A European Code of Practice for strain controlledthermo

Transcription

GROWTH Project n° GRD2-2000-30014
TMF-Standard
Final Meeting/Workshop, 20-23/09/05, Berlin
A European Code-of-Practice for
Strain-Controlled Thermo-Mechanical Fatigue Testing
Peter Hähner, JRC Institute for Energy, Petten, (NL)
Claudia Rinaldi, and Valerio Bicego, CESI, Milan (I)
Ernst Affeldt, MTU Aero Engines, München (D)
Henrik Andersson, KIMAB, Stockholm (S)
Tilmann Beck, University of Karlsruhe (D)
Thomas Brendel, MTU Aero Engines, München (D)
Hellmuth Klingelhöffer, BAM, Berlin (D)
Alain Köster, Ecole Nationale Superieure des Mines de Paris (F)
Hans-Joachim Kühn, BAM, Berlin (D)
Malcolm Loveday, NPL, Teddington (UK)
Massimo Marchionni, CNR-IENI, Milan (I)
Catherine Rae, University of Cambridge (UK)
TMF-Standard
WP6: Drafting of CoP
survey
WP1
1st draft
prel. CoP
val.CoP
WP7
Dissemination
WP2
Material
2002
WP3
WP4
Pre-normative R&D Validation tests
2003
2004
WP5
Statist. analysis
2005
TMF-Standard
Table of Contents of CoP
1-
INTRODUCTION
1.1 SCOPE AND USE
1.2 DEFINITIONS AND DESCRIPTION OF TERMS
1. 3 NORMATIVE REFERENCES
2-
EXPERIMENTAL: Set-up and specimens
2.1 APPARATUS
2.2 SPECIMENS
3-
TEST PREPARATORY ISSUES
3.1
3.2
3.3
3.4
4-
TEST EXECUTION
4.1
4.2
4.3
4.4
5-
EVALUATION OF E MODULUS
OPTIMISATION OF TEMPERATURE CONTROL LOOP
THERMAL STRAIN MEASUREMENT
ZERO STRESS TEST
TEST START
TEST STOP AND RESTART
TEST MONITORING
TERMINATION OF TEST
ANALYSIS AND REPORTING
5.1 ANALYSIS OF RECORDED DATA
5.2 REPORTING OF TEST METHODS
5.3 REPORTING OF RESULTS
Acknowledgements
References
Annex A Specimens (Informative)
Annex B Relevant material properties and experimental characteristics (Informative)
Annex C Representative TMF cycles frequently used (Informative)
Annex D Measurement scatter and uncertainties (Informative)
TMF-Standard
Definition of TMF cycles
0.4
D
L
H
P
0.3
B
Mechanical strain %
0.2
O
T = T0 + GT F(Zt)
0.1
E
0
-0.1
Hm = Hm,0 + GH F(Zt M)
G
M
F(x) = F(x + 2S) ,
x
-0.2
-0.3
-0.4
300
A
400
45°
90°
N
F
500
600
C
I
700
800
900
0 < M < 180° means that
H lags behind T
1000
Temperature °C
Mech. strain vs. temperature for typical TMF cycles
with R = 1
TMF-Standard
Examples of specimens used in the
“inner-circle” validation round robin
tubular
solid cyclindrical
flat
TMF-Standard
Dynamic T measurement and control
Use of ribbon TCs
Stability of T profile
Spot-welding of TCs
TMF-Standard
Comparison of tolerances and recommendations (1)
Definitions
issue
TMF-Standard
CoP
Definition of
Hm lags behind,
phase angle
if M > 0
Start point of
at Hm = 0 (Rd0) or
first TMF cycle T = Tmin (R>0),
always increasing T;
gradual increase of
'Hm not foreseen
ISO 12111.1
No definition
ASTM E 2368 - 04
Hm lags behind,
if M > 0
at Hm = 0 (Rd0) or
at Hm = 0 (Rd0) or
Hm = min|Hm| (R>0), Hm = min|Hm| (R>0),
always same
always same
direction;
direction
gradual cyclic
gradual cyclic
increase of 'Hm for increase of 'Hm for
large strain
large strain
amplitude tests or in amplitude tests or in
case of serrated
case of serrated
yielding
yielding
TMF-Standard
issue
ISO 12111.1
ISO 9513 Class 1
(for l0 < 15mm
Class 0.5 recomm.)
Alignment:
5% of both max.
max. allowable
AND min. mech.
bending
strain
Direct contact:
Detailed
Dynamic T
binding, pressure,
recommendations
measurement
and control
on appropr. methods spot welding
outside GL;
of fixing;
Pyrometry
No pyrometry
Humidity of air Not an issue
Not an issue
Extensometry
Apparatus & Specimens
TMF-Standard
CoP
ISO 9513 Class 1
(for l0 < 15mm
Class 0.5 recomm.)
5% of mech. Strain
range
Specimen
geometries
Detailed geometries
and machining
tolerances
recommended for
x Solid cylindrical,
x tubular,
x flat specimens
Tubular
specimens
5 < o.d. / w.t. < 10
ASTM E 2368 - 04
E83 Class B-2
E 606 (LCF):
5% of min. mech.
strain range
Direct contact:
binding, pressure,
spot welding
outside GL;
Pyrometry
Control of rel. air
humidity strongly
recommended
(extensometry)
Detailed geometries Examples for
and machining
x Solid cylindrical,
tolerances
x Tubular specimens
recommended for
Tubular specimens
x Solid
cylindrical,
preferred
x tubular,
x flat specimens
10 < o.d. / w.t. < 30 No recommendation
TMF-Standard
Comparison of tolerances and recommendations (3a)
issue
Max. Allowable Tolerances
Max.
temperature
deviation
Max.
temperature
gradients
within GL
TMF-Standard
CoP
The greater of
± 5°C or
'T [°C]
throughout test at
center of GL
The greater of
x ± 10°C or
'T [°C]
(axial)
x ± 5°C or
'T [°C]
(radial, &
circumferential)
x ± 7°C
(transverse
gradient in flat
specimens)
ISO 12111.1
ASTM E 2368 - 04
± 2°C
throughout test as
indicated by control
sensor
± 2°C
throughout test as
indicated by control
sensor
The greater of
± 5°C or
± 1.5% Tmax [°C]
(axial, radial, &
circumferential)
The greater of
± 3K or
± 1% Tmax [K]
(axial)
TMF-Standard
Comparison of tolerances and recommendations (3b)
issue
Max.
thermal strain
hysteresis
Max.
mechanical
strain deviation
Max.
phase angle
deviation
Max.
stress during
zero-stress test
TMF-Standard
CoP
5% 'Hth
No mention, as not a
directly controlled
variable
between
±2° at Tmax and
±5° at Tmin
|V|max < 5% 'Vand
V! < ±2% 'V
ISO 12111.1
ASTM E 2368 - 04
2.5% max(Hth)
? definition ?
5% 'Hth
2% 'Hm
2% 'Hm
±5°
±5°
< 2% of max.
tensile or
compressive stress
anticipated
“Insignificant” as
compared to tensile
or compressive
stresses anticipated
TMF-Standard
issue
TMF Practice Recommendations
Young’s
modulus E
measurement
Young’s
modulus
verification
Thermal strain
compensation
Thermal precycling
TMF-Standard
CoP
Static and pseudodynamic methods
described for the
determination of
E(T) before each
series of tests
Verification of
TMF system
recommended by
measuring the Emod at
RT, Tmin, Tmax and
one intermed. T
before each test:
< ± 5% deviation
from reference
value
Single-valued T
based NOT
recommended
extra water cooling
at specimen ends
recommended
(cf. T control
outside GL)
ISO 12111.1
ASTM E 2368 - 04
Static method
described for the
determination of
E(T) before each
series of tests
Static method
described for the
determination of
E(T) before each
series of tests
Verification of
extensometry
recommended by
measuring the Emod at RT before
each test
No recommendation
T based preferred
T based or t based
Usually 3 – 4 precycles to dynamic T
equilibrium
TMF-Standard
issue
Other Practices
Test
interruption
procedure
Failure criteria
associated with
force drop
TMF-Standard
CoP
Programmed stop:
Restart like
new test;
Unexpected stop:
Restart only
if last cycle
has been
recorded
Nf, x:
'V or Vmax decrease
by x% below
sloping tangent line
to previous
inflection point
ISO 12111.1
ASTM E 2368 - 04
Programmed stop
described
Programmed stop
described
5 – 50% peak
tensile force drop
from stabilized
value or projected
straight line
5 – 50% force drop
from previously
recorded peak force
TMF-Standard
Conclusions
TMF-Standard CoP on strain-controlled TMF
• contains the “essence” of 4 years work of 20 European laboratories
• has been validated by ~ 120 TMF tests (OOP and IP)
• comprises a lot of informative material and practical recommendations
• has contributed to improving & harmonizing the partners’ in-house TMF practices
• provides technical underpinning to the ISO standard
• is disseminated to all interested parties
Dissemination
• Original plan to run own CWA abandoned
• CoP to be published as a EUR Report
• To be distributed to all workshop participants
TMF-Standard
TMF-Standard
TMF-Standard
TMF-Standard
ANNEX C (Informative) Exemplary compilation of relevant material properties and experimental characteristics
Material properties of Nimonic90 1
Property
Symbol
Unit
Indicative
value
Mechanical properties
Density
U
g/cm3
8.2
Yield stress at Tmax
Vy
MPa
440 @ 850°C
Young’s modulus of elasticity
E
GPa
150
Q
1
0.3
Gibbs free enthalpy of plastic deformation
Gpl
eV
Gibbs free enthalpy of oxidation (800 – 1000°C)
Poisson ratio
Thermal properties
1.9 ???
Gox
eV
1.1
Specific heat
cp
J / kg °C
650
Thermal conductivity
O
W / m °C
24
Lin. coefficient of thermal expansion (400 – 850°C)
D
Electromagnetic properties
-6
10
°C1
15
Electrical conductivity
V
(P:
m)1
0.76
Magnetic permeability
P
1
1.1
TMF-Standard
Characteristics of experimental setup and TMF conditions
Parameter
Symbol
Unit
Specimen radius
Indicative
value
r
mm
3
Frequency of induction heating
Xind
kHz
200
Heating/cooling rate
T
°C / s
5
Minimum temperature
Tmin
°C
400
Maximum temperature
Tmax
°C
850
Quantity
Derived quantities
Symbol
Skin effect penetration depth of power
density
d
Formula
Unit
(4SVP0PX)1/2
mm
Indic.
value
0.61
Characteristic temperature of plastic deform.
Tc,pl
Gpl/kB
°C
22000
Characteristic temperature of oxidation
Tc,ox
Gox/kB
°C
12500
W
(Ucp/O)r2
(Ucp/O)rT
(E/(1-Q))DT’r
s
2.0
°C/mm
3.3
MPa
31
°C
10
Thermal relaxation time
Radial temperature gradient
Radial stress deviation
Characteristic temperature deviation
1.
T’
'V
'T
0.1 T
2
max /
Tc,ox
TMF-Standard
WP3: Pre-normative R&D
Task 1: Pre-cycling, start, interrupt, restart procedures
Task 2: Dynamic T measurement and control
Task 3: Thermal strain comp., deviations from nominal T
Task 4: T gradient effects in 3 sample geometries
(solid cylindrical, hollow cyl., solid rectangular)
Task 5: Deviations from nominal phase angle
TMF-Standard
WP4: Validation Tests:
0.4
RH = - 1, M = 180°
Tmin = 400°C, Tmax = 850°C
tcycle = 180s Ù dT/dt = r 5K/s
'Hm = 0.8% Ù Nf # 1000
2.) symmetrical triangular IP
mech. strain [%]
1.) symmetrical triangular OOP
0.2
0.0
-0.2
-0.4
400
500
600
700
800
900
RH = - 1, M = 0°
Tmin = 400°C, Tmax = 850°C
used by
tcycle = 180s Ù dT/dt = r 5K/s
“inner circle” and
'Hm = 0.6% Ù Nf # 1000
“outer circle” round robin participants
temperature [°C]
TMF-Standard
From these data various dimensionless parameters derive, which can be used to estimate the
lower bounds of systematic errors induced by the experimental set-up and the thermo-mechanical
fatigue conditions imposed, and to assess the influences of the various parameters affecting those
errors.
The induction heating of the above set-up causes a skin effect with very limited direct
bulk heating, as the ratio of the penetration depth to the specimen radius
d
r
1
1
| 20%
4SVP 0 PQ r
amounts to some 20 percent only. Accordingly, the specimen bulk is heated by heat
conduction with finite thermal relaxation time W | 2s, causing a temperature difference GT
| 10°C between inside and outside temperature.
The relative stress deviation associated with the radial temperature gradient induced by
surface heating and heat conduction to the bulk (lamp furnace or induction heater with
small penetration depth) reads
'V
Vy
DUcp
E
r 2T | 7 % .
O (1 Q )V y
On top of these systematic errors due to thermal relaxation there will always be
measurement and control uncertainties, which must be kept as low as possible by
appropriate maintenance and calibration of the measurement equipment as well as by an
optimization of the TMF testing techniques. In particular, the relative overall temperature
deviation in the gauge length should not exceed
'T
Tmax Tmin
2
Tmax
r0.1
| r2.2 % ,
Tc, ox Tmax Tmin if the rate of the relevant thermally activated process (here: oxidation) is to be maintained
ithi
10%
TMF-Standard
Schematic of various coil configurations
TMF-Standard
Dynamic T measurement and control:
Major issues in dynamic T control by thermocouples:
Inductive heating & resistive heating:
Heat transfer coefficient from specimen surface to TC
Heat conduction through TC wire: cold spot
=> appropriate TC attachment is crucial
Radiation heating
Reflectivity coefficients of TC and specimen
=> appropriate shielding of TC
=> Need for comprehensive trials using a combination of different methods
TMF-Standard
Dynamic T measurement and control (cont’d):
1.
Temperature control by ribbon TC within GL
(a)
(b)
Ribbon type thermocouples, applied to (a) a round specimen with 8 mm
diameter, and (b) a flat specimen 12 mm wide and 4 mm thick
TMF-Standard
Dynamic T measurement and control (cont’d)
4.
Prevention of “cold spot”
Wrapping configuration of spot-welded thermocouple
TMF-Standard
TC type
R/S
K/N
Material
Pt-based
Ni-based
Thermal contact
good
poor
Thermal conductivity
high
low
Error governed by
heat conduct.
therm. contact
Recommended
attachment
ribbon or
SW wrapping
SW
TMF-Standard
Failure criterion
1200
Stress Range, MPa
1000
800
600
400
200
Nf10
0
0
200
400
600
800
1000
1200
1400
N, cycles
Example of end of life criterion, based on 10% stress range drop below a
sloping tangent line to the saturated portion of the curve
TMF-Standard
Web-enabled Mat-DB - TMF-Standard data sets
To get access to TMF Standard data and documentation please register on the JRC Petten ODIN
website (https://odin.jrc.nl), register for Mat-DB and DoMa and mention under comments that you
request access to the TMF-Standard project data sets.
Selection of TMF-Standard data within the web-enabled Mat-DB data retrieval part
TMF-Standard
Selection of TMF Standard data within the web-enabled Mat-DB data retrieval part
TMF-Standard
Graphical output of TMF Standard data within the web-enabled Mat-DB data retrieval part

A European Code of Practice for strain controlledthermo

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