The effect of casting vacuum on thermodynamic and corrosion properties of Fe61Co7Zr8Mo5W2B17 in shape of cylinder of 3 mm in diameter and ribbon of 20?40μm in thickness and 2?3 mm in width were investigated with X-ra...The effect of casting vacuum on thermodynamic and corrosion properties of Fe61Co7Zr8Mo5W2B17 in shape of cylinder of 3 mm in diameter and ribbon of 20?40μm in thickness and 2?3 mm in width were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), dilatometer (DIL), scanning electron microscopy (SEM) and electrochemical station. It is found that high casting vacuum can improve the glass forming ability (GFA), the contraction degree during heating, and the pitting resistance of the glassy alloy, which can be ascribed to the fact that the dissolution of tungsten in the melt is improved under the high casting vacuum.展开更多
A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ~C and initial stress level of 250 MPa. Based on the experimental stress relaxation curve, the relationship between creep strain ...A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ~C and initial stress level of 250 MPa. Based on the experimental stress relaxation curve, the relationship between creep strain rate and stress has been derived. Then, a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve. Close agreement between computed results and experimental ones is obtained for stress relaxation data. The creep constitutive equation set has been integrated with the commercial FE （finite element） solver MSC.Marc via the user defined subroutine, CRPLAW, for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece. The temperature field, the radius-direction displacement field and the stress-strain field are calculated and analyzed. Furthermore, the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method.展开更多
In this paper, the authors consider the expansion problem of a wedge of gas into vacuum for the two-dimensional Euler equations in isothermal flow. By the bootstrapping argument, they prove the global existence of the...In this paper, the authors consider the expansion problem of a wedge of gas into vacuum for the two-dimensional Euler equations in isothermal flow. By the bootstrapping argument, they prove the global existence of the smooth solution through the direct method in the case 0 〈 θ 〈 -θ=arctan 1/（√2＋√5）, where θ is the half angle of the wedge. Furthermore, they get the uniform C^1,1 estimates of the solution to the expansion problem.展开更多
Switching expansion reduction(SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics.The experiments indicate that the simulation model well predicts the actual chara...Switching expansion reduction(SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics.The experiments indicate that the simulation model well predicts the actual characteristics.The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model.Through the mathematical reasoning in this paper,the polytropic exponent can be calculated by the air mass,heat,and work exchanges of the pneumatic container.For the air in a constant volume tank,when the heat-absorption is large enough to raise air temperature in discharging process,the polytropic exponent is less than 1;when the air is experiencing a discharging and heat-releasing process,the polytropic exponent exceeds the specific heat ratio(the value of 1.4).展开更多
We study the quantization of the Einstein-Hilbert action for a small true vacuum bubble without matter or scalar field. The quan- tization of action induces an extra term of potential called quantum potential in Hamil...We study the quantization of the Einstein-Hilbert action for a small true vacuum bubble without matter or scalar field. The quan- tization of action induces an extra term of potential called quantum potential in Hamilton-Jacobi equation, which gives expanding solutions, including the exponential expansion solutions of the scalar factor a for the bubble. We show that exponential expansion of the bubble continues with a short period, no matter whether the bubble is closed, fiat, or open. The exponential expansion ends spontaneously when the bubble becomes large, that is, the scalar factor a of the bubble approaches a Planck length lp. We show that it is the quantum potential of the small true vacuum bubble that plays the role of the scalar field potential suggested in the slow-roll inflation model. With the picture of quantum tunneling, we calculate particle creation rate during inflation, which shows that particles created by inflation have the capability of reheating the universe.展开更多
基金Project(51171091)supported by the National Natural Science Foundation of ChinaProject(JQ201012)supported by the Excellent Youth Project of Shandong Natural Science Foundation,ChinaProject(2012CB825702)supported by the National Basic Research Program of China
文摘The effect of casting vacuum on thermodynamic and corrosion properties of Fe61Co7Zr8Mo5W2B17 in shape of cylinder of 3 mm in diameter and ribbon of 20?40μm in thickness and 2?3 mm in width were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), dilatometer (DIL), scanning electron microscopy (SEM) and electrochemical station. It is found that high casting vacuum can improve the glass forming ability (GFA), the contraction degree during heating, and the pitting resistance of the glassy alloy, which can be ascribed to the fact that the dissolution of tungsten in the melt is improved under the high casting vacuum.
基金Project(2009CB724307)supported by the Major State Basic Research Development Program(973 Program)of China
文摘A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ~C and initial stress level of 250 MPa. Based on the experimental stress relaxation curve, the relationship between creep strain rate and stress has been derived. Then, a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve. Close agreement between computed results and experimental ones is obtained for stress relaxation data. The creep constitutive equation set has been integrated with the commercial FE （finite element） solver MSC.Marc via the user defined subroutine, CRPLAW, for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece. The temperature field, the radius-direction displacement field and the stress-strain field are calculated and analyzed. Furthermore, the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method.
基金supported by the National Natural Science Foundation of China(No.11371240)Shanghai Municipal Education Commission of Scientific Research Innovation Project(No.11ZZ84)+1 种基金the Fundamental Research Funds for the Central Universities(No.15CX02074A)the grant of “the First-Class Discipline of Universities in Shanghai”
文摘In this paper, the authors consider the expansion problem of a wedge of gas into vacuum for the two-dimensional Euler equations in isothermal flow. By the bootstrapping argument, they prove the global existence of the smooth solution through the direct method in the case 0 〈 θ 〈 -θ=arctan 1/（√2＋√5）, where θ is the half angle of the wedge. Furthermore, they get the uniform C^1,1 estimates of the solution to the expansion problem.
基金supported by the National Natural Science Foundation of China (No.50575202)
文摘Switching expansion reduction(SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics.The experiments indicate that the simulation model well predicts the actual characteristics.The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model.Through the mathematical reasoning in this paper,the polytropic exponent can be calculated by the air mass,heat,and work exchanges of the pneumatic container.For the air in a constant volume tank,when the heat-absorption is large enough to raise air temperature in discharging process,the polytropic exponent is less than 1;when the air is experiencing a discharging and heat-releasing process,the polytropic exponent exceeds the specific heat ratio(the value of 1.4).
基金supported by the National Natural Science Foundation of China(Grant No.61471356)
文摘We study the quantization of the Einstein-Hilbert action for a small true vacuum bubble without matter or scalar field. The quan- tization of action induces an extra term of potential called quantum potential in Hamilton-Jacobi equation, which gives expanding solutions, including the exponential expansion solutions of the scalar factor a for the bubble. We show that exponential expansion of the bubble continues with a short period, no matter whether the bubble is closed, fiat, or open. The exponential expansion ends spontaneously when the bubble becomes large, that is, the scalar factor a of the bubble approaches a Planck length lp. We show that it is the quantum potential of the small true vacuum bubble that plays the role of the scalar field potential suggested in the slow-roll inflation model. With the picture of quantum tunneling, we calculate particle creation rate during inflation, which shows that particles created by inflation have the capability of reheating the universe.
