Bulging Performance and Quality Control of Aluminum Alloy Tailor-welded Overlapping Sheets Based on Interface Friction

In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.

An embedded electron current layer observed at the edge of the plasma sheet in the Earth’s magnetotail

The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sheet.The ions were demagnetized inside the electron current layer,but the electrons were still frozen in with the magnetic field line.Thus,this decoupling of ions and electrons gave rise to a strong Hall electric field,which could be the reason for the formation of the embedded thin current layer.The magnetized electrons,the absence of the nongyrotropic electron distribution,and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer.The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection.The observations indicate that the embedded electric current layer,probably generated by the Hall electric field,even down to electron scale,is not a sufficient condition for magnetic reconnection.

Thermo-physical Characteristics of Nickel-coated Aluminum Powder as a Function of Particle Size and Oxidant

Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

The Electrical Conductive Effect of Nickel-coated Graphite/Two-component Silicone-rubber Sealant

Nickel-coated graphite particles and two-component silicone-rubber were compounded to form a conductive composite system. The electrical volume resistivity of the composites were examined and compared under constant tensile strains, cyclic heating-cooling, electric field and repeated cyclic tensile strains in order to study the mechanism of electrical conductivity behaviors of the conductive composites under stress, temperature and current. The results showed that a peak value of the electrical resistivity appeared previously and then gradually increasing with increasing tensile strain. The electrical resistivity displayed positive temperature coefficient effect during the temperature increasing and decreasing. Applying 5A direct current to the conductive composites lesulted in an increase in the electrical resistance immediately, but no changes were detected under lower currents. Under the repeated cyclic strain, the peak value of the electrical resistivity of each cycle increased with the test cycle. All the electrical resistivity changes were attributed to the conductive networks broken-up and rebuilt in the conductive composites.

Microstructure and performance of laser cladding TiB_2 and Nickel-coated graphite composite coating on stainless steel 9Cr18

The antiwear and antifriction coating, which contains TiB2 and Nickel-coated graphite, has been obtained on stainless steel 9Cr18 by laser cladding. The processing method, microstructure, interface, microhardness, tribological properties and the forming mechanisms of the coating are analyzed. Results show that the microstructure of the clad coating are mainly long plume-like primary phase sosoloid Ni-Fe which form the matrix framework, while the in-situ anomalous synthetical TiC grains and uhrafine TiB2 grains uniformly disperse among the framework. The hardness and wear resistance of the coating has been greatly improved, which can be attributed to the reinforcement mechanism of TiC, TiB2, FeC, Fe3C and Cr23 C6. etc. At the same time, the coating has friction-reducing ability.

Elastic-viscoplastic behaviors of polymer-blend geocell sheets:Numerical and experimental investigations

Polymer-blend geocell sheets(PBGS)have been developed as substitute materials for manufacturing geocells.Various attempts have been made to test and predict the behaviors of commonly used geogrids,geotextiles,geomembranes,and geocells.However,the elastic-viscoplastic behaviors of novel-developed geocell sheets are still poorly understood.Therefore,this paper investigates the elastic-viscoplastic behaviors of PBGS to gain a comprehensive understanding of their mechanical properties.Furthermore,the tensile load-strain history under various loading conditions is simulated by numerical calculation for widespread utilization.To achieve this goal,monotonic loading tests,short-term creep and stress relaxation tests,and multi-load-path tests(also known as arbitrary loading history tests)are performed using a universal testing machine.The results are simulated using the nonlinear three-component(NLTC)model,which consists of three nonlinear components,i.e.a hypo-elastic component,a nonlinear inviscid component,and a nonlinear viscid component.The experimental and numerical results demonstrate that PBGS exhibit significant elastic-viscoplastic behavior that can be accurately predicted by the NLTC model.Moreover,the tensile strain rates significantly influence the tensile load,with higher strain rates resulting in increased tensile loads and more linear load-strain curves.Also,parametric analysis of the rheological characteristics reveals that the initial tensile strain rates have negligible impact on the results.The rate-sensitivity coefficient of PBGS is approximately 0.163,which falls within the typical range observed in most geosynthetics.

Numerical simulation on sand sedimentation and erosion characteristics around HDPE sheet sand barrier under different wind angles

For the safety of railroad operations,sand barriers are utilized to mitigate wind-sand disaster effects.These disasters,characterized by multi-directional wind patterns,result in diverse angles among the barriers.In this study,using numerical simulations,we examined the behavior of High Density Polyethylene(HDPE)sheet sand barriers under different wind angles,focusing on flow field distribution,windproof efficiency,and sedimentation erosion dynamics.This study discovered that at a steady wind speed,airflow velocity varies as the angle between the airflow and the HDPE barrier changes.Specifically,a 90°angle results in the widest low-speed airflow area on the barrier’s downwind side.If the airflow is not perpendicular to the barrier,it prompts a lateral airflow movement which decreases as the angle expands.The windproof efficiency correlates directly with this angle but inversely with the wind’s speed.Notably,with a wind angle of 90°,wind speed drops by 81%.The minimum wind speed is found at 5.1H(the sand barrier height)on the barrier’s downwind side.As the angle grows,the barrier’s windproof efficiency improves,extending its protective reach.Sedimentation is most prominent on the barrier’s downwind side,as the wind angle shifts from 30°to 90°,the sand sedimentation area on the barrier’s downwind side enlarges by 14.8H.As the angle grows,sedimentation intensifies,eventually overtakes the forward erosion and enlarges the sedimentation area.

Flow field, sedimentation, and erosion characteristics around folded linear HDPE sheet sand fence: Numerical simulation study

Wind and sand hazards are serious in the Milan Gobi area of the Xinjiang section of the Korla Railway. In order to ensure the safe operation of railroads, there is a need for wind and sand protection in heavily sandy areas. The wind and sand flow in the region is notably bi-directional. To shield railroads from sand, a unique sand fence made of folded linear high-density polyethylene(HDPE) is used, aligning with the principle that the dominant wind direction is perpendicular to the fence. This study employed field observations and numerical simulations to investigate the effectiveness of these HDPE sand fences in altering flow field distribution and offering protection. It also explored how these fences affect the deposition and erosion of sand particles. Findings revealed a significant reduction in wind speed near the fence corner;the minimum horizontal wind speed on the leeward side of the first sand fence(LSF) decreased dramatically from 3 m/s to 0.64 m/s. The vortex area on the LSF markedly impacted horizontal wind speeds. Within the LSF, sand deposition was a primary occurrence. As wind speeds increased, the deposition zone shrank, whereas the positive erosion zone expanded. Close to the folded corners of the HDPE sand fence, there was a notable shift from the positive erosion zone to a deposition zone. Field tests and numerical simulations confirmed the high windproof efficiency(WE) and sand resistance efficiency(SE) in the HDPE sand fence. Folded linear HDPE sheet sand fence can effectively slow down the incoming flow and reduce the sand content, thus achieving good wind and sand protection. This study provides essential theoretical guidance for the design and improvement of wind and sand protection systems in railroad engineering.

Evidence of guide field magnetic reconnection in flapping current sheets

Based on current sheet flapping motion on 27 August 2018 in the dusk flank magnetotail,as recorded by instruments aboard Magnetospheric Multiscale(MMS)spacecraft,we present the first study of guide field reconnection observed in the flux rope embedded in kink-like flapping current sheets near the dusk-side flank of the magnetotail.Unlike more common magnetotail reconnections,which are symmetric,these asymmetric small-scale(λ_(i)~650 km)reconnections were found in the highly twisted current sheet when the direction normal to the sheet changes from the Z direction into the Y direction.The unique feature of this unusual reconnection is that the reconnection jets are along the Z direction-different from outflow in the X direction,which is the more usual situation.This vertical reconnection jet is parallel or antiparallel to the up-and-down motion of the tail’s current sheet.The normalized reconnection rate R is estimated to be~0.1.Our results indicate that such asymmetric reconnections can significantly enlarge current sheet flapping,with large oscillation amplitudes.This letter presents direct evidence of guide field reconnection in a highly twisted current sheet,characterized by enlarged current sheet flapping as a consequence of the reconnection outflow.

A new model of flow over stretching(shrinking)and porous sheet with its numerical solutions

The viscous fluid flow and heat transfer over a stretching(shrinking)and porous sheets of nonuniform thickness are investigated in this paper.The modeled problem is presented by utilizing the stretching(shrinking)and porous velocities and variable thickness of the sheet and they are combined in a relation.Consequently,the new problem reproduces the different available forms of flow motion and heat transfer maintained over a stretching(shrinking)and porous sheet of variable thickness in one go.As a result,the governing equations are embedded in several parameters which can be transformed into classical cases of stretched(shrunk)flows over porous sheets.A set of general,unusual and new variables is formed to simplify the governing partial differential equations and boundary conditions.The final equations are compared with the classical models to get the validity of the current simulations and they are exactly matched with each other for different choices of parameters of the current problem when their values are properly adjusted and manipulated.Moreover,we have recovered the classical results for special and appropriate values of the parameters(δ_(1),δ_(2),δ_(3),c,and B).The individual and combined effects of all inputs from the boundary are seen on flow and heat transfer properties with the help of a numerical method and the results are compared with classical solutions in special cases.It is noteworthy that the problem describes and enhances the behavior of all field quantities in view of the governing parameters.Numerical result shows that the dual solutions can be found for different possible values of the shrinking parameter.A stability analysis is accomplished and apprehended in order to establish a criterion for the determinations of linearly stable and physically compatible solutions.The significant features and diversity of the modeled equations are scrutinized by recovering the previous problems of fluid flow and heat transfer from a uniformly heated sheet of variable(uniform)thickness with variable(uniform)stretching/shrinking and injection/suction velocities.

Exact solutions for magnetohydrodynamic nanofluids flow and heat transfer over a permeable axisymmetric radially stretching/shrinking sheet

We report on the magnetohydrodynamic impact on the axisymmetric flow of Al_(2)O_(3)/Cu nanoparticles suspended in H_(2)O past a stretched/shrinked sheet.With the use of partial differential equations and the corresponding thermophysical characteristics of nanoparticles,the physical flow process is illustrated.The resultant nonlinear system of partial differential equations is converted into a system of ordinary differential equations using the suitable similarity transformations.The transformed differential equations are solved analytically.Impacts of the magnetic parameter,solid volume fraction and stretching/shrinking parameter on momentum and temperature distribution have been analyzed and interpreted graphically.The skin friction and Nusselt number were also evaluated.In addition,existence of dual solution was deduced for the shrinking sheet and unique solution for the stretching one.Further,Al_(2)O_(3)/H_(2)O nanofluid flow has better thermal conductivity on comparing with Cu/H_(2)O nanofluid.Furthermore,it was found that the first solutions of the stream are stable and physically realizable,whereas those of the second ones are unstable.

Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Migration and role of zinc in biogeochemical cycles in the Antarctic Ice Sheet and the Southern Ocean

Zinc(Zn),a widespread metal in the Earth’s crust,serves as a crucial nutrient in the Southern Ocean’s primary production.Studies on Zn in Antarctic snow and ice offer insights into the origins of this metal and its transport routes,as well as its impact on the biogeochemical processes within the Antarctic atmosphere–land–ocean system.This review examines research on the spatial and temporal distribution of Zn in Antarctic snow and ice,as well as in Southern Ocean waters.It includes an overview of advanced methods for sampling and analyzing Zn,along with explanations for the observed variations.The review also discusses various sources of Zn as a nutrient to the Southern Ocean.Finally,it addresses prospective issues related to the use of Zn isotopes in identifying atmospheric sources and their biogeochemical effects on the development of the Southern Ocean ecosystem.

Chemically Radiative MHD Flow of a Micropolar Nanofluid over a Stretching/ Shrinking Sheet with a Heat Source or Sink

This study examines the behavior of a micropolar nanofluidflowing over a sheet in the presence of a transverse magneticfield and thermal effects.In addition,chemical(first-order homogeneous)reactions are taken into account.A similarity transformation is used to reduce the system of governing coupled non-linear partial differ-ential equations(PDEs),which account for the transport of mass,momentum,angular momentum,energy and species,to a set of non-linear ordinary differential equations(ODEs).The Runge-Kutta method along with shoot-ing method is used to solve them.The impact of several parameters is evaluated.It is shown that the micro-rota-tional velocity of thefluid rises with the micropolar factor.Moreover,the radiation parameter can have a remarkable influence on theflow and temperature profiles and on the angular momentum distribution.

Some recent advances in remote sensing-based monitoring of changes in the Greenland Ice Sheet

The mass balance of the Greenland Ice Sheet(GrIS)plays a crucial role in global sea level change.Since the 1960s,remote sensing missions have been providing extensive and continuous observation data for change monitoring of the GrIS.In this paper,we present our recent research results from remote sensing-based GrIS change monitoring.First,historical satellite data are processed and used to fill data gaps and are combined with existing partial maps,completing an ice velocity map of the GrIS from the 1960s to 1980s.This map provides valuable data for estimating the historical mass balance of Greenland.Second,the monthly gravimetry-based mass balance of the GrIS from 2002 to 2020 is estimated by combining Gravity Recovery and Climate Experiment(GRACE)and GRACE Follow On(GRACE-FO)data.It is found that the GrIS has lost a total mass of approximately 4443±75 Gt during this period.Third,based on Global Land Ice Measurements from Space(GLIMS),an updated Greenland glacier inventory is achieved utilizing data collected between 2006 and 2020.This inventory provides more detailed and up-to-data glacier boundaries of Greenland.Overall,these advances provide essential data support for estimating the mass balance of the GrIS,contributing to the advancement of research on global sea level change.

Oscillating Performance of A Rigid Buoy Floating Between Two Ice Sheets with Finite Lengths

Global warming has led to major melting of ice in the polar Arctic,making it possible to open Arctic shipping lanes.In this case,the large number of ice sheets are extremely dangerous for ship navigation,so in this paper,a body floating on water confined between two finite ice sheets is investigated.The linearized potential flow theory is adopted,and water is considered an incompressible ideal fluid with a finite depth of the fluid domain.The ice sheets are treated as elastic plates,and the problem is solved by matching eigenfunction expansion.The fluid domain is divided into subregions on the basis of the water surface conditions,and the velocity potential of the subdomains is expanded via the separated variable method.By utilizing the continuity of pressure and velocity at the interfaces of two neighboring regions,a system of linear equations is established to obtain the unknown coefficients in the expansion,which in turn leads to analytical solutions for different motion modes in different regions.The effects of different structural drafts,and different lengths of ice sheets on both sides,etc.,on the hydrodynamic characteristics of floats are analyzed.The amplitude of motion of the float is explored,as is the wave elevation between the ice sheets and the float.

Numerical Study on 3D MHD Darcy-Forchheimer Flow Caused by Gyrotactic Microorganisms of the Bio-Convective Casson Nanofluid across a Stretched Sheet

A review of the literature revealed that nanofluids are more effective in transferring heat than conventional fluids.Since there are significant gaps in the illumination of existing methods for enhancing heat transmission in nanomaterials,a thorough investigation of the previously outlined models is essential.The goal of the ongoing study is to determine whether the microscopic gold particles that are involved in mass and heat transmission drift in freely.The current study examines heat and mass transfer on 3D MHD Darcy–Forchheimer flow of Casson nanofluid-induced bio-convection past a stretched sheet.The inclusion of the nanoparticles is a result of their peculiar properties,such as remarkable thermal conductivity,which are important in heat exchangers and cutting-edge nanotechnology.The gyrotactic microorganisms must be included to prevent the potential deposition of minute particles.The proposed flow dynamics model consists of an evolving nonlinear system of PDEs,which is subsequently reduced to a system of dimensionless ODEs utilizing similarity approximations.MATLAB software was utilized to create an effective code for the Runge-Kutta technique using a shooting tool to acquire numerical results.This method is extensively used to solve these issues since it is accurate to fourth order,efficient,and affordable.The influence of submerged factors on the velocity,temperature,concentration,and density of motile microorganisms is shown in the figures.Additionally,tables and bar charts are used to illustrate the physical characteristics of the Nusselt and Sherwood numbers for the densities of both nanoparticles and motile microorganisms.The dimensionless velocities are observed declining when the casson,magnetic,porosity,and forchheimer parameters grow,whereas the dimensionless temperature and concentration rise as the thermophoresis parameter rises.This work provides insights into practical applications such nanofluidic,energy conservation,friction reduction,and power generation.Furthermore,in a concentration field,the Brownian and thermophoresis parameters exhibit very distinct behaviours.However,the work makes a significant point that the flow of a Casson fluid including nanoparticles can be regulated by appropriately modifying the Casson parameter,thermophoresis parameter,and Brownian motion parameter.

A Physical Core-Loss Model for Laminated Magnetic Sheet Steels

A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation provides high simulation accuracy and performs dynamic core loss analysis on non-sinusoidal or pulse magnetic fields. The simulation examples use a high-grade electrical steel sheet 65CS400 by Epstein experimental data covering magnetic field 0.1 - 1.8 T and frequency 50 - 5000 Hz, and the average error of the simulated core loss is less than 4%. Since the simulation is converged by magnetic physical parameters, so the physical relevance of the similar laminated materials can be compared with the coefficient results. .

Casson Nanofluid Flow with Cattaneo-Christov Heat Flux and Chemical Reaction Past a Stretching Sheet in the Presence of Porous Medium

In the current work,inclined magnetic field,thermal radiation,and the Cattaneo-Christov heat flux are taken into account as we analyze the impact of chemical reaction on magneto-hydrodynamic Casson nanofluid flow on a stretching sheet.Modified Buongiorno’s nanofluid model has been used to model the flow governing equations.The stretching surface is embedded in a porousmedium.By using similarity transformations,the nonlinear partial differential equations are transformed into a set of dimensionless ordinary differential equations.The numerical solution of transformed dimensionless equations is achieved by applying the shooting procedure together with Rung-Kutta 4th-order method employing MATLAB.The impact of significant parameters on the velocity profile f(ζ),temperature distributionθ(ζ),concentration profileϕ(ζ),skin friction coefficient(Cf),Nusselt number(Nux)and Sherwood number(Shx)are analyzed and displayed in graphical and tabular formats.With an increase in Casson fluid 0.5<β<2,the motion of the Casson fluid decelerates whereas the temperature profile increases.As the thermal relation factor expands 0.1<γ1<0.4,the temperature reduces,and consequently thermal boundary layer shrinks.Additionally,by raising the level of thermal radiation 1<Rd<7,the temperature profile significantly improves,and an abrupt expansion has also been observed in the associated thermal boundary with raise thermal radiation strength.It was observed that higher permeability 0<K<4 hinders the acceleration of Casson fluid.Higher Brownian motion levels 0.2<Nb<0.6 correspond to lower levels of the Casson fluid concentration profile.Moreover,it is observed that chemical reaction 0.2<γ2<0.5 has an inverse relation with the concentration level of Casson fluid.The current model’s significant uses include heat energy enhancement,petroleum recovery,energy devices,food manufacturing processes,and cooling device adjustment,among others.Furthermore,present outcomes have been found in great agreementwith already publishedwork.

Novel Fabrication Technique Takes Transition Metal Telluride Nanosheets from Lab to Mass Production

Transition metal telluride nanosheets have shown enormous promise for fundamental research and other applications across various fields.Still,until now,mass fabrication has been impossible,leaving the material as something of a laboratory curiosity rather than an industrial reality.But a team of researchers from the Dalian Institute of Chemical Physics(DICP)of the Chinese Academy of Sciences has recently developed a novel exfoliation process–using chemical solutions to peel off thin layers from their parent compounds,creating atomically thin sheets–that looks set to finally deliver on the ultra-thin substance’s promise.