Influence of strain history on limit formability in metal forming

Abstract

The paper gives definitions and explanations about forming limits for bulk metal forming and sheet metal forming. The significance of stress state and strain history for limit strains realization is emphasized above all. For the case of upsetting, indicators in the system of principle surface strains are specified, as well as classic example of FLD, as a dependence of limit strain on stress ratio coefficient. For the case of sheet metal forming – deep drawing, the example of determining FLD at classic and two-phase - proportional forming – is shown. The specified experimental results are related to the area of biaxial tension-stretching and the area of pure deep drawing of axis-symmetrical pieces.