A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which ca...A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which can accurately describe the strain and stress states in IF.Based on strain analysis,the model can predict the material thickness distribution and neck height after IF.By considering contact area,strain characteristics,material thickness changes,and friction,the model can predict specific moments and corresponding values of maximum axial forming force and maximum horizontal forming force during IF.In addition,an IF experiment involving different tool diameters,flanging diameters,and opening hole diameters is conducted.On the basis of the experimental strain paths,the strain characteristics of different deformation zones are studied,and the stable strain ratio is quantitatively described through two dimensionless parameters:relative tool diameter and relative hole diameter.Then,the changing of material thickness and forming force in IF,and the variation of minimum material thickness,neck height,maximum axial forming force,and maximum horizontal forming force with flanging parameters are studied,and the reliability of the analytical model is verified in this process.Finally,the influence of the horizontal forming force on the tool design and the fluctuation of the forming force are explained.展开更多
Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to ob...Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to obtain a more substantial flange from thick plate. The finite element method （FEM） with DEFORM was utilized to simulate the novel upsetting-flanging process and the influence of geometric parameters on the flange height was studied in details. A series of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate section were discussed. The results showed that the newly upsetting-flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increases due to the work hardening after the upsetting-flanging process, which reveals better superiority in strength for the subsequent machining or assembling processes.展开更多
The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge ...The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge crack location and strain distribution along die profile radius in the flange.Non-axisymmetric stretch flanging process of AA-5052 sheet metal blanks was carried out by numerical simulation to predict the deformation behavior of flange,location and propagation of crack in flange and to investigate the effect of punch die clearance,flange length,die and punch profile radius and friction in the stretch flanging process.The experimental investigations were made to validate the simulations results.The results reveal that the crack length increases with the increase in the flange length.It is found that the flange length has a significant effect in circumferential direction as compared with the radial direction.The punch die clearance has the most significant effect in crack propagation in comparison with flange length.The circumferential strain is found to be larger in the case of punch having the profile radius less than the die profile radius,which leads to faster edge crack propagation.A close agreement is found between simulation and experimental results in terms of location of edge crack and forming load.展开更多
The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° ...The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° to 90° and employing aluminum as the test material. It is shown that the hole size has significant effects on the stress/strain distribution on the cylindrical flange. The magnitude of hoop strains increases and the flange thickness increases as the hole size increases. Likewise, the von Mises stress reduces with the increasing of hole size. Further, there is a threshold value of hole size（i.e., 80 mm） below which severe stresses occur, which lead to sheet fracturing thus failing the successful forming of cylindrical flange. Moreover, the formability reduces as the hole size is increased above the threshold size. Finally, it is concluded that 80 mm is the threshold size of hole for maximizing the formability of aluminum sheet in incremental hole flanging.展开更多
Based on pre punching to hot rolled martensitic and bainitic dual phase steels with similar elongation and work hardening index （n）, as well as similar thickness and hole expansion test using taper die, analysis of ...Based on pre punching to hot rolled martensitic and bainitic dual phase steels with similar elongation and work hardening index （n）, as well as similar thickness and hole expansion test using taper die, analysis of the hole expansion rate indicated significant difference in their flanging performance. The results indicated that mechanical property was not the only major factor that influenced flanging. Further analysis of the hole border microstructure, work hardening condition, and fracture property showed that the fracture property of sheets was the major factor that influenced flanging performance.展开更多
In this work,the magnetic pulse forming process was used to flange the AA 3003-O aluminum alloy tube to improve the flanging formability limit.The results show that there are critical discharge energy values for the f...In this work,the magnetic pulse forming process was used to flange the AA 3003-O aluminum alloy tube to improve the flanging formability limit.The results show that there are critical discharge energy values for the flanging dies with varied slope angle.The mechanism of magnetic pulse flanging process is the bulging in contrast to the expanding of the quasi-static flanging.For the flanging with 90 slope degree,the limited hoop strain at the outer fringe could be up to 0.54 without rapture,to which the limit of simple tension limit is improved by 85%in contrast.The 180 degree flanging at tube end can be achieved by one time magnetic pulse forming.展开更多
The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with...The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.展开更多
A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a doubl...A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.展开更多
Wrinkling is a common failure in the sheet metal forming of titanium owing to the relatively poor ability to shrink. It is important to predict wrinkling accurately in the sheet metal forming without costly trials. Th...Wrinkling is a common failure in the sheet metal forming of titanium owing to the relatively poor ability to shrink. It is important to predict wrinkling accurately in the sheet metal forming without costly trials. The ABAQUS/Explicit code was utilized to predict the wrinkling behavior in the sheet metal forming of Ti-15-3 alloy sheets. In terms of the comparison of wrinkling behavior between the simulation and experiment of the Fukui＇s conical cup tests at room temperature, the sensitivities of wrinkling simulation to various input parameters were evaluated comprehensively and quantitatively. Prediction of wrinkling and influence of rubber hardness on the winkling behavior in the rubber forming of convex flange were investigated quantitatively and validated by the rubber forming experiments. The excellent agreements between the simulations and the experiments conIirmed the accuracy of the prediction.展开更多
The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flangin...The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flanging process parameters with considerations of the multiple response (the average flanging height, regular flanging and maximum strain) is introduced. Various flanging parameters, such as the blank inner radius rb, blank inner width B0, are considered. An orthogonal array is used for the experimental design. Multiple response values are obtained using finite element analysis (FEA). Optimal process parameters are determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (flanging height, regular flanging and maximum strain). Analysis of variance (ANOVA) for the grey relational grade is implemented. The results showed good agreement with the experiment result. Grey relational analysis can be applied in multiple response optimi-zation designs.展开更多
In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrit...In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.展开更多
In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the ou...In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.展开更多
The type, morphology and sources of inclusion in steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during coo...The type, morphology and sources of inclusion in steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during cooling and solidification of steel. Exogenous inclusions arise primarily from the incidental chemical （reoxidation） and mechanical interaction of liquid steel with its surroundings （slag entrainment and erosion of lining refractory）. Types and causes for the nozzle clogging were also summarized. Reasons for bubble formation and bubble size distribution in steels were discussed thereafter. Finally, morphology and causes of inclusion-related defects in continuously cast steel products were reviewed, such as flange cracking in cans, slag spots and line defects on strips.展开更多
Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tu...Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.展开更多
In this paper,a failure evaluation criterion was proposed for the bolted casing-flange structure under impact loading.Subsequently,ballistic tests with eighteen bolted casing-flange structure specimens were conducted ...In this paper,a failure evaluation criterion was proposed for the bolted casing-flange structure under impact loading.Subsequently,ballistic tests with eighteen bolted casing-flange structure specimens were conducted to validate the failure evaluation criterion.Parameter studies were then carried out using the validated FE models.Both the experimental and numerical results demonstrated the accuracy of the failure evaluation criterion.The failure evaluation criterion provided a quick and easy way to determine the failure mode of the casing connection area by using the materials and dimensions of the structure.Based on the failure evaluation criterion,designing the structural failure mode of the bolted casing-flange structure to be between flange failure and bolt failure can improve the impact resistance of the connection area of the aero-engine casings.This investigation revealed that the impact failure is not the unique criterion in evaluating the containment of the casing connection area,structural failure should also be involved in the evaluation criteria.展开更多
This study aims to develop a framework based on the Nadal formula to assess train derailment risk. Monte Carlo simulation was adopted to develop 10000 sets of random parameters to assess train derailment risk subject ...This study aims to develop a framework based on the Nadal formula to assess train derailment risk. Monte Carlo simulation was adopted to develop 10000 sets of random parameters to assess train derailment risk subject to the curvature radius of the track, the difference between the flange angle and the equivalent conicity, and accelerations from 250 to 989.22 gal during horizontal earthquake. The results indicated that railway in Taiwan, China has no derailment risk under normal conditions. However, when earthquakes occur, the derailment risk increases with the unloading factor which is caused by seismic force. The results also show that equivalent conicity increases derailment risk;as a result, equivalent conicity should be listed as one of maintenance priorities. In addition, among all train derailment factors, flange angle, equivalent conicity and unload factors are the most significant ones.展开更多
In order to enhance the bearing capacity of structural components,save materials,and reduce cost,a glued laminated timber(glulam)I-beam that is theoretically suitable for engineering application was proposed.In this s...In order to enhance the bearing capacity of structural components,save materials,and reduce cost,a glued laminated timber(glulam)I-beam that is theoretically suitable for engineering application was proposed.In this study,18 glulam specimens were fabricated using larch dimension lumber and resorcinol-formaldehyde resin.Four-point bending tests were carried out to compare the ultimate bearing capacity,strain,and deflection of various specimens.The results showed that:(1)The typical failure mode at bending is the web shear failure parallel to grain.Before the failure,cracks and sounds appear at the beam web,which represent the sudden brittle failure.(2)The cross-sectional strain of glulam beam changed linearly with the beam height,indicating that the plane section assumption was basically established.(3)Stiffener could improve the initial flexural stiffness of glulam beam,which experiences an increase of 28.21%.Larger the shear span ratio,smaller the initial flexural stiffness.The initial flexural stiffness improves by 10-23.5%with the increase in the thickness of the lower flange.(4)The effects of stiffener and shear-span ratio on shear strength are relatively significant.After the stiffeners are set at the support and the loading point in pairs,the shear strength of the glulam beam increases by 15.05%averagely.With the increase in the shear-span ratio,the shearing strength of the glulam I-beam gradually reduces.The equation of the shearing strength with the shear span ratio is obtained,which is shown by high fitting precision.(5)The shear strength correlation,as proposed by Soltis and Rammer,is suitable not only for rectangular beams,but also for glulam I-beams.展开更多
基金supported in part by financial support from the National Key R&D Program of China(No.2023YFB3407003)the National Natural Science Foundation of China(No.52375378).
文摘A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which can accurately describe the strain and stress states in IF.Based on strain analysis,the model can predict the material thickness distribution and neck height after IF.By considering contact area,strain characteristics,material thickness changes,and friction,the model can predict specific moments and corresponding values of maximum axial forming force and maximum horizontal forming force during IF.In addition,an IF experiment involving different tool diameters,flanging diameters,and opening hole diameters is conducted.On the basis of the experimental strain paths,the strain characteristics of different deformation zones are studied,and the stable strain ratio is quantitatively described through two dimensionless parameters:relative tool diameter and relative hole diameter.Then,the changing of material thickness and forming force in IF,and the variation of minimum material thickness,neck height,maximum axial forming force,and maximum horizontal forming force with flanging parameters are studied,and the reliability of the analytical model is verified in this process.Finally,the influence of the horizontal forming force on the tool design and the fluctuation of the forming force are explained.
基金Project(51175445)supported by the National Natural Science Foundation of ChinaProject(2010DFA52130)supported by the International Cooperation Project of the Ministry of Science and Technology,ChinaProject(CX2013B277)supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to obtain a more substantial flange from thick plate. The finite element method （FEM） with DEFORM was utilized to simulate the novel upsetting-flanging process and the influence of geometric parameters on the flange height was studied in details. A series of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate section were discussed. The results showed that the newly upsetting-flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increases due to the work hardening after the upsetting-flanging process, which reveals better superiority in strength for the subsequent machining or assembling processes.
基金the Science and Engineering Research Board(SERB)Department of Science & Technology,Government of India for financially supporting this research
文摘The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge crack location and strain distribution along die profile radius in the flange.Non-axisymmetric stretch flanging process of AA-5052 sheet metal blanks was carried out by numerical simulation to predict the deformation behavior of flange,location and propagation of crack in flange and to investigate the effect of punch die clearance,flange length,die and punch profile radius and friction in the stretch flanging process.The experimental investigations were made to validate the simulations results.The results reveal that the crack length increases with the increase in the flange length.It is found that the flange length has a significant effect in circumferential direction as compared with the radial direction.The punch die clearance has the most significant effect in crack propagation in comparison with flange length.The circumferential strain is found to be larger in the case of punch having the profile radius less than the die profile radius,which leads to faster edge crack propagation.A close agreement is found between simulation and experimental results in terms of location of edge crack and forming load.
文摘The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° to 90° and employing aluminum as the test material. It is shown that the hole size has significant effects on the stress/strain distribution on the cylindrical flange. The magnitude of hoop strains increases and the flange thickness increases as the hole size increases. Likewise, the von Mises stress reduces with the increasing of hole size. Further, there is a threshold value of hole size（i.e., 80 mm） below which severe stresses occur, which lead to sheet fracturing thus failing the successful forming of cylindrical flange. Moreover, the formability reduces as the hole size is increased above the threshold size. Finally, it is concluded that 80 mm is the threshold size of hole for maximizing the formability of aluminum sheet in incremental hole flanging.
基金Sponsored by National Natural Science Foundation of China(51275003)
文摘Based on pre punching to hot rolled martensitic and bainitic dual phase steels with similar elongation and work hardening index （n）, as well as similar thickness and hole expansion test using taper die, analysis of the hole expansion rate indicated significant difference in their flanging performance. The results indicated that mechanical property was not the only major factor that influenced flanging. Further analysis of the hole border microstructure, work hardening condition, and fracture property showed that the fracture property of sheets was the major factor that influenced flanging performance.
基金Item Sponsored by National Basic Research Program of China[973 Program][2011CB012805]
文摘In this work,the magnetic pulse forming process was used to flange the AA 3003-O aluminum alloy tube to improve the flanging formability limit.The results show that there are critical discharge energy values for the flanging dies with varied slope angle.The mechanism of magnetic pulse flanging process is the bulging in contrast to the expanding of the quasi-static flanging.For the flanging with 90 slope degree,the limited hoop strain at the outer fringe could be up to 0.54 without rapture,to which the limit of simple tension limit is improved by 85%in contrast.The 180 degree flanging at tube end can be achieved by one time magnetic pulse forming.
文摘The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.
基金the National Natural Science Foundation of China(No.19832020)the Ministry of Education of China.
文摘A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.
文摘Wrinkling is a common failure in the sheet metal forming of titanium owing to the relatively poor ability to shrink. It is important to predict wrinkling accurately in the sheet metal forming without costly trials. The ABAQUS/Explicit code was utilized to predict the wrinkling behavior in the sheet metal forming of Ti-15-3 alloy sheets. In terms of the comparison of wrinkling behavior between the simulation and experiment of the Fukui＇s conical cup tests at room temperature, the sensitivities of wrinkling simulation to various input parameters were evaluated comprehensively and quantitatively. Prediction of wrinkling and influence of rubber hardness on the winkling behavior in the rubber forming of convex flange were investigated quantitatively and validated by the rubber forming experiments. The excellent agreements between the simulations and the experiments conIirmed the accuracy of the prediction.
基金Project (No. 50475020) supported by the National Natural ScienceFoundation of China
文摘The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flanging process parameters with considerations of the multiple response (the average flanging height, regular flanging and maximum strain) is introduced. Various flanging parameters, such as the blank inner radius rb, blank inner width B0, are considered. An orthogonal array is used for the experimental design. Multiple response values are obtained using finite element analysis (FEA). Optimal process parameters are determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (flanging height, regular flanging and maximum strain). Analysis of variance (ANOVA) for the grey relational grade is implemented. The results showed good agreement with the experiment result. Grey relational analysis can be applied in multiple response optimi-zation designs.
文摘In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.
文摘In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.
文摘The type, morphology and sources of inclusion in steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during cooling and solidification of steel. Exogenous inclusions arise primarily from the incidental chemical （reoxidation） and mechanical interaction of liquid steel with its surroundings （slag entrainment and erosion of lining refractory）. Types and causes for the nozzle clogging were also summarized. Reasons for bubble formation and bubble size distribution in steels were discussed thereafter. Finally, morphology and causes of inclusion-related defects in continuously cast steel products were reviewed, such as flange cracking in cans, slag spots and line defects on strips.
基金financial support of the National Natural Science Foundation of China (No. 50975235 and 50575184)the 111 Project(B08040)
文摘Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.
基金support from the National Natural Science Foundation of China(Nos.11772158,11502113)the Fundamental Research Funds for Central Universities,China(No.30917011103)。
文摘In this paper,a failure evaluation criterion was proposed for the bolted casing-flange structure under impact loading.Subsequently,ballistic tests with eighteen bolted casing-flange structure specimens were conducted to validate the failure evaluation criterion.Parameter studies were then carried out using the validated FE models.Both the experimental and numerical results demonstrated the accuracy of the failure evaluation criterion.The failure evaluation criterion provided a quick and easy way to determine the failure mode of the casing connection area by using the materials and dimensions of the structure.Based on the failure evaluation criterion,designing the structural failure mode of the bolted casing-flange structure to be between flange failure and bolt failure can improve the impact resistance of the connection area of the aero-engine casings.This investigation revealed that the impact failure is not the unique criterion in evaluating the containment of the casing connection area,structural failure should also be involved in the evaluation criteria.
文摘This study aims to develop a framework based on the Nadal formula to assess train derailment risk. Monte Carlo simulation was adopted to develop 10000 sets of random parameters to assess train derailment risk subject to the curvature radius of the track, the difference between the flange angle and the equivalent conicity, and accelerations from 250 to 989.22 gal during horizontal earthquake. The results indicated that railway in Taiwan, China has no derailment risk under normal conditions. However, when earthquakes occur, the derailment risk increases with the unloading factor which is caused by seismic force. The results also show that equivalent conicity increases derailment risk;as a result, equivalent conicity should be listed as one of maintenance priorities. In addition, among all train derailment factors, flange angle, equivalent conicity and unload factors are the most significant ones.
基金supported by the Natural Science Foundation of Jiang-su Province(Grant No.BK20181402)the National Natural Science Foundation of China(Grant No.51878354)+2 种基金a Project Funded by the National First-class Disciplines(PNFD)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)a Project Funded by the Co-Innovation Center of Efficient Processing and Utilization of Forest Resources,Nanjing Forestry University(Nanjing,210037,China).
文摘In order to enhance the bearing capacity of structural components,save materials,and reduce cost,a glued laminated timber(glulam)I-beam that is theoretically suitable for engineering application was proposed.In this study,18 glulam specimens were fabricated using larch dimension lumber and resorcinol-formaldehyde resin.Four-point bending tests were carried out to compare the ultimate bearing capacity,strain,and deflection of various specimens.The results showed that:(1)The typical failure mode at bending is the web shear failure parallel to grain.Before the failure,cracks and sounds appear at the beam web,which represent the sudden brittle failure.(2)The cross-sectional strain of glulam beam changed linearly with the beam height,indicating that the plane section assumption was basically established.(3)Stiffener could improve the initial flexural stiffness of glulam beam,which experiences an increase of 28.21%.Larger the shear span ratio,smaller the initial flexural stiffness.The initial flexural stiffness improves by 10-23.5%with the increase in the thickness of the lower flange.(4)The effects of stiffener and shear-span ratio on shear strength are relatively significant.After the stiffeners are set at the support and the loading point in pairs,the shear strength of the glulam beam increases by 15.05%averagely.With the increase in the shear-span ratio,the shearing strength of the glulam I-beam gradually reduces.The equation of the shearing strength with the shear span ratio is obtained,which is shown by high fitting precision.(5)The shear strength correlation,as proposed by Soltis and Rammer,is suitable not only for rectangular beams,but also for glulam I-beams.
