ACOSTA-Solid shell user element and ABAQUS shell elements ... · PDF fileACOSTA-Solid shell user element and ABAQUS shell elements A comparison INTALES GmbH, 1 st NL Workshop, Natters/TYROL,
Post on 16-Feb-2018
240 Views
Preview:
Transcript
ACOSTA- Solid shell user element
and
ABAQUS shell elements
A comparisonA comparison
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20101
- David Chipperfield -
1st Workshop
on Nonlinear Analysis of Shell Structures
AS 9100
Outline:
• The model is formulated in the
general purpose code ABAQUS.
• EXEN nodes are connected to
the body shell with kinematic
BOUND1ORIGIN
EXEN2 EXEN1
Model Desciption
2
the body shell with kinematic
coupling
• Model is constrained about
BOUND1 at the origin using
kinematic coupling
BOUND4
EXEN2
DAAV loads
EXEN1
DAAV loads
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/2010
Generation of Mesh
Shell Element:
• S4 (Abaqus)
Solid shell elements:
• HC24_9 (UEL , User element)
• SC8R (Abaqus)
Degrees of freedom:
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20103
Solid model Shell model
318 612 244 254
A numerical model for test purpose:
• Close to practical problems
• Reasonable computational costs
Generation of Mesh
Two different models
-Solid model displays frame thickness in mesh
Solid shells:
• More overall DOFs
• More elements in model due to
- Intersections
- Modelling of Frames
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20104
Solid model (HC29_9, SC8R) Shell model (S4)
- Modelling of Frames
Load Steps - Overview
• 3 Initial Loads;
• Thermal Loading - Initial thermal
loads
• Tank Loading - Pressure of the LOX
tank
• Aero Pressure – Aerodynamic
pressure on fuselage
5
• 2 Mechanical Loads;
• Flight simulation – Load to simulate
flight conditions, applied to DAAV
loads reference points and STN 31
nodes.
• Artificial load – create buckling,
applied to DAAV loads reference
points and STN 31 nodes
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/2010
STN 31
DAAV
Loads
Load steps - Order
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20106
4 Flight simulation
5 Artificial load (to create
buckling)
Load steps - Temperature
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20107
4 Flight simulation
5 Artificial load (to create
buckling)
Application:
All elements of the model are
subjected to initial thermal loads
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
Load steps – Tank Pressure
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20108
4 Flight simulation
5 Artificial load (to create
buckling)
Application:
LOX pressure load applied to
Lower cylinder and both
hemispheres
Load steps – Aero Pressure
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/20109
4 Flight simulation
5 Artificial load (to create
buckling)
Application:
Artificial aerodynamic pressure
applied to external sections
Load steps – Flight Simulation
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201010
4 Flight simulation
5 Artificial load (to create
buckling)
STN 31
DAAV
Loads
Application:
Booster loads applied to DAAV (up),
Tension loads applied to STN31
Load steps – Artifical Load
Step Describtion
1 Temperature
2 Tank pressure
3 Aero pressure
4 Flight simulation
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201011
4 Flight simulation
5 Artificial load (to create
buckling)
STN 31
DAAV
Loads
Application:
Artificial loads applied to DAAV
(down),
Compression loads applied to STN31
Mode of failure
Computations are aborted at
70% through step 5.
This is due to buckling that is This is due to buckling that is
induced through the articial
compression load applied
during step 5.
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201012
Problems with the SC8R, Part 1
Model using SC8R elements, did not deform about frames in step 1
as per UEL and Shell elements
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201013
Consequence:
Remodelling of frames with solid elements (C3D8)
UEL:
Problem does not occur for the user element, thus making the User
element is suitable to model massive structures
Undeformed frames (blue)
Problems with the SC8R, Part 2
SC8R model does not pass step 1 due to massive local distortion of
elements about the hemisphere end:
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201014
S4 SC8R
UEL:
The user element successfully passed the step with deformation of
the hemisphere similar to S4 model
Consequence:
Reduce the initial temperature load by 50% of original load
specification
Comparison of Convergence
100% Temp.
Step UEL S4 SC8R
1 12 12 n. c.
Number of increments and maximal step time
50% Temp.
UEL S4 SC8R
12 12 12
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201015
1 12 12 n. c.
2 12 12 -
3 12 12 -
4 12 12 -
5 20 18 -
max 4.68 4.72 0.63
12 12 12
12 12 12
12 12 12
12 12 15
22 15 20
4.69 4.72 4.71
Comparison of Local Strain Energy Density
Comparison of Total Strain Energy Density
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201016
Comparison of Total Strain Energy Density
Comparison of Displacements
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201017
Comparison of Displacements
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201018
Summery of Comparison:
• Similar total and local strain energy
density
• Diverging results for displacements
• Close coincidence of the results is
obtained for small and moderate
deformations
Summary
• Application of UEL for a practical problem has been
demonstrated
• More DOF for solid shell elements due to model differences
• UEL suitable to model massive structures
• UEL more stable than SC8R element of Abaqus for such large
structures
• Similar convergence• Similar convergence
• Similar total and local strain energy density
• Diverging results for displacements
INTALES GmbH, 1st NL Workshop, Natters/TYROL, 15/06/201019
top related