Sohini Chowdhury presented a progress seminar on laser-based additive manufacturing. The seminar covered the state of the art of additive manufacturing, a literature review of heat transfer analysis and process capabilities. The objectives of the proposed project are to develop a finite element heat transfer process model to compute temperature distribution, cooling rates and melt pool geometry during single and multi-layer additive manufacturing and compare results to experimental values. Future work will involve heat transfer analysis of multi-layer laser-based additive manufacturing using ANSYS to estimate temperature distribution, cooling rates and melt pool formation in different layers.

1. Progress Seminar
on
Laser Based Additive Manufacturing: State of Art,
Heat Transfer Analysis and Capabilities
By
Sohini Chowdhury
(MT/14/CIMA/01)
Under the Supervision
of
Dr. M.Chandrashekharan & Mr. N. Yadaiah
Department of Mechanical Engineering
North Eastern Regional Institute of Science & Technology
October 2015

2. Outline
 Introduction
 Literature Review
 Research objectives
 Theoretical background
 Conclusion
 Future work and Work Plan
 References
1

3. Introduction 2
 Additive manufacturing (AM) is a process for joining materials to make objects
from 3D model data, usually layer upon layer, as opposed to ‘subtractive
manufacturing’ methodologies” [Ref ].
General principle
3D CAD model data Sliced layers 3D object
Ref : American Society for Testing and Materials.

4. This results into molten pool formation and
solidification of the alloy powder as the beam
traverses across the length.
The alloy powder flows coaxially with the
laser beam and the particles absorbs the
energy from the beam.
Schematic of laser based AM process
3Introduction Contd…
Repeated traverse of the laser beam leads to
generation of multi layered component.
 As the particles are deposited, laser
provides sufficient thermal energy to melt
the particles along the deposition path.

5. Introduction Contd… 4
Advantages
 Ability to create almost any shape or geometric features
 No tooling is required
 Flexibility in design
 Reduction in waste
Disadvantages
 It requires more controllable process parameters.
 High feedstock cost.
 Not economical for mass production.
Applications
 Aerospace ( Fan blades, vanes etc)
 Automotive (Car wheel, gear box, car brake etc)
 Consumer (Jewellery, furniture, lightning etc)

6. year &Authors Work done by authors Remarks
(2006)
C.P. Paul et al.
Examined the influence of processing parameters in
fabricating multi-layered Colomony-6 components by
laser assistance.
Results were
compared with that
fabricated by GTAW
(2011)
A. Kumar et al.
Developed a FE based heat transfer model to simulate
the single track geometry of SS316L during LRM. In
this work, authors have examined the effect of laser
power, laser beam size, scan speed, powder feed rate
and powder stream diameter.
Correlated
experimental and
simulated results.
(2011)
E. Louvis et al.
Aluminium and its alloys are difficult to process than
stainless steels and commercially pure titanium. For
avoiding oxide film formation in Al components, SLM
process is implicated to break up these oxides if highly
dense (100%) aluminum components are to be formed.
Controlling
oxidation process
and disrupting oxide
films produced
within the
component with the
laser beam
5Literature Review

7. year &Authors Work done by authors Remarks
(2012)
B. Vayre et al.
For each shape and chosen manufacturing process, an
optimization is conducted to minimize the volume by
varying the value of parameters with specified
mechanical behavior (using FEA) and finally the
validation of the part, accomplished by a prototype.
It highlighted the
designing processes
for AM process.
(2012)
L. E. Murr et
al.
Comparative examples for SLM and EBM fabricated
components which includes Cu, Ti–6Al–4V, alloy
625 (a Ni-base superalloy), a Co-base superalloy, and
17-4 PH stainless steel for detecting micro structure
properties by altering the process parameters.
Experimental
comparison of 2 AM
processes.
(2013)
B. Cheng et al.
The process parameter effects (beam speed) on the
temperature profile along the melt scan and the
corresponding melt pool geometric characteristics
such as the length-depth ratio and the cross-sectional
area on Ti-6Al-4V were investigated for quality
control.
Numerical simulation
to establish
relationship between
process parameters and
melt pool geometry.
6Literature Review Contd…

8. year
&Authors
Work done by authors Remarks
(2014)
V. Manvatkar
et al.
A three-dimensional heat transfer and material flow
model is developed for numerical simulation of
temperature and velocity fields of SS316 material
and the effects of process parameters on the thermal
cycles, build geometry, cooling rates and
solidification parameters in a multilayer laser based
AM process are studied.
Comparison of
numerical results with
experimental data
obtained from an
independent literature.
(2014)
P. Michaleris
Finite element techniques are utilized for modeling
of metal deposition for heat transfer analysis of
metallic parts using both laser and electron beam
assisted AM ways and techniques for minimizing
errors are also implemented.
Quiet and deactive
element technique used
for FE technique.
(2014)
Y. Li et al.
Simulation was performed using FE method. Sound
metallurgical bonding of CP Ti powder between the
fully dense layers was achieved at laser power of
250W and scan speed of 200 mm/s.
Numerical simulation
using ANSYS
multiphysics and
experimental studies .
7Literature Review Contd…

9. year
&Authors
Work done by authors Remarks
(2014)
L.E. Murr
Microstructures and residual mechanical
properties are discussed for selected metal and
alloy components which includes Ti-6Al-4V, Co-
Cr-Mo super alloy, Ni-base super alloy systems
(Inconel 625, 718 and Rene 142), Nb and Fe in
contrast to more conventional wrought and cast
products
Residual properties of
EBM-fabricated
components are better
than conventional cast or
wrought products.
(2014)
H. Gong et al.
Laser or electron beam power fluctuations, surface
gas flow, and raw material characteristics
influences defect generation, in addition to the
effect of process parameters variations of Ti–6Al–
4V samples .
Defect generation is
experimentally studied.
(2015)
N. Shamsaeia
et.al.
To determine the mechanical properties of Ti-6Al-
4V parts so as to predict their performance while
in service. Also methods to optimize and control
the DLD process parameters.
Overview of
microstructure and post
–manufacture
mechanical properties.
8Literature Review Contd…

10. year
&Authors
Work done by authors Remarks
(2015)
E. Rodriguez
et al.
Approximation of absolute surface temperature
measurements of Ti-6Al-4V by electron beam
additive manufacturing technology using in situ
infrared thermography.
Synchronization of
thermal camera (IR) to
capture images at
different events.
(2015)
Y. Zhang et
al.
To construct build time estimation models more
rapidly and simply to meet the needs of price
quotation, design, process planning and
optimization in AM, with acceptable accuracy by
inputting less data.
Modeling method
derived from Grey
theory.
(2015)
A. R. Nassar
et al.
The microstructure and indentation hardness of a
Ti-6Al-4V component processed with a pulsed
laser beam and a continuous wave (CW) laser
beam were investigated. The pulsed-beam build
showed not much significant variation in
mechanical properties with that of CW beam.
Experimental work
performed for validating
mechanical properties.
9Literature Review Contd…

11. Objectives and proposed project title 10
Based on the detailed literature review and interest on an emerging
technology, laser based additive manufacturing process, the
motivation of present work has been directed to
‘Laser based additive manufacturing process: State of the
art, heat transfer analysis and capabilities’.
To achieve the present research objective, following modules are/will be accomplished either
simultaneously or sequentially:
 A comprehensive understanding of mechanism and physical processes involved in
additive manufacturing process.
 Development of a conduction heat transfer process model based on finite element
method using temperature dependent material properties, latent heat of fusion and
Gaussian distributed volumetric heat source to compute temperature distribution,
cooling rate, melt pool geometry etc.
 during single layer AM process
 during multi layer AM process
 Computed results are compared with experimental values which are adapted from an

12. Transient Heat conduction
(Governing) Equation:
Theoretical Background
Natural boundary condition (convection
and radiation heat losses)
( , , , 0) oT x y z t T 
Initial condition:
.
)()( QTkTvCp 
12
ρ - Density of the material.
Cp - Specific heat.
ν - Velocity vector .
T - Temperature variable .
 - Gradient operator.
k - Thermal conductivity .
Q - Rate of internal heat generation per unit
volume.
q – heat flux.
h- Coefficient for heat convection.
- Stephan-Boltzmann constant.
σ - Melt pool emissivity.

4 4
0 0( ) ( ) 0
T
k q h T T T T
n


     


13. Theoretical Background 12
Heat Source Models:
Gaussian distribution of circular disc heat source model
[Pavelic et al. (1969)] 2 2 2
3/2 2 2 2
6 3 3 3 3
( , , ) exp( )
f
f
f f
f Q x y z
q x y z
abc a b c
   
2 2 2
3/2 2 2 2
6 3 3 3 3
( , , ) exp( )r
r
r r
f Q x y z
q x y z
abc a b c
   
Double ellipsoidal heat source model
[Goldak et al. (1984)]
2 2
2 2
3 3( )
exp( )
P x y
q
tr r


 


14. Theoretical Background contd…
 Laser beam when irradiates on the top
surface of the powder bed, a fraction of
laser energy reflects and the remainder is
absorbed.
The absorbed laser energy melts the
powder, thereby yielding a small-size
molten pool.
 The majority of the incidence energy is
transferred via conduction through the
deposited layers.
 Heat is quickly conducted away by the
substrate at the bottom where as convection
and radiation is more profound at the lateral
surfaces.
Boundary conditions involved in AM
process
Adapted : Y. Li, D. Gu, Mater. Design, 2014.
13

15. 14
Conclusion
 A detailed study was undertaken to understand the mechanism and other significant
parameters of Additive Manufacturing process in general and lased based additive
manufacturing process in particular..
 An extensive literature review was conducted on the influence of different
parameters, experimental and numerical modeling of laser based AM.
 Also, the mathematical background involved in modeling of laser based AM such as
governing equation, boundary and initial conditions; and the type of heat source
models have studied.
 Heat transfer analysis of single layer laser based AM was performed to estimate the
thermal cycles and melt pool. However, it is not shown at this moment due to
verification of the model with experimental results is not done.
Future Work:
 Heat transfer analysis of multi-layer laser based additive manufacturing using FEM
(FE software ANSYS) to estimate the temperature distribution, cooling rates and melt
pool formation in different layers.
 & the detailed work plan as follows:

16. Plan of work
S.No. Proposed work Oct.-Dec.
2015
Jan.-March
2016
April May
2016
1 Literature review  
2 Numerical modeling  
3 Experimental work if any 
4 Thesis writing  
15

17. 16References
1. S. M. Thompson, L. Bian, S. Nima, and Y. Aref, Addit Manuf, 8, 36 (2015).
2. V. Manvatkar, A. De, and T. Debroy, Mater. Sci. Technol. 31, 8 (2015).
3. P. Michaleris, finite Elem. Anal. Des. 86 , 51(2014).
4. Y. Li, and D. Gu, Mater. Design. 63, 856 (2014).
5. F. Kong, and R. Kovacevic. Metall. Mater. Trans B. 41, 1310 (2012).
6. A. V. Gusarov, I. Yadroitsev, P. Bertand, and I. Smurov. Appl Surf Sci. 254, 9 (2007).
7. A. V. Gusarov, and I. Smurov, Appl Surf Sci, 255, 9 (2009).
8. A. V. Gusarov, and I. Smurov. Phys Procedia, 5, 94 (2010).
9. Y. W. Zhang, A. Faghri, C.W. Buckley, and T. L. Bergman. J Heat Transfer, 122, 8
(2000).

18. 17
10. T. B. Chen, and Y. W. Zhang. Appl. Phys A. 86, 20 (2007).
11. I.A. Roberts, R. Wang, C.J. Esterlin, M. Stanford , and D. J. Mynors, Int. J.
Mach. Tools. Manuf. 219, 84 (2005).
12. W. Hofmeister, M. Wert, J. Smugeresky, J. Philliber, M. Griffith, and M. Ensz,
JOM. 51 (7), (1999).
References contd…..
Thank You
for your kind attention