Breaking Process Research Articles

Effect of strain rate on specific fracture energy and micro-fracture surface properties of rock specimen under dynamic uniaxial compression

Effects of strain rate on specific fracture energy and micro-fracture surface properties of rock specimen were investigated at strain rates of ∼ 60–115.0 s-1. To achieve this, rock breakage was conducted under dynamic uniaxial compression using the split Hopkinson’s pressure bar. The fracture surface area of fine fragments (<8*10-3m) were measured using gas absorption method while the fracture surface area of large fragments (>8*10-3m) were measured using close-range photogrammetry. Results reveal that fracture surface area and specific fracture energy generally increase with strain rate during rock breakage under dynamic uniaxial compression. Similarly, the total fracture surface area of broken fragments also increased with dissipated energy. Results from scanning electron microscopy showed that fracture surface roughness and macro-crack abundance also increased with strain rate. Following energy requirement for rock breakage into size specifications for engineering applications, strain rate provides a reliable parameter for estimating specific fracture energy and fracture surface area at the forementioned strain rates. Accordingly, optimizing rock breakage processes using strain rate could reduce ore loss and energy wastage associated with production of unwanted fracture surfaces during rock breakage.

Modelling droplet size distribution in inline electrostatic coalescers for improved crude oil processing

Water-in-oil emulsions pose significant challenges in the petroleum and chemical industrial processes, necessitating the coalescence enhancement of dispersed water droplets in emulsified oils. This study develops a mathematical model to predict the evolution of water droplet size distribution in inline electrostatic coalescers (IEC) as a promising means to improve the water separation efficiency of current oil processing systems. The proposed model utilizes the population balance modelling approach to effectively simulate the dynamic and complex processes of coalescence and breakage of droplets in crude oil which directly influence the separation efficiency of the process. The method of classes as an effective mathematical technique is selected to solve the population balance equation (PBE). The accuracy of the model and considered assumptions agree well with experimental data collected from the literature. The results demonstrate the model's ability to accurately simulate droplet coalescence and breakage in emulsified oil while predicting droplet size distribution and water removal efficiency. The electric field strength, residence time, and fluid flow rate significantly influence the coalescence of droplets. At 4 kV and 5 m3/h after 4 s the mean diameter of droplets (D50) and separation efficiency reach the maximum of 94.3% and 432 µm, respectively. The model enables the optimization of operational conditions, resulting in increased performance and reliability of oil-processing systems while reducing the energy consumption and use of chemical demulsifiers. Additionally, utilization of the device in optimized conditions significantly reduces the size and weight of downstream separation equipment, which is particularly advantageous for heavy oils and offshore fields.

Matching of crushed highly decomposed granite particles using 3D SHOT descriptors

Owing to the complex morphology and the fragility of highly decomposed granite (HDG), it is still a challenge to track the breakage process of HDG particles within a deformed sample in geomechanics research. An HDG particle matching method is proposed in this paper for the first time to track and match HDG fragments with their mother particles from which they break off. First, the X-ray micro-computed tomography (μCT) images of HDG particles were acquired from a one-dimensional compression test and a certain number of HDG particles and fragments were selected and reconstructed. Second, the original and fracture surfaces of the fragments were identified and segmented. Then, the essential morphological features of the particles and fragments were represented with the key points. The neighbourhood information around the key points was encoded by the three-dimensional (3D) feature descriptor. Next, the mismatches were filtered out by the random sample consensus (RANSAC) algorithm based on the similarity of the local neighbourhood information. Finally, the influences of several parameters on the matching results were investigated. The capability and efficiency of the HDG particle matching method were demonstrated using the μCT data of ten HDG particles and 32 fragments that resulted from the crushing of these particles.

Yarn breakage detection in ring spinning through ring temperature drop

Yarn breakage or ends-down in ring spinning adversely affects spinning efficiency. An ends-down event may continue for an extended period of time before it is detected and attended to. This study explored a novel approach to detect yarn breakage or ends-down in ring spinning, through changes in ring temperature after an ends-down. Numerical simulation and experimental verification were used to examine the ring temperature changes during the yarn breakage process. The results showed that higher ambient temperature, spindle speed and yarn count (tex) resulted in a higher ring temperature and a longer ring cooling time. But the rate of ring temperature decrease immediately after yarn breakage was quite high, dropping 50% between equilibrium and ambient temperatures in approximately 16 s for most spinning conditions. The model and results of this study offer the basis for a new yarn breakage detection option in ring spinning based on the temperature change of the ring.

Research on high voltage pulse breakage technology. Part 1: The breakdown characteristics of water

As a clean and efficient technology, high voltage pulse breakage technology (HVP) has been widely researched due to its selective advantages. Water is commonly used as the dielectric medium for HVP. The ore particles are crushed in water, and water breakdown plays an important role during the breakage process. Till now, the water breakdown during breakage process has not been concentrated. Research on water breakdown is helpful to optimize HVP. The study consists of three parts. Part 1 deals with the breakdown characteristics of water under HVP. Part 2 focuses on the transformation of the breakdown mode and energy release mechanism during the discharge process. Part 3 deals with the solid breakdown characteristics. In this part, the critical breakdown characteristics and influencing factors were studied, the transformation of the breakdown mechanism was analyzed, the energy conversion efficiency during water breakdown was discussed, and the influence law of ore particles on water breakdown was revealed. The results indicate that: the main influencing factors of water breakdown are the energy stored in the system and the water gap. There is a transition from bubble ignition breakdown to ionization breakdown with increasing voltage. For ionization breakdown, the voltage efficiency is stable at around 80 %, and the energy efficiency is stable at around 65 %. The presence of ore particles affects water breakdown, which is mainly related to the composition of particles.

Spray-evaporation characteristics of n-pentanol/n-dodecane binary fuel at ultra-high injection pressure

The spray and evaporation characteristics of the fuel directly affect the combustion and emission performance of the engine. In this work, the atomization and evaporation characteristics of the n-pentanol/n-dodecane binary fuel were investigated by varying the injection pressure (100–300 MPa). Process of breaking, atomization, evaporation and oil-gas mixing were measured by schlieren technique. The liquid phase length of the spray was measured using the Mie scattering method. Numerical simulations were performed in a constant volume combustion chamber to further investigate the effects of injection pressure. The findings demonstrate that n-pentanol/n-dodecane binary fuel has slightly more liquid penetration than pure n-dodecane fuel, which may be attributed to n-pentanol's higher density. The results also show that the ultra-high injection pressure notably improved the spray penetration and reduced the droplet size that led to fragmentation of the fuel droplets and effectively improved the atomization characteristics. Moreover, a substantial reduction of over 20% in droplet size was observed with the increase in injection pressure from 100 to 200 MPa. However, it has been observed that the reduction in droplet size due to an increase in injection pressure diminishes when the pressure exceeds 200 MPa. In such cases, the size reduction is less than 10%, which implies that the impact of ultra-high injection pressure on size reduction is restricted. Although the impact of ultra-high injection pressure on fuel evaporation under evaporative conditions is limited, it can enhance fuel air mixing performance through intensified turbulence activity within the spray, thereby promoting greater air roll-up.

Study on impact of gap difference on plasma distribution of direct current vacuum circuit breaker with double-break

During the fault current breaking process of a mechanical direct current vacuum circuit breaker (DC VCB) with double-break (DB), the mechanism’s dispersion can result in a gap difference between the two breaks. A DB DC VCB breaking experiment platform is constructed in order to investigate the impact of gap difference on plasma distribution during the DB DC VCB breaking process. During the experiment, a high-speed camera is used to capture the vacuum arcing process at the two breaks under varying gap difference conditions. Then, the arc feature parameters and their variations during the zero-zone process are extracted using image processing techniques, and the distribution patterns of plasma and arc energy at the two breaks are analyzed and compared. When there is no gap difference between the two breaks of the experimental DB DC VCB, there are no significant differences in arc energy and the sizes of high-, medium-, and low-temperature plasma zones between the two breaks. When there is a gap difference between two breaks, the break with the smaller gap has larger high and medium-temperature plasma zones, more concentrated arc energy, higher particle concentration, lower arc diffusion velocity and arc energy decay velocity, and a greater amount of residual plasma after the extinguishing of the arc. When the gap difference exceeds a certain threshold, energy spots appear on the contact surfaces, and a high concentration corridor of residual particles remains between the contacts after the current crosses zero, forming a breakdown weak point that eventually leads to arc re-ignition (hence interruption failure) under the action of transient recovery voltage.

Modeling and simulation study on the ablation characteristics of DC contactor contact

The DC contactor can frequently break the high current control circuit, and the arc motion characteristic in the current breaking process is closely related to its electrical life and reliability. In this paper, a three-dimensional magnetohydrodynamic arc model of the DC contactor considering contact motion and external circuit characteristics is established. On this basis, the influence of the vapor produced by the contact ablation on the arc behavior is studied, and the ablation rate of the cathode in a single breaking process is calculated. The results show that the arc temperature is reduced, the motion speed is slowed down, and the arc burning time is shortened due to the presence of copper vapor produced by ablation. The ablation rate of the cathode during a single arc is 8.9 µg/C.

DEM-based 2D numerical simulation of the rock cutting process using a conical pick under confining stress

Many factors influence rock breakage during cutting processes, including cutting parameters (attack angle, cutting depth and cutting spacing), rock properties and stress conditions. The influence of confining stress on the linear cutting process is currently not well understood. In this study, a 2D discrete element numerical model is developed utilizing DEM software to simulate the linear cutting process of rock using a conical pick. The model accounts for different levels of confining stress to investigate their effect on the cutting process. The numerical model was first validated to ensure its rationality. Subsequently, the rock breakage process under different confining stresses was analysed by observing variations in cutter force, the development of crack extension, particle displacement, velocity variations, and alterations in internal stress. According to the results, the presence of confining stress facilitated the propagation and expansion of cracks within the original rock, particularly along the region where the free surface was present. Subsequently, during the cutting process under different stress conditions, it was observed that as the confining stress increased, the length of radial crack expansion decreased gradually along the tip of the cutter. Under higher stress conditions, a uniform distribution of mostly tensile cracks appeared inside the rock during the cutting process. Additionally, the regression analyses show that average cutting force and specific energy for rock breakage both exhibit an initial increase, followed by a decrease, with increasing confining stress. This indicates that the rock breakage efficiency was high when the confining stress was low and that a high confining stress can instead improve rock cutting. Through these analyses, insights were gained into the mechanisms underlying rock breakage during the linear cutting process using a conical pick under different levels of confining stress. Ultimately, these findings provide valuable knowledge for predicting and optimizing rock cutting processes under different stress conditions.

Key parameters and mechanisms of ice cores autonomously breaking with air reverse-circulation drill systems

In recent years, a new ice-drilling method for continuous coring with air reverse circulation (CCARC) using a rapid air movement (RAM) ice drill system has been proposed that uses a dual-wall aluminum drill pipe. CCARC ice-drilling technology can effectively prevent compressed air circulation losses in snow-firn cover and continuously obtain ice cores using CCARC. When removing embedded ice cores without lifting the drill to the ice-sheet surface, the drilling operation remains uninterrupted; therefore, it can significantly improve the ice core production rate. However, a prerequisite for the realization of CCARC ice drilling is that the core splitter set on the internal surface of the drill bit inner tube can autonomously break ice cores of equal length. To further improve CCARC ice-drilling technology, key parameters such as the horizontal load and lateral displacement required to break ice cores with different diameters and lengths during drilling must be investigated because they are important for ice-coring drilling operations and drill design. In this study, the mechanism, and key parameters of the ice core breaking process under different conditions were theoretically calculated and experimentally measured. Subsequently, the influence of the ice core temperature, diameter, and splitting length on ice core breaking was quantified, and the feasibility of the ice core breaking mode was demonstrated.

Numerical Simulations and an Updated Parameterization of the Breaking Internal Solitary Wave Over the Continental Shelf

AbstractThe breaking of internal solitary waves (ISWs) over slope‐shelf topography induces energy dissipation and enhances mixing. In this work, high‐resolution, laboratory‐scale simulations are employed to investigate the instability mechanisms and dissipation of ISWs. We find that the increasing nonhydrostatic pressure during deformation contributes to an adverse pressure gradient, which induces plunging flow for overturning. Shear instability and convective instabilities trigger wave breaking. Wave‐induced vortexes induce strong shearing and enhance the dissipation of energy by 1–2 orders of magnitude larger than that which occurs under stable conditions. Furthermore, based on laboratory results, we evaluate two commonly used parameterizations (Pacanowski &amp; Philander, 1981, https://doi.org/10.1175/1520-0485(1981)011&lt;1443:povmin&gt;2.0.co;2, i.e., PP81; Klymak &amp; Legg, 2010, https://doi.org/10.1016/j.ocemod.2010.02.005, i.e., KL10) in coarser‐resolution global ocean models by modifying the horizontal resolution from 100 grids every wavelength to approximately 30. The results show that PP81 and KL10 can both improve the estimation of the energy loss, but can only depict strong shear within the pycnocline and bottom boundary regions, respectively. Finally, an updated parameterization is presented that can effectively describe the strong shear in two regions during wave breaking. The flow field and dissipation are more consistent with the laboratory results using the new parameterization. This study improves the understanding of the mixing parameterizations in simulating the continuous processes of strong internal wave breaking.

Fully Nonlinear Evolution of Free-Surface Waves with Constant Vorticity under Horizontal Electric Fields

This work presents the results of a direct numerical simulation of the nonlinear free surface evolution of a finite-depth fluid with a linear shear flow under the action of horizontal electric fields. The method of time-dependent conformal transformation for the description of the combined effects of the electric fields and constant vorticity is generalized for the first time. The simulation results show that strong shear flow co-directed in the wave propagation direction leads to the formation of large-amplitude surface waves, and, for some limiting vorticity value, a wave breaking process with the formation of an air bubble in the liquid is possible. The oppositely directed shear flow can cause the retrograde motion of a surface wave (wave propagation in the opposite direction to the linear wave speed). The simulations conducted taking into account the electro-hydrodynamic effects demonstrate that a high enough external horizontal electric field suppresses these strongly nonlinear processes, and the surface waves tend to preserve their shape.

Probing the electroweak symmetry breaking history with gravitational waves

We perform three dimensional lattice simulation of the electroweak symmetry breaking process through two-step vacuum-like phase transitions with one step being first-order. Our results show that: 1) when the electroweak symmetry breaking is driven by the beyond Standard Model theories through the Higgs-portal, the gravitational wave spectra produced from the phase transitions are of broken power-law shape; 2) when the electroweak symmetry breaking is induced by a first-order phase transition of a high-scale theory respecting the global U(1) symmetry, cosmic strings can form and then decay through particle radiation. The two scenarios can be distinguished through probing the stochastic gravitational wave backgrounds. Our study suggests that the stochastic gravitational wave backgrounds provide an alternative way to probe the beyond Standard Model theories relevant to the electroweak symmetry breaking in the early Universe.

Architectural Strategy Development Through Evaluation of the Spatial Themes Prominent in the Formation of Istanbul's Identity from 1923 to the Present: Proposal of a Model

The core of the study is to capture a commonality between the themes that determine the spatial character of Istanbul and to present the change in the prominent spatial themes from the foundation of the republic to the present and to propose a model for developing an architectural strategy with the help of this change. This change was shaped by spatial preferences, class differences, socio-economic and cultural variables of the period and played a major role in determining the settlement of residences, industry-education-health structures and social areas. The scope of the study consists of the works of leading figures working on the construct ion of the thematic identity of metropolises and urban history. The method of the study consists of literature research that will make these studies and the effective links between them visible, and a data analysis that will provide a breakdown of prominent themes, based on twenty-year periods, and aiming to present the relationships between related thematic words. The findings of the study show that industrialization, housing supply and demand, squatting, socio-cultural life, urban population planning, interaction areas, imported designs and approaches have both an autonomous and interrelated place in the construction of Istanbul's hybrid urban identity. Separate thematic areas such as industrialization and housing trigger processes that directly affect each other's development. As a result, it is seen that the breaking processes of the transformation of the prominent spatial themes in Istanbul offer some forms of association that can provide references for future design products. Sharing comprehensive inferences about these processes with institutions for development and diversification will play an active role in developing new themes that can contribute to Istanbul's urban identity and increasing the agility of relating the current urban identity with contemporary possibilities.

Chemical Inhibition of RPA by HAMNO Alters Cell Cycle Dynamics by Impeding DNA Replication and G2-to-M Transition but Has Little Effect on the Radiation-Induced DNA Damage Response.

Replication protein A (RPA) is the major single-stranded DNA (ssDNA) binding protein that is essential for DNA replication and processing of DNA double-strand breaks (DSBs) by homology-directed repair pathways. Recently, small molecule inhibitors have been developed targeting the RPA70 subunit and preventing RPA interactions with ssDNA and various DNA repair proteins. The rationale of this development is the potential utility of such compounds as cancer therapeutics, owing to their ability to inhibit DNA replication that sustains tumor growth. Among these compounds, (1Z)-1-[(2-hydroxyanilino) methylidene] naphthalen-2-one (HAMNO) has been more extensively studied and its efficacy against tumor growth was shown to arise from the associated DNA replication stress. Here, we study the effects of HAMNO on cells exposed to ionizing radiation (IR), focusing on the effects on the DNA damage response and the processing of DSBs and explore its potential as a radiosensitizer. We show that HAMNO by itself slows down the progression of cells through the cell cycle by dramatically decreasing DNA synthesis. Notably, HAMNO also attenuates the progression of G2-phase cells into mitosis by a mechanism that remains to be elucidated. Furthermore, HAMNO increases the fraction of chromatin-bound RPA in S-phase but not in G2-phase cells and suppresses DSB repair by homologous recombination. Despite these marked effects on the cell cycle and the DNA damage response, radiosensitization could neither be detected in exponentially growing cultures, nor in cultures enriched in G2-phase cells. Our results complement existing data on RPA inhibitors, specifically HAMNO, and suggest that their antitumor activity by replication stress induction may not extend to radiosensitization. However, it may render cells more vulnerable to other forms of DNA damaging agents through synthetically lethal interactions, which requires further investigation.

Catalytic Current Collector Design to Accelerate LiNO3 Decomposition for High‐Performing Lithium Metal Batteries

AbstractLithium nitrate is an attractive lithium additive in the construction of high‐performance lithium metal anodes with a Li3N‐rich solid electrolyte interphase (SEI) layer. However, the eight‐electron transfer process induces high energy barriers between LiNO3 and Li3N. Herein, the inner Helmholtz plane is tuned on a Li deposition host to attain sluggish/rapid LiNO3 decomposition kinetics, resulting in different intermediate content distributions of Li species in the SEI. Notably, lithium oxynitride (LiNO) is identified as the decomposition intermediate, and experimental and simulation results confirm its role in obstructing LiNO3 decomposition. Moreover, the results reveal that the dipole–dipole interaction between LiNO and the polar V≡N bond can change the ionic/covalent character of the N═O bonds, considerably facilitating the energy transfer process of the N═O cleavage, and promoting a LiNO3 reduction to achieve a Li3N‐rich SEI. Consequently, when the electrolyte contains 0.37 m LiNO3, dendrite, and dead Li formation are suppressed effectively with the VN system, and an average Coulombic efficiency of 99.7% over 1000 cycles (1 mA cm−2, 1 mAh cm−2) can be attained. These results can promote the nitride oxidation break process and pave the way for fabricating high‐performance Li3N‐rich lithium metal batteries.

The effects of surfactants on plunging breakers

The effects of surfactants on a mechanically generated plunging breaker are studied experimentally in a laboratory wave tank. Waves are generated using a dispersively focused wave packet with a characteristic wavelength of $\lambda _0 = 1.18$ m. Experiments are performed with two sets of surfactant solutions. In the first set, increasing amounts of the soluble surfactant Triton X-100 are mixed into the tank water, while in the second set filtered tap water is left undisturbed in the tank for wait times ranging from 15 min to 21 h. Increasing Triton X-100 concentrations and longer wait times lead to surfactant-induced changes in the dynamic properties of the free surface in the tank. It is found that low surface concentrations of surfactants can dramatically change the wave breaking process by changing the shape of the jet and breaking up the entrained air cavity at the time of jet impact. Direct numerical simulations (DNS) of plunging breakers with constant surface tension are used to show that there is significant compression of the free surface near the plunging jet tip and dilatation elsewhere. To explore the effect of this compression/dilatation, the surface tension isotherm is measured in all experimental cases. The effects of surfactants on the plunging jet are shown to be primarily controlled by the surface tension gradient ( $\Delta \mathcal {E}$ ) while the ambient surface tension of the undisturbed wave tank ( $\sigma _0$ ) plays a secondary role.

The effect of magnetic field on the electric breakdown trajectory of high‐voltage electric pulse rock breaking

AbstractHigh‐voltage electric pulse drilling technology has the advantages of high rock‐breaking efficiency, low energy consumption for rock breaking, and good quality of well wall, which is a new and efficient potential rock‐breaking method. In this paper, we constructed a numerical simulation model of rock electric breakdown and realized the whole process of rock breaking and plasma channel generation by high‐voltage electric pulse. The results of the study showed that the change of magnetic field has a large influence on the formation of plasma channels inside the rock, and under the self‐magnetic field environment, the plasma channels inside the rock show branching, and the maximum penetration depth and maximum damage depth are higher than those under the non‐magnetic field environment. In the external magnetic field environment, the plasma channels gradually tend to develop “downward” (inside the rock), and the temperature distribution of the plasma channels inside the rock is more concentrated. In the presence of a magnetic field, the speed and degree of freedom of charged particles are limited. In an external magnetic field environment, the charged particles cause fewer particles to deviate, and the particles show a “downward” accumulation phenomenon. The research in this paper can provide certain theoretical and technical guidance for the development of electric pulse rock‐breaking technology and provide reference for the development and parameter optimization of electric pulse rock‐breaking tools.

Snubber Branch Design and Development of Solid-State DC Circuit Breaker

This research proposes a solid-state DC circuit breaker for low voltage DC system based on reverse-blocking IGCT. The circuit breaker topology gets easier as a result of reverse-blocking IGCTs' ability to withstand reverse voltage. To further enhance the breaking process, we develop a snubber branch with metal oxide varistors (MOV) and capacitance. The advantages and disadvantages of three distinct snubber branches-the no-snubber, the resistance-capacitance (RC), and the MOV-C snubber branch-are then contrasted. In addition to suppressing high-frequency oscillation caught by the parasitic MOV parameters, the structure with MOV-C snubber branch also blocks low frequency harmonics brought on by RC snubber branch. Moreover, this structure can slow down the rate at which the voltage rises during the breaking process. Comparatively speaking to the RC snubber branch and no-snubber branch structures, it is more appropriate for solid-state DC circuit breakers. Finally, a solid-state DC circuit breaker prototype based on RB-IGCT and MOV-C branch has been created. The maximum overvoltage is 1.5kV, and the rated voltage is 750V. The maximum breaking current is 10kA, and the rated current can be 2kA.

Determining key features of the operation of percussion downhole drilling machines

Dnipro University of Technology is a leading institution where an authoritative scientific school was formed to solve the fundamental issues of percussive-rotary drilling with the help of hydraulic hammers. This method makes it possible to intensify significantly the mining processes of rock mass breaking. In order to perform the specified function as fully as possible, hydraulic hammers are to work in a certain technological mode and have appropriate technical characteristics; the paper deals immediately with the analysis of those characteristics. The original designs of hydraulic hammers proposed by the authors are distinguished by a high degree of reliability of the interaction of individual parts and assemblies. Simulation of the operation of hydraulic hammers under appropriate mode-parametric support revealed a number of their significant advantages, i.e. in terms of creating effective conditions for rock mass disintegration. It has been proven convincingly that some features of the approaches to the implementation of a hydraulic well washing programme correspond to the stability of a high-quality process of the downhole work of percussion machines. As a result of the research, a composition of some rational formulations of flushing fluids, which contribute to a significant acceleration of the development of destructive processes, was clarified.