Material-independent design loads for car-bodies
A new algorithm for the generation of synthetic operational load sequences
A new algorithm for the generation of synthetic operational load sequences
From the beginning of railway transportation until today, most components of railway vehicles were made of steel and aluminium. For this reason, design and construction is focused on metallic material. An evident example is the development of the design loads for car-bodies of railway vehicles.
These design loads for trains were derived from old load assumptions made for steel bridges in the 1930s. They have been complemented by expected accelerations during the operation of the vehicles over the last centuries and are the state of the art still today. As it is, railway vehicles are designed as moving steel bridges. |
The actual design load cases are confirmed by many years of experience with the production and operation of railway vehicles. The structural parts of these vehicles were made of metallic material and with a common basic design. The experience of the last decades has shown, that these old design loads are not sufficient for new constructions, e.g. low-floor trams. The old design loads are also not sufficient for new construction material such as composite material and non-metallic joints.
Mat4Rail is carrying out research work to fill this prospective gap in the definition of design loads for car-bodies of railway vehicles. The research in development of better load assumptions for railway vehicles is the work of the project partners IMA Dresden, RISE and University of Bremen.
The newly developed load assumptions are based on the accepted normative design load cases. These load cases will be mixed to a representative sequence of synthetic operational loads. In the first step, the number of load cycles during the expected lifetime will be assigned to the design load cases. In the second step, the load cases will be ordered with respect to their percentage. Finally, the amplitudes of the load cases will be scaled by a linear exponential distribution. The result is a sequence of synthetic operational loads. |
This synthetic load sequence shall be similar to real operational loads. Therefore, the algorithm for the generation of synthetic operational loads was validated by a comparison with measured operational loads for car-bodies of trams and shall also be validated for car-bodies of other types of railway vehicles, such as regional trains and high-speed trains. Therefore, comprehensive existing measurement data is being analysed by IMA Dresden too.
The similarity between synthetic operational load sequences and real operational loads allows the material-independent strength design of railway car-bodies. The fitness for purpose of this method will also be evaluated during the Mat4Rail project by fatigue strength tests under variable amplitude on a component with bonded joints
The new algorithm for the generation of synthetic operation loads is an important step for an accepted certification method of components made of new materials such as composites or bonded joints in car-bodies of railway vehicles. IMA Dresden will also raise this topic in the European standardisation group for the applicable European norm EN 12663.
The new algorithm for the generation of synthetic operation loads is an important step for an accepted certification method of components made of new materials such as composites or bonded joints in car-bodies of railway vehicles. IMA Dresden will also raise this topic in the European standardisation group for the applicable European norm EN 12663.
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