Showing papers on "Functionally graded material published in 2020"

A simple nth-order shear deformation theory for thermomechanical bending analysis of different configurations of FG sandwich plates

Abstract: In this work, thermomechanical flexural analysis of functionally graded material sandwich plates with P-FGM face sheets and E-FGM and symmetric S-FGM core is performed by employing a nth-order shear deformation theory. A novel type of SFGM sandwich plates, namely, both P-FGM face sheets and a symmetric S-FGM hard core are considered. By employing only four unknown variables, the governing equations are obtained based on the principle of virtual work and then Navier method is used to solve these equations. Analytical solutions are deduced to compute the stresses and deflections of simply supported S-FGM sandwich plates. The effects of volume fraction variation, geometrical parameters and thermal load on thermomechanical flexural behavior of the symmetric FGM sandwich plates are investigated.

Development and characterization of 316L/Inconel625 functionally graded material fabricated by laser direct metal deposition

Abstract: Functionally graded material (FGM) is a composite with innovative structure and function, which has the good overall performance and meets working requirements in harsh environments. FGM has been widely used in aerospace, biological, nuclear, and photoelectric engineering fields. Laser direct metal deposition (LDMD) is an advanced manufacturing method that is excellent at fabricating objects with optimized geometries and minimizing weight using far less material and energy. In this paper, FGM with the constitution varying from 100% 316L stainless steel to 100% Inconel625 alloy was successfully fabricated using LDMD technology. Grain morphology, composition, mechanical properties and abrasive resistance were obtained to investigate the microstructure and mechanical performance of FGM. With the Inconel625 content increasing, primary dendrite arm spacing gradually increased, and white second phases began to precipitate along dendrites boundary when the content of Inconel625 exceeded 80%. Micro-hardness gradually increased from 216.47 HV at the bottom of FGM to 355.7 HV at the top. With micro-hardness and the hard phase volume increasing, the wear rate of FGM declined and the wear resistance was improved. The fracture element analysis showed that a large number of small and uneven distributed second phases led to the graded material fracture and the tensile fracture mechanism was of typical micro-porous aggregation toughness fracture.

On the surface elastic-based shear buckling characteristics of functionally graded composite skew nanoplates

Abstract: The prime objective of the present investigation is to predict the shear buckling characteristics of skew nanoplates made of a functionally graded material (FGM) in the presence of surface stress effect. For this purpose, the Gurtin-Murdoch surface theory of elasticity is applied to the higher-order shear deformation plate theory within the framework of the oblique coordinate system. Different types of the homogenization scheme including Reuss model, Voigt model, Mori-Tanaka model, and Hashin-Shtrikman bounds model are taken into consideration in order to extract the effective mechanical properties of FGM skew nanoplates. The Ritz method using Gram-Schmidt shape functions is utilized to obtain the surface elastic-based shear buckling loads of FGM skew nanoplates. It is indicated that by increasing the value of the index associated with the material property gradient, the significance of the surface stress type of size effect on the shear buckling behavior of a FGM skew nanoplate improves. Moreover, by changing the boundary conditions from simply supported ones to clamped ones, the influence of the skew angle on the surface elastic-based shear buckling load of a FGM skew nanoplate increases. Also, it is illustrated that by increasing the width to thickness ratio of a skew nanoplate, the free surface area increases which results in to enhance the effect of surface residual stress on its shear buckling characteristics.

Fabrication strategy of complicated Al2O3-Si3N4 functionally graded materials by stereolithography 3D printing

Abstract: For multi-ceramic materials based on the stereolithography (SL) principle, a 3D printing strategy was developed, and then an Al2O3-Si3N4 functionally graded material (FGM) ceramic part was fabricated using this strategy. Six groups of mixtures, with a Si3N4 content gradient of 20 vol% and a certain bimodal particle size distribution, were prepared using UV-curable pastes. A modified formula was proposed to evaluate the relationship between the actual minimum voidage of mixtures and the viscosities of their corresponding pastes. The viscosity of each paste was controlled using the prediction formula and optimization of dispersants. To design theprinting layer thickness, a mathematical relationship was established between Si3N4 content and curing depth of paste. The Al2O3-Si3N4 green body without deformation was printed using optimized parameters such as a layer thickness of 40 μm and a paste viscosity of ∼13,000 mPa·s. Finally, using debinding and sintering, denseparts having a complicated shape were obtained.

Wave based method for free vibration characteristics of functionally graded cylindrical shells with arbitrary boundary conditions

Abstract: The wave based method (WBM) is used to analyze the free vibration characteristics of functionally graded material (FGM) cylindrical shell with arbitrary boundary conditions. The motion relationship is described by the first-order shear deformation shell theory (FSDST). The displacement components and transverse rotations are expressed as wave function expansions. In accordance with the dynamic relationship, the final governing equation and global matrix are assembled by incorporating the boundary matrices. The natural frequency of the system is obtained by solving the determinant of the global matrix. By comparing the results with those in the literature, the validity of the proposed method is verified. In addition, the influences of power-law exponents and boundary conditions on natural frequencies are analyzed. The effects of geometric parameters including the ratio of thickness to radius and the ratio of length to the radius on natural frequencies are discussed. The purpose of this paper is to demonstrate the ease of application of the WBM for the free vibration of FGM cylindrical shells with arbitrary boundary conditions. Furthermore, the advantage of the WBM are: (1) the global matrix is easy to construct; (2) different boundary conditions can be conveniently adjusted; (3) it is with high computational efficiency and precision.

On modal analysis of axially functionally graded material beam under hygrothermal effect

Abstract: This investigation focuses on the modal analysis of an axially functionally graded material beam under hygrothermal effect. The material constants of the beam are supposed to be graded smoothly alo...

Wire arc additive manufacturing of functionally graded material for marine risers

Abstract: Functionally graded materials (FGM), whose structural properties are varied along their volume to perform an intended function, have a full application in the marine industry Under the corrosive marine environment, a corrosion-resistant alloy of duplex stainless steel, functionally graded with carbon-manganese steel along with the inner layer, is proposed here for the risers The interface strength of FGM, fabricated using Cold Metal Transfer – gas metal arc welding, based on Wire Arc Additive Manufacturing (WAAM) in the lab-scale, is compared with an X-52 Carbon Manganese steel to highlight the superiority of the proposed FGM The role of metal transfer characteristics on the microstructure formation at the layers adjacent to the interface is analyzed and correlated with the voltage-current waveform those obtained during the deposition process Based on the experimental studies carried out, it is seen that the yield strength of the FGM interface is very close to that of X52 steel, with a marginal increase of about 6% in the ultimate strength Based on the energy dispersive X-ray analysis, it is observed that there is no enrichment of chromium across the interface towards the carbon-manganese steel side It is vital for the corrosion-resistance of duplex stainless steel Proposed FGM shows advantages both in strength and durability and hence seen as a promising candidate for marine riser applications

Nonlinear Vibration Analysis of Sigmoid Functionally Graded Sandwich Plate with Ceramic-FGM-Metal Layers

Abstract: In the present study, free and forced nonlinear vibration characteristics of a sandwich functionally graded material (FGM) plate resting on Pasternak elastic foundation have been investigated. The formulation is based on non-polynomial higher-order shear deformation theory with inverse hyperbolic shape function. A new modified sigmoid law is presented to compute the effective material properties of sandwich FGM plate. The governing equilibrium equations have been formulated using Hamilton’s principle and the governing nonlinear coupled ordinary differential equations are derived using stress function method in conjunction with Galerkin approach. The resulting equations are then solved using fourth order Runge–Kutta time integration scheme for simply supported plate with immovable edges. Comprehensive parametric studies have been performed to analyze the influence of geometric configuration, volume fraction exponent, and elastic medium parameter on nonlinear time series analysis for different configurations of sandwich plate. A nonlinear complex behaviour of the plate is studied using time displacement response, phase-plane plot and Poincare map. For Pasternak foundation, system shows multi-loop periodic nature while it losses its periodicity and shows the quasi-periodic nature for Winkler foundation. In addition, it has been observed that the system shows quasi-periodic route to chaotic nature for thick plate to thin plate.

Production and Characterization of a Bone-Like Porous Ti/Ti-Hydroxyapatite Functionally Graded Material

Abstract: A new kind of functionally graded material (FGM) that mimics the inner porous structure and outer dense layer of human bone was produced using powder metallurgy. The inner part of the FGM material (16 mm in diameter) has porosity of approximately 60%, and its mechanical properties are compatible with cortical bone; however, the shell (1.8 mm in thickness) is composed of a layer of Ti-10% wt. hydroxyapatite (HA) and shows hydrophilic behavior and improved biofunction. Elastic moduli of the core and shell layer were calculated as 18.99 and 42.98 GPa, respectively, and those values are compatible with that of cortical bone. Addition of HA to the shell had a significant effect on the wettability (81.6% decrease) and cell viability (46% increase). Furthermore, the porosity of the shell layer (28.88%) is similar to that of human cortical bone. It is concluded that the developed Ti-HA FGM has promising properties for implant applications.

Experimental investigation on laser directed energy deposition of functionally graded layers of Ni-Cr-B-Si and SS316L

Abstract: Functionally Graded Material (FGM) is necessary for successful performance of two dissimilar materials joint, specifically when there is a large difference in the thermophysical properties of the materials and the joints are subjected to cyclic loading and extreme duty conditions. Laser Additive Manufacturing using Direct Energy Deposition (LAM-DED) is one of the advanced additive manufacturing processes favored for fabrication of FGMs. In the present work, an indigenously developed LAM-DED system is deployed for fabricating FGM of Ni-Cr-B-Si and SS316L. Parametric study is performed by varying the laser power, scan speed and powder feed rate and process parameter combination is identified for depositing uniform and continuous Ni-Cr-B-Si tracks with aspect ratio greater than 5. The identified process parameter combination is deployed for fabricating FGM of Ni-Cr-B-Si and SS316L and the composition of fabricated FGM is confirmed using Energy Dispersive Spectroscopy analysis. The surface topography analysis using Scanning Electron Microscopy indicates that the amount of partially melted powders increases with the increase in concentration of SS316L. Microstructure of as-built deposit is primarily dendritic with fine dendrites of ~5 µm. Micro-hardness and Single Cycle Automated ball indentation (SC-ABI) measurements indicates higher hardness and lower energy storage capacity for Ni-Cr-B-Si rich region as compared to SS316L rich region. The highest microhardness value of 645.23 HV1.96N is observed at the top layer of the graded deposit where Ni-Cr-B-Si fraction is 100%. SC-ABI testing indicates that the energy storage capacity of the material increases with increasing concentration of SS316L with similar trend for maximum displacement of the indenter. Further, LAM-DED deposits are heat-treated in muffle furnace at 900 Deg. C for two hours. The microstructural examination of thus heat-treated samples shows recrystallized grains in the Ni-Cr-B-Si rich region while dendritic microstructure is retained at the SS316L rich region. X-ray diffraction studies shows the difference in the diffraction patterns of as-built and heat-treated deposits with the absence of Ni3B phases in heat-treated samples. Microhardness studies indicate a large difference in hardness values in as-built and heat-treated deposits with a micro-hardness of 255.6 HV1.96N for 100% Ni-Cr-B-Si. SC-ABI studies show that heat treatment improves the energy absorbing capacity of the graded deposit. This study paves a way for the fabrication of Ni-Cr-B-Si and SS316L FGM with tailored mechanical and microstructural properties.

Impacts of laser cladding residual stress and material properties of functionally graded layers on titanium alloy sheet

Abstract: Laser cladding induces high tensile residual stress (RS), which can compromise the quality of a specimen. Therefore, it is critical to accurately predict the RS distribution in cladding and understand its formation mechanism. In this study, functionally graded material (FGM) layers were successfully deposited on the surface of a titanium alloy Ti6Al4V sheet by laser cladding technology. A corresponding thermo-mechanical coupling simulation model of the laser cladding process was developed to investigate the formation mechanism of RS in the laser cladding FGM layers. The results show that high tensile RS forms in cladding components. Subsequent cladding can effectively alleviate the RS in cladding components although the position of maximum RS remains unchanged. The measurement results of the longitudinal RS on the top and bottom surfaces of cladding components by the X-ray diffraction (XRD) method agreed with the simulation results, thereby proving the accuracy of the simulation. In addition, the formation mechanism of RS in the laser cladding FGM layers was revealed by discussing the individual impact of each material property on RS. It was indicated that the RS distribution in the laser cladding FGM layers was significantly affected by material properties (in particular, coefficient of thermal expansion and Young’s modulus), except for the temperature gradient induced by the laser cladding process.

Photo-Thermal-Elastic Interaction in a Functionally Graded Material (FGM) and Magnetic Field

Abstract: In this work, we aim to investigate the photo-thermal-elastic waves interaction in a nano-composite semiconductor, elastic and functionally graded material (FGM). The governing equations are taken in one dimension during the influence of initial magnetic field when the elastic medium is isotropic and the material properties are non-homogeneity. In the domain of Laplace transform the basic equations in non- dimensional forms are formulated in a vector matrix differential equation and are solved by the eigenvalue and eigenvector approach. The physical quantities are obtained by applying the numerical inversion method of the transforms. The numerical results of the physical quantities (carrier density, displacement, temperature, stresses and strains) are discussed and illustrated graphically.

An analytical study on wave propagation in functionally graded nano-beams/tubes based on the integral formulation of nonlocal elasticity

Abstract: In the context of integral formulation of Eringen’s nonlocal elasticity theory, flexural, axial and shear wave propagations in nano-beams/tubes made of functionally graded materials (FGMs) are anal...

Thermo-mechanical analysis of porous sandwich S-FGM plate for different boundary conditions using Galerkin Vlasov's method: A semi-analytical approach

Abstract: In the present paper, for the first time, an attempt has been made to obtain the solution for bending and stress under the thermal environment using Galerkin Vlasov's method. A non-polynomial based higher-order shear deformation theory with inverse tangent hyperbolic shape function is used to define the displacement field. The formulation is performed for the author's recently developed sandwich plate using a new modified sigmoid function-based functionally graded material (S-FGM) plate of different symmetric and non-symmetric configurations. Using a one-dimensional steady-state heat conduction equation, a new temperature distribution through the thickness based on modified sigmoid law is proposed. Three different types of porosity are considered viz. even, uneven but symmetric and uneven but non-symmetric. A new uneven non-symmetric porosity model is used in which micro-voids are varied in accordance with material property variation in the thickness direction in order to capture the accurate distribution of voids on the plate. The principle of virtual work is employed to derive equilibrium equations. An exact solution is obtained using the assumed solution with shape functions satisfying the edge boundary conditions. From the present study on static analysis, it is deduced that more refined and accurate results for plate in thermal environment, it is necessary to include the thermal effect on the stiffness of the plate in addition to the initial deflection of the plate. The effect of boundary conditions on stress and deflection distribution along the surface of the porous plate is studied, and it is observed that the distribution is prominently affected by the type of symmetric or asymmetric boundary conditions. The considerable increase in deflection and stress can be seen for even porosity distribution (P-1) in comparison to uneven symmetric (P-2) or uneven non-symmetric (P-3) porosity distribution. In addition, the maximum transverse shear stresses are offset more from the center of the sandwich plate with an increase in temperature differences with a maximum offset at ΔT = 300 K and minimum offset at ΔT = 0 K. Different examples are considered to check the accuracy and validation of the present formulation. The calculated outcomes and interpretations can be useful as a validation study for the imminent investigation of sandwich S-FGM plates having porosities in the thermal environment.

Free vibrations and static analysis of functionally graded sandwich plates with three-dimensional finite elements

Abstract: A three-dimensional modelling of free vibrations and static response of functionally graded material (FGM) sandwich plates is presented. Natural frequencies and associated mode shapes as well as displacements and stresses are determined by using the finite element method within the ABAQUS™ code. The three-dimensional (3-D) brick graded finite element is programmed and incorporated into the code via the user-defined material subroutine UMAT. The results of modal and static analyses are demonstrated for square metal-ceramic functionally graded simply supported plates with a power-law through-the-thickness variation of the volume fraction of the ceramic constituent. The through-the-thickness distribution of effective material properties at a point are defined based on the Mori-Tanaka scheme. First, exact values of displacements, stresses and natural frequencies available for FGM sandwich plates in the literature are used to verify the performance and estimate the accuracy of the developed 3-D graded finite element. Then, parametric studies are carried out for the frequency analysis by varying the volume fraction profile and value of the ceramic volume fraction.

Pull-in and freestanding instability of actuated functionally graded nanobeams including surface and stiffening effects

Abstract: Because of fasttechnological development, electrostatic nanoactuator devices like nanosensors, nanoswitches, and nanoresonators are highly considered by scientific community. Thus, this article presents a new solution technique in solving highly nonlinear integro-differential equation governing electrically actuated nanobeams made of functionally graded material. The modified couple stress theory and Gurtin–Murdoch surface elasticity theory are coupled together to capture the size effects of the nanoscale thin beam in the context of Euler–Bernoulli beam theory. For accurate modelling, all the material properties of the bulk and surface continuums of the FG nanoactuator are varied continuously in thickness direction according to power law. The nonlinearity arising from the electrostatic actuation, fringing field, mid-plane stretching effect, axial residual stress, Casimir dispersion, and van der Waals forces are considered in mathematical formulation. The nonlinear nonclassical equilibrium equation of FG nanobeam-based actuators and associated boundary conditions are exactly derived using Hamilton principle. The new solution methodology is combined from three phases. The first phase applies Galerkin method to get an integro-algebraic equation. The second one employs particle swarm optimization method to approximate the integral terms (i.e. electrostatic force, fringing field, and intermolecular forces) to non-integral cubic algebraic equation. Then, solved the system easily in last phase. The resulting algebraic model provides means for obtaining critical deflection, pull-in voltage, detachment length, minimum gap, and freestanding effects. A reasonable agreement is found between the results obtained from the present method and those in the available literature. A parametric study is performed to investigate the effects of the gradient index, material length scale parameter, surface energy, intermolecular forces, initial gap, and beam length on the pull-in response and freestanding phenomena of fully clamped and cantilever FG nanoactuators.

Fluorinated epoxy insulator with interfacial conductivity graded material for HVDC gaseous insulated pipeline

Abstract: In this paper, a novel procedure is put forward to fabricate epoxy insulators with surface functionally graded material (SFGM) with optimized surface conductivity as obtained from the field non-uniformity and the leakage current. For fabrication, a temperature control system is employed to form a spatial temperature gradient, thus regulating fluorination from top to bottom of the insulator surface. Flashover tests are reported under DC voltage, and with DC voltage with polarity reversal; the results show the effectiveness of the SFGM to improve the performance of the insulator. A trap distribution and carrier transport model are utilized to analyze the improved flashover characteristics.

Free vibration of joined cylindrical–hemispherical FGM shells

Abstract: Free vibration response of a joined shell system including cylindrical and spherical shells is analyzed in this research. It is assumed that the system of joined shell is made from a functionally graded material (FGM). Properties of the shells are assumed to be graded through the thickness. Both shells are unified in thickness. To capture the effects of through-the-thickness shear deformations and rotary inertias, first-order shear deformation theory of shells is used. The Donnell type of kinematic assumptions is adopted to establish the general equations of motion and the associated boundary and continuity conditions with the aid of Hamilton’s principle. The resulting system of equations is discretized using the semi-analytical generalized differential quadrature method. Considering the clamped and free boundary conditions for the end of the cylindrical shell and intersection continuity conditions, an eigenvalue problem is established to examine the vibration frequencies of the joined shell. After proving the efficiency and validity of the present method for the case of thin isotropic homogeneous joined shells, some parametric studies are carried out for the system of combined moderately thick cylindrical–spherical shell system. Novel results are provided for the case of FGM joined shells to explore the influence of power-law index and geometric properties.