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Phase field modeling and computer simulations were conducted to uncover the fundamental mechanism behind the peak in damping capacity observed in BaTiO3-reinforced composites, considering both insulating and conductive cases. The damping capacity curve obtained from these simulations, which varies with temperature, reveals dual peaks near Tc for both cases. The first peak, labeled Peak I, occurs below Tc and is attributed to temperature-induced domain reorientation. The second peak, labeled Peak II, occurs above Tc and arises from stress-induced phase transitions between paraelastic and ferroelastic states. This transition results in a double-loop strain–stress hysteresis, akin to the polarization-field hysteresis observed in ferroelectric systems at and above Tc. Between Peak I and Peak II, there is a dip in damping capacity just below Tc, caused by the diminished ferroelasticity of BaTiO3 particles near this critical temperature. In composite materials, the dual peaks merge into a single peak due to the heterogeneous nature of Tc, influenced by various factors that either raise or lower Tc. This convergence aligns with experimental observations. [ABSTRACT FROM AUTHOR]

In this research, blends are prepared of thermoplastic polyurethane (TPU), ground tire rubber (GTR) and its devulcanized version (dGTR). The primary objective is to produce thermoplastic elastomers wherein TPU is partially substituted by GTR or dGTR obtained from used tires, thereby forming a blend with a favorable cost/value ratio and a smaller environmental footprint. Throughout the experiment, the rubber content of the blends is varied between 0 and 50 wt% and the effect on mechanical properties is investigated. The blends are compounded with a twin‐screw extruder, after which sheet samples are produced by injection molding. With a view to a possible future industrial application, it is important that both the compounding and the injection molding of the specimens are easy to perform, even with a 50 wt% filler content. Increasing the amount of rubber phase reduce the tensile strength and elongation at break of the blends. Unfortunately, devulcanization did not significantly improve the properties of the blends. Overall, even at a (d)GTR content of 50 wt%, an elongation at break of 300% is achieved, which allows the use of the blends as thermoplastic elastomers. In addition, dynamic tests show that the rubber phase increases the damping capacity of the samples. [ABSTRACT FROM AUTHOR]

The inerter-based dynamic vibration absorber (DVA) is a promising technique for vibration control. In most studies, the inerter is usually mounted in the same direction as that of the motion, which may not adequately reflect the vibration suppression capability and the two-terminal inertial feature of the inerter, and even weakens the performance of vibration absorbers. Considering the potentiality of improving the control performance by unconventional mounting methods, a rarely studied structure of geometrically nonlinear inerters is introduced into the vibration absorber system. This novel vibration absorber is presented to investigate the following issues, that is, the unknown coupled dynamical behavior between the complex nonlinear force with inertia, damping, and stiffness terms generated by this structure and the vibration absorber system, the possibility of vibration absorption facilitated by this structure, and the full utilization of the two-terminal inertial feature of the inerter. The approximate solutions of the system are obtained using the harmonic balance method. The influence of each variable on the system response is analyzed, and the system parameters are optimized by using the grey wolf algorithm. In addition to the ordinary resonance phenomenon, there are also dynamic features such as soft characteristic jump behavior and response loops at certain parameter range. As a nonlinear system, this model is more stable than the nonlinear energy sink (NES). The optimized amplitude-frequency curves are equal-peak stable, similar to the linear vibration absorbers. The robustness of system parameters is high for small inerter-mass ratios or excitation amplitudes, which is better than DVAs. Compared to the classical linear vibration absorber, NES, and improved NES, the vibration suppression capacity and damping bandwidth of this model are enhanced. In comparison, it is also found that this model has smaller optimum parameters than the classical NES and equivalent inerter-enhanced DVA and NES. This model offers a new solution for the design and implementation of passive vibration absorbers with comprehensive performance. [ABSTRACT FROM AUTHOR]

Natural materials possess inherent multilength‐scale structures, showcasing outstanding mechanical properties such as strain‐stiffening, high damping, and shape‐memory features under ambient conditions. Such integrated properties are highly desirable for advanced materials in biomedical devices and soft robots but remain challenging in synthetic materials. Herein, a novel strategy of sequential ion treatment is employed to introduce micro/nanoscale‐ordered structures and molecular‐scale stimulus responses into hydrogel‐derived self‐assembly fibers under ambient conditions. The treated fibers exhibit strain‐stiffening properties with a high toughness of 257 MJ m−3 and 73% damping capacity comparable to spider silk. Owing to their cross‐linking network and reversible secondary structure, those fibers exhibit outstanding water‐stability, wet stretchability, and hydration‐responsive shape‐memory performance, with ultimate elongation of 407%, shape‐fixity ratio of 94%, and shape‐recovery rate of 97%. This work furthers the green fabrication of smart materials with multifunction and presents promising applications in diverse fields, including biomimetics and biomedicine. [ABSTRACT FROM AUTHOR]

AbstractSeismic uplift of a high-speed rail (HSR) cable-stayed bridge’s bearing affects train safety. Existing technique lacks improved seismic isolation in the vertical direction due to the bearing’s vertical stiffness. Based on the on-site dynamic test and train derailment table experiments and different software, the train running safety of the semi-floating system of the cable-stayed bridge-rail-train system was analyzed using different damping and isolation control strategies. The larger vertical seismic component increases the danger of flange climb derailment when subjected to near-fault earthquakes. After installing lateral/or viscous fluid dampers (VFDs) and magnetorheological (MR) bearing (A = 3.0), the bridge has an obvious bearing uplift response. Still, it is not enough to threaten the structure, and the seismic damping capacity of the bridge structure is improved, making the train ride safe. This research presents discoveries on the impact of bearing uplift on train operational safety. Specifically, it reveals that the lifting of the end bearings on both sides of the main girder is not synchronized. This investigation presents a technical reference for comparable initiatives. [ABSTRACT FROM AUTHOR]

In this study, the influence of the torsional rigidity of the connected shafts, couplings and the working body of the machine, as well as the damping capacity of the coupling, on the torsional impact moment generated in the machine transmission is investigated. Unlike existing classical calculation models, the torsional stiffness of the connected shafts, the torsional damping ability of the coupling and the effects of the moment ratio are taken into consideration together. Under these conditions an analytical expression for the shock moment or resonance coefficient is obtained. The main novelties in obtaining of this expression are the ratio of the torsional stiffness of the connected shafts with the torsional stiffness of the coupling and the acceptance of the moment of resistance of the working body of the machine depending on the torsional stiffness. It has been found that the considered factors have a significant effect on the resonance zone. Finally, different and overlapping conditions are determined when determining the value of the resonance coefficient characterizing the torque impact moment, calculated according to the classical and proposed models. [ABSTRACT FROM AUTHOR]

Although the physical properties of a structure, such as stiffness, can be determined using some statical tests, the identification of damping parameters requires a dynamic test. In general, both theoretical prediction and experimental identification of damping are quite difficult. There are many different techniques available for damping identification, and each method gives a different damping parameter. The dynamic indentation method, rheometry, atomic force microscopy, and resonant vibration tests are commonly used to identify the damping of materials, including soft materials. While the viscous damping ratio, loss factor, complex modulus, and viscosity are quite common to describe the damping of materials, there are also other parameters, such as the specific damping capacity, loss angle, half-power bandwidth, and logarithmic decrement, to describe the damping of various materials. Often, one of these parameters is measured, and the measured parameter needs to be converted into another damping parameter for comparison purposes. In this review, the theoretical derivations of different parameters for the description and quantification of damping and their relationships are presented. The expressions for both high damping and low damping are included and evaluated. This study is considered as the first comprehensive review article presenting the theoretical derivations of a large number of damping parameters and the relationships among many damping parameters, with a quantitative evaluation of accurate and approximate formulas. This paper could be a primary resource for damping research and teaching. [ABSTRACT FROM AUTHOR]

Materials based on hybrid bimetallic particles with a polyacrylamide shell can act as an efficient centers of energy dissipation in filled composites and reveal more effectiveness than nanoparticles, which, due to their higher surface-to-volume ratio and low interfacial adhesion, can affect the final composite performance. Two types of fillers were obtained as part of polymer-mediated synthesis and subsequent thermolysis and later encapsulated into a LDPE matrix. The metal-polymer complex increases the damping capacity of the hosting material up to 25% at higher concentration. However, the nanoparticles showed a strong increase at 5 wt% (by 20%) and then a sharp decline, which makes metal-polymer particles more suitable for damping purposes. [ABSTRACT FROM AUTHOR]

Commercial pure cast magnesium (Mg) was subjected to friction stir processing (FSP) at a rotational speed of 600 rpm and tool traverse speed of 60 mm/min. The samples extracted from cast Mg and friction stir processed magnesium have been analysed for the microstructure, hardness, and temperature-dependent damping capacity. The average grain size of as cast pure Mg is reduced from 780 to 26 μm after FSP. There is about a 15% increase in hardness after FSP. The dynamic mechanical analyser (DMA) measured the damping capacity using a three-point bending mode. The FSPed Mg sample exhibited 50% lower damping capacity than the cast Mg at room temperature. However, as the temperature increased, significantly above 80°C, the damping capacity of the FSPed magnesium was greater than that of the cast magnesium. At room temperature, the damping capacity of FSPed Mg was decreased because of the formation of tangled dislocations. In contrast, the increase in damping capacity above 80°C was due to the increased grain boundary area. [ABSTRACT FROM AUTHOR]

This work investigates the effects of a supertransus annealing treatment, followed by plastic deformation, on the damping properties of a Ti-11.5Mo-6Zr-4.5Sn alloy. In our study, no evidence of α″-phase was found. A heat treatment at 800°C for 180 min, followed by 16% tensile plastic deformation, successfully increased the energy dissipation of the alloy, with an increase up to 76% in quasi-static hysteresis, and up to 200% in dynamic damping factor. The results of metallographic analysis, mechanical tests, and X-ray powder diffraction suggest that this increase in damping capacity may be caused by reversible twinning, and not necessarily by stress-induced α'' martensite. [ABSTRACT FROM AUTHOR]

In this study, the influence of the torsional rigidity of the connected shafts, couplings and the working body of the machine, as well as the damping capacity of the coupling, on the torsional impact moment generated in the machine transmission is investigated. Unlike existing classical calculation models, the torsional stiffness of the connected shafts, the torsional damping ability of the coupling and the effects of the moment ratio are taken into consideration together. Under these conditions an analytical expression for the shock moment or resonance coefficient is obtained. The main novelties in obtaining of this expression are the ratio of the torsional stiffness of the connected shafts with the torsional stiffness of the coupling and the acceptance of the moment of resistance of the working body of the machine depending on the torsional stiffness. It has been found that the considered factors have a significant effect on the resonance zone. Finally, different and overlapping conditions are determined when determining the value of the resonance coefficient characterizing the torque impact moment, calculated according to the classical and proposed models.

A high-Zn Al–27Zn-1.5Mg-1.2Cu-0.08Zr alloy was prepared by traditional casting and melt spinning. The as-casted alloy consists of well-developed α-Al dendrites with many coarse η-phase and low solute concentration, coarse network precipitates at grain boundaries and the α-Al/η-phase eutectic structures at triple junctions. Due to these featured structures, the as-cast alloy exhibits a low tensile strength of 101 MPa with room temperature and high temperature (300 °C) damping capacity of 0.0058 and 0.027 respectively. Comparatively, the as-spun alloy reveals gradient cross-sectional microstructures after solidification: an ultrafine grained region near the wheel surface, a transition region and an equiaxed-grained region near the ribbon free surface, with changes of precipitate morphologies from granular shape to network shape via vermicular. High-density nano-sized η′-phase/GP-zones within α-Al grains result in a higher tensile strength (121 MPa) of as-spun alloy with room temperature and high temperature (300 °C) damping capacity of 0.0049 and 0.048 respectively. Fracture analysis shows that the as-casted alloy fails in a mixed-mode fracture, comprised predominantly of transgranular fracture, quasi-cleavage fracture, cleavage fracture and dimple fracture, whereas the as-spun alloy failed in cleavage fracture and dimple fracture.

This study focuses on the prediction of the fracture mechanics behaviour of a highly flexible adhesive (with a tensile elongation of 90%), since this type of adhesive is becoming widely used in automotive structures due to their high elongation at break and damping capacity. Despite their extensive applications, the understanding of their fracture mechanics behaviour under varying loading rates and temperatures remains limited in the literature. In addition, current prediction models are also unable to accurately predict their behaviour due to the complex failure mechanism that such bonded joints have. This study aims to determine whether a simple triangular cohesive zone model (CZM), which predefines the crack path, can reproduce the load–displacement curves of adhesives under various temperatures and strain rates. To achieve this, a calibrated CZM is used, adapting the model for reference joints and then validating it with independent test results conducted in a wide range of loading and environmental conditions. The tests were performed at speeds between 0.2 and 6000 mm/min and at three different temperatures ranging from −30 °C to 60 °C. Mode I fracture toughness was measured using the DCB (double cantilever beam) specimens. Using a simple triangular CZM may not be optimal for predicting the mechanical response of highly flexible adhesives with complex failure mechanisms and multiple crack paths. However, by correctly adjusting the cohesive zone properties for a limited set of reference conditions, it is possible to accurately predict the mechanical response of these joints across various test speeds and temperatures, significantly reducing costs and effort. [ABSTRACT FROM AUTHOR]

Migrating bedforms in alluvial rivers can exacerbate scour damage at instream structures and lead to structural failure. This study investigates the interaction between scour at instream structures and bedform migration. Both two-dimensional (submerged weirs) and three-dimensional (uniform and complex piers) structures are considered. Two components constitute live-bed scour depth: the dynamic scour amplification Δds caused by bedforms and the local flow-induced baseline scour depth dsNB. Results show that, for 2D structures, the baseline scour depth is negligible, while the live-bed scour is mainly caused by approaching bedforms. The dynamic scour amplification normalised by the approaching bedform height (Δds/Hb) decreases with the decrease of upstream angle and varies between 0.5 and 2. For uniform 3D structures, the local flow could cause a considerable baseline scour depth, and Δds/Hb varies between 0.25 and 0.5 and decreases with the increase in the flow capacity to damp bedforms. For complex 3D structures, flow pressurisation beneath the pile-cap magnifies Δds/Hb to near 1. In general, Δds/Hb is inversely correlated with ds_NB/y0, where y0 is flow depth. New equations are proposed for estimating the dynamic scour amplification at various instream structures with design rules recommended. [ABSTRACT FROM AUTHOR]

We performed a gas nitriding and quenching process (GNQP) on Ti–18 mass% Nb alloy to obtain a high damping capacity and wear resistance. GNQP was performed at temperatures of 1023, 1123, and 1223 K. The outermost surface of the GNQP specimen obtained at 1023 K mainly comprised TiO2, whereas that at 1223 K mainly comprised TiN. The surface and interior of the specimens exhibited higher hardness at 1223 K than that at 1023 K. Compared to the specimen obtained by solution–quenching (AQ), the unit volume of the α" martensite phase at a depth of 320 μm of the GNQP specimen obtained at 1023 K was similar, and that at 1223 K was higher. Such a difference can be related to the difference in the core hardness of the specimens. The wear amounts of all GNQP specimens were lower than those of the AQ specimen. The coefficient of friction of the GNQP specimen obtained at 1023 K was lower than that obtained at 1223 K. The surface constituent phase and surface roughness exhibited a strong influence on the wear at a load of 500 g. Meanwhile, the nitride layer and damping capacity were considered to be related to the wear at a load of 3000 g. [ABSTRACT FROM AUTHOR]

Polymers are ideally utilized as damping materials due to the high internal friction of molecular chains, enabling effective suppression of vibrations and noises in various fields. Current strategies rely on broadening the glass transition region or introducing additional relaxation components to enhance the energy dissipation capacity of polymeric damping materials. However, it remains a significant challenge to achieve high damping efficiency through structural control while maintaining dynamic characteristics. In this work, we propose a new strategy to develop hyperbranched vitrimers (HBVs) containing dense pendant chains and loose dynamic crosslinked networks. A novel yet weak dynamic transesterification between the carboxyl and boronic acid ester was confirmed and used to prepare HBVs based on poly (hexyl methacrylate‐2‐(4‐ethenylphenyl)‐5,5‐dimethyl‐1,3,2‐dioxaborinane) P(HMA‐co‐ViCL) copolymers. The ABn ${{AB}_{n}}$ ‐type of macromonomers, the crosslinking points formed by the dynamic covalent connection via the associative exchange, and the weak yet dynamic exchange reaction are the three keys to developing high‐performance HBV damping materials. We found that P(HMA‐co‐ViCL) 20k‐40‐60 HBV exhibited ultrahigh energy‐dissipation performance over a broad frequency and temperature range, attributed to the synergistic effect of dense pendant chains and weak dynamic covalent crosslinks. This unique design concept will provide a general approach to developing advanced damping materials. [ABSTRACT FROM AUTHOR]

Steel dampers are components used in building structures to reduce vibration and energy generated by dynamic loads such as earthquakes. Several factors affect the effectiveness of steel dampers in reducing energy, including the cross-sectional area, mass distribution, cross-sectional geometry, and material stiffness. The cross-sectional geometry or shape of the steel damper can affect how energy is absorbed and dissipated in the structural system. Cross sections with different geometric variations can have different mechanical responses to dynamic loads. This study aims to analyze which type of steel damper is effective in terms of stiffness and damping capacity against lateral cyclic loads. The steel damper cross-sectional variations used are slit steel dampers (SSDs), tapered steel dampers (TSDs), and oval steel dampers (OSDs). Cyclic testing of the dampers used displacement control with the same target deviation for all three damper types. The results showed that the stress and strain distributions of the oval steel damper were more even than those of the other two models. The variations in the energy dissipation capacities of the three cross-section variations are relatively the same. However, the slit steel damper type has the best stiffness compared to the other two types. This research is ultimately expected to influence the science of the structure of a building in preventing and anticipating earthquakes or other disasters. [ABSTRACT FROM AUTHOR]

Mg-0.8Si alloy plates were rolled at high strain rates of 15, 20, and 25 s−1, and the effects of the rolling strain rate on the microstructure, mechanical properties, and damping properties of the Mg-0.8Si alloy were studied. With the increasing strain rate, the area fraction of DRX in the HSRRed Mg-0.8Si alloy gradually increases, resulting in the decrease in dislocation density and dislocation tangles. A higher strain rate can enlarge the grain size of the Mg-0.8Si alloy, so the basal texture and tensile strength can both decrease because of the increased strain rate. The maximal elongation is 8.40% at 20 s−1. The damping properties of HSRRed Mg-0.8Si alloy increase with the strain rate and the critical strain amplitude gradually decreases. [ABSTRACT FROM AUTHOR]

Tire derived aggregates (TDA) has been used successfully in numerous civil engineering projects. However, considerably few researchers investigated its performance in dynamic applications, despite the high energy absorption ability of TDA. Moreover, testing TDA samples with larger aggregate size is troublesome due to the limitation in specimen sizes available in geotechnical laboratories. Therefore, this paper provides more insights on the dynamic behavior of TDA with larger aggregate sizes. This work also investigates the extent of specimen size effect on the dynamic properties of TDA and Granulated rubber (GR). A series of undrained strain-controlled cyclic triaxial tests were performed using three specimen sizes with diameters of 70, 101 and 152 mm. TDA samples had maximum aggregate size of 19.1 and 25.4 mm, however, the GR samples had only a maximum aggregate size of 4.75 mm. All tests were performed at consolidation stress range of 25 to 100 kPa and shear strain range of 0.1 to 10%. It was found that the 70 mm specimens overestimated the shear modulus of TDA samples by a maximum of 15 to 26%. However, no significant variation was found in the shear modulus that is mobilized by the 101 and 152 mm specimens. Also, GR samples were marginally influenced by specimen size. Furthermore, regardless of the aggregate size, the damping capacity is independent of specimen size. Lastly, it is recommended to use triaxial specimen size with a diameter four times larger than the maximum aggregate size of considered TDA material. [ABSTRACT FROM AUTHOR]

Mechanically robust hydrogel fibers have demonstrated great potential in energy dissipation and shock‐absorbing applications. However, developing such materials that are recyclable, energy‐efficient, and environmentally friendly remains an enormous challenge. Herein, inspired by spider silk, a continuous and scalable method is introduced for spinning a polyacrylamide hydrogel microfiber with a hierarchical sheath‐core structure under ambient conditions. Applying pre‐stretch and twist in the as‐spun hydrogel microfibers results in a tensile strength of 525 MPa, a toughness of 385 MJ m−3, and a damping capacity of 99%, which is attributed to the reinforcement of hydrogen‐bond nanoclusters within the microfiber matrix. Moreover, it maintains both structural and mechanical stability for several days, and can be directly dissolved in water, providing a sustainable spinning dope for re‐spinning into new microfibers. This work provides a new strategy for the spinning of robust and recyclable hydrogel‐based fibrous materials. [ABSTRACT FROM AUTHOR]

Hydrogels capable of swift mechanical energy dissipation hold promise for a range of applications including impact protection, shock absorption, and enhanced damage resistance. Traditional energy absorption in such materials typically relies on viscoelastic mechanisms, involving sacrificial bond breakage, yet often suffers from prolonged recovery times. Here, we introduce a hydrogel designed for friction-based damping. This hydrogel features an internal structure that facilitates the motion of a chain walker within its network, effectively dissipating mechanical stress. The hydrogel network architecture allows for rapid restoration of its damping capacity, often within seconds, ensuring swift material recovery post-deformation. We further demonstrate that this hydrogel can significantly shield encapsulated cells from mechanical trauma under repetitive compression, owing to its proficient energy damping and rapid rebound characteristics. Therefore, this hydrogel has potential for dynamic load applications like artificial muscles and synthetic cartilage, expanding the use of hydrogel dampers in biomechanics and related areas. Hydrogels capable of swift mechanical energy dissipation are desirable for various uses, but traditional energy absorption in hydrogels typically relies on viscoelastic mechanisms and often suffers from slow recovery. Here, the authors report a hydrogel design harnessing molecular friction to achieve efficient energy dissipation and rapid recovery. [ABSTRACT FROM AUTHOR]

Four different types of natural date palm tree fibers (DPTFs), including Rachis, Petiole, Bunch, and Mesh, were used as short fibers added to single lap adhesive joints subjected to quasi static and impact loading. The results show that the fibers have a remarkable effect on the static and impact strengths of the joints. Adding 2 wt% and 5 wt% of Bunch fibers to the adhesive layer impressively increased the impact strength by 196% and 62%, respectively. The analysis of fracture surfaces showed that DPTFs make the crack propagation more stable and increase the strength and the damping capacity of the joints. [ABSTRACT FROM AUTHOR]

An experimental device fixed with a laser displacement sensor was assembled to investigate the rebound behaviors and damping mechanism of rubber balls prepared with ethylene-propylene-diene monomer (EPDM)/chlorinated butyl rubber (CIIR) blends. The result showed that a prediction model was proposed to characterize the damping capacity by using the rebound height of the rubber balls. The lower rebound height corresponded to better damping capacity. A modified equation relating to the rebound height has been obtained from the theoretical derivation on the basis of the dynamic mechanical analysis, showing that the rebound height was affected by the deformation frequency, the external excitation, and the nature of rubber blends. Furthermore, the energy dissipation rate (EDR), defined by the ratio of the height loss to the rebound time, was proposed to further characterize the damping capacity. The EDR value was shown to be highest for the pure CIIR and lowest for the pure EPDM, exhibiting a decreasing trend with the increase in EPDM content in the rubber blends. It can be expected that the damping capacity of the EPDM/CIIR blends decreases with the decrease in external excitation, the conclusion of which plays a key role in the formulation design of viscoelastic damping rubber materials. [ABSTRACT FROM AUTHOR]

Non-invasive objective implant stability measurements are needed to determine the appropriate timing of prosthetic fitting after implant placement. We compared the early implant stability results obtained using resonance frequency analysis (RFA) and damping capacity analysis (DCA) depending on the implant length and bone density. Total 60, 4.0 mm diameter implants of various lengths (7.3 mm, 10 mm, and 13 mm) were used. In Group I, low-density bone was described using 15 PCF (0.24 g/cm3) polyurethane bone blocks, and in Group II, 30 PCF (0.48 g/cm3) polyurethane bone blocks were used to describe medium density bone. RFA was performed using an Osstell® Beacon+; DCA was performed using Anycheck®. Measurements were repeated five times for each implant. Statistical significance was set at P <0.05. In Group I, bone density and primary implant stability were positively correlated, while implant length and primary implant stability were positively correlated. In Group II, the implant stability quotient (ISQ) and implant stability test (IST) values in did not change significantly above a certain length. Primary implant stability was positively correlated with bone density and improved with increasing implant length at low bone densities. Compared with the Osstell® Beacon+, the simplicity of Anycheck® was easy to use and accessible. [ABSTRACT FROM AUTHOR]

Hybrid composites are an advanced solution that offers multifunctional capabilities, including exceptional strength-to-weight ratios, vibrational damping and impact absorption. This work describes the damping capacity and flexural behaviour of a hybrid fibrous-particulate system composed of glass/carbon fabrics and three distinct micro-inclusions: silica particles, carbon waste microfibres, and cement. A statistical methodology based on the full factorial design is applied to identify the effects of fibre stacking sequence, including carbon-C5, glass-G5, C2G3, G3C2, GCGCG and CG3C, microparticle inclusions and matrix/fibre volume fraction (40/60 and 60/40) on damping and bending responses. A non-linear finite element (FE) analysis is conducted to explore the stress distribution based on the stacking sequence and predict the failure mechanisms of the hybrid laminate. The results indicate significant interaction effects, with hybrid architectures showcasing approximately 33% higher performance compared to glass fibre composites. A greater dependence on the fibre layup sequence is found for the damping factor, flexural modulus and strength. Notably, the incorporation of silica microparticles leads to an increase in flexural strength. Furthermore, a greater volume fraction of the matrix phase enhances the rheological efficiency in terms of the fibre-particle interface. Carbon fibre layers placed symmetrically on both beam sides (CG3C) and bottom layers (G3C2) significantly enhance the bending performance of hybrid composites. [ABSTRACT FROM AUTHOR]

The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, as aging time increased at 450 °C, the dynamic phase transition splitting from B2 → R to B2 → R1 and B2 → R2 became evident. However, such a splitting process was not observed for the sample after aging at 400 °C. The reason for R-phase generation is attributed to non-uniformly distributed stress fields. The splitting of the internal friction peak, in conjunction with high-resolution transmission electron microscope and mechanic results, suggests a substantial occurrence of short-range segregation of Ni atoms in the B2-NiTi matrix. Furthermore, the specific damping capacity (SDC) exhibits a gradual increase with prolonged annealing time. Specifically, the sample with significant dynamic phase transition splitting reaches an SDC value of 0.60. [ABSTRACT FROM AUTHOR]

Designing materials capable of adapting their mechanical properties in response to external stimuli is the key to preventing failure and extending their service life. However, existing mechanically adaptive polymers are hindered by limitations such as inadequate load‐bearing capacity, difficulty in achieving reversible changes, high cost, and a lack of multiple responsiveness. Herein, we address these challenges using dynamic coordination bonds. A new type of mechanically adaptive material with both rate‐ and temperature‐responsiveness was developed. Owing to the stimuli‐responsiveness of the coordination equilibria, the prepared polymers, PBMBD‐Fe and PBMBD‐Co, exhibit mechanically adaptive properties, including temperature‐sensitive strength modulation and rate‐dependent impact hardening. Benefitting from the dynamic nature of the coordination bonds, the polymers exhibited impressive energy dissipation, damping capacity (loss factors of 1.15 and 2.09 at 1.0 Hz), self‐healing, and 3D printing abilities, offering durable and customizable impact resistance and protective performance. The development of impact‐resistant materials with comprehensive properties has potential applications in the sustainable and intelligent protection fields. [ABSTRACT FROM AUTHOR]

SiC-fiber-reinforced Al-Mg matrix composites with different mass fractions of Mg were fabricated by combining colloidal dispersion with a squeeze melt infiltration process. The microstructure, mechanical and damping properties, and the corresponding mechanisms were investigated. Microstructure analyses found that SiCf/Al-Mg composites presented a homogeneous distribution of SiC fibers, and the relative density was higher than 97% when the mass fraction of Mg was less than 20%; the fiber–matrix interface bonded well, and no obvious reaction occurred at the interface. The SiCf/Al-10Mg composite exhibited the best flexural strength (372 MPa) and elastic modulus (161.7 GPa). The fracture strain of the composites decreased with an increase in the mass fraction of Mg. This could be attributed to the strengthened interfacial bonding due to the introduction of Mg. The damping capacity at RT increased dramatically with an increase in the strain when the strain amplitude was higher than 0.001%, which was better than the alloys with similar composition, demonstrating a positive effect of the SiC fiber on improving the damping capacity of composite; the damping capacity at a temperature beyond 200 °C indicated a monotonic increase tendency with the testing temperature. This could be attributed to the second phase, which formed more strong pinning points and increased the dislocation energy needed to break away from the strong pinning points. [ABSTRACT FROM AUTHOR]

Dual plating of comminuted distal femoral fractures allows for early patient mobilization. An additional helically shaped medial plate avoids the medial vital structures of the thigh. The aim of this study is to investigate the biomechanical competence of an augmented lateral locking compression plate distal femur (LCP‐DF) using an additional straight versus a helically shaped medial LCP of the same length. Ten pairs of human cadaveric femora were instrumented with a lateral anatomical 15‐hole LCP‐DF. Following, they were pairwise instrumented with either an additional medial straight 14‐hole LCP (group 1) or a 90°‐helical shape LCP (group 2). All specimens were biomechanically tested under quasi‐static and progressively increasing combined cyclic axial and torsional loading until failure. Initial interfragmentary axial displacement and flexion under static compression were significantly smaller in group 1 (0.11 ± 0.12 mm and 0.21 ± 0.10°) versus group 2 (0.31 ± 0.14 mm and 0.68 ± 0.16°), p ≤ 0.007. Initial varus deformation under static compression remained not significantly different between group 1 (0.57 ± 0.23°) and group 2 (0.75 ± 0.34°), p = 0.085. Flexion movements during dynamic loading were significantly bigger in group 2 (2.51 ± 0.54°) versus group 1 (1.63 ± 1.28°), p = 0.015; however, no significant differences were observed in terms of varus, internal rotation, and axial and shear displacements between the groups, p ≥ 0.204. Cycles to failure and load at failure were higher in group 2 (25,172 ± 6376 and 3017 ± 638 N) compared to group 1 (22,277 ± 4576 and 2728 ± 458 N) with no significant differences between them, p = 0.195. From a biomechanical perspective, helical double plating may be considered a useful alternative to straight double plating, demonstrating ameliorated damping capacities during flexion deformation and safer application as the medial neurovascular structures of the thigh are avoided. [ABSTRACT FROM AUTHOR]

In this investigation, aluminum alloy (AA7075) composites reinforced with titanium (Ti) particulates (0–2.0 wt.% @ step of 0.5%) were designed and fabricated via a high vacuum casting route. The composite specimens are then analyzed for their physical, mechanical, thermogravimetric analysis, thermomechanical, and sliding wear behavior as per standards. The Taguchi orthogonal array was used for designing sliding wear trials, parametric optimization, and knowing the order of significance of parameters that control the output response of wear. This follows surface morphology studies to understand the prevalent wear mechanism responsible for surface damage. Finally, the entropy-VIKOR method was used to rank the composites as per their performance merits. The range of voids content is 2.39–1.68 %, tensile strength is 190–426 MPa, flexural strength is 452–299.8 MPa, impact strength is 13–77 J, and Vickers hardness is 171–193 HV. The order of material stability is ATI-0 < ATI-2 < ATI-1.5 > ATI-1.0 >ATI-0.5. The order of storage modulus is ATI-1.5 > ATI-1.0> ATI-0 > ATI-0.5 > ATI-2, while loss modulus is ATI-0.5 > ATI-2> ATI-1 > ATI-0 > ATI-1.5, and damping capacity is ATI-0 > ATI-0.5 > ATI-1.0 > ATI-1.5> ATI-2, respectively. The alloy composites having 2 wt.% Ti particulates shown to have overall optimized performance merits and confirmed with the results of hybrid ENTROPY-VIKOR. [ABSTRACT FROM AUTHOR]

As the lightest structural metal material, magnesium alloys possess good casting properties, high electrical and thermal conductivity, high electromagnetic shielding, and excellent damping properties. With the increasing demand for lightweight, high-strength, and high-damping structural materials in aviation, automobiles, rail transit, and other industries with serious vibration and noise, damping magnesium alloy materials are becoming one of the important development directions of magnesium alloys. A comprehensive review of the progress in this field is conducive to the development of damping magnesium alloys. This review not only looks back on the traditional damping magnesium alloys represented by Mg-Zr alloys, Mg-Cu-Mn alloys, etc. but also introduces the new damping magnesium materials, such as magnesium matrix composites and porous magnesium. But up to now, there have still been some problems in the research of damping magnesium materials. The effect of spiral dislocation on damping is still unknown and needs to be studied; the contradiction between damping performance and mechanical properties still lacks a good balance method. In the future, the introduction of more diversified damping regulating methods, such as adding other elements and reinforcements, optimizing the manufacturing method of damping magnesium alloy, etc., to solve these issues, will be the development trend of damping magnesium materials. [ABSTRACT FROM AUTHOR]

In the field of aerospace and advanced equipment manufacturing, accurate response analysis has been paid more attention, requiring a more comprehensive study of the variation of mechanical parameters with the service environment. The damping variation characteristics of 304 aluminum alloy, Sa564 high-strength alloy, GW63K magnesium alloy, and Q235 steel were investigated in this paper, which plays a significant role in the dynamic responses of structures. Variable damping ratios were revealed by the damping tests based on a dynamic mechanical analysis (DMA). The numerical method of temperature/frequency-dependent damping parameters in stochastic dynamics was focused on. With a large variation in the damping ratio, a numerical constitutive relation for temperature-dependent damping was proposed, and an efficient stochastic dynamics method was derived to analyze the responses of structures based on the pseudo excitation method (PEM) and variable damping theory. The computational accuracy and validity of the proposed method are confirmed during the vibration tests and numerical analysis. Based on the comparison results of the two damping models and the experiments on GW63K alloy, we proved that the proposed method is more accurate to the real response of the actual engineering structure. The differences in dynamic responses between the constant damping and experiments are significant, and more attention should be paid to the numerical method of stochastic dynamic response of variable damping materials in the aviation and aerospace fields and high-temperature environments. [ABSTRACT FROM AUTHOR]

Fe-based superelastic alloys, which show both superelasticity and high damping capacity, can be divided into four alloy systems based on the characteristics of the martensite transformation that is responsible for these effects, viz., Fe-Pt, Fe-Pd, Fe-Mn-Si, and Fe-Ni-Co. Since 2010, Fe-Ni-Co-Al-based alloys that exhibit a large superelastic effect have attracted widespread attention. In this paper, the characteristics of the phase transformation from austenite ( γ ) to martensite ( α ') and the effects of the martensite variants in Fe-Ni-Co-Al-based superelastic alloys are summarized. The effects of alloying elements, precipitates and texture on the thermoelastic martensite transformation and the superelastic properties are reviewed. The factors affecting the superelastic effect and recoverable strain along with the related mechanisms are discussed. In addition, research progress on the damping performance, microwire structures, and modeling of Fe-Ni-Co-Al-based superelastic alloys are outlined. Finally, the challenges and future developments of the superelastic effect in Fe-Ni-Co-Al-based alloy are explored. [ABSTRACT FROM AUTHOR]

The influence of the degree of plastic deformation at room temperature, followed by aging, on the amplitude dependence of internal friction and microstructure of the pre-hardened alloy ZA27 was investigated. The main structural mechanism affecting the amplitude dependence of internal friction under these treatments was analyzed. [ABSTRACT FROM AUTHOR]

The wine industry requires a considerable amount of energy, with an important fraction corresponding to the cooling and ventilation of above-ground aging warehouses. The large investments made in aging facilities can compromise the viability and competitiveness of wineries if their design is not optimized. The objective of this study was to provide guidance for the efficient design of new above-ground warehouses. To this end, multiple construction solutions (structure, envelopes, levels of integration, etc.) were characterized, and their costs and the resulting interior environments were analyzed. The results offer a comprehensive view of potential construction solutions and benchmark price ranges for viable and profitable designs. With a total cost of 300 EUR/m2, an average damping of 98% per day can be achieved. Increasing the costs does not imply better effectiveness. A double enclosure with internal insulation—with or without an air chamber—can achieve excellent results. Greater integration as a result of several enclosures being in contact with other rooms and/or the terrain allows for a high effectiveness to be achieved without air conditioning. Perimeter glazing and ventilation holes can reduce the effectiveness of the construction, resulting in greater instability and a lower damping capacity. [ABSTRACT FROM AUTHOR]

Base isolators used in buildings provide both a good acceleration reduction and structural vibration control structures. The base isolators may lose their damping capacity over time due to environmental or dynamic effects. This deterioration of them requires the determination of the maintenance and repair needs and is important for the long-term isolator life. In this study, an artificial intelligence prediction model has been developed to determine the damage and maintenance-repair requirements of isolators as a result of environmental effects and dynamic factors over time. With the developed model, the required damping capacity of the isolator structure was estimated and compared with the previously placed isolator capacity, and the decrease in the damping property was tried to be determined. For this purpose, a data set was created by collecting the behavior of structures with single degrees of freedom (SDOF), different stiffness, damping ratio and natural period isolated from the foundation under far fault earthquakes. The data is divided into 5 different damping classes varying between 10% and 50%. Machine learning model was trained in damping classes with the data on the structure's response to random seismic vibrations. As a result of the isolator behavior under randomly selected earthquakes, the recorded motion and structural acceleration of the structure against any seismic vibration were examined, and the decrease in the damping capacity was estimated on a class basis. The performance loss of the isolators, which are separated according to their damping properties, has been tried to be determined, and the reductions in the amounts to be taken into account have been determined by class. In the developed prediction model, using various supervised machine learning classification algorithms, the classification algorithm providing the highest precision for the model has been decided. When the results are examined, it has been determined that the damping of the isolator structure with the machine learning method is predicted successfully at a level exceeding 96%, and it is an effective method in deciding whether there is a decrease in the damping capacity. [ABSTRACT FROM AUTHOR]

Purpose: This paper is aimed to separate each mode and identify modal damping accurately in multimodal signals. A novel damping identification strategy based on DOA-VMD-EIM (variational mode decomposition optimized by dingo optimization algorithm combined with envelope integral method) for aeroengine mounting pedestals is presented in this work. Methods: Energy difference indicator is firstly constructed by difference between the total vibration energy of each component and vibration energy of original signal. Then, the variational mode decomposition (VMD) parameters combination (K, α, τ) is optimized by the dingo optimization algorithm (DOA) using the minimum energy difference index as optimization objective. Furthermore, combined with envelope integral method (EIM), the damping ratio is deduced. Finally, the proposed DOA-VMD-EIM method is verified numerically and experimentally. Results: Numerical analysis and test results indicate that the presented DOA-VMD-EIM technique can realize correct decomposition of each component of vibration signal, and obtain more accurate damping ratio results compared to classical half power bandwidth method (HPBM). Conclusions: It is experimentally verified that the proposed DOA-VMD-EIM damping method is effective. In addition, it is verified that the Fe-12Cr-3Al alloy mounting pedestal has better damping capacity. [ABSTRACT FROM AUTHOR]

On account of the dissipative martensite phase transformation, NiTi shape memory alloy can exhibit large pseudoelastic deformation and high damping capacity, making it a promising candidate in engineering vibration control. The main objectives of this paper are twofold: to investigate the free vibration behavior of the NiTi wires and to design a NiTi wire-based vibration isolator to verify its effectiveness in vibration control. The free vibration system consists of a mass and two antagonistic NiTi wires; finite element simulation on this system is carried out. The material model used in the simulation is created by implementing a generalized SMA model into commercial software by means of a user-defined material subroutine. Uniaxial tensile tests on the pseudoelastic NiTi wires and cables were conducted to determine the model parameters. Parametric analysis of the vibration system shows that the mass affects the frequency, the initial deflection affects the dissipation of the vibration energy in the first few cycles, and the pre-strain decreases the stabilized amplitude. Finally, a NiTi-based vibration isolator is designed, which can dissipate 95% of the vibration energy in 0.3 second, showing good ability to recenter the device in a short time. [ABSTRACT FROM AUTHOR]

Optical payloads are widely used in many fields, such as aerospace, drones, autonomous vehicles, or other highly precise instrumentation. Vibration is one of the causes that greatly affect the quality of data of highly precise optical payloads. Recently, many researcher focuses on isolating the vibration for the precise equipment, those study just only mention the overcoming of vibration in one or two directions, but in reality, an object will exist vibration in six directions in space. Therefore, it is necessary to find a new mechanism that can isolate vibration in six axes in space. The parallel mechanism is considered a viable system because of its strengths in accuracy, rigidity, and stability. In this research, the author proposes a novel 6-DOF passive vibration isolator based on the Steward platform with S-shaped legs. We have developed a 6-DOF passive vibration isolator using the S-shaped non-linear stiffness and damping characteristics. In this study, the model parameters of a vibration isolator device with legs using an S-shaped will be proposed. Based on geometrical parameters and vibration sources and some loads assuming the structure's durability problem will be calculated and evaluated the efficiency of the isolator at different frequencies. With the specially designed S-shaped it can be deformity like a spring, and with the change of structural and material parameters, we can adjust the system's stiffness and damping capacity. Due to the high static stiffness and low dynamic stiffness of each leg, and thus it is designable to isolate very well vibration isolation performance in all six directions. This research is organized as firstly the kinematics and 3D model are introduced. Secondly, the stiffness matrix of the novel 6-DOF passive vibration isolators is presented. Statics analysis of the 6-DOF passive vibration isolators revealed that the S-shaped structure provides sufficient load-carrying capacity and isolation due to its very good static nonlinear stiffness. The dynamic stiffness of the isolator in this study in each direction is very low but does not reduce the load-carrying capacity of the structure. By changing the structure and material parameters (which is very simple in a purely passive manner), we can completely adjust both the dynamic and static stiffness of the mechanism. The last series of numerical simulation results on displacement and a statics response in random excitation is carried out to show the effectiveness of the proposed 6-DOF passive vibration isolator, as well as the influence of structural parameters on vibration attenuation performance. The simulation results with the different exciting are shown to demonstrate the efficiency of the 6-DOF passive vibration isolators. Considering its simulation results A proposed new 6-DOF isolator will be applied in various engineering practices with multi-degree of freedom vibration isolation such as for precise optical payloa [ABSTRACT FROM AUTHOR]

In this study, the Mg-15Se binary system was, for the first time, investigated and synthesized using the powder metallurgy (PM) method, including microwave sintering and hot extrusion. The resulting material was shown to possess visible pores with a porosity of 2.91%, higher than other Mg materials synthesized using this method in the literature. Despite this, the material not only exhibited a comparable corrosion response with pure Mg but also a significantly superior mechanical response (76% greater damping capacity, 57% increase in hardness, and increases of 21%, 50%, and 51% for compressive yield strength, ultimate compressive strength, and fracture strain, respectively). Thus, this not only opens the door for future work concerning the addition of medicinal Se to nutritional Mg element and the optimization of process parameters but also could potentially be making inroads into the biomedical field with the use of selenium as a biomedical-oriented alloying element. [ABSTRACT FROM AUTHOR]

The effect of complex alloying with iron, nickel, aluminum, zinc, zirconium and titanium in an amount of 0.5 – 1.2% each on the damping capacity of binary alloys Mn – 50% Cu and Mn – 40% Cu in the range of amplitude-independent damping is studied after aging at 643 K for 0.5 – 40 h and natural aging for 7 months. It is shown that alloying of the Mn – Cu alloys in cast condition may either raise their damping capacity or leave it invariable. With increase of the aging time, the values of the frequency of resonance vibrations of specimens of the Mn – Cu alloys fall to a minimum and then grow to a maximum level. The high damping capacity of the multicomponent Mn – 45.6% Cu – 1% Fe – 1% Ni – 1% Zn – 0.9% Zr – 0.5% Ti alloy (ψ = 2.9%) and of the Mn – 35.8% Cu – 1%Fe – 1%Ni – 1%Al – 1.2% Zr alloy (ψ = 3.5%) cast and aged for 40 h at 643 K does not decrease after 7 months of natural aging at 293 K. [ABSTRACT FROM AUTHOR]

This work focused on producing and characterizing high silicon cast irons (microstructural analysis, tensile properties, damping capacity, elastic properties). Moreover, it also evaluated the influence of RE alloying on damping capacity. The samples present a step-casting geometry to verify the cooling rate's impact on their microstructures and, consequently, on the mechanical properties. The high Si SGI presented a fully ferritic matrix (i.e. pearlite < 5%) with uniform dispersed graphite nodules; however, those also RE alloyed showed a lower nodularity. The results show an average increase, relative to the base SGI, of 33% for tensile strength and 55% for yield strength (section thicknesses between 45 and 25 mm). A damping capacity increase was observed, reaching a maximum increase of 32% with the addition of RE. The beneficial impact lies in the possibility of increasing the damping capacity of SGI, without compromising its tensile strength, by balancing the graphite degeneration (induced by RE alloying) and strengthening the ferritic matrix (promoted by the high Si content). [ABSTRACT FROM AUTHOR]