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Material Modelling and Physically Based Models Bijish Babu/bijish_babu.pdf · Bijish Babu, Division...
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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