Three-point flexural test

This test is performed on a universal testing machine (tensile testing machine or tensile tester) with a three-point or four-point bend fixture.

However, this method has also some disadvantages: the results of the testing method are sensitive to specimen and loading geometry and strain rate.

The sample is placed on two supporting pins a set distance apart.

[2] in these formulas the following parameters are used: The fracture toughness of a specimen can also be determined using a three-point flexural test.

The stress intensity factor at the crack tip of a single edge notch bending specimen is[3] where

In a three-point bend test, a fatigue crack is created at the tip of the notch by cyclic loading.

A plot of the load versus the crack opening displacement is used to determine the load at which the crack starts growing.

This load is substituted into the above formula to find the fracture toughness

The ASTM D5045-14 [4] and E1290-08 [5] Standards suggests the relation where The predicted values of

are nearly identical for the ASTM and Bower equations for crack lengths less than 0.6

1940s flexural test machinery working on a sample of concrete
Test fixture on universal testing machine for three-point flex test
Single-edge notch -bending specimen (also called three-point bending specimen) for fracture toughness testing.