Disc Brake Rotor Thermal Expansion Management
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Solution Overview
Problem
Disc brake rotors face high mechanical and thermal stresses, leading to stress cracks in annular friction rings due to heating, which existing designs fail to adequately address.
Innovation Solution
A disc brake rotor design featuring a hat-shaped core with radially extending fins and angularly spaced projections on inboard and outboard friction rings, forming a mechanical interlock and allowing for thermal expansion without stress buildup, using an aluminum alloy core and aluminum ceramic composite friction rings to manage thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the friction rings are securely mounted to the core, then the mechanical connection is strong, but thermal expansion causes stress cracks in the friction rings
Solution Approach 1:
The mounting surface is segmented into multiple discrete mounting points (protrusions and recesses) rather than a continuous rigid connection. This segmentation allows localized thermal expansion at each mounting point while maintaining overall mechanical strength, preventing stress crack formation in the friction rings during thermal cycles.
Solution Approach 2:
The mounting structure uses protrusions with specific dimensional parameters (height, radius, spacing) that are optimized to provide mechanical retention while accommodating thermal expansion. The recesses are dimensioned to receive the protrusions with appropriate clearance, allowing the friction ring to expand radially without generating excessive stress.
2Manufacturing precision
If the friction rings are rigidly fixed to the core, then positioning is precise, but thermal stresses cannot be accommodated
Solution Approach 1:
The rigid continuous mounting is replaced with discrete segmented mounting points. Each protrusion-recess pair provides precise localized positioning while the spaces between mounting points allow for thermal expansion and stress relief, combining positioning accuracy with thermal tolerance.
Solution Approach 2:
The mounting structure transitions from a static rigid connection to a dynamic system that accommodates thermal deformation. The protrusions and recesses are designed to allow controlled movement and expansion during heating cycles while maintaining proper positioning during normal operation.
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 inhibits stress crack formation by allowing unrestricted expansion and reducing heat transfer, thereby enhancing the durability and reliability of disc brake rotors under high mechanical and thermal loads.
Implementation Method 1
radially extending fins located in the space defined by the inboard and outboard mounting surfaces
Implementation Method 2
The first projections are angularly aligned with the second projections. The first and second projections extend into the space between the inboard and outboard mounting surfaces and have a gap therebetween
Data Source
AI summary
A disc brake rotor includes a core including a hat-shaped section, an annular inboard mounting surface, and an annular outboard mounting surface axially spaced from the inboard mounting surface and connected to the inboard mounting surface. The hat-shaped section has a central mounting face and a cylindrical shoulder extending from a periphery of the mounting face. The outboard mounting surface has an interior peripheral edge radially spaced from the shoulder, and the inboard mounting surface has an interior peripheral edge engaged to the shoulder. An inboard friction ring includes radially extending first projections secured to the inboard mounting surface. The outboard friction ring includes radially extending second projections secured to the outboard mounting surface. The first projections are angularly aligned with the second projections. The first and second projections extend into the space between the inboard and outboard mounting surfaces and have a gap therebetween.