Research On Rules Of Rib Cavity Fill And Defects Of Web-rib Parts

In recent years, with the new type aircrafts, missiles, ships and automobiles developing to be small, lightweight, precision, high performance and low-cost, thin-web, high-rib parts are favored because of its light weight and small footprint. With the web-rib parts used more and more widely, finding a processing method which can guarantee performance, save costs and improve production efficiency is an urgent problem to be solved. Owing to the complex shape, bad degree of cavity filling and large forming load, such parts are difficult to be formed by traditional technology. Isothermal precision forging technology provides an important forming way for these parts. In order to get large-scale thin-web high-rib parts with accuracy control, metal flow law and defects formation mechanism during the isothermal forging process must be revealed.In this paper, double-web-rib and cross-web-rib components models with typical web-rib structures are designed. Research on isothermal forging process of LD10 aluminum alloy web-rib parts are performed by experiment and rigid-plastic FEM, and the metal filling behavior and defects formation mechanism are analyzed. The results show that the forming process of cross-web-rib parts can be divided into the initial stage, the cavity filling stage and the flash forming phase. Deformation region can be divided by regional stress-strain trend. During the isothermal forming process of cross-web-rib parts, metal in the cross-point position fills in fastest, metal in the edge fills inward due to the friction and finally performs as a concave because of the lack of metal. A larger radius should be chosen with meeting the design requirements. Draft angle increases, the cavity filling degree increases first and then decreases while the forming load increases first and then decreases, which all has a peak value. The larger the offset distance of cross-web-rib is, the more obvious the metal filling rate difference is in the web and rib cavities, the more different the filling degree is in the long ribs and the short ribs and the greater the possibility of folding is.For double-web-rib parts, the smaller the radius is, the more rapidly the metal turns the corner when fills the cavity, the more uneven the final distribution of the metal flow in the corner is, the larger the upper-web metal deforms, which make the folding occur more easily. The larger the radius is, the larger the under- web metal deforms, the smoother the metal flow line is. Distance between the ribs increases, the maximum deformation area moves outward, the horizontal flow of metal is more obvious in forming late, the breaking of rib occurs more easily.The folding evolution mechanism of double-web-rib parts and cross-web-rib parts is analyzed, back pressure forming method and pre-forging method are designed for preventing the folding defects of cross-web-rib parts. These methods are verified to control the metal flow behavior and prevent the folding defects effectively by numerical simulations and experiments.