2014 conference-dynamic-simulation-in-vehicle-engineering … · 2017. 9. 8. · −adams-optimizer...

Dr. Stefan Reichl, Dr. Martin Kuchler, Mario Prandstötter, Günther Pessl

3rd International Conference: Dynamic Simulation in Vehicle Engineering 2014Engineering Center Steyr, St. Valentin, May 22nd - 23rd

BMW Steyr Diesel Engine Development Center

ENTWICKLUNGDIESELMOTOREN

MULTIBODY AND STRUCTURAL DYNAMIC SIMULATIONS IN THE DEVELOPMENT OF NEW BMW 3- AND 4-CYLINDER DIESEL ENGINES

Stefan Reichl, BMW Steyr Seite 2

OVERVIEW

Introduction1

Modeling Process and Applications2

Project Examples in the Low Frequency Domain3

Project Examples in the High Frequency Domain4

Summary5

Conference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014


OVERVIEW

Introduction1




Summary5


Stefan Reichl, BMW SteyrConference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014 Seite 4

INTRODUCTIONDYNAMIC SIMULATION IN 3-, 4-, 6-CYL. ENGINES

− Modular design for 3-, 4- and 6-cylinder inline diesel engines (38% carry-over, 59% synergy parts)

− 70kW – 290kW / 220Nm – 760Nm

Structural Dynamics & Acoustics

Vibration / durability of auxiliary components

Vibration / durability of the exhaust system

Vibration / sound radiation of ETU

Transfer functions, transmission paths

Vibration / acoustic of air duct parts

Multi Body Dynamics

Cranktrain Dynamics

Durability of Crankshaft

Belt Drive Dynamics

Chain Drive Dynamics

Excitation ETU – Chassis


OVERVIEW

Introduction1


Process Examples in the Low Frequency Domain3

Process Examples in the High Frequency Domain4

Summary5



MODELING PROCESS AND APPLICATIONS (1)ENGINE GEARBOX ASSEMBLY MODELS

− The structural dynamic conformable meshing of the relevant engine parts is performed with ANSA by means of the appropriate CAD models.

− For each engine component an average temperature is determined based on measurements or thermo-mechanical calculations. The modulus of elasticity, the mass density and the poisson’s ratio of the engine part material at this average temperature are assigned to the corresponding FEM model. The material parameters are classified in a database which is based on correlative experiments.

− The build-up of sub-assembly FEM models is accomplished by modelling internal parts such as crankshafts, balancing shafts, flywheels etc. with ANSA and MEDINA.

Temperature (°C)

Mod

ulus

of

elas

tici

ty (M

Pa)

Aluminium alloys

Crankcase CAD model (left), crankcase FEM model (middle) and modulus of elasticity (right).


MODELING PROCESS AND APPLICATIONS (2)ENGINE GEARBOX ASSEMBLY MODELS

− The engine gearbox assembly models reach up to 60 million degrees of freedom and are assembled with ANSA by means of specific connector models and a once defined assembly specification.

4-cylinder engine gearbox assembly FEM model.


MODELING PROCESS AND APPLICATIONS (3)COMPARISON OF CALCULATED AND MEASURED DATA

− Global vertical bending natural vibration:

− Validation of the global vertical bending natural vibration of an engine gearbox assembly model on the basis of acceleration measurements at the corresponding right gearbox bearing on a roller dynamometer with full load.

Acceleration measurements in the local z-direction

Frequency range that can be associated with the global vertical bending natural vibration

High

Low

FrequencyE

ngin

e sp

eed

rang

e

Acceleration at the right gearbox bearing / local z-direction

Engine gearbox assembly model (left) and Campbell diagram of the measured acceleration (right).


MODELING PROCESS AND APPLICATIONS (4)COMPARISON OF CALCULATED AND MEASURED DATA

− Global vertical bending natural vibration:

− Comparison of the calculated global vertical bending natural frequency with the corresponding evaluated frequency range from the acceleration measurements.

Lower bound

Top bound

8.4 Hz

3.1 Hz

Calculated global vertical

bending natural frequency

Computed inertance (left), global vertical bending mode shape (middle) and frequency range (right).

Global vertical bending natural

vibration occurrence

Stefan Reichl, BMW SteyrConference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014

MODELING PROCESS AND APPLICATIONS (5)MBS MODEL

− Flexible Bodies: implementation via Craig-Bampton method (MSC.NASTRAN / MSC.ADAMS interface)

− ETU

− Crankshaft

− TVD hub

− Primary part with flex platesof dual mass flywheel or

− Torque converter

− Balancing Shafts

− Rigid Bodies:

− Pistons

− Conrods

− TVD: inertia ring, belt drive pulley

− Secondary part of dual mass flywheel

− Stiffness Curves:

− Flywheel, TVD, engine mounts, gears, …

350-500 DOFs (depending on EHD resolution)

Seite 10

dual mass flywheel with nonlinear torsional stiffness

belt drive reduced onto the decoupled pulley

engine / gear box mounts modeled with static

stiffness curves

cylinder pressure


MODELING PROCESS AND APPLICATIONS (6)EHD SUBROUTINE

− EHD subroutine implemented in MSC.ADAMS

− Numerical solution of Reynolds equations

− Consideration of crankshaft tilting and deformations of the bearing shells

− Load application via pressure distributions (MFORCEs) at crankshaft and bearing shells

− MFORCE: superposition of several load shape functions

− Only compressive forces are applied (in contrast to RBE-elements

H(φ,z) … Lubrication gap geometry with elastic deformation of the bearing shell

p … oil pressureφ… angleD … nominal bearing diameterB … bearing widthZ … relative bearing widthη… dynamic oil viscosityψ… clearance ωB …angular velocity

EHD - Parameter

Diameter

Supporting width

Clearance

Oil viscosity

Convexity

Resolution (number of load shape functions)

Reynolds equation (nonlinear PDE):

MFORCE (one load shape function)


MODELING PROCESS AND APPLICATIONS (7)INPUTS / OUTPUTS OF A FULL LOAD ENGINE RUN-UP

− Inputs:

− Ignition data: measured cylinder pressures

− Speed profile from test rig

− Outputs:

− Combustion chamber roof forces

− Piston side forces

− Forces & torques in the main bearings

− Radial forces in the balancing shaft bearings

− Gear teeth forces of balancing shafts

− Radial forces at the gearbox input shaft

− Rotational irregulatory of crankshaft

− Engine torque

− Engine and gearbox mounting forces

Time (s)

Eng

ine

spe

ed (r

pm)


MODELING PROCESS AND APPLICATIONS (8)LOAD GENERATION

− Calculated loads are further used for FEA / fatigue analyses of several engine parts and acoustic simulations

high

low

High

Low

FEA of normal velocity levels(2600 – 2800Hz)

Acoustic camera(2600 – 2800Hz)

low

high

Fatigue analysis of crankcase

Fatigue analysis of crankshaft


OVERVIEW

Introduction1




Summary5



PROJECT EXAMPLES IN THE LOW FREQUENCY DOMAIN (1)MBS-MODEL FOR START ANALYSES

− Rigid body model with reduced belt drive

− Engine and gear box mounts: nonlinear stiffnesses (static vs. dynamic)

− Cylinder pressures from measurements

starter


PROJECT EXAMPLES IN THE LOW FREQUENCY DOMAIN (2)STARTER

− Implementation of starter, planetary gear, sprockets, free wheel

− Starter: differential equations of a permanently excited DC machine

− Free wheel: user-written subroutine rotor

VTORQUE: starter VTORQUE: free wheel

planetary gear

sprocketParameter Description

U0,Batt Battery voltage

Ri,Batt Internal resistance battery

R30 Lead resistance

Rges Resistance starter

UB Carbon brushes voltage

Lrot Rotor inductivity

Cmot Motor constant

MR Friction torque starter

IAnker Mass of inertia rotor

i Gear ratios planetary gear,starter ring, sprocket

Equivalent circuit diagram of the permanently excited DC machine

Starter with planetary gear, sprocket and free wheel


PROJECT EXAMPLES IN THE LOW FREQUENCY DOMAIN (3)RIGID BODY MOTION DURING START

− Comparison between simulation and measurement data

MeasurementSimulationScale Factor: 5

Stefan Reichl, BMW Steyr

− Objective function: kinetic energy of ETU � MIN (reduction of the shaking during start)

− x-, y- and z-positions of left and right engine mount are varied in a possible range

− ADAMS-optimizer OPTDES-SQP

− Lateral displacement of ETU is reduced by 70%, roll angle by 8%!

− Lateral forces in engine mounts are decreased by 82%!

Conference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014 Seite 18

PROJECT EXAMPLES IN THE LOW FREQUENCY DOMAIN (4)OPTIMIZATION OF ENGINE MOUNT POSITIONS

global minimum

Kin

etic

Ene

rgy

Trajectory of the center of mass of the ETU

Maxima of lateral forces in engine / gear box mounts

Objective function

BasisOptimized variant

DZ

(mm

)


OVERVIEW

Introduction1




Summary5



PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (1)COMPARISON OF 2 CRANKSHAFTS

Crankshaft V1 Crankshaft V2

Benefits of Crankshaft V2

Mass crankshaft -2.2%

Moment of Inertia (crankshaft) -3.7%

Moment of inertia (cranktrain) -4.0%

CO2 emission (NEDC) -0.4%

Stiffness Reducion of Crankshaft V2

Bending stiffness (single throw) -13.8%

Torsional stiffness (single throw) -17.5%

Torsional stiffness (entire crankshaft) -14.2%

Stefan Reichl, BMW Steyr

− Shift in Eigenfrequencies of crankshaft V2

Conference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014 Seite 21

PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (2)COMPARISON OF 2 CRANKSHAFTS

1st vertical bending mode: -23Hz 1st lateral bending mode: -43Hz

1st torsional mode: -89Hz


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (3)MAIN BEARING FORCES (CRANKSHAFT V1)

1000 rpm

2000 rpm

3000 rpm

4000 rpm

5000 rpm

6000 rpm

Lateral Force

Bearing 1 Bearing 2 Bearing 3 Bearing 4 Bearing 5

Vertical Torque

Vert

ical

For

ceLa

tera

l Tor

que


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (4)LATERAL TORQUE (CRANKSHAFT V1 / V2)

− Comparison of the Lateral Torque (referred to ETU)

− Lateral torque gives information about the vertical bending of the crankshaft

− Stiffness reduction causes higher forces and torques => stresses in bearing supports increase


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (5)DEFORMATION OF THE CRANKSHAFTS

− One Cycle @ 4000rpm (point of nominal engine power)

Cra

nksh

aftV

1C

rank

shaf

tV2


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (6)DEFORMATION OF THE CRANKSHAFTS

− Deformation @ ignition cylinder 4

Cra

nksh

aftV

1C

rank

shaf

tV2

Bending Line for Crankshafts and Bearing Shells


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (7)PRESSURE DISTRIBUTION IN BEARING SHELLS

− Asperity pressure @ 4000rpm

− Maximum of asperity pressure: information about failure mode „pitting“

− Average of asperity pressure: information about failure mode „wear“


low high

Bearing Shells (Crankshaft V1)

Top

Bot

tom

#1 #2 #3 #4 #5 #1 #2 #3 #4 #5 #1 #2 #3 #4 #5


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (8)TORSIONAL VIBRATIONS

− Campbell diagrams of crankshaft twist angle

low high low high

f0 f0


− Order analysis of crankshaft twist angle

− TVD is adapted to the torsional Eigenfrequency of the system => a peak below and a peak above this point occur

− Torsional vibrations of crankshaft V2 are above the allowed limit

limit, 100°C limit, 100°C



− Order analysis of crankshaft twist angle

− Another type of TVD is used (broadband operating) in order to reduce the torsional vibrations

limit, 100°C


limit, 100°C


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (11)FATIGUE COMPUTATIONS

− FEMFAT Channel MAX is used for fatigue computations

− Material models are derived from test rig results

− Safety factors are calculated in main- and crank bearing fillets, oil drillings, …

-24.7%


PROJECT EXAMPLES IN THE HIGH FREQUENCY DOMAIN (13)FATIGUE COMPUTATIONS

− Distribution of safety factors

− Calculated Critical Area and Crack Initiation Site from the Test Rig correspond


low

high

Crack produced onTest Rig

low

high


OVERVIEW

Introduction1




Summary5



SUMMARY

− The introduced dynamic CAE processes are effectively applicable in an industrial development environment.

− The simulation results show good accordance to corresponding measurements.

− The CAE methods are continuously enhanced in the framework of the project work to further increase the quality of the computed results.

− Rigid body models with measured ignition data and electric components from starter etc. can perfectly be used for start analyses of the engine.

− Such models are applied for optimizations of the starting system, sensitivity analyses of belt drive and flywheel and optimizations of the engine mounts.

− If new designs of crankshafts or crankcase are evaluated, flexible multi body systems are used to calculate a full load engine run up. The interaction between crankshaft and crankcase plays an important role.

− A change in the stiffness of the crankshaft effects the main bearing forces and torques, the torsionaland bending vibrations, the pressure distributions in the bearing shells and the safety factors of specific parts.


SUMMARY

High End Methods

SimulationSpeed

AccuracyReliability

BMW Efficient Development

InnovationsInnovations

Innovations

Stefan Reichl, BMW SteyrConference Dynamic Simulation in Vehicle Engineering, May 22nd – 23rd 2014

BMW Motoren GmbH

Diesel Engine Development Center

Simulation/CAE

2014 conference-dynamic-simulation-in-vehicle-engineering … · 2017. 9. 8. · −adams-optimizer...

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