Search

Abstract: Tungsten Heavy Alloys (WHA) are finding increasing applications in the kinetic energy penetrators. For developing the accurate simulation models of deformation processes on WHA, it is essential to properly understand the flow stress behavior of these alloys considering the combined effects of strain, strain rate and temperature. This paper focuses on developing various constitutive models for 92.5 W-5.25Ni-2.25Fe alloy by using the flow stress data at six different temperatures (298 K, 573 K, 773 K, 973 K, 1173 K, 1373 K) and three different strain rates (1600, 2500, 4000 s −1 ). Four constitutive models, namely, modified Johnson-Cook (m-JC), modified Zerilli-Armstrong (m-ZA), modified Arrhenius (m-Arr) and modified Khan-Huan-Liang (m-KHL) models have been developed to predict the flow behavior. The predictions of these constitutive models have been compared with the experimental values using statistical measures like correlation coefficient, average absolute error and its standard deviation. Based on these statistical measures, m-Arr and m-ZA models have been found to be better models for predicting the flow stress values. In addition, using the flow stress curves, the strain rate sensitivity values have been computed for determining the efficiency of power dissipation and instability parameter for the deformation process. Superimposing the efficiency map over the instability map, the processing maps have been developed for better understanding of response of a material to the imposed experimental parameters. [ABSTRACT FROM AUTHOR]

Influence of roller and ball mill grinding technology applied for sucrose particles in a lipophilic suspension was investigated considering both particle properties and suspension's flow behavior. Especially particle surfaces after grinding were analyzed using a novel approach by combining atomic force microscopy (AFM) and AFM-local thermal analysis (AFM-LTA). This technique is able to characterize local distributions of different surface states on sucrose particles in nano- and microscale by determining local softening temperatures. For the first time, it was possible to demonstrate on molecular level that applied grinding technologies resulted in different surface characteristics with respect to adhesion forces and state of sucrose using AFM-LTA. Differences in flow behavior despite same particle size distributions and solid contents were traced back to the distribution of crystalline and amorphous areas on sucrose particle surfaces. [ABSTRACT FROM AUTHOR]

The flow behaviors in a series of novel gas-solids co-current downflow conical fluidized beds (conical downers; 7 m in height, 0.14 m inlet diameter, 0.02, 0.04, 0.07 and 0.14 m outlet diameters), which are expected to realize a high-density solids holdup along a downer-type pyrolyzer to strengthen the heat transfer efficiency, were systematically investigated by means of a numerical approach. A 2D, transient, Eulerian–Eulerian two fluid model based on the kinetic theory of granular flow with a k-ε turbulence model for gas phase was adopted to simulate the hydrodynamics of the conical downer and explore possibilities of achieving a high density solids holdup in the bed. In order to avoid the different effects of different boundary coefficients on the simulation results, a boundary condition which can realize the adjustment without changing the related parameters was used here. The results demonstrated that the conical downer was beneficial to the enhancement of solids holdup. This was more obvious at U g  = 1 m/s in this study. According to the analysis of the axial distributions of pressure and velocity, the unique hydrodynamics of three axial acceleration regions were characterized, which was different from traditional downer. In addition, it was found that the length of the third acceleration region increased with the increase in gas velocity but decrease in outlet diameter of the conical downer. Also, the conical downer was able to save a large amount of carrier gas and reduce the percentage of carrier gas in the follow-up mixture gas. These results are expected to be a guidance for the design of an efficient downer-type pyrolyzer in a triple-bed combined circulating fluidized bed gasifier. [ABSTRACT FROM AUTHOR]

Flow characteristics downstream of a rotational oscillating cylinder at Reynolds number Re = 300 was investigated. The experiments were conducted using a model cylinder in a recirculating open water channel and the flow field was captured by using the Particle Image Velocimetry (PIV) technique. The model cylinder was set to undergo clockwise-and-counterclockwise rotation at selected angular amplitude (angular amplitude α varying from 0° to 360°) and at the lock-on frequency ratio F r  = 1.0 (where F r  =  f n / f v , the ratio of the forcing frequency f n to the natural vortex shedding frequency f v ). The effects of rotational movement of the cylinder on the near wake downstream of the cylinder were interpreted in terms of the instantaneous vorticity patterns, as well as the time-averaged streamline topology, mean velocity distributions and Reynolds shear stress contours. Based on the observation of the flow patterns and vortex contours, it was deduced that the clockwise-and-counterclockwise rotation produced significant effect on the wake and modified the wake flow structures and vortex shedding patterns. The time-averaged streamline structures appeared to be non-symmetrical about the longitudinal axis of the flow. [ABSTRACT FROM AUTHOR]

Simulated multipass deformation experiments were carried out via torsion testing on a Ti-6Al-4V alloy in the two-phase region under both isothermal and continuous cooling conditions. Flow softening was observed during the isothermal multipass deformation tests as indicated by the evolution of the mean flow stress (MFS). The MFS values increased with interpass time from 2 s to 32 s. Using BSE-SEM characterization techniques, dynamic phase transformation (alpha to beta) and coarsening of the alpha phase took place. The quantitative results indicate that the alpha phase transforms into beta during straining, but it retransforms statically into alpha by amounts that increase with interpass time. The flow softening observed is the net result of softening by dynamic transformation and hardening by reverse transformation. [ABSTRACT FROM AUTHOR]

Background: Study on the synthesis of kojic acid derivatives (KADs) in solvent-free system using scalable reactors and their biological activities is still lacking. Methods: In this study, two types of KADs, were synthesized using saturated-fatty acid [lauric acid (LA)] and unsaturated-fatty acid [oleic acid (OA)] in stirred tank reactor (STR) and fluidized tank reactor (FTR). The yield and biological activities of the synthesized KADs were evaluated and compared. Results: The highest yield of KADs (42.95%) was obtained in the synthesis using OA, with molar ratio of 1:1, enzyme loading of 5% (w/v), temperature of 70°C, using immobilized lipase N435 in STR. However, FTR may provide biocatalyst protection and reusability with reduced loss of KADs yield up to three cycles. In antioxidant assay, the hydroxyl-unsaturated-fatty acid of kojic acid (HUFA-KA) showed better activity as compared to hydroxyl-saturated-fatty acid of kojic acid (HSFA-KA) at concentrations ranging from 125 to 2000 μg/mL. In contrast, HSFA-KA showed better cytotoxicity effect against G361 melanoma cell as compared to HUFA-KA. Conclusion: The yield of KADs obtained in STR was higher than that obtained in FTR. HUFA-KA could be used as potential lipophilic antioxidant while HSFA-KA has the potential to be used to treat melanoma skin disorder. [ABSTRACT FROM AUTHOR]

The flow and friction behaviors of 6061 aluminum alloy (Al6061) at elevated temperatures were investigated to form a B-pillar by hot stamping with Al6061 sheets. The modified Arrhenius and Cowper-Symonds model were developed based on hot tensile tests at temperatures of 350-500 °C and strain rates of 0.01-1 s−1. The coefficients of friction (COF) at temperatures of 300-500 °C were also measured. The tribological test results show that the COF ranged from 0.95 to 1.05 with a loading force of 1 N and from 1.2 to 1.53 with a loading force of 10 N. Finally, hot stamping of a B-pillar using Al6061 sheets with different solution heat treatment temperatures and lubricants was conducted. Stamping experiments show that the B-pillar wrinkled badly and cracked in cold stamping with or without lubricants. The B-pillar also cracked in hot stamping without lubricants, but B-pillars without cracks could be obtained under lubricated conditions. Further finite element simulations with the implementation of Cowper-Symonds constitutive equation and the tested COF values (as references) were used to investigate the crack mechanisms that arise in hot stamping. Simulation results show that the crack was due to adverse friction and large temperature difference between the sidewall and rounded corners caused by non-uniform cooling. Lubrication not only reduces the friction to promote metal flow but also weakens the temperature difference. Thus, parts without cracks can be obtained. [ABSTRACT FROM AUTHOR]

As-extruded AZ31 magnesium alloy samples were compressed at ambient temperature and strain rates of 1000–3000 s −1 . The fracture surfaces of cracked samples, the evolution of microstructures and macrotextures were detected. The received flow curves exhibit an abnormal behavior at strain rates above 1500 s −1 . A strain constitutive model based on strain equivalent principle was applied to analyze the flow curves of the damaged samples. The results indicate that the abnormal flow behaviors of the fractured samples are related to the increasing area of crack surfaces, and kinetic energy during dynamic crack nucleation and propagation. The initiation of the micro-crack also causes obvious flow softening in the cracked samples. The shapes of flow stresses of the intact samples are affected by twinning. [ABSTRACT FROM AUTHOR]

Interrupted hot compression tests were performed on a TiBw/TA15 composite with network architecture to study its flow behavior and microstructure evolution during a two-step deformation process. The microstructure was observed by electron backscatter diffraction (EBSD) and the high-temperature β grain boundaries were reconstructed through several special misorientation angles. The fraction of the primary α (α p ) phase declined during the heat preservation process. The flow stress exhibited a lower value due to softening upon reloading compared to that observed prior to the interruption. In addition, the hold time and deformation temperature were important factors influencing the composition of the matrix phase, and the α p phase disappeared with increasing hold time and temperature. The high-temperature β grains became longer with a larger average aspect ratio when the deformation temperature reached 1283 K. Both TiB reinforcement and the α p phase restrained the growth of β grains, preventing hot deformation at higher temperatures and resulting in longer inter-pass holding times due to the absence of the α p phase. The low strain rates resulted in a significant β phase grain growth because of sufficient time and the lack of constraints. The optimized process parameters, which can provide guidance to actual production, were obtained in this study. [ABSTRACT FROM AUTHOR]

In the previous work, we have reported that small dosages of the polymethylsilsesquioxane (PMSQ) microsphere can effectively improve the performance of the EVA pour point depressant (PPD) and the amount of EVA PPD adsorbed on the microsphere evidently influences the efficiency of the EVA/PMSQ composite particle. To further promote the adsorption of EVA on the microsphere and enhance the efficiency of the composite particle, here, the amino-functionalized PMSQ microspheres with different amino molar ratios (PAMSQ) are first synthesized and characterized. The flow behavior, exothermic crystallization and microstructure of the waxy crude oil undoped/doped with EVA, EVA/PMSQ and EVA/PAMSQ are systemically investigated. Results show that 50 ppm EVA PPD can greatly improve the flow behavior of the oil and small dosages (2.5 ppm) of PMSQ microsphere can significantly improve the performance of the EVA PPD. After the amino-functionalization, the flow improving efficiency of EVA/PAMSQ is further enhanced: the gelation point, G′ , G″ , apparent viscosity and yield stress of the oil sample decrease to a lower value. The best performance is found at adding 50 ppm EVA + 2.5 ppm PAMSQ-2 (with amino molar ratios at 15%). Compared to EVA/PMSQ, the EVA/PAMSQ exhibits a stronger nucleation effect to increase the WAT of the oil sample slightly, and outstandingly modifies the morphology of the precipitated wax crystals into larger and more compact flocs. The amino-functionalization facilitates more EVA PPDs adsorbing and concentrating on the PAMSQ microsphere, causing the formation of the EVA/PAMSQ composite particles. The composite particles provide stronger nucleation effect for the wax precipitation, resulting in larger and more compact wax microstructures and then further improving the flow behavior of the oil. The rheological improving performance of EVA/PAMSQ for the waxy crude oil increases with the increase of amino molar ratio and the efficiency of EVA/PAMSQ-2 reaches the best. When the amino molar ratio is too high (PMASQ-3), the PAMSQ-3 microsphere is unstable in oil phase and aggregates into large particle flocs, which inhibits the EVA adsorption on the PAMSQ-3 microsphere and then weakens the rheological improving efficiency of the EVA/PAMSQ-3 composite particle. [ABSTRACT FROM AUTHOR]

This paper presents an on-going study of light-weight alloy ZK60 magnesium. The uniaxial tensile tests were carried out with strain rate range of (0.0001–1000)/s −1 and with different stress states. Elemental data was identified through an iteration process using finite element analysis. The modified Johnson-Cook (J-C) model was calibrated to describe the flow stress as a function of strain and strain rate. The modified Mohr-Coulomb (M-C) model, considering the effects of strain, stress state and strain rate, was proposed with satisfactorily determined parameters. Compared by the original J-C fracture model, the modified M-C fracture model tracks the fracture behavior more accurately. To complement the macroscale fracture information, fractography reveals the fracture and deformation mechanism in microscale. The agreements between the simulations and tests further confirmed that the modified J-C material model and the modified M-C material model can give a precise estimate of the mechanical and fractural behavior of the ZK60 alloy. [ABSTRACT FROM AUTHOR]

In the hot metal gas forming process, the deformation conditions, such as temperature, strain rate and deformation degree, are often prominently changed. The understanding of the flow behavior of α-Ti seamless tubes over a relatively wide range of temperatures and strain rates is important. In this study, the stress-strain curves in the temperature range of 973-1123 K and the initial strain rate range of 0.0004-0.4 s−1 were measured by isothermal tensile tests to conduct a constitutive analysis and a deformation behavior analysis. The results show that the flow stress decreases with the decrease in the strain rate and the increase of the deformation temperature. The Fields-Backofen model and Fields-Backofen-Zhang model were used to describe the stress-strain curves. The Fields-Backofen-Zhang model shows better predictability on the flow stress than the Fields-Backofen model, but there exists a large deviation in the deformation condition of 0.4 s−1. A modified Fields-Backofen-Zhang model is proposed, in which a strain rate term is introduced. This modified Fields-Backofen-Zhang model gives a more accurate description of the flow stress variation under hot forming conditions with a higher strain rate up to 0.4 s−1. Accordingly, it is reasonable to adopt the modified Fields-Backofen-Zhang model for the hot forming process which is likely to reach a higher strain rate, such as 0.4 s−1. [ABSTRACT FROM AUTHOR]

The radial distribution of liquid velocity in the axial direction of a jet bubbling reactor has been measured by experimentation. Three different typical flow structures controlled by liquid jet, gas bubbling, and liquid jet coupled with bubbling are observed. A tank in series model is established on this basis. Calculated values in each region are in good agreement with measured values in jet, bubbling, and wall effect controlled areas. Axial flow rate, radial exchange rate, and jet controlled volume η are analyzed from energy input aspect under different ug and uj. Simulation results indicate that under the synergetic action of the liquid jet and gas bubbling effect, jet controlled area exhibits a “spindle” structure, and its size decreases with the increase of ug. When gas input power occupies about 67% of total energy consumption, the best synergy of liquid jet and gas bubbling is obtained. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1814–1827, 2018 [ABSTRACT FROM AUTHOR]

The once-through steam generator (OTSG) is an essential equipment with a key position in the primary side and the secondary side usually used in small modular reactors. It is valuable for designers of the OTSG to investigate the flow behavior in the primary side. A three-dimensional (3D) computational fluid dynamics (CFD) model is conducted in this paper to study the flow behaviors in the primary side of OTSG. The unstructured polyhedral meshes were used in this paper, and ANSYS FLUENT was the solving tool to solve the governing equations by using Realizable k  −  ɛ turbulence model with enhanced wall treatment. Through a series of cases, the velocity profiles and pressure drop through the primary side of the OTSG were calculated, and the influences of different inlet parameters and different structure designs on the coolant behaviors and flow distributions were studied. Ultimately some suggestions for improvements were proposed to achieve a more rational design with more uniform flow distributions and smaller pressure drops. It was found that the flow distribution in the primary side of an OTSG is a property of its structure, on which inlet conditions have little effect. The position of inlet nozzle has a significant impact on the flow distribution. [ABSTRACT FROM AUTHOR]

The integration of additive manufacturing into traditional manufacturing processes presents the future of engineered components with similar or superior performance levels to wrought or cast materials. In this work, the hot-deformation behavior and the microstructural changes of heat-treated SLM-printed IN718 specimens are investigated. Samples having the same shape and size were 3D-printed, homogenized (1100 °C, 1 h, and furnace-cooled), and hot-compressed, using a Gleeble® 3800 physical simulator at 1000 and 1050 °C and 0.1 and 0.01 s−1 strain rates. A 3D diagram showing the effect of temperature and strain rate on the flow stress behavior of IN718 during hot deformation is plotted. The dynamic recrystallization (DRX) mechanism was dominant in all specimens tested at 0.1 s−1, while dynamic recovery (DRV) dominated in 0.01 s−1 tests. Changing the strain rate from 0.01 to 0.1 s−1 at 1000 °C increased the peak stress from 150 to 290 MPa (93%), while with a temperature decrease from 1050 to 1000 °C at 0.1 s−1, the peak stress increased by 45%. Thus, the mechanical behavior was found to be more dependent on the strain rate than on the temperature. The DRX structure showed new grains developing at the boundaries of the original grains, whereas with the DRV structure, new grains grew within the original grains. A phenomenological model based on the Zener-Hollomon parameter was proposed in order to predict the size of recrystallized grains during hot deformation of the SLM-printed IN718 superalloy. The thermal softening due to recrystallization was compensated by precipitation hardening, as was revealed by phase analysis. [ABSTRACT FROM AUTHOR]

In this paper, the effect of POA PPD together with resin-stabilized asphaltenes on the flow behavior of model waxy oils was investigated through rheological test, DSC, microscopic observation and asphaltenes precipitation test. Compared to the POA or asphaltenes alone, POA/asphaltenes cannot further decrease the wax appearance temperature of oils, but can dramatically decrease the pour point, gelation point,G′, G″and apparent viscosity of oils. POA molecules can adsorb on the surface of asphaltenes, thus inhibiting the asphaltenes precipitation and forming the POA/asphaltenes composite particles. The composite particles can act as wax crystallization templates and then greatly change the wax crystals' morphology into large and spherical-like, thus improving the waxy oil flow behavior. [ABSTRACT FROM AUTHOR]

To clarify the microstructural evolution and hot workability of GH4282 during hot forming processes, the hot deformation behavior of this superalloy was investigated by isothermal compression tests in the temperature interval of 950-1210 °C and the strain rate range of 0.01-10 s−1 with a true strain of 0.7. The results show that the flow stresses decrease with an increase in the deformation temperature and a decrease in the strain rate. The characteristic of dynamic recrystallization is revealed by the flow curves. The variation rule of the flow stress can be well described by the hyperbolic sine type equation, and the thermal deformation activation energy is determined to be 498.118 kJ/mol. The optimum hot working parameters are 1100-1180 °C and 0.01-0.1 s−1, under which the fine and uniform microstructure can be obtained. [ABSTRACT FROM AUTHOR]

The utility of different constitutive models describing high-temperature flow behavior has been evaluated from the perspective of alloy development. Strain compensated Arrhenius model, modified Johnson-Cook (MJC) model, model D8A and artificial neural network (ANN) have been used to describe flow behavior of different model alloys. These alloys are four grades of SS 316LN with different nitrogen contents ranging from 0.07 to 0.22%. Grades with 0.07%N and 0.22%N have been used to determine suitable material constants of the constitutive equations and also to train the ANN model. While the ANN model has been developed with chemical composition as a direct input, the MJC and D8A models have been amended to incorporate the effect of nitrogen content on flow behavior. The prediction capabilities of all models have been validated using the experimental data obtained from grades containing 0.11%N and 0.14%N. The comparative analysis demonstrates that ‘N-amended D8A’ and ‘N-amended MJC’ are preferable to the ANN model for predicting flow behavior of different grades of 316LN. The work provides detailed insights into the usual statistical error analysis technique and frames five additional criteria which must be considered when a model is analyzed from the perspective of alloy development. [ABSTRACT FROM AUTHOR]

In order to study the flow behaviors of an Al-Zn-Mg-Cu alloy at elevated temperatures, uniaxial tensile tests were carried out in wide deformation temperature and strain rate ranges. The flow stress rapidly increases to a peak value and then slightly decreases with the increased strain, and the dynamic recovery (DRV) is the primary softening mechanism. A unified constitutive model based on dislocation density was developed. An iterative procedure was implemented into the developed model to describe the flow behaviors at time-variant deformation conditions (e.g. the strain rate is changed during hot deformation). The predicted flow stresses were in accord with the experimental results, suggesting that the flow behaviors of the studied Al alloy at elevated temperatures can be well reproduced by the developed model. Meanwhile, the variations of the product of the instantaneous work hardening (WH) rate and stress caused by dislocation evolution, the dislocation density changing rate, as well as the dislocation mean free path, were given to analyze the WH and DRV mechanisms of Al-Zn-Mg-Cu alloy. [ABSTRACT FROM AUTHOR]

Applications using foam material as distillation column internals have been demonstrated higher performance than classical mass transfer units, except for the operation range. In this paper, the novel Foam Ring Random Packing (FRRP) made of Carbon foam material has been developed to overcome this disadvantage. The hydraulic performance and the mass transfer efficiency of FRRP are measured as 300 mm i.d. diameter column. The experimental values of FRRP are compared with the values of traditional ring random packing. In general, the comparison results indicate that the hydrodynamics and mass transfer performances of FRRP has been intensified by the foam materials (best HETP 0.24 m and additional 20% operation range). In order to explain the cause of intensification, flow behavior experiments were also carried out on both FRRP and Raschig ring packing. Special emphases on the effects of orientations, liquid flow rate and feed point on wetting area were investigated. Compared with other traditional random packing, the results show that the FRRP has some advantages, such as better extensive wetting area (maintain no less than 80%) and more uniform wetting distribution (fluctuate within 20%). Finally, an analysis of wetting process on single FRRP was presented to help understand the flow pattern on the packing. All results indicate that FRRP has outstanding performance, which will be a potential candidate used in distillation process. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and processing characteristics of AZ91 alloy and nano- SiCp/AZ91 composite were compared at temperature ranges of 523 K-673 K and strain rates of 0.001-1 s-1. Positive impact of SiC nanoparticles on pinning grain boundaries and inhibiting grain growth was not obvious when deformation temperature was below 623 K, but was remarkable when the temperature was above 623 K. By comparing compressive stress-strain curves of AZ91 alloy and nano-SiCp/AZ91 composites, the addition of nanoparticles could improve the deformation ability of a matrix alloy under high-temperature conditions. There was no essential difference of deformation mechanism between AZ91 alloy and the composite, but hot deformation activation energy of the composite was significantly lower than that of the AZ91 alloy. The AZ91 alloy and the composite had the same workability region of 600 K-673 K and 0.001-1 s-1, while instability region for the composite was reduced compared with that of AZ91 alloy at high temperature. [ABSTRACT FROM AUTHOR]

The flow behavior and processing maps of homogenized AA7085 aluminum alloy were investigated by isothermal hot compression tests in the temperature range of 300∼450 °C with strain rates of 0.01∼10 s −1 . Microstructure was characterized using Optical microscopy (OM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the superimposed processing maps at different strains exhibit the optimized deformation parameters with the temperature of 390∼450 °C and strain rates lower than 0.1 s −1 . Microstructure characterization reveals that dynamic recovery and recrystallization are the main deformation mechanisms in the safe regions. At lower temperature and lower strain rate, the coarsening of particles between ɛ=0.5 and ɛ=0.7 may be responsible for the transformation of processing map from unstability to safe domain. [ABSTRACT FROM AUTHOR]

Hot tensile deformation behavior of AA7075 was studied on a Gleeble-3500 thermal simulation machine. The deformation temperatures were 300 °C, 350 °C, 400 °C, 450 °C, and strain rates were 0.01 s −1 , 0.1 s −1 , 1 s −1 . Electron backscatter diffraction (EBSD) technique was performed on the deformed specimens to investigate the microstructure evolution. The results showed that grain sizes can be refined with increasing deformation amount, temperature, and decreasing strain rate. A constitutive model coupling with the evolution of recrystallization, dislocation, grain size, and damage was established based on the experimental results. The comparisons between model predictions and experimental results were evaluated in terms of statistical methods, the minimum correlation coefficient value was 0.934, and the maximum average absolute relative error and root mean square error were 3.96% and 2.97 MPa, respectively. The results indicated a good prediction accuracy of the model in describing the flow behavior and microstructural evolution of AA7075. [ABSTRACT FROM AUTHOR]

The effects of heat treatment processing on the microstructures of Ti-6Al-4V alloy are systematically studied. Static globularization behavior of lamellar α phase is found when the alloy is cooled in air or furnace from 950–960 °C (below the β-transus temperature, about 975 °C). Three kinds of microstructures (basket-weave, globular-lamellar, and equiaxed microstructures) are obtained by different heat treatments. The uniaxial tensile tests of the studied alloy with different initial microstructures are conducted at the elevated temperature and different strain rates. It is found that the initial microstructures have obvious effects on the tensile properties and fracture mechanisms. The alloy with basket-weave microstructures exhibits the most obvious work hardening behavior and the highest strength. The alloy with globular-lamellar microstructures has the better ductility than that with basket-weave microstructures. Furthermore, the alloy with equiaxed microstructures has the best ductility, because the equiaxed α phases can delay the formation and coalescence of microvoids. Meanwhile, α phases are elongated, bent and spherized, which contributes to the flow softening during tensile deformation. Especially, the alloy with initial equiaxed microstructures finally transforms to bimodal microstructures after tensile fracture. Additionally, the alloys with three different initial microstructures all show a primary ductile fracture. [ABSTRACT FROM AUTHOR]

In the present study, high temperature (700–1100 °C) tensile deformation behavior of hot-rolled CrMnFeCoNi high-entropy alloy was investigated. A single face-centered cubic phase was retained in the hot deformed specimens under different deformation conditions. The flow behavior was significantly influenced by temperature and microstructure evolution. A strong temperature dependence of yield stress was observed with a drastic drop in yield strength from 413 MPa at 700 °C to 94 MPa at 900 °C. A profound increase in ductility was observed above 700 °C and a perceptive decrease in ductility was observed above 900 °C. Electron backscatter diffraction analysis indicates incomplete dynamic recrystallization at 700 °C leading to a significant difference in the flow behavior. [ABSTRACT FROM AUTHOR]

Statistical, power spectral and chaos analysis methods were used to analyze pressure fluctuations in a bubbling fluidized bed. Effects of superficial gas velocity, static bed height, particle size and position of pressure probe on the flow behavior were investigated. It was shown that the flow behavior in terms of Kolmogorov entropy at the bottom of the bed was more complex than that at the upper part of the bed. Kolmogorov entropy decreased with increasing static bed height or particle size. In the range of 1.05 < U g / U mf < 4.37, Kolmogorov entropy had a strong linear relationship with the average cycle frequency. The amplitude of pressure fluctuations increased with the superficial gas velocity and the static bed height. The average pressure increased linearly with the static bed height. The dominant frequency of pressure fluctuations in the bed decreased with the static bed height, but barely changed with the gas velocity when it reached a certain value. The changes of superficial gas velocity, static bed height, and particle size can be determined by the changes of the amplitude of pressure fluctuations, the average pressure and Kolmogorov entropy. [ABSTRACT FROM AUTHOR]

Rheological properties of poppy seed paste (PSP)/grape pekmez blends containing 10%, 15%, 20%, 25%, 30%, 35%, and 40% PSP were determined at different temperatures (10-40 °C). The PSP/grape pekmez blends behaved as a pseudoplastic fluid. The flow behavior index of the blends containing 10% PSP varied between 0.92 and 1.0, however, as the concentration of PSP increased to 40% the flow behavior index decreased to the range of 0.23-0.67. As the temperature increased the viscosity and the consistency coefficient ( K) decreased. The activation energies ( Ea) of the blends were found in the range of 23,054.8-66,059.1 kJ/kmol. The consistency coefficient increased from the range of 0.25-3.56 Pa sn to 35.63-203.01 Pa sn as the PSP concentration increased from 10% to 40%. The combined effect of the concentration, temperature and shear rate on the viscosity of the PSP/grape pekmez blends were described successfully by a simple equation. The blends showed a rheopectic time-dependent behavior. Practical applications Rheological properties of fluid foods are necessary for designing and evaluation of food processing lines, quality control and consumer acceptability. In this study, flow behavior and the effect of temperature and PSP concentration on the rheological properties of the PSP/grape pekmez blends were determined. The effect of concentration, temperature, and shear rate on viscosity was represented by a simple equation which can be used in engineering calculations. Time-dependent flow behavior of the PSP/grape pekmez blends was also determined that it is important for the estimation of changes in the flow behavior during processing. [ABSTRACT FROM AUTHOR]

Background: The aim of the present study was to evaluate gum productivity of a local strain, Xanthomonas axonopodis pv. vesicatoria, isolated from pepper plant, and its rheological behavior for the first time compared to the standard strain, Xanthomonas campestris DSM 19000 (NRRL B-1459). The influence of operational conditions (agitation rate and inoculum volume) on gum production and rheological properties of gums from the Xanthomonas strains were investigated. Results: The isolated strain of Xanthomonas showed similar xanthan yield compared to the standard strain. Furthermore, this study clearly confirmed that gum yield depended on bacterial strain, agitation rate, and inoculum size. The most suitable conditions for the gum production in an orbital shaker in terms of agitation rate and inoculum size were 180 rpm and 5%, respectively, resulting in an average production of 10.96 and 11.19 g/L for X. axonopodis pv.vesicatoria and X. campestris DSM 19000, respectively. Regarding the rheological properties, Ostwald-de-Waele and power law models were used to describe flow and oscillatory behavior of the gum solutions, respectively. Consistency of the novel gum solution remarkably was much higher than the commercial xanthan gum solution. Flow and oscillatory behavior and their temperature ramps showed that weak gel-like structure could be obtained with less gum concentrations when the novel gum was used. Conclusion: Therefore, yield and technological properties of the aqueous solutions of the exopolysaccharide synthesized by X. axonopodis pv. vesicatoria were observed to be more suitable for industrial production. [ABSTRACT FROM AUTHOR]

Hybrid aluminum matrix composites (HAMCs) are capable to meet recent demands of advanced engineering applications due to its tunable mechanical properties and lower cost. Stir casting is one of the prominent and economical method for processing of continuous reinforced HAMCs. In this method, flow pattern is the key factor for distribution of particles in the molten metal. Effective flow pattern can be achieved by optimizing stirring parameters i.e. blade angle, impeller size and stirring speed. However, complete study and optimization of flow is a challenge for research community. Finite element method simulation along with optimization technique is one of the effective combination to guide experimental research. In this paper, computational fluid dynamics has been used to simulate fluid flow during stir casting, whereas optimization of stirring parameters is done by Grey Taguchi method. Optimized parameters have been used for experimental synthesis of HAMCs. Furthermore, optical micrograph and hardness confirms about the uniform dispersion of reinforcements. These results may guide the researchers for the preparation of HAMCs with uniform particle distribution by stir casting route for industrial applications. [ABSTRACT FROM AUTHOR]

• A laser/ultra-high frequency (UHF) induction hybrid deposition method was proposed. • A multi-field coupling numerical model was developed to study the deposition process. • The UHF induction heat has pre-heating and slow-cooling effects on deposition process. • The influence of the UHF induction parameters on the deposition process was analyzed. • The UHF induction heat conduces to microstructure refinement of the deposited layer. In this study, ultra-high frequency (UHF) induction heat was combined with laser deposition, which is referred to as laser–UHF induction hybrid deposition. On the one hand, this method takes the conventional laser induction hybrid deposition as reference, which uses the heat effect of UHF induction heat to optimize the residual stress of the deposited layer. On the other, this method utilizes the strong Lorentz force generated by the UHF induction heat to accelerate the flow velocity of the molten metal, which will be beneficial for microstructure refinement. Given that the thermal process and flow behavior during deposition are critical factors for the microstructure, a numerical model coupled with temperature field, electromagnetic field, flow field, and mass transfer field was developed to investigate the thermal process and flow behavior during laser–UHF induction hybrid deposition. Results showed that the UHF induction heat in laser-UHF induction hybrid deposition has pre-heating and slow-cooling effects on the deposited layer compared with laser deposition. The Lorentz force generated by UHF induction heat enhanced the flow velocity and the heat convection in molten pool. Research on the UHF induction heat parameters indicates that increasing the current frequency or current density can strengthen the slow-cooling effect of the UHF induction heat, and the flow velocity of the molten metal can be increased by 12.1% and 24.6%. Moreover, the maximum temperature in the molten pool decreased with increasing current frequency or current density because of the enhanced heat convection. Laser–UHF induction hybrid deposition experiment was also conducted, and the detected elemental content of the deposited layer and temperature showed good consistency with the simulated results. The grain size in the microstructure of the experimental laser–UHF induction hybrid deposited layer can be refined to approximately 3.358 μm at high current density conditions because of the enhanced fluid flow and heat convection in molten pool. This work provides an effective tool for predicting the thermal process and flow behavior during laser–UHF induction hybrid deposition, which will be an essential reference for evaluating microstructure quality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coupling between the foam's physical and chemical characteristics. • Relationship between foam & soil characteristics to deduce the optimal conditioning. • High correlations between laboratory tests on treated soil and in-situ excavation. Earth pressure balance shield (EPBS) is the excavation technique responding to the technical construction complexity of the future line 16–1 of the Grand Paris Express project. Its principle is based on the capacity of the excavated ground to transmit the forces needed to counterbalance the earth and water pressures of the working face. Additives are injected into the soil; on the cutting wheel, in the excavation chamber and in the screw conveyor. Their role is to assure the soil conditioning by modifying the soil's workability and its hydromechanical and rheological parameters. Therefore, the soil conditioning produces a plastic medium able to transmit the pressure to maintain the front face. In addition, as a second objective, the additives aim to overcome uncertainties in the soil. Depending on the case, the additives can reduce the clogging, internal friction, abrasiveness, and permeability of the soil. The additives can include water, surfactant, polymer and bentonite. The combination of water and surfactant with or without polymer produces the foam. In order to increase the excavation perfomance, laboratory prelimenary tests are performed to deduce the optimal foam parameters. Since no test measuring the foam characteristics is standardized yet, this article sums up the tests mostly used in foam characterisation; half-life measurements, rheological tests, microstructural observations. As for the conditioned soil, slump test is frequently used by the tunnelling industry to recommend the optimal soil conditioning parameters in terms of workability. This test has been adapted in this study and the results are verified by rheological tests, then compared to the real foam injection data used for the project and their effect on mechanical parameters. For a specific type of excavated soil, the quality (type) of foam recommended by the laboratory work falls into the same choice of additive based on in-situ tunnelling excavation data. These findings are explained by the foams characteristics. Therefore, a correlation between foam and the conditioned soil (sandy soil with silt and low percentage of clay) with foam is deduced at different levels: micro, meso and macro (real) scales. [ABSTRACT FROM AUTHOR]

The bridging plugging method is an economical and practical fracture loss control technology. However, it is challenging to clarify the microscopic flow behavior and plugging process of lost circulation materials in fractures under formation conditions. This study uses the computational fluid dynamics–discrete element method to establish a wellbore-fracture model to study the flow behaviors of a plugging slurry in fractures. The model especially considers the interaction between the wellbore wall and the plugging slurry. The results show that the evolution process of the plugging layer can be divided into four stages based on the tracking of the information on the interaction of particles, fluid, and wall. The initial structure of the plugging layer is mainly a two-sphere bridge. The formation location and subsequent construction speed of the plugging layer depend on the particle size and concentration, respectively. The optimization of particle combination can effectively enhance the structural stress of the plugging layer. The liquid viscosity has a limited influence on the sealing, and the excessively high liquid pressure will destroy the stability of the initial bridging. Quantitative research on the evolution of the plugging layer can provide a reference for optimizing the formulation design of the plugging slurry system. [Display omitted] • Used CFD-DEM method to track particle-fluent flow in wellbore-fracture model. • Explained the double ball bridging structure in the fracture. • Explained the phenomenon of "sealing door" at the opening of the fracture. • Quantitatively evaluated the influencing factors of the plugging layer. [ABSTRACT FROM AUTHOR]

A fractured horizontal well is an effective technology to obtain hydrocarbons from tight reservoirs. In this study, a new semi-analytical model for a horizontal well intercepted by multiple finite-conductivity reorientation fractures was developed in an anisotropic rectangular tight reservoir. Firstly, to establish the flow equation of the reorientation fracture, all reorientation fractures were discretized by combining the nodal analysis technique and the fracture-wing method. Secondly, through coupling the reservoir solution and reorientation fracture solution, a semi-analytical solution for multiple reorientation fractures along a horizontal well was derived in the Laplace domain, and its accuracy was also verified. Thirdly, typical flow regimes were identified on the transient-pressure curves. Finally, dimensionless pressure and pressure derivative curves were obtained to analyze the effect of key parameters on the flow behavior, including fracture angle, permeability anisotropy, fracture conductivity, fracture spacing, fracture number, and fracture configuration. Results show that, for an anisotropic rectangular tight reservoir, horizontal wells should be deployed parallel to the direction of principal permeability and fracture reorientation should be controlled to extend along the direction of minimum permeability. Meanwhile, the optimal fracture number should be considered for economic production and the fracture spacing should be optimized to reduce the flow interferences between reorientation fractures.

The topical administration of non-steroidal anti-inflammatory drugs is described as an alternative route for inflammatory disease treatment and is frequently used because it determines local effects therapeutically, similar to oral administration, but with fewer side effects. [...]

The high-temperature flow behavior of TB8 titanium alloys with two different grain sizes was investigated in this present work. Results show that a significant characteristic of stress drop is visible at the start stage of the hot deformation process when the strain rates are 100 and 10−1 s−1. With the further increasing of strain, the flow stress initially rises to a maximum value and subsequently attains a plateau for the strain rates of 100 s−1 and a slight decrease for the strain rates of 10−1 s−1. Only dynamic recovery occurs under these deformation conditions. When the strain rates drop to 10−3 s−1, the dynamic recrystallization takes place during hot deformation. The values of deformation activation energy and materials constants at different strains were calculated. The processing maps at different strains were established for the fine- and coarse-grained alloys. The optimal processing parameter for hot processing was attained to be 900 °C/10−3 s−1 for fine-grained alloys and 950 °C/10−3 s−1 for coarse-grained alloys, respectively.

The hot deformation behavior of the aerospace Ti-10-2-3 alloy was investigated by isothermal compression tests at temperatures of 740 to 820 °C and strain rates of 0.0005 to 10 s−1. The results show that the studied alloy is extremely sensitive to deformation parameters, like the temperature and strain rate. The temperature mainly affects the magnitude of flow stress at larger strains, while the strain rate not only affects the value of flow stress but also the shape of the flow curves. At low strain rates, the flow stress increases with strain, followed by a broad peak and then remains almost constant. At high strain rates, the flow curves exhibit a hardening to a sharp peak at small strains, followed by a rapid dropping to a plateau caused by dynamic softening. In order to describe such flow behavior, a constitutive model considering the effect of deformation parameters was developed as an extension of an existing constitutive model. The modified constitutive model (MC) was obtained based on the original constitutive model (OC) by introducing a new parameter to compensate for the error between the experimental data and predicted values. Compared to the original model, the developed model provides a better description of the flow behavior of Ti-10-2-3 alloy at elevated temperatures over the specified deformation domain.

A three-dimensional mathematical model of gas−liquid two-phase flow has been established to study the flow behavior of liquid steel in the tundish. The effect of the argon flow rate and casting speed on the flow behavior of liquid steel, as well as the migration behavior of argon bubbles, was investigated. The results from the mathematical model were found to be consistent with those from the tundish water model. There were some swirl flows around the stopper when the annular argon blowing process was adopted; the flow of liquid steel near the liquid surface was active around the stopper. With increased argon flow rate, the vortex range and intensity around the stopper gradually increased, and the vertical flow velocity of the liquid steel in the vicinity of the stopper increased; the argon volume flow in the tundish and mold all increased. With increased casting speed, the vortex range and intensity around the stopper gradually decreased, the peak value of vertical flow velocity of liquid steel at the vicinity of the stopper decreased, and the distribution and ratio of argon volume flow between the tundish and the mold decreased. To avoid slag entrapment and purify the liquid steel, the argon flow rate should not be more than 3 L·min−1. These results provide a theoretical basis to optimize the parameters of the annular argon blowing at the upper nozzle and improve the slab quality.

With the rapid growth of energy consumption, enhanced oil recovery (EOR) methods are continually emerging, the most effective and widely used was polymer flooding. However, the shortcomings were gradually exposed. A novel decorated polyacrylamide might be a better alternative than polymer. In this work, the molecular structure and the properties reflecting the viscosity of decorated polyacrylamide, interfacial tension, and emulsification were examined. In order to better understand the interactions between decorated polyacrylamide and oil as well as the displacement mechanism, the displacement experiment were conducted in the etched-glass microscale model. Moreover, the coreflooding comparison experiments between decorated polyacrylamide and polymer were performed to investigate the displacement effect. The statistical analysis showed that the decorated polyacrylamide has excellent characteristics of salt tolerance, viscosity stability, and viscosification like polymer. Besides, the ability to reduce the interfacial tension in order 10−1 and emulsification, which were more similar to surfactant. Therefore, the decorated polyacrylamide was a multifunctional polymer. The displacement process captured by camera illustrated that the decorated polyacrylamide flooded oil mainly by means of ‘pull and drag’, ‘entrainment’, and ‘bridging’, based on the mechanism of viscosifying, emulsifying, and viscoelasticity. The results of the coreflooding experiment indicated that the recovery of decorated polyacrylamide can be improved by approximately 11⁻16% after water flooding when the concentration was more than 800 mg/L, which was higher than that of conventional polymer flooding. It should be mentioned that a new injection mode of ‘concentration reduction multi-slug’ was first proposed, and it obtained an exciting result of increasing oil production and decreasing water-cut, the effect of conformance control was more significant.

Magnesium matrix composites synergistically reinforced by SiC nanoparticles and second phases were prepared by 12 passes of multi-pass forging, varying the temperature. The effects of grain refinement and the precipitates on the hot deformation behavior were analyzed. Deformation zones which could be observed in the fine-grained nanocomposite before hot compression disappeared, and the trend of streamlined distribution for the precipitated phases was weakened. At the same compression rate, as the compression temperature increased, the number of precipitated phases decreased, and the grain size increased. For fine-grained nanocomposites, after the peak stress, there was no obvious dynamic softening stage on the stress–strain curve, and then the steady stage was quickly reached. The critical stress of the fine-grained nanocomposites was lower than that of the coarse-grained nanocomposites, which can be attributed to the large amounts of precipitates and significantly refined grains. The deformation mechanism of the coarse-grained nanocomposite was controlled by dislocation climb resulting from lattice diffusion, while the deformation mechanism for the fine-grained nanocomposite was dislocation climb resulting from grain boundary slip. The activation energy of the fine-grained nanocomposite was decreased, compared with the coarse-grained nanocomposite. The area of the workability region for the fine-grained nanocomposite was significantly larger than that of the coarse-grained nanocomposite, and there was no instability region at a low strain rate (0.001–0.01 s−1) under all deformation temperatures. The optimal workability region was 573 K /0.001–0.01 s−1 for the fine-grained nanocomposite, and the processing temperature was lower than the coarse-grained nanocomposite (623–673 K).