remote displacement static structural

Hi,

I'd like to receive your opinion about this topic: how can I apply two sequential remote displacement applied over the same body but with different displacements and point of application of the rotation? Basically I want that the body moves in two steps (or two different times) performing one displacement and one rotation about one point and a displacement and a rotation about another point.

I've tried to use the remote displacement tool creating two remote displacement one applied on a point for the first rotation giving the tabular data for the displacement and the other applied in a second point for the other rotation changing also the coordinates for the dispalcement. However when combining the two displacements the simulation doesn't behaves correctly. 

What can I do in order to make these two remote displaments act sequentially? is there a way to realize two successive displacements with rotations around different points? 

thank you for your time!

Comments

  • peteroznewmanpeteroznewman Member
    edited July 2019

    Please insert an image of the geometry, and indicate the two remote points and the axis of rotation.

    Are the remote displacements scoped to two separate faces of the body? Show which faces.

    Did you deactivate the second remote displacement during step 1?

    Did you deactivate the first remote displacement during step 2?

  • nylanyla Member
    edited July 2019

    this is the graph of the application of two remote displacements around different points

    Hi Peteroznewman, At the moment I can't post here any image so I will do my best to explain the situation.. I'm simulating the movement of a mandible when I apply these two rototranslations just to see how much is the movement of the mandible. I'm analyzing this movement on the sagittale plane that for me is YZ (Z is vertical, Y is backward) thus the two points have the X coordinate null and the rotation occurs around the X axis. The two remote displacements are scoped to the same face that is the teeth of the mandible. I don't know if it is correct to use two steps and I don't know how to link each other. I didn't deactivate the 2nd remote displacement during step 1 neither the first one during the 2nd displacment. I will try to do it tomorrow. So just to recap I have to insert 2 steps and during the firsy displacment when I set the tabular value for the displacements and the rotation I should start with 0,0,0 for coordinates and 0 for rotation then at step1 I insert the values for my first rototranslatoon and step 2 should be deactivated. Whilst regarding the second remote displacement I start always with 0,0,0 ,0 , then I deactivate step 1 and at step 2 I write the values of my second rototranslation? Exactly the values to be deactivated are the second rototranslation for my first remote displacement and the values of my first rototranslation for the second remote displacement? I hope to be clear.

    I've attached the image of the graph so you can observe that the problem occurs at substep 1.1 since the displacement starts from 0,6 while I want that it continues followinf the first displacement. I want a sequential movement, not two separated movements...

    Hope to be clear.

    Thank you for your kind advises!

  • peteroznewmanpeteroznewman Member
    edited July 2019

    Now that you have figured out how to insert an image, please reply with an image of the YZ plane so we can see the two points, labeled #1 and #2, and show the geometry they are attached to. Include information about the displacement of point #1 during step 1.  Obviously, point #2 moves during step 1, but you want to apply a displacement of point #2 from where it ended up after step #1. This can be done, I just want to try it out before I say how, to be sure it works.

    If you attach your .wbpz file, (File > Archive) after you reply, I can download and work with it. Say in your reply the release of Ansys you are using.

     

  • nylanyla Member
    edited July 2019

    Hi, 

    you can find attached all the images. As you can see I just want to get the secon displament starting form the end of the first one.

    thanks

    ..mandible in sagittal planefirst remote displacementsecond remote displacement (B point)total deformation

  • nylanyla Member
    edited July 2019

    Hi Peteroznewman,

    I'm working with Ansys 2019 R1.

    the second point is indipendent from the first one.

    Please if you have any idea give me a tip or suggest another command to be used..

    I can't upload here the file, so all the information is in the images and what I have previously said.

    Thank you!

  • peteroznewmanpeteroznewman Member
    edited July 2019

    Here is one solution, use a dummy body, put one General Joint between ground and the dummy body for making the first translation/rotation, put a second General Joint between the dummy body and the jawbone.

     

  • nylanyla Member
    edited July 2019

    Hi,

    thank you for your answear! I have some doubts about it. Please could you clear me what you mean by dummy body?

    is it a rectangle where two corners are my two points around which rotation occurs?

    in the details of the general joint there are a lot of settings. I've attached the image just to better understand...

    So:

    -free means that the body is able to move or rotates along that direction or around that axis, is it right?

    -the coordinate system is not the global coordinate system of my jaw, I'm not able to change it..

    -apply by remote attachement or direct?

    -regarding the body to be attached I should consider once the dumy body and then the teeth of mandible, is it right?

    -initial position unchanged?

    -stops what does it mean?

    Sorry for all these questions, but I hope to receive an answear..what about the remote displacement that I felt more confident about? there is no way to use that command?

    Thank you very much! 

    Best regards

    details of the general joint tool

     

  • peteroznewmanpeteroznewman Member
    edited July 2019

    -Please could you clear me what you mean by dummy body?

    You need to cascade two motions. This is accomplished by having an extra body that is present so that the first motion is applied between ground and the dummy body, which carries the jawbone with it for the ride. Then the displacements of the first joint remain constant during the second step when the second joint between the dummy body and the jawbone moves.

    -is it a rectangle where two corners are my two points around which rotation occurs?  Yes.

    -free means that the body is able to move or rotates along that direction or around that axis, is it right?

    Yes, and we move it with the joint load.

    -the coordinate system is not the global coordinate system of my jaw, I'm not able to change it.

    Expand the + sign under the joint, you will find the joint coordinate system, you can alter the orientation of that.

    -apply by remote attachment or direct?  Remote Attachment, read the ANSYS Help for details.

    -regarding the body to be attached I should consider once the dummy body and then the teeth of mandible, is it right?

    I made the dummy body rigid, you I can just pick a vertex. On the mandible, pick a few faces near the point on the rigid body.

    -initial position unchanged?  Yes.

    -stops what does it mean?

    If you leave a joint DOF Free, you can limit the range of motion. You don't need that because you are specifying the motion of the free DOF in a Joint Load.

    -what about the remote displacement that I felt more confident about? there is no way to use that command?

    Not that I have been able to figure out.

  • nylanyla Member
    edited July 2019

    Hi,

    first of all I really thank you for your time!

    then I've just finished to perform the procedure, I've got the desired movement, but I still have some questions for you and I will be grateful if you could solve these last doubts..

    - the first issue involves the construction of the rectangle.. I defined the two points but I didn't manage to create a rectangle by overlapping on the two edges, however I tried to be the more precise as possible to move my rectangle over those points. Then I've created a surface from that sketch and given a minimum thickness otherwise problems occurred. Do you think in this way it can be feasible? How should I have done in the right way?

    - Regarding the rototranslations I've specified in the connections the axes along which to move and the rotational axis, however as you can see from the picture it seems that only the first rototranslation occurs..why are the value of D,E and F 0? I noticed that you too got the same result. Moreover I had to define a translation at a time infact I have 6 "joint" in the analysis settings and I set the values of the second rototranslation as second step of course, right?

    -to achieve convergence I had to switch to large deflection maybe because the mandible is flexible (since I need the symmetry condition). is this an error?

    -To conclude the tabular data near the graph of the total deformation show three columns minimum , maximum and average, what do they mean? is that the minimum, maximum and average displacement? if yes, according to which reference system have they been computed? because to define the two general joints I set two coordinate system over the vertices of the rectangle which are oriented according to the my global reference system.

     

    Thank you for your help! I really appreaciated! 

    Have a good day!

     

  • peteroznewmanpeteroznewman Member
    edited July 2019

    - the first issue involves the construction of the rectangle

    The dummy body can be any size, and it shall be rigid. It can be any thickness (as long as you don't have gravity as a load). The two joints attach to this dummy body at a coordinate system. You are free to put the origin of these coordinate systems anywhere. If you orient the joint so an axis lies along the direction of the x and y translation components, then you can just translate along that one direction by the total length of the x and y components.

    - Regarding the rototranslations I've specified in the connections the axes along which to move and the rotational axis, however as you can see from the picture it seems that only the first rototranslation occurs..

    For time step 1, you have some values for translation and rotation of joint 1 and joint 2 is set to zero.  For time step 2, the values of joint 1 remain constant (are the same as time step 1), while the values for joint 2 become non-zero in time step 2.

    -to achieve convergence I had to switch to large deflection

    Yes, that is a required setting.

    -To conclude the tabular data near the graph of the total deformation show three columns minimum , maximum and average, what do they mean?

    They mean exactly what they are. If you have an edge or a body, then those three values will be different, but if you have a vertex, then those three values will be identical. For example, if you were to plot directional deformation of a body in the Y direction, and the top of the body moves -2 mm while the bottom of the body moves -8 mm then the maximum value would be -2 and the minimum value would be -8 and the average value would be between them.

  • nylanyla Member
    edited July 2019

    Hello,

    Thanks for your tips!!

    Just to be sure.. The dummy body can be any size as you said and it is related to the joint through the coordinate system which in turns can have the origin elsewhere even outside the dummy body, as in the picture, right? Then by selecting a vertex or face or edge as a scope to the dummy body everyting becomes connected, right?

    Moreover this rototranslations are simultaneous? I mean rotation and traslation occur together or there is first a rotation and then a translation?

    To conclude regarding the method using the remote displacement I've read that by using the APDL command D, node, %_FIX%in the preprocessing it is possibile to make the first step rototranslation values permanent during the displacement allowing the successive displacement to start from these last values, but I'm not able to let the displacement continue since the first rototranslation values keep constant along the first rototranslation values neglecting the second input, maybe another constraint would be necessary.

    This was just to let you know what I've read in the net. If you are able to deep dive in this I would be interested in understanding. However I'm satisfied of the results thanks to your suggestions thus I'll thank you one more time!

    Have a nice day!

  • peteroznewmanpeteroznewman Member
    edited July 2019

    The dummy body can be any size... ...can have the origin elsewhere even outside the dummy body?  Yes.

    Then by selecting a vertex or face or edge as a scope to the dummy body everything becomes connected, right?  Yes

    Moreover this rototranslations are simultaneous?  Yes.


    I have used the APDL command D, node, %_FIX% in the case where in Step 1, I apply a Force and don't know what the final displacement of object 1 will be, then in Step 2, I want to hold object 1 fixed at whatever value of displacement it ended at step 1 to begin a step 2 load on some other object.

    I couldn't imagine how to use this method in your case because you don't want the first object fixed during step 2, you actually want it to move as another object is given a displacement. That is why I thought to use a dummy body and cascaded joints. It makes the problem somewhat simple.

  • nylanyla Member
    edited July 2019

    Thank you very much for your help!!! You solved my problem!

    Best regards!

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