Study On The Blank Hold Force In Curved Surface Parts Deep Drawing

The curved surface parts account for a considerable proportion of the deep drawings. Thespherical parts are the typical curved surface ones. The research on force analysis in theforming procedure, deformative characteristics, deformative law and forming technologiesprovides the engineering practical theoretical basis as well as predicted design method for theimprovement of products quality and processing efficiency of curved surface parts. It’s also ofgreat significance to the development of deep drawing theory and production practice ofspherical parts. Predicted forming defects, optimized forming parameters, reducedmanufacturing cost, together with improved products quality can be achieved by means of thecomputer numerical simulation technology in the sheet metal forming procedure.Both wrinkling and crack are the main defects in the deep drawing of curved surfaceparts. With spherical parts as the main research subject, This paper builds a reasonablemechanical model to make force analysis, thereby getting the stress and strain characteristicsas well as possible forming defects of flange region, non-support region, and the contactregion between punch and sheet metal. To add the plane blank holder plate is the simplest andfeasible approach for defects prevention. A finite element numeric simulation model is built tomainly simulate and study the forming of spherical parts when the shapes of the holder plateand blank are square and circular respectively. The result shows that the forming of the squareblank under circular holder plate is the best. Then, A conclusion for square blank, that thevariable∧loading mode, the right combination of constant loading or variable∧loadingunder segment blank holder plate is best for spherical parts’ forming, is got by the simulationand study of the loading magnitudes and different modes of the blank holder force, whichinclude constant, variable linear increasing, linear decreasing,∧,∨, step increasing, stepdecreasing, segment blank holder plate constant combinations and variable combinations ofblank holder force loading modes. Finally, This paper simulates and studies the impacts of themain technological forming parameters for square blank, the blank’s relative thickness, thenormal anisotropy coefficient, and the frictional coefficient. We come to a conclusion that theblank is more likely to wrinkling and crack with smaller relative thickness. The smaller the normal anisotropy coefficient is, the more likely the sheet metal is to become thicker orthinner.The increase of the frictional coefficient may also lead to the decrease of critical blankhold force to prevent inner-wrinkle.