Tensile Testing Thin-Walled Surgical Tubing with a Long Travel Extensometer
Surgical tubing is used in a wide variety of applications, such as drains, feeding tubes, irrigation, and surgical procedures. The mechanical performance of the material used is critical, as failure could seriously endanger a patient. Tensile tests are frequently performed in product development and quality control to evaluate properties of material strength and strain at break.
In this application, we tested thin walled surgical tubes with the following dimensions: 0.062-inch outer diameter, 0.01-inch wall thickness, and 2.5-in length. The tubes were manufactured with a surface coating, and after many daily tests performed for the product's quality assurance, the coating builds up on the grip faces and causes an unknown amount of specimen slipping over time. Despite regularly changing the grip faces, this slipping is the cause for discrepancies in strain measurements between testing sites and users. We suggest using an extensometer for more consistent and accurate measures of strain between data sets.
For this series of tests, we used our 3345 electromechanical testing frame configured with a 100 lb load cell, 250 lb capacity pneumatic side action grips with 1-in x 1-in rubber-coated faces, and a long travel extensometer. The test was run for nine different specimens at a speed of 20 in/min. We suggest using rubber-coated faces for this application because they provide enough gripping strength, friction, and cushioning that prevents excessive slipping of the specimen in the grips. The thin-walled surgical tubes tend to yield under tension inconsistently over the length of the specimen, so we recommend the smallest gauge length possible. We used a 1-inch gauge length.
The graph and results show the repeatability of the test configuration. We conclude from the data that a long travel extensometer is appropriate for accurately measuring strain in thin-walled medical tubing, and is recommended for future testing applications.
The Instron® model XL (long travel) extensometer is a precise device for measuring strain in highly extensible materials such as elastomers, semi-rigid plastics and films.
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Instron 3300 Series Universal Testing Systems for Tensile, Compression, Bend, and other material property tests.
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