RAILWAY VEHICLE ENERGY ABSORBERS
Carlos Moreno, Dr Terry Williams (OLEO), Professor Richard Dashwood
and Dr Darren Hughes (WMG)
Industrial Sponsor: OLEO International – Academic Department: WMG
c.moreno@warwick.ac.uk
1. THE CHALLENGE
3. DESIGN APPROACH
Train crashes require large quantities of energy to be dissipated in a controlled manner.
Additionally, although the collision of a vehicle on tracks is predictable, over-riding still poses a
significant problem for the energy absorbers. This characteristic, coupled with the large amount
of energy involved, makes for an interesting engineering challenge.
The approach to find a suitable design cycles around the following categories: architecture,
material, manufacturing process and cost.
ARCHITECT
URE
Crashworthiness Requirements for Railway Bodies:
EN STANDARD REQUIREMENTS
QUANTIFICATION
Absorb energy in the event of front end
collision of identical train units and single 80
tonnes wagon at 36km/h closing speed.
1.2-2MJ energy absorption at the front end
interface of conventional train rake.
Reduce the risk of overriding.
Capability to resist a downward vertical load
of 150kN.
Limit the loads transmitted to the railway
vehicle.
Maximum axial load of 1500/2000kN
transmitted to the railway vehicle (depending
on the type of vehicle)
For some types of trains (i.e. metro vehicles), the energy absorption requirements are at
25km/h whereas for other types (intercity link trains), the requirement is at 36km/h. This
implies a 2-fold energy absorption increase (362/252=2) as the crash energy is proportional to
the square of the speed.
To-date, OLEO International existing products, deformation tubes, have been an elegant system
to cope with both the energy absorption and the over-riding prevention. However, simply
upgrading the energy absorption of the deformation tubes might not be acceptable due to the
limitation on the maximum load transmitted to the vehicle.
MANUFACTURI
NG
DESI
GN
MATERIA
LS
COS
T
ARCHITECTURE - The most efficient geometry to deal with oblique loading is commonly
attributed to crumple columns with a circular section. This has been confirmed by simulating
crash columns with different sections under axial and oblique loading.
A series of LS-Dyna models have been axially crushed by a vertical and a 10° inclined plate. The
energy absorption per unit weight has been calculated and then benchmarked against the
performance of a hexagonal column. The increase (or decrease) energy absorption is
tabulated under the ‘normalised’ column:
SAE - E/m [J/g]
AXIAL CRUSH
GEOMETRY
SQUARE
10° OBLIQUE CRUSH
NORMALISED
6.28
NORMALISED
81%
FAILED
FRUSTRA
5.90
76%
FAILED
CIRCULAR
9.40
121%
7.40
123%
CONE
10.00
128%
8.10
135%
HEXAGONAL
7.80
100%
6.00
100%
HEXAGONAL
TAPERED
7.50
96%
6.20
103%
DEFORMATION TUBE - UNDEFORMED
STATE
HEXAGONAL
PROFILE OBLIQUE
LOADING
DEFORMATION TUBE - DEFORMED STATE
CIRCULAR
PROFILE
OBLIQUE
LOADING
2. EXISTING SOLUTIONS
Unlike other sectors, such as automotive, the railway industry has coped with the crash energy
management issue with a wide range of different systems and there seems to be no consensus
about what design is the most effective with the problem at hand:
1. Deformation Tubes
2. Crumple Columns
3. Guided Crumpled Columns
4. Metal Splitting
5. Peeling Technology
6. Buckling Technology
CONE
OBLIQUE
LOADING
MATERIAL - Composites appear to offer a potential as a good energy absorbing material,
either used alone or more likely, coupled with metallic components. Recent work within the
materials group has highlighted this potential (in LCVTP). As the project progresses, the
application of composites in rail crash absorbers will be evaluated.
CRUMPLE COLUMNS
4. NEXT STEPS
Two main lines of research are being pursued to produce a railway vehicle crashworthy
energy absorber:
METAL SPLITTING
GUIDED CRUMPLE BOX
1.
2.
PEELING
BUCKLING
Enhanced Deformation Tubes. Deformation tube technology needs to be enhanced to be
able to absorb the new requirement of energy in order to maintain the existing
geometrical envelope. The use of alternative / advanced material crash columns coupled
with deformation tubes is being explored to increase the device’s energy absorption
without significantly increasing its weight.
Crumple Columns Optimised for Oblique Loading. Optimisation of composite columns
subjected to oblique loads by means of geometry design is being studied to produce a
lightweight energy absorber, tailored to the railway vehicles requirements.