Hydrogen dissolved from the moisture or the wire filler is formed on the surface of welded joint due to the driving of high-energy heat source.The diffused hydrogen in the welded joint could cause hydrogen embrittleme...Hydrogen dissolved from the moisture or the wire filler is formed on the surface of welded joint due to the driving of high-energy heat source.The diffused hydrogen in the welded joint could cause hydrogen embrittlement(HE).The important factors determining the HE resistance of welded joints are microstructure style,dislocation distribution,grains characteristics,precipitate particle,and residual stress.Different welding technologies show various heat sources and heat cycles,which result in different characteristics of fusion zone and heat-affected zone.Thus,the HE fracture behavior of welded joint produced by different welded technologies differs greatly.The current stage of HE behavior of welded joint was reviewed to provide fundamental reference for the scientists and engineers engaging in welding.The appearance of hydrogen atoms in the surface or interior of welded joint could weaken the bonding strength and change the fracture mode from ductile to sudden brittle fracture.Generally,the controlling of filler wire and heat input is a practical route to obtain the excellent welded joint with high HE resistance.The inhibition of hydrogen diffusion via the formation of fine coating and the aggregation of hydrogen atoms via the control of microstructure and precipitates are the effective routes to improve HE resistance.展开更多
The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most stud...The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most studies focus on macroscopic fracture mechanical properties,and the mechanism linking the macroscopic fracture with the microcrack growth during the cyclic dynamic direct tensile loading of brittle rocks is rarely studied.In this paper,a micro-macro fracture model explaining the stress-strain constitutive relationship is established at the last impact failure after being subjected to multiple cyclic direct tensile impacts of brittle rocks.This model is based on the wing crack extension model under direct tensile loading,the quasi-static and dynamic fracture toughness relationship,the suggested crack rate and strain rate relationship,the relationship of damage and dynamic tensile fatigue life N,the relationship of dynamic fracture toughness and dynamic tensile fatigue life N.The variations of dynamic mechanical properties of rocks with dynamic tensile fatigue life for different initial crack sizes and angles within the rocks are further discussed.The compressive strength,elastic modulus,crack initiation stress,limit crack extension length and crack extension rate descend and the failure strain ascends with an increment of dynamic tensile fatigue life in rocks.This study's results provide help for the safety and stability of the underground surrounding rocks under blasting working or seismic disasters.展开更多
Metallic materials,although composed of metallic bonds,exhibit a wide range of mechanical properties:some are ductile and deformable,while others undergo a pronounced ductile-to-brittle transition(DBT),displaying cera...Metallic materials,although composed of metallic bonds,exhibit a wide range of mechanical properties:some are ductile and deformable,while others undergo a pronounced ductile-to-brittle transition(DBT),displaying ceramic-like brittle behavior once below a critical temperature.For decades,the dominant mechanism driving the ductile-to-brittle transition of metals-whether dislocation nucleation or dislocation slip-has been a topic of ongoing debate.A new concept of dislocation source efficiency,however,suggests that both processes are complementary and essential for overall ductile deformation.The relative mobility of screw versus edge dislocations dictates the efficiency of dislocation sources,which in turn governs dislocation multiplication and ultimately the material’s ability to plastic deformation.Furthermore,we developed a new model that incorporates factors affecting dislocation activities,such as the initial dislocation density and the number of dislocation sources,offering promising toughening strategies for both metallic structural alloys and ceramics.展开更多
The phase field model can coherently address the relatively complex fracture phenomenon,such as crack nucleation,branching,deflection,etc.The model has been extensively implemented in the finite element package Abaqus...The phase field model can coherently address the relatively complex fracture phenomenon,such as crack nucleation,branching,deflection,etc.The model has been extensively implemented in the finite element package Abaqus to solve brittle fracture problems in recent studies.However,accurate numerical analysis typically requires fine meshes to model the evolving crack path effectively.A broad region must be discretized without prior knowledge of the crack path,further augmenting the computational expenses.In this proposed work,we present an automated framework utilizing a posteriori error-indicator(MISESERI)to demarcate and sufficiently refine the mesh along the anticipated crack path.This eliminates the need for manual mesh refinement based on previous experimental/computational results or heuristic judgment.The proposed Python-based framework integrates the preanalysis,sufficient mesh refinement,and subsequent phase-field model-based numerical analysis with user-defined subroutines in a single streamlined pass.The novelty of the proposed work lies in integrating Abaqus’s native error estimation and mesh refinement capability,tailored explicitly for phase-field simulations.The proposed methodology aims to reduce the computational resource requirement,thereby enhancing the efficiency of the phase-field simulations while preserving the solution accuracy,making the framework particularly advantageous for complex fracture problems where the computational/experimental results are limited or unavailable.Several benchmark numerical problems are solved to showcase the effectiveness and accuracy of the proposed approach.The numerical examples present the proposed approach’s efficacy in the case of a complex mixed-mode fracture problem.The results show significant reductions in computational resources compared to traditional phase-field methods,which is promising.展开更多
The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissip...The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissipation(LED)law,a novel compressive damage constitutive model for brittle coal is proposed.Utilizing the energy-defined damage method for mate-rials,the LED law is innovatively introduced to accurately characterize the energy dissipation during the loading process,and a novel formula for characterizing the damage variable of brittle coal is proposed.On this basis,considering that the constitutive model based on the hypothesis of strain equivalence is incapable of accurately describing the compaction effect exhibited by coal material during the compression process,a correction coefficient is proposed and apply it in the novel damage constitutive model.The established conventional monotone loading and single-cyclic loading-unloading uniaxial compression damage constitutive models have been validated using experimental data from cylindrical and cuboid coal specimens.In addition,compared with the constitutive model obtained via the traditional energy calculation method based on the hypothesis that the unloading curve is a straight line,the constitutive model employing LED law can describe the stress-strain state of brittle coal more precisely.This approach introduces a new perspective and enhances the convenience for constructing the constitutive model based on energy theory.展开更多
Brittle materials,such as silicon,glass,and ceramics,are widely used in engineering via adhesive bonding.The assessment of adhesive strength of brittle materials to other adherends is essential for their applications....Brittle materials,such as silicon,glass,and ceramics,are widely used in engineering via adhesive bonding.The assessment of adhesive strength of brittle materials to other adherends is essential for their applications.Compared with metals and composites,for which standard testing methods have been established,the experimental method for brittle adherends has been much less explored.During the adhesive strength test,the brittleness of these materials makes them prone to failure,rather than the interface.It remains a challenge to measure the adhesive strength of brittle adherends.Here we develop an experimental method to address this issue by using a strap joint specimen with a backing layer.We use a single crystal silicon wafer and two PCB(printed circuit board)strips as adherends to make a strap joint specimen.A steel backing layer is glued to the silicon wafer to prevent the failure of silicon.This method enables the measurement of adhesive strength up to 35 MPa.In contrast,that without backing layer can only measure the adhesive strength below 10 MPa.It is found that the backing layer can reduce the stress in the silicon remarkably,while it has much less effect on the stress in the adhesive layer.We confirm that the backing layer has a negligible effect on the measured adhesive strength but expands the working space greatly.Combining finite element analysis and experiments,we establish the phase diagram for the failure modes.This work provides guidance for the measurement of adhesive strength of brittle materials.展开更多
The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis ...The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis procedures were compared such as Oliver&Pharr and nominal hardness-based methods,which require area function of the indenter,and other methods based on energy,displacement,contact depth,and contact stiffness,which do not require calibration of the indenter.Elastic recovery of the imprint by the Knoop indenter was also utilized to evaluate elastic moduli of brittle solids.Expressions relating HIT/Er and dimensionless nanoindentation variables(e.g.,the ratio of elastic work over total work and the ratio of permanent displacement over maximum displacement)are found to be nonlinear rather than linear for brittle solids.The plastic hardness Hp of brittle solids(except traditional glasses)extracted based on Er is found to be proportional to E_(r)√H_(IT).展开更多
Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth...Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth and progressive failure.However,the theoretical mechanism of the growth direction evolution of the newly generated wing crack during progressive failure has rarely been studied.A novel analytical method is proposed to evaluate the shear stress effect on the progressive compressive failure and microcrack growth direction in brittle rocks.This model consists of the wing crack growth model under the principal compressive stresses,the direction correlation of the general stress,the principal stress and the initial microcrack inclination,and the relationship between the wing crack length and strain.The shear stress effect on the relationship between y-direction stress and wing crack growth and the relationship between y-direction stress and y-direction strain are analyzed.The shear stress effect on the wing crack growth direction during the progressive compressive failure is determined.The initial crack angle effect on the y-direction peak stress and the wing crack growth direction during the progressive compressive failure considering shear stress is also discussed.A crucial conclusion is that the direction of wing crack growth has a U-shaped variation with the growth of the wing crack.The rationality of the analytical results is verified by an experiment and from numerical results.The study results provide theoretical support for the evaluation of the safety and stability of surrounding rocks in deep underground engineering.展开更多
The internal microstructures of rock materials, including mineral heterogeneity and intrinsic microdefects, exert a significant influence on their nonlinear mechanical and cracking behaviors. It is of great significan...The internal microstructures of rock materials, including mineral heterogeneity and intrinsic microdefects, exert a significant influence on their nonlinear mechanical and cracking behaviors. It is of great significance to accurately characterize the actual microstructures and their influence on stress and damage evolution inside the rocks. In this study, an image-based fast Fourier transform (FFT) method is developed for reconstructing the actual rock microstructures by combining it with the digital image processing (DIP) technique. A series of experimental investigations were conducted to acquire information regarding the actual microstructure and the mechanical properties. Based on these experimental evidences, the processed microstructure information, in conjunction with the proposed micromechanical model, is incorporated into the numerical calculation. The proposed image-based FFT method was firstly validated through uniaxial compression tests. Subsequently, it was employed to predict and analyze the influence of microstructure on macroscopic mechanical behaviors, local stress distribution and the internal crack evolution process in brittle rocks. The distribution of feldspar is considerably more heterogeneous and scattered than that of quartz, which results in a greater propensity for the formation of cracks in feldspar. It is observed that initial cracks and new cracks, including intragranular and boundary ones, ultimately coalesce and connect as the primary through cracks, which are predominantly distributed along the boundary of the feldspar. This phenomenon is also predicted by the proposed numerical method. The results indicate that the proposed numerical method provides an effective approach for analyzing, understanding and predicting the nonlinear mechanical and cracking behaviors of brittle rocks by taking into account the actual microstructure characteristics.展开更多
As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stabilit...As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stability of various engineering applications.Based on the pre-peak and post-peak stages of the rock stress-strain curve,this study constructed a brittleness index BI^(*).The index quantifies the ability of rock to resist plastic deformation during the pre-peak crack growth stage and evaluates the intensity of strength drop during the post-peak softening stage.Another index,BII,was established based on the degree of pre-peak elastic energy accumulation and the instability characteristics of post-peak dissipated energy.This index reflects the essential properties of rock failure by revealing the energy evolution mechanism.Furthermore,by defining a damage variable from the energy dissipation over the entire deformation process,an index B_(D)was introduced to evaluate brittleness from the perspective of internal damage development.Triaxial compression and cyclic loading tests were conducted on rocks of different lithologies to evaluate the new index.The influences of confining pressure and lithology on rock brittleness were analyzed,along with the sensitivity analysis of various brittleness index parameters.The results indicated that the proposed brittleness indices accurately distinguish the brittleness differences among various lithologies and show effective consistency with the failure modes of specimens under different confining pressures.Meanwhile,different brittleness indices were affected by confining pressure and lithology to different degrees.The post-peak softening stage of rock played a particularly significant role in brittleness analysis.A brittleness classification system under different confining pressures and lithologies was established.The research results contribute to the enhancement and refinement of the rock brittleness evaluation system.展开更多
The brittleness index(BI)is crucial for predicting engineering sweet spots and designing fracturing operations in shale oil reservoir exploration and development.Seismic amplitude variation with offset(AVO)inversion i...The brittleness index(BI)is crucial for predicting engineering sweet spots and designing fracturing operations in shale oil reservoir exploration and development.Seismic amplitude variation with offset(AVO)inversion is commonly used to obtain the BI.Traditionally,velocity,density,and other parameters are firstly inverted,and the BI is then calculated,which often leads to accumulated errors.Moreover,due to the limited of well-log data in field work areas,AVO inversion typically faces the challenge of limited information,resulting in not high accuracy of BI derived by existing AVO inversion methods.To address these issues,we first derive an AVO forward approximation equation that directly characterizes the BI in P-wave reflection coefficients.Based on this,an intelligent AVO inversion method,which combines the advantages of traditional and intelligent approaches,for directly obtaining the BI is proposed.A TransUnet model is constructed to establish the strong nonlinear mapping relationship between seismic data and the BI.By incorporating a combined objective function that is constrained by both low-frequency parameters and training samples,the challenge of limited samples is effectively addressed,and the direct inversion of the BI is stably achieved.Tests on model data and applications on field data demonstrate the feasibility,advancement,and practicality of the proposed method.展开更多
Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the ...Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the isotropic-based brittleness assessment methods.This study introduces a new quantitative approach to assess shale brittleness anisotropy,integrating anisotro pic elastic responses and tensile fracturing mechanisms.The proposed model effectively reduces uncertainty in the causal relationship between Young's modulus and brittle failure.Comprehensive experimental validation encompassed 18samples from six groups of Chang 7 terrestrial shale in Ordos Basin.The optimal anisotropic tensile strength criterion(N-Z criterion,error<5%)was identified,enhancing the theoretical accuracy of the proposed model.Comparative experimental results demonstrate that the model adeptly predicts brittleness strength and directional variation characteristics across variations in mineral type,content and microstructure,underscoring its effectiveness.Additionally,theoretical predictions on shale samples with different organic matter reveal that brittleness strength and its anisotropy across varying OM are not monotonously decreasing.The research highlights that brittleness characteristics are influenced by both mineral type/content and microstructural distribution.Notably,the prevalence of isotropic brittle minerals is the primary determinant of brittleness strength,positively correlated.Conversely,ductile mineral conte nt(striped skeletal support-type OM and clay)negatively corre lates with brittlene ss strength,acting as se condary controlling factors.The impact of pore-filled OM on brittleness appears negligible.Rock physical modeling base d on equivalent media theory for shale with pore-filled and/or striped OM further elucidates the mechanisms driving these variations.These findings attach great importance in assessment of terrestrial shale geological and engineering"sweet-spots".展开更多
Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a ...Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a statistical damage constitutive model and energy evolution mechanisms.Initially,integrating the principle of effective stress and the Hoek-Brown criterion,a statistical damage constitutive model for gas-bearing coal is established and validated through triaxial compression tests under different gas pressures to verify its accuracy and applicability.Subsequently,employing energy evolution mechanism,two energy characteristic parameters(elastic energy proportion and dissipated energy proportion)are analyzed.Based on the damage stress thresholds,the damage evolution characteristics of gas bearing coal were explored.Finally,by integrating energy characteristic parameters with damage parameters,a novel brittleness index is proposed.The results demonstrate that the theoretical curves derived from the statistical damage constitutive model closely align with the test curves,accurately reflecting the stress−strain characteristics of gas-bearing coal and revealing the stress drop and softening characteristics of coal in the post-peak stage.The shape parameter and scale parameter represent the brittleness and macroscopic strength of the coal,respectively.As gas pressure increases from 1 to 5 MPa,the shape parameter and the scale parameter decrease by 22.18%and 60.45%,respectively,indicating a reduction in both brittleness and strength of the coal.Parameters such as maximum damage rate and peak elastic energy storage limit positively correlate with coal brittleness.The brittleness index effectively captures the brittleness characteristics and reveals a decrease in brittleness and an increase in sensitivity to plastic deformation under higher gas pressure conditions.展开更多
M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This st...M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This study proposes a deformation and aging technique to obtain a high-volume-fraction dispersion distribution of the hard nano-M23C6 phase by changing the nucleation sites from grain boundaries to deformation coherent twin boundaries produced during cold deformation.The M23C6 precipitation-strengthened austenitic stainless steel has a strength of up to 1.4 GPa but maintains favorable plasticity(>11%).This study provides a novel approach for the control of intergranular brittleness in metallic materials.展开更多
Brittleness analysis becomes important when looking for sweet spots in tightoil sandstone reservoirs. Hence, appropriate indices are required as accurate brittleness evaluation criteria. We construct a seismic rock ph...Brittleness analysis becomes important when looking for sweet spots in tightoil sandstone reservoirs. Hence, appropriate indices are required as accurate brittleness evaluation criteria. We construct a seismic rock physics model for tight-oil sandstone reservoirs with vertical fractures. Because of the complexities in lithology and pore structure and the anisotropic characteristics of tight-oil sandstone reservoirs, the proposed model is based on the solid components, pore connectivity, pore type, and fractures to better describe the sandstone reservoir microstructure. Using the model, we analyze the brittleness sensitivity of the elastic parameters in an anisotropic medium and establish a new brittleness index. We show the applicability of the proposed brittleness index for tight-oil sandstone reservoirs by considering the brittleness sensitivity, the rock physics response characteristics, and cross-plots. Compared with conventional brittleness indexes, the new brittleness index has high brittleness sensitivity and it is the highest in oil-bearing brittle zones with relatively high porosity. The results also suggest that the new brittleness index is much more sensitive to elastic properties variations, and thus can presumably better predict the brittleness characteristics of sweet spots in tight-oil sandstone reservoirs.展开更多
A nickel-based superalloy with good corrosion resistance was fabricated by directional solidification, and its microstructure and tensile properties at elevated temperatures were investigated. Microstructure observati...A nickel-based superalloy with good corrosion resistance was fabricated by directional solidification, and its microstructure and tensile properties at elevated temperatures were investigated. Microstructure observations reveal that the γ＇ precipitates are arrayed in the y matrix regularly with some MC, Ni5Hf and M3B2 particles distributed along the grain boundary. The tensile tests exhibit that the tensile properties depend on temperature significantly and demonstrate obvious anomalous yield and intermediate-temperature brittleness （ITB） behavior. Below 650℃, the yield strength decreases slightly but the ultimate tensile strength almost has no change. When the temperature is between 650 ℃ and 750 ℃, the yield and ultimate tensile strengths rise rapidly, and after then they both decrease gradually with temperature increasing further. The elongation has its minimum value at about 700 ℃. The TEM examination exhibits that sharing of the γ＇ by dislocation is almost the main deformation mechanism at low temperatures, but the γ＇ by-pass dominates the deformation at high temperatures. The transition temperature from shearing to by-pass should be around 800 ℃. The anomalous yield and intermediate-temperature brittleness behaviors should be attributed to the high content of γ＇. In addition, the carbides and eutectic structure also contribute some to the ITB behaviors of the alloy.展开更多
A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen wi...A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen with hydraulic pressure applied on its crack surface. Based on the newly derived formula, THM coupling fracture modes （including tensile, shear and mixed fracture mode） can be predicted by a new fracture criterion of stress intensity factor ratio, where the maximum axial load was measured by self-designed THM coupling fracture test. SEM analyses of THM coupling fractured surface indicate that the higher the temperature and hydraulic pressure are and the lower the confining pressure is, the more easily the intergranular （tension） fracture occurs. The transgranular （shear） fracture occurs in the opposite case while the mixed-mode fracture occurs in the middle case. The tested THM coupling fracture mechanisms are in good agreement with the predicted THM coupling fracture modes, which can verify correction of the newly-derived THM coupling stress intensity factor formula.展开更多
As the scale of complex system is growing larger and larger, interferences from internal and outer system can result in the collapse of one subsystem in a complex system. They will not only make one subsystem collapse...As the scale of complex system is growing larger and larger, interferences from internal and outer system can result in the collapse of one subsystem in a complex system. They will not only make one subsystem collapse but also influence the other subsystems. Moreover, the whole complex system can collapse consequently. The mechanism of collapse of complex system is clue to the brittleness of complex system that is presented and argued as the basic characteristic in this paper. It is the brittleness link entropy between subsystems that leads to the collapse of whole system. Effective ways that can be adopted to reduce the brittleness entropy can see the successful control of brittleness.展开更多
Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials.This study demonstrates the susceptibility of non-magne...Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials.This study demonstrates the susceptibility of non-magnetic single-crystal calcium fluoride(CaF_(2))to the magneto-plastic effect.The influence of magneto-plasticity on CaF_(2) was confirmed in micro-deformation tests under a weak magnetic field of 20 mT.The surface pile-up effect was weakened by 10-15 nm along with an enlarged plastic zone and suppressed crack propagation under the influence of the magnetic field.Micro-cutting tests along different crystal orientations on the(111)plane of CaF_(2) revealed an increase in the ductile-brittle transition of the machined surface with the aid of magneto-plasticity where the largest increase in ductile-brittle transition occurred along the[112]orientation from 512 nm to a range of 664-806 nm.Meanwhile,the subsurface damage layer was concurrently thinner under magnetic influence.An anisotropic influence of the magnetic field relative to the single-crystal orientation and the cutting direction was also observed.An analytical model was derived to determine an orientation factor M that successfully describes the anisotropy while considering the single-crystal dislocation behaviour,material fracture toughness,and the orientation of the magnetic field.Previously suggested theoretical mechanism of magneto-plasticity via formation of non-singlet electronic states in defected configurations was confirmed with density functional theory calculations.The successful findings on the influence of a weak magnetic field on plasticity present an opportunity for the adoption of magnetic-assisted micro-cutting of non-magnetic materials.展开更多
Renovation system of urban villages in Xi'an City was evaluated. Influence factors of urban village renovation were analyzed on the basis of brittleness theory, and an evaluation index system established through m...Renovation system of urban villages in Xi'an City was evaluated. Influence factors of urban village renovation were analyzed on the basis of brittleness theory, and an evaluation index system established through multi-level inconsistency decomposing. By incorporating the catastrophe theory with fuzzy mathematical theory, the mathematic model was created, and catastrophe membership function was obtained as well as evaluation results. Policies for the renovation of urban villages and new direction of the renovation were interpreted. The application case proved that catastrophe progression method was objective and effective and it could provide new concepts for the evaluation and adjustment of urban village renovation. Moreover, application of brittleness theory in the research on urban village renovation is of great instruction and reference value for the present urban construction.展开更多
基金supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX24_2524)National Natural Science Foundation of China(No.52005228).
文摘Hydrogen dissolved from the moisture or the wire filler is formed on the surface of welded joint due to the driving of high-energy heat source.The diffused hydrogen in the welded joint could cause hydrogen embrittlement(HE).The important factors determining the HE resistance of welded joints are microstructure style,dislocation distribution,grains characteristics,precipitate particle,and residual stress.Different welding technologies show various heat sources and heat cycles,which result in different characteristics of fusion zone and heat-affected zone.Thus,the HE fracture behavior of welded joint produced by different welded technologies differs greatly.The current stage of HE behavior of welded joint was reviewed to provide fundamental reference for the scientists and engineers engaging in welding.The appearance of hydrogen atoms in the surface or interior of welded joint could weaken the bonding strength and change the fracture mode from ductile to sudden brittle fracture.Generally,the controlling of filler wire and heat input is a practical route to obtain the excellent welded joint with high HE resistance.The inhibition of hydrogen diffusion via the formation of fine coating and the aggregation of hydrogen atoms via the control of microstructure and precipitates are the effective routes to improve HE resistance.
基金supported by the National Natural Science Foundation of China(Grant Nos.51708016,52438007 and 12172036)the R&D program of Beijing Municipal Education Commission(Grant No.KM202110016014)+1 种基金the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20200307)the Graduate Innovation Program of Beijing University of Civil Engineering and Architecture(Grant No.PG2025060).
文摘The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most studies focus on macroscopic fracture mechanical properties,and the mechanism linking the macroscopic fracture with the microcrack growth during the cyclic dynamic direct tensile loading of brittle rocks is rarely studied.In this paper,a micro-macro fracture model explaining the stress-strain constitutive relationship is established at the last impact failure after being subjected to multiple cyclic direct tensile impacts of brittle rocks.This model is based on the wing crack extension model under direct tensile loading,the quasi-static and dynamic fracture toughness relationship,the suggested crack rate and strain rate relationship,the relationship of damage and dynamic tensile fatigue life N,the relationship of dynamic fracture toughness and dynamic tensile fatigue life N.The variations of dynamic mechanical properties of rocks with dynamic tensile fatigue life for different initial crack sizes and angles within the rocks are further discussed.The compressive strength,elastic modulus,crack initiation stress,limit crack extension length and crack extension rate descend and the failure strain ascends with an increment of dynamic tensile fatigue life in rocks.This study's results provide help for the safety and stability of the underground surrounding rocks under blasting working or seismic disasters.
基金supported by the National Natural Science Foundation of China(Grant Nos.51971170 and 51922082)。
文摘Metallic materials,although composed of metallic bonds,exhibit a wide range of mechanical properties:some are ductile and deformable,while others undergo a pronounced ductile-to-brittle transition(DBT),displaying ceramic-like brittle behavior once below a critical temperature.For decades,the dominant mechanism driving the ductile-to-brittle transition of metals-whether dislocation nucleation or dislocation slip-has been a topic of ongoing debate.A new concept of dislocation source efficiency,however,suggests that both processes are complementary and essential for overall ductile deformation.The relative mobility of screw versus edge dislocations dictates the efficiency of dislocation sources,which in turn governs dislocation multiplication and ultimately the material’s ability to plastic deformation.Furthermore,we developed a new model that incorporates factors affecting dislocation activities,such as the initial dislocation density and the number of dislocation sources,offering promising toughening strategies for both metallic structural alloys and ceramics.
文摘The phase field model can coherently address the relatively complex fracture phenomenon,such as crack nucleation,branching,deflection,etc.The model has been extensively implemented in the finite element package Abaqus to solve brittle fracture problems in recent studies.However,accurate numerical analysis typically requires fine meshes to model the evolving crack path effectively.A broad region must be discretized without prior knowledge of the crack path,further augmenting the computational expenses.In this proposed work,we present an automated framework utilizing a posteriori error-indicator(MISESERI)to demarcate and sufficiently refine the mesh along the anticipated crack path.This eliminates the need for manual mesh refinement based on previous experimental/computational results or heuristic judgment.The proposed Python-based framework integrates the preanalysis,sufficient mesh refinement,and subsequent phase-field model-based numerical analysis with user-defined subroutines in a single streamlined pass.The novelty of the proposed work lies in integrating Abaqus’s native error estimation and mesh refinement capability,tailored explicitly for phase-field simulations.The proposed methodology aims to reduce the computational resource requirement,thereby enhancing the efficiency of the phase-field simulations while preserving the solution accuracy,making the framework particularly advantageous for complex fracture problems where the computational/experimental results are limited or unavailable.Several benchmark numerical problems are solved to showcase the effectiveness and accuracy of the proposed approach.The numerical examples present the proposed approach’s efficacy in the case of a complex mixed-mode fracture problem.The results show significant reductions in computational resources compared to traditional phase-field methods,which is promising.
基金supported by the National Science Fund for Distinguished Young Scholars(52225403)the National Natural Science Foundation of China(42077244).
文摘The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissipation(LED)law,a novel compressive damage constitutive model for brittle coal is proposed.Utilizing the energy-defined damage method for mate-rials,the LED law is innovatively introduced to accurately characterize the energy dissipation during the loading process,and a novel formula for characterizing the damage variable of brittle coal is proposed.On this basis,considering that the constitutive model based on the hypothesis of strain equivalence is incapable of accurately describing the compaction effect exhibited by coal material during the compression process,a correction coefficient is proposed and apply it in the novel damage constitutive model.The established conventional monotone loading and single-cyclic loading-unloading uniaxial compression damage constitutive models have been validated using experimental data from cylindrical and cuboid coal specimens.In addition,compared with the constitutive model obtained via the traditional energy calculation method based on the hypothesis that the unloading curve is a straight line,the constitutive model employing LED law can describe the stress-strain state of brittle coal more precisely.This approach introduces a new perspective and enhances the convenience for constructing the constitutive model based on energy theory.
基金supported by the National Key R&D Program of China(2021YFB3201700).
文摘Brittle materials,such as silicon,glass,and ceramics,are widely used in engineering via adhesive bonding.The assessment of adhesive strength of brittle materials to other adherends is essential for their applications.Compared with metals and composites,for which standard testing methods have been established,the experimental method for brittle adherends has been much less explored.During the adhesive strength test,the brittleness of these materials makes them prone to failure,rather than the interface.It remains a challenge to measure the adhesive strength of brittle adherends.Here we develop an experimental method to address this issue by using a strap joint specimen with a backing layer.We use a single crystal silicon wafer and two PCB(printed circuit board)strips as adherends to make a strap joint specimen.A steel backing layer is glued to the silicon wafer to prevent the failure of silicon.This method enables the measurement of adhesive strength up to 35 MPa.In contrast,that without backing layer can only measure the adhesive strength below 10 MPa.It is found that the backing layer can reduce the stress in the silicon remarkably,while it has much less effect on the stress in the adhesive layer.We confirm that the backing layer has a negligible effect on the measured adhesive strength but expands the working space greatly.Combining finite element analysis and experiments,we establish the phase diagram for the failure modes.This work provides guidance for the measurement of adhesive strength of brittle materials.
基金supported by the National Natural Science Foundation of China (Grant No.51705082)Fujian Provincial Minjiang Scholar Program (Grant No.0020-510759)+1 种基金Qishan Sholar program in Fuzhou University (Grant No.0020-650289)Fuzhou University Testing Fund of precious apparatus (Grant No.2023T018).
文摘The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis procedures were compared such as Oliver&Pharr and nominal hardness-based methods,which require area function of the indenter,and other methods based on energy,displacement,contact depth,and contact stiffness,which do not require calibration of the indenter.Elastic recovery of the imprint by the Knoop indenter was also utilized to evaluate elastic moduli of brittle solids.Expressions relating HIT/Er and dimensionless nanoindentation variables(e.g.,the ratio of elastic work over total work and the ratio of permanent displacement over maximum displacement)are found to be nonlinear rather than linear for brittle solids.The plastic hardness Hp of brittle solids(except traditional glasses)extracted based on Er is found to be proportional to E_(r)√H_(IT).
基金National Natural Science Foundation of China,Grant/Award Numbers:51708016,12172036R&D Program of Beijing Municipal Education Commission,Grant/Award Number:KM202110016014+1 种基金Government of Perm Krai,Research Project,Grant/Award Numbers:СED-26-08-08-28,С-26/628Graduate Innovation Program of Beijing University of Civil Engineering and Architecture,Grant/Award Number:PG2024035。
文摘Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth and progressive failure.However,the theoretical mechanism of the growth direction evolution of the newly generated wing crack during progressive failure has rarely been studied.A novel analytical method is proposed to evaluate the shear stress effect on the progressive compressive failure and microcrack growth direction in brittle rocks.This model consists of the wing crack growth model under the principal compressive stresses,the direction correlation of the general stress,the principal stress and the initial microcrack inclination,and the relationship between the wing crack length and strain.The shear stress effect on the relationship between y-direction stress and wing crack growth and the relationship between y-direction stress and y-direction strain are analyzed.The shear stress effect on the wing crack growth direction during the progressive compressive failure is determined.The initial crack angle effect on the y-direction peak stress and the wing crack growth direction during the progressive compressive failure considering shear stress is also discussed.A crucial conclusion is that the direction of wing crack growth has a U-shaped variation with the growth of the wing crack.The rationality of the analytical results is verified by an experiment and from numerical results.The study results provide theoretical support for the evaluation of the safety and stability of surrounding rocks in deep underground engineering.
基金supported by the National Natural Science Foundation of China(Grant No.11802332)the China Scholarship Council(Grant No.202206435003)the Fundamental Research Funds for the Central Universities(Grant No.2024ZKPYLJ03).
文摘The internal microstructures of rock materials, including mineral heterogeneity and intrinsic microdefects, exert a significant influence on their nonlinear mechanical and cracking behaviors. It is of great significance to accurately characterize the actual microstructures and their influence on stress and damage evolution inside the rocks. In this study, an image-based fast Fourier transform (FFT) method is developed for reconstructing the actual rock microstructures by combining it with the digital image processing (DIP) technique. A series of experimental investigations were conducted to acquire information regarding the actual microstructure and the mechanical properties. Based on these experimental evidences, the processed microstructure information, in conjunction with the proposed micromechanical model, is incorporated into the numerical calculation. The proposed image-based FFT method was firstly validated through uniaxial compression tests. Subsequently, it was employed to predict and analyze the influence of microstructure on macroscopic mechanical behaviors, local stress distribution and the internal crack evolution process in brittle rocks. The distribution of feldspar is considerably more heterogeneous and scattered than that of quartz, which results in a greater propensity for the formation of cracks in feldspar. It is observed that initial cracks and new cracks, including intragranular and boundary ones, ultimately coalesce and connect as the primary through cracks, which are predominantly distributed along the boundary of the feldspar. This phenomenon is also predicted by the proposed numerical method. The results indicate that the proposed numerical method provides an effective approach for analyzing, understanding and predicting the nonlinear mechanical and cracking behaviors of brittle rocks by taking into account the actual microstructure characteristics.
基金support from the National Natural Science Foundation of China(Grant Nos.12072102 and 12102129).
文摘As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stability of various engineering applications.Based on the pre-peak and post-peak stages of the rock stress-strain curve,this study constructed a brittleness index BI^(*).The index quantifies the ability of rock to resist plastic deformation during the pre-peak crack growth stage and evaluates the intensity of strength drop during the post-peak softening stage.Another index,BII,was established based on the degree of pre-peak elastic energy accumulation and the instability characteristics of post-peak dissipated energy.This index reflects the essential properties of rock failure by revealing the energy evolution mechanism.Furthermore,by defining a damage variable from the energy dissipation over the entire deformation process,an index B_(D)was introduced to evaluate brittleness from the perspective of internal damage development.Triaxial compression and cyclic loading tests were conducted on rocks of different lithologies to evaluate the new index.The influences of confining pressure and lithology on rock brittleness were analyzed,along with the sensitivity analysis of various brittleness index parameters.The results indicated that the proposed brittleness indices accurately distinguish the brittleness differences among various lithologies and show effective consistency with the failure modes of specimens under different confining pressures.Meanwhile,different brittleness indices were affected by confining pressure and lithology to different degrees.The post-peak softening stage of rock played a particularly significant role in brittleness analysis.A brittleness classification system under different confining pressures and lithologies was established.The research results contribute to the enhancement and refinement of the rock brittleness evaluation system.
基金supposed by the National Nature Science Foundation of China(Grant No.42304131)the Natural Science Foundation of Heilongjiang Province(Grant No.LH2023D012)+1 种基金the Heilongjiang Postdoctoral Fund(Grant No.LBH-Z22092)the Basic Research Fund for Universities in Xinjiang Uygur Autonomous Region(Grant No.XJEDU2023P166)。
文摘The brittleness index(BI)is crucial for predicting engineering sweet spots and designing fracturing operations in shale oil reservoir exploration and development.Seismic amplitude variation with offset(AVO)inversion is commonly used to obtain the BI.Traditionally,velocity,density,and other parameters are firstly inverted,and the BI is then calculated,which often leads to accumulated errors.Moreover,due to the limited of well-log data in field work areas,AVO inversion typically faces the challenge of limited information,resulting in not high accuracy of BI derived by existing AVO inversion methods.To address these issues,we first derive an AVO forward approximation equation that directly characterizes the BI in P-wave reflection coefficients.Based on this,an intelligent AVO inversion method,which combines the advantages of traditional and intelligent approaches,for directly obtaining the BI is proposed.A TransUnet model is constructed to establish the strong nonlinear mapping relationship between seismic data and the BI.By incorporating a combined objective function that is constrained by both low-frequency parameters and training samples,the challenge of limited samples is effectively addressed,and the direct inversion of the BI is stably achieved.Tests on model data and applications on field data demonstrate the feasibility,advancement,and practicality of the proposed method.
基金supported by the National Natural Science Foundation of China(42274175)Sichuan Provincial Joint Fund Project for Science,Technology and Education(2025NSFSC2035)Innovative Experimental Project at Institutions of Higher Education in Sichuan Province(Advanced Quantitative Rock Physics Investigations on the"Acoustic,Electrical,and Mechanical"Characte ristics of Unco nventional Reservoirs Subjected to Extre meHigh Temperature and High Pressure Environments)。
文摘Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the isotropic-based brittleness assessment methods.This study introduces a new quantitative approach to assess shale brittleness anisotropy,integrating anisotro pic elastic responses and tensile fracturing mechanisms.The proposed model effectively reduces uncertainty in the causal relationship between Young's modulus and brittle failure.Comprehensive experimental validation encompassed 18samples from six groups of Chang 7 terrestrial shale in Ordos Basin.The optimal anisotropic tensile strength criterion(N-Z criterion,error<5%)was identified,enhancing the theoretical accuracy of the proposed model.Comparative experimental results demonstrate that the model adeptly predicts brittleness strength and directional variation characteristics across variations in mineral type,content and microstructure,underscoring its effectiveness.Additionally,theoretical predictions on shale samples with different organic matter reveal that brittleness strength and its anisotropy across varying OM are not monotonously decreasing.The research highlights that brittleness characteristics are influenced by both mineral type/content and microstructural distribution.Notably,the prevalence of isotropic brittle minerals is the primary determinant of brittleness strength,positively correlated.Conversely,ductile mineral conte nt(striped skeletal support-type OM and clay)negatively corre lates with brittlene ss strength,acting as se condary controlling factors.The impact of pore-filled OM on brittleness appears negligible.Rock physical modeling base d on equivalent media theory for shale with pore-filled and/or striped OM further elucidates the mechanisms driving these variations.These findings attach great importance in assessment of terrestrial shale geological and engineering"sweet-spots".
基金Project(52274096)supported by the National Natural Science Foundation of ChinaProject(WS2023A03)supported by the State Key Laboratory Cultivation Base for Gas Geology and Gas Control,China。
文摘Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a statistical damage constitutive model and energy evolution mechanisms.Initially,integrating the principle of effective stress and the Hoek-Brown criterion,a statistical damage constitutive model for gas-bearing coal is established and validated through triaxial compression tests under different gas pressures to verify its accuracy and applicability.Subsequently,employing energy evolution mechanism,two energy characteristic parameters(elastic energy proportion and dissipated energy proportion)are analyzed.Based on the damage stress thresholds,the damage evolution characteristics of gas bearing coal were explored.Finally,by integrating energy characteristic parameters with damage parameters,a novel brittleness index is proposed.The results demonstrate that the theoretical curves derived from the statistical damage constitutive model closely align with the test curves,accurately reflecting the stress−strain characteristics of gas-bearing coal and revealing the stress drop and softening characteristics of coal in the post-peak stage.The shape parameter and scale parameter represent the brittleness and macroscopic strength of the coal,respectively.As gas pressure increases from 1 to 5 MPa,the shape parameter and the scale parameter decrease by 22.18%and 60.45%,respectively,indicating a reduction in both brittleness and strength of the coal.Parameters such as maximum damage rate and peak elastic energy storage limit positively correlate with coal brittleness.The brittleness index effectively captures the brittleness characteristics and reveals a decrease in brittleness and an increase in sensitivity to plastic deformation under higher gas pressure conditions.
基金supported by the National Natural Science Foundation of China(No.52250130).
文摘M23C6 chromium-rich carbides are common grain-boundary precipitations in Cr-containing steel.The presence of grain-boundary carbides often leads to intergranular brittleness and decreases mechanical properties.This study proposes a deformation and aging technique to obtain a high-volume-fraction dispersion distribution of the hard nano-M23C6 phase by changing the nucleation sites from grain boundaries to deformation coherent twin boundaries produced during cold deformation.The M23C6 precipitation-strengthened austenitic stainless steel has a strength of up to 1.4 GPa but maintains favorable plasticity(>11%).This study provides a novel approach for the control of intergranular brittleness in metallic materials.
基金supported by the National 973 project(Nos.2014CB239006 and 2011CB202402)the National Natural Science Foundation of China(Nos.41104069 and 41274124)+1 种基金Sinopec project(No.KJWX2014-05)the Fundamental Research Funds for the Central Universities(No.R1401005A)
文摘Brittleness analysis becomes important when looking for sweet spots in tightoil sandstone reservoirs. Hence, appropriate indices are required as accurate brittleness evaluation criteria. We construct a seismic rock physics model for tight-oil sandstone reservoirs with vertical fractures. Because of the complexities in lithology and pore structure and the anisotropic characteristics of tight-oil sandstone reservoirs, the proposed model is based on the solid components, pore connectivity, pore type, and fractures to better describe the sandstone reservoir microstructure. Using the model, we analyze the brittleness sensitivity of the elastic parameters in an anisotropic medium and establish a new brittleness index. We show the applicability of the proposed brittleness index for tight-oil sandstone reservoirs by considering the brittleness sensitivity, the rock physics response characteristics, and cross-plots. Compared with conventional brittleness indexes, the new brittleness index has high brittleness sensitivity and it is the highest in oil-bearing brittle zones with relatively high porosity. The results also suggest that the new brittleness index is much more sensitive to elastic properties variations, and thus can presumably better predict the brittleness characteristics of sweet spots in tight-oil sandstone reservoirs.
基金Projects(2012BAI18B05,2012BAI18B01)supported by the Twelfth Five-Year National Science&Technology Support Program of ChinaProject(2009CB93004)supported by the National Basic Researh Program of China
文摘A nickel-based superalloy with good corrosion resistance was fabricated by directional solidification, and its microstructure and tensile properties at elevated temperatures were investigated. Microstructure observations reveal that the γ＇ precipitates are arrayed in the y matrix regularly with some MC, Ni5Hf and M3B2 particles distributed along the grain boundary. The tensile tests exhibit that the tensile properties depend on temperature significantly and demonstrate obvious anomalous yield and intermediate-temperature brittleness （ITB） behavior. Below 650℃, the yield strength decreases slightly but the ultimate tensile strength almost has no change. When the temperature is between 650 ℃ and 750 ℃, the yield and ultimate tensile strengths rise rapidly, and after then they both decrease gradually with temperature increasing further. The elongation has its minimum value at about 700 ℃. The TEM examination exhibits that sharing of the γ＇ by dislocation is almost the main deformation mechanism at low temperatures, but the γ＇ by-pass dominates the deformation at high temperatures. The transition temperature from shearing to by-pass should be around 800 ℃. The anomalous yield and intermediate-temperature brittleness behaviors should be attributed to the high content of γ＇. In addition, the carbides and eutectic structure also contribute some to the ITB behaviors of the alloy.
基金Project(11072269)supported by the National Natural Science Foundation of ChinaProject(20090162110066)supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen with hydraulic pressure applied on its crack surface. Based on the newly derived formula, THM coupling fracture modes （including tensile, shear and mixed fracture mode） can be predicted by a new fracture criterion of stress intensity factor ratio, where the maximum axial load was measured by self-designed THM coupling fracture test. SEM analyses of THM coupling fractured surface indicate that the higher the temperature and hydraulic pressure are and the lower the confining pressure is, the more easily the intergranular （tension） fracture occurs. The transgranular （shear） fracture occurs in the opposite case while the mixed-mode fracture occurs in the middle case. The tested THM coupling fracture mechanisms are in good agreement with the predicted THM coupling fracture modes, which can verify correction of the newly-derived THM coupling stress intensity factor formula.
文摘As the scale of complex system is growing larger and larger, interferences from internal and outer system can result in the collapse of one subsystem in a complex system. They will not only make one subsystem collapse but also influence the other subsystems. Moreover, the whole complex system can collapse consequently. The mechanism of collapse of complex system is clue to the brittleness of complex system that is presented and argued as the basic characteristic in this paper. It is the brittleness link entropy between subsystems that leads to the collapse of whole system. Effective ways that can be adopted to reduce the brittleness entropy can see the successful control of brittleness.
基金supported by the Ministry of Education,Singapore,under its Academic Research Funds(Grant Nos.:MOE-T2EP50120-0010,MOE-T2EP50220-0010)the funding from the Ministère des Relations Internationales et de la Francophonie du Québec,Coopération Québec-Singapour,with which this work was partially supported。
文摘Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials.This study demonstrates the susceptibility of non-magnetic single-crystal calcium fluoride(CaF_(2))to the magneto-plastic effect.The influence of magneto-plasticity on CaF_(2) was confirmed in micro-deformation tests under a weak magnetic field of 20 mT.The surface pile-up effect was weakened by 10-15 nm along with an enlarged plastic zone and suppressed crack propagation under the influence of the magnetic field.Micro-cutting tests along different crystal orientations on the(111)plane of CaF_(2) revealed an increase in the ductile-brittle transition of the machined surface with the aid of magneto-plasticity where the largest increase in ductile-brittle transition occurred along the[112]orientation from 512 nm to a range of 664-806 nm.Meanwhile,the subsurface damage layer was concurrently thinner under magnetic influence.An anisotropic influence of the magnetic field relative to the single-crystal orientation and the cutting direction was also observed.An analytical model was derived to determine an orientation factor M that successfully describes the anisotropy while considering the single-crystal dislocation behaviour,material fracture toughness,and the orientation of the magnetic field.Previously suggested theoretical mechanism of magneto-plasticity via formation of non-singlet electronic states in defected configurations was confirmed with density functional theory calculations.The successful findings on the influence of a weak magnetic field on plasticity present an opportunity for the adoption of magnetic-assisted micro-cutting of non-magnetic materials.
文摘Renovation system of urban villages in Xi'an City was evaluated. Influence factors of urban village renovation were analyzed on the basis of brittleness theory, and an evaluation index system established through multi-level inconsistency decomposing. By incorporating the catastrophe theory with fuzzy mathematical theory, the mathematic model was created, and catastrophe membership function was obtained as well as evaluation results. Policies for the renovation of urban villages and new direction of the renovation were interpreted. The application case proved that catastrophe progression method was objective and effective and it could provide new concepts for the evaluation and adjustment of urban village renovation. Moreover, application of brittleness theory in the research on urban village renovation is of great instruction and reference value for the present urban construction.
