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, India

1

Assistant Professor/Mechanical Engineering, Francis Xavier Engineering College, Tirunelveli, India2

Assistant Professor/Mechanical Engineering, Francis Xavier Engineering College, Tirunelveli, India3

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.



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 0t 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

12

2

2

2

2

2

(1)

Where a is thermal diffusivity of the body

material ( ,

c

ka

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( 2kr (2)



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( 2krQk

(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 (0C).

T= temperature distribution (0C),

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.



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/KgoC)

Conductivity

(W/moC)

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%



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



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



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

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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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