www.ccsenet.or
36
These samples region at the c
order to provid 2.4 Fatigue Te
The fatigue te SHIMADZU
spot-welded te
These sample to provide sym
ends of the sp ratio and frequ
until fracture Applied force
3. Results and
The weld prof
Figure 3. W It can be seen
Because of th generated in t
rgmas
s were similar center of the as
de a tensile-sh ests
ests were perfo testing machin
est samples we
s were similar mmetry and to
pecimen. A sin uency used we
occurred or to range and num
d Discussion
file of 3.0-1.0 m
Weld profile of n from Figure
he unbalanced the thicker pla
to the sample ssembly repres
hear loading co formed at room
ne with a softw ere made accor
Figure 2. Dim r to the sample
o prevent a mo nusoidal wave
ere 0.1 and 8 H o a maximum 2
mber of cycles mm joint is sh
f 3.0-1.0 mm th 3a that the
heat resulting ate Hasanbaso
Modern Appli
s used in a wo sents the nugge
ondition, 38 mm m temperature
ware package s rding to the Fr
mension of fat es used in a wo
oment being ap e input with a
Hz respectivel 2x10
6
cycles. S s to failure wer
hown in Figure
hick joints a nugget is asym
g from unequal oglu Kacar,
ied Science
ork which was et. The overlap
m long shims w
in laboratory specifically des
rench standard
tigue test speci ork which was
pplied at the w constant load
ly. Specimens Specimens tha
re recorded and e 3.
macrograph b mmetric where
l thickness of 2007. Heat l
ISS
carried out by p is equal to th
were attached conditions us
signed for runn d A03-405 as sh
imens in mm s carried out by
weld, 60mm lo amplitude wa
were exposed at survived 2x1
d S-N curves f
b nugget corn e its centre lea
the joined ma loss in thicker
Vol. 6, No.
SSN 1913-1844
y Gean et al. 1 he width of the
at both ends o sing a 40 kN s
ning fatigue te hown in Figure
y Gean et al. ong shims wer
as selected wh d to a constant
10
6
cycles are for the joints w
ner c nugget ans to the thic
aterials, more t r plate is smal
5; May 2012
E-ISSN 1913-185
1999. The dar e metal sheet. I
of the specimen servo-hydrauli
ests. The doubl e 2.
1999. In orde re glued at bot
hereas the stres load amplitud
called run out were obtained.
d interface cker workpiece
thermal will b ller than that i
52
rk In
n. ic
le
er th
ss de
s.
e. be
in
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thinner plate. F
surface thickne
Wang be elon
non-un 3d sh
affecte
Differe spot w
separat interfac
Figu In addi
mm joi were a
primari materia
thickne
The ha
Figu
csenet.orgmas
hed by Canadian
r plate. This co Further evalua
e indentation w ess causes the
et al., 2010. T ngated paralle
niform manner hows interface
d zone HAZ ent from the m
elded equal sh tion, nugget m
ce of nugget an
ure 4. Weld pro ition, accordin
ints were spot lso the same, h
ily attributed t als were found
ess Zhang H ardness profiles
ure 5. Microhar
n Center of Scien
ondition causes ation of Figure
was very sligh e edge of shee
The microstru el to irregular
r from all the s e microstructu
. microstructure
heet thickness microstructure
nd base metal
ofile of 1.0-1.0 ng to the macro
t welded using however that a
to the asymmet d to be much h
Hongyan, 2006 s of weld nugg
rdness distribu
Moder
nce and Educati
s penetration i e 3a shows t
ht. The asymm ets warp to the
cture of weld n r direction as
ides of the sur ure where the
of spot welde austenitic stai
has regular dir as seen in Figu
0 mm thick joi oscopic examin
g the same we at the joint int
try nugget of 3 higher than a m
6. Therefore, get, HAZ heat
ution of the spo
rn Applied Scien
ion
s almost 100 that separation
metry of temp e thinner shee
nugget has a c shown in Fig
rrounding solid base metal an
d unequal she inless steel sho
rection and w ure 4.
ints: a macro nation Figure
elding schedule erface were 8.
3.0-1.0 mm joi minimum nugg
the weld nugg t affected zone
ot welded equa
nce
on the thicke n of the sheets
perature field d et and makes t
columnar struc gure 3c. It
d, in both the e nd the nugget
eet thicknesses ows that the nu
ide heat affect
ograph b nugg e 3 and Figure
e, the nugget .3 mm and 8.9
int. The measu get diameter o
get sizes of all e, and the base
al and unequal
Vol
er plate and ver s is about 20
distribution in the sheet sepa
ture in which t shows that so
electrode and s are separated
, the microstru ugget is symm
ted zone HAZ
get corner c n 4 when the 3
diameter at ce 9 mm respectiv
ured weld nugg of the 3-6 time
welded materi e metal are sho
thickness aust
l. 6, No. 5; May
ry slight on the mm Figure 3
n spot welded aration is high
the grains are olidification o
sheet directions d by very narr
ucture investig metry, there is
Z band appea
nugget d inte .0-1.0 mm and
enter of total th vely. This diffe
get sizes for al es the root of t
ials were accep own in Figure
tenitic stainles
y 2012
37
e thinner 3b and
unequal h enough
found to occurs in
s. Figure row heat
gation of no sheet
ars at the
erface d 1.0-1.0
hickness erence is
l welded the sheet
ptable. 5.
ss steel
j
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38
The hardness The highest h
However, hard joint because o
carbon, manga the carbon con
been used in hardness of th
microstructure
Interesting ph hardness com
hardness. This Hardness prof
In order to de study, the ten
stainless steel
As can be see 1.0-1.0 mm jo
This result dif Ozyurek 200
welded joint.
It seems that stiffness. As k
rotation of the
Figure 7. Defo
When there w
rgmas
of nugget for b hardness value
dness of the nu of the chemica
anese that affe ntent exceeds
this study had he thinner shee
e. henomenon occ
mpared to base s could be attr
file of thin she etermine the lo
nsile shear loa are compared
Figure en from Figure
oint even thou ffers from the
08. They foun the enhancem
known when t e joint. Figure
ormation mech
was certain amo both 3.0-1.0 m
of weld nugg ugget of 3.0-1
al composition ects the harden
about 0.08 d less than th
et of the 3.0-1. curs in a thin s
e metal unless ributed to the
et was more in oad range on th
ad bearing ca and results ar
e 6. Tensile she e 6, the tensile
ugh its nugget results obtaine
nd that increas ment in tensile
tensile load wa 7 shows the de
hanism of lap j
ount of rotation
Modern Appli
mm and 1.0-1.0 gets was over 2
.0 mm joint di n of base metal
nability. Spot w AWS, 1982; O
hat of percent 0 mm joint co
sheet of the 3. s the nugget e
asymmetric nu nfluenced by st
he fatigue test apacity of spo
e given graphi
ear load bearin e shear load be
diameter at th ed from a wor
ing of the nug shearing load
as applied in a eformation me
joint during lo load distributi
n, the tensile s
ied Science
0 mm joint was 250 HV 0.5 w
id not show m ls in which the
welds in thin sh Ozyurek, 2008
carbon. In ad ompared to bas
0-1.0 mm join edge in which
ugget that occ train hardening
ts, the strength ot welded equ
ically in Figure
ng capacity of earing capacity
he joint interfa rk which was c
gget diameter bearing capac
a lap joint, the echanism of lap
ading, a low on in a lap join
stress called pe
ISS
s found to be h which was obs
many difference ere is not so mu
heet can have r 8. As seen in
ddition, there w se metal becau
nt where there h its hardness
curred on the u g due to electr
h of weldment ual and unequ
e 6.
spot welded m y of 3.0-1.0 m
face is smaller carried out by
increased tens city of 3.0-1.0
e eccentricity o p joint during
load level, b nt
eeling stress i
Vol. 6, No.
SSN 1913-1844
higher than tha erved on the e
es compared to uch alloying el
relatively high Table 1, base
was no signifi use there was n
was no signif value was sim
unequal sheet rode indentatio
t was also dete ual sheet thick
materials mm joint is high
and it fail on Vural and Ak
sile-shear stren 0 mm joint is a
of the load pa loading.
plastic hinges
.e. the normal
5; May 2012
E-ISSN 1913-185
at of base meta edge of nugge
o that of 1.0-1. lements such a
h hardness whe metals that ha
icant change i no change in it
ficant change i milar to nugge
thickness join on.
ermined. In thi kness austeniti
her than that o n the thin shee
kkus 2004 an ngth of the spo
attributed to it ath resulted in
s, c schemati
stress acting i
52
al. et.
.0 as
en ad
in ts
in et
nt. is
ic
of et.
nd ot
ts a
ic
in
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Publish
the thro deform
at the peeling
Since l test N
bearing The S-N
F All dat
fatigue than 1.
was 0.7
Nordbe have b
calcula
where range-c
higher
csenet.orgmas
hed by Canadian
ough-thicknes mation in sheet
nugget circum g stress of 3.0-
Figure 8. The load bearing c
Nordberg, 2006 g capacity than
N curves, the r
Figure 9. Comp ta points belon
e life of the spe 0-1.0 mm join
7 kN. erg 2006 has
been analyzed. ated as follows
t
1
t
2
. The S cycle relation
and increasing
n Center of Scien
ss direction of thickness dire
mference Nor 1.0 mm joint w
a fracture mode
capacity of spo 6 this mecha
n 1.0-1.0 mm j results of fatig
parison of fatig nged to a mean
ecimens increa nts. The endur
s proposed a l Line load is
s:
S-N curve in as seen in Fig
g to much high
Moder
nce and Educati
the joint, exp ection. Increas
rdberg, 2006. was smaller th
e of tensile she ot welds under
nism can exp oint.
ue test of the s
gue strength of n value of three
ases as expecte ance limit of 3
line load meth the load divid
e
Figure 9 wil gure 10. At hi
her at lower loa
rn Applied Scien
ion
ressed as P sin ing of the join
. Due to the an that of 1.0-
ear test sample r coach-peel te
plain why 3.0- spot welded jo
f 3.0-1.0 mm a e tests. As show
ed. The 3.0-1.0 3.0-1.0 mm joi
hod when fatig ded by the wi
3 2
14 t 3
ll has slightly igh loads fatig
ads than that o
nce
n θ formed ar
nt rotation incr higher stiffne
1.0 mm joint a
s: a 3.0-1.0 m est is much lo
-1.0 mm joint ints are presen
and 1.0-1.0 mm wn in Figure 9
0 mm joints ex ints was 2.9 kN
gue data of dis idth of the joi
1 2
t t
y different pat gue strength o
of the 1.0-1.0 m
Vol
round the nug eased peeling
ss, joint rotati as shown in Fi
b mm joint b 1
ower than that t has a higher
nted in Figure 9
m joint based o 9, while the loa
xhibited much h N whereas tha
scontinuous jo int, and the w
ttern if it is d of the 3.0-1.0 m
mm joint.
l. 6, No. 5; May
gget and cause stress that led
ion and conse gure 8.
.0-1.0 mm join of under tens
r tensile shear 9.
on the load ran ad range decre
higher fatigue at of 1.0-1.0 m
oints like spot width of the jo
displayed in l mm joint was
y 2012
39
d plastic necking
equently,
nt ile-shear
ring load
nge eases, the
strength mm joints
welding int, e, is
1 ine load
s slightly
www.ccsenet.or
40
Figure 10. Similar to ten
also attributed 3.0-1.0 mm jo
occurred just Consequently,
initiated on bo started in the b
After initiatio propagating th
in Figure 12a circumference
behavior is si Khanna, 2007
Figu
rgmas
Comparison o nsile shearing l
d to its stiffnes oint can be us
on thin sheet , crack of 3.0-
oth sheet side base metal adj
a Figure 1
on, the crack hrough the wid
a. Different fr e due to high
imilar to fractu 7.
ure 12. The frac of fatigue stren
load bearing c ss. The explan
sed to explain t and it was s
-1.0 mm joint as shown in F
acent to the HA
1. Initial crack propagation
dth of the thin rom fracture of
peel stress an ure of coach p
a cture mode of
Modern Appli
ngth of 3.0-1.0 capacity, the e
nation of the e that in fatigu
smaller than t initiated just
igure 11. For b AZ area.
k location: a of 3.0-1.0 mm
sheet. Finally f 3.0-1.0 mm j
nd led to the peel samples
fatigue test sam
ied Science
mm and 1.0-1 enhancement in
enhancement in ue strength. Du
that of 1.0-1.0 on the thin sh
both 3.0-1.0 m
b 3.0-1.0 mm jo
m joint occur y, this mechani
oint, cracks of pull out fractu
at high load t
mples: a 3.0-
ISS
.0 mm joint ba n fatigue stren
n tensile shear ue to the high
0 mm joint w heet side wher
mm and 1.0-1.0
oint b 1.0-1.0 rred through t
ism led to the t f 1.0-1.0 mm j
ure mode as that reported i
b -1.0 mm joint
Vol. 6, No.
SSN 1913-1844
ased on the lin ngth of 3.0-1.0
ring load bear her stiffness, r
which rotated o reas that of 1.
0 mm joint spe
mm joint the thickness
tearing fractur oint propagate
shown in Figu in a previous
b 1.0-1.0 mm
5; May 2012
E-ISSN 1913-185
ne load range 0 mm joint wa
ring capacity o rotation of join
on both sheet 0-1.0 mm join
ecimens, crack
and continue re mode as see
ed at the nugge ure 12b. Thi
study Long
m joint
52
as of
nt s.
nt ks
ed en
et is
www.ccsenet.orgmas Modern Applied Science Vol. 6, No. 5; May 2012
Published by Canadian Center of Science and Education 41
Given SEM views in Figure 13 and Figure 14 are the comparison of the last fracture surfaces of the 3.0-1.0 mm and 1.0-1.0 mm joint specimens which were subjected to same load of 3.4 kN. As seen in Figure 13a, crack of
3.0-1.0 mm joint initiated on the inside of thin sheet. On the more half of thickness, it propagated slowly due to low peel stress and induced ductile fracture characterized by intergranular cracking. Ductile fracture changed to
brittle fracture characterized by transgranular cracking on the remaining thickness due to increased peel stress. The embrittlement of stainless steel was attributed to strain-induced martensite forming during the fatigue tests
Vural et al., 2006. Different view was given by fracture surface of 1.0-1.0 mm joint specimen as shown in Figure 13b. It displayed brittle fracture characterized by transgranular cracking on the entire thickness due to
high peel stress.
a b
Figure 13. Initial crack of fatigue test samples: a 3.0-1.0 mm joint b 1.0-1.0 mm joint
a b
Figure 14. Crack propagation zone: a 3.0-1.0 mm joint b 1.0-1.0 mm joint On the crack propagation zone, brittle fracture characterized by transgranular cracking was observed on both
3.0-1.0 mm and 1.0-1.0 mm joint specimens. They displayed wave of plastic deformation as shown in Figure 14. However, plastic deformation intensity of 1.0-1.0 mm joint was higher than that of 3.0-1.0 mm joint. It was
indicated by the number of waves in the same observation area as seen in Figure 14.
4. Conclusions
