DETERMINING ELASTIC MODULI OF HIGH-TEMPERATURE MATERIALS: THE IMPACT EXCITATION METHOD

Transcription

1 DETERMINING ELASTIC MODULI OF HIGH-TEMPERATURE MATERIALS: THE IMPACT EXCITATION METHOD Roger Morrell and Jerry Lord Parsons Conference, Sepemer 011

2 Elasic modulus measuremen mehods For meals, convenionally derived from he elasic par of a ensile es Exensomery Srain gauges Inerferomery Accuracy depends crucially on Alignmen Exensomery caliraion Asence of plasiciy Quasisaic modulus values

3 Elasic modulus measuremen mehods For oher maerials, alernaives are ofen used: Quasisaic mehods Flexure esing Dynamic mehods Resonance Naural frequency Ulrasonic pulse ransmission Ofen hese are quicker and simpler, and more adapale o measuremen a higher emperaures 3

4 Dynamic mehods - exising sandards Non-meallics ASTM C15 Concree, resonance ASTM C63 Glass, glass-ceramics, resonance ASTM C747 Caron and graphie, resonance ASTM C848 Ceramic whiewares, resonance ASTM C885 Refracories, resonance ASTM C1198 Advanced ceramics, resonance ASTM C159 Advanced ceramics, impac exciaion EN843-, EN80-5 Advanced echnical ceramics, ulrasonics, resonance and impac exciaion EN ISO Refracories, impac exciaion EN Rocks, resonance EN Advanced ceramic fire composies, resonance ISO Advanced ceramics, resonance Meallics ASTM E1875, Meals, resonance ASTM E1876, Meals, impac exciaion EN 331, ISO 331, Hardmeals, resonance 4

5 This presenaion: Impac exciaion mehod Applicaions o meal alloys (ASTM E1876 Uncerainies Use o high emperaures Exension o single crysal maerials Limiaions 5

6 Impac exciaion mehod Based on free - free viraion frequencies of a regular shaped es-piece (ar, rod, disc Viraions are excied y sriking he es-piece (wheelapper mehod Viraion sensed y high-frequency microphone or laser viromeer Eigenfrequencies are deermined from deeced signal y fas fourier ransform Elasic properies are deermined from fundamenal viraion modes via well-esalished equaions Commercial sysems are availale for doing his quickly and efficienly 6

7 Eigenfrequencies Flexural modes, FnF1 ~ 1 :.76 : 5.41 : 8.95 : Torsional modes, TnT1 ~ 1 :.01 : Longiudinal modes, LnL1 ~1 : : 3.. The sequence allows clear idenificaion of he frequency peaks oserved 7

8 Inensiy, a.u. Example FFTs for Nimonic 90 a RT Tes-piece size: x 8 x 70 mm Nimonic 90 Through-hickness flexure (F Flexure and orsion (T Sideways flexure (FS Longiudinal (L L1 800 FS1 FS FS T1 T T3 00 F1 F F3 F4 F5 F Frequency, Hz 8

9 9 Calculaions for recangular-secion ars Flexure: Torsion*: Longiudinal: Poisson s raio T L mf E f ( (1 1 ( ( (1 1 L L L L T A B Lmf G (.5( 4( B ( 1.03( ( ( ( A K f L E l 4 L m 1 ( 1 1 L K = hickness, = widh, L = lengh * Equaions for A and B recenly modified in ASTM C1876 = (EG - 1

10 Uncerainies - main facors Inpu value of Poisson s raio for E Minor effec for slender ars ( L < 0.05 Tes-piece dimensions Parallelism of faces eer han 0.01 mm Effecs of single and doule aper in es-pieces are unknown Minimal roughness of surfaces Elasic hickness less han micromeer hickness Accuracy of hickness measuremen mm on mm hickness gives 0.75% in E Equaions Uncerainies no well defined, u proaly eer han 0.1% for slender ars FFT compuer imease Beer han 1 par in 10 5 Overall uncerainy for isoropic maerial ypically: 1% in E and G, in 10

11 Example daa ses Maerial Assumed inpu Poisson s raio, ν Throughhickness flexure Through-hickness flexure and orsion In-plane flexure Longiudinal mode E, GPa E, GPa G, GPa ν E, GPa E, GPa 316 sainless seel ± ± ± ± ± ± <0.1 Ti-ase maerial ± ± ± ± ± ± <0.1 Nimonic ± ± ± ± ± < ± <0.1 Average and sandard deviaion for five srikes 11

12 Tesing a elevaed emperaure Meallic wireceramic frame suspension sysem ha keeps es-piece in posiion during exended esing Iner amosphere Auomaed impacor Auomaed daa recording a regular inervals NPL s IMCE sysem 1

13 Geing HT daa in a single run NPL s rick is measure F1 and T simulaneously Suppor a flexural nodes Srike locaion Then use he RT raio of F o F1, consan wih emperaure, o allow fundamenal mode equaion o e used. 13

14 Frequency, Hz HT es resuls - Nimonic Nimonic 90 ar frequencies F5 T F4 F3 F F Temperaure, C 14

15 Poisson's raio Young's modulus, GPa HT es resuls - Nimonic Nimonic 90 Young's modulus Shear modulus Nimonic 90 - Poisson's raio Temperaure, C Temperaure, C 15

16 Young's modulus, GPa Damping coefficien Temperaure limiaions When inernal damping ecomes excessive Tes-piece no longer rings well Frequency peaks ecome roadened and less inense Frequencies canno readily e deeced agains ackground noise Torsional viraions are ofen damped ou a lower emperaures han flexural modes Bu generally daa can e oained o higher emperaures han wih quasisaic mehods WC11Co Young's modulus Damping coefficien Temperaure, C WC11Co hardmeal: oxidaion-limied 16

17 Exending o exured maerials and single crysals Technique measures axial modulus In principle, es-pieces cu in differen orienaions can e used o deermine he anisoropy of E Shear modulus is more difficul, and Poisson s raio canno e defined Sricly, need o resor o ensor analysis For cuic single crysal alloys his can e done wih a minimum of hree es-pieces o define S 11, S 1 and S 44 17

18 Hermann e al. analysis for round ars E meas (, ( S 1 11 SJ 001 S S 11 S1 S44 J sin cos sin 4 (1 cos 4 8 G meas (, (( S SJ( Ploing 1E vs. J has slope -S and inercep S 11 Ploing 1(G(1- vs. 4J has slope +S and inercep S 44 Can e applied o recangular ars provided ha one of hem is very close o (001 o oain a good value for S 44 Hermann, W., Sockel, H.G., Han, J., Berram, A., in Superalloys 1996, ed. Kissinger R.D., e al. TMS, 1996, pp

19 1(G(1-, GPa -1 Single crysal alloy - example resuls E plo 1(G(1- plo E, GPa y = x y = x J CMSX Poor correlaion resuling from no accoun eing aken in rod heory of roaional orienaion of recangular es-piece aou long axis 4J 19

20 Single crysal alloy - example resuls Compliance, GPa Temperaure, C S S 11 S11 S44 S S1 S CMSX-486 0

21 Conclusions Accurae dynamic modulus measuremens can e made simply and economically on isoropic alloys o high emperaure using he impac exciaion mehod Temperaure limiaions are defined y he onse of significan damping or oxidaion Anisoropic maerials and single crysals need a more careful approach, u possile provided ha appropriaely orienaed es-pieces are availale 1

22 Acknowledgemens This work was performed in par under Maerials Merology funding from he Naional Measuremen Office of BIS (formerly DTI Thanks are due o Ken Harris (Cannon-Muskegon for maerials and Kah Clay (Hexma for single crysal orienaion measuremens Crown Copyrigh 011, reproduced y permission of he Conroller of HMSO and he Queen s Priner for Scoland