Abstract: The forming of barrel chamber is the key and difficult point in the radial forging process. The forming quality of inner wall of chamber is directly related to the accuracy and service life of barrel. The ring pattern on the inner wall is the main forming defect of chamber. The force characteristics and flow conditions of the inner wall of chamber during the radial forging process are analyzed. The forming causes of ring pattern defeact are analyzed from its forming position through finite element analysis and experiment, and the relevant judgment criteria for ring pattern are established. The stress analysis curves of inner wall material were compared with the forging experimental results of barrel. It is found that the generation of ring pattern is related to the instability of inner wall. When the tangential stress component of inner wall exceeds the critical value, the instability wrinkles appear. Further research show that the ring pattern on the inner wall is flattened in the subsequent forging process,and the defect of chamber can be eliminated when the forging ratio of forging section of chamber reaches the critical value. The results show that the tangential compressive stress of inner wall is more than 2 150 MPa during forging process, which leads to the instability of inner wall. When the forging ratio of forging section exceeds 28.5%, the ring pattern on the inner wall can be flattened. Key

Key words: precisionforgedchamber, innerwall, ringpattern, forming, wrinkle, defect, forgingratio