Breakage Behavior Research Articles

Discrete element numerical analysis for bearing characteristics of coral sand foundation considering particle breakage

Owing to the construction demands of island and reef engineering, studying the bearing and deformation characteristics of coral sand foundations is significant. This study used the discrete element method to simulate the plate loading test of coral sand foundations based on the actual experiments of coral sand foundations. The particle breakage of coral sand was considered by the fragment replacement method, and the influence of relative compactness on the particle breakage behaviour and compression deformation characteristics of coral sand foundations was analysed. The results show that the compression process of the coral sand foundation undergoes three stages: compaction, shear deformation, and failure. The bearing capacity, deformation modulus, and particle breakage rate of the coral sand foundation increase with the increasing relative compactness, but the growth trends are different significantly at different relative compactness. The numerical analysis indicates when the relative compactness of the foundation increases, the contact force and coordination number would increase, the relative displacement would decrease, causing more particle breakage. This microscopic phenomenon explains why the increasing trend of bearing capacity and deformation modulus of the foundation decreases with the increasing relative compactness.

Investigation on the Influence of the Bit Radius and Impact Velocity on Rock Fragmentation by Discrete Element Method

The bit–rock interaction is a key point in the fracture process observed in excavation applications, which makes its analysis relevant. As the discrete element method (DEM) has been successfully applied to study rock breakage behavior, we apply it in the present study to analyze various aspects of the bit–rock interaction. This research focuses on numerically analyzing the bit–rock interaction, encompassing the force penetration relationship (FPR), mechanical energy transfer to the rock, and the efficiency of the mechanical energy transfer process. In order to perform this analysis, we simulate various bit radii and impact velocities. In this study, we establish a power–law function to describe the relationship between the energy transferred to the rock and the force, both as functions of bit penetration. The least-squares method is employed to accomplish this determination. Remarkably, it was observed that the latter aligns with the Hertzian contact law when lower impact velocities of the bit are employed. Moreover, a bit-radius-dependent optimal velocity for the mechanical energy transfer process was determined, signifying its significance in the design of excavation tools. The primary conclusion drawn from this research is the quantification of the influence of both the bit impact velocity and the bit radius on the force penetration relationship during the bit–rock interaction. This quantification was achieved by employing the coefficients derived from the regression model established for the FPR. These findings hold practical implications for the enhancement of excavation tools’ efficiency during the design phase, thus contributing to advancements in the field of excavation engineering.

Discrete element simulation of the breakage behavior of porous granules utilizing bond models

AbstractIn the development of ships, the aspect of collision safety plays a major role. In this paper, the approach to improve the crashworthiness of ships is to fill the already existing double hull with a granular material. For this purpose, the material used is to be investigated numerically. A discrete element approach is applied for this in the paper presented. Since the breakage behavior of the particles is of particular interest, the discrete element method is used together with a bonded particle method. This approach is extended by a model which is able to take into account the micro-cracks occurring in the material and the energy dissipation caused by them. Using this and other models of the bonded particle method, simulations are carried out and compared with corresponding experiments. A particular focus is on uniaxial compression tests with single particles and particle systems. The single-particle tests are used to determine various simulation parameters relevant to individual particles in terms of geometry and material. In addition, the multi-particle tests provide insight into the behavior of several particles, their interaction and dynamics. These simulations can be used to test the extent to which it is possible to represent porous particles and their fracture behavior by numerical means.

Effect of Intensive Abrasion Breakage on Secondary Ball Mills for Magnetite

In order to investigate the breakage behavior of the feed in industrial secondary ball mills, the breakage characteristics of fine magnetite were analyzed. Magnetite particle breakage produces a bimodal particle size distribution that is consistent with the typical breakage characteristics of abrasion. The secondary ball mill can increase the surface area by reducing the diameter of steel balls to enhance the abrasion. Industrial application results show that after the abrasion of the secondary ball mill for grinding magnetite was enhanced, the circulating load of the grinding-classification system dropped by 29.90% and the specific energy of the secondary ball mill decreased by 39.14%. At the same time, the consumption of steel balls also dropped from 0.17 kg/t to 0.13 kg/t, a decrease of up to 20%. It should be noted that the reduction in the ball diameter should follow certain rules because if the energy of a single collision is lower than the critical breaking energy of the particles, the grinding process will be affected and thus have counterproductive effects.

Analysis of the Influence of Process and Formulation Properties on the Drying Behavior of Pharmaceutical Granules in a Semi-Continuous Fluid Bed Drying System

In the last decade, twin-screw wet granulation became an essential technology for continuous pharmaceutical tablet production. Consequently, interest in (semi-)continuous fluidized bed drying systems as a subsequent processing unit has grown. In parallel, it has become pivotal to fully understand and control manufacturing processes in line with in the quality-by-design paradigm. Formulation-generic prediction models would enormously facilitate digitally enhanced process development and require dedicated experimental data collection and process knowledge. To obtain this knowledge, three experimental campaigns were performed in this work. Firstly, an investigation into the effect of dryer process settings on drying behavior is presented. Secondly, the effect of active pharmaceutical ingredient properties on drying was assessed by producing granules of similar particle size and porosity and evaluating their drying and breakage behavior. Finally, additional experiments with varying active pharmaceutical ingredients and drug load were conducted to increase the genericity of the data set. This knowledge can be used in mathematical process modelling.

Experimental investigation of the impact breakage characteristics between grinding media and iron ore particle in ball mills

The particle breakage of the ball mill is an extremely complicated breakage process. It is difficult to quantify and describe the particle breakage behavior. In this study, a drop-ball experimental setup was developed to demonstrate the impact process of grinding media on ore particles. The quantitative analysis of the effects of particle size, impact energy, and the number of impacts on particle breakage behavior was performed separately. The results show that the breakage probability model and product size distribution model used can be excellent to predict the particle breakage behavior for the single-particle impact experiments. The breakage probability of particles is highly sensitive to impact energy and particle size, exponentially increasing with the increase of impact energy. In addition, the application of the tn-t10 relationship provides a convenient means to characterize and predict the particle size distribution. In multi-layer particle impact experiments, the captured thickness of ore particles is approximately 2 layers during the crushing process. The broken mass of iron ore particles is proportional to the number of concessive impacts at different impact energies. This paper provides theoretical and methodological support for the evaluation and optimization of particle breakage in ball mills.

Sanded Wheel–Rail Contacts: Experiments on Sand Crushing Behaviour

In railway operation, the sanding process is used to overcome low adhesion conditions in the wheel–rail contact. In the literature, previously conducted research has been experimental, e.g., measuring adhesion coefficients (ACs) under different contact conditions (dry, wet, …) or applying different sands. Under dry conditions, sanding can reduce measured ACs, while under wet conditions different types of rail sand can leave ACs unchanged or increase adhesion. Despite active research, the physical mechanisms causing the change in ACs under sanded conditions are still poorly understood. A possible remedy is the development of advanced models of sanding including local effects. As a basis for such a model, this study presents experimental results concerning single grain crushing behaviour of two types of rail sand under dry and wet contact conditions. Firstly, initial breakage behaviour is investigated with focus on the particle fragments’ size and spread as only fragments within the running band are available to influence the AC during roll-over. Secondly, single grain crushing tests are conducted under realistic wheel–rail load showing the formation of solidified clusters of sand fragments, as well as their size and thickness. This information is important for understanding mechanisms and for future physics-based modelling of the sanding process in wheel–rail contacts.

Optimization of Pelleting Parameters for Producing Composite Pellets Using Zeolitic Material From Fly Ash

Zeolitic material in powder form was prepared from fly ash by direct activation treatment. The resulted fly ash-based zeolite was pelletizing and the effect of different inorganic (calcium hydroxide, bentonite, kaolinite) and organic (dextrin) binders with varying percentage was investigated. The zeolitic materials were analyzed by XRF, XRD, SEM, FTIR, TG-DTG and Nitrogen adsorption/desorption isotherm. Compression and impact tests have been used to study the deformation and breakage behaviour of spherical granules. The best performance was obtained by zeolite granular containing 5 wt.% bentonite and 5 wt.% kaolinite with mechanical strength and satisfactory water resistance. The synthesis of pelletized zeolite from by-products derived from coal combustion provides not only environmental and economic benefits, but also contributes to achieving the principles of sustainable development.

Influence of the hydrophobicity of the starch-based coagulant on the coagulation of various pollutants in water and the study of its mechanism

<p indent="0mm">Parts of surface water in China, including some rivers and lakes, show the characteristics of micropollution containing excessive dissolved organic matter, which has become a key factor in restricting the improvement of water quality. Coagulation is one of the most popular technologies in the purification of surface water owing to its low cost and simple operation. However, traditional coagulants, including inorganic and organic synthetic polymer coagulants, usually show a low efficiency in removing organic micropollutants from surface water and pose the risk of secondary pollution. Furthermore, the molecular structures of organic micropollutants contain hydrophilic and a large number of hydrophobic groups. Considering these facts, in this study, starch (St), a natural polymer with the characteristics of environmental friendliness, wide source, and low cost, was used as the raw material and acrylamide and various quaternary ammonium salts containing different lengths of carbon chains were used as modifiers. Accordingly, four modified starch coagulants (CS-DMRCs) with the same charge density and good water solubility but different degrees of hydrophobicity were designed and fabricated using graft copolymerization. Kaolin particles, sodium humate (NaHA), and bovine serum albumin (BSA) were used as the simulated sources of inorganic colloids and different organic pollutants in the micropolluted turbid surface water. The effects of the hydrophobicity of four St-based coagulants on the removal of kaolin particles, NaHA, and BSA from their single, binary, and ternary pollutant aqueous systems were investigated systematically. Based on the apparent coagulation performance, the floc properties, including floc size, compactness, surface morphology, breakage and recovery behaviors, and the zeta potentials of the supernatants after coagulation, the coagulation mechanisms associated with the structural features of the St-based coagulants and treated pollutants were explored and discussed in detail. The St-based coagulants with a higher hydrophobicity showed better coagulation performance owing to the synergistic effects of charge neutralization, bridging flocculation, and hydrophobic association. In addition to these simulated water samples, a real micropolluted turbid surface water sample from the Jiuxiang River of Nanjing was tested and compared with the simulated water samples, further confirming the practicality of the hydrophobically modified cationic St-based coagulants. In summary, CS-DMRCs should have broad prospects in practical applications owing to their easy and simple fabrication and high efficiency in the purification of organic micropolluted turbid surface water.

On single particle breakage behavior of crushable weathered sands

On single particle breakage behavior of crushable weathered sands

Effects of Loading Stress and Velocity on Compression and Particle Breakage Behaviour of Waste Rocks in Backfill Coal Mining

Coal mine waste rocks, mainly broken gangue, can be used as filling materials to backfill into goafs. Under the overburden load, the backfill body is vulnerable to compressive deformation and particle breakage. With the increase in mining depth, the overlying strata will impose different loads on waste rock filling materials at different loading velocities, which further affect the material compressive deformation and particle breakage. In this paper, an experimental scheme and a loading device are designed to study the influence of loading stress and velocity on the compressive deformation and particle size distributions of the backfill materials before and after compression. The results show that the axial strain of the gangue filling materials increases rapidly with the axial stress and then gradually stabilizes, showing a logarithmic functional relationship. Increasing the loading velocity will destroy the contact structures among the gangue particles and cause a larger deformation to the filling materials. When the loading stress is relatively low (5 MPa), the gangue particles with a size larger than 20 mm have a stronger bearing capacity compared with particles of 16–20 mm, which are the first particles to be crushed under these conditions. Further increasing the loading velocity will increase the breakage degree of the filling materials. The breakage ratio (BM) has a logarithmic functional relationship with the loading stress and the loading velocity. When the ground stress is lower than 5 MPa, the content of coarse particles should be increased to enhance the bearing capacity of the gangue materials; when the ground stress is higher than 10 MPa, the content of fine particles should be increased to reduce the porosity ratio and the particle breakage ratio.

Micromechanics and Strain Localization in Sand in the Ductile Regime

AbstractCritical processes including seismic faulting, reservoir compartmentalization, and borehole failure involve high‐pressure mechanical behavior and strain localization of sedimentary rocks such as sandstone. Sand is often used as a model material to study the mechanical behavior of poorly lithified sandstone. Recent studies exploring the multi‐scale mechanics of sand have characterized the brittle, low‐pressure regime of behavior; however, limited work has provided insights into the ductile, high‐pressure regime of behavior via in‐situ measurements. Critical features of the ductile regime, including grain breakage, grain micromechanics, and volumetric strain behavior therefore remain under‐explored. Here, we use a new high‐pressure triaxial apparatus with in‐situ x‐ray tomography to provide new insights into deformation banding, grain breakage, and grain micromechanics in Ottawa sand subjected to triaxial compression under confining pressures between 10 and 45 MPa. We observed strain‐hardening at pressures above 15 MPa and strain‐neutral responses at pressures below 15 MPa. Compacting shear bands and grain breakage were observed at all pressures with no significant variation due to grain size, except for minor increases in breakage in less‐rounded sands. Grain breakage emerged at stress levels lower than the assumed yield threshold and more intense breakage was associated with thinner deformation bands. Contact sliding at inter‐grain contacts demonstrated a bifurcation into a bimodal distribution, with intense sliding within deformation bands and reduced but non‐negligible sliding outside of deformation bands, suggesting that off‐band zones remain mechanically active during strain hardening.

Creep and breakage behavior of broken rock in the caved zone of abundant mines under triaxial compression condition

It is essential to deeply understand the deformation behavior of overburden above the goaf after mining for the ecological restoration of abandoned mines and the reuse of underground space. Due to the large voids and complex structures, the broken rock in the caved zone is sensitive to time effects, and the deformation behavior is the most complicated. Therefore, a self-made broken rock specimen was made which can freely deform in the lateral direction and withstand confining pressure. A series of rheological tests were performed on these specimens under various confining pressures, axial pressures, and gradations. The research results show that the creep behavior of broken rock undergoes decelerated creep or stable creep stages, depending on its level of axial pressure, and there is no accelerated creep stage. Compared with the confining pressure, the axial pressure plays the main role in the creep deformation of the specimen. Moreover, the broken rock gradation of the triaxial creep experiment affects the relative breakage index Br. When the proportion of rock blocks of the original gradation increases with the particle size of each group, the relative breakage index Br is the largest; on the contrary, it is the smallest. The relative breakage index Br is positively correlated with the confining pressure. In addition, a fractional-order creep model for broken rock in the caved zone of the goaf was proposed, and its fitting results are better than those of the classical Burgers model. Based on the proposed fractional-order creep model, a long-term subsidence prediction model of the caved zone after mining is also proposed, which can provide a theoretical basis for the long-term stability analysis of the abandoned mine.

Investigation of breakage behavior and its effects on spray-dried agglomerated whey protein-lactose powders: Effect of protein and lactose contents.

Particle breakage of dairy powders occurs easily during many processes, reducing the powder functionality. The characteristics of particles and the applied stress from processing conditions on the particles are 2 main factors that can be manipulated to reduce breakage. In this study, we explored the effect of whey protein and lactose contents on dynamic breakage in agglomerated whey protein-lactose powders to provide useful information, in terms of particle characteristics, for controlling unwanted dairy powder breakage. A series of model agglomerates with different whey protein:lactose ratios were produced under the same spray-drying conditions, through a pilot plant trial. We evaluated physical characteristics, composition, and structure of samples; analyzed dynamic breakage under different mechanical stresses; and investigated the rehydration and water adsorption properties of model powders before and after breakage. The particle size and irregularity of agglomerates with more lactose was significantly higher than of samples that contained more protein. This resulted in higher particle breakage during dynamic breakage for samples with more lactose. The breakage of agglomerates was affected by the moisture content of powders and fatigue, where particle breakage happens when mechanical loads, lower than the strength of particles, occur multiple times. Breakage changed the morphology and surface composition of particles and decreased particle size. It also decreased the dispersibility of powders and increased the wetting time of wettable samples but decreased the wetting time of powders with poor wettability. Breakage accelerated time-dependent crystallization and decreased the crystallization temperature but did not affect the glass transition temperature of samples. Thus, under the same drying conditions, composition of powders significantly affected breakage, mainly by altering the physical properties of their particles, which resulted in deteriorated functionality.

Liquid flow and breakage behaviors of two liquid jets impacting on the wire mesh with different impinging angles

The flow and breakage behaviors of two liquid jets is of great importance for liquid–liquid mixing and reaction applications. However, the flow behaviors and breakage processes of two liquid jets impacting on the stainless steel wire mesh (SSM) is not clear. In this work, the high-speed photograph method was employed to study the behaviors of two liquid jets impacting on SSM. Effects of impinging angle (2θ), liquid initial velocity (u0), mesh number (M), and liquid jet diameter (D0) on liquid flow and breakage behaviors were investigated. Experimental results showed that the jets of water-water impacting on the SSM were broken into liquid jets and further broken into daughter droplets. The cone angle of dispersion increased with the increase of 2θ, u0, M, and D0, and reached the maximum value of 180°. The average diameter of daughter droplets at 2θ = 90° decreased maximally by 32%, compared with the condition of 2θ = 30°. For two liquid jets of water-n-hexane impacting on the SSM, a liquid sheet was formed. Under different operating conditions, the breakage mode of liquid sheet could be divided into marginal breakup and internal breakup. The breakage model at mesoscale is the result of surface tension and inertia force, both of which are relevant to the complex impact and flow behaviors. The liquid sheet length (Ls) decreased with the increase of u0 and M. A correlation to calculate Ls/D0 was proposed and the calculated results lied within ± 15% of the experimental values. This study provided a theoretical basis for the guidance of mass transfer enhancement and the reactor design with liquid–liquid system.

Fracture behavior analysis of brittle graphite sphere using a special bond model

High-Temperature Reactor–Pebble-bed Module (HTR-PM) takes the spherical fuel element design. Failure or not of fuel sphere would highly affect system operation and nuclear safety. Crush strength of fuel sphere is an important quality control measure, which is mainly determined by the graphite matrix. A bonded particle model (BPM) from discrete element method (DEM) is disclosed, validated, and applied in the fracture analysis of brittle graphite sphere. On the basis of validated BPM, the breakage behavior of nuclear fuel sphere under high-speed impact, that is, dynamic loading, is revealed in detail by a time-marching numerical simulation. This meshfree particle method can be effectively extended to the failure computation of different composite structures (e.g., particle-reinforced metal matrix composite) by defining heterogeneous bonds inside distinct material interface.

Breakage Assessment of Lath-Like Crystals in a Novel Laboratory-Scale Agitated Filter Bed Dryer

Agitated filter bed dryer is often the equipment of choice in the pharmaceutical industry for the isolation of potent active pharmaceutical ingredients (API) from the mother liquor and subsequent drying through intermittent agitation. The use of an impeller to promote homogeneous drying could lead to undesirable size reduction of the crystal product due to shear deformation induced by the impeller blades during agitation, potentially causing off-specification product and further downstream processing issues. An evaluation of the breakage propensity of crystals during the initial development stage is therefore critical. A new versatile scale-down agitated filter bed dryer (AFBD) has been developed for this purpose. Carbamazepine dihydrate crystals that are prone to breakage have been used as model particles. The extent of particle breakage as a function of impeller rotational speed, size of clearance between the impeller and containing walls and base, and solvent content has been evaluated. A transition of breakage behaviour is observed, where carbamazepine dihydrate crystals undergo fragmentation first along the crystallographic plane [00l]. As the crystals become smaller and more equant, the breakage pattern switches to chipping. Unbound solvent content has a strong influence on the breakage, as particles break more readily at high solvent contents. The laboratory-scale instrument developed here provides a tool for comparative assessment of the propensity of particle attrition under agitated filter bed drying conditions.

Understanding the effects of process parameters and material properties on the breakage mechanisms and regimes of a milling process

Milling is an important unit operation used as a particle design process in solid drug manufacturing processes. The size reduction process, where granules break into smaller fragments, governs the operation of the mill. The breakage behavior in a mill can be described through its breakage mechanisms, which are described using the critical screen size, breakage mode, and breakage rate. Breakage mechanisms are important because they determine the output quality attributes of the mill, such as the particle size distribution (PSD) and mass throughput. This study investigates the effect of process parameters and material properties on breakage mechanisms and determines its correlation to the output quality attributes. Additionally, dynamic data was collected and analyzed to determine the effect of process parameters and material properties on the transition of regimes and the evolvement of breakage modes. The findings in this study indicate that stronger granules undergo solely impact-attrition breakage mode, whereas weaker granules first undergo impact breakage mode and then transition into impact-attrition mode. Mass throughput is observed to be higher for impact mode than impact-attrition mode. Moreover, impact mode produces a wide and unimodal PSD, while impact-attrition mode produces a bimodal distribution.

Effect of Saturation on Shear Behavior and Particle Breakage of Coral Sand

Coral sand is the main filling material for the island–reef foundation. Under tidal actions, the saturation (Sr) of coral sand layers varies with the specific depths in the reclaimed foundation. Studying the Sr effect of coral sand’s mechanical behaviors is crucial for the stability of the reclaimed foundation of island–reefs. In this study, a “quantitative injection method” was designed to prepare coral sand with saturation ranging from 90% to 100%, and unconsolidated–undrained (UU) triaxial shear tests were conducted on coral sand under different effective confining pressures (σ3′). The results indicated that the stress–strain curves of coral sand under various conditions were of the strain-softening type. When σ3′ = 200, 400, 600, and 800 kPa, the shear strength of coral sand decreased exponentially by 13.1, 9.1, 16.8, and 15.2%, respectively, with the increase in Sr from 90% to 100%. As Sr rose, the internal friction angle (φ) dropped by 3.77°. The cohesion (c) was not significantly affected by Sr compared to φ. In consideration of the physical susceptibility of coral sand to breakage, relative breakage ratio (Br) and modified relative breakage index (Br*) were introduced to evaluate the particle breakage behaviors of coral sand samples with different Sr levels in the triaxial shear process. It was found that Br and Br* increase linearly with increasing Sr; the effect of Sr on the particle breakage of coral sand weakens significantly when σ3′ is sufficiently large. The median particle size (d50) of coral sand decreases with increasing Sr, and presents a negative linear correlation with both Br and Br*. Based on comparing the strength and particle breakage characteristics of coral sand samples with varying Sr levels, this study suggests that 92.5% should be considered as the Sr value of coral sand available for testing.

The influence of separately and combined bentonite and kaolinite as binders for pelletization of NaA zeolite from coal fly ash

Pelletization of zeolitic materials is required to facilitate their practical industrial and commercial applications. Zeolite-NaA was synthesized from fly ash by the fusion method and shaped into spherical granules. Bentonite, kaolinite, and a combination of bentonite with kaolinite were tested as binders with different contents from 5 to 10 wt%. The pellet formation was optimized. The physicochemical properties of binders, zeolite powder, and zeolite granular were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption isotherm, and scanning electron microscopy (SEM) among other techniques. Deformation and breakage behavior of spherical granulates by compression was also studied. The best performance was obtained by the pellet with 10% bentonite with satisfactory mechanical strength and water resistance. The XRD and SEM results revealed NaA zeolite granular with a typical cubic shape and high crystallinity formed on the surface of bentonite. This result presents a potential use of the coal fly ash to obtain pelletized NaA zeolite following the principles of circular economy and the sustainable development goals (SDGs), particularly SDG 12.