- Email: [email protected]
On fatigue life prediction under conditions of tensile hold
Scripta METALLURGICA
Vol. 21, pp. 1385-1387, 1987 Printed in the U.S.A.
ON FATIGUE LIFE ~ c ~ U N
Pergamon Journals, Ltd All rights reserved
I~tumk (ZRDITICRS (~ ~
PEg/)
s. va,l,m~ K~am~:on, ZL
~ni~y,
60208
( R e c e i v e d A u g u s t 7, 1987)
TerJBile hold "c..rL.ffi8~
~
~
..k8 ~
tq~mmet~t~. :LF),~
as , t e e 3 s ( 1 - - e ) , n.:LcknZ a.U.,=~('tO-~), m.-'_qsg a.Uoy(Z3), and ~
particalar, f a t l g ~ e
,o.Mn~(14).
~AI. ~ y ,
a
hn3~ lifetlmm data f~r otbmr mmtals are mbm~1 to fit the e ~ M ~ m : A
Nfwhere
+
B
(i),
Nz - ~ oZ c~ca,, to ~ttur,, the - t~m~ile ~ tim, A and B - ~ .
As ~own i n Fig. l ( a ar,:l b), ~ ho.lzl, Wlsmn.tn'cz'~dUamd. int:o t:bm fMfc.t~m c"y~..IJm, leads t o a d r m a t i c z'e(K,=ti~m .in t h e numl:mr o f cycZes t o f a i l u r e i n 96.SPb-3.S6n ~ 95.5R~3Sn1.5S~ ~ ( 1 4 ) , 304(8), 316(9) mtalnleml mtemla ~ Cz~bV staml(9). I~ lJ ~ that ibm clecrmm in Sf is m ~ t rapid for mall b-!~ t/rams, l%n~hmr ~ in i~m b-~a tlms 1rods to a limit in the number of cyclem to failure, Nf'. All ~ tlmted tw~mr g i ~ o m n ~ i ~ of ~=aln r ~ , ~ti~, and t ~ m n n ~ are m ~ o t ~ to m = v i ~ at l ~ s t Nf' ~ I ~ at ~ v a l ~ of t ~ - e i l e hold tim~. TO find the relation b e ~ n the Nf ~ tamsile ~ ! a t i m ~ to find tbl valu~ of Nf', t.he time t o f a i l u r e , if, is plotTad vmrm~ bold tlmm in Flg. 2(a ~ b ) . It is ~ for ~
that the following linmar ztlatlon bmt~mmm t i m to failure and h~]a E.I. (fC~" ~ hold ~ ) : t~ - ^ + B the
(2)
r,,,,~-,m-_ o f cMc/.es t o Z a i l u r e may be f o a ~ ms: tf Nf " %= where
a + stht "
(3),
Z~r + t~c
i s ~',e t.i.m p e r ~ . l e , %. i,, u , , . , , ~ t . m , .
1385 0036-9748/87 $3.00 + .00 Copyright (c) 1987 Pergamon Journals
Ltd.
1386
FATIGUE LIFE PREDICTION
V.he hold ~-4,, is ,-,-h lor~r than the m~-v t i m
A+~ ~
~.
-
21, No.
10
(as i n mcsl: p r a c t i ( m l carom) :
A =
+ s
(4) m,~ he uasd'£'~-da~:a .W',-a~ta~-,n ~
hold t ~ is on I ~ ~~a,~m~,hea~oR=~oua.
Vol.
(4)
short t o ~on~ hold ~ - , . s .
ok~ of a few houri, the flrl~c ~ m;. (4) n ~ m ~ t o :
in ~ .
(4)
~us, Nf', ~ lisi~ in the nud:er of cyclas to Zailure, is de~=mired by the slope of the r~latlan ~ ~ to failure and hold t i m (Fig. 2). Only a Eew taats are r,~ad to find thin valuas of U ~ constant~ A and B for each amplltu~m and t ~ and thus to predict ~ life of a ~atorial ~ m ~ e r ccndi~'4,~w o f t a r ~ t l e lx)ld ~.,.,.,,rldsd the hold t i m m are no~ v e r y e ~ r t , hecsum rsmp ttmm i s nsqlectmd. ~rm f a i l u r e ~ i s creep duminated a t h i s h ~ and s u f f ~ y l~r,~j t i m u . ~'LiS may not ]=e t n ~ i f the ramp plus hold ~'~-,* i s ~ r t . I n tamtt.s w i t h s o l d s ~ a t zoom t s m p s r a t u ~ , w , r y s h o r t hold ~ of a f~ ~ m y be u M d since f a t i g u m - l i f e s a t u r a t i ~ hecxmma evidsnt: sawn the hold ~'~,,- i s on the c~rlar of a f w minutam. Ho~m~r, for ~ teetln~ of steels and other high t a ~ alloys, ~ e longer hold ~ should he ~ q p l o ~ s i n e the salmn-at/on in fatigue life ~ evident at:hold ~ c~er one hour.
;~-t~:r would li~m to ~ m n k ~ f e ~
X.E. Fire for ~
discu~i~.
L~sf~" i. J.R. ( ~ , J.T. EarlL-~ and R.H. ~ , ~ at Elevated Ta~eraturem, ASIM STP 520, A~cml Society for ~ ~ Ma~Im~ 637(1973) 2. J. w a m i ~ , N ~ U l . Tram., 6A, 1367(1975) 3. J. W ~ h ~ , )brat1. Tram., aA, 7n(1977) 4. P.S. NaIya and S. NaJ,,.,~,-, Vmaa11. Trans., 8A, I~i(1977) 5. S. N~jm~ar and P.S. Nail,a, mrq. Mater. Ta~nol(xjy, ~02,~59(1980) 6. R. Halel, Fat:. ~IcJ. Mater. ~ . , ~, 339(1.980) 7. J.K. Tien, S.V. Nalr and V.C. ~ , Flow and ~ at Elevated T ~ , Amsricsn Society f a r )tM:a.ls, Nist~l. Park, Ohio 44073, 179(1985) 8. A.M. Erml and J. WataL~f, Nm~11. Trans., L~A, 1577(1962) 9. J.W. I ~ , S.W. Nam a ~ K-T. Rie, J. Mater. Sc/., 20, 3763(1.983) i0. s.v. Gol~Ikar, " ~ In~n-actlo, in ~i-Base S ~ o y . ' , , R~D ~ a s i s , ~ m m ] a s r P o l ~ . m ~ n i c mnatitm#.,, (].q82) 1.l.M.F. ~ end G.S. ~ m s , W~call. S c i . , 13, 25(1979) 12. A.H. Maleka, N ~ t a l l ~ Rav~, 7, 43(1962) 13. S. ~,4k, ~ of C r l e p - F a ~ ~ " , PhD ~heals, C~-z~11 t~tlvarsity (1982) 14. S. Valmman, M.E. Fine and D.A. Jeannotta~, ~ of 37th Electronic Conferer~e, I~R, New York, 598 (1987)
Vol.
21, No.
l0
FATIGUE
LIFE PREDICTION
1387
Steel= 1600
3OOO
0-304, 86GoK,ZU~t.1.0~ n-316, 873°K,~kEt=l.4q~ "-CrMoV, 838=1K,&~t-1.0%
Soldm, 1200
o- 95.5Pt>-3Sn-1.5~ 25=(3, Z~t=l.12% 2000
-3
- 96.5Pt>-3.5Sn 25°C, &et-O.75%
Z
800
Z
lO00
f=l
'0
J
&
i
200
400
600
200
400
tlst ' S
ttt,
a
600
mln
b
i,z~. z ] ~ f e ~ o f terwJ.Ze ~3,4 ~
an rzzdu=r of c3m].e= to fa43.uz~
0 K
o~ t ~ u m =
120
120
j
0
80
i
40
80
a ] u m FIG. 1= i
!
I
20O
400
600
Or
200
tkt , $
400 tkt , II~
a
b
~G. Effect
2
o f t.=rBi.l.e h o l d
"c.J.=e o n t i m e
to
~Li.),u=~
600
Vol. 21, pp. 1385-1387, 1987 Printed in the U.S.A.
ON FATIGUE LIFE ~ c ~ U N
Pergamon Journals, Ltd All rights reserved
I~tumk (ZRDITICRS (~ ~
PEg/)
s. va,l,m~ K~am~:on, ZL
~ni~y,
60208
( R e c e i v e d A u g u s t 7, 1987)
TerJBile hold "c..rL.ffi8~
~
~
..k8 ~
tq~mmet~t~. :LF),~
as , t e e 3 s ( 1 - - e ) , n.:LcknZ a.U.,=~('tO-~), m.-'_qsg a.Uoy(Z3), and ~
particalar, f a t l g ~ e
,o.Mn~(14).
~AI. ~ y ,
a
hn3~ lifetlmm data f~r otbmr mmtals are mbm~1 to fit the e ~ M ~ m : A
Nfwhere
+
B
(i),
Nz - ~ oZ c~ca,, to ~ttur,, the - t~m~ile ~ tim, A and B - ~ .
As ~own i n Fig. l ( a ar,:l b), ~ ho.lzl, Wlsmn.tn'cz'~dUamd. int:o t:bm fMfc.t~m c"y~..IJm, leads t o a d r m a t i c z'e(K,=ti~m .in t h e numl:mr o f cycZes t o f a i l u r e i n 96.SPb-3.S6n ~ 95.5R~3Sn1.5S~ ~ ( 1 4 ) , 304(8), 316(9) mtalnleml mtemla ~ Cz~bV staml(9). I~ lJ ~ that ibm clecrmm in Sf is m ~ t rapid for mall b-!~ t/rams, l%n~hmr ~ in i~m b-~a tlms 1rods to a limit in the number of cyclem to failure, Nf'. All ~ tlmted tw~mr g i ~ o m n ~ i ~ of ~=aln r ~ , ~ti~, and t ~ m n n ~ are m ~ o t ~ to m = v i ~ at l ~ s t Nf' ~ I ~ at ~ v a l ~ of t ~ - e i l e hold tim~. TO find the relation b e ~ n the Nf ~ tamsile ~ ! a t i m ~ to find tbl valu~ of Nf', t.he time t o f a i l u r e , if, is plotTad vmrm~ bold tlmm in Flg. 2(a ~ b ) . It is ~ for ~
that the following linmar ztlatlon bmt~mmm t i m to failure and h~]a E.I. (fC~" ~ hold ~ ) : t~ - ^ + B the
(2)
r,,,,~-,m-_ o f cMc/.es t o Z a i l u r e may be f o a ~ ms: tf Nf " %= where
a + stht "
(3),
Z~r + t~c
i s ~',e t.i.m p e r ~ . l e , %. i,, u , , . , , ~ t . m , .
1385 0036-9748/87 $3.00 + .00 Copyright (c) 1987 Pergamon Journals
Ltd.
1386
FATIGUE LIFE PREDICTION
V.he hold ~-4,, is ,-,-h lor~r than the m~-v t i m
A+~ ~
~.
-
21, No.
10
(as i n mcsl: p r a c t i ( m l carom) :
A =
+ s
(4) m,~ he uasd'£'~-da~:a .W',-a~ta~-,n ~
hold t ~ is on I ~ ~~a,~m~,hea~oR=~oua.
Vol.
(4)
short t o ~on~ hold ~ - , . s .
ok~ of a few houri, the flrl~c ~ m;. (4) n ~ m ~ t o :
in ~ .
(4)
~us, Nf', ~ lisi~ in the nud:er of cyclas to Zailure, is de~=mired by the slope of the r~latlan ~ ~ to failure and hold t i m (Fig. 2). Only a Eew taats are r,~ad to find thin valuas of U ~ constant~ A and B for each amplltu~m and t ~ and thus to predict ~ life of a ~atorial ~ m ~ e r ccndi~'4,~w o f t a r ~ t l e lx)ld ~.,.,.,,rldsd the hold t i m m are no~ v e r y e ~ r t , hecsum rsmp ttmm i s nsqlectmd. ~rm f a i l u r e ~ i s creep duminated a t h i s h ~ and s u f f ~ y l~r,~j t i m u . ~'LiS may not ]=e t n ~ i f the ramp plus hold ~'~-,* i s ~ r t . I n tamtt.s w i t h s o l d s ~ a t zoom t s m p s r a t u ~ , w , r y s h o r t hold ~ of a f~ ~ m y be u M d since f a t i g u m - l i f e s a t u r a t i ~ hecxmma evidsnt: sawn the hold ~'~,,- i s on the c~rlar of a f w minutam. Ho~m~r, for ~ teetln~ of steels and other high t a ~ alloys, ~ e longer hold ~ should he ~ q p l o ~ s i n e the salmn-at/on in fatigue life ~ evident at:hold ~ c~er one hour.
;~-t~:r would li~m to ~ m n k ~ f e ~
X.E. Fire for ~
discu~i~.
L~sf~" i. J.R. ( ~ , J.T. EarlL-~ and R.H. ~ , ~ at Elevated Ta~eraturem, ASIM STP 520, A~cml Society for ~ ~ Ma~Im~ 637(1973) 2. J. w a m i ~ , N ~ U l . Tram., 6A, 1367(1975) 3. J. W ~ h ~ , )brat1. Tram., aA, 7n(1977) 4. P.S. NaIya and S. NaJ,,.,~,-, Vmaa11. Trans., 8A, I~i(1977) 5. S. N~jm~ar and P.S. Nail,a, mrq. Mater. Ta~nol(xjy, ~02,~59(1980) 6. R. Halel, Fat:. ~IcJ. Mater. ~ . , ~, 339(1.980) 7. J.K. Tien, S.V. Nalr and V.C. ~ , Flow and ~ at Elevated T ~ , Amsricsn Society f a r )tM:a.ls, Nist~l. Park, Ohio 44073, 179(1985) 8. A.M. Erml and J. WataL~f, Nm~11. Trans., L~A, 1577(1962) 9. J.W. I ~ , S.W. Nam a ~ K-T. Rie, J. Mater. Sc/., 20, 3763(1.983) i0. s.v. Gol~Ikar, " ~ In~n-actlo, in ~i-Base S ~ o y . ' , , R~D ~ a s i s , ~ m m ] a s r P o l ~ . m ~ n i c mnatitm#.,, (].q82) 1.l.M.F. ~ end G.S. ~ m s , W~call. S c i . , 13, 25(1979) 12. A.H. Maleka, N ~ t a l l ~ Rav~, 7, 43(1962) 13. S. ~,4k, ~ of C r l e p - F a ~ ~ " , PhD ~heals, C~-z~11 t~tlvarsity (1982) 14. S. Valmman, M.E. Fine and D.A. Jeannotta~, ~ of 37th Electronic Conferer~e, I~R, New York, 598 (1987)
Vol.
21, No.
l0
FATIGUE
LIFE PREDICTION
1387
Steel= 1600
3OOO
0-304, 86GoK,ZU~t.1.0~ n-316, 873°K,~kEt=l.4q~ "-CrMoV, 838=1K,&~t-1.0%
Soldm, 1200
o- 95.5Pt>-3Sn-1.5~ 25=(3, Z~t=l.12% 2000
-3
- 96.5Pt>-3.5Sn 25°C, &et-O.75%
Z
800
Z
lO00
f=l
'0
J
&
i
200
400
600
200
400
tlst ' S
ttt,
a
600
mln
b
i,z~. z ] ~ f e ~ o f terwJ.Ze ~3,4 ~
an rzzdu=r of c3m].e= to fa43.uz~
0 K
o~ t ~ u m =
120
120
j
0
80
i
40
80
a ] u m FIG. 1= i
!
I
20O
400
600
Or
200
tkt , $
400 tkt , II~
a
b
~G. Effect
2
o f t.=rBi.l.e h o l d
"c.J.=e o n t i m e
to
~Li.),u=~
600