scholarly journals Bulk modulus of soft particle assemblies under compression

2021 ◽  
Vol 249 ◽  
pp. 14014
Author(s):  
David Cantor ◽  
Manuel Cárdenas-Barrantes ◽  
Itthichai Preechawuttipong ◽  
Mathieu Renouf ◽  
Emilien Azéma
Keyword(s):  
Bulk Modulus ◽  
Applied Pressure ◽  
Small Strain ◽  
Numerical Approach ◽  
Soft Particle ◽  
Medium Theory ◽  
Interparticle Friction ◽  
The Individual ◽  
Particle Assemblies ◽  
Pressure Controlled

Using a numerical approach based on the coupling of the discrete and finite element methods, we explore the variation of the bulk modulus K of soft particle assemblies undergoing isotropic compression. As the assemblies densify under pressure-controlled boundary conditions, we show that the non-linearities of K rapidly deviate from predictions standing on a small-strain framework or the, so-called, Equivalent Medium Theory (EMT). Using the granular stress tensor and extracting the bulk properties of single representative grains under compression, we propose a model to predict the evolution of K as a function of the sample’s solid fraction and a reference state as the applied pressure P→0. The model closely reproduces the trends observed in our numerical experiments confirming the behavior scalability of soft particle assemblies from the individual particle scale. Finally, we present the effect of the interparticle friction on K’s evolution and how our model easily adapts to such a mechanical constraint.

scholarly journals Rocking Behaviour of Multi-Block Columns Subjected to Pulse-Type Ground Motion Accelerations

2016 ◽  
Vol 10 (1) ◽  
pp. 150-157 ◽  
Author(s):  
Giovanni Minafò ◽  
Giuseppina Amato ◽  
Lorenzo Stella
Keyword(s):  
Ground Motion ◽  
Numerical Approach ◽  
Structural Members ◽  
Cross Sectional ◽  
Practical Engineering ◽  
Pulse Type ◽  
Single Block ◽  
The Individual ◽  
Acceleration Record ◽  
Rocking Response

Ancient columns, made with a variety of materials such as marble, granite, stone or masonry are an important part of the European cultural heritage. In particular columns of ancient temples in Greece and Sicily which support only the architrave are characterized by small axial load values. This feature together with the slenderness typical of these structural members clearly highlights as the evaluation of the rocking behaviour is a key aspect of their safety assessment and maintenance. It has to be noted that the rocking response of rectangular cross-sectional columns modelled as monolithic rigid elements, has been widely investigated since the first theoretical study carried out by Housner (1963). However, the assumption of monolithic member, although being widely used and accepted for practical engineering applications, is not valid for more complex systems such as multi-block columns made of stacked stone blocks, with or without mortar beds. In these cases, in fact, a correct analysis of the system should consider rocking and sliding phenomena between the individual blocks of the structure. Due to the high non-linearity of the problem, the evaluation of the dynamic behaviour of multi-block columns has been mostly studied in the literature using a numerical approach such as the Discrete Element Method (DEM). This paper presents an introductory study about a proposed analytical-numerical approach for analysing the rocking behaviour of multi-block columns subjected to a sine-pulse type ground motion. Based on the approach proposed by Spanoset al.(2001) for a system made of two rigid blocks, the Eulero-Lagrange method to obtain the motion equations of the system is discussed and numerical applications are performed with case studies reported in the literature and with a real acceleration record. The rocking response of single block and multi-block columns is compared and considerations are made about the overturning conditions and on the effect of forcing function’s frequency.

A Simple Approach to Characterize Finite Compressibility of Elastomers

2003 ◽  
Vol 76 (4) ◽  
pp. 912-922 ◽  
Author(s):  
Mark R. Gurvich ◽  
Thomas S. Fleischman
Keyword(s):  
Carbon Black ◽  
Bulk Modulus ◽  
Experimental Verification ◽  
Material Properties ◽  
Numerical Approach ◽  
Simple Approach ◽  
Experimental Measurements ◽  
Axially Loaded ◽  
Different Levels

Abstract A hybrid experimental-numerical approach is proposed for accurate dimensionless characterization of rubber finite compressibility. Rubber specimens in the form of bonded rubber disks are considered as elastomeric structures with unknown material properties. These properties are calculated by matching results of FEA with experimental measurements of radial deformations of the axially-loaded disks. The approach may be used for reliable characterization of Poisson's ratio, bulk modulus, or other characteristics of interest. Implementation of the approach is considered for two representative elastomeric compounds with different levels of carbon black. Good experimental verification of the approach is shown at different levels of loading. Moreover, the same parameters of finite compressibility are independently obtained using both compressive and tensile loads. Higher compressibility is observed for a compound with larger content of carbon black as expected.

A Computational Model for the Dynamics of Cerebrospinal Fluid in the Spinal Subarachnoid Space

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Eleuterio F. Toro ◽  
Ben Thornber ◽  
Qinghui Zhang ◽  
Alessia Scoz ◽  
Christian Contarino
Keyword(s):  
Cerebrospinal Fluid ◽  
Subarachnoid Space ◽  
Numerical Approach ◽  
Loop Model ◽  
Computationally Efficient ◽  
Spinal Subarachnoid Space ◽  
Inflow Condition ◽  
The Central Nervous System ◽  
Fluid Compartments ◽  
The Individual

Global models for the dynamics of coupled fluid compartments of the central nervous system (CNS) require simplified representations of the individual components which are both accurate and computationally efficient. This paper presents a one-dimensional model for computing the flow of cerebrospinal fluid (CSF) within the spinal subarachnoid space (SSAS) under the simplifying assumption that it consists of two coaxial tubes representing the spinal cord and the dura. A rigorous analysis of the first-order nonlinear system demonstrates that the system is elliptic-hyperbolic, and hence ill-posed, for some values of parameters, being hyperbolic otherwise. In addition, the system cannot be written in conservation-law form, and thus, an appropriate numerical approach is required, namely the path conservative approach. The designed computational algorithm is shown to be second-order accurate in both space and time, capable of handling strongly nonlinear discontinuities, and a method of coupling it with an unsteady inflow condition is presented. Such an approach is sufficiently rapid to be integrated into a global, closed-loop model for computing the dynamics of coupled fluid compartments of the CNS.

Aeromechanical Modeling of Rotating Fan Blades to Investigate High-Cycle and Low-Cycle Fatigue Interaction

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Priyanka Dhopade ◽  
Andrew J. Neely
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Low Cycle Fatigue ◽  
Numerical Approach ◽  
Combined Loading ◽  
Design Stage ◽  
Cycle Fatigue ◽  
Mechanics Analysis ◽  
The Individual ◽  
Loading Spectrum

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) loads. To improve engine reliability, durability and maintenance, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine while they are occurring simultaneously during a flight cycle. A fully coupled aeromechanical fluid–structure interaction (FSI) analysis in conjunction with a fracture mechanics analysis was numerically performed to predict the effect of representative fluctuating loads on the fatigue life of blisk fan blades. This was achieved by comparing an isolated rotor (IR) to a rotor in the presence of upstream inlet guide vanes (IGVs). A fracture mechanics analysis was used to combine the HCF loading spectrum with an LCF loading spectrum from a simplified engine flight cycle in order to determine the extent of the fatigue life reduction due to the interaction of the HCF and LCF loads occurring simultaneously. The results demonstrate the reduced fatigue life of the blades predicted by a combined loading of HCF and LCF cycles from a crack growth analysis, as compared to the effect of the individual cycles. In addition, the HCF aerodynamic forcing from the IGVs excited a higher natural frequency of vibration of the rotor blade, which was shown to have a detrimental effect on the fatigue life. The findings suggest that FSI, blade–row interaction and HCF/LCF interaction are important considerations when predicting blade life at the design stage of the engine. The lack of available experimental data to validate this problem emphasizes the utility of a numerical approach to first examine the physics of the problem and second to help establish the need for these complex experiments.

Influence of Porosity on the Interlaminar Shear Strength of Fibre-Metal Laminates

2008 ◽  
Vol 383 ◽  
pp. 35-52 ◽  
Author(s):  
Cláudio S. Lopes ◽  
Joris J.C. Remmers ◽  
Zafer Gürdal
Keyword(s):  
Shear Strength ◽  
Numerical Approach ◽  
Interlaminar Shear Strength ◽  
Cohesive Elements ◽  
Stress Concentrations ◽  
Fibre Metal Laminates ◽  
Perfect Bonding ◽  
Fibre Metal ◽  
Interlaminar Shear ◽  
The Individual

Structures manufactured in fibre-metal laminates (e.g. Glare) have been designed considering ideal mechanical properties determined by the Classical Lamination Theory. This means that among other assumptions, perfect bonding conditions between layers are assumed. However, more than often, perfect interfaces are not achieved or their quality is not guaranteed. When in laboratory, high-quality fibre-metal laminates are easily fabricated, but in the production line the complicated manufacturing process becomes difficult to control and the outcome products may not meet the quality expected. One of the consequences may be the poor adhesion of metalprepreg or prepreg-prepreg as the result of porosity. The interlaminar shear strength of fibre-metal laminates decreases considerably, due to porosity, as the result of insufficient adhesion between layers. Small voids or delaminations lead to stress concentrations at the interfaces which may trigger delamination-propagation at the aluminiumprepreg and prepreg-prepreg interfaces at load levels significantly lower than what is achievable for perfectly bonded interfaces. Mechanical experiments show a maximum drop of 30% on the interlaminar shear strength. In the present work, the effects of manufacturing-induced porosity on the interlaminar shear strength of fibre-metal laminates are studied using a numerical approach. The individual layers are modelled by continuum elements, whereas the interfaces are modelled by cohesive elements which are equipped with a decohesion law to simulate debonding. Porosity is included in the geometry of the interface by setting some of these elements to a pre-delaminated state.

Numerical Analysis of Optimal Design Parameters for a Cell Co-Culture Microfluidic Platform With an Integrated Pressure-Controlled Valve

2020 ◽  
Author(s):  
Saif Mohammad Ishraq Bari ◽  
Louis G. Reis ◽  
Thomas Holland ◽  
Gergana G. Nestorova
Keyword(s):  
Numerical Analysis ◽  
Optimal Design ◽  
Vertical Direction ◽  
Design Parameters ◽  
Adjacent Cell ◽  
Membrane Thickness ◽  
A Cell ◽  
3D Printed ◽  
The Individual ◽  
Pressure Controlled

Abstract This study reports the design, fabrication, and a two-dimensional numerical analysis to identify the optimal operating parameters of a novel microfluidic co-culture platform with an integrated pressure-controlled valve. Replica molding using 3D printed PDMS molds were used for the fabrication of the individual components of the device. Alternation of the position of the PDMS hydraulic valve permits individual manipulation of the cellular microenvironment of the two adjacent cell culture chambers (27.5 mm × 35 mm × 10 mm). The mathematical model analyzes the deflection profile of the valve in the vertical direction as a function of several parameters: valve thicknesses, the pressure exerted by the fluid inside the pressure chamber, and PDMS elasticity determined by the ratio of the elastomer base and the curing reagent. The valve understudy requires a deflection of 0.5 mm to completely isolate the two cell chambers. The combination of the optimal design parameters is identified using numerical analysis. Mathematical simulations show that the deflection of the membrane is inversely proportional to the valve membrane thickness and directly proportional to the pressure exerted by the fluid on the valve.

First-Principles Calculations of Structural and Elastic Properties of Hexagonal Boron Nitride

2009 ◽  
Vol 79-82 ◽  
pp. 1337-1340 ◽  
Author(s):  
Liu Xiao ◽  
Wen Jun He ◽  
Yan Sheng Yin
Keyword(s):  
Boron Nitride ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
Hexagonal Boron Nitride ◽  
Applied Pressure ◽  
Axial Ratio ◽  
First Principles Calculations ◽  
Calculation Results ◽  
Good Agreement

The lattice parameters, five independent elastic constants and the bulk modulus B on the applied pressure of hexagonal boron nitride (h-BN) are calculated by using a first-principles pseudopotential method. The calculation results are in good agreement with the experimental and theoretical values. It is found that the most stable structure of h-BN corresponds to the axial ratio c/a of about 2.652.

scholarly journals On the Horizontal Deviation of a Spinning Projectile Penetrating into Granular Systems

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Waseem Ghazi Alshanti
Keyword(s):  
General Theory ◽  
Dynamical Behavior ◽  
Numerical Approach ◽  
Granular Systems ◽  
Soft Particle ◽  
Impact Point ◽  
Two Dimensional ◽  
Rotation Direction ◽  
Spinning Projectile ◽  
The Right

The absence of a general theory that describes the dynamical behavior of the particulate materials makes the numerical simulations the most current powerful tool that can grasp many mechanical problems relevant to the granular materials. In this paper, based on a two-dimensional soft particle discrete element method (DEM), a numerical approach is developed to investigate the consequence of the orthogonal impact into various granular beds of projectile rotating in both clockwise (CW) and counterclockwise (CCW) directions. Our results reveal that, depending on the rotation direction, there is a significant deviation of the x-coordinate of the final stopping point of a spinning projectile from that of its original impact point. For CW rotations, a deviation to the right occurs while a left deviation has been recorded for CCW rotation case.

Identification of Picea pollen of Late Quaternary age in eastern North America: a numerical approach

1980 ◽  
Vol 58 (19) ◽  
pp. 2043-2058 ◽  
Author(s):  
H. J. B. Birks ◽  
Sylvia M. Peglar
Keyword(s):  
Discriminant Analysis ◽  
Picea Glauca ◽  
Late Quaternary ◽  
Numerical Approach ◽  
Eastern North America ◽  
Before Present ◽  
Morphological Variables ◽  
The Individual ◽  
Individual Grains ◽  
Simple Combination

Five collections of modern Picea glauca pollen, four of P. mariana, and two of P. rubens were examined in an attempt to distinguish the pollen of the species. Three morphological variables were recorded for individual grains in each collection. The sculpturing of the furrow membrane is not diagnostic, but the presence of an undulating margin to the cap and of irregular reticulation in the sacci characterize P. rubens pollen. Seven size variables were also measured for each grain. No simple combination of morphological and size criteria provides effective discrimination between P. glauca and P. mariana pollen.Linear discriminant analysis was applied to the size data for P. glauca and P. mariana. The mathematical assumptions of the method were tested, and to satisfy them, the discriminant analysis was confined to six of the seven variables measured. The discriminant analysis resulted in 91.5% of the pollen being correctly distinguished.The same six variables were measured on fossil Picea pollen from two Late Wisconsin sites in Minnesota and one Holocene sequence in Labrador. The individual fossil grains were assigned to either P. glauca or P. mariana by means of discriminant analysis. The Late Wisconsin spectra consist of both species, a result supported by macrofossil evidence. Picea glauca predominates in the early Holocene spectra from Labrador. It is replaced by P. mariana after about 5000 years before present, reflecting paludification and the spread of muskeg.The limitations of the procedure are discussed, and its potential is emphasized.

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