The highlights of NASA contract CR-167896, Fracture Mechanics Criteria for Turbine Engine Hot Section Components, are presented. The five technical tasks of the program are reviewed. Results of several tasks are presented

Orange, T. W.

English

NASA Technical Reports Server

PRE-HOST HIGH TEMPERATURE CRACK PROPAGATION 
Thomas W. Orange 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland •. Ohio 44135 
The Pre-HOST activities in Hi~h Temperature Crack Propa~ation are 
described in detail in NASA CR-167896, "Fracture Mechanics Criteria 
for Turbine En~ine Hot Section Components." What follows is a brief 
recap of the hi~hli~hts of that contract. 
This was a 14-month contract awarded in late 1980 to Pratt & 
Whitney Aircraft. The principal investi~ator was G. J. Mewers. The 
pro~ram consisted of five technical Tasks. 
In Task I, the Contractor was to "establish the locations, 
characteristic ~eometry, temperature levels, and stress levels in hot 
section components of typical advanced turbine en~ines which present 
crack initiation and crack propa~ation conditions that may 
si~nificantlY impact ensine operational safety or enSine maintenance 
costs." "The suitability and the limitations of the currently 
available methods for correlation and ~eneralization of crack 
propasation data such as linear elastic fractUre mechanics parameters· 
were to be evaluated. The kew results of this Task are shown in the 
first two fisures. 
In Task II, the Contractor was to identify "the empirical crack 
srowth predictive methods and data necessary for effective desi~n 
involvinS the potential crackins conditions identified in the 
preceedins Task I" and als~ "the test specimen desi~ns and the 
facility reauirements which can provide the reauired data under 
suitablY controlled thermomechanical crack propa~ation conditions." A 
suitable testin~ proSram was to be developed. 
In Task III, The Contractor was to "conduct an analysis to 
identify and define the nature and masnitude of the crack initiation 
and propa~ation mechanisms at the sites identified in Task I." "An 
analYsis of the correspondinS test specimen ~eometry and loadins" was 
also to be made. The component which received the Sreatest amount of 
analysis is the combustor liner shown in Fi~ure 3-1. A finite-element 
analysis had already been performed under another contract, and the 
results are shown in FiSure 5.2-3. The louver lip (location 1) is the 
area of interest. and contains stronS thermal sradients. A more 
detailed model, Fisure 5.3-8, was constructed for J-inte~ral analysis 
usins the MARC proSram (note the three contours). The calculated 
J-int~sral was found to be very sensitive to material property 
variations within the contour of inte~ration (Fi~~res 5.3-9 and 
5.3-10). The results of this analwsis indicate that the J-intesral 
calculation resident in the MARC pro~ram is not satisfactorw for this 
kind of problem. The specimens that were to be tested in Task IV were 
analyzed usinS a modified Shih-Hutchinson approach. 
Task IV consisted of the actual testin~. The specimens used were 
tubular specimens with short circumferential throush-thickness cracks 
as shown in Fisure 6.2-1, with the initial EDM slot beins about 0.040" 
Ions. The external-ridse specimens were used· for the isothermal 
tests, the internal-ridse for TMF tests. The TMF cycles that were used 
are shown in Fi~ure 6.2-2. Cycle I and Cycle II are linear, the 
"Faithful CYcle" is an approximation to the calculated louver-lip 
cycle shown earlier. The test matrix is shown in Tables 6-1 and 6-11. 
The data are correlated and ~eneralized in Task V. As shown in 
FiSures 7.4-2 and 7.4-3, The J-inte~ral 'was not entirelw successful in 
55 
https://ntrs.nasa.gov/search.jsp?R=19850002648 2020-03-20T21:17:25+00:00Z
correlatin~ the data. One should note, however, that all calculations 
were effectively based on the assumption that the crack be~an to open 
at maximum compressive load. If all cracks opened at the same 
percenta~e of max. load, then all calculations are in error by the 
same constant factor. Based on data spread, the crack tip openin~ 
displacement (which was calculated from the J-inte~ral) ~ave a 
somewhat better correlation. 
There are two si~nificant points to be noted. First, the 
J-inte~ral calculation resident in the MARC computer pro~ram is not 
satisfactorY for problems involvin~ thermal ~radients. Second, the 
specimens tested here were sparsely instrumented, and therefore we can 
only ~uess at how they actuallY responded to the thermal and 
mechanical cyclin~. 
56 
DOCIJf'lt:NHHIDN Of DMAGt RI:>Ul') 'N J''fU lll''''I/)IUR lI"(R) 
(Nl~r Ind I nner I 
rlgur@ II.~ (101 (rein (I of C.leul.t~d (.Ieullltd 
'_'~I~r (,Icul,ted 8·S0 Cllcullt~d 8·S0 fe-prrlture I'f) Strlln Ringe (SI 
CD"8USfOA DUIER liNERS 
).( ]8 20 1780 0.45 0 ll' Colli,,, 
0 Co.t Ing 5,,1 lit Ion 
0 Burning 
0 [.trnslv~ (r.el'ng 
1·) R4 8S 11110 0.45 0 Cr.ctlnt Ind Burnln, 
ISI.I .r to rl,ur~ ]·21 
) .4 51 liB 17110 0.45 0 (Itrnsl.e Crlctln, 
0 loc.llred DI,tres, 
) ·5 III 51 17110 0.45 0 [Itrnslve Crlctln, 
.(Onl Srvere Cr.ctl 
CD"IJUSlOA IIII(A lIN[RS 
)·6 27 10 I7lO 0.25 0 [roslon Ind Burning 
0 AlI.1 .nd Clrc~ferrntlll Crlc"n~ 
0 Dlllltlon Air HoI~ CrlClIn" 
].1 53 ]4 1730 0.37 0 "lid DilutIon Air 11O11! (r.dlnq 
0 (r.cllng In Aft End 
"DIES: 
~o"""9 lrpe: FlI. Coolld ... tlrlll; IIlItlllo,.1 Co.t Ing; ... tallle·Crra.le The""I Blrrl!!r 
(rIC. Inltl.tlon loc.tlon: Outlr lInlr; End of 10ll.lr IIp 
Innlr liner: End of 1000ver II, Ind clrc~'lrlntl.1 sr ... rld 
l'ner, ~st bl wel'.rflllirid or IVlntll.ll, rlpl.cl'. 
rAllURE CONS(QUENCES: 
Oul~r liner: AlI.1 cr.cts lin. toglther, rl,"ltln, In Ilntr defo ... tlon. ThiS dlfona.tlon •• , .ffrct Co-bustor 
'11t te-per.ture distribution vlth .n "Itl •• te effret on turbine perfonllncl .nd durlblllt,. 
Inner llnPr: IntersectIon of I.r, •• 11.1 .nd clrc~ferlntl.1 cr.cts Cln rl,.lt In Ilblr.tlon of plrcrs of the 
lIner, Clusln, srcond.r, '''191 to turbine bl.dls .nd VI .. S. 
TABLE 3-11 
IMPORTANT DAMAGE MECHANISMS FOR 
JT9D HIGH-PRESSURE TURBINE AIRFOILS 
Ai rfojJ 
First-Stage Turbine Vane 
Second-Stage Turbine Vane 
First-Stage Turbine Blade 
Second-Stage Turbine Blade 
D9~ag~h~e~ha"js~s 
o Cracking (oxidation-assisted) of leading edge 
and pressure-side wall. 
o Burning around leading edge cooling holes. 
o Leading edge cracking (early models). 
o Coating oxidation ana impact damage (later 
models). 
o Radial cracking of pressure- and suction-side 
wa 11 s. 
o Blade tip oxidation. 
o Stress rupture. 
o Impact damage. 
o Impact damage. 
o Stress rupture (early models). 
57 
0.002 
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g 0 
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-0.002 
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Figure 5.2-3 Strain-Temperature Response at Several locations Along Combustor 
11 ner louver. 
58 
(J1 
\0 I UNIFORM CRACK ~", \ LOADING TIP I 
CONTOUR 1 
CONTOUR 2 
CRACK .. I 
CONTOUR 3 
Figure 5.3-8 Coarse Grid Finite Element Mesh for J-Integral Test Cases. 
1275 
12'0 
1.225 
1.200 
a:: 
;;) 1.175 
~ 
Z 
81.150 
...J 
~ 
~ 1.125 
~ 1100 
l!) 
w 
~ 1.075 
.., 
1.050 
1.025 
1.000 
L 
a 
a:: 
.!!Qf!:!Q. 
~EIEAVE 
0 00 
I:. 02 
0 0 • 
0 0.8 
~ 
CONTOUR 1 
I 
o 
o 
I:. 
o 
I 
CONTOUR 2 
0.2 0.' o.e a., 
DISTANCE OF CONTOUR FROM CRACK TIP/CRACK LENGTH 
0 
o 
o 
I 
CONTOUR 3 
I 
1.0 
UNIFORM 
LOADING 
Figure 5.3-9 Effect of Elastic Modulus Variation on J-Integral Calculation 
using Coarse Grid. 
100 0 is} 9 
<> 
0.98 <> 
0.98 
OlM 
CRACK 
T1P 
UNIFORM 
LOADING 
0 is 0.92 
LEGEND I-
Z 
0 ,..4T j' 090 
« 0 0.0 
a:: I:. 10·' CRACK l!) 
w 0.88 <> 10. 3 T1P I-
~ o 10.2 
., 
-::r 0.88 ~ ~'-~ l!) w I- 0.11< ~  ~T., ~ TMIN _____ J 0.82 
0111 
0 
0.18 I 
CONTOUR 1 CONTOUR 2 CONTOUR 3 
L 
a 02 0.' 0.6 0.8 10 
DISTANCE OF CONTOUR FROM CRACK TIP/CRACK LENGTH 
Figure 5.3-10 Effect of Linear Temperature Gradient on J-Integral Calculation 
Using Coarse Grid. 
60 
EXTERNAL RIDGE SPECIMEN INTERNAL RIDGE SPECIMEN 
- . -~ 
1-------- 3.500------<-1 EXTENSOMETRY RIDGE 1-[ -4.185----1 
0.820 0.400 STARTER 
CRACK 
DIMENSIONS ARE NOMINAL VALUES. GIVEN IN INCHES 
Figure 6.2-1 Tubular Strain-Controlled Crack Propagation Specimens. 
STRAIN 
MAX. -r---'~~~~------------~====~--__ 
STRAIN 
RANGE 
MIN. 
STRAIN 
TEMPERATURE - TIME 
NO HOLD TIME HOLD TIME 
;~.:;' 14-1t-·"'-1~ 
TIME TIME 
1-60 SEC--j 
Figure 6.2-2 Strain-Temperature Cycles used in Thermomechanical Fatigue 
Testing. 
61 
TABLE 5-1 
CONDITIONS FOR ISOTHERMAL TESTING* 
Average 
Strain Minimum Maximum Cyclic Strain 
Test Temperature Range Strain Strain Rate Rate 
~ 1:.£l .L:EL.J!L lSI 1%1 ill!!!L lin!inl!min Conrnents 
1 -1 427 800 0.15 -0.075 0.075 60 0.18 
1-2 427 800 0.40 -0.20 0.20 10 0.08 
1-3 427 800 0.40 -0.45 -0.05 10 0.08 Mean Strain--0.25S 
1-4 427 800 0.25 -0.125 0.125 10 0.05 
1-6 649 1200 0.15 -0.075 0.075 2.0. 0.006 
1-7 649 1200 0.40 -0.20 0.20 1.0 0.008 
I-B 649 1200 0.40 0.05 0.45 1.0 0.008 Mean Strain-+O.25S 
1-9 760 1400 0.15 -0.075 0.075 1.0 0.003 
1-10 760 1400 0.25 -0.125 0.125 0.5 0.005 
1-11 760 1400 0.40 -0.20 0.20 1.0 0.004 
1-13 760 1400 0.25 -0.125 0.125 0.5 0~005 1 minute Hold Time 
1-14 871 1600 0.15 -0.075 0.075 1.0 0.003 
1-15 871 1600 0.175 -0.0875 0.0875 1.0 0.0035 
1-16 871 1600 0.40 -0.02 0.02 0.5 0.004 
1-18 927 1700 0.15 -0.075 0.075 1.0 0.003 
1-19 927 1700 0.25 -0.125 0.125 1.0 0.005 
1-20 927 1700 0.40 -0.20 0.20 0.5 0.004 
1-21 927 1700 0.25 -0.125 ~ 125 1.0 0.005 Mean Strain--0.25% 
1-22 927 1700 0.25 -0.125 0.125 0.5 0.005 1 minute Hold Time 
1-23 982 1800 O. 15 -0.075 0.075 1.0 0.003 
1-23a 982 1800 1.50 -0.75 0.75 1.0 0.030 Large Strain Range 
1-24 982 1800 0.25 -0.125 0.125 1.0 0.005 
1-25 982 1800 0.40 -0.20 0.20" 0.5 0.004 
1-26 982 1800 0.40 -0.20 0.20 0.5 0.004 Triangular Wave 
Shape 
* All tests hao a sinusoidal wave shape, zero mean strain, and no hold 
time, except where indicateo. 
TABLE 6-II 
CONDITIONS FOR THERMOHECHANICAL FATIGUE TESTING* 
Average 
Maximum Strain Minimum Maximum Cyclic Strain 
Test Temperature Range Strain Strain Rate Rate 
~ 1:.£l ~ .l!L {%l {%l .i£E.!!!L {1 n!i n 1 lJ!!i n Conrnents 
T-l 927 1700 0.15 -0.075 0.075 0.83 0.0025 
T-2 927 1700 0.25 -0.125 0.125 0.83 0.0042 
T-3 927 1700 0.40 -0.20 0.20 0.44 0.0035 
T-4 9,7 1700 0.25 -0.125 0.125 0.83 0.0042 Cycle II 
T -5 927 1700 0.40 -0.20 0.20 0.44 0.0035 Faithful Cycle 
T-6 927 1700 0.40 -0.20 0.20 0.30 0.0035 Faithful Cycle; ·1.125-
minute Hol0 Time 
T-7 982 1800 . e.25 -0.125 0.125 0.83 0.0042 
T-8 871 1600 0.25 -0.125 0.125 0.83 0.0042 
T-9 760 1400 0.25 -0.125 0.125 0.83 0.0042 
T-l0 649 1200 0.25 -0.125 0.125 0.83 0.0042 
T -11 927 1700 0.40 -0.20 0.20 0.30 0.0035 1.125-minute Hold Time 
T-12 871 1600 0.40 -0.20 0.20 0.44 0.0035 
,. All tests were Cycle I with no hold time except where inoicated. 
,. All tests hao a minimum temperature of 427°~ (800°F) and zero mean strain. 
62 
0\ 
W 
1~ • r 
....j 
'-' 
>-
'-' 
~ 
1.,:'1 ) 
10 • 
.1.1%1 TEST NO . 
o 015 T-l 
6 0.25 T-2 
o 040 T-3 
(fA 
O~O 
Ch 0 
o 
0 6 
o 
6 
6 
6 
o 
o 
o 
o 
o 
o 
51 I I I I I I I I I 
10 10 100 1000 
4J (IN. - LBIIN. 21. J-INTEGRAL RANGE 
FIgure 7.4-2 BOO to l700°F Cycle I Crack Growth Rates Based on J-Integral . 
Range. 
10- 2 
10- 3 
w 
... 
U 
>-!2 
~ 
~ 
~ 
10-
~ 
TEMP of 
0800-1800 
6800-1700 
0800-1600 
0800-1400 
0800-1200 
TEST NO. 
T·7 
T-2 
T-8 
T-9 
T-l0 
o~ 
o 
00 &,g 
~ 0 0 
000 n~G) 0 0 
~ 00 
g8 0 
o 0 
6 0 
o 
6 000 
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- 51 I I I I I I I I I I 
10 10 100 1000 
.1J !IN_-LBIIN_21. J-INTEGRAL RANGE 
re 7.4-3 Cycle I, 0.25 Percent Strain Range Crack Growth Rates Basea on 
J-Integral Range. 


Pre-HOST high temperature crack propagation

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