Abrasive Dust Research Articles

Lubricating property of MQL grinding of Al2O3/SiC mixed nanofluid with different particle sizes and microtopography analysis by cross-correlation

With the increased requirements for environmental protection, energy conservation, and low consumption, nanofluid minimal quantity lubrication (MQL) grinding, which is an environment-friendly machining method, has been paid increasing attention. Improving the lubricating property of nanofluids effectively is currently a main research trend. Meanwhile, optimizing mixed nanoparticle (NP) size ratio is an effective way for enhancing the lubricating property of MQL grinding. In the experiment, different sizes (30, 50, and 70nm) of Al2O3 and SiC NPs were mixed, and nanofluids were prepared at 2% (volume fraction) mixed NPs and base oil. The prepared nanofluids were then used in MQL grinding on a hard Ni-based alloy (inconel 718). The experiment was then evaluated by specific grinding force, removal rate of workpiece, surface roughness, morphology of grinding debris, and contact angle. The effect of the sizes of the Al2O3/SiC mixed NPs on MQL grinding performance was discussed in accordance with the period and amplitude, as well as cross-correlation coefficient, of the workpiece surface cross-correlation function curve profile. Experimental results suggest that different Al2O3/SiC mixed NP sizes affect the nanofluid MQL grinding performance variably. The highest removal rate of the workpiece [189.05mm3/(sN)] and the lowest RSm (0.0381mm) were achieved when the Al2O3/SiC mixed NP size ratio was 70:30. The lowest Ra (0.298μm) was obtained at 50:30. Meanwhile, the highest length ratio of the profile support (90%), the best morphology of abrasive dusts, and the largest wetting area of liquid drops were acquired at 30:70. Furthermore, a cross-correlation analysis of the workpiece surface profile curve under three size ratios (30:70, 50:30, and 70:30) was carried out. The cross-correlation function curve of the workpiece surface profile under 30:70 attained the shortest period, the largest amplitude, and the largest cross-correlation coefficient (0.67), thereby indicating good workpiece surface quality. Therefore, 30:70 was the best size ratio of the Al2O3/SiC mixed nanofluid.

ELECTROLYTIC-PLASMA TREATMENT OF INNER SURFACE OF TUBULAR PRODUCTS

While manufacturing a number of important tubular products stringent requirements have been imposed on quality of their inner surfaces. The well-known methods for inner surface treatment of pipes include sandblasting, chemical cleaning with acid reagents (oxalic, formic, sulfamic, orthophosphoric acids) and electrochemical polishing. Disadvantages of the chemical method are cleaning-up irregularities, high metal removal, limited number of reagent application, complicated selection of reagent chemical composition and concentration, complicated and environmentally harmful recycling of waste chemicals, high cost of reagents. Low productivity at a high cost, as well as hazardous impact on personnel due to high dispersion of abrasive dust are considered as disadvantages of sandblasting. Electrochemical polishing is characterized by the following disadvantages: low processing productivity because supply of high currents is rather difficult due to electrolyte scattering capacity away from the main electrode action zone, limited length of the cavity to be treated due to heating of flexible current leads at operating current densities, application of expensive aggressive electrolytes and high costs of their recycling. A new method for polishing and cleaning of inner surfaces of tubular products based on electrolyte-plasma treatment has been developed. In comparison with the existing methods the proposed methods ensures quality processing with high intensity while applying non-toxic, environmentally friendly and cheap electrolytes. The paper presents results of investigations on technological specific features of electrolyte-plasma treatment for inner surfaces of tubular products: influence of slotted nozzle width, electrolyte flow and rate on stability of gas-vapor blanket, current density and productivity. Results of the research have made it possible to determine modes that provide stability and high productivity in the process of electrolyte-plasma treatment of inner surfaces of tubular products.

Nonlinear Model of Vibrating Screen to Determine Permissible Spring Deterioration for Proper Separation

Springs of vibrating screens are prone to fatigue induced failure because they operate in a heavy duty environment, with abrasive dust and under heavy cyclic loads. If a spring breaks, the stiffness at supporting positions changes, and therefore the amplitude of motion and the static and dynamic angular inclination of deck motion also change. This change in the amplitude and in the inclination of motion produces a reduction in separation efficiency. Available models are useful to determine motion under nominal operating conditions when angular displacement is not significant. However in practice there is significant angular motion during startup, during shutdown, or under off-design operating conditions. In this article, a two-dimensional three-degree-of-freedom nonlinear model that considers significant angular motion and damping is developed. The proposed model allows the prediction of vibrating screen behavior when there is a reduction in spring stiffness. Making use of this model for an actual vibrating screen in operation in industry has permitted determining a limit for spring’s failure before separation efficiency is affected. This information is of practical value for operation and maintenance staff helping to determine whether or not it is necessary to change springs, and hence optimizing stoppage time.

Dust Emissions During the Sowing of Maize Dressed Seeds and Drift Reducing Devices

Mortality and sub-lethal effects on honey bees have been related to the sowing of maize seeds dressed with neonicotinoid insecticides. Pneumatic precision drills, used for commercial seed sowing, play a role in the dispersion of the abrasion dust because abrasion dust is emitted with the airstream generated by the drill's fan. The paper provides the results of the assessment of dust drift both from a conventional and a modified drill with a novel filtering-recycling system developed at CRA-ING. We employed maize seed treated with thiamethoxam, imidacloprid, clothianidin and fipronil. The tests assessed the residues produced both at soil level and in the air, during static sowing simulation tests carried out at fixed point. The results show that the use of the prototype allows a remarkable reduction of dust drift of about 86%, at ground level, and of 85% in the air, with respect to the conventional drill.

A device for pneumatic precision drills reducing the drift of the abrasion dust from dressed seed

The effect of drift of dust containing insecticide active ingredients (a.i.) derived from dressed seed and observed mortality or sub-lethal effects on honey bees (Apis mellifera L.) has been recently investigated. Pneumatic precision drills used in maize sowing were considered among the main causes of the phenomenon. To reduce dust spread, the drills have subsequently been equipped with air deflectors that redirect the vacuum fan air outlet towards the ground, resulting in an unsatisfactory 50% reduction of a.i. concentration, with continuing sub-lethal effects on honey bees. We developed an effective prototype device for pneumatic drills, which uses partial recirculation and filtration of the air. Static tests (simulating sowing of maize seed treated with imidacloprid) were carried out to evaluate the prototype's efficiency and to provide information on the main characteristics of dust particles. Gravimetric and chemical analyses of samples showed, respectively, reductions of 98% of the total dust and of 97%. of the a.i which resulted from the application of the prototype. Particles with diameter >5 μm were nearly completely eliminated. For particles with diameters <4 μm, a lower reduction was observed, the effect of which, anyway, was counterbalanced by the lower overall mass of fine particles.

Dressed to kill: 50 years of the spacewalk

The ISS has the equipment necessary to support controlled decompression. Future human missions to the moon or Mars, using smaller spacecraft, may have to dispense with it. Suits and ships alike will have to operate at the same pressure. The problem of ballooning will be overcome by a suit design that, at first glance, seems a retrograde development. NASA's latest prototype, known as the Z-suit, looks like an armoured robot from 1950s science fiction. Recent publicity photos show an astronaut wearing a white Z-suit uncannily like Buzz Lightyear's, but the outer fabric is a superficial layer of micrometeorite protection. Inside, there's a shell of hard composites tough enough to withstand contact with jagged rocks and abrasive surface dust on the moon and Mars. Whenever an astronaut on a planetary mission climbs out of a suit, there will be a danger of inhaling potentially toxic dust particles from outside the lander or habitat. The simple solution is to never expose astronauts to the suit's mucky exterior. Actually, this is easier than it sounds. The rear of the Z-suit features an airlock. When not in use, the entire thing is stored on the outside of a rover, docked to a 'suit portal'. Essentially a Z-suit is like a miniature spacecraft in its own right. Astronauts can swap at will between the suit and the airlock areas of a habitat or rover without waiting for the pressures to equalise. Ballooning is eliminated by pushing the rigidity of the suit to the logical extreme, until its fabric has no flexibility at all, except in the gloves and at the limb joints.

The assessment of dust drift from pneumatic drills using static tests and in-field validation

The utilization of dressed seed for sowing is a widespread practice to control certain pests with reduced doses of chemical products. The pneumatic drills used in maize (Zea mays L.) sowing have been shown to contribute to the dispersion of the abrasion dust produced by dressed seeds, causing environmental contamination. In recent years, several insecticides (neonicotinoids and fipronil) employed for maize dressing have been claimed to cause mortality and sub-lethal effects to honey bees (Apis mellifera L.). This paper reports a two-stage research study aimed at evaluating the amounts of dust emitted by a precision pneumatic drill during the sowing of maize dressed with clothianidin, fipronil, imidacloprid and thiamethoxam. In the first step, we assessed the dust drift in static tests performed in a simulated wind tunnel. Next, we compared the results with real sowing trials carried out in the field. The data were subjected to appropriate processing that provided a theoretical assessment of the spatial distribution of the pesticide concentration. The results demonstrated a good correspondence between the amounts of predicted drift at ground level during the static tests and the measured residues during the field trials. At the same time, no prediction was possible in terms of air concentrations of the active ingredient, suggesting that the dust drift in the air behaves differently from its deposition on the ground.

Van der Waals forces influencing adhesion of cells

Adhesion molecules, often thought to be acting by a 'lock and key' mechanism, have been thought to control the adhesion of cells. While there is no doubt that a coating of adhesion molecules such as fibronectin on a surface affects cell adhesion, this paper aims to show that such surface contamination is only one factor in the equation. Starting from the baseline idea that van der Waals force is a ubiquitous attraction between all molecules, and thereby must contribute to cell adhesion, it is clear that effects from geometry, elasticity and surface molecules must all add on to the basic cell attractive force. These effects of geometry, elasticity and surface molecules are analysed. The adhesion force measured between macroscopic polymer spheres was found to be strongest when the surfaces were absolutely smooth and clean, with no projecting protruberances. Values of the measured surface energy were then about 35 mJ m(-2), as expected for van der Waals attractions between the non-polar molecules. Surface projections such as abrasion roughness or dust reduced the molecular adhesion substantially. Water cut the measured surface energy to 3.4 mJ m(-2). Surface active molecules lowered the adhesion still further to less than 0.3 mJ m(-2). These observations do not support the lock and key concept.

Research on the Friction and Wear Properties of the Copper Matrix Composites Reinforced with Copperized Carbon Fibers

The aim of this paper is to develop a kind of copper matrix self-lubricious material with excellent friction and wear characteristics. The copper-graphite composites reinforced with short copper-coated carbon fibers (CF-C/Cu) were successfully developed using techniques of mechanical alloying, composite plating and hot press vacuum sintering. For comparison, copper-graphite composites without short copper-coated carbon fibers (C/Cu) were made under the same process. The wear testing was carried out using a rapid wear testing machine (M-200).Friction coefficient was measured by a micro-wear tester (UMT).The microstructure, abrasive dust and worn surface of the wear pins on the different condition such as load and wear time were examined by SEM. It was noted that the addition of copper-coated carbon fiber in the Cu-based composites can retard the transformation process which transforms from micro-cutting wear to adhesive wear and delamination. The abrasion loss of the composites with short copper-coated carbon fibers appeared a valley when the load increased from 10N to 30N. It showed that the addition of copper-coated carbon fiber enhanced the anti-friction and anti-wear property of copper matrix composite and better than the sample without carbon fibers.

Data from Apollo missions show how lunar dust degrades instruments

Apollo astronauts encountered very fine, powdery, abrasive lunar dust, which stuck to scientific instruments and caused damage and sometimes overheating and failure. To measure the effects of lunar dust, each of the first four Apollo expeditions left a set of solar cells on the Moon, and data were transmitted to Earth from 1969 to 1976.

A Comparison of Polymer Film and Glass Collectors for Concentrating Solar Power

This paper describes work to compare the optical properties and surface texture of glass and polymer film collectors. We also present the results of experiments designed to simulate collector cleaning processes (both contact and non-contact), and the degradation of glass and polymer reflecting surfaces owing to sand and dust abrasion. Finally we present initial results on the applicability of anti-soiling and self-cleaning coatings on glass and polymer film collector surfaces. Measurements, which include specular and hemispherical reflectance, surface roughness, and electron microscopy, indicate the excellent performance of currently available polymer film in terms of its optical performance and robustness in comparison with traditional glass collectors in CSP applications.

Research on the Performance Influence of Second Adhesive to Friction Materials

The friction materials have many species and they are being used widely, but people have higher requests to friction materials along with the development of technology. the friction material of this expermental optimization formula have the advantages of suitable and stable friction coefficient under high temperature, low wear rate, good restoration characteristics and so on. It can effcetively reduce heat fade of friction and wear under high temperature barking. fricton and wear performance of friction material with second adhesive is better than common preparation friction material , it has higher friction coefficient and lower wear rate, It was determined by physical chemical properities of tin and sulfer. while heating or wearing, the temperature of friction material reach melting temperature of tin, it will become molten state, and sulfer has strong oxidation, on the one hand, tin and sulfer occurred chemical reaction, generating sulfide, stannous (one sulfide tin),on the other hand, while the sulfer is being molten state, it will absorb some abrasive dust, at the same time of generating sulfide, abrasive dust will be adsorb and solidify to pits of friction surface, forming abrasive dust membrane, let the friction coefficient of sample become stable rapidly, reducing the wear rate of friction material.

Engineering solutions applied to pneumatic drills to reduce losses of dust from dressed seeds

Neonicotinoid insecticides (imidacloprid, clothianidin, thiamethoxam) and fipronil for maize (Zea mays L.) seed dressing have been claimed to play a role in honey bee (Apis mellifera L.) decline, since pneumatic precision drills used for sowing contribute to the dispersion of the abrasion dust produced by dressed seeds. The active ingredients (a.i.) can contaminate the environment and can lead to the exposure of operators and bystanders during sowing operations. To achieve a significant reduction of dust drift and to enhance the safety for the operators, CRA-ING studied and developed novel engineering solutions applicable to drills, based on an air-recycling/filtering system. In the first system, the air’s excess is forced outward through suitable filters placed on the modified lid of the seed hopper. It can be easily applied to commercial drills in use. The second system was specifically designed for new drills. It consists of a collector duct that receives the air expelled from the vacuum fan opening, creating constant pressure conditions. Part of the air is recycled into the seed hoppers, as the air in excess is directed outward through a single main filter. A third system, based on the second one, entails the use of an electrostatic filter to improve its efficiency. Moreover, to avoid the operator’s exposure to the dust during the seed loading, we show an integrated solution based on the use of a modified pre-charged plastic container that replace the drill’s hoppers. Preliminary tests ascertained the regular seed distribution with the drills equipped with the prototypes. Then, trials were carried out at fixed point and in field, for detecting the amounts of the drifted a.i., using commercial maize seed dressed with thiamethoxam, imidacloprid, clothianidin and fipronil. The test results show powder and a.i. drift reductions up to a maximum of 94.5% measured at ground level (with fipronil as a.i.) as a consequence of the use of the prototypes.

An Theoretical Study of the EDM Electrolytic Intermittent Grinding Compound Processing

Based on processing speed and processing accuracy for difficult-to-machine materials, this paper presents a new MEEC processing method, is based on the basic of MEEC increase on-process dressing grinding wheel, grinding wheel non conductive parts won't jam pore, the abrasive dust adhered to the grinding wheel continues to be removed, the grinding wheel always remain sharp, strengthened the grinding effect, greatly improving the grinding efficiency.

Anisodon sp. (Mammalia, Perissodactyla, Chalicotheriidae) from the Turolian of Dorn-Dürkheim 1 (Rheinhessen, Germany): morphology, phylogeny, and palaeoecology of the latest chalicothere in Central Europe

The rich mammalian fauna of the Turolian fossil site Dorn-Durkheim 1 (Rheinhessen, Rheinland-Pfalz, Germany) contains numerous remains of a chalicotheriine chalicothere. These are 171 dental remains, 1 fragment of a lower jaw symphysis, and 8 carpal and tarsal bones. A morphological description and comprehensive comparison with other Eurasian Chalicotheriinae are given. The Dorn-Durkheim 1 chalicothere was comparatively small in body size and resembled members of the Anisodon clade rather than Chalicotherium within the Chalicotheriinae. A phylogenetic analysis corroborates the assignment of the Dorn-Durkheim 1 chalicothere to Anisodon sp. We used low-magnification stereoscopic microwear analysis in order to reconstruct the diet of Anisodon sp. from Dorn-Durkheim 1. Counts of small pits are higher than in earlier Eurasian and American chalicotheres. Anisodon sp. from Dorn-Durkheim 1 most likely fed on leaves and fruit. There is no indication of the inclusion of highly abrasive material, grit, or dust in its diet. These results are in accordance with the interpretation of the Dorn-Durkheim 1 environment as a tropical savannah to woodland. The dating of the Dorn-Durkheim 1 fauna as Mammal Neogene (MN) 11 makes this Anisodon the latest known chalicothere in Central Europe. Based on morphological similarities with late Miocene chalicotheriines from Asia and southeastern Europe, we assume that it is an immigrant that arrived in the course of the expansion of faunas from the southeast at the beginning of the Turolian.

Engineering solutions applied to pneumatic drills to reduce losses of dust from dressed seeds

Neonicotinoid insecticides (imidacloprid, clothianidin, thiamethoxam) and fipronil for maize (Zea mays L.) seed dressing have been claimed to play a role in honey bee (Apis mellifera L.) decline, since pneumatic precision drills used for sowing contribute to the dispersion of the abrasion dust produced by dressed seeds. The active ingredients (a.i.) can contaminate the environment and can lead to the exposure of operators and bystanders during sowing operations. To achieve a significant reduction of dust drift and to enhance the safety for the operators, CRA-ING studied and developed novel engineering solutions applicable to drills, based on an air-recycling/filtering system. In the first system, the air’s excess is forced outward through suitable filters placed on the modified lid of the seed hopper. It can be easily applied to commercial drills in use. The second system was specifically designed for new drills. It consists of a collector duct that receives the air expelled from the vacuum fan opening, creating constant pressure conditions. Part of the air is recycled into the seed hoppers, as the air in excess is directed outward through a single main filter. A third system, based on the second one, entails the use of an electrostatic filter to improve its efficiency. Moreover, to avoid the operator’s exposure to the dust during the seed loading, we show an integrated solution based on the use of a modified pre-charged plastic container that replace the drill’s hoppers. Preliminary tests ascertained the regular seed distribution with the drills equipped with the prototypes. Then, trials were carried out at fixed point and in field, for detecting the amounts of the drifted a.i., using commercial maize seed dressed with thiamethoxam, imidacloprid, clothianidin and fipronil. The test results show powder and a.i. drift reductions up to a maximum of 94.5% measured at ground level (with fipronil as a.i.) as a consequence of the use of the prototypes.

CaSO4晶须/天然橡胶复合材料的制备与性能研究

用KH-560表面接枝处理CaSO4晶须，采用母炼胶法制备了CaSO4晶须/天然橡胶复合材料。研究了CaSO4晶须/NR复合材料的力学、磨耗及动态力学性能，与未处理的CaSO4晶须/NR复合材料性能比较，发现CaSO4晶须经表面接枝处理后，复合材料的拉伸强度、撕裂强度、300%定伸应力和邵尔A硬度均有提高，断裂伸长率和磨耗量减小，且横向磨损量比纵向小，其中经KH-560处理的晶须添加量为3份时复合材料横向磨损量为0.6499 cm−3/1.61km，磨耗性能最佳，而基体橡胶磨损量为0.7372 cm−3/1.61km。并用SEM对橡胶磨屑和橡胶磨损表面形貌用进行了分析；DMA表明CaSO4晶须经KH-560表面接枝处理后界面作用增强。 In the experimental test CaSO4-whisker being treated by agent KH-560 has been added to the rubber com-posites. The mechanical properties, abrasion and attrition behavior and dynamic mechanical properties of the rubber composites have been studied, comparing with the rubber composites adding the CaSO4-whisker without coupling agent KH-560. The SEM patterns of abrasive dust and the rubber composites worm surface were analysed. The experiments showed that adding CaSO4-whisker being treated by coupling agent KH-560 to rubber composites got better interfacial adhesion，wear resistant, tensile strength, tear strength, stress at 300% elongation and shore hardness. Then wear resis-tant of rubber composites adding 3% CaSO4-whisker (weight ratio of the whisker to the rubber) being treated by cou-pling agent KH-560 was the best (0.6499 cm−3/1.61km, compared with 0.7372 cm−3/1.61km of rubber composites without CaSO4-whisker). DMA indicates that rubber composites adding CaSO4-whisker being treated by agent KH-560 have better interface adhesion than rubber composites adding CaSO4-whisker without treated.

Risk mitigation measures for seed treatments using neonicotinoids

Background: In 2008 the poisoning of about 12000 bee colonies was reported in Germany. These poisonings were caused by the drift of dust particles containing the insecticidal substance clothianidin following the seeding of maize, treated with the insecticide Poncho Pro. Dust abrasion from coated seeds occurred because of inadequate seed dressing quality, resulting in high quantities of dust emitted into the environment. In order to cover this specific risk, Regulation (EC) No. 1107/2009 provides for special arrangements for the placing on the market of treated seeds. In addition, the Commission Directive 2010/21/EU lays down specific provisions relating to certain neonicotinoids and fipronil for seed coating and seeding. Results: According to these provisions the German authorities applied risk mitigation measures in the form of specific labels for certain products and seed bags of treated seeds. Conclusions: Dust within seed bags and drift from seeding actions is a common phenomenon for a number of crops. However, the quantity within the seed bags and the emission of dust can be reduced significantly by technical means (e.g. treatment recipe, facility equipment, deflector technique) and by additional mitigation measures (e.g. max. wind speed). These can be established within the authorization procedure by the Member States. Keywords: honeybee, poisoning, seed treatment, dust, guttation, risk mitigation

Dust drift during sowing of maize - effects on honey bees

Background: Bee poisoning incidents in southern Germany in 2008 revealed drift of insecticidal dusts of treated maize seed during sowing on adjacent areas with flowering bee forage plants as a considerable route of exposure. Consequently, improvements have been proposed for seed dressing quality regarding dust abrasion taking into account residue content of dust and for the sowing techniques as possible risk mitigation measures. To assess potential effects on honey bee colonies following insecticidal dust drift on adjacent non-target areas, in 2010 and 2011 two large-scale drift experiments were carried out during maize sowing using seed batches from two different years (2010: seed batch from 2008; 2011: seed batch from 2011). Results: Despite improvements of seed dressing quality regarding dust abrasion comparing the two seed batches (Heubach value 0.86 in 2010 and 0.45 in 2011) and the use of a precision air seeder with drift reducing deflector, in both experiments bee mortality was clearly increased, especially in semifield conditions. Conclusions: Drift of insecticidal dusts during sowing of maize may result in a risk for honey bees in field conditions. To exclude adverse effects on bees, especially during sowing of maize further improvements of seed treatment quality and machinery is needed. Keywords: maize, seed treatment, clothianidin, dust drift, honey bee poisoning

Bee poisoning incidents in the Pomurje region of Eastern Slovenia in 2011

In spring 2011 a high number of bee poisoning incidents was recorded during the sowing of maize in the Pomurje region of Slovenia. The sowing of maize in Pomurje started two weeks earlier than normal following an extremely dry period. In contrast to other parts of Slovenia, maize sowing in Pomurje coincidenced with flowering of oilseed rape on adjacent fields. More than 2500 colonies were affected representing nearly 10% of bee keepers in the region. Samples were taken from dead bees, pollen, nectar, honey combs, flowering oilseed rape and maize seeds collected in the field and subsequently analysed for pesticide residues. The active substance clothianidin was most frequently found and was detected in 24 out of 51 samples (47%) of which 12 dead bee samples (86%). Another neonicotoid, thiamethoxam, was found in 4 samples (8%) of which 2 dead bee samples (14%). The presence of clothianidin in dead bees and pollen in April 2011 is attributed to the sowing of maize treated with the insecticide Poncho Pro. The quality of seed coating for maize seeds treated with the insecticides Poncho or Cruiser collected at different suppliers was tested in a German laboratory. The results showed that abrasion of dust was below the maximum acceptable level of 2 g per 100 kg seeds for 18 out of 19 samples with one sample only slightly exceeding this level. The seed fulfilled the prescribed national quality standards for dust abrasion that were introduced following bee poisoning incidents in 2008. From 29 April 2011 onwards the use of maize seeds and oilseed rape seeds treated with Poncho Pro containing the active substance clothianidin and Cruiser containing the active substance thiamethoxam was prohibited. Further records of bee poisoning in May and subsequent findings of clothianidin and thiamethoxam in dead bees suggest that not all incidents can be attributed to the sowing of maize as route of exposure.