A new fracture toughness measurement method, named an X-specimen test that is based on the curved compact-tension test, was proposed to assess the fracture toughness of thin-walled tubing materials like Zircaloy fuel cladding. This technique offers applications of fracture mechanics for testing thin-walled tubes, which do not meet the requirements of the American Society for Testing and Materials standards in terms of the specimen configuration and loading state. The finite-element analysis was conducted to evaluate the feasibility of applying the X-specimen test to the measurement of cladding fracture toughness and to develop a relationship between the stress intensity factor and crack extension. Then fracture and fatigue tests were performed employing a hydraulic mechanical testing machine. The J-integral value was evaluated using the experimental results of the applied load, loadline displacement, and crack extension.
By means of a backtracking method, the stress intensity solutions were computed using fatigue results. A J-integral value of about 82 kN/m was obtained for Zircaloy fuel cladding. A comparison of the present test results and literature data shows that the X-specimen test is suitable for a quantitative evaluation of the fracture behavior of thin-walled tubing materials.