Cyclic Model Research Articles

Analysis of the seismic performance of a large underground station structure in complex stratum considering the influence of axial force

The large underground structure in saturated stratum is vulnerable to float during an earthquake. This results in a plethora of problems, such as uneven settlement, large internal force and structure damage. In this study, the seismic behavior of a three-story, two-span subway station in complex saturated stratum was investigated through water-soil fully coupled 3D finite element method. In the analysis, the nonlinear soil behavior was described by a cyclic mobility model and the structure was calculated using a nonlinear constitutive model which can consider the influence of axial force on its bending moment. Joints elements were used to model the contact surface between soil and structure. The development of the soil displacement and internal force of the station structure at different times during a huge earthquake was examined. The bearing capacity of the station structure members was analyzed. The results indicated that the vertical displacement was spatially distributed. The larger additional seismic stresses appeared in the bottom slab and side wall. Failed elements were observed in both the walls and slabs, and the walls were more easily damaged than the slab. The results provide useful reference for the large underground structure seismic design in the construction of urban underground space.

Numerical simulation and experimental validation of ratchetting deformation of short fiber-reinforced polymer composites

This paper proposes a micromechanical model based on the finite element method (FEM) to analyze the ratchetting deformation of short glass fiber-reinforced polymer composites (SFRPCs). To reasonably consider the complex mechanical characteristics of the polymeric matrix under asymmetrical stress-controlled cyclic loading, a damage-coupled nonlinear viscoelastic-viscoplastic (VE-VP) cyclic constitutive model was constructed. The cyclic constitutive model of the matrix was introduced into the FEM model utilizing a user-defined material, and the corresponding experimental validation of the matrix was conducted. Subsequently, the cyclic constitutive model was introduced into the analysis of the micro-FEM model of the composites. The random orientation was considered to generate fibers in the FEM. Based on the analysis of the microscale representative volume element (RVE) model, the effects of different fiber content and cyclic peak stress on the ratchetting of SFRPCs were studied in detail. After validation, the effects of the fiber length and fiber stiffness on the ratchetting deformation of SFRPCs are discussed based on the developed micro-FEM model. The results show that the increase in the fiber length and fiber stiffness reduced the ratchetting deformation of SFRPCs within a specific content range. The model can assess the ratchetting deformation and damage evolution within the composites to provide more accurate predictions of the ratchetting deformation of SFRPCs and guide the expanded application of SFRPCs in structures.

Traversable Lorentzian wormhole on the Shtanov-Sahni braneworld with matter obeying the energy conditions

In this paper we have explored the possibility of constructing a traversable wormhole on the Shtanov-Sahni braneworld with a timelike extra dimension. We find that the Weyl curvature singularity at the throat of the wormhole can be removed with physical matter satisfying the NEC ρ + p ≥ 0, even in the absence of any effective Λ-term or any type of charge source on the brane. (The NEC is however violated by the effective matter description on the brane arising due to effects of higher dimensional gravity.) Besides satisfying NEC the matter constituting the wormhole also satisfies the Strong Energy Condition (SEC), ρ + 3p ≥ 0, leading to the interesting possibility that normal matter on the brane may be harnessed into a wormhole. Incidentally, these conditions also need to be satisfied to realize a non-singular bounce and cyclic cosmology on the brane [1] where both past and future singularities can be averted. Thus, such a cyclic universe on the brane, constituted of normal matter can naturally contain wormholes. The wormhole shape function on the brane with a time-like extra dimension represents the tubular structure of the wormhole spreading out at large radial distances much better than in wormholes constructed in a braneworld with a spacelike extra dimension and have considerably lower mass resulting in minimization of the amount of matter required to construct a wormhole. Wormholes in the Shtanov-Sahni (SS) braneworld also have sufficiently low tidal forces, facilitating traversability. Additionally they are found to be stable and exhibit a repulsive geometry. We are left with the intriguing possibility that both types of curvature singularity can be resolved with the SS model, which we discuss at the end of the concluding section.

Anti-Pied-Piping

Abstract: Anti-pied-piping is a widespread but understudied phenomenon where a language targets a proper subpart of the logical focus for focus morphosyntax: for example, focus particle placement or focus movement. We show that anti-pied-piping is attested in over sixty languages from over forty distinct language groups. We present a theory of focus particle syntax/semantics that involves severing the pronounced position of a focus particle and the logical position of its corresponding semantic contribution, which successfully accounts for both anti-pied-piping and pied-piping behavior. Constraints on attested anti-pied-piping behavior and its interaction with movement show that particle placement takes place at particular, punctuated points in the derivation, in a cyclic model of syntactic structure building. We also discuss the relation of particle placement to other processes such as linearization and stress assignment.

Constitutive model for reinforcing bars including bar buckling and low-cycle fatigue

In this paper, a path-dependent cyclic stress–strain model for reinforcing bars that incorporates the effect of bar buckling, low-cycle fatigue damage and loading history is proposed. A comprehensive experimental campaign is conducted to investigate the hysteretic behaviour of buckling-prone bars and the test results are used to develop and calibrate cyclic average stress versus average strain relationship for reinforcing bars. The parameters considered in this study include the slenderness ratio of reinforcing bars, grade of reinforcing bars and the loading history. Through a detailed analysis of test results, the effect of geometrical nonlinearity on the hysteretic response of the bar is evaluated and an analytical model simulating the effect of buckling on hysteretic response of the bar is developed. The cyclic model proposed herein captures the post-buckling stress deterioration, reduction of compressive stresses due to residual tensile strains (i.e. plastic strains), and reduction of unloading and reloading stiffnesses due to buckling and low-cycle fatigue damage in reinforcing bars. Comparison between experimental and analytical results shows that the proposed model can reliably predict the cyclic response of reinforcing bars including the effects of buckling and low-cycle fatigue.

Spatial dynamics of synergistic coinfection in rock-paper-scissors models.

We investigate the spatial dynamics of two-disease epidemics reaching a three-species cyclic model. Regardless of their species, all individuals are susceptible to being infected with two different pathogens, which spread through person-to-person contact. We consider that the simultaneous presence of multiple infections leads to a synergistic amplification in the probability of host mortality due to complications arising from any of the co-occurring diseases. Employing stochastic simulations, we explore the ramifications of this synergistic coinfection on spatial configurations that emerge from stochastic initial conditions. Under conditions of pronounced synergistic coinfection, we identify the emergence of zones inhabited solely by hosts affected by a singular pathogen. At the boundaries of spatial domains dominated by a single disease, interfaces of coinfected hosts appear. The dynamics of these interfaces are shaped by curvature-driven processes and display a scaling behavior reflective of the topological attributes of the underlying two-dimensional space. As the lethality linked to coinfection diminishes, the evolution of the interface network's spatial dynamics is influenced by fluctuations stemming from waves of coinfection that infiltrate territories predominantly occupied by a single disease. Our analysis extends to quantifying the implications of synergistic coinfection at both the individual and population levels Our outcomes show that organisms' infection risk is maximized if the coinfection increases the death due to disease by 30% and minimized as the network dynamics reach the scaling regime, with species populations being maximum. Our conclusions may help ecologists understand the dynamics of epidemics and their impact on the stability of ecosystems.

Fiber-based approach for seismic analysis of steel members using finite particle method

This paper presents an enhanced fiber-based approach for the seismic analyses of the behavior of steel structural members. This approach is built based on the framework of the finite particle method. Specifically, a fiber-beam element is developed to model the behaviors of structural members more elaborately. A cyclic constitutive model for fiber is proposed by enhancing a uniaxial steel hysteretic constitutive relationship to consider large strain amplitude and low cyclic fatigue. In addition, a fiber-based fracture model is proposed for modeling the progressive failure process of members. The proposed enhanced approach combines the finite particle method and fiber-beam element with more elaborated constitutive and fracture models, and it has the advantages in evaluating the cross-sectional plastic development and dealing with non-linear and non-continuum problems, which is suitable for analyzing the cyclic fatigue, buckling, and fracture of steel structural members. The analyses of steel plates and steel tube member specimens are performed to verify the effectiveness of the proposed approach. The proposed method is applied to analyze the collapse of a Kiwitt-8 single-layer latticed dome subjected to different seismic loads, which shows the feasibility of the fiber-based approach for seismic collapse analysis.

A Cyclic Resistance Ratio Model of Sand-Fines Mixtures Based on Cyclic Triaxial Test

A Cyclic Resistance Ratio Model of Sand-Fines Mixtures Based on Cyclic Triaxial Test

A novel correlation models for predicting stress intensity factor of semi-elliptical crack in welded pipelines under cyclic internal pressure based on Bézier base XIGA

Pipelines are strategic infrastructures that are used for energy transfer in the world. Cracks in the residual stress field are the common defects in welded pipelines. These defects with cyclic internal pressure cause crack growth and decrease the fatigue life of pipelines. In this study, a novel correlation model is proposed to predict the stress intensity factor (SIF) of the semi-elliptical crack front in welded steel pipeline subjected to cyclic internal pressure. For this purpose, the Bézier extraction base extended isogeometric method is applied for numerical analysis and preparing a database of results based on the thermo elastic-plastic equation. Taguchi standard L25 orthogonal array was used as the analysis design to create the simulations. New correlations were proposed for SIF prediction using the multivariate linear regression method. These correlations were obtained based on a parametric study that included three parameters. These parameters are dimensionless crack geometry (a/c), pipe geometry (D/t), and loading (P/Pb) or (σres/E). The R-Square (R2) values of the presented model for the welding residual stress and cyclic internal pressure were obtained as 0.989 and 0.992, respectively. The results of FEM analysis with similar conditions were compared to the results of XIGA and correlation models to validate the presented method. The maximum difference between them is approximately 3.71% for the cyclic internal pressure, and 2.94% for the welding residual stress. RMSD for the cyclic internal pressure model is 0.49, and for the welding residual stress model is 0.51. Therefore, the proposed correlation models have acceptable accuracy in predicting the SIF and fatigue crack propagation rate of the semi-elliptical crack in the steel pipes.

The cyclic response behavior, failure mechanism, and life prediction model of 9% Cr‐based steel under different strain ratios in the low cyclic fatigue regime at 430°C

AbstractDuring steam turbine rotor operation, the startup and showdown processes can cause asymmetric loading stress, leading to fatigue damage. To research the cyclic deformation behavior and fatigue failure mechanisms of 9% Cr‐based steel under asymmetric loading conditions, the strain ratios including −1, 0, and 0.1 are introduced into the low cyclic fatigue tests at 430°C. The results show the cyclic softening behavior is observed under three strain ratios at 430°C. As the strain ratio increases, the crack initiation sources, plastic strain, and consumed energy present an increasing trend. Comparing the microstructure morphology at different strain ratios, the coarsening lath and carbides affect fatigue crack initiation. Besides, the grain rotation and dynamic recrystallization can be observed, resulting in the cyclic softening behavior during the fatigue test. Finally, a new fatigue life prediction model is proposed at 430°C.

Monotonic and Cyclic Modelling of Structural Steel for Finite Element Analysis

Nowadays, as a response to the promoted concept of performance-based seismic design, the finite element method (FEM) has become an omnipresent practice that supports the simulation of structural elements. This approach requires constitutive numerical models, which could reproduce both elastic and plastic behaviour of steel. Looking forward to a reliable FEM simulation, the modelling and calibration of steel undergoing monotonic and cyclic loading tests is investigated in this paper. With respect to monotonic tensile test, a sensitivity analysis regarding mesh refinement and finite element type is developed. Another inspected issue, such as high-strength steel modelling, taking into consideration low ductility and absence of yield plateau, is also presented. And finally, a model for structural steel, using the combined isotropic-kinematic hardening model, is introduced to simulate metal non-linear behaviour under ultra-low-cycle fatigue regime. All these numerical simulations are processed via Abaqus software package, and are validated by a set of experimental tests.

Modeling on magnetization behavior of ferromagnetic material during cyclic deformation

In this paper, a nonlinear magneto-mechanical coupling constitutive model is established to describe the magnetization behavior of ferromagnetic materials under cyclic elastoplastic deformation. The critical state is introduced into the hysteretic magneto-mechanical model. In the critical state, the magnetization rates of loading and unloading are different. A new nonlinear plastic effective magnetic field is proposed by considering the effect of pinning sites caused by cross slip dislocation to describe the magnetization behavior under asymmetric cyclic loading. The softening factor and activation condition of plastic modulus parameter are introduced based on the cyclic plastic constitutive model to describe the decrease of plastic modulus. A new magnetization model for ferromagnetic materials under cyclic plastic deformation is established by combining the magneto-mechanical coupling model with the cyclic plastic constitutive model. Compared with the experiments and existing models, it is shown that the proposed model can capture the deformation and magnetization behavior well under cyclic loading.

Full-process electric vehicles battery state of health estimation based on Informer novel model

Accurately estimating state of health (SOH) of the power battery, as the core component of electric vehicles (EVs), is of great significance to the safety of EVs and the sustainable development of energy. Given the difficulty in measuring the capacity of lithium-ion batteries (LIBs) during vehicle operation and the linearization of prediction caused by not considering the phenomenon of capacity regeneration, a novel SOH estimation framework based on Informer and the entire charging and discharging process is proposed, which can be applied to the entire life cycle of power batteries in actual complex scenarios. In this study, the charge-discharge capacity is reanalyzed based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to obtain a nonlinear representation of the capacity. User behavior characteristics based on frequency and hourly meteorological data were extracted as health indicators (HIs) of LIBs. To integrate charge-discharge and meteorological data at different time scales, multivariate statistical data were resampled. The global dependency between HIs and SOH of the model input was learned by the Informer network. The results show that Informer networks outperform the cyclic structure-based model in prediction accuracy and robustness across different data distributions, and have great promise for state estimation.

The influence of marketing communications agencies on activist brands’ moral competency development and ability to engage in authentic brand activism: Wieden+Kennedy ‘Just Does It’

To compel people to bring about social change, activist brands must develop moral competency to ensure that they are perceived as authentic. However, there is limited research on the processes underpinning brands’ moral competency development. Furthermore, prior research on authentic brand activism has largely conceived of brands as singular entities as opposed to networks of diverse actors. Consequently, little is known about how inter-organisational collaborations influence brands’ moral competency development and ability to engage in authentic activism. We address this gap by presenting a case study of Nike, Inc./Wieden+Kennedy campaigns from 2017 to 2021 centred on women’s empowerment and of controversies from this period surrounding discrimination of female employees at Nike, Inc. By locating brand activism within the advertising client–agency relationship, we develop a cyclical model of activist brands’ moral competency development. Our model highlights that moral competency is not a static feature of brands but develops dynamically, and we identify the mobilisation of interactional expertise as a key driver of moral competency development. Furthermore, our model shows that a brand’s moral competency is not developed by a single organisation but through inter-organisational collaborations. We also demonstrate the challenges emerging from these collaborations and develop practical implications for activist brands.

Study on ultra low cycle fatigue fracture behavior of Q690D high-strength steel after fire exposure

In order to investigate the fracture behavior of Q690D steel high-strength steel after exposure to elevated temperature due to the fire, standard coupon specimen, notched coupon specimen and pure shear specimen representing various stress states were tested under monotonic loading and ultra low cycle fatigue loading. For air cooling condition, the tensile test results of Q690D steel show that when exposed to the temperature above 500 °C (up to 800 °C), the strength decreases while the elongation increases. These variation trends are basically the same under different stress states, and the predictive equations are proposed to determine the residual strength and ductility after exposure to high temperature. The effect of exposed temperature on the ductility under monotonic loading is significantly greater than that on the ultra low cycle fatigue life. In addition, as compared with air cooling, water cooling can significantly reduce the deformation capacity and fatigue life of the specimens, and even lead to a failure mode close to brittle fracture. The Lode parameter enhanced cyclic void growth model (LCVGM) parameters of Q690D steel after being exposed to various temperatures and air cooling were calibrated based on the fracture failure test results, and the post-fire LCVGM of Q690D high-strength steel was established to facilitate the fracture evaluation. Finally, the LCVGM was employed to predict the post-fire ultra low cycle fatigue life of Q690D steel notched plane strain specimen, and its estimation accuracy was verified by the comparison between tests and simulations. This fracture prediction model LCVGM can be recommended to evaluate the post-fire seismic performance of Q690 high-strength steel members.

Experimental and numerical study of PEN FRP-strengthened circular RC columns under lateral cyclic loading with high axial compression ratio

This paper presents experimental studies and numerical simulations of circular reinforced concrete (RC) columns wrapped with Polyethylene Naphthalate fiber reinforced polymer (PEN FRP, a kind of large-rupture-strain FRP) and conventional CFRP. A total of seven columns were designed and fabricated, including a control column, three columns strengthened with CFRP, and three columns strengthened with PEN FRP. All columns were subjected to cyclic lateral load and a constant high axial load. The effectiveness of PEN FRP strengthening was systematically analyzed and discussed regarding the failure mode, displacement ductility, lateral cyclic load–displacement curve, stiffness degradation and energy dissipation capacity. The test results indicated that the control column exhibited inferior ductility and peak lateral strength, while FRP-strengthened columns possess better energy dissipation capacity and ductility. Further study found that PEN FRP was preferred to CFRP with similar tensile stiffness in seismic strengthening. Finally, based on the cyclic compression model of LRS FRP-strengthened concrete, the improved tensile model of FRP-strengthened concrete, and the cyclic stress–strain model of reinforcing steel, numerical simulations for seismic performance were carried out in OpenSees. It was found that the numerical simulation results of all FRP-strengthened RC columns were in excellent agreement with the test results. To better understand the effect of FRP confinement stiffness on the seismic performance of circular columns, parametric analysis was performed. Results showed that the numerical simulations need to consider the buckling of longitudinal reinforcement for accurately predicting the seismic behavior of FRP-strengthened columns of lower confinement stiffness.

Ultra low cycle fatigue behavior of Q690 high-strength steel welded T-stub joints: Experiments and fracture prediction analysis

The paper presented an experimental and numerical investigation of the ultra low cycle fatigue behavior of high-strength steel welded T-stub joints. The normal and funnel T-stub joints in Q690 high-strength steel were tested under monotonic tensile loading and ultra low cyclic loading. The cyclic response of normal T-stub joints varying from bolt diameter, flange size and weld form were studied. It is found that fracture mode of the T-stub joints is basically the same under tensile loading and cyclic loading, i.e., cracking behavior occurs at the weld toe of the flange and tensile-shear failure is observed. The different configuration parameters of normal T-stub joints in the study show no significant influence on the fatigue life of the joints. Comparing the ultra low cycle fatigue results between normal and funnel T-stub joints indicates that the funnel T-stub joints have better energy dissipation capacity. In addition, the ultra low cycle fatigue performance of Q690 steel and ER80-G weld metal under various stress states were analyzed and discussed. In order to numerically generate the overall fracture behavior of the T-stub joins, the Lode parameter enhanced cyclic void growth model was adopted in the numerical simulation and the model parameters were calibrated according to the test results of Q690 steel and weld metal. Comparison with the experimental monotonic and cyclic tests of welded T-stub joints shows that the Lode parameter enhanced cyclic void growth model can provide accurate predictions of the ultra low cycle fatigue of the joints.

Anionic entanglement-induced giant thermopower in ionic thermoelectric material Gelatin-CF3SO3K–CH3SO3K

Ionic thermoelectric (i-TE) technologies can power Internet of Things (IoT) sensors by harvesting thermal energy from the environment because of their large thermopowers. Present research focuses mostly on using the interactions between ions and matrices to enhance i-TE performance, but i-TE materials can benefit from utilizing different methods to control ion transport. Here, we introduced a new strategy that employs an ion entanglement effect. A giant thermopower of 28 ​mV ​K−1 was obtained in a quasi-solid-state i-TE Gelatin-CF3SO3K–CH3SO3K gel via entanglement between CF3SO3− and CH3SO3− anions. The anionic entanglement effect involves complex interactions between these two anions, slowing anionic thermodiffusion and thus suppressing bipolar effects and boosting p-type thermopower. A Au@Cu | Gelatin-CF3SO3K–CH3SO3K | Au@Cu i-TE device with a generator mode delivers a specific output energy density of 67.2 ​mJ ​m−2 K−2 during 2 ​h of discharging. Long-term operation of the i-TE generator for 10 days shows that the harvested energy density offers an average of 2 ​J ​m−2 per day in a cyclic working-reactivation model at a temperature difference of 6 ​K. The results demonstrate that anionic entanglement is an effective strategy for achieving giant thermopower with i-TE gels, so they have excellent potential for powering IoT sensors.

Glutathione kinetically outcompetes reactions between dimedone and a cyclic sulfenamide or physiological sulfenic acids

Dimedone and its derivates are used as selective probes for the nucleophilic detection of sulfenic acids in biological samples. Qualitative analyses suggested that dimedone also reacts with cyclic sulfenamides. Furthermore, under physiological conditions, dimedone must compete with the highly concentrated nucleophile glutathione. We therefore quantified the reaction kinetics for a cyclic sulfenamide model peptide and the sulfenic acids of glutathione and a model peroxiredoxin in the presence or absence of dimedone and glutathione. We show that the cyclic sulfenamide is stabilized at lower pH and that it reacts with dimedone. While reactions between dimedone and sulfenic acids or the cyclic sulfenamide have similar rate constants, glutathione kinetically outcompetes dimedone as a nucleophile by several orders of magnitude. Our comparative in vitro and intracellular analyses challenge the selectivity of dimedone. Consequently, the dimedone labeling of cysteinyl residues inside living cells points towards unidentified reaction pathways or unknown, kinetically competitive redox species.

Fatigue Performance Analysis of Adhesive-bonded Composite Joints Considering Size Effect

Adhesive bonding failure is one of the main failure modes threatening the safety of the wind turbine blade (WTB), which drives fatigue performance analysis of adhesive bonding becoming a vital issue. Attributed to the high cost and sample scarcity of full-scale structural testing of WTBs, fatigue analysis of adhesive-bonded composite joints becomes a critical way to investigate the bonding properties. Adhesive bonding distributes in WTB with different sizes; thus, the fatigue performance in different place have a large difference. The existing researches mainly perform fatigue properties studies on the standard specimens, while the effects of bonding size on structural fatigue properties are ignored. With these concerns, a finite element method based on Cyclic Cohesive Zone Model theory is proposed, and size effects on fatigue properties are studied for adhesive-bonded composite joints in this paper. The results can be used for fatigue performance analysis for WTB adhesive bonding.