I have simulated 2D deep drawing process using Abaqus software. I got the result for deformed cup output.In the output contour result, the maximum value of PEEQ is indicated in the Die corner Radius portion and the thinning is maximum at the Punch corner radius. I referred many journals in that the maximum PEEQ value is occurred in the maximum thinning area. But I got the results in different way,what is the exact solution for this.If there is any chance for error in my simulation.Please give your valuable suggestions.
Thank you,
with regards,
M.Subramanian
Hello Bala, I guess you carried out an 2D Rotation symmetric Simulation of an cylindrical metal part, right? You model the process with a punch, a drawing ring and a die, yes? You found in your simulation, that the max. of the equivalent strain occurs at the outer part towards the die Corner radius and the Maximum thining at the inner part side at the Punch Corner radius? The typical underlying failure is the cup base fracture. In Cup drawing the base is continuously punshed down and here the material is under tensile load throughout the process without material flowing in from the outer regions of the circular blank when passing through the drawing ring. So it is clear, this Region is continuously thinning until eventually the Cup fracture occurs. The material for the continuous shape change in this plastic forming need to come either from the upper regions where the material is drawn through the drawing ring and/or from the cup base Region. As the Cup base Region of the part is thinning the stresses are increasing and, exceeding the strain hardening stress Levels, the thinning continues. So what about the difference you observed. First of all the max. equivalent strain PEEQ is a combined value of all strain components following classical metal (Mises) plasticity (no sign effect). The max. thinning represents only the largest value respectively the place where this value occurs. Hence Your max. PEEK value can be larger, due to longitudinal and transversal strain components and tensile and compressive strain Tensor elements will contribute all by their absolute (positive) values. Friction at the inner, punch side of the part can be slightly higher due to local contact conditions than at the outer, die side which would lead to slightly different values. The thinning refers to the local thickness of the drawn part. Here the questions is, from where you will Count / calculate it? What is the reference for the calculation? Therefore it may appear in your simulations that the max. PEEK is found at the outside Cup base Corner Region while the max. thinning occurs on the inner side. If I didn't misunderstand / misinterpreted your discription there is no contradiction between your results and the literature Statements. If this doesn't answer your Problem you may load up Pictures of the different results.
Hi dear researcher, You can use PEEQ as a bursting criteria. There is no special common criterion for bursting. Based on your material properties (Isotropic or anisotropic), you should select the proper criteria for blank tearing. For more information see "Investigation of hydrodynamic deep drawing
for conical–cylindrical cups"
Warm Regards
SIR PLEASE REFER THIS JOURNAL -Influences of material parameters on deep drawing of thin-walled hemispheric surface part
Indeed, these two quantities are independent. PEEQ stands for the equivalent plastic strain, while thinning is the strain component in the thickness direction (it is also one of the principal strain components if through-thickness shear is negligible - e.g. with shells). So, you also need the in-plane strains to be able to relate equivalent strain and thinning! Thus you may have any combination of PEEQ and thinning for various loading modes. At punch radius the loading mode is plane strain, while at the cup edge you are in uniaxial compression. The results that you describe, if they refer to cylindrical cup drawing, then they are consistent - there is no error.
BTW, none of these should be used as a failure criterion in sheet metal forming. Use the FLD for regular industrial application, and some necking models for more advanced analysis.
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