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Letting the train take the strain

Train designers are now using the results of this project on how train structures perform in crashes in their latest designs. The project was in part a response to the growing insistence of buyers on safer trains. Unlike in the car industry, there are no European safety regulations covering vehicle design in the railway industry.
The partners have developed calculation tools that allow faster preparation of calculation models than is possible with finite element analysis packages already on the market. They have also decided to collaborate further in order to define detailed impact absorption criteria that could be incorporated in safety standards.

There is little understanding of how the different parts of train structures actually stand up to crashes, and there have been few detailed international safety standards that train operators can specify to the builders of their vehicles. All countries conform to the recommendations of the International Union of Railways on crashworthiness, but they adopt different structural specifications which all pay little attention to the effects of one train riding over another in a crash, one of the main causes of passenger injuries. Trains have in most cases been designed to crumple in a crash, to dissipate the enormous amount of energy released by the impact. This has meant that trains are usually very unfriendly places for people in crashes.

Overriding concerns

Railway companies are, however, increasingly insisting on designs to high safety standards, and various proposals have emerged in recent years for how trains should stand up to impacts. For example, British Rail proposed that the energy of a collision should be absorbed first by deformation of the end wall of a vehicle before other parts deform. It also proposed that vehicles would not ride over each other in a crash and that any collapse would be in areas not likely to be used by passengers or crew.
The Portuguese trainmaker Sorefame initiated the Brite-Euram project TRAINCOL to develop a better understanding of the effect of crashes on vehicle structures, as well as to develop design methodologies for safer carriages. An important aim of the project was to produce proposals for better regulations that would minimise passenger injury in crashes.

Railway modelling

The TRAINCOL project involved some of the leading railway engineering organisations in Europe. The work involved the use of computer aided design tools, as well as an assessment of how passengers would be affected if particular designs were involved in crashes. Such work has been done already for road vehicles such as coaches that, like trains, are built from sheet metal panels fitted to supporting frameworks.
One of the project partners, Cranfield Impact Centre, has a large amount of experience in the design and analysis of road coaches, and was able to transfer that knowledge to its TRAINCOL work. Ensuring that the computer models were valid required data from real crush tests. The partners therefore built train parts, sub-assemblies and complete carriages and carried out static and dynamic tests.
There were full scale and model tests. An important part of the TRAINCOL project was the static testing of typical end frame components to determine crush and hinge characteristics of components. The partners tested six types of carbon steel profiles under different loading conditions, six substructures with different geometries and made of different materials under axial crushing, and full scale end underframes under axial crushing.
There was good correlation between the theory and the test results. This has allowed the setting up of a database of mechanical characteristics of profiles for use with different software tools. The partners also learned more about how well different components and sub-assemblies dissipate energy through plastic deformation, and how good the results of reduced scale modelling are.
There were two crash tests of full scale vehicles, one in Portugal at the facilities of the train operator CP and the other in France at the facilities of the train company SNCF. The crash tests allowed the researchers to monitor effects such as displacement and strain, using techniques such as high-speed filming.

New dimension to design

IST, Instituto Superior Técnico of the Technical University in Lisbon made a very important contribution to the project. The Department of Mechanical Engineering has extensive research experience in crashworthiness analysis and tooling development for aided design of vehicle structures under impact conditions, along with active involvement in the field of computational dynamics of rigid and flexible mechanical systems (FEM and Multi-body dynamics).
The researchers applied a wide range of software tools to their analyses, from 1D to 3D models. In the case of 1D analysis, the aim was to minimize peak accelerations in a frontal collision while allowing deformations that would maintain a minimum survivable passenger space. Several design proposals have been produced.
The 2D analyses allowed rail vehicle underframes to be modelled by assemblies of rigid and flexible bodies with degrees of freedom in longitudinal, transversal and rotational motion. Rigid bodies and flexible members formed the basis of the 3D models that were used to assess the overall behaviour of the ends of rail vehicles.
Both the 2D and 3D models were found useful in speeding up the initial stages of designing structures, but because they are based on a large amount of simplification they are not suitable for detailed design work. The partners also developed an algorithm for design of both linear and non-linear structures, taking into account factors such as stress, displacement and eigen value.
The module can be used with commercially available finite element analysis codes as an alternative to existing trial and error systems, say the Traincol partners. The design sensitivity analysis code was based on an object oriented approach and implemented in C++ programming language. Tests of the software showed a good correspondence with various structures, and design improvements were found to be possible after just a few analysis steps.
To relate train design to passenger safety, the partners developed a model for what happens to passengers' bodies and their likely injuries should there be a crash. The model used various types of seats and dummy passengers. The injury modeling allowed for secondary impacts, such as passengers hitting the backs of the seats ahead of them.

On track for improvements

Overall the project produced design approaches that can substantially reduce the amount of time required to design safe structures. The partners nevertheless recommend that designers carry out detailed studies of simple elements, including possible tests of components, to ensure acceptable results. But use of the computer models should reduce the amount of testing needed for any design.
Some of the partners have decided to work together on developing crash test methods and design approaches to ensure the safety of drivers and passengers. The four-year project should begin in 1997. But the results of the first project are already being used in the design of trains. Sorefame, for example has used some of the techniques in the design of trains for the Central Line project in Lisbon.


Project Title:  
Advanced design of crash fail-safe train structures under service and impact conditions.

Industrial and Materials Technologies (BRITE-EURAM/CRAFT/SMT)

Contract Reference: BE-3385

Cordis DatabaseFor more information on this project,
go to the CORDIS Database Record