Ductile fracture simulation of full-scale circumferential cracked pipes: (I) Carbon steel

This paper reports ductile fracture simulation and comparison with carbon steel test data of full-scale cracked pipes via 3-D finite element damage analysis based on stress-modified fracture strain model. Although there are few test results and discussion of full-scale cracked pipes, it is not an easy task to properly evaluate fracture behaviour of large-scale components for various pipe sizes with different shape of a crack-like defect. In such a situation, finite element (FE) damage analysis can be a competitive alternative to characterize the fracture behaviour of cracked components such as crack initiation and maximum loads. In recent years, a simple FE method [1] to simulate ductile fracture has been developed based on the stress-modified fracture strain model [2,3]. The technique appropriately simulated ductile failure for miscellaneous cracked components [4,5]. However, for some cases, large-scale components using small element size, FE analysis couldn't give reliable values because of numerical instability. Element-size-dependent critical damage model enhanced by taking the effect of element-size on the ductile fracture damage analysis is introduced to overcome this problem and to be applicable to the large-scale structures. In order to validate proposed method, two types of carbon steel (A106 Gr. B and SA333 Gr. 6) pipes with a circumferential crack taken from [6] are considered, subjected to four-point bending only and combined loading. It is shown that predicted crack initiation and maximum loads are compared with experimentally measured values, showing overall good agreements. (C) 2014 Published by Elsevier Ltd.