Institute of Fundamental Technological Research

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

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

In the paper presents experimental studies the influence of the formation of the hot spots on a brake disc. The heat produced in the brake system often leads to the appearance of hot spots on the surfaces of friction pairs during rapid braking. Nature and extent of the intensity of the phenomenon depends greatly on the mechanical and thermal properties of these friction pair materials. The temperature distribution in the elements analyzed systems friction affects their thermal deformation, initiating the above phenomenon. Shown in the work of the results of tests and analyzes the formation of the hot bands and the hot spots on the brake discs used in high-speed railway vehicles, provided information on the temperature distribution on the surface. One of the consequences of such a process is the increased wear and reduce the coefficient of friction. Measurements of the hardness of the hot bands and surface roughness of brake discs showed the effects of such phenomena on the change on the structure of the cast iron and steel discs materials. An increase the hardness of this hot area on the discs surface of may result in increased maintenance costs. The costs caused by for a more frequent lathing of the brake discs can occur. These changes also influences to reduce the coefficient of friction in the friction pair.

hotspot, maintenance costs, friction, infrared thermography, thermal coupling

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

The heat produced between friction couple during braking induces thermal distortion in the disc and leads to appearance of hot bands. The Hot bands are generated by thermoelastic phenomena appearing in systems with high energy dissipation like brake or clutch systems. Systems exposed to thermoelastic instabilities show a characteristic temperature distribution that can lead to local material change, vibrations of the braking system element or coefficient of friction fluctuations. In the framework of studies there are presented results of experimental investigation on influence of the hot bands on properties of friction pair elements and parameters of the high-speed train brake system.

heat produced, friction coupling, breaking, hot bands, thermoelastic phenomena, friction fluctuations