Titanium Bearing Assembly with Sintered Bronze PTFE Composite
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Solution Overview
Problem
Titanium and its alloys exhibit poor sliding properties, leading to cold welding issues when paired with other materials like steel in aerospace applications, which can result in premature failure of plain bearing arrangements, especially under conditions of temperature changes and vibrations.
Innovation Solution
A plain bearing arrangement using a Teflon/fiber mixture embedded in sintered bronze as an intermediate element, which has a lower hardness than titanium, is introduced to prevent cold welding, with the sintered bronze providing a porous structure for the PTFE/fiber mixture and potentially sealed with a thin PTFE or ceramic film to prevent ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium or titanium alloys are used for the axle or shaft to achieve low weight and high strength, then weight is reduced and strength is improved, but sliding properties deteriorate leading to cold welding and seizing
Solution Approach 1:
A bearing element made of sintered bronze with embedded PTFE fibers is introduced as an intermediary component between the titanium axle/shaft and the bearing outer ring. This intermediate bearing element prevents direct contact between titanium and steel surfaces, eliminating cold welding and seizing while allowing the titanium components to maintain their weight and strength advantages.
2Device complexity
If a fixed bearing pair of titanium and steel is used to achieve structural simplicity, then device complexity is reduced, but contact corrosion and seizing occur
Solution Approach 1:
The bearing element is constructed as a composite material consisting of sintered bronze matrix with embedded PTFE fibers. This composite structure combines the load-bearing capability of bronze with the low-friction and non-sticking properties of PTFE, preventing contact corrosion and seizing while maintaining a relatively simple three-component structure.
3Reliability
If the bearing element is made softer to prevent cold welding, then sliding properties are improved, but compressive strength and surface hardness deteriorate
Solution Approach 1:
The bearing element exhibits local quality differentiation through its composite structure: the sintered bronze matrix provides high compressive strength and load-bearing capacity, while the embedded PTFE fibers provide low friction and cold welding prevention at the contact surface. This local differentiation allows the bearing to simultaneously achieve softness for sliding and hardness for strength.
Solution Approach 2:
The composite structure of sintered bronze with PTFE fibers combines materials with complementary properties: bronze provides structural strength and compressive resistance, while PTFE provides low friction and non-sticking characteristics. The synergistic combination resolves the contradiction between softness for sliding and hardness for strength.
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 solution effectively prevents cold welding, meeting and exceeding aerospace industry requirements by maintaining performance under lateral loads and vibration cycles, with the bearing arrangement supporting up to 1.5 kN over 200,000 test cycles without failure.
Implementation Method 1
The sliding bearing arrangement forms a loose bearing... The plain bearing arrangement used according to the invention comprises a bearing element and an axle or shaft... bearing element is designed to prevent galling to the axle or shaft
Implementation Method 2
a Teflon/fiber mixture embedded in sintered bronze... the sintered bronze providing a porous structure for the PTFE/fiber mixture
Data Source
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AI summary
The present invention relates to a pairing of cut surfaces or contact surfaces consisting of at least two individual components or structural elements, wherein at least one of the components or elements is made of titanium, aluminum, or alloys thereof, either together or with other metals, and another component or element in contact with, connected to, or connecting to it is made of, or equipped with, a material that has a lower hardness than titanium, aluminum, or alloys thereof, either together or with other metals. The pairing of cut surfaces or contact surfaces can be a screw or clamp connection, in particular a sliding bearing connection (14).