Kuscha, Schroeder, BMW AG
Pöschl, Niedhammer, Dassault Systèmes Deutschland GmbH
ADVANCED CRANKTRAIN SIMULATIONat BMW AG.SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016
CONTENTS.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 2
• Database structure overview
• Cranktrain components with different levels of detail
• Process automation and calculation tasks
• Fatigue strength calculation and example
• Calculation of cut loads and example
• NVH calculations and example
• Summary and outlook
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 3
DATABASE STRUCTURE OVERVIEW.
010_EGB
020_CRB
020_CRS
030_CNB
030_CTR
040_FCC
050_TVD
099_GAS
900_LOD
099_GAS
Model Topology
.spckModel Parameterization
.par.spck
Submodels
.sub.spck
CTR
CDR
GVT
SVTTop level model
.spck
Load case
Gas forces
060_AGB
060_AGT
060_AGW
…
010_EGB
020_CRB
020_CRS
030_CNB
030_CTR
040_FCC
050_TVD
099_GAS
900_LOD
099_GAS
060_AGB
060_AGT
060_AGW
…
CRANKTRAIN COMPONENTS WITHDIFFERENT LEVELS OF DETAIL.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 4
010_EGB 020_CRB 020_CRS 030_CTR
Engine block with gearbox
• Subtypes for different
engine types
• Rigid or flexible depending
on parameters
Crankshaft
• Subtypes for different
modelling approaches and
engine types
• 1D torsional multi mass
oscillator models
• 3D models, rigid or flexible
depending on parameters
Crank train
• Subtypes for different
modelling approaches
• Rigid or flexible depending
on parameters
• Interface piston to engine
block with translational joint
or piston-liner contact or
Simpack hydrodynamic
bearing
Crankshaft bearing
• Subtypes with different
modelling approaches
• Simple bushing
• IST hydrodynamic bearings
using impedance and online
FEM method
• Simpack hydrodynamic
bearings using approximating
and hydrodynamics method
030_CNB
Conrod bearing
• Subtypes with different
modelling approaches
• Constraint
• Simple bushing
• IST hydrodynamic bearings
using online FEM Method
• Simpack hydrodynamic
bearings using approximating
and hydrodynamics method
Piston-liner contact Hydrodynamic bearing
CRANKTRAIN COMPONENTS WITHDIFFERENT LEVELS OF DETAIL.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 5
040_FCC 050_TVD 060_AGB 060_AGT
Flywheel / Converter / Clutch
• Rigid or flexible depending on
parameters
• Degrees of freedom depending
on parameterization
• Could represent one or two
mass oscillators
Balancing shaft bearing
• Different models covering
radial and axial bearing
separately and in different
levels of detail
Balancing shaft gear drive
• Available for 3 and 4
cylinder engines
• Different modelling
approaches using gear pair
or a simple spring damper
coupling including
transmission ratio
Torsional vibration damper
• Subtypes for different
modelling approaches and
vibration damper types
• Rigid or flexible
• 1D or 3D modelling of damper
• Rubber or viscous damper
060_AGW
Balancing shaft
• Available as general
template
• For use in 3 and 4 cylinder
engines
• Rigid or flexible depending
on parameters
PROCESS AUTOMATISATION.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 6
• Process automatisation of fatigue strength and cut load calculation of a stepped runup implemented as Simpack solver script
• Calculations in separate process
• Control via GUI-widget or shell only (Linux)
Definition of stepped runup
Calculation and evaluation
period
Resultfile name and output
directory for Simpack results
Every configuration could be
saved and reused
Loads calculation and
stress file
Stress export for selected
nodes
Settings for cut plane loads
calculation
FEMFAT Interface files
FEMFAT job template and
material data, name and
directory for results
Selection of Simpack model
Start Simulation
FATIGUE STRENGTH CALCULATIONASSEMBLY OF SUBMODELS AND LOAD CASE.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016
010_EGB
010_CRB
020_CRS
030_CTR
040_FCC
050_TVD
099_GAS
030_CNB
Gas forces
• Defines cylinder pressure
time dependency by given
crankshaft angle, angular
frequency and ignition order
• Various engine subtypes
• Cylinder pressure acting at
rigid piston
Submodel
Load Case
Engine block with gearbox
• Flexible
Crankshaft bearing
• IST hydrodynamic bearing with
impedance method
• Implementation of Simpack
hydrodynamic bearing planned
Crankshaft
• 3D model
• Flexible
Conrod bearing
• Constraint
Crank train
• Rigid
• Piston with translational joint
Flywheel / Converter
• Flexible
• One mass oscillator,
primary side only
Torsional vibration damper
• Rigid
• 1D
900_LOD
Load brake
7
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 8
FATIGUE STRENGTH CALCULATIONDATA FLOW.
*body_irm.odb
*body_mod.odb
*body.stress
*model.sbr
Loads
mod
1
tq
tq
k
irml tq
tq
1
mod
1
x
x
k
irml x
x
1
Define material data
and analysis typeFatigue analysis
Integration
FEMFAT
Export
*model.spck
*job.ffj
RPM specific
safety against
fatigue failure
*material.ffd
Modal
stresses
Modal
coordinates
FATIGUE STRENGTH CALCULATIONEXAMPLE.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 9
Accepted value for endurance strength
Accepted value for endurance strength
• Operational stresses
• Material data
• Technology influence
Am
pli
tud
e S
tre
ss[N
/mm
2]
Mean Stress [N/mm2]
CALCULATION OF CUTTING LOADSDATA FLOW.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 10
*body_irm.odb
*body_mod.odb
*body.stress
*model.sbr
Loads
mod
1
tq
tq
k
irml tq
tq
1
mod
1
x
x
k
irml x
x
1
Modal
cut loads
l
ll
k
kk tqxtqxtx
,
*scr.odb
Python
Integration
FEMFAT
Export
*model.spck
Modal
stresses
mod
11
i
i
i
i
A
iiAkik
A
iiAi
dAnxxF
dAnxxF
mod
11
Ai
iiAkiAik
Ai
iiAiAi
dAnxxxxM
dAnxxxxM
ii
ii
l
lil
k
kiki tqxFtqxFtxF
,
l
lil
k
kiki tqxMtqxMtxM
,
Superposition
time domain
Modal
coordinates
*sup.odb
*sup.srf
ModeEigenkModeIRMlneSchnittebei :,:,:
irm
A
iiAlil
A
iiAi
i
i
i
i
dAnxxF
dAnxxF
11
irm
A
iiAliAil
A
iiAiAi
i
ii
i
ii
dAnxxxxM
dAnxxxxM
11
Mean valueTorsional moment at 5000 rpm
Torsional moment at 2000 rpm
CALCULATION OF CUTTING LOADSEXAMPLE.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 11
Definition of cutting planes
cp1 cp2
cp3 cp4 cp5 cp6
cp7 cp8
Input data for hardware testing
Amplitude
,…
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 12
NVH INTRODUCTION
rattling
knocking
howling
booming
beating
barking
piping
pumping
S: Many NVH-phenomena observed at engines are affected by the cranktrain as heart of the engine.
Our focus today: solid dynamics of crankshaft and its effects on the engine structure.
buzzing
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 13
NVH INTRODUCTION
Focusing structure born sound in time domain for linear elastic with linear strain kinematics continua:
Governing equations [“trinity” of mechanics]:
S: The big numerical solution part is already done by: , thanks a lot!
𝑢𝑖(𝑥𝑘) = 𝑢𝑖 𝑥𝑘 𝑥𝑘 ∈ 𝜕𝐵𝑢
𝑡𝑖(𝑥𝑘) = 𝑡𝑖(𝑥𝑘) 𝑥𝑘 ∈ 𝜕𝐵𝑡
𝜌 𝑢𝑖 = 𝜎𝑖𝑗,𝑗 + 𝜌𝑓𝑖
𝜀𝑖𝑗 =1
2𝑢𝑖,𝑗 + 𝑢𝑗,𝑖
𝜎𝑖𝑗 = 𝐶𝑖𝑗𝑘𝑙𝜀𝑘𝑙
𝜌 𝑢𝑖 = 𝜎𝑖𝑗,𝑗 + 𝜌𝑓𝑖
𝜀𝑖𝑗 =1
2𝑢𝑖,𝑗 + 𝑢𝑗,𝑖 + 𝑢𝑖,𝑛𝑢𝑛,𝑗
𝜎𝑖𝑗 ⇔ 𝜀𝑖𝑗
Q: Where is the damping?
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 14
MODELL DESCRIPTION.NVH
S: The “boundarys” between FE and MBS Simulations are vanishing and they have to.
Parameter identification
SIMPACK assembly of engine model
Division in substructures
Structural mechanics world Multibody dynamics world
?
?
NVH CALCULATIONASSEMBLY OF SUBMODELS AND LOAD CASE.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 15
010_EGB
010_CRB
020_CRS
030_CTR
040_FCC
050_TVD
099_GAS
030_CNB
Gas forces
• Defines cylinder pressure
time dependency by given
crankshaft angle, angular
frequency and ignition order
• Various engine subtypes
• Cylinder pressure acting at
flexible piston and flexible
cylinder
900_LOD
Load brake
Engine block with gearbox
• Flexible
Crankshaft bearing
• Simpack hydrodynamic
bearing with hydrodynamic
method
Crankshaft
• 3D model
• Flexible
Conrod bearing
• Constraint
Crank train
• Flexible
• Simpack bearing with
hydrodynamic method
Flywheel / Converter
• Flexible
• One mass oscillator,
primary side only
Torsional vibration damper
• Flexible
• 3D
060_AGx
Submodel
Load Case
Balancing shaft
• Flexible
• Gear pair
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 16
SOME RESULTS.NVH
CMA and damping experiments on subsystems by ICS Measurements at operating engine by BMW and AVL
Testing structural mechanics world Testing multibody dynamics world
Bringing it all together:
acce
lera
tio
n
Time [s]
HL1
HL2
Simulation
Measurement
S: Simulation matches very well the measurements in the focused frequency range. At all sensor positions. But not yet so perfect in all directions. This enable us to study in detail time dominated NVH phenomena within linear structures, but with full beauty of nonlinearity of MBS.
SUMMARY AND OUTLOOK.
SIMULIA European MBS User Group Meeting - Darmstadt - 9.11.2016 17
Engine database concept leads to fast model setup with easy exchangeability between different
components and levels of details
Process control with minimum user interference by usage of solver script
Fatigue strength calculation of crankshafts established as tool for design approval before
hardware testing
Calculation of cutting loads for hardware validation of fatigue strength calculation
NVH calculations are leading to better understanding of acoustic phenomena
Future Plans:
• Parallel calculation of different engine speeds
• Full scale introduction of Simpack hydrodynamic bearing and validation with measurements in
an operating fast running engine
• Further detailed calculation of NVH phenomena by growing together of MBS and FE models
and prediction of NVH quality in early stages of development
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