Brittle-fracture simulations of curved cleavage cracks in α-iron: A molecular dynamics study

T Suzudo,T Tsuru,K Ebihara

doi:10.1063/5.0026659

Abstract

Although body-centered-cubic (bcc) metals and alloys are ubiquitous as structural materials, they are brittle, particularly at low temperatures; however, the mechanism of their brittle fracture is not fully understood. In this study, we conduct a series of three-dimensional molecular dynamics simulations of the cleavage fracture of α-iron. In particular, we focus on mode-I loading starting from curved crack fronts or the so-called penny-shaped cracks. In the simulations, brittle fractures are observed at cleavages on the {100} plane, while the initial cracks become blunted on other planes as a result of dislocation emissions. Our modeling results agreed with a common experimental observation, that is, {100} is the preferential cleavage plane in bcc transition metals. In addition, dislocation emissions from the crack front were analyzed; the result supported the notion that plasticity in the vicinity of the crack front determines the preferential cleavage plane.

Highlights

Body-centered-cubic transition metals and alloys such as steel are ubiquitous in the infrastructure of automobiles, ships, bridges, and nuclear power stations
I, we conducted molecular dynamics deformation simulations of α-iron samples starting from a pennyshaped cleavage crack, whose crack front was sharp at the atomic level, to simulate brittle fractures
Throughout the current study, we considered the embeddedatom method (EAM) potential introduced by Ackland et al.,38 which is an improved version of Mendelev-II and has been adopted in the previous penny-shaped cleavage crack studies

Summary

Introduction

Body-centered-cubic (bcc) transition metals and alloys such as steel are ubiquitous in the infrastructure of automobiles, ships, bridges, and nuclear power stations These materials become brittle, especially at low temperatures, and their resulting mechanical failures may have catastrophic consequences. Brittle cracks in many materials showed anisotropic propagation, which could not be explained by this theory This limitation of Griffith’s theory was thought to be due to its continuum consideration; the atomistic consideration of the brittle fracture was studied with a newly introduced concept, called lattice trapping or bond trapping.. This limitation of Griffith’s theory was thought to be due to its continuum consideration; the atomistic consideration of the brittle fracture was studied with a newly introduced concept, called lattice trapping or bond trapping. This concept associates a straight crack front with a linear series of atomic bonds, which depends on the crack-front direction; anisotropic crack propagation ceased to be a mystery

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