Recent advancements in additive manufacturing(AM)have revolutionized the design and production of complex engineering microstructures.Despite these advancements,their mathematical modeling and computational analysis r...Recent advancements in additive manufacturing(AM)have revolutionized the design and production of complex engineering microstructures.Despite these advancements,their mathematical modeling and computational analysis remain significant challenges.This research aims to develop an effective computational method for analyzing the free vibration of functionally graded(FG)microplates under high temperatures while resting on a Pasternak foundation(PF).This formulation leverages a new thirdorder shear deformation theory(new TSDT)for improved accuracy without requiring shear correction factors.Additionally,the modified couple stress theory(MCST)is incorporated to account for sizedependent effects in microplates.The PF is characterized by two parameters including spring stiffness(k_(w))and shear layer stiffness(k_(s)).To validate the proposed method,the results obtained are compared with those of the existing literature.Furthermore,numerical examples explore the influence of various factors on the high-temperature free vibration of FG microplates.These factors include the length scale parameter(l),geometric dimensions,material properties,and the presence of the elastic foundation.The findings significantly enhance our comprehension of the free vibration of FG microplates in high thermal environments.In addition,the findings significantly enhance our comprehension of the free vibration of FG microplates in high thermal environments.In addition,the results of this research will have great potential in military and defense applications such as components of submarines,fighter aircraft,and missiles.展开更多
Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufactu...Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufacturing highlights the capability in manufacturing FGMs with a high geometrical complexity and manufacture flexibility.In this work,the 316L/CuSn10/18Ni300/CoCr four-type materials FGMs were fabricated using SLM.The microstructure and properties of the FGMs were investigated to reveal the effects of SLM processing parameters on the defects.A large number of microcracks were found at the 316L/CuSn10 interface,which initiated from the fusion boundary of 316L region and extended along the building direction.The elastic modulus and nano-hardness in the 18Ni300/CoCr fusion zone decreased significantly,less than those in the 18Ni300 region or the CoCr region.The iron and copper elements were well diffused in the 316L/CuSn10 fusion zone,while elements in the CuSn10/18Ni300 and the 18Ni300/CoCr fusion zones showed significantly gradient transitions.Compared with other regions,the width of the CuSn10/18Ni300 interface and the CuSn10 region expand significantly.The mechanisms of materials fusion and crack generation at the 316L/CuSn10 interface were discussed.In addition,FGM structures without macro-crack were built by only altering the deposition subsequence of 316L and CuSn10,which provides a guide for the additive manufacturing of FGM structures.展开更多
In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which ...In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.展开更多
The finite element method (FEM) and the boundary element method (BEM) are often adopted. However, they are not convenient to spatially vary thermal properties of functionally graded material (FGM). Therefore, the meth...The finite element method (FEM) and the boundary element method (BEM) are often adopted. However, they are not convenient to spatially vary thermal properties of functionally graded material (FGM). Therefore, the method of lines (MOL) is introduced to solve the temperature field of FGM. The basic idea of the method is to semi-discretize the governing equation into a system of ordinary differential equations (ODEs) defined on discrete lines by means of the finite difference method. The temperature field of FGM can be obtained by solving the ODEs. The functions of thermal properties are directly embodied in these equations and these properties are not discretized in the domain. Thus, difficulty of FEM and BEM is overcome by the method. As a numerical example, the temperature field of a plane problem is analyzed for FGMs through varying thermal conductivity coefficient by the MOL.展开更多
Micro-scale functionally graded material(FGM)pipes conveying fluid have many significant applications in engineering fields.In this work,the thermoelastic vibration of FGM fluid-conveying tubes in elastic medium is st...Micro-scale functionally graded material(FGM)pipes conveying fluid have many significant applications in engineering fields.In this work,the thermoelastic vibration of FGM fluid-conveying tubes in elastic medium is studied.Based on modified couple stress theory and Hamilton’s principle,the governing equation and boundary conditions are obtained.The differential quadrature method(DQM)is applied to investigating the thermoelastic vibration of the FGM pipes.The effect of temperature variation,scale effect of the microtubule,micro-fluid effect,material properties,elastic coefficient of elastic medium and outer radius on thermoelastic vibration of the FGM pipes conveying fluid are studied.The results show that in the condition of considering the scale effect and micro-fluid of the microtubule,the critical dimensionless velocity of the system is higher than that of the system which calculated using classical macroscopic model.The results also show that the variations of temperature,material properties,elastic coefficient and outer radius have significant influences on the first-order dimensionless natural frequency.展开更多
Zirconia/stainless steel (ZrO2/SUS316L) functionally graded materials (FGMs) were fabricated by tape casting and laminating. Microstructures of FGMs were observed by optical microscope. Fracture behavior of FGMs in di...Zirconia/stainless steel (ZrO2/SUS316L) functionally graded materials (FGMs) were fabricated by tape casting and laminating. Microstructures of FGMs were observed by optical microscope. Fracture behavior of FGMs in different loading modes and influences of different gradient changes on flexural strength were investigated. The results show that ZrO2/ SUS316L FGMs with graded components at interlayers are obtained after they are sintered in vacuum and pressureless condition at 1 350 ℃. TheⅠ?Ⅱ mixed mode crack creates in composite layer and grows to both sides zigzag while loading on ZrO2 layer. Flexural strengths are 496.4,421.7 and 387.5 MPa when gradient changes are 10%,15% and 20%,but flexural strengths of the corresponding fracture layers are 387.1,334.6 and 282.3 MPa since cracks of FGMs are affected by three-dimensional stress,respectively. The cracks are generated in ZrO2 layer and extend to SUS316L layer while loading is added on SUS316L layer,flexural strength does not change with the graded components and keeps consistent basically.展开更多
The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governi...The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governing equations of fractional order generalized thermoelasticity with three-phase lag model for functionally graded materials(FGM)(i.e., material with spatially varying material properties) are established. The analytical solution in the transform domain is obtained by using the eigenvalue approach.The inversion of Laplace transform is done numerically. The graphical results indicate that the fractional parameter has significant effects on all the physical quantities. Thus, we can consider the theory of fractional order generalized thermoelasticity an improvement on studying elastic materials.展开更多
A generalized form of material gradation applicable to a more broad range of functionally graded materials(FGMs) was presented.With the material model,analytical expressions of crack tip higher order stress fields in ...A generalized form of material gradation applicable to a more broad range of functionally graded materials(FGMs) was presented.With the material model,analytical expressions of crack tip higher order stress fields in a series form for opening mode and shear mode cracks under quasi-static loading were developed through the approach of asymptotic analysis.Then,a numerical experiment was conducted to verify the accuracy of the developed expressions for representing crack tip stress fields and their validity in full field data analysis by using them to extract the stress intensity factors from the results of a finite element analysis by local collocation and then comparing the estimations with the existing solution.The expressions show that nonhomogeneity parameters are embedded in the angular functions associated with higher terms in a recursive manner and at least the first three terms in the expansions must be considered to explicitly account for material nonhomogeneity effects on crack tip stress fields in the case of FGMs.The numerical experiment further confirms that the addition of the nonhomogeneity specific terms in the expressions not only improves estimates of stress intensity factor,but also gives consistent estimates as the distance away from the crack tip increases.Hence,the analytical expressions are suitable for the representation of crack tip stress fields and the analysis of full field data.展开更多
In this work,we extend the recently proposed adaptive phase field method to model fracture in orthotropic functionally graded materials(FGMs).A recovery type error indicator combined with quadtree decomposition is emp...In this work,we extend the recently proposed adaptive phase field method to model fracture in orthotropic functionally graded materials(FGMs).A recovery type error indicator combined with quadtree decomposition is employed for adaptive mesh refinement.The proposed approach is capable of capturing the fracture process with a localized mesh refinement that provides notable gains in computational efficiency.The implementation is validated against experimental data and other numerical experiments on orthotropic materials with different material orientations.The results reveal an increase in the stiffness and the maximum force with increasing material orientation angle.The study is then extended to the analysis of orthotropic FGMs.It is observed that,if the gradation in fracture properties is neglected,the material gradient plays a secondary role,with the fracture behaviour being dominated by the orthotropy of the material.However,when the toughness increases along the crack propagation path,a substantial gain in fracture resistance is observed.展开更多
Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient ...Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array,where the percentage of graphite particles were observed higher.Variable process parameters those influenced the rate of wear directly or indirectly were:applied load(15,25 and 35 N),slide velocity(1.5,2.5 and 3.5 m/s)and slide distance(750,1500 and 2250 m).Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance,whereas showing a decline during intermediate slide velocity.Signal-to-Noise ratio predicted the minimal tribo-condition,on‘smaller-the-better’basis.Analysis of Variance technique quantified the influence of affecting parameters,along with their interactions.Regression analysis was utilized for the validation of the experimental data.Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.展开更多
The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is...The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.展开更多
FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test ...FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test machine were utilized to characterize the microstructure,component,mechanical properties and the formation of the Ca-deficient apatite on the surface of these materials.The results indicate that an asymmetrical FeCrAl(f)/HA FGM,consolidating powders prepared by mixing HA with 3%–15%(volume fraction) is successfully prepared.Both of the matrix and FeCrAl fiber are integrated very tightly and bite into each other very deeply.And counter diffusion takes place to some extent in two phase interfaces.The elemental compositions of the FeCrAl(f)/HA FGM change progressively.Ca and P contents increase gradually with immersion time increasing,and thereafter approach equilibrium.The bone-like apatite layer forms on the materials surface,which possesses benign bioactivity,and the favorable biocompatibility can provide potential firm fixation between FeCrAl(f)/HA asymmetrical FGM implants and human bone.展开更多
Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanoc...Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.展开更多
This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the s...This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.展开更多
A typical contemporary computerized product develop me nt workflow is outlined in Fig.1. Product geometry information is first prep ared with computer-aided design (CAD) software. The CAD format can then be com munica...A typical contemporary computerized product develop me nt workflow is outlined in Fig.1. Product geometry information is first prep ared with computer-aided design (CAD) software. The CAD format can then be com municated to other downstream-computerized applications like, computer-aided e ngineering analysis (CAE), computer-aided manufacturing (CAM) and/or rapid prot otyping. Since design may need to be modified to incorporate new requirements, a loop back path is also depicted in Fig.1. The design engineers will check ac cording to their experience, result of physical test and CAE simulation to decid e whether redesign is needed or not. If the design passes all tests, its pr ototype or product can be produced. Otherwise, the current practice is to chang e its geometry and/or select a more appropriate material. The iteration repeat s until the latest version satisfies the engineering specification and customer requirements. Note that the material is homogeneous in the part to be designed. With the advent of functionally graded material (FGM) research, a new workflow will become possible. Components incorporating FGM’s can be designed to achieve levels of performance superior to that of homogeneous materials by combining the desirable properties of each constituent phase. Theoretically, the material composition can be tailo red within a component to achieve local control of properties; for example, form ability, corrosion resistance, hardness, toughness, and so on. By such local co ntrol, monolithic components can be created that integrate the function of multi ple discrete components, saving part count, space, weight, and enabling concepts that would otherwise be impractical. Controlling the spatial distribution of p roperties via composition will allow for control of the state of the entire comp onent (the state of residual stress in a component). There are various methods p roposed to produce FGM components. In particular, solid freeform fabrication ( SFF) methods are commonly used to directly fabricate an FGM part in an additive fashion directly from a computer controlled, layer-by-layer, additive process in which a standard CAD is sliced into a series of horizontal planes. Common SF F techniques being investigated include three-dimensional printing (3DP), Lamin ate Object Manufacturing (LOM), Extrusion Freeform Fabrication (EFF), Selective Laser Sintering (SLS) and even Stereolithography (SL). Fig.1 Current CAE design workflow Fig.2 Proposed CAE design workflow for FGM Albeit the feasibility to fabricate FGM components, one gap still needs to be fi lled for real life FGM product design; namely, where and how to grade the compon ent. This paper will, thus, address issues on incorporating FGM for design impr ovement. Rather than changing the geometry or reselecting a new material, a FGM approach can be employed in design enhancement as shown in Fig.2. The same geo metry and material is retained except that functional property in needed regions is selectively reinforced. As in conventional workflow, CAE simulation is perf ormed after CAD modelling. CAE simulation is preferred since physical test is v ery expensive and most of them are destructive. Moreover, the experience of the engineers may not be accurate. More importantly, the result of CAE simulation is used in this research to produce a stress intensity map for selective reinfor cement. The map will be converted to tool path control signals for generating FG component via SFF machine. On the implementation side, SolidWorks is used fo r CAD modeling, COSMOS/Works is used for CAE simulation. The model is then selec tively reinforced according to the simulation result to produce a FGM enriched p ath plan to drive the Z-corp machine. Case studies are performed to verify the approach. The preliminary result is positive. Future extension to material oth er than starch and plaster powders and enhancement other than stress distributio n may be explored. In conclusion, a CAE-based methodology for FGM product des ign展开更多
By virtue of a complete set of two displacement potentials,an analytical derivation of the elastostatic Green’s functions of an exponentially graded transversely isotropic substrate–coating system is presented.Three...By virtue of a complete set of two displacement potentials,an analytical derivation of the elastostatic Green’s functions of an exponentially graded transversely isotropic substrate–coating system is presented.Three-dimensional point–load and patch–load Green’s functions for stresses and displacements are given in line-integral representations.The formulation includes a complete set of transformed stress–potential and displacement–potential relations,with utilizing Fourier series and Hankel transforms.As illustrations,the present Green’s functions are degenerated to the special cases such as an exponentially graded half-space and a homogeneous two-layered half-space Green’s functions.Because of complicated integrand functions,the integrals are evaluated numerically and for numerical computation of the integrals,a robust and effective methodology is laid out which gives the necessary account of the presence of singularities of integration.Comparisons of the existing numerical solutions for homogeneous two-layered isotropic and transversely isotropic half-spaces are made to confirm the accuracy of the present solutions.Some typical numerical examples are also given to show the general features of the exponentially graded two-layered half-space Green’s functions that the effect of degree of variation of material properties will be recognized.展开更多
为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立...为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.展开更多
文摘Recent advancements in additive manufacturing(AM)have revolutionized the design and production of complex engineering microstructures.Despite these advancements,their mathematical modeling and computational analysis remain significant challenges.This research aims to develop an effective computational method for analyzing the free vibration of functionally graded(FG)microplates under high temperatures while resting on a Pasternak foundation(PF).This formulation leverages a new thirdorder shear deformation theory(new TSDT)for improved accuracy without requiring shear correction factors.Additionally,the modified couple stress theory(MCST)is incorporated to account for sizedependent effects in microplates.The PF is characterized by two parameters including spring stiffness(k_(w))and shear layer stiffness(k_(s)).To validate the proposed method,the results obtained are compared with those of the existing literature.Furthermore,numerical examples explore the influence of various factors on the high-temperature free vibration of FG microplates.These factors include the length scale parameter(l),geometric dimensions,material properties,and the presence of the elastic foundation.The findings significantly enhance our comprehension of the free vibration of FG microplates in high thermal environments.In addition,the findings significantly enhance our comprehension of the free vibration of FG microplates in high thermal environments.In addition,the results of this research will have great potential in military and defense applications such as components of submarines,fighter aircraft,and missiles.
基金Project(2020B090922002)supported by Guangdong Provincial Key Field Research and Development Program,ChinaProjects(51875215,52005189)supported by the National Natural Science Foundation of ChinaProject(2019B1515120094)supported by Guangdong Provincial Basic and Applied Basic Research Fund,China。
文摘Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufacturing highlights the capability in manufacturing FGMs with a high geometrical complexity and manufacture flexibility.In this work,the 316L/CuSn10/18Ni300/CoCr four-type materials FGMs were fabricated using SLM.The microstructure and properties of the FGMs were investigated to reveal the effects of SLM processing parameters on the defects.A large number of microcracks were found at the 316L/CuSn10 interface,which initiated from the fusion boundary of 316L region and extended along the building direction.The elastic modulus and nano-hardness in the 18Ni300/CoCr fusion zone decreased significantly,less than those in the 18Ni300 region or the CoCr region.The iron and copper elements were well diffused in the 316L/CuSn10 fusion zone,while elements in the CuSn10/18Ni300 and the 18Ni300/CoCr fusion zones showed significantly gradient transitions.Compared with other regions,the width of the CuSn10/18Ni300 interface and the CuSn10 region expand significantly.The mechanisms of materials fusion and crack generation at the 316L/CuSn10 interface were discussed.In addition,FGM structures without macro-crack were built by only altering the deposition subsequence of 316L and CuSn10,which provides a guide for the additive manufacturing of FGM structures.
基金National Natural Science Foundation of China[grant number U1730112],China.
文摘In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.
文摘The finite element method (FEM) and the boundary element method (BEM) are often adopted. However, they are not convenient to spatially vary thermal properties of functionally graded material (FGM). Therefore, the method of lines (MOL) is introduced to solve the temperature field of FGM. The basic idea of the method is to semi-discretize the governing equation into a system of ordinary differential equations (ODEs) defined on discrete lines by means of the finite difference method. The temperature field of FGM can be obtained by solving the ODEs. The functions of thermal properties are directly embodied in these equations and these properties are not discretized in the domain. Thus, difficulty of FEM and BEM is overcome by the method. As a numerical example, the temperature field of a plane problem is analyzed for FGMs through varying thermal conductivity coefficient by the MOL.
文摘Micro-scale functionally graded material(FGM)pipes conveying fluid have many significant applications in engineering fields.In this work,the thermoelastic vibration of FGM fluid-conveying tubes in elastic medium is studied.Based on modified couple stress theory and Hamilton’s principle,the governing equation and boundary conditions are obtained.The differential quadrature method(DQM)is applied to investigating the thermoelastic vibration of the FGM pipes.The effect of temperature variation,scale effect of the microtubule,micro-fluid effect,material properties,elastic coefficient of elastic medium and outer radius on thermoelastic vibration of the FGM pipes conveying fluid are studied.The results show that in the condition of considering the scale effect and micro-fluid of the microtubule,the critical dimensionless velocity of the system is higher than that of the system which calculated using classical macroscopic model.The results also show that the variations of temperature,material properties,elastic coefficient and outer radius have significant influences on the first-order dimensionless natural frequency.
基金Project (2007K06-13) supported by the Science and Technique Research and Development Program of Shaanxi Province, China
文摘Zirconia/stainless steel (ZrO2/SUS316L) functionally graded materials (FGMs) were fabricated by tape casting and laminating. Microstructures of FGMs were observed by optical microscope. Fracture behavior of FGMs in different loading modes and influences of different gradient changes on flexural strength were investigated. The results show that ZrO2/ SUS316L FGMs with graded components at interlayers are obtained after they are sintered in vacuum and pressureless condition at 1 350 ℃. TheⅠ?Ⅱ mixed mode crack creates in composite layer and grows to both sides zigzag while loading on ZrO2 layer. Flexural strengths are 496.4,421.7 and 387.5 MPa when gradient changes are 10%,15% and 20%,but flexural strengths of the corresponding fracture layers are 387.1,334.6 and 282.3 MPa since cracks of FGMs are affected by three-dimensional stress,respectively. The cracks are generated in ZrO2 layer and extend to SUS316L layer while loading is added on SUS316L layer,flexural strength does not change with the graded components and keeps consistent basically.
文摘The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governing equations of fractional order generalized thermoelasticity with three-phase lag model for functionally graded materials(FGM)(i.e., material with spatially varying material properties) are established. The analytical solution in the transform domain is obtained by using the eigenvalue approach.The inversion of Laplace transform is done numerically. The graphical results indicate that the fractional parameter has significant effects on all the physical quantities. Thus, we can consider the theory of fractional order generalized thermoelasticity an improvement on studying elastic materials.
基金Project(20080431344) supported by Postdoctoral Science Foundation of ChinaProject(51021001) supported by the National Natural Science Foundation of China
文摘A generalized form of material gradation applicable to a more broad range of functionally graded materials(FGMs) was presented.With the material model,analytical expressions of crack tip higher order stress fields in a series form for opening mode and shear mode cracks under quasi-static loading were developed through the approach of asymptotic analysis.Then,a numerical experiment was conducted to verify the accuracy of the developed expressions for representing crack tip stress fields and their validity in full field data analysis by using them to extract the stress intensity factors from the results of a finite element analysis by local collocation and then comparing the estimations with the existing solution.The expressions show that nonhomogeneity parameters are embedded in the angular functions associated with higher terms in a recursive manner and at least the first three terms in the expansions must be considered to explicitly account for material nonhomogeneity effects on crack tip stress fields in the case of FGMs.The numerical experiment further confirms that the addition of the nonhomogeneity specific terms in the expressions not only improves estimates of stress intensity factor,but also gives consistent estimates as the distance away from the crack tip increases.Hence,the analytical expressions are suitable for the representation of crack tip stress fields and the analysis of full field data.
基金E.Martínez-Paneda acknowledges financial support from the Royal Commission for the 1851 Exhibition through their Research Fellowship programme(RF496/2018).
文摘In this work,we extend the recently proposed adaptive phase field method to model fracture in orthotropic functionally graded materials(FGMs).A recovery type error indicator combined with quadtree decomposition is employed for adaptive mesh refinement.The proposed approach is capable of capturing the fracture process with a localized mesh refinement that provides notable gains in computational efficiency.The implementation is validated against experimental data and other numerical experiments on orthotropic materials with different material orientations.The results reveal an increase in the stiffness and the maximum force with increasing material orientation angle.The study is then extended to the analysis of orthotropic FGMs.It is observed that,if the gradation in fracture properties is neglected,the material gradient plays a secondary role,with the fracture behaviour being dominated by the orthotropy of the material.However,when the toughness increases along the crack propagation path,a substantial gain in fracture resistance is observed.
文摘Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array,where the percentage of graphite particles were observed higher.Variable process parameters those influenced the rate of wear directly or indirectly were:applied load(15,25 and 35 N),slide velocity(1.5,2.5 and 3.5 m/s)and slide distance(750,1500 and 2250 m).Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance,whereas showing a decline during intermediate slide velocity.Signal-to-Noise ratio predicted the minimal tribo-condition,on‘smaller-the-better’basis.Analysis of Variance technique quantified the influence of affecting parameters,along with their interactions.Regression analysis was utilized for the validation of the experimental data.Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.
基金Projects(50323008, 50574104) supported by the National Natural Science Foundation of ChinaProject (04JJ3084) supported by the Natural Science Foundation of Hunan Province, China
文摘The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.
基金Project(51274247)supported by the National Natural Science Foundation of ChinaProject(2012BAE06B00)supported by the National High Technology Research and Development Program to China+1 种基金Project(2011QNZT046)supported by the Fundamental Research Funds of Central South Universities of ChinaProject supported by Hunan Postdoctoral Scientific Program,China
文摘FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test machine were utilized to characterize the microstructure,component,mechanical properties and the formation of the Ca-deficient apatite on the surface of these materials.The results indicate that an asymmetrical FeCrAl(f)/HA FGM,consolidating powders prepared by mixing HA with 3%–15%(volume fraction) is successfully prepared.Both of the matrix and FeCrAl fiber are integrated very tightly and bite into each other very deeply.And counter diffusion takes place to some extent in two phase interfaces.The elemental compositions of the FeCrAl(f)/HA FGM change progressively.Ca and P contents increase gradually with immersion time increasing,and thereafter approach equilibrium.The bone-like apatite layer forms on the materials surface,which possesses benign bioactivity,and the favorable biocompatibility can provide potential firm fixation between FeCrAl(f)/HA asymmetrical FGM implants and human bone.
文摘Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.
文摘This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.
文摘A typical contemporary computerized product develop me nt workflow is outlined in Fig.1. Product geometry information is first prep ared with computer-aided design (CAD) software. The CAD format can then be com municated to other downstream-computerized applications like, computer-aided e ngineering analysis (CAE), computer-aided manufacturing (CAM) and/or rapid prot otyping. Since design may need to be modified to incorporate new requirements, a loop back path is also depicted in Fig.1. The design engineers will check ac cording to their experience, result of physical test and CAE simulation to decid e whether redesign is needed or not. If the design passes all tests, its pr ototype or product can be produced. Otherwise, the current practice is to chang e its geometry and/or select a more appropriate material. The iteration repeat s until the latest version satisfies the engineering specification and customer requirements. Note that the material is homogeneous in the part to be designed. With the advent of functionally graded material (FGM) research, a new workflow will become possible. Components incorporating FGM’s can be designed to achieve levels of performance superior to that of homogeneous materials by combining the desirable properties of each constituent phase. Theoretically, the material composition can be tailo red within a component to achieve local control of properties; for example, form ability, corrosion resistance, hardness, toughness, and so on. By such local co ntrol, monolithic components can be created that integrate the function of multi ple discrete components, saving part count, space, weight, and enabling concepts that would otherwise be impractical. Controlling the spatial distribution of p roperties via composition will allow for control of the state of the entire comp onent (the state of residual stress in a component). There are various methods p roposed to produce FGM components. In particular, solid freeform fabrication ( SFF) methods are commonly used to directly fabricate an FGM part in an additive fashion directly from a computer controlled, layer-by-layer, additive process in which a standard CAD is sliced into a series of horizontal planes. Common SF F techniques being investigated include three-dimensional printing (3DP), Lamin ate Object Manufacturing (LOM), Extrusion Freeform Fabrication (EFF), Selective Laser Sintering (SLS) and even Stereolithography (SL). Fig.1 Current CAE design workflow Fig.2 Proposed CAE design workflow for FGM Albeit the feasibility to fabricate FGM components, one gap still needs to be fi lled for real life FGM product design; namely, where and how to grade the compon ent. This paper will, thus, address issues on incorporating FGM for design impr ovement. Rather than changing the geometry or reselecting a new material, a FGM approach can be employed in design enhancement as shown in Fig.2. The same geo metry and material is retained except that functional property in needed regions is selectively reinforced. As in conventional workflow, CAE simulation is perf ormed after CAD modelling. CAE simulation is preferred since physical test is v ery expensive and most of them are destructive. Moreover, the experience of the engineers may not be accurate. More importantly, the result of CAE simulation is used in this research to produce a stress intensity map for selective reinfor cement. The map will be converted to tool path control signals for generating FG component via SFF machine. On the implementation side, SolidWorks is used fo r CAD modeling, COSMOS/Works is used for CAE simulation. The model is then selec tively reinforced according to the simulation result to produce a FGM enriched p ath plan to drive the Z-corp machine. Case studies are performed to verify the approach. The preliminary result is positive. Future extension to material oth er than starch and plaster powders and enhancement other than stress distributio n may be explored. In conclusion, a CAE-based methodology for FGM product des ign
文摘By virtue of a complete set of two displacement potentials,an analytical derivation of the elastostatic Green’s functions of an exponentially graded transversely isotropic substrate–coating system is presented.Three-dimensional point–load and patch–load Green’s functions for stresses and displacements are given in line-integral representations.The formulation includes a complete set of transformed stress–potential and displacement–potential relations,with utilizing Fourier series and Hankel transforms.As illustrations,the present Green’s functions are degenerated to the special cases such as an exponentially graded half-space and a homogeneous two-layered half-space Green’s functions.Because of complicated integrand functions,the integrals are evaluated numerically and for numerical computation of the integrals,a robust and effective methodology is laid out which gives the necessary account of the presence of singularities of integration.Comparisons of the existing numerical solutions for homogeneous two-layered isotropic and transversely isotropic half-spaces are made to confirm the accuracy of the present solutions.Some typical numerical examples are also given to show the general features of the exponentially graded two-layered half-space Green’s functions that the effect of degree of variation of material properties will be recognized.
文摘为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.
