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Topics related to LS-DYNA, Autodyn, Explicit STR and more.

Base ball deformation study using explicit analysis

    • Muhammad Tahir Faris
      Subscriber

      Hope you are well. I need some guidance. I am performing explicit analyse on base ball bat and base ball. But I am unable  ball is also not moving forward to the bat. Please guide me with the steps. It would be great help. I was following time integration lesson of ansys, but this simulation is not sloved completly thats why i am having trouble following to replicate. Please guide thanks alot.

       

      For simulation bat is moving 10 degree for that i used remote displacement but the ball is stand still and results are also wrong. I guess because not interaction is there between ball and bat. below is snap shot.

       

    • peteroznewman
      Subscriber

      "the bat is moving 10 degrees"

      1. over what time interval?
      2. about what axis of rotation?
      3. what is the distance of the tip of the bat to the axis of rotation?
      4. what is the initial velocity of the ball?
      5. what is the End Time for this simulation?

       

    • Muhammad Tahir Faris
      Subscriber

      Bat is moving 10 degree.

      Axis of rotation is X-axis 

      Initial velocity of ball is 10m/s 

      End Time is 1e-002.

      The ball is not moving at all. I have changed the speed as well but ball is stand still its not interacting with bat

    • peteroznewman
      Subscriber

      Use File Archive to save a .wbpz file and put that on Google Drive or OneDrive or the like. Paste the link in your reply. Then I can download the archive and take a look.

    • Muhammad Tahir Faris
      Subscriber

      okay

       

    • Muhammad Tahir Faris
      Subscriber
    • peteroznewman
      Subscriber

      Pay attention to the file extension! You uploaded a .wbpj file. That file is not useful to me.  I requested you upload a .wbpz file.  Do you see the z on the end? That is the file I need.  You won't have a file like that until you use Workbench and use the File Archive menu and complete the saving.

    • Muhammad Tahir Faris
      Subscriber

      sorry. let me share other file

       

    • Muhammad Tahir Faris
      Subscriber

       

       

       

    • Muhammad Tahir Faris
      Subscriber

      please check is it oky? or should I send you other file

       

    • Muhammad Tahir Faris
      Subscriber

      I am trying to solve it since 4 days ? and unable to correctly solve it.

    • peteroznewman
      Subscriber

      The reason the bat doesn't hit the ball is because it is rotating about the center of the yellow circle and you can see that the bat can't reach the ball. Even if you move the center of rotation to the end of the bat handle, it still won't reach the ball.  You will have to move the center of rotation even further to the right so that a circle will reach the ball. 

    • peteroznewman
      Subscriber

      Even if you move the rotation of the bat to a coordinate that is 2000 mm, a 10 degree angle is insufficient to reach the ball.

      Fix those two problems and the bat will hit the ball.

    • Muhammad Tahir Faris
      Subscriber
      I dont know how to fix it. I am new user can you help me in it. can you change this settle and share the file
    • Muhammad Tahir Faris
      Subscriber
      why ball dont move forward? It is also given a speed of 10m/s in forward direction
    • peteroznewman
      Subscriber

      Click on the Remote Displacement, and change the Z coordinate to -2000 mm or 2 m depending on your current units setting.  Change the 10 degrees to 20 degrees.

      If you want to see the ball get struck by the bat, click on Analysis Settings and in the Output Controls section, change the Result Number of Points to 1000 then Solve.

      On the Animation player control, click on the Result Set button (red circle), then click Play.

    • peteroznewman
      Subscriber

      The ball is moving forward at 10 mm/s.  Change your Units to meters and type in 10 and Solve.

    • Muhammad Tahir Faris
      Subscriber
      please share your file in achieve
    • Muhammad Tahir Faris
      Subscriber
      I also want to assign the hyperplastic material but when I select it from Engineering data. my simulation gives error please guide me for that as well. it say some of properties are missing
    • peteroznewman
      Subscriber

      Which exact material property do you want to use? 

      What are the values you want to use for the material constants?

    • Muhammad Tahir Faris
      Subscriber

      I went to Hyperelasticity and chose Elastomer Sample (Ogden) but in simulation it gives error.I havent added any material constant I just used library material

       

    • Muhammad Tahir Faris
      Subscriber

      result of things are working know. Thanks alot sir. I want to study the deformation of hyperelastic baseball at the time of contact. what option should is chose for studying contact force at the time of impact. and velocity of ball after contact.

    • peteroznewman
      Subscriber

      You opened a material that only has experimental data. This material is used for learning to fit hyperelastic material constants to experimental data. It is not a material that is ready to use. 

      If you want to find a material that provides the material constants, use the Explicit Materials data source, scroll down to Rubber 2 and click the + sign to add it to your model.

    • Muhammad Tahir Faris
      Subscriber

      With this ball just smashed. For ball to behave realistic what material should I used. with rubber 2. it was smashed 

    • peteroznewman
      Subscriber

      Wasn't that fun!

      The ball smashed because the Erosion Control setting for Explicit Dynamics was set to remove elements that had a Geometric Strain value greater than 1.5.  Change the Yes to a No and that won't happen.

    • Muhammad Tahir Faris
      Subscriber

      and how to measure the contact force between ball and bat and the ball exite velocity when it leaves the bat

    • peteroznewman
      Subscriber

      Note that when you changed 10 degrees of rotation to 20 degrees, you doubled the velocity of the bat.

      Use the Body filter and select the ball then insert a result Deformation > Directional Velocity. Set the direction to the Y axis.

      Here is a post about Contact Force vs Time. 

    • Muhammad Tahir Faris
      Subscriber

      Isnot the deformation unrealistic it is deforming the ball 100% but in reality it deform less then 50% how to correct that?

    • peteroznewman
      Subscriber

      Change the hyperelastic material properties to increase the stiffness of the ball.

      Where is the link to the lesson?

    • Muhammad Tahir Faris
      Subscriber

      Oky

    • peteroznewman
      Subscriber

      The contact force looks much better with a stiffer rubber.

    • Muhammad Tahir Faris
      Subscriber

      what values you used to increase stiffnness?

    • peteroznewman
      Subscriber

      I increased Material Constant C10 by a factor of 100.

    • Muhammad Tahir Faris
      Subscriber

      I have increased by factor of 1000 but still deformation is high. Can you please guide me how in lecture they have used hyperelastic material and replicate all that? I will be great help sir.

    • peteroznewman
      Subscriber

      I don't know which part of the course you are trying to replicate.

      Deformation is the distance of the node from its initial position to its current position. Wait a second and the deformation will be measured in meters!

      During the impact of the ball and the bat, you can measure the deformation of the ball relative to itself by plotting Strain instead of Deformation.  The strain of the ball is zero as it flys toward the bat, though the deformation of the ball is increasing.

    • Muhammad Tahir Faris
      Subscriber

      Thanks alot peter. It helped me great. I had it all now. Can you please guide my which lesson should i follow to enhance my knowledge into explicit study. Beacuse I still have less knowledge in side of analysis setting like how to check step size what is best end time all that. Is my mesh right or not. And please also teach me how you activated the path after giving 20' degree rotation that circular path. I am trying to activate it but unsuccessful.

       

      Loads of thanks at the end peter. You r the best man 

       

    • peteroznewman
      Subscriber

      The best way to learn is to keep building different models. 

      Read the Autodyn User's Manual in the ANSYS Help system for more information.
      https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/wb_adyn/wb_adyn.html

      Read this topic about meshing for Explicit Dynamics.

      I changed the Z coordinate of the Remote Displacement to make the bat swing about a center that would reach the ball.

      Good Luck!

    • Muhammad Tahir Faris
      Subscriber

      I have change and got result I am just asking about the circle in image how you got them active. When you change this remote displacement to 2000 and before as well. In both image I can see the path of rotation kv bat

    • peteroznewman
      Subscriber

      I took a screen snapshoot of Mechanical, pasted that image into PowerPoint, and used the drawing tools in PowerPoint to draw the circle on the image.

    • Muhammad Tahir Faris
      Subscriber

      Okay, Thanks alot mate ?

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