Abrasion Energy Research Articles

Influence of CGD structure on burden descending behavior in COREX shaft furnace

For improving the reducing gas flow in the center of a large-scale shaft furnace, the central gas distribution (CGD) device, a new technique, is proposed and installed in the shaft furnace. Because of its less-developed history, the solid flow in the shaft furnace with CGD is unclear. In this work, a three-dimensional cylindrical model of COREX-3000 shaft furnace in actual size is established based on DEM. Four types of burden, including pellet, lump ore, coke and flux, are taken into consideration in the model. The model is validated by experiment and then it is used to investigate the influence of CGD structure on solid flow patterns, burden descending velocity, interaction force and abrasive wear. The results show that the CGD structure has some effects on the solid flow patterns and burden descending velocity. As the CGD diameter increases, the interaction force between particles is decreased but the total abrasion energy on CGD is increased. As the CGD height increases, both the interaction force between particles and the total abrasion energy on CGD are decreased.

Numerical and Experimental Analysis of Impinging Synthetic Jets for Cooling a Point-Like Heat Source

High power light emitting diodes (LEDs) being used for low and high beam in automotive lighting need active cooling of their heat sinks by radial or axial fans. But the moving elements of the fan cause abrasion, noise, and high energy consumption. Synthetic jets can replace conventional fans with their disadvantages and allow the directed cooling of LEDs. Therefore, in this paper, flow and heat transfer characteristics of impinging synthetic jets are investigated numerically and experimentally as an alternative to cooling LEDs with fans. It is shown that the impact plate brings forward the laminar-turbulent transition of the jets temporally and spatially. The impact plate itself should not be positioned in the region of the free jet's transition height. Increasing the frequency of the synthetic jet has a greater influence on the heat transfer compared to an increase in amplitude. The maximum cooling performance is achieved for all jet configurations with moderate distances between the orifice and the impact plate. In this case, the jet reaches its highest mass flow and impulse and its lowest temperature.

Sand Transport and Abrasion within Simulated Standing Vegetation

Abstract.Crop residues help protect topsoil from depletion and abrasion due to wind erosion. Limited studies have focused on the type and orientation of canopies that help minimize the effects of erosion by wind. In this study, a series of wind tunnel experiments was conducted to measure sand transport and abrasion energies within simulated standing vegetation. Wind speed profiles, relative abrasion energies, and rates of sand discharge were evaluated during 3 min test runs at two different vegetation heights (150 and 220 mm) for each of three densities of simulated vegetation (i.e., 100 × 200 mm, 200 × 200 mm, and 300 × 200 mm spacing). Tests were also conducted for a bare sand surface. As expected, vegetation density was directly related to threshold velocity and inversely related to sand discharge. The densest configuration (i.e., 100 × 200 mm spacing) increased the threshold velocity of bare sand from 5.9 to 10 m s-1. The presence of vegetation was found to be effective in minimizing the abrasion experienced by the standing vegetation models by lowering the saltation of sand particles that could impact the simulated plants. The coefficient of abrasion (Can), a measure of kinetic energy via the impact of saltating particles, was affected by saltation discharge, although this did not depend on wind speed. The values of Can for all configurations were significantly different (p < 0.05) from the bare sand surface . Keywords: Abrasion energy, Sand discharge, Standing vegetation, Threshold wind velocity, Wind erosion.

Variable effects of saltation and soil properties on wind erosion of different textured soils

Wind erosion largely depends on saltation. Nevertheless, the effect of the composition of the saltation fraction of different textured soils is poorly understood, as is the relative influence of both saltation and soil properties on wind erosion. In order to answer these questions, wind erosion of six differently textured soils were simulated with a wind tunnel. The following saltation conditions were considered: injected saltation, in which the saltation fraction of each soil was added to the soil bed; no saltation, in which the soil eroded naturally, without injection of its saltation fraction; and only saltation, in which the saltation fraction was injected in absence of the soil bed. Results indicated that total erosion amounts increased as a function of the abrasion energy of the saltating particles but also with decreasing aggregation rate of the saltation fraction. The aforementioned agrees with a lower aggregate stability and higher amounts of the erodible fraction of sandy soils. Though saltation of individual sand grains produced impacts of higher kinetic energy on the soil surface of sandy soils than of fine textured soils, the relative erosion (quotient between the erosion occurred with and without saltation) was higher in finest soils, indicating a larger effect of saltation, probably due to the larger fragmentation of aggregates in these soils. Results of this study indicated that both the composition of the saltating fraction and also the intrinsic properties of the soil determined wind erosion.

Determination of the abrasion of aprons of dams by debris flow

This paper presents an empirical equation for the quantitative determination of the abrasion rate of concrete stilling basins by the impact of sediment in debris flow. The grain size in the experiments is not as big as the grain size of natural debris flow and the independent contribution of sediment impact on abrasion is not reported in previous studies. Therefore, the independent contribution of coarse-grain sediments impact on concrete slab investigated in this paper using two sets of experiments. Linear, power and exponential correlation equations were developed relating abrasion and cumulative potential energy per unit weight of concrete stilling basin using the first set of experiments. The equations were verified using a second set of experiments. The power equation was selected using the mean absolute relative error as the criterion. The study reveals that the reduced effect of water is less than 10% for dimensionless depth smaller than one.

Effect of canopy leaf distribution on sand transport and abrasion energy

Abstract During times when crop canopies are short or sparse, wind erosion can uncover plant roots, deplete the soil resource, and damage plants by abrasion and desiccation. Few studies have considered the effects of position and number of leaves on sand transport and the distribution of the sand abrasion energy. The objectives of this study were to determine the effects of number and distribution of leaves on threshold velocities, sand transport rates, and relative abrasion energy among simulated dicotyledonous plant canopies. Six canopies were tested in a wind tunnel with two levels of leaf area index (LAI), two different maximum leaf heights, and either two or four leaves per plant with maximum freestream wind speeds from 12 to 17 m s −1 . The leaf heights were selected to position the lowest leaves to be either intercepting saltating sand or largely above the saltation layer. The wind tunnel was a 1.52 W × 1.82 H × 15.3 L m push-type recirculating tunnel with the floor covered with a layer of sieved sand. Sand discharge and relative abrasion energy were measured during 3-min duration test runs. For canopies with two leaves, the experimental sand transport capacity was reduced most when the leaves were highest above the surface even though they were intercepting saltation when in their lowest positions. As expected, canopy LAI was directly related to threshold velocity and inversely related to sand transport capacity. Total abrasion energy impacting the target soil channel containers located vertically in the canopy increased with wind speeds above the threshold. Within canopies, high wind speeds increased height of maximum abrasion but often still caused less total abrasion per unit sand discharge than over a bare, sandy surface. When leaves were located nearest the surface, they modified the vertical abrasion profiles by deflecting a portion of the sand impact energy upward in the wind stream. Overall, the canopies modified both the profiles and normalized abrasion energy of the sand discharge when compared with a bare, sandy surface. Hence, it may be important to place test plants within a canopy of similar plants—to allow development of a fully developed velocity profile in the canopy by using a minimum upwind fetch of about 70 canopy heights in a wind tunnel—when conducting plant abrasion tests using sand to achieve results representative of plants in the interior of a field. In contrast, abrasion on inter-row flat soil containers was independent of wind speeds, but was higher without a canopy compared with measurements in the canopy for a given sand discharge.

The effect and mechanism of Nano-Cu lubricating additives on the electroless deposited Ni-W-P coating

The coating and deposition process with excellent anti wear and suitable for industrial application were developed, and the optimum bath composition and process were obtained by studying the influence of the bath composition, temperature and pH value on the deposition rate and the plating solution stability. Moreover, the tribological properties of nano-Cu lubricating additives and electroless deposited Ni-W-P coating as well as their synergistic effect are researched using ring-block abrasion testing machine and energy dispersive spectrometer. Research results show that Ni-W-P alloy coating and nano-Cu lubricating additive have excellent synergistic effect, e g, the wear resistance of Ni-W-P alloy coating (with heat treatment and the oil with nano-Cu additives) has increased hundreds times than 45 steel as the metal substrate with the basic oil, and zero wear is achieved, which breaks through the bottleneck of previous separate research of the above-mentioned two aspects.

Study of Compatibility of the Nano Lubricating Additives with the Electroless Deposited Ni-W-P Coating

Tribological properties as well as antiwear and friction reduction mechanism of wear self repair nano-ceramic and nano-Cu lubricating additives are researched using ring-block abrasion testing machine and Energy Dispersive Spectrometer. Research results show great difference between friction reduction performances of the above two additives, because their friction reduction mechanism are different, the former is ball bearing effect and the latter is soft film shear effect. In terms of wear-resistance, as for 45 steel, under heavy load, the self repair rate to the worn surface with the nano additives is less than the wearing rate of the friction pair. An effective way to solve the problem is electroless deposited Ni-W-P alloy coating on the surface of the 45 steel. The Ni-W-P alloy coating has high hardness, high wear resistance, and has excellent compatibility with nano lubricating additive, the wear resistance of Ni-W-P alloy coating (with heat treatment and the oil with nano additives) has increases hundreds times than 45 steel as the metal substrate with basic oil, zero wear is achieved, which break through the bottleneck of previous separate research of the above-mentioned the two.

Wear mechanism maps for the belt finishing of steel and cast iron

Belt finishing with different particles size results mainly in different thickness of the total mechanically deformed layer and surface profile projections that depend, to a great extent, on the change in the mechanism of wear. Such a modification often represents a transition in the nature of physical mechanisms (cutting, plowing or sliding), leading to a concomitant change in the rate of material removal. Transition in wear mechanism can also be associated with a change in the abrasiveness properties of the abrasive coated belts. This paper outlines a method by which these transitional regimes can be illustrated graphically on plots of grit size against abrasion energy or applied pressure in connection with the produced surface state (i.e. roughness) for a given wear rate. It is supported by numerous experiments which show that the quality of the finished surfaces is dependent on the wear state of the coated abrasive belt. The “maps” showing wear rates and mechanisms suggest the existence of promising way for increasing the efficiency of abrasive technological processes.

Magnetorheological finishing process for hard materials using sintered iron-CNT compound abrasives

The use of magnetorheological fluids for finishing is one of the most promising smart processes for the fabrication of ultra-fine surfaces, particularly three-dimensional millimeter or micrometer structures. This process is not readily applicable to hard-surface materials, like an Al 2O 3–TiC hard disk slider, if a conventional rotating tool is used. This is due to the rotational speed and the resulting actual impressed abrasion energy limits, and the consequent low efficiency of the material removal rate. In this study, the main mechanism responsible for the decrease of the material removal rate on hard materials for a wheel-type magnetorheological finishing process is examined, both theoretically and experimentally, and a solution to this problem is devised via two approaches. The first uses a rectilinear alternating motion to improve processing conditions, and the second focuses on the use of more effective abrasives, namely magnetizable abrasives made of iron powders sintered with carbon nanotubes, which are new abrasives that have not yet been introduced in the field of surface finishing. Furthermore, it is shown that these abrasives increase the lifetime of consumables (magnetorheological fluid and abrasives) and the material removal rate.

Characterization of abrasive grain’s behavior and wear mechanisms

Grinding is a finishing process largely used in motor industry, aeronautics, space industry and precision cutting tool manufacturers. The grinding process can be summarized by the action of a grinding wheel on a workpiece. The wheel is constituted by abrasive grains. Thus grinding is in fact the action of grains on the workpiece. The grain behavior changes according to numerous parameters (geometry, mechanical characteristics, wear mechanisms). In some cases abrasive wear is observed while micro-cutting is obtained in some other cases. In this paper two useful and complementary experimental approaches for the interface physics understanding is presented. The study of the cutting power is carried out using a high-speed scratch test device in order to understand the grain behavior and the wear mechanisms for several wheel surface speeds. In this paper an approach for the specific abrasion energy computation is also presented.

Elaboration and study of an elastic hard Si-based coating obtained at room temperature from a far cold remote nitrogen plasma

The reactivity of a far cold remote nitrogen plasma is used to dissociate SiH 4 in order to deposit, at ambient temperature, an elastic hard coating on various substrates. The deposition rate, independent of the substrate nature, is equal to 75 nm min −1. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses of the film deposited on silicon reveal the presence of covalent Si-N bonds and the incorporation of oxygen and hydrogen. Scanning electron microscopy observations show that the film is a dense layer with a non-columnar structure. The values of hardness and elastic modulus calculated from microindentation experiments are equal to 9 and 34 GPa for a 4 μm thick film deposited on polyvinyl chloride. For such a film, the specific abrasion energy calculated from scratch test is about 1300 N mm −2.

Abrasion of Rubber and Its Relation to Tire Wear

Abstract Sliding abrasion experiments reveal that the abrasion loss has to be expressed as a power function of the dissipated energy. Both the abrasion loss per unit energy dissipation and the power index depend on the compound and on the type of surface on which the experiment is being carried out. Hence the relative rating of a compound depends on pressure and on surface roughness. This nonlinear dependence on energy dissipation leads also to a rating dependence of slip of the wear of slipping wheels or the wear of tires. If the abrasion energy function for different compounds can be determined, then the wear ranking for different tires should be predictable using the slipping wheel theory. Experiments with tires running under controlled slip conditions show that this is not the case. Predictions differ even in ranking of compounds. Dissipation processes generate heat, so that temperature conditions in the contact area and their influence on the abrasion loss have to be considered in addition to mechanical rupture and fatigue. Laboratory experiments using slipping model wheels are being discussed which use testing conditions designed to generate different temperatures in the contact area. Compound rankings and ranking reversals are obtained which are in agreement with tire wear experiments under controlled slip conditions.

Fully computerized sclero-topometer for simulations and modelling of abrasive wear

The simultaneous knowledge of rheological properties of materials such as scratch hardness ( H s) and scratch toughness ( K c), which are intended to measure the resistance to fracture and to plastic deformation respectively, seems to be very useful for forecasting abrasive wear. A new, fully computerized sclerometer based on a programmable load, speed or depth scratch technique has been designed in order to perform automatic measurements of the brittleness index (ratio of the dynamic hardness to the toughness), which governs the ductile or brittle nature of abrasive wear. The metrological structure is composed in such manner that it can simultaneously perform measurements of the morphology of the scratch and the scratch arrangement. Most wear processes generate oriented surfaces which interact with the principal directions of their microstructures and the direction of their final applications. To understand how these interactions occur, a direct relationship between the surface-generating processes and their topographies and applications must be elaborated. This is one of the main reasons for these investigations. By using a 3D tactile profilometer, the ratio of removed to displaced volume (τ v) can be evaluated. In the same way the surface anisotropy evolution can be estimated with a 3D tactile or optical profilometer. Different criteria of abrasion can therefore be evaluated. Variation of the speed and spatial-temporal gradient of forces (normal, tangential and lateral) acting on the penetrator can lead to estimation of the value of E s, the specific abrasion energy. By calculating E s, τ v, H s, K c and H s/ K c—the characteristic parameters of abrasion—the wear resistance as well as the topographical parameters of the abraded surface can be forecast in some cases. The software, the hardware and mechanical equipment provide an original and useful technique for investigations of wear simulations. Modelling effort can thus be increased. From experimental and theoretical data concerning the abrasive process, we are inclined to think that this is not only a considerable help in the characterization of significant parameters but can also be very useful to predict the topographical parameters which characterize surfaces resulting from the abrasive process. Numerous experiments were performed with this apparatus on different alloyed metal materials such as ball-bearing steel, brass and alloyed aluminium. The results presented in this paper summarize the main findings of these scratch investigations.

Abrasion and Friction of Rubberlike Materials

Abstract The relationship between abrasion resistance and the coefficient of friction was observed in the early days of development of the modern synthetic rubbers. It has gained new interest in connection with the appearance on the market of polyester-isocyanate rubbers of the Vulcollan type. The abrasion of a rubber object in contact with a solid depends on the forces interacting at the surface of the two materials. These forces are again dependent on the forces pressing the two surfaces together, on the relative surface speed of the one object with respect to the other, and on the nature of the surfaces of the materials. Forces acting on the rubber surface and tending to pull the surface layer away from the bulk of the material deform the bulk rubber and excite counteracting cohesive forces. Abrasion of the rubber depends on the following two factors: 1) Development of frictional forces at the surface. 2) Counteraction of the force caused by the rubbing by cohesive force in the polymer adjacent to the surface layer. The question may be raised if it is possible to improve abrasion resistance by increasing the cohesive forces (1) without affecting the frictional forces and (2) if so, to what degree. With the help of the modified Cabot-Lambourn abrader, a number of experiments have been carried out that give some answers to the correlation of abrasion and friction. Abrasion is measured in terms of abrasion efficiency, i.e., weight loss per unit of energy. Correlations are established between: (a) Coefficient of friction and normal load. (b) Coefficient of friction and percentage loss of weight. (c) Coefficient of friction and carbon black loading. (d) Abrasion efficiency, coefficient of friction, and carbon black loading. (e) Abrasion efficiency and energy spent on abrasion. (f) Percentage of slip and torque obtained.

Power Transmission—Slippage-Abrasion. An Investigation of the Abrasion of Tread Compounds

Abstract The abrasion behavior of vulcanizates of the tire-tread type have been studied by the method of constant energy, with a test apparatus operating on the principle of the Dunlop-Lambourn machine. As a result of this work, the following facts were established. Up to a critical slippage, the value of which is characteristic of every individual vulcanizate, the abrasion, i.e., the amount of rubber worn off per unit of time, increases with the square of the slippage. The slippage increases linearly with the power transmitted. To this quadratic relation between the power transmitted and the slippage corresponds a linear dependence of the abrasion power, i.e., it is possible to assign a specific abrasion energy to every individual vulcanizate. The specific abrasion energy is inversely proportional to the temperature and also inversely proportional to the mean particle size of the abrasive material. A comparison of the measured specific abrasion energy with the corresponding value to be expected by theoretical calculation shows that the experimental value is too high by a factor of 106. From this, one is led to the conclusion that the abrasion power is practically completely consumed as heat in the abrasion boundary layer, an idea which is supported by measurements of the temperature of abrasion and a comparison of this with the calculated values. Above the critical slippage value, the simple linear dependence of the abrasive wear on the abrasion power no longer holds true, and a specific abrasion energy cannot be defined. In addition, the abrasion patterns described by Schallamach then appear, and any correlation between laboratory tests and road wear tests is lost.

A new leather

The use of magnetorheological fluids for finishing is one of the most promising smart processes for the fabrication of ultra-fine surfaces, particularly three-dimensional millimeter or micrometer structures. This process is not readily applicable to hard-surface materials, like an Al2O3–TiC hard disk slider, if a conventional rotating tool is used. This is due to the rotational speed and the resulting actual impressed abrasion energy limits, and the consequent low efficiency of the material removal rate. In this study, the main mechanism responsible for the decrease of the material removal rate on hard materials for a wheel-type magnetorheological finishing process is examined, both theoretically and experimentally, and a solution to this problem is devised via two approaches. The first uses a rectilinear alternating motion to improve processing conditions, and the second focuses on the use of more effective abrasives, namely magnetizable abrasives made of iron powders sintered with carbon nanotubes, which are new abrasives that have not yet been introduced in the field of surface finishing. Furthermore, it is shown that these abrasives increase the lifetime of consumables (magnetorheological fluid and abrasives) and the material removal rate.

Width of hard-surface roads

The use of magnetorheological fluids for finishing is one of the most promising smart processes for the fabrication of ultra-fine surfaces, particularly three-dimensional millimeter or micrometer structures. This process is not readily applicable to hard-surface materials, like an Al2O3–TiC hard disk slider, if a conventional rotating tool is used. This is due to the rotational speed and the resulting actual impressed abrasion energy limits, and the consequent low efficiency of the material removal rate. In this study, the main mechanism responsible for the decrease of the material removal rate on hard materials for a wheel-type magnetorheological finishing process is examined, both theoretically and experimentally, and a solution to this problem is devised via two approaches. The first uses a rectilinear alternating motion to improve processing conditions, and the second focuses on the use of more effective abrasives, namely magnetizable abrasives made of iron powders sintered with carbon nanotubes, which are new abrasives that have not yet been introduced in the field of surface finishing. Furthermore, it is shown that these abrasives increase the lifetime of consumables (magnetorheological fluid and abrasives) and the material removal rate.