Numerical And Experimental Investigations On Springback And Geometrical Profile Of ISF

Incremental sheet forming(ISF)is a dieless and flexible manufacturing technology,which has great potential to be widely used in producing low batches and multi-types metal sheet parts.This technology can significantly improve forming ability of metal sheets compared to conventional stamping.At present,double side incremental forming(DSIF)is an attractive research field due to its enhanced flexibility of local control by synchro motion of master tool and slave tool,so it can be used to fabricate parts with complex shapes including convex and concave features.With the support of National Natural Science Foundation of China(51675332),this work focused on study of springback in DSIF of single-layer sheet and ISF of laminated sheets with numerical simulation and comparison analysis with experimental results.The achievements of this work have great significance on controlling springback in DSIF and revealing deformation characteristics in ISF of laminated sheets.The main conclusions of this research are drawn as follows:1.The numerical models of DSIF were designed using LS-Dyna and prediction of springback was made in DSIF of ellipsoidal sheet metal part.Two strategies to control springback in DSIF namely squeezing strategy and reverse bending strategy were simulated,and comparisons were made between influences of squeezing amount and reverse bending angle on the springback.The experimental results were well consistent with numerical simulation,and analysis of simulation results showed that springback of unclamping was smaller than that of trimming and the smallest value of final springback was got when reverse bending angle is 24°?2.The experiments of DSIF of laminated sheets were designed and implemented considering of material types,relative thickness,and stacking sequence of two layers.The research focused on both sheet thinning and contours compatibility of sheets.It was found that in DSIF of Al/Steel laminated sheets,the best contours compatibility could be acquired when the thickness of Al alloy sheet is larger than that of steel sheet and the steel sheet was placed on the upper laminate at the same time.3.Based on the experimental study,the numerical simulation model with LS-Dyna were designed and analyzed.To get results with accuracy,different types of FEM model elements including solid element and shell element have been analyzed,and the shell elements showed 41.1% better performance in springback prediction accuracy.Besides,it was found that in the DSIF of Al/Steel laminated sheets,when Al alloy sheet was placed on the upper laminate,a degree of 60% reduction in springback can be achieved.