Energy Release Research Articles

Numerical and theoretical analysis of multi-pillar instability under elastic beams

With the increase of mining scale and depth, the cascading pillar failure (CPF) disaster has gradually become one of the core technical challenges for safe mining. This paper studies the CPF disaster of multi-pillar (P1-2, P2-3, P3-4 and P4-5) at 848 m level of Alhada Lead-Zinc Mine based on the RFPA2D numerical simulation software and stiffness theory. The numerical simulation results indicate that the load transfer effect induces the domino instabilities of double pillar (P2-3 and P3-4) and double pillar (P1-2 and P4-5), which is characterized by the ‘2 + 2’ compound failure mode. The physical essence of load transfer effect is revealed through numerical simulation, which is the elastic rebound of surrounding rockmass (such as roof-floor). In addition, the theoretical model of rebound overload mechanism of roof-multi-pillar-floor system is established based on the catastrophe theory, and the instability criterion, sudden jump and energy release of roof-multi-pillar-floor system are derived. Finally, the main influencing factors of load transfer effect such as pillar spacing and damage fracture zone are quantitatively analyzed, and the load transfer law shows that the load transfer effect decreases with the increasing pillar spacing and is hindered by the structural plane in the surrounding rockmass.

Enhancing the quality factor of aerosol jet printed RF spiral inductors through gold electroplating

Aerosol jet printing (AJP) outperforms inkjet printing by significantly reducing printed line width, effectively addressing issues such as bulging and surface irregularities. This technology allows for line widths as narrow as 10–100 μm with high aspect ratios, making it well-suited for radio frequency (RF) applications. Consequently, AJP emerges as a valuable tool for direct printing in RF applications. Among conductive inks, silver nanoparticle (Ag-NP) ink is preferred for its straightforward direct printing process and lower sintering temperature requirements. However, the conductivity of printed Ag NP traces falls markedly below that of bulk silver due to significant porosity, limiting its use in RF applications where a high-quality factor is essential. The quality factor of an inductor, indicative of its efficiency in energy storage and release, inversely correlates with its resistance. Our research combines AJP with selective electroplating to reduce the resistance of printed traces, thereby enhancing the inductor’s quality factor for RF applications. We fabricated spiral inductors on alumina substrates using silver NP ink and subsequently applied selective gold electroplating to these traces. This approach led to a significant increase in the inductors’ quality factor, improving it by a factor of 3–5 in the RF frequency range of 100–700 MHz.

Thermal shock triggers microexplosion combustion in graded fuel and oxidizer encapsulation microspheres with improved combustion efficiency

The combustion agglomeration of aluminum (Al) and the long heat and mass transfer distance between Al and oxidizer cause serious two-phase flow loss and slag accumulation in the engine of solid propellants. Here, we present an effective strategy by in-situ encapsulating graded nano-aluminum (nAl) and micron-aluminum (μAl) in ammonium perchlorate (AP) simultaneously by using hydroxymethyl cellulose (HMC) as adhesive and constructing a compact coupling fuel oxidizer complex high-energy microsphere (μAl/nAl@AP/HMC) to enhance the energy release efficiency and combustion efficiency. Compared with physical mixture (PM), the ignition delay time and combustion time of μAl/nAl@AP/HMC microspheres are reduced by 69.58 % and 69.87 %, owing to the decomposition process control of AP through the adsorption and spatial constraint effect on the interface between metal fuels and oxidizer. Furthermore, the nAl embedded in the AP surface forms a hot spot around the μAl to promote the combustion reaction, thereby shortening the cavitation threshold and tensile limit time of μAl and accelerating the occurrence of microexplosion. Microexplosion effect in μAl/nAl@AP/HMC microsphere significantly weakens combustion agglomeration and improves combustion efficiency and energy release efficiency by sharp shrinkage of combustion condensation products, which addresses the challenges on energy output and combustion efficiency in high-density solid propellants.

Characterization of energy dissipation of particle system in high velocity compaction

Energy transmission and dissipation during HVC lead to the uneven pressing force of the powder in the die cavity, which ultimately affects the densification and mechanical properties of powder metallurgy products. This study used the discrete element method (DEM) to monitor the energy transmission and dissipation of the powder system during HVC, investigate the relationship between the dissipation of kinetic energy and the impact energy during the loading stage, and consider the relationship between the strain energy release rate and the impact energy during the unloading stage. The results show that the boundary energy (impact energy) is mainly converted into strain, frictional, and damping energy, of which the kinetic energy is only an intermediate form and its attenuation equation is also obtained. The larger the porosity of the particle system is, the larger the dissipation factor β is, and the more serious the energy dissipation is. It can be found that the release rate of the strain energy gradually decreases with increasing impact energy, and the strain energy is significantly higher than the frictional energy in the green compacts.

Effects of vacuum degree on the detonation characteristics and energy release laws of RDX explosive

To explore the detonation characteristics and energy release laws of RDX explosives under varying degrees of vacuum, the influence of vacuum degree on the fireball characteristic parameters, shock wave propagation laws and detonation performance of columnar RDX charges were studied using the air-blast experiments and AUTODYN simulations, and the fireball temperature distributions were mapped with the colorimetric thermometry technique. The experimental results indicated that as the degree of vacuum increased, the combustion duration and zone area size of the explosive fireball were both extended, while its temperature decay rate was slowed down, making the afterburning effect more pronounced. Furthermore, the peak overpressure and positive impulse of the explosion shock wave showed a downward trend, with the reductions of 56.1 % and 53.5 %, respectively, with the increasing vacuum degree. Numerical simulation was also used to reveal the energy release laws of RDX explosive, and the comparison between the experimental and numerical results showed a good degree of concordance with an average error of 6.45 %. The results of the study could provide a reference for expanding the explosion theory of explosives in plateau environment and improving the performance of explosion-proof equipment.

Experimental study on the damage characteristics of cyclic disturbance and acoustic emission characteristics of different types of sandstones under high stress in deep mines

AbstractThree sandstone specimens common in rock engineering were selected to study the differences in the mechanical properties of rocks with different lithologies. The development and expansion of the internal cracks in the specimens were observed by combining the simulation system with the acoustic emission system. Through the combination of dynamic and static stresses, the deformation and damage of rocks under deep rock excavation and blasting were simulated. As the results show, the acoustic emission events of specimens with different lithologies under combined static and dynamic cyclic loading can be roughly divided into three phases: weakening, stabilizing, and surging periods. In addition, the acoustic emission characteristics of specimens with different lithologies show general consistency in different compression phases. The degree of fragmentation of specimens increases with the applied stress level; therefore, the stress level is one of the important factors influencing the damage pattern of specimens. The acoustic emission system was used to simulate the deformation and damage of rocks subjected to deep rock body excavation and engineering blasting. Cyclic dynamic perturbations under sinusoidal waves with a frequency of 5 Hz, a loading rate of 0.1 mm/min, a cyclic amplitude of 5 MPa, and a loading rate of 0.1 mm/min were applied to the three rock samples during the experiments. Among them, the fine‐grained sandstones are the most sensitive to the sinusoidal cyclic perturbation, followed by the muddy siltstone and the medium‐grained sandstones. On this basis, the acoustic emission energy release characteristics were analyzed, and the waveform characteristics in the damage evolution of the specimen under dynamic perturbation were studied by extracting the key points and searching for the main frequency eigenvalues.

Formation of transverse cracks in cross ply laminates in an environment of nonuniformly distributed fibers

This work is concerned with extracting characteristic features of transverse crack formation in cross ply laminates under axial tension considering nonuniform distribution of fibers in the ply cross section. The fiber-matrix debond crack initiation sites are determined first by the dilatation induced cavitation criterion for an epoxy matrix. The growth of the debond cracks is analyzed by calculating the energy release rates using the virtual crack closure technique. The kink-out of the debond cracks into the matrix is determined in short incremental steps by the maximum energy release rate criterion. Different scenarios are considered for the linking up of the kinked-out cracks to form continuous transverse cracks. By studying two different degrees of fiber distribution nonuniformity, the interactive effects due to the fiber distribution on the transverse crack formation are clarified.

Analytical Solutions for Circular Elastic Membranes Under Pressure

Abstract This study investigates the problem of a circular elastic membrane clamped or adhered at its boundary and subjected to uniform transverse pressure. Many analytical solutions for this classical problem have been developed previously, using either a series-based approach (notably accurate but lengthy and implicit) or approximate kinematics (relatively simple yet lacking accuracy). Here, we seek new analytical solutions using a perturbed spherical cap to represent the shape of the pressurized membrane. Our approach yields simple, explicit solutions of remarkable accuracy for the deformed profile, pressure–deflection relation, strain distributions, and energy release rate, which are directly applicable to emerging ultrathin membrane systems.

Development of a numerical model for disassembly phase of hypothetical core disruptive accident and application to a medium-sized mixed oxide fuelled fast reactor

Safety assessment of fast reactors involves analyzing Hypothetical Core Disruptive Accidents (HCDA) that could result in reactor core disassembly. HCDA is generally analyzed in three distinct phases that include pre-disassembly, disassembly and post-disassembly phases. In the present work, a new coupled neutronics-hydrodynamics computer code called FAst Reactor DISassembly (FARDIS-1) is developed in 2-D cylindrical coordinate geometry to model the super-prompt critical power excursion during the disassembly phase of HCDA in a sodium-cooled fast reactor (SFR). The modelling approach followed is essentially similar to the one used in VENUS-II code but with a few improvements. The code is benchmarked against the predictions of VENUS-II for a sample case of HCDA in the FFTF reactor model. This is followed by an analysis of the disassembly phase in a medium-sized (500 MWe) mixed oxide fuelled fast reactor. Two cases are assumed at the beginning of the disassembly phase: a sodium voided core (conservative) and a partially voided core (realistic) and the influence of several core neutronics parameters on the transients is elucidated through parametric studies. The peak power, thermal energy release, peak pressure, maximum temperature and work-potential are estimated and their trends are discussed.

Biomechanical functions analysis of the Mallard webbed foot: A study of macroscopic and microscopic material assembly and tendon morphology

The mallard webbed foot represents an exemplary model of biomechanical efficiency in avian locomotion. This study delves into the intricate material assembly and tendon morphology of the mallard webbed foot, employing both macroscopic and microscopic analyses. Through histological slices and scanning electron microscopy (SEM), we scrutinized the coupling assembly of rigid and flexible materials such as skin, tendon, and bone, while elucidating the biomechanical functions of tendons across various segments of the tarsometatarsophalangeal joint (TMTPJ). The histological examination unveiled a complex structural hierarchy extending from the external integument to the skeletal framework. Notably, the bone architecture, characterized by compact bone and honeycombed trabeculae, showcases a harmonious blend of strength and lightweight design. Tendons, traversing the phalangeal periphery, surrounded by elastic fibers, collagen fibers, and fat tissue. Fat chambers beneath the phalanx, filled with adipocytes, provide effective buffering, enabling the phalanx to withstand gravity, provide support, and facilitate locomotion. Furthermore, SEM analysis provided insights into the intricate morphology and arrangement of collagen fiber bundles within tendons. Flexor tendons in proximal and middle TMTPJ segments adopt a wavy-type, facilitating energy storage and release during weight-bearing activities. In contrast, distal TMTPJ flexor tendons assume a linear-type, emphasizing force transmission across phalangeal interfaces. Similarly, extensor tendons demonstrate segment-specific arrangements tailored to their respective biomechanical roles, with wavy-type in proximal and distal segments for energy modulation and linear-type in middle segments for enhanced force transmission and tear resistance. Overall, our findings offer a comprehensive understanding of the mallard webbed foot's biomechanical prowess, underscoring the symbiotic relationship between material composition, tendon morphology, and locomotor functionality. This study not only enriches our knowledge of avian biomechanics but also provides valuable insights for biomimetic design and tissue engineering endeavors.

Fatigue failure analysis of U75V rail material under Ⅰ+Ⅱ mixed-mode loading: Characterization using peridynamics and experimental verification

Fatigue failure behavior of U75V rail material under Ⅰ+Ⅱ mixed-mode loading is analyzed and characterized in this work. A fatigue crack propagation experiment was carried out on U75V rail material under mixed-mode loading for R = 0.1. Then, based on the Ordinary State-Based Peridynamic (OSB PD) theory, bond strain rate and bond energy release rate methods were used to characterize the fatigue failure behavior of the rail material. Finally, the simulation results were compared with experimental results in terms of crack propagation length, path and angle to evaluate the characterization effects of both methods. The conclusions were as follows: under single mode I loading, both methods could accurately characterize the fatigue failure behavior of the rail material. However, compared with the bond strain rate method, the bond energy release rate method could provide a more accurate characterization under I + II mixed-mode loading.

Experimental research on the fracture of Laminated bamboo lumber using compact tension specimens based on the net section method and digital image correlation technique

This investigation evaluates the significance of thickness (B) and initial crack length-to-width ratio (α) on the fracture toughness of Laminated bamboo lumber (LBL) compact tension (CT) specimens under mode Ⅰ fracture conditions. The digital image correlation (DIC) technique is employed to analyse the result, while the net section method is utilised to determine the critical strain energy release rate (GIc). The fracture mode observed in LBL is characterised as brittle fracture, and the critical stress intensity factor (KIc) of CT specimens achieved a maximum value of 25.58 MPa·mm1/2. The fracture energy, calculated by the net section method, was determined by analysing the crack extension length (ae) of the CT specimen obtained by the DIC technique. This study aims to establish the mathematical connection between GIc, ae, and critical load (PQ) in terms of the strain energy release rate context, which offers an innovative approach to analysing GIc data of CT specimens subjected to mode I fracture. The calculated value for GIc was determined to be 12.18 J/mm2.

Iron as recyclable metal fuel: Unraveling oxidation behavior and cyclization effects through thermogravimetric analysis, wide-angle X-ray scattering and Mössbauer spectroscopy.

The carbon-free chemical storage and release of renewable energy is an important task to drastically reduce CO2 emissions. The high specific energy density of iron and its recyclability makes it a promising storage material. Energy release by oxidation with air can be realized by the combustion of micron-sized iron powders in retro-fitted coal fired power plants and in fixed-bed reactors under milder conditions. An experimental parameter study of iron powder oxidation with air was conducted based on thermogravimetric analysis in combination with wide-angle X-ray scattering and Mössbauer spectroscopy. In agreement with literature the oxidation was found to consist of a very fast initial oxidation of the outer particle layer followed by much slower oxidation due to diffusion of iron ions through the Fe2O3/Fe3O4 layer being the ratelimiting step. Scanning electron microscopy analysis of the iron particle before and after oxidation reveal a strong particle morphology transformation. This impact on the reaction was studied by cyclization experiments. Up to 10 oxidation-reduction cycles show that both, oxidation and reduction rates, increase strongly with cycling due to increased porosity.

Repair of acrylic/glass composites by liquid resin injection and press moulding

This paper presents repair methods for in-situ polymerised acrylic (Elium®)/glass fibre (GF) composites focusing on mode-I fracture toughness recovery. GF/acrylic composites were first subjected to double cantilever beam (DCB) tests to measure their Mode-I fracture toughness. The delaminated samples after DCB tests were repaired and rejoined. Two repair methods were performed: liquid resin injection and press moulding at two different temperatures (130 °C and 160 °C). The repaired samples were subjected to a second set of DCB tests. The fracture behaviours of the four specimen groups (virgin, resin-injected, pressed at 130 °C, and pressed at 160 °C) were evaluated in terms of strain energy release rates (GIC) during crack initiation and propagation. The results showed that specimens repaired by resin injection exhibited the highest GIC values, about 30 % higher than the virgin state, due to the formation of a semi-interpenetrating polymer network (semi-IPN) at the joining interface. Scanning electron microscopy images provided insight into distinctive fracture behaviours for each test group.

Simulation of emission of the flare 27.04.2012 in spectral lines of Hydrogen, Helium and Calcium

Тhe article is devoted to analyses of solar flare SOL2012-04-27 emission in Hydrogen, Helium and Calcium spectral lines observed on horizontal solar equipment HSFA-2 in Ondˇrejov observatory. The integrated fluxes are calculated. The data collected are treated in the approach of the fast energy release followed by gas evaporation. The gas parameters are calculated with chromosphere conditions and spectral line self-absorption taken into account. Encompassing of six lines allows to reveal the temperature, density and extent of the gas with high degree of validity. The best agreement of the theory with observations is obtained in the model of the spread of inhomogeneous clouds, each of which has hot (T ≈ 18000 ÷ 19500 K) and cool regions (T ≈ 8000 ÷ 9000 K). On average, one cloud gives about ten percent of the total flux.

Clean energy pipeline energy storage system and its economy

The economic problem of a clean energy heating system under a peak and valley electricity pricing system is investigated, and a pipe network energy storage system is correspondingly proposed to solve this problem. The system makes use of large-capacity primary network pipe network water storage to store heat during the valley electricity hours when the electricity price is lower, and releases the stored heat to supply heat during the peak electricity hours when the electricity price is higher, with a view to reducing the operating time of the heating system during the peak electricity hours when the electricity price is higher. The principle of the system and the efficient regulation scheme are given, and a mathematical model of primary pipe network energy storage and release is established, and the reliability of the model is verified with a heating project in Qingdao as an example, and the results show that the maximum temperature deviation of the return temperature of the primary pipe network obtained by the calculation of the energy storage and release model is 0.23°C, and the maximum temperature hysteresis error is in 15%, which meets the requirements of engineering practice. Based on the energy storage model, the simulation of the actual heating economy of the project using the pipe network energy storage system was carried out, and the results showed that compared with the original scheme based on the maximum heat load adjustment of the proportion of heating units and boilers, the electricity consumption of the project using the pipe network heat storage scheme was increased by 18.8% in the whole heating season, the total operating costs were reduced by 14.5%, with an annual saving of 800,600 yuan in operating costs, and the payback period for the investment was relatively short, at 2.1 years, which is of good economy.

Discharge and ignition mechanism of high-entropy alloy induced by crack propagation under quasi-static compressive load

In order to reveal the discharge and ignition mechanism of high-entropy alloy under quasi-static compression load, the stress, potential and ignition evolution process of high-entropy alloy with prefabricated cracks were tested. The atomic structure and dislocation evolution of high-entropy alloy during crack propagation and compression were determined by molecular dynamics simulation, and the discharge mechanism of crack tip was analyzed at the micro level. Based on the calculation of Gibbs free energy, the products in the ignition reaction process were predicted. The results of mechanical/thermal/electrical characteristics induced by compressive load show that the discharge usually occurs near the ignition moment of specimen fracture, and the maximum potential signal can reach 34.2 V. The formation of crack group, crack propagation, local stress concentration, charge accumulation and release at the crack tip jointly induce the generation of discharge signals. With the propagation of cracks, a large number of stacking faults appear and a diamond-shaped failure zone is formed. The increase of disordered atoms leads to fracture. During the compression process, a large number of dislocations induce the separation of charges, which aggravates the discharge at the crack tip. In the Hf-Zr-Ti-Ta-Nb-Cu high-entropy alloy system, the reaction product Ta2O5 is preferentially generated, while in the Ti–Zr-Hf-Cu system, Ti2O3 is preferentially generated. The tip discharge and chemical bond fracture during crack propagation induce ignition, and the chemical bond recombines with energy release.

The excitation of whistler waves and wave-particle interaction in magnetic reconnection

A 2.5D PIC kinetic code is executed to simulate the excitation of electron whistlers and ion cyclotron whistler (L wave) during magnetic reconnection. Our simulation results suggest that quasi-parallel and anti-parallel whistler waves can be excited in the separatrix region near X-Line and in the outflow region, respectively. Electron whistlers play a crucial role in energy release and transfer, as the small mass of electrons allows them to move rapidly under the perturbation of a magnetic field during magnetic reconnection. The L wave excited near the separatrix region far from X-Line, it propagate obliquely to the local magnetic field. Velocity distribution functions (VDFs) indicate that these waves are associated with temperature anistropy instabilities of electron-beams (ion-beam). The electron whistler in the separatrix region is excited by cyclotron resonance due to the electron beam. The electron whistler observed in the outflow region is generated by Landau resonance owing to beam-mode, where the v∥ is close to the phase speed vph of the wave. Regarding L wave, their excitation mechanism is attributed to significant perpendicular temperature anisotropy instability (Ti⊥>Ti∥) of ion-beam, and satisfies cyclotron resonance condition. Meanwhile, our simulation results illustrate that the existence of energy conversion between particles and waves during the wave excitation by using the Wave-Particle Interaction Analyzer (WPIA).

Dynamic mechanical properties and energy release characteristics of Mg-Na-Al alloy under impact load

To investigate the ignition behavior of Mg-Na-Al alloy under impact load and its mechanical properties under different strain rates, the universal testing machine and Separated Hopkinson Pressure Bar (SHPB) experimental system were used to conduct static and dynamic mechanical performance tests of Mg-Na-Al alloy, and the mechanical properties of Mg-Na-Al alloy under different strain rates were discussed. The light gas gun experimental setup was used to launch Mg-Na-Al alloy projectiles and impact rigid target plates to study the energy release behavior of Mg-Na-Al alloy under impact loads. Finally, based on the 12.7mm ballistic gun experimental platform, the penetration of 12.7mm armor-piercing projectiles equipped with Mg-Na-Al alloy wind caps into the homogeneous armor steel plates with a thickness of 15mm, and the ignition test of the oil box behind the steel plates were conducted. The results indicate that the yield strength of Mg-Na-Al alloy under static compression is 265MPa, while under high strain rates (from 2490s-1 to 5640s-1), the yield strength of Mg-Na-Al alloy is 406~423MPa, which is 53%~60% higher than that under quasi-static compression. When reaching a certain impact velocity, the Mg-Na-Al alloy projectile breaks and induces ignition behavior, releasing energy. The 12.7mm armor-piercing projectile equipped with an Mg-Na-Al alloy wind cap penetrated the homogeneous armor steel plate with a thickness of 15mm and ignited. The released energy and the kinetic energy of the fragments ignited the oil box behind the steel plate.

On the limit behavior of lattice-type metamaterials with bi-stable mechanisms

This paper explores 2D lattice-type metamaterials featuring bi-stable unit cells and predefined symmetry configurations. Our investigation delves into the emergence of phase-transition patterns and probes the limit behavior of these lattice arrangements. We develop a macroscale generalized standard material model based on a quasi-convexified free energy framework and validate it through a specific lattice configuration—a 1D chain of bi-stable elements—where the relaxed free energy is analytically derived.To assess the limit behavior of the analyzed lattices, we elucidate the connection between energy release and topology at the microscale. This insight aids in identifying lattice configurations yielding high extrinsic energy dissipation density. We introduce the concept of dissipation efficiency and quantify it across all examined lattices under different loading conditions. Transverse loads prevail in the studied configurations and exhibit a detrimental effect by diminishing extrinsic energy dissipation during metamaterial phase transitions. To facilitate a comprehensive numerical assessment of diverse lattice configurations, we employ a surrogate model of the bistable element. This approach enables an efficient evaluation of sampling volumes constituted by numerous unit cells.