APPLICATION OF THE CTOD FRACTURE PARAMETER TO FAILURE ANALYSIS OF NOTCHED PRESSURE VESSELS (CRACK TIP OPENING DISPLACEMENT)

The Crack Tip Opening Displacement (CTOD) approach to failure analysis in the Elastic-Plastic Fracture Mechanics (E-PFM) regime was investigated. The CTOD - Temperature transition behavior for five pressure vessel and structural steels using three specimen sizes was determined. The practical aspects of CTOD testing were studied and the CTOD test results were compared with the results of other fracture toughness tests, such as the J-Integral and Charpy V-Notch.; The use of the Finite Element Method (FEM) for the analysis of elastic-plastic flawed structures was studied. 2-D and 3-D elastic-plastic FEM solutions for the three standard three-point bend specimen geometries and the five material properties tested above were performed. The appropriate FEM modeling parameters and a method of calculating CTOD from the computed displacements was determined. The FEM results were compared with experimental results in order to verify the accuracy of the analysis procedure.; Finally, the burst pressures of a series of notched pressure vessels from previous studies at the University of Kansas and at the Oak Ridge National Laboratory (HSST Program) were predicted using the CTOD test method and the FEM analysis procedure discussed above. Burst pressure predictions were within seven per cent of the experimentally measured burst pressures over the entire range of behavior from near linear elastic to near limit load. This analysis procedure provides a significant improvement over analysis methods currently used.