A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensi...A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized(DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg;RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β precipitates and basal γ precipitates.展开更多
Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Amon...Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors, friction between rolls and ring blank plays an important role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine the critical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring,rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM) under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.展开更多
Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver rol...Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver roll to study the inhomogeneity distribution of strain and temperature,fishtail coefficient,rolling force parameters.The results show that:(1)when the rotational speed of driver roll n increases,the strain distribution of the rolled ring becomes less homogeneous,and the temperature distribution more homogeneous yet,and leading to an optimal n value;(2)the fishtail coefficient firstly decreases,then increases with the increase of n;(3)the rolling force,contact area and rolling moment gradually descend with the increase of n.展开更多
Finite element model is constructed according to the principle and characteristics of radial-axial large ring rolling technology. Dynamic explicit finite element method is used to simulate the rolling process. An effe...Finite element model is constructed according to the principle and characteristics of radial-axial large ring rolling technology. Dynamic explicit finite element method is used to simulate the rolling process. An effective modeling method of guide roller is proposed. Simulation indicates that high quality ring product could be obtained when rational rotational speed of rollers and feed rate in the radial and axial rolling are assigned.展开更多
Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts o...Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin,rocket body and fuel tank because of light weight and high carrying capacity.How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve.In this work,constraining ring rolling(CRR)technique is first adopted to form TRTWTHR.However.unreasonable metal streamlines(UMS)and uncoordinated growth of three ribs easily occur in CRR of TRTWTHR,which makes the forming quality of TRTWTHR difficult to be controlled.Faced with this difficulty,an analytical model that can predict UMS and the height of three ribs in CRR of TRTWTHR is established so as to guide the process design of CRR.Subsequently,the reliability of the established analytical model and the feasibility of CRR of TRTWTHR are confirmed by FE simulation and experiment.Then,using the established analytical model,the window of UMS occurring relevant to the tapered angle of TRTWTHR and the location of the rib of middle end is developed.Finally,three uncoordinated growth modes among three ribs are found when the width of three ribs is identical and UMS do not occur,and the mechanisms of three uncoordinated growth modes are revealed.展开更多
A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR)process with four guide rolls.Based on the model,the calcula...A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR)process with four guide rolls.Based on the model,the calculation models for bending moment and normal stress at any section of the ring are deduced by force method.If the maximum section bending normal stress exceeds the yield stress of the ring materials,the ring will be distorted thus leading to the instability of the RARR process.According to this,a plastic instability criterion for the ultra-large RARR process with four guide rolls is developed,based on which a mathematical model to calculate the critical guide force for avoiding plastic instability of ring is obtained.The influence rule of the position of guide roll on the dangerous ring section of plastic instability is revealed,from which it is found the dangerous ring section mainly appears at the radial and axial deformation regions and the contact positions of the guide rolls and ring.The optimized layout of guide roll around the ring in favor of stability is determined to be about a1=61°and a2=119°.The plastic instability criterion is proven to be reliable from the aspects of the critical guide force,the section bending moment and normal stress and the dangerous ring section of plastic instability.Intelligent simulation case studies for the RARR process of ultra-large aluminum alloy ring indicate that the stable forming of the process can be effectively realized by regulating the guide force based on the plastic instability criterion.This work could provide a valuable guidance for the control of guide rolls and the optimization of the ultra-large RARR process with four guide rolls.展开更多
Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most pre...Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts,but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR.To solve this difficulty,an innovative constraining ring rolling process(CRR)is proposed in this paper to manufacture CRTSHR.To evaluate the proposed CRR and reveal its deformation behaviors,a thermomechanical coupled FE model for CRR of CRTSHR is established.Then,the experiment for CRR of CRTSHR is performed on a modified ring rolling machine,which proves that CRR of CRTSHR is feasible and the established FE model is reliable.Based on the reliable FE model,the metal flow mode in deformed CRTSHR is analyzed,and the deformation characteristics such as the stress state,strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed.Finally,the influences of key parameters such as the friction factor between ring and molds,the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.展开更多
In order to meet the requirements of high reliability,long-lifetime and lightweight in a new generation of aerospace,aviation,high-speed train,and energy power equipment,integrated components are urgently needed to re...In order to meet the requirements of high reliability,long-lifetime and lightweight in a new generation of aerospace,aviation,high-speed train,and energy power equipment,integrated components are urgently needed to replace traditional multi-piece,welded components.The applications of integrated components involve in a series of large-size,complex-shaped,highperformance components made of difficult-to-deform materials,which present a huge challenge for forming ultra-large size integrated components.In this paper,the developments and perspectives of several extreme forming technologies are reviewed,including the sheet hydroforming of ultra-large curved components,dieless hydroforming of ellipsoidal shells,radial-axial ring rolling of rings,in situ manufacturing process of flanges,and local isothermal forging of titanium alloy components.The principle and processes for controlling deformation are briefly illustrated.The forming of typical ultra-large size integrated components and industrial applications are introduced,such as the high strength aluminum alloy,3m in diameter,integrated tank dome first formed by using a sheet blank with a thickness the same as the final component,and a 16m diameter,integrated steel ring rolled by using a single billet.The trends for extreme forming of ultra-large size integrated components are discussed with a goal of providing ideas and fundamental guidance for the further development of new forming processes for extreme-size integrated components in the future.展开更多
Powder metallurgy(PM) Ti–22Al–24Nb–0.5Mo(at.%) alloys were prepared by hot isostatic pressing. In order to study the feasibility of PM + ring rolling combined process for preparing Ti_2AlNb rings, thermal mech...Powder metallurgy(PM) Ti–22Al–24Nb–0.5Mo(at.%) alloys were prepared by hot isostatic pressing. In order to study the feasibility of PM + ring rolling combined process for preparing Ti_2AlNb rings, thermal mechanical simulation tests of PM Ti_2AlNb alloys were conducted and two rectangular PM rings(150 mm in height, 75 mm in thickness,350 mm in external diameter) were rolled as a validation experiment. Experimental results show that the flow stress of Ti_2AlNb alloys exhibited a significant drop at the very beginning of the deformation(true strain/0.1), and became stable with the increase in strain. Stress instability phenomenon of PM Ti_2AlNb alloys was more obvious than that of wrought alloy. Flow stress fluctuation at the initial stage of deformation is related to phase transition of Ti_2AlNb alloys which strongly depends on heat treatment and thermal mechanical deformation process. Processing windows during initial stage of ring rolling process is very crucial. A sound PM Ti_2AlNb rectangular ring blank(height = 150 mm, thickness = 30 mm, external diameter = 750 mm) was successfully rolled in two passes by using the improved heat preservation method and optimized rolling parameters. Tensile properties of PM Ti_2AlNb alloy were improved, and the porosity was reduced after ring rolling.展开更多
基金financial support by Fundamental Research Funds for the National Key Research and Development Program of China(Project No.2016YFB0700403)the Venture&Innovation Support Program for Chongqing Overseas Returnees(Project No.cx2018057)+1 种基金the Chongqing Research Program of Basic Research and Frontier Technology(Project Nos.cstc2019jcyjmsxm0548 and cstc2019jcyj-msxm X0306)the Fundamental Research Funds for the Central Universities(Project No.2021CDJJMRH-001)。
文摘A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized(DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg;RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β precipitates and basal γ precipitates.
基金The authors thank the National Natural Science Foundation of China for Key Program of China(No.50335060)the National Science Found of China for Distinguished Young Scholars(No.50225518)for the support on this research.
文摘Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors, friction between rolls and ring blank plays an important role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine the critical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring,rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM) under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.
基金The authors are grateful for the financial support of Project Supported by:Chongqing Municipal Engineering Research Center of Institutions of Higher Education(cstc2011ptgc70007)Project Supported by Program for Innovation Team Building at Institutions of Higher Education in Chongqing(201028)Achievement Transfer Program of Institutions of Higher Education in Chongqing(kjzh11221).
文摘Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver roll to study the inhomogeneity distribution of strain and temperature,fishtail coefficient,rolling force parameters.The results show that:(1)when the rotational speed of driver roll n increases,the strain distribution of the rolled ring becomes less homogeneous,and the temperature distribution more homogeneous yet,and leading to an optimal n value;(2)the fishtail coefficient firstly decreases,then increases with the increase of n;(3)the rolling force,contact area and rolling moment gradually descend with the increase of n.
基金Supported by National Natural Science Foundation fro Key Program of China (50335060)
文摘Finite element model is constructed according to the principle and characteristics of radial-axial large ring rolling technology. Dynamic explicit finite element method is used to simulate the rolling process. An effective modeling method of guide roller is proposed. Simulation indicates that high quality ring product could be obtained when rational rotational speed of rollers and feed rate in the radial and axial rolling are assigned.
基金the National Natural Science Foundation of China (No. U2037204)the 111 Project (No. B17034)+1 种基金Innovative Research Team Development Program of Ministry of Education of China (No. IRT17R83)the National Natural Science Foundation of China (No. 52005375)
文摘Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin,rocket body and fuel tank because of light weight and high carrying capacity.How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve.In this work,constraining ring rolling(CRR)technique is first adopted to form TRTWTHR.However.unreasonable metal streamlines(UMS)and uncoordinated growth of three ribs easily occur in CRR of TRTWTHR,which makes the forming quality of TRTWTHR difficult to be controlled.Faced with this difficulty,an analytical model that can predict UMS and the height of three ribs in CRR of TRTWTHR is established so as to guide the process design of CRR.Subsequently,the reliability of the established analytical model and the feasibility of CRR of TRTWTHR are confirmed by FE simulation and experiment.Then,using the established analytical model,the window of UMS occurring relevant to the tapered angle of TRTWTHR and the location of the rib of middle end is developed.Finally,three uncoordinated growth modes among three ribs are found when the width of three ribs is identical and UMS do not occur,and the mechanisms of three uncoordinated growth modes are revealed.
基金supported by the National Natural Science Foundation of China (No. 51875468, 51575448)the Research & Development Institute of Northwestern Polytechnical University in Shenzhen (JCYJ20170815162709770)
文摘A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR)process with four guide rolls.Based on the model,the calculation models for bending moment and normal stress at any section of the ring are deduced by force method.If the maximum section bending normal stress exceeds the yield stress of the ring materials,the ring will be distorted thus leading to the instability of the RARR process.According to this,a plastic instability criterion for the ultra-large RARR process with four guide rolls is developed,based on which a mathematical model to calculate the critical guide force for avoiding plastic instability of ring is obtained.The influence rule of the position of guide roll on the dangerous ring section of plastic instability is revealed,from which it is found the dangerous ring section mainly appears at the radial and axial deformation regions and the contact positions of the guide rolls and ring.The optimized layout of guide roll around the ring in favor of stability is determined to be about a1=61°and a2=119°.The plastic instability criterion is proven to be reliable from the aspects of the critical guide force,the section bending moment and normal stress and the dangerous ring section of plastic instability.Intelligent simulation case studies for the RARR process of ultra-large aluminum alloy ring indicate that the stable forming of the process can be effectively realized by regulating the guide force based on the plastic instability criterion.This work could provide a valuable guidance for the control of guide rolls and the optimization of the ultra-large RARR process with four guide rolls.
基金the National Natural Science Foundation of China(No.U2037204)the Natural Science Foundation of Hubei Province(No.2019CFA041)+1 种基金the National Key Research and Development Program of China(No.2019YFB1704502)the Fundamental Research Funds for the Central Universities(No.2019-YB-016)for the support。
文摘Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts,but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR.To solve this difficulty,an innovative constraining ring rolling process(CRR)is proposed in this paper to manufacture CRTSHR.To evaluate the proposed CRR and reveal its deformation behaviors,a thermomechanical coupled FE model for CRR of CRTSHR is established.Then,the experiment for CRR of CRTSHR is performed on a modified ring rolling machine,which proves that CRR of CRTSHR is feasible and the established FE model is reliable.Based on the reliable FE model,the metal flow mode in deformed CRTSHR is analyzed,and the deformation characteristics such as the stress state,strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed.Finally,the influences of key parameters such as the friction factor between ring and molds,the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.
基金This work was funded in part by the National Key Research and Development Program of China(2017YFB0306304)the National Natural Science Foundation of China(51705102,U1637209).The authors wish to express their gratitude for the funding.
文摘In order to meet the requirements of high reliability,long-lifetime and lightweight in a new generation of aerospace,aviation,high-speed train,and energy power equipment,integrated components are urgently needed to replace traditional multi-piece,welded components.The applications of integrated components involve in a series of large-size,complex-shaped,highperformance components made of difficult-to-deform materials,which present a huge challenge for forming ultra-large size integrated components.In this paper,the developments and perspectives of several extreme forming technologies are reviewed,including the sheet hydroforming of ultra-large curved components,dieless hydroforming of ellipsoidal shells,radial-axial ring rolling of rings,in situ manufacturing process of flanges,and local isothermal forging of titanium alloy components.The principle and processes for controlling deformation are briefly illustrated.The forming of typical ultra-large size integrated components and industrial applications are introduced,such as the high strength aluminum alloy,3m in diameter,integrated tank dome first formed by using a sheet blank with a thickness the same as the final component,and a 16m diameter,integrated steel ring rolled by using a single billet.The trends for extreme forming of ultra-large size integrated components are discussed with a goal of providing ideas and fundamental guidance for the further development of new forming processes for extreme-size integrated components in the future.
文摘Powder metallurgy(PM) Ti–22Al–24Nb–0.5Mo(at.%) alloys were prepared by hot isostatic pressing. In order to study the feasibility of PM + ring rolling combined process for preparing Ti_2AlNb rings, thermal mechanical simulation tests of PM Ti_2AlNb alloys were conducted and two rectangular PM rings(150 mm in height, 75 mm in thickness,350 mm in external diameter) were rolled as a validation experiment. Experimental results show that the flow stress of Ti_2AlNb alloys exhibited a significant drop at the very beginning of the deformation(true strain/0.1), and became stable with the increase in strain. Stress instability phenomenon of PM Ti_2AlNb alloys was more obvious than that of wrought alloy. Flow stress fluctuation at the initial stage of deformation is related to phase transition of Ti_2AlNb alloys which strongly depends on heat treatment and thermal mechanical deformation process. Processing windows during initial stage of ring rolling process is very crucial. A sound PM Ti_2AlNb rectangular ring blank(height = 150 mm, thickness = 30 mm, external diameter = 750 mm) was successfully rolled in two passes by using the improved heat preservation method and optimized rolling parameters. Tensile properties of PM Ti_2AlNb alloy were improved, and the porosity was reduced after ring rolling.