# \*TIE for only 1 DoF **URL:** \ **Category:** Uncategorized\ **Created:** [September 2, 2022, 9:23am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244 "2022-09-02T09:23:33Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![OliverKunc](https://avatars.discourse-cdn.com/v4/letter/o/aca169/32.png) [@OliverKunc](https://calculix.discourse.group/u/OliverKunc)\ **Post date:** [September 2, 2022, 9:23am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/1 "2022-09-02T09:23:33Z")
How can I tie 2 surfaces together, but only w.r.t. 1 specific DoF? Moreover, this 1 DoF is w.r.t. a non-standard coordinate system, i.e. as a result of \*TRANSFORM. Example: frictionless “contact” of a bolt in a borehole. The pin is allowed to freely move in the direction of its main axis and to rotate about it, but it must follow the borehole for all other possible movements. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [September 2, 2022, 9:33am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/2 "2022-09-02T09:33:13Z")
Use MPC constraints instead of tie. ---
**Author:** ![OliverKunc](https://avatars.discourse-cdn.com/v4/letter/o/aca169/32.png) [@OliverKunc](https://calculix.discourse.group/u/OliverKunc)\ **Post date:** [September 2, 2022, 9:53am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/3 "2022-09-02T09:53:23Z")
Thanks for the reply. I had chosen an oversimplified example. The example is now changed. Would you still say that MPCs are the easiest way to do this? ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [September 2, 2022, 10:39am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/4 "2022-09-02T10:39:52Z")
Maybe you could just use contact with some specific settings. For example, it seems to be possible to simulate no separation contact with a workaround: [No separation contact](https://calculix.discourse.group/t/no-separation-contact/916) MPCs may also work, here’s a discussion about the use of them for modeling contact without actual contact algorithms: > [@Modeling surface contact with point-to-point linear contact](https://calculix.discourse.group/t/modeling-surface-contact-with-point-to-point-linear-contact/874): > > Hi, I’m following the book “Practical Finite Element Analysis for mechanical engineers”, and in section 14.7.2 I find an example where the base of a fitting is in contact with a plate and this contact is modeled as a point-to-point linear contact: All the nodes of the fitting’s base have their own MPCs. The plate is not represented in the model, the MPC linear contacts are grounded. I’m using PreProMax for the FEM except for the MPCs. The CalculiX manual mentions in point 6.7.2 th… ---
**Author:** ![Awareness](https://avatars.discourse-cdn.com/v4/letter/a/82dd89/32.png) [@Awareness](https://calculix.discourse.group/u/Awareness)\ **Post date:** [April 26, 2023, 1:57pm UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/5 "2023-04-26T13:57:45Z")
Why do not you try? This is excerpt from manual For example send dep indep nas areampc 123 c1 will connect the nodes in the set dep to element-faces described by nodes in- cluded in the set indep. The set dep must contain all nodes which should be ”glued” and the set indep should contain all nodes of the elements surfaces to which the dep nodes should be glued. The numbers ”123” are the degrees of freedom which will be connected (”t” will create a thermal connection, “p” a press-fit connection). The ”c” triggers the correction of the position of the de- pendent nodes to a position on the surface of the independent elements (highly recommended and default), ”u” would prevent the correction, “f” forces the dependent node away from the independent face. ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [April 30, 2023, 12:19pm UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/6 "2023-04-30T12:19:36Z")
Tie constraint and MPC generated are sensitive to surface definition of master and slave, it may lead to unexpected or wrong results. However, this not occurs for tied contact type. Another advantages using tied contact seems to be possible working for any element type (beam, shell and solid) at arbitrary plane e.g circular, flat or curves. However, setting parameter values for stick slope and/or friction still need more test to validated since it’s not officially documented. I’m only doing an opposite way from implementor reference document, setting to lowest values make it released at normal and/or tangential movement. ---
**Author:** ![OliverKunc](https://avatars.discourse-cdn.com/v4/letter/o/aca169/32.png) [@OliverKunc](https://calculix.discourse.group/u/OliverKunc)\ **Post date:** [May 2, 2023, 6:16am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/7 "2023-05-02T06:16:01Z")
Thanks for the hint! ```auto send dep indep abq areampc slide ``` should do it, however I am unable to test this atm. ---
**Author:** ![OliverKunc](https://avatars.discourse-cdn.com/v4/letter/o/aca169/32.png) [@OliverKunc](https://calculix.discourse.group/u/OliverKunc)\ **Post date:** [May 2, 2023, 6:25am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/8 "2023-05-02T06:25:49Z")
This is probably the way that Calc\_em suggested, “No separation contact”. From the example in the linked answer, people seem to have verified that it works. However contact simulation is computationally costly. I would prefer an MPC-variant because coupling DoF’s should not require the solution of anything. ---
**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\ **Post date:** [May 3, 2023, 6:28am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/9 "2023-05-03T06:28:39Z")
Is contact with TIED and low stick slope really nonlinear? It seems to just be linear springs, and any nonlinearity might just be for large deflections and fairly low-cost compared to full-blown contact. ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [May 3, 2023, 10:44am UTC](https://calculix.discourse.group/t/tie-for-only-1-dof/1244/10 "2023-05-03T10:44:14Z")
Interesting to conduct testing on computational times between MPC constraint and tied contact type, even it negligible for tie constraint. Hard point are seeking a percentage of sharing force or displacement based on master node projection to the slave. Only CGX as precessor can do automatically, another is not yet capable. Tied contact types with parameter setting can be use as alternative way of working, movement at normal and/or tangential also can be set.