•A hydrodynamic constitutive model for STF is employed to describe the complex dynamic behaviour.•An analytical model is developed for describing the dynamic squeezing behaviour of non-Newtonian ...fluids.•The strong interaction between the SPLTC and the STF during the fast flow of the STF near the periphery is obtained.•The effects of shear thickening behaviour on the dynamic response of the SPLTC-STF are obtained by the FSI simulation.
The compressive behaviour of sandwich panels with lattice truss core filled by shear thickening fluid (SPLTC-STF) at high strain-rates is performed analytically and numerically. Firstly, a hydrodynamic constitutive model for the shear thickening fluid (STF) involving shear thinning, shear thickening, and hydrostatic compressibility is undertaken to describe the dynamic behaviour of the STF. Then an analytical model based on the squeezing flow of viscous fluids is proposed. The squeezing resistance of the STF between the two panels of the SPLTC under various loading velocities is analysed using a fluid-structure interaction (FSI) simulation, by which the constitutive parameters of the STF are obtained. Finally, the dynamic response of the SPLTC-STF involving buckling and post-buckling of core struts in the STF is investigated using the FSI method. The enhanced energy absorption capacity of the SPLTC-STF observed in Ref 1 is numerically interpreted. The effects of shear thickening behaviour of STF on the dynamic response of SPLTC-STF are predicted, providing a method of optimal design for STF filled sandwich panels over a wide range of impulse loadings for dynamic energy absorption.
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Recently, the increasing vibration isolation demands drove the interest of viscous damper development towards employing non-Newtonian fluids that allow tailoring of highly customized damper ...characteristics. Several attempts have been made for using shear-thickening fluids; however, most of these studies measured only the final, resulting damping characteristic for a particular fluid rheology. This paper aims to give an analytical technique to predict the damping characteristic in the case of arbitrary fluid rheology for piston-type damper geometries with either an annular gap or circular hole(s) as restriction elements. The flow is approximated by laminar Poiseuille flow, and the governing equations are solved for arbitrary rheology. We present several force-velocity example characteristics for general rheologies, compare the analytical estimations against CFD computations, and provide a sample computation for nonlinear damper design.
Mechanisms for uplift and deformation of the Tibetan Plateau remain vigorously debated; hypotheses include stepwise growth, distributed thickening, and crustal channel flow, each with a distinct ...anisotropic signature. We have developed a new azimuthally anisotropic shear velocity model for the lithosphere beneath eastern Tibet, based on ambient noise tomography from 643 seismic stations. In our model, the Tibetan upper crust is characterized by strong anisotropy with fast axes that correlate with surface geology and mantle anisotropy, suggesting the occurrence of coherent deformation. However, a much different picture emerges in the middle and lower crust, where anisotropy is disordered and weaker beneath the plateau than along its margins, inconsistent with the prediction of large‐scale eastward crust flow in eastern Tibet. Our observations are best explained by heterogeneous crustal thickening beneath the plateau with complex flow in the middle and lower crust, accompanied by asthenospheric upwelling along the southeastern plateau margin.
Plain Language Summary
How the Tibetan Plateau uplifted and deformed remains debated. An azimuthally anisotropic shear velocity model beneath eastern Tibet was constructed to constrain its deformation style. The anisotropy of Tibetan upper crust displays continuously varying intensities and fast directions correlating well with surface geology and mantle anisotropy, confirming the occurrence of distributed coherent lithospheric deformation. Interestingly, middle‐lower crustal anisotropy is much weaker beneath the plateau proper than the northeastern and southeastern plateau margins, inconsistent with the prediction of large‐scale eastward crustal flow. Based on our observations and previous studies, we propose an episodic growth model for the plateau, in which heterogeneous crustal thickening was a primary driver at the early stage and the weakened middle‐lower crust flowed locally at a later stage without consistent directions. The southeastern plateau margin was raised likely by an additional mechanism of asthenospheric upwelling.
Key Points
We construct a high‐resolution azimuthally anisotropic Vsv model for eastern Tibet and its surroundings
An episodic deformation model with early crustal thickening and later disordered crustal flow was proposed for the plateau
The SE plateau margin was likely uplifted by asthenospheric upwelling
As a flexible protective material, shear thickening gel (STG)/Kevlar composite still has great potential to improve its impact resistance. In this paper, a novel STG/SiO2/Kevlar flexible protective ...composite was prepared by impregnating STG/SiO2 into Kevlar. Due to the excellent SiO2 enhancement effect, the STG/SiO2/Kevlar exhibited a higher safeguarding property than the STG/Kevlar. The maximum yarn pull‐out force of STG/SiO2/Kevlar reached 61.7 N, which was higher than the 41.9 N of STG/Kevlar. The uniform puncture results showed that the maximum bearing capacity of STG/Kevlar and STG/SiO2/Kevlar increased by 116.8% and 215.3%, respectively, compared with pure Kevlar. The impact test results indicated that 20 layers of STG/SiO2/Kevlar could not be penetrated by the knife stab and 24 layers of STG/SiO2/Kevlar could not be penetrated by 7.62 mm pistol bullets. Finally, the enhancement mechanism of impact resistance of STG/SiO2/Kevlar composites was studied.
A novel STG/SiO2/Kevlar flexible protective composite was prepared by impregnating STG/SiO2 into Kevlar. SiO2 improved the integrity and impact resistance of STG/SiO2/Kevlar composites by enhancing the shear‐thickening properties of STG and the friction during yarn sliding.
Thickening products (TPs) are a valid therapeutic strategy in patients with oropharyngeal dysphagia, their effect is mainly related to the bolus viscosity achieved. The aim of the study was to ...compare the information on the labels of 10 TPs of different thickening agents (hydrocolloids): modified starch-based, gum-based and mixtures. Viscosity was measured in SI units (mPa·s), using a rotational viscometer at 50 s−1 and 300 s−1, and the effect of oral amylase (α-SA) and shear thinning on the viscosity levels recommended by each manufacturer were assessed. Results were classified according to 3 textural classifications: National Dysphagia Diet (NDD), International Dysphagia Diet System (IDDSI) and Japanese Dysphagia Diet (JDD2013). Results are also presented in SI units (mPa·s) following a new proposed scientific labelling system developed in our laboratory at Hospital de Mataró and endorsed by eleven medical and scientific societies. The effect of α-SA was assessed after 30 s oral incubation of the thickened bolus.
All TPs fulfil Food for Special Medical Purposes labelling regulations, use 3 thickness levels, and 70% use the NDD descriptors. Viscosities at 50 s−1 ranged between 75 and 350 mPa s for level 1, 256–1280 for level 2 and 377–6205 for level 3. α-SA caused 98–99% decrease in viscosity for modified starch-based TPs (MS) and 16% or even an increment for gum-based TPs. Shear thinning decreased viscosity from 40 to 60% for MS-based TPs and 70–75% for gum-based TPs. This study showed that TPs are commercialised using the same descriptors for very different viscosities when measured in mPa·s. Shear rate and α-SA strongly affect viscosity but this is not described on the labels. We claim labels should include viscosity in SI Units (mPa·s at 50 s−1) and the effect of α-SA and shear thinning as main factors affecting the therapeutic effect and mode of action of thickening agents.
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We determined the lithospheric structure of northeastern Tibet using a receiver function study along a long north‐south profile. Our most important finding is that significant lithospheric thickening ...is observed beneath the growing northeastern Tibetan plateau, while the lithosphere is relatively thin beneath the well‐developed portions of Tibetan Plateau and Asian continent. These observations also detect a contrasting lithospheric structure across the South Qilian suture. Abrupt steps in the Moho and lithosphere‐asthenosphere boundary across this suture indicate that the South Qilian suture is a major tectonic boundary that might cut through the entire lithosphere. This study shows the importance of mantle lithospheric thickening in controlling the growth of Tibetan Plateau.
Plain Language Summary
It has long been suggested that the recent growth of northeastern Tibet since the Miocene is the consequence of the thickening and shortening of crust rather than the entire lithosphere. Here we used P and S receiver functions to image the crustal and lithospheric mantle structures across the northeastern margin of the Tibetan Plateau. Our receiver function results show significant lithospheric thickening beneath the growing northeastern Tibetan Plateau, which suggests that the lithospheric‐scale deformation controls the ongoing growth of Tibetan Plateau. Furthermore, abrupt Moho and lithosphere‐asthenosphere boundary steps are found across the South Qilian suture, indicating that the suture is a major tectonic boundary that might cut through the entire lithosphere.
Key Points
Lithospheric structure along an N‐S profile in northeastern Tibet is obtained from P and S receiver functions
Whole lithospheric thickening, instead of the crustal‐only shortening, controls the ongoing growth of Tibetan Plateau
Abrupt Moho and LAB steps are found across the South Qilian suture
In this work, shear thickening fluid (STF) was fabricated and encapsulated by using three different encapsulation methods for the first time. The mechanical properties of individual STF capsules were ...investigated to obtain optimal encapsulation method and formula. Much more energy can be absorbed for STF capsules during impact than that of quasi-static compression. The introduction of ultraviolet (UV) curable resin can significantly improve the static strength of STF capsule and thus enhance the handleability of STF capsule. The STF capsules synthesized through the two-step polymerization method show an elastic shell which can stand multiple impacts without any damage. This STF capsule possesses higher static strength and absorbs more strain energy than capsules synthesized through the other two methods. Furthermore, incorporation of the STF capsules into silicone gel enhances the energy absorption capacity of matrix material up to 71.3%.
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•A review of CO2 thickening as promising technology for oilfield application.•Specific CO2 thickeners eliminate viscous fingering and gravity segregation issues.•CO2 thickeners have ...been categorized into five types, depending on chemical nature.•Thickening methodology was described to attain optimal viscosity and solubility traits.•It is necessary to develop effective thickeners, while considering cost and toxicity.
The relatively low density and viscosity of carbon dioxide (CO2) in supercritical state create several drawbacks, including gravity override, viscous fingering, water production/treatment problems, and poor proppant transport for the petroleum industry. The introduction of CO2 thickeners offers a promising additive technology with sufficient solubility and viscosity enhancement attributes. The current article reviews the technical advances, challenges, and applicability of thickened CO2, particularly for hydrocarbon recovery. Different types of thickeners, including polymers, tailor-made surfactants, and small associating compounds, were investigated in terms of their nature, physicochemical traits, cost, and applications. The molecular weight and concentration, shear rate, co-solvent composition, temperature, and pressure play a significant role in the intermolecular forces and miscibility effect of thickeners in the presence of dense CO2. Binary co-polymers (non-fluorinated non-siloxane materials) and small molecule (associating) compounds are promising options for CO2 thickening owing to their enhanced performance, cost-effectiveness, and low ecological footprint. This study provides a comprehensive review of existing technologies, outline the gaps, potential, and required area for improvement.
Shear jamming, a relatively new type of phase transition from discontinuous shear thickening into a solid-like state driven by shear in dense suspensions, has been shown to originate from frictional ...interactions between particles. However, not all dense suspensions shear jam. Dense fumed silica colloidal systems have wide applications in the industry of smart materials from body armor to dynamic dampers due to extremely low bulk density and high colloid stability. In this paper, we provide new evidence of shear jamming in polypropylene glycol/fumed silica suspensions using optical in situ speed recording during low-velocity impact and explain how it contributes to impact absorption. Flow rheology confirmed the presence of discontinuous shear thickening at all studied concentrations. Calculations of the flow during impact reveal that front propagation speed is 3–5 times higher than the speed of the impactor rod, which rules out jamming by densification, showing that the cause of the drastic impact absorption is the shear jamming. The main impact absorption begins when the jamming front reaches the boundary, creating a solid-like plug under the rod that confronts its movement. These results provide important insights into the impact absorption mechanism in fumed silica suspensions with a focus on shear jamming.
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