Our expertise in railway systems refers mainly to experimental setup and testing, modeling techniques and simulation analysis.
Computer-aided modeling and analysis
The dynamical behavior of modern railway vehicles can be advantageously analyzed via a multibody formalism (for the mechanical vehicle component) possibly coupled with multiphysics models (for electrical actuators, pneumatic suspensions, hydraulic circuits, etc.).
With this aim in mind and to face the wide diversity of industrial issues we have had to cope with (in terms of models to be built as well as results to be provided), we have opted for an open-ended approach such as that underlying our symbolic multibody software ROBOTRAN, developed by the CEREM, the Center for Research in Mechatronics of the UCL (iMMC/CEREM). Starting from the general description of the system in terms of bodies, joints, constraints and forces, the multibody dynamical model is symbolically generated in a prescribed syntax and in the form of stand-alone computer files. The latters can be easily interfaced with standard numerical processes (time integration, modal analysis, …) and coupled with other fields (geometrical, electrical, hydraulic or pneumatic models, …) in a very versatile way. For instance, this modular approach has been successfully used to analyze independent wheel behavior, electrical actuation of high-speed bogies and secondary suspension performances, etc.
Beside this ROBOTRAN environment, a complementary approach is preferred for applications requiring specific wheel/rail models and advanced track design and trajectories. The SIMPACK program, which is especially renowned in the railway industry, is perfectly suitable in these cases. Additionally, we resort to the SIMPACK-SIMULINK co-simulation interface in dealing with weakly-coupled multiphysics problems involving the above-mentioned disciplines.
Experimental and testing facilities
The LEMSC, the UCL Laboratory of Mechanical Testing, Structure and Civil Engineering (iMMC/LEMS), has, since its foundation in 1972, acquired a strong expertise in the field of experimental set-up and testing of railway infrastructure.
The laboratory is accredited following standard EN ISO 17025.
It disposes of a large testing floor (≈ 260 m²) with the possibility to use four servo-actuators in parallel. Testing machines up to a 1000 kN capacity and a combined traction-torsion machine are also useful for some tests.
The LEMSC also has a wide ranging know-how in sensors and data acquisition.
All this equipment allows us to deal with many tests requests, which can be classified following the size of the “sample” :
1. Track or fastening systems components (mainly sleepers, pads, USP, UBM, springs) :
- Static and dynamic stiffnes
- Fatigue, creep tests
2. Whole fastening systems (discrete or continuous)
- Vertical stiffness (static & dynamic)
- Effect of repeated loading (i none inclined direction, biaxial)
- Freeze-thaw resistance
- Ultimate loading
3. Whole tracks ((floating) slab track, ballasted track with sleepers, level crossing ....):
- Determination of the frequency response
- Fatigue tests
- Loading with a real-scale bogie
Since a few years, the procedures of the railway tests are more and more fixed by standards (ISO, EN, DIN, …). The requirements of many of them can be met by the laboratory.