Surface Breakage Research Articles

Modelling breakage of steelmaking materials for simulation of mechanical degradation during handling

Mechanical degradation of steelmaking materials can have significant economic and environmental implications. Such degradation typically occurs as result of impacts during transportation and handling from their production site to the steelmaking furnace, in operations that include transfers in chutes, ship loading, stockpiling, reclaiming, wagon loading and discharging, etc. Predicting the extent of such degradation and attempting to prevent it, is worthwhile. Fortunately, mechanical degradation during such operations can now be predicted using different approaches, but a proper breakage model is required. The work presents results from single-particle breakage tests of iron ore lump, sinter, briquette, and pellet samples, besides coke, followed by fitting parameters of the Tavares UFRJ Breakage Model. These are then used to simulate degradation in a hypothetical handling circuit. Predictions demonstrate the high susceptibility of iron ore lump and briquette to fines generation, when compared to the other materials, and the occurrence of conditioning for briquettes and sinter, which is the increase in strength of particles surviving handling. Iron ore pellets and coke remained comparatively unaffected by the handling operations simulated, which is explained by their greater resistance to either body or surface breakage.

Investigate the effect of milling time on puncture resistance of STF impregnated Kevlar composites

Ball milling time is an important factor that affects the rheological properties of shear thickening fluid (STF), which is rarely studied. In this study, SiO2 particles with a diameter of 500 nm and PEG 200 were mixed and milled for 4, 6, 8, 16, and 24 h in an omnidirectional planetary ball mill to obtain the corresponding shear thickening fluids (STFs). Through TGA, SEM, DLS, and other characterization methods, it was found that a long ball milling duration would lead to the surface breakage and wear of SiO2 in STF. The effects of STFs with different milling durations on the inter-yarn friction and puncture resistance of STF-Kevlar composites were also studied. The results show that the STFs produced with a ball milling time of 4 h or 6 h are not uniform, with some semi-solid lump remained. Compared with other milling time durations, the peak viscosity of STF with a milling time of 8 h can better improve the friction between yarns in the fabric and the fabric puncture resistance.

Green Biocidal Nanotechnology Use for Urban Stone-Built Heritage—Case Study from Oradea, Romania

Heritage buildings clad with natural rock endure over time destruction caused by weathering mechanisms, pollution from urban areas, biodeterioration due to organisms, microorganisms, and also the anthropic factor. On the surface of the limestone samples taken from the ornamental natural rock with which the outside of Markovits-Mathéser house, Oradea, Romania, is clad, two species of fungi were inoculated in the laboratory: Aspergillus spp. and Cladosporium spp. Wollastonite was then applied, and from the imaging analysis (SEM), the inhibition of fungi by it is clearly observed (48 h after its application), which was also confirmed using the image segmentation method. It was also noted that the hydrophilicity of the aqueous suspension of wollastonite resulted in the absorption of water in the substrate, which in turn resulted in the drying out and surface breakage of the specimens. X-ray diffraction analysis showed the presence of the two phases (calcite and quartz) as in the starting sample, and also an additional phase assigned to wollastonite in the later phase of the experiment. An amorphous component, due to the applied gel composition, was also reported. This research highlights the fact that there are good premises for aqueous suspension of wollastonite to have a biocidal character for Aspegillus spp. and Cladosporium spp., when applied on natural stone used in the construction of heritage buildings located in temperate climates; due to its easy application, green and ecofriendly properties, and also low cost of acquisition and application.

Influence of elevated temperature and gas atmosphere on coke abrasion resistance. Part one: Pilot oven cokes

A novel approach was developed to examine coke abrasion resistance in-situ at temperatures of up to 950 °C and in a controlled gas atmosphere using rotational tribological testing. The originality of this approach lay in the ability to apply tribological testing to the porous coke surface at elevated temperatures under a controlled inert or CO2 reactive atmosphere. Coke wear characteristics were quantified via (i) the application of advanced microscopy and image analysis techniques, and (ii) analysis of the coefficient of friction (COF) during tribological testing.Two pilot oven cokes were examined in this study, which were generated from single coking coals of similar rank but different petrographic composition. The cokes tested showed a deterioration in abrasion resistance even at 400 °C, and this was accentuated at 950 °C.The COF and the severity of the wear as a function of temperature and gas atmosphere were markedly different between the two cokes. Coke C396 from a mid-to-low vol, medium vitrinite coal showed no statistically significant differences between the wear severity results recorded following room temperature testing and high temperature testing in a CO2 environment. Conversely, the more reactive coke C426 with a higher parent coal inertinite content showed clear differences in the extent of abrasive wear at room temperature and at high temperature in both inert and reactive gas atmospheres.This suggests that the reduction in abrasion resistance at elevated temperatures is accentuated in the coke with the highest coke reactivity index (CRI) and the highest content of inertinite maceral derived components (IMDC). Our research has shown that at room temperature, the IMDC show greater resistance to abrasion than the reactive maceral derived components (RMDC). This has implications for understanding the relevance of room temperature testing to the abrasion resistance of coke under practical blast furnace operation conditions. For example, a coke from a coal or blend with a comparatively high inertinite content may show lower resistance to abrasion in the blast furnace than would be expected from tumble drum indices. Larger sample numbers and cokes from a variety of single coals need to be tested in further work to verify these assertions.Finally, a novel method using micro-CT image analysis was developed to examine the wear path generated at the coke surface during tribological testing. The purpose of this was to assess the extent of the abrasive wear by comparing the rendered micro-CT images before and after tribological testing. A colour gradient scale was used to facilitate the quantitative assessment, whereby the colour of each voxel was based on the distance from the nearest voxel that is associated with solid phase.As expected, the specific surface area (SSA) calculated for the upper 1 mm of each sample decreased following tribological testing due to the generation of a wear track which is smoother than the initially rough, porous coke surface. In the C426 coke type examined, the SSA decreased the most for the sample tested in an argon atmosphere at 950 °C, matching the COF and quantified wear severity results, which showed there was a notable increase in abrasive wear to this coke as the temperature was raised from room to elevated temperature.Coupling this method of analysis with 3D visualisation techniques in further work would provide a powerful approach to examine and quantify mechanisms of coke surface breakage and the microstructural and/or microtextural features responsible for the breakage.

EFFECT OF ACID HYDROLYSES ON PROPERTIES OF CELLULOSE/POLY FURFURAL ALCOHOL (PFA) COMPOSITES FROM MAIZE STALK

The study investigated morphology and thermal properties of cellulose/poly furfural alcohol (PFA) composites prepared from maize stalk through acid mixtures. The cellulose nanocrystals (CNCs) were extracted from maize stalk via acid hydrolysis using mixtures of various acids.The prepared CNCs were encapsulated in a PFA matrix via in situpolymerization process using p-toluene sulfonic acid as catalyst. The properties of untreated maize stalk, cellulose and their nanocomposites were analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transmission infrared (FTIR) and thermogravimetric analysis (TGA). The crystallinity of maize stalk was generally increased after an acid hydrolysis dominated by H2SO4/HNO3 and H2SO4/HCl. The same trend was observed from TGA, except that H2SO4/H3PO4and H2SO4/HClO4dominated thermal stability trailed by H2SO4hydrolysed CNC nanocomposite. The surface breakage of fibers observed in SEM images was depended on the strength of acids used tohydrolysed the CNC. There was also evidence of aggregation and cracked PFA surface with addition of acid hydrolysed CNCs, dependent on the acids strength. The H2SO4/HClO4hydrolysed CNC/PFA displayed afairly good dispersion of CNCs in the PFA matrix with no surface breakage.

Effects of different breakage mechanisms on the physical, water sorption, and mechanical characteristics of infant milk formula

Two main breakage mechanisms, surface breakage and body breakage, were both found during laboratory dilute-phase pneumatic conveying and high-speed mixing of infant milk formula, respectively. Body breakage had a greater influence on powder physical properties, particle shapes, and surface compositions than surface breakage. In particular, the particle size of samples decreased by only 10% after surface breakage but by 60% after body breakage. For samples where body breakage predominated, significant changes to both water sorption and mechanical properties of the powder were seen while surface breakage had very little effect on them. Body breakage significantly increased the water sorption rate of samples, at around 10%–126% higher than the other samples for the first 3 h, which accelerated the time-dependent crystallization. Moreover, at a W 0.11 to 0.33, the final water contents of body breakage samples were 3.5%–22% higher than control samples. This decreased the crystallization temperature, by between 2 °C and 10 °C, and the overall molecular mobility of samples. These changes were due to the increase in the number of adsorbed monolayers, sorption surface area, and monolayer value of samples after body breakage. • Surface breakage affected physical properties but not water sorption behavior. • Body breakage greatly deteriorated physical and surface properties. • Body breakage increased water sorption rates, monolayer values and water contents. • Body breakage decreased the instant crystallization and overall molecular mobility. • Body breakage slightly decreased glass transition and α-relaxation temperatures.

Modeling breakage by impact of fragments of fired iron ore pellets

As soon as fired iron ore pellets suffer their first breakage event, fragments are created. During handling from the pelletizing plant to the steelmaker furnace, several stages of handling occur, so that if a well-formed and nearly spherical pellet breaks early in the handling chain, its fragments may also end up undergoing breakage. This is particularly important if one wishes to predict breakage during all handling stages. Unfortunately, no study in the past analyzed breakage of fragments of fired iron ore pellets, which will likely differ in comparison to the nearly spherical pellets owing to the irregular shapes of fragments. This work investigates breakage of fragments of iron ore pellets by impact using a pneumatic gun device, investigating the effect of fragment history and impact velocity on the breakage probability, the generation of fines by surface breakage as well as the fragment size distribution from body breakage. Results show that fragments are more amenable to surface breakage than well-formed pellets and also that their strength increases as fragment sizes reduce.

Investigation of the wear behavior of abrasive grits in a dry machining Inconel 718 narrow-deep-groove with a single-layer cubic boron nitride grinding wheel

The wear behavior of a single-layer electroplated cubic boron nitride (cBN) grinding wheel was investigated in creep feed grinding Inconel 718 narrow-deep-groove with a width of 2 mm. In this paper, the protrusion height of cBN grits on the side edge of the grinding wheel was measured by three-dimensional optical profiler, and a scanning electron microscope was used to detect the topography of worn cBN grit and the nickel bonding layer. The investigation results indicated that the steady wear stage of the grinding wheel shared more than 84.6% of the wheel life span, and the machining precision of the grinding wheel was kept at a high level. The fracture mode of the cBN grit was proven to be cleavage. The sources of the cleavage cracks were observed on the surface of wear flat or the side surface of the cBN grit. The holding strength of cBN grit could be weakened due to the joint surface breakage, the displacement of grit, or the cracks of the nickel bonding layer. The transition layer was contributed to the decrease of the bonding strength. Severe macro fractures and the concentration of pulled out grits were observed on the transition edge and the inner area of the side edge, separately. This study provides a deep understanding of the wear mechanism of a single-layer electroplated cBN grinding wheel.

Pressure-driven stochastization of flux surfaces in stellarator equilibria: a review of the experimental observations and their analysis

Stellarator vacuum fields are designed to have a dense set of nested flux surfaces, with only small islands and stochastic regions in the interior of the confinement region. As the plasma pressure is increased, pressure driven currents appear, and they can significantly modify the vacuum field. The question arises whether pressure driven currents can cause significant flux surface breakage. Both the Wendelstein 7-AS and large helical device stellarators had dedicated experimental campaigns to study the limit in those devices. This paper reviews the evidence that the flux surfaces in a significant fraction of the plasma volume were stochastized by the pressure-driven currents in the highest experiments. That phenomenon appears to have been the dominant source of pressure-driven flux surface loss in these experiments.

Insulator Surface Breakage Recognition Based on Multiscale Residual Neural Network

Insulators are one of the widely used important devices in power systems, and proposing an accurate and effective online monitoring method for insulator defects is an urgent need for intelligent and informative power systems. We propose a multiscale residual neural network (MSResNN) for insulator surface breakage recognition. The proposed multiscale convolution filter uses three different size convolution kernels for convolution filtering and performs feature maps fusion, which can enrich the spatial correlation and channel correlation of feature maps. We investigated the effects of different learning rates on the model performance and confirmed that the model performs best with learning rate of $10^{-6}$ . Compared with VGG16, Inception_v3, and Resnet50, the MSResNN model has significant advantages in detection capability and occupies less computational resources, and the detection speed can meet the industrial real-time detection requirements. Through dark–light and noise experiments, it is demonstrated that the proposed method is robust and can effectively deal with low-quality insulator images.

Modeling of degradation by impact of individual iron ore pellets

Mechanical degradation of iron ore pellets can have important economic and environmental implications. The work initially describes a pneumatic gun device that has been developed for characterizing breakage of pellets, by impacting them one-by-one against a target at controlled velocities, angles and against different types of surfaces. It shows that body breakage probability was only a function of the normal component of the impact and that pellets presented higher resistance and lower variability when subjected to impact than to slow compression. Mass loss due to surface breakage was well described using a model that accounts for the energy dissipated in the impact, including both normal and shear components. Parameters capturing their amenability to break either catastrophically or only undergoing surface breakage were estimated from data and the model has been validated on the basis of data from different sequences of impacts, also being used to predict the phenomenon of stabilization.

Impact of Almond Variety on "Amaretti" Cookies as Assessed through Image Features Modeling, Physical Chemical Measures and Sensory Analyses.

In the present study, the influence of almond variety on color, chemical, physical and sensory characteristics of “amaretti” cookies during the shelf life, was assessed. Four varieties were chosen for the study, two of which were local (Cossu, Arrubia) and two widely cultivated (Tuono, Texas). Almonds have been characterized in the content of proteins, crude fat, amygdalin and fatty acids profile. The evolution of the characteristics during the shelf life hasbeen measured through image data modeling, texture, physical chemical and sensory analyses. Data were then treated with a multivariate approach performing a PCA. Image analysis and fitting on log normal and powerlaw functions highlighted the influence of the variety on the total area affected by surface breakages, and on the distribution of the cracking surfaces dimension classes. Texture parameters (crust hardness, thickness and work of deformation) were negatively correlated to moisture content. Sensory profile confirmed the differences in tactile features measured through instrumental texture, while slight to no differences were found in odor profile. Consumer test showed an higher acceptability for Arrubia, Texas and Tuono samples throughout the shelf life, while Cossu samples were less accepted. Overall, the choice of almond variety influences product features and liking of almond products, therefore it represents an important phase to direct the choice of both farmers and confectionery manufacturers.

Effects of Off‐Fault Inelasticity on Near‐Fault Directivity Pulses

AbstractNear‐fault motion is often dominated by long‐period, pulse‐like particle velocities with fault‐normal polarization that, when enhanced by directivity, may strongly excite middle‐ to high‐rise structures. We assess the extent to which plastic yielding may affect amplitude, frequency content, and distance scaling of near‐fault directivity pulses. Dynamic simulations of 3‐D strike‐slip ruptures reveal significant plasticity effects, and these persist when geometrical fault roughness is added. With and without off‐fault yielding, these models (~M7) predict fault‐normal pulse behavior similar to that of observed pulses (periods of 2–5 s, amplitudes increasing with rupture distance until approaching a limit), but yielding systematically reduces pulse amplitude and increases the dominant period. Yielding causes near‐fault (< ~2 km) peak ground velocity (PGV) to saturate with respect to increases in both stress drop and epicentral distance, and, in that distance range, yielding may contribute significantly to the observed magnitude saturation of PGV. The results support the following elements for functional forms in empirical pulse models: (i) a fault‐normal distance saturation factor, (ii) a period‐dependent and along‐strike distance‐dependent factor representing directivity, and (iii) an along‐strike saturation factor to truncate growth of the directivity factor. In addition to the foregoing effects on long‐period fault‐normal pulses, the model with off‐fault plasticity is very efficient in suppressing the high‐frequency fault‐parallel acceleration pulses that otherwise develop when rupture breaks free surface. This effect is likely to inhibit the initiation of a sustained supershear rupture triggered by a strong free surface breakage.

Fuel pellet breakage in pneumatic transport and durability tests

Wood pellets for biofuel utilization are fragile and produce fines and dust when handled. Impact resistances of pellets were obtained by using tumbling box tester, ligno tester and rotary impact tester. The samples were sieved after each of the ten consecutive runs to generate a breakage vector of particle size classes: 0–1.00, 1.00–2.36, 2.36–3.15, 3.15–4.75 and > 4.75 mm. Similarly, a full-scale pneumatic blow wood pellets degradation experiment was conducted. The pellets were blown at different delivery pressures from 0.3 to 1 bars.The breakage patterns disclosed two independent mechanisms when analysed by multivariate modelling: surface breakage by the tumbling box and volume breakage by the rotary impact tester. The combination of these testers can describe the full outcome space for the pneumatic tests and it is possible to predict generation of fines and dust during pneumatic loading of wood pellets from a silo. The most severe damages corresponded to more than 10 times 500 revolutions in a tumbling box and 8 consecutive impacts at almost 20 m/s in the rotary tester. Furthermore, these results provided insights into pellet breakage mechanisms, evaluation of pneumatic pipe designs and construction of bench testing devices that purify the effect of surface vesus volume breakage.

Cathode materials with mixed phases of orthorhombic MoO3and Li0.042MoO3for lithium-ion batteries

MoO3is a promising cathode candidate for lithium-ion batteries and its electronic conductivity is usually improved by MoO3lithiation via reaction of MoO3with LiCl solutions. However, this process might increase the manufacturing complexity and result in surface breakage of MoO3cathodes. In this paper, by introducing lithium source into MoO3synthesis, MoO3can be lithiated through introduction of the Li0.042MoO3phase into the MoO3structure. XRD and ICP results indicate that the phase composition and lithium content can be regulated by changing the amount of lithium source in the reaction solutions. FESEM and specific surface area measurements show that the particle size becomes more uniform and the surface area is increased when the degree of MoO3lithiation is higher. The lithiated MoO3sample shows better cycling performance than that of pristine MoO3, which is mainly due to the enhanced conductivity and increased surface area of the lithiated MoO3.

Experimental Investigation on Micro Milling of Polyester/Halloysite Nano-Clay Nanocomposites.

Efficient machining of the polyester nanocomposite components requires a better understanding of machinability characteristics of such material, which has become an urgent requirement for modern industrial production. In this research, the micro-milling of polyester/halloysite nano-clay (0.1, 0.3, 0.7, 1.0 wt%) nanocomposites were carried out and the outcomes in terms of tool wear, cutting force, the size effect, surface morphology, and surface roughness were compared with those for plain polyester. In order to accomplish the machining of the material in ductile mode, the required feed per tooth was found to be below 0.3 µm. The degree of surface breakage was also found to decrease in ductile mode. A maximum flank wear VB of 0.012 mm after removing 196 mm3 of workpiece material was measured.

Investigation on ultra-precision lapping of A-plane and C-plane sapphires

Abstract A series of lapping experiments on A-plane and C-plane sapphires were accomplished using a precision single-side lapping machine. The differences in the material removal rate, surface topography, surface breakage and subsurface damage between the two sapphire orientations were explored. The influence of the lapping parameters, such as the abrasive disk speed, lapping time, lapping liquid flow rate and wander star wheel speed, were analysed for their effects on the material removal rate. The experimental results showed that the abrasive disk speed played the most prominent role in the material removal rate during sapphire lapping. Under the same lapping conditions, the removal rate of the C-plane sapphires could be 5.7 times higher than that of the A-plane sapphires. The main surface damage form of the A-plane sapphires after lapping was surface breakage, while that of the C-plane sapphires was surface scratching. After lapping, the A-plane sapphires had a greater subsurface damage depth than the C-plane sapphires. The subsurface cracks of the A-plane sapphires included transverse and radial cracks, while the subsurface cracks of the C-plane sapphires were mainly transverse cracks. The lapping surface quality of the C-plane sapphires was superior to the A-plane sapphires.

Mapping surface breakages of the 2018 Hualien earthquake by using UAS photogrammetry

Mapping surface breakages of the 2018 Hualien earthquake by using UAS photogrammetry

Surface breakage of fired iron ore pellets by impact

Surface breakage or attrition occurs when iron ore pellets are subjected to handling stages in which the stressing level is insufficient to cause their massive fracture. This breakage mechanism has been investigated for five types of industrial iron ore pellets from impacts against a steel target, leading to a model that accounts for the effect of pellet size, impact energy and angle. The model is then validated on the basis of two different tests. First, a tumbling test on a small drum (0.305 m diameter) is used to demonstrate the validity of the model to describe surface breakage by motion of the pellets at comparatively low velocities, such as those that are found during flow in hoppers and silos. The model is also validated on the basis of simulations of a RO-TAP® sieve shaker. It is demonstrated that it is able to predict with confidence results from the tests, proving to be a powerful tool when used in combination with simulations using the discrete element method, to predict mechanical degradation due to surface breakage during handling.

Fracture probability and fragment size distribution of fired Iron ore pellets by impact

Degradation that results from transportation and handling can have an important economic impact in steelmaking materials, given the lower value of the finer material that is generated. In spite of their higher strength when compared to lump iron ores, fired iron ore pellets also undergo some degradation, which increases with severity of the handling operations that occur from the pelletizing plant to the end user. Such degradation can occur in the form of fine debris lost from the surface of the pellet, in a mechanism of surface breakage, or as result of complete loss of integrity of the pellet (fracture), generating a wide range of fragments in size. The work deals with this second mechanism of breakage, describing the probability of fracture of pellets under impact conditions, the amenability of pellets to break under repeated impacts, besides the size distribution of the progeny for selected iron ore pellets, proposing appropriate experimental methods and models to describe them quantitatively.