THERMAL ANALYSIS OF WELDING IN T-JOINT PLATES USING FINITE ELEMENT ANALYSIS

International Journal of Research in Advanced Technology - IJORAT
Vol. 2, Issue 1, JANUARY 2016
1
All Rights Reserved © 2016 IJORAT
THERMAL ANALYSIS OF WELDING IN
T-JOINT PLATES USING FINITE
ELEMENT ANALYSIS
Mr. K.KRISHNAMOORTHY 1
, Mr.S.SHEIK SULAIMAN 2
, Mr.R.KARTHIKEYAN.3
Assistant Professor/Mechanical Engineering, Francis Xavier Engineering College, Tirunelveli, India1
ABSTRACT: Welding is highly reliable and efficient metal joining process. The thermal response of
materials to a welding heat source sometimes causes mechanical problems, e.g. residual stresses and
distortion and changes in mechanical properties due to changes in the microstructure. The finite element
method (FEM) is the most commonly used numerical technique, which provides accurate estimates of
thermal parameters for this analysis. Finite element analysis (FEA) is a tool used especially in determining
the thermal stresses and temperature distribution of the welded models, which are difficult to analyze by
hand calculations. The objective of the current work is to evaluate transient thermal analysis in arc welded T-
Joint 304L stainless steel plates. The object is modeled in 3D and analyzed using FEA with an element type of
SOLID70. Energy is input into the thermal model using moving circular area heat source. The results
obtained by thermal analysis are used to determine the temperature distribution and temperature histories.
Keywords: FEA analysis, Heat sources, Temperature distribution, Temperature histories.
I. INTRODUCTION
To produce high strength welded structures,
arc welding is an effective and economic joining
method attracting world welding community. Due to
non-uniform expansion and contraction of the weld
metal and surrounding base metal by heating and
cooling cycles during welding, thermal stresses
occurs in the weld and adjacent areas. During the
heating phase, the strains produced always induce
plastic deformation of the metal. The stresses
resulting from these strains combine and react to
produce internal forces that cause a variety of
welding distortions. Welded steel joints are
sometimes considered the weakest part in the object
owing to the possible reduced creep strength of the
weld metal and surrounding heat affected zone
(HAZ). Finite Element Analysis (FEA) as a reliable
method for this analysis.
During welding processes, heat can be
transmitted by conduction, convection and radiation.
For welding processes where an electric arc is used as
the welding heat source, heat conduction through the
metal body is the major mode of heat transfer and
heat convection is less significant as for as the
temperature field in the welded body is concerned.
The heat flow in the welding process presents a very
complex situation, which currently defies the detailed
analysis by analytical calculations. However, this
problem can be simplified by considering conduction
only (on the basis of the limited effect of radiation)
and treating the convection by making use of an arc
efficiency parameter.

2
II. HEAT SOURCE
The temperature vs. time
relationship of welded components and structure can
be theoretically obtained by carrying out a heat-
transfer analysis of a welding process. This involves
many complicated heat-flow phenomena including
heat radiation, convection, heat conduction as well as
fluid flow of melting weld metal. This process would
require solving many constitutive differential
equations using finite element or finite different
methods that are time consuming despite the fact that
the computing power continuous to improve.
Therefore, from a practical point of view, analytical
solutions for the heat-transfer problem in welding are
preferable despite their limitations. Their major
advantage is that they are given in the closed form
equation that could provide the temperature-time
information for the welding thermal problems in a
rabid and convenient way. In most welding processes
performed on thick plates, the heat flow in three
dimensional (3D). For cases of high power or fast
moving heat sources, the heat flow along the travel
direction of the heat source can be neglected, hence,
the one-dimensional heat flow can be used to model
this situation. The solution to the heat-conduction
equation is based on the concept of an instantaneous
heat source that is widely used in heat-conduction
analysis. The concept of instantaneous heat sources
assumes that the heat is released instantaneously at
time 0t in an infinite medium of initial
temperature 0T either across a plane for a uniaxial
conduction, along a line for biaxial conduction is in a
point for triaxial conduction. The general governing
heat-conduction is as follows,
t
T
az
T
y
T
x
T















 1
2
2
2
2
2
2
(1)
Where a is thermal diffusivity of the body
material ( ,






c
k
a

where k- thermal
conductivity,  - density, c- specific heat of the
material)
III.GAUSSIAN - DISTRIBUTED AREA
HEAT SOURCE
The Gaussian-distributed heat source is a
simplified model for a local concentration of a
welding heat input when its density is assumed to
follow the Gaussian distribution. Normally, the
temperature field in the vicinity of the heat source is
particularly dependent on the heat-flow density of the
heat source. However, the temperature at the far field
is less sensitive to the heat flow density; therefore,
the distributed heat source gives a similar
temperature distribution if the heat source is replaced
by a concentrated point source in the centre of its
area. Hence, the Gaussian-distributed heat source can
be used to simulate the welding heat source to give a
better prediction of the temperature field near the
source center to overcome the weakness point and
line heat source, which would predict an infinitely
high temperature at the source location. The Gaussian
heat source is used to simulate the welding arc,
welding flame, or welding beam where the heat
source density at an arbitrary point
is represented by
)exp( 2
kr (2)

3
where is the maximum value of the heat source
density; r is the distance from to the centre of
the heat source and k is the
coefficient determining the concentration of the heat
source, also known as distribution parameter, which
represents the width of the Gaussian distribution
curve (higher value of corresponds to a more
concentrated heat source).A schematic illustration of
the Gaussian area heat source.
Fig. (1) Gaussian distributed area heat source
Let us assume that Q is the total output of the heat
source. The heat equilibrium condition
Q= (3)
Subsequently, the maximum density of the heat
source, depending on the heat output, Q, and
distribution parameter k as = and equation
becomes,
)exp( 2
kr
Qk


(4)
It is worth noting that when the heat density
, this means that this Gaussian-distributed
density heat source will predict a finite temperature at
the heat source centre, which is more realistic than
the point or line heat source that give an unrealistic
infinite temperature.
Where,
q = heat flux (W/m2
),
k = distribution parameter (m-2
),
r = radius of the circular heat source (m),
ρ = density of the material (kg/m3
).
c = specific heat (kJ/kg K),
T0= initial temperature of the plate (0
C).
T= temperature distribution (0
C),
v= welding speed (mm/sec),
a= thermal diffusivity (m2
/sec),
t= time (sec),
x= Distance along in x-direction (mm),
y= Distance along in y-direction (mm).
IV.FINITE ELEMENT ANALYSIS
The finite element method (FEM) (its
practical application often known as finite element
analysis (FEA)) is a numerical technique for solving
problems of Engineering and Mathematical Physics.
In this method, a body or a structure in which the
analysis to be carried out is subdivided into smaller
elements of finite dimensions called finite elements.
Then the body is considered as an assemblage of
these elements connected at a finite number of joints
called „Nodes‟ or nodal points. The properties of each
type of finite element is obtained and assembled
together and solved as whole to get solution. In this
T-joint have two plates (Fig. 2) have dimensions,
horizontal plate length=100mm, width=50mm,
thickness=6mm and vertical square plate have same
thickness and size=50mm. The finite element
meshing is shown in (Fig. 3). It have 8476 nodes and
6175 brick node elements.

4
Fig. (2) Finite Element model of T-joint plates Fig. (3) Finite Element meshing of T-joint plates
V.MATERIAL PROPERTIES
Temperature
(ºc)
Specific
heat
(J/Kgo
C)
Conductivity
(W/mo
C)
Density
(Kg/m3
)
Yield
stress
(Mpa)
Thermal
expansion
coefficient
×10ˉ5
/ºc
Young‟s
modulus
(Mpa)
Poisson‟s
ratio
0 462 14.6 7900 256 1.7 199 0.294
100 496 15.1 7880 218 1.74 193 0.295
200 512 16.1 7830 186 1.8 185 0.301
400 540 18 7750 155 1.91 167 0.318
600 577 20.8 7660 149 1.96 159 0.326
800 604 23,9 7560 91 2.02 151 0.333
1200 676 32.2 7370 25 2.07 60 0.339
1300 692 33.7 7320 21 2.11 20 0.342
1550 700 120 7300 10 2.16 10 0.388
Table1: Temperature dependent thermal, physical and mechanical properties of 304L austenitic stainless steel. [1].
VI.THERMAL ANALYSIS
A thermal analysis calculates the temperature
distribution and related thermal quantities in a system or
component. In this work transient thermal analysis was
used To calculate the heat input for arc welding procedures,
the following formula can be used
(5)
Where Q = heat input (W), V = voltage (V), I = current (A)
=26 V, =210 A, η= 60%

5
In this thermal analysis of T-joint have
totally 25 load steps were involved in the moving
area heat source. Totally 10 seconds was consumed
to complete the welding process. The nodal
temperature solutions were obtained from the thermal
analysis. In 3D analysis, during a time step, the
welding arc is allowed to stay at the element with
constant heat flux and then moved to next element.
VII.RESULTS
The moving continuous area heat source of
the welded plates traveled along both sides of the
vertical plate simultaneously and same direction.
Under all these conditions, the thermal analysis
carried out and the data obtained from analysis saved
to a file. The thermal analysis results are shown in
following figures from 4 - 13
Fig. (4) Temperature distribution at .3sec
Fig. (5) Temperature distribution at 2 sec
Fig. (6) Temperature distribution at 8 sec
Fig. (7)Temperature distribution at 10sec

6
Fig. (8) Temperature distribution after cooling at 100sec
Fig. (9) Temperature history at node 386
Fig.(10)Temperature history at node 410
Fig.(11)Temperature history at node 425
Fig. (12) Temperature distribution after cooling at
400sec
Fig. (13) Temperature history after cooling at node 4283

7
VII CONCLUSION
 The normal results of welded T-joint was
obtained from thermal analysis, Show us the
temperature distribution at the parts. It is so
difficult to obtain this distribution from the
experiments.
 Finite element method is an efficient technique
in welding analysis. Differences in physical,
mechanical and chemical properties of base
metals cause non uniform temperature
distribution and heat transfer.
 The obtained temperature distribution and
temperature history is used to find out the
residual stress produced in welding.
ACKNOWLEDGMENT
I am using this opportunity to express my gratitude to
everyone who supported me throughout the project. I
am thankful for their aspiring guidance, invaluably
constructive criticism and friendy advice during the
project work. I am sincerely grateful to them for
sharing their truthful and illuminating views on a
number of issues related to the project.
I would also like to thank to all the people who
provided me with the facilities being required and
conductive conditions for my project.
REFERENCES
[1] S.Nadimi., R.J.Khoushehmehr., B.Rohini and
A.Mostafapour, “Investigation and Analysis of
Weld Induced Residual Stresses in Two
Dissimilar Pipes by Finite Element Modelling.”
Journal of Applied sciences 8 (6): 1014-1020,
2008.
[2] ANSYS guide, ANSYS release 10.0
[3] Z.Barsoum, Residual Stress Prediction and
Relaxation in Welded Tubular Joint.
[4] Xiangyang Lu and Tasnim Hassan., “Residual
Stresses in Butt and Socket Welded Joints.”
Transactions, SMiRT 16, Washington DC,
August 2001.
[5] J.J.Dike., A.R.Ortega., C.H.Cadden., “Finite
Element Modeling and Validation of Residual
Stresses in 304L Girth Welds.” 5th
International
Conference on Trends in Welding Research, June
1-5, 1998, Pine Mountain, GA.
[6] Naeem Ullah Dar., Ejaz M.Qureshi., and M.M.I
Hammouda., “Analysis of Weld-induced
Residual Stresses and Distortions in Thin-walled
Cylinders.” Journal of Mechanical Science and
Technology 2 (2009) 1118-1131.
[7] N.T. Nguyen., “Thermal Analysis of Welds.”
ETRS Pvt Ltd, WIT press, Australia, 2004.
[8] John.A.Goldak and Mehdi Akhlaghi.,
“Computational Welding Mechanics.”
Publication by Springer.

THERMAL ANALYSIS OF WELDING IN T-JOINT PLATES USING FINITE ELEMENT ANALYSIS

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THERMAL ANALYSIS OF WELDING IN T-JOINT PLATES USING FINITE ELEMENT ANALYSIS