The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This stud...The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This study investigates the time-varying response of rocks and roof resistance in coal mines in the Zagros Mountains using a novel approach that combines numerical simulation,relaxation testing,and rock displacement studies.The results show that rocks exhibit significant time-dependent behavior,with changes in rock mechanical properties over time.A comprehensive viscoelastic-plastic model is devel-oped to accurately describe the time-varying strain-softening response of rocks and simulate laboratory tests.The model integrates the Burgers and strain-softening models,simulating stress relaxation curves and rock displacement over time.The study reveals that the rock mass displays significant nonlinear behavior,with changes in rock mechanical properties over time.The findings of this study highlight the importance of considering the time-varying response of rocks and roof resistance in coal mine stability analysis.The results provide valuable insights into the time-dependent behavior of rock mass in coal mines in Iran,which can inform mining practices and mitigate potential hazards.Results in this study can contribute to developing strategies for improving roof stability and reducing the likelihood of roof collapses.展开更多
It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size...It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.展开更多
Modified ethylene-vinyl acetate copolymer(EVAM)and amino-functionalized nano-silica(NSiO_(2))par-ticles were employed as the base materials for the synthesis of the nanocomposite pour point depressant designated as EV...Modified ethylene-vinyl acetate copolymer(EVAM)and amino-functionalized nano-silica(NSiO_(2))par-ticles were employed as the base materials for the synthesis of the nanocomposite pour point depressant designated as EVAM-g-NSiO_(2).This synthesis involved a chemical grafting process within a solution system,followed by a structural characterization.Moreover,combining macro-rheological performance with microscopic structure observation,the influence of the nanocomposite pour point depressant on the rheological properties of the model waxy oil system was investigated.The results indicate that when the mass ratio of NSiO_(2) to EVAM is 1:100,the prepared EVAM-g-NSiO_(2) nanocomposite pour point depressant exhibits excellent pour point reduction and viscosity reduction properties.Moreover,the nanocomposite pour point depressant obtained through a chemical grafting reaction demonstrates structural stability(the bonding between the polymer and nanoparticles is stable).The pour points of model waxy oils doped with 500 mg/kg ethylene-vinyl acetate copolymer(EVA),EVAM,and EVAM/SiO_(2) were reduced from 34℃ to 23,20,and 21℃,respectively.After adding the same dosage of EVAM-g-NSiO_(2) nanocomposite pour point depressant,the pour point of the model wax oil decreased to 12℃ and the viscosity at 32℃ decreased from 2399 to 2396.9 mPa·s,achieving an impressive viscosity reduction rate of 99.9%.Its performance surpassed that of EVA,EVAM,and EVAM/SiO_(2).The EVAM-g-NSiO_(2) dispersed in the oil phase acts as the crystallization nucleus for wax crystals,resulting in a dense structure of wax crystals.The compact wax crystal blocks are difficult to overlap with each other,pre-venting the formation of a three-dimensional network structure,thereby improving the low-temperature flowability of the model waxy oil.展开更多
Selecting proper descriptors(also known feature selection,FS)is key in the process of establishing mechanical properties prediction model of hot-rolled microalloyed steels by using machine learning(ML)algorithm.FS met...Selecting proper descriptors(also known feature selection,FS)is key in the process of establishing mechanical properties prediction model of hot-rolled microalloyed steels by using machine learning(ML)algorithm.FS methods based on data-driving can reduce the redundancy of data features and improve the prediction accuracy of mechanical properties.Based on the collected data of hot-rolled microalloyed steels,the association rules are used to mine the correlation information between the data.High-quality feature subsets are selected by the proposed FS method(FS method based on genetic algorithm embedding,GAMIC).Compared with the common FS method,it is shown on dataset that GAMIC selects feature subsets more appropriately.Six different ML algorithms are trained and tested for mechanical properties prediction.The result shows that the root-mean-square error of yield strength,tensile strength and elongation based on limit gradient enhancement(XGBoost)algorithm is 21.95 MPa,20.85 MPa and 1.96%,the correlation coefficient(R^(2))is 0.969,0.968 and 0.830,and the mean absolute error is 16.84 MPa,15.83 MPa and 1.48%,respectively,showing the best prediction performance.Finally,SHapley Additive exPlanation is used to further explore the influence of feature variables on mechanical properties.GAMIC feature selection method proposed is universal,which provides a basis for the development of high-precision mechanical property prediction model.展开更多
Titanium-silicon(Ti-Si)alloy system shows significant potential for aerospace and automotive applications due to its superior specific strength,creep resistance,and oxidation resistance.For Si-containing Ti alloys,the...Titanium-silicon(Ti-Si)alloy system shows significant potential for aerospace and automotive applications due to its superior specific strength,creep resistance,and oxidation resistance.For Si-containing Ti alloys,the sufficient content of Si is critical for achieving these favorable performances,while excessive Si addition will result in mechanical brittleness.Herein,both physical experiments and finite element(FE)simulations are employed to investigate the micro-mechanisms of Si alloying in tailoring the mechanical properties of Ti alloys.Four typical states of Si-containing Ti alloys(solid solution state,hypoeutectoid state,near-eutectoid state,hypereutectoid state)with varying Si content(0.3-1.2 wt.%)were fabricated via in-situ alloying spark plasma sintering.Experimental results indicate that in-situ alloying of 0.6 wt.%Si enhances the alloy’s strength and ductility simultaneously due to the formation of fine and uniformly dispersed Ti_(5)Si_(3)particles,while higher content of Si(0.9 and 1.2 wt.%)results in coarser primary Ti_(5)Si_(3)agglomerations,deteriorating the ductility.FE simulations support these findings,highlighting the finer and more uniformly distributed Ti_(5)Si_(3)particles contribute to less stress concentration and promote uniform deformation across the matrix,while agglomerated Ti_(5)Si_(3)particles result in increased local stress concentrations,leading to higher chances of particle fracture and reduced ductility.This study not only elucidates the micro-mechanisms of in-situ Si alloying for tailoring the mechanical properties of Ti alloys but also aids in optimizing the design of high-performance Si-containing Ti alloys.展开更多
A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of ...A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.展开更多
Increasingly,attention is being directed towards time-dependent diffusion magnetic resonance imaging(TDDMRI),a method that reveals time-related changes in the diffusional behavior of water molecules in biological tiss...Increasingly,attention is being directed towards time-dependent diffusion magnetic resonance imaging(TDDMRI),a method that reveals time-related changes in the diffusional behavior of water molecules in biological tissues,thereby enabling us to probe related microstructure events.With ongoing improvements in hardware and advanced pulse sequences,significant progress has been made in applying TDDMRI to clinical research.The development of accurate mathematical models and computational methods has bolstered theoretical support for TDDMRI and elevated our understanding of molecular diffusion.In this review,we introduce the concept and basic physics of TDDMRI,and then focus on the measurement strategies and modeling approaches in short-and long-diffusion-time domains.Finally,we discuss the challenges in this field,including the requirement for efficient scanning and data processing technologies,the development of more precise models depicting time-dependent molecular diffusion,and critical clinical applications.展开更多
To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main compon...To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.展开更多
Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.Thi...Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.展开更多
Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological s...Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.展开更多
Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)...Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)K and at ambient pressure(81.5 kPa).From the experimental data,excess molar volume(V_(m)~E),thermal expansion coefficients(α),deviations in isentropic compressibility(Δκ_(S)),viscosity(Δ_η),and refractive index(Δn_(D))were calculated.These values were then correlated using the Redlich-Kister polynomial equation,with fitting coefficients and standard deviations determined.Additionally,the Prigogine-Flory-Patterson(PFP)theory and the Extended Real Associated Solution(ERAS)model were employed to correlate the excess molar volume,while the Perturbed Chain Statistical Associating Fluid Theory(PC-SAFT)was used to predict the density of mixtures.展开更多
A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to ...A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.展开更多
Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations,playing a crucial role in promoting green and low-...Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations,playing a crucial role in promoting green and low-carbon extraction methodologies.In this study,grouting reinforcement processes were examined by conducting grouting experiments on a fractured rock with varying negative pressures(0-100 kPa),followed by uniaxial compression testing of the grout-reinforced bodies.This investigation explored the diffusion patterns of grout under negative pressure and established a constitutive model of damage-bearing capacity for bodies reinforced by negative pressure grouting.It further studied the enhancement effect of negative pressure on the load-bearing capacity of the reinforced bodies and analyzed the instability mechanism of damage and failure in these bodies.The results indicated that the diffusion of grout under negative pressure is influenced by four types of forces,which alter the extent of grout diffusion within the fractured rock mass.Introducing a damage constitutive model that serially connects pore and framework elements characterizes the damage and failure behavior of groutreinforced bodies under different negative pressures.As the negative pressure increases,changes in porosity,water-to-cement ratio,and admixture quantity occur in the grout-reinforced specimens,with the strength mean curve showing a trend of first increasing and then decreasing,reaching a threshold at a negative pressure of 60 kPa.With increasing negative pressure,the negative pressure damage variable decreases and then increases,and the stronger the interfacial microelement connections caused by the negative pressure,the greater the bearing capacity,ultimately manifesting in different failure modes.展开更多
Machine learning models can predict material properties quickly and accurately at a low computational cost.This study generated novel hybridized nanocomposites with unsaturated polyester resin as the matrix and Areca ...Machine learning models can predict material properties quickly and accurately at a low computational cost.This study generated novel hybridized nanocomposites with unsaturated polyester resin as the matrix and Areca fruit husk fiber(AFHF),tamarind fruit fiber(TFF),and nano-sized coconut shell powder(NCSP).It is challenging to determine the optimal proportion of raw materials in this composite to achieve maximum mechanical properties.This task was accomplished with the help of ML techniques in this study.The tensile strength of the hybridized nanocomposite was increased by 134.06% compared to the neat unsaturated polyester resin at a 10:5:2 wt.% ratio,AFHF:TFF:NCSP.The stiffness and impact behavior of hybridized nanocomposites were similar.The scanning electron microscope showed homogeneous reinforcement and nanofiller distribution in the matrix.However,the hybridized nanocomposite with a 20:5:0 wt.% combination ratio had the highest strain at break of 5.98%,AFHF:TFF:NCSP.The effectiveness of recurrent neural networks and recurrent neural networks with Levenberg’s algorithm was assessed using R2,mean absolute errors,and minimum squared errors.Tensile and impact strength of hybridized nanocomposites were well predicted by the recurrent neural network with Levenberg’s model with 2 and 3 hidden layers,80 neurons and 80 neurons,respectively.A recurrent neural network model with 4 hidden layers,60 neurons,and 2 hidden layers,100 neurons predicted hybridized nanocomposites’Young’s modulus and elongation at break with maximum R2 values.The mean absolute errors and minimum squared errors were evaluated to ensure the reliability of the machine learning algorithms.The models optimize hybridized nanocomposites’mechanical properties,saving time and money during experimental characterization.展开更多
The use of additive manufacturing techniques in the development of unconventional materials can help reduce the environmental impact of traditional construction materials.In this paper,the properties of a 3D-printed b...The use of additive manufacturing techniques in the development of unconventional materials can help reduce the environmental impact of traditional construction materials.In this paper,the properties of a 3D-printed biocomposite were evaluated.Biofilaments obtained by mixing pulverized bamboo fibers with polylactic acid(PLA)resin were extruded during the manufacturing process.To assess the effect of incorporating plant fibers,an analysis was conducted on the morphology,elemental chemical composition,crystallinity index,principal functional groups,thermal stability,surface roughness,microhardness,density,tensile strength,elastic modulus,and strain percentage of reinforced samples.The results were comparedwith those obtained from the characterization of standard PLAfilaments(unreinforced).The fused deposition modeling(FDM)technique was employed to print biocomposite specimens.Additionally,the influence of the printing parameters(infill density,build orientation,and layer thickness)on the physical,tribological,andmechanical properties of the biocomposites was analyzed.These results were compared with those obtained for specimens printed with pure PLA.The findings indicate that incorporating 10%vegetable filler into PLA filaments enhanced the strength and stiffness of the biocomposite under axial loads.Finally,the strength of the biocomposite subjected to axial loads was compared with the standardized values for wood-plastic composites,demonstrating the feasibility of its use for non-structural purposes in civil construction.展开更多
With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This...With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This study investigates the influence of prefabricated crack dip angles on the mechanical properties of anchored rock masses in deep soft rock roadways.By constructing similarity models of NPR(Negative Poisson’s Ratio)and PR(Positive Poisson’s Ratio)anchored solids,biaxial compression experiments under varying crack dip angles were conducted.Strain gauges,3D Digital Image Correlation(3D DIC),and acoustic emission monitoring were employed to systematically analyze the strength characteristics,deformation-damage evolution,and energy dissipation mechanisms of the two types of anchor systems.The results show that:(1)The stress-strain curves of anchored solids with prefabricated cracks exhibit a distinct bimodal characteristic.Compared to PR anchors,NPR anchors show 20%and 23%improvements in peak strength and elastic modulus,respectively,with residual strength enhanced by up to 34%.(2)Owing to high pre-tightening force and large deformation capacity,NPR anchors maintain superior integrity under increasing crack dip angles,demonstrating more uniform free-surface displacement and localized shear-tensile composite crack patterns.(3)Acoustic emission analysis reveals that NPR anchors exhibit higher cumulative energy absorption(300%improvement over PR anchors)and lack low-rate energy development phases,indicating enhanced ductility and impact resistance at high crack dip angles.(4)Crack dip angle critically governs failure mechanisms by modulating the connectivity between shear cracks and prefabricated fissures:bimodal effects dominate at low angles,while vertical tensile crack propagation replaces bimodal behavior at high angles.The study proposes prioritizing NPR anchor cables in deep engineering applications and optimizing support parameters based on crack dip angles to mitigate stress concentration and ensure the long-term stability of surrounding rock.展开更多
Negative Poisson ratio(NPR)steel is a new material with high strength and toughness.This study conducted tensile tests at elevated temperatures to investigate the mechanical properties of NPR steel at high temperature...Negative Poisson ratio(NPR)steel is a new material with high strength and toughness.This study conducted tensile tests at elevated temperatures to investigate the mechanical properties of NPR steel at high temperatures.The stress−strain curve,ultimate strength,yield strength,modulus of elasticity,elongation after fracture,and percentage reduction of area of NPR steel bars were measured at 9 different temperatures ranging from 20 to 800℃.The experimental results indicate that high-temperature environments significantly affect the mechanical properties of NPR steel.However,compared to other types of steel,NPR steel exhibits better resistance to deformation.When the test temperature is below 700℃,NPR steel exhibits a ductile fracture characteristic,while at 800℃,it exhibits a brittle fracture characteristic.Finally,based on the experimental findings,a constitutive model suitable for NPR steel at high temperatures is proposed.展开更多
Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remai...Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remains poorly understood.This study aimed to investigate the mechanical properties and failure mechanisms of carbonaceous mudstone filler under different temperature-moisture coupled conditions.Triaxial shear tests were conducted under four temperaturemoisture coupled conditions:dry-heat to dry-cold(DHDC),wet-cold to wet-heat(WCWH),dry-cold to wet-heat(DCWH),and dry-heat to wet-cold(DHWC).The effects of these conditions on the strength characteristics,relative breakage ratio,failure mode,and microscopic morphology were examined.A segmented prediction model based on the DuncanChang model was applied to validate the experimental results under the DHWC condition.The failure mechanisms under different conditions were also analyzed.The results indicate that the degradation of carbonaceous mudstone increases in the following order:DHDC,WCWH,DCWH,and DHWC.Under the DHDC condition,the stress-strain curves exhibit strain-softening behavior,while other conditions show strain-hardening behavior,with peak deviatoric stress occurring at 2%and 4%axial strains,respectively.The shear strength decreases by up to 40%under the DHWC condition but remains nearly unchanged under the DHDC condition,showing a positive correlation with particle breakage.As the number of cycles increases,the failure surfaces gradually move downward.Higher confining pressure shifts failure mode from shear failure to shear slip or localized compression,and eventually to overall compression or expansion failure.The modified Duncan-Chang model accurately predicts the experimental results.These findings provide important guidance for the application of carbonaceous mudstone filler in highway embankment construction in humid mountainous regions.展开更多
A brittle creep and time-dependent fracturing process model of rock is established by incorporating the stress corrosion model into discrete element method to analyze the creep behavior and microcrack evolution in bri...A brittle creep and time-dependent fracturing process model of rock is established by incorporating the stress corrosion model into discrete element method to analyze the creep behavior and microcrack evolution in brittle rocks at a micro-scale level.Experimental validation of the model is performed,followed by numerical simu-lations to investigate the creep properties and microcrack evolution in rocks under single-stage loading,multi-stage loading,and confining pressure,at various constant stress levels.The results demonstrate that as the stress level increases in single-stage creep simulations,the time-to-failure progressively decreases.The growth of microcracks during uniaxial creep occurs in three stages,with tensile microcracks being predominant and the spatial distribution of microcracks becoming more dispersed at higher stress levels.In multi-stage loadingunloading simulations,microcracks continue to form during the unloading stage,indicating cumulative damage resulting from increased axial stress.Additionally,the creep behaviour of rocks under confining pressure is not solely determined by the magnitude of the confining pressure,but is also influenced by the magnitude of the axial stress.The findings contribute to a better understanding of rock deformation and failure processes under different loading conditions,and they can be valuable for applications in rock mechanics and rock engineering.展开更多
Experimental studies were conducted on two high-strength steel plate-frame structures with different truss spacings under various impact velocities to investigate the dynamic mechanical properties of hull plate-frame ...Experimental studies were conducted on two high-strength steel plate-frame structures with different truss spacings under various impact velocities to investigate the dynamic mechanical properties of hull plate-frame structures under drop weight impact.The results showed that decreasing the main beam spacing can effectively increase the structural stiffness,reduce the maximum deformation,and increase the damage range.Furthermore,to simulate the impact tests accurately,static and dynamic tensile tests at different strain rates were carried out,and the Cowper-Symonds model parameters were fitted via experimental data.The material properties obtained from the tensile tests were used as inputs for numerical simulations with the numerical results coincide with the experimental results.A systematic analysis and discussion were conducted on the effects of truss spacing and truss width on the dynamic response of the reinforced plates,and an optimal range for the ratio of truss spacing to truss width was proposed.In addition,a mesh size sensitivity analysis for ship hull plate frame collision simulations was performed.The applicability of the EPS,MMC,and RTCL failure criteria in the simulation of plate-frame structures was investigated via finite element simulations of falling weight impact tests.The research findings provide a reference for ship hull structure design and resilience assessment.展开更多
文摘The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This study investigates the time-varying response of rocks and roof resistance in coal mines in the Zagros Mountains using a novel approach that combines numerical simulation,relaxation testing,and rock displacement studies.The results show that rocks exhibit significant time-dependent behavior,with changes in rock mechanical properties over time.A comprehensive viscoelastic-plastic model is devel-oped to accurately describe the time-varying strain-softening response of rocks and simulate laboratory tests.The model integrates the Burgers and strain-softening models,simulating stress relaxation curves and rock displacement over time.The study reveals that the rock mass displays significant nonlinear behavior,with changes in rock mechanical properties over time.The findings of this study highlight the importance of considering the time-varying response of rocks and roof resistance in coal mine stability analysis.The results provide valuable insights into the time-dependent behavior of rock mass in coal mines in Iran,which can inform mining practices and mitigate potential hazards.Results in this study can contribute to developing strategies for improving roof stability and reducing the likelihood of roof collapses.
基金supported by the National Natural Science Foundation of China (Grant Nos.12202294 and 12022208)the Project funded by China Postdoctoral Science Foundation (Grant No.2022M712243)the Fundamental Research Funds for the Central Universities (Grant No.2023SCU12098).
文摘It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.
基金supported by the National Natural Science Foundation of China(No.52076036)supported by the National Natural Science Foundation of China(No.52174020).
文摘Modified ethylene-vinyl acetate copolymer(EVAM)and amino-functionalized nano-silica(NSiO_(2))par-ticles were employed as the base materials for the synthesis of the nanocomposite pour point depressant designated as EVAM-g-NSiO_(2).This synthesis involved a chemical grafting process within a solution system,followed by a structural characterization.Moreover,combining macro-rheological performance with microscopic structure observation,the influence of the nanocomposite pour point depressant on the rheological properties of the model waxy oil system was investigated.The results indicate that when the mass ratio of NSiO_(2) to EVAM is 1:100,the prepared EVAM-g-NSiO_(2) nanocomposite pour point depressant exhibits excellent pour point reduction and viscosity reduction properties.Moreover,the nanocomposite pour point depressant obtained through a chemical grafting reaction demonstrates structural stability(the bonding between the polymer and nanoparticles is stable).The pour points of model waxy oils doped with 500 mg/kg ethylene-vinyl acetate copolymer(EVA),EVAM,and EVAM/SiO_(2) were reduced from 34℃ to 23,20,and 21℃,respectively.After adding the same dosage of EVAM-g-NSiO_(2) nanocomposite pour point depressant,the pour point of the model wax oil decreased to 12℃ and the viscosity at 32℃ decreased from 2399 to 2396.9 mPa·s,achieving an impressive viscosity reduction rate of 99.9%.Its performance surpassed that of EVA,EVAM,and EVAM/SiO_(2).The EVAM-g-NSiO_(2) dispersed in the oil phase acts as the crystallization nucleus for wax crystals,resulting in a dense structure of wax crystals.The compact wax crystal blocks are difficult to overlap with each other,pre-venting the formation of a three-dimensional network structure,thereby improving the low-temperature flowability of the model waxy oil.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB3702404)the National Natural Science Foundation of China(Grant No.52104370)+4 种基金the Reviving-Liaoning Excellence Plan(XLYC2203186)Science and Technology Special Projects of Liaoning Province(Grant No.2022JH25/10200001)the Postdoctoral Research Fund for Northeastern(Grant No.20210203)Independent Projects of Basic Scientific Research(ZZ2021005)CITIC Niobium Steel Development Award Fund(2022-M1824).
文摘Selecting proper descriptors(also known feature selection,FS)is key in the process of establishing mechanical properties prediction model of hot-rolled microalloyed steels by using machine learning(ML)algorithm.FS methods based on data-driving can reduce the redundancy of data features and improve the prediction accuracy of mechanical properties.Based on the collected data of hot-rolled microalloyed steels,the association rules are used to mine the correlation information between the data.High-quality feature subsets are selected by the proposed FS method(FS method based on genetic algorithm embedding,GAMIC).Compared with the common FS method,it is shown on dataset that GAMIC selects feature subsets more appropriately.Six different ML algorithms are trained and tested for mechanical properties prediction.The result shows that the root-mean-square error of yield strength,tensile strength and elongation based on limit gradient enhancement(XGBoost)algorithm is 21.95 MPa,20.85 MPa and 1.96%,the correlation coefficient(R^(2))is 0.969,0.968 and 0.830,and the mean absolute error is 16.84 MPa,15.83 MPa and 1.48%,respectively,showing the best prediction performance.Finally,SHapley Additive exPlanation is used to further explore the influence of feature variables on mechanical properties.GAMIC feature selection method proposed is universal,which provides a basis for the development of high-precision mechanical property prediction model.
基金supported by the Natural Science Foundation of Hunan Province(Grant No.2023JJ40353)the National Key Research and Development Program of China(No.2019YFE03120001).
文摘Titanium-silicon(Ti-Si)alloy system shows significant potential for aerospace and automotive applications due to its superior specific strength,creep resistance,and oxidation resistance.For Si-containing Ti alloys,the sufficient content of Si is critical for achieving these favorable performances,while excessive Si addition will result in mechanical brittleness.Herein,both physical experiments and finite element(FE)simulations are employed to investigate the micro-mechanisms of Si alloying in tailoring the mechanical properties of Ti alloys.Four typical states of Si-containing Ti alloys(solid solution state,hypoeutectoid state,near-eutectoid state,hypereutectoid state)with varying Si content(0.3-1.2 wt.%)were fabricated via in-situ alloying spark plasma sintering.Experimental results indicate that in-situ alloying of 0.6 wt.%Si enhances the alloy’s strength and ductility simultaneously due to the formation of fine and uniformly dispersed Ti_(5)Si_(3)particles,while higher content of Si(0.9 and 1.2 wt.%)results in coarser primary Ti_(5)Si_(3)agglomerations,deteriorating the ductility.FE simulations support these findings,highlighting the finer and more uniformly distributed Ti_(5)Si_(3)particles contribute to less stress concentration and promote uniform deformation across the matrix,while agglomerated Ti_(5)Si_(3)particles result in increased local stress concentrations,leading to higher chances of particle fracture and reduced ductility.This study not only elucidates the micro-mechanisms of in-situ Si alloying for tailoring the mechanical properties of Ti alloys but also aids in optimizing the design of high-performance Si-containing Ti alloys.
基金supported by the National Natural Science Foundation of China(Grant No.52375340,51975263,52405366).
文摘A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.
基金supported by the Ministry of Science and Technology of the People’s Republic of China(No.2021ZD0200202)the National Natural Science Foundation of China(No.82122032)the Science and Technology Department of Zhejiang Province(Nos.202006140 and 2022C03057).
文摘Increasingly,attention is being directed towards time-dependent diffusion magnetic resonance imaging(TDDMRI),a method that reveals time-related changes in the diffusional behavior of water molecules in biological tissues,thereby enabling us to probe related microstructure events.With ongoing improvements in hardware and advanced pulse sequences,significant progress has been made in applying TDDMRI to clinical research.The development of accurate mathematical models and computational methods has bolstered theoretical support for TDDMRI and elevated our understanding of molecular diffusion.In this review,we introduce the concept and basic physics of TDDMRI,and then focus on the measurement strategies and modeling approaches in short-and long-diffusion-time domains.Finally,we discuss the challenges in this field,including the requirement for efficient scanning and data processing technologies,the development of more precise models depicting time-dependent molecular diffusion,and critical clinical applications.
基金supported by the National Natural Science Foundation of China(Grant No.52125903)the China Postdoctoral Science Foundation(Grant No.2023M730367)the Fundamental Research Funds for Central Public Welfare Research Institutes of China(Grant No.CKSF2023323/YT).
文摘To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.
基金the National Natural Science Foundation of China(Nos.52374147,42372328,and U23B2091)National Key Research and Development Program of China(No.2023YFC3804200)Xinjiang Uygur Autonomous Region Science and Technology Major Program(No.2023A01002).
文摘Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.
基金supported by the National Natural Science Foundation of China(Grant Nos.41877267,41877260)the Priority Research Program of the Chinese Academy of Science(Grant No.XDA13010201).
文摘Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.
基金Bu-Ali Sina University for providing financial support for conducting this study。
文摘Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)K and at ambient pressure(81.5 kPa).From the experimental data,excess molar volume(V_(m)~E),thermal expansion coefficients(α),deviations in isentropic compressibility(Δκ_(S)),viscosity(Δ_η),and refractive index(Δn_(D))were calculated.These values were then correlated using the Redlich-Kister polynomial equation,with fitting coefficients and standard deviations determined.Additionally,the Prigogine-Flory-Patterson(PFP)theory and the Extended Real Associated Solution(ERAS)model were employed to correlate the excess molar volume,while the Perturbed Chain Statistical Associating Fluid Theory(PC-SAFT)was used to predict the density of mixtures.
基金funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan Grant No.AP19678033“The study of the transport and optical properties of hydrogen at high pressure.”。
文摘A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.
基金the funding support from the Natural Science Foundation of China(Grant No.52130402)the Anhui Province Graduate Education Quality Engineering Project(Grant No.2023cxcysj088)the China Scholarship Council Grants Program(Grant No.202308340082).
文摘Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations,playing a crucial role in promoting green and low-carbon extraction methodologies.In this study,grouting reinforcement processes were examined by conducting grouting experiments on a fractured rock with varying negative pressures(0-100 kPa),followed by uniaxial compression testing of the grout-reinforced bodies.This investigation explored the diffusion patterns of grout under negative pressure and established a constitutive model of damage-bearing capacity for bodies reinforced by negative pressure grouting.It further studied the enhancement effect of negative pressure on the load-bearing capacity of the reinforced bodies and analyzed the instability mechanism of damage and failure in these bodies.The results indicated that the diffusion of grout under negative pressure is influenced by four types of forces,which alter the extent of grout diffusion within the fractured rock mass.Introducing a damage constitutive model that serially connects pore and framework elements characterizes the damage and failure behavior of groutreinforced bodies under different negative pressures.As the negative pressure increases,changes in porosity,water-to-cement ratio,and admixture quantity occur in the grout-reinforced specimens,with the strength mean curve showing a trend of first increasing and then decreasing,reaching a threshold at a negative pressure of 60 kPa.With increasing negative pressure,the negative pressure damage variable decreases and then increases,and the stronger the interfacial microelement connections caused by the negative pressure,the greater the bearing capacity,ultimately manifesting in different failure modes.
文摘Machine learning models can predict material properties quickly and accurately at a low computational cost.This study generated novel hybridized nanocomposites with unsaturated polyester resin as the matrix and Areca fruit husk fiber(AFHF),tamarind fruit fiber(TFF),and nano-sized coconut shell powder(NCSP).It is challenging to determine the optimal proportion of raw materials in this composite to achieve maximum mechanical properties.This task was accomplished with the help of ML techniques in this study.The tensile strength of the hybridized nanocomposite was increased by 134.06% compared to the neat unsaturated polyester resin at a 10:5:2 wt.% ratio,AFHF:TFF:NCSP.The stiffness and impact behavior of hybridized nanocomposites were similar.The scanning electron microscope showed homogeneous reinforcement and nanofiller distribution in the matrix.However,the hybridized nanocomposite with a 20:5:0 wt.% combination ratio had the highest strain at break of 5.98%,AFHF:TFF:NCSP.The effectiveness of recurrent neural networks and recurrent neural networks with Levenberg’s algorithm was assessed using R2,mean absolute errors,and minimum squared errors.Tensile and impact strength of hybridized nanocomposites were well predicted by the recurrent neural network with Levenberg’s model with 2 and 3 hidden layers,80 neurons and 80 neurons,respectively.A recurrent neural network model with 4 hidden layers,60 neurons,and 2 hidden layers,100 neurons predicted hybridized nanocomposites’Young’s modulus and elongation at break with maximum R2 values.The mean absolute errors and minimum squared errors were evaluated to ensure the reliability of the machine learning algorithms.The models optimize hybridized nanocomposites’mechanical properties,saving time and money during experimental characterization.
基金a derivative product of the project INV-ING-3788 financed by the Vicerectory of Research of the Universidad Militar Nueva Granada,validity 2023.
文摘The use of additive manufacturing techniques in the development of unconventional materials can help reduce the environmental impact of traditional construction materials.In this paper,the properties of a 3D-printed biocomposite were evaluated.Biofilaments obtained by mixing pulverized bamboo fibers with polylactic acid(PLA)resin were extruded during the manufacturing process.To assess the effect of incorporating plant fibers,an analysis was conducted on the morphology,elemental chemical composition,crystallinity index,principal functional groups,thermal stability,surface roughness,microhardness,density,tensile strength,elastic modulus,and strain percentage of reinforced samples.The results were comparedwith those obtained from the characterization of standard PLAfilaments(unreinforced).The fused deposition modeling(FDM)technique was employed to print biocomposite specimens.Additionally,the influence of the printing parameters(infill density,build orientation,and layer thickness)on the physical,tribological,andmechanical properties of the biocomposites was analyzed.These results were compared with those obtained for specimens printed with pure PLA.The findings indicate that incorporating 10%vegetable filler into PLA filaments enhanced the strength and stiffness of the biocomposite under axial loads.Finally,the strength of the biocomposite subjected to axial loads was compared with the standardized values for wood-plastic composites,demonstrating the feasibility of its use for non-structural purposes in civil construction.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174096 and 52304110).
文摘With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This study investigates the influence of prefabricated crack dip angles on the mechanical properties of anchored rock masses in deep soft rock roadways.By constructing similarity models of NPR(Negative Poisson’s Ratio)and PR(Positive Poisson’s Ratio)anchored solids,biaxial compression experiments under varying crack dip angles were conducted.Strain gauges,3D Digital Image Correlation(3D DIC),and acoustic emission monitoring were employed to systematically analyze the strength characteristics,deformation-damage evolution,and energy dissipation mechanisms of the two types of anchor systems.The results show that:(1)The stress-strain curves of anchored solids with prefabricated cracks exhibit a distinct bimodal characteristic.Compared to PR anchors,NPR anchors show 20%and 23%improvements in peak strength and elastic modulus,respectively,with residual strength enhanced by up to 34%.(2)Owing to high pre-tightening force and large deformation capacity,NPR anchors maintain superior integrity under increasing crack dip angles,demonstrating more uniform free-surface displacement and localized shear-tensile composite crack patterns.(3)Acoustic emission analysis reveals that NPR anchors exhibit higher cumulative energy absorption(300%improvement over PR anchors)and lack low-rate energy development phases,indicating enhanced ductility and impact resistance at high crack dip angles.(4)Crack dip angle critically governs failure mechanisms by modulating the connectivity between shear cracks and prefabricated fissures:bimodal effects dominate at low angles,while vertical tensile crack propagation replaces bimodal behavior at high angles.The study proposes prioritizing NPR anchor cables in deep engineering applications and optimizing support parameters based on crack dip angles to mitigate stress concentration and ensure the long-term stability of surrounding rock.
基金Projects(41702320,52104125)supported by the National Natural Science Foundation of ChinaProject(ZR2021MD005)+2 种基金supported by the Natural Science Foundation of Shandong Province,ChinaProject(TMduracon2022002)supported by the Engineering Research Center of Marine Environmental Concrete Technology,Ministry of Education,China。
文摘Negative Poisson ratio(NPR)steel is a new material with high strength and toughness.This study conducted tensile tests at elevated temperatures to investigate the mechanical properties of NPR steel at high temperatures.The stress−strain curve,ultimate strength,yield strength,modulus of elasticity,elongation after fracture,and percentage reduction of area of NPR steel bars were measured at 9 different temperatures ranging from 20 to 800℃.The experimental results indicate that high-temperature environments significantly affect the mechanical properties of NPR steel.However,compared to other types of steel,NPR steel exhibits better resistance to deformation.When the test temperature is below 700℃,NPR steel exhibits a ductile fracture characteristic,while at 800℃,it exhibits a brittle fracture characteristic.Finally,based on the experimental findings,a constitutive model suitable for NPR steel at high temperatures is proposed.
基金the financial support by the National Natural Science Foundation of China(52378440,42477143)the Key Science and Technology Program in the Transportation Industry(2022-MS1-032,2022-MS5-125)+2 种基金the Postgraduate Scientific Research Innovation Project of Hunan Province(CX20251302)the Science and Technology Innovation Program of Hunan Province(2024RC3166)the Guangxi Key Research and Development Program(AB23075184)。
文摘Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remains poorly understood.This study aimed to investigate the mechanical properties and failure mechanisms of carbonaceous mudstone filler under different temperature-moisture coupled conditions.Triaxial shear tests were conducted under four temperaturemoisture coupled conditions:dry-heat to dry-cold(DHDC),wet-cold to wet-heat(WCWH),dry-cold to wet-heat(DCWH),and dry-heat to wet-cold(DHWC).The effects of these conditions on the strength characteristics,relative breakage ratio,failure mode,and microscopic morphology were examined.A segmented prediction model based on the DuncanChang model was applied to validate the experimental results under the DHWC condition.The failure mechanisms under different conditions were also analyzed.The results indicate that the degradation of carbonaceous mudstone increases in the following order:DHDC,WCWH,DCWH,and DHWC.Under the DHDC condition,the stress-strain curves exhibit strain-softening behavior,while other conditions show strain-hardening behavior,with peak deviatoric stress occurring at 2%and 4%axial strains,respectively.The shear strength decreases by up to 40%under the DHWC condition but remains nearly unchanged under the DHDC condition,showing a positive correlation with particle breakage.As the number of cycles increases,the failure surfaces gradually move downward.Higher confining pressure shifts failure mode from shear failure to shear slip or localized compression,and eventually to overall compression or expansion failure.The modified Duncan-Chang model accurately predicts the experimental results.These findings provide important guidance for the application of carbonaceous mudstone filler in highway embankment construction in humid mountainous regions.
基金supported by the National Natural Science Foundation of China(grant numbers 42172312,52211540395)support from the Institut Universitaire de France(IUF).
文摘A brittle creep and time-dependent fracturing process model of rock is established by incorporating the stress corrosion model into discrete element method to analyze the creep behavior and microcrack evolution in brittle rocks at a micro-scale level.Experimental validation of the model is performed,followed by numerical simu-lations to investigate the creep properties and microcrack evolution in rocks under single-stage loading,multi-stage loading,and confining pressure,at various constant stress levels.The results demonstrate that as the stress level increases in single-stage creep simulations,the time-to-failure progressively decreases.The growth of microcracks during uniaxial creep occurs in three stages,with tensile microcracks being predominant and the spatial distribution of microcracks becoming more dispersed at higher stress levels.In multi-stage loadingunloading simulations,microcracks continue to form during the unloading stage,indicating cumulative damage resulting from increased axial stress.Additionally,the creep behaviour of rocks under confining pressure is not solely determined by the magnitude of the confining pressure,but is also influenced by the magnitude of the axial stress.The findings contribute to a better understanding of rock deformation and failure processes under different loading conditions,and they can be valuable for applications in rock mechanics and rock engineering.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52171311 and 5227127).
文摘Experimental studies were conducted on two high-strength steel plate-frame structures with different truss spacings under various impact velocities to investigate the dynamic mechanical properties of hull plate-frame structures under drop weight impact.The results showed that decreasing the main beam spacing can effectively increase the structural stiffness,reduce the maximum deformation,and increase the damage range.Furthermore,to simulate the impact tests accurately,static and dynamic tensile tests at different strain rates were carried out,and the Cowper-Symonds model parameters were fitted via experimental data.The material properties obtained from the tensile tests were used as inputs for numerical simulations with the numerical results coincide with the experimental results.A systematic analysis and discussion were conducted on the effects of truss spacing and truss width on the dynamic response of the reinforced plates,and an optimal range for the ratio of truss spacing to truss width was proposed.In addition,a mesh size sensitivity analysis for ship hull plate frame collision simulations was performed.The applicability of the EPS,MMC,and RTCL failure criteria in the simulation of plate-frame structures was investigated via finite element simulations of falling weight impact tests.The research findings provide a reference for ship hull structure design and resilience assessment.
