New constraint parameters based on crack tip plastic zone: Theoretical derivations and effectiveness verification

摘要

In structural integrity assessment, it is important to measure the in-plane and out-of-plane constraint effects which have strong influences on fracture toughness. Based on the improved analytical solution of crack tip plastic zone size, four new constraint parameters are derived theoretically, i.e. r(p0)(1/2), r(pmax)(1/2), A(pz)(1/4) and chi(p). By means of three-dimensional finite element method and test data validation, the effectiveness of new constraint parameters has been studied in three kinds of materials, i.e. Aluminum alloy 2024-T351, Shoreham Reactor vessel steel (K12539) and Carbon steel 34XH3MA. Then the prediction models of fracture toughness are established for these materials. Lastly, the application range and extensive application are discussed. The results show that the newly proposed constraint parameters can effectively characterize both the in-plane and out-of-plane constraint effects, and are applicable under small- and moderate-scale yielding conditions. For a given specimen, these constraint parameters are approximately linearly proportional to mode I stress intensity factors. Additionally, in the materials under consideration, there are also linear relations between the proposed constraint parameters and the experimental fracture toughness. (C) 2019 Elsevier Ltd. All rights reserved.