Welded Joints

BITSPilaniPilani Campus

VINAYAK KALLURI

BITSPilaniPilani Campus

BITS Pilani, Pilani Campus

Welding

Welding is used for making permanent joints.

A weld is defined by the American Welding society

(AWS) as a localized fusion of materials or nonmetals

produced either by heating the materials to the required

welding temperatures with or without the application of

pressure, or by the application of pressure alone, and with

or without the use of filler materials


Classification of welding processes

Gas Solid StateArc Resistance Misc

Carbon arcMetal arcMIGTIGPlasma arcSubmerged arcElectro-slag

Oxy-acetyleneAir-acetyleneOxy-hydrogen

ButtSpotSeamProjectionPercussion

Friction

Ultrasonic

Diffusion

Explosive

Thermit

Electron-beam

Laser

Welding Process


MASTER CHART OF WELDING AND

ALLlED PROCESSES


Welding from automation point of view

0xyfuel gas welding (OFW) Shielded metal arc welding (SMAW)


Gas tungsten arc welding (GTAW) Gas metal arc welding (GMAW)

Welding from automation point of view


Welding -Fundamentals


Welded Joints


SPECIFICATION OF WELD SYSTEM

The AWS standard welding symbol


ARC AND GAS WELDING SYMBOLS


Fillet welds

(a) The number beside triangle indicates the leg size. The arrow

need to point only to one weld when the weld on all sides is

same.

(b) Here the weld symbol indicates that he weldment is

intermittent and staggered at 60 mm length at an interval of

200 mm (centre to centre distance).


Circle on the weld symbol indicates that the welding is to go

all around.

Fillet welds


Square butt welded on both

sides.

Single V with 60o bevel and

root opening of 2 mm

Double V Single bevel

Different groove preparations for butt joints


T joint for thick plates U and J joints for thick plates

Corner weld, meant

only for light loads

Edge weld for sheet metal

and light loads

Different groove preparations for fillet joints


Stress Analysis and Design of Welded Joints

Butt joint

Lap joint or Fillet joint

Parallel fillet joint (weldment parallel to the load)

Transverse fillet joint (weldment perpendicular to the load direction)

Shear welded joint

Both primary and secondary shear stresses act

Line weld concept is useful

Bending welded joint

Throat shear stress equal to 1/1.414 times the bending stress acts.

Line weld concept is useful


ANALYSIS OF BUTT JOINTS

/F hl = /F h l =

Typical butt joints with possible loading. Reinforcements, though can

increase the area taking the load, normally for fatigue loading induce

stress concentration at location like A and hence normally removed

by grinding or machining.


Typical transverse fillet weld

( ) ( )

sincos

2

135sin45sin

cos

sin

+=

=

=

=

hht

FF

FF

oo

n

s

B

C

D


The stresses at any angle in the weldment are

( ) ( )hl

F

hl

F

tl

F

A

F ss 2sincossinsincossin +

=+

===

( ) ( )hl

F

hl

F

tl

F

A

F nn cossincossincoscos 2 +

=+

===

( ) ( ) ( )[ ]222222 cossinsincossincos3' +++=+=hl

F

The resultant von-Mises stress is

( ) ( ) ( )

sincossincos

2

135sin45sin

cos

sin

+=

+=

=

=

=

ht

hht

FF

FF

oo

n

s


The stresses at any angle in the weldment are

hl

F

hl

F

hl

F

o

o

o

623.0

196.1

16.2'

,62.5at occurs stress Mises- vonmaximum The

5.62

5.62

5.62

'

max

0

=

=

==

=

=

=


Parallel Fillet Weld: Welding Code Method

/ 0 .707 1.414 /F hl F hl = =

( )

htFor

ht

707.0,45

sincos

0 ==

+=


Problem

The figure (b=d=50mm) shows a

horizontal steel bar of thickness h = 5

mm loaded in steady tension and welded

to a vertical support. Find the load F

that will cause an allowable shear stress

is 140 MPa in the throats of the welds.


Minimum Weld-Metal Properties

Table 93


Stresses Permitted by the AISC Code for Weld Metal

Table 94


aM = Fa

/V A =

/Mr J =

Primary shear stress:

Secondary shear stress:

Twisting moment:

[ ] ( )[ ] ++=+=

=

22

areas weldment theof cetroid about the

weldments theof area ofmoment polar Second

iiiyyxxiiGrAIIrAJ

J

i

SHEAR WELDED JOINT


An example of unequal weldments

2- weldmentof size leg

1- weldmentof size leg

707.0

707.0

2

1

22

11

=

=

=

=

h

h

hd

hb

btdtAAA 2121 +=+=

The total throat area against primary shear

Secondary shear estimation needs the estimation of the total

second polar moment of area of the two weldments together.

( ) ( ) ( ) ( )

( ) ( ) ( ) ( )1212

;12

;12

1212;

12;

123

2

3

2

22

3

2

2

3

2

2

3

1

3

1

11

3

1

1

3

1

1

2

1

btbtIIJ

btI

btI

dtdtIIJ

dtI

dtI

yxGyx

yxGyx

+=+===

+=+===


The centroid G can be

located as follows.

A

yAyAy

A

xAxAx

2211

2211

+=

+=

( )[ ] ( ) ( )[ ]( ) ( )222211

2

2

2

22

22

11

21

;

rAJrAJJ

yyxxryxxr

GG +++=

+=+=

An example of unequal weldments


The concept of line weldments

size throat unit weldfor area ofmoment polar Second

707.0

=

=

u

u

J

hJJ

dG 12/2/

0707.0 3dJ

dy

xhdA u =

=

==

The different patterns and their properties are listed in

Table 9-1.


Torsional Properties of Fillet Welds

(Table 9-1, page:484)

uhJJ 707.0=


Few torsion cases and equivalent line weldment diagrams

Note: check the orientation


A torque T=2 kN-m is applied to the weldment as shown.

Estimate the maximum shear stress in the weld.

Problem


A 20 mm thick steel bar is welded to a vertical support by

two fillet welds. Find the safe bending force F if the

permissible shear stress in the welds is 180 MPa.

Problem


BENDING WELDED JOINT

A

V=' stress,shear Primary


BENDING WELDED JOINT-Contd.

Secondary shear stress: A throat shear of is induced. where is the bending stress calculated by the following formula. In deriving

the formula the weldments have been treated as line welds and also the

distance between them is treated as simply equal to d, which is the

depth of the rectangular pattern.

bdh

M

hbd

Md

I

Mc

bdhhII

bdI

u

u

414.1

2/707.0

2/

2707.0707.0

2

2

2

2

===

==

=


Bending Properties of Fillet Welds

(Table 9-2; page:488-489)

uhII 707.0=


Bending Properties of Fillet Welds - contd.

(Table 9-2; page:488-489)


Few bending cases and equivalent line weldment diagrams


The Fig shows a welded steel bracket loaded by a static

force. Find the factor of safety if the allowable shear stress

in the weld throat is 120 MPa.

Problem


Welded Joint under Fatigue loading

The conventional methods will be used

In fatigue, the Gerber criterion is best; however, you

will find that the Goodman criterion is in common use.

For the surface factor, forged surface should always be

assumed for weldments unless a superior finish is

specified and obtained.


Fatigue Stress-Concentration Factors, Kfs

Table 95


The weldment is subjected to a completely reversed force F.

The hot rolled steel bar is 10 mm thick and is of AISI 1010

steel. The vertical support is of AISI 1010 steel. The

electrode is 6010. Estimate the completely reversed load F

the bar will carry.

Problem


kN 22.09Fa

) 0& 1n(For SFK

n

1KK

5)-9 (Table 2.7K

MPa 7.82S

0.59k

1k

0.656(427)272k

MPa 213.50.5SS

MPa 427S

4)-9 (table electrode For the

mm 721.14A

fseafs

f

fsafs

fs

se

c

b

-.995

a

ut

1

e

ut

2

=

====

=+

=

=

=

=

==

==

=

=

ma

ut

m

e

A

SS


kN 4.73F

SFK

(assume) 1K

MPa 4.721S

0.85k

1k

0.917(320)7.75k

MPa 1600.5SS

MPa 320S

20)-A (table 1010 AISI member, For the

a

seafs

fs

se

c

b

0.718-

a

ut

'

e

ut

=

==

=

=

=

=

==

==

=

Aa

kN. 22.09 values} two{abovemin F ==

Documents

Welded Joints