Dissimilar-Metal Guide Wire Welding With Reduced Heat-Affected Zone
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Solution Overview
Problem
Existing guide wires face a challenge in balancing column strength and flexibility, as improvements in one characteristic often compromise the other, leading to unsatisfactory performance in navigating body lumens without damaging them.
Innovation Solution
A method of joining dissimilar metallic materials like nitinol and stainless steel using electrical current and a follow-up axial force to form a weld nugget, which increases solid-state deformation without risking melting, resulting in a guide wire with enhanced strength and kink resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the guide wire is made stiffer to improve column strength, then it can support balloon catheters better, but it may damage the blood vessel or passageway due to excessive rigidity
Solution Approach 1:
The guide wire is divided into multiple segments with different material compositions and mechanical properties. The proximal portion contains high-strength materials for column strength, while the distal portion contains flexible materials for vessel safety, resolving the contradiction between supporting catheters and preventing vessel damage
Solution Approach 2:
Different portions of the guide wire are assigned different material properties: the proximal portion has high strength and rigidity to support balloon catheters, while the distal portion has high flexibility to navigate tortuous vasculature safely, allowing each section to optimize its local function
2Ease of operation
If the guide wire is made more flexible to improve navigation through tortuous vasculature, then it can avoid damaging the blood vessel, but it loses the ability to support balloon catheters effectively
Solution Approach 1:
The guide wire is segmented into proximal and distal portions with differentiated material compositions, allowing the distal portion to be highly flexible for navigation while the proximal portion maintains strength for catheter support
Solution Approach 2:
The guide wire exhibits spatially varying mechanical properties where the distal portion is optimized for flexibility and the proximal portion for strength, enabling both navigation ease and catheter support capability simultaneously
3Strength
If electrical current is applied to weld dissimilar metallic materials, then the materials can be joined together, but the materials may melt instead of undergoing solid-state deformation
Solution Approach 1:
A follow-up axial force is applied preliminarily to the work pieces before welding to pre-compress the interface, ensuring solid-state deformation occurs instead of melting when electrical current is subsequently applied for welding dissimilar metallic materials
Solution Approach 2:
The welding process uses periodic application of axial force and electrical current in sequence: first applying follow-up axial force to pre-compress, then applying electrical current for welding, creating a controlled cyclic process that prevents melting and ensures solid-state deformation
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 method produces guide wires with consistent strength characteristics and reduced heat-affected zones, improving kink resistance and maintaining weld integrity, thus addressing the limitations of previous technologies in directly welding incompatible materials.
Implementation Method 1
the applied electrical (e.g., DC, AC, or both) current serves to heat the portions of the members to be joined so that they undergo solid state deformation, such that the materials are not melted, but deform and form a weld joint while in a solid state
Implementation Method 2
A follow up axial force that is greater than the first axial force is applied as solid state deformation occurs and a weld nugget forms between the members
Implementation Method 3
the separate members are aligned with one another, and a first axial force is applied while delivering electrical (e.g., DC, AC, or both) current through the separate members so as to weld the separate members to one another
Data Source
AI summary
The present disclosure is directed to a multi-segment device, such as an intravascular guide wire. The multi-segment device includes an elongate first portion comprising a first metallic material, an elongate second portion comprising a different metallic material, the first and second elongate portions being directly joined together end to end by a solid-state weld, and a heat affected zone surrounding an interface of the weld where the first and second portions are joined together, wherein the heat affected zone has an average thickness of less than about 0.20 mm.