Fahrzeugdynamik

Railroad trains sometimes experience very high longitudinal and buffer forces. These can have a negative influence on the running behavior and, in an emergency, lead to component damage or derailment. Measurements and investigations in this area are carried out at the Chair of Rail Vehicles. Special load cells and strain gauges are used to measure stresses and deformations. For the approval of vehicles, load spectra are required, which are often determined by parallel measurements of more than 100 channels under static and dynamic loading.

The frequency range relevant to vehicle dynamics and stable operation is 0-20 Hz and is not audible here. However, there are also higher-frequency forms of vibration that are triggered, for example, by cornering and that are perceived by the passenger as vibrations or droning due to unfavorable resonances from the chassis or car body. Here, the existing MKS calculation programs were used to create models that take into account both driving dynamics and acoustics in order to combat the problem as close to the source as possible.

The forces and movements at the wheel-rail interface, which is only a few square millimeters in size, have a decisive influence on the running behavior of a rail vehicle. Lateral and vertical forces during travel are transmitted only over this relatively small contact area, resulting in undesirable wear of both wheel and rail if an optimized wheel and rail profile is not available. By measuring the wheel and rail profile, root cause analysis and profile optimization can be performed to avoid the causes or take corrective action. As a result, railroads can not only increase the uptime of their railcars, but also operate them more safely, efficiently and with less wear and maintenance.

The key to increasing productivity and reducing noise in rail freight is the bogie, which has been completely redesigned in this project. These goals will be achieved through optimum weight-saving design, wear reduction, the use of diagnostic techniques and telematics, and safe driving stability at high speeds. The acoustic design is expected to reduce noise emissions by 18 dB compared to current technology. In addition, the self-steering axles can save 30% of energy when driving on curves, as they can be steered with significantly less effort.

Rail breaks are a major operational hazard and, in extreme cases, can lead to derailments. Until now, these breaks have been detected at a very late stage by maintenance personnel and by walking along the track. With acceleration sensors on a wheel set and appropriate signal processing, vehicles could detect these rail breaks in the network much earlier or provide indications for maintenance. Other discontinuities, such as switch and rail impacts, must be excluded.

If a car derails in a long freight train (e.g., 600 meters), the locomotive engineer may not notice it immediately due to the high moving masses, which could lead to the destruction of several kilometers of track or other disasters. Automatic, undetected emergency braking would only occur when the main air line is disconnected, which does not necessarily have to happen immediately in the event of a derailment. A pneumatic derailment detector integrated into the braking system of each car should trigger emergency braking in an emergency and minimize damage. The technical design of such a detector is based on acceleration measurements and the corresponding position on the freight car obtained during real derailment tests.