Railway Wheel Web Geometry for Lower Rim Thermal Stress
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Solution Overview
Problem
Existing railway vehicle wheels face issues with increased weight and the generation of tensile residual stress in the rim due to thermal expansion during braking, which can lead to crack propagation and reduced durability.
Innovation Solution
A wheel design with a linear web connecting the rim and boss, where the rim center is closer to the flange than the boss, and the web's plate-thickness center line forms an angle less than 90° with the axial direction, satisfying the formula L≥0.0223α−1.363, to reduce thermal stress and constrain thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the web is given a curved cross-sectional shape to reduce thermal stress of the rim, then thermal stress is reduced, but the weight of the wheel increases
Solution Approach 1:
The patent changes the geometric parameters of the web by defining a specific linear configuration characterized by the angle α (between the web's plate-thickness center line and the radial direction) and the ratio L (distance from rim side face to web outer end divided by rim width). This parameter optimization allows the web to maintain appropriate rigidity while reducing thermal stress, eliminating the need for curved shapes that would increase weight.
Solution Approach 2:
Instead of using a curved web shape to reduce thermal stress (as in prior art), the patent inverts the approach by using a linear web shape with specifically optimized parameters. This inversion demonstrates that a simpler geometric form can achieve the same stress-reduction effect when properly parameterized, thereby avoiding the weight penalty of curved designs.
2Stress or pressure
If high thermal stress is generated in the rim during braking, then the compressive residual stress may reverse to tensile residual stress, but this leads to crack propagation and reduced durability
Solution Approach 1:
The patent applies preliminary anti-action by designing the web's geometry (angle α and ratio L) to preemptively counteract the thermal expansion forces that would otherwise generate tensile residual stress in the rim during braking. The linear web configuration with optimized parameters creates a stress-distributing structure that prevents the compressive residual stress from reversing to tensile, thereby preventing crack initiation and propagation before they can occur.
3Weight of moving object
If the web has a linear shape to reduce weight, then weight is reduced, but thermal stress control becomes more difficult
Solution Approach 1:
The patent resolves this contradiction by identifying critical geometric parameters (angle α and ratio L) that control the thermal stress behavior of the linear web. By optimizing these parameters within specific ranges, the linear web achieves both weight reduction and effective thermal stress control, proving that parameter optimization can compensate for the simplicity of the linear geometry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves a reduction in wheel weight and suppresses the generation of tensile residual stress, enhancing durability and reducing stress concentration while maintaining rigidity against lateral forces.
Implementation Method 1
the temperature of the wheel, particularly the temperature of a rim that forms an outer circumferential portion of the wheel rises. As a result, thermal expansion of the rim occurs, and thermal stress is generated in the rim
Implementation Method 2
the web has a plate-thickness center line that has a linear shape when the wheel is viewed in a longitudinal section... the wheel satisfies Formula (1)... a reduction in the weight of the wheel as well as suppression of the generation of tensile residual stress in the rim can both be achieved
Data Source
AI summary
A wheel includes a boss, a rim, and a web. The rim includes a tread and a flange. A center of the rim in the axial direction of the wheel is disposed closer to the flange in the axial direction than a center of the boss in the axial direction is. The web has a plate-thickness center line that has a linear shape when the wheel is viewed in its longitudinal section. When an angle that the plate-thickness center line forms with the axial direction is denoted by a, a distance in the axial direction from a side face of the rim to an outer end of the plate-thickness center line is denoted by Pw, a length of the rim in the axial direction is denoted by Wr, and Pw/Wr is denoted by L, the wheel satisfies the expression L≥0.0223α−1.363. Where, the angle α is 90° or less.