Contents lists available at ScienceDirect Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech Effect of competing mechanisms on fracture toughness of metals with ductile grain structures Yan Li a, ⁎ , Min Zhou b a Department of Mechanical and Aerospace Engineering, California State University, Long Beach, CA 90840, USA b The George W. Woodruff School of Mechanical Engineering, School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA ARTICLEINFO Keywords: Fracture toughness J-integral Cohesive finite element method Transgranular and intergranular fracture ABSTRACT The fracture toughness of ductile materials depends on the combined effect of plastic dissipation intheconstituentsandenergyspentoncreatingnewcracksurfaces.Thedesignofpolycrystalline metals with improved fracture toughness requires in-depth understanding of two levels of competing mechanisms: the competition between plastic deformation and crack formation as well as the competition between transgranular and intergranular fracture. Currently, no sys- tematic approach exists to analyze the effects of the two competitions. The fundamental chal- lenges lie in the difficulty in separating the two forms of energy dissipation and inadequate knowledge about the correlation between fracture mechanisms and material fracture toughness. In this paper, a multiscale framework based on the Cohesive Finite Element Method (CFEM) is developed to quantify the two levels of competitions and to predict the fracture toughness of ductile materials by calculating the J-integral at the macroscale. The fracture surface energy for the crack paths associated with different types of failure mechanisms is evaluated through ex- plicit simulation of crack propagation at the microstructure level. The calculations carried out here concern the AZ31 Mg alloy, but the overall approach applies to other materials as well. Resultsindicatethataproperbalancebetweentransgranularandintergranularfailurecanleadto optimized fracture toughness. Microstructures with refined grain sizes and balanced bonding strength in grains and grain boundaries can best promote the manifestation of favorable failure mechanisms, and as a result, enhance fracture toughness. 1. Introduction From the energy point of view, a crack can grow only when the energy available at the crack tip is sufficient to balance out the energy required for crack propagation. Therefore, a key aspect of designing high toughness materials is to promote favorable failure mechanisms which can lead to maximized energy dissipation. For brittle materials, the most effective way to improve fracture toughness is to create tortuous crack paths since, in the absence of plasticity, the total energy released is transformed into surface energy alone. This can be achieved by, for example, introducing refined second-phase reinforcements, appropriately balanced in- terphase bonding strength and interface stiffness, and through grain bridging [1–5]. For ductile materials, the fracture resistance depends on the sum of energy spent on both surface generation and bulk plastic deformation. Osovski et al. [6] studied the effect of loading rate on ductile fracture toughness. They found that the total plastic dissipation and the plastic dissipation associated with the https://doi.org/10.1016/j.engfracmech.2018.11.006 Received 22 May 2018; Received in revised form 31 October 2018; Accepted 1 November 2018 ⁎ Corresponding author. E-mail address: [email protected] (Y. Li). Engineering Fracture Mechanics 205 (2019) 14–27 Available online 07 November 2018 0013-7944/ © 2018 Elsevier Ltd. All rights reserved. T
Effect of competing mechanisms on fracture toughness of metals with ductile grain structures
Jun 12, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
