Modelling of the ductile-brittle fracture transition in steel structures with large shell elements: A numerical study

Abstract

In this paper, the strain energy density (SED) criterion is proposed for predicting the ductilebrittle fracture transition (DBFT) in ships and offshore structures. In finite element simulations, these structures are discretized by relatively large shell elements which precludes the modelling of the local stress and strain states in the vicinity of a crack. Critical values of the SED are determined based on local simulations of fracture for a range of temperatures and plane stress states. The local simulations of fracture are based on combined use of the Gurson model for ductile damage and fracture and the Richie-Knott-Rice (RKR) criterion for brittle fracture. After calibrating the Gurson model and the RKR criterion to existing experiments on offshore steel, critical values of the SED are found by analysing a representative plate element with a generic through-thickness crack using a refined solid element mesh. The proposed failure model is evaluated by simulating drop tests on steel-plated structures found in the literature. The present study indicates that the SED criterion is a useful concept for practical design of ships and offshore structures at sub-zero temperatures, but further assessment against experimental data is necessary to fully establish its credibility.

Thermal analysis of marine structural steel EH36 subject to non-spreading cryogenic spills. Part I: experimental study

“…On this account, knowledge about the structural performance of steel members subject to the spillage of cryogenic liquids is limited. A few studies in recent years have investigated the structural behaviour of steel at low temperatures (Berejnoi and Ipiña 2015;Majzoobi et al 2016;Bruchhausen et al 2017;Paik et al 2017;Nam et al 2018;Li et al 2019;Paik et al 2020). These studies confirmed the risk of ductile-to-brittle fracture transition in steel at cryogenic temperatures, which might lead to disastrous structural failures in LNG carriers and offshore structures.…”

Ultimate Compressive Strength of Steel Stiffened-Plate Structures Triggered by Brittle Fracture under Cryogenic Conditions

“…It is recognised that structural steel behaviour is predominantly ductile at temperatures higher than the temperature of the ductile-to-brittle fracture transition, as shown in Figure 1. As the temperature decreases approaching cryogenic condition, the material behaves predominantly in a brittle manner with partial or no ductility [33][34][35][36][37][38][39][40]. Majzoobi et al [41] observed that the ductile-to-brittle fracture transition of carbon steel occurs at about -80°C, and the material behaviour becomes entirely brittle at -196°C.…”

“…modelling the weld toes using shell elements along the plate-stiffener junction. A similar approach was used to model weld toes by Kim et al [44] and Nam et al [35].…”

Thermal analysis of marine structural steel EH36 subject to non-spreading cryogenic spills. Part II: finite element analysis

“…Therefore, for a safer Accidental Limit State (ALS) design of ships and offshore structures, it is necessary to accurately predict their performance in cryogenic conditions. Thus far, a number of experimental and numerical studies have investigated the structural performance of offshore structures and ships in low or cryogenic temperatures (Ehlers and Østby 2012;Nam et al 2018;Paik et al 2020). In these studies, uniform temperature, was applied throughout the structure (i.e.…”