Investigation of the applicability and effectiveness of unified constraint parameters on A516 Gr70 steel specimens under ductile fracture

In our previous study, a unified parameter λ based on crack-tip plastic strain energy was proposed which using BS1501-224 28B steel specimens at a low temperature showed promise to quantify both in-plane and out-of-plane constraints concurrently. In this study, a large number of A516 Gr70 steel specimens with wide-ranging changes in thicknesses and crack lengths were tested at the materials’ upper shelf (−15^oC) to further validate the applicability of λ. A series of numerical models were conducted based on the experimental data and the applicability and effectiveness of parameter λ were studied. A comparison between parameter λ and another unified constraint parameter A_p was discussed to justify using this new method. It is found that parameter λ can be used for specimens with large plasticity and it performs better than parameter A_p. What is more, an application method of using parameter λ to predict the fracture toughness of nonstandard specimens was proposed which sets out a method to incorporate it into engineering assessments.