Clarify the mechanical properties of different laminations and the fracture mechanism of continental shale under in-situ stress can provide theoretical basis for more comprehensive evaluation of the fracability of con...Clarify the mechanical properties of different laminations and the fracture mechanism of continental shale under in-situ stress can provide theoretical basis for more comprehensive evaluation of the fracability of continental shale oil reservoir.The Chang 72continental shale was used to investigate the mechanical properties of laminations and the effect of natural structure on the crack propagation of the shale.The XRD and thin section tests show that the laminations contain two types:bright sandy lamination with void structure and dark muddy lamination with layer structure.The real-time CT uniaxial compression tests were conducted to investigate the differences of mechanical properties between the muddy lamination and sandy lamination.It found that the uniaxial compression strength and elastic modulus of the sandy lamination are higher,forming a simple crack with large opening,and the Poisson's ratio of the muddy lamination is large,forming obvious lateral deformation and more secondary cracks.On this basis,the cuboid-shaped continental shale specimens were tested under true triaxial compression conditions to study the effect of laminations and interface cracks on crack propagation combining AE and CT techniques.It found that nascent cracks connected laminations and interface cracks to form fracture network under appropriate loading condition,tensile cracks developed in sandy lamination and shear cracks occurred in muddy lamination because of deformation dissonance and brittleness index differences,and more secondary cracks formed in muddy lamination with smaller fracture toughness.Moreover,the combination relationships between nascent and natural cracks mainly conclude direct penetration and deflection,which is affected by the filling degree and morphology of interface cracks and the relationship of lamination types.These conclusions show that laminar continental shale is conducive to forming complex fracture network,which can provide a theoretical basis for the proposal of indicators and methods for fracability evaluation.展开更多
This paper discusses the analysis and design of a very thin slotless permanent magnet （PM） brushless motor whose stator laminations are manufactured from a single strip of steel that is edge wound into a spiral （li...This paper discusses the analysis and design of a very thin slotless permanent magnet （PM） brushless motor whose stator laminations are manufactured from a single strip of steel that is edge wound into a spiral （like a ＂Slinky＂） and then fitted over the windings that are preformed on the outside surface of a non-conducting former. Analytical and finite element analysis （FEA） are used to determine the con- strained optimum dimensions of a motor used to drive a rim driven thruster in which the motor rotor is fit- ted onto the rim of the propeller and the stator is encapsulated in the thin Kort nozzle of the thruster. The paper describes the fabrication of a demonstrator motor and presents experimental results to validate the theoretical calculations. Experimental motor performance results are also reported and compared with those of a slotted motor that fits within the same active radial dimensions as the slotless motor. The slotless motor, which has longer active length and endwindings, and thicker magnets than the slotted motor, was found to be less efficient and more expensive （prototype cost） than the slotted machine.展开更多
Hongfeng Lake is an eutrophic freshwater atificial reservior.It began to restore water in 1960. Three sediment cores were taken from both about 25m of water in the center of Hongfeng bake in May 1991. The stratigraphy...Hongfeng Lake is an eutrophic freshwater atificial reservior.It began to restore water in 1960. Three sediment cores were taken from both about 25m of water in the center of Hongfeng bake in May 1991. The stratigraphy of the three cores was easily matched .by using prominent marking horizons and characteristic aqnences of laminations. In three layer Samples studied, diatom and other algae taxa appear in repeating apuences. The presence of laminations may reflect either the regular changes of physical-chemical conditions within the lake or the variation in the intensity of erosion and transport of material from the catchment, pat iculaly where instability in the lake-water system has occult as a result of human activities. The larninations were mainly cantal by seasonal variation of envionmental conditions,particularly climate.Unlike t of the previous examples, they have ben fo￣ at most recent Sediments, in a small freshwater lake in the eastern slOPe of the QinghaiXiZang Plateau, China in a subtropical climate, which is adenly controlled by ￣theastern and southwestern mon￣n. It is believed that it's the first reported instanceOf laminated lake sediments from China.展开更多
Based on the first-order shear deformable beam theory, a refined model for composite beams containing a through-the-width delamination is presented, and the deformation at the delamination front is considered. Differe...Based on the first-order shear deformable beam theory, a refined model for composite beams containing a through-the-width delamination is presented, and the deformation at the delamination front is considered. Different from the ordinary delami- nated beam theory, each of the perfectly bonded portions of the new model is constructed as two separated beams along the interface without assuming a plane section at the de- lamination front. The governing equations of the delaminated portions and bonded ones are established, combined with continuity conditions of displacements and internal forces. Solutions of delaminated composite beams with different boundary conditions, delamina- tion locations and sizes axe shown in excellent agreement with the finite element results, showing efficiency and applicability of the present model.展开更多
Liquid ball-milling dispersant method was used to prepare the ZrO2-doped carbon laminations from mesocarbon microbeads（MCMBs）. After sintering at 1 300 ℃ in nitrogen atmosphere, the effect of ZrO2 concentration on ...Liquid ball-milling dispersant method was used to prepare the ZrO2-doped carbon laminations from mesocarbon microbeads（MCMBs）. After sintering at 1 300 ℃ in nitrogen atmosphere, the effect of ZrO2 concentration on sintering behavior, electric conductivity as well as bending strength of the carbon laminations was investigated in detail. The results showed that the volumetric shrinkage rate of the carbon laminations decreased from 38.2% to 30.9% when the ZrO2 concentration in raw materials varied from 0 to 16 wt%. Compared with undoped carbon lamination, the samples had high-electric conductivity and excellent bending strength in all cases. The electric conductivity achieved the maximum value of 225 S/cm, and the bending strength of the carbon lamination was 119.24 MPa for a concentration of 8 wt% ZrO2 in raw materials. In addition, the electric conductivity and bending strength reducing were observed when the ZrO2 concentration was higher than 8 wt%. The catalytic effect on graphitization for the carbon laminations was the most effective when the ZrO2 concentration was set at 8 wt% in raw materials.展开更多
Let X be a compact set which is laminated by parabolic Riemiann surfaces. For the CR positive line bundle L, there exists an integer N ∈ N such that for any s 〉 N and any continuous v ∈∧^（0,1）X×L^×s, t...Let X be a compact set which is laminated by parabolic Riemiann surfaces. For the CR positive line bundle L, there exists an integer N ∈ N such that for any s 〉 N and any continuous v ∈∧^（0,1）X×L^×s, there exists a continuous u ∈ L^×s solving δb^-u = v.展开更多
The combinatorial Mandelbrot set is a continuum in the plane, whose boundary is defined as the quotient space of the unit circle by an explicit equivalence relation. This equivalence relation was described by Douady(1...The combinatorial Mandelbrot set is a continuum in the plane, whose boundary is defined as the quotient space of the unit circle by an explicit equivalence relation. This equivalence relation was described by Douady(1984) and, separately, by Thurston(1985) who used quadratic invariant geolaminations as a major tool. We showed earlier that the combinatorial Mandelbrot set can be interpreted as a quotient of the space of all limit quadratic invariant geolaminations with the Hausdorff distance topology. In this paper, we describe two similar quotients. In the first case, the identifications are the same but the space is smaller than that used for the Mandelbrot set. The resulting quotient space is obtained from the Mandelbrot set by "unpinching" the transitions between adjacent hyperbolic components. In the second case we identify renormalizable geolaminations that can be "unrenormalized" to the same hyperbolic geolamination while no two non-renormalizable geolaminations are identified.展开更多
Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding str...Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.展开更多
Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design o...Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design optimization of variable stiffness of fiber-reinforced composite laminates has attracted widespread attention from scholars and industry. In these aerospace composite structures, numerous cutout panels and shells serve as access points for maintaining electrical, fuel, and hydraulic systems. The traditional fiber-reinforced composite laminate subtractive drilling manufacturing inevitably faces the problems of interlayer delamination, fiber fracture, and burr of the laminate. Continuous fiber additive manufacturing technology offers the potential for integrated design optimization and manufacturing with high structural performance. Considering the integration of design and manufacturability in continuous fiber additive manufacturing, the paper proposes linear and nonlinear filtering strategies based on the Normal Distribution Fiber Optimization (NDFO) material interpolation scheme to overcome the challenge of discrete fiber optimization results, which are difficult to apply directly to continuous fiber additive manufacturing. With minimizing structural compliance as the objective function, the proposed approach provides a strategy to achieve continuity of discrete fiber paths in the variable stiffness design optimization of composite laminates with regular and irregular holes. In the variable stiffness design optimization model, the number of candidate fiber laying angles in the NDFO material interpolation scheme is considered as design variable. The sensitivity information of structural compliance with respect to the number of candidate fiber laying angles is obtained using the analytical sensitivity analysis method. Based on the proposed variable stiffness design optimization method for complex perforated composite laminates, the numerical examples consider the variable stiffness design optimization of typical non-perforated and perforated composite laminates with circular, square, and irregular holes, and systematically discuss the number of candidate discrete fiber laying angles, discrete fiber continuous filtering strategies, and filter radius on structural compliance, continuity, and manufacturability. The optimized discrete fiber angles of variable stiffness laminates are converted into continuous fiber laying paths using a streamlined process for continuous fiber additive manufacturing. Meanwhile, the optimized non-perforated and perforated MBB beams after discrete fiber continuous treatment, are manufactured using continuous fiber co-extrusion additive manufacturing technology to verify the effectiveness of the variable stiffness fiber optimization framework proposed in this paper.展开更多
Three types of Al/Al−27%Si laminated composites,each containing 22%Si,were fabricated via hot pressing and hot rolling.The microstructures,mechanical properties and thermo-physical properties of these composites were ...Three types of Al/Al−27%Si laminated composites,each containing 22%Si,were fabricated via hot pressing and hot rolling.The microstructures,mechanical properties and thermo-physical properties of these composites were investigated.The results demonstrated that the three laminated composites exhibited similar microstructural features,characterized by well-bonded interfaces between the Al layer and the Al−27%Si alloy layer.The tensile and flexural strengths of the composites were significantly higher than those of both Al−22%Si and Al−27%Si alloys.These strengths increased gradually with decreasing the layer thickness,reaching peak values of 222.5 and 407.4 MPa,respectively.Crack deflection was observed in the cross-sections of the bending fracture surfaces,which contributed to the enhanced strength and toughness.In terms of thermo-physical properties,the thermal conductivity of the composites was lower than that of Al−22%Si and Al−27%Si alloys.The minimum reductions in thermal conductivity were 6.8%and 0.9%for the T3 laminated composite,respectively.Additionally,the coefficient of thermal expansion of the composites was improved,exhibiting varying temperature-dependent behaviors.展开更多
Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4...Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4/TB8 titanium(Ti)laminates,inspired by theheterostructures of natural biological shells,were fabricated using a hybrid diffusion bonding-hot rolling process followed by an aging treatment,resulting in an architected micro structure.The laminate achieves an ultra-high yield stress of 1020 MPa and proper uniform elongation of 4.2%at 500℃.The TB8 layers with high-density nano-precipitates and dislocations act as hard zone,contributing to high strength.The TC4 layers,with their bimodal structure consisting of coarse and fine grains characterized by equiaxed and lamellar structures,experience more plastic strain than the TB8 layers.The hetero deformation associated with the detwinning ofαgrains in the TC4 layer induces toughening at high temperatures.展开更多
Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The tech...Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The techniques of FESEM/EDS,grazing incident beam X-ray diffraction(GIXRD),and electrochemical methods of potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)were used to characterize the coatings.The results revealed that the coatings produced using the bipolar waveform exhibited lower porosity and higher thickness than those produced using the unipolar one.The corrosion performance of the specimens’cut edge was investigated using EIS after 1,8,and 12 h of immersion in a 3.5 wt.%NaCl solution.It was observed that the coating produced using the bipolar waveform demonstrated the highest corrosion resistance after 12 h of immersion,with an estimated corrosion resistance of 5.64 kΩ·cm^(2),which was approximately 3 times higher than that of the unipolar coating.Notably,no signs of galvanic corrosion were observed in the LMCs,and only minor corrosion attacks were observed on the magnesium layer in some areas.展开更多
Lightweight and mechanically robust composites are widely utilized as structural components in many different sectors.These structural components often face the challenge of dynamic impact loads.Therefore,research on ...Lightweight and mechanically robust composites are widely utilized as structural components in many different sectors.These structural components often face the challenge of dynamic impact loads.Therefore,research on how to improve the impact resistance of structural materials has always been highly important.In this study,on the basis of a scalable bottom-up assembly route,we prepare multilayered nacre-like composites with enhanced impact resistance.The multilayered nacre-like composites have a brick-and-mortar structure at the nanoscale and a rigid‒soft laminate structure at the microscale.The experimental results revealed that the hierarchically designed composites demonstrated hierarchical toughening behavior under quasistatic loading conditions and exhibited greatly improved impact resistance under dynamic loading conditions.This study provides a theoretical basis for the relationship between the structure and dynamic mechanical properties of multilayered nacre-like composites and provides new ideas for the future research and development of impactresistant composites.展开更多
This study aims to investigate the propagation of harmonic waves in nonlocal magneto-electro-elastic(MEE)laminated composites with interface stress imperfections using an analytical approach.The pseudo-Stroh formulati...This study aims to investigate the propagation of harmonic waves in nonlocal magneto-electro-elastic(MEE)laminated composites with interface stress imperfections using an analytical approach.The pseudo-Stroh formulation and nonlocal theory proposed by Eringen were adopted to derive the propagator matrix for each layer.Both the propagator and interface matrices were formulated to determine the recursive fields.Subsequently,the dispersion equation was obtained by imposing traction-free and magneto-electric circuit open boundary conditions on the top and bottom surfaces of the plate.Dispersion curves,mode shapes,and natural frequencies were calculated for sandwich plates composed of BaTiO3 and CoFe2O4.Numerical simulations revealed that both interface stress and the nonlocal effect influenced the tuning of the dispersion curve and mode shape for the given layup.The nonlocal effect caused a significant decrease in the dispersion curves,particularly in the high-frequency regions.Additionally,compared to the nonlocal effect,the interface stress exerted a greater influence on the mode shapes.The generalized analytical framework developed in this study provides an effective tool for both the theoretical analysis and practical design of MEE composite laminates.展开更多
A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free b...A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free boundary condition in other directions.In the present study,partial-periodic model for composite laminate beam structures is particularly studied.Three-point bending experiments for laminate beam specimens with different laying parameters are firstly used to verify the present partial-periodic model.In addition,a detailed finite element method(FEM)model is also used to further quantitatively compare with the present partial-periodic model for composite laminate beams with different laying parameters.The results indicate that the proposed partial-periodic model is capable of providing accurate predictions in most cases.The computational time cost of the proposed partial-periodic model is much lower than that of the detailed FEM model as well.Convergence studies are also conducted for the present partial-periodic model with different model sizes and element sizes.It is suggested that the proposed partial-periodic model has the potential to be used as an accurate and time-saving tool for predicting the structural properties of composite laminate beam structures.展开更多
The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest...The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest,the nexus between process,structure,and properties within laminated HEAs remains largely uncharted.There is a vast space for investigating the effect of the typical heterogeneous interface on the macroscopic mechanical properties.This study focuses on the influence of the characteristic het-erogeneous interface on macroscopic mechanical properties of laminated HEAs,particularly anisotropy.Using the 3D-printed Fe_(50)Mn_(30)Co_(10)Cr_(10)-CoCrNi HEA as a model,we investigate the impact of interface geometry on mechanical characteristics.Tensile tests show that the reduced interface spacing increases yield strength.This laminated HEA displays significant anisotropy in strength and ductility,depending on the loading direction relative to the interface.Electron microscopic observations suggest that finer layer spacing enhances interface and dislocation strengthening,increasing yield strength.Anisotropic behaviors are confirmed to be mediated by interface orientation,explained in terms of deformation compatibility and crack development at the interface.This research offers fundamental insights into the relationship between heterogeneous interfaces and the mechanical properties in laminated HEAs.The knowledge is vital for designing,fabricating,and optimizing laminated HEAs through additive manufacturing,advancing their engineering applications.展开更多
This study developed a five-layer Mg alloy laminate(pure Mg/AZ31/AZ91/AZ31/pure Mg)through an innovative synergistic strategy involving Al-element gradient design,extrusion,and short-term annealing.Microstructural cha...This study developed a five-layer Mg alloy laminate(pure Mg/AZ31/AZ91/AZ31/pure Mg)through an innovative synergistic strategy involving Al-element gradient design,extrusion,and short-term annealing.Microstructural characterization revealed hierarchical heterogeneities in grain size,texture intensity,dislocation density,and precipitated phases,accompanied by the formation of annealing twinning in pure Mg layer—a phenomenon rarely documented in Mg alloys.Mechanical tests demonstrated significant strengthening effects in all annealed samples,particularly in the 300℃/30 min annealed sample,which achieved the optimal comprehensive mechanical properties.The enhanced strength originated from the synergistic interaction among element-diffusion-induced solid solution strengthening,nanoscale β-Mg_(17)Al_(12) precipitation,and hetero-deformation-induced(HDI)strengthening.This approach breaks the strength-ductility trade-off induced by traditional annealing processes,offering a new paradigm for designing high-performance Mg alloy laminates.展开更多
Laminated metal composites(LMCs)have widespread application prospects and are set to become indispensable in addressing modern engineering challenges owing to their capability of leveraging the synergy between differe...Laminated metal composites(LMCs)have widespread application prospects and are set to become indispensable in addressing modern engineering challenges owing to their capability of leveraging the synergy between different metals and tailoring performance by flexibly regulating the layered configuration.The plastic forming process,as a promising advanced manufacturing technology,has been increasingly adopted for the fabrication of LMC components due to its advantages of high material utilization rate,high production efficiency,and excellent mechanical properties of the product.This review delved into the research progress on the plastic-forming process of LMCs,including rolling,extrusion,spinning,etc.It outlined the forming principles,unique characteristics,bonding mechanisms,and the influence of key process parameters on deformation,microstructure,and property.This review focused on the heterogeneous deformation and interfacial regulation of LMCs,providing insights into the mechanisms of heterogeneous deformation,damage and fracture,and formation mechanisms of intermetallic compounds.It also delineated the experimental characterization and numerical modeling methods to elucidate the heterogeneous deformation behavior,as well as the approaches to evaluating and enhancing the performance of LMCs.Finally,the challenges and prospects of manufacturing high-performance LMCs by plastic forming process are orchestrated.展开更多
Mg/Al laminate with ZK60Mg and TiB2/6061Al as constitute layers was fabricated through the porthole die co-extrusion and hot rolling.The effects of rolling and roll temperatures on the microstructure,interfacial struc...Mg/Al laminate with ZK60Mg and TiB2/6061Al as constitute layers was fabricated through the porthole die co-extrusion and hot rolling.The effects of rolling and roll temperatures on the microstructure,interfacial structure,mechanical properties,and crack propagation paths were studied.The results show that the intermetallic compounds layer shows an intermittent form.The strong strain/dislocation hardening ability of Mg/Al laminate is attributed to the coupled effects of interlocking Al/βinterface,strain gradient,andβlayer with nanotwins and stacking faults.The complex dislocation structures such as network,loop,and array are found in the Al layer.Dislocation slip is the main deformation mode of the Al layer,while dislocation slip and dynamic recrystallization are the main deformation modes of the Mg layer.As roll temperature increases,prismatic〈a〉slip replaces the basal〈a〉slip as the most important slip mode.At a rolling temperature of 400℃ and a roll temperature of 150℃,an optimal synergy of mechanical properties is achieved,with ultimate tensile strength,shear strength,and elongation of 262.1 MPa,36.4 MPa,and 18.1%,respectively.As the rolling temperature increases,the fracture mode of Mg/Al laminate changes from discontinuous plastic shrinkage to transverse and longitudinal cracks.With increasing the roll temperature,the through cracks tend to form,indicating the plasticity and bonding quality of Mg/Al laminate are effectively enhanced.展开更多
Heterogeneous laminated structure(HLS)design offers new opportunities to enhance the mechanical performance of high-entropy alloys(HEAs)through synergistic effects from heterogeneity.However,it remains challenging to ...Heterogeneous laminated structure(HLS)design offers new opportunities to enhance the mechanical performance of high-entropy alloys(HEAs)through synergistic effects from heterogeneity.However,it remains challenging to introduce the HLS into HEAs via severe plastic deformation due to their strong work-hardening capacity.In this study,a specially designed multi-level HLS,characterized by alterna-tively stacked micro-grained soft CoCrFeNi layers and nanostructured ultra-hard Al_(0.3)CoCrFeNi layers con-taining a three-phase microstructure(composed of nanograined face-centered cubic matrix,(Al,Ni)-rich B2 precipitates,and Cr-richσprecipitates),is controllably introduced into FCC HEAs via a conventional thermo-mechanical processing involving hot-pressing,cold-rolling,and annealing.Meanwhile,thermo-mechanical processing induces Al element diffusion across the layer interface,resulting in the formation of an interfacial transition layer and the establishment of a strong interface bonding between the neigh-boring CoCrFeNi and Al_(0.3)CoCrFeNi layers.As a result,the multi-level HLSed CoCrFeNi/Al_(0.3)CoCrFeNi com-posite exhibits a yield strength as high as 1127±25.4 MPa while maintaining a large fracture elongation(up to(26.3±2.4)%).Such an excellent strength-ductility synergy surpasses that of most previously reported high-performance monolithic bulk CoCrFeNi and Al_(0.3)CoCrFeNi HEAs prepared through care-ful chemical composition optimization and/or thermo-mechanical processing.Strong hetero-deformation induced strengthening benefited from the apparent microstructural/microhardness difference and the strong interface bonding between the neighbouring CoCrFeNi and Al03CoCrFeNi layers,together with si-multaneous activation of multiple strain hardening mechanisms containing mechanical twinning,stack-ing faults and precipitation strengthening,is responsible for the excellent strength-ductility combination.This multi-level HLS and its fabrication strategy provide an enlightening way to develop strong and duc-tile HEAs and can also be applied to high-performance designs of other metallic materials.展开更多
基金funded by the National Natural Science Foundation of China(42102309 and 42007243)the Natural Science Foundation of Liaoning Province(2023-MSBA-120)the National Key Research and Development Program(2022YFB3304705)。
文摘Clarify the mechanical properties of different laminations and the fracture mechanism of continental shale under in-situ stress can provide theoretical basis for more comprehensive evaluation of the fracability of continental shale oil reservoir.The Chang 72continental shale was used to investigate the mechanical properties of laminations and the effect of natural structure on the crack propagation of the shale.The XRD and thin section tests show that the laminations contain two types:bright sandy lamination with void structure and dark muddy lamination with layer structure.The real-time CT uniaxial compression tests were conducted to investigate the differences of mechanical properties between the muddy lamination and sandy lamination.It found that the uniaxial compression strength and elastic modulus of the sandy lamination are higher,forming a simple crack with large opening,and the Poisson's ratio of the muddy lamination is large,forming obvious lateral deformation and more secondary cracks.On this basis,the cuboid-shaped continental shale specimens were tested under true triaxial compression conditions to study the effect of laminations and interface cracks on crack propagation combining AE and CT techniques.It found that nascent cracks connected laminations and interface cracks to form fracture network under appropriate loading condition,tensile cracks developed in sandy lamination and shear cracks occurred in muddy lamination because of deformation dissonance and brittleness index differences,and more secondary cracks formed in muddy lamination with smaller fracture toughness.Moreover,the combination relationships between nascent and natural cracks mainly conclude direct penetration and deflection,which is affected by the filling degree and morphology of interface cracks and the relationship of lamination types.These conclusions show that laminar continental shale is conducive to forming complex fracture network,which can provide a theoretical basis for the proposal of indicators and methods for fracability evaluation.
文摘This paper discusses the analysis and design of a very thin slotless permanent magnet （PM） brushless motor whose stator laminations are manufactured from a single strip of steel that is edge wound into a spiral （like a ＂Slinky＂） and then fitted over the windings that are preformed on the outside surface of a non-conducting former. Analytical and finite element analysis （FEA） are used to determine the con- strained optimum dimensions of a motor used to drive a rim driven thruster in which the motor rotor is fit- ted onto the rim of the propeller and the stator is encapsulated in the thin Kort nozzle of the thruster. The paper describes the fabrication of a demonstrator motor and presents experimental results to validate the theoretical calculations. Experimental motor performance results are also reported and compared with those of a slotted motor that fits within the same active radial dimensions as the slotless motor. The slotless motor, which has longer active length and endwindings, and thicker magnets than the slotted motor, was found to be less efficient and more expensive （prototype cost） than the slotted machine.
文摘Hongfeng Lake is an eutrophic freshwater atificial reservior.It began to restore water in 1960. Three sediment cores were taken from both about 25m of water in the center of Hongfeng bake in May 1991. The stratigraphy of the three cores was easily matched .by using prominent marking horizons and characteristic aqnences of laminations. In three layer Samples studied, diatom and other algae taxa appear in repeating apuences. The presence of laminations may reflect either the regular changes of physical-chemical conditions within the lake or the variation in the intensity of erosion and transport of material from the catchment, pat iculaly where instability in the lake-water system has occult as a result of human activities. The larninations were mainly cantal by seasonal variation of envionmental conditions,particularly climate.Unlike t of the previous examples, they have ben fo￣ at most recent Sediments, in a small freshwater lake in the eastern slOPe of the QinghaiXiZang Plateau, China in a subtropical climate, which is adenly controlled by ￣theastern and southwestern mon￣n. It is believed that it's the first reported instanceOf laminated lake sediments from China.
基金supported by the National Natural Science Foundation of China (No.10932001)the Fanzhou Foundation (No.20070501)the Scientific Research Foundation for Returned Scholars of Ministry of Education of China
文摘Based on the first-order shear deformable beam theory, a refined model for composite beams containing a through-the-width delamination is presented, and the deformation at the delamination front is considered. Different from the ordinary delami- nated beam theory, each of the perfectly bonded portions of the new model is constructed as two separated beams along the interface without assuming a plane section at the de- lamination front. The governing equations of the delaminated portions and bonded ones are established, combined with continuity conditions of displacements and internal forces. Solutions of delaminated composite beams with different boundary conditions, delamina- tion locations and sizes axe shown in excellent agreement with the finite element results, showing efficiency and applicability of the present model.
基金Funded by the Foundation of Jiangsu Key Laboratory of Fine Petrochemical Engineering
文摘Liquid ball-milling dispersant method was used to prepare the ZrO2-doped carbon laminations from mesocarbon microbeads（MCMBs）. After sintering at 1 300 ℃ in nitrogen atmosphere, the effect of ZrO2 concentration on sintering behavior, electric conductivity as well as bending strength of the carbon laminations was investigated in detail. The results showed that the volumetric shrinkage rate of the carbon laminations decreased from 38.2% to 30.9% when the ZrO2 concentration in raw materials varied from 0 to 16 wt%. Compared with undoped carbon lamination, the samples had high-electric conductivity and excellent bending strength in all cases. The electric conductivity achieved the maximum value of 225 S/cm, and the bending strength of the carbon lamination was 119.24 MPa for a concentration of 8 wt% ZrO2 in raw materials. In addition, the electric conductivity and bending strength reducing were observed when the ZrO2 concentration was higher than 8 wt%. The catalytic effect on graphitization for the carbon laminations was the most effective when the ZrO2 concentration was set at 8 wt% in raw materials.
基金Supported by the National Natural Science Foundation of China(11271359)
文摘Let X be a compact set which is laminated by parabolic Riemiann surfaces. For the CR positive line bundle L, there exists an integer N ∈ N such that for any s 〉 N and any continuous v ∈∧^（0,1）X×L^×s, there exists a continuous u ∈ L^×s solving δb^-u = v.
基金supported by National Science Foundation of USA (Grant No. DMS-1201450)supported by National Science Foundation of USA (Grant No. DMS-1807558)supported by the Russian Academic Excellence Project ‘5-100’
文摘The combinatorial Mandelbrot set is a continuum in the plane, whose boundary is defined as the quotient space of the unit circle by an explicit equivalence relation. This equivalence relation was described by Douady(1984) and, separately, by Thurston(1985) who used quadratic invariant geolaminations as a major tool. We showed earlier that the combinatorial Mandelbrot set can be interpreted as a quotient of the space of all limit quadratic invariant geolaminations with the Hausdorff distance topology. In this paper, we describe two similar quotients. In the first case, the identifications are the same but the space is smaller than that used for the Mandelbrot set. The resulting quotient space is obtained from the Mandelbrot set by "unpinching" the transitions between adjacent hyperbolic components. In the second case we identify renormalizable geolaminations that can be "unrenormalized" to the same hyperbolic geolamination while no two non-renormalizable geolaminations are identified.
基金supported by the National Key R&D Program of China (No. 2018YFA0707300)the National Natural Science Foundation of China (No. 52374376)the Introduction Plan for High end Foreign Experts, China (No. G2023105001L)。
文摘Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.
基金supports for this research were provided by the National Natural Science Foundation of China(No.12272301,12002278,U1906233)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2023A1515011970,2024A1515010256)+1 种基金the Dalian City Supports Innovation and Entrepreneurship Projects for High-Level Talents,China(2021RD16)the Key R&D Project of CSCEC,China(No.CSCEC-2020-Z-4).
文摘Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design optimization of variable stiffness of fiber-reinforced composite laminates has attracted widespread attention from scholars and industry. In these aerospace composite structures, numerous cutout panels and shells serve as access points for maintaining electrical, fuel, and hydraulic systems. The traditional fiber-reinforced composite laminate subtractive drilling manufacturing inevitably faces the problems of interlayer delamination, fiber fracture, and burr of the laminate. Continuous fiber additive manufacturing technology offers the potential for integrated design optimization and manufacturing with high structural performance. Considering the integration of design and manufacturability in continuous fiber additive manufacturing, the paper proposes linear and nonlinear filtering strategies based on the Normal Distribution Fiber Optimization (NDFO) material interpolation scheme to overcome the challenge of discrete fiber optimization results, which are difficult to apply directly to continuous fiber additive manufacturing. With minimizing structural compliance as the objective function, the proposed approach provides a strategy to achieve continuity of discrete fiber paths in the variable stiffness design optimization of composite laminates with regular and irregular holes. In the variable stiffness design optimization model, the number of candidate fiber laying angles in the NDFO material interpolation scheme is considered as design variable. The sensitivity information of structural compliance with respect to the number of candidate fiber laying angles is obtained using the analytical sensitivity analysis method. Based on the proposed variable stiffness design optimization method for complex perforated composite laminates, the numerical examples consider the variable stiffness design optimization of typical non-perforated and perforated composite laminates with circular, square, and irregular holes, and systematically discuss the number of candidate discrete fiber laying angles, discrete fiber continuous filtering strategies, and filter radius on structural compliance, continuity, and manufacturability. The optimized discrete fiber angles of variable stiffness laminates are converted into continuous fiber laying paths using a streamlined process for continuous fiber additive manufacturing. Meanwhile, the optimized non-perforated and perforated MBB beams after discrete fiber continuous treatment, are manufactured using continuous fiber co-extrusion additive manufacturing technology to verify the effectiveness of the variable stiffness fiber optimization framework proposed in this paper.
基金supported by the National Natural Science Foundation of China(No.52274369)the National Key Laboratory of Science and Technology on High-strength Structural Materials,China(No.623020034).
文摘Three types of Al/Al−27%Si laminated composites,each containing 22%Si,were fabricated via hot pressing and hot rolling.The microstructures,mechanical properties and thermo-physical properties of these composites were investigated.The results demonstrated that the three laminated composites exhibited similar microstructural features,characterized by well-bonded interfaces between the Al layer and the Al−27%Si alloy layer.The tensile and flexural strengths of the composites were significantly higher than those of both Al−22%Si and Al−27%Si alloys.These strengths increased gradually with decreasing the layer thickness,reaching peak values of 222.5 and 407.4 MPa,respectively.Crack deflection was observed in the cross-sections of the bending fracture surfaces,which contributed to the enhanced strength and toughness.In terms of thermo-physical properties,the thermal conductivity of the composites was lower than that of Al−22%Si and Al−27%Si alloys.The minimum reductions in thermal conductivity were 6.8%and 0.9%for the T3 laminated composite,respectively.Additionally,the coefficient of thermal expansion of the composites was improved,exhibiting varying temperature-dependent behaviors.
基金financially supported by the Natural Science Foundation of Changsha,China(No.kq2402015)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF-2021R1A2C3006662 and NRF-2022R1A5A1030054)supported by Brain Pool Program through the NRF of Korea,funded by the Ministry of Science and ICT(No.NRF-RS_(2)02300263999)
文摘Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4/TB8 titanium(Ti)laminates,inspired by theheterostructures of natural biological shells,were fabricated using a hybrid diffusion bonding-hot rolling process followed by an aging treatment,resulting in an architected micro structure.The laminate achieves an ultra-high yield stress of 1020 MPa and proper uniform elongation of 4.2%at 500℃.The TB8 layers with high-density nano-precipitates and dislocations act as hard zone,contributing to high strength.The TC4 layers,with their bimodal structure consisting of coarse and fine grains characterized by equiaxed and lamellar structures,experience more plastic strain than the TB8 layers.The hetero deformation associated with the detwinning ofαgrains in the TC4 layer induces toughening at high temperatures.
文摘Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The techniques of FESEM/EDS,grazing incident beam X-ray diffraction(GIXRD),and electrochemical methods of potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)were used to characterize the coatings.The results revealed that the coatings produced using the bipolar waveform exhibited lower porosity and higher thickness than those produced using the unipolar one.The corrosion performance of the specimens’cut edge was investigated using EIS after 1,8,and 12 h of immersion in a 3.5 wt.%NaCl solution.It was observed that the coating produced using the bipolar waveform demonstrated the highest corrosion resistance after 12 h of immersion,with an estimated corrosion resistance of 5.64 kΩ·cm^(2),which was approximately 3 times higher than that of the unipolar coating.Notably,no signs of galvanic corrosion were observed in the LMCs,and only minor corrosion attacks were observed on the magnesium layer in some areas.
基金supported by the Fundamental Research Funds for the Central Universities(WK2340000112)the National Key Research and Development Program of China(2021YFA0715700)the National Natural Science Foundation of China(22222508,22475205).
文摘Lightweight and mechanically robust composites are widely utilized as structural components in many different sectors.These structural components often face the challenge of dynamic impact loads.Therefore,research on how to improve the impact resistance of structural materials has always been highly important.In this study,on the basis of a scalable bottom-up assembly route,we prepare multilayered nacre-like composites with enhanced impact resistance.The multilayered nacre-like composites have a brick-and-mortar structure at the nanoscale and a rigid‒soft laminate structure at the microscale.The experimental results revealed that the hierarchically designed composites demonstrated hierarchical toughening behavior under quasistatic loading conditions and exhibited greatly improved impact resistance under dynamic loading conditions.This study provides a theoretical basis for the relationship between the structure and dynamic mechanical properties of multilayered nacre-like composites and provides new ideas for the future research and development of impactresistant composites.
基金supported by the Ministry of Science and Technology Taiwan under Grant No.MOST 109-2628-E-009-002-MY3.
文摘This study aims to investigate the propagation of harmonic waves in nonlocal magneto-electro-elastic(MEE)laminated composites with interface stress imperfections using an analytical approach.The pseudo-Stroh formulation and nonlocal theory proposed by Eringen were adopted to derive the propagator matrix for each layer.Both the propagator and interface matrices were formulated to determine the recursive fields.Subsequently,the dispersion equation was obtained by imposing traction-free and magneto-electric circuit open boundary conditions on the top and bottom surfaces of the plate.Dispersion curves,mode shapes,and natural frequencies were calculated for sandwich plates composed of BaTiO3 and CoFe2O4.Numerical simulations revealed that both interface stress and the nonlocal effect influenced the tuning of the dispersion curve and mode shape for the given layup.The nonlocal effect caused a significant decrease in the dispersion curves,particularly in the high-frequency regions.Additionally,compared to the nonlocal effect,the interface stress exerted a greater influence on the mode shapes.The generalized analytical framework developed in this study provides an effective tool for both the theoretical analysis and practical design of MEE composite laminates.
基金financial support from the National Key Research and Development Plan(2022YFB3707700)the National Natural Science Foundation of China(11872138 and 12172074)+1 种基金the Liaoning Revitalization Talents Program(XLYC2001003)the Dalian Excellent Young Science and Technology Talent Program(2023RY025).
文摘A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free boundary condition in other directions.In the present study,partial-periodic model for composite laminate beam structures is particularly studied.Three-point bending experiments for laminate beam specimens with different laying parameters are firstly used to verify the present partial-periodic model.In addition,a detailed finite element method(FEM)model is also used to further quantitatively compare with the present partial-periodic model for composite laminate beams with different laying parameters.The results indicate that the proposed partial-periodic model is capable of providing accurate predictions in most cases.The computational time cost of the proposed partial-periodic model is much lower than that of the detailed FEM model as well.Convergence studies are also conducted for the present partial-periodic model with different model sizes and element sizes.It is suggested that the proposed partial-periodic model has the potential to be used as an accurate and time-saving tool for predicting the structural properties of composite laminate beam structures.
基金supported by the National Natural Science Foundation of China(No.12272392 and 11790292)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040303)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2022020).
文摘The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest,the nexus between process,structure,and properties within laminated HEAs remains largely uncharted.There is a vast space for investigating the effect of the typical heterogeneous interface on the macroscopic mechanical properties.This study focuses on the influence of the characteristic het-erogeneous interface on macroscopic mechanical properties of laminated HEAs,particularly anisotropy.Using the 3D-printed Fe_(50)Mn_(30)Co_(10)Cr_(10)-CoCrNi HEA as a model,we investigate the impact of interface geometry on mechanical characteristics.Tensile tests show that the reduced interface spacing increases yield strength.This laminated HEA displays significant anisotropy in strength and ductility,depending on the loading direction relative to the interface.Electron microscopic observations suggest that finer layer spacing enhances interface and dislocation strengthening,increasing yield strength.Anisotropic behaviors are confirmed to be mediated by interface orientation,explained in terms of deformation compatibility and crack development at the interface.This research offers fundamental insights into the relationship between heterogeneous interfaces and the mechanical properties in laminated HEAs.The knowledge is vital for designing,fabricating,and optimizing laminated HEAs through additive manufacturing,advancing their engineering applications.
基金supported by the Joint Foundation of Hubei Province(No.2024AFD113)Hubei Provincial Department of Education Science and Technology Plan Project(No.D20231804)+3 种基金Natural Science Fund Project of Hubei Province(No.2024AFD099)Hubei Province Technological Innovation Special Major Project(No.2023BEB015)Doctoral Scientific Research Foundation of Hubei University of Automotive Technology(No.BK202336)Hubei University of Automotive Technology 2024 Annual Unveiling the List and Taking Command(ULTC)Projects.
文摘This study developed a five-layer Mg alloy laminate(pure Mg/AZ31/AZ91/AZ31/pure Mg)through an innovative synergistic strategy involving Al-element gradient design,extrusion,and short-term annealing.Microstructural characterization revealed hierarchical heterogeneities in grain size,texture intensity,dislocation density,and precipitated phases,accompanied by the formation of annealing twinning in pure Mg layer—a phenomenon rarely documented in Mg alloys.Mechanical tests demonstrated significant strengthening effects in all annealed samples,particularly in the 300℃/30 min annealed sample,which achieved the optimal comprehensive mechanical properties.The enhanced strength originated from the synergistic interaction among element-diffusion-induced solid solution strengthening,nanoscale β-Mg_(17)Al_(12) precipitation,and hetero-deformation-induced(HDI)strengthening.This approach breaks the strength-ductility trade-off induced by traditional annealing processes,offering a new paradigm for designing high-performance Mg alloy laminates.
基金supported by the National Natural Science Foundation of China(Grant Nos.52305361,52105337,52475354,and 52090043)the BK21 Four program(SNU Materials Education/Research Division for Creative Global Leaders)+1 种基金the China Postdoctoral Science Foundation(Grant No.2023M741245),and the National Key Research and Development Program of China(Grant No.2022YFB3706903)support from the Ko-rean Ministry of Trade,Industry and Energy(MOTIE,Korea)(Grant No.20022438).
文摘Laminated metal composites(LMCs)have widespread application prospects and are set to become indispensable in addressing modern engineering challenges owing to their capability of leveraging the synergy between different metals and tailoring performance by flexibly regulating the layered configuration.The plastic forming process,as a promising advanced manufacturing technology,has been increasingly adopted for the fabrication of LMC components due to its advantages of high material utilization rate,high production efficiency,and excellent mechanical properties of the product.This review delved into the research progress on the plastic-forming process of LMCs,including rolling,extrusion,spinning,etc.It outlined the forming principles,unique characteristics,bonding mechanisms,and the influence of key process parameters on deformation,microstructure,and property.This review focused on the heterogeneous deformation and interfacial regulation of LMCs,providing insights into the mechanisms of heterogeneous deformation,damage and fracture,and formation mechanisms of intermetallic compounds.It also delineated the experimental characterization and numerical modeling methods to elucidate the heterogeneous deformation behavior,as well as the approaches to evaluating and enhancing the performance of LMCs.Finally,the challenges and prospects of manufacturing high-performance LMCs by plastic forming process are orchestrated.
基金supported by the National Natural Science Foundation of China(Nos.52175338 and 52222510)Science Fund for Distinguished Young Scholars of Shandong Province(No.ZR2021JQ21)+1 种基金Key Research and Development Program of Shandong Province(No.2021ZLGX01)The Excellent Young Team Project of Central Universities(No.2023QNTD002).
文摘Mg/Al laminate with ZK60Mg and TiB2/6061Al as constitute layers was fabricated through the porthole die co-extrusion and hot rolling.The effects of rolling and roll temperatures on the microstructure,interfacial structure,mechanical properties,and crack propagation paths were studied.The results show that the intermetallic compounds layer shows an intermittent form.The strong strain/dislocation hardening ability of Mg/Al laminate is attributed to the coupled effects of interlocking Al/βinterface,strain gradient,andβlayer with nanotwins and stacking faults.The complex dislocation structures such as network,loop,and array are found in the Al layer.Dislocation slip is the main deformation mode of the Al layer,while dislocation slip and dynamic recrystallization are the main deformation modes of the Mg layer.As roll temperature increases,prismatic〈a〉slip replaces the basal〈a〉slip as the most important slip mode.At a rolling temperature of 400℃ and a roll temperature of 150℃,an optimal synergy of mechanical properties is achieved,with ultimate tensile strength,shear strength,and elongation of 262.1 MPa,36.4 MPa,and 18.1%,respectively.As the rolling temperature increases,the fracture mode of Mg/Al laminate changes from discontinuous plastic shrinkage to transverse and longitudinal cracks.With increasing the roll temperature,the through cracks tend to form,indicating the plasticity and bonding quality of Mg/Al laminate are effectively enhanced.
基金supported by the National Natural Science Foundation of China(No.52361021)the Major Discipline Academic and Technical Leaders Training Program of Jiangxi Province(No.20232BCJ23001)+1 种基金the Jiangxi Provincial Natural Science Foundation(No.20232ACB214003)the Jiangxi Province Major Science&Technology Research&Development Project(No.20223AAG01009).
文摘Heterogeneous laminated structure(HLS)design offers new opportunities to enhance the mechanical performance of high-entropy alloys(HEAs)through synergistic effects from heterogeneity.However,it remains challenging to introduce the HLS into HEAs via severe plastic deformation due to their strong work-hardening capacity.In this study,a specially designed multi-level HLS,characterized by alterna-tively stacked micro-grained soft CoCrFeNi layers and nanostructured ultra-hard Al_(0.3)CoCrFeNi layers con-taining a three-phase microstructure(composed of nanograined face-centered cubic matrix,(Al,Ni)-rich B2 precipitates,and Cr-richσprecipitates),is controllably introduced into FCC HEAs via a conventional thermo-mechanical processing involving hot-pressing,cold-rolling,and annealing.Meanwhile,thermo-mechanical processing induces Al element diffusion across the layer interface,resulting in the formation of an interfacial transition layer and the establishment of a strong interface bonding between the neigh-boring CoCrFeNi and Al_(0.3)CoCrFeNi layers.As a result,the multi-level HLSed CoCrFeNi/Al_(0.3)CoCrFeNi com-posite exhibits a yield strength as high as 1127±25.4 MPa while maintaining a large fracture elongation(up to(26.3±2.4)%).Such an excellent strength-ductility synergy surpasses that of most previously reported high-performance monolithic bulk CoCrFeNi and Al_(0.3)CoCrFeNi HEAs prepared through care-ful chemical composition optimization and/or thermo-mechanical processing.Strong hetero-deformation induced strengthening benefited from the apparent microstructural/microhardness difference and the strong interface bonding between the neighbouring CoCrFeNi and Al03CoCrFeNi layers,together with si-multaneous activation of multiple strain hardening mechanisms containing mechanical twinning,stack-ing faults and precipitation strengthening,is responsible for the excellent strength-ductility combination.This multi-level HLS and its fabrication strategy provide an enlightening way to develop strong and duc-tile HEAs and can also be applied to high-performance designs of other metallic materials.
