Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak...Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.展开更多
As known, there is a large number of dentin tubules in dentin.These tubules have varying radii and are shaped into radially parallel pattern. Theanisotropy of microstructure of dentin shows that dentin should be treat...As known, there is a large number of dentin tubules in dentin.These tubules have varying radii and are shaped into radially parallel pattern. Theanisotropy of microstructure of dentin shows that dentin should be treated as a ma-terial of varying transverse isotropy. In this Part, the elastic stress-strain relationsand the quadratic strength criterion are established in the form of having varyingtransverse isotropy, in the framework of micromechanics to take into account of theeffect of the microstructures-dentin tubules. Simplified forms for isotropic and ho-mogeneous cases, as well as the corresponding plane stress form of the stress-strainrelations are also given. These theoretical models are very well supported by theexperiments shown later in the continued paper (Part Ⅱ).展开更多
For the research on steel structure in fire,it is very important to determine the properties of structural steel at elevated temperature.Up to now,the high-temperature properties of material is believed to be related ...For the research on steel structure in fire,it is very important to determine the properties of structural steel at elevated temperature.Up to now,the high-temperature properties of material is believed to be related to only temperature state,which is not precise enough to simulate the behavior of steel structures under different combinations of heating,cooling,loading,and unloading.To analyze the influence of the temperature-load history on the steel properties,a series of tests were carried out under different temperature-load paths about steel Q235,which is widely used in steel structures in China.In this paper,the method to set the temperature-load paths was introduced;the variety regulation of steel properties changing with temperature was analyzed under different paths;according to experimental results,the formulas of elastic modulus and yield strength at elevated temperature were fitted,and the stress-strain-temperature 3D relationships of structural steel under different paths were presented.展开更多
Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stres...Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stress and time,but also it has the corresponding relations to the triaxial stress-strain curves of rock.The deformation properties of soften-strain,harden-strain and ideal plasticity presented by conventional triaxial compressive test curves under the different stress states were utilized,and the creep characteristics,the creep starting stress and the different entire creep process curves of rock were studied systematically according to creep experiment results,and the relations of the triaxial stress-strain curves to the creeping starting stress,the terminating curve,the different creep processes,and the different creep fracture properties were established.The relations presented in this paper were verified partially by the creep experiment results of five types of rock.展开更多
To completely understand the rate-dependent stress-strain behavior of the porous nanocrystalline materials,it is necessary to formulate a constitutive model that can reflect the complicated experimentally observed str...To completely understand the rate-dependent stress-strain behavior of the porous nanocrystalline materials,it is necessary to formulate a constitutive model that can reflect the complicated experimentally observed stress-strain relations of nanocrystalline materials.The nanocrystalline materials consisting grain interior and grain boundary are considered as viscoplastic and porous materials for the reasons that their mechanical deformation is commonly governed by both dislocation glide and diffusion,and pores commonly exist in the nanocrystalline materials.A constitutive law of the unified theory reflecting the stress-strain relations was established and verified by experimental data of bulk nanocrystalline Ni prepared by hydrogen direct current arc plasma evaporation method and hot compression.The effect of the evolution of porosity on stress-strain relations was taken into account to make that the predicted results can keep good agreements with the corresponding experimental results.展开更多
-A nonlinear model for the stress-strain behaviour of normally consolidated clays is presented based on the experimental results. It is indicated that the volume strain under pure shear is a power function of stress r...-A nonlinear model for the stress-strain behaviour of normally consolidated clays is presented based on the experimental results. It is indicated that the volume strain under pure shear is a power function of stress ratio and the normalized stress-strain curve is a standard hyperbola. According to the model, the coefficient of pore pressure induced by shear stress and the critical stress ratio which governs the influence of the negative dilatancy are suggested. It is shown by some triaxial tests that the proposed model can be used to study the negative dilatancy and to describe the stress-strain-pore pressure adequately for soft clays.展开更多
A general shape of tensile stress-strain curves of woven fabrics is first recognised by puttingtested and predicted results together.An exponential function with two parameters is then selectedfor the prediction of te...A general shape of tensile stress-strain curves of woven fabrics is first recognised by puttingtested and predicted results together.An exponential function with two parameters is then selectedfor the prediction of tensile stress-strain relationship.The predicted results by using the proposedfunction show excellent agreement with experimental data.展开更多
Although there are methods for testing the stress-strain relation and strength,which are the most fundamental and important properties of metallic materials,their application to small-volume materials and tube compone...Although there are methods for testing the stress-strain relation and strength,which are the most fundamental and important properties of metallic materials,their application to small-volume materials and tube components is lim-ited.In this study,based on energy density equivalence,a new dimensionless elastoplastic load-displacement model for compressed metal rings with isotropy and constitutive power law is proposed to describe the relations among the geometric dimensions,Hollomon law parameters,load,and displacement.Furthermore,a novel test method was developed to determine the elastic modulus,stress-strain relation,yield and tensile strength via ring compression test.The universality and accuracy of the method were verified within a wide range of imaginary materials using finite element analysis(FEA),and the results show that the stress-strain curves obtained by this method are consistent with those inputted in the FEA program.Additionally,a series of ring compression tests were performed for seven metallic materials.It was found that the stress-strain curves and mechanical properties predicted by the method agreed with the uniaxial tensile results.With its low material consumption,the ring compression test has the potential to be as an alternative to traditional tensile test when direct tension method is limited.展开更多
In this paper the relationship between microstructure and stress-strain behavior in tensile test of high strength pipeline steel was investigated.The steel with polygonal ferrite-bainite(PF + B) microstructure has a &...In this paper the relationship between microstructure and stress-strain behavior in tensile test of high strength pipeline steel was investigated.The steel with polygonal ferrite-bainite(PF + B) microstructure has a 'round-house' type tensile stress-strain curve with low Y/T ratio,highly uniform elongation and high n-value,which means PF + B microstructure has the best deformability(i.e.Ideal stress-strain behavior) among the four microstructures.The steel with acicular ferrite-martensite&austenite(AF + MA) microstructure has a 'continuous-yielding' type tensile stress-strain curve,whose deformability is worse than that of PF + B microstructure.Both the steels of polygonal ferrite-acicular ferrite(PF + AF) and polygonal ferrite-pearlite (PF+P) microstructure have 'luders elongation' type tensile stress-strain curve with high Y/T ratio,low uniform elongation and low n-value,which means PF + AF and PF + P microstructures have the worst deformability among the four microstructures.展开更多
Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trach...Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trachea,which leads to a variety of serious complications.In this study,inspired by the structure of the native trachea,a wavy non-uniform ligament chiral tracheal stent is proposed,in which J-shaped stress-strain behavior and negative Poisson's ratio response are achieved by replacing the tangential ligament of tetrachiral and anti-tetrachiral hybrid structure with a wavy non-uniform ligament.Through the combination of theoretical analysis,finite element analysis and experimental tests,a wide range of desired J-shaped stress-strain curves are explored to mimic the native porcine trachea by tailoring the stent geometry.Besides,the negative Poisson’s ratio and auxetic diameter curves versus axial strain of the stent are also studied in detail,thus contributing to the enhancement of cross-section ventilation and reducing the migration of the stent.This novel tracheal stent with a unique microstructure shows a potential to perfectly match the physiological activities of the native trachea and thereby reduce potential complications.展开更多
The loading-unloading-reloading process could affect the tensile deformation of metals with the combined function of stress relaxation and work hardening, which has been reported in multiple experiments. Nevertheless,...The loading-unloading-reloading process could affect the tensile deformation of metals with the combined function of stress relaxation and work hardening, which has been reported in multiple experiments. Nevertheless, the effects of different unloading positions and unloading times have not been investigated. In this study, unloading-reloading tests on three materials (AL6061, HSLA and Q195) were conducted. The stress exhibits a rapid rise momentarily upon reloading and stabilizes afterward while the post stress-strain curve deviates up or down from the monotonic tensile curve. The ductility is enhanced by the unloading-reloading process in general. Different unloading positions and unloading times have different degrees of influence on the stretching of these metals. The effect of loading conditions on a medium manganese steel was further studied. The functions to modify the post stress-strain relationship after unloading-reloading were established.展开更多
Austenite can be retained at ambient temperature in steels by alloying and processing control. The transformation from austenite to martensite occurs under a certain conditions : thermal or deformation. Stress-strain ...Austenite can be retained at ambient temperature in steels by alloying and processing control. The transformation from austenite to martensite occurs under a certain conditions : thermal or deformation. Stress-strain induced martensitic transformation is important to improve the plasticity of steels which is called transformation induced plasticity (TRIP). Strength-ductility balance of the steels is greatly superior to that of other high strength steels due to the TRIP effect. A new type of steels-TRIP steel is展开更多
This paper presents results which concern regularities of propagation of discontinuous zones from mined-out space in rock massif with inclined bedding structure. The dependencies of maximal height of these zones from ...This paper presents results which concern regularities of propagation of discontinuous zones from mined-out space in rock massif with inclined bedding structure. The dependencies of maximal height of these zones from the inclination angle of productive beds were found. The mechanical model of rock massif was chosen as viscoelastic and transversely isotropic. Finite element method was used for calculation performing. Coulumb-Mohr and maximal elongation criteria were used for determination of discontinuous zones.展开更多
The paper discusses geometrical characteristics and strength parameters of fan blades equipped with replaceable active part it end ended to improve the fan adjustability owing to replacement or removal of the active p...The paper discusses geometrical characteristics and strength parameters of fan blades equipped with replaceable active part it end ended to improve the fan adjustability owing to replacement or removal of the active part, which allows the fan to maintain a wide range of ventilation modes.展开更多
The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied.Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have...The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied.Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated.It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well.Moreover,a parametric study has been carried out to investigate the influence of essential parameters on the shear strength parameters of these materials.According to the research,increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials.Furthermore,the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.展开更多
The stress,strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal resistivity.Furthermore,the coal resistivity regularity and ...The stress,strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal resistivity.Furthermore,the coal resistivity regularity and mechanism were analyzed at different stages of complete stress-strain process,which includes the two kinds of coal body with typical conductive characteristics.The results indicate that coal resistivity with different conductive characteristics has different change rules in complete stress-strain process.It is mainly represented at the densification and flexibility phases before dilatation occurs.The variation of resistivity can be divided into two kinds,named down and up.Dilatation of coal samples occurred between 66%σ_(max) and 87%σ_(max).Because of dilatation,coal resistivity involves sudden change.The overall representation is shifting from reducing into improving or from slow improving into accelerated improving.Thus,coal resistivity always shows an increasing tendency at the plastic stage.After peak stress,coal body enters into failure stage.The expanding and communicating of macro fracture causes further improvement of coal resistivity.The maximum value of resistivity rangeability named λ reached 3.49.Through making real-time monitoring on coal resistivity,variation rules of resistivity can be deemed as precursory information so as to reflect the dilatation and sudden change before coal body reaches buckling failure,which can provide a new technological means for forecasting the dynamic disaster of coal petrography.展开更多
In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, ...In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.展开更多
A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual ...A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual phase (DP) steels with two different martensite volume fractions. The results show that there exist great differences in the stress-strain contribution of martensite and ferrite to DP steel. The stress-strain partitioning coefficient is not constant in the whole strain range, but decreases with increasing the true strain of DP steel. The softening effect caused by the dilution of carbon concentration in martensite with the increase of martensite volume fraction has great influence on the strain contribution of martensite. The strain ratio of ferrite to martensite almost linearly increases with increasing the true strain of DP steel when the martensite volume fraction is 22%, because martensite always keeps elastic. But the strain ratio of ferrite to martensite varies indistinctively with the further increase in true strain of DP steel above 0.034 when the martensite volume fraction is 50%, because plastic deformation happens in martensite. The stress ratio of martensite to ferrite decreases monotonously with increasing the true strain of DP steel whether the martensite volume fraction is 22% or 50%.展开更多
The mechanical performance of recycled aggregate concrete (RAC) is investigated. An experiment on the complete stress-strain curve under uniaxial compression loading of RAC is carried out. The experimental results ind...The mechanical performance of recycled aggregate concrete (RAC) is investigated. An experiment on the complete stress-strain curve under uniaxial compression loading of RAC is carried out. The experimental results indicate that the peak stress, peak strain, secant modulus of the peak point and original point increase with the strength grade of RAC enhanced. On the contrary, the residual stress of RAC decreases with the strength grade enhancing, and the failure of RAC is often broken at the interface between the recycled aggregate and the mortar matrix. Finally, the constitutive model of stress-strain model of RAC has been constituted, and the results from the constitutive model of stress-strain meet the experiment results very well.展开更多
基金The authors acknowledge the financial support from Natural Sciences and Engineering Research Council of Canada through its Discovery Grant program(RGPIN-2022-03893)École de Technologie Supérieure(ÉTS)construction engineering research funding.
文摘Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.
基金The project supported by the National Natural Science Foundation of China (19525207).
文摘As known, there is a large number of dentin tubules in dentin.These tubules have varying radii and are shaped into radially parallel pattern. Theanisotropy of microstructure of dentin shows that dentin should be treated as a ma-terial of varying transverse isotropy. In this Part, the elastic stress-strain relationsand the quadratic strength criterion are established in the form of having varyingtransverse isotropy, in the framework of micromechanics to take into account of theeffect of the microstructures-dentin tubules. Simplified forms for isotropic and ho-mogeneous cases, as well as the corresponding plane stress form of the stress-strainrelations are also given. These theoretical models are very well supported by theexperiments shown later in the continued paper (Part Ⅱ).
文摘For the research on steel structure in fire,it is very important to determine the properties of structural steel at elevated temperature.Up to now,the high-temperature properties of material is believed to be related to only temperature state,which is not precise enough to simulate the behavior of steel structures under different combinations of heating,cooling,loading,and unloading.To analyze the influence of the temperature-load history on the steel properties,a series of tests were carried out under different temperature-load paths about steel Q235,which is widely used in steel structures in China.In this paper,the method to set the temperature-load paths was introduced;the variety regulation of steel properties changing with temperature was analyzed under different paths;according to experimental results,the formulas of elastic modulus and yield strength at elevated temperature were fitted,and the stress-strain-temperature 3D relationships of structural steel under different paths were presented.
基金Project(50774090) supported by the National Natural Science Foundation of China
文摘Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stress and time,but also it has the corresponding relations to the triaxial stress-strain curves of rock.The deformation properties of soften-strain,harden-strain and ideal plasticity presented by conventional triaxial compressive test curves under the different stress states were utilized,and the creep characteristics,the creep starting stress and the different entire creep process curves of rock were studied systematically according to creep experiment results,and the relations of the triaxial stress-strain curves to the creeping starting stress,the terminating curve,the different creep processes,and the different creep fracture properties were established.The relations presented in this paper were verified partially by the creep experiment results of five types of rock.
基金Project(10502025) supported by the National Natural Science Foundation of ChinaProject(101005) supported by the Fok Ying Tong Education FoundationProject(BK2007528) supported by the Natural Science Foundation of Jiangsu Province,China
文摘To completely understand the rate-dependent stress-strain behavior of the porous nanocrystalline materials,it is necessary to formulate a constitutive model that can reflect the complicated experimentally observed stress-strain relations of nanocrystalline materials.The nanocrystalline materials consisting grain interior and grain boundary are considered as viscoplastic and porous materials for the reasons that their mechanical deformation is commonly governed by both dislocation glide and diffusion,and pores commonly exist in the nanocrystalline materials.A constitutive law of the unified theory reflecting the stress-strain relations was established and verified by experimental data of bulk nanocrystalline Ni prepared by hydrogen direct current arc plasma evaporation method and hot compression.The effect of the evolution of porosity on stress-strain relations was taken into account to make that the predicted results can keep good agreements with the corresponding experimental results.
文摘-A nonlinear model for the stress-strain behaviour of normally consolidated clays is presented based on the experimental results. It is indicated that the volume strain under pure shear is a power function of stress ratio and the normalized stress-strain curve is a standard hyperbola. According to the model, the coefficient of pore pressure induced by shear stress and the critical stress ratio which governs the influence of the negative dilatancy are suggested. It is shown by some triaxial tests that the proposed model can be used to study the negative dilatancy and to describe the stress-strain-pore pressure adequately for soft clays.
文摘A general shape of tensile stress-strain curves of woven fabrics is first recognised by puttingtested and predicted results together.An exponential function with two parameters is then selectedfor the prediction of tensile stress-strain relationship.The predicted results by using the proposedfunction show excellent agreement with experimental data.
基金Supported by National Natural Science Foundation of China(Grant Nos.11872320 and 12072294)
文摘Although there are methods for testing the stress-strain relation and strength,which are the most fundamental and important properties of metallic materials,their application to small-volume materials and tube components is lim-ited.In this study,based on energy density equivalence,a new dimensionless elastoplastic load-displacement model for compressed metal rings with isotropy and constitutive power law is proposed to describe the relations among the geometric dimensions,Hollomon law parameters,load,and displacement.Furthermore,a novel test method was developed to determine the elastic modulus,stress-strain relation,yield and tensile strength via ring compression test.The universality and accuracy of the method were verified within a wide range of imaginary materials using finite element analysis(FEA),and the results show that the stress-strain curves obtained by this method are consistent with those inputted in the FEA program.Additionally,a series of ring compression tests were performed for seven metallic materials.It was found that the stress-strain curves and mechanical properties predicted by the method agreed with the uniaxial tensile results.With its low material consumption,the ring compression test has the potential to be as an alternative to traditional tensile test when direct tension method is limited.
文摘In this paper the relationship between microstructure and stress-strain behavior in tensile test of high strength pipeline steel was investigated.The steel with polygonal ferrite-bainite(PF + B) microstructure has a 'round-house' type tensile stress-strain curve with low Y/T ratio,highly uniform elongation and high n-value,which means PF + B microstructure has the best deformability(i.e.Ideal stress-strain behavior) among the four microstructures.The steel with acicular ferrite-martensite&austenite(AF + MA) microstructure has a 'continuous-yielding' type tensile stress-strain curve,whose deformability is worse than that of PF + B microstructure.Both the steels of polygonal ferrite-acicular ferrite(PF + AF) and polygonal ferrite-pearlite (PF+P) microstructure have 'luders elongation' type tensile stress-strain curve with high Y/T ratio,low uniform elongation and low n-value,which means PF + AF and PF + P microstructures have the worst deformability among the four microstructures.
基金supported by the National Key Research and Development Program of China(No.2020YFC1107103)the National Natural Science Foundation of China(No.51821093)the Research Project of Public Welfare Technology Application of Zhejiang Province,China(No.LGF21H010006).
文摘Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trachea,which leads to a variety of serious complications.In this study,inspired by the structure of the native trachea,a wavy non-uniform ligament chiral tracheal stent is proposed,in which J-shaped stress-strain behavior and negative Poisson's ratio response are achieved by replacing the tangential ligament of tetrachiral and anti-tetrachiral hybrid structure with a wavy non-uniform ligament.Through the combination of theoretical analysis,finite element analysis and experimental tests,a wide range of desired J-shaped stress-strain curves are explored to mimic the native porcine trachea by tailoring the stent geometry.Besides,the negative Poisson’s ratio and auxetic diameter curves versus axial strain of the stent are also studied in detail,thus contributing to the enhancement of cross-section ventilation and reducing the migration of the stent.This novel tracheal stent with a unique microstructure shows a potential to perfectly match the physiological activities of the native trachea and thereby reduce potential complications.
文摘The loading-unloading-reloading process could affect the tensile deformation of metals with the combined function of stress relaxation and work hardening, which has been reported in multiple experiments. Nevertheless, the effects of different unloading positions and unloading times have not been investigated. In this study, unloading-reloading tests on three materials (AL6061, HSLA and Q195) were conducted. The stress exhibits a rapid rise momentarily upon reloading and stabilizes afterward while the post stress-strain curve deviates up or down from the monotonic tensile curve. The ductility is enhanced by the unloading-reloading process in general. Different unloading positions and unloading times have different degrees of influence on the stretching of these metals. The effect of loading conditions on a medium manganese steel was further studied. The functions to modify the post stress-strain relationship after unloading-reloading were established.
文摘Austenite can be retained at ambient temperature in steels by alloying and processing control. The transformation from austenite to martensite occurs under a certain conditions : thermal or deformation. Stress-strain induced martensitic transformation is important to improve the plasticity of steels which is called transformation induced plasticity (TRIP). Strength-ductility balance of the steels is greatly superior to that of other high strength steels due to the TRIP effect. A new type of steels-TRIP steel is
文摘This paper presents results which concern regularities of propagation of discontinuous zones from mined-out space in rock massif with inclined bedding structure. The dependencies of maximal height of these zones from the inclination angle of productive beds were found. The mechanical model of rock massif was chosen as viscoelastic and transversely isotropic. Finite element method was used for calculation performing. Coulumb-Mohr and maximal elongation criteria were used for determination of discontinuous zones.
文摘The paper discusses geometrical characteristics and strength parameters of fan blades equipped with replaceable active part it end ended to improve the fan adjustability owing to replacement or removal of the active part, which allows the fan to maintain a wide range of ventilation modes.
文摘The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied.Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated.It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well.Moreover,a parametric study has been carried out to investigate the influence of essential parameters on the shear strength parameters of these materials.According to the research,increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials.Furthermore,the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.
基金supported by the Research Project of Chinese Ministry of Education of China(No.113031A)the Basic Scientific Research Business Expenses of Central University of China (Nos.3142015001 and 3142015020)the New Century Talent Supporting Project by Education Ministry of China(No. NCET-11-0837)
文摘The stress,strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal resistivity.Furthermore,the coal resistivity regularity and mechanism were analyzed at different stages of complete stress-strain process,which includes the two kinds of coal body with typical conductive characteristics.The results indicate that coal resistivity with different conductive characteristics has different change rules in complete stress-strain process.It is mainly represented at the densification and flexibility phases before dilatation occurs.The variation of resistivity can be divided into two kinds,named down and up.Dilatation of coal samples occurred between 66%σ_(max) and 87%σ_(max).Because of dilatation,coal resistivity involves sudden change.The overall representation is shifting from reducing into improving or from slow improving into accelerated improving.Thus,coal resistivity always shows an increasing tendency at the plastic stage.After peak stress,coal body enters into failure stage.The expanding and communicating of macro fracture causes further improvement of coal resistivity.The maximum value of resistivity rangeability named λ reached 3.49.Through making real-time monitoring on coal resistivity,variation rules of resistivity can be deemed as precursory information so as to reflect the dilatation and sudden change before coal body reaches buckling failure,which can provide a new technological means for forecasting the dynamic disaster of coal petrography.
基金supports provided by Natural Science Foundation of Shanghai(contract No.03ZR14022)the“Tenth Five”National Key Technological Research and Development Program(contract No.2001BA803B03)National Natural Science Foundation of China(contract No.50225517)are gratefully acknowledged.
文摘In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.
文摘A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual phase (DP) steels with two different martensite volume fractions. The results show that there exist great differences in the stress-strain contribution of martensite and ferrite to DP steel. The stress-strain partitioning coefficient is not constant in the whole strain range, but decreases with increasing the true strain of DP steel. The softening effect caused by the dilution of carbon concentration in martensite with the increase of martensite volume fraction has great influence on the strain contribution of martensite. The strain ratio of ferrite to martensite almost linearly increases with increasing the true strain of DP steel when the martensite volume fraction is 22%, because martensite always keeps elastic. But the strain ratio of ferrite to martensite varies indistinctively with the further increase in true strain of DP steel above 0.034 when the martensite volume fraction is 50%, because plastic deformation happens in martensite. The stress ratio of martensite to ferrite decreases monotonously with increasing the true strain of DP steel whether the martensite volume fraction is 22% or 50%.
基金Supported by the Fund of Hunan Provincial Construction Department(No.06-468-8)
文摘The mechanical performance of recycled aggregate concrete (RAC) is investigated. An experiment on the complete stress-strain curve under uniaxial compression loading of RAC is carried out. The experimental results indicate that the peak stress, peak strain, secant modulus of the peak point and original point increase with the strength grade of RAC enhanced. On the contrary, the residual stress of RAC decreases with the strength grade enhancing, and the failure of RAC is often broken at the interface between the recycled aggregate and the mortar matrix. Finally, the constitutive model of stress-strain model of RAC has been constituted, and the results from the constitutive model of stress-strain meet the experiment results very well.
