Simcenter 3D analysis of aero engine structures

Mardi, 26 avril 2022
L’analyse de structures par éléments finis : applications,
innovations et défis
Tanguy Mertens, Product Manager Structure Solutions
(Siemens)
Jean-Philippe Ponthot, Professeur (Aérospatiale et
Mécanique, ULiège)

LIEGE CREATIVE, en partenariat avec :

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Structural Design &
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Mertens Tanguy
21st
April 2022
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Simcenter 3D
The most comprehensive,
fully-integrated CAE solution

What is Simcenter 3D?
Common engineering desktop
Integrating multiple disciplines
World-class solvers
Simulating for engineering insight
Data & Process Management
Connecting simulation to development
Integrated applications
Achieving agile simulation processes

Whole Engine
Thermo-Mechanical
(Structural Focus)

What Challenges Does A Gas Turbine Thermal & Structural Departments Face
How to create a correct 2D abstraction
efficiently
How to efficiently model
all the missions What is the interplay between
flow, thermal & structural
phenomena?
How to effectively
collaborate
How to interpret
the results

Bolts
Seals
3D geometry
Cuts
Projections
Modifications
How To Create A Correct 2D Abstraction Efficiently

How to efficiently model all the missions
A state Time definition Missions
Trans-Atlantic +
Refueling
50,000 ft
July 4th
A limited set of parameters drives the complete simulation

How To Effectively Collaborate
Modeling and validation on
subsystem level
Assembly thermo-
mechanically bolted together
Mission, boundary conditions
inherited from subsystem

Predict Tip Clearance to Optimize Engine Performance
Simcenter solutions
Minimize clearance between blades and case to
optimize engine performance
Challenge
2D System Modeling
Only way to model full
engine system
Thermal-Mechanical
Coupling
Include thermal and
structural loads and their
interactions
Clearance
Use expression to quickly
compute clearance

Combined 3D Cyclic Symmetry and 2D Axisymmetric Simulation
Simcenter solutions
• Avoid excessive vibrations at typical engine
operating frequencies (RPMs)
• Predict engine life using high cycle fatigue
methods
Challenge
Enable non-axisymmetric loads
Enable multi-stage modeling of
blades/disks
Rather than performing individual
blade/disk analyses in isolation
Account for engine stages of
different cyclic symmetry sector
counts in the same model

Siemens Aero Engine Demo Model
From a 3D CAD perspective
Engine Assembly Compressor Assembly

From a 2D thermal-mechanical analysis perspective
2D Engine Assembly

From a 2D thermal-mechanical analysis perspective
2D Engine Assembly
Compressor rotor stages 3-6

From a 2D-3D thermal-mechanical analysis perspective
2D-3D compressor rotor stages 3-6 2D-3D Mesh

2D-3D Mesh
Meshing details
• 3D solid cyclic symmetry sector
• 2D axisymmetric solid
• 2D plane stress with thickness

2D-3D Mesh
Multi-stage details
• Analysis model stage 1:
• 72 blades (cyclic symmetry sectors)
• 5.000° sector angle
• 81 blades (cyclic symmetry sectors)
• 4.444° sector angle
• 85 blades (plane stress blade thickness)
• 87 blades (plane stress thickness)

Simcenter Nastran Enabling Technology
Cyclic symmetry support for 3D sector meshes
Cyclic symmetry details
• Couple sector face pairs
• Enforce consistent cylindrical displacements
• Equivalent meshes on face pairs not required
• Planar sector faces not required
• Unequal sector angles for the stages permitted
Stage 1 coupled faces
Stage 2 coupled faces
Engine Axis
Engine Axis
11 sectors of both stages

Simcenter Nastran Enabling Technology
2D-3D coupling to enable multi-stage cyclic symmetry analyses
2D-3D coupling details
• Couple axisymmetric edges to equivalent 3D faces
• Enforce consistent displacements at the 2D-3D
interface
• Equivalent / aligned 2D and 3D meshes not
required
• This coupling enables multi-stage cyclic symmetry
modeling
• Axisymmetric elements connect the engine
stages
Stage 1 coupled edge - face
Stage 2 coupled edge - face

Pre-stressed cyclic modes calculation
Simcenter Nastran multi-step nonlinear kinematics
• SOL 402 is a multi-step, structural solution that supports a combination of subcase types (static linear,
static nonlinear, nonlinear dynamic, preload, modal, Fourier, buckling and complex eigenvalues
extraction) and large rotation kinematics.
Solution Setup Loads
Angular Velocity Temperature
Glue / Contact

Combined Results from 2D and 3D regions
2D axisymmetric and 3D cyclic symmetry with multiple stages
Combined results
• Cyclic mode 3 expansion of results
Cyclic Index 0
294 Hz
Cyclic Index 1
403 Hz
Cyclic Index 2
1053 Hz
Cyclic Index 3
1062 Hz
Cyclic Index 4
1065 Hz

Component
Mechanical
Integrity & Lifing

Process Amelioration
Accurate cooling performance prediction
Cooling Flow Metal Temperature Structural
Faster Engineering Insight
Performance Synthesis
Better Decisions
Complex Geometry

Simcenter solutions
Engines are governed
by physics of
aerodynamics,
thermal, and
structural
Need scalability to
analyze for single
physics or multiple
physics.
Challenge
CFD
Solution
Thermal
Solution
Structural
Solution
Flow Definitions
Stress and Deflections
Cooling Flow
Metal Temperature
Structural
Process Amelioration
Multiphysics Component Simulation

Advanced Material Modeling
Simcenter solutions
Aero-engine depend
on high performance
materials that operate
in extreme conditions
Need ability to
accurately model
nonlinear behavior of
materials.
Need ability to
manage materials.
Challenge
Temperature Dependent Plasticity
and Creep Materials
Mulitilinear plasticity models with
hardening
High temperature creep materials
User-Defined
Link in proprietary advanced
material models
Damage
Play failure and delamination
models for composites
Material Databases
Links to commercial or in-house
material databases

Advanced Material Modeling
Lifing analyzed on a long multistep
mission combining rotational speed, high
temperatures, pressures.
Structure integrity depends advanced
materials such as combined creep and
plasticity
Applied
Force
Unsymmetric
Cyclic
Load
Unsymmetric Cyclic
Load
time
Mission

Blade Manufacture
Hot-to-Cold Solution
Simcenter solutions
Blade geometry is
first defined for
operating shape
Operating shape is
the manufactured
shape + deformation
from thermal and
pressure loads
How do you reverse
engineer to get
manufactured shape?
Challenge
Pressure and thermal
loads mapped from
CFD to structural
“Unrun” structural
solution for hot to
cold – start with
operating FEM shape
and iterate to
manufactured FEM
shape
Create new deformed
geometry
Operating
Geometry (Hot)
Manufactured
Geometry (Cold)

Dynamic Loading On Links For Strength And Fatigue
Simcenter solutions
Compressors are unstable at low
speeds.
Variable stator angles adjust air
flow for speed changes and
maintain stability and
performance
Challenge
Stress Evaluation
Ensure that stresses are
acceptable for complete range
of motion
FE Kinematics
FE model of blades with large
rotation

Manufacturing and Assembly Simulation
Simcenter solutions
Aero-engines are
assembled in stages
with press fits and
bolt tightening
sequences.
Need to understand
the stress and
deflections from the
assembly process and
include pre-stress
effects with service
loads
Challenge
Multistep Solutions
• Add components in a series of
steps
• Sequence the actual tightening of
bolts
• Evaluate effect of bolt failure
Initial Strain
• Include residual stress/strain from
manufacturing into components of
an assembly

Bolted Assembly of Hub and Flanges
Press Fit
Flange 1 to Hub
Bolts Tightened
Bolt 2 and 3
Press Fit
Flange 2 to Hub
Rotating Service
Load
Bolts Tightened
Bolt 1 and 4
Modes
Service Loads
Assembly Steps

Thank you.

de structures par éléments finis :
applications, innovations et défis
Jean-Philippe PONTHOT, University of Liège, Belgium
Romain Boman, Luc Papeleux
Department of Aerospace and Mechanical Engineering
JP.Ponthot@uliege.be
M.L. Cerquaglia, B.J. Bobach, E.F. Sanchez-Fernandez, M. Lacroix, S. Février,
C. Laruelle, Y. Crutzen, G. Tanaka
Liège Creative, 26 avril 2022

Contents
2
1. Introduction/General context
2. Roll forming of complex parts
3. Wear/ Rotor Stator interactions in an aeroengine
4. Additive Manufacturing (macroscopic scale)
5. Alternative discretization techniques: PFEM

3
J.-P. Ponthot
Our lab within the university
Numerical simulation
Solid mechanics
Fluid-Structure Interactions
Finite element method
Software development
Computational Mechanics
hydroforming of a tube
Dept of Aerospace and
Mechanical Engineering
(Faculty of Applied Sciences)

Our main simulation code: Metafor
4
Implicit Finite-Element solver
for the numerical simulation of large deformations of solids
ALE Formalism, remeshing.
Thermomechanical time-integration schemes.
Modeling of cracks,
fracture.
Contact algorithms.
Nonlinear constitutive laws.
Mesh generation from medical
images.
Fluid finite elements.
Monolithic schemes.
Coupling with
extenal solvers.
Metal Forming applications Crash / Impact
Biomechanics Fluid/structure
interaction

pin
shoulder
welded
zone
advancing
side
retreating
side
Software development and numerical simulation of
problems involving large strains, contacts, coupled thermo-
mechanics and complex material behavior modeling:
Metal forming processes (deep drawing and
springback, superplastic forming, cold rolling,
Impact simulation and crashworthiness
Tire mechanics & rubber
Biomechanics
Research interests

6
Industrial partners
= owns a Metafor license

Contents
7

Roll forming
8
Industrial application Roll forming
until the desired cross section is obtained
Roll forming mill
Process description

U-channel
9
Forming of a symmetrical U-channel
Experimental mill (ArcelorMittal R&D, Montataire, France)
6 stands (15°, 32°, 50°, 68°, 80°, 90°)
Final bending radii: 6 mm
Inter-stand distance : 0.5 m
Sheet : 2000 x 200 x 1.6 mm
Sheet velocity: v = 200 mm/s
Coulomb friction = 0.2
DP980 steel ( Y0 = 697.34 MPa)
Numerical parameters
Symmetry
Friction drives the sheet
Two layers of EAS elements
Dynamic implicit scheme (Chung-Hulbert)
Process parameters

U-channel
10
Numerical vs. experimental springback
The final shape has been digitised using a high precision 3D measurement device
and fits well both numerical curves (courtesy of ArcelorMittal)
Lagrangian : (21 320 FEs)
ALE : (12 768 FEs)
CPU Times:
ALE is
2.6x faster!
DEFORMATION LONGITUDINALE J1 PEAU SUP EN FONCTION DE LA DISTANCE DE PROFILAGE
-0,20%
-0,10%
0,00%
0,10%
0,20%
0,30%
0,40%
9,00E+02 1,40E+03 1,90E+03 2,40E+03 2,90E+03 3,40E+03 3,90E+03 4,40E+03 4,90E+03
Distance de profilage en mm
Déformation
Ingénieur
METAFOR
MES. EXP.

Forming of a rocker panel
11
Simulation of an industrial line
Process parameters
16 stands unsymmetrical shape
Material: DP980
Sheet: 5950 x 165 x 1.5 mm
Mesh
1 FE through the thickness
FE length: from 3mm to 30mm
155 652 dofs
stand #1
stand #16
forming
direction
closed
cross section

Roll Forming of a Complex part
12

Contents
13

Recent Fan Blade Out Problem
14
Southwest WN1380 New-York-Dallas, April 17, 2018
Boeing 737-700/ CFM56-7B24 flying at 32 000 feet

Industrial application
15
Accidental buckling of blade in a low pressure
compressor due to fan blade-out.
Low pressure
compressor
Fan

Industrial application
16
Casing

Context and motivation
Reduction of emissions and fuel consumption reduction in aero engines
Contrails!

Context and motivation
One way of increasing engine efficiency is to
decrease the clearance between the
rotating blades and the casing (thus
avoiding leakage flows)
A reduction of 25% of the clearance means
an increase of 1% of the engine efficiency.
Increasing by 1% engine efficiency leads to
saving 200 000 liters of fuel per year for a
middle range aircraft*!
From the mechanical point of view, the
clearance becomes so small that sometimes
the blades come into contact with the casing
(the shaft deforms during e.g. brutal
manoeuvers or gusts
To mitigate the contact forces, aircraft
engine manufacturers use an abradable
coating
*Lattime S.B., Steinez B.M. Turbine Engine Clearance Control Systems:
Current Practices and Future Directions. Report NASA/TM-2002-211794

Wear in Blade-Casing interaction
20
Abradable seal :
Abradable
Casing
Blade
Abradable thickness ~ 2-3 mm

Low Pressure Compressor = Booster
Typical booster architecture
Industrial partner: Safran Aero Boosters
Yellow and red: rotating parts
Blue: fixed parts
Typical clearance: 2% blade chord e.g. 1mm for a 50 mm compressor blade

Typical abradable material
The ideal abradables material must resist erosion (due to particle impacts
but must be easily worn when hit by a blade.
Typical abradables material (e.g. METCO 601NS, DURABRADE)
Al-Si12% to resist erosion
Polyester to allow abrasion by the blade
Manufactured by thermal spray coating
E ~ 1500 MPa

In case of contact the blades start to vibrate
Worst case scenario:
What is sometimes observed is a synchronization of the blade
frequency with the engine configuration
In other words the blade vibrates an integer number of times per
revolution and interacts with the abradable (8 times per
revolution in the figure on the right)
Under some (unknown) conditions, the blade can start to vibrate with a large amplitude
and hits the abradables several times during a revolution
Two basic scenarios:
The abradables is worn and there is no longer any interaction
with the blades
The self-excited process quickly leads to blade failure
Blade tearing due to fatigue

A wear model for abradable materials
We have to manage contact between the blade and casing, as well as wear of
abradable material, while keeping computational time under control!

Wear update over a surface
Wear surface is represented
thanks to isoparametric
coordinates .
Wear profile is stored at the
nodes (green dots), and can
be interpolated.
3D Wear evolution algorithm in isoparametric space

Wear update over a surface
The sponge-blackboard problem:

ONERA bench test
27
Bench test developed at ONERA/Centrale Lille,
France, PhD of Sarah Baïz
Etude expérimentale du contact aube/abradable :
contribution à la caractérisation mécanique des
matériaux abradables et de leur interaction
dynamique sur banc rotatif avec une aube.
N.B. Curvature is opposite to a aeroengine casing,
but it allows a better view of the phenomenon
VP = drum velocity
DN & DT = Normal and tangential displacement
FN = Normal Force
T = strain at the base of the blade

ONERA Benchtest: fast camera imaging
28

ONERA Benchtest: numerical model
29

Numerical results
Numerical results also
exhibit 9 bounces

Comparison experimental /numerical

Comparison experimental /numerical
9 wear zones in each case !
Max wear experimental = ~65
µm
Max wear numerical = ~70 µm

Experimental approach: Safran Aero Boosters
Experimental set up:
Thermal camera imaging during the test
Wear pattern (8 lobes)

Experimental approach
EO = Engine Order
EO8 means 8 interactions per revolution
(8 lobes )
Drawbacks of experimental approach:
High cost!
Low flexibility to test different blade designs
Test rig availability
Numerical model?

Parametric studies can be undertaken
Typical wear pattern at different angular speeds (N is the number of lobes, T = torsional mode, F = Flexure/bending mode)

8 lobes bending mode: experimental and numerical results

Wear pattern and gage signal evolution
Wear pattern evolution Gage signal evolution
N.B. The last two pictures show that the abradable has been broken in

Blisk model
56 blades
One of the blades is a little bit longer
A small mass (29 gr) to trigger unbalance
Casing is not exactly centered!
12 926 hexahedral elements
67 776
Diameter =~500 mm

Contents
41

Additive manufacturing test 3D (Metz)
& collaboration with A-M Habraken (Uliège)
42
107 Layers
(175mm)
[2] ment Bourlet. Développement de la fabrication additive par procédé arc-fil pour les aciers : caractérisation
microstructurale et mécanique des dépôts en nuances ER100 et 316L pour la validation des propriétés d'emploi de pièces
industrielles. Autre [cond-mat.other]. Ecole nationale supérieure d'arts et métiers - ENSAM, 2019. Français. NNT :
2019ENAM0058 . tel-02860062

Additive manufacturing test 3D (Metz)
43

Experimental curves
44
Substrate temperatures (TKc5-8) :

Experimental curves
45
Temperatures in the wall (TKvr1-8):
Interruption during building
(not modeled)

Metafor model
46
Convection
+
Radiation
TKvr1-8
TKc5-8

Metafor simulation
47
With remeshing:
Taking all the cluster: 144
tests in ~18h
Cluster No Remesh Remeshing
CPU ( 12 Cores) ~1d15h ~7h30
CPU ( 1 core) ~3-4d ~18h
No Remesh Remeshing
Nelem 56724 56724
5634
Hanging
nodes
N/A 464

Experimental curves
48
Source: [2]
Remark:
All data was fit in time to the
Metafor results on peak 3

Best parameters yet
49
Constant
Substrate
Conductivity
5.0
Deposit Material:
Niccolini

Best parameters yet
50
Tkvr1
Constant
Substrate
Conductivity
5.0
Deposit Material:
Niccolini

Best parameters yet
51
Tkvr2
Constant
Substrate
Conductivity
5.0
Deposit Material:
Niccolini

Best parameters yet
52
Tkvr3
Constant
Substrate
Conductivity
5.0
Deposit Material:
Niccolini

Contents
53

PFEM
54
New developments in PFEM
Particle Finite Element Method

Motivation for PFEM
55
Avoid distortions such as those encountered in updated
Lagrangian formulation for solid mechanics
Combine the advantages of classical FEM and particle
methods (e.g. SPH)
at the nodes like in particle methods
Evolution is computed thanks to a FEM discretization
Use Lagrangian representation to easily track
evolution of interfaces
so there is no need for an interface tracking algorithm

PFEM: how does it work?
56
The first step in the PFEM is discretizing the continuum with
some particles/nodes
The particles carry all the physical and mathematical
The equations are written in their Lagrangian form.Thus
external boundaries are easily determined by following the
particle motion.

At each time step a new mesh is quickly built and
boundaries are determined thanks to the shape
technique.This mesh is used to solve the weak form
using classical FEM over one time step.
Distorted elements and external boundaries are
determined thanks to the shape algorithm
Classical FEM computation

PFEM in the literature
58
Seminal contribution from E. Onate and S. Idelsohn:
Idelsohn S.R., Oñate E., Del Pin F., The particle finite element
method: a powerful tool to solve incompressible flows with free-
surfaces and breaking waves, IJNME (2004)
Oñate E, Idelsohn SR, Del Pin F, Aubry R. The particle finite
element method. An overview. International Journal of
Computational Methods 2004; 1(2):267 307.
See e.g. Cremonesi et al., Arch. Of Comput. Methods in Eng.
2020, for a recent overview.

PFEM: Examples
59
Dam break Problem set
Physical parameters
Numerical parameters
PSPG+Picard
Pressure sensor location

PFEM: Examples
60
Dam break Results

Fluid-Structure
Interactions
61

PFEM
CUPyDO
(Python)
(C++)
(C++)
(C++)
Implementation: coupling codes through Python
Communications are
performed through
memory (No I/O files)
No full execution of
coupled codes
No system calls
SWIG: Simplified Wrapper and Interface Generator, http://www.swig.org
62
Multi-Physics/Multi-scale: coupling different codes

Examples
63
Geometrical parameters
FSI parameters
BGS Aitken relaxation
Dam break against an elastic obstacle Problem set
Solid properties
Fluid properties

PFEM: Examples
64
Dam break against an elastic obstacle Results

Examples: FEM & PFEM coupling
65
Filling of an elastic container Problem set
Geometrical parameters
FSI parameters
BGS Aitken relaxation
IQN-ILS(30)
Solid properties
Fluid properties

Elastic container filling (PFEM & FEM coupling)

PFEM: Examples
67
Dam break against an elastic obstacle 3D Results

3D results including contact
68

3D results including contact
69

PFEM
70
Thermo-mechanically coupled
PFEM with phase change

71
Motivation: numerical simulation of weld pools
multi-physics simulations at meso-scale
Solid
Liquid
Solid
Liquid
Heat source (e.g. Laser LPBF, laser welding )
Heat source
Heat transfer
Melt pool fluid dynamics
Melting & solidification
Residual stresses
and distortion after cooling
transient & coupled
unknown & evolving
Interfaces

Equations to solve:
Liquid, mushy & solid regions solved using same mesh using:
Navier-Stokes equations (NSE) - Lagrangian form
Heat equation
72
Latent heat
absorption
flow resistance
of mushy zone
(and solid)
Surface tension/
Marangoni terms

Equations to solve
Momentum equation for newtonian fluids
Surface tension
Resulting surface force term
73
Normal force Tangential Marangoni force
Note:
Marangoni coefficient
usually negative
surface force drives
fluid away from heat
source
= curvature
= outward normal
= surface tension at
= Marangoni coefficient
Surface tension term

Surface tension example
74
Transition from a cube to a sphere
Yellow arrows represent unit outward normals

Gallium melting
Validate
Latent heat
solid flow resistance
buoyancy
Compare front evolution
Sim. by Saldi (2012)
Sim. by Brent et al. (1988)
Exp. by Gau & Viskanta (1986)
75
(pure Gallium)

Melting of a sample with moving laser
80
Laser heat flux:
Laser position:

Equations to solve
External heat source from laser
81

Temperature isocontours
82

83
Blue: solid particle ( =0)
Yellow: liquid particle ( =1)

84
Fixed laser: generating a Keyhole
Blue: solid particle ( =0)
red: liquid particle ( =1)

Conclusions
PFEM handles well
free surface deformation
Thermo-mechanical problems
phase change with latent heat
surface tension & Marangoni effect
adaptive mesh refinement
Fluid-Structure interactions
Still a lot of work till realistic SLM (Selective
on the way!
85

Conclusion
86
Conclusions
Thank you for your attention!
JP.Ponthot@uliege.be

Simcenter 3D analysis of aero engine structures

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