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Assembly Interference Analysis

Good Afternoon all.

I'm looking for some guidance. I would like to run a simulation in which I can determine the contact pressure and the stress between two 3-dimensional parts. I'm not familiar with contact mechanic simulation and I am not interested in transient forces. I would like to know stresses and deflections of both parts, post-assembly. I presume I can do this with the Optistruct implicit solver but I'm not sure how to setup the contact card.

Can someone walk me through the pre-processing part of doing a press-fit analysis with Optistruct? I can provide geometry and boundary conditions, but I'm lost when it comes to contact and Optistruct capabilities.

Thanks.

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Altair Forum User

There are tutorials available in OptiStruct help which talks about creating contacts. Please refer to the tutorials:

OS-1360: NLSTAT Analysis of Gasket Materials in Contact

OS-1365: NLSTAT Analysis of Solid Blocks in Contact

http://training.altairuniversity.com/analysis/structural/nonlinear/compression-of-a-rubber-spring-nlgeom/

Rahul_P1

The HyperWorks Ebook - http://www.altairuniversity.com/free-study-guide-book/

discusses contacts and how to model them in HyperWorks

Altair Forum User

Let me get this straight. After reading the book about contact, I think I might know how to do this a little better, but I need to know if this is the correct approach.

Real Problem Definition: I have two components. One is cooled and the other is heated before they are slipped together and brought to room temperature. At room temperature they expand and interfere resulting in contact pressure between the two components.

Simulation Approach: Model the inner component at it's cooled state and make sure to define it's temperature at the cooled state and impose heating to room temperature. Define contacts on the interfering meshed surface of the inner component. Model the outer component at it's heated temperature, define it's temperature as hot and impose cooling. Place contacts on the inner surface of the outer component so that penetration cannot occur between the mating surfaces of the two parts. (Make sure to constrain at least one node on each part and attempt to minimize constraint influence on contact pressures at the mating surfaces.)

Can anyone confirm that this simulation approach is correct?

Update: I'm going to try just meshing and creating contacts that have interference between the two parts. Not sure if Optistruct will do this or if I'll have to use RADIOSS but I'll report back.

Altair Forum User

BUMP.

Got the contact analysis to work with a non-realistic interference of 1mm which led to large compliance warnings. That was fine, but now I'm trying to do a real test case. I have some housing geometry and a small insert fit together. I'm receiving two errors and no results. I have an interference of 0.1mm and a mesh size of 0.001 in. Can anyone guide me in these errors? I can also supply the model if needed. Not sure what I need to do to fix this.

*** WARNING # 2616

Slave and Master for CONTACT interface 1 point to the same set or

surface. This self-contact may result in poor quality of contact elements,

redundant contact conditions, and patchy pressure distribution, especially on

curved contact surfaces.

Also, pre-penetration condition will be ignored for this CONTACT interface

(to avoid self-compressing the bodies due to false pre-penetrations).

*** WARNING # 2625

CONTACT interface 1 includes areas that have self-contact condition

and apparently pre-penetrations. To avoid detecting false pre-penetrations

(which may appear across thin solids with self-contact on both sides)

declare SRCHDIS smaller than minimum thickness of respective solids.

Or, if it is known that there are no true pre-penetrations in

self-contact areas, use CONTPRM,SFPRPEN,NO.

*** ERROR # 941 ***

NON-CONVERGENT NONLINEAR ITERATIONS FOR SUBCASE 1