Nitinol Tube Lobe Interlocking for Weld-Free Tubular Joints
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Solution Overview
Problem
Existing methods for joining Nitinol tubing to other tubular structures, such as stainless steel, often require welding and the use of intermediate metal components, which are costly and complex, especially for more intricate product forms like tubing.
Innovation Solution
The method involves creating lobe features on the ends of Nitinol and corresponding tubular components, which interlock through translation, rotation, or hinging motions, eliminating the need for welding and intermediate components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding is used to join Nitinol tube to stainless steel tube, then the tubes can be joined together, but the cost increases and manufacturing complexity increases due to intermediate metal components and specialized welding procedures
Solution Approach 1:
The patent replaces the welding process (thermal/chemical joining) with a mechanical interlocking system using lobes. The lobes on the Nitinol tube engage with corresponding features on the stainless steel tube through mechanical insertion and radial expansion, eliminating the need for welding procedures, intermediate metal components, and associated thermal processes.
Solution Approach 2:
The joining mechanism is divided into discrete lobe features that can be independently formed and engaged. Each lobe acts as a separate joining element that can be inserted and locked independently, allowing for modular assembly and simplifying the overall joining process compared to continuous welding operations.
2Strength
If welding is used to join Nitinol tube to stainless steel tube, then the tubes can be joined together, but the manufacturing cost increases due to intermediate metal components and specialized procedures
Solution Approach 1:
The patent replaces the welding process (thermal/chemical joining) with a mechanical interlocking system using lobes. The lobes on the Nitinol tube engage with corresponding features on the stainless steel tube through mechanical insertion and radial expansion, eliminating the need for welding procedures, intermediate metal components, and associated thermal processes.
Solution Approach 2:
The lobe features are formed directly on the tube surfaces through relatively simple mechanical or laser-based processes, replacing expensive intermediate metal components and specialized welding consumables. The joining mechanism uses the existing tube materials rather than requiring additional costly intermediate materials.
3Device complexity
If mechanical lobe features are used to join tubes, then welding and intermediate components are eliminated, but the joint must provide both strength and torsional flexibility
Solution Approach 1:
The lobe features are designed with elastic deformation capabilities that allow them to dynamically adapt to torsional and bending loads. The lobes can elastically deform to accommodate relative motion between the Nitinol and stainless steel tubes while maintaining the mechanical interlock, providing both strength and flexibility.
Solution Approach 2:
The mechanical properties of the lobe features are optimized to change under different loading conditions. The lobes exhibit different stiffness characteristics under axial, torsional, and bending loads, allowing the joint to be strong in compression while flexible in torsion, matching the functional requirements of the assembled structure.
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
This approach allows for a strong, self-aligning mechanical joint with torsional flexibility, avoiding the costs and complexities associated with traditional welding methods, while effectively utilizing the superelastic properties of Nitinol.
Implementation Method 1
Nitinol's superelastic behavior by interpenetration of lobe features between the respective tubes which may be achieved by translating the tubes together on a longitudinal axis
Implementation Method 2
using Nitinol's shape memory behavior by cooling the Nitinol tube, deforming the lobe features, positioning the lobe features in the desired penetrated position then heating the Nitinol so it returns to its original shape
Data Source
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AI summary
The present invention relates to mechanical joining of Nickel Titanium tubes, also known as Nitinol, to other tubular components. Such mechanical joining may be achieved by interpenetration of lobe features between the respective tubes by translating the tubes together on a longitudinal axis, a transverse axis, by a combination of translation and rotational motion or by a hinging motion, or by use of the shape-memory effect. The Nitinol superelasticity is used to accommodate the lobe deformation required for assembly and to snap the lobe back into its original shape to complete the mechanical joint.