-
7/25/2019 288_15.pdf
1/22
Large Bolted Joints
TESTS OF A 9 BOLTS
Preliminary Report
-
7/25/2019 288_15.pdf
2/22
SYNO PSIS
Presented
in
t h i s
r epor t
are
th e r e s u l t s of calibration t e s t s
t o f
individual ASTM
A49
al loy s tee l b o l t s . The b olts
te s te d
were
7/8
i n .
nominal
diameter.
R e su lt s o f t w en ty d i r e c t tension and
thirty torqued
tension
t e s t s
are
reported.
This
is a preliminary r epor t and w i l l eventually be re-written
to
i n cl ud e i nf o rm a ti o n
on similar t es t s conducted on the same bolt lots
at the University of l l inois
INTRODUCTION
At the February
14
1963
meeting
of Committee 15 of th e Research
Council on Riveted and Bolted Structural
J o in ts
was recommended that
Lehigh University
and
the
U ni ve rs it y o f ~ n o s conduct t es t s
on
bolts
from
the
same
lo t
to determine i f -testing procedures constitute a vari-
-
7/25/2019 288_15.pdf
3/22
TEST
PREPARATION
Two
l ot s
of 7/ 8 in . diameter, heavy hexagon head, A49
bolts
were t e s t e d . B efore
t e st i n g ,
l l
bol t s
were st arriped w i t h a lo t de s i gna t i on
and
bol t
n u ~ b e r
In
a d d i t i o ~
each
,bolt
had
h o ~ e s ~ r i l e d
in
the
centers
, o f
the head
and nut ends ,to accommodate th e C-frame
extensometer.
~ ~ l t s d e s i g n a t e ~
as
~ o t
w e r e 9 ~ in . long
w i t ~
in . of cut
t h r e a d . Those l a b e l l e d Lot
:U
were
in long
with 1 in of rol led
thread. In t e st s, one hardened w as he r was u se d u nde r .n A194 Grade
2Hnut
heavy
hexagon).
Each lo t te s te d
with 1/8 in .
an d 9/16
in .
of
~ h r e a d in
the
grip .
This gave grip
lengths of
8 \ and 8-11/16
in .
fo r
Lot
b o l t s , .an d 4-1/8 in . an d 4-9/16 in .
grip
for the, LI bol t s
A representative sample of twenty b o lts and
nuts
from
the
lo t
were checked
fo r
tolerance
by
using the NC2A
go
and no-go
ring
gages
and
th e NC2B
and no-go plug gages. A ll
specimens
tested were accept
-
7/25/2019 288_15.pdf
4/22
TEST PRO E URE
a. ~ O R Q U TENSION
TESTS
Specimens
from
both lots were tested in
th e
Model M
Skidmore-
Wilhelm calibrating device. Ten
bolts
from the
L
lo t
were also tested
in a solid block of A44 steel .
For
l l tests conducted in the Skidmore-Wilhelm calibrator
the
nut
was turned
by using
a hand
wrench unti l
a lI snug
tension
of
ten
kips was
reached in the bolt. Bolt load, elongation and
turn-of-
the-nu,t
( in
degrees)
measurements were
taken
t
5
and
10
kips .
The
nut
was
then
rotated
in
45 i nc rement s (1/8
tur n-of-the-nu t)
with a pneu
matic impact wrench un t i l f i lure oc curred either by fracture or by
thread stripping.
Bolt
elongation and load data were taken at each
45 increment
of
nut rotat ion.
From the
tests
done in
the
Skidmore-Wilhelm device a mean
elongation
t
a snug lo ad
of ten
kips was determined
for
the L
lo t
-
7/25/2019 288_15.pdf
5/22
-4
b. DIRECT
TENSION TESTS
As a preliminary check
the
bolt being tested was
loaded
to the
specified proof load and then unloaded
to check
th e
STM
requirement
of
minimum
'permissible
set (0.0005
in . ) .
No
bolts were rejected
by this
t e s t
,The 'bolt wa s then'
reloaded and
elongation
readings
were,
taken
.
t
ten kip interva1s unt i l
th e inel st ic range
was
reached.
At th is
point
load readings
were taken
fo r
every 0.01 in. of elongation
in
the
.
bol t The direct
tension
tes ts were
conducted
in
a
300 kip Baldwin
hydraulic
test ing machine at a strain
rate
of
approximately 0.01
in . per
'minute.
A
detailed descr ip ti on o f the procedures
used
in the calibrating
of bolts is
given in
Reference 1. The reader is referred specifically to
Figures
1
and
2
of
this
,report for the specific set ups
used
in the
direct
and
torqued tension tests
-
7/25/2019 288_15.pdf
6/22
-5-
kips, i e .
th e load
to which the bolt may be loaded so that af ter un
loadi.ng there is no more than
0.0005
permanent
set) ,
and the speci
fied
minimum ultimate load is 69.3
kips.
Four
fai lure modes were
noticed.
All the B lo t b olts failed
in the
direc t
tension
tests
on
a
jagged
diagonai
through
th e
threads.
Two of the B lo t bol ts
tested
in
torqued
tension
with
1/8 in .
thread in
grip failed by thread
stripping
as
did
two
bolts in direct tension
with
the
same
amount
thread
under
the nut.
In a l l four cases,
the
nut
and
bol t thread was so
badly
damaged that i t was impossible to t e l l
which thread had o r ig ina ll y f ai led . The LI specimens
tested
in direc t
tension
with
9/16
in . thread in grip failed on a jagged d iago na l as
noticed with the B direct tension tes ts . However th re e bol ts with
1/8 in . thread in
the
grip, failed on a level
plane, through
th e
threads,
a t
th e juncture of the thread
runout
and
bol t
shank.
The
other
two
LI
b olt s fa ile d in
the
diagonal manner previously noted. All bolts
tested
-
7/25/2019 288_15.pdf
7/22
-6-
Figure 5 shqws a typic l re la t ionship
between the
di rec t
and
torqued
tension
tes ts .
Bo 1ts
tested
in direct
tension
gave
greater
u l t i ~
mate loads
and
sustained
greater
deformations
to fa i lure than did those
tested
in
torqued tension.
Bolt s t es te d
in
the
solid A440 s tee l
blo.ck
gave
greater
loads
for fewe r
turns as, is indicated in Fig. 6.
Although
there
is , a
broad
scat ter of
the data
associated with each tes t there
is
a defini te separa
t ion of the
two mean
curves.
The bolt load is
related
to the number of
turns
from a snug
bolt load of 10
kips
in Figs . 7, 8, 9 and
10 .
The data
s,hown
in
Figse
7 and 8 refers to t es t s
conducted
in the
Skidmore-Wilhelm
calibra tor .
Figure 8 presents the
resul ts of
t es t s done
in
a solid A440 steel block.
The mean ~ u r v e s from
;Figs.
8 and 9 (with 1/8
thread in grip) are
plotted
in Fig. 10
to
compare with resul ts
of tests
on
A325 bol ts( l ) .
The snug
load
for
the
A325
bolts
was
8
kips.
The load-elongation
relationship
of A490 and A325 bolts
torqued
-
7/25/2019 288_15.pdf
8/22
CONCLUSIONS
The
following conclusions
are
based
on
the resul ts
of 50
t e s t s
of
individual
b o l t s . Twenty 7/8
x
bolts and thirty 7/8
x
b o l t s .
These
resul ts and
conclusions
are
,not greatly different from those
reported
in a more comprehensive study of A354 alloy steel
bolts(2).
Similar resul ts
and
conclusions,
based on
a
l imited
number
of t e s t s ,
were also ~ e p o r t e d in Ref. 3 .
1. Bolts from
the, same
l o t ,
and with
the
same
amount of
, thread
in grip,
gave
greater ult imate
strength in
direct t ens ion . tes ts than
was achieved in
torqued
tension t e s t s . For the l ? t specimens t h i s
increase
was
10
to 5 percent of the ult imate
torqued, tension
value,
and
for the L1 l o t
b o l t s th e in cre as e
was about 26
percent.
2.
A
lesser
amount o f thread in grip
gave an i n ~ r e a s e in
the
u lt imat e bo lt
strength
in
both
the
t o r q u ~ d
and
d i r e c t
tension
tests .
ei Figures
1
to 4).
-
7/25/2019 288_15.pdf
9/22
-8-
4. The a v e r ~ g e load a t
turn from
snug was less
than the
specified
proof load
for both
lo t s
tes ted
in
the
Skidmore-Wilhelm
device.
Three
the
ten in long
LI lo t
bol ts
tes ted
did give
loads
grea ter
than.
t he spec if ied
proof lo ad (55.45 kips)
a t
turn from snug.
None of
the
lo t
bolts
reached proof load at
turn from
snug
e
(See i g s ~
2
arid 4, ,and 7 and 8).
5. Figure 6 indicates that the LI specimens, w ith 1/8 thread in
gr ip
torqu ed in solid s tee l did reach proof load
a t
turn from snug .
,Also
this plot shows
that
achieve
the same bol t elongation) fewer turns
of the nut are required in specimens torqued in th e so lid s te el block
than
is
r equired fo r
t ~ o s e
tested
in
the
less
rigid
Skidmore-Wilhelm
device.
If one s s u m e ~ that the load vs . elongation character is t ics of the
bolts,
tes ted in torqued tension, are
not
influenced
by
the mate ria l gripped ,
then (from
Fig.
6) one observes that the bol t load
at t u ~ n
is indeed
above proof
load for
those
tested in
the
solid
s teel
block. Figure
8
shows
that proof load
was
also reached at turn for
most
specimens tor
qued in
solid steel
with
9/16 t ~ r e d grip.
-
7/25/2019 288_15.pdf
10/22
TABLE 1
-
9-
A490 BOLTS
- 7/8 DIAMETER
TORQUED TENSION ( in
Skidmore Wilhelm)
L1 AB AB
L1
LI
L1
DIRECT
TENSION
AB
olt Lot
8 8-11/16
4-1/8
4-9/16 8t 8 ~ 4-1/8 4-9/16
1/8
9/16
1/8
9/16
1/8 .9/16 1/8 9/16
5 5 5 5 5
73.2
76.0
72.1
65.4
61.8
61.1
58.4
1.59
;1.69 0.54 0.17 2.80 2.18 2.80 3.00
0.0779 0.0846 0.051
0.065
0.053 0.070
0.026
0.031
65 61 67 59 52 50 40 34
0.12 0.18 0.137 0.245 .0.08 0.114 0.075 0.11
0.028
0.029 0.015
0.017 0 .028 0 .031 0.016
0.018
106 102 110 104
48.8 41.1
53.4
50.0
1-3/8
1-3/4
1-5/8
i n s ~ .
kips
ins .
kips
ins.
ins.
kips
kips
ins
ominal Grip
Thread in Grip
.Noe
of Specimens
Tested
Mean
Ult.
Load
Std.
Dev. from Ult. Load
Mean Eloug.
at
Ult.
Mean Rupture Load
Mean Elong.
after rupture
Mean Elong.
at Proof
Load
Min.
Spec.
Ult.
Load
Mean Load
at Turn
Ave. Turns to Failure
-
7/25/2019 288_15.pdf
11/22
.16
1412
10
~ x ~ i bolts, CutThreads
1
Fracture
of
Bolt
8
liS
Thread in
Grip
6
t=
t f ....
~ ~ j ~ ~ n
S p ~ ~ d
Ultimate
4
I grip
-
w i
J
L
= thread in
grip
Proof
Load
- -55.45 kips
.02
2
6
4
8
BOLT
LOAD
kips _
BOLT ELONGATION
inches
FIG
o
1 DIRECT TENSION CALIBRATION AB LOT BOLTS
-
7/25/2019 288_15.pdf
12/22
8
6
1. -
. proof
JD0 9 _
kips-
I f f
II
i
I
urn 0 Nut rom Snug
la x9
lt
i
bolts,
CutThreads
Fracture of Bolt
14
12
lIe Thread in Grip
o
06 08 .10
B O L ~
ELONGATION inches
4
-
- ..... - ~
-
-
7/25/2019 288_15.pdf
13/22
. .
. I
.14
12.
IQ06
.
9 r6Threod
in Grip
7
X5 bolts Rolled
hre ds
.06
.
hre d
in Grip 6 9 3 k i p s M ~ n Specified
lti mate
Load.
d
. .
. .:
.
.
.
e
_
. . .
__
~
_. tZ:
.
.0 4
r ~ ~ t ~
55.45 kips
.02.
2
40
80
60
BOLT LOAD
kips
BOLT
ELONGATION
- inches
FIG.
3 DIRECT TENSION CALIBRATION LI LOT BOLTS
-
7/25/2019 288_15.pdf
14/22
8
Thread in Grip
r l . : ~
14
+
2
t .
Proof
Load
5 5 4 ~
kips
.10
8
06
6 Thread Grip
Y8
U
x
5 ~ 2
bolts, Rolled Threads
.04
02
20
40
6
BOLT LOAD
(kips)
BOLT ELONGATION (inches)
FIG
o
4 TORQUED
TENSION CALIBRATION
LI LOT BOLTS
f
f
-
7/25/2019 288_15.pdf
15/22
_
I
.14
.
_ irect
TniQl
.10
l 8 X 5 ~
Bolts
~ 8 T h r e a d
in rip
.0806
e
e
.
Proof Lood
55.45
kips
.04
. Torqued
in
k i d m o r e ~ i l h e l m
.02
60:
20
4
8
BOLT
LOAD
kips
BOLT ELONGATION
inches
FIG
5 COMPM ISON
OF
LOAD ELONGATION CHARACTERISTICS
OF
LI LOT
BOLTS
FOR DIFFERENT LOADING METHO S
-
7/25/2019 288_15.pdf
16/22
1.50
~ u x 5 ~ Bolts
2
I/s Thread
Grip
~ o r q u e d
in _.
Solid Steel
Block
o
0
TorquecJ in
Colibroting
Device-
1.00
0.50
0.25
1.25
TUR S-
O ~ T H 0 15
NUT
FROM
, SNUG
II
-
7/25/2019 288_15.pdf
17/22
_ _ .
ao
, :
6
BOLT LOAD
(kips)
2
_ Proof . OO
-
7/25/2019 288_15.pdf
18/22
80
:
i .
l/aThreod in Grip
9 6
Thread
in Grip
Comparison
of
Load-Turns
Data for D-ifferent
Lengths of Thread in
Grip 1
a
x
r
Bolts
Tests Conducted in Skidmore-Wilhe-Im
o F7 C ::_ >
i
c; [ , , , , , , , . , , , , , ,
20
6
4
BOLT LOAD
kips
5
o
5
1 5
2 0
AVERAGE NUMBER
OF
TURNS
FROM SNUG OF 10
KIPS
Fig 8
-
7/25/2019 288_15.pdf
19/22
8
Thread
in
Grip
llwead in
Grip _
. Proof
11VV4.
--
. 4 5 i i p r ~
Comparison
of L o a d ~ T u r n s
Data
for
Different
Lengths of Thread
in Grip. J
a
x ~ ; B o l t s
.
Tests Oondvcted in
Solid
Steel
Block
o
a= Ft
2
..
6
4
BOLT LOAD
. kipS
5
o
0.5
1.0
-
1.5
2.0
AVERAGE -NUMBER OF -TURNS
FROM SNUG
ELONGATION
OF
Fig
9
.
-
7/25/2019 288_15.pdf
20/22
80
-
-
-
---
-
-
--
- - -
~ ~ A 3 5 8 B LOT
la
x
5
bolts, Rolled Threads
~ h r e a d in Grip
,
- - -
- - - - - - - - - - - - -
- - - Torqued in S. W.
- Torqued in Solid Steel Block
-A325 Proof Load
1 -
36.05kips
A490
~ o o f
L o a ~
55.45
kips
o
- - ,
I , , I , , , , , I , I , I I ,
20
60
40
BOLT LOAD
kips)
0.5
o
0.5-
1.0
1 5
2.0
AVERAGE NU MBER OF TURNS
FROM
SNUG
F ig
10
COMPA TZISON OF LOAD:-TVRt-rs DATA FOR
7 8 x A3 5
A:ND
A49
BOLTS
-
7/25/2019 288_15.pdf
21/22
8
5 ~ 5 k i p s
A325,8B LOT
LOT
II
x5
at
Bolts,Rolled Threads
I ~ T h r e a d in Grip
II-
Turn from
liS
II
. - nug
_ _ _ _ _
36 05 klEL
o
_ _
IIooo
2
4
6
BOLT LOAD
: (kips)
Aa LOT A490 BOLTS
Thread
in
Grip
l
6
-
7/25/2019 288_15.pdf
22/22
=....
~ . ~ . - : . . . . . :
43
TURNS TO FAILURE
Mean Curve
Establised for A325
Bolts
Showing . . . . . - ~ - . . - . . .........
. ..
catter
Band
L ot Tested
in
Solid Block
U ott l Skidmore-Wilhelm
3
o
4
THREAD L N TH
UNDER THE 2
NUT inches)
Fig
EFFECT
OF THRE D LENGTH ON
ROT TION C P CITY
