Rectangular section control technology （RSCT） was introduced to achieve high-precision profile control during silicon steel rolling. The RSCT principle and method were designed, and the whole RSCT control strategy w...Rectangular section control technology （RSCT） was introduced to achieve high-precision profile control during silicon steel rolling. The RSCT principle and method were designed, and the whole RSCT control strategy was developed. Specifically, RSCT included roll contour design, roiling technology optimization, and control strategy development, aiming at both hot strip mills （HSMs） and cold strip mills （CSMs）. Firstly, through the high-performance variable crown （HVC） work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs, a hot strip with a stable crown and limited wedge, ：local spot, and single wave was obtained, which was suitable for cold rolling. Secondly, an approximately rectangular section was obtained by edge varying contact （EVC） work roll contour design, edge-drop setting control, and. closed loop control in the upper-stream, stands of CSMs. Moreover, complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs. In addition, the RSCT approach was applied in several silicon-steel production plants, where an outsicanding performance and remarkable economic benefits were observed.展开更多
The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distri...The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distribution and relation between corner radius and internal pressure were analyzed.The influence of lubricant was discussed.Microstructure and hardness of different region were observed.It is shown that thickness reduction in the transition region between the corner and center region is the biggest.Friction condition has influence both on the thickness distribution and calibration pressure of the corner.As the increase of the axial feeding,the calibration pressure is decreased.There is only little change for the microstructure,but the hardness is increased by 23.3% for the transition region.展开更多
Profile requirements of silicon steel strip are extremely high and the thickness difference of cold-rolled products is usually less than 7μm,and the profile quality of hot-rolled strip is the key to ensure the thickn...Profile requirements of silicon steel strip are extremely high and the thickness difference of cold-rolled products is usually less than 7μm,and the profile quality of hot-rolled strip is the key to ensure the thickness difference of cold-rolled products.In order to produce the silicon steel strip with high-precision shape,the concept of quasi-rectangular rolling during hot continuous rolling was put forward;the equipment configuration and technical method of approximate rectangular section control were studied.Through the roughing multi-target load distribution technology and the roll configuration technology for uniform wear of a 4-high rolling mill,the strip crown of transfer bar was reduced and the profile control stability was guaranteed.Configuring variable contact back-up roll technology on all stands in the finishing rolling process,equipped with symmetry variable taper work roll and long-stroke intelligent shifting strategy in the downstream stands,and using side rolling lubrication technology can make the roll wear more uniform,reduce the edge drop of silicon steel strip,improve the profile quality,and make the strip section of finishing exit"quasi-rectangular".In addition,induction furnace and side heater were also equipped to guarantee the temperature uniformity of the strip,so as to improve the stability of profile control.The whole control technology is based on the 1580-mm hot continuous rolling production line,designed,and developed according to the characteristics of equipment and products,and has been successfully applied,which can obtain the approximate rectangular strip section satisfying the flatness quality,and improve the strip section precision of silicon steel and other products.展开更多
The article presents the results of calculations of the effective thermal conductivity kef for bundles of steel rectangular sections obtained for a few analytical models. This coefficient expresses the ability of the ...The article presents the results of calculations of the effective thermal conductivity kef for bundles of steel rectangular sections obtained for a few analytical models. This coefficient expresses the ability of the bundles to heat transfer. The knowledge about the values of the kef coefficient of the section bundles is essential to correctly identify the parameters of their heat treatment process. The quality of the Calculation results were verified by the experimental measurement data. These measurements were performed in the guarded hot plate apparatus. It should be noted, that none of the eleven analyzed models of effective thermal conductivity is suitable for evaluation of thermal properties of the section bundles.展开更多
Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting...Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.展开更多
We study the spontaneous emission(SE) of an excited nonrelativistic two-level system(TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS’s transitions and the center-of-mass motion o...We study the spontaneous emission(SE) of an excited nonrelativistic two-level system(TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS’s transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initially being at rest are obtained, it is found that in the first order of the mass M, the frequency of the emitted photon is smaller than the transition frequency of the TLS and the SE rate is smaller than the SE rate Γfof the TLS fixed in the same waveguide. The SE rate for the TLS initially being moving is obtained in the second order of the mass M. The SE rate is smaller than Γfbut it is dependent not only on the atomic mass but also on the initial momentum. The carried frequency of the emitted photon is decreased when it travels along the direction of the initial momentum, whereas it is increased when it travels in the opposite direction of the initial momentum.展开更多
This paper investigates the torsion analysis of coated bars with a rectangular cross-section. Two opposite faces of a bar are coated by two isotropie layers with different materials of the original substrate that are ...This paper investigates the torsion analysis of coated bars with a rectangular cross-section. Two opposite faces of a bar are coated by two isotropie layers with different materials of the original substrate that are perfectly bonded to the bar. With the Saint- Venant torsion theory, the governing equation of the problem in terms of the warping function is established and solved using the finite Fourier cosine transform. The state of stress on the cross-section, warping of the cross-section, and torsional rigidity of the bar are evaluated. Effects of thickness of the coating layers and material properties on these quantities are investigated. A set of graphs are provided that can be used to determine the coating thicknesses and material properties so as to keep the maximum von Mises stress on the cross-section below an allowable value for effective use of the coating layer.展开更多
The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspect...The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspects, the method proposed in thispaper is similar io Hutchinson's. However, the computation is simple since theintroduction is avoided of stretched coordinates. The method can be used to analyseinitial post-bifurcation of plates and shells in the plastic range.展开更多
The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured r...The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured results, it shows that there exist big errors when applying this model to the numerical simulation of small-section rectangular tube＇ s welding temperature field and deformation. Based on a simple analysis of the errors, a contact model is presented. The heat transfer and stress analysis between small-section rectangular tubes and clamping fixture are simulated by using direct constraints method, and then the laws of the temperature distribution, which coincide with experiment, are obtained. A further numerical analysis of the stress and deformation are made, it shows that a ＂T＂ shaped stress-field is formed in the vicinity of the weld. As the stress-field departs from the centroid of tubes＇, this leads to the small rectangular tubes not only have a longitudinal deflection, but also have a transverse bending and deformation.展开更多
The ultimate strength of reinforced concrete(RC) rectangular members subjected to combined bending,shear and torsion is obtained from the limit analysis proposed in the present paper. Based on a warped failure surface...The ultimate strength of reinforced concrete(RC) rectangular members subjected to combined bending,shear and torsion is obtained from the limit analysis proposed in the present paper. Based on a warped failure surface determined by external loads, and a reasonable assumed stress distribution balancing external loads but not violating the yield condition, the bending-shear-torsion interaction can be derived from equilibrium conditions.According to the definition of lower-bound theorem in limit analysis, the calculated ultimate loads will be carried safely by the structure. The present method is a simple approach to obtain carrying capacities for RC elements under complex external loads. After comparing with the test results, a good agreement has been observed. The present method can be extended to explain the failure mechanism of RC members subjected to axial loads, and it is possible to develop a simple unified theory of RC members for engineering.展开更多
The three-dimensional premixed H2-O2 detonation propagation in rectangular ducts is simulated using an in-house parallel detonation code based on the second-order space-time conservation element and solution element（...The three-dimensional premixed H2-O2 detonation propagation in rectangular ducts is simulated using an in-house parallel detonation code based on the second-order space-time conservation element and solution element（CE/SE） scheme.The simulation reproduces three typical cellular structures by setting appropriate cross-sectional size and initial perturbation in square tubes.As the cross-sectional size decreases,critical cellular structures transforming the rectangular or diagonal mode into the spinning mode are obtained and discussed in the perspective of phase variation as well as decreasing of triple point lines.Furthermore,multiple cellular structures are observed through examples with typical aspect ratios.Utilizing the visualization of detailed three-dimensional structures,their formation mechanism is further analyzed.展开更多
An exact analytical solution is obtained for convective heat transfer in straight ducts with rectangular cross-sections for the first time.This solution is valid for both H1 and H2 boundary conditions,which are relate...An exact analytical solution is obtained for convective heat transfer in straight ducts with rectangular cross-sections for the first time.This solution is valid for both H1 and H2 boundary conditions,which are related to fully developed convective heat transfer under constant heat flux at the duct walls.The separation of variables method and various other mathematical techniques are used to find the closed form of the temperature distribution.The local and mean Nusselt numbers are also obtained as functions of the aspect ratio.A new physical constraint is presented to solve the Neumann problem in non-dimensional analysis for the H2 boundary conditions.This is one of the major innovations of the current study.The analytical results indicate a singularity occurs at a critical aspect ratio of 2.4912 when calculating the local and mean Nusselt numbers.展开更多
The equivalent filter modeling of a rectangular dielectric post in a rectangular waveguide is obtained through the variational expression of input impedance. The reflection coefficient expressed in components of netwo...The equivalent filter modeling of a rectangular dielectric post in a rectangular waveguide is obtained through the variational expression of input impedance. The reflection coefficient expressed in components of network is in good agreement with the results given by K. Siakavara, et al. (1991), The method can be applied to design filter.展开更多
基金Item Sponsored by National Natural Science Foundation of China(51304017)National Key Technology Research and Development Program of the 12th Five-year Plan of China(2012BAF04B02)Fundamental Research Funds for Central Universities of China(FRF-SD-12-013B)
文摘Rectangular section control technology （RSCT） was introduced to achieve high-precision profile control during silicon steel rolling. The RSCT principle and method were designed, and the whole RSCT control strategy was developed. Specifically, RSCT included roll contour design, roiling technology optimization, and control strategy development, aiming at both hot strip mills （HSMs） and cold strip mills （CSMs）. Firstly, through the high-performance variable crown （HVC） work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs, a hot strip with a stable crown and limited wedge, ：local spot, and single wave was obtained, which was suitable for cold rolling. Secondly, an approximately rectangular section was obtained by edge varying contact （EVC） work roll contour design, edge-drop setting control, and. closed loop control in the upper-stream, stands of CSMs. Moreover, complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs. In addition, the RSCT approach was applied in several silicon-steel production plants, where an outsicanding performance and remarkable economic benefits were observed.
基金Funded by the National Natural Science Foundation of China(50525516)
文摘The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distribution and relation between corner radius and internal pressure were analyzed.The influence of lubricant was discussed.Microstructure and hardness of different region were observed.It is shown that thickness reduction in the transition region between the corner and center region is the biggest.Friction condition has influence both on the thickness distribution and calibration pressure of the corner.As the increase of the axial feeding,the calibration pressure is decreased.There is only little change for the microstructure,but the hardness is increased by 23.3% for the transition region.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51975043)Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-19-002A3)Beijing Natural Science Foundation(3182026)for the support to this research.
文摘Profile requirements of silicon steel strip are extremely high and the thickness difference of cold-rolled products is usually less than 7μm,and the profile quality of hot-rolled strip is the key to ensure the thickness difference of cold-rolled products.In order to produce the silicon steel strip with high-precision shape,the concept of quasi-rectangular rolling during hot continuous rolling was put forward;the equipment configuration and technical method of approximate rectangular section control were studied.Through the roughing multi-target load distribution technology and the roll configuration technology for uniform wear of a 4-high rolling mill,the strip crown of transfer bar was reduced and the profile control stability was guaranteed.Configuring variable contact back-up roll technology on all stands in the finishing rolling process,equipped with symmetry variable taper work roll and long-stroke intelligent shifting strategy in the downstream stands,and using side rolling lubrication technology can make the roll wear more uniform,reduce the edge drop of silicon steel strip,improve the profile quality,and make the strip section of finishing exit"quasi-rectangular".In addition,induction furnace and side heater were also equipped to guarantee the temperature uniformity of the strip,so as to improve the stability of profile control.The whole control technology is based on the 1580-mm hot continuous rolling production line,designed,and developed according to the characteristics of equipment and products,and has been successfully applied,which can obtain the approximate rectangular strip section satisfying the flatness quality,and improve the strip section precision of silicon steel and other products.
文摘The article presents the results of calculations of the effective thermal conductivity kef for bundles of steel rectangular sections obtained for a few analytical models. This coefficient expresses the ability of the bundles to heat transfer. The knowledge about the values of the kef coefficient of the section bundles is essential to correctly identify the parameters of their heat treatment process. The quality of the Calculation results were verified by the experimental measurement data. These measurements were performed in the guarded hot plate apparatus. It should be noted, that none of the eleven analyzed models of effective thermal conductivity is suitable for evaluation of thermal properties of the section bundles.
文摘Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.
基金supported by the Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province, China (Grant No. 2020RC4047)the National Natural Science Foundation of China (Grant Nos. 11975095, 12075082, and 11935006)。
文摘We study the spontaneous emission(SE) of an excited nonrelativistic two-level system(TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS’s transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initially being at rest are obtained, it is found that in the first order of the mass M, the frequency of the emitted photon is smaller than the transition frequency of the TLS and the SE rate is smaller than the SE rate Γfof the TLS fixed in the same waveguide. The SE rate for the TLS initially being moving is obtained in the second order of the mass M. The SE rate is smaller than Γfbut it is dependent not only on the atomic mass but also on the initial momentum. The carried frequency of the emitted photon is decreased when it travels along the direction of the initial momentum, whereas it is increased when it travels in the opposite direction of the initial momentum.
文摘This paper investigates the torsion analysis of coated bars with a rectangular cross-section. Two opposite faces of a bar are coated by two isotropie layers with different materials of the original substrate that are perfectly bonded to the bar. With the Saint- Venant torsion theory, the governing equation of the problem in terms of the warping function is established and solved using the finite Fourier cosine transform. The state of stress on the cross-section, warping of the cross-section, and torsional rigidity of the bar are evaluated. Effects of thickness of the coating layers and material properties on these quantities are investigated. A set of graphs are provided that can be used to determine the coating thicknesses and material properties so as to keep the maximum von Mises stress on the cross-section below an allowable value for effective use of the coating layer.
文摘The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspects, the method proposed in thispaper is similar io Hutchinson's. However, the computation is simple since theintroduction is avoided of stretched coordinates. The method can be used to analyseinitial post-bifurcation of plates and shells in the plastic range.
文摘The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured results, it shows that there exist big errors when applying this model to the numerical simulation of small-section rectangular tube＇ s welding temperature field and deformation. Based on a simple analysis of the errors, a contact model is presented. The heat transfer and stress analysis between small-section rectangular tubes and clamping fixture are simulated by using direct constraints method, and then the laws of the temperature distribution, which coincide with experiment, are obtained. A further numerical analysis of the stress and deformation are made, it shows that a ＂T＂ shaped stress-field is formed in the vicinity of the weld. As the stress-field departs from the centroid of tubes＇, this leads to the small rectangular tubes not only have a longitudinal deflection, but also have a transverse bending and deformation.
基金the National Natural Science Foundation of China(No.51178265)
文摘The ultimate strength of reinforced concrete(RC) rectangular members subjected to combined bending,shear and torsion is obtained from the limit analysis proposed in the present paper. Based on a warped failure surface determined by external loads, and a reasonable assumed stress distribution balancing external loads but not violating the yield condition, the bending-shear-torsion interaction can be derived from equilibrium conditions.According to the definition of lower-bound theorem in limit analysis, the calculated ultimate loads will be carried safely by the structure. The present method is a simple approach to obtain carrying capacities for RC elements under complex external loads. After comparing with the test results, a good agreement has been observed. The present method can be extended to explain the failure mechanism of RC members subjected to axial loads, and it is possible to develop a simple unified theory of RC members for engineering.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10732010 and 10972010)
文摘The three-dimensional premixed H2-O2 detonation propagation in rectangular ducts is simulated using an in-house parallel detonation code based on the second-order space-time conservation element and solution element（CE/SE） scheme.The simulation reproduces three typical cellular structures by setting appropriate cross-sectional size and initial perturbation in square tubes.As the cross-sectional size decreases,critical cellular structures transforming the rectangular or diagonal mode into the spinning mode are obtained and discussed in the perspective of phase variation as well as decreasing of triple point lines.Furthermore,multiple cellular structures are observed through examples with typical aspect ratios.Utilizing the visualization of detailed three-dimensional structures,their formation mechanism is further analyzed.
基金Project supported by the Shahrood University of Technology (No. 17024),Iran
文摘An exact analytical solution is obtained for convective heat transfer in straight ducts with rectangular cross-sections for the first time.This solution is valid for both H1 and H2 boundary conditions,which are related to fully developed convective heat transfer under constant heat flux at the duct walls.The separation of variables method and various other mathematical techniques are used to find the closed form of the temperature distribution.The local and mean Nusselt numbers are also obtained as functions of the aspect ratio.A new physical constraint is presented to solve the Neumann problem in non-dimensional analysis for the H2 boundary conditions.This is one of the major innovations of the current study.The analytical results indicate a singularity occurs at a critical aspect ratio of 2.4912 when calculating the local and mean Nusselt numbers.
文摘The equivalent filter modeling of a rectangular dielectric post in a rectangular waveguide is obtained through the variational expression of input impedance. The reflection coefficient expressed in components of network is in good agreement with the results given by K. Siakavara, et al. (1991), The method can be applied to design filter.
