Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR), used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. H...Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR), used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. However, it is recognized that unless we can give reasonable explanations of these curious precursory phenomena that continue to be serendipitously observed from time to time, such high technology of GPS or InSAR is difficult to be efficiently used. Therefore, a proper model revealing the relation between earthquake evolution and stress variation, such as the phenomena of stress buildup, stress shadow and stress transfer (SSS), is crucial to the GPS or InSAR based earthquake prediction. Here we address this question through a numerical approach of earthquake development using an intuitive physical model with a map-like configuration of discontinuous fault system. The simulation provides a physical basis for the principle of stress-forecasting of earthquakes based on SSS and for the application of GPS or InSAR in earthquake prediction. The observed SSS associated phenomena with images of stress distribution during the failure process can be continuously simulated. It is shown that the SSS are better indicators of earthquake precursors than that of seismic foreshocks, suggesting a predictability of earthquakes based on stress-forecasting strategy.展开更多
Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial ...Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber's embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.展开更多
The stress transfer mechanism of steel fibre reinforced concrete is studied. The solutions for the stress and displacement were regarded as the superposition of ' the elementary solutions' and ' the improv...The stress transfer mechanism of steel fibre reinforced concrete is studied. The solutions for the stress and displacement were regarded as the superposition of ' the elementary solutions' and ' the improved solutions'. The elementary solutions were found by using two-dimensional elastic theory and the improved solutions were found by using the Love displacement function method. The calculated results indicate that the solutions possess good convergence. By comparing the three-dimensional solutions with the shear-lag solutions, evident difference may be found.展开更多
The interaction between the India-Eurasia collision and the Western Pacific subduction and their contribution to recent geodynamics of the Asian continent are discussed. We perform a comparative analysis of the data a...The interaction between the India-Eurasia collision and the Western Pacific subduction and their contribution to recent geodynamics of the Asian continent are discussed. We perform a comparative analysis of the data available from world literature and new data on the slow strain and earthquake migration from the India-Eurasia collision and the Western Pacific subduction zones. Based on the concepts of wave dynamics of the deformation processes, a localization scheme is constructed illustrating the migration of slow strain fronts in central and eastern Asia, and the wave geodynamic impact of collision and subduction on the Asian continent is shown.展开更多
After Mw 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the ...After Mw 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the 25th April event using models of regional faults designed according to south Tibet-Nepal structure, and show that some indicative significant stress increases. We calculate static stress changes caused by the displacement of a fault on which dislocations happen and an earthquake occurs. A Mw 7.3 earthquake broke on 12 May at a distance of - 130 km SEE of the Mw 7.8 earthquake, whose focus roughly located on high Coulomb stress change (CSC) site. Aftershocks (first 15 days after the mainshock) are associated with stress increase zone caused by the main rupture. We set receiver faults with specified strikes, dips, and rakes, on which the stresses imparted by the source fault are resolved. Four group normal faults to the north of the Nepal earthquake seismogenic fault were set as receiver faults and variant results followed. We provide a discussion on Coulomb stress transfer for the seismogenic fault, which is useful to identify potential future rupture zones.展开更多
In this paper the elastic stress transfer from the fiber to the matrix is analysed for fiber-reinforced composites when the fiber is loaded axially.The dependence of the elastic stress transfer on the as- pect ratio o...In this paper the elastic stress transfer from the fiber to the matrix is analysed for fiber-reinforced composites when the fiber is loaded axially.The dependence of the elastic stress transfer on the as- pect ratio of the fiber,the volume fraction of the fiber,the fiber-to-matrix elastic modulus ratio and the Poisson's ratio of the fiber and the matrix has been shown in detail.展开更多
By employing the elastic and elastic plastic finite element method(FEM), the effects of matrix feature on the stress transfer mechanisms of short fiber composites are studied. In the calculation, the variations in ma...By employing the elastic and elastic plastic finite element method(FEM), the effects of matrix feature on the stress transfer mechanisms of short fiber composites are studied. In the calculation, the variations in matrix modulus, yield strength and hardening modulus are considered. It is concluded that large deformation of matrix is harmful to the improvement of the mechanical performances of the composites.展开更多
In this paper, the effects of interface properties on the stress transfer between matrix and fiber in short fiber reinforced metal matrix composites (SFRMMCs) is studied with the method of the elasto plastic finite ...In this paper, the effects of interface properties on the stress transfer between matrix and fiber in short fiber reinforced metal matrix composites (SFRMMCs) is studied with the method of the elasto plastic finite element. The interface properties include Young’s modulus, thickness and elasto plastic performances. In the calculation an interfacial layer with given thickness is introduced into the single fiber model. It is shown that, for a soft interface, the variation in interfacial properties influences the stress transfer greatly.展开更多
To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics)anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors...To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics)anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors,a comparative indoor physical model test was conducted in this study using loess mudstone slope as a typical case,and multi-attribute response data,such as slope displacement,BFRP anchor strain and axial force,were obtained.Based on the variation law of slope displacement,it can be concluded that the deformation displacement of the slope on the side reinforced by BFRP anchors is smaller than that of slopes reinforced with steel anchors;the bearing capacity of BFRP anchor is given priority in time,and the anchoring effect of BFRP anchor at the top of the slope is given priority,and the axial force value of anchor is characterized by a surface amplification effect in space;the axial force is higher around the anchor head and tends to decay as a negative exponential function as the anchor extends in the direction of the interior of the slope;the shear stress of BFRP anchor and anchorage body are unevenly distributed along the axial direction,with the maximum value occurring in the free section near the slope surface and decreases as the BFRP anchor extends towards the interior of the slope.These results can provide a theoretical basis for the optimal design of BFRP anchors.展开更多
A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites(FRC) subjected to uniaxial tensile loading along the fiber direction.The matrix damage ...A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites(FRC) subjected to uniaxial tensile loading along the fiber direction.The matrix damage and interfacial debonding,which are the main failure modes,are considered in the model.The maximum stress criterion with the linear damage evolution theory is used for the matrix.The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory,in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents(fiber and matrix).The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions,which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers.The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope.The relation curves between damage,debonding and ineffective region lengths with external strain loading are obtained.展开更多
Understanding the roles of interlayers in reinforcement efficiencies by layered graphene is very important in order to produce strong and light graphene based nanocomposites. The present paper uses the finite element ...Understanding the roles of interlayers in reinforcement efficiencies by layered graphene is very important in order to produce strong and light graphene based nanocomposites. The present paper uses the finite element method to evaluate the interfacial strain transfers and reinforcement efficiencies in layered graphene-polymer composites. Results indicate that the presence of compliant interlayers in layered graphene plays significant roles in the transfers of strain/stress from matrix to graphene and subsequently the reinforcement effectiveness of layered graphene. In general, the magnitude of shear strain transferred onto the rigid graphene decreases as the thickness of the interlayer increases. This trend becomes insignificant as the graphene becomes sufficiently large(s>25,000). The shear strain at the interface of graphene-matrix is also greatly influenced by the interlayer modulus. A stiffer interlayer would result in a higher shear strain transferred on the graphene. The performance of the interlayers is further affected by the property of the composite and the architecture of the layered graphene stack. If a composite contains more graphene phase, the efficiency of reinforcement by a layered graphene becomes improved. If a graphene stack contains more interlayers, the effectiveness of reinforcement at the edges of the graphene becomes negatively affected.展开更多
Melting heat transfer in the boundary layer flow of a couple stress fluid over a stretching surface is investigated. The developed differential equations are solved for homotopic solutions. It is observed that the vel...Melting heat transfer in the boundary layer flow of a couple stress fluid over a stretching surface is investigated. The developed differential equations are solved for homotopic solutions. It is observed that the velocity and the boundary layer thickness are decreasing functions of the couple stress fluid parameter. However, the temperature and surface heat transfer increase when the values of the couple stress fluid parameter increase. The velocity and temperature fields increase with an increase in the melting process of the stretching sheet.展开更多
A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved...A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved in the transient heat transfer and the cure kinetics of the resin, and the distributions of internal temperature and cure degree of the composite at any instant time were obtained. The self-consistent field micro-mechanics model was used to predict the cure-dependent mechanical properties of the composites. Thermal expansion and cure shrinkage were included in the analysis. The thermo-elastic mechanical governing equations were solved using the incremental stress-strain relationship based FEM and the residual stress development was predicted. The present results were validated by the comparisons with the pertinent literature. The numerical example of a half cylinder was presented. The results show that it is necessary to carry out the three-dimensional analysis due to the complex distributions of temperatures, cure degrees and process-induced stress for thick parts, which can be predicted at any point within composite structures in the present analysis.展开更多
To help comfort for an amputee, it is important to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. An interfacial stress sensor was presented which ...To help comfort for an amputee, it is important to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. An interfacial stress sensor was presented which was capable of measuring compressive pressure and shear stress simultaneously. A mathematical model was built and an experiment was conducted to obtain the transfer function of interfacial stress sensor to compressive pressure. The results show that the sensor is capable of measuring a range of 30-217 kPa compressive pressure with a relative error of 32.15% in lower range and 6.22% in upper range.展开更多
基金supported by the National Key Basic Research Science Foundation (No.2007CB209400)the National Natural Science Foundation of China (No.40638040,10672028)the Chinese Postdoctoral Science Foundation (No.20070421048)
文摘Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR), used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. However, it is recognized that unless we can give reasonable explanations of these curious precursory phenomena that continue to be serendipitously observed from time to time, such high technology of GPS or InSAR is difficult to be efficiently used. Therefore, a proper model revealing the relation between earthquake evolution and stress variation, such as the phenomena of stress buildup, stress shadow and stress transfer (SSS), is crucial to the GPS or InSAR based earthquake prediction. Here we address this question through a numerical approach of earthquake development using an intuitive physical model with a map-like configuration of discontinuous fault system. The simulation provides a physical basis for the principle of stress-forecasting of earthquakes based on SSS and for the application of GPS or InSAR in earthquake prediction. The observed SSS associated phenomena with images of stress distribution during the failure process can be continuously simulated. It is shown that the SSS are better indicators of earthquake precursors than that of seismic foreshocks, suggesting a predictability of earthquakes based on stress-forecasting strategy.
基金supported by the National Natural Science Foundation of China(10662005)
文摘Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber's embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.
文摘The stress transfer mechanism of steel fibre reinforced concrete is studied. The solutions for the stress and displacement were regarded as the superposition of ' the elementary solutions' and ' the improved solutions'. The elementary solutions were found by using two-dimensional elastic theory and the improved solutions were found by using the Love displacement function method. The calculated results indicate that the solutions possess good convergence. By comparing the three-dimensional solutions with the shear-lag solutions, evident difference may be found.
文摘The interaction between the India-Eurasia collision and the Western Pacific subduction and their contribution to recent geodynamics of the Asian continent are discussed. We perform a comparative analysis of the data available from world literature and new data on the slow strain and earthquake migration from the India-Eurasia collision and the Western Pacific subduction zones. Based on the concepts of wave dynamics of the deformation processes, a localization scheme is constructed illustrating the migration of slow strain fronts in central and eastern Asia, and the wave geodynamic impact of collision and subduction on the Asian continent is shown.
基金supported by the International Cooperation and Exchange Program(Grant 41461164004)General Program(Grant 41174004)of National Natural Science Foundation of China+2 种基金the National International Science and Technology Cooperation Project(Grant 2015DFR21100)the Basic Research Fund Division Mission(Grant 2015IES0305)the Basic Research Project(Grant 2014IES010102)of Institute of Earthquake Science,China Earthquake Administration
文摘After Mw 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the 25th April event using models of regional faults designed according to south Tibet-Nepal structure, and show that some indicative significant stress increases. We calculate static stress changes caused by the displacement of a fault on which dislocations happen and an earthquake occurs. A Mw 7.3 earthquake broke on 12 May at a distance of - 130 km SEE of the Mw 7.8 earthquake, whose focus roughly located on high Coulomb stress change (CSC) site. Aftershocks (first 15 days after the mainshock) are associated with stress increase zone caused by the main rupture. We set receiver faults with specified strikes, dips, and rakes, on which the stresses imparted by the source fault are resolved. Four group normal faults to the north of the Nepal earthquake seismogenic fault were set as receiver faults and variant results followed. We provide a discussion on Coulomb stress transfer for the seismogenic fault, which is useful to identify potential future rupture zones.
文摘In this paper the elastic stress transfer from the fiber to the matrix is analysed for fiber-reinforced composites when the fiber is loaded axially.The dependence of the elastic stress transfer on the as- pect ratio of the fiber,the volume fraction of the fiber,the fiber-to-matrix elastic modulus ratio and the Poisson's ratio of the fiber and the matrix has been shown in detail.
文摘By employing the elastic and elastic plastic finite element method(FEM), the effects of matrix feature on the stress transfer mechanisms of short fiber composites are studied. In the calculation, the variations in matrix modulus, yield strength and hardening modulus are considered. It is concluded that large deformation of matrix is harmful to the improvement of the mechanical performances of the composites.
文摘In this paper, the effects of interface properties on the stress transfer between matrix and fiber in short fiber reinforced metal matrix composites (SFRMMCs) is studied with the method of the elasto plastic finite element. The interface properties include Young’s modulus, thickness and elasto plastic performances. In the calculation an interfacial layer with given thickness is introduced into the single fiber model. It is shown that, for a soft interface, the variation in interfacial properties influences the stress transfer greatly.
基金the financial support by the National Key R&D Program of China(No.2018YFC1504901)Science and technology development project of China Railway 11th Bureau Group Co.,LTD(20210601)+4 种基金Science and technology development project of China Railway Lanzhou Bureau Group Co.,LTD(2021046-2)Science and technology program of Gansu Province(Grant No.21JR7RA739)Science and Technology Development Project of China Railway Research Institute Co.Ltd(2017-KJ008-Z008-XB)Science and technology development project of China Railway Ninth Bureau Group Co.,Ltd(DLF-ML-JSFW-202109)The Science and Technology Foundation of Guizhou Province(NO.ZK[2022]Key018)。
文摘To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics)anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors,a comparative indoor physical model test was conducted in this study using loess mudstone slope as a typical case,and multi-attribute response data,such as slope displacement,BFRP anchor strain and axial force,were obtained.Based on the variation law of slope displacement,it can be concluded that the deformation displacement of the slope on the side reinforced by BFRP anchors is smaller than that of slopes reinforced with steel anchors;the bearing capacity of BFRP anchor is given priority in time,and the anchoring effect of BFRP anchor at the top of the slope is given priority,and the axial force value of anchor is characterized by a surface amplification effect in space;the axial force is higher around the anchor head and tends to decay as a negative exponential function as the anchor extends in the direction of the interior of the slope;the shear stress of BFRP anchor and anchorage body are unevenly distributed along the axial direction,with the maximum value occurring in the free section near the slope surface and decreases as the BFRP anchor extends towards the interior of the slope.These results can provide a theoretical basis for the optimal design of BFRP anchors.
文摘A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites(FRC) subjected to uniaxial tensile loading along the fiber direction.The matrix damage and interfacial debonding,which are the main failure modes,are considered in the model.The maximum stress criterion with the linear damage evolution theory is used for the matrix.The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory,in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents(fiber and matrix).The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions,which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers.The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope.The relation curves between damage,debonding and ineffective region lengths with external strain loading are obtained.
基金supported by NASA Kentucky under NASA award No.:NNX15AR69H
文摘Understanding the roles of interlayers in reinforcement efficiencies by layered graphene is very important in order to produce strong and light graphene based nanocomposites. The present paper uses the finite element method to evaluate the interfacial strain transfers and reinforcement efficiencies in layered graphene-polymer composites. Results indicate that the presence of compliant interlayers in layered graphene plays significant roles in the transfers of strain/stress from matrix to graphene and subsequently the reinforcement effectiveness of layered graphene. In general, the magnitude of shear strain transferred onto the rigid graphene decreases as the thickness of the interlayer increases. This trend becomes insignificant as the graphene becomes sufficiently large(s>25,000). The shear strain at the interface of graphene-matrix is also greatly influenced by the interlayer modulus. A stiffer interlayer would result in a higher shear strain transferred on the graphene. The performance of the interlayers is further affected by the property of the composite and the architecture of the layered graphene stack. If a composite contains more graphene phase, the efficiency of reinforcement by a layered graphene becomes improved. If a graphene stack contains more interlayers, the effectiveness of reinforcement at the edges of the graphene becomes negatively affected.
基金supported by the Deanship of Scientific Research(DSR),King Abdulaziz University,Jeddah,Saudi Arabia
文摘Melting heat transfer in the boundary layer flow of a couple stress fluid over a stretching surface is investigated. The developed differential equations are solved for homotopic solutions. It is observed that the velocity and the boundary layer thickness are decreasing functions of the couple stress fluid parameter. However, the temperature and surface heat transfer increase when the values of the couple stress fluid parameter increase. The velocity and temperature fields increase with an increase in the melting process of the stretching sheet.
基金the National Natural Science Foundation of China(Grant No.10502016)Development Program for Outstanding Young Teachers in Harbin Institute of Technology(Grant No.HITQNJS.2006.020)
文摘A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved in the transient heat transfer and the cure kinetics of the resin, and the distributions of internal temperature and cure degree of the composite at any instant time were obtained. The self-consistent field micro-mechanics model was used to predict the cure-dependent mechanical properties of the composites. Thermal expansion and cure shrinkage were included in the analysis. The thermo-elastic mechanical governing equations were solved using the incremental stress-strain relationship based FEM and the residual stress development was predicted. The present results were validated by the comparisons with the pertinent literature. The numerical example of a half cylinder was presented. The results show that it is necessary to carry out the three-dimensional analysis due to the complex distributions of temperatures, cure degrees and process-induced stress for thick parts, which can be predicted at any point within composite structures in the present analysis.
基金National Natural Science Foundations of China(No.60976058,No.61274078)Innovation Program of Shanghai Municipal Education Commission,China(No.13ZZ049)Fundamental Research Funds for the Central Universities of Xidian University,China(No.K5051304005)
文摘To help comfort for an amputee, it is important to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. An interfacial stress sensor was presented which was capable of measuring compressive pressure and shear stress simultaneously. A mathematical model was built and an experiment was conducted to obtain the transfer function of interfacial stress sensor to compressive pressure. The results show that the sensor is capable of measuring a range of 30-217 kPa compressive pressure with a relative error of 32.15% in lower range and 6.22% in upper range.