Testing Railway Vehicles to Improve Vehicle/Track Interaction
By Robert Masar • March, 2006
Significant increases in high-speed international traffic throughout Europe have led European railways to establish new comprehensive technical rules to ensure acceptable parameters for vehicle/track interaction. Current measuring systems and data collection and processing capabilities have made it possible to test and homologate new railway vehicles before they go into service, and to test existing vehicles when operating conditions change.
It is also necessary to ensure that the existing level of safety and reliability is not compromised when changes in design (such as new track conditions) or operating practices (such as the introduction of higher speeds), either of which may result in higher wheel/rail lateral or vertical forces, may occur.
In March 2005, The European Committee for Standardization and the Technical Committee for Railway Applications (CEN/TC 256) approved the European Standard EN 14343:2005: Railway applications – Testing for acceptance of running characteristics of railway vehicles – Testing of running behavior and stationary tests. EN 14343 provides a much-needed standardization for testing methods and acceptance thresholds which the following countries must implement: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. The Standard applies principally to all vehicles used in public transport which operate without restriction on standard gauge tracks (1 435 mm).
The testing of running characteristics is part of the type-testing of newly developed vehicles, or those that have had relevant design modifications, or changes in their operating regimes. Testing of vehicles' running characteristics consists of preliminary approval tests (mainly stationary tests) and tests of running behavior (on-track tests).
Vehicle parameters relevant to running characteristics include: planned maximum permissible speed of the vehicle, planned permissible cant deficiency, the smallest curve radius to be negotiated, wheel arrangement, wheelbase and distance between bogie centers, center of gravity height, weight of the vehicle, wheel force and axle force distribution, unsprung mass, primary suspended mass, secondary suspended mass, moments of inertia of vehicle body (around z-axis), torsional stiffness of vehicle body, torsional stiffness of bogie frame, tractive effort, dimensions of wheel and wheelset, wheel profiles, characteristics of primary and secondary vertical suspension, characteristics of axle guiding, characteristics of secondary lateral suspension, rotational torque of bogie, and moment of inertia of bogie (around z-axis).
Running behavior covers running safety, track loading and ride characteristics. Parameters used for the assessment include: forces between wheel and rail, lateral forces between wheelset and axle-box (lateral axle-box forces), and accelerations. The structure of the test elements is shown in Figure 1. click here to view
