 V, with a significant reduction in grinding force is illustrated through the present simulation study.

Estimation of Ice Thickness and the Features of Subglacial Media Detected by Ground Penetrating Radar at the Baishui River Glacier No. 1 in Mt. Yulong, China

Using ground-penetrating radar (GPR), we measured and estimated the ice thickness of the Baishui River Glacier No. 1 of Yulong Snow Mountain. According to the position of the reflected media from the GPR image, combined with the radar waveform amplitude and polarity change information, the ice thickness and the changing medium position at the bottom of this temperate glacier were identified. Water paths were found in the measured ice, including ice caves and crevasses. A debris-rich ice layer was found at the bottom of the glacier, which produces strong abrasion and ploughing action at the bedrock surface. This results in the formation of different detrital layers stagnated at the ice-bedrock interface and numerous crevasses on the bedrock surface. Based on the obtained ice thickness and differential GPS data, combined with Landsat images, the kriging interpolation method was used to obtain grid data. The average ice thickness was 52.48 m and between 4740 and 4890 m above sea level, with a maximum depth of 92.83 m. The bedrock topography map of this area was drawn using digital elevation model from the Shuttle Radar Topography Mission. The central part of the glacier was characterized by small ice basins with distributed ice steps and ice ridges at the upper and lower parts.

The wear resistance increasing of low-carbon deposited metal with different manganese content due to the receipt of metastable austenite in the structure

ABSTRACT It has been established that heating of a low-carbon deposited metal containing ~5, ~8 % Mn and additionally ~3% Cr having a martensitic structure to an intercritical temperature interval (ITI) provides a secondary metastable austenite, which undergoes a dynamic deformation martensitic transformation (self-hardening effect under loading). This significantly increases the wear resistance at dry sliding friction and impact abrasive action of the shot stream. The deposited metal with a higher manganese content (~14%) yield to the wear resistance under conditions of dry sliding friction of a metal containing 5% and 8% of manganese, but has a higher wear resistance than it when subjected to impact-abrasive action of the shot stream.

Study the effect of concentration ratio (magnetic abrasive powder and castor oil) in magnetic abrasive finishing process

The new technology can however be incorporated in conventional machine tools in order to minimize cost of new equipment. In present work, the effect of magnetic abrasive powder and castor oil mixture in magnetic abrasive finishing process is investigated. The lower concentration of lubricating oil results in higher heat accumulation which further decreased the cutting efficiency due to blunting action of abrasives. On the other hand, the larger quantity of lubricating oil prevents blunting which resulted in higher cutting efficiency.

Growth of ZnO nanorods on cotton fabrics via microwave hydrothermal method: effect of size and shape of nanorods on superhydrophobic and UV-blocking properties

In this present research, a novel microwave hydrothermal method was applied to cotton fabrics to develop a superhydrophobic surface by rapid synthesis of aligned ZnO nanorods on the surface of the cotton fabric. A two-step approach was used to grow the ZnO nanorods. Firstly, the cotton fabric was coated by a seed layer of ZnO nanocrystals, synthesized using the microwave-assisted sol gel method. Secondly, the ZnO nanorods were grown rapidly on the seeded cotton fabrics using the microwave hydrothermal method. Moreover, a layer of non-fluorinated silane was applied on the as-grown nanorods to fabricate a superhydrophobic surface. Non-fluorinated silane was selected as it is less harmful to the skin than fluorinated silanes. The effect of the zinc nitrate hexahydrate (Zn(NO3)2·6H2O) concentration, reaction time and microwave power on the growth of ZnO nanorods was investigated in detail using scanning electron microscopy. The surface topography and roughness of the nanorods grown on the fabrics were studied using atomic force microscopy. EDS analysis and X-ray diffraction techniques were used to study the structural properties of the ZnO nanorods. The ultraviolet protection properties were investigated by a UV–Vis-NIR spectrophotometer. The ZnO nanorods grown on the cotton fabrics exhibited excellent UV blocking properties. A maximum UPF value of 114 was observed for the ZnO nanorods grown on the cotton fabric with 100 mM of zinc nitrate hexahydrate (Zn(NO3)2·6H2O). The superhydrophobic properties were examined based on contact angle and roll-off angle measurements, where a maximum water contact angle of 170.2° and a minimum roll-off angle of 1° were found for 25 mM of zinc nitrate hexahydrate. The ZnO-OTMS coated fabrics were evaluated for superhydrophobic durability against mechanical abrasion, laundering, chemical and UV action. Moreover, the ZnO-OTMS coated fabrics showed excellent potential for separation of floating and underwater oil layers or an oil–water mixture.

An Investigation on Surfactant Added PMWEDM of Inconel 718

This paper shows the impact of different process parameters and powder characteristics on the material removal rate and surface roughness obtained in surfactant added Powder Mixed Wire Electric Discharge Machining (PMWEDM). Inconel-718 is selected as the workpiece material, which has ample application in the industries handling environment of extreme stress, pressure and temperature. It has high work hardening properties along with high rupture strength, fatigue, and creep, making it extremely difficult to machine. So, additives having different thermo-physical properties are studied to improve the machining efficiency. The additives experimented includes aluminium, silicon carbide, graphite, and aluminium oxide. It is found that the electrostatic force present creates an agglomeration effect with dielectric additive powders, causing inhomogeneity in the mixture. So, a surfactant SPAN20 is used here to maintain the homogeneity of the mixture. The obtained MRR and SR are then modelled and optimised through Particle Swarm Optimization technique (PSO). It is observed that the addition of SPAN20 has improved the MRR by 13.56% and, SR by 45.05%. Also, it has been found that due to the combined abrasive action, abrasive powders increase MRR significantly than others. Furthermore, it is found that low grit size powders with lower density produces better machined surfaces.

Effects of Heat Treatment Condition and Counter Materials on the Wear Behavior of Laser Direct Energy Deposited Fe-8Cr-3V-2Mo-2W Alloy

This study aimed to investigate the wear performance of laser direct energy deposited Fe-8Cr3V-2Mo-2W alloy under various wear environments, in terms of different heat treatment conditions. Ball on disk tribology tests were performed using high-carbon steel and zirconia balls as counter materials. The wear rates of the alloy depended significantly on both the wear sliding speed and the wear load. Microstructural observations of the worn surface and the wear debris indicated intensive tribo-oxidative wear that was presumably responsible for the strong dependency of the wear rate on the wear sliding speed. Regardless of the type of counter materials, the alloy in the as-built state had better wear performance than the alloy with heat treatments. Therefore, the use of the alloy without post heat treatment would be favorable to obtain long-term durability of the alloy in severe wear environments. The wear tests with two different counter materials of high-carbon steel and zirconia showed the high-carbon steel counter material had a higher wear rate than the zirconia. This was thought to be due to that strong third-body abrasive actions of the high-carbon steel counter material, evidenced by the severe abrasive wear of the counter material.

Tribological behavior of NiAl-based intermetallic compounds in artificial seawater

The solid-lubricating material is a promising candidate for the tribo-pairs exposed in a seawater environment. In this paper, the tribological properties of NiAl-based intermetallic compounds in the seawater were investigated. The results revealed that NiAl–Cr(Mo)–Ag alloy exhibits the lowest friction coefficient (~0.1) and wear rate (~10−7 mm3/Nm) compared to NiAl and NiAl–Cr(Mo) alloys, which is attributed to the solid-lubricating action of Ag. NiAl–Cr(Mo) alloy displays the highest friction coefficient, resulting from the severe abrasive action of the tribo-pair. The wear features of NiAl and NiAl–Cr(Mo) alloys are delamination and plowing effect, respectively. However, the worn surface of NiAl–Cr(Mo)–Ag alloy is almost smooth. Abrasive wear is dominated by the wear mechanisms of NiAl-based intermetallic compounds, while corrosion wear is mild.

Experimental Investigation on Wear Behavior of Additively Manufactured Components of IN718 by DMLS Process

Direct metal laser sintering (DMLS) is a promising technology having applications in diverse areas like aerospace, automotive and energy. This technique is capable of fabricating complex components from hard to machine materials like Inconel and titanium alloys with relative ease. Inconel 718 is a widely preferred material for high-end applications involving challenging environments such as elevated temperatures and pressures, wherein the wear behavior of the material is of utmost significance. So this study aimed to investigate the wear behavior of DMLS IN718 specimens and compare it with that of conventionally cast specimens manufactured by vacuum induction melting (VIM) process. The testing of the specimens was done using a pin-on-disk wear tester against two different disks; IN718 is made by VIM casting process and wrought En-31 under varying normal load and sliding velocity. Also, the DMLS IN718 specimens were built in two orientations, i.e., horizontal and angular. It was observed that the wear rate increased with an increase in load and sliding velocity. The coefficient of friction showed a decreasing trend while sliding against IN718 but exhibited a random behavior with En-31. The wear behavior of the DMLS and conventionally cast-made IN718 specimens was found to be in a similar range, and the built orientation in DMLS did not significantly impact the wear behavior. The subsequent scanning electron microscope images of the wear tracks revealed that the mechanism of wear was a combination of adhesive wear and delamination wear resulting from abrasive action.

Abrasion Behavior of Steel-Fiber-Reinforced Concrete in Hydraulic Structures

This study investigated two types of abrasion resistance of steel–fiber-reinforced concrete in hydraulic structures, friction abrasion and impact abrasion using the ASTM C1138 underwater test and the water-borne sand test, respectively. Three water-to-cementitious-material ratios (0.50, 0.36, and 0.28), two impact angles (45° and 90°), plain concrete, and steel–fiber-reinforced concrete were employed. Test results showed that the abrasive action and principal resistance varied between the two test methods. The average impact abrasion rates (IARs) of concrete were approximately 8–17 times greater than the average friction abrasion rate (FARs). In general, the impact abrasion loss of the concrete surface impacted at a vertical angle was higher than that of impacted at a 45 degree angle. Moreover, the average FAR and IAR decreased when the concrete was reinforced with steel fibers. The steel fibers acted as shields to prevent the concrete material behind the fibers from abrasion, thus improving abrasion resistance. In both the underwater and waterborne sand flow methods, the resistance to abrasion of concrete without steel fibers increased as the water/cementitious material ratio (w/cm) decreased, and the concrete compressive strength also increased.

Study on the Wear and Abrasion Effect of Metal Nano-Coating Plug Connectors Under Atmospheric Corrosion Conditions

The plug connector is the most widely used type of separable connector; however, the sliding friction that occurs during the plug-in process causes wear and wiping effects. Wear is a form of damage that occurs to the anti-corrosion coating during the sliding process, and wiping refers to the cleaning effect of corrosion products during the sliding process. Both have negative and positive effects on electrical contact reliability in corrosive environments. Therefore, wear and wiping are key factors in studying the life and reliability of connectors in atmospheric corrosion environments. Atmospheric corrosion is the main mechanism leading to connector contact failure. There have been many related studies on simple connector atmospheric corrosion, but research on the influence of wear and wipe on atmospheric corrosion and the influence of contact resistance degradation is still not comprehensive. To study the influence of wear and wiping on contact reliability during the plug connector-mating process, this work evaluates the metal nano-coating connector plugging process as the object, and the contact resistance degradation model under atmospheric corrosion as the basis, and the effect of wear and wiping on corrosion degradation as the research tool. Ultimately, the influence of wear and wiping on contact resistance is studied in detail. Finally, combined with the actual usage of the plug-in connector, the contact reliability of metal nano-coating plug connectors under the action of abrasion and wiping is studied.

Mechanistic force modeling in drilling of SiCp/Al matrix composites considering a comprehensive abrasive particle model

SiCp/Al composite is one of the key light metal matrix composites widely used in aerospace and electronics industries due to its excellent material properties. Understanding the mechanism of abrasive particle action and the cutting force generation is crucial for achieving desired hole quality and machining accuracy. However, there is no research on cutting force modeling in drilling of SiCp/Al composites. This paper proposes an energy-based mechanistic modeling method to predict the cutting force in drilling of SiCp/Al composites for the first time. A new comprehensive abrasive particle model considering different particle action mechanisms, such as cracking, debonding, and squeezing, is presented to depict the energy consumed by abrasive particle action. Experiments with a wide range of particle volume fractions and feed rates, and different particle sizes were carried out to validate the accuracy of the proposed model. Results show that the proposed model can accurately predict the cutting force with an average error of 6.55% in drilling of SiCp/Al composites. Furthermore, the energy consumed on abrasive particle action is estimated to be 8.2–13.6% of total cutting energy. The proposed model on SiCp/Al composites can be extended to other particle reinforced metal matrix composites.

MECHANO-PHYSICO-CHEMICAL MODELING OF THE PROCESS OF DESTRUCTION OF THE PART SURFACE IN A FREE ABRASIVE MEDIUM

The analysis of the phenomena in the zone of collision of the working medium granules with the parts surface is presented. It is noted that the abrasive granules of are embedded in the processed part surface by the grains protruding from the bundle. It is indicated that the contact of the abrasive granule with the part surface carried out within small size areas, determined by the strength of the collision, the number and state of the active grains, their level of fixation, dimensions and physical and mechanical properties of the part material. The behavior of a single granule moving relative to the processed part is considered. The main types of abrasive grain action on the processed surface are highlighted, that is, cutting, plastic deformation and friction, it is noted that over time, abrasive grain can initially perform only friction, then plastic deformation, then cutting. It is established that such an alternation of the abrasive grains work is associated with the nature of the movement of the granules on the surface of the processed part. High-speed video recording of single processing traces showed that granules leave on contact surfaces the processing traces that are difficult to outline, differ in depth and location on the surface. It was determined that the track depth changes in the direction of granule movement and is calculated by the speed of its movement, as well as by the strength and frequency of penetration into the material of the part during contact. Electron microscopic studies show the presence of adhesive spots and oxide films at the contact sites. This confirms that in the process under consideration, as well as during grinding, polishing, and finishing, continuous exposure of juvenile surfaces occurs. It was established that the interaction of active juvenile surfaces and plastically deformed volumes of metal with aggressive components of the working medium leads to the formation of secondary weakened structures on their surface, the layer thickness of which is 0.05 ... 0.08 μm. The parameters of the processing mode that determine the nature of the physical and mechanical processes of interaction of the single granule and the processed part are established. The differences of the vibrating abrasive treatment method from the known finishing methods are considered. The mechanism of destruction of the part material is shown and the stages of mechanical and physicochemical modeling of the process of vibrating abrasive treatment are presented.

Advanced Materials for Future Lunar Extravehicular Activity Space Suit

AbstractThis review focuses on advanced materials already used and suitable for application in (future) lunar extravehicular activity space suits. A historical and current literature/market survey is presented. Different functional layers of an astronaut garment are defined with emphasis on the external layers subjected to abrasive action of lunar regolith and degradation via exposure to space radiation/vacuum environment. Requirements are defined that would need to be fulfilled by these layers and suitable materials candidates are reviewed based on their key properties, including mechanical durability. Smart materials, combining additional functionalities, such as garment health monitoring, are also considered. The lead topic is the subject of an ongoing ESA‐funded research activity.

A Complex Evaluation of the State of the Surface Layer of Austenitic Stainless Steel after Abrasive Impact

The effect of various methods of abrasive impact (filing with standard and impregnated abrasive tools) on the surface layer of 12X18H10T austenitic stainless steel has been investigated, which included the analysis of the interrelation of the measured properties obtained by the methods of direct indentation, Kelvin probe, micro-X-ray spectral analysis, and raster microscopy. The results of the study have demonstrated an interrelation between the obtained values of the electron work function of the studied surfaces and the measured modulus of elasticity and corrosion resistance of the samples after abrasive action. There has been observed significant changes in the properties of the thin surface layer observed after the filing with an impregnated abrasive tool.

A Study of New Washing Process Which Combines Deflection and Abrasion Action

This study aimed to determine the optimum washing of laboratory washing model that design to stimulate the active washing process and passive commercial washing machine are compared in order to determine the best washing result. Variables of the study include water speed, washing time and radial nozzle inclination angle. The rotational system of an automatic washing machine has two major technical difficulties. One is the collision of the tub against the frame at the beginning of its early spinning stage. A factor that causes such instability of the rotational object can be attributed to the deflection of the liquid inside the liquid balancer due to the unbalance mass. Proposed a new washing technology and new design of the washing machine can be as a base of its new type. These machines have better outcome data; improve quality of washing process and effective use of washing liquid. New washing machine is simple design, does not have rotary parts at all and uses active process of washing process with squeezing of linens and more productive then known washing machines. Also, this machine can recycle and feed cleaned washing liquid. Additionally, in use of ultrasonic technology of washing process, new machine today will be perfect design.