Faceted Ball-and-Socket Joint With Floating Keys for Stress Relief
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Solution Overview
Problem
Conventional ball-and-socket joint designs face stress concentration issues due to significant load on balls, leading to material fatigue, and are limited by size constraints in applications like downhole drilling where compactness is required, making it difficult to use larger balls without compromising the strength of neighboring components.
Innovation Solution
A ball-and-socket joint assembly with a faceted ball end and floating independent keys provides an increased bearing surface area for torque transmission, using high-strength materials like alloy steel and silicon carbide, and a polygonal key chamber design to distribute stress and maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If larger balls are used to increase bearing surface area, then stress concentration is reduced, but the size constraints in compact applications like downhole drilling are violated
Solution Approach 1:
The ball surface is segmented into multiple faceted surfaces instead of a smooth sphere, and multiple smaller keys are used instead of a single large ball. This segmentation increases the total bearing surface area while keeping individual components smaller, resolving the contradiction between stress distribution and compact size
Solution Approach 2:
The design transitions from a single spherical ball to a faceted ball end with multiple flat surfaces, adding dimensional complexity to the contact interface. This allows torque transmission to occur across multiple discrete contact zones, effectively increasing the bearing surface area within the same overall envelope dimensions
2Reliability
If higher-grade materials with greater hardness are used, then material fatigue resistance is improved, but stress concentration at contact points remains a potential failure point
Solution Approach 1:
By segmenting the contact interface into multiple faceted surfaces and multiple keys, the load is distributed across numerous discrete contact zones rather than concentrated at a few points. This segmentation reduces peak contact stress even when using high-hardness materials, preventing stress concentration from becoming a failure initiation point
Solution Approach 2:
The faceted surfaces provide locally optimized contact zones with specific geometric properties that distribute stress evenly across each contact interface. This local quality enhancement ensures that even small contact areas maintain uniform stress distribution, preventing localized stress concentration
Data Source
AI summary
A joint assembly for use in transmitting torque comprises a ball and socket arrangement. The socket is comprised in a housing, and further comprises a key chamber with a substantially regular polygonal profile defining interior faces. The ball is provided on a ball stud component, and has a plurality of convexly curved facets. The ball is inserted in the socket with a plurality of keys, such that the keys are disposed between the ball facets and a corresponding interior face. Each key provides a bearing surface that mates with a corresponding facet, and a surface opposite the bearing surface to mate with the interior face. The sides of the key define a biconvex profile.