Tension Curves Research Articles

Tailoring W/O emulsions for application as inner phase of W/O/W emulsions: Modulation of the aqueous phase composition

This work focused on evaluating the effect of adding sodium chloride (0.2% w/w NaCl), gallic acid (0.5% w/w GA) or GA/NaCl (0.5%/0.2% w/w) blend, as well as PGPR concentration (1.5–4.5% w/w) on the stability and structure of water-in-oil (W/O) emulsions aiming their application as an internal phase of water-in-oil-in-water (W/O/W) emulsions. The GA/NaCl and water (control) systems showed similar interfacial tension curves, but the addition of GA or NaCl promoted a remarkable reduction in the interfacial tension. The presence of GA and/or NaCl promoted subtle changes in interface viscoelasticity, showing that interface properties were mostly impacted by PGPR. All emulsions showed Newtonian behavior, but kinetic stability was improved in the presence of NaCl (NaCl or GA/NaCl) and in the highest PGPR concentration. In addition to good stability, the GA/NaCl system stabilized by 4.5% PGPR can present functional properties, due to the presence of GA, which makes this system a promising alternative to produce double emulsions with a wider application. • Aqueous phase composition affected the characteristics of W/O emulsions. • Gallic acid and NaCl decreased the tension between water-sunflower oil interface. • Gallic acid and NaCl in aqueous phase improved kinetic stability of emulsions.

A novel experiment-based approach on nonlinear bending analysis of thermoplastic composite laminates

A novel experiment-based approach, in which we proposed a new physical model for the carbon fibre reinforced thermoplastic (CFRTP) composite with stress-strain nonlinearity and material bimodularity, is presented for the nonlinear bending analysis of CFRTP composite laminates. The nonlinear stress-strain curves in tension, compression and shear are determined by experiments. The bimodular nonlinear model is validated through comparisons of tensile, compressive and three-point bending experimental data against the finite element analysis results firstly. Numerical investigations are then carried out for the symmetric angle-ply CFRTP composite laminates. The effects of the material nonlinearity, bimodularity, fibre orientation, plate aspect ratio, width-to-thickness ratio, boundary conditions and load distributions on the nonlinear bending load-central deflection and load-bending moment curves of CFRTP laminate plates are discussed in detail.

Исследование адсорбции противоизносных присадок на поверхности бутосила в масляных дисперсиях

The method for evaluating the adsorption capacity of surfactants for plastic lubricants on inorganic thickener, such as silica gel, bentonite, carbon black, colloidal graphite, and others was proposed. The Gibbs adsorption values were calculated based on surface tension curves of samples in oil media, and the adsorption isotherms for each of the media were plotted based on the calculated data. According to the results of the study of the surface tension and refractive index of DF-11 additive solutions in heptane, it was found that 1% of the mass goes to fill the butosil surface, and the rest of its amount remains in the volume. But for the A-22 additive in the reference medium, the filling of the butosil surface occurs at a concentration of 2 % mass. It is shown that the additive A-22 should be used at higher concentrations than DF-11 to improve tribological parameters of silica gel lubricants. It was found that use of butasil based silica-gel grease the mixture of the industrial oil I-40A and PMS-400 as a dispersion medium, allows to reduce concentration of DF-11 and A-22 additives.

Tensile, compressive, and fatigue strength of a quasi-isotropic carbon fiber reinforced plastic laminate with a punched hole

The mechanical properties of a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate with a punched hole were investigated. During the punching process, pressure was applied to the laminate through the upper and lower blank holders of a punching machine; the clearance between the punch and blank holders was set to be small to suppress damage in the CFRP laminates. Due to the dragging of plies encountered during punching, the surface of the punched hole was relatively uneven as compared to that of the drilled hole. However, the effect of the uneven surface created during the punching process was not as significant on the tensile and compressive strength of the open hole as compared to the manufacturing damages generated by drilling processes. The stress–number of cycles to failure curves for the open-hole tension–tension fatigue tests also showed comparable results between the punched- and drilled-hole specimens. These results indicate that there were no significant differences in the mechanical properties of CFRP laminates with a punched hole, and thus present the possibility of a highly productive hole-making process using the punching method.

Impact of Adsorption Layer Properties on Drainage Behavior of Microscopic Foam Films: The Case of Cationic/Nonionic Surfactant Mixtures

Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.

Atomistic simulation of deformation behaviors polycrystalline CoCrFeMnNi high-entropy alloy under uniaxial loading

Molecular dynamics is used to examine the evolution of dislocations and FCC → HCP phase transformation, as well as deformation twinning for a typical polycrystalline CoCrFeMnNi high-entropy alloy. It is found the discrepancy of the stress-strain curve for tension and compression owing to the strength mechanism during deformation. The grain refinement behavior is only observed in samples of compression, which leads to the difference of flow stress compared with the tension. At the early plastic stage, FCC → HCP phase transformation is the major deformation behavior. Three paths of FCC → HCP phase transformation for inducing plasticity are analyzed, and the mechanism of spontaneous nucleation of stacking faults is the mainly approach to the transformation. For large strain, the pattern of twinning induced plasticity plays a critical role on the plastic deformation of the HEA. The results are qualitatively consistent with experiments and provide a fundamental understanding of plastic deformation in FCC polycrystalline CoCrFeMnNi HEA.

A Method to Incorporate Grain Boundary Strength and its Effects on Plastic Deformation in FCC Polycrystals

A three-dimensional (3D) crystal plasticity finite element method (CPFEM) is developed to investigate the effect of grain boundary strength on heterogeneous strain partitioning in FCC polycrystals. The proposed method incorporates electron backscatter diffraction (EBSD) maps into finite element analyses. The numerical analysis accounts for crystallographic texture, its evolution and 3D grain morphologies. Furthermore, grain boundaries are also mapped with a special finite element framework that allows material properties to be assigned to the grain boundaries. The material parameters and the grain boundary strengths are obtained by calibration to experimental uniaxial tension curves for single and polycrystals. Numerical simulations of uniaxial tension are performed and the effects of grain boundary strength on the onset of non-uniform deformation is investigated. The predicted local strain evolution is compared with corresponding experimental results from digital image correlation (DIC) measurements of an AA5754 aluminium sheet. The results showed that an excellent agreement was reached when the grain boundary properties were set so that the hardness was five times that of the average polycrystal response.

Surgical Management of Pseudoexfoliative Glaucoma: A Review of Current Clinical Considerations and Surgical Outcomes.

Pseudoexfoliative glaucoma (PEXG) is the most common cause of secondary open-angle glaucoma worldwide. It is more aggressive and often more resistant to conventional treatments than primary open-angle glaucoma, yet there is currently no clear consensus on best management practices. This review explores current literature on PEXG to assess the safety and efficacy of currently available surgical techniques, and discusses clinical considerations on the diagnosis and management of the disease. A PubMed and Google Scholar search identified 2271 articles. These were reviewed to exclude irrelevant or duplicate data. A total of 47 studies reporting specifically on PEXG were retained and analyzed. One of the most significant ophthalmic consequences of pseudoexfoliative (PEX) syndrome is the compromising of the blood-aqueous barrier resulting in the leakage of inflammatory cytokines and extracellular matrix material into the anterior chamber. Considering the high risk of developing PEXG and the aggressive nature of this type of glaucoma, accurate and timely diagnosis of PEX is critical. Therefore, systematic attentive examination for PEX deposits is crucial. Patients diagnosed with PEX need frequent glaucoma assessments. Patient information is key to improving compliance. Gonioscopy and diurnal tension curves or 24-hour intraocular pressure (IOP) monitoring are integral part of the diagnostic work-up and risk-assessment of PEXG. Because of the lability of IOP in PEX, clinical decisions on the basis of single IOP measurements should be avoided. Cataract extraction was shown to provide persistent IOP-lowering effect in the order of 10% in PEXG. A number of other surgical options may offer wider IOP reduction, and both XEN 45 gel stents and angle-based glaucoma procedures were suggested to achieve better outcomes in PEXG than in primary open-angle glaucoma. Yet, more significant IOP reductions may be achieved with filtering surgery or glaucoma drainage device. Same day postoperative IOP monitoring is recommended to treat the frequent IOP spikes following surgery, and more aggressive anti-inflammatory therapy may reduce the rates of postoperative adverse events in PEXG. Specific studies of the surgical management of PEXG remain scarce in the medical literature, and more long-term and comparative studies are warranted to define more robust recommendations.

Совершенствование численных методов расчета контактных напряжений при холодной прокатке полосы

The influence of a contact surface shape of the deformation zone during cold rolling of a band on the rolling force subject to parameters of the strain strengthening curve of billet material and band tension has been studied by numerical methods. The comparison of the obtained results and well-known ones allowed one to set that in case of the presense of strain strengthening, the replacement of the arc of contact by the chord resulted in a decrease in calculated force of rolling, whose value depends on the presence of the fore tension and the back tension and parameters of strain strengthening of metal.

Equal Load-Carrying Design of Lapped Joints of Al–Cu Dissimilar Materials

In order to avoid the adverse effects of additional moment and stress concentration of traditional lap joints, a new lap joint was put forward, according to the concept of “equal load-carrying”. Through static analysis and brazing characteristics consideration, the equal load-carrying design method of Al–Cu lap joint based on brazing method was established. Through three types of brazing, the relationship among two fracture modes, brazing process and static tension curve of lap joint, was analyzed. The results demonstrated that the selection of solder was required to simultaneously meet the requirements of brazability and mechanical properties. A certain relationship existed between the fracture mode of the lap joint and the static tensile curve, while the segments of the static tensile curve corresponded to the fracture paths of the two fracture modes. When the brazing holding time was quite short, the interface bonding was poor, while the bearing capacity of the joint was low; when the holding time was suitable, the bearing capacity of the joint reached the corresponding highest, while the fracture mode conformed to the equal load-carrying design; when the brazing holding time was quite long, the bearing capacity of the joint remained at a high level, but the fracture mode was the same as the holding time was quite short.

Homogenized pouch cell material modelling and a comparison study

Simulation of the mechanical response of lithium-ion battery cells is preferably over experimental due to the explosive nature of them. There are several mechanical modelling methods for representing pouch cells; this study introduces a modified homogenized model. The model uses mechanical responses of layers from literature to establish an average behavior of a pouch cell. Data is normalized, then unified tension and compression stress-strain curves are gathered. These properties are used to build a homogenized pouch cell model by using a tension and compression plasticity model. A stress state dependent failure model (GISSMO) is utilized to demonstrate the damage of cell. Finally, experimental studies from literature are employed for validation. As a result, the model simulates peak forces of all experimental studies with a very low deviation. Homogenizing pouch cell with the proposed approach eliminates modeling detail without compromising the overall mechanical response of the cell. The model is seen to be suitable for applications that do not require a precise mechanical response, such as a battery module or pack analysis.

Dynamic surface properties and dilational rheology of acidic and lactonic sophorolipids at the air-water interface

This study analyzes the equilibrium and dynamic surface tension curves of acidic and lactonic sophorolipids (SLs). It also investigates the dilational properties of the surface adsorptive film. Given their high hydrophobicity, lactonic SLs have lower surface tension and critical micelle concentration (CMC) than acidic SLs. As cNaCl increases, the CMC values and the corresponding surface tension (γcmc) of acidic and lactonic SLs decrease gradually. For dynamic surface properties, lactonic SLs have a high diffusive rate from the bulk phase to the subsurface. At 0.05 CMC, the initial adsorption of acidic and lactonic SLs is diffusion-controlled. As csurfactant increases, the values of diffusion coefficient (D) show a downward trend, and the mechanism is mixed kinetic diffusion. Adding NaCl increases the D values of acidic and lactonic SLs, and the influence degree for acidic SLs is more considerable than that for lactonic SLs.As frequency (ω) increases (0.005∼0.5 Hz), the dilational elasticity increases, and the phase angle decrease. The dilational elasticity of acidic and lactonic SLs shows a low-frequency dependence. Compared with acidic SLs, lactonic SLs have better dynamic surface properties, which decrease the gradient of interfacial tension because of the interface deformation. Consequently, the lactonic SLs exhibit a relatively small dilational elasticity. At 0.1 Hz, the dilational elasticity of acidic and lactonic SLs reaches the maximum values at 0.05CMC and 0.075CMC, respectively. When csurfactant rises near CMC, the phase angle increases obviously, and the dilational elasticity further decreases. This result is attributed to the fast exchange of surfactant molecules between the interface and the micelles.

Tearing analysis of PVC coated fabric under uniaxial and biaxial central tearing tests

In this study, detailed uniaxial and biaxial central tearing tests of a type of PVC coated polyester fiber fabric for buildings were carried out. The characteristics of the damage morphology, the formation of the triangle area at the crack tip, crack propagation, and failure modes during the entire tearing process were studied. The influence of crack orientation, crack length, and load ratio on tearing behaviors were analyzed, and it was found that the two parameters of crack orientation and length could be combined into a single variable of the number of cutting-off yarns in the direction perpendicular to crack propagation. For the uniaxial central tearing test, four widely used theoretical models were used to fit the experimental results, which led to the conclusion that Thiele’s empirical formula was the most suitable theory for predicting the tearing strength of PVC fabrics. Finally, the strain of all yarns across the crack section before and at the moment of crack propagation was recorded by the DIC equipment, and the load borne by each yarn was calculated based on the uniaxial tension curve of this material. In this way, the strain and load distributions were obtained for the first time, from which it was observed that the maximum strain almost always concentrated in the del-zone at crack tips, and the number of cutting-off yarns significantly affected the strain distribution. Specifically, the more yarns were cut off, the more difficult it was for other yarns far from the crack to exert their load-carrying capacity.

Causes of, and countermeasures to, increased ventilatory drive in tetraplegia.

Causes of, and countermeasures to, increased ventilatory drive in tetraplegia.

Estimation of Cold Roll Forming Characteristics of Wrought Magnesium Alloy with Tension-Compression Asymmetry

In recent years, the movement for banning the sale of gasoline cars and diesel vehicles, especially in Europe, and allowing only electric passenger cars has been accelerated. For examples, Germany’s federal council, the Bundesrat, has passed a resolution calling for a ban on combustion engine cars by 2030. If the ban were to go through, German citizens would only be permitted to purchase electric or hydrogen-fueled cars. In Norway, until 2025 there is a movement for legislation prohibiting the registration of new gasoline passenger cars and diesel cars. Beginning in 2025 in the Netherlands, a bill prohibiting the sale of new cars gasoline and diesel vehicles was submitted to Congress. Under the circumstances, the demand for light-weight products for automotive industries has increased due to global trends in environmental preservation. Although demands for magnesium has risen dramatically, production of magnesium alloy sheet still remains at a very low level. This study seeks to establish a guideline for roll design in the roll forming of wrought magnesium alloys to extend practical use of roll-formed products of wrought magnesium alloys. A three-dimensional elasto-plastic analysis by the finite-element method has been conducted to express exact roll-forming behavior of wrought magnesium alloys that have different stress-strain curves in tension and compression. Simple V-sections were formed by a tandem six-stand roll forming machine to demonstrate the effectiveness of the simulation methods with different stress-strain curves in the case of tension and compression. Also, spring-back analysis has been performed to investigate the exact cold roll-forming phenomenon for wrought magnesium alloy sheets.

Surface tension of supercooled graphene oxide nanofluids measured with acoustic levitation

The surface tensions of graphene oxide nanofluids of five mass concentrations were measured by the oscillation droplet method in an acoustic levitator. The oscillation information of the suspension droplets was obtained by combining acoustic levitation with image recognition technology, and a shape correction coefficient a was introduced to modify the Rayleigh equation. Over the temperature ranging from − 7 to 10 °C, the surface tension of the graphene oxide nanofluids increases with increasing mass concentration and decreases with increasing temperature. Compared with the surface tension changes caused by an increase in the mass concentrations of nanofluids from 0.08 to 0.12% at − 7 °C, the surface tension slowly increases from 79.144 to 80.664 mN m−1 when the mass concentration increases from 0.02 to 0.08%. The change rate of the surface tension with temperature is linear in both supercooled and non-supercooled states. For nanofluids with a mass concentration of 0.02%, the values are − 0.185 and − 0.186, respectively, which are basically the same. However, with an increase in mass concentration, the surface tension increases abnormally in supercooled state. For nanofluids with mass concentrations of 0.05% and 0.08%, the curve of the surface tension has an inflection point at − 1.0 °C, while for mass concentrations of 0.10% and 0.12%, the inflection point is at 1.0 °C. All inflection points are distributed around the triple point temperature of water.

Constitutive modeling of polymers accounting for their hyperelasticity, plasticity, creep and viscoelastic relaxation

The hyperelastic Yeoh model has been generalized to account for creep, plasticity and viscoelasticity of polymers. The general tensorial model developed is applied to several rheometric situations: the tensile test used to measure the stress-strain curve in tension, as well as the creep and recovery tests. The resulting equations are compared to the experimental results acquired in the present work for several monolithic synthetic fibers used as specimens. The comparison revealed that the proposed phenomenological rheological constitutive equation is capable of reproducing the experimental data with a uniformly valid set of physical parameters. Moreover, it was possible to accurately predict the residual plastic deformation of the fibers.

Study on the surface activity and aggregation behavior of a polyether surfactant for acidification

Four kinds of biological phenolamine resin block ethers (BPPC) surfactants with different molecular weights were synthesized from biological phenol, formaldehyde and polyvinyl polyamines. The structure of BPPC was characterized by Ft-ir and H NMR. The surface properties of BPPC polyether surfactant and the change curve of surface tension with concentration in aqueous solution at different temperature were studied by surface tension method. The results showed that the critical micelle concentration (cmc) of BPPC and the γcmc increased with the increase of EO content. With the increase of molecular weight, number of branched chains and length of branched chains, cmc and γcmc decreased. The thermodynamic calculation results show that BPPC shows enthalpy/entropy compensation during micellization in aqueous solution. The compensation temperature T was all (300±2) K, and with the increase of molecular weight, number of branched chains and length of branched chains, the stability of BPPC formed in aqueous solution was enhanced.

Using the Water Drinking Test as an Alternative to Modified Diurnal Tension Curve in Assessment of Short- Term Intraocular Pressure Fluctuation

Using the Water Drinking Test as an Alternative to Modified Diurnal Tension Curve in Assessment of Short- Term Intraocular Pressure Fluctuation

Effect of surfactants on adsorption behavior of nanoparicles at gas-liquid surface

Silica nanoparticles (NPs) are more and more useful in many engineering areas, but the dynamic behaviors of adsorption of NPs at surface are not clear, especially when there exist surfactants on the surface. The modified NPs with the nonionic dimethyl silane are partially hydrophobic, and in this paper, the surface behavior is investigated which is determined by interfacial tension and surface compression modulus. It is concluded that the dimethyl silane coverage, the brine salinity and the surfactant would affect the NPs’ adsorption. Higher salinity in brine or higher dimethyl silane coverage causes lower steady state surface tension, which is related to the hydrophobicity and adsorption amount of NPs at the surface. When the cationic surfactant concentration is lower than critical micelle concentration (CMC), the surface tension of mixture system is a little bit higher than cationic surfactant’s. Cationic surfactant can be adsorbed at NPs’ surface to change the hydrophobicity based on the electrostatic attraction, and then some surfactants are dissolved in liquid phase together with NPs, while the anionic surfactant will not do so. In the shrinking droplet process, the surface tension of the NPs with 1.5 μmol/m<sup>2</sup> dimethyl silane decreases from ~59 mN/m at the steady state to ~50 mN/m, which proves that the NPs’ adsorption density can be higher even after infinite long time equilibrium due to the repulsive force between the NPs. Besides, the curve of interfacial tension (IFT) versus surface area shows three parts with different declining slopes. In the first part, the relatively low adsorption of NPs at the surface means weak interaction between NPs. Then in the second part, due to the irreversible adsorption, the spacing between NPs decreases with adsorption amount increasing and surface area lowering, so the increasing of NPs’ interaction leads to high surface compression modulus. After that, the IFT curve keeps flat since the NPs assembly reaches to the closest peck. With the increase of NPs’ hydrophobicity, the compression modulus increases up to ~70 mN/m, which satisfies the Gibbs criterion to resist coarsening of the foam or emulsion. However, for the mixing system, increasing surfactant concentration leads to a lower surface tension at steady state, then the surface tension difference or compression modulus decreases too. Finally, we find that the compression modulus order from high to low is as follows: NPs, cationic surfactant-NPs, anionic surfactant-NPs, surfactants. This investigation is meaningful for accounting for the enhancement of foam or emulsion stability with NPs affected by salinity and surfactant.