[Lecture] Advances in predicting running stability in terms of wheel-rail contact geometry
Speaker: Prof. Dr.-Ing. habil. Oldrich Polach, Independent consultant and assessor
Time: 15:00, July 12, 2023
Venue:
https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzhlMjNiNjMtMDA2ZC00ZTdjLTgwZjAtNGE0MzMzNWVjNWQx%40thread.v2/0?context=%7b%22Tid%22%3a%220b6b9a6a-d9d6-4ef0-a36f-5dc22f35388b%22%2c%22Oid%22%3a%22b3a4a853-427e-4c6d-b1c2-e9007d3c7aa4%22%7d
Abstract:
This lecture presents the phenomenon of running instability demonstrating itself in form of bogie or vehicle hunting. Different methods and criteria used for stability assessment as well as a high sensitivity to the wheel‒rail contact conditions can lead to significant differences between the prediction and the properties of the vehicle in service. An overview of the stability assessment methods using computer simulations will be presented, and the results of stability prediction compared.
Wheel‒rail contact geometry, traditionally assessed by the equivalent conicity value for the wheelset displacement amplitude of 3 mm, has an important effect on the stability prediction. Author’s investigations show, that the equivalent conicity is not sufficient to represent the typical influencing phenomena. A two-parametric characterisation of the wheel‒rail contact geometry using the so-called nonlinearity parameter together with the equivalent conicity value is presented and its use to assess the wheel profiles and vehicle behaviour is illustrated.
Biography:
Oldrich Polach is an independent consultant and assessor and Honorary Professor at the Technische Universität Berlin (Institute of Technology) in Berlin, Germany. From 2001 to 2016 he was Chief Engineer Dynamics in Bombardier Transportation, Winterthur, Switzerland, responsible for dynamics specialists in Business Unit Bogies Europe. He acted for 20 years as a member of the working group “Interaction Vehicle‒Track” of the European Committee for Standardisation CEN TC 256. Professor Polach is a well-recognised expert in railway vehicle dynamics and wheel-rail contact and author of a method for calculation of creep forces used in multibody simulation tools, particularly under traction or braking. He had been teaching Railway Vehicle Dynamics at the ETH Swiss Federal Institute of Technology Zürich, Switzerland from 2001 to 2018 and has been teaching this course at the Department of Rail Vehicles of the Technische Universität Berlin since 2005. He is a member of the editorial boards of the international journals Vehicle System Dynamics, Railway Engineering Science, and International Journal of Heavy Vehicle Systems.
