For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-p...For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.展开更多
Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is app...Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is applied to measure the out-of-plane deformation of structures with one-shot projection.Through color fringe recognizing,decoding and triangulation processing for the captured images corresponding to each deformation state,the feasibility of the method is testified by the measurement of elastic deflections of a flexible square plate,showing good agreement with those from the calibrated displacement driver.The plastic deformation of two alloy aluminum rectangular tubes is measured to show the technique application to surface topographic evaluation of the buckling structures with large displacements.展开更多
In this paper,the Reynolds number,velocity,pressureand kinetic energy of the BCF processing hot air-floware analyzed with the help of the aero-dynamic theory,and their distributions inside the texturing tube are ob-ta...In this paper,the Reynolds number,velocity,pressureand kinetic energy of the BCF processing hot air-floware analyzed with the help of the aero-dynamic theory,and their distributions inside the texturing tube are ob-tained by pressure measuring.展开更多
Our previous study showed an association between advanced glycation end products （AGEs） and neural tube defects （NTDs）. To understand the molecular mechanisms underlying the effect of AGEs on neural tube developme...Our previous study showed an association between advanced glycation end products （AGEs） and neural tube defects （NTDs）. To understand the molecular mechanisms underlying the effect of AGEs on neural tube development, C57BL/6 female mice were fed for 4 weeks with com- mercial food containing 3% advanced glycation end product bovine serum albumin （AGE-BSA） or 3% bovine serum albumin （BSA） as a control. After mating mice, oxidative stress markers including malondialdehyde and H202 were measured at embryonic day 7.5 （E7.5） of ges- tation, and the level of intracellular reactive oxygen species （ROS） in embryonic cells was determined at E8.5. In addition to evaluating NTDs, an enzyme-linked immunosorbent assay was used to determine the effect of embryonic protein administration on the N-（carboxymethyl） lysine reactivity of acid and carboxyethyl lysine antibodies at E10.5. The results showed a remarkable increase in the incidence of NTDs at El0.5 in embryos of mice fed with AGE-BSA （no hyperglycemia） compared with control mice. Moreover, embryonic protein administration resulted in a noticeable increase in the reactivity of N-（carboxymethyl） lysine and N（ε）-（carboxyethyl） lysine antibodies. Malondialdehyde and H2O2 levels in embryonic cells were increased at E7.5, followed by increased intracellular ROS levels at E8.5. Vitamin E supplementation could partially recover these phenomena. Collectively, these results suggest that AGE-BSA could induce NTDs in the absence of hyperglycemia by an underlying mechanism that is at least partially associated with its capacity to increase embryonic oxidative stress levels.展开更多
In this study,two sandblasting textures,namely,quartz and high-chromium(Cr)stainless steel sands,were used for sandblasting of the internal surface L80-13Cr tubing and casing.The contrastive analysis on the properties...In this study,two sandblasting textures,namely,quartz and high-chromium(Cr)stainless steel sands,were used for sandblasting of the internal surface L80-13Cr tubing and casing.The contrastive analysis on the properties of the pipes before and after abrasive blasting was conducted,including the metallographic phase detection of the internal surface,simulating accelerated corrosion tests,and residual stress tests for the pipe after abrasive blasting.Based on the analysis results,it is explained why the API standard requires that no scale appears on the internal surface of L80-13Cr and iron contamination when internal sandblasting media are applied.The results show that abrasive blasting can effectively remove scales on the internal surface of L80-13Cr tubing and casing and improve corrosion resistance.The abrasive blasting process does not produce obvious residual stress on the internal surface of the tubing and casing.Also,the de-rusting effect of stainless sand is better than that of quartz sand,and the former does not produce iron contamination.展开更多
The highway tunnel system in China has in recent years surpassed Europe, the United States, and other developed countries in terms of mileage, scale, complexity, and technical achievement. Much scientific research has...The highway tunnel system in China has in recent years surpassed Europe, the United States, and other developed countries in terms of mileage, scale, complexity, and technical achievement. Much scientific research has been conducted, and the results have greatly facilitated the rapid development of China＇s highway tunnel building capacity. This article presents the historical development of highway tunneling in China, according to specific charac- teristics based on construction and operation. It provides a systematic analysis of the major achievements and chal- lenges with respect to construction techniques, operation, monitoring, repair, and maintenance. Together with future trends of highway tunneling in China, suggestions have been made for further research, and development prospects have been identified with the for a Chinese-style highway aim of laying the foundation tunnel construction method and technical architecture.展开更多
The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qual...The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient, and changes the velocity profile. If the outlet contains more than one exit, the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.展开更多
基金Project(51164030)supported by the National Natural Science Foundation of China
文摘For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.
文摘Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is applied to measure the out-of-plane deformation of structures with one-shot projection.Through color fringe recognizing,decoding and triangulation processing for the captured images corresponding to each deformation state,the feasibility of the method is testified by the measurement of elastic deflections of a flexible square plate,showing good agreement with those from the calibrated displacement driver.The plastic deformation of two alloy aluminum rectangular tubes is measured to show the technique application to surface topographic evaluation of the buckling structures with large displacements.
文摘In this paper,the Reynolds number,velocity,pressureand kinetic energy of the BCF processing hot air-floware analyzed with the help of the aero-dynamic theory,and their distributions inside the texturing tube are ob-tained by pressure measuring.
基金supported by the grant from Shaanxi Technology Committee of China,No.2013JM4001the China Scholarship Council(CSC)
文摘Our previous study showed an association between advanced glycation end products （AGEs） and neural tube defects （NTDs）. To understand the molecular mechanisms underlying the effect of AGEs on neural tube development, C57BL/6 female mice were fed for 4 weeks with com- mercial food containing 3% advanced glycation end product bovine serum albumin （AGE-BSA） or 3% bovine serum albumin （BSA） as a control. After mating mice, oxidative stress markers including malondialdehyde and H202 were measured at embryonic day 7.5 （E7.5） of ges- tation, and the level of intracellular reactive oxygen species （ROS） in embryonic cells was determined at E8.5. In addition to evaluating NTDs, an enzyme-linked immunosorbent assay was used to determine the effect of embryonic protein administration on the N-（carboxymethyl） lysine reactivity of acid and carboxyethyl lysine antibodies at E10.5. The results showed a remarkable increase in the incidence of NTDs at El0.5 in embryos of mice fed with AGE-BSA （no hyperglycemia） compared with control mice. Moreover, embryonic protein administration resulted in a noticeable increase in the reactivity of N-（carboxymethyl） lysine and N（ε）-（carboxyethyl） lysine antibodies. Malondialdehyde and H2O2 levels in embryonic cells were increased at E7.5, followed by increased intracellular ROS levels at E8.5. Vitamin E supplementation could partially recover these phenomena. Collectively, these results suggest that AGE-BSA could induce NTDs in the absence of hyperglycemia by an underlying mechanism that is at least partially associated with its capacity to increase embryonic oxidative stress levels.
文摘In this study,two sandblasting textures,namely,quartz and high-chromium(Cr)stainless steel sands,were used for sandblasting of the internal surface L80-13Cr tubing and casing.The contrastive analysis on the properties of the pipes before and after abrasive blasting was conducted,including the metallographic phase detection of the internal surface,simulating accelerated corrosion tests,and residual stress tests for the pipe after abrasive blasting.Based on the analysis results,it is explained why the API standard requires that no scale appears on the internal surface of L80-13Cr and iron contamination when internal sandblasting media are applied.The results show that abrasive blasting can effectively remove scales on the internal surface of L80-13Cr tubing and casing and improve corrosion resistance.The abrasive blasting process does not produce obvious residual stress on the internal surface of the tubing and casing.Also,the de-rusting effect of stainless sand is better than that of quartz sand,and the former does not produce iron contamination.
基金supported by grants from the National Natural Science Foundation of China(No.51378434)the National Basic Research Program of China 973 Program(No.2010CB732105)+1 种基金the National Natural Science Foundation of High-Speed Rail Joint Fund(No.U1134208)the National Science and Technology Support Plan of China(No.2013BAB10B00)
文摘The highway tunnel system in China has in recent years surpassed Europe, the United States, and other developed countries in terms of mileage, scale, complexity, and technical achievement. Much scientific research has been conducted, and the results have greatly facilitated the rapid development of China＇s highway tunnel building capacity. This article presents the historical development of highway tunneling in China, according to specific charac- teristics based on construction and operation. It provides a systematic analysis of the major achievements and chal- lenges with respect to construction techniques, operation, monitoring, repair, and maintenance. Together with future trends of highway tunneling in China, suggestions have been made for further research, and development prospects have been identified with the for a Chinese-style highway aim of laying the foundation tunnel construction method and technical architecture.
基金supported by the Key Project of National Natural Science Foundation of China (10532010)
文摘The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient, and changes the velocity profile. If the outlet contains more than one exit, the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.
