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Complex Loading Sequence with Contact

Hello,

I try to simulate a high detailed model of a screw with OptiStruct. Currently the screw will be pretensioned with the pretension function and in the next LoadStep it will be rotated. Now in the following LoadSteps i want to add enforced displacements on the Contact Surface of the screw head. My main problem is the sequence with the enforced displacements. How can every single Loadstep use the results of the previous Loadstep (Stress, Displacement, Contact...)? For the pretension Loadstep i use the function STATSUB(PRETENS), but i dont know if the displacements will be freezed for the next Loadstep and i use CNTNLSUB to consider the contact.

The next poblem is, how can i enable/disable contacts between severally LoadSteps without using MODCHG (Older Version of OptiStruct than 14.210)?

Thanks!

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Altair Forum User

Hi @Kaali,

Maybe this comment from help can answer your 1st Question:

5.If displacement boundary conditions specified by non-zero SPC or SPCD’s which exist in preceding subcase (say, Subcase 1) are removed in the subsequent nonlinear subcase (say, Subcase 2), then the SPC force resulting from non-zero SPC or SPCD in Subcase 1 would be gradually ramped down to zero in Subcase 2.

I will check if there is any workaround to disable contacts without using MODCHG.

Altair Forum User

Hi Prakash,

thank you for your answer. In the last Days I tried a lot of different models. I only can use the preceding displacements, if i use NLGEOM instead of NLSTAT as Type for the Non-Linear Quasi-Static subcase. But how can i set different SPC's in combination with/without Nload? For Example i want to Push down the blue part in the first sbcase with a force. In the second subcase i want to freeze the vertical displacements of the first subcase and translate the blue part along the part beneath.

Thanks!

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Altair Forum User

Hi Kaali,

If the loading is a continuation sequence, you can use CNTNLSUB card to continue the Non-linear subcase where it stopped.

So in first subcase you have a set of SPCs and loads and in second subcase you have another set but the deformation will be carried to the second. The end of 1st subcase will be the beginning of second subcase