Showing papers on "Functionally graded material published in 2021"

Advances in additive manufacturing of metal-based functionally graded materials

Abstract: Over the 2010s technological improvements allowed metal additive manufacturing to graduate from a prototyping tool to a widespread, full-scale manufacturing process. Among the capabilities still un...

Nonlinear forced vibrations of FGM sandwich cylindrical shells with porosities on an elastic substrate

Abstract: The nonlinear forced vibrations of functionally graded material (FGM) sandwich cylindrical shells with porosities on an elastic substrate are studied. A step function and a porosity volume fraction are introduced to describe the porosities in FGM layers of sandwich shells. Using the Donnell’s nonlinear shallow shell theory and Hamilton’s principle, an energy approach is employed to gain the nonlinear equations of motion. Afterwards, the multi-degree-of-freedom nonlinear ordinary differential equations are carried out by using Galerkin scheme, and subsequently the pseudo-arclength continuation method is utilized to perform the bifurcation analysis. Finally, the effects of the core-to-thickness ratio, porosity volume fraction, power-law exponent, and external excitation on nonlinear forced vibration characteristics of FGM sandwich shells with porosities are investigated in detail.

Buckling and postbuckling response of nonlocal strain gradient porous functionally graded micro/nano-plates via NURBS-based isogeometric analysis

Abstract: The prime objective of the present investigation is to analyze the nonlinear buckling and postbuckling characteristics of micro/nano-plates made of a porous functionally graded material (PFGM) in the presence of nonlocality and strain gradient size dependencies. In accordance with this purpose, a modified porosity-dependent power-law function is put to use to estimate the effective mechanical properties of PFGM micro/nano-plates with various porosity distribution patterns. To solve the constructed nonlinear nonlocal strain gradient problem, the non-uniform rational B-spline (NURBS)-based isogeometric analysis is utilized as an efficient discretization technique. It is concluded that by taking the geometrical nonlinearity into account and moving to deeper part of the postbuckling regime, the significance of the both nonlocality and strain gradient size dependencies decreases. Also, by increasing the material property gradient index, an enhancement in the nonlocal and strain gradient size effects is found which is more considerable at deeper part of the postbuckling domain. In addition, it is demonstrated that for a PFGM micro/nano-plate, the value of the porosity index has a negligible influence on the significance of size dependencies, and this observation is the same for the both types of simply supported and clamped boundary conditions.

Dynamic stability of nonlocal strain gradient FGM truncated conical microshells integrated with magnetostrictive facesheets resting on a nonlinear viscoelastic foundation

Abstract: The objective of this investigation is to predict the size-dependent dynamic stability of truncated conical microshells made of a functionally graded material (FGM) integrated with magnetostrictive facesheets. The microshells are subjected to a combination of axial compressive load and magnetic field in the presence of the nonlocality and strain gradient size dependencies. The conical microshells are assumed to be surrounded by a two-parameter Winkler-Pasternak medium augmented via a Kelvin-Voigt viscoelastic approach taking a nonlinear cubic stiffness into account. The nonlocal strain gradient-based differential equations of motion are constructed based upon the third-order shear deformation conical shell theory including the magnetic permeability tensor together with the magnetic fluxes. The discretization process within the framework of the generalized differential quadrature technique is employed to achieve the nonlocal strain gradient-based load-frequency responses. It is found that increasing the material gradient index results in to decrease the nonlocal strain gradient frequency obtained for a specific value of the axial compression within the prebuckling regime. However, within the postbuckling domain, an increment in the value of the material gradient index plays an opposite role. Also, the gap between the load-frequency curves associated with various material gradient indexes are more prominent for the nonlocal strain gradient cases in comparison with the classical one.

Recent progress and scientific challenges in multi-material additive manufacturing via laser-based powder bed fusion

Abstract: Multi-material additive manufacturing provides a new route for fabricating components with tailored physical properties. Laser-based powder bed fusion (L-PBF), also known as selective laser melting...

Vibration characteristics of porous FGM plate with variable thickness resting on Pasternak's foundation

Abstract: In the paper, free vibration analysis of tapered Functionally Graded Material (FGM) plate with the inclusion of porosity has been performed. The tapered porous FGM plate is considered resting on a two-parameter (Winkler and Pasternak) elastic foundation. The displacement model of the kinematic equation for the plates in the present formulation is based on the First-order shear deformation theory (FSDT). The governing equation for free vibration analysis of FGM plates is obtained using Hamilton's principle. Simple power-law, Exponential Law, and Sigmoid law are used for tailored the material properties in the thickness direction of FGM plates. The solution of the resulting partial differential equation is obtained by using Galerkin-Vlasov's method with different boundary conditions. The solutions for uniform and uniform varying thick plates are investigated, and a comparative study is examined by comparing the results obtained with FSDT and Higher-order shear deformation theory (HSDT). The findings of the comparative study with the present approach provide pertinent outcomes for the vibration analysis of tapered FGM plates. The analytical solution for vibration analysis is presented to reveal the effects of porosity parameter, volume exponent, span ratio, aspect ratio, porosity distribution, and boundary conditions. Also, the elastic foundation parameter on tapered FGM plate increases the non-dimensional frequency, and the Pasternak foundation effect always dominates over the Winkler foundation.

Postbuckling analysis of hydrostatic pressurized FGM microsized shells including strain gradient and stress-driven nonlocal effects

Abstract: Herein, with the aid of the newly proposed theory of nonlocal strain gradient elasticity, the size-dependent nonlinear buckling and postbuckling behavior of microsized shells made of functionally graded material (FGM) and subjected to hydrostatic pressure is examined. As a consequence, the both nonlocality and strain gradient micro-size dependency are incorporated to an exponential shear deformation shell theory to construct a more comprehensive size-dependent shell model with a refined distribution of shear deformation. The Mori–Tanaka homogenization scheme is utilized to estimate the effective material properties of FGM nanoshells. After deduction of the non-classical governing differential equations via boundary layer theory of shell buckling, a perturbation-based solving process is employed to extract explicit expressions for nonlocal strain gradient stability paths of hydrostatic pressurized FGM microsized shells. It is observed that the nonlocality size effect causes to decrease the critical hydrostatic pressure and associated end-shortening of microsized shells, while the strain gradient size dependency leads to increase them. In addition, it is found that the influence of the internal strain gradient length scale parameter on the nonlinear instability characteristics of hydrostatic pressurized FGM microsized shells is a bit more than that of the nonlocal one.

Free vibration of FGM conical–spherical shells

Abstract: Natural frequencies of a conical–spherical functionally graded material (FGM) shell are obtained in this study. It is assumed that the conical and spherical shell components have identical thickness. The system of joined shell is made from FGMs, where properties of the shell are graded through the thickness direction. The first order shear deformation theory of shells is used to investigate the effects of shear strains and rotary inertia. The Donnel type of kinematic assumptions are 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 are discretized using the semi-analytical generalized differential quadrature (GDQ) method. Considering various types of boundary conditions for the shell ends and intersection continuity conditions, an eigenvalue problem is established to examine the vibration frequencies. After proving the efficiency and validity of the present method for the case of thin isotropic homogeneous joined shells with the data of conventional finite element software, parametric studies are carried out for the system of combined moderately thick conical–spherical joined shells made of FGMs and various types of end supports.

Vibration analysis of porous magneto-electro-elastically actuated carbon nanotube-reinforced composite sandwich plate based on a refined plate theory

Abstract: In this article, the free vibration response of sandwich plates with porous electro-magneto-elastic functionally graded (MEE-FG) materials as face sheets and functionally graded carbon nanotube-reinforced composites (FG-CNTRC) as core is investigated. To this end, four-variable shear deformation refined plate theory is exploited. The properties of functionally graded material plate are assumed to vary along the thickness direction of face sheets according to modified power-law expression. Furthermore, properties of FG-CNTRC layer are proposed via a mixture rule. Hamilton’s principle with a four-variable tangential–exponential refined theory is used to obtain the governing equations and boundary conditions of plate. An analytical solution approach is utilized to get the natural frequencies of embedded porous FG plate with FG-CNTRC core subjected to magneto-electrical field. A parametric study is led to fulfill the effects of porosity parameter, external magnetic potential, external electric voltage, types of FG-CNTRC, and different boundary conditions on dimensionless frequencies of porous MEE-FG sandwich plate. It is noteworthy that the numerical consequences can serve as benchmarks for future investigations for this type of structures with porous mediums.

Analysis of porosity effect on free vibration and buckling responses for sandwich sigmoid function based functionally graded material plate resting on Pasternak foundation using Galerkin Vlasov’s method:

Abstract: The objective of the present paper is to study the effect of porosity on vibration and buckling responses for sandwich plate supported with different boundary conditions at the edges. The formulati...

Structural integrity and mechanical properties of the functionally graded material based on 316L/IN718 processed by DED technology

Abstract: Additive manufacturing is a one of the most promising technology nowadays that offers the advantages not only in building products of complex shapes but also of complex materials. A complex structure is characteristic for Functionally Graded Composites, which basics, principles and applicability have been widely investigated over the last years. The present study is focused on the detailed investigation of mechanical and structural properties of FGC consisting of stainless steel 316L and Inconel 718 processed by Blown Powder Directed Energy Deposition system. Mechanical properties within single layers and over layers transitions were investigated with the use of tensile tests and fracture toughness tests. Metallographic and fractographic investigations were carried out. Metallographic investigation revealed the differences in the interfaces between single material layers, nucleation processes and subsequent growth of the grains of the used materials. It has been shown that the formation of transition region between deposited single material layers is dependent on the order of material deposition since different deposition parameters are used for certain material. Evaluation of the tensile properties showed that the mechanical properties of a single material layers are in very good agreement regardless of the deposition height. However, the types of interfaces considering to the results of fractographic observations affect the tensile performance of the Functionally Graded Composite. The fracture toughness test results demonstrate changes in the mechanism of crack propagation at the interface between materials with respect to the type of transition. Furthermore, the material layers interfaces turned out to be the weakest points of the Functionally Graded Composite.

On vibration of functionally graded sandwich nanoplates in the thermal environment

Abstract: This paper deals with the free vibration response of rectangular functionally graded material sandwich nanoplates with simply supported boundary conditions. The material properties of the FGM layer...

Understanding of process and material behaviours in additive manufacturing of Invar36/Cu10Sn multiple material components via laser-based powder bed fusion

Abstract: Bimetallic components and functionally graded material (FGM) samples manufactured by additive manufacturing reported in previous publications generally have macro defects such as insufficient powder melting, cracking, and porosity at the interfaces of dissimilar materials. There is little understanding of the causes of these defects. The motivation of this research was to explain why the un-melted particles and cracks were always present at the materials' interface when using laser-based powder bed fusion (PBF-LB) to process powder mixtures composed of two materials with significant different thermo-physical properties. In this study, the influence of laser volume energy density (VED) and material composition ratio on the melting status of laser-processed powder layers was investigated both experimentally and theoretically. Experimental results show that VED, sufficient to melt the high melting point Invar36 alone, is insufficient to melt the Invar36/Cu10Sn mixture. This phenomenon is because Cu10Sn copper alloy has lower laser beam absorptivity, higher thermal conductivity and lower melting temperature. When the Cu10Sn powder partially covers the surface of a powder layer, the laser energy absorption is reduced. Its high thermal conductivity causes heat to dissipate more quickly. These two factors make it difficult for Invar36 located below Cu10Sn to reach its melting point. Computational fluid dynamic and discrete element method simulation is conducted to understand this phenomenon, and it shows that increasing VED can improve the melting of the Invar36/Cu10Sn powder mixture.

Selective compositional range exclusion via directed energy deposition to produce a defect-free Inconel 718/SS 316L functionally graded material

Abstract: In this research, additively manufacturing a functionally graded material (FGM) with a compositional range of Ni-based Inconel superalloy (Inconel 718) and Fe-based stainless steel (SS 316L) via directed energy deposition (DED) was examined. The microstructural transformation, defect behavior, and Vickers hardness of the material were each determined as a function of the discrete chemical composition of the FGM varied in steps of 10 wt% of the two materials across its length. In particular, for the specific compositions of 30 wt% Inconel 718/70 wt% SS 316L and 20 wt% Inconel 718/80 wt% SS 316L, critical pores and cracks (defects) initiated by ceramic oxides occurred due to the presence of intermetallic and carbide compounds. In addition, the results of electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses of the FGM demonstrate that the thermal and residual stresses due to constitutional supercooling and columnar-to-equiaxial transition (CET) became concentrated at the grain boundaries, thereby further contributing to the formation of the defects. The measured Vickers hardness was inevitably found to be minimal near the defective compositional range regardless of laser parameter optimization due to the reduced generation of segregants in the inter-dendritic regions and the increased formation of precipitates at the grain boundaries. The results of microstructural and mechanical analyses indicate that deliberate and strategic removal of the defective compositional range helped obtain a robust FGM composed of Inconel 718 and SS 316L without noticeable defects.

Metallic glass properties, processing method and development perspective: a review

Abstract: This review paper aims to outline the development of Metallic Glass and its progress to functionally graded material. The review begins with the fundamental theory of producing the Metallic Glass and the challenges. Namely, the concept of glass-forming ability, alloy system of Metallic Glass, supercooling process, the mechanical and thermal characteristics. The authors presented the Metallic Glass processing method as pre and post-processing for further description. The different alloy systems of Metallic Glass produced by researchers created properties suitable for various industrial applications. Consequently, the authors point a focus on the Functionally Graded Material (FGM) of the Metallic Glass (MG) areas where further research needs to be researched. In distinction, the Functionally Graded Material Metallic Glass novelty is to combine the crystalline and amorphous structure state in one product. Preliminary researches selected by the authors convince the promising aspect of the Functionally Graded Material Metallic Glass.

Dynamic and stability analysis of functionally graded material sandwich plates in hygro-thermal environment using a simple higher shear deformation theory:

Abstract: A new simple “four-variable shear deformation” plate model is proposed in this work to demonstrate the hygro-thermal environment effects on dynamic and buckling of functionally graded material “san...

Finite element approach of axial bending coupling on static and vibration behaviors of functionally graded material sandwich beams

Abstract: This study deals with the analysis of multilayer composite and functionally graded materials (FGM) structures. The material properties of the FGM beam are assumed to vary according to the power law distribution of its constituent’s volume fraction over the cross section. The analytical analysis seems to be cumbersome. A finite element approach is investigated in this work for the static and free vibration behaviors of the 2D FGM beams with variable constituents over the cross section. The analyses are carried out in arbitrary axes and the axial, bending and shear couplings are considered. In this study, the classical beam theory, Timoshenko first-order and higher order shear models are described and implemented. The different models are compared to benchmark solutions found in the literature. Effects of boundary conditions, slenderness ratio, and the FGM power law parameter are investigated under static and free vibration analyses. FGM and multilayer sandwich beams are also analyzed. It is proven that the axial bending and shear coupling affect the behavior of the FGM beams in both statics and dynamics. In the presence of short beams, shear effect is important and leads to cross-section warping. The classical beam theory fails in this context. All models are close in the case of slender beams.

Analysis of 2D heat conduction in nonlinear functionally graded materials using a local semi-analytical meshless method

Abstract: This paper proposes a local semi-analytical meshless method for simulating heat conduction in nonlinear functionally graded materials. The governing equation of heat conduction problem in nonlinear functionally graded material is first transformed to an anisotropic modified Helmholtz equation by using the Kirchhoff transformation. Then, the local knot method (LKM) is employed to approximate the solution of the transformed equation. After that, the solution of the original nonlinear equation can be obtained by the inverse Kirchhoff transformation. The LKM is a recently proposed meshless approach. As a local semi-analytical meshless approach, it uses the non-singular general solution as the basis function and has the merits of simplicity, high accuracy, and easy-to-program. Compared with the traditional boundary knot method, the present scheme avoids an ill-conditioned system of equations, and is more suitable for large-scale simulations associated with complicated structures. Three benchmark numerical examples are provided to confirm the accuracy and validity of the proposed approach.