Effect Of Stirring Research Articles

Effect of Friction Stir Welding Parameters on Welding Joint Characteristics : A review

Effect of Friction Stir Welding Parameters on Welding Joint Characteristics : A review

Glycerol-assisted dynamic hydrothermal synthesis of nickel phyllosilicate for enhanced CO2 methanation: Synergistic effect of stirring and viscous solvent

To address the shortcomings of poor convection and product agglomeration of the static hydrothermal method, the dynamic hydrothermal method together with the viscous solvent-assisted dynamic hydrothermal method were proposed to synthesize Ni-phyllosilicate in this work. Stirring seemed to be powerful to accelerate the synthesis with significant increase of Ni content from 11.80 wt% (static synthesis) to 23.13 wt% (dynamic synthesis). The further modification of glycerol increased the shearing force to exfoliate the Ni-phyllosilicate nanosheets during dynamic synthesis, whose thickness could reach 1.17 nm with improved metal utilization ratio after reduction. As a result, the activity of CO2 methanation was enhanced with large TOFCO2 of 3.5 × 10−2 s−1 and small Ea of 65.13 kJ·mol−1. In situ DRIFTS analysis confirmed the existence of high actively intermediate of m-HCOO− and *CO, which could be further hydrogenated into CHx species. In short, the synergistic effect of dynamic stirring and glycerol modification drove the enhancement of catalytic activity, and also provided the possibility of large-scale production of Ni-phyllosilicate using hydrothermal method.

Effect of magnetic stirring on microstructure of Co deposit in electrowinning

The effect of magnetic stirring was investigated on the microstructure of Co deposits during electrowinning in a chloride solution. The microstructure of Co deposits obtained before and after using the magnetic stirring was systemically characterized. Cyclic voltammograms were carried out to investigate the electro-reduction of Co2+ ions. The nucleation and growth of Co deposits were discussed based on chronoamperometry. The evolution of H2 inevitably accompanied with the reduction of Co2+ ions in the electrowinning. It had a great influence on the structure of Co deposits. The introducition of magnetic stirring can reduce this negative influence effectively by promoting the detachment of H2 bubbles on the substrate. The magnetic stirring also changed the nucleation and growth of Co deposits. Finally, columnar Co crystals with intensively preferred orientation were prepared. The modification of microstructure by magnetic stirring is contributed to prepare high-quality Co electrodeposits.

Effect of Alternating Magnetic Field on the Organization and Corrosion Resistance of 2205 Duplex Stainless Steel Narrow-Gap Laser-MIG Hybrid Weld Head

In this study, an alternating magnetic field is applied in the narrow-gap laser-MIG hybrid welding of 2205 duplex stainless steel with a thickness of 25 mm to achieve the purpose of balancing the ration of the two phases, refining the grains and improving the corrosion resistance. With the help of OM, EBSD, TEM, and other microstructural analysis methods, the organization evolution of a 2205 duplex stainless steel narrow-gap laser arc hybrid weld under the effect of alternating magnetic field is revealed. The corrosion resistance of the welded joints is investigated by electrochemical tests. The results show that the use of a 40 mT applied alternating magnetic field can not only effectively inhibit the generation of porosity and unfused defects in the weld, but also that the addition of an alternating magnetic field improves the ratio of austenite to ferrite in the weld, and the ratio of the two phases is increased from 0.657 without a magnetic field to 0.850. The weld grain preferential orientation is affected by the magnetic field, and the weld austenite grains are shifted from the Goss texture to the Copper texture. Under the electromagnetic stirring effect of the applied magnetic field, the average austenite grain size decreased from 4.15 μm to 3.82 μm, and the average ferrite grain size decreased from 4.99 μm to 4.08 μm. In addition, the effect of the alternating magnetic field increases the density of twins in the organization. Electrochemical test results show that the addition of an alternating magnetic field increases the corrosion potential by 75.2 mV and the pitting potential by 134.5 mV, which indicates that the corrosion resistance of the cover-welded specimens is improved by the effect of an alternating magnetic field. The improvement in corrosion resistance mainly depends on the austenite grain refinement and the increase in the austenite content.

Development of a new method for determination of bisphenol A based on stirrer-assisted switchable hydrophilic solvent-based liquid phase microextraction coupled with electrochemical sensor

In this work, a novel stirrer-assisted liquid-phase microextraction method using switchable hydrophilic solvents was developed for the extraction and preconcentration of bisphenol A from real samples prior to electrochemical analysis. For the first time, the effect of stirring while switching the extraction solvent (N,N-dipropylamine, DPA) was investigated, and the use of stirring instead of temperature change, which is a time-consuming process, hazardous acids (e.g., HCl), and dry ice was used for bisphenol A extraction based on switchable solvents. Various parameters such as solvent type, solvent volume, stirring time, and stirring speed were optimized. The optimized conditions were 100 μl DPA, 2 min extraction time, 30 s stirring time, 700 rpm stirring speed, and solution pH of 7.0. A theoretical study was also conducted to show the effects of stirring on the homogenization of the phases. The proposed method offers some advantages, such as simplicity, use of a small amount of inexpensive and less hazardous reagents, rapid extraction, and shorter analysis time. Under the optimized conditions for the developed method, LOQ and LOD were obtained to be 0.01 and 0.003 μM, respectively. Moreover, the calibration curves were linear in the range of 0.01–250 μM. The proposed method was used for the determination of bisphenol A in food and water samples.

Keyhole stability, arc behavior, and molten pool flow in narrow-gap oscillating laser-arc hybrid welding of titanium alloy

In the study, the keyhole stability, arc behavior and molten pool flow were investigated to clarify the welding process stability in narrow-gap oscillating laser-arc hybrid welding of titanium alloy. At an oscillating frequency of 300 Hz and amplitude of 1 mm, a concave weld with low porosity was produced. Compared with non-oscillating laser, the keyhole opening size increased about twofold, and the standard deviation of arc deflection angle differences decreased by approximately 87.6 %. Owing to the stirring effect of beam oscillation, a stable keyhole with larger opening size was formed, which facilitated the escape of bubbles from the keyhole. More excitation electrons were generated and erupted outward from the keyhole, and both plasma temperature and density increased by approximately 55.2 %. An enhanced electric channel was formed between the welding wire tip and groove center. As a result, the arc burnt stably at the groove bottom, which could melt the groove bottom synchronously, and suppress sharp corners and lack of fusion. The impact caused by droplets was cushioned as the liquid metal flowed towards the rear molten pool orderly with a circular path. Consequently, the liquid metal near the keyhole fluctuated slightly, indicating that the keyhole stability was enhanced. Besides, dendrites were fragmented and more equiaxed grains were produced due to the strong disturbance of dendrites by liquid metal in the whole mushy zone.

Seasonal Patterns of Picocyanobacterial Community Structure in the Kuroshio Current.

The nutrient-scarce, warm, and high-salinity Kuroshio current has a profound impact on both the marine ecology of the northwestern Pacific Ocean and the global climate. This study aims to reveal the seasonal dynamics of picoplankton in the subtropical Kuroshio current. Our results showed that one of the picocyanobacteria, Synechococcus, mainly distributed in the surface water layer regardless of seasonal changes, and the cell abundance ranged from 104 to 105 cells mL-1. In contrast, the maximum concentration of the other picocyanobacteria, Prochlorococcus, was maintained at more than 105 cells mL-1 throughout the year. In the summer and the autumn, Prochlorococcus were mainly concentrated at the water layer near the bottom of the euphotic zone. They were evenly distributed in the euphotic zone in the spring and winter. The stirring effect caused by the monsoon determined their distribution in the water column. In addition, the results of 16S rRNA gene diversity analysis showed that the seasonal changes in the relative abundance of Synechococcus and Prochlorococcus in the surface water of each station accounted for 20 to 40% of the total reads. The clade II of Synechococcus and the High-light II of Prochlorococcus were the dominant strains in the waters all year round. Regarding other picoplankton, Proteobacteria and Actinobacteria occupied 45% and 10% of the total picoplankton in the four seasons. These data should be helpful for elucidating the impacts of global climate changes on marine ecology and biogeochemical cycles in the Western Boundary Currents in the future.

Processing of calcium sulfoaluminate eco-cement coatings containing microencapsulated phase change materials

On the one hand, calcium sulfoaluminate (CSA) eco-cements release about 40% less carbon dioxide (CO2) than Portland cement during fabrication; on the other hand, phase change materials dispersed in a cementitious matrix can help to optimise the indoor temperature of buildings, reducing carbon dioxide emissions related to heating/air conditioning. However, this is only economically viable if it is used as a thin layer (a coating). In addition, the combination of both materials supposes a double environmental benefit. Consequently, the main objective of this work is the preparation of a suitable homogeneous and well-adhered bilayer sample, composed of CSA and CSA-MPCM. To achieve this, in the first step, the effect of pH, temperature and stirring was studied for microencapsulated phase change material (MPCM) aqueous suspensions (47.3 wt%); second, the MPCM (45 wt% with respect to dry cement) was dispersed in a CSA paste; then, in a third step, a homogeneous well-adhered coating of CSA-MPCM, with undamaged MPCM, was obtained on a CSA matrix. This was achieved through rheological measurements and checked by microscopy. Finally, the corresponding CSA and CSA-MPCM mortars were characterised through their mechanical properties (compression) (70 and 13 MPa at 7 days, respectively) and thermal conductivity (2.06 and 1.19 W/mK, respectively).

Stirring effect of CuS deposition over cotton thread for photocatalysis and electrical application

In the present work CuS coated cotton thread was synthesized by co-precipitation method with (WS) and without stirring effect (WOS). XRD and FESEM were used to analyze the structural morphology of CuS over thread. The crystallite size for WS and WOS were 25.1 nm and 22.1 nm. The band calculated were 1.48 and 1.60 eV for WS and WOS. The XPS analysis confirm the presence of Cu+, Cu2+, Cu° charge state. MB organic dye was tested for degradation and reported degradation up to 94% of 50 ml MB dye in 20 min with using low catalytic weight 0.4 gm. IV measurement was also taken to study the electronic properties of coated threads. The high current under light presence and high degradation of MB dye through WOS thread is discussed in this work.

The research on weld pool morphology and passive film characteristic of high-nitrogen stainless laser-arc hybrid weld joint

In this paper, the dynamic weld pool morphology and metallographic structure on each zone of high-nitrogen stainless hybrid weld was investigated. By electrochemical test, the corrosion mechanism and evolution characteristic of passive film on weld surface was analyzed. It was found that by the laser keyhole stirring effect, the weld laser zone exhibited better ferrite dendrites distribution and corrosion resistance. By polarization method, it is observed that the weld passive film exhibited different morphology characteristic in each evolution stage. The passive film had strong regional tendency to ferrite dendrites structure in early stage. And the addition of molybdenum optimized the semiconductor properties of outer weld passive layer. For the failure stage, the passive film was greatly affected by Cr depleted zone and combined with the mode of cracking and dissolution.

The effect of electromagnetic stirring on processes of alloy crystallization and the macro- and microstructure of continuously cast billets for production of pipes which are resistant to hydrogen sulfide

The effect of electromagnetic stirring on processes of alloy crystallization and the macro- and microstructure of continuously cast billets for production of pipes which are resistant to hydrogen sulfide

Microstructure and mechanical properties of AISI 410S ferritic stainless steel narrow gap weld using flux strip constraining arc welding

The achievement of high comprehensive mechanical properties in welded joints of ferritic stainless steels has attracted considerable attention in the manufacturing industry. Here, a low heat input flux strip constrained arc welding (FSCAW) was performed on a hot-rolled AISI 410S sheet. Defect free joints with a small HAZ width were obtained by one side welding both sides formation. The microstructure of HAZ consists of fine ferrite grains and a small amount of M23C6-decorated martensite due to short high-temperature residence time and rapid cooling rate, resulting in high toughness and hardness. Influenced by the stirring effect of the constraining arc and the promotion of heterogeneous grain nucleation by Ti-rich MX particles originating from the transition of alloying elements in the flux strip, the fusion zone (FZ) exhibits a unique precipitates-strengthened martensite+austensite uniform microstructure with weak martensitic texture. This translates into a simultaneous increase in impact toughness and hardness of FSCAW FZ compared to the MAG joint with a non-uniform mixed microstructure, strong martensitic texture, and large grain size. This work establishes the potential for using FSCAW welding to join ferrite stainless steels.

Oscillating energy deposition of 17-4 PH alloy reinforced with tungsten carbide particles

17-4 PH is a martensitic precipitation-hardening stainless steel, renowned for its exceptional strength and high-temperature resistance, making it extensively employed in the fabrication of aircraft engines and flight control systems. The strengthening method of this alloy involves precipitation strengthening through thermal treatment. However, it is also susceptible to grain growth, which can diminish the alloy's mechanical properties and corrosion resistance. This research proposes to use circular oscillating laser deposition of 17-4 PH alloy reinforced with tungsten carbide (WC) and compares it with Gaussian laser deposition. The research findings indicate that the circular oscillating laser induces a stirring effect on the molten pool, facilitating the transformation of columnar dendrites into equiaxed grains and thereby refining the grain size. The convection, intensified by the high temperature and stirring effect, promotes the melting and diffusion of WC particles. The reaction between W, C elements, and 17-4 PH alloy facilitates the precipitation of hard phase carbides. Compared to Gaussian laser deposition, the microhardness of the 7 wt% WC/17-4 PH material prepared by circular oscillating laser deposition increased by 21.25 %, and the wear rate decreased by 70.06 %. The electrochemical test results have revealed that the 7 wt%WC/17-4 PH composite material fabricated using Gaussian laser exhibits optimal corrosion resistance. The circular oscillating laser induces carbide deposition at grain boundaries, resulting in the formation of microcells and exacerbating the corrosion.

Effect of Magnet Alternate Stirring on the Internal Quality of Sn-Pb Alloy

A permanent magnet stirrer was built to study the effect of different magnetic field stirring modes on the solidification quality of Sn-20 wt-% Pb alloy ingots. The internal quality of the ingot can be improved by adjusting both the stirring speed and the modes. When the continuous magnetic stirring mode was adopted, the higher the stirring speed, the higher the flutter height at the ingot edge. When the stirring speed was 200 rpm, the flutter height reached 4.12 mm. The rotating magnetic field can significantly refine the grain size of the ingot. When the stirring speed of the magnetic field was increased from 0 rpm to 200 rpm, the grain size of the ingot reduced from 301 μm to 241 μm. By fixing the magnetic field stirring speed to 200 rpm and adjusting the mode to the alternate stirring process, the flutter height at the ingot edge reduced to 1.86 mm, which stabilized the liquid level of the molten alloy in the crucible. In addition, the grain size of the ingot was shortened to 223 μm, and the elemental homogeneity within the ingot was optimized.

Effect of microstructure on mechanical, electrochemical, and biological properties of Ti/HA surface composites fabricated by FSP method

This study investigated the effect of microstructure on the mechanical, electrochemical, and biological properties of Ti/HA surface composites fabricated using the FSP method. The microstructure was altered by various traverse speeds of 30–75 mm/min. Microstructural studies revealed that lower traverse speeds (30–45 mm/min) resulted in fewer defects like voids and cracks compared to higher speeds (60–75 mm/min). A more heterogeneous distribution of HA particles in the Ti matrix was observed at higher traverse speeds due to a higher stirring effects and cooling rates. Mechanical investigations showed that ultimate tensile strength decreased with increasing traverse speed. The values for samples at 30, 45, 60, and 75 mm/min were obtained as 855 MPa, 746 MPa, 754 MPa, and 542 MPa, with a ± 4% standard deviation respectively. Electrochemical tests showed that the corrosion resistance decreased with increasing traverse speed due to more pitting corrosion occurring specifically at the interfaces between Ti/HA phases. All samples exhibited high biocompatibility, but cell viability was highest in the sample produced at a speed of 75 mm/min which had a higher amount of defects and surface agglomeration of HA particles affecting cell growth and proliferation. These findings demonstrate how processing conditions can significantly impact material properties including susceptibility to localized forms of corrosion as well as cell response over time.

Optimization and scale-up of Clostridium perfringens type D culture and epsilon-toxin production: Effects of stirring, glucose and pH adjustment

The effects of some main bacteria culture parameters including mixing rate, glucose (GC) concentration, steps of GC addition, and steps of pH adjustment on both C. perfringens bacteria growth and its epsilon toxin production in a bench-scale 20-L glass carboy were investigated. The optimized mixing rate of 300 rpm, GC concentration of 4 g L−1, and 3-step addition of GC resulted in the bacteria and toxin concentrations of 0.16 g L−1 and 330 ng mL−1, respectively. Also, the induction of a pH shock at the reaction time of 180 min led to the remarkable enhancement of toxin production (367 ng mL−1). Upon applying both optimized conditions for GC addition and pH adjustment, the high toxin concentration of 433 ng mL−1 was obtained. Using the constant mixing rate technique, the process was scaled up to a 1500-L industrial bioreactor, where its performance was close to the bench-scale bioreactor (i.e., toxin concentration of 419 ng mL−1). The results revealed the reliability of this method to economically improve and scale up the bacteria culture process, which can be further used for other microbial fermentations.

Effect mechanism of arc oscillation on microstructure and mechanical performance of SUS304 weld seams manufactured by local dry underwater double pulsed MIG welding

An innovative local dry underwater double pulsed MIG (LDU-DPMIG) technique was successfully applied to fabricate SUS304 weld seams, in which the stirring effect on the molten pool was realized via a double pulsed current waveform. The weld formation, phase morphology and distribution, grain structure characteristics, microhardness, and tensile properties of underwater weld seams were comprehensively analyzed in this study, especially the mechanism differences between local dry underwater single pulsed MIG (LDU-SPMIG) and LDU-DPMIG were revealed. The results demonstrated that the stirring effect caused by arc oscillation contributed to the enhancement of the molten pool fluidity during the solidification process, which effectively facilitated the smooth elements allocations between austenite and ferrite and the evolution of δ-ferrite phase structure from skeleton to lath. In addition, the grain structure in the DPMIG weld centre transformed from slender columnar dendrites to fine equiaxed dendrites. Due to the pronounced stirring effects in uniform composition distribution, ferrite morphology evolution, grain refinement, and increased twin activity, DPMIG weld seams exhibited an attractive enhancement in weld mechanical performances, with the optimal low frequency of 3 Hz, the average microhardness, ultimate tensile strength, and elongation enhanced by the highest 18.1%, 8.9%, and 16.3% compared with SPMIG weld seam. These results are expected to offer a novel approach to regulate and control the microstructure and mechanical performance of underwater weld seams and facilitate the application of LDU-DPMIG in ocean engineering equipment.

Synergistic Effects of Stirring and Aeration Rate on Carotenoid Production in Yeast Rhodotorula toruloides CCT 7815 Envisioning Their Application as Soap Additives

The production of carotenoids by microbial organisms has gained significant interest due to the growing demand for natural products. Among the non-model oleaginous red yeasts, Rhodotorula toruloides stands out as an appealing host for natural carotenoid production. R. toruloides possesses the natural ability to metabolize a wide range of substrates, including lignocellulosic hydrolysates, and convert them into lipids and carotenoids. In this study, we focused on utilizing xylose, the main component of hemicellulose, as the major substrate for R. toruloides. We conducted a comprehensive kinetic evaluation to examine the impact of aeration and agitation on carotenoid production. Results in stirred-tank reactor demonstrated that under milder conditions (300 rpm and 0.5 vvm), R. toruloides accumulated over 70% of its cell mass as lipids. Furthermore, the highest carotenoid yields were achieved at high agitation rates (700 rpm), with carotenoid levels reaching nearly 120 µg/mL. Several carotenoids were identified, including β-carotene, γ-carotene, torularhodin, and torulene, with β-carotene being the major carotenoid, accounting for up to 70% of the total carotenoid content. The carotenoid-rich extract produced by R. toruloides under evaluated conditions was successfully incorporated into soap formulations, demonstrating the addition of antioxidant properties. This work provides a comprehensive understanding of xylose conversion into natural carotenoids by R. toruloides, presenting a promising avenue for their application in cosmetics. Furthermore, this study highlights the potential of a renewable and cost-effective approach for carotenoid production in the soap industry.

Integrated modeling of microstructure-property-distortion relationship in friction stir additive manufacturing

A Monte Carlo model is established to simulate grain morphologies and combined with a precipitate evolution model to predict the mechanical properties of different zones in different layers of friction stir additive manufacturing (FSAM). Subsequently, a subregion model is established by considering the different mechanical properties at different locations to predict the residual states in FSAM. Results indicate that equiaxed grains are formed in the stirring zone and that the average grain size can be decreased by increasing the build height. The yield strengths in the stirring and heat-affected zones increase along the build direction and decrease with increasing temperature. The error between the predicted and experimental yield strengths is 3.3%. By considering changes in the mechanical properties in the stirring and heat-affected zones, the distortion error between the experimental test and numerical model can be reduced by 25% compared with that between the experimental test and the conventional model. The predicted residual stresses can be reduced by considering the strength reduction caused by the friction stirring effect. As the number of built layers increases, the maximum distortion in FSAM increases.

IMPACT OF LONGSHORE SEDIMENT TRANSPORT ON THE DESIGN AND MAINTENANCE OF LOW-ENERGY, NON-TIDAL SANDY BEACHES

When low-energy, non-tidal lake beaches have a flood safety function, such as at the Houtribdijk, the Netherlands, sediment losses can directly affect the functioning of the beach (fig. 1). Detailed understanding of morphodynamic processes is needed to enable reliable predictions of the morphological development and the design of efficient maintenance strategies. Ton et al. (2021) showed that the development of these beaches is driven by both cross-shore and longshore processes. Wave action causes a distinct cross-shore profile shape to develop, with a steep beach face and a gently sloped platform around the depth of closure. However, on top of that, the combined effect of large-scale horizontal flow circulations (caused by gradients in storm surge level across the lake, Ton et al., submitted) and wave-induced sediment stirring was found to be an important driver of sediment losses along the beaches. In this work, we research how longshore transport (LST) can best be determined for low-energy lake beaches and classify and quantify the uncertainties related to this method.