Variable-Density Preform for Brake Rotor Thermal Cycling
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Solution Overview
Problem
Current methods for producing reinforced composites face challenges such as impracticality, high costs, limited versatility, and susceptibility to differential coefficients of thermal expansion (CTE) issues, leading to residual stress and thermal cycling problems in components like brake drums and disk brake rotors.
Innovation Solution
A method for creating variable density preforms using a slurry with reinforcement particles and a die cavity design that allows for a decreasing pressure gradient, enabling the formation of preforms with controlled particle density gradients, which are then infiltrated with a molten matrix material to reduce CTE effects and enhance mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional materials are used for components like brake drums and disk brake rotors, then manufacturing is simple and cost-effective, but the components suffer from residual stress during thermal cycling and limited performance under field service conditions
Solution Approach 1:
The patent applies local quality by creating a variable density preform where reinforcement particles are distributed non-uniformly throughout the matrix material. The preform has regions of different particle concentrations, with higher density near the friction surface to enhance wear resistance and thermal cycling resistance, while maintaining lower density in other regions to reduce overall weight. This gradient structure resolves the contradiction by providing enhanced reliability only where needed rather than uniformly throughout the entire component.
2Reliability
If reinforcement particles are uniformly distributed in the matrix material, then manufacturing is straightforward, but the components still experience differential CTE effects and residual stress
Solution Approach 1:
The patent employs parameter changes by systematically varying the reinforcement particle concentration throughout the preform structure. Instead of uniform distribution, the particle volume fraction changes continuously or in steps from one region to another. This gradient in particle concentration creates a corresponding gradient in CTE properties, allowing the material to better accommodate thermal expansion differences and reduce residual stress during thermal cycling, while the manufacturing process controls this distribution through controlled slurry infiltration.
3Manufacturing precision
If centrifugal casting is used to create gradient distribution of reinforcement, then particle density varies radially, but the process is impractical and subject to Coriolis effects that preclude uniform concentric particle density
Solution Approach 1:
The patent uses an intermediary approach by introducing a porous preform as a intermediate structure before final infiltration with matrix material. The preform itself serves as a template that guides the infiltration process and establishes the desired particle gradient. This intermediary step allows for controlled particle distribution without the complexities of direct centrifugal casting, as the preform can be manufactured separately with controlled porosity and particle arrangement, then infiltrated in a simpler subsequent process.
4Strength
If preforms with high reinforcement density are used, then wear resistance and thermal conductivity improve, but the preforms become difficult to infiltrate and manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating regions of varying reinforcement density within the preform structure. High reinforcement concentration is localized in regions where wear resistance and thermal conductivity are most critical (such as near the friction surface), while other regions maintain lower reinforcement content. This localized high-density approach provides the necessary mechanical properties without requiring the entire preform to be densely reinforced, thereby facilitating easier infiltration and reducing overall manufacturing complexity.
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 method results in preforms with improved wear resistance, thermal conductivity, and reduced residual stress, enabling the production of lightweight, high-performance components like brake drums and disk brake rotors with extended service life and enhanced thermal cycling resistance.
Implementation Method 1
introducing the slurry under pressure into the inlet end or orifice, wherein the at least one exit end or orifice is operative with the at least one die cavity and flow path to provide for a decreasing pressure gradient along the flow path and flow path direction
Implementation Method 2
infiltration casting of matrix materials into porous reinforcement 'preforms'
Data Source
AI summary
Provided are novel devices and methods for making a variable density preform, the methods comprising obtaining a slurry comprising a reinforcement particle component and a liquid component; obtaining a die cavity having at least one inlet opening and at least one exit opening defining at least one die cavity flow path therebetween directed toward the exit opening, the at least one exit opening suitably sized or configured to provide for exit of the at least one liquid component while impeding or blocking exit of the at least one reinforcement particle component; and introducing the slurry under pressure, and for a sufficient time period, through the inlet orifice into the die cavity flow path to provide for a decreasing pressure gradient along the flow path direction, to provide for a variable density of the at least one particle component, the particle density increasing in the at least one flow path direction.