# Selection master and slave in contact

**URL:** https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804
**Category:** General Questions
**Created:** [June 10, 2024, 6:45am UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804 "2024-06-10T06:45:10Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![waluyo](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/waluyo/32/3419_2.png) [@waluyo](https://prepomax.discourse.group/u/waluyo)
#### Post date: [June 10, 2024, 6:45am UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804/1 "2024-06-10T06:45:10Z")

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One of the unclear stages for me is when selecting master and slave in contact pairs. Is there any hint or suggestion which surface defines as master and the other one as slave.

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### Author: ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)
#### Post date: [June 10, 2024, 7:14am UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804/2 "2024-06-10T07:14:18Z")

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Yes, there are some rules. Master should:

- belong to the rigid or stiffer component,
- have a coarser mesh,
- be the larger surface,
- be the less curved surface.

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### Author: ![AsuraEquation](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@AsuraEquation](https://prepomax.discourse.group/u/AsuraEquation)
#### Post date: [June 10, 2024, 7:41am UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804/3 "2024-06-10T07:41:16Z")

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See the 3th comment of this post  
[Bolts shear contact not working correctly - General Questions - PrePoMax](https://prepomax.discourse.group/t/bolts-shear-contact-not-working-correctly/1734/2).

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### Author: ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)
#### Post date: [June 10, 2024, 7:49am UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804/4 "2024-06-10T07:49:20Z")

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Just keep in mind that the belt drive example should have the opposite master-slave assignments. Also, this Ansys nomenclature (target-contact) can be unintuitive.

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### Author: ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [June 11, 2024, 11:35pm UTC](https://prepomax.discourse.group/t/selection-master-and-slave-in-contact/1804/5 "2024-06-11T23:35:04Z")

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probably there’s no specific criteria in CalculiX when using Mortar contact type.