Measurement Of Elastic Modulus Research Articles

Toward the realization of reproducible Atomic Force Microscopy measurements of elastic modulus in biological samples

The validation of the AFM method for elastic modulus E measurement in soft materials (E <5MPa) is still missing. The interest of measurements in materials with E <5MPa is mainly biological, including soft tissues and single cells. For the diagnosis of malignant human tumors, a change in cell elasticity, within tissues, has recently been recognized as a marker of metastatic potential. To measure a cell elasticity difference, reproducible E measurements in biological samples are needed. In this work a robust method for a metrological validation of E measurements in the range 500–5000kPa was developed, based on the realization of thick E standard samples and on the study of the interactions between the measurement process and the sample at micro- and nano-scale. E measurement reproducibility limit of 4% has been reached. This allows designing a very sensitive and reproducible measurement of E in biological samples representing thus a powerful diagnostic tool for cancer detection.

Al2O3–Al(OH)3-Based castable porous structures

Porous structures attained on the Al2O3–Al(OH)3 system present great technological appeal due to their high refractoriness, chemical resistance, compatibility with biological tissues and competitive costs. Due to these features, they can be used in many applications such as thermal insulation, hot gas filtration and catalyst support. This study presents a novel route to produce large parts of this kind of structure based on castable aqueous suspensions of calcined alumina (α-Al2O3), aluminum hydroxide (Al(OH)3) and hydratable alumina (ρ-Al2O3). After determination of the most favorable condition for dispersion, suspensions containing different proportions of calcined alumina, Al(OH)3 and hydratable alumina were cast and fired. Structures’ sintering behavior was followed by dilatometry and porosity, pore size, mechanical strength, and elastic modulus measurements. Microstructure evolution was assessed using scanning electron microscopy. Varying the firing temperatures, several levels of total porosity were attained as well as a wide range of mechanical strength, rigidity and pore configuration.

A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues.

This paper describes an approach to actuate magnetically arrays of microtissue constructs for long-term mechanical conditioning and subsequent biomechanical measurements. Each construct consists of cell/matrix material self-assembled around a pair of flexible poly(dimethylsiloxane) (PDMS) pillars. The deflection of the pillars reports the tissues' contractility. Magnetic stretching of individual microtissues via magnetic microspheres mounted on the cantilevers has been used to elucidate the tissues' elastic modulus and response to varying mechanical boundary conditions. This paper describes the fabrication of arrays of micromagnetic structures that can transduce an externally applied uniform magnetic field to actuate simultaneously multiple microtissues. These structures are fabricated on silicon-nitride coated Si wafers and contain electrodeposited Ni bars. Through-etched holes provide optical and culture media access when the devices are mounted on the PDMS microtissue scaffold devices. Both static and AC forces (up to 20 μN on each microtissue) at physiological frequencies are readily generated in external fields of 40 mT. Operation of the magnetic arrays was demonstrated via measurements of elastic modulus and dynamic stiffening in response to AC actuation of fibroblast populated collagen microtissues.

Correlation Between Laser-Induced Surface Acoustic Waves and Nanoindentation on Elastic Modulus Measurement of a Nanoporous Zeolite Thin Film

Porous thin films are challenging for mechanical characterization due to their soft, thin, and delicate nature. In this study, a nanoporous zeolite thin film is characterized with both laser-induced surface acoustic wave technique (LiSAW) and nanoindentation. The LiSAW technique measured moduli of 38 GPa and 35 GPa for the non-calcined and calcined zeolite films respectively, whereas the respective nanoindentation results of 51 GPa and 47 GPa demonstrated significant substrate influence even at indentation depths within 10 % of film thickness. More accurate indentation results were achieved through an alternative indentation analysis scheme, but at the cost of significant computation time. The results show the distinctive advantage of the LiSAW technique on porous thin films while demonstrating the challenges and current adaptations of traditional nanoindentation.

Massage induces an immediate, albeit short-term, reduction in muscle stiffness.

Using ultrasound shear wave elastography, the aims of this study were: (a) to evaluate the effect of massage on stiffness of the medial gastrocnemius (MG) muscle and (b) to determine whether this effect (if any) persists over a short period of rest. A 7-min massage protocol was performed unilaterally on MG in 18 healthy volunteers. Measurements of muscle shear elastic modulus (stiffness) were performed bilaterally (control and massaged leg) in a moderately stretched position at three time points: before massage (baseline), directly after massage (follow-up 1), and following 3 min of rest (follow-up 2). Directly after massage, participants rated pain experienced during the massage. MG shear elastic modulus of the massaged leg decreased significantly at follow-up 1 (-5.2 ± 8.8%, P = 0.019, d = -0.66). There was no difference between follow-up 2 and baseline for the massaged leg (P = 0.83) indicating that muscle stiffness returned to baseline values. Shear elastic modulus was not different between time points in the control leg. There was no association between perceived pain during the massage and stiffness reduction (r = 0.035; P = 0.89). This is the first study to provide evidence that massage reduces muscle stiffness. However, this effect is short lived and returns to baseline values quickly after cessation of the massage.

Measurement of elastic modulus and ultrasonic wave velocity by piezoelectric resonator

A piezoelectric ceramic resonator is used for the ‘electrical’ measurement of elastic properties, i.e. Young’s modulus and ultrasonic wave velocity in metallic materials. Piezoelectric response is precisely calculated for the piezoelectric ceramic ring fixed at the end of a metallic rod. The piezoelectric ring serves as both an actuator as well as a sensor. The experimental setup and method of measurement using higher overtones is explained in detail and practically demonstrated for a set of different metallic materials. Young’s moduli and ultrasonic wave velocities are measured within 3% relative error. The presented method is suitable for an advanced engineering class or physics laboratory training.

Basis function sampling: a new paradigm for material property computation.

Wang-Landau sampling, and the associated class of flat histogram simulation methods have been remarkably helpful for calculations of the free energy in a wide variety of physical systems. Practically, convergence of these calculations to a target free energy surface is hampered by reliance on parameters which are unknown apriori. Here, we derive and implement a method built upon orthogonal functions which is fast, parameter-free, and (importantly) geometrically robust. The method is shown to be highly effective in achieving convergence. An important feature of this method is its ability to attain arbitrary levels of description for the free energy. It is thus ideally suited to insilico measurement of elastic moduli and other material properties related to free energy perturbations. We demonstrate the utility of such applications by applying our method to calculate the Frank elastic constants of the Lebwohl-Lasher model of liquid crystals.

Influence of Specimen Size on the Impulse Excitation Technique

The Impulse Excitation technique is a nondestructive and very convenient testing method. It could be applied at different circumstances such as high temperatures, low temperatures and controlled humidity. The Impulse Excitation technique is based on the analysis of the vibration of a test sample after it was impulse excited. The elastic properties of a test specimen are related to its mechanical resonance frequency. In this paper, the regular of resonance frequency changed with specimen’s size was discussed. Elastic modulus of glass with different length, width and thickness were measured, and ceramic composite material with small size was tested. The results indicate that the resonance frequency of specimen changed with its size regularly, and the specimen with small size has poor accuracy of elastic modulus measurement.

Effects of Eu:Ag codoping on structural, magnetic and mechanical properties of lead tellurite glass ceramics

Structural, magnetic and mechanical properties of lead tellurite glass ceramics doped with variable amounts of Eu2O3 (0–10mol%) and codoped with fixed amounts of Ag2O (0.50mol%) or Ag metallic nanoparticles, AgNPs, (0.33mol%) have been studied. The investigation of the samples was performed by X-ray diffraction (XRD), EPR spectroscopy, magnetic susceptibility and elastic modulus measurements. XRD investigation shows that the studied samples were glass ceramics. XRD data were used to determine the nature and the quantitative ratio of the crystalline phases present in the samples. EPR spectroscopy was used to obtain information on the presence of europium and silver paramagnetic centers (Eu2+, Ag0, and Ag2+). No EPR signals assignable to these paramagnetic centers were registered. Magnetic susceptibility data show that the magnetic behavior of the studied glass ceramics is due to the europium ions present in the host matrix as Eu3+ and Eu2+ ions that show a very important clustering tendency. The fact that the paramagnetic Eu2+ ions are involved in aggregates explains why these ions were not detected by EPR in spite of the fact that Eu2+ ions are present in appreciable amounts. The level of the europium doping and the nature of the silver codopants (Ag2O or AgNPs) influence the structural, magnetic and mechanical behavior of the samples. In general, the structural effect of the codoping with Ag2O (that provides Ag+ ions capable to enter the host matrix) is more important than that of the AgNPs.

Evaluation of Physical and Mechanical Properties of Structural Components of Ti-Nb Alloy

By the results of X-ray analysis, microstructural analysis, nanohardness and elastic modulus measurements it was defined that non-equilibrium phases during the process of crystallization are formed in the titanium-niobium alloy with 40wt.% of Nb. The minimum of non-equilibrium phases is formed at the Ti-40wt.% Nb alloy. The uniform grain structure, which consists of β-phase grains with the minimum of elastic modulus, is formed in the alloy ingot. Such structure and complex of properties allows using this alloy for severe plastic deformation.

Effect of cold storage on shear-induced platelet aggregation and clot strength.

Platelets (PLTs) participate in hemostasis and save lives following trauma. PLTs for transfusion are maintained at room temperature (RT, 22°C), limiting viability to 5 days because of metabolic compromise and high risk of bacterial contamination. RT storage may result in weaker clots, delaying hemorrhage control, whereas cold storage (4°C) could permit longer PLT shelf life and result in a more hemostatic product. In this study, we characterized the effect of storage temperature on shear-induced PLT aggregation, clot formation, and strength. PLTs obtained from phlebotomized blood or by apheresis were stored at RT or 4°C for 5 days, and PLT aggregation and clot strength were assessed at 37°C. We studied PLT aggregation at steady and complex patterns of shear rates (500-2,500 per second) by flow cytometry, and the kinetics of clot formation and strength were measured using turbidity and dynamic mechanical analysis, respectively. PLT aggregation was higher in 4°C-stored samples on Day 5 compared with fresh or RT-stored samples at all shear rates tested (fresh vs. 4°C and RT vs. 4°C, p < 0.05). PLTs stored at 4°C for 5 days formed significantly stronger clots compared with fresh or RT-stored samples as quantified by turbidity and elastic moduli measurements (fresh vs. 4°C and RT vs. 4°C, p < 0.05). Our results show that cold-stored PLTs are more responsive to aggregation stimuli and form stronger clots, presumably because of thicker fibrin strands. These data suggest that the superior functionality of cold-stored PLTs may support faster hemostasis for acutely bleeding in trauma patients compared with RT-stored PLTs.

The effect of hip rotation on shear elastic modulus of the medial and lateral hamstrings during stretching

Regarding hamstring stretching methods, many studies have investigated the effect of stretching duration or frequency on muscle stiffness. However, the most effective stretching positions for hamstrings are unclear because it is impossible to quantify muscle elongation directly and noninvasively in vivo. Recently, a new ultrasound technology, ultrasonic shear wave elastography, has permitted noninvasive and reliable measurement of muscle shear elastic modulus, which has a strong linear relationship to the amount of muscle elongation. This study aimed to investigate the effect of hip internal and external rotation on shear elastic modulus of the lateral and medial hamstrings, respectively, during stretching in vivo using ultrasonic shear wave elastography. Twenty-three healthy men (age, 23.0 ± 2.1 years) were recruited for this study. To investigate the effect of hip rotation on the elongation of the medial and lateral hamstrings, shear elastic modulus of the biceps femoris (BF) and semitendinosus (ST) was measured at rest (a supine position with 90° knee flexion, 90° hip flexion, and hip neutral rotation) and in seven stretching positions (with 45° knee flexion and hip internal, external, and neutral rotation) using ultrasonic shear wave elastography. In both BF and ST, the shear elastic modulus in the rest position was significantly lower than that in all stretching positions. However, no significant differences were seen among stretching positions. Our results suggest that adding hip rotation at a stretching position for the hamstrings may not have a significant effect on muscle elongation of the medial and lateral hamstrings.

Thermal Expansion Mismatch Analysis of Nano‐bonded Refractory Castables

A mathematical model to predict the thermomechanical stresses was used to understand the expansion mismatch damage in castables, evaluated by hot elastic modulus measurements. The results indicated that via elastic modulus evaluation and the tensile stress calculation, the critical interactions among the particles leading to the formation of flaws were identified. To assure the materials' integrity, it is fundamental to keep a low Δα between the components and not only a low overall linear thermal expansion coefficient. For multicomponent compositions, a second‐phase raw material with different properties should be added as finer particles to minimize the thermomechanical stresses generated.

An investigation of atherosclerotic markers in patients with posterior semi-circular canal benign paroxysmal positional vertigo

This study aims to investigate the presence and incidence of arteriosclerosis in patients with benign paroxysmal positional vertigo (BPPV). A total of 89 patients who were admitted to the ear, nose, throat outpatient clinic with complaint of vertigo and were diagnosed with BPPV based on the positive Dix-Hallpike test results were included (BPPV group) between January 2010 and July 2010. Data from otological asymptomatic controls (n=129) who were referred to the radiology department from other clinics for ultrasound examination were obtained. Intima-media thickness and arteriosclerosis measurements were carried out. Arteriosclerosis measurement was performed through a Doppler ultrasound. No statistically significant difference in carotid, femoral intima-media thicknesses and elastic modulus measurements between the controls and BPPV group. In the BPPV group, carotid artery cross-sectional compliance, cross-sectional distensibility, femoral artery cross-sectional compliance and cross-sectional distensibility were statistically significantly lower. Our study results suggest that atherosclerotic changes may play a role in the underlying etiology of BPPV.

Elastic modulus measurement of polymer matrix nano- composites reinforced by platelet nano-clays

Polymer-clay nano-composite materials, in which nano-meter thick layers of clay dispersed in polymer matrix, have generally higher mechanical properties than normal polymeric materials. A new threedimensional unit cell model has been developed for modeling three constituent phases including inclusion, interphase and matrix. The total elastic modulus of nano-composite is evaluated. Numerical results are in good agreement with the previous proposed theoretical modeling. Higher matrix and inclusion elastic modulus both can dramatically increase the total elastic modulus.

Acute Effects of Static Stretching on Muscle Hardness of the Medial Gastrocnemius Muscle Belly in Humans: An Ultrasonic Shear-Wave Elastography Study

This study investigated the acute effects of static stretching (SS) on shear elastic modulus as an index of muscle hardness and muscle stiffness and the relationship between change in shear elastic modulus and change in muscle stiffness after SS. The patients were 17 healthy young males. Muscle stiffness was measured during passive ankle dorsiflexion using a dynamometer and ultrasonography before (pre) and immediately after (post) 2 min of SS. In addition, shear elastic modulus was measured by a new ultrasound technique called ultrasonic shear wave elastography. The post-SS values for muscle stiffness and shear elastic modulus were significantly lower than the pre-SS values. In addition, Spearman's rank correlation coefficient indicated a significant correlation between rate of change in shear elastic modulus and rate of change in muscle stiffness. These results suggest that SS is an effective method for decreasing shear elastic modulus as well as muscle stiffness and that shear elastic modulus measurement using the shear wave elastography technique is useful in determining the effects of SS.

Magnesium fluoride role on alumina–magnesia cement-bonded castables

Mineralizing agents can be a suitable alternative to speed up and anticipate (T<1200°C) spinel (MgAl2O4) generation, improving the overall performance of refractory castables at high temperatures. Nevertheless, only a few studies have investigated the impact of magnesium fluoride on the properties of such materials. Considering this aspect, aqueous suspensions and alumina–magnesia cement-bonded compositions with and without MgF2 were evaluated in order to better understand its effect on the castable׳s phase evolution. Thermogravimetric tests, X-ray diffraction, thermodynamic analysis, apparent porosity, hot elastic modulus and sintering assisted measurements were carried out to evaluate the compositions. The mineralizing agent reacted with calcium aluminate cement in the initial processing steps giving rise to CaF2. Additionally, the prepared suspensions also revealed that solid state reactions between reactive alumina and MgF2 induced spinel formation at relatively low temperatures (800°C). Due to the presence of these two fluorides (MgF2 and CaF2), a liquid phase was formed at temperatures close to 1000°C, increasing the MgAl2O4 generation rate. The transformations identified in the suspension compositions were in tune with the castables׳ in situ hot elastic modulus results. These later measurements also revealed that the liquid phase presented a transient feature, as it was completely consumed during transformations at high temperatures. Nevertheless, the samples showed a marked thermal expansion due to spinel formation, indicating that an additional component to counterbalance this volumetric expansion (such as small amounts of fumed silica) must be simultaneously added to this castable material.

Evolution of microstructure and mechanical properties during thermomechanical processing of a low-density multiphase steel for automotive application

The evolution of the microstructure and mechanical properties in a low-density, low-alloy steel containing 6.57Al–3.34Mn–0.18C (wt.%) has been investigated as a function of processing. The steel was designed to have a duplex microstructure with ferrite as the major phase and austenite as the minor phase within the temperature range 800–1350°C. The steel was processed to sheet form, which was thermomechanically treated and characterised by a variety of techniques such as optical metallography, scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, transmission electron microscopy, tensile testing and density and elastic modulus measurements. The amount of austenite was found to decrease with an increase in the annealing temperature. While C and Mn partitioned into the austenite phase, Al partitioned into the ferrite. The tensile elongation increased with an increase in the amount of austenite in the microstructure. However, the austenite showed only a small transformation induced plasticity effect during tensile deformation due to its high stability. After annealing, mostly κ-carbide precipitates with a (Fe+Mn)/Al ratio of 3.6 appeared in the ferrite matrix, along with some cementite and complex carbides. These precipitates became coarser (330nm) during a short time overageing treatment at 400°C, causing a significant increase in elongation. The κ-carbides were found to have a close to Nishiyama–Wasserman type orientation relationship with the ferrite matrix. Although the Young’s modulus of the steel dropped due to the large amount of Al added, the reduced density was found to be beneficial for automotive applications, overriding the effect of a drop in Young’s modulus.

WE‐E‐9A‐01: Ultrasound Elasticity

Principles and techniques of ultrasound‐based elasticity imaging will be presented, including quasistatic strain imaging, shear wave elasticity imaging, and their implementations in available systems. Deeper exploration of quasistatic methods, including elastic relaxation, and their applications, advantages, artifacts and limitations will be discussed. Transient elastography based on progressive and standing shear waves will be explained in more depth, along with applications, advantages, artifacts and limitations, as will measurement of complex elastic moduli. Comparisons will be made between ultrasound radiation force techniques, MR elastography, and the simple A mode plus mechanical plunger technique. Progress in efforts, such as that by the Quantitative Imaging Biomarkers Alliance, to reduce the differences in the elastic modulus reported by different commercial systems will be explained.Dr. Hall is on an Advisory Board for Siemens Ultrasound and has a research collaboration with them, including joint funding by R01CA140271 for nonlinear elasticity imaging.Learning Objectives: Be reminded of the long history of palpation of tissue elasticity for critical medical diagnosis and the relatively recent advances to be able to image tissue strain in response to an applied force. Understand the differences between shear wave speed elasticity measurement and imaging and understand the factors affecting measurement and image frame repletion rates. Understand shear wave propagation effects that can affect measurements, such as essentially lack of propagation in fluids and boundary effects, so important in thin layers. Know characteristics of available elasticity imaging phantoms, their uses and limitations. Understand thermal and cavitational limitations affecting radiation force‐based shear wave imaging. Have learning and references adequate to for you to use in teaching elasticity imaging to residents and technologists. Be able to explain how elasticity measurement and imaging can contribute to diagnosis of breast and prostate cancer, staging of liver fibrosis, age estimation of deep veinous fhrombosis, confirmation of thermal lesions in the liver after RF ablation.

Strengthening of dental adhesives via particle reinforcement

The bond between methacrylic polymer adhesives and dental restoratives is not perfect and may fail either in the short or in the long term. This study aims to evaluate the effects of particle incorporation in a self-etch model adhesive on mechanical and physical properties that are relevant during application and service. Filled adhesives containing 5, 10, 15 or 25wt% glass fillers were compared to their unfilled counterpart in terms of water sorption and solubility; viscosity and dynamic viscosity during polymerization were recorded using rheological measurements and compared to FTIR analysis of the real-time degree of cure. Elastic modulus and ultimate tensile strength measurements were performed in uniaxial tension; the energy to fracture was used to calculate the fracture toughness of the adhesives. Finally, the experimental adhesives were applied on dentin substrate to test the bond strength using the microtensile test. Results showed that the incorporation of 5–10wt% nanofiller to self-etching dental adhesives is efficient in accelerating the polymerization reaction and increasing the degree of cure without compromising the film viscosity for good wettability or water sorption and solubility. Fillers increased the elastic modulus, tensile strength and fracture toughness to a plateau between 5 and 15wt% filler concentration, and despite the tendency to form agglomerations, active crack pinning/deflection toughening mechanisms have been observed. The bond strength between resin composite and dentin was also improved when adhesives with up to 10wt% fillers were used, with no additional improvements with further packing. The use of fillers to reinforce dental adhesives may therefore be of great practical benefit by improving curing and mechanical properties.