Mechanical Engineering Faculty Research


Weibull Stress Model for Cleavage Fracture Under High-Rate Loading

Document Type


Publication Date



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 (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 I . Present results indicate that σw-min and σu are weak functions of loading rate 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 I is sufficient to preclude use of the static σu value for high loading rates.

Publication Title

Fatigue & Fracture of Engineering Materials & Structures





First Page


Last Page