Learning Forum

[Daniel Miano]

I am doing the Course: "Modeling a Bolted Pressure Vessel Using Ansys Mechanical". I was able to run the initial design, but after changing the bolt diameter parameter I got an error near the end.  It said I exceeded the numerical problem size limits (screenshot below). I'm using a student license. I'm assuming this course/model was intended to be used on the student license. Does anyone know what the issue is?   I deleted the parameter to modify the bolt diameter and tried to run the initial model that originally worked and I still get the same error.  

Thanks,

Dan

[Ashish Khemka]

Hi Dan,

Did you follow the steps as indicated in the course and see this error? Please comment.

Regards,

Ashish Khemka

[Daniel Miano]

HI Ashish,

 

To my knowledge I followed the steps as indicated.  The number of nodes and number of elements are under 128k.  Do the combined number of nodes and elements need to be under 128k, or each need to be under 128k?

[mjmiddle]

Check the nunber of nodes and elements under the statistics in the details of the mesh object in the Outline.

Student problem size limitation are discussed here:

/forum/forums/topic/limitations-to-student-license/

"In a Structural model you add the number of elements to the number of nodes in the mesh, the sum should be less than 32k.  That is more strictly enforced and sometimes, the solver goes off and creates a lot of contact elements and refuses to run because the additional elements created push the model over the 32k limit even though the mesh you see in Mechanical was < 32k."

I can't confirm exactly the 32k limit discussed in that forum post except when using SPEOS. The structural limit looks to be 128K nodes/elements:

https://www.ansys.com/academic/students/ansys-student

[Daniel Miano]

Thanks.  The node count is 125,531 and the element count is 26,233.  That adds to more than 128k so I'm guessing that's the problem.  My Mesh looks exactly like the video and I double checked my element size, so I'm wondering if this model was not verified to run on the Student version?

 

[Daniel Miano]

 

I removed part of the vessel and changed the fixed support to the surface around the green circle in the image below. Now the total nodes + elements = 114,991 and I get the same error.

Then I changed the element size to 0.7mm and now the nodes = 36,635 / elements =  8,162. This model runs, but I had to increase the element size larger than the tutorial instructions (0.5mm)

 

[mjmiddle]

Yes, you made the mesh coarser. Keep in mind there are contact elements not seen in Ansys that add to the count, and that would be why your 115K mesh still wouldn't run. These are only produced as it writes the APDL input file for the solver. You could open the ds.dat in the soluton directory to see these elements, but you have to study the format of the file a bit to understand it.

It appears the Innovation Course examples were not all thoroughly tested to run on the Ansys Student version.

[Ashish Khemka]

Hi Dan,

We will look into this model.

Regards,

Ashish Khemka