A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The...A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The improvement of mechanical properties is attributed to the refinement and increased chemical heterogeneity of the martensitic substructure,rather than the refinement of prior austenite grain(PAG),as well as the Transformation-Induced Plasticity(TRIP)effect facilitated by small austenite grains.The role of local segregation of Ni during CQT in the formation of Ni-rich austenite grains,Ni-rich martensite laths and Ni-poor martensite laths,was investigated and verified by DICTRA simulations.This study highlights the important influence of Ni partitioning behavior during CQT,providing insights into microstructural evolution and mechanical properties.展开更多
Low-carbon urban development in China can pave the way to achieve the dualcarbon goal.Exploring how land use changes(LUCs)impact carbon storage(CS)under multi-climate scenarios in different urban agglomerations helps ...Low-carbon urban development in China can pave the way to achieve the dualcarbon goal.Exploring how land use changes(LUCs)impact carbon storage(CS)under multi-climate scenarios in different urban agglomerations helps to formulate differential scientific carbon mitigation policies.In this regard,this study constructs an integrated model of SD-PLUS-InVEST to simulate LUCs and CS changes under multi-climate change-based scenarios(SSP126,SSP245,SSP585)for three major urban agglomerations(3UAs)in the Yangtze River Economic Belt.Results demonstrate that land use demand in the 3UAs changes considerably in each scenario.Construction land in the 3UAs remains the most important growth category for the coming decade,but its increase varies in different scenarios.CS in the Yangtze River Delta Urban Agglomeration(YRDUA)and Mid-Yangtze River Urban Agglomeration(MYRUA)shows a similar downward trend under different scenarios,with scenario SSP245 decreasing the most,to 184,713.526 Tg and 384,459.729 Tg,respectively.CS in the Cheng-Yu(Chengdu-Chongqing)Urban Agglomeration(CYUA)exhibits the opposite upward trend,with scenario SSP126 increasing the most to 153,007.973 Tg.The major cause of CS loss remains the conversion of forest land to construction land in the YRDUA and MYRUA under different scenarios.However,in the CYUA,the conversion of forest land to cultivated land is the major driver of CS loss under scenario SSP126.In contrast,the conversion of cultivated land to construction land dominantly drives CS loss under scenarios SSP245 and SSP585.The conversion of water body to other land use types is the major cause of CS gain in the YRDUA and MYRUA under different scenarios.At the same time,in the CYUA,the driver is the conversion of cultivated land to forest land.These findings demonstrate the significance of the low-carbon development in urban agglomerations at different development stages at home and abroad.展开更多
Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-d...Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.展开更多
Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effe...Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effectively,even when the scraps are co-mingled and have higher costs for further sorting and separation.In this work,we explore an alloy design concept by creating a compositionally flexible domain that can recycle multiple alloy grades and yet maintain relatively consistent properties across chemical variations.This is demonstrated through the Fe-Cr-Ni-Mn system to identify compositionally flexible austenitic stainless steels(CF-ASS)and accommodate the recycling of mixed austenitic stainless steel scraps.Alloys within the nominal composition spaces exhibit relatively consistent mechanical properties and corrosion resistance despite significant variations in different alloy compositions.We illustrate how we can utilise the compositionally flexible austenitic stainless steels to recycle mixed 200 and 300-series stainless steel and ferronickel scraps,demonstrating its practical viability.While this demonstration focuses on the stainless steel system,the underlying principles can be extended to other systems related to mixed scrap recycling.展开更多
In this work,refill friction stir spot welding（RFSSW） was used to weld 2 mm-thick 5083-O alloy.The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear pro...In this work,refill friction stir spot welding（RFSSW） was used to weld 2 mm-thick 5083-O alloy.The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear property.Results showed that a surface indentation of 0.3 mm effectively eliminated the welding defects.Microhardness of the stir zone（SZ） was higher than that of the base material（BM） and the hardness decreased with increasing the heat input during welding.The optimum failure load of 7.72 k N was obtained when using rotating speed of 2300 rpm,plunge depth of 2.4 mm and refilling time of 3.5 s.Three fracture modes were obtained during the lap shear test and all were affected by the hook defect.展开更多
The nonlinear behaviors and vibration reduction of a linear system with a nonlinear energy sink(NES)are investigated.The linear system is excited by a harmonic and random base excitation,consisting of a mass block,a l...The nonlinear behaviors and vibration reduction of a linear system with a nonlinear energy sink(NES)are investigated.The linear system is excited by a harmonic and random base excitation,consisting of a mass block,a linear spring,and a linear viscous damper.The NES is composed of a mass block,a linear viscous damper,and a spring with ideal cubic nonlinear stiffness.Based on the generalized harmonic function method,the steady-state Fokker-Planck-Kolmogorov equation is presented to reveal the response of the system.The path integral method based on the Gauss-Legendre polynomial is used to achieve the numerical solutions.The performance of vibration reduction is evaluated by the displacement and velocity transition probability densities,the transmissibility transition probability density,and the percentage of the energy absorption transition probability density of the linear oscillator.The sensitivity of the parameters is analyzed for varying the nonlinear stiffness coefficient and the damper ratio.The investigation illustrates that a linear system with NES can also realize great vibration reduction under harmonic and random base excitations and random bifurcation may appear under different parameters,which will affect the stability of the system.展开更多
In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of tem...In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.展开更多
Formation of intermetallic compounds （IMCs） during friction stir welding （FSW） of alu- minum/magnesium （AI/Mg） alloys easily results in the pin adhesion and then deteriorates joint formation. The severe pin adhe...Formation of intermetallic compounds （IMCs） during friction stir welding （FSW） of alu- minum/magnesium （AI/Mg） alloys easily results in the pin adhesion and then deteriorates joint formation. The severe pin adhesion transformed the tapered-and-screwed pin into a tapered pin at a low welding speed of 30 mm/min. The pin adhesion problem was solved with the help of ultrasonic. The weldability of Al/Mg alloys was significantly improved due to the good material flow induced by mechanical vibration and the fragments of the IMCs on the surface of a rotating pin caused by acoustic streaming, respectively. A sound joint with ultrasonic contained long Al/Mg interface joining length and complex mixture of AI/Mg alloys in the stir zone, thereby achieving perfect metallurgical bonding and mechanical interlocking. The ultrasonic could broaden process window and then improve tensile properties. The tensile strength of the Al/Mg joint with ultrasonic reached 115 MPa.展开更多
In this paper, the energy absorption mechanism of empty and foam-filled aluminum tubes with different cross-sections （circular, square and elliptic） under bending load is investigated numerically. The load-displacem...In this paper, the energy absorption mechanism of empty and foam-filled aluminum tubes with different cross-sections （circular, square and elliptic） under bending load is investigated numerically. The load-displacement curves of the present simulations are in very good agreement with those of published experimental data. Here, the existing analytical formulations are reviewed and compared with experimental results. In addition, the effects of different cross-sections and wall thicknesses on the energy absorption capacity and specific energy absorption of these tubes are fully investigated. The results indicate that the energy absorption of an elliptic foam-filled tube with 1.5 mm and 2 mm thicknesses increases about 45% and 73% in comparison with a square one, respectively.展开更多
Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability a...Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability and microstructure of target sheet in overlapping sheets bulging process. Sheet sliding experiment was performed to measure interface friction coefficient of 5 A02/SUS304 in different lubricating conditions and normal pressure. Overlapping sheets bulging experiment of 5 A02/SUS304 was carried out to investigate the influence of interface friction on limit bulging height, wall thickness distribution, microstructure and fracture morphology of 5 A02 bulging specimens. The results showed that increase of the interface friction coefficient of 5 A02/SUS304 could effectively improve the limit bulging height and deformation uniformity of 5 A02. And the fracture style of 5 A02 transformed from toughness fracture of dimples-micropores gathered to fault slip separation fracture. Therefore, target sheet bulging formability is improved with the increase of interface friction coefficient.展开更多
This paper studies the vibration absorber for a fluid-conveying pipe,where the lever-type nonlinear energy sink(LNES)and spring supports are coupled to the asymmetric ends of the system.The pseudo-arc-length method in...This paper studies the vibration absorber for a fluid-conveying pipe,where the lever-type nonlinear energy sink(LNES)and spring supports are coupled to the asymmetric ends of the system.The pseudo-arc-length method integrated with the harmonic balance method is used to investigate the steady-state responses analytically.Meanwhile,the numerical solution of the fluid-conveying pipe is calculated with the Runge-Kutta method.Moreover,a special response,called the collapsible closed detached response(CCDR),is first observed when the vibration response of mechanical structures is studied.Then,the relationship between the CCDR and the main structure primary response(PR)is obtained.In addition,the closed detached response(CDR)is also observed to research the resonance response of the fluid-conveying pipe.The appearance of either the CCDR or the CDR does affect the resonance attenuation.Furthermore,the mentioned two phenomena underline that the trend of vibration responses under external excitation goes continuous and gradual.Besides,the main advantage of the LNES is presented by contrasting the LNES with the nonlinear energy sink(NES)coupled to the same pipe system.It is found that the LNES can reduce the resonance response amplitude by 91.33%.展开更多
The high performance of Ni single crystal superalloys during high temperature low stress creep service,is intrinsically determined by the combined effects of microstructural evolution and the dislocation behaviour.In ...The high performance of Ni single crystal superalloys during high temperature low stress creep service,is intrinsically determined by the combined effects of microstructural evolution and the dislocation behaviour.In the field of the evolution of dislocation network,two main recovery mechanism based on dislocation migration dominate the process.One is superdislocations shearing intoγ’rafts through a two-superpartials-assisted approach.Another is the compact dislocations migrating alongγ/γ’interface.These two mechanisms are similarly climb-rate-controlled process.In this work,a model for the minimum creep rate based on thermodynamic and kinetic calculations and using an existing detailed dislocation dynamics model has been built by taking the dislocation migration behaviours as well as the rafted microstructure into consideration,which can well reproduce the([100]tensile)creep properties of existing Ni superalloy grades,without the need to make the dislocation parameter values composition dependent.展开更多
We present an electron backscattered diffraction(EBSD)-trained deep learning(DL)method integrating traditional material characterization informatics and artificial intelligence for a more accurate classification and q...We present an electron backscattered diffraction(EBSD)-trained deep learning(DL)method integrating traditional material characterization informatics and artificial intelligence for a more accurate classification and quantification of complex microstructures using only regular scanning electron microscope(SEM)images.In this method,EBSD analysis is applied to produce accurate ground truth data for guiding the DL model training.An U-Net architecture is used to establish the correlation between SEM input images and EBSD ground truth data using only small experimental datasets.The proposed method is successfully applied to two engineering steels with complex microstructures,i.e.,a dual-phase(DP)steel and a quenching and partitioning(Q&P)steel,to segment different phases and quantify phase content and grain size.Alternatively,once properly trained the method can also produce quasi-EBSD maps by inputting regular SEM images.The good generality of the trained models is demonstrated by using DP and Q&P steels not associated with the model training.Finally,the method is applied to SEM images with various states,i.e.,different imaging modes,image qualities and magnifications,demonstrating its good robustness and strong application ability.Furthermore,the visualization of feature maps during the segmenting process is utilised to explain the mechanism of this method’s good performance.展开更多
Taking the MK7-3 of USA hydraulic buffer arresting device as the research subject,the dynamical model for the shipboard aircraft arresting system is established,and the magneto-rheological(MR) damper is applied to pul...Taking the MK7-3 of USA hydraulic buffer arresting device as the research subject,the dynamical model for the shipboard aircraft arresting system is established,and the magneto-rheological(MR) damper is applied to pulley shock absorbers for shipboard aircraft block system.Due to the effect of the MR damper has not been known completely and so far MR damper model has not been defined,we use a set of characteristic test of the MR damper,through the process of parameters identification,to establish the dynamical model for the MR damper based on the Bingham plastic model.Then,the fuzzy control rules are designed,the buffer control for the pulley buffer of shipboard aircrafts is completed in touchdown moment based on MR technology. Compared with blocking device of hydraulic pulley buffer in the same condition,the simulations results show that the proposed MR pulley buffer can effectively recognize the impact energy for shipboard block system and reduce the pull peak of arresting cable.It improves significantly safety during landing of the air vehicles and lowers the risk of accidents.展开更多
So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristi...So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristic tests and parameters' identification are made to the MR damper by the experimental platform. The dynamical model of the damper is constructed based on the Bingham plastic model,and the buffer control strategy of aircraft undercarriage based on MR technology is established.Finally,the fuzzy control algorithm is applied to the process of automatic control for landing buffer of aircraft undercarriage.The simulation results show that the proposed MR damper pulley buffer can effectively recognize the impact energy.The research has a better application in the engineering.展开更多
A three-dimensional finite volume model was established by the ANSYS FLUENT software to simulate the material flow behavior during the friction stir spot welding （FSSW） process. Effects of the full-threaded pin and ...A three-dimensional finite volume model was established by the ANSYS FLUENT software to simulate the material flow behavior during the friction stir spot welding （FSSW） process. Effects of the full-threaded pin and the reverse-threaded pin on the material flow behavior were mainly discussed. Results showed that the biggest material flow velocity appeared at the outer edge of the tool shoulder. The velocity value became smaller with the increase of the distance away from the tool surface. In general, material flows downwards along the pin thread when the full-threaded pin is used. Meanwhile, both the materials of the upper and the lower plates flow towards the lap interface along the pin thread when the reverse-threaded pin is used. The numerical simulation results were investigated by experiment, in which 2A12 aluminum alloy was used as the research object. The effective sheet thickness （EST） and stir zone （SZ） width of the joint by the reverse-threaded pin were much bigger than those by the full-threaded pin. Accordingly, cross tension failure load of the joint by the reverse-threaded pin is 23% bigger than the joint by the full-threaded pin.展开更多
AIM：To investigate the effects of hydrogen-rich saline（HRS）on microglia activation and Sirtuin type 1（Sirt1）in rats with N-methyl-N-nitrosourea（MNU）-induced retinitis pigmentosa（RP）.METHODS：Rats were divided...AIM：To investigate the effects of hydrogen-rich saline（HRS）on microglia activation and Sirtuin type 1（Sirt1）in rats with N-methyl-N-nitrosourea（MNU）-induced retinitis pigmentosa（RP）.METHODS：Rats were divided into norm（N）group,model（M）group and HRS（H）group.Rats in M and H groups were given saline and HRS respectively prior to and after administration of MNU.At one day（d1）and d3 afterwards,electroretinogram and histological examination were performed to confirm the effects of HRS on retinal function and structure of MNU-induced RP.Immunofluorescence staining of anti-ionized calcium-binding adapter molecule 1（Iba1）,a maker of microglia cells,was performed,with quantitative real-time polymerase chain reaction（qRT-PCR）for its m RNA quantification.Moreover,Sirt1 m RNA and protein expression in the retinas were detected by Western blot and qRT-PCR.RESULTS：HRS preserved the retinal function and mitigated the reduction of photoreceptor degeneration in MNU-treated retinas.The presence of microglia cells was somewhat more obvious in H group than that in M group at d1.HRS suppressed the further activation of microglia cells,with the number of microglia cells less than that of M group at d3.Results of qRT-PCR of Iba1 were consistent with those of immunofluorescence staining,with the m RNA expression of Iba1 in H group more intensive than that of M group at d1（P〈0.05）,while less than that of M group at d3（P〈0.05）.Furthermore,the Sirt1 m RNA and protein expression decreased after MNU administration,while HRS mitigated the MNU-induced downregulation of Sirt1.CONCLUSION：HRS can effectively keep microglia activation induced by MNU to an appropriate extent,while upregulate Sirt1 in MNU-induced RP.展开更多
The rotational tool is put forward, which is composed of the one-spiral-flute shoul- der and the rotational pin with screw. Using the turbulent model of the FLUENT software, material plastic flow behavior during the p...The rotational tool is put forward, which is composed of the one-spiral-flute shoul- der and the rotational pin with screw. Using the turbulent model of the FLUENT software, material plastic flow behavior during the process of friction stir welding of Ti6A14V alloy is researched by the numerical simulation method and then the effect of rotational tool geometry on material flow during the welding process is attained. The results show that the flow direction of the material near the rotational tool is mainly the same as the rotational direction of the tool while the material near tool flows more violently than the other regions. For the tapered rotational pin, the flow velocity of material inside the workpiece decreases with the increase of the distance away from the workpiece surface because of the change of pin diameter. For the rotational tool, the flute added to the shoulder and the screw added to the pin can greatly increase the flow velocity of material during the welding process while the peak value of the flow velocity of material appears on the flute or the screw. Moreover, the rotational tool with the one-spiral-flute shoulder is better than the tool with the concentric- circles-flute shoulder. Decreasing the width of pin screw and increasing the diameter of pin tip are both good for the increase of flow velocity.展开更多
Incorporating aluminum particles into viscous medium was proposed to improve the thermal conductivity of the viscous medium and the efficiency of warm viscous pressure forming(WVPF)process.The influence of aluminum pa...Incorporating aluminum particles into viscous medium was proposed to improve the thermal conductivity of the viscous medium and the efficiency of warm viscous pressure forming(WVPF)process.The influence of aluminum particles on a viscous medium was investigated through settling,thermal conductivity,and compression experiments.Warm viscous pressure bulging(WVPB)experiments were conducted on polyetherimide(PEI)and AZ31B magnesium alloy sheets to determine the influence of the aluminum particles size and fraction on the forming efficiency and formed specimens based on the heating preparation times and profile curves,wall thicknesses and surface roughness values of the bulging specimens.The results show that the thermal conductivity of the viscous medium and the WVPF efficiency can be greatly improved via the addition aluminum particles with appropriate size and fraction under certain temperature condition,but have less influence on other properties of viscous medium.展开更多
基金sponsored by the National Natural Science Foun-dation of China(Grant Nos.52271122,52203384).
文摘A cyclic quenching treatment(CQT)succeeded in turning a 2.3 GPa maraging steel with a Charpy impact energy of 9 J into a new grade with the same strength but a Charpy impact energy of 20 J upon 4 cyclic treatments.The improvement of mechanical properties is attributed to the refinement and increased chemical heterogeneity of the martensitic substructure,rather than the refinement of prior austenite grain(PAG),as well as the Transformation-Induced Plasticity(TRIP)effect facilitated by small austenite grains.The role of local segregation of Ni during CQT in the formation of Ni-rich austenite grains,Ni-rich martensite laths and Ni-poor martensite laths,was investigated and verified by DICTRA simulations.This study highlights the important influence of Ni partitioning behavior during CQT,providing insights into microstructural evolution and mechanical properties.
基金Key Project of National Social Science Fund,No.23AZD032National Natural Science Foundation of China No.42371258Program of China Scholarship Council No.202306850036。
文摘Low-carbon urban development in China can pave the way to achieve the dualcarbon goal.Exploring how land use changes(LUCs)impact carbon storage(CS)under multi-climate scenarios in different urban agglomerations helps to formulate differential scientific carbon mitigation policies.In this regard,this study constructs an integrated model of SD-PLUS-InVEST to simulate LUCs and CS changes under multi-climate change-based scenarios(SSP126,SSP245,SSP585)for three major urban agglomerations(3UAs)in the Yangtze River Economic Belt.Results demonstrate that land use demand in the 3UAs changes considerably in each scenario.Construction land in the 3UAs remains the most important growth category for the coming decade,but its increase varies in different scenarios.CS in the Yangtze River Delta Urban Agglomeration(YRDUA)and Mid-Yangtze River Urban Agglomeration(MYRUA)shows a similar downward trend under different scenarios,with scenario SSP245 decreasing the most,to 184,713.526 Tg and 384,459.729 Tg,respectively.CS in the Cheng-Yu(Chengdu-Chongqing)Urban Agglomeration(CYUA)exhibits the opposite upward trend,with scenario SSP126 increasing the most to 153,007.973 Tg.The major cause of CS loss remains the conversion of forest land to construction land in the YRDUA and MYRUA under different scenarios.However,in the CYUA,the conversion of forest land to cultivated land is the major driver of CS loss under scenario SSP126.In contrast,the conversion of cultivated land to construction land dominantly drives CS loss under scenarios SSP245 and SSP585.The conversion of water body to other land use types is the major cause of CS gain in the YRDUA and MYRUA under different scenarios.At the same time,in the CYUA,the driver is the conversion of cultivated land to forest land.These findings demonstrate the significance of the low-carbon development in urban agglomerations at different development stages at home and abroad.
基金Project(282522)supported by the European Union's Research and Innovation Funding Programme
文摘Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.
基金financially supported by the National Key Research and Development Program(No.2023YFB3712403)the National Natural Science Foundation of China(Nos.52201112,52071066,U22A20106,and U22A20173).
文摘Recycling-oriented alloy design is a crucial part of material sustainability,as it reduces the need for raw material extraction and minimises environmental impact.This requires that scraps be reused or repurposed effectively,even when the scraps are co-mingled and have higher costs for further sorting and separation.In this work,we explore an alloy design concept by creating a compositionally flexible domain that can recycle multiple alloy grades and yet maintain relatively consistent properties across chemical variations.This is demonstrated through the Fe-Cr-Ni-Mn system to identify compositionally flexible austenitic stainless steels(CF-ASS)and accommodate the recycling of mixed austenitic stainless steel scraps.Alloys within the nominal composition spaces exhibit relatively consistent mechanical properties and corrosion resistance despite significant variations in different alloy compositions.We illustrate how we can utilise the compositionally flexible austenitic stainless steels to recycle mixed 200 and 300-series stainless steel and ferronickel scraps,demonstrating its practical viability.While this demonstration focuses on the stainless steel system,the underlying principles can be extended to other systems related to mixed scrap recycling.
基金supported by the National Natural Science Foundation of China (No.51204111)
文摘In this work,refill friction stir spot welding（RFSSW） was used to weld 2 mm-thick 5083-O alloy.The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear property.Results showed that a surface indentation of 0.3 mm effectively eliminated the welding defects.Microhardness of the stir zone（SZ） was higher than that of the base material（BM） and the hardness decreased with increasing the heat input during welding.The optimum failure load of 7.72 k N was obtained when using rotating speed of 2300 rpm,plunge depth of 2.4 mm and refilling time of 3.5 s.Three fracture modes were obtained during the lap shear test and all were affected by the hook defect.
基金Project supported by the National Natural Science Foundation of China(Nos.11772205 and11572182)the Liaoning Revitalization Talents Program of China(No.XLYC1807172)
文摘The nonlinear behaviors and vibration reduction of a linear system with a nonlinear energy sink(NES)are investigated.The linear system is excited by a harmonic and random base excitation,consisting of a mass block,a linear spring,and a linear viscous damper.The NES is composed of a mass block,a linear viscous damper,and a spring with ideal cubic nonlinear stiffness.Based on the generalized harmonic function method,the steady-state Fokker-Planck-Kolmogorov equation is presented to reveal the response of the system.The path integral method based on the Gauss-Legendre polynomial is used to achieve the numerical solutions.The performance of vibration reduction is evaluated by the displacement and velocity transition probability densities,the transmissibility transition probability density,and the percentage of the energy absorption transition probability density of the linear oscillator.The sensitivity of the parameters is analyzed for varying the nonlinear stiffness coefficient and the damper ratio.The investigation illustrates that a linear system with NES can also realize great vibration reduction under harmonic and random base excitations and random bifurcation may appear under different parameters,which will affect the stability of the system.
基金the National Natural Science Foundation of China (No.51204111)the Education Department Foundation of Liaoning Province (No.L2012047)the State Key Lab of Advanced Welding and Joining in Harbin Institute of Technology (AWJ-M13-07)
文摘In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.
基金supported by the National Natural Science Foundation of China(No.51204111)the Program for Liaoning Excellent Talents in University(No.LJQ2015084)+1 种基金the China Postdoctoral Science Foundation(No.2016M590821)Guangdong Provincial Key Laboratory of Advanced Welding Technology for Ships(No.2017B030302010)
文摘Formation of intermetallic compounds （IMCs） during friction stir welding （FSW） of alu- minum/magnesium （AI/Mg） alloys easily results in the pin adhesion and then deteriorates joint formation. The severe pin adhesion transformed the tapered-and-screwed pin into a tapered pin at a low welding speed of 30 mm/min. The pin adhesion problem was solved with the help of ultrasonic. The weldability of Al/Mg alloys was significantly improved due to the good material flow induced by mechanical vibration and the fragments of the IMCs on the surface of a rotating pin caused by acoustic streaming, respectively. A sound joint with ultrasonic contained long Al/Mg interface joining length and complex mixture of AI/Mg alloys in the stir zone, thereby achieving perfect metallurgical bonding and mechanical interlocking. The ultrasonic could broaden process window and then improve tensile properties. The tensile strength of the Al/Mg joint with ultrasonic reached 115 MPa.
文摘In this paper, the energy absorption mechanism of empty and foam-filled aluminum tubes with different cross-sections （circular, square and elliptic） under bending load is investigated numerically. The load-displacement curves of the present simulations are in very good agreement with those of published experimental data. Here, the existing analytical formulations are reviewed and compared with experimental results. In addition, the effects of different cross-sections and wall thicknesses on the energy absorption capacity and specific energy absorption of these tubes are fully investigated. The results indicate that the energy absorption of an elliptic foam-filled tube with 1.5 mm and 2 mm thicknesses increases about 45% and 73% in comparison with a square one, respectively.
基金Funded by the National Natural Science Foundation of China(No.51575364)the Program for Liaoning Innovation Talents in University(No.LR2017069)the Shenyang Science and Technology Innovation Support Program for Young Talented People(No.RC180189)
文摘Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability and microstructure of target sheet in overlapping sheets bulging process. Sheet sliding experiment was performed to measure interface friction coefficient of 5 A02/SUS304 in different lubricating conditions and normal pressure. Overlapping sheets bulging experiment of 5 A02/SUS304 was carried out to investigate the influence of interface friction on limit bulging height, wall thickness distribution, microstructure and fracture morphology of 5 A02 bulging specimens. The results showed that increase of the interface friction coefficient of 5 A02/SUS304 could effectively improve the limit bulging height and deformation uniformity of 5 A02. And the fracture style of 5 A02 transformed from toughness fracture of dimples-micropores gathered to fault slip separation fracture. Therefore, target sheet bulging formability is improved with the increase of interface friction coefficient.
基金Project supported by the National Natural Science Foundation of China (Nos.11902203 and 12022213)the General Scientific Research Foundation of Liaoning Educational Committee (No.JYT2020035)。
文摘This paper studies the vibration absorber for a fluid-conveying pipe,where the lever-type nonlinear energy sink(LNES)and spring supports are coupled to the asymmetric ends of the system.The pseudo-arc-length method integrated with the harmonic balance method is used to investigate the steady-state responses analytically.Meanwhile,the numerical solution of the fluid-conveying pipe is calculated with the Runge-Kutta method.Moreover,a special response,called the collapsible closed detached response(CCDR),is first observed when the vibration response of mechanical structures is studied.Then,the relationship between the CCDR and the main structure primary response(PR)is obtained.In addition,the closed detached response(CDR)is also observed to research the resonance response of the fluid-conveying pipe.The appearance of either the CCDR or the CDR does affect the resonance attenuation.Furthermore,the mentioned two phenomena underline that the trend of vibration responses under external excitation goes continuous and gradual.Besides,the main advantage of the LNES is presented by contrasting the LNES with the nonlinear energy sink(NES)coupled to the same pipe system.It is found that the LNES can reduce the resonance response amplitude by 91.33%.
基金the National Natural Science Foundation of China(No.51722101)the Key Research and Development Project(No.2017YFB0703001)。
文摘The high performance of Ni single crystal superalloys during high temperature low stress creep service,is intrinsically determined by the combined effects of microstructural evolution and the dislocation behaviour.In the field of the evolution of dislocation network,two main recovery mechanism based on dislocation migration dominate the process.One is superdislocations shearing intoγ’rafts through a two-superpartials-assisted approach.Another is the compact dislocations migrating alongγ/γ’interface.These two mechanisms are similarly climb-rate-controlled process.In this work,a model for the minimum creep rate based on thermodynamic and kinetic calculations and using an existing detailed dislocation dynamics model has been built by taking the dislocation migration behaviours as well as the rafted microstructure into consideration,which can well reproduce the([100]tensile)creep properties of existing Ni superalloy grades,without the need to make the dislocation parameter values composition dependent.
基金financially supported by the National Natural Science Foundation of China(Grants No.51722101,U1808208)financial support provided by the National Key R&D Program(Grant No.2017YFB0703001)major scientific and technological innovation projects of Shandong Province(Grant No.2019TSLH0103)。
文摘We present an electron backscattered diffraction(EBSD)-trained deep learning(DL)method integrating traditional material characterization informatics and artificial intelligence for a more accurate classification and quantification of complex microstructures using only regular scanning electron microscope(SEM)images.In this method,EBSD analysis is applied to produce accurate ground truth data for guiding the DL model training.An U-Net architecture is used to establish the correlation between SEM input images and EBSD ground truth data using only small experimental datasets.The proposed method is successfully applied to two engineering steels with complex microstructures,i.e.,a dual-phase(DP)steel and a quenching and partitioning(Q&P)steel,to segment different phases and quantify phase content and grain size.Alternatively,once properly trained the method can also produce quasi-EBSD maps by inputting regular SEM images.The good generality of the trained models is demonstrated by using DP and Q&P steels not associated with the model training.Finally,the method is applied to SEM images with various states,i.e.,different imaging modes,image qualities and magnifications,demonstrating its good robustness and strong application ability.Furthermore,the visualization of feature maps during the segmenting process is utilised to explain the mechanism of this method’s good performance.
基金the National Natural Science Foundation of China(No.61074090)the Program for Liaoning Excellent Talents in University(No.LR2011005)the Aviation Industry Corporation of China Innovation Funds(No.cxy2011SH)
文摘Taking the MK7-3 of USA hydraulic buffer arresting device as the research subject,the dynamical model for the shipboard aircraft arresting system is established,and the magneto-rheological(MR) damper is applied to pulley shock absorbers for shipboard aircraft block system.Due to the effect of the MR damper has not been known completely and so far MR damper model has not been defined,we use a set of characteristic test of the MR damper,through the process of parameters identification,to establish the dynamical model for the MR damper based on the Bingham plastic model.Then,the fuzzy control rules are designed,the buffer control for the pulley buffer of shipboard aircrafts is completed in touchdown moment based on MR technology. Compared with blocking device of hydraulic pulley buffer in the same condition,the simulations results show that the proposed MR pulley buffer can effectively recognize the impact energy for shipboard block system and reduce the pull peak of arresting cable.It improves significantly safety during landing of the air vehicles and lowers the risk of accidents.
基金the National Natural Science Foundation of China(No.61074090)the Program for Liaoning Excellent Talents in University of China (No.LR2011005)the Innovation Funds of Aviation Industry Corporation of China(No.cxy2011SH)
文摘So far the magneto-rheological(MR) effect mechanism of MR damper has not been known completely, especially in the impact load,and the problem becomes more complicated and difficult for analyzing.A set of characteristic tests and parameters' identification are made to the MR damper by the experimental platform. The dynamical model of the damper is constructed based on the Bingham plastic model,and the buffer control strategy of aircraft undercarriage based on MR technology is established.Finally,the fuzzy control algorithm is applied to the process of automatic control for landing buffer of aircraft undercarriage.The simulation results show that the proposed MR damper pulley buffer can effectively recognize the impact energy.The research has a better application in the engineering.
基金This work is supported by the National Natural Science Foundation of China （No. 51204111 ）, the Natural Science Foundation of Liaoning Province （ No. 2013024004 and No. 2014024008）.
文摘A three-dimensional finite volume model was established by the ANSYS FLUENT software to simulate the material flow behavior during the friction stir spot welding （FSSW） process. Effects of the full-threaded pin and the reverse-threaded pin on the material flow behavior were mainly discussed. Results showed that the biggest material flow velocity appeared at the outer edge of the tool shoulder. The velocity value became smaller with the increase of the distance away from the tool surface. In general, material flows downwards along the pin thread when the full-threaded pin is used. Meanwhile, both the materials of the upper and the lower plates flow towards the lap interface along the pin thread when the reverse-threaded pin is used. The numerical simulation results were investigated by experiment, in which 2A12 aluminum alloy was used as the research object. The effective sheet thickness （EST） and stir zone （SZ） width of the joint by the reverse-threaded pin were much bigger than those by the full-threaded pin. Accordingly, cross tension failure load of the joint by the reverse-threaded pin is 23% bigger than the joint by the full-threaded pin.
基金Supported by the Natural Science Foundation of China(No.81300836)the Foundation of Open Sharing Platform of Science and Technology of Shaanxi Province,China(No.2015FWPT-02)
文摘AIM：To investigate the effects of hydrogen-rich saline（HRS）on microglia activation and Sirtuin type 1（Sirt1）in rats with N-methyl-N-nitrosourea（MNU）-induced retinitis pigmentosa（RP）.METHODS：Rats were divided into norm（N）group,model（M）group and HRS（H）group.Rats in M and H groups were given saline and HRS respectively prior to and after administration of MNU.At one day（d1）and d3 afterwards,electroretinogram and histological examination were performed to confirm the effects of HRS on retinal function and structure of MNU-induced RP.Immunofluorescence staining of anti-ionized calcium-binding adapter molecule 1（Iba1）,a maker of microglia cells,was performed,with quantitative real-time polymerase chain reaction（qRT-PCR）for its m RNA quantification.Moreover,Sirt1 m RNA and protein expression in the retinas were detected by Western blot and qRT-PCR.RESULTS：HRS preserved the retinal function and mitigated the reduction of photoreceptor degeneration in MNU-treated retinas.The presence of microglia cells was somewhat more obvious in H group than that in M group at d1.HRS suppressed the further activation of microglia cells,with the number of microglia cells less than that of M group at d3.Results of qRT-PCR of Iba1 were consistent with those of immunofluorescence staining,with the m RNA expression of Iba1 in H group more intensive than that of M group at d1（P〈0.05）,while less than that of M group at d3（P〈0.05）.Furthermore,the Sirt1 m RNA and protein expression decreased after MNU administration,while HRS mitigated the MNU-induced downregulation of Sirt1.CONCLUSION：HRS can effectively keep microglia activation induced by MNU to an appropriate extent,while upregulate Sirt1 in MNU-induced RP.
基金supported by the National Natural Science Foundation of China(No. 61074090)
文摘The rotational tool is put forward, which is composed of the one-spiral-flute shoul- der and the rotational pin with screw. Using the turbulent model of the FLUENT software, material plastic flow behavior during the process of friction stir welding of Ti6A14V alloy is researched by the numerical simulation method and then the effect of rotational tool geometry on material flow during the welding process is attained. The results show that the flow direction of the material near the rotational tool is mainly the same as the rotational direction of the tool while the material near tool flows more violently than the other regions. For the tapered rotational pin, the flow velocity of material inside the workpiece decreases with the increase of the distance away from the workpiece surface because of the change of pin diameter. For the rotational tool, the flute added to the shoulder and the screw added to the pin can greatly increase the flow velocity of material during the welding process while the peak value of the flow velocity of material appears on the flute or the screw. Moreover, the rotational tool with the one-spiral-flute shoulder is better than the tool with the concentric- circles-flute shoulder. Decreasing the width of pin screw and increasing the diameter of pin tip are both good for the increase of flow velocity.
基金Project(51575364)supported by the National Natural Science Foundation of ChinaProject(2014ZE54024)supported by the Aviation Science Foundation of ChinaProject(LJQ2015083)supported by the Liaoning Excellent Talents in University,China
文摘Incorporating aluminum particles into viscous medium was proposed to improve the thermal conductivity of the viscous medium and the efficiency of warm viscous pressure forming(WVPF)process.The influence of aluminum particles on a viscous medium was investigated through settling,thermal conductivity,and compression experiments.Warm viscous pressure bulging(WVPB)experiments were conducted on polyetherimide(PEI)and AZ31B magnesium alloy sheets to determine the influence of the aluminum particles size and fraction on the forming efficiency and formed specimens based on the heating preparation times and profile curves,wall thicknesses and surface roughness values of the bulging specimens.The results show that the thermal conductivity of the viscous medium and the WVPF efficiency can be greatly improved via the addition aluminum particles with appropriate size and fraction under certain temperature condition,but have less influence on other properties of viscous medium.
