Based on the experimental result that Cr and C segregated on the prior grain boundaries of austenite in overheated steels,causing the inheritance of fracture mode after re-austeni- tization,a thermodynamic analysis is...Based on the experimental result that Cr and C segregated on the prior grain boundaries of austenite in overheated steels,causing the inheritance of fracture mode after re-austeni- tization,a thermodynamic analysis is conducted through the calculation of equilibrium segregation amount of Cr and C in grain boundary at 860 and 1050℃ and the segregation kinetics of Cr is also calculated.Thermodynamic calculation gives an evidence that the segregation of Cr and C at grain boundaries may be regarded as one of the mechanisms of the fracture inheritance in overheated steels.展开更多
A concept of ensemble averaged stellar reactors is developed to study the dynamics of processes occurring in stars, allocated in the ~200 pc solar neighborhood. According to the effective temperature value, four stell...A concept of ensemble averaged stellar reactors is developed to study the dynamics of processes occurring in stars, allocated in the ~200 pc solar neighborhood. According to the effective temperature value, four stellar classes are identified, for which the correlation coefficients and standard deviation are counted. The theory of the buoyancy terrestial elements is generalized to stellar systems. It was suggested that stars are over-heated due to the shift parameters of the nuclear processes occurring inside the stars, which leads to the synthesis of transuranium elements until the achievement of a critical nuclear mass and star explosion. The heavy transuranium elements sink downward and are concentrated in the stellar depth layers. The physical explanation of the existence of the critical Chandrasekhar star limit has been offered. Based on the spatial analysis of overheated stars, it was suggested that the withdrawal of the stellar reactor from the equilibrium state is a consequence of extragalactic compression inside the galaxy arm due to the arm spirality (not to be confused with the spirality of the galaxy itself).展开更多
The growth of fixed assets investment in China soared to a high record in the first quarter of 2004 after gross domestic product （GDP） bounced substantially in 2003. A bubble is emerging posing threats to Chinese ec...The growth of fixed assets investment in China soared to a high record in the first quarter of 2004 after gross domestic product （GDP） bounced substantially in 2003. A bubble is emerging posing threats to Chinese economic development. In order to cool down the overheated investment, Chinese government should promptly take effective measures in macroeconomic control to limit or guide the red-hot investment in some sectors and slow down its growth, thus implements the changes from administrative-driven investment to enterprise-driven investment and from investment-driven economic growth to consumption-driven growth.展开更多
Based on macroeconomic analysis since 2003, this article holds that a trend towardsoverheating has surfaced in Chinas economy. Chinas rapid economic expansion hasaffected the quality of its growth, with rising materia...Based on macroeconomic analysis since 2003, this article holds that a trend towardsoverheating has surfaced in Chinas economy. Chinas rapid economic expansion hasaffected the quality of its growth, with rising material and energy consumption and imbalancedeconomic structure as the main manifestations. Regarding macroeconomic policy options in2004, decision-makers should shift the policy focus from control of deflation to preventionof inflation; the pace of economic growth should be properly set; a balance betweenconsumption and investment should be strengthened by controlling excessive expansion ofinvestment, and industrial restructuring should be conducted in a coordinated manner onthe basis of properly controlling the overly rapid industrial growth; policies should becontinued to boost exports and sustainable growth of foreign investment; and more effortsshould be made to accelerate the change in the mode of economic growth.展开更多
Chongqing and Shanghai announced on January 27 they would launch a long-awaited pilot property tax beginning January 28. The move is part of a larger Central Government effort to cool the housing market. The results o...Chongqing and Shanghai announced on January 27 they would launch a long-awaited pilot property tax beginning January 28. The move is part of a larger Central Government effort to cool the housing market. The results of the trial program will determine how the tax is rolled out in other locations, according to the Ministry of Finance.展开更多
The phenomena of thermal runaway and accidental deformation due to external stresses in lithium batteries or film capacitors consti-tute their primary failure mechanisms.Therefore,monitoring and early warning of overh...The phenomena of thermal runaway and accidental deformation due to external stresses in lithium batteries or film capacitors consti-tute their primary failure mechanisms.Therefore,monitoring and early warning of overheating or localized strain are of great value for the safe use of lithium batteries or film capacitors;however,this function usually requires a system of multiple complex sensors.The realization of the above multiple hazards using a single sensor for monitoring and alarm functions has not been reported.Here,we exploit the thermally induced conductivity and modulus change during solid-liquid conversion of low melting point polyalloys to modulate the electronic relaxation polariza-tion and interfacial polarization in the composites for dielectric switching,and the reduction of alloy particle spacing during bending/compres-sive strain can be used to generate switchable tunneling effects for insulator-conductor transition.By synergizing dielectric switching and insula-tor-conductor transition,the final flexible thermoplastic polyurethane elastomer/low-melting-point polyalloy composite film achieves the func-tional integration of multi-level overheating warning and small deformation monitoring.展开更多
Battery safety is influenced by various factors,with thermal runaway being one of the most significant concerns.While most studies have concentrated on developing one-time,self-activating mechanism for thermal protect...Battery safety is influenced by various factors,with thermal runaway being one of the most significant concerns.While most studies have concentrated on developing one-time,self-activating mechanism for thermal protection,such as temperature-responsive electrodes,and thermal-shutdown separators,these methods only provide irreversible protection.Recently,reversible temperature-sensitive electrolytes have emerged as promising alternatives,offering both thermo-reversibility and self-protective properties.However,further research is crucial to fully understand these thermal-shutdown electrolytes.In this study,we propose lower critical solution temperature(LCST)phase behavior poly(benzyl methacrylate)/imidazolium-based ionic liquid mixtures to prepare temperature-sensitive electrolytes that provide reversible thermal shutdown protection of batteries.This electrolyte features an appropriate protection temperature(~105℃)and responds quickly within a 1 min at 105℃,causing cells to hardly discharge as the voltage suddenly drops to 3.38 V,and providing efficient thermal shutdown protection within 30 min.Upon cooling back to room temperature,the battery regains its original performance.Additionally,the electrolyte exhibits excellent cycling stability with the capacity retention of the battery is 91.6%after 500 cycles.This work provides a viable solution for preventing batteries from thermal runaway triggered by overheating.展开更多
The tube failures took place frequently in the superheater of 2x600MW units in a power plant.According to the condition of tube failures,the mechanical property and microstructure on running and failed tubes were test...The tube failures took place frequently in the superheater of 2x600MW units in a power plant.According to the condition of tube failures,the mechanical property and microstructure on running and failed tubes were tested and evaluated.The chemical composition and structure phase of inner oxide scale and deposit inside of the tubes were examined.The fractured surfaces of failed tube samples were observed.And the material examination was performed for original tube steels SA213-T91 and SA213-T22.The results show that raw materials of SA213-T91 and SA213-T22 tube in superheater are qualified.Besides,the characteristics of the SA213-T91 and SA213-T22 tube failure are typical short-term overheated rupture.The rupture temperature is located between two phase Ac1~Ac3 of the two steels.It is recognized that putting SA213-T22 tubes in operation under the condition of long-term over heating causes the rupture of SA213-T91 and SA213-T22.展开更多
The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with ...The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.展开更多
Through the long time track examination and disintegration to SF6 circuit breaker, we obtain the massive monitor data and massive pictures. The criteria of resuming insulation discharge failure conforming to CSO2/CH2S...Through the long time track examination and disintegration to SF6 circuit breaker, we obtain the massive monitor data and massive pictures. The criteria of resuming insulation discharge failure conforming to CSO2/CH2S>7, is quite broad to SO2 and the H2S concentration permission. Even if it reaches 100μL/L, it will not be in danger immediately to the safe operation of equipment. We may plan, arrange, and overhaul calmly. When obtaining the bare conductor overheating failure, it has not involved the resuming insulation. We may use the resuming insulation discharge failure criterion.展开更多
Aero-engine turbine blades may suffer overheating during service,which can result in severe microstructural and mechanical degradation within tens of seconds.In this study,the thermal cycling creep under(950℃/15 min+...Aero-engine turbine blades may suffer overheating during service,which can result in severe microstructural and mechanical degradation within tens of seconds.In this study,the thermal cycling creep under(950℃/15 min+1100℃/1 min)-100 MPa was performed on a directionally solidified superalloy,DZ125.The effects of overheating and thermal cycling on the creep properties were evaluated in terms of creep behavior and microstructural evolution against isothermally crept specimens under 950℃/100 MPa,950℃/270 MPa,and 1100℃/100 MPa.The results indicated that the thermal cycling creep life was reduced dramatically compared to the isothermal creep under 950℃/100 MPa.The plastic creep deformation mainly occurred during the overheating stage during the thermal cycling creep.The thermal cycling creep curve exhibited three stages,similar to the 1100℃isothermal creep,but its minimum creep rate occurred at a lower creep strain.The overheating events caused severe microstructural degradation,such as substantial dissolution ofγ'phase,earlier formation of raftedγ'microstructure,widening of theγchannels,and instability of the interfacial dislocation networks.This microstructural degradation was the main reason for the dramatic decrease in thermal cycling creep life,as the thermal cycling promoted more dislocations to cut intoγ'phase and more cracks to initiate at grain boundaries,carbides,and residual eutectic pools.This study underlines the importance of evaluating the thermal cycling creep properties of superalloys to be used as turbine blades and provides insights into the effect of thermal cycling on directionally solidified superalloys for component design.展开更多
Overheating of the engine, the transmission and the hydraulic device is a problem when the construction machinery works on plateau. To solve this problem, we proposed an electro-controlled hydraulic driving fan coolin...Overheating of the engine, the transmission and the hydraulic device is a problem when the construction machinery works on plateau. To solve this problem, we proposed an electro-controlled hydraulic driving fan cooling system (ECHDFCS). The system was applied to a 50-wheel loader. We carried out the coolant temperature simulation using fluid modeling software FLOWMASTER, followed by laboratory experiments and road tests. The results show that ECHDFCS can adjust the cooling capability of the system automatically based on machine heat dissipation requirements. The coolant temperature is consequently remained within an appropriate range. The simulation results are consistent with the experiment results when the experiment is performed on the plain, but are different from the road tests in some investigated parameters on the plateau.展开更多
Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing ...Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing these byproducts is an effective method to judge the internal operation condition of electric equipment. In order to study characters of SF6byproducts at different temperature of overheated faults in the electric equipment, a series of overheated faults of electric equipment were simulated. SF6is very stable and not significantly decomposed at 200oC, 250oC and 300oC. SF6is significantly decomposed to SO2, H2S and HF at 350oC. The concentration of SO2, H2S and HF was 7.2, 1.6 and 1.9 μL/L after heating for 5 hours in environment of SF6with 3616 μL/L water, and it was increased to 23.0, 3.0 and 1.2 μL/L 3 hours later. SF6is more easily to be decomposed and decomposed more rapidly at higher temperature. The concentration of SO2, H2S and HF was 62.2, 15.6 and 3.6 μL/L after heating for 5 hours in environment of SF6with 4064 μL/L water, and it was increased to 91.4, 25.2 and 2.3 μL/L 3 hours later. SF6will be decomposed to format HF, which is strongly corrosive and whose concentration is likely to decrease when it is above a certain concentration.展开更多
Thermal barrier coatings(TBC)on superalloy blade/vane enable an increase in turbine inlet temperature(TIT)and aero-engine efficiency.However,the deposition of dust on TBC significantly ablates superalloys and becomes ...Thermal barrier coatings(TBC)on superalloy blade/vane enable an increase in turbine inlet temperature(TIT)and aero-engine efficiency.However,the deposition of dust on TBC significantly ablates superalloys and becomes a bottleneck for advanced engine development.This paper presents a comprehensive mod-eling approach,based on an experiment involving dust deposition on a TBC-coated substrate,aimed at understanding the fundamental cause of substrate ablation.The results show that a significant increase in surface roughness is obtained experimentally with dust accumulation.The temperature field within the TBC-substrate system is disturbed by surface roughening.Consequently,the film cooling is seriously destroyed.While the dust accumulated on the TBC surface also contributes to heat insulation by increas-ing the effective TBC thickness,localized overheating of the substrate occurs and then leads to ablation and premature failure of the substrate.This elucidation of the overheating mechanism could inform the development of strategies to resist dust accumulation in advanced aero engines.展开更多
Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin re...Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.展开更多
The master alloy ingots (MAI) with the nominal composition Zr 52.5 Ti 5Cu 17.9 Ni 14.6 Al 10 and Fe 61 Co 7Zr 10 Mo 5W 2B 15 (at%) were prepared by arc melting in Ti gettered Ar atmosphere. The Zr based buttons of 6 m...The master alloy ingots (MAI) with the nominal composition Zr 52.5 Ti 5Cu 17.9 Ni 14.6 Al 10 and Fe 61 Co 7Zr 10 Mo 5W 2B 15 (at%) were prepared by arc melting in Ti gettered Ar atmosphere. The Zr based buttons of 6 mm and 9 mm in diameter were fully amorphous, but those of 13 mm in diameter experienced crystallization. The glass forming ability (GFA) of Fe based alloys was relatively lower, and the buttons obtained were fully crystallized. The microhardness of the Zr based buttons was about 500(Hv), and the Fe based rod obtained by injection technique exhibited a high Vickers hardness of 1329. In addition, an amorphous crystalline transition layers were observed in both the buttons and the rods.展开更多
Every new generation of antennas is characterized by increased accuracy and faster transmission speeds.However,patch antennas have been known to damage human health.This type of antenna sends out electromagnetic waves...Every new generation of antennas is characterized by increased accuracy and faster transmission speeds.However,patch antennas have been known to damage human health.This type of antenna sends out electromagnetic waves that increase the temperature of the human head and prevent nerve strands from functioning properly.This paper examines the effect of the communication between the patch antenna and the brain on the head’s temperature by developing a hypothetical multi-input model that achieves more accurate results.These inputs are an individual’s blood and tissue,and the emission power of the antenna.These forces depend on the permeability and conductivity characteristics of the metal from which the antenna is fabricated.The proposed model is the first one that links the material the antenna is manufactured from and the head’s temperature.The results show that there are only a small number of materials that should be used as antenna covers.These materials are in the form of thin films.By using these thin films at different temperatures,the risk to the head can be reduced.This paper finds that the best results were obtained when the patch antenna was made of one of the following materials operating at a specific temperature:traditional materials at 305°K;casting cast steel at around 295°K;bismuth telluride(Bi2Te3)at 290°K;or barium sodium niobate at 310°K.展开更多
Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasio...Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasion.One of the major problems for the technology,however,is the overheating of transducers.In this study,we modified the transducer design in order to solve the overheating problem.We simulated the performance of the modified design by finite element analysis and fabricated the newly designed transducer.By measuring the actual performance data,we proved that the new design can effectively reduce temperature rise while keeping the acoustic intensity field unaffected.展开更多
文摘Based on the experimental result that Cr and C segregated on the prior grain boundaries of austenite in overheated steels,causing the inheritance of fracture mode after re-austeni- tization,a thermodynamic analysis is conducted through the calculation of equilibrium segregation amount of Cr and C in grain boundary at 860 and 1050℃ and the segregation kinetics of Cr is also calculated.Thermodynamic calculation gives an evidence that the segregation of Cr and C at grain boundaries may be regarded as one of the mechanisms of the fracture inheritance in overheated steels.
文摘A concept of ensemble averaged stellar reactors is developed to study the dynamics of processes occurring in stars, allocated in the ~200 pc solar neighborhood. According to the effective temperature value, four stellar classes are identified, for which the correlation coefficients and standard deviation are counted. The theory of the buoyancy terrestial elements is generalized to stellar systems. It was suggested that stars are over-heated due to the shift parameters of the nuclear processes occurring inside the stars, which leads to the synthesis of transuranium elements until the achievement of a critical nuclear mass and star explosion. The heavy transuranium elements sink downward and are concentrated in the stellar depth layers. The physical explanation of the existence of the critical Chandrasekhar star limit has been offered. Based on the spatial analysis of overheated stars, it was suggested that the withdrawal of the stellar reactor from the equilibrium state is a consequence of extragalactic compression inside the galaxy arm due to the arm spirality (not to be confused with the spirality of the galaxy itself).
文摘The growth of fixed assets investment in China soared to a high record in the first quarter of 2004 after gross domestic product （GDP） bounced substantially in 2003. A bubble is emerging posing threats to Chinese economic development. In order to cool down the overheated investment, Chinese government should promptly take effective measures in macroeconomic control to limit or guide the red-hot investment in some sectors and slow down its growth, thus implements the changes from administrative-driven investment to enterprise-driven investment and from investment-driven economic growth to consumption-driven growth.
文摘Based on macroeconomic analysis since 2003, this article holds that a trend towardsoverheating has surfaced in Chinas economy. Chinas rapid economic expansion hasaffected the quality of its growth, with rising material and energy consumption and imbalancedeconomic structure as the main manifestations. Regarding macroeconomic policy options in2004, decision-makers should shift the policy focus from control of deflation to preventionof inflation; the pace of economic growth should be properly set; a balance betweenconsumption and investment should be strengthened by controlling excessive expansion ofinvestment, and industrial restructuring should be conducted in a coordinated manner onthe basis of properly controlling the overly rapid industrial growth; policies should becontinued to boost exports and sustainable growth of foreign investment; and more effortsshould be made to accelerate the change in the mode of economic growth.
文摘Chongqing and Shanghai announced on January 27 they would launch a long-awaited pilot property tax beginning January 28. The move is part of a larger Central Government effort to cool the housing market. The results of the trial program will determine how the tax is rolled out in other locations, according to the Ministry of Finance.
基金financially supported by the National Natural Science Foundation of China (No.51503158)Key R&D Program of Hubei Province (No.2023BAB104)Open Project Program of High-Tech Organic Fibers Key Laboratory of Sichuan Province(No.PLN2024-08)
文摘The phenomena of thermal runaway and accidental deformation due to external stresses in lithium batteries or film capacitors consti-tute their primary failure mechanisms.Therefore,monitoring and early warning of overheating or localized strain are of great value for the safe use of lithium batteries or film capacitors;however,this function usually requires a system of multiple complex sensors.The realization of the above multiple hazards using a single sensor for monitoring and alarm functions has not been reported.Here,we exploit the thermally induced conductivity and modulus change during solid-liquid conversion of low melting point polyalloys to modulate the electronic relaxation polariza-tion and interfacial polarization in the composites for dielectric switching,and the reduction of alloy particle spacing during bending/compres-sive strain can be used to generate switchable tunneling effects for insulator-conductor transition.By synergizing dielectric switching and insula-tor-conductor transition,the final flexible thermoplastic polyurethane elastomer/low-melting-point polyalloy composite film achieves the func-tional integration of multi-level overheating warning and small deformation monitoring.
基金funded by the National Natural Science Foundation of China(no.22075155)the Zhejiang Provincial Natural Science Foundation of China(No.LY24B030002)+2 种基金Ningbo Natural Science Foundation(2023J089)the China Scholarship Council(CSC)the Ningbo Science and Technology Bureau(2024QL036).
文摘Battery safety is influenced by various factors,with thermal runaway being one of the most significant concerns.While most studies have concentrated on developing one-time,self-activating mechanism for thermal protection,such as temperature-responsive electrodes,and thermal-shutdown separators,these methods only provide irreversible protection.Recently,reversible temperature-sensitive electrolytes have emerged as promising alternatives,offering both thermo-reversibility and self-protective properties.However,further research is crucial to fully understand these thermal-shutdown electrolytes.In this study,we propose lower critical solution temperature(LCST)phase behavior poly(benzyl methacrylate)/imidazolium-based ionic liquid mixtures to prepare temperature-sensitive electrolytes that provide reversible thermal shutdown protection of batteries.This electrolyte features an appropriate protection temperature(~105℃)and responds quickly within a 1 min at 105℃,causing cells to hardly discharge as the voltage suddenly drops to 3.38 V,and providing efficient thermal shutdown protection within 30 min.Upon cooling back to room temperature,the battery regains its original performance.Additionally,the electrolyte exhibits excellent cycling stability with the capacity retention of the battery is 91.6%after 500 cycles.This work provides a viable solution for preventing batteries from thermal runaway triggered by overheating.
文摘The tube failures took place frequently in the superheater of 2x600MW units in a power plant.According to the condition of tube failures,the mechanical property and microstructure on running and failed tubes were tested and evaluated.The chemical composition and structure phase of inner oxide scale and deposit inside of the tubes were examined.The fractured surfaces of failed tube samples were observed.And the material examination was performed for original tube steels SA213-T91 and SA213-T22.The results show that raw materials of SA213-T91 and SA213-T22 tube in superheater are qualified.Besides,the characteristics of the SA213-T91 and SA213-T22 tube failure are typical short-term overheated rupture.The rupture temperature is located between two phase Ac1~Ac3 of the two steels.It is recognized that putting SA213-T22 tubes in operation under the condition of long-term over heating causes the rupture of SA213-T91 and SA213-T22.
基金Projects(51174121,51274125)supported by the National Natural Science Foundation of ChinaProject(2010R50016-30)supported by Zhejiang Province Science and Technology Innovation Team of Key Projects,ChinaProject supported by the K.C.Wong Magna Fund of Ningbo University,China
文摘The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.
文摘Through the long time track examination and disintegration to SF6 circuit breaker, we obtain the massive monitor data and massive pictures. The criteria of resuming insulation discharge failure conforming to CSO2/CH2S>7, is quite broad to SO2 and the H2S concentration permission. Even if it reaches 100μL/L, it will not be in danger immediately to the safe operation of equipment. We may plan, arrange, and overhaul calmly. When obtaining the bare conductor overheating failure, it has not involved the resuming insulation. We may use the resuming insulation discharge failure criterion.
基金supported by the“National Key Research and Development Program of China(Grant No.2016YFB0701403)”the“National Natural Science Foundation of China(Grant Nos.51631008 and 91860201)”+1 种基金the“111 Project(No.B170003)”financial support to the reported work.Stoichko Antonov would like to acknowledge financial support from the Alexander von Humboldt Foundation。
文摘Aero-engine turbine blades may suffer overheating during service,which can result in severe microstructural and mechanical degradation within tens of seconds.In this study,the thermal cycling creep under(950℃/15 min+1100℃/1 min)-100 MPa was performed on a directionally solidified superalloy,DZ125.The effects of overheating and thermal cycling on the creep properties were evaluated in terms of creep behavior and microstructural evolution against isothermally crept specimens under 950℃/100 MPa,950℃/270 MPa,and 1100℃/100 MPa.The results indicated that the thermal cycling creep life was reduced dramatically compared to the isothermal creep under 950℃/100 MPa.The plastic creep deformation mainly occurred during the overheating stage during the thermal cycling creep.The thermal cycling creep curve exhibited three stages,similar to the 1100℃isothermal creep,but its minimum creep rate occurred at a lower creep strain.The overheating events caused severe microstructural degradation,such as substantial dissolution ofγ'phase,earlier formation of raftedγ'microstructure,widening of theγchannels,and instability of the interfacial dislocation networks.This microstructural degradation was the main reason for the dramatic decrease in thermal cycling creep life,as the thermal cycling promoted more dislocations to cut intoγ'phase and more cracks to initiate at grain boundaries,carbides,and residual eutectic pools.This study underlines the importance of evaluating the thermal cycling creep properties of superalloys to be used as turbine blades and provides insights into the effect of thermal cycling on directionally solidified superalloys for component design.
基金Funded by the Innovation Foundation of Guangzhou, P. R. China (No. 2005V42C0021)
文摘Overheating of the engine, the transmission and the hydraulic device is a problem when the construction machinery works on plateau. To solve this problem, we proposed an electro-controlled hydraulic driving fan cooling system (ECHDFCS). The system was applied to a 50-wheel loader. We carried out the coolant temperature simulation using fluid modeling software FLOWMASTER, followed by laboratory experiments and road tests. The results show that ECHDFCS can adjust the cooling capability of the system automatically based on machine heat dissipation requirements. The coolant temperature is consequently remained within an appropriate range. The simulation results are consistent with the experiment results when the experiment is performed on the plain, but are different from the road tests in some investigated parameters on the plateau.
文摘Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing these byproducts is an effective method to judge the internal operation condition of electric equipment. In order to study characters of SF6byproducts at different temperature of overheated faults in the electric equipment, a series of overheated faults of electric equipment were simulated. SF6is very stable and not significantly decomposed at 200oC, 250oC and 300oC. SF6is significantly decomposed to SO2, H2S and HF at 350oC. The concentration of SO2, H2S and HF was 7.2, 1.6 and 1.9 μL/L after heating for 5 hours in environment of SF6with 3616 μL/L water, and it was increased to 23.0, 3.0 and 1.2 μL/L 3 hours later. SF6is more easily to be decomposed and decomposed more rapidly at higher temperature. The concentration of SO2, H2S and HF was 62.2, 15.6 and 3.6 μL/L after heating for 5 hours in environment of SF6with 4064 μL/L water, and it was increased to 91.4, 25.2 and 2.3 μL/L 3 hours later. SF6will be decomposed to format HF, which is strongly corrosive and whose concentration is likely to decrease when it is above a certain concentration.
基金National Natural Science Foundation of China(No.51901175)China Postdoctoral Science Foundation Grant(Nos.2020T130499 and 2019M653602)HPC platform in Xi'an Jiaotong University.
文摘Thermal barrier coatings(TBC)on superalloy blade/vane enable an increase in turbine inlet temperature(TIT)and aero-engine efficiency.However,the deposition of dust on TBC significantly ablates superalloys and becomes a bottleneck for advanced engine development.This paper presents a comprehensive mod-eling approach,based on an experiment involving dust deposition on a TBC-coated substrate,aimed at understanding the fundamental cause of substrate ablation.The results show that a significant increase in surface roughness is obtained experimentally with dust accumulation.The temperature field within the TBC-substrate system is disturbed by surface roughening.Consequently,the film cooling is seriously destroyed.While the dust accumulated on the TBC surface also contributes to heat insulation by increas-ing the effective TBC thickness,localized overheating of the substrate occurs and then leads to ablation and premature failure of the substrate.This elucidation of the overheating mechanism could inform the development of strategies to resist dust accumulation in advanced aero engines.
基金The work was financially supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0703600,2021YFA0716302,and 2021YFA0718703)the National Natural Science Foundation of China(Grant Nos.51825104 and 52192602)China Postdoctoral Science Foundation(Grant No.2022T150691).
文摘Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.
文摘The master alloy ingots (MAI) with the nominal composition Zr 52.5 Ti 5Cu 17.9 Ni 14.6 Al 10 and Fe 61 Co 7Zr 10 Mo 5W 2B 15 (at%) were prepared by arc melting in Ti gettered Ar atmosphere. The Zr based buttons of 6 mm and 9 mm in diameter were fully amorphous, but those of 13 mm in diameter experienced crystallization. The glass forming ability (GFA) of Fe based alloys was relatively lower, and the buttons obtained were fully crystallized. The microhardness of the Zr based buttons was about 500(Hv), and the Fe based rod obtained by injection technique exhibited a high Vickers hardness of 1329. In addition, an amorphous crystalline transition layers were observed in both the buttons and the rods.
基金This research was funded by King Khalid University—KSA,grant number(R.G.P.2/35/40)and the APC was funded by King Khalid University—KSA.
文摘Every new generation of antennas is characterized by increased accuracy and faster transmission speeds.However,patch antennas have been known to damage human health.This type of antenna sends out electromagnetic waves that increase the temperature of the human head and prevent nerve strands from functioning properly.This paper examines the effect of the communication between the patch antenna and the brain on the head’s temperature by developing a hypothetical multi-input model that achieves more accurate results.These inputs are an individual’s blood and tissue,and the emission power of the antenna.These forces depend on the permeability and conductivity characteristics of the metal from which the antenna is fabricated.The proposed model is the first one that links the material the antenna is manufactured from and the head’s temperature.The results show that there are only a small number of materials that should be used as antenna covers.These materials are in the form of thin films.By using these thin films at different temperatures,the risk to the head can be reduced.This paper finds that the best results were obtained when the patch antenna was made of one of the following materials operating at a specific temperature:traditional materials at 305°K;casting cast steel at around 295°K;bismuth telluride(Bi2Te3)at 290°K;or barium sodium niobate at 310°K.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.10904093 and 61031003)the Science and Technology Grant Scheme funds from Shenzhen Government(No.08CXY-23).
文摘Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasion.One of the major problems for the technology,however,is the overheating of transducers.In this study,we modified the transducer design in order to solve the overheating problem.We simulated the performance of the modified design by finite element analysis and fabricated the newly designed transducer.By measuring the actual performance data,we proved that the new design can effectively reduce temperature rise while keeping the acoustic intensity field unaffected.
