This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element couplin...This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element coupling stress resulting from the combination of mechanical and thermal loading,using geometric nonlinear finite element analysis.A topological model is then developed to minimize compliance while meeting displacement and frequency constraints to fulfill design requirements of structural members.Since the conventional Lagrange multiplier search method is unable to handle convergence instability arising from large deformation,a novel Lagrange multiplier search method is proposed.Additionally,the proposed method can be extended to multi-constrained geometrically nonlinear topology optimization,accommodating multiple physical field couplings.展开更多
Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction...Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction and operation of tunnel engineering.This study investigated the thermo-mechanical damage behavior of the composite interface between alkali-resistant glass fiber-reinforced concrete(ARGFRC)and granite,focusing on a plateau railway tunnel.Laboratory triaxial tests,laser scanning,XRD analysis,numerical simulations,and theoretical analyses were employed to investigate how different initial curing temperatures and joint roughness coefficient(JRC)influence interfacial damage behavior.The results indicate that an increase in interface roughness exacerbates the structural damage at the interface.At a JRC of 19.9 and a temperature of 70℃,crack initiation in granite was notably restrained when the confining pressure rose from 7 MPa to 10 MPa.Roughness-induced stress distribution at the interface was notably altered,although this effect became less pronounced under high confining pressure conditions.Additionally,during high-temperature curing,thermal stress concentration at the tips of micro-convex protrusions on the granite surface induced microcracks in the adjacent ARGFRC matrix,followed by deformation.These findings provide practical guidelines for designing concrete support systems to ensure tunnel structural safety in high-altitude regions with harsh thermal environments.展开更多
This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A tempe...This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.展开更多
This study presents an effective hybrid simulation approach for simulating broadband ground motion in complex near-fault locations.The approach utilizes a deterministic approach based on the spectral element method(SE...This study presents an effective hybrid simulation approach for simulating broadband ground motion in complex near-fault locations.The approach utilizes a deterministic approach based on the spectral element method(SEM),which is used to simulate low-frequency ground motion(f<1 Hz)by incorporating an innovative efficient discontinuous Galerkin(DG)method for grid division to accurately model basin sedimentary layers at reduced costs.It also introduces a comprehensive hybrid source model for high-frequency random scattering and a nonlinear analysis module for basin sedimentary layers.Deterministic outcomes are combined with modified three-dimensional stochastic finite fault method(3D-EXSIM)simulations of high-frequency ground motion(f>1 Hz).A fourth-order Butterworth filter with zero phase shift is employed for time-domain filtering of low-and high-frequency time series at a crossover frequency of 1 Hz,merging the low and high-frequency ground motions into a broadband time series.Taking an Ms 6.8 Luding earthquake,as an example,this hybrid method was used for a rapid and efficient simulation analysis of broadband ground motion in the region.The accuracy and efficiency of this hybrid method were verified through comparisons with actually observed station data and empirical attenuation curves.Deterministic method simulation results revealed the effects of mountainous topography,basin effects,nonlinear effects within the basin’s sedimentary layers,and a coupling interaction between the basin and the mountains.The findings are consistent with similar studies,showing that near-fault sedimentary basins significantly focus and amplify strong ground motion,and the soil’s nonlinear behavior in the basin influences ground motion to varying extents at different distances from the fault.The mountainous topography impacts the basin’s response to ground motion,leading to barrier effects.This research provides a scientific foundation for seismic zoning,urban planning,and seismic design in nearfault mountain basin regions.展开更多
Hydraulic asphalt concrete(HAC)has been increasingly employed as an appropriate impervious structure in hydraulic and hydropower engineering.However,asphalt mortar,usually seen as the matrix of HAC composite,is partic...Hydraulic asphalt concrete(HAC)has been increasingly employed as an appropriate impervious structure in hydraulic and hydropower engineering.However,asphalt mortar,usually seen as the matrix of HAC composite,is particularly prone to damage under combined stress and seepage interactions,and the mesoscale investigations on the damage-seepage coupling behavior of HAC under complex stress states remain limited.This research develops a numerical three-dimensional mesoscale model composed of asphalt mortar and polyhedral aggregate to investigate the stress-damage-seepage coupling behavior in HAC.In this model,asphalt mortar yields the viscoelastic continuum damage law and aggregate obeys the Mazars’elastic-brittle damage law;simultaneously,the effective permeability coefficient of asphalt mortar is assumed to follow an exponential function of damage.The predicted deviatoric stress-strain and hydraulic gradient-seepage curves both are in good agreement with the reported experimental results,which shows the proposed model is valid and reasonable.The simulated results indicate that the damaged asphalt mortar can induce localized areas of high permeability,which in turn affects the overall impervious performance of HAC.展开更多
To reveal the influence of coupled effects of dry-wet cycling and precompression stress(CEDWCPS)on the damage evolution of limestone with horizontal fissure(LHF),a series of degradation and uniaxial compression tests ...To reveal the influence of coupled effects of dry-wet cycling and precompression stress(CEDWCPS)on the damage evolution of limestone with horizontal fissure(LHF),a series of degradation and uniaxial compression tests were conducted,and a corresponding piecewise damage constitutive model(PDCM)was established.We found that both dry-wet cycling and precompression stress deteriorate the physical properties,alter the microscopic characteristics,and reduce the mechanical properties of the LHF.These degradations are particularly pronounced under the CEDWCPS,although the magnitude of these changes gradually diminishes with the progression of dry-wet cycling.Meanwhile,they also reduce the deformation degree,prolong the micropore compaction stage,shorten the unstable crack propagation stage,lower the frequency and intensity of AE events,decrease the high-amplitude and high-frequency AE signals,enlarge crack scales,and shorten the crack initiation time.Among the changes of these indicators,the dry-wet cycling plays a dominant role.The crack types of LHF under the CEDWCPS(LHFCEDWCPS)are predominantly tensile cracks,supplemented by shear cracks.The failure mode can be defined as tensileshear composite failure.Finally,the established PDCM effectively captures the nonlinear deformation of micropore and the linear deformation of the matrix in LHFCEDWCPS,with all corresponding R^(2) consistently exceeding 0.97.展开更多
This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior...This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior.The specimens exhibit violent chemical reaction during the fracture process under the impact loading,and the size distribution of their residual debris follows Rosin-Rammler model.The dynamic fracture toughness is obtained by the fitting of debris length scale,approximately 1.87 MPa·m~(1/2).Microstructure observation on residual debris indicates that the failure process is determined by primary crack propagation under quasi-static compression,while it is affected by multiple cracks propagation in both particle and matrix in the case of dynamic impact.Impact test demonstrates that the novel energetic fragment performs brilliant penetration and combustion effect behind the front target,leading to the effective ignition of fuel tank.For the brittleness of as-cast W-ZrTi ESM,further study conducted bond-based peridynamic(BB-PD)C++computational code to simulate its fracture behavior during penetration.The BB-PD method successfully captured the fracture process and debris cloud formation of the energetic fragment.This paper explores a novel as-cast metallic ESM,and provides an available numerical avenue to the simulation of brittle energetic fragment.展开更多
High geo-stress and high temperature in deep rock engineering increase the possibility of engineering and geological disasters in discontinuous rocks.However,the influence of thermomechanical coupling on the shear beh...High geo-stress and high temperature in deep rock engineering increase the possibility of engineering and geological disasters in discontinuous rocks.However,the influence of thermomechanical coupling on the shear behavior and damage evolution of prefractured granite remains immature.In this context,true triaxial laboratory tests and discrete element method simulations under different confining pressures(σ3=3 MPa,σ2=4 MPa,andσ3=80 MPa,σ2=100 MPa)and temperatures(25℃-500℃)were carried out on rough granite fractures with two different orientations.Results indicate that high temperature and high confining pressure increase the peak strength of the prefractured specimen,leading to more microcracks in the host rock and more gouges between the surfaces.Thermal strengthening at low temperatures(<300℃)and residual stick-slip only occur under a greater confining pressure for prefractured specimens.High confining pressure suppresses generation of the thermal microcracks in the heating stage.Cracks first initiate in the asperities on the fracture surfaces,and then propagate into the rock matrix during the mechanical loading stage.In addition,prefractured granite with a larger fracture angle is characterized by smaller peak and residual strength,faster residual slip,fewer new cracks on the specimen surface,and a more pronounced thermal strengthening effect on peak strength.The slip tendency analysis indicates that a higher maximum principal stress(s1)and a large fracture angle(45°-75°)generally result in a higher potential for fracture slip or activation.This study will contribute to a better understanding of the fracture shear mechanism under true triaxial thermomechanical coupling conditions and provides new insights into the stability evaluation of deep dynamic geological hazards.展开更多
As the main geomaterials for coral reefs oil or gas extraction and underground infrastructure construction,coral reef limestone demonstrates significantly distinct mechanical responses compared to terrigenous rocks.To...As the main geomaterials for coral reefs oil or gas extraction and underground infrastructure construction,coral reef limestone demonstrates significantly distinct mechanical responses compared to terrigenous rocks.To investigate the mechanical behaviour of coral reef limestone under the coupling impact of size and strain rate,the uniaxial compression tests were conducted on reef limestone samples with length-to-diameter(L/D)ratio ranging from 0.5 to 2.0 at strain rate ranging from 10^(−5)·s^(−1)to 10^(−2)·s^(−1).It is revealed that the uniaxial compressive strength(UCS)and residual compressive strength(RCS)of coral reef limestone exhibits a decreasing trend with L/D ratio increasing.The dynamic increase factor(DIF)of UCS is linearly correlated with the logarithm of strain rate,while increasing the L/D ratio further enhances the DIF.The elastic modulus increases with strain rate or L/D ratio increasing,whereas the Poisson’s ratio approximates to a constant value of 0.24.The failure strain increases with strain rate increasing or L/D ratio decreasing,while the increase in L/D ratio will inhibit the enhancing effect of the strain rate.The high porosity and low mineral strength are the primary factors contributing to a high RCS of 16.7%–64.9%of UCS,a lower brittleness index and multiple irregular fracture planes.The failure pattern of coral reef limestone transits from the shear-dominated to the splitting-dominated failure with strain rate increasing or L/D ratio decreasing,which is mainly governed by the constrained zones induced by end friction and the strain rate-dependent crack propagation.Moreover,a predictive formula incorporating coupling effect of size and strain rate for the UCS of reef limestone was established and verified to effectively capture the trend of UCS.展开更多
Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to re...Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.展开更多
The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous mill...The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous milling process becomes a key factor affecting the performance of composites,and the high milling temperature induces a variety of processing defects.This paper obtained the temperature variation data during the end milling process of CFRP laminates through experiments.After data fitting,the data were transformed into a function of heat flux density varying with time.In the finite element analysis,a double-ellipsoid moving heat source model was introduced,and a moving heat source subrou-tine was written based on the time-varying function of heat flux density to more accurately describe the thermal effects dur-ing the milling process and simulate the changes in the temperature field during milling.The Hashin failure criterion is a-dopted as the basis of fiber and matrix failure,and the simulation results of the temperature field are input into the thermal-force coupling simulation model as the predefined field conditions for solving and analyzing by means of sequential thermal-force coupling,so as to establish a thermal-force coupling simulation and analysis model for milling processing of CFRP end faces.The model simulation results can provide a basis for exploring the damage evolution law of CFRP material under the influence of temperature.展开更多
This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and...This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.展开更多
Aqueous rechargeable Ni-Fe batteries exhibit unique advantages in large-scale energy storage thanks to their affordability,safety,and reliability.However,their limited energy density and Coulombic efficiency stem from...Aqueous rechargeable Ni-Fe batteries exhibit unique advantages in large-scale energy storage thanks to their affordability,safety,and reliability.However,their limited energy density and Coulombic efficiency stem from unfavorable OH^(−)adsorption capability and low electrochemical activity of Fe sites,result in electrode kinetic delays for Fe anodes.Here,we report Mn and S co-modified FeOOH(MSFF)nanosheets as an advanced anode in Ni-Fe batteries,synthesized from a facile one-step surface-redox-etching method at room temperature.Based on the strong electronic coupling effect between Mn and S atoms,such MSFF anode presents fast electron transport capability,enhanced OH^(−)-adsorption capability,and redox reactivity.Specifically,the MSFF anode can achieve a high areal capacity of 2 mAh cm^(−2)at 10 mA cm^(−2),which retains a staggering 96%of the initial capacity after undergoing 9000 cycles at a higher current density of 30 mA cm^(−2).In addition,the assembled Ni-Fe battery can provide a capacity of 0.85 mAh cm^(−2)at 16 mA cm^(−2),significantly outperforming most recently reported aqueous rechargeable batteries.This work may offer an innovative and feasible approach for modulating the local electronic structure of high-performance Ni-Fe battery electrode materials.展开更多
Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extrac...Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extracting sustainable and clean energy fromthe salinity gradient energy.However,the scarcity of research investigating the intricate multi-factor coupling effects on the energy conversion performance,especially the trade-offs between ion selectivity and mass transfer in nanochannels,of NRED poses a great challenge to achieving breakthroughs in energy conversion processes.This numerical study innovatively investigates the multi-factor coupling effect of three critical operational factors,including the nanochannel configuration,the temperature field,and the concentration difference,on the energy conversion processes of NRED.In this work,a dimensionless amplitude parameter s is introduced to emulate the randomly varied wall configuration of nanochannels that inherently occur in practical applications,thereby enhancing the realism and applicability of our analysis.Numerical results reveal that the application of a temperature gradient,which is oriented in opposition to the concentration gradient,enhances the ion transportation and selectivity simultaneously,leading to an enhancement in both output power and energy conversion efficiency.Additionally,the increased fluctuation of the nanochannel wall from s=0 to s=0.08 improves ion selectivity yet raises ion transport resistance,resulting in an enhancement in output power and energy conversion efficiency but a slight reduction in current.Furthermore,with increasing the concentration ratio cH/cL from 10 to 1000,either within a fixed temperature field or at a constant dimensionless amplitude,the maximumpower consistently attains its optimal value at a concentration ratio of 100 but the cation transfer number experiences amonotonic decrease across this entire range of concentration ratios.Finally,uponmodifying the operational parameters fromthe baseline condition of s=0,c_(H)/c_(L)=10,andΔT=0 K to the targetedconditionof s=0.08,c_(H)/c_(L)=50,andΔT=25 K,there is a concerted improvement observed in the open-circuit potential,short-circuit current,andmaximumpower,with respective increments of 8.86%,204.97%,and 232.01%,but a reduction in cation transfer number with a notable decrease of 15.37%.展开更多
The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3 D thermo-mechanica...The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3 D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 ℃ at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.展开更多
The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear...The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.展开更多
This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,...This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,and the material coefficients are quasi-periodic,i.e.,they depend not only on the microscale information but also on the macro location.Also,a mutual interaction between displacement and temperature fields is considered in the problem,which is our particular interest in this study.The multiscale asymptotic expansions of the temperature and displacement fields are constructed and associated error estimation in nearly pointwise sense is presented.Then,a finite element-difference algorithm based on the multiscale analysis method is brought forward in detail.Finally,some numerical examples are given.And the numerical results show that the multiscale method presented in this paper is effective and reliable to study the nonlinear thermo-mechanical coupling problem of composite structures with quasiperiodic properties.展开更多
Based on the theory of elastic-plastic finite element method, the high-speed hot continuous rolling process of a billet is simulated and analyzed in vertical and horizontal passes. The billet is dragged into the passe...Based on the theory of elastic-plastic finite element method, the high-speed hot continuous rolling process of a billet is simulated and analyzed in vertical and horizontal passes. The billet is dragged into the passes by contact friction force between the billet and rollers. The rollers and billet are represented by respectively rigid and deformable bodies, and three-dimensional models are developed for the billet and rollers. The distribution of deformation field, effective strain, rolling force and temperature field are accurately calculated for the whole rolling process （including unstable and stable stages）. In addition, the rolling pressure on the width symmetry center is compared with that in the in-situ experimental measurements. It is revealed that various heat exchange phenomena among the billet, rollers and surroundings can result in unbalanced temperature distribution on the cross section. Rolling force and strain can change significantly when the billet is moved towards or away from the roller gap, and keep almost invariable in the stable stage. It is expected that the simulation results would be useful for practical manufacture and provide the theoretical foundation for improvement of process planning and optimization of process parameters.展开更多
High geo-temperature is one of the inevitable geological disasters in deep engineering such as resource extraction,space development,and energy utilization.One of the key issues is to understand the mechanical propert...High geo-temperature is one of the inevitable geological disasters in deep engineering such as resource extraction,space development,and energy utilization.One of the key issues is to understand the mechanical properties and failure mechanism of high-temperature rock disturbed by low-temperature airflow after excavation.Therefore,.the experimental and numerical investigation were carried out to study the impact of cooling rate on mechanical properties and failure mechanism of high temperature sandstone.First,uniaxial compression experiments of high temperature sandstone at different real-time cooling rates were carried out to study the mechanical properties and failure modes.The experimental results indicate that the cooling rate has a significant effect on the mechanical properties and failure modes of sandstone.The peak strain,peak stress,and elastic modulus decrease with an increase in cooling rate,and the fragmentation degree after failure increases gradually.Moreover,the equivalent numerical model of heterogeneous sandstone was established using particle flow code(PFC)to reveal the failure mechanism.The results indicate that the sandstone is dominated by intragrain failure in the cooling stage,the number of microcracks is exponentially related to the cooling rate,and the higher the cooling rate,the more cracks are concentrated in the exterior region.Under axial loading,the tensile stress is mostly distributed along the radial direction,and the damage in the cooling stage is mostly due to the fracture of the radial bond.In addition,axial loading,temperature gradient and thermal stress mismatch between adjacent minerals are the main reasons for the damage of sandstone in the cooling stage.Moreover,the excessive temperature gradient in the exterior region of the sandstone is the main reason for the damage concentration in this region.展开更多
In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,th...In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.展开更多
基金supported by grants from the National Natural Science Foundation of China (51478130)the Guangzhou Municipal Education Bureau’s Scientific Research Project, China (2024312217)+1 种基金the China Scholarship Council (201808440070)the 111 Project of China (D21021).
文摘This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element coupling stress resulting from the combination of mechanical and thermal loading,using geometric nonlinear finite element analysis.A topological model is then developed to minimize compliance while meeting displacement and frequency constraints to fulfill design requirements of structural members.Since the conventional Lagrange multiplier search method is unable to handle convergence instability arising from large deformation,a novel Lagrange multiplier search method is proposed.Additionally,the proposed method can be extended to multi-constrained geometrically nonlinear topology optimization,accommodating multiple physical field couplings.
基金funded by the National Natural Science Foundation of China(Nos.52209130 and 52379100)Shandong Provincial Natural Science Foundation(No.ZR2024ME112).
文摘Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction and operation of tunnel engineering.This study investigated the thermo-mechanical damage behavior of the composite interface between alkali-resistant glass fiber-reinforced concrete(ARGFRC)and granite,focusing on a plateau railway tunnel.Laboratory triaxial tests,laser scanning,XRD analysis,numerical simulations,and theoretical analyses were employed to investigate how different initial curing temperatures and joint roughness coefficient(JRC)influence interfacial damage behavior.The results indicate that an increase in interface roughness exacerbates the structural damage at the interface.At a JRC of 19.9 and a temperature of 70℃,crack initiation in granite was notably restrained when the confining pressure rose from 7 MPa to 10 MPa.Roughness-induced stress distribution at the interface was notably altered,although this effect became less pronounced under high confining pressure conditions.Additionally,during high-temperature curing,thermal stress concentration at the tips of micro-convex protrusions on the granite surface induced microcracks in the adjacent ARGFRC matrix,followed by deformation.These findings provide practical guidelines for designing concrete support systems to ensure tunnel structural safety in high-altitude regions with harsh thermal environments.
文摘This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.
基金National Natural Science Foundation of China under Grant Nos.U2139208 and 52278516Key Laboratory of Earthquake Engineering and Engineering Vibration,China Earthquake Administration under Grant No.2024D15Key Laboratory of Soft Soil Characteristic and Engineering Environment,Tianjin Chengjian University under Grant No.2022SCEEKL003。
文摘This study presents an effective hybrid simulation approach for simulating broadband ground motion in complex near-fault locations.The approach utilizes a deterministic approach based on the spectral element method(SEM),which is used to simulate low-frequency ground motion(f<1 Hz)by incorporating an innovative efficient discontinuous Galerkin(DG)method for grid division to accurately model basin sedimentary layers at reduced costs.It also introduces a comprehensive hybrid source model for high-frequency random scattering and a nonlinear analysis module for basin sedimentary layers.Deterministic outcomes are combined with modified three-dimensional stochastic finite fault method(3D-EXSIM)simulations of high-frequency ground motion(f>1 Hz).A fourth-order Butterworth filter with zero phase shift is employed for time-domain filtering of low-and high-frequency time series at a crossover frequency of 1 Hz,merging the low and high-frequency ground motions into a broadband time series.Taking an Ms 6.8 Luding earthquake,as an example,this hybrid method was used for a rapid and efficient simulation analysis of broadband ground motion in the region.The accuracy and efficiency of this hybrid method were verified through comparisons with actually observed station data and empirical attenuation curves.Deterministic method simulation results revealed the effects of mountainous topography,basin effects,nonlinear effects within the basin’s sedimentary layers,and a coupling interaction between the basin and the mountains.The findings are consistent with similar studies,showing that near-fault sedimentary basins significantly focus and amplify strong ground motion,and the soil’s nonlinear behavior in the basin influences ground motion to varying extents at different distances from the fault.The mountainous topography impacts the basin’s response to ground motion,leading to barrier effects.This research provides a scientific foundation for seismic zoning,urban planning,and seismic design in nearfault mountain basin regions.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3005603-01)the Natural Science Foundation Science of Anhui Province(Grant No.2308085US02).
文摘Hydraulic asphalt concrete(HAC)has been increasingly employed as an appropriate impervious structure in hydraulic and hydropower engineering.However,asphalt mortar,usually seen as the matrix of HAC composite,is particularly prone to damage under combined stress and seepage interactions,and the mesoscale investigations on the damage-seepage coupling behavior of HAC under complex stress states remain limited.This research develops a numerical three-dimensional mesoscale model composed of asphalt mortar and polyhedral aggregate to investigate the stress-damage-seepage coupling behavior in HAC.In this model,asphalt mortar yields the viscoelastic continuum damage law and aggregate obeys the Mazars’elastic-brittle damage law;simultaneously,the effective permeability coefficient of asphalt mortar is assumed to follow an exponential function of damage.The predicted deviatoric stress-strain and hydraulic gradient-seepage curves both are in good agreement with the reported experimental results,which shows the proposed model is valid and reasonable.The simulated results indicate that the damaged asphalt mortar can induce localized areas of high permeability,which in turn affects the overall impervious performance of HAC.
基金supported by the Yunnan Province Science and Technology Plan Project(No.202403AA080001-4)the Key Research and Development Project of Guangxi,China(No.guikeAB24010144)the National Key Research and Development Project of China(Nos.2021YFB3901402 and 2018YFC1504802)。
文摘To reveal the influence of coupled effects of dry-wet cycling and precompression stress(CEDWCPS)on the damage evolution of limestone with horizontal fissure(LHF),a series of degradation and uniaxial compression tests were conducted,and a corresponding piecewise damage constitutive model(PDCM)was established.We found that both dry-wet cycling and precompression stress deteriorate the physical properties,alter the microscopic characteristics,and reduce the mechanical properties of the LHF.These degradations are particularly pronounced under the CEDWCPS,although the magnitude of these changes gradually diminishes with the progression of dry-wet cycling.Meanwhile,they also reduce the deformation degree,prolong the micropore compaction stage,shorten the unstable crack propagation stage,lower the frequency and intensity of AE events,decrease the high-amplitude and high-frequency AE signals,enlarge crack scales,and shorten the crack initiation time.Among the changes of these indicators,the dry-wet cycling plays a dominant role.The crack types of LHF under the CEDWCPS(LHFCEDWCPS)are predominantly tensile cracks,supplemented by shear cracks.The failure mode can be defined as tensileshear composite failure.Finally,the established PDCM effectively captures the nonlinear deformation of micropore and the linear deformation of the matrix in LHFCEDWCPS,with all corresponding R^(2) consistently exceeding 0.97.
文摘This paper prepared a novel as-cast W-Zr-Ti metallic ESM using high-frequency vacuum induction melting technique.The above ESM performs a typical elastic-brittle material feature and strain rate strengthening behavior.The specimens exhibit violent chemical reaction during the fracture process under the impact loading,and the size distribution of their residual debris follows Rosin-Rammler model.The dynamic fracture toughness is obtained by the fitting of debris length scale,approximately 1.87 MPa·m~(1/2).Microstructure observation on residual debris indicates that the failure process is determined by primary crack propagation under quasi-static compression,while it is affected by multiple cracks propagation in both particle and matrix in the case of dynamic impact.Impact test demonstrates that the novel energetic fragment performs brilliant penetration and combustion effect behind the front target,leading to the effective ignition of fuel tank.For the brittleness of as-cast W-ZrTi ESM,further study conducted bond-based peridynamic(BB-PD)C++computational code to simulate its fracture behavior during penetration.The BB-PD method successfully captured the fracture process and debris cloud formation of the energetic fragment.This paper explores a novel as-cast metallic ESM,and provides an available numerical avenue to the simulation of brittle energetic fragment.
基金support from the National Key Research and Development Program of China(Grant No.2022YFE0137200)supported by the Taishan Scholars Program and Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering Safety(Grant No.SKLGME023003).
文摘High geo-stress and high temperature in deep rock engineering increase the possibility of engineering and geological disasters in discontinuous rocks.However,the influence of thermomechanical coupling on the shear behavior and damage evolution of prefractured granite remains immature.In this context,true triaxial laboratory tests and discrete element method simulations under different confining pressures(σ3=3 MPa,σ2=4 MPa,andσ3=80 MPa,σ2=100 MPa)and temperatures(25℃-500℃)were carried out on rough granite fractures with two different orientations.Results indicate that high temperature and high confining pressure increase the peak strength of the prefractured specimen,leading to more microcracks in the host rock and more gouges between the surfaces.Thermal strengthening at low temperatures(<300℃)and residual stick-slip only occur under a greater confining pressure for prefractured specimens.High confining pressure suppresses generation of the thermal microcracks in the heating stage.Cracks first initiate in the asperities on the fracture surfaces,and then propagate into the rock matrix during the mechanical loading stage.In addition,prefractured granite with a larger fracture angle is characterized by smaller peak and residual strength,faster residual slip,fewer new cracks on the specimen surface,and a more pronounced thermal strengthening effect on peak strength.The slip tendency analysis indicates that a higher maximum principal stress(s1)and a large fracture angle(45°-75°)generally result in a higher potential for fracture slip or activation.This study will contribute to a better understanding of the fracture shear mechanism under true triaxial thermomechanical coupling conditions and provides new insights into the stability evaluation of deep dynamic geological hazards.
基金supported by the National Natural Science Foundation of China(Nos.52222110,52401354,and 52301353).
文摘As the main geomaterials for coral reefs oil or gas extraction and underground infrastructure construction,coral reef limestone demonstrates significantly distinct mechanical responses compared to terrigenous rocks.To investigate the mechanical behaviour of coral reef limestone under the coupling impact of size and strain rate,the uniaxial compression tests were conducted on reef limestone samples with length-to-diameter(L/D)ratio ranging from 0.5 to 2.0 at strain rate ranging from 10^(−5)·s^(−1)to 10^(−2)·s^(−1).It is revealed that the uniaxial compressive strength(UCS)and residual compressive strength(RCS)of coral reef limestone exhibits a decreasing trend with L/D ratio increasing.The dynamic increase factor(DIF)of UCS is linearly correlated with the logarithm of strain rate,while increasing the L/D ratio further enhances the DIF.The elastic modulus increases with strain rate or L/D ratio increasing,whereas the Poisson’s ratio approximates to a constant value of 0.24.The failure strain increases with strain rate increasing or L/D ratio decreasing,while the increase in L/D ratio will inhibit the enhancing effect of the strain rate.The high porosity and low mineral strength are the primary factors contributing to a high RCS of 16.7%–64.9%of UCS,a lower brittleness index and multiple irregular fracture planes.The failure pattern of coral reef limestone transits from the shear-dominated to the splitting-dominated failure with strain rate increasing or L/D ratio decreasing,which is mainly governed by the constrained zones induced by end friction and the strain rate-dependent crack propagation.Moreover,a predictive formula incorporating coupling effect of size and strain rate for the UCS of reef limestone was established and verified to effectively capture the trend of UCS.
基金the support provided by the National Natural Science Foundation of China(Grant Nos.52278336 and 42302032)Guangdong Basic and Applied Research Foundation(Grant Nos.2023B1515020061).
文摘Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.
文摘The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous milling process becomes a key factor affecting the performance of composites,and the high milling temperature induces a variety of processing defects.This paper obtained the temperature variation data during the end milling process of CFRP laminates through experiments.After data fitting,the data were transformed into a function of heat flux density varying with time.In the finite element analysis,a double-ellipsoid moving heat source model was introduced,and a moving heat source subrou-tine was written based on the time-varying function of heat flux density to more accurately describe the thermal effects dur-ing the milling process and simulate the changes in the temperature field during milling.The Hashin failure criterion is a-dopted as the basis of fiber and matrix failure,and the simulation results of the temperature field are input into the thermal-force coupling simulation model as the predefined field conditions for solving and analyzing by means of sequential thermal-force coupling,so as to establish a thermal-force coupling simulation and analysis model for milling processing of CFRP end faces.The model simulation results can provide a basis for exploring the damage evolution law of CFRP material under the influence of temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.11902002 and 51705002)the Sichuan Provincial Natural Science Foundation(Grant No.2022NSFSC0275)the University Outstanding Youth Researcher Support Program of the Education Department of Anhui Province,and the Teaching Project of the Education Department of Anhui Province(Grant No.2022xxsfkc023).
文摘This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.
基金financially supported by National Natural Science Foundation of China(Nos.52407242,52162025)Specific Research Fund of the Innovation Platform for Academicians of Hainan Province(No.YSPTZX202123).
文摘Aqueous rechargeable Ni-Fe batteries exhibit unique advantages in large-scale energy storage thanks to their affordability,safety,and reliability.However,their limited energy density and Coulombic efficiency stem from unfavorable OH^(−)adsorption capability and low electrochemical activity of Fe sites,result in electrode kinetic delays for Fe anodes.Here,we report Mn and S co-modified FeOOH(MSFF)nanosheets as an advanced anode in Ni-Fe batteries,synthesized from a facile one-step surface-redox-etching method at room temperature.Based on the strong electronic coupling effect between Mn and S atoms,such MSFF anode presents fast electron transport capability,enhanced OH^(−)-adsorption capability,and redox reactivity.Specifically,the MSFF anode can achieve a high areal capacity of 2 mAh cm^(−2)at 10 mA cm^(−2),which retains a staggering 96%of the initial capacity after undergoing 9000 cycles at a higher current density of 30 mA cm^(−2).In addition,the assembled Ni-Fe battery can provide a capacity of 0.85 mAh cm^(−2)at 16 mA cm^(−2),significantly outperforming most recently reported aqueous rechargeable batteries.This work may offer an innovative and feasible approach for modulating the local electronic structure of high-performance Ni-Fe battery electrode materials.
基金funded by the National Natural Science Foundation of China[52106246]the Postgraduate Research&Practice innovation Program of Jiangsu Province[KYCX24_1641].
文摘Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extracting sustainable and clean energy fromthe salinity gradient energy.However,the scarcity of research investigating the intricate multi-factor coupling effects on the energy conversion performance,especially the trade-offs between ion selectivity and mass transfer in nanochannels,of NRED poses a great challenge to achieving breakthroughs in energy conversion processes.This numerical study innovatively investigates the multi-factor coupling effect of three critical operational factors,including the nanochannel configuration,the temperature field,and the concentration difference,on the energy conversion processes of NRED.In this work,a dimensionless amplitude parameter s is introduced to emulate the randomly varied wall configuration of nanochannels that inherently occur in practical applications,thereby enhancing the realism and applicability of our analysis.Numerical results reveal that the application of a temperature gradient,which is oriented in opposition to the concentration gradient,enhances the ion transportation and selectivity simultaneously,leading to an enhancement in both output power and energy conversion efficiency.Additionally,the increased fluctuation of the nanochannel wall from s=0 to s=0.08 improves ion selectivity yet raises ion transport resistance,resulting in an enhancement in output power and energy conversion efficiency but a slight reduction in current.Furthermore,with increasing the concentration ratio cH/cL from 10 to 1000,either within a fixed temperature field or at a constant dimensionless amplitude,the maximumpower consistently attains its optimal value at a concentration ratio of 100 but the cation transfer number experiences amonotonic decrease across this entire range of concentration ratios.Finally,uponmodifying the operational parameters fromthe baseline condition of s=0,c_(H)/c_(L)=10,andΔT=0 K to the targetedconditionof s=0.08,c_(H)/c_(L)=50,andΔT=25 K,there is a concerted improvement observed in the open-circuit potential,short-circuit current,andmaximumpower,with respective increments of 8.86%,204.97%,and 232.01%,but a reduction in cation transfer number with a notable decrease of 15.37%.
基金Project(51605234)supported by the National Natural Science Foundation of ChinaProjects(2019JJ50510,2019JJ70077)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(18B285,18B552)supported by Scientific Research Fund of Hunan Provincial Education Department,China。
文摘The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3 D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 ℃ at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.
基金supported by the National Natural Science Foundation of China(Grant No.51974173)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2020QD122).
文摘The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.
基金financially supported by the National Natural Science Foundation of China(11501449)the Fundamental Research Funds for the Central Universities(3102017zy043)+2 种基金the China Postdoctoral Science Foundation(2016T91019)the fund of the State Key Laboratory of Solidification Processing in NWPU(SKLSP201628)the Scientific Research Program Funded by Shaanxi Provincial Education Department(14JK1353).
文摘This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,and the material coefficients are quasi-periodic,i.e.,they depend not only on the microscale information but also on the macro location.Also,a mutual interaction between displacement and temperature fields is considered in the problem,which is our particular interest in this study.The multiscale asymptotic expansions of the temperature and displacement fields are constructed and associated error estimation in nearly pointwise sense is presented.Then,a finite element-difference algorithm based on the multiscale analysis method is brought forward in detail.Finally,some numerical examples are given.And the numerical results show that the multiscale method presented in this paper is effective and reliable to study the nonlinear thermo-mechanical coupling problem of composite structures with quasiperiodic properties.
基金Funded by National Natural Science Foundation of China (No. 51004047)Scientific Research Fund of Hunan Provincial Education Department (No. 10B020)Provincial Natural Science Foundation of Hunan (No. 09jj4024)
文摘Based on the theory of elastic-plastic finite element method, the high-speed hot continuous rolling process of a billet is simulated and analyzed in vertical and horizontal passes. The billet is dragged into the passes by contact friction force between the billet and rollers. The rollers and billet are represented by respectively rigid and deformable bodies, and three-dimensional models are developed for the billet and rollers. The distribution of deformation field, effective strain, rolling force and temperature field are accurately calculated for the whole rolling process （including unstable and stable stages）. In addition, the rolling pressure on the width symmetry center is compared with that in the in-situ experimental measurements. It is revealed that various heat exchange phenomena among the billet, rollers and surroundings can result in unbalanced temperature distribution on the cross section. Rolling force and strain can change significantly when the billet is moved towards or away from the roller gap, and keep almost invariable in the stable stage. It is expected that the simulation results would be useful for practical manufacture and provide the theoretical foundation for improvement of process planning and optimization of process parameters.
基金supported by the National Natural Science Foundation of China (41941018)supported by Beijing Natural Science Foundation (8212033)+1 种基金supported by the Fundamental Research Funds for the Central Universities (2021YJSLI13,2021JCCXLJ05)supported by Innovation Fund Research Project (SKLGDUEK202221).
文摘High geo-temperature is one of the inevitable geological disasters in deep engineering such as resource extraction,space development,and energy utilization.One of the key issues is to understand the mechanical properties and failure mechanism of high-temperature rock disturbed by low-temperature airflow after excavation.Therefore,.the experimental and numerical investigation were carried out to study the impact of cooling rate on mechanical properties and failure mechanism of high temperature sandstone.First,uniaxial compression experiments of high temperature sandstone at different real-time cooling rates were carried out to study the mechanical properties and failure modes.The experimental results indicate that the cooling rate has a significant effect on the mechanical properties and failure modes of sandstone.The peak strain,peak stress,and elastic modulus decrease with an increase in cooling rate,and the fragmentation degree after failure increases gradually.Moreover,the equivalent numerical model of heterogeneous sandstone was established using particle flow code(PFC)to reveal the failure mechanism.The results indicate that the sandstone is dominated by intragrain failure in the cooling stage,the number of microcracks is exponentially related to the cooling rate,and the higher the cooling rate,the more cracks are concentrated in the exterior region.Under axial loading,the tensile stress is mostly distributed along the radial direction,and the damage in the cooling stage is mostly due to the fracture of the radial bond.In addition,axial loading,temperature gradient and thermal stress mismatch between adjacent minerals are the main reasons for the damage of sandstone in the cooling stage.Moreover,the excessive temperature gradient in the exterior region of the sandstone is the main reason for the damage concentration in this region.
基金supported by the National Natural Science Foundation of China(Grants 11471262,11202032)the Basic Research Project of National Defense(Grant B 1520132013)supported by the State Key Laboratory of Science and Engineering Computing and Center for high performance computing of Northwestem Polytechnical University
文摘In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.
