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Ankit Gupta

Bio: Ankit Gupta is a academic researcher from Shiv Nadar University. The author has contributed to research in topic(s): Finite element method & Functionally graded material. The author has an hindex of 13, co-authored 57 publication(s) receiving 726 citation(s). Previous affiliations of Ankit Gupta include Indian Institute of Technology Dhanbad & Tennessee Technological University.
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Journal ArticleDOI
Abstract: In this article, an extensive review related to the structural response of the functionally graded materials (FGMs) and structures have been presented. These are high technology materials developed by a group scientist in the late 1980's in Japan. The emphasis has been made here, to present the structural characteristics of FGMs plates/shells under thermo-electro-mechanical loadings under various boundary and environmental conditions. This paper also provides an overview of different fabrication procedures and the future research directions which is required to implement these materials in the design and analysis appropriately. The expected outcome of present review can be treated as milestone for future studies in the area of high technology materials and structures, and would be definitely advantageous for the researchers, scientists, and designers working in this field.

253 citations

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Abstract: This paper deals with the vibration characteristics of shear deformable functionally graded material (FGM) plates. The theoretical models are based on Taylor's series expansion of in-plane and transverse displacements in thickness coordinate defining the plate deformations. Poisson's ratio of the FGM plates are assumed to be constant, whereas the effective mechanical properties i.e. Young's moduli and material densities vary continuously in thickness coordinate according to the volume fraction of constituents. A C0 continuous isoparametric finite element formulation has been employed to accomplish the results, and the accuracy of the formulation is demonstrated by comparing with the available literature. Parametric study has been performed for volume fraction indices, thickness ratios, aspect ratio and various boundary constraints. Natural frequencies of the FGM plates with various unconventional boundary constraints have also been presented.

60 citations

Journal ArticleDOI
TL;DR: The current trends and challenges that FRAM is bringing to AM ecosystem are reported, including the impact of fiber orientations and fraction on the performance of parts, improving the printing parameters, and other subjects.
Abstract: In the last few years, utilizing fiber reinforced additive manufacturing (FRAM)-based components in several industries has become quite popular. Compared to conventional AM technologies, FRAM offered complementary solutions to their needs. In general, fibers have been traditionally used in many manufacturing processes for various reasons. However, using conventional methods, there are obstacles in obtaining the desired complex geometries and low setup costs. AM offers possible avoidance of these limitations. Shape complexity, infill density, and manufacturing lead times are no longer barriers. Bridging AM with fiber reinforced materials offers a vast opportunity for lightweight and strong parts. Depending on the affinity, fibers with different structures can be mixed with different matrix materials and, thus, create stronger parts with improved mechanical properties. Process parameters like raster angle, infill speed, layer thickness, and nozzle temperature also strongly impact physical properties of FRAM products and are considered carefully. FRAM-based components are used in many industries such as aerospace, motorsports, and biomedicine, where the weight, strength, and complexity of parts are critical. Hence, numerous industrial companies and research facilities are investigating the implementation and adaptation of FRAM to their requirements. Studies are generally conducted on new materials, new FRAM technologies, the effect of fiber orientations and fraction on the performance of parts, improving the printing parameters, and other subjects. This study reports the current trends and challenges that FRAM is bringing to AM ecosystem.

58 citations

Journal ArticleDOI
Abstract: This paper examines the influence of porosities on the flexural and free vibration response of functionally graded material (FGM) plates based on the authors’ recently developed non-polynomial higher-order shear and normal deformation theory. The theory accommodates the nonlinear variation in the in-plane and transverse displacements in the thickness coordinates. It also contains the hyperbolic shear strain shape function in the displacement field with only four unknowns. A new mathematical model has also been proposed to incorporate the effects of porosity in the FGM plate. Various numerical examples have been solved to ascertain the accuracy, efficiency, and applicability of the present formulation. The effects of porosity, volume fraction index, plate thickness, aspect ratio, boundary conditions and temperature have been discussed in details. The obtained results can be treated as a benchmark for future studies.

44 citations

Journal ArticleDOI
Abstract: In the present study, a new non-polynomial based higher order shear and normal deformation theory is proposed and implemented for the vibration response of geometrically imperfect functionally graded material (FGM) plates. The present theory accounts for nonlinear variation in the in-plane and transverse displacements, respectively in the thickness coordinate. This theory contains the trigonometric shear strain shape functions and having only four unknowns in the displacement field. It is variationally consistent and accommodates thickness stretching effects without employing shear correction factor. Two micromechanics models (Mori-Tanaka and Voigt) have been employed to determine the effective material properties of the plate, and are graded continuously through the thickness direction according to a simple power law and exponential law. The accuracy and efficiency of the proposed theory have been conferred by comparing the results with an existing 3D exact solution and various higher order theories. Frequency parameters with various side-to-thickness ratios, boundary conditions, imperfection sizes, volume fraction indexes and exponential indexes have been computed for perfect and imperfect FGM plate. It is found that the proposed theory is not only accurate but also simple in predicting the free vibration responses of functionally graded ceramic-metal plates.

30 citations

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Journal ArticleDOI
TL;DR: These updated recommendations take into account all rTMS publications, including data prior to 2014, as well as currently reviewed literature until the end of 2018, and are based on the differences reached in therapeutic efficacy of real vs. sham rT MS protocols.
Abstract: A group of European experts reappraised the guidelines on the therapeutic efficacy of repetitive transcranial magnetic stimulation (rTMS) previously published in 2014 [Lefaucheur et al., Clin Neurophysiol 2014;125:2150-206]. These updated recommendations take into account all rTMS publications, including data prior to 2014, as well as currently reviewed literature until the end of 2018. Level A evidence (definite efficacy) was reached for: high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the painful side for neuropathic pain; HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC) using a figure-of-8 or a Hl-coil for depression; low-frequency (LF) rTMS of contralesional M1 for hand motor recovery in the post-acute stage of stroke. Level B evidence (probable efficacy) was reached for: HF-rTMS of the left M1 or DLPFC for improving quality of life or pain, respectively, in fibromyalgia; HF-rTMS of bilateral M1 regions or the left DLPFC for improving motor impairment or depression, respectively, in Parkinson's disease; HF-rTMS of ipsilesional M1 for promoting motor recovery at the post-acute stage of stroke; intermittent theta burst stimulation targeted to the leg motor cortex for lower limb spasticity in multiple sclerosis; HF-rTMS of the right DLPFC in posttraumatic stress disorder; LF-rTMS of the right inferior frontal gyrus in chronic post-stroke non-fluent aphasia; LF-rTMS of the right DLPFC in depression; and bihemispheric stimulation of the DLPFC combining right-sided LF-rTMS (or continuous theta burst stimulation) and left-sided HF-rTMS (or intermittent theta burst stimulation) in depression. Level A/B evidence is not reached concerning efficacy of rTMS in any other condition. The current recommendations are based on the differences reached in therapeutic efficacy of real vs. sham rTMS protocols, replicated in a sufficient number of independent studies. This does not mean that the benefit produced by rTMS inevitably reaches a level of clinical relevance. (C) 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V.

308 citations

Journal ArticleDOI
Abstract: A first known study is conducted on the vibrations of functionally graded material (FGM) rectangular plates with porosities and moving in thermal environment. The FGM plates contain porosities owing to the technical issues during the preparation of FGMs. Two types of porosity distribution, namely, even and uneven distribution, are considered. The geometric nonlinearity is taken into account by using von Karman nonlinear plate theory. The out-of-plane equation of motion of the system is derived based on the D'Alembert's principle with the consideration of the thermal effect and longitudinal speed. Then the Galerkin method is employed to discretize the partial differential equation of motion to a set of ordinary differential equations. These time-varying ordinary differential equations are solved analytically by means of the method of harmonic balance. The accuracy of approximately analytical solutions is verified by the adaptive step-size fourth-order Runge–Kutta technique. Additionally, the stability of steady-state solutions is analyzed for the analytical solutions. Vibration characteristics such as natural frequency and nonlinear frequency response are shown. The present model is a hardening-spring system based on the nonlinear frequency response results. Effects of some key parameters are investigated on the vibration of rectangular FGM plates with porosities and moving in thermal environment.

160 citations

Journal ArticleDOI
05 Dec 2019-Materials & Design
Abstract: As the application of additive manufacturing (AM) reaches an unprecedented scale in both academia and industry, a reflection upon the state-of-the-art developments in the design for additive manufacturing (DfAM) and structural optimisation, becomes vital for successfully shaping the future AM-landscape. A framework, highlighting both the interdependencies between these two central aspects in AM and the necessity for a holistic approach to structural optimization, using lightweight strategies such as topology optimization and/or latticing, was established to summarize the reviewed content. Primarily focusing on isotropic material considerations and basic stiffness-optimal problems, these concepts have already found wide application, bridging the gaps between design and manufacturing as well as academia and industry. In pursuit of streamlining the AM-workflow towards digitally print-ready designs, studies are increasingly investigating mathematically-based structural optimization approaches in conjunction with DfAM-specific constraints, providing a portfolio of solutions like generative design, which is gaining traction in industry. Besides an overview on economically-driven to performance-driven design optimizations, insight into commercial AM-specific software is provided, elucidating potentials and challenges for the community. Despite the abundance of AM design methods to-date, computationally inexpensive solutions for common engineering problems are still scarce, which is constituting one of many key challenges for the future.

146 citations

Journal ArticleDOI
Abstract: A novel quasi-3D hyperbolic theory is presented for the free vibration analysis of functionally graded (FG) porous plates resting on elastic foundations by dividing transverse displacement into bending, shear, and thickness stretching parts. The elastic foundation can be chosen as Winkler, Pasternak or Kerr foundation. Three different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. A Galerkin method is developed for the solution of the eigenvalue problem of the presented quasi-3D hyperbolic plate model. The presented quasi-3D hyperbolic theory is simple and easy to implement since it uses only five-unknown variables to determine fourfold coupled (axial-shear-bending-stretching) vibration responses. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, stiffness of foundation parameters, mode numbers, and geometry on the natural frequencies of imperfect FG plates.

128 citations

Journal ArticleDOI
12 Oct 2017-
Abstract: A major advantage of additive manufacturing (AM) technologies is the ability to print customized products, which makes these technologies well suited for the orthopedic implants industry. Another advantage is the design freedom provided by AM technologies to enhance the performance of orthopedic implants. This paper presents a state-of-the-art overview of the use of AM technologies to produce orthopedic implants from lattice structures and functionally graded materials. It discusses how both techniques can improve the implants’ performance significantly, from a mechanical and biological point of view. The characterization of lattice structures and the most recent finite element analysis models are explored. Additionally, recent case studies that use functionally graded materials in biomedical implants are surveyed. Finally, this paper reviews the challenges faced by these two applications and suggests future research directions required to improve their use in orthopedic implants.

119 citations

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Author's H-index: 13

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