Loop Area Research Articles

The effect of pre-deformation loading on the cyclic hysteresis behavior of nanocrystalline NiTi alloy：A molecular dynamic study

In this work, the effect of pre-deformation loading on the cyclic hysteresis behavior of nanocrystalline NiTi alloy is investigated by the molecular dynamic. The nanocrystalline NiTi is subjected to a large monotonic pre-deformation loading firstly to generate the irrecoverable deformation on the initial model. After this pre-deformation treatment, the other cyclic loading is exerted on the nanocrystalline NiTi to estimate the effect of pre-deformation on cyclic hysteresis behavior. The simulation results show that the plateau length of phase transition and the hysteresis loop area decreases with the increase of pre-deformation loading. When the nanocrystalline NiTi model undergoes a pre-deformation of martensite plasticity, the hysteresis curve transforms from sigmoidal-shaped to shuttle-shaped, and the MD simulation also reveals that the hysteresis behavior is gradually dominated by the dislocation motion instead of the phase transition. The corresponding micro mechanism of this degeneration of super-elasticity could be explained by the fact that the dislocations brought by the pre-deformation hinder the reverse phase transition, which results in the accumulation of residual martensite phase and disordered structure. Furthermore, the models with different grain sizes and temperatures are also considered in the MD simulation. The simulation results proved that the dislocation motion is enhanced by the temperature increase, which brings a higher hysteresis energy under a large pre-deformation loading. For the grain size effect, the reduction of the grain size leads to a higher dislocation density, which results in a more obvious phase transition degeneration phenomenon for the model with a smaller grain size.

Characterization of thixotropic properties of fresh cement‐based materials

AbstractAccurate evaluation of the thixotropy of mixtures is crucial for the design and production of self‐compacting concrete, pumped concrete, and 3D printed concrete. However, there is no uniform standard for the assessment of the thixotropy of fresh cement‐based materials. In this paper, four widely used test procedures (thixotropic index, static yield stress growth curve, thixotropic hysteresis loop area, and three‐stage curve) are compared to determine the relationships between them. The results show that the test procedures based on the break‐down (destruction) process (thixotropic index, thixotropic hysteresis loop area, and degree of breakdown) are difficult to distinguish between reversible and irreversible thixotropic structures and to accurately assess the thixotropy of mixtures. The short‐term structural build‐up rate Rthix is more suitable for characterizing the thixotropic properties. The three‐stage curve can characterize both the degree of structural damage and the reconstruction ability of the paste, nano‐attapulgite clay can significantly improve the structural recovery degree of the mixture at the early hydration stage. This study will provide guidance and a theoretical framework for choosing the thixotropic characterization method of cement‐based materials in practical engineering applications.

Analysis of amplitude and frequency-dependent scaling behavior of dynamic hysteresis loop and thermal properties of BaZr0.05Ti0.95O3 ceramic

In this work, single-phase BaZr0.05Ti0.95O3 (BZT) ceramic was prepared through a conventional solid-state reaction route. The structural identity was analyzed by X-ray diffraction (XRD) and Rietveld refinement, which reveals the single-phase perovskite structure of the synthesized sample having an orthorhombic structure and space group Amm2. Scanning electron microscope (SEM) study gives an idea about the well-dense grains with clear grain boundaries of the BZT sample. Frequency and amplitude-dependent Polarization-Electric field (P-E) and Strain-Electric field (S-E) loops were studied. The parameters like remnant polarization (Ec), coercive field (Pr), loop area (<A>), energy storage efficiency (η), field-induced maximum strain (Smax) and inverse piezoelectric coefficient (d33*) were calculated. The scaling behavior of the hysteresis loops area as a function of frequency and field strength is studied. The thermal conductivity and thermal diffusivity as a function of temperature were investigated.

The damage mechanism of tension-tension fatigue interaction with creep damage of the compacted graphite cast iron alloy at high temperatures

The tension-tension fatigue test of the compacted graphite cast iron (CGI) alloy was carried out by RDL100 universal testing at 500 °C and 550 °C, respectively. A tension-tension trapezoidal load is applied to the CGI specimen. Because of the time-dependent deformation at elevated temperatures, the stress–strain curve presents hysteresis loops, and the area of the hysteresis loop increases gradually with continuous cyclic loading and sustained loading times. Intergranular and transgranular cracks in the microstructure accelerate the CGI alloy fracture failure. The fatigue life is sensitive to the short loading time and decreases with the sustained loading time exponentially under the tension-tension fatigue condition. The short holding time has a great influence on the fatigue life of CGI. The fatigue behavior of CGI alloys and the influence of holding time on the fatigue life can be characterized by y = aexp(bx) (a and b are constants, can be fitted through the test data). In addition, the fatigue life of CGI alloy can be predicted by the ductility depletion method. But the equivalent stress amplitude needs to be modified to eliminate the effects of oxidation damage.

Расчет системы амортизации шасси пассажирского самолета при ударном нагружении

The paper considers the shock absorption system of an advanced domestic mainline passenger aircraft, which includes oleo-pneumatic shock absorbers and wheels equipped with the pneumatic tires. Nonlinear mathematical models of single-active and two-active oleo-pneumatic shock absorbers of telescopic landing gear supports are proposed. The models take into account the process of polytropic gas compression, the forces of hydraulic resistance to the working fluid flow and the forces of dry friction arising in the system moving parts. To describe the vertical compression reaction of the pneumatic tires, the V.L. Biderman structural model was introduced, which parameters were determined by test results using the least squares method. Motion equations of the landing gear elements were obtained by the analytical mechanics methods involving the Ostrogradsky --- Hamilton variational principle of least action. Constraints imposed on the system were introduced using the penalty functions method. The problem statement of carrying out virtual computational experiments on the landing gear dvops was considered. In a wide range of the impact energies, models of shock absorbers of a passenger aircraft landing gear were validated, for which time realizations of the system state vector were determined, and areas of hysteresis loops of the shock absorber load characteristics were evaluated by the numerical integration. Satisfactory compliance of the results of simulated characteristics of the natural objects was shown. The obtained results could be used to improve the absorption quality criteria by numerical optimization methods, calculate the landing impacts and analyze the aircraft oscillations when moving on the runway

Constructing an urban cooling network based on PLUS model: Implications for future urban planning

Many studies on mitigation of the surface urban heat island (SUHI) are conducted from the perspective of landscape patch allocation, and few studies have investigated the overall impact of network connectivity on SUHI. In this study, an ecological network framework is proposed to identify the key patches and cooling corridors. Based on surface temperature inversion data, morphological spatial pattern analysis (MSPA) and landscape connectivity indexes are used to identify heat island and cold island patches with high ecological value on which to construct the network. The innovative patch-generating land use simulation (PLUS) model is introduced to construct a resistance surface, and Circuit theory (CT) is used to connect cold islands and heat islands in cooling corridors. The results show that from 1999 to 2019, land surface temperature (LST) increased significantly in the city of Haikou, the extreme LST became more and more significant, and the area with the highest temperatures showed a southward trend. The connectivity between cold and heat island patches declined, and the Loop, Bridge and Branch areas in heat islands increased. The latter scenario is conducive to the construction of cooling corridors. The land cover index had a great influence on SUHI, and the resistance surface presented a distribution pattern with high values in the northwest and low values in the southeast, which is consistent with the distribution of LST. Finally, we extracted the resultant cold-heat island cooling network, which was mainly concentrated along the southern edge of the study area, and found that corridor construction faced fewer obstacles in 2019 than in 1999. This study can guide urban planners to reinforce the parts of ecological networks that will mitigate the urban heat island effect.

RESULTS OF LABORATORY STUDIES OF THE EXPANDATE FORMATION PROCESS

The expanded preparation of feeds is carried out using high-temperature (80–140 °C) expanders. These expanders perform the task of preparing food products and feeds under high pressure (1–10 MPa). The expansion process is accompanied by chemical changes such as denaturation of proteins, amino acids, vitamins, starch, and enzymes. Additionally, there is a transformation of the physical and mechanical properties of the feed components, converting them into expandates. The laboratory research aims to establish the regularities of the compression pressure changes with the deformation of feed components and the density of the obtained expandates under various technological parameters. The study explores the impact of the granulometric composition of the feed, its moisture, and temperature on the deformation diagram, representing the relationship between stress and material deformation. For this purpose, testing was conducted using the Heckert FP-100/1 testing machine and additional devices and equipment. As research factors, the feed's moisture W (10 %, 20 %, 30 %), temperature T (80 °C, 110 °C, 140 °C), and the average particle diameter of ground feed components Dμ (0.5 mm, 1.5 mm, 2.5 mm) were selected. The study was conducted using a full-factor experiment, comprising a total of 27 experiments with three repetitions. For each experiment, a relationship of compression pressure changes with deformation (elastic hysteresis) of the feed components ΔP(εz) was obtained. The research criteria include: the area SΔP enclosed inside the elastic hysteresis loop ΔP(εz); the coefficient of mechanical losses (or relative hysteresis) Ψ, calculated as the ratio of the hysteresis loop area SΔP to the area enclosed between the stress-strain curve and the abscissa axis, where deformations SP1 are plotted; the height of the obtained expandate sample ha; and the density of the obtained expandates ρa. As a result of the laboratory research on the expandation process, dependencies of the compression pressure changes with the deformation of feed components ΔP(εz) were established. Additionally, correlations of the area of the elastic hysteresis loop SΔP, the coefficient of mechanical losses Ψ, the height of the obtained expandate sample ha, and the density of the obtained expandates ρa with the feed's moisture W, temperature T, and the average particle diameter of ground components Dμ were determined. By solving the compromise task of minimizing the coefficient of mechanical losses Ψ and maximizing the density of the obtained expandates ρa, the following rational technological parameters were obtained, ensuring the most effective feed expansion process: Dμ = 0.5 mm, T = 119.2 °C, W = 19.1%, ρa = 292.9 kg/m3.

Enhanced supercapacitors and LPG sensing performance of reduced graphene oxide/cobalt chromate pigments for energy storage applications

It is imperative that an initial inquiry be conducted as soon as possible since the production of monolayer of carbon atoms (rGO) composites is the root cause of their poor performance in supercapacitor and LPG sensors. Here, an effort is undertaken to construct a cobalt chromate pigments-reduced graphene oxide (CoCr2O4/rGO) by solution combustion method for the supercapacitor and LPG sensor. The proposed method is efficient and easy in terms of its application to the production of CoCr2O4/rGO polycrystalline composite on a wide scale. Within the scope of this work is an investigation into the improved supercapacitor and LPG sensing behaviour of CoCr2O4/rGO polycrystalline composite. We have implemented a simple method that has been identified for mass-producing reduced graphene oxide. The Solution combustion technique was used, and it was successful in achieving this goal for the very first time. X-ray diffraction technique is used analyse crystallinity, phase, and structural investigation. The nature of gas sensing behaviour with a step function of LPG gas at 500 ppb was studied at room temperature for rGO, The CoCr2O4 pigments and 0.5CoCr2O4+0.5rGo polycrystalline composite samples. The gas response is maximum for 0.5CoCr2O4+0.5rGo polycrystalline composite in the order of 97% in compare with the reduced graphene oxide sample which shows the lowest sensitivity in the order of 26% on exposure of liquified petroleum gas (LPG). The recorded response and recovery times of 0.5CoCr2O4+0.5rGo polycrystalline composite is found to be 40 s and 52 s respectively in comparison to the rGO sample about 58 and 74 s respectively. By adding rGo to the material, the cyclic voltammetry (CV) findings demonstrate improved current density and area of CV loop with increased scan rate. In three-electrode reveals the system, a CoCr2O4-rGo material exhibits a specific capacitance of 226 F/g. Thus, the results reveals that rGo is contributing significantly to the enhancement of a supercapacitor's performance of CoCr2O4.

Probing magnetization dynamics of iron oxide nanoparticles using a point-probe magneto-optical method

Magnetic nanoparticles (MNPs) are promising as local heat generators for magnetic hyperthermia under AC magnetic fields. The heating efficacy of MNPs is determined by the AC hysteresis loop area, which in turn is affected by the dynamic magnetic properties of the nanoparticles. Whilst inductive-based AC magnetometers can measure the average magnetic behavior of samples, the use of the magneto-optical Faraday effect with a focused laser spot allows point-probe measurements to be made, and without some of the magnetic field limitations imposed by inductive methods. In this work, the AC magnetic properties of different sized iron oxide MNPs in suspension were measured by AC magnetometry and AC susceptibility techniques. AC hysteresis loops measured by magneto-optical magnetometry were validated using a commercial inductive AC magnetometer, and compared to the magnetization relaxation behavior revealed by fitting the AC susceptibility data. The spatial sensitivity of the point-probe magneto-optical method is also demonstrated by measuring the AC hysteresis loop from large (&amp;gt;1 μm) MNP aggregates dried onto glass slides. These aggregated particles are found to be magnetically softer than in their suspension form, suggesting interparticle coupling mechanisms could occur when the nanoparticles form dense aggregates.

Experimental Study on the Reciprocating Shear Characteristics and Strength Deterioration of Argillaceous Siltstone Rockfill Materials

The reciprocating shear mechanical properties and strength deterioration mechanisms of rockfill materials are of great research significance for high-fill slope stability analysis. To study the shear strength characteristics of argillaceous siltstone rockfill materials with different fabric characteristics under reciprocating shear loading, we analyzed the shear strength, hysteresis loop area, damping ratio, shear strength parameter, and shear stiffness of coarse-grained soils with different coarse grain contents using a coarse-grained soil direct shear testing machine capable of reciprocating shear and revealed their strength deterioration mechanism. The test results show that the shear strength of argillaceous siltstone rockfill materials is significantly affected by the coarse grain content and the number of reciprocating shears. Specifically, the shear strength increases with the coarse grain content and decreases with the number of reciprocating shears. The hysteresis loop area is positively correlated with the coarse grain content and negatively correlated with the number of reciprocating shears. The damping ratio is not related to the coarse grain content but tends to decrease with the number of reciprocating shears. Soil cohesion and the internal friction angle increase with the coarse grain content and decrease with the number of reciprocating shears. The soil failure shear stiffness is linearly correlated with the coarse grain content, and the normalized shear stiffness is logarithmically related to the number of reciprocating shears. According to these relationships, an empirical formula for the shear stiffness of argillaceous siltstone rockfill materials under different coarse grain contents and different numbers of reciprocating shears can be established to provide a basis for analyzing rockfill stability.

Computational modelling of the mechanical performance of nitinol guidewires in an idealised tortuous path for medical device applications

Guidewires are critically important components in medical implant and device delivery systems and their desired clinical performance or “steerability” requires a good torque response, i.e., the rotation of the (distal) guidewire tip should follow exactly the (proximal) applied input rotation. However, guidewires can suffer from phenomena known as lag (tip rotation is significantly less than the input rotation) and whip (the lag is suddenly recovered). Nitinol is a common guidewire material that can give superior performance but has been known to exhibit lag and whip depending on the specific material formulation and processing route. In this study, the torsional response of Nitinol guidewires is investigated using computational modelling (the finite element method) and analytical approaches, with a view to gaining a fundamental understanding of the mechanisms behind the lag and whip phenomena and how these relate to the specific material properties of a range of Nitinol variants and the geometrical configuration of the wire during torsion. An idealised vascular geometry is considered; this consists of a curved section and a straight section of varying length where the curved section is representative of geometries that are encountered in tortuous path navigation in the vasculature.The results capture the experimentally observed phenomena and reveal the relationship between material properties and guidewire performance. The stress state in the wire, which is dictated by the stress plateaus in the Nitinol material response, leads to the generation of a net moment within the wire which requires net work to be done during rotation of the wire. Analysis of idealised hypothetical materials show that the transformation strain is also an important parameter. The analysis reduced the performance of the guidewire material to a single metric that is given in terms of the energy dissipated during transformation, i.e., the area of the hysteresis loop. The results show that the combination of torsion and the bending of the wire in the curved path are critically important in the generation of lag and whip, and that both are accentuated by increasing the length of the straight section once the phenomena are active.

Structural and Magnetic Properties of Perovskite Functional Nanomaterials La1-xRxFeO3 (R = Co, Al, Nd, Sm) Obtained Using Sol-Gel.

Perovskite is the largest mineral on earth and has a variety of excellent physical and chemical properties. La1-xRxFeO3 (R = Co, Al, Nd, Sm) were synthesized using the sol-gel method and analyzed by XRD, TG-DTA, and VSM. With the increase in the Co2+ doping content, the diffraction peak drifted in the direction of a larger angle. The grain size of La1-xRxFeO3(R = Co) is mainly concentrated between 50.7 and 133.5 nm. As the concentration of Co2+ increased, the magnetic loop area and magnetization increased. La1-xRxFeO3(R = Al) is an orthorhombic perovskite structure, the grain size decreased with the increase in Al3+ doping concentration, and the minimum crystallite is 17.9 nm. The magnetic loop area and magnetization increased with the increase in Al3+ ion concentration. The enclosed area of the M-H curve of the sample decreased, and the ferromagnetic order gradually weakened and tended to be antiferromagnetic, which may be due to the increase in sintering temperature, decrease in the iron oxide composition, and changes in the magnetic properties. Proper doping can improve the magnetization of La1-xRxFeO3(R = Nd), refine the particles, and obtain better magnetic performance. As the Nd3+ ion concentration increased, the magnetic properties of the samples increased. Ms of La0.85Co0.15FeO3 prepared by different calcination time increases with the increase in calcination time. As the Sm3+ ion concentration increased, the magnetic properties of the samples increased. Proper doping can improve the magnetization of La1-xRxFeO3(R = Sm), refine the particles, and generate better magnetic performance.

An information theoretic Bayesian uncertainty analysis of AEM systems over Menindee Lake, Australia

SUMMARY Long-range, active-source airborne electromagnetic (AEM) systems for near-surface conductivity imaging fall into two categories: helicopter (rotary-wing) borne or fixed-wing aircraft borne. A multitude of factors such as flying height, transmitter loop area and current, source waveforms, aerodynamic stability and data stacking times contribute to the geological resolvability of the subsurface. A comprehensive comparison of the relative merits of each system considering all such factors is difficult, but test flights over well-constrained subsurface geology with downhole induction logs are extremely useful for resolution studies. However, given the non-linear nature of the electromagnetic inverse problem, handling transmitter–receiver geometries in fixed-wing aircraft is especially challenging. As a consequence of this non-linearity, inspecting the closeness of downhole conductivities to deterministic inversion results is not sufficient for studying resolvability. A more comprehensive picture is provided by examining the variation in probability mass of the depth-wise Bayesian posterior conductivity distributions for each kind of AEM system within an information theoretic framework. For this purpose, probabilistic inversions of data must be carried out. Each acquiring system should fly over the same geology, survey noise levels must be measured and the same prior probabilities on conductivity must be used. With both synthetic models as well as real data from over the Menindee calibration range in New South Wales, Australia, we shed new light on the matter of AEM inverse model uncertainty. We do this using two information theoretic attributes derived from different Kullback–Leibler divergences—Bayesian information gain, and a strictly proper scoring rule, to assess posterior probabilities estimated by a novel Bayesian inversion scheme. The inversion marginalizes fixed-wing geometry attributes as generic nuisance parameters during Markov chain sampling. This is the first time-domain AEM study we know of, that compares nuisance marginalized subsurface posterior conductivities from a fixed-wing system, with rotary-wing derived posterior conductivities. We also compare field results with induction log data where available. Finally, we estimate the information gain in each case via a covariate shift adaptation technique that has not been used before in geophysical work. Our findings have useful implications in AEM system selection, as well as in the design of better deterministic AEM inversion algorithms.

Assessment of the Interelectrode Distance Effect over the Omnipole with High Multielectrode Arrays.

The development of high-density multielectrode catheters has significantly advanced cardiac electrophysiology mapping. High-density grid catheters have enabled the creation of a novel technique for reconstructing electrogram (EGM) signals known as "omnipole," which is believed to be more reliable than other methods, especially in terms of orientation independence. This study aims to evaluate how distance affects the omnipolar reconstruction of EGMs by comparing different configurations. Using an animal set up of perfused isolated rabbit hearts, recordings were taken using an ad hoc high-density epicardial multielectrode catheter. Inter-electrode distances ranging from 1 to 4 mm were analysed for their effect on the quality of resulting EGMs. Two biomarkers were computed to evaluate the robustness of the reconstructions: the areas contained within the bipolar loops and the amplitudes of the omnipoles. We hypothesised that both bipolar and omnipolar electrograms would be more robust at shorter inter-electrode distances. The results showed that an increase in distance triggers an increase in loop areas and amplitudes, which supports the hypothesis. This finding provides a more reliable estimate of wavefront propagation for the cross-omnipolar reconstruction method. These results emphasise the importance of distance in cardiac electrophysiology mapping and provide valuable insights into the use of high-density multielectrode catheters for EGM reconstruction.Clinical Relevance- The results of this study have direct clinical relevance in the application of the described techniques to recording systems in the cardiac electrophysiology laboratory, enabling clinicians to obtain more precise characterisation of signals in the myocardium.

Monte Carlo simulation of a magnetic nanoparticles system under an external rotating magnetic field

The magnetic response of an identical magnetic nanoparticles (MNP) system to a rotating external field (RMF) is studied via Monte Carlo simulations. The field of amplitude H0 and frequency ω, was applied in the y−z plane rotating clockwise. The energy was modeled by the Stoner–Wohlfarth scheme for fixed or random orientations of the anisotropy, and is in contact with a thermal bath at a temperature T. Interparticle dipolar interactions were also considered.In the non-interacting system and for low temperature, hysteresis is observed in the z magnetization component Mz for both orientations of the anisotropy axis and only in the y component (My) for the random case. Furthermore, the loop areas were estimated, and increased with ω for all orientations and (My,Mz) components. At higher temperatures the superparamagnetic state is observed, so both the blocking temperatures TB and loop areas were estimated. The values of TB were close from the room temperature TR=300K for all components, and the areas decreased with T but they are practically not zero at TB.When dipolar interactions are included a new scenario is revealed. In the low temperature regime, the blocked state is present for both My and Mz for all anisotropy orientations, and extends beyond the interval of amplitudes H0 estimated theoretically for the model without interactions and fixed anisotropy. The loops are displaced with respect to the origin of the magnetization-external field plane. When the temperature is raised, the blocked state extends for a larger range than the model without interactions, and the loop displacement decreases with T. These behaviors could be explained by observing that the average dipolar field per particle produces an effective field – the sum of both dipolar and external field – that is asymmetric with respect to the zero field line at low temperatures, becomes half-wave symmetric at higher temperatures, so the the centered character of the loops is restored . In addition, the loop areas show a peak for all orientations of the anisotropy axes in an intermediate range of temperatures. This result can be associated with a dominance of the anisotropy induced by the dipolar field.Finally, by comparing the areas of the loops of the models with and without interactions, it was found that the non-interacting model have larger areas at low temperatures that vanish near the room temperature, unlike the areas of the model with interactions due to the extension of the blocked state.

Cyclic bond behavior in reinforced concrete flexural members exposed to elevated temperatures

After enduring fire incidents, many reinforced concrete (RC) structures require assessment of their ability to withstand future seismic loads. A critical factor contributing to seismic behavior of such structures is residual bond between steel and concrete under cyclic loading. This paper examines cyclic bond-slip behavior in RC flexural members that have experienced elevated temperatures. Twenty-six modified beam-end specimens with different diameters of longitudinal reinforcement, concrete strengths, and confinement levels were fabricated. The specimens were subjected to a variety of heating regimes and a natural cool down before loading of their longitudinal rebar in a monotonic or cyclic pattern. The decrease in bond strength after 2-hr exposure to temperatures of 400, 600, and 700 °C were 23, 58, and 65 percent for monotonic loading but 30, 60, and 65 percent for cyclic loading, respectively. Elevated temperatures also caused a decrease in slope and area of hysteretic bond-slip loops. Cyclic bond strength was 25–45% less than monotonic bond strength and better correlated with the residual compressive strength of concrete, unlike monotonic bond strength, which was better correlated with the square root of this property. A model was proposed for backbone bond-slip curves of RC flexural members that are exposed to elevated temperatures.

Effects of mixed corrosion damage on constitutive relation and ductile fracture behavior of butt-welded joints under cyclic loading

The corrosion damage of welded connection regions posed a threat to the reliability and durability of welded steel structures. In this paper, the morphology scanning and cyclic loading tests of butt-welded joints exposed to the salt spray corrosion environment were conducted to investigate the effects of corrosion damage on surface characteristics and hysteresis behavior of butt-welded joints. Three-dimension scanning test results showed that the butt-welded joint under the salt spray environment suffered a kind of mixed corrosion damage. Compared with the thickness loss caused by uniform corrosion, pitting damage tended to cause serious local geometric defects, aggravating the geometric discontinuity problem. For the corroded butt-welded joint, the hysteresis loop area and cycles decreased significantly with the increase of corrosion damage, and the ductile fracture behavior under the cyclic loading gradually disappeared. The numerical comparative analysis of models with two different patterns of corrosion damage showed that the pitting damage caused a severer hysteresis behavior degradation of butt-welded joints compared to the uniform corrosion damage under the same volumetric loss ratio. Particularly, the pitting damage had a significant effect on reducing cyclic deformation and energy dissipation. According to the above experimental and numerical analysis, a modified cyclic plastic fracture criteria considering pitting damage and a nonlinear cyclic constitutive model considering mixed corrosion for the corroded butt-welded joint were proposed respectively to equivalently consider the influence of corrosion geometric damage by weakening the material properties.

Effect of CoFe2O4 mole percentage in the scaling behaviour of dynamic hysteresis loop in eco-friendly (1-x)(0.94Na0.5Bi0·5TiO3-0.06BaTiO3)–x(CoFe2O4) particulate composite

Many technological applications of ferroelectric materials are fundamentally connected to domain reversal under the electric field. Here the polarization reversible mechanism has been studied in (1-x)(0.94Na0·5Bi0·5TiO3-0.06BaTiO3)–x(CoFe2O4) (NBBT-CFO) (x = 0, 15, 25 and 35 mol%) particulate composites through the electric field and frequency-dependent scaling behavior of their hysteresis loop. Along with this, the role of the CFO on the polarization reversal processes of NBBT has been investigated systematically. Three-stage behaviour has been observed in the polarization reversal for all the systems. The observed scaling parameter β value for the composites is found to be less than parent NBBT, which has been discussed based on the pinning effect that arises due to the CFO phase. The induced pinning effect in the composites is due to the high leakage current which is confirmed by the leakage current density (J) measurement. The scaling relation of loop area <A> versus E0 and ƒ for the composites is followed by the power law <A>∝f−0.265E01.320 in the saturated region. The present findings may be useful in technological applications related to polarization reversal.

The silent impact of underground climate change on civil infrastructure

Urban areas increasingly suffer from subsurface heat islands: an underground climate change responsible for environmental, public health, and transportation issues. Soils, rocks, and construction materials deform under the influence of temperature variations and excessive deformations can affect the performance of civil infrastructure. Here I explore if ground deformations caused by subsurface heat islands might affect civil infrastructure. The Chicago Loop district is used as a case study. A 3-D computer model informed by data collected via a network of temperature sensors is used to characterize the ground temperature variations, deformations, and displacements caused by underground climate change. These deformations and displacements are significant and, on a case-by-case basis, may be incompatible with the operational requirements of civil structures. Therefore, the impact of underground climate change on civil infrastructure should be considered in future urban planning strategies to avoid possible structural damage and malfunction. Overall, this work suggests that underground climate change can represent a silent hazard for civil infrastructure in the Chicago Loop and other urban areas worldwide, but also an opportunity to reutilize or minimize waste heat in the ground.

Experimental study on cyclic-bend-over-sheave (CBOS) characteristics of an HMPE fibre rope under dynamic loading

Cyclic bending over sheave (CBOS) is one of the most typical usage scenarios of marine handling ropes, where the rope will be subjected to both tensile deformation and bending deflection. In this paper, the CBOS characteristics of a 24 mm high module polyethylene (HMPE) marine handling rope subjected to dynamic tension are investigated by a series of full-scale experimental tests at the diameter ratio of D/d=400/24, where D=400mm is the sheave diameter. The variations in useful life, strain, stiffness and surface temperature have been measured at different loading conditions. Two stages of temperature variation at the bending section of the rope are found, and those stages are associated with the variation in the area of hysteresis loop from the tension-strain figure. On the other hand, the CBOS lifetime is found to decrease with the increasing average, amplitude and period of the dynamic loading, while the nominal stiffness increases with the average magnitude and period of loading but decreases with increasing amplitude. On this basis, two empirical equations taking into account the loading conditions are proposed through regression analysis. The obtained coefficients have good agreement with the present experimental results.