The combustion and detonation processes of energetic materials exhibit remarkable complexity and ultra-fast transient characteristics.While reactive molecular dynamics has been extensively employed to investigate the ...The combustion and detonation processes of energetic materials exhibit remarkable complexity and ultra-fast transient characteristics.While reactive molecular dynamics has been extensively employed to investigate the reaction dynamics of energetic materials,its utility is often constrained to capturing only fundamental reaction events and species information,thereby limiting mechanistic investigations of complex reaction pathways.To elucidate the topological features of energetic material reaction networks and identify critical reaction pathways with high fidelity,this study presents ReacNetwork-an advanced large-scale reaction network analysis methodology that synergistically integrates complex network theory with molecular simulation techniques.Specifically,we have developed a multi-dimensional feature screening protocol based on node centrality metrics and K-shell decomposition algorithms.Takingα-Hexahydro-1,3,5-trinitro-1,3,5-triazine(α-RDX)as the subject,we successfully constructed a comprehensive high-temperature thermal decomposition reaction network consisting of 1,134 distinct chemical species and 3,626 elementary reactions.Through systematic application of community detection algorithms and global topological feature extraction techniques,we achieved effective dimensionality reduction and successfully identified the dominant reaction pathway within theα-RDX thermal decomposition network.The computational results not only validate the well-established initial reaction mechanism dominated by N-NO2 homolytic bond cleavage,but also provide unprecedented visualization ofα-RDX framework ring-opening dynamics and subsequent radical chain propagation networks.展开更多
Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture ...Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture mechanics analysis.These two classes of problems respectively embody material non-uniformity and geometric discontinuity,thereby imposing more stringent requirements on numerical methods in terms of high-order field continuity and accurate defect representation.Based on the classical Kirchhoff-Love plate theory,a numerical manifold method(MLS-NMM)incorporating moving least squares(MLS)interpolation is developed for bending analysis of FGM plates and fracture simulation of homogeneous plates with defects.The method constructs an H^(2)-regular approximation with high-order continuous weighting functions and,combined with the separation of mathematical and physical covers,establishes a unified framework that accurately handles material gradients and cracks without mesh reconstruction.For the crack tip,a singular physical cover incorporating the Williams asymptotic field is introduced to achieve local enrichment,enabling the natural capture of displacement discontinuity and stress singularity.Stress intensity factors are extracted using the interaction integral method,and the dimensionless J-integral shows a maximum relative error below 1.2%compared with the reference solution.Numerical results indicate that MLS-NMM exhibits excellent convergence performance:using 676 mathematical nodes,the nondimensional central deflection of both FGM and homogeneous plates agrees with reference solutions with a maximum relative error below 0.81%,and no shear locking occurs.A systematic analysis reveals that for a simply supported on all four edges(SSSS)FGM square plate with a/h=10,the nondimensional central deflection increases by 212%as the gradient index nrises from 0 to 5.For a homogeneous plate containing a central crack with c/a=0.6,the nondimensional central deflection increases by approximately 46%compared with the intact plate.Under weak boundary constraints(e.g.,SFSF),the deformation is markedly amplified,with the deflection reaching more than three times that under strong constraints(SCSC).The proposed method provides an efficient,reconstruction-free numerical tool for high-accuracy bending and fracture analyses of FGM and cracked thin-plate structures.展开更多
As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal...As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal materials at various scales and dimensions.Conventional methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and interfaces.However,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal materials.From the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear surfaces.The relationship between the fractal dimensions and properties of metal material surfaces and interfaces is summarized.Starting from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be developed.It is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.展开更多
From a life cycle perspective,the material flow analysis is utilized to investigate the lithium material flows in international trade from 2000 to 2019.The results reveal that at the global level,the total volume of l...From a life cycle perspective,the material flow analysis is utilized to investigate the lithium material flows in international trade from 2000 to 2019.The results reveal that at the global level,the total volume of lithium trade grew rapidly,reaching 121116 t in 2019.Lithium trade was dominated by lithium minerals,lithium carbonate and lithium hydroxide rather than final lithium products,indicating an immaturity in global lithium industry.At the intercontinental level,Asia’s import trade and Oceania’s export trade led the world,accounting for 81.22%and 39.68%,respectively.At the national level,China,Japan and Korea became the main importers,while Chile and Australia were the main exporters.In addition,China’s trade volume far exceeded that of the United States.China’s exports were dominated by lithium-ion batteries,while the United States mainly imported lithium-ion batteries,proving that the development of China’s lithium industry was relatively faster.展开更多
This study assesses the potential and benefits of reducing plastic consumption at the institutional level by taking the Beijing Institute of Petrochemical Technology(BIPT)in China as the case.By tracking the plastic m...This study assesses the potential and benefits of reducing plastic consumption at the institutional level by taking the Beijing Institute of Petrochemical Technology(BIPT)in China as the case.By tracking the plastic material flow on the BIPT campus,we provide insights into the efforts required to achieve a plastic-free campus.A mixed-methods approach was employed,encompassing material flow analysis,quantitative analysis of influencing factors,examination of best practices in universities,and market price-based valuation of plastic reduction.The main conclusions are as follows:(1)Each student consumed an average of 9.2 kg of plastics for daily use on BIPT campus in the base year of 2020,with campus canteens,off-campus cafés,and shops(offline and online)contributing to 36%,31%and 30%respectively.(2)BIPT has a reduction potential of 45%,equivalent to 4.1 kg per student annually,yielding benefits of 45 RMB from savings in oil material and production energy,avoiding plastic waste,and reducing carbon emission.(3)If all global tertiary institutions set a target of reducing plastics by 4.1 kg per student,1.94 Mt of plastics could be avoided by 2035.(4)Greater reductions and benefits could be achieved if tertiary institutions extend their efforts across all campus activities,with substantial indirect and long-term contributions ranging from more sustainable campus management to fostering a transition towards a green economy.These findings highlight that plastic-free initiatives require contextual construction and environmental education both on and off campus.展开更多
This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-...This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-oped using the material point method.To reduce the computational cost of Monte Carlo simulations,response surface models are created as surrogate models for the material point system to approximate its dynamic behavior.An adaptive randomized greedy algorithm is employed to construct a sparse polynomial chaos expansion model with a fixed order,effectively balancing the accuracy and computational efficiency of the surrogate model.Based on the sparse polynomial chaos expansion,sensitivity analysis is conducted using the global finite difference and Sobol methods.Several examples of structural dynamics are provided to demonstrate the effectiveness of the proposed method in addressing structural dynamics problems.展开更多
Biomedical applications necessitate natural or synthetic biomaterials that can maintain,improve,or even replace damaged tissue or a biological function,facilitating healing for people who have suffered from an injury ...Biomedical applications necessitate natural or synthetic biomaterials that can maintain,improve,or even replace damaged tissue or a biological function,facilitating healing for people who have suffered from an injury or disease.Metallic biomaterials show superior mechanical properties with greater service life than other materials.Biodegradable materials can avoid the inevitable second operation of removing the implant in the case of temporary implantation,reducing the risk of infections,medical complications,healing time,and cost.Magnesium(Mg),zinc(Zn),iron(Fe),and their alloys are potential biodegradable metallic materials.The characteristics of biodegradable metallic materials are variable and depend on many factors,such as alloying elements,microstructure,existing phases,and thermomechanical treatment.The current review emphasizes the impact of alloying element addition on the characteristics of metallic biodegradable materials,with particular attention to the relationships between alloying elements,microstructure,mechanical performance,corrosion,and biocompatibility.Mg alloys show good mechanical and corrosion properties with excellent biocompatibility.Using biocompatible alloying elements can improve Mg alloy mechanical and corrosion properties without af-fecting their biocompatibility.However,critical limitations are still maintained,like rapid degradation and gas bubble formation.Zn alloys could overcome the limitations of Mg alloys with appropriate degradation rates,ease of casting and processing,and good biocompatibility.Alloying,particularly with Mg,Li,and Cu,combined with thermomechanical treatment,can significantly affect the microstructure and mechanical performance of Zn alloys and overcome the problem of unsuitable mechanical properties.Fe alloys have excellent mechanical performance,formability,and biocompatibility with a low degradation rate.Applying surface treatment,using novel structures,alloying with the appropriate amount of alloying elements,and using advanced manufacturing techniques may present a way to solve the problems associated with biodegradable metallic materials,which could open new horizons and increase their applicability in biomedical applications.展开更多
In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach...In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach adopted and relevant theories in organizing the materials.Then,the teaching plan of this speaking unit is provided and some activities are designed to create an authentic and optimal situation for students to practice their speaking skill.展开更多
To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic...To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic materials,namely,zirconia ceramics(ZrO_(2)),cobalt-chromium alloy(Co-Cr),and titanium-zirconium alloy(Ti-13Zr),under various crack configurations.A three-dimensional finite element model of a single-crown prosthesis incorporating predefined cracks was established,and both axial and oblique multidirectional loads were applied.Using LS-DYNA software,the deformation patterns,principal stress distribution,and energy release characteristics during crack propagation were systematically analyzed.The experimental results indicate that Ti-13Zr alloy exhibited the highest crack resistance,making it particularly suitable for patients with insufficient bone volume or limited implant space.Co-Cr alloy demonstrated favorable structural stability and mechanical performance under high-load conditions.In contrast,due to its inherent brittleness,ZrO_(2)was more prone to rapid fracture propagation in long-span or high-stress scenarios,although it remains a preferred option for anterior esthetic zones and patients with metal sensitivities.Furthermore,the simulation outcomes were theoretically validated using Griffith's energy-based fracture criterion,reinforcing the accuracy of failure predictions based on principal stress analysis.This study elucidates the differences in clinical applicability among prosthetic materials and reveals their distinct fracture mechanisms,thereby providing a theoretical foundation for optimizing material selection and structural design.The findings contribute to improving the long-term safety and functional stability of implant-supported dental restorations.展开更多
The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimiz...The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.展开更多
The erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industr...The erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al_(2)O_(3) spinel partially decomposes,and the released[Mg]reacts with Al_(2)O_(3) inclusions in the steel to form MgO·Al_(2)O_(3) inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al_(2)O_(3) spinel,iron diffuses into the spinel form MgAl_(1.9)Fe_(0.1)O_(4),which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al_(2)O_(3) spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al_(2)O_(3),and MgO·Al_(2)O_(3) spinel forms on the inner wall of the crucible,indicating that floating inclusions adhere to the spinel surface,thereby reducing the incorporation into the steel and improving molten steel cleanliness.These findings provide a theoretical foundation for broader application of MgO·Al_(2)O_(3) spinel as a crucible material in the field of high-quality steel.展开更多
A numerical method is presented for the large deflection in elastic analysis of tensegrity structures including both geometric and material nonlinearities.The geometric nonlinearity is considered based on both total L...A numerical method is presented for the large deflection in elastic analysis of tensegrity structures including both geometric and material nonlinearities.The geometric nonlinearity is considered based on both total Lagrangian and updated Lagrangian formulations,while the material nonlinearity is treated through elastoplastic stress-strain relationship.The nonlinear equilibrium equations are solved using an incremental-iterative scheme in conjunction with the modified Newton-Raphson method.A computer program is developed to predict the mechanical responses of tensegrity systems under tensile,compressive and flexural loadings.Numerical results obtained are compared with those reported in the literature to demonstrate the accuracy and efficiency of the proposed program.The flexural behavior of the double layer quadruplex tensegrity grid is sufficiently good for lightweight large-span structural applications.On the other hand,its bending strength capacity is not sensitive to the self-stress level.展开更多
To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Thr...To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Three different materials （composite resin, ceramage and ceramic） were studied and two loading conditions （vertical and oblique load） were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.展开更多
Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was...Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial field.The temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature results.The thermal deformation was closely related to the temperature difference between the surface and inside of the casting.The numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting material.Also,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.展开更多
Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the...Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the longitudinal direction according to a power law. Taking the solution of the corresponding homogeneous beam as the initial guess and obtaining a convergence region by adjusting an auxiliary parameter, the analytical expressions for large deformation of the AFG beam are provided. Results obtained by the HAM are compared with those obtained by the finite element method and those in the previous works to verify its validity. Good agreement is observed. A detailed parametric study is carried out. The results show that the axial material variation can greatly change the deformed configuration, which provides an approach to control and manage the deformation of beams. By tailoring the axial material distribution, a desired deformed configuration can be obtained for a specific load. The analytical solution presented herein can be a helpful tool for this procedure.展开更多
This paper, based on the material processes and relational processes, aims to analysis the deep meaning of chapter one of Pride and Prejudice. The relevant theories will come first in this paper. I will then analyze t...This paper, based on the material processes and relational processes, aims to analysis the deep meaning of chapter one of Pride and Prejudice. The relevant theories will come first in this paper. I will then analyze this extract from three aspects: the analysis of the objective plane of narration, the analysis of Mrs. Bennet' s discourse and the analysis of Mr. Bennet' s discourse.展开更多
Material dematerialization is a basic approach to reduce the pressure on the resources and environment and to realize the sustainable development. The material flow analysis and decomposition method are used to calcul...Material dematerialization is a basic approach to reduce the pressure on the resources and environment and to realize the sustainable development. The material flow analysis and decomposition method are used to calculate the direct material input (DMI) of 14 typical mining cities in Northeast China in 1995–2004 and to analyze the demateri- alization and its driving factors in the different types of mining cities oriented by coal, petroleum, metallurgy and multi-resources. The results are as follows: 1) from 1995 to 2006, the increase rates of the DMI and the material input intensity of mining cities declined following the order of multi-resources, metallurgy, coal, and petroleum cities, and the material utilizing efficiency did following the order of petroleum, coal, metallurgy, and multi-resources cities; 2) during the research period, all the kinds of mining cities were in the situation of weak sustainable development in most years; 3) the pressure on resources and environment in the multi-resources cities was the most serious; 4) the petro- leum cities showed the strong trend of sustainable development; and 5) in recent years, the driving function of eco- nomic development for material consuming has continuously strengthened and the controlling function of material utilizing efficiency for it has weakened. The key approaches to promote the development of circular economy of min- ing cities in Northeast China are put forward in the following aspects: 1) to strengthen the research and development of the technique of resources’ cycling utilization, 2) to improve the utilizing efficiency of resources, and 3) to carry out the auditing system of resources utilization.展开更多
An analytical solution for buckling of an eccentrically stiffened sandwich truncated conical shell is investigated. The shell consists of two functionally graded material （FGM） coating layers and a core layer which ...An analytical solution for buckling of an eccentrically stiffened sandwich truncated conical shell is investigated. The shell consists of two functionally graded material （FGM） coating layers and a core layer which are metal or ceramic subjected to an axial compressive load and an external uniform pressure. Shells are reinforced by stringers and rings, in which the material properties of shells and stiffeners are graded in the thickness direction following a general sigmoid law distribution. Two models of coated shell-stiffener arrangements are investigated. The change of the spacing between stringers in the meridional direction is taken into account. A couple set of three-variable- coefficient partial differential equations in terms of displacement components are solved by the Galerkin method. A closed-form expression for determining the buckling load is obtained. The numerical examples are presented and compared with previous works.展开更多
This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material ...This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material for the specimens consists of a single hole model(25% void/cell,16% void/cell and 10% void/cell)and a four-hole model(25%void/cell).Using a representative volume element(RVE),we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue.Next,the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part(single hole cell)in the contact area.The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation(DNS)method.Finally,by comparing the computational time and%deviations,we draw conclusions about the reliability and effectiveness of the proposed method.展开更多
A set of constitutive equations are derived based on the authors'lower bound yield loci for porous materials. By using these equations, the conditions for shear localization in porous materials are then investigat...A set of constitutive equations are derived based on the authors'lower bound yield loci for porous materials. By using these equations, the conditions for shear localization in porous materials are then investigated and the results are compared with those of Gurson's equations and the finite element analysis. The advantages of the present constitutive equations are fully illustrated.展开更多
基金support from the National Natural Science Foundation of China(Grant No.22275018).
文摘The combustion and detonation processes of energetic materials exhibit remarkable complexity and ultra-fast transient characteristics.While reactive molecular dynamics has been extensively employed to investigate the reaction dynamics of energetic materials,its utility is often constrained to capturing only fundamental reaction events and species information,thereby limiting mechanistic investigations of complex reaction pathways.To elucidate the topological features of energetic material reaction networks and identify critical reaction pathways with high fidelity,this study presents ReacNetwork-an advanced large-scale reaction network analysis methodology that synergistically integrates complex network theory with molecular simulation techniques.Specifically,we have developed a multi-dimensional feature screening protocol based on node centrality metrics and K-shell decomposition algorithms.Takingα-Hexahydro-1,3,5-trinitro-1,3,5-triazine(α-RDX)as the subject,we successfully constructed a comprehensive high-temperature thermal decomposition reaction network consisting of 1,134 distinct chemical species and 3,626 elementary reactions.Through systematic application of community detection algorithms and global topological feature extraction techniques,we achieved effective dimensionality reduction and successfully identified the dominant reaction pathway within theα-RDX thermal decomposition network.The computational results not only validate the well-established initial reaction mechanism dominated by N-NO2 homolytic bond cleavage,but also provide unprecedented visualization ofα-RDX framework ring-opening dynamics and subsequent radical chain propagation networks.
基金supported by Beijing Natural Science Foundation(L233025)。
文摘Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture mechanics analysis.These two classes of problems respectively embody material non-uniformity and geometric discontinuity,thereby imposing more stringent requirements on numerical methods in terms of high-order field continuity and accurate defect representation.Based on the classical Kirchhoff-Love plate theory,a numerical manifold method(MLS-NMM)incorporating moving least squares(MLS)interpolation is developed for bending analysis of FGM plates and fracture simulation of homogeneous plates with defects.The method constructs an H^(2)-regular approximation with high-order continuous weighting functions and,combined with the separation of mathematical and physical covers,establishes a unified framework that accurately handles material gradients and cracks without mesh reconstruction.For the crack tip,a singular physical cover incorporating the Williams asymptotic field is introduced to achieve local enrichment,enabling the natural capture of displacement discontinuity and stress singularity.Stress intensity factors are extracted using the interaction integral method,and the dimensionless J-integral shows a maximum relative error below 1.2%compared with the reference solution.Numerical results indicate that MLS-NMM exhibits excellent convergence performance:using 676 mathematical nodes,the nondimensional central deflection of both FGM and homogeneous plates agrees with reference solutions with a maximum relative error below 0.81%,and no shear locking occurs.A systematic analysis reveals that for a simply supported on all four edges(SSSS)FGM square plate with a/h=10,the nondimensional central deflection increases by 212%as the gradient index nrises from 0 to 5.For a homogeneous plate containing a central crack with c/a=0.6,the nondimensional central deflection increases by approximately 46%compared with the intact plate.Under weak boundary constraints(e.g.,SFSF),the deformation is markedly amplified,with the deflection reaching more than three times that under strong constraints(SCSC).The proposed method provides an efficient,reconstruction-free numerical tool for high-accuracy bending and fracture analyses of FGM and cracked thin-plate structures.
基金financially supported by the National Key R&D Program of China(No.2022YFE0121300)the National Natural Science Foundation of China(No.52374376)the Introduction Plan for High-end Foreign Experts(No.G2023105001L)。
文摘As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal materials at various scales and dimensions.Conventional methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and interfaces.However,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal materials.From the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear surfaces.The relationship between the fractal dimensions and properties of metal material surfaces and interfaces is summarized.Starting from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be developed.It is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.
基金supported by the National Natural Science Foundation of China(Nos.71671187,71874210,71633006)the Natural Science Foundation of Hunan Province,China(No.2024JJ6539)+1 种基金the National Social Science Fund of China(No.22&ZD098)the Social Sciences Fund of Hunan Province,China(No.24YBQ138)。
文摘From a life cycle perspective,the material flow analysis is utilized to investigate the lithium material flows in international trade from 2000 to 2019.The results reveal that at the global level,the total volume of lithium trade grew rapidly,reaching 121116 t in 2019.Lithium trade was dominated by lithium minerals,lithium carbonate and lithium hydroxide rather than final lithium products,indicating an immaturity in global lithium industry.At the intercontinental level,Asia’s import trade and Oceania’s export trade led the world,accounting for 81.22%and 39.68%,respectively.At the national level,China,Japan and Korea became the main importers,while Chile and Australia were the main exporters.In addition,China’s trade volume far exceeded that of the United States.China’s exports were dominated by lithium-ion batteries,while the United States mainly imported lithium-ion batteries,proving that the development of China’s lithium industry was relatively faster.
基金funded by Key Project of Education and Teaching Reform and Research at Beijing Institute of Petrochemical Technology(ZD20200508).
文摘This study assesses the potential and benefits of reducing plastic consumption at the institutional level by taking the Beijing Institute of Petrochemical Technology(BIPT)in China as the case.By tracking the plastic material flow on the BIPT campus,we provide insights into the efforts required to achieve a plastic-free campus.A mixed-methods approach was employed,encompassing material flow analysis,quantitative analysis of influencing factors,examination of best practices in universities,and market price-based valuation of plastic reduction.The main conclusions are as follows:(1)Each student consumed an average of 9.2 kg of plastics for daily use on BIPT campus in the base year of 2020,with campus canteens,off-campus cafés,and shops(offline and online)contributing to 36%,31%and 30%respectively.(2)BIPT has a reduction potential of 45%,equivalent to 4.1 kg per student annually,yielding benefits of 45 RMB from savings in oil material and production energy,avoiding plastic waste,and reducing carbon emission.(3)If all global tertiary institutions set a target of reducing plastics by 4.1 kg per student,1.94 Mt of plastics could be avoided by 2035.(4)Greater reductions and benefits could be achieved if tertiary institutions extend their efforts across all campus activities,with substantial indirect and long-term contributions ranging from more sustainable campus management to fostering a transition towards a green economy.These findings highlight that plastic-free initiatives require contextual construction and environmental education both on and off campus.
基金support from the National Natural Science Foundation of China(Grant Nos.52174123&52274222).
文摘This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-oped using the material point method.To reduce the computational cost of Monte Carlo simulations,response surface models are created as surrogate models for the material point system to approximate its dynamic behavior.An adaptive randomized greedy algorithm is employed to construct a sparse polynomial chaos expansion model with a fixed order,effectively balancing the accuracy and computational efficiency of the surrogate model.Based on the sparse polynomial chaos expansion,sensitivity analysis is conducted using the global finite difference and Sobol methods.Several examples of structural dynamics are provided to demonstrate the effectiveness of the proposed method in addressing structural dynamics problems.
文摘Biomedical applications necessitate natural or synthetic biomaterials that can maintain,improve,or even replace damaged tissue or a biological function,facilitating healing for people who have suffered from an injury or disease.Metallic biomaterials show superior mechanical properties with greater service life than other materials.Biodegradable materials can avoid the inevitable second operation of removing the implant in the case of temporary implantation,reducing the risk of infections,medical complications,healing time,and cost.Magnesium(Mg),zinc(Zn),iron(Fe),and their alloys are potential biodegradable metallic materials.The characteristics of biodegradable metallic materials are variable and depend on many factors,such as alloying elements,microstructure,existing phases,and thermomechanical treatment.The current review emphasizes the impact of alloying element addition on the characteristics of metallic biodegradable materials,with particular attention to the relationships between alloying elements,microstructure,mechanical performance,corrosion,and biocompatibility.Mg alloys show good mechanical and corrosion properties with excellent biocompatibility.Using biocompatible alloying elements can improve Mg alloy mechanical and corrosion properties without af-fecting their biocompatibility.However,critical limitations are still maintained,like rapid degradation and gas bubble formation.Zn alloys could overcome the limitations of Mg alloys with appropriate degradation rates,ease of casting and processing,and good biocompatibility.Alloying,particularly with Mg,Li,and Cu,combined with thermomechanical treatment,can significantly affect the microstructure and mechanical performance of Zn alloys and overcome the problem of unsuitable mechanical properties.Fe alloys have excellent mechanical performance,formability,and biocompatibility with a low degradation rate.Applying surface treatment,using novel structures,alloying with the appropriate amount of alloying elements,and using advanced manufacturing techniques may present a way to solve the problems associated with biodegradable metallic materials,which could open new horizons and increase their applicability in biomedical applications.
文摘In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach adopted and relevant theories in organizing the materials.Then,the teaching plan of this speaking unit is provided and some activities are designed to create an authentic and optimal situation for students to practice their speaking skill.
基金Funded by the National Key R&D Program of China(No.2023YFC2412300)the Technology Development Project of Shan-dong Weigao Orthopedic Materials Co.,Ltd.(No.20221h0074)the Independent Innovation Research Fund of Wuhan University of Technology(No.104972024ZHZXhp0027)。
文摘To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic materials,namely,zirconia ceramics(ZrO_(2)),cobalt-chromium alloy(Co-Cr),and titanium-zirconium alloy(Ti-13Zr),under various crack configurations.A three-dimensional finite element model of a single-crown prosthesis incorporating predefined cracks was established,and both axial and oblique multidirectional loads were applied.Using LS-DYNA software,the deformation patterns,principal stress distribution,and energy release characteristics during crack propagation were systematically analyzed.The experimental results indicate that Ti-13Zr alloy exhibited the highest crack resistance,making it particularly suitable for patients with insufficient bone volume or limited implant space.Co-Cr alloy demonstrated favorable structural stability and mechanical performance under high-load conditions.In contrast,due to its inherent brittleness,ZrO_(2)was more prone to rapid fracture propagation in long-span or high-stress scenarios,although it remains a preferred option for anterior esthetic zones and patients with metal sensitivities.Furthermore,the simulation outcomes were theoretically validated using Griffith's energy-based fracture criterion,reinforcing the accuracy of failure predictions based on principal stress analysis.This study elucidates the differences in clinical applicability among prosthetic materials and reveals their distinct fracture mechanisms,thereby providing a theoretical foundation for optimizing material selection and structural design.The findings contribute to improving the long-term safety and functional stability of implant-supported dental restorations.
文摘The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.
基金supported by National Key Research and Development Program of China(2021YFB3701404)the National Natural Science Foundation of China(Grant Nos.52174302 and 52304347)+4 种基金the Fundamental Research Funds for the Central Universities(N2409008)Postdoctoral Fellowship Program of CPSF(GZB20230122)Doctoral Start-up Foundation of Liaoning Province(2023-BSBA-107)China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202320)Young Elite Scientist Sponsorship Program by Cast(Grant No.YESS20240132).
文摘The erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al_(2)O_(3) spinel partially decomposes,and the released[Mg]reacts with Al_(2)O_(3) inclusions in the steel to form MgO·Al_(2)O_(3) inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al_(2)O_(3) spinel,iron diffuses into the spinel form MgAl_(1.9)Fe_(0.1)O_(4),which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al_(2)O_(3) spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al_(2)O_(3),and MgO·Al_(2)O_(3) spinel forms on the inner wall of the crucible,indicating that floating inclusions adhere to the spinel surface,thereby reducing the incorporation into the steel and improving molten steel cleanliness.These findings provide a theoretical foundation for broader application of MgO·Al_(2)O_(3) spinel as a crucible material in the field of high-quality steel.
基金support of the research reported here by Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education, Science and Technology (NRF2010-0019373)
文摘A numerical method is presented for the large deflection in elastic analysis of tensegrity structures including both geometric and material nonlinearities.The geometric nonlinearity is considered based on both total Lagrangian and updated Lagrangian formulations,while the material nonlinearity is treated through elastoplastic stress-strain relationship.The nonlinear equilibrium equations are solved using an incremental-iterative scheme in conjunction with the modified Newton-Raphson method.A computer program is developed to predict the mechanical responses of tensegrity systems under tensile,compressive and flexural loadings.Numerical results obtained are compared with those reported in the literature to demonstrate the accuracy and efficiency of the proposed program.The flexural behavior of the double layer quadruplex tensegrity grid is sufficiently good for lightweight large-span structural applications.On the other hand,its bending strength capacity is not sensitive to the self-stress level.
基金Founded by National Natural Science Foundation of China(No.51305306)Hubei Province Science and Technology Support Program(No.2013BCB025)Fundamental Research Funds for the Central University(No.2042014kf0274)
文摘To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Three different materials （composite resin, ceramage and ceramic） were studied and two loading conditions （vertical and oblique load） were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.
基金Project supported by Research Funds from Chosun University(2009),Korea
文摘Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial field.The temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature results.The thermal deformation was closely related to the temperature difference between the surface and inside of the casting.The numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting material.Also,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.
基金Project supported by the China Postdoctoral Science Foundation(No.2018M630167)
文摘Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the longitudinal direction according to a power law. Taking the solution of the corresponding homogeneous beam as the initial guess and obtaining a convergence region by adjusting an auxiliary parameter, the analytical expressions for large deformation of the AFG beam are provided. Results obtained by the HAM are compared with those obtained by the finite element method and those in the previous works to verify its validity. Good agreement is observed. A detailed parametric study is carried out. The results show that the axial material variation can greatly change the deformed configuration, which provides an approach to control and manage the deformation of beams. By tailoring the axial material distribution, a desired deformed configuration can be obtained for a specific load. The analytical solution presented herein can be a helpful tool for this procedure.
文摘This paper, based on the material processes and relational processes, aims to analysis the deep meaning of chapter one of Pride and Prejudice. The relevant theories will come first in this paper. I will then analyze this extract from three aspects: the analysis of the objective plane of narration, the analysis of Mrs. Bennet' s discourse and the analysis of Mr. Bennet' s discourse.
基金Under the auspices of Key Program of National Natural Science Foundation of China (No. 40635030)National Natu-ral Science Foundation of China (No. 40571041)
文摘Material dematerialization is a basic approach to reduce the pressure on the resources and environment and to realize the sustainable development. The material flow analysis and decomposition method are used to calculate the direct material input (DMI) of 14 typical mining cities in Northeast China in 1995–2004 and to analyze the demateri- alization and its driving factors in the different types of mining cities oriented by coal, petroleum, metallurgy and multi-resources. The results are as follows: 1) from 1995 to 2006, the increase rates of the DMI and the material input intensity of mining cities declined following the order of multi-resources, metallurgy, coal, and petroleum cities, and the material utilizing efficiency did following the order of petroleum, coal, metallurgy, and multi-resources cities; 2) during the research period, all the kinds of mining cities were in the situation of weak sustainable development in most years; 3) the pressure on resources and environment in the multi-resources cities was the most serious; 4) the petro- leum cities showed the strong trend of sustainable development; and 5) in recent years, the driving function of eco- nomic development for material consuming has continuously strengthened and the controlling function of material utilizing efficiency for it has weakened. The key approaches to promote the development of circular economy of min- ing cities in Northeast China are put forward in the following aspects: 1) to strengthen the research and development of the technique of resources’ cycling utilization, 2) to improve the utilizing efficiency of resources, and 3) to carry out the auditing system of resources utilization.
基金supported by the Vietnam National Foundation for Science and Technology Development(No.107.02-2015.11)
文摘An analytical solution for buckling of an eccentrically stiffened sandwich truncated conical shell is investigated. The shell consists of two functionally graded material （FGM） coating layers and a core layer which are metal or ceramic subjected to an axial compressive load and an external uniform pressure. Shells are reinforced by stringers and rings, in which the material properties of shells and stiffeners are graded in the thickness direction following a general sigmoid law distribution. Two models of coated shell-stiffener arrangements are investigated. The change of the spacing between stringers in the meridional direction is taken into account. A couple set of three-variable- coefficient partial differential equations in terms of displacement components are solved by the Galerkin method. A closed-form expression for determining the buckling load is obtained. The numerical examples are presented and compared with previous works.
文摘This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material for the specimens consists of a single hole model(25% void/cell,16% void/cell and 10% void/cell)and a four-hole model(25%void/cell).Using a representative volume element(RVE),we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue.Next,the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part(single hole cell)in the contact area.The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation(DNS)method.Finally,by comparing the computational time and%deviations,we draw conclusions about the reliability and effectiveness of the proposed method.
文摘A set of constitutive equations are derived based on the authors'lower bound yield loci for porous materials. By using these equations, the conditions for shear localization in porous materials are then investigated and the results are compared with those of Gurson's equations and the finite element analysis. The advantages of the present constitutive equations are fully illustrated.
