Non-Circular Structural Joint with Continuous Curvature Mandrel
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Solution Overview
Problem
Aerospace structures face challenges in achieving high structural stiffness and strength while minimizing mass, particularly at joints where subcomponents are connected, and existing joints often experience localized load concentration due to geometric discontinuities, leading to inefficient load transfer.
Innovation Solution
A structural joint featuring a mandrel with continuous 1st and 2nd derivatives, formed by alternating bumps and dimples, which provides a non-circular geometry that allows for efficient transfer of all six load components without geometric discontinuities, using a sleeve to integrate with the mandrel, fabricated from metallic or polymeric composite materials for weight savings and uniform stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional joints with geometric discontinuities (flats, cusps, steps) are used to prevent rotation and transfer loads, then rotational constraint is achieved, but localized stress concentrations occur that reduce joint efficiency and strength
Solution Approach 1:
The patent applies continuous curvature to the mandrel geometry, eliminating flats, cusps, and steps. The mandrel features a smoothly varying cross-section along its length with continuous first and second derivatives, creating a curvature-based solution that distributes stress uniformly while maintaining rotational constraint through the non-circular profile.
Solution Approach 2:
The patent changes the geometric parameters of the mandrel by varying the cross-sectional shape continuously along its length. The non-circular cross-section parameters (eccentricity, orientation) change smoothly to provide rotational constraint while avoiding discrete geometric discontinuities that cause stress concentrations.
2Strength
If bolted, pinned, or riveted joints are used to connect subcomponents, then structural assembly is achieved, but load transfer is concentrated at fastener locations creating inefficient load distribution
Solution Approach 1:
The patent merges the mandrel and sleeve into an integrated joint structure where the non-circular mandrel fits within a matching sleeve. This combination creates a unified load path that distributes forces continuously along the joint length, eliminating the need for separate fasteners and achieving efficient load transfer through the integrated geometry.
Solution Approach 2:
The patent uses an asymmetric non-circular mandrel cross-section that fits within a corresponding asymmetric sleeve. This asymmetric geometry provides inherent rotational constraint and creates a continuous load path that distributes stresses uniformly, replacing the discrete fastener-based load transfer of symmetric traditional joints.
3Ease of manufacture
If glued joints are used to connect structural members, then assembly is simplified, but load transfer occurs primarily at the ends of the joint creating localized stress peaks
Solution Approach 1:
The patent uses continuous curvature in the mandrel geometry to distribute load transfer along the entire length of the joint. The smoothly varying cross-section creates continuous contact with the sleeve, replacing the end-concentrated load transfer of glued joints with a distributed load path that maintains assembly simplicity while improving strength.
4Weight of moving object
If lightweight materials are used to reduce mass, then weight savings are achieved, but structural stiffness and strength at joints become more challenging to maintain
Solution Approach 1:
The patent employs composite materials for both the mandrel and sleeve, allowing optimization of mechanical properties for weight-critical applications. The continuous curvature geometry works synergistically with composite material anisotropy to achieve high stiffness and strength at minimal mass, particularly through tailored fiber orientations that follow the stress flow paths.
Solution Approach 2:
The continuous curvature geometry eliminates stress concentrations that would be particularly detrimental in lightweight structures. By distributing stresses uniformly along the joint length, the curved geometry maximizes the efficiency of lightweight materials, allowing high strength-to-weight ratio performance without the penalty of localized stress peaks.
Data Source
AI summary
A structural joint is formed of a mandrel having a plurality of bumps and dimples formed thereon which is fitted into a sleeve. The bumps and dimples form a non-circular geometry at all points along the length of the mandrel. The bumps are defined by surfaces which have 1st and 2nd derivatives which are continuous.