The application of acoustic emission signal analysis for characterization of sheet metal forming operations is discussed in this paper. Two particular sheet metal forming operations are examined: punch stretching and deep drawing. The acoustic emission signal characteristics, including the energy content, the spectral properties, and time series behaviors, as functions of the process state, are experimentally studied. Using plastic work analysis, an analytical relationship between acoustic emission energy rate and punch stretching parameters (punch feed rate, workpiece thickness, punch size, holder diameter, amount of plastic deformation, and workpiece material properties) is developed and supporting experimental results presented. During the forming processes, acoustic emission signal features show strong correlations with punch/workpiece contact, yielding, deformation, flange wrinkling, necking and fracture. Therefore, acoustic emission can be effectively used for in-process monitoring of sheet metal forming operations.

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