Korea-Australia Rheology Journal最新文献

Magnetorheological materials, including MR Fluids, MR Elastomers, MR Greases, MR Foams, MR Gels, and MR Plastomers are smart materials whose rheological properties change reversibly under magnetic fields. This review examines their development, characteristics, and applications, emphasizing MR Polymer Gels and MR plastomer as an emerging class addressing key limitations of conventional MR materials technologies. Each MR material has distinct trade-offs and MR Fluids offer rapid response but suffer sedimentation. MR Elastomers eliminate sedimentation but need continuous applied magnetic fields and show limited load capacity. MR Greases combine lubrication with controllable viscosity and MR Foams provide lightweight structures with tunable damping but reduced field response. MR Gels bridge MR fluid and MR elastomer properties while reducing sedimentation. MR Plastomer composed of carbonyl iron powder in lightly cross-linked polymers demonstrate superior sedimentation stability, rapid response, and strong field induced changes. The review covers MR Plastomer classification by particle distribution into isotropic or anisotropic types and matrix composition. Fabrication techniques include mixing, curing, and field assisted alignment. Critical properties examined are mechanical, magnetic, and electrical. Their Performance factors analyzed include carbonyl iron content, additives, polymer selection, and applied field effects. MR Plastomer damper performance is assessed through damping force, dynamic range, response time, and energy dissipation. Outstanding challenges include matrix stability, particle redistribution, and predictive modeling. Future priorities encompass microstructure optimization, durability enhancement via advanced formulations, and physics based models for adaptive structures, vibration isolation system, and sensing applications.

Wine is commonly described through aroma, taste, grape variety, terroir, ageing, and quality, but it is also a liquid experienced tactually in the mouth. This Perspective is a conceptual contribution rather than a report of new rheological experiments. Its purpose is to organize established knowledge on wine viscosity, oral tribology, astringency, and sensory texture into a compact rheological interpretation of wine mouthfeel. Typical dry table wines are low-viscosity liquids that behave nearly as Newtonian fluids, and their bulk viscosities are only slightly higher than that of water. Bulk viscosity is therefore a necessary baseline, but it cannot by itself explain descriptors such as body, smoothness, dryness, roughness, warmth, prickling, and astringency. These impressions arise from coupled physicochemical, tribological, trigeminal, and perceptual processes involving wine composition, temperature, ageing state, saliva, oral surfaces, friction, lubrication, tannin-salivary protein interactions, and sensory descriptor assignment. The central contribution of this article is to express these processes using a reduced oral-state framework. In this view, different wines can generate similar mouthfeel when they produce comparable oral rheological or tribological states, whereas wines with similar bulk viscosities can be perceived differently when their lubrication, frictional, or salivary interaction states diverge. This framework also explains why trained and untrained tasters may encounter partially common oral stimuli while assigning different sensory language. Wine mouthfeel is therefore not reducible to viscosity alone, but neither is it merely subjective; it is a mapped response from material properties to oral state, perception, language, and judgment.

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Squeeze flow behavior of multi-phase shear thickening fluid (MSTF) consisting of SiO₂ particles, ZnO particles with different shapes and polyethylene glycol (PEG 400) is investigated. The squeeze measurements are performed under constant volume mode. Due to the adhesion force of ZnO particles, particles are easier to contact with each other, normal stress and critical gap of MSTF increases. When the additive is tetrapod-like ZnO (T-ZnO) particles, critical gap increases by 17.65% and normal stress increases by 166.09% compared with that of Neat shear thickening fluid (STF). Moreover, it turns out that normal stress is significantly increased at large squeeze velocity, appropriate volume fraction of ZnO particles and low temperature. Based on bi-viscous model, the squeeze flow model of MSTF is established. Additionally, the radial velocity, shear stress, and squeeze pressure during the squeeze process are derived. The results of the theoretical analysis show that the radial velocity is affected by the non-Newtonian index of STF. The pressure gradient is equal to the shear stress gradient. With the increase of the volume fraction of ZnO particles, the shear stress and normal force decrease firstly and then increase. The experimental data proves the accuracy of this model.

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The influence of surfactant type on the aggregation structure and rheological behavior of multi-walled carbon nanotube (MWCNT) suspensions in N-methyl-2-pyrrolidone (NMP) was investigated through combined rheological measurements and scaling analysis. The MWCNT concentration was fixed at 1 wt%, which is above percolation threshold, and four types of suspensions were prepared: a surfactant-free suspension, and suspensions containing the nonionic surfactant Tween 80, the cationic surfactant CTAB, and the anionic surfactant SDBS. The rheological properties of the suspensions were characterized under both steady as well as oscillatory shear measurement. All the surfactants acted to reduce the suspension viscosity and to increase the storage modulus. The extent of viscosity reduction and modulus enhancement was relatively larger for CTAB and SDBS than for Tween 80. Shear viscosity and storage modulus were measured while varying the MWCNT concentration from 0.8 to 1.2 wt% to estimate the intrinsic viscosity and fractal dimension. Both parameters were lower for the Tween 80 system compared with those containing CTAB or SDBS. Microscopic observations of diluted suspensions showed that aggregates formed with Tween 80 were relatively small, whereas those formed with CTAB and SDBS were larger and exhibited more interconnected network structures. These structural differences are consistent with the lower intrinsic viscosity, which scales with the average aggregate size, and the smaller fractal dimension, which indicates a morphology closer to a string-like rather than a plane-like network. Overall, the rheological analyses, including fractal dimension and microscopic observations, indicate that Tween 80 provides the most effective dispersion among the surfactants examined.

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Fractal dimension (d_f), intrinsic viscosity ([η]), and storage modulus (G′) of MWCNT suspensions prepared with different surfactant conditions: surfactant-free (N/S), Tween 80 (Tw 80), CTAB, and SDBS.

This study examines the interfacial rheological properties of magnetorheological fluids in oil-based systems, with a particular focus on liquid–liquid interfaces, including particle-laden emulsions and multilayer films. In this work, interfacial shear rheology of MRF without magnetic fields has been investigated, with exclusive emphasis on interfacial viscoelastic behaviour. Experimental (using bi-conical IRS) techniques are employed to assess the interfacial behaviour, and we thoroughly studied and quantified how MRF particles form films and behave at the oil interface under different shear conditions. Our analysis establishes a direct link between interfacial rheological behaviour and interfacial structural organisation, particularly particle coverage and network formation. Steady shear experiments visualise the evolution of interfacial particle assemblies, revealing irreversible rearrangements that govern viscoelastic behaviour.

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The present work experimentally studies the rheological behavior of two materials commonly used in the food industry using two powder rheometers. The Anton Paar MCR 302e rheometer equipped with a powder cell was one of the two devices used. A second rheometer, a specific unit powder rheology device manufactured by Freeman Technology (FT4) was used to measure non-aerated powder. Two different powders from the food industry were chosen to carry out the comparison: sugar and flour. Wheat flour is a highly cohesive material, classified as Geldart C particles, the test of which are strongly conditioned by the previous pre-compaction of the sample. Sugar was chosen because it is a complex cubic geometry, being different from that of most particles, which are spherical. Compressibility parameters, such as bulk density or Hausner ratio, cohesion strength, wall friction parameters and warren spring cohesion were measured. This work conducts an in-depth study of rheological behavior based on the morphology of the particle, which was measured with a Malvern microscope (Morphologi4). Cohesive strength results show that wheat flour is twice as cohesive as sugar. In addition, the square morphology and large size of the sugar particles greatly influence several parameters and can be quantified in terms of energy expended with the downward movement of the blades by up to 100 mJ more than in the case of flour. Depending on the measurement methodology, differences in the hopper angle of (11,^circ ) and (31,^circ ) are observed.

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Four serious errors exist in the above paper.

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Yield stress is a key parameter in the study of soft materials, but its value depends on the experimental criterion used to define it. In this work, three representative systems are analyzed: a BBQ sauce as a low-strength colloidal dispersion, a hair gel as an intermediate polymer hydrogel, and a chitosan hydrogel as an example of a rigid polyelectrolyte network. The rheological results show that the obtained yield stress values vary depending on the method used. The comparison between systems shows that the concentration and type of polymer determine the magnitude of (:{G}^{{prime:}}), (:{G}^{{prime:prime:}}) and (:{tau:}_{0}) with chitosan being the strongest material due to its rigid structure and stronger interactions. The determination of the yield stress should not be interpreted as an absolute value but rather as an interval, considering the point at which the material begins to change its structure until it becomes completely liquid.

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Accurate simulation of blood flow dynamics in thoracic aortic aneurysms (TAA) is crucial for patient-specific risk assessment and treatment planning. However, high-fidelity computational fluid dynamics (CFD) models are computationally expensive and often impractical for real-time clinical use. In this study, we propose a Graph Neural Network (GNN)-based surrogate model to predict transient wall shear stress (WSS) components on the aneurysm wall using unstructured mesh data derived from CFD simulations. The model is trained on 70% of the cardiac cycle data and tested on the remaining 30%. We demonstrate that the GNN can accurately reproduce spatial and temporal WSS distributions, with average relative errors of approximately 5.5%, 6.5%, and 9% for (hbox {WSS}_x), (hbox {WSS}_y), and (hbox {WSS}_z) components, respectively. Spatial error analyses reveal strong correlation between prediction error and flow complexity, particularly in regions near the aneurysm inlet where velocity gradients are highest. Our findings suggest that GNN-based models offer a promising, low-cost alternative for real-time hemodynamic assessment in complex vascular geometries.

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This study investigates the rheological behavior of soft colloidal suspensions composed of chitin-derived microgels, carboxymethyl chitin (CMCH) and its sulfated derivative (CMCHS), dispersed in Newtonian (water) and non-Newtonian (hyaluronic acid, HA) fluids. Flow and oscillatory measurements clarify the dual influence of particle deformability and matrix viscoelasticity on macroscopic response. Sulfate groups reduces crosslinking density and elastic modulus, producing softer CMCHS microgels. In Newtonian media, both systems exhibit three flow regimes: dilute, soft glassy, and jammed, with CMCHS requiring higher concentrations to reach jamming due to greater deformability. The Wu–Morbidelli fractal model revealed that CMCHS formed more compact aggregates (D_f = 1.9) within a weak-link dominated network (α = 0.6), whereas CMCH formed looser aggregates (D_f = 1.75) with transition region between weak and strong connections (α = 0.51). In HA-based suspensions, viscoelastic confinement by entangled polymer chains produced compact intra-floc structures (D_f ≈ 2.1) but softer, polymer-mediated inter-floc junctions. The overall response was governed by the polymer network, which suppressed the dilute regime, induced an apparent yield stress, and reduced the sensitivity of elasticity to particle concentration. This dual control enables tunable rheology in soft colloidal systems, offering design principles for advanced biomedical, cosmetic, and industrial formulations.

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