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© FraunhoferInstitute of Materials Science and Engineering
On-line monitoring of material degradation dueto fatigue by using sensor principles based onmicromagnetic and ultrasonic NDT
Gerd Dobmann and Christian Boller Fraunhofer-IZFP, Campus E 3 1,Saarbruecken, Germany
gerd.dobmann@izfp.fraunhofer.de
Symposium on Structural Health Monitoring andNon-Destructive Testing, on November 29, 2013,at Lyon, France
© FraunhoferInstitute of Materials Science and Engineering
Outline: Motivation
NPP, primary circuit austenitic stainless steel pipes, lifetime extensionand lifetime management
CFRP manufactering for airplane components and car bodies, SHM
Micromagnetic techniques
High temperature EMAT
Fatigue results austenitic steel
Fatigue of CFRP
Development of the Ultrasonic Testing Facility
Reference material
Selected results for CF-PPS
Online-Thermography
3D-Scanning-Laser-Vibrometry, microphone
UT
Microstructural changes in the VHCF-range
Conclusion
© FraunhoferInstitute of Materials Science and Engineering
Motivation for Fatigue Monitorin in the NuclearIndustry, PWR, primary circuit pipesSurgeline and Pressurizer Sprayline
© FraunhoferInstitute of Materials Science and Engineering
Motivation and background for VHCF of CFRP
Increasingly use of CFRP in theaircraft and automotive industry
Airbus A350 (June 14, 2013)
Development of anUS-Testing Facilityfor CFRP
?[Hosoi et. al.]
109
CF-EP [0/902]s
© FraunhoferInstitute of Materials Science and Engineering
Micro-magnetic
Multiple parameter
Microstructure
and
Stress Analysis
– 3MA
microstructureparameters:
vacanciesdissolved atoms
dislocationsprecipitates
grain boundariesphase boundaries
inclusionspores
mechanical propertieshardness, yield strength
tensile strength, upper shelfFATT
Micro-magnetic parameters
3MA
Strengtheningby
lattice defectsis
impeding ofdislocationmovement
lattice defectsimpede
Bloch wallmovements
3MA – Micromagnetic Properties / StrengtheningEffects
© FraunhoferInstitute of Materials Science and Engineering
GMR measurements insitu (online in real time) on meta-stable austeniticstainless steels
Material: AISI 321 (German Grade 1.4541 - Ti-stabilized and 1.4550 - Nb-stabilized)
To separate between high carbon, low Ti/Nb, then phase transformation ’ deformation-induced martensite
or low carbon, high Ti/Nb, no phase transformation
or higher service temperatures, > 280°C, very low or no martensite
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Fatigue Characterization due to eddy current transferimpedance
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Servo-hydraulic testing machine with integrated EMAT-Probes
EMAT
Transmitter
Receiver
In-Situ EMAT Measurements (Electromagnetic AcousticTransducer)
Constant total strain amplitude 0.8 ≤ εa,t ≤ 1.6%Strain ratio: R=-1f=0.01Hz; T=100s
Temperature range: AT ≤ T ≤ 300°C
Elevated temperatures prohibit use oftraditional (couplant demanding) US-probes
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
0 20 40 60 80 100
0
-0.5
-1
1
0.5
Am
plit
ude
[V]
Time [µs]Time Of Flight(TOF)
Amplitude
Experimental Set-Up and Measuring Quantities
Radialpolarizedshearwaves
Transmitter
Receiver
σ
Trigger
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Development of Dtofmean and sa
EMAT TOF Stress Amplitude
εa,t = 1.6%
Ambient Temperature
εa,t = 1.6%
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Development of Dtofmean and sa
EMAT TOF
300°C
Stress Amplitude
εa,t = 1.6%εa,t = 1.6%
Fatigue of Austenitic Steels, Primary Circuit
© FraunhoferInstitute of Materials Science and Engineering
Transmitter
T R
RT
Receiver
Transmitterand receiverintegrated insame probe
Rayleigh waves(on surface)
Radial polarized shear waves(in volume)
EMAT Concept for Fatigue Characterisation of High PerformancePipes
© FraunhoferInstitute of Materials Science and Engineering
Monitoring Single-Edge-Bending SB(B)-Tests
© FraunhoferInstitute of Materials Science and Engineering
Monitoring Single-Edge-Bending SB(B)-Tests
turning point
© FraunhoferInstitute of Materials Science and Engineering
Insitu monitoring of fatigue experiments by using micromagnetic quantitiesand UT TOF show the potential for sensor developments applied in ageingmanagement and to shorten fracture mechanical destructive tests.
http://www.intechopen.com/books/nuclear-power-control-reliability-and-human-factors/non-destructive-testing-for-ageing-management-of-nuclear-power-components
Conclusions Part I
© FraunhoferInstitute of Materials Science and Engineering
Motivation
Carbon fiber reinforced plastics (CFRP): lightweight materials
Increasingly gain significance for industrial applications such as e.g.aerospace structures and automotive body parts
Request for nondestructive testing (NDT) techniques for qualityassurance of CFRP components during production and in operation
covering materials characterization and defect and damagedetection as well as
monitoring and evaluation of ageing phenomena (fatigue) and failureprediction
CFRP components in service: subjected to oscillating loads
amount up to 1011 cycles in a typical lifespan of more than 20 years
special interest on fatigue of CFRP in the very high cycle regime, i.e.more than 108 loading cycles.
© FraunhoferInstitute of Materials Science and Engineering
Motivation: Very High Cycle Fatigue (VHCF) Testing
[MTS]
Servo-hydraulicoscillation device (5 Hz):
≈ 6.5 years
[Rumul]
Mechanical resonancepulsator (100 Hz):
≈ 4 month
[WKK]
Ultrasonic testing device (20 kHz)(effective test frequency ≈ 2 kHz):
≈ 6 days
Fatigue behavior of CFRP: investigated in the past up to about N=107
loading cycles so far because of missing testing devices
Collaborative project with the Institute of Materials Science andEngineering at the University of Kaiserslautern, Germany (WKK):
Development of a three point bending ultrasonic fatigue testing system
Combination with online monitoring of the fatigue processes
© FraunhoferInstitute of Materials Science and Engineering
Ultrasonic Fatigue Setup (University Kaiserslautern)
Machine frame
Loading device
Plane table
Measuring andcontrolling device
Visual display andoperating unit
Control devicelaser vibrometer
Data acquisition
Ultrasonic generator
Compressedair valve
Laser vibrometer
© FraunhoferInstitute of Materials Science and Engineering
Development of the US-Testing Facility – Shoulderunit
© FraunhoferInstitute of Materials Science and Engineering
Online Monitoring of Ultrasonic Fatigue Processes
© FraunhoferInstitute of Materials Science and Engineering
Investigated CFRP Material
90°
0° 400 µm
Tepex® dynalite 207-C22/50 % (CF-PPS, Bond Laminates)
Orthotropic fiber fabric layout (200 g/m³)
Polyphenylensulfide(PPS)-matrix, thermoplast,
density: ρPPS = 1.35 g/cm³
Glass transition and melting temperature: Tg = 90°C, TM = 285°C
Commercially available, reproducible quality
E11 58 GPa G12 3.16 GPa 12 0.001
E22 58 GPa G13 6.65 GPa 13 0.1
E33 3.35 GPa G23 6.65 GPa 23 0.1
Reference Material
© FraunhoferInstitute of Materials Science and Engineering
Temperature distribution of a CF-PPS specimenat N = 9 x 108, a = 4.2 MPa
© FraunhoferInstitute of Materials Science and Engineering
Temperature distribution of a CF-PPS specimenat N = 4 x 108, a = 5.9 MPa
© FraunhoferInstitute of Materials Science and Engineering
Ultrasonic Fatigue Setup (University Kaiserslautern)
© FraunhoferInstitute of Materials Science and Engineering
Sample Vibration and Radiation Time Signals During Loading
© FraunhoferInstitute of Materials Science and Engineering
Fast Fourier Transform of Laser Vibrometer Time Signals
© FraunhoferInstitute of Materials Science and Engineering
Higher Harmonics Distortion Factor of Time Signals
CF-PPS
© FraunhoferInstitute of Materials Science and Engineering
Short Time Fourier Transform of Laser Vibrometer Signals
CF-PPS N: number of loading cycles, Nf: number of cycles to failure
© FraunhoferInstitute of Materials Science and Engineering
Suggestion for a VHCF damage model for CF-PPS
N
N1 N2 N3 N4
severalmatrix cracks
increasingamountof matrix cracks
high concentrationof matrix cracksand delaminations
© FraunhoferInstitute of Materials Science and Engineering
Ultrasonic fatigue system for CFRP, operation frequency of 20 kHz,developed at Kaiserslautern, Germany
Online monitoring during fatiguing
Infrared camera: Temperature control to prevent overheating
Laser vibrometer: Sample vibration during loading
Microphone: Sound radiation during loading
Evaluation of the sample vibration and radiation time signals and theirchange with the number of loading cycles
FFT: frequency spectrum, distortion factor
STFT: time frequency spectrum
Offline characterization of the specimens: initial state, during loadingpauses, and after fatigue
Conclusion Part II
© FraunhoferInstitute of Materials Science and Engineering
41
Acknowledgement I
The funding of the Federal Ministry of Economics and Technology, theMinistry of Science and Education and the National Science Foundation(DFG) of Germany is very much acknowledged.Thanks to MPA and WK, Kaiserslautern for co-operation concerning thefatigue and fracture mechanics research.
I acknowledge furthermore the contribution of my colleagues Iris Altpeter,Klaus Szielasko, Ralf Tschuncky, and Gerhard Hübschen to the R&D.
© FraunhoferInstitute of Materials Science and Engineering
Acknowledgement II
Financial support from the German Science Foundation (DFG)within the Priority Program 1466: Life∞- „ Infinite Life for cyclically loaded high-performance materials” and the fruitful cooperationwith WKK, Technical University Kaiserslautern, the team of DietmarEifler.
© FraunhoferInstitute of Materials Science and Engineering
Literature
• G. Dobmann: Non-destructive Testing for Ageing Management of Nuclear Components,Nuclear Power - Control, Reliability and Human Factors, 2011, ISBN: 978-953-307-599-0
• H.-J. Salzburger: EMATs and its Potential for Modern NDE - State of the Art and LatestApplications, Proceedings of the IEEE International Ultrasonics Symposium 1, 2009,621-628
• H.-J. Salzburger, F. Niese, and G. Dobmann: EMAT pipe inspection with guided waves,Welding in the world 56 (2012), 5-6
• H.-J. Bassler: Cyclic deformation behavior and strain-induced development of martensitein case of the austenitic stainless steel X 6 CrNiTi 18 10 (in German), Ph.D.-thesis at theUniversity Kaiserslautern, 1999
• M. Lang: Non-destructive characterization of the cyclic deformation behavior and thedevelopment of strain-induced martensite in case of the austenitic stainless steel X6CrNiTi 1810 by use of sensitive magnetic sensors (in German), Ph.D.-thesis at theUniversity of the Saarland, Saarbrücken, 2000
• I. Altpeter et al: Early detection of damage in thermo-cyclically loaded austeniticmaterials, ENDE 2011 proceedings, ISO press, ENDE 2011 conference, March 10-12,Chennai
• German patent DE 3820475: Magnetfeldsensor mit ferromagnetischer, dünner Schicht,filed on 16.06.1988
• A. Yashan,: To eddy current (EC) and magnetic leakage flux (ET) testing with GMRsensors (in German), Ph.D.thesis at the Saar university, Saarbrücken, 2008
• ESIS P2-92, Procedure for determining the fracture toughness of materials,(1992).
© FraunhoferInstitute of Materials Science and Engineering
• ESIS P6-98, Procedure to measure and calculate material parameters for the local approach tofracture using notched tensile specimens, European Structural Integrity Society. Ed. K.-H.Schwalbe, GKSS Geeshacht (1998)
• ASTM E 399-90, Standard test method for plane-strain fracture toughness of metallicmaterials, Annual Book of ASTM Standards Vol. 03.01, American Society for Testing andMaterials (1997)
• ASTM E 1737-96, Standard test method for J-integral characterization of fracture toughness,Annual Book of ASTM Standards Vol. 03.01, American Society for Testing and Materials (1997)
• ASTM E 1820-96, Standard test method for measurement of fracture toughness, Annual Bookof ASTM Standards Vol. 03.01, American Society for Testing and Materials (1997)
• D. Backe et al., The Minerals, Metals & Materials Society (2012), pp 855-863• U. Rabe et al., 2012, htStructural Integrity Society (1992)
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