The finite strip method in structural analysis has been extended, and elastic-plastic large deformation spline finite strip method based on the Updated-Lagrange method (U. L. method) was established to simulate roll f...The finite strip method in structural analysis has been extended, and elastic-plastic large deformation spline finite strip method based on the Updated-Lagrange method (U. L. method) was established to simulate roll forming process of channel section with outer edge. The deformation characteristics of strip was analyzed, and the three-dimensional displacement field, strain field and stress field of deformed strip were got. The calculation example proves that the peak transverse pressing membrane strain is on the corner part of the deformed strip, and the peak longitudinal stretching strain is on the outer edge part of the deformed strip in front of rolls. In addition, the transverse deformation of the deformed strip is principal, and the longitudinal deformation is small.展开更多
Sheet metal forming is one of the most preferred manufacturing processes in automotive and aerospace industries. However, due to increase in fuel prices and more stringent environmental regulation, these industries ar...Sheet metal forming is one of the most preferred manufacturing processes in automotive and aerospace industries. However, due to increase in fuel prices and more stringent environmental regulation, these industries are facing many challenges to meet the criteria. Due to this, many efforts in design and manufacturing were considered and presented.Those efforts were implementing lighter-weight materials like aluminum and magnesium（but they have higher elasticity as compared to steel） and implementing higher-strength steel with lower thickness. The main challenge found in both cases is springback after deformation. Springback is the elastic recovery after the part is unloaded. In this paper, the 3D channels with large length were deformed numerically and springback at different section was predicted. For this purpose, tailorwelded blank was considered. The geometric change along the long axis was also discussed. In addition, the effect of flange springback on wall springback was also analyzed. It was found that different section produced different springback and greater influence of flange springback. To validate the numerical simulation approach, the experiments on one case were performed and compared.展开更多
U-channel forming tests were performed to investigate the surface topography evolvement of hot-dip galvanized(GI) and galvannealed(GA) steels and the effects of die hardness on sheet metal forming(SMF). Experimental r...U-channel forming tests were performed to investigate the surface topography evolvement of hot-dip galvanized(GI) and galvannealed(GA) steels and the effects of die hardness on sheet metal forming(SMF). Experimental results indicate that the surface roughness values of the two galvanized steels increase with the number of forming,i.e.,the surface topographies of galvanized steels are roughened in SMF. Moreover,GI steel has a better ability of damage-resistance than GA steel. The mechanisms of topography evolvement are different in the forming of GI and GA steels. Scratch is the main form of surface damage in the forming of GI steels. The severity of scratch can be decreased by increasing die hardness. GA steel results in exfoliating of the coating firstly and then severe scratching. The surface topography of galvannealed steels can be improved by increasing die hardness. However,the hardness should not be too high.展开更多
Blind equalization based on adaptive forgetting factor, recursive least squares （RLS） with constant modulus algorithm （CMA）, is investigated. The cost function of CMA is simplified to meet the second norm form to ...Blind equalization based on adaptive forgetting factor, recursive least squares （RLS） with constant modulus algorithm （CMA）, is investigated. The cost function of CMA is simplified to meet the second norm form to ensure the stability of RLS-CMA, and thus an improved RLS-CMA （RLS-SCMA） is established. To further improve its performance, a new adaptive forgetting factor RLS-SCMA （ARLS-SCMA） is proposed. In ARLS-SCMA, the forgetting factor varies with the output error of the blind equalizer during the iterative process, which leads to a faster convergence rate and a smaller steady-state error. The simulation results prove the effectiveness under the condition of the underwater acoustic channel.展开更多
The paper investigates the elastic behavior of the metal after unloading. For this purpose the strip of metal with tensile gauge length was simulated with high and low strength material. Further the channel forming wa...The paper investigates the elastic behavior of the metal after unloading. For this purpose the strip of metal with tensile gauge length was simulated with high and low strength material. Further the channel forming was modeled for combination of materials to predict the spring-back and compared the results. It is observed that the Young’s modulus (E-value) decreases with the increase in plastic strain. The strength of the material has no effect on the decrease in the E-value after unloading during tension test. However in channel forming the E-value after unloading depends on the starting E-value, spring-back angle and maximum strain achieved in the channel. The proposed mathematical equations to determine the E-value after unloading from the tension test and channel forming test gives very good prediction with each other. It is also found that the lowest spring-back occurred in the channel with the composite Hard-Soft material.展开更多
Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of v...Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of voltage,shape of channel and discharge cycles on laws of metal flow were studied.Results showed that forming depth of micro channel and thinning of sheet thickness increased as the increasing of the voltage.Mold-filling capacity of components formed by two molds with different structures had been increased when the voltage was increased.Mold with semicircle structure facilitate the material flow and the forming depth of parts was relative large.Semicircle structure was better than taper structure in mold-filling capacity.A number of small pulse discharges can improve the forming quality and deformation,but local thinning in sheet metal leads to non-uniform distribution of thickness.展开更多
文摘The finite strip method in structural analysis has been extended, and elastic-plastic large deformation spline finite strip method based on the Updated-Lagrange method (U. L. method) was established to simulate roll forming process of channel section with outer edge. The deformation characteristics of strip was analyzed, and the three-dimensional displacement field, strain field and stress field of deformed strip were got. The calculation example proves that the peak transverse pressing membrane strain is on the corner part of the deformed strip, and the peak longitudinal stretching strain is on the outer edge part of the deformed strip in front of rolls. In addition, the transverse deformation of the deformed strip is principal, and the longitudinal deformation is small.
文摘Sheet metal forming is one of the most preferred manufacturing processes in automotive and aerospace industries. However, due to increase in fuel prices and more stringent environmental regulation, these industries are facing many challenges to meet the criteria. Due to this, many efforts in design and manufacturing were considered and presented.Those efforts were implementing lighter-weight materials like aluminum and magnesium（but they have higher elasticity as compared to steel） and implementing higher-strength steel with lower thickness. The main challenge found in both cases is springback after deformation. Springback is the elastic recovery after the part is unloaded. In this paper, the 3D channels with large length were deformed numerically and springback at different section was predicted. For this purpose, tailorwelded blank was considered. The geometric change along the long axis was also discussed. In addition, the effect of flange springback on wall springback was also analyzed. It was found that different section produced different springback and greater influence of flange springback. To validate the numerical simulation approach, the experiments on one case were performed and compared.
基金Project(50605043) supported by the National Natural Science Foundation of China
文摘U-channel forming tests were performed to investigate the surface topography evolvement of hot-dip galvanized(GI) and galvannealed(GA) steels and the effects of die hardness on sheet metal forming(SMF). Experimental results indicate that the surface roughness values of the two galvanized steels increase with the number of forming,i.e.,the surface topographies of galvanized steels are roughened in SMF. Moreover,GI steel has a better ability of damage-resistance than GA steel. The mechanisms of topography evolvement are different in the forming of GI and GA steels. Scratch is the main form of surface damage in the forming of GI steels. The severity of scratch can be decreased by increasing die hardness. GA steel results in exfoliating of the coating firstly and then severe scratching. The surface topography of galvannealed steels can be improved by increasing die hardness. However,the hardness should not be too high.
基金financially supported in part by the National Natural Science Foundation of China(Grant No.61201418)Fundamental Research Funds for the Central Universities(Grant No.DC12010218)Scientific and Technological Research Project for Education Department of Liaoning Province(Grant No.2010046)
文摘Blind equalization based on adaptive forgetting factor, recursive least squares （RLS） with constant modulus algorithm （CMA）, is investigated. The cost function of CMA is simplified to meet the second norm form to ensure the stability of RLS-CMA, and thus an improved RLS-CMA （RLS-SCMA） is established. To further improve its performance, a new adaptive forgetting factor RLS-SCMA （ARLS-SCMA） is proposed. In ARLS-SCMA, the forgetting factor varies with the output error of the blind equalizer during the iterative process, which leads to a faster convergence rate and a smaller steady-state error. The simulation results prove the effectiveness under the condition of the underwater acoustic channel.
文摘The paper investigates the elastic behavior of the metal after unloading. For this purpose the strip of metal with tensile gauge length was simulated with high and low strength material. Further the channel forming was modeled for combination of materials to predict the spring-back and compared the results. It is observed that the Young’s modulus (E-value) decreases with the increase in plastic strain. The strength of the material has no effect on the decrease in the E-value after unloading during tension test. However in channel forming the E-value after unloading depends on the starting E-value, spring-back angle and maximum strain achieved in the channel. The proposed mathematical equations to determine the E-value after unloading from the tension test and channel forming test gives very good prediction with each other. It is also found that the lowest spring-back occurred in the channel with the composite Hard-Soft material.
基金Item Sponsored by the National Natural Science Foundation of China[No.5083500250805035]
文摘Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of voltage,shape of channel and discharge cycles on laws of metal flow were studied.Results showed that forming depth of micro channel and thinning of sheet thickness increased as the increasing of the voltage.Mold-filling capacity of components formed by two molds with different structures had been increased when the voltage was increased.Mold with semicircle structure facilitate the material flow and the forming depth of parts was relative large.Semicircle structure was better than taper structure in mold-filling capacity.A number of small pulse discharges can improve the forming quality and deformation,but local thinning in sheet metal leads to non-uniform distribution of thickness.
