# RBDO: When the constraint function is implicit

**URL:** <https://uqworld.org/t/rbdo-when-the-constraint-function-is-implicit/1820>\
**Category:** UQ Resources\
**Tags:** rbdo, metamodeling\
**Created:** [March 9, 2023, 2:25pm UTC](https://uqworld.org/t/rbdo-when-the-constraint-function-is-implicit/1820 "2023-03-09T14:25:38Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Mr121Tony](https://uqworld.org/user_avatar/uqworld.org/mr121tony/32/1070_2.png) [@Mr121Tony](https://uqworld.org/u/Mr121Tony)\
**Post date:** [March 9, 2023, 2:25pm UTC](https://uqworld.org/t/rbdo-when-the-constraint-function-is-implicit/1820/1 "2023-03-09T14:25:38Z")

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[Beam\_Deflection.zip](https://uqworld.org/uploads/short-url/46GHnDJSWiqTJs99ou6vRJWSjYv.zip) (697.8 KB)

Hello, everyone:  
The above is a test procedure I did. The problem is that one end of the cantilever is fixed, and the other end is subject to a concentrated force. Its section is rectangular. The RBDO design is used to find the minimum cross-sectional area which does not exceed the allowable beam deflection. Beam\_RBDO is calculated according to the analytic formula and can be run successfully.

I simulated this problem with abaqus to calculate its deflection, and then made a myUQLinkModel model with UQLink module as the limit state function in RBDO, that is, to replace the role of uq\_Constriant. I think there is no problem with the other codes, but there is an error in the calculation. I don’t know why, can you help me to answer it?

 ![1](https://uqworld.org/uploads/default/original/2X/5/56d07b0a35ca585842675cccb5026b9c772d9f2c.png)  
 ![2](https://uqworld.org/uploads/default/original/2X/3/3ba57d51324545ca599323ba5706b01a75849fb9.png)

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**Author:** ![styfen.schaer](https://uqworld.org/user_avatar/uqworld.org/styfen.schaer/32/849_2.png) [@styfen.schaer](https://uqworld.org/u/styfen.schaer)\
**Post date:** [March 9, 2023, 2:44pm UTC](https://uqworld.org/t/rbdo-when-the-constraint-function-is-implicit/1820/2 "2023-03-09T14:44:24Z")

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Dear @Mr121Tony

Do I see it correctly that the error occurs in your own `readabaqusOutput.m` file when you try to read the output file? Have you checked that the output file is generated and that all paths are correct so that the output file is visible to Matlab when the outputs are parsed?

Best regards  
Styfen

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**Author:** ![Mr121Tony](https://uqworld.org/user_avatar/uqworld.org/mr121tony/32/1070_2.png) [@Mr121Tony](https://uqworld.org/u/Mr121Tony)\
**Post date:** [March 10, 2023, 1:31am UTC](https://uqworld.org/t/rbdo-when-the-constraint-function-is-implicit/1820/3 "2023-03-10T01:31:08Z")

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Dear @styfen  
Thank you very much. You are right. I find the py file has some mistakes. I have solve the problem and the program works successfully.  
Best regards  
Student