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Ivan

imposed displacement between two nodes with skew/frame

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I am trying to set up imposed displacement between two nodes with moving skew or frame (not sure which should be used). Coordinate system of imposed displacement should be aligned between those two nodes and updated throught simulation. The function curve is defined so the distance between nodes should be gradually reduced. The required behaviour is similar to pretensioned spring but with prescribed displacements throughout simulation. 

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Hi Ivan,

If i understood you correctly you can use a  a /FRAME/MOV for this. 

A simple example is provided for the same. Two similar components are provided with an imposed velocity. For the left side component a function for imposed velocity is created and a moving frame is defined for that component . For the right side component the imposed velocity function defined is 0, but the created reference frame for the other component is recalled here. The relative motion with respect to the reference frame is measured which makes the other component to rotate.

 

skew.PNG

 

Please check the video file attached along which shows the animation of the same.

 

frame.avi

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Hi,

 

I have already checked that thread about frame/skew, but I am still confused. 

 

You can check the sample I am trying to solve. I have set up imposed displacement, but it is not responding as required. If you delete the imposed diplacement you will get desired behaviour which is provided by spring (darker blue). I would like to get the same response with imposed displacement to have control over relative distance throughout simulation (prescibed by curve function).

imposed diplacement.jpg

planestrain_hinge.hm

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Thanks George, it does work with SKEW/MOV2.

 

I have some more queries:

1. Which control cards should be requested to output contact forces/pressures and strains for quad elements in 2D plane strain analysis? 

2. The run terminates with:

Quote

MESSAGE ID :          142
  ** STOP : ZERO OR NEGATIVE VOLUME FOR 2D-ELEMENT

There is also a lot of hourglassing. The property for hyperelastic material are exactly the same as in Example 42 - Rubber Ring: Crush and Slide. Can you suggest some solution?

3. What are recommended shell property settings for nearly incompressible hyperelastic materials in 3D analysis?

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Hi Ivan,

I doubt whether we can output contact forces/pressures and strains for plane strain analysis. I'll check regarding this and will update you.

The element distortion happening results in negative volume. the high imposed displacement in the node distorts the element. You can try ramping the load. Normally  starting from a zero load, and zero solution, we gradually ramp up the load until we achieve the desired total load. This gradual ramping up the load from a value close to zero is often a more robust approach.

You can try with Isolid=17, which has full integration formulation.

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Hi George,

 

I have tried with Isolid=17, which eliminates horglassing, but the run stil terminates with negative volume. There is also the problem with contact type 3 stiffness between soft (rubber) and hard (wood) parts. Attached are excerpts form Radioss User Guide 2017 which discusses such situations. To get the stiffnes ratio of hard over soft material the Young's or bulk modulus is required, but I only have ogden material parameters. I have also unsuccessfully tried type 5 interface with arbitrary contact stiffness scale factor of 170.

planestrain_hinge_convolute.hm

convolute.gifsoft part.jpgstiffness.jpg

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Hi Ivan,

I modified some contacts, contact parameters and also updated the imposed displacement load curve.

plane_strain.gif

 

The files are also attached for your reference.

planestrain_hinge_convolute.h3d

planestrain_hinge_convolute_0000.rad

planestrain_hinge_convolute_0001.rad

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