Research On The Deformation Inhomogeneity Of The Barrel And The Rifling In The Same Forging Wall Thickness Direction

In the process of barrel forging,the uniformity of deformation in the direction of wall thickness is an important index to evaluate the quality of barrel forming.In order to produce a better performance barrel,it is necessary to study the material deformation inhomogeneity in the direction of barrel wall thickness.This article takes a certain type of automatic rifle barrel as the research object,and carries out the following research.The symmetrical finite element model of the radial forging of the barrel is established by using the finite element software ABAQUS.The accuracy of the two-dimensional axisymmetric model is verified by comparing the stress distribution state calculated by the three-dimensional precision forging model and the measured value of the forging pressure of the hammer head.According to the model,the equivalent plastic strain and shear stress state of the wall thickness in the process of precision forging are analyzed in detail.The results show that after precision forging,there are obvious deformation inhomogeneity in the direction of barrel wall thickness,which is caused by two main reasons.One is that the equivalent plastic strain in the direction of barrel forging forming area is not consistent,which results in different hardening degree of materials.The second is that in the radial forging process,there is a large shear stress in the middle layer and the outer layer of the barrel wall thickness direction,and the shear stress will form a shear texture,thus weakening the strength performance of the material.Based on the above analysis results,the influence of process parameters on the equivalent plastic strain in the wall thickness direction and the shear stress distribution in the middle layer is further analyzed by single variable method.In order to improve the non-uniformity of the deformation in the direction of the wall thickness of the barrel after forging,the average equivalent plastic strain fluctuation coefficient ? and the average shear stress fluctuation degree ? are taken as the evaluation indexes,and the optimal forging process scheme is obtained by combining the orthogonal test design,grey correlation analysis and principal component analysis.In order to accurately evaluate the influence of precision forging process on the mechanical properties of the barrel in the direction of wall thickness,standard tensile test and self-designed transverse bulging test were used to measure the longitudinal and transverse mechanical properties of the barrel materials,and it was found that the mechanical properties of the barrel in the direction of wall thickness before and after forging were compared.After forging,there is obvious mechanical property gradient in the direction of the wall thickness of the barrel.The strength shows that the value of the outer layer is the largest,the value of the middle layer and the inner layer is lower,and the elongation shows that the value of the inner layer is significantly lower than that of the middle layer and the outer layer.After stress relief,the mechanical properties of the barrel material are recovered,but the recovery of the transverse elongation is not obvious,and the mechanical properties of each layer are still different,and the distribution law is similar to that before stress relief.In order to further analyze the influence of forging deformation inhomogeneity on the service performance of the barrel,the influence of residual stress on the radial dimension accuracy of the barrel caused by the deformation inhomogeneity in the direction of the barrel wall thickness is obtained through a large number of simulations.Besides,the dynamic response of the barrel with residual stress under the action of bore pressure is established,and the influence rule of residual stress on the dynamic stress in the direction of the barrel wall thickness is analyzed.