An updated continuum damage model to investigate fracture process of structures in DBTT region

Abstract

In the Ductile-Brittle Transition Temperature (DBTT) region, it is not realistic to take unique fracture stress or fracture strain as the fracture criterion to investigate the fracture properties. In this paper, an updated continuum damage model was proposed, in which the fracture energy density, a function of the stress triaxiality, temperature and strain rate in the transition region was taken as the critical damage factor. Uniaxial tension tests were carried out to get the basic material properties at different temperatures, to calibrate the fracture model constants and verify the validity of the damage model. The fracture behaviour of pipes with penetrating cracks under the internal pressure was experimentally investigated with the load-deflection curves and the crack propagation length captured from tests. The J -R curves were obtained from the testing results for different temperatures. Based on the Finite Element Analyses (FEA) with the proposed fracture criterion of the updated continuum damage model, the loading level of pipes with penetrating cracks were estimated and compared with the experimental results. Meanwhile the fracture processes of the pipeline structures in the transition region were reproduced. The experimental and numerical results agreed very well in present calculations. It has been shown that the fracture process in the transition region strongly depends on both the stress and strain states, and could be effectively predicted using the continuum damage model.

Correlation of Microstructure with Anisotropy of Low‐Temperature Toughness in Two API X70 Pipeline Steels

“…The DBTT is generally determined as the temperature with energy corresponding to the average of the upper shelf energy and the lower shelf energy. [30,31] According to the energy data, curves of the Charpy impact absorbed energy versus the temperature are fitted with the Boltzmann function (Figure 6). These curves indicate that the high CT steel has a greater USE than the low CT steel, but the DBTT of the high CT steel is higher than that of the low CT steel.…”

On Continuum Damage Modeling of Fiber Reinforced Viscoelastic Composites with Microcracks in terms of Invariants

“…Because, according to expression (51), the above-mentioned are arbitrary, the necessary and sufficient condition for validity of this equation is Γ = 0 coefficients being zero ( = 1, 2,4,7,10,12,14,16,17,19,22,24,25,27,29,30,33,34,37,38,40,43,45,46,49,50). In this situation, expression providing the dissipative stress is obtained as follows:…”

“…Chaboche has proposed a thermodynamic framework for continuum damage mechanics (CDM) for isotropic damage [15]. Furthermore, an updated continuum damage model was proposed, in which the fracture energy density, a function of the stress triaxiality, temperature, and strain rate in the transition region were taken as the critical damage factor [16]. Li et al presented a damage model and its numerical solution by means of fast Fourier transforms (FFT) [17].…”