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October 30, 2024 at 11:34 amgambra77Subscriber
hello eveyone,
I´ve been simulating and studying the behavior of a part that suffers the force of preload, here are the main data:
- Material: AL6082-T6
- Bolt: M8 12.9 quality
- Yield strengh 250MPa
To know the preload I have to apply, I used the T(torque)=K(friction coefficient)*D(diameter)*F(preload)
- T=31Nm
- D=8
- K=0.15 (most websites say this is the most common)
Here is my problem: When i put the preload of 25KN Ansys says that it breaks because of the tensile strengh. I dont know if is somethng related to the material, the connections or the preload.
The deformations are also no correlated to reality because if you put 25KNthe 3mm gap becomes 2mm but in reality is 1mm the final dimension. The connectors are configured like this:
- Between parts where movement and no stress happens "No separation"
- Between the main body an the pipets "Frictional" and the coefficient 1,1 for aluminum-aluminum and 0,61 Steel-Aluminum
Here are the photos showing the main information:
Material used for the body not the bolt, the bolt is AISI4037
The results: the sum of the deformations has to give 2
If someone knows what is wrong i would be delighted.
Aitor
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October 31, 2024 at 3:03 pmpedram.samadianSubscriber
Hi,
I created a simple cube model with similar material properties under a tensile stress higher than the tensile strength and ran it using a Static Structural solver successfully without any errors. Where on the part do you apply the load? Can you please provide the exact error message indiacted in the message file? The sentence “Ansys says that it breaks because of the tensile strengh” is not clear to me.
Thanks,
Pedram
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October 31, 2024 at 3:17 pmgambra77Subscriber
Hi,
There is no error message, but the tension surpasses the tensile ultimate strength so i assume that it brakes in tat point. I used von misses stress.
The load is applied in the bolt with the bolt pretension function. Exactly in the bolt face that is not in contact (the contact that appears in the image)
I dont know if i did the model well.
thanks,
Aitor
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October 31, 2024 at 6:15 pmpedram.samadianSubscriber
Hi Aitor,
I see now. Is your bolt design finalized? I think the preload is too high. The bolted joints should be designed based on the proof strength/load of the bolt, which is the maximum strength/load that a bolt can withstand without acquiring a permanent (plastic) deformation. The proof strength is typically considered to be 85% of the yield strength, and the recommended preload is typically between 75 to 90% of the corresponding proof load. You may find useful information in the following video:
?start=448&end=587You probably need to change the bolt design or modify the preload. I hope this works.
Thanks,
Pedram
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November 3, 2024 at 7:14 pmgambra77Subscriber
Thaks!
To set the preload i used de T=K*F*D formula.
I will see the video and see how the simulation goes
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November 4, 2024 at 10:52 amgambra77Subscriber
Hello again,
I saw the video and setting the values the video and you gived to me, the preload is 26,625KN. Is a 12.9 M8 bolt and the proof load is 3550 kg. So the preload value doesn´t change a lot.
I will contiunue searching for information, but thank you!
Aitor
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November 4, 2024 at 7:58 pmpedram.samadianSubscriber
Hi Aitor,
Thanks for the update. Best of luck.
Pedram
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