The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold...The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.展开更多
Discarding any assumption about displacement models and stress distribution andintroducing δ-function into the present study, we established the state equation for thecontinuous orthotropic open cylindrical shells. A...Discarding any assumption about displacement models and stress distribution andintroducing δ-function into the present study, we established the state equation for thecontinuous orthotropic open cylindrical shells. An thentical exocl solution is presentedfor the statics of thin. moderately thick and thick laminated continuous openrylindrical shells. Numerical results are obtained and compared with those calculatedusing SAP5.展开更多
A theoretical investigation of heat flow, solidification and solid shell resistance “Ic” has been undertaken by using a mathematical model and previous plant trials. The ultimate purpose is to develop operating cond...A theoretical investigation of heat flow, solidification and solid shell resistance “Ic” has been undertaken by using a mathematical model and previous plant trials. The ultimate purpose is to develop operating conditions and therefore to improve the surface quality for continuously cast steel slabs. A new simple criterion called mold thermomechanical rigidity “MTMR” has been proposed to evaluate and to improve these purposes. The parameters of MTMR and its non-dimensional number which use to control the surface defects are present in this investigation. Previous plant trails of slab surface defects formation have been investigated thermo-mechanically with this criterion. The predications show that this criterion is very sensitive of operating parameters and is a significant qualitative tool to evaluate the surface quality. From examination of the behavior of MTMR, the susceptibility and mechanism of surface defects formations with MTMR have been primarily discussed.展开更多
Tomodel amultibody systemcomposed of shell components,a geometrically exact Kirchho-Love triangular shell element is proposed.The middle surface of the shell element is described by using the DMS-splines,which can ex...Tomodel amultibody systemcomposed of shell components,a geometrically exact Kirchho-Love triangular shell element is proposed.The middle surface of the shell element is described by using the DMS-splines,which can exactly represent arbitrary topology piecewise polynomial triangular surfaces.The proposed shell element employs only nodal displacement and can automatically maintain C1 continuity properties at the element boundaries.A reproducing DMS-spline kernel skill is also introduced to improve computation stability and accuracy.The proposed triangular shell element based on reproducing kernel DMS-splines can achieve an almost optimal convergent rate.Finally,the proposed shell element is validated via three static problems of shells and the dynamic simulation of aexible multibody system undergoing both overall motions and large deformations.展开更多
On the basis of the thin-shell theory and on the use of the transfer matrix approach, this paper presents the vibrational response and buckling analysis of three-lobed cross-section cylindrical shells, with circumfere...On the basis of the thin-shell theory and on the use of the transfer matrix approach, this paper presents the vibrational response and buckling analysis of three-lobed cross-section cylindrical shells, with circumferentially varying thickness, subjected to uniform axial membrane loads. A Fourier approach is used to separate the variables, and the governing equations of the shell are formulated in terms of eight first-order differential equations in the circumferential coordinate, and by using the transfer matrix of the shell, these equations are written in a matrix differential equation. The transfer matrix is derived from the non-linear differential equations of the cylindrical shells with variable thickness by introducing the trigonometric series in the longitudinal direction and applying a numerical integration in the circumferential direction. The natural frequencies and critical loads beside the mode shapes are calculated numerically in terms of the transfer matrix elements for the symmetrical and antisymmetrical vibration modes. The influences of the thickness variation of cross- section and radius展开更多
With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation ...With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation shell solidification in wide and thick slab continuous casting mold was developed by using the commercial program ANSYS. The evolutions of strand-mold system thermal behaviors, including the air gap formation and the mold flux film dynamical distribution in shell/mold gap and shell temperature field, and the evolutions of shell deformation and stress distribution of peritectic steel solidified in a 2120 mm wide and 266 mm thick slab continuous casting mold were analyzed. The results show that the air gap formation and the thick mold flux film distribution mainly concentrate in the regions 0–21 mm and 0–7 mm, 0–120 mm and 0–100 mm off the shell wide and narrow faces corners, and thus the hot spots are given rise to form in the regions 15–55 mm and 15–50 mm off the shell wide and narrow face corners. The shell server deformation occurs in the off-corners in the middle and lower parts of the mold. The stress evolution in shell surface is tensile stress, while that in shell solidification front is compressive stress.展开更多
Solidification behavior in the mold region plays an important role in production efficiency and steel quality.To investigate shell growth within a mold,the sulfur prints of the entire shell thickness profile the menis...Solidification behavior in the mold region plays an important role in production efficiency and steel quality.To investigate shell growth within a mold,the sulfur prints of the entire shell thickness profile the meniscus to 100 mm below the mold were obtainedadding FeS tracer into molten steel during bloom continuous casting of hypo-peritectic steel.The law of shell thickness evolution along mold height and circumference was analyzed.The results show that there are three weak regions of solidification,which are in the mold upper part,in the mold lower part,and just below mold exit,possibly resulting periodic fluctuation of air gap between the shell and the mold,the impingement of melt jets on the solidification front,and the decreasing cooling intensity,respectively.Initial solidification point along casting direction appears at approximately 35 mm below the meniscus.Overall,the solidified shell thickness in the inner side of the mold is a little larger than that in the outer side,and the former and the latter reach 25.5 and 24.3 mm at the mold exit,respectively.The non-uniform shell growth in the inner side of the bloom is provided,while shell thicknesses in the narrow face and the outer side follow relatively regular growth.Out of the mold,the thinnest shells on the transverse section exist in the regions of 60–90 mm and 40–70 mm the corners of the inner and outer sides,respectively,i.e.,the of-corners.展开更多
A model experiment investigating entrapment of inclusions and bubbles on the solidified shell was performed using molten steel,and the conditions for inclusion and bubble entrapment and mechanism of entrapment were st...A model experiment investigating entrapment of inclusions and bubbles on the solidified shell was performed using molten steel,and the conditions for inclusion and bubble entrapment and mechanism of entrapment were studied. The results were applied to the flow behavior in the casting mold of a continuous caster.At the solid-liquid interface, entrapment of inclusions is greatly reduced by the existence of a low velocity flow,e.g.,0.05m/s.The above-mentioned interfacial flow velocity dependency of inclusion entrapment is considered to be largely influenced by changes in the thickness of the concentration boundary layer,which depend on the interfacial flow velocity.Specifically,bubbles and inclusions which enter the concentration boundary layer are drawn to the solid-liquid interface by a suction force which is several orders larger than the Saffman's force.In addition to the above-mentioned suction force,the so-called cleaning effect is determined by fluid-dynamic forces such as drag force,etc.which act on particles,and furthermore,by resident time of particles at the solid-liquid interface,which depends on the solidification rate.In a FC mold with a 2-stage electromagnetic brake,flotation of bubbles entrained in the jet flow from the nozzle is accelerated with the large DC magnetic field.This is attributed to the braking effect of the DC field on the nozzle jet and the upward flow by the buoyancy of the bubbles.As a result,the interfacial flow velocity can be normalized by increasing the strength of the magnetic field,and entrapment of large bubbles and inclusions can be reduced.展开更多
基金supported by the National Natural Science Foundation of China (No.60672145)
文摘The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.
文摘Discarding any assumption about displacement models and stress distribution andintroducing δ-function into the present study, we established the state equation for thecontinuous orthotropic open cylindrical shells. An thentical exocl solution is presentedfor the statics of thin. moderately thick and thick laminated continuous openrylindrical shells. Numerical results are obtained and compared with those calculatedusing SAP5.
文摘A theoretical investigation of heat flow, solidification and solid shell resistance “Ic” has been undertaken by using a mathematical model and previous plant trials. The ultimate purpose is to develop operating conditions and therefore to improve the surface quality for continuously cast steel slabs. A new simple criterion called mold thermomechanical rigidity “MTMR” has been proposed to evaluate and to improve these purposes. The parameters of MTMR and its non-dimensional number which use to control the surface defects are present in this investigation. Previous plant trails of slab surface defects formation have been investigated thermo-mechanically with this criterion. The predications show that this criterion is very sensitive of operating parameters and is a significant qualitative tool to evaluate the surface quality. From examination of the behavior of MTMR, the susceptibility and mechanism of surface defects formations with MTMR have been primarily discussed.
基金supported in part by the National Natural Science Foundations of China under Grants 11290151,11672034 and 11902363。
文摘Tomodel amultibody systemcomposed of shell components,a geometrically exact Kirchho-Love triangular shell element is proposed.The middle surface of the shell element is described by using the DMS-splines,which can exactly represent arbitrary topology piecewise polynomial triangular surfaces.The proposed shell element employs only nodal displacement and can automatically maintain C1 continuity properties at the element boundaries.A reproducing DMS-spline kernel skill is also introduced to improve computation stability and accuracy.The proposed triangular shell element based on reproducing kernel DMS-splines can achieve an almost optimal convergent rate.Finally,the proposed shell element is validated via three static problems of shells and the dynamic simulation of aexible multibody system undergoing both overall motions and large deformations.
文摘On the basis of the thin-shell theory and on the use of the transfer matrix approach, this paper presents the vibrational response and buckling analysis of three-lobed cross-section cylindrical shells, with circumferentially varying thickness, subjected to uniform axial membrane loads. A Fourier approach is used to separate the variables, and the governing equations of the shell are formulated in terms of eight first-order differential equations in the circumferential coordinate, and by using the transfer matrix of the shell, these equations are written in a matrix differential equation. The transfer matrix is derived from the non-linear differential equations of the cylindrical shells with variable thickness by introducing the trigonometric series in the longitudinal direction and applying a numerical integration in the circumferential direction. The natural frequencies and critical loads beside the mode shapes are calculated numerically in terms of the transfer matrix elements for the symmetrical and antisymmetrical vibration modes. The influences of the thickness variation of cross- section and radius
基金Item Sponsored by National Outstanding Young Scientist Foundation of China(50925415)Fundamental Research Funds for the Central Universities of China(N100102001)Postdoctoral Science Foundation of China(2012M510822)
文摘With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation shell solidification in wide and thick slab continuous casting mold was developed by using the commercial program ANSYS. The evolutions of strand-mold system thermal behaviors, including the air gap formation and the mold flux film dynamical distribution in shell/mold gap and shell temperature field, and the evolutions of shell deformation and stress distribution of peritectic steel solidified in a 2120 mm wide and 266 mm thick slab continuous casting mold were analyzed. The results show that the air gap formation and the thick mold flux film distribution mainly concentrate in the regions 0–21 mm and 0–7 mm, 0–120 mm and 0–100 mm off the shell wide and narrow faces corners, and thus the hot spots are given rise to form in the regions 15–55 mm and 15–50 mm off the shell wide and narrow face corners. The shell server deformation occurs in the off-corners in the middle and lower parts of the mold. The stress evolution in shell surface is tensile stress, while that in shell solidification front is compressive stress.
基金This work was supported by the National Natural Science Foundation of China(51604021).
文摘Solidification behavior in the mold region plays an important role in production efficiency and steel quality.To investigate shell growth within a mold,the sulfur prints of the entire shell thickness profile the meniscus to 100 mm below the mold were obtainedadding FeS tracer into molten steel during bloom continuous casting of hypo-peritectic steel.The law of shell thickness evolution along mold height and circumference was analyzed.The results show that there are three weak regions of solidification,which are in the mold upper part,in the mold lower part,and just below mold exit,possibly resulting periodic fluctuation of air gap between the shell and the mold,the impingement of melt jets on the solidification front,and the decreasing cooling intensity,respectively.Initial solidification point along casting direction appears at approximately 35 mm below the meniscus.Overall,the solidified shell thickness in the inner side of the mold is a little larger than that in the outer side,and the former and the latter reach 25.5 and 24.3 mm at the mold exit,respectively.The non-uniform shell growth in the inner side of the bloom is provided,while shell thicknesses in the narrow face and the outer side follow relatively regular growth.Out of the mold,the thinnest shells on the transverse section exist in the regions of 60–90 mm and 40–70 mm the corners of the inner and outer sides,respectively,i.e.,the of-corners.
文摘A model experiment investigating entrapment of inclusions and bubbles on the solidified shell was performed using molten steel,and the conditions for inclusion and bubble entrapment and mechanism of entrapment were studied. The results were applied to the flow behavior in the casting mold of a continuous caster.At the solid-liquid interface, entrapment of inclusions is greatly reduced by the existence of a low velocity flow,e.g.,0.05m/s.The above-mentioned interfacial flow velocity dependency of inclusion entrapment is considered to be largely influenced by changes in the thickness of the concentration boundary layer,which depend on the interfacial flow velocity.Specifically,bubbles and inclusions which enter the concentration boundary layer are drawn to the solid-liquid interface by a suction force which is several orders larger than the Saffman's force.In addition to the above-mentioned suction force,the so-called cleaning effect is determined by fluid-dynamic forces such as drag force,etc.which act on particles,and furthermore,by resident time of particles at the solid-liquid interface,which depends on the solidification rate.In a FC mold with a 2-stage electromagnetic brake,flotation of bubbles entrained in the jet flow from the nozzle is accelerated with the large DC magnetic field.This is attributed to the braking effect of the DC field on the nozzle jet and the upward flow by the buoyancy of the bubbles.As a result,the interfacial flow velocity can be normalized by increasing the strength of the magnetic field,and entrapment of large bubbles and inclusions can be reduced.
