Curvature Radius and Springback of Magnesium Alloy Panel during Bending Forming
The work aims to study the springback of magnesium alloy panels in bending with variable curvature,analyze the change law of the curvature radius and springback amount of the panels,establish a geometric model of bending,and determine the material property parameters,as well as the process plan and parameters of bending.Using numerical simulation and ex-perimental research methods,two kinds of mesh panels with rib height ratio of 4∶3 and 5∶2 were tested under the conditions of 3 mm,5 mm and 7 mm in descending order at 260 ℃.The distribution law of the equivalent stress during the experiment was analyzed.The maximum equivalent stress increased with the increase of the pressure height.The maximum equivalent stress at the pressure height of 5 mm and 7 mm exceeded the tensile strength of the panel at the pressure speed of 1 mm/s at 260 ℃.The maximum equivalent stress increased with the increase of the ratio of reinforcement height.The influence of bending parameters on the springback of a magnesium alloy panel was analyzed.The springback of the panel increased with the increase of bending height.With the increase of the ratio of rib height,the rebound of the wall panel decreased.In addition,when the maximum equivalent stress was less than the tensile strength,the rebound rate of the wall panel was 45％when the ratio of reinforcement to height was 4∶3,and 30％when the ratio of reinforcement to height was 5∶2.The rebound rate was a certain value inde-pendent of the compressive height,and the rebound rate gradually decreased when the maximum equivalent stress exceeded the tensile strength.The relationship between the curvature radius of a magnesium alloy panel and the buckling height was analyzed.With the increase of buckling height,the buckling radius of magnesium alloy panel decreased.In conclusion,the simulated value of wall panel rebound is in good agreement with the experimental value,and the maximum relative error is 6.91％.The simulation re-sults are in good agreement with the experimental results,and the maximum relative error is 4.21％.The material properties are Poisson ratio 0.35,friction coefficient 0.3,mass density 1.77×10-9 kg/mm3,elastic modulus 29.6 GPa at 260 ℃.For these two types of panels,the optimal bending process is that the temperature is 260 ℃ and the pressure is 3 mm,5 mm,and 7 mm respectively.
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