Weibull stress model for cleavage fracture under high‐rate loading

Abstract

This paper examines the effects of loading rate on the Weibull stress model for prediction of cleavage fracture in a low‐strength, A515‐70 pressure vessel steel. Interest focuses on low‐to‐moderate loading rates (K˙I < 2500 MPa √m s−1 ). Shallow cracked SE(B) specimens were tested at four different loading rates for comparison with previous quasi‐static tests on shallow notch SE(B)s and standard C(T)s. To utilize these dynamic experimental data, we assume that the Weibull modulus (m) previously calibrated using quasi‐static data remains invariant over the loading rates of interest. The effects of dynamic loading on the Weibull stress model enter through the rate‐sensitive material flow properties, the scale parameter (σu ) and the threshold Weibull stress (σw‐min ). Rate‐sensitive flow properties are modelled using a viscoplastic constitutive model with uniaxial, tension stress–plastic strain curves specified at varying plastic strain rates. The analyses examine dependencies of σw‐min and σu on K˙I . Present results indicate that σw‐min and σu are weak functions of loading rate K˙I for this pressure vessel steel. However, the predicted cumulative probability for cleavage exhibits a strong sensitivity to σu and, consequently, the dependency of σu on K˙I is sufficient to preclude use of the static σu value for high loading rates.

A K0‐based calibration procedure for the Weibull stress cleavage model

“…Petti and Dodds have subsequently coupled the microscopic crack driving force, σ w , with the macroscopic crack driving force, K JI , with a constraint function to characterize the plasticity‐induced constraint loss in fracture specimens. Many research efforts have confirmed the close agreement between the experimentally measured macroscopic fracture toughness with the three‐parameter Weibull stress model. The calibration of the three‐parameter Weibull stress model often requires significant experimental efforts with carefully controlled and instrumented results.…”

Study of Weibull parameters at different loading rates for 20MnMoNi55 steel using Beremin model

“…Ruggeiri et al [14] studied the impact of constraint loss on T 0 using the Weibull stress model. In the year 2001, Gao et al [15] investigated the influence of loading rate on the Weibull parameters at low to moderate loading range and they found that m is invariant in low loading range, but σ u is strongly rate sensitive. Gao et al [16] also proposed that σ u must be calibrated in dynamic loading range.…”

Análisis metodológico del esfuerzo normal σyy basado en deflexión elástica

“…Sin ISSN: 2594-1925 embargo, Kim (2011) y Huang (2017) determinan los esfuerzos normales basado en pruebas experimentales en elementos estructurales, con el objetivo de determinar parámetros de experimentales de fatiga de los estos elementos. Actualmente, algunas metodologías probabilísticas de análisis de esfuerzo-resistencia parten del hecho de la existencia de este esfuerzo normal sin especificar el modo de determinación del mismo [1][2][3], [17][18][19].…”