This paper introduces a hybrid multi-objective optimization algorithm,designated HMODESFO,which amalgamates the exploratory prowess of Differential Evolution(DE)with the rapid convergence attributes of the Sailfish Op...This paper introduces a hybrid multi-objective optimization algorithm,designated HMODESFO,which amalgamates the exploratory prowess of Differential Evolution(DE)with the rapid convergence attributes of the Sailfish Optimization(SFO)algorithm.The primary objective is to address multi-objective optimization challenges within mechanical engineering,with a specific emphasis on planetary gearbox optimization.The algorithm is equipped with the ability to dynamically select the optimal mutation operator,contingent upon an adaptive normalized population spacing parameter.The efficacy of HMODESFO has been substantiated through rigorous validation against estab-lished industry benchmarks,including a suite of Zitzler-Deb-Thiele(ZDT)and Zeb-Thiele-Laumanns-Zitzler(DTLZ)problems,where it exhibited superior performance.The outcomes underscore the algorithm’s markedly enhanced optimization capabilities relative to existing methods,particularly in tackling highly intricate multi-objective planetary gearbox optimization problems.Additionally,the performance of HMODESFO is evaluated against selected well-known mechanical engineering test problems,further accentuating its adeptness in resolving complex optimization challenges within this domain.展开更多
Compressive mechanical behavior and microstructure evolution of Ti−5.7Al−2.9Nb−1.8Fe−1.6Mo−1.5V−1Zr alloy under extreme conditions were systematically investigated.The results show that strain rate and temperature hav...Compressive mechanical behavior and microstructure evolution of Ti−5.7Al−2.9Nb−1.8Fe−1.6Mo−1.5V−1Zr alloy under extreme conditions were systematically investigated.The results show that strain rate and temperature have a significant influence on the mechanical behavior and microstructure.The alloy exhibits a positive strain rate sensitivity and negative temperature sensitivity under all temperature and strain rate conditions.The hot-rolled alloy is composed of a bimodal structure including an equiaxed primary α_(p) phase and a transformedβphase.After compression deformation,the bimodal deformed structural features highly rely on the temperature and strain rate.At low temperature and room temperature,the volume fraction and size of α_(p) phase decrease with increasing temperature and strain rate.At high temperature,the volume fraction of the α_(p)hase is inversely correlated with temperature.A modified Johnson−Cook constitutive model is established,and the predicted results coincide well with the experimental results.展开更多
The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets ...The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets are placed on a visco-Pasternak medium in a hygro-temperature environment with nonlinear rules.The viscoelastic material characteristics of nanosheets are based on Kelvin’s model.The unique point of this study is to consider the change of nonlocal and length-scale coefficients according to thickness,similar to the laws of the material properties.The Galerkin approach based on the Kirchhoff-love plate theory is applied to determine the natural frequency and critical buckling load of the viscoelastic FGP nanosheet with various boundary conditions.The accuracy of the proposed method is verified through reliable publications.The outcome of this study highlights the significant effects of the nonlocal and length-scale parameters on the vibration and buckling behaviors of viscoelastic FGP nanosheets.展开更多
The influence of ultrasonic vibrations on microstructure and mechanical properties of the AZ91-C magnesium alloy after ultrasonic assisted friction stir welding(UaFSW)in comparison with conventional friction stir weld...The influence of ultrasonic vibrations on microstructure and mechanical properties of the AZ91-C magnesium alloy after ultrasonic assisted friction stir welding(UaFSW)in comparison with conventional friction stir welding(FSW)was investigated.The FSW was applied at the rotational speed of 1400 r/min and welding speed of 40 mm/min and no defects were observed.Using the same welding parameters,the process was carried out with inducing ultrasonic vibrations to the weld line at the amplitude of 15μm.The microstructure of the specimens was observed with optical and scanning electron microscopy.The results indicate that a very fine microstructure is obtained in UaFSW with respect to that of conventional FSW.Moreover,β-Mg17Al12 coarse dendrites are segregated to very fine and partly spherical particles that homogeneously distribute inα-Mg matrix.This remarkably-modified morphology of microstructure attributed to severe plastic deformation comes from ultrasonic vibration and friction stirring effect.Tensile and hardness tests were performed to evaluate the mechanical properties of the welds.According to the results,the vibration greatly improves the mechanical properties of the conventional FSW joint.The tensile strength and hardness are increased from 195 MPa and HV 79 in conventional FSW to 225 MPa and HV 87 in UaFSW,respectively.展开更多
The microstructure evolution, mechanical and corrosion properties of Al-11Si-2Cu-0.8Zn die cast alloy treated with Bi, Sb and Sr additions were investigated. The results of mechanical testing showed that all additions...The microstructure evolution, mechanical and corrosion properties of Al-11Si-2Cu-0.8Zn die cast alloy treated with Bi, Sb and Sr additions were investigated. The results of mechanical testing showed that all additions increased impact toughness, ultimate tensile strength, and elongation of the alloy as a result of change in eutectic Si morphology. The analysis of fracture surfaces revealed that with addition of Sr and to lesser extent Bi and Sb, the alloy exhibited a predominantly ductile fracture rather than quasi-cleavage brittle fracture. Moreover, with the additions of Sr, Bi and Sb, the quality index increased to 164.7 MPa, 156.3 MPa and 152.6 MPa respectively from 102 MPa for the base alloy. Polarization corrosion tests conducted in sodium chloride solution showed that the corrosion potential shifted to more negative values with additions of Sb, Bi and Sr, respectively. Corrosion immersion tests also revealed that the element additions have a detrimental effect on the corrosion rate of alloys, due to the increase of boundaries between the Al and eutectic Si phases.展开更多
In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with...In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,martensite.The variation of the prior austenite grain size is believed to vary the end results of the martensite.This undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,etc.This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure.The results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter increases.The block and packet sizes in the martensite also increase.The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology.With respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.展开更多
This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of prim...This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt%resulted in a loss of modification, possibly due to the formation of Al8 MgB iS i4 compound before the precipitation of the primary Mg2 Si. Additionally, the structure of the pseudo-eutectic Mg2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al5 Fe Si（β）, Al2Cu（θ） and Al5Cu2Mg8Si6（Q） intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg2 Si particles.展开更多
The Mg-6Al-4Zn alloy was fabricated by mechanical alloying(MA)and hot pressing to serve as biodegradable metal implant.The influence of addition of 1%Si(mass fraction)on the microstructure,mechanical properties and bi...The Mg-6Al-4Zn alloy was fabricated by mechanical alloying(MA)and hot pressing to serve as biodegradable metal implant.The influence of addition of 1%Si(mass fraction)on the microstructure,mechanical properties and bio-corrosion behavior of Mg-6Al-1Zn alloy was studied using X-ray diffractometry,transmission electron microscopy,compression test,as well as immersion,electrochemical test and MTT assay.The results showed that the addition of 1%Si to Mg-6Al-1Zn alloy led to the formation of fine Mg2Si phase with polygonal shape,and increased compressive strength,elongation and improved corrosion resistance.Furthermore,the cell viability of Saos-2 cells has been improved by addition of 1%Si to Mg-6Al-1Zn alloy.According to the results,the magnesium ions released in the methylthiazol tetrazolium(MTT)test have not shown any cell toxicity.All these indicated that the addition of 1%Si improved the properties of Mg-6Al-4Zn alloy for using as a biodegradable implant.展开更多
This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely ...This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely wall angle(35°-55°),feed rate(1-4 m/min),spindle rotational speed(50-1000 r/min),and lubricant(grease and hydraulic oil)are varied to probe detailed processing effects.The pre-and post-SPIF mechanical properties and microstructures are characterized by conducting tensile tests and optical microscopy,respectively.It is shown that an increase in the wall angle,feed rate and rotational speed causes microscopic variations in the alloys such that the grains of AA5754 and the second phase particles of AA6061 elongate.As a result,the ultimate tensile strength of the formed parts is increased by 10%for AA5754 and by 8%for AA6061.And,the ductility of AA5754 is decreased from 22.9%to 12%and that of AA6061 is decreased from 16%to 10.7%.Regarding the lubricant effect,it is shown that the mechanical properties remain insensitive to the type of lubricant employed.These results indicate that SPIF processing modifies the microstructure of Al alloys in a way to enhance the strength at the cost of ductility.展开更多
As bifunctional oxygen evolution/reduction electrocatalysts,transition-metal-based single-atom-doped nitrogen-carbon(NC)matrices are promising successors of the corresponding noblemetal-based catalysts,offering the ad...As bifunctional oxygen evolution/reduction electrocatalysts,transition-metal-based single-atom-doped nitrogen-carbon(NC)matrices are promising successors of the corresponding noblemetal-based catalysts,offering the advantages of ultrahigh atom utilization effciency and surface active energy.However,the fabrication of such matrices(e.g.,well-dispersed single-atom-doped M-N4/NCs)often requires numerous steps and tedious processes.Herein,ultrasonic plasma engineering allows direct carbonization in a precursor solution containing metal phthalocyanine and aniline.When combining with the dispersion effect of ultrasonic waves,we successfully fabricated uniform single-atom M-N4(M=Fe,Co)carbon catalysts with a production rate as high as 10 mg min-1.The Co-N4/NC presented a bifunctional potential drop ofΔE=0.79 V,outperforming the benchmark Pt/C-Ru/C catalyst(ΔE=0.88 V)at the same catalyst loading.Theoretical calculations revealed that Co-N4 was the major active site with superior O2 adsorption-desorption mechanisms.In a practical Zn-air battery test,the air electrode coated with Co-N4/NC exhibited a specific capacity(762.8 mAh g(-1))and power density(101.62 mW cm^(-2)),exceeding those of Pt/C-Ru/C(700.8 mAh g^(-1) and 89.16 mW cm^(-2),respectively)at the same catalyst loading.Moreover,for Co-N4/NC,the potential difference increased from 1.16 to 1.47 V after 100 charge-discharge cycles.The proposed innovative and scalable strategy was concluded to be well suited for the fabrication of single-atom-doped carbons as promising bifunctional oxygen evolution/reduction electrocatalysts for metal-air batteries.展开更多
Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 allo...Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.展开更多
In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron mi...In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron microscopy(SEM),X-ray diffractometry(XRD),compression test,and shape memory testing.The xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering process.The results revealed that the addition of Ag has a significant effect on the pore size and shape,whereas the smallest pore size of 11μm was found with the addition of 0.41 at%along with a relative density of 72%.The fracture stress and strain increased with the addition of Ag,reaching the minimum values around 0.41 at%Ag.Therefore,this composition showed the maximum stress and strain at fracture region.Moreover,0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages,obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys,which can be recommended for their promising and potential response for biomaterial applications.展开更多
Effects of multiple strengthening treatments （i.e. ag mechanical properties and stability of nanoscale prec in this research. Various tests such as hardness, tensi ng either at three or four consecutive temperatures...Effects of multiple strengthening treatments （i.e. ag mechanical properties and stability of nanoscale prec in this research. Various tests such as hardness, tensi ng either at three or four consecutive temperatures） on pitated phases in an AA2090 alloy have been evaluated e, electrical resistance, differential scanning calorimetric （DSC）, and transmission electron microscopy （TEM） have been performed. The results show that the ultimate tensile strength （UTS） and the yield strength of the samples aged at four consecutive temperatures （i.e. natural aging＋190℃＋150℃＋100℃） can be increased approximately to 660 and 610 MPa, respectively. It is also found that precipitation of T1 phase occurs during multiple aging process of the alloy and the higher amounts of enthalpies shown in DSC charts are linked to higher volume fraction of this precipitate. Furthermore, TEM observations reveal that T1 phase has plate shape morphology and its crystal structure is in the form of hcp with lattice parameters of a=0.467 nm and c=0.878 nm.展开更多
Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation...Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation behavior. Thermal analysis and microstructural observations showed that Zn-0.5A1-0.5Mg is composed of FCC-A1 ＋ HCP- Zn ＋ Mg2（Zn,A1）ll while a new phase a-Mg3Bi2 appeared after the addition of Bi to the Zn-0.5A1-0.5Mg ternary alloy. The results revealed that the quaternary Zn-A1-Mg-Bi alloys have higher tensile strength, elongation and hardness but slightly lower corrosion resistance than those of the temary Zn-AI-Mg alloy. Based on the MTT assay, the Zn-A1-Mg and Zn-A1-Mg-Bi alloys were found to be biocompatible, and thus, they can be considered for further investigation in an in vivo environment.展开更多
The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by opti...The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by optical microscope,X-ray diffraction,scanning electron microscope and Feritscope,while the mechanical properties were determined by hardness and tensile tests.The results revealed that the content of retained austenite decreased by about 2% after multi-step tempering.However,the content of retained austenite increased from 3.6% to 5.1% by increasing multi-step tempering temperature.The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 ℃,while above 920 ℃,hardness and tensile strength decreased.In addition,the maximum values of hardness,ultimate and yield strength were obtained via triple tempering at 520 ℃,while beyond 520 ℃,the hardness,ultimate and yield strength decreased sharply.展开更多
Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of a...Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectrometry. The kinetics of grain growth in isothermal annealing was investigated. The XRD results show that, although the grain sizes of both material systems increase as the annealing temperature rises, the Si-containing system displays a relatively smaller grain size, i.e., 60 nm compared with 72 nm in Mg-6Al-1Zn system, after being exposed to 350 ℃ for 1 h. The second-phase intermetallic particle Mg2Si formed during the isothermal annealing of Mg-6Al-1Zn-1Si system could influence not only the activation energy but also the exponent of kinetic equation. Higher hardness values obtained in the Si-containing system would be due to the formation of Mg2Si intermetallic phase.展开更多
Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformatio...Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.展开更多
Polymeric sponge replication method is one of the common ways for ceramic foam production. The existence of central triangular voids in the struts results in a decrease of mechanical properties limiting their applicat...Polymeric sponge replication method is one of the common ways for ceramic foam production. The existence of central triangular voids in the struts results in a decrease of mechanical properties limiting their applications. To remove this defect, some additives consisting of Al powder particles and silica sol are added to ceramic slurries consisting of Al2O3 and ZrO2 （partially stabilized zirconia）. With increasing temperature for pyrolyzing and sintering of raw materials, first the Al powder and then the glass phase which consisted of melted Al2O3, ZrO2 and SiO2 was soaked into hollow struts. SEM investigations showed that the center of foam struts were free of hollows. XRD considerations depicted that a ZrO2 phase with tetragonal crystallographic structure is present in the produced foam which could be the reason of improved toughness and mechanical properties. Compressive strength of foams increased significantly due to the decrease of closed porosity. The Weibull statistical study showed remarkable increasing of the Weibull module and its value for foams with 10, 20 and 30 ppi was 5.91, 6.06 and 6.53 respectively.展开更多
In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas l...In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.展开更多
The effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties,microstructure,and texture of the all...The effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties,microstructure,and texture of the alloy.The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture.After the pre-aging treatment and natural aging treatment(T4 P treatment),in contrast to the sheet with a uniform particle size distribution,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio(r) and strain hardening exponent(n).After solution treatment,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution.Additionally,they possess almost identical weak recrystallization textures,and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.展开更多
基金supported by the Serbian Ministry of Education and Science under Grant No.TR35006 and COST Action:CA23155—A Pan-European Network of Ocean Tribology(OTC)The research of B.Rosic and M.Rosic was supported by the Serbian Ministry of Education and Science under Grant TR35029.
文摘This paper introduces a hybrid multi-objective optimization algorithm,designated HMODESFO,which amalgamates the exploratory prowess of Differential Evolution(DE)with the rapid convergence attributes of the Sailfish Optimization(SFO)algorithm.The primary objective is to address multi-objective optimization challenges within mechanical engineering,with a specific emphasis on planetary gearbox optimization.The algorithm is equipped with the ability to dynamically select the optimal mutation operator,contingent upon an adaptive normalized population spacing parameter.The efficacy of HMODESFO has been substantiated through rigorous validation against estab-lished industry benchmarks,including a suite of Zitzler-Deb-Thiele(ZDT)and Zeb-Thiele-Laumanns-Zitzler(DTLZ)problems,where it exhibited superior performance.The outcomes underscore the algorithm’s markedly enhanced optimization capabilities relative to existing methods,particularly in tackling highly intricate multi-objective planetary gearbox optimization problems.Additionally,the performance of HMODESFO is evaluated against selected well-known mechanical engineering test problems,further accentuating its adeptness in resolving complex optimization challenges within this domain.
基金supported by the National Natural Science Foundation of China(Nos.11972202,52075272)the Major Project of Ningbo Science and Technology Innovation,China(Nos.2021Z099,2023Z005)+3 种基金National Key Laboratory of Shock Wave and Detonation Physics,China(No.JCKYS2023212005)State Key Laboratory for Advanced Metals and Materials,China(No.2023-Z04)Zhejiang Provincial Natural Science Foundation,China(No.LMS25E050015)the K.C.Wong Magna Fund from Ningbo University,China.
文摘Compressive mechanical behavior and microstructure evolution of Ti−5.7Al−2.9Nb−1.8Fe−1.6Mo−1.5V−1Zr alloy under extreme conditions were systematically investigated.The results show that strain rate and temperature have a significant influence on the mechanical behavior and microstructure.The alloy exhibits a positive strain rate sensitivity and negative temperature sensitivity under all temperature and strain rate conditions.The hot-rolled alloy is composed of a bimodal structure including an equiaxed primary α_(p) phase and a transformedβphase.After compression deformation,the bimodal deformed structural features highly rely on the temperature and strain rate.At low temperature and room temperature,the volume fraction and size of α_(p) phase decrease with increasing temperature and strain rate.At high temperature,the volume fraction of the α_(p)hase is inversely correlated with temperature.A modified Johnson−Cook constitutive model is established,and the predicted results coincide well with the experimental results.
文摘The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets are placed on a visco-Pasternak medium in a hygro-temperature environment with nonlinear rules.The viscoelastic material characteristics of nanosheets are based on Kelvin’s model.The unique point of this study is to consider the change of nonlocal and length-scale coefficients according to thickness,similar to the laws of the material properties.The Galerkin approach based on the Kirchhoff-love plate theory is applied to determine the natural frequency and critical buckling load of the viscoelastic FGP nanosheet with various boundary conditions.The accuracy of the proposed method is verified through reliable publications.The outcome of this study highlights the significant effects of the nonlocal and length-scale parameters on the vibration and buckling behaviors of viscoelastic FGP nanosheets.
文摘The influence of ultrasonic vibrations on microstructure and mechanical properties of the AZ91-C magnesium alloy after ultrasonic assisted friction stir welding(UaFSW)in comparison with conventional friction stir welding(FSW)was investigated.The FSW was applied at the rotational speed of 1400 r/min and welding speed of 40 mm/min and no defects were observed.Using the same welding parameters,the process was carried out with inducing ultrasonic vibrations to the weld line at the amplitude of 15μm.The microstructure of the specimens was observed with optical and scanning electron microscopy.The results indicate that a very fine microstructure is obtained in UaFSW with respect to that of conventional FSW.Moreover,β-Mg17Al12 coarse dendrites are segregated to very fine and partly spherical particles that homogeneously distribute inα-Mg matrix.This remarkably-modified morphology of microstructure attributed to severe plastic deformation comes from ultrasonic vibration and friction stirring effect.Tensile and hardness tests were performed to evaluate the mechanical properties of the welds.According to the results,the vibration greatly improves the mechanical properties of the conventional FSW joint.The tensile strength and hardness are increased from 195 MPa and HV 79 in conventional FSW to 225 MPa and HV 87 in UaFSW,respectively.
文摘The microstructure evolution, mechanical and corrosion properties of Al-11Si-2Cu-0.8Zn die cast alloy treated with Bi, Sb and Sr additions were investigated. The results of mechanical testing showed that all additions increased impact toughness, ultimate tensile strength, and elongation of the alloy as a result of change in eutectic Si morphology. The analysis of fracture surfaces revealed that with addition of Sr and to lesser extent Bi and Sb, the alloy exhibited a predominantly ductile fracture rather than quasi-cleavage brittle fracture. Moreover, with the additions of Sr, Bi and Sb, the quality index increased to 164.7 MPa, 156.3 MPa and 152.6 MPa respectively from 102 MPa for the base alloy. Polarization corrosion tests conducted in sodium chloride solution showed that the corrosion potential shifted to more negative values with additions of Sb, Bi and Sr, respectively. Corrosion immersion tests also revealed that the element additions have a detrimental effect on the corrosion rate of alloys, due to the increase of boundaries between the Al and eutectic Si phases.
文摘In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,martensite.The variation of the prior austenite grain size is believed to vary the end results of the martensite.This undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,etc.This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure.The results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter increases.The block and packet sizes in the martensite also increase.The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology.With respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.
文摘This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt%resulted in a loss of modification, possibly due to the formation of Al8 MgB iS i4 compound before the precipitation of the primary Mg2 Si. Additionally, the structure of the pseudo-eutectic Mg2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al5 Fe Si（β）, Al2Cu（θ） and Al5Cu2Mg8Si6（Q） intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg2 Si particles.
文摘The Mg-6Al-4Zn alloy was fabricated by mechanical alloying(MA)and hot pressing to serve as biodegradable metal implant.The influence of addition of 1%Si(mass fraction)on the microstructure,mechanical properties and bio-corrosion behavior of Mg-6Al-1Zn alloy was studied using X-ray diffractometry,transmission electron microscopy,compression test,as well as immersion,electrochemical test and MTT assay.The results showed that the addition of 1%Si to Mg-6Al-1Zn alloy led to the formation of fine Mg2Si phase with polygonal shape,and increased compressive strength,elongation and improved corrosion resistance.Furthermore,the cell viability of Saos-2 cells has been improved by addition of 1%Si to Mg-6Al-1Zn alloy.According to the results,the magnesium ions released in the methylthiazol tetrazolium(MTT)test have not shown any cell toxicity.All these indicated that the addition of 1%Si improved the properties of Mg-6Al-4Zn alloy for using as a biodegradable implant.
文摘This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely wall angle(35°-55°),feed rate(1-4 m/min),spindle rotational speed(50-1000 r/min),and lubricant(grease and hydraulic oil)are varied to probe detailed processing effects.The pre-and post-SPIF mechanical properties and microstructures are characterized by conducting tensile tests and optical microscopy,respectively.It is shown that an increase in the wall angle,feed rate and rotational speed causes microscopic variations in the alloys such that the grains of AA5754 and the second phase particles of AA6061 elongate.As a result,the ultimate tensile strength of the formed parts is increased by 10%for AA5754 and by 8%for AA6061.And,the ductility of AA5754 is decreased from 22.9%to 12%and that of AA6061 is decreased from 16%to 10.7%.Regarding the lubricant effect,it is shown that the mechanical properties remain insensitive to the type of lubricant employed.These results indicate that SPIF processing modifies the microstructure of Al alloys in a way to enhance the strength at the cost of ductility.
基金supported by Global Frontier Program through the Global Frontier Hybrid Interface materials(GFHIM)of the National Research Foundation of Korea(NRF)funded by the ministry of science,ICT and Future Planning(2013M3A6B1078874)co-supported by Busan Innovation Institute of Industry,Science&Technology Planning(BISTEP)+1 种基金the financial support of Federal Ministry of Education and Research(BMBF)under the“Make Our Planet Great Again-German Research Initiative”(MOPGAGRI),57429784implemented by the German Academic Exchange Service Deutscher Akademischer Austauschdienst(DAAD)。
文摘As bifunctional oxygen evolution/reduction electrocatalysts,transition-metal-based single-atom-doped nitrogen-carbon(NC)matrices are promising successors of the corresponding noblemetal-based catalysts,offering the advantages of ultrahigh atom utilization effciency and surface active energy.However,the fabrication of such matrices(e.g.,well-dispersed single-atom-doped M-N4/NCs)often requires numerous steps and tedious processes.Herein,ultrasonic plasma engineering allows direct carbonization in a precursor solution containing metal phthalocyanine and aniline.When combining with the dispersion effect of ultrasonic waves,we successfully fabricated uniform single-atom M-N4(M=Fe,Co)carbon catalysts with a production rate as high as 10 mg min-1.The Co-N4/NC presented a bifunctional potential drop ofΔE=0.79 V,outperforming the benchmark Pt/C-Ru/C catalyst(ΔE=0.88 V)at the same catalyst loading.Theoretical calculations revealed that Co-N4 was the major active site with superior O2 adsorption-desorption mechanisms.In a practical Zn-air battery test,the air electrode coated with Co-N4/NC exhibited a specific capacity(762.8 mAh g(-1))and power density(101.62 mW cm^(-2)),exceeding those of Pt/C-Ru/C(700.8 mAh g^(-1) and 89.16 mW cm^(-2),respectively)at the same catalyst loading.Moreover,for Co-N4/NC,the potential difference increased from 1.16 to 1.47 V after 100 charge-discharge cycles.The proposed innovative and scalable strategy was concluded to be well suited for the fabrication of single-atom-doped carbons as promising bifunctional oxygen evolution/reduction electrocatalysts for metal-air batteries.
文摘Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.
基金Project(Q.J130000.2524.12H60)supported by the Ministry of Higher Education of Malaysia and Universiti Teknologi Malaysia。
文摘In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were investigated.The study was conducted using optical and scanning electron microscopy(SEM),X-ray diffractometry(XRD),compression test,and shape memory testing.The xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering process.The results revealed that the addition of Ag has a significant effect on the pore size and shape,whereas the smallest pore size of 11μm was found with the addition of 0.41 at%along with a relative density of 72%.The fracture stress and strain increased with the addition of Ag,reaching the minimum values around 0.41 at%Ag.Therefore,this composition showed the maximum stress and strain at fracture region.Moreover,0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages,obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys,which can be recommended for their promising and potential response for biomaterial applications.
文摘Effects of multiple strengthening treatments （i.e. ag mechanical properties and stability of nanoscale prec in this research. Various tests such as hardness, tensi ng either at three or four consecutive temperatures） on pitated phases in an AA2090 alloy have been evaluated e, electrical resistance, differential scanning calorimetric （DSC）, and transmission electron microscopy （TEM） have been performed. The results show that the ultimate tensile strength （UTS） and the yield strength of the samples aged at four consecutive temperatures （i.e. natural aging＋190℃＋150℃＋100℃） can be increased approximately to 660 and 610 MPa, respectively. It is also found that precipitation of T1 phase occurs during multiple aging process of the alloy and the higher amounts of enthalpies shown in DSC charts are linked to higher volume fraction of this precipitate. Furthermore, TEM observations reveal that T1 phase has plate shape morphology and its crystal structure is in the form of hcp with lattice parameters of a=0.467 nm and c=0.878 nm.
文摘Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation behavior. Thermal analysis and microstructural observations showed that Zn-0.5A1-0.5Mg is composed of FCC-A1 ＋ HCP- Zn ＋ Mg2（Zn,A1）ll while a new phase a-Mg3Bi2 appeared after the addition of Bi to the Zn-0.5A1-0.5Mg ternary alloy. The results revealed that the quaternary Zn-A1-Mg-Bi alloys have higher tensile strength, elongation and hardness but slightly lower corrosion resistance than those of the temary Zn-AI-Mg alloy. Based on the MTT assay, the Zn-A1-Mg and Zn-A1-Mg-Bi alloys were found to be biocompatible, and thus, they can be considered for further investigation in an in vivo environment.
文摘The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by optical microscope,X-ray diffraction,scanning electron microscope and Feritscope,while the mechanical properties were determined by hardness and tensile tests.The results revealed that the content of retained austenite decreased by about 2% after multi-step tempering.However,the content of retained austenite increased from 3.6% to 5.1% by increasing multi-step tempering temperature.The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 ℃,while above 920 ℃,hardness and tensile strength decreased.In addition,the maximum values of hardness,ultimate and yield strength were obtained via triple tempering at 520 ℃,while beyond 520 ℃,the hardness,ultimate and yield strength decreased sharply.
文摘Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectrometry. The kinetics of grain growth in isothermal annealing was investigated. The XRD results show that, although the grain sizes of both material systems increase as the annealing temperature rises, the Si-containing system displays a relatively smaller grain size, i.e., 60 nm compared with 72 nm in Mg-6Al-1Zn system, after being exposed to 350 ℃ for 1 h. The second-phase intermetallic particle Mg2Si formed during the isothermal annealing of Mg-6Al-1Zn-1Si system could influence not only the activation energy but also the exponent of kinetic equation. Higher hardness values obtained in the Si-containing system would be due to the formation of Mg2Si intermetallic phase.
基金financial support under the University Research Grant No.Q.J130000.3024.00M57
文摘Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.
文摘Polymeric sponge replication method is one of the common ways for ceramic foam production. The existence of central triangular voids in the struts results in a decrease of mechanical properties limiting their applications. To remove this defect, some additives consisting of Al powder particles and silica sol are added to ceramic slurries consisting of Al2O3 and ZrO2 （partially stabilized zirconia）. With increasing temperature for pyrolyzing and sintering of raw materials, first the Al powder and then the glass phase which consisted of melted Al2O3, ZrO2 and SiO2 was soaked into hollow struts. SEM investigations showed that the center of foam struts were free of hollows. XRD considerations depicted that a ZrO2 phase with tetragonal crystallographic structure is present in the produced foam which could be the reason of improved toughness and mechanical properties. Compressive strength of foams increased significantly due to the decrease of closed porosity. The Weibull statistical study showed remarkable increasing of the Weibull module and its value for foams with 10, 20 and 30 ppi was 5.91, 6.06 and 6.53 respectively.
文摘In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.
基金financially supported by the National Key Research and Development Program of China (No.2016YFB0300801)the National Natural Science Foundation of China (No.51571023)+3 种基金Zhejiang Provincial Natural Science Foundation of China (No.LQ17E010001)the Beijing Municipal Natural Science Foundation (No.2172038)the Beijing Laboratory of Metallic Materials and Processing for Modern Transportation (No.FRF-SD-B-005B)sponsored by the K.C.Wong Magna Fund in Ningbo University
文摘The effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties,microstructure,and texture of the alloy.The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture.After the pre-aging treatment and natural aging treatment(T4 P treatment),in contrast to the sheet with a uniform particle size distribution,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio(r) and strain hardening exponent(n).After solution treatment,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution.Additionally,they possess almost identical weak recrystallization textures,and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.
