Abstract ：

Understanding the time-dependent behavior of rocks has long been a critical challenge, hindered by complex multiscale failure mechanisms and time effects. Prolonged exposure to environmental factors such as groundwater and corrosive ions causes significant time-dependent behavior in the surrounding rock, posing potential risks to tunnel safety. In this study, the discrete element method was adopted to investigate the influence of environmental erosion on the time-dependent performance of rocks and mechanical response of tunnel linings at the structural level. To simulate rock erosion, an inhomogeneous erosion parallel bond model (IEPBM) was proposed, conceptualizing the erosion process as the gradual dissolution of bonding cementation between microscopic structures. The Weibull function was introduced to represent the inhomogeneous erosion of rock materials. The IEPBM was validated by comparing the simulation results with indoor tests, confirming the model's reliability. The model incorporated an updated bonding radius multiplier to simulate microstructural changes during erosion. Subsequently, the effects of the erosion degree, erosion rate, and inhomogeneity on the time-dependent mechanical behavior of the rock were explored. The results indicated that the creep behavior induced by environmental erosion was a macroscopic deformation process, with rock failure resulting from the accumulation of microscopic damage. The model successfully captured three creep stages: attenuation, stability, and acceleration. Additionally, erosion degree and rate significantly affected the multiscale creep properties of rocks, with highly inhomogeneous rocks potentially failing after relatively minor erosion. Finally, the time- dependent mechanical response of the tunnel lining owing to surrounding rock erosion was analyzed at the structural level. The erosion of the surrounding rock increases the stress on the lining, compromising the longterm safety of the tunnel structure and contributing to lining failures observed in modern tunnels.

Keyword ：

Environmental erosion Long-term safety Surrounding rock Tunnel Creep behavior DEM

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Abstract ：

This paper examines non-homogeneous geo-material halfspaces under the axisymmetric indentation of a circular rigid plate. A multilayered model is proposed to approximate arbitrary variations of the elastic parameters in geo-materials with depth. The non-homogeneous geo-material halfspaces can have variable shear modulus and Poisson's ratio with depth. Numerical verification is performed for the contact problem of a non-homogeneous halfspace with variable shear modulus and constant Poisson's ratio. Results illustrate the effects of material inhomogeneity on the elastic fields of a non-homogeneous halfspace.

Keyword ：

Geo-materials Axisymmetric indentation Non-homogeneity Elastic fields Circular rigid plate

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Abstract ：

This paper presents an isolation pile-soil lateral interaction model that considers not only the relative linear sliding at the pile-soil interface but also the pile group-soil interaction. The model allows for the calculation of the pile-soil interaction force using the elastic continuum method combined with the displacement compatibility relationship at the pile-soil interface, thus enabling the total lateral ground displacement to be obtained. The proposed method is validated by comparisons with the elastic foundation method (EFM) and the boundary element method (BEM). The advantages of the proposed method in calculating the lateral ground deformation resisted by isolation piles are demonstrated. The mechanical mechanism of the isolation pile's lateral resistance effect on ground deformation can be summarized as follows: the combination of positive and negative resistance effects drives the lateral ground displacements along the depth direction from the original inhomogeneity caused by the tunnel excavation to a relatively homogeneous state. The soil parameters including Poisson's ratio, internal friction angle and ground volume loss; the isolation pile parameters including the distance of the tunnel axis from the pile axis, the pile length, the buried depth of the pile top and the relative pile bending stiffness; and isolation pile-soil interface parameters including relative pile shaft-soil stiffness and relative pile tip-soil stiffness all exert a significant influence on the lateral resistance effect of the isolation pile. In light of that the resistance effects at different depths below the surface are not uniform, it is of the utmost importance to assess the resistance performance of the isolation pile in accordance with the location and lateral deformation requirements of the protected structure in actual engineering.

Keyword ：

Tunneling Resistance effect Pile-soil interaction force Isolation piles Resisting mechanism Lateral ground movements Elastic continuum method

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Abstract ：

The mechanical properties of the electrodes are dynamic change during the cycle, which will affect the wave propagation characteristics in the lithium-ion battery. It is feasible for the non-destructive characterization of lithium-ion batteries based on the relationship between the wave characteristic and the state of charge (SOC). In this research, an ultrasonic bulk wave detection technique for detecting the SOC of multi-area lithium-ion batteries using arrayed flexible sensors is proposed. Firstly, the simulation model of type 1-3 piezoelectric composites was established based on the finite element simulation software COMSOL, and the effects of different structural parameters, such as piezoelectric phase volume fraction, composite thickness, and piezoelectric column aspect ratio, on their properties were analyzed. Based on the simulation optimization results, a 5x5 1-3 piezoelectric composite sensor was designed and prepared. The ultrasonic bulk wave detection system for lithium-ion batteries was built with the optimized arrayed sensor, and the connection between SOC and wave propagation properties was experimentally investigated, and the inhomogeneity of the SOC of lithium-ion batteries was visualized and analyzed. Furthermore, the ultrasonic flexible sensing detection approach has also been shown to be a sensitive means of determining the SOC of multiarea lithium-ion batteries.

Keyword ：

ultrasonic bulk wave 1-3 type flexible array sensors state of charge lithium-ion battery

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Abstract ：

In this study, Al-Zn-Mg-Cu alloy components were prepared using wire arc additive manufacturing (WAAM). Through multi-scale characterisation technology, performance testing and slow strain rate tensile (SSRT) testing, the microstructure, mechanical properties and stress corrosion cracking (SCC) susceptibility of WAAM Al-Zn-Mg-Cu components were studied, revealing the generation mechanism of inhomogeneity and anisotropy. The results show that with the increase of WAAM thermal cycles, the matrix precipitates (MPs), grain boundary precipitates (GBPs) and precipitation-free zones (PFZ) evolve in different paths and increase to varying degrees, resulting in performance decrease and increase in stress corrosion susceptibility, so the inhomogeneity is mainly attributed to differences in precipitated phases. The Inter-layer inclined to the scanning direction and the Inner-layer inclined to the building direction led to anisotropy in tensile strength and SCC behaviour, so the anisotropy is mainly attributed to the grain orientation and fracture mode.

Keyword ：

WAAM Al-Zn-Mg-Cu anisotropy mechanical properties stress corrosion cracking (SCC) inhomogeneity

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In this study, a 3D meso-scale numerical simulation method is established for analyzing the shear failure of carbon fiber reinforced polymer (CFRP) strengthened RC beams without stirrups. The inhomogeneity of concrete, the bond-slip relationship between steel bars and concrete, and the interaction between CFRP and concrete are considered. Based on this method, effects of shear-span ratio and CFRP fiber ratio on the shear performance and nominal shear strength size effect of CFRP strengthened RC beams are investigated. Results indicate that the size effect of CFRP strengthened RC beams is obvious, however, the shear-span ratio has little impact on the size effect of nominal shear strength of RC beams. The CFRP fiber ratio enhances the shear strength of RC beams on the one hand, while weakens the shear size effect of RC beams on the other hand. However, its influence on the shear performance of RC beams remains basically unchanged with varying shear-span ratios, indicating that there is no coupling effect between the shear-span ratio and CFRP fiber ratio. The shear-span ratio significantly influences both the shear bearing capacity of RC beams and the shear contribution of CFRP sheets, with the increase in the shear-span ratio, the shear bearing capacity of RC beams decreases to varying degrees, and the shear contribution of CFRP sheets increases initially and then decreases. Finally, the shear strength size effect law (SEL) of CFRP strengthened RC beams is proposed, which can quantitatively describe the effects of the shear-span ratio and the CFRP fiber ratio. © 2024 Elsevier Ltd

Keyword ：

Numerical methods Size determination Bearing capacity Fibers Shear strength Concrete beams and girders Carbon fiber reinforced plastics Shear flow

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Abstract ：

Segmentation of breast tumors from dynamic contrast-enhanced magnetic resonance (DCE-MR) images is a critical step in the diagnosis of breast cancer and subsequent efficacy assessment. However, the irregular shape and size of breast tumors, as well as the inhomogeneity of the background, pose challenges to accurately segmenting tumors in DCE-MR images. To address this, our study proposes a breast tumor segmentation model based on U-net++ and a breast region localization (BRL) module for more precise segmentation in DCE-MRI. This model helps doctors accurately locate the tumor position and perform lesion region segmentation. The BRL module effectively localizes the breast region, inhibits confusion of tissues in the chest cavity, and accelerates the convergence of the subsequent segmentation network. U-Net++ applies a residual network structure to segment the lesion region. Experimental results show that our proposed segmentation model achieves accurate segmentation of breast tumors, with a Dice coefficient of 0.78 and a sensitivity of 0.89.

Keyword ：

magnetic resonance imaging deep learning Breast cancer image segmentation

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Abstract ：

Nanosized metals usually exhibit ultrahigh strength but suffer from low homogeneous plasticity. The origin of a strength-ductility trade-off has been well studied for pure metals, but not for random solid solution (RSS) alloys. How RSS alloys accommodate plasticity and whether they can achieve synergy between high strength and superplasticity has remained unresolved. Here, we show that face-centered cubic (FCC) RSS AuCu alloy nanowires (NWs) exhibit superplasticity of similar to 260% and ultrahigh strength of similar to 6 GPa, overcoming the trade-off between strength and ductility. These excellent properties originate from profuse hexagonal close-packed (HCP) phase generation (2H and 4H phases), recurrence of reversible FCC-HCP phase transition, and zigzag-like nanotwin generation, which has rarely been reported before. Such a mechanism stems from the inherent chemical inhomogeneity, which leads to widely distributed and overlapping energy barriers for the concurrent activation of multiple plasticity mechanisms. This naturally implies a similar deformation behavior for other highly concentrated solid-solution alloys with multiple principal elements, such as high/medium-entropy alloys. Our findings shed light on the effect of chemical inhomogeneity on the plastic deformation mechanism of solid-solution alloys.

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Domain-wall-pinning is one of the ways to realize magnetic hardening for permanent magnet materials. The sintered 2:17 Sm-Co magnets, a most typical pinning-controlled magnet, have complex nano-scaled cellular structures including cellular matrix phase, cell wall phase, and lamellar Zr-rich phase. In this paper, a multiple domain-wall-pinning with cell wall phase dominating and Zr-rich phase participating was proposed through micromagnetic simulation. The simulation results were supported by magnetic domain observation and macroscopic magnetic measurement analysis, which provided a key reference for the correlation between the magnetic properties and microstructure of this kind of magnet. Furthermore, the squareness of the demagneti-zation curve for the magnet was affected by multiple pinning, including multiple pinning phases and the internal inhomogeneity inside a pinning phase. Our finding can enrich the magnetic hardening mechanism and provide theoretical guidance for the optimization of magnetic properties of the pinning-controlled permanent magnets.

Keyword ：

Pining effect Magnetic domain motion Permanent magnetic materials Magnetization reversal mechanism

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This study presents a novel rate-dependent bond-based peridynamic model for predicting the mechanical behavior of brittle aluminosilicate glass under quasi-static and dynamic flexure loading. To achieve this, the damage criterion is modified with reference to the concept of strain rate in the classical continuum mechanics (CCM). Additionally, a peridynamic (PD) model with inhomogeneous critical stretch based on the Weibull distribution is proposed to account for the randomly distributed defects in glass and investigate their effect on crack initiation and propagation. The accuracy and rationality of the improved PD model are verified by comparing the calculated strength and fracture modes with the experimental results under quasi-static Ball-On-Ring (BOR) and dynamic low-velocity impact tests. The results show that the rate effect increases the damage threshold of glass, enhancing strength and damage ratio. Notably, flexural failures induced by tensile stress are observed under both static and dynamic loading. The rate-dependent inhomogeneous PD model indicates that glass inhomogeneity reduces strength while increasing crack propagation velocity (CPV). The introduction of pre-existing defects alters the symmetrical crack propagation pattern typically observed in homogeneous materials, resulting in a more randomized crack propagation path. Overall, the results can provide a promising approach for predicting the mechanical behavior of brittle materials.

Keyword ：

Flexure loading Peridynamic Aluminosilicate glass Rate-dependent Inhomogeneous

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