Bijish Babu, Division of Material Mechanics Material Modelling and Physically Based Models Bijish Babu Division of Material Mechanics
Bijish Babu, Division of Material Mechanics
Material Modelling and Physically Based Models
Bijish Babu Division of Material Mechanics
Bijish Babu, Division of Material Mechanics
Process: Forming
Process: Metal Deposition Process: Welding
Process: Heat Treatment
Manufacturing chain
Process: Milling
Bijish Babu, Division of Material Mechanics
Microstructural Mechanism Map
Typical isothermal forming
Arbitrary path
Bijish Babu, Division of Material Mechanics
Stress-strain behaviour of SS 304 stainless steel at 650ºC
LEDS Low Energy Dislocation Substructures
Dislocation density
Bijish Babu, Division of Material Mechanics
Material Model
Physically based Constitutive Model
Stress-Strain Data Phase, Texture, Morphology
Grains, Sub-cells, Precipitates
Dislocations, Vacancies
Bijish Babu, Division of Material Mechanics
Dislocation Dynamics
Annihilation
Creation
Recovery
Hardening
mobile Dislocation
Density Immobile
Dislocation Density
Courtesy: Ashby & Frost!
Bijish Babu, Division of Material Mechanics
Physics of Deformation
Strain hardening
Recovery & Recrystallization
Dislocations Vacancies Grains, Subcells
Strain Energy
Courtesy: Ashby & Frost!
Bijish Babu, Division of Material Mechanics
Flow Stress
!
" y = m#Gb $i +" th 1% kT&Fb3 ln
˙ ' ref˙ ' p
(
) *
+
, -
(
) * *
+
, - -
1q(
)
* *
+
,
- -
1p
Long Range Short Range
Bijish Babu, Division of Material Mechanics
Evolution Equations
( )223
2 eqieqv
vv
pi
pi kT
GbccDc
bm
!!"!"! # $$%$&
= !!!
Immobilisation Glide Climb
Vacancy Creation Jogs Self Diffusion Temperature
!
˙ c vex = "
m#Gb2
Qvf
$i + %c j
4b2
&
' (
)
* + ,0
b˙ - .Dvm
1/2
0
1 2
3
4 5 cv . cv
eq( ) + cveq Qvf
T 2
0
1 2
3
4 5 6T
Bijish Babu, Division of Material Mechanics
Parameter optimisation
Bijish Babu, Division of Material Mechanics
GMoP – In-house optimisation tool
Bijish Babu, Division of Material Mechanics
316L-Low Strain Rates
Bijish Babu, Division of Material Mechanics
316L-Low High Rates
Bijish Babu, Division of Material Mechanics
!-" Phase Transformation Ti-6Al-4V
Bijish Babu, Division of Material Mechanics
Diffusion in Ti-6Al-4V
Bijish Babu, Division of Material Mechanics
Parameters for Ti-6Al-4V
Bijish Babu, Division of Material Mechanics
Ti-6Al-4V (20-300°C)
Bijish Babu, Division of Material Mechanics
Ti-6Al-4V (400-700°C)
Bijish Babu, Division of Material Mechanics
Ti-6Al-4V (800-1100°C)
Bijish Babu, Division of Material Mechanics
Stress Relaxation in Ti-6Al-4V
Bijish Babu, Division of Material Mechanics
• Connects Macro to Nano Scales • Parameters are accessible from conventional mechanical
tests • Easy to implement in a standard FE code • Has already been used for forming, welding, MD and
heat treatment simulations
Summary