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Measure Elongation of Tire Rubber

For automotive tire manufacturers, it’s critical to understand the elongation properties of the rubber in order to predict how tires will behave on the road. As an elastomer, tire rubber can be quite stretchy.

Let’s take a look at elastomer testing challenges:

While most common standards, such as ASTM D412 and ISO 37, don’t require an extensometer, they are usually recommended to ensure accurate and repeatable results. When it comes to picking an extensometer, there are dozens of available options – so how do you pick the right one?

Important considerations:

  • Travel – Keeping in mind that tire rubber and other elastomers tend to be quite stretchy, you’ll want to make sure your extensometer has sufficient vertical travel, and high accuracy throughout the entire elongation.
  • Throughput – Many extensometers have to be put on manually, and some can’t stay on through break – which can slow down the testing process. If you test a lot of specimens, automatic contacting and non-contacting extensometers can significantly increase your throughput.
  • Operator Influence – Extensometers that require the operator to manually take them on an off invites variance from test to test, and from operator to operator. For the most consistent results, you’ll want to remove as many operator-specimen interactions as possible.
  • Non-Ambient Testing – Elastomers are often tested at a wide range of temperatures. If that’s the case for your application, you’ll want to make sure your extensometer can be used with an environmental chamber.

Top 3 extensometers for testing tire rubber and elastomers:

  1. A Non-Contacting Video Extensometer:

The AVE 2 and SVE 2 non-contacting video extensometers are very popular because they save the operator a lot of time, they have a large field of view capable of measuring high elongations, and they’re the only option on our list here that can be used with an environmental chamber for non-ambient testing.

Features and Benefits:

  • Large field of view allows you to measure up to 840mm/34.46in to provide strain at failure results for most materials
  • Meets or exceeds the accuracy requirements for elastomers, including ASTM D412 and ISO 37
  • Wider application range because they can be used with environmental chambers over a wide temperature range
  • Prevents premature damage to the specimen by measuring strain without touching for the most accurate results
  • Consistent results regardless of operator due to automatic gauge length measurement

2. Automatic Contacting Extensometer

The AutoX750 is also popular for testing tire rubber because of their high accuracy and long vertical travel. They can also increase specimen throughput by allowing labs to take advantage of automatic gauge length positioning and attachment to the test specimen – freeing up the operator from having to do these time consuming steps themselves.

Features and Benefits:

  • High travel – up to 750 mm/29.52 in in vertical travel – and measure strain through break with most materials
  • Various knife edge options and the ability to adjust the clamping force to accommodate different materials
  • Very high resolution and accuracy ( +/- 1um)
  • Automatic attachment eliminates operator influences
  • Automatic centering improves repeatability
  • The AutoXBiax can measure both axial and transverse strain simultaneously

3. XL Long Travel Extensometer

The XL Long Travel Extensometer is also a good option for measuring the elongation of tire rubber. It’s specifically designed to deliver precision measurements for highly extensible materials, and permits testing the sample through rupture without damaging the extensometer or otherwise disrupting the test routine.

Features and Benefits:

  • High travel – up to 750 mm/29.52 in in vertical travel – and measure strain through break
  • Counterbalanced for minimum force on sample
  • Adjustable clamping force on the knife edges reduces premature failure of the specimen
  • Quick release clamps for efficient specimen insertion and removal

 

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