Fatigue to Fracture Testing for Vascular Stents
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Solution Overview
Problem
Current methods for testing the durability of vascular implants like stents do not accurately predict their endurance limit or fatigue life, leading to uncertainty about when and where they may fail under physiological and non-physiological conditions.
Innovation Solution
A system and method for fatigue to fracture testing involving a mock vessel with controlled compliance, pressurized fluid expansion, and high-speed camera monitoring to simulate pulsatile blood pressure conditions and assess the time of initial failure or fracture in vascular prostheses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If testing to success is performed to prove durability, then reliability of the implant is improved, but the ability to predict endurance limit and fatigue life deteriorates
Solution Approach 1:
The patent applies preliminary action by performing fatigue testing to fracture before final product certification. Multiple stents are tested to failure at various cycle counts to establish S-N curves and endurance limits in advance, rather than only performing limited durability testing on final products. This preliminary failure data enables accurate prediction of implant life under physiological conditions.
2Measurement precision
If testing to fracture is performed to determine endurance limit, then measurement precision of fatigue life is improved, but the complexity of the testing system deteriorates
Solution Approach 1:
The patent uses finite element analysis (FEA) models as virtual copies of the physical stent to predict fracture locations and validate testing protocols. The FEA models replicate the geometric and material properties of the stent, allowing virtual fatigue testing and fracture pattern prediction before physical testing, thereby reducing the complexity of physical test setup and interpretation.
Solution Approach 2:
The patent introduces FEA modeling as an intermediary between physical testing and endurance limit determination. The FEA model serves as a mediator that translates complex physical fracture data into simplified S-N curves and endurance limit parameters, making the interpretation of fatigue test results more straightforward and reducing the complexity of analyzing fracture data.
3Measurement precision
If high-speed camera monitoring is added to detect fracture, then measurement precision of failure time is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical fracture detection methods (such as acoustic emission sensors or strain gauges) with high-speed optical camera monitoring. The high-speed camera captures visual evidence of fracture events, providing precise timing and location data without requiring complex mechanical sensing systems. This substitution simplifies the monitoring approach while maintaining high measurement precision.
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 provides valuable data on the fatigue and endurance limits of stents, enabling manufacturers to redesign them for enhanced durability and minimize the likelihood of failure during implantation.
Implementation Method 1
repeatedly expanding the mock vessel and medical implant therewithin using a pressurized fluid
Implementation Method 2
simulate pulsatile blood pressure conditions
Implementation Method 3
providing a high speed camera to monitor the deflection of the test sample by direct visualization of the medical implant
Data Source
AI summary
The invention generally relates to systems and methods for stress testing to failure tubular mesh devices, specifically, one or more stents or mesh grid tubes. A radial compression method of stress to fatigue is developed by placing a tubular medical implant within a lower than normal compliance test vessel. A radial expansion method of stress to fatigue is developed by placing higher than normal compliance tubes within a tubular medical implant. A method for radial expansion and radial compression is conducted by placing a higher than normal compliance tube through the mesh device and the placing the tube and device within a lower than normal compliance test vessel. Each method is tested on a tester that operates by delivering pulsatile flow with varying pressures, frequencies and testing parameters. Fracture of the test subject is visualized by high speed camera.