| As a metal material with high specific strength,high specific stiffness,and good electromagnetic shielding properties,magnesium alloys have been widely used in manufacturing fields such as automobiles,ships,and aerospace.Compared with common metal materials in the manufacturing industry,magnesium alloys have the disadvantage of poor ductility at room temperature,which greatly affects the further application of magnesium alloy materials.With the development of new sheet metal forming technologies,the trial production cycle of new products has become shorter,and people have gradually increased the requirements for lightweight product parts.Using traditional manufacturing processes to form magnesium alloy thin-walled parts no longer has an advantage.Due to its unique process characteristics,single point incremental forming(SPIF)can fabricate complex thin-walled parts with high requirements for mechanical properties and dimensional accuracy,as well as large deformation of parts.SPIF process has simple requirements for forming equipment,low noise during the forming process,and good flexibility of forming parts.It is very suitable for trial production,small batch and of diversity products.The research object is a regular pentagonal conical part that is made by AZ31 B magnesium alloy.The effects of process parameters on the wall thickness uniformity and springback of the part during single point incremental hot forming were studied using numerical simulation.The main research contents are as follows:(1)To obtain the stress-strain relationships of AZ31 B magnesium alloy at different temperatures,hot tensile tests were conducted on magnesium alloy samples to obtain the stress-strain curves at temperatures of 200 ℃,225 ℃,250 ℃,275 ℃,300 ℃,and 350 ℃.Then,based on the tensile test data,the elastic modulus,thickness anisotropy index,strain hardening index,and strain hardening coefficient of AZ31 B magnesium alloy samples along the rolling direction of 0 °,45 °,and 90 ° are calculated and averaged.Finally,the calculated parameters of AZ31 B magnesium alloy are input into the material model,and a finite element model of single point incremental hot forming for AZ31 B magnesium alloy is established.The established finite element model was used to calculate regular pentagonal conical parts with different forming angles,and the minimum wall thickness of the numerical simulation parts were compared with the theoretical forming minimum wall thickness to verify the correctness of the established simulation model.(2)The effect of feed rate,layer spacing,tool diameter and friction coefficient on uniformity of wall thickness and average spingback of formed parts was studied.The simulation results shows that the feed rate and layer spacing were inversely proportional to the wall thickness and directly proportional to the spingback of the formed part.The diameter of the forming tool head is proportional to the uniformity of the wall thickness of the forming part,and inversely proportional to the average springback of the forming part The coefficient of friction has little effect on the uniformity of wall thickness and the average springback of the formed parts.(3)Based on the orthogonal experimental method,process parameters optimization were performed in which the effect of feed rate,layer spacing,tool diameter and friction coefficients on uniformity of wall thickness and average springback of the formed part was analyzed and decided the optimal parameter combination of single point incremental hot forming process,namely tool diameter of 9 mm,feed rate of 200 mm/min,layer spacing of 0.2 mm and friction coefficient of 0.2.(4)A single point incremental thermal forming physical test was carried out for AZ31 B magnesium alloy conical parts with five sides,and the parts were formed by the combination of optimal process parameters.The results show that the minimum error value of wall thickness is less than 5% and the average value of springback is less than1 mm. |
PDF Full Text Request