Energy Dissipation Mode Research Articles

Experimental Study on Repairing and Strengthening Seismically Damaged RC Frames by Installing H-Shaped Steel

Seismic disaster investigations worldwide have revealed that a large number of reinforced concrete (RC) frame structures have been damaged or even collapsed. However, most of these buildings exhibit minor or moderate damage and can be repaired and strengthened. “Strong columns and weak beams, strong joints and weak components” is the concept of seismic design of buildings, and the failure of beam–column joints and columns is considered nonideal. For RC frame structures with damaged joints and columns, a method for repairing and strengthening damaged frames by installing H-shaped steel and pouring grout is proposed. By applying a pseudo static load, a frame structure specimen was damaged to simulate earthquake damage. After removing the crushed concrete, the damaged frame was repaired by pouring grout. Then, the structure was further strengthened by installing H-shaped steel on the columns using post-installed anchors. Through loading tests, seismic indices such as strength, deformation capacity, energy dissipation and failure mode of the frame before and after strengthening were compared. The results showed that the seismic performance of the repaired and strengthened frames exceeded that of the original frame, and the failure mode of the frame changed from joint shear and column-end bending to ideal beam-end yielding. Installing H-shaped steel and pouring grout could effectively strengthen the damaged frame, which provides a solution for repairing and upgrading damaged RC framed structures with a nonideal failure mode.

Seismic performance and failure mechanisms evaluation of multi-story elliptic and mega-elliptic bracing frames: Experimental and numerical investigation

In recent decades, researchers have evaluated the seismic performance of the innovative Elliptic-Braced Resisting Frames (ELBRFs) only in single-story single-span configurations. Although numerical studies have investigated the behavior of multi-story ELBRF configurations, the lack of laboratory data has cast doubt on the reliability of these numerical results. To address this gap in knowledge, this article evaluates the seismic performance and failure mechanisms of multi-story ELBRFs through a laboratory program and compares them with a developed type of this bracing system known as Mega Elliptic-Braced Resisting Frames (MELBRF). The key contribution of this research is the provision of laboratory test data for multi-story ELBRF and MELBRF systems, which can be utilized to validate numerical models and investigate their seismic characteristics. In this study, laboratory tests are used to examine the cyclic behavior and to calculate parameters such as strength, ductility, stiffness, energy dissipation, seismic performance, and failure modes in multi-story specimens. To this end, an experimental test of a 1/6 scale single-span four-story ELBRF specimen and a two-span four-story MELBRF specimen under cyclic quasi-static loading was conducted. Next, the seismic behavior of the proposed specimens is compared with other types of bracing systems such as X-, V-, Inverted-V, Two-Story X-, and Two-tiered diagonal braced frames in a story-base model under cyclic quasi-static loading through nonlinear FEM analyses. The results indicated that the yielding of elliptic braces would delay the failure mode of adjacent elliptic columns and thus help tolerate significant nonlinear deformation to the point of ultimate failure. The response modification factor in ELBRF and MELBRF is 7.3 and 6.5, respectively. Symmetrical behavior, high energy absorption, appropriate stiffness, and high ductility in comparison with conventional systems are some of the advantages of the proposed systems.

Influence of GUP corrected Casimir energy on zero tidal force wormholes in modified teleparallel gravity with matter coupling

In recent times, the study of the Casimir effect in quantum field theory has garnered increasing attention because of its potential to be an ideal source of exotic matter needed for stabilizing traversable wormholes. It has been confirmed through experimental evidence that this phenomenon involves fluctuations in the vacuum field, leading to a negative energy density. Motivated by the above, we have investigated Casimir wormholes with corrections from the Generalized Uncertainty Principle (GUP) within the framework of matter-coupled teleparallel gravity. Our analysis includes three well-known GUP models: the Kempf, Mangano, and Mann (KMM) model, the Detournay, Gabriel, and Spindel (DGS) model, and a third model called Model II. For a broader analysis, we have considered two well-known model functions for the teleparallel theory: a linear f(T,T)=αT+βT and a quadratic model f(T,T)=ηT2+χT. The shape function solutions corresponding to both models are examined in the absence of tidal forces in spacetime. We also demonstrate the crucial role played by the parameters of the f(T,T) models in the violation of the energy conditions. With the increasing interest in detecting gravitational waves from astrophysical objects, we have thoroughly discussed the perturbation of the wormhole solutions in the scalar, electromagnetic, axial gravitational, and Dirac field backgrounds. We employ the 3rd order WKB expansion to find the complex frequencies associated with the quasinormal modes of energy dissipation. Additionally, we also calculate the active mass and total gravitational energy for the wormhole geometry. The amount of exotic matter involved in sustaining these wormholes is also found in this paper. Furthermore, the physical stability of such Casimir wormholes is examined using the Tolman–Oppenheimer–Volkoff equation.

Spectro-spatial analysis of van der Pol-type phononic crystals

Abstract The application of phononic chains as metamaterials demonstrates their remarkable capability to manipulate the propagation of waves. These periodic structures yield frequency-dependent behavior of material comprising characteristics with many possible engineering applications. In this paper, we investigate the weak and general nonlinear behaviors of the van der Pol-type damped phononic chains. The analysis of wave propagation is initially conducted for a one-dimensional structure, and subsequently, is extended to consider the wave motion through two-dimensional and three-dimensional lattices. Results are obtained using the method of multiple scales and a Spectro-spatial analysis by employing the numerical method of the 4th-order Runge–Kutta. A new phase-diagram relation within the chain’s unit cell is also introduced aiming to enhance the numerical findings. Our results indicate that in the weakly nonlinear regime, the van der Pol-type damping closely follows the linear dispersion curve, regardless of the initial amplitude. This suggests a symmetry between energy pumping and dissipation modes, where hardening and softening behaviors align with linear characteristics of common damping mechanisms, such as viscous damping. Additionally, the formulation demonstrates the existence of limit-cycle stability in the motion of each mass. For the general damped system, it is observed that a special frequency exists where the system converges, for all wave numbers similar to the synchronization effect. Hence, the motion and the frequency of all masses are synced. Additionally, non-reciprocal wave propagation is observed, resulting in a bandgap structure with a symmetry breaking occurring near the limit cycle. These results are promising in the fields of wave emitters, wave filters, and signal encryption.

Anomalous size effect of impact resistance in carbon nanotube film

Dynamic mechanical behavior and size-related impact resistance of CNT films are studied by employing laser-induced projectile impact test (LIPIT) and coarse-grained molecular dynamics (CGMD) simulation. The energy dissipation mechanisms of the CNT films are investigated via CGMD simulations. An evident anomalous thickness-dependent effect is directly observed in the experiment, consistent with simulation phenomena. The mechanisms underlying this anomalous thickness-dependent effect are investigated at the atomic scale. The disparities between experiments and simulations are discussed. Our analysis of energy dissipation modes, deformation behaviors during impact, and impact area reveals that kinetic energy change predominantly governs the deformation mode. Meanwhile, a plugging failure mode near the exit face of CNT film is identified at high impact velocity (∼160 m/s), leading to a deterioration in impact resistance and a corresponding reduction in SEA with increasing CNT film thickness. These findings provide a feasible strategy for the protection design of CNT film in broaden protective application scenarios.

Experimental analysis of the cyclic behavior of rammed earth walls reinforced with arundo donax natural fiber

This experimental study analyzes the seismic behavior of rammed earth walls with Arundo donax natural fiber inclusions, also called "caña brava” (REWC), and without inclusions (REW). The experimental program consists of two stages: physical and mechanical characterization of materials, where properties such as particle size, density, Atterberg limits, and compressive and flexural strength were determined; and dynamic tests, which included compressive and cyclic load tests on REW and REWC walls. The walls were subjected to cyclic loading with derivatives between 0.2 % and 1.4 % in-plane combined with a constant vertical compressive stress of 13 kPa to simulate seismic forces in the presence of gravity loads. The results regarding loading, hysteretic response, energy dissipation, stiffness degradation, and failure mode are compared. In addition, the envelope curves of the load-displacement hysteretic responses are analyzed using a capacity spectrum approach. It is observed that the inclusion of Arundo donax natural fiber negatively affects the mechanical properties of the walls and their hysteretic response. It is also observed that the energy dissipation is affected by the inclusion of Arundo donax natural fiber. However, the stiffness behavior is similar in all the walls. Rigid body failure modes are identified in all the walls, but the walls, including Arundo donax natural fiber, form failure planes that divide the wall into two bodies.

An experimental and numerical analysis of slit plate as replaceable fuse in moment resisting frame

This study contributes to the ongoing progress in developing cost-effective structural fuse solutions for steel structures, emphasizing enhanced strength, ductility, and energy dissipation capacity. These fuses are strategically placed to coincide with plastic hinge locations under lateral load. During minor seismic events, they provide substantial rotational stiffness, while during medium to large earthquakes, they leverage their post-yield strength for effective energy dissipation. Three varieties of beam-column sub-assemblages viz. single oval slit damper fuse (SOSDF), dual oval slit damper fuse (DOSDF) and single elliptical slit damper fuse (SESDF), featuring advanced replaceable fuses were evaluated using both experimental and numerical analyses under quasi-static loading conditions. The seismic performance of these specimens was comprehensively assessed, focusing on characteristics such as moment-carrying capacity concerning rotation, energy dissipation, ductility, and failure modes. The findings indicate that all specimens exhibited stable hysteresis, with connections utilizing SESDF and DOSDF showing slightly higher moment carrying capacities (19 % and 10 %, respectively) compared to those employing SOSDF. According to AISC 2016 standards, all three connections were classified as full-strength connections. Moreover, the ductility of specimens incorporating SESDF was notably higher as 3.5, marking a 28 % and 26 % increase over the ductility of SOSDF and DOSDF connections, respectively. In major seismic events, damage was confined solely to the fuse components, with no damage observed in the beam and column. Detailed finite element analysis using ABAQUS CAE further corroborated these findings, demonstrating good alignment between experimental and simulated results.

A tunable high-order micro-perforated panel metamaterial with low-frequency broadband acoustic absorption

We proposed a tunable high-order micro-perforated panel metamaterial for broadband absorption, in which the energy dissipation modes is reconstructed by the cavity partition plates. Owing to the more degrees of freedom in impedance design, the metamaterial not only obtains multiple perfect absorption peaks with broader bandwidth, but also allows for flexible frequency regulations. By coupling 12 high-order cells, the metamaterial finally achieves a smooth spectrum with 94% average absorption across the range of 300–3200 Hz, which is verified by the simulation and experiment. This metamaterial could have great applications in noise control engineering owing to the extraordinary performance.

Towards direct superlubricity and superlow wear via amino modification of polyhydroxy alcohol solutions

Friction remains as the primary mode of energy dissipation and components wear, and achieving superlubricity shows high promise in energy conservation and lifetime wear protection. The results in this work demonstrate that direct superlubricity combined with superlow wear can be realized for steel/Si3N4 contacts on engineering scale when polyhydroxy alcohol solution was selectively modified by amino group. Macroscopic direct superlubricity occurs because 3-amino-1,2-propanediol molecules at the friction interface could be induced to rotate and adsorb vertically on the friction surface, forming in-situ thick and dense molecular films to passivate the asperity contacts. Furthermore, amino modification is also conducive to improving the lubrication state from boundary to mixed lubrication regime by strengthening the intermolecular hydrogen bonding interaction, presenting enhanced load-bearing capability and reduced direct solid asperity contacts. Thus, direct superlow average friction of 0.01 combined with superlow wear are achieved simultaneously. The design principle of direct superlubricity and superlow wear in this work indeed offers an effective strategy to fundamentally improve energy efficiency and provide lifetime wear protection for moving mechanical assemblies.

Color coded metadevices toward programmed terahertz switching

Terahertz modulators play a critical role in high-speed wireless communication, non-destructive imaging, and so on, which have attracted a large amount of research interest. Nevertheless, all-optical terahertz modulation, an ultrafast dynamical control approach, remains to be limited in terms of encoding and multifunction. Here we experimentally demonstrated an optical-programmed terahertz switching realized by combining optical metasurfaces with the terahertz metasurface, resulting in 2-bit dual-channel terahertz encoding. The terahertz metasurface, made up of semiconductor islands and artificial microstructures, enables effective all-optical programming by providing multiple frequency channels with ultrafast modulation at the nanosecond level. Meanwhile, optical metasurfaces covered in terahertz metasurface alter the spatial light field distribution to obtain color code. According to the time-domain coupled mode theory analysis, the energy dissipation modes in terahertz metasurface can be independently controlled by color excitation, which explains the principle of 2-bit encoding well. This work establishes a platform for all-optical programmed terahertz metadevices and may further advance the application of composite metasurface in terahertz manipulation.

Mechanical Behaviors of Hybrid Composites with Orthogonal Spiral Wire Mesh and Polyurethane Elastomer

This work aims to significantly improve the mechanical properties of conventional rigid lattice structures under repeatable large deformations. A novel hybrid material is proposed based on the concept of interpenetrating composite materials. The material utilizes a woven TC4 orthogonal spiral wire mesh as the skeleton and PU elastomer (OSWM‐PU) as the matrix. The uniaxial tensile tests demonstrate that OSWM‐PU possesses the excellent load‐bearing capacity, allowing for large deformations (≥60%) while maintaining partial integrity even after matrix fracture. Optical measurements and simulation analysis reveal that Poisson's ratio can be adjusted within a certain range by manipulating the microscopic parameters (p, d) of the longitudinal helical filaments. Cyclic tensile experiments further demonstrate that OSWM‐PU exhibits exceptional energy absorption performance, multiple energy dissipation modes, and a more pronounced Mullins effect. The stress relaxation experiment reveals the significant influence of the volume fraction of the skeleton on long‐term loading conditions. The orthogonal spiral wire skeleton exhibits a superior hooking effect without dividing the matrix, enabling OSWM‐PU to possess enhanced collaborative deformation capability and inherent designability in the orthogonal direction. These characteristics make it highly promising for applications in various robot joints and as flexible aircraft skin, offering excellent prospects for utilization.

Mechanical and electrical performances of ternary Cu-2.8%Ni-0.7%Si alloy modulated by ultrasonic solidification

One-dimensional (1D) and three-dimensional (3D) ultrasounds were introduced into the solidification process of ternary Cu-2.8wt%Ni-0.7wt%Si alloy together with the in-situ measurements of acoustic fields. In the case of 1D ultrasound, stable cavitation was the main form of acoustic energy transmission. The grain size of α-Cu dendrites was reduced because stable cavitation improved the wetting between impurities and alloy melt, which further promoted nucleation process. When 3D ultrasounds were applied, transient cavitation was the dominant mode of acoustic energy dissipation. This induced local high undercooling in alloy melt, causing a significant increase in bulk nucleation rates and the formation of numerous tiny α-Cu equiaxed grains. Meanwhile, as ultrasonic dimension increased, the strengthened acoustic streaming accelerated solute and thermal diffusion and weakened the preferred orientation of growing α-Cu grains. The proportion of low-angle grain boundaries (LAGBs) increased consequently, which suppressed the nucleation and growth of δ-Ni2Si discontinuous precipitates (DPs) during subsequent annealing treatment. The tensile strength and electrical conductivity of 3D ultrasonically solidified alloy after annealing reached 688.2 MPa and 2.7×107 S/m respectively, showing obvious advantages in synergetic mechanical and electrical performances.

Numerical investigation of no-load startup in a high-head Francis turbine: Insights into flow instabilities and energy dissipation

The presented paper numerically investigates the internal flow behaviors and energy dissipation during the no-load startup process toward a Francis turbine. Passive runner rotation is implemented through the angular momentum balance equation accompanied by dynamic mesh technology and user defined function. Three phases of rotational speed are identified: stationary, rapid increase, and slow increase. Head exhibits a monotonic decrease, rapid rise and fall, and eventual fluctuation. Flow rate shows quasi-linear increase. The pressure fluctuations in the vaneless region are primarily dominated by the frequencies induced by Rotor-Stator Interaction and a broad frequency range below 50 Hz, and below 30 Hz in the draft tube. Runner inlet experiences positive to negative incidence angles, causing intense flow separation and unstable structures. Draft tube exhibits large-scale recirculation and evolving vortex structures. Energy loss analysis based on the entropy production method highlights the runner and draft tube as primary contributors. The energy loss within the runner exhibits an initial increase, subsequent decrease, and then a rise again during the stationary and rapid speed increase phases. While the draft tube shows a rapid increase during the phase of rapid speed increase. Turbulent fluctuations significantly contribute to entropy production loss, with trends matching total entropy production. Maximum energy loss locations correspond to runner inlet and draft tube wall, emphasizing the importance of unstable flow and vortex generation. This study establishes foundational insights into unstable hydrodynamics and energy dissipation modes during hydraulic turbine no-load startup, paving the way for further research.

Research on cavitation characteristics of water-jet pumps with different blade tip clearances based on entropy production theory

Water-jet pumps are widely used in ship and other power fields. An axial-flow water-jet pump is studied with different size of tip clearance, and the cavitation characteristics are studied based on the theory of entropy production. Modified SST with curvature correction and modified Zwart cavitation model based on vortex identification are adopted, and the numerical calculation method is verified by reference experiments of a model pump. Under normal operating conditions, the results show that when the size of the tip clearance varies from 1.6‰ to 7.9‰ of the impeller diameter, efficiency takes a linear decrease accordingly, and the total entropy production increases linearly. At the same time, the main energy dissipation mode changes from wall dissipation to turbulent dissipation. Under severe cavitation conditions the total entropy production adds 30%. The water-jet pump shows that the entropy production in the impeller section is the highest, which accounts for 40%-50% and is closely related to the vortex and cavitation flow field in the tip clearance of the impeller. The tip leakage vortex region causes cavitation, but significant energy dissipation occurs at the outer edge of leakage vortex and on the nearby wall area, while the attached cavitation on the blade surface is the main source of turbulent dissipation.

Bouligand-like structured CNT film with tunable impact performance through pitch angle and intertube interaction

The Bouligand structure, characterized by a helicoidal arrangement of fibers, is prevalent in arthropods. Leveraging the exceptional impact resistance inherent in this structure, mantis shrimp could effortlessly crack the shells of shellfish using their dactyl club. Drawing inspiration from this natural phenomenon, we propose a novel Bouligand-like structured carbon nanotube film (BCNF) that combines the Bouligand structure with super-strong one-dimensional carbon nanotubes (CNTs). Through systematic investigation via molecular dynamics simulations, we explore the impact resistance and energy dissipation properties of BCNF. Our results reveal that the impact behaviors under different velocities can be tuned by adjusting the pitch angle of BCNFs. At an impact velocity of 1 km/s, the projectile exhibits three typical phenomena after impact, including embedding in the film, bouncing back, and penetration. At an impact velocity of 2 km/s, all films are penetrated. Furthermore, to enhance the impact resistance of BCNF, we introduce intertube crosslinking bonds, forming a crosslinked Bouligand-like structured CNT film (CBCNF). The study demonstrates that crosslinking effectively modulates the energy dissipation mode of the film. With increasing crosslinking density, the predominant energy dissipation mode shifts from interface sliding and bending of the CNTs to the fracture and collapse of CNTs. This research provides valuable insights into the microstructure design of CNT-based films and offers theoretical guidance for their applications in impact protection.

Experimental and numerical study of corrugated steel-plain concrete composite structures under contact explosions

This paper investigates the dynamic response and blast resistance of corrugated steel-plain concrete (CSPC) composite structures subjected to contact blast. A series of explosive tests were conducted to investigate the acceleration, deformation, and damage patterns of CSPC plates under varying blast loads and arrangements of shear connectors, and these findings were compared with reinforced concrete (RC) plates. The results suggested that CSPC plates exhibited superior ductility and blast resistance, and effectively mitigated concrete collapse. The CSPC slab primarily underwent elastic deformation when the TNT charge was small, with the rebound deformation of the concrete and steel plates acting as a significant mode of energy dissipation. As for larger TNT charges, the maximum deformation of the plate progressively increased, especially when exceeding 0.3 kg, the deformation rebound ratio decreased significantly, and the plastic deformation increased. For further increased explosive loads, the concrete and steel plates exhibited a pronounced strain rate effect with a slowed growth rate of deformation. By examining different configurations of shear connectors, it was discovered that the adhesive strength between concrete and steel plates was closely related to the energy dissipation mode, and the elastic recovery capability and deformation resistance of the CSPC structure significantly deteriorated when the shear connectors were shorter, sparser or thinner. A numerical model based on LS-DYNA was designed to further analyze the blast resistance characteristics of CSPC plates. An engineering collapse coefficient Kz was established to predict the failure level of the CSPC plates. This paper provides useful insights for the optimal design and damage assessment of CSPC composite structures.

Tough Hydrogels for Load-Bearing Applications.

Tough hydrogels have emerged as a promising class of materials to target load-bearing applications, where the material has to resist multiple cycles of extreme mechanical impact. A variety of chemical interactions and network architectures are used to enhance the mechanical properties and fracture mechanics of hydrogels making them stiffer and tougher. In recent years, the mechanical properties of tough, high-performance hydrogels have been benchmarked, however, this is often incomplete as important variables like water content are largely ignored. In this review, the aim is to clarify the reported mechanical properties of state-of-the-art tough hydrogels by providing a comprehensive library of fracture and mechanical property data. First, common methods for mechanical characterization of such high-performance hydrogels are introduced. Then, various modes of energy dissipation to obtain tough hydrogels are discussed and used to categorize the individual datasets helping to asses the material's (fracture) mechanical properties. Finally, current applications are considered, tough high-performance hydrogels are compared with existing materials, and promising future opportunities are discussed.

Multiple energy dissipation modes in dynamic polymer networks with neutral and ionic junctions.

Polymer networks with controlled ratios of neutral and ionic dynamic crosslink points were prepared from ethylene glycol, boric acid, and lithium hydroxide. Both neutral and ionic sites led to the emergence of distinct damping modes separate from the glass transition. This work highlights the potential of polymer networks for multimodal damping spectra through dynamic bond selection.

A New Multi-Mechanism Synergistic Acoustic Structure for Underwater Low-Frequency and Broadband Sound Absorption

The acoustic absorption characteristics of anechoic coatings attached to the surface of underwater vehicles are closely related to their acoustic stealth. Owing to the essential property of local resonance, the narrow sound-absorption band cannot meet the underwater broadband sound absorption requirements. To this end, a multi-mechanism synergistic composite acoustic structure (MMSC−AS) was designed according to the integration of multiple acoustic dissipation mechanisms in this paper. Then, the acoustical calculation model for MMSC−AS was developed by using the graded finite element method (G-FEM), and the feasibility and the correctness of the established acoustical calculation model were verified. The underwater sound absorption behaviors of MMSC−AS were studied, and the optimization of the sound absorption characteristics of the MMSC−AS was also carried out. The results indicated that the calculation accuracy of the G-FEM was better than that of the FEM under the condition of the same mesh elements. Moreover, there were many sound wave regulation mechanisms in the MMSC−AS, and the synergy between the mechanisms enriched the mode of sound acoustic energy dissipation, which could widen the absorption band with effect. This study provides theoretical and technical basis for breaking through the challenge of low-frequency and broadband acoustic structure design of underwater vehicles.

In-plane shear behaviour of concrete sandwich panels reinforced with various geogrids

Seismic occurrences have caused severe damage and even the collapse of fragile unreinforced masonry structures. New technologies are replacing these conventional methods of construction; concrete sandwich panels (CSP) are one such technique gaining popularity. In-plane diagonal shear strength of concrete sandwich panels is studied experimentally, and the effect of incorporating geogrids on the deformation capability and load-bearing capacity is reported. Two forms of geogrid material, plastic uniaxial geogrid (PUG) and polyester biaxial geogrids (PBG2 and PBG3) are used to improve the strength and ductility of concrete sandwich panels. Diagonal compression tests have been carried out better to understand the behavior of CSP under in-plane strength. This paper also discusses the effect of the different mixes, the effect of geogrids, load-deformation behaviour, shear capacity, deflection ductility factor, mode of failure, shear strength, and energy dissipation. In contrast to the control specimen, specimens cast with plastic geogrid had a 13.7% and 26% improvement in shear capacity and load-bearing capability for the two types of micro-concrete mixes used in this study. The conclusion reached is that plastic uniaxial geogrid is effective in improving the concrete sandwich panels’ load-bearing capacity, shear capacity, and deformation ability. Polyester biaxial geogrids enhanced the ductility of the concrete sandwich panels.