How to Perform a 3 Point Bend Test on a Universal Testing Machine

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Bend testing (also flex or flexural testing) is commonly performed to measure the flexural strength and modulus of all types of materials and products.  This test is performed on a universal testing machine (tensile testing machine or tensile tester) with a 3 point or 4 point bend fixture.  Most common for product testing is the 3 point test.

The key analysis when performing bend testing are:

1. Flexural Modulus - This measures the slope of a stress / strain curve and is an indication of a material's stiffness
2. Flexural Strength - This measures the maximum force that a material with withstand before it breaks or yields.  Yield is where you have pushed a material past its recoverable deformation and it will no longer go back to the shape it once was.
3. Yield Point - The yield point is the point where the material essentially "gives up" or the point where if you were to continue to bend the product, the force will not continue to increase and will then start to decrease or break.

The video below shows a bend test.  The actual part is a pen, but the same test can be run on nearly any product or material.  As you can see from the video, there is a point during the test where the bent area of the red pen turns white.  This happens to occur around the same time as the yield point.  

Test Report from ADMET's MTESTQuattro Testing Software: