Research On Internal Wrinkling And Forming Limit Of Strip Metal In-plane Bending Under Unequal Compressing

In-plane bending of strip metal under unequal compressing, using of the unequal plastic deformation, is an advanced plastic forming technology which can meet the demand of the advanced plastic processing. The internal wrinkling and the forming limit are the key problems urgently to be solved for research and development of the process. In this dissertation, the internal wrinkling and the forming limit of the process have been thoroughly investigated by using rigid-plastic FEM simulation combining with theoretical analysis and experiment. The new achievements made are as follows:A new wave function with more explicit physical meaning of internal wrinkling is established and a critical compressive stress equation is deduced by energy method A new criteria of internal wrinkling is developed, and combining with the FEM simulation system developed, the failure is studied. The result shows that the new failure criteria is reliable.The effects of the forming parameters on the internal wrinkling are analyzed b the new failure criteria combining with the FEM simulation system developed. The results show that the internal wrinkling is possible to occur with the decrease of the relative compression width, the relative compression thickness, or the strain-hardening exponent; the effect of the strength coefficient is very small; and the effect of the friction factor may be ignored. The results can serve as a significant guide to the design and optimization of the forming parameters.With the new failure criteria and the FEM simulation system, the databases of the forming limit and the forming parameters are established; the relationshipbetween forming results and parameters is established by using regression analysis The program for process parameters determination is developed, based on which th forming parameters can be decided rapidly and exactly. Used in the forming process,the result shows that the program is reliable and practical.The achievements of this study are important for the development of the advanced in-plane bending process and the unequal deformation theory.