scholarly journals Soft inclusion in a confined fluctuating active gel

2018 ◽  
Vol 97 (3) ◽  
Author(s):  
Amit Singh Vishen ◽  
J.-F. Rupprecht ◽  
G. V. Shivashankar ◽  
J. Prost ◽  
Madan Rao
Keyword(s):  
Soft Inclusion

Theoretical analysis of a rolling-sliding elastohydrodynamic lubrication line contact with a subsurface inclusion

2019 ◽  
Vol 233 (8) ◽  
pp. 1197-1207
Author(s):  
Armando Félix Quiñonez ◽  
Guillermo E Morales Espejel
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Transient Effects ◽  
Mean Velocity ◽  
The Matrix ◽  
Soft Inclusion ◽  
The Mean ◽  
Von Mises ◽  
Fully Coupled

This work investigates the transient effects of a single subsurface inclusion over the pressure, film thickness, and von Mises stress in a line elastohydrodynamic lubrication contact. Results are obtained with a fully-coupled finite element model for either a stiff or a soft inclusion moving at the speed of the surface. Two cases analyzed consider the inclusion moving either at the same speed as the mean velocity of the lubricant or moving slower. Two additional cases investigate reducing either the size of the inclusion or its stiffness differential with respect to the matrix. It is shown that the well-known two-wave elastohydrodynamic lubrication mechanism induced by surface features is also applicable to the inclusions. Also, that the effects of the inclusion become weaker both when its size is reduced and when its stiffness approaches that of the matrix. A direct comparison with predictions by the semi-analytical model of Morales-Espejel et al. ( Proc IMechE, Part J: J Engineering Tribology 2017; 231) shows reasonable qualitative agreement. Quantitatively some differences are observed which, after accounting for the semi-analytical model's simplicity, physical agreement, and computational efficiency, may then be considered as reasonable for engineering applications.

Regularizing Biomechanical Maps for Partially Known Material Properties

2017 ◽  
Vol 09 (02) ◽  
pp. 1750020 ◽  
Author(s):  
Yue Mei ◽  
Mahsa Tajderi ◽  
Sevan Goenezen
Keyword(s):  
Inverse Problem ◽  
Elastic Modulus ◽  
Problem Formulation ◽  
Small Region ◽  
Parameter Distribution ◽  
Atherosclerotic Plaques ◽  
Surgical Interventions ◽  
Constrained Minimization Problem ◽  
Soft Inclusion ◽  
Unique Parameter

We present the solution of the inverse problem for partially known elastic modulus values, e.g., the elastic modulus is known in some small region on the boundary of the domain from measurements. The inverse problem is posed as a constrained minimization problem and regularized with two different regularization types. In particular, the total variation diminishing (TVD) and the total contrast diminishing (TCD) regularizations are employed. We test both regularization strategies with theoretical diseased tissues, such as a stiff tumor surrounded by healthy background tissue and an atherosclerotic plaque having a soft inclusion surrounded by a stiff cap. In the present study, it is assumed that no traction data is available and the absolute elastic modulus distribution is calibrated from partially known elastic modulus values. We observe that this calibration fails with TVD regularization, while TCD regularization yields well-recovered absolute elastic modulus reconstructions in the presence of high noise levels in the displacement data. Finally, we investigate this problem analytically and provide an explanation for these observations. This work will advance efforts in parameter identification of heterogeneous materials as it provides a methodology to incorporate partially known parameters into the inverse problem formulation that will ultimately drive the inverse solution to an absolute and unique parameter distribution. This has great importance in classifying breast tumors based on their elastic modulus values and in planning surgical interventions of atherosclerotic plaques.

scholarly journals Second gradient substitution model for high contrast bi-phase structure

2020 ◽  
Vol 14 (2) ◽  
pp. 116-126
Author(s):  
Trinh Duy Khanh
Keyword(s):  
Phase Structure ◽  
Homogeneous Model ◽  
Homogeneous Boundary Condition ◽  
Higher Order ◽  
Material Behavior ◽  
Equivalent Model ◽  
Potential Candidate ◽  
Substitution Model ◽  
Second Gradient ◽  
Soft Inclusion

Lightweight structures with soft inclusion material, such as hollow core slabs, foam sandwich wall, pervious pavement ... are widely used in construction engineering for sustainable goals. Voids and soft inclusion can be modeled as a very soft material, while the main material is modeled with its original rigidity, which is so much higher than inclusion's one. In consequence, highly contrast bi-phase structure attracts the interests of scientists and engineers. One important demand is how to build a homogeneous equivalent model to replace the multi-phase structure which requires much resources and time to perform structure analysis. Various homogenization schemes have succeeded in establishing a homogeneous substitution model for composite materials which fulfill the scale separation condition (characteristic length of heterogeneity is very small in comparison to structure dimensions). Herein, elastic stiffness matrix of a homogeneous model which replaces a bi-phase material is computed by a higher-order homogenization scheme. A non-homogeneous boundary condition (a polynomial inspired from Taylor series expansion) is used in computation. Homogeneous substitution model constructed from this computation process, can give engineers a fast and effective tool to predict the behavior of bi-phase structure. Instead of a classical Cauchy continuum, second gradient model is selected as a potential candidate for substituting the composite material behavior because of the separation scale (volume ratio of inclusion to matrix phase reaches unit). Keywords: generalized continuum; second-gradient medium; higher-order homogenization; non-homogeneous boundary conditions; representative volume element.

Behavior of a Horizontal Fluid Filled Crack Under Moving Hertzian Load

2005 ◽  
Author(s):  
X. Jin ◽  
L. M. Keer ◽  
E. L. Chez
Keyword(s):  
Half Plane ◽  
Continuous Distribution ◽  
Contact Stresses ◽  
Hertzian Contact ◽  
Subsurface Crack ◽  
Intensity Factors ◽  
Crack Volume ◽  
Rolling Body ◽  
Soft Inclusion ◽  
Edge Dislocations

Numerical analysis is presented for a fluid filled subsurface crack in an elastic half plane loaded by Hertzian contact stresses. The opening volume of the horizontal Griffith crack is fully occupied by an incompressible fluid. In the presence of friction, a moving Hertzian line contact load is applied at the surface of the half plane. The stress intensity factors at the tips of the fluid filled crack are analyzed on condition that the change of the opening crack volume vanishes due to the fluid incompressibility. The method used is that of replacing the crack by a continuous distribution of edge dislocations. As a cycle of rolling can be viewed as shifting the Hertzian contact stresses across the surface of the half plane, the results of this analysis may prove useful in the prediction of rolling fatigue of an elastic rolling body containing a soft inclusion.

The M-Integral Analysis for a Nano-Inclusion in Plane Elastic Materials Under Uni-Axial or Bi-Axial Loadings

2009 ◽  
Vol 77 (2) ◽  
Author(s):  
Tong Hui ◽  
Yi-Heng Chen
Keyword(s):  
Surface Effect ◽  
Continuum Theory ◽  
Elastic Materials ◽  
Hard Inclusion ◽  
Surface Parameters ◽  
Integral Analysis ◽  
Axial Tension ◽  
Soft Inclusion ◽  
Tension Loading ◽  
M Integral

This paper deals with the M-integral analysis for a nano-inclusion in plane elastic materials under uni-axial or bi-axial loadings. Based on previous works (Gurtin and Murdoch, 1975, “A Continuum Theory of Elastic Material Surfaces,” Arch. Ration. Mech. Anal., 57, pp. 291–323; Mogilevskaya, et al., 2008, “Multiple Interacting Circular Nano-Inhomogeneities With Surface/Interface Effects,” J. Mech. Phys. Solids, 56, pp. 2298–2327), the surface effect induced from the surface tension and the surface Lamé constants is taken into account, and an analytical solution is obtained. Four kinds of inclusions including soft inclusion, hard inclusion, void, and rigid inclusions are considered. The variable tendencies of the M-integral for each of four nano-inclusions against the loading or against the inclusion radius are plotted and discussed in detail. It is found that in nanoscale the surface parameters for the hard inclusion or rigid inclusion have a little or little influence on the M-integral, and the values of the M-integral are always negative as they would be in macroscale, whereas the surface parameters for the soft inclusion or void yield significant influence on the M-integral and the values of the M-integral could be either positive or negative depending on the loading levels and the surface parameters. Of great interest is that there is a neutral loading point for the soft inclusion or void, at which the M-integral transforms from a negative value to a positive value, and that the bi-axial loading yields similar variable tendencies of the M-integral as those under the uni-axial tension loading. Moreover, the bi-axial tension loading increases the neutral loading point, whereas the bi-axial tension-compression loading decreases it. Particularly, the magnitude of the negative M-integral representing the energy absorbing of the soft inclusion or void increases very sharply as the radius of the soft inclusion or void decreases from 5 nm to 1 nm.

Effect of Silver on Superplastic Deformation in YBa2Cu3O7–x/Ag Composites

2002 ◽  
Vol 17 (5) ◽  
pp. 1172-1177
Author(s):  
Jondo Yun ◽  
Ye T. Chou ◽  
Martin P. Harmer
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Superplastic Deformation ◽  
Close Agreement ◽  
Silver Content ◽  
Strain Rates ◽  
Compression Tests ◽  
Fine Grained ◽  
Soft Inclusion ◽  
Activation Energy Of Deformation

Superplastic deformation was studied in fine-grained (0.7–1.1 μm) YBa2Cu3O7–x/Ag composites containing 2.5–25 vol% Ag. The compression tests were conducted in the temperature range of 750–875 °C and at strain rates of 10−5 to 10−3/s. For the YBa2Cu3O7−x/25%Ag composites with grain size of 0.7–1.1 μm, deformed at 800–850 °C and 10−5 to 10−3/s, the stress exponent, grain size exponent, and the activation energy of deformation were 2.0 ± 0.1, 2.5 ± 0.7, and 760 ± 100 kJ/mol, respectively. These values were the same as those of the pure YBa2Cu3O7−x, indicating that the deformation of the composite was controlled by that of the rigid YBa2Cu3O7−x phase. However, the strain rate was increased by the addition of silver as explained by the soft inclusion model of Chen. The dependence of the flow stress on the silver content was in close agreement with the prediction of the model.

scholarly journals Formation Mechanism of Voids around Hard Inclusion during Hot Rolling Processes

2018 ◽  
Vol 37 (8) ◽  
pp. 717-723
Author(s):  
Rong Cheng ◽  
Jiongming Zhang ◽  
Bo Wang
Keyword(s):  
Formation Mechanism ◽  
Hot Rolling ◽  
Rolling Process ◽  
Relative Displacement ◽  
Hard Inclusion ◽  
Hot Rolling Process ◽  
The Matrix ◽  
Soft Inclusion ◽  
Contact Surfaces ◽  
Plastic Slab

AbstractTo investigate the mechanism by which voids form around hard inclusions, the deformations of a plastic slab with hard and soft inclusions that form inside it during the hot rolling process have been simulated with a finite element method. By comparing plastic strain distributions, the relative displacements of contact surfaces, and the deformations between hard and soft inclusions have preceded analysis of the formation mechanism of these voids. The variations of strain measurements between the matrix and hard inclusions cause relative displacement of their contact surfaces. Therefore, voids occur at the front and rear of the hard inclusions. Trials on the slab deformations using a titanium ball instead of the soft inclusion inside the slab during the hot rolling process are conducted. The simulated shapes of the soft inclusions with different reductions mostly agree with the experimental results.

scholarly journals On Simulation of Impact Damage in Composite Laminate

1995 ◽  
Vol 4 (1) ◽  
pp. 096369359500400
Author(s):  
Y. Xiong
Keyword(s):  
Impact Strength ◽  
Prediction Model ◽  
Stress Analysis ◽  
Variational Approach ◽  
Composite Laminate ◽  
Impact Damage ◽  
Finite Width ◽  
Compression After Impact ◽  
Soft Inclusion ◽  
The Impact

A complex variational approach is proposed for the stress analysis of a finite composite laminate containing soft inclusion of elliptical shape which simulates the impact damage. The finite width correction is avoided by using this approach in the prediction model for the compression-after-impact strength of laminates. Comparisons with the FEM and test date are made and presented to verify the accuracy of the approach proposed.

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