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1
New On-line Monitoring Methodology for Improving
Performance of Ageing Critical Structures, Systems and
Components
Technical Meeting on Fatigue Assessment in Light Water Reactors for Long Term
Operation: Good Practices and Lessons Learned
6-8 July, Areva, Erlangen Germany
Dr. Bakirov M.
2
General approaches to calculation of load of equipment in Russian and ASME codes
are very similar. But, there are some differences
.
0,2 0,2min ,T T
m m pR n R n
For pressure-loaded elements , the following values of nominal allowable stresses :
Russian norms (PNAE G-7-002-86): ASME code:
Comparison of Russian and ASME codes
0.22,6; 1,5mn n
.
;10
9;
5.1;
3;
3min
2.0
20
2.020
00 T
ppT
mmm
RRRRS
ASME: events are grouped (PNAE G-7-002-86 very similar)
Condition I – normal operation
Condition II –faults that occur with moderate frequency
Condition III – infrequent faults that may accure
Condition IV –limiting faults postulated but not expected.
3
, МПаaF
0N
, МПаaF
0N
, МПаaF 0N- permissible amplitude of conditional elastic stress
- permissible number of cycles
Including influence of the environment Excluding influence of the environment
Fatigue curve
Determination of acceptable number of cycles or allowable stress amplitude for a
given number of cycles is carried out through the estimated fatigue curves or
according to formulae (adjusted calculation).
Calculated fatigue curves are determined by taking into account of dominancy of
average cycle stress and safety factors nσ =2 и nN = 10 (In
ASME nN = 20)
maxF aF
4
Fatigue cracks
Strength, Life time, Environment,
Structures, Surface condition,
Manufacturing defects have significant
influence on born and growing of fatigue
cracks.
One solution is in the extrapolation of
formulas of linear elastic fracture
mechanics for stress intensity factor
(SIF) on essentially nonlinear stage of
deformation using functions of plasticity
amendments.
Conditions of cyclic loading under given initial crack sizes are determined
by the magnitude of SIF (∆K) , stress ratio (R) and number of cycles (N).
💔
5
Fatigue crack growth
Diagram of cyclic crack growth is represented
with a broken line, the segments of which are
approximated by the Paris-law equation:
where the characteristics of the material Co, m
depending on loading conditions (class and
condition of the metal, temperature, working
environment, frequency of cycles.
0
m
eff
daC K
dN
4 1eff
KK
R
Material Co m
Alloy steels of the type Cr-Mo-V, Cr-Ni-Mo-V and welds
2,7 2,810-11
Carbon steels and their welded joints 3,1 1,5 10-
11
Chromium-Nickel corrosion-resistant austenitic steel and welds
3,3 5,210-12
6
Probability of Failure and Microstructure Changing on LTO
Slip
Slip
Slip
Brittle Fracture
(unstable cracks)
Visible growth and
connection of cracks
Fine cracks visible with
naked eye
Cracks visible with
dyes penetrants
Very fine microscopic cracks that
may or may not propagate
Str
ess
levels
Time of operation
Level A
Beginning of defect
formation
Level B
Formation of
acceptable operational
defects
Level C
Formation of
unacceptable
operational defects.
! LTM is required !
Level D
Further operation is
impossible
Ultra
Low
Risk
Low
Risk
Medium
Risk
High
Risk
Ultra
High Risk
Catastr
ophe
P(t)
6
7
mo
nit
ori
ng o
f in
tegri
ty
time of operation
design-experimental analysis
of the accumulated damage
T0 +1 +2 +3 +4 +5
P, MPa T, 0С
σ, MPa T, 0С
L, mm Alloy of abilities of:
Monitoring integrity&loads
and FAM Stress analysis
ai
ai→ [a]
Philosophy of the on-line monitoring
8
Examples of practical application of the on-line
monitoring philosophy
Example № 1. Design-experimental on-line monitoring of
operational damageability of steam generator’s critical zones on
WWER-1000 Units.
Example № 2. Design-experimental on-line monitoring of thermal
stratification of surge line on WWER-1000 Units.
9
Object of investigation: nozzle of the collector the vessel of PGV-1000M steam
generator (weld joint № 111).
Weld joint №111
Headache
During 10 years born and growing of cracks in
welding zone №111 (non-compensated damage) !
Opera
tional
cra
cks
Example № 1. History
Statistics of WJ №111 cracking from 1998-2013
Primary circuit
of WWER-1000
Critical nozzle
10
Main stages of New Failure Analysis 1. Development of the on-line monitoring procedure.
2. Development of technology of on-line monitoring of metal integrity based
on ultrasonic (US) and acoustic emission (AE) methods and strain –
displacement-temperature.
3. Design of the monitoring system architecture.
4. Manufacturing of the monitoring system components.
5. Manufacturing and testing of the system components on a full-scale test-
bench.
6. Mounting of the monitoring system on steam generators of the
Novovoronezh NPP, Unit 5.
7. Development of FEM model of the primary circuit.
8. Analysis of on-line monitoring results.
9. Teaching and calibration of FEM model.
10.Design- FEM of life time stress-strain analysis.
11.Real-time investigation of causes of failure.
12.Development of compensation procedure and checking its effectiveness.
11
Monitoring of the technical state of the inspected object
Non-destructive inspection of
the metal condition during
scheduled maintenance
Ultrasonic inspection of the
metal integrity by the
phased-array techniques
On-line monitoring of the metal condition and
of the actual thermo-force loading during NPP unit operation
Measuring of the actual
mechanical properties
Assessment of residual
stresses using magnetic
methods
Ultrasonic on-line monitoring
of the metal integrity
Acoustic-emission
on-line monitoring of the
propagating defects
Design-experimental modeling of the operational damageability and
justification of strength and survivability of the inspected object
Preliminary strength
analysis
Selection of places for mounting
of sensors of the on-line
monitoring system
Calibration of the finite-element
modulus using experimental data
Monitoring of the thermo-force loading:
- deformations in the most loaded zones,
- relative displacements,
- local temperature fields,
- work parameters (pressure, temperature, etc.)
Development of
compensating
measures
Stage 1. Development of the on-line monitoring procedure
12
Stage 2. Development of technology of on-line monitoring of metal
integrity based on ultrasonic (US) and acoustic emission (AE) methods
Acoustic waveguide with US sensors
AE antenna with high-temperature AE sensors Experimental data
+
US monitoring
AE monitoring
Problem issues:
Long time of monitoring (1 year).
Surface temperature 320 0С.
High level of radiation.
Unavailable access for service.
13
Stage 3. Development of the monitoring system architecture
ARCHITECTURE
On-line monitoring of growth of
hazardous defects by US method
On-line monitoring of origination and growth of
defects in WJ №111 (100 % along a perimeter)
by AE method Expert US inspection of the WJ №111 (1-3
critical zone of a perimeter) during unit
planned outage
Monitoring of metal integrity
Monitoring of leakage
Monitoring of actual thermo-force
operational loading
+
+
BASE FUNCTIONS
14
Stage 4. Designing of the monitoring system components
Fastening of AS sensors Fastening of US sensors
Control of displacements of equipment supports Electronic module
15
Stage 5. Manufacturing and testing of the system
components on a full-scale test-bench
Full-scale test-bench with mounted components
Server
Electronic module
16
Stage 6. Mounting of the monitoring system on steam
generators of the Novovoronezh NPP, Unit 5
Components of the AE subsystem Components of the US subsystem
Electronic module Strain gauges+thermocouple Displacement sensors
17
+0.0
+4.0
+8.0
+12.0
+16.0
+20.0
+24.0
+28.0
+32.0
+36.0
+40.0
+44.0
+48.0
+60
+120
+180
+240
+300
+360
+420
+480
+540
+600
+660
+720
+780SX [MPa]
SY [MPa]
SZ [MPa]
SI [MPa]
STEP=1
Distance from first point on the line
Y-v
alu
es
Hydro-tests of the secondary circuit
Critical zone
Distribution of stresses in the crack front
The maximum level of
relative-elastic stresses
(720 MPa) in the zone of
the defect are fixed in the
mode of hydro-tests of the
secondary circuit.
Stage 7. Development of FEM model of the primary circuit
18
23.08 Осевые деформации на СС 111 5ПГ-4 при
прохождении температурной аномалии № 8
-60,00
-50,00
-40,00
-30,00
-20,00
-10,00
0,00
10,00
6:00 6:30 7:00 7:30 8:00 8:30 9:00
Время, ч
Деф
ор
мац
ия
, 0.5
*10
-5
А (СС111, 0º, ос.) Б (СС111, 90º, ос.) В (СС111, 180º, ос.)
Г (СС111, 225º, ос.) Е (СС111, 315º, ос.)
Stage 8. Analysis of on-line monitoring results
New defect
Conclusion. Non-design thermo-force loads lead to born and growing of
operational cracks.
Revealed thermal shocks! High non-design loads
AE monitoring Expert US inspection
19
Comparison of calculation and experimental data
in the control nozzles of FEM-model in different
operational modes and at different levels of work
loading parameters
Comparison of calculation and
experimental data in such operating modes
and time periods when only one loading
parameter changes, and the other
parameters do not change
Adjustment of the calculative
modulus: improvement of the
software, refinement of the
monitored object’s geometry,
changing of the finite-element mesh
in definite zones, correction of the
boundary condition, etc.
The calculative modulus is calibrated
The
cal
cula
tive
mod
ulus
mus
t be
adju
sted
- data do not coincide
2
1
2
Comparison of calculation and
experimental data in cases when
simultaneous changing of two or more
loading parameters is observed
1
FEM-modulus works efficiently,
the loading processes in different
operational modes are modeled reliably
2
1
- data coincide
Stage 9. Teaching leeds calibration of FEM model
20
Stage 10. Design-experimental stress analysis
0
6
12
18
24
30
36
42
48
54
60
66
72
0 5 10 15 20
Число циклов нагружения
То
лщ
ин
а с
тен
ки
, м
м
ΔTCC №111 = 30 C ΔTCC №111 = 60 C ΔTCC №111 = 90 C
Conclusion. Thermal shocks cause stresses exceeding the yield strength value . Growth of
initial defects to a through wall crack can occur at small number of cyclic loads initiated by
thermal shocks.
σ, MPa
а→[a]
dL/dN
21
Stage 11. Real-time investigation of thermal shocks causes
This program was made specially for express analysis of technical needs of NPP staffs
23.08 Расход периодической продувки
0
5
10
15
20
25
30
35
23.08.12
0:00
23.08.12
2:00
23.08.12
4:00
23.08.12
6:00
23.08.12
8:00
23.08.12
10:00
23.08.12
12:00
Дата, время
Расхо
д,
м3/ч
Расход воды периодической продувки ПГ-4
23.08 Давление в 2 контуре
0
10
20
30
40
50
60
70
80
90
100
23.08.12
0:00
23.08.12
2:00
23.08.12
4:00
23.08.12
6:00
23.08.12
8:00
23.08.12
10:00
23.08.12
12:00
Дата, время
Да
вл
ен
ие
, кгс
/см
2
Давление пара в ПГ-4 Давление питательной воды в коллекторе №2
Conclusion. Absence of water discharge in the SG blowdown system causes cooling
down of water in blowdown pipelines, pressure jumps in secondary circuit lead to
back streaming of cold water to SG and to formation of a thermal shock.
SG blowdown is switched off Pressure jumps in secondary circuit
+
22
~ ~ ~ ~
~
~
~
~
~
~
~
~
~ в расширитель продувки
ПГ-1 ПГ-2 ПГ-3 ПГ-4
1 2
3
Conclusions.
1. Compensating measures on modification of SG blowdown regalement
had been applied.
2. Effectiveness of compensating measures was confirmed – the subsequent
on-line monitoring of SG on Novovoronezh NPP, Unit 5 during 2 years show
shat thermal shocks do not occur, dominating thermo-force factor of
operational damaging was successfully eliminated.
Stage 12. Development of compensation procedure and
checking its effectiveness
Scheme of cut-off of SG blowdown pipelines
23
Example № 2. History of stratification influence
Object of investigation: surge line of the primary circuit pressurizer system of
WWER-1000 Unit.
Recommendations of the audit
RE.NNPP.NSO.11.13
It is necessary to carry out analysis
of international experience on
thermal stratification study as
regards to the primary circuit
pipelines, and also to provide
assessments of thermal fatigue
effects on WWER-1000 NPPs.
Objective
Estimate real level of stratification for substantiation of long time extension
for additional 30 years.
Surge line
24 24 24
The effect of thermal stratification
(physics)
Stratification occurs at horizontal sections of pipelines when coolant having different temperatures flows with low rates and causes stratification of the whater on «cold» (lower) and «hot» (upper) layers.
25
1. Development of the monitoring system architecture .
2. Laboratory tests of strain gauges at temperatures up to 400 0С.
3. Mounting of the monitoring system on surge line
of the Novovoronezh NPP, Unit 5 during all fuel company (1
year).
4. Analysis of on-line monitoring results.
5. Development of FEM model of the surge line.
6. Teaching and modernization FEM model and calculation by
using of experimental data.Recommendation to NDT control.
7. Analysis of results of surge line’s weld joints non-destructive
inspection in recommended zones.
8. Development of compensating procedures and check of their
effectiveness.
Main stages of work
26
Stage 1. Development of the monitoring system architecture
Monitoring of temperatures and
deformations in control sections
of the surge line
26 26
Scheme of thermocouples and strain gauges location
ARCHITECTURE BASE FUNCTIONS
27
Def
orm
atio
n
Time, sec
Def
orm
atio
n
Time, sec
Stage 2. Laboratory tests of strain gauges at temperatures
up to 400 0С
28
Mounting of thermocouples
Electronic module
Mounting of strain gauges
Mounting of protective covers
Stage 3. Mounting of the monitoring system on surge line
of the Novovoronezh NPP, Unit 5
29 29
Stage 4. Analysis of on-line monitoring results
22-23.02 Распределение температур в сечении IV
20
70
120
170
220
270
320
370
22.02.14
0:00
22.02.14
6:00
22.02.14
12:00
22.02.14
18:00
23.02.14
0:00
23.02.14
6:00
23.02.14
12:00
23.02.14
18:00
24.02.14
0:00
Дата, время
Тем
пер
ату
ра,
0С
IV-T1 IV-T2 IV-T3 IV-T4 IV-T5
21.02-23.02 Тепловая мощность средневзвешенная
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
21.02.14 0:00 22.02.14 0:00 23.02.14 0:00 24.02.14 0:00
Дата, время
Мо
щн
ость
, М
Вт
Тепловая мощность средневзвешенная
22-23.02 Распределение температур в сечении I
20
70
120
170
220
270
320
370
22.02.14
0:00
22.02.14
6:00
22.02.14
12:00
22.02.14
18:00
23.02.14
0:00
23.02.14
6:00
23.02.14
12:00
23.02.14
18:00
24.02.14
0:00
Дата, время
Тем
пер
ату
ра,
0С
I-T1 I-T2 I-T3 I-T4 I-T5 TГЦТ1 TГЦТ2
22-23.02 Распределение температур в сечении II
20
70
120
170
220
270
320
370
22.02.14
0:00
22.02.14
3:00
22.02.14
6:00
22.02.14
9:00
22.02.14
12:00
22.02.14
15:00
22.02.14
18:00
22.02.14
21:00
23.02.14
0:00
Дата, время
Тем
пер
ату
ра,
0С
II-T1 II-T2 II-T3 II-T4 II-T5
22-23.02 Распределение температур в сечении III
20
70
120
170
220
270
320
370
22.02.14
0:00
22.02.14
3:00
22.02.14
6:00
22.02.14
9:00
22.02.14
12:00
22.02.14
15:00
22.02.14
18:00
22.02.14
21:00
23.02.14
0:00
Дата, времяТ
ем
пер
ату
ра,
0С
III-T1 III-T2 III-T3 III-T4 III-T5
In sections I, II, III stratification is absent
!!!Big thermal stratification in section IV!!!
Conclusion. Temperature
difference at control section IV
due to thermal stratification
reached 160°С, high thermal-
force stresses were revealed.
30
Stage 5. Development of FEM model of the surge line
ДТ
31
Stage 6. Design-experimental stress analysis
Conclusion. Zones of maximum accumulated cyclic damage locate at
outer surface of the dissimilar weld joint №7.
Weld №7
T, C σ, MPa
a→[a]
32
Conclusion. It is necessary to develop effective compensating procedure to solve the
problem of stratification cracking of dissimilar weld of surge line.
Thermal stratification
Stage 7. Analysis of results of surge line’s weld joints
non-destructive inspection in recommended zones
Cracks visible with dyes penetrants
33 33
Input parameters: roller size, force of rolling, number of loading cycles, velocity of rolling. Output parameters: surface roughness, loads on roller, distribution of residual stresses, new mechanical properties of surface
FEM modeling of the hardening process Surface rolling
hammering
Conclusions.
1. It is not possible to change operational modes of the pressurizer system and
additional cyclic loads caused by thermal stratification will influence in future.
2. Simple and original solution: change strength properties of metal in surface layer
where operational cracks had been found, i.e. increase yield and ultimate strength
by use of the hardening method (surface rolling hammering)
Stage 8. Development of compensating procedure and
check of their effectiveness
34 FEM model of the test-bench 3-D model of the test-bench
Calculation of reaction of the support
Stage 8.1. Design of the laboratory test-bench
35 35
Stage 8.2. Manufacturing of the laboratory test-bench,
testing of the technology and rolling modes
36
37
38 38
Video of the rolling process on the laboratory test bench
39
Using the technology of continuous registration of load
/indentation depth diagram in agreement with ISO 14577 it
is possible to solve a problem of reconstruction of
conventional stress – strain diagram.
t
P
P
t
Indentation diagram
d D
t
P
Stages of convertation of indentation diagram
f(∆t/D)
P
2 4
d P σ ×
× p
σp σm
f(∆l/l0)
S
The method is based on the phenomenon of the similarity of
indentation diagram with plastic hardening part of stress – strain
diagram. It was taken as a basis of new Russian standard GOST
56232 -2014 Determination of «stress – strain» diagram in the
course of ball instrumental indentation.
FEM - distribution of plastic strain
Stage 8.3. Selection of the method for measurement of
metal mechanical properties after hardening
Hardness tester Mubatec-HU1
Different zones of dissimilar welded joint were tested by
hardnes stester Mubatec-HU1 using ball instrumental
indentation technique.
0
50
100
150
200
250
300
350
400
450
0 10 20 30 40 50 60 70 80
Depth, mkm
Fo
rce,
N
Base Metal
HAZ
Welding 2
Welding 1
Welded seam
0
100
200
300
400
500
600
700
800
900
1000
0 2 4 6 8 10 12
Strain, %
Str
es
s,
MP
a Base Metal
HAZ
Welding 2
Welding 1
Welded seam
1 2 3 4 5
Stress – strain diagrams for all tested materials were derived
which will be used while constructing of numerical model Material HB
Rp0,2,
MРa Rm,
MРa
1 Base Metal 198 456 581
2 Heat Affected Zone 274 693 814
3 Welding 1 197 412 617
4 Welding 2 211 456 647
5 Welded seam 233 534 679
Stage 8.4. Selection of control zones for measurement
of metal mechanical properties
41
Hardness tester Mubatec-
HU1 - Testing of sample tube
Inspection of surge line on
NPP Kozlodui
(Bulgaria 2015)
0
200
400
600
800
1000
1200
1400
1600
0 50 100 150
Depth, mkm
Fo
rce, N
Initial
Rolled
0
100
200
300
400
500
600
700
800
900
0 2 4 6 8 10
Strain, %
Str
ess, M
Pa
Initial
Rolled
The results of rolling of sample 10GN2MFA tube were
tested by ball indentation method.
Stage 8.5. Analysis of results of measurement of metal
mechanical properties before and after hardening
Conclusion. Hardness of rolled surface increases
approximately 1.5 times and Yield strength – 2 times
more then those of initial material and + Bonus –
condition the surface!
Изменеие микротвердости по глубине
205
210
215
220
225
230
235
240
0 100 200 300 400 500 600 700
Глубина от поверхности, мкм
Ми
кр
отв
ер
до
сть
42 42
Stage 8.6. Measurement of residual stresses by the drill-hole method using strain gauges
43 43
Stage 8.7. Execution of cyclic loading tests (pure bending) of prism-type samples
F
F
incision
Fatigue crack
44
М incision
Stage 8.8. Execution of cyclic loading tests (pure bending) of corset-type samples
Fatigue crack
45 45
Results of tests of corset-type samples
Conclusion. The results demonstrated high effectiveness of the metal
hardening procedure, considerable rise of cyclic durability of hardened
samples was confirmed.
Results of tests of prism-type samples
Stage 8.9. Analysis of the results of cyclic loading tests
46 46
Stage 8.10. Manufacturing and testing of the full-scale facility for surface hardening
47 47
Video of the rolling process by the full-scale facility
48
Conclusion
1. Using of multipara metrical on-line monitoring of
survervalence (Patent RU№2014104752/07 (007605),
12.02.2014) showed high effectivenes for precise assessment
of residual lifetime (damageability) in critical zones
considering the PLiM issues.
2. Rolling hammering procedure were designed. Its
procedure decrease cycling damage in 3 times.
3. Designed method of instrumental indentation for non-
destructive testing of mechanical properties, showed its
effectiveness for control different zones of joint wield before
and after hammering.
4. Based on this monitoring we designed labor-educational
stand for fast learning of multipara metrical on-line
monitoring of survervalence for explaining to engineers
from NPPs.
• Specialized labor-educational training stand
49
50
NEW METHODOLOGY OF ON-LINE EXPERIMENTAL-CALCULATED MONITORING (AGEING MANAGEMENT) FOR IMPROVING PERFORMANCE OF
A SYSTEM, STRUCTURES OF COMPONENT - MUBATEC RESOURCE-EXPERT – BASIC PRINCIPLES
Analysis of initial design
documentation
Analysis of operation history, including fail by loss of strength
Analysis of inspection, monitoring,
maintenance history
Analysis of materials and
material properties and environment
condition
Development of monitoring programe
Implementation of 3D laser scanning in order
to restore the actual geometry of the structure
and thermal survey to determine the
temperature fields
Carrying out finite element
calculation. Load stress
can come arise from the
design.
Expert analysis critical areas (zone) and installation
of expert sensors - temperature, strain,
displacement, vibration, acoustic emission,
ultrasonic testing – for training and verification 3D
finite element model and receiving real data from
operation loads
Improvement of calculation
program (correction of the
boundary conditions, changes in
the finite element partition,
geometry change, fixing and
loading conditions)
Calculation of the factual
accumulated operational
defectiveness
(variations of stress σ – strain ε)
Initial examination of the objectRecovery of deficit information and verify the
information about real condition
Step 1
Step2
Finite element simulation of operation loading
by use design data
Step3
Determination of the most
loaded zones
Finite element training and stress-strain calculations by use intelligent finite element model. Managing
ageing, evaluating critical zones and estimation residual service life timeStep
5
Calculation code teaching
Evaluation of stress and strain state
in critical areas
Comparison of the calculated values with
the experimental data of deformations and
displacements
NO YES
Clarification of the factual survivability of critical areas of the structure as a result of laboratory
tests of scale models – BENEFITS and CHALLENGE of on-line monitoring
Step6*
critical areas
* Schematic illustration of the different regimes of stable fating crack propagation
Particular qualities :
• The unified electronic monitoring system based on modules National
Instruments
• Very fast communication of experimental data from slow channels
and fast channels in on-line mode
Assembling and installation of a unified electronic self-
contained monitoring system of acquisition and
transmission data. Collection and performance data.
Design and installation of control systems for
collecting, processing and transmission
monitoring
Step4
Slow channels
Fast channels
According to the factual data
obtained geometry design
finite element 3Dimentional
finite element model for the
calculation of stress-strain state
Overview of traditional performance test
Critical zone
Time, τ
Tota
l str
ess,
σ
σ max
σ min
F
A
B
C
D
E
A’
F’ F”
A”
FEM stress-strain variations
10-2
10-4
10-6
10-8
one lattice spacing per cycle
regime I regime II
regime IIIm
1
K1c
1 mm/week
1 mm/min
1 mm/hour
1 mm/day Cra
ck g
row
th r
ate
at 5
0 H
z
Stress intensity range ∆K (log ∆K)
Cra
ck p
rop
agat
ion
rat
e da
/dN
(mm
/cyc
le)
Kth
Finite element model on-line
teaching (improving software)
Static and dynamic failure
analysis by use on-line
monitoring data
Real critical zone discovery
Risk management of safety and
dependability
Cycles to failure, N
∆σStre
ss a
mp
litu
de,
∆σ
Nc
Step 6*
Probability of failure P
A scale model
of the critical
zone
Additional
control sensors
PROCESS COMPUTER
Generation of load sequence
Measurement of ∆ε, ∆σ
Evaluation storage
Damage parameter = ∆ σ ∙ ∆ε
Performance stress-strain variation
Plastic zone
Low-cycle fatigue test
Tensile Test
Strain concentration crack initiation and
growth
Schematic diagram illustrating the various stages of damage critical zone in an engineering component and the approaches used to estimate the residual life
Design testing programs by use data of on-line experimental-calculated monitoring
Damage parameter = ∆σ∙∆ε
Recourse correction
Critical zone marginal state assessment
Additional
control sensorsTest specimen
P
P
P
σ
ε
ε
P
P
P
u
P
v
Test specimen manufacture and testing formechanical properties estimation
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