Steel Process/Product Modeling

Research Overview

October 29, 2012

PART I

Thermo-mechanical Modeling and Experimental Validation of High Temperature Material Processes

K. Chandrashekhara, S. Lekakh and V. Richards

Missouri S & T

October 29, 2012

Finite Element Modeling and Analysis

Solid Mechanics

Geometric/Material Nonlinearities

Static/Dynamic

Ballistic

3D Detailed Geometry

Finite Element Analysis

Stress/strain

Fatigue/Fracture

Deformation

Damage/Failure

Heat Transfer

Input Output

Process History

Load/Boundary Conditions

Thermo-Mechanical

Contact

Experimental Validation Design Verification

Design Modification

Steel Metallurgy Cold rolling process- void closure Hot radial forging - Process parameters - Void closure

Metal casting Investment shell crack prevention

Ballistic simulation

Examples of Previous Works

20% thickness reduction

40% thickness reduction Global –local finite element model

Defect

Neural Network Model

0 1 2 3 4 5

-1

-0.8

-0.6

-0.4

-0.2

0

Void size (mm)

Void

reduction

Simulation result

NNk prediction

3D Cold Rolling Process Modeling

Hot Radial Forging Process

Problems needed to be solved:

Increasing material strength

Porosity reduction

Smooth surface finish

Considerable material saving

Radial Forging

Machining

Chrome Plating

Fielding

Billet Radial Forging Rough Machining Autofrettage Finish Machining Chrome Plate Inspection Field

Axial Feed

Rotational Feed

Gripper

Workpiece

Mandrel

Die

Die Motion

Approaches for Modeling Radial Forging (ABAQUS/CAE) Die

Motion

Workpiece

Mandrel

Die

Die arrangement

Radial forging process

3D finite element model

Die

Die

Tubular workpiece

Mandrel 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

0

20

40

60

80

100

120

140

160

True strain

Tru

e s

tress (

MP

a)

strain rate = 0.1

strain rate = 1

strain rate = 5

strain rate = 10

Rate/temperature-dependent elasto-viscoplastic material properties

Residual stress distribution after three axial feeds

(a) Outside (b) Inside

(b) Inside (a) Outside

Residual strain distribution after three axial feeds (a) Before deformation (b) After 1st stroke

(c) After 4th stroke (d) After 12th stroke

Cross-section deformation at different strokes

Practical Application 1: Forging Process Optimization

Global-local approach

The critical radial reduction and plastic strain for pore closure were determined for the different void size and location reduce and closes.

Practical Application 2: Prediction of Void Closure

Example 3. Shell Crack Prevention in Investment Casting

Pattern (FOPAT) Shelling Pattern removal

Ceramic shell

FOPAT foam

Finite element model of complex FOPAT and

ceramic shell

Experimental data (shell/pattern properties)

Example 4. Ballistic Simulation

(a) Real bullet size (b) Model of the bullet

Glass

PC

Bullet velocity versus time

What we can do for new steel technology center?

• To analyze metallurgical thermo-mechanical problems

• To develop a new set of experimental property data based on inverse modeling

• To develop complicated thermo-mechanical models (solid or semisolid)

• Variety of virtual experiments for process analysis and optimization

Show us your problems and we will try to solve it using thermo-mechanical modeling

PART II Computational Materials Science:

Atomistic Modeling of Materials Behavior

Julia Medvedeva and Mohsen Asle Zaeem

Missouri S & T

October 29, 2012

1. First-principles investigations of solids

1 2

2( ) ( ) ( ) ( )k k k

xc i i iV r r r r

phase stability, elastic properties,

microstructure, precipitation, impurity distribution

Fe3AlC

Solving Schrödinger equation:

2. Microscopic mechanisms of deformation behavior

]0121[

]0110[

γs, σmax -

cleavage

energy and

stress

(i) Fracture (ii) Slip

γus, σshear

stacking fault energies

Brittle/ductile fracture criterion: D = 0.3 S/US > 1

Ti3SiC2 Dislocation characteristics

3. Phase Field‐Finite Element Models for Microstructural EvolutionSolidification

Cubic Metals(FCC/BCC)

HCP Metals

Example: Al-3%Cu.

Example: AZ91. Example: Mg crystallization (3D).

Example: AM 30.

Predicting size and shape of dendrites, concentration profiles, secondary dendrite arm spacing, …

Grain Growth and Recrystallization

FCC/BCC/HCP Metals

Example: grain growth in Cu-Ni-Si in presence of pre-aging Ni2Si precipitates

Grain Growth 

Predicting size and shape of grains during heat treatment and annealing;Predicting Ziner pinning relations: n

f

pcg

V

rr

)(

Example: grain growth in Al alloy.

3. Phase Field‐Finite Element Models for Microstructural Evolution

Martensitic Phase Transformation

Example: Tetragonal to monoclinic transformation in Zr oxide.

Oxidation of Metals

Predicting kinetics of oxidation, volume fraction of oxide surfaces, concentration profiles, growth stresses, ….

Precipitation

Predicting size and shape of precipitates, concentration profiles, coarsening rates, etc., at different heat treat treatment and annealing processes.

Example: Spinodaldecomposition, Al alloy.

Example: Evolution of precipitates in a Ni-based super alloy.

Example: Coarsening of precipitates in Al-Zn alloy at high temperatures and under applied load.

Phase transformation in steel and other metallic alloys.

Solid State Phase Transformation