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

Murali, Aravind

Permalink

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

Description

Title

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

Author(s)

Murali, Aravind

Issue Date

2022-04-28

Director of Research (if dissertation) or Advisor (if thesis)

Thomas, Brian G

Department of Study

Mechanical Science and Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

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

Abstract

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.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Aravind Murali

Owning Collections