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- Landström Voortman, Eric, 1993, et al.
(author)
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Improved Finite Element Modelling of Tread Braked Wheel Performance Verified by Brake Rig Tests
- 2023
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Conference paper (other academic/artistic)abstract
- The objective of the present study is to validate a finite element material model for railway wheel steel against brake rig test results. The material model for pearlitic ER7 wheel steel has been calibrated for thermomechanical loading based upon the regulatory requirements for brake rig tests using specimen test results. The material model has shown better adherence to thermomechanical results compared to previous material models, but ultimately full-scale validation is required. To verify and further develop the model, a combined experimental and numerical campaign was launched. Using a custom-built brake rig at Chalmers University, two different designs of European freight wheels are tested at power levels of 30 and 50 kW for durations of up to 45 min with maximum temperatures exceeding 600 °C. Wheel rim displacements are measured during experiments and residual stresses are measured before and after each test using an instrument employing the elastoacoustic effect. Temperatures are measured using thermocouples on the wheel web, sliding thermocouples on the tread and a high-speed thermographic camera. The experimental results are then compared to finite element simulations at the same brake power levels using the aforementioned material model. The results show possible correspondence between the experimental and finite element results, indicating that the numerical model may be accurate enough for preliminary predictions of braking damage, while also highlighting challenges of thermal model assumptions.
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| 2. |
- Landström Voortman, Eric, 1993, et al.
(author)
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Thermomechanical testing and modelling of railway wheel steel
- 2023
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In: International Journal of Fatigue. - : Elsevier BV. - 0142-1123. ; 168
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Journal article (peer-reviewed)abstract
- Studies of thermal effects of tread braking on railway wheels show that the wheel temperatures may reach above 600 °C, at which the mechanical properties of the wheel steel are significantly impaired. Computational models that simulate the thermomechanical behaviour of the wheels are commonly based on results from laboratory tests which do not reflect actual in-service scenarios. Anisothermal testing and modelling are omitted due to the difficulties in designing relevant experiments and implementation of the results. In this paper, a preexisting numerical material model is extended in order to implement fully anisothermal behaviour. This is done by performing several thermomechanical experiments mimicking real-world service and worst-case scenarios ranging from room temperature up to 650 °C. The results from the laboratory testing are then used in combination with data from traditional isothermal tests to optimise the numerical material model by calibrating its material parameters. As part of this process it was found necessary to include a time- and temperature-dependent, non-recoverable (irreversible) mechanism for material softening and microstructural changes which occur above 400 °C. Finite element simulations with the material model using the new parameters and the softening law show markedly improved adherence to anisothermal and strain-controlled experimental results compared to the preexisting model(s). The results demonstrate that anisothermal testing is a requirement for models that are intended to simulate material behaviour for thermomechanical loads and thermally induced microstructural changes.
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