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1

Design of Functionally Graded Composites through Friction Stir Processing

Sai B. V. Hima Sekhar

Journal of Mechanical and Energy Engineering

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2021

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Vol. 5, No 2

95--101

EN

An Investigation was conducted to produce Aluminium based Functionally graded material (FGM) composites by Friction stir processing (FSP). A reinforcement strategy featuring the use of Alumina and TiC reinforcements was investigated, where holes were drilled in an Aluminium plate, filled with reinforcements and stirred using FSP. A mathematical model was formulated for the positioning of holes in such a manner that the composition of the reinforcements varies from maximum to minimum over a given length. Samples were subjected to various numbers of FSP passes from one to three with a 100% overlap and its influence on particle distribution and homogeneity was studied using Scanning electron microscopy (SEM) at cross sections parallel to the tool traverse direction. A progressive gradient in hardness values was observed for the surface composites at all the passes.

2

Stress and deformation analysis of clamped functionally graded rotating disks with variable thickness

Thawait Amit K., Sondhi Lakshman, Sanyal Shubhashis, Bhowmick Shubhankar

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

202--211

EN

The present study reports the linear elastic analysis of variable thickness functionally graded rotating disks. Disk material is graded radially by varying the volume fraction ratios of the constituent components. Three types of distribution laws, namely power law, exponential law and Mori-Tanaka scheme are considered on a concave thickness profile rotating disk, and the resulting deformation and stresses are evaluated for clamped-free boundary condition. The investigation is carried out using element based grading of material properties on the discretized elements. The effect of grading on deformation and stresses is investigated for each type of material distribution law. Further, a comparison is made between different types of distributions. The results obtained show that in a rotating disk, the deformation and stress fields can be controlled by the distribution law and grading parameter n of the volume fraction ratio.

3

Thermal buckling of temperature-dependent functionally graded Timoshenko beams

Chen Wei-Ren, Chen Chun-Sheng, Chang Heng

Archive of Mechanical Engineering

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2019

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Vol. LXVI, nr 4

393--415

EN

Thermal buckling behavior of a functionally graded material (FGM) Timoshenko beam is studied based on the transformed-section method. The material and thermal properties of the FGM beam are assumed to vary across the beam thickness according to a power-law function, a sigmoid function and an exponential function. The results of buckling temperature for the FGM beams with respective temperature-dependent and temperature-independent properties under uniform and non-linear temperature rises are presented. Some results are compared with those in the published literature to verify the accuracy of the present work. The effects of the material distributions, temperature fields, temperature-dependent properties and slenderness ratios on the thermal buckling behaviors of FGM beams are discussed. It is believed that the present model provides engineers with a simple and effective method to study the effects of various parameters of the FGM beam on its thermal buckling behavior.

4

A homogenization procedure and a physical discrete model for geometrically nonlinear transverse vibrations of a clamped beam made of a functionally graded material

Rahmouni A., Benamar R.

Diagnostyka

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2017

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Vol. 18, No. 3

15--20

EN

Functionally graded materials are used in aircrafts, space vehicles and defence industries because of their good thermal resistance. Geometrically nonlinear free vibration of a functionally graded beam with clamped ends (FGCB) is modeled here by an N-dof discrete system presenting an equivalent isotropic beam, with effective bending and axial stiffness parameters obtained via a homogenization procedure. The discrete model is made of N masses placed at the ends of solid bars connected by rotational springs, presenting the flexural rigidity. Transverse displacements of the bar ends induce a variation in their lengths giving rise to axial forces modeled by longitudinal springs. The nonlinear semi-analytical model previously developed is used to reduce the vibration problem, via application of Hamilton’s principle and spectral analysis, to a nonlinear algebraic system involving the mass and rigidity tensors mij and kij and the nonlinearity tensor bijkl. The material properties of the (FGCB) examined is assumed to be graded according to a power rule of mixture in the thickness direction. The fundamental nonlinear frequency parameters found for the (FGCB) are in a good agreement with previously published results showing the validity of the present equivalent discrete model and its availability for further applications to non-uniform beam.

5

Efficiency of Active Damping of Torsional Vibration in Shaft Made of Gradent Material with Piezoceramic Fraction

Przybyłowicz P. M.

Machine Dynamics Problems

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2008

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Vol. 32, No. 4

95-106

EN

The paper is concerned with the problem of active reduction of torsional vibratio shafts. The solution based on application of a functionally graded material is preset The material of the shaft consists of two components - a passive host material, which be a laminate with strong shear stiffness, and active fraction in form of a piezoelei ceramic. One component gradually passes into the other according to the g exponential distribution. Three cases varying by the level of internal friction in the pas fraction are analysed in terms of the efficiency of the active approach. For mode natural damping in the matrix, best distributions of the active phase are found.

6

Projektowanie tworzyw z gradientem rozmieszczenia faz otrzymywanych metodą zagęszczania w ultrawirówce

Rozmus M., Mitiuszew W., Jaworska L, Rylko N.

Kompozyty

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2008

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R. 8, nr 1

64-69

PL

Kompozyty polikrystalicznego diamentu PCD są okrągłymi dyskami składającymi się z cienkiej warstwy polikrystalicznego diamentu związanego z warstwą podłożową z węglika spiekanego. Dostępne komercyjnie PCD są zazwyczaj wytwarzane przez wysokociśnieniowe spiekanie proszków diamentowych z kobaltową fazą wiążącą. Obecność kobaltu aktywuje proces grafityzacji diamentu. Różnica rozszerzalności temperaturowej warstwy PCD i podłoża z węglika spiekanego może powodować wystąpienie naprężeń szczątkowych i następnie delaminację materiału. Modyfikacja właściwości tego materiału jest możliwa przez zastosowanie odpowiedniego rodzaju materiału fazy wiążącej, na przykład Ti3SiC2, który wykazuje pseudoplastyczne właściwości. Celem badań było wykonanie matematycznych obliczeń rozkładu faz dla materiałów gradientowych diament-Ti3SiC2, które były weryfikowane z rozkładem faz w kompozytach po procesie spiekania techniką HP-HT. W pracy zaproponowano algorytm do opisu sedymentacji grup sferycznych cząstek o różnorodnych rozmiarach i z różnorodnych materiałów. Główne obliczenia dla tego układu i prawdziwych warunków procesu zagęszczania wirówkowego HCP są wykonane za pomocą równania Barnea-Mizrahi. Proces osadzania dla układu diament-Ti3SiC2 przeprowadzono w ultrawirówce UP 65M z prędkością obrotową rotora 20 000 obr/min. Rozkład rozmiarów ziaren dla proszków diamentu i Ti3SiC2 zmierzono z użyciem aparatury Shimadzu. Rozkład twardości dla kompozytu diamentowego z gradientem składu fazowego zmierzono i porównano do koncentracji diamentu i węglika W, zależnej od czasu opadania proszków t diamentu i węglika oraz od odległości.

EN

The polycrystalline diamond PCD compacts are a round disks composite of a thin layer of sintered polycrystalline diamond bonded to a cemented tungsten carbide substrate. Commercially available PCD are usually made by high pressure sintering diamond powders with the cobalt bonding phase. The existence of cobalt promotes the graphitisation process of diamond. The differential thermal expansion of PCD layer and tungsten carbide substrate may result in residual stresses and next, delamination of material. Modification properties of these materials is possible using suitable kind of the bonding phase material, for example the ceramics Ti3SiC2 material, which is exhibiting pseudoplastics behaviour. The aim of the research was execution of mathematical calculations of the phases distribution for the phase graded diamond - Ti3SiC2 compacts which were verified with phases distribution in compacts after the high pressure - high temperature sintering process. An algorithm to describe sedimentation of the group of spherical particles of different sizes and different materials was proposed. Main calculations for this system and for real conditions of the high-speed centrifugal compaction process are made using the Barnea-Mizrahi equation. Deposition process for diamond - Ti3SiC2 was carried out using the ultra centrifuge UP 65M with rotational speed of 20 000 rpm. Particle size distribution for the diamond and Ti3SiC2 powders were measured using Shimadzu apparatus. Hardness distribution for diamonds composite with phase composition gradient was measured and compared to the concentration of diamond and carbide W for diamond and Ti3SiC2 powders dependence on distance.

7

Kompozyty diamentowe z ceramiczną fazą wiążącą - modyfikacja mikrostruktury w aspekcie łączenia z korpusem narzędzia

Jaworska L., Rozmus M., Twardowska A., Królicka B.

Kompozyty

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2006

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R. 6, nr 3

3-7

PL

Jednym z najlepszych i coraz powszechniej stosowanych materiałów narzędziowych jest diament. Wyróżniamy trzy podstawowe grupy materiałów diamentowych: polikrystaliczne spieki diamentowe PCD, warstwy diamentowe otrzymywane metodami CVD oraz monokryształy diamentu naturalnego i syntetycznego. Największe znaczenie dla obróbki skrawaniem mają materiały PCD. Modyfikacja ich właściwości jest możliwa poprzez zastosowanie odpowiedniego rodzaju fazy wiążącej, np. tworzywa ceramicznego Ti3SiC2, charakteryzującego się pseudoplastycznymi właściwościami. Wprowadzając ten materiał w ilości 30% masy, otrzymano materiał o wysokim współczynniku odporności na kruche pękanie K(IC) wynoszącym 8 MPa x m1/2 , i przeszło trzykrotnie wyższej wartości wytrzymałości na ściskanie średnicowe, a także o zwiększonej odporności temperaturowej w stosunku do najczęściej wytwarzanych materiałów z kobaltową fazą wiążącą. Zastosowanie Ti3SiC2 jako fazy wiążącej diament w materiale o mikrostrukturze gradientowej pozwoli na bezpośrednie spajanie ostrza skrawającego z korpusem narzędzia bez konieczności stosowania warstwy pośredniej w postaci węglika spiekanego. Przedstawiono wyniki wstępnych prób zagęszczania materiału o strukturze gradientowej metodą wirówkową. Materiał gradientowy zapewni narzędziu skrawającemu twardą, odporną na zużycie ścierne warstwę powierzchniową i podłoże umożliwiające lutowanie.

EN

One of the most popular tools materials is diamond. Currently there are three groups of diamond based cutting tool materials available namely polycrystalline diamond compacts PCD, CVD diamond and single crystal natural and synthetic diamond. The most significance for machining have PCD materials. The PCD compacts are a round disks comprising a thin layer of sintered polycrystalline diamond bonded to a cemented tungsten carbide substrate (Fig. 1). Commercially available PCD are usually made by high pressure sintering diamond powders with the cobalt bonding phase. The existence of cobalt promotes the graphitisation process of diamond. The differential thermal expansion of PCD layer and tungsten carbide substrate may result in residual stresses and next, delamination of material. Modification properties of these materials are possible using suitable kind of the bonding phase material, for example the ceramics Ti3SiC2 material, which is exhibiting pseudoplastics behaviour. The 30 wt. % Ti3SiC2 addition to the diamond composite is resulted high fracture toughness, K\c is 8 MPa x m1/2, compressive strength is three times more than for compacts with the cobalt bonding phase (Table 1). The thermal resistance of these materials were increased also. The decomposition of Ti3SiC2 takes place during the high pressure sintering process (Fig. 2). Observations of microstructure of prepared composites showed that mixing diamond and Ti3SiC2 powder produces composites of very low porosity (Fig. 3) and indicated that the bonding material has a multiphase composition (Fig. 4). Using the Ti3SiC2 bonding phase in the gradient composition material allows for the direct brazing of the edge to the tools body without intermediate sintered carbides layer. These functional graded materials will provide the cutting tools hard, wear resistant surface and good brazing substrate. The grading material was compacted using the centrifugal method.

8

Stability of functionally graded plate under in-plane time-dependent compression

Tylikowski A.

Mechanics and Mechanical Engineering

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2004

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Vol. 7, nr 2

5-12

EN

Functionally graded materials have gained considerable attention in the high temperature applications. Linear dynamics equations taking into account a coupling of in-plane and transverse motions are used. Material properties are graded in the thickness direction of the plate according to volume fraction power law distribution. An oscillating temperature causes generation of in-plane time-dependent forces destabilizing the plane state of the plate equilibrium. The asymptotic stability and almost-sure asymptotic stability criteria involving a damping coefficient and loading parameters are derived using Liapunov's direct methods. Effects of power law exponent of the stability domains are studied.