Symposium on Structural Health Monitoring and on … · • ASTM E 399-90, Standard test method for...

$: Symposium on Structural Health Monitoring and on … · • ASTM E 399-90, Standard test method for plane-strain fracture toughness of metallic$
© 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

[email protected]

Symposium on Structural Health Monitoring andNon-Destructive Testing, on November 29, 2013,at Lyon, France


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


Motivation for Fatigue Monitorin in the NuclearIndustry, PWR, primary circuit pipesSurgeline and Pressurizer Sprayline


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


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


Multiple-Sensor Concept


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


Materials


Fatigue Characterization due to eddy current transferimpedance



GMR Sensor


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



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



Development of Dtofmean and sa

EMAT TOF Stress Amplitude

εa,t = 1.6%

Ambient Temperature

εa,t = 1.6%



Development of Dtofmean and sa

EMAT TOF

300°C

Stress Amplitude

εa,t = 1.6%εa,t = 1.6%



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


Monitoring Single-Edge-Bending SB(B)-Tests


Monitoring Single-Edge-Bending SB(B)-Tests

turning point


Statistical experience up to now


Magnetic Flux Leakage Sensors


MFL-Monitoring


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


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.


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


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


Development of the US-Testing Facility – Shoulderunit


Online Monitoring of Ultrasonic Fatigue Processes


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


Temperature distribution of a CF-PPS specimenat N = 9 x 108, a = 4.2 MPa


Temperature distribution of a CF-PPS specimenat N = 4 x 108, a = 5.9 MPa


Ultrasonic Fatigue Setup (University Kaiserslautern)


Sample Vibration and Radiation Time Signals During Loading


Fast Fourier Transform of Laser Vibrometer Time Signals


Higher Harmonics Distortion Factor of Time Signals

CF-PPS


Short Time Fourier Transform of Laser Vibrometer Signals

CF-PPS N: number of loading cycles, Nf: number of cycles to failure


Ultrasonic Immersion Technique: Set-up


Ultrasonic Images: Immersion Technique


Suggestion for a VHCF damage model for CF-PPS

N

N1 N2 N3 N4

severalmatrix cracks

increasingamountof matrix cracks

high concentrationof matrix cracksand delaminations


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


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.


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.


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).


• 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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