AN ENGINEERING TOOL FOR FRACTURE-TOUGHNESS TESTING

A chevron notch four-point bend geometry fracture specimen is presented which complements the chevron notched short rod and short bar geometry used in ASTM E1304, the newest standard for fracture toughness testing. Although the four-point bend samples require slightly more material, sample preparation is less involved. Therefore total testing costs are lower using this four-point bend geometry when testing materials with low to moderate toughness to yield strength ratios. To test the new four-point bend samples, a stand alone toughness tool has been developed which allows a fracture toughness measurement to be made in about 30 seconds. It is shown that the fracture toughness values, measured using this toughness tool, are identical to the values obtained when loading the samples in a servo hydraulic testing system using a four-point bend fixture in displacement control. The fracture toughness values obtained using either loading method agree with fracture toughness values obtained according to ASTM E399.