TY - BOOK

T1 - Characterization and Modeling of the Thermomechanical Fatigue Behavior of Brake Disks for High Speed Trains

AU - Raninger, Peter

N1 - no embargo

PY - 2014

Y1 - 2014

N2 - The friction brake system in trains is essential in view of safety considerations. Despite the fact that in modern trains regenerative systems dissipate most parts of the kinetic energy in routine brake applications there are good reasons why a robust friction brake system is mandatory. It must be able to stop the train without further assistance in every possible in-service situation, since other systems are prone to failure. This is not only relevant for emergency braking but also for more frequent service brakings with comparable levels of dissipated energy. The brake blending between different brake systems, such as the friction brake, the regenerative system and track brake/eddy current brake provides a wide range of design options for the brake system and the brake management. For railway applications a great number of disk geometries and materials is available, and multiple types can be used simultaneously on the same train type. Optimized brake blending between different disk sets of the friction brake system is thus required as well. The main objective of this work is the development of a simulation tool for the design of brake disks and the brake management on high speed trains that ensures safe in-service operation and at the same time prevents oversizing. For this reason, both the characterization and the modeling of the thermomechanical fatigue behavior of railway brake disks is carried out in the scope of this work. The reference disk, that is used for component testing is a wheel mounted brake disk. This type is used for multiple unit trains, where the engines are spread over the axles of the whole train and little space is available for the usually applied axle mounted brake disks. Wheel mounted brake disks consist of two friction rings, which are mounted to the opposing sides of the wheel. The mechanical system is thus different from axle mounted brake disks, where both friction surfaces are part of one component. A major factor for the fatigue life of brake disks is the characteristics of the thermal distribution on the friction surface which is highly non-uniform. Only scarce information is available on these characteristics for wheel mounted brake disks as well as the corresponding damage mechanisms. The investigations in this work follow a threefold strategy consisting of 1) the systematic investigation of thermal images obtained from a test rig program, 2) a profound damage analysis and 3) the thermomechanical modeling of the braking process. The thermal images provide the necessary information on the thermal evolution on the friction surface. The damage analysis reveals the governing mechanisms for crack initiation and growth. Based on the obtained information a strategy for finite element modeling is developed, which includes the braking process, the non-uniform thermal loading, the viscoplastic behavior of the disk material and the damage behavior. In a final step the simulation results are compared to the results from component testing for verification purposes.

AB - The friction brake system in trains is essential in view of safety considerations. Despite the fact that in modern trains regenerative systems dissipate most parts of the kinetic energy in routine brake applications there are good reasons why a robust friction brake system is mandatory. It must be able to stop the train without further assistance in every possible in-service situation, since other systems are prone to failure. This is not only relevant for emergency braking but also for more frequent service brakings with comparable levels of dissipated energy. The brake blending between different brake systems, such as the friction brake, the regenerative system and track brake/eddy current brake provides a wide range of design options for the brake system and the brake management. For railway applications a great number of disk geometries and materials is available, and multiple types can be used simultaneously on the same train type. Optimized brake blending between different disk sets of the friction brake system is thus required as well. The main objective of this work is the development of a simulation tool for the design of brake disks and the brake management on high speed trains that ensures safe in-service operation and at the same time prevents oversizing. For this reason, both the characterization and the modeling of the thermomechanical fatigue behavior of railway brake disks is carried out in the scope of this work. The reference disk, that is used for component testing is a wheel mounted brake disk. This type is used for multiple unit trains, where the engines are spread over the axles of the whole train and little space is available for the usually applied axle mounted brake disks. Wheel mounted brake disks consist of two friction rings, which are mounted to the opposing sides of the wheel. The mechanical system is thus different from axle mounted brake disks, where both friction surfaces are part of one component. A major factor for the fatigue life of brake disks is the characteristics of the thermal distribution on the friction surface which is highly non-uniform. Only scarce information is available on these characteristics for wheel mounted brake disks as well as the corresponding damage mechanisms. The investigations in this work follow a threefold strategy consisting of 1) the systematic investigation of thermal images obtained from a test rig program, 2) a profound damage analysis and 3) the thermomechanical modeling of the braking process. The thermal images provide the necessary information on the thermal evolution on the friction surface. The damage analysis reveals the governing mechanisms for crack initiation and growth. Based on the obtained information a strategy for finite element modeling is developed, which includes the braking process, the non-uniform thermal loading, the viscoplastic behavior of the disk material and the damage behavior. In a final step the simulation results are compared to the results from component testing for verification purposes.

KW - Thermomechanical Fatigue

KW - Cyclic Viscoplasticity

KW - Damage

KW - Fracture Mechanics

KW - Infrared Thermography

KW - Damage Analyses

KW - Thermomechanische Ermüdung

KW - zyklische Viskoplastizität

KW - Schädigung

KW - Bruchmechanik

KW - Schadensanalysen

KW - Infrarotthermographie

M3 - Doctoral Thesis

ER -