W7-X Test Welding

8/12/2019 W7-X Test Welding

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Finite element numericalsimulation of a TIG welding

test

A.Capriccioli, P.Frosi


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Foreward

This is a preliminary analysis about finite element

simulation of a TIG welding test of two plates in AISI

316 LN stainless steel.

Two uncoupled steps of analysis are executed:thermal and then mechanical one.

The main strategy adopted is the birth and death

technique.

The analysis is carried out with Ansys rel.10


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Main general analysiss aims

Thermal shrinkage calculation

Residual stress field calculation

Restraints choice and placement

Best sequences specifications

Study of the effect of material property

changes


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Special aims of this analysis

To build a simplified fem model in order toevaluate the feasibility of developing a largerfem model that can simulate a real TIGwelding test

To know the CPU time and the amount ofHard Disk demand for the simplified model(on a office PC) to assess the real request forthe complete model on a faster machine

Check if the final global strain of the firstmodel is correctly foreseen


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Geometry

The geometrical model has the length that

is one third of the real longitudinal

dimension (z)

The width of the single plate is chosen to

have a acceptable total node number

The caulker has a variable gap

Scheme for subsequent passes Lateral restraints position


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FEM MODEL

The connection

between rigionswith different mesh

density is obtained

with contact

element with the

multi-point-

constraint option.

The connectionbetween the plates

and the edge

restraints is made

with coupling nodes

DOF.

The model has

about 91000elements and 82000

nodes.


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Caulkers elementsThe elements that

simulate the filling

material are

collected in

groups that

represent the

different passes.

These elements

are subjected to

birth technique:

they are killed at

the beginning of

the analysis and

then reactivated at

the proper time

when the heatsource passes.

There are 80

elements in axial

direction whose

length is about

4 mm.


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Heat Affected Zone elements

These elements

represent the

mushy zone

whose final

temperatures are

checked to find

out if the basic

material is

molten during

welding. Theseregion have the

same mesh

density of filling

material.


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Convection elements

These elements

overlay brickelements all over

the plates. We can

choose the film

coefficient and the

bulk temperature


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Radiative elements

These elements

overlay the elements

describing filling

material. They are

killed at the

beginning of the

analysis and then

reactivated one byone at the same time

of the underlying

brick element to

simulatate the

radiative heat loss of

the molten metal

drop.


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thermal conductivity

0

5

10

15

20

25

30

35

40

45

0 500 1000 1500 2000 2500 3000 3500

temperature

(W/m

K)

anlitical formula extrapolated values keep constant

AISI 316 Material Property

3926210292.410378.510756.1 TTT

Tsolidus= 1370 C= 1643 K

Tliquidus= 1400 C

= 1673 K


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specific heat AISI 316 LN

0

100

200

300

400

500

600

700

800

900

1000

0 500 1000 1500 2000 2500 3000 3500

temperature (K)

(J/k

gK)

analitical formula extrapolated values keep constant

37241050.31077.543.028.456 TTTCp


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density AISI 316 LN

7200

7300

7400

7500

7600

7700

7800

7900

8000

8100

0 500 1000 1500 2000 2500 3000 3500

temperature (K)

(kg/m

3)


28410488.610103.4038.8 TT


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entalpy (J/m3)

0.E+00

2.E+09

4.E+09

6.E+09

8.E+09

1.E+10

1.E+10

0 500 1000 1500 2000 2500

temperature (K)

(J/m3)

constructed from previous values literature extrapolated values


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thermal expansion coeff. (1/K)

0.0E+00

5.0E-06

1.0E-05

1.5E-05

2.0E-05

2.5E-05

0 500 1000 1500 2000 2500 3000 3500

temperature (K)

(m/m

k)


263106585.1109348.43153.16 TT

m


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Young Modulus (Pa)

0.0E+00

5.0E+10

1.0E+11

1.5E+11

2.0E+11

2.5E+11

0 500 1000 1500 2000 2500 3000 3500

temperature (K)

(GP

a)

Young mod (GPa) extrapolated values keep constant

TE 2

101221.83795.200


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Poisson's coefficient

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0 500 1000 1500 2000 2500 3000 3500

temperature (K)


T5

10169.72921.0


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Yield strength (Pa)

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

3.5E+08

4.0E+08

0 200 400 600 800 1000 1200 1400 1600 1800

temperature (K)

(Pa

)

OUTOKUMPU web site extrapolated values


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ultimate strength (Pa)

0.E+00

1.E+08

2.E+08

3.E+08

4.E+08

5.E+08

6.E+08

7.E+08

0 200 400 600 800 1000 1200 1400 1600 1800

temperature (K)

(Pa)

OUTOKUMPU web site extrapolated values


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Thermal analysis

The axial length of model is 315 mm

There are 80 elements in axial direction whose length is about 4 mm.

Every pass is constituted by 80 load step plus 3 for cooling.

The welding speed chosen is 0.25 mm/s.

The total time for a single pass is about 1265 s (~21 min)

The cooling total time between each pass is 5 times the single pass weldingtime

The thermal analysis is concerned till the forth pass (up and down side)

The CPU time is about 11 hours [Pentiun 4 (R) 3.2 GHz - 2Gb Ram]

The Hard Disk space is about 40 Gb


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1st pass: step n. 40


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1st pass: step n. 80


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1st pass: final cooling step


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2nd upside pass: step n. 40


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2nd upside pass: step n. 80


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2nd upside pass: final cooling step


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2nd downside pass: step n. 40


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2nd downside pass: step n. 80


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2nd downside pass: final cooling step


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3rd upside pass: step n. 40


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3rd upside pass: step n. 80


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3rd upside pass: final cooling step


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3rd downside pass: step n. 40


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3rd downside pass: step n. 80


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3rd downside pass: final cooling step


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4th upside pass: step n. 40

4 h id 80


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4th upside pass: step n. 80

4 h id fi l li


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4th upside pass: final cooling step

4th d id t 40


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4th downside pass: step n. 40

4th d id t 80


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4th downside pass: step n. 80

4th d id fi l li t


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4th downside pass: final cooling step

Structural analysis


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Structural analysis

Only the first pass has been executed.

The need of CPU time is 3 days, and the Hard Disk space is about 21 Gb


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W7-X Test Welding

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