Creep Response of Rotating Composite Discs having Exponential Hyperbolic Linear and Constant Thickness Profiles

The study compares the steady state creep response of rotating Al-SiC discs having constant, linear, hyperbolic and exponential thickness with different thickness profiles. All the discs are assumed to have equal volume with the same average thickness. The creep behaviour of the disc material is described by threshold stress based law while the yielding is assumed to follow Tresca criterion. The variable thickness disc is observed to have superior creep response, expressed in terms of stresses and strain rates, to a constant thickness disc. Amongst variable thickness discs, the creep response is observed to be superior for linear thickness disc, when the inner thickness of all the discs is kept the same. However, for the same outer thickness, the disc having hyperbolic thickness profile exhibits the best creep response.

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Influence of anisotropy on creep in functionally graded variable thickness rotating disc

The Journal of Strain Analysis for Engineering Design ◽

10.1177/0309324721999971 ◽

2021 ◽

pp. 030932472199997

Author(s):

Kishore Khanna ◽

Vinay Kumar Gupta ◽

Neeraj Grover

Keyword(s):

Axial Direction ◽

Functionally Graded ◽

Strain Rates ◽

Lower Yield ◽

Rotating Disc ◽

Creep Response ◽

Varying Thickness ◽

Disc Material ◽

Lower Yield Strength ◽

Tangential Directions

The study is carried out to develop a mathematical model to analyze creep response of a varying thickness rotating disc made of anisotropic functionally graded 6061Al-SiCw.composite. The thickness and content of reinforcement (SiCw) in the disc are assumed to decrease radially according to power law. The yielding of disc material is according to Hill’s criterion and creeping as per threshold stress based law. The developed model is used to obtain the creep stresses and strain rates in the disc for various types of materials’ anisotropy. The stresses and strain rates are noticed to depend on the materials’ anisotropy. The study reveals that the presence of kind of anisotropy wherein the disc material exhibits lower yield strength toward the radial and tangential directions than the axial direction is beneficial in reducing the creep stresses and creep rates in the disc, in comparison to isotropic FGM disc. An anisotropic FG disc, which has highest and the lowest yield strengths, respectively, along the axial and radial directions shows superior creep response.

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Effect of Disc Geometry on the Steady State Creep in a Rotating Disc Made of Functionally Graded Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.736.183 ◽

2012 ◽

Vol 736 ◽

pp. 183-191 ◽

Cited By ~ 5

Author(s):

Manish Garg ◽

B.S. Salaria ◽

V.K. Gupta

Keyword(s):

Steady State ◽

Creep Behaviour ◽

Pure Aluminum ◽

Functionally Graded ◽

Steady State Creep ◽

Strain Rates ◽

Rotating Disc ◽

Graded Materials ◽

Functionally Graded Composite ◽

Silicon Carbide Particles

The steady state creep behaviour of a rotating FGM disc having linearly varying thickness has been investigated. The disc is assumed to be made of functionally graded composite containing non-linearly varying radial distribution of silicon carbide particles in a matrix of pure aluminum. The creep behaviour of the composite has been described by threshold stress based law. The effect of varying the disc thickness gradient has been analyzed on the stresses and strain rates in the FGM disc. It is observed that the radial and tangential stresses induced in the FGM disc decrease throughout with the increase in thickness gradient of the disc. The strain rates also decrease with the increase in thickness gradient of the FGM disc, with a relatively higher decrease near the inner radius. The increase in disc thickness gradient results in relatively uniform distribution of strain rates and hence reduces the chances of distortion in the disc.

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Three-dimensional elasticity analysis of functionally graded rotating cylinders with variable thickness profile

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406211416916 ◽

2011 ◽

Vol 226 (3) ◽

pp. 585-594 ◽

Cited By ~ 10

Author(s):

E Ghafoori ◽

M Asghari

Keyword(s):

Variable Thickness ◽

Three Dimensional ◽

Functionally Graded ◽

Numerical Results ◽

Constant Thickness ◽

Rotating Cylinders ◽

Hollow Structures ◽

Thickness Profile ◽

Axisymmetric Structure ◽

Three Dimensional Elasticity

A three-dimensional elasticity solution for the analysis of functionally graded rotating cylinders with variable thickness profile is proposed. The axisymmetric structure has been divided in several divisions in the radial direction. Constant mechanical properties and thickness profile are assumed within each division. The solution is considered for four different thickness profiles, namely constant, linear, concave, and convex. It is shown that the linear, concave, and convex thickness profiles have smaller stress values compared to a constant thickness profile. The effects of various grading indices as well as different boundary conditions, namely solid, free–free hollow and fixed–free hollow structures are discussed. A series of numerical results using zirconia as outer surface ceramic and aluminium as inner surface metal are presented. Parametric study has then been carried out to give a better understanding of how different stress, strain, and displacement components change along radial and axial directions of the rotating structures. Numerical results show that for a given grading index, the structures with a concave thickness profile have the smaller circumferential strain and stress compared to other thickness profiles.

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Analysis of Creep in Rotating Disks Based on the Tresca Criterion and Associated Flow Rule

Journal of Applied Mechanics ◽

10.1115/1.4011292 ◽

1956 ◽

Vol 23 (2) ◽

pp. 231-238

Author(s):

A. M. Wahl

Keyword(s):

Steady State ◽

Creep Rate ◽

Constant Temperature ◽

Variable Thickness ◽

Constant Thickness ◽

Flow Rule ◽

Test Results ◽

Rotating Disks ◽

Tresca Criterion ◽

Associated Flow Rule

Abstract An analysis of creep deformations in rotating disks based on the Tresca criterion and the associated flow rule is presented. Assuming steady-state creep conditions and a creep rate equal to a function of stress times a function of time, the method is applied to the following cases: (a) Disk with constant thickness and constant temperature, (b) disk with variable thickness and constant temperature, and (c) disk with variable thickness and variable temperature. In many cases, the equations can be expressed in closed form. Comparison is made with test results on rotating disks at elevated temperature as reported in a previous paper. Based on certain stress-creep-rate relations, the method is also applied to the problem of calculating the transient change in stress when the stress distribution changes from an initial to a steady-state condition during the starting period. It is suggested that the simplification effected by the use of these methods may be of value for design purposes pending the development of more accurate methods based on test results.

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THE EFFECT OF CERAMIC IN COMBINATION OF TWO SIGMOID FUNCTIONALLY GRADED ROTATING DISKS WITH VARIABLE THICKNESS

International Journal of Computational Methods ◽

10.1142/s0219876212400294 ◽

2012 ◽

Vol 09 (02) ◽

pp. 1240029 ◽

Cited By ~ 4

Author(s):

M. BAYAT ◽

B. B. SAHARI ◽

M. SALEEM

Keyword(s):

Variable Thickness ◽

Functionally Graded ◽

Rotating Disks ◽

Thickness Profile ◽

Metal Ceramic ◽

Graded Material ◽

The One ◽

Rotating Load ◽

Power Law Distributions ◽

Different Thickness

This paper presents elastic solutions of a disk made of functionally graded material (FGM) with variable thickness subjected to rotating load. The material properties are represented by combination of two sigmoid FGM (S-FGM) namely aluminum–ceramic–aluminum and the disk's different thickness profiles are assumed to be represented by power law distributions. Hollow disks are considered and the solutions for the displacements and stresses are given under appropriate boundary conditions. The effects of the material grading index n and the geometry of the disk on the displacements and stresses are investigated. The results are compared with the known results in the literature on metal–ceramic–metal FGMs. Also the solutions are compared S-FGM versus FGM and non FGM and variable thickness versus uniform thickness. It is found that a sigmoid functionally graded disk with concave thickness profile has smaller displacements and stresses compared with concave or linear thickness profile. It is also observed that an S-FGM rotating functionally graded disk with metal–ceramic–metal combination can be more efficient than the one with ceramic–metal or metal–ceramic.

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Nanocrystalline FCC Thin Films Are More Prone to RT Creep Than What We Think

Volume 11: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2009-10578 ◽

2009 ◽

Author(s):

Nikhil Karanjgaokar ◽

Ioannis Chasiotis

Keyword(s):

Thin Films ◽

Grain Size ◽

Steady State ◽

Yield Strength ◽

Time Scales ◽

Room Temperature ◽

Primary Creep ◽

Steady State Creep ◽

Strain Rates ◽

Creep Response

Although nanocrystalline (Nc) metallic thin films are excellent candidate materials for Microelectromechanical Systems (MEMS) and microelectronics due to their outstanding yield strength, serious reliability concerns arise from their increased room temperature creep rates. A comprehensive experimental investigation was carried out to extract the strain-rate dependent mechanical behavior of Au (38 nm grain size) and Ni (20 nm grain size) micron-thin films conducted for the very first time at strain rates in the broad range of 10−6 – 10 /s which spans time scales from ms to hours. Nc-Au films demonstrated a clear bi-linear change in their inelastic properties, i.e. the elastic limit and its yield strength, while the Nc-Ni films showed a linear increase in their inelastic properties over the same loading rates. This unexpected trend for the Au films emphasized the significant contribution of room temperature (RT) creep at strain rates between 10−6 – 10−4 /s, at which rate, larger grain size materials are not prone to creep at RT. This realization prompted a series of novel microscale creep experiments, the first of their kind, at time scales of 104–105 s. An important finding was that the first stage of creep, primary creep, proceeds at a very fast rate, of the order of 10−7 /s, lasting for 5–6 hours after the application of a stress. Furthermore, multi-stage creep experiments revealed that the primary creep rate decreased with the order of creep cycle, while the steady state creep response remained the same in all creep cycles. This creep response of nanocrystalline FCC films was modeled via a non-linear viscoelastic creep model that captured the effect of applied stress on both primary and steady-state creep regimes.

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Exact solution for free vibration analysis of linearly varying thickness FGM plate using Galerkin-Vlasov’s method

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420720980491 ◽

2020 ◽

pp. 146442072098049

Author(s):

V Kumar ◽

SJ Singh ◽

VH Saran ◽

SP Harsha

Keyword(s):

Free Vibration ◽

Variable Thickness ◽

Vibration Analysis ◽

Shear Deformation Theory ◽

Free Vibration Analysis ◽

Functionally Graded ◽

Constant Thickness ◽

Engineering Structures ◽

Property Variation ◽

Varying Thickness

The present paper investigates the free vibration analysis for functionally graded material plates of linearly varying thickness. A non-polynomial higher order shear deformation theory is used, which is based on inverse hyperbolic shape function for the tapered FGM plate. Three different types of material gradation laws, specifically: a power (P-FGM), exponential (E-FGM), and sigmoid law (S-FGM) are used to calculate the property variation in the thickness direction of FGM plate. The variational principle has been applied to derive the governing differential equation for the plates. Non-dimensional frequencies have been evaluated by considering the semi-analytical approach viz. Galerkin-Vlasov’s method. The accuracy of the preceding formulation has been validated through numerical examples consisting of constant thickness and tapered (variable thickness) plates. The findings obtained by this method are found to be in close agreement with the published results. Parametric studies are then explored for different geometric parameters like taper ratio and boundary conditions. It is deduced that the frequency parameter is maximum for S-FGM tapered plate as compared to E- and P-FGM tapered plate. Consequently, it is concluded that the S-FGM tapered plate is suitable for those engineering structures that are subjected to huge excitations to avoid resonance conditions. In addition, it is found that the taper ratio is significantly affected by the type of constraints on the edges of the tapered FGM plate. Some novel results for FGM plate with variable thickness are also computed that can be used as benchmark results for future reference.

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