Hysteretic Characteristics Research Articles

Comparison of the Hysteresis Response of Super-Coiled Polymer Actuators

Abstract In recent years, super-coiled polymer (SCP) actuators have been investigated as a higher yield, low-cost alternative to conventional actuators. A major challenge has been finding appropriate general and industry uses for these actuators due to their hysteretic response. This paper seeks to compare the response for SCP actuators based on different thread weights and sizes and thus suggest possible directions for their use. The actuators were produced through coiling and heat training controlled via Arduino. The responses were obtained by supplying a controlled voltage to the system. The response was filmed and processed using matlab; the resulting displacement and strain were used to observe the hysteretic characteristics. Based on the characteristics noted, different applications were recommended for these SCP actuators. It is recommended that this research into SCP actuators be furthered by developing hysteresis models for compensation, control, and exploring their use in robotic systems and tactile mechanisms.

Effects of steel shim geometric characteristics and imperfections on the behavior of unbonded elastomeric bridge bearings subjected to large lateral displacements

Unbonded laminated elastomeric bridge bearings are designed to accommodate service-level deformations, but during an earthquake they can experience deformation demands that are significantly larger than those for which they were designed. Because these bearings are critical elements of a bridge, they must perform reliably even under seismic-level demands. The effects of the characteristics and condition of the steel shims on the seismic behavior of these bearings have received limited attention in the literature. Yet, the manufacturing process of these bearings sometimes introduces imperfections. For instance, during vulcanization, the steel shims might get rotated or bent. In this context, this paper investigates how manufacturing imperfections and the thickness characteristics of steel shims affect the behavior of unbonded elastomeric bridge bearings subjected to successive cycles of large lateral displacement. Finite element analysis is used to study the deformation pattern of these bearings, their hysteretic response characteristics, and the damageability of their steel shims. It is observed that imperfections can increase a bearing’s roll-off and risk of instability. Imperfections can also increase a bearing’s effective lateral stiffness and damage, quantified though a specific plastic-energy-based damage factor. Plastic damage in the shims is found to be appreciably dependent on their thickness. Under cyclic displacement, damage manifests itself more in the form of spreading of the yielded area rather than increased peak strain ductility. Plastic strains in the steel shims do not get close to the fracture limit, and all the bearings exhibit fairly stable hysteretic loops under the adopted loading protocol.

Quasi-static cyclic test on seismic performance of steel reinforced concrete frame with replaceable energy-dissipating member

In view of damage controlling and earthquake-resilient performance, the steel reinforced concrete (SRC) frame with replaceable energy-dissipating member (REDM) is proposed. The REDM is consisted of high damping concrete (HDC) wall panel and several fuses made by low yielding-point (LYP) steel. At first, low-cyclic reversed loading test on fuse is carried out to explore its shear capacity and hysteretic behavior. The suitable dimension and shape of fuse is determined for further study. Then the quasi-static cyclic test considering two loading patterns is applied on two SRC-REDMs. One specimen is loaded until overall failure while another is repaired by installing a new set of REDM during the loading history. The analyses and comparisons are conducted in terms of failure mode, yielding pattern, hysteretic characteristics, stress distribution, stiffness degradation, dynamic characteristics, ductility and energy dissipation. The failure mode is summarized as bending-shear failure of the wall panel, local buckling of fuses and beam hinge failure mechanism of SRC frame. The hysteretic loops are plump while large energy dissipation capacity is represented. The seismic performance is verified by high bearing capacity and ductility. The bearing capacity and stiffness of repaired specimen is significantly rehabilitated. The new REDM has dissipated much more hysteresis energy than that of non-repairing case. The earthquake-resilient behavior is confirmed by the significant recovery in mechanical properties.

MSA-based seismic fragility analysis of RC structures considering soil nonlinearity effects and time histories compatible to uniform hazard spectra

In the present study, an updated ground motion simulation framework based on spectral compatible time histories is proposed for the evaluation of seismic performance of mid-rise reinforced concrete structures with multi-stripe analysis (MSA) based probabilistic seismic hazard analysis. The seismic fragility functions are generated for two numbers of three storied instrumented test buildings of which one is founded on individual flexible footings and other one is a base isolated building. The fragility analysis is carried out for different performance levels under a series of input ground motions (IGMs) by considering uncertainty in soil structure interaction and uncertainty in ground motion. IGMs are obtained from the uniform hazard response spectrum (UHRS) with different return period thus conserving the frequency content of input motion during the scaling of high intensity earthquakes. The UHRS compatible synthetic time histories are applied at rock level and amplified surface motion obtained from soil amplification studies considering soil nonlinearity are applied to the buildings supported on soil springs. Nonlinear time history analysis is performed by modelling hysteretic characteristic of columns using modified Takeda model. The fragility curves obtained from the proposed methodology are compared with that using simple scaling of accelerograms generally performed in literature. The proposed technique gives conservative result for structure with individual flexible footings while no marked differences are observed for base isolated structure.

Seismic performance of steel staggered truss frame equipped with brace-type hybrid dampers with multiple nonlinear stages

This paper explores the effectiveness of a brace-type hybrid damper (BTHD) to enhance the seismic performance of a steel staggered truss frame. The study commenced by overcoming the severe abrasion of the friction component in the previous study and improving the hysteretic behaviour of the BTHD. An improved solution using BTHD was proposed and examined via numerical analysis. Stable friction behaviour played an important role in the multi-stage hysteretic energy dissipation characteristics. A simplified model composed of the friction behaviour, plasticity behaviour, and stopper mechanism was created in ABAQUS. The results were compared to a detailed finite element (FE) model and good accuracies were achieved. Parameter studies were conducted to investigate the influence of the length of the slotted hole, friction force, and yielding strength of the steel strips. To demonstrate the effectiveness of the BTHD, a conventional steel staggered truss frame (SSTF) was designed and built. The idea of SSTF composed of BTHDs (i.e. hybrid damper-SSTF) was designed and built simultaneously. The two structures had the same initial stiffness and ultimate strength. The cyclic pushover analysis and nonlinear dynamic analysis revealed that the deformation pattern of the structure was controlled, and the formation of a weak storey was thus prevented.

EESD special issue: AI and data‐driven methods in earthquake engineering – (Part 1)

EESD special issue: AI and data‐driven methods in earthquake engineering – (Part 1)

Anisotropic Vector Play Model and its Application in Magnetization Analysis

An anisotropic vector play model was developed by the superposition of scalar play models. An analytical identification method was derived for a uniaxially anisotropic term. Computed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BH</i> loops accurately reconstructed the measured anisotropic hysteretic characteristics of non-oriented silicon steel sheet. Its application to magnetization analysis by a physical magnetization model using multi-domain particles enhanced the prediction accuracy of the stress-dependent loss property.

Neural network model for hysteretic characteristic of shape memory alloy

Shape memory alloy has obvious hysteretic characteristics, which is crucial for the utilization of shape memory alloy, so a rational model is needed to describe them. In the current paper, a model for shape memory alloy based on the neural network is established, in which the activation function is modified so that it can naturally describe the hysteretic curve of shape memory alloy. The proposed neural network model is used to simulate temperature-induced hysteresis and stress-induced hysteresis, and the results show that the proposed model has a good effect and has certain adaptability. The reason why the proposed neural network model can describe hysteresis is qualitatively explained, and it is further pointed out that the model can be regarded as a generalized model of the Preisach model. The model is further extended to accommodate hysteretic curves under different conditions. The proposed neural network model has a simple form and high accuracy, especially in comparison with traditional models, and can be used for the modelling of shape memory alloys or other materials with hysteretic characteristics.

Theoretical and Experimental Analysis of a Winding Rope Fluid Viscous Damper

This paper investigated a winding rope fluid viscous damper (WRFVD) that uses the frictional amplification mechanism of a winding rope to obtain the operating characteristics of a viscous damper-like device. The WRFVD combined the advantages of fluid viscous dampers and friction dampers. It not only retained the mechanical characteristics of the fluid viscous damper but also reduced manufacturing costs. First, the construction and working principles of the WRFVD were introduced. A theoretical model that could accurately simulate the hysteretic characteristics of the damper was derived. Then, a series of dynamic tests were performed on six prototypes of the WRFVD. The dynamic performance under different displacement amplitudes and device parameters was analyzed based on the test results. In addition, the theoretical model was validated by experimental results. Finally, a series of parametric analyses of the WRFVD were performed. The experimental results showed that the WRFVD is a type of velocity-dependent damper with smooth and plump hysteretic curves under sinusoidal displacement excitation. Fatigue loading tests showed that the WRFVD had excellent fatigue resistance capacity and stable operational performance. The established theoretical model was reasonable and satisfactorily reproduced the hysteretic properties of the WRFVD. The parametric analyses showed that it was not recommended to improve the performance of the WRFVD by the method of adjusting the damping coefficient and pretightening load. It was reasonable to adjust the performance of the WRFVD by setting a smaller velocity exponent, an appropriate winding turn of winding ropes, and a suitable friction coefficient.

Development of numerical model capturing cyclic behavior of Two-Side clamped infill plates

This study aims to propose a simple numerical model methodology for two-side clamped infill steel plates with various aspect ratios, slenderness ratios and even different steel grades. The modeling element constructed using the methodology expects to be directly implemented into computer structural software for nonlinear time-history analyses of structures employing two-side clamped infill plates. The suggested model is constructed with their force–displacement relation including nonlinear and cyclic effects which can be defined by modeling parameters evaluated from empirical equations. The empirical equations are developed using regression analyses to agree with the parametric analysis results with detailed finite element models of two-side clamped infill plates. A proposed numerical model including the hysteretic characteristics was validated by comparison with existing experimental results conducted by other studies. It is confirmed to utilize the proposed numerical model that can accurately represent cyclic behavior over entire response ranges including buckling, tension field action representing the post-buckling behavior, and fracture of steel plates.

Superelastic pendulum isolator with multi-stage variable curvature for seismic resilience enhancement of cold-regional bridges

This study develops a novel superelastic pendulum isolator with multi-stage variable curvature (SPIVC) to enhance the seismic resilience of the cold-regional bridges. The SPIVC comprises the improved conical friction pendulum bearing (CFPB) with flat surface, spherical surface and inclined surface connected in series and re-centering devices fabricated by copper-based shape memory alloy (CuSMA). The novel SPIVC features the deformation accommodation under service loadings and seismic isolation under seismic shaking. The numerical model of the SPIVC is developed within OpenSees using the experimentally observed parameters. A typical continuous bridge is selected as benchmark bridge to investigate the seismic performance of the SPIVC system in cold regions. To achieve optimum parameters of the SPIVC, a cost-effective design method is developed based on the hysteretic characteristics of the re-centering device. The seismic performance of cold-regional bridge with SPIVCs under near-fault earthquakes is investigated and assessed by case study. Results show that the proposed method is effective to capture the isolator parameters. Case studies demonstrate the re-centering and seismic isolation performance of the SPIVC system employing the optimum parameters for bridges in cold regions, i.e., the novel SPIVC system can perform the dual control of the girder displacement, permanent isolator displacement and the seismic shear of the piers for each ambient temperature. The achieved findings can be employed to guide the resilience enhancement of the cold-regional structures and potential seismic applications.

A survey of Bouc-Wen hysteretic models applied to piezo-actuated mechanical systems: Modeling, identification, and control

Hysteretic nonlinearity behavior ubiquitously occurs in mechanical systems, particularly in high-precision instruments, which severely degrades system output performance. Consequently, it is unavoidable to establish an accurate hysteretic model to describe the hysteretic characteristic of various mechanical systems and to compensate for the system error caused by hysteresis. The piezo-actuated mechanism is one of the most frequent mechanical systems that occurs hysteretic phenomenon, explained in detail in this survey. Bouc-Wen (BW) model has been popularly applied in modeling hysteretic attributes due to the outstanding advantage of simple structure and identification process. This paper presents the latest BW model applications and investigates different BW models, identification methods, and control strategies in light of various application demands based on the BW model systematically. In addition, this survey is meaningful in choosing an appropriate modeling approach and control means for system design according to the distinct requirements, and in providing future research direction.

Random networks of disconnected nanoparticles in dielectric layers as a source of electric responsivity

Many efforts are currently focused on materials with responsive features for neural-inspired devices. Different approaches are followed, based on various mechanisms – from ferroelectric switching to structural phase changes, from magnetic tunnel junctions to metal filament formation. Here we analyze an alternative strategy based on an unconventional electrical response arising from percolative charge transport and charge trapping in discrete random networks of oxide nanostructures in a dielectric matrix. After an analysis of the mechanisms which can potentially be a source of a plastic response in this class of systems, we report evidence of this behavior in a system comprising an alkali-germanosilicate amorphous matrix with incorporated Ga-oxide nanostructures. The active material – consisting in a film 70 nm thick interfaced to p-type Si and Au electrodes – gives a responsive behavior to pulsed bias which is accompanied by bias dependent electric conduction, with resistivity changes of an order of magnitude by applying 2 V, as well as a dielectric response with hysteretic features, as expected by the model. The results represent a first proof of concept of an unexplored strategy for the design of responsive systems.

Development of small-scale buckling-restrained brace analog for physical experiments of structural systems

Experimental testing is critical for evaluating the performance of novel structural systems. However, the cost of full-scale testing can be limiting. Small-scale testing provides a lower cost alternative that can produce reliable data if each component of the scaled model is properly developed. Given their stable hysteretic behavior, buckling-restrained braces (BRBs) are featured in several seismic force-resisting systems. The design of typical BRBs involves an axially yielding steel core that is prevented from buckling by a concrete casing. Designs for adaptable and easy-to-implement small-scale BRBs that can be included in structural testing have not been established. In this work, a small-scale BRB analog is developed that utilizes a core steel yielding plate that is prevented from buckling by a pair of steel casing plates. A flexural yielding mechanism is employed in the small-scale BRB analog, which allows for practical dimensions and the ability to independently tune brace stiffness and strength. Prototype braces were fabricated and validated through quasi-static cyclic testing in which they exhibited the full and stable hysteretic behavior characteristic of BRBs. To aid in the use of this BRB analog by others, numerical results were utilized to generate empirical equations that relate the strength and stiffness of the scaled BRB to the archetypical geometry of the core plate. Given its ability to deliver a stable hysteretic performance, the wide range of strength and stiffnesses that it can provide, and its easy reusability, the developed device is a good choice for experiments where a small-scale BRB analog is needed.

Self-centring damper with multi-energy-dissipation mechanisms: Insights and structural seismic demand perspective

An innovative self-centring damper equipped with shape memory alloy elements and wedge-shaped friction plates (i.e. SMA-VFSD) characterised by multiple energy-dissipation mechanisms was developed. First, the notion and rationale of the damper was illustrated. Then, an analytical model enabling quantification of the hysteretic behaviour of the proposed SMA-VFSD was derived. A numerical parametric study using validated modelling techniques was subsequently conducted. The good agreement between the hysteretic responses of numerical models and analytical predictions confirmed the promise of the proposition and the adequacy of the analytical design model. Resorting to the analytical model, sensitivity analyses covering a wider spectrum of design parameters were performed, and the influence of essential parameters on the hysteretic behaviour of the damper was examined. Finally, the constant-ductility-based non-linear spectral analyses of an equivalent single-degree-of-freedom (SDOF) system representing steel frames equipped with SMA-VFSDs were performed to quantify the structural seismic demand and examine the effectiveness of the damper in improving the structural seismic performance. Two conventional self-centring systems characterised by flag-shaped hysteretic features were also studied for comparison. The analysis results showed that the multiple energy-dissipation mechanisms of the SMA-VFSDs are beneficial in reducing the structural inelastic seismic demand, highlighting the potential of the damper towards performance advances in self-centring structures.

Influence of Loading Sequence Effect on Cyclic Hysteresis Characteristics of an Al–Mg–Si Alloy

The alloy materials of automotive chassis are subjected to sequential time-varying loads due to road unevenness. The continuous change of the loading mode and the stress ratio leads to cyclic plasticity of the material, which induces cyclic hardening. The estimation of hardening effects seriously affects the structural's fatigue properties. Therefore, herein, a hardening model and the corresponding fatigue life prediction model are proposed. Then, the loading sequence effect's influence on an Al–Mg–Si alloy's cyclic hysteretic characteristics is analyzed. The steering knuckle is taken as the verification object. The acquired load spectrum is transformed into three sequential forms according to the equivalent damage principle for the verification test. The test results verify the conjecture of the loading sequence effect and confirm the accuracy of the proposed prediction model.

Large magnetic anisotropy and magnetostriction in thin films of CoV2O4

Spinel Cobalt Vanadate CoV$_2$O$_4$ has been grown on (001) SrTiO$_3$ substrates. Using torque magnetometry experiments, we find that the previously observed temperature induced anisotropy change, where the easy axis changes from the out of plane [001] direction to a biaxial anisotropy with planar <100> easy axes, occurs in a gradual second-order structural phase transition. This work characterizes this transition and the magnetic anisotropies in the (001), (100), and (-110) rotation planes, and explores their field dependence up to 30~T. Below 80~K, hysteretic features appear around the hard axes, i.e., the out-of-plane direction in (-110) and (010) rotations and the planar <110> directions in (001) rotations. This is due to a Zeeman Energy that originates from the lag of the magnetization with respect to the applied magnetic field as the sample is rotated. The appearance of the hysteresis, which persist up to very high fields, shows that the anisotropy at low temperature is rather strong. Additionally, field dependent distortions to the symmetry of the torque response in increasing applied fields shows that magnetostriction plays a large role in determining the direction and magnitude of the anisotropy.

Mechanism analysis of hysteretic aerodynamic characteristics on variable-sweep wings

Variable-sweep wings have large shape-changing capabilities and wide flight envelops, which are considered as one of the most promising directions for intelligent morphing UAVs. Aerodynamic investigations always focus on several static states in the varying sweep process, which ignore the unsteady aerodynamic characteristics. However, deviations to static aerodynamic forces are inevitably caused by dynamic sweep motion. In this work, first, unsteady aerodynamic characteristics on a typical variable-sweep UAV with large aspect ratio were analyzed. Then, deep mechanism of unsteady aerodynamic characteristics in the varying sweep process was studied. Finally, numerical simulation method integrated with structured moving overset grids was applied to solve the unsteady fluid of varying sweep process. The simulation results of a sweep forward-backward circle show a distinct dynamic hysteresis loop surrounding the static data for the aerodynamic forces. Compared with the static lift coefficients , at the same sweep angles, dynamic lift coefficient in sweep forward process are all smaller, while dynamic sweep backward lift coefficient are all larger. In addition, dynamic deviations to static lift coefficient are positively related with the varying sweep speeds. Mechanism study on the unsteady aerodynamic characteristics indicates that three key factors lead to the dynamic hysteresis loop in varying sweep process. They are the effects of additional velocity caused by varying sweep motion, the effects of flow hysteresis and viscosity. The additional velocity induced by sweep motion affects the transversal flow direction along the wing and the effective angle of attack at the airfoil profile. The physical properties of flow, the hysteresis and viscosity affect the unsteady aerodynamic characteristics by flow separation and induced vortexes.

Dynamic modelling of liquid crystal elastomer actuators based on a physics-phenomenon-combined approach

Liquid crystal elastomer-based actuators (LCEAs) exhibit large, reversible deformation, which demonstrates superior advantages in developing remote controlled, light-weighted soft robots. However, deformation of LCEAs undergoes complicated physical dynamics and exhibits highly nonlinear hysteretic characteristics, posing challenges in the realization of related applications. It is necessary to develop a dynamic model that captures the characteristics of LCEAs. With this purpose, this paper proposes a dynamic modelling approach for LCEAs to provide a hybrid model for LCEAs with reduced computational complexity and high precision. In the research, a modelling scheme based on a physics-phenomenon-combined approach for LCEAs is proposed, which considers the elastic free energy, the nematic free energy and dissipation of the LCEA. Physics-based models are then developed to describe these energies. Meanwhile, a phenomenon-based model is proposed to characterise the hysteresis as a component of the nematic free energy. The above models are combined together to provide the final hybrid model for the LCEA. To verify the proposed model, a photo-responsive LCEA experimental platform is established and experiments are conducted. Model parameters are identified based on the nonlinear least-squares method. The experimental results demonstrate the proposed model as an excellent representative to characterise LCEAs' dynamic behaviours.

A novel clevis-based beam-column model to investigate the hysteretic characteristics of steel moment connections: Experimental and numerical simulations

Following the 1994 Northridge and 1995 Hyogo-ken Nambu earthquakes, the potential for possible deterioration and failures in the connections of steel structures due to strong ground motions has been studied and explored. The most typical connection deteriorations have been fractures and deformation softening, as reported in earlier studies. The present study investigates the connection behavior uncertainties in fracture and deformation softening conditions. The connection behavior uncertainties were analyzed by applying a clevis-based mechanical connection under two loading protocols exhibiting far- and near-field earthquakes. In this connection, steel coupons on both sides of a middle pin were used to transfer the bending moment. Two notch patterns were formed on the steel coupons to create fracture conditions. Deformation softening cases were developed by reducing coupons’ cross-sections in various configurations. To compare the uncertainties, seven indicators were considered: (1) capping rotation, (2) fracture rotation, (3) yield bending strength, (4) capping bending strength, (5) residual bending strength, (6) negative post-yield stiffness, and (7) Park and Ang's damage index. The results of various tests, subsequent numerical studies, and nonlinear regression analyses show that some connection behavioral indicators have many uncertainties that should be seriously considered when analyzing structures with these types of connections. In addition to having varying dispersion, different indicators are also dependent on loading protocol characteristics.