Elevated Temperature Neutron Measurements of Thermal Residual Stresses in a Sic Fibre Reinforced Al Alloy

1994 ◽  
Vol 376 ◽  
Author(s):  
Monica Ceretti ◽  
M. Kocsis ◽  
A. Lodini
Keyword(s):  
Residual Stresses ◽  
Al Alloy ◽  
Thermal Residual Stresses ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix ◽  
Al 7075 ◽  
Sic Whiskers ◽  
Stress Free State ◽  
Increasing Temperature

ABSTRACTThe main objective of the present investigation is to determine the evolution of residual stresses by neutron powder diffraction in an Al/SiC composite (Al 7075 reinforced by 27 vol.% SiC whiskers), originating from thermal treatment and mechanical loading. The results show that residual stresses in the matrix and in the reinforcement decrease in magnitude with increasing temperature and they reach the stress free state at the 'equivalent temperature'. As the temperature further increases, these stresses increase numerically in a reverse sense for both phases. The data obtained are analysed in terms of a simple model based on Eshelby's equivalent inclusion method.

scholarly journals Analysis of Line Contact Elastohydrodynamic Lubrication with the Particles under Rough Contact Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Keying Chen ◽  
Liangcai Zeng ◽  
Juan Chen ◽  
Xianzhong Ding
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Thickness Distribution ◽  
Traction Force ◽  
Elastohydrodynamic Lubrication ◽  
Equation System ◽  
Line Contact ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix

A numerical solution for line contact elastohydrodynamic lubrication (EHL) occurring on the rough surface of heterogeneous materials with a group of particles is presented in this study. The film thickness disturbance caused by particles and roughness is considered into the solution system, and the film pressure between the contact gap generated by the particles and the surface roughness is obtained through a unified Reynold equation system. The inclusions buried in the matrix are made equivalent to areas with the same material as that of the matrix through Eshelby’s equivalent inclusion method and the roughness is characterized by related functions. The results present the effects of different rough topographies combined with the related parameters of the particles on the EHL performance, and the minimum film thickness distribution under different loads, running speeds, and initial viscosities are also investigated. The results show that the roughness morphology and the particles can affect the behavior of the EHL, the traction force on a square rough surface is smaller, and the soft particles have more advantages for improving the EHL performance.

The Stress Field and Intensity Factor due to Crazes Formed at the Poles of a Spherical Inhomogeneity

1994 ◽  
Vol 61 (4) ◽  
pp. 803-808 ◽  
Author(s):  
Z. M. Xiao ◽  
K. D. Pae
Keyword(s):  
Stress Intensity Factor ◽  
Intensity Factor ◽  
Stress Field ◽  
Elastic Moduli ◽  
Superposition Principle ◽  
Numerical Examples ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix ◽  
Good Agreement

The problem of two penny-shaped crazes formed at the top and the bottom poles of a spherical inhomogeneity has been investigated. The inhomogeneity is embedded in an infinitely extended elastic body which is under uniaxial tension. Both the inhomogeneity and the matrix are isotropic but have different elastic moduli. The analysis is based on the superposition principle of the elasticity theory and Eshelby’s equivalent inclusion method. The stress field inside the inhomogeneity and the stress intensity factor on the boundary of the craze are evaluated in the form of a series which involves the ratio of the radius of the penny-shaped craze to the radius of the spherical inhomogeneity. Numerical examples show the interaction between the craze and the inhomogeneity is strongly affected by the elastic properties of the inhomogeneity and the matrix. The conclusion deduced from the numerical results is in good agreement with experimental results given in the literature.

Two-Ellipsoidal Inhomogeneities by the Equivalent Inclusion Method

1975 ◽  
Vol 42 (4) ◽  
pp. 847-852 ◽  
Author(s):  
Z. A. Moschovidis ◽  
T. Mura
Keyword(s):  
Computer Program ◽  
Strain Field ◽  
Applied Strain ◽  
Stress And Strain ◽  
Isotropic Matrix ◽  
Equivalent Inclusion Method ◽  
Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix ◽  
Final Stress

The problem of two ellipsoidal inhomogeneities in an infinitely extended isotropic matrix is treated by the equivalent inclusion method. The matrix is subjected to an applied strain field in the form of a polynomial of degree M in the position coordinates xi. The final stress and strain states are calculated for two isotropic ellipsoidal inhomogeneities both in the interior and the exterior (in the matrix) by using a computer program developed. The method can be extended to more than two inhomogeneities.

Precipitate phases in an Al-SiC composite

1984 ◽  
Vol 42 ◽  
pp. 490-491
Author(s):  
S.R. Nutt ◽  
R.W. Carpenter
Keyword(s):  
Fracture Toughness ◽  
Composite Material ◽  
Alloy Powder ◽  
Heat Treating ◽  
Matrix Alloy ◽  
Al Alloy ◽  
Unreinforced Alloy ◽  
The Matrix ◽  
Sic Whiskers ◽  
Sic Composites

The modulus of many aluminum alloys can be greatly increased by the addition of small amounts of silicon carbide. The resulting composite material is also stronger than the unreinforced alloy, but exhibits poor fracture toughness. The reason for the low ductility of Al-SiC composites is unknown, although results presented here indicate that embrittling phases present in the matrix alloy may be partially responsible. The purpose of this work has been to study the distribution of precipitate phases in Al-SiC composites, focusing particular attention on interface regions. The material studied was fabricated by adding SiC whiskers to a 2124 Al alloy powder, consolidating, then heat treating to a T6 temper.

Strain contrast in SiC whisker reinforced Al2O3

1986 ◽  
Vol 44 ◽  
pp. 498-499
Author(s):  
P. Angelini ◽  
W. Mader
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Thermal Expansion ◽  
Quantitative Analysis ◽  
Residual Stresses ◽  
Strain Field ◽  
Ceramic Materials ◽  
Spherical Particles ◽  
The Matrix ◽  
Sic Whiskers

Whisker reinforced ceramic materials offer the potential for increased fracture toughness and fracture strength. Residual stresses resulting from differences in thermal expansion properties of the matrix and the whisker can develop during cooling and affect mechanical properties. TEH strain contrast of large inclusions has previously been observed for nearly spherical particles of ZrO2 in Al2O3 matrix grains. The formation of strain contrast oscillations was explained and a quantitative analysis of strains around ZrO2 inclusions in Al2O3 was performed. The present research is concerned with characterizing by TEM the strain field present in Al2O3 reinforced with SiC whiskers.

Numerical methods for solving the equivalent inclusion equation in semi-analytical models

2021 ◽  
pp. 135065012110001
Author(s):  
Zhiqiang Yan ◽  
Mengqi Zhang ◽  
Shulan Jiang
Keyword(s):  
Matrix Material ◽  
Current Method ◽  
Equation System ◽  
Analytical Models ◽  
Equivalent Inclusion Method ◽  
Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix ◽  
Convergence Mechanism ◽  
Computing Accuracy

Equivalent inclusion method is the basis for semi-analytical models in tackling inhomogeneity problems. Equivalent eigenstrains are obtained by solving the consistency equation system of the equivalent inclusion method and then stress disturbances caused by inhomogeneities are determined. The equivalent inclusion method equation system can only be solved numerically, but the current fixed-point iteration method may not be able to achieve deep convergence when the Young's modulus of inhomogeneity is lower than that of the matrix material. The most significant innovation of this paper is to reveal the non-convergence mechanism of the current method. Considering the limitation, the Jacobian-free Newton Krylov algorithm is selected to solve the equivalent inclusion method equation. Results indicate that the new algorithm has significant advantages of computing accuracy and efficiency compared with the classic method.

Effects of Near-surface Composites on Frictional Rolling Contact Solved by a Semi-analytical Model

2021 ◽  
pp. 1-23
Author(s):  
Mengqi Zhang ◽  
Zhiqiang Yan
Keyword(s):  
Analytical Model ◽  
Surface Displacement ◽  
Normal Pressure ◽  
Element Model ◽  
Rolling Contact ◽  
Near Surface ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix ◽  
Tangential Traction

Abstract A semi-analytical model (SAM) to tackle the steady-state elastic frictional rolling contact problem involving composites is presented. Specifically, the frictional rolling contact is categorized into two subtypes, namely normal and tangential problems, and the conjugate gradient method (CGM) is used to figure out the normal pressure and tangential traction. In SAM, the equivalent inclusion method (EIM) is applied to analyze the influence of composites on the matrix, and the displacement disturbance resulting from such composites is added to the total surface displacement, which implements the coupling between surface contact and composites. The accuracy of the proposed model is verified by the finite element model. The effects of composites on the frictional rolling contact behavior are investigated. The results indicate that Young's modulus, as well as the size and location of the composites, are correlated with the distributions of tangential traction, subsurface stresses and the sizes of stick and sliding zones.

Residual Stresses in Al2O3/SiC (Whisker) Composites Containing Interfacial Carbon Films

1988 ◽  
Vol 32 ◽  
pp. 471-479 ◽  
Author(s):  
Alias Abuhasan ◽  
Paul K. Predecki
Keyword(s):  
Residual Stresses ◽  
Carbon Coating ◽  
Carbon Film ◽  
Carbon Films ◽  
X Ray Diffraction ◽  
The Matrix ◽  
Sic Whiskers ◽  
Residual Strains ◽  
Residual Microstresses ◽  
Good Agreement

AbstractResidual strains and stresses were measured in hot-pressed α-Al2O3 composites containing 25 wt% β (cubic) SiC whiskers with and without a 50-100Å thick carbon coating. X-ray diffraction methods were used including the separation of macrostresses from the microstresses in the -Al2O3 and SiC phases by the method of Noyan and Cohen. The presence of the carbon coating on the whiskers reduced the magnitude of the residual microstresses in the whiskers by ˜13% and in the matrix by ˜10%. The measured residual stresses in the whiskers and the reduction due to the carbon film were in good agreement with calculations from recent models proposed by Hsueh, Becher and Angelini, and by Li and Bradt.

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