scholarly journals Mechanics of Microspheres Reinforced Hollow Microcells

2021 ◽  
Vol 88 (4) ◽  
Author(s):  
George Youssef ◽  
Somer Nacy ◽  
Nha Uyen Huynh
Keyword(s):  
Strain Energy ◽  
Mechanical Response ◽  
Compressive Load ◽  
Energy Parameter ◽  
Analytical Framework ◽  
Static Response ◽  
Reinforcement Density ◽  
Static Loads ◽  
Deformation Response ◽  
Stiffening Effect

Abstract Emerging polymeric foams exhibiting unique microstructure of microspherical shells with reinforcing dense microspheres creates a new opportunity for impact-tolerant foam paddings in sport gears applications. This paper describes the static response of reinforced microcell consisting of an outer spherical shell and uniformly distributed microspheres while quantifying the stiffening effect. The distribution of the microspheres is illustrated using the Fourier series, allowing tuning of the reinforcing strategy. Expressions of the external and internal works are derived, whereas the Ritz energy method is adopted to calculate the deformations due to a compressive load distributed over a range of areas. Emphasis is given to the effect of the geometrical attributes of the microcell and the reinforcing microspheres on the resulting deformation response and stiffening effect. The framework is used to investigate the response of several case studies to elucidate the effects of relative radii ratio, reinforcement density, microcell wall thickness, and loading configurations on the stiffness. A new normalized strain energy parameter is introduced to simplify and accelerate the analysis while providing insights on the underpinnings of the observed buckling response. The results strongly suggest the viability of the newly discovered foam microstructure in managing static loads while providing an opportunity to strategically tune the mechanical response using the analytical framework presented herein.

The Role of Mechanical Tension in Neurons

2010 ◽  
Vol 1274 ◽  
Author(s):  
Taher Saif ◽  
Jagannathan Rajagopalan ◽  
Alireza Tofangchi
Keyword(s):  
Mechanical Response ◽  
Mechanical Forces ◽  
Active Tension ◽  
Mechanical Tension ◽  
Deformation Response ◽  
Linear Force ◽  
Tension Regulation ◽  
Over Time

AbstractWe used high resolution micromechanical force sensors to study the in vivo mechanical response of embryonic Drosophila neurons. Our experiments show that Drosophila axons have a rest tension of a few nN and respond to mechanical forces in a manner characteristic of viscoelastic solids. In response to fast externally applied stretch they show a linear force-deformation response and when the applied stretch is held constant the force in the axons relaxes to a steady state value over time. More importantly, when the tension in the axons is suddenly reduced by releasing the external force the neurons actively restore the tension, sometimes close to their resting value. Along with the recent findings of Siechen et al (Proc. Natl. Acad. Sci. USA 106, 12611 (2009)) showing a link between mechanical tension and synaptic plasticity, our observation of active tension regulation in neurons suggest an important role for mechanical forces in the functioning of neurons in vivo.

The influence of load direction, microstructure, raster orientation on the quasi-static response of fused deposition modeling ABS

2019 ◽  
Vol 25 (3) ◽  
pp. 462-472 ◽  
Author(s):  
Oluwakayode Bamiduro ◽  
Gbadebo Owolabi ◽  
Mulugeta A. Haile ◽  
Jaret C. Riddick
Keyword(s):  
Additive Manufacturing ◽  
Fused Deposition Modeling ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Bead Geometry ◽  
Static Response ◽  
Load Direction ◽  
Content Type ◽  
Fused Deposition ◽  
Deposition Modeling

Purpose The continual growth of additive manufacturing has increased tremendously because of its versatility, flexibility and high customization of geometric structures. However, design hurdles are presented in understanding the relationship between the fabrication process and materials microstructure as it relates to the mechanical performance. The purpose of this paper is to investigate the role of build architecture and microstructure and the effects of load direction on the static response and mechanical properties of acrylonitrile butadiene styrene (ABS) specimens obtained via the fused deposition modeling (FDM) processing technique. Design/methodology/approach Among additive manufacturing processes, FDM is a prolific technology for manufacturing ABS. The blend of ABS combines strength, rigidity and toughness, all of which are desirable for the production of structural materials in rapid manufacturing applications. However, reported literature has varied widely on the mechanical performance due to the proprietary nature of the ABS material ratio, ultimately creating a design hurdle. While prior experimental studies have studied the mechanical response via uniaxial tension testing, this study has aimed to understand the mechanical response of ABS from the materials’ microstructural point of view. First, ABS specimen was fabricated via FDM using a defined build architecture. Next, the specimens were mechanically tested until failure. Then finally, the failure structures were microstructurally investigated. In this paper, the effects of microstructural evolution on the static mechanical response of various build architecture of ABS aimed at FDM manufacturing technique was analyzed. Findings The results show that the rastering orientation of 0/90 exhibited the highest tensile strength followed by fracture at its maximum load. However, the “45” bead direction of the ABS fibers displayed a cold-drawing behavior before rupture. The morphology analyses before and after tensile failure were characterized by a scanning electron microscopy (SEM) which highlighted the effects of bead geometry (layers) and areas of stress concentration such as interstitial voids in the material during build, ultimately compromising the structural integrity of the specimens. Research limitations/implications The ability to control the constituents and microstructure of a material during fabrication is significant to improving and predicting the mechanical performance of structural additive manufacturing components. In this report, the effects of microstructure on the mechanical performance of FDM-fabricated ABS materials was discussed. Further investigations are planned in understanding the effects of ambient environmental conditions (such as moisture) on the ABS material pre- and post-fabrication. Originality/value The study provides valuable experimental data for the purpose of understanding the inter-dependency between build parameters and microstructure as it relates to the specimens exemplified strength. The results highlighted in this study are fundamental to the development of optimal design of strength and complex ultra-lightweight structure efficiency.

scholarly journals INFLUENCE OF PRINTING AND LOADING DIRECTION ON MECHANICAL RESPONSE IN 3D PRINTED MODELS OF HUMAN TRABECULAR BONE

2018 ◽  
Vol 18 ◽  
pp. 24 ◽  
Author(s):  
Tomáš Doktor ◽  
Ivana Kumpová ◽  
Sebastian Wroński ◽  
Maciej Śniechowski ◽  
Jacek Tarasiuk ◽  
...  
Keyword(s):  
Trabecular Bone ◽  
Mechanical Response ◽  
Plastic Region ◽  
Human Donor ◽  
Deformation Response ◽  
Human Trabecular Bone ◽  
Loading Mode ◽  
Loading Direction ◽  
3D Printed ◽  
X Ray Computed

The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D model was obtained by X-ray computed tomography. Then a series of cubical samples was prepared by additive manufacturing technique and tested by uniaxial compression loading mode. Mechanical response was compared in nine different combinations of direction of 3D printing and loading direction. The results show neglectible influence on the deformation response in elastic region (stiffness) and significant changes of the behaviour in plastic region (stress and strain at yield point, strain at full collapse).

CONSISTENT APPROXIMATION FOR THE STRAIN ENERGY OF A 3D ELASTIC BODY ADEQUATE FOR THE STRESS STIFFENING EFFECT

2004 ◽  
Vol 04 (02) ◽  
pp. 279-292 ◽  
Author(s):  
YU. VETYUKOV
Keyword(s):  
Elastic Body ◽  
Strain Energy ◽  
Conventional Approach ◽  
Deformation Model ◽  
Geometrically Nonlinear ◽  
Consistent Approximation ◽  
New Strategy ◽  
Geometric Stiffening ◽  
Angular Velocities ◽  
Stiffening Effect

Starting from the fully geometrically nonlinear deformation model of a 3D elastic body, a consistent approximation for the strain energy in the vicinity of a pre-deformed state is obtained. This allows for the stress (geometric) stiffening effect to be taken into account. Additional terms arise in the strain energy approximation in comparison to the conventional approach, in which stiffening is incorporated in the form of a so-called geometric stiffness matrix. Computational costs of the new model are of the same order as that of the conventional approach. When compared to the fully geometrically nonlinear theory, the numerical analysis shows the suggested model to describe the dynamics of an elastic rotating structure better than the conventional approach. A new strategy is suggested to treat the non-constant pre-deformation, which is important for the flexible multibody simulations when angular velocities and interaction forces vary in time.

Multiscale modeling of plasticity in a copper single crystal deformed at high strain rates

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Sagar Chandra ◽  
M. K. Samal ◽  
V. M. Chavan ◽  
R. J. Patel
Keyword(s):  
Single Crystal ◽  
Multiscale Modeling ◽  
Crystal Plasticity ◽  
Mechanical Response ◽  
Md Simulations ◽  
Dislocation Dynamics ◽  
Copper Single Crystal ◽  
Deformation Response ◽  
Discrete Dislocation ◽  
Dynamics Simulations

AbstractA hierarchical multiscale modeling approach is presented to predict the mechanical response of dynamically deformed (1100 s−1−4500 s−1) copper single crystal in two different crystallographic orientations.Anattempt has been made to bridge the gap between nano-, micro- and meso- scales. In view of this, Molecular Dynamics (MD) simulations at nanoscale are performed to quantify the drag coefficient for dislocations which has been exploited in Dislocation Dynamics (DD) regime at the microscale. Discrete dislocation dynamics simulations are then performed to calculate the hardening parameters required by the physics based Crystal Plasticity (CP) model at the mesoscale. The crystal plasticity model employed is based on thermally activated theory for plastic flow. Crystal plasticity simulations are performed to quantify the mechanical response of the copper single crystal in terms of stressstrain curves and shape changes under dynamic loading. The deformation response obtained from CP simulations is in good agreement with the experimental data.

Large Deformation Isotropic Elasticity—On the Correlation of Theory and Experiment for Incompressible Rubberlike Solids

1973 ◽  
Vol 46 (2) ◽  
pp. 398-416 ◽  
Author(s):  
R. W. Ogden
Keyword(s):  
Mathematical Analysis ◽  
Energy Function ◽  
Strain Energy ◽  
Mechanical Response ◽  
Strain Energy Function ◽  
Usual Practice ◽  
Principal Axes ◽  
Simple Tension ◽  
Isotropic Elasticity ◽  
Strain Invariants

Abstract Many attempts have been made to reproduce theoretically the stress-strain curves obtained from experiments on the isothermal deformation of highly elastic ‘rubberlike’ materials. The existence of a strain-energy function has usually been postulated, and the simplifications appropriate to the assumptions of isotropy and incompressibility have been exploited. However, the usual practice of writing the strain energy as a function of two independent strain invariants has, in general, the effect of complicating the associated mathematical analysis (this is particularly evident in relation to the calculation of instantaneous moduli of elasticity) and, consequently, the basic elegance and simplicity of isotropic elasticity is sacrificed. Furthermore, recently proposed special forms of the strain-energy function are rather complicated functions of two invariants. The purpose of this paper is, while making full use of the inherent simplicity of isotropic elasticity, to construct a strain-energy function which: (i) provides an adequate representation of the mechanical response of rubberlike solids, and (ii) is simple enough to be amenable to mathematical analysis. A strain-energy function which is a linear combination of strain invariants defined by ϕ(α)=(α1α+α2α+α3α)/α is proposed; and the principal stretches α1, α2, and α3 are used as independent variables subject to the incompressibility constraint α1α2α3=1. Principal axes techniques are used where appropriate. An excellent agreement between this theory and the experimental data from simple tension, pure shear and equibiaxial tension tests is demonstrated. It is also shown that the present theory has certain repercussions in respect of the constitutive inequality proposed by Hill.

scholarly journals Evolution of anisotropy in soft tissue

2014 ◽  
Vol 470 (2161) ◽  
pp. 20130548 ◽  
Author(s):  
J. G. Murphy
Keyword(s):  
Linear Theory ◽  
Energy Function ◽  
Anisotropic Material ◽  
Strain Energy ◽  
Mechanical Response ◽  
Essential Feature ◽  
Sufficient Conditions ◽  
Strain Energy Function ◽  
Phenomenological Approach ◽  
Reduced Form

The phenomenological approach to the modelling of the mechanical response of arteries usually assumes a reduced form of the strain-energy function in order to reduce the mathematical complexity of the model. A common approach eschews the full basis of seven invariants for the strain-energy function in favour of a reduced set of only three invariants. It is shown that this reduced form is not consistent with the corresponding full linear theory based on infinitesimal strains. It is proposed that compatibility with the linear theory is an essential feature of any nonlinear model of arterial response. Two approaches towards ensuring such compatibility are proposed. The first is that the nonlinear theory reduces to the full six-constant linear theory, without any restrictions being imposed on the constants. An alternative modelling strategy whereby an anisotropic material is compatible with a simpler material in the linear limit is also proposed. In particular, necessary and sufficient conditions are obtained for a nonlinear anisotropic material to be compatible with an isotropic material for infinitesimal deformations. Materials that satisfy these conditions should be useful in the modelling of the crimped collagen fibres in the undeformed configuration.

Analysis of Hysteresis Loop on the Basis of Variable-Amplitude Loading

2016 ◽  
Vol 250 ◽  
pp. 94-99
Author(s):  
Bogdan Ligaj
Keyword(s):  
Plastic Strain ◽  
Hysteresis Loop ◽  
Strain Energy ◽  
Energy Parameter ◽  
Stress Strain ◽  
Variable Amplitude Loading ◽  
Loading Cycle ◽  
Variable Amplitude ◽  
Plastic Strain Energy

The aim of this paper is to present a method to be used for analysis of stress-strain loops under variable amplitude loading. The method for determination of plastic strain energy parameter ΔWpl consists in determination of envelopes around stress-strain branches (increasing and decreasing) formed in effect of application of a loading program. The method involves development of envelopes to determine energy parameter from the highest (for the highest loading cycle) to the lowest (for the lowest cycle). The paper includes results of stress-strain loop for steel C45.

The Effect of Creep on Human Lumbar Intervertebral Disk Impact Mechanics

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
David Jamison ◽  
Michele S. Marcolongo
Keyword(s):  
Mechanical Response ◽  
Compressive Load ◽  
Fluid Phase ◽  
Constant Load ◽  
Time Of Day ◽  
Intervertebral Disk ◽  
Fluid Loss ◽  
Loading Conditions ◽  
Impact Mechanics ◽  
Continuous Displacement

The intervertebral disk (IVD) is a highly hydrated tissue, with interstitial fluid making up 80% of the wet weight of the nucleus pulposus (NP), and 70% of the annulus fibrosus (AF). It has often been modeled as a biphasic material, consisting of both a solid and fluid phase. The inherent porosity and osmotic potential of the disk causes an efflux of fluid while under constant load, which leads to a continuous displacement phenomenon known as creep. IVD compressive stiffness increases and NP pressure decreases as a result of creep displacement. Though the effects of creep on disk mechanics have been studied extensively, it has been limited to nonimpact loading conditions. The goal of this study is to better understand the influence of creep and fluid loss on IVD impact mechanics. Twenty-four human lumbar disk samples were divided into six groups according to the length of time they underwent creep (tcreep = 0, 3, 6, 9, 12, 15 h) under a constant compressive load of 400 N. At the end of tcreep, each disk was subjected to a sequence of impact loads of varying durations (timp = 80, 160, 320, 400, 600, 800, 1000 ms). Energy dissipation (ΔE), stiffness in the toe (ktoe) and linear (klin) regions, and neutral zone (NZ) were measured. Analyzing correlations with tcreep, there was a positive correlation with ΔE and NZ, along with a negative correlation with ktoe. There was no strong correlation between tcreep and klin. The data suggest that the IVD mechanical response to impact loading conditions is altered by fluid content and may result in a disk that exhibits less clinical stability and transfers more load to the AF. This could have implications for risk of diskogenic pain as a function of time of day or tissue hydration.

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