A symbol is an expression of meaning,while blank symbols express special meanings.By focusing on the application of blank symbols in Japanese architecture and indoor designs,we analyzed the aesthetic principles in Jap...A symbol is an expression of meaning,while blank symbols express special meanings.By focusing on the application of blank symbols in Japanese architecture and indoor designs,we analyzed the aesthetic principles in Japanese architecture and indoor designs from the perspective of semiotics,such as“Kongji,”“Emptiness,”and“Dying out,”and their minimalist and pure design concepts.Traditional Chinese culture was also further explored,especially the profound influence of the“Chan sect”and the philosophy of“unity of heaven and mankind”on Japanese architecture and designs.This study aims to facilitate the coexistence and mutual appreciation of Chinese and Japanese architectural designs.展开更多
How to restore the destroyed forest after forest fire is a key question that man must face. This paper reviewed the research situation and history on the forest restoration burned blanks and summed up the research met...How to restore the destroyed forest after forest fire is a key question that man must face. This paper reviewed the research situation and history on the forest restoration burned blanks and summed up the research methods used into four scales: seed-bank scale, community scale, ecosystem scale and landscape scale. The new technologies such as GIS & Remote Sensing used to vegetation restoration were also summarized. The strategies and developing trend of vegetation restoration research on burned blanks were discussed.展开更多
Daxing抋n Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing抋n Mountains on May 6, 19...Daxing抋n Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing抋n Mountains on May 6, 1987 devastated more than 1.33?06 hm2 of natural forests, which leaded to the formation of some mosaic areas with different burn intensities. Two forest farms of Tuqiang Forest Bureau (124?5-122?8E, 53?4-52?5N) were chosen as a typical area to analyze the post-fire landscape change by drawing and comparing the two digital forest stand maps of 1987 and 2000. The landscape lands of forest were classi-fied into 12 types: coniferous forest, broadleaf forest, needle-broadleaf mixed forest, shrub, nursery, harvested area, burned blanks, agricultural land, swamp, water, built-up, grass. The results showed that: 1) The burned blanks was almost restored, some of them mainly converted into broadleaf forest land during the process of natural restoration, and coniferous forest land by the artificial re-forestation, and the others almost changed into swamp or grass land; 2) The proportion of forest area increased from 47.6% in 1987 to 81.3% in 2002. Therefore, a few management countermeasures, such as the enhancing peoples consciousness of fire-proofing and constructing species diversity, were put forward for forest sustainable development.展开更多
Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of ta...Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of tailor-welded blanks(TWBs) on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.展开更多
The deformation mechanism of C5191 phosphor bronze sheet under ultra-high-speed blanking was investigated.By virtue of a DOBBY-OMEGA F1 ultra-high-speed press,the ultra-high-speed blanking test was conducted on C5191 ...The deformation mechanism of C5191 phosphor bronze sheet under ultra-high-speed blanking was investigated.By virtue of a DOBBY-OMEGA F1 ultra-high-speed press,the ultra-high-speed blanking test was conducted on C5191 phosphor bronze sheets with a thickness of 0.12 mm at 3000 strokes per minute.The microstructures of the blanked edges were characterized and analyzed separately by electron back-scatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that grains in the blanked edges are stretched along the blanking direction.Strong{001}<100>cube textures(maximum pole densities of 9 and 12,respectively)and secondarily strong{011}<011>textures(maximum pole densities of 4 and 7,respectively)are formed in local zones.Additionally,deformation twins are found in the shear zone of the blanked edges which are rotated and coarsened due to the blanking-induced extrusion and local thermal effect which can further form into sub-grains with clear and high-angle boundaries.The C5191 phosphor bronze sheet is subjected to adiabatic shear during ultra-high-speed blanking,accompanied with dynamic recrystallization.展开更多
The process of laser bull welding of zinc-coated steel(SGCD3 and WLZn)blanks was presented.whose edges were prepared by laser cutting.The properties of the butt joints.such as tensile strength.bending,stamping.weld ...The process of laser bull welding of zinc-coated steel(SGCD3 and WLZn)blanks was presented.whose edges were prepared by laser cutting.The properties of the butt joints.such as tensile strength.bending,stamping.weld shape,and corrosion-resisant were tested.The experiments of laser cutting and welding were carried ont on a custom-made system designed.which is a set of equipment for wide sheet butt welding based on a laser cutting-welding combination process.The experiments proved the technological feasibility of laser butt welding for thin zinc coated steel sheets whose edges were prepared by laser cutting on the same equipment.展开更多
To study the influence of blank holder type on the drawability of 5182-O aluminum sheet at room temperature, the flat blank holder and curved blank holder were employed during the deep drawing process. The microstruct...To study the influence of blank holder type on the drawability of 5182-O aluminum sheet at room temperature, the flat blank holder and curved blank holder were employed during the deep drawing process. The microstructures were characterized by optical microscopy (OM). The results reveal that the limiting drawing ratio (LDR) of 5182-O aluminum alloy sheet is 1.7 using the flat blank holder. The drawn cup have severe earring. Compared with using flat blank holder, the LDR of 5182-O aluminum alloy sheet is enhanced to 2.0 using curved blank holder. In addition, the earring ratio also reduces and flange wrinkling is prevented when the curved blank holder is used. These are due to a more uniform sheet flow in different directions with curved blank holder.展开更多
Experimental and numerical analyses for the effect of the thickness of gap generator blank(GGB) on the formability of the outer blanks were investigated. The thickness of the GGB has the greatest impact on the thinn...Experimental and numerical analyses for the effect of the thickness of gap generator blank(GGB) on the formability of the outer blanks were investigated. The thickness of the GGB has the greatest impact on the thinning of the lowest blank. In addition, the friction at different regions and the additional interlayer contacts can also affect the thinning of different regions as well as increase the punch force. This work will enhance the understanding of simultaneous multi-layered blanks forming and will help the composite design engineers to tailor requirement-specific hybrid parts such as fiber metal laminates(FMLs) and functionally graded structures(FGSs) for hi-tech applications.展开更多
Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidi...Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidification, analyze the interaction between shell and molten steel, and compare the temperature distribution under different technological conditions. The results indicate that high superheating degree can lengthen the liquid-core depth and make the crack and breakout possible, so suitable superheating should be controlled within 35℃ according to the simulation results. Casting speed which is one of the most important technological parameters of improving production rate, should be controlled between 0. 85 m/min and 1.05 m/min and the caster has great potential in the improvement of blank quality.展开更多
Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named "ca...Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named "casting-rolling compound forming technology" is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.展开更多
Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the d...Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.展开更多
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The ...By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM.展开更多
The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite elemen...The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.展开更多
The elastoplastic mechanical properties of the weld and heat affected zone metals have comparatively major impact on the forming process of tailor-welded blanks. A few scholars investigated the elastoplastic mechanica...The elastoplastic mechanical properties of the weld and heat affected zone metals have comparatively major impact on the forming process of tailor-welded blanks. A few scholars investigated the elastoplastic mechanical properties of the weld and heat affected zone, but they only simply assumed that it was a uniform distribution elastoplastic material different from the base materials. Four types of tailor-welded blanks which consist of ST12 and 304 stainless steel plates are selected as the research objects, the elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals are obtained based on the nanoindentation tests, and the Erichsen cupping tests are conducted by combining numerical simulation with physical experiment. The nanoindentation tests results demonstrate that the elastoplastic mechanical properties of the weld and heat affected zone metals are not only different from the base materials, but also varying between the weld metals and the heat affected zone metals. Comparing the Erichsen cupping test resulted from numerical with that from experimental method, it is found that the numerical value of Erichsen cupping test which consider the elastoplastic mechanical properties of the weld and heat affected zone metals have a good agreement with the experimental result, and the relative error is only 4.8%. The proposed research provides good solutions for the inhomogeneous elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals, and improves the control performance of tailor-welded blanks forming accuracy.展开更多
A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron ...A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron microscopy were used to analyze its morphologies and microstructures. The results show that the microstructures of the pipe blank are homogeneous and the precipitates are uniformly distributed d 25~70 nm spherical or sphere like Al 12 (Fe,V) 3Si particles, its mechanical properties at room temperature and 350 ℃ after densification by extrusion are σ b=412 MPa, δ =7.6% and σ b=187 MPa, δ =7.6%, respectively. The analyses indicate that the proper match of the motion rates of atomizer and substrate can produce deposited blanks with uniform thickness and relatively high cooling rate.展开更多
Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and...Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.展开更多
In order to improve leaching efficiency of vanadium from stone coal,the combination of blank roasting and bioleaching using Bacillus mucilaginosus(B.mucilaginosus)mutants was evaluated.The atmospheric and room tempera...In order to improve leaching efficiency of vanadium from stone coal,the combination of blank roasting and bioleaching using Bacillus mucilaginosus(B.mucilaginosus)mutants was evaluated.The atmospheric and room temperature plasma(ARTP)technique was used to generate B.mucilaginosus mutants.The results showed that a mutant B.mucilaginosus BM-50,after ARTP irradiation for 50 s,had the highest acid production.The total content of the organic acid produced by B.mucilaginosus BM-50 was nearly doubled compared with the wild strain after 2 days.After 20 days,vanadium leaching rate with B.mucilaginosus BM-50 reached 18.2%,which was improved compared with the original bacteria(15.3%).A pretreatment via blank roasting for stone coal further improved the vanadium dissolution by bioleaching,namely,68.3%vanadium was extracted,which was much higher than that without blank roasting.It is shown that bioleaching by bacterial mutants by ARTP irradiation combined with blank roasting has great potential for improving vanadium recovery from low-grade vanadium bearing stone coal.展开更多
The study of multipoint blank holder force(BHF) control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method (FEM) simulation, the configuration of multipoint blank ho...The study of multipoint blank holder force(BHF) control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method (FEM) simulation, the configuration of multipoint blank holder cylinders and the setting of local BHF are optimized, and the influences of the multipoint BHF on the hydromechanical deep drawing and conventional hydroforming processes are studied. The desired fluid pressure and whole BHF are predicted for hydromechanical deep drawing process. Finally, simulation results are testified by forming experiment, and they are in agreement very well.展开更多
At first, a series of finite element method (FEM) simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank ho...At first, a series of finite element method (FEM) simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force (VBHF) was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.展开更多
A new enhanced inter-cell interference coordination (elCIC) is adopted for managing almost blank sub-frame (ABS),which jointly exploits the time, frequency and power dimensions to improve the resource utilization....A new enhanced inter-cell interference coordination (elCIC) is adopted for managing almost blank sub-frame (ABS),which jointly exploits the time, frequency and power dimensions to improve the resource utilization. In particular, a non-uniform two tier heterogeneous network ( HetNet) is considered, where the pico cells are located close to the macro cell and the number of users in each pico cell is different. To alleviate the interference caused by the co-channeldeployment,the macro cells employ low power ABS (LP- ABS), and the resource blocks (RBs) are divided into twoparts during an ABS. One is exclusively reserved for macro cell users ad the other is reserved for pico cell users. Themacro cells are allowed to use different percentages of RBs and different powers for their own transmission during the LP- ABS. The user association,resource allocation,ABS proportion,the frequency band partition parameter and the transmission power of macro cells are considered, aiming at maximizing the proportional fairness utility of the system. An iterative algorithm is also proposed and simulation results demonstrate that the proposed algorithm can improve both the system throughput and user fairness compared with the existing schemes.展开更多
基金Department of Education in Yunnan Province Fund for Scientific Research,Research on the Origin Tracing of the Traditional Architectures of Limi People of Yunnan Yi Ethnic Group(No.2022Y658).
文摘A symbol is an expression of meaning,while blank symbols express special meanings.By focusing on the application of blank symbols in Japanese architecture and indoor designs,we analyzed the aesthetic principles in Japanese architecture and indoor designs from the perspective of semiotics,such as“Kongji,”“Emptiness,”and“Dying out,”and their minimalist and pure design concepts.Traditional Chinese culture was also further explored,especially the profound influence of the“Chan sect”and the philosophy of“unity of heaven and mankind”on Japanese architecture and designs.This study aims to facilitate the coexistence and mutual appreciation of Chinese and Japanese architectural designs.
文摘How to restore the destroyed forest after forest fire is a key question that man must face. This paper reviewed the research situation and history on the forest restoration burned blanks and summed up the research methods used into four scales: seed-bank scale, community scale, ecosystem scale and landscape scale. The new technologies such as GIS & Remote Sensing used to vegetation restoration were also summarized. The strategies and developing trend of vegetation restoration research on burned blanks were discussed.
基金Under the auspices of the National Science Foundation of China (No. 30270225 40331008) and the Chinese Academy of Sciences (SCXZY0102).
文摘Daxing抋n Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing抋n Mountains on May 6, 1987 devastated more than 1.33?06 hm2 of natural forests, which leaded to the formation of some mosaic areas with different burn intensities. Two forest farms of Tuqiang Forest Bureau (124?5-122?8E, 53?4-52?5N) were chosen as a typical area to analyze the post-fire landscape change by drawing and comparing the two digital forest stand maps of 1987 and 2000. The landscape lands of forest were classi-fied into 12 types: coniferous forest, broadleaf forest, needle-broadleaf mixed forest, shrub, nursery, harvested area, burned blanks, agricultural land, swamp, water, built-up, grass. The results showed that: 1) The burned blanks was almost restored, some of them mainly converted into broadleaf forest land during the process of natural restoration, and coniferous forest land by the artificial re-forestation, and the others almost changed into swamp or grass land; 2) The proportion of forest area increased from 47.6% in 1987 to 81.3% in 2002. Therefore, a few management countermeasures, such as the enhancing peoples consciousness of fire-proofing and constructing species diversity, were put forward for forest sustainable development.
基金Project(51275444) supported by the National Natural Science Foundation of ChinaProject(20121333110003) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(E2014203271) supported by the Natural Science Foundation–Steel and Iron Foundation of Hebei ProvinceChina
文摘Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of tailor-welded blanks(TWBs) on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.
基金The authors are grateful for the financial supports from Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology of China(JSJMYWX2020-01)Zhejiang Provincial Natural Science Foundation of China(LY18E050005)the Startup Foundation for Introducing Talent of Nanjing Institute of Industry Technology(YK18-13-02)of China.
文摘The deformation mechanism of C5191 phosphor bronze sheet under ultra-high-speed blanking was investigated.By virtue of a DOBBY-OMEGA F1 ultra-high-speed press,the ultra-high-speed blanking test was conducted on C5191 phosphor bronze sheets with a thickness of 0.12 mm at 3000 strokes per minute.The microstructures of the blanked edges were characterized and analyzed separately by electron back-scatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that grains in the blanked edges are stretched along the blanking direction.Strong{001}<100>cube textures(maximum pole densities of 9 and 12,respectively)and secondarily strong{011}<011>textures(maximum pole densities of 4 and 7,respectively)are formed in local zones.Additionally,deformation twins are found in the shear zone of the blanked edges which are rotated and coarsened due to the blanking-induced extrusion and local thermal effect which can further form into sub-grains with clear and high-angle boundaries.The C5191 phosphor bronze sheet is subjected to adiabatic shear during ultra-high-speed blanking,accompanied with dynamic recrystallization.
文摘The process of laser bull welding of zinc-coated steel(SGCD3 and WLZn)blanks was presented.whose edges were prepared by laser cutting.The properties of the butt joints.such as tensile strength.bending,stamping.weld shape,and corrosion-resisant were tested.The experiments of laser cutting and welding were carried ont on a custom-made system designed.which is a set of equipment for wide sheet butt welding based on a laser cutting-welding combination process.The experiments proved the technological feasibility of laser butt welding for thin zinc coated steel sheets whose edges were prepared by laser cutting on the same equipment.
基金Project(CDJZR14130009)supported by the Fundamental Research Funds for the Central Universities,China
文摘To study the influence of blank holder type on the drawability of 5182-O aluminum sheet at room temperature, the flat blank holder and curved blank holder were employed during the deep drawing process. The microstructures were characterized by optical microscopy (OM). The results reveal that the limiting drawing ratio (LDR) of 5182-O aluminum alloy sheet is 1.7 using the flat blank holder. The drawn cup have severe earring. Compared with using flat blank holder, the LDR of 5182-O aluminum alloy sheet is enhanced to 2.0 using curved blank holder. In addition, the earring ratio also reduces and flange wrinkling is prevented when the curved blank holder is used. These are due to a more uniform sheet flow in different directions with curved blank holder.
基金Project(2010DFA52030)supported by the International Scientific Cooperation,ChinaProject(51175024)supported by the National Natural Science Foundation of China
文摘Experimental and numerical analyses for the effect of the thickness of gap generator blank(GGB) on the formability of the outer blanks were investigated. The thickness of the GGB has the greatest impact on the thinning of the lowest blank. In addition, the friction at different regions and the additional interlayer contacts can also affect the thinning of different regions as well as increase the punch force. This work will enhance the understanding of simultaneous multi-layered blanks forming and will help the composite design engineers to tailor requirement-specific hybrid parts such as fiber metal laminates(FMLs) and functionally graded structures(FGSs) for hi-tech applications.
文摘Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidification, analyze the interaction between shell and molten steel, and compare the temperature distribution under different technological conditions. The results indicate that high superheating degree can lengthen the liquid-core depth and make the crack and breakout possible, so suitable superheating should be controlled within 35℃ according to the simulation results. Casting speed which is one of the most important technological parameters of improving production rate, should be controlled between 0. 85 m/min and 1.05 m/min and the caster has great potential in the improvement of blank quality.
基金supported by Key Program of National Natural Science Foundation of China(Grant No.51135007)National Natural Science Foundation of China(Grant No.51075290)
文摘Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named "casting-rolling compound forming technology" is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.
基金This work was financiallysupportedbythe Research Grants(NN-8501)from Ministry ofCommerce,Industry and Energyin Republic ofKorea.
文摘Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.
基金Project supported by the National Natural Sciences Foundation of China(No. 50335060).
文摘By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM.
基金supported by the Hebei Provincial Natural Science Foundation of China(No.E2007000591).
文摘The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.
基金Supported by National Natural Science Foundation of China(Grant No.51275444)Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20121333110003)Natural Science Foundation-Steel and Iron Foundation of Hebei Province,China(Grant No.E2014203271)
文摘The elastoplastic mechanical properties of the weld and heat affected zone metals have comparatively major impact on the forming process of tailor-welded blanks. A few scholars investigated the elastoplastic mechanical properties of the weld and heat affected zone, but they only simply assumed that it was a uniform distribution elastoplastic material different from the base materials. Four types of tailor-welded blanks which consist of ST12 and 304 stainless steel plates are selected as the research objects, the elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals are obtained based on the nanoindentation tests, and the Erichsen cupping tests are conducted by combining numerical simulation with physical experiment. The nanoindentation tests results demonstrate that the elastoplastic mechanical properties of the weld and heat affected zone metals are not only different from the base materials, but also varying between the weld metals and the heat affected zone metals. Comparing the Erichsen cupping test resulted from numerical with that from experimental method, it is found that the numerical value of Erichsen cupping test which consider the elastoplastic mechanical properties of the weld and heat affected zone metals have a good agreement with the experimental result, and the relative error is only 4.8%. The proposed research provides good solutions for the inhomogeneous elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals, and improves the control performance of tailor-welded blanks forming accuracy.
文摘A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron microscopy were used to analyze its morphologies and microstructures. The results show that the microstructures of the pipe blank are homogeneous and the precipitates are uniformly distributed d 25~70 nm spherical or sphere like Al 12 (Fe,V) 3Si particles, its mechanical properties at room temperature and 350 ℃ after densification by extrusion are σ b=412 MPa, δ =7.6% and σ b=187 MPa, δ =7.6%, respectively. The analyses indicate that the proper match of the motion rates of atomizer and substrate can produce deposited blanks with uniform thickness and relatively high cooling rate.
文摘Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.
基金Project(2015ZX07205003)supported by Major Science and Technology Program for Water Pollution Control and Treatment of China
文摘In order to improve leaching efficiency of vanadium from stone coal,the combination of blank roasting and bioleaching using Bacillus mucilaginosus(B.mucilaginosus)mutants was evaluated.The atmospheric and room temperature plasma(ARTP)technique was used to generate B.mucilaginosus mutants.The results showed that a mutant B.mucilaginosus BM-50,after ARTP irradiation for 50 s,had the highest acid production.The total content of the organic acid produced by B.mucilaginosus BM-50 was nearly doubled compared with the wild strain after 2 days.After 20 days,vanadium leaching rate with B.mucilaginosus BM-50 reached 18.2%,which was improved compared with the original bacteria(15.3%).A pretreatment via blank roasting for stone coal further improved the vanadium dissolution by bioleaching,namely,68.3%vanadium was extracted,which was much higher than that without blank roasting.It is shown that bioleaching by bacterial mutants by ARTP irradiation combined with blank roasting has great potential for improving vanadium recovery from low-grade vanadium bearing stone coal.
基金This project is supported by Doctoral Fundation of China(No.20010487002) and Municipal Key Technology R&D Program of Guangzhou, China(No, 2002Z3-0211).
文摘The study of multipoint blank holder force(BHF) control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method (FEM) simulation, the configuration of multipoint blank holder cylinders and the setting of local BHF are optimized, and the influences of the multipoint BHF on the hydromechanical deep drawing and conventional hydroforming processes are studied. The desired fluid pressure and whole BHF are predicted for hydromechanical deep drawing process. Finally, simulation results are testified by forming experiment, and they are in agreement very well.
文摘At first, a series of finite element method (FEM) simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force (VBHF) was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.
基金The National Science and Technology Major Project(2016ZX03001011-005)the National Natural Science Foundation of China(No.61571123,61521061)+1 种基金the Research Fund of National Mobile Communications Research Laboratory of Southeast University(No.2017A03)Qing Lan Project
文摘A new enhanced inter-cell interference coordination (elCIC) is adopted for managing almost blank sub-frame (ABS),which jointly exploits the time, frequency and power dimensions to improve the resource utilization. In particular, a non-uniform two tier heterogeneous network ( HetNet) is considered, where the pico cells are located close to the macro cell and the number of users in each pico cell is different. To alleviate the interference caused by the co-channeldeployment,the macro cells employ low power ABS (LP- ABS), and the resource blocks (RBs) are divided into twoparts during an ABS. One is exclusively reserved for macro cell users ad the other is reserved for pico cell users. Themacro cells are allowed to use different percentages of RBs and different powers for their own transmission during the LP- ABS. The user association,resource allocation,ABS proportion,the frequency band partition parameter and the transmission power of macro cells are considered, aiming at maximizing the proportional fairness utility of the system. An iterative algorithm is also proposed and simulation results demonstrate that the proposed algorithm can improve both the system throughput and user fairness compared with the existing schemes.