Stable Cyclic Behavior Research Articles

Pull-in features of nanoswitches in the Casimir regime with account of contact repulsion

The cantilever tip of a nanoswitch in close proximity to the ground plate is considered with account of electrostatic, elastic, van der Waals (Casimir), and also contact repulsive forces. The van der Waals (Casimir) and contact repulsive forces are computed for a Si cantilever and either Au or Ni ground plates using the Lifshitz theory and the method of pairwise summation with account of surface roughness. It is shown that at short separations an impact of the van der Waals (Casimir) force leads to the pull-in and collapse of a cantilever onto the ground plate if the contact repulsion is disregarded. Taking into consideration contact repulsion, the nanoswitch is demonstrated to have the stable cyclic behavior with no pull-in when switching voltage on and off.

Cyclic Behavior of Concrete-Filled Tube Columns with Bidirectional Moment Connections Considering the Local Slenderness Effect

In this research, the cyclic behavior of concrete-filled thin tube (CFTT) columns with bidirectional moment connections was numerically studied within the context of thin-walled structures. Novel considerations in the design of CFTT columns with slenderness sections are proposed through a parametric study. A total of 70 high-fidelity finite element (FE) models are developed using ANSYS software v2022 calibrated from experimental research using similar 3D joint configurations. Furthermore, a comparison of different width-to-thickness ratios in columns was considered. The results showed that the models with a high slenderness ratio reached a stable cyclic behavior until 0.03 rad of drift, and a flexural strength of 0.8 Mp was reached for 4% of the drift ratio according to the Seismic Provisions. However, this effect slightly decreased the strength and the dissipated energy of the moment connection in comparison to columns with a high ductility ratio. Moreover, an evaluation of concrete damages shows concrete cracked for cyclic loads higher than 3% of drift. Finally, the joint configurations studied can achieve a good performance, avoiding brittle failure mechanisms and ensuring the plastic hinges in the beams.

Morphologically tailored NiMn2O4nanocubic material for high energy-power density asymmetric supercapacitor and non-enzymatic H2O2 sensing

Developing an advanced material for energy storage and sensors is considered a key solution to meet future energy demands and economic challenges. The inverse spinel-structured NiMn2O4 emerges as a promising electrode material for next-gen energy storage due to its notable power capability, high energy density, and excellent cyclic stability. Nanostructuring enhances features not achievable in bulk materials, with a mixed morphology of nano-cubic and nanoflakes optimizing surface-to-volume ratio for effective use in energy storage devices. The addition of PVP as a surfactant, transforms the diffusion-controlled behavior to a capacitive mechanism, enhancing energy density and cyclic stability. Electrodes exhibit a specific capacitance of 816 F g−1 at 1 A g−1 and stable cyclic behavior over 5000 cycles in 1 M KOH. The constructed ASC device shows 96% cyclic stability over 10,000 cycles, maintaining an energy density of 8.8 Wh kg−1 at 6400 W kg−1 and reaching a maximum of 36.55 Wh kg−1 at 400 W kg−1. Electronic structural characteristics explained through density functional theory (DFT) contribute insights. Furthermore, the non-enzymatic NiMn4/GCE H2O2 sensor demonstrates high sensitivity, a low detection limit, and remarkable selectivity against various biological interferences across a broad concentration range.

Additive manufacturing of NiTi architected metamaterials

Additive manufacturing has revolutionized the creation of complex and intrinsic structures, offering tailored designs for enhanced product performance across various applications. Architected cellular or lattice structures exemplify this innovation, customizable for specific mechanical or functional requirements, boasting advantages such as reduced mass, heightened load-bearing capabilities, and superior energy absorption. Nonetheless, their single-use limitation arises from plastic deformation resulting from localized yield damage or plastic buckling. Incorporating NiTi shape memory alloys (SMAs) presents a solution, enabling structures to recover their original shape post-unloading. In this study, an NiTi architected metastructure, featuring auxetic behavior and a negative Poisson's ratio, was designed and fabricated via laser powder bed fusion (LPBF). The samples exhibit promising superelastic performance with recoverable deformation strains at room temperature. Comprehensive characterization processes evaluated the functional performance of the fabricated metastructures. The metastructure geometry promoted microstructure formation primarily along the wall thickness. Cycling compression tests, conducted at three applied force levels, demonstrated stable cyclic behavior with up to 3.8 % reversible deformation strain, devoid of plastic buckling or yielding damage. Furthermore, the NiTi metastructures displayed robust energy absorption capacity and damping behavior, underscoring their potential for reusable energy dissipators in various industries including aerospace, automotive, construction, and etc.

Investigation of low‐disturbance seismic retrofit method for steel column bases using curved members

AbstractSeismic retrofit has always been a very important subject in recent years. However, typical retrofit techniques such as load‐resisting systems, damper devices, and seismic isolation systems will cause considerable disturbances to the structural system, such as increased force demand, and the building's occupants will need to be temporarily relocated during the construction. A design of the low‐disturbance retrofit method for steel column bases that uses the advantages of the curved member has been proposed in the study to improve seismic performance and reduce the mentioned demerits above. The basic mechanism of the curved member retrofit system was first analytically evaluated by preliminary modeling, followed by a parametric study to verify the effective shape. Four curved member specimens were tested with variations in fabrication processes and boundary conditions. Several aspects, including overall behavior, strength backbones, and deformation shapes of the specimens, were examined upon measured responses. The hysteretic performance of the curved member retrofit system is verified to achieve a stable cyclic behavior with limited strength degradation. A set of physical equations for estimating the lateral loads were established and verified by developing numerical models with a good agreement that enabled them to accurately represent the measured responses in the test.

Experimental study on cyclic behaviour of low yield point steel buckling-restrained braces

Low yield point steel is an advanced high-performance material that was deemed to provide reliable cyclic properties based on previous research. This paper presents experimental investigations into low yield point steel buckling-restrained braces (BRBs). Cyclic tests were conducted on nine full-scale specimens made of three grades of low yield point steels in China, including LY100, LY160, and LY225, with the nominal yield strengths of 100 MPa, 160 MPa, and 225 MPa, respectively. The failure modes, hysteresis behaviour, and mechanical indexes were analysed. Results showed that low yield point steel BRBs featured cyclic hardening behaviour with the strain hardening adjustment factor ω of 1.35–2.94, and the LY100 BRB exhibited more significant cyclic hardening (ω = 2.50–2.94) than the other two. Moreover, specimens showed tension–compression asymmetry behaviour with the compression strength adjustment factor β of 1.07–1.51, proving that the maximum compressive loads exceeded 7–51 % of tensile ones. The low yield point steel BRBs could produce stable cyclic behaviour and energy dissipation with the cumulative ductility factor of 491.16–3279.23 upon the acceptance stipulated in American and Chinese codes. Based on the test results, the performance of low yield point steel BRBs was evaluated, and suggestions were proposed for design purposes.

Numerical and experimental investigation on seismic performance of proposed steel slit dampers

Steel slit dampers (SSDs) are yielding dampers made of steel plates with several slits. This type of damper absorbs energy through the yielding of steel strips. In this study, the seismic behavior of proposed SSDs is investigated. To achieve this purpose, the finite element models of the one-column and two-column SSDs with different slit dimensions and number of slits are created. Then, the developed models are only subjected to cyclic loading. Afterward, experimental specimens of dampers with the highest ultimate and maximum strength are fabricated and tested. Based on the obtained experimental results, the SR1 damper with steel strips in the shape of square root function and the E1 damper with elliptical slits possess the highest energy absorption among the tested specimens. Furthermore, the tested two-column slit dampers have higher initial strength than one-column slit dampers. Also, the one-column slit dampers have more stable cyclic behavior and less strength drop in the applied displacement cycles.

Li reaction pathways in Ge and high-performance Ge nanocomposite anodes for Li-ion batteries

Ge is a highly researched anode material for Li-ion batteries (LIBs) owing to its high theoretical Li storage capacity and higher electrical conductivity compared to that of Si. However, Li reaction pathways in Ge have not been definitively established due to the formation of various and complicated Li-Ge alloy phases during lithiation/delithiation. Evaluation of the Li storage characteristics of bulk and nanocrystalline Ge demonstrated that nanocrystalline Ge showed higher Li reversibility than bulk Ge. Various cutting-edge ex situ techniques were used to analyze nanocrystalline Ge, and the Li reaction pathways in Ge were thoroughly demonstrated. To enhance the electrochemical Li storage characteristics of Ge, a Ge-based nanocomposite, Ge/Al2O3/C, was synthesized via simple one-pot mechanical solid-state reduction using GeO2, Al, and C. Ge/Al2O3/C exhibited very stable cyclic behavior at a current density of 100 mA g−1 over 300 cycles (capacity retention after 300 cycles: ∼95 %). Moreover, Ge/Al2O3/C exhibited excellent rate capability with high reversible capacity and stable cyclic behavior at a high 1C-rate. The superior electrochemical performance of Ge/Al2O3/C was attributed to the nanoscale dimensions of Li-active nanocrystalline Ge (∼10 nm) and Li-inactive Al2O3 (∼12 nm) embedded uniformly in the amorphous carbon matrices. The size of nanocrystalline Ge in nanocomposite was consistently maintained during repeated cycles owing to the anti-agglomeration effect of the uniformly distributed Li-inactive Al2O3 and amorphous carbon matrices. We anticipate that the electrochemical Li reaction pathways in Ge and the resulting high-performance nanocomposite anodes will be highly useful in investigating high-performance Ge-based anodes for LIBs.

Soft‐template assisted preparation of hierarchically porous graphitic carbon nitride layers for high‐performance supercapacitors

AbstractStrong π–π interaction between two‐dimensional graphitic carbon nitride (CN) layers may cause the stacking phenomenon, which leads to the decrease of its surface area and thus the capacitive properties. Hard templates are usually used to avoid the stacking phenomena. However, the use of them needs redundant removing process and may cause environmental pollution. As a result, in this work, P123 was used as the soft template to expand the inter‐layer distance and create more mesopores in the CN sheets. Benefit from the synergistic effect between the unique porous structure and the high nitrogen doping level, the formed graphitic CN (P2‐g‐CN) could exhibit high specific capacitances (520.5 and 176.0 F g−1 at the current density of 0.5 and 50 A g−1), stable cyclic behavior and satisfied energy density. The superior energy storage performances and the facile synthetic approach of P2‐g‐CN indicate its promising application as high‐performance electrode for supercapacitors and other energy storage devices.

Deformation mechanisms of selective laser melted 316L austenitic stainless steel in high temperature low cycle fatigue

To investigate the low cycle fatigue (LCF) properties of SLM (Selective laser melting) 316L at 550 °C high temperature, a series of LCF tests at different strain amplitudes is conducted on SLM 316L and traditional 316L. In contrast to the cyclic hardening behavior of traditional 316L, SLM 316L is shown to have a stable cyclic softening behavior and higher fatigue life due to its higher strength (yield strength is 1.9 times of traditional 316L). The coarsening of cellular sub-structure, evolution of geometrically necessary dislocations (GND) and texture direction contribute to the cyclic softening behavior of SLM 316L. Fractographic observations illustrate that strain amplitude has a significant influence on initiation and propagation of transgranular fatigue cracks, and lack-of-fusion defects near the surface are key initiation sites of fatigue cracks. Additionally, the life prediction method of the non-Masing model is suitable for SLM 316L.

Structural Performance of Cold‐Formed Steel Moment‐Resisting Frame Assembled by Bolts

AbstractMoment Resisting Frame is one of the framing systems used to construct the building. In this paper, the test results of the beam‐to‐column connection assembled by bolted joints are reported. The beams and columns are cold‐formed steel, and the beams are proposed to use the built‐up members composed of channel‐oriented toe‐to‐toe. Test results from the beam‐to‐column subassemblage showed a stable cyclic behaviour, and the strength deterioration occurred after the ultimate design story drift. The in‐elastic behaviour occurred only in the bolted joint region up to the design story drift level that was expected in the ultimate limit state design.

Self-activated, urea modified microporous carbon cryogels for high-performance CO2 capture and separation

Conventionally, porous carbons were synthesized using corrosive chemical activating agents. On contrary, we designed a single-step synthesis method for the preparation of a series of self-activated heteroatom (N)-doped carbon cryogels from potassium hydrogen phthalate (KHP) and urea at various temperatures (700–1000 °C), in the absence of any activating agent. To highlight the effectiveness of N-doping in porosity generation and CO2 adsorption/separation, a comparative analysis was drawn with a series of undoped carbon cryogels. Notably, the N-doped cryogels exhibit a highly porous structure with remarkable specific surface area (SSA; 2084 m2 g−1), micropore volume (1.1806 cm3 g−1), well-defined pore size distribution, and abundant narrow micropores (<1.04 nm). Additionally, a considerable mechanical strength (compressive strength = 0.621 MPa and compressive modulus = 8.86 MPa) was also observed. Moreover, the porous cryogel endowed with sufficient pyrrolic nitrogen content (≈51.4 at %) lead to high CO2 adsorption (280.57 mg/g at 273 K and 171.31 mg/g at 298 K at 1 bar) and an excellent ideal adsorbed solution theory (IAST)-based CO2/N2 selectivity (≈115) at 273 K, surpassing the CO2 adsorption/separation performance of previously reported N-doped carbons and resorcinol-based carbon gels. Furthermore, the moderate heat of adsorption (36.109 kJ mol−1) and stable cyclic behavior of CO2 adsorption-desorption under flue gas conditions (i.e., 15% CO2/85% N2) unveils the physisorption nature of adsorption which governs the energy-effective regeneration process. Summarizing, the present work demonstrates the successful fabrication of highly porous carbon cryogels as efficient CO2 adsorbents, thereby opening new synthetic avenues for self-activating porous carbon formation.

Design, manufacturing, and performance evaluation of a novel smart roller bearing equipped with shape memory alloy wires

In this study, a new type of seismic isolation device, called shape memory alloy (SMA) wire-based roller bearing (SMA-RB) is developed and introduced. The SMA-RB has been designed, manufactured, and experimentally tested. This bearing consists of cylindrical roller bearings and SMA wires with straight or cross configurations, as supplementary damping elements. In such a smart bearing, the superelastic (SE) SMA wires are passed through the hooks/pulleys attached to the supporting plates of the bearings in different configurations. The rollers provide lateral flexibility, and SMA wires supply energy dissipation and self-centering (SC) properties. In the manufacturing stage, a new mechanism for coupling wires (i.e. SMA wire joiner/coupler) is proposed. The results show that SMA wires, made of nickle titanium (NiTi), provide a SC damping mechanism with almost zero residual deformation which can effectively control the device from over-displacement. While using pulleys and newly designed wire joiners in the SMA-RB, the bearing can experience a stable cyclic behavior. Since the rollers generate a negligible amount of frictional force, the SE NiTi wires with a flag-shaped hysteresis mainly contribute to the overall shear hysteretic response of the SMA-RB. A triangular-shaped constitutive model can be used to accurately describe the hysteretic behavior of SMA-RB with different wire configurations.

Analytical and numerical study on the cyclic behavior of buckling-restrained SMA-based self-centering damper

Owing to the unique superelasticity and satisfactory energy dissipation capacity, shape memory alloys (SMAs) show great potential in earthquake engineering. This study focused on establishing analytical method and finite element (FE) model for the buckling-restrained SMA (BRSMA) based self-centering (SC) dampers. For the BRSMA-based SC damper, the lateral deformation of the slender SMA component is constrained by the surrounding buckling-restrained plates (BRPs). Hence, the SMA component avoids buckling induced instability and the damper accordingly exhibits stable cyclic behavior under tension–compression loadings. Although the compressive behavior has been obtained through cyclic loading tests, an in-depth understanding on the corresponding force-displacement relationship is required. As such, a simple analytical method was proposed for estimating the compressive strength capacity of the BRSMA-based SC damper. Besides, the FE model was built to provide additional information that was difficult to obtain in physical model tests. The accuracy of the analytical method and FE model was confirmed by the testing results. The verified FE model was further used to conduct the parametric analysis. The parameters of interest included the shape of the reduced section, the dimension of the BRSMA components, the gap between the BRSMA components and BRPs and the number of bolts. The findings of this paper not only promote understanding on the cyclic behavior of this new damper, but also provide suggestions and guidelines for future design.

Evaluation of seismic performance of rotational-friction slip dampers in near-field and far-filed earthquakes

In this study, the performance of rotational-friction slip dampers in steel structures with different heights is investigated by the use of fragility curves. The use of dampers is one of the methods for vibration control of structures by simultaneously increasing both the structural stiffness and damping. Rotational-friction slip dampers are among the passive control devices that dampen the earthquake energy through their stable cyclic behavior. To study the performance of these devices in steel structures, 3, 6 and 9-story steel moment frame structures are designed, and the mentioned dampers are attached to the structure by Chevron braces. To account for the earthquake uncertainty, with the aid of incremental dynamic analysis (IDA), the damper-equipped structure is subjected to both near-field and far-field ground motion records. The acceleration and drift engineering demand parameters are selected as the functions to quantify the damage states, and the design, modeling and material properties uncertainties are considered in accordance with FEMA P-695. Evaluation of statistical results and comparison of the fragility curves, shows that the probability of failure at different damage states decreases when the dampers are added to the structure. This decrease is more remarkable in low-rise structures and near-fault ground motions.

Graphene analogue metal organic framework with superior capacity and rate capability as an anode for lithium ion batteries

Metal–organic frameworks (MOFs), are enormously versatile materials, have vast potential in electrochemical energy storage systems (ESS) owing to their extraordinary surface area, high electronic conductivity, and suitable porosity. Herein, we synthesize porous, 2D graphene analogue conductive metal–organic framework, Ni3(2,3,6,7,10,11-hexaaminotriphenylene)2 (designed as Ni-MOF) nanofilaments (NFs), and utilise it as a competitive active lithium-ion battery (LIB) anode material for the first time. The Ni-MOF NF electrode supply extraordinarily high reversible capacities of ~1,079, 917, 790, and 626 mAh g−1 at specific currents of 0.1, 1, 2, and 5 A g−1, correspondingly. After cycling at diverse specific currents varying from 0.1 to 50 A g−1 for ten cycles each and afterward up to 150 cycles at 0.1 A g−1, the Ni-MOF NF anode supply a capacity of 845 mAh g−1. The full cell of 2D Ni-MOF NFs anode couple with nickel cobalt manganese oxide (NCM622) cathode provide a large energy density of 423 W h kg−1 with highly stable cyclic behaviour. The full cell attained a 431 mAh g−1 of capacity even after 200 cycles at a high specific current of 1 A g−1. These outstanding performances demonstrate the high application potential of 2D Ni-MOF NFs as a next-generation LIB anode.

AgSbS2-xSex thin films: Structure, composition, morphology and photodetection properties

Photodetectors using silver antimony seleno-sulfide (AgSbS2-xSex) thin films were fabricated and their photo sensing properties in the visible range were evaluated. The thin films were synthesized by combining chemical bath deposition and thermal evaporation techniques. The Sb2S3 thin films were deposited using chemical bath deposition followed by thermal evaporation of silver, varying the thickness from 10 to 80 nm proceeded by selenization via dipping in Na2SeSO3. The thin films were fabricated as glass/Sb2S3/Ag/Se layers with different silver thickness heated at 350 °C for 30 min. X-ray diffraction results showed the cubic structure of AgSbS2-xSex films. Elemental analysis, chemical composition and morphological studies were done using various techniques. The optical absorption in the UV–vis-NIR region spectra of the films with varying Ag content illustrated a wide spectral range for photodetector studies. The bandgap values calculated using Tauc plot method indicated within 1.53–1.75 eV, suitable for photodetector application. The current-voltage studies in the dark and illumination revealed that all the samples were photosensitive in the visible region. Methodical analysis of photoresponse was done using LEDs of various wavelengths at bias voltage of 0.5 and 1 V. All the samples showed a stable and good cyclic photoresponse behavior in the wavelength region between 395–740 nm. Further, the extensive photodetector application of the material was demonstrated by measuring the photoresponse using UV–vis LEDs and different laser power densities. The sensitivity and responsivity factors were calculated. With increase in Ag content, the conductivity of the films was increased and so the photocurrent response. This work asserts the application of AgSbS2-xSex thin films as a photodetector which has been explored till date for its photovoltaic properties only.

Cyclic behavior of an innovative braced ductile thin shear panel

This study aimed to investigate the cyclic behavior of an innovative braced ductile thin shear panel (BDSP) component consisting of a concentric rectangular thin shear panel, a surrounding flange plate, and X-shaped brace segments. A total of eight BDSP specimens at a one-third scale were designed, considering the influence of shear panel thickness, shear panel dimension, and stiffening rib space. The tests were performed by applying a reversed cyclic lateral load. All specimens exhibited a high initial lateral stiffness and stable cyclic behavior and failed in the shear panel region. The adoption of stiffening ribs reduced the ductility of test specimens but enhanced the lateral strength and energy dissipation. Pinching of the lateral force versus drift ratio was observed for the BDSP specimens without stiffening ribs, which exhibited considerably high deformability and limited energy dissipation. Additionally, the specimens without stiffening ribs experienced elastic shear buckling behavior and developed a tension field mechanism in the shear panel region along the main diagonal direction. The overstrength factor (RΩ) value of 1.4 was conservatively recommended for the BDSP specimens without stiffening ribs.

Self-healing gallium phosphide embedded in a hybrid matrix for high-performance Li-ion batteries

Self-healing materials have recently received considerable attention for improving the Li storage in anodes with high theoretical capacity that suffer from the mechanical instability triggered by the large volume change that occurs during electrochemical reactions. Ga has recently been explored for self-healing liquid metal electrodes in Li-ion batteries because it can be melted near room temperature. Previous reports have demonstrated the ultra-long cycling stability of these Ga-based electrodes owing to their self-healing properties. Unfortunately, despite these efforts, the performance of these Ga-based self-healing electrodes have not been fully satisfactory, particularly in terms of capacity. More importantly, the self-healing mechanism of liquid Ga has not been clearly investigated. Here, we synthesized GaP as a novel self-healing anode with an ultra-high capacity and stability. Self-healing in this Ga-based alloy occurred via the liquid-solid-liquid transition of Ga during lithiation/delithiation. In addition, by confining the liquid Ga in an appropriate binder (poly(acrylic acid)) through strong hydrogen bonding, stable cyclic behavior of the GaP was achieved. Furthermore, the TiO2-C hybrid matrix promoted the mechanical integrity and electrical conductivity of the GaP (GaP@TiO2-C). Consequently, the GaP@TiO2-C electrode showed superb cyclic performance (1012.0 mAh g−1 at 0.5 A g−1 after 500 cycles) and great rate capability. Various post-mortem analyses, including X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy, revealed the in-depth electrochemical reaction and self-healing mechanism of the GaP electrode. This study provides insight into the development of self-healing electrodes with high capacities and long cycling stabilities.

Achieving high porosity and large recovery strain in Ni-free high Zr-containing Ti-Zr-based shape memory alloy scaffolds by fiber metallurgy

Highly porous Ti-40Zr-8Nb-2Sn (at.%) shape memory alloy scaffolds were prepared by fiber metallurgy using rapidly solidified alloy fibers for the application of cancellous bone replacement. The phase constituents of alloy fibers and scaffolds were investigated by means of X-ray diffraction (XRD), superelastic behavior of alloy fibers was investigated by means of the dynamic mechanical analyzer (DMA), microstructures and mechanical properties of scaffolds were investigated by means of scanning electron microscopy (SEM) and compressive test, respectively. As-spun alloy fibers consisted of only β phase at room temperature. Clear superelastic behavior was observed in the as-spun alloy fibers at temperatures between 153 K and 298 K. The scaffolds showed three-dimensional networks with fiber-fiber bonds, whose porosity and pore size was about 80% and larger than 100 μm, respectively. The compressive yield stress and elastic modulus of the scaffold annealed at 973 K for 1.8 ks were about 4.0 MPa and 0.3 GPa, respectively, similar to those of cancellous bone. Recoverable strain in the scaffold was improved from 2.8% to 4.0% after annealed at 973 K due to the absence of α phase formed in the as-sintered scaffold. Stable cyclic superelastic behavior was observed in the annealed scaffolds at room temperature.