Energy Dissipation Mechanisms Research Articles

Seismic behavior of a novel liftable connection for modular steel buildings: Experimental and numerical studies

Modular steel buildings (MSBs) have achieved considerable popularity in multi-to-high rise constructions due to the favorable mechanical characteristic, eco-friendliness, cost-effectiveness, and enhanced construction efficiency. As the critical part of MSBs, the inter-module connection has an important influence on determining the seismic performance of MSBs. This study presented an experimental-numerical investigation on an innovative fully prefabricated liftable connection (FPLC) for MSBs. To study the seismic performance of the FPLC, quasi-static tests were conducted on four full-scale specimens. The seismic behavior of the specimens, including failure mode, hysteretic response, strength and stiffness degradation, deformation characteristic, etc. was evaluated and compared in detail. The effect of the section of the twin-beams, the dog-bone weakening of the beam and the connecting method between the corner fitting and twin-beams on the seismic behavior of the FPLC was revealed. Moreover, the feasibility for seismic application of the FPLC was evaluated according to Chinese code GB 50,011–2010 and Eurocode 3 Part 1–8. The results indicated that the proposed FPLC met the limit of elastic and elastic-plastic inter-story drift ratios required by GB 50,011–2010. According to Eurocode 3 Part 1–8, the FPLC with welded beams should be classified as “semi-rigid” connections, while the FPLC, whose beams were connected to the column walls by the steel angles and bolts, was classified as a “pinned” connection. Then, a refined finite element model (FEM) was developed and verified by the test results. Furthermore, the verified FEM was utilized to analyze the distribution of the equivalent plastic strain, the stress variation path, and the yielding area of the twin-beams to further reveal the energy dissipation and damage mechanism of the FPLC. Finally, a simplified FEM was established and the comparison with the test results proved its reliability and efficiency. The present study will contribute to provide a comprehensive understanding on seismic performance and design of the inter-module connection for MSBs.

A thermo-mechanical model of the thermal evolution and incorporation of metamorphic soles in Tethyan ophiolites: a case study from Oman

Abstract Ophiolites are remnants of oceanic crust and mantle, now typically found within continental mountain ranges like the Alps. Particularly in areas once part of the Tethys Ocean, ophiolites are often accompanied by narrow stripes of metamorphic rocks, commonly referred to as metamorphic soles. These metamorphic soles typically exhibit peak metamorphic conditions characteristic of either granulite or amphibolite facies. Geochronological studies of Tethyan ophiolites indicate that the development of these metamorphic soles occurred almost simultaneously with the crystallization of the ophiolite’s crustal sequence. Geological evidence also suggests that the metamorphism of the sole rocks took place concurrently with deformation, likely at the same time as the ophiolite’s obduction. In our research, we explore the metamorphic effects of shearing in an ophiolite sequence overlying a crustal sequence. Our findings reveal that strong lithologies like ophiolites can produce additional heat through the dissipation of mechanical energy, which can potentially explain the high temperatures found in metamorphic-sole rocks. In addition, heating-driven softening of the footwall rocks eventually leads to the migration of the active shear zone from the mantle sequence into the upper crustal domain. This migration may be responsible for the metamorphic sole incorporation at the base of the ophiolite. Finally, we demonstrate that stopping the shearing process rapidly cools these rocks, corresponding with the findings from thermochronological studies from Oman ophiolite.

Insight into the fracture energy dissipation mechanism in elastomer composites via sacrificial bonds and fillers.

Most tough elastomer composites are reinforced by introducing sacrificial structures and fillers. Understanding the contribution of fillers and sacrificial bonds in elastomer composites to the energy dissipation is critical for the design of high-toughness materials. However, the energy dissipation mechanism in elastomer composites remains elusive. In this study, using a tearing test and time-temperature superposition, we investigate the effect of fillers and sacrificial bonds on the energy dissipation of elastomer composites consisting of poly(lipoic acid)/silver-coated Al fillers. We found that the fillers and sacrificial bonds mutually enhance both the intrinsic fracture energy and the bulk energy dissipation, and moreover the sacrificial bonds play a more important role in enhancing fracture toughness than the fillers. It is unreasonable to rely solely on the loss factor for bulk energy dissipation. The addition of sacrificial bonds results in a chain segment experiencing greater binding force compared to the addition of fillers. This suggests that the chain segment consumes more energy during its movement. By calculating the length of the Kuhn chain segment and the Kuhn number, it is evident that the addition of sacrificial bonds results in a greater binding force for the chain segment than the addition of fillers, and this enhanced binding force increases the energy consumption during the motion of the chain segment.

A Numerical Study on the Energy Dissipation Mechanisms of a Two-Stage Vertical Pump as Turbine Using Entropy Generation Theory

Utilizing a two-stage vertical pump as turbine (TVPAT) is an economically method for constructing small-scale pumping and storage hydropower stations at high head-low discharge sites, such as underground coal mines. The energy dissipation mechanisms in flow passages are theoretically important for performance prediction and geometric parameter optimization. In this paper, the energy dissipation within the TVPAT has been studied using entropy generation theory, which can be applied to visual, locate and quantify energy dissipation. The numerical solution of entropy dissipation components was extracted on turbine modes in different flow rates using the steady-state single-phase SST k-ω turbulence model. The numerical results show that the energy dissipation in TVPAT mainly comes from turbulent fluctuation (43.6%-72.1%) and blade surface friction (27.8%-58.2%). The runners are the main source of turbulent entropy (SD′ ) generation (47.2%-83.3%). The contribution of the return channel and spiral case to the generation under overload conditions is significant, accounting for 33.6% and 14.3 at 1.3QBEP, respectively. Flow field analysis reveals that high generation within a runner are located in the striking flow region of the leading edge, the flow squeezing region in the blade channel, and the wake region of tailing edge. The mismatch between the placement angle of the blades or guide vanes and the liquid flow angle is an important incentive for SD′ generation. Moreover, hydraulic energy is consumed through the interaction between mainstream and local inferior flows such as separation and vortices, as well as the striking and friction between local fluid and wall surfaces.

Development of an ion gel-based CO2 separation membrane composed of Pebax 1657 and a CO2-philic ionic liquid.

A tough ion gel membrane containing a CO2-philic ionic liquid, 1-ethyl-3-methylimidazolium tricyanomethanide ([Emim][C(CN)3]), was developed, and its CO2 permeation properties were evaluated under humid conditions at elevated temperatures. Pebax 1657, which is a diblock copolymer composed of a polyamide block and a polyethylene oxide block, was used as the gel network of the ion gel membrane to prepare a tough ion gel with good ionic liquid-holding properties. The polyamide block formed a semicrystalline structure in [Emim][C(CN)3] to toughen the ion gel membrane via an energy dissipation mechanism. The polyethylene oxide block exhibited good compatibility with [Emim][C(CN)3] and contributed to the retention of the ionic liquid in the ion gel. The developed ion gel membrane showed a good CO2 separation performance of 1677 barrer CO2 permeability and 37 CO2/N2 permselectivity under humid conditions of 75% relative humidity at an elevated temperature of 50 °C, which corresponds to an exhaust gas from a coal-fired power plant.

Energy dissipation mechanism of tip-leakage cavitation in mixed-flow pump blades

Tip leakage flow is one of the significant factors influencing the internal flow stability of mixed-flow pumps, and in severe cases, it can lead to channel blockage and energy loss. In order to gain a deeper understanding of the energy dissipation mechanism induced by tip leakage vortex cavitation, this study is based on the Wray–Agarwal (WA) turbulence model and the homogeneous flow model, investigating the cavitation flow characteristics of mixed-flow pumps. Additionally, the entropy production theory is employed to evaluate the energy losses within the mixed-flow pump and analyze the components of energy loss in the impeller and guide vanes. The research results reveal that with increasing cavitation intensity, the low-pressure region at the leading edge of the blade extends toward the trailing edge, influencing the static pressure distribution on the blade's pressure side. Leakage flow and the spatial distribution of leakage vortices move closer to the suction side of the blade with increasing cavitation intensity. Cavitation primarily affects the energy losses in the impeller region, with turbulent dissipation being the main source of energy loss. High turbulent dissipation zones are concentrated at the trailing edge of the blade, correlating with recirculation vortices and trailing-edge vortices. This study provides theoretical insights with practical implications for enhancing the cavitation performance of mixed-flow pumps, offering valuable guidance for design and operation.

DETERMINATION OF THE UPPER LIMIT OF THE LOAD-LOADING CAPACITY OF BENDING REINFORCED METAL-COMPOSITE RING PLATES IN CONTACT WITH A LIQUID INCOMPRESSIBLE MEDIUM 1. PROBLEM FORMULATION AND CALCULATION METHOD

The problem of determining the load-bearing capacity of a bendable reinforced annular plate resting on an incompressible liquid base is considered. The internal opening of the structure is closed with a continuous, absolutely rigid insert. The connection between the insert and the plate can be rigid or hinged. The structure is supported on the outer edge, and it is possible to move the support in the vertical direction, for example in the case of a movable jamming. In the limiting state, liquid flow from one front surface of the plate to another surface is not allowed. The materials of the components of the composition are isotropic and rigid-plastic, having the same yield limits in tension and compression. Plastic flow in the phases of the composition is associated with piecewise linear yield criteria (such as the Tresk's or Ishlinsky - Ivlev's yield conditions). The limit state of such a composite plate is described within the framework of the classical theory of transverse bending. Reinforcement structures have axial and radial symmetry. Two reinforcement options are considered: laying two families of fibers along radially symmetrical spiral trajectories and reinforcement in the radial and circumferential directions. The rein-forcing fibers are assumed to be continuous and have constant cross sections along their length, which gives rise to significant heterogeneity of the structures under consideration in the radial direction. The plastic flow of a metal-composition is calculated using a structural model that takes into account the presence of a plane stress state in all substructural elements. Structural formulas have been written that make it possible to determine the coordinates of corner points on piecewise linear yield curves of the compositions under consideration, taking into account their dependence on non-uniform reinforcement parameters: angles and densities. An extremal principle has been formulated that makes it possible to obtain an upper (kinematic) estimate of the maximum load for this type of structure. The formulated problem is discretized along the polar radius. Nodal values of the sagging speed and mechanical energy dissipation were used as unknown grid functions. A numerical algorithm for solving the formulated discretized problem has been developed, based on the application of the simplex method of linear programming theory.

Extreme resilience and dissipation in heterogeneous elasto-plastomeric crystals.

We present a microstructure-topology-based approach for designing macroscopic, heterogeneous soft materials that exhibit outstanding mechanical resilience and energy dissipation. We investigate a variety of geometric configurations of resilient yet dissipative heterogeneous elasto-plastomeric materials that possess long-range order whose microstructural features are inspired by crystalline metals and block copolymers. We combine experiments and numerical simulations on 3D-printed prototypes to study the extreme mechanics of these heterogeneous soft materials under cyclic deformation conditions up to an extreme strain of >200% with strain rates ranging from quasi-static (5.0 × 10-3 s-1) to high levels of >6.0 × 101 s-1. Moreover, we investigate the complexity of elastic and inelastic "unloading" mechanisms crucial for the understanding of shape recovery and energy dissipation in extreme loading situations. Furthermore, we propose a simple but physically intuitive approach for designing microstructures that exhibit a nearly isotropic behavior in both elasticity and inelasticity across different crystallographic orientations from small to large strains. Overall, our study sets a significant step toward the development of sustainable, heterogeneous soft material architectures at macroscopic scales that can withstand harsh mechanical environments.

Revealing the impact of buried interfacial nanostructure in perovskite solar cells

The buried interfacial that usually accompanied by nanoscale void defects has recently been addressed due to its adverse effect on the efficiency and lifetime of perovskite solar cells (PSCs). However, the in-depth understanding of its impact on the fundamental optoelectronic characteristics remains unexplored, especially for the quantitative analysis of efficiency reduction in terms of structural or physical parameter factors, which are challenging for experiment study. Herein, an electro-optical simulation model is established to investigate the effect of buried interfacial nanostructures on device photovoltaic performance. The energy dissipation processes related to photovoltaic parameters were quantitatively identified, in which the optical loss and charge transport loss dominate the drop in short-circuit current and fill factor, respectively, and result in performance degradation. The device optoelectronic performance is further discussed with various factors, including structural (interfacial void size and geometrical shape) and physical (carrier mobility and trap density) factors. We found that the geometrical shape rather than the size of void determines the energy dissipation mechanism, of which specific nanostructures, such as narrow ones, could normally trade off light absorption, carrier transport route, and defect density, being relatively benign to the device performance. Finally, a dielectric filling strategy is proposed to suppress the negative impact of these imperfect nanostructures, which may provide new insights towards device construction engineering for achieving efficient PSCs.

Tunable underwater sound absorption characteristics of 0-3 piezoelectric anechoic coating.

Piezoelectric composite materials (PCMs) with shunt damping circuits are used widely in hydroacoustics because of the flexible adjustability of their parameters. PCMs offer good underwater sound absorption, but shortcomings remain, such as poor low-frequency sound absorption, narrow bandwidth, and a single dissipation mechanism. In this paper, the tunable underwater sound absorption of a 0-3 PCM combined with a cavity structure and shunt circuit (PCMC) is studied systematically. First, the equivalent material parameters of 0-3 PCM are derived based on the Yamada model, and then a theoretical electroacoustic model is established for solving the absorption coefficient and is mutually verified with the numerical simulation method. On this basis, the tunable absorption characteristics of the structure are analyzed. The results show that coupling the energy dissipation mechanism of 0-3 PCM with the acoustic mechanism of the cavity structure not only achieves strong absorption at lower frequencies but also enriches the absorption mode in the mid-high frequencies by connecting the shunt circuits. Moreover, the influence of piezoelectric control variables and acoustic cavity morphology characteristics on structural sound absorption performance is further explored. Finally, the acoustic performance of PCMC is improved further via shape optimization and parameter optimization.

Rate-independent hysteretic energy dissipation in collagen fibrils.

Nanoindentation cycles measured with an atomic force microscope on hydrated collagen fibrils exhibit a rate-independent hysteresis with return point memory. This previously unknown energy dissipation mechanism describes in unified form elastoplastic indentation, capillary adhesion, and surface leveling at indentation velocities smaller than 1 μm s-1, where viscous friction is negligible. A generic hysteresis model, based on force-distance data measured during one large approach-retract cycle, predicts the force (output) and the dissipated energy for arbitrary indentation trajectories (input). While both quantities are rate independent, they do depend nonlinearly on indentation history and on indentation amplitude.

Analysis of thermoelastic dissipation in microbeam resonators covered with multiple partial coatings

Thermoelastic dissipation (TED) is a mechanism for intrinsic energy dissipation that governs the upper limit on microresonators’ quality factor (Q-factor). The demands for high performance and diverse functionality have led to the development of MEMS resonators with increasingly complex structural geometries and materials. This work proposes an analytical framework to evaluate TED behavior in microbeam resonators coated with multiple partial coatings. By determining the one-way thermoelastic coupled equation in the thickness direction, the temperature function is obtained for each region, and TED model is derived by capturing the energy loss of each region within the framework of thermal energy method. The effectiveness of present framework is verified by comparing it with experimental data and finite element method (FEM) results. The developed TED model has an explicit closed-form expression that converges rapidly, and retaining only leading terms yields a simple TED model. Rules for applying the simple TED model to ensure accuracy are discussed. TED behaviors considering finite thermal contact conductance are comprehensively investigated. A methodology for a mixture of multiple partial coatings to suppress TED is proposed. This work is helpful in suppressing the TED and achieving high Q-factors for the microbeam resonators.

Surface-grafting modification of attapulgite nanorods with polysiloxane coupling agents for highly-efficient mechanical and triboelectric performance enhancement of silicone rubbers

The quest for polymeric materials that combine mechanical robustness with high triboelectric charge density is paramount in a novel kind of triboelectric nanogenerators (TENGs) that can directly convert mechanical energy into electricity in a clean and green way. Silicone rubbers (SRs) are one of the most frequently-used triboelectric materials owing to their excellent processability and high tendency of being negatively charged via contact electrification (CE), but their potential can be further maximized by strategic doping with nanomaterials. Herein, we introduced a novel kind of naturally occurring clay mineral attapulgite nanorods with surfaces modified by elaborately-synthesized polysiloxane coupling agents (PCA@ATP) to elevate the mechanical and triboelectric performance of silicone rubbers (SRs) efficiently. The modified SRs not only amplified the tensile strength by over 21 % with the addition of only 4 phr PCA@ATP, but also possessed a significant increase by 40.11 % in triboelectric charge density (ρ(Q)). Moreover, the ρ(Q) of modified SR films showed a continuously increasing trend with a further increase of PCA@ATP content. Particularly, SR films doped with 8 phr PCA@ATP showcased a ρ(Q) enhancement by 59 %, rendering them as exceptional candidates for TENGs. Through rigorous experimentation, we observed that increasing the impact frequency and PCA@ATP content consistently enhanced both the output voltage and current of the SR-based TENGs. In comparison to undoped SR films, doping with 4 phr and 8 phr PCA@ATP resulted in an impressive 122 % and 146.68 % boost in voltage and a 393 % and 508.53 % surge in power, respectively. This highly-efficient mechanical and triboelectric performance enhancement of SRs can be ascribed to the homogeneous incorporation of 1D inorganic nanomaterials PCA@ATPs with high Young's modulus, dielectric constant, and topologically-reinforced interface, leading to a comprehensive improvement of mechanical energy transfer, conversion, storage, and dissipation efficiency. This study presents a pioneering strategy for crafting robust triboelectric materials with superior CE performance, paving the way for more effective mechanical energy harvesting.

The jet composition of GRB 230307A: Poynting-flux-dominated outflow?

ABSTRACT The jet composition of GRB plays an important role in understanding the energy dissipation and radiation mechanisms in GRB physics, but it is poorly constrained from the observational data. Recently, an interesting long-duration GRB 230307A with redshift z = 0.065 has attracted great attention. The lack of detected thermal emission and mini-structure of prompt emission light curve of this burst suggest that the outflow is Poynting-flux-dominated and point towards the ICMART model. In this paper, we invoke two independent methods to investigate the jet composition of GRB 230307A. The high magnetization parameter (σ > 7 or ever large) for R0 = 1010 cm that is used to suppress thermal component, strongly suggests that a significant fraction of the outflow energy is likely in a Poynting flux entrained with the baryonic matter. Moreover, it is found that the radiation efficiency of this burst for typical values ϵe = 0.1 and ϵB = 0.01 can reach as high as $~50{{\ \rm per\ cent}}$ which disfavours the internal shock model, but is consistent with ICMART model. Finally, a possible unified picture to produce GRB 230307A originated from a compact star merger is also discussed.

Emergence of nanoscale viscoelasticity from single cancer cells to established tumors

Tumors are complex materials whose physical properties dictate growth and treatment outcomes. Recent evidence suggests time-dependent physical properties, such as viscoelasticity, are crucial, distinct mechanical regulators of cancer progression and malignancy, yet the genesis and consequences of tumor viscoelasticity are poorly understood. Here, using Wide-bandwidth AFM-based ViscoElastic Spectroscopy (WAVES) coupled with mathematical modeling, we probe the origins of tumor viscoelasticity. From single carcinoma cells to increasingly sized carcinoma spheroids to established tumors, we describe a stepwise evolution of dynamic mechanical properties that create a nanorheological signature of established tumors: increased stiffness, decreased rate-dependent stiffening, and reduced energy dissipation. We dissect this evolution of viscoelasticity by scale, and show established tumors use fluid-solid interactions as the dominant mechanism of mechanical energy dissipation as opposed to fluid-independent intrinsic viscoelasticity. Additionally, we demonstrate the energy dissipation mechanism in spheroids and established tumors is negatively correlated with the cellular density, and this relationship strongly depends on an intact actin cytoskeleton. These findings define an emergent and targetable signature of the physical tumor microenvironment, with potential for deeper understanding of tumor pathophysiology and treatment strategies.

A pseudo-Double-Network Hydrogel Built upon Layered Double Hydroxides with Self-Strengthening Properties.

While great achievements have been made in the development of mechanically robust nanocomposite hydrogels, incorporating multiple interactions on the bases of two demensional inorganic cross-linkers to construct self-strengthening hydrogels has rarely been investigated. To this end, we propose here a new method for the coupling the dynamic covalent bonds and non-covalent interactions within a pseudo double-network system. The pseudo first network, formed through the Schiff Base reation between Tris-modified layered double hydroxides (Tris-LDHs) and oxidized dextran (ODex), is linked to the second network built upon non-covalent interactions between Tris-LDHs and poly(acrylamide-co-2-acrylamido-2-methyl-propanesulfonate) (p-(AM-co-AMPS). The swelling and mechanical properties of the resulting hydrogels have been investigated as a function of the ODex and AMPS contents. The as-prepared hydrogel can swell to 420 times of its original size and retain more than 99.9 wt.% of water. Mechanical tests show that the hydrogel can bear 90 % of compression and is able to be stretched to near 30 times of its original length. Cyclic tensile tests reveal that the hydrogels are capable of self-strengthening after mechanical training. The unique energy dissipation mechanism based on the dynamic covalent and non-covalent interactions is considered to be responsible for the outstanding swelling and mechanical performances.

Energy Dissipation in Tribological Stressed Greases

Lubricating greases that are subject to a continuous friction process are in a non-equilibrium state. In processes far from equilibrium, there is a possibility that dissipative structures will form. In this work, the conjecture is pursued that this is also possible in loaded grease films. On the one hand, the shear process is considered in interaction with structural degradation, and on the other hand, the behavior of energy dissipation mechanisms is investigated. In the two models presented, it is shown that there are conditions under which it is possible to trigger self-organization processes. The next step must be the development of suitable experiments.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper (EWMD) and parallel springs are proposed in this work to enhance the reliability of engineering equipment. The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations (2–7 mm) and impact heights (100–200 mm) are investigated using experimental and numerical methods. The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD, including stiffness softening, negative stiffness, and stiffness hardening. The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage. Under impact loads, the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage (150 mm), resulting in the best impact isolation effect of metallic buffer. However, the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage. Interestingly, quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon. Moreover, with increasing impact loads, the stiffness hardening point progressively shifts to an earlier stage.

Highly stretchable polymer semiconductor thin films with multi-modal energy dissipation and high relative stretchability

Stretchable polymer semiconductors (PSCs) have seen great advancements alongside the development of soft electronics. But it remains a challenge to simultaneously achieve high charge carrier mobility and stretchability. Herein, we report the finding that stretchable PSC thin films (<100-nm-thick) with high stretchability tend to exhibit multi-modal energy dissipation mechanisms and have a large relative stretchability (rS) defined by the ratio of the entropic energy dissipation to the enthalpic energy dissipation under strain. They effectively recovered the original molecular ordering, as well as electrical performance, after strain was released. The highest rS value with a model polymer (P4) exhibited an average charge carrier mobility of 0.2 cm2V−1s−1 under 100% biaxial strain, while PSCs with low rS values showed irreversible morphology changes and rapid degradation of electrical performance under strain. These results suggest rS can be used as a parameter to compare the reliability and reversibility of stretchable PSC thin films.

Numerical and Experimental Investigations of Particle Dampers Attached to a Pipeline System

The structure of pipeline systems is complex, and the working environment is harsh. Under the excitation of the engine equipment foundation and pump fluid, it is easy to generate excessive vibration, which seriously affects the safe operation of the equipment. Particle damping achieves structural vibration suppression through the principle of particle collision dissipation. Due to the drawbacks of traditional pipeline vibration reduction methods, this article introduces a particle damping technology for pipeline system vibration suppression and designs particle dampers based on the structural characteristics of pipelines. We analyzed the energy dissipation mechanism of particle damping, revealed the influence of the materials, structure, external excitation, and other parameters of the pipeline particle dampers on the energy dissipation characteristics of the particle damping, established a pipeline vibration reduction test system with particle damping, and verified its effectiveness in pipeline system vibration reduction. This study can provide a technical reference for vibration reduction in pipeline systems.