Simulation And Experimental Study On Plastic Stretching Of TP304 Stainless Steel Capillary Under Pulsed Current Field

TP304 stainless steel capillary tube is widely used in medical equipment,micro-components and other fields because of its good low-temperature strength,corrosion resistance,surface smoothness,and hot workability.In order to meet the characteristics of high-volume and high-efficiency,enterprises often adopt cold stretching processes.However,in the process of capillary plastic drawing,due to the characteristics of microscopic size anisotropy,work hardening,etc.it is very easy to appear in the process of cold stretching,such as stress concentration and cause breaks,surface wrinkles,damage and other unfavorable factors,The pulse current with appropriate parameters during the stretching process can effectively improve the plastic deformation of the capillary,promote the dislocation slip process in the microscopic state,and prevent the tensile fracture caused by the local stress concentration.In this paper,the crystal plasticity finite element is used to simulate the microscopic state of the capillary tube under the pulse current field and the changes of stress-strain field,temperature field and electric field during the plastic stretching process.The initial sample adopts f 0.3×0.1mm TP304 stainless steel capillary produced by a certain factory.Based on the Fortran language,the user subroutine was developed in the Abaqus software,and the crystal plasticity constitutive equation based on the dislocation density under the pulse current field was proposed and the UMAT subroutine was written.The program realizes the finite element simulation of plastic stretching under the capillary pulse current field.The main content and conclusions of this article are as follows:The stress-strain curve,temperature and equivalent current density values of different current density,frequency,and stretching rate in the capillary electroplastic tensile experiment are compared.The pure electroplastic effect and Joule heating effect of the pulse current under different factors are separated,which provides a quantitative basis for determining the parameters of the crystal plasticity constitutive equation based on the dislocation density under the pulse current field.Based on the theory of crystal plasticity,the constitutive equation of crystal plasticity based on the dislocation density under the pulse current field is reconstructed and proposed.This constitutive is based on the evolution of the microscopic state under the multi-field coupling of thermoelectricity and force.The parameters of the constitutive equation are determined by fitting it with the stress-strain curve of the capillary overall tensile experiment in Chapter 3.After establishing the finite element model of plastic stretching under the pulse current field of TP304 stainless steel capillary and determining the simulation scheme,the stress-strain field,temperature field,electric field and Dislocation density field distribution cloud diagram and scatter pole diagram under different current density values and stretching rate conditions are output.Finally,the reasons for the changes of each output field under different conditions are compared and analyzed.