Trends in the Development of Machinery and Associated Technology ” TMT 2010 , Mediterranean Cruise , 11-18 September 2010 EXPERIMENTAL DETERMINATION OF FORMING LIMIT DIAGRAM
Forming limit diagrams (FLDs) are a convenient and often used tool for the classification of the formability and for the evaluation of the forming process of sheet materials. Forming limits of sheet metal are represented in the forming limit diagram (FLD) occurring by various deformation states. The paper introduces a experiment method for determination of forming limit curve for whole range of the FLD for sheet metal.
PREDICTION OF MATERIAL NECKING IN DIGITAL ENVIRONMENT
Modern production which is based on metal forming tends to the increased analysis of forming processes in digital environment before the actual production set-up. For all these activities, the quality input data of used material is necessary. Simulations of sheet metal forming demand the input data of friction between the analysed objects, flow curve, yield point, material's anisotropy as well as the level and the course of a forming limit curve. Some aspects of predicting the forming limit diagrams in digital environment are discussed in this paper in order to omit expensive and time consuming experimental work. Improved method of numerical determination of FLD’s in digital environment based on the spatial and time determination of material necking is presented. Influential parameters of Marciniak testing procedure such as the coefficient of friction, mesh size and sampling rate of data acquisition in digital environment have been analysed as well.
Determination of the Forming Limit Diagrams Using Image Analysis by the Corelation Method
Abstract This paper deals with a new method of strain measurement applied to the experimental determination of the forming limit diagrams of thin steel sheets. This method uses the correlation technique to determine the displacement field between two images taken on the same area of the sample at two different strain levels. The strains are calculated from this field. The range of strains determined between two images may be very wide. This allows to compare the initial image to one before the sample fracture or two successive images during the straining. This method shows that the strain localization may occur early during the forming process and so the onset of localized necking is not a sudden phenomenon. A method is proposed to draw the forming limit diagrams for necking.