Maintaining stable high temperatures under pressure remains a challenge in high-pressure,high-temperature experiments using multi-anvil presses(MAPs).Temperature fluctuations exceeding 10℃ at high pressures are commo...Maintaining stable high temperatures under pressure remains a challenge in high-pressure,high-temperature experiments using multi-anvil presses(MAPs).Temperature fluctuations exceeding 10℃ at high pressures are common and particularly problematic with LaCrO_(3) heaters,which can experience significant power fluctuations and even failure due to substantial resistance changes—an issue conventional thyristorcontrolled heating systems cannot effectively manage.To address this limitation,we have developed the Multi-Anvil Stable Temperature controller(MASTer),a high-performance heating system optimized for MAP experiments.MASTer enables precise,high-speed measurement of heating parameters and power output control,incorporating a gentle regulation strategy to enhance stability.It ensures consistent heating across various heater types,including LaCrO_(3),with power fluctuations limited to±0.1 W and temperature fluctuations to within±2℃ in most cases.The design,operating principles,user interface,functionality,and performance of the heating system are discussed in detail.展开更多
Existing linkage-optimization methods are designed for mechanical presses; few can be directly used for servo presses, so development of the servo press is limited. Based on the complementarity of linkage opti- mizati...Existing linkage-optimization methods are designed for mechanical presses; few can be directly used for servo presses, so development of the servo press is limited. Based on the complementarity of linkage opti- mization and motion planning, a phase-division-based linkage-optimization model for a drawing servo press is established. Considering the motion-planning principles of a drawing servo press, and taking account of work rating and efficiency, the constraints of the optimization model are constructed. Linkage is optimized in two modes： use of either constant eccentric speed or constant slide speed in the work segments. The performances of optimized link- ages are compared with those of a mature linkage SL4- 2000A, which is optimized by a traditional method. The results show that the work rating of a drawing servo press equipped with linkages optimized by this new method improved and the root-mean-square torque of the servo motors is reduced by more than 10%. This research pro- vides a promising method for designing energy-saving drawing servo presses with high work ratings.展开更多
A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank m...A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity,the kinematic parameters of the slide,connecting rod and crank were formulated approximately. On the basis of the results above,three inertia forces and the input moment in the mechanism during its idle running were investigated and formulated by dynamic analysis. A verification experiment was performed on a slider-crank mechanism at a high-speed press machine. The forces derived from the established formulas were compared respectively with those obtained by the ADAMS software and the classical method of connecting rod mass substitution. It was experimentally found that the proposed formulas have an improved performance over related earlier techniques. By use of these results,a 1 000 kN 1 250 rpm four-point high-speed press machine was designed and manufactured. The slide of this press is driven by four sets of slider-crank mechanisms with symmetrical layout and opposite rotation directions to counterbalance the horizontal inertia forces. Four eccentric counterbalance blocks were designed to counterbalance the vertical force after their mass and equivalent eccentric radius were formulated. The high-speed press machine designed by the proposed counterbalance method has worked with satisfactory performance and good dynamic balance for more than four years in practical production.展开更多
Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing t...Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.展开更多
The 2024 MRE HP Special Volume selects papers on new theoretical and experimental developments in the use of static largevolume presses(LVPs)1–3 and dynamic compression4,5 for studies under extreme high-pressure and ...The 2024 MRE HP Special Volume selects papers on new theoretical and experimental developments in the use of static largevolume presses(LVPs)1–3 and dynamic compression4,5 for studies under extreme high-pressure and high-temperature(HPHT)conditions.It also continues the previous year’s6 contemporary focus on superhydrides7–11 with extremely high superconducting temperatures Tc and addresses some controversial issues.12–14 In addition,it explores unconventional pressure-induced chemistry,particularly novel chemical stoichiometry and its impact on geochemistry and cosmochemistry in the deep interiors of Earth and other planets.18–21.展开更多
High-pressure and high-temperature(HPHT)experiments in large-volume presses(LVPs)benefit from reliable,available,and affordable heaters to achieve stable and homogeneous heating and,in some circumstances,X-ray transpa...High-pressure and high-temperature(HPHT)experiments in large-volume presses(LVPs)benefit from reliable,available,and affordable heaters to achieve stable and homogeneous heating and,in some circumstances,X-ray transparency for monitoring of properties of an in situ experiment using X-ray diffraction and contrast imaging techniques.We have developed heaters meeting the above requirements,and we screen the ternary system TiB2–SiC–hexagonal(h)BN(denoted as TSB)to enable manufacture of X-ray transparent heaters for HPHT runs.Heaters fabricated using optimized TSB-631(60%TiB2–30%SiC–10%hBN by weight)have been tested in modified truncated assemblies,showing excellent performance up to 22 GPa and 2395 K in HPHT runs.TSB-631 has good ceramic machinability,outstanding reproducibility,high stability,and negligible temperature gradient for runs at 3–7 GPa with cell assemblies with truncated edge lengths of 8–12 mm.The fabricated heaters not only show excellent performance in HPHT runs,but also demonstrate high X-ray transparency over a wide X-ray wavelength region,indicating potential applications for in situ X-ray diffraction/imaging under HPHT conditions in LVPs and other high-pressure apparatus.展开更多
Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prep...Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.展开更多
To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 ...To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 and 4 passes.The corrosion behavior and mechanical properties of alloys were investigated by optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),electrochemical tests,immersion tests and tensile tests.The results showed that mechanical properties improved after ECAP 1 pass;however,the corrosion resistance deteriorated due to high-density dislocations and fragmented secondary phases by ECAP.In contrast,synchronous improvement in the mechanical properties and corrosion resistance was achieved though grain refinement after ECAP 4 passes;fine grains led to a significant improvement in the yield strength,ultimate tensile strength,elongation,and corrosion rate of 103 MPa,223 MPa,30.5%,and 1.5843 mm/a,respectively.The enhanced corrosion resistance was attributed to the formation of dense corrosion product films by finer grains and the barrier effect by high-density grain boundaries.These results indicated that Mg-1Zn-1Ca alloy has a promising potential for application in biomedical materials.展开更多
The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results s...The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results show that the interface region can be divided into four zones from base metal to deposited metal:carbon-depleted zone(CDZ),partial melting zone(PMZ),planar growth zone(PGZ),and brownish feature zone(BFZ).Dimensions of these zones do not significantly change during aging.However,type I carbides noticeably increase in size in the PMZ,and precipitates clearly occur in the PGZ.The main reason for their growth and occurrence is continuous carbon migration.The highest micro-hardness appears in the PGZ and BFZ regions,which is related to carbon accumulation and precipitates in these regions.Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials.The CDZ,composed of only ferrite,has lower strength and fractures at the boundary between CDZ and base metal.The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h,and the interface region maintains high strength without significant deformation.展开更多
To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0....To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.展开更多
Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2...Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.展开更多
Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent lumine...Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent luminescent material applications.At present,YAGG:Ce^(3+),Cr^(3+)powders exhibit good persistent performance,but their persistent performance of ceramics still needs to be further improved to meet the new requirements.In this work,(Y_(0.998)Ce_(0.002))_(3)(Al_(1-x)Cr_(x))_(2)Ga_(3)O_(12) ceramics with different Cr^(3+)doping concentrations were prepared by solid-state reaction,including air pre-sintering,hot isostatic pressing(HIP)post-treatment and air annealing,to investigate the effects of Cr^(3+)doping concentration on the microstructure,optical properties and persistent performance of the ceramics.The results showed that as the doping concentration of Cr^(3+)increased from 0.025%to 0.2%(in atom),no significant effect of Cr^(3+)concentration on the morphology of pre-sintered ceramics or HIP post-treatment ceramics was observed,but the in-line transmittance gradually increased while the persistent performance gradually decreased.Among them,YAGG:Ce^(3+),Cr^(3+)ceramics doped with 0.025%Cr^(3+)showed the strongest initial luminescence intensity exceeding 6055 mcd/m^(2) and a persistent time of 1030 min after air pre-sintering combined with HIP post-treatment and air annealing.By optimizing the Cr^(3+)doping concentration and the fabrication process,the persistent luminescence(PersL)performance of the YAGG:Ce^(3+),Cr^(3+)ceramics was obviously improved.展开更多
Against the backdrop of persistent security problems and external interference,many people in the Central African Republic are calling for solutions rooted in the country’s own realities.In this interview,Bienvenu Pa...Against the backdrop of persistent security problems and external interference,many people in the Central African Republic are calling for solutions rooted in the country’s own realities.In this interview,Bienvenu Paya-Ngbouhou,editor in chief of the newspaper L’Hirondelle,reflects on the need to understand the nation’s internal dynamics,the role of the press in peacebuilding,and opportunities for cooperation with partners such as China.展开更多
Find It What did people use years ago to print things?Each year,the world produces millions of pounds of paper.A lot goes into the trash.Recycling means waste can be used again.To recycle paper,you usually need specia...Find It What did people use years ago to print things?Each year,the world produces millions of pounds of paper.A lot goes into the trash.Recycling means waste can be used again.To recycle paper,you usually need special tools and machines.But what if you could recycle paper by yourself?You could turn used paper into writing paper.展开更多
Zn–Ag alloys are highly promising materials for fabricating biodegradable orthopedic implants.Nonetheless,they suffer from inferior strength.A Zn–2.5Ag alloy was alloyed with different contents of Mg(0.08,0.5,and 1 ...Zn–Ag alloys are highly promising materials for fabricating biodegradable orthopedic implants.Nonetheless,they suffer from inferior strength.A Zn–2.5Ag alloy was alloyed with different contents of Mg(0.08,0.5,and 1 wt.%)and then processed by equal channel angular pressing.Tensile tests and microstructure observation were conducted to investigate the impact of Mg addition on the microstructure and mechanical properties of Zn–2.5Ag alloy.Zn–2.5Ag alloy exhibits an ultrahigh elongation(EL)of 120.4%but a poor yield strength(YS)of 90.1 MPa,because of phase boundary sliding(PBS).Mg addition inhibits PBS and thus dramatically enhances YS but lowers EL.Specifically,YS of Zn–2.5Ag alloys containing Mg of 0.08%,0.5%,and 1%is 257.0,291.8,and 322.6 MPa,respectively.The alloys with 0.08%and 0.5%Mg possess an EL of around 30%,while the alloy with 1%Mg has an EL of only 11.0%.YS and EL of Zn–2.5Ag–0.5Mg alloy surpass that needed by orthopedic implants by 45.9%and 106.0%,respectively.Grain refinement strengthening is the main contributor to high strength.It is speculated that deformation twinning suppression and<c+a>pyramidal slip activation contribute to good ductility.展开更多
Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)techniq...Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)technique for developing highstrength pure titanium.The MSP processes of spherical Ti powders of 15–53μm,53–105μm,and 75–180μm were systematically investigated through multi-particle fnite element method(MPFEM)compared with conventional one-step pressing(OSP)technique.The relative density,phase constitution,microstructure,and compressive mechanical properties of the sintered bulk pure titanium were characterized.Simulation results demonstrate that the MSP technique signifcantly increases the relative density of green compacts by 3.2%,3.3%,and 5.2%,respectively,compared with OSP technique.Experimental results indicate the relative density of the sintered specimens prepared by MSP spherical powders increases by 5.4%,4.5%,and 4.5%,respectively,compared to OSP,and the yield strength improves by 16%,13%,and 18%.For the sintered specimens prepared by MSP irregular powder of 15–53μm,the relative density increases by 6.0%and the yield strength increases by 15%.The enhancement of relative density and yield strength is mainly because the MSP technique mitigates stress concentration between powder particles.Compared to spherical powder,irregular powder exhibits stronger mechanical interlocking owing to the greater propensity for displacement and deformation,which facilitates mutual wedging and interlocking,resulting in superior strength performance.展开更多
To efficiently search out the optimal cam contour,a software integrated optimization method considering cam mechanism’s kinematic and dynamic characteristics was presented,and its effectiveness was demonstrated by a ...To efficiently search out the optimal cam contour,a software integrated optimization method considering cam mechanism’s kinematic and dynamic characteristics was presented,and its effectiveness was demonstrated by a case study of the cam contour optimization for an offset press open-close gripper mechanism.The acceleration curve and the residual vibration model of the follower were separately studied.A symmetric harmonic trapezoidal curve was designed to control the follower’s acceleration,and single-DOF lumped parameter torsional vibration model was proposed to describe the follower’s residual vibration.Accordingly,corresponding motion curve design software and Simulink vibration model of the follower were developed respectively,and they were integrated into an automatic optimization platform with iSIGHT.The multi-objective optimization with objectives of minimizing both the acceleration and the residual vibration of the follower was completed within the platform by using NSGA-II algorithm.An appropriate point with lower acceleration and residual vibration was chosen from Pareto front as an optimal solution of the follower’s motion curve.Based on the follower’s new motion curve,the actual cam contour was generated by inverse kinematic simulation in COSMOSMotion.The offset press that installed our new designed cam exhibited a lower vibration than the previous machine,and the maximum measured acceleration of the offset press at a printing speed of 15000 r/h is reduced by 7.7%.展开更多
1 Move over Simone Biles,because grey whales might just be the next Olympic champions.This conclusion can be drawn from a new study that filmed these amazing animals doing underwater headstands(头倒立)and other moves....1 Move over Simone Biles,because grey whales might just be the next Olympic champions.This conclusion can be drawn from a new study that filmed these amazing animals doing underwater headstands(头倒立)and other moves.2 As part of a seven-year project,scientists used drones(无人驾驶飞机)to observe a group of 200 grey whales off the coasts of Oregon,Washington,northern California and southern Canada.The new study findings,published in Animal Behaviour,revealed that grey whales do headstands by pressing their mouths against the ocean floor while searching for something to eat.Scientists also noticed that when doing headstands,grey whales move like human synchronized swimmers.展开更多
In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 ...In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars(Grant No.T2225027)the National Key R&D Program of China(Grant No.2023YFA1608902).
文摘Maintaining stable high temperatures under pressure remains a challenge in high-pressure,high-temperature experiments using multi-anvil presses(MAPs).Temperature fluctuations exceeding 10℃ at high pressures are common and particularly problematic with LaCrO_(3) heaters,which can experience significant power fluctuations and even failure due to substantial resistance changes—an issue conventional thyristorcontrolled heating systems cannot effectively manage.To address this limitation,we have developed the Multi-Anvil Stable Temperature controller(MASTer),a high-performance heating system optimized for MAP experiments.MASTer enables precise,high-speed measurement of heating parameters and power output control,incorporating a gentle regulation strategy to enhance stability.It ensures consistent heating across various heater types,including LaCrO_(3),with power fluctuations limited to±0.1 W and temperature fluctuations to within±2℃ in most cases.The design,operating principles,user interface,functionality,and performance of the heating system are discussed in detail.
基金Supported by National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2015ZX04003004)
文摘Existing linkage-optimization methods are designed for mechanical presses; few can be directly used for servo presses, so development of the servo press is limited. Based on the complementarity of linkage opti- mization and motion planning, a phase-division-based linkage-optimization model for a drawing servo press is established. Considering the motion-planning principles of a drawing servo press, and taking account of work rating and efficiency, the constraints of the optimization model are constructed. Linkage is optimized in two modes： use of either constant eccentric speed or constant slide speed in the work segments. The performances of optimized link- ages are compared with those of a mature linkage SL4- 2000A, which is optimized by a traditional method. The results show that the work rating of a drawing servo press equipped with linkages optimized by this new method improved and the root-mean-square torque of the servo motors is reduced by more than 10%. This research pro- vides a promising method for designing energy-saving drawing servo presses with high work ratings.
基金supported by the National Natural Science Foundation of China (No.50575175)
文摘A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity,the kinematic parameters of the slide,connecting rod and crank were formulated approximately. On the basis of the results above,three inertia forces and the input moment in the mechanism during its idle running were investigated and formulated by dynamic analysis. A verification experiment was performed on a slider-crank mechanism at a high-speed press machine. The forces derived from the established formulas were compared respectively with those obtained by the ADAMS software and the classical method of connecting rod mass substitution. It was experimentally found that the proposed formulas have an improved performance over related earlier techniques. By use of these results,a 1 000 kN 1 250 rpm four-point high-speed press machine was designed and manufactured. The slide of this press is driven by four sets of slider-crank mechanisms with symmetrical layout and opposite rotation directions to counterbalance the horizontal inertia forces. Four eccentric counterbalance blocks were designed to counterbalance the vertical force after their mass and equivalent eccentric radius were formulated. The high-speed press machine designed by the proposed counterbalance method has worked with satisfactory performance and good dynamic balance for more than four years in practical production.
基金Funded by the Natural Science Foundation of Hubei Province (No. 2004AA101E04)
文摘Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.
基金financial support from the Shanghai Key Laboratory of MFree,China(Grant No.22dz2260800)the Shanghai Science and Technology Committee,China(Grant No.22JC1410300).
文摘The 2024 MRE HP Special Volume selects papers on new theoretical and experimental developments in the use of static largevolume presses(LVPs)1–3 and dynamic compression4,5 for studies under extreme high-pressure and high-temperature(HPHT)conditions.It also continues the previous year’s6 contemporary focus on superhydrides7–11 with extremely high superconducting temperatures Tc and addresses some controversial issues.12–14 In addition,it explores unconventional pressure-induced chemistry,particularly novel chemical stoichiometry and its impact on geochemistry and cosmochemistry in the deep interiors of Earth and other planets.18–21.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.22090041 and 22401297)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022B1515120014).
文摘High-pressure and high-temperature(HPHT)experiments in large-volume presses(LVPs)benefit from reliable,available,and affordable heaters to achieve stable and homogeneous heating and,in some circumstances,X-ray transparency for monitoring of properties of an in situ experiment using X-ray diffraction and contrast imaging techniques.We have developed heaters meeting the above requirements,and we screen the ternary system TiB2–SiC–hexagonal(h)BN(denoted as TSB)to enable manufacture of X-ray transparent heaters for HPHT runs.Heaters fabricated using optimized TSB-631(60%TiB2–30%SiC–10%hBN by weight)have been tested in modified truncated assemblies,showing excellent performance up to 22 GPa and 2395 K in HPHT runs.TSB-631 has good ceramic machinability,outstanding reproducibility,high stability,and negligible temperature gradient for runs at 3–7 GPa with cell assemblies with truncated edge lengths of 8–12 mm.The fabricated heaters not only show excellent performance in HPHT runs,but also demonstrate high X-ray transparency over a wide X-ray wavelength region,indicating potential applications for in situ X-ray diffraction/imaging under HPHT conditions in LVPs and other high-pressure apparatus.
基金support from CAS Project for Young Scientists in Basic Research(YSBR-025)and the Technology Innovation(RCJJ-145-24-39)R.P.Guo acknowledges the financial support from the National Natural Science Foundation of China(No.52401104)+1 种基金the Fundamental Research Program of Shanxi Province(No.202203021221072)the China Postdoctoral Science Foundation(No.2024M753298).
文摘Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.
基金financially supported by the National Natural Science Foundation of China(No.52374395)the Natural Science Foundation of Shanxi Province,China(Nos.20210302123135,202303021221143)+5 种基金the Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi Province,China(Nos.202104021301022,202204021301009)the Central Government Guided Local Science and Technology Development Projects,China(No.YDZJSX20231B003)the Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant(No.075-15-2022-1133)the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT of Korea through the Research Institute of Advanced Materials(No.2015R1A2A1A01006795)the China Postdoctoral Science Foundation(No.2022M710541)the Research Project supported by Shanxi Scholarship Council of China(No.2022-038)。
文摘To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 and 4 passes.The corrosion behavior and mechanical properties of alloys were investigated by optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),electrochemical tests,immersion tests and tensile tests.The results showed that mechanical properties improved after ECAP 1 pass;however,the corrosion resistance deteriorated due to high-density dislocations and fragmented secondary phases by ECAP.In contrast,synchronous improvement in the mechanical properties and corrosion resistance was achieved though grain refinement after ECAP 4 passes;fine grains led to a significant improvement in the yield strength,ultimate tensile strength,elongation,and corrosion rate of 103 MPa,223 MPa,30.5%,and 1.5843 mm/a,respectively.The enhanced corrosion resistance was attributed to the formation of dense corrosion product films by finer grains and the barrier effect by high-density grain boundaries.These results indicated that Mg-1Zn-1Ca alloy has a promising potential for application in biomedical materials.
基金Major Scientific and Technological Project of Gansu(22ZD6GA008)Excellent Doctorate Project of Gansu(23JRRA806)National Natural Science Foundation of China(52175325,51961024,52071170)。
文摘The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results show that the interface region can be divided into four zones from base metal to deposited metal:carbon-depleted zone(CDZ),partial melting zone(PMZ),planar growth zone(PGZ),and brownish feature zone(BFZ).Dimensions of these zones do not significantly change during aging.However,type I carbides noticeably increase in size in the PMZ,and precipitates clearly occur in the PGZ.The main reason for their growth and occurrence is continuous carbon migration.The highest micro-hardness appears in the PGZ and BFZ regions,which is related to carbon accumulation and precipitates in these regions.Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials.The CDZ,composed of only ferrite,has lower strength and fractures at the boundary between CDZ and base metal.The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h,and the interface region maintains high strength without significant deformation.
基金National Natural Science Foundation of China(52105385)Stable Support Plan Program of Shenzhen Natural Science Fund(20220810132537001)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2022A1515010781)Joint Fund of Henan Province Science and Technology R&D Program(225200810002)Fundamental Research Funds of Henan Academy of Sciences(240621041)。
文摘To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.
基金National Key R&D Program of China(2023YFE3812005)International Partnership Program of Chinese Academy of Sciences(121631KYSB20200039)+1 种基金National Center for Research and Development(WPC2/1/SCAPOL/2021)Chinese Academy of Sciences President’s International Fellowship Initiative(2024VEA0005,2024VEA0014)。
文摘Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.
基金National Key R&D Program of China(2023YFB3506600)。
文摘Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent luminescent material applications.At present,YAGG:Ce^(3+),Cr^(3+)powders exhibit good persistent performance,but their persistent performance of ceramics still needs to be further improved to meet the new requirements.In this work,(Y_(0.998)Ce_(0.002))_(3)(Al_(1-x)Cr_(x))_(2)Ga_(3)O_(12) ceramics with different Cr^(3+)doping concentrations were prepared by solid-state reaction,including air pre-sintering,hot isostatic pressing(HIP)post-treatment and air annealing,to investigate the effects of Cr^(3+)doping concentration on the microstructure,optical properties and persistent performance of the ceramics.The results showed that as the doping concentration of Cr^(3+)increased from 0.025%to 0.2%(in atom),no significant effect of Cr^(3+)concentration on the morphology of pre-sintered ceramics or HIP post-treatment ceramics was observed,but the in-line transmittance gradually increased while the persistent performance gradually decreased.Among them,YAGG:Ce^(3+),Cr^(3+)ceramics doped with 0.025%Cr^(3+)showed the strongest initial luminescence intensity exceeding 6055 mcd/m^(2) and a persistent time of 1030 min after air pre-sintering combined with HIP post-treatment and air annealing.By optimizing the Cr^(3+)doping concentration and the fabrication process,the persistent luminescence(PersL)performance of the YAGG:Ce^(3+),Cr^(3+)ceramics was obviously improved.
文摘Against the backdrop of persistent security problems and external interference,many people in the Central African Republic are calling for solutions rooted in the country’s own realities.In this interview,Bienvenu Paya-Ngbouhou,editor in chief of the newspaper L’Hirondelle,reflects on the need to understand the nation’s internal dynamics,the role of the press in peacebuilding,and opportunities for cooperation with partners such as China.
文摘Find It What did people use years ago to print things?Each year,the world produces millions of pounds of paper.A lot goes into the trash.Recycling means waste can be used again.To recycle paper,you usually need special tools and machines.But what if you could recycle paper by yourself?You could turn used paper into writing paper.
基金financial support of the National Natural Science Foundation of China(Nos.52001142 and 51975263).
文摘Zn–Ag alloys are highly promising materials for fabricating biodegradable orthopedic implants.Nonetheless,they suffer from inferior strength.A Zn–2.5Ag alloy was alloyed with different contents of Mg(0.08,0.5,and 1 wt.%)and then processed by equal channel angular pressing.Tensile tests and microstructure observation were conducted to investigate the impact of Mg addition on the microstructure and mechanical properties of Zn–2.5Ag alloy.Zn–2.5Ag alloy exhibits an ultrahigh elongation(EL)of 120.4%but a poor yield strength(YS)of 90.1 MPa,because of phase boundary sliding(PBS).Mg addition inhibits PBS and thus dramatically enhances YS but lowers EL.Specifically,YS of Zn–2.5Ag alloys containing Mg of 0.08%,0.5%,and 1%is 257.0,291.8,and 322.6 MPa,respectively.The alloys with 0.08%and 0.5%Mg possess an EL of around 30%,while the alloy with 1%Mg has an EL of only 11.0%.YS and EL of Zn–2.5Ag–0.5Mg alloy surpass that needed by orthopedic implants by 45.9%and 106.0%,respectively.Grain refinement strengthening is the main contributor to high strength.It is speculated that deformation twinning suppression and<c+a>pyramidal slip activation contribute to good ductility.
基金supports from the National Natural Science Foundation of China(No.52404382)the Key Research and Development Project of Shaanxi Province(No.2023-YBGY-090).
文摘Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)technique for developing highstrength pure titanium.The MSP processes of spherical Ti powders of 15–53μm,53–105μm,and 75–180μm were systematically investigated through multi-particle fnite element method(MPFEM)compared with conventional one-step pressing(OSP)technique.The relative density,phase constitution,microstructure,and compressive mechanical properties of the sintered bulk pure titanium were characterized.Simulation results demonstrate that the MSP technique signifcantly increases the relative density of green compacts by 3.2%,3.3%,and 5.2%,respectively,compared with OSP technique.Experimental results indicate the relative density of the sintered specimens prepared by MSP spherical powders increases by 5.4%,4.5%,and 4.5%,respectively,compared to OSP,and the yield strength improves by 16%,13%,and 18%.For the sintered specimens prepared by MSP irregular powder of 15–53μm,the relative density increases by 6.0%and the yield strength increases by 15%.The enhancement of relative density and yield strength is mainly because the MSP technique mitigates stress concentration between powder particles.Compared to spherical powder,irregular powder exhibits stronger mechanical interlocking owing to the greater propensity for displacement and deformation,which facilitates mutual wedging and interlocking,resulting in superior strength performance.
基金the Foshan Science and Technology Innovation Team Project(No.FS0AA-KJ919-4402-0060)the National Natural Science Foundation of China(No.62263018)。
文摘To efficiently search out the optimal cam contour,a software integrated optimization method considering cam mechanism’s kinematic and dynamic characteristics was presented,and its effectiveness was demonstrated by a case study of the cam contour optimization for an offset press open-close gripper mechanism.The acceleration curve and the residual vibration model of the follower were separately studied.A symmetric harmonic trapezoidal curve was designed to control the follower’s acceleration,and single-DOF lumped parameter torsional vibration model was proposed to describe the follower’s residual vibration.Accordingly,corresponding motion curve design software and Simulink vibration model of the follower were developed respectively,and they were integrated into an automatic optimization platform with iSIGHT.The multi-objective optimization with objectives of minimizing both the acceleration and the residual vibration of the follower was completed within the platform by using NSGA-II algorithm.An appropriate point with lower acceleration and residual vibration was chosen from Pareto front as an optimal solution of the follower’s motion curve.Based on the follower’s new motion curve,the actual cam contour was generated by inverse kinematic simulation in COSMOSMotion.The offset press that installed our new designed cam exhibited a lower vibration than the previous machine,and the maximum measured acceleration of the offset press at a printing speed of 15000 r/h is reduced by 7.7%.
文摘1 Move over Simone Biles,because grey whales might just be the next Olympic champions.This conclusion can be drawn from a new study that filmed these amazing animals doing underwater headstands(头倒立)and other moves.2 As part of a seven-year project,scientists used drones(无人驾驶飞机)to observe a group of 200 grey whales off the coasts of Oregon,Washington,northern California and southern Canada.The new study findings,published in Animal Behaviour,revealed that grey whales do headstands by pressing their mouths against the ocean floor while searching for something to eat.Scientists also noticed that when doing headstands,grey whales move like human synchronized swimmers.
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by the International Cooperative Scientific Research Platform of SUES,China。
文摘In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.
