Energy Dissipation Mechanisms Research Articles

Analysis on sound absorption in Sonic Black Holes

Exploration of Acoustic black holes (ABHs) for sound wave manipulation is referred to as Sonic black holes (SBHs). Different from the ideal SBH structure with continuously varied wave propagation boundary formed by putting extensive number of rings inside, the wave trapping and energy dissipation mechanism of practically realized SBH structure with discrete varied wave propagation boundary formed by quite limited number of rings inside are still not clear. To fill the gap, finite element simulations are performed to assess the sound absorption performance of a practical discrete SBH structure and explore the sound absorption mechanism behind. The validity of the FEM results is demonstrated through comparisons with experimental data obtained through impedance tube tests. Analyses reveal that the physical mechanism underpinning the sound absorption of practically realized SBH device is attributed to the combined effects of the ABH-induced wave speed changes, energy trapping and the spatially graded local resonances of series cavities formed by the space between two adjacent rings. While shedding light on the underlying sound attenuation mechanism, studies provide guidelines for further investigations on SBH structures.

A breathable and highly impact-resistant shear-thickened fluid (STF) based TENG via hierarchical liquid-flow spinning for intelligent protection

Impact resistant and force-sensitive yarns are the crucial components of intelligent wearable protective textiles. However, it is still a challenge to combine liquid impact resistant materials with yarns. In this paper, shear-thickened fluid (STF) based hierarchical wrapping core-spun yarns were produced by liquid flow spinning for the impact resistance and intelligent monitoring, which exhibited multi-superiority of protectivity, sensitivity, flexibility, breathability and washability. In terms of protection, STF fabric (STFF) performed improved impact resistance and energy absorption capacity, absorbing 73.5 % of the applied force. Numerically simulation analysis indicated that energy dissipation mechanism of STFF could be ascribed to the combination of the yarn surface deformation and STF core shear thickening of STF yarn (STFY). The STFF was still skin-friendly without breakage and leakage after 10,000 times cyclic friction. Its air permeability was up to 189 mm/s. Moreover, a STFF-based TENG was constructed by weaving with Kevlar yarn, which showed self-powered sensing ability to recognize impact force with great durability over 10,000 cycles. For energy harvesting, the fabric exhibits excellent triboelectric performance of 22 V open-circuit voltage (VOC), 225 nA short-circuit current (ISC), and 30 nC short-circuit transferred charge (QSC). In addition, STF-based TENG fabric enables the sensing of various forces, frequencies and different contact materials. Finally, the early warning, protection, motion monitoring and energy harvesting of STFF for intelligent protective applications were demonstrated, opening new avenues for the sensing function integration of protective textiles.

High Impact Resistance of 2D MXene with Multiple Fracture Modes.

Two-dimensional (2D) transition metal carbides/nitrides (MXenes) are promising nanomaterials due to their remarkable mechanical and electrical properties. However, the out-of-plane mechanical properties of MXene under impact loading remain unclear. Here, particular impact-resistant fracture behaviors and energy dissipation mechanisms of MXene were systemically investigated via molecular dynamics (MD) simulation. Specifically, it was found that the specific penetration energy of MXene exceeds most conventional impact-resistant materials, such as aluminum and polycarbonate. Two kinds of novel energy dissipation mechanisms, including radial fracture and crushed fracture under different impact velocities, are revealed. In addition, the sandwiched atomic-layer structure of MXene can deflect cracks and restrain their propagation to some extent, enabling the cracked MXene to retain remarkable resistance. This work provides in-depth insights into the impact-resistance of MXene, laying a foundation for its future applications.

Quantitative Study of the Weakening Effect of Drilling on the Physical and Mechanical Properties of Coal-Rock Materials.

Coal seam drilling is a simple, economical, and effective measure commonly used to prevent and control rock burst. Following rock burst, coal exhibits significant dynamic characteristics under high strain-rate loading. Our purpose was to determine the physical processes associated with impact damage to drilled coal rock, and its mitigation mechanism. An impact test was carried out on prefabricated borehole coal specimens, and the impulse signals of the incident and transmission rods were monitored. The crack initiation, expansion, and penetration of coal specimens were video-recorded to determine the mechanical properties, crack expansion, damage modes, fragmentation, and energy dissipation characteristics of coal specimens containing different boreholes. The dynamic compressive strength of the coal specimens was significantly weakened by boreholes under high strain-rate loading; the dynamic compressive strength and the dynamic modulus of elasticity of coal rock showed a decreasing trend, with increasing numbers of boreholes and a rising and decreasing trend with increasing borehole spacing; the number and spacing of boreholes appeared to be design parameters that could weaken coal-rock material under high strain-rate loading; during the loading of coal and rock, initial cracks appeared and expanded in the tensile stress zone of the borehole side, while secondary cracks, which appeared perpendicular to the main crack, expanded and connected, destroying the specimen. As the number of boreholes increased, the fractal dimension (D) and transmission energy decreased, while the reflection energy increased. As the borehole spacing was increased, D decreased while the reflective energy ratio decreased and increased, and the transmissive energy ratio increased and decreased. Drilling under high strain modifies the mechanical properties of impact damaged coal rock.

Experimental study on self-centering steel connections based on phased energy dissipation mechanism

Traditional steel beam-column connections and column bases often experience yield or buckling, which makes repair difficult. The recent development of resilient seismic structures has addressed this issue. Resilient seismic structures can achieve self-centering functionality through prestressed steel strands and dissipate energy through energy dissipation elements, while protecting the main components such as beams and columns from damage. This paper presents an experimental study on connections that combine friction and plastic deformation of T-stub to achieve energy dissipation. Four specimens were designed by varying the cross-sectional form of the T-stub flanges and the material of the friction plates. Quasi-static tests were conducted under low-cycle reversed loading to observe the test phenomena. The test results including moment-rotation response, deformation, stiffness, energy dissipation capacity, force of high strength strands and strain were analyzed to investigate the seismic performance of the connections. It was found that weakening the cross-section of the T-stub enabled uniform yielding and energy dissipation. Reducing the friction force between the friction plates and the T-stub web enhanced the self-centering capability while decreased the energy dissipation capacity. Overall, the connections exhibited good seismic performance.

Investigation on energy dissipation mechanism in a double-suction centrifugal pump based on Rortex and enstrophy

Since double-suction centrifugal pumps consume quantities of energy, revealing critical factors for energy dissipation is helpful for energy-saving design. This study aims to investigate the relationship between energy dissipation and vortex based on Rortex method in a double-suction centrifugal pump. Detached eddy simulation was applied to obtain the flow field. Enstrophy was used to present the strength of the local rigid vortex and shear. The results indicate that the local shear dominates energy dissipation in the pump. Owing to jet flows, the energy loss on blade leading edges (LE) and trailing edges (TE) were 102-103 times that of the middle region at 0.4Qd and ten times at 1.4Qd. The energy dissipation on pressure sides (PS) was ten times greater than that on suction sides (SS) at the TE, while flow separation at the middle of SS caused by wake flow increased energy dissipation to nearly ten times that of PS. Jet-wake flow near volute inlet was the dominant factor for energy dissipation at part-load, while separation flows in volute discharge was more significant at overload. The induced high local shear strength was responsible for energy dissipation. Therefore, reducing local shear is a potential energy-saving approach in pumps.

Seismic behaviors of self-centering steel structural joints with phased energy dissipation

To reduce residual deformation in steel moment-resisting frames under seismic actions and facilitate rapid post-earthquake functionality recovery, a self-centering steel structural joint with phased energy dissipation was proposed. This joint achieves self-centering capability through the restorative force provided by prestressing steel strands. Additionally, it employs two energy dissipation mechanisms, namely frictional sliding between the friction plate and the T-stub web and the plastic deformation of the T-stub itself, at different stages to dissipate seismic energy. This approach enables effective phased energy dissipation. Cyclic loading tests were conducted on four full-scale specimens with varying initial prestressing forces of steel strands and bolt pretension. This study obtained seismic performance parameters of the specimens, including hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation. Furthermore, the phased energy dissipation mechanisms of these specimens at different loading stages were investigated. It was found that the loading process of the specimens could be divided into three stages: elastic stage, sliding stage, and strengthening stage. During the elastic stage, the specimens remained closed, with all components in an elastic state. As the loading progressed to the sliding stage, the specimens dissipated energy through frictional sliding between the friction plate and the T-stub web. In the strengthening stage, the primary energy dissipation mechanism of the specimens was the plastic deformation of the T-stub. Moreover, the initial prestressing force of the steel strands had significant influence on the bending capacity and self-centering capability, while the bolt pretension mainly affected the energy dissipation capacity and bending capacity of the specimens.

Dynamic damage and energy dissipation of fiber-reinforced cemented tailings backfill under confinement

ABSTRACT In this paper, the mechanical damage characteristics and energy dissipation patterns of fibre-reinforced cemented tailings backfill (FRCTB) under different strain rates are investigated based on the Hopkinson pressure bar apparatus equipped with confining pressure facilities, and this investigation is conducted by combining the theories of box fractal dimension and energy dissipation. The findings reveal notable observations: under lower confining pressures, the strain rate strengthening effect exhibits pronounced influences on both failure patterns and energy dissipation. However, as the confining pressure escalates, the strengthening effect gradually diminishes. The dissipation energy density displays an increasing trend with the rise in confining pressure, while the energy dissipation rate exhibits a quadratic decline as the strain rate increases. The stress-strain curves of FRCTB, under both unconfined and confined conditions, can be subdivided into four and five distinct segments, respectively. Under the lower confining pressure conditions, the fractal dimension exhibits linear growth with the increasing dissipation energy. As the confining pressure increases, this trend gradually transforms into a cubic function. Remarkably, a strong resemblance emerges between the fractal dimension, energy dissipation rate, strain rate, and confining pressure, reflecting the intricate interplay among these crucial mechanical parameters.

Microcosmic mechanism of metal–organic framework enhanced thermoplastic polyurethane exposed to laser-induced shock wave

Incorporating nano-particles into polymer matrix has enabled improving shock wave mitigation (SWM) ability. Vast majority of researchers adopted inorganic nano-materials to enhance polymer matrix. Due to the incompatibility between inorganic nano-particles and polymers, complicated interface modification processes were often used. Metal–organic frameworks (MOFs) have good compatibility with polymers and show excellent SWM capabilities. However, they are brittle and experience lattice collapse after shock loading. Based on this, thermoplastic polyurethane (TPU) enhanced by zeolitic imidazolate framework-8 (ZIF-8) was proposed and prepared. The mixtures can not only improve the SWM ability of polymers, but also address the brittleness of MOFs. Additionally, scholars often use simulation methods to study energy dissipation mechanism of materials, rarely evidences of microstructural changes observed to support theoretical speculations. In this work, by analyzing surface morphology and molecular structural changes, energy dissipative mechanism was investigated. With addition amount of 5 wt% and 10 wt% ZIF-8 particles in TPU, the pressure can be reduced by 0.074 GPa and 0.1478 GPa than neat TPU. TPUM-10 had a stronger deformation resistance and SWM ability. Moreover, main chemical structures were remained unchanged after shock. The increased ability of SWM may relate to hydrogen bond forming process and delayed material failure.

Dissipation mechanisms of crack-parallel stress effects on fracture process zone in concrete

The effect of crack-parallel stresses on the fracture properties of quasi-brittle materials has recently received significant attention in the fracture mechanics community. A new experiment, the so-called gap test, was developed to reveal this effect. While the finite element crack band model (CBM) with the physically realistic Microplane damage model M7 was quite successful in capturing the damage and fracture during the gap test, some questions remain, particularly the near doubling of the fracture energy at moderate crack parallel compression, which was underestimated by about 30%. Presented here is an in-depth meso-mechanical investigation of energy dissipation mechanisms in the Fracture Process Zone (FPZ) during the gap test of concrete, an archetypal quasi-brittle material. The Lattice Discrete Particle Model (LDPM) is here used to simulate the quasi-brittle material at the mesoscale, which is the length scale of major heterogeneities. The LDPM can capture accurately the frictional sliding, mixed-mode fracture, and FPZ development. The model parameters characterizing the given mix design are first calibrated by standard laboratory tests, namely the hydrostatic, unconfined compression, and four-point bending (4PB) tests. The experimental data used characteristic of the given mix design are calibrated by the Brazilian split-cylinder tests and by gap tests of different sizes with and without crack-parallel stresses. The results show that crack-parallel stresses affect not only the length but also the width of the FPZ. It is found that the energy dissipation portion under crack-parallel compression is significantly larger than it is under tension, which is caused by micro-scale frictional shear slips, as intuitively suggested in previous work. For large compressive stresses, the failure mode changes to inclined compression-shear bands consisting of axial splitting microcracks. Several complications experienced in the numerical modeling of gap tests are also discussed, and the solutions provided.

An energy dissipation metamaterial based on Coulomb friction and vibration

Compared with traditional energy dissipation structures, negative stiffness metamaterials can repeatedly dissipate energy without incurring irreversible plastic deformation. The existing negative stiffness structures are generally multistable, and their energy dissipation mechanism is either through internal component vibration or friction. In this paper, a self-recoverable negative stiffness structure was proposed which can dissipate energy through both vibration and Coulomb friction. The structure consists of an external I-shaped structure and a buckle-like structure composed of a plug and cantilever beams inside. The proposed structure achieves monostable characteristics by utilizing the concept of self-contact. To investigate the mechanical properties, quasi-static loading-unloading experiments were performed and verified using finite element simulation. The energy dissipated in the proposed structure by vibration and friction was quantified theoretically. The influence of geometric parameters on energy dissipation was studied using simulation and analytical methods. This type of metamaterial has the potential to be employed in the production of multi-functional metamaterial structures such as deformable robots or reusable bumpers.

Time-dependent mechanical behavior of tough hydrogels under multiaxial stretching

ABSTRACT Understanding the time-dependent mechanical behavior of tough and viscoelastic hydrogels under complex external loading is crucial. In this study, we utilized tough and viscoelastic hydrogels synthesized through the copolymerization of methacrylic acid and methacrylamide as a model system to investigate their mechanical behavior under multiaxial stretching across a wide range of strain rates. Three stretching modes examined were uniaxial, pure shear, and equal biaxial stretching. Our findings show that under equal biaxial stretching, the hydrogels exhibit higher mechanical properties and energy dissipation compared to uniaxial and pure shear stretching, owing to the greater contribution of hydrogen bonds to energy dissipation in the former stretching mode. Additionally, employing the time-elongation separability method during the stretching process, we observed that the relaxation of dynamic hydrogen bonds in the hydrogels only depends on stretching time, independent of the elongation ratio and stretching modes. We anticipate that this study will yield valuable contributions to the design of durable load-bearing soft materials, particularly in dealing with complex deformation and strain rate responses.

Bimetallic Zeolitic Imidazole Frameworks for Improved Stability and Performance of Intrusion-Extrusion Energy Applications.

Hydrophobic flexible zeolitic imidazole frameworks (ZIFs) represent reference microporous materials in the area of mechanical energy storage, conversion, and dissipation via non-wetting liquid intrusion-extrusion cycle. However, some of them exhibit drawbacks such as lack of stability, high intrusion pressure, or low intrusion volume that make them non-ideal materials to consider as candidates for real applications. In this work, we face these limitations by exploiting the hybrid ZIF concept. Concretely, a bimetallic SOD-like ZIF consisting of Co and Zn ions was synthesized and compared with Co-ZIF (ZIF-67) and Zn-ZIF (ZIF-8) showing for the first time that the hybrid ZIF combines the good stability of ZIF-8 with the higher water intrusion volume of ZIF-67. Moreover, it is shown that the hybrid-ZIF approach can be used to tune the intrusion/extrusion pressure, which is crucial for technological applications.

Unravelling the fluorescence kinetics of light-harvesting proteins with simulated measurements

The plant light-harvesting pigment-protein complex LHCII is the major antenna sub-unit of PSII and is generally (though not universally) accepted to play a role in photoprotective energy dissipation under high light conditions, a process known Non-Photochemical Quenching (NPQ). The underlying mechanisms of energy trapping and dissipation within LHCII are still debated. Various models have been proposed for the underlying molecular detail of NPQ, but they are often based on different interpretations of very similar transient absorption measurements of isolated complexes. Here we present a simulated measurement of the fluorescence decay kinetics of quenched LHCII aggregates to determine whether this relatively simple measurement can discriminate between different potential NPQ mechanisms. We simulate not just the underlying physics (excitation, energy migration, quenching and singlet-singlet annihilation) but also the signal detection and typical experimental data analysis. Comparing this to a selection of published fluorescence decay kinetics we find that: (1) Different proposed quenching mechanisms produce noticeably different fluorescence kinetics even at low (annihilation free) excitation density, though the degree of difference is dependent on pulse width. (2) Measured decay kinetics are consistent with most LHCII trimers becoming relatively slow excitation quenchers. A small sub-population of very fast quenchers produces kinetics which do not resemble any observed measurement. (3) It is necessary to consider at least two distinct quenching mechanisms in order to accurately reproduce experimental kinetics, supporting the idea that NPQ is not a simple binary switch.

Aromatic Donor–Acceptor Charge‐Transfer Interactions Reinforced Supramolecular Polymer Electrolyte for Solid‐State Lithium Batteries

AbstractPolymer electrolytes have great potential to realize solid‐state lithium metal batteries with high energy density and intrinsic safety. However, the poor mechanical strength and uncontrolled electrolyte/electrode interface cannot guarantee the stable operation during long‐term cycling. Herein, a supramolecular polyurethane material reinforced by aromatic charge‐transfer interactions is synthesized as electrolyte matrix with high stiffness, excellent toughness, and unique mechanical energy dissipation capacity. The optimized electrolyte network can dynamically adapt to the volume fluctuating Li metal and, importantly, eliminate stress‐concentrating behavior under deformed state. As a result, the Li/Li symmetric cells can stably work for more than 3500 h without short circuit. And the LiFePO4/Li batteries show superior electrochemical performance over 1200 cycles with a capacity retention of 95.4% at 0.33 C. The supramolecular approach to tune the mechanical properties of the polymers is believed to provide a new strategy for designing solid electrolytes with desirable comprehensive mechanical properties for solid‐state batteries.

The Vibration Attenuation Characteristics of Dynamic Vibration Absorbers Array for Tuned and Mistuned Bladed Disk

Abstract Dynamic vibration absorbers array (DVAA) is a newly developed and promising technique for vibration attenuation of integrally bladed disk (blisk) by mounting underneath the disk. In this paper, the vibration attenuation characteristics and energy dissipation mechanism of DVAA for tuned and mistuned blisk are parametrically studied, where the viscous and frictional damping are both considered. The lumped parameter model of a blisk is employed for the convenience of parametrical study. Analytical power flow formulas within the blisk–DVAA system are derived to characterize the dynamic interaction between blisk and DVAA. Four typical modes of a blisk with different nodal diameters and deformation characteristics are selected to evaluate the performance of DVAA. Then, the effects of the mass ratio, the frequency ratio and the damping ratio of DVAA on the vibration of tuned and mistuned blisk are addressed. Numerical results show that a light DVAA can significantly mitigate the resonant amplitudes of the tuned and mistuned blisk. Such damper is effective for the modes with different modal characteristics and can provide robust vibration attenuation performance against random mistuning.

Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels (FSP) under high-velocity impact using the explicit non-linear finite element method. Based on the geometric topology of the FSP system, three FSP configurations with the same areal density are derived, namely multi-layer, gradient core and asymmetric face sheet, and three key structural parameters are identified: core thickness (tc), face sheet thickness (tf) and overlap face/core number (no). The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity (BLV), deformation modes, energy dissipation mechanism, and specific penetration energy (SPE). The results show that the FSP system exhibits a significant configuration dependence, whose ballistic performance ranking is: asymmetric face sheet > gradient core > multi-layer. The mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP system. Both BLV and SPE increase with tf, while the raising tc or no leads to an increase in BLV but a decrease in SPE. Further, a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis, based on which the ballistic optimization procedure is also conducted and a design chart is established. This study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

THE INFLUENCE OF CORAL REEF SPUR AND GROOVE MORPHOLOGY ON WAVE ATTENUATION

Wave energy dissipation on coral reefs provides protection from coastal hazards to over 200 million people globally (Ferrario et al. 2014). The mechanisms of wave energy dissipation over the complex morphologies of the fore-reef slope have typically been overlooked (Duce et al. 2016). Here we focus on wave attenuation by the elongated troughs and depressions typical of fore-reef slopes known as spurs and grooves (SaGs).

Change of Spectral Properties of Magnetic Field Fluctuations across Different Types of Interplanetary Shocks

The interaction between interplanetary (IP) shocks and the solar wind has been studied in the past for the understanding of energy dissipation mechanisms within collisionless plasmas. Compared to the study of fast shocks, other types of IP shocks, including slow mode shocks (i.e., fast forward, fast reverse, slow forward, and slow reverse shocks) remained largely unnoticed. We analyze magnetic field fluctuations observed by the Wind spacecraft from 1995 to 2021 upstream and downstream of the IP shocks using a continuous wavelet transform. The evolution of spectral indices in the ion inertial and transition ranges and the changes in distributions of characteristic ion length scales with respect to the spectral break and proton beta are presented. We found that spectral indices in both inertial and transition ranges and the characteristic length scale distributions are statistically conserved across three types of IP shocks, suggesting that mechanisms associated with the energy dissipation are unaffected by the shocks. The results obtained for the transition range of fast reverse shocks show a larger difference between upstream and downstream plasmas and this will be further studied.

Experimental Investigation of the Relationship of Failure Mode and Energy Dissipation in Grouted Rockbolt Systems under Pullout Load

In underground engineering, the deformation of surrounding rock caused by “three heights and one disturbance” leads to the failure of grouted rockbolt systems, which causes huge economic losses to the mining industry. The research shows that the failure process of grouted rockbolt systems is the result of energy accumulation and release, but the relationship between failure mode and energy dissipation is rarely studied. Based on this, the load transfer behavior, energy dissipation, failure mode and failure mechanism of the grouted rockbolt systems are investigated from the perspective of energy in this study using the indoor pullout test. Test results show that the load decreases rapidly, and the absorbed energy decreases due to the whole-body splitting crack. The absorbed energy of the specimen in the splitting crack mode is lower than that in the pullout failure mode. When the pullout load reaches its peak, the pullout load of the specimen with split failure mode decreases sharply. Meanwhile, the load of the specimen with pullout failure mode is relatively slow, and the energy absorption rate decreases gradually due to the occurrence of cracks. However, the reduction in the energy absorption rate under pullout failure is lower than that under split failure. The radial pressure in the grouted rockbolt systems increases due to the wedge action. When the radial pressure exceeds the tensile strength of concrete, the specimen will experience split failure, otherwise pullout failure will occur.