# rzmehdipour

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1. ## Inconsistency in results of symmetric problem

Hi all. I sent a message in HyperForm section but as I did not get any response I repeat it here because this is a forming simulation by RADIOSS. Please take a look at following link and help me in this regard. Thanks in advance.
2. ## Simulation results interpretation

Hi all, For a multi stage cylindrical deep drawing simulation I used a quarter of whole model to speed up the process. Attached is the final frame of 6th stage. In this photo I have used symmetry to show the complete model. As you see just on symmetry planes (xz and yz) there are some inconsistencies for thickness which are apparently different from other areas. As this is an axisymmetric model and I have chosen DDQ as material, is this computational error or what? In DDQ properties r0=r45=r90=1.5 so this can not be related to anisotropy and rolling direction. I have used HyperForm's Multistage and as I have modeled a quarter of whole system in positive X and Y, I defined Blank symmetry : -X -Y. It has fixed DOFs 156 for nodes on YZ plane and DOFs 246 for nodes on XZ plane which is correct. Look to hear your opinions. Thanks in advance.

4. ## Forming Setup

Hi. It seems there is a tool design mistake. As this is the first drawing stage, punch diameter must be considered at least 50% of blank diameter. Of course this depends on material, but %50 is a maximum value for draw reduction when drawing CRDQ steel. For other materials punch diameter must be larger than this. For next drawing stages, draw reduction is much smaller than this. Any way it seems in this clip that punch size is smaller than what it should be. This will cause the material not to flow properly and will end with failure.
5. ## Axisymmetric forming simulation

Hi all, Is it possible to simulate axisymmetric forming process in Hyperform by defining a section-cut of tool components and part using 1-D or 2-D elements? For example for cylindrical deep drawing, tube endforming and the same. Thanks in advance.
6. ## Permissible values for thickness in Topology optimization

Thanks again. In fact I don't have any previous experience in size optimization. It seems I have to try it.
7. ## Permissible values for thickness in Topology optimization

Thank you very much. By setting DISCRETE to 3 result was much better than the original one and was OK for me. But generally it would be useful if ALTAIR developers make it possible for user to define desired thickness steps for such optimization problems.
8. ## Permissible values for thickness in Topology optimization

Hi there, I wanted to know if it's possible to define thickness steps when performing topology optimization using Optistruct. For example assume there is a body of PSHELL elements, Initial thickness is 10 and base thickness is 2.5 and between these two values only 6 is permissible. Or in another case only 8.5 and 2.5 are possible for final part. How can I go with this kind of problems? The real problem is to decrease some deflections of sheet metal parts by adding welded patches so thickness in different regions can not be any value. For example if initial thickness is 2.5 mm then I want to improve strength by only welding some 6 mm thickness patches to it so optimization output must be only 2.5 and 8.5 mm thickness. Please let me know if my question is not clear. Thanks in advance.

Thanks a lot
10. ## FLD and rolling direction

Thanks again. You're right. But physically material does not act according to average values, but real ones. I mean in real world material will behave differently in different directions. So how can we consider rolling direction in simulations? Sometimes considering rolling direction is quite necessary in first forming stage and forming the sheet in wrong direction will cause failure.
11. ## FLD and rolling direction

Thanks for your reply but my question is : As formability is not the same in different directions (relative to rolling one), how is it possible to predict the result without specifying rolling direction on raw material. Is there any default direction for rolling?
12. ## FLD and rolling direction

Hi all, 1- As sheet metal resistance to thinning is not the same in different directions (which is the subject of Lankford coefficients), how can we define FLD curve without considering rolling direction? 2- In Radioss one-step forming simulation in which we define r0, r45 and r90 during material definition, is there a pre-defined sheet rolling direction? Is it X axis or what? Thanks in advance.
13. ## Springback and rolling direction

Hi all, I wanted to know if actual springback after forming depends on sheet rolling direction. As anisotropy coefficients (r0, r45 and r90) affect thickness reduction, I think they must be important in springback analysis but during routine process (as defined in related tutorial) which is performing springback analysis following an incremental forming simulation, they are ignored at all. Am I wrong? Thanks in advance.
14. ## FLD or thickness reduction?

And you made me another question. Can we compare thickness reduction percentage from simulation with max permissible elongation of material? I think the latter one is from one-directional tensile test while the first in resulted from complex loading state. I mean as it is apparent from FLC, permissible major strain can be higher when there is minor strain and it seems it can be even higher than max elongation of the material. Am I right?
15. ## FLD or thickness reduction?

Dear kpavan, Thank you very much for your reply. Let me tell you that I have used tensile test results to define the material in simulation. I mean I have entered stress-strain data to define the material. As for max elongation, in fact it is very marginal in some regions at third forming stage (both material and simulation results are about 25%). In forming stages 1 and 2 I have used blank holder but stage three is a crash forming process. So my question is while thickness reduction from simulation is acceptable, why FLD shows failure in some regions. Are thicknesses from simulation unreal? Or do I have to define some properties of material other than stress-strain curve? Thanks in advance
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