Thinning Phenomenon Research Articles

A highly efficient method of thermal stress bending with non-thinning and grain refinement

Thickness thinning is one of the processing defects that tend to occur in traditional stamping or mechanical bending of plate (tube). In the field of high mechanical performance requirements (such as pressure vessel), the thinning phenomenon can not be ignored. Thermal stress forming has excellent characteristics of forming without thinning, but the forming angle of the method is small, thus limiting the promotion and application of the process in the field of forming. To solve the problem, an applying baffles method (ABM) to both ends of workpiece based on thermal stress forming is proposed. A coupled thermodynamic model about ABM is developed, and the bending angle and deformation mechanism are investigated. Finally, the grain size and thickness of the deformed region are observed. The results show that ABM can increase the bending angle by 14.26 times compared with the traditional method. The bending angle of ABM is determined by both the temperature difference and the baffle, and the baffle plays a major role. Compared with the traditional method, ABM can obtain smaller grain size and increase the microhardness by 1.39 times. ABM can increase the thickness of the upper surface by 121 μm and the thickness of the lower surface by 47 μm. For upper surface thickening, ABM is 9.31 times greater than the traditional method. This thickening will effectively avoid thinning problems in stamping (mechanical bending). This method can make thermal stress forming a high-quality process in the forming field.

Construction of 3D printable Pickering emulsion gels using complexes of fiber polysaccharide-protein extracted from Haematococcus pluvialis residues and gelatin for fat replacer

Structural fat replacers that can meet the requirements of various forms of reduced-fat foods are essential for the application of fat replacement, and emulsion gels emerge as a potential alternative for fat replacers. In this study, fiber polysaccharide-protein extracted from Haematococcus pluvialis residues (FPHRs) formed FPHRs-Gelatin complexes with gelatin. Fourier transformed infrared spectroscopy confirmed the formation of hydrogen bonds between FPHRs and gelatin, the secondary structure order of the protein was enhanced. Three-phase contact angle determination showed that the contact angle of FPHRs-Gelatin complexes was 104°–114°. By exploring the effect of FPHRs concentration, gelatin concentration, and oil-water ratio on the emulsion gels, the Pickering emulsion gels were formed when the FPHRs and gelatin concentration were 2 wt% and 3 wt%, respectively. What's more, these emulsion gels had shear thinning phenomenon, low frequency dependence as well as excellent thixotropy when the oil-water ratio was 0.6, which indicated that they had strong structural support and great recovery capacity to be used as 3D printed materials. The 3D objects printed by the FPHRs-Gelatin complexes emulsion gels had superior print resolution and shape fidelity. This study provides a new type of emulsion gel with structure that can be used as an ideal fat replacer in food processing, the construction of a new 3D emulsion gel material is of great significance for broadening the applications of gelatin-based gels and microalgal food.

Characterization of magnetorheological fluids based on capillary magneto-rheometer

Magnetorheological fluids (MRFs) are a class of smart magnetic controlled materials whose rheological properties can be controlled by a magnetic field. These materials have advantages of short response time, high dynamic range and low energy consumption. Due to their excellent properties, MRFs have a widely application potential in the field of impact mitigation. As the shear rate dependent viscosity of MRFs is astonishing for the shear thinning effect, thus it is crucial to study the rheological properties cross a wide range of shear rates for guiding the design and application of MRFs based adaptive impact absorbers. Commercial rotational rheometers are usually used to test the rheological properties of MRFs, but their range of measuring shear rates are limited. Commercial capillary rheometers are designed to measure the rheological behavior over a wide range of shear rates, but they’re usually lack of ability to measure with magnetic field. In order to study the rheological properties of MRFs under higher shear rate and applied magnetic field, a lab-made speed-controlled capillary magneto-rheometer is developed in the presnt work; The expressions for equivalent shear rate and apparent viscosity of MRFs under the dimensional constraint of the set-up are derived. In addition, the theoretical expression of shear rate of MRFs is modified by Rabinowitsch correction. Then, the rheological properties of three particle volume fractions (10%, 15%, and 20%)of MRFs with different magnetic field strengths (6 mT, 13 mT, 20 mT, and 25 mT)are tested and analyzed, and the rheological characteristic curves of MRFs with shear rate range of 101s−1–105s−1 are obtained with the normalized characterization using Mason number. According to the experimental results, the MRFs show an obvious shear thinning phenomenon as shear rate increases, and in the Mason number based normalized characterization, the curves of different particle volume fractions are collapse to a master curve.

On the Magnetohydrodynamic (MHD) Peristaltic Flow of a Hyperbolic Tangent Fluid in a Tapered Asymmetric Channel

We have considered the peristaltic mechanism of incompressible viscous hyperbolic tangent fluid with the impact of uniform magnetic field. The tapered asymmetric channel is assumed to be designed due to a peristaltic wave train on the non uniform walls taking different amplitudes and phase. This model anticipates the shear thinning phenomenon very precisely and are being used frequently in laboratory experiments and industries. Here we consider the Reynolds number to be small enough and wavelength for simplification of two dimensional equations of a hyperbolic tangent fluid. The non-linear governing equations for the tangent hyperbolic fluid are solved by utilising Regular perturbation methodology. The exact solutions for the pressure gradient and pressure rise are determined analytically. Its behaviour is discussed computationally with reference to different physical parameters.

Microstructures and mechanical properties of non-thinning and penetrating friction stir welded 2219-T6 aluminum alloy

The aim of this paper is to offer a novel friction stir welding technique to achieve non-thinning and lack of kissing bond welds with excellent mechanical properties. In the conventional friction stir welding (CFSW) process, a certain size spindle tilting angle and a shoulder plunge depth were applied in order to obtain high-quality welds. However, what was the reason for the thinning phenomenon of weld and thus the weakening of weld bearing capacity? The reduction of spindle tilting angle and shoulder plunge depth was likely to cause the welding tool not being able to reach the weld root, and thus, it was engendered for the kissing bond or the absence of complete penetration. In the present study, a novel welding tool with large size shoulder and Archimedes spiral groove was designed in order to achieve non-thinning and lack of kissing bond welds. The microstructures and mechanical properties of the joints obtained by the non-thinning and penetrating friction stir welding (NTPFSW) and the penetrating friction stir welding (PFSW) had been analyzed in detail. Compared with PFSW, NTPFSW had a narrow shoulder-affected zone. The thickness of NTPFSW joint is 0.1 mm thicker than that of BM and 0.22 mm thicker than that of PFSW joint. The stir zones (SZ) obtained by the PFSW and NTPFSW were both composed of fine equiaxed grains. The grains in the upper part of NTPFSW joint were larger in size, and the number of precipitates (θ’ phase) was less. NTPFSW completely eliminated the weld thinning phenomenon, and the tensile properties were 365 Mpa, which is 2% higher than that of PFSW.

Colloidal exchange flow in ducts

Buoyancy-driven exchange flow, i.e. drainage of a heavy colloidal suspension by an immiscible light pure fluid in a vertical duct, is studied analytically. A lubrication model is developed for two-dimensional channel and axisymmetric pipe geometries. The outcome transport equations are solved numerically to capture the effect of important governing dimensionless parameters: Péclet number, precursor film thickness, Reynolds number, mixtures’ viscosity ratio, initial volume fraction of hard-sphere particles, particles concentration within the precursor film, and capillary number. Recent study of colloidal film flow over a flat surface reveals interface thinning over time due to diffusion impact on suspension viscosity. However, the current model suggests that there is no such thinning phenomenon observed for colloidal flows within confined geometry unless in the absence of surface tension. The extent of the mixed particle zone along the duct grows as the Péclet number is decreased. Precursor film thickness is found to decrease the capillary ridge height forming at heavy suspension front. Either an increase in the Reynolds number or a decrease in light-to-heavy-fluid viscosity ratio extends the interpenetration rate of mixtures. As the bulk volume fraction of particles is increased close to 50 %, interesting secondary fronts emerge within the flow that coincide with the range where the diffusion coefficient is minimized. The heavy suspension layer drains slightly faster when the gradient in particle concentration between the bulk and precursor film regions is maximum. Finally, the non-monotonic impact of surface tension on the extent of mixtures’ exchange zone is uncovered via simulations conducted at various capillary numbers.

Structure, physicochemical characterisation and properties of pectic polysaccharide from Premma puberula pamp.

Food manufacturers are increasingly demanding novel natural emulsifiers. In the current study, physicochemical properties of pectin were obtained from Premna puberula Pamp. (PP) were studied systematically to develop natural emulsifiers further. The structural characterisation was performed using gas chromatography-mass spectrometry, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and nuclear magnetic resonance. We discovered that PP was high-methoxy pectin with rich arabinose and galactose side chains (Ara + Gal)/Rha = 3.27 and Mη = 292.25 kDa) and was mainly amorphous material with a small amount of microcrystalline structure. Moreover, PP exhibited an excellent thermal stability and shear thinning phenomenon, a characteristic of non-Newtonian fluids. It exhibited significantly considerable emulsification performance. Additionally, its gelling properties and antioxidant effects were better than commercial pectins (citrus pectin and apple pectin). Therefore, P. puberula containing homogalacturonan (32.57%) and rhamnogalacturonan-I (36.45%) is a potential source of natural emulsifier and rheological modifier, which can be used in a variety of products.

Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

New bio-based polyester with excellent spinning performance: poly(tetrahydrofuran dimethanol-co-ethylene terephthalate).

With the excessive consumption of fossil energy, technologies that transform bio-based resources into materials have received more and more attention from researchers in recent decades. In this paper, a series of poly(ethylene 2,5-tetrahydrofuran dimethyl terephthalate; PEFTs) with different components were synthesized from 2,5-tetrahydrofuran dimethanol (THFDM), terephthalic acid (TPA), and ethylene glycol (EG). Their chemical structures and compositions were determined by FTIR, 1H NMR, and 13C NMR. With the increase in THFDM content, the crystallization, T m, and tensile strength of PEFTs gradually decrease because the introduced THFDM breaks the order of molecular chains, while the thermal stability and T g remain stable. PEFTs seem to present a significant shear thinning phenomenon, which was indicated by the rheological test. Electrospinning technology was used to explore the spinnability of PEFT; it was found that PEFTs have better spinning performance than PET. In addition, due to the good hydrophobicity and porosity of PEFT nanofiber films, they have potential application value in the manufacture of hydrophobic nanofiber and filter films.

Advanced Prediction Model for Pipe Wall Thinning Tendency by Flow Accelerated Corrosion at Junction Piping

Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate, and residual lifetime of piping based on wall thickness measurements. However, noticeable case of the wall thinning occurred in branch and junction piping (tee tube). There is a problem to manage the wall thickness beneath reinforcing plate of the tee tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. In this study, numerical analysis for the tee tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. It was found that a localized wall thinning distribution occurs in the area where the reinforcing plate of the tee tube exists. And this tendency is affected by Reynolds number. In previous studies, a model was introduced to predict this trend, but in this study, the model was improved to take into account the effect of the Reynolds number.

Pickering emulsions stabilized by β-cyclodextrin and cinnamaldehyde essential oil/β-cyclodextrin composite: A comparison study

Here, a cinnamaldehyde essential oil (CEO)/β-Cyclodextrin (β-CD) composite with a high embedding rate (91.74 ± 0.82%) was prepared. Its structure was characterized by Fourier transform infrared spectrometer (FT-IR) and X-ray diffractometer (XRD). Pickering emulsions prepared by β-CD and CEO/β-CD at different concentrations (1–5%) were comparatively investigated. The CEO/β-CD emulsions had better storage stability. Rheological results confirmed the emulsions were all gel-like elastic emulsions and had shear thinning phenomenon. Fluorescence microscopy and scanning electron microscopy (SEM) results confirmed that the most of excessive β-CD was adsorbed on the surface of emulsion droplets as crystals, formed thick protective shell in β-CD emulsions, while the most of excessive composites were distributed in the aqueous phase forming a stable network structure in CEO/β-CD emulsions. It caused these two emulsions had different rheological properties, and different changing trends in droplet size.

Exploring the feasibility of developing novel gelatin powders from salted, dried cannonball jellyfish (Stomolophus meleagris)

Cannonball jellyfish, often commercialized as salted, dried jellyfish (SDJ), is an emerging fishery in the USA and a great source of collagen, which can be utilized for developing novel marine gelatin powders. The aim of this study was to determine the feasibility of producing gelatin powders with gelling properties from SDJ using a mild acid hydrolysis and freeze-drying procedure as well as to evaluate their physico-chemical properties. The findings revealed that the resultant gelatin powders had a moisture (g/100 g, dry basis, d.b.), crude protein (g/100 g, d.b.), ash content (g/100 g, d.b.) and water activity values of 4.82, 29.54, 56.61, and 0.09, respectively. Sodium, Al, and S were the main minerals detected in the jellyfish gelatin powders, which were agglomerated and had irregular morphologies with a mean particle size of 12.8 μm. Gels prepared with 5, 6.67, and 10% (w/v) jellyfish gelatin powder had Bloom values lower than 4.2 g; melting temperatures between 15.09 and 16.12 °C and their rheological behavior was effectively characterized by the Herschel-Bulkley flow model, which revealed non-Newtonian behavior and shear thinning phenomena. Higher apparent viscosities, yield stress, and consistency index values were observed in the gels prepared at higher concentrations of jellyfish gelatin powders and at lower evaluated temperatures. This study illustrates (for the first time) the feasibility of producing novel marine gelatin powders from SDJ, which have the potential to be used as gelling, thickening and/or binding agents in several food applications.

The Effect of Cellulose Nanocrystal Suspension Treatment on Suspension Viscosity and Casted Film Property.

Cellulose nanocrystals (CNCs) have attracted significant interest in different industrial sectors. Many applications have been developed and more are being explored. Pre-treatment of the suspension plays a critical role for different applications. In this study, different pre-treatment methods, including homogenization, ultrasonication, and mixing with a magnetic stirrer were applied to a CNC suspension. After treatment, the rheological behaviors of the treated CNC suspensions were characterized using a rotational viscometer. The treated suspensions were then used to cast films for characterization by ultraviolet-visible (UV-Vis) and Fourier transform near-infrared spectroscopy (FT-NIR). All the CNC suspensions demonstrated a shear thinning phenomena. Homogenization or ultrasonication significantly decreased the suspension viscosity compared with the suspension mixed by a magnetic stirrer. The viscosity of CNC suspension changed with time after treatment and settlement of treated CNC suspensions in room conditions increased the viscosity dramatically with time. Different UV and visible light interferences were observed for the CNC films generated from suspensions treated by different methods. The degree of crystallinity of the CNC films evaluated by FT-NIR showed that the film from suspension treated by homogenization and ultrasonication has the highest degree of crystallinity. Pre-treatments of CNC suspension affected the suspension viscosities and formed film properties.

Peristaltic Transport of Hyperbolic Tangent Fluid in a Tapered Asymmetric Channel

Objectives: The study intends to investigate the problem of peristalsis transport of hyperbolic tangent fluid in a tapered asymmetric channel. Methods: The two-dimensional equations of a hyperbolic tangent fluid have been simplified under the suspicions of low Reynolds number and long wavelength approximations. The reduced equations are solved by using standard perturbation technique. The numerical results obtained are presented in the graphical form for various values of physical parameters and are discussed. Findings: It is showing that for the larger values of non-uniform parameter, pressure rise diminishes and the axial velocity diminishes at the core part of the channel and increases at the right and left side of the channel for the increasing values of non-uniform parameter. Applications: Hyperbolic tangent fluid model anticipate the shear thinning phenomenon very accurately and are being used mostly in laboratory experiments and industries. Keywords Reynolds number, Hyperbolic tangent fluid, peristaltic transport, tapered asymmetric channe

Economical improvement on the performances of a soybean flour-based adhesive for wood composites via montmorillonite hybridization

Bond performance and cost are key factors that significantly affect the commercial utilization of soybean-based adhesives in wood composites. A desired soybean-based adhesives with reduced adhesive cost and improved bond performance and technological applicability was developed in this study by organic-inorganic hybridization through combining montmorillonite clay (MMC) with thermochemically modified soybean flour (TMSF) for better crosslinking efficiency. The results showed that the species of inorganic filler and the level of MMC as filler had important effects on the performance of the modified adhesive. The soybean-based adhesive with 20% MMC addition achieved a 9.0% decrease of adhesive cost along with a 24.5% increase in weather resistance and improved technological applicability (in terms of the decreased viscosity and alleviated shear thinning phenomenon), which was suitable for producing outdoor-use plywood. The improved water resistance of the TMSF-based adhesive was attributed to the reinforcement from the organic-inorganic hybridization of adhesive of partially intercalated MMC, the good dispersion of MMC particles in adhesive and the better crosslinking efficiency of TMSF to crosslinker than native soybean flour. Thus, this novel strategy could effectively expand the applications of TMSF-based adhesives in environmentally friendly wood composites.

Experimental Study on Permeability Coefficient in Layered Fine Tailings under Seepage Condition

Nearly half of the tailings dams in China are in a state of high-security risks and overservice, and the safety of these tailings dams has always been a concern for relevant scholars. The seepage characteristics of tailings are one of the essential factors affecting the safety of tailings dam. Now, due to the improvement of mineral processing technology, there are many fine tailings dam; the study of the seepage characteristics of the tailings dam is no longer applicable. Fine-grained tailings form uneven deposition in these tailings dams, resulting in the permeability of tailings not conforming to the previous law. Therefore, it is of great significance to study the permeability of fine-grained tailings with uneven deposition. In this paper, the physical model of the simulated tailings dam is established to study the influence of the dry beach slope on the distribution and deposition law of fine tailings during discharge. The test results show that the average particle size of tailings decreases along the length of dry beach, showing the phenomenon of coarsening upstream and thinning downstream. Then, based on the data of fine tailings deposition, the variation characteristics of the permeability coefficient of layered tailings under stable and unstable seepage conditions are studied. The test results show that the variation process of tailings permeability coefficient can be divided into four stages: rapid compaction stage, slow compaction stage, failure stage, and stable stage. Under stable and unstable seepage conditions, the permeability coefficients of unstratified tailing sand are about 10% and 15% higher, respectively, than those in the initial state. The permeability coefficient of layered tailings formed by uneven settlement changes more obviously, which is about 12% and 20% higher than the initial state.

On the thinning variations in hydrostatic forming of sheet metal

In sheet metal forming, thinning phenomenon is one of the most concerned topics to ameliorate the final quality of the manufactured parts. The thinning variations depend on many input parameters, such as technological parameters, geometric shape of die, workpiece’s materials, and forming methods. Hydrostatic forming technology is particularly suitable for forming thin-shell products with complex shapes. However, due to the forming characteristics, the thinning variations in this technology are much more intense than in other forming methods. Therefore, in this paper, an empirical study is developed to determine the thinning variations in hydrostatic forming for cylindrical cup. Measurement of thickness at various locations of deformed products are conducted to investigate the thickness distribution and determine the dependence of the largest thinning ratio on the input parameters (including the blank holder pressure, the relative depth of the die and the relative thickness of the workpiece). The results are expressed in charts and equation which allow determining the effect of each input parameter on the largest thinning ratio.

Numerical investigation of plastic flow and residual stresses generated in hydroformed tubes

During tube hydroforming process, the friction conditions between the tube and the die have a great importance on the material plastic flow and the distribution of residual stresses of the final component. Indeed, a three-dimensional finite element model of a tube hydroforming process in the case of square section die has been performed, using dynamic and static approaches, to study the effect of the friction conditions on both plastic flow and residual stresses induced by the process. First, a comparative study between numerical and experimental results has been carried out to validate the finite element model. After that, various coefficients of friction were considered to study their effect on the thinning phenomenon and the residual stresses distribution. Different points have been retained from this study. The thinning is located in the transition zone cited between the straight wall and the corner zones of hydroformed tube due to the die–tube contact conditions changes during the process. In addition, it is clear that both die–tube friction conditions and the tube bending effects, which occurs respectively in the tube straight wall and corner zones, are the principal causes of the obtained residual stresses distribution along the tube cross-section.

In situ synthesis of Mn3O4/graphene nanocomposite and its application as a lubrication additive at high temperatures

Graphene-based nanoadditives are widely used in the field of lubrication due to their two-dimensional (2D) structure and excellent mechanical properties. However, researches on the high-temperature performances and rheological properties of graphene-based lubricant are still insufficient. In this study, Mn3O4/graphene (Mn3O4#G) nanocomposite is synthesized in situ by hydrothermal method, and it is used as nanoadditive in lithium grease. When the concentration of Mn3O4#G is 0.03 wt%, the coefficient of friction (COF) and wear scar depth can be reduced by 35% and 76% (100 °C, 150 N), respectively. In addition, when the temperature is 120 °C, the grease with 0.03 wt% Mn3O4#G can still achieve stable lubrication performance. On the contrary, pure grease (P.G) has already failed to lubricate at the temperature of 80 °C. According to the computational fluid dynamics (CFD) results, the shear thinning phenomenon of the grease can be observed. And the central suction effect occurring in the friction area will be conducive for the nanoadditives to enter the friction contact area.

Preparation and foaming behavior of poly (lactic acid)/poly (butylene succinate)/cellulose fiber composite for hot cups packaging application

This research aims to prepare foamed hot cups and lids from cellulose fiber (CF)-reinforced biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blend composites for improved strength and thermal resistance. The effects of adding cellulose on physical, chemical, thermal, and mechanical properties of PLA/PBS/CF were investigated. The composite foams were prepared by twin screw extruder. The results revealed that the viscosity decreased as cellulose fiber was added. All the prepared composites show a shear thinning phenomenon, which is caused by orientation of fibers in the flow direction. A lower content of the CF in the PLA/PBS matrix manifested itself by lower melt viscosity in the whole range of shear rates. The tensile strength, tensile modulus, and percentage of elongation at break increased when the amount of added cellulose fiber increased. The crystallinity of composite foams analyzed by X-Ray Diffraction (XRD) showed higher degree of crystallinity when adding cellulose fiber. The thermal degradation temperature of PLA/PBS/CF composites measured by Thermal Gravimetric Analysis (TGA) showed higher than PLA. The conclusion of this research is that adding cellulose fiber 15 phr improved mechanical and thermal properties.