Institute of Fundamental Technological Research

This paper presents the results of experimental and numerical studies on reliability and monitoring issues of railway infrastructure in terms of safety and operation. The state of knowledge concerning methods of assessing track condition, in particular rail joints used in continuous welded rail track of railway lines is described. Experimental results of rail joints used in track transition zones and the results of numerical studies/tests of the rail vehicle-track model are outlined. It is demonstrated, basing on the analyses of the experimental results, that not only should the rail joints used in continuous welded rail track be diagnosed during their acceptance, but also during their operation. It is proven that the currently used methodology for testing welded rail joints applied during acceptance testing of contact track is not fully correct and leads to misinterpretation of the measurement results. Moreover, the results of numerical simulation tests presented in this paper confirm the possibility of diagnosing the condition of rail joints by any vehicle passing over such a track equipped with a suitable system.

operational safety,numerical and experimental studies,rail vehicle dynamics,continuous welded rail track,operational safety

Artykuł poświęcony jest badaniom rozkładu ciepła wywołanego tarciem w ukła-dach hamulcowych stosowanego w pojazdach szynowych dużej prędkości. W pracy zapre-zentowano wyniki eksperymentalnych badań przeprowadzone na rzeczywistym obiekcie w skali 1:1. Nowością w pracy jest fakt analizy układu hamulcowego, w którym para cierna charakteryzowała się segmentacją powierzchni ciernej okładziny o dwóch materiałach ciernych. Materiałami tymi był kompozyt i spiek. W pracy przedstawiono także teoretyczną analizę i wyniki numeryczne ilustrujące dystrybucję ciepła w elementach modelu tarczy hamulcowej. Wykorzystano w tym celu na metodę elementów skończonych.

systemy hamulcowe dużych prędkości, ciepło tarcia, okładzina hamulcowa spiekana-kompozytowa

The paper presents a simple and fast method for predicting the vibrations of a vehicle moving on a track with a given technical condition. In the proposed approach, transfer function matrix models describing the dynamics of train components caused by the interaction of the rail vehicle-track system were used to analyze. The propagation of vibrations generated from the interaction of the wheel set with the track to selected elements of the rail vehicle is approximated by frequency-dependent homogeneous relations. The developed numerical vehicle-track model was generated on the basis of recorded accelerations at selected measurement points of a real rail vehicle and from track geometric data collected by a measuring trolley at given speeds of the entire system. The developed method is based on a model of the rail vehicle system.

Pracę poświęcono eksperymentalnym i numerycznym badaniom dotyczącym występowania gorących punktów w elementach hamulców tarczowych stosowanego w pojazdach szynowych dużej prędkości. W pracy zaprezentowano wyniki eksperymentalnych badań przeprowadzone na rzeczywistym układzie hamulcowym dedykowanym do takich pojazdów. W badaniach eksperymentalnych wykorzystano technikę termografii w podczerwieni, która pozwoliła scharakteryzować omawiane zjawiska cieplne. Uzyskane wyniki badań doświadczanych potwierdzono analizami numerycznymi, przy wykorzystaniu z walidowanego modelu układu hamulcowego. Wykorzystano w tym celu metodę elementów skończonych. Otrzymane wyniki numeryczne ilustrują zjawisko powstawania gorących obszarów na powierzchni tarczy hamulcowej wywołane przez termoelastyczne zaburzenia występujące na jej powierzchni.

gorące obszary, badania numeryczne, badania eksperymentalne, układ hamulcowy, pociągi dużych prędkości

A braking systems during friction interaction convert mechanical energy into heat energy. The corresponding heating is a major design parameter as it influences the tribological and mechanical performances (wear of the materials, friction performances, risks of cracks, vibrations, etc.). During breaking process in such breaking systems, different locations of thermal overheating areas of material of friction pair may occur, usually named as hot spots or hot bands. These spot and bands are characterized by very high temperature gradients. This brake systems exposed to thermoelastic instabilities show a characteristic temperature distribution on break disc surface that can lead to local material change. The interaction of thermal energy and thermal expansion of the material of the friction braking effect on the local increase in temperature leading to a dominant impact frictional forces in this area. Often destabilization of the braking process is a consequence of such a rise in temperature. The difficulty of understanding and modeling all of these phenomena still remains due to the complex interactions of thermal, mechanical, and tribological effects. Experimental investigation is still nowadays a major instrument for detecting and understanding the physical effects. In this presentation, we propose to consider an example

braking system, hot spots, hot bands, braking tests, infrared testing

Thermoelastic instabilities are typically observed in frictional systems, which transform large quantity of kinetic energy into thermal energy. To this group we can include a high speed train brake system. This brake systems exposed to thermoelastic instabilities show a characteristic temperature distribution on break disc surface that can lead to local material change, vibrations of the braking system element coefficient of friction fluctuations. When reaching a critical sliding velocity, experiments show a nonhomogeneous and often periodic temperature distribution on the sliding surface. The mechanism of the phenomenon is caused by the interaction of heat generation and thermal expansion. A local rise in surface temperature results in a thermal expansion of the material nearby. Such a region of elevated temperature therefore is slightly higher than the surrounding topography and therefore carries a dominating part of the frictional load. A following rise in heat can destabilize the process. Two basic forms of thermoelastic instabilities can be commonly observed such as hot spots and hot bands.

high speed train braking, infrared technology, hot spotting, hot banding, brake disc, heat transfer