Study On The Forming Characteristics Of Natural Bulging Area Of Tube Under Liquid Impact Forming

Tube hydroforming technology based on structural lightweight and integration is now widely used in various fields.The technology takes the tube as the blank,bulges the tube into the desired shape under the combined action of liquid pressure and axial load.But it must rely on the high pressure hydraulic power source and the corresponding control system,which has the disadvantages of high manufacturing cost and low forming efficiency.Liquid Impact Forming is a new tube forming technology developed on the basis of stamping and hydraulic bulging.By changing the volume of tube cavity by impact load,the liquid pressure can be rapidly increased.This technology does not need high pressure hydraulic power source,and has high forming efficiency and certain research value.At present,many scholars have made some achievements in the study of tube clamping area in Liquid Impact Forming,but there is a lack of research on tube natural bulging area under Liquid Impact Forming.Therefore,based on the forming characteristics of tube natural bulging area under Liquid Impact Forming,the following research is carried out in this paper:(1)Theoretical analysis of mechanical behavior of clamping area and natural bulging area of tube under Liquid Impact Forming.Based on material mechanics and other systems,the stress conditions of the clamping area and the natural bulging area of the tube in the forming process are analyzed,and the relevant mechanical equilibrium formula is obtained,as well as the mathematical model of the fluid pressure and the volume change of the cavity.According to the theory of elastoplastic mechanics,the stress and strain in the natural bulging area of the tube are analyzed,and the mathematical model of stress-strain and liquid pressure,as well as the mathematical model of residual contact pressure are all obtained.(2)Numerical simulation and analysis of mechanical behavior of natural bulging area of tube under Liquid Impact Forming.This article systematically introduces the numerical simulation method of ANSYS and DYNAFORM.The liquid pressure curves under different load parameters are obtained by ANSYS.It is found that the limit liquid pressure of AA6010single-layer tube is about 17 MPa.SS304 single-layer tube is not broken.The smaller the mold is,the greater the liquid pressure value is,and the liquid pressure has no obvious relation with the speed.Furthermore,the influence of different load parameters on the stress and strain in the natural bulging area of tubes is analyzed.(3)Analysis on the forming law of natural bulging area of tube under Liquid Impact Forming.Based on the obtained fluid pressure curve and DYNAFORM post-processing module,the influence of different load parameters on the bulging height and wall thickness distribution in the natural bulging area of the tube is studied,and the fracture situation of the tube is analyzed by the limit diagram of tube impact hydroforming.(4)Experimental study on Liquid Impact Forming of tubes.The Liquid Impact Forming test is carried out to measure the bulging height and wall thickness distribution in the natural bulging area of the tube after forming.By analyzing and discussing with the numerical simulation results,the forming characteristics of the natural bulging area under the Liquid Impact Forming of tube and the feasibility of this method are further verified.Based on the forming mechanism of tube under Liquid Impact Forming,the mechanical behavior and forming law of natural bulging region of tube are studied.The forming characteristics of the natural bulging area of tubes were studied by constructing the related mathematical model,and the forming characteristics of the natural bulging area of tubes are verified by numerical simulation and Liquid Impact Forming test,which laid the foundation for the subsequent development of the Liquid Impact Forming technology of tubes.