Frequency Dependence Of Elastic Moduli Research Articles

Impact of Lallemantia royleana seed mucilage on the physicochemical, textural, rheological, and in-mouth breakdown behavior properties of cold-set whey protein isolate emulsion-filled gel

This work focused on the Lallemantia royleana seed mucilage (LRSM) effect on the rheological, physicochemical, and microstructural attributes, and the in vivo oral breakdown of cold-set emulsion-filled gel (EFG) based on the whey protein isolate (WPI). Emulsions containing 0.1 and 0.5% LRSM displayed the largest and smallest droplet sizes (3.38 vs. 1.26 μm) and polydispersity index (0.60 vs. 0.23), respectively. Also, the 0.1–0.5% LRSM-WPI EFGs compared to the control had greater elastic modulus in the linear viscoelastic (LVE) region (7006.1–7167.8 vs. 4438.3 Pa), flow-point stress (484.6–540.1 vs. 327.8 Pa), network strength (7227.8–7451.2 vs. 5380.1 Pa.s1z), network extension (10.91–11.44 vs. 10.05), lower LVE limit (1.74–2.26 vs. 2.53 %), same loss tangent (0.17), similar frequency dependence of elastic modulus (0.087–0.091 vs. 0.095), and inhomogeneous microstructures. Hardness, springiness, and chewiness at 0.1% and adhesiveness and cohesiveness at 0.5% LRSM-WPI EFGs were the highest. Raising the LRSM from 0% to 0.5% improved the water-holding capacity (75.49%–87.68%), swelling ratio (0.20%–2.59%), and decreased syneresis (11.08%–9.13%). The 0.5% LRSM-WPI EFG compared to the control needed a higher chew duration (16.22 vs. 11.80 s) and chew cycle (24.76 vs. 18.31), and its bolus had a smaller particle size (0.94 vs. 1.65 mm).

Pressure and frequency dependence of elastic moduli of fluid‐saturated dual‐porosity rocks

AbstractThe elastic moduli of subsurface rocks saturated with geofluid often depend on the wave frequency and confining pressure due to the wave‐induced fluid flow and their significant intrinsic compressibility. Therefore, the knowledge of the pressure‐dependent dispersion of elastic moduli is usually used in broad practical scenarios such as geofluid discrimination and in situ abnormal pressure detection. We propose a simple dual‐porosity model to describe the pressure and frequency dependence of elastic moduli of fluid‐saturated rocks. First, we follow the idea of the Shapiro dual‐porosity model to yield more accurate formulas for pressure‐dependent stiff porosity and crack porosity. Then the new formulas for stiff and crack porosities are utilized to express the bulk and shear moduli of dry rocks as a function of pressure. Further, the bulk and shear moduli of a modified frame (i.e. a rock skeleton with the dry stiff pores and fluid‐saturated cracks) are formulated with the pressure‐dependent elastic moduli of dry rock. In order to consider the wave energy attenuation induced by fluid in cracks, the frequency‐independent fluid modulus imbedded in the formulas for bulk and shear moduli of a modified frame is replaced with a frequency‐dependent one incorporating the effect of viscoelastic relaxation. The effective bulk and shear moduli of entire fluid‐saturated body can be computed by inserting the pressure‐dependent stiff porosity and elastic moduli of a modified frame into the Gassmann equation. Moreover, appropriate simplification is performed on the central equations in the case of low porosity and weak deformation of stiff pores to yield an approximate model. Modelling results show that the proposed model can reasonably account for the nonlinear variation of bulk and shear moduli with the elevating effective pressure and cautiously predict the wave dispersion and attenuation. We validate our model by comparing the predicted elastic moduli with the corresponding results given by Shapiro model–based equations and with the laboratory measurements of five different fluid‐saturated rock samples.

Spinodal strain glass in Mn-Cu alloys

Strain glasses (STGs), which are characterized by nanodomains of martensite formed via a strain glass transition, can produce many unusual properties not possessed by normal martensitic alloys. These nanodomains originate from the formation of short-range strain ordering by the disruption of otherwise long-range strain ordering or normal martensitic transformation through sufficient atomic/nanoscale random stress/strain field. So far the atomic/nanoscale randomness is known to be from either point defects, dislocations, or nanoprecipitates. Here we report a spinodal STG alloy Mn60Cu40, which stems from nanoscale composition modulations (5-20 nm) formed in the early stage of spinodal decomposition, which is identified by STEM-EDS and HRTEM. For short-time (<50 min) aged sample, a strain glass transition was identified by its typical signatures including invariance of global face-centered cubic (fcc) structure with cooling, frequency dependence of elastic moduli at STG transition temperature (Tg) following a Vogel-Fulcher relationship, non-ergodicity as manifested by zero-field-colling/field-cooling curves, and the formation of martensitic face-centered tetragonal (fct) nanodomains. For long-time (≥50 min) aged sample, a normal martensitic transition from fcc to fct appears with cooling, being consistent with literatures. As the result, a temperature vs. aging-time phase diagram of spinodal STG was established and shows a crossover from STG to martensite above a critical aging time. The spinodal STG exhibits a non-magnetic Elinvar behavior, i.e., nearly constant elastic modulus over a wide temperature range, together with high-damping capacity. We anticipate that the spinodal STG and associated novel properties may also be found in other metallic and ceramic spinodal materials.

Effect of microbial transglutaminase on the mechanical properties and microstructure of acid-induced gels and emulsion gels produced from thermal denatured egg white proteins

In the current study, the impact of microbial transglutaminase (MTGase)-mediated crosslinking on the thermally denatured egg white protein (TD-EWP) made in alkaline pH in relation to their gelling properties of in gel and emulsion gel systems was investigated. Unlike native EWP that was not a good substrate for MTGase due to its compact structure, SDS-PAGE and gel solubility data showed the TD-EWP was sufficiently cross-linked by MTGase. The MTGase significantly (p < 0.05) increased the gel strength, fracture stress, fracture strain, and TPA parameters and decreased the frequency dependence of elastic modulus and stress dependence of creep compliance of TD-EWP gel and emulsion gel samples. The enhanced mechanical properties of the TE-EWP gelled samples treated with MTGase may be suitable for delivering sensitive compounds as well as in fabricating tailored scaffolds in tissue engineering and biomedical products.

Strain glass in Ti50−xNi35+xCu15 shape memory alloys

Ti-Ni-based shape memory alloys exhibit three types of martensitic structures of B19′ (monoclinic), R (trigonal) and B19 (orthorhombic). So far, the strain glass has been reported in former two martensitic alloys, however, whether it exists in the third one is still unknown. Here, we report a finding of the strain glass in Ti-Ni-Cu B19-martensitic alloys. Our established phase diagram of Ti50−xNi35+xCu15 shows that the strain glass emerges at x ≥ 7, as evidenced by three experimental signatures: (I) invariance of average structure; (II) frequency dependence of elastic moduli at a strain glass transition temperature Tg; (III) formation of nanodomains.

Tilt strain glass in Sr and Nb co-doped LaAlO3 ceramics

Strain glass, a glassy state of lattice strain, has been found in Ti50-xNi50+x alloys and later in many metallic ferroelastic/martensitic systems, where shear or shuffle serves as a primary order parameter (POP). Another class of non-metallic ferroelastic ceramics are also known to widely exist and commonly possess a polyhedral tilt as the POP. So far, it is unclear whether a “tilt” strain glass exists. Here, we report a finding of a tilt strain glass in La1-xSrxAl0.95Nb0.05O3-δ ceramics. With increasing Sr2+ dopants, the ferroelastic transition from cubic to rhombohedral phases is gradually suppressed. At a critical concentration (xc ∼10%), a strain glass transition emerges, characterized by five sets of evidence: (I) an invariance of average structure; (II) frequency dependence of elastic moduli at a strain glass transition temperature Tg; (III) non-ergodicity; (IV) formation of rhombohedral nanodomains; (V) a gradual increase of tilt angle upon cooling. Surprisingly, the established phase diagram shows an increase of Tg with increasing dopants (a positive correlation), which is different from previous strain glass phase diagrams. The positive and negative correlations can be explained as a balance between two factors of strain glass transition: a global transition factor producing a negative contribution competes with a local field one producing a positive contribution. Our discovery of strain glass in ceramics may also bring novel properties as in metals.

Evaluation of thermal hydrolysis efficiency of mechanically dewatered sewage sludge via rheological measurement

In this study, laboratory tests of both low temperature (60–90 °C) and high temperature (120–180 °C) thermal hydrolysis (LTHP and HTHP) were performed on mechanically dewatered high-solid sludges (at total solid of 14.2 wt% and 18.2 wt%) to evaluate the extent of organic solubilization through rheological measurements. The effects of treatment temperature and duration on organic solubilization and viscoelastic behavior of the sludge were comprehensively investigated. The results indicated that the organic solubilization contents including soluble chemical oxygen demand, soluble protein, and soluble polysaccharides increased logarithmically with the treatment time. Protein solubilized considerably faster than polysaccharides during thermal hydrolysis. The rheological curves exhibited the Payne effect in the amplitude sweep oscillation test. The elastic modulus in linear viscoelastic regime decreased logarithmically with treatment time. The viscoelastic behavior of sludge was well modeled by the Kaye–Bernstein–Kearsly–Zapas (KBKZ) model with paralleled Maxwell elements to describe the frequency dependence of elastic modulus and viscous modulus. With respect to the relaxation spectrum, the relaxation modulus first decreased with relaxation time and then increased. The relaxation modulus in each Maxwell element decreased with the treatment temperature and duration. Furthermore, in the HTHP, the influence of treatment temperature on enhancing organic solubilization and decreasing viscoelasticity exceeded the influence of treatment duration. In contrast, the treatment duration played a more important role than temperature in the LTHP. The content of organic matters was linearly related and logarithmically related to the elastic modulus in the LTHP and in the HTHP, respectively. The rheology analyses demonstrated that viscoelastic properties could be used as indicators to estimate the extent of organic matter solubilization in thermal hydrolysis process. The developed viscoelastic model provided insights for future research in numerically simulating the fluid dynamics of sludge.

Effect of high shear homogenization on rheology, microstructure and fractal dimension of acid-induced SPI gels

High shear homogenization (HSH) (4000–16,000rpm) was used to homogenize soy protein isolate (SPI) dispersions. These dispersions were subsequently gelled by acidification. The rheological properties, creep–recovery behavior, gel microstructure, fractal characteristics of these SPI gels were studied. The results showed that the application of high shear homogenization significantly (P<0.05) decreased the particle size and lowered the polydispersity index of the SPI dispersions. The SPI gels produced by using the homogenized dispersions significantly (P<0.05) increased the gel strength, increased the frequency dependence of elastic modulus and weakened the order and increased the chaos/disorder in the network structure. The application of high shear homogenization during dispersion stage also reduced the voids/pores in SPI gel microstructure and increased the gel compactness.

Elastic Hardening at a Novel Phase Transition in Cage Compound CeRu2Al10

Elastic properties of the cage compound CeRu 2 Al 10 have been investigated by means of ultrasonic measurement. We found a sudden elastic hardening in all moduli below T 0 =27.3 K at which a novel phase transition occurs, and an abrupt elastic softening was observed in longitudinal moduli at T 0 . The magnitude of hardening in C 11 is the largest. We discuss these elastic behaviors from the viewpoint of a CDW transition and a spin-Peierls transition. We estimated the strain dependence of T 0 along the a -, b -, and c -axes from the Ehrenfest relation. No frequency dependence of elastic moduli was observed in the whole temperature range measured.

Viscoelastic Properties of Foamed Thermoplastic Vulcanizates and their Dependence on Void Fraction

Experimental techniques to measure the viscoelastic mechanical properties of foamed elastomers at high frequencies were developed and applied to study foamed thermoplastic vulcanizates. The measurements were performed for foams with a wide range of void fractions such that a transition from a true porous solid to a foam was present. The frequency and time dependence of the dynamic and relaxation moduli, respectively, were measured and were shown to depend on the loss factor of the elastomer. The measured variation of the dynamic and the relaxation moduli with the void fraction did not depend on frequency and time in the frequency and time range of interest. This suggested that the time and frequency dependence of elastic moduli was determined mostly by the void fraction and the corresponding material microstructure. Property measurement results were compared to predictions for porous solids using the Mori-Tanaka method as well as methods for cellular solids.

Representation of the anelastic behaviour of a solid having a gaussian relaxation spectrum

The approximate representation obtained in a previous paper for the frequency dependence of the energy dissipation taking place in a vibrating solid with a Gaussian relaxation spectrum has been extended, for the same spectrum, to the frequency dependence of elastic modulus as well as to the time dependence of after-effect and creep. The procedure followed in order to obtain these representations appears susceptible of application to other types of spectra.