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

Transcription

1 Symposium on Structural Health Monitoring and Non-Destructive Testing, on November 29, 2013, at Lyon, France On-line monitoring of material degradation due to fatigue by using sensor principles based on micromagnetic and ultrasonic NDT Gerd Dobmann and Christian Boller Fraunhofer-IZFP, Campus E 3 1, Saarbruecken, Germany gerd.dobmann@izfp.fraunhofer.de

2 Outline: Motivation NPP, primary circuit austenitic stainless steel pipes, lifetime extension and 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

3 Motivation for Fatigue Monitorin in the Nuclear Industry, PWR, primary circuit pipes Surgeline and Pressurizer Sprayline

4 Motivation and background for VHCF of CFRP Increasingly use of CFRP in the aircraft and automotive industry [Hosoi et. al.] CF-EP [0/90 2 ] s? 10 9 Airbus A350 (June 14, 2013) Development of an US-Testing Facility for CFRP

5 3MA Micromagnetic Properties / Strengthening Effects Micro-magnetic Multiple parameter Microstructure and Stress Analysis 3MA Strengthening by lattice defects is impeding of dislocation movement mechanical properties hardness, yield strength tensile strength, upper shelf FATT microstructure parameters: vacancies dissolved atoms dislocations precipitates grain boundaries phase boundaries inclusions pores Micro-magnetic parameters lattice defects impede Bloch wall movements 3MA

6 Multiple-Sensor Concept

7 Fatigue of Austenitic Steels, Primary Circuit GMR measurements insitu (online in real time) on meta-stable austenitic stainless steels Material: AISI 321 (German Grade Ti-stabilized and Nbstabilized) 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

8 Materials

9 Fatigue of Austenitic Steels, Primary Circuit Fatigue Characterization due to eddy current transfer impedance

10 GMR Sensor

11 Fatigue of Austenitic Steels, Primary Circuit

12 Fatigue of Austenitic Steels, Primary Circuit

13 Fatigue of Austenitic Steels, Primary Circuit In-Situ EMAT Measurements (Electromagnetic Acoustic Transducer) Transmitter Constant total strain amplitude 0.8 ε a,t 1.6% Strain ratio: R=-1 f=0.01hz; T=100s Temperature range: AT T 300 C EMAT Elevated temperatures prohibit use of traditional (couplant demanding) US-probes Servo-hydraulic testing machine with integrated EMAT- Probes Receiver

14 Fatigue of Austenitic Steels, Primary Circuit Experimental Set-Up and Measuring Quantities Transmitter 1 Trigger 0.5 σ Radial polarized shear waves Amplitude [V] Amplitude Receiver Time [µs] Time Of Flight (TOF)

15 Fatigue of Austenitic Steels, Primary Circuit Development of Dtof mean and s a EMAT TOF Ambient Temperature Stress Amplitude ε a,t = 1.6% ε a,t = 1.6%

16 Fatigue of Austenitic Steels, Primary Circuit Development of Dtof mean and s a 300 C EMAT TOF ε a,t = 1.6% Stress Amplitude ε a,t = 1.6%

17 EMAT Concept for Fatigue Characterisation of High Performance Pipes Transmitter T R Receiver Transmitter and receiver integrated in same probe R T Rayleigh waves (on surface) Radial polarized shear waves (in volume)

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

19 Monitoring Single-Edge-Bending SB(B)-Tests turning point

20 Statistical experience up to now

21 Magnetic Flux Leakage Sensors

22 MFL-Monitoring

23 Conclusions Part I Insitu monitoring of fatigue experiments by using micromagnetic quantities and UT TOF show the potential for sensor developments applied in ageing management and to shorten fracture mechanical destructive tests.

24 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 quality assurance of CFRP components during production and in operation covering materials characterization and defect and damage detection as well as monitoring and evaluation of ageing phenomena (fatigue) and failure prediction 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.

25 Motivation: Very High Cycle Fatigue (VHCF) Testing Fatigue behavior of CFRP: investigated in the past up to about N=107 loading cycles so far because of missing testing devices [MTS] [Rumul] Mechanical resonance Servo-hydraulic pulsator (100 Hz): oscillation device (5 Hz): 4 month 6.5 years [WKK] Ultrasonic testing device (20 khz) (effective test frequency 2 khz): 6 days Collaborative project with the Institute of Materials Science and Engineering 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

26 Ultrasonic Fatigue Setup (University Kaiserslautern) Measuring and controlling device Machine frame Visual display and operating unit Loading device Laser vibrometer Control device laser vibrometer Plane table Data acquisition Compressed air valve Ultrasonic generator

27 Development of the US-Testing Facility Shoulder unit

28 Online Monitoring of Ultrasonic Fatigue Processes

29 Investigated CFRP Material Reference Material 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 G GPa E22 58 GPa G GPa E GPa G GPa µm

30 Temperature distribution of a CF-PPS specimen at N = 9 x 108, a = 4.2 MPa

31 Temperature distribution of a CF-PPS specimen at N = 4 x 108, a = 5.9 MPa

32 Ultrasonic Fatigue Setup (University Kaiserslautern)

33 Sample Vibration and Radiation Time Signals During Loading

34 Fast Fourier Transform of Laser Vibrometer Time Signals

35 Higher Harmonics Distortion Factor of Time Signals CF-PPS

36 Short Time Fourier Transform of Laser Vibrometer Signals CF-PPS N: number of loading cycles, Nf: number of cycles to failure

37 Ultrasonic Immersion Technique: Set-up

38 Ultrasonic Images: Immersion Technique

39 Suggestion for a VHCF damage model for CF-PPS high concentration of matrix cracks and delaminations increasing amount of matrix cracks N1 N2 several matrix cracks N3 N N4

40 Conclusion Part II 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 their change with the number of loading cycles FFT: frequency spectrum, distortion factor STFT: time frequency spectrum Offline characterization of the specimens: initial state, during loading pauses, and after fatigue

41 Acknowledgement I The funding of the Federal Ministry of Economics and Technology, the Ministry 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 the fatigue 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. 41

42 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 cooperation with WKK, Technical University Kaiserslautern, the team of Dietmar Eifler.

43 Literature. G. Dobmann: Non-destructive Testing for Ageing Management of Nuclear Components, Nuclear Power - Control, Reliability and Human Factors, 2011, ISBN: H.-J. Salzburger: EMATs and its Potential for Modern NDE - State of the Art and Latest Applications, Proceedings of the IEEE International Ultrasonics Symposium 1, 2009, 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 martensite in case of the austenitic stainless steel X 6 CrNiTi (in German), Ph.D.-thesis at the University Kaiserslautern, 1999 M. Lang: Non-destructive characterization of the cyclic deformation behavior and the development of strain-induced martensite in case of the austenitic stainless steel X6 CrNiTi 1810 by use of sensitive magnetic sensors (in German), Ph.D.-thesis at the University of the Saarland, Saarbrücken, 2000 I. Altpeter et al: Early detection of damage in thermo-cyclically loaded austenitic materials, ENDE 2011 proceedings, ISO press, ENDE 2011 conference, March 10-12, Chennai German patent DE : Magnetfeldsensor mit ferromagnetischer, dünner Schicht, filed on A. Yashan,: To eddy current (EC) and magnetic leakage flux (ET) testing with GMR sensors (in German), Ph.D.thesis at the Saar university, Saarbrücken, 2008 ESIS P2-92, Procedure for determining the fracture toughness of materials,(1992)

44 ESIS P6-98, Procedure to measure and calculate material parameters for the local approach to fracture using notched tensile specimens, European Structural Integrity Society. Ed. K.-H. Schwalbe, GKSS Geeshacht (1998) ASTM E , Standard test method for plane-strain fracture toughness of metallic materials, Annual Book of ASTM Standards Vol , American Society for Testing and Materials (1997) ASTM E , Standard test method for J-integral characterization of fracture toughness, Annual Book of ASTM Standards Vol , American Society for Testing and Materials (1997) ASTM E , Standard test method for measurement of fracture toughness, Annual Book of ASTM Standards Vol , American Society for Testing and Materials (1997) D. Backe et al., The Minerals, Metals & Materials Society (2012), pp U. Rabe et al., 2012, htstructural Integrity Society (1992)