research project no. 30 - ductile iron society · research project no. 30 ... fatigue test report...

RESEARCH PROJECT No. 30

MONOTONIC AND CYCLIC DESIGN DATA FOR DUCTILE IRON CASTINGS

Reported by John M. Tartaglia, Paige E. Ritter

and Richard B. Gundlach Climax Research Services

Wixom, Michigan

DUCTILE IRON SOCIETY

Issued by the Ductile Iron Society for the use of its Member Companies- Not for General Distribution

DUCTILE IRON SOCIETY 28938 Lorain Road

North Olmsted, Ohio 44070

(440)734-8040

FEBRUARY 2000

Casting Type

Brinell Hardness Results

Condition 5 7/8" Keel Bars

~ell Hardness (CRS) ·----~·-- ··-----:-H=~--::;-=-~t'='-;o=-coc+----2cc-12=-c19 --- 2~1·----z1i9 ___ Av;~e Brinell Hardness (Foun-dry} _______________ HBS3ooo - · -==--- -----=-- ---=---- 231--

Tensile Properties Sample 10 Symbol Units 11 12 13 Average Ultimate Tensile Strength Su MPa 754 761 761 759 ~:~!o OffseJ Yi~ld Stre~:9_t~(~nginee!fri9I~==---=-- Sys=-- MPa _ _:_1_3~-=-41~=-~-408-~~=41~= Percent Elongation %EL % 7.8 8.0 8.5 8.1 PercentReductiOnArea____________ %RA %--~---7.3 8.1 7.6 ·---=r:r-Monotonic Strain Harder!LI'!g Exponent n -~----0.2!_ ______ 0.2_1 ____ Q:2f~ Monotonic Strength C_~_f!!.C::i~!l!_________ K MPa a 1310 1282 1296 Modulus of Elasticity E GPa 166 169 173 169--

Incremental Step Test (1ST) Results Tensile Sample 10 Symbol Units 14 15 Average Q.~~_Qf!s~t_Yjeld Strer~_g!~_(Eng. -l~~i<m) _____ -~~---- MPa __ --~~L_ ___ ill_ _________ 470_ 0..:2_~_Q_ff.!_~ Yield ~tr~'!9!.h{~r19.:_:_<:;ompr~~si~n) . Sys' MPa 447 ____ i7_§_ ____________ ~{)2 <:;}'c;:li_c_St~ng!~~9-~ffi.c::i~r1t{fensio~-- _______ K' ------~-~~--- __ !_()()?_ _1041 _ _ _____ __!()?4 Q}t_c_!!c;: Str~_n£fth Coefficient{9_omp!essiol1) ____________ _!S'_ _____ fv1Pei_ ____ !_4f3~ ______ 1551 _____________ _ 1510 Cyclic Strain Hardening Exponent (Tension) n' 0.12 0.13 0.12 cyCiiCStr:arnHarC!enTrlQ -Exponeiif(COnliiressJOilf ____ "' ____ ·-----~- -o:1s-- -- cf19 ------- ---- o.19 -

I. ~

Tensile Properties After the Incremental Step Testing Tensile Sample 10 Symbol Units 14 15 ~ltil'l'l_ateTensileSt~~n_gt~-- __________ _ ______ S~--- MPa_ b b ________ _ Cl:~~-9_ffse!_'(ield _§_t_r"engt~-~!!9l!l~~ring) _ .. __ §~~----MP~_ _ b ____ !>_ _ .... _______ _ r:_ercen_!~L()_ngation _________________ _!oEL --~--- _____ b _____ __!?______ ___ ___ __ Percent Reduction Area %RA % b b ------------------------ ---- - ~----- -----~-------- ---------- ----------

IIJ!~n()tOI1ic::Stral'!_ljl!~9.~ning Expon~r1L _ _ ______ _1'1 b ____ !>___ _ _______ _ Monotonic Strength Coefficient K- -- ----M-Pa·- - b -- b ____ _ ModUIUSOf-EI8stiCftY ______ ----- --------- --------- --- ----------E-.. - ------GPa-- --- ___ b___ _ __ b _____ ------------

a. Unavailable. Extensometer was removed early due to audible cracking. b. Broke during incremental step testing.

39

Casting Type


Condition 6 Y-Biocks

~efiHaranes5ccRS>~_---~-===~==~-=----~-=~---==- H;;~t5oo =~~{- -~ ~~l~ ~-~f; _ -~-1~1!--~---~~~? ___ v;~~9 Brinell Hardness (Foundry) HBS3000 --- --- --- --- ---

Tensile Properties

Average_ 244

214--255

Sample ID Symbol Units WC27 WC28 WC29 Averag_e Ultimate Tensile Strength ____ ~~---~---- ___ Su___ _ _ M~~-- __ ?~~ _ 783 753 _ 754

~:r~~~tff~~n~i=~~;trength(f:ll9Ln~~i!!g} -~ __ ~~t _ __ M~~- -~ ~~:-- {~J-- _ ~~J ~~~ Percent Reduction Area--~--- -- - -o/oRA ---- · %--- --4-:9--- -SA~--~~7.1-~- - ---- ----- 6.8 Monotonic Strain Hardenin£tE:xponent-~·-------n---~--~-~---- -~~0.26-~- --0~~0.19 ____ -·---- --~- ---- - 0.20

Monotonic Strength Coeffi~ent --~---K~-MPa-- -1262-- ~- -1282-- ~ 12o7- ~ ~===--_ __ _ ____ ~125Q. _ Modulus of Elasticity E GPa 168 171 171 170

Incremental Step Test (1ST) Results Tensile Sample ID Symbol Units WC1 WC2 WC3 0.2% Offset Yield Strength (En~g,__. _-T=e-=--n_s_io~n_.!_) --:---~--cS:c-Ly.c:.s',----M~Pa ____ -+ 504 505 507 ----~-~~~--0.2% Offset Yield StreQgth (Eng.- Compression) Sys' MPa _n5.!Q ___ 508 ____ 5!_1_·---------~----~--~clic Stre'!9th Coefficient (Tension) K' MPa 986 993 979 cycliCStrengih Coefficient(Co,:np.:e5sTon)~ --~ --K'-- MPa 1686 -1648~-~oo-=_::-__ --===--:~---=-=-=-== Cyclic Strain Hardening Exponent (Tension) - n' 0.11 0.11 0.10 Cyclic Strain Hardening Exponent (Compressionf n' 0.18- __ ().19 ___ 0.19 ---- ~ ------------ - - - -

Tensile Properties After the Incremental Step Testing

Average 505 510

-~- ---- -----

986 1611 0.11_ --0.19

Tensile Sample ID Symbol Units WC1 WC2 WC3 Average Ultimate Tensile Strength Su MPa 787 793 783 788 0.2% Offset Yield Strength (Engineering) ~----_-:S~y::--s~~~M-=o"c-:-P0_a ___ --~50_6 ______ 5_1_2 ___ 5_14 __ ~~------~=-~~--·-_-::_-::_-::_-_ -__ :__ ___ --=-~10~--~ Percent Elongation o/oEL " __ Percent Reduction Area o/oRA % Mon~on~Str~nHa~en~~-o-n~e~n7t_::_::_::_::_::_::_::_::_::_::_::_::n_::_::~--~-~~---~·-=--=-0~.2~0~_-_--_-=o~.1~9=~--~-~~~---~2~0~-----~-~=---~-~-~~~~~-==-----=~~~~ Monotonic Strength Coefficient K MPa 1427 1358 1427 _ 1404

~"M'-'-o::c.d.:.:uc:::lu::..:.s.:c:..o=-cf-=cE=-Ia::..:.s.:.sti"'ci't:..y=:::==:.::..-~------- -~----~=E--~--G~=-=p=-a-+--159~--~ 156 ~-164 ---- -----------~ -~ 160

40

Casting Type


Condition 7 3" Y-Biocks

' "< ,,.,., -''!f-c: ,_.'>,?': <

28 58 68 98 Average 252 244 255 250

ID Units SA 6A ~~~~~-~~~-------------------~~~~~~~----~~----~~----~----~~----~=---~~~~ 1~8::-r:-in_e::-11 -o-:H-'-ar--cd:-n-'-es"-'s_,('=C-'-R-=-=S_,_) ~"""'" ___ ----------~------------'-'Hc:=B-=::S-=-3=-00=-:0=-+ __ _:2::::5=5 -~---24_4 ________________ _ ---

---~------ -- . --------- --Brinell Hardness (Foundry) HBS3000 229 241 248 235 241 248 240

;o-w:-•\' ",,._ "•' -"? "j "),•,

Tensile Properties Sam_pJe ID Svmbol Units 85A 86A 828 Foundry_ Value Ultimate Tensile Strength _ -~---- MP~ __ 78_1_ ____ __I§§_ _____ ]__76 ___ ?_7~------ _ __ 0.2% Offset Yield Strength (Engineering) ______ §~_ MPa~-~§ _____ 4?_1 ____ ~34_~--~-~ _______ _ Percent Elongation -------~--------_______!oEh_ __ % _____ 3.9_ -----~ _____ !:§ __ __§_.() _______ _ Percent Reduction Area %RA % 3.6 4.3 3.9 ---1::-:-"'-'---:----:-"-~'-':--'--'--'--'--=-:C----~------~-----~-------- ---------~--- ----------- -----------------Monotonic Strain Hardening Exponent _________ n _________ ~?§. _ __ 0.2~-- ___ _Q:~.§. ______ _::-:::- ________________ _ Monotonic Strength Coefficient K MPa 1641 1538 1586 ---Modulus of Elasticity - ---E-- GPa 17!r --- -176 - - 172---- -w-6 - - -- -- -

Incremental Step Test (1ST) Results Tensile Sample ID Symbol Units 868 898 0.2% Offset Yield Strength (Eng.- Tension) ____ _§!~_· ___ MPa __ --~85 ______ ...:.49=-1'----------------- _________________________ _

- - -

--- -

-- ---

Average

4.4 3.9

0.25 1588 174

Average

0.2% Offset Yield Strength (E'!9:_- Compression) Sys' MPa 485 _4~9~0 __________ _

~~trength Coefficient (T ensio!!L__ ___________ _K_' ~--- MPa __ =:-111z -~= ~_1!!Z____ -~-----=~~===~----~ ~~-=- -- -~~~~=--Cyclic Strength Coefficient (Compressionl ____________ ~------ MPa ___ _'1593 ______ 1689 ____________________________ _

488 487 1117 1641

Cyclic Strain Hardening Exponent (Tension) n' 0.14 0.13 t-=-<~=---=-"-='-'--'-'-=-'=-=-:-:.:.:s~-r_:-_:c_:_::_:_:~c=_:_:_=-:_::_:2_._,_ --------------- --------~--- - ---------" ------ ---- - " -- -------Cyclic Strain Hardening Exponent (Compression) n' 0.19 0.20

Tensile Properties After the Incremental Step Testing Tensile Sample ID Symbol Units 868 898 Ultimate Tensile Strength -------~- --~-- MP~ 681 _____ ]~()___________ _ _ _ _ _ _ ___ _ 0.2% Offset Yield Strength (Engineering) ___ Sys _ MPa __ 48~-- __ 497 ____________ ________ ___ _ Percent Elongation %EL % 2.0 3.0 Percent Reduction Area ----- o/oRA 0/o 1 :g-----~2]}~~--------- --------------------- ---=-= -------- -------------------------------~--- --- -----------------~--- -------- ----- --MonotonicStrainHardening_Exponent ______ _~!____________ 0.21 __ 0.22 _____ ____ __ _ __ Monotoni~ Strength C~~ffi<;i~n!__________ _ ____ K_ MPa 1441 1524 _ Modulus of Elasticity E GPa 158 161

-

0.13 0.20

Average 705 490 2.5

-- ----- --- -2.4

0.21 1482 160

41

Condition 8 Casting Type 1" diameter circular bars

' ,,

Brinell Hardness Results 10 Units II 1-3 111-7 II 2-4 112-5 II 3-2 II 3-8 Average

--Brinell Hardness (CRS) HBS3000 255 265 257 265 250 257 258 ·------- --- --- ------------Brinell Hardness (Foundry) HBS3000 --- --- --- --- --- --- ---

'!- >', , I - ,, t' < ,,,, ''•Yi I'~' ,

Tensile Properties Sample 10 Symbol Units II 1-3 II 1-7 112-4 Avera_g_e Ultimate Tensile Strength Su MPa 864 868 856 863

,,-~~---~----~- -- ~---·---- ----- ------

0.2% Offset Yield Strength (Engineering) ~ MPa 471 475 478 475 - ------------ ------- ----------

Percent Elongation %EL % 6.3 6.2 6.4 6.3 Percent Reduction Area %RA % 6.2 5.7 5.3

'-cl-

5.7 -~--~-----

Monotonic Strain Hardening Exponent n 0.26 0.25 0.25 0.25 - . ---- --------~-------

Monotonic Strength Coefficient K MPa 1793 1765 1710 1756 Modulus of Elasticity GPa -- -------------------·----- ---- --------- --T76 -E 175 175 177

,, 7 -- k ,_ " ·ffi>~ljjll!l.

Incremental Step Test (1ST) Results Tensile Sample 10 Symbol Units II 2-5 II 3-2 II 3-8 Average 0.2% Offset Yield Strength (Eng.- Tension) ,-~-~MPa_ 500 502 498 500

-------------------------------- ----------------- --- ---- --

0.2% Offset Yield Strength (Eng. - Compression) Sys' MPa 505 507 502 504 -------------------------------------- --- -------- - -

Cyclic Strength Coefficient (Tension) K' MPa 1220 1255 1234 1237 ---------------------- ------------------------------------------ ·---------- --

C_yclic Strength Coefficient (<;:ompression) K' MPa 1786 1827 1855 1823 ----·------- --0.14 ----0.15----o.:rs·-------- ------- -- ------ ----

Cyclic Strain Hardening Exponent (Tension) n' 0.15 ------------------ --

Cyclic Strain Hardening Exponent (Compression) n' 0.20 0.21 0.21 - ---------6:2T

' ,,., ,<,.,

Tensile Properties After the Incremental Step Testing Tensile Sample 10 Symbol Units II 2-5 II 3-2 Average Ultimate Tensile Strength ____ Su MPa 844 803 823

----------~--- -- -- --------- --- -g1% Offset Yield Streng!~:! (Engineering) ___ -~~------~E_a __ 506 499 502 t--------- ----~----------------------------- -------- ---- ---- ---- -----------~-- - -·

Percent Elongation _____________ %EL % _ 4.9 3.3 4.1 f------7·~--·---- -~----------~-~--~--- ------·~-

Percent Reduction Area %RA % 4.5 3.4 4.0 ·----- ------------ -----·-------,.-~------ --0.24- -- -0.24 ---~-- ----- ---- -----~---~-- ---- - --------

Monotonic Strain Hardening ~xponent .. _______ n ____________________ 0.24 - --- .. ----------~---. ·- -------. ------- -------- ----- ---

Monotonic Strength Coeffi~i~!1_L _________________ K MPa 1738 1786 1762 -----·------~---- -- T63-- - -·-T6C ----~ ---~ --· ------- ------------ ---. - - -----

Modulus of Elasticity E GPa 162

42

APPENDIX C:

INDIVIDUAL STRAIN-LIFE FATIGUE TEST RESULTS

43

Fatigue Test Report

Customer: Ductile Iron Society Material: Low Hardness, Condition #2

Test Program: S7621L Date: 11-May-99

Test Conditions: Fully Reversed (R = -1.0), Strain Control, Triangle Waveform at a constant frequency of 1Hz.

Fatigue Test Data

Specimen Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) I (HB) Amplitude at Half Life (ksi) at Half-Life Cycles_il)

Test bars from near edge of plates. D·5 0.3140 185 0.30% 100.59 0.196% 2,725 (2) D-6 0.3135 179 0.50% 114.93 0.537% 1,115

D-27 0.3140 197 0.70% 138.60 0.843% 711 D-12 0.3115 187 1.00% 141.65 1.432% 299 D-1 0.3130 187 0.25% 112.63 0.048% 34,510 D-3 0.3135 183 0.30% 119.89 0.120% 11,955

D-22 0.3130 195 0.50% 126.82 0.483% 1,436 D-29 0.3140 197 0.70% 129.50 0.876% 464 D-2 0.3135 185 1.00% 132.56 1.469% 166

D-23 0.3135 187 0.25% 113.00 0.048% 28,564 D-18 0.3130 187 0.20% 96.19 0.015% 109,007 D-19 0.3140 179 0.18% 87.81 0.009% 515,837 D-28 0.3155 197 0.30% 123.49 0.106% 9,375 D-26 0.3140 195 0.20% 96.57 0.013% 137,850 D-20 0.3120 179 0.18% 88.14 0.020% 494,009 D-9 0.3135 180 0.15% 70.73 0.018% 5,000,000 NF D-13 0.3120 0 Spare Specimen · Not Tested D-14 0.3140 0 Spare Specimen · Not Tested

Notes: 1. NF = No Failure, Data not used in the analysis 2. The extensometer slipped during the test on sample D-5. Data from this sample were not used in the analysis.

44

Fatigue Test Report

Customer: Ductile Iron Society Test Program: S7621L Material: Low Hardness, Condition #2 . Date: 11-May-99

Specimen Group: Fully Reversed (R = -1.0), Strain Control, Triangle Waveform Test Conditions at a constant frequency of 1Hz.

Fatigue - Life Calculations

The fatigue life relationships listed in ASTM E606, Paragraph Xl.l.2 were calculated using regression techniques to solve for fatigue life as a function of stress and strain. The regression equations were then converted to the following standard forms:

ilcr ilEP

dE Nf

2Nf

ilcr/2 = 104.9059 * (2Nf)A·0.0621

dEp/2 = 0.5059 * (2Nf)A·0.6827

ilE/2 = 0.0041 * (2Nf)A·0.0621 + 0.5059 * (2Nf)A·0.6827

Where the variables are:

= true stress range =true plastic strain range =true strain range = cycles to failure = reversals to failure

and the calculated constants are:

cr' f = fatigue strength coefficient b = fatigue strength exponent

E' f = fatigue ductility coefficient c =fatigue ductility exponent E =Young's modulus

= 723.3262 MPa = ·0.0621 = 0.5059 = ·0.6827

= 177202 MPa

45

Fatigue Test Report

Customer: Ductile Iron Society Material: Medium Hardness, Condition #4

Test Program: S7621l Date: 11-May-99


Fatigue Test Data

Specimen Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) I (HB) Amplitude at Half life (ksi) at Half-life Cycles (1)

Test bars from near edge of plates. WB-27 0.3150 241 0.30% 131.08 0.080% 20,244 WB-7 0.3130 241 0.50% 147.99 0.408% 1,846 WB-4 0.3120 226 0.70% 148.53 0.797% 416

WB-13 0.3160 229 1.00% 156.62 1.376% 215 WB-8 0.3150 229 0.25% 115.38 0.040% 46,038

WB-23 0.3145 231 0.30% 131.16 0.080% 17,258 WB-25 0.3150 226 0.50% 134.61 0.455% 1,156 WB-15 0.3150 229 0.70% 149.34 0.803% 618 WB-24 0.3140 229 1.00% 159.39 1.364% 155 WB-17 0.3145 229 0.25% 114.66 0.041% 16,713 WB-16 0.3150 229 0.20% 97.81 0.012% 265,868 WB-29 0.3140 241 0.18% 88.93 0.007% 1,367,155 WB-28 0.3155 229 0.20% 96.41 0.014% 161,749 WB-9 0.3150 229 0.18% 88.21 0.009% 5,000,000 NF

WB-26 0.3130 229 0.50% 156.02 0.614% 2,503 WB-18 0.3140 231 0.20% 98.45 0.008% 275,279 WB-22 0.3160 0 Spare Specimen · Not Tested WB-10 0.3155 0 Spare Specimen · Not Tested

Notes: 1. NF = No Failure, Data not used in the analysis

46

Fatigue Test Report

Customer: Ductile Iron Society Test Program: S7621L Material: Medium Hardness, Condition #4 . Date: 11-May-99


Fatigue - Life Calculations


~cr

~EP

~E

Nf 2Nf

ft..cr/2 = 129.8076 * (2Nf)~-0.0737

~Ep/2 = 0.4941 * (2Nf)A·0.6862

~E/2 = 0.0053 * (2Nf)~-0.0737 + 0.4941 * (2Nf)~-0.6862





E' f =fatigue ductility coefficient c =fatigue ductility exponent E =Young's modulus

= 895.0234 MPa = ·0.0737 = 0.4941 = ·0.6862

= 168238 MPa

47

Fatigue Test Report

Customer: Ductile Iron Society Material: High Hardness/Thick Section, Condition #7


Test Conditions: Fully Reversed {R = -1.0), Strain Control, Triangle Waveform at a constant frequency of 1Hz.

Fatigue Test Data

Specimen Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) I {HB) Amplitude at Half Life {ksi) at Half-Life Cycles (1)

Test bars from near edge of plates. 8-48-A 0.3160 252 0.30% 127.81 0.097% 16,524 8-9A-A 0.3165 252 0.50% 138.28 0.445% 541 (2) 8-4A 0.3155 252 0.70% 158.98 0.775% 679 8-6A 0.3170 244 1.00% 157.79 1.383% 174

8-8A-8 0.3150 244 0.25% 114.47 0.047% 30,421 8-68 0.3170 244 0.30% 126.44 0.107% 12,249 8-58 0.3170 255 0.50% 146.61 0.427% 1,445 8-78 0.3170 241 0.70% 155.71 0.801% 493

8-88-8 0.3150 241 1.00% 163.86 1.357% 60 8-88-A 0.3150 241 0.25% 114.80 0.048% 25,421 8-2A 0.3165 244 0.20% 97.96 0.013% 175,922

8-48-8 0.3145 252 0.18% 89.71 0.008% 215,936 8-98 0.3150 252 0.50% 146.06 0.430% 1,330

8-8A-A 0.3155 244 0.20% 97.93 0.014% 80,876 8-28 0.3170 241 0.18% 88.62 0.009% 89,964 8-5A 0.3155 248 0.15% 75.19 0.004% 5,000,000 NF 8-3A 0.3160 0 Spare Specimen · Not Tested

8-9A-8 0.3150 0 Spare Specimen · Not Tested

Notes: 1. NF = No Failure, Data not used in the analysis 2. The extensometer slipped during the test on sample 8-9A-A. Data from this sample were not used in the analysis.

48

Fatigue Test Report

Customer: Ductile Iron Society Test Program: S7621L Material: High Hardness/Thick Section, Condition #7 Date: ll·May-99

Specimen Group: Fully Reversed (R = ·1.0), Strain Control, Triangle Waveform Test Conditions at a constant frequency of 1Hz.

Fatigue· Life Calculations


~cr

~&p

~&

Nf 2Nf

~cr/2=cr'f * (2Nf)Ab

~cr/2 = 142.5936 * (2Nf)A·0.0871

~&p/2 = 0.5725 * (2Nf)A·0.7283

~&/2 = 0.0056 * (2Nf)A·0.0871 + 0.5725 * (2Nf)A·0.7283


=true stress range =true plastic strain range =true strain range = cycles to failure = reversals to failure


cr' f b

t:' f c E

= fatigue strength coefficient = fatigue strength exponent

=fatigue ductility coefficient =fatigue ductility exponent =Young's modulus

= 983.1829 MPa = ·0.0871 = 0.5725 = -0.7283

= 174444 MPa

49

Fatigue Test Report

Customer: Ductile Iron Society Material: High Hardness, Condition #8


Test Conditions: Fully Reversed (R = ·1.0), Strain Control, Triangle Waveform at a constant frequency of 1Hz.

Fatigue Test Data

Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) (HB) Amplitude at Half Life (ksi) at Half·Life Cycles (1)

11-2-5 0.3140 266 0.30% 128.93 0.09~ 23,623 11-1-12 0.3140 266 0.50% 150.07 0.416% 1,809 11-1-5 0.3155 269 0.70% 160.82 0.778% 693 11-2-6 0.3145 269 1.00% 172.40 1.329% 190 11-3-3 0.3155 269 0.25% 117.39 0.045_% 30,544 11-2-2 0.3160 269 0.20% 100.60 0.012% 143,352 11-1-9 0.3140 266 0.15% 75.51 0.004% 5,000,000 NF 11-2-3 0.3160 269 1.00% 171.92 1.334% 389 11-1-6 0.3150 269 0.70% 159.71 0.784% 650 11-1-2 0.3160 269 0.50% 136.97 0.464% 170 (2)

11-3-11 0.3150 266 0.30% 128.15 0.098% 21,715 11-1-10 0.3140 269 0.25% 117.96 0.038_% 80,729 11-2-9 0.3155 269 0.20% 98.99 0.013% 227,582 11-3-4 0.3160 269 0.50% 149.62 0.420% 1,826 11-1-4 0.3145 269 0.18% 91.22 0.008% 5,000,000 NF 11-2-7 0.3160 269 0.5Q% 159.87 0.620% 2,663 11-3-7 0.3135 269 0.20% 94.13 0.037% 5,000,000 NF 11-1-8 0.3140 0 S_l)_are Specimen - Not Tested

Notes: 1. NF = No Failure, Data not used in the analysis 2. The extensometer slipped during the test on sample 11-1-2. Data from this sample was not used in the analysis.

50

Fatigue Test Report

Customer: Ductile Iron Society Test Program: S7621L Material: High Hardness, Condition #8 Date: ll·May-99


Fatigue • Life Calculations


8cr 8ep

8E Nf

2Nf

8cr/2=cr'f * (2Nf)"b

8cr/2 = 149.6236 * (2Nf)"·0.0829

8ep/2 = 0.8125 * (2Nf)"·0.7219

8EI2=[cr'f/E] * (2Nf)"b + e'f * (2Nf)"c

8e/2 = 0.0061 * (2Nf)"·0.0829 + 0.8125 * (2Nf)"·0.7219





e' f =fatigue ductility coefficient c =fatigue ductility exponent E =Young's modulus

= 1031.6547 MPa = ·0.0829 = 0.8125 = -0.7219

= 169617 MPa

51

Customer: Ductile Iron Society Material: All Test Data

Fatigue Test Report

Test Conditions: Fully Reversed (R = -1.0), Strain Control, Triangle Waveform

at a constant frequency of 1Hz.

Fatigue Test Data

Test Program: -=S~76~2;;.;;1;=L-=-=--Date: 23-Feb-00

Specimen Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) (HB) Amplitude at Half Life (ksi) at Half-Life Cycles

Condition #2 D-5 0.3140 185 0.30% 100.6 0.196% 2,725 D-6 0.3135 179 0.50% 114.9 0.537% 1,115

D-27 0.3140 197 0.70% 138.6 0.843% 711 D-12 0.3115 187 1.00% 141.7 1.432% 299 D-1 0.3130 187 0.25% 112.6 0.048% 34,510 D-3 0.3135 183 0.30% 119.9 0.120% 11,955

D-22 0.3130 195 0.50% 126.8 0.483% 1,436 D-29 0.3140 197 0.70_% 129.5 0.876% 464 D-2 0.3135 185 1.00% 132.6 1.469% 166

D-23 0.3135 187 0.25_% 113.0 0.048% 28,564 D-18 0.3130 187 0.20_% 96.2 0.015% 109,007 D-19 0.3140 179 0.18.%_ 87.8 0.009% 515,837 D-28 0.3155 197 0.30% 123.5 0.106% 9,375 D-26 0.3140 195 0.20% 96.6 0.013% 137,850 D-20 0.3120 179 0.18% 88.1 0.020% 494,009 D-9 0.3135 180 0.15% 70.7 0.018% 5,000,000

Condition #4 WB-27 0.3150 241 0.30% 131.1 0.080% 20,244 WB-7 0.3130 241 0.50% 148.0 0.408% 1,846 WB-4 0.3120 226 0.70% 148.5 0.797% 416

WB-13 0.3160 229 1.00% 156.6 1.376.%_ 215 WB-8 0.3150 229 0.25% 115.4 0.040% 46,038

WB-23 0.3145 231 0.30% 131.2 0.080% 17,258 WB-25 0.3150 226 0.50% 134.6 0.455% 1,156 WB-15 0.3150 229 0.70% 149.3 0.803% 618 WB-24 0.3140 229 1.00% 159.4 1.364% 155 WB-17 0.3145 229 0.25% 114.7 0.041% 16,713 WB-16 0.3150 229 0.20% 97.8 0.012% 265,868 WB-29 0.3140 241 0.18% 88.9 0.007% 1,367,155 WB-28 0.3155 229 0.20% 96.4 0.014% 161,749 WB-9 0.3150 229 0.18% 88.2 0.009% 5,000,000

WB-26 0.3130 229 0.50% 156.0 0.614% 2,503 WB-18 0.3140 231 0.20% 98.5 0.008% 275,279

52

Customer: Ductile Iron Society Material: All Test Data

Fatigue Test Report


Fatigue Test Data, continued

Test Program: -::S-:::-76.;;:2;;.:;1:-::L=-=--Date: 23-Feb-00

Specimen Diameter Hardness Maximum Strain Stress Range Plastic Strain Range Total ID (in.) (HB) Amplitude at Half Life (ksi) at Half-Life Cycles

Condition #7 8-48-A 0.3160 252 0.30% 127.8 0.097% 16,524 B-9A-A 0.3165 252 0.50% 138.3 0.4-45% 541 B-4A 0.3155 252 0.70% 159.0 0.775% 679 8-6A 0.3170 244 1.00% 157.8 1.383% 174

8-8A-B 0.3150 244 0.25% 114.5 0.047% 30,421 8-68 0.3170 244 0.30% 126.4 0.107% 12,249 8-58 0.3170 255 0.50% 146.6 0.427% 1,445 8-78 0.3170 241 0.70% 155.7 0.801% 493

8-88-8 0.3150 241 1.00_% 163.9 1.357% 60 8-88-A 0.3150 241 0.25% 114.8 0.048% 25,421 8-2A 0.3165 244 0.20% 98.0 0.013% 175,922

8-48-8 0.3145 252 0.18% 89.7 0.008% 215,936 8-98 0.3150 252 0.50% 146.1 0.430% 1,330

8-8A-A 0.3155 244 0.20% 97.9 0.014% 80,876 8-28 0.3170 241 0.18% 88.6 0.009% 89,964 8-5A 0.3155 248 0.15% 75.2 0.004% 5,000,000

Condition #8 11-2-5 0.3140 266 0.30% 128.9 0.099% 23,623

11-1-12 0.3140 266 0.50% 150.1 0.416% 1,809 11-1-5 0.3155 269 0.70% 160.8 0.778% 693 11-2-6 0.3145 269 1.00% 172.4 1.329% 190 11-3-3 0.3155 269 0.25% 117.4 0.045% 30,544 11-2-2 0.3160 269 0.20% 100.6 0.012% 143,352 11-1-9 0.3140 266 0.15% 75.5 0.004% 5,000,000 11-2-3 0.3160 269 1.00% 171.9 1.334% 389 11-1-6 0.3150 269 0.70% 159.7 0.784% 650 11-1-2 0.3160 269 0.50% 137.0 0.464% 170

11-3-11 0.3150 266 0.30% 128.2 0.098% 21,715 11-1-10 0.3140 269 0.25% 118.0 0.038% 80,729 11-2-9 0.3155 269 0.20% 99.0 0.013% 227,582 11-3-4 0.3160 269 0.50% 149.6 0.420% 1,826 11-1-4 0.3145 269 0.18% 91.2 0.008% 5,000,000 11-2-7 0.3160 269 0.50% 159.9 0.620% 2,663 11-3-7 0.3135 269 0.20% 94.1 0.037% 5,000,000

53

Fatigue Test Report

Customer: Ductile Iron Society Test Program: S7621L Material: All Materials Combined Date: 11-May-99

Test Conditions: Fully Reversed (R - ·1.0), Strain Control, Triangle Waveform at a constant frequency of 1Hz.

Fatigue • Life Calculations

The fatigue life relationships listed in ASTM E606, Paragraph X1.1.2 were calculated using regression

techniques to solve for fatigue life as a function of stress and strain. The regression equations were then converted to the following standard forms:

/'icr/2 = 140.8964 * (2Nf)A·0.0844

0.5988 * (2Nf)A ·0. 7073

/'iE/2 = 0.0057 * (2Nf)A·0.0844 + 0.5988 * (2Nf)A·0.7073

Mr &p

/'iE Nf

2Nf


= true stress range = true plastic strain range = true strain range = cycles to failure = reversals to failure


a' f = fatigue strength coefficient b = fatigue strength exponent

E' f = fatigue ductility coefficient c = fatigue ductility exponent E = Young's modulus

= 971.4807 MPa = ·0.0844 = 0.5988 = ·0.7073

= 169617 MPa

971.4807 971.4807

169617 169617

54

875

• 850 ro a.. 825 ~ -..c 800 -C> c: 775 IV ....

U5 750 ~ ·c;;

725 c: IV 1- 700 2 ro

~ 675

5 650 u ·c:

625 0 -0 c: 600 0 ~

575

550 180 200 220 240 260 280

Brinell Hardness (HBS3000)

Figure 10: Ultimate tensile strength before and after cyclic tests as a function of hardness.

540

520

500

- 480 ro a.. ~ - 460 ..c OJ c: 440 Q) .... -(/)

420 u Q)

>= 400 ~ 0 N 0 380

360

340

320 180

•

200

__._ Monotonic Yield Strength in Tension (Before Cyclic Testing) ~ Cyclic Yield Strength in Tension -e- Cyclic Yield Strength in Compression ~- Monotonic Yield Strength in Tension (After Cyclic Testing)

220 240 260


280

Figure 11: 0.2% offset yield strength before and after cyclic testing as a function of hardness.

19

-::R. 0 -c .Q -ro Ol c 0 w

16

14 • 12

10

8

6

4

2 -+-- Monotonic Percent Elongation (Before Cyclic Testing)

--...- Monotonic Percent Elongation (After Cyclic Testing)

o+=======~====~======~======~----~ 180 200 220 240 260 280


Figure 12: Percent elongation before and after cyclic testing as a function of hardness.

180

175

-ro 170 a.. Q_ ~ :!J 165 U) ro w - 160 0 !/) ::J ::J "0 0 155 ~

150

145 180

• • •

• • • •

• ------

y ---------~~ ------~--- y

__..... Monotonic Modulus of Elasticity in Tension (Before Cyclic Testing)

- .. - Monotonic Modulus of Elasticity in Tension (After Cyclic Testing)

200 220 240 260


280

Figure 13: Modulus of elasticity before and after cyclic testing as a function of hardness.

20

2000

1800

1600 ro Q.

~ 1400 c Q)

"13 IE 1200 Q) 0 (.)

.I::. 0, 1000 c Q) ....

Ci5 800

600

400 180

•

•

---- Monotonic Strength Coefficient in Tension (Before Cyclic Testing)

__....__ Monotonic Strength Coefficient in Tension (After Cyclic Testing)

200 220 240 260


280

Figure 14: Strength coefficient before and after cyclic testing as a function of hardness.

2000

1800

1600 -ro Q.

~ 1400 -c Q) "13 1200 IE Q) 0 () 1000 .I::. 0, c Q) 800

.!::> (f)

600

400

180

.. .......-· . .......-· .........

. .......-· . .......-·

1111 ......

.......- .........

•

.1111

. .......-· .........

--11!-8....- . .., ___ _ ~------ ... . ----- ... ••

-T""-------...

---- Monotonic Strength Coefficient in Tension (Before Cyclic Testing)

-...-- Cyclic Strength Coefficent in Tension

--.- Cyclic Strength Coefficient in Compression

200 220 240 260


280

Figure 15: Monotonic and cyclic strength coefficients as a function of hardness.

21

0.26

0.24

0.22 :s - 0.20 c: Q) c: 0 a. 0.18 X w C)

0.16 c: ·c: Q) "0 0.14 .... 111 I c: 0.12 ·~ -en

0.10

0.08

0.06 180

• •

-e- Monotonic Strain Hardening Exponent in Tension (Before)

_ .. _ Monotonic Strain Hardening Exponent in Tension (After)

200 220 240 260


280

Figure 16: Monotonic strain hardening exponent before and after cyclic testing as a function of hardness.

0.26

0.24

0.22 ~

..s 0.20 -c: Q) 0.18 c: 0 a. 0.16 X w C)

0.14 c: ·c: Q)

0.12 -e 111 I 0.10 c: ·~

0.08 Ci5

0.06

0.04

0.02 180

-· --·---·-·

•

. ._ .... ----.

•

-· •

·------~---------- . --. __ __.-- .

-y---

---- Monotonic Strain Hardening Exponent in Tension (Before)

-•- Cyclic Strain Hardening Exponent in Tension

--11- Cyclic Strain Hardening Exponent in Compression

200 220 240 260


280

Figure 17: Monotonic strain hardening exponent before cyclic testing and cyclic strain hardening exponents as a function of hardness.

22

600

500

~400 ~ II) II)

~300 C/)

(I)

2 1-200

100

0

0.000 0.002 0.004

--..- Monotonic Tension (Before Cyclic Testing) ......-- Cyclic Tension -+- Cyclic Compression --<>- Monotonic Tension (After Cyclic Testing)

0.006 0.008 0.010 0.012 0.014

True Strain

a) Lowest Hardness Sample (186 HBS)

0.016

800.-----------------------------------------------,

600

200

- Monotonic Tension (Before Cyclic Testing) -y- Cyclic Tension

- Cyclic Compression --<>- Monotonic Tension (After Cyclic Testing)

0

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016

True Strain

b) Highest Hardness Sample (270 HBS)

Figure 18: Predicted stress-strain curves for a) low hardness (Condition #2), and b) high hardness materials (Condition #8).

23

1.50 .-------------------------------,

- 1.25 ~

~ s 1.00 Q) "0 ::J

;t:::

~ 0.75

4: c

~ 0.50 CIJ

jg 0 1- 0.25

180

•

·~------· ~~ • • --------· . ------------

200 220

•

240


- 500 Reversals

____._ 1000 Reversals

· · • · · · 50000 Reversals

-'9-- 100000 Reversals

--.- 5000000 Reversals

260

Figure 19: Predicted cyclic strain at selected fatigue lives as a function of hardness.

280

24

APPENDIX A:

MICROSTRUCTURES

25

Condition

1

. .• . . .. ·. .. . ... • e ~· • tl • • •• • • . · •• e. •. • ., •. • • ·~ .. ·.~ . ~ . • 4 • • .·• l>. • ' •

)• •••. ~If• .. •· ••• • " # ............. ~

• II!•; . tat·. •.. ... • . ~.. ; .. - . . . . . .. .. . . ,. , ..... . ._· •· . ;,, -· ... •· .. · . . ; \. .• -.•. . •••••••• • • • • • • • • ••

' . ..... , ...• -... . . .. ... .. . .. .. .• • 4t • .• .. . .• . '. .• . ..• ·. .

As-Polished, 1 OOx

2% Nital, 100x

Hardness Material Type Yield Strength % Nodularlty (HBS3000) (MPa)

186 1• round 356 94

%Ferrite

37

26

Condition

2

• • • • • . : . . . -·;: . . . . . -; ' . . .• : . ·~ . ... . •. ·: . . : . . . . , . . .. .. . . . . . ' :-• _,._ .. . . . ....... ' . ... . .. . • • . • • • ~ A ... . .. . . . . ... . . . .•" . . •.

• • ., • . . • ' ••••• ·~ ... p..

• lit • • If • . • . . ...... . ... . ~ . ., . . . ~ : •.... ~ . ~

• •. .. It ·• . • I • •

. • • • - ' ••.••••• #

•• • •••• ·• • ••••• ~ *"

As-Polished, 1 OOx

2% Nital, 100x

Hardness Material Type Yield Strength % Nodularity (HBS3000) (MPa)

189 1·Y-block 368 95

%Ferrite

51

27

. ·•.·· •. . . ·,· I . .,,, . . . . . ,·.. . . " .;,. .. ; : ~:· .. • ..... ..• . . ' . .. . . . •... . •. . .... ... .. ··~. . .. . . . . .. . . .. .~ ~ ...... • I!.. .... •• , • . • •

• • -~... .. • • • . •• & .••. .• ·•· : .. ... e .• • ~. t •.... • • • • •••• , ... . ' .. , .. , . . ... ·.•. .. . ..

.. · it • . • . • • •• I e • • • • • • • .! ' • • ••• •• ,., •••••• J •• • • • •• • • • ••• ••• • • • • • . !l • •• t • .• ... . • •• I • '· .... ., -. . .....~ ..

• • •• ., • •• • • • 11 •• . .. . . . . . . .. '. As-Polished, 1 OOx

2% Nital, 1 OOx

Hardness Material Type Yield Strength •t. Nodularity %Ferrite Condition (HBS3000) (MPa)

3 205 2"Y-block 389 85 35

28

• . • . . ··: .- •. -=-- .... ·- .•. ··•·· .. . . '...... . •

... • .' .... .r • .. • • : .... ~ . . • ·-· ·-·. .. . •. • • •• • r-:····· . • .. ·e ..... . • • • • • • •• . . . ' .. . ' .. . . . . . .. . . Ill .. • .... ~. ., • ... '.' • • • •• ., .. • ,. a . ,,. t• '• •. • • # • • • • • ..... • : ·.. •• ·-r~··· • ··. • •• • • • • "'# I •• , e . • ' • •. Ill •• .. a ,. • . ..... ...... . .. . .. •.. .• • . • t . ... . • • ••• .. ""'- . . .. .• . . . .. . . ., . •. . .... . . l•. • '~~ •. • ~ • ..... • • • •. • •. • • ,.. •. . .. •. . ... •. ~e·'' . • • • , .. ..

•• • • . ••• ·• •• j • ~· ••• • • • '.. . .... ! . . . .. . . .. . ... . ·• .. .. . . .. ,. , . '. .. .. ~... . '. . ....... . . ·-··· . .. . . . . . . . '" . .. . . .. .

••• -t • -~. • • :. • • ; • • :- •: .. ~ . - .. . .. .··.. . • " . . . • ·!'.. ... .·. .. • .,

. .. ..

• As-Polished, 100x

2% Nital, 1 OOx

Hardness Material Type Yield Strength % Nodularity %Ferrite Condition (HBS3000) (MPa)

4 228 2·Y-Biock 439 91 25

29

Condition

5

••••• .. ·. ., .. . . ~ ~ -- .. ·~, .•

... . . .. . ...... ~ . . . . , . . .

. . ,. ... . . \ .. . . •. . . . . . . ......... . .. .•. . . . ·. .. ~ .

. . . ~. . . . . . • •. I •• ". • ••• • .•

t ... •• : ·.:' ·: ••• • •• • • • ••• • • •• • • . .. . ... '\ .. ,. . . ' .. ••• . ~

•• • • ... l •• ,. .. t. • • . . . ~ ..

• •• v .••. : ••• • • 1' • . .... ~

As-Polished, 100x

2% Nital, 1 OOx


236 7/8• Keel bars 419 96

•

%Ferrite

16

30

Condition

6

• . ' . . . .. •• . A\ ~ • - : • • • ••• ---. .... .: . , .. . .· . . ,. . . " .. , ~ .. .

ff. •• •• • • , •••. ·-~ .. . • • •. • .- .+ •• , •

• • • • • • . ' •' ••' ·I

'" . ~ . . ~ . .. . ~ ' .. . ·.. " .· ...._. ....... . . . . . . . .. ' ... ... . . . . . ,. - ~ . .., .• . ..... - •... . ·". . . . . ~: . . ... . . •. . ..· ... . . - . . " •• •. ~ .··.. ~ #/.~. ':. ,. • • . :· ••• ••• • • • ••••• · ... '·. . . . .. . . . . . . .. • '. ~. . . . . . •. . . . . ...... . ... ... . '; .... ' .·• . . ... =·· ......... : . •· ..•

'. . -··· .......... , .. · .. '!. •.. . . • • . • . . · .• ··~ .. - . .: . . - . . .. ,_. As-Polished, 100x

2% Nital, 1 OOx


244 2" Y-block 447 94

%Ferrite

14

31

. \ \ , . ... ... • •• .. ,... • ~~~;.

.. \ . ~

• .. . • . .. . . • . ' ~ • .. ,.

~ _ .. . ' - . e· e• ~ . .

-~ • •• • ' ~ '. -· • • •• .. . ·~ • - .. .. •"

••• • • • • •• • •. , • • • • , • • " • • • •• · ..

·.

As-Polished, 1 OOx

2% Nital, 1 OOx

Hardness Material Type Yield Strength % Nodularity %Ferrite Condition (HBS3000) (MPa)

7 250 3"Y-Biock 437 89 <1%

32

Condition

8

• ...

.. - ~ .. -.· .• . . • . . ... "· ..• !. •.•

·:_.,. \ .... ~ ~ .. , .,

• • #II • • . ...: • ~ . .. . . . . .. \ '. . . •.• . . .. ,. . . ~ ~. . ..•. • .•• "

.. .. . . .. ., . .. , .... , .... • ••• • . fl/f' •

• • • • • As-Polished, 1 OOx

2% Nital, 1 OOx

. .... • I

• • • "e • • • •

~

Hardness Material Type Yield Strength "• Nodularity (HBS3000) (MPa)

270 1" round 474 93

%Ferrite

<1%

33

APPENDIX B:

INDIVIDUAL MECHANICAL TEST RESULTS

34

Condition 1 Casting Type 1" diameter circular bars

Brlnell Hardness Results

J::ID::--:---:-:--:-:----:------~ -------~--~-----~----,~U~n'-"its=---c-+---.,-1-=-=2c-___ ---"-1-=-8'-~---=2=cc-_c_1 ____ ~ 2-9 ~-- 3-4 ___ ---~-7 _ --~v~rage_ Brinell Hardness (CRS) -----------~H-;-;B~So-::3~00~0~+----=1_8=-:7'--------'-185 183 187 189 187 __ _!8_§ __ Brinell Hardness (Foundry) HBS3000

Tensile Properties Sample ID Symbol Units 1-2 1-8 2-1 Average Ultimate Tensile Strength Su MPa ___ -~08 _____ -~ 586 ~-~~-- _____ ~ __ _ __ _ _____ __E)Q1__ 0.2% Q_ffset Yield Stre11_gth (Engineering) __§y_~--- MPa 347 365 357 --------~- __ __}~§_ Pe_r:_cen_!_E!()_11_9ati~_ _ --~-~_!~EL --~-- % _____ !1_.!3__ g:.f! ____ ~ !!1.___ ---~---- _ ____ __ _ 11.9 Percent Reduction Area %RA % 11.3 11.5 10.7 11.1 cc·---~----~- ------~---------- . . ---- c--------~- ------------------- -------------------~ -- --- ----M_~!_l_2tOniC Strain_l:!_arde~illgj.:)(pon~!l_! __________________ _!l_ ________________ 0.1 ?'__ _Q~ _____ _(L1_§___~ __ _____ _ _ 0.17

~~~f-Wa~JriY~~ffi~i-~--~----~ -- ----~~------~-- ----~~- - -i~~-------~*-- --- ------- -- --- -~~~---Incremental Step Test (1ST) Results Tensile Sample ID Symbol Units 2-9 3-4 3-7 Average Q.~_r~_Q1f!~~eld Stre11_gt_~ J~1!9· -Tension) Sys' ---~~- _425 -~--1~~-- 42§__~-- _____ -~-------- __ _1n_ _ 0.2% Offset Yield Strength (Eng. - Compression) Sys' MPa 427 434 423 ___ __1_28 __ ~lie Strength Coefficient (Tension) ------~__E MPa 800 807 772 793 £yclic_ Strength Coe_f!i_~~_lltjgompressiQ!!j ______ ~· MPa __ 111Q___ 1160 ____ !!1Q______ --~~------ ---1147--Cycli~§trai'!_!::!ard~ing Expone!lt (Tension) n' 0.10 0.10 0.10 ----- --0.10--Cyclic Strain Hardening Exponent (Compression) n' _if.16 ____ D.16 ___ o:16 ___________ ~~----- -- ------0.16--

Tensile Properties After the Incremental Step Testing Tensile Sample ID Symbol Units 3-4 3-7 Average

!Jitimate Tensile _Stre11_gt_b __ --~---------- ___ _____§_L!______ MPa__ _ __ ~98 ___ §_8_5 __ ------~~-------------~--------- 592 ~~ ·----- ----·-

Q:?!~_Offset Yield_:)_!r"eng!_h (Eng!ll~ering) -----~---~ys __ -~ MP~-- __ _1_32 _____ 4_17_ --~----- _____________________________ _ 425

Percent Elon~tiorl__~-~-- ------------~--~-%EL ___ -~J'o_ __ _ -~3 _ --~ _1~0~.3--~ _ ~--- _______ _ 9.3 ··--------

p_er_c~n_t_R_e_d_u~~_ll-~r~~ _________________ ll,t'o~-~---~-- % ____ 1_.1_ ________ 8_.3 __ ~-------~---------------- 7.7 --------

Mol1_oton~_§!!"~!l!_!::!a!~ening_ E)(p_Qn~_11_!_ ___ ~- ____ 11 ___________ ~ _0~·~13 ____ 0_.1_3 ______________________ --------~--- __ _ 0.13 ---~~--·

~ono!o_!ljc Stre_11_9!~(;oeff~ie_nt __ ~--~- K MPa 869 855 Modulus of Elasticity -- -- -E--~- GPa ___ f-- -158 ______ 162- --~-- --

862 160

35

Condition 2 Casting Type 1" Y-Biocks

.. +: ~c;':, >"1Jt%&::i : . ,''-~'ill'•:: ·· ·>L+',ll'''' . , · , . ·. : ,, :"'.:,'iii&_, .• ; :;lw£' ··1

Brinell Hardness Results 10 Units 01 c-:------------- ---------- ·-------------- ·--------------~~~-=-·---- -------- [)~ ___ Q~---- __ o_1 _____ _o_5 ___ Q~_ ·--~~-ra_g~ Brinell Hardness (CRS) HBS3000 8-nnefi HarCiness(Foun-drv) _____________ -------- HBS3ooo

201 197 198 180 179 180 189

Tensile Properties Sample 10 Symbol Units 01 02 03 Average Ultimate Tensile Strength Su MPa 606 609 619 611 g]%=6_!fset Yield Strengtt!_(gilgineeri!!9l_--~_: _____ _§}'~_-___ MP~ _ ~~68 -~~---~? __ 369 ____ -_- ~-==~:-==:~-=- - -=~§13~ ~~~<::ent Elongation_ _____ ------ _______ % EL ____ % ______ ! 3. 9 ___ ____1ll __ J_U___ __ __ ___ _ _________ _ _1 ~.I__ Percent Reduction Area %RA % ~.2 __ 12.0 __ ~.1__ ____________________ .. _!~J __ ~onotonic S!!'!L'!!::!ardenTng~xponen!___ ___________ _!1__ _ _______ __Q._!l__ _o. f7' _ __ 0.17_ _ _ _ _ _ _ . 0.17 ~o~!onic Str~_r~_gt~_g_o~_ff~cLe_l'l_t _______ _ _____ !5 _____ MP_i! 876 883 903 ___ _ __ 887 Modulus of Elasticity E GPa -170-- -171- - -168-- 170

Tensile Properties After the Incremental Step Testing Tensile Sample 10 Symbol Units 04 05 06 Ultimate Tensile Strength Su MPa 591 580 --~60:::_1.:___ ____________ _

Average 591 433 0.2% Offset Yield Strength (Engin~ering) Sys MPa __ 429 _ 433 438

---~-------------~----~---

Percent Elongation_____ %EL % 11.3 11.9 11.9 _____________ 11.7 Percent Reduction Area %RA % 11.4 11.1 10.4 Monotonic Strain Hardening Exponent - ---,--- -------- -0.12--o:-11-- 0.12 --···-------------·-- -------

~~~~:~~~t~f!~r~~C_()~lfJcJ~~i----=_~=-===-~~~-=-~-~-~~: = -~~---·=- ~~-=:~-=-~;~:==-=-===~ ==-__:-=-=~====--

10.9 ---------~----

0.11 _!304 ··-155

36

Casting Type

Brinell Hardness Results 10 Brinell Hardness (CRS) Brinell Hardness (Foundry)

Tensile Properties

Units HBS3000 HBS3000


WA1 197

~ > ~ c, '

WA2 197

!&'

WA3 WA16 WA27 WA29 Ave~~ 198 217 207 215 205

187--217 :''''

Sample 10 Symbol Units WA16 WA27 WA29 Average Ultimate Tensile Strength Su MPa 644 624 626 631 ,_ ····----------~-0.2% Offset Yield Strength (Engineering) Sys MPa 401 377 391 -~---~- ______ _390 __ eercent Elongation %EL % _ --~I_____ 9.9 9.5 _____________ .. .. . . ~ ~:Z:._ Percent Reduction Area %RA % 9.1 8.9 8.6 8.9 Monotonic Strain Hardening Exponent n -0.16 __ ().17 ___ 0.16 ----~------~---·- -0.16-Mo-notonic Stre'!9th Coefficient ~----1<---MPa~- - 9~- 938 - ----896- ----- - ··· · ·-·· - -- ---- -- · · - ---924--MOdlrlusoTBasti~----------------~E-----GPa- --168--1-68 ·---~166-- ----- ·····-~ ····---- -- · --168 __ _

Incremental Step Test (1ST) Results Tensile Sample 10 Symbol Units WA1 WA2 WA3 Average 0.2% Offset Yield Strength (Eng.- Tension) Sys' MPa 452 444 445 447 Q.~GZo- off~t '!2eld stre_!l_glil(En~L:_ com~~~sl_o~L~=~d-sys' --==~MP<!~~~ . _ 4~~~----=~:=i46 ~~~=--~4_4_7_~---~------------ :-==-~-~- -- ·-==--119_--_-~}'cl~ §!!.~~gth Co~!fi~it:!n! f!:-e_l"lsi~J'!L ~- _ __ _ _ _ _IS' ___ --~Pa__ 821 f!.!i_ ____ !!_1~-- ___ _ _f!1~--<?~!t?...§!r..t:!l'!91tl__~effi<?!~n~ (Co_l!lp!es~i()J'!L _ ____ __!<~--- ___ _MPa _ .. __ !~L ~ -~-g2] ____ 12_4_1______ _ __ __ __ _______ __12~?-Cypi!C?..§!r:ain_tt_<_udenLng_E_)(p_on~nt (TensionL_~-~~-- ___ _!!_~ _ ----~---- _ 0.1 0 ___ 0._1 0 ____ Q._1Q__ _ __ ~ _ ____ _ _ (): 19_ ... Cyclic Strain Hardening Exponent (Compression) n' 0.16 0.16 0.17 0.16

Tensile Properties After the Incremental Step Testing Tensile Sample 10 Symbol Units WA1 WA2 WA3 Average l~Jitimate Tensile Strengjh Su MPa 636 631 633 ·---·--------·-· ____ J333 _ ~~2%Q!f~E;!t Yield Stre_!!gth (Engineeringl __________ s_ys. MPa __ __1§§_ _____ 445 ----~-445 ·--------~----~---~--~----- .. _ --~!~---!:'~~~~~!9ngati~----~---~------------~-- %~-'=------~ _____ ···--·----··----·-·-----~---------~~-------- _________ _ J=>~~<?~_n_t B_e~~~~~C>.I'! Ar~~ -~-~----~--~---------- __ ~-OjoRJ\_ ________ % ________ _________ ____ ~------···----------- _____________ _ _M()~n<>!C>!1J~~~!ii_n_!:'_ard~_nil1_9~)(p_onent _______________ _l"l ________ -~!~ _____ 0.14__ 0.14_____ _ -----~ _Q-1~---MQ.J'!Otolli~_Stre_~!~. ~-~-ffi~ient_ _____________ -----~ _ _ -~Pa _____ 91Z_ ____ 952 -----~~§____ ___ _ __ _________ _ . _9~~- _ Modulus of Elasticity E GPa 160 155 159 158

37

Casting Type



~-~----~-- ____ ---~-----~-------- Units WB1 _____ W_8_2 __ W_B_~ ___ \,IYB5 ___ W86 ____ WB)~ _A_verage Brinell Hardness {CRS) HBS3000 223 231 241 231 231 212 228 Brinell Hardness {FoundrY) ----------------------HBS3000 ----=---- ------=-:::-- - ---___ --- --=---=-- -- --=._-·- -- -=~=-- -2fi-~241-

Tensile Properties Sample 10 ~mbol Units W83 W85 WB6 Averag_e Ultimate Tensile Streng_th Su MPa 742 736 698 __ 725 __ _ 0.2% Offset Yield Streng!tlj_E=-n _ _,g.__in_e'--'e'--ri_n""g)'--------::-=Sc-<y~s ____ M---=-:-P-'-a--t--- _4'--'4-=-6 ____ __:_4--'-44-=--------::c42--=5'---------------- ___ _ -~_38 __ _

t;;;P:-"e"-'rc=-=e"-'n:'-:t E~l-=-o'-?ng.._,•a::::ti-=-o:_:_n -=--------________ 7%:-::oE=--L~---o::-:yg----+_1=-1-=-.2___ 11.2 8.8 _______________________ "!_!)j_ __ Percent Reduction Area %RA % 8.8 8.9 7.0 8.2 ~notonic Strain Hardening Exponent n 0.18 0.18 0.18 ---------------------==--------0.=-18=-----~otonic Strength Coefficient K MPa 1124 1124 1 062 11 03 Modulus of Elasticity E GPa --~--- 168-~-166- ----------------- 168

Incremental Step Test (1ST) Results Tensile Sample 10 Symbol Units WB1 WB2 WB14 Averag_e 0.2°~_0ffset Yield Strength (Eng.- Tension) ----:----~S-'--ys=:-'------:Mc:cP=a=---1----481 _____ 496 481 _________________ -------~8_6 __ 0.2% Offset Yield Streng!!1 (Eng.- Compression) Sys' MPa 481 502 482 488 CYclic Strength Coefficient (Tension) K' MPa 903 979 883 _____ ---~-~---~- -922 _ Cyclic Strength Coefficient (Compression) K' MPa --~_50_L ___ 1469 ____ 13_7_9 ________ ----------~~- ____ --~1_5_Q_ __ CyclicStrainHardeningExponent(Tension) n' 0.10 0.11 0.10 0.10 Cyclic Strain Hardening Exp_o_n __ e_n_t~(~C_o_m_p-re-~s-s~io-n)--------n-· ---------- -- - o:fs-- ---().17- --0.17- -- -- -- - -- ------- --- -- - - - - o:Ta-

Tensile Properties After the Incremental Step Testing Tensile Sample 10 Symbol Units W81 WB2 WB14 Average

~l!i_l!!ate T_ensile Strength ----,------,-------,-----------==-S-=-u ___ .c.:cM'-=P-=-a'-- _6_38~------'7-=2=--7 __ --,-7-=-04c-_____ ~-------------- _ _ __ _§90 __ t;:0::-.2 __ %_o_O-:-ff-::s::-e_t Y_i_e:-:-ld_S_t_re_n~g~th __ ("-._E_n_.,g_in_e_e_rin~g._,_) ____ ---=-:-S=ys-=--___ M-=-P:--a_--t---48_5 ______ 5 __ 0_4 ____ 4_8_2 __________________________ _j_9_Q__ Percent Elongation %EL % ~~~=--'~~~------------~~-----'--=---~-------------------------------

e:--e_rce~n_tR~ed~u_ct~i_on~A-~~a~~~-~--------%-oRA _____ % __ -+~o~=---~~-~~~--------------------~~ Monotonic Strain Hardening Exponent n 0.17 0.16 0.15 0.16 Monotonic Strength Coefficient K MPa 1158 1186 1083 1142 Modulus of Elasticity E GPa 155 156 162 ---- 158=--

38

Ductile Iron Society

Research Project No. 30

Monotonic and Cyclic Design Data for Ductile Iron Castings

Reported by

John M. Tartaglia, Paige E. Ritter, and Richard B. Gundlach

Climax Research Services Wixom, Michigan

February 23, 2000

ABSTRACT

Data on the low and high cycle fatigue response as well as monotonic (non-cyclic) and cyclic flow properties are required by design engineers for the proper design of many components. Although these properties data are available in SAE standard J1099, June 1998, "Technical Report on Fatigue Properties" for many competing materials, no readily available source exists for such information on ductile/nodular cast iron. Typical tensile and compression properties of ductile iron are well known, but the (1) monotonic and cyclic strength coefficients, (2) strain and stress versus fatigue life (reversal) constants, and (3) the variation in elastic modulus after repetitive cycling have not been published in the open literature or handbooks.

In this study, many of the important constants used by engineers in the design of structural components, i.e., items (1) and (3) above, were determined for eight materials that are representative of the hardness range, nodularity, and nodule sizes typical for ferrite-pearlite SAE grade 05506 nodular iron. Testing included chemistry, hardness, microstructural characterization, tensile testing and incremental step testing of all eight materials. Four of the eight materials were selected for strain-life fatigue testing with fully-reversed axial loading. The selected materials represent the full range expected for this grade of ductile iron. Hardness was used as the principle criterion for selecting and ranking materials to test, with the original cross-sectional area of the castings used as a secondary selection criterion. All mechanical property data were analyzed with respect to the parent hardness and microstructure for each material.

Uniaxial, strain-controlled fatigue testing was chosen for several reasons. Uniaxial loading was chosen due to the uniformity of stress state between the surface and the interior of the specimen; the ability to monitor the stress and strain simultaneously; the ability to measure the tensile and compression data independently (as these values differ for ductile iron); the ability to easily and precisely relate stress-tostrain mathematically; and to be consistent with the manner in which other investigators obtain fatigue data for designers. Traditional bending fatigue testing methods (such as rotational bending or plate bending) and S-N testing (wherein the load is controlled, but the strain is not monitored), violate these necessary conditions. Strain-controlled incremental step testing (1ST) was conducted since it offered an economical and quick way to generate the cyclic strain hardening constants, but strain-life testing was required to obtain the additional life regression constants for design usage.

Although the monotonic properties varied with hardness before and after fatigue testing, cyclic stressstrain properties and fatigue lives remained relatively independent of hardness. All the constants in SAE standard J1099, June 1998, were determined for four of the materials, which represent three hardness levels covering the range in hardness for grade 05506.

INTRODUCTION.

Data on the low and high cycle fatigue response as well as monotonic (non-cyclic) and cyclic flow properties are required by design engineers for the proper design of many components. Although these property data are available in SAE standard J1099, June 1998, "Technical Report on Fatigue Properties" for many competing materials, no readily available source exists for such information on ductile/nodular cast iron.

Many potential applications for ductile iron will subject castings to variable loads and intermittent peak overload stresses. The practice of designing components with finite life expectancies under such conditions is called safe-life design. Strain-life and cyclic stress-strain data are required to design with a safe-life approach; these data are currently unavailable to the public for cast irons. Consequently, safelife designs will not be applied to ductile iron castings, and the use of ductile iron for these applications may have been overlooked.

Furthermore, many components subjected to fatigue loads are notched. The applied stress on the notched component may be below the nominal proportional limit or yield strength of the material and most of the component may behave in an elastic manner; however, the material at the root of the notch can behave in a plastic manner due to the stress concentration where the localized stress exceeds the yield strength. As long as there is elastic constraint surrounding the local plastic zone at the notch, the strains can be calculated more easily than the stress. The fatigue behavior of the material at the root of a notch is best considered in terms of strain, and strain-life data are required to qualify the design of the notched component.

The stress-strain behavior obtained from a monotonic (single cycle to fracture) tension or compression test can be quite different from that obtained under cyclic loading. The yield strength in tension or compression will be reduced after applying a load of the opposite sign that causes inelastic (or plastic) deformation, i.e., loading beyond the proportional limit or yield strength, which is usually encountered in the finite-life region of the fatigue curve. Even one single reversal of plastic strain can change the stressstrain behavior of metals. Soft materials with low strength tend to cyclically harden and hard materials tend to cyclically soften.

Determining the cyclic stress-strain curve is required to quantify the amount that a material will cyclically harden or soften during fatigue cycling. Monitoring both the stress and strain during fatigue testing is necessary to obtain appropriate design data. This is one of the primary reasons why fatigue tests are conducted in strain-control where the strain in the specimen is controlled by the fatigue machine and the stress is monitored. This contrasts with simple S-N (stress versus cycles to failure) fatigue limit testing wherein the load is controlled and the strain is not monitored.

In addition to the necessity of using strain-controlled testing, uniaxial strain-life and incremental step tests are performed to generate the cyclic strain hardening behavior and strain-life regression constants for design usage. Uniaxial strain-life and incremental step tests are desirable over the simple traditional bend testing because accurate design values for ductile iron cannot be determined using those methods. For instance, the accuracy of rotational bend testing relies on the test material having nearly identical tensile and compressive properties. Ductile irons behave very differently in tensile and compressive applications, making these tests of limited usefulness to mechanical behavior modelers and component designers. Furthermore, fatigue properties calculated from plate bend tests are of limited value because the stress state continually changes between the surface and the interior of the specimen, whereas uniaxial testing allows for uniform stress state in the specimen. Incremental step testing is conducted because it offers an economical and quick way to generate the cyclic stress-strain curves from which the cyclic strain hardening constants are calculated. Strain-life testing is required to obtain additional life regression constants for design usage.

This study was conducted under CRS Project S-7621.

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Typical tensile and compression properties of ductile iron are well known, but the (1) monotonic and cyclic strength coefficients, (2) strain and stress versus fatigue life (reversal) constants, and (3) the variation in elastic modulus after repetitive cycling have not been published in the open literature.

The objective of this investigation was to determine many of the important constants used by engineers in the design of structural components , i.e., monotonic and cyclic strength coefficients, strain and stress versus fatigue life (reversal) constants, and the variation in elastic modulus after repetitive cycling, for eight materials that are representative of "typical" ferrite-pearlite SAE grade D5506 nodular iron. Based on this initial determination, four of the eight materials were selected for complete characterization, i.e., including item (2) above. The materials selected represent the full range of properties expected for this grade of ductile iron using hardness as the principle determinant. All data were correlated with the parent hardness and microstructure of each material.

PROCEDURES

DUCTILE IRON CASTINGS

Eight grade D5506 ductile iron heats were supplied by Ductile Iron Society (DIS) member foundries. The objective was to obtain castings that cover the full hardness range for D5506 (187-255 HB) in a range of cast section sizes. The categories were established as follows: three material conditions with nominally 187 HB, two material conditions with nominally 223 HB, and three material conditions with nominally 255 HB hardness. Monotonic and cyclic property tests were conducted on all eight material conditions in an initial survey. Based on the results, four ductile iron heats representative of the overall range of material characteristics for Grade D5506 ductile iron were selected for a subsequent comprehensive survey. The eight sets of castings ranged in cast section size from 25 mm (1 inch) diameter rounds to 75 mm (3 inch) Y-blocks.

CHEMISTRY

A comprehensive chemical analysis was performed on the eight materials. Two samples were removed from the end of a bar for each material. On one sample from each material condition, all outer edges of the casting were either cut or ground off to remove the cast surface before analyzing the carbon content. The other sample was used to determine the other elemental concentrations. Concentrations of fourteen elements were determined by the following methods: carbon and sulfur contents by combustometric methods; copper and magnesium by atomic absorption spectrophotometry; and phosphorus, silicon, manganese, chromium, nickel, molybdenum, aluminum, titanium, cerium, and tin by optical emission spectrometry on a remelted and chill-cast sample. The remainder of the bar was used for hardness testing, tensile testing, and microstructural analysis.

TENSILE TESTS

Three standard round tensile specimens were machined from separate bars for each of the eight ductile iron materials in accordance with ASTM standard E 8-99. The specimens had gauge sections 50 mm (2 inches) long and 13 mm (0.5 inch) in diameter. Both resistance strain gauges and an extensometer were mounted on the specimens. The specimens were tested to fracture in a screw-driven tensile machine.

The ultimate tensile strength, 0.2% offset yield strength, fracture elongation, and percent reduction of area were determined in accordance with ASTM standard E 8-99. The fracture elongations of the specimens were determined by reassembling the specimen halves subsequent to fracture and measuring the final gauge length.

The elastic modulus was determined by linear regression of the stress-strain (gauge) data in the elastic region in accordance with ASTM standard E 111-97. The monotonic strength coefficient (K) and the strain hardening exponent (n) were determined by log true stress-log true strain regression of the

3

extensometer data in the plastic region in accordance with ASTM standard E 646-98. The K and n constants characterize the stress-strain response in a (monotonic) tensile test in the plastic region.

The following parameters based on SAE standard J1099, June 1998, "Technical Report on Fatigue Properties" were determined from the tensile tests:

Sys = 0.2% Offset Yield Strength (engineering) Su =Ultimate Tensile Strength (engineering) %RA = Percent Reduction of Area %EI = Percent Elongation E = Modulus of Elasticity K =(monotonic) Strength Coefficient n =(monotonic) Strain Hardening Exponent

BRINELL HARDNESS

Samples were removed from the grip ends of each tensile specimen after the tensile testing for Brinell hardness measurement. The Brinell measurements were performed in accordance with ASTM standard E10-98 using a 3000 kg load, a 10 mm steel ball, and a 15 second dwell time. The average of three hardness tests was used to provide the baseline for all subsequent comparisons.

METALLOGRAPHY

Metallographic samples were taken from the gauge region of one fractured tensile specimen half and mounted with a transverse polish plane. The samples were polished using conventional methods for ductile cast iron, and etched in 2% nital. The samples were examined optically and the nodularity, nodule count, and ferrite content were measured using computerized automated image analysis techniques.

INCREMENTAL STEP TESTING -INITIAL SURVEY OF CYCLIC PROPERTIES

Three specimens conforming to the requirements of ASTM standard E 606-98 were machioed with gauge length and diameter of 3.81 em (1.5 inches) and 0.95 em (0.375 inch), respectively, for each of the eight material conditions. Incremental step tests (1ST) were performed on an MTS closed-loop servohydraulic machine by cycling the specimens at a series of strain levels until the stress-strain hysteresis loops were stabilized at each strain. Data from these hysteresis curves were used to calculate an average cyclic strength coefficient (K') and the cyclic strain hardening coefficient (n').

The tests were performed in fully reversed strain control using a constant ramp time of 1 0 seconds. The specimens were cycled at ±0.1% increments from ±1.5, ±1.4, ±1.3 ... ±0.2%, and ±0.1% total strain for each "unloading" 1ST block. The specimens were then reloaded starting with ±0.1% total strain and continuing in a similar progression to ±1.5% total strain. The entire process was repeated until the cyclic stress-strain curve was stabilized upon unloading, i.e., no change in the load-strain values between the last two unloading 1ST blocks was observed. The seventh 1ST pass {where one pass unloads from ±1.5% to ±0.1 %, and then reloads from ±0.1% back to ±1.5% total strain) was compared to the sixth pass and analyzed for the cyclic stress-strain curve at saturation.

The following parameters based on SAE standard J1099, June 1998, "Technical Report on Fatigue Properties" were determined from the incremental step tests:

n = Cyclic Strain Hardening Exponent K' = Cyclic Strength Coefficient S'ys = 0.2% Offset Cyclic Yield Strength (engineering)

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TENSILE TESTING AFTER INCREMENTAL STEP TESTING

After performing incremental step testing, the 1ST samples were tested for tensile properties in the same manner (including modulus determination with strain gauges) as described earlier for the monotonic properties. The post-cyclic tensile properties were recorded and the elastic modulus, sometimes called the "service" modulus, was calculated for comparison to the monotonic properties.

DETERMINATION OF CYCLIC PROPERTIES- FINAL SURVEY

Four of the eight materials with widely differing properties were selected for axial strain-control low-cycle fatigue tests. (Due to the costs involved with testing, it was not possible to perform these tests on all eight material conditions.) Conditions #2, 4, and 8 were chosen to represent the low, medium, and high hardness regime of SAE Grade D5506 ductile iron, respectively. Condition #7 was very similar to Condition #8 in hardness and microstructure, but behaved somewhat differently throughout the study. This was attributed to the significantly larger cross section of the casting; therefore, it was included in the study to observe the differences caused by the cast cross-sectional areas.

Sixteen axial fatigue test specimens were machined for each material using low stress machining procedures in accordance with ASTM standards E 606-98 and E 466-96, with the exception of the Condition #7 which had sufficient material for only fifteen specimens. The gauge diameter and length of the test specimens were 8 mm and 16 mm, respectively.

Axial strain-controlled low-cycle fatigue tests were performed under the guidelines of ASTM E 606-98 to develop a strain-life curve over the range from approximately 100 cycles to approximately 5,000,000 cycles. Each specimen was cycled using fully reversed triangular waveform loading at a frequency of 1 Hz. The tests were conducted at the following total strain amplitudes: one at 0.15%, one at 0.18%, three at 0.20%, two at 0.25%, two at 0.30%, three at 0.50%, two at 0.70%, and two at 1.00%. Those tests with anticipated lives exceeding 1 million cycles were changed to load-control mode at 50 Hz after 100,000 cycles (i.e., load saturation) to conserve machine time and cost. Strain-life curves (e-N,) were developed from the results.

The total strain-reversals (2 times life) equation is as follows: !l.e/2 = (cr(/E)*(2Nr)b + e((2Nt . This equation models the strain-life behavior of materials being loaded in the plastic region. The following parameters were determined based upon SAE J1099, June 1998, "Technical Report on Fatigue Properties" from the strain-life fatigue tests in accordance with the procedures stated in ASTM standard E 739-98.

cr( =Fatigue Strength Coefficient b = Fatigue Strength Exponent e,' = Fatigue Ductility Coefficient c =Fatigue Ductility Exponent

Note- for each specimen, the plastic strain range at half-life was calculated as follows:

• The elastic strain amplitude at half-life was calculated by dividing the stress amplitude by the elastic modulus. For specimens with total strain amplitudes of 0.25% or less, where there was no significant plastic strain, the elastic modulus from the tensile tests conducted prior to incremental step testing was used for this calculation. For specimens with total strain amplitudes of 0.30% or more, where there was significant plastic strain, the elastic modulus measured after the incremental step tests was used.

• The calculated elastic strain amplitude was then subtracted from the total strain range at half-life to determine the plastic strain amplitude.

5

• The total strain amplitude curve was calculated by adding the predicted elastic and plastic strain amplitudes. The calculation for the total strain-reversals curve was performed using the elastic modulus from the tensile tests conducted prior to incremental step testing.

The calculation for the total strain-reversals regression curve was . performed using the elastic modulus from the tensile tests conducted prior to incremental step testing.

RESULTS AND DISCUSSION

MATERIAL CHARACTERIZATION

Eight ductile iron materials ranging in hardness from 186 to 270 HBS were evaluated in this investigation. The test bars represented a wide range in cast section size varying from 25 mm (1 inch) rounds to 75 mm (3 inch) Y-blocks. All the castings were produced with the intent to cover the full range of properties (see SAE standard J434 Jun86), especially the Brinell hardness range, for SAE grade 05506. Table 1 contains the descriptions, microstructural analyses, and chemical compositions of all the materials employed in this study. Pearlite content ranged from a low of 49% to greater than 99%. Optical micrographs for the eight ductile iron samples are presented in Appendix A.

Overall, the eight materials were an appropriate group of alloys representing the full range of properties attainable in Grade 05506, with a wide range in hardness, microstructure and section size. There was sufficient variation in hardness and strength to determine their influence on high-cycle fatigue properties, and there was sufficient variation in microstructure and ductility to study their effects on low-cycle strainlife properties.

From the onset of the study, it was discovered that most properties varied with hardness. Therefore, the following discussions each significant monotonic and dynamic property is evaluated and correlated with hardness.

The hardness was directly proportional to the amount of pearlite in the microstructure. As shown in Figure 1, hardness increased linearly with increasing pearlite content. Linear regression of the nodule count and percent nodularity with respect to hardness showed no significant correlation, see Figures 2 and 3. Therefore, correlations of hardness with other mechanical properties are independent of graphite structure for these samples.

MECHANICAL PROPERTIES

All of the average monotonic mechanical property data and the incremental step testing data are given in Table 2. All samples met the typical minimum tensile strength of 550 MPa required for SAE grade 05506. Two samples at the low end of the hardness range were somewhat below the typical minimum yield strength of 380 MPa. One material at the high end of the hardness range did not quite meet the typical minimum elongation (6%). The strain-life fatigue constants for each condition are shown in Table 3. The individual values for the three tests comprising each average are shown in Appendix B. Linear regression constants and predicted values of many characteristic properties at 186 HBS and 270 HBS, based upon the data presented in Table 2, are tabulated in Table 4. The corresponding linear regression lines are superimposed on all the figures. The coefficients of determination (r) varied from 0 to 1, indicating increasing correlation from none to perfect correlation between the particular property and hardness. Note the strain-life constants and the plot intercepts are based on reversals-to-failure (2N,).

The strain-life (reversals) data are plotted in Figures 4 through 7 for material conditions #2, 4, 7, and 8, respectively. The raw data are shown in Appendix C. Each plot also shows the linear logarithmic regression lines predicted for the elastic and plastic strain amplitude components, calculated from the strain-life data, as well the logarithmic total curve obtained by adding these two components.

6

Figure 8 shows that when all the raw data for the four conditions are plotted simultaneously, the data scatter was minimal (approximately% a logarithmic decade), and no clear distinction in fatigue life data was obtained as a function of hardness. A few data points revealed the expected trend of high hardness exhibiting lower and higher lives at higher and lower applied strains, respectively.

Figure 9 shows a summary plot of all the total strain-life predictions. No clear-cut trend was revealed, but there was some slight separation in the predicted fatigue life for the high hardness materials as compared to that of the low and medium hardness materials. The high hardness conditions #7 and 8 exhibited higher lives in the high cycle (low strain) regime, but only the thin section condition #8 showed higher life in the low cycle (high strain) regime. Predicted strain values at various lives for the low hardness, medium hardness, high hardness/thick cross-section, and high hardness samples (conditions #2, 4, 7, and 8, respectively) are summarized in Table 5.

CORRELATION OF MECHANICAL PROPERTIES WITH HARDNESS

A correlation of ultimate tensile strength with Brinell hardness is shown in Figure 10. The monotonic ultimate tensile strength increased with hardness, and showed a very slight reduction in strength between the monotonic tensile test results before and after cyclic testing. Note that one outlying point (condition #7 with high hardness/thick cross section, represented by an open symbol) was not used in the regression.

A correlation of 0.2% offset yield strength with hardness is shown in Figure 11. The monotonic yield strength prior to cyclic testing displayed more dependence on hardness than after cyclic testing. There was very little difference between the cyclic yield strength in tension, in compression, and the yield strength after cyclic testing.

Tensile elongation was strongly affected by hardness, see Figure 12. The elongation dropped uniformly after cyclic testing. This indicates that the materials harden with cyclic testing but the rate of change in elongation as a function of hardness remained the same.

The monotonic modulus of elasticity (Young's modulus) was nearly independent of hardness with some scatter in the data, see Figure 13. After cyclic testing there was an overall decrease in the modulus values and data scatter, as is consistent with the observed behavior historically. There was a significant reduction of scatter in the data, and the development of a slight modulus dependence upon hardness as well. At 186 HBS, the elastic modulus after cyclic testing decreased by approximately 13.8 GPa. At 270 HBS, the elastic modulus decreased by only 10.3 GPa after cyclic testing.

The strength coefficient in monotonic tension is correlated with hardness in Figure 14. The strength coefficient was a strong function of hardness. As observed with the ultimate tensile strength, there were no significant changes in the strength coefficients before and after cyclic testing.

Figure 15 shows the strength coefficient in cyclic testing as a function of hardness. The strength coefficients in cyclic tension and cyclic compression were less dependent on hardness than the monotonic values, and the cyclic tension values changed less with increasing hardness than the cyclic compression values. The cyclic tension strength coefficient was similar in value to the monotonic coefficient at low hardness values, but the cyclic value diverged rapidly with increasing hardness. Since monotonic compression tests were not performed and a tension cycle preceded the first compression cycle in the cyclic tests, monotonic values were unavailable for comparison to the cyclic compression strength coefficients.

A correlation of the monotonic tension strain hardening exponent obtained in monotonic tension testing with hardness is shown in Figure 16. The strain hardening exponent increased with increasing hardness. It was lower for all hardness values after cyclic testing, but the strain hardening exponent after cyclic testing exhibited a stronger correlation with hardness. At low hardness values the monotonic and cyclic values were different, but at high hardness the regression lines converged. "

7

Figure 17 shows that the cyclic strain hardening exponents in tension and compression are shown to be slightly less of a function of hardness when compared to the monotonic tension strain hardening exponents. The cyclic tension exponents were similar in value to the monotonic tension exponents at low hardness, but the monotonic and cyclic values diverged as hardness increased. The rate of change as a function of hardness was equal in both cyclic tension and cyclic compression. Note that the monotonic strain hardening exponent was excluded because it is equal to the cyclic strain hardening exponent in tension, once the cyclic test specimen has reached strain saturation. The act of conducting a tensile test on the cyclic test sample is essentially the same as continuing the cyclic test an additional quarter cycle.

Stress-strain curves were predicted for the lowest and highest hardness samples using the equation:

using the strength coefficients (K) and strain hardening exponent (n) values calculated from the incremental step test results and the monotonic tensile results before and after cyclic testing. The predicted curves are shown in Figure 18. The low and high hardness materials cyclically strain-hardened in tension within the strain range used while conducting these tests. (A comparison can not be made between cyclic and monotonic compression because the monotonic compression data are unavailable.)

At very low cyclic strains, a greater level of cyclic strain hardening occurred in tension than in compression (as shown by the higher stress values obtained at, for example, 0.001 strain). The trend quickly reversed itself with increasing strain values, and the strain value for this trend reversal decreased with increasing hardness. The cyclic compression curves behaved similarly to the monotonic tension curve before cyclic testing in that each curve predicted the same proportional increase in true stress at a given true strain. However, the cyclic tension curve is neither parallel to the monotonic tension curve nor the cyclic compression curve; the predicted curves indicate that the materials would transform from cyclic strain hardening to strain softening at levels of strain higher than what was used in testing (That is, materials strained in excess of 1.5% would conceivably strain soften as indicated by the cyclic tension curve intersecting with, and falling below the monotonic curve.)

The predicted cyclic strains at selected fatigue lives are presented in Figure 19 and Table 5. The calculated constants from the fatigue life tests were used to predict the cyclic strains at various expected fatigue lives. The strain limits for high cycle life predictions were independent of hardness, which is a somewhat surprising result that may be an artifact of testing only two specimens at the lowest cyclic strain level. Conversely, the strain limits for expected low cycle lives increased with increasing hardness. (Only the predicted cyclic strains at 500 and 1000 cycles showed a modest increase with hardness.) As a result, Figure 8 and the last column of Table 3 can be treated as a valid combined data set to describe the general cyclic behavior of Grade 05506 ductile iron over its full hardness range.

8

CONCLUSIONS

1. This study compared the chemistries, microstructures, tensile properties, and fatigue properties of several ductile iron materials covering the entire range in hardness (187-255 HBS3000) for SAE grade D5506.

2. All the constants contained in SAE standard J1 099, June 1998, were determined for four materials. The tensile properties and monotonic and cyclic strain hardening coefficients and exponents were determined for all eight materials. The cyclic strain-life coefficients and exponents were determined for four of the materials, covering the full range of hardness.

3. Although the monotonic properties varied with hardness before and after fatigue testing, cyclic stressstrain properties and fatigue lives remained primarily independent of hardness. One set of constants may be used to describe the general cyclic properties of the Grade D5506, regardless of the differing hardness, microstructure, and tensile properties.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the help of Mr. Richard V. Wagner for the extensive mechanical testing performed. The authors would also like to thank lntermet Corporation, Wagner Casting, Bay Engineered Castings, and John Deer Waterloo for providing the castings used in this study.

CONTACT

John M. Tartaglia, Ph. D. Climax Research Services 51229 Century Court Wixom, Ml48393 Tel: (248) 960-4900 Fax: (248) 960-5973 E-mail: [email protected]

REFERENCES

1. Rice, Richard C., editor, "SAE Fatigue Design Handbook", 3'd edition; Society of Automotive Engineers, Inc., Warrendale, PA, pgs. 22-25

9

Table 1: Material Characterization Properties and Chemical Compositions of Eight Grade 05506 Ductile Irons.

Condition Number Symbol Units 1 2 3 4 5 6 7 8 tRank Based On Hardness)

Casting Type 1" diameter 1" Y-Biocks 2" Y-Biocks 2" Y-Biocks 7/8" Round 2" Y-Biocks 3" Y-Biocks

1" diameter circular bars Keel Bars circular bars

Material Properties

Brinell Hardness HBS 186 189 205 228 236 244 250 270 3000

Pearlite Content % 63.0 49.3 65.2 74.7 84.2 86.3 99.4 99.7

Ferrite Content % 37.0 50.7 34.8 25.3 15.8 13.7 0.7 0.3

Nodule Count per mm2 176 187 210 356 196 300 68 147

Nodularity % 94 95 85 91 96 94 89 93

Chemistry Data

Carbon c wt% 3.70 3.68 3.75 3.70 3.65 3.75 3.56 3.60

Sulfur s wt% 0.009 0.013 0.01 0.01 0.016 0.011 0.012 0.009

Phosphorus p wt% 0.022 0.012 0.016 0.017 0.019 0.017 0.017 0.021

Silicon Si wt% 2.38 2.39 2.72 2.85 2.18 2.61 2.41 2.10

Manganese Mn wt% 0.29 0.26 0.23 0.25 0.23 0.25 0.31 0.35

Chromium Cr wt% 0.04 0.04 0.02 0.02 0.09 0.02 0.05 0.09

Nickel Ni wt% 0.02 0.03 0.02 0.02 0.05 0.02 0.03 0.04

Molybdenum Mo wt% <0.01 0.01 <0.01 <0.01 0.01 <0.01 0.01 0.01

Aluminum AI wt% 0.026 0.022 0.037 0.04 0.034 0.042 0.019 0.029

Copper Cu wt% 0.13 0.44 0.53 0.54 0.40 0.66 0.36 0.62

Magnesium Mg wt% 0.031 0.039 0.026 0.038 0.044 0.036 0.057 0.049

Titanium Ti wt% 0.006 < 0.005 <0.005 <0.005 0.007 <0.005 <0.005 <0.005

Cerium Ce wt% 0.0048 0.0028 0.0069 0.0081 0.0056 0.0069 0.0047 0.0063

Tin Sn wt% <0.005 0.006 0.005 0.006 < 0.005 0.008 0.037 <0.005

Carbon Equivalent CE* 4.50 4.48 4.66 4.66 4.38 4.63 4.37 4.41

*CE = wt% C + 1/3 (wt% Si + wt% P)

10

Table 2: Monotonic Tensile and Cyclic Property Results.

Condition Number: (Rank Based On Hardness) Symbol Units 1 2 3 4 5 6 7 8

Brinell Hardness HBS 186 189 205 228 236 244 250 270 3000

Tensile Properties

Ultimate Tensile Strength (Engineering) Su MPa 604 612 631 725 759 754 775 863

0.2% Offset Yield Strength (Engineering) Sys MPa 356 368 389 439 419 447 437 474

Percent Elongation %EI % 11.9 13.7 9.7 10.4 8.1 7.7 4.4 6.3

Percent Reduction Area %RA % 11.2 12.1 8.9 8.2 7.7 6.8 3.9 5.7

Modulus of Elasticity E GPa 177 170 168 168 169 170 174 176

Monotonic Strength Coefficient K MPa 910 887 924 1100 1300 1250 1590 1760

Monotonic Strain Hardening Exponent n 0.17 0.17 0.16 0.18 0.21 0.20 0.25 0.25

Incremental Step Test (1ST) Results

0.2% Offset Yield Strength (Engineering-Tension) Svs' MPa 427 434 447 486 470 505 488 500

0.2% Offset Yield Strength (Engineering-Compression) Sys' MPa 428 444 449 488 462 510 487 505

Cyclic Strength Coefficient (Tension) K' MPa 793 754 816 922 1020 986 1120 1230

Cyclic Strength Coefficient (Compression) K' MPa 1140 1140 1230 1450 1510 1610 1640 1820

Cyclic Strain Hardening Exponent {Tension) n' 0.10 0.09 0.10 0.10 0.12 0.11 0.13 0.15

Cyclic Strain Hardening Exponent (Compression) n' 0.16 0.15 0.16 0.18 0.19 0.19 0.20 0.21

Testing Properties After Incremental Step Testing

Ultimate Tensile Strength Su" MPa 592 591 634 690 a 788 705 823

0.2% Offset Yield Strength (Engineering) s " ys MPa 425 433 449 490 a 510 490 503

Percent Elongation %EI % 9.3 11.7 8.0 5.5 a 6.9 2.5 4.1

Percent Reduction Area %RA % 7.7 10.9 7.5 5.8 a 6.3 2.4 4.0

Monotonic Strain Hardening Exponent n" 0.13 0.11 0.14 0.16 a 0.19 0.21 0.24

Monotonic Strength Coefficient K" MPa 862 804 938 1140 a 1400 1480 1770

Modulus of Elasticity E" GPa 160 155 158 158 a 160 160 162

a. samples fractured during incremental step testing.

11

Table 3: Strain-Life Fatigue Test Data Results

Condition Number Symbol Units 2 4 7 8 Combined (Rank Based On Hardness)

Brinell Hardness HBS 189 228 250 270 221 3000

Fatigue Strength cr', MPa 723 895 983 1030 971

Coefficient

Fatigue Strength b -0.062 -0.074 -0.087 -0.083 -0.084

Exponent

Fatigue Ductility E't 0.506 0.494 0.573 0.813 0.599

Coefficient

Fatigue Ductility c -0.683 -0.686 -0.728 -0.722 -0.707

Exponent

Modulus of Elasticity E GPa 177 168 174 170 170

Table 4: Linear Regression Constants and Predicted Values as a Function of Brinell Hardness

Intercept Coefficient of Predicted Predicted Property Symbola Units at Slope Determination Value at Value at

Ordinate (,-2) 186 HBS 270 HBS

Monotonic Ultimate Tensile Strength (Before Cyclic Testing) Su MPa 34.7 0.44 0.98 595 848

Monotonic Ultimate Tensile Strength (After Cyclic Testing) Su" MPa 32.1 0.43 0.97 584 834

Monotonic 0.2% Yield Strength in Tension (Before Cyclic Testing) Sys MPa 115 0.19 0.94 363 475

Monotonic 0.2% Yield Strength in Tension (After Cyclic Testing) s , ys MPa 258 0.14 0.87 432 511

Cyclic 0.2% Yield Strength in Tension Sys-11 MPa 269 0.13 0.81 436 511

Cyclic 0.2% Yield Strength in Compression Sys-c' MPa 244 0.15 0.87 432 517

Monotonic Percent Elongation (Before Cyclic Testing) %EI % 29.0 -0.09 0.78 12.6 5.1

Monotonic Percent Elongation (After Cyclic Testing) %EI' % 26.0 -0.08 0.76 10.1 3.0

Monotonic Modulus of Elasticity in Tension (Before Cyclic Testing) E GPa 169 0.00 0.00 171 171

Monotonic Modulus of Elasticity in Tension (After Cyclic Testing) E" GPa 148 0.01 0.49 157 161

Monotonic Strength Coefficient in Tension (Before Cyclic Testing) K MPa -1075 1.47 0.89 810 1660

Monotonic Strength Coefficient in Tension (After Cyclic Testing) K" MPa -1280 1.60 0.97 775 1700

Cyclic Strength Coefficient in Tension K,' MPa -268 0.79 0.93 740 1190

Cyclic Strength Coefficient in Compression Kc' MPa -433 1.20 0.99 1110 1810

Monotonic Strain Hardening Exponent in Tension (Before Cyclic Testing) N -0.04 0.001 0.77 0.16 0.24

Monotonic Strain Hardening Exponent in Tension (After Cyclic Testing) n' -0.15 0.001 0.95 0.11 0.23

Cyclic Strain Hardening Exponent in Tension n,' -0.02 0.001 0.77 0.09 0.14

Cyclic Strain Hardening Exponent in Compression nc' 0.02 0.001 0.96 0.15 0.21

Pearlite Content %P % -51 0.57 0.90 55 103

Ferrite Content %F % 151 -0.57 0.90 45.1 -2.6

Nodule Count Nod Ct. per mm2 283 -0.35 0.01 219 190

Nodularity Nod % 92 0.000 0.00 92 92

a. Single prime (') symbolizes cyclic properties. Double prime (") symbolizes monotonic properties after cyclic testing.

13

Table 5: Predicted Cyclic Strain at Selected Fatigue Reversals.

Reversal, 2N1 Low Hardness Medium Hardness High Hardness-Thick Cross-Section High Hardness

(Condition #2), l'lE/2 (%) (Condition# 4), l'lE/2 (%) (Condition #7), l'lE/2 (%) (Condition #8), l'l.E/2 (%)

186 HB 228 HB 250 HB 270 HB

500 1.01 1.03 0.95 1.28

1,000 0.72 0.75 0.68 0.90

5,000 0.39 0.43 0.38 0.47

10,000 0.33 0.36 0.32 0.39

50,000 0.24 0.27 0.24 0.28

100,000 0.22 0.25 0.22 0.25

500,000 0.19 0.21 0.18 0.21

1,000,000 0.18 0.20 0.17 0.20

5,000,000 0.16 0.17 0.15 0.17

14

c: ~ 0 60 (.)

c: ., :J

~ 40 c:

~ .II :::!: 20

0

•

160

•

I

200 220 240 260 280


Figure 1: Pearlite and ferrite percentage as a function of hardness.

400

350 • 300 •

'"E E 250 lii .e c: 200 :J • 0 (.) • .!! 150 • :J .., 0 z

100

• 50

0

180 200 220 240 260 280


Figure 2: Nodule count as a function of hardness.

100.--------------------------------------.

• 95 • • •

f • .!!! :J • "8 z 90 c: • ~ ., Q.

85 •

80+-------~------~------.-------.------4

180 200 220 240 260 280


Figure 3: Nodularity as a function of hardness.

15

2.8

2.4

2.0 1.8 1.6 1.4 1.2 - 1.0

~ 0.9 0 .._.. 0.8 Q)

'"C 0.7 ::J :!: 0.6 a.

0.5 E <(

0.4 c: "Cii ..... ..... 0.3 C/)

0.2

\ •· \

~c--..:_ -.\

\

• Condition #2 Data -- Total Strain Regression - - Elastic Strain Regression

Plastic Strain Regression

---\:--..,..__

0.1 -'---,-------r-----'-t-----.--~----,,..-----....o..-r---'

100 1000 10000 100000 1000000 10000000

Reversals (2N1)

Figure 4: Strain-life fatigue data and predictions for Low-Hardness, Condition #2.

2.6 2.4 2.2 2.0 1.8 1.6 1.4

1.2 -~ ~ 1.0 Q) 0.9

'"C 0.8 ::J :!: 0.7 0.. E 0.6 <( c: 0.5 -~

0.4 ..... U)

0.3

0.2

100

·\

1000 10000

• Condition #4 Data -- Total Strain Regression - - Elastic Strain Regression - · ·- Plastic Strain Regression

100000 1000000 10000000

Reversals (2N1)

Figure 5: Strain-life fatigue data and predictions for Medium-Hardness, Condition #4.

16

-~ 0 -Q) "'C ::J

:'!:::: c. E <( c

2.4 2.2 2.0 1.8 1.6 1.4 1.2

1.0 0.9 0.8 0.7 0.6

0.5

0.4

-~ - 0.3 (/)

0.2

,.,,. \~ \ \

\ ., •·

• Condition #7 Data -- Total Strain Regression - - Elastic Strain Regression - · ·- Plastic Strain Regression

......__ ......__,......__

. --\;. ~ . ......__ . ......__ \ ......__......__

\ \

......__

0.1~.--------r----~~,-------T-------~----~-,~

100 1000 10000 100000 1000000 10000000

Reversals (2N1)

Figure 6: Strain-life fatigue data and predictions for High-Hardness, Thick Section, Condition #7.

3.5 3.0

2.5

2.0 1.8 1.6 1.4 -~ 0 1.2 -Q) 1.0

"'C ::J

:'!:::: 0.8

c. E 0.6 <( c -~ 0.4 -(/)

0.2

100 1000 10000

• Condition #8 Data -- Total Strain Regression - - Elastic Strain Regression -- · ·- Plastic Strain Regression

100000 1000000 10000000

Reversals (2N1)

Figure 7: Strain-life fatigue data and predictions for High-Hardness, Condition #8.

17

3.5 3.0 2.5 • Condition #2 Data

• Condition #4 Data 2.0

Condition #7 Data • 1.5 0 Condition #8 Data - -- Total Strain Regression

::§?. 0

1.0 Elastic Strain Regression -Q) - · ·- Plastic Strain Regression "C 0.8 ::I

:!:::: a. 0.6 . ~ ~ '

E <( r::: 0.4 -~ -CJ)

0.2

100 1000 10000 100000 1000000 10000000

Reversals (2Nt)

Figure 8: Strain-life fatigue data for all four conditions with predictions for the combined data set.

4.0 ..-:---------....,......-.,...-....,......--------.,...----, 3.5 l :~:. --- ~ ' "-t-

3.0 i it;\ t· ~ . ' ...

2.5

2.0

1.5 -cf?. -Q) 1.0 "C ::I 0.8

:!:::: a. E o.6 <( r::: -~ 0.4 -CJ)

0.2

100 1000

-- Condition #2 - Low Hardness --· Condition #4- Medium Hardness --·- Condition #7- High Hardness/

Thick Section - · ·- Condition #8 - High Hardness

I'' i'l,'

,---,---~, ...... ·-·t---, ··;·--~--··; .. -----,+k--

i ';

10000 100000

Reversals (2Nt)

···----·····-·-.:.~:~' ~-

1000000

; i ll!li; l· ·· •. L~.l.~i-~ --, : I : ! : : ~

ill. )jl

10000000

Figure 9: Predicted total strain-life curves for each individual condition.

18

research project no. 30 - ductile iron society · research project no. 30 ... fatigue test report...

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