Analysis Of Hysteresis Loops Research Articles

Structural performance and damage prediction using a novel digital cloning technique

This paper presents a novel, mechanics-based framework to create digital twins for earthquake-affected pinched structures, like reinforced concrete framed buildings. It uses robust and accurate structural health monitoring (SHM) results delivered by the hysteresis loop analysis method as an input to create digital twin models to predict nonlinear dynamic responses of previously damaged structures under potential future seismic events. Method validation is implemented using unique real-world data from the Bank of New Zealand (BNZ) building in Wellington, New Zealand, which experienced severe structural damage due to three earthquakes (Events 1, 2, and 3) between 2013 and 2016.Results show the digital twin derived from the SHM results of Event 1 can predict the inter-story displacement of the BNZ building for Events 2 and 3 with average correlation coefficients of ∼0.95 and ∼0.97 between predicted and measured responses, respectively. Moreover, the maximum difference between the measured and predicted peak values of inter-story displacements was 13 mm, a negligible difference in inter-story drift ratio (IDR). These results were accurate and consistent for all stories. Finally, the accuracy of this framework in capturing IDR values makes it a promising tool for assessing potential future structural collapse risk and its consequent financial risks using well-known incremental dynamic analysis methods.

DIC analysis of mechanical response of tooth aligners under simulated swallowing acts

In this work, the mechanical and deformation behavior of clear Polyethylene Terephthalate-glycol (PET-g) aligners, under cyclic loading was investigated using a full-field optical technique: the Digital Image Correlation. In particular, the PET-g aligners thermoformed from 0.88 mm thick discs, were subjected to cyclic compression tests for 13000 load cycles from 0 to 50 N in the atmospheric environment (~25°C). This number of cycles was chosen because it simulates, on average, the intraoral load associated with the swallowing acts that an aligner is subjected to during the time of use of 1 week. At the same time, the results from the analysis of hysteresis loops obtained by the DIC technique were compared with those obtained by the testing machine. The mechanical response of clear aligners was evaluated in terms of maximum displacement, energy loss and relative stiffness along the load direction to seven different stages of the 13000 load cycles. A comparable trend was found between the measurements obtained by Digital Image Correlation analysis and the analysis of the hysteresis loops obtained from the cyclic compression tests. Furthermore, the morphological features of the PET-g aligner at the end of the tests were analyzed by optical microscopy (OM). The OM analyses showed that the surface of PET-g aligner was affected by morphological variations such as high depressions and cracks.

ОПРЕДЕЛЕНИЕ ВЯЗКОУПРУГИХ ХАРАКТЕРИСТИК ЭЛЕМЕНТОВ МНОГОСЛОЙНЫХ КОНСТРУКЦИЙ НА ОСНОВЕ АНАЛИЗА ДИССИПАЦИИ ЭНЕРГИИ

The deteriorating operating conditions of roads is one of the most important problems facing specialists in the road industry. It is mainly associated with a reduction in the rigidity of road pavements made as extended multi-layer structures. To identify the causes of rigidity reduction, non-destructive testing is used, which is based on solving the inverse coefficient problem of restoring the elastic constants based on the response on the surface. Purpose of the study: We aimed to provide a rationale for a new pavement condition indicator that would take into account the history of deformation and loading from a source on the surface, based on which it would be possible to solve the inverse problem of restoring the elastic and viscous characteristics of pavement layers. Methods: To do that, we performed mathematical modeling of the stress-strain state of a multi-layer medium based on the solution of a system of dynamic Lame equations. Viscosity is taken into account by introducing tangents of the angles of wave energy losses in the materials of layers. Results: The results obtained in modeling for the first time made it possible to establish the relationship between changes in the modulus of elasticity as well as tangents of the angles of energy losses in pavement layers and the amount of energy dissipation in the structure. Discussion: It should be noted that it is possible to switch from the bowl of maximum dynamic deflections as the main pavement condition indicator to the analysis of hysteresis loops on the road structure surface, recorded at different distances from the point of load application and being an analogue of the full bowl of dynamic deflections showing the history of the test object loading.

Sediment and carbon dynamics during an episodic flood in an intermittent river

AbstractThe contribution of intermittent rivers and ephemeral streams (IRES) to the global carbon cycle has largely been overlooked. Flood events can impact hydrological processes, carbon (C) transport, and carbon dioxide (CO2) emissions. This study monitored river flow and sediment concentrations in an intermittent river during a flood event. Water samples were measured for water quality factors and C transport indices. CO2 partial pressure (pCO2) and CO2 flux (FCO2) were also analyzed. Remote sensing data were used to analyze soil erosion in the basin. Results indicate that the total sediment load from the flood was approximately 5503.1 t, with sediment concentrations showing a direct relationship with flow discharge. By completing a hysteresis loop and soil erosion level analysis, soil erosion from the river source and runoff surface scour were found to be the primary sources of sediment. The flood significantly increased particulate organic carbon and decreased dissolved organic carbon. During the flood, pCO2 ranged between 669 and 1229 ppm, indicating that the IRES served as a carbon source, with pH and total dissolved solids being the main influencing factors. The FCO2 varied between 20.16 and 568.33 mg m−2 h−1 and revealed a significant positive correlation with pCO2. After the flood ended, CO2 emissions increased and remained high for a long time. The study findings have substantial implications for IRES responses to extreme flood events, which are predicted to increase in intensity under climate change.

Correlation Between IASCC Susceptibility and Magnetic Properties of Stainless Steel Irradiated with Xenon Ions

In order to investigate the correlation between irradiation-assisted stress corrosion cracking (IASCC) susceptibility and the magnetic properties of austenitic stainless steel after ion irradiation, the magnetic properties and phase transformation were studied using a vibrating sample magnetometer and synchrotron radiation grazing incidence X-ray diffraction (GIXRD) on an irradiated specimen up to 25 displacements per atom. GIXRD indicated that the body-centered-cubic (BCC) phase was introduced in austenitic stainless steel by ion irradiation. Then, magnetic hysteresis loop analysis was conducted to give a quantitative analysis on the BCC magnetic phase under different irradiation damage and annealing temperature conditions. Based on the fact that postirradiation annealing will eliminate IASCC susceptibility at 550°C for 1 h, a correlation between IASCC susceptibility and magnetic properties was discussed, and a corresponding IASCC evaluation method was developed.

High Energy Storage Density in Nanocomposites of P(VDF-TrFE-CFE) Terpolymer and BaZr0.2Ti0.8O3 Nanoparticles.

Polymer materials are actively used in dielectric capacitors, in particular for energy storage applications. An enhancement of the stored energy density can be achieved in composites of electroactive polymers and dielectric inorganic fillers with a high dielectric permittivity. In this article, we report on the energy storage characteristics of composites of relaxor terpolymer P(VDF-TrFE-CFE) and BaZr0.2Ti0.8O3 (BZT) nanoparticles. The choice of materials was dictated by their large dielectric permittivity in the vicinity of room temperature. Free-standing composite films, with BZT contents up to 5 vol.%, were prepared by solution casting. The dielectric properties of the composites were investigated over a wide range of frequencies and temperatures. It was shown that the addition of the BZT nanoparticles does not affect the relaxor behavior of the polymer matrix, but significantly increases the dielectric permittivity. The energy storage parameters were estimated from the analysis of the unipolar polarization hysteresis loops. The addition of the BZT filler resulted in the increasing discharge energy density. The best results were achieved for composites with 1.25–2.5 vol.% of BZT. In the range of electric fields to 150 MV/m, the obtained materials demonstrate a superior energy storage density compared to other P(VDF-TFE-CFE) based composites reported in the literature.

Rheological and Thermal Conductivity Study of Two-Dimensional Molybdenum Disulfide-Based Ethylene Glycol Nanofluids for Heat Transfer Applications

The rheological behavior of two-dimensional (2D) MoS2-based ethylene glycol (EG) nanofluids (NFs) was investigated at low volume concentrations (0.005%, 0.0075%, and 0.01%) in a wide temperature range of 0–70 °C and at atmospheric pressure. A conventional two-step method was followed to prepare NFs at desired volume concentrations. Based on the control rotational (0.1–1000 s−1 shear rate) and oscillation (0.01–1000% strain) methods, the viscoelastic flow curves and thixotropic (3ITT (three interval thixotropic) and hysteresis loop) characteristics of NFs were examined. Shear flow behavior revealed a remarkable reduction (1.3~14.7%) in apparent dynamic viscosity, which showed concentration and temperature dependency. Such remarkable viscosity results were assigned to the change in activation energy of the ethylene glycol with the addition of MoS2. However, the nanofluids exhibited Newtonian behavior at all temperatures for concentrations below 0.01% between 10 and 1000 s−1. On the other hand, strain sweep (@1Hz) indicated the viscoelastic nature of NFs with yielding, which varied with concentration and temperature. Besides, 3ITT and hysteresis loop analysis was evident of non-thixotropic behavior of NFs. Among all tested concentrations, 0.005% outperformed at almost all targeted temperatures. At the same time, ~11% improvement in thermal conductivity can be considered advantageous on top of the improved rheological properties. In addition, viscosity enhancement and reduction mechanisms were also discussed.

Reconstructing asynchrony for mechanical ventilation using a hysteresis loop virtual patient model

BackgroundPatient-specific lung mechanics during mechanical ventilation (MV) can be identified from measured waveforms of fully ventilated, sedated patients. However, asynchrony due to spontaneous breathing (SB) effort can be common, altering these waveforms and reducing the accuracy of identified, model-based, and patient-specific lung mechanics.MethodsChanges in patient-specific lung elastance over a pressure–volume (PV) loop, identified using hysteresis loop analysis (HLA), are used to detect the occurrence of asynchrony and identify its type and pattern. The identified HLA parameters are then combined with a nonlinear mechanics hysteresis loop model (HLM) to extract and reconstruct ventilated waveforms unaffected by asynchronous breaths. Asynchrony magnitude can then be quantified using an energy-dissipation metric, Easyn, comparing PV loop area between model-reconstructed and original, altered asynchronous breathing cycles. Performance is evaluated using both test-lung experimental data with a known ground truth and clinical data from four patients with varying levels of asynchrony.ResultsRoot mean square errors for reconstructed PV loops are within 5% for test-lung experimental data, and 10% for over 90% of clinical data. Easyn clearly matches known asynchrony magnitude for experimental data with RMS errors < 4.1%. Clinical data performance shows 57% breaths having Easyn > 50% for Patient 1 and 13% for Patient 2. Patient 3 only presents 20% breaths with Easyn > 10%. Patient 4 has Easyn = 0 for 96% breaths showing accuracy in a case without asynchrony.ConclusionsExperimental test-lung validation demonstrates the method’s reconstruction accuracy and generality in controlled scenarios. Clinical validation matches direct observations of asynchrony in incidence and quantifies magnitude, including cases without asynchrony, validating its robustness and potential efficacy as a clinical real-time asynchrony monitoring tool.

All-inorganic halide perovskite tuned robust mechanical-energy harvester: Self driven posture monitor and power source for portable electronics

Scavenging electric power at ambient from biomechanical movements and mechanical vibrations using piezoelectric nanogenerators (PNGs) has become an accessible energy alternative for the development of self-powered electronic systems and miniaturized power sources for small-scale wearable/portable devices. Here, caesium lead chloride (CsPbCl3)-embedded β-phase comprising polyvinylidene fluoride (PVDF) hybrid films turns to a suitable functional material for piezoelectric-based mechanical energy harvesters. Incorporation of CsPbCl3 in the PVDF matrix enables high crystallinity and nucleation of electroactive β-phase ∼86% in the PVDF with piezoelectric coefficient d33 of 49 pm/V, much higher as compared to pristine PVDF. Dielectric study as a function of perovskite concentration at room temperature reveals dielectric constant of ∼ 66 and low dissipation factor of 0.21 at 1 kHz for optimized hybrid. Saturated ferroelectric P-E hysteresis loop analysis of the synthesized samples indicates variation in remanent polarization with perovskite content. The fabricated PNG delivered instantaneous output voltage of 168 V and peak-to-peak output current of 2 μA. High sensitivity of the flexible PNGs enables us to measure even a slight deformation due to bending by 2˚. Considering its good flexibility and high electrical output performance, optimized PNG was utilized for the fabrication of wearable self-powered posture sensor to monitor regular movement of our spine. Walking based wearable PNGs are also devised for powering up normal android mobile phone batteries. Fatigue test of PNG for continuous 10,000 cycle operation, even after 5 months from the fabrication time, highlights its robustness. Considering such simple and unique amalgamation of polymer and perovskite, these highly flexible PNGs can be easily integrated in portable electronic devices and with the advantage of biomechanical movements as the source of power.

Low Cycle Fatigue Behavior of Al-Mg-Si Alloys Extruded Parts

Over the past years, Al-Mg-Si alloys have been largely applied in automotive industry, which has required a deep knowledge of their mechanical properties and the influence of precipitates distribution on their mechanical behavior. This work evaluated the main mechanical properties of AA6005, AA6063, and AA6351 alloys by means of tensile and low cycle fatigue tests with 0.005 seg-1 deformation rate and 0.3% < εat <1.2% strain amplitudes. Besides, the hysteresis loop and internal stress analysis were investigated to analyze hardening and softening phenomena and to evaluate the friction and back stresses, respectively. Macro and microstructural were performed focusing in intermetallic distribution. Concerning the low cycle fatigue behavior, AA6351 presented shorter lives for strain amplitudes higher than 0.5%, and AA6005 showed the highest fatigue strength and fatigue ductility. AA6063 showed the lowest fatigue strength due to the presence of coarse particles (Fe,Mn)SiAl. During internal stress analysis, the highest value of friction stress for AA6351 indicates the effect of hardener precipitates are the most relevant role for cyclic loadings and the lowest back-to-friction stress ratio indicating that deformation is controlled by particles. In the other hand, AA6063 showed the lowest friction stress due to low amount of fine precipitates.

Investigating flood processes in karst catchments by combining concentration-discharge relationship analysis and lateral flow simulation

Concentration-Discharge (C-Q) relationship analyses allow better understanding catchment water origin and hydrological process variability across time (from storm-event to pluriannual scale). Though, those approaches mostly include integrative methods that consider catchments as a whole. The aim of this article is to assess the potential of a combined approach to investigate the spatio-temporal variability of flood processes within catchments (across river reaches and seasons), focusing on karst areas. The methodology consists in combining C-Q relationship analysis in nested catchments and simulation of lateral exchanges at the reach scale. For that, we analyze high-frequency records of discharge and electrical conductivity (EC) in karst catchments, in which EC informs on water residence time. Contributions of pre-event water (PEW) and event water (EW) during storm events are investigated through hysteresis loop analysis at each gauging station. Combined with lateral EC simulation at the reach scale, they make it possible to infer runoff processes during storms. A unary karst catchment in a temperate/mountainous climate (Loue River) and a binary catchment in a Mediterranean climate (Cèze River) were selected in France, and their conceptual models of water origin and hydrological process variability were drawn. In the Loue catchment, summer and fall storm events are characterized by contributions of PEW through piston-type flows, whereas decreasing EC values in winter and spring storm events indicate the major contribution of EW through surface runoff and fast infiltration. Within the catchment, EW contribution increases downstream, due to the canyon river morphology grading into open valleys. Regarding the Cèze catchment, contributions of EW are higher, indicating that fast infiltration and surface runoff are the dominant processes, associated with a PEW signature in summer and fall. Within the catchment, PEW contribution is found higher in karstified areas. These results show that flood process seasonality is mainly related to karst aquifer saturation rate, while intra-site variability is linked to karst area extension and river morphology. Results are encouraging to extend this approach to a variety of sites, notably those affected by significant surface water-groundwater interaction and groundwater flooding. Such approach, by providing a discretized information on flood processes, could help refining lumped hydrological models, or facilitate the use of semi-distributed ones.

Over-distension prediction via hysteresis loop analysis and patient-specific basis functions in a virtual patient model

Background and objectiveRecruitment maneuvers (RMs) with subsequent positive-end-expiratory-pressure (PEEP) have proven effective in recruiting lung volume and preventing alveolar collapse. However, a suboptimal PEEP could induce undesired injury in lungs by insufficient or excessive breath support. Thus, a predictive model for patient response under PEEP changes could improve clinical care and lower risks. MethodsThis research adds novel elements to a virtual patient model to identify and predict patient-specific lung distension to optimise and personalise care. Model validity and accuracy are validated using data from 18 volume-controlled ventilation (VCV) patients at 7 different baseline PEEP levels (0–12cmH2O), yielding 623 prediction cases. Predictions were made up to ΔPEEP = 12cmH2O ahead covering 6x2cmH2O PEEP steps. ResultsUsing the proposed lung distension model, 90% of absolute peak inspiratory pressure (PIP) prediction errors compared to clinical measurement are within 3.95cmH2O, compared with 4.76cmH2O without this distension term. Comparing model-predicted and clinically measured distension had high correlation increasing to R2 = 0.93–0.95 if maximum ΔPEEP ≤ 6cmH2O. Predicted dynamic functional residual capacity (Vfrc) changes as PEEP rises yield 0.013L median prediction error for both prediction groups and overall R2 of 0.84. ConclusionsOverall results demonstrate nonlinear distension mechanics are accurately captured in virtual lung mechanics patients for mechanical ventilation, for the first time. This result can minimise the risk of lung injury by predicting its potential occurrence of distension before changing ventilator settings. The overall outcomes significantly extend and more fully validate this virtual mechanical ventilation patient model.

Real-world application of hysteresis loop analysis for stiffness identification of an instrumented building across multiple seismic events

The BNZ building in Wellington, New Zealand was significantly damaged, and eventually demolished, due to the cumulative impact of three main earthquakes between 2013 and 2016. Although the building was equipped with a set of accelerometers, lack of an accurate SHM method allowed the damage level to remain hidden to engineers and property owners. An accurate SHM method would have quantified the seriousness of the damage in this building over each of three major events, enabling proper retrofit and better decision making.This study uses the hysteresis loop analysis (HLA) SHM method to investigate lateral stiffness changes for this structure, and the trajectory of damage accumulation for each story over all three events. HLA indicates the building suffered average stiffness reductions of 24%, 21% and 9% due to each event in the x direction, respectively, and 34%, 3% and 16% in the y direction. The first story lost ∼65% of its initial stiffness by the end of the third event. Between event differences or consistency, over all six stories, all events, and both directions, is ∼5% on average, providing an accurate, continuous SHM trajectory.HLA shows very good robustness and consistency in estimating elastic stiffness changes due to damage in this real-world, full-scale case analysis. Consistent, accurate estimation can help optimize decisions after major events. They also offer the future potential to build a virtual building model accurately predict forward what might happen to an already damaged structure in future events.

Structural Properties and Dielectric Hysteresis of Molecular Organic Ferroelectric Grown from Different Solvents

A comparative analysis of crystal structure, Raman spectra, and dielectric hysteresis loops was carried out for organic ferroelectric crystals of 2-methylbenzimidazole (MBI) grown from ethanol (MBIet), acetone (MBIac), deuterated acetone (MBId-ac), or prepared by sublimation from gas phase (MBIgas). Raman spectroscopy shows identical frequencies of molecular vibrations in all studied crystals, proving the same molecular structure. At the same time, a detailed analysis of the asymmetry of the powder XRD reflection profiles indicates the presence of nano-scaled regions with the same MBI symmetry and crystal structure but slightly different sizes and unit cell parameters. The formation of the MBI modifications is associated with possible penetration of solvent molecules into the voids of the MBI crystal structure. Dielectric hysteresis loops in MBIet and MBId-ac crystals at room temperature demonstrate significantly different values of coercive fields Ec. Analysis of hysteresis loops within the framework of the Kolmogorov-Avrami-Ishibashi (KAI) model shows that the polarization switching in MBId-ac occurs much faster than in MBIet crystals, which in the KAI model is associated with different values of the characteristic frequency ω0 and the activation field Ea of the domains wall motion.

Spin compensation, critical and discontinuous transitions behaviors in a ferrimagnet of spins 5/2 and 7/2

We apply Monte Carlo simulation techniques to study the magnetic behavior of a mixed ferrimagnetic Ising model on sites of a square lattice of LxL size, with L = 120, where 5/2 spins are alternated with 7/2 spins. We consider an antiferromagnetic interaction next-neighbor, ferromagnetic interactions next-nearest-neighbor, and an external magnetic field in the Hamiltonian that defines the model. We characterize the effects of an external magnetic field on the behavior of the system through the analysis of spin compensation points, discontinuous transitions, and hysteresis loops at various temperatures in the total magnetization and magnetic susceptibility. At the end, we study the phase diagrams of the critical, compensation and discontinuous transition temperatures. The physical phenomena experienced by the system under study are relevant to the application in magneto-optical recordings, in the synthesis and construction of molecular-based magnets and have technological applications in the manipulation and storage of magnetic information. We found some phenomena not reported in previous works on the same system.

Growth and characterization of the dynamical axion insulator candidateMn2Bi2Te5with intrinsic antiferromagnetism

Intrinsic antiferromagnetic ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ crystals, a candidate of dynamical axion insulator proposed theoretically recently, were successfully grown by the self-flux method. The crystal structure and chemical composition of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ crystals were experimentally substantiated. Temperature-dependent resistivity of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ shows a metallic behavior $(d\ensuremath{\rho}/dT&gt;0)$ when temperature $T&gt;25\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and a subsequently semiconductorlike feature $(d\ensuremath{\rho}/dT&lt;0)$. Magnetic measurement verifies that ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ is ferromagnetic at $ab$ plane but antiferromagnetic along the $c$ axis, whose N\'eel temperature is around 20 K. Analysis of magnetic hysteresis loops measured at different temperatures substantiates that critical indices of magnetic-paramagnetic phase transition in ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ are satisfied to the prediction of Landau mean-field theory. When $T&lt;20\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, there are unconventional Hall effects, including both anomalous Hall effect and topological Hall effect, when magnetic field $B&lt;3.4\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. Based on theoretical electronic-band structure of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$, the anomalous Hall effect of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ can be described by the Karplus-Luttinger (Berry curvature) mechanism, while the topological Hall effect of ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$, under $B&lt;3.4\phantom{\rule{0.16em}{0ex}}\mathrm{T}$, is attributed to noncollinear spin structure. Our results strongly suggest that ${\mathrm{Mn}}_{2}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$ is an axion insulator.

Effect of Co Substitution and Thermo-Magnetic Treatment on the Structure and Induced Magnetic Anisotropy of Fe84.5-xCoxNb5B8.5P2 Nanocrystalline Alloys.

In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe84.5-xCoxNb5B8.5P2 (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on a semi-industrial scale by the melt-spinning technique. The subsequent nanocrystallization processes were carried out under different conditions (with/without magnetic field). The comprehensive studies have been carried out using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hysteresis loop analyses, vibrating sample magnetometry and Mössbauer spectroscopy. Moreover, the frequency (up to 300 kHz) dependence of power losses and permeability at a magnetic induction up to 0.9 T was investigated. On the basis of some of the results obtained, we calculated the values of the activation energies and the induced magnetic anisotropies. The X-ray diffraction results confirm the surface crystallization effect previously observed for phosphorous-containing alloys. The in situ microscopic observations of crystallization describe this process in detail in accordance with the calorimetry results. Furthermore, the effect of Co content on the phase composition and the influence of annealing in an external magnetic field on magnetic properties, including the orientation of the magnetic spins, have been studied using various magnetic techniques. Finally, nanocrystalline Fe64.5Co20Nb5B8.5P2 cores were prepared after transverse thermo-magnetic heat treatment and installed in industrially available portable heating equipment.

Structural, dielectric and ferroelectric properties of Cu2+- and Cu2+/Bi3+-doped BCZT lead-free ceramics: a comparative study

Perovskite-type Ba0.98Ca0.02Zr0.02Ti0.98O3 (BCZT), Ba0.98Ca0.02Zr0.02Ti0.976Cu0.008O3 (BCZTC) and Ba0.9725Bi0.005Ca0.02Zr0.02Ti0.976Cu0.008O3 (BCZTCB) lead-free ceramics were synthesised via solid-state reaction method at a sintering temperature of 1380 °C. Effects of CuO and Bi2O3/CuO doping on structural, microstructural, dielectric and ferroelectric properties were investigated systematically. X-ray diffraction technique confirmed the existence of pure perovskite phase with the tetragonal structure in pure and in the doped BCZT ceramics at room temperature. The dielectric analysis demonstrated two anomalies around 24 °C and 126 °C for BCZT, which were identified as orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC) phase transition temperature, respectively. The TO-T temperature shifted to below 16 °C, while the TC increased to 132 °C for the BCZTCB sample. The physical mechanisms of the conduction processes were investigated through impedance spectroscopy, and the values of resistance, conductivity and activation energies associated with the grain and grain boundaries were evaluated. The activation energy was determined to be higher for doped samples than for pure BCZT. Further, the dopant-dependent ferroelectric nature of the ceramic samples was evidenced by the analysis of characteristic hysteresis loop, and a value of remnant polarization (Pr = 4.59 μC/cm2) was obtained for the BCZTCB ceramic sample. Furthermore, the d33 value, which was 54 pC/N for pure BCZT, was determined to be 140 pC/N and 64 pC/N for BCZTC and BCZTCB, respectively.

On the influence of ϰ-carbides on the low-cycle fatigue behavior of high-Mn light-weight steels

High-manganese light-weight steels offer a great potential for structural purposes in the mobility sector due to their reduced density combined with outstanding mechanical properties. As many of the envisaged applications of these materials will suffer from cyclic loading during their service life, the fundamentals of their fatigue behavior must be studied extensively. In the present work, the low-cycle fatigue (LCF) properties of an austenitic Fe-29.8Mn-7.65Al-1.11C light-weight steel were investigated. Two microstructurally different conditions are directly compared: a homogenized, fully austenitic condition and an aged, austenitic, ϰ-carbide-containing condition. Results elaborated by total strain-controlled fatigue tests are discussed considering microstructural insights revealed by scanning electron microscopy and synchrotron diffraction analysis. Although fatigue properties are improved upon aging due to ϰ-carbide formation for lower strain amplitudes as compared to homogenized counterparts, the cyclic deformation behavior is characterized by cyclic softening at increased strain levels. Shearing of the ϰ-carbides and their mechanical dissolution due to the onset of plastic deformation are found to be the underlying mechanisms. Determination of LCF parameters for both conditions was realized by evaluation of the fatigue life based on the Coffin-Manson law and Basquin equation, eventually providing explanations for the Masing and non-Masing behavior of the aged and homogenized condition, respectively, deduced from analysis of half-life hysteresis loops.

Evaluation of Pinching Effects on a Real Concrete Building Seismic Performance by Resimulating Displacement Responses Using HLA SHM Results

Assessment of structural damage state immediately after earthquakes can play an important role in decreasing economic and life losses, and in optimizing decision-making for affected buildings. These advantages highlight the need for rapid, accurate, and automated structural health monitoring (SHM) methods, as well as the need for generalizable model development methods to accurately resimulate nonlinear response to find the root causes of structural damage and identify elements for retrofit. This study tracked lateral stiffness changes for a real instrumented RC building subjected to three damaging earthquakes between 2013 and 2016 using the proven hysteresis loop analysis (HLA) SHM method. An idealized trilinear force–deformation pinching model created from HLA results is proposed to resimulate highly nonlinear pinching behavior of the building under these events. The proposed model facilitates assessment of the pinching region and its characteristics in terms of seismic response, stiffness and strength degradation, and the overall seismic performance of this RC building. Average correlation coefficients between measured and resimulated interstory displacement were 0.90, 0.97, and 0.97 across all stories for the three events, respectively. Resimulated interstory displacement error was less than 4% on average over all stories and events. These good resimulation results further validated the HLA method. More importantly, the proposed model clearly showed how pinching region length and its participation in dissipating energy increases as cumulative earthquake-induced damage increases in the building, potentially helping hide significant damage from typical detection methods. Thus, in addition to presenting a generalizable nonlinear modeling approach for postevent structural assessment, the overall results bring attention to the significant role that pinching plays in seismic energy dissipation and response for RC buildings.