Research On Influence Of Hydraulic Pressure On Single Point Incremental Forming Accuracy

Single Point Incremental Forming(SPIF)is a technique of local dynamic loading and integral cumulative uneven deformation.The metal sheet is formed according to a preset forming trajectory to finally obtain the desired formed part.The technology has the advantages of small forming force,low energy consumption,low noise,etc.and can meet the needs of customers for diversification and rapid prototyping.However,due to the inherent characteristics of single point incremental forming,it is easy to cause defects such as low forming precision and low forming efficiency,which limit the wide application of this technology.This study intends to introduce Hydraulic pressure support into single point incremental forming technology and develop a new type of hydraulic Support Single Point Incremental Forming to overcome the inherentity defects of single point incremental moldless forming.The important focus of this study is the influence of hydraulic pressure support on the forming precision of the parts,thus the forming quality of the parts can be effectively improved.It has important theoretical and engineering practical significance.Based on the single point incremental forming principle of hydraulic support,the mechanical model of single point incremental forming of hydraulic support is established.The theoretical calculation formula of stress triaxiality and stress state softening coefficient of contact area is obtained by theoretical derivation,and the hydraulic analysis is analyzed.The influence mechanism of the pressure on the forming force.A three-dimensional solid finite element simulation model for hydraulic pressure support single point incremental forming is established.Through simulation analysis,the forming force,equivalent stress,equivalent plastic strain,residual stress,axial error and thickness reduction of the hydraulic pressure support during forming are obtained.The law of the influence of the thin rate is obtained.The special fixture and hydraulic system needed for hydraulic pressure support single point incremental forming were developed.The single point incremental forming experiment of hydraulic pressure support was carried out.Through the analysis of the surface roughness and surface topography of the workpiece,the hydraulic pressure parameters were obtained.The influence of forming precision and surface topography is verified by experiments.The Box-Behnken test design method(BBD)was used to design the hydraulic pressure support single point incremental forming test program.The influence of different process parameters on the axial error distribution was obtained through comprehensive tests.Therefore,the purpose of improving the precision of the workpiece can be achieved by the optimal combination of hydraulic pressure and process parameters.