After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of...After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of triaxial extension tests were conducted on sandstone under confining pressures of 10,30,50 and 70 MPa.Elastic energy and dissipated energy were separated by single unloading,the input energy u_(t),elastic energy u_(e),and dissipated energy u_(d)at different unloading stress levels were calculated by the integrating stress−strain curves.The results show that tensile cracks dominate fracture under lower confining pressure(10 MPa),and shear cracks play an increasingly important role in fracture as confining pressure increases(30,50 and 70 MPa).Based on the phenomenon that u_(e)and u_(d)increase linearly with increasing u_(t),a possible energy distribution mechanism of fracture mode transition under triaxial extension was proposed.In addition,it was found that peak energy storage capacity is more sensitive to confining pressure compared to elastic energy conversion capacity.展开更多
Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static ...Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.展开更多
Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses ...Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m.Various uniaxial and triaxial tests at different strain rates,along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths.Subsequently,a new empirical dilatancy coefficient is proposed based on the energy dissipation method.The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing,and plastic failure characteristics of marble under triaxial compression are gradually strengthened.Furthermore,compared to the constant confining pressure,the volume expansion is relatively lower under unloading condition.The energy dissipation is closely linked to the process of dilatancy,with a rapid increase of dissipated energy coinciding with the beginning of dilatancy.A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve,of which change trend is consistent with the actual dilatancy response in marble under different stress paths.The existing empirical and theoretical dilatancy models are analyzed,which shows that the empirical dilatancy coefficient based on the energy background is more universal.展开更多
To determine the ultimate bearing capacity of foundations on sloping ground surface in practice, energy dissipation method was used to formulate the beating capacity as programming problem, and full-scale model experi...To determine the ultimate bearing capacity of foundations on sloping ground surface in practice, energy dissipation method was used to formulate the beating capacity as programming problem, and full-scale model experiments were investigated to analyze the performance of the soil slopes loaded by a strip footing in laboratory. The soil failure is governed by a linear Mohr-Coulomb yield criterion, and soil deformation follows an associated flow rule. Based on the energy dissipation method of plastic mechanics, a multi-wedge translational failure mechanism was employed to obtain the three bearing capacity factors related to cohesion, equivalent surcharge load and the unit gravity for various slope inclination angles. Numerical results were compared with those of the published solutions using finite element method and those of model experiments. The bearing capacity factors were presented in the form of design charts for practical use in engineering. The results show that limit analysis solutions approximate to those of model tests, and that the energy dissipation method is effective to estimate bearing capacity of soil slope.展开更多
The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When th...The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When the stochastic stress waves transmit through rocks, the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods. The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods. The results show the harder the rock, the less absorption of energy, the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock. When the whole stress energy doubles either by doubling the duration time or by increasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to the whole stress energy (i.e. energy dissipation ratio) is decreased to 10%-15%. When doubling the duration time, the cutoff frequency to fracture rock remains constant. However, with the increase of the amplitude of stress wave, the cutoff frequency increases accordingly.展开更多
Based on the compression mechanism for analyzing the cavity expansion problem in soil under high stresses,generalized non-linear failure criterion and large strain and energy conservation in plastic region during the ...Based on the compression mechanism for analyzing the cavity expansion problem in soil under high stresses,generalized non-linear failure criterion and large strain and energy conservation in plastic region during the cavity expanding were adopted.The energy conservation equation was established and the limited pressure of cavity expansion under high stresses was given based on the energy dissipation analysis method,in which the energy generated from cavity expansion is absorbed by the volume change and shear strain caused in soil.The factors of large strain and dilatation were considered by the proposed method.The analysis shows that the limited pressure is determined by failure criterion,stress state,large deformation characteristic,dilatation and strength of soil.It is shown from the comparison that the results with the proposed method approximate to those of the in-situ method.The cavity expansion pressure first decreases and then increases nonlinearly with both of shear modulus and dilatation increasing.展开更多
In terms of viscoelasticity, the relevant theory of wave i n granular media is analyzed in this paper. Under the conditions of slight deforma tion of granules, wave equation, complex number expressions of propagation ...In terms of viscoelasticity, the relevant theory of wave i n granular media is analyzed in this paper. Under the conditions of slight deforma tion of granules, wave equation, complex number expressions of propagation vecto r and attenuation vector, attenuation coefficient expressions of longitudinal wa ve and transverse wave, etc, are analyzed and deduced. The expressions of attenu ation coefficients of viscoelastic longitudinal wave and transverse wave show th a t the attenuation of wave is related to frequency. The higher the frequency is, the more the attenuation is, which is tested by the laboratory experiment. In a ddi tion, the energy dissipation is related to the higher frequency wave that is abs orbed by granular media. The friction amongst granular media also increase the e nergy dissipation. During the flowing situation the expression of transmission f actor of energy shows that the granular density difference is the key factor whi ch leads to the attenuation of vibrating energy. This has been proved by the exp eriment results.展开更多
Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinf...Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.展开更多
This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain...This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.展开更多
Experiments on grouting-reinforced rock mass specimens with different particle sizes and features were carried out in this study to examine the effects of grouting reinforcement on the load-bearing characteristics of ...Experiments on grouting-reinforced rock mass specimens with different particle sizes and features were carried out in this study to examine the effects of grouting reinforcement on the load-bearing characteristics of fractured rock mass.The strength and deformation features of grouting-reinforced rock mass were analyzed under different loading manners;the energy evolution mechanism of grouting-reinforced rock mass specimens with different particle sizes and features was investigated;the energy dissipation ratio and post-peak stress decreasing rate were employed to evaluate the bearing stability of grouting-reinforced rock mass.The results show that the strength and ductility of granite-reinforced rock mass(GRM)under biaxial loading are higher than that of sandstone-reinforced rock mass(SRM)under uniaxial loading.Besides,the energy evolution characteristics of grouting-reinforced rock mass under uniaxial and biaxial loading mainly could be divided into early,middle,and late stages.In the early stage,total,elastic,and dissipation energies were quite small with flatter curves;in the middle stage,elastic energy increased rapidly,whereas dissipation energy increased slowly;in the late stage,dissipation energy increased sharply.The energy dissipation ratio was used to represent the pre-peak plastic deformation.Under uniaxial loading,this ratio increased as the particle size increased and the pre-peak plastic deformation of grouting-reinforced rock mass became larger;under biaxial loading,it dropped as the particle size increased,and the pre-peak plastic deformation of grouting-reinforced rock mass became smaller.The post-peak stress decline rate A_(v) was used to assess the post-peak bearing performance of grouting-reinforced rock mass.Under uniaxial loading,parameter A_(v) exhibited reduction as the particle size kept increasing,and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was greater,and the bearing capacity was greater;under biaxial loading,A_(v) increased with the particle size,and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was low and the bearing capacity was reduced.The findings are considered instrumental in improving the stability of the roadway-surrounding rock by granite and sandstone grouting.展开更多
Abstract:At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.Accor...Abstract:At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to incomplete statistics,as of 2023,80%of coal mine rock bursts accidents in China occur in mining roadway.In view of this phenomenon,the cyclic impact test of post-peak sandstone is designed,focusing on the post-peak stress state of sandstone,and exploring the post-peak dynamic response of sandstone.The post-peak sandstone specimens were prepared by a uniaxial compressor,and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment.The results show that:1)The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure,indicating that the impact tendency of sandstone after peak decreased under lower axial pressure.On the contrary,the post-peak sandstone had strong impact tendency under higher axial pressure;2)The higher the axial pressure,the lower the dynamic strength of the post-peak sandstone,indicating that the axial pressure promoted the failure process of the post peak sandstone;3)It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure;4)Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure,and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level.The research shows that when the roadway surrounding rock was in the post-peak stress state,reducing the static stress was the key to prevent the secondary ground pressure disaster.The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment,and promote the research and exploration of post-peak mechanical properties of coal and rock.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for prope...Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for proper design and construction of geogrid reinforced earth structures. Based on the calibrated model of sand and geogrid, a series of numerical pullout tests are conducted using PFC^(3D) under special considerations of particle angularity and aperture geometry of the geogrid. In this work, interface characteristics regarding the displacement and contact force developed among particles and the deformation and force distribution along the geogrid are all visualized with PFC^(3D) simulations so that new understanding on how geogrid-soil interaction develops under pullout loads can be obtained. Meanwhile, a new variable named fabric anisotropy coefficient is introduced to evaluate the inherent relationship between macroscopic strength and microscopic fabric anisotropy. A correlation analysis is adopted to compare the accuracy between the newly-proposed coefficient and the most commonly used one. Furthermore, additional pullout tests on geogrid with four different joint protrusion heights have been conducted to investigate what extent and how vertical reinforcement elements may result in reinforcement effects from perspectives of bearing resistance contribution, energy dissipation, as well as volumetric response. Numerical results show that both the magnitude and the directional variation of normal contact forces govern the development of macroscopic strength and the reinforcing effects of joint protrusion height can be attributed to the accelerated energy dissipation across the particle assembly and the intensive mobilization of the geogrid.展开更多
In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gu...In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.展开更多
Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study a...Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study aims to reveal the dynamic and cyclic behavior of steel plated shear wall.Finite element method of analysis was implemented in order to simulate the behavior of such a wall structure.To determine the dynamic behavior of un-stiffened plate shear wall,two different analytical models were implemented.The post buckling strength of steel plate subjected to lateral loading was also employed.The story shear-drift diagrams of steel shear wall system were presented.The strength and ductility of the system obtained from the analysis were compared with those of steel shear wall tests reported before.The pertinent parameters of the steel shear wall system such as plate thickness,column and beam stiffness and the plate aspect ratio were recognized and their effects were recorded.The effect of stiffeners on the behavior of the SPSW was also investigated.展开更多
To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire m...To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire materials(EPMWM)for vibration isolation was previously investigated.In this paper,a study focusing on the impact-resistance of EPMWM with the consideration of ambient temperature is presented.The quasi-static and low-velocity impact mechanical behavior of EPMWM under different temperatures(25℃-300℃)are systematically studied.The results of the static compression test show that the damping energy dissipation of EPMWM increases with temperature while the nonlinear damping characteristics are gradually enhanced.During the impact experiments,the impact energy loss rate of EPMWM was between 65%and 85%,while the temperatures increased from 25℃to 300℃.Moreover,under the same drop impact conditions,the overall deformation of EPMWM decreases in the temperature range of 100℃-200℃.On the other hand,the impact stiffness,energy dissipation,and impact loss factor of EPMWM significantly increase with temperature.This can be attributed to an increase in temperature,which changes the thermal expansion coefficient and contact state of the internal wire helixes.Consequently,the energy dissipation mode(dry friction,air damping,and plastic deformation)of EPMWM is also altered.Therefore,the EPMWM may act as a potential candidate material for superior energy absorption applications.展开更多
Reinforced concrete(RC)structures are generally designed to carry quasi-static gravity loads through almost indispensable components namely slab,however,it may be subjected to high intense loads induced from the impac...Reinforced concrete(RC)structures are generally designed to carry quasi-static gravity loads through almost indispensable components namely slab,however,it may be subjected to high intense loads induced from the impact of projectiles generated by the tornado,falling construction equipment,and also from accidental explosions during their construction and service lifespan.Impacts due to rock/boulder falls do occur on the structures located especially in hilly areas.Such loadings are not predictable but may cause severe damage to the slab/structure.It stimulates structural engineers and researchers to investigate and understand the dynamic response of RC structures under such impulsive loading.This research work first investigates the performance of 1000×1000×75 mm^(3)conventionally reinforced two-way spanning normal strength concrete slab with only tension reinforcement(0.88%)under the concentric impact load(1035 N)using the finite element method based computer code,ABAQUS/Explicit-v.6.15.The impact load is delivered to the centroid of the slab using a solid-steel cylindroconical impactor(drop weight)with a flat nose of diameter 40 mm,having a total mass of 105 kg released from a fixed height of 2500 mm.Two popular concrete constitutive models in ABAQUS namely;Holmquist-Johnson-Cook(HJC)and Concrete Damage Plasticity(CDP),with strain rate effects as per fib MODEL CODE 2010,are used to model the concrete material behavior to impact loading and to simulate the damage to the slab.The slab response using these two models is analyzed and compared with the impact test results.The strain rate effect on the reinforcing steel bars has been incorporated in the analysis using the Malvar and Crawford(1998)approach.A classical elastoplastic kinematic idealization is considered to model the steel impactor and support system.Results reveal that the HJC model gives a little overestimation of peak displacement,maximum acceleration,and damage of the slab while the predictions given by the CDP model are in reasonable agreement with the experimental test results/observations available in the open literature.Following the validation of the numerical model,analyses have been extended to further investigate the damage response of the slab under eccentric impact loadings.In addition to the concentric location(P1)of the impacting device,five locations on a quarter of the slab i.e.,two along the diagonal(P2&P3),the other two along the mid-span(P4&P5),and the last one(P6)between P3 and P5,covering the entire slab,are considered.Computational results have been discussed and compared,and the evaluation of the most damaging location(s)of the impact is investigated.It has been found that the most critical location of the impact is not the centroid of the slab but the eccentric one with the eccentricity of 1/6th of the span from the centroid along the mid-span section.展开更多
基金Project(52074352)supported by the National Natural Science Foundation of ChinaProject(2023JJ30680)supported by the National Science and Technology Major Project of China。
文摘After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of triaxial extension tests were conducted on sandstone under confining pressures of 10,30,50 and 70 MPa.Elastic energy and dissipated energy were separated by single unloading,the input energy u_(t),elastic energy u_(e),and dissipated energy u_(d)at different unloading stress levels were calculated by the integrating stress−strain curves.The results show that tensile cracks dominate fracture under lower confining pressure(10 MPa),and shear cracks play an increasingly important role in fracture as confining pressure increases(30,50 and 70 MPa).Based on the phenomenon that u_(e)and u_(d)increase linearly with increasing u_(t),a possible energy distribution mechanism of fracture mode transition under triaxial extension was proposed.In addition,it was found that peak energy storage capacity is more sensitive to confining pressure compared to elastic energy conversion capacity.
基金National Natural Science Foundation of China-NSAF(Grant No.U2330202)the National Natural Science Foundation of China(Grant Nos.52175162 and 51805086)+1 种基金Fujian Provincial Technological Innovation Key Research and Industrialization Projects(Grant Nos.2023XQ005 and 2024XQ010)The National Independent Innovation Demonstration Platform Project of Fujian Province(2024QZFX07)。
文摘Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.
基金Project(2022NSFSC0279)supported by the General Project of Sichuan Natural Science Foundation,ChinaProject(Z17113)supported by the Key Scientific Research Fund of Xihua University,ChinaProject(SR21A04)supported by the Research Center for Social Development and Social Risk Control of Sichuan Province,Key Research Base of Philosophy and Social Sciences,Sichuan University,China。
文摘Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m.Various uniaxial and triaxial tests at different strain rates,along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths.Subsequently,a new empirical dilatancy coefficient is proposed based on the energy dissipation method.The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing,and plastic failure characteristics of marble under triaxial compression are gradually strengthened.Furthermore,compared to the constant confining pressure,the volume expansion is relatively lower under unloading condition.The energy dissipation is closely linked to the process of dilatancy,with a rapid increase of dissipated energy coinciding with the beginning of dilatancy.A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve,of which change trend is consistent with the actual dilatancy response in marble under different stress paths.The existing empirical and theoretical dilatancy models are analyzed,which shows that the empirical dilatancy coefficient based on the energy background is more universal.
基金Project(50408020) supported by the National Natural Science Foundation of Chinaproject(05-0686) supported by the Program of New Century Excellent Talents in Universityproject(200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China
文摘To determine the ultimate bearing capacity of foundations on sloping ground surface in practice, energy dissipation method was used to formulate the beating capacity as programming problem, and full-scale model experiments were investigated to analyze the performance of the soil slopes loaded by a strip footing in laboratory. The soil failure is governed by a linear Mohr-Coulomb yield criterion, and soil deformation follows an associated flow rule. Based on the energy dissipation method of plastic mechanics, a multi-wedge translational failure mechanism was employed to obtain the three bearing capacity factors related to cohesion, equivalent surcharge load and the unit gravity for various slope inclination angles. Numerical results were compared with those of the published solutions using finite element method and those of model experiments. The bearing capacity factors were presented in the form of design charts for practical use in engineering. The results show that limit analysis solutions approximate to those of model tests, and that the energy dissipation method is effective to estimate bearing capacity of soil slope.
基金Projects(50404010, 50574098) supported by the National Natural Science Foundation of Chinaproject(05jj10010) supported by the Hunan Provincial Natural Science Foundation of Distinguished Young Scholars
文摘The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When the stochastic stress waves transmit through rocks, the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods. The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods. The results show the harder the rock, the less absorption of energy, the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock. When the whole stress energy doubles either by doubling the duration time or by increasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to the whole stress energy (i.e. energy dissipation ratio) is decreased to 10%-15%. When doubling the duration time, the cutoff frequency to fracture rock remains constant. However, with the increase of the amplitude of stress wave, the cutoff frequency increases accordingly.
基金Projects(2010RS4016,10JJ60708) supported by Hunan Provincial Science Foundation,ChinaProjects(201018,201108,201121) supported by Hunan Provincial Transportation Science and Technology Progress and Innovation Plan of China
文摘Based on the compression mechanism for analyzing the cavity expansion problem in soil under high stresses,generalized non-linear failure criterion and large strain and energy conservation in plastic region during the cavity expanding were adopted.The energy conservation equation was established and the limited pressure of cavity expansion under high stresses was given based on the energy dissipation analysis method,in which the energy generated from cavity expansion is absorbed by the volume change and shear strain caused in soil.The factors of large strain and dilatation were considered by the proposed method.The analysis shows that the limited pressure is determined by failure criterion,stress state,large deformation characteristic,dilatation and strength of soil.It is shown from the comparison that the results with the proposed method approximate to those of the in-situ method.The cavity expansion pressure first decreases and then increases nonlinearly with both of shear modulus and dilatation increasing.
文摘In terms of viscoelasticity, the relevant theory of wave i n granular media is analyzed in this paper. Under the conditions of slight deforma tion of granules, wave equation, complex number expressions of propagation vecto r and attenuation vector, attenuation coefficient expressions of longitudinal wa ve and transverse wave, etc, are analyzed and deduced. The expressions of attenu ation coefficients of viscoelastic longitudinal wave and transverse wave show th a t the attenuation of wave is related to frequency. The higher the frequency is, the more the attenuation is, which is tested by the laboratory experiment. In a ddi tion, the energy dissipation is related to the higher frequency wave that is abs orbed by granular media. The friction amongst granular media also increase the e nergy dissipation. During the flowing situation the expression of transmission f actor of energy shows that the granular density difference is the key factor whi ch leads to the attenuation of vibrating energy. This has been proved by the exp eriment results.
基金Project(51165022)supported by the National Natural Science Foundation of ChinaProject(20122117)supported by the Lanzhou Science and Technology Bureau Foundation,ChinaProject(1310RJZA036)supported by the Natural Science Foundation of Gansu Province,China
文摘Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.
基金Project(52174069) supported by the National Natural Science Foundation of ChinaProject(8202033) supported by the Beijing Natural Science Foundation,ChinaProject(KCF2203) supported by the Henan Key Laboratory for Green and Efficient Mining&Comprehensive Utilization of Mineral Resources (Henan Polytechnic University),China。
文摘This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.
基金Project(2023YFC2907600)supported by the National Key Research and Development Program of ChinaProject(202203a07020011)supported by the Major Science and Technology Projects of Anhui Province,China+4 种基金Project(T2021137)supported by the National Talent Project,ChinaProject(T000508)supported by the Leading Talent Project of the Special Support Plan of Anhui Province,ChinaProject(GXXT-2021-075)supported by the University Synergy Innovation Program of Anhui Province,ChinaProject(2022AH010053)supported by the Excellent Scientific Research and Innovation Team of Universities in Anhui Province,ChinaProject(2022CX1004)supported by the Anhui University of Science and Technology Postgraduate Innovation Fund Project,China。
文摘Experiments on grouting-reinforced rock mass specimens with different particle sizes and features were carried out in this study to examine the effects of grouting reinforcement on the load-bearing characteristics of fractured rock mass.The strength and deformation features of grouting-reinforced rock mass were analyzed under different loading manners;the energy evolution mechanism of grouting-reinforced rock mass specimens with different particle sizes and features was investigated;the energy dissipation ratio and post-peak stress decreasing rate were employed to evaluate the bearing stability of grouting-reinforced rock mass.The results show that the strength and ductility of granite-reinforced rock mass(GRM)under biaxial loading are higher than that of sandstone-reinforced rock mass(SRM)under uniaxial loading.Besides,the energy evolution characteristics of grouting-reinforced rock mass under uniaxial and biaxial loading mainly could be divided into early,middle,and late stages.In the early stage,total,elastic,and dissipation energies were quite small with flatter curves;in the middle stage,elastic energy increased rapidly,whereas dissipation energy increased slowly;in the late stage,dissipation energy increased sharply.The energy dissipation ratio was used to represent the pre-peak plastic deformation.Under uniaxial loading,this ratio increased as the particle size increased and the pre-peak plastic deformation of grouting-reinforced rock mass became larger;under biaxial loading,it dropped as the particle size increased,and the pre-peak plastic deformation of grouting-reinforced rock mass became smaller.The post-peak stress decline rate A_(v) was used to assess the post-peak bearing performance of grouting-reinforced rock mass.Under uniaxial loading,parameter A_(v) exhibited reduction as the particle size kept increasing,and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was greater,and the bearing capacity was greater;under biaxial loading,A_(v) increased with the particle size,and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was low and the bearing capacity was reduced.The findings are considered instrumental in improving the stability of the roadway-surrounding rock by granite and sandstone grouting.
基金Projects(U23B2093,52034009)supported by the National Natural Science Foundation of ChinaProject(2022YFC3004602)supported by the National Key Research and Development Program of ChinaProject(BBJ2024009)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Abstract:At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to incomplete statistics,as of 2023,80%of coal mine rock bursts accidents in China occur in mining roadway.In view of this phenomenon,the cyclic impact test of post-peak sandstone is designed,focusing on the post-peak stress state of sandstone,and exploring the post-peak dynamic response of sandstone.The post-peak sandstone specimens were prepared by a uniaxial compressor,and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment.The results show that:1)The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure,indicating that the impact tendency of sandstone after peak decreased under lower axial pressure.On the contrary,the post-peak sandstone had strong impact tendency under higher axial pressure;2)The higher the axial pressure,the lower the dynamic strength of the post-peak sandstone,indicating that the axial pressure promoted the failure process of the post peak sandstone;3)It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure;4)Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure,and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level.The research shows that when the roadway surrounding rock was in the post-peak stress state,reducing the static stress was the key to prevent the secondary ground pressure disaster.The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment,and promote the research and exploration of post-peak mechanical properties of coal and rock.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Projects(51278216,51478201)supported by the National Natural Science Foundation of China
文摘Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for proper design and construction of geogrid reinforced earth structures. Based on the calibrated model of sand and geogrid, a series of numerical pullout tests are conducted using PFC^(3D) under special considerations of particle angularity and aperture geometry of the geogrid. In this work, interface characteristics regarding the displacement and contact force developed among particles and the deformation and force distribution along the geogrid are all visualized with PFC^(3D) simulations so that new understanding on how geogrid-soil interaction develops under pullout loads can be obtained. Meanwhile, a new variable named fabric anisotropy coefficient is introduced to evaluate the inherent relationship between macroscopic strength and microscopic fabric anisotropy. A correlation analysis is adopted to compare the accuracy between the newly-proposed coefficient and the most commonly used one. Furthermore, additional pullout tests on geogrid with four different joint protrusion heights have been conducted to investigate what extent and how vertical reinforcement elements may result in reinforcement effects from perspectives of bearing resistance contribution, energy dissipation, as well as volumetric response. Numerical results show that both the magnitude and the directional variation of normal contact forces govern the development of macroscopic strength and the reinforcing effects of joint protrusion height can be attributed to the accelerated energy dissipation across the particle assembly and the intensive mobilization of the geogrid.
文摘In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.
文摘Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study aims to reveal the dynamic and cyclic behavior of steel plated shear wall.Finite element method of analysis was implemented in order to simulate the behavior of such a wall structure.To determine the dynamic behavior of un-stiffened plate shear wall,two different analytical models were implemented.The post buckling strength of steel plate subjected to lateral loading was also employed.The story shear-drift diagrams of steel shear wall system were presented.The strength and ductility of the system obtained from the analysis were compared with those of steel shear wall tests reported before.The pertinent parameters of the steel shear wall system such as plate thickness,column and beam stiffness and the plate aspect ratio were recognized and their effects were recorded.The effect of stiffeners on the behavior of the SPSW was also investigated.
基金supported by the National Natural Science Foundation of China(grant number 51805086)the Natural Science Foundation of Fujian Province,China(grant number 2018J01763)。
文摘To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire materials(EPMWM)for vibration isolation was previously investigated.In this paper,a study focusing on the impact-resistance of EPMWM with the consideration of ambient temperature is presented.The quasi-static and low-velocity impact mechanical behavior of EPMWM under different temperatures(25℃-300℃)are systematically studied.The results of the static compression test show that the damping energy dissipation of EPMWM increases with temperature while the nonlinear damping characteristics are gradually enhanced.During the impact experiments,the impact energy loss rate of EPMWM was between 65%and 85%,while the temperatures increased from 25℃to 300℃.Moreover,under the same drop impact conditions,the overall deformation of EPMWM decreases in the temperature range of 100℃-200℃.On the other hand,the impact stiffness,energy dissipation,and impact loss factor of EPMWM significantly increase with temperature.This can be attributed to an increase in temperature,which changes the thermal expansion coefficient and contact state of the internal wire helixes.Consequently,the energy dissipation mode(dry friction,air damping,and plastic deformation)of EPMWM is also altered.Therefore,the EPMWM may act as a potential candidate material for superior energy absorption applications.
文摘Reinforced concrete(RC)structures are generally designed to carry quasi-static gravity loads through almost indispensable components namely slab,however,it may be subjected to high intense loads induced from the impact of projectiles generated by the tornado,falling construction equipment,and also from accidental explosions during their construction and service lifespan.Impacts due to rock/boulder falls do occur on the structures located especially in hilly areas.Such loadings are not predictable but may cause severe damage to the slab/structure.It stimulates structural engineers and researchers to investigate and understand the dynamic response of RC structures under such impulsive loading.This research work first investigates the performance of 1000×1000×75 mm^(3)conventionally reinforced two-way spanning normal strength concrete slab with only tension reinforcement(0.88%)under the concentric impact load(1035 N)using the finite element method based computer code,ABAQUS/Explicit-v.6.15.The impact load is delivered to the centroid of the slab using a solid-steel cylindroconical impactor(drop weight)with a flat nose of diameter 40 mm,having a total mass of 105 kg released from a fixed height of 2500 mm.Two popular concrete constitutive models in ABAQUS namely;Holmquist-Johnson-Cook(HJC)and Concrete Damage Plasticity(CDP),with strain rate effects as per fib MODEL CODE 2010,are used to model the concrete material behavior to impact loading and to simulate the damage to the slab.The slab response using these two models is analyzed and compared with the impact test results.The strain rate effect on the reinforcing steel bars has been incorporated in the analysis using the Malvar and Crawford(1998)approach.A classical elastoplastic kinematic idealization is considered to model the steel impactor and support system.Results reveal that the HJC model gives a little overestimation of peak displacement,maximum acceleration,and damage of the slab while the predictions given by the CDP model are in reasonable agreement with the experimental test results/observations available in the open literature.Following the validation of the numerical model,analyses have been extended to further investigate the damage response of the slab under eccentric impact loadings.In addition to the concentric location(P1)of the impacting device,five locations on a quarter of the slab i.e.,two along the diagonal(P2&P3),the other two along the mid-span(P4&P5),and the last one(P6)between P3 and P5,covering the entire slab,are considered.Computational results have been discussed and compared,and the evaluation of the most damaging location(s)of the impact is investigated.It has been found that the most critical location of the impact is not the centroid of the slab but the eccentric one with the eccentricity of 1/6th of the span from the centroid along the mid-span section.
