Torque Tube Double EMF Joints for Bending-Resistant Fittings

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Solution Overview

Problem

Current methods for attaching end fittings to torque tubes, such as riveting, welding, or electromagnetic forming, face challenges like labor intensity, heat-affected zones, crack propagation, and failure under bending stress, particularly in aluminum tubing used in lightweight mechanical systems like vehicle and aircraft drive shafts, where traditional electromagnetic joints are prone to failure due to induced bending stress.

Innovation Solution

A torque tube assembly with a double electromagnetic (EMF) joint system, where the torque tube is formed around fittings using electromagnetic pulse forming, creating multiple torque and fitting lands to distribute stress effectively, thereby enhancing the connection's strength and resistance to bending moments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If electromagnetic pulse forming is used to attach end fittings to torque tubes, then the connection strength and fatigue resistance are improved, but cracks may form in the tubing during forming

Engineering Contradiction:

Improveconnection strengthVSAvoidcrack formation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent divides the single EMF joint into multiple EMF joints (first EMF joint and second EMF joint) positioned at different locations along the torque tube. This segmentation distributes the forming stress across multiple locations rather than concentrating it at one point, preventing crack formation while maintaining connection strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates different land structures (first plurality of lands and second plurality of lands) at different locations along the torque tube. Each location has optimized local geometry with specific land dimensions and spacing tailored to the local stress conditions, preventing crack formation in high-stress areas while maintaining strong connections.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If traditional riveting methods are used to attach end fittings, then the connection is simple to manufacture, but labor costs are high and rivets can loosen over time

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidrivet loosening

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces the mechanical riveting system with an electromagnetic pulse forming system. Instead of using rivets that can loosen, the system uses controlled electromagnetic pulses to plastically deform the torque tube material and create permanent mechanical interlocking lands, eliminating the loosening problem while maintaining manufacturing feasibility.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If welding or brazing is used to attach end fittings, then the joint strength is high, but heat affected zones and crack propagation occur

Engineering Contradiction:

Improvejoint strengthVSAvoidheat affected zone

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent replaces thermal joining processes (welding/brazing) with a cold-forming electromagnetic pulse process. The electromagnetic pulses generate localized plastic deformation through electromagnetic forces and shock waves, creating strong mechanical interlocking without thermal cycles, thus eliminating heat affected zones and associated cracking problems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If a single EMF joint is used to connect torque tube and fitting, then the manufacturing process is simple, but the joint fails under induced bending stress

Engineering Contradiction:

Improvejoint configurationVSAvoidbending stress resistance

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The patent divides the connection into multiple EMF joints (first and second joints) positioned at different locations along the torque tube. This segmentation allows the bending stresses to be distributed across multiple joint locations rather than concentrated at a single joint, enabling the system to withstand higher bending moments while maintaining manufacturing simplicity.

Inventive Principle:

Principle #1Segmentation

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 double EMF joint system significantly reduces material stress by up to 51% compared to single EMF joints under torque, bending, and tension loads, ensuring a durable and reliable connection that maintains a tight torsional joint without the drawbacks of traditional methods.

Implementation Method 1

deformation-free, electromagnetically formed joint

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The electromagnetic pulse creates shock waves that deform the torque tube around the end fitting

Methodology Applied

Scientific EffectShock wave: Shock Wave

Data Source

PatentUS11378132B2Driver-driven connection having multiple electro-magnetically formed joints

Publication Date: 2022.07.05 THE BOEING CO

AI summary

A torque tube assembly includes a torque tube, and a fitting attached to the torque tube by a first EMF joint and by a second EMF joint. The first EMF joint comprises a first plurality of torque lands formed proximate a first end of the torque tube and a first plurality of fitting lands formed proximate a first end of the fitting. The second EMF joint comprises a second plurality of torque lands formed distal to the first end of the torque tube and a second plurality of fitting lands formed distal to the first end of the fitting.