Dissimilar friction stir spot welding of AA2024-T3/AA7075-T6 aluminum alloys under different welding parameters and media

This paper studies the friction stir spot welding of AA2024-T3/AA7075-T6 Al alloys in the ambient and underwater environments by clarifying the nugget features,microstructure,fracture and mechanical properties of the joints.The results show that the water-cooling medium exhibits a significant heat absorption capacity in the AA2024-T3/AA7075-T6 welded joint.Nugget features such as stir zone width,circular imprints,average grain sizes,and angular inter-material hooking are reduced by the watercooling effect in the joints.Narrower whitish(intercalated structures)bands are formed in the underwater joints while Mg2Si and Al2CuMg precipitates are formed in the ambient and the underwater welded joints respectively.An increase in tool rotational speed(600e1400 rpm)and plunge depth(0.1 e0.5 mm)increases the tensile-shear force of the welded AA2024-T3/AA7075-T6 joints in both the ambient and underwater environments.The maximum tensile-shear forces of 5900 N and 6700 N were obtained in the ambient and the underwater welds respectively.

Dynamic Simulation Analysis of the Working Device of a ZL50 Loader

In this study,assuming a certain type of wheel loader as the main objective of the research,the performances of the working device of the loader are investigated on the basis of an in-house code.After creating a three-dimensional model of the working device using Solidworks,this model has been imported into the dynamic simulation software ADAMS,and the simulation problem has been completed by adding the relevant constraints and loadings.The load stress curve relating to the main connecting point of the working device has been obtained in the frame work of this approach and it has been shown that the movement characteristics are compatible with(i.e.,they match)the actual working conditions.The present study may be regarded as a theoretical basis for the design and improvement of the working device of a vast category of wheel loaders.

Enhancement of Photo-Thermal Conversion Performance of the Nanofluids Through Spectral Complementarity between Silver and Cesium Tungstate Oxide Nanoparticles

Nanofluids with full-spectrum absorption properties are highly desirable for direct solar thermal energy conversion applications.In this work,Ag and CsW03 nanofluids,which exhibit absorption both in the visible and near-infrared(NIR)region,are integrated to obtain two>component hybrid nanofluids.The hybrid nanofluids show broad band absorption with a solar weighted absorption fraction of 99.6%,compared to 18%and 54%for the base liquid(ethylene glycol)and CsW03 nanofluids,respectively.The highest photo-thermal conversion performance for the hybrid nanofluids is obtained with Ag/CsW03 weight ratio of 3/7.The solar thermal conversion efficiency of the optimum hybrid nanofluids is 67%,10%and 15%higher than single Ag and CsW03 nanofluids.The two-component hybrid nanofluid provides an alternative for making the best use of solar energy.

Achieving high yield of Ti3C2Tx MXene few-layer flakes with enhanced pseudocapacior performance by decreasing precursor size

Ti3C2Tx,a most studied member of MXene family,shows promise as a candidate electrode for pseudocapacitor due to its electronic conductivity and hydrophilic surface.However,the unsatisfactory yield of Ti3C2Tx few-layer flakes significantly restricted it in real applications.Here,we proposed a simple solution to boost the yield of Ti3C2Tx few-layer flakes by decreasing precursor size.When using the small500 mesh Ti3AlC2 powders as raw material,high yield of 65%was successfully achieved.Moreover,the asreceived small flakes also exhibit an enhanced pseudocapacior performance owing to their excellent electrical conductivity,expanded inte rlayer space and more O content on the surface.This work not only sheds light on the cost effective mass production of Ti3C2Tx few-layer flakes,but also provides an efficient solution for the design of MXene electrodes with high pseudocapacior performance.

Analysis of Hydrocarbon Mixture Performance of a Dual-Channel Swirl Engine

In order to understand and improve the oil and gas mixing performance of a dual-channel vortex chamber diesel engine,the BH175F dual-channel vortex chamber combustion system was used as the research foundation,and the oil-gas mixture process of the combustion system was numerically analyzed.By analyzing the cylinder temperature,cylinder pressure,mixing process and combustion process of the combustion system,the mixture performance of the combustion system was studied.Results indicated that:The mixture of the compression Top Dead Center(TDC)started to enter the main combustion chamber through the start-up hole;when the piston reached 4°After Top Dead Center(ATDC),the mixture started to enter the main combustion chamber through the connecting channels A and B,and the high-concentration mixture entered the main combustion from the start-up hole;when the piston continued running down to 20°and 25°ATDC,it could be seen that the main combustion chamber mixture was already relatively uniform;besides,when the equivalence ratio was between 0.8 and 1,the air-ftiel mixture was unevenly distributed in the main combustion chamber.It provides guidance for further improvement of the combustion system.

Simulation of Combustion Flow of Methane Gas in a Premixed Low-Swirl Burner using a Partially Premixed Combustion Model

Because the rotational current stabilizes the flame by creating a recirculation zone,it may increase the risk of reversal.For this reason,low-spin combustion is used to stabilize the flame while preventing flashbacks.Therefore,in this study,the combustion flow of methane gas in a low-swirl burner is simulated using a partially premixed combustion model.Furthermore,the fuel flow rate is considered constant.The research parameters include swirl angle(θ=35°–47°),equivalence ratio(φ=0.6–0.9)and inlet axial flow radius(R=0.6–0.7)and effect of these parameters on temperature distribution,flame length,flame rise length,velocity field,and streamlines of the number of pollutant species are investigated.The contours of streamline,temperature distribution,and velocity distribution are also presented for analysis of flow physics.The results show that with increasing the fuel-air ratio,the strength of the axial flow decreases,and the position of the maximum flame temperature shifts toward the inlet of the reactants.The results also reveal that by increasing the swirl angle of the flow,the position of the minimum velocity value(opposite to the direction of the axis)tends towards the outlet.The results also indicate that the maximum temperature of the combustion chamber increases with increasing the swirl angle,and inθ=35°,the maximum temperature is 1711℃and inθ=41°,this value is 1812℃.Finally,by increasing the swirl angle toθ=47°,the maximum flame temperature position is found at a considerable distance from the inlet and is 1842℃.