A Weibull stress model to predict cleavage fracture in plates containing surface cracks

Abstract

This study applies recent advances in probabilistic modelling of cleavage fracture to predict the measured fracture behaviour of surface crack plates fabricated from an A515‐70 pressure vessel steel. Modifications of the conventional, two‐parameter Weibull stress model introduce a non‐zero, threshold parameter (σw‐min ). The introduction of σw‐min brings numerical predictions of scatter in toughness data into better agreement with experimental measurements, and calibration of this new parameter requires no additional experimental data. The Weibull modulus (m) and scaling parameter (σu ) are calibrated using a new strategy based on the toughness transferability model, which eliminates the non‐uniqueness that arises in calibrations using only small‐scale yielding toughness data. Here, the Weibull stress model is calibrated using toughness data from deep‐notch C(T) and shallow‐notch SE(B) specimens, and is then applied to predict the measured response of surface crack plates loaded in different combinations of tension and bending. The model predictions accurately capture the measured distributions of fracture toughness values.

Modeling ductile to brittle fracture transition in steels—micromechanical and physical challenges

“…Bakker and Koers 1991;Xia and Cheng 1997). Gao et al (1999) have proposed a modified expression given by:…”

Bonded-cell model for particle fracture

“…The applicability of this distribution to quasibrittle materials has been questioned by some authors and deviations from the Weibull statistics have been observed [80][81][82][83]. Strictly speaking, there are no cracks in our system, and stress concentration is a consequence of cell-induced disorder.…”

A micromechanics approach to assess effects of constraint on cleavage fracture toughness: a weibull stress model

“…The next section describes numerical analyses for fracture specimens extracted from an A515-70 pressure vessel and an API X80 pipeline steel weld that were tested in the experimental program. Gao et al (1999) describes the uniaxial stress-strain curve for the A515-70 pressure vessel steel at the test temperature, 2 J 7 − = T°C and °C. Minami et al (1995) provides the uniaxial true stress vs. logarithm strain curves for the API X80 pipeline steel (base plate and overmatch weld material) at the test temperature, 28 − = T 5 − = T°C.…”

“…The research code WSTRESS (Ruggieri, 2001 ). Gao et al (1999) provides the true stress-logarithmic strain curve at the test temperatures (°C and °C) for this material used in the finite element analyses of the specimens.…”