Top 4 Tensile Testing Mistakes

1) Grips- Make sure that your grips are rated high enough to hold your sample and avoid slippage. Also, if using pneumatic grips, check that your air pressure is 60 psi. Using the correct grip faces is important for tensile testing. Most plastic film companies use Rubber Covered inserts to prevent sample slippage. Serrated inserts are too aggressive for plastic films and will result in sample breaks at the grip.

2) Sample preparation- Preparing a sample WITHOUT jagged edges or nicks is vital to ensure accurate tensile results. Those imperfections will affect your results and your ability to provide consistent results. Many companies spend a lot of money on their tensile testers, but do not buy the proper sample cutter to prepare their samples. Thwing-Albert offers the JDC Sample Cutter for standard samples and the 240-7A Cutter for Dogbone or other shaped sample sizes.

3) Load Cell- Equipping your tensile tester with an appropriate load cell is a key factor in tensile testing. As a general rule, testing should be performed at about 50% of the capacity of the load cell. If testing goes below 10% of the capacity of the load cell, the accuracy is not as great. For example, between 10% and 100% of the capacity of the load cell, Thwing-Albert load cells have an accuracy of .25% of the MEASURED VALUE. Below 10% of the capacity of the load cell, the accuracy changes to .025% of the CAPACITY OF THE LOAD CELL. If you test to close to the capacity of your load cell, you run the risk of overloading the load cell.

4) Consistency-Always using the same gauge length (the space between the grips), using the same test speed, preparing the samples the same way, and inserting the sample the same way for every test is a great way to obtain consistent repeatable results. The sample testing procedure should be the same whether the 1st shift is doing the testing or the 3rd shift is doing the testing.