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CBUSH spring inclined with respect to the coordinate system

Valued Contributor
Valued Contributor

Hi, I would like to create a spring inclined with respect to the coordinate system, using NX Nastrain 12.

  1. How do I obtain a MONOAXIAL spring with stiffness defined only in the spring direction?
    Maybe using a CBUSH1D element with turned proprieties (but I am not able to do it)? I attach a simple example but it is not work properly.
  2. How do I obtian a spring with stiffness in all 6 DOF according to a new coordinate system alligned along the spring (i.e. in the particular case that the spring is inclined).
    Maybe using a CBUSH element with turned proprieties (but I am not able to do it)? I attach a simple example but it not work properly.
  3. I do not understand the meaning of the "element orientation" data (i.e. Uniaxial, Enable CSYS Override and Specify vector) and the "spring damper" data (i.e. Offset definition). I searched on the help but it is still not clear, can you explain clearly?MeshAssociatedData.PNG

     Regards,

    A

 

 

3 REPLIES 3

Re: CBUSH spring inclined with respect to the coordinate system

Siemens Phenom Siemens Phenom
Siemens Phenom

If GA and GB are non-coincident, the default for both CBUSH and CBUSH1D is uniaxial:

 

CBUSH Remark 5:

 

For noncoincident grids, if neither GO or X1, X2, X3 is specified and no CID is specified, then the line AB is the element x-axis, and the y-axis and z-axis are considered undefined. This option is valid only when K1 (or B1) or K4 (or B4) or both are specified on the PBUSH entry (but K2, K3, K5, K6 or B2, B3, B5, B6 are not specified). If K2, K3, K5, or K6 (or B2, B3, B5, or B6) are specified, a fatal message will be issued.

 

CBUSH1D Remark 1:

 

For noncoincident grids GA ≠ GB and if CID is blank, the line GA to GB is the element axis.

 

The issue is that the displacement coordinate system at node 3 is not aligned with the spring direction. In the attached updated models, I've created a cartesian csys rotated 30 degrees so that the X axis of the local csys is aligned with the uniaxial spring direction. I then modified the nodal displacement csys of node 3 to point to the new csys. With this change, both springs have a displacement magnitude of 1.0 in the uniaxial direction.

Re: CBUSH spring inclined with respect to the coordinate system

Valued Contributor
Valued Contributor

Thank you @JimB for your answer. Now the model is correct.
Can you help me with question number 3? I do not understand the settings of the image.

Re: CBUSH spring inclined with respect to the coordinate system

Siemens Phenom Siemens Phenom
Siemens Phenom

For CBUSH1D:

 

Enable CSYS Override: If this is off, CID is not written (the condition documented in Remark 1 quoted in my reply above(. If this is on, you select an actual CSYS, which is exported to the input deck and the label of this csys is set as CID on CBUSH1D

 

For CBUSH:

 

Uniaxial: If this is on, the other two Element Orientation inputws are hidden on the dialog and none of the orientation fields (CID on CBUSH1D; CID / GO / X1, X2, X3 on CBUSH) are written to the input deck. This leads to the condition documented in Remark 3 quoted in my reply above.

 

Enable CSYS Override: If this is on, you select an actual CSYS, which is exported to the input deck and the label of this csys is set as CID on CBUSH/CBUSH1D. X1, X2 and X3 are not written to the input deck.

 

Specify Vector: This vector sets X1, X2 and X3 on CBUSH. CID is not written to the input deck

 

Under Spring Damper:

 

If Offset Definition = GA-GB line, the location input sets S on CBUSH. This is the parametric location (varies between 0.0 and 1.0) along the element X axis.. OCID and S1, S2, S3 are not written to the input deck.

 

If Offset Definition = Coordinate System, then a coordinate system is selected and Components 1, 2 and 3 are specified. The ID of the selected csys is written to OCID and the components are written to S1, S2 and S3. S is not written to the input deck.