Elastic visco-plastic model of steel solidification with local damage and failure

A nonlinear elastic visco-plastic thermo-mechanical steel microstructure model is coupled with a Gurson-Tvergaard-Needleman (GTN) model to predict local damage and failure in the columnar solidification zone of a steel casting. The new model operates on two scales - a micro-scale model of a representative unit cell in the columnar zone as well as a macro-scale model of a tensile specimen to match micro-scale observations with experiments. The micro-scale model aims to investigate inter-granular embrittlement at intermediate temperatures during solidification processes. This embrittlement occurs due to pro-eutectoid ferrite film formation and precipitation at the prior austenite grain boundaries. This behavior of the unit cell is then mapped onto macro-model tensile specimens to measure reduction in ductility. The effects of ferrite films and test temperature are studied by calculating the micro-strains, macro-strains and void fractions at which cracks begin to form during the process. The developed model shows good agreement with experimental data. It is then further used to study the impact of the presence of the ferrite films, temperature of the steel as well different types of loading on the micro-scale mechanical behavior which depends on the particular location on the cast strand. The presence of ferrite films at the austenite grain boundaries is a significant driver of intermediate-temperature embrittlement as predicted by the model. This is further exacerbated by increase in test temperature. An increase in temperature causes an overall reduction in the strength of the steel but also increases the strength of the grain matrix in comparison to the strength of the ferrite films. This difference in strength between the grain matrix and grain boundary causes further strain concentration leading to premature embrittlement. This temperature effect has a ten-fold greater impact on embrittlement compared to the different types of loading on the micro-scale.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Murali, Aravind

Contributors dc:contributor

• Thomas, Brian G

• Steel
• Continous Casting
• Gurson-Tvergaard-Needleman
• GTN
• Multi-Scale
• Embrittlement

Statement dc:rights

• Copyright 2022 Aravind Murali

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115390

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115390