Dr. Jy-An Wang
Materials Science and Technology Division
Oak Ridge National Laboratory

3-D Non-coplanar Spiral Crack Front Fracture Toughness Evaluation

ABSTRACT: A new method, designated as Spiral Notch Torsion Test (SNTT), is developed to measure the intrinsic fracture toughness K_IC of structural materials. The SNTT overcomes many of the limitations inherent in traditional techniques and makes it possible to standardize fracture toughness testing. It is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments, including others such as ceramics, their composites, and concrete. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45 deg pitch. The K_IC values are obtained with the aid of a three-dimensional finite-element computer code, TOR3D-KIC, developed at Oak Ridge National Laboratory (ORNL). The latest development including using Abaqus routine for J-integral evaluation; and using torque load vs torque-ends rotation angle curve for a direct measurement of J-integral value, instead evaluated by the 3-D spiral crack front FEA J-integral contour study. The fundamental mechanism of SNTT approach is also discussed in the talk.

BIOGRAPHY: John Jy-An Wang is a Senior Research Staff Member at Oak Ridge National Laboratory (ORNL). He received a B.S from National Central University at Taiwan, Republic of China, in 1977; and received a Ph.D. from University of California, Berkeley, in 1988, major in mechanics of material and structural dynamics. Since 1989 he has been working at Oak Ridge National Laboratory as an R&D Staff. During his residence at ORNL he has published over 200 technical reports, conference papers, and Journal articles on subjects related to fracture toughness evaluation, non-linear material behavior characterization, material damage modeling, the neutron radiation embrittlement predictions for pressure vessel steels, reactor pressure vessel surveillance program, and the development of the material aging database. He also invented the Spiral Notch Torsion Fracture Test (SNTT) for evaluating Mode I fracture toughness (KIC), and SNTT Technology won a 2002 R&D 100 Awards. He has been developing MELCOT System for high voltage power transmission system reliability investigation and won a 2009 R&D 100 Award.