Guide Wire Variable Hardness Shaft Twisting Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional guide wires experience reduced operability and resilience due to strong twisting stress caused by the difference in hardness between the first and second shafts, leading to low durability against twisting stress.
Innovation Solution
A guide wire design featuring a second shaft with a variable hardness portion that gradually decreases in hardness from the distal end to the proximal end, with a low hardness portion located closer to the proximal end, and a length longer than the shaft's diameter, improving durability against twisting stress. The production method involves joining the first and second shafts and subjecting the second shaft to heat treatment to soften specific portions, enhancing the guide wire's overall durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the second shaft is made of a material with high elastic modulus to ensure torquability, then torquability is improved, but twisting stress increases due to hardness difference with the first shaft
Solution Approach 1:
The second shaft is designed with non-uniform hardness distribution, having a softer portion near the joint interface with the first shaft and a harder portion toward the proximal end. This local quality variation allows the shaft to maintain torquability while reducing twisting stress concentrations at the joint, thereby improving durability against twisting stress.
Solution Approach 2:
The hardness parameter of the second shaft is changed along its length, transitioning from softer material at the distal end (near the joint) to harder material at the proximal end. This parameter change optimizes both torquability and resistance to twisting stress, resolving the contradiction between strength and reliability.
2Ease of manufacture
If the second shaft has uniform hardness to simplify manufacturing, then ease of manufacture is improved, but twisting stress concentrations occur at the joint interface
Solution Approach 1:
Instead of uniform hardness, the second shaft incorporates a specific hardness distribution pattern with a softer portion at the joint interface and harder portion elsewhere. This local quality variation reduces stress concentrations at the joint while maintaining overall structural integrity and torquability.
3Device complexity
If the variable hardness portion length is shortened to reduce structural complexity, then device complexity is reduced, but twisting stress resistance decreases
Solution Approach 1:
The length of the variable hardness portion in the second shaft is optimized to be greater than its diameter. This dimensional relationship ensures sufficient stress distribution along the shaft length, improving twisting stress resistance while maintaining reasonable structural complexity.
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 guide wire exhibits improved durability against twisting stress, maintaining torquability while reducing stress concentrations at the joint interface, as demonstrated by performance evaluations through twisting and tensile tests.
Implementation Method 1
a step of subjecting a portion of the second shaft member, which is located closer to the proximal end side of the second shaft member than the joint part of the first shaft member and the second shaft member, to heat treatment to soften the portion
Data Source
AI summary
A guide wire that is durable against twisting stress includes a first shaft and a second shaft having a distal end joined to a proximal end of the first shaft. The second shaft is formed of a material exhibiting an elastic modulus higher than that of a material forming the first shaft. The second shaft includes a variable hardness portion including a first portion having a hardness that gradually decreases from a distal end to a proximal end of the first portion, and a second portion arranged proximally of the first portion, and exhibiting a hardness lower than the hardness of the distal end of the first portion. The length of the variable hardness portion in the axial direction of the guide wire is longer than the diameter of the second shaft.