Problematics
T
he number of phases at deep drawing process is one of the basic parameters. The natural wish is to use a single phase process for all products, which is of course not possible. Each additional phase means more and more expenses (additional tools, a need for bigger presses, more cycles, more manpower etc.). For the presented case (picture on the right) our client planned a single phase, but several doubts arose if it will be at all possible to manufacture the product in a single phase.
Problematics of deep drawing:
- checking of manufacturability of deep drawing process on the criteria of wrinkling, thining and fracture of the blank
- setting of the technological window of good parameters
Solution
With an extensive analysis in Abaqus software we were able to come to the following results:
- selection of basic (density, young modulus, Poisson coefficient) and non-linear material data (logarythmic plastic strain curve, forming limit curve - figs 1 and 2) for prediction of plastic behaviour of blank and isolation of critical areas
- mathematical model of the process and meshing
- calculation of drawing and blank holder forces (figs 3 and 4)
- display of strains in several directions on highly stressed areas and checking of the forming limit criterion (fig. 5)
- thining analysis, which gives insight into areas of excessive thining of the blank (fig. 6)
All results indicate a safe and stable process without appearance of foreseen problems. The results were confirmed with a dedicated deep drawing analyses software package.
Benefits
- elimination of risks
- less tool trials - shorter time to market and lower costs
- technology check prior to tool production and up-front elimination of eventual problems and excessive costs
- use of true material data for further structural analyses with strain hardening taken into account - a very important aspect, used for a long time, enabling truly optimised products in terms of material usage and weight
Figure 1: An example of logarithmic stress-strain curve for sheet metal
Figure 2: Forming limit diagram (FLD)
Figure 3: Blank holder force
Figure 4: Drawing force
Figure 5: The results of forming limit criterion
Figure 6: Thinning
