Mode Of Breakage Research Articles

Analysis of particle corner-breakage effect on pile penetration in coral sand: model tests and DEM simulations

Although particle corner breakage has been proved to be the primary mode of particle breakage for coral sand, current studies of pile penetration have continued to present the particle fracture breakage mode, causing the mechanism of pile behaviours in coral sand to remain unclear. This study investigates the particle corner-breakage effect on pile penetration in coral sand at both the macro- and microscales via indoor pile penetration model testing and three-dimensional discrete element method (DEM) simulations. According to the study findings, DEM simulations revealed that particle corner breakage has a more obvious soil contraction effect than fracture breakage. Thus, this study is the first to explain the particular turn of the pile skin friction in coral sand by the dual effects of breakable corners. Next, relationships between the particle breakage mode and the controversial breakage zone around pile tips have been accomplished. Moreover, the decrease in effective contacts and the change in soil skeleton have been proved to be essential factors behind the narrower penetration-affected width in breakable corner grains. The study suggests that neglecting the particle corner-breakage effect can lead to a hidden danger affecting engineering safety in angular granular soil.

Characterising tensile strength and elastic moduli of altered igneous rocks at comminution scale using the Short Impact Load Cell

The primary breakage properties of rocks such a strength (σ) and elastic moduli (i.e. Young's modulus (E) and Poisson's ratio (ѵ)) are not usually characterised at comminution scale. Traditional comminution tests such as the Bond Work Index grinding test and the Drop Weight Test are used for describing the breakage behaviour of different ores. Nevertheless, these tests do not decouple the ore characteristics from the mode of breakage. The primary breakage properties control the initiation and propagation of fractures in rocks and exert control over the resultant progeny of breakage events when the rock is stressed. However, how these properties change as the particle size decreases in comminution is not clear yet. This work explores the change of primary breakage properties and the derived quantities estimated using the Short Impact Load Cell (SILC) (e.g. apparent stiffness and mass-specific fracture energy) within a particle size relevant to ball milling, using a suite of real ores.The results of this work show that the median values of strength in populations of cylindrical (minicore) particles do not vary with size within the range size studied (3–30 mm) for all the ore types studied. In contrast, the stiffness and the mass-specific fracture energy derived from the primary breakage properties data show a size dependency for all of the ore types in agreement with Weibull's weakest link theory. The degree of variation of the primary breakage properties has also been studied over a range of particle sizes. The results show that this degree of variation tends to increase for some of the rocks as the particle size decreases, but the variation is size-independent for other rock types. These results align with previous results in the literature that indicate the size independency of tensile strength in small samples but are contrary to earlier researchers' findings that suggest that the variance decreases with size. The ore dependent nature of the primary breakage properties found in this work requires further research. Understanding the behaviour of the primary breakage properties in a comminution context might help to characterise the comminution potential of ores better, as well as to develop characterisation and modelling techniques that are more responsive to the ore characteristics.

HPGR Rolls Surface Wear: In-line Scanning of a Laboratory-Scale HPGR

High pressure grinding rolls have been utilized in various operations during the past four decades, simply due to their inherent mode of breakage that offers metallurgical benefits with pronounced energy reduction. For every new application, wear and in particular roll surface wear protection has always been the focal point of HPGR trade-off studies. Wear remains an important issue throughout a mine’s life given inevitable variations in the ore deposits properties. Hence, the capability of continuous scanning of rolls provides ample information about any deviations in the design values as well as their effect on the wear pattern. In part I of this manuscript, we present the feasibility of in-line scanning of roll surface in a 200 × 100 mm lab-scale HPGR. First, the in-line scanning was developed in a mock-up roll and then the scanner was moved to the laboratory-scale HPGR. We present the choice of scanners and the methods adopted to achieve high-level accuracy of determining wear. Even though we planned for micron-level precision of scanning, the inherent variability in shaft rotation was higher than the variability in the roll diameter due to wear. The hundred-kilogram mass processed in the HPGR was not sufficient to create enough wear that is discernible to the in-line scanner. Yet, the method tested is a promising avenue for in-line scanning of HPGR rolls.

The effect of breakage energies on the mineral liberation properties of ores

A number of previous researchers have noticed that the degree of mineral liberation in a given size fraction is the same regardless of where in a comminution circuit a sample is collected. This behaviour has been observed for a range of ore types, and was found to be independent of the mode of breakage. This provides a useful heuristic for modelling the particle characteristics in mineral comminution and separation circuits. However, the published research does not explicitly consider the effect on the liberation behaviour of minerals of the amount of energy applied to break the ore. In this study, a gold-bearing pyrite ore and a copper sulphide ore were comminuted over a wide range of energy levels, using impact breakage. The liberation properties of the product particles were characterised using a Mineral Liberation Analyser (MLA). It was found that that the amount of impact energy applied did not significantly affect the degree of liberation of the minerals in a given size fraction, measured using particle sections. This provides sound experimental evidence to support the heuristic model.

Mode of wood fibre breakage during thermoplastic melt processing

During polymer composite melt processing thermomechanical wood pulp fibres (WF) have a different breakage mode than described for other natural fibres and glass fibre. During repeated bending, expected during twin-screw extrusion and injection moulding, WF fail by a mode related to their cross-section dimensions. Generally, fibres with large lumens relative to wall thickness ovalise and buckle. Conversely fibres with small lumens relative to wall thickness generally fracture. Confocal microscopy of WF extracted from the polymer matrix after melt processing showed a high degree of cross-section collapse of the bent and twisted fibres. The ability to cross-sectionally collapse during composites processing may make the fibres more resilient to repeated bending stresses and help with fibre length retention. Observations suggest fractures were initiated from the edges of the bent fibres and propagated across the fibre.

On the limitation of using the JKRBT in investigating incremental breakage

Interest in understanding the response of particles to low-energy (incremental) breakage has increased significantly in comminution in recent years, mainly due to the recognition that a large proportion of impacts in tumbling mills is insufficient to cause breakage at the first collision event. Likewise, degradation during handling is another field in which low-energy breakage is of great relevance. The investigation of this mode of breakage, however, is very tedious when conducted in drop weight testers, so that more convenient alternatives for testing have been sought. A device, called JK Rapid Breakage Tester (JKRBT), has been proposed as a more convenient alternative to other breakage testers, mainly the Drop Weight Tester, being used in recent studies that investigate incremental breakage. The present work demonstrates, through experiments and simulations, that care should be exercised when using this device in investigating breakage by low-energy impacts, since testing of iron ore pellets resulted in significantly more breakage than expected, when compared to a drop test. This has been confirmed by simulations using the discrete element method, which demonstrated that ricocheting of a fraction of particles can happen against the rotor, resulting in overestimation of breakage for the set energy level. Such effect has been observed to be relevant not only in the case of nearly spherical shapes, such as the iron ore pellets studied, but also in the case of very irregularly-shaped particles.

DEM study on the effect of particle breakage on the macro- and micro-behavior of rockfill sheared along different stress paths

The behavior of crushable rockfill sheared along different stress paths is studied using the discrete element method. Rockfill particles are modeled as breakable agglomerates, and reasonable consistency is found between the predicted and experimental results. The simulation highlights the influence of agglomerate breakage on both the macro- and micro-behavior of the assembly. The evolution of both the number and mode of agglomerate breakage during shearing is significantly influenced by the confining pressure, deviator stress ratio, and loading direction. The relationship between the deviator stress ratio on the macro-scale and the deviator fabric on the micro-scale along different stress paths is explored.

Impact Performance of Thin Glass-Polycarbonate Composite Panels

Safety glass is usually the proper designer choice when glazing may be subjected to the impact of a person. In order to avoid people injuries, glass products must comply with appropriate safety practices. Existing technical standards classify safety glass products by mode of breakage and post-breakage behavior. Critical demanding applications in terms of self-weight saving, like high efficiency elevator cars in buildings or aircrafts and other means of transportation interiors in aerospatial and automotive industries, are currently driving the innovation in the development of safety glass. In this framework, glass-polycarbonate composite panels offer a lightweight alternative which is at once able to preserve the aesthetic and safety aspects of traditional laminated safety glass. The aim of this paper is to present an experimental investigation on the performance under impact of thin glass layer with a cellular polycarbonate backing joined together by an auto-adhesive interlayer film. Different coatings (mirror and paint) at the glass-adhesive interface are also taken into account.

Linking impact-related progeny sizes of cement clinker to modes of single-particle breakage

Fragmentation of particulate solids is an important process in many industrial activities, particularly in the mineral, cement and glass industries to comminute the raw materials to a required size. Understanding of processes and mechanisms responsible for fragmentation of particulate solids is a hard task. This may bring great precision for designing and controlling the comminution process. This work aims to contribute to understanding fragmentation of cement clinker particles under impact loading. For this purpose, six narrow-size classes of Portland clinker were fragmented with varying specific impact energy levels in a drop weight test apparatus. Then, breakage probabilities and functions of these size classes were determined from the product size distributions. The calculated breakage functions show evidences for the modes of breakage (meridian cracks to oblique cracks and shattering) given in the literature. Results of this study indicate that self-similarity of progeny size distributions can only be achieved, regardless of particle size and impact energy, if the particles have the same breakage probability, that is the same mode of breakage.

Cutting performance and life prediction of an Al2O3/TiC micro–nano-composite ceramic tool when machining austenitic stainless steel

The cutting performance and failure modes of an Al2O3/TiC micro–nano-composite ceramic tool in the machining of austenitic stainless steel were investigated. Orthogonal test and range analysis were employed to determine the optimal cutting parameters. The largest metal removal amount was got at the speed of 80m/min, the feed rate of 0.15mm/r and the depth of cut of 0.1mm. The wear resistance of Al2O3/TiC micro–nano-composite ceramic tool were better than that of the alumina-based ceramic tool only reinforced by micro-scale TiC particles. Failure modes of the present tool were cutting edge fracture and tool material peeling off, which mainly resulted from the subcritical crack growth in the tool. The ceramic tool life was predicted based on the dynamic fatigue behavior of the tool material. Due to the inherent fatigue behavior of ceramics, the tensile stress distributing in ceramic tool would cause cracks initiation and promote the cracks extension. The life of ceramic tool for the failure mode of breakage was closely related to the fatigue behavior of the tool material. So, the ceramic tool life could be predicted by calculating the fatigue life of tool material. The stochastic tool life well scattered in the tool life prediction interval.

Symmetry breakage in the vertebrate embryo: When does it happen and how does it work?

Asymmetric development of the vertebrate embryo has fascinated embryologists for over a century. Much has been learned since the asymmetric Nodal signaling cascade in the left lateral plate mesoderm was detected, and began to be unraveled over the past decade or two. When and how symmetry is initially broken, however, has remained a matter of debate. Two essentially mutually exclusive models prevail. Cilia-driven leftward flow of extracellular fluids occurs in mammalian, fish and amphibian embryos. A great deal of experimental evidence indicates that this flow is indeed required for symmetry breaking. An alternative model has argued, however, that flow simply acts as an amplification step for early asymmetric cues generated by ion flux during the first cleavage divisions. In this review we critically evaluate the experimental basis of both models. Although a number of open questions persist, the available evidence is best compatible with flow-based symmetry breakage as the archetypical mode of symmetry breakage.

Evaluation of the Performance Characteristics of Bilayer Tablets: Part I. Impact of Material Properties and Process Parameters on the Strength of Bilayer Tablets

Bilayer tableting technology has gained popularity in recent times, as bilayer tablets offer several advantages over conventional tablets. There is a dearth of knowledge on the impact of material properties and process conditions on the performance of bilayer tablets. This paper takes a statistical approach to develop a model that will determine the effect of the material properties and bilayer compression process parameters on the bonding strength and mode of breakage of bilayer tablets. Experiments were carried out at pilot scale to simulate the commercial manufacturing conditions. As part of this endeavor, a seven-factor half-fraction factorial (2(7-1)) design was executed to study the effect of bilayer tablet compression process factors on the bonding strength of bilayer tablets. Factors studied in this work include: material properties (plastic and brittle), layer ratio, dwell time, layer sequence, first- and second-layer forces, and lubricant concentration. Bilayer tablets manufactured in this study were tested using the axial tester, as it considers both the interfacial and individual layer bonding strengths. Responses of the experiments were analyzed using PROC GLM of SAS (SAS Institute Inc, Cary, North Carolina). A model was fit using all the responses to determine the significant interactions (p < 0.05). The results of this study indicated that nature of materials played a critical role on the strength of bilayer compacts and also on mode of fracture. Bilayer tablets made with brittle materials in both the layers are strongest, and fracture occurred in the first layer indicating that interface is stronger than layers. Significant interactions were observed between the selected factors and these results will provide an insight into the interplay of material properties, process parameters, and lubricant concentration on the bonding strength and mode of breakage of bilayer tablets.

Study on Stability of Consequent Rock Slope by Simulation Experiment

Based on similarity theory, the geologic mechanics model is established and to be used for studying distortion and breakage mechanism of consequent rock slope. The paper introduces the design and process of the experimentation. Through experimentation of a slope model, the stability of a slope is studied. After analyzing the phenomenon and data of the experimentation, it is found that the major deformation model is slippage. The mode of breakage is sliding and fracturing. The process of slippage is graded. The more hinder the position of coast is, the smaller the obliquity of rip face is. The deformation and breakage of bedding slope firstly arises at the dig face near the earth's surface.

Modeling breakage rates in mills with impact energy spectra and ultra fast load cell data

A new era in modeling particle size distribution in grinding mills started at the beginning of 2000s. A direct estimation of breakage parameters became possible via computation of collision energy by discrete element method (DEM) and material breakage data. The material breakage data can be obtained for primary modes of breakage. In this study, impact and abrasion are assumed to be the primary modes of particle breakage, which are readily studied in the laboratory. The impact breakage mode is studied in a drop-weight apparatus and in a specialized device known as the ultra fast load cell. The abrasion mode of breakage is studied in a laboratory scale ball mill. Next, the particle breakage versus energy data is converted into breakage rates via impact energy spectra of the grinding mill computed by a DEM code. The fundamental material breakage information is converted into energy based breakage distribution function. The verification of the modeling concepts is shown for a 90 cm laboratory scale ball mill. In the batch mill, approximately a 10 kg mass of limestone in the 30 mm size is ground with around 100 kg of 50 mm steel ball charge. The breakage rate and the breakage distribution functions constitute the parameters of the energy based batch population balance model. It is shown that accurate particle size distribution predictions are possible with this modeling approach for different grinding regimes.

Analysis of impact damage of agglomerates: effect of impact angle

The effect of impact angle on the breakage of two types of agglomerates of a synthetic detergent formulation is analysed. The agglomerates are in the same size range (0.60–0.71 and 1.00–1.18 mm) with the same formulation but have different structures arising from the processing method. In contrast to previous work reported in the literature for other materials, it is observed that for the types of agglomerates used in this work the extent of breakage increases as the impact angle is decreased from normal in the velocity range tested (15–35 m s −1). Furthermore, when the agglomerates break in the chipping regime, i.e. by surface damage at low impact velocities (less than 15 m s −1), the normal component of the impact velocity determines the extent of breakage independent of the impact angle. However, at higher impact velocities where fragmentation occurs, the role of the tangential component of the impact velocity becomes increasingly important. The difference in the failure mode of agglomerates tested here and those reported in the literature is thought to be the main reason for the dissimilarity. The granules examined here are sensitive to shearing because of the synthetic detergent formulation and their failure is predominantly due to ductile failure, whilst the previous materials fail mainly through brittle and semi-brittle mode of breakage.

Photocatalytic degradation of poly(bisphenol-A-carbonate) in solution over combustion-synthesized TiO 2: mechanism and kinetics

Nano-sized, high surface area TiO 2, synthesized by a solution combustion method, was employed for the photodegradation of poly(bisphenol-A-carbonate) in solution. The products formed during degradation were detected using UV-Vis spectroscopy, FT–IR and GC/MS. The mechanism of breakage during photocatalytic degradation can be attributed to concerted rearrangement (Photo-Fries) and non-concerted cage recombination (oxidation). The degradation was followed by determining the molecular weight distribution using gel permeation chromatography (GPC) and modeled with continuous distribution kinetics. The mode of breakage was purely by random chain scission and showed the presence of weak and strong photodegradable links. The presence of combustion-synthesized TiO 2 catalyst did not alter the degradation mechanism but increased the degradation rates by an order of magnitude compared to the photodegradation rate. However, the presence of commercial Degussa P-25 catalyst did not cause a significant increase in degradation rates compared to the photodegradation rate. The higher photoactivity of combustion-synthesized TiO 2 compared to that of Degussa P-25 for the photodegradation of polycarbonate may be due to reduced band-gap, higher hydroxyl content, higher surface area, nano-size and crystallinity of the combustion-synthesized TiO 2.

Effect of Metal Oxides on Thermal Degradation of Poly(vinyl acetate) and Poly(vinyl chloride) and Their Blends

The role of metal oxides on the thermal decomposition of poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAC) and their blends was investigated by thermogravimetry (TGA). While the degradation of PVAC was mildly affected by the presence of metal oxides, the degradation of PVC was greatly influenced by metal oxides. Both polymers followed a two-step degradation mechanism involving chlorine or acetate radical removal followed by polyolefinic backbone breakage. The isokinetic temperatures and rate determined from the compensation plots indicated that the mode of olefinic backbone breakage is the same for both the polymers. FTIR studies after the first stage showed the disappearance of the C-Cl of PVC and C=O and C-O groups of PVAC, suggesting the formation of a polyolefinic chain. Blends of PVC-PVAC were obtained by solution blending by dissolving the polymers in tetrahydrofuran. Scanning electron microscopy and TGA showed complete miscibility of polymers in the blend. The first-stage degradation of the blend was greatly influenced by the presence of PVC and metal oxides, suggesting that hydrogen chloride liberated from PVC influenced the decomposition behavior of PVAC. The second-stage degradation (olefinic breakage) of the blends was mildly affected by the metal oxides and the breakage was similar to that of pure polymers.

Measurement of the motion of grinding media in a vertically stirred mill using positron emission particle tracking (PEPT)

The application of PEPT has allowed a detailed study of the motion of media in a stirred grinding mill. Further analysis of this motion has identified the main differences between this media motion and the classical theory of motion within fluid mixing. Three regions have been classified within the mill and it was found that the impeller speed altered the relative position of these regions. Three different impellers were also studied which gave different forms of motion. This fundamental knowledge was then applied to the mode of breakage within the mill. Results have shown that the size of these regions influences the breakage process.

Tracer studies and breakage testing in pilot-scale stirred mills

A tracer technique is used to provide parameters that describe mixing and breakage in stirred mills. The results are also used to test the accuracy of mixing and breakage models. Tracer studies have been undertaken using a 39-litre vertical Sala agitated mill and a 4-litre horizontal Netzsch mill. The experimental residence time distribution (RTD) of the mills is analysed both in terms of a single mean residence time and a non-linear least squares fit to an optimal number of perf ect mixers of unequal size in series. Results show a strong dependence of RTD on flow rate, minimal dependence on stirrer speed, and support the concept that the RTD's of liquid tracers and solid tracers subject to breakage are similar. A very accurate match to the experimental RTD curves car be achieved with the multiple uneven mixers in series model. Size distribution results from solid tracer tests are used to determine the breakage characteristics of the pilot-scale Sala mill. The population balance model for a single perfect mixer with steady state hold-up is used as the basis for solution of a constrained non-linear optimisation inverse problem for mill breakage rate and breakage function. Experimental results indicate that the breakage rate is first order as hypothesised. The population balance model using optimal breakage parameters provides a reasonable fit to experimental data for cumulative passing percentage as a function of particle size for discrete times. Both the breakage rates and cumulative breakage functions are roughly power law dependent on particle size. Analysis of the size distribution of breakage products indicates that the mode of particle breakage, as indicated by the tracer breakage parameters, is a function of time. This demonstrates that the assumption of time independent breakage parameters in the population balance model may not be valid. Accurate determination of breakage parameters is strongly influenced by the transport characteristics of the slurry through the mill. The work shows that particle breakage in pilot-scale stirred mills is a complex function of both particle and specific mill characteristics. Therefore, in order to gain insight into the appropriate physical processes at work in an industrial scale mill, it is important to perform experiments with and analyse a system that matches the real mill as closely as possible.

Structure-Property Relationship of Blended Cotton Yarns Made from Low and High Tenacity Fibers

The tensile response of staple yams is usually determined by their structure and the mechanical properties of their constituent fibers. Yarn structure is influenced by the radial disposition of fibers along the yam length, commonly known as migration, and the packing density of the fibers in the yarn cross section. These, in turn, are affected by fiber properties, yarn factors, and the dynamics of preparatory and spinning pro cesses. Yarn structure development is further complicated when the yarn is spun from blends of different fiber types because the blending method usually profoundly influ ences the position and orientation of the fibers in the yam matrix. This investigation is concerned with the effect of fiber properties and yarn structure on the tensile properties of ring spun yarns made from a 50:50 blend of high (Pima) and low (Upland) tenacity cotton fibers spun using intimate and drawframe blending techniques. The drawframe blended yarn in this work is produced by arranging all high tenacity fiber slivers in the center of the drawframe creel to determine if preferential positioning in the core of the yam helps to improve the strength of drawframe blended yarn compared with intimate blended yarns. The findings reveal that intimate blended yam has better tensile strength than drawframe blended yarn, even though more high strength Pima cotton fibers are positioned in the core of the yam. This is because non-uniform fiber distribution re sulting from blending of different fibers affects the migratory behavior of fibers. The tensile failure of such yams is governed by the mode of fiber breakage and fiber slippage as determined by the yarn structure—fiber distribution and migration—rather than predominantly by fiber breakage compared with strength.