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The deformation and damage to seasonal permafrost roadbeds, as seasons shift, stems from the intricate interplay of temperature, moisture, and stress fields. Fundamentally, the frost heave and thaw-induced settlement of soil represent a multi-physics coupling phenomenon, where various physical processes interact and influence each other. In this investigation, a comprehensive co-coupling numerical simulation of both the temperature and moisture fields was successfully executed, utilizing the secondary development module within the finite element software, COMSOL Multiphysics 6.0. This simulation inverted the classical freezing–thawing experiment involving a soil column under constant temperature conditions, yielding simulation results that were in excellent agreement with the experimental outcomes, with an error of no more than 10%. Accordingly, the temperature, ice content, and liquid water content distributions within the seasonal permafrost region were derived. These parameters were then incorporated into the stress field analysis to explore the intricate coupling between the moisture and temperature fields with the displacement field. Subsequently, the frost heave and thaw settlement deformations of the roadbed were calculated, accounting for seasonal variations, thereby gaining insights into their dynamic behavior. The research results show that during the process of freezing and thawing, water migrates from the frozen zone towards the unfrozen zone, with the maximum migration amount reaching 20% of the water content, culminating in its accumulation at the interface separating the two. Following multiple freeze–thaw cycles, this study reveals that the maximum extent of freezing within the roadbed reaches 2.5 m, while the road shoulder experiences a maximum freezing depth of 2 m. A continuous trend of heightened frost heave and thaw settlement deformation of the roadbed is observed in response to temperature fluctuations, leading to the uneven deformation of the road surface. Specifically, the maximum frost heave measured was 51 mm, while the maximum thaw settlement amounted to 13 mm. [ABSTRACT FROM AUTHOR]

Polymer film melt stretching exhibits a unique stress–strain behavior, featuring a stress plateau followed by a sudden increase with increasing the strain. This phenomenon poses a challenge to conventional melt-extension theories and methods. To address this, we derive a simplified flow theory according to the symmetric characteristics of thin melt-stretching, and propose a modified multi-mode Leonov model (m-Leonov) that accounts for molecular orientation effects, a crucial factor in accurately simulating the process. In order to improve the computational efficiency, an iterative algorithm was developed to decouple the interdependence between governing and constitutive equations. The computational results reveal that the viscoelastic nature of the film contributes to a delay in the transformation of stretching forces, leading to the observed stress plateau. Significantly, our m-Leonov model successfully predicts both the plateau and the subsequent abrupt increase in stress, across various temperatures and stretching rates. These simulations closely agree with experimental data, underlining the robustness of our approach. Our findings would enhance the understanding of rheological complexities in film stretching, offering potential applications in various materials and polymer processing. [ABSTRACT FROM AUTHOR]

The pipe-roof method is an increasingly popular pre-construction soil support system for underground space development for its superior safety. Whilst the load-bearing and deformation characteristics of pipe-roof structures has been the subject of much research, uncertainties surrounding the interactions between the pipe-roof and the surrounding soil remain. This paper fills this gap by describing small-scale laboratory testing and complementary theoretical analysis exploring the development of pipe-roof deformation, soil deformation mechanism and displacement field, and soil pressures acting on the pipe-roof. The results show that deformation of the pipe-roof itself leads to a partially mobilized soil arching effect, resulting in a 'tower-shaped' soil displacement mechanism. In addition, the earth pressure distribution above the pipe-roof is arch-shaped, forming a minor principal stress arch. The experimental results inform a theoretical model for the calculation of the soil earth pressure acting on the pipe-roof, considering the interaction between the pipe-roof deformation and the principal stress rotation. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 5%. The proposed model is closed-form and suitable for routine use in design. [ABSTRACT FROM AUTHOR]

The stress evolution, total charging time and capacity utilization of pulse charging (PC) method are investigated in this paper. It is found that compared to the conventional constant current (CC) charging method, the PC method can accelerate the charging process but will inevitably cause an increase in stress and a decrease in capacity. The charging speed for PC method can be estimated by the mean current. By introducing stress control, a modified PC method called the PCCC method, which starts with a PC operation followed by a CC operation, is proposed. The PCCC method not only can accelerate charging process but also can avoid the stress raising and capacity loss occurring in the PC method. Furthermore, the optimal pulsed current density and switch time in the PCCC method is also discussed. [ABSTRACT FROM AUTHOR]

This paper presents an optimization method, including the identification of local stress measurements and a two-stage back analysis, to determine in situ stress under complex conditions. Firstly, the macro-regional distribution characteristics of in situ stress can be interpreted by analyzing regional geological conditions, topography, as well as rock mass failure phenomena. Then, a stereographic projection method (SPM) is used to determine the distribution features of stress tensor on an arbitrary plane. On this basis, some representative measured data, which can reflect the distribution characteristics of in situ stress in the study area can be identified. After that, a first-stage back analysis by finite difference method (FDM) is used to calculate the field stresses from the selected in situ measured data. The obtained boundary stresses are taken to consist of a constant term, a term that varies linearly with depth, and a hyperbolic term. Further, a second-stage back analysis by discrete element method (DEM) is carried out to determine the local field stresses which are significantly affected by discontinuities and excavations. The FDM back analysis results can serve as the initial input stress conditions for DEM analysis, and the optimum stress conditions for DEM analysis will be reasonably obtained by using the uniform design method through the second-stage back analysis. To show the feasibility of the optimized method, it is applied to the Wudongde Hydropower Station to determine in situ stress. Based on local stress measurements by borehole stress relief method using hollow inclusion strain gauges, some representative measured data are selected by SPM. The unknown state of stress in the station is estimated through the first-stage back analysis by FDM. For some local key areas, encountered discontinuities or excavations in the vicinity, the local field stresses are calculated through the second-stage back analysis by DEM. Finally, the results are compared with those elicited from the borehole stress relief method. It is shown that the calculated results by the first-stage back analysis agree well with the measured ones on the whole, but the discrepancy is large in the vicinity of discontinuities as well as excavation disturbance. However, the calculated results by the second-stage back analysis roughly coincide with the measured data with lower allowable error. [ABSTRACT FROM AUTHOR]

Abstract This article sheds light on advantages of fast charging methods with time-varying current. Analytical solutions of concentration and stress for charging processes with general time-varying currents are derived. A fast charging protocol for a multistage constant current of gradually decreasing value is first evaluated. A properly designed multistage constant-current method is able to simultaneously suppress stress overflow and accelerate charging, but stress undulation induced by sharp switching between stages is inevitable. A charging scheme with a nonlinear exponential current is then investigated. The applied current varies continuously and smoothly with time so stress undulation is avoided. Suggestions for the design of an exponential current method are proposed to achieve the best charging acceleration without sacrificing charging capacity or increasing risk of mechanical failures. A well-designed exponential-current method is superior to a multistage constant-current method in accelerating charging speed. [ABSTRACT FROM AUTHOR]

Intercalation of lithium ions into the electrodes of lithium ion batteries is affected by the stress of active materials, leading to energy dissipation and stress dependent voltage hysteresis. A reaction-diffusion-stress coupling model is established to investigate the stress effects under galvanostatic and potentiostatic operations. It is found from simulations that the stress hysteresis contributes to the voltage hysteresis and leads to the energy dissipation. In addition, the stress induced voltage hysteresis is small in low rate galvanostatic operations but extraordinarily significant in high rate cases. In potentiostatic operations, the stresses and stress induced overpotentials increase to a peak value very soon after the operation commences and decays all the left time. Therefore, a combined charge-discharge operation is suggested, i.e., first the galvanostatic one and then the potentiostatic one. This combined operation can not only avoid the extreme stress during operations so as to prevent electrodes from failure but also reduce the voltage hysteresis and energy dissipation due to stress effects. [ABSTRACT FROM AUTHOR]

A previously developed damage identification strategy, named Pseudo - Excitation (PE), was enhanced using a statistical processing approach. In terms of the local dynamic equilibrium of the structural component under inspection, the distribution of its vibration displacements, which are of necessity to construct the damage index in the PE, was re-defined using sole dynamic strains based on the statistical method. On top of those advantages inheriting from the original PE compared with traditional vibration-based damage detection including the independence of baseline signals and pre-developed benchmark structures, the enhanced PE (EPE) possesses improved immunity to the interference of measurement noise. Moreover, the EPE can facilitate practical implementation of online structural health monitoring, benefiting from the use of sole strain information. Proof-of-concept numerical study was conducted to examine the feasibility and accuracy of the EPE, and the effectiveness of the proposed statistical enhancement in re-constructing the vibration displacements was evaluated under noise influence; experimental validation was followed up by characterizing multi-cracks in a beam-like structure, in which the dynamic strains were measured using Lead zirconium titanate (PZT) sensors. For comparison, the original PE, the Gapped Smoothing Method (GSM), and the EPE were respectively used to evaluate the cracks. It was observed from the damage identification results that both the GSM and EPE were able to achieve higher identification accuracy than the original PE, and the robustness of the EPE in damage identification was proven to be superior than that of the GSM. [ABSTRACT FROM AUTHOR]

Abstract: A semi-analytical method based on the cohesive model has been developed to investigate the progressive growth of interface delamination in an axisymmetric thin film electrode driven by diffusion-induced stresses under the assumption that the electrode remains elastic during the Li-ion diffusion process. The evolutions of the cohesive zone and debonding zone with respect to charging time have been predicted. The cohesive zone propagates in an accelerating manner and the debonding zone advances in a slowing down manner. The key parameters that control the interfacial stresses and delamination have been identified from the obtained governing equations. And according to the discussions on the key parameters, design insights into the geometry, charging velocity and material properties of the electrode have been provided. [Copyright &y& Elsevier]

High temperature conventional triaxial compression test of shale were carried out by using the MTS815 servo-controlled testing machine, based on the results of the tests, the relationships between confining pressure and the characteristic of shale stress-strain curve, peak strength, elastic modulus, Poisson's ratio, peak strain were investigated,and the general regulation is obvious. According to the characteristics of volumetric strain,the stress-strain curves were classified into three types. They are dilatation type,compression-dilatation type,compression type,and the confining pressure has conspicuous dilatation effect on shale. At the same temperature, when confining pressure rises from 5 MPa to 25 MPa, shale peak strength (σ1 - σ3) is comparatively lower, indicating stronger plastic deformation', and peak strength and elastic modulus increase with uprising confining pressure. When confining pressure is lower than 15 MPa, shale Poisson' s ratio increases with increasing confining pressure while peak axial strain and peak circle strain decreases with increasing confining pressure. When confining pressure is higher than 15 MPa, shale Poisson's ratio decreases slightly with the increasing confining pressure, while peak axial strain and peak circle strain increase slightly with the increasing confining pressure. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, structural configuration of layered Li-ion battery electrode plates is evaluated by analytically formulating the diffusion induced stress. Both symmetric electrode and asymmetric bilayer electrode are discussed. The thickness ratio and the modulus ratio of current collector to active plate are analytically identified to be the important influence parameters on the stress. Applying a material with smaller elastic modulus for current collector could reduce the peak stresses in both current collector and active plate. Increasing the thickness of current collector would reduce the stress in itself while promote the stress in active plate. Therefore, from mechanical viewpoint on designing an electrode, the material for current collector should be as soft and flexible as possible. And the thickness of current collector should be in an appropriate range. Basically, it should be as small as possible on the precondition that the mechanical strength is satisfied. Finally, effects of three charging conditions, i.e. uniform, galvanostatic, and potentiostatic, on the diffusion induced stress is discussed. It is found the maximum stresses for three cases are linear to the total amount of intercalated lithium ions. Based on the stresses, an optimized charging operation, i.e. first galvanostatic followed by potentiostatic, is suggested. [Copyright &y& Elsevier]

We report the magnetic and magnetocaloric properties of Dy1-xHoxMnO3 (0 ≤ x ≤ 1). Large entropy change of 12.5 J/kg K and refrigeration capacity of 312 J/kg at 7 T for HoMnO3 is calculated based on isothermal magnetization measurements. The peak temperature of magnetic entropy change for all samples keeps the same 10.5 K, indicating that Ho3+ doping only affects the value of magnetic entropy. An unambiguous intrinsic structural transition near 7 K is first observed by strain measurement, which is believed as the origin of magnetic symmetry transition of Dy1-xHoxMnO3 and induces the magnetocaloric effect with the cooperation interaction between Dy3+/Ho3+and Mn3+ spins. [ABSTRACT FROM AUTHOR]

Wenchuan earthquake, Ms 8.0 in magnitude and occurred on May 12, 2008 in Sichuan Province, China, triggered a lot of landslides, rock collapses, debris flow, etc. The Tangjiashan landslide, with its total volume 20.37 million m3, was the biggest and the most notable one for its effects. Based on the field geological investigation and the typical acceleration records of the main shock obtained in the period of the earthquake, numerical simulation of the whole sliding process of Tangjiashan landslide has been carried out by DDA method. It is shown that the Tangjiashan landslide was a high-speed landslide, behaved with nonlinear features in the whole sliding process. The total duration of the landslide was about 30 s while nearly all of their slipping displacements were carried out in the beginning 25 s, with the maximum sliding velocity about 30 m/s, and the average 15-17 m/s in the beginning 25 s. The crash of rock blocks induced a much higher stresses near the middle and lower parts of the landslide, with the maximum value of 6-7 MPa. The dynamic earthquake load caused an incessant deformation of the landslide, resulting in the reduction of mechanical parameters, especially the shear strength on the sliding surface and the ratio of friction coefficient on sliding surface in kinematical and static conditions are no more than 0.35. DDA simulation considering the displacement-based parameter reduction has been developed in the original DDA code, and its results primarily reflect the evolvement process of a landslide under strong seismic loads. [ABSTRACT FROM AUTHOR]

Mechanical properties and lithiation-induced stress are crucial to the performance and durability of lithium-ion batteries. Here, we report the evolution of elastic modulus and stress in a silicon/polyvinylidene fluoride (PVDF) composite electrode coated on a copper foil, along with a model for analyzing the large change in the radius of curvature of the composite electrode/copper foil cantilever. The radius of curvature of the cantilever is captured by a video camera during lithiation/delithiation. The elastic modulus of the composite electrode decreases from about 0.64 GPa to 0.18 GPa during lithiation. It decreases further to about 0.10 GPa after delithiation, which is caused by the fracture of the electrode. The magnitude of the compressive stress increases lineally during lithiation and decreases suddenly to reach a steady state value during delithiation. [ABSTRACT FROM AUTHOR]

We have investigated the martensitic transformation, exchange bias, magnetoresistance (MR) and strain in Ni 50− x Fe x Mn 36 Sn 14 ( x =1, 2, 3, 4) Heusler alloys. With the increase of Fe content, the austenite phase could be stabilized with L 2 1 structure and hence the martensitic transition shifts to a lower temperature and finally disappears. This behavior can be understood by the weakening of Ni–Mn hybridization to suppress AFM interactions and enhancement of Fe–Fe ferromagnetic exchange interactions. The same reason can account for the slight decrease of exchange bias field ( H EB ) with the increase of the Fe content from x =1 to 2 and the disappearance of H EB for x =3. We observed MR effect for x =3, and a maximum MR value of −52% was achieved, which can be explained by the change in the electronic structure during martensitic transformation induced by the magnetic field. In addition, a large strain of 0.207% in Ni 49 Fe 1 Mn 36 Sn 14 was observed due to the changes of lattice parameters during the martensitic transformation induced by temperature. [ABSTRACT FROM AUTHOR]

Concrete-filled double skin steel tubular (CFDST) columns with galvanized corrugated steel tubes are a novel type of composite members. Such column consists of a layer of concrete sandwiched between an outer corrugated steel tube and an inner flat or a corrugated steel tube. It is expected to combine the advantages of each component, and have additional advantages in corrosion resistance, local stability, and ductility. In this study, a total of 21 large-scale stub specimens were fabricated to investigate the axial behaviour of the proposed columns. The test results indicated that such columns are feasible and competitive in local stability and ductility. Generally, a larger axial bearing capacity can be obtained by retaining the inner flat steel tube in the proposed CFDST members while better ductility is gained if corrugated steel tubes are used as both inner and outer skins. Strain/stress analysis of the column surfaces indicated that the confinement provided by the thin-walled corrugated steel tubes on the sandwiched concrete was sufficient. The axial bearing capacity resisted by the corrugated steel tubes was negligible due to its unique configuration together with the accompanied local bending effect. Based on the test results, four available design models for predicting the axial bearing capacities of traditional CFDSTs were adopted to assess their applicability for the newly proposed columns with galvanized corrugated steel tubes, with specific design suggestions proposed eventually. • Concepts of CFDST with galvanized corrugated steel tubes. • Axial-load tests conducted on 21 large scaled stub columns comparatively. • Strain/stress analysis of outer shells via elastic-plastic analysis methods. • Feasibility evaluations of available models and suggestions for design. [ABSTRACT FROM AUTHOR]