Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
1 19.05.2011
Structural Vibrations of Passenger Car Bodies
Caused by Track Excitations
Dipl.-Ing. Christian Mängel
Prof. Dr.-Ing. Markus Hecht
SIMPACK User Meeting 2011
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
2 19.05.2011
Chair of Rail Vehicles
Main Focuses of Research
• Acoustics of rail vehicles – Quiet track
– Measurement and noise reduction of vehicles
• Construction of rail vehicles – Simulation of vehicle dynamics
– Detachble cab …
• Safety of rail vehicles – Rail breakage detection
– Crash simulation …
• Telematics and maintenance in freight transport – Condition based maintenance for freight wagons
– Durability optimisation of wheels
– Automatic tread check …
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
3 19.05.2011
Lightweight Constructions of Railway Vehicles
Demands on modern passenger car bodies:
• Low weight to reduce the energy consumption and the track forces
• Good ride comfort on board even at high speed
• High and flexible seating capacity
• Continuous (clear and open) passenger compartment
The car body becomes more susceptible to structure
vibrations
These structural vibrations strongly affect the riding comfort of
passenger cars.
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
4 19.05.2011
Consequence for Simulations
To simulate the dynamic behavior of railway vehicles and to predict the ride
comfort, structural vibrations have to be included in a simulation model
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
5 19.05.2011
Aim of Research
Methods to improve the ride comfort of the vehicle:
• Using an active vibration reduction system
• Increasing the stiffness of the car body structure to achieve higher
eigenfrequencies
– In general: higher vehicle
weight
– Stiffener which significantly
influence the design of the
interior desing
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
6 19.05.2011
Aim of Research
• Method for designing and sizing structural components in an early
development stage.
• In 2006 a project started in which methods for laying out rail vehicles
with good ride comfort are investigated
• One conclusion of the study is that there is a correlation of the bending
modes of the car body, the velocity and the design of the vehicle
• With a rising velocity there are conditions with increasing or decreasing
ride comfort
• This is already known for vertical excitation and bending modes
𝑣 =4 𝑎∗ ∙ 𝑓
𝑁
N = 1, 3 ,4 … N = 2, 4, 6 …
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
7 19.05.2011
Resonance Velocity for vertical Bending Mode
The use of odd or even numbers (N) depends on the bending mode:
2a*
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
8 19.05.2011
Average NMV (Mean Comfort) - EN 12299
N_mv_
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Co
mfo
rt N
_M
V
0 50 100 150 200 250 300 350 400 450
Velocity [km/h]
Influence of the resonance velocity for bending modes on the ride comfort
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
9 19.05.2011
Periodic Vehicle Excitations
The previous characteristics can be caused by a periodic excitation
– Periodic track irregularities
– Imbalanced wheel sets or
– Out-of-round wheels
– Hunting oscillation etc.
[Knothe/Stichel]
Polar Plot of Wheel Roughness Data
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
10 19.05.2011
Resonance Velocity for lateral Bending Mode
Resulting question:
• Is there a high correlation between the lateral and rotational motions of
the bogies?
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
11 19.05.2011
Linear Analysis
• Simplification, e.g. rail wheel contact is not completely described
• Especially lateral track irregularities do not have to excite every wheel
set in the same way
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
12 19.05.2011
Non linear Analysis
Correlation between the bogies
• Regarding:
– Stochastic track irregularities
– Dynamic behavior of the vehicle
– Gauge clearance
– Etc.
• Validation through measurements
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
13 19.05.2011
Influence on Car Body Eigenfrequencies
Investigation of characteristic car body eigenfrequencies, their
corresponding excitation due to track irregularities and the
dynamic behavior of the bogies regarding
– Vehicle concept
– Primary and secondary suspension, especially yaw dampers
– Connections between car bodies
– Asymmetric structures
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
14 19.05.2011
Typical Mode Shapes of a Flexible Car Body
First vertical bending
First lateral bending
First rhombic mode/diagonal distorsion
First Torsion
First Breathing
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
15 19.05.2011
Vehicle Concepts
• Parameter
– Length of the car body
– Bogie spacing
– Wheelbase
– Primary and secondary suspension
– Eigenfrequencies of the car body
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
16 19.05.2011
Vehicle Concepts
• Elastic car bodies from ANSYS
• Incorporation of the FE-Modell into SIMPACK with FEMBS
• Car bodies are described by
– 30 eigenmodes
– Mass, center of mass, I-Tensor
– Geometry
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
17 19.05.2011
Variation in Car Body Design
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
18 19.05.2011
Variation in Car Body Design
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
19 19.05.2011
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
v [
km
/h]
0 5 10 15 20 25 30
f [Hz]
1·10-3
1·10-2
1·10-1
[ m
/s^2
]
Simulations Results: Vertical Acceleration
1st rhombic mode 1st vertical bending 2nd vertical bending 3rd rhombic mode
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
20 19.05.2011
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
v [
km
/h]
0 5 10 15 20 25 30
f [Hz]
1·10-3
1·10-2
1·10-1
[ m
/s^2
]
Simulations Results: Vertical Acceleration
1st rhombic mode 2nd rhombic mode Only lateral track excitation
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
21 19.05.2011
Conclusion
• The critical resonance velocities for different bending modes
of the carbody structure can be shown for vertical bending
forms as well as for lateral track excitations influencing the
lateral or rotational movement of the bogies
• For the latter the secondary suspension predominantly
influences the effect of the resonance velocities
Institut für Land- und Seeverkehr
Fachgebiet Schienenfahrzeuge
22 19.05.2011
Further Work
• Evaluation of the interaction between the modes in the
resonance velocity
• Influence of the coupling of car bodies
• Effect of resonance velocities on lightweight freight carrying
cars on track forces