General Mechanical

General Mechanical

Topics related to Mechanical Enterprise, Motion, Additive Print and more.

Simple Tension only Truss

    • learn13
      Subscriber

      Tension only link180 elements from beams within workbench v.19 are proving troublesome.


      I've attached a version I've attempted and was hoping for some pointers on what may be going wrong.


       

    • peteroznewman
      Subscriber

      One of several things that is wrong is you have many links along each line body. That doesn't work, especially for links in compression.


      To correct that, click on the Mesh branch in the Outline. In the Details window, for Element Size, where it says Default, type 400 inches and remesh. Now you will only have one link on each line body.


      In 19.2, you can change Beams to Links inside Mechanical without using APDL code, which is where you made the change.
      Change the Model Type to Link. (If you shift-click, you can do four at once).



      Not sure why you have Bonded Contact between the two cross-members. I expect that was automatically created by Workbench and you didn't notice it was there. You can suppress that if you don't want it.


      Another problem is you don't have sufficient constraints to have a Static solution. You have only one Fixed Support. You need another vertex to have a constraint in the X-Y plane. 


      I changed Displacement 2 to provide the four vertex corners a Z=0 constraint, while leaving all others free.
      To allow it so solve, I added an X=0 Displacement Support at the top left vertex.



      Did you confirm that your Mesh Edit merged 4 nodes?



      With all the above changes, and if I suppress your Command Object, the model solves.



      But if I unsuppress the Command Object, the code in it causes the Solver to fail.  Here is that code for other Community members to look at:



      • /gopr

      • allsel

      • *GET,maxsec,SECP,NUM,max,

      • *GET,maxetype,ETYP,0,NUM,max,


      • allsel

      • /prep7

      • esel,s,mat,,rope

      • *GET,xsec,SECP,matid,PROP,AREA,


      • ET,maxetype+1,180,,,1,

      • SECTYPE,maxsec+1,link,

      • SECDATA,xsec,

      • allsel


      • allsel

      • esel,s,mat,,rope

      • emodif,all,type,maxetype+1

      • emodif,all,SECNUM,maxsec+1

      • allsel

      • /nopr

      • /solu


      Here is the error message in the Solution Output


       *** ERROR ***                           CP =       0.609   TIME= 12:52:09
       The section number must be greater than zero.                          
        Line= *GET,xsec,SECP,matid,PROP,AREA,                                 
        The *GET command is ignored.                                           


      You can fix that and see if there are other errors in your code.


      Regards,
      Peter

    • learn13
      Subscriber

      @peteroznewman


      Thank you for your reply and your help. I have access to v.19.0 and am unable to change from beams to links without ADPL.


      With respect to the tension only aspect of the model, I found that it requires the large deformation definition to be turned on. 


       


      Additionally, the links below can be used by those in the future to get started should they run into similar difficulties.


      /forum/forums/topic/how-to-create-link180-element-in-tension-in-ansys-workbench/


      http://www.ansystips.com/2018/04/tension-only-link180.html


      https://www.sharcnet.ca/Software/Ansys/17.0/en-us/help/ans_elem/Hlp_E_LINK180.html

    • shehabi
      Subscriber

       


      I have tried the same Principles but unfortunately i always get a tension force in my link180. the file is attached below. i will be glad for any support.


       


      https://www.dropbox.com/s/1jihbfx5onrns74/balken%20%20seil.wbpj?dl=0

    • peteroznewman
      Subscriber

       @shehabi,


      Please start a New Discussion and take your content from the post above and paste it into the new discussion.


      The reason is you will own the new discussion, which means you will get automatically notified whenever anyone posts a reply.


      Right now, learn13 is getting notified of these replies to his discussion.


      Also, it's better if you can insert some images,but at this time, the site is having some technical difficulties and the insert image button is not working.

    • peteroznewman
      Subscriber

      @shehabi,


      You have put a .wbpj file in your dropbox. This file is useless on its own.  You need to save an Archive, which is a .wbpz file and put that in dropbox.


       

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