Comparisons of Fracture Toughness Measurements by the Short Rod and ASTM Standard Method of Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-78)

Abstract

A multilaboratory blind comparison testing program evaluated the accuracy of the short rod method of measuring the fracture toughness of metallic materials. Valid comparisons between values measured according to ASTM Standard Method of Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-78) and values of the plane-strain critical stress intensity factor as measured by the short rod method of fracture toughness measurement (KIcSR) were obtained for several steels, aluminum alloys, and titanium. The KIcSR values measured by the short rod method were consistently low, averaging 6% below the measurements according to ASTM Standard Method E 399. A 4% adjustment in the short rod calibration constant that had been previously evaluated only to ±7% brings the two sets of measurements into very good agreement. The short rod method thus appears to be a viable alternative for measuring the fracture toughness of metallic materials.

The Mechanical Properties of Inorganic Thermoelectric Materials: A Review on Characterization Methods and Correlations

“…This testing method, if carried out correctly, has the advantage of directly measuring the material's fracture toughness, even on miniature size specimens with the aid of testing jigs and setups such as "Fracjack". [48] Yet, for obtaining adequate results, the specimen's fabrication must be of high quality and machining should be made by skilled technicians, because the required standard specimen includes many details (see Figure 7), and most of the ceramic and semiconducting materials suffer from poor machinability. Up to date, as far as we know, no TE materials tested by this technique were reported.…”

“…Conventional fracture toughness tests are conducted on large specimens with fatigue crack introduced into them as to create as close as possible conditions to those defined by the linear elastic fracture mechanics (LEFM). [47,48] That means, that the plasticity at the crack tip and tri-axiality are limited (smallscale yield conditions) due to the restraining volume of the specimen. ASTM E 399 [49] standard, states five types of specimens and loading setups that stand in these conditions.…”

“…After the test is concluded, the recorded data is processed to evaluate the fracture toughness of the material, if all the validation criteria of the standard are met. This testing method, if carried out correctly, has the advantage of directly measuring the material‘s fracture toughness, even on miniature size specimens with the aid of testing jigs and setups such as “Fracjack” [48] . Yet, for obtaining adequate results, the specimen‘s fabrication must be of high quality and machining should be made by skilled technicians, because the required standard specimen includes many details (see Figure 7), and most of the ceramic and semiconducting materials suffer from poor machinability.…”

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