PET Bottle pressurized
PET Bottle pressurized
(OP)
Strange problem on simulating a pressurized bottle .
On Abaqus/Explicit i'm using the folowings :
1. Density : 1.37E-009 tonne/mm3
2. Young's Modulus : 3100 MPa
3. Internal Pressure Load : 0.4 MPa
Now the strange thing is that I'm having a huge deformation.
In practice with a pressure of 0.4 MPa (4 athmospheres) i have around 0.5-1 mm deformation, but in abaqus the simulation results in a huge deformation and sometimes in errors without any result.
The strangiest part is that if i use 1.37 density (PET density in g/cm3) the results seems to folow the practice.
I'm new to abaqus is there a missed calculation of units or what is wrong ?
On Abaqus/Explicit i'm using the folowings :
1. Density : 1.37E-009 tonne/mm3
2. Young's Modulus : 3100 MPa
3. Internal Pressure Load : 0.4 MPa
Now the strange thing is that I'm having a huge deformation.
In practice with a pressure of 0.4 MPa (4 athmospheres) i have around 0.5-1 mm deformation, but in abaqus the simulation results in a huge deformation and sometimes in errors without any result.
The strangiest part is that if i use 1.37 density (PET density in g/cm3) the results seems to folow the practice.
I'm new to abaqus is there a missed calculation of units or what is wrong ?





RE: PET Bottle pressurized
The Poision Ratio is 0.37
Any ideea about this problem ?
RE: PET Bottle pressurized
It could also be the way in which you're applying the pressure? The default is instantaneous loading which isn't applicable for what seems like a quasi-static analysis. Are you using this or something like 'smooth step' loading?
RE: PET Bottle pressurized
It could be a pressure problem !
RE: PET Bottle pressurized
I'm afraid I can't help much with the former kind of analysis, haven't ever done any. Just recheck your units I guess and make sure the kinetic energy of the system is coming out roughly as expected.
RE: PET Bottle pressurized
It seems to me that the problem is much complex that i initialy thought.
RE: PET Bottle pressurized
What you should do is apply the load gradually. This will give you the final deformed shape of the container. The way to do this is to slowly ramp the load up to the desired final load through use of the *amplitude keyword.
The reason your analysis sort of worked when the material had a very high density is that the effect of the shock loading would have been lessened, resulting in a deformed shape that is close to what you expected.
RE: PET Bottle pressurized
2. Tried the same problem in Abaqus/Standard and it gives a a fast result and it is running smoothly
MechIrl what do you think a Abaqus/Standard result is ok for this kind of problem ?
Thanks in advance
RE: PET Bottle pressurized
In terms of your model failing in explicit I don't really get what you mean by 100 smooth steps. Why not just apply the load in one smooth step (choose the 'smooth step' option with *amplitude). You will need to use mass scaling to increase the time increment size for a reasonable run-time.
RE: PET Bottle pressurized
*Amplitude, name=Amp-1, time=TOTAL TIME, definition=SMOOTH STEP
0.01, 0.004, 0.02, 0.008, 0.03, 0.012, 0.04, 0.016
0.05, 0.02, 0.06, 0.024, 0.07, 0.028, 0.08, 0.032
0.09, 0.036, 0.1, 0.04, 0.11, 0.044, 0.12, 0.048
0.13, 0.052, 0.14, 0.056, 0.15, 0.06, 0.16, 0.064
0.17, 0.068, 0.18, 0.072, 0.19, 0.076, 0.2, 0.08
0.21, 0.084, 0.22, 0.088, 0.23, 0.092, 0.24, 0.096
0.25, 0.1, 0.26, 0.104, 0.27, 0.108, 0.28, 0.112
0.29, 0.116, 0.3, 0.12, 0.31, 0.124, 0.32, 0.128
0.33, 0.132, 0.34, 0.136, 0.35, 0.14, 0.36, 0.144
0.37, 0.148, 0.38, 0.152, 0.39, 0.156, 0.4, 0.16
0.41, 0.164, 0.42, 0.168, 0.43, 0.172, 0.44, 0.176
0.45, 0.18, 0.46, 0.184, 0.47, 0.188, 0.48, 0.192
0.49, 0.196, 0.5, 0.2, 0.51, 0.204, 0.52, 0.208
0.53, 0.212, 0.54, 0.216, 0.55, 0.22, 0.56, 0.224
0.57, 0.228, 0.58, 0.232, 0.59, 0.236, 0.6, 0.24
0.61, 0.244, 0.62, 0.248, 0.63, 0.252, 0.64, 0.256
0.65, 0.26, 0.66, 0.264, 0.67, 0.268, 0.68, 0.272
0.69, 0.276, 0.7, 0.28, 0.71, 0.284, 0.72, 0.288
0.73, 0.292, 0.74, 0.296, 0.75, 0.3, 0.76, 0.304
0.77, 0.308, 0.78, 0.312, 0.79, 0.316, 0.8, 0.32
0.81, 0.324, 0.82, 0.328, 0.83, 0.332, 0.84, 0.336
0.85, 0.34, 0.86, 0.344, 0.87, 0.348, 0.88, 0.352
0.89, 0.356, 0.9, 0.36, 0.91, 0.364, 0.92, 0.368
0.93, 0.372, 0.94, 0.376, 0.95, 0.38, 0.96, 0.384
0.97, 0.388, 0.98, 0.392, 0.99, 0.396, 1., 0.4
Exactly what you are sayng. It was just an expression mistake when i said 100 smooth steps
Thanks again for helping me
RE: PET Bottle pressurized
RE: PET Bottle pressurized
Yes, you are right : the mesh part is huge (it's a botte having an complex design), and the thickness of the shell is .4 mm, varing to .75 - 1 mm at the bottom and on the neck
Abaqus Standard gives me a solution that follows the practice.
By the way, my interest is to calculate the final volume. Any ideea on how to do that. I have the displacement of elements but i don't have a clue how to calculate the final volume (after deformation).
Tried to export the result as VRML, import to CAD, converted to surfaces and calculate the volume.
But this method is too complex and i'm afraid that it could not be a relaible volume beaucause of the import and convert steps taking place.
You know anything about, how i could resolve this issue ?
RE: PET Bottle pressurized
Which CAD package did you use to import the VRML? It never seems to work out for me :(
RE: PET Bottle pressurized
RE: PET Bottle pressurized
The main thing is that you have to convert the facet features in a solid or a surface quilt to do operations like cut/trim or manufacturing operations
You were not eable to import vrml ? or you just have difficulties after import of the model as vrml ?