Papers by Keyword: FGM

Abstract: One off the most powerful assembly technique is the shrink-fitting process.It is found in many fields such us mechanics, petroleum, military industries as well as in nuclear power plants etc. This article developed an analytical formulation of shrink-fitted Functionally Graded Material axisymmetric thick-walled cylinder based on the linear plane elasticity theory. The stresses and displacement fields in the thick cylindrical shells are calculated using the laws of linear elasticity. The resulting displacements and stresses are analyzed, and particularly the residual contact pressure and her relationship with the interference values. The results show that the variation of the FGM material composition has a clear effect on the fit pressure in the intersection area of the two fitted cylinders. The value of this pressure affects the distribution of radial and tangential stresses in the FGM cylinder walls. Subsequently, we highlighted the influence of the interference value, on the residual contact pressure which increases with the increase of the interference value. The stresses are modeled for a case study using MATLAB software. keywords. shrink-fit, FGM, Interference, residual stress, Elasticity.

Abstract: In this work, functionally graded materials were synthesized by centrifugal technique at different volume fractions (0, 0.5, 1, 1.5, and 2% Vf) with different rotational speed of (0, 600, 800, 1000 and 1200) r.p.m and different rotational time (0, 1, 2, 3 and 4) min. The hardness and tribological properties were characterized to study the graded and non-graded nanocomposites and the pure epoxy material. Using a pin-on-disc machine, sliding wear tests are conducted with the following parameters: rotation speed (400 rpm), normal load (30 N), filler content (0–2% Vf), and sliding distance (0.15 km). The hardness and wear parameters of graded composites were investigated and compared to those of epoxy composites with homogeneous filling. This work demonstrates that incorporating Al2O3 nanoparticles improves graded composites' hardness and sliding wear resistance. Epoxy–Al2O3 epoxy composites with a volume fraction of 2 had the lowest specific wear rate of all samples. The FGMs had superior sliding wear performance compared to homogenous composites. The maximum difference in hardness and coefficient of friction occurred at (FGM), which is loaded from the rich side of the nanoalumina at (Vf = 2%, N = 1200 r.p.m and T = 6 min), where the maximum value was 168% and 78 % as compared with neat epoxy, respectively. The wear rate of the functionally graded samples was enhanced by (87.7%) compared with neat epoxy if loaded from the alumina-rich side.

Abstract: To determine the maximum velocity of a rotating hollow shaft it is mandatory to understand the effects of material & geometrical properties variations. In this paper, mechanical behavior & maximum rotational speed of a hollow FGM shaft in elastic zone is investigated. The analysis is based on small deformation in plane-strain state. Young's modulus, density & yield stress are assumed to vary as a power-law function of radial coordinate. Introducing dimensionless parameters, the equilibrium equation has been analytically solved. For the case of equal exponent parameters, numerical results compared the effect of density & yield stress variation on displacement, strain & stress elements. The results are compared with a homogeneous shaft & a variable material properties case. It shows material properties’ variation may have a considerable effect on the stress & strain components & radial displacement & causes yielding onset from the inner radius of the shaft.

Abstract: The investigation of static crack and its growth is essential issue as to confirm reliability and to avoid catastrophic consequences which leads to the loss of life in case of engines, reactors, aerospace other industrial applications since most of the failures start from the crack. In this study, an edge crack in 3D elastic functionally graded material (FGM) is solved by extended finite element method (XFEM). Linear elastic fracture mechanics (LEFM) theory is used to determine the stresses near the crack front. Stress intensity factor (SIF) is calculated using interaction integral at the crack front.

Abstract: This study compared the ballistic performance of alumina (Al₂O₃)/ zirconia (ZrO₂) functionally graded material (FGM) specimens with various levels of thickness and ZrO₂ content and a pure Al₂O₃ single-layer ceramic composite (PCM). Ballistic tests were conducted with 0.3-inch armor-piercing (AP) projectiles, and finite element code LS-DYNA was used to examine energy absorption, stress distribution, and ceramic cone failure in the specimens. The findings are as follows: First, regarding energy absorption per unit of areal density, the 5% FGMs had the highest ballistic performance, which increased by up to 8%. By contrast, the ballistic performance of the 15% FGMs declined significantly to lower than that of the PCM. Second, the capability of the ceramic cone to withstand stress damage and projectiles was significantly greater in the 5% FGMs than in the 15% FGMs. Third, the wave impedance variations increased with the ZrO₂ content in each layer, thereby enhancing the interactions between impact waves and aggravating ceramic damage. Thus, the intensities of transmission and reflection waves in the 15% FGMs increased, thereby causing reductions in its ballistic performance.

Abstract: The manufacture of graded materials has gained an enormous interest during the last decade due to the diversity of industrial and biological materials systems that require or are actually designed to implement that criterion; those natural or artificial materials offer multiple possibilities of applications. In this work, a novel uniaxial and sequential compaction device has been successfully designed and fabricated, in order to obtain samples with three different layers; this new device is suitable for both conventional and non-conventional powder metallurgy (PM) techniques. In addition, this device allowed us to use different combinations of powders and space-holder particles, irrespective of their nature, sizes, morphologies and proportions. It has no restriction about applying different compaction pressures for every layer, which may result in increasing or decreasing porosity. This compaction device is especially powerful if the aim is obtaining samples with radial graded porosity for biomedical applications (replacement of cortical bone involved in different joints and dental restorations) and nuclear applications (mimicking burnt used nuclear fuel). Specifically in this work, different samples with radial graded porosity were fabricated and then microstructurally and mechanically characterized: i) Commercially pure titanium (CP Ti) samples, starting from blends CP Ti with 20 vol.%, 40 vol.% and 60 vol.% of Sodium Chloride (NaCl) as space holder, which were placed in core, intermediate and external layers, respectively; processing conditions were 800 MPa of compaction pressure and 1250 °C for 2h in high vacuum of sintering; and ii) CeO₂ samples, starting from blends CeO₂ with 0.5 vol.%, 3.0 vol.% and 7.5 vol.% of Ethylene Bis Stearamide (EBS) as space holder, which were placed in core, intermediate and external layers, respectively; processing conditions were 460 MPa in external layer and 700 MPa in core and intermediate layers of compaction pressure, and 1700 °C during 4h in static air of sintering. This new device has proved to have unique advantages for solving problems of structural integrity in conventional PM manufacturing in a simple, economic and reproducible way.

Abstract: A four-layer functionally gradient material (FGM) of Cu/Ti₃SiC₂ was fabricated by hot pressing (HP) in vacuum. Oxidation behavior of Cu/Ti₃SiC₂ FGM was also investigated. The results show that the oxidation dynamics of Cu/Ti₃SiC₂ FGM at 600~800 °C for 30 h in air followed parabolic rate law. The hardness was increased with increasing content of Ti₃SiC₂. Thermal shock resistance was well owing to the effect of thermal stresses mitigated with FGM.

Abstract: In this study, the contact problem for a graded elastic half-plane in frictional contact with a rigid stamp is considered. The plane contact problem is assumed to be linear elastic and the Poisson's ratio is assumed to be constant. Analytical formulation of the study includes Fourier transforms of the governing equations and boundary conditions. The resulting integral equation is solved numerically. Contact pressure, in-plane stress and the stress intensity factor at the sharp edges of the contact are evaluated and demonstrated for various stamp profiles. The results are compared with a closed form solution for homogeneous isotropic half-plane indented by rigid stamps. The effects of the nonhomogeneity parameter, coefficient of friction and stamp profiles on the contact and in-plane stresses are analyzed in detail.

Abstract: Aluminium based FGM rings, reinforced by in-situ primary Si and primary Si/ Mg₂Si hybrid reinforcement were successfully fabricated by centrifugal casting and micro structural, chemical, hardness and corrosion characteristics were evaluated. It was observed that in Al-20Si ring the primary Si particles were present mostly in inner region and few in outer region where as in Al-20Si-3Mg ring both the primary silicon and Mg₂Si were completely found in the inner region only resulting in a graded FGM structure. The hardness values were measured along radial direction of samples and variations corresponding to micro structural variation were analysed. Optical Emission spectroscopic studies have revealed the remarkable compositional changes along radial direction. Corrosion characteristics were also evaluated both in particle rich and depleted regions.

Abstract: In this work Al-Si-Cu Functionally Graded Material (FGM) is developed using centrifuge technique. The method used in this work to produce FGM is totally different compared to other centrifugal process which helped in producing solid cylindrical parts. The FGM is characterized through Microstructure and Hardness and it is found that the Cu segregated at the bottom of the casting and Si at the top due to the density difference. Similarly the hardness and the ultimate tensile strength at the bottom of the casting and at the top of the casting region is more when compared to region in-between the top and bottom of the casting.