Viscoelastic Research Papers - Academia.edu (original) (raw)

Eukaryotic cells and biological materials are described from a rheological point of view. Single cells possess typical microrheological properties which can affect cell behaviour, in close connection with their adhesion properties. Single... more

Eukaryotic cells and biological materials are described from a rheological point of view. Single cells possess typical microrheological properties which can affect cell behaviour, in close connection with their adhesion properties. Single cell properties are also important in the context of multicellular systems, i.e. in biological tissues. Results from experiments are analyzed and models proposed both at the cellular scale and the macroscopic scale. To cite this article: C. Verdier et al., C. R. Physique 10 (2009).

The in vivo assessment of the biomechanical properties of the skeletal muscle is a complex issue because the muscle is an anisotropic, viscoelastic and dynamic medium. In this article, these mechanical properties are characterized for the... more

The in vivo assessment of the biomechanical properties of the skeletal muscle is a complex issue because the muscle is an anisotropic, viscoelastic and dynamic medium. In this article, these mechanical properties are characterized for the brachialis muscle in vivo using a noninvasive ultrasound-based technique. This supersonic shear imaging technique combines an ultra-fast ultrasonic system and the remote generation of transient mechanical forces into tissue via the radiation force of focused ultrasonic beams. Such an ultrasonic radiation force is induced deep within the muscle by a conventional ultrasonic probe and the resulting shear waves are then imaged with the same probe (5 MHz) at an ultra-fast framerate (up to 5000 frames/s). Local tissue velocity maps are obtained with a conventional speckle tracking technique and provide a full movie of the shear wave propagation through the entire muscle. Shear wave group velocities are then estimated using a time of flight algorithm. Thi...

The physical-chemical, thermal and rheological properties of starches isolated from four commercial potato cultivars (Colparina, Huayro, Canchan and Yungay) were evaluated and characterized. The starches presented ovoid and spherical... more

The physical-chemical, thermal and rheological properties of starches isolated from four commercial potato cultivars (Colparina, Huayro, Canchan and Yungay) were evaluated and characterized. The starches presented ovoid and spherical shapes, with average size from 20.08 ± 2.48 to 25.33 ± 6.54 μm and B-type granules, with amylose content from 15.49 ± 2.02 to 32.10 ± 0.14% and relative crystallinity, between 34.6 and 37.3%. The rheological properties measured using a dynamic rheometer, showed predominance storage module (G') on the loss module (G'') during the frequency range (0.01-3.20 Hz) studied, which would classify them as weak gels. The starches presented low syneresis, high clarity, pasting temperature from 65.70 ± 0.31 °C to 67.70 ± 0.23 °C, gelatinization start temperature (To); peak temperature (Tp); gelatinization final temperature (Tf) and gelatinization enthalpy (ΔH) values between 57.90 ± 0.24 and 62.23 ± 0.17 °C; 61.18 ± 0.01 and 64.85 ± 0.01 °C; 65.5 ± 0.31 and 68.34 ± 0.29 °C; 11.49 ± 0.8 and 15.43 ± 0.51 J/g, respectively. The starches evaluated had suitable properties to be used as ingredients in specific foods to improve their textural characteristics.

Beam is basic components in industrial structural design whose damping properties are often very important to reduce vibration. Viscoelastic materials are generally polymers; there is enormous variability in the composition of... more

Beam is basic components in industrial structural design whose damping properties are often very important to reduce vibration. Viscoelastic materials are generally polymers; there is enormous variability in the composition of viscoelastic materials. Rubber is a unique material that is both elastic and viscous. Rubber parts can therefore function as shock and vibration isolators and/or as dampers. In this research Butyl rubber is viscoelastic material which is acting as the damping layer, steel and aluminum patches are used as constrained layer. Here, change in length of patch and damping layer is varied for constant length and thickness of base layer. The lengths of patches are varied as 25%, 50%, 75% and 100%. These patches also arranged in segment and hybrid. Two sets of specimens are prepared for aluminium and steel constrained layer. Damping characteristics of beam are determined by experimental and analytically by using FFT analyzer and ANSYS software respectively.

An unexpected property of unskilled overarm throws is that wrist flexion velocity at ball release does not increase in throws of increasing speed. We investigated the nature of the interaction torques and wrist mechanical properties that... more

An unexpected property of unskilled overarm throws is that wrist flexion velocity at ball release does not increase in throws of increasing speed. We investigated the nature of the interaction torques and wrist mechanical properties that have been proposed to produce this property. Twelve recreational throwers made seated 2-D throws, which were used as a model for unskilled throwing. Joint motions were computed from recordings made with search coils; joint torques were calculated from inverse dynamics. Wrist flexion velocity at ball release was actually smaller in fast throws than in slow throws. This was associated in fast throws with the decrease in a large wrist flexor muscle torque (i.e., a calculated residual torque) in the last 40 ms before ball release, and its reversal to an extensor torque. Consequently, wrist flexor muscle torque was unable to oppose a small maintained wrist extensor interaction torque that arose from continuing elbow extension acceleration. The decrease in wrist flexor muscle torque was not associated with a decrease in wrist flexor EMG activity, nor with an increase in wrist extensor EMG activity. These findings support the hypothesis that the smaller wrist flexion velocity at ball release in fast 2-D throws results from a wrist extensor interaction torque and from a large wrist extensor viscoelastic torque. We propose that in fast 3-D throws skilled subjects decelerate elbow extension before ball release to help overcome these wrist extensor torques.

A series viscous-elastic-plastic (VEP) indentation model was expanded to include analysis of the common trapezoidal testing condition, consisting of constant loading---and unloading---rates with an intervening creep hold period. This full... more

A series viscous-elastic-plastic (VEP) indentation model was expanded to include analysis of the common trapezoidal testing condition, consisting of constant loading---and unloading---rates with an intervening creep hold period. This full VEP model was applied to analyze nanoindentation test of three polymers and five different types of bone. The full VEP solution allows for direct determination of the viscous term as calculated from the creep hold, while the elastic and plastic material parameters were determined from a non-linear curve-fit of the unloading displacement-time data. Additionally, the use of the trapezoidal loading procedure permitted analysis of the unloading load-displacement data with traditional Oliver-Pharr analysis; the material properties from this analysis compared well with those obtained with VEP analysis. Using the full VEP solution and fitted material constants the loading and creep hold displacement-time curves were simulated and matched well to both polymer and bone experimental data. The full VEP solution shows great promise in for obtaining material parameters for many viscoelastic materials such as hydrated bone, polymers, and other biological tissues.

Ballistic impact on a polyurea retrofitted high strength structural steel plate is simulated and validated. A soft material model for polyurea, which is capable of capturing complex mechanical behavior characterized by large strains,... more

Ballistic impact on a polyurea retrofitted high strength structural steel plate is simulated and validated. A soft material model for polyurea, which is capable of capturing complex mechanical behavior characterized by large strains, hysteresis, rate sensitivity, stress softening (Mullins effect), and deviatoric and volumetric plasticity, is calibrated against several uniaxial tension experiments and a three-dimensional release wave experiment to capture both the material point and bulk behaviors. A porous plasticity model is employed to model the high strength structural steel and localization elements are included to capture adiabatic shear bands and strain localization. The computational capabilities of these models are demonstrated by the prediction of the target plate displacement, which shows excellent agreement with experiments.