SYMPOSIA PAPER Published: 01 January 2003

An Innovative Technique for Measuring Fracture Toughness of Metallic and Ceramic Materials


A new method is introduced for measuring fracture toughness, KIC, of materials ranging from metallic alloys to brittle ceramics. A valid value of KIC is determined using a round-rod specimen having a grooved spiral line with a 45° pitch. When this uniquely configured specimen is subjected to pure torsion, an equibiaxial tensile/compressive stress-strain state is created to effectively simulate that of conventional test methods using a compact-type specimen with a thickness equivalent to the full length of the spiral line. KIC values are estimated from the fracture load and crack length with the aid of a 3-D finite element analysis. KIC of a mullite ceramic material yields 2.205 MPa√m, which is 0.2% higher than the vendor's data. KIC of A302B steel is estimated to be 55.8 MPa √m, which shows higher than compact tension (CT) test value by~2%. 7475-T7351 aluminum yields 51.3 MPa√m, which is higher than vendor's value in the TL orientation by -0.8% and higher than 0.5T-CT value by 6%. Good agreement between the KIC values obtained by different methods indicates the proposed method is theoretically sound and experimental results are reliable.

Author Information

Wang, JA
Oak Ridge National Laboratory, TN
Liu, KC
Oak Ridge National Laboratory, TN
McCabe, DE
Oak Ridge National Laboratory, TN
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Developed by Committee: E08
Pages: 757–770
DOI: 10.1520/STP11105S
ISBN-EB: 978-0-8031-5472-8
ISBN-13: 978-0-8031-2899-6