IT Support of NDE and SHM with Application
of the Metal Magnetic Memory Method
Mirosław WITOS, Mariusz ZIEJA, Bartłomiej KURZYK
Air Force Institute of Technology
Warsaw, Poland,
7th International Symposium on NDT in Aerospace 16 – 18 November 2015, Bremen, Germany
We4-A3
Outline: Introduction Motivation Metal Magnetic Memory Method SWOT Analysis IT Support of the MMM Method/Applications Conclusion
1F mode1F mode
Introduction
How to detect level of fatigue of ferromagnetic and metastable paramagnetic alloys
before damage and the accident?
Some problems of material fatigue in aviation
Motivation
Diagnostics and prognostics of technical condition is a difficult task when
we do not know:
• the history of real material stresses,
• dynamics and degree of diversification of the material degradation
process.
The MMM method is a standardized, but still controversial NDT method whose: • authors (prof. Dubov, Vlasov) and its users in 27 countries has
been declaring the possibility of reliable identification of the material degradation early phase, including detection of residual stress concentration zones;
• opponents question its credibility and desirability of conducting MMM tests in power engineering and transport.
Does the Metal Magnetic Memory Method
(ISO 24497:2007) can be used for
the diagnosis of critical components in aviation?
SWOT/TOWS Analysis of MMM method and applications Information Technology (IT) point of view
For the purpose of ordering the current state of knowledge about the MMM
method, identifying its real diagnostic capabilities and defining research needs,
a SWOT/TOWS analysis was made.
Max. risk Low POD
Low risk Max. POD
SWOT or TOWS analysis helps you get a better understanding of the strategic choices that you face.
IT support is required at every level
Strengths of the MMM Method
The MMM method bases on three reliable foundations : • magneto-mechanical effects and nonlinear relationships
of microstructure with magnetic properties of a material; • measurements of the magnetic field (DC and low-frequency
component) distribution near a tested object using current capabilities of electronic vector magnetometers, encoders and digital data registration;
• numerical analysis of measurement data, during which the inverse problem of magnetostatics that is burdened with the ambiguity with observing the principles of the signal analysis theory is solved.
Strengths of the MMM Method Fundamentals
Lűders’ bands
Cold working
Strengths of the MMM Method Example: work hardening phenomena
Work hardening (cold working) is the strengthening of a metal by plastic
deformation carried out at temperature below the so-called recrystallization
temperature of the metal (typically below 30% of the melting point).
Plastic deformation changes mechanical
parameters of material, among others:
a) increase:
- yield point σy,
- ultime tensile strength σult,
- hardness and microhardness,
- nonlinearity;
b) decrease: ductility, notch impact energy
150
200
250
300
350
400
0.1 1 10
s [MPa]
Strain e [%]
Virgin load
After drawing
S235 steel
Lűders’ bands
Other result of plastic deformation is: • the loss of isotropy, • changing magnetic parameters, • stress inducted magnetization.
Strengths of the MMM Method Example: work hardening phenomena
Lűders’ bands
Cold working
S.M. Thompson (1991), The magnetic properties of plastically deformed steels, Durham theses, Durham University
M.F. Fischer (1928): Note on the effect of repeated stresses on the magnetic properties of steel. Bureau of Standards Journal of Research 1(5), 721-732
Δ𝚩 = 𝑓 𝜇 𝜎𝑚𝑎𝑥 , 𝐇 , 𝜎𝑖𝑗 , 𝑁
𝐌 = 𝐌𝑖 +𝐌𝑟 = 1 + 𝑘𝐻 1 + 𝑘𝜎 1 + 𝑘𝑇 𝐌𝟎
with Mi – the induction magnetization; Mr – the residual magnetization; M0 – initial state of magnetizing; kH, ks,kT – appropriately influence of external field, stress and temperature.
Strengths of the MMM Method Stress inducted magnetization
In the macroscopic scale a constitutive law is copying magnetic properties of the testing element
𝐁 = 𝜇𝐇 = 𝜇0 𝐇+𝐌
with : m0 – magnetic permeability of vacuum, M – material magnetization [A/m], H – external magnetic field [A/m], B – magnetic induction [T].
Ewing J.A. (1900): Magnetic induction in iron and other metals.
Strengths of the MMM Method Magneto-mechanical effects
Magneto-mechanical effects have been known for over 150 years,
but only a few grades of steel have designated parameters
of magnetic and magneto-mechanical.
01 02
Effect of short-term working blades in the range of resonance excitations
The reference blade
Strengths of the MMM Method Example: MMM NDT of LP steam turbine blade
(Detection of magnetic anomalies)
The model of the measuring signal S=A + P + I
Strengths of the MMM Method Example: In quest of fatigue risk
Compressor of SO-3 turbo jet engine
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0
400
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Flexible support & unbalance effects
Unequal load
effect
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SNDŁ-1b/SPŁ-2b
sensor & unbalance effects
DB
Strengths of the MMM Method Example: Ex post facto analysis
Fatigue cracking axis of the tram
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0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300
x [mm]
H2 [A/m]
1
1
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0 10 20 30 40 50 60 70 80 90
L [mm]
H2 [A/m]2 2
Good compatibility MMM results with the
average stress during a cross-section changes
Strengths of the MMM Method The measurements of the magnetic field
NDE: Scanning devices of Energodiagnostika Ltd and Eddy Sun Ltd. (fluxgate 2D sensors with μP and encoder) and data loggers
…
Precise measurement of the magnetic field is not an issue in the XXI century.
Wireless Sensor Application Board of RTX company
(3D magnetometer, A/D card, Wi-Fi, battery)
NDE & SHM: Possible adaptation of existing solutions
6D platform of Honeywell company with USB 2.0
SensorTag of TI company with LE 4.0 Bluetooth and battery
3D MEMS magnetometer
MAGEYE magnetic field camera of Matesy company MO C-MOS (Faraday effect) Resolution: ~ 10 μm
Fieldrange: 0.01 – 160 kA/m
8x8 mm
The required new software
Strengths of the MMM Method Detection of magnetic anomalies
Measurement – Expected value (Trend) = Magnetic anomaly
MagCam magnetic field camera 128x128 2D Hall sensor Work area: 13x13 mm Resolution: 100 μm
Fieldrange: up 796 kA/m
8x8 mm
http://www.magcam.com http://www.matesy.de
IT Support: The algorithms used in geophysics UXO detection, image analysis, …
Objects possible to NDE&SHM with the help of the MMM method
Diagnostic class of the object for passive
magnetic observer
Class of the degradation process of material
Model objects of NDE&SHM with using
passive magnetic observer
Stationary object Cold working, low cycle fatigue (LCF), high cycle fatigue (HCF)
Railway rails, transmission pipelines, load-bearing structures of steel bridges and halls, masts, pressure cylinders
Thermal stresses, Heat Affected Zone (HAZ) Welding joints, bodies of turbines
Hydrogen brittleness, chemical and electrochemical corrosion
Fittings chemical, sea drilling platforms and wind turbines
Stationary object in electromagnetic fields
Cold working, LCF, HCF Electricity pylons, stators and bodies of generators and electric engines
Movable object Cold working, LCF, HCF, very high cycle fatigue (VHCF), erosion, corrosion
Vehicles, shafts, gears, bearings, blades of the compressor and low-pressure turbine
Creep, thermo-mechanical fatigue (TMF) Blades of medium- and high-pressure turbine
Movable object in electromagnetic fields
Cold working, LCF, HCF, VHCF Armature of the generator and electric engines
Special object Ionising radiations, very low temperature (cryogenic), stroke burdens
Elements of a nuclear reactor, cryogenic installations, crash test, unexploded ordnance (UXO)
Weaknesses of the MMM method & applications (ISO 24497:2007) The applications uses theory of magnetism to improve safety
Weaknesses of the MMM Method: 1. The MMM has been standardised only as an auxiliary method of testing the quality of welds.
2. In description of the MMM method and ISO 24497 standard, i.a., • the influence of microstructure type (i.a. changing in the HAZ), • processes of material degradation, • classes of tested objects,
on: • expected diagnostic symptoms, • requirements for the measurement chain, • interpretation of test results,
has been omitted!
Each NDT and SHM method has its weaknesses, whose recognition decreases the
risk of wrong diagnosis and should stimulate its author and users to corrective
actions. The MMM method has its weaknesses too.
3. The MMM methodology does not also take account of the peculiarity of the operation of aeronautical engineering.
Weaknesses of the MMM method & applications The application uses theory of magnetism to improve safety (ISO 24497:2007)
During taxiing and flight changes the location of critical components and stress relative to
the Earth's magnetic field.
Requires a new methodology for interpreting the MMM results.
Opportunity of the MMM Method
All weaknesses of the MMM method and its applications (ISO 24497
methodologies, sensors and software) may be eliminated on the basis of:
• existing technology level of the physical values measurement and data
analysis;
• research and development works carried out on the basis of due diligence
in research and verification of results obtained in inter-laboratory tests.
The Earth’s magnetic field
StochasticPeriodic
edisturbanc
Aperiodic
crustcorem ttt
,,, rBrBrBrB
where:
Bcore – the core field generated in Earth’s conducting, fluid outer core (about 95% Bm)
Bcrust – the crustal field from Earth’s crust/upper mantle (about 4% Bm)
Bdisturbance – the combined disturbance field from electrical currents flowing in upper
atmosphere and magnetosphere, which also induce electrical current in the
sea and the ground
Object and sensor position are known at geographic coordinates system (gravity),
the Earth’s magnetic field components are at geomagnetic coordinates system.
The geomagnetic coordinates system is moving relatively to gravity one.
The Earth is a geoid, but coordinate systems base on a ellipsoid.
IT Support Bcore verified models
StochasticPeriodic
edisturbanc
Aperiodic
crustcorem ttt
,,, rBrBrBrB
Determination of the expected value for Bcore is based on free of charge
low degree models, i.a:
The International Geomagnetic Reference Field, IGRF-12 (degree 13, 195 Gauss
coefficients)
The World Magnetic Model, WMM-2015 (order 12, 168 Gauss coefficients)
The source code is in public domain and not licensed or under copyright .
Note: The data and charts produced from IGRF and WMM models characterize only the long-
wavelength portion of the Earth’s internal magnetic field (waveband of 2500 km).
Consequently, a magnetic sensor may observe spatial and temporal magnetic anomalies
(typically of magnitude 200 nT, but often much larger until some thousand nT) when referenced
to the models.
IT Support Bcore + Bcrust verified models
NGDC NOAA also provides geomagnetic models EMM2015 (free) and HDGM (paid) with higher spatial resolution. These models are suitable for applications where higher navigational accuracy is required. The EMM2015 is an epoch 2015 release of the Enhanced Magnetic Model, intended to calculate the magnetic field for both the Earth's internal magnetic field as well as the crustal field. It extends to degree and order 720, resolving magnetic anomalies down to 56 km wavelength. The source code and coefficients are free in public domain.
The purple areas indicate full HDGM model resolution of 28 km, based on coverage by ship and airborne magnetic surveys. Other areas have a reduced resolution of 133 km based on
satellite data only
StochasticPeriodic
edisturbanc
Aperiodic
crustcorem ttt
,,, rBrBrBrB
IT Support The NDE & SHM expert system
Verified numerical models of Earth’s magnetism
(WMM of NOAA) enable to obtain an accurate reference
signal (aperiodic component of BE)
Bm_ref = BE_A 5 nT (1 0,0001)BE_A
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October 2011
Z [nT]
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October 2011
F [nT]
Main phase
Recovery phase
First phase
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Y [nT]
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October 2011
X [nT]
Bremen, 16.11.2016 (WMM 2015) Declination D = 2.1037o
Inclination I = 68.0985o
Horizontal intensity H = 18450.6 nT Nord comp. X = 18438.1 nT East comp. Y = 677.3 nT Vertital comp. Z = 45893.6 nT Total field F = 49463.6 nT
IT Support of new sensors for MMM applications (NDT & SHM)
x-axis
y-axis
z-axis 1 16
6DOF MEMS platform: magnetometer 3D, 16-bit accelerometer 3D, 14-bit Size: 3x3x1.2 mm, fs = 800 Hz, I2C and SPI
Fixed distance (5 mm) between 16 the 3D magnetometers USB 2.0
IT Support New algorithm
Analysis and automatic correction of errors of the incremental encoder in measurement data acquired using the Energodiagnostika Ltd. probe type 2M
Analysis of the 53 ND37 steam turbine blades by statistical pattern of the MMM results
IT Support Statistical analysis of MMM data
The blades of a turbine
stage
MMM measurement
(Bx, By, Bz)ij
2-2-3 sigma method
Nb
1
2
…
Statistical pattern of blades and rotor
Diagnosis
IT Support The NDE & SHM expert system
Taking account of the needs of present MMM method's users in the scope of independent operation of instruments produced by Energodiagnostika Ltd. and binary *.mms files - a source of a huge, but not systematic empirical knowledge.
The EXPERT MMM software for NDT and SHM applications will contain a system
core and 6 relational databases:
database containing descriptive data,
material database,
database containing measurement data,
database containing procedures of external
devices' operation,
database containing diagnostic rules,
database containing models,
and coded, automatic daily work that will monitor actions
taken by a software user.
IT Support The NDE & SHM expert system
H=[0, 0, 50] A/m
Conclusion
1. IT support of Metal Magnetic Memory method allows for new diagnostic capabilities in NDT and SHM of ferromagnetic objects.
2. The existing MMM method's algorithms (ISO 24497) detect and identify only features of magnetic anomalies. The algorithms do not perform the qualitative analysis of the current material stress level, nor the structure degradation degree, since they do not take account of: the material type (magnetic and magneto-mechanical parameters), object's working time (number of load cycles), calibration curves.
3. Genuine local magnetic anomaly can be a place of: cracks, residual stress concentration, heterogeneity of microstructure, changes in geometry (cross section)
Tae-Kyu Lee, J.W. Morris, Jr., Seungkyun Lee and J. Clarke: Detection of fatigue damage prior to crack initiation with scanning SQUID microscopy. Review of Progress in Quantitative Nondestructive Evaluation, Vol. 25
IT Support of NDE And SHM with Application
of the Metal Magnetic Memory Method
Mirosław WITOS, Mariusz ZIEJA, Bartłomiej KURZYK
Air Force Institute of Technology
Warsaw, Poland,
7th International Symposium on NDT in Aerospace 16 – 18 November 2015, Bremen, Germany
We4-A3
Thank you for your attention
Any questions?
More info: http://www.researchgate.net/profile/Miroslaw_Witos
