Stress Distribution In Matrix Research Articles

Noise Reduction Mechanism and Analysis of TC4 with Dimple Textured Surfaces

Improving the friction-induced noise suppression performance of TC4 has far-reaching significance for its wide application in the field of robots and semiconductors. The friction noises of TC4 with solid lubricant (Sn-Ag-Cu) filled into dimples (TCS) and TC4 were predicted by simulation analysis. The noise reduction performance of TCS during dry rotary sliding was discussed. TCS with dimple size of 0.6 mm (TCS-0.6) exhibited the prominent performance of noise reduction, which was attributed to the synergistic effect of dimples and solid lubricant. During the dry sliding process, the debris were contained by dimples, the stress distribution in matrix was modified by lubricant, and the defects were decreased. Hence, the roughness of worn surface was reduced, which was beneficial to obtaining the stable friction coefficient. Inhibiting the unstable vibration by controlling the friction coefficient of the system can effectively demote the friction-induced noise.

Prediction model of matrix crack density in ceramic matrix composites under arbitrary matrix stress distribution

A prediction model of matrix crack density in ceramic matrix composites under arbitrary matrix stress distribution was proposed. The matrix was separated into many small segments whose strength was determined by stochastic defect theory. By comparing the matrix strength and stress distribution, the matrix cracking process was simulated. The model proposed in this paper can theoretically simulate the matrix crack density of any matrix stress distribution, especially when the interface shear stress increases under cyclic loading, which can contribute to the prediction of fatigue life.

Influence of the Shape of the Test Specimen Produced by 3D Printing on the Stress Distribution in the Matrix and in Long Reinforcing Fibers

Abstract The stress distribution in specimens designed for the tensile testing is evaluated in the article. The reinforcement consists of long fibers that copy the outer contour of the specimen. The fibers are inserted within the curvature at the edge of the specimen with the neck. The stress distribution in fibers and matrix of dogbone specimen and specimen of rectangular shape is analyzed and compared. The analysis of stress state is analyzed in FEM software ADINA. Long fibers deposited in specimen were modeled using rebar elements.

Spontaneous formation of fluid escape pipes from subsurface reservoirs

Ubiquitous observations of channelised fluid flow in the form of pipes or chimney-like features in sedimentary sequences provide strong evidence for significant transient permeability-generation in the subsurface. Understanding the mechanisms and dynamics for spontaneous flow localisation into fluid conductive chimneys is vital for natural fluid migration and anthropogenic fluid and gas operations, and in waste sequestration. Yet no model exists that can predict how, when, or where these conduits form. Here we propose a physical mechanism and show that pipes and chimneys can form spontaneously through hydro-mechanical coupling between fluid flow and solid deformation. By resolving both fluid flow and shear deformation of the matrix in three dimensions, we predict fluid flux and matrix stress distribution over time. The pipes constitute efficient fluid pathways with permeability enhancement exceeding three orders of magnitude. We find that in essentially impermeable shale (10−19 m2), vertical fluid migration rates in the high-permeability pipes or chimneys approach rates expected in permeable sandstones (10−15 m2). This previously unidentified fluid focusing mechanism bridges the gap between observations and established conceptual models for overcoming and destroying assumed impermeable barriers. This mechanism therefore has a profound impact on assessing the evolution of leakage pathways in natural gas emissions, for reliable risk assessment for long-term subsurface waste storage, or CO2 sequestration.

Finite element modeling of consolidation process of SiC fiber-reinforced titanium matrix composites via matrix-coated fiber method

The consolidation process of SiCf/Ti-6Al-4 V composites by matrix-coated fiber (MCF) method via hot pressing was investigated using finite element modeling (FEM). By analyzing the elastic–plastic contact deformation of the representative aligned coated fibers, the consolidation maps delineating the time–temperature–pressure relationship for full densification were constructed. Both the flow coefficient and the contact area coefficient used to describe the contact deformation were calculated according to the model. In addition, the effect of fiber content on matrix stress distribution was analyzed. The results show that fiber content is a significant factor that influences the densification process. Higher fiber content will lower the consolidation rate.

Numerical Simulation to the Process of Damage Evolution of Defect Cartilage

Objective To understand the stresses distribution and process of damage evolution of both matrix and fiber in the defect cartilage under load of compression. The numerical results may provide a reference to both of the design for cartilage alternatives and clinical repair of defect cartilage. Methods The thickness of different layers of cartilage was obtained by a kind of experiment, in which the displacement in different layers zone cartilage under the compression load was obtained by the digital correlation technique. The multi-layer cartilage model with fiber and defect was established by the multi-physics analysis software ANSYS, with the different layers of the cartilage refer to the experimental results. According to the strength condition, the cartilage damage evolution process was simulated by the method of modifying the stiffness of the elements. The influence of the different defect depth to the damage evolution of cartilage was considered in parameter study. Result The simulation results have shown that the stress distribution in matrix was related to the cartilage defect depth. The minimum stress was distributed in the deep areas and below the damage area, stress concentration was located in the both sides of the defect area in the cartilage matrix, and the damaged area developed gradually from surface to deep, the maximum stress located at both sides of defect area. The stress distribution of cartilage fibers related with their location, the compressive stresses are mainly distributed in the middle and deep area, which are greater than those of undamaged. Conclusion In the process of damage evolution, the damaged area gradually developed from the surface to the deep. In the case of defect value of 60%, the maximum equivalent stresses in matrix will be increased in the process of damage evolution; in the case of defect value of 5%, the maximum axial stresses in fibers will be increased in the process of damage evolution.

Mechanical Behaviors of Sic Particle Reinforced Al Matrix Composites: A Study Based on Finite Element Method

The effects of SiC particle size, volume fraction and tensile strain on the deformation behaviors of SiC particle reinforced Al matrix composites were studied by finite element method using microstructure based model. The results showed that the addition of reinforcements will result in no-uniform stress distribution in matrix. The maximum stress in the particles increases, and the minimum stress in the matrix decreases when the SiC particle volume fraction increases, indicating more load being transferred from matrix to particles with increasing the SiC particle volume fraction. It also showed that as the tensile strain and SiC particle size increase, the maximum stress in the particles increases. It can thus be concluded that small-sized SiC particles can endure more loads and improve the mechanical properties of the composites.

The effect of matrix creep property on the consolidation process of SiC/Ti–6Al–4V composite

The consolidation process was discussed by using finite element analysis (FEA) in SCS–6SiC/Ti–6Al–4V composite fabricated by means of fiber coating method. With consolidation time and temperature changing, the effect of Ti–6Al–4V creep property on the matrix stress distribution was analyzed. The results indicated that the magnitude of matrix stress decreased remarkably and should be more close to the practical consolidation process when taking the effect of matrix creep property into account. In addition, the more time and the higher temperature the consolidation process took, the more obvious the effect of matrix creep property on the consolidation was. The selection of consolidation parameter such as time and temperature could be based on the simulation results.

1758 長繊維強化複合材料におけるモードI応力状態での3次元メゾメカニクス応力評価(G03-3 応力解析,G03 材料力学)

Long fiber reinforced plastics (FRP) are used as the primary component of airplanes. Therefore the increase of the strength and toughness of FRP have been hoped. In many studies about FRP, the macro-mechanics approach without considering inhomogeneities of FRP has been applied. However, the effects of meso-scale factor, for example, fiber, matrix and interface, on the stress field around crack tips or fracture strength cannot be considered. In this study, the matrix stress and fracture mechanics parameters in FRP were analyzed from the viewpoint of the three-dimensional meso-mechanics. FRP model based on this mechanics is modeled as discrete models composed of fiber and matrix. As a result, the average energy release rate of inhomogeneous FRP for long cracks was same as that of homogeneous FRP. For very long cracks in comparison with fiber diameter, the matrix stress of IFRP model could be separated into four regions (Region I, Region II, Region III (IIIa, IIIb)) following the crack tip. For short cracks, the Region IIIa vanished from the matrix stress distribution.

き裂を有する長繊維強化複合材料のマトリックス相応力分布の3次元有限要素解析(S07-3 複合材料I,S07 メゾスケールにおける先進材料の力学と強度・機能評価)

Three-dimensional meso-mechanical analysis was conducted by the finite element method (FEM) in order to determine the elastic stress distribution around a crack tip in fiber-reinforced plastics (FRP). FRP plates were modeled as a typical 'one-fiber slice' model, represented by the fiber-resin model. The fibers were arranged in a square array with a fiber volume fraction of 0.60 Matrix crack is parallel to the fiber direction and is subjected to model I loading. The stress intensity factor, K_<lm>, and the average energy release rate was calculated for the above inhomogeneous FRP, and compared with those for a homogeneous FRP. For the long crack, the average energy release rate for the inhomogeneous FRP was equal to that obtained for the homogeneous FRP. For long crack, the matrix-stress distribution ahead of delamination can be divided into three regions: Region I, II and III (IIIa, IIIb) in the order of increasing distance from crack tip. The matrix-sterss in Region I had a singularity of 1/√r, but was smaller than that of the homogeneous FRP. Region IIIa has a singularity, too. But stress intensity factor of Region III was not equal to that of Region I. Region II was transitional region from Region I to IIIa.

931 FRP 中の層間はく離き裂近傍における弾性応力分布の 3 次元メゾメカニックス解析

Three-dimensional meso-mechanical analysis was conducted by the finite element method (FEM) in order to determine the elastic stress distribution around a crack tip in fiber-reinforced plastics (FRP). FRP plates were modeled as a typical 'one-fiber slice' model, represented by the fiber-resin model. The fibers were arranged in a square array with a fiber volume fraction of 0.60. Matrix crack plane parallel to the fiber direction was placed in the matrix and is subjected to mode I loading. The half-crack length normalized by fiber diameter was varied from a/d_f=0.2 to 200. For long crack, the matrix-stress distribution ahead of delamination front can be divided into three regions : Region I, II and III (IIIa, IIIb) in the order of increasing distance from crack tip. The matrix-stress in Region I had a singularity of 1/√<r>, but was smaller than that of homogeneous FRP. Region IIIa has a singularity, too. But stress intensity factor of Region III was not equal to that of Region I. Region II was transitional region from Region I to IIIa.

On the local elastic–plastic behaviour of the interface in titanium/silicon carbide composites

Abstract The purpose of this study is to conduct a high-resolution nonlinear finite element analysis of the elastic–plastic behaviour of titanium/silicon carbide composites subject to transverse loading. This class of metal matrix composites is designed for the next generation of supersonic jet engines and deserves careful assessment of its behaviour under thermo mechanical loads. Three aspects of the work are accordingly examined. The first is concerned with the development of a representative unit cell capable of accurately describing the local elastic–plastic behaviour of the interface in metal matrix composites under thermal and mechanical loads. The second is concerned with the determination of the influence of mismatch in the mechanical properties between the inhomogeneity and the matrix upon the induced stress fields and the plastic zone development and its growth. The third is concerned with unloading and the role played by the interface upon residual stresses. It is found that the maximum interfacial stress in the matrix appears in the case involving cooling from the relieving temperature with subsequent applied compressive loading. It is also found that the mismatch in mechanical properties between the matrix and the inhomogeneity introduces significant changes in the stress distribution in the matrix. Specifically, it is observed that the maximum radial and tangential stresses in the matrix take place at the interface. The plastic deformation of the matrix leads to a relaxation of these stresses and assists in developing a more uniform interfacial stress distribution. However, the matrix stresses and the resulting equivalent plastic strains still reach their maximum values at that interface. The results show similarities in the patterns of the interfacial stress distribution and plastic zone development for all ranges of fibre volume fractions and loading levels examined. However, they also show marked differences in both the magnitude and patterns of matrix stress distribution between the adjacent inhomogeneities as a result of interaction effects between the fibres.

Transition from Small to Large Interlaminar Cracks in Fiber-Reinforced Laminated Composites.

The boundary element method was used to determine the elastic stress distribution near the tip of a delamination crack in fiber-reinforced plastics(FRP). FRP composites were modeled by a two-dimensional laminated structure composed of isotropic matrix and orthotropic fiber. A straight crack parallel to the fiber direction is placed in the matrix and is subjected to mode I or II loading. The stress intensity factor and the energy release rate were calculated as a function of the crack length for the above inhomogeneous model, and compared with those for a homogeneous model. For large cracks, the energy release rate for the inhomogeneous model is equal to that obtained for the homogeneous model for both mode I and II loadings. For small cracks, the energy release rate is larger for the inhomogeneous model than for the homogeneous model. The transition condition from small to large cracks was defined for the cases of mode I and II. The characteristics of the elastic matrix stress distribution ahead of the crack tip for the inhomogeneous model were discussed in comparison with the solution for the homogeneous model.

Effect of interphase modulus and cohesive energy on the critical aspect ratio in short-fibre composites

The effect of interphase modulus and cohesive energy on critical fibre length in short-fibre reinforced brittle composites has been investigated employing computer simulation. The simulation consists of a two-dimensional computer model based upon a discrete network of grid points. Failure is defined in terms of an energy criterion, where the energy is calculated on the basis of a two- and three-body interaction between the grid points. Simulation results show that for a whisker-type fibre, a thick interphase (i.e. Ai>Af where A represents the cross sectional area) with an elastic modulus less than that of the matrix in combination with an increased interphase toughness greatly reduce the critical aspect ratio, for both metal-matrix and ceramic-reinforced brittle polymer composites. The results also show a variation in the failure mode from tensile failure in the matrix to tensile and shear failure in the interphase as a function of the fibre-interphase modulus ratio. In particular, a significant increase in the load transfer efficiency in metal-matrix composites is found, for an interphase modulus Ei less than the matrix modulus Em. Better load transfer properties in metal-matrix composites cause the yield point to occur at higher values of applied strain, and hence may significantly increase the toughness (area under the stress-strain curve) for certain metal-matrix composites. The computer results are compared with the predictions of Cox's shear-lag theory as well as with a new theoretical development presented in this work. The new theory is found to provide a better description of the fibre and matrix stress distribution.