LIMIT STRAINS OF ANISOTROPIC AND SUPERPLASTIC SHEET METAL FORMING

摘要

A study of stretch forming and deep drawing of sheet metals, analysing its parameters, the diagrams of limit strains and fracture strains DLC and DLF, the limit strain and fracture strain theories in sheet metal, features of the actual engineering practice and its costs is presented in the present work. Various theories of the limit strains are reviewed and some experimental results from new processes and high performance materials are discussed from the point of view of the plastic anisotropy and the theory of plasticity. The main characteristics of the sheet metal forming processes are identified and are based in the press shop practice. The main objectives of the sheet metal forming industries in optimising this fabrication process is presented. The principal characteristics of a trustful software of numerical simulation of the drawing process are analysed considering the actual tendency to use software in the design of stamping dies and process analysis. A new approach to the influence of geometric and material defects in the limit strains of sheet metals are done using the strain gradient model that produces the local necking. As a result of the analysis, the definition of new concept is presented : the equivalent defect parameter. The limit strains are obtained using a software developed by the author.