Mechanics of Biological Systems and Materials, Volume 5: Proceedings of the 2012 Annual Conference on Experimental and Applied Mechanics represents one of seven volumes of technical papers presented at the Society for Experimental Mechanics SEM 12th International Congress & Exposition on Experimental and Applied Mechanics, held at Costa Mesa, California, June. The opinions expressed herein are those of the individual authors and not necessarily those of the Society for Experimental Mechanics, Inc.
Synthesis and Characterization
The growth mechanism of the mother-of-pearl-like carbonate composite is similar to the construction of natural mother-of-pearl aragonite platelets [39,40]. Poly(KAMPS) forms strong gels, which results in bonding at the interface between the aragonite nanorods and leads to the adhesion of a "brick" arrangement of aragonite nanorods that mimics the natural structure of mother-of-pearl.
Nanoindentation
Experimental
This was confirmed by FTIR, and the adsorption of positively charged NH3 quantum dots confirmed the presence of polyelectrolyte layers at the interface between aragonite nanorods [38]. The interface between the two rigid (inorganic) components determines the mechanical properties of the composite, which will be improved if the inorganics are modified by polymers [42,43].
Results and Discussion
Conclusions
Since the mechanical properties of the bark and those of the pith differ, separate mechanical tests were performed. The influence of both the moisture content and the location of the samples along the trunk was studied.
Introduction
Abstract The purpose of this study is to investigate the mechanical properties of sunflower stems. An increase in the moisture content of bark and pith was found to reduce their Young's modulus.
Specimen Preparation and Testing Conditions
Specimen Manufacturing
Mechanical Tests
Typical Results and Discussion
Mechanical Properties of Bark and Pith
Influence of the microstructure
It can therefore be concluded that the increase in the modulus of elasticity of bark and pith samples along the stem is caused by the decrease in porosity.
Conclusion
However, it is unclear how cells coordinate mechanical interactions with each other and with extracellular matrix (ECM) to initiate, regulate, or maintain tubular patterns. Remarkably, a very large spatial scale of tubular patterns is found by cell-COL self-organization in the fluid phase, leading to the formation of long-range (~1 cm) epithelial tubes.
Introduction
Our results suggest a potential mechanism that cells can use to form and coordinate long-range tubular patterns independent of those controlled by distributed biochemical factors and provide a new strategy to engineer/regenerate tubular organs. In the second assay, we thus created semi-liquid/semi-solid environments to maximize cell-COL interactions in the liquid phase.
Methods and Materials
- Cell Culture and Maintenance
- Preparation of Type I Collagen (COL)
- Preparation of Perfusion Chambers
- Preparation of Gels
- Timelapse Microscopy and Image Analysis
For confocal scanning microscopy, the microscope is equipped with lasers with three wavelengths (405, 475 and 594 nm), photomultiplier tubes (H10425 and H7422-40, Hamamatsu). For two-photon scanning microscopy, the microscope is equipped with a Mai-TaiTM femtosecond laser source (Spectra-Physics).
Results
Cells Developed Tubulo-Lobular Patterns in Response to Collagen Concentration in ECM
Olympus IX71 equipped with automatic XYZ stages (MS-2000, ASI) and piezoelectric objective stages (P-721 Pifoc, Physik Instrument) were used for the fast multi-position, z-scan, and time-lapse autofocus microscope. For phase-contrast and/or epi-fluorescence microscopy, the microscope was equipped with motorized excitation and emission filters with a shutter control (lambda 10–3, Sutter), an electronically multiplexed CCD camera (ImagEM, C9100-13, Hamamatsu, 512512 pixels, with water cooled at 95C) and a 120 W fluorescent light bulb (X-CITE 120Q, EXFO, Lumen Dynamics Group Inc.).
Cells Developed Long-Scale Tubular Patterns in the Presence of Collagen Molecules in the Liquid Phase
1-1.5 cm and diameter ~300 mm in the 62 cm2 chamber under the same cultivation conditions - on low-adhesive substrates.
Force but Not Morphogen Is Required for Tubular Pattern Formation
Discussion
Synergistic Mechanical Effects in Tubular Pattern Formation
Mechanical Force in the Initiation and the Maintenance of Tubular Patterns
Mechanical Force in the Self-Organizations of Cells and Surrounding Micro-environments
Bellusci S, Grindley J, Emoto H et al (1997) Fibroblast growth factor 10 (FGF10) and branching morphogenesis in the embryonic mouse lung. Wei C, Larsen M, Hoffman MP et al (2007) Self-organization and branching morphogenesis of primary salivary epithelial cells.
Introduction
Time-resolved force profiling gives us information on the strength and energy of membrane bond formation and the equilibrium strength of the membrane bond. Our data suggest the importance of membrane composition, particularly membrane cholesterol content and cytoskeletal proteins, particularly F-actin, on membrane mechanical properties as well as membrane-cytoskeleton adhesion.
Materials and Methods
- Cell Culture
- Plasma Membrane Cholesterol Manipulation
- Plasma Membrane Cholesterol Quantification
- Cell Cytoskeleton F-actin Disruption
- Optical Tweezers, Displacement Measurements, and Calibration
- Dynamic Tether Force Measurements: Single-Speed Pulling Protocol
- Statistical Analysis
An emission bandpass filter (Chroma, 60525 nm, Brattleboro, VT) was placed in front of the QPD to specifically select the fluorescent emission from the bead. The fluorescent image of the captured bead was projected onto the center of a position-sensing quadrant photodetector (QPD) (QP50-6SD; Pacific silicon sensor, Westlake village, CA) to measure the displacement of the bead from the capture center.
Results
- Dynamic Plasma Membrane Tether Force
- Plasma Membrane Tether Formation Force (F max )
- Tether Formation Energy (E tf )
- Plasma Membrane Tether Equilibrium Forces (F eq )
Incubation of the cells in DMEM containing 5 mM MbCD for cholesterol depletion resulted in significant increases of Etfto J). The energy of bond formation decreases significantly to 5825 (1018J) in response to cholesterol enrichment of the cells by incubating them in DMEM containing 5 mM cholesterol-MbCD.
Conclusions
Extensive research has recently been done to identify the hardening mechanisms in nacre, with the toughness of the organic component being argued to have the greatest influence on the overall toughness. Analysis of the experimental data from the upper shell suggests that the intrinsic toughness of the organic adhesive accounts for only about 3% of the total toughness of the interface, while the main contribution to the toughness comes from a variety of extrinsic strengthening mechanisms, including bridging of ligaments and buckling of cracks. and process zone effect.
Introduction
The fracture toughness of the interface is therefore relatively low, and a material such as Nacre must rely on other powerful hardening mechanisms to prevent cracking in the transverse direction. Overall, the results highlight the significant role that the structural design plays in defining fracture toughness properties along the interface.
![Fig. 5.1 View of the cross section of a punctured red abalone shell [19] along with an SEM image showing the brick and mortar microstructure.](https://thumb-ap.123doks.com/thumbv2/azdoknet/10595062.0/38.892.121.773.90.406/view-cross-section-punctured-abalone-showing-mortar-microstructure.webp)
Fracture Experiments
Sample Preparation
Experimental Setup
Fracture Experiment Results
Chevron Notch Test
A comparison between these three toughness characteristics is shown in Fig.5.3b which suggests consistency between these hypotheses and the experiment.
In-situ “Half Chevron” Geometry
In addition, for the top layer, a relatively whiter diffuse “process zone” in front of the crack tip was captured through in-situ differential interference contrast (DIC) imaging on the smooth surface of the fracture specimen. Figure 5.4 presents an SEM micrograph of the crack wall from a smooth upper shell fracture sample in which the junction opening (i.e. inelastic deformation) is clearly visible.
Fracture Toughness Estimation for the Organic Interface
The asymptotic stress field can then be related to the size of the inelastic region, noting that the maximum height of that region occurs at an angle ¼ 30 ;from the crack line. This leads to a value of JIC¼ 5.5 J/m2 for the internal stability of the interface process zone.
Conclusions
Barthelat F et al (2007) On the mechanics of pearl: a key feature in hierarchical material structure. Smith BL et al (1999) Molecular mechanical origin of durability of natural adhesives, fibers and composites.
Introduction
Determining this relationship will have a major impact on the design of composite architectures that can improve the performance of mechanically protective armor. This information can in turn be used in the design of composite architectures that can improve the performance of mechanically protective coatings and armor.
Experimental Procedure
We expect to determine the optimal combination of layers that provide the best curing properties. We also expect that the optimum combination is likely to resemble that found in wild specimens, since molluscan organisms are thought to have arrived at the best hardening properties through natural selection processes.
Results and Discussion
Bezares J, Asaro RJ, Hawley M (2010) Macromolecular structure of the nacre organic framework in Haliotis rufescens: implications for. Lopez MI, Chen PY, McKittrick J, Meyers MA (2011) Growth of nacre in abalone: seasonal and feeding effects.
Introduction
In subsequent analyses, we performed computational thermal stress analysis of the bilayer discs and various dental restorations using ANSYS. The validity of the analytical thermal models was determined by comparing the results of a one-dimensional model with those of the two-dimensional models and by comparing the corresponding results with those of the FEA models.
Construction of the Ceramic Disks
Analysis of Heat Transfer Problem
The transient heat transfer problem is solved using the separation of variables method and the final expression for the transient heat convection process will be:. eb2nt sinð Þbn cosðbnÞ. where the values of forbn are the characteristics of the transcendental equation tanð Þ ¼bn Bi bn. Here, the terms h, K, Ti, and Tare represent the average heat transfer coefficient used in cooling, the thermal conductivity of the ceramic material, the initial temperature, and the ambient temperature.
Results and Discussion
Images from the high-speed camera clearly showed the microcracks, which exhibited more light intensity compared to the surface without microcracks. It was found that microcracks were induced immediately after the specimen started to yield.
Introduction
Through the current optical technique, the hardening effects of microcracks on the overall mechanical properties have been investigated for the first time at a macroscopic level. In three-dimensional engineering, synchrotron radiation (SR) based computed tomography (CT) [19] is the widely used technique to visualize the microcracks.
Material and Methods
In two-dimensional technique, the most popular methods are basic fuchsin with a bright field microscope [15], basic fuchsin with fluorescent light [16], scanning electron microscope [17] and laser scanning confocal microscopy (LSCM) [18]. Through the studies, it was widely accepted that the cement line is the weakest part of the bone tissue and the path of fracture propagation.
Experimental Results
Quasi-Static Tensile Testing
Dynamic Tensile Testing
Discussion
Conclusion
Pithious M, Subit D, Chabrand P (2004) Comparison of compact failure of bone under two different loading rates: experimental and modeling approaches. Schaffler MB, Pitchford WC, Chol K, Riddle JM (1994) Examination of compact bone microdamage using backscattered electron microscopy.
Introduction
A major step in the development of robots as we know them today was the creation of the first sketch for the production of a humanoid machine. The most important contribution to the rise of "smart" robots was the development of the digital computers, where the ENIAC computer made in 1946 is the first recorded one [8].
Making a Humanlike Robot
Some of the applications currently being considered for humanoid robots in Japan and the US include assisting patients in rehabilitation, the elderly in nursing homes, and others in need of physical or emotional support [5]. Furthermore, humanoid robots already show promise in treating children with autism, by boosting communication and interaction skills to reduce the severity of the disorder [15].
Ethics and Concerns of Humanlike Robots
Potential applications of remote-controlled humanoid robots may include remote surgery or performing physical functions that require the participation of an expert or designated person without the need for their physical presence. For human-like robots to become a commercially successful product that works like our peers or become useful household appliances, we will need to make them perform valuable everyday tasks that a human can do, while it is very complex to put them into a robot.
Capabilities, Challenges, and Potentials
The mechanical properties, porosity, HA/PHB volume fractions and surface adhesion of the resulting HA-PHB composites were investigated and compared with the original HA scaffolds. All the HA-PHB composites showed a slight increase in strength with the addition of PHB.
Introduction
In one case PHB filled the visible porosity of HA scaffolds, while in the other case PHB covered the trabecular meshwork of HA scaffolds. The physical and mechanical properties of the various HA-PHB composites were characterized and compared to those of the original HA scaffolds by microscopy imaging and compression testing.
Materials and Methods
- HA Scaffolds
- Recovery of PHB Particles
- Fabrication of HA-PHB Composites
- Physical Characterization
- Microscopy
- Mechanical Testing
The particle size distributions of the PHB recovered by the two methods were analyzed with a 90Plus/BI-MAS particle size analyzer (Brookhaven Instruments Corporation, Holtsville, NY) capable of measuring particles in the 2 nm–3 mm range. Second, HA scaffolds were placed in flat-bottom centrifuge tubes and approximately 10 mL of the PHB particle solutions were pipetted over the scaffolds.
Results and Discussion
However, the volume fraction of PHB and the porosity of the HA-PHB composites vary. Accordingly, the porosity of the HA-PHB (acetone) composite coated with PHB has a greater porosity (~67%) than the HA-PHB (pH) and HA-PHB (mixed) composites filled with PHB (~54%) .
Conclusions
Russias J et al (2006) Fabrication and mechanical properties of PLA/HA composites: a study of in vitro degradation. Peroglio M et al (2010) Mechanical properties and cytocompatibility of poly(epsilon-caprolactone)-infiltrated biphasic calcium phosphate.
Introduction
Summary The preparation of collagen sponges from type I collagen isolated from cortical bovine femur is reported. In the present study, we demonstrate an elegant and relatively easy way for the isolation of type I collagen from cortical bovine femur, which can be used in the manufacture of collagen sponges by the freeze-drying method.
Materials and Methods
- Collagen Isolation
- Verification of Complete Bone Demineralization
- Verification of Collagen Integrity and Purity
- Preparation of Collagen Sponges
- Optical Microscopy
- Scanning Electron Microscopy (SEM)
The appearance of collagen sponges was observed using a VHX100 digital microscope system equipped with a CCD camera (Keyence Corporation, Osaka, Japan). The internal structure was analyzed by imaging a collagen sponge, cut lengthwise with a razor blade.
Results and Discussion
Collagen Isolation
Collagen Sponges
An important step in this direction is the development of predictive computational models of hydrocephalic brain mechanics. Our preliminary results indicate that CSF viscosity has a significant impact on brain tissue deformation.
Introduction
IFEM belongs to the class of immersed methods in which the discretization of the fluid domain is completely independent of the discretization of the immersed solid domain. The velocity field of a solid is obtained by limiting the velocity field in the equations of motion of the fluid to the solid region.
Problem Formulation
- FSI Problem
- Constitutive Behavior
- Variational Formulation of the FSI Problem
- Discretization
We next adopt constitutive models for the fluid and the immersed solid and then present the variational formulation of the problem. Understanding the constitutive behavior of the brain parenchyma is still an active field of research.
Results
Specifically, we choose a mode consistent with the Brezzi-Babuska inf-sup condition for the Navier-Stokes component of the problem. 01 g cm/s, then the corresponding value of the maximum range of parenchymal displacement is approximately 0.
Conclusion
Boffi D, Gastaldi L, Heltai L, Peskin CS (2008) On the hyper-elastic formulation of the immersed boundary method. West J (2004) Application of the level determination method to hydrocephalus: simulation of ventricular motion.
Introduction
The neurological deficits that occur in MS patients have been mainly attributed to the abnormalities in the white matter. Detection of demyelinated lesions in vivo will provide a useful tool for the development of therapies aimed at promoting the remyelination process and protecting axonal functions in the brain.
Materials and Methods
MS is an autoimmune demyelinating disease of the central nervous system (CNS) [8] that affects approximately 400,000 people in the United States and two million people worldwide [9]. The shape of the nose cone naturally ensured that the mouse's jaw remained closed, providing a connection between the mouse's head and the bite bar.
Results
The spectrum of this measured displacement was calculated and showed the resonant frequencies of the system, which are the frequencies at which the output displacement increases. The mechanical properties of the damaged tissue gradually increase to match their primary values after about a week.
Conclusion
Summary Magnetic resonance elastography (MRE) is a non-invasive imaging technique that enables quantitative measurement of the mechanical properties of biological tissue. The mechanical properties of the tissue are derived by fitting the measured displacement data to the equations governing wave propagation.
Introduction
Magnetic Resonance Elastography
We aim to demonstrate the utility of MRE for cancer staging by detecting the viscoelastic properties of brain tumor in a mouse model of high-grade glioma. Preliminary results indicate elastographic sensitivity to the presence of brain tumors in the living mouse.
Glioma in the Mouse Model
Methods
Animal Preparation and Study Design
Acquisition of MR Elastography Data
Determination of Tissue Mechanical Properties
Results
Discussion and Conclusion
Pattison AJ, Lollis SS, Perrinez PR, Perreard IM, Mcgarry MDJ, Weaver JB, Paulsen KD (2010) Temporal harmonic magnetic resonance elastography of the normal feline brain. Atay SM, Kroenke CD, Sabet A, Bayly PV (2008) Measurement of the dynamic shear modulus of muscle brain tissue in vivo by magnetic resonance elastography.
Introduction
Correlation of multi-scale modeling and experimental results for the elastic moduli of cortical and trabecular bone. Multi-scale models of cortical and trabecular bones as interpenetrating composite materials were developed [9] and experimentally verified for cortical bone [10].
Materials and Methods
Sample Preparation
Recent studies [7, 8] have shown that cortical and trabecular bone are interlocking composite materials with continuous mineral and organic phases. Correlation between multiscale modeling and experimental results for the elastic moduli of cortical and trabecular bones is the main objective of this study.
Compression Testing
Modeling the mechanical properties of bone has long been a challenging task due to the complexity of its hierarchical structure. The amounts and distributions of the porosities of cortical and trabecular bones, which provide important input to the theoretical model, were described in detail in [11].
Structural Characterization
These excellent mechanical properties of bone are the result of its multilayer hierarchical structure from nano to macro scales. Several models of the elastic properties of bone have been proposed based on analytical and computational approaches [3–6].
Modeling Procedure
- Level I. Nanoscale
- Level II. Sub-microscale
- Level III. Microscale
- Level IV. Mesoscale
- Modeling of Treated Bones
The self-consistent scheme was used to obtain the effective elastic properties of that hydroxyapatite foam. The elastic properties of the osteonal lamellae were obtained by following the homogenization scheme of Sun and Li [14].
Results and Discussion
Modeling of treated (DM and DP) cortical and trabecular bones followed the same multi-scale modeling procedure described in Sects.15.3.1to15.3.4. Preliminary data illustrating the comparison between the elastic moduli of trabecular bone assessed from experiment and calculated theoretically are shown in Fig. 15.5.
Conclusions
The fresh bone density, apparent bone density, bone tissue density as well as porosity ratio are obtained for the cancellous bone in human cervical spine. The obtained mechanical properties as well as corresponding analysis will be a significant contribution to the database of cancellous bone in human cervical spine.
Introduction
Abstract Cancellous bone in the vertebral bodies of the human cervical spine was tested under compression and tension at a strain rate of 103/s. Since the cancellous bone in human cervical spine is small and more porous, testing has special problems such as sample preparation and measurements.
Specimen Preparation and Quasi-static Testing
The postyield region of the stress-strain curve with large fluctuations may indicate more non-uniformity in the sample. The elastic modulus (E) is defined as the slope of the most linear region of the stress-strain curve;
Bone Density and Characterization
In this study, more emphasis will be placed on modeling the non-linear profile of stress-strain curves. Using the mean stress-strain curve (fm(e), as given in Equation 16.1) as the reference curve, then the empirical nonlinear constitutive equation can be expressed as
Conclusion
Voo LM, Pintar FA, Yoganandan N, Liu YK (1998) Static and dynamic bending responses of the human cervical spine. Keaveny TM, Borchers RE, Gibson LJ, Hayes WC (1993) Theoretical analysis of the experimental artifact in trabecular bone compressive modulus.
Introduction
The degree of accuracy of the camera setup in the in-plane and out-of-plane direction was determined experimentally through rigorous testing and post-processing. Instead of applying a speckle pattern to the composite portion of the restoration, the speckle pattern was applied to the tooth surface prior to the restoration.
Procedure
However, in our study, we examined the feasibility of using a standard DIC setup and measured the resulting crown movements during the restoration process.
Results and Discussion
Determination of Measurement Accuracy
The second experiment investigated the out-of-plane accuracy of the DIC system by aligning the system parallel to the displacement direction. 17.8 (a) In-plane displacement of a single point on the surface of the precision apparatus as a function of micrometer position with a linear polynomial fit to the data (b) Out-of-plane displacement of a single point on the surface of the precision apparatus as a function of micrometer position with a linear polynomial fit to the data.
Concluding Remarks
But what if the methodology for collecting and preparing samples for property characterization causes a significant change in the numerical value of the property being characterized? We consider several possible sources of variability in the tensile properties exhibited by a given type of natural silk: (1) sample diameter, (2) sample volume, (3) sample source, preparation methods and test conditions, (4) effects of degumming and coiling of the microstructure and cross-section of the sample, and (5) a limitation of the offset yield criterion.
Background
Abstract In the context of materials engineering, the science (and art) of biomimicry assumes that nature can provide useful lessons about the chemistry, processing, structure, and achievable properties of materials. Or what if the property characterization method is inherently incapable of giving an accurate result, or if the property is substantially variable between samples of nominally the same material.
Sample Diameter
Sample Volume
Sample Source, Preparation Methods and Testing Conditions
Effects of Degumming and Reeling on Sample Microstructure and Cross-Section
A Limitation of the Offset Yield Criterion
18.3) Similarly, by considering the intersection of QD and TH, we can obtain an expression for the offset yield stress of sample B:. On that basis, Eq.18.3 allows us to estimate that the offset yield stress exceeded the proportional limit with the amount.
Conclusions
A key mechanism for its mechanical performance is the progressive locking generated by the waves of the mineral tablets from which it is made. The analytical model captures the trends of tapered fiber pullout and provides useful predictions of the influence of various parameters on WOP.
Introduction
We performed single fiber pull-out tests on a tapered steel fiber in an epoxy matrix, which showed an improvement in work-at-pull (WOP) of up to 27 times for tapered fibers compared to straight fibers. The experimental results indicated the existence of an optimal taper angle to maximize WOP while preventing the brittle fracture of the matrix.
Pullout Experiments
This indicates that the WOP of tapered fibers is less sensitive to the friction coefficient. Likewise, the draw energy for case 5 is about 10 times greater than the dissipated energy for a straight fiber when both straight and narrow fibers are untreated.
Analytical Model
While the frictional resistance is the most important factor contributing to WOP for straight fibers, elastic and plastic deformation of the matrix due to fiber-matrix interference becomes more important during the drawing of tapered fibers. Figure 19.5 shows the effect of the frictionf, strength to stiffness ratiosy=A shrinkage strainSon the normalized steady state pullout force, which was taken as the pullout force divided by the pullout force for a straight fiber.
Conclusions
However, with traditional indentation measurements, it is often difficult to determine the true sample deformation due to machine compliance and system offset. An inverse method was developed to extract the mechanical properties of the sample from the measured displacement fields.
Introduction
In the present work, a new method is presented in which the full-field displacement of the surface of a transparent sample, including materials such as polymers, gels, and biological materials, is measured independently of the indenter. This method tracks the movement of discrete particles, such as microbeads, near the surface of the specimen during an indentation test.
Background
Measurement of full-field displacement of the sample surface near the indenter allows mechanics models that relate both in-plane displacements and out-of-plane displacements to the applied load that can be used to extract elastic properties. The aim of this work is to use numerical modeling to assess the effect of measurement error on the ability to extract modulus of elasticity and Poisson's ratio from experiments.
Numerical Model Methods
Using these parameters with a Poisson's ratio of 0.3, the maximum in-plane deflection is 0.57 mm towards the center of the indenter and occurs at the edge of the indenter. To account for variations in simulations due to added random noise, 1,000 simulations were performed for each set of parameters, allowing the effect of the parameters on the coefficients of variation of calculated elastic properties to be investigated.
Numerical Model Results
Similarly, Fig.20.2b shows that the variation of initially decreases as the magnification increases, reaching a minimum between 10 and 20. The variation of n(Fig.20.3b) is greatest when the particle density is 100 mm2 and Poisson's ratio is around 0.1.
Conclusion
Silicone-based contact lens materials are a practical application of hydrogels used in daily life, on which the investigation of mechanical and surface frictional behaviors can contribute to improving their clinical performance. In this study, the tribological and mechanical properties of senofilcon-A contact lenses were systematically studied through nanotribological and nanoindentation methods in both liquid and dehydrated conditions.
Introduction
It was found that the friction force is proportional to the normal load and the solid-solid contact dominates the friction of the silicone hydrogel. It was also found that the coefficient of friction increases with speed following a power law fashion.
Experimental Setup
Quasi-static yielding was used with a maximum load of 500 mN and a 10 s pause to capture material creep. Then indentation occurred at different times during the dehydration process to capture the degree of hydrogel hardening.
Results and Discussion
From Fig.21.4, one can also get the impression that the COF value of the hydrogel depends on the velocity. The load-discharge curves obtained at different points on the surface were quite stable, see Fig. 21.5.
Conclusion
Abstract To study the mechanical behavior of the vertebrate cornea under intraocular pressure, digital volume correlation (DVC) has been performed on a series of volume images generated through swept source optical coherence tomography (SSOCT). The deformation solutions of DVC were obtained after calculating their mean and standard deviation values.
Introduction
Then, several reconstructed volumes were acquired consecutively, introducing a rigid body translation of 10 mm between successive volume images, and the mean and standard deviation of the strain were also identified. The volume deformation process of both phantom and porcine corneal specimens during inflation tests from 2 to 2.25 kPa was then visualized and the distribution patterns of displacement and load fields analyzed for stiffness identification.
Methods
Experimental Set-up for Inflation Test
Swept Source Optical Coherence Tomography
Digital Volume Correlation
Noise Study
Stationary Test
Rigid Body Translation
In addition, deformation solutions for the central z-slices and those for the z-slices at both ends show some discrepancies. This is because the values tend to be noisier near the edges due to the calculation algorithm in the Davis software.
Influence of Sub-Volume Size
Results
In general for both phantom and cornea, the central region of the z-slice has positive exx strain, while in the clamped peripheral region it is compressive. In addition, according to the result of the noise investigation, it can be perceived that a small pressure change occurred during the rigid body translation.
Conclusions
The effects of noise and spatial sampling on the identification of material parameters by magnetic resonance elastography. The effect of noise and spatial sampling has then been investigated while locally identifying a viscoelastic model with OVFM.
Introduction
The main problem with these extractions is dealing with experimental noise and spatial derivatives that are required during processing. The main problem with these extractions is the handling of experimental noise: the calculation of the spatial derivatives of the displacement field, which is required during processing, is prone to noise and changes the parameter identification.
Experimental Data
The aim of this work is to present some implementations of the promising optimized virtual fields method initially presented in [1].
Indentification Method
Where is the Cauchy stress tensor, ~uande, or the virtual displacement vector and the associated virtual strain tensor, T~ is the surface density of boundary forces, is the material density, and @V is the external surface of the volume Vm. (1) was chosen to set the virtual cam field equal to zero at the boundary of the volume Vm so that the second term in equation 23.1 disappears, and (23.2) to choose special optimized virtual fields [1] so that to reduce influence of Gaussian central noise in identification.
Simulated Data
In this work, virtual fields were defined using a piecewise function (444 linear 8-node brick finite elements). It is worth noting the similarity between the experimental data (Figure 23.1c) and the simulated viscoelastic waves (Figure 23.2b).
Results and Discussion
Spatial Sampling Impact
Identification Noise Robustness
The error bars and average identified shear modulus values presented in Figure 23.4 are globally independent of space: their spatial average values can be calculated. Then, as the noise amplitude increases, the relative error of the average identified shear modulus increases.
Experimental Data Analyses
Moreover, the error bars formed by the minimum to maximum identified storage shear modulus increase with the noise level. The fact that this phenomenon is not observed in the experimental data has not yet been explained.
Conclusion
Pierron F, Bayly PV, Namani R (2010) Application of the virtual field method to magnetic resonance elastography data, Society for Experimental Mechanics. Rigid registration was performed between the first and subsequent frames using features outside the craniotomy to compensate for unintentional movement of the surgical microscope.
Introduction
We present a completely noninvasive technique to track cortical surface deformation using intraoperative stereovision during open cranial neurosurgery. In this paper, we propose to average the cortical surface deformation over an integer multiple of harmonic surface deformation cycles in order to establish a reference state.
Methods
- Two-Frame Optical Flow Computation
- Averaging Cortical Surface Deformation Over Time
- Displacement Field Local Smoothing
- Cortical Surface Strain Estimation
For each pixel in the exposed cortical surface, the displacement components of the first Nframe images were then averaged. The in-plane strain of the cortical surface was estimated using the Eulerian formulation based on the deformation gradient of the locally smoothed displacement field.
Results
Discussion and Conclusion
In this case, it may be possible to generate the average cortical surface by averaging the cortical surface deformation from all available image pairs. These results are not surprising given that cortical surface movement is induced by blood pressure emanating from these large blood vessels.
Introduction
However, there is a precipitation transformation that occurred at stress relief temperature that has a strong effect on the wire properties. In this work, it was observed that the high temperature stress relief process causes the cable to lose ductility significantly.
Experiment
Results
Bending Effect on the Cable
Effect of Thermal Set on Wire Properties
If we compare the properties of the wire before and after heat treatment, we can see a large loss of ductility due to the aging effect. The same wire after heat treatment demonstrates that the reduction surface of the heat treated wire is close to zero.
Summary
In this study, the results show that the thermal hardening process has a strong effect on the wire properties due to aging at elevated temperatures. The MP35N wire with low ductility due to aging effects at elevated temperatures was also tested for fatigue performance.
Introduction
The cubic specimens of enamel were prepared from bovine incisors and the retention compression tests were conducted to obtain the stress-time and strain-time relationship of enamel under compressive load. The long-term elastic modulus of the enamel was evaluated from the stress and strain relationships at the end of the ramp-hold tests and the relaxation behavior of the enamel was estimated from the normalized stress-time curves of the ramp-hold -tests.
Material and methods
To obtain the viscoelastic parameters of the constitutive model, ramp holder compression tests were performed using the Instron tensile testing machine (Fig.26.3). Finite element analyzes were performed using ABAQUSTM and the iteration loop was performed in MATLABTM.
Results and Discussion
26.1, ER, E0, gi and ti are relaxation modulus, instantaneous modulus, Prony constant and time constant respectively. 26.5 (a) The normalized stress-time curves and (b) the mean and standard deviation of normalized stress-time curves.
Conclusion
After design and fabrication were completed, mechanical characterization was performed to investigate the mechanical properties of the tissue constructs. Mechanical test results showed that PEGDA fabric constructs had higher tensile strength at room temperature compared to physiological body temperature.
Background
The role of the mold is to allow the PEGDA to polymerize into the desired shape. Knowledge of the mechanical and material properties of the PEGDA constructs in terms of fabrication process parameters such as layer thickness, photoinitiator concentration, temperature, time is necessary to design and effectively use PEGDA for tissue engineering constructs [15,16].
Materials and Methods
PEGDA Hydrogel Specimen Preparation
An extensive evaluation of the pullability of PEGDA hydrogels was performed in this study as a function of layer thickness, photoinitiator concentration, temperature, time, and strain rate. Other objectives of this study include: (1) culturing cells in three dimensions and creating several different internal architectures for nutrient delivery. 2) perform cell viability assays to achieve the best cell viability relative to the photoinitiator while obtaining a successful scaffold structure and (3) characterize the mechanical properties of cell-injected PEGDA, at room and body temperature and for different interior architectures.
Cell Viability Tests
The two probes used in the Live/Dead Invitrogen assay were virtually non-fluorescent until interaction with cells occurred reducing background fluorescence error in quantification of cell viability. Fluorescence microscopy images of the segmented PEGDA network constructs were used to examine the viability of cells in different layers of the constructs and to determine whether the cells are viable.
Design and Manufacture of the Setup and Instrumentation
Experiment and Data Analysis
Results
Figure 27.5 shows cell viability in PEGDA structures with channels containing two different concentrations (0.2% and 1%) of photoinitiator over a period of seven days. The quantitative measurement of cell viability of channeled PEGDA constructs is currently underway.
Conclusions
Yasar O, Dinh M, Lan Shih-Feng, Starly B (2008) Fabrication of micropatterned hydrogels using maskless photopolymerization for tissue engineering applications Proceedings of ASME Bioengineering Conference, Florida, USA. Kim JY (2008) Fabrication of a sff-based three-dimensional scaffold using a precision deposition system in tissue engineering.
Introduction
In modeling, as in the initial formation of bones, bone is created by the activation of bone-forming cells or osteoblasts. Mechanical testing of the PDMS strips was performed to determine the material properties of the PDMS for model input.
Fabrication of PDMS Membranes
Based on an interstitial fluid flowing through this network, loading of the bones (such as the long bones in walking) produces a gradient flow of fluid from high to low pressure with the cyclic nature of the far field motion. To develop this work, a computer model of a PDMS well substrate was constructed and finite element analysis (FEA) was used to perform parametric tests to evaluate the well base thickness.
Determination of PDMS Material Properties
The tensile test results of the fabricated PDMS samples are comparable to generally accepted values. Since the use of PDMS as a substrate for microloading bone cells was envisaged, the deformation behavior of the material well below the 25% strain range had to be defined.
Parametric Modeling of the Substrate Geometry
The results showed that this strain range resulted in uniform, linear loading in all three regions (top, middle, and bottom), Figure 28.2. 2, 4 and 6: refers to the diameter of the plate used in mm. LRefers to a load-controlled test setup.
![Fig. 15.1 Hierarchical structure of main bone constituents and porosity for cortical and trabecular bones (Modified from [10])](https://thumb-ap.123doks.com/thumbv2/azdoknet/10595062.0/104.892.178.720.341.1039/hierarchical-structure-constituents-porosity-cortical-trabecular-bones-modified.webp)
